Thermoformable paperboard-based laminate and a method for manufacturing said laminate

Abstract

The present invention relates to a thermoformable paperboard-based laminate comprising: a paperboard layer, said paperboard layer comprising: 50-99 wt% kraft fibers based on the total fiber content of the paperboard layer, and 1-50 wt% recycled fibers based on the total fiber content of the paperboard layer, wherein said recycled fibers are treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267- 1; at least one compostable barrier layer applied on at least one side of the paperboard layer, wherein the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with strain at break of at least 5%; wherein the laminate exhibits a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD).

Description

[0001] THERMOFORMABLE PAPERBOARD-BASED LAMINATE

[0002] Technical field

[0003] The present disclosure relates to thermoformable paperboard-based laminates for food packaging, and to methods for manufacturing such laminates.

[0004] Background

[0005] Thermoformed fiber-based tray containers, commonly manufactured from polymer-coated paperboard, are extensively used for packaging chilled and readymade foods. These containers offer moisture resistance and facilitate heat-sealing of the tray with a cover, ensuring food preservation and protection. However, with the growing emphasis on sustainability and the circular economy, there is an increasing demand to incorporate recycled fibers into such packaging solutions.

[0006] Used food service board (FSB), such as used beverage cartons (UBC), represent a promising and abundant source of recycled fibers, offering the potential to align with sustainability goals. However, FSB is particularly challenging to process for food packaging applications due to its complex composition, which includes layers of paper, plastic, and aluminum. This multi-material structure complicates fiber extraction, purification, and preparation for reuse in high-performance applications. Additionally, fibers recovered from FSB often contain high levels of fines and ash, which can negatively impact mechanical properties, stretchability, and barrier performance.

[0007] The integration of recycled cellulose fibers (hereinafter also referred to simply as recycled fibers), and particularly fibers recycled from FSB or UBC, into fiber-based packaging presents several challenges, particularly in thermoforming of deepdrawn trays where mechanical and functional properties are critical. These challenges include: - Recycled fibers often exhibit poor stretchability and formability due to fiber shortening during recycling processes. This compromises their ability to meet the high mechanical demands of deep-drawing applications.

[0008] - The presence of contaminants in recycled fibers can result in the migration of impurities, such as mineral oil hydrocarbons (MOSH / MOAH), causing odor and taste issues that are unacceptable for food packaging.

[0009] - The hornification and degradation of fibers during recycling significantly reduce their strain-at-break performance, particularly in the cross-direction (CD) of the material.

[0010] Despite these limitations, the need for sustainable packaging solutions necessitates the development of new approaches to maximize the use of recycled fibers without compromising performance. The present disclosure seeks to address these challenges, providing a viable and environmentally friendly solution for fiber-based trays with high recycled content.

[0011] Summary of the invention

[0012] It is an object of the present disclosure to provide laminates for thermoforming of paperboard-based tray containers with a high recycled fiber content, particularly including fibers derived from used food service board (FSB), such as used beverage cartons (UBC), that can meet sustainability and circular economy goals without compromising performance or safety in food packaging applications.

[0013] It is a further object of the present disclosure to overcome technical challenges associated with using recycled fibers, such as poor stretchability, risk of impurity migration, and reduced mechanical properties, ensuring the production of high- quality, thermoformable, and functional materials suitable for deep-drawing applications.

[0014] It is a further object of the present disclosure to provide a laminate structure with enhanced strength, stretchability, and barrier properties, including resistance to moisture, grease, odors, and tastes, while ensuring compatibility with compostable and biodegradable solutions for environmentally friendly packaging.

[0015] 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.

[0016] The present disclosure provides a laminate structure incorporating a specifically processed recycled cellulose fiber component, coupled with a compostable barrier coating, to enhance stretchability, strength, and barrier properties. By addressing technical challenges previously associated with the incorporation of recycled cellulose fibers in thermoformable paperboard, the present disclosure contributes to a sustainable future for food packaging solutions.

[0017] The present inventors have surprisingly found that by incorporating a recycled fiber component which has been treated to remove fines, e.g. by washing and / or fractionation, and refined to a Schopper Riegler value in the range of 14-30 into the kraft fibers used for the fiber-based tray material, it is possible to significantly enhance the mechanical and formability properties of the material without compromising its functionality. Specifically, the use of recycled fibers from used food service board (FSB) or used beverage carton (UBC), treated to remove fines and impurities, results in improved stretchability and strength, particularly in deep- drawing applications.

[0018] Furthermore, when combined with a compostable barrier coating, such as a semicrystalline polyhydroxyalkanoate (PHA) layer, the resulting laminate also exhibits excellent barrier properties against moisture, grease, and odors, while remaining compatible with food safety requirements and sustainable end-of-life options, such as compostability. These findings enable the production of highly sustainable and functional thermoformed containers suitable for food packaging.

[0019] According to a first aspect illustrated herein, there is provided a thermoformable paperboard-based laminate comprising: a paperboard layer, said paperboard layer comprising:

[0020] 50-99 wt% kraft fibers based on the total fiber content of the paperboard layer, and

[0021] 1-50 wt% recycled fibers based on the total fiber content of the paperboard layer, wherein said recycled fibers are treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267- 1; at least one compostable barrier layer applied on at least one side of the paperboard layer, wherein the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with strain at break of at least 5%; optionally a primer layer between the paperboard layer and the barrier layer; and optionally at least one outermost sealing layer on at least one side of the paperboard layer; wherein the thermoformable paperboard-based laminate exhibits a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD).

[0022] It was surprisingly found that the above type of recycled fiber fraction, when added to the main kraft fiber fraction, did not reduce strain at break of the paperboard layer as compared to a paperboard made solely from the kraft fibers. If further combining the recycled fiber fraction with at least one strength enhancement agent before refining, the strength and stretch properties of the paperboard layer could even be improved.

[0023] 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, coated, or uncoated, and produced in a variety of thicknesses, depending on the end-use requirements. The paperboard layer may comprise or consist of fibers, referred to herein as the total fiber content of the paperboard layer, and optionally one of more non-fibrous additives, referred to herein as the total additive content of the paperboard layer. The fibers may comprise the cellulose fibers as such and any residual amounts of hemicellulose or lignin derived from the plant-based materials used in the production of the fibers. Common non-fibrous additives include, but are not limited to one or more of calcium carbonate, clay (kaolin), talc, titanium dioxide, alum (aluminum sulfate), rosin, synthetic sizing agents (AKD, ASA), starch or modified starch, polyvinyl alcohol (PVA), latex (synthetic resins), silicone, fluorochemicals, synthetic resins (acrylics, styrene-butadiene), natural binders (casein, soy protein), optical brightening agents (OBAs), organic and inorganic colorants, antimicrobial agents, fire retardants, barrier polymers (for example polyethylene or PLA), plasticizers, antifoaming agents, retention aids, waxes (paraffin or microcrystalline).

[0024] In some embodiments, the paperboard layer comprises or consists of 70-100 wt% fibers, referred to herein as the total fiber content of the paperboard layer, and 0- 30 wt% non-fibrous additives, referred to herein as the total additive content of the paperboard layer. In some embodiments, the paperboard layer comprises or consists of 80-100 wt% fibers and 0-20 wt% non-fibrous additives. In some embodiments, the paperboard layer comprises or consists of 90-100 wt% fibers and 0-10 wt% non-fibrous additives.

[0025] The paperboard layer comprises 50-99 wt% of kraft fibers and 1-50 wt% of the recycled fibers, based on the total fiber content of the paperboard layer. In some embodiments the paperboard layer comprises 65-95 wt% of kraft fibers and 5-35 wt% of the recycled fibers, based on the total fiber content of the paperboard layer.

[0026] The paperboard layer is preferably compostable. A compostable paperboard layer allows for the provision of a compostable thermoformable paperboard-based laminate.

[0027] The recycled fibers have been obtained by treating recycled fibers, e.g., by washing and / or fractionation, to remove fines, and refining the recycled fibers to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267- 1. In some embodiments, the recycled fibers are first treated to remove fines to form a fines depleted recycled fiber fraction, and the fines depleted recycled fiber fraction is then refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267-1.

[0028] The term fines as used herein generally refers to particles significantly smaller in size than cellulose fibers. In some embodiments, the term cellulose fines as used herein refers to fine cellulosic or non-cellulosic particles, which are able to pass through a mesh 200 sieve (equivalent hole diameter 76 pm) of a conventional laboratory fractionation device (SCAN-CM 66:05). The fines content may for example be determined according to ISO 10376:2011 by sieving through a Mesh 200 sieve.

[0029] In some embodiments, the recycled fibers are subjected to a multi-step process comprising washing, fractionation, and refining, each designed to improve the quality and functionality of the fibers for their intended use in the paperboard layer. In some embodiments, the recycled fibers are also bleached to further improve the quality and functionality of the fibers for their intended use in the paperboard layer.

[0030] Non-limiting examples of multi-step processes to improve the quality and functionality of the fibers for their intended use in the paperboard layer include:

[0031] Washing - Washing - Refining

[0032] Fractionation - Washing - Refining

[0033] Washing - Fractionation - Refining

[0034] Fractionation - Bleaching - Washing - Refining

[0035] Fractionation - Washing - Bleaching - Washing - Refining.

[0036] The washing step(s) may involve treating the recycled fibers with water or an aqueous solution in one or more steps to remove fines and impurities such as dirt, inks, adhesives, and other contaminants. This can be achieved using equipment such as drum washers, pressurized washing units, or flotation cells. For example, flotation deinking systems may be used when the recycled fibers originate from printed paper sources, as they effectively separate ink particles from the fibers by generating air bubbles that attach to the ink and float it to the surface for removal. In some embodiments, chemical agents such as surfactants, dispersants, or enzymes may be added during washing to further enhance the removal of specific contaminants, such as sticky residues or biological impurities.

[0037] The fractionation step(s) may involve separation of the recycled fibers into different size fractions to optimize their properties for paperboard production. The primary objective of the fractionation is the removal of fines. This is typically carried out using mechanical fractionators, such as pressure screens, centrifugal cleaners, or laboratory fractionation devices equipped with mesh screens. Pressure screens utilize rotating elements to force fibers through slots or perforations while rejecting smaller particles such as fines and other undesirable components. Centrifugal cleaners, on the other hand, exploit differences in density between fibers and contaminants, causing lighter, high-quality fibers to separate from heavier fines and debris.

[0038] A relatively small portion of fines in recycled fiber fractions, particularly in fibers from used food service board (FSB) or used beverage carton (UBC), is responsible to a high degree for the high levels of impurities, high water retention and / or high drainage resistance of the fiber fractions. Treatment, e.g., by washing and / or fractionation, to remove fines can remove a significant portion of the particulate contaminants resulting in a fiber fraction with higher purity.

[0039] By removing fines, which can negatively affect fiber bonding and paperboard strength, the treatment, e.g., washing and / or fractionation, ensures the recycled fibers are optimized for high-performance applications.

[0040] In the refining step, the recycled fibers are subjected to mechanical treatment to enhance their physical properties, particularly their bonding potential. Refining may be conducted using disk refiners, conical refiners, or other mechanical refining equipment. During refining, the fibers are subjected to controlled shear and compression forces, which modify their surface structure and fibrillation. For instance, disk refiners may be used to expose microfibrils on the surface of the fibers, increasing their surface area and improving fiber-to-fiber bonding.

[0041] The degree of refining is controlled to achieve a Schopper Riegler (SR) value in the range of 14-30, as measured according to ISO 5267-1. This range ensures the fibers maintain an optimal balance of drainage properties and strength characteristics, making them suitable for incorporation into the paperboard layer. For example, an SR value closer to 14 may be selected for applications requiring faster drainage and higher bulk, whereas a value closer to 30 may be preferred for applications demanding higher strength and smoothness in the final paperboard product. In some embodiments, the recycled fibers are refined to a Schopper Riegler value in the range of 17-25 as measured according to ISO 5267-1.

[0042] The present disclosure is advantageous since it provides for incorporation of significant amounts of recycled fibers, and particularly fibers derived from used food service board (FSB) or used beverage carton (UBC), in thermoformable laminates. Used food service board (FSB) and used beverage cartons (UBC) represent a promising and abundant source of recycled fibers. Thus, in some embodiments, the recycled fibers are derived from used food service board (FSB), preferably from used beverage carton (UBC). In some embodiments a part of the recycled fibers is derived from old corrugated containers (OCC). In some embodiments, the recycled fibers comprise up to 30 wt% of fibers derived from used OCC, and at least 70 wt% of fibers derived from used FSB or UBC.

[0043] The recycled fibers used in the present disclosure may typically comprise an amount of high yield pulp fibers, i.e. , fibers obtained from high yield pulp processes, such as thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), pressure groundwood pulp (PGW), or stone groundwood pulp (SGW). In some embodiments, the recycled fibers comprise at least 30 wt%, preferably at least 50 wt%, high yield pulp fibers.

[0044] The treatment of the recycled fibers preferably reduces the content impurities, such as inorganic impurities or extractives. The ash content refers to the inorganic residue remaining after the paperboard is incinerated at high temperature. It provides an estimate of the content of mineral fillers (e.g., calcium carbonate, clay, titanium dioxide) and other inorganic additives present in the recycled fibers. In some embodiments, the recycled fibers have an ash content of less than 5 wt% as determined according to ISO 1762:2015 at 525°C.

[0045] In some embodiments, the recycled fibers have an extractive content of less than 1 wt%, and preferably less than 0.8 wt%, as determined according to TAPPI T204. The extractive content refers to the amount of soluble substances (extractives) present in the recycled fibers. These extractives can include resins, waxes, fats, oils, tannins, and certain low-molecular-weight carbohydrates, which are naturally occurring or introduced during processing.

[0046] The recycled fibers preferably have a plastics content of less than 2 wt%, more preferably less than 1 wt%, based on dry weight. The recycled fibers are preferably free from optical brightening agents (OBA).

[0047] The treatment of the recycled fibers preferably reduces the content of fines in the recycled fibers. The fines content may for example be determined according to ISO 10376:2011 by sieving through a Mesh 200 sieve. In some embodiments, the recycled fibers have a fines content of less than 30 wt%, as determined according to ISO 10376:2011.

[0048] In some embodiments, the recycled fibers, treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267-1 , have a mean fiber length Lc(l) of above 0.8 mm, preferably above 0.9 mm, and more preferably above 1.0, as determined according to ISO 16065.

[0049] The kraft fibers are preferably the main component of the paperboard layer by weight. The kraft fibers may comprise softwood kraft fibers or a combination of softwood and hardwood fibers. In some embodiments, the kraft fibers are softwood kraft fibers. In some embodiments, the paperboard layer comprises 1-20 wt%, and more preferably 5-20 wt% hardwood kraft fibers based on the total fiber content of the paperboard layer. In some embodiments, the kraft fibers are virgin kraft fibers.

[0050] In some embodiments, the kraft fibers are delignified and / or bleached. In some embodiments, the lignin content in the kraft fibers is below 10 wt%. In some embodiments, the kraft fibers have a kappa number below 60, preferably below 50 and more preferably below 40, as determined according to ISO 302:2015 or TAPPI / ANSI T236.

[0051] In some embodiments, the kraft fibers comprise 5-25 wt%, preferably 10-20 wt%, of hemicellulose.

[0052] In some embodiments, the paperboard layer further comprises at least one strength enhancement agent. In some embodiments, the strength enhancement agent is selected from the group consisting of a highly refined cellulose or microfibri Hated cellulose (MFC), a cationic polysaccharide, for example cationic starch, or an anionic polysaccharide, for example sodium carboxymethyl cellulose (NaCMC), or a combination of at least two thereof.

[0053] In some embodiments, the strength enhancement agent is added to the recycled fibers after the treatment to remove fines (for example after washing or after fractionation) such that the recycled fibers are refined together with the strength enhancement agent. When the recycled fibers are refined together with the strength enhancement agent the refining can be low, medium or high consistency refining. Preferably, the refining is done at a consistency above 10 wt%.

[0054] In some embodiments the strength enhancement agent is added to the recycled fibers after the refining, or to a mixture of the kraft fibers and the recycled fibers. The inclusion of the strength enhancement agent in the paperboard layer is designed to improve the mechanical properties of the final product, including tensile strength, burst strength, and internal bonding strength, without significantly compromising bulk and formation properties. In some embodiments, the strength enhancement agent comprises highly refined cellulose. Highly refined cellulose, through mechanical or chemical processing, has a fine, fibrillated structure that allows it to enhance fiber bonding within the paperboard layer. It improves the tensile and tear strength of the paperboard layer by increasing the surface area available for hydrogen bonding between fibers, while also maintaining the bulk and porosity benefits of the high-bulk softwood pulp. This strength enhancement agent is particularly beneficial in paperboard products where strength is a priority but excessive densification should be avoided. The highly refined cellulose can be produced from wood cellulose fibers, both from hardwood and softwood fibers or a combination thereof. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made from pulp including pulp from virgin fiber, e.g. mechanical, chemical and / or thermomechanical pulps. It can also be made from broke or recycled paper. The HRC may consist mainly of highly refined cellulose-based material, but may also comprise some of non-fibrous additives. In some embodiments, the highly refined cellulose has an SR value in the range of 50-84, preferably in the range of 55-84, or in the range of 60-84, as determined by standard ISO 5267-1. In some embodiments, the paperboard layer comprises the highly refined cellulose in an amount of 0.5-50 kg / tn based on the total dry weight of the paperboard layer.

[0055] In some embodiments, the strength enhancement agent comprises microfibrillated cellulose (MFC). MFC consists of cellulose fibers that have been mechanically or chemically treated to produce a network of nanoscale fibrils, which significantly enhance fiber bonding and the mechanical properties of the paperboard. The addition of MFC at the disclosed levels improves the strength of the paperboard layer by promoting fiber entanglement and increasing the fiber-to-fiber bonding surface area, resulting in a paperboard layer with high tensile, burst, and tear strength. MFC shall in the context of the patent application mean a cellulose particle, fiber or fibril having a width or diameter of from 20 nm to 1000 nm. Various methods exist to make MFC, such as single or multiple pass refining, prehydrolysis followed by refining or high shear disintegration or liberation of fibrils. One or several pre-treatment steps is usually required in order to make MFC manufacturing both energy efficient and sustainable. The cellulose fibers of the pulp used when producing MFC may thus be native or pre-treated enzymatically or chemically, for example to reduce the quantity of hemicellulose or lignin. The cellulose fibers may be chemically modified before fibrillation, wherein the cellulose molecules contain functional groups other (or more) than found in the original cellulose. Such groups include, among others, carboxymethyl (CM), aldehyde and / or carboxyl groups (cellulose obtained by N-oxyl mediated oxidation, for example "TEMPO"), or quaternary ammonium (cationic cellulose). After being modified or oxidized in one of the above-described methods, it is easier to disintegrate the fibers into MFC. MFC can be produced from wood cellulose fibers, both from hardwood and softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made from pulp including pulp from virgin fiber, e.g. mechanical, chemical and / or thermomechanical pulps. It can also be made from broke or recycled paper. In some embodiments, the microfibrillated cellulose (MFC) has an SR value in the range of 85-100, preferably in the range of 90-100, or in the range of 90-98, as determined by standard ISO 5267-1. In some embodiments, the paperboard layer comprises the MFC in an amount of 0.5-50 kg / tn based on the total dry weight of the paperboard layer.

[0056] In some embodiments, the strength enhancement agent comprises a cationic polysaccharide, such as cationic starch. Cationic polysaccharides, which are positively charged, are effective at improving paperboard strength by enhancing the electrostatic attraction between fibers, particularly when combined with anionic fibers or fillers. These additives form strong ionic bonds within the fiber network, which increases the internal bonding strength of the paperboard layer, more preferably a cationic polysaccharide, such as a cationic starch. In some embodiments, the paperboard layer comprises the cationic polysaccharide in an amount of 0.5-50 kg / tn based on the total dry weight of the paperboard layer.

[0057] In other embodiments, the strength enhancement agent comprises an anionic polysaccharide, such as anionic carboxymethyl cellulose (CMC). Anionic polysaccharides, which are negatively charged, interact with cationic components within the pulp to promote strong fiber bonding. Anionic polysaccharides may enhance the retention of fines and fillers, further contributing to the overall strength and consistency of the final paperboard product. In some embodiments, the paperboard layer comprises the cationic polysaccharide in an amount of 0.2-20 kg / tn based on the total dry weight of the paperboard layer.

[0058] In some embodiments, the strength enhancement agent comprises a combination of two or more strength enhancement agents selected from highly refined cellulose, m icrofi brillated cellulose, cationic polysaccharides, and anionic polysaccharides.

[0059] The paperboard layer preferably has a basis weight suitable for conversion into deep 3D shaped articles by thermoforming techniques, such as deep drawing techniques. In some embodiments, the paperboard layer has a basis weight in the range of 100-500 g / m2. In some embodiments, the paperboard layer has a grammage in the range of 100 to 500 g / m2, preferably in the range of 100 to 350 g / m2, 120 to 350 g / m2, 135 to 350 g / m2, or 150 to 350 g / m2.

[0060] The paperboard layer preferably has a relatively low density, or high bulk. In some embodiments, the paperboard layer has a grammage in the range of 100 to 500 g / m2, preferably in the range of 100 to 350 g / m2, 120 to 350 g / m2, 135 to 350 g / m2, or 150 to 350 g / m2, and a density of less than 850 kg / m3, preferably less than 750 kg / m3, and more preferably less than 650 kg / m3.

[0061] The paperboard layer has a stretchability of at least 3% in the machine direction (MD). In some embodiments, the paperboard layer has a stretchability of at least 3.5%, and preferably at least 4% in the machine direction (MD). In some embodiments, the paperboard layer has a stretchability in the range of 3-8.5%, preferably in the range of 3.5-8.5%, and more preferably in the range of 4-8.5%, in the machine direction (MD).

[0062] The paperboard layer further has a stretchability of at least 5% in the cross direction (CD). In some embodiments, the paperboard layer has a stretchability of at least 5.5%, and preferably at least 6% in the cross direction (CD). In some embodiments, the paperboard layer has a stretchability in the range of 5-14%, preferably in the range of 5.5-14%, and more preferably in the range of 6-14%, in the cross direction (CD).

[0063] In some embodiments, the paperboard layer has a combination of any of the mentioned stretchability ranges in the machine direction (MD) and any of the mentioned stretchability ranges in the cross direction (CD).

[0064] In some embodiments, the paperboard layer has a stretchability of at least 5%, and preferably at least 10%, in both machine direction (MD) and cross direction (CD). The stretchability is important to ensure thermoformability of the laminate, especially for deep-drawing applications. In some embodiments, the paperboard layer has a stretchability of at least 6%, at least 7%, at least 8%, at least 9%, or at least 10%, in both machine direction (MD) and cross direction (CD). In some embodiments, the paperboard layer has a stretchability of 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, or 12% or less.

[0065] In some embodiments, the paperboard layer has a Scott Bond value of at least 120 J / m2, preferably at least 150 J / m2, and more preferably at least 170 J / m2, as determined according to TAPPI T569.

[0066] The thermoformable paperboard-based laminate comprises at least one compostable barrier layer applied on at least one side of the paperboard layer.

[0067] The barrier layer is compostable. A compostable barrier layer allows for the provision of a compostable thermoformable paperboard-based laminate.

[0068] The term compostable as used herein for the thermoformable paperboard-based laminate and the different layers making up the thermoformable paperboard-based laminate means that the material is at least industrially compostable as determined according to any one of the standards ISO 18606:2013, EN 13432:2000, ASTM D6400-22, or ASTM D6868-21. In some embodiments, the material is home compostable as determined according to EN 13432:2000. The barrier layer may be applied directly on the paperboard layer, or it can be applied to the paperboard layer via a primer layer which improves adhesion between the paperboard layer and the barrier layer.

[0069] The barrier layer can be applied by conventional coating or lamination techniques, such as dispersion coating, extrusion coating or film lamination. The barrier layer can be applied in-line, offline or in converting lines.

[0070] The barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with a strain at break of at least 5%. In some embodiments, the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with a strain at break of at least 6%, at least 7%, at least 8%, at least 9%, or at least 10%. In some embodiments, the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with a strain at break of 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, or 12% or less. In some embodiments, the barrier layer comprises a combination of two or more semicrystalline polyhydroxyalkanoate (PHA) polymers wherein the combination of semicrystalline polyhydroxyalkanoate (PHA) polymers has a strain at break of at least 5%. In some embodiments, the combination of semicrystalline polyhydroxyalkanoate (PHA) polymers has a strain at break of at least 6%, at least 7%, at least 8%, at least 9%, or at least 10%. In some embodiments, the combination of semicrystalline polyhydroxyalkanoate (PHA) polymers has a strain at break of 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, or 12% or less. Unless specified otherwise, the strain at break of the semicrystalline polyhydroxyalkanoate (PHA) polymer or combination of semicrystalline polyhydroxyalkanoate (PHA) polymers in the present disclosure is determined according to ISO 527-1 :2019.

[0071] The barrier layer may be applied as a single layer, or as two or more sub-layers, wherein each sub-layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with a strain at break of at least 5%. A barrier coating applied as two or more sub-layers may improve barrier properties and reduce the occurrence of pinholes. The composition of each sub-layer can be tailored to achieve desired properties. In some embodiments, the barrier layer is applied as two sub-layers, wherein the strain at break of the first sub-layer is higher than the strain at break of the second sub-layer. In some embodiments, the barrier layer has a grammage in the range of 10 to 100 g / m2, preferably in the range of 15 to 50 g / m2.

[0072] In some embodiments, the number of pinholes in the barrier layer is less than 10 pinholes / m2, and preferably less than 5 pinholes / m2, as determined according to standard EN 13676:2001.

[0073] PHA is preferably the main component of the barrier layer based on dry weight. In some embodiments, the barrier layer comprises PHA in an amount of 60-99.9 wt%, preferably in an amount of 70-99.9 wt%, and more preferably in an amount of 90-99.9 wt%, based on the total dry weight of the barrier layer.

[0074] In some embodiments, the PHA has a crystallinity in the range of 10-50%, preferably in the range of 15-40%. When different PHA types are used in different layers or a blend of different PHA types are used, the average crystallinity should be in the same interval.

[0075] In some embodiments, the PHA has a melting point in the range of 100-175 °C, and preferably in the range of 110-170 °C. The glass transition temperature (Tg) of the PHA is preferably above 0 °C.

[0076] The PHA can be a homopolymer or co-polymer or a combination thereof. In some embodiments, the PHA is a PHA co-polymer, i.e. , a PHA wherein two or more different types of monomers are linked in the same PHA polymer chain. Such PHA co-polymers are well known to the skilled person. In some embodiments, the PHA is a short chain length or medium chain length PHA.

[0077] In some embodiments, the PHA is selected from the group consisting of poly(3- hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3- hydroxy hexanoate) (PHBH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHOHH), poly(3- hydroxyoctanoate-co-3-hydroxydecanoate) (PHOHD), and poly(3- hydroxyoctanoate-co-3-hydroxydodecanoate) (PHDHDD), or a mixture thereof. The skilled person understands that the PHA co-polymers are not limited to those listed here.

[0078] The barrier layer of the present disclosure, comprising PHA polymer with a strain at break of at least 5%, not only enables good barrier properties (i.e. acting as a barrier for liquids, grease, odor and taste), but also provides good thermoformability for deep-drawing applications and enables compostability of the laminate and products formed thereof.

[0079] The barrier layer preferably has good adhesion to the paperboard layer. In some embodiments, the barrier layer exhibits an adhesion to the paperboard layer >4, preferably >5, according to the cross-cut test (scale 1-5, where 5 is the highest adhesion).

[0080] In some embodiments, the thermoformable paperboard-based laminate further comprises a primer layer between the paperboard layer and the barrier layer. The primer layer acts to improve the adhesion of the barrier layer to the paperboard layer.

[0081] In some embodiments, the primer layer is compostable. A compostable primer layer allows for the provision of a compostable thermoformable paperboard-based laminate.

[0082] In some embodiments, the primer layer comprises a vinyl alcohol polymer, preferably selected from the group consisting of polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH) copolymers, or modified ethylene-vinyl alcohol copolymers, such as carboxylated polyvinyl alcohol.

[0083] In some embodiments the primer layer has a grammage in the range of 1 to 10 g / m2, preferably in the range of 1 to 8 g / m2.

[0084] In some embodiments, the thermoformable paperboard-based laminate further comprises at least one outermost sealing layer on at least one side of the paperboard layer. In preferred embodiments, the thermoformable paperboard- based laminate comprises at least one outermost sealing layer on at least one side of the paperboard layer which is not provided with a barrier layer. The outermost sealing layer is configured to provide a functional barrier, enhancing the resistance of the laminate to external factors such as liquids, grease, and air permeability, while facilitating downstream manufacturing processes.

[0085] The outermost sealing layer(s) are preferably heat sealable, enabling the formation of secure seals during packaging applications without requiring additional adhesives or mechanical fasteners. The heat-sealable nature of the outermost sealing layer may allow for efficient and reliable sealing under a range of temperature and pressure conditions, suitable for use with existing packaging machinery.

[0086] The outermost sealing layer(s) may be formed from a cold sealable adhesive or a hot sealable adhesive or a pressure sensitive adhesive.

[0087] In some embodiments, the outermost sealing layer is compostable. The outermost sealing layer is preferably made of compostable materials, enabling environmentally sustainable end-of-life disposal. A compostable outermost sealing layer allows for the provision of a compostable thermoformable paperboard-based laminate. Suitable materials for the outermost sealing layer(s) include, but are not limited to, bio-based polymers such as polyhydroxyalkanoates (PHA), polylactic acid (PLA), or blends thereof. In some embodiments, the outermost sealing layer comprises or consists of the same material as the barrier layer.

[0088] The outermost sealing layer(s) may be applied through processes such as dispersion coating, extrusion coating, film lamination, or other suitable techniques that ensure uniform adhesion and consistent functional performance.

[0089] The grammage and composition of the outermost sealing layer(s) are optimized to balance its barrier properties, heat-sealing performance, and compostability.

[0090] The grammage of the outermost sealing layer is preferably less than 50 g / m2. In order to achieve a continuous and substantially defect free film, a grammage of the outermost sealing layer of at least 8 g / m2, preferably at least 12 g / m2is typically required. In some embodiments, the grammage of the outermost sealing layer is in the range of 8-50 g / m2, preferably in the range of 12-50 g / m2.

[0091] The paperboard-based laminate of the present disclosure is thermoformable. Thermoforming of the paperboard-based laminate refers to a manufacturing process in which a sheet of the thermoformable paperboard-based laminate is heated to a pliable temperature and then shaped into a desired form using a mold and pressure. This process allows the paperboard-based laminate to achieve complex three-dimensional shapes while retaining structural integrity. An example of thermoforming is deep drawing, where the paperboard-based laminate is stretched into a deep cavity, forming intricate shapes with significant depth and contour.

[0092] In some embodiments, the thermoformable paperboard-based laminate has a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD). Unless specified otherwise, the stretchability of the thermoformable paperboard-based laminate in the present disclosure is determined according to ISO 1924-3:2005.

[0093] The thermoformable paperboard-based laminate has a stretchability of at least 3% in the machine direction (MD). In some embodiments, the thermoformable paperboard-based laminate has a stretchability of at least 3.5%, and preferably at least 4% in the machine direction (MD). In some embodiments, the thermoformable paperboard-based laminate has a stretchability in the range of 3- 8.5%, preferably in the range of 3.5-8.5%, and more preferably in the range of 4- 8.5%, in the machine direction (MD).

[0094] The thermoformable paperboard-based laminate further has a stretchability of at least 5% in the cross direction (CD). In some embodiments, the thermoformable paperboard-based laminate has a stretchability of at least 5.5%, and preferably at least 6% in the cross direction (CD). In some embodiments, the thermoformable paperboard-based laminate has a stretchability in the range of 5-14%, preferably in the range of 5.5-14%, and more preferably in the range of 6-14%, in the cross direction (CD).

[0095] In some embodiments, the thermoformable paperboard-based laminate has a combination of any of the mentioned stretchability ranges in the machine direction (MD) and any of the mentioned stretchability ranges in the cross direction (CD).

[0096] In some embodiments, the thermoformable paperboard-based laminate has a stretchability of at least 5%, and preferably at least 10%, in both machine direction (MD) and cross direction (CD). The stretchability is important to ensure thermoformability of the laminate, especially for deep-drawing applications. In some embodiments, the thermoformable paperboard-based laminate has a stretchability of at least 6%, at least 7%, at least 8%, at least 9%, or at least 10%, in both machine direction (MD) and cross direction (CD). In some embodiments, the thermoformable paperboard-based laminate has a stretchability of 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, or 12% or less.

[0097] The thermoformable paperboard-based laminate may further exhibit one or more of the following properties:

[0098] - a COBB 600 value for the PHA coated side of less than 15 g / m2, preferably less than 12 g / m2, and more preferably less than 10 g / m2, as determined in accordance with ISO 535:2014;

[0099] - a KIT grease resistance value for the PHA coated side of above 6, preferably above 8, and more preferably above 10, as determined in accordance with TAPPI T559 cm-12;

[0100] - a tensile index above 50 Nm / g as determined according to ISO 1924-2 in both machine direction (MD) and cross direction (CD);

[0101] - a bending resistance (L&W, 15°, MD) above 50 mN, preferably above 70 mN, and more preferably above 90 mN, as determined in accordance with ISO 2493-1 or ISO 2493-2; - a bending resistance (L&W, 15°, CD) above 15 mN, preferably above 25 mN, and more preferably above 35 mN, as determined in accordance with ISO 2493-1 or ISO 2493-2;

[0102] - industrially compostable as determined according to ISO 18606:2013.

[0103] The mineral oil migration rate in the gas phase through the thermoformable paperboard-based laminate can be estimated by a gravimetric measurement using heptane as a simulant as set out in European patent EP 3274 185 B1. In some embodiments, the thermoformable paperboard-based laminate has a heptane vapor transmission rate (HVTR) of less than 20 g / m2, preferably less than 15 g / m2, and more preferably less than 10 g / m2.

[0104] Examples of laminate structures of the inventive thermoformable paperboardbased laminate include but are not limited to:

[0105] - PAPERBOARD LAYER / BARRIER LAYER

[0106] - SEALING LAYER / PAPERBOARD LAYER / BARRIER LAYER

[0107] - SEALING LAYER / BARRIER LAYER / PAPERBOARD LAYER / BARRIER LAYER

[0108] - SEALING LAYER / PAPERBOARD LAYER / PRIMER LAYER / BARRIER LAYER

[0109] - SEALING LAYER / BARRIER LAYER / PRIMER LAYER / PAPERBOARD LAYER / PRIMER LAYER / BARRIER LAYER

[0110] According to a second aspect illustrated herein, there is provided a thermoformed packaging product formed from the thermoformable paperboard-based laminate described herein with reference to the first aspect. The thermoformable paperboard-based laminate used in the packaging products according to the second aspect may be further defined as set out above with reference to the first aspect.

[0111] Thermoformed or deep-drawn packaging products formed using the described thermoformable paperboard-based laminate are sustainable, high-performance, and versatile for applications requiring durability, flexibility, and environmental compliance. The described thermoformable paperboard-based laminate is ideal for forming food trays, clamshell packaging, cups, and other containers that demand high mechanical strength, moisture and grease resistance, and sustainability. These products are particularly suitable for industries such as:

[0112] Food and Beverage: For example, for packaging products for ready meals, snacks, and beverages.

[0113] Healthcare: For example, for medical trays requiring sterilizable and compostable materials.

[0114] Consumer Goods: For example, for durable and eco-friendly packaging for nonfood items.

[0115] According to a third aspect illustrated herein, there is provided a method for manufacturing a thermoformable paperboard-based laminate, the method comprising: providing a paperboard layer comprising:

[0116] 50-99 wt% kraft fibers based on the total fiber content of the paperboard layer, and 1-50 wt% recycled fibers based on the total fiber content of the paperboard layer, wherein the recycled fibers are treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267-1 ; applying at least one compostable barrier layer on at least one side of the paperboard layer, wherein the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with strain at break of at least 5%; optionally applying a primer layer between the paperboard layer and the barrier layer; and optionally applying an outermost sealing layer on at least one side of the paperboard layer; wherein the obtained laminate exhibits a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD).

[0117] Each of paperboard layer, the compostable barrier layer, and the optional primer layer and outermost sealing layer according to the third aspect may be further defined as set out above with reference to the first aspect.

[0118] In some embodiments, the paperboard layer is provided by: i) preparing a mixture of a pulp suspension comprising 50-99 wt% kraft fibers based on the total fiber content of the pulp suspension with a pulp suspension comprising 1-50 wt% recycled fibers based on the total fiber content of the pulp suspension, wherein the recycled fibers have been treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267-1 ; and ii) manufacturing a paperboard layer from the pulp suspension mixture.

[0119] The paperboard layer manufacturing may typically comprise applying the pulp suspension mixture onto a moving wire or forming fabric to form a continuous web, wherein water is removed through drainage, and the fibers interlock to form a cohesive fiber mat. The web can be formed as a single layer web or as a multilayer web using one or more headboxes or curtain or slot die type applicators, or a multilayer headbox. The web is subjected to pressing to further reduce its water content and enhance fiber bonding, followed by drying through contact with heated cylinders or other drying methods to achieve the desired moisture content. The dried web is then optionally calendered to improve surface smoothness and thickness uniformity and may be further processed by coating or lamination to impart additional functional properties.

[0120] In some embodiments a primer layer is first applied on a side of the paperboard layer onto which the barrier layer is to be applied. The primer layer improves adhesion between the paperboard layer and the barrier layer. The primer layer can be applied by conventional coating techniques, such as by dispersion coating.

[0121] The barrier layer may be applied directly on the paperboard layer, or it can be applied to the paperboard layer via a primer layer which improves adhesion between the paperboard layer and the barrier layer. The barrier layer can be applied by conventional coating or lamination techniques, such as dispersion coating, extrusion coating or film lamination. The barrier layer can be applied inline, offline or in converting lines.

[0122] In some embodiments, at least one outermost sealing layer is applied on at least one side of the paperboard layer. In preferred embodiments, at least one outermost sealing layer is applied on at least one side of the paperboard layer which is not provided with a barrier layer. The outermost sealing layer is configured to provide a functional barrier, enhancing the resistance of the laminate to external factors such as liquids, grease, and air permeability, while facilitating downstream manufacturing processes. The outermost sealing layer is preferably heat sealable, enabling the formation of secure seals during packaging applications without requiring additional adhesives or mechanical fasteners.

[0123] The outermost sealing layer(s) may be applied through processes such as dispersion coating, extrusion coating, film lamination, or other suitable techniques that ensure uniform adhesion and consistent functional performance.

[0124] While the invention is described herein 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 is not 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. A thermoformable paperboard-based laminate comprising: a paperboard layer, said paperboard layer comprising:50-99 wt% kraft fibers based on the total fiber content of the paperboard layer, and1-50 wt% recycled fibers based on the total fiber content of the paperboard layer, wherein said recycled fibers are treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267- 1 ; at least one compostable barrier layer applied on at least one side of the paperboard layer, wherein the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with strain at break of at least 5%; optionally a primer layer between the paperboard layer and the barrier layer; and optionally at least one outermost sealing layer on at least one side of the paperboard layer; wherein the thermoformable paperboard-based laminate exhibits a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD).

2. The laminate according to claim 1 , wherein the paperboard layer comprises 65-95 wt% of the kraft fibers and 5-35 wt% of the recycled fibers.

3. The laminate according to any one of the preceding claims, wherein the recycled fibers are derived from used food service board (FSB), preferably from used beverage carton (UBC).

4. The laminate according to any one of the preceding claims, wherein the recycled fibers comprise at least 30 wt%, preferably at least 50 wt%, high yield pulp fibers.

5. The laminate according to any one of the preceding claims, wherein the treatment to remove fines comprises washing and / or fractionation.

6. The laminate according to any one of the preceding claims, wherein the recycled fibers have an ash content of less than 5 wt% as determined according to ISO 1762:2015 at 525°C.

7. The laminate according to any one of the preceding claims, wherein the recycled fibers have a fines content of less than 30 wt% as determined according to ISO 10376:2011.

8. The laminate according to any one of the preceding claims, wherein the recycled fibers have a mean fiber length Lc(l) of above 0.8 mm, preferably above 0.9 mm, and more preferably above 1.0 mm, as determined according to ISO 16065.

9. The laminate according to any one of the preceding claims, wherein the recycled fibers are refined to a Schopper Riegler value in the range of 17-25 as measured according to ISO 5267-1.

10. The laminate according to any one of the preceding claims, wherein the paperboard layer has a grammage in the range of 120 to 500 g / m2, preferably in the range of 170 to 350 g / m2, and a density of less than 850 kg / m3, preferably less than 750 kg / m3, and more preferably less than 650 kg / m3.

11. The laminate according to any one of the preceding claims, wherein the paperboard layer has a Scott Bond value of at least 120 J / m2, preferably at least 150 J / m2, and more preferably at least 170 J / m2, as determined according to TAPPI T569.

12. The laminate according to any one of the preceding claims, wherein the PHA has a crystallinity in the range of 10-50%, preferably in the range of 15-40%.

13. The laminate according to any one of the preceding claims, wherein the barrier layer has a grammage in the range of 10 to 100 g / m2, preferably in the range of 15 to 50 g / m2.

14. The laminate according to any one of the preceding claims, wherein the primer layer is compostable.

15. The laminate according to any one of the preceding claims, wherein the primer layer comprises a vinyl alcohol polymer, preferably selected from the group consisting of polyvinyl alcohol (PVOH), ethylene- vinyl alcohol (EVOH) copolymers, or modified ethylene-vinyl alcohol copolymers, such as carboxylated polyvinyl alcohol.

16. The laminate according to any one of the preceding claims, wherein the outermost sealing layer is compostable.

17. The laminate according to any one of the preceding claims, having at least one of the following properties:- a COBB 600 value for the PHA coated side of less than 15 g / m2as determined in accordance with ISO 535:2014;- a KIT grease resistance value for the PHA coated side of above 6 as determined in accordance with TAPPI T559 cm-12;- a tensile index above 50 Nm / g as determined according to ISO 1924-2 in both machine direction (MD) and cross direction (CD);- a bending resistance (L&W, 15°, MD) above 50 mN, preferably above 70 mN, and more preferably above 90 mN, as determined in accordance with ISO 2493-1 or ISO 2493-2;- a bending resistance (L&W, 15°, CD) above 15 mN, preferably above 25 mN, and more preferably above 35 mN, as determined in accordance with ISO 2493-1 or ISO 2493-2;- industrially compostable as determined according to ISO 18606:2013.

18. A thermoformed packaging product formed from the laminate according to any one of the preceding claims.

19. A method for manufacturing a thermoformable paperboard-based laminate, the method comprising: providing a paperboard layer comprising:50-99 wt% kraft fibers based on the total fiber content of the paperboard layer, and 1-50 wt% recycled fibers based on the total fiber content of the paperboard layer, wherein the recycled fibers are treated to remove fines, and refined to a Schopper Riegler value in the range of 14-30 as measured according to ISO 5267-1 ; applying at least one compostable barrier layer on at least one side of the paperboard layer, wherein the barrier layer comprises a semicrystalline polyhydroxyalkanoate (PHA) polymer with strain at break of at least 5%; optionally applying a primer layer between the paperboard layer and the barrier layer; and optionally applying an outermost sealing layer on at least one side of the paperboard layer; wherein the obtained laminate exhibits a stretchability of at least 3% in the machine direction (MD) and a stretchability of at least 5% in the cross direction (CD).