Polymer coated paper and paperboard

Abstract

The present invention relates to a paper or paperboard comprising at least one sizing coating layer and a first coating layer formed by extrusion coating of a furandicarboxylic acid (FDCA) based resin onto the sizing coating layer, characterized in that the FDCA based resin comprises at least 50 % by weight of a FDCA based polymer and that the sizing coating layer comprises at least 50 % by weight of a sizing polymer. The invention also relates to a paperboard cup or tray and a method for coating said paper or paperboard.

Description

[0001] POLYMER COATED PAPER AND PAPERBOARD

[0002] Technical field

[0003] The present disclosure relates to polymer coated paper and paperboard suitable for food, personal or home care packages, such as cups, trays, tubes, blister packages and other containers. More specifically, the present disclosure relates to paper or paperboard comprising at least one sizing coating layer and at least one coating layer formed by extrusion coating of a FDCA based resin.

[0004] Background

[0005] Coating of paper or paperboard with polymer is often done to combine the mechanical properties of the paperboard with the barrier and sealing properties of a polymer film. Paperboard provided with even a relatively small amount of a suitable polymer material can provide the properties needed to make the paperboard suitable for many demanding applications.

[0006] Paper or paperboard as such is generally suitable for the packaging of dry food products. However, untreated paperboard is of limited use in direct contact with moist or greasy products, because moisture will affect the mechanical properties of the packaging and absorbed oil or grease will cause staining of the paper or paperboard. These effects will impair the protective function as well as the appearance of the packaging.

[0007] Extrusion coating or lamination drastically expands the range applications for paper or paperboard. The thin polymer coating imparts resistance to liquids, oil or grease and moisture and also in some instances heat resistance. The polymer coatings can also be used for heat sealing. Depending on the application, the paper or paperboard may be extrusion coated onto one or both sides.

[0008] Extrusion coating is a process by which a molten polymer material is applied to a substrate, such as paper or paperboard to form a very thin, smooth and uniform coating layer. The coating can be formed by the extruded polymer itself, or the molten polymer can be used as an adhesive to laminate a solid polymer film onto the substrate. Common polymer resins used in extrusion coating include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). A big disadvantage with these polymers, such as PE and PET that they are a petrol-based polymer and their production and disposal have negative environmental impacts. There is therefore a need to find more sustainable polymers when making polymer coated paper or paperboard.

[0009] Polyethylene terephthalate (PET) has many interesting properties and multiply uses such as frozen food and heated food products including both microwave oven and oven. Despite its thermal stability, the PET polymer might lose barrier properties when exposed to heat and moisture, due to for example chain relaxation but also due to hydrolysis. Thus, polyethylene terephthalate (PET) may show hydrolytic degradation under high temperature and moist conditions, which leads to reduced barrier properties and mechanical properties.

[0010] Furandicarboxylic acid (FDCA) based polymers are a more sustainable polymer option since these are derived from renewable sources, such as vegetable or plantbased feedstocks like wood, sugarcane, sugar beet, or other agricultural crops or residues. These are then converted to saccharides such as fructose or glucose and then to intermediates before obtaining the FDCA. This bio-based origin of FDCA based polymers makes it more environmentally friendly.

[0011] One challenge with the use of FDCA based polymers, such as polyethylene furanoate (PEF), as a coating layer, is to have sufficient adhesion between the polymer layer and the paper or paperboard. Also, there is a need for the FDCA based polymer to have good dimensional stability and stretchability to manage the converting process.

[0012] 3D-forming, such as thermoforming or deep drawing, of paper or paperboard products into cups, plates, tubes, bowls or trays is a challenging process for the paper or paperboard substrate. Thermoforming involves heating the paper or paperboard and suction and / or pressing it to the desired shape in a specific form. Deep drawing uses vacuum or heat, pressure and vacuum to stretch and compress the paper or paperboard into the desired shape. It is important that the paper or paperboard product being formed maintains its structural form after the forming process, especially in high humidity environments. It is also important that the paper or paperboard is provided with good barrier properties to make it suitable for packaging of food packages also after formation of the package.

[0013] When making cups or trays, at least one rim is normally formed. The rim is formed by curling the paperboard to create a smooth and stable rim for the cup. When making trays the rim is in the form of a flat, curved or patterned, or embossed flange. It is important that the paperboard is stretchable so that it does not crack or tear which would negatively affect the rigidity and the barrier properties of the cup or tray. Also, the paperboard should have sufficient rigidity to maintain the shape and structural design after formation of the rim.

[0014] There is a need to find a more sustainable polymer coating that would provide the coated paper or paperboard with good barrier properties, especially good grease resistance, chemical resistance, formability, stretchability and rigidity.

[0015] Description of the invention

[0016] It is an object of the present disclosure to provide a paper or paperboard coated with FDCA based resin having good barrier properties, especially grease and oxygen barrier properties.

[0017] It is a further object of the present disclosure to provide a paper or paperboard coated with FDCA based resin having good adhesion to the paper or paperboard or other coating layers.

[0018] It is a further object of the present disclosure to provide a coated paper or paperboard that is stretchable and rigid to make it suitable for 3D forming, such as thermoforming or deep drawing, to form a package.

[0019] It is a further object of the present disclosure to provide a coated paper or paperboard that is more sustainable.

[0020] It is a further object of the present disclosure to provide a paper or paperboard suitable for making packages comprising a rim, such as a curved rim in paperboard cups or a flat, curved or textured flange in paperboard trays. Another object of the present disclosure to provide a method for manufacturing of a polymer coated paper or paperboard, which is stretchable, rigid, formable and having good barrier properties.

[0021] The above mentioned objects, as well as other objects as will be realized by the skilled person in the light of the present disclosure are achieved by the various aspects of the present disclosure.

[0022] According to a first aspect illustrated herein, there is provided a paper or paperboard comprising at least one sizing coating layer and a first coating layer formed by extrusion coating of a furandicarboxylic acid (FDCA) based resin onto the sizing coating layer, characterized in that the FDCA based resin comprises at least 50 % by weight of a FDCA based polymer and that the sizing coating layer comprises at least 50 % by weight of a sizing polymer.

[0023] It has been found that the use of a sizing coating layer and a FDCA based resin layer makes it possible to provide the coated paper or paperboard with good barrier properties, especially grease barrier properties, at the same time as the paper or paperboard has good stretchability, rigidity and formability which is needed to form packages, such as trays or cups. The improved stretchability also improves the crack resistance during converting of the coated paper or paperboard. Furthermore, it has been found that the improved stretchability, rigidity and formability of the coated paper or paperboard reduces delamination problems of the coated paper or paperboard.

[0024] The FDCA based resin preferably comprises at least 70 % by weight, preferably at least 90 % by weight, of said FDCA based polymer. The FDCA based resin of the invention may also consist, or substantially consist, of the FDCA based polymer. For some end use, it is preferred that the FDCA resin consists, or substantially consists, of the same FDCA polymer since such mono-material coating is easier to recycle.

[0025] The paper or paperboard according to any of the preceding claims wherein the FDCA based polymer has a melting temperature (Tm) below 210 °C, preferably below 200 °C. It is preferred that the melting temperature is between 175-210 °C and even more preferred between 185-200 °C. The melting temperature is determined by differential scanning calorimetry according to standard ASTM D3418-21 . The coated paper or paperboard is often heat treated in order to the product to be formed, in e.g. thermoforming or deep drawing. It is therefore necessary for the FDCA based polymer to be stable after being subjected to such heat treatment. With stable is meant that the FDCA based polymer both is mechanically stable and having maintained barrier properties even after heat treatment. The barrier properties, such as grease barrier, water vapor transmission rate and oxygen transmission rate should be at a good value, i.e. not deviating more than 20% from the original value, preferably not more than 15% from the original value, at least 2 weeks after heat treatment, preferably after 4 weeks.

[0026] The FDCA based polymer preferably has an intrinsic viscosity of less than 0.9 dl / g, preferably between 0.5-0.9 dl / g, and even more preferred between 0.5-0.7 dl / g as determined according to ISO 1628. It has been found that the use of a FDCA based polymer with the mentioned intrinsic viscosity will improve the bonding of the FDCA based resin and the runnability of the polymer in the extruder. It is also believed that the FDCA based polymer with the lower intrinsic viscosity would be less prone to degradation compared other polymers such as PET.

[0027] The FDCA based polymer preferably has a crystallinity of between 5-40%, preferably between 10-35% and even more preferred between 15-25%. Crystallinity is measured according to ASTM E794-06 (2018). Low crystallinity is preferred since it will improve sealability, both heat sealability and ultrasonic sealing properties and adhesion of the FDCA based polymer. Also, the stability, stretchability and barrier properties has also been found to improve for FDCA based polymers having a lower crystallinity.

[0028] The FDCA based resin may comprises a molecular spacer in an amount of 1-5 % by weight, preferably between 2-4 % by weight. It has been found that an addition of a molecular spacer, preferably diethylene glycol, monoethylene glycol, triethylene glycol or mixtures of any of these glycols, to the FDCA based resin will improve the adhesion of the coating layer to the paper or paperboard surface even further. It is preferred to use a biobased diethylene glycol as a molecular spacer.

[0029] The FDCA based polymer is preferably polyethylene furanoate (PEF), polybutylene furanoate (PBF), polytrimethylene furandicarboxylate (PTF), polypentamehylene furanoate (PPeF), polyheamethylene furanoate (PHF) or polypropylene furanotate (PPF). It is preferred that the FDCA based polymer is polyethylene furanoate (PEF).

[0030] The sizing polymer is preferably polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, carboxymethylcellulose and / or starch, e.g. thermoplastic starch, cationic starch, anionic starch, native starch, acetylated starch, hydroxypropylated starch or carboxymethylated starch. The sizing polymer is preferably cationic starch, polyvinyl alcohol or carboxymethyl cellulose. It is preferred that the sizing coating layer comprises between 50-100 % by weight of the sizing polymer, preferably between 60-90 wt-% and even more preferred between 70-85 % by weigth. It has been found that by using a sizing polymer, in combination with the FDCA based coating, the stretchability and rigidity of the coated paper or paperboard is improved.

[0031] The sizing coating may further comprise 1-30 % by weight of a sizing agent, based on the dry weight of the sizing coating. The sizing agent is preferably rosin resin, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) and / or styrene-maleic anhydride (SMA). The addition of a sizing agent has also shown to improve the barrier properties of the paper or paperboard.

[0032] The sizing coating may further comprise 0-30 % by weight of humectant or softeners, such as metal salt, sugar alcohol, glycerol, polyethylene glycol. The sizing coating may also comprise between 0-20 % by weight of fillers, preferably clay, calcium carbonate, talcum, silica and / or carbon black.

[0033] The sizing coating layer preferably has a grammage of less than 10 gsm, preferably between 0.1-10 gsm and even more preferred between 0.5-8 gsm. It has been found sufficient to use a very thin sizing coating layer and still be able to achieve the mentioned advantages. The sizing coating layer is preferably added in at least one layer, preferably two layers, and on at least one surface of the paper or paperboard. The sizing coating layer may also comprise a sugar alcohol or a divalent metal salt. It may be preferred that the sizing coating layer comprises between 0.5-10 % by weight of a sugar alcohol or divalent metal salt. The addition of a sugar alcohol or divalent metal salt will stabilize the moisture content in the paper or paperboard during extrusion coating of the FDCA based resin. It may be preferred that the sugar alcohol and divalent metal salt is sorbitol, xylitol, calcium chloride or calcium acetate.

[0034] The formulation of a resin used for coating may vary greatly depending on the intended use of the coated paper or paperboard. The FDCA based resin may include a wide range of ingredients in varying quantities to improve the end performance of the product or processing of the coating. The FDCA based resin can comprise other polymeric or non-polymeric coating components. In other words, the FDCA based resin can be a blend of the FDCA based polymer and another polymer. The FDCA based resin preferably comprises at least one additional component selected from the group consisting of a polymer other than a FDCA based polymer, a colorant, (e.g. Titanium dioxide or carbon black), a dye, a filler or a pigment (e.g. CaCOsor talc). The FDCA based resin my also comprise other additives such as lubricants, slip agents, plasticizers, antioxidants and / or UV stabilizers.

[0035] The term coating, as used herein, refers to an operation in which the surface of a substrate is covered with a composition to impart a desired properties, finish or texture to the substrate. The coating can be applied to one side or both sides of the paper or paperboard. The coating may be added by extrusion coating or lamination. In some embodiments the first coating layer is the only coating layer applied to the paper or paperboard. In some embodiments the first coating layer is a single coating layer. In some embodiments the first coating layer is a multiply coating layer. The first coating layer is preferably located on the inside on a package formed from the coated paper or paperboard.

[0036] The paper or paperboard may also comprise at least one second coating layer disposed on top of the first coating layer. It may be preferred to add more than one coating layer on the paper or paperboard to form a multilayer coating. The second coating layer can have the same composition as the first coating layer. As the FDCA based coating layer provides good stability of the film formation and adhesion of the FDCA based resin to the paper or paperboard, it may preferably be used as the first (or innermost) coating layer applied directly onto the paper or paperboard surface. The extrusion coated FDCA based coating layer may serve to promote adhesion of subsequently applied or coextruded polymeric coating layers. The extrusion coated FDCA based coating layer may serve as an adhesive for a polymeric film in an extrusion film lamination process.

[0037] In some embodiments, the paper or paperboard extrusion coated with the FDCA based resin, further comprises at least one additional polymeric coating layer disposed on top of the extrusion coated FDCA based resin, wherein the additional polymeric coating layer has a composition different from the extrusion coated FDCA based resin.

[0038] It may be preferred that the second coating layer has a different composition than the first coating layer. The second coating layer preferably comprises a FDCA based polymer, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and / or polylactic acid (PLA). In a preferred embodiment, the at least one additional coating layer comprises a FDCA based polymer, preferably polyethylene furanoate (PEF).

[0039] In some embodiments, the at least one additional coating layer is formed by extrusion coating or by extrusion film lamination.

[0040] The first and eventual second coating layer / s are preferably applied to the paper or paperboard at a combined grammage of less than 60 gsm, preferably less than 50 gsm, more preferably less than 40 gsm. It may be preferred that the first and eventual second coating layer / s is applied in an amount of 10-60 gsm, preferably between 15-50 gsm and even more preferred between 20-40 gsm. It has been found that it is possible to add small amount of coating layer / s and still be able to achieve sufficient adhesion and stability of the film.

[0041] The paper or paperboard may also comprise at least one additional coating layer added to the opposite side on the paper or paperboard from the first coating layer. The additional coating layer is preferably located on the outside on a package formed from the coated paper or paperboard. The additional coating layer may comprise a FDCA based polymer, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and / or polylactic acid (PLA).

[0042] Paper generally refers to a material manufactured in sheets or rolls from the pulp of wood or other fibrous substances comprising cellulose fibers, used for e.g. writing, drawing, or printing on, or as packaging material. Paper can either be bleached or unbleached and produced in a variety of thicknesses, depending on the end-use requirements.

[0043] Paperboard generally refers to strong, thick paper or cardboard comprising cellulose fibers used for example as flat substrates, trays, boxes and / or other types of packaging. Paperboard can either be bleached or unbleached and produced in a variety of thicknesses, depending on the end-use requirements.

[0044] The paper or paperboard according to the present disclosure comprises at least one cellulose based ply. It may be preferred that the paper or paperboard is a multiply paperboard product comprising at least two cellulose based plies, preferably at least three cellulose plies. Each of the cellulose based plies can have a certain composition of pulp fibers, such as bleached and / or unbleached Kraft pulp, sulfite pulp, dissolving pulp, thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), broke, and / or mixtures thereof. The chemimechanical pulps such as CTMP or HT-CTMP may also be bleached or unbleached. The paper or paperboard preferably comprises at least 40% of chemimechanical pulp. It may be preferred that the at least one cellulose based ply comprises at least 50 % by weight of high consistency (HC) refined pulp, preferably at least 60 % by weight or even more preferred at least 70 % by weight of HC refined pulp. The HC refined pulp preferably has a Schopper Riegler (SR) value between 23-40 measured according to EN ISO 5267-1 , preferably a SR value between 23-35. The HC refined pulp will improve the stretchability of the paper or paperboard. The different plies can have different grammages and / or thicknesses and may contain different amounts of additives, such as internal sizing agents. The internal sizing agent may be rosin resin, ASA and / or AKD. The total amount of internal sizing is preferably in the range of 0.2-5 kg / tn. Due to the high temperature in the heat treatment, e.g. autoclaving, sterilization or retorting, the internal sizing will improve the dimensional stability of the coated paper or paperboard after heat treatment.

[0045] It may be preferred that the paper or paperboard is free from optical brightening agents and per- and polyfluoroakyl substances (PFAS) since these might discolor the paper or paperboard.

[0046] The paper or paperboard may comprise recycled fibers. It is preferred that the paperboard comprises between 5-50 % by weight of recycled fibers. The paper or paperboard comprising the recycled fibers will preferably fulfill the requirements for paper and board for food contact according to BfR XXXVI as of 01 .04.2021 . It is preferred that the recycled fibers are located in the midply of a multiply paperboard substrate. It may be possible that one ply of a multiply paperboard substrate comprises between 50-85 % by weight of recycled fibers. The use of at least one FDCA based coating improves the stability and makes it possible to use a high amount of recycled fibers.

[0047] In some embodiments, the grammage of the fiber-based substrate is in the range of 80-550 gsm, preferably in the range of 100-500 gsm and even more preferred in the range of 120-450 gsm. Unless otherwise stated, the grammage is determined according to the standard ISO 536. It has been found that by applying a FDCA based coating to the paperboard it is possible to reduce the grammage of the paperboard and still be able to provide a stable and rigid coated paperboard product that is suitable for many different packaging applications.

[0048] The paper or paperboard, prior to application of any FDCA based coating layer, preferably has a PPS (Parker Print-Surf) Smoothness in the range of 1 .5-15 pm, preferably between 2-12 pm measured according to ISO 8791-4 at 1 .0 MPa. It has been found that the PPS smoothness of the paper or paperboard surface is important to further improve the bonding of the coating layer to the paper or paperboard surface. It has been found that a PPS smoothness in the range of 1 .5-15 pm will improve the bonding of the FDCA based resin coating layer. The paper or paperboard, prior to application of any coating layer, preferably has a stretch of at least 6% (CD) measured according to ISO1924-3, preferably above 7% and even more preferred above 8%. It has been found that the combination of a stretchable paper or paperboard with a FDCA based coating layer improves the forming properties.

[0049] The paper or paperboard preferably has a thickness above 100pm, preferably above 180 pm and even more preferred above 200 pm, preferably between 200-800 pm measured according to ISO 534, even more preferred between 180-700 pm. It has been found that a high thickness of the paper or paperboard will improve the compression and contact in the extruder, which will improve the adhesion of the FDCA based coating to the paper or paperboard.

[0050] The paper or paperboard may further comprise a peeling layer located between the sizing coating layer and the first coating layer. The peeling layer is preferably a pressure sensitive adhesive, hot melt adhesive, water or solvent based adhesive or re-sealable adhesive. The peeling layer preferably has a grammage between 0.8-12 gsm, preferably between 1.6-8 gsm. The peeling layer will facilitate separation and recycling of the coated paper or paperboard and polymer layer, respectively.

[0051] The paper or paperboard may further comprise a pigment layer located between the paper or paperboard and the first coating layer. The pigment layer preferably has a grammage of 4-20 gsm. The pigment layer may be added in one, two or several coating steps. The pigment layer will give the paper or paperboard improved printability or light barrier properties. The FDCA based polymers is usually very transparent and will not give the paper or paperboard good light barrier properties. Any known commonly used pigment can be used. It is preferred that the pigment used is titanium dioxide and / or carbon black. It may be preferred to provide the paper or paperboard with improved light barrier by the use of pigment in a separate pigment layer and not by addition of the pigment to the FDCA based resin. The use of a separate pigment layer will facilitate the recycling of the coated product.

[0052] The paper or paperboard may further comprise a primer layer located between the paper or paperboard and the first coating layer. The primer layer preferably has a grammage of 1-12 gsm, preferably 2-10 gsm. The primer layer will improve the adhesion of the first coating layer to the paper or paperboard. It is preferred that the primer layer also is stable after heat treatment, e.g. autoclaving, sterilization or retorting. The primer layer may comprise polyvinyl amine (PVAm), polyethylene imine (PEI), organosilanes, polyurethane, melamine, epoxy-based primers and / or acrylic co-polymers. It is also possible to add pigment into the primer layer to improve the light barrier properties.

[0053] The inventive paper or paperboard is particularly useful in the manufacture of paperboard cups or trays comprising at least one rim. According to a second aspect illustrated herein, there is provided a paperboard cup or tray comprising the paper or paperboard according to the first aspect described herein wherein said cup comprises at least one rim. The paperboard cup or tray may be formed by thermoforming or deep drawing. The cup comprises at least one rim being formed by curling the paper or paperboard into a smooth and stable rim, i.e. a curled rim. The tray comprises at least one rim being formed as a flange on top of the tray. The cup or tray can be used for packaging dry, wet or semidry food products such as ready meals for heating in oven or micro-oven. The cup or tray may also be used for frozen food applications, such as frozen ready meals or ice cream.

[0054] The paperboard cup or tray preferably has an oxygen transmission rate below 50 cc / m2 / day at 23 C / 50% RH measured according to ASTM F1927-20, preferably below 20 cc / m2 / day at 23 C / 50% RH. It is important that the oxygen transmission rate is stable also after forming the cup or tray to provide the cup or tray with good oxygen barrier properties.

[0055] The paperboard cup or tray preferably has a water vapor transmission rate (WVTR) below 20 g / m2 / day at 23 C / 50% RH measured according to ASTM D1249-20. It is important that the VWTR value is stable also after forming to provide the cup or tray with good water vapor resistance.

[0056] The coated paper or paperboard or the paperboard cup or tray preferably has a KIT value above 11 , preferably above 12, measured according to TAPPI T559. KIT is a value of grease resistance. It is important that the coated paper or paperboard has improved grease resistance.

[0057] The coated paper or paperboard or the paperboard cup or tray preferably also has a fat resistance above 48 hours, preferably above 56 hours, according to the modified ASTM F119-82 method evaluated at 60 °C and 0% RH. It is important that the coated paper or paperboard has a very high fat resistance which makes it suitable for packaging greasy products, such as pizza, bakery products, fresh food products, including fish and berries as well as frozen food products.

[0058] According to a third aspect illustrated herein, there is provided a method for manufacturing a coated paper or paperboard substrate, wherein said method comprises the steps of: providing a paper or paperboard substrate, providing a sizing composition, applying the sizing composition to a surface of the paper or paperboard substrate to form a sizing coating layer, providing a FDCA based resin, applying the FDCA based resin to the sizing coating layer by extrusion coating to form a first coating layer, cooling the FDCA based resin, thereby forming the coated paper or paperboard substrate, wherein the FDCA based resin comprises at least 50 % by weight of a FDCA based polymer and that the sizing coating layer comprises at least 50 % by weight of a sizing polymer.

[0059] The method may further comprise a cooling step. The cooling step is preferably done by the use of a chill roll. The chill roll preferably has an extended chill nip. The cooling step is preferably done at a temperature of between 5-60 °C for a time of at least 0.15 s, preferably between 0.15-10 seconds. It may be possible to use more than one chill roll placed subsequent of each other during the cooling step. It is important to cool the extruded FDCA resin for a sufficient time, especially when extruding a FDCA based polymer, in order to achieve sufficient adhesion to the sizing coating layer.

[0060] The pressure used during the extrusion coating of the FDCA based resin is preferably between 30-800 kPa, preferably between 40-500 kPa and even more preferred between 50-350 kPa. By using increase pressure during extrusion coating the adhesion of the FDCA based resin can be improved. The sizing composition is preferably applied by a size press, film press, curtain unit, rod coater, blade coater, spraying or brush or roller application. The sizing composition may be added as a single layer or more than one layer, preferably two layers. The sizing composition can be added to only side of the paper or paperboard or to both sides of the paper or paperboard.

[0061] The method may further comprise the step of applying at least one second coating layer disposed on top of the first coating layer. The at least one second coating layer may comprise a FDCA based polymer, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and / or polylactic acid (PLA). In a preferred embodiment, the at least one additional coating layer comprises a FDCA based polymer, preferably polyethylene furanoate (PEF), that has a different composition from the first extrusion coated FDCA based resin.

[0062] In some embodiments, the at least one second coating layer is formed by extrusion coating or by extrusion film lamination. In a preferred embodiment, the at least one second coating layer is formed by coextrusion coating together with the first FDCA based resin, preferably by the use of a twin extruder.

[0063] The method may further comprise the step of drying the paper or paperboard substrate to a moisture content of between 5-14 % by weight before application of FDCA based resin, preferably between 8-11 % by weight. The moisture content is measured according to ISO 287. By reducing the moisture content of the paper or paperboard substrate it is possible to improve the stretch of the paper or paperboard substrate as well as the adhesion of the sizing coating layer to the paper or paperboard. It is also important that the surface moisture content of the paper or paperboard substrate is controlled so that it is not too low. Too low moisture content will make the paper or paperboard more brittle and not as stretchable and consequently less suitable for forming packages.

[0064] The method may further comprise the step of subjecting the paper or paperboard substrate to a flame, plasma, ozone and / or corona treatment before applying the FDCA based coating. By treating the paper or paperboard substrate with flame, plasma, ozone and / or corona treatment the surface energy of the paper or paperboard substrate is increased. Also, the flame, plasma, ozone and / or corona treatment will remove impurities from the surface of the paper or paperboard substrate. Increased surface energy and removal of impurities will affect the bonding properties in a positive way.

[0065] The method may further comprise the step of applying a peeling layer between the sizing coating layer and the first coating layer. The peeling layer may be a pressure sensitive adhesive, water or solvent based adhesives and / or re-sealable adhesives. It is preferred that the peeling layer has a grammage between 0.8-12 gsm. The peeling layer will facilitate recycling of the coated paper or paperboard substrate. It will be easier to remove the at least one FDCA based coating layer from the paper or paperboard substrate. In this way it is possible to both recycle and reuse the polymer coating layer / s and the paper or paperboard substrate.

[0066] The FDCA based resin of the third aspect may be further defined as set out above with reference to the first aspect.

[0067] Unless otherwise stated, the unit “% by weight” mentioned in the present disclosure refers to % by weight of the total dry weight of the relevant layer, composition, resin or the like.

[0068] Description of the figure

[0069] Figure 1 describes an example of a paperboard (1 ) according to the present invention. The paperboard (1 ) comprises two coating layers of FDCA based resin (2, 2). The paperboard also comprises a sizing coating layer (3) to improve the stretchability and rigidity and a peeling layer (4) that will facilitate recycling of both the paperboard (1 ) and the FDCA based coatings (2, 2).

[0070] While the 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 elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMS1 . Paper or paperboard comprising at least one sizing coating layer and a first coating layer formed by extrusion coating of a furandicarboxylic acid (FDCA) based resin onto the sizing coating layer, characterized in that the FDCA based resin comprises at least 50 % by weight of a FDCA based polymer and that the sizing coating layer comprises at least 50 % by weight of a sizing polymer.

2. The paper or paperboard according to claim 1 , wherein said FDCA based resin comprises at least 70 % by weight, preferably at least 90 % by weight, of said FDCA based polymer.

3. The paper or paperboard according to any of the preceding claims wherein the FDCA based polymer has a melting temperature (Tm) below 210 °C, preferably below 200 °C.

4. The paper or paperboard according to any of the preceding claims wherein the FDCA based polymer has an intrinsic viscosity of less than 0.9 dl / g, preferably between 0.5-0.9 dl / g, as determined according to ISO 1628.

5. The paper or paperboard according to any of the preceding claims wherein the FDCA based polymer has a crystallinity between 5-40%, preferably between 10- 35% and even more preferred between 15-25%, measured according to ASTM E794-06 (2018).

6. The paper or paperboard according to any of the preceding claims wherein the FDCA based polymer is polyethylene furanoate (PEF), polybutylene furanoate (PBF), polytrimethylene furandicarboxylate (PTF), polypentamehylene furanoate (PPeF), polyheamethylene furanoate (PHF) or polypropylene furanotate (PPF).

7. The paper or paperboard according to any of the preceding claims wherein the sizing polymer is polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, carboxy methyl cellulose and / or starch, e.g. thermoplastic starch, cationic starch, anionic starch.

8. The paper or paperboard according to any of the preceding claims wherein the sizing coating further comprises 1 -30 % by weight of a sizing agent.

9. The paper or paperboard according to claim 8 wherein the sizing agent is rosin resin, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) and / or styrenemaleic anhydride (SMA).

10. The paper or paperboard according to any of the preceding claims wherein the sizing coating layer has a grammage of less than 10 gsm.11 . The paper or paperboard according to any one of the preceding claims, wherein the FDCA based resin comprises at least one additional component selected from the group consisting of a polymer other than a FDCA based polymer, a colorant, a dye, a filler or a pigment.

12. The paper or paperboard according to any one of the preceding claims, wherein the paper or paperboard further comprises at least one second polymer coating layer disposed on top of the first coating layer.

13. The paper or paperboard according to claim 12, wherein the at least one second polymer coating layer comprises a FDCA based polymer, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and / or polylactic acid (PLA).

14. The paper or paperboard according to any one of the preceding claims, wherein the first and / or second coating layer / s are applied to the paper or paperboard at a grammage of less than 50 gsm, preferably less than 40 gsm, more preferably less than 35 gsm.

15. The paper or paperboard according to any of the preceding claims wherein the paper or paperboard is a multiply paperboard product comprises at least two cellulose based plies, preferably at least three cellulose based plies.

16. The paper or paperboard according to any of the preceding claims wherein the paper or paperboard further comprises a peeling layer located between the paper or paperboard and the sizing coating layer.

17. A paperboard cup or tray comprising the paper or paperboard according to any of the preceding claims wherein said paperboard cup or tray comprises at least one rim.

18. A method for manufacturing a coated paper or paperboard substrate, wherein said method comprises the steps of: a) providing a paper or paperboard substrate, b) providing a sizing composition, c) applying the sizing composition to a surface of the paper or paperboard substrate to form a sizing coating layer, d) providing a FDCA based resin, e) applying the FDCA based resin to the sizing coating layer by extrusion coating to form a first coating layer, f) cooling the FDCA based resin, thereby forming the coated paper or paperboard substrate, characterized in that the FDCA based resin comprises at least 50 % by weight of a FDCA based polymer and that the sizing coating layer comprises at least 50% by weight of a sizing polymer.

19. The method according to claim 18 wherein the cooling step is done in a chill roll at a temperature of between 5-60 °C for a time of at least 0.15 s, preferably between 0.15-10 seconds.

20. The method according to any of the claims 18 or 19 wherein the pressure used during extrusion coating of the FDCA based resin is between 30-800 kPa, preferably between 40-500 kPa and even more preferred between 50-350 kPa.

21. The method according to any of the claims 18-20 wherein the sizing composition is applied by a size press, film press, curtain unit, rod coater, blade coater spraying or brush or roller application.

22. The method according to any of the claims 18-21 , wherein the method further comprises the steps of:applying at least one second polymer coating layer disposed onto of the first polymer coating layer.

23. The method according to claim 22, wherein the at least one second polymer coating layer comprises a FDCA based polymer, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP) and / or polylactic acid (PLA).

24. The method according to any of the claims 18-23 wherein the method further comprises the step of drying the paper or paperboard substrate to a moisture content of between 5-14 % by weight before application of FDCA based resin.

25. The method according to any of the claims 18-24 wherein the method further comprises the step of subjecting the paper or paperboard substrate to a flame, plasma and / or corona treatment before applying the sizing coating composition.

26. The method according to any of the claims 18-25 wherein the method further comprises the step of applying a peeling layer between the sizing coating layer and the first polymer coating layer.

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