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Title:
MULTILAYER FILMS FOR NAKED COLLATION OF PACKED PRODUCTS
Document Type and Number:
WIPO Patent Application WO/2017/002033
Kind Code:
A1
Abstract:
Oriented multilayer films for naked collation of packed products so as to form packs of 6 or 10 or more packed products, comprising at least a core layer, an inner layer and an outer layer, said layers consisting of olefin (co)polymers, in which the outer layer comprises (co)polymers having a melting temperature comprised between 65°C and 85°C;the inner layer comprises (co)polymers having a melting temperature comprised between 65°C to 105°C and the core layer comprises propylene and/or butene (co)polymers having a melting temperature higher than 140°C; wherein the film covering the individual packed products is formed of one or more olefin (co)polymers having a melting temperature higher than 120°C; the inner layer of the multi-package film being in contact with the film wrapped around the individual products (film O) forming the pack; the outer layer and the inner layer (layer A) of the multi-package film are of the same thickness, comprised between 0.35 and <0.5 μm. The films of the invention exhibit antiscratch properties and in the multi-package the layer (A) of the naked collated film does not stick to the film (O).

Inventors:
DI COSTANZO, Carmelo (Via Don Minzoni 26, Lanciano, 66034, IT)
PASQUINI, Gino (Via Sacchetti, 59/A, Treglio, 66030, IT)
QUADRINI, Ombretta (Via Spaventa 17, Altino, 66040, IT)
SANTILLI, Fausto (Via San Rocco, 72/C, San Vito Chietino, 66038, IT)
DE IULIIS, Davide (Via Alessandro Volta 6, Lanciano, 66034, IT)
Application Number:
IB2016/053884
Publication Date:
January 05, 2017
Filing Date:
June 29, 2016
Export Citation:
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Assignee:
IRPLAST S.P.A. (Strada Provinciale Val D'Elsa Snc -, Zona Industriale Terrafino, Empoli, 50053, IT)
International Classes:
B32B7/02; B32B27/08; B32B27/32; B65D71/06; B65D75/38
Foreign References:
EP2520428A12012-11-07
Attorney, Agent or Firm:
BIANCIARDI, Ezio (BUGNION S.p.A, Via di Corticella 87, Bologna, 40128, IT)
Download PDF:
Claims:
1 . A multilayer film for naked collation of packed products so as to form packs of 6 or 10 or more packed products, comprising at least a core layer, an inner layer and an outer layer, said layers consisting of olefin (co)polymers, wherein:

- outer layer (B): one or more (co)polymers having a melting temperature comprised between 65°C and 85°C;

- inner layer (A): one or more (co)poiymers having a melting temperature comprised between 65°C and 105°C;

- core layer: one or more propylene and/or butene ( copolymers having a melting temperature higher than 140°C;

wherein the film covering the individual packed products is formed of one or more olefin (co)polymers having a melting temperature higher than 120°C up to 165°C;

the inner layer of the multi-package film being in contact with the film wrapped around the individual products (film O) forming the pack; wherein the outer layer (B) and the inner layer (A) of the multilayer film are of the same thickness, between 0.35 and <0.5 μηι,

2. The multilayer film according to claim 1 , wherein the outer layer and the inner layer are of the same thickness, between 0,4 and 0.45 μητι.

3. The multilayer film according to claim 1 or 2, wherein the film is heat- shrinkable and biaxiaily or uniaxiaily oriented.

4. The multilayer film according to claim 3, wherein the film is heat- shrinkable biaxiaily.

5. The multilayer film according to claim 3 or 4, wherein the heat- shrinkage value determined using the OPMATC4 test at 130°C for 5 minutes in the air in the MD and TD for a biaxiaily oriented film, or in the MD for a uniaxiaily oriented film, is in the range between 5 and 70%.

8. The multilayer film according to any one of claims 1 to 6, wherein the (co)polymers constituting the outer layer (B) and the inner layer (A) are the same or different from each other.

7. The multilayer film according to any one of claims 1 to 6, wherein the (co)poiymers of the inner layer (A) and the outer layer (B) are selected from ethylene copolymers comprising one or more linear or branched alpha-o!efin comonomers having 3 to 12 carbon atoms, and from propylene copolymers, comprising one or more linear or branched a!pha-olefin comonomers having 4 to 12 carbon atoms, optionally ethylene.

8. The multilayer film according to any one of claims 1 to 7, wherein the (co)poiymer of the core is polypropylene.

9. The multilayer film according to any one of claims 1 to 8, wherein the core layer contains amorphous hydrocarbon resins.

10. The multilayer film according to any one of claims 1 to 9, having a thickness between 10 and 60 pm, the core layer having a thickness of 8-38 μΐΎΊ.

1 1 . The multilayer film according to any one of claims 1 to 10, obtainable by extrusion and subsequent biaxial simultaneous stretching in the MD machine direction and in the TD transversal direction.

12. The multilayer film according to claim 1 1 , wherein the biaxial stretching process comprises the following steps:

- coextrusion of a multilayer plate of the film of the invention, having a thickness preferably comprised between about 1 and about 4 mm; - plate quenching on a cooled roller, preferably between 10 and

40°C;

- plate heating at a temperature between about 100° and about 500°C, preferably by means of infrared rays;

- obtaining the film by stretching the plate, said stretching taking place by gripping the edges of the plate of a greater thickness with a set of pliers or clamps independently driven by linear synchronous induction motors, each piier or clamp sliding on a rail and being pulled by a permanent magnet or by a pair of permanent magnets, pushed by the magnetic wave created by the pole pieces of the motors; each section of the stretching frame having a series of linear synchronous induction motors arranged contiguously, and supplied by alternating currents with modulated phase and frequency so as to vary continuously the clamp (pliers) speed and thus the longitudinal stretch ratios of the film; the transversal stretch ratios being regulated by modifying the divergence of the rails on which the pliers or clamps slide; the stretching frame comprises one or more sections located inside an oven having temperatures comprised between about 80°C and 210°C; the longitudinal stretch ratios are generally comprised between about 3: 1 to about 10: 1 and the transversal stretch ratios between about 3:1 to about 10: 1 .

13. The multilayer film according to any one of claims 1 to 12, comprising more than three layers.

14. The multilayer film according to any one of claims 1 to 13, wherein the sealing temperature between the outer /outer layers (B/B), the inner /inner layers (A/A), the outer/inner layers (B/A) and the inner /outer layers (A/B) is comprised between 65°C and <80°C.

15. Use of the naked collation films according to any one of claims 1 to 14, to form packs in which the film around the pack exhibits no scratches and there is no stickiness between the layer (A) of the multi-package film and the film (O) of the films around the individual packets.

18. The use according to claim 15, wherein the films are fed from a reel on high-speed packaging lines, the speed being comprised between 70-100 packs/minute, with a percentage of rejects lower than 1 %, the rejects being the percentage of rejected packs with respect to those produced by the packaging line.

17. A process for forming a naked collation pack comprising the multilayer film according to any one of claims 1 to 14, comprising:

- preparing a group of individual packed products placed one adjacent to the other so as to form a carton, each individual packet being wrapped within a polyolefin film (0);

- wrapping the carton in the film for naked collation, wherein the inner layer (A) is in contact with the film (O);

- closing the film for naked collation on the two opposite sides of the carton, said sides being of smaller size, by folding and sealing the outer layer (B) of the naked collation film with itself or with (A), and on one of the carton sides arranged longitudinally, by sealing the layer (A) with layer (B), at temperatures comprised between 65°C and <80°C.

18. The process according to claim 17, wherein the naked collation film is obtained by biaxial stretching, using stretch ratios of 8.3: 1 in the

MD and 7: 1 in the TD.

19. The process according to claim 17 or 18, wherein the outer layer (B) contains sliding agents.

20. A pack that is obtainable using the process according to any one of claims 17 to 19.

Description:
DESCRIPTION

MULTILAYER FILMS FOR NAKED COLLATION OF PACKED

Technical Field

The present invention concerns a multilayer film for packaging (naked collation) products packed so as to form packs (multi-packages) of 6 or more pieces, which can be removed without using cutting tools such as knives, scissors, etc., said film having a sealing temperature comprised between 65°C and <80°C, the film around the packs substantially not exhibiting scratches when the multi-package is moved on conveyor belts constituted by rigid materials commonly used in these sectors, said properties being combined with minimum adhesion (stickiness) of the inner layer (A) of the multi-package film with the film (0) wrapped around the individual packets.

More specifically, the present invention concerns multilayer films, preferably heat-shrinkable films, for packaging packets of cigarettes so as to form packs of 6 or 10 or more pieces, one alongside the other, having a sealing temperature comprised between 65°C and <80°C, preferably between 70°C and 80°C, more preferably between 75°C and 80°C, even more preferably between 75°C and 78°C, under the temperature, sealing time and pressure conditions reported in the characterization (Method A and Method B), between the outer layer/outer layer (B/A), the outer layer/inner layer (B/B), the inner layer/inner layer (A/A) and between the inner layer/outer layer (A/B) of the multilayer film, while simultaneously substantially reducing the risk of sealing taking place between the inner layer of the multilayer film and the film covering the individual packets of the pack. State of the Art

It is well known in the art that the aim of naked collation is to wrap and keep together a number of packets, generally packets of cigarettes, packaged in groups of 8, 10 or more units. Packaging is carried out using a multilayer film that has the advantage of eliminating the paper or cardboard boxes previously used. The industrial advantages of naked collation are evident, in that it makes it possible to avoid the use of paper boxes or cartons, which require a separate process for preparation and additionally in the end, after being filled, they must be wrapped in a film so as to prevent the paper or cardboard from being damaged during transport by friction with foreign objects. Therefore, the system of naked collation makes it possible to eliminate one step in the packaging process for packaging packets of cigarettes. The essential characteristic (necessary condition) that is required of a film for naked collation is that it must be capable of sealing to itself. The two surfaces of the multilayer film , the inner and the outer surface, must therefore be seaiable according to any one of the following manners: outer/outer, inner/inner, inner/outer, or outer/inner surfaces; moreover, the film for the multi-package must not be sealed to the outer layer of the film used to wrap the individual packets of cigarettes (film (O)). This property is required so as to prevent the film around the individual packets of cigarettes from being torn or damaged when the film around the outer package is removed. In commercial terms, any breakage or damage affecting the film (O) results in the packet of cigarettes no longer being acceptable for the market and it is thus considered a production reject.

Moreover, the multilayer film must have good mechanical properties, above ail in the longitudinal direction (MD) to enable high-speed packaging without breakage and to maintain the cutting length for application in the naked collation.

It is also well known that when the groups of naked collated packets of cigarettes reach the points of sale, the package film is removed so as to collect and display the individual packets of cigarettes.

The use of a multilayer film with an acrylic coating for the multi-package is known. These films have several drawbacks: - high cost, owing to the fact that following preparation of the film, the step of spreading the acrylic resin on the film must be carried out;

- there are environmental issues as regards recycling and disposal of the acrylic resins;

- during packaging of the packs, after a few hours of operation, white dust from the acrylic resin is released on the rollers of the machines used for packaging. This makes it necessary to interrupt the process and clean the machines to prevent the dust from being dispersed in the work environment, as it is a health hazard for personnel. Moreover, the dust must be prevented from depositing on the individual packets. However, the most significant drawback of this type of multi-package film is that it requires the use of cutting tools, such as knives or scissors, for its removal from the assembled groups of packets. As this procedure has created considerable inconvenience for users, above ail in terms of safety, having films available for naked collation that can be removed from the cigarette packets without the use of cutting tools has become a more pressing need.

Furthermore, films for naked collation need to have good antiscratch properties even during movement of the multi-package on rigid surfaces, for example metal surfaces, normally used in machines for the preparation of multi-packages.

Multilayer films with antiscratch properties are known in the prior art.

See for example US patent 4,502,263, in which this property is obtained using a sealing (heat seaiable) layer formed of (% by weight):

(a) 68.5 to 89.7% of an E-P-B (ethyiene-propylene-butylene) terpoiymer and a P-B copolymer, in which in the polymer mixture (% by weight) E ranges between 0.1 and 7%, P between 53 and 89.9% and B between 10 and 40%;

(b) 5 to 15% of a low molecular weight hydrocarbon resin;

(c) 5 to 15% of a polypropylene homopolymer;

(d) 0.3 to 1 .5% of silicone (poiydiorganosiioxane). Also known from US patent 4,734,318 is a film having improved antiscratch properties and comprising a core layer of polypropylene coated on both surfaces with an intermediate layer of polypropylene containing as additives (% by weight) 0.1 to 1 % of a pigment and 0.2 to 1 % of an oxyaikyiamine. The outer layers (top layers) have the same composition as the sealing layer described in the US patent discussed hereinabove. US patent 4,883,698 discloses metaiizable multilayer films in which hydrogenated resins based on olefin polymers with inorganic pigments and polydiorganosiioxanes are used in the sealing layer to confer antiscratch properties. The components that enable to obtain antiscratch properties are those known from the patents described above.

US patent 5,302,427 claims a multilayer film in which the polypropylene of the core layer is degraded with peroxides and the sealing layer comprises a polymer mixture of the same type as that described for the component (a) of the sealing layer of the film of US patent 4,502,263, together with a poiydiorganosiloxane and silica particles.

Furthermore, patent EP 2,520,428 filed by the Applicant discloses a multilayer film for naked collation that is made up of a core consisting of a polypropylene homopolymer and sealing layers formed of a P-B polymer having a melting temperature comprised between 65°C and 105°C.

Yet, the availability of a film offering improved scratch resistance during movement of the multi-package on rigid surfaces remains a need, !n fact, it has been observed that in applications, scratches may form on the surface of the film during transport (movement) of the pack when it comes into contact with supports or rigid surfaces, for example, the conveyor belts commonly employed for this purpose.

The methods used by manufacturing industries to check the sealability of the inner layer (A) of the film for naked collation and the outer layer of the film (O) around the individual packets of the multi-package consist in subjecting the outer layer of the film (O) to sealing coupled with the layer

(A) of the multi-package film, ensuring that at the sealing temperature of the layers (A/A), (B/A), (A/B) and (B/B) to form the muiii-package, sealing (A/O) does not take place. In fact, in the case in which sealing does take place, the film cannot be used to form the multi-package. Yet, the Applicant has found that even if sealing (A/O) has not occurred and sealing between the other layers indicated above has taken place correctly, there can be stickiness between the layer (A) and the film (0) causing breakage of the film around the individual cigarette packets when the multi-package film is removed to collect the individual packets, this latter procedure usually being carried out by users. From the industrial standpoint, breakage of the film (O) around the individual packets constitutes damage that needs to be reduced.

The need exists to have available multilayer films for naked collation packaging of single products to obtain multi-packages having the following combination of properties:

- sealing temperature comprised between 65°C and <80°C, preferably between >75°C and <80°C;

- anti-scratch properties for moving the multi-package on rigid surfaces, so that the films are not scratched during packaging of the groups of packed products and/or during transport of the pack thus obtained on supports or rigid surfaces;

- the naked collation or multi-package films should be easily removable without using cutting tools, so that removal of the packaging and collection of the individual packets, for example cigarettes, is carried out safely.

- the naked collation films wound on reels should be usable for producing packs (naked collated packages) on high-speed packaging lines, on the order of 70-100 packs/minute, without resulting in adhesion with the rollers of the packaging line and with the film around the individual packed products (e.g. the individual packets of cigarettes), the percentage of rejects being lower than 1 %, preferably lower than 0.1 %, and more preferably lower than 0.01 %, the rejects being calculated as reported herein below;

- in particular, the percentage of rejects owing to scratches, on the packaging line, substantially tends toward zero;

- a substantial reduction of the stickiness phenomenon between the layer (A) of the naked collation film and the film (O) also in the step of removing the multi-package by sellers to collect the individual packets.

Multilayer films that make it possible to solve this technical problem and have the combination of the above-mentioned properties have been surprisingly and unexpectedly found by the Applicant.

Asm of the invention

An object of the present invention consists of a multilayer film for naked collation of packed products so as to form packs of 6 or 10 or more packed products, comprising at least a core layer, an inner layer and an outer layer, said layers consisting of olefin (co)poiymers, in which:

- an outer layer (B): one or more olefin (co)polymers having a melting temperature comprised between 65°C and 85°C;

- an inner layer (A): one or more olefin (co)polymers having a melting temperature comprised between 65°C and 105°C;

- a core layer: one or more propylene and/or butene polymers having a melting temperature higher than 140°C;

wherein the film covering the individual packed products (film (O)) is formed of one or more olefin (co)polymers having a melting temperature that is higher than 120°C up to 165°C; the inner layer (A) of the multi- package film being in contact with the film (O) wrapped around the individual products forming the pack (carton);

wherein the outer layer (layer B) and the inner layer (layer A) of the multi- package film are of the same thickness, comprised between 0,35 and <0.5 μηπ. Detailed description of the invention

The film of the invention has antiscratch properties; in fact, the outer layer (B) of the multilayer film is not scratched neither in the packaging step nor in the step of transporting the pack (multi-package) during movement when it comes into contact with rigid supports such as guides made of metal, Teflon etc.

Preferably, the (co)polymers of the outer layer (B) of the multi-package have a melting temperature comprised between 65°C and 8Q°C, more preferably between 70°C and 78°C.

Preferably, the (co)polymers of the inner layer have a melting temperature comprised between 70°C and 90°C, even more preferably between 70°C and 80°C.

Preferably, the polymers of the core layer are propylene homopolymers, preferably having a melting temperature higher than 160°C.

Preferably, the melting temperature of the olefin (co)polymers constituting the film (O) wrapped around the individual packed products is comprised between >120°C-170°C, more preferably 125°C-165°C.

Preferably, the outer layer (B) and the inner layer (A) of the multi-package film are of a thickness comprised between 0.4 and 0.45 μηη, the two layers being of the same thickness.

Preferably, the multilayer films of the invention are heat shrinkabie and oriented biaxially or uniaxially, preferably biaxially. The heat shrinkage value is determined using the OPNATC4 heat shrinkage test (Oriented Polypropylene Manufacturers' Association) at 130°C for 5 minutes in the air. Generally, the heat shrinkage value in the MD and TD for a biaxially oriented film, or in the MD for a uniaxially oriented film, is in comprised between 5 and 70%, preferably between 8 and 40%, more preferably 9- 15%, and even more preferably 10-13%. To obtain the biaxial heat shrinkage, the profiles of the longitudinal (MD) and transversal (TD) stretch ratios are modified at the same time. A profile of the stretch ratio is understood as the curve obtained by plotting in a graph, respectively, for longitudinal stretching, the stretch ratio (film speed at the point considered in the stretching oven)/(initial film speed at the inlet of the oven or stretching frame) as ordinates, and the distance between the oven inlet and the point considered in the oven as the abscissas. For transversal stretching, the ratio (distance between the stretching rails at the point considered in the oven)/(distance between the rails at the oven entrance) is represented as ordinates, and the distance as described for the profile of the longitudinal stretch ratio, as abscissas.

The profile of the longitudinal stretch ratio shows an increasing trend or it can show a maximum peak followed by a decrease no greater than about 20% with respect to the maximum value.

The profile of the transversal stretch ratio (TD) shows the same trend described for the profile of the longitudinal stretch ratio.

The multi-package film of the present invention is preferably obtained by simultaneous stretching of the film in the MD and TD, operating at temperatures comprised between 155°C and 165°C and maintaining a constant stretch ratio in both the MD and TD, then cooling the film at temperatures comprised between 145°C and 125°C and decreasing the stretch ratio by a percentage preferably <15% with respect to the maximum value of the stretch ratio in the MD and TD direction.

To obtain uniaxial heat shrinkage in the MD, the transversal stretch profile is modified so as to decrease the stretch ratio in the TD. This is achieved by using a stretch profile in the TD that has a decrease between 15 and 30%, preferably equal to about 25%, with respect to the maximum value of the function.

By operating in this manner, the heat shrinkage values in the TD are very limited, lower than 5%, and preferably lower than 4%.

According to a preferred embodiment, the heat shrinkage values of the uniaxial film in the MD are generally comprised between 15 and 20%.

Following the stretching step, the film is wound on reels (extrusion mother reel) of very long lengths, even as much as 20,000 meters. By cutting these latter reels, reels called extrusion daughter reels are obtained and they preferably have a diameter of up to 1 ,000 mm. The reels for naked collation application are then obtained from the daughter reels.

The packed products are preferably packets of cigarettes arranged one alongside the other.

The (co)poiymers constituting the outer layer (B) and the inner layer (A) are the same or different from each other. These layers can be constituted by one or more ( copolymers having melting temperatures within the limits indicated above for the outer layer (B) and for the inner layer (A), respectively.

The (co)poiymers that can be used for the inner layer (A) and the outer layer (B) of the multilayer film are ethylene copolymers comprising one or more linear or branched aipha-olefin comonomers having 3 to 12, preferably 3 to 8 carbon atoms. Propylene, butene, particularly butene-1 , hexene, octene, decene and dodecene can be cited as examples. The amount of butene, hexene, octene, decene and dodecene is generally not greater than 50% (% by weight), preferably ranging from 15% to 35%, more preferably from 20% to 30%.

The copolymers preferably used are propyiene-based and comprise one or more linear or branched aipha-olefin comonomers having 4 to 12 carbon atoms, preferably 4 to 8, the comonomer optionally being ethylene. Ethylene, butene, preferably butene-1 , hexene, octene, decene and dodecene can be cited as examples of olefin comonomers. The amount of butene, hexene, octene, decene and dodecene, expressed as % by weight on the copolymer, is generally not greater than 40%, preferably in the range of 10% to 30%, more preferably 20% to 28%. The amount of ethylene (% by weight) is in the range of 0-20%, preferably 0-15%, and more preferably 0-5%.

Together with the above-mentioned monomers, monomers containing more than one olefinic unsaturation can also be used in the ethylene- based copolymers and in the propyiene-based copolymers. The following diens can be mentioned: linear, conjugated or non-conjugated diens having 4 to 20 carbon atoms, or cyclic diens in which the ring has 5 or 6 carbon atoms, preferably vinylcycloaikenes, such as vinylcyclohexene; aromatic compounds, such as cyciopentadiene; vinyiaromatic compounds such as styrene, 2,4-vinylstyrene, optionally one or more hydrogen atoms of the ring being substituted with saturated aikyi groups with 1 to 12 carbon atoms or unsaturated alkyl groups with 2 to 12 carbon atoms, optionally one or more carbon atoms of the ring being substituted by heteroatoms, preferably nitrogen, oxygen, and sulphur.

The following can be cited as conjugated dienes: butadiene, isoprene, piperyiene, 1 ,3~hexadiene, 1 ,3~octadiene, 2,4-decadiene, cyciopentadiene; and as non-conjugated dienes: 1 ,4-hexadiene, 7-methyi- 1 ,6~octadiene; cyclic non-conjugated dienes such as norbornene, ethylidene norbornene, 4-vinylcyclohexene and vinyl aromatic monomers such as styrene, 2,4-vinyistyrene etc.

The amount of dienes (expressed as % by weight with respect to the copolymer) is comprised between 0 and 25%, preferably between 0.5 and 10%, more preferably 0.1 -3%.

Preferred examples of Propylene/butene-1 copolymers. These copolymers are amorphous and they have an isotacticity index (I!) preferably comprised between about 30% and 77%. The corresponding crystalline part has a melting point within the above-mentioned limits.

The amount of extractabies of the copolymers utilized in the inner (A) and the outer (B) layers is preferably comprised between >60%-70% and it is determined at 50°C for 2 hours according to the FDA 177 - 1520 Standard.

The (co)polymers of the inner layer (A) of the multilayer film differ from the (co)polymers of the film (O). For example, if (A) comprises a propylene (co)polymer and an olefin t, the film (O) contains an ethylene or butene (co)polymer or a propylene copolymer and at least an olefin comonomer t' in which t' differs from t. If (A) contains an ethylene (copolymer and an olefin q, the film (0) contains a propylene or butene (co)po!ymer or an ethylene copolymer with an olefin comonomer q' differing from q.

The olefin monomers t, t\ q and q' are selected from those mentioned hereinabove.

As stated above, the polymers of the core layer are preferably propylene homopoiymers.

The propylene homopoiymers generally have an amount of exfractables in hexane, this amount being determined using the method indicated hereinabove, preferably lower than 10% by weight, generally lower than 3% by weight.

According to a preferred embodiment, in addition to the (co)poiymers stated above, the core can also contain amorphous hydrocarbon resins. These resins have a softening point in the range of about 130°C to about 180°C, preferably between about 130°C and 160°C, determined according to AST E28. Preferably, these are low molecular weight synthetic resins, the numerical average molecular weight thereof is preferably comprised between 200-1000. Those formed by a styrene, methylstyrene, vinyltoluene, indene, pentadiene propylene copolymer can be cited as preferred examples. Hydrocarbon resins are generally used in the form of masterbatches, in which the resin (% by weight) ranges between 40 and 60%, the remaining part being a propylene homopolymer. Generally, the amount of the masterbatch utilized is between 10-20% by weight, with respect to the core polymer.

When the core contains a hydrocarbon resin, the core polymer is preferably a propylene homopolymer.

The film (O) is preferably constituted by propylene polymers, optionally containing hydrogenated resins. The film can undergo treatments for increasing the surface tension, for example by means of corona treatment. Alternatively, the film (O) can be constituted by propylene/ethylene copolymers having a sealing temperature in the range of 105 to 120°C. Such films (O) are well known in the art.

The olefin (co)polymers described above are obtained by polymerization with Zeigier Natta catalysts or by catalysis using metaliocenes.

Polymerization for obtaining the (co)polymers be carried out using the suspension technique, in an inert diluent, in an emulsion or in the gaseous phase, with temperatures generally in the range of 0°C to 150°C at a pressure generally in the range of 1 to 300bar, optionally using a molecular weight regulator, for example hydrogen. Polymerization by means of metaliocenes can take place using catalysts comprising the reaction product, selected from:

1 ) a bis-cyciopentadienyl derivative of the general formula:

containing oxygen groups bound to the transition metal, in which !Vl is a metal selected from group ! lib to group Vb or of the ianthanide series of the Periodic Table of the elements; Cpi and Cp2, equal to or differing from each other, represent the following groups bound to M with deiocalized π bonds, in particular with an eta 5 bond when the groups are chosen from among cyclopenfadiene, indene, fluorene, or derivatives thereof, substituted in the case of indene and fluorene also with the hydrogenated phenyl ring(s) and with substituents in both the phenyl and the cyclopentadienyl rings, also with heteroatoms; or with π bonds for example in the case of cyclooctatriene; or said groups Cpi Cp2 constrained with M by means of a bivalent linking bridge, for example of the -R- type, wherein R is an alkyiene, preferably having 1 to 4 carbon atoms, - Si(R')2- wherein R' is an alkyl having 1 to 10 C atoms, preferably 1 to 6 carbon atoms; or an aryi optionally containing heteroatoms, such as O, !M, or alkylaryi or aryialkyi having 7 to 20 carbon atoms; L.2 or L.3 equal to or differing from each other, represent an OR a group, wherein R a is an aryl group, optionally the carbon atoms of the ring being substituted also by heteroatoms, and optionally containing substituents for example of the alkyi type having 1 to 10 carbon atoms with

2) a cocataiyst selected from among the compounds represented by the following formulas:

2a) alumoxane, having the general formula:

in the form of a cyclic compound or in the form of a linear polymeric compound having the formula:

Alumoxane is generally a mixture of the two forms indicated above. Rb is an alkyi group having 1 to 5 C atoms, preferably methyl, m is an integer from 1 to 30, preferably from 4 to 20;

m is an integer from 3 to 20, preferably from 4 to 20;

2b) (Li-H) + (A)- wherein (A)- is a compatible non coordinating anion, preferably it is

(B Q q )- wherein Li is a neutral Lewis base,

(Li-H) + is a Bronsted acid,

B is an element of the group from Ilia up to Via of the Periodic Table of the elements with metalloid characteristics, preferably boron, phosphorous or arsenic in the valence state of 3 or 5, silicon, more preferably boron in the valence state of 3;

Q equal to or differing from each other, are selected from the following groups: hydrides, halides, alkyls, aryls optionally substituted, for example with halogens, preferably F, alkoxides, aryioxides, dialky!amido, also RoCOO " wherein Ro ranges from 1 to 20 atoms, of the condition that Q can be equal to halide only once;

q is an integer equal to the valence of B plus 1 .

The preferred cocataiyst component 2) is 2b). The alumoxane compound 2a) of the catalytic system is preferably prepared by reaction of trimethyialuminium and water, obtaining a mixture of linear and cyclic compounds. They are generally prepared by putting into contact a solution of triaikyiaiuminium with water in suitable organic solvents, for example aliphatic hydrocarbons.

As is known, aiuminoxanes are compounds containing AI-O-AI bonds, having a molar ratio in the O/AI range, obtainable in the art by reaction, under controlled conditions, of an aikyi aluminium, or alkyl aluminium haiide, with water, and, in the case of trimethyialuminium, also with a hydrate salt, such as hexahydrate aluminium sulphate, pentahydrate copper sulphate and pentahydrate iron sulphate.

The molar ratio between Al of the alumoxane component 2a) with respect to the amount of the metal of component 1 (metailocene) is comprised between 10000: 1 and 100: 1 , preferably between 5000: 1 to 500: 1 , In the case of the boron compound 2b), the ratio ranges from (0.1 -4): 1 and preferably from (0.5-2.0): 1 .

These catalysts are obtained for example by direct reaction of bis- cyclopentadienyl metal dialkyl, preferably dimethyl, with the corresponding phenols. The reaction gives substantially quantitative yields. The corresponding phenol can be utilized in excess as it can also serve as a reaction solvent. Other solvents are for example cyciohexane, methyicyclohexane, hexane, diethyiether, benzene, toluene, etc.

The thickness of the multilayer film is generally comprised between 10 and 80 μηη, preferably 12-40 μιτι, and more preferably 18-30 μητ

The core layer has a thickness of 8-38 μητι.

The multilayer films of the invention are obtainable by extrusion and subsequent biaxial simultaneous stretching in the IV1D machine direction and in the TD transversal direction. To obtain good mechanical properties, in particular in the MD, biaxial stretching in a fiat die filming process is preferably used and preferably carried out using Lisim® technology. This technology uses a biaxial simultaneous stretching process, for example as disclosed in US patent 4,853,802 and subsequent patents describing this technology.

The biaxial stretching process comprises the following steps:

- coextrusion of a multilayer plate of the film of the invention, having a thickness preferably comprised between about 1 and about 4 mm;

- plate quenching on a cooled roller, preferably between 10° and 40°C;

- plate heating at a temperature between about 100° and about 500°C, preferably by means of infrared rays;

- stretching of the plate so as to obtain the film, said stretching taking place by gripping the edges of the plate of a greater thickness with a set of pliers or clamps independently driven by linear synchronous induction motors, each pliers or clamp sliding on a rail and being pulled by a permanent magnet or by a pair of permanent magnets, pushed by the magnetic wave created by the pole pieces of the motors; each section of the stretching frame having a series of linear synchronous induction motors arranged contiguously, and supplied by alternating currents with modulated phase and frequency so as to vary continuously the clamp (pliers) speed and thus the longitudinal stretch ratios of the film; the transversal stretch ratios being regulated by modifying the divergence of the rails on which the pliers or clamps slide;

the stretching frame comprises one or more sections located inside an oven having temperatures comprised between about 80°C and 210°C, preferably 120°C-190°C; the longitudinal stretch ratios are generally comprised between about 3: 1 to about 10: 1 and the transversal stretch ratios between about 3:1 to about 10: 1 .

The temperatures in the above-mentioned parts of the apparatus are selected so as to enable the biaxial orientation of the polymeric chains of the polymers utilized. The longitudinal stretch ratio can be considered as equal to the ratio between the speed of the film exiting the stretching frame (oven) and the speed of the film entering the oven.

The transversal stretch ratio can be considered as equal to the ratio between the width of the film at the exit from the stretching frame and the width of the film at the entrance to the stretching frame.

The option offered by the simultaneous stretching apparatus to vary the MD stretch ratio over a wide range makes it possible to obtain improved mechanical properties in the longitudinal (MD) direction. This makes it possible to use multilayer films in high-speed machines for naked collation, for example even with a working speed of 1000 individual packets/minute corresponding to 100 cartons (multi-package packs)/m inute. In fact, it is possible to maintain the cutting length in spite of the high speed of the line.

The multilayer film of the invention can also be formed of more than three layers, provided that the inner layer, the core layer and the outer layer are as defined above. There can be 5 or more layers, for example 7. The additional layers are the same as or different from the preceding layers, or such as to confer specific properties to the multilayer, for example antistatic, barrier, anti-fog, mechanical, flame retardant, optical, electrical properties, etc.

The additional layers can be based on olefin (co)polymers or polymers such as EVA (ethyl vinyl acetate polymer), EVOH (ethyl vinyl alcohol polymer), hydrocarbon resins, poiyamides; if desired, compatibilizing polymers, etc. can be used.

The multilayer film can also be subjected to surface treatments, for example corona, flame treatment, etc., so as to obtain improved and longer-lasting printabiiity and metallizability, while at the same time maintaining flexibility and mechanical properties, as long as the sealing temperature is kept within the limits indicated. The multilayer films of the present invention can also be printed for example using a primer if necessary, and subsequent deposition of a layer of ink, followed by flexographic or rotogravure printing.

As stated previously, the sealing temperature between the outer/outer layers (B/B), the inner/inner layers (A/A), the outer/inner layers (B/A) and the inner/outer layers (A/B) of the multilayer film of the invention is comprised between 65°C and <80°C, preferably between 70°C and 80°C, more preferably between 75°C and 80°C, and even more preferably between 75°C and 78°C, the sealing being carried out according to Method A and preferably with Method B to assess stickiness, as described in the examples.

A further object of the present invention consists in the use of the multilayer films of the invention for naked collation packaging, particularly so as to obtain packs in which the film around the pack (multi-package) exhibits improved scratch resistance to the degree that the film substantially does not have scratches and the stickiness between the layer (A) of the naked collation film around the multi-package and the film (0) around the individual packets is much reduced, substantially absent.

The Applicant has unexpectedly and surprisingly found that the films of the present invention, wound in reels that are used for forming packs on highspeed packaging lines, e.g. at a speed comprised between 70100 packs/minute, not only do not exhibit any adhesion to the packaging line rollers and to the film (O) around the individual packed units, but they also exhibit improved scratch resistance and a much reduced stickiness between the layer (A) of the multi-package film and the film (O) around the individual packets, the percentage of rejects being lower than 1 %, preferably lower than 0.1 %, more preferably lower than 0.01 %, the rejects owing to scratches fending toward zero, the rejects being the percentage of rejected packs (e.g. non-conforming owing to defective sealing or because scratches are present) with respect to the total number of packs produced by the packaging line. As stated previously, this was a pressing need on the market, which, after lengthy research, the Applicant has surprisingly and unexpectedly been able to solve.

It has been unexpectedly and surprisingly found by the Applicant that using the multilayer film of the invention, excellent sealabiiity is obtained at the low temperatures indicated between the layers of the film, between the outer layer/outer layer (B/B), between the outer layer/inner layer (B/A), the inner layer/outer layer (A/B) and also between the inner layer/inner layer (A/A), while reducing or substantially eliminating at the same time the risk of sealing, and the stickiness between the inner layer (A) of the multilayer film and the film (O) covering the individual packets of the pack being substantially absent, even after storage for over 2 months in areas without air conditioning, such as warehouses. Moreover, the presence of scratches on the multi-package film is substantially eliminated.

As stated previously, the film of the invention can be easily removed from the multi-package without using cutting tools, so that removal of the package is carried out safely and without breakage, when the pack is being opened, owing to stickiness between the film (O) around the individual packets of cigarettes and the inner layer (A) of the multi- package.

A further object of the present invention is a process for forming a pack (naked collation) using the film of the present invention, comprising:

- preparing a group of individual packed products placed one adjacent to the other so as to form a carton, each individual packet being wrapped within a polyolefin film (O);

- wrapping the carton in the film for naked collation in which the inner layer (A) is in contact with the film (0);

- closing the film for naked collation on the two opposite sides of the carton, said sides being of smaller size, by folding and sealing the outer layer (B) of the naked collation film with itself or with (A), and on one of the carton sides arranged longitudinally (lengthwise) by sealing the layer (A) with layer (B), ai temperatures comprised between 85°C and <80°C, preferably between 70°C and 80°C, more preferably between 75°C and 80°C, and even more preferably between 75°C and 78°C.

As stated previously, in the naked collation process of the present invention, any risk of sealabiiity between the inner layer (A) of the multilayer film and the film (0) covering the individual packets of the pack is substantially eliminated.

A further object of the invention consists of a pack that can be obtained using the film of the invention for naked collation, comprising the individual products or packets packed, in which the inner layer (A) of the film substantially does not stick to the film (O) around the individual packets of cigarettes.

The pack is preferably prepared using a naked collation film comprising in the core, in addition to a homopolymer, preferably a propylene homopolymer, amorphous hydrocarbon resins as defined above.

The Applicant has surprisingly and unexpectedly found that the compactness of the pack can be further improved by using a film for naked collation according to the invention, obtained by biaxial stretching, using the stretch ratios of 6.3: 1 in the MD and 7: 1 in the TD.

As stated previously, the prepared pack shows greater compactness, and therefore improved machinability, that is, it can be moved more easily during the production process on a high-speed packaging line, the speed generally being on the order of 70-100 packs/minute.

The compact multi-package pack thus obtained slides more easily on the conveyor belts and in the respective guides and it is substantially free of scratches. This represents a remarkable advantage in terms of industrial production, in that productivity proves to improve, the number of rejects being further reduced. The pack is defined as "compact" based on the following test: when held hanging from the shorter side and set in a horizontal position, the pack does not bend substantially (it is not slack). It has been surprisingly and unexpectedly found that the above-mentioned stretch ratios that make it possible to obtain a film for preparing a pack with improved compactness, also increase the mechanical properties (elastic modulus) and the heat shrinkage of the naked collation film.

The Applicant has unexpectedly and surprisingly found that it is possible to improve the scratch resistance of the multi-package film, without using the formulations indicated in the prior art described hereinabove, and in addition, by markedly simplifying the compositions of the prior art in terms of industrial processes. This outcome is totally unexpected and surprising, for no indications in this regard are revealed in the prior art.

The Applicant has surprisingly and unexpectedly found that further improvement is possible as regards the scratch resistance of the multilayer film, if sliding agents are added in the outer layer (B), which comes into contact with supports or rigid surfaces during transport of the packs on production lines, said sliding agents preferably being PMMA having an average particle diameter comprised between 2 and 8 μιτι, preferably between 3 and 5 μηη.

The commercially available product ABVT26SNC© manufactured by the Schulman company is preferably used as this type of additive. The particles thereof have a diameter of 4 μπη.

Optionally, the additive indicated is used in combination with other sliding agents of the class of polydiorganosiioxanes. Among the latter, the commercial product ABVT30SNC® is used; it is produced by the same company as the sliding additive cited above and the particles thereof have a diameter of 4 μπη. Both of these sliding agents are preferably used in the form of masterbatches, in which the concentration of the sliding agent is comprised between about 10% and 30% by weight, the remaining part of the masterbatch being constituted by propylene polymers, preferably propylene homopolymers or copolymers as indicated above.

Using the films of the present invention for packaging, rejects due to scratches are substantially eliminated. From the point of view of industrial production, the films of the invention offer extremely significant advantages, in that rejects due to scratches and rejects due to stickiness between the layer (A) of the multilayer film and the film (0) around the individual packets are, as stated, much reduced, overall much less than 0.01 %.

It should be noted that considering a production of 100 multi-packages (cartons)/ in, rejects amounting to 1 % lead to one pack to be rejected per minute and therefore in one work shift of 8h (1 shift), there are 1X8X60=4,800 rejected products,

Considering rejects equal to 0.01 %, the number of rejected products after 8 hours drops to 4.80.

The Applicant has unexpectedly and surprisingly devised a method for manufacturing a pack that is capable of revealing sealabiiity in advance between the layer (A) of the film of the multi-package film and the film (O) of the individual packets, using Method B disclosed below.

In other words, Method A described herein below for determining sealabiiity (A/A), (B/B), (A/B) and (B/A) between the layers of the multi- package and therefore for assessing the capacity of the film to form a multi-package and at the same time also for assessing the absence of sealabiiity between the layer (A) of the multi-package film and the film (O) at the sealing temperature, represents only one condition that is necessary but not sufficient to ensure that the layer (A) of the multi-package film will not seal with the film (O) around the individual packets during the manufacturing process.

Method B devised by the Applicant regarding stickiness represents a further condition needed to form the multi-package and at the same time it is sufficient to substantially reduce the risk of sealabiiity to zero in the manufacturing stage and therefore in the stage of collecting the individual packets from the multi-package.

The films of the invention constitute a very significant means for the manufacturing industry, for example the tobacco industry, in that when used for the multi-package, they show reduced or no stickiness between the film (0) around the individual packet and the layer (A) of the naked collation film. The following examples are provided as illustrative, non- limiting examples of the invention.

Melting point of the polymers

The melting point was determined by DSC.

lation of the tensile st

modulus of the multi-package film

The determinations were carried out according to the ASTM D882 standard using an Instron dynamometer, in both the !VID and TD directions of the film. The elastic modulus was also determined 48 hours after preparation of the film, which was kept at room temperature (20-25°C). Determination of the mechanical resistance of the seal obtained with the film

Method A

Samples having a width of 10 mm are cut out from the film and sealed as described in the examples using a sealing machine, for example a "DT Industries SENCORP" model provided with automatic control of temperature, pressure and contact time of the two sealing bars with the piece to be sealed. The sealing conditions are the following:

- upper bar heated, lower bar not heated;

- contact time between the bars: 0.2s

- contact pressure of the bars: 5psi.

The sealing temperature is set at the required value. See Tables 2 and 3. The mechanical resistance was measured using an Instron dynamometer. Method A enables testing of seaiability between the layers of the multi- package film (A/A), (A/B), (B/A), (B/B) and therefore the capacity of the film of the invention to be used for the multi-package. The absence of AO sealabiiity makes it possible to exclude sealabiiity between the layer (A) of the multi-package film and the film (0) covering the individual packets. Method B

Samples having a width of 10 mm are cut out from the film and sealed as described in the examples using a sealing machine, for example a "BRUGGER HSG-C" model provided with automatic control of temperature, pressure and contact time of the two sealing bars with the piece to be sealed. The sealing conditions are the following:

- upper bar heated, lower bar heated;

- contact time between the bars: 0.6s

- contact pressure of the bars: 5.8psi (60N/15cm 2 ).

The sealing temperature is set at the required value. See Tables 2 and 3. The mechanical resistance was measured using an Instron dynamometer. Method B ensures that the film can be used for the multi-package if the layers of the film (A/A), (A/B), (B/A) and (B/B) are sealed at the sealing temperature used. The absence of sealing of the layer (A) of the multilayer film with the film (O) around the individual packets ensures the possibility of collecting the individual integral packets, without rejects and further ensures that the layer (A) of the multi-package film does not stick to the film (O) around the individual packets at the sealing temperature. The combination of these characteristics ensures that the film can be used for the multi-package and that the amount rejects in the pack manufacturing process is below the limits reported above.

Determination of the isotactic polypropylene content in polypropylene (isotacticity index - Π)

The determination the isotactic polypropylene in a mixture with the amorphous is carried out by extracting the sample using n-hexane as solvent at 50°C for two hours according to the FDA 177 1520 Standard. The insoluble fraction is then recovered and weighed. The isotactic index is given by the formula:

Heat shrinkage of the film is determined according to the OPMA TC 4 standard by heating a sample of 20cm x 1 cm in size at 130°C for 5 minutes in the air.

Heat shrinkage in the MD or TD is calculated using the following formula:

(11 - L2)x 100 in which:

L1 is the length of the film prior to heat treatment

L2 is the length of the film following heat treatment.

Heat shrinkage can also be indicated by the number obtained in the above equation preceded by the negative sign (-).

Extractables in n-hexane

Determination is carried out according to the FDA 177 - 1520 Standard. Analysis of the polymers in the film

The analysis is carried out by means of IR spectroscopy. The polymers of each layer can be isolated by layer peeling, controlling the amount of layer removal by means of electronic microscopy.

Determination of the antiscratch properties of the film

Determination is realized using an apparatus for determining the friction coefficient (COF according to the ASTM D 1894 method).

Strips (samples) that are 64x127 mm in size are cut from the film, the longer side (127 mm) being cut in the MD direction. The strip is then wound lengthwise around the sled of the COF measuring device, the side of the strip to be tested facing outwards. After eliminating any creases present on the sample, the two shorter sides are joined with adhesive tape.

At this point, the metal plate that has a smooth surface is removed from the COF measuring device and the metal plate that has a rough surface is used. The sample is tested on the surface of this latter plate by moving the sled (200 grams in weight) at the speed of 150 mm/m in. The COF value indicated by the measuring device is recorded. The film is removed and the test is repeated under the same conditions, using a second sample of the film.

The area of the sample that proves to be scratched after performance of the test under the conditions described above is then evaluated.

For this purpose, the two strips are transferred onto a glossy sheet of paper, positioning them so that, upon testing, the untreated side of each strip faces the sheet. The two shorter sides of each strip are fixed to the glossy sheet of paper by means of adhesive tape. One then proceeds with metallization of the samples fixed to the sheet. The scratched part of the surface does not possess the necessary characteristics to be metallized and as a result at the end of the metallization process, the samples have clear spots, corresponding to the scratched surface, on a meta!ized background. The metallized samples are covered with a second sheet of glossy paper (hereinafter: upper glossy sheet), overlapping the first sheet, and the four sides of the two overlapping glossy sheets are fixed with adhesive tape. For each strip, the outlines of the scratched areas are marked on the upper glossy sheet and then coloured in using a permanent marker. At this point, a sheet of glossy graph paper is rested on the upper glossy sheet, aligned with the sides of the samples and positioned so as to contain the previously coloured areas. In practical terms, the lower and left (or right) edges of the sheet of glossy graph paper function as the x~axis and the y-axis, respectively. The sheet of glossy graph paper is fixed using adhesive tape and the small squares corresponding to the areas coloured with the marker are counted, also including in the total sum the small squares that are only partially coloured.

The antiscratch property is expressed as the percentage of scratched surface area with respect to the total surface area tested and it is given by the following formula: (A/B) x 100

in which:

A = the sum of the coloured small squares of the two samples

B = the total sum of the small squares corresponding to the surfaces of the two samples.

The samples are visibly free of scratches when the non-metallized surface proves to be equal to less than 25% of the surface of the sample.

The Applicant has found that the test can be carried out even without performing the metallization process, substantially obtaining the same results.

Haze

The Haze values are determined according to the ASTM D 1003 standard. Determination of scratch intensity

This determination is based on the Haze test and non-metallized samples are used, said samples being obtained as described above for the test used to determine the scratchabiiity of the film.

Scratch intensity is determined on a sample

by means of the formula:

l(A - B)/B] x 100

in which:

A is the average value (5 determinations per sample) obtained from the Haze measurements taken only in the scratched points of the sample. B is the average value (5 determinations per sample) measured on a sample of the film cut from the reel, and not subjected to the test.

EXAMPLE 1

Films for "naked collation"

A film according to the present invention was prepared by means of a process comprising the following steps:

1 ) coextrusion of a three-layer plate:

Three films were flat-die coextruded, having the following compositions (% by weight): core layer

83.5% propylene homopolymer HP 522H® marketed by Base!!, !!

(isotacticity index) = 98, Tme¾ng = 163°C 3.5% antistatic masterbatch AT 4082PP® marketed by Constab

13% amorphous resin.

outer layer

93% elastomeric propyiene~butene~1 copolymer (% by weight butene- 1 26%) TAFMER® XM7070 marketed by Mitsui Chem., Tmeiting = 75 C C

6% sliding masterbatch ABVT3 NSC®, marketed by Schu!man

1 % antibiock masterbatch based on SiC particles having a diameter of 2 μιτΊ, marketed by Constab

inner layer

93% TAFMER® XIV!7070 as defined above

6% antibiock masterbatch ABVT30N® marketed by Schulman

1 % antibiock masterbatch based on silica particles having a diameter of 2 pro, marketed by Constab,

The amounts of polymeric components in each layer are such that in the final film having a thickness of 25 μιη after biaxial stretching, the individual layers proved to be of the following thicknesses:

core layer 23.76 μπι

outer layer 0.42 μηη

inner layer 0.42 μηι

The profile of the sets of temperatures of the three extrusion lines was as follows:

core layer 240°C-260°C

outer layer 160°C~195°C

inner layer 160°C-195°C.

The extrusion lines were equipped with a filter for removing any gels or foreign bodies from the melted polymer. The three melt lines were fiat-die coextruded at T=245°C.

2) Cooling and quenching of the coextruded plate

The coextruded plate obtained in step 1 ) was cooled and quenched on a thermostated roller at T=30°C, immersed by one third in a water bath at T=39°C.

3) Trimming of the plate edges and heating in an IR battery

The plate edges were trimmed to about 5cm and then the plate was passed through a battery of IR panels having temperatures comprised between 160°C and 270°C,

4) Simultaneous biaxial stretching on a stretching apparatus

A L!S!M® production line was used for the biaxial stretching process. The multilayer film was stretched in both the longitudinal direction (MD) and in the transversal direction (TD), setting the following stretch ratios on the machine:

MD= 6.30 (ratio between the outlet speed / inlet speed);

TD^ 6.99 (ratio of the distance between the rails at the oven exit / distance between the rails at the oven entrance);

the film outlet speed from the oven being 243m/min.

At the oven exit, the profile of the stretch ratios in both the MD and TD revealed a peak followed by a decrease <15% (with respect to the peak).

The temperatures of the various sections of the oven are comprised within the following ranges:

preheating section 158°C-170°C

simultaneous stretching section 157°C~170°C

stabilization section 157°C-146°C

5) Winding the film in a reel

At the oven exit, the film passes through the pulling section for the following procedures:

edge trimming

X-ray scanning for checking thickness. At the exit of the pulling section, the film was wound in a reel having a width of 6,150 mm.

Film properties

The mechanical and sealing properties of the film were evaluated.

Mechanical properties

The results obtained are reported in Table 1 .

Table 1

(n.d.= not determined)

Heat shrinkage

The film of the invention shows biaxial heat shrinkage of 10.40% in the MD and 8.96% in the TD, under the conditions indicated above. The seal resistance of the film sealed onto itself was determined, along with the sea! resistance of the film of the invention with a commercially available three-layer film, ST!LALA® LTS20, marketed by BIMO/IRPLAST, having a thickness of 25 μΜ, used for the individual packets of cigarettes (film (O)), having a film core identical to that of the film in the example of the invention, and in which the inner layer and the outer layer are constituted by copolymers C2/C3/C4

(with C2+C4< 9% by weight) having Tmeiting = 132°C. The resistance to sealing obtained by sealing the outer layer (B) with the inner layer (A) (B/A) of the multi-package film (naked collation).

Table 2 reports the resistance to sealing at the temperatures indicated.

" THIDI! 2

The data reported in the table, as obtained with Method A and with Method B show that the film of the invention is capable of sealing the outer layer with the inner layer already at a temperature of 75°C. The value of the resistance to sealing determined at the temperature of 75°C ensures that the pack comprising the individual packets of cigarettes is sealed. The seal resistance of the inner layer (A) of the multi-package film sealed with the film (O) used to package the individual cigarette packets

Table 3 reports the values obtained for seal resistance: Table 3

The hyphens indicate that at the temperatures indicated the determination was not carried out.

5 The data reported in the table as obtained with Method A show that up to the sealing temperature of 80°C, the film around the individual packets of cigarettes was not sealed by the film of the invention. Incidentally, it should be noted that this also occurs at temperatures higher than 80 o C, up to 1 10°C, under the conditions used in the sealing test.

i n The data obtained with Method B show that there is stickiness at temperatures higher than 90°C and therefore the film cannot be used for multi-package application at temperatures of 90°C or higher.

Method B defines the maximum temperature at which application is possible without stickiness.

15 Application using a FOCKE® machine of Focke & Company

The film was tested in an industrial "naked collation overwrap" application for packaging packs of 10 packets of cigarettes. The test conditions were as follows: Movement of the multi-package pack on metal guides; production speed of 700 packets/min (70 cartons/min). Sea!ability between the inner layer (A)/outer layer (B), the outer layer (B)/inner layer (A), the inner layer (A)/inner layer (A), and the outer layer (B)Zouter layer (B) of the film of the invention was obtained at 75°C and there was no sealability between the inner layer (A) of the film of the invention and the film (O) around the individual packets of cigarettes.

During the manufacturing process, it was not necessary to stop the packaging machines for cleaning, as the film did not release dust.

The higher mechanical properties in the MD direction made for greater precision and constancy in the cutting length.

This is an advantage with respect to films lacquered with an acrylic solution that are commonly used for naked collation.

Opening the multi-package

The multi-package film of the pack obtained with the FOCKE® machine was opened by slightly twisting the pack by hand. No adhesion of the film of the invention to the cigarette packets was observed.

Antiscratch properties

Using the method described above, the scratched surface of the film sample proved to be equal to less than 25% of the treated area. Therefore, the film of the invention passed the test. It should be noted that this value was obtained using a very rigorous laboratory test. The check for scratches was carried out after formation of the multi-package, which was then moved on metal guides having rigid surfaces.

Moreover, visual inspection of the pack by the operator and supervisors of the tobacco manufacturing plant also confirmed the absence of scratches. Stickiness

To assess stickiness on the packaging line, one out of every 20 multi- package packs was collected and, when opening it, the presence or absence of stickiness between the film (O) around the individual packets and the layer (A) of the multi-package film was checked. Using this test, it was found that stickiness was not present in any of the packs collected from the line.

Application using a GD ® machine manufactured by G.D. S.p.A.

The application example with the FOCKE ® machine was repeated, but using a GD ® machine with a production speed of 800 packets/min (80 cartons (packsVmin), and moving the packs on metal guides.

During the manufacturing process, it was not necessary to stop the packaging machines for cleaning, as the film did not release dust.

The higher mechanical properties in the MD direction made for greater constancy in the cutting length.

Sealability between the inner layer/outer layer, the outer layer/inner layer, the outer layer/outer layer, the inner layer/inner layer of the film of the invention was obtained at 75°C and there was no sealability between the inner layer of the film of the invention and the film around the individual packets of cigarettes.

Opening the multi-package

The multi-package film of the pack obtained with the GD ® machine was opened by slightly twisting the pack by hand. No adhesion of the film of arette packets was observed.

Using the method described above, the scratched surface of the film sample proved to be equal to less than 25% of the treated area. Therefore, the film of the invention passed the test. The check for scratches was carried out after formation of the multi-package, which was moved on guides having rigid surfaces.

Moreover, the visual inspection of the pack by the operator and supervisors of the tobacco manufacturing plant also confirmed the absence of scratches.

Stickiness

The evaluation test adopted was as described hereinabove. All the packs collected proved to be conformant and no stickiness was observed between the layer (A) of the multi-package film and the film (0) around the packets contained in the packs that had been collected. Example 2 (COMPARATIVE)

Example 1 was repeated, but the thickness was 0.8 m for both the outer layer and the inner layer of the multilayer film.

Moreover, the film used was not heat-shrinkable and it had a lower elastic modulus with respect to that of Example 1 , thus proving to be less tensilized.

The comparative film for naked collation was prepared according to a process comprising the following steps:

1 ) coextrusion of a three-layer plate

Three films were flat-die coextruded, having the following compositions (% by weight):

core layer

98% propylene homopoiymer HP 522H® marketed by Basel! as defined hereinabove

istatic masterbatch ASPA2446® by Schulman.

95% copolymer TAFMER® XM7070 (Mitsui) as described above 5% antiblock masterbatch ABVT34® SC by Schulman.

inner layer

95% copolymer TAFMER® XM7070 as described above

5% antiblock masterbatch ABVT34® SC as defined above.

The amounts of polymeric components in each layer are such that in the final film, after biaxial stretching, the individual layers proved to be of the following thicknesses:

core layer 23 μηη

outer layer 0.8 μηπ

inner layer 0.8 μητ The profile of the sets of temperatures of the three extrusion lines was as follows:

core layer 230°C-265°C

outer layer 160°C-185°C

inner layer 160°C-185°C.

The three extrusion lines were equipped with a filter for removing any gels or foreign bodies from the melted polymer.

The three melt lines were coextruded in a fiat die at T=245°C.

2) Cooling and quenching of the coextruded plate

The coextruded plate obtained in step 1 ) was cooled and quenched on a thermostated roller at T~28°C, immersed by one third in a water bath at T=30°C.

3) Trimming of the plate edges and heating in an IR battery

The plate edges were trimmed to about 5cm and then the plate was passed through a battery of IR panels having temperatures in the range of: 190°C-270°C.

4) Simultaneous biaxial stretching on a stretching device

An LIS IM ® device was used for biaxial stretching. The multilayer film was stretched in both the longitudinal direction (MD) and in the transversal direction (TD), setting the following stretch ratios on the machine:

MD= 6,20 (ratio between the outlet speed and the inlet speed);

TD-7.040 (ratio of the final distance / initial distance of the stretching rails);

the film outlet speed from the oven being 280 m/min.

The temperatures of the various sections of the oven are comprised within the following ranges:

preheating section: 154°C-174°C

simultaneous stretching section: 158 0 C-162°C

stabilization section: 162°C-168°C

5) Winding the film in a reel At the oven exit, the film passes through the pulling section for the following procedures:

edge trimming

X-ray scanning for checking thickness.

At the exit from the pulling section, the film was wound in a reel having a width of 6.150 mm.

Film properties

The mechanical and sealing properties of the film were assessed. The results obtained are reported in Table 4.

Sealing test

Seal resistance was measured as regards the film of comparative Example 2 sealed with itself and with a commercially-available three-layer film, STILAN® LTS20, marketed by BIMO/IRPLAST and used for the packaging of the individual packets of cigarettes (film (O)), having a core identical to that of comparative Example 2 and in which the inner layer and the outer layer are constituted by polyolefin copolymers having a Tme¾ng = 132°C. The thickness is identical to that of comparative Example 2.

Table 4

Properties Example 1

Tensile strength at break MD 1760

(MPa) TD 2304

Elongation at break MD 105

(%) TD 88

Elastic modulus MD 1816 (MPa) at t=0h TD 2226

Elastic modulus

MD 2432

after ageing for 48h at r.t.

(MPa) TD 2772 Resistance to sealing of the film of comparative Example 2, obtained by sealing the outer layer (B) (B/A) with the inner layer (A) of the multi- package

Table 5 reports the resistance to sealing, said sealing being obtained by sealing the outer layer with the inner layer of the film of comparative Example 2 at the various temperatures indicated herein below.

Table 5

The data reported in the table, as obtained with Method A show that the film of comparative Example 2 is capable of sealing the outer layer with the inner layer at a temperature of 75°C. The value of the resistance to sealing determined at the temperature of 75°C ensures that with the sealing, the packaging of groups of packets is achieved.

The seal resistance of the inner layer (A) of the multi-package film sealed with the film (Qs (A/O) used to package the individual packets

Table 6 reports the values obtained for seal resistance.

Table 6

The data reported in the table as obtained with Method A show that at the sealing temperature of 75°C of the film of comparative Example 2, the film around the individual packets of cigarettes was not sealed by the film of comparative Example 2,

Application using the FOCKE ® machine

The same application described for the film of Example 1 was repeated, but using the film of comparative Example 2.

Sealability between the inner layer and the outer layer of the film of comparative Example 2 was obtained at 75°C and there was no sealability between the inner layer and the film around the individual packets of cigarettes.

During the manufacturing process, it is not necessary to stop the packaging machines for cleaning, as the film did not release dust.

Opening the multi-package

The multi-package obtained as indicated above with the FOCKE ® machine using the film of comparative Example 2 was opened by slightly twisting the pack by hand. No adhesion of the film of comparative Example 2 to the cigarette packets was observed.

Antiscratch properties

Using the evaluation method described above, the scratched surface proved to be >55% of the treated area. Visual inspection of the multi- package was carried out on the packaging line following movement on the metal guides and the presence of scratches on about 70% of the packs was revealed, confirming the test results.

These scratch test results lead to the conclusion that the film cannot be used as a multi-package film. Therefore, the stickiness test was not performed.

Application using the GD ® machine

The same application described for the film of Example 1 was repeated, but using the film of comparative Example 2. During the manufacturing process, it was not necessary to stop the packaging machines for cleaning, as the film did not release dust.

Sealability between the inner layer/outer layer, the outer layer/inner layer, the outer layer/outer layer, the inner layer/inner layer of the film of comparative Example 2 was obtained at 75°C and no sealing took place between the inner layer of the multilayer film and the film around the individual packets of cigarettes.

Opening the multi-package

The multi-package obtained with the GD® machine was opened by slightly twisting the pack by hand. No adhesion of the film of the invention to the observed.

Using the evaluation method described above, the scratched surface proved to be >55% of the treated area. Visual inspection of the multi- packages was also carried out on the packaging line following movement on the metal guides and the presence of scratches on about 70% of the packs was revealed. This confirms the results of the antiscratch test.

These scratch test results lead to the conclusion that the film cannot be used as a multi-package film. Therefore, the stickiness test was not performed.

EXAMPLE 3 Example 1 was repeated, but a hydrogenated resin was added to the core in the form of a masterbatch (amount of resin: 13% by weight of the masterbatch) marketed as DPPH7025 ® by Polyone.

The amount of propylene homopoiymer HP 522H ® in the core was brought to 70,5% by weight and 13% by weight of regranulated (reclaimed) polypropylene was added.

The data obtained were substantially the same as those obtained in Example 1 , but the pack showed greater compactness, that is to say, when suspended by the shorter side and put in a horizontal position, the pack did not bend (was not slack). The heat shrinkage in the MD amounted to 1 1 .50% and 9.40% in the TD.

Using the test described above, no presence of scratches was observed on the packs and stickiness was not observed between the layer (A) of the film of the invention and the film (O) around the individual packets.

Example 4 (COMPARATIVE)

Comparative Example 2 was repeated, but using the same type and the same amount of hydrogenated resin in the core as in Example 3.

The results regarding the presence of scratches on the packs were similar to those obtained in comparative Example 2.