Method for manufacturing a laminate and laminate

Abstract

The present invention relates to a method for manufacturing a laminate (8) comprising a paper substrate and a microfibrillated cellulose (MFC) layer. An MFC suspension containing 50 to 100% by weight of MFC is provided. A wet MFC layer (1) is formed by casting the suspension onto a metal belt support (2), and the dry content of the formed wet MFC layer (1) is 1 to 40% by weight. A paper substrate having a Gurley-Hill air permeability of less than 10,000 s / 100 ml is provided and joined to the wet MFC layer (1) positioned on the metal belt support (2) to form a laminate structure (6). The laminate structure (6) positioned on the metal belt support (2) is dewatered to form the laminate (8). The dewatering includes at least one drying step including drying by at least one non-contact drying device (7), and the metal belt support (2) is heated during at least one drying step. The present invention also relates to the laminate (8) and a packaging material comprising the laminate (8).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminate including a paper substrate and a barrier layer, the barrier layer being a microfibrillated cellulose (MFC) layer, and the laminate having good barrier properties such as oxygen barrier properties and water vapor barrier properties, and good adhesiveness between the paper substrate and the barrier layer. Further, the present disclosure relates to a laminate including a paper substrate and an MFC layer, a packaging material including the laminate, and the use of the laminate in a packaging material.

Background Art

[0002] In many applications of paper packaging, barrier properties against oxygen, grease, water vapor, and / or aroma are required. However, paper inherently does not have these properties. Most commonly, the barrier properties of a paper substrate are created by adding one or more barrier coatings and / or laminated barrier layers based on plastic 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 the paper that was originally biodegradable may become non-biodegradable and, in some cases, non-recyclable. Further, in order to improve a barrier including 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 the polymer and / or various polymer layers used. Therefore, it becomes even more difficult to decompose and recycle the fiber portion of the paper substrate provided with such an improved barrier. Also, in the case of lamination, an adhesive may be required to adhere the barrier layer to the paper to form a laminate, which further increases the amount and number of non-renewable and / or non-recyclable components in the package laminate.

[0003] Recently, microfibrillated cellulose (MFC) films have been developed that form dense, transparent or translucent films or coatings with barrier properties such as oxygen, aroma, and grease barrier properties by fibrillating cellulose fibers to obtain cellulose nanofibers, suspending them, for example, in water, and then reconstituting and recombining them. MFC films and coatings are not only recyclable and biodegradable but also based on renewable raw materials. In many cases, MFC films and coatings require additives such as film formers, dispersants, plasticizers, softeners, rheology modifiers, and / or mineral fillers. It is important to retain these additives within the MFC film or coating.

[0004] To provide an MFC film on a paper substrate, a self-standing MFC film can be produced from an MFC suspension and then laminated to the paper substrate using, for example, one or more adhesive layers.

[0005] One approach for producing a self-standing MFC film from an MFC suspension is to use the film casting method, i.e., casting the MFC suspension onto a non-porous support such as a plastic or metal support to form a film, and then dehydrating and / or drying the film. The casting method has been demonstrated to be capable of producing MFC films with very smooth surfaces having excellent barrier properties such as oxygen barrier properties and / or water vapor barrier properties.

[0006] Another way to produce self - standing MFC films from MFC suspensions is to use wet - laying techniques, i.e., applying a layer of the MFC suspension onto a dewatering wire or membrane and dewatering it on the wire or membrane by vacuum and / or gravity and / or capillary dewatering and / or press dewatering. However, one of the drawbacks 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, retention agents and / or flocculants may be required to prevent the removal of 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 cause clogging of the wire or membrane during dewatering. Also, other very small dissolved or solid particles dispersed in the aqueous phase of the MFC suspension, such as mineral fillers, tend to penetrate through the wire or membrane during the dewatering step.

[0007] Self - standing MFC films produced by the casting method or the wet - laying method have low elasticity, which may make it difficult to handle the web in lamination. Furthermore, lamination of the self - standing MFC film to a paper substrate requires an adhesive to adhere the MFC film to the paper substrate.

[0008] Alternatively, an MFC coating or barrier layer can also be directly produced on a paper substrate by coating an MFC suspension on the paper substrate by coating techniques such as size press or film press, spraying, blade coating, rod coating or curtain coating. However, due to the high viscosity of the MFC suspension, it may be difficult to apply the MFC suspension to the paper substrate by coating techniques. Also, since a large amount of water is added, especially in the case of low - basis - weight substrates, the coating process becomes very difficult.

[0009] Therefore, there is still room for improvement in the manufacturing method of a laminate including a paper substrate and a barrier layer (where the barrier layer is an MFC layer).

[0010] Description of the Invention An object of the present invention is an improved method for manufacturing a laminate including a paper substrate and a barrier layer, where the barrier layer is an MFC layer, and the laminate has good barrier properties such as oxygen barrier properties and water vapor barrier properties, and good adhesiveness between the paper substrate and the barrier layer, and provides a method for eliminating or reducing at least some of the drawbacks of the prior art methods.

[0011] 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.

[0012] 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 for manufacturing a laminate including a paper substrate and a microfibrillated cellulose (MFC) layer, comprising: - providing an MFC suspension including 50% to 100% by weight of MFC and a suspension medium based on the total dry weight; - forming a wet MFC layer by casting the MFC suspension onto a casting surface of a metal belt support, wherein the formed wet MFC layer has a dry content of 1% to 40% by weight, preferably 2% to 25% by weight, more preferably 3% to 15% by weight, and most preferably 3.5% to 8% by weight, and the formed wet MFC layer is formed from an amount of the MFC suspension corresponding to 8 to 70 g / m 2 , preferably 10 to 50 g / m 2 , most preferably 15 to 40 g / m 2 of the dry weight, to form a wet MFC layer; - Providing a paper-based substrate web, wherein the paper-based substrate of the paper-based substrate web has a Gurley-Hill air permeability value of less than 10,000 seconds / 100 ml, preferably less than 5,000 seconds / 100 ml, more preferably less than 1,000 seconds / 100 ml, as measured in accordance with standard ISO 5636-5:2013, to provide a paper-based substrate web; - Joining the paper-based substrate web to the wet MFC layer positioned on the casting surface of the metal belt support to form a laminate structure positioned on the casting surface of the metal belt support, wherein the wet MFC layer has a dry content of 1 to 40 wt%, preferably 2 to 25 wt%, more preferably 3 to 15 wt%, most preferably 3.5 to 8 wt%, and the paper-based substrate web has a dry content of at least 70 wt%, preferably at least 80 wt%, most preferably at least 85 wt% when joined to the wet MFC layer; - Subjecting the laminate structure to moisture removal to form the laminate comprising the paper-based substrate and the MFC layer, wherein the formed laminate has an average dry content of at least 80 wt%, the laminate structure is positioned on the casting surface of the metal belt support during moisture removal, the moisture removal includes at least one drying step, the drying step includes drying the laminate structure by at least one non-contact drying device disposed on the opposite side of the metal belt support of the laminate structure, and the metal belt support is heated during at least one drying step; - Separating the laminate from the metal belt support A method comprising.

[0014] Surprisingly, it has been found that a laminate comprising a paper substrate and a barrier layer, having good barrier properties such as oxygen barrier properties and water vapor barrier properties, and good adhesion between the paper substrate and the MFC layer, can be produced, wherein the barrier layer is an MFC layer. This laminate is produced by forming a wet MFC layer from the above MFC suspension by casting on the casting surface of a metal belt support, bonding the wet MFC layer having the above dry content to a paper substrate web having the above air permeability and dry content, and then drying the laminate structure using non-contact drying equipment positioned on the laminate structure side opposite the metal belt support, in combination with contact drying by heating the metal belt support, to remove water from the laminate structure. The MFC layer is held on the casting surface of the metal belt support on which it is formed during the bonding step and water removal.

[0015] In particular, surprisingly, according to a first aspect of the present disclosure, by using non-contact drying equipment positioned on the laminate structure side opposite the metal belt support and heating the metal belt support for contact drying, it has been found that it is possible to dry the wet MFC layer of the laminate structure positioned on the casting release surface of the metal belt support, i.e., positioned between the metal belt support and the paper substrate. Thus, surprisingly, it has been found that by using non-contact drying equipment in combination with contact drying by heating the metal belt support, it is possible to dry a wet MFC layer containing a relatively large amount of moisture by water and water vapor permeating through the paper substrate.

[0016] Also, by combining a non-contact drying device on one side of the laminate structure and a contact drying device (heated metal belt support) on the other side of the laminate structure, the wet MFC layer of the laminate structure can be efficiently dried. The non-contact drying device efficiently removes water and water vapor from the side surface of the laminate structure opposite to the metal belt support, and the drying rate, that is, the penetration rate of water and water vapor into the paper substrate, is improved by heating the metal belt support. Due to efficient drying, an MFC layer with a thickness necessary to produce good barrier properties can be provided on the paper substrate in a highly productive manner.

[0017] According to the first aspect of the present invention, by laminating a wet MFC layer with a paper substrate web and then drying the laminate structure, the difficulty of handling a self-supporting dry MFC film with low elasticity in the lamination process with the paper substrate is avoided.

[0018] Furthermore, surprisingly, it has been found that by using the method according to the first aspect of the present invention, strong adhesion of the MFC layer to the surface of the paper substrate can be obtained. Without being bound by any theory, the strong adhesion is considered to be due to mechanical connection by fibers and fibrils, ionic interactions, and / or other types of intermolecular interactions. Therefore, the need to use an adhesive between the paper substrate and the MFC layer is reduced or eliminated.

[0019] By using the method according to the first aspect of the present disclosure, the MFC layer is held on the casting surface of the metal belt support from casting to after drying and is then separated or peeled off from the metal belt support, so that a laminate can be efficiently manufactured. Due to the fact that the MFC layer is formed on the casting surface of the metal belt support and held until after drying, the minimum fibril fraction in the MFC layer and the material efficiency and retention of, for example, nanofillers and water-soluble additives (if present) are also promoted, and the use of retention agents and / or flocculating drainage agents in the MFC suspension is reduced or eliminated. The minimum fibril fraction contributes positively to the barrier properties. Also, the retention of additives is advantageous compared to wire dewatering where the retention of water-soluble additives is limited. Further, a high smoothness and uniformity are obtained on the surface of the MFC layer that contacts the metal belt support. The use of the metal belt support is also advantageous for, for example, the dimensional stability of the MFC layer for adhesion to the metal belt support. Further, the advantage of the method of the first aspect is that since the MFC layer is held on the casting surface of the metal belt support from casting to after drying, drying is suppressed and optional dewatering is suppressed, so that curling can be at least substantially eliminated or controlled.

[0020] Also, the method according to the first aspect means that a laminate having good barrier properties such as oxygen barrier properties and water vapor barrier properties can be manufactured from almost completely bio-based materials, preferably cellulose-based materials, thereby facilitating the recycling of used laminates and enabling the provision of a barrier substrate that can be regarded as a single-component substrate (less than 5% of other additives or plastics), and reducing carbon dioxide emissions. The laminate may also have excellent barrier properties against oil, grease, and / or aroma.

[0021] As described above, the method of the first aspect of the present disclosure includes providing an MFC suspension containing 50 wt% to 100 wt% of MFC based on the total dry weight of the MFC suspension. The MFC suspension is composed of a suspension medium in which a mixture of a cellulose-based material and optional additional components and / or additives is suspended. Preferably, the MFC suspension is an aqueous suspension containing an aqueous suspension mixture of a cellulose-based material and optional additional components and / or additives.

[0022] In the context of a patent application, microfibrillated cellulose (MFC) shall mean cellulose particles, fibers or fibrils with a width or diameter of 20 nm to 1000 nm.

[0023] There are various methods for producing MFC, such as purification one or more times, purification after preliminary hydrolysis, high-shear decomposition or fibril liberation. To achieve both energy efficiency and sustainability in the production of MFC, usually one or more pretreatment steps are required. Therefore, the cellulose fibers of the pulp used in the production 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 before fibrillation, in which case the cellulose molecules contain functional groups other than (or more than) the functional groups 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.

[0024] MFC can be manufactured from hardwood and / or softwood wood 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.

[0025] As described above, the MFC suspension used in the method of the first aspect contains MFC between 50% and 100% by weight based on the total dry weight. In some embodiments, the MFC suspension contains MFC between 60% and 100% by weight, preferably between 70% and 100% by weight, more preferably between 80% and 100% by weight, based on the total dry weight. The MFC layer of the laminate produced by the method of the first aspect can contain MFC between 50% and 100% by weight, for example between 60% and 100% by weight, preferably between 70% and 100% by weight, more preferably between 80% and 100% by weight, based on the total dry weight, which is related to the amount of MFC in the MFC layer itself.

[0026] The MFC of the MFC suspension may be composed of one or more MFC fractions. In some embodiments, the MFC of the MFC suspension contains one fraction of fine-grade MFC. In some embodiments, the MFC of the MFC suspension contains two or more fractions of MFC of different fine grades. In some embodiments, the MFC of the MFC suspension contains 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 Schopper-Riegler value of the coarse MFC is usually 80 - 100 SR°, for example, 80 - 99 SR°, 90 - 99 SR°, or 95 - 99 SR°, while the fine MFC is fibrillated to a Schopper-Riegler value exceeding the measurement range determined by standard ISO 5267-1 (the theoretical value is about 100 SR° or more). In some embodiments, the fine-grade MFC is chemically derivatized such as carboxymethylated MFC.

[0027] In addition to MFC, the MFC suspension may contain film-forming agents, dispersants, fillers, pigments, wet strength improvers, cross-linking agents, plasticizers, softeners, humectants, adhesion primers, wetting agents, biocides, colorants, defoamers, hydrophobizing agents such as alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), waxes, rosin resins, 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, starches, silica, precipitated calcium carbonate, cationic polysaccharides, and rheology modifiers. Therefore, these additives or chemicals may be process chemicals or film performance chemicals added to impart specific properties to the final MFC layer and / or to facilitate the production of the MFC layer.

[0028] In some embodiments, the MFC suspension further comprises at least one additive selected from the group consisting of film-forming agents, dispersants, plasticizers, softeners, mineral additives, humectants, cross-linking agents, light or UV blockers, lubricants, dyes, and rheology modifiers.

[0029] In some embodiments, the suspension medium is water or contains water, and the MFC suspension further comprises at least one water-soluble additive. In some embodiments, the suspension medium is water or contains water, and the MFC suspension further comprises at least one water-soluble polymer capable of forming a film and / or improving the bonding between cellulose fibers. Typical examples of such polymers include natural gums or polysaccharides or their derivatives such as carboxymethylated cellulose (CMC), starch, polyvinyl alcohol (PVOH), or analogs thereof.

[0030] In some embodiments, the suspension medium is water or contains water, and the MFC suspension further comprises at least one water-soluble additive selected from the following group: PVOH and its derivatives and analogs, starch, CMC, sorbitol, polyethylene glycol.

[0031] The 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. The PVOH may have a degree of hydrolysis in the range of, for example, 80 to 99 mol%, preferably in the range of 88 to 99 mol%.

[0032] According to the first aspect of the method, until after drying, the MFC layer is formed and held on a metal belt support which is a non-porous support, so that the additive containing a water-soluble additive is retained to a greater extent in the layer compared to the case where a porous support is used. Also, the additive, particularly the water-soluble additive, may be carried to the paper substrate together with water during the removal of water through the paper substrate, thereby possibly improving the properties of the paper substrate. In an embodiment where starch is used as an additive in the MFC suspension, the starch is carried to the paper substrate or the boundary region between the MFC layer and the paper substrate together with water during water removal, and can promote the adhesion between the formed MFC layer and the paper substrate.

[0033] In some embodiments, the MFC suspension does not contain a retention agent and a flocculant. According to the first aspect of this method, until after drying, the MFC layer is formed and held on a metal belt support which is a non-porous support, so the need for a retention agent and / or a flocculant may be reduced or eliminated.

[0034] In some embodiments, the MFC suspension contains an additive of 50 wt% or less, for example 40 wt% or less, 30 wt% or less, 25 wt% or less, based on the total dry weight of the MFC film. For example, the MFC suspension can contain an additive of 1 to 50 wt%, or 1 to 40 wt%, or 1 to 30 wt%, or 1 to 25 wt%, based on the total dry weight of the MFC film.

[0035] In some embodiments, the MFC suspension contains a plasticizer such as sorbitol, glycol or other polyols in an amount of 0.5 to 20 wt% based on the total dry weight.

[0036] In some embodiments, the MFC suspension contains up to 20% of a mineral filler (conventional filler or nanofiller) such as non-flaky minerals like bentonite, kaolin, talcum, mica, montmorillonite, organic clay, graphene, graphene oxide, calcium carbonate (PCC or GCC), silicon dioxide, gypsum, or combinations thereof.

[0037] As described above, the method of the first aspect includes a step of forming, for example, a wet MFC layer on the casting surface of the metal belt support. The wet MFC layer is formed on the casting surface of the metal belt support by casting an MFC suspension on the metal belt support by a method such as cast coating.

[0038] The term "casting", when used for film formation or layer formation, refers to a known term for a method of depositing a suspension on a support (usually an endless support) by contact or non-contact deposition and leveling methods to form a wet web or layer. Examples of such deposition and flattening methods include curtain coating / application, slot die casting, or a method of applying an MFC suspension using a spray or similar device and flattening it using a doctor blade or rod.

[0039] It is important to apply the MFC suspension to the casting surface of the metal belt support so that a homogeneous wet MFC layer is formed, that is, the wet MFC layer should be as homogeneous as possible and have as uniform a thickness as possible. As described above, the formed wet MFC layer has a basis weight (basis weight) of 8 - 70 g / m 2 , for example, 9 - 70 g / m 2 or 10 - 70 g / m 2 , preferably 10 - 50 g / m 2 , most preferably 15 - 40 g / m 2 and is formed from an amount of MFC suspension corresponding thereto. The dried MFC layer is preferably semi-transparent.

[0040] According to the method of the first aspect, the formed wet MFC layer has a dry content of 1 to 40% by weight, preferably 2 to 25% by weight, more preferably 3 to 15% by weight, and most preferably 3.5 to 8% by weight during formation (i.e., during application to the metal belt support or immediately after application / formation on the metal belt support). Therefore, the dry content of the MFC suspension is 1 to 40% by weight, preferably 2 to 25% by weight, more preferably 3 to 15% by weight, and most preferably 3.5 to 8% by weight.

[0041] The metal belt support on which the wet MFC layer is formed is a metal belt, i.e., a belt-shaped support made of metal, such as steel. The metal belt support may be a continuous conveyor belt. As described above, the metal belt support has a casting surface on which the MFC suspension is cast. Preferably, the metal belt support has a smooth casting surface, i.e., a smooth surface on which the MFC suspension is cast. In some embodiments, the metal belt support has a vent sensor roughness of 200 ml / min or less, preferably 150 ml / min or less, more preferably 100 ml / min or less when measured according to ISO 8791-2:2013, and / or a Parker Print Surf (PPS) smoothness of the surface of the generated MFC layer that contacts the casting surface of the metal belt support when measured at a clamping pressure of 1.0 MPa in accordance with ISO 8791-4 is 10 μm or less, preferably 0.1 to 5 μm, and most preferably 0.3 to 5 μm. Alternatively, the casting surface of the metal belt support is textured. Also, the metal belt support has a back surface on the opposite side of the casting surface.

[0042] Preferably, the MFC suspension is in direct contact with the casting surface of the metal belt support after casting. However, in some embodiments, a coating for controlling adhesion and peelability can be applied to the casting surface of the metal belt support before casting the MFC suspension onto the casting surface. Examples of such coatings are poly(aminoamide) epihalohydrin polymers (PAE) resins, polyvinyl alcohol resins (PVOH), polyvinyl alcohol copolymers, starch, ethylene glycol, vegetable oils, fatty acids, and sugar alcohols.

[0043] The formed wet MFC layer can be a web composed of one or more layers or sub-layers made in one or more casting units, or a single-layer or multi-layer web. Thus, in some embodiments, the wet MFC layer includes a single web layer or two or more web layers formed on top of each other.

[0044] As described above, the method of the first aspect includes the step of providing a paper substrate web. The paper substrate of the paper substrate web has a Gurley-Hill air permeability value of less than 10,000 seconds / 100 ml, preferably less than 5,000 seconds / 100 ml, more preferably less than 1,000 seconds / 100 ml or 200 seconds / 100 ml when measured in accordance with Standard ISO 5636-5:2013. The Gurley-Hill air permeability value of the paper substrate less than 10,000 seconds / 100 ml facilitates the movement of moisture from the wet MFC layer through the paper substrate when removing moisture according to the first aspect of the method.

[0045] Paper generally refers to a thin sheet made from wood pulp or other fibrous materials including cellulose fibers, and is used for writing, drawing, or printing on packaging materials, or as a packaging material. The paper substrate 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 or recycled paper. The paper used as a substrate according to the present disclosure is manufactured using methods known in the art.

[0046] 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 10 to 100 g / m 2 .

[0047] The paper substrate used in the method of the first aspect may include one layer or multiple layers. In one embodiment, the paper substrate includes 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.

[0048] The paper substrate can be subjected to surface sizing or surface treatment on at least one side of the paper substrate. Such surface sizing or surface treatment forms part of the paper substrate in the context of the present disclosure.

[0049] As described above, the method of the first aspect includes the step of joining a web of the paper substrate to a wet MFC layer positioned on the casting surface of the metal belt support to form a laminate structure positioned on the casting surface of the metal belt support. Thus, the joining step means that the paper substrate web is joined to the wet MFC layer already positioned on the casting surface of the metal belt support, that is, the paper substrate web is joined to the opposite side of the wet MFC layer compared to the metal belt support. By the joining step, a laminate structure including the wet MFC layer and the paper substrate web is formed. The wet MFC layer is positioned between the metal belt support and the paper substrate web after joining.

[0050] According to the method of the first aspect, when the paper substrate web is joined to the wet MFC layer, the wet MFC layer has a dry content of 1 to 40% by weight, preferably 2 to 25% by weight, more preferably 3 to 15% by weight, and most preferably 3.5 to 8% by weight. When the paper substrate web is joined to the wet MFC layer, it has a dry content of at least 70% by weight, preferably at least 80% by weight, and most preferably at least 85% by weight. The specified range of dry content facilitates penetration into the paper substrate and at the same time enables rapid removal of moisture from the wet MFC layer through the paper substrate. The dry contents of the wet MFC layer and the paper substrate web can be measured in accordance with standard ISO 638 or by spectrometry. Alternatively, the dry content can also be measured by using a device or instrument used to measure the moisture content and calculating the dry content from the measured value of the moisture content. The dry content and the moisture content can be measured under ambient conditions.

[0051] As described above, the method of the first aspect includes subjecting a laminate structure positioned on the casting surface of a metal belt support to water removal to form a laminate including a paper substrate and an MFC layer. The average dry content of the formed laminate is at least 80% by weight, for example 80 to 99.9% by weight, preferably 85 to 99% by weight, 86 to 98% by weight, 90 to 99.5% by weight, or 92 to 99% by weight. Thus, during the step of removing water, the moisture is removed such that the laminate has a predetermined average dry content, i.e., the moisture is removed until a predetermined average dry content is obtained and the laminate is formed. The average dry content can be measured under ambient conditions. The average dry content can be measured by spectroscopy (NIR, IR), optical methods, microwave-based methods, radiography, electrical methods, dielectric methods or, for example, using terahertz technology. Alternatively, the average dry content of the laminate can also be measured in accordance with standard ISO 638. In another alternative, the average moisture content can be measured to determine the average dry content. The moisture content can be measured under ambient conditions. The laminate structure is positioned on the casting surface of the metal belt support during water removal. The water removal includes at least one drying step, i.e., the water removal can include one, two, three, or more drying steps. The laminate structure is dried by non-contact drying by at least one non-contact drying device disposed on the surface of the laminate structure on the opposite side of the metal belt support between each of the at least one drying steps (i.e., disposed at a position away from the laminate structure on the laminate structure side opposite the metal belt support). Also, the metal belt support is heated during at least one drying step.

[0052] Accordingly, the laminate structure is dried by a combination of non-contact drying by at least one non-contact drying device and heating of the metal belt support during each drying step. Heating the laminate structure by heating the metal belt support during non-contact drying of the laminate structure means that contact drying of the laminate structure is also provided on the wet MFC layer side in contact with the metal belt support.

[0053] Accordingly, when the laminate structure is subjected to one of at least one drying step, the laminate structure is subjected to non-contact drying by at least one non-contact drying device and is positioned on the casting surface of the heated metal belt support. Accordingly, the laminate structure is dried by performing non-contact drying and contact drying simultaneously.

[0054] Accordingly, after the joining step, the laminate structure is dried in one or more drying steps by non-contact drying by one or more non-contact drying devices. The laminate structure is positioned on the casting surface of the metal belt support during non-contact drying. One or more non-contact drying devices are positioned on one side of the laminate structure (i.e., not in contact with the laminate structure), the metal belt support is positioned on the other side of the laminate structure (i.e., in contact with the MFC layer), and is heated during non-contact drying.

[0055] In some embodiments, during the drying step, the metal belt support is heated to a temperature above 30°C, preferably 30 - 150°C, more preferably 45 - 150°C, and even more preferably 60 - 100°C. For example, the metal belt support can be heated by steam heating of the metal belt, hot air, electric heating, induction heating, or radiant heat sources. Depending on the process configuration, the metal belt support can also be heated to a temperature within the above temperature range during other steps or parts of steps of the method of the first aspect, for example, during the step of forming the wet MFC layer and / or during an optional dehydration step and / or during an optional dehydration step. In some embodiments, the metal belt support is heated to a temperature within the above predetermined temperature range during all steps of the method of the first aspect or at least between the formation of the wet MFC layer on the metal belt support and the separation of the laminate from the metal belt support.

[0056] According to the method of the first aspect, since the wet MFC layer is positioned on the casting surface of the metal belt support and the paper substrate is positioned on the MFC layer surface on the opposite side of the metal belt support, in order to dry the wet MFC layer, water from the wet MFC layer needs to penetrate / move through the paper substrate. Surprisingly, a wet MFC layer containing a relatively large amount of water in a laminate structure positioned on the casting surface of the metal belt support according to the first aspect of the method can be dried by heating the metal belt support by using one or more non-contact drying devices positioned on the surface of the laminate structure on the opposite side of the metal belt support by water permeating through the paper substrate from the MFC layer and by a paper substrate having a Gurley-Hill air permeability of less than 10000 seconds / 100 ml.

[0057] Therefore, during at least one drying step of the method of the first aspect, by using one or more non-contact drying devices and heating the metal belt support, water penetrates / moves from the wet MFC layer through the paper substrate.

[0058] Also, by using the method of the first aspect, it was found that the MFC layer adheres strongly to the surface of the paper substrate. Without being bound by any theory, the strong adhesion is considered to be due to the mechanical connection of fibers and fibrils and / or intermolecular interactions. Therefore, the need to use an adhesive between the paper substrate and the MFC layer is reduced or eliminated.

[0059] Therefore, the paper substrate can be positioned directly on top of the wet MFC layer, i.e., in direct contact. Thus, in some embodiments, the provided laminate does not include an adhesive or an adhesion layer between the paper substrate and the MFC layer. Alternatively, an adhesive such as an adhesive chemical / agent or an adhesion-promoting chemical / agent, or an adhesion coating that further promotes adhesion, may be provided between the MFC layer and the paper substrate, i.e., on the wet MFC layer or on the paper substrate before bonding. For example, adhesion can be promoted by an anionic, cationic, or non-ionic polymer. The adhesive can be any adhesive commonly used in the manufacture of laminates for use as packaging products. The adhesive is typically provided in a liquid form such as a dispersion, emulsion, or solution. One or more adhesive layers can be provided between the paper substrate and the MFC layer. However, to prevent the transport of water and steam through the paper substrate, between the MFC layer and the paper substrate, only a small amount of adhesive such as less than 4 g / m 2 less than, less than 2 g / m 2 or only a small amount of adhesive such as 0.1 - 1.5 g / m 2 can be used. Alternatively, an adhesive that allows water and steam to pass through, such as an adhesive selected from natural rubbers or polysaccharides or their derivatives such as starch, CMC, methylcellulose, polyelectrolyte solutions, polyvinyl alcohol or its derivatives or analogs, needs to be used.

[0060] Each of the one or more non-contact drying devices may be any known suitable drying device based on non-contact drying technology. For example, each of the one or more non-contact drying devices may be selected from the group of hot gas impingement drying devices such as hot air impingement drying devices or hot steam impingement drying devices, air dryers, microwave drying devices, ultraviolet (UV) drying devices, electron beam drying devices, infrared (IR) drying devices, and near-infrared (NIR) drying devices. When multiple non-contact drying devices are used, these non-contact drying devices may be of the same type or different types.

[0061] As described above, the method of the first aspect includes the step of separating the laminate from the metal belt support, that is, separating (e.g., peeling) the dried laminate structure from the metal belt support after drying. The laminate may have an average dry content (i.e., in the thickness direction) of at least 80% by weight, such as 80 - 99.9% by weight, preferably 85 - 99% by weight, 86 - 98% by weight, 90 - 99.5% by weight, or 92 - 99% by weight at the time of separation.

[0062] In some embodiments, the laminate is further dried after being separated from the metal belt support. The further drying can be performed by non-contact drying, for example, by using one or more non-contact drying devices, which can be any known suitable drying device based on non-contact drying technology selected from the group of non-contact drying devices provided in connection with at least one drying step of the first aspect. Alternatively, or additionally, cylinder drying based on contact drying with a heated cylinder can also be utilized. One of the advantages of cylinder drying is that by contacting the paper side of the laminate with the heated cylinder, the moisture uniformity in the thickness direction of the laminate is improved.

[0063] The joining of the method of the first aspect can be carried out by positioning the paper substrate web, for example, on top of a wet MFC layer positioned on the casting surface of a metal belt support, for example, by unwinding the paper substrate web from a roll and guiding the paper substrate web to be positioned, for example, on top of a wet MFC layer positioned on the casting surface of a metal belt support.

[0064] Preferably, the metal belt support having the cast wet MFC layer and the paper substrate web are conveyed at the same or substantially the same speed prior to the joining step to avoid or minimize damage to the wet MFC layer during joining.

[0065] In some embodiments, the MFC layer and the paper substrate web, i.e., the metal belt support provided with the laminate structure, are downstream of at least one non-contact drying device that is at least partially guided around a guide roll to apply tension to the paper substrate and thus cause the paper substrate web to apply pressure to the wet MFC layer during joining.

[0066] In some embodiments, the MFC layer and the paper substrate web, i.e., the metal belt support provided with the laminate structure, are downstream of the joining of the wet MFC layer and the paper substrate web but upstream of the drying by at least one non-contact drying device, and are at least partially guided around a guide roll to apply tension to the paper substrate and cause the paper substrate web to apply pressure to the wet MFC layer during joining.

[0067] In some embodiments, a metal belt support having a wet MFC layer and a paper substrate web, i.e., a laminate structure, is conveyed through one or more press devices, such as one or more press nips formed by a press element and a counter element, to further enhance or facilitate the bond between the MFC layer and the paper substrate. The one or more press devices can be provided at any suitable location, such as downstream of at least one non-contact drying device. In some embodiments, the metal belt support with the laminate structure is conveyed through at least one press nip selected from the group consisting of a press nip located upstream of at least one non-contact drying device, a press nip located downstream of at least one non-contact drying device, and a group of press nips located between two separate non-contact drying devices. In some embodiments, the linear load of at least one press device is from 1 to 150 kN / m, preferably from 5 to 100 kN / m. In some embodiments, the absolute pressure of at least one press device is from 1 to 25000 kPa, preferably from 3 to 17000 kPa.

[0068] In some embodiments, the metal belt support provided with the laminate structure does not pass through any press device or press nip. Thus, in these embodiments, the method according to the first aspect is carried out without using any press device or press nip, i.e., without any press device or press nip.

[0069] In some embodiments, the method of the first aspect further includes the additional step of pre-drying the wet MFC layer positioned on the casting surface of the metal belt support before the step of joining the paper substrate web to the wet MFC layer. The pre-drying can be performed such that the dry content increases in units of 0 - 20%, preferably in units of 1 - 20% or 1 - 10%. In some embodiments, the step of pre-drying the wet MFC layer includes heating and drying the wet MFC layer such that the dry content of the wet MFC layer increases by evaporation before the step of joining the wet MFC layer to the paper substrate web. Heating may also reduce the viscosity of the liquid phase of the MFC suspension. Thus, in embodiments including the pre-drying step, the wet MFC layer is pre-dried before the joining step after the wet MFC layer is formed on the casting surface of the metal belt support. For example, when the dry content of the wet MFC layer is 1 - 20 wt%, or 1 - 15 wt%, or 1 - 10 wt%, it may be necessary to perform the pre-drying step. For example, the pre-drying can be performed by evaporation, impingement drying with hot gas / air, IR, NIR, microwave, thermal heating, other methods well-known in the art, or combinations thereof. For example, the heating can be performed by heating the metal belt support, i.e., the heated metal belt support can be utilized in the pre-drying step.

[0070] In some embodiments, the method of the first aspect further includes the step of dehydrating the wet MFC layer positioned on the casting surface of the metal belt support before the step of joining the paper substrate web to the wet MFC layer, and the dehydration of the wet MFC layer is performed by applying a press fabric in direct contact with the wet MFC layer and passing the wet MFC layer disposed between the press fabric and the metal belt support through a pressing device. These embodiments can also include the pre-drying step as described above before the dehydration step. The dehydration may be performed to remove 10 - 70%, such as 20 - 65% or 30 - 60% of the water in the wet MFC layer.

[0071] In some embodiments, the moisture removal of the method of the first aspect further includes dehydrating the laminate structure positioned on the casting surface of the metal belt support after the bonding step and before at least one drying step. The dehydration of the laminate structure is performed by applying a press fabric that directly contacts the paper base web of the laminate structure and passing the laminate structure disposed between the press fabric and the metal belt support through a pressing device. Alternatively, the dehydration of the laminate structure in these embodiments is performed by applying a porous wire or membrane that directly contacts the paper base web and passing the laminate structure disposed between the porous wire or membrane and the metal belt support through a vacuum dehydration device where the porous wire or membrane covers one or more vacuum cavities and water is removed from the laminate structure. The dehydration may be performed to remove 10-70%, such as 20-65% or 30-60%, of the water in the wet MFC layer.

[0072] In some embodiments, the moisture removal of the method of the first aspect includes at least two drying steps, and further includes dehydrating the laminate structure positioned on the casting surface of the metal belt support between the two drying steps. The dehydration of the laminate structure is performed by applying a press fabric that directly contacts the paper base web of the laminate structure and passing the laminate structure disposed between the press fabric and the metal belt support through a pressing device. Alternatively, the dehydration of the laminate structure in these embodiments is performed by applying a porous wire or membrane that directly contacts the paper base web and passing the laminate structure disposed between the porous wire or membrane and the metal belt support through a vacuum dehydration device where the porous wire or membrane covers one or more vacuum cavities and water is removed from the laminate structure.

[0073] A press fabric means a permeable fabric that can remove water from a web by either absorbing water or removing water through the fabric. The press fabric may be a press felt (dewatering felt). Press fabrics and press felts are commonly used today for dewatering paper and paperboard webs. Known suitable press fabrics or press felts can be used. Multiple press fabrics, i.e., two or more press fabrics continuous in the machine direction, can be used.

[0074] The fact that the MFC layer remains positioned on the casting surface of the metal belt support during at least one drying step and an optional dewatering step allows for controlled drying and dewatering of the MFC layer, and also means that a high smoothness and high density surface can be obtained. Controlled drying and optional controlled dewatering can mean no shrinkage or shrinkage of less than 10%, less than 5%, or less than 3%. Also, contact between the controlled drying and optional controlled dewatering and the metal belt support enables the transfer of a texture image from the metal belt support to the MFC layer. Furthermore, the method of the present disclosure enables the formation of a dense and compact single surface, i.e., the MFC layer surface, and the paper substrate provides strength and good convertibility.

[0075] In some embodiments, the paper substrate web is pre-wetted prior to the bonding step to pre-wet the paper substrate. Without being bound by any theory, it is believed that pre-wetting the paper substrate promotes capillary water transport from the wet MFC layer through the paper substrate for bonding. Also, during the step of drying the laminate structure, the pre-wetted paper substrate is dried to a new dimension under constrained conditions.

[0076] In some embodiments, the paper substrate web is optionally pre-heated prior to the bonding step, in combination with the aforementioned pre-wetting, to lower the viscosity of the water when entering the bonding step, improving the movement of water through the paper substrate.

[0077] In some embodiments, the obtained laminate has an oxygen transmission rate (OTR) of less than 15 cc / m 2 / 24 h, preferably less than 10 cc / m 2 / 24 h, and more preferably less than 5 cc / m 2 / 24 h, as measured in accordance with standard ASTM F1927-20 at a relative humidity of 50% and a temperature of 23°C.

[0078] In some embodiments, when the obtained laminate is measured in accordance with standard ASTM F1249-20 at a relative humidity of 50% and a temperature of 23°C, it has a water vapor transmission rate (WVTR) of less than 100 g / m 2 / 24 h, preferably less than 75 g / m 2 / 24 h, and more preferably less than 50 g / m 2 / 24 h. Thus, the laminate according to the present disclosure becomes an interesting and viable alternative to conventional materials using aluminum foil layers.

[0079] In some embodiments, the outermost surface of the MFC layer of the obtained laminate, i.e., the surface of the MFC layer that was in contact with the metal belt support, has a Bentsen roughness of 200 ml / min or less, preferably 150 ml / min or less or 100 ml / min or less, as measured in accordance with ISO 8791-2:2013, and / or a Parker Print Surf (PPS) smoothness of 10 μm or less, preferably 0.1 - 5 μm, most preferably 0.3 - 5 μm, as measured at a clamp pressure of 1.0 MPa in accordance with ISO 8791-4. High smoothness means that the laminate is suitable for vacuum deposition coating.

[0080] Vacuum coating, or vacuum deposition coating, refers to a family of processes used to deposit layers of metals, metal oxides, and other inorganic and organic compositions, typically atom by atom or molecule, onto solid surfaces. Multiple layers of the same or different materials can be combined. The 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 utilized. For example, a laminate according to the present disclosure may be provided with a vacuum coating layer comprising a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

[0081] In some embodiments, the resulting laminate has a thermal expansion coefficient of >50 J / m as measured by TAPPI 569. 2 , preferably >80 J / m 2 It has a Scott Bond value of

[0082] In some embodiments, the resulting laminate has a Z strength value, as measured by TAPPI 541, of >200 kPa, preferably >250 kPa.

[0083] As mentioned above, the dry basis weight (basis weight) of the MFC layer of the laminate is between 8 and 70 g / m2, measured according to ISO 536:2019. 2 , preferably 10 to 50 g / m 2 , and most preferably 15 to 40 g / m 2 It is.

[0084] In some embodiments, the MFC of the MFC suspension has a water retention value (WRV) of >120%, such as 150-350%, measured according to standard ISO 23714.

[0085] In some embodiments, the resulting laminate has at least 10 KIT values measured in accordance with standard ISO16532-2 when measured from the MFC layer side.

[0086] 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.

[0087] 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.

[0088] However, the laminate of the present invention can further be provided with an outermost polymer layer on one or both sides. The outermost polymer layer preferably provides mechanical protection such as liquid barrier properties and print protection to the laminate surface. It is also preferred that the outermost polymer layer is heat sealable.

[0089] In some embodiments, the laminate of the present disclosure is provided with a first outermost polymer layer, preferably a polyethylene layer, disposed on a paper substrate.

[0090] In some embodiments, the laminate of the present disclosure further comprises a second outermost polymer layer, preferably a polyethylene layer, disposed on the MFC layer.

[0091] The outermost polymer layer may, of course, prevent repulping, but may still be necessary or desirable in some applications. The additional polymer layer can be applied, for example, by extrusion coating, film lamination, or dispersion coating after forming the laminate.

[0092] The outermost polymer layer is generally composed of either a thermoplastic polymer commonly used for the protective layer and / or heat-sealing layer of paper-based packaging laminates, or a polymer particularly used for packaging boards for liquids or foods. Examples include polyethylene (PE), polyethylene terephthalate (PET), polyethylene furanoate (PEF), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), starch, cellulose, and the like. Polyolefins such as polyethylene, particularly low-density polyethylene (LDPE) and high-density polyethylene (HDPE), are the most common and versatile polymers used for packaging boards for liquids and foods. The polymers used are preferably manufactured from renewable materials.

[0093] 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. In some embodiments, the outermost polymer layer comprises polypropylene or polyethylene. In a preferred embodiment, the outermost polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0094] 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 from the extruded plastic itself, or the molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate.

[0095] 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 the outermost polymer layer is typically required. In some embodiments, the basis weight of the outermost polymer layer ranges from 6 to 50 g / m 2 , preferably from 8 to 50 g / m 2 or 10 to 25 g / m 2 or 10 to 20 g / m 2 or 12 to 20 g / m 2 and the outermost polymer layer is provided by extrusion coating. In some embodiments, the basis weight of the outermost polymer layer ranges from 2 to 10 g / m 2 and the outermost polymer layer is provided by a foamed film.

[0096] According to a second aspect of the present disclosure, a laminate comprising a paper substrate and an MFC layer is provided, which laminate is obtained by the method of the first aspect.

[0097] According to a third aspect of the present disclosure, a laminate comprising a paper substrate and an MFC layer, wherein the MFC layer contains 50 wt% to 100 wt% of MFC based on the total dry weight and has a basis weight of 8 to 70 g / m 2 , for example 9 to 70 g / m 2 or 10 to 70 g / m 2A laminate is provided having a basis weight of at least 80% by weight average dry content. The laminate has an oxygen transmission rate (OTR) of less than 15 cc / m 2 / 24 h, preferably less than 10 cc / m 2 / 24 h, more preferably less than 5 cc / m 2 / 24 h, measured in accordance with Standard ASTM F1249-20 at 50% relative humidity and 23 °C, and a water vapor transmission rate (WVTR) of less than 100 g / m 2 / 24 h, preferably less than 75 g / m 2 / 24 h, more preferably less than 50 g / m 2 / 24 h. In some embodiments, the laminate does not include a laminate adhesive or an adhesion layer between the paper substrate and the MFC layer, i.e., the laminate does not include a laminate adhesive and an adhesion layer between the paper substrate and the MFC layer.

[0098] Preferably, the basis weight of the paper substrate ranges from 10 to 200 g / m 2 and more preferably from 10 to 100 g / m 2 . The paper substrate may have a filler content of 0 to 20% by weight, such as 1 to 20% by weight or 3 to 15% by weight.

[0099] In some embodiments, the outermost surface of the MFC layer of the laminate of the third aspect has a Bentsen roughness of 200 ml / min or less, preferably 150 ml / min or less, more preferably 100 ml / min or less, measured in accordance with ISO 8791-2:2013, and / or a PPS smoothness of 10 μm or less, preferably 0.1 to 5 μm, most preferably 0.3 to 5 μm, measured at a clamp pressure of 1.0 MPa in accordance with ISO 8791-4.

[0100] The laminate, MFC layer and paper substrate according to the third aspect can be further defined as described above with reference to the method of the first aspect.

[0101] The laminates of the second and third aspects can be used as is or combined with one or more additional layers such as one or more additional paper or cardboard layers 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, an outermost polymer layer (corresponding to the above-described outermost polymer layer) can be provided on one or both sides as needed. Other examples of additional layers that can be combined with the laminate obtained by the method of the first aspect include additional polymer layers having a plurality of polymers 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.

[0102] For example, the laminate can be used as a packaging material, such as for food or liquid packaging, or in packaging materials. For example, the laminate can be part of a flexible packaging material such as a stand-up pouch or bag. Thus, the laminate can be used as the bag material for a box when packaging dry foods such as cereal. Further, the 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 can also be included in, for example, closures, lids, or labels. The laminate 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 containing the laminate obtained by the method of the first aspect or the laminate according to the third aspect.

[0103] According to a fourth aspect of the present disclosure, a method for manufacturing a packaging material is provided, the method including: i) providing a base layer of paper or cardboard; and ii) laminating a laminate according to the second or third aspect to the base layer of paper or cardboard using at least one adhesive layer to obtain a packaging material.

[0104] As described above, 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 material for packaging.

[0105] 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 typically has 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 typically have a density at least 100 kg / m 3 3 higher than that of the intermediate layer, preferably at least 200 kg / m 3 3 higher.

[0106] The base layer of the paper or paperboard can be made from pulp from virgin fibers, such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from waste paper or recycled paper. In addition to the base layer of paper or paperboard and the laminate according to the second or third aspect, the packaging material can include additional layers or coatings designed to improve the performance and / or appearance of the packaging material.

[0107] The packaging material usually has a first outermost surface intended to function as the outer surface or printing surface, and a second outermost surface intended to function as the inner surface of the packaging container. It is preferable that the side surface of the base layer of the paper or paperboard constituting the laminate of the present invention is intended to function as the inner surface of the packaging container.

[0108] In some embodiments, the basis weight of the paper or paperboard base layer is at least 100 g / m 2 . In some embodiments, the paper or paperboard base layer is at least 150 g / m 2 , 200 g / m 2 , 250 g / m 2 , 300 g / m 2 , 350 g / m 2 , or 400 g / m 2 . The basis weight of the paper or paperboard base layer is preferably 1000 g / m 2 , 800 g / m 2 , or less than 600 g / m 2 . Unless otherwise specified, the basis weight is determined in accordance with standard ISO 536.

[0109] In some embodiments, the paper or paperboard base layer has a density of less than 700 kg / m 3 , preferably less than 600 kg / m 3 . Unless otherwise specified, the density is determined in accordance with standard ISO 534.

[0110] The paper or paperboard base layer may be a single layer of paperboard or a multi-layer of paperboard. In some embodiments, the paper or paperboard base layer is a multi-layer paperboard. In some embodiments, the paper or paperboard base layer is a multi-layer paperboard composed of two or more layers. In some embodiments, the paper or paperboard base layer is a multi-layer paperboard composed of three or more layers. In some embodiments, the paper or paperboard base layer is a multi-layer paperboard composed of a low-density intermediate layer sandwiched between two high-density outer layers.

[0111] In some embodiments, the paper or paperboard base layer is a foamed paperboard. In some embodiments where the paper or paperboard base layer is a multi-layer paperboard, at least one of the layers, preferably the intermediate layer, is formed as a foam.

[0112] The tie layer can generally include any suitable adhesive commonly used in paper or paperboard-based packaging laminates, or adhesives specifically used for liquid or food packaging boards. In the present invention, various types of adhesives and adhesive coating methods can be used.

[0113] The tie layer may include one or more adhesive polymers. The tie layer may consist of only one or more adhesive polymers, or may further include other additives for improving the properties of the adhesive layer. In some embodiments, the tie layer includes at least 50% by weight of an adhesive polymer or a mixture of adhesive polymers based on the dry weight. In some embodiments, the tie layer includes or consists of one or more adhesive polymers selected from the group consisting of polyolefins, polyesters, polyurethanes, and acrylic copolymers. In some embodiments, the bonding layer includes or consists of one or more of polypropylene and polyethylene, such as low-density polyethylene (LDPE) or high-density polyethylene (HDPE). In some embodiments, the adhesive layer includes or consists of a component selected from an adhesive thermoplastic polymer such as a modified polyolefin mainly based on LDPE or LLDPE copolymer, or a graft copolymer having a functional group-containing monomer unit such as a carboxyl group or a glycidyl functional group, for example, a (meth)acrylic acid monomer or maleic anhydride (MAH) monomer, (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 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).

[0114] In some embodiments, the adhesion layer comprises at least 50% by weight of a water-soluble polymer or a mixture of water-soluble polymers, based on the dry weight. The water-soluble polymer of the adhesion layer is soluble in cold water for a certain period of time, or 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.

[0115] The adhesion layer can be applied by any suitable method known in the art. The total coating weight of one or more adhesion layers is usually in the range of 1 - 20 g / m 2 . In some embodiments, the total coat weight of one or more adhesion layers is in the range of 2 - 15 g / m 2 , more preferably in the range of 3 - 12 g / m 2 .

[0116] According to a fifth aspect of the present disclosure, a packaging material obtained by the method according to the fourth aspect is provided.

[0117] The packaging material may further have an outermost polymer layer provided on one or both sides. The outermost polymer layer preferably provides liquid barrier properties and mechanical protection of the packaging material surface. It is also preferred that the outermost polymer layer is heat-sealable. The polymer layer can be further defined as described above with reference to the first aspect.

[0118] In some embodiments, the packaging material includes a first outermost polymer layer, preferably a polyethylene layer, disposed on a base layer of paper or cardboard.

[0119] In some embodiments, the packaging material further includes a second outermost polymer layer, preferably a polyethylene layer, disposed on a laminate according to the second or third aspect.

[0120] According to a sixth aspect of the present disclosure, it is provided to use the laminate obtained by the method of the first aspect or the laminate according to the third aspect as a packaging material or within a packaging material.

[0121] Some examples of possible structures of the laminate according to the present disclosure are shown below. - A / B - C / A / B / C - C / A / B - A / B / C Wherein, A is a paper substrate, B is an MFC layer, and C is a sealing and / or liquid barrier such as a polyolefin.

[0122] Some examples of possible structures of the packaging material according to the present disclosure are shown below. - C / E / D / A / B / C - C / E / D / B / A / C Wherein, A is a paper substrate, B is an MFC layer, C is a sealing and / or liquid barrier such as a polyolefin, D is a tie layer, and E is a paper or paperboard-based layer.

Brief Description of the Drawings

[0123]

Figure 1

Figure 2

Figure 3

[0124] Detailed Description of the Drawings Figure 1 shows a schematic diagram of an embodiment of a method according to a first aspect of the present disclosure. By casting an MFC suspension with a casting unit 3, a wet MFC layer 1 is formed on the casting surface of a continuous metal belt support 2. A paper substrate web 4 is unwound from a roll 5 and guided and conveyed so as to be joined to the wet MFC layer 1, that is, positioned on top of the wet MFC layer positioned on the casting surface of the metal belt support 2, thereby forming a laminate structure 6. The laminate structure 6 formed by the joining and positioned on the casting surface of the metal belt support 2 is then subjected to moisture removal in a drying step. In the drying step, the laminate structure 6 is dried to form a laminate 8, and this drying is performed by non-contact drying with a non-contact drying device 7 in combination with heating of the metal belt support 2. The non-contact drying device 7 is disposed on the opposite side of the metal belt support 2 of the laminate structure 6. The metal belt support 2 is partially guided around a guide roll 9 on the downstream side of the non-contact drying, and the guide roll 9 applies tension to the paper substrate web 4 and applies pressure to the paper substrate web 4 against the wet MFC layer 1 during joining. After drying, the laminate 8 is separated from the metal belt support 2 and wound onto a roll 10.

[0125] Figure 2 shows a schematic diagram of another embodiment of the process according to the present disclosure. The embodiment of Figure 2 mainly corresponds to the embodiment of Figure 1. However, in the embodiment of Figure 2, the laminate structure 6 is dried by two non-contact drying devices 7 in combination with heating of the metal belt support 2, and the laminate structure 6 is conveyed through a press nip 11 during drying by the two non-contact drying devices 7.

[0126] Figure 3 shows a schematic diagram of another embodiment of the process according to the present disclosure. The embodiment of Figure 3 mainly corresponds to the embodiment of Figure 2. However, in the embodiment of Figure 3, the laminate structure 6 is dried by four non-contact drying devices 7 in combination with heating of the metal belt support 2, and the laminate structure 6 is conveyed through a press nip 11 after being dried by two non-contact drying devices 7.

[0127] Generally, products, materials, layers, and processes are described in terms 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.

[0128] 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 clear that such other modifications and changes can be made without departing from the spirit and scope of the present invention.

Examples

[0129] Examples Method In the following examples, the following measurement methods were used. · The Shopper-Leeglider value (SR°) was measured in accordance with Standard ISO 5267-1. · The basis weight was determined in accordance with ISO 536:2019. · The thickness (single sheet) was determined in accordance with ISO534. · The PPS 1.0 MPa smoothness was determined in accordance with ISO 8791-4. · The water vapor transmission rate (WVTR) was measured at a relative humidity of 50% and a temperature of 23 °C in accordance with Standard ASTM F1249-20. · The oxygen transmission rate (OTR) was measured at a relative humidity of 50% and a temperature of 23 °C in accordance with Standard ASTM F1927-20. · The air resistance (Gurley Hill, G-H) value was measured in accordance with ISO 5636-5. The maximum value by the device was 42,300 seconds / 100 ml. · The oil grease resistance (OGR) was determined in accordance with the modified ASTM F119-82 where the fabric to which grease is applied is normal cotton rather than cotton flannel rifle cleaning fabric. · The Cobb60 water absorption was measured for 60 seconds in accordance with SCAN P12:64. · The density was determined in accordance with ISO 534:2011. · The Bentzen roughness was determined in accordance with ISO 8791-2:2013. · The Scott bond was determined in accordance with TAPPI 569. · The Z-strength was determined in accordance with TAPPI 541.

[0130] Comparative Example 1 (Lamination without Adhesive) A barrier substrate containing highly purified cellulose pulp prepared on a dehydrated fabric (wire) was formed into a thin sheet and then dried. The basis weight of the sheet was 31.4 gsm, the thickness was 47 μm, the Gurley Hill value was 14,100 seconds / 100 ml, and it was confirmed that there was no barrier property. The OTR measured at 23°C / 50% RH was unacceptable, and the oil resistance and grease resistance measured with chicken fat (60°C) were also unacceptable. The substrate was not calendered and did not contain a surface sizing agent. The PPS 1.0 MPa smoothness was 6.23 μm (upper surface).

[0131] As described above, two sheets of the barrier substrate containing highly purified cellulose were exposed to 80% high humidity and then laminated using a calender nip at 80°C and a nip load of 80 kN / m. The following properties were obtained. Thickness (70 μm), Gurley Hill value 31,700 seconds / 100 ml, OTR - unacceptable, OGR 45 / 60 minutes (two parallel measurements). Therefore, although a slight increase in oil and grease resistance was measured, no improvement in the barrier was observed.

[0132] Comparative Example 2 (Lamination Using PVOH Adhesive) A 5% PVOH solution was coated on the dry barrier substrate of Comparative Example 1 to obtain a coating weight of approximately 5 gsm. This acted as an adhesive between two similar barrier substrates. After wet gravure lamination, the sheet was pressed at 80°C and 150 kN / m using a calender nip. A lamination with the following properties was obtained. Basis weight: 67.1 g / m 2, thickness 75um, Gurley value 42 300 seconds / 100ml (maximum value), PPS 1.0MPa 3.29um, OTR - failed, OGR 180 minutes. As expected, the wet gravure lamination of the two barrier substrates improves the barrier properties, especially in terms of oil resistance, grease resistance, and air permeability. However, the gas barrier property could not be improved.

[0133] Comparative Example 3 (Laminated Barrier Substrate and SC Paper) The dry barrier substrate of Comparative Example 1 was laminated to a 42 g / m 2 supercalendered (SC) machine paper having the following properties. Similar to Comparative Example 2, that is, using PVOH as the adhesive, PPS 1.0, smoothness 1.2μm, thickness 42μm, opacity 89%. The amount of PVOH adhesive was about 6 - 8 gsm. The pressing was performed using a cutting roll used to process the lamination 10 times. The resulting laminate did not have an OTR barrier, while the OGR was 120 minutes, but the sample had a very large curl.

[0134] Comparative Example 4 (Lamination Using PVOH Adhesive) The dry barrier substrate of Comparative Example 1 was laminated to a base cup stock (paperboard) in the same manner as described in Comparative Example 3. In this case, the OGR was 32 hours, and the OTR was 633 cc / m 2 / day and 510 cc / m 2 / day at 23°C / 50%RH (two parallel measurements). This indicates that the barrier properties are improved when using a thicker substrate.

[0135] Comparative Example 5 (Coating) The dry barrier substrate of Comparative Example 1 above was coated with only PVOH solution, and the coating weight was about 7.5 gsm. The resulting OTR value was 397 cc / m 2 / day at 23°C / 50%RH, and the OGR exceeded 24 hours. It was confirmed that the coating on this substrate exhibits excellent barrier properties.

[0136] Example 6 In this example, an MFC suspension containing 87 wt% MFC (obtained from enzymatically treated pulp and subsequently fibrillated into MFC) and 13 wt% sorbitol based on the dry content of the MFC suspension was used. The solid content of the MFC suspension was 3.6 wt%. The MFC suspension was cast onto a metal belt support to form a wet MFC layer. The thickness of the cast wet MFC layer was 490 - 540 μm, and the dry basis weight was 18 - 20 g / m 2 , the casting width was 500 mm, and the running speed was 3.3 m / min. A paper substrate of grade Endura MG Kraft 42 g / m 2 , with Gurley-Hill air permeability value of 13 s / 100 ml and Cobb60 water absorption of 36 g / m 2 was used. The web was rewound into a roll, and the paper substrate web was conveyed and guided onto the wet MFC layer positioned on the metal belt support and joined to the wet MFC layer to form a laminate structure positioned on the metal belt support. When joining the paper substrate web to the wet MFC layer, the dry content of the wet MFC layer was 3.6 wt%, and the dry content of the paper substrate web was 92 wt%. The laminate structure was dried by a combination of a hot air impingement dryer positioned on the laminate structure surface on the opposite side of the metal belt support, a steam-heated metal belt support, and an infrared dryer positioned on the laminate structure surface on the opposite side of the metal belt support and downstream of the hot air impingement device. The specific drying rate was about 50 kg(H2O) / m 2 hour. Drying was carried out until the dry content of the laminate structure reached 90 wt%, thereby forming a laminate containing the paper substrate and the MFC layer. Subsequently, the laminate was peeled off from the metal belt support. The results of Example 6 are shown in Table 1 below. Two different tests of 6:1 and 6:2 were performed. Furthermore, the measurements of OTR and WVTR were performed twice in each test.

[0137] The OTR and WVTR properties of the laminate indicate a high oxygen barrier and a moderate water vapor barrier for the laminate. Measurement of the smoothness of Bendtsen and PPS on the outer surface of the MFC (which was in contact with the metal belt support during laminate formation) showed that the surface of the MFC layer was smooth. The Scot Bond value and Z-strength value of the laminate indicate good adhesion between the MFC layer and the paper substrate (without adhesive). Overall, the results indicate a fully renewable, biodegradable, recyclable packaging product with excellent barrier properties. TIFF2025523639000002.tif162170

Claims

1. A method for producing a laminate (8) comprising a paper substrate and a microfibrillated cellulose (MFC) layer, - A step of providing an MFC suspension comprising 50% to 100% by weight of MFC based on total dry weight and a suspension medium, - A wet MFC layer (1) is formed by casting the MFC suspension onto the casting surface of the metal belt support (2), wherein the formed wet MFC layer (1) has a dry content of 1 to 40% by weight, preferably 2 to 25% by weight, more preferably 3 to 15% by weight, and most preferably 3.5 to 8% by weight, and the formed wet MFC layer (1) has a density of 8 to 70 g / m² ２ Preferably 10 to 50 g / m ２ Most preferably 15 to 40 g / m ２ To form a wet MFC layer (1) from an amount of the MFC suspension corresponding to the dry basis weight, - A step of providing a paper-based web (4), wherein the paper-based material of the paper-based web (4) has a Gurley-Hill air permeability value of less than 10,000 seconds / 100 ml, preferably less than 5,000 seconds / 100 ml, more preferably less than 1,000 seconds / 100 ml, measured in accordance with standard ISO 5636-5:2013, - A step of bonding the paper substrate web (4) to the wet MFC layer (1) positioned on the casting surface of the metal belt support (2) in order to form a laminate structure (6) positioned on the casting surface of the metal belt support (2), wherein the wet MFC layer (1) has a dry content of 1 to 40% by weight, preferably 2 to 25% by weight, more preferably 3 to 15% by weight, and most preferably 3.5 to 8% by weight, and the paper substrate web (4), when bonded to the wet MFC layer (1), has a dry content of at least 70% by weight, preferably at least 80% by weight, and most preferably at least 85% by weight, - A step of subjecting the laminate structure (6) to dewatering in order to form the laminate (8) comprising the paper substrate and the MFC layer, wherein the formed laminate (8) has an average dry content of at least 80% by weight, the laminate structure (6) is positioned on the casting surface of the metal belt support (2) during dewatering, and the dewatering includes at least one drying step, the drying step including subjecting the laminate structure (6) to drying by at least one non-contact drying device (7) positioned on the surface of the laminate structure (6) opposite to the metal belt support (2), the metal belt support (2) is heated during the at least one drying step, - The step of separating the laminate (8) from the metal belt support (2) A method that includes this.

2. The method according to claim 1, wherein the MFC suspension further comprises at least one additive selected from the group consisting of film-forming agents, dispersants, plasticizers, softeners, mineral additives, humectants, crosslinking agents, light or ultraviolet blocking agents, lubricants, dyes, and rheological modifiers.

3. The method according to claim 1 or 2, wherein the suspension medium is water or contains water, and the MFC suspension further comprises at least one water-soluble additive.

4. The method according to claim 3, wherein the MFC suspension comprises at least one water-soluble additive selected from the group consisting of polyvinyl alcohol and its derivatives and analogs, starch, carboxymethylcellulose, sorbitol, and polyethylene glycol.

5. The method according to claim 1 or 2, wherein the MFC suspension does not contain a retaining agent and a flocculant.

6. The method according to claim 1 or 2, wherein the non-contact drying device (7) is selected from the group consisting of a high-temperature gas impact drying device, a high-temperature steam impact drying device, an air dryer, a microwave drying device, an ultraviolet drying device, an electron beam drying device, an infrared drying device, and a near-infrared drying device.

7. The method according to claim 1 or 2, wherein the joining step is performed by positioning the paper substrate web (4) on the wet MFC layer (1) positioned on the casting surface of the metal belt support (2).

8. The method according to claim 7, wherein the metal belt support (2) on which the wet MFC layer (1) and the paper substrate web (4) are provided is at least partially guided around a guide roll (9) downstream of drying by at least one non-contact drying device (7) to provide pressure of the paper substrate web (4) onto the wet MFC layer (1) during bonding.

9. The method according to claim 1 or 2, wherein a metal belt support (2) having a laminate structure (6) is transported through at least one press nip (11) selected from the group consisting of a press nip positioned upstream of the at least one non-contact drying device (7), a press nip positioned downstream of the at least one non-contact drying device (7), and a press nip positioned between two separate non-contact drying devices (7).

10. The method according to claim 1 or 2, which is performed without using any pressnips.

11. The method according to claim 1 or 2, further comprising the step of pre-drying the wet MFC layer (1) positioned on the casting surface of the metal belt support (2) before the step of joining the paper substrate web (4) to the wet MFC layer (1).

12. The method according to claim 1 or 2, further comprising the step of dewatering the wet MFC layer (1) positioned on the casting surface of the metal belt support (2) prior to the step of joining the paper substrate web (4) to the wet MFC layer (1), wherein the step of dewatering the wet MFC layer (1) is performed by applying a press fabric in direct contact with the wet MFC layer (1) and passing the wet MFC layer (1) positioned between the press fabric and the metal belt support (2) through a press machine.

13. The moisture removal further includes a step of dewatering the laminate structure (6) positioned on the casting surface of the metal belt support (2) after the bonding step but before the at least one drying step, wherein the step of dewatering the laminate structure (6) is - Apply a press fabric that is in direct contact with the paper substrate web (4), and guide the laminate structure (6) placed between the press fabric and the metal belt support (2) through the press machine, or - A porous wire or membrane is applied to the paper substrate web (4) in direct contact with it, and the laminate structure (6) placed between the porous wire or membrane and the metal belt support (2) is guided through a vacuum dewatering device, wherein the porous wire or membrane covers one or more vacuum cavities, thereby removing water from the laminate structure (6) through the vacuum dewatering device. The method according to claim 1 or 2, as performed by...

14. The moisture removal comprises at least two drying steps, further comprising a step of dewatering the laminate structure (6) positioned on the casting surface of the metal belt support (2) during the drying steps, the step of dewatering the laminate structure (6) is - Apply a press fabric that is in direct contact with the paper substrate web (4), and guide the laminate structure (6) placed between the press fabric and the metal belt support (2) through the press machine, or - A porous wire or membrane is applied to the paper substrate web (4) in direct contact with it, and the laminate structure (6) placed between the porous wire or membrane and the metal belt support (2) is guided through a vacuum dewatering device, wherein the porous wire or membrane covers one or more vacuum cavities, thereby removing water from the laminate structure (6) through the vacuum dewatering device. The method according to claim 1 or 2, as performed by...

15. 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.

16. The method according to claim 1 or 2, wherein the formed wet MFC layer (1) consists of one layer or two or more web layers formed on each other.

17. The method according to claim 1 or 2, wherein the paper substrate web (4) is subjected to at least one pre-wetting step before the bonding step.

18. The laminate (8) measured 15 cc / m² at a relative humidity of 50% and 23°C in accordance with the ASTM F1927-20 standard. ２ Less than 24 hours, preferably 10 cc / m³ ２ Less than 24 hours, more preferably 5 cc / m³ ２ The method according to claim 1 or 2, having an oxygen permeability (OTR) of less than 24 hours.

19. The laminate (8) has a water vapor transmission rate (WVTR) of less than 100 g / m ２ / 24 hours, preferably less than 75 g / m ２ / 24 hours, more preferably less than 50 g / m ２ / 24 hours, measured in accordance with standard ASTM F1249-20 at a relative humidity of 50% and 23°C, according to the method of claim 1 or 2.

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