Packaging film

Abstract

The present invention relates to a sealable paper-based film comprising: a paper layer; a first adhesive layer comprising a water sensitive adhesive; a first polymer film and a first barrier layer, wherein said first barrier layer is in direct contact with said first polymer film; a second adhesive layer comprising a water stable adhesive; a second polymer film and a second barrier layer; and a continuous or discontinuous sealing layer; wherein said first polymer film is connected to said paper layer via said first adhesive layer; and said first barrier layer is connected to said second polymer film via said second adhesive layer, to a process for the preparation of the sealable paper- based film, to uses of the sealable paper-based film, to a package or a sealed package comprising the sealable paper-based film, and to processes for the preparation of the package or sealed package.

Description

[0001] PACKAGING FILM

[0002] Field of the invention

[0003] The present invention relates to sealable packaging films and processes for their production.

[0004] Background of the invention

[0005] Packaging films, in particular packaging films for foodstuffs, need to be both durable and have high barrier properties, e.g. against water, water vapour and / or oxygen. This is to ensure that the product to be packaged is protected during transit, storage and retail. The amount of water, water vapour and / or oxygen that penetrates through the film has to be minimised so the packaged product does not deteriorate prior to use (i.e. it has an acceptable shelf-life). Plastic mono- or multi-material films or aluminium foil have typically been employed to achieve these goals.

[0006] However, there is increasing consumer and regulatory pressure to offer packaging that is more sustainable and environmentally-friendly. In particular, there is a desire to expand the use of paper-based packaging such that the packaging can be more easily recycled after use in the existing paper recycling infrastructure. However, to date, the manufacture of paper-based packaging films having the necessary high barrier properties has been challenging.

[0007] Accordingly, there exists a need to provide paper-based packaging films that have high barrier properties, and therefore a long shelf-life for the product contained within, which are also easily recycled after use.

[0008] Summary of the invention

[0009] Viewed from a first aspect, the present invention relates to a sealable paperbased film comprising: a paper layer; a first adhesive layer comprising a water sensitive adhesive; a first polymer film and a first barrier layer, wherein said first barrier layer is in direct contact with said first polymer film; a second adhesive layer comprising a water stable adhesive; a second polymer film and a second barrier layer; and a continuous or discontinuous sealing layer; wherein said first polymer film is connected to said paper layer via said first adhesive layer; and said first barrier layer is connected to said second polymer film via said second adhesive layer.

[0010] Viewed from a further aspect, the present invention relates to a process for preparing a sealable paper-based film, the process comprising the steps of:

[0011] (i) laminating a first polymer film onto a paper layer using a first adhesive layer, wherein said first adhesive layer comprises a water sensitive adhesive;

[0012] (ii) applying a first barrier layer directly onto said first polymer film;

[0013] (iii) optionally applying a first protective varnish layer onto said first barrier layer;

[0014] (iv) laminating a second polymer film onto said first barrier layer or said first protective varnish layer using a second adhesive layer, wherein said second adhesive layer comprises a water stable adhesive;

[0015] (v) applying a second barrier layer onto said second polymer film to give a precursor film;

[0016] (vi) optionally applying a second protective varnish layer onto said second barrier layer;

[0017] (vii) optionally applying one or more ink layers onto said paper layer to produce the desired printed design; and

[0018] (viii) either (a) applying a sealing layer which is a heat sealable layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires heat seal functionality; or (b) applying a release lacquer layer onto said paper layer or said ink layer and applying a sealing layer which is a cold seal adhesive layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires cold seal functionality.

[0019] Viewed from a further aspect, the present invention relates to a sealable paperbased film prepared according to the process as hereinbefore described.

[0020] Viewed from a further aspect, the present invention relates to a package comprising a sealable paper-based film as hereinbefore described.

[0021] Viewed from a further aspect, the present invention relates to a process for preparing a package, the process comprising the steps of:

[0022] (i) preparing a sealable paper-based film according to the process as hereinbefore described; and

[0023] (ii) forming said sealable paper-based film into a package.

[0024] Viewed from a further aspect, the present invention relates to a product enclosed by a sealable paper-based film as hereinbefore described.

[0025] Viewed from a further aspect, the present invention relates to a process for enclosing a product, the process comprising the steps of:

[0026] (i) wrapping a product in a sealable paper-based film as hereinbefore described; and

[0027] (ii) sealing said sealable paper-based film around said product to form a sealed package.

[0028] Viewed from a further aspect, the present invention relates to a package or a sealed package made according to a process as hereinbefore described.

[0029] Viewed from a further aspect, the present invention relates to the use of a sealable paper-based film as hereinbefore described to form a package and / or to enclose a product.

[0030] Brief description of the drawings Additional features and advantages of the present invention are described in, and will be apparent from, the description of the presently preferred embodiments which are set out below with reference to the drawings in which:

[0031] Figure 1 is a diagram of a sealable paper-based film according to the present invention. The depicted sealable paper-based film comprises a paper layer 100, a first adhesive layer 200, a first polymer film 301 and a first barrier layer 302, a second adhesive layer 400, a second polymer film 501 and a second barrier layer 502, and a sealing layer 600. The sealing layer may be continuous or discontinuous, but the one depicted in Figure 1 is a discontinuous sealing layer.

[0032] Detailed description of the invention

[0033] As used herein, the phrase "layer" refers to a building block of the sealable paper-based films of the present invention. A layer is a structure of a single material type or a homogenous blend of materials. A layer has a relatively insignificant thickness as compared to its respective length and width.

[0034] As used herein, the phrase "is connected to" means that the layer in question is near the other layer, with or without any intervening material.

[0035] As used herein, the phrase "in direct contact with" means that the layers in question are in contact with each other, without any intervening material.

[0036] As used herein, the phrase "fibre" means a cellulosic fibre, which is generally extracted from plants, seeds or trees; such fibres contain mainly cellulose, hemicellulose and lignin, if the latter is not entirely removed in the pulping and bleaching processes.

[0037] As used herein, the phrase "uncoated" in the context of a paper layer means that the paper layer is untreated with formulated coating colours, e.g. that no pigment(s), starch or binder materials have been applied to any of the surfaces thereof.

[0038] As used herein, the phrase "coated" in the context of a paper layer means that the paper layer is treated with at least one formulated coating colour, e.g. pigment(s), starch and / or binder materials have been applied on at least one of the surfaces thereof.

[0039] As used herein, the phrase "water sensitive adhesive" means a type of adhesive that has an affinity for water. The bond between two layers to which a water sensitive adhesive has been applied will weaken in the presence of water as the bonds of the adhesive (e.g. hydrogen bonds) themselves weaken or break, such that when a peel test is carried out after sample submersion in water at temperature of <40°C for 10 to 20 minutes, the bonding strength is reduced by >50%, preferably >75% and most preferably >90%, against the reference bonding strength determined according to the ASTM F904 standard, updated July 18, 2022.

[0040] A "water stable adhesive" should achieve an initial bond strength between the two layers to which it has been applied of at least 1N / 15 mm, preferably at least 1.5N / 15 mm and more preferably above 2N / 15mm in a peel test carried out according to the ASTM F904 standard, updated July 18, 2022. Thus, as used herein, the phrase "water stable adhesive" means a type of adhesive that has little or no affinity for water and therefore maintains at least 90% of its initial strong bonding between the laminated layers, when the film is in the presence of water at temperature of 40°C for at least 10 days.

[0041] As used herein, the phrase "heat seal" is a material(s) with a thermoplastic surface that is able to form and seal a flexible package using heat application under pressure for a short duration of time, referred to as dwell time. Dwell time is the time the heating elements are in direct contact with the packaging material. Usually heating elements, such as clamps, plates, bars, etc. are used to apply heat in a specific contact area by applying pressure for a short duration of time to achieve desired bonding between two thermoplastic surfaces of a packaging material. The specific temperature, pressure and dwell time to achieve a desired seal strength according to ASTM F88, updated on August 3, 2023, are also dependent on other factors such as seal surface design, material and surface characteristics, contamination, etc. As used herein, the phrase "cold seal" is a water-based cohesive substance used to seal a variety of packaging materials. Cold seal is a type of self-seal adhesive and only requires pressure to achieve a desired bond to form and seal a flexible package. Cold seal does not require heat to create a bond between the surfaces of a material or between the surfaces of two materials. Cold seal adhesives seal only to themselves when these are coated onto substrates. The coated surfaces of the substrates have to be brought into contact with each other and are bonded together through pressure and not heat. Cold sealing is referred to as "self-seal" where the bond strength depends on the adhesive selection for the specific application.

[0042] Viewed from a first aspect, the present invention relates to a sealable paperbased film comprising: a paper layer; a first adhesive layer comprising water sensitive adhesive; a first polymer film and a first barrier layer, wherein said first barrier layer is in direct contact with said first polymer film; a second adhesive layer comprising a water stable adhesive; a second polymer film and a second barrier layer; and a continuous or discontinuous sealing layer; wherein said first polymer film is connected to said paper layer via said first adhesive layer; and said first barrier layer is connected to said second polymer film via said second adhesive layer.

[0043] In the sealable paper-based films of the present invention, the paper layer is any type of uncoated or coated paper, which comprises predominantly cellulose fibres.

[0044] In the sealable paper-based films of the present invention, the surface of the paper layer which is opposite the first adhesive layer may be modified with a coating colour layer. Preferably, the coating colour layer comprises starch, pigments and / or binders. In the sealable paper-based films of the present invention, the surface of the paper layer which is to be opposite the first adhesive layer may be modified with one or more ink layers to produce a desired printed design prior to lamination of the first polymer film. If a coating colour layer is present, the one or more ink layers may be present on the coating colour layer. In alternative sealable paper-based films of the present invention, the paper layer may be unprinted.

[0045] In the sealable paper-based films of the present invention, the paper layer may further comprise an inorganic filler. The inorganic filler may be selected from kaolinite, talc, mica, calcium carbonate, titanium dioxide, calcium sulphate dihydrate, and combinations thereof. The use of inorganic fillers aids the visual appearance and print quality of the paper layer, e.g. increased brightness and whiteness, reduced sheet porosity, improved smoothness, improved ink absorbency, increased sheet opacity etc.

[0046] In the sealable paper-based films of the present invention, the cellulose fibres of the paper layer are bleached or unbleached, or a blend thereof, preferably bleached. The bleached fibres may be produced using oxygen delignification followed by Elemental Chlorine Free (ECF) or Total Chlorine Free (TCF) methods. For ECF fibres, chlorine dioxide and hydrogen peroxide are the main bleaching agents, while for TCF fibres, hydrogen peroxide is the main bleaching agent.

[0047] In preferred sealable paper-based films of the present invention, the fibres of the paper layer are non-recycled fibres (i.e. virgin fibres). In alternative sealable paperbased films of the present invention, the fibres of the paper layer are recycled fibres. In further alternative sealable paper-based films of the present invention, the fibres of the paper layer are a blend of virgin and recycled fibres.

[0048] In the sealable paper-based films of the present invention, the fibres are woodbased fibres or non-wood-based fibres, or a blend thereof, preferably wood-based fibres.

[0049] Examples of types of packaging papers that may be used in the sealable paperbased films of the present invention are machine glazed (MG) or machine finished (MF) bleached and unbleached kraft grades, as well as coated-one-side bleached or unbleached papers (CIS).

[0050] In preferred sealable paper-based films of the present invention, the weight of the paper layer is in the range 40 to 125 gsm, preferably 40 to 70 gsm, most preferably 45 to 55 gsm. The use of a paper layer having a weight in these ranges ensures that the resultant film remains flexible.

[0051] The sealable paper-based films of the present invention are predominantly made of paper, meaning that they can easily be recycled in the existing recycling paper infrastructure. Thus, in preferred sealable paper-based films of the present invention, the weight of the paper layer is at least 80% based upon the total weight of the sealable paper-based film, preferably at least 85% based upon the total weight of the sealable paper-based film, more preferably at least 90% based upon the total weight of the sealable paper-based film, even more preferably at least 95% based upon the total weight of the sealable paper-based film. Where a coating colour layer is present on the paper layer, the weight of the paper layer also includes the weight of the coating colour layer.

[0052] In preferred sealable paper-based films of the present invention, the first polymer film comprises at least one oriented or unoriented polymer in a mono or multilayer structure. Preferably, the first polymer film comprises at least one polymer selected from low-density polyethylene, high-density polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene terephthalate, polyamide, ethylene vinyl alcohol, poly(vinyl alcohol), polylactic acid, or combinations thereof. More preferably, the first polymer film comprises polypropylene.

[0053] In preferred sealable paper-based films of the present invention, the surface of the first polymer film to which the first barrier layer is applied can be modified prior to the application of the first barrier layer in order to improve the deposition and adhesion of the first barrier layer. Preferred surface modification methods are corona, flame or plasma treatments. In preferred sealable paper-based films of the present invention, the first polymer film has a thickness of less than or equal to 6 microns, preferably less than 5 microns, more preferably less than 3 microns. At such low thicknesses, the first polymer film is able to provide a suitable surface to enable direct barrier layer deposition to enhance the barrier properties of the sealable paper-based film of the present invention, whilst ensuring that the sealable paper-based film is still predominantly fibre based.

[0054] In preferred sealable paper-based films of the present invention, the first polymer film has a thickness of more than or equal to 0.6 microns, preferably more than or equal to 1.5 microns, more preferably more than or equal to 2 microns.

[0055] In preferred sealable paper-based films of the present invention, the first polymer film has a thickness in the range 0.6 to 6 microns, preferably 1.5 to 4 microns, more preferably 2 to 3 microns.

[0056] In the sealable paper-based films of the present invention, the first adhesive layer comprises a water sensitive adhesive. In the paper recycling process, the presence of water causes the interlayer bonding strength of such adhesive to weaken thus enabling easier delamination and separation of the bonded paper layer from the polymer film, aiding the recyclability of the sealable paper-based film of the present invention. The paper layer will be rewetted and fibres separated in the conventional repulping process to form pulp, which can be used to make recycled paper or other fibre-based recycled products, such as moulded fibre packaging and inserts. The fibre recovery from the film structure in the recycling process is preferably >95%, more preferably >99%. Thus, in preferred sealable paper-based films of the present invention, the first adhesive layer comprises a water sensitive adhesive selected from starch, sugar derivatives, cellulose, amino resin, (poly)acrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, maleic acid-modified ethylene copolymers, methyl cellulose, carboxymethyl cellulose, carboxy-functional polyester, polyethylene succinate, polybutylene succinate, ionomers, hydrophilic polyurethane, ethylene vinyl acetate copolymer, ethylene butyl acrylate, ethylene acrylic acid copolymer, polyethylene / polypropylene grafted with maleic anhydride, and combinations thereof.

[0057] The water sensitive adhesive may be selected from starch, (poly)acrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, methyl cellulose, carboxymethyl cellulose, carboxy-functional polyester, polyethylene succinate, polybutylene succinate, ethylene vinyl acetate copolymer, ethylene butyl acrylate, ethylene acrylic acid copolymer, and combinations thereof.

[0058] In one embodiment, the water sensitive adhesive comprises starch.

[0059] In one embodiment, the water sensitive adhesive comprises (poly)acrylate.

[0060] In one embodiment, the water sensitive adhesive comprises polyvinyl alcohol.

[0061] In one embodiment, the water sensitive adhesive comprises polyvinyl acetate.

[0062] In one embodiment, the water sensitive adhesive comprises polyacrylic acid.

[0063] In one embodiment, the water sensitive adhesive comprises methyl cellulose.

[0064] In one embodiment, the water sensitive adhesive comprises carboxymethyl cellulose.

[0065] In one embodiment, the water sensitive adhesive comprises carboxy-functional polyester.

[0066] In one embodiment, the water sensitive adhesive comprises polyethylene succinate.

[0067] In one embodiment, the water sensitive adhesive comprises polybutylene succinate.

[0068] In one embodiment, the water sensitive adhesive comprises ethylene vinyl acetate copolymer.

[0069] In one embodiment, the water sensitive adhesive comprises ethylene butyl acrylate.

[0070] In one embodiment, the water sensitive adhesive comprises ethylene acrylic acid copolymer. In preferred sealable paper-based films of the present invention, the dry weight of the first adhesive layer is less than or equal to 2.5 gsm, preferably less than or equal to 1.5 gsm, more preferably less than or equal to 1 gsm.

[0071] In preferred sealable paper-based films of the present invention, the first barrier layer comprises a metal, a metal oxide, or an inorganic oxide. When metals such as aluminium are used in the first barrier layer, the water barrier properties of the sealable paper-based films are enhanced. When metal oxides such as aluminium oxide (AIOX) or inorganic oxides such as silicon oxide (SiOx) are used in the first barrier layer, the oxygen and other gas barrier properties are enhanced. Preferably, the first barrier layer comprises aluminium. Preferably, the first barrier layer comprises aluminium, aluminium oxide (AIOX) or silicon oxide (SiOx). More preferably the first barrier layer comprises aluminium oxide (AIOX) or silicon oxide (SiOx), particularly when gas barrier is a major requirement. Most preferably, the first barrier layer comprises aluminium oxide (AIOX).

[0072] In preferred sealable paper-based films of the present invention, the first barrier layer has a thickness of less than or equal to 0.1 microns. At such low thicknesses, the first barrier layer is able to provide suitable barrier properties whilst ensuring that the sealable film is still predominantly fibre based.

[0073] In preferred sealable paper-based films of the present invention, the second polymer film comprises at least one oriented or unoriented polymer in a mono or multilayer structure. Preferably, the second polymer film comprises at least one polymer selected from low-density polyethylene, high-density polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene terephthalate, polyamide, ethylene vinyl alcohol, poly(vinyl alcohol), polylactic acid, or combinations thereof. More preferably, the second polymer film comprises polypropylene.

[0074] In preferred sealable paper-based films of the present invention, the surface of the second polymer film to which the second barrier layer is applied can be modified prior to the application of the second barrier layer in order to improve the deposition and adhesion of the second barrier layer. Preferred surface modification methods are corona, flame or plasma treatments.

[0075] In preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene and the second polymer film comprises polypropylene.

[0076] In preferred sealable paper-based films of the present invention, the second polymer film has a thickness of less than or equal to 6 microns, preferably less than 5 microns, more preferably less than 3 microns. At such low thicknesses, the second polymer film is able to provide a suitable surface to enable direct barrier layer deposition to enhance the barrier properties of the sealable paper-based film of the present invention, whilst ensuring that the sealable paper-based film is still predominantly fibre based.

[0077] In preferred sealable paper-based films of the present invention, the second polymer film has a thickness of more than or equal to 0.6 microns, preferably more than or equal to 1.5 microns, more preferably more than or equal to 2 microns.

[0078] In preferred sealable paper-based films of the present invention, the second polymer film has a thickness in the range 0.6 to 6 microns, preferably 1.5 to 4 microns, more preferably 2 to 3 microns.

[0079] In the sealable paper-based films of the present invention, the second adhesive layer comprises a water stable adhesive. A water stable adhesive ensures that the first barrier layer and second polymer film remain strongly bonded not only throughout the useable lifetime of the resultant sealable paper-based film, but also in the paper recycling process where excessive water is present. Thus, in preferred sealable paperbased films of the present invention, the second adhesive layer comprises a water stable adhesive which is a polyurethane type laminating adhesive or a water-based type laminating adhesive. Examples of polyurethane type laminating adhesives include solvent-free polyurethane adhesives and solvent-based polyurethane adhesives.

[0080] Polyurethane adhesives are renowned for their versatility and durability in bonding various materials. In one embodiment, the polyurethane adhesive comprises isocyanate and polyol.

[0081] The isocyanate component serves as the reactive element in polyurethane adhesive formulation. Typically, diisocyanates such as toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI) are utilized. Isocyanates facilitate the crosslinking process, allowing the adhesive to cure and form a strong bond.

[0082] The polyol component is typically polyether or polyester compounds containing hydroxyl (OH) groups. Polyols contribute to the adhesive's flexibility, strength, and adhesion properties.

[0083] Water-based type laminating adhesives typically comprise an aqueous emulsion of vinyl and / or acrylic polymers. They may further comprise an ionic or nonionic polyurethane, a polyethylenimine; and a carbodiimide. These types of adhesives are well known in the art.

[0084] In preferred processes of the present invention, the dry weight of the second adhesive layer is less than or equal to 2.5 gsm, preferably less than or equal to 1.5 gsm, more preferably less than or equal to 1 gsm.

[0085] In preferred processes of the present invention, the second barrier layer comprises a metal, a metal oxide, or an inorganic oxide. When metals such as aluminium are used in the second barrier layer, the water barrier properties of the sealable paper-based films are enhanced. When metal oxides such as aluminium oxide (AIOX) or inorganic oxides such as silicon oxide (SiOx) are used in the second barrier layer, the oxygen and other gas barrier properties are enhanced. The second barrier layer can be made of the same material as the first barrier layer to further enhance the desired barrier performance of the sealable paper-based films of the present invention. The second barrier layer can be made of a different material from the first barrier layer, thereby allowing the barrier properties of the sealable paper-based films of the present invention to be customised. Preferably, the second barrier layer comprises aluminium, aluminium oxide (AIOX) or silicon oxide (SiOx). More preferably, the second barrier layer comprises aluminium. In preferred sealable paper-based films of the present invention, the second barrier layer has a thickness of less than or equal to 0.1 microns. At such low thicknesses, the second barrier layer is able to provide suitable barrier properties whilst ensuring that the sealable film is still predominantly fibre based.

[0086] In preferred sealable paper-based films of the present invention, the first barrier layer comprises aluminium oxide (AIOX) and the second barrier layer comprises aluminium. Alternatively, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium oxide ( Al Ox) . The use of this combination of barrier materials is useful when moisture barrier properties, as well as gas barrier properties, are required.

[0087] In particularly preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium oxide (AIOX) and the second barrier layer comprises aluminium. In alternative particularly preferred sealable paperbased films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium oxide (AIOX).

[0088] In alternative preferred sealable paper-based films of the present invention, the first barrier layer comprises silicon oxide (SiOx) and the second barrier layer comprises aluminium. Alternatively, the first barrier layer comprises aluminium and the second barrier layer comprises silicon oxide (SiOx). The use of this combination of barrier materials is useful when moisture barrier properties, as well as gas barrier properties, are required.

[0089] In alternative particularly preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises silicon oxide (SiOx) and the second barrier layer comprises aluminium. In alternative particularly preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises silicon oxide (SiOx).

[0090] In alternative preferred sealable paper-based films of the present invention, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium. The use of this combination of barrier materials is useful when further enhanced and more robust moisture barrier properties are required.

[0091] In alternative particularly preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium.

[0092] Preferred sealable paper-based films of the present invention can further comprise a first protective varnish layer on the surface of the first barrier layer which is opposite to the first polymer film. The first protective varnish layer protects the first barrier layer against scratching and / or cracking during further processing (e.g. second polymerfilm lamination, second barrier layer deposition, printing, converting, forming, filling, sealing processes etc.) which can reduce the barrier properties.

[0093] Preferred sealable paper-based films of the present invention can further comprise a second protective varnish layer on the surface of the second barrier layer which is opposite to the second polymer film. The second protective varnish layer protects the second barrier layer against scratching and / or cracking during further processing (e.g. printing, converting, forming, filling, sealing processes etc.) which can reduce the barrier properties.

[0094] Preferred sealable paper-based films of the present invention further comprise an ink layer printed on the uncoated or coated surface of the paper layer which is opposite the first adhesive layer.

[0095] When cold seal functionality is required, preferred sealable paper-based films of the present invention further comprise a conventional release lacquer layer, which comprises as a main ingredient a polyamide (e.g. one made from a dimeric fatty acid) and a polyamine (e.g. a diamine), on the surface of the paper layer which is opposite the first adhesive layer or on the surface of the coating colour layer which is opposite the paper layer or on the surface of the ink layer which is opposite the paper layer. The packaging films are usually stored as reels before they are further processed into final packaging. Under those storing conditions, it is inevitable that the surface of the film carrying the paper layer, or the coating colour layer, or the printed layer (in the case that an ink layer has been applied) comes into contact with the other surface of the film comprising the cold seal adhesive layer. Since films are stored as reels, a considerable pressure is exerted onto at least a part of the stored film, which may be sufficient for initiating undesired cold seal activation (i.e. blocking) during storage. The release lacquer layer prevents cold seal adhesion to the opposite film surface and potential reel blocking, from occurring. The release lacquer layer does not react with the cold seal adhesive layer under the conditions of reel storage. When the film is reeled and stored, the cold seal adhesive layer comes into contact with the release lacquer layer, and no cold sealing takes place.

[0096] In preferred sealable paper-based films of the present invention, the sealing layer is present on the surface of the second barrier layer which is opposite the second polymer film or, if present, on the surface of the second protective varnish layer which is opposite the second barrier layer.

[0097] In the sealable paper-based films of the present invention, the sealing layer is either a continuous layer or a discontinuous layer (i.e. a patterned layer). Preferably, the sealing layer is a discontinuous layer, to minimize the non-fibre components of the sealable paper-based films of the present invention.

[0098] In the sealable paper-based films of the present invention, the sealing layer either comprises a heat seal material or a cold seal adhesive.

[0099] In preferred sealable paper-based films of the present invention, the sealing layer comprises a heat seal material which is polyolefin-based. More preferably, the heat seal material is selected from acrylate, polyethylene and polypropylene copolymers, and combinations thereof. In alternative preferred sealable paper-based films of the present invention, the sealing layer comprises a cold seal adhesive containing natural rubber latex, and it is selected from polyisoprene latex, styrene-butadiene copolymer latex, and combinations thereof.

[0100] Preferred sealable paper-based films of the present invention further comprise additional polymer layers and barrier layers, which are preferably present between the previous barrier layer (e.g. the second barrier layer in the case of the addition of a third polymer film) and the sealing layer. For example, preferred sealable paper-based films of the present invention further comprise a third polymer film and a third barrier layer, wherein the second barrier layer is connected to the third polymer layer via a third adhesive layer comprising a water-stable adhesive. Preferred features of the third polymer film, the third barrier layer and the third adhesive layer are as described above.

[0101] Viewed from a further aspect, the present invention relates to a process for preparing a sealable paper-based film, the process comprising the steps of:

[0102] (i) laminating a first polymer film onto a paper layer using a first adhesive layer, wherein said first adhesive layer comprises a water sensitive adhesive;

[0103] (ii) applying a first barrier layer directly onto said first polymer film;

[0104] (iii) optionally applying a first protective varnish layer onto said first barrier layer;

[0105] (iv) laminating a second polymer film onto said first barrier layer or said first protective varnish layer using a second adhesive layer, wherein said second adhesive layer comprises a water stable adhesive;

[0106] (v) applying a second barrier layer onto said second polymer film to give a precursor film;

[0107] (vi) optionally applying a second protective varnish layer onto said second barrier layer;

[0108] (vii) optionally applying one or more ink layers onto said paper layer to produce the desired printed design; and (viii) either (a) applying a sealing layer which is a heat sealable layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires heat seal functionality; or

[0109] (b) applying a release lacquer layer onto said paper layer or said ink layer and applying a sealing layer which is a cold seal adhesive layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires cold seal functionality.

[0110] In the processes of the present invention, the paper layer is any type of uncoated or coated paper, which comprises predominantly cellulose fibres.

[0111] The processes of the present invention may further comprise the step of modifying the surface of the paper layer which is opposite the first adhesive layer with a coating colour layer. Preferably, the coating colour layer comprises starch, pigments and / or binders.

[0112] The processes of the present invention may further comprise the step of modifying the surface of the paper layer which is to be opposite the first adhesive layer with one or more ink layers to produce a desired printed design prior to lamination of the first polymer film. If a coating colour layer is present, the one or more ink layers may be applied onto the coating colour layer.

[0113] In the processes of the present invention, the paper layer may further comprise an inorganic filler. The inorganic filler may be selected from kaolinite, talc, mica, calcium carbonate, titanium dioxide, calcium sulphate dihydrate, and combinations thereof. The use of inorganic fillers aids the visual appearance and print quality of the paper layer, e.g. increased brightness and whiteness, reduced sheet porosity, improved smoothness, improved ink absorbency, increased sheet opacity etc.

[0114] In preferred processes of the present invention, the cellulose fibres of the paper layer are bleached or unbleached, or a blend thereof, preferably bleached. The bleached fibres may be produced using oxygen delignification followed by Elemental Chlorine Free (ECF) or Total Chlorine Free (TCF) methods. For ECF fibres, chlorine dioxide and hydrogen peroxide are the main bleaching agents, while for TCF fibres, hydrogen peroxide is the main bleaching agent.

[0115] In preferred processes of the present invention, the fibres of the paper layer are non-recycled fibres (i.e. virgin fibres). In alternative preferred processes of the present invention, the fibres of the paper layer are recycled fibres. In further alternative processes of the present invention, the fibres of the paper layer are a blend of virgin and recycled fibres.

[0116] In preferred processes of the present invention, the fibres are wood-based fibres or non-wood-based fibres, or a blend thereof, preferably wood-based fibres.

[0117] Examples of types of packaging papers that may be used in the processes of the present invention are machine glazed (MG) or machine finished (MF) bleached or unbleached kraft grades, as well as coated-one-side bleached or unbleached papers (CIS).

[0118] In preferred processes of the present invention, the weight of the paper layer is in the range 40 to 125 gsm, preferably 40 to 70 gsm, and most preferably 45 to 55 gsm. The use of a paper layer having a weight in these ranges ensures that the resultant film remains flexible.

[0119] The sealable paper-based films prepared by the process of the present invention are predominantly made of paper, meaning that they can easily be recycled in the existing paper recycling infrastructure. Thus, in preferred processes of the present invention, the weight of the paper layer is at least 80% based upon the total weight of the sealable paper-based film, preferably at least 85% based upon the total weight of the sealable paper-based film, more preferably at least 90% based upon the total weight of the sealable paper-based film, even more preferably at least 95% based upon the total weight of the sealable paper-based film. Where a coating colour layer is present on the paper layer, the weight of the paper layer also includes the weight of the coating colour layer. In the processes of the present invention, a first polymer film is laminated onto a paper layer in step (i) prior to a first barrier layer being applied to the first polymer film in step (ii). This allows for a thicker and more thermally and dimensionally stable composite film to be prepared, as opposed to applying the barrier layer onto the very thin first polymer film (e.g. less than or equal to 6 microns) prior to lamination to the paper layer.

[0120] In preferred processes of the present invention, the first polymer film comprises at least one oriented or unoriented polymer in a mono or multilayer structure. Preferably, the first polymer film comprises at least one polymer selected from low- density polyethylene, high-density polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene terephthalate, polyamide, ethylene vinyl alcohol, poly(vinyl alcohol), polylactic acid, or combinations thereof. More preferably, the first polymer film comprises polypropylene. Where the first polymer film has a multilayer structure, this is preferably formed by a coextrusion process.

[0121] In preferred processes of the present invention, the surface of the first polymer film to which the first barrier layer is applied can be modified prior to the application of the first barrier layer in order to improve the deposition and adhesion of the first barrier layer. Thus, preferred processes of the present invention comprise between steps (i) and (ii) a further step of modifying the surface of the first polymer film to which the first barrier layer is to be applied, preferably by a modification method which is a corona, flame or plasma treatment.

[0122] In preferred processes of the present invention, the first polymer film has a thickness of less than or equal to 6 microns, preferably less than 5 microns, more preferably less than 3 microns. At such low thicknesses, the first polymer film is able to provide a suitable surface to enable direct barrier layer deposition to enhance the barrier properties of the sealable paper-based films of the present invention, whilst ensuring that the sealable paper-based film is still predominantly fibre based. In preferred processes of the present invention, the first polymer film has a thickness of more than or equal to 0.6 microns, preferably more than or equal to 1.5 microns, more preferably more than or equal to 2 microns.

[0123] In preferred processes of the present invention, the first polymer film has a thickness in the range 0.6 to 6 microns, preferably 1.5 to 4 microns, more preferably 2 to 3 microns.

[0124] In the processes of the present invention, the first adhesive layer comprises a water sensitive adhesive. In the paper recycling process, the presence of water causes the interlayer bonding strength of such adhesive to weaken thus enabling easier delamination and separation of the bonded paper layer from the polymer film, aiding the recyclability of the sealable paper-based film of the present invention. The paper layer will be rewetted and fibres separated in the conventional repulping process to form pulp, which can be used to make recycled paper or other fibre-based recycled products, such as moulded fibre packaging and inserts. The fibre recovery from the film structure in the recycling process is preferably >95%, more preferably >99%. Thus, in preferred processes of the present invention, the first adhesive layer comprises a water sensitive adhesive selected from starch, sugar derivatives, cellulose, amino resin, (poly)acrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, maleic acid- modified ethylene copolymers, methyl cellulose, carboxymethyl cellulose, carboxyfunctional polyester, polyethylene succinate, polybutylene succinate, ionomers, hydrophilic polyurethane, ethylene vinyl acetate copolymer, ethylene butyl acrylate, ethylene acrylic acid copolymer, polyethylene / polypropylene grafted with maleic anhydride, and combinations thereof.

[0125] The water sensitive adhesive may be selected from starch, (poly)acrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, methyl cellulose, carboxymethyl cellulose, carboxy-functional polyester, polyethylene succinate, polybutylene succinate, ethylene vinyl acetate copolymer, ethylene butyl acrylate, ethylene acrylic acid copolymer, and combinations thereof.

[0126] In one embodiment, the water sensitive adhesive comprises starch. In one embodiment, the water sensitive adhesive comprises (poly)acrylate.

[0127] In one embodiment, the water sensitive adhesive comprises polyvinyl alcohol.

[0128] In one embodiment, the water sensitive adhesive comprises polyvinyl acetate.

[0129] In one embodiment, the water sensitive adhesive comprises polyacrylic acid.

[0130] In one embodiment, the water sensitive adhesive comprises methyl cellulose.

[0131] In one embodiment, the water sensitive adhesive comprises carboxymethyl cellulose.

[0132] In one embodiment, the water sensitive adhesive comprises carboxy-functional polyester.

[0133] In one embodiment, the water sensitive adhesive comprises polyethylene succinate.

[0134] In one embodiment, the water sensitive adhesive comprises polybutylene succinate.

[0135] In one embodiment, the water sensitive adhesive comprises ethylene vinyl acetate copolymer.

[0136] In one embodiment, the water sensitive adhesive comprises ethylene butyl acrylate.

[0137] In one embodiment, the water sensitive adhesive comprises ethylene acrylic acid copolymer.

[0138] In preferred processes of the present invention, the dry weight of the first adhesive layer is less than or equal to 2.5 gsm, preferably less than or equal to 1.5 gsm, more preferably less than or equal to 1 gsm.

[0139] In preferred processes of the present invention, the first barrier layer comprises a metal, a metal oxide, or an inorganic oxide. When metals such as aluminium are used in the first barrier layer, the water barrier properties of the sealable paper-based films are enhanced. When metal oxides such as aluminium oxide (AIOX) or inorganic oxides such as silicon oxide (SiOx) are used in the first barrier layer, the oxygen and other gas barrier properties are enhanced. Preferably, the first barrier layer comprises aluminium, aluminium oxide (AIOX) or silicon oxide (SiOx). More preferably the first barrier layer comprises aluminium oxide (AIOX) or silicon oxide (SiOx), particularly when gas barrier is a major requirement. Most preferably, the first barrier layer comprises aluminium oxide (AIOX).

[0140] In preferred processes of the present invention, the first barrier layer is applied in step (ii) directly to the surface of the first polymer film (which has itself already been laminated to the paper layer in step (i)) via chemical or physical vapour deposition (CVD or PVD), or preferably via cathode sputtering in the case of metals.

[0141] In preferred processes of the present invention, the first barrier layer has a thickness of less than or equal to 0.1 microns. At such low thicknesses, the first barrier layer is able to provide suitable barrier properties whilst ensuring that the sealable film is still predominantly fibre based.

[0142] In preferred processes of the present invention, the second polymer film comprises at least one oriented or unoriented polymer in a mono or multilayer structure. Preferably, the second polymer film comprises at least one polymer selected from low-density polyethylene, high-density polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene teraphthalate, polyamide, ethylene vinyl alcohol, poly(vi nyl alcohol), polylactic acid and combinations thereof. More preferably, the second polymer film comprises polypropylene. Where the second polymer film has a multilayer structure, this is preferably formed by a coextrusion process.

[0143] In preferred processes of the present invention, the surface of the second polymer film to which the second barrier layer is applied can be modified prior to the application of the second barrier layer in order to improve the deposition and adhesion of the second barrier layer. Thus, preferred processes of the present invention comprise between steps (iv) and (v) a further step of modifying the surface of the second polymer film to which the second barrier layer is to be applied, preferably by a modification method which is a corona, flame or plasma treatment.

[0144] In preferred processes of the present invention, the first polymer film comprises polypropylene and the second polymer film comprises polypropylene. In preferred processes of the present invention, the second polymer film has a thickness of less than or equal to 6 microns, preferably less than 5 microns, more preferably less than 3 microns. At such low thicknesses, the second polymer film is able to provide suitable barrier properties whilst ensuring that the sealable film is still predominantly fibre based.

[0145] In preferred processes of the present invention, the second polymer film has a thickness of more than or equal to 0.6 microns, preferably more than or equal to 1.5 microns, more preferably more than or equal to 2 microns.

[0146] In preferred processes of the present invention, the second polymer film has a thickness in the range 0.6 to 6 microns, preferably 1.5 to 4 microns, more preferably 2 to 3 microns.

[0147] The use of a water stable adhesive in step (iv) of the processes of the present invention ensures that the first barrier layer and second polymer film remain strongly bonded not only throughout the useable lifetime of the resultant sealable paper-based film, but also in the paper recycling process where excessive water is present. Thus, in preferred processes of the present invention, the second adhesive layer comprises a water stable adhesive which is a polyurethane type laminating adhesive or a waterbased type laminating adhesive. Examples of polyurethane type laminating adhesives include solvent-free polyurethane adhesives and solvent-based polyurethane adhesives.

[0148] In preferred processes of the present invention, the dry weight of the second adhesive layer is less than or equal to 2.5 gsm, preferably less than or equal to 1.5 gsm, more preferably less than or equal to 1 gsm.

[0149] In preferred processes of the present invention, the second barrier layer comprises a metal, a metal oxide, or an inorganic oxide. When metals such as aluminium are used in the second barrier layer, the water barrier properties of the sealable paper-based films are enhanced. When metal oxides such as aluminium oxide (AIOX) or inorganic oxides such as silicon oxide (SiOx) are used in the second barrier layer, the oxygen and other gas barrier properties are enhanced. The second barrier layer can be made of the same material as the first barrier layer to further enhance the desired barrier performance of the sealable paper-based films of the present invention. The second barrier layer can be made of a different material from the first barrier layer, thereby allowing the barrier properties of the sealable paper-based films of the present invention to be customised. Preferably, the second barrier layer comprises aluminium, aluminium oxide (AIOX) or silicon oxide (SiOx). More preferably, the second barrier layer comprises aluminium.

[0150] In preferred processes of the present invention, the second barrier layer is applied in step (v) directly to the surface of the second polymer film (which has itself already been laminated to the structure in step (iv)) via chemical or physical vapour deposition (CVD or PVD), or preferably via cathode sputtering in the case of metals.

[0151] In preferred processes of the present invention, the second barrier layer has a thickness of less than or equal to 0.1 microns. At such low thicknesses, the second barrier layer is able to provide suitable barrier properties whilst ensuring that the sealable film is still predominantly fibre based.

[0152] In preferred processes of the present invention, the first barrier layer comprises aluminium oxide (AIOX) and the second barrier layer comprises aluminium. Alternatively, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium oxide (AIOX). The use of this combination of barrier materials is useful when moisture barrier properties, as well as gas barrier properties, are required.

[0153] In particularly preferred processes of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium oxide (AIOX) and the second barrier layer comprises aluminium. In alternative particularly preferred processes of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium oxide (AIOX).

[0154] In alternative preferred processes of the present invention, the first barrier layer comprises silicon oxide (SiOx) and the second barrier layer comprises aluminium. Alternatively, the first barrier layer comprises aluminium and the second barrier layer comprises silicon oxide (SiOx). The use of this combination of barrier materials is useful when moisture barrier properties, as well as gas barrier properties, are required.

[0155] In alternative particularly preferred processes of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises silicon oxide (SiOx) and the second barrier layer comprises aluminium. In alternative particularly preferred processes of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises silicon oxide (SiOx).

[0156] In alternative preferred processes of the present invention, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium. The use of this combination of barrier materials is useful when further enhanced and more robust moisture barrier properties are required.

[0157] In alternative particularly preferred sealable paper-based films of the present invention, the first polymer film comprises polypropylene, the second polymer film comprises polypropylene, the first barrier layer comprises aluminium and the second barrier layer comprises aluminium.

[0158] Preferred processes of the present invention further comprise the step (iii) of applying a first protective varnish layer on the surface of the first barrier layer which is opposite to the first polymer film. The first protective varnish layer protects the first barrier layer against scratching and / or cracking during further processing (e.g. second polymerfilm lamination, second barrier layer deposition, printing, converting, forming, filling, sealing processes etc.) which can reduce the barrier properties. The rotogravure printing process or a suitable off line metered coater can be used to carry out this step, for example.

[0159] Preferred processes of the present invention further comprise the step (vi) of applying a second protective varnish layer on the surface of the second barrier layer which is opposite the second polymer film. The second protective varnish layer protects the second barrier layer against scratching and / or cracking during further processing (e.g. converting, forming, filling, sealing processes etc.) which can reduce the barrier properties. The rotogravure printing process or a suitable off line metered coater can be used to carry out this step, for example.

[0160] The processes of the present invention may comprise the step (vii) of applying one or more ink layers on the surface of the paper layer which is opposite the first adhesive layer or, if present, on the surface of the coating colour layer which is opposite the paper layer to produce the desired printed design. Preferably, the ink layer is printed using a rotogravure, flexographic, offset or digital printing process.

[0161] If the sealable paper-based film requires cold seal functionality, preferred processes of the present invention further comprise in step (viii-b) applying a conventional release lacquer layer, which comprises as a main ingredient a polyamide (e.g. one made from a dimeric fatty acid) and a polyamine (e.g. a diamine), on the surface of the paper layer which is opposite the first adhesive layer or on the surface of the coating colour layer which is opposite the paper layer or on the surface of the ink layer which is opposite the paper layer. The packaging films are usually stored as reels before they are further processed into final packaging. Under those storing conditions, it is inevitable that the surface of the film carrying the paper layer, or the coating colour layer, or the printed layer (in the case that an ink layer has been applied) comes into contact with the other surface of the film comprising the cold seal adhesive layer. Since films are stored as reels, a considerable pressure is exerted onto at least a part of the stored film, which may be sufficient for initiating undesired cold seal activation (i.e. blocking) during storage. The release lacquer layer prevents cold seal adhesion to the opposite film surface and potential reel blocking, from occurring. The release lacquer layer does not react with the cold seal adhesive layer under the conditions of reel storage. When the film is stored as a reel, the cold seal adhesive layer comes into contact with the release lacquer layer, and no cold sealing takes place.

[0162] In the processes of the present invention, the sealing layer is applied in step (viii) to the surface of the second barrier layer which is opposite the second polymer film 1 or, if present, to the surface of the second protective varnish layer which is opposite the second barrier layer.

[0163] In the processes of the present invention, the sealing layer is either a continuous layer or a discontinuous layer (i.e. a patterned layer). Preferably, the sealing layer is a discontinuous layer to minimize the non-fibre components of the sealable paper-based films of the present invention.

[0164] In the processes of the present invention, the sealing layer either comprises a heat seal material (when the sealing layer is a heat sealable layer) or a cold seal adhesive (when the sealing layer is a cold seal adhesive layer).

[0165] In preferred processes of the present invention, the sealing layer comprises a heat seal material which is polyolefin-based. More preferably, the heat seal material is selected from acrylate, polyethylene, and polypropylene copolymers, and combinations thereof.

[0166] In alternative preferred processes of the present invention, the sealing layer comprises a cold seal adhesive containing natural rubber latex, and it is selected from polyisoprene latex, styrene-butadiene copolymer latex, and combinations thereof.

[0167] In preferred processes of the present invention, additional steps can be carried out in order to provide additional polymer films (e.g. a third polymer film etc.) and additional barrier layers (e.g. a third barrier layer etc.) in the precursor film, prior to the sealing layer being applied in step (viii). For example, a preferred process of the present invention, after the completion of step (vii) and prior to the commencement of step (viii), comprises the following steps:

[0168] (a) laminating a third polymer film onto said second barrier layer or said second protective varnish layer using a third adhesive layer, wherein said third adhesive layer comprises a water stable adhesive; and

[0169] (b) applying a third barrier layer onto said third polymer film.

[0170] Preferred features of the third polymer film, the third barrier layer and the third adhesive layer are as described above. Preferred methods for the manufacture of the third polymer film and the third barrier layer are as described above. Viewed from a further aspect, the present invention relates to a sealable paperbased film prepared according to the process as hereinbefore described.

[0171] Viewed from a further aspect, the present invention relates to a package comprising a sealable paper-based film as hereinbefore described.

[0172] Viewed from a further aspect, the present invention relates to a process for preparing a package, the process comprising the steps of:

[0173] (i) preparing a sealable paper-based film according to the process as hereinbefore described; and

[0174] (ii) forming said sealable paper-based film into a package.

[0175] Preferred processes of the present invention further comprise the steps of filling the package with a product and sealing the package. Preferably, the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).

[0176] Viewed from a further aspect, the present invention relates to a product enclosed by a sealable paper-based film as hereinbefore described.

[0177] Preferably, the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).

[0178] Viewed from a further aspect, the present invention relates to a process for enclosing a product, the process comprising the steps of:

[0179] (i) wrapping a product in a sealable paper-based film as hereinbefore described; and

[0180] (ii) sealing said sealable paper-based film around said product to form a sealed package.

[0181] Preferably, the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer). Viewed from a further aspect, the present invention relates to a package or a sealed package made according to a process as hereinbefore described.

[0182] Viewed from a further aspect, the present invention relates to the use of a sealable paper-based film as hereinbefore described to form a package and / or to enclose a product.

[0183] Preferably, the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).

Claims

Claims1. A sealable paper-based film comprising: a paper layer; a first adhesive layer comprising a water sensitive adhesive; a first polymer film and a first barrier layer, wherein said first barrier layer is in direct contact with said first polymer film; a second adhesive layer comprising a water stable adhesive; a second polymer film and a second barrier layer; and a continuous or discontinuous sealing layer; wherein said first polymer film is connected to said paper layer via said first adhesive layer; and said first barrier layer is connected to said second polymer film via said second adhesive layer.

2. A sealable paper-based film as claimed in claim 1, wherein the weight of said paper layer is at least 80% based upon the total weight of the sealable paper-based film, preferably at least 85% based upon the total weight of the sealable paper-based film, more preferably at least 90% based upon the total weight of the sealable paper-based film, even more preferably at least 95% based upon the total weight of the sealable paper-based film.

3. A sealable paper-based film as claimed in claim 1 or claim 2, wherein said first polymer film and / or said second polymer film comprises at least one oriented or unoriented polymer in a mono or multilayer structure preferably wherein the at least one oriented or unoriented polymer is selected from low-density polyethylene, high- density polyethylene, polypropylene, polybutylene, polyisobutylene, polyethylene terephthalate, polyamide, ethylene vinyl alcohol, poly(vinyl alcohol), polylactic acid, or combinations thereof.

4. A sealable paper-based film as claimed in claim 3, wherein said first polymer film and / or said second polymer film comprises polypropylene.

5. A sealable paper-based film as claimed in any one of claims 1 to 4, wherein said first polymer film and / or said second polymer film has a thickness of less than or equal to 6 microns, preferably less than 5 microns, more preferably less than 3 microns.

6. A sealable paper-based film as claimed in any one of claims 1 to 5, wherein said first barrier layer and / or said second barrier layer comprises aluminium, aluminium oxide (AIOX) or silicon oxide (SiOx).

7. A sealable paper-based film as claimed in any one of claims 1 to 6, wherein said first barrier layer and / or said second barrier layer has a thickness of less than or equal to 0.1 microns.

8. A sealable paper-based film as claimed in any one of claims 1 to 7, wherein said first polymer film comprises polypropylene, said second polymer film comprises polypropylene, said first barrier layer comprises aluminium and said second barrier layer comprises aluminium oxide (AIOX) or silicon oxide (SiOx).

9. A sealable paper-based film as claimed in any one of claims 1 to 7, wherein said first polymer film comprises polypropylene, said second polymer film comprises polypropylene, said first barrier layer comprises aluminium and said second barrier layer comprises aluminium.

10. A sealable paper-based film as claimed in any one of claims 1 to 7, wherein said first polymer film comprises polypropylene, said second polymer film comprisespolypropylene, said first barrier layer comprises aluminium oxide (AIOX) or silicon oxide (SiOx) and said second barrier layer comprises aluminium.

11. A sealable paper-based film as claimed in any one of claims 1 to 10, wherein said water sensitive adhesive is selected from starch, sugar derivatives, cellulose, amino resin, (poly)acrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, maleic acid- modified ethylene copolymers, methyl cellulose, carboxymethyl cellulose, carboxyfunctional polyester, polyethylene succinate, polybutylene succinate, ionomers, hydrophilic polyurethane, ethylene vinyl acetate copolymer, ethylene butyl acrylate, ethylene acrylic acid copolymer, polyethylene / polypropylene grafted with maleic anhydride, and combinations thereof.

12. A sealable paper-based film as claimed in any one of claims 1 to 11, wherein said water stable adhesive is a polyurethane type laminating adhesive or a water-based type laminating adhesive.

13. A process for preparing a sealable paper-based film, the process comprising the steps of:(i) laminating a first polymer film onto a paper layer using a first adhesive layer, wherein said first adhesive layer comprises a water sensitive adhesive;(ii) applying a first barrier layer directly onto said first polymer film;(iii) optionally applying a first protective varnish layer onto said first barrier layer;(iv) laminating a second polymer film onto said first barrier layer or said first protective varnish layer using a second adhesive layer, wherein said second adhesive layer comprises a water stable adhesive;(v) applying a second barrier layer onto said second polymer film to give a precursor film;(vi) optionally applying a second protective varnish layer onto said second barrier layer;(vii) optionally applying one or more ink layers onto said paper layer to produce the desired printed design; and(viii) either (a) applying a sealing layer which is a heat sealable layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires heat seal functionality; or(b) applying a release lacquer layer onto said paper layer or said ink layer and applying a sealing layer which is a cold seal adhesive layer onto said second barrier layer or said second protective varnish layer of said precursor film to give said sealable paper-based film, if the film requires cold seal functionality.

14. A sealable paper-based film prepared according to the process as claimed in claim 13.

15. A package comprising a sealable paper-based film as claimed in any one of claims I to 12.

16. A process for preparing a package, the process comprising the steps of:(i) preparing a sealable paper-based film according to the process as claimed in claim 13; and(ii) forming said sealable paper-based film into a package.

17. A product enclosed by a sealable paper-based film as claimed in any one of claims 1 to 12, preferably wherein the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instantcoffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).

18. A process for enclosing a product, the process comprising the steps of:(i) wrapping a product in a sealable paper-based film as claimed in any one of claims 1 to 12; and(ii) sealing said sealable paper-based film around said product to form a sealed package, preferably wherein the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).

19. A package made according to the process of claim 16 or a sealed package made according to the process of claim 18.

20. Use of a sealable paper-based film as claimed in any one of claims 1 to 12 to form a package and / or to enclose a product, preferably wherein the product is selected from confectionery products, biscuits, snacks, dry powdered soups, dry spices, coffee (e.g. ground coffee, instant coffee), tea (e.g. ground tea) and soluble drink powder (e.g. hot chocolate powder, creamer).