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 is provided that contains 25 to 90% by weight of MFC and 10 to 50% by weight of a filler component. The suspension has a dry content of 2.5 to 50% by weight. A wet MFC layer (1) is formed by casting the suspension onto a metal belt support (2). A paper substrate having a Gurley Hill air permeability of less than 10000 seconds / 100 ml is provided and joined to the wet MFC layer positioned on the metal belt support to form a laminate structure (7). The laminate structure positioned on the metal belt support is dewatered to form a laminate. The dewatering includes at least one drying step that includes drying by at least one non-contact drying device (9), and the metal belt support is heated during at least one drying step. The present invention also relates to the laminate and a packaging material comprising the laminate.

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 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, since non-renewable raw materials are used, the carbon dioxide emissions of the materials may increase, and paper that is 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 processing, 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 in water, for example, 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 manufactured from an MFC suspension and then laminated to the paper substrate using, for example, one or more adhesive layers.

[0005] One approach for manufacturing 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 method of manufacturing a self-standing MFC film from an MFC suspension is to use wet laying techniques, i.e., applying a layer of the MFC suspension to a dewatering wire or membrane and dewatering it on the wire or membrane by means of 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 type of MFC used, and very fine MFCs cannot be used because they may pass through or penetrate the wire or clog the wire or membrane during dewatering. Furthermore, 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 or wet laying method are of low elasticity, which may make web handling difficult in lamination. Furthermore, lamination of the self-standing MFC film to a paper substrate requires an adhesive to bond the MFC film to the paper substrate.

[0008] Alternatively, an MFC coating or barrier layer can also be formed directly on a paper substrate by coating the paper substrate with an MFC suspension by coating techniques such as size press or film press, spraying, blade coating, rod coating or curtain coating.

[0009] However, the solids content of the MFC suspension used to form the MFC coating is generally low. Therefore, a large amount of moisture is transferred to the receiving substrate, and particularly in the case of substrates with a low basis weight, the coating process becomes difficult. Furthermore, to dry the coating layer, a greater drying capacity is required. As the solids content of the MFC suspension increases, the difficulties associated with the transfer of a high content of water to the substrate are reduced, but when the viscosity increases significantly, the risk of problems with runnability caused by dilatancy or shear, such as streaks, beads, stalagmites, and / or non-uniform flattening after flattening of the applied MFC suspension, becomes high. Such problems are likely to occur particularly under high shear conditions due to the shear-thinning rheology of MFC.

[0010] Furthermore, when forming an MFC coating or layer directly on a paper substrate using a coating device equipped with a metering blade, high shear (stress) is applied to the coating between the blade and the paper substrate. At this point, the coating layer is very sensitive to shear-induced stress and fluidity, that is, there is a possibility of shear-induced defects occurring in the coating at this point. Also, the runnability of the coater depends greatly on the rheological properties of the coating at the actual solids content under the blade. As soon as the coating is applied on the paper substrate, water is removed from the coating by being absorbed into the paper substrate. Therefore, water is removed from the coating between the point of application of the coating on the paper substrate and the point of influence by the metering blade. Therefore, the solids content of the coating changes between the point of application and the point of shear applied by the blade, and the rheology and runnability may not be predictable.

[0011] To improve the barrier properties, fillers or pigments can be applied to the MFC suspension. However, including fillers and pigments, particularly high aspect ratio fillers and nano-fillers, in the MFC suspension increases the risk of shear-induced defects and rheological dilatancy.

[0012] Therefore, there is still room for improvement in the method of 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.

[0013] Description of the Invention An object of the present invention is to provide an improved method for manufacturing a laminate including a paper substrate and a barrier layer, where the barrier layer is an MFC layer, the laminate has good barrier properties such as oxygen barrier properties and good adhesion between the paper substrate and the barrier layer, and eliminates or reduces at least some of the disadvantages of the prior art methods.

[0014] 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.

[0015] The present invention is defined by the appended independent claims. Embodiments are described in the appended dependent claims and the following description.

[0016] According to a first aspect described herein, a method of manufacturing a laminate including a paper substrate and a microfibrillated cellulose (MFC) layer, comprising: - providing an MFC suspension comprising 25 to 90 wt% MFC based on the total dry weight of the MFC suspension, 10 to 50 wt% filler component based on the total dry weight of the MFC suspension, and a suspension medium, wherein the MFC suspension has a dry content of 2.5 to 50 wt%, preferably 3 to 45 wt%, most preferably 4 to 40 wt%; - forming a wet MFC layer by casting the MFC suspension onto the casting surface of a metal belt support; - Providing a paper substrate web, wherein the paper substrate of the paper substrate web has a Gurley 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 ISO5636-5:2013, and providing the paper substrate web; - Joining the paper 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 2.5 to 50 wt%, preferably 3 to 45 wt%, most preferably 4 to 40 wt%, and the paper 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 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, and subjecting to moisture removal; - Separating the laminate from the metal belt support A method comprising.

[0017] 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 good adhesion between the paper substrate and the MFC layer, can be produced, wherein the barrier layer is the 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, combining the wet MFC layer having the above dry content with a paper substrate web having the above air permeability and dry content, and then drying the laminate structure using a non-contact drying device positioned on the laminate structure side opposite the metal belt support, and removing water from the laminate structure by combining with contact drying by heating the metal belt support. 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.

[0018] In particular, surprisingly, according to the first aspect of the present disclosure, by using a non-contact drying device 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 surface of the metal belt support, that is, positioned between the metal belt support and the paper substrate. Thus, surprisingly, by using a non-contact drying device in combination with contact drying by heating the metal belt support, it has been found that it is possible to dry a wet MFC layer containing a relatively large amount of moisture with water and water vapor permeating through the paper substrate.

[0019] In addition, 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 on the opposite side of 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. Through 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.

[0020] According to a first aspect of the present invention, by bonding a wet MFC layer to 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.

[0021] 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 thought to be due to mechanical linkage 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.

[0022] 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 then separated or peeled 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 positively contributes to the barrier properties. Also, the retention of the water-soluble additive is advantageous compared to wire dewatering where the retention of the additive is limited. Further, a high smoothness and uniformity are obtained on the surface of the MFC layer in contact with the metal belt support. The use of the metal belt support is also advantageous, for example, for the dimensional stability of the MFC layer for adhesion to the metal belt support. Further, an 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.

[0023] Also, according to the method of the first aspect, when directly coating an MFC suspension onto a paper substrate using a conventional general coating technique, it is possible to avoid problems associated with the high shear (stress) applied to the MFC suspension during the application and leveling stages. When directly forming an MFC coating or layer onto a paper substrate using a coating device equipped with a metering blade, high shear (stress) is applied to the coating between the blade and the paper substrate. This is very sensitive to shear-induced stress and fluidity, that is, there is a possibility of shear-induced defects occurring in the coating at this point. Also, the running performance of the coater greatly depends on the rheological properties of the coating at the actual solid content under the blade. According to the method of the present disclosure for manufacturing a laminate including a paper substrate and an MFC layer, the MFC suspension is cast onto a metal belt support to form a wet MFC layer, and the paper substrate is combined with the wet MFC layer positioned on the metal belt support. Thus, the MFC suspension is not directly applied onto the paper substrate but onto the metal belt support, so problems associated with the high stress applied to the MFC suspension during the application and leveling stages can be avoided. Therefore, typical rheology-related running performance problems in the coating method can be avoided. Also, in the method of the present disclosure, it becomes possible to use high aspect ratio microfibrils, fillers with a high shape factor, and fibrils with a high aspect ratio such as nanofillers in a high content. However, when these are included in the MFC suspension, the risk of shear-induced defects and rheological dilatancy increases when used in conventional coating procedures.

[0024] As described above, the method of the first aspect of the present disclosure includes the step of providing an MFC suspension including 25 to 90% by weight of MFC based on the total dry weight of the MFC suspension and 10 to 50% by weight of a filler component based on the total dry weight of the MFC suspension. Also, the MFC suspension includes a suspension medium in which MFC, the filler component, and optional additional components and / or additives are suspended. Preferably, the MFC suspension is an aqueous suspension including an aqueous suspension mixture of MFC, the filler component, and optional additional components and / or additives.

[0025] 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.

[0026] There are various methods for producing MFC, such as purification one or more times, purification after pre-hydrolysis, high-shear decomposition or fibril release. To bring both energy efficiency and sustainability to 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, for example, pretreated enzymatically or chemically 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.

[0027] MFC can be produced from softwood and / or hardwood 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 produced 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.

[0028] As described above, the MFC suspension used in the method of the first aspect contains 25 to 90% by weight of MFC based on the total dry weight. In some embodiments, the MFC suspension contains 35 to 85% by weight, preferably 35 to 75% by weight, more preferably 45 to 75% by weight of MFC based on the total dry weight. The MFC layer of the laminate produced by the method of the first aspect can contain 25 to 90% by weight of MFC, such as 35 to 85% by weight, preferably 35 to 75% by weight, more preferably 45 to 75% by weight based on the total dry weight, which is related to the amount of MFC in the MFC layer itself.

[0029] The MFC of the MFC suspension may be composed of one or more fractions of MFC. In some embodiments, the MFC of the MFC suspension 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 fine grade and one fraction of coarse grade, and the coarse grade may be, for example, an additive. The Schopper - Riegler value of the coarse MFC in this case is usually 80 to 100 SR°, for example, 80 to 99 SR°, 90 to 99 SR°, or 95 to 99 SR°, while the fine MFC is fibrillated to a Schopper - Riegler value exceeding the measurement range (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.

[0030] As described above, the MFC suspension used in the method of the first aspect contains 10 to 50% by weight of a filler component based on the total dry weight. In some embodiments, the filler component has a BET specific surface area of more than 15 m 2 / g, preferably more than 20 m 2 / g, or more than 30 m 2 / g, or more than 40 m 2 / g, for example 50 to 750 m 2 / g super, and includes one or more fillers such as mineral fillers. In some embodiments, the filler component may include one or more plate-like fillers. As used herein, the plate-like filler means a filler with a high shape factor or flaky shape such as minerals and pigments. Each plate-like filler can have a high shape factor, that is, a shape factor >8, preferably >10 or >15, for example 25-100. As used herein, the "shape factor" is measured using the method and apparatus for electrical conductivity described in British Patent No. A2240398, US Patent No. A-5128606, and European Patent No. -A-528078, and using the equations derived in these patent specifications, and is a measure of the average value (weight average basis) of the ratio of the average particle diameter to the particle thickness of a population of particles of various sizes and shapes. The high shape factor filler improves the bending effect of the MFC layer. By using the method of the first aspect for providing the MFC layer on the paper substrate, at least some of the shear-related difficulties associated with high shape factor fillers related to conventional coating processes are avoided or at least reduced. Also, the high shape factor filler improves the light barrier properties such as ultraviolet light of the formed MFC layer.

[0031] In some embodiments, the filler component includes one or more fillers selected from phyllosilicates. In some embodiments, the filler component includes kaolinite (kaolin), talcum, bentonite, mica, montmorillonite, organic clay, graphene, graphene oxide, or combinations thereof. Some fillers can be modified to be effective visible light and / or ultraviolet light blocking additives.

[0032] In some embodiments, the filler component includes a first filler fraction consisting of one or more fillers selected from phyllosilicates, and based on the total dry weight of the first filler fraction, at least 90% by weight of the first filler fraction has an average diameter (d less than 2 μm, preferably less than 1 μm, for example less than 0.8 μm 50It has a (value). In some embodiments, the filler component comprises a first filler fraction consisting of kaolinite (kaolin), talcum, bentonite, mica, montmorillonite, organic clay, graphene, graphene oxide, or a combination thereof, and based on the total dry weight of the first filler fraction, at least 90% by weight of the first filler fraction has an average diameter (d 50 value) and an average (mean) equivalent particle diameter (d 50 value) is measured by well-known methods, such as by dynamic light scattering, by sedimenting the particulate material in a fully dispersed state in an aqueous medium.

[0033] In some embodiments, the filler component comprises a second filler fraction consisting of one or more fillers selected from nanofilicates, and based on the dry weight, at least 90% by weight of the second filler fraction has an average diameter (d 50 value) less than 100 nm, preferably less than 80 nm, such as less than 70 nm. In some embodiments, the second filler fraction consists of nanokaolinite, nanotalcum, nanobentonite, nanomica, nanomontmorillonite, nanoorganic clay, nanographene, graphene oxide, or a combination thereof, and based on the dry weight, at least 90% by weight of the second filler fraction has an average diameter (d 50 value) less than 100 nm, preferably less than 80 nm, such as less than 70 nm.

[0034] In some embodiments, the filler component includes the first filler fraction and does not include the second filler fraction. In some embodiments, the filler component includes the second filler fraction and does not include the first filler fraction. In some embodiments, the filler component includes the first filler fraction and the second filler fraction. In some embodiments, the weight ratio of the first filler fraction to the second filler fraction in the MFC suspension is 98 / 2, 95 / 5, 90 / 10, 88 / 12, 85 / 15, 80 / 20, and 75 / 25.

[0035] In some embodiments, the MFC suspension further comprises a water-soluble binder of 45 wt% or less. In some embodiments, the MFC suspension comprises a water-soluble binder of 2-45 wt%, such as 5-40 wt% or 5-35 wt%. The water-soluble binder may comprise one or more film-forming agents or may be composed of one or more film-forming agents. In some embodiments, the water-soluble binder comprises at least one component (i.e., film-forming agent) selected from the group of synthetic polymers, natural polysaccharides, and their derivatives. In some embodiments, the water-soluble binder comprises polyvinyl alcohol (PVOH) or its derivatives or analogs, carboxymethyl cellulose (CMC), starch, or combinations thereof.

[0036] PVOH may be a single type of PVOH or a mixture of two or more types of PVOH with different degrees of hydrolysis, viscosities, etc. PVOH may have a degree of hydrolysis in the range of, for example, 80-99 mol%, preferably in the range of 88-99 mol%.

[0037] Accordingly, the water-soluble binder of the present invention comprises or consists of one or more water-soluble film-forming components, i.e., one or more water-soluble components capable of forming a film and / or improving the bonding between cellulose fibers. Since MFC is not water-soluble at room temperature, it is not considered a water-soluble binder in this context. The water-soluble binder not only promotes film formation but also stabilizes the MFC and the filler, enabling a more consistent wet MFC layer as well as a dry MFC layer.

[0038] In addition to MFC, the MFC suspension may contain a filler component and an optional water-soluble binder, as well as conventional papermaking additives or chemicals such as film formers, dispersants, pigments, wet strength improvers, crosslinking agents, plasticizers, softeners, humectants, adhesion primers, wetting agents, biocides, colorants, defoamers, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), waxes, rosin resins, stearates, starches, silica, precipitated calcium carbonate, and rheology modifiers such as hydrophobizing agents. 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 manufacture of the MFC layer.

[0039] In some embodiments, the MFC suspension further comprises at least one additive selected from the group consisting of dispersants, plasticizers, softeners, humectants, crosslinking agents, light or UV blockers, lubricants, dyes, and rheology modifiers.

[0040] In some embodiments, in addition to MFC, the filler component, and the optional water-soluble binder, the MFC suspension contains additives that are 45 wt% or less, for example 5 - 45 wt%, based on the total dry weight of the MFC suspension.

[0041] In some embodiments, the MFC suspension contains a plasticizer such as sorbitol, glycol, or other polyols in an amount of 0.5 - 20 wt% based on the total dry weight.

[0042] In some embodiments, the MFC suspension does not contain retention aids, fixing agents, and flocculants, especially their cationic versions.

[0043] In some embodiments, the suspension medium is water or contains water.

[0044] According to a 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 additives including water-soluble additives and components are retained to a greater extent within the MFC layer compared to when a porous support is used. Also, additives and components, particularly water-soluble additives and components, are carried with water to the paper substrate during water removal through the paper substrate, whereby the properties of the paper substrate may be improved. In embodiments where starch is used as a component of the MFC suspension, the starch is carried with water to the paper substrate or the boundary region between the MFC layer and the paper substrate during water removal, and can promote adhesion between the formed MFC layer and the paper substrate.

[0045] According to a first aspect of this method, until after drying, since the MFC layer is formed and held on a metal belt support which is a non-porous support, the need for a retention agent and / or a flocculant may be reduced or eliminated.

[0046] 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.

[0047] The term "casting", when used for film formation or layer formation, refers to a known 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 leveling methods include curtain coating / application, slot die casting, or methods of dispensing the MFC suspension using a spray or similar device and leveling using a doctor blade or rod.

[0048] 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, i.e., the wet MFC layer should be as homogeneous as possible and have as uniform a thickness as possible. The formed wet MFC layer has a basis weight (grammage) of 3 to 70 g / m 2 , preferably 8 to 70 g / m 2 , for example 9 to 70 g / m 2 , 10 to 70 g / m 2 , 10 to 50 g / m 2 , or 15 to 40 g / m 2 and can be formed with an amount of MFC suspension corresponding to the basis weight (grammage) at the time of drying.

[0049] According to the method of the first aspect, the MFC suspension has a dry content of 2.5 to 50 wt%, preferably 3 to 45 wt%, most preferably 4 to 40 wt%. Thus, the formed wet MFC layer has a dry content of 2.5 to 50 wt%, preferably 3 to 45 wt%, most preferably 4 to 40 wt% at the time of formation (i.e., during or immediately after application to the metal belt support).

[0050] In some embodiments, the MFC suspension has a dry content of 10 to 50 wt%, preferably 12 to 45 wt%, most preferably 15 to 40 wt%. Thus, in these embodiments, a relatively high dry content of the MFC suspension can be utilized, which means that less water migrates to the paper substrate and the immobilization of the MFC layer is faster. The faster the immobilization of the MFC layer, the less penetration into the paper substrate and the higher the concentration of the MFC layer may be.

[0051] The metal belt support on which the wet MFC layer is formed is a metal belt, that is, 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, that is, 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 of 10 μm or less, preferably 0.1 to 5 μm, 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.

[0052] 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 polymer (PAE) resin, polyvinyl alcohol resin (PVOH), polyvinyl alcohol copolymer, starch, ethylene glycol, vegetable oil, fatty acid, and sugar alcohol.

[0053] The formed wet MFC layer can be a web composed of one or more layers or sub-layers made by 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.

[0054] 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 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 air permeability value of the paper substrate less than 10,000 seconds / 100 ml promotes the movement of moisture from the wet MFC layer through the paper substrate when removing moisture according to the first aspect of the method.

[0055] 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. 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.

[0056] The paper substrate used in the method of the first aspect preferably has a basis weight in the range of 10 to 200 g / m2, more preferably in the range of 10 to 100 g / m2.

[0057] 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.

[0058] 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.

[0059] 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 that is 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.

[0060] 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 2.5 to 50 wt%, preferably 3 to 45 wt%, more preferably 4 to 40 wt%. When the paper substrate web is joined to the wet MFC layer, it has a dry content of at least 70 wt%, preferably at least 80 wt%, most preferably at least 85 wt%. 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 spectroscopy. 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.

[0061] As described above, the method of the first aspect includes the step of removing moisture from the laminate structure to form a laminate including a paper substrate and an MFC layer. The formed laminate has an average dry content (i.e., in the thickness direction) of at least 80% by weight, for example 80 to 99.9% by weight, preferably 85 to 99% by weight or 86 to 98% by weight or 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 formed 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 spectroscopic methods (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 moisture removal. The moisture removal includes at least one drying step, for example 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 during 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 to the metal belt support). Also, the metal belt support is heated during at least one drying step.

[0062] Thus, the laminate structure is dried during each of the at least one drying steps by a combination of non-contact drying by at least one non-contact drying device and heating of the metal belt support. 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.

[0063] Thus, when the laminate structure is subjected to at least one of the drying steps, the laminate structure is subjected to non-contact drying by at least one non-contact drying apparatus and is positioned on the casting surface of a heated metal belt support. Thus, the laminate structure is dried by performing non-contact drying and contact drying simultaneously.

[0064] Thus, 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 apparatuses, the laminate structure is positioned on the casting surface of the metal belt support during non-contact drying, one or more non-contact drying apparatuses are positioned on one side of the laminate structure (i.e., do not contact the laminate structure), the metal belt support is positioned on the other side of the laminate structure (i.e., contacts the MFC layer), and is heated during non-contact drying.

[0065] 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 be heated to a temperature within the above temperature range during other steps or parts of the steps of the method of the first aspect, for example, during the step of forming the wet MFC layer, and / or during the step of bonding the paper substrate web to 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 - mentioned 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. Without being bound by any theory, it is believed that the high - temperature surface of the metal belt support may promote the reaction between the components of the water - soluble binder component and the filler component.

[0066] 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 side opposite to 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 of a laminate structure containing a relatively large amount of water, 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 using one or more non - contact drying devices positioned on the surface of the laminate structure on the side opposite to the metal belt support by water permeating through the paper substrate from the MFC layer, and by a paper substrate having an air permeability of less than 10000 seconds / 100 ml Gurley Hill.

[0067] Thus, during at least one drying step of the method of the first aspect, water penetrates / moves from the wet MFC layer through the paper substrate by using one or more non-contact drying devices and heating the metal belt support.

[0068] Also, by using the method of the first aspect, it has been found that the MFC layer adheres strongly to the surface of the paper substrate. Without being bound by any theory, the strong adhesion is thought to be due to mechanical connection of fibers and fibrils and / or intermolecular interactions. Thus, the need to use an adhesive between the paper substrate and the MFC layer is reduced or eliminated.

[0069] Thus, the paper substrate can be positioned directly on top of the wet MFC layer, i.e., in direct contact. Thus, in some embodiments, the laminate provided 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 nonionic 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 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, in order not to impede the transport of water and steam through the paper substrate, between the MFC layer and the paper substrate, less than 4 g / m 2 less than, 2 g / m 2 less than 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, for example, an adhesive selected from natural rubbers or polysaccharides or derivatives thereof such as starch, CMC, methylcellulose, polyelectrolyte solutions, polyvinyl alcohol or its derivatives or analogs, needs to be used.

[0070] Each of the one or more non-contact drying apparatuses may be any known suitable drying apparatus based on non-contact drying technology. For example, each of the one or more non-contact drying apparatuses may be selected from the group consisting of hot gas impingement drying apparatuses such as hot air impingement drying apparatuses or hot steam impingement drying apparatuses, air dryers, microwave drying apparatuses, ultraviolet (UV) drying apparatuses, electron beam drying apparatuses, infrared (IR) drying apparatuses, and near-infrared (NIR) drying apparatuses. When a plurality of non-contact drying apparatuses are used, these non-contact drying apparatuses may be of the same type or different types.

[0071] As described above, the method of the first aspect includes the step of separating the laminate from the metal belt support, that is, the step of separating (for example, 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, 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 at the time of separation.

[0072] In some embodiments, the laminate is further dried after being separated from the metal belt support. The further drying can be carried out by non-contact drying, for example, by using one or more non-contact drying apparatuses, which can be any known suitable drying apparatus based on non-contact drying technology selected from the group of non-contact drying apparatuses provided in relation to 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 used. One of the advantages of cylinder drying is that by bringing the paper side of the laminate into contact with the heated cylinder, the moisture uniformity in the thickness direction of the laminate is improved.

[0073] 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, the paper substrate web can be unwound from a roll and conveyed and induced to be positioned, for example, on top of a wet MFC layer positioned on the casting surface of a metal belt support.

[0074] 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.

[0075] In some embodiments, the wet MFC layer and the paper substrate web, i.e., the metal belt support having the laminate structure, are conveyed through one or more press devices, for example, 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, for example, downstream of at least one non-contact drying device. In some embodiments, the metal belt support having 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 press nip located between two separate non-contact drying devices. In some embodiments, the linear load of at least one press device is 1 to 150 kN / m, preferably 5 to 100 kN / m. In some embodiments, the absolute pressure of at least one press device is 1 to 25000 kPa, preferably 3 to 17000 kPa.

[0076] In some embodiments, the metal belt support provided with the laminate structure does not pass through any press equipment or press nip. Thus, in these embodiments, the method according to the first aspect is carried out without using any press equipment or press nip, i.e., without any press equipment or press nip.

[0077] In some embodiments, the method of the first aspect further includes a further 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 carried out such that the dry content increases in units of 0 to 20%, preferably in units of 1 to 20% or 1 to 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 after the wet MFC layer is formed on the casting surface of the metal belt support and before the joining step. For example, when the dry content of the wet MFC layer is 2.5 to 20% by weight, it may be necessary to carry out the pre-drying step. For example, the pre-drying can be carried out 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 carried out by heating the metal belt support, i.e., the heated metal belt support can be utilized in the pre-drying step.

[0078] In some embodiments, the method of the first aspect further includes dehydrating the wet MFC layer positioned on the casting surface of the metal belt support before joining the paper substrate web to the wet MFC layer. The dehydration of the wet MFC layer is performed by applying a press fabric in direct contact with the wet MFC layer and guiding the wet MFC layer disposed between the press fabric and the metal belt support through a pressing device. These embodiments may also include a preliminary 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.

[0079] In some embodiments, the water 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 joining step and before at least one drying step. The dehydration of the laminate structure is performed by applying a press fabric in direct contact with the paper substrate web of the laminate structure and guiding 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 in direct contact with the paper substrate web and guiding 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.

[0080] In some embodiments, the water removal of the method of the first aspect includes at least two drying steps, and further includes a step of dehydrating a 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 in direct contact with the paper base web of the laminate structure and guiding 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 in direct contact with the paper base web and guiding the laminate structure disposed between the porous wire or membrane and the metal belt support through a vacuum dewatering device where the porous wire or membrane covers one or more vacuum cavities and water is removed from the laminate structure.

[0081] A press fabric means a permeable fabric that can remove water from a web by 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 webs of paper and paperboard. 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.

[0082] During at least one drying step and an optional dehydration step, the fact that the MFC layer remains positioned on the casting surface of the metal belt support enables controlled drying and dehydration of the MFC layer, and also means that a highly smooth and dense surface can be obtained. Controlled drying and optional controlled dehydration can mean no shrinkage or shrinkage of less than 10%, less than 5%, or less than 3%. Also, due to the contact between the controlled drying and optional controlled dehydration and the metal belt support, it becomes possible to transfer the texture image from the metal belt support to the MFC layer. Therefore, the method of the present invention enables the provision of a glossy surface by the presence of the filler component and the suppression of drying and optional suppression of dehydration on the metal belt support. Also, by the method of the present disclosure, it becomes possible to form a dense and compact single surface, i.e., the MFC layer surface, and the paper substrate provides strength and good convertibility.

[0083] In some embodiments, the paper substrate web is pre-wetted prior to the bonding step in order to pre-wet the paper substrate. Without being bound by any theory, it is thought that pre-wetting the paper substrate promotes capillary water transport from the wet MFC layer through the paper substrate during bonding. Also, during the step of drying the laminate structure, the pre-wetted paper substrate is dried to a new dimension under constrained conditions.

[0084] In some embodiments, the paper substrate web is optionally pre-heated prior to the bonding step, in combination with the aforementioned pre-wetting, in order to lower the viscosity of the water when entering the bonding step, and the movement of water through the paper substrate is improved.

[0085] In some embodiments, the resulting laminate has an oxygen transmission rate (OTR) of less than 50 cc / m 2 / 24 h, preferably less than 40 cc / m 2 / 24 h, more preferably less than 30 cc / m 2 / 24 h, measured in accordance with standard ASTM F1927-20 at a relative humidity of 50% and a temperature of 23 °C.

[0086] In some embodiments, when measured at 50% relative humidity and 23°C in accordance with standard ASTM F1249-20, the resulting laminate has a water vapor transmission rate (WVTR) of less than 100 g / m 2 ² / 24 h, preferably less than 75 g / m 2 ² / 24 h, more preferably less than 50 g / m 2 ² / 24 h. Thereby, the laminate according to the present disclosure becomes an interesting and viable alternative to conventional materials using an aluminum foil layer.

[0087] In some embodiments, the outermost surface of the MFC layer of the resulting laminate, i.e., the surface of the MFC layer that was in contact with the metal belt support, has a vent sens roughness of 200 ml / min or less, preferably 150 ml / min or less, or 100 ml / min or less, measured according to 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, 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.

[0088] 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-by-molecule, onto a solid surface. Multiple layers of the same material or different materials can be combined. The process can be further specified based on the vapor source. Physical vapor deposition (PVD) uses a liquid or solid source, and chemical vapor deposition (CVD) uses chemical vapor. Atomic layer deposition (ALD) can also be utilized. For example, the laminate according to the present disclosure may be provided with a vacuum coating layer containing 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.

[0089] In some embodiments, the obtained laminate has a Scott bond value of >50 J / m when measured by TAPPI 569, 2 preferably >80 J / m 2 when measured by TAPPI 569.

[0090] In some embodiments, the obtained laminate has a Z-strength value of >200 kPa, preferably >250 kPa when measured by TAPPI 541.

[0091] As described above, the dry basis weight (basis weight) of the MFC layer of the laminate is measured in accordance with ISO 536:2019 and is 3 - 70 g / m 2 preferably 8 - 70 g / m 2 for example 9 - 70 g / m 2 10 - 70 g / m 2 10 - 50 g / m 2 or 15 - 40 g / m 2 when measured in accordance with ISO 536:2019.

[0092] In some embodiments, the MFC of the MFC suspension has a water retention value (WRV) of >120%, such as 150 - 350%, when measured in accordance with standard ISO 23714.

[0093] In some embodiments, the obtained laminate has a KIT value of at least 10 when measured in accordance with standard ISO16532 - 2 from the MFC layer side.

[0094] In some embodiments, the obtained laminate has a transparency of less than 25%, preferably less than 15%, when measured in accordance with standard DIN 53147.

[0095] There is a need for an improved solution to replace barrier layers and substrates of packaging materials, such as aluminum foil and barrier plastic layers like polyolefin films, 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.

[0096] 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.

[0097] 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 against the laminate surface. It is also preferred that the outermost polymer layer is heat sealable.

[0098] 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.

[0099] In some embodiments, the laminate of the present disclosure is provided with a second outermost polymer layer, preferably a polyethylene layer, disposed on an MFC layer.

[0100] The outermost polymer layer, while potentially interfering with repulping, 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.

[0101] The outermost polymer layer is generally composed of either a thermoplastic polymer commonly used for the protective layer and / or heat - seal layer of paper - based packaging laminates, or a polymer particularly used for packaging boards of 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, etc. Polyolefins such as polyethylene, especially low - density polyethylene (LDPE) and high - density polyethylene (HDPE), are the most common and versatile polymers used for packaging boards of liquids and foods. The polymers used are preferably manufactured from renewable materials.

[0102] 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 contains polypropylene or polyethylene. In a preferred embodiment, the outermost polymer layer contains polyethylene, more preferably LDPE or HDPE.

[0103] In some embodiments, the outermost polymer layer is formed by extrusion - coating a polymer onto the 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 by the extruded plastic itself, or the molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate.

[0104] The basis weight of each of the outermost polymer layers is preferably less than 50 g / m 2 2. To achieve a continuous and substantially defect-free film, when provided by extrusion coating, at least 6 g / m 2 , preferably at least 8 g / m 2 , or at least 12 g / m 2 of the basis weight of the outermost polymer layer is typically required. In some embodiments, the basis weight of the 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 or 12 - 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 is in the range of 2 - 10 g / m 2 and the outermost polymer layer is provided by a foamed film.

[0105] According to a second aspect of the present disclosure, a laminate comprising a paper substrate and an MFC layer is provided, and the laminate is obtained by the method of the first aspect.

[0106] According to a third aspect of the present disclosure, a laminate comprising a paper substrate and an MFC layer is provided, the MFC layer comprising 25 - 90 wt% MFC based on the total dry weight and 10 - 50 wt% filler component based on the total dry weight, and having an average dry content of at least 80 wt%. The laminate has an oxygen transmission rate (OTR) of less than 50 cc / m 2 / 24 h, preferably less than 40 cc / m 2 / 24 h, more preferably less than 30 cc / m 2 / 24 h, measured in accordance with standard ASTM F1927 - 20 at a relative humidity of 50% and a temperature of 23°C, and a water vapor transmission rate 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 2has a water vapor transmission rate (WVTR) of less than 24 hours. 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.

[0107] Preferably, the basis weight of the paper substrate is in the range of 10 to 200 g / m 2 and more preferably in the range of 10 to 100 g / m. 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. 2

[0108] In some embodiments, the outermost surface of the MFC layer of the laminate according to the third aspect has a Bent sen roughness of 200 ml / min or less, preferably 150 ml / min or less, more preferably 100 ml / min or less, measured according to ISO 8791-2:2013, and / or a Parker Print Surf (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 according to ISO 8791-4.

[0109] 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.

[0110] The laminates of the second and third aspects can be used as is or can be 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, for example one or more paper or cardboard layers, to form a laminate material, the laminate material can, if desired, be provided with an outermost polymer layer (corresponding to the above-described 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 such as multiple polymer layers of the same or different polymers on each side, a protective varnish layer, a decorative layer on top of the laminate, and a sealing layer that can be activated (melted) by heat.

[0111] For example, the laminate can be used as a packaging material such as for food or liquid packaging, or for use in packaging materials. For example, the laminate can form part of a flexible packaging material such as a self-standing 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 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, for example, in 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 that include a laminate obtained by the method of the first aspect or a laminate according to the third aspect.

[0112] According to a fourth aspect of the present disclosure, there is provided a method of manufacturing a packaging material, the method including: i) providing a base layer of paper or cardboard; and ii) using at least one adhesive layer to laminate a laminate according to the second or third aspect to the base layer of paper or cardboard to obtain a packaging material.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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. Preferably, 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.

[0117] In some embodiments, the basis weight of the paper or paperboard base layer is at least 100 g / m 2 ². In some embodiments, the paper or paperboard base layer is at least 150 g / m 2 ², 200 g / m 2 ², 250 g / m 2 ², 300 g / m 2 ², 350 g / m 2 ², or 400 g / m 2 ². The basis weight of the paper or paperboard base layer is preferably 1000 g / m 2 ², 800 g / m 2 ², or 600 g / m 2 ² or less. Unless otherwise specified, the basis weight is determined in accordance with standard ISO 536.

[0118] In some embodiments, the paper or paperboard base layer has a density of less than 700 kg / m 3 ³, preferably less than 600 kg / m 3 ³. Unless otherwise specified, the density is determined in accordance with standard ISO 534.

[0119] The paper or paperboard base layer may be a single layer of paperboard or a multi-layer 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.

[0120] 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 layer, preferably the intermediate layer, is formed as a foam.

[0121] The tie layer can generally include any suitable adhesive commonly used in paper or paperboard-based packaging laminates, or adhesives specifically used in liquid or food packaging laminates. In the present invention, various types of adhesives and adhesive coating methods can be used.

[0122] The tie layer may include one or more adhesive polymers. The tie layer may be composed 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 wt% of an adhesive polymer or a mixture of adhesive polymers based on 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 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, such as (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA)), ethylene glycidyl (meth)acrylate copolymer (EG(M)A), or MAH-grafted polyethylene (MAHg-PE). Another example of such a modified 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).

[0123] 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.

[0124] 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 and more preferably in the range of 3 - 12 g / m 2 .

[0125] According to a fifth aspect of the present disclosure, a packaging material obtained by the method according to the fourth aspect is provided.

[0126] 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 surface of the packaging material. 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.

[0127] In some embodiments, the packaging material is provided with a first outermost polymer layer, preferably a polyethylene layer, disposed on a base layer of paper or cardboard.

[0128] In some embodiments, the packaging material is provided with a second outermost polymer layer, preferably a polyethylene layer, disposed on the laminate according to the second or third aspect.

[0129] According to a sixth aspect of the present disclosure, there is provided the use of 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.

[0130] 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.

[0131] 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

[0132]

Figure 1

[0133] Detailed Description of the Drawings Figure 1 shows a schematic view 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. Optionally, a shearing unit 4 is used to further control and adjust the orientation of the particles and / or fibrils. A paper substrate web 5 is unwound from a roll 6 and guided and conveyed so as to be joined to the wet MFC layer 1, that is, positioned on the wet MFC layer 1 positioned on the casting surface of the metal belt support 2, thereby forming a laminate structure 7. The laminate structure 7 formed by the joining and positioned on the casting surface of the metal belt support 2 is then subjected to a moisture removal treatment. The moisture removal includes a drying step of drying the laminate structure 7 to form a laminate 8, and the drying is performed by combining non-contact drying by a non-contact drying device 9 and contact drying by heating the metal belt support 2 during drying. The non-contact drying device 9 is disposed on the opposite side of the metal belt support 2 of the laminate structure 7. Optionally, the moisture removal includes a further step of dehydrating the laminate structure 7 by a dehydration unit 10 before drying by the non-contact drying device 9. The laminate structure 7 is positioned on the metal belt support during drying and optional dehydration. After drying, the laminate 8 is separated from the metal belt support 2 (not shown).

[0134] Generally, products, materials, layers, processes are described from the perspective of "including" various components or steps, but products, materials, layers, processes may also be "essentially composed of" or "composed of" various components and steps.

[0135] 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.

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 25 to 90% by weight of MFCs based on the total dry weight of the MFC suspension, 10 to 50% by weight of filler components based on the total dry weight of the MFC suspension, and a suspension medium, wherein the MFC suspension has a dry content of 2.5 to 50% by weight, preferably 3 to 45% by weight, most preferably 4 to 40% by weight, - A wet MFC layer (1) is formed by casting the MFC suspension onto the casting surface of the metal belt support (2), - A step of providing a paper-based web (5), wherein the paper-based material of the paper-based web (5) 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 (5) to the wet MFC layer (1) positioned on the casting surface of the metal belt support (2) in order to form a laminate structure (7) positioned on the casting surface of the metal belt support (2), wherein the wet MFC layer (1) has a dry content of 2.5 to 50% by weight, preferably 3 to 45% by weight, most preferably 4 to 40% by weight, and the paper substrate web (5), when bonded to the wet MFC layer (1), has a dry content of at least 70% by weight, preferably at least 80% by weight, most preferably at least 85% by weight, - A step of subjecting the laminate structure (7) 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 (7) is positioned on the casting surface of the metal belt support (2) during dewatering, the dewatering includes at least one drying step, the drying step includes drying the laminate structure (7) by at least one non-contact drying device (9) positioned on the opposite side of the metal belt support (2) of the laminate structure (7), and the metal belt support (2) is heated during 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 filler component comprises one or more plate-shaped fillers.

3. The method according to claim 1 or 2, wherein the filler component comprises a first filler fraction consisting of kaolinite, talcum, bentonite, mica, montmorillonite, organic clay, graphene, graphene oxide, or a combination thereof, and at least 90% by weight of the first filler fraction has an average diameter of less than 2 μm based on dry weight.

4. The method according to claim 1 or 2, wherein the filler component comprises a second filler fraction consisting of nanokaolinite, nanotalcam, nanobentonite, nanomica, nanomontmorillonite, nanoorganic clay, nanographene, nanographene oxide, or a combination thereof, and at least 90% by weight of the second filler fraction has an average diameter of less than 100 nm based on dry weight.

5. The method according to claim 3, wherein the weight ratios of the first fraction to the second fraction are 98 / 2, 95 / 5, 90 / 10, 88 / 12, 85 / 15, 80 / 20, and 75 / 25.

6. The method according to claim 1 or 2, wherein the MFC suspension further comprises up to 45% by weight, preferably 2 to 45% by weight, of a water-soluble binder.

7. The method according to claim 6, wherein the water-soluble binder comprises at least one component selected from the group consisting of synthetic polymers, natural polysaccharides, and derivatives thereof.

8. The method according to claim 7, wherein the water-soluble binder comprises polyvinyl alcohol or an analog thereof, carboxymethylcellulose, starch, or a combination thereof.

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

10. The method according to claim 1 or 2, wherein the non-contact drying equipment (9) is selected from the group consisting of a high-temperature gas impact drying equipment, a high-temperature steam impact drying equipment, an air dryer, a microwave drying equipment, an ultraviolet drying equipment, an electron beam drying equipment, an infrared drying equipment, and a near-infrared drying equipment.

11. The method according to claim 1 or 2, wherein the joining step is performed by positioning the paper substrate web (5) on the wet MFC layer (1) positioned on the casting surface of the metal belt support (2).

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

13. 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 bonding the paper substrate web (5) to the wet MFC layer (1).

14. 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 (5) 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 guiding the wet MFC layer (1) positioned between the press fabric and the metal belt support (2) through a press machine.

15. The moisture removal further includes a step of dewatering the laminate structure (7) 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 dewatering step of the laminate structure (7) is - Apply a press fabric that is in direct contact with the paper substrate web (5), and guide the laminate structure (7) placed between the press fabric and the metal belt support (2) through the press machine, or The method according to claim 1 or 2, wherein a porous wire or membrane is applied in direct contact with a paper substrate web (5), and a laminate structure (7) placed between the porous wire or membrane and a metal belt support (2) is guided through a vacuum dewatering device, the method being carried out by guiding, the porous wire or membrane covering one or more vacuum cavities, thereby removing water from the laminate structure (7).

16. The moisture removal comprises at least two drying steps, further comprising a step of dewatering the laminate structure (7) positioned on the casting surface of the metal belt support (2) during the drying steps, the step of dewatering the laminate structure (7) - Apply a press fabric that is in direct contact with the paper substrate web (5), and guide the laminate structure (7) 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 (5) in direct contact with it, and the laminate structure (7) 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 (7) through the vacuum dewatering device. The method according to claim 1 or 2, as performed by...

17. The method according to claim 1 or 2, wherein the MFC suspension contains MFCs in an amount between 50% by weight and 90% by weight based on the total dry weight.

18. The formed wet MFC layer (1) has a density of 3 to 70 g / m². ２ The method according to claim 1 or 2, formed from the MFC suspension in an amount equivalent to the dry basis weight of the MFC.

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

20. The method according to claim 1 or 2, wherein the paper substrate web (5) is subjected to at least one pre-wetting step before the bonding step.

21. The laminate (8) was measured at 50% relative humidity and 23°C in accordance with the ASTM F1927-20 standard, with a volume of 50 cc / m². ２ Less than 24 hours, preferably 40 cc / m³ ２ Less than 24 hours, more preferably 30 cc / m³ ２ The method according to claim 1 or 2, having an oxygen permeability (OTR) of less than 24 hours.

22. The laminate (8) was measured at 50% relative humidity and 23°C in accordance with the ASTM F1249-20 standard, with a weight of 100 g / m². ２ Less than 24 hours, preferably 75 g / m² ２ Less than 24 hours, more preferably 50 g / m² ２ The method according to claim 1 or 2, having a water vapor transmission rate (WVTR) of less than 24 hours.

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