Method for manufacturing a barrier substrate and barrier substrate

Abstract

The present invention relates to a method for producing a barrier substrate comprising a microfibrillated cellulose (MFC) film and a polymer film. The method comprises providing a suspension comprising between 50 and 100% MFC by weight, based on the total dry weight, and having a dry content of 1 to 40% by weight. A wet MFC film is formed from the suspension by casting it onto a non-porous support, and the wet MFC film positioned on the support is dehydrated and / or dried to a dry MFC film having a moisture content of 20% by weight or less. A polymer film is applied onto the dry MFC film positioned on the support to form an intermediate substrate, which is pressed in at least one nip to form a barrier substrate. The present invention also relates to the barrier substrate obtained by this method, a laminate comprising the barrier substrate and a paper or paperboard substrate, and a packaging material comprising the barrier substrate or laminate.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a barrier substrate comprising a barrier film and a polymer film, wherein the barrier film is a microfibrillated cellulose (MFC) film. Further, the present disclosure relates to a barrier substrate obtainable by the method, a laminate comprising a paper or paperboard substrate and the barrier substrate, a packaging material comprising the barrier substrate or laminate, and the use of the barrier substrate or laminate in a packaging material. [Background technology]

[0002] Many applications of paper and paperboard packaging require barrier properties against oxygen, grease, water vapor, and / or aromas. However, paper and paperboard substrates do not inherently possess these properties. Most commonly, the barrier properties of paper and paperboard substrates are created by adding one or more barrier coatings and / or laminated barrier layers based on plastic or other non-renewable materials. A drawback of these coatings and barrier layers is that they use non-renewable raw materials, which can increase the carbon footprint of the material and can render otherwise biodegradable paper or paperboard non-biodegradable and, in some cases, non-recyclable. Furthermore, improving the barrier, including barrier coatings and / or laminated barrier layers based on plastic or other non-renewable materials, typically requires increasing the amount of polymer and / or various polymer layers used. Therefore, the ability to break down and recycle the fiber portion of a paper or paperboard substrate with such improved barriers becomes even more difficult.

[0003] Recently, microfibrillated cellulose (MFC) films have been developed in which cellulose fibrils obtained by fibrillation of cellulose fibers are suspended, for example, in water, and then reorganized and recombined to form a dense film with barrier properties such as oxygen, aroma, and grease barrier properties. MFC films are not only recyclable and biodegradable, but are also based on renewable raw materials.

[0004] One approach to producing MFC films is to use a film casting method, i.e., to cast an MFC suspension onto a non-porous substrate, such as a plastic or metal substrate, to form a film, which is then dehydrated and / or dried. Casting methods have been demonstrated to produce MFC films with very smooth surfaces and excellent barrier properties, such as oxygen and / or water vapor barrier properties.

[0005] Another approach to producing MFC films is to use the wet-laid technique, which involves applying a layer of MFC suspension to a dewatering wire or membrane and then dewatering it on the wire or membrane by vacuum, gravity, capillary dewatering, press dewatering, or a combination of these, followed by drying or liquid evaporation. However, one drawback of this approach is that film additives dissolved or emulsified in the aqueous phase of the MFC suspension are largely removed from the MFC layer during dewatering. Therefore, retention and / or flocculation agents may be required to prevent the removal of film additives. However, retention and / or flocculation agents usually adversely affect barrier properties and do not guarantee complete retention. This approach also imposes limitations on the type of MFC that can be used; very fine MFC cannot be used because they may pass through or penetrate the wire or clog the wire or membrane. Furthermore, other very small dissolved or solid particles dispersed in the aqueous phase of the MFC suspension, such as mineral nanofillers, tend to penetrate through the wire or membrane during the dewatering step.

[0006] It is known to include MFC films in laminates comprising a barrier substrate and one or more additional layers or films. For example, barrier substrates comprising MFC films and laminates comprising MFC films and paper or paperboard substrates have been disclosed for use in packaging materials or applications, such as liquid or food packaging. Such barrier substrates and laminates can be manufactured almost entirely from biobased materials, preferably cellulose-based materials, thereby facilitating the repulping and recycling of used packaging materials comprising the barrier substrate and laminate, and enabling aluminum foil-free laminate structures, for example, for aseptic packaging. However, such barrier substrates and laminates may also include one or two outermost polymer layers or films. The outermost polymer layer or film preferably provides liquid barrier properties and mechanical protection to the surface of the barrier substrate or laminate. The outermost polymer layer or film is also preferably heat-sealable. The outermost polymer layer may also be used for decorative purposes, such as printing or protecting the print.

[0007] Typically, freestanding MFC films, such as those produced by casting or wet-laid processes, have limited strength properties, such as tear strength, burst strength, and tensile strength. This can create problems in lamination or coating processes because the MFC films must withstand significant forces during the lamination or coating process. Thus, the limited strength properties can lead to runnability problems and web breakage or defects for such MFC films when used in lamination or coating processes.

[0008] Lamination of MFC films with other substrates or layers, such as polymer films and / or paper or paperboard substrates, can be accomplished using wet glue or extruded adhesive layers. When wet glue is used in lamination, it is important that the MFC film has sufficient strength, particularly wet strength, to withstand the wet glue. Furthermore, when MFC films are used in extrusion lamination or extrusion coating, it is important that the MFC film has sufficient tear strength and tensile strength (including elongation at break) to withstand the forces applied during the lamination or extrusion process. The tear strength and tensile strength of MFC films can be improved by adding reinforcing agents to the MFC film or by increasing the basis weight of the MFC film. However, adding reinforcing agents and / or increasing the basis weight can reduce production efficiency.

[0009] Thus, there remains room for improvement in methods for producing barrier substrates comprising a barrier film and a polymer film, where the barrier film is an MFC film and such laminate comprises a barrier substrate. Summary of the Invention

[0010] It is an object of the present invention to provide an improved method for manufacturing a barrier substrate comprising a barrier film and a polymer film, wherein the barrier film is an MFC film, which method reduces the difficulties associated with the limited strength properties of the MFC film in lamination or coating processes and which eliminates or reduces at least some of the disadvantages of prior art methods.

[0011] The above objectives, as well as other objectives which will be realized by those skilled in the art in light of the present disclosure, are accomplished by various aspects of the present disclosure.

[0012] The present invention is defined by the accompanying independent claims. Embodiments are set out in the accompanying dependent claims and the following description.

[0013] According to a first aspect described herein, there is provided a method for producing a barrier substrate comprising a microfibrillated cellulose (MFC) film and a polymer film, the method comprising: - providing an MFC suspension containing between 50% and 100% by weight of MFC, based on the total dry weight, wherein the dry content of the MFC suspension is between 1 and 40% by weight; - forming a wet MFC film of said MFC suspension by casting it onto a non-porous support; - dehydrating and / or drying the wet MFC film positioned on the non-porous support to a dry MFC film having a moisture content of 20% by weight or less; - applying a first polymer film onto a first side of the dried MFC film positioned on the non-porous support to form an intermediate substrate; - pressing the intermediate substrate positioned on the non-porous support in at least one nip to form the barrier substrate; - separating the barrier substrate from the non-porous support; Includes.

[0014] Thus, the method of the first aspect provides a barrier substrate comprising a barrier film, an MFC film, and a polymer film.

[0015] In the method according to the first aspect, the polymer film is applied to the MFC film in connection with or during its manufacture, i.e., while the MFC film is still positioned on the non-porous support used to form the MFC film by a casting technique, a barrier substrate comprising the MFC film and the polymer film is thus formed on the non-porous support, and after formation the barrier substrate is removed from the non-porous support to form a free-standing barrier substrate.

[0016] By providing the MFC film with a polymer film while it is already positioned on a non-porous support, the MFC film is supported by the non-porous support during the polymer film application procedure, eliminating problems associated with the limited strength properties of the MFC film during the polymer film application process.

[0017] Also, by providing the MFC film with a polymer film already associated with its manufacture, the MFC film is contained within a barrier substrate already associated with its manufacture and is therefore reinforced by the polymer film within the freestanding barrier substrate. Thus, when the freestanding barrier substrate is used in a subsequent lamination or coating process, the MFC film is supported / reinforced by the polymer film, thereby offsetting the limited strength properties of the MFC film.

[0018] The term film as used herein generally refers to a thin continuous sheet-forming material, such as a thin substrate, that has good barrier properties to gases, aromas, grease or oils, e.g., oxygen and / or water vapor barrier properties. Films can also be thought of as thin papers (e.g., nanopaper or micropaper) or membranes, depending on the composition of the MFC suspension from which they are formed.

[0019] As described above, the method of the first aspect includes providing an MFC suspension containing between 50% and 100% MFC by weight, based on the total dry weight of the MFC suspension. The MFC suspension has a dry content of 1 to 40% by weight. The MFC suspension is comprised of a suspension medium in which a mixture of cellulose-based material and, optionally, additives is suspended. Preferably, the MFC suspension is an aqueous suspension comprising an aqueous suspension mixture of cellulose-based material and, optionally, additives.

[0020] In the context of the patent application, microfibrillated cellulose (MFC) is intended to mean cellulose particles, fibres or fibrils with a width or diameter between 20 nm and 1000 nm.

[0021] There are various methods for producing MFC, including one or more purification steps, prehydrolysis followed by purification, high-shear degradation, or fibril release. To combine energy efficiency and sustainability in MFC production, one or more pretreatment steps are usually required. Thus, the cellulose fibers of the pulp used to produce MFC can be natural or enzymatically or chemically pretreated, for example, to reduce the amount of hemicellulose or lignin. Cellulose fibers can be chemically modified before fibrillation, in which case the cellulose molecules contain functional groups other than (or more than) those found in the original cellulose. Such groups include, among others, carboxymethyl (CM), aldehyde, and / or carboxyl groups (cellulose obtained by oxidation, e.g., 2,2′,6,6′-tetramethylpiperidine-N-oxyl (TEMPO)), or quaternary ammonium (cationic cellulose). After being modified by one of the above methods, the fibers are easily fibrillated by MFC.

[0022] MFCs can be made from wood cellulose fibers, either hardwood or softwood. They can also be made from microbial sources, agricultural fibers such as straw pulp, bamboo, bagasse, or other non-wood fiber sources. They can be made from pulp, including pulp from virgin fibers, such as mechanical, chemical, and / or thermomechanical pulps. They can also be made from waste or recycled paper.

[0023] As noted above, the MFC suspension used in the method of the first aspect comprises between 50% and 100% MFC by weight, based on the total dry weight. In some embodiments, the MFC suspension comprises between 60% and 100%, preferably between 70% and 100%, and more preferably between 80% and 100% MFC by weight, based on the total dry weight. The MFC film of the barrier substrate produced by the method of the first aspect can comprise between 50% and 100%, for example between 60% and 100%, preferably between 70% and 100%, and more preferably between 80% and 100% MFC by weight, based on the total dry weight, which relates to the amount of MFC in the film itself.

[0024] The MFC of the MFC suspension may be composed of one or more fractions of MFC. In some embodiments, the MFC of the MFC suspension includes one fraction of fine-grade MFC. In some embodiments, the MFC of the MFC suspension includes two or more fractions of different fine-grade MFC. In some embodiments, the MFC of the MFC suspension includes one fine-grade fraction and one coarse-grade fraction, where the coarse-grade fraction may be, for example, an additive. In this case, the Schopper-Riegler value of the coarse MFC is typically 80-100 SR°, e.g., 80-99 SR°, 90-99 SR°, or 95-99 SR°, while the fine MFC is fibrillated to a Schopper-Riegler value beyond the measurement range determined by standard ISO 5267-1 (theoretical value is approximately 100 SR° or greater). In some embodiments, the fine-grade MFC is chemically derivatized, such as carboxymethylated MFC.

[0025] In addition to MFC, the MFC suspension may contain conventional papermaking additives or chemicals such as film formers, dispersants, fillers, pigments, wet strength agents, crosslinkers, plasticizers, softeners, humectants, adhesive primers, wetting agents, biocides, colorants, defoamers, hydrophobizing agents such as alkyl ketene dimers (AKDs), alkenyl succinic anhydrides (ASAs), waxes, rosin resins, mineral additives (fillers) such as bentonite, kaolin, talc, mica, montmorillonite, organoclays, graphene and graphene oxide, stearates, starch, silica, precipitated calcium carbonate, cationic polysaccharides, rheology modifiers, etc. Thus, these additives or chemicals may be process chemicals or film performance chemicals added to impart specific properties to the final film and / or to facilitate the production of the film.

[0026] In some embodiments, the MFC suspension further comprises at least one additive selected from the group of film formers, dispersants, plasticizers, softeners, mineral additives, humectants, and rheology modifiers.

[0027] In some embodiments, the suspension medium is or comprises water, and the MFC suspension further comprises at least one water-soluble additive. In some embodiments, the suspension medium is or comprises water, and the MFC suspension further comprises at least one water-soluble polymer capable of forming a film and / or improving the bond between the cellulose fibers. Typical examples of such polymers are natural gums or polysaccharides, such as carboxymethyl cellulose (CMC), starch, polyvinyl alcohol (PVOH), or derivatives thereof, or analogs thereof.

[0028] In some embodiments, the suspension medium is or comprises water, and the MFC suspension further comprises at least one water soluble additive selected from the group consisting of PVOH and derivatives or analogs thereof, starch, CMC, sorbitol, polyethylene glycol.

[0029] The PVOH may be a single type of PVOH, or a mixture of two or more types of PVOH with different degrees of hydrolysis, viscosities, etc. The PVOH may have a degree of hydrolysis in the range of, for example, 80 to 99 mol %, preferably 88 to 99 mol %.

[0030] According to a first aspect of the method, because the MFC film is formed and retained on a non-porous support until after dehydration and / or drying (and even after the polymer film application and pressing steps), film additives, including water-soluble film additives, are retained to a greater extent within the MFC film than when a porous support is utilized. In some embodiments, the MFC suspension is free of cationic or amphoteric retention agents, fixatives, and flocculants.

[0031] In some embodiments, the MFC suspension comprises 50 wt% or less, e.g., 35 wt% or less, 30 wt% or less, 25 wt% or less, or 20 wt% or less, of the additive, based on the total dry weight of the MFC film. For example, the MFC suspension can comprise 1-50 wt%, or 1-35 wt%, or 1-30 wt%, or 1-25 wt%, or 1-20 wt% of the additive, based on the total dry weight of the MFC film.

[0032] In some embodiments, the MFC suspension comprises 0.5 to 20 wt. % of a plasticizer, such as sorbitol, glycols, other polyols, or combinations thereof, based on the total dry weight of the MFC suspension.

[0033] In some embodiments, the MFC suspension comprises up to 30 wt. % nanocrystals and / or cellulose derivatives, based on the total dry weight of the MFC suspension.

[0034] In some embodiments, the MFC suspension comprises up to 20 wt. % of a mineral filler (conventional filler or nanofiller), such as bentonite, kaolin, talc, mica, montmorillonite, organoclay, graphene, graphene oxide, or combinations thereof, based on the total dry weight of the MFC suspension.

[0035] As described above, the method of the first aspect includes forming a wet MFC membrane on a non-porous support. The wet MFC film is formed on the non-porous support by casting, e.g., cast coating, the MFC suspension onto the non-porous support, e.g., a casting surface of the non-porous support. As described above, the MFC suspension has a dry content of 1 to 40 wt. %. Thus, the formed wet MFC film has a dry content of 1 to 40 wt. % as formed (i.e., during application to the metal belt support or immediately after application / formation to the metal belt support).

[0036] The term "casting," when applied to film formation, is a well-known term that refers to the deposition of a suspension onto a support to form a wet web by contact or non-contact deposition and leveling methods, such as curtain coating / application, slot die casting, or using a spray or similar device to dispense the MFC suspension and then leveling using a doctor blade or rod.

[0037] In the method of the first embodiment, the non-porous support on which the wet MFC film is formed may be a metal belt (i.e., a belt made of metal), such as a steel belt, a polymer belt, or a polymer-coated belt. The metal belt may be coated with, for example, a ceramic material. The non-porous support may be a continuous or endless non-porous support, such as a conveyor belt.

[0038] In some embodiments, the nonporous support is a metal belt support having a smooth casting surface, i.e., a smooth surface onto which the MFC suspension is cast. In some embodiments, the metal belt support has a casting surface that provides a Bendtsen roughness of 200 ml / min or less, preferably 150 ml / min or less, and more preferably 100 ml / min or less, as measured according to ISO 8791-2:2013, and / or a Parker Printsurf (PPS) smoothness of 10 μm or less, preferably 0.1 to 5 μm or less, and most preferably 0.3 to 5 μm or less, as measured according to ISO 8791-4, on the side of the produced MFC film that contacts the casting surface of the metal belt support. Alternatively, the casting surface of the metal belt support is textured. The metal belt support also has a backside opposite the casting surface.

[0039] It is important to apply the MFC suspension to the casting surface of the non-porous support to ensure that a homogeneous wet MFC film is formed; that is, the wet MFC film should be as uniform and as even in thickness as possible. The resulting wet MFC film should have a dry basis weight (basis weight) of 2 to 70 g / m². 2 , preferably 3 to 70 g / m 2 , e.g., 8 to 70 g / m 2 , 10~60g / m 2 , 10~50g / m 2 , or 15 to 40 g / m 2 The dried MFC film can be translucent or transparent.

[0040] According to the method of the first aspect, the MFC suspension has a dry content of 1 to 40 wt%, preferably 2 to 25 wt%, more preferably 3 to 15 wt%, and most preferably 3.5 to 8 wt%. The formed wet MFC film therefore has a dry content of 1 to 40 wt%, preferably 2 to 25 wt%, more preferably 3 to 15 wt%, and most preferably 3.5 to 8 wt% as formed.

[0041] Preferably, the MFC suspension is in direct contact with the casting surface of the non-porous support after casting. However, in some embodiments, a coating for controlling adhesion and release properties can be applied to the casting surface of the non-porous support before casting the MFC suspension onto the casting surface. Examples of such coatings are poly(aminoamide) epihalohydrin polymer (PAE) resin, polyvinyl alcohol resin (PVOH), polyvinyl alcohol copolymer, starch, ethylene glycol, vegetable oil, fatty acid, and sugar alcohol.

[0042] The formed wet MFC film can be a monolayer or multilayer film made in one or more casting units, or a single-ply or multi-ply film. Thus, in some embodiments, the wet MFC film is comprised of a single film layer or two or more film layers formed on top of each other.

[0043] As described above, the method of the first aspect involves dehydrating and / or drying the wet MFC film to form a dry MFC film having a moisture content of 20% by weight or less, preferably 10% by weight or less, and most preferably 5% by weight or less. In some embodiments, the dry MFC film has a moisture content of 1-20% by weight. The moisture content can be measured under ambient conditions. For example, the moisture content can be measured using spectroscopic methods such as infrared (IR) spectroscopy, near-infrared (NIR) spectroscopy, or Raman spectroscopy, particularly infrared methods suitable for single-sided measurements. Alternatively, the dry content can be measured to determine the moisture content. For example, the dry content can be measured according to Standard 638, and the moisture content can be calculated based on the dry content measurement. During dehydration and / or drying, the wet MFC film is positioned on a non-porous support. Dehydration and drying, respectively, can be performed using any method known in the art suitable for providing a dry MFC film.

[0044] For example, dewatering can be performed by wet pressing a wet MFC film positioned on a nonporous support, e.g., by applying a press fabric directly to the wet MFC film and mechanically dewatering the wet MFC film positioned between the press fabric and the nonporous support by passing it through a press device. Optionally, mechanical dewatering can be combined with evaporation by heat or radiation. The press fabric refers to a permeable fabric capable of removing water from the wet MFC film by absorbing it or removing it through the fabric. The press fabric may also be a press felt (dewatering felt). Press fabrics and press felts are commonly used today for dewatering paper and paperboard webs. Any known suitable press fabric or press felt can be used. The press device refers to a device with one or more nips through which the wet MFC film is pressed and dewatered. The press device may have a metal backing surface, e.g., a hard roller. An external load element can be used to press the nonporous support and backing surface together to generate pressure. The press device may also have an extended nip. For example, the press device may be a belt press. Dewatering may be carried out in one or more substeps, i.e., the dewatering step may comprise one or more substeps.

[0045] For example, drying can be carried out by contact drying such as cylinder drying, infrared (IR) drying, near infrared (NIR) drying, microwave (MW) drying, ultraviolet (UV) drying, electron beam (EB) drying, hot gas impingement drying such as hot air impingement drying, other radiation drying, or a combination thereof. Drying can be carried out in one or more substeps, i.e., the drying step can comprise one or more substeps.

[0046] In some embodiments, the method of the first aspect includes a dehydration step of dehydrating the wet MFC film to a dry MFC film. In some embodiments, the method of the first aspect includes a drying step of drying the wet MFC film to a dry MFC film. In some embodiments, the method of the first aspect includes a dehydration step and a drying step of dehydrating and drying the wet MFC film to a dry MFC film, respectively.

[0047] In embodiments that include a dehydration step, the method may further include pre-drying the wet MFC film prior to the dehydration step. For example, if the dry content of the wet MFC film is 1-20 wt. %, or 1-15 wt. %, or 1-10 wt. %, a pre-drying step may need to be performed. Pre-drying can be performed by any of the drying techniques described above for the drying process.

[0048] In embodiments where the non-porous support is a metal belt support, the metal belt support can be heated to a temperature greater than 30°C before or immediately after the wet MFC film is applied to the metal belt support, preferably such that at least the casting surface of the metal belt is between 30 and 150°C, more preferably between 45 and 150°C, and even more preferably between 60 and 100°C, and the temperature of the metal belt support can be maintained during part of the method for producing the barrier substrate, e.g., at least some process steps for producing the dried MFC film, or during the complete method for producing the barrier substrate. By increasing the temperature of the metal belt support, and thus the temperature of the applied wet MFC film, the efficiency of pre-drying, dewatering, and / or drying of the wet MFC film can be further increased.

[0049] Thus, after dehydration and / or drying, a dry MFC film having a moisture content of 20% by weight or less, preferably 10% by weight or less, most preferably 5% by weight or less is obtained. The obtained dry MFC film is still positioned on the non-porous support. The dry MFC film has a second surface opposite the first surface, and the second surface is in contact with the non-porous support (possibly via a coating on the non-porous support).

[0050] In some embodiments, the dry MFC film has a density of 2 to 70 g / m 2 , preferably 3 to 70 g / m 2 , for example, 4 to 70 g / m 2 , 8~70g / m 2 , 10~60g / m 2 , 10~50g / m 2 , or 15 to 40 g / m 2 The dry basis weight is

[0051] In some embodiments, the dried MFC film has a machine direction tensile index of 15 to 150 Nm / g, or 20 to 140 Nm / g, or 30 to 120 Nm / g, measured according to standard ISO 1924-3 with a test span (initial distance between clamps) of 20 mm and a speed of 2 mm / min.

[0052] In some embodiments, the average film thickness of the dried MFC film is 5-60 μm, preferably 10-50 μm, 15-45 μm, or 20-40 μm. Specific average film thicknesses may be 5-10 μm, 10-15 μm, 15-20 μm, 20-25 μm, 25-30 μm, 30-35 μm, 35-40 μm, 40-45 μm, 45-50 μm, 50-55 μm, or 55-60 μm. The average film thickness can be defined as the average thickness across the entire width of the film. The thickness of the MFC film can be measured, by way of non-limiting examples, using white light interferometry, laser profilometry, or optically by cutting a sample (either cast or not in resin) along a line in the cross-machine direction and taking a microscopic image (e.g., scanning electron microscopy or other applicable method) of the cut cross section through the thickness direction.

[0053] In some embodiments, the width of the second web of dry MFC film is 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m, or 2 to 4 m.

[0054] In some embodiments, the dried MFC film has an oxygen transmission rate (OTR) of 50 cc / m as measured according to standard ASTM F1927-20 at 50% relative humidity and 23°C. 2 / less than 24 hours, preferably 20cc / m 2 / less than 24 hours, most preferably 10cc / m 2 / less than 24 hours.

[0055] In some embodiments, the dried MFC film has a water vapor transmission rate (WVTR) of 100 g / m2 measured according to standard ASTM F1249-20 at 50% relative humidity and 23°C. 2 / less than 24 hours, preferably 50g / m 2 / less than 24 hours, more preferably 20 g / m 2 / less than 24 hours.

[0056] In some embodiments, the dried MFC film has a KIT value of at least 10, preferably 12, when measured according to standard ISO 16532-2.

[0057] In some embodiments, the dry MFC film has 10 particles / m 2 Less than 6 pieces / m 2 Has less than a pinhole.

[0058] As described above, the method of the first aspect includes applying a first polymer film to a first surface of a dry MFC film to form an intermediate substrate, the dry MFC film being positioned on a non-porous support during the step of applying the first polymer film.

[0059] In some embodiments, the first polymer film comprises or consists of a thermoplastic polymer. In some embodiments, the first polymer film comprises or consists of a polymer selected from the group consisting of polyolefins and polyesters. In some embodiments, the first polymer film comprises or consists of a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters. In some embodiments, the first polymer film comprises or consists of polypropylene or polyethylene. In some embodiments, the first polymer film comprises or consists of polyethylene, more preferably LDPE or HDPE.

[0060] The first polymer film may comprise or consist of any of the thermoplastic polymers typically used for protective and / or heat-sealable layers of paper- or paperboard-based packaging laminates, or polymers specifically used for liquid or food packaging boards. Examples include polyethylene (PE), polyethylene terephthalate (PET), polyethylene furanoate (PEF), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), starch, cellulose, etc. Polyethylene, particularly low-density polyethylene (LDPE) and high-density polyethylene (HDPE), is the most common and versatile polymer used for liquid and food packaging boards. The polymers used are preferably manufactured from renewable sources. Thermoplastic polymers are useful because they can be easily processed by extrusion coating techniques to form very thin, uniform films with excellent liquid barrier properties. The first polymer film can be applied, for example, by extrusion coating or film lamination. The first polymer film may have an average thickness of 5 to 100 μm, or 8 to 60 μm, or 10 to 40 μm. The first polymer film may include one or more sub-layers.

[0061] In some embodiments, the first polymer film comprises or consists of an adhesive thermoplastic polymer, such as a modified polyolefin based primarily on LDPE or LLDPE copolymers, or a graft copolymer having functional group-containing monomer units, such as carboxyl or glycidyl functional groups, such as (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA)), ethylene glycidyl (meth)acrylate copolymer (EG(M)A), or MAH-grafted polyethylene (MAHg-PE). Another example of such a modified or adhesive polymer is a so-called ionomer or ionomeric polymer. Preferably, the modified polyolefin is ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0062] Extrusion coating is a process in which molten plastic material is applied to a substrate to form a very thin, smooth, and uniform layer. The coating can be formed from the extruded plastic itself, or the molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate. Common plastic resins used in extrusion coating include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

[0063] In some embodiments, the first polymer film is applied in a molten state by extrusion coating onto a first side of a dry MFC film positioned on a non-porous support.

[0064] In some embodiments, the first polymer film is applied to the first surface of the dry MFC film in the form of a solid film. In these embodiments, the solid first polymer film can include an adhesive selected from polysaccharides, such as starch or starch derivatives, hemicellulose cellulose, and cellulose derivatives, that provide adhesion between the first polymer film and the MFC film. Alternatively, in these embodiments, an adhesive selected from polysaccharides, polyvinyl alcohol, polyurethane, polyolefin, or polyester can be applied to the first surface of the dry MFC film or to the solid first polymer film before the solid first polymer film is applied to the dry MFC film. Alternatively, the solid first polymer film can include a thermoplastic polymer that can be combined with heating and melted during a subsequent pressing step.

[0065] In some embodiments, the first polymer film is a solid film, and a vacuum coating layer is provided on at least one surface of the solid first polymer film. The vacuum coating layer can be inorganic or organic. In some embodiments, the vacuum coating layer is an inorganic vacuum coating layer, such as a metal, metal oxide, or ceramic vacuum coating layer.

[0066] In some embodiments, at least one surface of the solid first polymer film is metallized. In some embodiments, the metallized surface of the solid first polymer film is formed by vapor deposition of a metal or metal oxide onto the surface of the solid first polymer film, i.e., a vacuum coating layer comprising a metal or metal oxide is provided on the surface of the solid first polymer film.

[0067] In some embodiments, the vacuum coating layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, and preferably comprises aluminum oxide.

[0068] Vacuum coating, or vacuum deposition coating, refers to a family of processes used to vapor-deposit layers of metals, metal oxides, and other inorganic and organic compositions onto solid surfaces, typically atom by atom or molecule by molecule. Multiple layers of the same or different materials can be combined. Processes can be further specified based on the vapor source: physical vapor deposition (PVD) uses liquid or solid sources, while chemical vapor deposition (CVD) uses chemical vapors. Atomic layer deposition (ALD) can also be used.

[0069] Vacuum coating typically results in very thin coatings. The vacuum coating layer can include one or more sublayers. In some embodiments, the total thickness of the vacuum coating layer ranges from 10 to 600 nm, preferably from 10 to 250 nm, and more preferably from 50 to 250 nm. This compares favorably with conventional aluminum foils used in packaging laminates, which typically have foil thicknesses in the range of about 3 to 12 μm.

[0070] In some embodiments, the vacuum coating layer is applied to the solid first polymer film by PVD or CVD, hi some embodiments, the vacuum coating layer is applied to the solid first polymer film by ALD, PVD, CVD, or variants of PVD and CVD, such as plasma-enhanced chemical vapor deposition (PECVD).

[0071] One preferred type of vacuum coating is an aluminum metal PVD coating, which is often used for its barrier properties, particularly water vapor barrier properties. Such coatings consist essentially of aluminum metal and can typically have a thickness of 50 to 250 nm, although thicknesses of less than 50 nm are also useful and may be preferred in some embodiments. The thickness of the vacuum coating layer corresponds to less than 1% of the aluminum metal material typically found in conventional thickness aluminum foil for packaging, or 6.3 μm. Thus, in some embodiments, the vacuum coating layer comprises aluminum.

[0072] The thickness of the vacuum coated layer can also be characterized by the optical density of the layer. In some embodiments, the vacuum coated layer has an optical density of 1.8 or greater, preferably 2.0 or greater, 2.5 or greater, 2.7 or greater, or 3.0 or greater.

[0073] Aluminum oxide vacuum coated layers, also known as AlOx coatings, can provide similar barrier properties to aluminum metal coatings, but with the added benefit that thin AlOx coatings are transparent to visible light.

[0074] In some embodiments, the vacuum coating layer is an organic vacuum coating layer. In some embodiments, the vacuum coating layer comprises carbon.

[0075] The organic vacuum coating may be, for example, a vacuum coated carbon layer, such as a diamond-like carbon (DLC) layer formed from carbon or an organic compound.

[0076] Optionally, one or more top layers can be applied over the vacuum coating layer. For example, one or more protective layers can be applied over the vacuum coating layer to protect the sensitive vacuum coating layer before applying the solid first polymer film to the MFC film. Alternatively, or in addition, one or more primer layers can be applied over the vacuum coating layer to improve adhesion of the vacuum coating layer.

[0077] In some embodiments, a precoat layer is applied to the solid first polymer film prior to vacuum coating deposition.

[0078] In some embodiments, the first polymer film is a foamed film. In these embodiments, the first polymer film is applied in the form of a foam. In some embodiments, the first polymer film has a density of 100 to 1000 kg / m 3 , 150~750kg / m 3, or 250 to 500 kg / m 3 and low density films such as polymer films having a density of 0.1 to 0.5.

[0079] As previously mentioned, the method of the first aspect includes pressing an intermediate substrate (including an MFC film and a first polymer film applied thereon) positioned on a non-porous support in at least one nip to form a barrier substrate. The pressing step presses the first polymer film and the MFC film together to form the barrier substrate, i.e., improves adhesion between the first polymer film and the MFC film.

[0080] Each of the at least one nip may be selected from the group consisting of a lamination nip, a calendar nip, a smoothing roll nip, a press nip, a belt nip, and an extended nip including one belt and a support belt. The linear load of each of the at least one nip may be 0.1 to 200 kN / m, preferably 1 to 150 kN / m, and most preferably 5 to 100 kN / m. In some embodiments, the absolute pressure of the at least one press device is 1 to 25,000 kPa, preferably 3 to 17,000 kPa.

[0081] In some embodiments, pressing the intermediate substrate is combined with heating the intermediate substrate to improve adhesion between the first polymer film and the MFC film. Depending on the polymer of the first polymer film and the method of application of the first polymer film, heating may be necessary to bond the first polymer film and the MFC film to each other. In some embodiments, the intermediate substrate is heated before entering the pressing step, i.e., before entering at least one nip. For example, the temperature of the dry MFC film or intermediate substrate may be 60 to 250°C, e.g., 70 to 250°C or 80 to 250°C, before or upon entering at least one nip. Additionally or alternatively, one or more of the at least one nip may be heated, for example, by heating one or more nip rolls or by introducing hot air into the nip.

[0082] In some embodiments, the first polymer film is heated before contacting the MFC film to soften or melt the first polymer film and improve adhesion between the MFC film and the first polymer film. For example, the temperature of the first polymer film may be 80 to 350°C, e.g., 120 to 300°C or 140 to 250°C, before or upon contact with the MFC film. At least one nip following the point of contact between the MFC film and the first polymer film may be cooled.

[0083] In some embodiments, the first polymer film is extruded onto a first roll that is a chilled or unquenched roll and forms one or more nips. Thus, in these embodiments, the first polymer film is applied to the dry MFC film by the first roll while the dry MFC film and the first polymer film are pressed together by the first roll.

[0084] In some embodiments, the method further comprises subjecting the barrier substrate to at least one cooling nip after the pressing step. For example, the barrier substrate may be cooled to a temperature of 10 to 70°C. The cooling step may be particularly important when heat is applied in the pressing step. The cooling step may be performed to avoid blocking and, for example, to control curl of the barrier substrate. The cooling step can be performed before or after removing the barrier substrate from the non-porous support, but is preferably performed after removal from the non-porous support.

[0085] As mentioned above, the method of the first aspect includes the step of separating the barrier substrate from the non-porous support, i.e., separating (e.g., peeling) the barrier substrate from the non-porous support after the pressing step.

[0086] In some embodiments, the method of the first aspect further comprises, after separating and removing the barrier substrate from the non-porous support, applying a second polymer film to a second side of the MFC film of the barrier substrate, the second side of the MFC film being opposite the first side of the MFC film.

[0087] The definition of the second polymer film may correspond to the definition of the first polymer film. Thus, in some embodiments, the second polymer film comprises or consists of a thermoplastic polymer. In some embodiments, the second polymer film comprises or consists of a polymer selected from the group consisting of polyolefins and polyesters. In some embodiments, the second polymer film comprises or consists of a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters. In some embodiments, the second polymer film comprises or consists of polypropylene or polyethylene. In some embodiments, the second polymer film comprises or consists of polyethylene, more preferably LDPE or HDPE.

[0088] The second polymer film may comprise or consist of a thermoplastic polymer typically used for protective and / or heat-sealable layers in paper- or paperboard-based packaging laminates, or, in particular, any of the polymers used in the aforementioned liquid or food packaging. The second polymer film may be applied, for example, by extrusion coating, film lamination, or dispersion coating. For example, dispersion coating may be performed using dispersions of PVOH, polysaccharides, latex emulsions such as styrene / acrylate, acrylic and acrylic copolymers, vinyl acetate, polyurethane, styrene / butadiene, etc.

[0089] In some embodiments, the second polymer film is applied in molten form onto the second side of the dried MFC film by extrusion coating.

[0090] In some embodiments, the second polymer film is applied to the second surface of the dry MFC film in the form of a solid film. In these embodiments, the solid second polymer film can include an adhesive selected from polysaccharides, such as starch or starch derivatives, hemicellulose cellulose, and cellulose derivatives, that provide adhesion between the second polymer film and the MFC film. Alternatively, in these embodiments, an adhesive selected from polysaccharides, polyvinyl alcohol, polyurethane, polyolefin, or polyester can be applied to the second surface of the MFC film or to the solid second polymer film before the solid second polymer film is applied to the MFC film.

[0091] In some embodiments, the second polymer film is a solid film, and at least one surface of the solid second polymer film is provided with a vacuum coating layer, which can be defined above in relation to the solid first polymer film.

[0092] In some embodiments, at least one surface of the solid second polymer film is metallized. In some embodiments, the metallized surface of the solid second polymer film is formed by vapor deposition of a metal or metal oxide onto the surface of the solid second polymer film, i.e., a vacuum coating layer comprising a metal or metal oxide is provided on the surface of the solid second polymer film, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0093] In some embodiments, a precoat layer is applied to the solid second polymer film prior to vacuum coating deposition.

[0094] In some embodiments, the second polymer film is a foamed film. In these embodiments, the second polymer film is applied in the form of a foam.

[0095] The basis weight of each of the first polymer film and the optional second polymer film is preferably 50 g / m 2 To achieve a continuous, substantially defect-free film, when provided by extrusion coating, the basis weight of each polymer film is typically at least 6 g / m 2 , preferably at least 8 g / m 2 In some embodiments, the basis weight of each of the first polymer film and the optional second polymer film should be between 6 and 50 g / m 2 The range is preferably 10 to 20 g / m 2 and the polymer film is provided by extrusion coating. In some embodiments, the basis weight of each of the first polymer film and the optional second polymer film is in the range of 2 to 10 g / m 2 and the polymer film is provided by a foamed film.

[0096] In some embodiments, the resulting barrier substrate has a viscosity of 20 cc / m as measured according to standard ASTM F1927-20 at 50% relative humidity and 23° C. 2 / less than 24 hours, preferably 15cc / m 2 / less than 24 hours, most preferably 10cc / m 2 / Has an oxygen transmission rate (OTR) of less than 24 hours.

[0097] In some embodiments, the resulting barrier substrate has a viscosity of 50 cc / m 2 measured according to standard ASTM F1249-20 at 50% relative humidity and 23° C. 2 / less than 24 hours, preferably 30cc / m 2 / less than 24 hours, most preferably 20cc / m 2 / Has a water vapor transmission rate (WVTR) of less than 24 hours.

[0098] In some embodiments, the resulting barrier substrate has a KIT value of at least 10, preferably 12, when measured according to standard ISO 16532-2.

[0099] According to a second aspect of the present disclosure, there is provided a barrier substrate comprising an MFC film and a first polymer film, the barrier substrate being obtainable by the method of the first aspect.

[0100] The barrier substrate obtained by the method of the first aspect can be used as is, or it can be combined with one or more further layers, for example one or more further layers of paper or paperboard, to form a laminate material.

[0101] According to a third aspect of the present disclosure, there is provided a method of manufacturing a laminate, the method comprising: - providing a paper or paperboard substrate; - providing a barrier substrate according to the method according to the first aspect; - bonding a first surface of the paper or paperboard substrate with the MFC film of the barrier substrate using at least one bonding layer to obtain a laminate; Includes.

[0102] Paper generally refers to a material made from wood pulp or other fibrous substances containing cellulose fibers in thin sheets and used for writing, drawing, or printing on or as packaging. Paper can be bleached or unbleached, coated or uncoated, and produced in a variety of thicknesses, depending on the end-use requirements. Paper can be a single-ply material or a multi-ply material made up of two or more layers.

[0103] Paperboard generally refers to a strong, thick paper or board containing cellulose fibers used for boxes and other types of packaging. Paperboard can be either bleached or unbleached, coated or uncoated, and can be produced in a variety of thicknesses, depending on the end-use requirements. Paperboard can be a single-ply material or a multi-ply material made up of two or more layers. A common type of multi-ply paperboard consists of a lower density middle layer (sometimes called a "bulk layer") sandwiched between two higher density outer layers. The lower density middle layer is typically 750 kg / m². 3 less than, preferably less than 700, less than 650, less than 600, less than 550, less than 500, less than 450, less than 400, or less than 350 kg / m 3 The higher density outer layer can have a density of less than 100 kg / m². The higher density outer layer typically has a density at least 100 kg / m² higher than the middle layer. 3 higher, preferably at least 200 kg / m higher than the intermediate layer 3 It has a high density.

[0104] The paper or paperboard used as a substrate in accordance with the present disclosure can be made from pulp made from virgin fibers, including, for example, mechanical pulp, semi-chemical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from waste paper or recycled paper or paperboard. The paper or paperboard used as a substrate in accordance with the present disclosure can be manufactured using methods known in the art.

[0105] In some embodiments, the paper or paperboard substrate comprises at least 10% recycled material, such as at least 20%, at least 40%, at least 50%, at least 60%, or at least 70% recycled material, which can be either pre-consumer grade or post-consumer grade.

[0106] The paper substrate used in the method of the third embodiment is preferably 10 to 200 g / m 2 in the range of 20 to 100 g / m 2 Unless otherwise stated, the basis weight is determined according to standard ISO 536.

[0107] The paperboard substrate used in the method of the third embodiment preferably has a weight of 120 to 600 g / m 2 or 120 to 450 g / m 2 range, more preferably 200 to 500 g / m 2 or 180-380g / m 2 Unless otherwise stated, the basis weight is determined according to standard ISO 536.

[0108] The paper or paperboard substrate may be a single-ply paper or paperboard or may be multi-ply paper or paperboard. In some embodiments, the paperboard substrate is a multi-ply paperboard. In some embodiments, the paperboard substrate is a multi-ply paperboard consisting of two or more plies. In some embodiments, the paperboard substrate is a multi-ply paperboard consisting of three or more plies. In some embodiments, the paperboard substrate is a multi-ply paperboard made up of a lower density middle layer sandwiched between two higher density outer layers.

[0109] In some embodiments, the paperboard substrate is a foam-molded paperboard. In some embodiments, the paperboard substrate is a multi-layer paperboard, at least one layer, preferably the middle layer, is a foam-molded paperboard. In some embodiments, the paperboard substrate is a multi-layer paperboard, at least one of the layers, preferably the middle layer, is a high-loft layer.

[0110] The paper or paperboard substrate can be optionally coated, such as with a mineral coating, to improve smoothness and printability. Such a mineral coating can be provided on one or both sides of the substrate and, in the context of this disclosure, becomes part of the substrate. The paper or paperboard substrate can be subjected to a surface sizing or treatment on at least one side of the substrate. Such a surface sizing or treatment becomes part of the paper or paperboard substrate in the context of this disclosure. Preferably, the surface sizing composition used for surface sizing comprises starch or a starch derivative.

[0111] The tie layer may generally comprise any suitable adhesive commonly used in paper or paperboard based packaging laminates, or adhesives used in liquid or food packaging laminates in particular. A wide variety of adhesives and adhesive coating methods may be used in the present invention.

[0112] The cling layer may comprise one or more adhesive polymers. The cling layer may consist solely of one or more adhesive polymers, or may further comprise other additives to enhance the properties of the adhesive layer. In some embodiments, the cling layer comprises at least 50% by weight of an adhesive polymer or a mixture of adhesive polymers on a dry weight basis. In some embodiments, the cling layer comprises or consists of one or more adhesive polymers selected from the group consisting of polyolefins, polyesters, polyurethanes, and acrylic copolymers. In some embodiments, the cling layer comprises or consists of one or more of polypropylene and polyethylene, such as LLDPE, LDPE, MDPE, or HDPE.

[0113] In some embodiments, the adhesive layer comprises or consists of a component selected from adhesive thermoplastic polymers such as modified polyolefins based primarily on LDPE or LLDPE copolymers, or graft copolymers having functional group-containing monomer units such as carboxyl or glycidyl functional groups, such as (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA)), ethylene glycidyl (meth)acrylate copolymer (EG(M)A), or MAH-grafted polyethylene (MAHg-PE). Another example of such a modified or adhesive polymer is a so-called ionomer or ionomeric polymer. Preferably, the modified polyolefin is ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0114] In some embodiments, the cling layer comprises at least 50% by weight of a water-soluble polymer or mixture of water-soluble polymers on a dry weight basis. The water-soluble polymer of the cling layer is soluble in cold water for a period of time, or in hot water, for example, at temperatures below or above 100° C. In some embodiments, the water-soluble polymer is selected from the group consisting of PVOH or a derivative or analog thereof, CMC, starch, alginate, and hemicellulose, preferably PVOH.

[0115] The adhesion layer(s) may be applied by any suitable method known in the art. The total coat weight of the adhesion layer(s) is typically from 1 to 30 / m 2 In some embodiments, the total coat weight of the one or more cling layers is in the range of 2 to 25 g / m 2 More preferably, it is in the range of 3 to 20 g / m 2 The range is.

[0116] In some embodiments, the first polymer film or the second polymer film of the barrier substrate can function as an adhesive layer. The first polymer film or the second polymer film can be heat activated before bonding to the paper or paperboard substrate.

[0117] The method of the third aspect may further include providing the laminate with an outermost polymer layer on one or both sides. However, the first polymer film of the barrier substrate may also constitute the outermost polymer layer of the laminate. The outermost polymer layer preferably provides liquid barrier properties and mechanical protection to the laminate surface. It is also preferred that the outermost polymer layer be heat-sealable. The outermost polymer layer may be applied, for example, by extrusion coating, film lamination, or dispersion coating after forming the laminate. The outermost polymer layer is generally composed of a thermoplastic polymer commonly used for protective and / or heat-sealable layers in paper-based packaging laminates, or polymers used in liquid or food packaging, in particular. In some embodiments, the outermost polymer layer comprises polypropylene or polyethylene. In preferred embodiments, the outermost polymer layer comprises polyethylene, more preferably LDPE or HDPE. The basis weight of the outermost polymer layer may correspond to the basis weight of the first polymer layer.

[0118] The laminate produced by the method of the third aspect is a paper or paperboard-based laminate, i.e., a laminate formed primarily from paper or paperboard, such as a paper or paperboard-based packaging laminate. The laminate typically has a first outermost surface intended to function as the exterior or printing surface, and a second outermost surface intended to function as the interior surface of the packaging container. The side of the paper or paperboard substrate that constitutes the MFC film may be intended to function as the interior surface of the packaging container.

[0119] According to a fourth aspect of the present disclosure, there is provided a laminate obtainable by the method of the third aspect. The laminate obtainable by the method of the third aspect can be used as is, or can be combined with one or more further layers.

[0120] For example, the barrier substrates and laminates of the present invention can be used as or in packaging materials, such as food or liquid packaging. For example, the barrier substrates and laminates can be part of flexible packaging materials, such as opaque or translucent freestanding pouches or bags. Thus, the barrier substrates and laminates can be used as box sacks when packaging dry foods such as cereals. Furthermore, the barrier substrates and laminates can be used as wrapping substrates, such as flow wrap materials, as laminate materials for paper, paperboard, or plastics, and / or as substrates for disposable electronic devices. The barrier substrates and laminates can also be included in closures, lids, or labels, for example. The barrier substrates and laminates can be incorporated into any type of package, such as boxes, bags, wraps, wrapping films, cups, containers, trays, bottles, etc. The present disclosure also relates to packaging products comprising the barrier substrate obtained by the method of the first aspect or the laminate obtained by the method of the third aspect. Furthermore, the present disclosure relates to the use of a barrier substrate obtainable by the method of the first aspect or a laminate obtainable by the method of the third aspect as or in a packaging material.

[0121] Some examples of possible structures for barrier substrates according to the present disclosure are given below. - MFC film / polymer film - MFC film / adhesive / polymer film - MFC film / adhesive / metallized layer / polymer film - Polymer film / MFC film / Polymer film - Polymer film / MFC film / adhesive / polymer film - Polymer film / MFC film / adhesive / metallized layer / polymer film - MFC film / polymer film / metallized layer / polymer film

[0122] Some examples of possible constructions of laminates according to the present disclosure are given below. - Paperboard / adhesion layer / MFC film / polymer film - Paperboard / Cling layer / MFC film / Adhesive / Polymer film - Paperboard / Cling layer / MFC film / Adhesive / Metallized layer / Polymer film - Polymer film / Paperboard / Cling layer / MFC film / Polymer film - Polymer film / Paperboard / Cling layer / MFC film / Polymer film / Polymer film - Polymer film / Paperboard / Cling layer / MFC film / Adhesive / Polymer film - Polymer film / Paperboard / Cling layer / MFC film / Adhesive / Metallized layer / Polymer film

[0123] Example Example 1 - Extrusion coating of polyolefin onto MFC film Hardwood pulp was enzymatically treated and then mechanically degraded under conditions such as those described in WO2007091942A1.

[0124] The MFC suspension was then mixed with 10 wt% polyvinyl alcohol, 10 wt% clay, and 5 wt% sugar alcohol (based on MFC dry solids). The MFC suspension was then cast coated onto a metal belt using slot die technology to a concentration of 15 g / m at 5.0 wt%. 2 A thin wet MFC film (dry weight) of 1000 cc / m² was formed. The wet MFC film was dehydrated and dried on a metal belt until the moisture content was less than 4% by weight to form a dry MFC film, after which the dry MFC film was contacted with a polyolefin melt. The dry MFC film was still positioned on the metal belt when the polyolefin melt was applied onto the dry MFC film. A polyolefin melt, metallocene-LDPE, was applied in an amount of 20 gsm to form a barrier substrate. The melt was fused onto the MFC film at a temperature of 80°C and a pressure of 10 kN / m and leveled. The barrier substrate was then subjected to a cooling step. The resulting barrier substrate had a viscosity of 1-10 cc / m², measured at 23°C and 50% RH according to ASTM F1927-20. 2 / day OTR value and 20g / m2 measured at 23°C and 50% RH according to ASTM F1249-20 2 had a WVTR value of less than / day.

[0125] Example 2 - Lamination of metallized biaxially oriented PP with MFC film The MFC film was produced in the same manner as described in Example 1. After drying, while the dried MFC film was still attached to the metal belt, a biaxially oriented metallized polypropylene film with an adhesive layer was attached to the dried MFC film to form an intermediate substrate. The intermediate substrate was further heated and melted in a nip at a nip temperature of 160°C (top roll, not metal belt) and a nip pressure of 5-10 kN / m to ensure good adhesion with the MFC film, forming a barrier substrate. The resulting barrier substrate had a viscosity of 3 cc / m2, measured at 23°C and 50% RH according to ASTM F1927-20. 2 / 3g / m measured at 23°C and 50% RH according to ASTM F1249-20 and OTR value less than 24 hours 2 The barrier substrate structure prior to the addition of any additional layers was MFC film / adhesive / metallized layer / BOPP.

[0126] Generally, products, materials, layers, and processes are described in terms of "comprising" various components or steps, but products, materials, layers, and processes may also "consist essentially of" or "consist of" various components and steps.

[0127] Other modifications and variations will become apparent to those skilled in the art in view of the above detailed description of the invention, and it is evident, however, that such other modifications and variations can be made without departing from the spirit and scope of the invention.

Claims

1. A method for producing a barrier substrate comprising a microfibrillated cellulose (MFC) film and a polymer film, - A step of providing an MFC suspension containing MFCs between 50% by weight and 100% by weight, based on total dry weight, wherein the MFC suspension has a dry content of 1% to 40% by weight. - The step of forming a wet MFC film of the MFC suspension by casting it onto a non-porous support, - A step of dehydrating and / or drying the wet MFC film positioned on the non-porous support to a dry MFC film having a moisture content of 20% by weight or less, - A step of applying a first polymer film onto a first surface of the dried MFC film positioned on the non-porous support in order to form an intermediate substrate, - The step of pressing the intermediate substrate positioned on the non-porous support with at least one nip to form the barrier substrate, - A step of separating the barrier substrate from the non-porous support. A method that includes this.

2. The method according to claim 1, wherein the first polymer film comprises a thermoplastic polymer.

3. The method according to claim 2, wherein the first polymer film comprises a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters.

4. The method according to claim 2 or 3, wherein the first polymer film comprises polyethylene.

5. The method according to claim 2 or 3, wherein the first polymer film is applied to the first surface of the dry MFC film in a molten state by extrusion coating.

6. The method according to claim 2 or 3, wherein the first polymer film is applied to the first surface of the dry MFC film in the form of a solid film.

7. The method according to claim 6, wherein at least one surface of the solid first polymer film is metallized.

8. The method according to claim 7, wherein the metallized surface of the solid first polymer film is formed by vapor deposition of a metal or metal oxide onto the solid first polymer film, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

9. The method according to claim 2 or 3, wherein the first polymer film is a foamed film.

10. The method according to claim 1 or 2, wherein, after the barrier substrate is separated from the non-porous support, a second polymer film is applied to a second surface of the MFC film, the second surface of the MFC film being opposite to the first surface of the MFC film.

11. The method according to claim 10, wherein the second polymer film comprises a thermoplastic polymer.

12. The method according to claim 11, wherein the second polymer film comprises a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters.

13. The method according to claim 11, wherein the second polymer film contains polyethylene.

14. The method according to claim 11, wherein the second polymer film is applied to the second surface of the dry MFC film in a molten state by extrusion coating.

15. The method according to claim 11, wherein the second polymer film is applied to the second surface of the dry MFC film in the form of a solid film.

16. The method according to claim 15, wherein at least one surface of the solid second polymer film is metallized.

17. The method according to claim 16, wherein the metallized surface of the solid second polymer film is formed by vapor deposition of a metal or metal oxide onto the solid second polymer film, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

18. The method according to claim 11, wherein the second polymer film is a foamed film.

19. The method according to claim 1 or 2, wherein the MFC suspension contains MFCs in an amount between 70% by weight and 100% by weight based on the total dry weight.

20. The aforementioned dried MFC film has a density of 2 to 70 g / m². ２ The method according to claim 1 or 2, having a basis weight.

21. The method according to claim 1 or 2, wherein each of the at least one nip is selected from the group consisting of a lamination nip, a calender nip, a smoothing roll nip, a press nip, a belt nip, and an extension nip.

22. A method for manufacturing a laminate, - A step of providing a paper or cardboard substrate, - A step of providing a barrier substrate according to the method of claim 1 or 2, - To obtain a laminate, the first surface of the paper or cardboard substrate is bonded to the MFC film of the barrier substrate using at least one adhesive layer. A method that includes this.

23. The method according to claim 22, further comprising the step of providing an outermost polymer layer on one or both sides of the laminate.