"PACKAGING FOR FOOD PRODUCTS MADE OF A MULTILAYER FILM"

FIELD OF THE INVENTION

The present invention concerns a packaging for food products made of a bi- axially orientated polypropylene (BOPP) multilayer film, as well as a substrate for making packaging for food products that comprises that multilayer film. Advantageously, but not exclusively, the packaging for food products is of the stand-up pouch type.

BACKGROUND OF THE INVENTION

Packages of the stand-up pouch type are known in the art. Such packages are designed to stand in an upright position and, for this purpose, they generally have a substantially planar bottom surrounded by at least two edges obtained by folding the film from which the packages are made. Such film is generally a multilayer film and has a rigidity that is such as to allow the body of the stand-up pouch to keep a stand-up configuration without collapsing.

The above-mentioned folds of the film, which surround the planar bottom of the pouches, confer a greater rigidity, so that the pouch is supported in a stable manner in the stand-up position. Usually the known stand-up pouches comprise a closure element at the top, generally a zipper, a spout or a valve made of plastic material.

In the known stand up pouches, the film used to produce the pouch has a structure comprising BOPP//PE or BOPET//PE, or BOPET//Aluminum//PE, or BOPET/metallized plastic film//PE, with PE which can be replaced for cast PP film. Other examples of multilayer films used for producing stand up pouches comprise functionalization materials such as acetates, acrylates, polyamides or derivatives thereof.

As an example, W02019/102303 discloses a pouch made of a polyolefin (oriented polypropylene OPP, low density polyethylene LDPE and linear low polyethylene LLDPE), with a polyester (poly(ethylene terephthalate) (PET)), a polyacrylate and ethylene vinyl alcohol EVOH. Films of this material are available as multilayer films including functional tie layers, which contain a functional polymer. It is noted that no mention is made about the design of the film, in particular about the thicknesses of the layer, or other details. Such document also describes a hook-and-loop type of reclosable closure member that is adhered to the inner surface of the pouch, and it is disclosed the use of adhesives, ultrasonic bond, mechanical attachment or a suitable tie layer.

US2019/382165 discloses film materials for making pouches, made of thermoplastic materials such as polypropylene (PP), polyethylene (PE), metallocene-polyethylene (mPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), biaxially-oriented polyethylene terephthalate (BPET), high density polyethylene (HDPE), polyethylene terephthalate (PET), styrenic block copolymers, elastomeric alloys, thermoplastic polyurethanes, thermoplastic copolyesters, thermoplastic polyamides, polymers and copolymers of polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), saran polymers, ethylene/vinyl acetate copolymers, cellulose acetates, polystyrene, polycarbonates, styrene acryloacrylonitrile, aromatic polyesters, linear polyesters and thermoplastic polyvinyl alcohols. The pouches can comprise zipper strips made of thermoplastic material, mainly based on polyethylene. This document does not provide any structural details of the film.

US2018/273250 discloses a bag provided with a zipper and made of a plastic material such as, for example, polypropylene, polyethylene or bioplastics. No information is given about the structure of the film used to manufacture the bag.

JP2019182463 discloses bags with spouts manufactured apparently by sealing a flat side wall section of the bag body against a flange with the spout protruding through an opening in that wall section. The wall comprises a barrier layer having an oxygen-blocking function, and comprising an ethylene-vinyl alcohol EVOH copolymer.

EP1954581 discloses a pouch made of two sheets of heat sealable material, and comprising a spout to dispense a liquid contained inside the pouch. The spout is part of a pre-fabricated article that comprises the spout and a boat shaped or circular base, preferentially with grooves, wherein the base is used to seal in a leak-proof manner against the inner layer of the bag substrate.

A problem of the known stand up pouches with regards to a Circular Economy is that the substrates from which they are made are of the multi material type, and as such are difficult or expensive to recycle. This is due to the presence of various of the above-mentioned materials which, when associated with each other, in particular with polypropylene, cannot be recycled for further applications.

A recycling method for plastic materials, in particular polyolefins like polypropylene and polyethylene, that is regarded most energy efficient is known as “material recycling” which involves melting, filtration, and re-pelletizing of the plastic components. Since aluminum foil would not melt, and BoPET would degrade under the conditions of material recycling of polyolefins both of them should be avoided.

A further inconvenience of the known structures is that they entail rather high unit weights, because the materials on which they are based have an insufficient stiffness for this kind of package, and more quantity of material has to be used.

Another aspect of the known stand up pouches is that they are usually provided with a zipper, or a valve, which is generally made of polyethylene. The presence of such zipper or valve can lead to problems related to the sealing of the film, which in the sector of food packaging must be hermetic, and in some cases airtight, for example in the case of pouches designed to keep a food product in a protective atmosphere.

It is therefore necessary to devise a multilayer film, in particular for the realization of food packaging of the type above disclosed, which can overcome at least one of the drawbacks of the known art.

In particular, a purpose of the present invention is that of providing a packaging of the stand-up pouch type that is easy and inexpensive to be recycled.

Another purpose of the present invention is that of providing a packaging made of a multilayer film that has very good sealing performance, in particular with zippers and valves made of polyethylene.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants of the main inventive idea. In accordance with the aforesaid objectives and purposes, the present invention concerns a packaging of the stand-up pouch type made of a substrate comprising a bi-axially orientated polypropylene (BOPP) multilayer film having improved sealing properties.

Advantageously, the BOPP multilayer film has an inner side and an outer side, with the inner face forming the inside of the pouch, the inner side of the multilayer film providing improved sealing properties suitable to form edges of the pouch.

According to an embodiment the outer side is coated with a thin metal or metal oxide layer, by means of a vacuum deposition process, or printed for decoration or for providing information for the consumer.

The BOPP multilayer film used to produce the packaging may have a thickness of between 10 pm and 120 pm, and is obtained by co-extrusion with flat head extrusion die and sequential stretching respectively in the machine direction (MD) and in a direction transverse to the machine direction (TD).

According to one aspect of the present invention, the film comprises at least:

- a core layer, made of polypropylene, having an outer face and an inner face,

- an inner intermediate layer, or inner interlayer, adjacent to the inner face of the core layer and based on polypropylene or polyethylene,

- an inner skin layer, adjacent to the inner interlayer, and based on polypropylene or polyethylene, and

- an outer skin layer in correspondence with the outer face of the core layer.

According to other embodiments, the outer skin layer, disposed at the outer face of the core layer, is based on polypropylene.

At least the inner skin layer is made of sealable material, in particular of a heat sealable material. According to a feature of the invention, the inner skin layer is made of a material that has a lower melting point with respect to the other layers of the film. Preferably, the material of the inner skin layer has a seal initi tion temperature that is lower than the softening point of the other layers of the multilayer film.

Advantageously, the material of the inner skin layer is made of a material comprising a heat-sealing enhancer which ensures the seal initiation temperature of the film to be below 100°C, more preferably below 80°C, even more preferably between 70°C and 80°C.

Preferably, also the outer skin layer may be made of a sealable material, in particular a heat sealable material.

It is advantageous to provide that the outer skin layer is treated to improve its ability to be printed, and preferably also to improve its ability to be laminated.

According to an embodiment, the multilayer film also comprises an outer intermediate layer, or outer interlayer, adjacent to both the outer face of the core layer and the outer skin layer, and based on polypropylene.

Preferably, the thickness of the inner skin layer plus the thickness of the inner interlayer amount to at least 10% of the overall thickness of the multilayer film. More preferably, the thickness of the inner skin layer plus the thickness of the inner interlayer represent 10-30% of the overall thickness of the multilayer film, even more preferably represent 12-25% of the overall thickness of the multilayer film It is preferable that the inner skin layer has a thickness greater than the thickness of the outer skin layer.

Advantageously, the thickness of the inner interlayer and the inner skin layer, taken together, is at least twice the thickness of the outer interlayer and the outer skin layer, taken together. In accordance with embodiments, the core layer is voided, that is the core layer contains a plurality of voids, or cavities, within the thermoplastic matrix material of the core layer. Such voids or cavities allow to make the film opaque. The film may also comprise solid particles, for example pigments, inside the voids. According to other embodiments, the core layer comprises pigment particles embedded in its thermoplastic material matrix.

According to another aspect, the invention relates to a substrate for making packaging for food products, and which comprises a BOPP multilayer film with improved sealing properties as indicated above, laminated with its outer side against another BOPP film. Such laminates are known to be advantageous with regards to protection of barrier layers or printing as positioned between the two laminate members.

Preferably the substrate comprises a first BOPP film as indicated above, and a second BOPP film having at least a core layer, an inner skin layer and an outer skin layer, this latter being made of propylene homopolymer, the inner skin layer of the second BOPP film being laminated against the outer skin layer of the first BOPP film

In accordance with another embodiment, the substrate comprises a first BOPP film as indicated above, and a second multilayer BOPP film having at least a core layer, an inner skin layer, an outer skin layer and an outer intermediate, or tie, layer disposed between the core layer and the outer skin layer, with the outer skin layer made of a blend of semicrystalline polyamide and amorphous polyamide, the inner skin layer of the second BOPP film being laminated against the outer skin layer of the first BOPP film.

In accordance with a further embodiment, the substrate comprises a first BOPP film as indicated above, and a second multilayer BOPP film having at least a core layer, an inner skin layer, an outer skin layer and at least one intermediate layer disposed between the core layer and one between the inner skin layer and the outer skin layer, the intermediate layer being a barrier layer, with said inner layer of the second BOPP film being laminated against the outer skin layer of the first BOPP film. The barrier layer may be made of an ethylene vinyl alcohol based material, or a polyvinyl alcohol based material or the like.

According to another aspect, the invention relates to a packaging for food products, preferably of the stand-up pouch type and made with the above- mentioned substrate.

Advantageously the packaging comprises a flat bottom and a closure element at the top, the closure element being made of a plastic material. Preferably the closure element is made of polyethylene or polypropylene.

More preferably, the closure element is a zipper, a spout or a valve.

Still more preferably, the closure element is directly coupled, i.e. sealed with the body of the packaging, made of the above multilayer film.

More precisely, the closure element is directly coupled to the inner skin layer of the substrate, which is the inner skin of the (first) BOPP film as mentioned above.

The first BOPP film may have an inner skin layer made of at least 70% by weight of polypropylene based resins. Said resins comprise preferably propylene co- or terpolymer and a softener agent. The first BOPP film may also comprise an inner interlayer made of at least 45% by weight of a polypropylene. Such variant of the first film is suitable to be coupled with a closure element made of polypropylene.

In alternative, if the closure element is made of polyethylene, the first BOPP film may have an inner skin layer made of at least 40% by weight of a polyethylene and an inner interlayer made of at least 45% by weight of a polyethylene.

According to another aspect, the present invention also relates to the use of a bi-axially oriented polypropylene (BOPP) film as mentioned above for making a stand-up pouch. In particular, the BOPP film comprises a core layer, made of polypropylene-based material, having an outer face and an inner face, an inner intermediate layer, adjacent to the inner face of the core layer and made of a polypropylene-based material or of a polyethylene-based material, an inner skin layer, adjacent to the inner intermediate layer and made of a polyethylene-based material or of a polypropylene-based material. The BOPP film may also comprise an outer skin layer disposed at the outer face of the core layer.

According to a further aspect, the present invention also relates to a method for producing a packaging, preferably a stand-up pouch, starting from a BOPP film as mentioned above, and comprising the steps of handling the film so as to shape it into a packaging, and heat welding predetermined areas of the film so as to stabilize the obtained shape. The heat welding step is preferably performed by ultrasonic welding or digital welding.

Advantageously, the method also provides a step of sealing a closure element directly to the inner skin layer of the film, preferably through digital welding.

It should be noted that polyethylene or polyamide at the percentages according to this invention have been found to be fully compatible with the concept of material recycling.

ILLUSTRATION OF DESIGNS

These and other features of the present invention will become apparent from the following description of some embodiments provided by way of non- restrictive example, with reference to the accompanying drawings wherein:

- Fig. 1 is a perspective/front view of a packaging according to one embodiment described herein;

- Fig. 2 is a perspective/front view of a packaging according to another embodiment described herein;

- Fig. 3 and 4 are sectional view of a film for producing the packaging of Fig. 1 and 2 according to two embodiments.

To facilitate understanding, the same reference numbers have been used, where possible, to identify identical common elements in the figures. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

It will be now referred in detail to the possible embodiments of the invention, one or more examples of which are illustrated in the attached drawings. Each example is provided for illustration purpose and is not intended as a limitation of the invention. For example, one or more illustrated or described characteristics, as being part of an embodiment, can be varied or adapted to, or associated with, other embodiments to produce further embodiments. The invention is intended as comprising such possible modifications and variants.

Before describing the embodiments, it is also clarified that the present description is not limited to its application to the details of building and of disposition of the components as described in the following description using the attached drawings. The present description can include other embodiments and be realized or practiced in other various ways. Moreover, it is clarified that phraseology and terminology used here is for description purposes and shall not be considered as limiting.

The whole technical and scientific wording used hereinbefore in the following description has the same meaning as commonly understood by a person of ordinary skill in the technical field of the present invention, except if defined otherwise. Even if methods and materials which are equivalent to the ones described here can be used in practice or during trial tests, in the following the methods and materials are described as examples. In case of conflict the present application prevails, definitions included. The materials, methods and examples have purely illustrative purpose and shall not be intended as limitative. All the proportions expressed in percentages are referred to the weight of a specific compound with respect to the total weight of the composition (w/w or wt%), except if indicated otherwise.

All the ranges expressed in percentage indicated in the following are provided with the prevision that the sum with respect to the whole composition, or the whole material, is 100%, except if indicated otherwise.

Ranges which can be derived from the combination of two or more discrete values described are also included in the present description, except if indicated otherwise.

A package according to the present invention is illustrated in fig. 1, and indicated as a whole with reference number 10. The package 10 illustrated is of the stand-up pouch type, and preferably intended for use in the food sector, but it can be of different type, and can be used for containing different types of products, such as for examples soaps or detergents.

The package 10 comprises a body 11 made of a film that will be described more in detail in the following. The film comprises a heat sealable material at least at its internal surface, that is the surface of the film that is oriented inside the package 10.

Preferably the body 11 presents a top portion 12, which is substantially flat, and a bottom portion 13 on which the package 10 is destined to rest (as illustrated in fig. 1).

For this purpose, the bottom portion 13 presents a substantially planar surface lying essentially horizontally in use, and has a couple of bottom edges 13 A (only one of which can be seen in fig. 1) coupled to each other at both ends. For example, the bottom portion 13 is obtained, as already known, by means of a gusset bottom portion. The bottom portion 13 presents also two bottom welds 14, one at each bottom edge 13 A.

By welds it is intended, in the context of this description, parts of a film which are reciprocally united, or coupled, by sealing. In the context of the relevant technical field, sealing means reciprocally uniting two parts of a film (or of two films) while the material of the film is not totally molten (i.e. still in a semi crystalline state), but the molten proportion of the material is enough to enable the reciprocal join of two parts of film. The body 11 can be made of one foil of the film that is suitably folded and sealed, advantageously by heat welding of the films, in particular at edge portions of the film that, due to the folding, enter into reciprocal contact.

The body 11 of the package 10 preferably comprises two longitudinal welds 15, which extend from the bottom portion 13 to the top portion 12 of the body 11, and at least a top weld 16 at the top portion 12, advantageously at the top edge 12A of the top portion 12.

It is noted that such top weld 16 is optional. When it is provided, it is possible to provide that the body 11 comprises an opening member (not illustrated in fig. 1) suitable to make it easier to open the top end of the package 10. Such opening member may be, for example, a weakened line suitable to be teared up by hand.

Preferably the package 10 also comprises a closure member 17 of the openable type. With openable type it is intended that the closure member can be successively open and closed at more occasions in the time. In the embodiment of fig. 1 the closure member 17 is a zipper.

The zipper 17 is coupled to the body 11 of the package 10 by means of heat welding at the internal surfaces of the foils of film material, where the heat sealable material is provided. It is preferable to provide that the closure member 17 is made of plastic material, more preferably of polyolefin, even more preferably of polyethylene or polypropylene.

In case the package 10 also comprises the opening member, the latter is positioned above the closure member 17, i.e. between the closure member 17 and the top weld 16 at the top edge 12A of the package 10.

In fig. 2 it is illustrated a second embodiment of the package of the invention. The parts in common with the first embodiment will not be described again, for sake of simplicity, but will be referred to with the same reference number with respect to fig. 1, to which 10 is added.

The package 20 according to the second embodiment mainly differs from the package 10 according to the first embodiment in that the closure member 27 is a spout. The spout 27 is coupled to the body 21 of the package 20 by welding, preferably at the top edge 22 A of the top portion 22.

Advantageously, the spout 27 comprises a closure cap 27A, for example of the screw cap type, which makes it of the openable type, as mentioned above. The spout 27 is also preferably made of a plastic material, more preferably of polyolefin, even more preferably of polyethylene or polypropylene.

The package 20 of the second embodiment also differs from the package 10 of the first embodiment in that the body 21 has a gusset bottom portion 23 but also gusset lateral portions 25 A. This conformation implies that the body 21 comprises two couples of lateral welds 25, and two top edges 22A which each comprise a respective top weld 26 (fig. 2).

It is noted that the closure cap of the package according to the second embodiment may be provided on the package according to the first embodiment and, vice versa, the zipper of the package of the first embodiment may be provided on the package according to the second embodiment.

Moreover, it is specified that the kind of openable closure element to be applied to the package according to the invention is not limited to zippers or spouts, but may be of any other type suitable to be applied to a package, for example valves or the like.

Whatever the kind of closure element being used, it is advantageously made of plastic material, preferably of polyolefin, more preferably of polyethylene or polypropylene.

Also, the type of package shall not be intended to be limited to the two examples provided above, but it can be of any kind, preferably of the stand-up pouch type. The package may be produced by any kind of known methods and/or any kind of known apparatus.

As mentioned above, the welds 14, 15, 16, 24, 25, 26 of the package 10, 20 are obtained by sealing, in particular by heat sealing. The heat sealing is applied to pre-determined portions of the film based on the geometry and dimensions of the package to be obtained.

Heat sealing can be carried out through various alternative techniques or devices, such as for example hot bar sealers, continuous heat sealers, impulse heat sealers, hot melt adhesives, hot wire sealing, induction sealing, induction welding heat sealing, ultrasonic welding or digital welding.

Among these alternatives, ultrasonic welding is advantageous, as it is a reliable and economic alternative for typical thermal processes that ensures tight weld seals despite product contamination, repeatable and analyzable weld processes, the saving of packaging material due to smaller sealing lines, and increased OEE. Ultrasonic welding is particularly well suited for packaging processes with high production rate equipments and applications with challenging process monitoring and validation requirements.

Equal to thermal processes, ultrasonic welding also generates material melts to achieve molecular bonding of the layers. The main difference is that heat is generated internally in the packaging material itself rather than by conduction from the external layers to the inside sealing surfaces. During the ultrasonic welding process, mechanical vibrations are transferred into the packaging material, for example by a sonotrode. The deformation resulting from ultrasonic vibrations causes friction among the molecular chains of the surfaces of the layers of the packaging material.

Focusing the energy by means of tool design or component-integrated energy directors causes the material to melt in pre-determined locations. The initial melt increases the absorption of energy, which in turn leads to acceleration of melting. The cold ultrasonic tools quickly dissipate the generated heat so that the produced seal is very strong and stable, immediately after welding. Consequently, thermal loads affecting the packaging materials and the packed products are very low.

Another heat sealing technique that is advantageous is digital welding. Such technique is based on a heat transfer, but the device, in particular the sealing member (for example, jaws) is heated by a plurality of circuits, so it allows to control different temperatures in different parts of the sealing member.

This entails the advantage of a better control of energy consumption. It has also been observed that the stability of temperature is increased when used in a large number of sealing cycles. This peculiarity gives benefits to all kind of sealing processes, in particular for producing stand-up pouches.

In particular, digital welding is well suited for sealing the closure member, especially when this latter is a spout. Higher temperatures can be applied locally in the closure member sealing zone, improving the seal strength of this area which is the most problematic for seal integrity.

The package according to the invention is made of a multilayer film that has been studied and developed by the Applicant in order to overcome the drawbacks of the prior art.

Fig. 3 illustrates a first embodiment of the multilayer film 100. The multilayer film 100 comprises a core layer 101 having an outer face 101 A and an inner face 10 IB, and made of a material based on polypropylene. With inner face and outer face, it is here intended the face of the film that will be oriented towards the inside and the outside of the package, respectively.

On the inner face 10 IB of the core layer 101 an inner intermediate layer 102, or inner interlayer, is applied which is made of a polyethylene-based or polypropylene-based material. The inner interlayer 102 is provided to allow to apply an inner skin layer to the core layer 101.

On the inner interlayer 102 the inner skin layer 103 is applied, made of a polyethylene-based or polypropylene-based material that is heat sealable. Preferably, the material of the inner skin 103 has a seal initiation temperature which is lower than the softening point of the other layers of the multilayer film 100.

It is to be precised that, in the present application, with seal initiation temperature it is intended the lowest temperature at which a certain seal strength is accomplished, usually set to 1.5 N/25mm seal width. Sealing temperature relates to the temperatures of the sealing jaws that perform the sealing of the film. Moreover, as previously mentioned, sealed is to be construed as joined while the material is still in a semi-crystalline state. With softening point, it is intended the temperature at which the film starts to shrink, and the seals to crumple.

By providing a multilayer film 100 the layers of which are all made of a material that is based on polypropylene or polyethylene, the Applicant provides a film that is of the mono material type, as it is made of layers of polyolefin-based materials.

This makes the multilayer film 100 of the invention easy and inexpensive to be recycled for further uses after the package according to the invention is discarded. In this way, also known as material recycling, the packages made from such multilayer films can be recycled as plastic material by cutting, washing, eventually filtrating, melting and re-pelletizing rather than through pyrolysis, cracking of the pyrolysis oils after complete de-chlorification (for even traces of chlorine corrode the pyrolysis and cracker equipments), and separating and purifying products coming from the cracker, and subsequent polymerization of those monomers, this process being known as chemical recycling.

Advantageously, the multilayer film 100 also comprises an outer skin layer 104 applied on the outer face 101 A of the core layer 101. The outer skin layer 104 is made of a polypropylene-based material, which is preferably treated in order to increase its ability to be printed and laminated. It is to be observed that the inner interlayer 102 and the inner skin layer 103 are not treated.

It is noted that at least the inner skin layer 103 is made of a heat sealable material, but advantageously the outer skin layer 104 can also be made of a heat sealable material.

In a first variant of the first embodiment, the inner interlayer 102 and the inner skin 103 are both made of a polypropylene-based material. Doing so, the film is easier to be recycled, and provides polypropylene-based recycled material.

In a second variant of the first embodiment, the inner interlayer 102 and the inner skin 103 are both made of a polyethylene-based material.

This solution provides a film that is more compatible with the closure elements made of polyethylene, and which are to be welded on such inner skin layer 103, as mentioned above.

The multilayer film 100 may have an overall thickness SO comprised between 10 pm and 120 pm, more preferably between 30 pm and 100 pm. The overall thickness SO of the film 100 is given by the sum of the thicknesses S 1, S2, S3, S4 of the core layer 101, the inner interlayer 102, the inner skin layer 103 and the outer skin layer 104, if this latter is present.

Preferably the thickness of the inner skin layer 103 and the inner interlayer 102, taken together, amounts to at least 10% of the overall thickness of the multilayer film. Otherwise said, the sum of the thickness S2 of the inner interlayer 102 and the thickness S3 of the inner skin 103 amounts to at least 10% of the overall thickness SO of the multilayer film 100 (S2 + S3 > 10% SO).

More preferably the sum of the thicknesses S2, S3 of the inner interlayer 102 and skin layer 103 is between 10% and 30 % of the thickness SO, even more preferably between 12% and 25% of the overall thickness SO (12%S0 < S2+S3 < 25%S0). In particular the thickness S2 of the inner interlayer 102 amounts preferably to at least 9% of the overall thickness SO of the film 100, and the thickness S3 of the inner skin layer 103 preferably amounts to at least 1% of the thickness SO of the film 100.

In accordance with embodiments of the invention, the thickness S2 of the interlayer is comprised between 9% and 20%, preferably between 10% and 18% of the overall thickness SO of the film 100. Still according to embodiments, the thickness S3 of the inner skin layer 103 is comprised between 1% and 6%, preferably between 1,5% and 5% of the overall thickness SO of the film.

The thickness S4 of the outer skin layer 104 amounts preferably to 0,5 -2,5% the thickness SO of the film 100. It is preferable also that the inner skin layer 103 be thicker than the outer skin surface 104.

Doing so, sealability of the film 100 is increased, in particular when the material of the inner skin layer 103 has a seal initiation temperature lower than the softening point of the other layers 101, 102, 104.

Advantageously the film 100 is a bi-axially oriented polypropylene film, so that it has an increased rigidity with respect to other known materials which are not bi-axially oriented, such as for example cast polypropylene or the like.

Given that the multilayer film 100 is more rigid it is possible to provide a lower quantity of film, with respect to non bi-axially oriented films, to obtain a package which can stand up by itself. In particular it is possible to provide films having a lower thickness with respect to the films of the prior art.

According to embodiments of the invention, one or more of the layers 101, 102, 103, 104 that make the multilayer film 100 include additives. For example, the core layer 101 comprises one or more between a slip agent, an antistatic agent and a softener agent, this latter being suitable to modulate the crystallinity of the core layer 101. Such modulation of crystallinity supports the formation of strong and leak-proof seals (or welded edges) by facilitating the core to yield to any misalignment between the two surfaces to be sealed against each other or between the sealing tools and film surface.

Preferably the core layer 101 is mainly made of a polypropylene homopolymer. More preferably the core layer comprises 75-94 wt% of polypropylene, 0.05-0.2 wt% of a first slip agent, optionally up to 0.15 wt% of a second slip agent, 0.02-0.15 wt% of a anti-static agent and 5-20 wt% of a polypropylene-based softener agent, more preferred 82-92 wt% of polypropylene, 0.08-0.18 wt% of a first slip agent, up to 1 wt% of a second slip agent, 0.02-0.12 wt% of an anti-static agent and 5-15 wt% of a polypropylene- based softener agent.

Preferably, the inner interlayer comprises either propylene ethylene copolymers, in its polypropylene-based material variant, or of polyethylene copolymers with hexene- 1, butene- 1, or octene-1 in its polyethylene-based material variant.

Advantageously, in the polypropylene-based variant, the inner interlayer 102 comprises 25-55 wt% of a propylene co- or terpolymer, optionally comprising antiblocking agent, 40-70 wt% of a polypropylene-based softener agent and optionally up to 20% of a propylene homopolymer and 0.1-2 wt% of a first slip agent, 0-3 wt% of a second slip agent, 0.1- 1.2 wt% of an anti-static agent, more advantageously 30-50 wt% of a propylene co- or terpolymer, optionally comprising antiblocking agent, 50-70 wt% of a polypropylene-based softener agent, and optionally up to 12% of a propylene homopolymer and 0.1-2 wt% of a first slip agent, 0-3 wt% of a second slip agent, 0.1-1.2 wt% of an anti-static agent.

Advantageously, in the polyethylene-based version the inner interlayer 102 preferably comprises 20 to 60, preferably 20-40 wt% of a polypropylene terpolymer, optionally comprising antiblocking agent, and 40 to 80, preferably 60-80 wt% of polyethylene copolymer containing hexene- 1, butene- 1, or octene- 1 as comonomer, with a density of less than 0.94, preferably below 0.93.

The inner skin layer 103 preferably comprises at least one antiblocking agent of the mineral and/or organic type, and a heat-sealing enhancer, suitable to lower the seal initiation temperature of polypropylene or polyethylene blend.

Preferably, in the polypropylene-based variant, the inner skin layer 103 comprises 35-65 wt% preferably 40 to 60% of a propylene terpolymer, 30-50 wt%, preferably 35-45 wt% of a polypropylene-based softener agent, optionally 10-25 wt% of a heat-sealing enhancer based on olefinic resin, further 0.20 to 1.2% of an organic antiblocking agent, and 0.20 to 1.2% of a mineral antiblocking agent, preferably 20-30 wt% of a propylene terpolymer comprising antiblocking agent, 30-40 wt% of a polypropylene-based softener agent, 15-25 wt% of a heat-sealing enhancer based on olefmic resin, 10-30 wt% of a polypropylene co- or terpolymer, further 0.25 to 1% of an organic antiblocking agent, and 0.25 to 1% of a mineral antiblocking agent. The antiblocking agents may be provided as a propylene co- or terpolymer based masterbatch.

In the polyethylene-based version, instead, the inner skin layer 103 preferably comprises 45-70, preferably 50-65 wt% of polyethylene copolymer containing hexene-1, butene-1, or octene-1 as comonomer, 15-30 wt% of a heat-sealing enhancer based on olefmic resin, 10-35 wt% of a polypropylene co- or terpolymer, further 0.2 to 1.2% of an organic antiblocking agent, and 0.2 to 1.2% of a mineral antiblocking agent, preferentially 52-62 wt% of polyethylene copolymer containing hexene- 1 as comonomer, 18-28 wt% of a heat-sealing enhancer based on olefmic resin, 10-30 wt% of a polypropylene co- or terpolymer, further 0.25 to 1% of an organic antiblocking agent, and 0.25 to 1% of a mineral antiblocking agent. Preferred are variants comprising polyethylene with a density of less than 0.94, preferably of less than 0.93, most preferred a metallocene polyethylene of a density of less than 0.93.

It is possible to provide that the outer skin layer 104 comprises 99.65-99.85 wt% of a propylene co- or terpolymer, and 0.15 to 0.35 wt% of an organic or an inorganic antiblocking agent or combinations thereof, preferably provided as a propylene co- or terpolymer based masterbatch.

In fig. 4 is illustrated a multilayer film according to a second embodiment of the invention. The features in common with the multilayer film of the first embodiment will not be described, for simplicity, and will be referred to with the same reference numbers, but to which 100 is added.

The multilayer film 200 of the second embodiment also comprises, between the outer face 201 A of the core layer 201 and the outer skin layer 204 an outer intermediate layer 205, or outer interlayer, made of a polypropylene-based material.

Otherwise said, the outer interlayer 205 is directly applied on the outer face 201 A of the core layer 201, and the outer skin layer 204 is directly applied on the outer interlayer 205.

The features described for the multilayer film 100 according to the first embodiment are maintained for the multilayer film 200 according to the second embodiment.

It is to be mentioned that outer interlayer 205 has a thickness S5 which amounts to 2, 5-7, 5% of the overall thickness SO of the multilayer film 200. It results that the sum of the thicknesses S4, S5 of the outer skin layer 204 and of the outer interlayer 205 amounts to 3-10% of the overall thickness SO of the film 200 (3%S0 < S4+S5 < 10%S0).

Advantageously the sum of the thicknesses S2, S3 of the inner interlayer 202 and of the inner skin layer 203 is greater than the sum of the thicknesses S4, S5 of the outer interlayer 205 and of the outer skin layer 204 (S2+S3 > S4+S5).

Preferably the outer interlayer 205 is made of a polypropylene homopolymer.

Fig. 4 is also suitable to illustrate a multilayer film according to a third embodiment of the invention.

The multilayer film 200 of the third embodiment also comprises, between the outer face 201 A of the core layer 201 and the outer skin layer 204, an outer intermediate layer 205, or outer interlayer, here now made mainly of a polypropylene grafted with maleic anhydride, optionally blended with a propylene homopolymer.

Otherwise said, the outer interlayer 205 is directly applied on the outer face 201 A of the core layer 201, and the outer skin layer 204 is directly applied on the outer interlayer 205.

In this third embodiment the outer skin layer comprises a blend of an amorphous polyamide and a semi-crystalline polyamide. The outer skin layer of this composition provides an improved gas, in particular oxygen barrier, and in additional embodiments, can be coated with a thin metal or metal oxide layer, for example by means of a vacuum deposition process. Such combinations of interlayer and skin layer as in this third embodiment are of the type described in EP 3463876.

The other features described for the multilayer film 100 according to the first embodiment are maintained for the multilayer film 200 according to the third embodiment.

It is to be mentioned that outer interlayer 205 has a thickness S5 which amounts to 2, 5-7, 5% of the overall thickness SO of the multilayer film 200. It results that the sum of the thicknesses S4, S5 of the outer skin layer 204 and of the outer interlayer 205 amounts to 3-10% of the overall thickness SO of the film 200 (3%S0 < S4+S5 < 10%S0).

Advantageously the sum of the thicknesses S2, S3 of the inner interlayer 202 and of the inner skin layer 203 is greater than the sum of the thicknesses S4, S5 of the outer interlayer 205 and of the outer skin layer 204 (S2+S3 > S4+S5).

Advantageously, the outer skin layer 204 is treated so that adhesion of the deposited metal or metal oxide layer and its barrier performance is improved.

In other embodiments, any of the three embodiments of a film of the present invention may have a core layer (101, 201) that contains a plurality of voids, or cavities, within the thermoplastic matrix material thereof Such voids, or cavities, are also denominated vacuoles. The presence of vacuoles enables to have an opaque film, due to scattering of light, and which could also have an aesthetic pearl effect. It also leads to a film having an enlarged thickness, with respect to a non-voided film made with the same raw material.

The vacuoles are preferably made in a thermoplastic matrix material of the polyolefinic type, more preferably in a polypropylene homopolymer matrix material.

In order to obtain a voided core layer usually polymeric and/or inorganic particles, so-called void-initiating particles, have been added to the thermoplastic matrix material. These particles are preferably incompatible with said matrix material at the temperature of monoaxial or biaxial orientation. Suitable polymeric and inorganic particles encompass those being made of polybutylene terephthalate, nylon, solid or hollow preformed glass spheres, metal beads or spheres, ceramic spheres, calcium carbonate and mixtures thereof. It is preferred that the average diameter of these void initiating particles is in the range from about 0.1 to about 10 pm. Usually, particle sizes in the range from 2 to 4 pm furnish satisfactory results. Calcium carbonate particles are preferred as a void- initiating particles. Upon orientation of a co-extruded multilayered film the core layer will become a void-filled matrix.

In addition to the above particles, pigment particles may also be added to the thermoplastic material, so as to confer a predetermined color to the film. Usually, particle size of the pigments range from about 0.01pm to about 1pm, preferably from O.OImhi to 0.5mhi. It also possible to provide only pigment particles in the thermoplastic material matrix, so as to obtain a film that is pigmented but not voided.

In other additional embodiments, any of the three embodiments of a film according to this invention described before may be laminated with its outer skin layer against a coextmded transparent second biaxially oriented polypropylene (BOPP) film “A” by either adhesive (using a water or solvent based dispersion of an adhesive) or extrusion lamination (using a polyethylene melt extruded through a flat die as the adhesive) to form the substrate for making the pouch. In all such embodiments one or both the laminate members of the substrate may be printed for decoration or to provide information for the consumer, either in direct print mode or in reverse print mode.

In such additional embodiments the second transparent BOPP film A comprises

- a core layer, predominantly made of propylene homopolymer,

- an inner skin layer the outer surface of which is in correspondence with the inner surface of the core layer, predominantly made of a propylene co-, ter- or homopolymer, treated to facilitate printing and/or adhesion to the adhesive,

- optionally an inner interlayer between the core and the inner skin layers, predominantly made of propylene homopolymer,

- an outer skin layer with its inner surface in correspondence with the outer surface of the core, with its outer surface being the outer surface of the package, predominantly made of propylene homopolymer,

- optionally an outer interlayer between the core and the inner skin layers, predominantly made of propylene homopolymer.

With outer surface and inner surface, hereinbelow it is intended the surface of a layer which is oriented towards the outside of the package and the inside of the package to be made with the film, respectively.

With predominantly made of, in the context of these additional embodiments, it is intended made of at least 80%, preferably more than 90% in weight, unless diversely indicated.

In other embodiments of laminated transparent BOPP film A, the outer skin layer is made of at least 90%, preferably more than 95% by weight, of a blend of an amorphous polyamide and a semi-crystalline polyamide, while the outer interlayer between the core and the outer skin layer of film A is predominantly made of polypropylene grafted with maleic anhydride, optionally blended with a propylene homopolymer. The outer skin layer in this embodiment is particularly advantageous in the process of manufacturing the stand-up pouch in that it tends significantly less to stick to the sealing jaws that provide the heat to form the numerous sealed edges that are required to manufacture a gas and leak -proof Such combinations of interlayer and skin layer as in this third embodiment are of the type described in EP 3463876.

In a further embodiment of laminated transparent BOPP film A, at least one of the layers of such film is a barrier layer. More precisely, the BOPP film A can comprise a core layer with a polypropylene homopolymer base, a first and a second outer skin layer based on polypropylene copolymer, terpolymer and/or homopolymer, the barrier layer being positioned between the core layer and one of the outer skin layers, like the intermediate layers of the previous embodiments.

The barrier layer may be made of any suitable material such as, for example, ethylene vinyl alcohol based material, polyvinyl alcohol based material or the like.

Advantageously an adhesive layer is also provided to couple the barrier layer with a respective adjoining layer, i.e. the core layer and an outer skin layer.

It is possible to provide that the core layer of the second multilayer film A is voided, as explained above for the first multilayer film 100, 200. In particular, the core of the first film 100, 200 and/or the core of the second film A may be voided, and possible contain pigments.

Advantageous embodiments of the packaging comprise a body made with the above-mentioned substrate comprising the film according to the invention.

The multilayer film 100, 200 described above provides good sealing performance combined with high stiffness which makes it particularly suitable for stand-up pouches and bags. Such film is suitable to be used for making packages for the food industry, such as for example pet food, cereals, dried fruit or coffee. Provided with sealed-in zippers such pouches or bags can be reclosed after partial withdrawing their contents. Provided with sealed-in reclosable spouts or snouts such pouches can be used as packages for liquids i.e. in the beverage and detergent industries.

The film has the further advantages of controlled slip properties and a polyethylene compatible inner skin layer. Another advantage of the above film is that it is a mono material film, as it is a polypropylene-based laminate, optionally containing layers of polyethylene-based material. Such features make it highly recyclable, and suitable for the so-called circular economy, uncompromised by the presence of the polyethylene-based material.

Contemporaneously the film has a simplified structure with respect to known multimaterial films, and has an improved water vapour barrier when compared to blown polyethylene and cast polypropylene.

The invention will now be described with reference to some specific examples employing the following materials.

MATERIALS

LyondellBasell Adsyl5C99F (former name Adsyl 7623XCP) is a polyolefin terpolymer C2C3C4 containing antiblocking additives;

Ineos KS 384 is a polypropylene terpolymer containing 0.9-1.1 g/kg of silica as antiblocking agent, with respect to the total weight of the material;

LyondellBasell Adsyl5C39F is a polyolefin terpolymer C2C3C4 containing antiblocking additives;

EDHAF EDF ABO50CP is a masterbatch comprising co- or terpolymer of polypropylene as a carrier resin, and 4.5-5.5 wt% of PMMA particles having a diameter of 4 pm, as an antiblocking agent;

LyondellBasell - A. Schulman ABVT22SC is an organic antiblocking masterbatch containing 4.6-5.4 wt% of a polymeric antiblocking additive;

EDHAF EDF SAF 30 is a masterbatch based on a polypropylene homopolymer as a carrier, containing Erucamide as slip agent, ETA, PM REF NR 39090 and GMS, PM REF NR 56486, E471 as antistatic agents;

LyondellBasell - A. Schulman ASPERA 2358 is a slip and antistatic masterbatch on a polypropylene homopolymer film grade;

Ampacet ANSLIP 12 400140 is a slip and antistatic masterbatch on a polypropylene homopolymer film grade;

EDHAF EDF SLF60 is a masterbatch comprising a polypropylene homopolymer as a carrier, and Emcamide as slip agent;

Constab SL05035 is a slip masterbatch comprising Emcamide as slip agent in a polypropylene homopolymer;

LyondellBasell - A. Schulman SPER 6 is a slip masterbatch comprising Emcamide as slip agent in a polypropylene homopolymer;

EDHAF EDF ABS50CP is an antiblocking masterbatch comprising 4.5 -5.5 wt% of 4 pm diameter silica particles as antiblocking agent;

LyondellBasell - A. Schulman ABPP05SC is an antiblocking masterbatch containing 4.6-5.4 wt% of silica particles in a polypropylene terpolymer;

Sabic PP521P is a polypropylene homopolymer;

Ineos 100GD02 is a polypropylene homopolymer;

ExxonMobil Vistamaxx3980FL is a propylene-based elastomer comprising semicrystalline copolymers of propylene and ethylene;

Mitsui XM7070 is a ex-olefin copolymer resin based on propylene and having a melting point of 70-80°C;

Ineos PF6130LA is a polyethylene copolymer containing hexene- 1 as comonomer produced with metallocene catalyst.

EXAMPLE 1

Composition

- outer skin layer: thickness 1.0 pm; Composition: Adsyl5C99F 97 wt% ABO50CP 3 wt%;

- outer interlayer: thickness 2.5-3.0 pm; Composition: PP521P 100%;

- core layer: thickness 36-37.5 pm; Composition: 100GD02 87 wt% SAF 30

1.5 wt% SLF60 1.5 wt% Vistamaxx3980FL 10 wt%;

- inner interlayer: thickness 7.5-8.0 pm; Composition: Adsyl5C99F 40% Vistamaxx3980FL 60%;

- inner skin layer: thickness 1.5-2.0 pm; Composition: Adsyl5C99F 25% Vistamaxx3980FL 35% XM707020% ABO50CP 10% ABS50CP 10%.

The overall film thickness was 50 pm.

In the core layer, Vistamaxx3980FL is used to make the material softer, it provides a good seal integrity and hot tack.

In the inner interlayer and the inner skin layer, Vistamaxx3980FL is used to have a tacky material, and XM7070 is used to have a low minimum sealing temperature (only in the inner skin layer). Both layers are soft and with a reduced melting temperature to have a good seal integrity, the thickness and its composition support also an increased sealing strength and hot tack.

EXAMPLE 2 Composition

- outer skin layer: thickness 1.0 pm; Composition: Adsyl5C99F 97 wt% ABO50CP 3 wt%;

- outer interlayer: thickness 2.5-3.0 pm; Composition: PP521P 100%;

- core layer: thickness 54.0-56.0 pm; Composition: 100GD02 87 wt% SAF 30 1.5 wt% SLF60 1.5 wt% Vistamaxx3980FL 10 wt%;

- inner interlayer: thickness 9.0-10.0 pm; Composition: Adsyl5C99F 40% Vistamaxx3980FL 60%;

- inner skin layer: thickness 1.5-2.0 pm; Composition: Adsyl5C99F 25% Vistamaxx3980FL 35% XM707020% ABO50CP 10% ABS50CP 10%.

The overall film thickness was 70 pm.

EXAMPLE 3 Composition

- outer skin layer: thickness 1.0 pm; Composition: Adsyl5C99F 97 wt% ABO50CP 3 wt%;

- outer interlayer: thickness 2.5-3.0 pm; Composition: PP521P 100%;

- core layer: thickness 36-37.5 pm; Composition: 100GD02 87 wt% SAF 30

1.5 wt% SLF60 1.5 wt% Vistamaxx3980FL 10 wt%;

- inner interlayer: thickness 7.5-8.0 pm; Composition: Adsyl5C99F 30% PF6130LA 70%;

- inner skin layer: thickness 1.5-2.0 pm; Composition: PF6130LA 57% XM7070 23% ABO50CP 10%ABS50CP 10%.

The overall film thickness was 50 pm.

As PF6130LA is a metallocene polyethylene, it is quite compatible with polypropylene and polyethylene used for the closure elements such as, for example, zippers, spouts, valves or the like.

EXAMPLE 4 Composition

- outer skin layer: thickness 1.0 pm; Composition: Adsyl5C99F 97 wt% ABO50CP 3 wt%;

- outer interlayer: thickness 2.5-3.0 mhi; Composition: PP521P 100%;

- core layer: thickness 54.0-56.0 pm; Composition: 100GD02 87 wt% SAF 30 1.5 wt% SLF60 1.5 wt% Vistamaxx3980FL 10 wt%; - inner interlayer: thickness 9.0-10.0 pm; Composition: Adsyl5C99F 30%

PF6130LA 70%;

- inner skin layer: thickness 1.5-2.0 pm; Composition: PF6130LA 57% XM7070 23% ABO50CP 10%ABS50CP 10%.

The overall film thickness was 70 pm. EXAMPLE 5

The film according to EXAMPLE 4 has been extrusion laminated against a 15 pm thick BOPP film with an inner corona treated skin made of a propylene terpolymer and an outer skin made of propylene homopolymer. The overall thickness of the laminate has been 90 pm. It is clear that modifications and/or additions of parts may be made to the packaging and the multilayer film as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of packaging or film, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

In the following claims, the references in brackets have the only scope of facilitating reading and shall not be considered as limitative factors as far as the scope of protection intended in the specific claims is concerned.