Method for manufacturing a film comprising highly refined cellulose

Description

1 / 21 METHOD FOR MANUFACTURING A FILM COMPRISING HIGHLY REFINED CELLULOSE Technical field

[0001] This disclosure relates to a method for manufacturing a barrier film, for example, for a paper or cardboard-based packaging material, this film being recyclable and exhibiting good barrier properties, in particular, gas and water vapor barrier properties. Furthermore, this disclosure relates to a method for manufacturing a laminate of paper or cardboard-based packaging material, a barrier film, and a laminate of paper or cardboard-based packaging material comprising the barrier film. Background

[0002] Barrier films comprising cellulose fibers or polymers (cellulose-based barrier films), including films comprising high amounts of highly refined cellulose, nanocellulose, or microfibrillated cellulose (MFC), are known in the art. Depending on how they are produced, cellulose-based barrier films may exhibit particularly advantageous strength and / or barrier properties, in addition to being biodegradable and recyclable (or repulpable). Such barrier films can be used, for example, in the manufacture of packaging materials and can be laminated or otherwise applied to the surface of paper or cardboard materials. The use of cellulose-based barrier films in packaging materials often facilitates the repulping and recycling of used packaging materials. Petition 870250091038, dated 06 / 10 / 2025, page 5 / 36 2 / 21

[0003] However, the barrier properties of cellulose-based barrier films can be sensitive to moisture or higher relative humidity. In particular, the gas barrier properties of these barrier films tend to deteriorate at high temperatures and high humidity, such as when exposed to tropical conditions or conditions that allow condensation.

[0004] One approach to improving the oxygen and water vapor barrier properties described in the art involves applying the cellulose-based film with a coating layer that provides additional barrier properties. To improve the repulpability and recyclability of the film thus produced, it is often preferable that such coating layers be applied as water-based solutions or dispersions. However, difficulties may arise in applying water-based coatings and surface treatments to cellulose-based substrates. When such water-based solutions or dispersions are applied to a thin cellulose-based network or substrate, the network may break or exhibit dimensional stability problems. Wrinkling, shrinkage, and / or waviness of the sheet may occur.This is due to the sorption and penetration of water into the hydrophilic substrate, affecting, for example, the hydrogen bonds between fibrils, fibers, and additives. Therefore, controlling sheet tension can be difficult in the machine direction. Furthermore, handling the sheet in the direction transverse to the machine can be challenging.

[0005] One solution to this problem is to increase the solids content of the solutions or dispersions. Petition 870250091038, dated 06 / 10 / 2025, page 6 / 36 3 / 21 applied, although this often results in greater layer weight and higher solution viscosity. Applying a solution / dispersion with high viscosity can generate higher stresses in the substrate.

[0006] Another solution is to provide a cellulose-based film with high moisture resistance properties, for example, by adding moisture-resistant agents. This, on the other hand, makes repulping and recycling the film more difficult.

[0007] Another solution is to provide the cellulose-based film with hydrophobic chemicals, such as internal bonding agents, which reduce wettability and protect the bonds between fibers. The disadvantage of this method, especially with high amounts of internal bonding agents, is that the barrier properties of the film may be negatively affected and that pulping may be inefficient, which can lead to increased waste in recycling.

[0008] Therefore, there is still room for improvement in the production methods of cellulose-based barrier films, for example, for paper or cardboard-based packaging materials, that have good barrier properties, such as water vapor barrier properties, and that are repulpable and / or recyclable. Description of the invention

[0009] One objective of the present invention is to provide an improved method for manufacturing a barrier film, for example, for a paper or cardboard-based packaging material, wherein the barrier film has good barrier properties, such as barrier properties of Petition 870250091038, dated 06 / 10 / 2025, page 7 / 36 4 / 21 oxygen and / or water vapor, and whose method eliminates or alleviates at least some of the disadvantages of the prior art methods.

[0010] Another objective of the present invention is to provide a method for manufacturing a barrier film, for example, for a paper or cardboard-based packaging material, a barrier film that has good barrier properties and is repulpable and / or recyclable.

[0011] The aforementioned objectives, as well as other objectives that will be achieved by those skilled in the art in light of this disclosure, are achieved through the various aspects of this disclosure.

[0012] According to a first aspect in the present illustrated document, a method is provided for manufacturing a film comprising highly refined cellulose, the method comprising the steps of: a) provide a net comprising at least 50% highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as measured in accordance with ISO 5267-1, the percentage calculated on the total dry weight of the net, which net has a density in the range of 700 to 1500 kg / m3, as measured in accordance with ISO 534, preferably 800 to 1350 kg / m3, more preferably 900 to 1350 kg / m3 and a wet tensile strength retention value (MD), as measured in accordance with ISO 3781:2011, of less than 15%, preferably less than 10% and more preferably less than 5%, Petition 870250091038, dated 06 / 10 / 2025, page 8 / 36 5 / 21 (b) applying an aqueous solution or dispersion comprising a polymer to the network, wherein the aqueous solution or dispersion has a solids content of between 5 and 50% by weight, preferably between 7.5 and 35% by weight or more preferably between 10 and 30% by weight, and c) Dry the applied mesh with the water-based solution or dispersion to a solids content of at least 80% by weight, thus forming the film.

[0013] The inventive method is based on the finding that it is possible to coat a network containing a large amount of highly refined cellulose with an aqueous solution or dispersion with very low solids content. This is achieved by providing a network with a density between 700-1500 kg / m3 and a wet tensile strength (DM) retention within the claimed range. It has been found that a film produced according to the inventive method is easily repulpable and recyclable, but does not exhibit problems of dimensional instability or network rupture during processing (e.g., coating or impregnation). Furthermore, the application of the aqueous solution or dispersion with such low solids content provides uniform coverage of the network and allows for good barrier properties with low coating thicknesses.

[0014] The term film, as used in this document, generally refers to a thin material formed in the form of a continuous sheet. Depending on the network composition, the film may also be considered a thin paper or even a membrane.

[0015] The term highly refined cellulose, Petition 870250091038, dated 06 / 10 / 2025, page 9 / 36 6 / 21 as used in this document refers preferably to refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, preferably in the range of 80 to 98, more preferably in the range of 85 to 98, as determined by ISO 5267-1. Refining, or beating, of cellulose pulps refers to the mechanical treatment and modification of cellulose fibers to impart the desired properties.

[0016] Highly refined cellulose can be produced from different raw materials, for example, bleached or unbleached softwood pulp or hardwood pulp. In some embodiments, highly refined cellulose is produced from unbleached kraft pulp. Highly refined cellulose is preferably never-dried cellulose. In some embodiments, highly refined cellulose is highly refined native cellulose. In the context of the application, native cellulose refers to cellulose that has not been chemically modified.

[0017] In some embodiments, highly refined cellulose has a water retention value (WRV) of at least 2.0 g / g, preferably at least 2.2 g / g.

[0018] The netting comprises at least 50% by weight of highly refined cellulose. In some embodiments, the netting may comprise at least 70% by weight of highly refined cellulose or at least 80% by weight of highly refined cellulose, such as between 70% and 99.9% by weight or 80% and 99.9% by weight of highly refined cellulose, all percentages calculated based on the total dry weight of the netting. The netting may also comprise hardwood and / or softwood cellulosic fibers, such as between 49% and 0% by weight or 30% and 0% of Petition 870250091038, dated 06 / 10 / 2025, page 10 / 36 7 / 21 cellulosic fibers. Such cellulosic fibers preferably have a Schopper-Riegler index between 15 and 45, as determined by ISO 5267-1, more preferably between 20 and 35. More preferably, the cellulosic fibers are bleached kraft pulp, never dried. The netting may also comprise other ingredients or additives, as described below.

[0019] In some embodiments, highly refined cellulose is microfibrillated cellulose (MFC).

[0020] Microfibrillated cellulose (MFC) should be understood in the context of the patent application as a cellulose particle, fiber or fibril with a width or diameter of 20 nm to 1000 nm.

[0021] There are several methods for producing MFC, such as single or multiple pass refining, pre-hydrolysis followed by refining, or disintegration by high shear or fibril release. Generally, one or more pretreatment steps are necessary to make MFC manufacturing energy efficient and sustainable. The cellulose fibers of the pulp used in MFC production can be native or enzymatically or chemically pretreated, for example, to reduce the amount of hemicellulose or lignin.

[0022] MFC can be produced from wood cellulose fibers, both hardwood and softwood. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It can be made from cellulose, including virgin fiber cellulose, such as mechanical, chemical, and / or thermomechanical cellulose. Also Petition 870250091038, dated 06 / 10 / 2025, page 11 / 36 8 / 21 can be made from scraps or recycled paper.

[0023] There are different acronyms for MFC, such as cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, fibril aggregates, nanoscale cellulose fibrils, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregates, and cellulose microfibril aggregates. MFCs can also be characterized by various physical or physicochemical properties, such as their large surface area or their ability to form a gelatinous material with a low solids content (1-5% by weight) when dispersed in water.

[0024] The basis weight (also called basis weight) of the net, in total dry weight, is typically less than 110 g / m2, preferably in the range of 15 to 100 g / m2 or in the range of 20 to 60 g / m2. Films without holes with basis weights in these ranges have been found to exhibit good oxygen barrier properties.

[0025] The network exhibits a wet tensile strength retention (DM) of less than 10%. Preferably, less than 5%. In some embodiments, the wet tensile strength retention (DM) may be less than 3%, preferably less than 2% or less than 1%, such as between 0.1 and 10%, or 0.1 and 5%, 0.1 and 3%, 0.1 and 2% or 0.1 and 1%. Wet tensile strength retention is measured according to ISO 3781:2011; the standard used for tensile strength testing is 19242:2008. Wet tensile strength retention may, for example, be regulated to remain within the claimed range by optimizing the amount of Petition 870250091038, dated 06 / 10 / 2025, page 12 / 36 9 / 21 resistance agents in wet environment and resistance agents in dry environment in the network.

[0026] In some embodiments, the network has a wet tensile strength (DM) less than 0.3 kN / m, preferably less than 0.2 or less than 0.15, preferably between 0 - 0.29, or 0.1 - 0.29 or 0 - 0.2 or 0.1 - 0.2 or 0 - 0.15 or 0.1 - 0.15, as measured in accordance with ISO 3781:2011.

[0027] In some embodiments, the network comprises less than 5% by weight, preferably less than 3% by weight or less than 2% by weight, such as 0 to 5% by weight, or 0 to 3% by weight or 0 to 2% by weight, in dry weight, of moisture-resistant agents. The term moisture-resistant agents, as used herein, refers to moisture-resistant chemicals, typically moisture-resistant resins, that improve the tensile properties of a cellulose-containing network in the wet state by cross-linking the cellulose fibers with covalent bonds. Moisture-resistant agents may include permanent and temporary moisture-resistant agents and may include, for example, urea resins, melamine resins, polyamidoamine-epichlorohydrin (PAAE) and dialdehyde-amido resins.

[0028] In some embodiments, the network has a dry tensile strength (DM), measured in accordance with ISO 1942-2, of at least 3 kN / m, preferably at least 5 kN / m or at least 6 kN / m.

[0029] Preferably, the network comprises at least 5 kg / ton of dry strength agents, more preferably at least 6 kg / ton or at least 10 kg / ton Petition 870250091038, dated 06 / 10 / 2025, p. 13 / 36 10 / 21 of dry strength agents, preferably in the range of 5-30 kg / ton, or 5-20 kg / ton or 10-20 kg / ton, as calculated on the dry weight of the net. The term dry strength agents, as used in this document, refers to dry strength chemicals that improve the tensile properties of a cellulose-containing net in the dry state, for example, by forming hydrogen bonds. Dry strength agents improve friction between fibers, increasing the initial wet strength of the net. Dry strength agents may include, for example, natural gums or polymers such as cationic starch, carboxymethylcellulose (CMC) and guar gum, and synthetic polymers such as polyacrylamide (cationic, anionic and amphoteric), glyoxylated polyacrylamides (GPAMs) and polyvinylamines.In some embodiments, the network comprises natural gums and a surface-active polymer preferably selected from the group of modified hydrophobic proteins or polysaccharides.

[0030] Preferably, the net supply stage comprises the supply stage of a first net comprising the said quantity of highly refined cellulose, this first net being subjected to dewatering in at least one extended clamping press, such as a shoe press or a metal belt press. Wet pressing preferably occurs at a temperature (wet net temperature) between 40 and 95°C and, more preferably, between 50 and 95°C and, more preferably, between 50 and 95°C, and with a clamping length of at least 10 mm, preferably at least 15 mm and, more preferably, at least 20 mm. The load Petition 870250091038, dated 06 / 10 / 2025, page 14 / 36 11 / 21 linear is preferably 500 to 3000 N / m. Optionally, the wet press clamping comprises at least one surface roller, belt or felt with a temperature of 50 to 250°C, such as 60 to 180°C. An example of a wet press configuration contains two shoe nips, such as Symbelt or OptiPress Linear from Valmet or NipcoFlex from Voith GmbH. The dewatering of the extended nip can be integrated or part of a normal press section. Preferably, the dewatered sheet is subsequently dried and then calendered, for example, with a soft nip machine or extended nip calender, preferably at a temperature above 60°C, such as 70-250°C (roll temperature). A preferred configuration is a station with two soft nips (e.g., soft-hard roll and hard-soft roll). Preferably, before dehydration and / or calendering of the extended nip, the leaf is subjected to steam at a quantity of, for example, 1-5 g / m2 on at least one side, at a temperature above 60°C.As an alternative to using a soft calender, a metal belt calender, such as the Valzone from Valmet, can be used, preferably under the following conditions: heated roll surface temperature: 50 to 250 °C, heated steel belt surface temperature: 50 to 250 °C, contact loads: 10 to 250 kN / m, preferably 20 to 150 kN / m. The sheet can be moistened with water before calendering the metal belt, preferably in a proportion of 0.5 to 5 g / m².

[0031] Without adhering to any particular theory, it is believed that the optimized shoe press and the higher solids content after the pressing section allow for the greater strength required for in-line coating. In addition Petition 870250091038, dated 06 / 10 / 2025, p. 15 / 36 12 / 21 In addition, the in-line calender with pre-steaming allows for better bonding to the sheet and, consequently, better dimensional stability. In particular, soft-tip calendering provides a more homogeneous density, which reduces dimensional stability problems during and after coating. Furthermore, the sheet is easier to repulp / recycle.

[0032] The net can be manufactured on wide machines, preferably with a net width greater than 3 m and up to greater than 3.5 m at high speeds, such as above 400 m / min, such as between 500 - 1500 m / min.

[0033] In some embodiments, the water-based solution or dispersion has a water retention value (WRV) ÂAGWR, measured according to the TAPPI TM701PM-01 standard, between 10 and 500 g / m2, preferably between 10 and 300, or 10 and 100 g / m2. The use of a solution or dispersion with such a WRV minimizes the amount of water released onto the sheet, which further increases dimensional stability. In this way, the sheet can be processed and dried without problems of rupture.

[0034] In some embodiments, the aqueous solution or dispersion has a Brookfield viscosity of 250 to 3500 mPa, preferably 300 to 2500 mPa, measured according to the SCAN-P50:84 standard, spindle number 6 at 100 rpm. A viscosity within the claimed range facilitates uniform application of the coating to the sheet.

[0035] Preferably, the aqueous solution or dispersion comprises a polymer selected from the group consisting of polyvinyl alcohol (PVOH), a modified polyvinyl alcohol, a polysaccharide or a Petition 870250091038, dated 06 / 10 / 2025, page 16 / 36 13 / 21 Modified polysaccharide, or a combination thereof. The polysaccharide or modified polysaccharide is preferably selected from the starch, carboxymethylcellulose (CMC), chitosan, and cellulose nanocrystals (CNC) groups. The polymer is preferably selected to provide barrier properties, such as additional oxygen barrier properties or liquid or water vapor barrier properties. The polymer may also be crosslinked. The aqueous solution or dispersion may also comprise pigments, such as 0 to 15% by weight of pigments, calculated based on the total solids content of the aqueous solution or dispersion. The aqueous solution or dispersion is preferably applied to the mesh in an amount that provides a coating layer with a basis weight between 1 and 10 g / m², preferably 1 to 5 g / m². The coated barrier film preferably has a moisture content of 2 to 8% by weight, such as between 3 and 7% by weight.

[0036] The network formation stage may involve the formation of a multilayer network. Thus, the network may be formed by two or more layers of network containing a high cellulose content, such as two, three, or even four layers. The use of a multilayer network allows the manufacturer to design the network so that the initial wet network strength is improved, facilitating the coating of the network with a low-solids dispersion or solution, while the wet strength is low enough to allow repulping. This can be achieved, for example, by forming one layer (first network layer) containing a high amount of highly refined cellulose to provide barrier performance and another layer (second layer of Petition 870250091038, dated 06 / 10 / 2025, page 17 / 36 14 / 21 mesh) containing a high quantity of thicker fibers to provide dimensional stability. This first mesh layer can be made more hydrophilic and thinner to allow for re-pulping and re-pulping of the layer (even if it is denser), and this second mesh layer can be made to allow for faster liquid penetration, but simultaneously provide sufficient strength and dimensional stability for coating and conversion.

[0037] In some modalities, the multilayer network formation stage comprises - to form a first layer of the network comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said first layer of the network, and - to form a second network layer comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said second network layer. Applying the second network layer on top of the first network layer to form a multi-layered network.

[0038] The network formation can, for example, be done in a paper machine-type process. In one embodiment, a multilayer network can be formed by applying a first coating layer over a substrate (such as a wire) to form a first network layer, after which a second coating layer is applied over the first layer to form a second network layer. Preferably, the first network layer Petition 870250091038, dated 06 / 10 / 2025, page 18 / 36 15 / 21 is at least partially dehydrated before the application of the second coating layer. Alternatively, a multilayer network can be formed by applying a first coating layer over a first substrate (such as a first wire) and partially dehydrating said first coating layer over the substrate to form a first network layer, and applying a second coating layer over a second substrate (such as a second wire) and partially dehydrating said second coating layer over the second substrate to form a second network layer, after which said second network layer is applied over said first network layer to form the multilayer network.

[0039] In some modalities, the multilayer network formation stage comprises - to form a first layer of netting comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value, as measured by ISO 5267-1, in the range of 80 to 100, as calculated based on the total fiber content of said first layer of netting, and - forming a second network layer comprising cellulose fibers and less than 50% by weight of highly refined cellulose fibers with a Schopper-Riegler (SR) value, as measured by ISO 5267-1, in the range of 80 to 100, as calculated based on the total fiber content of said second network layer. Applying the second network layer on top of the first network layer to form a multi-layered network.

[0040] In some modalities, the method of Petition 870250091038, dated 06 / 10 / 2025, page 19 / 36 16 / 21 formation of the multilayer network includes - to form a first layer of netting comprising between 80-100% by weight of highly refined cellulose with a Schopper-Riegler (SR) value, as measured by ISO 5267-1, in the range of 80-100, as calculated based on the total fiber content of said first layer of netting, and - to form a second network layer comprising between 65-95% by weight of cellulosic fibers and 5-35% by weight of highly refined cellulose with a Schopper-Riegler (SR) value, as measured by ISO 5267-1, in the range of 80-100, as calculated based on the total fiber content of said second network, Applying the second network layer on top of the first network layer to form a multi-layered network.

[0041] The cellulosic fibers in the second layer preferably have a Schopper-Riegler index between 15 and 45, as measured by ISO 5267-1, more preferably between 20 and 35. The cellulosic fibers are preferably hardwood pulp or longwood fibers. The cellulosic fibers may be a mixture of hardwood pulp and longwood fibers. Hardwood pulp may be preferable, as hardwood fibers have been shown to improve the formation of the multilayer barrier film. The pulp may be virgin fiber, for example, mechanical, semi-chemical, chemical, chemical-thermomechanical and / or thermomechanical pulps. It may be preferable that the cellulosic fibers be made from kraft pulp, more preferably bleached kraft pulp.

[0042] Preferably, the solution or Petition 870250091038, dated 06 / 10 / 2025, page 20 / 36 17 / 21 aqueous dispersion is applied to the first layer of the network, which contains a high quantity of highly refined cellulose. In this way, the barrier properties are optimized.

[0043] In some embodiments, the second layer comprises an additive selected from the natural gum group, preferably guar gum, and nanoparticles, preferably nano PCC. Preferably, this additive is added to the second layer in an amount of 1 to 15 kg / ton, calculated based on the dry weight of said second layer. In this way, the friction between fibers is improved, which further increases the initial moisture resistance. It has been shown that it is beneficial to add this natural gum or nanoparticles to the layer comprising the coarser cellulosic fibers (i.e., the second layer), since if these chemicals are added to the layer comprising the highly refined cellulose (the first layer), dehydration can be a challenge.

[0044] Although the second mesh layer may contain a small amount of moisture-resistant agents, such as between 0 and 5 kg / ton or 0.1 and 5 kg / ton, it is preferable that the first mesh layer does not contain any moisture-resistant agents. As described above, if the layer containing a large amount of highly refined cellulose is made more hydrophilic, rewetting and repulping of the film are facilitated.

[0045] In some applications, the first layer has a basis weight in the range of 8 to 30 g / m2, preferably in the range of 12 to 25 g / m2, and the second layer has a basis weight in the range of 12 to 90 g / m2, Petition 870250091038, dated 06 / 10 / 2025, page 21 / 36 18 / 21 preferably in the range of 15 to 35 g / m2. Preferably, the first layer has a lower basis weight than the second layer.

[0046] The resulting film, composed of highly refined cellulose, is easily repulpable and recyclable. Preferably, the resulting film has a rejection rate, according to the PTS RH-021 / 97 standard, of less than 5%, preferably less than 3%.

[0047] The method allows the manufacture of a film with high barrier properties. In some embodiments, the barrier film obtained, comprising highly refined cellulose, has an oxygen transfer rate (OTR), measured in accordance with ASTM F1927-98 at 50% relative humidity and 23 °C, of ​​less than 100 cc / m2 / 24h / atm, preferably less than 50 cc / m2 / 24h / atm, more preferably less than 20 cc / m2 / 24h / atm and / or a KIT value of at least 10, preferably at least 12, as measured in accordance with ISO 16532-2.

[0048] In some embodiments, the resulting barrier film exhibits a water vapor transfer rate (WVTR), measured according to ASTM F1249-20 at 50% RH / 23 °C, of ​​less than 40 g / m² / 24 h, preferably less than 20 g / m² / 24 h, and more preferably less than 15 g / m² / 24 h. The resulting film, comprising highly refined cellulose, may preferably exhibit an oxygen transfer rate (OTR), measured according to ASTM F1927-98 at 85% relative humidity and 23 °C, of ​​less than 150 cc / m² / 24 h / atm, preferably less than 100 cc / m² / 24 h / atm, and more preferably less than 75 Petition 870250091038, dated 06 / 10 / 2025, p. 22 / 36 19 / 21 cc / m2 / 24 h / atm.

[0049] In some embodiments, the resulting film, comprising highly refined cellulose, has a wet tensile strength (MD or CD) greater than 0.1 kN / m, as measured in accordance with ISO 3781:2011. This facilitates the subsequent conversion of the resulting barrier film.

[0050] Furthermore, the method allows the fabrication of a film with high barrier properties that contains little or no synthetic polymer. In some embodiments, the resulting film contains less than 10% by weight, preferably less than 5% by weight, of synthetic polymers, calculated based on the total weight of the film. Preferably, the resulting film contains no fluorochemicals.

[0051] According to a second aspect illustrated in this document, a film comprising highly refined cellulose is provided, wherein the film can be obtained by the inventive method described with reference to the first aspect.

[0052] According to a third aspect in the present illustrated document, a method is provided for manufacturing a laminate of packaging material based on paper or cardboard, comprising the steps of: - perform the method according to the first aspect in order to form the aforementioned barrier film, and - Laminate said barrier film with a paper- or cardboard-based material to form said paper- or cardboard-based packaging material laminate.

[0053] The barrier film can be laminated to the paper-based or cardboard-based material using an adhesive layer. Petition 870250091038, dated 06 / 10 / 2025, p. 23 / 36 20 / 21 bonding in the form of an extrusion coating or in the form of a water-based solution or dispersion using liquid coating methods. In some embodiments, the water-based solution or dispersion comprising a polymer applied to the sheet in the first aspect method can be used as an adhesive layer and / or to improve adhesion to the cardboard.

[0054] According to a fourth aspect illustrated in this document, a paper or cardboard-based packaging material laminate is provided, obtained by the method according to the third aspect.

[0055] In some embodiments, the paper- or cardboard-based packaging material comprises additional polymer layers, such as extruded or laminated polyolefin layers applied to one or both sides of the laminate of the paper- or cardboard-based packaging material. This / these polymer layer(s) may comprise any of the thermoplastic polymers commonly used in paper- or cardboard-based packaging materials in general or polymers used in liquid packaging cardboard in particular. Examples include polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polylactic acid (PLA), polyglycolic acid (PGA), and polyhydroxyalkanoates (PHA). Polyethylenes, especially low-density polyethylene (LDPE) and high-density polyethylene (HDPE), are the most common and versatile polymers used in liquid packaging cardboard. Polyolefins may also be oriented, such as biaxially oriented or even vacuum-coated, or both.

[0056] Thus, a possible laminated structure is Polyolefin / Cardboard / water-soluble adhesive / film of Petition 870250091038, dated 06 / 10 / 2025, page 24 / 36 21 / 21 barrier / polyolefin / polyolefin

[0057] Thermoplastic polymers are useful because they can be conveniently processed by extrusion coating techniques to form very thin and homogeneous films with good liquid barrier properties. In some embodiments, the polymer layer comprises polypropylene or polyethylene. In preferred embodiments, the polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0058] Although the invention has been described with reference to several exemplary embodiments, those skilled in the art will understand that various alterations can be made and equivalents can be used to replace elements of the invention without departing from the scope of the invention. Furthermore, various modifications can be made to adapt a specific situation or material to the teachings of the invention without departing from the essential scope of the invention. Therefore, it is intended that the invention is not limited to the specific embodiment disclosed as the best contemplated mode for carrying out this invention, but that the invention includes all embodiments that fall within the scope of the appended claims. Petition 870250091038, dated 06 / 10 / 2025, p. 25 / 36

Claims

1 / 5 CLAIMS 1. Method for manufacturing a barrier film comprising highly refined cellulose, the method characterized in that it comprises the steps of: a) providing a net comprising at least 50% highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as measured in accordance with ISO 5267-1, the percentage calculated on the total dry weight of the net, which net has a density in the range of 700 to 1500 kg / m3, as measured in accordance with ISO 534, and a wet tensile strength retention (MD), as measured in accordance with ISO 3781:2011, of less than 15%, b) applying an aqueous solution or dispersion containing a polymer to the net, which aqueous solution or dispersion has a solids content between 5 and 50% by weight, and c) drying the net applied with the water-based solution or dispersion to a content composed of solids comprising at least 80% by weight, thus forming the film.

2. A method, according to any of the preceding claims, characterized in that the highly refined cellulose has a water retention value (WRV) of at least 2.0 g / g, preferably at least 2.2 g / g, as measured according to ISO 23714:2014.

3. A method according to any of the preceding claims, characterized in that the highly refined cellulose is microfibrillated cellulose (MFC).

4. Method, according to any of the preceding claims, characterized in that the Petition 870250091038, dated 06 / 10 / 2025, page 26 / 36 2 / 5 network has a wet tensile strength (DM) of less than 0.3 kN / m, as measured in accordance with ISO 3781:2011.

5. Method according to claim 4, characterized in that the network comprises less than 5% by dry weight of wet strength agents.

6. A method, according to any of the preceding claims, characterized in that the network has a dry tensile strength (DM), measured according to ISO 1924-2, of at least 3 kN / m.

7. Method according to claim 6, characterized in that the network comprises at least 5 kg / ton of dry strength agents.

8. A method, according to any of the preceding claims, characterized in that the net supply step comprises the steps of: - forming a first net comprising at least 50% highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, measured in accordance with ISO 5267-1, the percentage being calculated on the total dry weight of the net, and - subjecting the first net to dewatering in at least one prolonged squeeze press.

9. Method according to claim 8, characterized in that the net supply step further comprises the steps of: - at least partially drying said first net, and - at least partially calendering said first dried net.

10. Method, according to any of the preceding claims, characterized in that the aqueous solution or dispersion comprises a polymer selected from the group consisting of a polyvinyl alcohol, a modified polyvinyl alcohol, a polysaccharide or a modified polysaccharide, or combinations thereof.

11. A method, according to any of the preceding claims, characterized in that the network provisioning step comprises the step of forming a multilayer network.

12. Method according to claim 11, characterized in that the step of forming the multilayer network comprises - forming a first network layer comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said first network layer, and - forming a second network layer comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said second network layer - applying the second network layer over the first network layer to form a multilayer network.

13. Method according to claim 11, characterized in that the step of forming the multilayer network comprises - forming a first network layer comprising at least 50% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said first network layer, and - forming a second network layer comprising cellulose fibers and less than 50% by weight of highly refined cellulose fibers with a Schopper-Riegler (SR) value in the range of 80 to 100, as calculated based on the total fiber content of said second network layer - applying the second network layer over the first network layer to form a multilayer network.

14. Method according to claim 13, characterized in that the step of forming the multilayer network comprises: - forming a first network layer comprising between 80-100% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80-100, as calculated based on the total fiber content of said first network layer, and - forming a second network layer comprising between 65-95% by weight of cellulosic fibers and 5-35% by weight of highly refined cellulose with a Schopper-Riegler (SR) value in the range of 80-100, as calculated based on the total fiber content of said second network, - applying the second network layer over the first network layer to form a multilayer network.

15. Method, according to any one of claims 13 or 14, characterized in that the water-based solution or dispersion is applied to the first mesh layer. Petition 870250091038, dated 06 / 10 / 2025, p. 29 / 36 5 / 5 16. A method, according to any of the preceding claims, characterized in that the resulting film comprising highly refined cellulose has a wet tensile strength (MD or CD) greater than 0.1 kN / m, as measured in accordance with ISO 3781:2011.

17. Barrier film, characterized in that it is obtained by the method according to any one of claims 1 to 16.

18. A method for manufacturing a paper- or cardboard-based packaging material laminate, characterized in that it comprises the steps of: - carrying out the method according to any one of claims 1 to 16 so as to form said barrier film, and - laminating said barrier film with a paper- or cardboard-based material so as to form said paper- or cardboard-based packaging material laminate.

19. Laminated packaging material based on paper or cardboard, characterized in that it is obtained by the method according to claim 18. Petition 870250091038, dated 06 / 10 / 2025, pp. 30 / 36