DESCRIPTION

The present invention relates to a coextruded film having an adhesive surface such as to allow it to be thermally laminated, without the use of glues, on a coated plastic film resulting in a multilayer flexible laminated film with an internal coating, preferably with a print enclosed in its interior, said laminated film being suitable for being wound on reel and for being used to make flexible food packages such as tray closure, pouches and similar manufactured articles in plastic, in particular as closure film (top) of food container trays and/or film for making pouches for foods.

More particularly the present invention relates to a flexible thermally laminated multilayer laminated film formed by

a coextruded unoriented film

coupled to

- a backing flexible plastic film, in particular a biaxially oriented film, preferably in a single material, which is coated on the surface, for example printed and/or metallised and/or with lacquering such as PVOH (polyvinyl alcohol), PVDC (polyvinylidene chloride), ceramic coatings with a base of SiO _x , with a base of Al ₂ O _x , lacquerings with cellulose and the like,

where the two films are adhered one to the other by means of simple thermal lamination without the use of glues.

Even more particularly the present invention relates to a thermally laminated multilayer film, as defined above, wherein the plastic flexible backing film is at least printed, said film being able to have been previously coated on the surface with another coating before printing.

Moreover the present invention relates to a process for obtaining, preferably in continuous mode and in-line with the process of printing, a printed multilayer flexible laminated film ready for use, for example on a packaging machine, without requiring offline phases of processing nor the usual times for curing (for the cross-linking of the adhesives and for the decay of the aromatic amines).

Packaging has for some time become also an important advertising vehicle and in some cases the main promoter of the sale itself of the product contained, thanks on the one hand to the possibility of making packagings with high transparency and brilliancy, and on the other hand to the possibility of using personalised printing which reproduces attractive and inviting images on the packaging itself.

In the case of packaging of food products the legislation in force requires that the inks of the printed surfaces not be directly in contact with the food product (REGULATION (EC) No. 2023/2006 of 22 December 2006 - Point 3 of the annexe).

This has led, in some cases, to printing of the outer surface of the packaging resulting however subject to scratches and abrasions during the normal handling of the packagings, with the consequent damaging of the print. The same applies in the case of other types of coating (metallizing, PVDC, PVOH, SiO _x Al ₂ O _x , and the like).

To avoid the aforesaid disadvantages and protect the print or the other types of coating use can be made of a second membrane glued over the printed surface in such a way as to enclose the ink, as a sandwich, between the two films, obtaining an internal print.

This type of printed multilayer film is particularly used for the top of food container trays and is made up generally of a printed film in bi-oriented materials (PET, PP, PA) bonded to a welding film in PE.

This solution is currently the most widespread not only because it appears aesthetically more attractive, offering the guarantee of maintaining the quality of the print, above all in the case of handling of the packaging, but also because it allows the obtaining of a multilayer film wherein the films which enclose the print can have different functions - for example on one side a film with high heat resistance, on the other a film extremely sensitive to heat, therefore with good sealing capacities.

To date the system commonly used for making this multilayer film is the lamination of the printed film and of the welding film via dedicated units which use spreadable glues (polyurethane, acrylic, water-based epoxy amines, water-based casein latex adhesives) deposited on one of the two films in such a way as to act as a bonding agent between the two films.

This solution (both in the case of the solvent technology and in the case of the solvent- less technology) suffers however from the disadvantage of generally requiring a step off- line with respect to the process of printing in order to be able to perform the gluing of the two films, which prevents the process of production of the multilayer film from being in continuous mode and in-line with the printing process.

Additionally, this operation of gluing off-line with respect to the process of production of the multilayer film entails a high consumption of electrical energy necessaiy both for the lamination and diying, and subsequently also for the cross-linking of the spreadable glues (in hot chambers), in addition to entailing waiting times of several hours (48 or more) for the cross-linking of the glue. Moreover the use of glue (with and without solvents) entails the risk of the formation of aromatic amines (risk inherent in all the bondings with two-component polyurethane adhesives) and in some cases has limits in the overall transparency of the multilayer film due to the formation of bubbles or unsightly defects due to the spreadable adhesive and to the quality of the bonding, as well as entailing a high environmental impact connected to the possible bonding solvents, abundantly released into the atmosphere during the process of bonding.

WO 2005/108066 describes a method for obtaining credit cards or the like containing a metallic foil and an inner layer of PET which is coated on both sides by a plurality of vaiious films symmetrical with respect to the PET, wherein each film is applied to the PET by means of a respective step of lamination since the films are separated one from the other and they are not part of a coextruded film.

This document therefore provides, in the central core of the multilayer laminated sheet, the presence of a sheet of PET which is not comparable to a film due to the different thickness relating to definition of a film and to a sheet.

Therefore this document does not describe a flexible packaging with an internal print, formed exclusively by thin plastic films and obtained by means of the thermal lamination of two films, one of which having a treated and/or printed surface. US 6489038 describes a multilayer Film which can be laminated with heat on a backing for the production of composites for graphic products such as books, CD, brochure covers and the like, where the backing is paper, cardboard, plastic, metal and the multilayer film is oriented at least mono-axially and comprises a base layer in polypropylene, a first outer layer in polypropylene and a second outer layer composed of a mixture of two different EVAs with a different residue of vinyl acetate, said second outer layer being intended for contact with the backing.

This document however does not describe or suggest flexible packagings for foods because the films containing residues of vinyl acetate in amounts as reported in said patent would be unlikely compatible with the law concerning the material intended for the contact with food, if "vinyl acetate residue" is considered to be the free monomer: the Regulation CE N. 10/2011 indicates indeed a value of 12mg/kg of food as a Specific Migration Limit (SML) for vinyl acetate.

Additionally, the mixing of two different types of EVAs for obtaining the external layer requires the use of a specific extruder also equipped with a specific designed mixing section in order to assure the reproducibility of the mixing ratio between the two EVAs, thus increasing the production costs of said multilayer film and/or limiting the performing of the extrusion to the only producers having a proper equipment.

US 4,897,533 describes a method for making a credit card by lamination of an adhesive- coated polyester film to a plastic card of PVC, using a heating element placed upstream of two lamination rollers which are not heated.

However said implant results to be more complex to be controlled since it requires an additional specific heating equipment to be placed inside the production implant.

Moreover said patent does not describe a flexible packaging for foods.

The object of the present invention is that of overcoming, at least in part, the disadvantages of the prior art by providing a method for obtaining a multilayer flexible laminated film with internal print (sandwiched between two films) adapted for the use in food application, which does not require either glues or a dedicated system, and which is a just-in-time method, that is to say without the need to wait several hours (48 or more) for cross-linking of the glue. A further object of the present invention is that of obtaining such a multilayer film which shows a good transparency and overall brilliancy as required for film for food packagings, and which is lacking unsightly or surface defects such as bubbles. Yet a further object of the present invention is that of obtaining such a multilayer film printed by means of a continuous production process which is easy, economical, simple as not to require a great number of equipment to be controlled, and which does not provide for phases off-line with respect to the printing phases. A further object of the present invention is that of reducing the environmental impact linked to the manufacture of the multilayer film as the use of glues and possible bonding solvents is eliminated, abundantly released into the atmosphere during the process of bonding. A fuither object of the present invention is that of improving the food safety for the consumer, given that the use of bonding solvents is excluded (there is not therefore the problem of retention of the solvent, well known to those who bond with glues) just as it is eliminated the risk of the formation of aromatic amines, suspected to be carcinogenic and potentially migrating in the food (the legislation in force - Regulation (EC) 10/201 1, point 2 of annexe II clearly limits its migration into the food),

These and other objects are achieved by the multilayer laminated film 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 object of the present invention relates to a thermally laminated multilayer film, normally of the flexible type, which has enclosed a print and/or another coating in its interior, particularly suitable for being wound on a reel and for being used as closure film (top) of food container trays, as film for pouches or for similar manufactured articles.

In fact, the object of the present invention is a flexible packaging for food with an inner coating and/or print, which is obtained from two films, one of which having a treated and/or printed surface, said two films adhering permanently one to the other only by means of thermo-lamination without glue. In particular, the present multilayer laminated film, intended to be used as flexible packaging film for food, is formed by

a flexible plastic coextruded film, which is multi-layer and unoriented having two opposite sides, said film not containing metal coatings, metal layers and/or prints, and being able to be unwound from a reel

bonded, by means of thermal lamination, to

a plastic flexible film, in particular a bi-oriented film, preferably made by a single material, having a coated and/or treated surface, for example printed and/or with lacquering, preferably at least printed.

The present laminated film is characterised in that the side of said coextruded multi-layer film which is in contact with the surface of said plastic film is a sticky film or has permanent adhesive properties such as to adhere permanently to said plastic flexible backing film without the use of glues, said adhesion bonding being obtained through the effect of the heat and of the pressure.

Preferably the side of said coextruded film which is in contact with said plastic film is formed by one or more sticky polymers/resins, preferably made by a single sticky polymer/resin.

The term "film" is here intended to identify a plane thin semi-finished product whose thickness is very small with respect to its length and wideness, generally equal to or lower than 0,25 mm (ISO 472). The semi-fmished products having a thickness greater than said value are identified with the term "sheet" (ISO 472) and show a flexibility lower than that of said films.

In a preferred embodiment the thermally laminated multilayer film defined above encloses in its interior at least one print and is formed by a plastic backing bi-oriented film, where the surface of said backing film turned towards the interior of the multilayer film is at least printed and optionally coated with other coatings and/or treatments below said print.

The term "adhesive properties " is intended here to identify the capacity of a surface to glue firmly onto another through the effect of only pressure and/or of temperature, This quantity can be measured according to the standard ASTM F904-98 which, in particular, supplies a method for measuring the force necessaiy for separating the two glued surfaces. Adhesive properties considered adequate in the case of a flexible multilayer film are those with force of delamination >1.2N/15 mm, The term "sticky polymer" is here intended to identify polymers that are naturally sticky to the touch, including polymers which are already sticky at room temperature, for example at 25-30°C, even if the softening temperature thereof is higher, and which show adhesion to substrate under the application of a pressure so that the polymer surface does not slip with respect of the contacting substrate.

In particular, the stickiness of a film can be empirically assessed, for example by pressing the sticky side of the film on the hand palm for 5 seconds, evaluating the sensation (sticky/non-sticky) associated to the removal of the film. The term "coating" is intended here to identify any type of coating known in the art for polymeric films such as for printing, metallizing, lacquering such as PVOH (polyvinyl alcohol), PVDC (polyvinylidene chloride), ceramic coatings with a base of SiO _x , with a base of Al ₂ O _x , lacquerings with cellulose and the like. The term "coating" thus identifies, in the present description, a very thin layer of material, generally lower than 1-2 μιη, applied by means of a coating process, i.e. by applying to a substrate a thin layer of a material in the form of a fluid or powder, in compliance with the vocabulary of ISO 472: thus "coating" is not to be considered as a stratification of material in view of that vocabulary.

For the sake of simplicity here below the terms "with another coating", "with another type of coating", "with different coating" shall indicate all the types of coating known in the art with the exception of printing where this is already explicitly mentioned. The terms "coated on the surface ", "with a surface coated (coating) and/or treated", are used here as synonyms.

The term "multilayer material " is used here as a synonym of laminate, laminated film, or poly-bonded material, and is referred to thin multilayer structures, obtained by coupling/bonding pre-existing films of different materials. With "thermal lamination " the intent here is to identify a process of hot lamination of film without the use of glues where the adhesion at the interface of the two films is obtained through the sole effect of the temperature and/or pressure, exploiting the adhesive/sticky properties which some polymeric materials, or combination thereof, show, for example when they are in a state of softening under the heat.

With the term "coextruded" the intent here is to identify a film obtained from the process of extrusion of two or more different materials, in the molten state, through a single die, planar or annular, with two or more orifices placed in such a way that the extruded parts melt and weld together in a laminar structure before cooling, for example by means of quenching, so as to form a single film composed by a plurality of materials.

Coextrusion can be performed according to a technique known as bubble blowing, flat head, extrusion coating or the like. The present coextruded film is preferably obtained by using screw extruders and bubble blowing or flat head extrusion, without the aid of any type of glue.

Thus the term "coextruded film" is intended here to identify a product as above defined, formed by two or more different polymers, which is obtained by a co-extrusion process with two or more extruders conveying the respective melts to a single die in such a way that they go out contemporaneously from the die, in a distinctive state and not admixed one to another, wherein said respective materials that form the coextruded film are arranged in layers. Films containing internally metal coating, metal layer, prints and/or other coating cannot be obtained by means of said coextrusion process.

To the best of the Applicant's knowledge a multilayer film is not known in the art where the printed and/or metallized side of a plastic backing film in polyester is adhered to a coextruded film by simple thermal lamination without the use of glues and/or adhesives. In fact the use of thermal lamination between an adhesive coextruded film and a bi- oriented film is not known in the art for making flexible films, while the use of thermal lamination is more widespread for making semi-rigid or rigid structures basing on a flat leaf of a non-bi-oriented polymer, in extruded form, therefore hot as coming from the extrusion head and an adhesive flexible film heated by the contact with the molten polymer of the sheet. It should also be said that machines are not even available that are able to form this bonding for flexible films in a simple manner. Finally consideration should be made of the fact that the ink, once dry, constitutes a coating with low affinity and low compatibility with plastic materials so that to date use has always been made of glues which cross link and harden to obtain good cohesion between the two bonded surfaces.

Without wishing to be bound to any type of theoiy, it is presumable that during thermal lamination a material with sticky or permanent adhesive properties succeeds, when hot, in co-penetrating slightly the other material along the zone of contact of the two layers without damaging the ink or the coating, thanks also to the "chemical affinity" of the polymers of the layers placed in contact which allows both layers to bond to the interface in such a way as to cause a high force of adhesion which prevents the delamination thereof. The greater the similarity (otherwise referred to as chemical affinity) between the materials, the greater the adhesion between the two films.

It should be noted that the surface of the backing film which is opposite 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 multilayer film with internal print, metallizing or coating will be obtained which has an outer surface also respectively metallized, printed or coated with another coating. Further features of the invention will be made clearer by the following detailed description, referred to a purely non-limiting example thereof, illustrated in the accompanying drawings in which:

Figure 1 is a vertical sectioned view, partially interrupted, of a thermally laminated multilayer film in accordance with the invention, suitable for use as top for food container trays;

Figure 2 is a sectioned view, partially interrupted, of a first coextruded film suitable for forming the multilayer film of Figure 1 ;

Figure 3 is a sectioned view, partially interrupted, of a second coextruded film suitable for forming the multilayer film of Figure 1 ;

Figure 4 is a schematic view of the line of production in continuous mode of the multilayer film of Figure 1. Referring to Figure 1, a description will now be given of a preferred embodiment of the multilayer laminated film of the present invention, in the form of a planar flexible laminated film for food packaging, denoted overall by reference numeral 10, which has as internal coating at least one print.

Said laminated film 10 has usually such a total thickness as to be a flexible film, generally comprised between 30 and 250pm,

It is understood that what will now be described is applicable also in the case wherein the internal coating is different from the print, without thereby departing from the spirit of the present invention.

Said multilayer film 10 is formed by a first film 3, here below indicated also as backing film, made by a polymeric plastic material, in particular a bi-oriented film, preferably made by a single material, with thickness typically from 5 to 40 μηα, and also greater, generally up to ΙΟΟμηι, provided such as to maintain the inherent flexibility of a film with thickness smaller than 250 μιη.

Examples of polymers suitable for making the film 3 can be polyethylene terephthalate (PET), polypropylene (PP), polyamide (PA), polyvinyl chloride (PVC), polystyrene (PS), cellophane or also biopolymers such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), polyhydroxybutyrates (PHB), in the bi-oriented or non-bi-oriented form, preferably bi-oriented. The polymers as above defined are preferred excluding PVC. It is to be noted that PVC, PET, PETG polymers as such are not sticky polymers.

Said backing film 3 is in particular suitable to be printed, as well as to be coated with another type of coating, for example metallized, without thereby departing from the scope of the invention.

Said 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 discharge treatment, plasma treatment, chemical treatment, treatment with primer and/or with optional functional lacquerings (PVDC, PVOH, SiO _x , Al ₂ O _x ). Said backing film 3, which is not sticky, can generally be wound in a reel 30 (Fig. 4) so as to be unwound during the process in order to obtain the print 5 for the formation of the multilayer film 10 which is the object of the present invention. The starting film wound into the reel 30 (pre-existing film) can therefore be a film without any treatment and/or surface coating or be a film which has been treated and/or coated previously and which therefore already has a coating, including the print, applied on its surface intended to be turned to the interior of the multilayer material. The print 5 of images (shown in bold with interposed empty spaces which in actual fact do not exist but serve only for clarity of depiction) on the backing film 3 can be obtained through various technologies known in the art, for example by means of flexographic or rotogravure or digital or UV printing. Said multilayer film 10 is moreover formed by a second flexible coextruded multi-layer film 4 having typically a total thickness equal to or lower than 200μιη.

Said coextruded film 4, which is an un-oriented film, is in turn constituted at least by a first outer layer 1 with adhesive/sticky properties, preferably made by a single polymer or resin with adhesive/sticky properties, said film having a thickness typically from 5 to 100 μτη, but also greater; and by

a second outer layer 2, neither sticky nor adhesive, opposite to the layer 1, having typical thickness from 10 to 100 μη , but also greater. The two layers 1 and 2 are made in polymeric materials appropriately selected so as to be chemically compatible one with the other so as to remain firmly joined during the coextrusion, exploiting the hot co-penetration of one material in the other, when in molten form, along the zone at the interface between the two layers. The non-orientation of the coextruded film 4 is advantageous in that it allows to obtain a film with high resistance to tear along both the machine direction and the transverse direction since the polymeric chains are not aligned in a specific direction.

On the contrary, the mono- and bi-oriented films are typically characterized by the easiness of tear propagation along one or both directions depending on the orientation of stretch; the non-orientation further avoids to use expensive and hindering equipments for the stretch.

The polymer which forms the layer with adhesive properties 1 is an extmdable resin having in itself sticky or adhesive properties in regards to the polymer of the backing film 3.

The adhesive properties of this resin of the layer 1 , which appear completely when hot, are due mainly to the type of material or mixture thereof: said resin is in fact chosen from among polar resins, non-polar resins yet sticky through low density and/or molecular weight, non-polar and non-sticky resins (except at the thermo-lamination temperatures) yet capable of adhering strongly to the backing 3 through chemical affinity, polyolefins with tackifying additives such as to be sticky, tackifying resins or combinations thereof. Said layer 1 can also be optionally surface treated by corona discharge treatment or plasma treatment before being subjected to thermal lamination.

More particularly the aforesaid resins show a Tg (glass transition temperature) well below the ambient temperature and a softening point (Vicat softening point) slightly lower than the material of the backing film 3 as will be made clear by the detailed description given here below.

As polar resins (a) mention can be made, for example, of EVA (ethylene-vinyl acetate copolymer), ethylene-acrylic esters copolymers such as for example EMA (ethylene- methyl acrylate copolymer), EBA (ethylene-butyl acrylate copolymer), EEHA (ethylene- 2-ethyIhexyl acrylate copolymer), EEA (ethylene-ethyl acrylate copolymer), ethylene- acrylic acids copolymers such as EAA (ethylene-acrylic acid copolymer), EMAA (ethylene-methacrylic acid copolymer), where the content of polar comonomer (VA, MA, EHA, BA, AA, MAA) is variable, considering that the greater its content, the greater the resulting tackiness; 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, ionomers and the like, where the content of polar comonomers (e.g. acrylic esters, maleic anhydride, vinyl acetate) is variable, considering that the greater its content, the greater the resulting tackiness. EVA or EMA or EAA is preferred as polar resin. As non-polar but sticky resin (b) mention can be made, for example, of polyolefm-type plastomers and elastomers, having generally a density equal to or lower than 0.910 g/cm , such as for example very low density polyethylene (VLD-PE), metallocene very low density polyethylene (mVLD-PE), propylene-ethylene copolymers in the form of elastomers and plastomers, and the like.

As non-polar and not necessarily sticky resin (c) yet able to adhere strongly through chemical affinity, mention can be made, for example, of styrene/butadiene copolymers, for example styrene/butadiene/styrene (SBS), styrene-ethylene/butylene-styrene (SEBS), styrene/butadiene/butylene/styrene (SBBS), styrene-isoprene (SIS).

As tackifying resins (d) mention can be made for example of hydrocarbon resins and as tackifying material to be added to the polyolefins to make them sticky mention can be made for example of polyisobutylene,

The resins/polymers of layer 1 are preferably selected from those listed in the groups (a), (b) and (d), more preferably the layer 1 is composed of a sole sticky resin at room temperature selected from (a), (b) and (d), still more preferably said layer 1 is formed by a single resin of EVA wherein the percentage content of VA is equal to or greater than 8% by weight up to a maximum of 70%, preferably between 10% and 40%.

The layer 2 of the coextruded film 4 forming the multilayer film 10 is intended to come into contact with the product contained in the container tray: it is a welding layer (and therefore by its nature not sticky or adhesive) and is constituted by a polymeric resin of an extrudable thermoplastic polymer, chosen from among those which are compatible during welding with the polymer of the container tray so as to allow hermetic closure thereof.

The polymer used to form the layer 2 can be typically a polyolefin, for example PE in all its variants, optionally with the addition of PB (polybutylene) to make a structure with facilitated opening, PP, EVA (with low content of vinyl acetate, generally below 10% by weight or with high content of vinyl acetate yet with a high content of additives of antiblocking and/or slipping agents such as to reduce the tackiness thereof), ionomer and the like; or also a polymer of different type such as polystyrene (PS), PET and similar polymers, or combinations thereof. The layer 2 is preferably formed by the polymers as above indicated excluding PP, more preferably the layer 2 is formed by PE in all its variants. Said layer 2 has preferably a thickness greater than 3 μη . This layer 2 can contain in its interior additives of various type (alone or in combination one with the other) depending on the required function, such as for example anti-fog additives, anti-UV additives, antiblocking additives, slipping agents, antistatic agents, antibacterial agents, colorants, oxygen scavengers, antioxidant agents, nucleating agents, processing aids.

An example of coextruded film 4 formed by a layer 1 and a layer 2 can be a film formed by a bi-layer PE-EVA where the content of VA in the EVA is approximately 28% by weight. Between said layers 1 and 2 one or more additional layers (N layers) can be included, as illustrated in Figure 3, capable of imparting 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 confer rigidity,

- one or more layers of linear polyolefins with 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 closabiiity for the packaging made, etc.

These layers N can contain in their interior additives of various type (alone or in combination one with the other) depending on the required function, such as for example anti-fog additives, anti-UV additives, antiblocking additives, slipping agents, antistatic agents, antibacterial agents, colorants, oxygen scavengers, antioxidant agents, nucleating agents, processing aids.

The process to obtain a thermally laminated multilayer film having an internal coating will be described here below: more particularly the obtaining of the preferred multilayer film 10 having an internal print 5 and other possible coatings inside and below said print 5 takes place through a process described here with reference to Figure 4. Said process provides essentially for a phase of thermal lamination performed by means of a simple passage of the two different films 3 and 4 through two lamination presser rollers whereof only one is heated: in this way in the final multilayer laminated film 10 the print 5, like any other type of coating possibly present as an alternative or in addition to the print, is incorporated as a sandwich between the backing film 3 and the adhesive layer 2 of the coextruded film 4, without requiring the use of glues and/or adhesives.

If the film 3 unwound from the reel 30 is not already printed, the process which leads to the obtaining of the final multilayer laminated film 10 with internal print 5, optionally containing also other types of internal coating, in accordance with the present invention, provides for the performance, preferably in continuous mode and in line, and therefore in a single step, of a first phase of printing followed by a successive phase of thermal lamination. The aforementioned process therefore leads to a printed final multilayer laminated film and optionally containing also other types of coating, which is ready for use, for example on a packaging machine.

Referring to the present process carried out in line and in continuous mode, the first phase of printing of the backing 3, unwound from reel 30, takes place using techniques and machines for printing 20 known in the art, with various types of ink (for flexo graphic, 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, also unwound from a reel, so that the print 5 is in contact with the layer 1 of the coextruded film 4 having adhesive properties.

Once in contact one with the other, the film 3 and 4 are made to pass through two opposite thermal lamination cylinders 12, 13 pressing and co-operating one with the other and which are formed by a presser cylinder in steel 13 and by a heated cylinder in rubber 12, which is also a 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 of the pressure of the presser cylinder 13 exerted against the heated cylinder 12: thanks to the intrinsic adhesive properties of the layer 1, when in softened form, a multilayer material is obtained with strong adhesion at the interface between the backing film 3 and the coextruded film 4.

It is understood that what has been said above in relation to the thermal lamination can also be repeated in the case wherein the coating 5 applied to the backing 3 is different from the print, without thereby departing from the spirit of the present invention.

The thermal lamination between the two different films can be performed at a temperature, for example of 50-150°C, preferably 60-90°C, and normally the higher the temperature the greater the adhesion which is obtained, always seeking to come as close as possible to the softening temperature of the adhesive layer 1 , while the film 3 remains at ambient temperature.

In practice the softening which the adhesive layer 1 undergoes during the phase of thermal lamination is such as to make it adhere to the backing film 3, also in the case wherein said film 3 has not softened, by means of the sole application of pressure on its surface.

Values of adhesion considered acceptable are >1.2 N/15mm, measured according to the ASTM method mentioned previously.

The abovementioned process for obtaining the multilayer laminated film in accordance with the present invention is enormously advantageous in terms of cost (at least the passage off-line of bonding with glue is avoided) and of saving of time (not only because the printing and the bonding take place in line, therefore in a single phase, but also because the waiting times inevitably required by the cross-linking of the glues are avoided and which can also be a few days).

Finally the process described for the obtaining of the printed multilayer laminated film and/or with another internal coating enjoys a favourable environmental impact if compared with the solvent bonding technologies.

Moreover the multilayer laminated film obtained from the abovementioned process has an improved combination of properties:

- total lack of aromatic amines (whose formation represents instead an inevitable potential risk of the polyurethane adhesives through a reaction between free isocyanate and water);

reduced quantity of residual solvent (which is present in the case of rotogravure or flexographic prints with solvent) or total lack of the same (in case of digital prints or UV print);

- improved aesthetic appearance since there is no trace of bubbles or unsightly defects due to the adhesive for the bonding;

resistance of the print 5, or of another coating, to impact and to scratches but also thanks to the fact that the print, in the final multilayer laminated film 10, is incorporated as a sandwich between the backing film 3 and the coextraded film 4.

It should be noted that the present process of thermal lamination, if performed in line and in continuous mode, is particularly advantageous when the print on the backing film 3 is formed by means of digital technology: this method, being enormously faster with respect to the flexographic method or with rotogravure, can allow the formation overall of a multilayer film 10 for top with an extremely high production rate Gust-in-time process) with considerable advantages from the economic viewpoint.

The present process for the manufacture of a preferred printed multilayer laminated film 10 in accordance with the invention is carried out advantageously in a system comprising: an optional printing machine 20 for forming in continuous mode a print 5 on the plastic backing film 3 unwound from a first reel 30,

a pair of opposing presser cylinders of theraial lamination 13 and 2, 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, in such a way 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 to be obtained in the multilayer film 10 is different from the print, the abovementioned system in accordance with the invention will provide a unit 20 suitable for applying a coating on the film 3 instead of a printing machine, without thereby departing from the scope of the present invention.

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