Multilayer metallized paper-based packaging material

Abstract

The present invention relates to a multi-layer paper-based packaging material (1) with a metallic appearance comprising, from its inner side to its outer side: a paper layer (2) having a grammage in the range of 30 to 120 g / m2; at least one inorganic barrier layer (3) selected within the list of: metals, metalloids, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and an ink layer (4), wherein at least a portion of the ink layer is transparent or translucent.

Description

[0001] MULTILAYER METALLIZED PAPER-BASED PACKAGING MATERIAL

[0002] Field of the invention

[0003] Background of the invention

[0004] Plastic packaging is used frequently in the economy and in people's daily lives. It has multiple advantages, such as its flexibility and its light weight. Such a weight reduction contributes to fuel saving and CO2reduction during transport, for example. Its barrier properties help to reduce food waste due a positive effect on increasing shelf life. The barrier properties also help to secure food safety and quality. Typically, such barrier properties include gas barrier, for example to oxygen and water vapor (moisture), and if possible, also, liquid tightness.

[0005] One way to provide good moisture barrier in paper-based packaging materials, is the introduction of a metal or metalloid layer in a so-called "metallized" layer. In the present description, the word "metallized" (for instance in the expression "metallized barrier paper layer") is meant to encompass the deposition at the surface of paper or paperboard, of metal or metalloid atoms. One can even consider embodiments comprising the deposition of an alloy of metal and metalloid. Metalloids are close to metals in some of their characteristics. Aluminium oxide and silicon oxide are examples of metalloids.

[0006] In order to achieve a metallic appearance (e.g. lustre) in a paperbased packaging material, it is usual to apply a metal laminate or to print metallic pigments. However, these approaches render the resulting packaging harder to recycle due to the difficulty in separating the materials (i.e. the metal from the polymer in the laminate or the metallic pigment from the underlying surface). In addition, the inclusion of additional layers and / or printing steps increases both material cost and processing time.

[0007] It is the object of the present invention to address at least one of the foregoing problems.

[0008] Summary of the invention

[0009] The first aspect of the present invention relates to a multi-layer paper-based packaging material with a metallic appearance comprising, from its inner side to its outer side: a paper layer having a grammage in the range of 30 to 120 g / m2; at least one inorganic barrier layer selected within the list of: metals, metalloids, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and an ink layer, wherein at least a portion of the ink layer is transparent or translucent.

[0010] The multi-layer paper-based packaging material may further comprise a paperboard on the inner side of the paper layer.

[0011] The multi-layer paper-based packaging material may further comprise at least one organic barrier layer (5) located between the paper layer and the at least one inorganic barrier layer, the at least one organic barrier layer comprising a polymer selected within the list of: polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, 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. The multi-layer paper-based packaging material may further comprise at least one organic heat seal layer located between the at least one inorganic barrier layer and the ink layer, said heat seal layer in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2. The at least one organic heat seal layer may comprise an ionomer, optionally wherein the ionomer is an acrylic or methacrylic acid polymer and / or wherein the counterion is sodium.

[0012] The multi-layer paper-based packaging material may further comprise an outermost layer of an overprint varnish (OPV), optionally wherein the overprint varnish outermost layer is a styrene acrylic varnish.

[0013] The at least one inorganic layer may comprise metals or metalloids selected within the list of: aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx), optionally wherein said metals and / or metalloids are deposited either by vacuum deposition or transfer metallization.

[0014] The ink layer may be produced from an ink selected within the list of: waterbased inks, solvent-less inks, or a combination thereof. The ink layer may exclude metallic pigments.

[0015] In embodiments, the multi-layer paper-based packaging material does not include a metal laminate.

[0016] A second aspect of the present invention relates to a method of producing a multi-layer paper-based packaging material with a metallic appearance comprising: a)providing a paper layer having a grammage in the range of 30 to 120 g / m2; b) providing at least one inorganic barrier layer over the paper layer, the at least one inorganic barrier layer comprising metals, metalloids, oxides thereof, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and c) providing an ink layer over the inorganic barrier, wherein at least a portion of the ink layer is transparent or translucent.

[0017] The method may further comprise providing a paperboard on the inner side of the paper layer.

[0018] The method may further comprise providing at least one organic barrier layer between the paper layer and the at least one inorganic barrier layer, the organic barrier layer comprising a polymer selected within the list of: polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, in an amount of 0.5 to 20 g / m2.

[0019] The method may further comprise providing at least one organic heat seal layer between the at least one inorganic barrier layer and the ink layer, said heat seal layer being applied in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2.

[0020] The method may further comprise providing an outermost layer of an overprint varnish (OPV), optionally wherein the overprint varnish outermost layer is a styrene acrylic varnish.

[0021] The at least one inorganic layer may comprise metals or metalloids selected within the list of: aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx), optionally wherein said metals and / or metalloids are deposited either by vacuum deposition or transfer metallization. Providing the ink layer may comprise depositing an ink selected within the list of: water-based inks, solvent-less inks, or a combination thereof, optionally wherein the ink does not include metallic pigments.

[0022] A third aspect of the present invention relates to a tridimensional closed packaging item made of a multi-layer metallized paper-based packaging material according to the first aspect of the present invention, which is obtained by forming, filling with an edible product for human or animal consumption, and then sealing said packaging material.

[0023] A fourth aspect of the present invention relates to the use of a multi-layer metallized paper-based packaging material according to the first aspect of the present invention, for packing an edible product for human or animal consumption.

[0024] A fifth aspect of the present invention relates to a packaged edible product, comprising a multi-layer metallized paper-based packaging material according to the first aspect of the present invention, filled with an edible product for human or animal consumption.

[0025] As used in this specification, 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".

[0026] Brief description of the drawings

[0027] 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: Figure 1 shows a multi-layer paper-based packaging material (1) according to the present invention, which comprises a paper layer (2) over which is deposited (in order) an inorganic barrier layer (3) and an ink layer (4), the ink layer having at least one portion that is transparent or translucent;

[0028] Figure 2 shows a multi-layer paper-based packaging material (1) according to the present invention, which comprises a paper layer (2) over which is deposited (in order) an organic barrier layer (5), an inorganic barrier layer (3), an organic heat seal layer (6), an ink layer (4), and an overcoat varnish (7), the ink layer having at least one portion that is transparent or translucent.

[0029] Detailed description of the invention

[0030] Generally, in the present specification, "extrusion coating", it is meant a method to provide a layer of polymer by using an extruder which forces melted thermoplastic resin (e.g. polyethylene) through a horizontal slot-die onto a moving web of substrate (e.g. paper). The resulting product is a permanently coated web structure.

[0031] By "extrusion lamination", it is meant a similar process to extrusion coating, whereby a polymer resin is extruded between two substrates (e.g. a layer of paper and another layer of polymeric film), and acts as a bonding agent.

[0032] By "adhesive lamination", it is meant a process whereby one paper material is coated with adhesive and laminated to a second paper or paperboard material. In a lamination process, two thick layers of material are combined, either by extrusive lamination or adhesive lamination, whereby the thickness of each layer is far greater than the thickness obtained by dispersion coating.

[0033] By "dispersion coating", it is meant a coating technique whereby an aqueous dispersion of fine polymer particles or polymer solution is applied to the surface of paper or board as such, 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. Dispersion coating can create a much thinner layer than extrusion lamination and / or adhesive lamination, since the polymer is mixed in an aqueous water solution. This brings advantages in terms of quantity of polymer usage, its barrier performance and recyclability of resulting paper structure. The target of dispersion coating is to achieve a barrier layer against water, water vapour, grease, oil, gas, etc. by environmentally friendly coating. Another target is to prepare surface of paper material for a vacuum deposition process.

[0034] By "fibre", it is meant a cellulosic fibre, which is generally extracted from plants, seeds or trees; such fibres contain not only cellulose molecules, but also hemi-cellulose as well as lignin.

[0035] Multilayer Structure

[0036] The multilayer structure comprises the following layers, from outer surface to inner surface:

[0037] - a paper layer;

[0038] - an inorganic barrier layer; and

[0039] - an ink layer, wherein at least a portion of the ink layer is transparent and / or translucent.

[0040] In embodiments, the multilayer structure further comprises a paperboard on the inner side of the paper layer. The paperboard provides a more rigid and robust structure.

[0041] The multilayer structure may comprise further layers in addition to those described herein. For example, the multilayer structure may include additional layers external to the layers described herein and / or between the layers described herein. In embodiments, the multilayer structure comprises additional organic barrier layers and / or additional inorganic barrier layers.

[0042] Preferably, the multilayer structure does not include a metal laminate or metallised film. These constructions, comprising metal bonded to a plastic, have traditionally been used to provide a lustre to packaging materials, but are difficult to recycle.

[0043] Paper Layer

[0044] The multilayer structure includes a paper layer as its principle structural component. Paper refers to material comprised of fibres obtained by the pulping of plant sources, such as trees, and is increasingly produced by recycling. Substantially any thickness of paper that possesses the material properties required for the final packaging product may be used in the present invention. The paper should be sufficiently robust that it effectively protects the contents of the final packaged product during transport and storage, but should be sufficiently flexible to permit forming into the final packaged product. In general, paper used for the paper layers of the present invention may have grammage (i.e. weight per unit area) of from about 30 g / m2to about 120 g / m2.

[0045] Organic Barrier Layer

[0046] In embodiments, the multilayer structure further comprises at least one organic barrier layer located between the paper layer and the at least one inorganic barrier layer. The organic barrier layer provides a barrier to the passage of gases (such as oxygen) and moisture through the multilayer packaging. In addition, the at least one organic barrier layer provides a more suitable surface for the deposition and adhesion of the inorganic barrier layer compared to the preceding paper layer. The at least one organic barrier layer may comprise a polymer.

[0047] The at least one organic barrier layer comprises PVOH, EVOH, BVOH, or mixtures thereof.

[0048] 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.

[0049] In embodiments, the at least one organic barrier layer is provided by depositing an aqueous solution of the polymer onto the paper layer, the solution having a concentration of xx g / L, and then drying. Inorganic Barrier Layer

[0050] The multilayer structure includes an inorganic barrier layer. The inorganic barrier layer provides a barrier to the passage of gases (such as oxygen) and moisture through the multilayer packaging.

[0051] The inorganic barrier layer comprises metals, metalloids, oxides thereof, or a combination thereof. The thickness of the inorganic barrier layer is from about 1 to about 100 nm. Substantially any metal, metalloid, or oxide thereof may be used that provides sufficient barrier properties, robustness, and flexibility in the thickness that it is applied. In addition, the metal, metalloid, or oxide thereof must be food safe.

[0052] In embodiments, the inorganic barrier layer comprises aluminium, aluminium oxide (AIOX), silicon oxide (SiOx), or combinations thereof.

[0053] Substantially any suitable methodology may be used to deposit the inorganic barrier layer. In embodiments, the inorganic barrier layer is deposited by vacuum deposition or transfer metallization onto the preceding layer, typically the paper layer or the at least one organic barrier layer.

[0054] Heat Sealing Layer

[0055] The multilayer structure includes a heat sealing layer. The inclusion of a heat sealing layer permits the multilayer structure to be converted to a packaged product without the application of adhesives by heat sealing, such as by a form, fill, and seal machine. The heat sealing layer also contributes to the overall barrier properties of the multilayer structure. The heat sealing layer may be a thermoplastic organic polymer. Substantially any food safe thermoplastic polymer may be used, on condition that it has the requisite material properties of robustness and flexibility in the thickness used. In embodiments, the heat sealing layer comprises an ionomer. The ionomer may be an acrylic or methacrylic acid homopolymer or copolymer with counter ions, such as sodium. In a preferred embodiment, the ionomer is an ethylene acrylic acid copolymer with sodium counter ions.

[0056] The heat sealing layer may be deposited as an aqueous dispersion and subsequently dried onto the surface of the preceding layer, typically the inorganic barrier layer.

[0057] In embodiments, the heat seal layer is located between the at least one inorganic barrier layer and the ink layer. The heat seal layer in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2.

[0058] Ink Layer

[0059] The multilayer structure includes an ink layer. The ink layer is used to improve the aesthetic qualities of the packaging and / or present information regarding the contents of the packaging. In particular, it has been surprisingly found that the use of an ink layer including at least a portion that is translucent or transparent in combination with an underlying inorganic barrier layer provides a lustrous finish to the multilayer structure without needing to incorporate a metallized film or metallic pigments. At least a portion of the ink layer is transparent or translucent. In embodiments, at least a portion of the ink layer is transparent and at least one portion of the ink layer is translucent.

[0060] Transparency (i.e. the unhindered transmission of light through the portion) may be achieved through the portion of the ink layer being absent of colorant. Alternatively, transparency may be achieved through not depositing ink onto the portion. The at least one portion of the ink layer that is transparent allows the lustre and coloration of the underlying at least one inorganic barrier layer to be observed directly.

[0061] Translucency (i.e. the partial transmission of light through the portion) may be achieved through the portion of the ink layer containing a reduced quantity of pigment, either due to the ink that is used containing a reduced quantity of pigment or through the deposition of a reduced quantity of ink. For the foregoing, "reduced quantity" is in comparison with inks and deposition used to achieve solid markings. The at least one portion of the ink layer that is translucent allows the lustre of the underlying at least one inorganic barrier layer to be observed, while presenting the coloration of the colorant used in the ink layer. For example, a yellow pigment may be used to produce a gold effect, while an orange pigment (or combination of yellow and red pigments) may be used to produce a copper effect.

[0062] In embodiments, the ink layer is produced from an ink selected within the list of: water-based inks, solvent-less inks, or a combination thereof. Preferably the ink layer does not include metallic pigments.

[0063] The ink layer may be provided by any suitable technique. In embodiments, the ink layer is provided by inkjet printing, laser printing, or screen printing. Overprint Varnish

[0064] Optionally, the multilayer structure includes an overprint varnish (7). The OPV is used to improve the aesthetic qualities of the packaging and also lowers water vapour transmission and protects the paper layer from water external to the packaging.

[0065] The OPV may have a thickness of between about 0.5 and about 10 g / m2. Preferably the OPV is a styrene acrylic varnish. The OPV may be applied using any suitable application technique.

[0066] Method of Production

[0067] The method of producing a multi-layer paper-based packaging material with a metallic appearance comprising: a) providing a paper layer having a grammage in the range of 30 to 120 g / m2; b) providing at least one inorganic barrier layer over the paper layer, the at least one inorganic barrier layer comprising metals, metalloids, oxides thereof, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and c) providing an ink layer over the inorganic barrier, wherein at least a portion of the ink layer is transparent or translucent.

[0068] The method may further comprise providing a paperboard on the inner side of the paper layer.

[0069] Provision of the paperboard may be the final step in producing the multilayer structure. The paperboard may be unformed (e.g. as a flat sheet that is subsequently formed). Alternatively, the paperboard may be formed, such as a tube, prior to attaching to the paper layer. Provision of the paperboard on the inner side of the paper layer may comprise adhesive lamination.

[0070] The method may further comprise providing at least one organic barrier layer between the paper layer and the at least one inorganic barrier layer, the organic barrier layer comprising a polymer selected within the list of: polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, in an amount of 0.5 to 20 g / m2.

[0071] The method may further comprise providing at least one organic heat seal layer between the at least one inorganic barrier layer and the ink layer, said heat seal layer being applied in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2.

[0072] The method may further comprise the step of providing an overprint varnish on the outer surface of the ink layer.

[0073] The method may further comprise the step of rehydrating the paper layer.

[0074] The method may be a batch method or a continuous method. The method may be a rol l-to-rol I process, wherein the paper layer is unspooled from an initial roll and the multilayer packaging material spooled onto a final roll, with processing to convert the paper to the multilayer packaging material, such as the provision of the further layers (e.g. the at least one organic barrier layer, the at least one inorganic barrier layer, and at least one organic heat seal layer) occurring to the length of material that is exposed between the initial and final roll. Exemplary Embodiments

[0075] In figure 1 is illustrated a first embodiment of the invention. In this embodiment, the multilayer structure 1 comprises in order, from its inner side (i.e. the side of the material which is turned towards the inside of the package made thereof) towards its outer side (i.e. the outer side of the package made thereof):

[0076] - a highly smooth paper layer 2 of grammage 62 g / m2,

[0077] - an inorganic vacuum deposited layer 3 of aluminium having a thickness of between 50 and 100 nm, which provides mainly moisture vapour barrier properties, and

[0078] - an ink layer 4 comprising at least one portion that is translucent, the at least one portion that is translucent comprising a yellow pigment, such that the package visually presents as gold.

[0079] In figure 2, is depicted a structure similar to that described above in relation to figure 1.

[0080] However, in this second exemplary embodiment of the invention, further layers are incorporated:

[0081] - a highly smooth paper layer 2 of grammage 62 g / m2,

[0082] - an organic barrier layer 5 of polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH) that provides mainly gas (especially oxygen) barrier properties and is applied as an aqueous solution in weight of 6 g / m2

[0083] - an inorganic vacuum deposited layer 3 of aluminium having a thickness of between 50 and 100 nm, which provides mainly moisture vapour barrier properties,

[0084] - a heat sealing layer 6 of methacrylic acid ionomer-based coating which serves as a heat seal layer and is applied as an aqueous dispersion in weight of 5 g / m2, - an ink layer 4 comprising at least one portion that is translucent, the at least one portion that is translucent comprising a yellow pigment, such that the package visually presents as gold, and

[0085] - an outermost acrylic based overprint varnish layer 7, which is applied as an aqueous dispersion in weight of 1 g / m2.

Claims

Claims1. A multi-layer paper-based packaging material (1) with a metallic appearance comprising, from its inner side to its outer side: a paper layer (2) having a grammage in the range of 30 to 120 g / m2; at least one inorganic barrier layer (3) selected within the list of: metals, metalloids, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and an ink layer (4), wherein at least a portion of the ink layer is transparent or translucent.

2. The multi-layer paper-based packaging material according to claim 1, further comprising a paperboard on the inner side of the paper layer.

3. The multi-layer paper-based packaging material according to claim 1 or claim 2, further comprising at least one organic barrier layer (5) located between the paper layer and the at least one inorganic barrier layer, the at least one organic barrier layer comprising a polymer selected within the list of: polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, 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.

4. The multi-layer paper-based packaging material according to any one of the preceding claims, further comprising at least one organic heat seal layer (6) located between the at least one inorganic barrier layer and the ink layer, said heat seal layer in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2.

5. The multi-layer paper-based packaging material according to claim 4, wherein the at least one organic heat seal layer comprises an ionomer, optionally wherein the ionomer is an acrylic or methacrylic acid polymer and / or wherein the counterion is sodium.

6. The multi-layer paper-based packaging material according to any one of the preceding claims, further comprising an outermost layer of an overprint varnish (OPV) (7), optionally wherein the overprint varnish outermost layer is a styrene acrylic varnish.

7. The multi-layer paper-based packaging material according to any one of the preceding claims, wherein the at least one inorganic layer comprises metals or metalloids selected within the list of: aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx), optionally wherein said metals and / or metalloids are deposited either by vacuum deposition or transfer metallization.

8. The multi-layer paper-based packaging material according to any one of the preceding claims, wherein the ink layer is produced from an ink selected within the list of: water-based inks, solvent-less inks, or a combination thereof.

9. The multi-layer paper-based packaging material according to any one of the preceding claims, wherein the ink layer does not include metallic pigments.

10. The multi-layer paper-based packaging material according to any one of the preceding claims, wherein the multi-layer paper-based packaging material does not include a metal laminate.

11. A method of producing a multi-layer paper-based packaging material with a metallic appearance comprising: a) providing a paper layer having a grammage in the range of 30 to 120 g / m2; b) providing at least one inorganic barrier layer over the paper layer, the at least one inorganic barrier layer comprising metals, metalloids, oxides thereof, or a combination thereof, said inorganic layer having a thickness comprised between 1 and 100 nm; and c) providing an ink layer over the inorganic barrier, wherein at least a portion of the ink layer is transparent or translucent.

12. The method according to claim 11, further comprising providing a paperboard on the inner side of the paper layer.

13. The method according to claim 11 or claim 12, further comprising providing at least one organic barrier layer between the paper layer and the at least one inorganic barrier layer, the organic barrier layer comprising a polymer selected within the list of: polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol co-polymer (BVOH), or a combination thereof, in an amount of 0.5 to 20 g / m2.

14. The method according to any one of claims 11 to 13, further comprising providing at least one organic heat seal layer between the at least one inorganic barrier layer and the ink layer, said heat seal layer being applied in an amount comprised between 2 and 20 g / m2, preferably in an amount comprised between 4 and 9 g / m2.

15. The method according to any one of claims 11 to 14, further comprising providing an outermost layer of an overprint varnish (OPV), optionally wherein the overprint varnish outermost layer is a styrene acrylic varnish.

16. The method according to any one of claims 11 to 15, wherein the at least one inorganic layer comprises metals or metalloids selected within the list of: aluminium, aluminium oxide (AIOx), or silicon oxide (SiOx), optionally wherein said metals and / or metalloids are deposited either by vacuum deposition or transfer metallization.

17. The method according to any one of claims 11 to 16, wherein providing the ink layer comprises depositing an ink selected within the list of: water-based inks, solvent-less inks, or a combination thereof, optionally wherein the ink does not include metallic pigments.

18. A tridimensional closed packaging item made of a multi-layer metallized paper-based packaging material according to any one of the preceding claims 1 to 10, which is obtained by forming, filling with an edible product for human or animal consumption, and then sealing said packaging material.

19. Use of a multi-layer metallized paper-based packaging material according to any one of the preceding claims 1 to 10, for packing an edible product for human or animal consumption.

20. A packaged edible product, comprising a multi-layer metallized paperbased packaging material according to any one of the preceding claims 1 to 10, filled with an edible product for human or animal consumption.

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