Multilayer metallized paper-based packaging material

Abstract

The present invention relates to a multi-layer metallized paper-based packaging material comprising, from its outer side to its inner side: (i) a paper layer; (ii) at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof; (iii) at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof; (iv) at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer; and (v) a top coat layer comprising at least one polyolefin.

Description

[0001] MULTILAYER METALLIZED PAPER-BASED PACKAGING MATERIAL

[0002] Field of the invention

[0003] The present invention relates to a multi-layer metallized paper-based packaging material, to a method for its production, and to uses of the packaging material including in a tridimensional closed packaging item.

[0004] Background of the invention

[0005] Plastic-based sachets for use in, for example, hot beverage machines are well-established. Such sachets may contain, for example, powdered edible substances which, when placed in a hot beverage machine, are injected with high temperature water under high pressure in order to reconstitute the powder and prepare a hot beverage. For example, a sachet filled with milk powder may be used to prepare hot / foamed milk for addition to a coffee beverage (which may or may not be prepared by the same machine).

[0006] The use of plastic-based materials results in a sachet having a very high strength. This is advantageous because the sachets are exposed to extremely harsh conditions during extraction in existing extraction machines: the water employed for extraction is typically at a temperature of ~95-100 °C and the pressure can be extremely high.

[0007] However, there is increasing pressure, both from consumers and legislators, 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 easily recycled after use. Sachets for hot beverage machines and more generally packaging that are predominantly paper-based are known, but the materials required to meet these environmentally-friendly goals mean that the final packaging like sachets are inherently less robust than current plastic-based sachets and they are not able for example to withstand the necessarily harsh conditions of extraction in existing machines (e.g. they may crack and / or burst in the machine). There is also a need to ensure the packaging material used to prepare the sachets or the packaging has the required high gas and moisture barrier properties to ensure the packaged product is safe and has an acceptable shelf life.

[0008] Accordingly, there exists a need to provide packaging materials, for example for use in sachets for hot beverage machines, that have high barrier properties, can withstand the harsh conditions applied during extraction therein, and which are also easily recycled after use.

[0009] Accordingly, there is also a need to provide an alternative to plastic packaging that offers robustness and viability as well as high oxygen barrier even within 3D shaped paper based packaging.

[0010] Summary of the invention

[0011] Viewed from a first aspect, the present invention relates to a multi-layer metallized paper-based packaging material comprising, from its outer side to its inner side:

[0012] (i) a paper layer;

[0013] (ii) at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof;

[0014] (iii) at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof;

[0015] (iv) at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer; and

[0016] (v) a top coat layer comprising at least one polyolefin.

[0017] Viewed from a further aspect, the present invention relates to a method for preparing a multi-layer metallized paper-based packaging material, the method comprising the steps of:

[0018] (i) providing a paper layer; (ii) forming at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, on the paper layer;

[0019] (iii) forming at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof on the organic barrier layer(s);

[0020] (iv) forming at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer on the inorganic barrier layer(s); and

[0021] (v) forming a top coat layer comprising at least one polyolefin on the organic heat seal layer(s).

[0022] Viewed from a further aspect, the present invention relates to a multilayer metallized paper-based packaging material obtained by or obtainable by the method as hereinbefore described.

[0023] Viewed from a further aspect, the present invention relates to a method of preparing a tridimensional closed packaging item, the method comprising the steps of:

[0024] (i) forming a multi-layer metallized paper-based packaging material according to the method hereinbefore described;

[0025] (ii) filling the multi-layer metallized paper-based packaging material with an edible product for human or animal consumption; and

[0026] (iii) sealing the packaging material to form the tridimensional closed packaging item.

[0027] Viewed from a further aspect, the present invention relates to a tridimensional closed packaging item obtained by or obtainable by the method as hereinbefore described.

[0028] Viewed from a further aspect, the present invention relates to the use of a multi-layer metallized paper-based packaging material as hereinbefore described, for packaging an edible product for human or animal consumption. Viewed from a further aspect, the present invention relates to a packaged edible product comprising a multi-layer metallized paper-based packaging material as hereinbefore described filled with an edible product for human or animal consumption.

[0029] Brief description of the drawings

[0030] 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 shows a first embodiment of a multilayer structure according to the present invention;

[0032] Figure 2 shows a second embodiment of a multilayer structure according to the present invention;

[0033] Figure 3 is a bar graph showing the results of seal strength testing of a material according to the present invention and a comparative material;

[0034] Figure 4 is a photograph showing the results of a hot water contact test on a comparative material;

[0035] Figure 5 is a photograph showing the results of a hot water contact test on a material according to the present invention;

[0036] Figure 6 is a photograph showing the results of a burst pressure test on a comparative material; and

[0037] Figure 7 is a photograph showing the results of a burst pressure test on a material according to the present invention; and

[0038] Figure 8 shows a third embodiment of a multilayer structure according to the present invention.

[0039] Detailed description of the invention As used herein, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including but not limited to".

[0040] As used herein, the phrase "layer" refers to a building block of the packaging materials 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.

[0041] As used herein, the phrase "outer side" refers to the side of the packaging material which is turned towards / faces the outside of a package ultimately made thereof. The outer side therefore does not come into contact with the packaged product.

[0042] As used herein, the phrase "inner side" refers to the side of the packaging material which is turned towards / faces the inside of a package ultimately made thereof. The inner side will therefore be in contact with the packaged product.

[0043] 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.

[0044] As used herein, the term "machine direction (MD)" is used to describe the direction of paper that is parallel to the direction of travel during the manufacture of the paper. The term "cross direction (CD)" refers to the direction that is perpendicular to the machine direction. Paper properties vary significantly between these two directions.

[0045] As used herein, the term "aqueous dispersion coating method" refers to a coating technique whereby an aqueous dispersion of fine polymer particles or polymer solution is applied to the surface of a substrate, in order to form a solid, non-porous film after drying. Dispersion coating can be performed by gravure, flexo-gravure, rod, blade, slot-die, curtain air knife, roll coating or any other known method of paper coating.

[0046] As used herein, the term "aqueous solution deposition method" refers to a coating technique whereby an aqueous polymer solution is applied to the surface of a substrate, in order to form a solid, non-porous film after drying. Aqueous coating can be performed by gravure, flexo-gravure, rod, blade, slot-die, curtain air knife, roll coating or any other known method of paper coating.

[0047] As used herein, the term "extrusion method" refers to when a layer of material is provided by using an extruder which forces melted thermoplastic resin (e.g. polyethylene) through a horizontal slot-die onto a moving web of substrate. The resulting product is a permanently coated web structure.

[0048] Viewed from a first aspect, the present invention relates to a multi-layer metallized paper-based packaging material comprising at least, from its outer side to its inner side:

[0049] (i) a paper layer;

[0050] (ii) at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or vinyl alcohol copolymers or a combination thereof;

[0051] (iii) at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof;

[0052] (iv) at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer; and

[0053] (v) a top coat layer comprising at least one polyolefin. In preferred multi-layer metallized paper-based packaging materials of the present invention, the at least one polyolefin present in the top coat layer has a melting temperature greater than 95 °C, preferably greater than 100 °C. Such polyolefins are able to withstand the high temperatures and pressures employed in commercial hot beverage machines such that when the packaging materials of the present invention are used in such a context (e.g. to enclose edible products, such as milk powder, in a sachet ready for extraction in the machine to prepare a beverage), the top coat layer does not melt and is therefore able to protect the underlying organic heat seal layer, and therefore the sachet as a whole, from damage (e.g. cracking and / or bursting) during extraction. Advantageously, the presence of a top coat layer does not negatively impact the gas or moisture barrier properties of the packaging material, meaning that the multi-layer metallized paper-based packaging materials of the present invention maintain the desired low oxygen transmission rate (OTR) and water vapour transmission rate (WVTR) values needed for such an application.

[0054] Thus, in preferred multi-layer metallized paper-based packaging materials of the present invention, the top coat layer comprises at least one polyolefin selected from polyethylene, such as ionomer thermoplastic ethylene methacrylic acid copolymer with zinc (Zn), sodium (Na), lithium (Li) or other metal ions, low- density polyethylene (LDPE), linear low-density polyethylene (LLDPE), mediumdensity polyethylene (MDPE) or high-density polyethylene (HDPE), polypropylene (PP), a copolymer of polyethylene, a copolymer of polypropylene, or combinations thereof. More preferably, the top coat layer comprises polyethylene, particularly preferably low-density polyethylene, or a copolymer of polyethylene. When the top coat layer comprises a copolymer of polyethylene, the comonomer is preferably one or more (e.g. one) a-olefins. Particularly preferably, the comonomer is selected from propylene, 1-butene, 1-pentene, 4- methyl-l-pentene, 1-hexene, 1-octene, and mixtures thereof. In preferred multi-layer metallized paper-based packaging materials of the present invention, the top coat layer is present in an amount of 2 to 50 g / m2, preferably in an amount of 7 to 15 g / m2, more preferably in an amount of 10 to 12 g / m2.

[0055] In preferred multi-layer metallized paper-based packaging materials of the present invention, the top coat layer has a thickness comprises between 2pm to 50pm, preferably 30pm.

[0056] Preferred multi-layer metallized paper-based packaging materials of the present invention have a paper content of at least 80 wt% based upon the total weight of the packaging material, preferably greater than 85 wt%, more preferably greater than 90 wt%. Multi-layer metallized paper-based packaging materials having such a paper content are recyclable in a standard paper stream recycling process. Thus, preferred multi-layer metallized paper-based packaging materials of the present invention are recyclable in paper recycling.

[0057] In preferred multi-layer metallized paper-based packaging materials of the present invention, the paper layer has a grammage in the range of 30 to 120 g / m2.

[0058] In the multi-layer metallized paper-based packaging materials of the present invention, the at least one organic barrier layer comprises a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof. Preferably, the at least one organic barrier layer comprises polyvinylalcohol (PVOH). These polymers are water soluble, meaning that the packaging material has a high recyclability due to the ease of separation of the paper layer from the rest of the materials of the structure in a paper stream recycling process.

[0059] The presence of at least one organic barrier layer in the multi-layer metallized paper-based packaging materials of the present invention provides gas (particularly oxygen) barrier properties to a product subsequently packaged by the material. In preferred multi-layer metallized paper-based packaging materials of the present invention, the at least one organic barrier layer is present in an amount of 0.5 to 20 g / m2, preferably in an amount of 1 to 10 g / m2, more preferably in an amount of 2 to 8 g / m2.

[0060] In preferred multi-layer metallized paper-based packaging materials of the present invention, the at least one inorganic barrier layer has a thickness between 1 and 200 nm, preferably between 50 and 200 nm, more preferably between 100 and 200 nm.

[0061] In preferred multi-layer metallized paper-based packaging materials of the present invention, the inorganic barrier layer comprises metals or metalloids selected from aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx). Preferably, the inorganic barrier layer comprises aluminium.

[0062] The presence of at least one inorganic barrier layer in the multi-layer metallized paper-based packaging materials of the present invention provides moisture barrier properties to a product subsequently packaged by the material.

[0063] The multi-layer metallized paper-based packaging materials of the present invention comprise at least one organic heat seal layer comprising an ionomer grafted to an acrylic or methacrylic polymer. An organic heat seal layer made from such a material achieves excellent resistance to mechanical stress (in particular to bending, stretching, and shearing forces applied to the material during manufacturing of a tridimensional package therefrom). This mechanical resistance protects the whole structure, and especially the adjacent inorganic barrier layer, against damage, and more particularly against irreversible cracking. Furthermore, grafting the acrylic or methacrylic acid polymer with a ionomer has been found to modify the molecular set-up of the material: molecules of acrylic or methacrylic acid-ionomer form a matrix of molecules over the surface of the coating made therefrom, such that the organic heat seal layer yields superior seal integrity of formed and filled tridimensional packages and eventually enabling barrier retention in the final tridimensional package. In preferred multi-layer metallized paper-based packaging materials of the present invention, the at least one organic heat seal layer is present in an amount of 2 to 20 g / m2, preferably in an amount of 4 to 9 g / m2.

[0064] In preferred multi-layer metallized paper-based packaging materials of the present invention, the ionomer grafted to the acrylic or methacrylic polymer in the at least one organic heat seal layer is a sodium ionomer.

[0065] In preferred multi-layer metallized paper-based packaging materials of the present invention, the acrylic or methacrylic polymer in the at least one organic heat seal layer comprises one or more monomers selected from ethyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl methacrylate, isobomyl acrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, n-hexyl methacrylate, n-propyl methacrylate, acrylonitrile, vinyl acetate, and 2-ethylhexyl acrylate, or combinations thereof.

[0066] In preferred multi-layer metallized paper-based packaging materials of the present invention, the acrylic or methacrylic polymer grafted with an ionomer in the at least one organic heat seal layer has a molecular weight comprised between 85 and 90 g / mol.

[0067] In preferred multi-layer metallized paper-based packaging materials of the present invention, the paper layer is covered on its outer side with an ink layer. Preferably, the ink layer comprises a water-based ink, a solvent-less ink, or a combination thereof.

[0068] In preferred multi-layer metallized paper-based packaging materials of the present invention, the ink layer is present in an amount of 0.5 to 5 g / m2.

[0069] In preferred multi-layer metallized paper-based packaging materials of the present invention, the paper layer, or the ink layer if present, is covered on its outer side by an outermost over-print varnish (OPV) layer. Preferably, the overprint varnish layer comprises a styrene acrylic varnish. The presence of an OPV layer results in the packaging material having improved resistance to hygroexpansive strain, as it imparts improved barrier properties to moisture under high humidity conditions.

[0070] In preferred multi-layer metallized paper-based packaging materials of the present invention, the over-print varnish layer is present in an amount of 0.5 to 10 g / m2.

[0071] Preferred multi-layer metallized paper-based packaging materials of the present invention have a Water Vapour Transmission Rate (WVTR) below 0.5 g / m2 / day (measured at 23 °C, 85% Relative Humidity) and / or an Oxygen Transmission Rate (OTR) below 0.1 cm3 / m2 / day bar (measured at 23 °C, 50% Relative Humidity). These values are measured after subjecting the sample to an in-plane tensile pre-straining up to 2% and also after subjecting the sample to a Gelboflex testing apparatus in 3 cycles, according to flexibility testing standard ASTM F392 or equivalent.

[0072] Preferred multi-layer metallized paper-based packaging materials of the present invention have a strain at break under in-plane tensile loading up to 5% in machine direction and up to 15% in the cross-machine direction of the paper, according to ISO 527-1 measurement standard

[0073] Preferred multi-layer metallized paper-based packaging materials of the present invention have the top coat layer which is an aqueous coating deposition.

[0074] According to an example of the invention, the multi-layer metallized paper-based packaging material comprises a cardboard layer and such that the cardboard layer is the outermost layer of the multi-layer metallized paper-based packaging material.

[0075] According to an example of the invention, the cardboard layer has a thickness comprises between 150pm to 350pm. Preferably, the cardboard layer has a thickness of 215pm.

[0076] According to the invention, the carboard layer has a grammage comprises between 150gsm and 350gsm, preferably 170gsm. According to the invention, an adhesive is localized between the cardboard layer and the paper layer.

[0077] Preferably the adhesive comprises a polyvinyl alcohol (PVOH); an ethylene vinyl alcohol (EVOH); a butenediol vinyl alcohol co-polymer (BVOH); a polyolefin such as a polyethylene (PE), a polypropylene (PP) or a polyethylene co-polymers; an acrylate such as a polyacrylate, a polymethacrylate, a styrene acrylate, a vinyl acetate and combinations thereof; a polyurethane (PU); a polyester; a casein; a starch; a sugar or sugar derivative; a cellulose or cellulose derivative; or a mixture thereof; preferably wherein the adhesive layer comprises an acrylate.

[0078] The adhesive has a grammage comprises between 3gsm and 5gsm, preferably 4gsm. The adhesive has a thickness comprises between 3pm and 5pm, preferably 4pm.

[0079] Viewed from a further aspect, the present invention relates to a method for preparing a multi-layer metallized paper-based packaging material, the method comprising the steps of:

[0080] (i) providing a paper layer;

[0081] (ii) forming at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, on the paper layer;

[0082] (iii) forming at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof on the organic barrier layer(s);

[0083] (iv) forming at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer on the inorganic barrier layer(s); and

[0084] (v) forming a top coat layer comprising at least one polyolefin on the organic heat seal layer(s).

[0085] In preferred methods of the present invention, the multi-layer metallized paper-based packaging material has a paper content of at least 80 wt% based upon the total weight of the packaging material, preferably greater than 85 wt%, more preferably greater than 90 wt%. Multi-layer metallized paper-based packaging materials having such a paper content are recyclable in a standard paper stream recycling process. Thus, multi-layer metallized paper-based packaging materials prepared by the method of the present invention are preferably recyclable in paper recycling.

[0086] In preferred methods of the present invention, the paper layer used in step (i) has a grammage in the range of 30 to 120 g / m2.

[0087] In preferred methods of the present invention, the at least one organic barrier layer is formed in step (ii) by an aqueous solution deposition method or an aqueous dispersion coating method. Preferably, the at least one organic barrier layer is formed in step (ii) by an aqueous solution deposition method.

[0088] In the methods of the present invention, the at least one organic barrier layer formed in step (ii) comprises a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof. Preferably, the at least one organic barrier layer formed in step (ii) comprises polyvinylalcohol (PVOH). These polymers are water soluble, meaning that the packaging material has a high recyclability due to the ease of separation of the paper layer from the rest of the materials of the structure in a paper stream recycling process.

[0089] The presence of at least one organic barrier layer in the multi-layer metallized paper-based packaging materials prepared by the method of the present invention provides gas (particularly, oxygen) barrier properties to a product subsequently packaged by the material.

[0090] In preferred methods of the present invention, the at least one organic barrier layer formed in step (ii) is present in an amount of 0.5 to 20 g / m2, preferably in an amount of 1 to 10 g / m2, more preferably in an amount of 2 to 8 g / m2.

[0091] In preferred methods of the present invention, the at least one inorganic barrier layer is formed in step (iii) by depositing said metals and / or metalloids on the at least one organic barrier layer by either vacuum deposition or transfer metallization. Preferably, the at least one inorganic barrier layer is formed in step (iii) by vacuum deposition.

[0092] In preferred methods of the present invention, the at least one inorganic barrier layer formed in step (iii) has a thickness between 1 and 200 nm, preferably between 50 and 200 nm, more preferably between 100 and 200 nm.

[0093] In preferred methods of the present invention, the inorganic barrier layer formed in step (iii) comprises metals or metalloids selected from aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx). Preferably, the inorganic barrier layer formed in step (iii) comprises aluminium.

[0094] The presence of at least one inorganic barrier layer in the multi-layer metallized paper-based packaging materials prepared by the method of the present invention provides moisture barrier properties to a product subsequently packaged by the material.

[0095] The multi-layer metallized paper-based packaging materials prepared by the method of the present invention comprise at least one organic heat seal layer comprising an ionomer grafted to an acrylic or methacrylic polymer. An organic heat seal layer made from such a material achieves excellent resistance to mechanical stress (in particular to bending, stretching, and shearing forces applied to the material during manufacturing of a tridimensional package therefrom). This mechanical resistance protects the whole structure, and especially the adjacent inorganic barrier layer, against damage, and more particularly against irreversible cracking. Furthermore, grafting the acrylic or methacrylic acid polymer with a ionomer has been found to modify the molecular set-up of the material: molecules of acrylic or methacrylic acid-ionomer form a matrix of molecules over the surface of the coating made therefrom, such that the organic heat seal layer yields superior seal integrity of formed and filled tridimensional packages and eventually enabling barrier retention in the final tridimensional package. In preferred methods of the present invention, the at least one organic heat seal layer is formed in step (iv) by an aqueous solution deposition method or an aqueous dispersion coating method. Preferably, the at least one organic heat seal layer is formed in step (iv) by aqueous dispersion coating method.

[0096] In preferred methods of the present invention, the at least one organic heat seal layer formed in step (iv) is present in an amount of 2 to 20 g / m2, preferably in an amount of 4 to 9 g / m2.

[0097] In preferred methods of the present invention, the ionomer grafted to the acrylic or methacrylic polymer in the at least one organic heat seal layer formed in step (iv) is a sodium ionomer.

[0098] In preferred methods of the present invention, the acrylic or methacrylic polymer in the at least one organic heat seal layer formed in step (iv) comprises one or more monomers selected from ethyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl methacrylate, isobomyl acrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, n-hexyl methacrylate, n-propyl methacrylate, acrylonitrile, vinyl acetate, and 2- ethylhexyl acrylate, or combinations thereof.

[0099] In preferred methods of the present invention, the acrylic or methacrylic polymer grafted with an ionomer in the at least one organic heat seal layer formed in step (iv) has a molecular weight comprised between 85 and 90 g / mol.

[0100] In preferred methods of the present invention, the top coat layer is formed in step (v) by an extrusion method or an aqueous dispersion coating method. Preferably, the top coat layer is formed in step (v) by an extrusion method.

[0101] In preferred methods of the present invention, the at least one polyolefin present in the top coat layer formed in step (v) has a melting temperature greater than 95 °C, preferably greater than 100 °C. Such polyolefins are able to withstand the high temperatures and pressures employed in commercial hot beverage machines such that when the packaging materials prepared by the method of the present invention are used in such a context (e.g. to enclose edible products, such as milk powder, in a sachet ready for extraction in the machine to prepare a beverage), the top coat layer does not melt and is therefore able to protect the underlying organic heat seal layer, and therefore the sachet as a whole, from damage (e.g. cracking and / or bursting) during extraction. Advantageously, the presence of a top coat layer does not negatively impact the gas or moisture barrier properties of the packaging material, meaning that the multi-layer metallized paper-based packaging materials prepared by the method of the present invention maintain the desired low oxygen transmission rate (OTR) and water vapour transmission rate (WVTR) values needed for such an application.

[0102] In preferred methods of the present invention, the top coat layer formed in step (v) comprises at least one polyolefin selected from polyethylene, such as ionomer thermoplastic ethylene methacrylic acid copolymer with zinc (Zn), sodium (Na), lithium (Li) or other metal ions, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE) or high-density polyethylene (HDPE), polypropylene (PP), a copolymer of polyethylene, a copolymer of polypropylene, or combinations thereof. More preferably, the top coat layer formed in step (v) comprises polyethylene, particularly preferably low-density polyethylene, or a copolymer of polyethylene. When the top coat layer comprises a copolymer of polyethylene, the comonomer is preferably one or more (e.g. one) a-olefins. Particularly preferably, the comonomer is selected from propylene, 1-butene, 1-pentene, 4-methyl-l- pentene, 1-hexene, 1-octene, and mixtures thereof.

[0103] In preferred methods of the present invention, the top coat layer formed in step (v) is present in an amount of 5 to 20 g / m2, preferably in an amount of 7 to 15 g / m2, more preferably in an amount of 10 to 12 g / m2.

[0104] Preferred methods of the present invention further comprise the step of: (vi) forming an ink layer on the outer side of the paper layer.

[0105] Preferably, the ink layer comprises a water-based ink, a solvent-less ink, or a combination thereof. In preferred methods of the present invention, the ink layer formed in step

[0106] (vi) is present in an amount of 0.5 to 5 g / m2.

[0107] Preferred methods of the present invention further comprise the step of:

[0108] (vii) forming an over-print varnish layer on the outer side of the paper layer or, if present, the outer side of the ink layer.

[0109] Preferably, the over-print varnish layer formed in step (vii) comprises a styrene acrylic varnish. The presence of an OPV layer results in the packaging material having improved resistance to hygroexpansive strain, as it imparts improved barrier properties to moisture under high humidity conditions.

[0110] In preferred methods of the present invention, the over-print varnish layer formed in step (vii) is present in an amount of 0.5 to 10 g / m2.

[0111] In preferred methods of the present invention, the multi-layer metallized paper-based packaging material has a Water Vapour Transmission Rate (WVTR) below 0.5 g / m2 / day (measured at 23 °C, 85% Relative Humidity) and / or an Oxygen Transmission Rate (OTR) below 0.1 cm3 / m2 / day bar (measured at 23 °C, 50% Relative Humidity). These values are measured after subjecting the sample to an in-plane tensile pre-straining up to 2% and also after subjecting the sample to a Gelboflex testing apparatus in 3 cycles, according to flexibility testing standard ASTM F392 or equivalent.

[0112] In preferred methods of the present invention, the multi-layer metallized paper-based packaging material has a strain at break under in-plane tensile loading up to 5% in machine direction and up to 15% in the cross-machine direction of the paper.

[0113] According to another example of the method of the invention, at least the paper layer, the organic barrier layer, the inorganic barrier layer, the organic heat seal layer and the top coat layer form a film that is laminated on the cardboard layer during a final step (vi).

[0114] According to another example of the method of the invention, the film made at least by the paper layer, the organic barrier layer, the inorganic barrier layer, the organic heat seal layer and the top coat layer made during step (i), (ii), (iii), (iv) and (v), is laminated on the cardboard layer with an adhesive.

[0115] Preferably the adhesive comprises a polyvinyl alcohol (PVOH); an ethylene vinyl alcohol (EVOH); a butenediol vinyl alcohol co-polymer (BVOH); a polyolefin such as a polyethylene (PE), a polypropylene (PP) or a polyethylene co-polymers; an acrylate such as a polyacrylate, a polymethacrylate, a styrene acrylate, a vinyl acetate and combinations thereof; a polyurethane (PU); a polyester; a casein; a starch; a sugar or sugar derivative; a cellulose or cellulose derivative; or a mixture thereof; preferably wherein the adhesive layer comprises an acrylate.

[0116] Viewed from a further aspect, the present invention relates to a multilayer metallized paper-based packaging material obtained by or obtainable by the method as hereinbefore described.

[0117] Viewed from a further aspect, the present invention relates to a method of preparing a tridimensional closed packaging item, the method comprising the steps of:

[0118] (i) forming a multi-layer metallized paper-based packaging material according to the method as hereinbefore described;

[0119] (ii) filling the multi-layer metallized paper-based packaging material with an edible product for human or animal consumption; and

[0120] (iii) sealing the packaging material to form the tridimensional closed packaging item.

[0121] Preferably, the tridimensional closed packaging item is a sachet. More preferably, the tridimensional closed packaging item is a sachet for use in a beverage machine (e.g. a hot beverage machine).

[0122] In preferred methods of the present invention, the edible product is a powder, preferably selected from milk powder, chocolate powder, coffee powder, emulsified fat powder (e.g. a creamer), and combinations thereof. Viewed from a further aspect, the present invention relates to a tridimensional closed packaging item obtained by or obtainable by the method as hereinbefore described.

[0123] Viewed from a further aspect, the present invention relates to the use of a multi-layer metallized paper-based packaging material as hereinbefore described, for packaging an edible product for human or animal consumption.

[0124] Preferably, the edible product is a powder, preferably selected from milk powder, chocolate powder, coffee powder, emulsified fat powder (e.g. a creamer), and combinations thereof.

[0125] Viewed from a further aspect, the present invention relates to a packaged edible product comprising a multi-layer metallized paper-based packaging material as hereinbefore described filled with an edible product for human or animal consumption.

[0126] Preferably, the edible product is a powder, preferably selected from milk powder, chocolate powder, coffee powder, emulsified fat powder (e.g. a creamer), and combinations thereof.

[0127] Viewed from a further aspect, the present invention relates to a tridimensional packaging item enable to store food or beverage for human or animal consumption, the packaging item being made at least from the multi-layer metallized paper-based packaging material comprising the cardboard layer.

[0128] Examples

[0129] A first embodiment of the invention is illustrated in Figure 1. In this embodiment, the multilayer structure 1 comprises in order, from its outer side (i.e. the side of the material which is turned towards the outside of the package ultimately made thereof) towards its inner side (i.e. the inner side in contact with the packaged product in a package made thereof): a paper layer 2; - an organic barrier layer 3, which provides mainly gas (especially oxygen) barrier properties;

[0130] - an inorganic barrier layer 4, which provides mainly moisture barrier properties;

[0131] - an organic heat seal layer 5; and

[0132] - a top coat layer 6.

[0133] Figure 2 depicts a similar structure to that described above in relation to Figure 1. However, in this second exemplary embodiment of the invention, the outer side of the paper layer 2 is covered with two additional layers as follows, in order from the outside face to the inside of the packaging material:

[0134] - an outermost over-print varnish layer 8; and

[0135] - an ink layer 7.

[0136] Figure 8 depicts a similar structure to that described above in relation to Figure 1. However, in this third exemplary embodiment of the invention, the outermost layer of the structure is a cardboard layer 10 covering the paper layer 2. More precisely, the cardboard layer 10 is attached to the paper layer 2 with an adhesive 9. The adhesive 9 may comprises a polyvinyl alcohol (PVOH); an ethylene vinyl alcohol (EVOH); a butenediol vinyl alcohol co-polymer (BVOH); a polyolefin such as a polyethylene (PE), a polypropylene (PP) or a polyethylene copolymers; an acrylate such as a polyacrylate, a polymethacrylate, a styrene acrylate, a vinyl acetate and combinations thereof; a polyurethane (PU); a polyester; a casein; a starch; a sugar or sugar derivative; a cellulose or cellulose derivative; or a mixture thereof; preferably wherein the adhesive layer comprises an acrylate.

[0137] The following examples exemplify the invention without limiting the scope of the present invention. of materials Two packaging materials were prepared having the constructions shown in Table 1 below. The amounts of each layer present are given in g / m2.

[0138] The materials were prepared by (i) forming an organic barrier layer on a paper layer via an aqueous solution deposition method; (ii) forming an inorganic barrier layer on the organic barrier layer via a vacuum deposition method; and (iii) forming an organic heat seal layer on the inorganic barrier layer via an aqueous dispersion coating method. In the case of Example A, a top coat layer was additionally formed on the organic heat seal layer via an extrusion method. Table 1

[0139] Example 2 - testing of materials

[0140] • Test 1: seal strength

[0141] In a first test, 15 mm strips of a material (either example CE1 or A) were cut and pressure sealed to another 15 mm strip of the same material. The pressure sealing was conducted at a range of different sealing temperatures and the sealed structure was then allowed to cool to room temperature.

[0142] Tensile testing was carried out by manually pulling the two strips away from one another to determine the maximum force each seal could withstand before failing. The results are shown in Figure 3. The material of the present invention (material A) demonstrated similar or improved seal strength at a range of different sealing temperatures versus the material of the comparative example (CE1), thus demonstrating that the inclusion of a top coat layer does not negatively impact the seal strength (for example when the materials are used to form packages such as sachets) and instead can improve it.

[0143] • Test 2: hot water contact

[0144] In a second test, 50 mm strips of a material (either example CE1 or A) were cut and then each exposed to a hot water jet (at a temperature of 90-95°C) dripping for 40 seconds using a B2B Nespresso system. Methylene blue was then applied to each material to visualise any cracks in the structure.

[0145] After the test, material CE1 was found to be significantly cracked, as shown in Figure 4. However, in the case of material A of the present invention, no cracks were noted upon treatment with methylene blue (Figure 5) indicating that the top coat layer works to prevent the organic heat seal layer from being solubilised and etched during a hot water extraction.

[0146] • Test 3: burst pressure

[0147] In a third test, a sample of a material (either example CE1 or A) was inserted into a B2B Nespresso system and subjected to the usual high pressure and high temperature water conditions employed during hot water extraction of a coffee capsule. Methylene blue was then applied to each material to visualise cracks in the structure.

[0148] After the test, material CE1 was found to be significantly cracked, as shown in Figure 6. However, in the case of material A of the present invention, no cracks were noted upon treatment with methylene blue (Figure 7) indicating that the top coat layer works to prevent the organic heat seal layer from being damaged as a result of the high pressure encountered in such a hot water extraction. Test 4: Heat seal failure test

[0149] In a fourth test, 50 mm strips of a material (either example CE1 or A) were cut and pressure sealed to another 50 mm strip of the same material at a sealing temperature of 140 °C. The sealed structure was then allowed to cool to room temperature.

[0150] To investigate seal failure during hot water extraction, hot water (at a temperature of 90-95 °C) was poured on the seal and the two strips were immediately manually pulled apart. Such an experiment simulates a hot water extraction, for example in a hot beverage machine, and so evaluates the usefulness of the tested materials in products (e.g. sachets) for use in such machines.

[0151] The material of the comparative example (CE1) failed immediately upon being in contact with the hot water. However, the material of the present invention (material A) was able to maintain the seal for an extended period of time prior to failure, indicating its usefulness in an application involving hot water, such as in a hot beverage machine. Material A was found to perform in a similar fashion to materials currently used in hot beverage machines, which are predominantly plastic-based.

Claims

Claims1. A multi-layer metallized paper-based packaging material comprising at least, from its outer side to its inner side:(i) a paper layer;(ii) at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or vinyl alcohol copolymers or a combination thereof;(iii) at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof;(iv) at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer; and(v) a top coat layer comprising at least one polyolefin.

2. A multi-layer metallized paper-based packaging material as claimed in claim 1, wherein the at least one polyolefin present in the top coat layer has a melting temperature greater than 95 °C, preferably greater than 100 °C.

3. A multi-layer metallized paper-based packaging material as claimed in claim 1 or claim 2, wherein the top coat layer comprises at least one polyolefin selected from polyethylene, such as ionomer thermoplastic ethylene methacrylic acid copolymer with zinc (Zn), sodium (Na), lithium (Li) or other metal ions, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE) or high-density polyethylene (HDPE), polypropylene (PP), a copolymer of polyethylene, a copolymer of polypropylene, or combinations thereof.

244. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 3, wherein the top coat layer comprises polyethylene, preferably low-density polyethylene, or a copolymer of polyethylene.

5. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 4, wherein the top coat layer is present in an amount of 2 to 50 g / m2, preferably in an amount of 7 to 15 g / m2, more preferably in an amount of 10 to 12 g / m2.

6. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 5, wherein the top coat layer has a thickness comprises between 2pm to 50pm.

7. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 6 which is recyclable in paper recycling, and preferably has a paper content of at least 80 wt% based upon the total weight of the packaging material, more preferably greater than 85 wt%, even more preferably greater than 90 wt%.

8. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 7, wherein the inorganic barrier layer comprises metals or metalloids selected from aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx), preferably aluminium.

9. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 8, wherein the ionomer grafted to the acrylic or methacrylic polymer in the at least one organic heat seal layer is a sodium ionomer.

10. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 9, wherein the packaging material has:(i) a Water Vapour T ransmission Rate (WVTR) below 0.5 g / m2 / day (measured at 23 °C, 85% Relative Humidity); and / or(ii) an Oxygen Transmission Rate (OTR) below 0.1 cm3 / m2 / day bar (measured at 23 °C, 50% Relative Humidity); and / or(iii) a strain at break under in-plane tensile loading up to 5% in machine direction and up to 15% in the cross-machine direction of the paper.

11. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 10, in which the top coat layer is an aqueous coating deposition.

12. A multi-layer metallized paper-based packaging material as claimed in any one of claims 1 to 11, comprising a cardboard layer and such that the cardboard layer is the outermost layer of the multi-layer metallized paperbased packaging material.

13. A multi-layer metallized paper-based packaging material as claimed in claim 12, in which the cardboard layer has a thickness comprises between 150pm to 350pm.

14. A method for preparing a multi-layer metallized paper-based packaging material according to any of preceding claims 1 to 13, the method comprising the steps of:(i) providing a paper layer;(ii) forming at least one organic barrier layer comprising a polymer selected from polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, on the paper layer;(iii) forming at least one inorganic barrier layer comprising metals, metalloids, or a combination thereof on the organic barrier layer(s);(iv) forming at least one organic heat seal layer comprising an acrylic or methacrylic acid polymer grafted with at least one type of ionomer on the inorganic barrier layer(s); and(v) forming a top coat layer comprising at least one polyolefin on the organic heat seal layer(s).

15. A method for preparing a multi-layer metallized paper-based packaging material according to preceding claims 14 and in combination with claims 12 or 13, in which at least the paper layer, the organic barrier layer, the inorganic barrier layer, the organic heat seal layer and the top coat layer form a film that is laminated on the cardboard layer during a final step (vi).

16. A method for preparing a multi-layer metallized paper-based packaging material according to preceding claims 14, in which the film is laminated on the cardboard layer with an adhesive.

17. A multi-layer metallized paper-based packaging material obtained by or obtainable by the method of claim 14.

18. A tridimensional closed packaging item obtained by or obtainable by the method of claim 14.

19. Use of a multi-layer metallized paper-based packaging material according to any one of claims 1 to 13, for packaging an edible product for human or animal consumption.

120. A packaged edible product comprising a multi-layer metallized paper-based packaging material according to any one of claims 1 to 13 filled with an edible product for human or animal consumption.

21. A tridimensional packaging item enable to store food or beverage for human or animal consumption, the packaging item being made at least from the multi-layer metallized paper-based packaging material according to claims 12 or 13.28

Images