Shaped wood article and manufacturing method for same

Abstract

The main component of this shaped wood article is cellulose. The shaped wood article has one or both of characteristics (1) a flexural modulus of at least 4000 MPa, and (2) a flexural strength of at least 50 MPa. Wood pellets used as a material for the shaped wood article may comprise cellulose, hemicellulose, and lignin. A manufacturing method for the shaped wood article has: a step in which a solution is obtained by dissolving a cellulose-containing starting material in an organic acid; a step in which water or an alkali is added to the solution causing solids to precipitate; a step in which the solids are collected; and a step in which the collected solids are thermoformed. The main component of the solids is cellulose.

Description

Wood molded products and their manufacturing method

[0001] The present disclosure relates to a molded wood product and a method for manufacturing the same.

[0002] In recent years, growing concern about environmental issues has led to calls for the development of materials derived from biomass resources instead of petroleum-based materials. In particular, there is a demand for the use of woody biomass, which does not compete with food and does not increase atmospheric carbon dioxide.

[0003] Examples of thick, hard molded products using wood biomass include resin-infused wood, which is wood that has been infused with resin, acetylated wood, and wood plastic (WPC). Both resin-infused wood and acetylated wood require wood that has been pre-processed into a predetermined shape, which presents a problem in that the shape cannot be significantly altered during the production of the molded product (hereinafter referred to as "shaping"). Wood plastic (WPC) is a composite material made from wood and plastic and is generally produced from wood flour and thermoplastic plastic. For example, WPC is produced by mixing wood flour from cedar thinnings or factory waste with plastic. Such WPC can be thermoformed and molded into desired shapes. However, like resin-infused wood, WPC uses petroleum-derived resin or plastic, and therefore is not 100% biomass-based, and adverse environmental impacts after disposal or landfilling cannot be completely eliminated.

[0004] Improvements in molding processability have been investigated for environmentally friendly molded products using wood biomass. For example, Patent Document 1 (JP-A-7-276320) discloses a wooden product obtained by alkalizing wood flour, bringing it into contact with an allyl group-containing compound to perform an allylation treatment, and then charging the resulting allylated wood flour into a mold and molding it under heat and pressure.

[0005] Patent Document 2 (JP 2005-67064 A) discloses a fiber-reinforced plastic containing lignocellulose fibers with eliminated cell cavities as a reinforcing agent. In Patent Document 2, an epoxy resin is used as the matrix resin. Patent Document 3 (JP 2016-169382 A) discloses a lignocellulose derivative in which the α-position of the phenylpropane unit constituting lignin is modified with at least one characteristic group selected from the group consisting of an acyloxy group, an oxy group, and a thio group. Patent Document 3 also describes that molded articles can be produced by adding various synthetic polymers as matrix materials to fibers or fiber aggregates containing this lignocellulose derivative.

[0006] There is also a technology called pulp molding, in which a fiber material (pulp) obtained by dissolving plant fibers in water is shaped in a mold into a three-dimensional shape. Many proposals have been made for this technology as well. For example, Patent Document 4 (JP 2001-48151 A) discloses a pulp molded body obtained by making a pulp slurry containing an agent that suppresses hydrogen bonding between pulp fibers, followed by dehydration, pressure, and drying. This molded body has a density of 0.4 to 2 g / cm ３ , and the thickness is described as being 0.2 to 3 mm.

[0007] Japanese Patent Laid-Open No. 7-276320 Japanese Patent Laid-Open No. 2005-67064 Japanese Patent Laid-Open No. 2016-169382 Japanese Patent Laid-Open No. 2001-48151

[0008] The woodwork proposed in Patent Document 1 is obtained by bonding together wood flour, the surface of which has been allylated to form a plastic, and solidifying it by heating and pressurizing. Therefore, the woodwork described in Patent Document 1 is considered to lack sufficient strength as a molded product. Furthermore, the techniques of Patent Documents 2 and 3 require a synthetic polymer matrix material in addition to lignocellulose. Therefore, the biomaterial content of the molded products described in Patent Documents 2 and 3 is low.

[0009] The technology of Patent Document 4 involves solidifying a slurry of pulp dispersed in water to form a molded product (i.e., a paper product), and is merely an improved technology of conventional pulp molding. With the technology of Patent Document 4, the cellulose fibers are only held together by hydrogen bonds, making it difficult to obtain a molded product with a smooth surface. In addition, the technology has high gas permeability and is not a substitute for conventional plastic products.

[0010] An object of the present disclosure is to provide a wood mold that is made from cellulose, particularly lignocellulose, and more preferably wood biomass, and that has excellent moldability and improved mechanical properties.

[0011] From another perspective, woody biomass and the like are composed of a mixture of natural polymers called lignocellulose. Specifically, lignocellulose is composed of two types of carbohydrate polymers, cellulose and hemicellulose, and an aromatic polymer called lignin. Cellulose, hemicellulose, and lignin each have different chemical behaviors. Therefore, processing lignocellulose, which is a complex of these three components, is difficult, and decomposition or separation into each component requires considerable chemical and mechanical energy.

[0012] A typical method for separating cellulose from lignocellulose is the cooking method. Specifically, wood fibers (cellulose fibers) are extracted by adding chemicals (cooking agents) such as sodium sulfite and sodium hydroxide and auxiliary agents such as anthraquinone to wood chips and boiling them to dissolve them. The lignin and resin components that solidify the wood fibers are separated as black liquor, which is then incinerated. The cellulose fibers extracted by the cooking method have a natural cellulose type I crystalline structure, making them difficult to dissolve in solvents and non-thermoplastic. Previously, there was no technology for shaping such cellulose fibers; the only proposals that have been made so far have been molded products in which cellulose fibers are partially derivatized and dispersed in a synthetic polymer matrix, as exemplified in References 1-3.

[0013] Therefore, another object of the present disclosure is to provide a technology for shaping raw materials such as wood biomass containing lignocellulose using a simple process and under conditions with low energy and environmental loads, and further to provide a method for producing wood molded products without using synthetic polymers.

[0014] The present inventors discovered that a molded product can be easily obtained by dissolving raw materials such as woody biomass containing cellulose or lignocellulose in an organic acid, then adding water or alkali to precipitate the solid matter, which is then thermoformed, and thus completed the disclosed woody molded product and manufacturing method.

[0015] That is, the woody molded product of the present disclosure contains cellulose as a primary component. This woody molded product satisfies either or both of the following (1) and (2): (1) The flexural modulus obtained in a bending test conforming to the specifications of ISO 527-1 is 4000 MPa or more. (2) The flexural strength obtained in a bending test conforming to the specifications of ISO 527-1 is 50 MPa or more.

[0016] In one embodiment, the wood-based molded product may further contain lignin. The wood-based molded product containing lignin has a specific gravity of 0.5 g / cm ３ It may be more than that.

[0017] In another embodiment, the specific gravity of the wood molded product is 0.9 g / cm ３ It may be more than that.

[0018] The wood molding product has an infrared absorption spectrum of 1715 to 1720 cm －１ It may show an absorption peak in the region of

[0019] The woody molded product may further contain a fibrous material, which may have a cellulose I type crystal structure.

[0020] The woody molded product may contain lignin in a total amount ranging from 15% by weight to 80% by weight.

[0021] The wood-based molded product may further contain hemicellulose and lignin. The total lignin content of the wood-based molded product may be 20% by weight or more and 45% by weight or less. The polysaccharide composition ratios of the wood-based molded product, as determined by sugar composition analysis, may satisfy the following: Glucan: 40% by weight or more and 80% by weight or less Xylan: 0.1% by weight or more and 3.0% by weight or less Arabinan: 0.2% by weight or more and 3.0% by weight or less Mannan: 1.0% by weight or more and 5.0% by weight or less

[0022] From another aspect, the present disclosure relates to wood pellets used as a molding material for any of the aforementioned wood-based molded products. In one embodiment, the wood pellets contain cellulose, hemicellulose, and lignin. The wood pellets have an infrared absorption spectrum of 1715 to 1720 cm. －１ The wood pellets show an absorption peak in the range of 0.01 to 0.5. The total amount of lignin in the wood pellets is 20% by weight or more and 45% by weight or less. The polysaccharide composition ratios obtained by sugar composition analysis of the wood pellets satisfy the following: Glucan: 40% by weight or more and 80% by weight or less Xylan: 0.1% by weight or more and 3.0% by weight or less Arabinan: 0.2% by weight or more and 3.0% by weight or less Mannan: 1.0% by weight or more and 5.0% by weight or less

[0023] In another embodiment, the wood pellets contain cellulose, hemicellulose, and lignin. The cellulose has a cellulose type I crystalline structure. The total amount of lignin in the wood pellets is 10% by weight or more and 45% by weight or less. The polysaccharide composition ratios obtained by sugar composition analysis of the wood pellets satisfy the following: glucan: 55% by weight or more and 80% by weight; xylan: 0.1% by weight or more and 5.0% by weight or less; arabinan: 0.2% by weight or more and 1.0% by weight or less; and mannan: 1.0% by weight or more and 3.0% by weight or less.

[0024] From another perspective, the method for producing the above-mentioned woody molded product includes the steps of: (1) dissolving a cellulose-containing raw material in an organic acid to obtain a cellulose-containing solution; (2) adding water or an alkali to the cellulose-containing solution to precipitate a solid; (3) recovering the solid; and (4) thermoforming the recovered solid. The main component of this solid is cellulose.

[0025] In the step of precipitating the solid content, the cellulose-containing solution may be adjusted to a pH of 3 or higher.

[0026] The recovered solid content may be thermoformed under conditions of a temperature of 60°C or higher and 210°C or lower and a pressure of 100 Pa or higher and 400 Pa or lower. This production method may further include a step of deliquoring the recovered solid content before thermoforming. This production method may further include a step of pulverizing the cellulose-containing raw material to obtain a cellulose-containing powder before dissolving the cellulose-containing raw material in an organic acid.

[0027] The woody molded product disclosed herein reproduces the high-order structure of cellulose derived from cellulose-containing raw materials, particularly woody biomass. This woody molded product can have improved physical properties compared to wood. Furthermore, this woody molded product can have strength and elastic modulus equivalent to those of general-purpose resins.

[0028] Lignocellulose contained in woody biomass forms a strong higher-order structure in which cellulose, hemicellulose, and lignin are intricately intertwined. Specifically, in lignocellulose, cellulose, a linear polymer, forms a crystalline structure through intramolecular and intermolecular hydrogen bonds to form strong microfibrils, which are entangled with hemicelluloses such as xylan and glucomannan, and lignin, an irregular aromatic polymer, fills the voids in the matrix of these polysaccharides to form a strong complex. For this reason, it has been difficult to shape woody biomass itself.

[0029] According to the manufacturing method of the present disclosure, the higher-order structure derived from raw materials such as cellulose and hemicellulose is dissolved by dissolving in an organic acid, and the resulting precipitated solids are then regenerated by the release of water molecules during the thermoforming and dewatering processes. According to the manufacturing method of the present disclosure, synthetic polymer-free, low-environmental-impact wood molded products can be obtained from cellulose-containing raw materials, or even wood biomass, using simple processes and low energy loads. This manufacturing method is socially useful.

[0030] FIG. 1 is a photograph showing a wood molded product (sheet) obtained by a manufacturing method according to one embodiment of the present disclosure. FIG. 2 is a photograph showing a wood molded product (sheet) obtained by a manufacturing method according to another embodiment of the present disclosure. FIG. 3A is an electron microscope photograph (magnification: 50x) showing the surface condition of the wood molded product of FIG. 1. FIG. 3B is an electron microscope photograph (magnification: 1000x) showing the surface condition of the wood molded product of FIG. 1. FIG. 4A is an electron microscope photograph (magnification: 50x) showing the surface condition of the wood molded product of FIG. 2. FIG. 4B is an electron microscope photograph (magnification: 1000x) showing the surface condition of the wood molded product of FIG. 2. FIG. 5 is a photograph showing a wood molded product (molded body) obtained by a manufacturing method according to yet another embodiment of the present disclosure. FIG. 6 is a photograph showing a wood molded product of Example 12. FIG. 7 is a photograph showing a wood molded product of Example 13. FIG. 8 is a photograph showing a wood molded product of Example 14. FIG. 9 is a photograph showing a molded body of Example 15. Fig. 10 is a photograph showing the molded article of Example 16. Fig. 11 is a photograph showing the molded article of Example 17.

[0031] An example of a preferred embodiment 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 within the scope 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.

[0032] In this specification, 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). In this disclosure, "weight percent" means "weight percent," not "mass concentration."

[0033] [Wood Molded Product] The wood molded product of the present disclosure can be produced using a raw material containing cellulose, as described below. The wood molded product of the present disclosure conceptually includes molded products made only of cellulose.

[0034] The wood-based molded product of the present disclosure contains cellulose as an essential component. However, the wood-based molded product of the present disclosure may contain lignin in addition to cellulose. Furthermore, the wood-based molded product may further contain hemicellulose and / or lignin in addition to cellulose. In a preferred embodiment, the wood-based molded product contains cellulose, hemicellulose, and lignin.

[0035] Woody molded products containing lignin can be obtained, for example, by using woody biomass as at least a part of the cellulose-containing raw material. Woody biomass contains a certain amount of lignin and hemicellulose. Molded products containing lignin exhibit reduced shrinkage during thermoforming. As will be described in detail later, it is believed that lignin interferes with the shrinkage that occurs when cellulose hydrogen bonds are reconstructed to form a higher-order structure during the manufacturing process of woody molded products, resulting in a molded product with a desired shape. On the other hand, when using only cellulose-containing raw materials that do not contain lignin, molded products with reduced shrinkage can be obtained by adjusting precipitation conditions, molding conditions, etc. during the manufacturing process described below.

[0036] The woody molded product of the present disclosure contains a component derived from a cellulose-containing raw material, i.e., cellulose, as a primary component. In this disclosure, the term "primary component" refers to a component whose content is at least 40% by weight. The cellulose content in the woody molded product may be 80% by weight or more, 90% by weight or more, or even 100% by weight.

[0037] A preferred embodiment of the wood molded product may further contain lignin, or may further contain lignin and / or cellulose. This embodiment of the wood molded product can be obtained using a raw material containing lignocellulose, which has a higher-order structure consisting of cellulose, hemicellulose, and lignin, such as wood biomass. In this case, the main components of the wood molded product of the present disclosure may be cellulose, hemicellulose, and lignin, which may be present in the form of lignocellulose. Furthermore, the total content of cellulose, hemicellulose, and lignin (or the content as lignocellulose) in the wood molded product may be 60% by weight or more, 80% by weight or more, 90% by weight or more, or 100% by weight.

[0038] (Mechanical Properties of Molded Wood Products) The molded wood products of the present disclosure further have one or both of the following properties (1) and (2): (1) A flexural modulus of 4000 MPa or more obtained in a bending test conforming to the standards of ISO 527-1. (2) A flexural strength of 50 MPa or more obtained in a bending test conforming to the standards of ISO 527-1.

[0039] For example, among general-purpose resins, ABS resin has a bending strength of 64 MPa and a bending modulus of 2500 MPa, polycarbonate (PC) has a bending strength of 85 MPa and a bending modulus of 2300 MPa, and polyethylene terephthalate (PET) has a bending strength of 76 to 103 MPa and a bending modulus of 2800 to 4200 MPa (https: / / www.plastic-kakou.net / material / plastic.html). Furthermore, among woods, kiri has a bending strength of 34.3 MPa and a bending modulus of 4900 MPa, and cedar has a bending strength of 63.7 MPa and a bending modulus of 7350 MPa (https: / / www.toishi.info / sozai / woods / ). Therefore, it can be said that the wood molded products of the present disclosure that satisfy (1) and / or (2) above have mechanical properties equivalent to or superior to those of general-purpose resins, and even have properties comparable to those of wood.

[0040] The flexural modulus (Young's modulus) of the molded wood product of the present disclosure is 4000 MPa or more, but may be 4500 MPa or more, 5000 MPa or more, or 8000 MPa or less, or 7000 MPa or less, depending on the application and shape. The flexural modulus of the present disclosure may be 4000 to 8000 MPa, 4000 to 7000 MPa, 4500 to 8000 MPa, 4500 to 7000 MPa, 5000 to 8000 MPa, or 5000 to 7000 MPa.

[0041] The bending strength (maximum stress) of the molded wood product of the present disclosure is 50 MPa or more, but may be 55 MPa or more, 60 MPa or more, or 100 MPa or less, or 90 MPa or less, depending on the application and shape. The bending strength (maximum stress) of the molded wood product may be 50 to 100 MPa, 50 to 90 MPa, 55 to 100 MPa, 55 to 90 MPa, 60 to 100 MPa, or 60 to 90 MPa.

[0042] The maximum elongation of the wood molded product in a bending test may be 1.0 GL% or more, 1.5 GL% or more, or 5.0 GL% or less, or 4.5 GL% or less. The maximum elongation of the wood molded product may be 1.0 to 5.0 GL%, 1.0 to 4.5 GL%, 1.5 to 5.0 GL%, or 1.5 to 4.5 GL%.

[0043] In this disclosure, the bending properties of wood-based molded products are measured by a bending test in accordance with ISO 527-1. For the bending test, test specimens molded to specified dimensions or machined by cutting or punching are used. Before measurement, the test specimens are conditioned in an environment of 25°C and 50% RH for 12 hours. Measurement is performed using a three-point bending test at a bending speed of 2 mm / min.

[0044] The tensile properties of a molded wood product can be appropriately set depending on its application and shape. For example, the tensile modulus (Young's modulus) of the molded wood product may be 100 MPa or more, 200 MPa or more, or 3000 MPa or less. The tensile modulus (Young's modulus) of the molded wood product may be 100 to 3000 MPa, or 200 to 3000 MPa.

[0045] The tensile strength (maximum stress) of the wood molded product may be 4.0 MPa or more, 6.0 MPa or more, 10.0 MPa or more, 20.0 MPa or more, or 80.0 MPa or less, or 70.0 MPa or less. The tensile strength (maximum stress) of the wood molded product may be 4.0 to 80.0 MPa, 4.0 to 70.0 MPa, 6.0 to 80.0 MPa, 6.0 to 70.0 MPa, 10.0 to 80.0 MPa, 10.0 to 70.0 MPa, 20.0 to 80.0 MPa, or 20.0 to 70.0 MPa.

[0046] The maximum elongation in a tensile test of the woody molded product may be 1.0% GL or more, 1.5% GL or more, or 5.0% GL or less, or 4.5% GL or less. This maximum elongation may be 1.0 to 5.0% GL, 1.0 to 4.5% GL, 1.5 to 5.0% GL, or 1.5 to 4.5% GL.

[0047] In this disclosure, the tensile properties of wood-based molded products are measured by a tensile test in accordance with ISO 527-1. For the tensile test, test specimens machined to specified dimensions by punching are used. Prior to measurement, the test specimens are conditioned in an environment of 25°C and 50% RH for 12 hours. Measurements are performed at a tensile speed of 10 mm / min.

[0048] (Density of Wood Molded Product) The wood molded product of the present disclosure has a high specific gravity. That is, the density of this wood molded product is high. The specific gravity of this wood molded product measured in accordance with JIS Z 8807 "Method for measuring density and specific gravity of solids" is 0.5 g / cm ３ More than 0.6 g / cm ３More preferably, 0.8 g / cm ３ More preferably, 0.9 g / cm ３ The specific gravity of the wood molded product is particularly preferably 2.5 g / cm3 or more. ３ Preferably less than 2.0 g / cm ３ More preferably, less than 1.5 g / cm ３ The specific gravity of the wood molded product is particularly preferably less than 0.5 g / cm ３ 2.5g / cm or more ３ may be less than 0.6 g / cm ３ 2.5g / cm or more ３ may be less than 0.8 g / cm ３ 2.5g / cm or more ３ may be less than 0.9 g / cm ３ 2.5g / cm or more ３ may be less than 0.9 g / cm ３ 2.0g / cm or more ３ may be less than 0.9 g / cm ３ 1.5g / cm or more ３ It may be less than.

[0049] The density of a molded wood product can be adjusted, for example, by the pressure applied during thermoforming in the manufacturing process. High-pressure pressurization can produce a high-density molded wood product. Increasing the density of a molded wood product tends to improve its mechanical strength. In order to obtain a molded wood product with the desired strength, the molding temperature, molding time, etc. may be adjusted in addition to the pressure applied during thermoforming.

[0050] The density of the woody molded product may be adjusted appropriately depending on the material. For example, when the woody molded product contains lignin as a constituent component, a relatively high strength can be obtained due to the formation of a higher-order structure. The density of this lignin-containing woody molded product is 0.5 g / cm. ３ 2.5g / cm or more ３ may be less than 0.5 g / cm ３ 1.5g / cm or more ３ may be less than 0.5 g / cm ３ 1.3g / cm or more ３The total lignin content of the wood molded product may be 15% by weight or more and 80% by weight or less. By including lignin, a wood molded product having a smooth surface can be obtained. The total lignin content of the wood molded product may be 15% by weight or more and 80% by weight or less. The total lignin content will be described later.

[0051] (Infrared absorption spectrum of wood molded product) The wood molded product of the present disclosure has an infrared absorption spectrum of 1715 to 1720 cm －１ It may exhibit an absorption peak having a peak top in the range of wavenumber 1715 to 1720 cm －１ The absorption at 1715 to 1720 cm occurs due to the C═O stretching vibration. Specifically, it is an absorption peak due to the C═O stretching vibration of the aldehyde group (formyl group). －１ The presence of this absorption peak means that some or all of the hydroxyl groups of the cellulose contained in this woody molded product are formylated.

[0052] As described below, the woody molded product of the present disclosure is produced by dissolving a cellulose-containing raw material in an organic acid and then thermoforming the resulting solid matter by adding water or alkali. When the cellulose-containing raw material is dissolved in an organic acid, formyl groups are introduced into some or all of the hydroxyl groups of the cellulose. These formyl groups are saponified and converted back to hydroxyl groups in the precipitation process by adding alkali. These hydroxyl groups contribute to the formation of hydrogen bonds. This hydrogen bonding-mediated reconstruction of the higher-order structure can result in a molded product with high strength. On the other hand, if all formyl groups are completely saponified, this can cause deformation and shrinkage, particularly in woody molded products with a low lignin content, when the higher-order structure is reconstructed by hydrogen bonding. Therefore, when using a cellulose-containing raw material with a low lignin content, it is preferable to use cellulose that is at least partially formylated. By adding water instead of alkali in the precipitation process, a woody molded product containing at least partially formylated cellulose can be obtained.

[0053] The wood molded product of the present disclosure may further contain a fibrous material. By including this fibrous material, the wood molded product can be obtained with excellent strength. The presence of the fibrous material in the wood molded product can be confirmed by observation with a scanning electron microscope.

[0054] The fibrous material in the wood-based molded product may be derived from the raw material wood biomass. For example, it may be cellulose fibers that were not destroyed by grinding or the like during the manufacturing process. The fibrous material may also be a dissolved residue from the dissolution process. According to the present disclosure, even such fibrous material can be embedded in lignin and hemicellulose to produce a uniform wood-based molded product. In particular, in wood-based molded products with a high lignin content, the fibrous material is embedded in the lignin matrix, resulting in a wood-based molded product with a smoother surface.

[0055] In the present disclosure, the fibrous material may have a cellulose type I crystal structure. The presence of the cellulose type I crystal structure can be confirmed by X-ray diffraction measurement. For example, a freeze-dried sample of a wood-based molded product can be measured using an X-ray diffraction measurement device (e.g., Rigaku's "SmartLab"). Specifically, measurement can be performed by powder X-ray diffraction using a non-reflective silicon plate. Cellulose type I crystals having a parallel chain structure are known to exhibit high-intensity diffraction around 2θ = 22.5° and, by peak separation, around 16.7° and 14.8°. Therefore, the presence or absence of the cellulose type I crystal structure can be determined by confirming the presence or absence of high-intensity diffraction peaks around 2θ = 22.5°, 16.7°, and 14.8° in an X-ray diffraction diagram measured on a sample taken from a wood-based molded product.

[0056] (Total Lignin Amount of Wood Molded Product) As mentioned above, the wood molded product of the present disclosure preferably contains lignin. By including lignin, a wood molded product with a smooth surface can be obtained, even when the product contains a fibrous material having a cellulose type I crystal structure. Furthermore, by including a predetermined amount of lignin, cracks and splits during thermoforming can be suppressed. From this perspective, the total lignin amount of the wood molded product may be 2% by weight or more, 5% by weight or more, 7% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 21% by weight or more, or 90% by weight or less, 89% by weight or less, 85% by weight or less, 80% by weight or less, 70% by weight or less, 50% by weight or less, 48% by weight or less, 45% by weight or less, or 44% by weight or less.

[0057] For example, the total lignin content of the wood molded product is 2 to 90% by weight, 2 to 89% by weight, 2 to 85% by weight, 2 to 80% by weight, 2 to 50% by weight, 2 to 48% by weight, 2 to 45% by weight, 2 to 44% by weight, 5 to 90% by weight, 5 to 89% by weight, 5 to 85% by weight, 5 to 80% by weight, 5 to 50% by weight, 5 to 48% by weight, 5 to 45% by weight, 5 to 44% by weight, 7 to 90% by weight, 7 to 89% by weight, 7 to 85% by weight, 7 to 80% by weight, 7 to 50% by weight, 7 to 48% by weight, 7 to 45% by weight, 7 to 44% by weight, 10 to 90% by weight, 10 to 89% by weight, 10 to 85% by weight, 10 to 80% by weight, 10 to 50% by weight, The range may be 10-48 wt%, 10-45 wt%, 10-44 wt%, 15-90 wt%, 15-89 wt%, 15-85 wt%, 15-80 wt%, 15-50 wt%, 15-48 wt%, 15-45 wt%, 15-44 wt%, 20-90 wt%, 20-89 wt%, 20-85 wt%, 20-80 wt%, 20-50 wt%, 20-48 wt%, 20-45 wt%, 20-44 wt%, and 21-90 wt%, 21-89 wt%, 21-85 wt%, 21-80 wt%, 21-50 wt%, 21-48 wt%, 21-45 wt%, 21-44 wt%. Preferably, the total lignin content of the wood-based molded product may be any of the following: 2% by weight or more and 90% by weight or less, 5% by weight or more and 89% by weight or less, 7% by weight or more and 85% by weight or less, 10% by weight or more and 85% by weight or less, 15% by weight or more and 80% by weight or less, 10% by weight or more and 50% by weight or less, 15% by weight or more and 48% by weight or less, 20% by weight or more and 45% by weight or less, or 21% by weight or more and 44% by weight or less.

[0058] The total lignin content in a wood-based molded product can be adjusted by selecting a cellulose-containing raw material, particularly woody biomass. For example, by selecting wood as the woody biomass of the cellulose-containing raw material and adjusting the species and amount of wood, the desired total lignin content can be achieved. Increasing the total lignin content can result in a wood-based molded product with high hydrophobicity and a large contact angle. Adjusting the total lignin content also allows for control of the biodegradation rate of the wood-based molded product. Wood-based molded products with high total lignin content tend to have a slow biodegradation rate, while wood-based molded products with low total lignin content tend to have a fast biodegradation rate. However, since lignin is also a wood component, it is ultimately biodegraded in the same way as woody biomass. Furthermore, the wood-based molded product disclosed herein is formed by reconstructing the hydrogen bonds of cellulose. Therefore, if a wood-based molded product is left in a wet state for a long period of time, these hydrogen bonds are relaxed, making it more susceptible to the action of biodegrading enzymes, etc. For example, if the wood molded product of the present disclosure is used as an interior material for a passenger car, it is expected that it will be easily biodegradable after the car is scrapped by processing it into shredder dust or the like and keeping it in a moist state.

[0059] In this disclosure, the total amount of lignin in a woody molded product is determined as the sum of the amount of acid-soluble lignin and the amount of acid-insoluble lignin. The method for quantifying the total lignin amount will be described later in the Examples.

[0060] (Preferred Components of Woody Molded Product) The woody molded product of the present disclosure may further contain hemicellulose together with lignin. When general woody biomass is used as the cellulose-containing raw material, the woody molded product may contain lignin and hemicellulose derived from this woody biomass.

[0061] In a preferred embodiment, the woody molded product contains cellulose, hemicellulose, and lignin. When the total lignin content is 20% by weight or more and 45% by weight or less, the polysaccharide composition ratios obtained by sugar composition analysis may be as follows: glucan: 40% by weight or more and 80% by weight or less, xylan: 0.1% by weight or more and 3.0% by weight or less, arabinan: 0.2% by weight or more and 3.0% by weight or less, and mannan: 1.0% by weight or more and 5.0% by weight or less.

[0062] The sugar composition ratio of the woody molded product can be controlled within a desired range by adjusting the type and blend ratio of woody biomass in the cellulose-containing raw material. For example, the above sugar composition ratio can be achieved by mixing an appropriate amount of woody biomass with waste paper pulp, which is essentially composed of cellulose, to form the raw material. The sugar composition ratio of the woody molded product can also be adjusted by changing the conditions of the manufacturing process (e.g., the precipitation process).

[0063] The woody molded product may contain an organic acid, as long as the effects of the present disclosure are not impaired. Examples of such organic acids include α-keto acids and carboxylic acids having a formyl group. The organic acid may be one or more selected from the group consisting of formic acid, glyoxylic acid, and pyruvic acid.

[0064] The amount of organic acid contained in the wood molded product is not particularly limited, but for example, from the viewpoint of not impairing the mechanical properties and durability, the amount of this organic acid may be 10.0 wt % or less, 8.0 wt % or less, 6.0 wt % or less, 4.0 wt % or less, 1.0 wt % or less, 0.1 wt % or less, or 100 ppm or less, and the lower limit may be 0.

[0065] The shape of the woody molded product of the present disclosure is not particularly limited, but for example, its thickness may be 1 mm or more, 5 mm or more, or 10 mm or more. This woody molded product can have physical properties similar to those of the raw cellulose-containing material, such as woody biomass. It can also have physical properties that exceed those of the raw material. The woody molded product of the present disclosure can be applied in fields such as medicine, clothing, and housing equipment, for example, as films, fibers, wallpaper, etc. that require functions such as antibacterial properties, UV absorption, and metal adsorption.

[0066] [Wood pellets] The wood pellets of the present disclosure can be used as a molding material for the above-mentioned molded wood products. For example, the molded wood products of the present disclosure can be obtained using the wood pellets as a material and known thermosetting resin thermoforming technology or pulp molding technology.

[0067] In the manufacturing process for woody molded products described below, the solids recovered by adding water or alkali to a solution in which a cellulose-containing raw material is dissolved in an organic acid and precipitating the solution may be used as the wood pellets of the present disclosure. These wood pellets may contain water. While the amount of moisture contained in the wood pellets is not particularly limited, from the viewpoint of facilitating the production of woody molded products of the present disclosure, the solids concentration of the wood pellets may be 1% by weight or more, 5% by weight or more, 10% by weight or more, or 80% by weight or less, 60% by weight or less, or 50% by weight or less. The solids concentration of the wood pellets may be 1 to 80% by weight, 5 to 60% by weight, or 10 to 50% by weight.

[0068] The wood pellets may be packaged in moisture-proof packaging, which has a water vapor permeability of 50 cc / m ２ ・It may be less than 20cc / m ２ - days or less. Packing wood pellets in moisture-proof packaging allows them to be stored for the required period, and after the required period of storage, they can be subjected to the thermoforming process described below. As long as the wood pellets have the moisture content described above, they can also be compressed and packaged. For example, wood pellets can be compressed to 1 / 5 to 1 / 10 of their original volume using a device that compresses and packages waste, etc., and then packaged in moisture-proof packaging. Packaging in this manner improves the storage and transportation efficiency of the wood pellets. Packaged wood pellets can be removed from the moisture-proof packaging as needed and used.

[0069] From the viewpoint of storage stability, the pH of the water contained in the wood pellets is preferably 6 or less, and more preferably 2 or more, and more preferably 3 or more. The pH of the water contained in the wood pellets may be 2 to 6, or may be 3 to 6. This pH can be adjusted by washing the solid content recovered by precipitation.

[0070] (Preferred embodiment 1 of wood pellets) In a preferred embodiment, the wood pellets have an infrared absorption spectrum with a wave number of 1715 to 1720 cm －１The wood pellets of this embodiment 1 can be obtained, for example, in the process of producing a wood molded product by carrying out a step of precipitating solids from a solution in which a cellulose-containing raw material is dissolved in an organic acid under conditions that do not result in complete saponification.

[0071] The wood pellets of this aspect 1 contain cellulose, hemicellulose, and lignin, and the total lignin content is 20% by weight or more and 45% by weight or less. Since the total lignin content is within this range and the lignin is not completely saponified, excessive shrinkage when the hydrogen bonds of hydroxyl groups are reconstructed is suppressed. From this perspective, the total lignin content of the wood pellets of aspect 1 may be 15% by weight or more and 48% by weight or less.

[0072] The wood pellets of this embodiment 1 may have a total lignin content of 20% by weight to 45% by weight, and the polysaccharide composition ratios obtained by sugar composition analysis may satisfy the following: glucan: 40% by weight to 80% by weight, xylan: 0.1% by weight to 3.0% by weight, arabinan: 0.2% by weight to 3.0% by weight, and mannan: 1.0% by weight to 5.0% by weight.

[0073] Glucan is a polysaccharide derived primarily from cellulose, while xylan, arabinan, and mannan are polysaccharides derived from hemicellulose. When the composition ratio of cellulose-derived glucan is within the above range, the strength of the resulting wood-based molded product is improved. On the other hand, if the content of hemicellulose-derived polysaccharides exceeds the above range, the wood-based molded product may become discolored during thermoforming. Furthermore, if the content of mannan, a typical sugar component of hemicellulose, is less than the above range, the cellulose content becomes relatively high, and the wood-based molded product may deform or shrink during thermoforming.

[0074] (Preferred Aspect 2 of Wood Pellets) In another preferred aspect, the wood pellets contain cellulose having a cellulose type I crystalline structure. This cellulose may be contained as a fibrous material. Wood pellets of aspect 2 containing cellulose having a cellulose type I crystalline structure can produce wood molded products with excellent strength.

[0075] The wood pellets of this embodiment 2 contain cellulose, hemicellulose, and lignin, and have a total lignin content of 10% to 45% by weight. The wood pellets may have polysaccharide composition ratios determined by sugar composition analysis as follows: Glucan: 55% to 80% by weight, Xylan: 0.1% to 5.0% by weight, Arabinan: 0.2% to 1.0% by weight, and Mannan: 1.0% to 3.0% by weight. A wooden pallet with a total lignin content within the above ranges and containing glucan, xylan, arabinan, and mannan in the above-mentioned proportions can suppress shrinkage during thermoforming and produce a wood molded product with excellent strength and little discoloration.

[0076] [Method for manufacturing a molded wood product] The method for manufacturing a molded wood product disclosed herein includes the steps of (1) dissolving a cellulose-containing raw material in an organic acid to obtain a cellulose-containing solution, (2) adding water or an alkali to the cellulose-containing solution to precipitate a solid, (3) recovering the solid, and (4) thermoforming the recovered solid. The main component of the solid is cellulose.

[0077] The cellulose-containing raw material may be a raw material substantially consisting of cellulose (for example, pulp), or a raw material containing cellulose as lignocellulose. Preferably, it is woody biomass.

[0078] In pulp with a cellulose type I crystalline structure, similar to natural cellulose, the cellulose forms a strong higher-order structure through hydrogen bonds, inhibiting its formability. Furthermore, the main component of woody biomass is lignocellulose, which has a higher-order structure consisting of cellulose, hemicellulose, and lignin. Due to its higher-order structure, lignocellulose was previously thought to be insoluble in solvents such as water and organic solvents under mild conditions. The present inventors previously discovered that formylation of lignocellulose, the main component of woody biomass, in an organic acid, such as formic acid, inhibits intramolecular and intermolecular hydrogen bonding by cellulose, solubilizes hemicellulose and lignin, and allows lignocellulose to dissolve in organic acids under mild conditions. Furthermore, they discovered that this effect is also effective for cellulose-containing raw materials (e.g., pulp) containing a cellulose type I crystalline structure.

[0079] That is, in the manufacturing method of the present disclosure, the cellulose-containing raw material is esterified (e.g., formylated) in an organic acid, thereby eliminating the hydrogen bonds between the cellulose molecules and the lignin molecules. As a result, the cellulose-containing raw material dissolves in the organic acid, yielding a cellulose-containing solution. When the cellulose-containing raw material is lignocellulose containing lignin, the lignin also dissolves in the organic acid. When the cellulose-containing raw material contains hemicellulose, the hemicellulose also dissolves in the organic acid. In other words, in the present disclosure, the cellulose-containing solution may further contain lignin and hemicellulose in addition to cellulose. Note that the main component of the wood molded product of the present disclosure is cellulose.

[0080] Furthermore, the present inventors have found that adding water or alkali to a cellulose-containing solution precipitates a solid containing cellulose. The authors have also found that the loss of liquid components (e.g., water) from this solid through deliquoring and thermoforming reconstructs the hydrogen-bonded higher-order structure, restoring the original cellulose structure. Furthermore, they have found that the physical properties (specific gravity, strength, etc.) of the molded product obtained by thermoforming the recovered solid are improved compared to the cellulose-containing raw material (e.g., woody biomass) used. The mechanism behind this is thought to be that hydroxyl groups of cellulose are regenerated by saponification (deformylation), forming intermolecular or intramolecular hydrogen bonds in cellulose, and preferably insolubilizing hemicellulose and lignin, resulting in the formation of a higher-order structure derived from natural products. Based on this mechanism, the manufacturing method disclosed herein can produce woody molded products with excellent moldability and properties comparable to those of general-purpose resins using cellulose-containing raw materials, preferably lignocellulose, particularly woody biomass, without using petroleum-based chemicals that have a significant environmental impact.

[0081] Each step will be described in detail below.

[0082] (1) Step of dissolving a cellulose-containing raw material in an organic acid to obtain a cellulose-containing solution In this step, the cellulose-containing raw material is dissolved in an organic acid to obtain a cellulose-containing solution (hereinafter, sometimes simply referred to as a "solution"). The cellulose-containing raw material may contain cellulose, and may be a raw material containing cellulose in the form of lignocellulose. An example of a raw material containing cellulose mainly in the form of lignocellulose is woody biomass.

[0083] For example, the cellulose-containing raw material used in the present disclosure may be low-purity cellulose, high-purity cellulose, or dissolving pulp with a high α-cellulose purity. Furthermore, waste paper pulp with a low α-cellulose purity can also be used as the cellulose-containing raw material of the present disclosure. A preferred cellulose-containing raw material contains lignin in addition to cellulose. Mechanical pulp is preferred as such a cellulose-containing raw material, and woody biomass such as wood chips is more preferred.

[0084] These cellulose-containing raw materials may be used alone or in combination. For example, woody biomass and waste paper pulp may be mixed and used. It is particularly preferable that the cellulose-containing raw material contains woody biomass containing lignin.

[0085] (Woody biomass) Biomass generally means "renewable, biologically derived organic resources (excluding fossil fuels)." There are no particular limitations on the woody biomass used in the production method of the present disclosure, and materials derived from wood such as broad-leaved trees and coniferous trees that contain a large amount of lignocellulose are preferably used.

[0086] Lignocellulose is a mixture of natural polymers primarily consisting of cellulose, hemicellulose, and lignin. The cellulose, hemicellulose, and lignin contents vary depending on the type of woody biomass selected, but the composition is not particularly limited in the production method of the present disclosure. Two or more types of woody biomass containing lignocellulose with different compositions may be used as the cellulose-containing raw material. Herbaceous biomass such as bagasse, rice straw, and bran may also be used in combination within a range that achieves the effects of the present disclosure. Woody biomass or herbaceous biomass may be pulverized before use as necessary.

[0087] (Pulp) Pulp refers to cellulose extracted from plant materials such as wood through mechanical or chemical processing. Examples include mechanical pulp, which is produced by mechanically processing wood directly or while heat-treating it. Mechanical pulp is classified into groundwood pulp (GP), refined groundwood pulp (RGP), thermomechanical pulp (TMP), chemical thermomechanical pulp (CTMP), etc., depending on the production method. Among these, groundwood pulp is preferred. Chemical pulp, which is produced by chemically treating wood, may also be used as the cellulose-containing raw material of the present disclosure. Examples of chemical pulp include rayon pulp and dissolving pulp. Pulp may also be used after being disintegrated.

[0088] (Dissolution) In this specification, "dissolution" refers to a state in which the shape of the cellulose-containing raw material in the organic acid cannot be recognized visually. Even when fibrous materials derived from lignocellulose are observed in the solution by microscopic observation or the like, the state is defined as "dissolution" if the shape of the cellulose-containing raw material itself has disappeared. Furthermore, in the present disclosure, a liquid in such a "dissolved" state is defined as a "solution." It is preferable that the cellulose-containing raw material is uniformly dissolved in the organic acid, but the cellulose-containing raw material may be partially dissolved in the organic acid. In the case of partial dissolution, a cellulose-containing solution can be obtained by removing the insoluble portion by filtration or the like.

[0089] (Organic Acid) The type of organic acid is not particularly limited as long as the effects of the present disclosure can be obtained, but 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 wood flour, 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. Formic acid, which can be produced using wood gas (a mixed gas of carbon dioxide and hydrogen) as a raw material, is particularly preferred.

[0090] The amount of organic acid to be mixed with the cellulose-containing raw material is appropriately selected depending on the type and shape of the cellulose-containing raw material, the type of organic acid, etc. From the viewpoint of improving dissolution efficiency, the amount of organic acid is preferably 4 parts by weight or more, more preferably 9 parts by weight or more, per 1 part by weight of the cellulose-containing raw material. From the viewpoint of improving production efficiency, the amount of organic acid is preferably 200 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 49 parts by weight or less, per 1 part by weight of the cellulose-containing raw material. The amount of organic acid per 1 part by weight of the cellulose-containing raw material may be 4 to 200 parts by weight, 4 to 100 parts by weight, 4 to 49 parts by weight, 9 to 200 parts by weight, 9 to 100 parts by weight, or 9 to 49 parts by weight. As long as the effects of the present disclosure are obtained, the organic acid may be added to the cellulose-containing raw material as is, or may be added to the cellulose-containing raw material as a solution of the desired concentration.

[0091] As long as a cellulose-containing solution is obtained, the dissolution conditions are not particularly limited and are appropriately selected depending on the type and shape of the cellulose-containing raw material, 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 reduction, the dissolution temperature is preferably 100° C. or lower.

[0092] From the viewpoint of promoting dissolution, stirring treatment may be performed, or stirring treatment accompanied by pulverization may be performed. By performing stirring treatment accompanied by pulverization in an organic acid, it becomes possible to dissolve the cellulose-containing raw material under milder conditions. In other words, the production method of the present disclosure may include a step of dissolving the cellulose-containing raw material by stirring while pulverizing it in an organic acid. Examples of devices for stirring treatment accompanied by pulverization include a bead mill, a colloid mill, a disc refiner, a conical refiner, etc.

[0093] (Pressure Adjustment) The manufacturing method of the present disclosure may further include a step of pressurizing or depressurizing the cellulose-containing raw material using a pressure adjustment means before mixing the cellulose-containing raw material with the organic acid and / or after mixing the cellulose-containing raw material with the organic acid. It is presumed that the pressure fluctuations applied to the cellulose-containing raw material by this pressure adjustment relax the rigid higher-order structure of cellulose, particularly lignocellulose, and significantly improve its solubility in organic acid. This pressure adjustment enables dissolution at a relatively low temperature, reducing the energy required for heating and / or keeping warm during dissolution. From the perspective that the pressure fluctuations efficiently introduce the organic acid into the structure of the cellulose-containing raw material, it is preferable to pressurize or depressurize the cellulose-containing raw material after adding the organic acid.

[0094] When reducing the pressure, it is preferable to reduce the pressure in the range of 1.0 kPa to 10.0 kPa (absolute pressure). When increasing the pressure, 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 in pressure treatment, and gauge pressure based on atmospheric pressure is used when a pressure higher than atmospheric pressure is indicated by a reduction in pressure treatment.

[0095] The pressure adjusting means used for pressurizing and / or depressurizing 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.

[0096] (Cellulose-containing solution) The solids concentration of the cellulose-containing solution obtained by dissolving a cellulose-containing raw material in an organic acid is preferably 0.5 (w / v)% or more, more preferably 1.0 (w / v)% or more, and even more preferably 1.5 (w / v)% or more. From the viewpoint of ease of production, the concentration of this solution is preferably 20 (w / v)% or less, more preferably 10 (w / v)% or less, and even more preferably 8.0 (w / v)% or less. The solids concentration of the cellulose-containing solution may be 0.5 to 20 (w / v)%, 0.5 to 10 (w / v)%, 0.5 to 8.0 (w / v)%, 1.0 to 20 (w / v)%, 1.0 to 10 (w / v)%, 1.0 to 8.0 (w / v)%, 1.5 to 20 (w / v)%, 1.5 to 10 (w / v)%, or 1.5 to 8.0 (w / v)%. The cellulose-containing solution may further contain known additives such as pigments, as long as the effects of the present disclosure are not impaired.

[0097] (2) Step of adding water or alkali to the cellulose-containing solution to precipitate solids In this step, water or alkali is added to the cellulose-containing solution obtained by dissolving the cellulose-containing raw material, thereby regenerating solubilized cellulose, preferably lignocellulose, and precipitating insolubilized solids. The main component of this solid is cellulose. From the viewpoint of improving the yield in the solid-liquid recovery step described below, the cellulose-containing solution may be concentrated before this step. Known concentration methods such as evaporation and vacuum concentration can be used as appropriate.

[0098] In this step, water or alkali is added to the cellulose-containing solution, whereby the esterified cellulose is partially or completely deesterified and insolubilized by hydrogen bonding with the regenerated hydroxyl groups. When lignin and hemicellulose are present in the cellulose-containing solution, the deesterified cellulose precipitates in a microdispersed state within the lignin and hemicellulose matrix. Note that when formic acid is used in the previous step, cellulose deformylation occurs in this step.

[0099] Addition of an alkali to a cellulose-containing solution promotes deesterification of the esterified cellulose, or in other words, saponification (hydrolysis) of the esterified cellulose.

[0100] The method for precipitating the solid content is not particularly limited as long as the effects of the present disclosure can be obtained. For example, the precipitation of the solid content may be performed by a water-addition and mixing treatment, an alkali treatment, or a dialysis treatment. Two or more treatments selected from the group consisting of a water-addition and mixing treatment, an alkali treatment, and a dialysis treatment may also be combined.

[0101] (Hydration and Mixing Treatment) In the present disclosure, the term "hydration and mixing treatment" refers to adding water (e.g., distilled water) to a cellulose-containing solution and mixing it to precipitate solids. During the precipitation process, the esterified cellulose may be partially hydrolyzed (saponified).

[0102] The amount of water added to the cellulose-containing solution is appropriately selected depending on the solids concentration in the solution. The amount of water added may be adjusted so that the cellulose-containing solution has a pH of 3 or higher, preferably a pH of 5 or higher, and more preferably a pH of 6 or higher. For example, the amount of water in the hydration and mixing treatment may be 100 times or more, 200 times or more, 1000 times or less, or 800 times or less by volume relative to the cellulose-containing solution. The temperature in the hydration and mixing treatment is not particularly limited, but is usually 10 to 50°C, and may be room temperature (20°C ± 5°C). To promote the reaction, the mixture may be stirred and mixed while being heated or kept warm.

[0103] (Alkali Treatment) In the present disclosure, "alkali treatment" refers to adding an alkali to a cellulose-containing solution to cause a hydrolysis (saponification) reaction. By promoting saponification through alkali treatment, the physical properties of the woody molded product can be adjusted. Note that in this process, it is sufficient to precipitate solids containing cellulose, and intentional saponification treatment is not essential as long as the effects of the present disclosure can be obtained.

[0104] The alkali used in the alkali treatment is not particularly limited, and can be appropriately selected from alkali metal hydroxides, alkaline earth metal hydroxides, quaternary ammonium hydroxides, ammonia, etc. Alkali metal hydroxides are preferred, and sodium hydroxide is preferably used. These alkalis may be dissolved in a solvent such as water to prepare an alkali solution of the desired concentration, and the resulting solution may be added to the cellulose-containing solution.

[0105] The temperature of the alkali treatment is not particularly limited as long as the effects of the present disclosure can be obtained, but from the viewpoint of promoting the hydrolysis reaction, the temperature is preferably 10° C. or higher, more preferably 20° C. or higher. From the viewpoint of suppressing discoloration, the temperature of the alkali treatment is preferably 80° C. or lower, more preferably 60° C. or lower. To control the temperature within this range, the alkali treatment may be carried out while cooling the cellulose-containing solution.

[0106] As long as the precipitated solids can be recovered, the pH of the solution after treatment is not particularly limited. For example, the solution after addition of water or alkali may have a pH of 2.0 or higher, a pH of 2.5 or higher, or a pH of 3.0 or higher. From the viewpoint of promoting the precipitation of solids, the pH is preferably 6.0 or higher, more preferably 7.0 or higher. If the pH exceeds 11, the alkali may react with the ester group of the esterified cellulose to form an excess of alkali salt. From this viewpoint, the pH is preferably less than 11.0, and more preferably 10.5 or lower.

[0107] (Dialysis Treatment) One variation of this process is dialysis treatment. "Dialysis treatment" refers to precipitating solids by contacting a cellulose-containing solution with a solvent through a semipermeable membrane (dialysis membrane). Specifically, the cellulose-containing solution is placed inside the semipermeable membrane and contacted with a solvent (e.g., distilled water) outside the semipermeable membrane. Due to the concentration gradient inside and outside the semipermeable membrane, distilled water penetrates the inside of the semipermeable membrane, causing a hydrolysis reaction to proceed, regenerating hydroxyl groups in the cellulose, forming intramolecular or intermolecular hydrogen bonds, and precipitating as solids. Furthermore, if lignin and hemicellulose are present in the cellulose-containing solution, the hemicellulose and lignin are insolubilized along with the cellulose, producing solids containing a higher-order structure similar to lignocellulose. To promote the hydrolysis reaction, the solvent may be replaced at predetermined intervals.

[0108] In the dialysis treatment, the amount of solvent used for the cellulose-containing solution is appropriately selected depending on the solids concentration in the solution. For example, the amount of solvent in the dialysis treatment may be 100 times or more, 200 times or more, 1000 times or less, or 800 times or less by volume relative to the cellulose-containing solution. The temperature for the dialysis treatment is not particularly limited, but is usually 10 to 50°C, and may be room temperature (20°C ± 5°C). To promote the reaction, the dialysis treatment can be performed while heating or keeping the temperature.

[0109] As long as the effects of the present disclosure can be obtained, the material of the semipermeable membrane used in the dialysis treatment is not particularly limited, and may be a regenerated cellulose membrane or a synthetic polymer membrane. Examples of synthetic polymer membranes include an ethylene-vinyl alcohol copolymer membrane, an acrylonitrile-sodium methacrylate sulfonate copolymer membrane, and a polycarbonate-polyethylene glycol copolymer membrane. From the viewpoint of improving yield, the molecular weight cutoff of the semipermeable membrane is preferably 1,000 to 5,000, and more preferably 1,000 to 3,500.

[0110] (3) Step of recovering solid content In this step, solid-liquid separation is carried out to recover the solid content precipitated by the addition of water or alkali.

[0111] The method for separating and recovering the solid content is not particularly limited, and suction filtration, centrifugation, etc. can be used as appropriate. In the case of filtration, the filter material is not particularly limited, as long as it is a filter material that can filter out the solid content. For example, filter paper corresponding to the two types specified in JIS P3801 "Filter Paper (for Chemical Analysis)" can be used as the filter material. An example of these two types of filter paper is No. 131 manufactured by Advantec Co., Ltd. In the case of centrifugation, a swing rotor can be used to settle and recover the solid content under conditions of 4000 G for about 10 minutes. Alternatively, a general-purpose solid-liquid separation device can be used. Examples of such solid-liquid separation devices include a screw press, a roller press, a rotary drum screen, a belt screen, a vibrating screen, and a multi-plate vibrating filter.

[0112] The recovered solids mainly contain cellulose. The solids may contain cellulose that is at least partially esterified (e.g., formylated). When lignocellulose or woody biomass is used as the cellulose-containing raw material, the recovered solids may contain hemicellulose and lignin in addition to cellulose (or esterified cellulose). The solids may contain at least partially esterified hemicellulose and at least partially esterified lignin.

[0113] In addition, the recovered solids may contain organic acid-derived components, alkali-derived components, etc., depending on the case. Therefore, the solids may be washed after solid-liquid separation. Distilled water can be used for washing. After washing, it is preferable to dehydrate the solids using known means. For example, a pool washer, a diffuser washer, a twin-roll press, etc. may be used for dehydrating the solids. Note that, if water is added to the cellulose-containing solution in the previous step to precipitate the solids and the pH of the solution is adjusted to approximately neutral or a desired weak acidity, the washing process may be omitted. That is, only the dehydration process may be performed without the washing process. Known means can also be used for this dehydration process. Furthermore, an apparatus that performs solid-liquid separation, washing, and deliquification processes simultaneously may be used. Examples of such apparatus include an extractor / decker, a valveless filter, a suction filter, a disk extractor, a disk valveless filter, and a disk thickener.

[0114] The solids recovered in this process may be partially in the form of lumps. The solids recovered in this process may be stored, distributed, or otherwise used as a molding material for wood-based molded products. That is, the solids recovered in this process may be made into the wood pellets described above. Preferred embodiments of the wood pellets are as described above. These wood pellets may be used as a molding material for thermoforming, which will be described later. Furthermore, they may be used as a material for other known thermoforming or pulp molding processes.

[0115] (4) Step of thermoforming the solid content In this step, the solid content (preferably the dehydrated solid content) recovered in the previous step or wood pellets is thermoformed to obtain a wood molded product having a predetermined shape.

[0116] (Solid content) The solid content used in this step may be the solid content recovered in the previous step. It may be a dehydrated solid content or a non-dehydrated solid content. Wood pellets whose moisture content has been adjusted to a level suitable for storage or transportation may be used as the molding material in this step.

[0117] (Thermoforming) "Thermoforming" refers to the use of a mold to impart a specific shape to a material that has been softened by heating to a predetermined temperature. The thermoforming method is not particularly limited as long as it produces the molded wood product of the present disclosure, and vacuum molding, press molding, compressed air molding, and other methods can be used as appropriate. In the manufacturing method of the present disclosure, the solid content or wood pellets recovered in the previous step may be heated in a predetermined mold, and may further be pressurized as necessary. After heating or after heating and pressurization, the solid content or wood pellets may be trimmed into a predetermined shape using known means such as cutting. Furthermore, when processing into a complex shape, a preform can be prepared in advance. That is, the preform is prepared by not completely drying the solid content or wood pellets while maintaining their plasticity. This preform may then be compressed, heated, and dried in a mold to produce a molded wood product of the desired shape.

[0118] The heating temperature during molding may be 60 to 210°C, 70 to 180°C, 80 to 150°C, or 90 to 140°C. If the molding temperature is below 60°C, the molding time will be long and the number of shots will decrease. If the molding temperature exceeds 210°C, there is a risk of discoloration of the molded product.

[0119] The pressure during molding may be approximately 100 to 400 Pa. Specific pressing conditions include pressing at 400 kg for 30 minutes (first press) followed by pressing at 3000 kg for 60 minutes (second press). In other words, applying a certain amount of pressure in the first press and then applying a higher pressure in the second press results in a more uniform wood molded product. The same mold may be used for the first and second presses as a continuous process. Alternatively, a preform may be produced in the first press.

[0120] Known thermoforming techniques for thermosetting resins can be used for thermoforming, such as transfer molding, injection molding, casting, compression molding, etc. In thermoforming of thermosetting resins, gas is generated from the molding material during curing, and processes and designs are in place to vent this gas, making these suitable for use in the thermoforming process of the present disclosure.

[0121] Pulp injection molding (PIM) may be applied to thermoforming the solid matter or wood pellets recovered in the previous process, i.e., the solid matter or wood pellets are filled into a mold and heated and pressurized to obtain the molded wood product of the present disclosure.

[0122] (Drying) As long as the effects of the present disclosure can be obtained, the wood molded product may be dried before and / or after thermoforming of the recovered solid content. The recovered solid content may also be dehydrated. Drying further improves the physical properties (specific gravity, strength, etc.) of the wood molded product. That is, the reformation of hydrogen bonds by cellulose and the like increases during thermoforming, resulting in a high-specific gravity, strong wood molded product. From a similar perspective, drying the wood molded product can increase the reformation of hydrogen bonds by cellulose and the like.

[0123] The deliquification may be carried out by pressurizing the mold after placing the recovered solid content or wood pellets in the mold, or by creating a negative pressure inside the mold. Deliquification by pressurizing the mold and deliquification by creating a negative pressure inside the mold may be used in combination. Deliquification by applying pressure to the mold and / or deliquification by creating a negative pressure inside the mold may also be combined with deliquification by heating. Deliquification may also be carried out before heating during the first pressing, or simultaneously with heating.

[0124] Specifically, the recovered solids or wood pellets may be placed in a mold and left to stand while maintaining a weak pressure. This weak pressure forces the moisture out of the solids. A weak pressure of approximately 1 / 100 to 1 / 1000 of the pressure applied in the second press during thermoforming is sufficient. Furthermore, to improve the efficiency of deliquoring and drying, the solids may be heated while maintaining a weak pressure. The drying temperature may be approximately 50 to 90°C. The deliquoring and drying time may be, for example, approximately 3 to 12 hours, depending on the amount of solids and the deliquoring and drying conditions.

[0125] According to the manufacturing method of the present disclosure, it is possible to obtain a thick woody molded product having a predetermined thickness, without being limited to the shape of a sheet or film, which opens up a wide range of applications for cellulose-containing raw materials, which have traditionally had limited applications.

[0126] (Pulverization) Depending on the cellulose-containing raw material used, an optional step of pulverizing the cellulose-containing raw material to obtain a cellulose-containing powder before dissolving the cellulose-containing raw material in an organic acid may be further included. Pulverization can make it easier for the cellulose-containing raw material to be dissolved in the organic acid. When the cellulose-containing raw material is pulp, beating may be performed. Furthermore, when the cellulose-containing raw material is wood chips or the like, pulverization may be performed. Examples of beating machines include disc refiners, shoppers, mills, etc. Examples of pulverizers include shredders, absolute mills, choppers, grinder mills, turbo mills, etc. This step is effective, for example, when lignocellulose, particularly woody biomass, is used as the cellulose-containing raw material. For example, woody biomass is pulverized to obtain woody biomass powder (hereinafter sometimes referred to as "wood flour").

[0127] When carrying out the crushing process using woody biomass as a raw material, crushing using a device (also called an "intermediate crusher") that crushes materials on the order of several tens of mm to sizes of several mm to several hundred μm is preferred, as this reduces structural destruction of the cellulose, lignin, etc. in the woody biomass and maintains the crystallinity of cellulose and the antibacterial and ultraviolet absorption properties specific to lignin even after crushing.

[0128] From the viewpoint of good workability, a powder containing no particles with a particle size of less than 100 μm is preferred, and a powder containing no particles with a particle size of 80 μm or less is more preferred. The particle size of the powder is measured by a sieve classification method using a JIS standard sieve.

[0129] For example, methods for pulverizing woody biomass include compression pulverization, impact pulverization, shear pulverization, etc. Dry pulverization or wet pulverization may be used. Dry pulverization is preferably used because it allows pulverization to the micron level and is low cost.

[0130] From the viewpoint of reducing energy and costs involved in pulverization, preferred pulverizers for woody biomass include jaw crushers, gyratory crushers, crushing rolls, hammer mills, roller mills, cutter mills, hammer crushers, and Willey mills. Two or more types of pulverizers may be used in combination. A Willey mill, which pulverizes by shear and impact, is preferred. Woody biomass may be pulverized continuously or batchwise. Before pulverization by the pulverizer, the woody biomass may be broken into small pieces (chips) using a known cutter, chipper, or the like. These pulverizers can be used not only for pulverizing woody biomass but also for pulp crushing. For example, when pulp is pulverized, a disc refiner, a turbo mill, or a crushing device combining these may be suitably used.

[0131] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0132] (Test 1) [Example 1] - [Example 3] Wood sheets of Examples 1 to 3 were produced using the raw material (woody biomass) shown in Table 1 according to the following procedure. Specifically, chips of the raw material (woody biomass) were pulverized using a Willey mill equipped with a 20-mesh sieve, and the resulting powder was then classified using a JIS standard sieve. Particles that passed through a 500 μm sieve but not a 355 μm sieve were collected to obtain wood flour (particle diameter 355-500 μm).

[0133] The obtained wood flour was placed in a 50 ml vial in the amount shown in Table 1, and 10 ml of 80 wt % formic acid (manufactured by Nacalai Tesque) was added to the vial under a nitrogen gas atmosphere. The vial was then placed in a vacuum desiccator and left to stand for 30 minutes under a reduced pressure of -0.098 MPa, after which the temperature was raised to 40°C under normal pressure and stirring was initiated. After 6 days, it was confirmed by visual inspection that the wood flour had disappeared and a homogeneous solution had been obtained.

[0134] Next, the vial containing this solution was ice-cooled and stirred while being saponified by adding dropwise 10N aqueous sodium hydroxide solution until the pH reached the value shown in Table 1. During the addition of the aqueous sodium hydroxide solution, foaming of the solution and precipitation of solid matter were observed. The resulting sample was filtered under reduced pressure, and the residue was washed with distilled water until the filtrate became neutral (pH 7-8), recovering the precipitated solid matter. The resulting solid matter was dehydrated and then heated to 80°C under a load of 2.5 kg to obtain a wood sheet. The yield (%) calculated from the weight of the resulting sheet and the amount of wood flour added is shown in Table 1. A photograph of the appearance of the wood sheet of Example 1 is shown in Figure 1.

[0135] Example 4 The wood sheet of Example 4 was obtained in the same manner as in Examples 1-3, except that the type of raw material (woody biomass) and dissolution conditions were as shown in Table 1, and dialysis treatment was performed and water was added instead of saponification treatment. A photograph of the appearance of the wood sheet of Example 4 is shown in Figure 2. The dialysis treatment was carried out by transferring the entire amount of the solution containing dissolved woody biomass to a dialysis membrane (manufactured by Funakoshi Co., Ltd., product name "Spectra / Pore 7, MWCO 1000") and immersing it in distilled water. The distilled water was replaced twice a day, and the dialysis treatment continued until the distilled water became neutral (pH 7-8).

[0136] [Specific Gravity] The specific gravity (g / cm 3 ) of the wood sheets of Examples 1-4 was measured in accordance with JIS Z 8807 "Method for measuring density and specific gravity of solids." ３ The average of five measurements is shown in Table 1.

[0137] [Scanning Electron Microscope Observation] The surface condition of the wood sheets of Examples 1 and 4 was observed using a scanning electron microscope. Figure 3 shows the surface condition of Example 1 (magnifications of 50x (3A) and 1000x (3B)). Figure 4 shows the surface condition of Example 4 (magnifications of 50x (4A) and 1000x (4B)).

[0138]

[0139] [Example 5] Cedar sapwood chips were crushed using a Willey mill equipped with a 20-mesh sieve and then classified using a JIS standard sieve. Particles that passed through a 1000 μm sieve but not a 500 μm sieve were collected to obtain wood flour (particle size 500-1000 μm).

[0140] Next, under a nitrogen atmosphere, the wood flour was mixed with 80 ml of 80 wt% formic acid (Nacalai Tesque) to a wood flour concentration of 2% (w / v), and then allowed to stand for 30 minutes under a reduced pressure of -0.098 MPa. The mixture was then heated to 40°C under normal pressure and stirred for 8 days to obtain a wood flour solution. To the resulting solution, 60 ml of 10N sodium hydroxide solution was added dropwise under ice cooling to adjust the pH to 3.0. The precipitated solid was then recovered by centrifugation (centrifugal force: 10,000 g, time: 10 min). The solid was washed five or more times with ultrapure water, then placed in a stainless steel star-shaped mold and heated to 80°C for 24 hours under a load of 2.5 kg to obtain the molded product of Example 5 (thickness: 3.65-5.97 mm, yield: 82.0%). A photograph of the appearance of the molded product of Example 5 is shown in Figure 5.

[0141] (Test 2) [Example 6] to [Example 11] The raw material (woody biomass) chips shown in Tables 2 and 3 were each pulverized using a Willey mill equipped with a 20-mesh sieve, and then classified using a JIS standard sieve. Particles that passed through a 1000 μm sieve but did not pass through a 500 μm sieve were collected to obtain wood flour (particle diameter 500 to 1000 μm).

[0142] Next, the obtained wood flour was dissolved in 80% by weight formic acid (manufactured by Nacalai Tesque) in the same manner as in Example 1. Subsequently, saponification was carried out by adding dropwise 10N sodium hydroxide solution under ice cooling. The pH of the solution after saponification is shown in Tables 2 and 3. Each obtained sample was filtered under reduced pressure, and the solid content was recovered by washing the filter residue with distilled water until the filtrate became neutral (pH 7-8).

[0143] Next, each recovered solid was added to 50 ml of distilled water to prepare a dispersion. After filtering the resulting dispersion, the solid was recovered and heated at 80°C for 24 hours under a load of 2.5 kg to obtain wood sheets with a thickness of 20-50 μm.

[0144] [Comparative Example 1] to [Comparative Example 3] The raw material (woody biomass) chips shown in Table 4 were each pulverized using a Willey mill equipped with a 20-mesh sieve, and then classified using a JIS standard sieve. Particles that passed through a 1000 μm sieve but did not pass through a 500 μm sieve were collected to obtain wood flour (particle diameter 500 to 1000 μm).

[0145] Next, each wood flour was dissolved in 80% by weight formic acid (manufactured by Nacalai Tesque) in the same manner as in Example 1. The resulting solutions were then cast onto cellophane, left overnight on a lidded culture dish at room temperature, and then vacuumed for 3 hours to obtain sheets with thicknesses of 20-50 μm. In Comparative Examples 1-3, the solution was not subjected to precipitation treatment (insolubilization treatment).

[0146] [Evaluation of Tensile Properties] The sheets of Examples 6-11 and Comparative Examples 1-3 were punched into dumbbell shapes (No. 7 dumbbells) to prepare test specimens for tensile testing. A tensile testing machine (trade name "Universal Tensile Tester (Tensilon) RTG-1310" manufactured by A&D Co., Ltd.) was used for the tensile testing. Tensile tests (tensile speed: 2 mm / min, grip distance: 20 mm, gauge length: 12 mm) were conducted in accordance with the provisions of ISO 527-1, and the maximum stress (unit: MPa), maximum elongation (unit: %), and modulus of elasticity (Young's modulus) (unit: MPa) of Examples 6-11 and Comparative Examples 1-3 were measured (temperature: 23°C, humidity: 50%). The average of five measurements for each test is shown in Tables 2-4.

[0147]

[0148]

[0149]

[0150] As shown in Table 1, the manufacturing method of the examples allows for the production of wood molded products with high specific gravity without using petroleum-based chemicals that have a large environmental impact. Also, as shown in Tables 2-4, the wood molded products of the examples, which were subjected to precipitation treatment with the addition of water or alkali, have superior mechanical properties compared to the molded products of the comparative examples.

[0151] (Test 3) In Test 3, the woody molded products of Examples 12 and 13 were produced using a cellulose-containing raw material that was substantially free of lignin and had an extremely low hemicellulose content.

[0152] Example 12: 18 g of cotton linters (manufactured by Southern Cellulose, α-cellulose content 99% or more) was weighed into a 1 L medium bottle, and 500 g of 80 wt % formic acid (manufactured by Nacalai Tesque, Inc.) was added. A vacuum pump was then connected to the medium bottle to reduce the pressure for 30 minutes, after which 382 g of 80 wt % formic acid and a stirrer were added. The mixture was stirred at 500 rpm in a 50°C oil bath for 7 days to obtain a uniform solution (concentration 2 wt %, total weight 900 g).

[0153] The resulting solution was placed in a 1 L eggplant-shaped flask, and the solvent was removed using an evaporator until the total weight of the contents was approximately 200 g, yielding a concentrated solution. This concentrated solution was placed in a 2 L Erlenmeyer flask, and distilled water was added until the total volume of the solution was approximately 1 L. Then, while cooling the Erlenmeyer flask and vigorously stirring, 10 N aqueous sodium hydroxide solution was added until the pH of the contents reached approximately 12. The pH of the contents was confirmed using a commercially available pH meter. Subsequently, distilled water was added to a total volume of approximately 1.8 L, and the mixture was stirred slowly overnight at room temperature to precipitate the solids. The resulting treated solution was filtered using filter paper (ADVANTEC No. 131, 150 mm diameter), and the filtration residue was washed with distilled water until the filtrate became neutral (pH 7-8). The filtration residue was suspended in 1 L of distilled water and centrifuged at 4000 G for 10 minutes using a swing-out rotor to recover the solids of Example 12. Fourier transform infrared spectroscopy (FTIR analysis) of the solid content of Example 12 was performed, and the infrared absorption spectrum showed a peak at 1715-1720 cm －１It was confirmed that there was no absorption peak due to the formyl group in the region.

[0154] [Example 13] The solid content of Example 13 was obtained in the same manner as in Example 12, except that no alkali was added as the precipitation treatment. Specifically, the concentrated solution obtained in the same manner as in Example 12 was placed in a 2 L Erlenmeyer flask, and distilled water was added so that the total volume of the solution became approximately 1 L. Distilled water was then added until the total volume of the solution became approximately 1.8 L, and the solution was slowly stirred overnight at room temperature. After that, the solution was filtered, washed, and centrifuged under the same conditions as in Example 12 to recover the solid content of Example 13. Fourier transform infrared spectroscopy (FTIR analysis) of the solid content of Example 13 revealed a peak at 1715 cm in the infrared absorption spectrum. －１ It was confirmed that the compound exhibited an infrared absorption peak due to the formyl group.

[0155] [Preparation and Physical Properties of Woody Molded Products] The solids of Examples 12 and 13 were each placed in a mold equipped with a polypropylene sheet and compacted using a spoon. Next, a Kimtowel was pressed against the surface of the solids to dehydrate them, and this process was repeated 5-6 times. A polypropylene sheet and a metal plate were then placed on top of the solids, and the solids were placed in a heat press set at 80°C. They were pressed at 400 kg for 30 minutes, and then at 3,000 kg for 60 minutes. A 2.5 kg block was then placed on the molded product, and the product was dried overnight in a fan dryer at 80°C. The molded product was then placed on a silica gel plate and dried under reduced pressure overnight to obtain the molded products of Examples 12 and 13. Photographs of the appearance of the molded products of Examples 12 and 13 are shown in Figures 6 and 7.

[0156] The yield (wt%) and specific gravity (g / cm ３ The specific gravity (°C) and contact angle (degrees) are shown in Table 5. The yield was calculated as the ratio of the weight of the molded body to the weight of the raw materials used. The specific gravity was measured as described above. The contact angle was measured according to the following method.

[0157] [Contact Angle] The contact angle in this disclosure is a dynamic contact angle, which measures the change in contact angle immediately after dropping a droplet. Measuring the dynamic contact angle requires specifying the time. A contact angle meter (manufactured by Nick Corporation) was used to measure the contact angle. Three measurements were taken in contact angle measurement mode with a maximum measurement time of 601 seconds (0-1 second and 1-601 seconds), and the average value was calculated. The maximum contact angle from 0-1 second after dropping distilled water is shown in Table 5.

[0158]

[0159] As shown in Table 5, it was confirmed that a high specific gravity and hydrophilic wood molded product could be obtained from a raw material containing cellulose as the main component.

[0160] (Test 4) [Example 14] and [Example 16] The raw material (woody biomass) chips shown in Table 6 were each pulverized using a Willey mill equipped with a 20-mesh sieve, and then classified using a JIS standard sieve. Particles that passed through a 1000 μm sieve but not a 500 μm sieve were collected to obtain wood flour (particle diameter 500-1000 μm). In Table 5, the moisture content of the cedar wood flour of Example 14 was 8.40 wt%, and the moisture content of the eucalyptus wood flour of Example 16 was 10.03 wt%.

[0161] Next, 18 g of the obtained wood flour was weighed into a 1 L medium bottle, and 500 g of 80 wt% formic acid (manufactured by Nacalai Tesque, Inc.) was added. Next, a vacuum pump was connected to the medium bottle and the pressure was reduced for 30 minutes, after which 382 g of 80 wt% formic acid and a stirrer were added. The mixture was stirred at 300 rpm for 7 days in a 50°C oil bath to obtain a homogeneous solution (wood flour concentration 2 wt%, total weight 900 g).

[0162] The resulting solution was placed in a 1 L eggplant-shaped flask, and the solvent was removed using an evaporator until the total weight of the contents was approximately 350 g, yielding a concentrated solution. This concentrated solution was placed in a 2 L Erlenmeyer flask, and distilled water was added to bring the total volume to approximately 1 L. Distilled water was then added to a total volume of approximately 1.8 L, and the mixture was slowly stirred overnight at room temperature to precipitate the solids. The resulting treated solution was filtered using filter paper (ADVANTEC No. 131, 150 mm diameter), and the filtration residue was washed with distilled water until the filtrate became neutral (pH 7-8). The filtration residue was suspended in 1 L of distilled water and centrifuged at 4000 G for 10 minutes using a swing rotor to recover the solids of Examples 14 and 16. Fourier transform infrared spectroscopy (FTIR) analysis of the solids of Examples 14 and 16 was performed, revealing a peak at 1720 cm in the infrared absorption spectrum. －１ It was confirmed that the compound had an infrared absorption peak due to the formyl group.

[0163] Examples 15 and 17 The solid contents of Examples 15 and 17 were obtained in the same manner as in Examples 14 and 16, except that the raw materials shown in Table 6 were used and saponification treatment with alkali was performed as the precipitation treatment. Specifically, the concentrated liquid obtained in the same manner as in Examples 14 and 16 was placed in a 2-L Erlenmeyer flask, and distilled water was added to bring the total volume to approximately 1 L. Then, while cooling the Erlenmeyer flask, a 10 N aqueous solution of sodium hydroxide was added with stirring until the pH of the contents reached approximately 12. Subsequently, distilled water was added to bring the total volume to approximately 1.8 L, and the mixture was slowly stirred overnight at room temperature. The solid contents of Examples 15 and 17 were recovered by filtration, washing, and centrifugation under the same conditions as in Examples 14 and 16. The bagasse used in Example 17 was sugarcane bagasse (water content: 7.34 wt%).

[0164] [Preparation and Physical Properties of Woody Molded Products] The solids of Examples 14-17 were each placed in a mold equipped with a polypropylene sheet and compacted using a spoon. Next, a Kimtowel was pressed against the surface of the solids to dehydrate them, and this process was repeated 5-6 times. A polypropylene sheet and a metal plate were then placed on the solids, and the solids were placed in a heat press set at 80°C and pressed at 0.65 MPa for 30 minutes and 4.9 MPa for 60 minutes. A 2.5 kg block was then placed on the molded product, which was then dried overnight in a fan dryer at 80°C. The molded product was then placed on a silica gel plate and dried under reduced pressure overnight to obtain the molded products of Examples 14-17. Photographs of the appearance of the molded products of Examples 14-17 are shown in Figures 8-11. The surfaces of the molded products of Examples 14-17 were smoother and less irregular than those of Examples 12 and 13. In Examples 14-17, it was thought that by using woody biomass as the raw material, lignin or hemicellulose filled the gaps between the cellulose fibers, resulting in smoothing.

[0165] Yield (wt%), thickness (mm), specific gravity (g / cm3) of the molded bodies of Examples 14-17 ３ The yield, specific gravity, contact angle, ash content (wt%), and total lignin content (wt%) are shown in Table 6. The methods for measuring the yield, specific gravity, and contact angle were as described above. The ash content and total lignin content were measured according to the NREL method. The specific methods are as follows.

[0166] [Ash Content] A sample taken from each compact was placed in an electric furnace and treated using a temperature program that included holding at 105°C for 12 minutes, heating to 250°C at a rate of 10°C / min, holding at 250°C for 30 minutes, heating to 575°C at a rate of 20°C / min, holding at 575°C for 3 hours, and then cooling to 105°C. The residue after treatment was weighed, and the ratio of the weight of the residue to the weight of the sample before treatment was calculated as the ash content (wt%).

[0167] [Total Lignin Amount] A 300 mg sample was collected from each compact, crushed as necessary, and then placed in a test tube with 3.0 ml of 72 wt% sulfuric acid. The sample was then placed in a water bath at 30 °C for hydrolysis. After 60 minutes of standing, the sample was crushed with a glass rod every 5-10 minutes to remove any lumps. 84 ml of deionized water was then added to the test tube to adjust the sulfuric acid concentration to 4 wt%. Subsequently, further hydrolysis was carried out in an autoclave at 121 °C for 1 hour. The resulting reaction solution was filtered, and the residue was washed with water to obtain a filtrate containing acid-soluble lignin and a filtrate containing acid-insoluble lignin. The dry weight of the residue was measured to determine the amount of acid-insoluble lignin. The absorbance of the resulting filtrate at 205 nm was measured using 4% sulfuric acid as a reference cell, and the amount of acid-soluble lignin in the filtrate was calculated using an extinction coefficient of 110 (L / g cm). The amount of acid-insoluble lignin and the amount of acid-soluble lignin were each measured twice and averaged. The sum of the obtained amounts of acid-insoluble lignin and acid-soluble lignin was taken as the total lignin amount, and the percentage of each amount relative to the total weight of the measured sample is shown in Table 6.

[0168]

[0169] [Sugar Composition Analysis] The molten bodies of Examples 14-16 were subjected to sugar composition analysis using the NREL method. Specifically, a sample was collected from each molten body and hydrolyzed under the same conditions as in the analysis of total lignin content. The reaction solution was then filtered to obtain a filtrate. An appropriate amount of calcium carbonate was added to the filtrate to neutralize it, followed by centrifugation (centrifugal force: 10,000 g, time: 10 min) to obtain a supernatant. This supernatant was filtered through a filter with a pore size of 0.2 μm and then subjected to high-performance liquid chromatography (HPLC measurement) under the following measurement conditions. Column: Two Aminex HPX-87P (Biorad) columns; Mobile phase: Ultrapure water; Flow rate: 0.6 mL / min; Column temperature: 65°C; Detector: Refractive index detector (RID); Retention time: 50 min; Injection volume: 5 μl. Calibration curves were prepared for six monosaccharides (cellobiose, glucose, xylose, galactose, arabinose, and mannose) at concentrations ranging from 0.1 to 5.0 mg / ml. The HPLC measurements were used to determine the content of each monosaccharide after hydrolysis in each molded body, and the sugar composition of Examples 14-16 was calculated by converting the content to polysaccharides (glucan, xylan, galactan, arabinan, and mannan). The results are shown in Table 7.

[0170] [Evaluation of Tensile Properties and Flexural Properties] Test pieces (width 1 cm, length 5 cm) for tensile tests and flexural tests were cut out from the molded articles of Examples 14 to 16, respectively. A Universal Tensile Tester (Tensilon) RTG-1310 manufactured by A&D Co., Ltd. was used as the measuring device, and the tensile properties and flexural properties were measured in accordance with the provisions of ISO 527-1 (temperature 23°C, humidity 50%). The measurement conditions were as follows. The results obtained are shown in Table 7 below. Tensile test Load cell: 1000 N Tensile speed: 10 mm / min Grip distance: 20 mm Bending test (three-point bending test) Load cell: 1000 N Bending speed: 2 mm / min Support distance: 30 mm

[0171]

[0172] The results of Test 4 confirmed that smooth wood molded products with minimal cracking and deformation were obtained in Examples obtained using cellulose-containing raw materials, particularly woody biomass. Furthermore, as shown in Table 7, the bending properties (maximum stress and modulus) of the wood molded products of Examples 14-17 were confirmed to be equivalent to or superior to those of general-purpose resins such as ABS resin (flexural strength 64 MPa, flexural modulus 2500 MPa) and polycarbonate (flexural strength 85 MPa, flexural modulus 2300 MPa). The above evaluation results clearly demonstrate the superiority of the present disclosure. The manufacturing method of the present disclosure can be applied to the use of various plant biomass.

Claims

1. It contains cellulose as its main component, The cellulose is a cellulose in which the hydroxyl groups are not substituted, or a cellulose in which some of the hydroxyl groups are formylated, A wood-based molded product that satisfies either or both of the following (1) and (2). (1) The bending modulus obtained in a bending test conforming to the provisions of ISO 527-1 is 4000 MPa or more. (2) The bending strength obtained in a bending test conforming to the provisions of ISO 527-1 is 50 MPa or more.

2. It further contains lignin and has a specific gravity of 0.5 g / cm 3 The above-mentioned woody molded product according to claim 1.

3. Its specific gravity is 0.9 g / cm 3 The above-mentioned woody molded product according to claim 1 or 2.

4. In the infrared absorption spectrum, 1715 to 1720 cm -1 The woody molded product according to claim 1 or 2, which exhibits an absorption peak in the region of

5. 3. The woody molded product according to claim 1, further comprising a fibrous material having a cellulose I type crystal structure.

6. Further comprising lignin, 2. The wood molded product according to claim 1, wherein the total lignin content is 15% by weight or more and 80% by weight or less.

7. Further comprising hemicellulose and lignin, The total lignin content is 20% by weight or more and 45% by weight or less, 2. The woody molded product according to claim 1, wherein the composition ratio of polysaccharides obtained by sugar composition analysis satisfies the following: Glucan: 40% by weight or more and 80% by weight or less Xylan: 0.1% by weight or more and 3.0% by weight or less Arabinan: 0.2% by weight or more and 3.0% by weight or less Mannan: 1.0% by weight or more and 5.0% by weight or less

8. Contains cellulose, hemicellulose and lignin, In the infrared absorption spectrum, 1715 to 1720 cm -1 It shows an absorption peak in the region of The total lignin content is 20% by weight or more and 45% by weight or less, The composition ratio of polysaccharides obtained by sugar composition analysis satisfies the following: Glucan: 40% by weight or more and 80% by weight or less Xylan: 0.1% by weight or more and 3.0% by weight or less Arabinan: 0.2% by weight or more and 3.0% by weight or less Mannan: 1.0% by weight or more and 5.0% by weight or less 3. Wood pellets as a molding material for the wood molded product according to claim 1 or 2.

9. Contains cellulose, hemicellulose and lignin, The cellulose has a cellulose I type crystal structure, The total lignin content is 10% by weight or more and 45% by weight or less, The composition ratio of polysaccharides obtained by sugar composition analysis satisfies the following: Glucan: 55% by weight or more and 80% by weight or less Xylan: 0.1% by weight or more and 5.0% by weight or less Arabinan: 0.2% by weight or more and 1.0% by weight or less Mannan: 1.0% by weight or more and 3.0% by weight or less 3. Wood pellets as a molding material for the wood molded product according to claim 1 or 2.

10. A process for producing a cellulose-containing solution comprising: dissolving a cellulose-containing raw material in an organic acid; A step of adding water or an alkali to the cellulose-containing solution to precipitate solids; recovering the solids; thermoforming the recovered solids; It has The method for producing a woody molded product according to claim 1, wherein the main component of the solid matter is cellulose.

11. The method for producing a woody molded product according to claim 10, wherein in the step of precipitating the solid content, the cellulose-containing solution is adjusted to a pH of 3 or more.

12. 12. The method for producing a molded wood product according to claim 10 or 11, wherein the recovered solid content is placed in a mold and thermoformed at a temperature of 60° C. to 210° C. and a pressure of 100 Pa to 400 Pa.

13. The method for producing a molded wood product according to claim 10 or 11, further comprising a step of deliquoring the recovered solids before thermoforming.

14. The method for producing a woody molded product according to claim 10 or 11, further comprising a step of pulverizing the cellulose-containing raw material to obtain a cellulose-containing powder before dissolving the cellulose-containing raw material in the organic acid.

15. A wood-based molded product containing cellulose as its main component and satisfying either or both of the following (1) and (2). (1) The flexural modulus obtained in a bending test conforming to the provisions of ISO 527-1 is 4000 MPa or more and 7000 MPa or less. (2) The bending strength obtained in a bending test conforming to the provisions of ISO 527-1 is 50 MPa or more and 90 MPa or less.

16. A wood-based molded product containing cellulose as its main component and satisfying both of the following (1) and (2). (1) The flexural modulus obtained in a bending test conforming to the provisions of ISO 527-1 is 4000 MPa or more and 7000 MPa or less. (2) The bending strength obtained in a bending test conforming to the provisions of ISO 527-1 is 50 MPa or more.