Paperboard with improved light barrier properties

Abstract

The present invention relates to a paperboard having improved light barrier properties, comprising at least three plies; a top layer sheet and a back layer sheet; and a middle layer sheet. The top sheet comprises at least 80 wt% of a chemical pulp. The intermediate plies comprise at least 40 wt% of CTMP from spruce, calculated based on the total fiber weight of the respective plies, wherein the CTMP from spruce has a brightness of between 40 and 60 according to ISO 2470-1: 2016. The back layer sheet comprises at least 80 wt% of an unbleached hardwood or softwood kraft pulp, calculated based on the total fiber weight of the back layer sheet, wherein a) if the unbleached kraft pulp in the back ply is from hardwood, this hardwood unbleached kraft pulp exhibits a Kappa number according to ISO 302: 2015 of at least 15, b) if the unbleached kraft pulp in the back ply is from softwood, this softwood kraft pulp exhibits a Kappa number according to ISO 302: 2015 of at least 20. The invention also relates to a packaging material, a liquid packaging container made of said packaging material and a method of manufacturing a paperboard.

Description

Technical Field

[0001] The present disclosure relates to paperboard, packaging material comprising the paperboard, containers made from the packaging material, and methods of producing paperboard. Background Art

[0002] Fiber-based packaging materials used for product packaging (such as beverages or food packaging) are often coated with a polymer coating to provide a barrier against liquids, moisture, and flavors. Furthermore, beverages are often sensitive to light because it can induce undesirable chemical reactions that can produce off-flavors or degrade vitamins or nutrients. Visible or UV light can further alter the color of a beverage. Other products, such as pharmaceuticals or cosmetics, are also light-sensitive. Conventionally used polymer coatings offer poor gas barrier properties. Consequently, packaging materials for beverages and other light-sensitive products are often provided with one or more layers of aluminum foil to ensure high gas, aroma, and light barrier properties. However, the addition of polymer and aluminum layers adds significant costs and makes recycling the material more difficult. Furthermore, due to its high carbon footprint, there is a desire to replace aluminum foil in paper and paperboard-based packaging materials.

[0003] Aseptic packaging for long-shelf-life beverage products such as milk and juice is typically made from liquid packaging board (LPB), which comprises a multi-layer paperboard-based substrate, an outermost heat-sealable polyolefin (e.g., polyethylene, PE) layer, and an innermost polyolefin and aluminum layer. The aluminum layer, needed to provide light and oxygen barrier properties, is typically incorporated between the polyethylene (PE) layers to create the following structure: PE / paperboard / PE / aluminum / PE.

[0004] In the prior art, attempts have been made to replace aluminum foil with more environmentally friendly and / or more easily recyclable solutions. Barrier cellulose films, such as microfibrillated cellulose (MFC) films, or additional coated oxygen barrier layers, such as PVOH layers, have been proposed as alternatives to aluminum foil to provide oxygen barrier properties. However, such alternative solutions do not provide the desired light barrier properties. It has further been proposed to include light-absorbing or light-reflecting pigments or particles in the coating. US Pat. No. 739,460 BB discloses a packaging material comprising a heat-sealable layer blended with light-absorbing pigments comprising carbon black and titanium dioxide. Such solutions are generally expensive and cumbersome, and can further complicate the recycling of the paperboard due to contamination of the plastic. Furthermore, such pigments can alter the mechanical properties of the packaging material and degrade the sealability. Other solutions include using barrier layers comprising black polyethylene or polyester. However, such barrier layers are difficult to recycle.

[0005] Therefore, there remains a need for more sustainable solutions to replace aluminum foil in paper and paperboard based packaging materials while maintaining acceptable light barrier properties. At the same time, there is a need to replace aluminum foil with alternative solutions that facilitate the repulping and recycling of used packaging materials. Summary of the Invention

[0006] An object of the present disclosure is to provide an alternative to aluminum foil, which is commonly used as a barrier film, for providing light barrier properties in packaging materials for beverage packaging or pharmaceutical packaging.

[0007] Another object of the present disclosure is to provide a paperboard having inherent light barrier properties that is suitable for beverage packaging.

[0008] Another object of the present disclosure is to provide a paperboard-based packaging material for the packaging of beverages or medicines, which packaging material exhibits high light and gas barrier properties and which facilitates repulping of the board compared to packaging materials using conventional aluminum foil or other light barrier solutions of the prior art.

[0009] The above-mentioned objects and other objects that will be appreciated by those skilled in the art from this disclosure are achieved through various aspects of the present disclosure.

[0010] According to a first aspect shown herein, there is provided a paperboard

[0011] Comprising at least three plies: a top ply and a back ply, and an intermediate ply disposed between the top ply and the back ply

[0012] wherein the top sheet comprises at least 80 wt% chemical pulp, calculated based on the total fiber weight of the top sheet,

[0013] wherein the middle ply comprises at least 40 wt%, preferably at least 50 wt%, of CTMP from spruce, calculated on the total fiber weight of the middle ply, wherein the CTMP from spruce has a brightness of between 40 and 60 according to ISO 2470-1:2016, and

[0014] The back layer comprises at least 80 wt%, preferably 80-100 wt%, of unbleached kraft pulp from hardwood and / or from softwood, based on the total fiber weight of the back layer.

[0015] a) if the unbleached kraft pulp in the back ply is from hardwood, such hardwood unbleached kraft pulp exhibits a kappa value according to ISO 302:2015 of at least 15, preferably between 15 and 40, most preferably at least 20, preferably between 20 and 40, and

[0016] b) If said unbleached kraft pulp in the back ply is from softwood, such softwood kraft pulp exhibits a kappa number according to ISO 302:2015 of at least 20, preferably 20-90, preferably at least 30-90, 40-90.

[0017] It has been found that the use of CTMP from spruce with a brightness between 40 and 60 in at least one middle ply of the paperboard in combination with a backing ply comprising unbleached hardwood or softwood pulp with a kappa number within the claimed range results in excellent light barrier properties without negatively impacting printing properties. Furthermore, the light barrier properties of the paperboard according to the invention are less sensitive to creasing and converting than prior art solutions using aluminum foil or other light-barrier coatings.

[0018] The present invention effectively limits UV and light transmission between 200 nm and 800 nm, preferably such that the transmission at, for example, 250 nm is less than 0.1% and preferably 0%, and / or such that the light transmission through the paperboard at 700 nm is less than 2%, preferably less than 1% and more preferably between 0-0.2%. Light transmission can be measured, for example, using a UV-Vis spectrophotometer (Agilent Cary 100 UV-Vis spectrophotometer) and calibrated for opacity and complete transparency.

[0019] CTMP with brightness within the claimed range can be achieved by adjusting the temperature and pressure during CTMP production and treating the pulp with sodium hydroxide (NaOH) at an optimized pulp consistency and process residence time. The spruce CTMP is preferably unbleached. The spruce CTMP can also be high-temperature CTMP (HT-CTMP), which has been treated or manufactured to exhibit the claimed brightness. The pressure and temperature used in CTMP production, as well as the potential treatment with sodium hydroxide, depends on the wood raw material, particularly its age and storage.

[0020] In an embodiment, the middle ply comprises CTMP from spruce having a brightness within the stated range of 40-80 wt%, preferably 50-80 wt%. The remainder of the middle ply can be, for example, a chemical pulp, such as unbleached kraft pulp, preferably with a low kappa number, or CTMP from, for example, pine, poplar, birch, or eucalyptus, or a mixture thereof. In a preferred embodiment, the remainder of the middle ply is unbleached kraft pulp having a brightness of 40-60% according to ISO 2470-1:2016.

[0021] Preferably, the top sheet comprises 80 wt%, most preferably 80-100 wt% bleached chemical pulp, preferably from softwood. In an embodiment, the top sheet comprises 100 wt% bleached chemical pulp, preferably bleached kraft pulp. In a preferred embodiment, the top sheet comprises 100 wt% bleached chemical pulp (calculated based on the total weight of the top sheet) having a brightness according to ISO 2470-1:216 of at least 70%, preferably at least 75%, and most preferably 77-90%. Preferably, the bleached chemical pulp of the top sheet is kraft pulp from hardwood or softwood or a mixture thereof. In an embodiment, the bleached chemical pulp of the top sheet comprises at least 30 wt% hardwood pulp, for example 30-70 wt%, or 30-100 wt% hardwood pulp.

[0022] In an embodiment, the top sheet comprises less than 7 wt%, preferably less than 5 wt% filler, based on the total weight of the top sheet.

[0023] In an embodiment, the back layer comprises 100 wt% of the unbleached hardwood or softwood kraft pulp (having a kappa number within the range), calculated based on the total fiber weight of the back layer. The kappa number of the kraft pulp can be controlled by adjusting the concentration of the cooking chemicals and the cooking temperature, pressure and time in the production of the pulp.

[0024] Paperboard generally refers to a strong, thick paper or cardboard containing cellulose fibers used for boxes and other types of packaging. Typically, uncoated paperboard has a grammage of between 150-400 gsm, preferably 180-400 gsm, or 200-350 gsm, and a density of 500-900 kg / m 3 Between, preferably 600-850kg / m 3 between.

[0025] The grammage of the top sheet, back sheet and middle sheet can be optimized to provide the desired strength and light barrier properties. For example, the grammage weight split can be:

[0026] - Top sheet: 20-100gsm, preferably 20-50gsm

[0027] -Middle layer: 110-200gsm, preferably 110-150gsm

[0028] -Back layer: 20-100gsm, preferably 20-50gsm

[0029] In an embodiment, the CTMP from spruce has a fiber bundle (shive) content of less than 8 wt%, preferably less than 5 wt%, for example 0-5 wt% fiber bundles or 0.1-5 wt%. Such a low fiber bundle content further improves the light barrier properties because the risk of spots with low fiber content is reduced in this way. To ensure that the CTMP from spruce has a low fiber bundle content, the pulp can be classified and / or refined using, for example, a double-disc refiner.

[0030] In some embodiments, the CTMP from spruce used to produce paperboard comprises a fine fraction that is capable of passing through a 200 mesh sieve and exhibits a water retention value (WRV) value of less than 280%, preferably less than 250%, according to ISO 23714:2014. Fine fractions with such low WRVs have good scattering properties, thereby further improving the opacity of the paperboard.

[0031] In some embodiments, the interlayer sheet further comprises a dye and / or a high-opacity pigment and / or a high-reflectivity pigment, preferably selected from carbon black, titanium dioxide, calcined clay, and ground or precipitated calcium carbonate (PCC). Such dyes and / or high-opacity pigments and / or reflective pigments further reduce light transmission through the paperboard. Compared to prior art solutions that rely solely on such dyes and / or high-opacity pigments to provide light-blocking properties, the present invention allows for the use of less dye and / or high-opacity pigment. In embodiments, the interlayer sheet comprises less than 15 wt% of dye and high-opacity pigment, e.g., in an amount of 0.1-10 wt%, preferably less than 1 wt%, e.g., 0.1-0.9 wt%, based on the total weight of the interlayer sheet. The dye and / or high-opacity pigment may be mixed or co-added with microfibrillated cellulose (MFC), carboxymethyl cellulose (CMC), and / or fines. In this context, fines are intended to define a fine fraction capable of passing through a 200-mesh sieve. The MFC, CMC and / or fines provide a high surface area for the dye / pigment to spread onto and help improve retention so that less dye / pigment can be used.

[0032] In an embodiment, the CTMP from spruce is a never-dried pulp having a brightness between 40 and 60. The use of never-dried pulp helps control the brightness and amount of fines in the CTMP.

[0033] In some embodiments, the paperboard of the present invention comprises at least a first intermediate ply and a second intermediate ply, wherein the first intermediate ply and the second intermediate ply comprise:

[0034] - 40-80 wt%, preferably between 50-80 wt%, of CTMP from spruce, having a brightness of 40-60 according to ISO 2470-1:2016, and

[0035] -20-60wt%, preferably 20-50wt% chemical pulp

[0036] All percentages are calculated based on the total fiber weight of the corresponding ply.These embodiments enable the board manufacturer to use the same pulp mixture in at least two middle plies, which facilitates production.

[0037] The amount of CTMP from spruce and the amount of chemical pulp as defined herein refer to the total amount of CTMP or chemical pulp originating from dried pulp or never-dried pulp, respectively (including eg potential broke).

[0038] In an embodiment, the paperboard comprises at least a first middle ply and a second middle ply, wherein the first middle ply comprises 40-80 wt%, preferably 50-80 wt% of CTMP having a brightness greater than 60, for example between 60 and 100, and 60-20 wt%, preferably 50-20 wt% of chemical pulp, and wherein the second middle ply comprises at least 40 wt%, preferably between 40-80 wt%, more preferably between 50-80 wt% of CTMP from spruce having a brightness of 40-60 according to ISO 2470-1:2016, all percentages being calculated based on the total fiber weight of the respective plies. The remaining pulp of the middle ply is preferably chemical pulp, for example bleached or unbleached kraft pulp. In these embodiments, the first middle ply is preferably arranged adjacent to the top ply, and the second middle ply is preferably arranged adjacent to the back ply. These embodiments enable paperboard manufacturers to optimize both the printing properties and the light barrier properties of the paperboard. By placing the interlayer sheet comprising CTMP from spruce with the low brightness adjacent to the back layer and the CTMP with higher brightness adjacent to the top layer, the light-blocking properties are optimized while the printing properties of the top layer are not negatively impacted. The paperboard may further comprise a third interlayer sheet disposed between the first and second interlayer sheets, wherein the third interlayer sheet comprises 40-80 wt% CTMP from spruce with a brightness of 40-60 according to ISO 2470-1:2016 and 60-20 wt% chemical pulp. The paperboard may comprise additional interlayer sheets, such as a fourth and a fifth interlayer sheet, disposed between the first and second interlayer sheets.

[0039] Preferably, the CTMP from spruce has been fibrillated to a Schopper Riegler value (SR) between 15 and 35, preferably between 20 and 30, as measured by ISO 5267-1. This is preferably achieved by low consistency (LC) fibrillation, most preferably at a consistency of up to 10%. In this way, both the optical and strength properties of the paperboard are optimized. As used herein, optical properties are intended to include transmittance and opacity.

[0040] According to a second aspect shown herein, there is provided a packaging material comprising:

[0041] - a paperboard according to the first aspect, wherein the first side of the backsheet is adapted to form the inside of a package formed therefrom, and the second side of the topsheet is adapted to form a printed side of a package formed therefrom; and

[0042] - An oxygen barrier layer applied on the first side of the backsheet.

[0043] Preferably, the packaging material of the present invention does not contain any aluminum foil. It has been found that when using the paperboard according to the first aspect in a beverage packaging material, no aluminum foil is required to provide light blocking. The oxygen barrier layer applied to the first side of the backing sheet can be a transparent layer, i.e., a layer having a transmittance (transparency) of greater than 20%, or at least 30%, or 35-100%, or 40-95%, measured according to ISO 22891:2013. The present invention enables the use of a transparent oxygen barrier layer while still maintaining high light barrier properties in the paperboard.

[0044] The packaging material may further comprise a pigment coating on the second side of the top sheet, which pigment coating may for example be a mineral coating comprising 60-95 wt% pigment and 40-5 wt% binder.

[0045] In a preferred embodiment, the oxygen barrier layer comprises a layer applied as a water-based solution or dispersion or as a barrier film.

[0046] The water-based solution or dispersion preferably contains an oxygen barrier chemical selected from the following list: polyvinyl alcohol (PVOH), polyhydroxyalkanoate (PHA), a polysaccharide such as microfibrillated cellulose (MFC), carboxymethyl cellulose (CMC) or cellulose nanocrystals, vinyl acetate, or a mixture of any of these. In a preferred embodiment, the oxygen barrier chemical is MFC or cellulose crystals made from unbleached pulp, such as the fibrillated fine fraction from CTMP production. Packaging materials containing such a water-based solution or dispersion-coated oxygen barrier layer can be easily repulped and recycled.

[0047] The oxygen barrier layer may alternatively or additionally comprise a cellulose-based barrier film, preferably a film formed from microfibrillated cellulose (MFC), or a translucent paper, such as high-density (HD) paper, glassine, tracing paper, parchment, thin kraft paper or machine-glazed (MG) paper. In the context of this patent application, microfibrillated cellulose (MFC) shall mean cellulose particles, fibers or fibrils having a width or diameter of 20 nm to 1000 nm. Such a cellulose-based barrier film or translucent paper preferably has a grammage between 25-60 gsm, a flow rate of 850-1300 kg / m² according to ISO 2471:2008. 3 The cellulose-based barrier film may have a density between 100% and 200% and an opacity below 90% or below 85%. According to ISO 22891:2013, the cellulose-based barrier film may also have a transmittance of 20% or more, preferably above 30%, and most preferably between 35% and 100% or between 40% and 95%. It has been found that when using paperboard according to the present invention, cellulose-based barrier films that do not provide any light-barrier properties can be used. In this way, other barrier properties of the film, such as oxygen barrier properties, can be more effectively optimized.

[0048] The oxygen barrier film may further comprise a polymer based layer, such as an oriented polyethylene (PE) or polypropylene (PP) film,

[0049] In a preferred embodiment, the packaging material comprises a barrier film to which a vacuum coating layer has been applied. The barrier film may have a pre-coating layer applied prior to the vacuum coating layer. Vacuum coating refers to a range of processes, including but not limited to metallization, for depositing a layer of material onto a solid surface, either atomically or molecularly. These methods operate at pressures well below atmospheric pressure (i.e., under vacuum). The process can be further specified based on the vapor source; physical vapor deposition (PVD) uses liquid or solid sources, while chemical vapor deposition (CVD) uses chemical vapors. While the average thickness of the vacuum coating layer herein is preferably in the range of 10-600 nm, more preferably 10-250 nm, the thickness of the deposited layer can range from a single atom to several millimeters. Due to the use of the paperboard of the present invention, such deposited layers can be made very thin, although this may result in a loss of light-barrier properties, particularly during paperboard conversion. Most preferably, the vacuum coating layer comprises an inorganic vacuum coating layer, such as a metal, metal oxide, or ceramic vacuum coating layer, preferably an aluminum or aluminum oxide vacuum coating layer. Such an aluminum oxide vacuum coating layer may comprise Al2O3 or AlOx. AlOx is particularly preferred due to its good water vapor barrier properties. However, AlOx does not provide any light barrier properties. The present invention enables the use of vacuum coating layers containing AlOx in packaging materials that still provide good light barrier properties.

[0050] In some embodiments, the packaging material comprises a cellulose-based barrier film laminated to the first surface of the backsheet via an adhesive composition applied in the form of a dispersion, latex, or solution of an adhesive polymer in an aqueous carrier. This adhesive polymer may be applied in one or more layers. The use of this water-based adhesive further facilitates the repulping and recycling of the packaging material. The adhesive composition may preferably comprise polyvinyl alcohol (PVOH) or a derivative thereof (such as carboxylated PVOH), styrene-acrylate (SA) latex, styrene-butadiene (SB) latex, starch, starch derivatives, cellulose derivatives (such as carboxymethyl cellulose (CMC)), or polyolefins. The PVOH may be fully or partially hydrolyzed.

[0051] The packaging material may be provided with additional barrier and / or heat-sealable layers, such as polymer layers. In embodiments, the packaging material comprises an innermost layer of a thermoplastic polymer. On the printed side, the packaging material may be provided with a thermoplastic polymer layer and / or a dispersion- or solution-coated barrier layer. The barrier layer on the printed side may be extrusion-coated or dispersion-coated onto the top sheet. The dispersion- or solution-coated barrier layer may, for example, comprise a dispersion of latex and, optionally, a pigment and / or polyvinyl alcohol (PVOH), for example. The thermoplastic polymer is preferably polyethylene or polypropylene.

[0052] According to a third aspect shown herein, there is provided a container, in particular a beverage packaging container, made from the packaging material according to the second aspect, wherein a first side of the backsheet with an optional barrier layer forms the inner side of the container, and a second side of the topsheet with an optional barrier layer or coating layer forms the outer side of the container. In this case, the inner side is intended to define the side that comes into contact with the contents of the container, while the outer side is intended to define the printed side of the container.

[0053] According to a fourth aspect shown herein, there is provided a method of manufacturing a multi-ply paperboard comprising a top ply and a back ply and at least one middle ply arranged between the top ply and the back ply, the method comprising the steps of:

[0054] - forming a top sheet from a first pulp mixture comprising at least 80 wt% chemical pulp,

[0055] - forming the middle ply from a second pulp mixture comprising at least 40 wt%, preferably at least 50 wt%, of CTMP from spruce, calculated on the total fiber weight of the paper mixture, wherein the CTMP has a brightness of 40 to 60 according to ISO 2470-1:2016

[0056] - forming the backsheet from a third pulp mixture comprising at least 80 wt% of unbleached kraft pulp from hardwood and / or from softwood, wherein:

[0057] a) if said unbleached kraft pulp forming the back ply is from hardwood, such hardwood pulp exhibits a kappa number according to ISO 302:2015 of at least 15, and

[0058] b) if said unbleached kraft pulp forming the back ply is from softwood, such softwood kraft pulp exhibits a kappa number according to ISO 302:2015 of at least 20,

[0059] - The multi-ply web thus formed is dewatered, pressed and dried to form a multi-ply paperboard.

[0060] In embodiments, the remaining pulp in the second pulp mixture is unbleached kraft pulp having a brightness according to ISO 2470-1:2016 between 40-60%.

[0061] The first pulp mixture preferably comprises 100 wt% bleached chemical pulp having a brightness according to ISO 2470-1:216 of at least 70%, preferably at least 75% and most preferably in the range of 77-90%, calculated on the total weight of the first pulp mixture.

[0062] In an embodiment, the CTMP from spruce in the second pulp mixture is provided by the following steps:

[0063] - Provide the first CTMP from spruce,

[0064] - fractionating the first CTMP from spruce to provide at least a first fraction and a second fraction, wherein the first fraction comprises 50-100 wt % fines, preferably 80-100 wt % or 95-100 wt %, said fines being able to pass through a 200 mesh sieve.

[0065] In this embodiment, the method further comprises the step of applying the first fraction between at least one of the top sheet and the middle sheet and / or between the middle sheet and the back sheet.The second fraction is preferably used as CTMP in the second pulp mixture.

[0066] The method of the fourth aspect may be further defined by the features defining the paperboard of the first aspect.

[0067] Although the present invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of the present invention. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the basic scope of the present invention. Therefore, it is intended that the present invention is not limited to the specific embodiments disclosed as the best mode for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims.

Claims

1. A paperboard comprising at least three plies; a top ply and a back ply, and an intermediate ply arranged between said top ply and said back ply, wherein the top sheet comprises at least 80 wt% of chemical pulp, calculated based on the total fiber weight of the top sheet, wherein the middle ply comprises at least 40 wt% of CTMP from spruce, calculated on the total fiber weight of the middle ply, wherein the CTMP from spruce has a brightness according to ISO 2470-1:2016 of between 40 and 60%, and wherein the back ply comprises at least 80 wt% of unbleached kraft pulp from hardwood and / or from softwood, calculated on the total fiber weight of the back ply, wherein a) if the unbleached kraft pulp in the back ply is from hardwood, such hardwood unbleached kraft pulp exhibits a kappa number according to ISO 302:2015 of at least 15, b) If said unbleached kraft pulp in the back ply is from softwood, this softwood kraft pulp exhibits a kappa number of at least 20 according to ISO 302:2015.

2. The paperboard according to claim 1, wherein the remaining pulp in the middle ply is unbleached kraft pulp having a brightness between 40-60% according to ISO 2470-1:2016.

3. The paperboard according to any of the preceding claims, wherein the top sheet comprises 100 wt% of bleached chemical pulp having a brightness according to ISO 2470-1:216 of at least 70%, preferably at least 75% and most preferably in the range of 77-90%.

4. The paperboard according to claim 3, wherein the top sheet comprises less than 7 wt%, preferably less than 5 wt% of fillers, calculated on the total weight of the top sheet.

5. Paperboard according to any of the preceding claims, wherein the CTMP from spruce has a fiber bundle content of less than 8 wt%, preferably less than 5 wt%.

6. Board according to any of the preceding claims, wherein the CTMP from spruce used for the production of the board comprises a fine fraction in an amount of 10-35 wt%, preferably 10-25 wt%, said fine fraction being able to pass through a 200 mesh sieve and said fine fraction exhibiting a water retention value (WRV) value according to ISO 23714:2014 of less than 280%, preferably less than 250%.

7. The paperboard according to any one of the preceding claims, wherein the paperboard comprises at least a first intermediate ply and a second intermediate ply, and wherein the first intermediate ply and the second intermediate ply comprise: - between 40 and 80 wt% of CTMP from spruce having a brightness between 40 and 60 according to ISO 2470-1:2016, -20-60wt% chemical pulp, All percentages are calculated based on the total fiber weight of the corresponding ply.

8. The paperboard according to any one of claims 1 to 6, wherein the paperboard comprises at least a first intermediate ply and a second intermediate ply, wherein the first intermediate layer comprises 40-80 wt% of CTMP having a brightness higher than 60 according to ISO 2470-1:2016 and 60-20 wt% of chemical pulp, and Wherein the second intermediate ply comprises at least 40 wt%, preferably between 40-80 wt% of CTMP from spruce having a brightness between 40-60 according to ISO 2470-1:2016, all percentages being calculated based on the total fiber weight of the respective ply.

9. The paperboard of claim 8, wherein the first intermediate ply is positioned adjacent to the top ply, and the second intermediate ply is positioned adjacent to the back ply.

10. The paperboard according to claim 8 , wherein the paperboard comprises a third intermediate ply arranged between the first and second intermediate plies, wherein the third intermediate ply comprises 40-80 wt% of CTMP from spruce having a brightness between 40 and 60 according to ISO 2470-1:2016, and 60-20 wt% of chemical pulp, all percentages being calculated based on the total fiber weight of the respective ply.

11. Packaging materials, including: - a paperboard according to any one of claims 1 to 10, wherein the first side of the back sheet is adapted to form the inside of a package formed therefrom, and the second side of the top sheet is adapted to form a printed side of a package formed therefrom; and - An oxygen barrier layer applied on the first side of the backsheet.

12. The packaging material according to claim 11, wherein the packaging material does not contain any aluminum foil.

13. The packaging material according to any one of claims 11 or 12, wherein the oxygen barrier layer is applied as a water-based solution or dispersion or as a barrier film.

14. The packaging material according to claim 13, wherein the oxygen barrier layer is applied as a water-based solution or dispersion comprising an oxygen barrier chemical selected from the following list: polyvinyl alcohol (PVOH), polyhydroxyalkanoate (PHA), polysaccharide, vinyl acetate or a mixture of any of these.

15. The packaging material according to claim 13, wherein the oxygen barrier layer is a cellulose-based barrier film, preferably a film formed from microfibrillated cellulose (MFC), or a translucent barrier paper, such as glassine, machine glazed paper (MG) or greaseproof paper.

16. A container made from the packaging material according to any one of claims 11 to 15, wherein the first side of the backsheet forms the inside of the container and the second side of the topsheet forms the outside of the container.

17. A method for producing a multi-ply paperboard comprising a top ply and a back ply and at least one middle ply arranged between the top ply and the back ply, the method comprising the steps of: - forming a top sheet from a first pulp mixture comprising at least 80 wt% chemical pulp, - forming an intermediate ply from a second pulp mixture comprising at least 40 wt% of CTMP from spruce, calculated on the total fiber weight of the pulp mixture, wherein the CTMP has a brightness of between 40 and 60 according to ISO 2470-1:2016 - forming the backsheet from a third pulp mixture comprising at least 80 wt% of unbleached kraft pulp from hardwood and / or from softwood, wherein: a) if said unbleached kraft pulp forming the back ply is from hardwood, such hardwood pulp exhibits a kappa number according to ISO 302:2015 of at least 15, preferably between 15 and 40, most preferably at least 20, preferably between 20 and 40, and b) if said unbleached kraft pulp forming the back ply is from softwood, such softwood kraft pulp exhibits a kappa number according to ISO 302:2015 of at least 20, preferably between 20 and 90, preferably at least 30-90 or 40-90, - The multi-ply web thus formed is dewatered, pressed and dried to form a multi-ply paperboard.

18. The method for producing a multi-ply paperboard according to claim 17, wherein the remaining pulp in the second pulp mixture is unbleached kraft pulp having a brightness between 40-60% according to ISO 2470-1:2016.

19. Method for producing a multi-ply paperboard according to any of claims 17-18, wherein the first pulp mixture comprises 100 wt% of bleached chemical pulp having a brightness according to ISO 2470-1:216 of at least 70%, preferably at least 75% and most preferably in the range of 77-90%.

20. The method for producing a multi-ply paperboard according to any one of claims 17 to 19, wherein the CTMP from spruce in the second pulp mixture is provided by the following steps: - Provide the first CTMP from spruce, - fractionating the first CTMP from spruce to provide at least a first fraction and a second fraction, wherein the first fraction comprises 50-100 wt% fines capable of passing through a 200 mesh screen, wherein the second fraction is used as the CTMP from spruce in a second pulp mixture, and wherein the method further comprises applying the first fraction between at least one of the top ply and the middle ply and / or between the middle ply and the back ply.