WO2020007711A1

WO2020007711A1 - Thermally laminated polyethylene-based "monomaterial" laminate for recyclable flexible packaging

Info

Publication number: WO2020007711A1
Application number: PCT/EP2019/067197
Authority: WO
Inventors: Massimo CENTONZE; Simonetta LANATI
Original assignee: Industria Termoplastica Pavese S.P.A.
Priority date: 2018-07-06
Filing date: 2019-06-27
Publication date: 2020-01-09
Also published as: EP3817918A1; IT201800006996A1

Abstract

A description is given of a sealable laminate (10) composed of a non-oriented multilayer flexible film (4) thermally laminated onto a flexible backing film in plastic (3), said multilayer film (4) being a coextruded film, which can be unwound from a reel, not containing metal coatings, metal layers and/or prints and having two opposing sides (1; 2), each of said opposing sides being polyethylene based and the side (1) of said 10 coextruded film (4) which is in contact with said backing film (3) formed by a sticky (co)polymer (sticky film) or with heat adhesive properties so as to be thermally laminated onto said film in plastic (3) said laminate (10) being characterised in that said backing film (3) is a flexible polyethylene film coextruded in a bubble, generally mono- oriented, optionally with a surface provided with one or more coatings and/or processes 15 (5), superimposed, preferably at least one print (5), wherein said coatings and/or processes (5) are interposed or trapped between said multilayer film (4) and said plastic film (3) and enclosed between said films (3, 4).

Description

THERMALLY LAMINATED POLYETHYLENE-BASED

"MONOMATERIAL" LAMINATE FOR RECYCLABLE FLEXIBLE

PACKAGING DESCRIPTION

The present invention relates to a flexible laminated film, of the "mono-material" type and completely recyclable, which is formed by

- a non-oriented coextruded film based on polyethylene and/or ethylene copolymers,

bonded with

- a flexible plastic backing film consisting of one or more layers of non-oriented polyethylene, optionally coated on the surface, e.g. printed and/or metallized and/or lacquered with PVOH (polyvinyl alcohol), PVDC (polyvinylidene chloride), SiO_x- based ceramic coatings, Al₂O_x-based coatings, cellulose lacquers and the like, where the two bonded films are joined one to the other by simple thermal lamination without the use of glue.

More specifically, the present invention relates to a thermally laminated laminate, as defined above, wherein the plastic backing film in polyethylene is a bubble-extruded film, optionally stretched mono-axially and/or irradiated.

Packaging has notoriously many roles related to the protection and preservation of food, but has for some time become an important advertising vehicle and in some cases the main promoter of the actual sale of the product contained, thanks on the one hand to the possibility of using the print that reproduces attractive images on the packaging itself and on the other hand thanks to the possibility of creating packaging with high transparency and brilliance. In the case of food packaging, current legislation requires that inks from printed surfaces do not come into direct contact with food (REGULATION (EC) No. 2023/2006 of 22 December 2006 - Point 3 of the Annex).

This has led to the printing of the outer surface of the packaging, but found to be subject to scratches and abrasions during normal handling of the packages. To protect the print (or other types of coating), a second film can be used, glued over the printed surface so as to enclose the ink, sandwiched between the two films, obtaining an internal print. This type of printed laminate is particularly used as a closing film (top) for plastic trays, and is generally made up of a printed backing film coupled with a sealing film in PE (intended for direct contact with the tray on which the laminate will be sealed), where the backing film is made of PET, PP, biaxially oriented PA (not recycled) thanks to their high transparency, brilliance and thermal resistance.

For some time now, the recycling of packaging material has been indicated by the European Community as one of the forms of recovery of waste material (according to the technical standard UNI EN 13430:2005 Packaging - Requirements for packaging recoverable by recycling of materials).

Recently, however, the pressure to encourage the use of recycling as a replacement for waste-to-energy recovery has been truly impressive, since the European Community itself has established that by 2030 all plastic packaging must be recyclable. (European strategy for plastics in the circular economy - Communication of the European Commission of 16/1/2018 SWD (2018) 16 Final).

However, the films currently most used for flexible packaging are multilayer laminates of completely different and incompatible polymers, such as biaxially oriented PET laminated with PE, biaxially oriented PP laminated with PE, biaxially oriented PA laminated with PE.

The reason for the use of incompatible materials lies in the fact that in order to obtain a combination of various functions in a single film it is necessary to combine different polymers in terms of characteristics and performance, and that, unfortunately, they are also not very compatible one with the other: for example, polyethylene is not currently used as a backing layer because it has a lower thermal resistance than PET, PP and PA (all of which have a thermal resistance higher than 150°C) such as not to allow it to be placed directly in contact with the sealing bars without running the risk of melting and sticking In addition, PE normally has an insufficient brilliance and not comparable to that of the aforementioned biaxially oriented polymers.

On the other hand, PET, PP and PA are not suitable for use on their own as flexible packaging films because they suffer from performance limitations such as fragility, impact resistance, poor sealing, ease of tearing, etc. that only polyethylene can overcome.

If then the lamination is carried out by means of two-component polyurethane adhesives, with or without solvent, to the multiplicity of polymers present in the structure of the known laminates, thee is the added presence of a third unwanted component in any process of recycling of the packaging: the adhesives.

Patent application WO2016050686, in the name of the Applicant, describes a process of forming a laminate by glue-free thermal lamination, using only pressure and temperatures to bond biaxially oriented PET, PP, or PA backing films with a coextruded PE-based film to form a laminate structure for flexible food packaging. However, this application does not describe a bubble-extruded PE backing film which is laminated to a PE-based film by thermal lamination.

US 8,356,459 describes a multilayer film where the PE backing film, preferably biaxially oriented, is coated with a layer of sticky polymer by using extrusion coating technology: other layers (e.g. heat-sealing layers) can then be applied to the same PE backing.

Therefore, the technology used in said patent requires as many successive phases as there are layers to be applied to the PE backing film, which is to be considered a standalone film with very low thickness as is suitable for biaxially oriented films, on which "functions" will later be introduced such as adhesive capacity (by depositing layer 20) and heat-sealing capacity (by adding layer 22). Moreover, this patent does not describe a PE backing film obtained by blown extrusion (bubble).

In the light of the new needs for recycling/disposing of food packaging, it would therefore be highly desirable to have available a packaging, obtainable in a simple and fast way, that exhibits properties similar to those of multilayer laminates known in the art for the same use, but which is more easily re-extruded to be completely recyclable. It should be noted that the materials obtained from the recycling of plastic polymers may exhibited unwanted blemishes and/or surface defects, such as dots/infusions, due to the fact that they merge together articles consisting of multilayer multi-materials with different rheology and thermoplastic behaviour: therefore, it is also highly desirable to have available a packaging consisting of several similar layers which, once ground and re-extruded, is melted to form a single phase (homogeneous phase).

The object of the present invention is to overcome, at least in part, the disadvantages of the prior art by providing a laminate, optionally with internal printing (sandwich between two films), suitable for but not limited to food use, for example suitable as a closing film (top) of trays, films for pouches or similar products, which is highly recyclable in order to have an increasingly reduced environmental impact.

A further object of the present invention is to obtain such a laminate, in particular which, once ground and re-extruded, is melted to form a single phase (homogeneous phase), which shows a good overall transparency as required for food packaging films, and which is free from blemishes or surface defects such as bubbles, and which has mechanical performances and machinability similar to those of films made with virgin materials so as to meet the requirements of the flexible packaging market and can be used on traditional packaging machines, without any specific modification to them.

Another obj ect of the present invention is to obtain such a printed laminate by means of a continuous production process that is simple, economical and convenient Another further object of the present invention is to reduce the environmental impact connected to the packaging that comprises the aforementioned laminate, because the use of glues and any coupling solvents, abundantly released into the atmosphere during the lamination process, is eliminated. Yet another further object of the present invention is to improve food safety for the consumer, since the use of bonding solvents is excluded (there is therefore no problem of solvent retention, well known to those who bond using solvent adhesives) as well as eliminating the risk of the formation of aromatic amines, suspected carcinogens and potentially migrating in food (current legislation - Regulation (EC) 10/2011, point 2 of Annex P clearly limits the migration in food). It should be noted that the excess of residual solvent in the laminates with solvent adhesives, in addition to representing a risk of modification of the organoleptic properties of any food contained, the solvents being always very aggressive from the olfactory point of view towards food, is also a potential cause of delamination of the two laminated films with resulting serious consequences for the packaging made.

These and other objects are achieved by the laminate in accordance with the invention having the features listed in the appended independent claim 1. Advantageous embodiments of the invention are disclosed by the dependent claims.

An objective of the present invention relates to a thermally laminated laminate, normally of a flexible type, particularly suitable to be wound in reels and to be used as a closing film (top) for food trays, as a film fin· pouches or for similar articles, and which can optionally enclose in its interior a print and/or a coating different from the print.

In practice, the object of the present invention is a flexible packaging of the monomaterial type, optionally with an internal coating and/or print, comprising a laminate between two films, one based on bubble-extruded polyethylene and the other based on polyethylene and/or ethylene copolymers, such as for example EVA, which adhere permanently one to the other by simple thermal lamination, without the use of glues.

The Applicant has found that the ethylene copolymers and polyethylene fuse well together, once re- extruded together, if the ethylene monomer in said copolymers is high content (with respect to the total content of monomers), thus forming a single phase (homogeneous phase).

Furthermore, the Applicant has found that even in the case wherein the present laminate contains coatings (including functional lacquers) and/or internal print and/or additional layers (generally made with polymers other than polyethylene and ethylene copolymers as defined above), it can be considered that the laminate is made of a single material in that any other materials other than polyethylene and/or ethylene copolymers do not significantly affect: the thermoplastic and/or rheological behaviour of polyethylene, in all its variations as defined above and in the following paragraphs. In feet, tests carried out by the Applicant have shown that, when the laminate is formed mainly of polyethylene and ethylene copolymers as mentioned above, it is easy to reextrude the laminate of the present invention in that it melts homogeneously forming a single phase (homogeneous phase) without exhibiting unwanted blemishes and/or surface defects.

Without being bound to any theory, it is presumable that the mass content of ethylene comonomers mentioned above is such, with respect to polyethylene, as not to influence, in any case, the order of magnitude of the softening temperature and/or melting temperature of the polyethylene and/or ethylene copolymers.

The term " compatibility " here is understood to mean that two polymers can be coextruded in a traditional coextrusion plant and remain firmly bonded/fused one on the other, at the interface, without the need for a specific adhesive or binder in feet, two materials are all the more incompatible the more easily the two layers of the two contact materials can be separated manually in the product made.

Even i£ to date, there is no technical standard that establishes which composition an article must have in order to be considered recyclable, i.e. there is no reference that specifies in what percentage two or more components must be mixed in order for the product obtained by grinding and re-extruding them can generate a new product that is acceptable to the market for its intended use, the Applicant has found through studies and experiments that:

- Recyclability is all the greater if the packaging is made up of similar, highly compatible layers;

- two components are highly incompatible when their mixing never leads to a single homogeneous phase but to two clearly distinguishable phases (observable for example through morphological analysis with electron microscope, e.g. SEM) or, in the case wherein one component is present in much smaller quantities than the other, to a main matrix in which aggregates of variable sizes are dispersed and interact with the visible radiation, thus limiting the transparency of the film.

In addition, the Applicant has also found thiat if tbe polyethylene of the backing film is bubble extruded (blown extruded) and is a high density polyethylene (>0:935g/cm3), and it is preferably irradiated, it is possible to obtain a backing film having also good rigidity and thermal resistance, even comparable to that of a backing film in PET, PA, PP and in any case sufficient to ensure machinability thereof on traditional packaging systems with acceptable transparency and brilliance.

Therefore, by blown extruding the PE it is possible to use it as a backing layer, currently not used in that PE generally has a lower thermal resistance than PET, PP and PA so as not to allow it to be placed directly in contact with the sealing bars without running the risk of melting and sticking.

The Applicant has also observed that this backing film as defined above can be advantageously bonded by thermal lamination to a film, also of the coextruded multilayer type, all based on polyethylene and/or ethylene copolymers with a sealing layer (i.e. the layer that will be in contact with the contents of the packaging) with a softening point lower than 100°C so as to create a PE-PE laminate without any glue, completely recyclable and suitable for use in traditional packaging machines.

The resulting laminate therefore has the main advantage of being substantially made up of a single material (polyethylene), i.e. PE in all its variants including also copolymers that are very compatible with the polyethylene itself and therefore of being classified, according to the recycling code provided by EC Directive 94/62, as low-density polyethylene LDPE or PE-LD with code 04 or as high-density polyethylene HD-PE with code 02 depending on the average density value that is obtained in the thermal laminate and not as 07, the latter code identifying all other plastic materials, not recyclable. The present laminate is therefore made up of

- a flexible coextruded plastic film, multilayer and non-oriented, which can be unwound from a reel, and having two opposite sides, each based on polyethylene and/or ethylene copolymers, said coextruded film not containing metal coatings, metal layers and/or prints,

laminated by thermal lamination to

- a flexible plastic backing film (co-)extruded in bubble fimn, optionally stretched and/or irradiated, but not biaxially oriented, consisting of one or more layers of polyethylene, and optionally having a coated and/or processed surface, for example printed and/or lacquered, preferably at least printed, said coatings being neither adhesive nor sticky. In addition, said blown extruded backing film has in itself non- adhesive and/or sticky opposite surfaces. The term "polyethylene-based film” is used here to identify a polymeric material with a very high content of homopolymer polyethylene, for example higher than 50% higher by weight with respect to the total weight of the material up to a content of 100% homopolymer polyethylene, and in any case such a content that the material can be considered a "monomaterial".

The term "ethylene copolymers-based film" here means a polymeric material or mixture of polymeric materials with a very high overall ethylene monomer content, e.g. higher than 50% with respect to the total monomers content, and in any case such that it can be considered a "monomaterial" .

The Applicant has then found that a surface treatment that oxidises and modifies the surface, such as corona (or plasma) treatment, applied on both sides intended to bond one to the other of the two films that come into contact, is particularly advantageous as it strongly contributes in this thermal lamination technique to substantially increasing the adhesion between the two films, an aspect of considerable importance in the properties of the finished article.

With regard to the polyethylene backing film, the term "oriented" here is intended to identify

- a mild degree of orientation, mainly in the machine direction, but also in part in the transversal direction, such as that which can be obtained during bubble extrusion, which requires certain stretch ratios. With the term "stretched" here is intended to identify

- a greater but single-direction orientation, for example like that obtainable in a special stretching machine (MDO) using the process and plant described in the Italian patent application No. 102017000085388 in the name of the Applicant, incorporated herein in its entirety for reference.

Therefore, the orientation of the PE of the present plastic backing: fiftn is due at least to the bubble coextrusion, although any subsequent treatment of stretching gives a further improvement of the property as will be explained below in detail.

In fact, during the formation of the bubble, the backing film undergdes a slight stretching/physiological stretching (orientation substantially in one direction only), thanks to the feet that in the blown extrusion section there is a radius of the circumference of the bubble greater than the radius of the extrusion head and the ratio between these two magnitudes is called BUR (blown-up ratio). It should be noted that the polyethylene (PE) backing film can also be optionally irradiated because, as will be explained in detail here below, it has been found that irradiation with ionizing radiation increases even further the thermal resistance of the PE extruded in abubble and of the PE subjected to stretching: irradiation will preferably be performed on the side of the backing film opposite to that which will be thermally laminated to the coextruded film 4.

The improved thermal resistance of the PE backing film of the present invention means that when the laminate according to the present invention comes into contact with the sealing bars to seal the laminate to cover the tray, this backing film will be in contact with the sealing bars but will not soften and will not stick to them.

The present laminate is also characterised in that it is a flexible packaging suitable for food use but of the "monomaterial" type, and therefore completely recyclable, also in light of tiie feet that it is flee of adhesives/glues.

The term " monomateriaF is understood here to identify polymers of a similar nature which, during the extrusion phase for recycling, do not separate into different phases, thus avoiding imperfections or surface defects such as dots and infusions that worsen the transparency and brilliance of the film, making it unattractive for the packaging market, where transparency is one of the most appreciated qualities of a film.

The sidefof the multilayer coextruded film, which is in contact with said PE backing film, is made with a sticky polymer film or with permanent adhesive properties such as to adhere permanently to said PE backing film without the use of adhesives, said laminating being obtained only by the effect ofheat and pressure of thermal lamination.

Preferably, the side of said coextruded film in contact with the said plastic backing film consists of a layer formed by one or more sticky polymers/resins based on polyethylene and/or ethylene copolymers, but also possibly copolymers chemically similar to PE, such as those based on styrene-butadiene, styrene-isoprene, which due to the high content of the aliphatic hydrocarbon are in fact compatible with the PE. The term "film" here is intended to identify a flat and thin semi-finished product in which the thickness is very small compared to the length and width, generally less than or equal to 0.25 mm (ISO 472). Above this value there are semi-finished products identified by the term sheet or leaf (ISO 472) which have less flexibility with respect to films.

The term "adhesive properties" is intended here to identify the ability of one surface to bond firmly to another due to the effect of pressure and/or temperature alone. This quantity can be measured according to the standard ASTM F904-98 which, in particular, provides a method for measuring the force required to separate the two bonded surfaces.

Adhesive properties considered adequate in the case of a flexible laminate are those with a delamination force >1.2N/15mm.

The term "sticky polymer " here is understood to identify polymers based on polyethylene and/or ethylene copolymers that are spontaneously sticky to the touch, including those that are already sticky at room temperature, for example at 25-30°C, although having higher softening temperatures, and that exhibit adhesion to substrates when pressure is applied so that the surface of this polymer does not flow with respect to the substrate with which it is placed in contact.

In particular, the stickiness of a film can be assessed empirically, for example by pressing the sticky side of the film on the palm of a hand for 5 seconds, evaluating the (sticky/non-sticky) feeling associated with removing the film.

The term "coating" here is intended to identify any type of coating known in the art for polymeric films such as printing, metallization, PVOH (polyvinyl alcohol), PVDC (polyvinylidene chloride), SiOx-based ceramic coatings, Al₂O_x-based, cellulose lacquers, and the like.

The term“coating” therefore identifies in the present description an extremely thin layer of material, generally less than 1 to 2 microns thick, applied by a coating process, i.e. by applying a thin layer of material in the form of a fluid (liquid) on a substrate, in accordance with the nomenclature defined in ISO 472: therefore, a coating is not to be considered as a stratification of material in the light of this nomenclature.

Therefore, such a coating, provided it is applied in a very thin layer, does not adversely affect the "monomaterial" recycling either on the final properties of the monomaterial recycled product such as imperfections, surface defects, spots and infusions, or on the achievement of a single homogeneous phase, such as not to be incompatible.

For the sake of simplicity, here below the terms "with another coating", "with another type of coating", " with different coating" will indicate all the types of coating known in the art with the exception of printing where this is already explicitly mentioned.

The terms " surface coated", "with a coated and/or processed surface " are used here as synonyms.

The term "laminate" is used here as a synonym for laminated, polylaminated, and refers to thin multilayer structures, obtained by laminating pre-existing films of different materials.

“ Thermal lamination" here is understood to identify a process of hot lamination of film without the use of glues where the adhesion at the interface between the two films is obtained only by the effect of temperature and/or pressure, exploiting the adhesive/sticky properties of some polymeric materials or their combinations, with heat when they are in a state of softening.

The term "coextruded" is understood here to identify a film obtained from the process of extruding two or more different materials, in the molten state, plasticized in individual extruders and then conveyed into a single head, flat or annular, which allows a film to be obtained in which the individual layers coexist as separate entities.

When we talk about the process of (co-)extrusion, we always think of the transformation of granule into film, therefore of a physical transformation of the form in which the polymer is found. Coextrusion can be performed according to a known technique with blow moulding in bubble, flat head or the like. Preferably the present coextruded film is obtained by coextrusion using screw extruders and blow-moulding or flat-head extrusion, without the aid of any type of glue.

The greater the similarity (also called chemical affinity) between the coextruded materials, the greater the adhesion between the two layers.

It should be noted that the surface of the backing film that is opposite to that in contact with the coextruded film can also be coated, for example printed and/or metallized and/or coated with another type of coating without thereby departing from the spirit of the present invention: in this case a laminate with printing, metallization or coating inside will be obtained that has an external surface also respectively metallized, printed or coated with another coating, provided that these coatings are applied in a very thin layer such as not to be incompatible with "monomaterial" recycling. Further features of the invention will be made dearer by the following detailed description, referred to a purely illustrative, and therefore non-limiting embodiment illustrated in the accompanying drawings, in which:

Figure 1 is a vertical section view, partially interrupted, of a thermally laminated laminate according to the invention, suitable for use as a top for food trays;

Figure 2 is a section view, partially interrupted, of a first coextruded film suitable for forming the laminate of Fig 1;

Figure 3 is a section view, partially interrupted, of a second coextruded film suitable for forming the laminate of Fig 1;

Figure 4 is a schematic view of the continuous thermal lamination production line of the laminate of Fig 1;

Figure 5 is a schematic view of the continuous production line of the film forming the backing of the present laminate.

Referring to Figure 1, a description will now be given of a preferred embodiment of the laminate that is the subject of the present invention, in the form of laminated film, flexible and planar, denoted overall by reference numeral 10, which has as internal coating at least one print 5.

Said laminate 10 normally has a total thickness such as to result in a flexible film, generally comprised between 30 and 250mm. It is understood that what will now be described is applicable also in the case wherein the internal coating is different from printing or is non-existent, without departing from the spirit of the present invention. Said laminate 10 is made up of a first non-biaxially oriented film 3, hereinafter also referred to as backing film, which is a film made up of one or more layers of polyethylene coextruded into a bubble, and having a total thickness typically varying from 5 to 60mm, but also greater, generally up to 100mm, provided that it maintains the inherent flexibility of a film with a thickness of less than 250mm.

“ Non-biaxially oriented film " here is intended to identify a film that has not been subjected to two distinct and separate phases of stretch, i.e. longitudinal stretch and transverse stretch, in the biaxially orientation machine. Said backing film 3 in extruded PE, or coextruded, in the form of a bubble (respectively single-layer or multilayer) is a film oriented in one direction only and is particularly suitable for being printed, as well as being coated with another type of coating, for example metallized, or with any functional lacquering (PVDC, PVOH, SiO_x, Al₂O_x) or even primer that aid the adherence of the inks without thereby departing from the obj ect of the invention, provided that these coatings are applied in a very thin layer so as not to be incompatible with "monomaterial" recycling.

Said backing film 3 can optionally be stretched in the machine direction, i.e. in the same direction in which it is naturally oriented after blown extrusion, by passing through an annealing station or MDO (machine direction orientation) in order to increase its rigidity.

Said oriented backing film 3 can also be optionally pre-treated before being printed so as to be prepared for adhesion of the ink, for example by means of corona, plasma, chemical treatment, and can also be irradiated, preferably irradiated with ionizing radiation.

Said oriented backing film 3, which is not sticky, can generally be wound in a reel 30 (Fig. 4) so that it can be unwound during the process to obtain print 5 for the realization of the laminate 10, the subject of the present invention. The oriented film 3 wound in the reel 30 (pre-existing film) can therefore be

- a film without any treatment and/or surface coating to be subjected to a treatment and/or surface coating to be performed off-line, at a later stage, in a special unit, before being thermally laminated,

or

- a film that has been previously treated and/or coated and therefore already has a coating, including printing, applied to its surface intended to be turned to the interior of the laminate, and therefore ready to be thermally laminated.

- a simple coextruded film, without pre-treatment of any kind, which will be thermally laminated even without any printing.

As mentioned, the laminate 10 in accordance with the invention also includes a coextruded film 4: it should be noted that the use of polyethylene, in all its variants, as coextruded film 4, gives this laminate a sealing capacity even with low SITs (sealing initiation temperature, which is the minimum temperature at which the polymer begins to seal).

In addition, the use of polyethylene, in all its variants, allows modulation of the strength of the sealing, it being possible to form seals with facilitated openings, as well as conferring considerable toughness and robustness, resistance to tearing, etc.

It should be noted that, as far as the Applicant is aware, the laminating between a PE film 3 and a flexible film 4 in PE, understood in all its variations, has never been made because there was no polyethylene available that had an adequate combination of high rigidity and thermal resistance and high transparency and brilliance so as to assimilate it to traditional biaxially oriented backings.

The film from which this backing film 3 is derived is a blown extruded PE film, in particular obtained according to the process and plant described in the Italian patent application No. 102017000085388 in the name of the Applicant, incorporated herein in its entirety for reference.

Referring to Figure 5, starting from the area on the left, the first phase of the above process to obtain the present oriented PE backing film 3 is represented by the bubble (co-)extrusion of the relative polymer. In this extrusion, said film undergoes a certain inflation, the extent of which is indicated by the BUR ("blow up ratio"): this BUR represents the numerical ratio between the diameter (or radius) of the film in a bubble (at its widest point) and the diameter (or radius) of the annular extrusion head from which the bubble originates.

Since the BUR influences the orientation of the polymer molecules, if working with a high BUR, the film is extended or stretched in the transverse direction to reach the final diameter of the bubble: this BUR is not to be confused with the ability to withstand the stretching to which the film can subsequently be subjected after extrusion.

The bubble extrusion is carried out using one or more ring extruders fed by PE granules, depending on the number of layers required for the coextruded film 3: in Figure 5 only one extruder is shown for simplicity of illustration, and is denoted by reference numeral

100.

The blown extrusion system is well-known equipment in its own right which generally consists of a worm screw which conveys the molten material into an annular extrusion head 15, which can be fed simultaneously by several extruders 100, each fed with a respective polymeric material chosen to form the relative layer of the multilayer film 3.

Since the apparatus of blown extrusion is in itself known in the art, details of its operation or even less so those of the relative drive rolls 200 (nip-rolls) that determine the flattening of the bubble to form the flat film 3 will not be discussed. It should be noted that even if film 3 is defined as PE film, said film can be made from several layers, each made with a different type of PE, to confer the many functions that are needed in the field of packaging, such as controlled tearing, toughness, barrier to steam and gases, etc.

As polyethylene polymers suitable for the production of various layers of backing film 3, LD-PE (low-density polyethylene), MD-PE (medium-density polyethylene), HD-PE (high-density polyethylene), LLD-PE (low-linear density polyethylene) mLLD-PE (metallocene low-linear density polyethylene), or mixtures thereof may be cited, in order to ensure good mechanical properties. If this backing film 3 is intended to be printed on the surface, it can be advantageously corona treated in special equipment 500 (Fig. 5), placed downstream of the rolls 200, and then wound in a reel 30 to be printed off-line at a later time. Said corona treatment equipment 500 can also be arranged, in addition or alternatively,

- downstream of a section 300 of stretching and/or annealing (Fig. 5) provided downstream of the drive rolls 200

or

- after a phase of radiation or irradiation with ionizing radiation, which takes place in a special section after stretching and/or annealing of section 300, in that, in any case, the corona treatment is intended to increase the wettability of the surface being treated and to facilitate the adherence of the ink and, in some cases, facilitate the subsequent lamination of the film 3 to the other film by thermal lamination. In one or more of the layers of the extruded PE film 3 it is possible to provide for the addition of one or more additives of various types depending on the required functionality, for example coloured masterbalches (white, but also other colours), antifog, anti-blocking (e.g. silica), slip agents, anti-static, anti-condensation, antimicrobial, anti UV, antioxidant, processing aids, nano fillers, dyes, oxygen scavengers, antioxidants, nucleating agents, and other additives known in the art

These additives are not stated in the abovementioned formulations but can be added in one or more of the layers forming the backing film 3, if required. As mentioned above, one of the two sides of the blown extruded film 3 can optionally be subjected to a phase of irradiation.

Irradiation is a technology based on the exposure of objects to controlled doses df high- energy ionising radiation (gamma rays, X-rays or electron beams).

By actings appropriately on the irradiation power, it is also possible to simultaneously irradiate one or more of the layers below the external surface, if present, so as to confer a further improved mechanical resistance and resistance to the diffusion of gases and vapours (increase in barrier properties). The irradiation can be in line with the production of film 3 (the section of which is not shown in Fig. 5 for the sake of simplicity), or off-line at a later time: in the latter case, the film 3 coming out of the rolls 200 of the bubble extruder 100 is wound in reel 30 in a winding section 40 to be stored and treated with irradiation off-line at a later time.

During irradiation, film 3 is sent to a special irradiation station (vacuum chamber containing an electron emitter) where it is subjected to abeam of ionising radiation, for example by means of a bombardment with high-energy electrons, in particular accelerated electrons with energy from 0.05 to 10Mev, emitted by a specific electron beam emitter.

In particular, among the effects of irradiation an increase in thermal resistance, improved mechanical properties and resistance to chemical agents, probably due to the formation of new bonds (e.g. cross-linking) have been observed.

Once the blown coextruded film 3, optionally irradiated, has been obtained, it is wound in a reel ready to be used as is; or said reel of film 3 can be sent to a further processing phase such as surface printing on the surface of the external layer 10, of the film 3, for example to protect the print, and then sent to the thermal lamination section for the realization of the laminate of the present invention.

In a preferred embodiment, the coextruded film 3 coming directly out of the rolls 200 is subjected to a treatment of stretching and/or annealing in a special section 300 and then irradiated.

In this preferred embodiment, the coextruded film 3 coming directly from the rolls 200 is sent to the section 300 of stretching and/or annealing treatment (Fig. 5) consisting of a section of MDO (Machine Direction Orientation) that performs a mono-axial stretching in the direction of the machine and/or annealing section as described in detail below.

In addition to the weak stretching in blown extrusion, there is also a more important longitudinal orientation (of 1: 2 or higher) which gives the film greater rigidity and elastic modulus, greater transparency. The higher rigidity of the PE film stretched in this way allows it to approach processes and machining that are not normally possible for a traditional non-stretched PE film, such as rotogravure printing or coating or step printing. The passage in the stretching and/or annealing section 300 can be carried out in line with the bubble extrusion phase, or it can be carried out at a later time off-line by working on the backing film 3 unwound from a reel 30 prepared in the winding section

40.

In the stretching and/or annealing section 300, the following steps are carried out in succession, as shown in Fig 5:

- Preheating: the film 3 is brought to the softening temperature by passing it through the first heating rollers 50;

and then

- Stretching: the following stretching rollers, divided by a narrow slit, stretch and elongate the film 3 up to ten times thanks to their rotation at a speed higher than that of the heating rollers 50;

and/or

- Annealing: the film 3 is tempered by the annealing rolls 70 and subjected to tension; the heat blocks the physical characteristics reached by the film in the previous and then

- Cooling: the film 3 is brought back to room temperature by passing through a series of cold rollers 80, and then coming out of section 300.

The film coming out of the treatment section 300, which is a stretched (mono-axial stretching) and/or annealed film 3', can then be sent to the irradiation phase (if the irradiation is to be carried out in line - section not illustrated in Figure 5) or to the phase of winding in a reel 30 in the winding station 11 (if the irradiation is to be carried out off-line at a later time).

The rolls 50, 60, 70, 80 associated with the various phases that take place in the treatment section 300 ate independent of each other and rotate at different speeds in that designed to carry out different operations. Obviously, the operating conditions of said rolls and of the above-mentioned stretching and/or annealing phases depend on the type of film to be treated.

It should be noted, however, that the above-mentioned stretching operation that takes place in the treatment section 300 should not be confused with the slight physiological stretching that film 3 undergoes during the formation ofthe film bubble during extrusion in extruder 1 , thanks to the feet that in the treatment section 300 the stretching conditions can be set to obtain the desired degree of stretching and consequently the orientation (mono-orientation) required.

In fact, the use of biaxially oriented backing films, as in the prior art, requires instead expensive and cumbersome stretching stations that must operate off-line, plants not necessary in the present invention because the slight orientation already obtainable in bubble extrusion and subsequent stretching/annealing is sufficient to give the properties of rigidity and resistance required of films of flexible packaging.

It is therefore understood that the treatment of stretching and/or annealing in station 300 is optional, although it is preferred in that advantageous in terms of the final properties of the backing film 3 of the present laminate.

The stretched and annealed film 3' is then advantageously sent to the irradiation section described above in relation to Fig. 4, repeating the same operations described above in relation to the coextruded film 3, in order to obtain an irradiated film.

Once the oriented backing film 3 has been obtained, optionally irradiated and/or corona treated, it is possible, if required by the final use, to carry out printing 5 of images (represented in bold with interposed empty spaces that in reality do not exist but serve only for clarity of representation) on the backing film 3 using various technologies known in the art, for example by flexo printing or rotogravure or digital or UV printing.

Said laminate 10 is also formed by a second flexible film 4, of the multilayer and coextruded type, not oriented, having a total thickness typically lower than or equal to 200 mm.

Said coextruded film 4, which is a non-oriented film based on polyethylene and/or ethylene copolymers, in turn consists of at least - a first outer layer 1 based on polyethylene and/or ethylene copolymers, with adhesive/sticky properties, preferably formed by a single polymer or resin with adhesive/sticky properties, typically 5 to 100 mm thick but also thicker, and

- a second outer layer 2 based on polyethylene and/or ethylene copolymers, not sticky or adhesive, opposed to layer 1, with a typical thickness of 10 to 100 mm, but also higher.

The two layers 1 and 2 of the non-oriented coextruded film 4 are made of polymeric materials based on polyethylene and/or ethylene copolymers.

In particular, the polymer of layer 2 (i.e. the sealing layer that will be in contact with the contents of the packaging) has advantageously a softening point of less than 100°C.

Layer 2 also has a softening temperature (VICAT) - measured according to the standard ISO 306 - at least 10°C lower, preferably at least 20°C lower, than the temperature of the polymer of the backing film 3.

The polymer with a base of polyethylene and/or ethylene copolymers forming the layer with adhesive properties 1 is an extrudable resin having in itself adhesive or sticky properties with respect to that of the polymer of the backing film 3.

The adhesive properties of the resin of this layer 1, which appear completely with heat, are mainly due to the type of material: said resin with a base of polyethylene and/or ethylene copolymers is in feet chosen from polar resins, non-polar but sticky resins for low density and/or molecular weight, non-polar and non-sticky resins (except at thermal lamination temperatures) yet able to adhere strongly to the backing film 3 due to chemical affinity, polyolefins with tackifying additives such as to be sticky, tackifying resins or combinations of the above-mentioned resins. Said layer 1 can also be optionally treated on the surface by corona treatment or plasma treatment before undergoing thermal lamination.

In particular, the above-mentioned resins show a Tg (glass transition temperature) well below room temperature and a Vicat softening point slightly lower than the material of the backing film 3 as will be evident from the detailed description given below. As polar resins (a) mention can be made, for example, of EVA (ethylene-vinyl acetate copolymer), ethylene-acrylic ester copolymers such as EMA (ethylene-methyl acrylate copolymer), EBA (ethylene-butyl acrylate copolymer), EEHA (ethylene-2-ethylhexyl acrylate copolymer), EEA (ethylene-ethylacrylate copolymer), ethylene-acrylic copolymers such as EAA (ethylene-acrylic add copolymer) EMAA (ethylene- methacrylic add copolymer), where the content of polar co-monomer (VA, MA, BA, EHA, EA, AA, MAA) is variable, taking into account that the higher its content, the greater the resulting tackiness; ethylene/acrylic esters/maleic anhydride terpolymers, ethylene/vinyl acetate/maleic anhydride terpolymers, ethylene/acrylic add /maleic anhydride terpolymers, ethylene/acrylic arid/terbuthylacrylate terpolymers, and the like, where the content of polar comonomers (e.g. acrylic esters, maleic anhydride, vinyl acetate) is variable, taking into account that the greater its content, the greater the resulting stickiness. Preferred as polar resins are EVA or EMA or EAA. As non-polar yet sticky resin (b) mention can be made, for example, of elastomers and plastomers of the polyolefin type generally having a density equal to or less than 0.910 g/cm³, such as for example VLD-PE (very low density polyethylene), mVLD-PE (very low density polyethylene metallocene), ULD-PE (ultra-low density polyethylene), elastomers and plastomers containing butadiene and styrene (hot-melt), propylene- ethylene copolymers and the like.

As a non-polar and not necessarily sticky resin yet able to adhere strongly by chemical affinity (c), we can mention, for example, some LLD-PEs with densities between 0.915 and 0.920 g/cm³ which, due to their specific type of polymerization and/or catalysis, have a component of low Vicat polymer chains and also some ethylene-propylene or styrene-butadiene copolymers with rubber properties and highly compatible with PE, such as styrene/butadiene copolymers, e.g. SBS (styrene-butadiene/styrene), SEBS (styrene-ethylene/butylene-styrene), SBBS (styrene/butadiene/butylene/styrene), SIS (styrene-isoprene) with a high ethylene or butadiene or butene, which due to the high content of the aliphatic hydrocarbon(s) are in fact compatible with polyethylene.

As tackifying resins (d) we can dte for example hydrocarbon resins and as tadrifying agents to be added to polyolefins to make them sticky we can dte for example polyisobutylene. Preferably the resins/polymers used for layer 1 are chosen from those listed in groups (a), (b) and (d), more preferably layer 1 is composed of a single resin, which is sticky at room temperature, chosen from (a), (b), even more preferably said layer 1 is formed by a single EVA resin in which the VA percentage content is equal to or greater than 8% by weight up to a maximum of 70%, preferably between 10% and 40%.

Layer 2 of the coextruded film 4 forming the laminate 10, is intended to come into contact with the product contained in the package: it is a sealing layer (and therefore by its nature not sticky or adhesive) and consists of a polymeric resin of an extrudable thermoplastic polymer based on polyethylene.

The polymer used to form layer 2 can typically be PE in all its variations, possibly with the addition of PB (polybutylene) to create a structure with facilitated opening, but also polar copolymers such as EVA or EMA or the like (with a low content of polar comonomer, generally less than 8% in weight or with a high content of polar comonomer, but with strong addition of anti-blocking and/or slip agents, so as to reduce the stickiness thereof), and the like, and possible combination of the same.

Preferably layer 2 is made up of PE in all its variants. In addition, said layer 2 should preferably be more than 3 mm thick.

This layer 2 can contain various types of additives (alone or in combination one with the other) depending on the required functionality, for example antifog, anti-UV, anti- blocking, slip, anti-static, antibacterial, dyes, oxygen scavengers, antioxidants, nucleating agents, process aid.

An example of coextruded film 4 formed by a layer 1 and a layer 2 can be a two-layer film formed by PE (layer 2) /EVA (layer 1) where the VA content in the EVA is about 28% by weight.

Between these layers 1 and 2 one or more additional layers (N layers) can be included, as shown in Figure 3, able to give to the coextruded film 4 various technological functions, such as for example

- a layer of EVOH or of polyamide to confer barrier properties, and/or

- a layer of HD-PE to give rigidity, - one or more layers of linear polyolefins having high-toughness to confer particular mechanical strength,

- one or more layers with various additives, as specified below

- one or more layers with hot-melt pressure-sensitive resins to ensure re- scalability of the packaging, etc.

These N layers can contain various types of additives (alone or in combination one with the other) depending on the required functionality, such as antifog, anti-UV, antiblocking, slip, anti-static, antibacterial, dyes, oxygen scavengers, antioxidants, nucleating agents, process aid.

The process to obtain a thermally laminated laminate with an internal coating, e.g. a print or other types of coating as indicated above, to be considered optional and not distinctive of the present patent, will be described below: in particular, tire obtaining of the preferred laminate 10 with an internal print 5 and any other coatings inside and below said print 5, is done through a process described here with reference to Figure 4.

Said process essentially provides fin: a thermal lamination phase carried out by simply passing the two different films 3 and 4 through two lamination press rolls, only one of which is heated: in this way, in the final laminate 10, the optional print 5, like any other type of coating that may be present as an alternative or in addition to the print, is sandwiched between tiie backing film 3 and the adhesive layer 2 of the coextruded film 4, without requiring the use of adhesives and/or glues. If the film 3 unwound from the reel 30 is not already printed, the process that leads to obtaining the final laminate 10 with internal print 5, optionally containing also other types of internal coatings, according to the present invention, may or may not involve the execution, preferably in continuous and in-line, and therefore in a single step, of a first printing phase followed by a subsequent phase of thermal lamination.

The abovementioned thermal lamination process then leads to an optionally printed final laminate or one containing other types of coating, which is ready for use, e.g. on a packaging machine.

Referring to the present process conducted in line and continuously, the first phase of printing of the backing film 3, wound from reel 30, is carried out using techniques and printing machines 20 known in the art, with various types of ink (for flexographic printing, rotogravure, digital, UV printing) and with different levels of coverage of the images.

Subsequently, the printed backing film 3 is placed in contact with the coextruded film 4, which is also unwound from a reel, so that the print 5 is in contact with layer 1 of the coextruded film 4 having adhesive properties.

Once in contact one with the other, they are passed through two opposing cylinders of thermal lamination 12, 13 pressing and co-operating one with the other, which are formed by a presser cylinder in heated steel 12 and by a cylinder in rubber 13, also presser, so that the two layers 1 and 3 are made to adhere one to the other through the sole effect of the heat applied to the coextruded film 4 (which causes a slight softening at least of said film) and the pressure of presser cylinder 13 exerted against the heated cylinder 12 : thanks to the intrinsic adhesive properties of layer 1 , when in softened form, a laminate is obtained with strong adhesion at the interface between the backing film 3 and the coextruded film 4.

It is also possible to provide in the abovementioned system an optional cooling roll 14 (Fig. 4) located downstream of the two opposing thermal lamination cylinders 12, 13.

It is understood that what has been said above in relation to thermal lamination can be repeated also in the case wherein the coating 5 applied to the backing film 3 is different from the printing, or even is not present, without thereby departing from the scope of the present invention.

The thermal lamination between the two different films can be carried out at a temperature of for example, 50-150°C, preferably 90°C-150°C, and normally the higher the temperature, the greater the adhesion that is obtained, always trying to get as close as possible to the temperature of softening of the adhesive layer 1, while the film 3 remains at room temperature.

In practice, the softening that the adhesive layer 1 undergoes during the thermal lamination phase is such as to make it adhere to the backing film 3, also in the case wherein said film 3 is not softened, by simply applying pressure on its surface. Adhesion values considered acceptable are >1.2N/15mm, measured according to the ASTM method previously mentioned.

The aforementioned process for obtaining the laminate according to the present invention is enormously advantageous in terms of cost (at least the off-line passage of laminating with glue is avoided) and time saving (not only because the printing and the lamination take place in line, therefore in a single phase, but also because the waiting times inevitably required by the crosslinking of the glues, which can even be of a few days, are avoided).

Finally, the process described for obtaining the printed laminate and/or another internal coating has a favourable environmental impact if compared with solvent-based lamination technologies. In addition, the laminate obtained from abovementioned process has an improved combination of properties:

- total absence of aromatic amines (the formation of which represents an inevitable potential risk of polyurethane adhesives by reaction between free isocyanate and water)

- reduced quantity of residual solvent (present instead in the case of rotogravure or flexo printing with solvent) or total absence of the same (in the case of digital printing or UV printing)

- improved aesthetic appearance as there is no trace ofbubbles or blemishes due to the adhesive for the lamination;

- resistance of the print 5, or of another coating, to impact and scratches, but also thanks to the fact that the print, in the final laminate 10, is sandwiched between the backing film 3 and the coextruded film 4.

It should be noted that the present thermal laminating process, if carried out in line and continuously, is particularly advantageous when printing on the backing sheet 3 is carried out using digital technology: this method, being enormously faster than the flexographic or rotogravure method, can make it possible to produce a laminate 10 for a top (closing film) with an extremely high production speed (just-in-time process) with considerable advantages from an economic point of view. The process for the production of a preferred printed laminate 10 according to the present invention allows to obtain continuously, and in line with the printing process, a flexible printed laminate ready for use, for example on a packaging machine, without requiring off-line processing phases or the usual curing times (for the crosslinking of the adhesives and for the decaying of the aromatic amines).

This process is carried out advantageously in a plaint comprising

an optional printing machine 20 to make a continuous print 5 oil the plastic backing film 3 unwound from a first reel 30,

a pair of opposing presser cylinders of thermal lamination 13 and 12, of which at least one is heated, to thermally laminate said printed backing film 3 placed in contact with said coextruded film 4 which is unwound from a second reel, so that said print 5 is in contact with the layer with adhesive properties 1 of said coextruded film 4. It is understood that in the case wherein the internal coating 5 to be obtained in laminate

10 is different from the printing, the aforementioned system according to the invention will provide a unit 20 suitable for applying a coating on film 3 instead of a printing machine, without thereby departing from the scope of the present invention. It is understood that in tile case wherein the laminate is without printing and/or other coatings, the thermal lamination takes place in the same way but avoiding the passage of the film 3 in tiie printing system 20.

The present invention is not limited to the particular embodiments previously described and illustrated in the accompanying drawings, but numerous detail changes can be made thereto, within reach of a person skilled in the art, without thereby departing from the scope of the invention itself as defined in the appended claims.

The following is an indicative and non-exhaustive example of the present invention.

Example 1

A thermally laminated film was prepared starting from a coextiuded backing film 3 with a thickness of 60mm in PE having an average density of 0.950 g/cm³, corona treated on the side intended for contact with a coextruded film 4 and it has been thermally laminated on said blown coextruded film 4 having a total thickness of 50mm and consisting of two layers respectively composed of LD-PE (layer 2 of film 4) and EVA 28% VA (layer 1 of film 4) wherein the side 1 was corona treated. The lamination was carried out using the temperature of the heated cylinder 12 shown in Figure 4, i.e. at the temperature of 100°C, with a pressure of 6 bar.

The abovementioned thamally laminated film was then subjected to a series of tests as stated here below

All the measured values are in line with what is normally required in the field of flexible packaging films.

In particular, the Value of adhesion between the layers, one of the most critical parameters for the application, is well above the value of 1.2N/15mm previously mentioned and assumed in many cases as the value of supply specifications.

Claims

1. Flexible packaging, of the mono-material type, comprising a heat-sealable laminated film (10) constituted by a flexible non-oriented multilayer film (4) which is a thermally laminated on a non-biaxially oriented flexible plastic backing film (3), said multilayer film (4), which can be unwound from a reel, being a coextruded film not containing metal coatings, metal layers and/or prints and having at least two opposite layers (1; 2)

each of said opposite layers (1,2) being a polyethylene-based layer and/or based on ethylene copolymers or mixtures thereof, and

the layer (1) of said coextruded film (4) which is in contact with said backing film (3) is formed by a (co)polymer with adhesive properties so as to be thermally laminated onto said film in plastic (3),

said laminate (10), which can be unwound from a reel, being characterised in that said backing film (3) is a flexible blown (co)extruded film in polyethylene,

the opposite surfaces of said backing film (3) being non-adhesive and/or sticky, and

one or more non-adhesive coatings and/or treatments (5) can be interposed and/or enclosed between said multilayer film (4) and said plastic film (3).

2. Flexible packaging according to claim 1, wherein the polymer of the side (2) of the multilayer coextruded film (4) has a softening temperature, measured according to the standard ISO 306, which is at least 10°C lower, preferably at least 20°C, than the softening temperature of the polymer of said backing film (3).

3. Flexible packaging according to claim 1 or 2, wherein the side of the layer (1) of the multilayer coextruded film (4) and the side of the backing film (3) which is laminated in contact with said side of said layer (1) are pre-treated by corona treatment or plasma treatment before laminating.

4. Flexible packaging including the laminated film (10) according to claim 1 or 2 or 3, wherein the layer (1) with adhesive properties of said coextruded film (4) is a layer made in an extrudable polyethylene-based polymer or based on ethylene copolymers, selected from among the following groups

(a) polar resins such as for example EVA (ethylene-vinyl acetate copolymer), ethylene/acrylic esters copolymers such as for example EMA (ethylene-methyl acrylate copolymer), EBA (ethylene-butyl acrylate copolymer), EEA (ethylene-ethyl acrylate copolymer), EEHA (ethylene-2-ethylhexyl acrylate copolymer), ethylene-acrylic acids copolymers such as EAA (ethylene-acrylic acid copolymer), EMAA (ethylene- methacrylic acid copolymer), wherein the content of polar comonomer (VA, MA, BA, EA, EHA, AA, MAA) is variable considering that the greater its content, the higher the resulting tackiness, provided that the content of ethylene monomer is at least 50%; ethylene/acrylic esters/maleic anhydride terpolymers, ethylene/vinyl acetate/maleic anhydride terpolymers, ethylene/acrylic acid/maleic anhydride terpolymers, ethylene/acrylic acid/tert-butyl acrylate terpolymers and the like, wherein the content of polar comonomers (e.g. acrylic esters, maleic anhydride, vinyl acetate) is variable, considering that the greater its content, the higher the resulting thermal adhesive property, provided that the content of ethylene monomer is at least 50%; preferably EVA, EMA or EAA;

(b) non-polar but sticky resins such as polyethylene-based plastomers and elastomers, having generally a density equal to or lower than 0.910 g/cm3, such as for example very low density polyethylene (VLD-PE), metallocene very low density polyethylene (mVLD-PE), ULD-PE (ultra-low density polyethylene), elastomers and plastomers containing styrene and butadiene (hot melt), propylene-ethylene copolymers and the like;

(c) resin with chemical affinity to PE such as some LLD-PE having a density range between 0.915 and 0.920 g/cm3 which have a part of the polymeric chains with low Vicat value due to specific polymerization and/or catalysis thereof; ethylene- propylene copolymer or styrene-butadiene copolymers having rubber properties and with chemical affinity with the PE, like resins selected from styrene/butadiene copolymers, for example styrene/butadiene/styrene (SBS), styrene-ethylene/butylene- styrene (SEBS), styrene/butadiene/butylene/styrene (SBBS), styrene-isoprene (SIS) having such a high content of ethylene or butadiene or butene which due to the high content of the aliphatic hydrocarbon are in fact compatible with polyethylene;

said resins (a), (b), (c) being optionally added with

tackifying resins such as hydrocarbon resins and/or with a tackifying agent such as polyisobutylene.

more preferably said side (1) being made of a resin which is sticky at ambient temperature and is chosen from among those of (a), (b) and added with the tackifying resins and/or with a tackifying agent.

5. Flexible packaging including the laminated film (10) according to any one of the preceding claims, wherein said backing film (3) is formed of one or more layers of polyethylene, optionally surface pie-treated in such a way as to be prepared for ink adhesion, for example by means of corona treatment, chemical treatment, primer treatment and/or with optional functional lacquerings (PVDC, PVOH, SiOx, Al₂O_x).

6. Flexible packaging which includes the laminated film (10) according to any one of the preceding claims, wherein one or more of the layers of the backing film (3) contain one or more additives of various type depending on the required function, such as for example coloured masterbatches (white but also other colours), anti-fog additives, anti-blocking additives (e.g. silica), slip agents, antistatic agents, anti-condensation agents, antibacterial agents, anti-UV additives, antioxidant agents, processing aids, nano-fillers, dyes, oxygen scavengers, nucleating agents and others known in the art (alone or in combination one with the other).

7. Flexible packaging which includes the laminated film (10) according to any one of the preceding claims, wherein said second outer layer (2) opposite to said layer (1) of said coextruded film (4) is formed at least by a non-sticky polymer.

8. Flexible packaging which includes the laminated film (10) according to claim 7, wherein said non-sticky polymer of the layer (2) is an extrudable polymeric material selected from a polyolefin, such as PE in all its variants, optionally added with PB (polybutylene) to obtain a structure with facilitated opening; polar copolymers such as EVA or EMA or the like (with a low content of polar comonomer, generally lower than 8% by weight or with a high content of polar comonomer but with high quantities of additives of anti-blocking and/or slip agents, such as to reduce the tackiness thereof); and also mixtures thereof,

said polymer of the layer (2) also being able to contain in its interior additives of various type depending on the required function, such as for example anti-fog additives, anti-UV additives, anti-blocking additives, slip agents, antistatic agents, antibacterial agents, dyes, oxygen scavengers, antioxidant agents, nucleating agents, processing aids and the like known in the art (alone or in combination one with the other).

9. Flexible packaging which includes the laminated film (10) according to claim 7 or 8, wherein one or more additional layers (N layers) are placed between said external layers (1) and (2) of said non-oriented coextruded film (4), said additional layers being able to impart various technological functions to the coextruded film (4), for example a layer of EVOH and/or polyamide to confer barrier properties, one or more layers of HD-PE to confer rigidity, linear polyolefin layers having high toughness to confer particular mechanical strength, layers added with anti-UV agents to confer a barrier to UV rays, layers with hot-melt pressure-sensitive resins to ensure re-closure of the package made, etc.,

said additional layers (N) optionally containing in their interior additives of various type depending on the required function, such as for example anti-fog additives, anti-UV additives, anti-blocking additives, slip agents, antistatic agents, antibacterial agents, dyes, oxygen scavengers, antioxidant agents, nucleating agents, processing aids (alone or in combination one with the other).

10. Packaging according to any one of preceding claims 1 to 9, wherein said side of said layer (1) of said coextruded film (4) can be treated with corona treatment.

11. Packaging according to any one of preceding claims 1 to 10, wherein said backing film (3) of said laminated film (10) is a flexible mono-oriented polyethylene film and has a surface optionally coated with one or more non-sticky coatings and/or overlapping (5) processes, preferably at least one print (5).

12. Process for obtaining, preferably in continuous mode and in-line, the laminated film (10) as defined by any one of the preceding claims, optionally with an internal print (5), said process comprising the steps of

performing an optional printing, on said plastic backing film (3) unwound from a first reel (30) by passage through a printing machine (20);

placing said backing film (3) having an optional print (5) in contact with said coextruded film (4), unwound from a second reel, so that the side (1) of said coextruded film (4) having adhesive properties is in contact with said print (5), if present, or with said backing film (3),

passing said superimposed films (3,4) through two opposing presser cylinders of thermal lamination (13,12) of which at least one is heated so as to soften the layer of the side (1) with adhesive properties of said coextruded film (4), and

exerting a pressure on both said superimposed films (3,4).

13. Process according to claim 12, wherein the temperature of thermal lamination is between 50-150°C, preferably between 90°-150°C, depending on the softening temperature of the polymer of the side (1) having adhesive properties; the pressure being comprised between 1 and 10 bar.

14. Process for preparing a reel (30) of a plastic backing film (3) as defined in the preceding claims, to be used in the thermal lamination process as defined in claims 12- 13, said process comprising the steps of

- bubble co-extruding a film (3) as defined in the preceding claims;

- subjecting said coextruded film (3) to an optional stretching and/or annealing treatment;

- subjecting said coextruded film (3), optionally subjected to stretching and/or annealing treatment, to a surface irradiation treatment using ionizing radiations which are apt to traverse at least one of the outer layers of said coextruded film (3).

15. Plant for manufacturing a laminated film (10) as defined in any one of the preceding claims 1-11, which optionally encloses in its interior a print (5) by means of a process as defined in any one of the preceding claims,

said plant comprising

an optional printing machine (20) for forming in continuous mode a print (5) on said plastic backing film (3) unwound from a first reel (30),

a pair of opposing presser cylinders of thermal lamination (13,12), of which at least one is heated, to thermally laminate said optionally printed backing film (3) placed in contact with said coextruded film (4) which is unwound from a second reel, placing in contact said print (5) with the side (1) having adhesive properties of said coextruded film (4).