Method for manufacturing laminated material and laminated material

Abstract

This invention provides a novel method for manufacturing laminated materials using biomass raw materials and without the need for heat bonding. [Solution] A method for manufacturing a laminated material, wherein a first adherend and a second adherend are laminated with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, The process involves forming the lignocellulose-containing solution into a film to obtain an adhesive film, An adhesive step of placing the adhesive film between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive film, It is equipped with, In the bonding step, a solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend. A method for producing a laminate, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing laminated materials and to laminated materials. [Background technology]

[0002] Traditionally, techniques have been used to create new laminated materials by bonding pieces of wood together. Examples of such laminated materials include LVL (Laminated Veneer Lumber) and CLT (Cross-Laminated Timber).

[0003] Furthermore, techniques for bonding metal plates, ceramic plates, and other materials are also known. Adhesives are used to laminate these materials. However, commonly used adhesives include those that release formaldehyde and isocyanate-based adhesives. In recent years, there has been a trend to reduce the use of these adhesives due to concerns about preventing sick building syndrome and the harmful effects of isocyanates. In addition, other adhesives are synthesized from fossil fuels and are not sustainable.

[0004] Adhesives derived from natural biomass resources can address these problems. For example, a technique is known in which wood is dissolved in formic acid, a sheet material made from wood is created by a casting method, and this sheet material is laminated between two pieces of wood and heat-pressed to bond the two pieces of wood (see Patent Document 1). Another technique is known in which cedar boards are bonded together using an adhesive for wood pieces containing glucomannan and an alkali compound (see Patent Document 2). Furthermore, a technique is known in which LVL is produced from cedar boards using an adhesive mixed with phenols and kraft lignin (see Patent Document 3). In addition, an adhesive for wood lamination containing oligosaccharides, phosphates, and calcium is known (see Patent Document 4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2024-18714 [Patent Document 2] Japanese Patent Publication No. 2021-107551 [Patent Document 3] Japanese Patent Publication No. 2023-176532 [Patent Document 4] International Publication No. 2015 / 072437 [Overview of the project] [Problems that the invention aims to solve]

[0006] The technology disclosed in Patent Document 1 is, for example, a technology for obtaining laminated material by heating and pressing wood pieces together via a sheet material. The technology disclosed in Patent Document 2 is a technology that uses glucomannan. Currently, glucomannan is mainly produced from konjac, and this technology has the problem of hindering food supply. Furthermore, the technology disclosed in Patent Document 3 uses phenols and kraft lignin as adhesive raw materials. Kraft lignin is a wood-derived product produced from the paper industry, but phenol is a raw material derived from fossil fuels, resulting in an adhesive whose raw materials are dependent on fossil fuels. The technology disclosed in Patent Document 4 uses sugar or oligosaccharides, phosphates and calcium salts. This technology does not use raw materials derived from fossil fuels, but it uses sugars, in particular sucrose. Sucrose is the main component of sugar and is produced from sugarcane, etc., and has the problem of hindering food supply. While it is possible to produce sugars from wood, it is considered more difficult than producing sugars from herbaceous plants (such as sugarcane), and therefore it is not a practical technology.

[0007] The primary objective of this disclosure is to provide a novel method for manufacturing laminated materials that utilizes biomass raw materials and does not require heat bonding. Furthermore, this disclosure also aims to provide a novel laminated material. [Means for solving the problem]

[0008] (First aspect) The inventors of this disclosure have diligently studied to solve the above-mentioned problems. As a result, they have found that in a method for manufacturing a laminate in which a first adherend and a second adherend are laminated with an adhesive layer in between, a lignocellulose-containing solution is prepared by dissolving a plant material containing lignocellulose in formic acid, the lignocellulose-containing solution is formed into a film to form an adhesive film, the adhesive film is placed between the first adherend and the second adherend, and an adhesive step is provided in which the first adherend and the second adherend are bonded together via the adhesive film, and in the adhesive step, a predetermined solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend, thereby bonding the first adherend and the adhesive film together without the need for heat bonding, and a suitable laminate can be manufactured. In the bonding process, by applying a predetermined solvent to at least one of the surfaces of the second adherend and the surface of the adhesive film facing the second adherend, the second adherend and the adhesive film are bonded together without the need for heat pressing.

[0009] The invention relating to the first aspect of this disclosure was completed by further consideration based on the above findings. Specifically, the first aspect of this disclosure provides the invention in the following aspects.

[0010] A method for manufacturing a laminate, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, The process involves forming the lignocellulose-containing solution into a film to obtain an adhesive film, An adhesive step of placing the adhesive film between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive film, It is equipped with, In the bonding step, a solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend. A method for producing a laminate, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

[0011] (Second Embodiment) Furthermore, the inventors of the present disclosure have conducted intensive studies to solve the above-described problems. As a result, in a method for producing a laminate in which at least a first adherend and a second adherend are laminated via an adhesive layer, the method includes: preparing a lignocellulose-containing solution in which a plant material containing lignocellulose is dissolved in formic acid; removing at least a part of liquid components from the lignocellulose-containing solution to obtain a solid; mixing the obtained solid with a predetermined solvent to obtain an adhesive paste containing the solvent; then placing the adhesive paste between the first adherend and the second adherend, and providing an adhesion step of adhering the first adherend and the second adherend via the adhesive paste. It has also been found that by providing the above steps, the first adherend and the second adherend are adhered to each other via the adhesive layer without requiring thermocompression bonding, and a laminate can be suitably produced.

[0012] The invention according to the second aspect of the present disclosure has been completed through further studies based on such findings. That is, the second aspect of the present disclosure provides the invention of the following embodiments.

[0013] A method for producing a laminate, wherein at least a first adherend and a second adherend are laminated via an adhesive layer, the method comprising: a step of preparing a lignocellulose-containing solution in which a plant material containing lignocellulose is dissolved in formic acid; a step of removing at least a part of liquid components from the lignocellulose-containing solution to obtain a solid; a step of mixing the solid with a solvent to obtain an adhesive paste containing the solvent; an adhesion step of placing the adhesive paste between the first adherend and the second adherend, and adhering the first adherend and the second adherend via the adhesive paste; and comprising: A method for producing a laminate, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

[0014] (Third aspect) Furthermore, the inventors of this disclosure have diligently studied to solve the above-mentioned problems. As a result, they have found that, in a method for manufacturing a laminate in which a first adherend and a second adherend are laminated with an adhesive layer in between, by providing an adhesion step in which a lignocellulose-containing solution is prepared by dissolving a plant material containing lignocellulose in formic acid, some of the liquid components in the lignocellulose-containing solution are removed to obtain an adhesive paste containing formic acid, the adhesive paste is placed between the first adherend and the second adherend, and the first adherend and the second adherend are bonded together via the adhesive paste without the need for heat bonding, thereby producing a suitable laminate.

[0015] The invention relating to the third aspect of this disclosure was completed by further consideration based on the above findings. Specifically, the third aspect of this disclosure provides the invention in the following aspects.

[0016] A method for manufacturing a laminate, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, A step of removing some of the liquid components from the lignocellulose-containing solution to obtain an adhesive paste containing formic acid, An adhesive step of placing the adhesive paste between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive paste, A method for manufacturing laminated material, comprising the features described above.

[0017] (Laminated wood) The laminate of the present disclosure is a laminate in which a first adherend and a second adherend are laminated with at least an adhesive layer in between, wherein the first adherend is formed of at least one selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold and paper, the thickness of the first adherend is 2 mm or more, the adhesive layer is substantially formed from plant-derived components, and the infrared absorption spectrum of the adhesive layer is 1715-1725 cm⁻¹ -1 The laminated material exhibits an absorption peak in the region. Such a laminated material can be suitably manufactured, for example, by using the manufacturing method of the first, second, or third embodiment of this disclosure. [Effects of the Invention]

[0018] According to this disclosure, a novel method for manufacturing laminated materials is provided that utilizes biomass raw materials and does not require heat bonding.

[0019] Furthermore, this disclosure provides novel laminated materials.

[0020] For example, according to this disclosure, various plant materials containing lignocellulose, such as small pieces of wood or wood powder, can be used as raw materials for adhesives (adhesive films, adhesive pastes) that bond adherends. Furthermore, such adhesives do not need to use raw materials that disrupt the food supply or raw materials derived from fossil fuels. [Modes for carrying out the invention]

[0021] Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments.

[0022] In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Alternatively, the upper and lower limits, upper and lower limits, or lower and lower limits described separately may be combined to form numerical ranges. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0023] [Method for manufacturing laminated materials] The present disclosure is a method for manufacturing a laminated material in which a first adherend and a second adherend are laminated together via an adhesive layer, and the method utilizes a lignocellulose-containing solution obtained by dissolving a lignocellulose-containing plant material in formic acid. The present disclosure includes the following first, second, and third embodiments of the method for manufacturing a laminated material.

[0024] The manufacturing method and the laminated material of this disclosure will be described in detail below. In the following descriptions, matters specific to the first, second, and third embodiments will be clearly indicated as relating to which embodiment. On the other hand, matters common to the first, second, and third embodiments will be described in relation to this disclosure, and descriptions for each individual embodiment will be omitted.

[0025] (Step of preparing a lignocellulose-containing solution) In the method for manufacturing the laminated material of this disclosure, the first, second, and third embodiments all involve a step of preparing a lignocellulose-containing solution obtained by dissolving a plant material containing lignocellulose (hereinafter sometimes simply referred to as "plant material") in formic acid. The step of preparing the lignocellulose-containing solution will be described below.

[0026] The plant material containing lignocellulose is not particularly limited and includes, for example, at least one selected from the group consisting of woody biomass such as coniferous trees, broad-leaved trees, and the bark of coniferous or broad-leaved trees; herbaceous biomass such as herbaceous plants; crops; unused parts of crops; foliage; fruit peels; cotton; and hemp.

[0027] The woody biomass may be coniferous trees (such as Japanese cedar, cypress, and Japanese red pine) or broad-leaved trees (such as eucalyptus, beech, sawtooth oak, olive, and citrus fruits). Two or more types may be used in combination. From the viewpoint of effectively utilizing declining forest resources, woody biomass that was previously discarded can be suitably used. For example, wood powder generated during lumbering, or small pieces (chips) that cannot be used as scraps, may be used as plant materials. From the viewpoint of giving laminated lumber a high-quality appearance, so-called high-grade woods such as Japanese cedar and Japanese cypress are preferred. According to this disclosure, wood powder, chips, etc. generated during the lumbering of high-grade wood can be effectively utilized as plant materials.

[0028] Woody biomass may be natural wood or sawn lumber cut from natural wood. There are no particular limitations on the shape of the woody biomass; for example, it can be used in the form of plates, chips, powder, etc., as appropriate.

[0029] Examples of herbaceous biomass include sugarcane bagasse, rice straw, wheat, wheat bran, tomatoes, onions, Moso bamboo, and weeds. Two or more types may be used in combination.

[0030] Lignocellulose forms a complex, higher-order structure in which cellulose, hemicellulose, and lignin are intricately intertwined. Specifically, cellulose, a linear polymer, forms a crystalline structure through intramolecular and intermolecular hydrogen bonding, constituting strong microfibrils (cellulose microfibrils). Hemicellulose such as xylan and glucomannan are intertwined with these microfibrils, and lignin, an irregular aromatic polymer, fills the voids in this polysaccharide matrix.

[0031] In plant materials containing lignocellulose, the total content (or content as lignocellulose) of cellulose, hemicellulose, and lignin is not particularly limited. From the viewpoint of imparting an appearance similar to natural wood, the total content of cellulose, hemicellulose, and lignin may be 90% by weight or more, 95% by weight or more, 98% by weight or more, or 100% by weight. Some or all of the hydroxyl groups of this cellulose, hemicellulose, and lignin may be formylated.

[0032] In the laminated material of this disclosure, when preparing a lignocellulose-containing solution obtained by dissolving lignocellulose-containing plant material in formic acid, pulverized lignocellulose-containing plant material can be used. That is, before mixing the lignocellulose-containing plant material with formic acid, the lignocellulose-containing plant material can be pulverized to adjust it to a desired size. The size of the pulverized material is not particularly limited as long as the laminated material of this disclosure can be obtained, and the maximum diameter in plan view may be 50 mm or less, 40 mm or less, or 30 mm or less. From the viewpoint of dust prevention, the size of the plant material is preferably 0.1 mm or larger in maximum diameter in plan view.

[0033] The concentration of formic acid (formic acid solution) to be mixed with the lignocellulose-containing plant material is not particularly limited, but is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, with an upper limit of, for example, 100% by mass. Various concentrations of commercially available formic acid (formic acid solution) are available and can be used in this disclosure. Formic acid solution is generally an aqueous solution of formic acid. Formic acid can be produced using wood gas (a mixed gas of carbon dioxide and hydrogen) as a raw material. Formyl groups are bonded to the solid components of the lignocellulose-containing solution obtained by dissolving the lignocellulose-containing plant material in formic acid.

[0034] In preparing a lignocellulose-containing solution, other organic acids (organic acids different from formic acid) may be mixed in addition to formic acid. The type of organic acid is not particularly limited, but typical organic acids are carboxylic acids. They may be aliphatic carboxylic acids or aromatic carboxylic acids. From the viewpoint of excellent solubility of plant materials, α-keto acids and carboxylic acids having a formyl group are preferred, and organic acids selected from the group consisting of glyoxylic acid and pyruvic acid are particularly preferred.

[0035] Here, "dissolution" refers to a state in which the shape of the plant material mixed with formic acid cannot be visually recognized. Even if fibrous material derived from lignocellulose in the plant material can be observed by microscopic observation, if the shape of the plant material itself has disappeared, it is defined as "dissolution." In this disclosure, a liquid in such a "dissolved" state is defined as a "solution," and a solution in which lignocellulose-containing plant material is dissolved in formic acid is referred to as a "lignocellulose-containing solution." It is preferable that the lignocellulose-containing plant material dissolves uniformly in formic acid, but the plant material may be partially dissolved in formic acid. In the case of partial dissolution, a lignocellulose-containing solution may be obtained by removing the undissolved portion by filtration or the like.

[0036] In the method for manufacturing laminated materials according to this disclosure, in the step of preparing a lignocellulose-containing solution, it is preferable to subject the mixed solution obtained by mixing the lignocellulose-containing plant material and the formic acid to solid-liquid separation to prepare a lignocellulose-containing solution from which at least a portion of the solid content has been removed. Conventional known methods such as filtration, centrifugation, and membrane separation can be used for solid-liquid separation. By performing solid-liquid separation and then manufacturing the adhesive (adhesive film, adhesive paste) described later, the adhesive strength can be further increased. Alternatively, the solid obtained by solid-liquid separation may be dissolved in formic acid and used in the lignocellulose-containing solution, or it may be used for other purposes.

[0037] The amount of formic acid to be mixed with the lignocellulose-containing plant material is appropriately selected depending on the type and shape of the plant material, the concentration of formic acid, etc. From the viewpoint of improving dissolution efficiency, the amount of formic acid may be 4 parts by weight or more, or 9 parts by weight or more, per 1 part by weight of the lignocellulose-containing plant material. From the viewpoint of improving manufacturing efficiency, the amount of formic acid may be 200 parts by weight or less, 100 parts by weight or less, or 50 parts by weight or less, per 1 part by weight of the lignocellulose-containing plant material. As long as the effects of this disclosure are obtained, formic acid may be added directly to the lignocellulose-containing plant material, or it may be added to the lignocellulose-containing plant material as a solution of the desired concentration.

[0038] As long as a lignocellulose-containing solution can be obtained, the dissolution conditions are not particularly limited and can be appropriately selected depending on the type and shape of the plant material containing lignocellulose, the concentration of formic acid, etc. For example, from the viewpoint of high dissolution efficiency, the dissolution temperature may be 20°C or higher, 30°C or higher, or 40°C or higher. From the viewpoint of energy reduction, the dissolution temperature may be 100°C or lower, 90°C or lower, or 80°C or lower. The dissolution time can be appropriately set according to the dissolution temperature.

[0039] From the viewpoint of promoting dissolution, the plant material containing lignocellulose may be mixed with formic acid and then subjected to stirring, or stirring accompanied by grinding may be performed. By performing stirring accompanied by grinding in formic acid, dissolution of the plant material becomes possible under milder conditions. Examples of equipment for stirring accompanied by grinding include bead mills, colloid mills, disc refiners, and conical refiners.

[0040] From the viewpoint of promoting dissolution, pressurization or depressurization may be performed using pressure adjustment means before mixing the plant material with formic acid, and / or after mixing the plant material containing lignocellulose with formic acid. It is believed that the pressure fluctuations applied to the plant material by the pressure adjustment means relax the rigid higher-order structure of cellulose, especially lignocellulose, in the plant material, thereby improving its solubility in formic acid. Pressurization or depressurization allows for dissolution at relatively low temperatures, reducing the energy required for heating and / or heat retention during dissolution. From the viewpoint of efficiently introducing formic acid into the tissue of the plant material through pressure fluctuations, it is preferable to pressurize or depressurize after adding formic acid to the plant material.

[0041] When reducing pressure, it is preferable to reduce the pressure within the range of 1.0 kPa to 10.0 kPa (absolute pressure). When increasing pressure, it is preferable to increase the pressure within the range of 200 kPa to 1000 kPa (gauge pressure). In this specification, absolute pressure is used when the pressure obtained by the pressure reduction process is lower than atmospheric pressure, and gauge pressure based on atmospheric pressure is used when the pressure obtained by the pressure increase process is higher than atmospheric pressure.

[0042] The pressure adjustment means used for pressurized or depressurized processing are not particularly limited. The pressure may be adjusted to the aforementioned pressure range using known means such as aspirators, ejectors, compressors, or mechanical pumps.

[0043] The solid content concentration of the lignocellulose-containing solution obtained by dissolving plant material in formic acid is not particularly limited, but from the viewpoint of ease of removal of liquid components, the solid content concentration of the lignocellulose-containing solution may be 0.5(w / v)% or more, 1.0(w / v)% or more, 1.5(w / v)% or more, or 2.0(w / v)% or more. From the viewpoint of ease of manufacture, the solid content concentration of the lignocellulose-containing solution may be 20(w / v)% or less, 15(w / v)% or less, or 10(w / v)% or less. The lignocellulose-containing solution may further contain known additives such as dyes, to the extent that the effects of this disclosure are not hindered.

[0044] (adherent) In the method for manufacturing the laminated material of this disclosure, an adhesive (adhesive film or adhesive paste) is placed between a first adherend and a second adherend, and an adhesive step is performed to bond the first adherend and the second adherend via the adhesive. In the first embodiment, the adhesive film is the adhesive, and in the second and third embodiments, the adhesive paste is the adhesive. Furthermore, the adhesive layer of the laminated material of this disclosure is formed when the solvent in the adhesive dries.

[0045] Hereafter, any descriptions relating to "the object to be attached" may be interpreted as relating to "the first object to be attached" and "the second object to be attached."

[0046] The material of the adherend is not particularly limited, as long as it adheres firmly to the adhesive. The materials of the first adherend and the second adherend may be the same or different. As described later, the adhesive film and adhesive paste used as the adhesive contain some or all of the hydroxyl groups of a plant-derived component that have been formylated. Formylated plant-derived components, such as lignin and hemicellulose, are hydrophobic and can exhibit strong adhesion even if the material of the adherend is lipophilic. For example, the material of the adherend may be selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold, and paper. The surface of the adherend may be corona treated as needed.

[0047] In this disclosure, the type of plastic used for the adherend is not particularly limited. For example, polyethylene, polypropylene, ABS (acrylonitrile-butadiene-styrene copolymer), polystyrene, polymethyl methacrylate, polylactic acid, PEEK (polyetheretherketone resin), polycarbonate, polyurethane, polyester, PET (polyethylene phthalate), LCP (liquid crystal polymer), etc., can be used. The plastic may also be in foam form. Polyethylene is preferably used.

[0048] In this disclosure, the metal used as the adherend can be iron, stainless steel, nickel, copper, silver, gold, aluminum, tinplate, etc. Furthermore, as the ceramic, pottery or other ceramic materials can be used.

[0049] From the viewpoint of obtaining a laminate made from plant materials, preferred substrate materials are paper, pulp molds, and biomass materials. The paper may be kraft paper, hardwood pulp (LBKP), or softwood pulp (NBKP). Softwood pulp (NBKP) is suitable because it is strong and tear-resistant even when thin, and has high strength, making it widely applicable. Depending on the relationship between desired strength and cost, hardwood pulp (LBKP) or a mixture of softwood pulp (NBKP) may be used.

[0050] The pulp mold may be a thick wall with a film thickness of 5 to 10 mm, a thermoformed mold, a pulp injection mold (PIM), or a pulp foaming mold (PF), and can be appropriately selected according to the desired load-bearing capacity, for example. A thick wall can be preferably used from the viewpoint of obtaining a substrate with a thick film thickness and high load-bearing capacity. In the case of a thick wall, the pulp material adsorbed and laminated on the shaping mold can be dried and solidified as is without press molding. In this case, the adhesive of this disclosure can be bonded to the smooth surface adsorbed on the shaping mold. This results in a pulp mold with a modified surface.

[0051] PIM is a technology for molding pulp by injection molding. It can produce pulp molds with complex structures such as interlocking structures, bosses, and ribs as adherends. In this case, for example, an adhesive can be pre-installed in the mold, and pulp fibers mixed with starch as a binder can be injected into the molding machine as the adherend material. Specifically, after the adherend material is filled into the mold containing the adhesive, the mold repeatedly performs subtle opening and closing movements to evaporate moisture from the adherend material and dry it, while also heating the adhesive. After the adherend material has dried, the mold is cooled and the solidified laminate is removed, thereby obtaining a surface-modified pulp mold. Furthermore, the adherend used in this disclosure may be a foam product obtained by mixing paper powder, industrial starch, and synthetic resin, foaming it with steam, and extruding it. This foam product has environmental advantages compared to other plastic foams and has the advantage of being usable in the same way as existing plastic foam products. By modifying the surface of the laminate made from this foam product using the adhesive of this disclosure, a more desirable appearance and feel can be imparted to the laminate in a desired shape.

[0052] The biomass material may be woody biomass, herbaceous biomass, or a mixture thereof. Examples of herbaceous biomass include sugarcane bagasse, rice straw, wheat, wheat bran, tomatoes, onions, and Moso bamboo.

[0053] A typical woody biomass is wood. The type of wood is not particularly limited; it may be hardwood or softwood. Furthermore, the part of the wood is not particularly limited; it may be heartwood, sapwood, or transitional wood, and may even be a part with knots, black streaks, discoloration, etc., or a part with a coarse texture and lacking in aesthetic appeal. According to this disclosure, even if the material of the adherend is low-grade wood with an appearance that is not normally used as exterior material, by laminating and integrating it with adhesive, it is possible to create a laminated material with a beautiful and high-quality appearance.

[0054] Wood fiberboard or laminated timber may be used as the adherend, to the extent that the effects of this disclosure are not hindered. Conventionally, wood fiberboard is a material made by mixing small pieces of wood with an adhesive such as ureamelamine resin or modified phenolic resin and then heat-pressing it, and laminated timber is a material made by bonding small pieces of wood with an adhesive such as resorcinol resin or aqueous polymer isocyanate. However, as the adherend for this disclosure, wood fiberboard or laminated timber using the adhesive of this disclosure, as described later, is preferably used. Furthermore, as described later, the adhesive of this disclosure contains a plant-derived component in which some or all of the hydroxyl groups have been formylated, such as lignocellulose. Even if some of this formylated lignocellulose decomposes, the products are formic acid, lignin, cellulose, and hemicellulose, and do not adversely affect the natural environment. With such an adherend, the shavings (sawdust in the case of wood) do not contain adhesive as a so-called chemical substance, so they can be safely landfilled or incinerated when disposed of.

[0055] As raw materials for wood-based boards and laminated timber, small pieces cut and shredded from demolition waste and thinned timber are mainly used. While finely shredding the wood causes it to lose its natural properties, weakening its resistance and making it more susceptible to mold, these problems are mitigated by laminating and integrating it with the adhesive disclosed herein. Laminated materials containing the adhesive, with wood-based boards or laminated timber as the substrate, exhibit excellent durability. In particular, laminated materials using the adhesive disclosed herein, with wood-based boards or laminated timber as the substrate, are 100% plant-based materials and are highly biodegradable. The aforementioned herbaceous biomass can also be used as a raw material for wood-based boards and laminated timber.

[0056] The type of wood-based board is not particularly limited. For example, fiberboard (fiberboard) obtained by molding fibrous wood chips, particleboard obtained by molding chip-shaped wood chips, oriented strand board (OSB), parallel strand lumber (PSL), oriented strand lumber (OSL), etc. can be appropriately selected. The fiberboard may be medium-density fiberboard (MDF), hard fiberboard (hardboard), or soft fiberboard (insulation board).

[0057] The type of laminated timber is not particularly limited. In terms of classification by joining method, it may be a scarf joint, finger joint, or butt joint. Joining with a finger joint, which has high adhesive strength, is preferred. It may also be cross-laminated timber (CLT), laminated veneer lumber (LVL), or plywood. Examples of raw material tree species include Douglas fir, redwood, SPF (spruce, pine, fir), Western red cypress, Western hemlock, Japanese cedar, and Japanese larch.

[0058] In the method for manufacturing laminated materials of this disclosure, it is not necessary to heat the adhesive when bonding the adherends. Therefore, adherends can be suitably bonded even when the thickness of the adherends to be bonded is large. Specifically, when the thickness of the adherends is, for example, 2 mm or more, it becomes difficult to place the adhesive between the first adherend and the second adherend and heat the adhesive to a high temperature, but by employing the method for manufacturing laminated materials of this disclosure, the first adherend and the second adherend can be suitably bonded. In this disclosure, the thickness of the adherends may be, for example, 2 mm or more, 4 mm or more, or 20 mm or more, and there is no particular upper limit, but examples include 100 mm.

[0059] From the viewpoint of improving adhesion to the adherend, the adherend may have its surface polished using known polishing methods. As polishing methods, for example, various grades of abrasive paper can be used.

[0060] <First aspect> In a first embodiment of the method for manufacturing a laminated material according to the present disclosure, the process involves first preparing a lignocellulose-containing solution in which a plant material containing lignocellulose is dissolved in formic acid, and then forming the obtained lignocellulose-containing solution into a film to obtain an adhesive film.

[0061] In this process, the liquid component is removed from the lignocellulose-containing solution to recover the solid component. By forming this solid component into a film, an adhesive film is obtained. In other words, the adhesive film can be described as a solid substance formed in the shape of a film by the evaporation of the liquid component (solvent such as formic acid) from the lignocellulose-containing solution. The method for obtaining the adhesive film by removing the liquid component from the lignocellulose-containing solution is not particularly limited. For example, the liquid component may be removed by casting the lignocellulose-containing solution into a container of a desired size and shape and drying it to obtain the adhesive film of this disclosure, or the dried solid component may be formed into a sheet to obtain the adhesive film of this disclosure. Furthermore, from the viewpoint of improving drying efficiency, the lignocellulose-containing solution may be concentrated before drying using known concentration methods such as evaporation concentration or vacuum concentration. Water or alkali may be added to the lignocellulose-containing solution as a precipitating agent, as long as the effects of this disclosure are obtained. The adhesive film of this disclosure may be obtained by forming the solid component precipitated by the addition of water or alkali into a sheet and drying it. Since some of the components contained in the plant raw material may be lost in the method using a precipitating agent, the casting method is preferred.

[0062] The adhesive film obtained in this way has the formic acid added during dissolution removed as a liquid component. This adhesive film is a regenerated solid from the dissolved plant material. The solid component is, for example, made up of substantially plant-derived components alone.

[0063] The plant-derived components mainly consist of cellulose. The plant-derived components may also include lignin and hemicellulose along with cellulose. Preferably, the plant-derived components include one or more selected from the group consisting of cellulose, hemicellulose, and lignin. Some or all of the hydroxyl groups of cellulose, hemicellulose, and lignin may be formylated. The plant-derived components may further include tannins, catechins, polyphenols such as flavonoids, terpenes, etc.

[0064] Furthermore, the adhesive film or solid obtained by removing the liquid component from the lignocellulose-containing solution may be washed to further remove organic acid-derived components, alkali-derived components, etc. For washing, distilled water can be used, for example.

[0065] As long as the effects of this disclosure are obtained, the thickness of the resulting adhesive film is not particularly limited and can be adjusted, for example, by the solid content concentration of the lignocellulose-containing solution. For example, from the viewpoint of suitably bonding the first adherend and the second adherend, the average thickness of the adhesive film may be 10 μm or more, 100 μm or more, or 200 μm or more. From the viewpoint of easy integration with the adherend, the average thickness of the adhesive film may be 2000 μm or less, 1000 μm or less, 800 μm or less, or 600 μm or less. The "average thickness" described herein is the average thickness of the adhesive film before bonding with the adherend, and is the average value of multiple measurements taken using known means.

[0066] In the first embodiment, the adhesive film functions as an adhesive for bonding a first adherend to a second adherend. More specifically, as described below, in the first embodiment, during the bonding process between the first adherend and the second adherend, a predetermined solvent is applied to at least one of the surfaces of the first adherend and the surface of the adhesive film facing the first adherend. In other words, the adhesive film and the solvent function as an adhesive. When bonding the adherend and the adhesive film, if the predetermined solvent is not applied to at least one of the surfaces, the adhesive film cannot adhere to the adherend without heat and pressure bonding.

[0067] The adhesive film exhibits, for example, an infrared absorption spectrum of 1715–1725 cm⁻¹. -1 It shows an absorption peak with a peak top in the region of 1715-1725 cm⁻¹. -1 The absorption at 1715-1725 cm⁻¹ is caused by C=O stretching vibrations. Specifically, it is an absorption peak caused by C=O stretching vibrations of the aldehyde group (formyl group). In this disclosure, 1715-1725 cm⁻¹ -1 The presence of this absorption peak indicates that some or all of the hydroxyl groups of cellulose, hemicellulose, and lignin contained in this adhesive film as plant-derived components are formylated. The presence of this absorption peak distinguishes the adhesive film in this disclosure from those simply cut into sheets from wood or formed into sheets by accumulating wood powder or the like.

[0068] In the infrared absorption spectrum of the adhesive film, the peak intensity (peak height) caused by the C=O stretching vibration is 1000 cm². -1 ~1200cm -1 Compared to the peak intensity of cellulose occurring in the region, it is preferably 5% or more, more preferably 15% or more, and particularly preferably 30% or more greater. This is because a larger peak intensity due to C=O stretching vibration indicates a higher degree of formylation, and it is believed that the formylated plant-derived components contribute to improving the adhesion strength of the adhesive film to the adherend.

[0069] The infrared absorption spectrum of the adhesive film further comprises any one or all of absorption peaks including the OH stretching vibration of cellulose and hemicellulose (3200 to 3600 cm -1 -1 vicinity), the CH stretching vibration of cellulose, hemicellulose and lignin (2840 to 3000 cm -1 -1 vicinity), the skeletal vibration of the benzene ring of lignin (1600 cm -1 -1 vicinity), the C-O stretching vibration of cellulose and hemicellulose (1060 cm -1 -1 vicinity), and the like.

[0070] As described above, the adhesive film is formed by molding a lignocellulose-containing solution into a film shape, and can be substantially formed from plant-derived components. The plant-derived component may be one or more selected from the group consisting of cellulose, hemicellulose and lignin. The plant-derived component may include all of cellulose, hemicellulose and lignin, and may include these in the form of lignocellulose. Here, the form of lignocellulose means a form in which cellulose, hemicellulose and lignin form a complicatedly entangled higher-order structure. Specifically, it means a form in which cellulose, which is a linear polymer, forms a crystal structure through intramolecular and intermolecular hydrogen bonds to constitute strong microfibrils (cellulose microfibrils), hemicelluloses such as xylan and glucomannan are entangled with the microfibrils, and lignin, which is an irregular aromatic polymer, is filled into voids in the matrix of these polysaccharides.

[0071] The total content of hemicellulose and lignin in the adhesive film is also not particularly limited. From the viewpoint of improving adhesiveness to an adherend and increasing pencil hardness, the total content of hemicellulose and lignin may be 5% by weight or more, may be 10% by weight or more, and may be 15% by weight or more.

[0072] The adhesive film may include a plant-derived fibrous substance. By laminating and integrating an adhesive film containing the fibrous substance on an adherend, a laminated material excellent in durability can be obtained. The presence of this fibrous substance can be confirmed by scanning electron microscope observation.

[0073] The fibrous material in the adhesive film may be the aforementioned cellulose microfibrils. For example, the fibrous material may be cellulose fibers that were not completely dissolved during the manufacturing process of the adhesive film. This fibrous material may have a cellulose type I crystal structure. The presence of a cellulose type I crystal structure can be confirmed by X-ray diffraction measurement. For example, a sample of the adhesive film taken from the laminated material and freeze-dried can be measured using an X-ray diffraction measuring device (for example, Rigaku's "SmartLab"). Specifically, it can be measured by powder X-ray diffraction using an anti-reflective silicon plate. It is known that cellulose type I crystals with a parallel chain structure exhibit high-intensity diffraction around 2θ = 22.5°, and, by peak separation, around 16.7° and 14.8°. Therefore, by checking the presence or absence of high-intensity diffraction peaks around 2θ = 22.5°, 16.7°, and 14.8° in the X-ray diffraction pattern of a sample taken from a wood molded product, the presence or absence of a cellulose type I crystal structure can be determined.

[0074] According to this disclosure, for example, an adhesive film made of 100% plant material can be obtained, but the adhesive film may also contain divalent or higher fatty acids and / or their anhydrous forms as components other than plant-derived components and plant materials. When it is desired to obtain a more glossy appearance while surface modifying the laminate, and / or to integrate the adherend and the adhesive film under milder conditions, it is preferable to include divalent or higher fatty acids and / or their anhydrous forms in the adhesive film. The reason why the above-mentioned excellent effect is obtained by including divalent or higher fatty acids and / or their anhydrous forms in the adhesive film is thought to be due to the interaction between the plant-derived components and plant materials in the adhesive film and the divalent or higher fatty acids and / or their anhydrous forms.

[0075] The adhesive film of this disclosure is formed into a film from a lignocellulose-containing solution obtained by dissolving lignocellulose-containing plant material in formic acid, and therefore has a length of 1715-1725 cm. -1The presence of absorption peaks indicates that some or all of the hydroxyl groups of cellulose, hemicellulose, and lignin included as plant-derived components have been formylated, and the cellular structure as wood has been dismantled. The adhesive film or laminate of this disclosure, which contains such plant-derived components and plant materials, and also contains divalent or higher fatty acids and / or their anhydrous forms, is essentially different from a molded product obtained by simply blending divalent or higher fatty acids and / or their anhydrous forms with wood powder, wood, wood chips, etc., and then heat-treating it.

[0076] Furthermore, when divalent or higher fatty acids and / or their anhydrous forms are included in the adhesive film, the ductility and adhesive strength (adhesion) of the adhesive film may also be improved.

[0077] In this specification, divalent or greater fatty acids are also referred to as polycarboxylic acids. Furthermore, in this specification, "and / or" is used to mean both "and" and "or". For example, divalent or greater fatty acids and / or their anhydrides include all of (i) divalent or greater fatty acids, (ii) anhydrides of divalent or greater fatty acids, and (iii) divalent or greater fatty acids and anhydrides of divalent or greater fatty acids, and is equivalent to at least one selected from the group consisting of divalent or greater fatty acids and anhydrides of divalent or greater fatty acids.

[0078] Examples of divalent or higher fatty acids include succinic acid, adipic acid, malic acid, tartaric acid, malonic acid, fumaric acid, maleic acid, oxalic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,6-pyridinedicarboxylic acid, acetonedicarboxylic acid, 3-oxoglutaric acid, 2,3-naphthalenedicarboxylic acid, azelaic acid, hexadecanedioic acid, docosanedionic acid, α,ω-alkanedicarboxylic acids, citric acid, and 1,2,3,4-butanetetracarboxylic acid. Polysaccharides are also examples of divalent or higher fatty acids. Examples of polysaccharides include polyuronic acids such as alginic acid and pectin; polyuronic acids obtained by oxidizing the primary hydroxyl groups of cellulose; and carboxymethylcellulose. Divalent or higher fatty acids and / or their anhydrides may be included individually or in combination of two or more. The divalent or greater fatty acid and / or its anhydride is preferably citric acid and / or its anhydride.

[0079] If the adhesive film contains divalent or higher fatty acids and / or their anhydrous forms, the content is preferably 3 to 200 parts by weight, more preferably 15 to 150 parts by weight, even more preferably 20 to 100 parts by weight, and particularly preferably 25 to 75 parts by weight, based on 100 parts by weight of the total of plant-derived components and plant materials constituting the adhesive film. If the adhesive film contains divalent or higher fatty acids and / or their anhydrous forms, it is preferable that the components excluding those said components consist substantially of plant-derived components and plant materials.

[0080] The adhesive film may contain hydroxy acids and / or ammonium dihydrogen phosphate as plant-derived components and non-plant-derived components. Here, hydroxy acids include carboxylic acids and alcohols. Specific examples of hydroxy acids include glycolic acid, lactic acid, glyceric acid, hydroxybutyric acid, citramalic acid, isocitric acid, leucic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineradicic acid, cerebronic acid, quinic acid, shikimic acid, and the like.

[0081] The aforementioned components that may be included in the adhesive film, namely at least one selected from the group consisting of divalent or higher fatty acids, anhydrides of divalent or higher fatty acids, hydroxy acids, and ammonium dihydrogen phosphate, are considered to have the function of a crosslinking agent. Here, a crosslinking agent means one that crosslinks molecules of lignocellulose. If the adhesive film of this disclosure contains at least one selected from the group consisting of divalent or higher fatty acids, anhydrides of divalent or higher fatty acids, hydroxy acids, and ammonium dihydrogen phosphate, a crosslinked structure by covalent bonds may be formed in the adhesive film of this disclosure.

[0082] If the adhesive film of this disclosure contains divalent or higher fatty acids and / or their anhydrous forms, polyhydric alcohols and / or sugars may be used together with the divalent or higher fatty acids and / or their anhydrous forms. Examples of polyhydric alcohols and sugars include glycerin, ethylene glycol, sucrose, starch, chitin, chitosan, cellulose, dextran, pullulan, β-1,3-glucan, β-1,6-glucan, glucose, cellooligosaccharides, mannose, mannooligosaccharides, xylose, xylooligosaccharides, amino acids, peptides, proteins, and the like.

[0083] Furthermore, while this disclosure makes it possible to manufacture a laminate made of 100% plant-based materials, the adhesive film or laminate may also contain additives other than plant-derived components and plant materials (for example, conductive agents, magnetic powders, antibacterial agents, flame retardants, antioxidants, UV absorbers, etc.) to the extent that they do not impair the effects of this disclosure. If the adhesive film contains additives, the amount is preferably 1 to 500 parts by weight, more preferably 3 to 100 parts by weight, and even more preferably 5 to 75 parts by weight, based on 100 parts by weight of the total of plant-derived components and plant materials constituting the adhesive film. If the adhesive film contains additives, it is preferable that the components excluding the additives consist substantially of plant-derived components and plant materials.

[0084] The density of the adhesive film is not particularly limited and can be adjusted depending on the type of raw material, dissolution conditions, etc. For example, the density of the adhesive film may be 0.2 g / cm³. 3The above is sufficient, and 0.3 g / cm³ 3 The above is sufficient, and 0.5 g / cm³ 3 It may be above 0.8 g / cm³ or more, and also 1.2 g / cm³ 3 The following may be used: 1.1 g / cm³ 3 The following may be used: 1.0 g / cm³ 3 The following may apply: The density of the adhesive film is the apparent density measured in accordance with JIS Z 8807 "Method for measuring the density and specific gravity of solids".

[0085] The basis weight of the adhesive film placed between the first adherend and the second adherend is preferably 5 to 500 g / m². 2 , comfortably 20-300g / m 2 To a certain extent, more preferably 100-200 g / m 2 It is a matter of degree. The higher the basis weight of the adhesive film, the stronger the adhesive strength.

[0086] The tensile properties of the adhesive film are set appropriately depending on the application of the laminate, etc., but from the viewpoint of ease of molding, the Young's modulus of this adhesive film may be 0.05 GPa or higher, or 1.0 GPa or higher. From the viewpoint of durability, a preferred Young's modulus is 4.0 GPa or less. From the viewpoint of durability, the maximum stress of the adhesive film may be 0.5 MPa or higher, or 5.0 MPa or higher, or 10 MPa or higher. From the viewpoint of ease of molding, a preferred maximum stress is 80 MPa or less. From the viewpoint of ease of molding, the maximum elongation of the adhesive film may be 0.5% or higher, or 1.5% or higher. From the viewpoint of durability, a preferred maximum elongation is 5.0% or less.

[0087] As stated above, the thickness of the adhesive film is set appropriately depending on the application of the laminated material, etc., and is not particularly limited. The thickness of the adhesive film may be reduced as long as effects such as improved appearance of the adherend, surface hydrophobicity, and increased pencil hardness are achieved. For example, the average thickness of the adhesive film may be 2000 μm or less, 500 μm or less, or 200 μm or less. By using a thinner adhesive film, the amount of plant resources used as raw materials for the adhesive film is reduced, and a laminated material that reflects the physical properties of the adherend itself (e.g., hardness and wood grain) can be obtained. On the other hand, when using wood-based boards or the like as the adherend, a thicker adhesive film can be used to modify the surface, such as for decoration. The average thickness of the adhesive film in this disclosure is the average value measured multiple times using known means.

[0088] From the viewpoint of obtaining high heat resistance, the glass transition temperature Tg of the adhesive film may be 180°C or higher, 190°C or higher, or 200°C or higher. The upper limit is not particularly limited, but a preferred glass transition temperature Tg is 280°C or lower. The glass transition temperature of the adhesive film is measured by dynamic viscoelasticity measurement. Details of the measurement method and measurement conditions will be described later in the examples.

[0089] The adhesive film of this disclosure is preferably homogeneous with few color patterns. In laminated materials in which such an adhesive film is laminated to, for example, wood, the wood grain of the wood is transmitted through the adhesive film, and an appearance similar to that of the wood can be maintained. Furthermore, when laminated timber is used as the substrate, the joints of the laminated timber are covered and concealed by the adhesive film, so a good appearance can be obtained. On the other hand, a sheet made by simply thinly slicing wood may retain the wood grain, and when this is bonded to wood with an adhesive, the wood grain of the sheet and the wood grain of the substrate may mix, resulting in a poor appearance.

[0090] In the first embodiment, during the bonding process, a predetermined solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend. As a result, when the adhesive film and the first adherend are laminated, the solvent penetrates the adhesive film, and the adhesive film and the first adherend are firmly bonded without the need for heating and pressing the adhesive film. Furthermore, if the solvent is applied to at least one of the surface of the second adherend and the surface of the adhesive film facing the second adherend during the bonding process, when the adhesive film and the second adherend are laminated, the solvent penetrates the adhesive film, and the adhesive film and the second adherend are firmly bonded without the need for heating and pressing the adhesive film. In this disclosure, heating and pressing are not necessary during the bonding process, but they may be performed.

[0091] The solvent to be applied preferably contains at least one selected from the group consisting of ketones, alcohols, aromatic compounds, polyhydric alcohols, organic acids, and aprotic polar solvents. Specific examples of solvents include water, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, aromatic compounds such as benzene, toluene, and xylene, alkaline aqueous solutions such as sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, calcium hydroxide aqueous solution, and sodium carbonate aqueous solution, polyhydric alcohols such as ethylene glycol and glycerol, organic acids such as formic acid, acetic acid, glyoxylic acid, and pyruvic acid, and aprotic polar solvents such as dimethyl sulfoxide, NN-dimethylformamide, and N,N-dimethylacetamide. Among these, the solvent preferably contains formic acid.

[0092] When the solvent contains formic acid, the concentration of the formic acid (formic acid solution) applied to the surface of the adhesive film and / or adherend is not particularly limited, but is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, with an upper limit of, for example, 100% by mass. Various concentrations of commercially available formic acid (formic acid solution) are available and can be used in this disclosure. The formic acid solution is generally an aqueous solution of formic acid. The formic acid solution may be further diluted with the solvent and applied to at least one of the surface of the adherend and the adhesive film. The type of solvent is not particularly limited, but a solvent that shows solubility for any of cellulose, hemicellulose, and lignin produced when plant material containing lignocellulose is dissolved in formic acid is preferred. Specific examples of solvents in formic acid solutions include water, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, aromatic compounds such as benzene, toluene, and xylene, polyhydric alcohols such as sodium hydroxide aqueous solution, ethylene glycol, and glycerol, alkaline aqueous solutions such as acetic acid, glyoxylic acid, potassium hydroxide aqueous solution, calcium hydroxide aqueous solution, and sodium carbonate aqueous solution, organic acids such as pyruvic acid, and aprotic polar solvents such as dimethyl sulfoxide, NN-dimethylformamide, and N,N-dimethylacetamide.

[0093] The amount of solvent applied to the surface of the first adherend and the surface of the adhesive film facing the first adherend (the total amount applied if applied to both the first adherend and the adhesive film) is preferably 0.05 g or more, more preferably 0.15 g or more, even more preferably 0.25 g or more per 1 cm² of the adhesive film, and also preferably 1.0 g or less, more preferably 0.7 g or less, even more preferably 0.5 g or less, with a preferred range being 0.25 to 0.5 g. The same applies to the amount of solvent applied to the surface of the second adherend and the surface of the adhesive film facing the second adherend (the total amount applied if applied to both the second adherend and the adhesive film).

[0094] In the first embodiment, the temperature in the bonding process (the temperature applied to the laminate of the first adherend, adhesive film, and second adherend) is preferably 0°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, and also preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 50°C or lower, with a preferred range of approximately 20 to 50°C. When heating is performed in the bonding process, the temperature in the bonding process is preferably 40°C or higher, more preferably 60°C or higher, even more preferably 80°C or higher, and also preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower, with a preferred range of approximately 80 to 200°C.

[0095] In the first embodiment, the pressure in the bonding process (pressure applied to the laminate of the first adherend, adhesive film, and second adherend) is preferably 0.01 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and also preferably 100 MPa or less, more preferably 50 MPa or less, and even more preferably 5 MPa or less, with a preferred range of approximately 0.5 to 5 MPa. When heat bonding is performed in the bonding process, the pressure in the bonding process is preferably 0.01 MPa or more, more preferably 0.2 MPa or more, even more preferably 0.4 MPa or more, and also preferably 100 MPa or less, more preferably 10 MPa or less, and even more preferably 2 MPa or less, with a preferred range of approximately 0.4 to 2 MPa.

[0096] <Second aspect> In a second aspect of the method for manufacturing a laminated material according to the present disclosure, the steps include: preparing a lignocellulose-containing solution by dissolving a plant material containing lignocellulose in formic acid; removing at least a portion of the liquid components from the obtained lignocellulose-containing solution to obtain a solid; and mixing the obtained solid with a predetermined solvent to obtain an adhesive paste containing the solvent.

[0097] Methods for obtaining a solid by removing at least some of the liquid components from a lignocellulose-containing solution include heating and / or reducing the pressure of the lignocellulose-containing solution to evaporate the liquid components. Membrane separation can also be employed. Examples of liquid components include formic acid and solvents contained in the lignocellulose-containing plant material.

[0098] The solid material of the second embodiment may contain residual liquid components, or all liquid components may be removed. The solid material of the second embodiment is the same as the adhesive film of the first embodiment, except that its shape may be a film or not. Therefore, the composition of the solid material of the second embodiment is the same as that of the adhesive film described in the first embodiment above, and is referenced in the description of the solid material. Also, for example, the solid material of the second embodiment, like the adhesive film, has an infrared absorption spectrum of, for example, 1715-1725 cm⁻¹. -1 It shows an absorption peak with its peak top in the region.

[0099] In the second embodiment, a solid obtained from a lignocellulose-containing solution is mixed with a predetermined solvent to obtain an adhesive paste containing the solvent.

[0100] The solvent to be mixed preferably contains at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents. Specific examples of solvents include water, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, aromatic compounds such as benzene, toluene, and xylene, alkaline aqueous solutions such as sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, calcium hydroxide aqueous solution, and sodium carbonate aqueous solution, polyhydric alcohols such as ethylene glycol and glycerol, organic acids such as formic acid, acetic acid, glyoxylic acid, and pyruvic acid, and aprotic polar solvents such as dimethyl sulfoxide, NN-dimethylformamide, and N,N-dimethylacetamide. Among these, the solvent preferably contains formic acid.

[0101] When the solvent contains formic acid, the concentration of the formic acid (formic acid solution) to be mixed is not particularly limited, but is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, with an upper limit of, for example, 100% by mass. Various concentrations of commercially available formic acid (formic acid solution) are available and can be used in this disclosure. As stated above, the formic acid solution is generally an aqueous solution of formic acid. The formic acid solution may be further diluted with the solvent and applied to at least one of the surface of the adherend and the adhesive film. The type of solvent is not particularly limited, but a solvent that shows solubility for any of the cellulose, hemicellulose, and lignin produced when plant material containing lignocellulose is dissolved in formic acid is preferred. Similar to the first embodiment, specific examples of solvents in the formic acid solution include water, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, aromatic compounds such as benzene, toluene, and xylene, alkaline aqueous solutions such as sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, calcium hydroxide aqueous solution, and sodium carbonate aqueous solution, polyhydric alcohols such as ethylene glycol and glycerol, organic acids such as acetic acid, glyoxylic acid, and pyruvic acid, and aprotic polar solvents such as dimethyl sulfoxide, NN-dimethylformamide, and N,N-dimethylacetamide.

[0102] In the second embodiment, the concentration of formic acid in the adhesive paste is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and also preferably 96% by mass or less, more preferably 94% by mass or less, and even more preferably 92% by mass or less, with a preferred range of 50 to 92% by mass. The solid content concentration in the adhesive paste is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 9% by mass or more, and also preferably 90% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less, with a preferred range of 9 to 30% by mass.

[0103] In a second embodiment, an adhesive paste is placed between the first adherend and the second adherend, and an adhesive bonding step is performed to bond the first adherend and the second adherend via the adhesive paste. As described above, in the laminated material of this disclosure, it is not necessary to heat and press during the bonding step, or it may be heat and press.

[0104] In the second embodiment, the amount of adhesive paste to be placed between the first adherend and the second adherend is such that the adhesive area is 1 cm². 2 Preferably, the amount is 0.01g or more, more preferably 0.04g or more, even more preferably 0.06g or more, and also preferably 1.0g or less, more preferably 0.5g or less, even more preferably 0.3g or less, with a preferred range being 0.06g to 0.5g.

[0105] Furthermore, in the second embodiment, the temperature in the bonding process (the temperature applied to the laminate of the first adherend, adhesive paste, and second adherend) is preferably 0°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, and also preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 50°C or lower, with a preferred range of approximately 20 to 50°C. If heating is performed in the bonding process, the temperature in the bonding process is preferably 40°C or higher, more preferably 60°C or higher, even more preferably 80°C or higher, and also preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower, with a preferred range of approximately 80 to 200°C.

[0106] In the second embodiment, the pressure in the bonding process (pressure applied to the laminate of the first adherend, adhesive paste, and second adherend) is preferably 0.01 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and also preferably 100 MPa or less, more preferably 50 MPa or less, and even more preferably 5 MPa or less, with a preferred range of approximately 0.5 MPa to 5 MPa. When heat bonding is performed in the bonding process, the pressure in the bonding process is preferably 0.01 MPa or more, more preferably 0.2 MPa or more, even more preferably 0.4 MPa or more, and also preferably 100 MPa or less, more preferably 10 MPa or less, and even more preferably 2 MPa or less, with a preferred range of approximately 0.4 MPa to 2 MPa.

[0107] <Third aspect> In a third aspect of the method for manufacturing a laminated material according to the present disclosure, after a step of preparing a lignocellulose-containing solution in which a plant material containing lignocellulose is dissolved in formic acid, some of the liquid components in the obtained lignocellulose-containing solution are removed to obtain an adhesive paste containing formic acid.

[0108] Methods for removing some of the liquid components from a lignocellulose-containing solution include, as in the second embodiment, heating and / or reducing the pressure of the lignocellulose-containing solution to partially evaporate the liquid components. Membrane separation can also be employed. Examples of liquid components include formic acid and solvents contained in the lignocellulose-containing plant material.

[0109] In the third embodiment, since some of the liquid components in the lignocellulose-containing solution are removed, formic acid remains in the resulting adhesive paste.

[0110] The adhesive paste of the third embodiment may further contain a solvent. Examples of solvents are the same as those in the second embodiment.

[0111] In the third embodiment, the concentration of formic acid in the adhesive paste is the same as in the second embodiment. The solid content concentration in the adhesive paste is also the same as in the second embodiment.

[0112] In the third embodiment, as in the second embodiment, an adhesive paste is placed between the first adherend and the second adherend, and an bonding step is performed to bond the first adherend and the second adherend via the adhesive paste. As described above, in the laminated material of this disclosure, it is not necessary to heat and press during the bonding step, or it may be heat and press.

[0113] In the third embodiment, the amount of adhesive paste placed between the first adherend and the second adherend is the same as in the second embodiment.

[0114] Furthermore, in the third embodiment, the temperature in the bonding process (the temperature applied to the laminate of the first adherend, adhesive paste, and second adherend) is the same as in the second embodiment.

[0115] In the third embodiment, the pressure in the bonding process (pressure applied to the laminate of the first adherend, adhesive paste, and second adherend) is the same as in the second embodiment.

[0116] [Laminated wood] The laminate of the present disclosure is a laminate in which a first adherend and a second adherend are laminated with at least an adhesive layer in between, wherein the first adherend is formed of at least one selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold and paper, the thickness of the first adherend is 2 mm or more, the adhesive layer is substantially formed from plant-derived components, and the infrared absorption spectrum of the adhesive layer is 1715-1725 cm⁻¹ -1 It is characterized by showing an absorption peak in the region.

[0117] The laminated material of this disclosure can be suitably manufactured by utilizing the laminated material of this disclosure as described above. The laminated material of this disclosure will be described in detail below.

[0118] The laminate of this disclosure comprises at least an adherend and an adhesive layer laminated and integrated on the surface of the adherend. For example, the laminate of this disclosure preferably includes an adhesive layer laminated and integrated such that the main surface of at least one surface of the adherend and the main surface of the adhesive layer are in contact. In this disclosure, the surface with the largest contact area between the adherend and the adhesive layer is referred to as the "main surface". The number of adherends and adhesive layers included in the laminate is not particularly limited, and multiple adherends and adhesive layers may be laminated alternately and integrated. In other words, the laminate of this disclosure has a layer structure composed of adherends and adhesive layers. For example, the laminate may include a first adherend and an adhesive layer laminated and integrated on the surface of the first adherend, or it may include a first adherend and a second adherend laminated and bonded to the first adherend via an adhesive layer.

[0119] For convenience, in this disclosure, in embodiments where adherends are bonded to both sides of the adhesive layer, one will be referred to as the "first adherend" and the other as the "second adherend," and the laminated material of this disclosure is not limited to a two-layer or three-layer structure. Within the scope to which the effects of this disclosure can be obtained, the laminated material may include layers other than the adhesive layer and adherends.

[0120] Here, the "adhesive layer" is a layer formed by the evaporation of the solvent from the aforementioned adhesive film or adhesive paste. "Laminated and integrated" does not simply mean that the adherend and the adhesive layer are on top of each other, but rather that the adhesive layer is firmly fixed to the surface of the adherend. As long as the adhesive layer and the adherend are firmly fixed, the interface between the adherend and the adhesive layer may be clear or unclear. "Laminated adhesion" means that the first adherend and the second adherend are firmly fixed (i.e., integrated) via the adhesive layer.

[0121] The laminated material of this disclosure is manufactured by bonding an adherend to an adhesive layer without using chemical substances such as adhesives, and as described above, heat pressing is not required for bonding. The adhesive layer is formed by an adhesive film or adhesive paste using a lignocellulose-containing solution, as described above. Since the solvent is removed as a liquid component, this adhesive layer can be formed from substantially only plant-derived components. For example, when a plant material is used as the adherend, a laminated material consisting substantially of plant-derived components and plant material is obtained.

[0122] In this disclosure, "substantially" means, for example, that the content of plant-derived components in the adhesive layer is 90% by weight or more, preferably 95% by weight or more, and ideally 100% by weight. When plant materials are used as the adherend, the total content of plant materials and plant-derived components in the laminate is 90% by weight or more, preferably 95% by weight or more, and ideally 100% by weight. In this case, the laminate can be said to be 100% plant material.

[0123] According to this disclosure, a laminate made of 100% plant-based materials can be obtained, but the adhesive layer or the laminate may contain plant-derived components and components other than plant-based materials, to the extent that it does not impair the effects of this disclosure. For example, when imparting a desired function to the laminate, the adhesive layer may contain known additives. Examples of such additives include conductive agents, magnetic powders, antibacterial agents, flame retardants, antioxidants, and ultraviolet absorbers.

[0124] By adding a conductive agent to the adhesive layer, a laminate can be obtained that suppresses the accumulation of static electricity and reduces electrostatic discharge during the drying period. Furthermore, by adding magnetic powder to the adhesive layer, a laminate can be obtained that can be attracted and fixed with magnets, or a laminate that can shield electromagnetic waves emitted from the sun, electronic devices, etc. Laminates obtained by adding an antibacterial agent to the adhesive layer can be used in sanitary and toiletry fields and hygiene material applications where antibacterial and antiviral properties are required. In addition, the addition of an antibacterial agent has the effect of suppressing the biodegradation of the laminate itself and changes in appearance due to bacterial growth. Laminates obtained by adding a flame retardant to the adhesive layer can be used in the construction field where fire resistance is required. Laminates obtained by adding an antioxidant or ultraviolet absorber to the adhesive layer can be used in the construction field where weather resistance and light resistance are required.

[0125] According to this disclosure, a laminate made of 100% plant materials can be obtained, but the adhesive layer or the laminate may contain divalent or higher fatty acids and / or their anhydrous forms as plant-derived components and components other than plant materials. When it is desired to obtain a more glossy appearance while surface modifying the laminate, and / or to integrate the adherend and the adhesive layer under milder conditions, it is preferable that the adhesive layer contains divalent or higher fatty acids and / or their anhydrous forms. Among the organic acids mentioned above, divalent or higher fatty acids that are not completely removed as liquid components from the plant solution are preferred. The specific divalent or higher fatty acids are as described above.

[0126] In the method for manufacturing the laminated material of the present disclosure described above, there is no need to heat the adhesive when bonding the first adherend and the second adherend. Therefore, adherends can be suitably bonded even when the thickness of the adherends to be bonded is large. For example, when the thickness of the adherend is 2 mm or more, it becomes difficult to place the adhesive between the first adherend and the second adherend and heat the adhesive to a high temperature, but by employing the method for manufacturing the laminated material of the present disclosure, the first adherend and the second adherend can be suitably bonded. In the laminated material of the present disclosure, the thickness of the adherend may be, for example, 2 mm or more, 4 mm or more, or 20 mm or more, and there is no particular upper limit, but for example, 100 mm is one example.

[0127] Furthermore, in the laminated material of this disclosure, the thickness of the adhesive layer is preferably 10 μm or more, more preferably 50 μm or more, even more preferably 100 μm or more, and also preferably 2000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, with a preferred range being 100 to 200 μm. [Examples]

[0128] The present disclosure will be explained in more detail below with reference to examples.

[0129] (Examples 1-5) <Manufacturing of adhesive films> In a 1L glass container, 6g of eucalyptus wood powder, a plant material containing lignocellulose, and 294g of formic acid were placed. A magnetic stirrer tip and Teflon balls (Teflon is a registered trademark) were then added for magnetic stirring. Thirty Teflon balls, each with a diameter of 1 / 2 inch, were added. This 1L glass container was immersed in an oil bath heated to 40°C and stirred at 40°C for 9 days to obtain a lignocellulose-containing solution in which the lignocellulose-containing plant material dissolved in the formic acid. The obtained lignocellulose-containing solution was subjected to centrifugation (10,000 rpm, 10 min) to separate the supernatant from the precipitate. The obtained supernatant (lignocellulose-containing solution) was spread on a polypropylene tray (5cm long, 8cm wide), and the formic acid was evaporated to produce an adhesive film. The weight of the supernatant placed in the polypropylene tray was 10g, 15g, 20g, 30g, and 40g in Examples 1-5, respectively. The thickness of the adhesive film (5cm long, 8cm wide) obtained after drying the formic acid was 42μm, 63μm, 83μm, 125μm, and 167μm in Examples 1-5, respectively, and the basis weight of the adhesive film (1m²) was also determined. 2 The weight per square meter is 50g / m². 2 75g / m 2 100g / m 2 150g / m 2 200g / m 2The resulting adhesive films were each cut to a size of 12 mm x 25 mm and used to bond the first adherend and the second adherend, which was wood. In Examples 1 to 5, the weights of the adhesive films after cutting were 15 mg, 23 mg, 30 mg, 45 mg, and 60 mg, respectively.

[0130] <Manufacturing of laminated timber> As the first and second adherends, pieces of wood (cedar) measuring 50 mm in length, 25 mm in width, and 5 mm in thickness were prepared. The size of the area where the first and second adherends were bonded via the adhesive film was 12 mm x 25 mm, respectively. 0.5 g of formic acid was applied to one side of the first adherend to coat it. Next, the adhesive film obtained above was placed on the first adherend, which was wet with formic acid, to allow the formic acid to soak into the adhesive film. Next, 0.5 g of formic acid (98% purity) was applied to the surface of the adhesive film and left to stand for about 10 minutes. Next, the second adherend was placed on top of the adhesive film, sandwiching the adhesive film between the first and second adherends, and bonding was performed at room temperature (25°C) to produce a laminated material in which the first adherend, adhesive layer (adhesive film), and second adherend were stacked in this order. Commercially available clips were used for bonding. In the resulting laminate, the adhesive film sandwiched between the first and second adherends dried to form an adhesive layer.

[0131] (Comparative Example 1) <Manufacturing of laminated timber> In Example 1, a laminate was manufactured in the same manner as in Example 1, except that the surfaces of the first adherend and the adhesive film were not coated with formic acid. The laminate consisted of a first adherend, an adhesive layer (adhesive film), and a second adherend in this order, but the first adherend and the second adherend were not bonded together by the adhesive film.

[0132] (Examples 6-11) <Manufacturing of adhesive films> The adhesive film was manufactured in the same manner as in Examples 1-5, except that the wood powder shown in Table 2 was used as the lignocellulose-containing plant material, and the weight of the lignocellulose solution (supernatant) was set to the weight (g) shown in Table 2.

[0133] <Manufacturing of laminated timber> Laminates were manufactured in the same manner as in Examples 1-5, except that the adhesive film obtained in Example 6-11 was used, in which the first adherend, adhesive layer (adhesive film), and second adherend were laminated in that order.

[0134] (Examples 12-13) <Manufacturing of adhesive paste> In a 1L glass container, 6g of eucalyptus wood flour (a plant material containing lignocellulose) and 294g of formic acid were placed, and 30 1 / 2-inch diameter Teflon balls were added. This 1L glass container was immersed in an oil bath heated to 40°C. The contents of the container were stirred at 40°C for 9 days using a stirring device equipped with a Teflon crescent blade, a Teflon stirring shaft, and a stirring motor, to obtain a lignocellulose-containing solution in which the lignocellulose-containing plant material dissolved in the formic acid. The obtained lignocellulose-containing solution was subjected to centrifugation (10,000 rpm, 10 min) to separate the supernatant from the precipitate. The obtained supernatant (lignocellulose-containing solution) was concentrated using a rotary evaporator, and some of the formic acid was removed by distillation. The concentration was continued until the wood flour content in the concentrated liquid was 10 wt%, to produce an adhesive paste.

[0135] <Manufacturing of laminated timber> As the first and second adherends, pieces of wood (cedar) measuring 50 mm in length, 25 mm in width, and 5 mm in thickness were prepared. The size of the area where the first and second adherends were bonded via adhesive film (paste) was 12 mm x 25 mm, respectively. 0.30 g of adhesive paste was applied to the portion of the first adherend that would be bonded to the second adherend. Next, the second adherend was placed on top of the adhesive paste applied to the first adherend, sandwiching the adhesive paste between the first and second adherends. Bonding was performed at room temperature (25°C) to produce a laminated material in which the first adherend, adhesive layer (adhesive paste), and second adherend were layered in this order. A commercially available clip was used during bonding. In the resulting laminated material, the adhesive paste sandwiched between the first and second adherends dried and became an adhesive layer.

[0136] [Infrared absorption spectrum of the adhesive layer of laminated material] Fourier transform infrared spectroscopy (FTIR analysis) was performed on the adhesive layer of the laminated material obtained in each example and comparative example. The infrared absorption spectrum was found to be in the 1715-1725 cm⁻¹ range. -1 We confirmed that the region exhibits an infrared absorption peak originating from the formyl group. The results are shown in Tables 1 to 3.

[0137] [Bonding strength between the laminated material's substrate and the adhesive layer] For each laminated material obtained in the examples, the shear bond strength was measured in accordance with the method specified in JIS K6851-1994 (Test method for tensile shear bond strength of adhesives for wood). A Shimadzu AGX-V2 tensile testing machine was used for the measurement, and a load cell with a load of 20 kN (kilonewtons) was used. The stress (bond strength) was determined by dividing the maximum strength at which the sample fractured by the bonded area. The results are shown in Tables 1 to 3.

[0138] [Table 1]

[0139] [Table 2]

[0140] [Table 3]

[0141] As described above, this disclosure provides inventions in the following embodiments. Item 1. A method for manufacturing a laminate, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, The process involves forming the lignocellulose-containing solution into a film to obtain an adhesive film, An adhesive step of placing the adhesive film between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive film, It is equipped with, In the bonding step, a solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend. A method for producing a laminate, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents. Item 2. A method for manufacturing a laminate, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, A step of removing at least some of the liquid components from the lignocellulose-containing solution to obtain a solid, A step of mixing the solid material with the solvent to obtain an adhesive paste containing the solvent, An adhesive step of placing the adhesive paste between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive paste, Equipped with, A method for producing a laminate, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents. Item 3. A method for manufacturing a laminate, wherein a first adherend and a second adherend are laminated with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, A step of removing some of the liquid components from the lignocellulose-containing solution to obtain an adhesive paste containing formic acid, An adhesive step of placing the adhesive paste between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive paste, A method for manufacturing laminated material, comprising the features described above. Item 4. A method for producing a laminated material according to any one of items 1 to 3, wherein in the step of preparing the lignocellulose-containing solution, the mixed solution obtained by mixing the plant material containing the lignocellulose and the formic acid is subjected to solid-liquid separation to prepare the lignocellulose-containing solution from which at least a portion of the solid content has been removed. Item 5. A method for manufacturing a laminated material according to any one of items 1 to 4, wherein the temperature during the bonding step is between 0°C and 50°C. Item 6. The lignocellulose-containing solution further comprises a solvent, The method for producing a laminated material according to any one of claims 1 to 5, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents. Item 7. A method for manufacturing a laminate according to any one of items 1 to 6, wherein the first adherend is formed of at least one selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold and paper. Item 8. A laminate in which a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The first adherend is formed from at least one material selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold, and paper. The thickness of the first adherend is 2 mm or more. The adhesive layer is substantially formed from plant-derived components. In the infrared absorption spectrum of the adhesive layer, 1715-1725 cm⁻¹ -1 A laminated material that shows an absorption peak in the region.

Claims

1. A method for manufacturing a laminated material, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, The process involves forming the lignocellulose-containing solution into a film to obtain an adhesive film, The bonding step involves placing the adhesive film between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive film. It is equipped with, In the bonding step, a solvent is applied to at least one of the surface of the first adherend and the surface of the adhesive film facing the first adherend. A method for producing a laminated material, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

2. A method for manufacturing a laminated material, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, A step of removing at least some of the liquid components from the lignocellulose-containing solution to obtain a solid, A step of mixing the solid material with the solvent to obtain an adhesive paste containing the solvent, The bonding step involves placing the adhesive paste between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive paste, Equipped with, A method for producing a laminated material, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

3. A method for manufacturing a laminated material, wherein a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The process involves preparing a lignocellulose-containing solution in which plant material containing lignocellulose is dissolved in formic acid, A step of removing some of the liquid components from the lignocellulose-containing solution to obtain an adhesive paste containing formic acid, The bonding step involves placing the adhesive paste between the first adherend and the second adherend, and bonding the first adherend and the second adherend via the adhesive paste, A method for manufacturing laminated material, comprising the features described above.

4. A method for producing a laminated material according to any one of claims 1 to 3, wherein in the step of preparing the lignocellulose-containing solution, the mixed solution obtained by mixing the lignocellulose-containing plant material and the formic acid is subjected to solid-liquid separation to prepare the lignocellulose-containing solution from which at least a portion of the solid content has been removed.

5. A method for manufacturing a laminated material according to any one of claims 1 to 3, wherein the temperature in the bonding step is in an environment of 0°C or higher and 50°C or lower.

6. The lignocellulose-containing solution further comprises a solvent, The method for producing a laminated material according to any one of claims 1 to 3, wherein the solvent comprises at least one selected from the group consisting of ketones, alcohols, aromatic compounds, alkaline aqueous solutions, polyhydric alcohols, organic acids, and aprotic polar solvents.

7. The method for manufacturing a laminate according to any one of claims 1 to 3, wherein the first adherend is formed from at least one selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold and paper.

8. A laminate in which a first adherend and a second adherend are laminated together with at least an adhesive layer in between, The first adherend is formed from at least one material selected from the group consisting of biomass material, plastic, metal, ceramic, glass, pulp mold, and paper. The thickness of the first adherend is 2 mm or more. The adhesive layer is substantially formed from plant-derived components. In the infrared absorption spectrum of the adhesive layer, 1715–1725 cm⁻¹ -1 A laminated material that shows an absorption peak in the region.

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