Tree bark solution, water repellent, bark molded article, and laminated material

Abstract

The present invention provides a tree bark solution capable of imparting water repellency to a surface of an article.　The tree bark solution contains tree bark and an organic acid.

Description

Bark solutions, water repellents, bark moldings, and laminates

[0001] The present disclosure relates to bark solutions, water repellents, bark moldings, and laminates.

[0002] Conventionally, plant materials, such as wood, have been used for various purposes, such as building materials and furniture components. In particular, the use of high-quality wood is preferred for the surface layer of components, as it provides a beautiful, luxurious appearance and a pleasant feel. However, high-quality wood is generally expensive. Furthermore, due to the depletion of forest resources in recent years, it has become difficult to obtain high-quality wood. Furthermore, wood is difficult to pressure-mold, and must be cut and processed.

[0003] Therefore, techniques for bonding thin wood slices to various substrates have been disclosed. For example, Japanese Utility Model Laid-Open Publication No. 5-35208 (Patent Document 1) proposes a decorative board that expresses a more luxurious wood texture by carving different pseudo-vascular groove recesses into the surface of a wood board without concealing the original surface vascular groove recesses. Japanese Patent Laid-Open Publication No. 5-50408 (Patent Document 2) discloses a decorative building material in which a wood grain pattern that gives a luxurious feel to the surface of a wood board is formed by pressing the surface of the wood board to form a wood grain-like uneven pattern and coloring it. Japanese Patent Laid-Open Publication No. 8-60800 (Patent Document 3) proposes a composite wood column in which a rectangular core wood is located in the center, a planar covering wood is located around the core wood, and the core wood and covering wood are bonded together. Patent Document 3 discloses a technology for providing a high-quality wood column at an affordable price by using high-quality wood as the covering wood.

[0004] Furthermore, as environmental pollution has become a more serious problem in recent years, pulp molds have been attracting attention as a material that can help eliminate plastics. Pulp molds are paper products made by dissolving and entangling plant fibers (mainly waste paper) in water, papermaking them in a mold, and then drying them. They are primarily used as packaging containers. Furthermore, molding techniques using thermoformed molds have been proposed to obtain thinner, more complex-shaped pulp molds. However, because pulp molds are made of paper, they are permeable and breathable, which presents a problem in that they cannot be used for certain applications.

[0005] As a material with reduced water permeability and breathability, Japanese Patent Laid-Open Publication No. 2000-309322 (Patent Document 4) discloses a waterproof pulp molded container in which a synthetic resin film layer is laminated on one side of a pulp molded product and a waterproof layer is either laminated on the other side with a synthetic resin film layer or coated with a waterproof paint.

[0006] Meanwhile, growing concern about environmental issues in recent years has led to calls for the development of materials derived from biomass resources instead of petroleum-based materials, particularly woody biomass, which does not compete with food and does not increase atmospheric carbon dioxide.

[0007] The main component of woody biomass is a natural polymer mixture called lignocellulose. Lignocellulose is a strong, higher-order structure composed of cellulose, hemicellulose, and lignin intricately intertwined with one another. Specifically, in lignocellulose, cellulose, a linear polymer, forms a crystalline structure through intramolecular and intermolecular hydrogen bonds to form strong microfibrils. Hemicelluloses such as xylan and glucomannan are entangled with these microfibrils, and lignin, an irregular aromatic polymer, fills the voids in the polysaccharide matrix to form a strong complex. Therefore, lignocellulose as a whole is insoluble in solvents such as water and organic solvents under mild conditions. To dissolve lignocellulose as a whole in these solvents, pretreatment is required, either to physically destroy the plant cell walls by grinding using a ball mill or to separate the cell wall components by high-temperature reactions in a solvent containing a catalyst. The significant energy and cost burdens required for grinding and high-temperature reactions pose a major problem in the utilization of woody biomass.

[0008] Thus, in order to dissolve lignocellulose, studies have been conducted to accelerate the decomposition reaction by relaxing hydrogen bonds through chemical decomposition at high temperatures. For example, attempts have been made to dissolve lignocellulose by using high-temperature heat treatment in organic solvents, acid or alkali decomposition reactions, and high-temperature hydrothermal reactions.

[0009] For example, Japanese Patent No. 3155603 (Patent Document 5) discloses a method for producing a liquefied solution of lignocellulosic materials, such as wood, by heating the material in the presence of an acid catalyst, a cyclic ester, and a polyhydric alcohol. This method is a wood liquefaction method that promotes acid decomposition of wood in chemicals, and requires the use of an acid catalyst such as sulfuric acid and a polyhydric alcohol-based chemical such as polyethylene glycol, as well as heating to a reaction temperature of about 150°C.

[0010] Patent Document 1: Japanese Utility Model Application Publication No. H5-35208 Patent Document 2: Japanese Patent Application Publication No. H5-50408 Patent Document 3: Japanese Patent Application Publication No. H8-60800 Patent Document 4: Japanese Patent Application Publication No. 2000-309322 Patent Document 5: Japanese Patent No. 3155603

[0011] The present disclosure aims to provide a bark solution that can impart water repellency to the surface of an article. It also aims to provide a water repellent agent containing the bark solution that can impart water repellency to the surface of an article. It also aims to provide a bark molding and a laminated material that utilize the bark solution or the water repellent agent.

[0012] After extensive research, the inventors of the present disclosure have found that a bark solution containing bark and an organic acid can be applied to the surface of an article and dried to impart water repellency to the surface of the article (i.e., can be used as a water repellent). They have also found that the bark solution can be used to obtain bark molded products and laminated materials with excellent water repellency. The present disclosure is an invention that was completed based on these findings and further research.

[0013] That is, the present disclosure provides the following aspects of the invention. (Bark solution) A bark solution containing bark and an organic acid. (Water repellent) A water repellent containing the bark solution. (Bark molded product) A bark molded product formed from the solid content of the bark solution. (Laminated material) A laminated material composed of a laminate containing at least a substrate and a sheet material, wherein the sheet material contains bark.

[0014] According to the present disclosure, it is possible to provide a bark solution that can impart water repellency to the surface of an article. That is, since the bark solution of the present disclosure can be used as a water repellent, it is possible to provide a water repellent that can impart water repellency to the surface of an article. Furthermore, it is also possible to provide bark molded products and laminated materials that use the bark solution.

[0015] The bark solution of the present disclosure is characterized by containing bark and an organic acid. The bark solution of the present disclosure can impart water repellency to the surface of an article, such as a substrate or a molded product. That is, when the bark solution of the present disclosure is applied to the surface of an article and dried to form a sheet material, the surface of the sheet material exhibits excellent water repellency. As described below, such a sheet material is an example of a bark molded product formed from the solid content of the bark solution of the present disclosure.

[0016] The resin solution of the present disclosure can be used as a water repellent. That is, the water repellent of the present disclosure includes the bark solution of the present disclosure, which can impart water repellency to the surface of an article. In the water repellent of the present disclosure, the proportion of the bark solution is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may even be 100% by mass (i.e., the water repellent of the present disclosure is a bark solution).

[0017] The laminated material of the present disclosure is composed of a laminate including at least a substrate and a sheet material, and the sheet material is characterized in that the bark-containing sheet material surface of the laminated material of the present disclosure can exhibit excellent water repellency. As described below, the sheet material of the laminated material of the present disclosure can be formed using the bark solution of the present disclosure.

[0018] Preferred embodiments of the present disclosure will be described in detail below. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0019] In this disclosure, the range "X to Y" means "X or more and Y or less." Unless otherwise noted, all test temperatures are room temperature (20°C ± 5°C), and "wt%" means weight percent, not mass concentration. Furthermore, the unit of weight "t (ton)" means "metric ton."

[0020] [Bark Solution] The bark solution of the present disclosure contains bark and an organic acid. In the bark solution, the bark is dissolved in a solution containing an organic solvent. As described above, the resin solution of the present disclosure can be used as a water repellent. That is, the water repellent of the present disclosure contains the bark solution. In other words, the bark solution of the present disclosure can also be referred to as a water repellent. The bark solution of the present disclosure will be described in detail below, including an embodiment in which the bark solution of the present disclosure is a water repellent.

[0021] Conventionally, the main raw material for woody biomass has been the xylem of trees (specifically, the trunk part inside the bark), and when using woody biomass, the bark is generally removed in its entirety. In contrast, the bark solution of the present disclosure is characterized by the use of bark.

[0022] A typical bark product is cork, which is the bark of the cork oak, a member of the Fagaceae family, and is used for a variety of purposes. Cork layers are also formed on broad-leaved and coniferous trees other than cork oak. For example, cypress bark roofing, which is made from cypress bark, is known.

[0023] Trees thicken their trunks by producing xylem cells on the inside and phloem cells on the outside, in the cambium. The phloem and the outer epidermal layer form the bark. In trees, the cork cambium forms at the innermost epidermal layer, forming cork tissue with cell walls to protect the trunk. The outer part of the innermost cork tissue is called the outer bark, and the inner part is called the inner bark. Bark is classified into outer bark and inner bark. Outer bark is further classified into the epidermis, periderm, cortex, etc. Inner bark is further classified into primary nodes, secondary nodes, cambium, secondary xylem, etc. The bark solution of the present disclosure preferably contains at least one of outer bark and inner bark, and more preferably contains both outer bark and inner bark. These barks are easily separated from the xylem by visual inspection because they differ in color and shape from the xylem.

[0024] As mentioned above, the main component of woody biomass, such as that of broad-leaved trees and conifers, is a natural polymer mixture called lignocellulose, which forms a strong, high-order structure in which cellulose, hemicellulose, and lignin are intricately intertwined.

[0025] In contrast, the main components of bark contained in the bark solution of the present disclosure are lignocelluloses such as cellulose, hemicellulose, and lignin, but bark also contains components that are different from the components that make up the xylem. For example, the outer bark that forms the outside of the bark contains suberin, a highly hydrophobic component formed by combining aliphatic components with ferulic acid, caffeic acid, and glycerol. The bark solution of the present disclosure preferably also contains suberin. In this specification, "main component" means a component whose content is at least 50% by weight or more.

[0026] In the present disclosure, the tree species from which the bark is obtained is not particularly limited, and bark from various tree species can be used, such as broad-leaved trees (eucalyptus, beech, etc.) and coniferous trees (cedar, cypress, red pine, etc.). The type of tree species from which the bark contained in the bark solution of the present disclosure is obtained may be only one type, or two or more types.

[0027] From the viewpoint of more suitably exerting the effects of the invention of the present disclosure, the proportion of bark in the solids contained in the bark solution of the present disclosure is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 60% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 100% by weight. The upper limit can be, for example, 100% by weight, 90% by weight, or 85% by weight. Preferred ranges include 20 to 100% by weight, 20 to 90% by weight, 20 to 85% by weight, 40 to 100% by weight, 40 to 90% by weight, 40 to 85% by weight, 60 to 100% by weight, 60 to 90% by weight, 60 to 85% by weight, 80 to 100% by weight, 80 to 90% by weight, 80 to 85% by weight, and 90 to 100% by weight.

[0028] The bark solution of the present disclosure may contain biomass other than bark in addition to bark. The biomass is preferably biomass containing lignocellulose. There are no particular limitations on the biomass, and woody biomass such as the xylem of broad-leaved trees (eucalyptus, beech, etc.) and coniferous trees (cedar, cypress, red pine, etc.), and herbaceous biomass such as rice, sugarcane, wheat, tomato, onion, moso bamboo, and bran may be appropriately selected and used. Among these, the xylem of trees is preferred as biomass other than bark. When the bark solution of the present disclosure contains biomass other than bark, the type of biomass may be only one type, or two or more types.

[0029] From the viewpoint of more suitably exerting the effects of the invention of the present disclosure, the proportion of biomass other than bark in the solid content contained in the bark solution of the present disclosure may be, for example, 80% by weight or less, 60% by weight or less, 40% by weight or less, 20% by weight or less, 15% by weight or less, 5% by weight or less, 0% by weight or less, and the lower limit when biomass other than bark is contained may be 1% by weight, 3% by weight, 5% by weight or less, and a preferred range is 0% by weight or less. up to 80% by weight, 0 to 60% by weight, 0 to 40% by weight, 0 to 20% by weight, 0 to 15% by weight, 0 to 5% by weight, 1 to 80% by weight, 1 to 60% by weight, 1 to 40% by weight, 1 to 20% by weight, 1 to 15% by weight, 1 to 5% by weight, 3 to 80% by weight, 3 to 60% by weight, 3 to 40% by weight, 3 to 20% by weight, 3 to 15% by weight, 3 to 5% by weight, 5 to 80% by weight, 5 to 60% by weight, 5 to 40% by weight, 5 to 20% by weight, 5 to 15% by weight, etc.

[0030] From the viewpoint of more suitably exerting the effects of the present invention, the proportion of biomass (bark, and optionally biomass other than bark) in the solid content of the bark solution of the present disclosure is preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, even more preferably 99% by weight or more, and even more preferably 100% by weight. It is preferable that the solid content of the bark solution of the present disclosure is substantially biomass (the proportion of biomass in the solid content is, for example, 95% by weight or more, even 99% by weight or more, or even 100% by weight).

[0031] The organic acid is not particularly limited as long as it can dissolve the bark. A typical organic acid is a carboxylic acid. It may be an aliphatic carboxylic acid or an aromatic carboxylic acid. From the viewpoint of excellent solubility of the bark powder, α-keto acids and carboxylic acids having a formyl group are preferred, and organic acids selected from the group consisting of formic acid, glyoxylic acid, and pyruvic acid are particularly preferred.

[0032] In the bark solution of the present disclosure, the content of the organic acid is appropriately selected depending on the type and size of the biomass (bark and optionally other biomass) contained in the bark solution, the type of organic acid, and other factors. From the viewpoint of improving the dissolution efficiency of biomass such as bark, the content of the organic acid is preferably 4 parts by weight or more, more preferably 9 parts by weight or more, per part by weight of biomass contained in the bark solution. From the viewpoint of facilitating the production of a bark molded product (described later), the content of the organic acid is preferably 200 parts by weight or less, more preferably 49 parts by weight or less, per part by weight of biomass contained in the bark solution. Preferred ranges for the content of the organic acid per part by weight of biomass contained in the bark solution include 4 to 200 parts by weight, 4 to 49 parts by weight, 9 to 200 parts by weight, and 9 to 49 parts by weight. As described below, an organic acid solution (e.g., an aqueous organic acid solution) may be used to prepare the bark solution of the present disclosure. In this case, the content of the organic acid refers to the content of the organic acid.

[0033] In the bark solution of the present disclosure, the concentration of bark is preferably 0.5% by weight or more, more preferably 1% by weight or more, even more preferably 2% by weight or more, and is preferably 50% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less, with preferred ranges being 0.5 to 50% by weight, 0.5 to 30% by weight, 0.5 to 20% by weight, 1 to 50% by weight, 1 to 30% by weight, 1 to 20% by weight, 2 to 50% by weight, 2 to 30% by weight, and 2 to 20% by weight.

[0034] Furthermore, the solids concentration in the bark solution of the present disclosure is preferably 0.5% by weight or more, more preferably 1% by weight or more, and even more preferably 2% by weight or more, and is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less, with preferred ranges being 0.5 to 50% by weight, 0.5 to 30% by weight, 0.5 to 20% by weight, 1 to 50% by weight, 1 to 30% by weight, 1 to 20% by weight, 2 to 50% by weight, 2 to 30% by weight, and 2 to 20% by weight.

[0035] The surface of the sheet material obtained by drying the bark solution of the present disclosure has a water contact angle, measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds, of preferably 95° or more, more preferably 100° or more, and even more preferably 105° or more, with the upper limit being, for example, 150° or less, 140° or less, or 130° or less, and preferred ranges being 95 to 150°, 95 to 140°, 95 to 130°, 100 to 150°, 100 to 140°, 100 to 130°, 105 to 150°, 105 to 140°, or 105 to 130°. Specific methods for measuring the water contact angle on the surface of the sheet material are described in the Examples.

[0036] (Preparation of Bark Solution) The bark solution of the present disclosure can be produced, for example, by dissolving bark powder in an organic acid. Bark powder can be produced by pulverizing the bark.

[0037] Generally, in the grinding of woody biomass, a device that grinds materials of several hundred mm or more in size to about several tens of mm is called a "coarse grinder," and a device that grinds materials of the order of several tens of mm to about several mm to several hundred μm is called a "medium grinder." When simply referring to a "grinder," this "medium grinder" is meant. Furthermore, a device that aims to grind materials to the order of several μm is called a "fine grinder," and a device that aims to produce fine powder of several μm or less is called an "ultrafine grinder."

[0038] In this specification, powder containing particles with a particle diameter of 0.35 mm or more is referred to as "coarse powder," and the pulverization process to obtain this coarse powder is referred to as "coarse pulverization." Therefore, in the pulverization process of the present disclosure, "coarse pulverization" is performed using a "pulverizer." The coarse powder obtained in the pulverization process of the present disclosure has not been subjected to advanced pulverization treatment using a "fine pulverizer" or an "ultrafine pulverizer." Therefore, there is little structural destruction of cellulose, lignin, etc. in the biomass, and, for example, the crystallinity of cellulose and the antibacterial and ultraviolet absorption properties specific to lignin are maintained even after pulverization. Furthermore, since advanced pulverization treatment using a "fine pulverizer" or an "ultrafine pulverizer" is not required, the generation of fine powder is suppressed.

[0039] The particle size of the particles contained in the coarse bark powder (hereinafter sometimes referred to as bark powder) may be 0.10 mm to 3.0 mm, 0.15 mm to 2.0 mm, 0.20 mm to 1.0 mm, 0.25 mm to 0.75 mm, 0.30 mm to 0.55 mm, or 0.35 mm to 0.50 mm. From the viewpoint of improving safety, a coarse powder that does not contain particles with a particle size of less than 100 μm is preferred, and a coarse powder that does not contain particles with a particle size of 80 μm or less is more preferred. An even more preferred coarse powder is a coarse powder with a particle size in the range of 0.35 mm to 0.50 mm. The particle size of the coarse powder is measured by a section classification method using a JIS standard sieve.

[0040] The method for coarsely grinding the bark is not particularly limited as long as the aforementioned coarse powder can be obtained, and known grinding methods such as compression grinding, impact grinding, and shear grinding can be used. Dry grinding or wet grinding may be used. As described above, according to the manufacturing method of the present disclosure, a grinding method sufficient to obtain a coarse powder is sufficient. Therefore, dry grinding, which allows grinding to the micron level and is low cost, is preferably used. If necessary, wet grinding may be used in combination with the mixing step described below, or the coarse powder and organic acid may be mixed and then wet-ground. When wet grinding is used in combination with the mixing step, the particle size of the coarsely ground material obtained in the grinding step may be larger than the aforementioned range. When wet grinding is used in combination with the mixing step, the concentration of the organic acid used may be adjusted, or the retention time (dissolution time) in the dissolution step described below may be adjusted.

[0041] From the viewpoint of reducing energy and costs in the crushing process, preferred crushers include jaw crushers, gyratory crushers, crushing rolls, hammer mills, roller mills, cutter mills, hammer crushers, Willey mills, and stone mills. Two or more types of crushers may be used in combination. Willey mills and stone mills, which crush by shear and impact, are preferred. Coarse crushing of bark may be carried out continuously or batchwise. Before the crushing process, the bark may be broken into small pieces (chips) using a known cutter, chipper, etc.

[0042] For example, in the case of woody biomass, trees are harvested from natural forests, the bark is stripped, and the trees are cut into logs or the like, and then processed into chips through a process known as debarking or chipping. The bark used in the present disclosure may be obtained by similarly processing bark stripped from trees into chips to obtain wood chips, which are then coarsely pulverized in a pulverization process. In this pulverization process, the pulverization ratio (B / A), which is the ratio of the particle size B (several mm) of the crushed material to the size A (several cm) of the material to be pulverized, can be selected from a range of 1 / 20 to 1 / 2. This pulverization ratio (B / A) may be approximately 1 / 10, or may be approximately 1 / 3 to 1 / 4. A larger pulverization ratio (B / A) has the advantage of allowing for the selection of a wider variety of chips for the bark. Bond's law is also known regarding pulverization. Bond's law states that the work required to pulverize a given weight of material to be pulverized is inversely proportional to the square root of the particle size of the material. According to this law, the smaller the particle size of the pulverized material and the larger the pulverization ratio (B / A), the greater the work required. Therefore, although there is a balance to be taken into account with the dissolution process described below, it is preferable that the particle size of the pulverized material is as large as possible and the pulverization ratio (B / A) is as small as possible.

[0043] Furthermore, as mentioned above, the pulverization method may be impact, shear, or friction, and is not limited to compression pulverization, which requires hardness. Depending on the pulverization method, the crystallinity of the pulverized product may change. For example, Japanese Patent No. 6137525 describes a method for producing decrystallized cellulose, which includes a step of deheating and pulverizing a cellulose-containing raw material under a temperature condition of -5 to 25°C by applying shear force to decrystallize the cellulose. As such, the cellulose in the pulverized product may be decrystallized depending on the pulverization method. For this reason, it is preferable to select a pulverization method taking into account the desired crystallinity of the pulverized product in relation to the dissolution time described below.

[0044] The bark powder thus obtained is mixed with an organic acid to dissolve the bark powder in the organic acid. It is preferable that the bark powder and the organic acid are mixed uniformly. The type and content of the organic acid contained in the bark solution are as described above.

[0045] The method for mixing the bark powder and the organic acid is not particularly limited, and the organic acid may be added to the bark powder as is, or may be added to the crude powder as an organic acid solution (e.g., an aqueous organic acid solution). The solvent is not particularly limited as long as it is a good solvent for the organic acid, but water is preferably used from the viewpoints of safety and availability.

[0046] When added to bark as an organic acid solution, the organic acid concentration is not particularly limited and can be appropriately selected depending on the type of biomass, particle size, type of organic acid, dissolution conditions, etc. For example, a high-concentration organic acid solution can uniformly dissolve the coarse powder in a short time. From the perspective of improving dissolution efficiency, the organic acid concentration may be 80% by weight or more, with an upper limit of 100% by weight. On the other hand, the lower the concentration of the organic acid solution, the greater the mechanical strength of the resulting bark molded product. This is presumably because, during the dissolution process described below, the organic acid undergoes an ester reaction with lignocellulose. With a low-concentration organic acid solution, the degree of esterification is low, allowing cellulose crystallites in the lignocellulose to remain, contributing to improved strength of the molded product. Furthermore, if the organic acid concentration is less than 75% by weight, the vapor pressure of the organic acid decreases and does not exceed the explosion limit, ensuring operational safety. Furthermore, a low organic acid concentration can reduce the level of corrosion resistance required for the equipment, thereby reducing equipment costs. Furthermore, when the organic acid is formic acid, it forms an azeotrope with water, and therefore, in order to obtain a highly concentrated aqueous formic acid solution, high energy costs are incurred for recovering, regenerating, or purifying the formic acid. From the viewpoint of reducing energy costs, a low-concentration aqueous formic acid solution is preferred.

[0047] The bark powder is dissolved in the organic acid to obtain a solution containing the bark. In the bark dissolution step, the bark powder may be partially dissolved in the organic acid. In the case of partial dissolution, the bark solution of the present disclosure is obtained by removing the insoluble portion by filtration or the like. In this specification, "dissolved" refers to a state in which the shape of the bark powder in the organic acid cannot be recognized visually. Even when fibrous material derived from the bark is observed in the solution by microscopic observation or the like, the state is defined as "dissolved" if the shape of the bark powder itself has disappeared. Furthermore, in this disclosure, a liquid in such a "dissolved" state is defined as a "solution."

[0048] As long as the bark solution of the present disclosure is obtained, the dissolution conditions in the dissolution step are not particularly limited and are appropriately selected depending on the type of bark, the particle size of the bark powder, the type of organic acid, etc. From the viewpoint of high dissolution efficiency, the dissolution temperature is preferably 20°C or higher, more preferably 30°C or higher. From the viewpoint of energy saving, the dissolution temperature is preferably 100°C or lower. The dissolution time (retention time) can be appropriately adjusted while checking the dissolved state of the bark powder.

[0049] To promote dissolution, the dissolution process may involve stirring or grinding. Stirring in an organic acid with grinding allows for milder conditions for dissolving the bark. In the dissolution process, grinding may be continued until a bark solution is obtained, or the grinding process may be performed for a predetermined period of time before switching to a grinding process without grinding. Examples of equipment for grinding include a bead mill, colloid mill, disc refiner, and conical refiner. In this grinding process, grinding may be performed using a jet mill, high-pressure homogenizer, stone mill, or the like. This type of grinding is called wet grinding. Wet grinding can further simplify the grinding of the bark in the grinding process.

[0050] In the dissolving step, a compound of the general formula M is dissolved in water together with an organic acid, if necessary. a M b (SO4)2 (where M a is a trivalent metal, and M b is NH or a monovalent metal). The metal salt represented by this general formula is a double salt also known as "alum." It may also be a hydrate of the metal salt. The combined use of an organic acid and alum improves the solubility of the bark powder in the organic acid.

[0051] Specific examples of trivalent metals include aluminum, iron, and chromium. Specific examples of monovalent metals include sodium and potassium. A preferred metal salt is aluminum potassium sulfate. Aluminum potassium sulfate dodecahydrate may also be used as the metal salt.

[0052] From the viewpoint of obtaining a significant effect when used in combination with an organic acid, the amount of metal salt added is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and even more preferably 5 parts by weight or more, per 100 parts by weight of bark powder. From the viewpoint of obtaining a solution or molded product with a high lignocellulose content, the amount of metal salt added is preferably 30 parts by weight or less, more preferably 25 parts by weight or less, and even more preferably 20 parts by weight or less.

[0053] The method may further include a pressure adjustment step in which pressure is increased or decreased using a pressure adjustment means before and / or after mixing the bark powder and the organic acid. It is believed that the pressure fluctuations applied to the bark powder in this pressure adjustment step relax the rigid higher-order structure of lignocellulose, significantly improving its solubility in organic acids. This pressure adjustment step enables dissolution at a relatively low temperature, reducing the energy required for heating and / or heat retention in the dissolution step. From the viewpoint that the pressure fluctuations efficiently introduce the organic acid into the tissue of the bark powder, it is preferable to increase or decrease the pressure after adding the organic acid to the bark powder. Depending on the methods and conditions in the crushing and dissolution steps, this pressure adjustment step may be omitted.

[0054] When the pressure is reduced in the pressure adjusting step, it is preferable to reduce the pressure in the range of 1.0 kPa to 10.0 kPa (absolute pressure). When the pressure is increased in the pressure adjusting step, it is preferable to increase the pressure in the range of 200 kPa to 1000 kPa (gauge pressure). In this specification, absolute pressure is used when a pressure lower than atmospheric pressure is indicated by a reduction treatment, and gauge pressure based on atmospheric pressure is used when a pressure higher than atmospheric pressure is indicated by a pressurization treatment.

[0055] The pressure adjusting means used in the pressure adjusting step is not particularly limited, and the pressure is adjusted to the above-mentioned range by known means such as an aspirator, an ejector, a compressor, or a mechanical pump.

[0056] For example, the bark solution of the present disclosure can be produced by the above method. Even when the bark solution of the present disclosure contains biomass other than bark, raw biomass, which is the raw material for the biomass, can be subjected to the above-mentioned crushing step, dissolution step, etc., and dissolved in an organic acid together with the bark.

[0057] [Bark Molded Product] The bark molded product of the present disclosure is formed from the solid content of the bark solution of the present disclosure. That is, the bark molded product of the present disclosure is formed from the solid content containing bark, from which liquid components such as organic acids contained in the bark solution of the present disclosure have been removed.

[0058] Specifically, the bark moldings of the present disclosure can be obtained by adding a predetermined shape during the process of removing liquid components, including unreacted organic acids, from a bark solution. Therefore, bark moldings are fundamentally different from particle boards, which are made by solidifying wood flour into a predetermined shape using known adhesives. For example, the bark moldings of the present disclosure may be substantially free of adhesive components. Here, the term "free" means that no adhesive is intentionally added during the manufacturing process of the bark moldings, and that the adhesive components are not detected in the bark moldings by commonly used analytical methods. Furthermore, the term "adhesive components" refers to the constituent components of conventionally known synthetic adhesives, and does not refer to adhesive components, such as lignin, that are naturally contained in the raw biomass.

[0059] The bark extrusion product may contain functional groups derived from organic acids, provided that the effects of the present disclosure are not impaired. Note that "the bark extrusion product contains functional groups derived from organic acids" does not mean that the bark extrusion product contains unreacted organic acids, but rather that the organic acids are ester-bonded to the components of the extrusion product. Specifically, lignocellulose is composed of cellulose, hemicellulose, and lignin. The bark extrusion product of the present disclosure, which contains functional groups derived from organic acids, can be obtained by forming ester bonds between at least a portion of the cellulose, hemicellulose, and lignin and an organic acid. The bark extrusion product of the present disclosure contains substantially no unreacted organic acids at the end of extrusion. Note that, depending on the storage conditions and storage period of the extrusion product of the present disclosure, some of the ester bonds of the organic acids bound to the cellulose, hemicellulose, and lignin of the bark extrusion product may hydrolyze to produce organic acids. Therefore, this does not exclude the bark extrusion product of the present disclosure from containing organic acids produced by hydrolysis.

[0060] As mentioned above, the main components of bark are lignocelluloses such as cellulose, hemicellulose, and lignin, but bark also contains components that are different from the components that make up the xylem. For example, the outer bark, which forms the outside of the bark, contains suberin, a highly hydrophobic component formed by the combination of aliphatic components with ferulic acid, caffeic acid, and glycerol. The bark molded product of the present disclosure also preferably contains suberin.

[0061] The proportion of bark in the bark molded product of the present disclosure is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 60% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 100% by weight. The upper limit is, for example, 100% by weight, 90% by weight, 85% by weight, etc. Preferred ranges include 20 to 100% by weight, 20 to 90% by weight, 20 to 85% by weight, 40 to 100% by weight, 40 to 90% by weight, 40 to 85% by weight, 60 to 100% by weight, 60 to 90% by weight, 60 to 85% by weight, 80 to 100% by weight, 80 to 90% by weight, 80 to 85% by weight, 90 to 100% by weight, etc.

[0062] The bark extrusion product of the present disclosure may contain biomass other than bark in addition to bark. The biomass is preferably biomass containing lignocellulose. There are no particular limitations on the biomass, and woody biomass such as the xylem of broad-leaved trees (eucalyptus, beech, etc.) and coniferous trees (cedar, cypress, red pine, etc.), and herbaceous biomass such as rice straw and bran are appropriately selected and used. Among these, the xylem of trees is preferred as biomass other than bark. When the bark extrusion product of the present disclosure contains biomass other than bark, the type of biomass may be only one type or two or more types.

[0063] From the viewpoint of more suitably exerting the effects of the present invention, in the bark molded product of the present disclosure, the proportion of biomass other than bark may be, for example, 80% by weight or less, 60% by weight or less, 40% by weight or less, 20% by weight or less, 15% by weight or less, 5% by weight or less, or 0% by weight. When biomass other than bark is contained, the lower limit may be 1% by weight, 3% by weight, or 5% by weight, and a preferred range is 0 to 80% by weight. %, 0 to 60 weight%, 0 to 40 weight%, 0 to 20 weight%, 0 to 15 weight%, 0 to 5 weight%, 1 to 80 weight%, 1 to 60 weight%, 1 to 40 weight%, 1 to 20 weight%, 1 to 15 weight%, 1 to 5 weight%, 3 to 80 weight%, 3 to 60 weight%, 3 to 40 weight%, 3 to 20 weight%, 3 to 15 weight%, 3 to 5 weight%, 5 to 80 weight%, 5 to 60 weight%, 5 to 40 weight%, 5 to 20 weight%, 5 to 15 weight%, and the like.

[0064] From the viewpoint of more suitably exerting the effects of the present invention, the proportion of biomass (bark and optionally biomass other than bark) in the bark extrusion product of the present disclosure is preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, even more preferably 99% by weight or more, and even more preferably 100% by weight. It is preferable that the bark extrusion product of the present disclosure is composed essentially of biomass only (the proportion of biomass is 95% by weight or more, even more preferably 99% by weight or more, and even more preferably 100% by weight).

[0065] The surface of the bark molding of the present disclosure has a water contact angle, measured by dropping 70 μL of distilled water onto the surface of the bark molding and photographing the droplet after 1000 milliseconds. The water contact angle is preferably 95° or more, more preferably 100° or more, and even more preferably 105° or more. The upper limit can be, for example, 150° or less, 140° or less, or 130° or less. Preferred ranges include 95 to 150°, 95 to 140°, 95 to 130°, 100 to 150°, 100 to 140°, 100 to 130°, 105 to 150°, 105 to 140°, and 105 to 130°. Specific methods for measuring the water contact angle on the bark molding surface (sheet material surface) are described in the Examples.

[0066] The bark contained in the bark molding of the present disclosure is solubilized bark powder. The bark molding may contain fibrous material derived from the bark. The fibrous material may have a cellulose type I crystal structure. The fibrous material derived from the bark is considered to be cellulose fibers that were not destroyed during the grinding process. The presence of this fibrous material can be confirmed by scanning electron microscopy.

[0067] The density of the bark molding is, for example, 1.20 g / cm 3 Preferably less than 1.15 g / cm 3 Preferably, 1.10 g / cm or less 3 More preferably, the density is 1.20 g / cm 3 From the viewpoint of excellent mechanical strength, the density of the bark extrusion is 0.20 g / cm or less. 3 More than 0.30 g / cm 3 The above is more preferable.

[0068] In one embodiment, the density of the bark molding of the present disclosure is 16 g / cm 3 Preferably, when the bonding amount of functional groups (particularly the degree of formylation) is 0.35 to 0.60, the density of the molded article is 1.2 g / cm 3 1.6g / cm or more 3The bark molding has high stress and excellent foldability. By reducing the particle size of the coarse powder and dissolving it, the amount of functional groups bonded can be increased. Note that when the particle size of the coarse powder is reduced to increase the amount of functional groups bonded, the density may be excessively reduced, making it impossible to obtain the desired foldability. Note that the density of the bark molding of the present disclosure is the apparent density measured in accordance with JIS Z8807 "Method for measuring density and specific gravity of solids."

[0069] The bark molded product of the present disclosure preferably has mechanical properties that allow it to be deformed without cracking or the like. The tensile properties of the bark molded product are set appropriately depending on its application and shape. From the viewpoint of ease of deformation, the Young's modulus of the molded product is preferably 0.05 GPa or more, more preferably 1.0 GPa or more. From the viewpoint of durability, the preferred Young's modulus is 4.0 GPa or less. From the viewpoint of durability, the maximum stress of the bark molded product is preferably 0.5 MPa or more, more preferably 5.0 MPa or more, even more preferably 10 MPa or more, and particularly preferably 20 MPa or more. From the viewpoint of ease of deformation, the preferred maximum stress is 80 MPa or less. From the viewpoint of ease of deformation, the maximum elongation of the bark molded product is preferably 0.5% or more, more preferably 1.5% or more. From the viewpoint of durability, the preferred maximum elongation is 5.0% or less. The Young's modulus, maximum stress, and maximum elongation of the bark molded product are measured by a tensile test in accordance with the provisions of ISO 527-1.

[0070] For example, by grinding the bark more finely to reduce the particle size of the coarse powder and using a high concentration of organic acid in the dissolution process, a bark solution containing fewer crystalline components with cellulose type I structure can be obtained. The bark extrusions obtained from this bark solution have high maximum elongation and excellent surface smoothness. On the other hand, by reducing the bark grinding ratio to increase the particle size of the coarse powder, lowering the concentration of the organic acid used in the dissolution process, or shortening the dissolution time, a bark solution containing a large amount of crystalline components with cellulose type I structure can be obtained. The bark extrusions obtained from this bark solution have high maximum stress (strength). Thus, the desired bark extrusions can be obtained by selecting the methods and conditions for each process, taking into consideration the properties required for the bark extrusions, the energy efficiency and productivity in the grinding process, the dissolution efficiency in the dissolution process, the energy required to recover the organic acid, and the like.

[0071] From the viewpoint of obtaining high heat resistance, the glass transition temperature Tg of the bark molded product of the present disclosure is preferably 100°C or higher, more preferably 200°C or higher, even more preferably 210°C or higher, and particularly preferably 220°C or higher. Although there is no particular upper limit, a preferred glass transition temperature Tg is 280°C or lower. The bark molded product of the present disclosure may be a molded product in which the glass transition temperature Tg is not observed. The glass transition temperature of the bark molded product of the present disclosure is measured by dynamic viscoelasticity measurement. Details of the measurement method and measurement conditions will be described later in the examples.

[0072] The bark moldings of the present disclosure are of the general formula M a M b (SO4)2 (where M a is a trivalent metal, and M b is NH4 or a monovalent metal). Examples of this metal salt include the metal salts mentioned above in relation to the method for producing a bark solution. When this bark molded product contains the metal salt, the content of the metal salt in this bark molded product is preferably 1 part by weight or more, more preferably 5 parts by weight or more, per 100 parts by weight of the bark molded product. The preferred content of the metal salt is 20 parts by weight or less. The bark molded product may further contain known additives such as pigments, as long as the effects of the present disclosure are not impaired.

[0073] The bark extrusions of the present disclosure have excellent solubility in organic acids. The amount of insoluble matter in organic acids in bark extrusions is, for example, 5.0 wt. % or less. In this specification, the amount of insoluble matter in organic acids is determined by a dissolution test in which a coarse powder obtained by coarsely crushing a bark extrusion is mixed with 50 parts by weight of organic acid per 1 part by weight of the coarse powder, and the resulting solution is passed through a 20-mesh sieve to measure the weight of the residue remaining on the nodes. The proportion (wt. %) of this residue relative to the coarse powder mixed with the organic acid is calculated as the amount of insoluble matter. In this dissolution test, a pressure adjustment step of reducing or increasing the pressure may be performed before and / or after mixing the organic acid and the coarse powder.

[0074] The bark extrusion product of the present disclosure contains cellulose, hemicellulose, and lignin, at least a portion of which has an organic acid ester-bonded. Cellulose, hemicellulose, and lignin each have a unique number-average molecular weight. Therefore, multiple peaks may be detected in a chromatogram obtained by dissolving the extrusion product of the present disclosure in dimethyl sulfoxide (DMSO) and measuring it by gel permeation chromatography (GPC). Typically, a first peak and a second peak are detected in descending order of molecular weight. The number-average molecular weight of the first peak may be 50,000 to 10,000,000, 100,000 to 5,000,000, or 200,000 to 2,000,000. The number-average molecular weight of the second peak may be 500 to 100,000, 800 to 50,000, or 1,000 to 10,000. When the molecular weights of the cellulose, hemicellulose, and lignin are close to each other, the multiple peaks may overlap and be detected as a single peak.

[0075] The bark extrusion product of the present disclosure contains, for example, cellulose, hemicellulose, and lignin, at least a portion of which is ester-bonded to an organic acid. Therefore, the bark extrusion product of the present disclosure may contain insoluble matter that is not soluble in DMSO. When the bark extrusion product of the present disclosure contains insoluble matter that is not soluble in DMSO, the amount of insoluble matter in DMSO in the extrusion product is not particularly limited, but may be, for example, more than 0 wt% to 80 wt% or less, such as 5.0 to 80 wt%. The method and conditions for measuring the amount of insoluble matter in DMSO are described later in the Examples. Note that the presence of a component that is insoluble in DMSO does not mean that the component is insoluble in the aforementioned organic acid. It simply means the presence of a component that is soluble in organic acids such as formic acid but not in DMSO, and therefore cannot be measured for molecular weight by GPC.

[0076] The shape of the bark molded product of the present disclosure is not particularly limited, but a typical example of a bark molded product is a sheet or film. Sheets and films containing bark can be obtained, for example, by a manufacturing method including a step of casting a bark solution onto a substrate (or onto a second sheet material described below) and a step of drying the bark solution on the substrate (or onto the second sheet material described below). The thickness of the film or sheet can be selected depending on the application, but for example, the film may have a thickness of 10 to 300 μm, preferably 10 to 150 μm, and more preferably 10 to 100 μm. The sheet may have a thickness of 300 to 600 μm.

[0077] In order to more effectively exert the effects of the present invention, the surface of the bark extrusion product of the present disclosure preferably has an uneven shape. The uneven shape of the surface of the bark extrusion product can be adjusted, for example, by the bark concentration in the bark solution, the heat-pressing conditions described below, and the like.

[0078] Conventionally, sheets and films formed from lignocellulose obtained by pulverizing raw biomass are brittle when dry and crack when folded. In contrast, the sheets and films formed from the bark solution of the present disclosure can be produced without pulverizing the bark, and therefore contain, for example, fibrous material derived from bark lignocellulose. The inclusion of this fibrous material improves the foldability of the sheets and films. The sheets and films formed from the bark solution of the present disclosure do not crack when folded, preferably at an angle of 90 degrees or more.

[0079] The bark molded product of the present disclosure can also be obtained by subjecting the bark solution of the present disclosure to solid-liquid separation, and then molding the resulting solid content under heat and pressure to form a bark-containing woody molded product. Solid-liquid separation can be performed by centrifugation, filtration, etc. Heating and pressure molding of the solid content can be performed by placing the solid content in a mold and compression molding it while heating.

[0080] The bark molding of the present disclosure is, in other words, a bark molding containing bark and possessing properties derived from bark. This bark molding can possess the properties of cellulose, hemicellulose, and lignin. As described above, the main components of bark are lignocelluloses such as cellulose, hemicellulose, and lignin, but bark also contains components different from the components that make up the xylem. For example, the outer bark that forms the outer surface of the bark contains suberin, a highly hydrophobic component formed by the combination of aliphatic components with ferulic acid, caffeic acid, and glycerol. As described above, the bark molding of the present disclosure preferably also contains suberin. By including suberin in the bark molding of the present disclosure, the bark molding can be endowed with the high hydrophobicity inherent to suberin. Bark moldings can be applied, for example, as films, fibers, wallpaper, etc. that require functions such as antibacterial properties, UV absorption, metal adsorption, and water repellency, in fields such as medicine, clothing, and housing equipment. Molded products in the form of films or sheets are particularly useful.

[0081] [Laminated Material] The laminated material of the present disclosure is constituted by a laminate including at least a substrate and a sheet material, and the sheet material is characterized by including bark.

[0082] The sheet material in the laminated material of the present disclosure can be composed of the bark component of the present disclosure described above. Therefore, the configuration of the sheet material in the laminated material of the present disclosure can be exemplified as the same configuration as the bark component described above, except for the feature that it is laminated with a substrate.

[0083] The laminated material of the present disclosure is composed of a laminate including at least a substrate and a sheet material. For example, the laminated material of the present disclosure preferably includes a sheet material in which at least one main surface of the substrate and the main surface of the sheet material are laminated and integrated. The number of substrates and sheet materials included in the laminated material is not particularly limited, and multiple substrates and sheet materials may be alternately laminated and integrated. In other words, the laminated material of the present disclosure has a laminated structure including a substrate and a sheet material. For example, the laminated material may include a first substrate and a sheet material laminated and integrated on the surface of the first substrate, or may include a first substrate and a second substrate laminated and bonded to the first substrate via the sheet material.

[0084] In this disclosure, for convenience, in an embodiment in which substrates are bonded to both sides of a sheet material, one will be referred to as a "first substrate" and the other will be referred to as a "second substrate," and the laminated material of the present disclosure is not limited to a two-layer structure or a three-layer structure. The laminated material may include layers other than the sheet material and the substrates as long as the effects of the present disclosure can be obtained.

[0085] The laminated material of the present disclosure may also include a second sheet material between the substrate and the sheet material containing bark. As described below, the second sheet material does not necessarily include bark, and preferably includes, for example, biomass other than bark. The second sheet material is disposed between the substrate and the sheet material containing bark as needed, for example, to enhance adhesion between the substrate and the sheet material containing bark.

[0086] Here, "sheet material" means a thin, flat member, and is a concept that includes so-called sheets and films. Furthermore, "laminated and integrated" does not simply mean a state in which a sheet material and an adjacent layer (e.g., a substrate, a second sheet material provided as needed, etc.) are overlapped, but means a state in which the sheet material is firmly adhered to the surface of the substrate, etc. As long as the sheet material and the substrate, etc. are firmly adhered, the interface between the sheet material and the substrate, etc. may be clear or unclear. "Laminated adhesion" means a state in which the first substrate and the second substrate are firmly adhered (i.e., integrated) via the sheet material.

[0087] As described below, the laminated material of the present disclosure is produced by thermocompression bonding a substrate or the like to a sheet material without using chemicals such as adhesives. As described above, the sheet material is formed by removing the liquid component from a bark solution obtained by dissolving bark in an organic acid. Because the organic acid is removed as a liquid component, the sheet material can be formed substantially from plant-derived components only. For example, when a plant material is used as the substrate, a laminated material substantially consisting of plant-derived components and plant material is obtained.

[0088] Here, "substantially" means, for example, that the content of plant-derived components in the sheet material is 90% by weight or more, preferably 95% by weight or more, and ideally 100% by weight. When a plant material is used as the substrate, the total content of the plant material and plant-derived components in the laminate is 90% by weight or more, preferably 95% by weight or more, and ideally 100% by weight.

[0089] Another method for implementing the disclosed technology is to apply a bark solution to the surface of a substrate and then dry it to form a sheet layer on the surface of the substrate.

[0090] The method for applying the bark solution to the surface of the substrate is not particularly limited, and any conventional application method can be used, including a method in which a brush or roller is soaked in the bark solution and applied to the surface of the substrate, a dip coating method in which the substrate is immersed in the bark solution and then pulled out, a casting method in which the bark solution is spread on the surface of the substrate and the film thickness is adjusted with a bar coater, and a spray coating method.

[0091] This application method is preferably used because it makes it easy to laminate a sheet material made of bark onto a substrate having a curved surface.

[0092] Among these application methods, the brush method, dip coating method, and spray coating method are preferred because they can be applied to curved surfaces, and spray coating method is especially preferred because it makes it easier to achieve a uniform thickness for the bark sheet layer.The spray coating method can also be used with an air compressor connected to the spray coating device, which allows the solution to be sprayed evenly using pressurized air.

[0093] After applying the bark solution to the surface of the substrate, the next step of heat pressing can be carried out while the formic acid solvent remains, or after the formic acid has been partially or completely evaporated.

[0094] According to the present disclosure, for example, a laminated material made from 100% plant materials can be obtained. However, the sheet material or laminated material may contain plant-derived components and components other than plant materials, as long as the effects of the present disclosure are not impaired. For example, to impart desired functions to the laminated material, the sheet material may contain known additives. Examples of such additives include conductive agents, magnetic powders, antibacterial agents, flame retardants, antioxidants, and ultraviolet absorbers.

[0095] Adding a conductive agent to a sheet material can suppress static buildup and reduce electrostatic discharge during dry periods. Adding magnetic powder to a sheet material can produce a laminate that can be attached and fixed with a magnet, or a laminate that can block electromagnetic waves emitted from the sun, electronic devices, etc. Adding an antibacterial agent to a sheet material can produce a laminate that can be used in the sanitary and toiletry fields and hygienic material applications where antibacterial and antiviral properties are required. Furthermore, adding an antibacterial agent can suppress biodegradation of the laminate material itself and changes in appearance due to bacterial growth. Adding a flame retardant to a sheet material can be used in the construction field where fire resistance and other properties are required. Adding an antioxidant or ultraviolet absorber to a sheet material can be used in the construction field where weather resistance and light resistance are required.

[0096] According to the present disclosure, a laminated material made from 100% plant materials can be obtained, but the sheet material or laminated material may contain divalent or higher fatty acids and / or their anhydrides as components other than plant-derived components and plant materials. When it is desired to obtain a glossier appearance while surface-modifying the laminated material, and / or when it is desired to integrate the substrate or the sheet material under milder conditions, it is preferable that the sheet material contain divalent or higher fatty acids and / or their anhydrides. Of the organic acids mentioned above, divalent or higher fatty acids that are not completely removed as liquid components from the plant solution are preferred. Specific divalent or higher fatty acids will be described in detail in the (Sheet Material) section.

[0097] (Substrate) Hereinafter, descriptions regarding "substrate" can be interpreted as descriptions regarding "first substrate" and "second substrate".

[0098] The material of the substrate is not particularly limited as long as it is firmly bonded to the sheet material. The materials of the first substrate and the second substrate may be the same or different. As described below, the sheet material of the present disclosure includes bark. Since formylated plant-derived components, such as lignin, are hydrophobic, it is believed that even if the substrate material is lipophilic, they are activated by heating to exhibit strong adhesive properties. For example, the substrate material may be selected from the group consisting of biomass materials, plastics, metals, ceramics, glass, pulp molds, cloth, and paper. If necessary, the surface of the substrate may be corona-treated.

[0099] In the present disclosure, the type of plastic used for the substrate is not particularly limited. For example, polyethylene, polypropylene, ABS (acrylonitrile-butadiene-styrene copolymer), polystyrene, polymethyl methacrylate, polylactic acid, PEEK (polyether ether ketone resin), polycarbonate, polyurethane, polyester, PET (polyethylene phthalate), LCP (liquid crystal polymer), cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polybutylene succinate, PHA (polyhydroxyalkanoate), PHBH (3-hydroxybutyrate-co-3-hydroxyhexanoate polymer), etc. can be used. The plastic may be a foam. Polyethylene is preferably used.

[0100] In the present disclosure, the metal used for the substrate may be iron, stainless steel, nickel, copper, silver, gold, aluminum, tinplate, etc. Furthermore, the ceramic may be pottery such as earthenware.

[0101] The fabrics used in the present disclosure may be natural fibers such as hemp, cotton, silk, and wool, synthetic fibers such as polyester, nylon, acrylic, and polyurethane, regenerated fibers such as rayon and Tencel, and semi-synthetic fibers made by chemically modifying natural polymers such as cellulose acetate fiber and promix fiber. Among these, hemp and cotton are preferred from the viewpoint of obtaining a laminated material made from plant materials.

[0102] From the viewpoint of obtaining a laminated material made from plant materials, preferred substrate materials are paper, pulp mold, and biomass materials. Paper may be kraft paper, hardwood pulp (LBKP), or softwood pulp (NBKP). Softwood pulp (NBKP) is thin but strong, tear-resistant, and has high strength, making it suitable for a wide range of applications. In terms of the relationship between desired strength and cost, hardwood pulp (LBKP) or a mixture of hardwood pulp (LBKP) and softwood pulp (NBKP) may be used.

[0103] The pulp mold may be a thick wall mold with a 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 depending on, for example, the desired load-bearing capacity. Thick walls are preferably used from the viewpoint of obtaining a substrate with a thick film thickness and high load-bearing capacity. In the case of thick walls, the pulp material adsorbed and laminated on the shaping mold can be dried and solidified as is without press molding. In this case, the sheet material of the present disclosure can be bonded to the smooth surface adsorbed on the shaping mold. This results in a pulp mold with a modified surface.

[0104] PIM is a technology for molding pulp by injection molding. Complex pulp mold structures, including interlocking structures, bosses, and ribs, can be obtained as the substrate. In this case, the sheet material of the present disclosure is placed in a mold in advance, and pulp fibers containing starch as a binder are injected into the molding machine as the substrate raw material. Specifically, after the substrate raw material is filled into the mold containing the sheet material, the mold repeatedly opens and closes delicately to remove moisture from the substrate raw material and dry it, while the sheet material is heated. After the substrate raw material is dried, the mold is cooled and the solidified molded product is removed, resulting in a surface-modified pulp mold. Furthermore, the substrate used in this disclosure may be a foam product obtained by extrusion molding a mixture of paper powder, industrial starch, and synthetic resin, foamed with steam, and then extruded. This foam product has environmental advantages over other plastic foams and can be used in the same way as existing plastic foam products. By modifying the surface of a molded article made from this foam product with the sheet material of the present disclosure, it is possible to impart a more desirable appearance and feel to the molded article of a desired shape.

[0105] The biomass material may be woody biomass, herbaceous biomass, or a mixture thereof. Examples of herbaceous biomass include sugarcane bagasse, rice straw, wheat, bran, tomato, onion, and moso bamboo.

[0106] A typical example of woody biomass is wood. The type of wood is not particularly limited, and may be a broadleaf tree or a conifer. Furthermore, the part of the wood is also not particularly limited, and may be any of heartwood, sapwood, and transitional wood. It may also be a part with knots, black streaks, discoloration, or the like, or a part with a rough texture and lacking in aesthetic appeal. According to the present disclosure, even if the material of the substrate is a low-grade wood with an appearance that is not normally used as an exterior material, it is possible to produce a laminated material with a beautiful and luxurious appearance by laminating and integrating sheet materials.

[0107] Wood boards or laminated lumber may be used as substrates to the extent that the effects of the present disclosure are not impaired. Conventionally, wood boards are materials made by mixing small pieces of wood with adhesives such as urea-melamine resins or modified phenolic resins and then thermocompressing them. Laminated lumber is a material made by bonding small pieces of wood together with adhesives such as resorcinol resins or aqueous polymeric isocyanate-based adhesives. However, wood boards or laminated lumber made using the adhesives described below are preferably used as substrates in the present disclosure. For example, in wood boards obtained using a "bark solution obtained by dissolving bark in an organic acid" as an adhesive, the organic acid is thought to evaporate when heated during bonding. Furthermore, as described below, the adhesives of the present disclosure contain plant-derived components, such as lignocellulose, in which some or all of the hydroxyl groups have been formylated. Even if some of this formylated lignocellulose decomposes, the products are formic acid, lignin, cellulose, and hemicellulose, which do not adversely affect the natural environment. In the case of such a substrate, the chips (sawdust in the case of wood) do not contain adhesives as so-called chemicals, and therefore, when disposed of, they can be safely disposed of by landfill or incineration.

[0108] The raw materials for wood boards and laminated lumber are mainly small pieces cut and shredded from demolition waste, thinned wood, etc. Although fine cutting causes the original properties of raw wood to be lost, reducing resistance and making it more susceptible to mold, these problems are alleviated by laminating and integrating the sheet material of the present disclosure. Laminated materials using wood boards or laminated lumber as a base material and including sheet materials laminated and integrated onto this base material, etc., are highly durable. In particular, laminated materials using wood boards or laminated lumber as a base material obtained using the adhesive of the present disclosure are made from 100% plant materials and are highly biodegradable. The herbaceous biomass described above can also be used as a raw material for wood boards and laminated lumber.

[0109] The type of wood board is not particularly limited. For example, fiberboard obtained by molding fibrous wood chips, particleboard obtained by molding chip-like 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).

[0110] The type of laminated lumber is not particularly limited. In terms of classification based on joining method, any of scarf joint, finger joint, and pad joint is acceptable. Finger joints, which have high adhesive strength, are preferred. Cross-laminated timber (CLT), laminated veneer lumber (LVL), and plywood are also acceptable. Examples of raw material tree species include Douglas fir, European red pine (redwood), SPF (spruce, pine, and fir), American cypress, American larch, Japanese cedar, and larch.

[0111] The thickness of the substrate is not particularly limited. Examples of the thickness of the substrate include 1 mm or more, 8 mm or more, and 50 mm or less, 30 mm or less, and preferred ranges include 1 to 50 mm, 1 to 30 mm, 8 to 50 mm, and 8 to 30 mm.

[0112] (Sheet Material) In the present disclosure, the sheet material is characterized by including bark. As described above, the configuration of the sheet material in the laminated material of the present disclosure can be exemplified as the same configuration as the bark molded product described above, except for the feature that the sheet material is integrated with the surface of a layer adjacent to the sheet material (e.g., the substrate, an optional second sheet material, etc.). In the following description, for explanations common to the sheet material and the bark molded product (e.g., the proportion and type of bark in the bark molded product, the type and content of biomass other than bark, metal salts, the density, mechanical properties, glass transition temperature Tg, thickness, etc.), the explanation of the bark molded product described above will be quoted here, and a separate explanation of the sheet material will be omitted as appropriate.

[0113] As described above, the present disclosure provides a sheet material made from 100% plant materials, but the sheet material may also contain divalent or higher fatty acids and / or their anhydrides as components other than plant-derived components such as bark and plant materials. When it is desired to obtain a glossier appearance while surface-modifying the laminated material, and / or when it is desired to integrate the substrate or the like with the sheet material under milder conditions, it is preferable for the sheet material to contain divalent or higher fatty acids and / or their anhydrides. The reason for the excellent effects achieved by including divalent or higher fatty acids and / or their anhydrides in the sheet material is thought to be due to the interaction between the plant-derived components and plant materials in the sheet material and the divalent or higher fatty acids and / or their anhydrides.

[0114] Such sheet material has a thickness of 1715 to 1725 cm -1 Some or all of the hydroxyl groups of the cellulose, hemicellulose, and lignin contained as plant-derived components have been formylated, and the cellular structure of wood has been disassembled, so that an absorption peak of 1000 ppm or more is present. A sheet material or laminate material containing such plant-derived components and plant materials and containing divalent or higher fatty acids and / or anhydrides thereof is essentially different from a molded product obtained by simply blending wood flour, wood, wood chips, etc. with divalent or higher fatty acids and / or anhydrides thereof and heat treating the mixture.

[0115] When a divalent or higher fatty acid and / or anhydride thereof is contained in the sheet material, the ductility and adhesive strength (adhesiveness) of the sheet material are also improved.

[0116] In this specification, divalent or higher fatty acids are also referred to as polycarboxylic acids. In addition, in this specification, "and / or" is used to mean both "and" and "or." For example, divalent or higher fatty acids and / or their anhydrides include (i) divalent or higher fatty acids, (ii) anhydrides of divalent or higher fatty acids, and (iii) divalent or higher fatty acids and anhydrides of divalent or higher fatty acids, and are the same as at least one selected from the group consisting of divalent or higher fatty acids and anhydrides of divalent or higher fatty acids.

[0117] 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, docosanedioic acid, α,ω-alkanedicarboxylic acids, citric acid, and 1,2,3,4-butanetetracarboxylic acid. Examples of divalent or higher fatty acids include polysaccharide polycarboxylic acids. Examples of polysaccharide polycarboxylic acids include polyuronic acids such as alginic acid and pectin; polyuronic acids obtained by oxidizing the primary hydroxyl groups of cellulose; and carboxymethyl cellulose. The divalent or higher fatty acids and / or anhydrides thereof may be used alone or in combination of two or more. The divalent or higher fatty acid and / or anhydride thereof is preferably citric acid and / or anhydride thereof.

[0118] When the sheet material contains a divalent or higher fatty acid and / or anhydride thereof, the content thereof 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, relative to 100 parts by weight of the total of the plant-derived components and plant materials that make up the sheet material. When a divalent or higher fatty acid and / or anhydride thereof is contained, it is preferable that the constituent components excluding said components consist essentially of plant-derived components and plant materials.

[0119] The sheet material may contain hydroxy acids and / or ammonium dihydrogen phosphate as components other than plant-derived components and plant materials. Here, hydroxy acids encompass carboxylic acids and alcohols. Specific examples of hydroxy acids include glycolic acid, lactic acid, glyceric acid, hydroxybutyric acid, citramalic acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinelaic acid, cerebronic acid, quinic acid, and shikimic acid.

[0120] The components that may be contained in the sheet material, i.e., at least one selected from the group consisting of divalent or higher fatty acids, divalent or higher fatty acid anhydrides, hydroxy acids, and ammonium dihydrogen phosphate, are considered to function as a crosslinking agent. Here, the crosslinking agent refers to an agent that crosslinks lignocellulose molecules. When the sheet material of the present disclosure contains at least one selected from the group consisting of divalent or higher fatty acids, divalent or higher fatty acid anhydrides, hydroxy acids, and ammonium dihydrogen phosphate, a crosslinked structure formed by covalent bonds may be formed in the sheet material of the present disclosure.

[0121] When the sheet material contains a divalent or higher fatty acid and / or anhydride thereof, a polyhydric alcohol and / or a sugar may be used together with the divalent or higher fatty acid and / or anhydride thereof. 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, cellooligosaccharide, mannose, mannooligosaccharide, xylose, xylooligosaccharide, amino acid, peptide, protein, etc.

[0122] Furthermore, as described above, the present disclosure provides a laminated material made from 100% plant materials. However, the sheet material or laminated material may contain components other than plant-derived components and plant materials (e.g., additives such as conductive agents, magnetic powders, antibacterial agents, flame retardants, antioxidants, and UV absorbers) to the extent that the effects of the present disclosure are not impaired. When the sheet material contains additives, the content of the additives 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, per 100 parts by weight of the total of the plant-derived components and plant materials that make up the sheet material. When the sheet material contains additives, it is preferable that the components excluding the additives consist essentially of plant-derived components and plant materials.

[0123] It is preferable that the sheet material has a uniform color pattern with few patterns. In a laminated material in which such a sheet material is laminated on, for example, a wood substrate, the grain of the wood substrate is visible through the sheet material, and the same appearance as the substrate can be maintained. Furthermore, when laminated wood is used as the substrate, the joints of the laminated wood are covered and concealed by the sheet material, resulting in a good appearance. On the other hand, wood grain may remain in sheets simply made by thinly slicing wood, and when these are adhered to the wood substrate with an adhesive or the like, the grain of the sheet and the grain of the substrate may be mixed, resulting in a poor appearance.

[0124] From the viewpoint of more suitably exerting the effects of the present invention, it is preferable that the surface of the bark-containing sheet material has an uneven shape. The uneven shape of the surface of the bark-containing sheet material can be adjusted, for example, by the bark concentration in the bark solution, the heat-pressure bonding conditions of the sheet material, etc.

[0125] In the laminated material of the present disclosure, the bark-containing sheet material may be a single layer or multiple layers.

[0126] The surface of the bark-containing sheet preparation has a water contact angle, measured using a bark molded product, of preferably 95° or more, more preferably 100° or more, and even more preferably 105° or more, with the upper limit being, for example, 150° or less, 140° or less, or 130° or less, and preferred ranges include 95 to 150°, 95 to 140°, 95 to 130°, 100 to 150°, 100 to 140°, 100 to 130°, 105 to 150°, 105 to 140°, and 105 to 130°. Specific methods for measuring the water contact angle on the surface of the sheet material are described in the Examples.

[0127] (Second Sheet Material) The laminated material of the present disclosure may also include a second sheet material between the substrate and the sheet material containing bark. As described below, the second sheet material does not necessarily include bark, and preferably includes, for example, biomass other than bark. The second sheet material is disposed between the substrate and the sheet material containing bark as needed, for example, to enhance adhesion between the substrate and the sheet material containing bark.

[0128] The second sheet material preferably contains biomass other than bark. The biomass is preferably biomass containing lignocellulose. There are no particular limitations on the biomass, and woody biomass such as the xylem of broad-leaved trees (eucalyptus, beech, etc.) and coniferous trees (cedar, cypress, red pine, etc.), and herbaceous biomass such as rice, sugarcane, wheat, tomato, onion, moso bamboo, and bran are appropriately selected and used. Among these, the xylem of trees is preferred as biomass other than bark. The type of biomass contained in the second sheet material may be only one type, or two or more types.

[0129] From the viewpoint of more suitably exerting the effects of the present invention, the proportion of biomass in the second sheet material is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 60% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 100% by weight. The upper limit can be, for example, 100% by weight, 90% by weight, or 85% by weight. Preferred ranges include 20 to 100% by weight, 20 to 90% by weight, 20 to 85% by weight, 40 to 100% by weight, 40 to 90% by weight, 40 to 85% by weight, 60 to 100% by weight, 60 to 90% by weight, 60 to 85% by weight, 80 to 100% by weight, 80 to 90% by weight, 80 to 85% by weight, and 90 to 100% by weight.

[0130] In the second sheet material, the proportion of biomass is preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, even more preferably 99% by weight or more, and even more preferably 100% by weight. It is preferable that the second sheet material is composed substantially only of biomass (the proportion of biomass is 95% by weight or more, even more preferably 99% by weight or more, and even more preferably 100% by weight).

[0131] The second sheet material can be obtained by a manufacturing method including, for example, a step of casting a biomass solution onto a substrate and a step of drying the biomass solution on the substrate. The thickness of the second sheet material can be selected depending on its application, but may be, for example, 10 to 600 μm, and preferably 300 to 600 μm.

[0132] In the laminated material of the present disclosure, the second sheet material may be a single layer or multiple layers.

[0133] [Method for Manufacturing Laminated Material] The laminated material of the present disclosure can be manufactured by, for example, a manufacturing method including the following steps (1) to (3): (1) dissolving bark powder in an organic acid to obtain a bark solution (dissolving step), or a step of preparing the bark solution; (2) removing the liquid component from the bark solution to obtain a sheet material containing bark (sheet forming step); (3) laminating a sheet material on the surface of a substrate (first substrate) and thermocompression bonding the sheet material to obtain a laminated material in which the sheet material and the substrate (first substrate) are integrated together (in the case of including a second sheet material, laminating the second sheet material and the sheet material in this order on the surface of the substrate (first substrate) and thermocompression bonding the sheet material to obtain a laminated material in which the sheet material, the second sheet material, the substrate (first substrate), and the like are integrated together in this order) (Lamination Step 1).

[0134] Furthermore, when the laminated material of the present disclosure includes a second substrate in addition to the first substrate, the laminated material of the present disclosure can be produced, for example, by a production method including the following steps (1) to (3): (1) dissolving bark powder in an organic acid to obtain a bark solution (dissolving step) or a step of preparing the bark solution; (2) removing the liquid component from the bark solution to obtain a sheet material containing bark (sheet forming step); and (3) placing a sheet material between the first substrate and the second substrate and heat-pressing the sheet material to laminate and bond the first substrate, sheet material, and second substrate in this order (when a second sheet material is included, placing the second sheet material between the first substrate and the second substrate and heat-pressing the sheet material to laminate and bond the first substrate, second sheet material, sheet material, and second substrate in this order) (lamination step 2).

[0135] In these manufacturing methods, a laminated material is produced by placing a sheet material obtained by removing liquid components containing organic acids from the bark solution, placing the surface of the sheet material in contact with the surface of the aforementioned substrate, and laminating and adhering them together. The organic acids are removed as liquid components. As a result, as described above, a bark-containing sheet material can be obtained that is essentially composed of plant-derived components. Therefore, the sheet material can be made from 100% plant-based materials, free of residual organic solvents and other chemicals that contribute to sick building syndrome. Furthermore, the sheet material and the substrate are integrated by thermocompression without the use of adhesives. For example, when woody biomass is selected as the substrate material, this manufacturing method can produce a laminated material made from 100% plant-based materials, free of residual adhesive-derived chemicals. Adhesive-free manufacturing methods reduce the use of chemicals in each process, particularly eliminating the need for highly volatile organic solvents. Therefore, such manufacturing methods offer excellent operational safety.

[0136] Furthermore, with the manufacturing method of the present disclosure, even if the substrate material is so-called low-grade wood or wood whose aesthetics have been impaired by aging or the like, it is possible to impart an excellent appearance by laminating and integrating the sheet material of the present disclosure. Furthermore, because bark powder is used as the raw material for the sheet material, it is possible to obtain a laminated material with a luxurious appearance by effectively utilizing, for example, bark generated during the sawing of high-quality wood. Furthermore, in addition to bark, biomass resources such as building waste, thinned wood, unused crops, and agricultural waste can also be effectively utilized as plant raw materials for the sheet material.

[0137] Each step will be described in detail below.

[0138] (1) Dissolution step In the dissolution step, bark is dissolved in an organic acid to obtain a bark solution. That is, the dissolution step can be said to be a step of preparing the bark solution described above. The preparation of the bark solution is as described above.

[0139] In the method of manufacturing a laminated material, the dissolution step can be substituted by providing the bark solution of the present disclosure.

[0140] (2) Sheet Forming Step In this step, the liquid component is removed from the bark solution to recover the solid content, which is then formed into a sheet to obtain the sheet material of the present disclosure.

[0141] The method for removing the liquid component from the bark solution to obtain the sheet material is not particularly limited. For example, the sheet material of the present disclosure may be obtained by casting the bark solution into a container of a desired size and shape and drying it to remove the liquid component, or by forming the solid content after drying into a sheet. Furthermore, from the viewpoint of improving drying efficiency, the bark solution may be concentrated before drying using known concentration methods such as evaporation and vacuum concentration. Water or alkali may be added to the bark solution as a precipitant, as long as the effects of the present disclosure are obtained. The sheet material of the present disclosure may be obtained by forming the solid content precipitated by adding water or alkali into a sheet and drying it. Since methods using a precipitant may result in the loss of some of the components contained in the bark, casting methods are preferred.

[0142] The organic acid added during dissolution has been removed as a liquid component from the sheet material obtained in this way, and this sheet material can be said to be a regeneration of the dissolved bark as a solid component.

[0143] As described above, the bark mainly contains cellulose. The bark may contain lignin and hemicellulose in addition to cellulose. Furthermore, as described above, the bark preferably contains suberin. The bark contains one or more selected from the group consisting of cellulose, hemicellulose, and lignin. Some or all of the hydroxyl groups of the cellulose, hemicellulose, and lignin may be formylated. The bark may further contain polyphenols such as tannins, catechins, and flavonoids, terpenes, and the like.

[0144] Furthermore, the sheet material or solid content obtained by removing the liquid component from the bark solution may be washed to further remove organic acid-derived components, alkali-derived components, etc. Distilled water can be used for washing.

[0145] As long as the effects of the present disclosure are obtained, the thickness of the resulting sheet material is not particularly limited and can be adjusted, for example, by the solids concentration of the bark solution. From the viewpoint of being able to conceal the appearance of the substrate surface, the average thickness of the sheet material may be 10 μm or more, 100 μm or more, or 200 μm or more. From the viewpoint of being easily integrated with the substrate, etc., the average thickness of the sheet material may be 2000 μm or less, 1000 μm or less, 800 μm or less, or 600 μm or less. Note that the "average thickness" described here is the average thickness of the sheet material before being heat-pressed and bonded to the substrate, and is the average value of measurements taken multiple times using known means.

[0146] (3) Lamination Process This process is a process for obtaining a laminated material from the aforementioned sheet material and a substrate, etc. (specifically, a substrate, a second sheet material, etc.). Specifically, the sheet material is laminated on the substrate, etc., and then heat-pressurized. More specifically, this process may be a process for obtaining a laminated material in which the sheet material and the first substrate, etc. are integrated by laminating the sheet material so that the surface of the sheet material contacts the surface of the first substrate, etc., and then heat-pressurizing the sheet material to obtain a laminated material in which the sheet material and the first substrate, etc. are integrated. Alternatively, this process may be a process for laminating and adhering the first substrate, etc., and the second substrate, etc., by placing a sheet material between the first substrate, etc., and the second substrate, etc., and then heat-pressurizing the sheet material so that both surfaces of the sheet material contact the surface of the first substrate, etc., and the surface of the second substrate, etc., respectively. Alternatively, this process may be a process for laminating and adhering the first substrate, etc., to the surface of the first substrate, etc., and then heat-pressurizing the sheet material to integrate the sheet material and the first substrate, etc., and then further laminating and heat-pressurizing the second substrate, etc., to the surface of the sheet material integrated with the first substrate, etc., to laminate and adhering the first substrate, etc., to the second substrate, etc., via the sheet material. According to the sheet material of the present disclosure, a laminated material in which the substrate, etc., and the sheet material are integrated can be obtained without using an adhesive, etc.

[0147] The material of the substrate is selected from the group consisting of wood, plastic, metal, ceramic, pulp mold, and paper. The above-mentioned types of substrates may be appropriately selected and used. The materials of the first substrate and the second substrate may be the same or different.

[0148] According to the present disclosure, even low-quality wood that has conventionally had problems with appearance can be suitably used as a substrate. There are no particular limitations on the shape and size of the substrate, but a shape with a substantially flat surface can be suitably used from the viewpoint of adhesion to the sheet material. From the viewpoint of obtaining a laminated material of plant materials, wood, pulp mold, and paper are preferred as the substrate, wood is more preferred, and sawn natural wood is even more preferred. However, wood boards, laminated lumber, plywood, etc. can also be used as long as they do not contain residual organic solvents, adhesives, etc. Wood boards, laminated lumber, plywood, etc. obtained using the adhesive of the present disclosure described below are more preferred.

[0149] A known heat press or the like can be used for thermocompression bonding of the sheet material and the substrate. The thermocompression conditions are appropriately set depending on the type and size of the sheet material and the substrate. From the viewpoint of facilitating lamination and integration of the sheet material and the substrate, the thermocompression temperature may be 60°C or higher, 80°C or higher, 100°C or higher, or 150°C or higher. From the viewpoint of avoiding discoloration and deformation of the sheet material and the substrate, the thermocompression temperature may be 220°C or lower, 200°C or lower, or 190°C or lower.

[0150] When the sheet material contains a divalent or higher fatty acid and / or anhydride thereof, the temperature for the thermocompression bonding may be 20° C. or higher, preferably 30° C. or higher, and more preferably 70° C. or higher. When the sheet material contains a divalent or higher fatty acid and / or anhydride thereof, the temperature for the thermocompression bonding may be 220° C. or lower, preferably 130° C. or lower, and more preferably 110° C. or lower. In this way, a sheet material containing a divalent or higher fatty acid and / or anhydride thereof can be integrated with a substrate or the like under milder conditions than a sheet material that does not contain a divalent or higher fatty acid and / or anhydride thereof.

[0151] From the viewpoint of facilitating lamination and integration of the sheet material and the substrate, the pressure of thermocompression bonding may be 0.5 MPa or more, or may be 3 MPa or more. From the viewpoint of avoiding deformation of the sheet material and the substrate, the pressure of thermocompression bonding may be 15 MPa or less, and preferably 10 MPa or less. The time of thermocompression bonding is appropriately selected depending on the temperature and pressure. Here, the pressure during thermocompression bonding means the pressure applied to the sheet material on the substrate. The load (unit: N) applied to the heat press machine is multiplied by the area of ​​contact between the substrate and the sheet material (unit: m 2 ) to obtain the pressure (unit: Pa) during thermocompression bonding.

[0152] From the viewpoint of improving adhesion between the sheet material and the substrate, the surface of the substrate may be polished using a known polishing means before laminating the sheet material. In other words, this manufacturing method may include polishing the surface of the substrate before laminating the sheet material. For example, this manufacturing method may further include polishing the first substrate before laminating the sheet material, or may further include polishing the first substrate and the second substrate before placing the sheet material. As the polishing means, for example, various grades of abrasive paper can be used.

[0153] When preparing a sheet material containing divalent or higher fatty acids and / or their anhydrides, the timing of adding the divalent or higher fatty acids and / or their anhydrides may be any of the following: (i) a method in which divalent or higher fatty acids and / or their anhydrides are mixed with the bark and organic acid during the (1) dissolving step in which bark is dissolved in an organic acid to obtain a bark solution; (ii) a method in which divalent or higher fatty acids and / or their anhydrides are mixed after the (1) dissolving step in which bark is dissolved in an organic acid to obtain a bark solution and before the (2) sheet forming step; or (iii) a method in which divalent or higher fatty acids and / or their anhydrides are mixed after preparing a sheet material that does not contain divalent or higher fatty acids and / or their anhydrides through the (2) sheet forming step. In the case of (iii), methods such as applying or impregnating the divalent or higher fatty acids and / or their anhydrides to a sheet material that does not contain divalent or higher fatty acids and / or their anhydrides may be used.

[0154] When various additives such as hydroxy acids, ammonium dihydrogen phosphate, polyhydric alcohols, sugars, and the above-mentioned additives are added to the sheet material, the timing of adding them is the same as when divalent or higher fatty acids and / or anhydrides thereof are added to the sheet material.

[0155] When the laminated material of the present disclosure includes a second sheet material between the substrate and the first substrate, the second sheet material can be laminated to the substrate and the first sheet material by heat and pressure bonding, similar to the first sheet material. As described above, for example, the raw biomass can be subjected to the above-mentioned crushing process, dissolution process, etc., similar to the bark, and dissolved in an organic acid. The second sheet material can be obtained by preparing a biomass solution in the same manner as the bark solution, except that biomass is used as the raw material, and removing the liquid component from the biomass solution.

[0156] [Surface Modification Method for Molded Articles] The technology disclosed herein can be applied to the surface modification of molded articles made of various materials. This surface modification method includes (1) dissolving bark in an organic acid to obtain a bark solution (dissolution step), (2) removing liquid components from the obtained bark solution to obtain a bark-containing sheet material (sheet formation step), and (3) laminating this sheet material onto the surface of a molded article and thermocompression bonding (surface modification step). This surface modification method can, for example, impart a desired appearance to the molded article, improve durability by hydrophobizing the surface, or increasing hardness. Furthermore, it can also be applied to repair and improve the appearance of wood molded articles whose appearance has deteriorated over time. From the perspective of durability after surface modification, it is preferable that the sheet material be integrated with the molded article by thermocompression bonding.

[0157] The material of the molded product is not particularly limited as long as it can be heat-pressed to a sheet material containing bark, but the materials mentioned above for the substrate are preferably used. A molded product made of a material selected from the group consisting of wood, plastic, metal, ceramic, pulp mold, and paper is preferred. The molded product may be composed of a single member or a combination of multiple members. The materials of these components may be the same or different. It is preferred that the material of the component forming the surface of the molded product is selected from the group consisting of wood, plastic, metal, ceramic, pulp mold, and paper.

[0158] Here, "wood-based molded product" refers to a molded product made primarily from wood. The components of a wood-based molded product may be lumber or solid wood cut from natural wood, or may be plywood or laminated lumber made from multiple lumber pieces. If the appearance of a wood-based molded product having such components on its surface is damaged by damage or deterioration over time, the good appearance of the wood-based molded product can be restored by laminating the above-mentioned bark-containing sheet material on the surface and repairing it by heat and pressure bonding.

[0159] Regarding this surface modification method, the details of the dissolving step and the sheet forming step are as described above. Regarding the surface modification step, the substrate in the lamination step described above can be replaced with a molded product. In the present disclosure, the surface modification step does not require the use of adhesives or the like. Even when this surface modification method is applied to building materials, furniture, etc., the occurrence of sick building syndrome due to residual adhesives or other chemicals can be avoided.

[0160] [Adhesive] As described above, substrates made of various materials are bonded together via the sheet material of the present disclosure. In other words, the sheet material of the present disclosure can be used as an adhesive for bonding members made of various materials. Furthermore, the bark solution described above can also be used to bond various members. That is, the adhesive of the present disclosure includes a bark solution obtained by dissolving bark in an organic acid and / or a sheet material obtained by removing the liquid component from the bark solution. From another perspective, the present disclosure provides a bonding method that includes adding a bark solution obtained by dissolving bark in an organic acid and / or a sheet material obtained by removing the liquid component from the bark solution to an object to be bonded and heating the resulting mixture. As described above, some or all of the hydroxyl groups of the bark solution and the sheet material may be formylated. It is believed that the formylated component acts as an adhesive.

[0161] The adhesive of the present disclosure preferably contains a bark solution obtained by dissolving bark in an organic acid, the bark being one or more selected from the group consisting of cellulose, hemicellulose, and lignin, and some or all of the hydroxyl groups of the cellulose, hemicellulose, and lignin being formylated.Furthermore, the bark contained in the adhesive preferably contains suberin.

[0162] The plant materials and organic acids described above for the bark solution and sheet material are preferably used.

[0163] The bonding method using this adhesive is preferably thermal bonding. It may be a wet method or a dry method. For example, a bark solution obtained by dissolving bark in an organic acid can be used as an adhesive for producing wood boards. Wood boards may be fiberboards (fiberboards) made by pulverizing wood into fibers and then molding them, or particleboards (fiberboards) made by crushing wood into chips and then molding them. Examples of fiberboards include hardboards, insulation boards, and MDF (medium-density fiberboards). Particleboards and fiberboards can be obtained by adding the bark solution to small pieces or fibers of various woods, mixing them, and then pressing them under high humidity and pressure. These can be used to produce bark-containing wood boards made from 100% plant materials, free of chemicals such as organic solvents.

[0164] The preferred requirements for the adhesive are the same as those for the sheet material of the present disclosure, and therefore, the description of the preferred requirements for the adhesive will be omitted in this section.

[0165] When the sheet material of the present disclosure is to be used as an adhesive for joining components made of various materials, it is preferable that the adhesive be a sheet material containing a divalent or higher fatty acid and / or its anhydride, because this allows for milder conditions when integrating the substrate and the sheet material. Including a divalent or higher fatty acid and / or its anhydride in the sheet material also improves the ductility and adhesive strength (adhesion) of the sheet material. The preferred content range and timing of incorporation of the divalent or higher fatty acid and / or its anhydride in a sheet material containing a divalent or higher fatty acid and / or its anhydride, as well as the preferred thermocompression temperature range when using the sheet material as an adhesive for joining components, are as described above. Therefore, the ranges are omitted here.

[0166] Hereinafter, a more detailed description will be given using fiberboard as an example.

[0167] In the wet process, wood is defibrated with an organic acid (e.g., formic acid) to prepare a pulp solution. This pulp solution contains a bark solution obtained by dissolving bark in the organic acid as an adhesive. A sizing agent is added to the pulp solution as needed to impart water resistance and strength, and the fibers dispersed in the solution are then cast onto a wire mesh and dehydrated to form a mat. The resulting wet mat is compressed and dehydrated in a prepress, followed by drying under heat and pressure to produce a fiberboard.

[0168] In dry processes, a large amount of adhesive is usually required to bond the dry fibers. However, according to the technology of the present disclosure, by adding an organic acid (e.g., formic acid) during the manufacturing process, a bark solution obtained by dissolving bark in the organic acid can be present as an adhesive component. According to the present disclosure, since a large amount of water is not used as in wet processes, dehydration on a wire mesh is not required, and fiberboards with smooth surfaces can be obtained. In this method, it is sufficient that formylated plant-derived components are present together with the fibers during heat pressing. Therefore, the organic acid needs to be added at least before heat pressing. For example, it may be added during the bark defibration or just before the board is sent to the dryer.

[0169] The following describes its application to particle board. Particle boards are classified into single-layer, three-layer, and multi-layer types depending on their structure. Three-layer boards are composed of small pieces on both surface layers (front and back layers) and relatively coarse pieces in the inner layer (core layer). Multi-layer boards are composed of a continuous progression from fine pieces to coarse pieces from the surface to the center layer. The adhesive of the present disclosure can be applied to any of these structures.

[0170] Specifically, in the particleboard manufacturing process, wood is cut, crushed, and dried, and then adhesive is sprayed onto the resulting wood pieces using a glue blender and mixed to homogenize (gluing). By using the adhesive of the present disclosure instead of conventional adhesives, particleboard made from 100% plant materials can be obtained that does not emit formaldehyde or other substances.

[0171] For example, when manufacturing a three-layer board, small pieces of wood of different sizes are used to glue the surface and core layers together, and then the surface layer, core layer, and surface layer are laminated in this order to form a three-layer mat. This three-layer mat is compressed at high temperature and pressure, and the formylated plant-derived components bond and integrate the individual wood pieces to obtain a three-layer board.

[0172] In addition, oriented strand board (OSB) is intended to be used in building structures (as a base) to increase its strength, without taking into consideration its surface properties. By producing OSB using the adhesive of the present disclosure and then laminating and adhering the sheet material of the present disclosure to the surface of the OSB, a high-strength laminated material with a decorated surface can be obtained.

[0173] In view of the above, the technology of the present disclosure is a method for bonding wood pieces, which includes adding an organic acid to fragmented wood and heating the resulting mixture, and is also a method for manufacturing a wood board. In another view, the present disclosure is a method for bonding biomass pieces, which includes adding an organic acid to fragmented biomass material and heating the resulting mixture, and is also a method for manufacturing a biomass product.

[0174] The present disclosure will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0175] The bark solution (water repellent), bark film, wood flour (trunk) solution, and wood flour (trunk) film used in the examples and comparative examples were produced by the following methods.

[0176] <Preparation of Bark Solution> Cedar bark was pulverized using a home mixer (coffee mill) to obtain cedar bark pulverization. Cedar bark was obtained and used in a state where it had been stripped from a cedar log. Next, the cedar bark pulverization of the weight shown in Table 1 was placed in a 50 mL capped vial, and 20 mL of an 80 wt% formic acid aqueous solution (manufactured by Nacalai Tesque) was added. The vial was then placed in a desiccator, and the pressure was reduced by suction at -0.1 MPa for 30 minutes, followed by stirring at 50°C. After stirring at 50°C for 7 days, it was visually confirmed that the cedar bark pulverization had dissolved, and a bark solution (water repellent) was obtained.

[0177]

[0178] <Preparation of Bark Film> The bark solution (water repellent) obtained above was cast onto a lidded culture dish lined with OPP film (polypropylene film). The culture dish was covered and left overnight in a draft chamber at room temperature, then the lid was removed and the bark solution was cast and left in the draft chamber until it dried. After drying, a bark sheet material (bark molded product) was formed on the OPP film.

[0179] <Preparation of wood flour (stem) solution> Eucalyptus (stem) chips were pulverized using a Wiley mill equipped with a 20-mesh sieve, and the resulting wood flour was classified using a JIS standard sieve. Particles that passed through a 500 μm sieve but did not pass through a 355 μm sieve were collected to obtain eucalyptus wood flour (particle diameter 355 μ to 500 μ).

[0180] Next, 400 mg of eucalyptus wood flour was placed in a 50 mL capped vial, and 20 mL of an 80 wt% formic acid solution (manufactured by Nacalai Tesque) was added. The vial was then placed in a desiccator, and the pressure was reduced by suction at -0.1 MPa for 30 minutes, after which the solution was stirred at 50°C. After stirring at 50°C for 7 days, the eucalyptus wood flour had disappeared visually, and a eucalyptus lignocellulose solution was obtained.

[0181] In this specification, when the weight (wg) of wood flour or bark used is expressed as w / W x 100, the weight % when wood flour or bark is dissolved in formic acid is expressed as Wg (80 wt % aqueous solution).

[0182] <Preparation of wood flour (trunk) sheet> The wood flour solution obtained above was cast onto an OPP film (polypropylene film), and then left to stand overnight in a lidded culture dish at room temperature. After that, the pressure was reduced for 3 hours to form a wood flour sheet material (wood flour molded product) on the OPP film.

[0183] <Laminated Material Preparation Example 1 (Comparative Examples 1 to 8 and Examples 6 to 15)> Beech wood (stem) scraps (4 cm x 5 cm x 1 cm) and cedar wood (stem) scraps (4 cm x 5 cm x 1 cm) were prepared as the substrates shown in Table 2. The surfaces of these substrates were polished using abrasive paper #80-120, abrasive paper #100-120, and abrasive paper #120-240, in that order. Each sheet material (2.5 cm x 3.5 cm) shown in Table 2 was laminated onto the polished surface to obtain a laminated material. Lamination was performed using a heat press at the temperature shown in Table 2 (140°C or 220°C) and pressure (4.9 MPa) for 10 minutes. For Examples 8 to 15, which included two layers of sheet material, a second sheet material (eucalyptus (stem) sheet material) and a sheet material containing bark (bark sheet material) were layered on the substrate, and the laminated materials were obtained by laminating them using a heat press. During lamination, the OPP film was peeled off from the sheet material. It was visually confirmed that each sheet material after heat and pressure bonding was integrated with the substrate and could not be peeled off.

[0184] (Measurement of Water Contact Angle) The water contact angle of the surface of the obtained laminate was measured using the following procedure. The contact angle estimation device used was an LSE-ME5 (wide lens specification) manufactured by Nick Corporation. 70 μL of distilled water was dropped onto the surface of the sheet side of the laminate, and the droplet was photographed after 1000 milliseconds to calculate the contact angle. The results are shown in Table 2.

[0185] (Cross-cut test) A cross-cut test of the laminate obtained in Example 8-15 was carried out in accordance with the provisions of JIS K5600-5-6. The test jig used to make the cross-cut slits was a multi-blade cutter for cross-cut testing (055 series) manufactured by Allgood Co., Ltd. The tape used to peel off the cross-cut test specimens was 24 mm x 6.5 m of cellophane tape (CT-248 cellophane tape is a registered trademark) manufactured by Nichiban Co., Ltd. The number of damages in the cross-cut portion after tape peeling was visually counted and graded from 0 to 5 according to the criteria in JIS K5600-5-6 Table 1. The results are shown in Table 2.

[0186]

[0187] <Examples of Laminated Material Production by Spray Coating (Examples 16-19)> (Example 16) Following the procedure described above in <Preparation of Bark Solution>, cedar bark was dissolved in 80% formic acid at a concentration of 2 wt %. This cedar bark solution was spray-coated onto the surface of beech wood substrate using a commercially available spray coating device. The spray-coated test specimen was allowed to air dry to evaporate the formic acid, forming a cedar bark coating on the surface of the substrate. The test specimen was then heat-pressed for 10 minutes at a temperature of 220°C and a pressure of 2.0 MPa using a heat press. This spray coating and heat pressing process was repeated two more times to obtain a test specimen with cedar bark spray-coated onto the beech wood surface.

[0188] Example 17: Following the procedure described above in "Preparing a bark solution," cedar bark was dissolved in 80% formic acid at a concentration of 2 wt%. Following the procedure described above in "Preparing a bark film," eucalyptus wood flour was dissolved in 80% formic acid at a concentration of 2 wt%, and a film was then produced. This eucalyptus film was hot-pressed at 220°C onto the surface of a beech wood substrate to produce a laminate. Next, the surface of this laminate was spray-coated with cedar bark solution and hot-pressed three times using the same procedure as in Example 16, yielding a laminate of the substrate, eucalyptus film, and cedar bark layer.

[0189] Example 18 A laminated material was obtained in the same manner as in Example 16, except that the beech wood of the substrate was changed to cedar.

[0190] Example 19 A laminated material was obtained in the same manner as in Example 17, except that the beech wood of the substrate was changed to cedar.

[0191] <Measurement results of contact angle of spray-coated laminate> The measurement results of the contact angle of the laminates produced in Examples 16 to 19 are shown in Table 3. As shown in Table 3, the contact angle of the laminates whose surfaces were spray-coated with cedar bark exhibited hydrophobicity exceeding 114°C.

[0192]

[0193] Disclosed Items Each of the following items discloses a preferred embodiment.

[0194] Item 1. A bark solution containing bark and an organic acid. Item 2. The bark solution according to Item 1, wherein the bark accounts for 20% by weight or more of the solid content of the bark solution. Item 3. The bark solution according to Item 1 or 2, wherein the surface of a sheet material obtained by drying the bark solution has a water contact angle of 95° or more, as measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds. Item 4. The bark solution according to any one of Items 1 to 3, wherein the organic acid comprises at least one selected from the group consisting of α-keto acids and carboxylic acids having a formyl group. Item 5. The bark solution according to any one of Items 1 to 4, wherein the bark concentration is 0.5% by weight or more. Item 6. The bark solution according to any one of Items 1 to 5, wherein the organic acid content is 4 parts by weight or more per part by weight of biomass contained in the bark solution. Item 7. Item 8. A bark molding formed from the solid content of the bark solution according to any one of Items 1 to 6. Item 8. The bark molding according to Item 7, which is a sheet or film. Item 9. The bark molding according to Item 7 or 8, wherein the surface of the bark molding has a water contact angle of 95° or more, measured by dropping 70 μL of distilled water onto the surface of the bark molding and photographing the droplet after 1000 milliseconds. Item 10. A laminated material formed of a laminate including at least a substrate and a sheet material, wherein the sheet material includes bark. Item 11. The laminated material according to Item 10, wherein the proportion of bark in the sheet material is 20% by weight or more. Item 12. The laminated material according to Item 10 or 11, wherein the surface of the sheet material has a water contact angle of 95° or more, measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds. Item 13. Item 14. A laminated material according to any one of items 10 to 12, wherein the substrate comprises at least one material selected from the group consisting of biomass materials, plastics, metals, ceramics, glass, molded pulp, cloth, and paper. Item 15. A water repellent comprising a bark solution containing bark and an organic acid, wherein the bark accounts for 20% by weight or more of the solid content of the bark solution.Item 15. A water repellent containing a bark solution according to Item 14, wherein the surface of a sheet material obtained by drying the bark solution has a water contact angle of 95° or more, as measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds. Item 16. A water repellent containing a bark solution according to Item 14 or 15, wherein the organic acid comprises at least one selected from the group consisting of α-keto acids and carboxylic acids having a formyl group. Item 17. A water repellent containing a bark solution according to any one of Items 14 to 16, wherein the bark concentration is 0.5% by weight or more. Item 18. A bark molded product formed from the solid content of the water repellent containing the bark solution according to any one of Items 14 to 17. Item 19. The bark molded product according to Item 18, which is a sheet or film. Item 20. Item 18 or 19, wherein the surface of the bark molding is measured by dropping 70 μL of distilled water onto the surface of the bark molding and photographing the droplet after 1000 milliseconds. The bark molding according to item 18 or 19, wherein the contact angle of water is 95 ° or more.

Claims

1. A water repellent comprising bark and a bark solution containing an organic acid, wherein the proportion of the bark in the solid content of the bark solution is 20% by weight or more.

2. A water repellent containing bark solution according to claim 1, wherein the content of the organic acid is 4 parts by weight or more per 1 part by weight of biomass contained in the bark solution.

3. A water repellent containing the bark solution according to claim 1, wherein the surface of the sheet material obtained by drying the bark solution has a contact angle of water of 95° or more, as measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds.

4. A water repellent comprising the bark solution according to any one of claims 1 to 3, wherein the organic acid comprises at least one selected from the group consisting of α-keto acids and carboxylic acids having a formyl group.

5. A water repellent containing the bark solution according to any one of claims 1 to 3, wherein the bark concentration is 0.5% by weight or more.

6. A bark molding formed from the solid content of a water repellent agent containing the bark solution according to any one of claims 1 to 3.

7. The bark molding according to claim 6, which is a sheet or film.

8. The bark molding according to claim 6, wherein the surface of the bark molding has a water contact angle of 95° or more, as measured by dropping 70 μL of distilled water onto the surface of the bark molding and photographing the droplet after 1000 milliseconds.

9. A laminated material comprising at least a substrate and a laminated body including a sheet material, wherein the sheet material includes bark, and the proportion of the bark in the sheet material is 20% by weight or more.

10. The laminate according to claim 9, wherein the surface of the sheet material has a water contact angle of 95° or greater, as measured by dropping 70 μL of distilled water onto the surface of the sheet material and photographing the droplet after 1000 milliseconds.

11. The laminate according to claim 9 or 10, wherein the substrate comprises at least one material selected from the group consisting of biomass materials, plastics, metals, ceramics, glass, molded pulp, cloth, and paper.

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