Method for manufacturing laminate and laminate

Abstract

The present invention relates to a method for manufacturing a laminate comprising a paper or paperboard substrate and a microfibrillated cellulose (MFC) film. A first web comprising a paper or paperboard substrate is provided. A second web of the MFC film is provided, and the MFC film has a) an MFC content of 50 to 100% by weight based on the total dry weight, b) a moisture content of 5 to 20% by weight, and c) a ratio of the machine direction tensile index to the cross direction tensile index of 0.8 to 1.4. The first web and the second web are joined using at least one adhesive layer provided between the webs so as to form a laminate. The MFC film of the laminate is further dried until it has a moisture content of less than 4% by weight. The present invention also relates to the laminate and a packaging material comprising the laminate.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a laminate comprising a base material of paper or cardboard and a barrier film, wherein the barrier film is a microfibrillated cellulose (MFC) film. Further, the present disclosure relates to a laminate comprising a base material of paper or cardboard and an MFC film, a packaging material comprising the laminate, and the use of the laminate in a packaging material.

Background Art

[0002] In many applications of paper and cardboard packaging, barrier properties against oxygen, grease, water vapor and / or aroma are required. However, paper and cardboard base materials do not inherently have these properties. Most commonly, the barrier properties of paper and cardboard base materials are created by adding one or more barrier coatings and / or laminated barrier layers based on plastics or other non-renewable materials. The disadvantages of these coatings and barrier layers are that, due to the use of non-renewable raw materials, the carbon dioxide emissions of the materials may increase, and paper and cardboard, which are originally biodegradable, may become non-biodegradable and, in some cases, non-recyclable. Furthermore, in order to improve the barrier comprising a barrier coating and / or a laminated barrier layer based on plastic or other non-renewable materials, it is usually necessary to increase the amount of polymer and / or various polymer layers used. Therefore, it becomes even more difficult to decompose and recycle the fiber portion of a paper or cardboard base material provided with such an improved barrier.

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

[0004] Laminates comprising a paper or paperboard substrate and an MFC film are disclosed for use, for example, in packaging materials or applications such as liquid or food packaging materials. Such laminates can be manufactured from substantially completely bio-based materials, preferably cellulose-based materials, thereby facilitating the repulping and recycling of packaging materials including used laminates and enabling, for example, an aluminum foil-free laminate structure for aseptic packaging. However, such laminates are further provided with an outermost polymer layer on one or both sides. The outermost polymer layer preferably provides liquid barrier properties and mechanical protection against the laminate surface. Preferably, the outermost polymer layer is also heat sealable. The outermost polymer layer is also used for decorative purposes such as printing and protection of printing.

[0005] To provide an MFC film on a paper substrate or a paperboard substrate, a self-supporting MFC film can be manufactured from an MFC suspension and then laminated to the paper substrate or the paperboard substrate.

[0006] One approach for manufacturing a self-supporting MFC film from an MFC suspension is to use a film casting method, i.e., casting an MFC suspension on a non-porous support such as a plastic or metal support to form a film, and then dehydrating and / or drying the film. It has been demonstrated that the casting method can produce MFC films with very smooth surfaces having excellent barrier properties such as oxygen barrier properties and / or water vapor barrier properties.

[0007] Another approach to manufacturing self - standing MFC films is to use wet - laying techniques, i.e., applying a layer of MFC suspension to a dewatering wire or membrane and dehydrating it on the wire or membrane by vacuum, gravity, capillary dewatering, press dewatering, or a combination thereof, 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 mostly removed from the MFC layer during dewatering. Therefore, a retention agent and / or a flocculant may be required to prevent the removal of the film additives. However, retention agents and / or flocculants usually have an adverse effect on barrier properties and do not guarantee complete retention. Also, in this approach, there are limitations on the MFC types used, and very fine MFCs cannot be used because they may pass through or penetrate the wire, or clog the wire or membrane. Also, 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.

[0008] Generally, self - standing MFC films, such as those manufactured by casting or wet - laying methods, have low elasticity (i.e., high brittleness). This can lead to conversion difficulties, such as when such MFC films are unwound from a reel and transported to or during a lamination step for lamination with a paper or paperboard substrate, making web handling difficult in the lamination step. Therefore, when used for lamination, their brittleness can cause problems with runnability, resulting in web breakage or defects such as torn edges, cracks, and wrinkles in such MFC films.

[0009] One approach to reducing the brittleness problem of MFC films is to use a humectant in the MFC film. However, a humectant, especially a large amount of it, can change the relative moisture content of the MFC film, and when laminating the MFC film between two polymer layers, for example, when laminating between a tie layer (used to laminate the MFC film to a paper or cardboard substrate) and a liquid barrier layer (i.e., the outermost polymer layer), further problems may occur. Trapped moisture and potential VOCs (volatile organic compounds) can cause peeling problems and swelling. Naturally, the greater the amount of trapped moisture, the higher the risk of back layer peeling. Therefore, using a high concentration of humectant increases this risk. Also, elevated temperatures in post-treatments such as printing and processing of the laminate, forming and sealing of the final product (such as a packaging product) including the laminate, or filling and storage of the product in the final product can increase the risk of back layer peeling.

[0010] Therefore, there is still room for improvement in the method for manufacturing a laminate including a paper or cardboard substrate and a barrier film (where the barrier film is an MFC film).

[0011] Description of the Invention The object of the present invention is an improved method for manufacturing a laminate including a paper or cardboard substrate and a barrier film, where the barrier film is an MFC film, and this method reduces the difficulty of the brittleness of the MFC film in the handling of the web related to the lamination to the paper or cardboard substrate, and eliminates or reduces at least some of the drawbacks of the prior art methods, and provides such a method.

[0012] The above object, as well as other objects realized by those skilled in the art in view of the present disclosure, are achieved by various aspects of the present disclosure. The present invention is defined by the appended independent claims. Embodiments are described in the appended dependent claims and the following description.

[0013] According to a first aspect described herein, a method of manufacturing a laminate comprising a base material of paper or cardboard and a microfibrillated cellulose (MFC) film, comprising: - providing a first web comprising a base material of paper or cardboard; - providing a second web of MFC film, the MFC film having a) an MFC content of 50 to 100 wt% based on the total dry weight, b) a moisture content of 5 to 20 wt%, preferably 5 to 15 wt%, and c) a ratio of the machine direction tensile index to the cross direction tensile index of 0.8 to 1.4, preferably 0.8 to 1.2, most preferably 0.9 to 1.1; - joining the first web and the second web using at least one adhesive layer provided between the first web and the second web to form the laminate; - further drying the MFC film of the laminate until the moisture content is less than 4 wt%, preferably less than 2 wt%, most preferably less than 1.5 wt%. Including.

[0014] Thus, the method of the first aspect provides a laminate comprising a base material of paper or cardboard and a microfibrillated cellulose (MFC) film which is a barrier film. Thus, the laminate is a barrier laminate.

[0015] Generally, self-supporting MFC films, such as those made by casting or wet lay-up methods, have low elasticity (i.e., high brittleness). This can lead to conversion problems such as difficulties in handling the web in the lamination process. For example, difficulties in handling the web can include those that occur when such an MFC film is transported to a substrate such as a paper or cardboard substrate (e.g., after being unwound from a reel), and / or during the lamination process for laminating with the substrate. Therefore, when used for lamination, its brittleness can cause problems with running performance, resulting in the web being damaged or defects such as torn edges and cracks in such MFC films.

[0016] A general problem regarding the brittleness of self-supporting MFC films in the handling of webs related to lamination is, at least in part, due to the fact that self-supporting MFC films are manufactured to have a low moisture content, that is, they are dried to a low moisture content, usually less than 5 wt%, for example, 1.5 - 4.5 wt%. In fact, it is desirable to produce self-supporting MFC films with a low moisture content. This is because it is desirable for the moisture content of the MFC film in the laminate to be low, for example, to avoid problems such as peeling due to moisture escaping or evaporating from the MFC film during a conversion process step at high temperature. Further, when forming a package using the laminate at a later stage, when sealing the seams of the package, moisture may evaporate from the wet MFC film, potentially causing delamination. Additionally, the barrier properties such as oxygen barrier and water vapor barrier of the MFC film may decrease if the moisture content in the film is high, so a low moisture content is desirable for the barrier properties. Also, the MFC film is manufactured with a low moisture content to ensure sufficient film formation and cross-linking during the manufacture of the MFC film. Further, the MFC film is manufactured with a low moisture content to promote the dimensional stability of the manufactured MFC film. However, as described above, when using a low moisture content MFC film in a lamination process, running problems and web breakage or defects may occur due to its brittleness. Also, the disadvantages of a low moisture content MFC film are low strain at break and higher strain rate sensitivity.

[0017] According to the method according to the first aspect, in the handling step of the web of the MFC film, such as unwinding and conveying from a reel for the lamination process, particularly for the lamination on a paper or cardboard substrate, the problems due to the brittleness of the self-supporting MFC film can be essentially reduced or alleviated. At the same time, the dimensional stability of the MFC film is promoted, and a low moisture content in the MFC film of the formed laminate is brought about. Also, according to the method according to the first aspect, the problems related to the brittleness of the self-supporting MFC film in the lamination process can be essentially reduced or alleviated without using a humectant or at least without using a large amount of humectant. More specifically, using a specific MFC film having an MFC content of 50 to 100% by weight, a moisture content of 5 to 20% by weight, and a ratio of the tensile index in the machine direction to the tensile index in the transverse direction of 0.8 to 1.4 based on the total dry weight, and an additional drying step for drying the MFC film of the laminate, that is, after joining the MFC film and the paper or cardboard substrate using at least one adhesive layer to form the laminate, by bringing the moisture content to less than 4% by weight, the problem of brittleness of the MFC film during web handling in the lamination process is essentially reduced or alleviated. At the same time, the dimensional stability of the MFC film is promoted, and the moisture content of the MFC film of the formed laminate becomes low.

[0018] By using a specific MFC film having a moisture content of 5 to 20% by weight and including an additional drying step of the MFC film after joining, the MFC film has a moisture content that can reduce the problem of brittleness before joining, and the moisture content of the MFC film in the laminate becomes low after joining. Therefore, when handling the web of the MFC film in the lamination process, that is, before joining the MFC film to the paper or cardboard substrate, it is possible to reduce the problem of brittleness. Also, due to the MFC film having a ratio of the longitudinal tensile index to the transverse tensile index of 0.8 to 1.4, the dimensional stability of the MFC film is promoted even during web handling of the MFC film before joining when the moisture content is 5 to 20% by weight.

[0019] Paper generally refers to a thin sheet made from wood pulp or other fibrous substances containing cellulose fibers, and is used for writing, drawing, or printing on packaging materials, or as a packaging material. Paper can be either bleached or unbleached, coated or uncoated, depending on the requirements of the end use, and can be manufactured in various thicknesses. Paper can be a single-layer material or a multi-layer material composed of two or more layers.

[0020] Paperboard generally refers to strong, thick paper or cardboard containing cellulose fibers used for boxes and other types of packaging materials. Paperboard can be either bleached or unbleached, coated or uncoated, depending on the requirements of the end use, and can be manufactured in various thicknesses. Paperboard can be a single-layer material or a multi-layer material composed of two or more layers. A common type of multi-layer paperboard is composed of a lower-density intermediate layer (sometimes called the "bulk layer") sandwiched between two higher-density outer layers. The lower-density intermediate layer can typically have a density of less than 750 kg / m 3 3, 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 3. The higher-density outer layers can typically have a density at least 100 kg / m 3 3 higher than the intermediate layer, preferably at least 200 kg / m 3 3 higher than the intermediate layer.

[0021] The paper or paperboard used as a substrate according to the present disclosure can be made from pulp from virgin fibers, such as mechanical pulp, semi-chemical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from waste paper, recycled paper, or paperboard. The paper or paperboard used as a substrate according to the present disclosure is manufactured using methods known in the art.

[0022] 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.

[0023] The paper substrate used in the method of the first aspect preferably has a basis weight in the range of 10 to 200 g / m 2 and more preferably in the range of 20 to 100 g / m 2 . Unless otherwise specified, the basis weight is determined in accordance with standard ISO 536.

[0024] The paperboard substrate used in the method of the first aspect preferably has a basis weight in the range of 120 to 600 g / m 2 or 120 to 450 g / m 2 and more preferably in the range of 200 to 500 g / m 2 or 180 to 380 g / m 2 . Unless otherwise specified, the basis weight is determined in accordance with standard ISO 536.

[0025] The paper or paperboard substrate may be a single layer of paper or paperboard, or a multi-layer of paper or paperboard. In some embodiments, the paperboard substrate is a multi-layer paperboard. In some embodiments, the paperboard substrate is a multi-layer paperboard composed of two or more layers. In some embodiments, the paperboard substrate is a multi-layer paperboard composed of three or more layers. In some embodiments, the paperboard substrate is a multi-layer paperboard composed of a lower density intermediate layer sandwiched between two higher density outer layers.

[0026] In some embodiments, the paperboard substrate is a foamed paperboard. In some embodiments where the paperboard substrate is a multi-layer paperboard, at least one layer, preferably the intermediate layer, is a foam. In some embodiments where the paperboard substrate is a multi-layer paperboard, at least one of the layers, preferably the intermediate layer, is a bulky layer.

[0027] The paper or paperboard substrate can optionally be 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 the present disclosure, forms part of the substrate. The paper or paperboard substrate can be subjected to surface sizing or surface treatment on at least one side of the substrate. Such surface sizing or surface treatment forms part of the paper or paperboard substrate in the context of the present disclosure. Preferably, the surface sizing composition used for surface sizing contains starch or a starch derivative.

[0028] As used herein, the term "film" generally refers to a thin continuous sheet-forming material, such as a thin substrate having good barrier properties against gases, aromas, greases or oils, for example, oxygen barrier properties and / or water vapor barrier properties. Depending on the composition of the MFC suspension from which it is formed, the MFC film can also be considered as a thin paper (such as nanopaper or micropaper) or a membrane.

[0029] In the context of a patent application, microfibrillated cellulose (MFC) shall mean cellulose particles, fibers or fibrils having a width or diameter of 20 nm to 1000 nm.

[0030] There are various ways to manufacture MFC, such as one or more purifications, purification after preliminary hydrolysis, high-shear decomposition, or fibril liberation. To achieve both energy efficiency and sustainability in the manufacture of MFC, usually one or more pretreatment steps are required. Thus, the cellulose fibers of the pulp used in the manufacture of MFC can be natural or pretreated enzymatically or chemically, for example, to reduce the amount of hemicellulose or lignin. The cellulose fibers can be chemically modified prior to fibrillation, in which case the cellulose molecules contain functional groups other than (or more than) those found in the original cellulose. Such groups include, inter alia, carboxymethyl (CM), aldehyde and / or carboxyl groups (cellulose obtained by oxidation, such as 2,2’,6,6’-tetramethylpiperidine-N-oxyl (TEMPO)-mediated oxidation), or quaternary ammonium (cationic cellulose). After being modified or oxidized by one of the above methods, the fibers are easily defibrated by MFC.

[0031] MFC can be manufactured from hardwood and / or softwood pulp cellulose fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. For example, it can be manufactured from pulp containing virgin fibers such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from waste paper or recycled paper.

[0032] As described above, the MFC film of the second web contains 50 wt% to 100 wt% of MFC based on the total dry weight. In some embodiments, the MFC film contains 60 wt% to 100 wt%, preferably 70 wt% to 100 wt%, more preferably 80 wt% to 100 wt% of microfibrillated cellulose based on the total dry weight, which is related to the amount of microfibrillated cellulose in the film itself.

[0033] In some embodiments, the basis weight of the MFC film provided for the second web (i.e., the provided MFC film with a moisture content of 5 to 20% by weight) is 4 to 80 g / m 2 , preferably 10 to 60 g / m 2 or 15 to 50 g / m 2 or 18 to 45 g / m 2 or 20 to 40 g / m 2 . The specific basis weight of the provided MFC film is 4 to 10 g / m 2 , 10 to 20 g / m 2 , 20 to 30 g / m 2 , 30 to 40 g / m 2 , 40 to 50 g / m 2 , 50 to 60 g / m 2 , 60 to 70 g / m 2 , or 70 to 80 g / m 2 .

[0034] In some embodiments, the density of the MFC film provided for the second web, when measured in accordance with ISO 534:2011, is 700 to 1400 kg / m 3 , for example 800 to 1300 kg / m 3 or 850 to 1200 kg / m 3 .

[0035] In some embodiments, the average film thickness of the provided MFC film of the second web is 5 to 60 μm, preferably 10 to 50 μm, 15 to 45 μm, or 20 to 40 μm. The specific average film thickness may be 5 to 10 μm, 10 to 15 μm, 15 to 20 μm, 20 to 25 μm, 25 to 30 μm, 30 to 35 μm, 35 to 40 μm, 40 to 45 μm, 45 to 50 μm, 50 to 55 μm, or 55 to 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 example, using white light interferometry, laser profilometry, or optically, by cutting the sample with a line in the machine transverse direction (whether cast in resin or not) and taking a microscopic image in the thickness direction of the cut cross-section (e.g., by scanning electron microscopy or other applicable methods).

[0036] In some embodiments, the width of the provided MFC film of the second web is 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m, or 2 to 4 m.

[0037] In some embodiments, the provided MFC film of the second web has an oxygen transmission rate (OTR) of less than 50 cc / m 2 / 24 h, preferably less than 20 cc / m 2 / 24 h, and most preferably less than 10 cc / m2 / 24 h, as measured in accordance with standard ASTM F1927-20 at 50% relative humidity and 23 °C.

[0038] In some embodiments, the provided MFC film of the second web has a water vapor transmission rate (WVTR) of less than 100 g / m 2 / 24 h, preferably less than 50 g / m 2 / 24 h, more preferably less than 20 g / m 2 / 24 h, as measured in accordance with standard ASTM F1249-20 at 50% relative humidity and 23 °C.

[0039] In some embodiments, the provided MFC film of the second web has at least 10, preferably 12 KIT values when measured in accordance with standard ISO16532-2.

[0040] In some embodiments, the provided MFC film of the second web has less than 10 pinholes per m 2 and most preferably less than 6 pinholes per m. 2 has.

[0041] The MFC of the MFC film may be composed of one or more fractions of MFC. In some embodiments, the MFC of the MFC film comprises one fraction of fine-grade MFC. In some embodiments, the MFC of the MFC film comprises two or more fractions of MFC of different fine grades. In some embodiments, the MFC of the MFC film comprises one fraction of a fine grade and one fraction of a coarse grade, and the coarse grade may be, for example, an additive. In this case, the Shopper-Riegler value of the coarse MFC is usually 80 to 100 SR°, for example, 80 to 99 SR°, 90 to 99 SR°, or 95 to 99 SR°, but the fine MFC fibrillates to a Shopper-Riegler value exceeding the measurement range (the theoretical value is about 100 SR° or more) determined by standard ISO 5267-1. In some embodiments, the fine-grade MFC is chemically derivatized such as carboxymethylated MFC.

[0042] In addition to MFC, the MFC film may contain a film-forming agent, a dispersant, a filler, a pigment, a wet strength improver, a cross-linking agent, a plasticizer, a softening agent, a humectant, an adhesion primer, a wetting agent, a biocide, a colorant, an antifoaming agent, a hydrophobing agent such as alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), wax, rosin resin, mineral additives (fillers) such as bentonite, kaolin, talcum, mica, montmorillonite, organic clay, graphene and graphene oxide, and conventional papermaking additives or chemicals such as stearates, starch, silica, precipitated calcium carbonate, cationic polysaccharides, and rheology modifiers. Thus, these additives or chemical substances may be process chemicals or film performance chemicals added to impart specific properties to the final product film and / or to facilitate the production of the film. In some embodiments, the MFC film contains at least one additional polymer capable of forming the film and / or improving the bonds between cellulose fibers. Typical examples of such polymers are natural gums or polysaccharides or their derivatives such as carboxymethylated cellulose (CMC), hemicellulose, starch, polyvinyl alcohol (PVOH), or analogs thereof. In some embodiments, the MFC film contains at least one additive selected from the following group: PVOH and its derivatives or analogs, polysaccharides such as starch and CMC, sorbitol, and polyethylene glycol.

[0043] PVOH may be a single type of PVOH or a mixture of two or more types of PVOH with different degrees of hydrolysis or viscosities. PVOH may have a degree of hydrolysis in the range of, for example, 80 to 99 mol%, preferably 88 to 99 mol%.

[0044] In some embodiments, the MFC film contains additives at 50 wt% or less, such as 35 wt% or less, 30 wt% or less, 25 wt% or less, or 20 wt% or less, based on the total dry weight of the MFC film. For example, the MFC film can contain 1 - 50 wt%, or 1 - 35 wt%, or 1 - 30 wt%, or 1 - 25 wt%, or 1 - 20 wt% of additives based on the total dry weight of the MFC film.

[0045] In some embodiments, the MFC film contains one or more humectants and / or plasticizers, such as sugar alcohols (e.g., sorbitol), glycols, or other polyols, at 0 - 30 wt%, or 0.5 - 20 wt%, or 3 - 15 wt% based on the total dry weight.

[0046] In some embodiments, the MFC film contains up to 20 wt% of mineral fillers (conventional fillers or nano fillers), such as bentonite, kaolin, talcum, mica, montmorillonite, organoclay, graphene, graphene oxide, or combinations thereof.

[0047] In some embodiments, the MFC film contains up to 30 wt% of nanocrystals and / or cellulose derivatives based on the total dry weight.

[0048] The MFC film can be a single - layer or multi - layer film, or a single - layer or multi - layer ply. Thus, in some embodiments, the MFC film is composed of a single film layer or two or more film layers stacked on top of each other.

[0049] In some embodiments, in addition to MFC, the MFC film contains one or more additional cellulose pulp fractions, such as a cellulose pulp fraction with a Schopper - Riegler value of ≤70 SR°, such as 15 - 70 SR° or 25 - 60 SR° as determined by standard ISO 5267 - 1, and / or additional fractions of ordinary cellulose fibers and / or lignocellulose fibers.

[0050] The MFC film is preferably formed from an MFC suspension, preferably an aqueous MFC suspension (i.e., containing water as the suspension medium), and contains MFC and optional additives and / or chemicals and / or further cellulose pulp fractions as defined above. The MFC suspension is preferably cast onto a non-porous support such as a metal belt, particularly a steel belt, a polymer belt, or a polymer-coated belt, using known casting techniques, to form a wet MFC film. The non-porous support is typically an endless belt. Preferably, the wet MFC film is dehydrated and / or dried on the non-porous support using methods known in the art to obtain an MFC film having a moisture content of 5 to 20% by weight. After peeling the MFC film from the non-porous support, a web of MFC film having a moisture content of 5 to 20% by weight is obtained.

[0051] The term "casting", when used in film formation, refers to a known term for depositing a suspension onto a support (usually an endless belt) by contact or non-contact deposition and leveling methods to form a wet web. Examples of such deposition and leveling methods include curtain coating / applying, slot die casting, or administering the MFC suspension using a spray or similar device and leveling using a doctor blade or rod.

[0052] As described above, the MFC film used in the method of the first aspect, i.e., the MFC film of the second web provided to the lamination process, has a moisture content of 5 to 20% by weight, preferably 5 to 15% by weight, or 6 to 15% by weight, or 6 to 14% by weight, or 7 to 13% by weight. The moisture content of the MFC film provided to the lamination process can be determined, for example, in accordance with the standard ISO 638 by determining the dry content, by calculating the moisture content, or by spectroscopy. Alternatively, the moisture content can also be determined using the apparatus or equipment used to determine the dry moisture content. The moisture content can be measured under ambient conditions. The specific moisture content of the MFC film is such that the second web of the MFC film is rewound before the MFC film is joined to the first web to form a laminate, i.e., during conveyance until joining with the first web, and is suitable for handling the web, and thus problems regarding the brittleness of the MFC film are reduced.

[0053] The ductility of the MFC film can be explained by the tensile strength of the MFC film and the strain at break. In some embodiments, the MFC film has a tensile index in the machine direction of at least 20 Nm / g, preferably at least 30 Nm / g or at least 40 Nm / g. In some embodiments, the MFC film has a strain at break in the machine direction of at least 1.5%, for example 2 to 20% or 3 to 15%.

[0054] Also, as described above, the MFC film used in the method of the first aspect has a ratio of the machine direction (MD) tensile index to the cross direction (CD) tensile index of 0.8 to 1.4, preferably 0.8 to 1.2, and most preferably 0.9 to 1.1. This means that the microfibrils have no or essentially no orientation, thereby contributing to the high dimensional stability (low moisture absorption expansion) of the MFC film. The specified MD / CD ratio of the tensile index can be obtained during the production of the MFC film, for example, by manufacturing the MFC film by a casting technique on a non-porous casting support and ensuring that there is no speed difference between the MFC suspension flowing out of the casting unit and the casting support on which the MFC is cast to form the wet MFC film.

[0055] The tensile index in the machine direction, the strain at break, and the MD / CD ratio of the tensile index are measured using a vertical testing machine such as a Zwick vertical tensile testing machine in accordance with standard ISO 1924-3, with the following minor modifications: test span (distance between clamps): 20 mm (ISO 1924-3 100 mm); constant elongation rate: 2 mm / min (ISO 1924-3 100 mm / min); sample width 15 mm (in accordance with ISO 1924-3); sample length: 55 mm (ISO 1924-3 defines that it must be the length that can be clamped); load cell: 0.5 kN.

[0056] The dimensional stability of the MFC film used in the first aspect of the method can be further promoted by using suppressed dehydration and / or drying, that is, by manufacturing the MFC film by a casting technique on a non-porous casting support and maintaining the manufactured MFC film in contact with the non-porous casting support until the moisture content reaches 5 to 20% by weight (i.e., maintaining the manufactured MFC film in contact with the non-porous casting support during dehydration and / or drying until the moisture content reaches 5 to 20% by weight).

[0057] In some embodiments, the MFC film comprises at least one crosslinking chemical and / or at least one other chemical having free hydroxyl groups that bind to water. These chemicals contribute to reducing the moisture absorption expansion rate of the MFC film. Examples of such chemicals include citric acid, glyoxal, ammonium zirconium carbonate, urea formaldehyde, melamine formaldehyde resin, metal salts, zirconium chelates, reactive starches such as dialdehyde starch, amino resins, and the like.

[0058] As described above, the first web comprising a paper or paperboard substrate and the second web of the MFC film are joined using at least one adhesive layer (i.e., tie layer) provided between the first web and the second web to form a laminate. The joining can be carried out at a lamination station including one or more lamination nips such as a pressure roller nip. Thus, the first web and the second web are joined and laminated at a lamination station including one or more lamination nips, and the first web and the second web are pressed together at one or more lamination nips with at least one adhesive layer disposed between the first web and the second web. In some embodiments, the lamination nip is formed between two rolls at least one of which is coolable. In some embodiments, the lamination nip is formed between a cooling roll and a nip roll or pressure roll that is not temperature-controlled. In some embodiments, the nip roll or pressure roll may be a heating roll.

[0059] The adhesive layer can generally include any suitable adhesive commonly used for paper or paperboard-based packaging laminates, or adhesives specifically used for liquid or food packaging laminates. In the present invention, various types of adhesives and adhesive coating methods can be used.

[0060] Typically, the adhesive layer is composed of one or more adhesive polymers. The adhesive layer may consist of only one or more adhesive polymers, or may further contain other additives for improving the properties of the adhesive layer.

[0061] In some embodiments, the adhesive layer contains at least 50 wt% of an adhesive polymer or a mixture of adhesive polymers based on the dry weight.

[0062] In some embodiments, the adhesive layer contains or consists of one or more adhesive polymers selected from the group consisting of polyolefins, polyesters, polyurethanes, and acrylic copolymers. In some embodiments, the adhesive layer contains or consists of one or more adhesive polymers selected from the group consisting of polyolefins and polyesters. In some embodiments, the adhesive layer contains or is composed of one or more of polypropylene and polyethylene, such as low density polyethylene (LDPE or LLDPE), medium density polyethylene (MDPE), or high density polyethylene (HDPE). In some embodiments, the adhesive layer contains or consists of components selected from adhesive thermoplastic polymers such as modified polyolefins mainly based on LDPE or LLDPE copolymers, or graft copolymers having functional group-containing monomer units such as carboxyl groups or glycidyl functional groups, for example (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 graft polyethylene (MAHg-PE). Another example of such a modified polymer or adhesive polymer is a so-called ionomer or ionomer polymer. Preferably, the modified polyolefin is ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0063] In some embodiments, the adhesive layer comprises at least 50 wt% of a water-soluble polymer or a mixture of water-soluble polymers based on dry weight. The water-soluble polymer of the adhesive layer is soluble in cold water for a certain period of time or is soluble in warm water at a temperature, for example, below 100 °C or above 100 °C. In some embodiments, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH) or its derivatives or analogs, carboxymethyl cellulose (CMC), starch, alginate, and hemicellulose, preferably PVOH.

[0064] The adhesive layer can be applied by any suitable method known in the art. The adhesive layer can be applied, for example, as a solution or dispersion in an aqueous or organic solvent carrier using a liquid coating method known in the art, or in a molten form using extrusion coating. Extrusion coating is a process of applying a molten plastic material to a substrate to form a very thin, smooth, and uniform layer. In embodiments where the adhesive layer comprises one or more adhesive polymers selected from the group consisting of polyolefins, polyesters, polyurethanes, and acrylic copolymers, extrusion coating is preferably utilized for the application of the adhesive layer.

[0065] In embodiments where the adhesive layer comprises a water-soluble polymer, the adhesive layer may be formed in the form of a solution or dispersion that is spread into a thin and uniform layer on the substrate during application and then dried by a liquid film coating process. The adhesive layer can be applied by a contact or non-contact coating method.

[0066] In some embodiments, at least one adhesive layer is applied in the form of a foam. The foam coating is advantageous because it can form a film even with a higher solids content and a lower moisture content compared to a non-foam coating. Since the moisture content of the foam coating is lower, the problem of rewetting of the barrier substrate is also reduced. The foam can be formed using a polymeric or non-polymeric blowing agent. Examples of polymeric blowing agents include PVOH, hydrophobically modified starch, hydrophobically modified ethyl hydroxyethyl cellulose, and the like.

[0067] In some embodiments, the adhesive layer further comprises a crosslinking agent capable of crosslinking the water-soluble polymer. Crosslinking improves the water vapor barrier properties of the adhesive layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes such as citric acid, glyoxal, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent may be, for example, 1 to 20 wt%, preferably 1 to 15 wt% based on the dry weight of the adhesive layer.

[0068] In some embodiments, the adhesive layer comprises PVOH and citric acid. Crosslinking PVOH with citric acid improves the water vapor barrier properties of the adhesive layer.

[0069] In some embodiments, the adhesive layer comprises one or more additional polymers in a total amount of 0 to 50 wt% based on the dry weight.

[0070] In some embodiments, the adhesive layer further comprises, based on the dry weight, up to 50 wt% of microfibrillated cellulose (MFC), nanocrystalline cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose, hemicellulose, or a combination thereof, which are chemically modified cellulose derivatives.

[0071] In some embodiments, one adhesive layer is provided between the first web and the second web to form a laminate. In some embodiments, two or more adhesive layers are provided between the first web and the second web to form a laminate. The total coat weight of the one or more adhesive layers is typically in the range of 1 to 20 g / m 2 2. In some embodiments, the total coat weight of the one or more adhesive layers is in the range of 2 to 15 g / m 2 2, and more preferably in the range of 3 to 12 g / m 2 2.

[0072] In some embodiments, at least one adhesive layer is provided on the surface of the first web prior to joining the first web to the second web of the MFC film. Thus, in these embodiments, at least one adhesive layer is provided on the surface of the first web, and in the joining step, the first web is joined to the second web of the MFC film by the adhesive layer provided between the first web and the second web after joining. The adhesive layer may be provided on the surface of the first web by extrusion coating. In these embodiments, the joining may include joining the first web to the second web using the adhesive layer provided between the first web and the second web at a lamination station including at least one lamination nip.

[0073] In some embodiments, at least one adhesive layer is provided on the surface of the MFC film of the second web before bonding to the first web. Thus, in these embodiments, at least one adhesive layer is provided on the surface of the MCF film, and the adhesive layer provided between the first web and the MCF film after bonding causes the first web to be bonded to the MFC film in the bonding step. The adhesive layer may be provided on the surface of the MCF film by extrusion coating. In these embodiments, the bonding may include bonding the first web to the second web using the adhesive layer provided between the first web and the second web at a lamination station including at least one lamination nip. In these embodiments, it is particularly advantageous to use an anhydrous adhesive such as an anhydrous adhesive or a foaming adhesive.

[0074] In some embodiments, the bonding includes bonding the first web and the second web at a lamination station including a lamination nip, for example, by supplying or injecting the composition or component used to form the adhesive layer into the lamination nip, an adhesive layer is formed between the first web and the second web at the lamination nip, and at least one adhesive layer is provided between the first web and the second web at the lamination nip. The adhesive may be extruded into the laminating nip.

[0075] In embodiments where multiple adhesive layers are used to bond the first web and the second web, all of the adhesive layers can be provided on the first web, or on the second web, or formed and provided in the lamination nip between the first web and the second web by injection. Alternatively, in embodiments where multiple adhesive layers are used to bond the first web and the second web, one or more adhesive layers may be provided on the first web, and / or one or more adhesive layers may be provided on the second web, and / or one or more adhesive layers may be formed and provided in the lamination nip between the first web and the second web.

[0076] In some embodiments, the second web is guided prior to joining according to the method of the first aspect via at least one spreading roll (also referred to as a spreader roll), preferably via at least one spreading roll, and then via a configuration including a web stabilization unit on the side opposite the support member (i.e., the second web is guided between the support member and the web stabilization unit on the side opposite the support member). In these embodiments, wrinkles, curls and / or air ingress at the joint can be prevented or substantially reduced. The support member and the web stabilization unit on the opposite side may be a mechanical contact device (flat / cylindrical) or a non-contact device (air levitation). A suitable known spreading roll that provides a spreading action for the second web can be used.

[0077] As described above, the laminated MFC film is further dried until it has a moisture content of less than 4% by weight, preferably less than 2% by weight, most preferably less than 1.5% by weight or less than 1% by weight. Further drying the laminated MFC film to a moisture content of less than 4% by weight can be selected from the group consisting of contact drying, infrared (IR) drying, near-infrared (NIR) drying, microwave (MW) drying, ultraviolet (UV) drying, electron beam (EB) drying, hot gas impingement drying such as thermal gas impingement drying, other types of radiation drying, and combinations thereof.

[0078] In some embodiments, further drying the laminated MFC film is radiation drying selected from the following group: IR drying, NIR drying, MW drying, UV drying, EB drying, and combinations thereof.

[0079] In some embodiments, further drying the laminated MFC film is selected from the following group: IR drying, UV drying, EB drying, and combinations thereof.

[0080] By using radiation drying, especially IR drying, UV drying and / or EB drying, a sterilizing effect, i.e., the sterilization and / or inactivation of potential microorganisms and / or enzymes, can be achieved, and / or in addition to the drying effect, a crosslinking effect can be achieved. Also, especially when EB drying is utilized, further drying may mean that the viscosity of the adhesive layer changes due to depolymerization.

[0081] Preferably, the step of further drying the MFC film of the laminate is performed by applying heat or radiation onto the surface of the laminate containing the MFC film.

[0082] For example, the moisture content of the MFC film of the laminate can be measured, for example, online by spectroscopy, such as an infrared moisture sensor based on a typical single-head package equipped with a halogen light source focused on the sheet. Part of the beam is absorbed, part is reflected (scattered) and collected, and detected. Thus, the moisture content of the MFC film is measured from the MFC side of the laminate. The moisture content can be determined under ambient conditions. Alternatively, the dry content of the MFC film can be measured and the moisture content can be determined using the dry content.

[0083] For example, the moisture content of the paper or paperboard substrate of the laminate after further drying the MFC film can be 2 to 9 wt%, preferably 3 to 8 wt%, more preferably 3 to 7 wt% or 3 to 6 wt%. The moisture content of the paper or paperboard substrate can be determined by determining the dry content in accordance with ISO 638 and calculating the moisture content, or by using a spectroscopic method.

[0084] In some embodiments, the step of providing the first web includes providing a first reel of the first web and unwinding the first web from the first reel. Thus, in these embodiments, the unwound first web is joined to the second web.

[0085] In some embodiments, the step of providing the second web includes providing a second reel of the second web of the MFC film and unwinding the second web from the second reel. In these embodiments, the MFC film of the unwound second web is joined to the first web.

[0086] In some embodiments, the method of the first aspect is - providing a first reel of a first web comprising a paper or paperboard substrate and unwinding the first web from the first reel; - providing a second reel of a second web of an MFC film, the MFC film having a) an MFC content of 50 to 100 wt% based on the total dry weight, b) a moisture content of 5 to 20 wt%, preferably 5 to 15 wt%, and c) a ratio of the machine direction tensile index to the cross direction tensile index of 0.8 to 1.4, preferably 0.8 to 1.2, most preferably 0.9 to 1.1, providing the second web and unwinding the second web from the second reel; - joining the unwound first web and the unwound second web using at least one adhesive layer provided between the first web and the second web to form a laminate; - further drying the MFC film of the laminate until it has a moisture content of less than 4 wt%, preferably less than 2 wt%, most preferably less than 1.5 wt%.

[0087] In some embodiments, the method is a manufacturing and in-line or continuous process of the MFC film, and the step of providing the second web of the MFC film includes providing the second web of the MFC film directly from the manufacturing of the MFC film, i.e., without winding the MFC film onto a reel. Thus, in these embodiments, the step of providing the second web of the MFC film is Forming a wet MFC film of the MFC suspension by casting on a non-porous support, dehydrating and / or drying the wet MFC film on the non-porous support to provide an MFC film having a moisture content of 5 to 20% by weight, and peeling the MFC film from the non-porous support to provide a web of the MFC film having a moisture content of 5 to 20% by weight (i.e., the second web). may include.

[0088] There is a need for improved solutions to replace barrier plastic layers such as aluminum foil and polyolefin films as the barrier layer and substrate of packaging materials with alternatives that facilitate the repulping and recycling of used packaging materials. The laminate according to the present disclosure can advantageously be manufactured from substantially completely bio-based materials, preferably cellulose-based materials, thereby facilitating the repulping and recycling of used packaging materials containing the laminate according to the present disclosure.

[0089] The laminate according to the present disclosure is an alternative to conventional materials that use barrier plastic layers such as polyolefin films and / or aluminum foil layers and can be more easily repulped and recycled. In some embodiments, the laminate has a defect rate compliant with PTS RH 021 / 97 of less than 30%, preferably less than 20%, more preferably less than 10%, and most preferably less than 5%. The laminate according to the present disclosure can at least reduce the use of barrier plastic layers and / or aluminum foil layers used in conventional materials.

[0090] However, the laminate of the present invention may further have an outermost polymer layer provided on one or both sides. The outermost polymer layer preferably provides mechanical protection such as liquid barrier properties and print protection against the laminate surface. It is also preferred that the outermost polymer layer is heat sealable.

[0091] In some embodiments, the method of the first aspect further includes providing a first polymer layer of the outermost layer on the laminate over the MFC film, and the step of further drying the MFC film of the laminate is performed before the step of providing the first polymer layer of the outermost layer on the laminate. In some embodiments, the outermost first polymer layer comprises a thermoplastic polymer. In some embodiments, the outermost first polymer layer comprises a polymer selected from the group consisting of polyolefins and polyesters. In some embodiments, the outermost first polymer layer comprises a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters. In some embodiments, the outermost first polymer layer comprises polypropylene or polyethylene. In some embodiments, the outermost first polymer layer comprises polyethylene, more preferably LDPE or HDPE. By performing the step of further drying the MFC film of the laminate before the step of providing the first polymer layer of the outermost layer on the laminate, the moisture trapped between the adhesive layer (adhesion layer) and the first polymer layer of the outermost layer is reduced.

[0092] In some embodiments, the method of the first aspect further includes providing a second polymer layer of the outermost layer on a paper or paperboard substrate on the laminate, and the step of further drying the MFC film of the laminate is performed before the step of providing the second polymer layer of the outermost layer on the laminate. In some embodiments, the outermost second polymer layer comprises a thermoplastic polymer. In some embodiments, the outermost second polymer layer comprises a polymer selected from the group consisting of polyolefins and polyesters. In some embodiments, the outermost second polymer layer comprises a polymer selected from the group consisting of thermoplastic polyolefins and thermoplastic polyesters. In some embodiments, the outermost second polymer layer comprises polypropylene or polyethylene. In some embodiments, the outermost second polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0093] The outermost first polymer layer and the outermost second polymer layer can each generally include a thermoplastic polymer commonly used for protective layers and / or heat-sealable layers of paper or paperboard-based packaging laminates, or alternatively any polymer used particularly 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), are the most common and versatile polymers used for liquid and food packaging boards. The polymers used are preferably manufactured from renewable materials. The outermost first polymer layer and the outermost second polymer layer may include the same polymer or different polymers.

[0094] The outermost polymer layer, although it may naturally prevent repulping, may still be necessary or desirable in some applications. The outermost first polymer layer and / or the outermost second polymer layer can be applied, for example, by extrusion coating, film lamination (i.e., lamination of solid films) or dispersion coating. Thermoplastic polymers are useful because they can be easily processed by extrusion coating techniques and can form very thin and homogeneous films with excellent liquid barrier properties.

[0095] In some embodiments, the outermost polymer layer is formed by extrusion coating a polymer onto a laminate. Extrusion coating is a process of applying a molten plastic material to a substrate to form a very thin, smooth, and uniform layer. The coating can be formed of 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).

[0096] The basis weight of each of the outermost polymer layers is preferably less than 50 g / m 2 . To achieve a continuous and substantially defect-free film, when provided by extrusion coating, a basis weight of at least 6 g / m 2 , preferably at least 8 g / m 2 , or at least 12 g / m 2 of each of the outermost polymer layers is typically required. In some embodiments, the basis weight of each outermost polymer layer is in the range of 6 - 50 g / m 2 , preferably 8 - 50 g / m 2 or 10 - 25 g / m 2 or 10 - 20 g / m 2 , and the outermost polymer layer is provided by extrusion coating. In some embodiments, the basis weight of each outermost polymer layer is in the range of 2 - 10 g / m 2 , and the outermost polymer layer is provided by a foamed film.

[0097] According to a second aspect of the present disclosure, there is provided a laminate comprising a paper or paperboard substrate and an MFC film joined by at least one adhesive layer provided between the paper or paperboard substrate and the MFC film, the laminate being obtained by the method of the first aspect.

[0098] The laminate obtained by the method of the first aspect can be used as it is. Alternatively, it can also be made into a laminate material in combination with one or more additional layers, for example, one or more additional layers of paper or cardboard and / or other layers. When the laminate is combined with one or more additional layers, such as one or more paper or cardboard layers, to form a laminate material, the laminate material can be provided, if necessary, with an outermost polymer layer (corresponding to the above outermost polymer layer) on one or both sides. Other examples of additional layers that can be combined with the laminate obtained by the method of the first aspect include additional polymer layers where there are multiple polymer layers of the same or different polymers on each side, protective varnish layers, decorative layers on top of the laminate, and sealing layers that can be activated (melted) by heat.

[0099] For example, the laminate or laminate material can be used as a packaging material, such as for packaging food or liquids, or in packaging materials. For example, the laminate or laminate material can be part of a flexible packaging material, such as an opaque or translucent stand-up pouch or bag. Thus, the laminate or laminate material can be used as the bag material for a box when packaging dry foods such as cereal. Further, the laminate or laminate material can be used as a wrapping substrate, such as a flow wrap material, as a laminate material of paper, cardboard, or plastic, and / or as a substrate for disposable electronic devices. The laminate or laminate material can also be included in, for example, closures, lids, or labels. The laminate or laminate material can be incorporated into any type of package, such as boxes, bags, wraps, wrapping films, cups, containers, trays, bottles, etc. The present disclosure is also related to packaging products containing the laminate or laminate material obtained by the method of the first aspect.

[0100] The laminate produced by the method of the first aspect is a paper or paperboard-based laminate, i.e., a laminate mainly formed from paper or paperboard, such as a paper or paperboard-based packaging laminate. The laminate usually has a first outermost surface intended to function as the outer or printed surface and a second outermost surface intended to function as the inner surface of the packaging container. The side surface of the paper or paperboard substrate constituting the MFC film may be intended to function as the inner surface of the packaging container.

[0101] In some embodiments, 10 or 15 g / m 2 LDPE is used as the laminate adhesive, and 10 or 15 g / m 2 LDPE is used as the coating on the MFC film side (back side), and 20 g / m 2 is used as the coating on the opposite side (upper side). When liquid packaging board is used as the paper substrate, the oxygen transmission rate of the produced laminate is less than 1 cc / m 2 / day, less than 10 cc / m 2 / day, for example, 0.1 - 5 cc / m 2 / day or 5 - 10 cc / m 2 / day (in accordance with standard ASTM F1927 - 20) at 23°C and 50% relative humidity (RH). The produced laminate has a water vapor transmission rate of less than 1 g / m 2 / day at 23°C and 50% RH, less than 10 g / m 2 / day at 38°C and 85% RH, for example, 0.1 - 5 g / m 2 / day or 5 - 10 g / m 2 / day (in accordance with standard ASTM F1249 - 20).

[0102] Some examples of possible structures of the laminate according to the present disclosure are shown below. - A / B / C - D / A / B / C - A / B / C / D - D / A / B / C / D - D / A / B / C / D / D - D / D / A / B / C / D / D In the formula, A is a paper base material or cardboard base material, B is a tie layer (adhesive layer), C is an MFC film, and D is a seal and / or liquid barrier such as polyolefin.

[0103] Generally, products, materials, layers, and processes are described from the perspective of "including" various components or steps, but products, materials, layers, and processes may also be "essentially composed of" or "composed of" various components and steps.

[0104] Considering the above detailed description of the present invention, other modifications and changes will be apparent to those skilled in the art. However, it is obvious that such other modifications and changes can be implemented without departing from the spirit and scope of the present invention.

Claims

1. A method for manufacturing a laminate comprising a base material of paper or cardboard and a microfibrillated cellulose (MFC) film, comprising: - providing a first web comprising a base material of paper or cardboard; - providing a second web of MFC film, wherein the MFC film has a) an MFC content between 50% and 100% by weight based on the total dry weight, b) a moisture content of 5 to 20% by weight, preferably 5 to 15% by weight, and c) a ratio of the tensile index in the machine direction to the tensile index in the cross direction of 0.8 to 1.4, preferably 0.8 to 1.2, most preferably 0.9 to 1.1; - joining the first web and the second web using at least one adhesive layer provided between the first web and the second web so as to form the laminate; - further drying the MFC film of the laminate until it has a moisture content of less than 4% by weight, preferably less than 2% by weight, most preferably less than 1.5% by weight A method comprising the steps of.

2. The method according to claim 1, wherein the step of providing the first web comprises providing a first reel of the first web and unwinding the first web from the first reel.

3. The method according to claim 1 or 2, wherein the step of providing the second web comprises providing a second reel of the second web and unwinding the second web from the second reel.

4. The method according to any one of claims 1 to 3, wherein the step of further drying the MFC film of the laminate is performed by applying heat or radiation onto the surface of the laminate comprising the MFC film.

5. The method according to any one of claims 1 to 4, wherein the step of further drying the MFC film of the laminate is selected from the group consisting of contact drying, infrared drying, near-infrared drying, microwave drying, ultraviolet drying, electron beam drying, hot gas impingement drying such as thermal gas impingement drying, other types of radiation drying, and combinations thereof.

6. The method according to claim 5, wherein the step of further drying the MFC film is selected from the group consisting of infrared drying, ultraviolet drying, electron beam drying, and combinations thereof.

7. The method according to any one of claims 1 to 6, further comprising the step of providing a first polymer layer of the outermost layer on the MFC film to the laminate, wherein the step of further drying the MFC film of the laminate is carried out before the step of providing a first polymer layer of the outermost layer to the laminate.

8. The method according to claim 7, wherein the first polymer layer of the outermost layer comprises a polymer selected from the group consisting of a thermoplastic polyolefin and a thermoplastic polyester.

9. The method according to claim 8, wherein the first polymer layer of the outermost layer comprises polyethylene.

10. The method according to any one of claims 7 to 9, wherein the first polymer layer of the outermost layer is provided by extrusion coating.

11. The method according to any one of claims 1 to 10, further comprising the step of providing a second polymer layer of the outermost layer on a substrate of paper or paperboard to the laminate, wherein the step of further drying the MFC film of the laminate is carried out before the step of providing a second polymer layer of the outermost layer to the laminate.

12. The method according to claim 11, wherein the second polymer layer of the outermost layer comprises a polymer selected from the group consisting of a thermoplastic polyolefin and a thermoplastic polyester.

13. The method according to claim 12, wherein the second polymer layer of the outermost layer comprises polyethylene.

14. The method according to any one of claims 10 to 13, wherein the second polymer layer of the outermost layer is provided by extrusion coating.

15. The method according to any one of claims 1 to 14, wherein the MFC film has an MFC content between 70% and 100% by weight based on the total dry weight.

16. The MFC film has a basis weight of 4 to 80 g / m ２ , preferably 10 to 60 g / m ２ The method according to any one of claims 1 to 15, having a basis weight of.

17. The method according to any one of claims 1 to 16, wherein the MFC film comprises at least one crosslinking agent.

18. The method according to any one of claims 1 to 17, wherein the MFC film has a tensile index in the machine direction of at least 20 Nm / g, preferably at least 30 Nm / g or at least 40 Nm / g.

19. The method according to any one of claims 1 to 18, wherein the MFC film has an elongation at break in the machine direction of at least 1.5%, preferably at least 2%, most preferably at least 3%.

20. The method according to any one of claims 1 to 19, wherein at least one of the at least one adhesive layer is provided on the surface of the first web before the step of joining.

21. The method according to any one of claims 1 to 20, wherein at least one of the at least one adhesive layer is provided on the surface of the second web before the step of joining.

22. The method according to any one of claims 1 to 17, wherein the step of joining comprises joining the first web and the second web using the at least one adhesive layer in a lamination station including at least one lamination nip.

23. The method according to any one of claims 1 to 22, wherein the step of joining comprises joining the first web and the second web in a lamination station including a lamination nip, and at least one of the at least one adhesive layer is formed and provided between the first web and the second web in the lamination nip.

24. The method according to any one of claims 1 to 12, wherein the adhesive layer comprises at least 50% by weight of an adhesive polymer or a mixture of adhesive polymers based on the dry weight.

25. The method according to claim 24, wherein the adhesive layer comprises one or more adhesive polymers selected from the group consisting of polyolefins, polyesters, polyurethanes, and acrylic copolymers.

26. The method according to any one of claims 1 to 23, wherein the adhesive layer comprises at least 50% by weight of a water-soluble polymer or a mixture of water-soluble polymers based on the dry weight.

27. A laminate comprising a base material of paper or paperboard and a microfibrillated cellulose (MFC) film obtained by the method according to any one of claims 1 to 26.

28. A packaging material comprising the laminate according to claim 27.

29. Use of the laminate according to claim 27 as a packaging material or in a packaging material.

Images