Plant-based material, method for producing plant-based material, modified wood and cellulose molded body

Abstract

A plant-based material has: a tubular cell including a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of a surface belonging to the cell wall and with a portion in contact with the cell lumen. A spring constant of the polymer, calculated by an atomic force microscope (AFM) force curve measurement, is 0.4 N / m or more.

Description

Technical Field

[0001] This disclosure relates to plant-based materials, methods for manufacturing plant-based materials, modified wood, and cellulose molded articles. Background Technology

[0002] Previously, it was known that modified wood was produced by altering the properties of wood, such as its strength and dimensional stability.

[0003] For example, Non-Patent Document 1 discloses a modified eucalyptus material, which fills the cell lumen with a polymer by injecting styrene or methyl methacrylate into the cell lumen of the eucalyptus material and allowing it to polymerize. Additionally, Non-Patent Document 2 discloses a modified poplar material formed by covering the surface of the cell lumen of poplar material with a polymer film. Existing technical documents Non-patent literature

[0004] Non-patent document 1: Denise Ortigosa Stolf et al., "Wood-Polymer Composite: Physical and Mechanical Properties of Some Wood Species Impregnated withStyrene and Methyl Methacrylate", Materials Research, 2004, Vol. 7, No. 4, p.611-617. Non-patent document 2: Dengkang Guo et al., "Improving physical properties of wood-polymer composites by building stable interface structure between swelled cell walls and hydrophobic polymer", Wood Science and Technology, 2021, 55, p. 1401-1417. Summary of the Invention The problem that the invention aims to solve

[0005] The purpose of this disclosure is to provide plant-based materials with high strength. Methods for solving problems

[0006] The plant-based material disclosed herein comprises: tubular cells including a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of the surface belonging to the cell wall and in contact with the cell lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy (AFM), is 0.4 N / m or greater.

[0007] The method for manufacturing plant-based materials disclosed herein includes the steps of: injecting an emulsion containing water and polymer particles as solvent into a plant structure containing tubular cells; and removing the solvent from the plant structure by heating and drying. Invention Effects

[0008] According to the plant-based materials disclosed herein, it is possible to provide plant-based materials with high strength. Attached Figure Description

[0009] Figure 1A This is a SEM image of a cross-section of the cell wall of a polymer in the plant-based material of Embodiment 1, which has a surface in contact with the intracellular lumen side of the cell wall. Figure 1B This is a schematic cross-sectional view showing the intracellular cavity of the tubular cells of the plant material in Embodiment 1. Figure 2A It is a schematic cross-sectional view showing the tubular cells of plant material perpendicular to the fiber direction. Figure 2B This is a SEM image showing cross-sections of cell walls in the earlywood and latewood of coniferous trees. Figure 3A It is a schematic perspective three-dimensional view of untreated tubular cells that have not undergone polymer injection. Figure 3B It is a cross-sectional view of the untreated tubular cells in a state without polymer injection, perpendicular to the fiber direction. Figure 3C It is a cross-sectional view showing the untreated tubular cells in their untreated state, parallel to the fiber direction. Figure 3D It is a cross-sectional view showing the untreated tubular cells in their untreated state, parallel to the fiber direction. Figure 4A It is a schematic perspective three-dimensional diagram of a tubular cell showing the general overall contact between the polymer and the inner surface of the cell wall. Figure 4BIt is a cross-sectional view of a tubular cell perpendicular to the fiber direction, showing the state of approximately overall contact between the polymer and the inner surface of the cell wall. Figure 4C It is a cross-sectional view of a tubular cell, parallel to the fiber direction, showing the state of approximately overall contact between the polymer and the inner surface of the cell wall. Figure 4D It is a cross-sectional view of a portion of the tubular cell structure parallel to the fiber direction, showing the state of approximately overall contact between the polymer and the inner surface of the cell wall. Figure 5A It is a simplified perspective stereoscopic view of a tubular cell showing the state in which the polymer is in contact with about half of the inner surface of the cell wall. Figure 5B It is a cross-sectional view of a tubular cell perpendicular to the fiber direction, showing the state in which the polymer is in contact with about half of the inner surface of the cell wall. Figure 5C It is a cross-sectional view of a tubular cell, parallel to the fiber direction, showing the state in which the polymer is in contact with about half of the inner surface of the cell wall. Figure 5D It is a cross-sectional view of a portion of the structure of a tubular cell, parallel to the fiber direction, showing the state in which the polymer is in contact with about half of the inner surface of the cell wall. Figure 6A It is a schematic perspective three-dimensional diagram of a tubular cell showing the state of contact between a polymer and a portion of the inner surface of the cell wall. Figure 6B It is a cross-sectional view of a tubular cell perpendicular to the fiber direction, showing the state of the polymer in contact with a portion of the inner surface of the cell wall. Figure 6C It is a cross-sectional view of a tubular cell, parallel to the fiber direction, showing the state of the polymer in contact with a portion of the inner surface of the cell wall. Figure 6D It is a cross-sectional view of a portion of the structure of a tubular cell, parallel to the fiber direction, showing the state of the polymer in contact with a part of the inner surface of the cell wall. Figure 7A This is a schematic cross-sectional view illustrating an example of the process of impregnating plant-based materials in the manufacturing method of plant-based materials according to Embodiment 1. Figure 7B This is a schematic cross-sectional view showing another example of the process of impregnating plant-based materials in the manufacturing method of plant-based materials according to Embodiment 1. Figure 7C This is a schematic cross-sectional view showing the step of removing solvent from the plant material in the manufacturing method of the plant material according to Embodiment 1. Figure 8AIt is a schematic cross-sectional view showing the tubular cells of untreated plant material perpendicular to the fiber direction. Figure 8B It means Figure 8A A rough cross-sectional view of the area of ​​the cell wall in the cross-section of the cell cavity of a plant material. Figure 8C It means Figure 8A A schematic cross-sectional view of the area of ​​the voids in the cell cavity of a plant-based material. Figure 9A It is a schematic cross-sectional view showing the tubular cells of the modified plant material perpendicular to the fiber direction. Figure 9B It means Figure 9A A schematic cross-sectional view of the area of ​​the apparent cell wall, including the cell wall and polymer, in the cross-section of the intracellular cavity of the plant material. Figure 9C It means Figure 9A A schematic cross-sectional view of the area of ​​the voids in the cell cavity of a plant-based material. Detailed Implementation

[0010] (The insights that form the basis of this disclosure) To curb global warming, reducing the increase of carbon dioxide, a greenhouse gas, has become a crucial global issue. Therefore, plant-based resources that can absorb carbon dioxide are receiving significant attention in the pursuit of a decarbonized society aimed at mitigating its effects. To sustainably achieve the aforementioned benefits of plant-based resources, the development and high-value-added utilization of their uses are essential, requiring a "logging-use-planting" cycle.

[0011] Timber varies greatly in strength, dimensional stability, weather resistance, and abrasion resistance depending on the tree species, necessitating consideration of appropriate applications. Examples of applications include exterior and interior building materials, furniture, and acoustic materials. High-strength timber has a wide range of applications, therefore over-harvesting and depletion are considered problems depending on the species. On the other hand, low-strength timber faces the challenges of increasing stockpiles and the abandonment of plantations.

[0012] As a primary application for plant-based materials requiring high strength, such as in building materials, flooring materials have many requirements regarding strength and durability. For example, they need dent resistance to withstand heavy objects like office furniture, surface hardness to resist scratches from falling objects, resistance to degradation even when exposed to hot water, and peel resistance to prevent peeling from repeated friction from caster furniture. Since decorative materials in flooring are exposed on the surface of the flooring's constituent elements, high design flexibility is also required. Furthermore, in the case of such interior building materials, it is particularly desirable to avoid harmful substances. In addition, if high-strength plant-based materials are lightweight, transportation costs can be reduced, and they are easier to handle during construction, thus potentially expanding their use. Against this backdrop, there is a desire to develop a material that, through a highly safe method that uses virtually no harmful VOCs, maintains the advantages of plant-based materials composed of plant structures containing tubular cells—namely, lightweight—while preserving design flexibility and improving strength.

[0013] In recent years, modified wood, which involves chemically modifying wood to alter properties such as strength and dimensional stability, has attracted attention. For example, Non-Patent Literature 1 discloses a modified wood that fills the cell cavities with polymers by injecting styrene or methyl methacrylate into the cell cavities of eucalyptus, a type of hardwood, and then polymerizing it. Wood modified by this method and materials containing it are called WPC (Wood-Polymer Composites or Wood-Plastic Composites). However, since almost all the voids within the cells of WPC are filled, the lightweight properties that are an advantage of wood are compromised. Furthermore, WPC's appearance is similar to resin products, lacking the warm luster of wood, which is also a concern. This is because the refractive indices of wood cells and resins are similar. Appearance is an indispensable factor when using wood for industrial purposes.

[0014] Furthermore, for example, Non-Patent Document 2 discloses a modified poplar material obtained by covering the surface of the cell wall of poplar, a type of broadleaf tree, with a polymer film. Specifically, the following modification process is proposed: Step 1: N-hydroxymethylacrylamide and hydroxyethyl methacrylate are impregnated into the cell wall and a grafting reaction is carried out, thereby introducing and fixing carbon-carbon double bonds into the cell wall; Step 2: The fixed carbon-carbon double bonds are used as active sites for polymerization of vinyl monomers such as polystyrene. N-hydroxymethylacrylamide and hydroxyethyl methacrylate, containing OH groups, are impregnated into the cell wall while cleaving the hydrogen bonds of OH groups from components such as cellulose that constitute the cell wall of the poplar material. By this method, the grafting reaction is carried out not only on the cell wall surface but also throughout the cell wall, thus introducing multiple active sites. However, the formation of multiple hydrogen bonds between wood components is the main reason for the high strength of wood. Therefore, from the viewpoint of improving strength, impregnating the wood components with agents to cleave hydrogen bonds is not preferred. Furthermore, Non-Patent Document 2 neither describes nor teaches the spring constant of the polymer. Additionally, to obtain the modified poplar material described in Non-Patent Document 2, highly toxic volatile organic compounds (VOCs) are used, thus posing a safety concern regarding the industrial use of the modified poplar material.

[0015] To achieve the aforementioned objectives, the inventors conducted in-depth research and discovered that by injecting an emulsion containing water as a solvent and polymer particles into a plant structure, and then removing the water as a solvent by heating and drying, a polymer can be formed in a manner that leaves voids in the cell lumen while simultaneously covering the surface of the cell wall on the luminal side of the tubular cells. Furthermore, it was found that the spring constant of this polymer, calculated using force curves determined by atomic force microscopy, is 0.4 N / m or higher, thereby demonstrating the high strength of the plant-based material disclosed herein, thus completing the plant-based material of this disclosure as a novel material. Additionally, wood, bamboo, and herbaceous plants can be used as the plant structure.

[0016] The following describes the various methods of this disclosure.

[0017] (A summary of one aspect of this disclosure) The plant-based material of the first embodiment comprises: tubular cells containing a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of the surface belonging to the cell wall and in contact with the cell lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy (AFM), is 0.4 N / m or more.

[0018] Based on the above configuration, the polymer, which is in contact with at least a portion of the cell wall surface belonging to the tubular cells and the portion in contact with the cell lumen, can suppress the buckling and destruction of the tubular cells, thus becoming a lightweight and high-strength material.

[0019] The second type of plant-based material relates to the plant-based material of the first type described above. In the second type, the polymer can be a thermoplastic resin.

[0020] The third type of plant-based material relates to the plant-based material of the first or second type described above. In the third type, the polymer may comprise one selected from the group consisting of vinyl acetate resin, acrylic resin, and styrene-acrylic copolymer resin.

[0021] The plant-based materials described above can be easily prepared using emulsions with water as the dispersion medium.

[0022] The fourth type of plant-based material relates to any of the first to third types of plant-based materials described above. In the fourth type, the average film thickness of the polymer can be 0.1 μm or more and 10 μm or less.

[0023] The fifth type of plant-based material involves any of the first to fourth types of plant-based materials described above. In the fifth type, in a cross section belonging to the plant-based material and orthogonal to the direction of extension of the tubular cells, the percentage of the area of ​​the polymer relative to the area of ​​the cell cavity, i.e., the polymer filling rate, can be more than 30% and less than 55%.

[0024] The plant-based material of the sixth method relates to the plant-based material of any of the first to fifth methods mentioned above. In the sixth method, the tubular cells can be plant cells of wood.

[0025] The seventh method of plant-based material relates to the plant-based material of the sixth method above. In the seventh method, the wood can be coniferous wood.

[0026] The method for manufacturing plant-based materials in the eighth manner includes the steps of: injecting an emulsion containing water and polymer particles as solvent into a plant structure containing tubular cells; and removing the solvent from the plant structure by heating and drying.

[0027] The ninth method for manufacturing plant-based materials relates to the eighth method for manufacturing plant-based materials described above. In the ninth method, the step of injecting the emulsion into the plant structure includes: immersing the plant structure in the emulsion; and removing the plant structure immersed in the emulsion from the emulsion.

[0028] The tenth type of plant material relates to any of the first to seventh types of plant material described above. In the tenth type, in a cross section belonging to the plant material and orthogonal to the direction in which the tubular cells extend, the intracellular cavity may contain the polymer and voids.

[0029] The eleventh type of plant-based material relates to any of the first to seventh and tenth types of plant-based materials described above. In the eleventh type, the spring constant of the polymer can be 0.5 N / m or more.

[0030] The twelfth type of plant-based material comprises: tubular cells including a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of the surface belonging to the cell wall and in contact with the cell lumen. In a cross-section belonging to the plant-based material and orthogonal to the direction of extension of the tubular cells, the ratio of the area of ​​the polymer to the area of ​​the cell lumen, expressed as a percentage, i.e., the polymer filling rate, is 30% or more and 55% or less.

[0031] The thirteenth type of plant material relates to the plant material of the first or twelfth type described above. In the thirteenth type, the polymer may not be impregnated in the cell wall.

[0032] Here, "polymer not impregnated in cell wall" means that there is no polymer for modification among the components of the cell wall such as cellulose, hemicellulose, and lignin, and the cell wall itself is in an unswelled state compared to its state before modification.

[0033] The modified wood of the fourteenth method comprises: tubular cells including a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of the surface belonging to the cell wall and in contact with the cell lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy, is 0.4 N / m or more.

[0034] The fifteenth type of cellulose molded body comprises: a tubular cell including a cell lumen and a cell wall surrounding the cell lumen; and a polymer in contact with at least a portion of the surface belonging to the cell wall and in contact with the cell lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy, is 0.4 N / m or more.

[0035] Hereinafter, plant-based materials and their manufacturing methods according to embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0036] (Implementation Method 1) Figure 1AThis is a SEM image of a cross-section of the cell wall of the earlywood of cedar, which is a plant structure and has a polymer 7 in contact with the cell cavity 4 side of the cell wall 2, in the plant material 10 of Embodiment 1. Figure 1B This is a schematic cross-sectional view showing a cross-section of the intracellular cavity 4 of the tubular cells of the plant material in Embodiment 1. It should be noted that... Figure 1B It means facing Figure 1A A schematic diagram of a cell wall 2 in a cell cavity 4 having a polymer 7 disposed on its surface.

[0037] like Figure 1A and Figure 1B As shown, the plant-based material 10 of Embodiment 1 includes tubular cells containing cell walls 2 and a polymer 7 in contact with at least a portion of the surface of the cell wall 2 on the side of the cell cavity 4. The spring constant of the polymer 7, calculated by force curve measurement using atomic force microscopy, is 0.4 N / m or more. The cell cavities 4 surrounded by the cell walls 2 of the plant-based material 10 are arranged in a lattice pattern. In this plant-based material 10, the polymer 7 provided on the surface of the cell wall 2 on the side of the cell cavity 4 forms a film. By forming a film of polymer 7, the voids in the cell cavity 4 are reduced while leaving voids, the increase in density is suppressed, and the lightweight nature characteristic of plant-based materials is maintained. In addition, by suppressing cell wall buckling and rupture by the polymer 7, higher strength than the original plant-based material can be obtained.

[0038] According to Embodiment 1, the plant-based material, by having a polymer in contact with at least a portion of the surface of the cell wall of the tubular cells on the intracellular lumen side, can suppress the buckling and damage of the tubular cells, thus becoming a lightweight and high-strength material.

[0039] The following describes the elements that constitute this plant material.

[0040] <Plant Structures> The plant material in this first embodiment contains tubular cells.

[0041] Plant structures are composed of tubular cells. Examples of plant structures include wood, bamboo, and herbaceous plants.

[0042] As timber, both broadleaf and coniferous trees can be cited. Examples of broadleaf trees include: ash, acer dentata, red oak, light-leaved acer, poplar, maple, Korean locust, benzoin, walnut, persimmon, Chinese tallow tree, cork tree, paulownia, paulownia, camphor tree, chestnut, beech, Japanese beech, cherry blossom, walnut, cornelian cherry, linden, white oak, birch, red nanmu, boxwood, horse chestnut, sweetgum, black locust, catalpa, spring elm, alder, beech, magnolia, birch, locula, water oak, water walnut, willow, poplar, mulberry, acacia, red ironwood, large-flowered dipterocarpus, African mahogany, acacia, yellow birch, American tulip tree, yellow willow, Ipe. tree), Green-stalked Mulberry, Erima, Okoume, African Balsa, Alder, Kapur, Kapok, Rainbow Eucalyptus, Quince, Calophyllum, Gubas, Geronggang, Kempas, Cordia, Ebony, Afrormosia, Coconut, Rubberwood, Sapele, Gelton, Jarrah, Jongkong, Silver Beech, Spanish Toon, S cepter, soft maple, deep red willow, tauren, daomu, tagasan, teak, natau, hard maple, linden, balsa, beech, hickory, purpleheart, pulai, black walnut, black cherry, black bean wood, perupok, ash, white oak, white willow, makore, mahogany, Malass, mansonia, Melina, Mersawa, Merbau, Mengeris, monkeybon, light red willow, labra, lamin, guaiac, red oak, rosewood, etc. Examples of coniferous trees include Chinese fir, cypress, red pine, black pine, Northeast yew, ginkgo, podocarpus, spruce, torreya, larch, podocarpus konoya, cypress, hemlock, Japanese cypress, Sakhalin fir, juniper, Japanese cypress, Japanese five-needle pine, fir, kauri, red pine, Caribbean pine, pine, Klingi pine, southern yellow pine, western yellow pine, radiata pine, twisted pine, spruce, Thai conifers, North American redwood, North American hemlock, North American juniper, North American podocarpus, North American pine, North American fir, red pine, Firsburg pine, northern larch, Mercus pine, Mexican cypress, redwood, etc.

[0043] Bamboo materials include Phyllostachys edulis, Phyllostachys mosoides, Phyllostachys aurea, and Phyllostachys pubescens.

[0044] Herbaceous plant materials include rice, wheat, sugarcane, reeds, cedar, corn, and kenaf. The cell walls of tubular cells contain cellulose as a major component. Furthermore, the above descriptions are illustrative and not limited to these examples.

[0045] Compared to herbaceous plants, wood grows thicker and is stronger, making it an important component in structural works such as buildings and furniture since ancient times. Mechanical properties of wood include compressibility, tensile properties, and bending properties. Compressibility can be evaluated using stress-strain curves obtained from commercially available Autograph Testers, universal testing machines, tensile-compression testing devices, and compression testing machines. Compressibility properties typically allow for quantitative comparison and evaluation of compressive strength, compressive modulus of elasticity, and buckling strain. Compressive strength can be calculated from the upper yield point of the stress-strain curve, the compressive modulus of elasticity from the slope of the stress-strain curve, and buckling strain is the strain up to the upper yield point. If wood is envisioned for practical use as a flooring material as described above, improving its compressive strength properties would greatly contribute to expanding its applications.

[0046] Wood, especially coniferous wood, is soft and easily dented by impacts and scratched by friction. Therefore, broadleaf trees are sometimes called hardwoods, and coniferous trees are sometimes called softwoods. This is because the cellular structures of coniferous and broadleaf woods differ.

[0047] Figure 2A It is a schematic cross-sectional view showing the tubular cells that make up the plant structure, perpendicular to the fiber direction. Figure 2B This is a figure showing SEM images of cross-sections perpendicular to the fiber direction of tubular cells in the earlywood 5 and latewood 6 of Chinese fir, a coniferous tree.

[0048] like Figure 2BAs shown, coniferous wood is an aggregate of various tubular cells ranging from 1 to 6 mm in length. The whiter portion of the wood grain forming the annual rings of coniferous wood is called earlywood (or springwood), composed of cells that grow rapidly from spring to early summer. Conversely, the darker, brownish portion of the wood grain is called latewood (or autumnwood), composed of cells that grow rapidly from early summer to late summer. For coniferous wood, the cells that make them up are quite different in earlywood (5) and latewood (6). Earlywood (5) cells have a large outer diameter, up to approximately 70 μm, with thin cell walls and large cavities (4) within the cells, the thinnest cells being less than 1 μm thick. This high porosity and low density are considered the main reasons for its low strength. On the other hand, latewood (6) is characterized by small outer diameters, down to less than 10 μm, with thick cell walls, the thickest cells approaching 5 μm thick, resulting in a low porosity. Compared to broadleaf trees, coniferous wood grows straighter and has fewer branches, thus providing a stable supply of homogeneous raw materials, making it easier to utilize industrially. Furthermore, its high porosity results in lightweight properties and ease of processing. Additionally, the fewer cell types and simpler tissue structure of coniferous wood lead to less variation in properties due to species differences.

[0049] <Polymer> Polymer 7 is in contact with plant material 10. For example, polymer 7 is in contact with at least a portion of the surface of the cell wall 2 of the tubular cells 1 of plant material 10 on the intracellular lumen side. In other words, polymer 7 is in contact with at least a portion of the surface belonging to the cell wall 2 and in contact with the intracellular lumen 4. Alternatively, polymer 7 may be a membrane formed along the cell wall 2 of the intracellular lumen 4.

[0050] Figure 3A A schematic perspective stereoscopic view of tubular cell 1 in the case of no polymer contact (i.e., no treatment). Figure 3B A cross-sectional view showing the structure of tubular cell 1 perpendicular to the fiber direction when the polymer is not in contact. Figure 3C A cross-sectional view showing the tubular cell 1 in the absence of polymer contact, parallel to the fiber direction, and Figure 3D A cross-sectional view showing a portion of the cross-sectional structure of tubular cell 1 parallel to the fiber direction when the polymer is not in contact.

[0051] Figure 4A A schematic perspective three-dimensional view of the tubular cell 1 showing the general overall contact between polymer 7 and the inner surface of cell wall 2. Figure 4B A cross-sectional view of the tubular cell 1 perpendicular to the fiber direction, showing the condition that the polymer 7 is in approximately overall contact with the inner surface of the cell wall 2. Figure 4CA cross-sectional view of the tubular cell 1, parallel to the fiber direction, showing the condition where polymer 7 is in approximately complete contact with the inner surface of cell wall 2. Figure 4D A cross-sectional view of a portion of the structure of the tubular cell 1, parallel to the fiber direction, showing the condition that the polymer 7 is in approximately overall contact with the inner surface of the cell wall 2.

[0052] Figure 5A A schematic perspective three-dimensional diagram showing the tubular cell 1 in contact with approximately half of the inner surface of the cell wall 2, representing the polymer 7. Figure 5B This is a cross-sectional view of the tubular cell 1, perpendicular to the fiber direction, showing the situation where polymer 7 is in contact with approximately half of the inner surface of cell wall 2. Figure 5C This is a cross-sectional view of the tubular cell 1, parallel to the fiber direction, showing the situation where polymer 7 is in contact with approximately half of the inner surface of cell wall 2. Figure 5D A cross-sectional view of a portion of the tubular cell 1, parallel to the fiber direction, showing the situation where polymer 7 is in contact with approximately half of the inner surface of cell wall 2.

[0053] Figure 6A A schematic perspective three-dimensional view of the tubular cell 1 showing the polymer 7 in contact with a portion of the inner surface of the cell wall 2. Figure 6B A cross-sectional view of the tubular cell 1 perpendicular to the fiber direction, showing the situation where polymer 7 is in contact with a portion of the inner surface of cell wall 2. Figure 6C A cross-sectional view of the tubular cell 1, parallel to the fiber direction, showing the situation where polymer 7 is in contact with a portion of the inner surface of cell wall 2, and... Figure 6D A cross-sectional view of a portion of the tubular cell 1, parallel to the fiber direction, showing a portion of the structure in which the polymer 7 is in contact with a part of the inner surface of the cell wall 2.

[0054] like Figures 4A to 4D As shown, the contact between the polymer and at least a portion of the surface of the cell wall on the luminal side of the plant material is not limited to the case where the polymer 7 is in approximately full-surface contact with the inner surface of the cell wall 2. It can be as follows: Figures 5A to 5D As shown, the polymer 7 is in contact with approximately half of the inner surface of the cell wall 2. This can also be achieved as follows: Figures 6A to 6D As shown, polymer 7 is in contact with a portion of the inner surface of cell wall 2.

[0055] Furthermore, the polymer does not need to be in uniform contact with the intracellular lumen side of the cell wall; for example, it can also be as follows: Figures 5A to 5DAs shown, polymers may appear in areas with a higher concentration or a lower concentration. Furthermore, the amount of polymer in contact with the luminal surface of the cell wall does not need to be uniform. For example, in multiple cross-sections perpendicular to the fiber direction of the tubular cell, polymers may be formed in one cross-section to completely fill the voids, while no polymers may be formed in other cross-sections. Additionally, in the cross-sections perpendicular to the fiber direction of the tubular cell, there may be cell walls in multiple tubular cells with polymers completely filling the voids, cell walls with polymers formed on the luminal surface, and cell walls with no polymers formed.

[0056] That is, the main structure of the multiple tubular cell cross-sections constituting plant materials is as follows: Figure 1B A hollow structure with a cell wall, as shown, is acceptable, where the polymer contacts the surface of the cell wall on the intracellular lumen side.

[0057] For example, the spring constant of the polymer, calculated using force curves obtained by atomic force microscopy (AFM), is greater than 0.4 N / m and less than 0.8 N / m. Detailed explanations of the spring constant of the polymer are provided below.

[0058] The polymer is, for example, composed of thermoplastic resins. Examples of thermoplastic resins include vinyl acetate resins, acrylic resins, styrene-based resins, styrene-acrylic copolymer resins, polyolefin resins, polyvinyl chloride resins, polyurethane resins, ABS resins, polyamide resins, polyacetal resins, polycarbonate resins, polyester resins, polyvinyl alcohol, and polyethylene glycol. Thermoplastic resins can be copolymers of multiple components or mixtures of multiple thermoplastic resins. From the viewpoint of being able to be used as dispersions of polymer particles such as emulsions, and of film-forming properties and film hardness after impregnation, vinyl acetate resins, acrylic resins, and styrene-acrylic copolymer resins are particularly preferred. Furthermore, it is believed that polymers composed of thermoplastic resins do not depend on the components constituting the polymer; as long as the strength of the polymer is the same, the strength of the plant-based material will also be the same. On the other hand, it is believed that the characteristics of the components constituting the polymer are reflected to some extent in the characteristics of the plant-based material. For example, if the polymer contains a large amount of flame-retardant components, the flame retardancy of the plant-based material is also improved.

[0059] <Density> For example, the volume (cm³) can be calculated by measuring the lengths of the three sides of the cuboid sapwood of the plant material. 3 In addition to the separately measured weight (g) of the plant material, the density (g / cm³) of the plant material can be calculated. 3 ).

[0060] The density of the plant material in Implementation Method 1 is greater than 0.33 g / cm³. 3 And it is 0.85g / cm 3 the following.

[0061] For example, when the plant structure is cedar, the preferred density of the plant material is 0.34 g / cm³. 3 Above and 0.85g / cm 3 The following is more preferably 0.35 g / cm³. 3 Above and 0.85g / cm 3 the following.

[0062] Additionally, for example, in the case where the plant structure is cypress, the density of the plant material is greater than 0.49 g / cm³. 3 And it is 0.85g / cm 3 The following applies. When the plant structure is cypress, the preferred density of the plant material is 0.50 g / cm³. 3 Above and 0.85g / cm 3 The following is more preferably 0.51 g / cm³. 3 Above and 0.85g / cm 3 the following.

[0063] <Compressive strength in the radial direction> Wood exhibits anisotropy, and its mechanical strength varies depending on the radial direction (R direction), tangential direction (T direction), and fiber direction (L direction) of the wood's annual rings, with the fiber direction typically exhibiting the highest strength. When using wood-based panels to showcase the aesthetic appeal of the wood grain as flooring material, the compressive strength in the radial direction becomes important. The plant-based material in Embodiment 1 exhibits a compressive strength in the radial direction greater than 2.5 MPa and less than 30 MPa.

[0064] For example, when the plant structure is cedar, the compressive strength in the radial direction is preferably 2.6 MPa or more and 30 MPa or less, more preferably 3 MPa or more and 30 MPa or less.

[0065] For example, when the plant structure is cypress, the compressive strength in the radial direction is greater than 6 MPa and less than 30 MPa. When the plant structure is cypress, the compressive strength in the radial direction is preferably 6.1 MPa or more and less than 30 MPa, more preferably 6.5 MPa or more and less than 30 MPa.

[0066] Specifically, when the plant structure is wood, the radial direction is from the center of the annual rings outwards. In other words, the radial direction is the radial direction.

[0067] Compressive strength can be evaluated, for example, by obtaining stress-strain curves using commercially available Autogrip testing machines, universal testing machines, tensile compression testing apparatuses, and compression testing machines. Alternatively, compressive strength can also be evaluated by measuring under a microscope using a micro-compression testing machine. Measurements using a micro-compression testing machine are particularly effective when the plant-based material specimens are thin, small, or have inconsistent grain orientation.

[0068] Furthermore, compressive strength varies depending on the size of the test specimen, the ratio of early to late material, the density of the specimen, and the annual ring inclination angle. Therefore, in compressive strength testing, it is preferable to evaluate the specimen with as consistent a size, density, and annual ring inclination angle as possible. The test specimen may be, for example, a cube measuring 1 cm or 2 mm square.

[0069] The compressive strength in the radial direction of the plant material of Embodiment 1, measured by the above method, serves as an indicator of the strength of the plant material. More specifically, the upper yield point in the stress-strain curve of the plant material indicates that damage such as cell wall buckling or rupture has occurred in the plant material.

[0070] <Polymer Filler Ratio> Polymer fill factor represents the proportion of the polymer area in a cross-section of the cell lumen relative to the total area of ​​the cell lumen. A polymer fill factor is, for example, greater than 10% and less than 60%.

[0071] Polymer filling rate can be derived, for example, by observing the cross-section of the tubular cells of the unmodified plant material perpendicular to the fiber direction and the cross-section of the tubular cells of the modified plant material perpendicular to the fiber direction using a scanning electron microscope (SEM).

[0072] <Polymer content> The polymer content is calculated as the weight percentage (wt%) of the modified polymer in the modified plant-based material. The polymer content in the plant-based material is, for example, 5 wt% or more and 65 wt% or less. Preferably, the polymer content in the plant-based material is 7 wt% or more and 63 wt% or less, more preferably 9 wt% or more and 60 wt% or less. The polymer content in the plant-based material can be adjusted by regulating the concentration of polymer particles in the emulsion impregnated during the modification process. Alternatively, the polymer content in the plant-based material can be adjusted by increasing the number of impregnation cycles: impregnating with the emulsion, removing the solvent, and then impregnating with the emulsion again.

[0073] <Polymer spring constant> For example, the spring constant of the polymer, calculated by force curve determination using an atomic force microscope, is 0.4 N / m or more and 0.8 N / m or less. Preferably, the spring constant is 0.5 N / m or more and 0.8 N / m or less.

[0074] By using the spring constant, as shown in equation (1) below, the longitudinal elastic modulus (Young's modulus) E (N / m), which is one of the compressive characteristics, can be calculated. 2 ). E=kL / A (1) Here, A represents the cross-sectional area (m²). 2 L represents length (m). The spring constant k (N / m) is an indicator of the hardness and deformation difficulty of a component. For example, under the same applied force (N), a component with a large spring constant is hard and difficult to deform, while a component with a small spring constant is soft and easy to deform. In a non-uniform composite material composed of multiple materials, the average value of the composite material block is calculated in the compressive strength measurement as described above. On the other hand, the spring constant can be calculated locally, for example, using a method such as force curve measurement using atomic force microscopy. Therefore, by calculating the spring constant of a specific material component of the composite material, the hardness of that specific material component can be derived. That is, in this disclosure, by calculating the spring constant, the hardness of the polymer of the plant-based material can be derived.

[0075] For example, when using an atomic force microscope probe to measure a spring constant k = 0.4 N / m and a thickness L = 1 × 10⁻⁶, -7 In the case of the force curve of the polymer film with diameter m, if the contact area between the probe and the polymer film is A = 1 × 10⁻⁶ m, -17 m 2 According to equation (1), the Young's modulus of the polymer film can be calculated as E = 4 × 10⁻⁶. 9 N / m 2 In reality, the contact area between the probe and the polymer film cannot be measured. Therefore, the theoretical calculation formula (such as the JKR model) of the contact model that assumes the shape of the probe tip as a sphere can be fitted with the force curve, and the elastic modulus can be calculated based on the fitting parameters.

[0076] In addition, the cross-section of the tubular cells of the plant material perpendicular to the fiber direction can be ground, and the local elastic modulus of the plant material can be measured using quantitative nanomechanical mapping (PF-QNM) on a Bruker AXS MultiMode 8 scanning probe microscope. In this study, the elastic modulus of the cell wall of *Cunninghamia lanceolata* was 7 to 9 GPa, and the elastic modulus of the polymer portion with a spring constant of 0.5 N / m was 5 × 10⁻⁶. 9 N / m 2 .

[0077] <Polymer film thickness> The polymer film thickness is not limited, but is, for example, 0.1 μm or more and 30 μm or less, preferably 0.1 μm or more and 10 μm or less. In the method for manufacturing plant-based materials described later, the polymer film thickness can be controlled by changing the concentration of the solid components in the emulsion or the resin concentration in the solvent.

[0078] <Methods for Manufacturing Plant-Based Materials> The method for manufacturing plant-based materials according to Embodiment 1 includes the following steps. Figures 7A to 7C This is a schematic cross-sectional view showing each step of the manufacturing method of the plant-based material according to Embodiment 1. (1) The process of injecting an emulsion containing water and polymer particles as solvent into plant-based materials. (2) The process of removing solvent from plant materials by heating and drying

[0079] (1) The process of injecting emulsion into plant materials The process of injecting an emulsion containing water as a solvent and polymer particles into a plant-based material can be carried out by various methods. For example, the emulsion can be injected into the plant-based material by coating it with the emulsion. Alternatively, the plant-based material can be impregnated with the emulsion to inject the emulsion into the plant-based material. The plant-based material impregnated with the emulsion can also be injected into the plant-based material under reduced pressure. Alternatively, the plant-based material impregnated with the emulsion can be degassed under reduced pressure and then injected into the plant-based material under pressure. Furthermore, these methods can be combined to inject the emulsion into the plant-based material.

[0080] In addition, the process of injecting emulsion into plant-based materials, for example, Figure 7A and Figure 7B As shown, it can include: (1-1) The process of impregnating plant-based materials in an emulsion ( Figure 7A , Figure 7B ),and (1-2) The process of removing the impregnated plant material from the emulsion.

[0081] Figure 7A and Figure 7B This is a schematic cross-sectional view illustrating an example of the process of impregnating plant-based materials in the manufacturing method of plant-based materials according to Embodiment 1.

[0082] <Lotion> like Figure 7AAs shown, the emulsion 12 impregnated with plant-based materials comprises water as solvent 16 and polymer particles 14. The polymer particles 14 are dispersed in solvent 16, for example. The emulsion 12 is, for example, an o / w (oil-in-water) type emulsion. By using water as solvent 16, the possibility of the slow release of highly volatile organic compounds (VOCs) can be reduced. Therefore, industrial materials using plant-based materials can reduce the likelihood of causing sick building syndrome.

[0083] It is known that emulsions form a continuous film through the evaporation of the dispersion medium and the molten adhesion of polymer particles. This molten adhesion of polymer particles begins with deformation of the polymer particles at a temperature higher than the minimum film-forming temperature (MFT) of the emulsion. In the case of plasticizer-free emulsions, the MFT is mostly the same as the glass transition temperature (Tg) of the polymer particles. In the case of emulsions containing plasticizers, the MFT can be significantly reduced depending on the type of plasticizer. By placing the formed polymer at a temperature higher than the MFT, the molten adhesion of polymer particles is further promoted, and the polymer chains interdiffusion, forming a dense and high-strength film.

[0084] like Figure 7B As shown, only solvent 16 penetrates the cell wall 2. The polymer particles 14 dispersed in emulsion 12 have a localized increased concentration on the surface of the cell wall 2 on the intracellular lumen side, and melt and adhere on the surface of the cell wall on the intracellular lumen side, forming a melt-adhesive (specifically, a portion of the melt-adhesive polymer particles) 15.

[0085] It is known that solids are impermeable to the cell walls of plant structures (such as wood (coniferous wood)). Similarly, polymer particles contained in emulsions will not penetrate the cell walls of plant structures. Therefore, when an emulsion comes into contact with the cell walls of the intracellular cavity of a plant structure, only water, acting as a dispersion medium, is absorbed by the cell walls, and the locally highly concentrated polymer particles contained in the emulsion melt and adhere to each other.

[0086] The solvent used in emulsions is one that can penetrate cell walls. By using a solvent, it is possible to prevent the polymer from completely filling the gaps in the cell lumen. Water is preferred as a solvent from the viewpoints of reducing harm to humans, environmental impact, and VOCs. Furthermore, from the same viewpoint, green solvents can also be used. Specific examples of green solvents include ethanol obtained by saccharifying sugarcane, corn, and cellulose materials; 1,3-butanediol and glycerol as extracts from natural sources; 3-methoxy-3-methyl-1-butanol, which is biodegradable; and ethylene glycol, propylene glycol, and their derivatives as regeneration solvents for various materials such as plastic products. When using water-soluble resins, the resin penetrates into the cell wall, easily causing an increase in material density and darkening. When using highly polar green solvents, dissolution of wood-derived components and lignin leaching can easily cause discoloration. Therefore, an aqueous dispersion of resin, such as an emulsion, is more preferable.

[0087] (2) The process of removing solvent from plant materials by heating and drying Figure 7C This is a schematic cross-sectional view showing the process of removing solvent from plant-based materials by heating and drying. The water, from which the solvent is removed, forms polymer 7 from the molten binder.

[0088] After the emulsion is injected into the plant-based material, it is dried by heating the water used as a solvent. It should be noted that various methods can be used for drying, such as combining methods that use fans to blow air or drying under reduced pressure.

[0089] The upper limit of the heating temperature in this disclosure is any temperature at which significant changes such as carbonization, burning, or deterioration of appearance of the wood occur. For example, heating can be carried out at temperatures below 300°C.

[0090] The lower limit of the heating temperature in this disclosure is above the minimum film-forming temperature (MFT) of the emulsion. When the ambient temperature during the emulsion injection process is higher than the MFT, the melting and bonding of polymer particles and film formation will not be significantly affected by the heating process. However, to remove moisture, a heating process is preferred; for example, heating can be performed at 40°C or higher, or at 60°C or higher, or at 110°C or higher. The heating temperature can be appropriately adjusted to achieve the desired wood color.

[0091] By heating at a temperature higher than the polymer's Tg, the polymer particles soften, and the melting and bonding of the polymer particles together, as well as the entanglement and interdiffusion of polymer chains, are promoted. Furthermore, this heat-drying process evaporates trace amounts of moisture and additives such as plasticizers remaining in the polymer, thereby forming a denser, continuous coating. Depending on the type of polymer, sometimes cross-linking of the polymer chains occurs through heating, resulting in a more robust film formation.

[0092] These processes enable the manufacture of plant-based materials in which polymers come into contact with plant structures.

[0093] Emulsions are widely recognized as adhesives in the timber, construction, and wood research industries. However, as disclosed herein, no modification has been reported to date that allows an emulsion to be injected into the intracellular lumen of a plant structure and form a polymer on the intracellular lumen side of the cell wall, a modification that would not be readily conceived even by those skilled in the art.

[0094] (Example) The present disclosure will now be described in more detail through examples. It should be noted that the following examples are merely illustrative, and the present disclosure is not limited to these examples.

[0095] (Example 1) <Impregnation> Sapwood blocks of cedar were impregnated with Polysol BX-8004 (manufactured by Resonac) as an emulsion, and the pressure was reduced to below 0.01 MPa (0.1 atm) at room temperature and maintained for 10 minutes. After returning to normal pressure, the pressure was increased to 0.85 MPa (8.5 atm) and maintained for 2 hours.

[0096] <Drying> The sapwood block of cedar wood impregnated with the emulsion was removed, and any remaining emulsion was wiped off. After drying at room temperature and pressure for 24 hours, it was then heated and dried at 110°C and pressure for 60 hours, thus obtaining the plant-based material of Example 1. The main components of the emulsion used are shown in Table 2. By heating in a temperature range higher than the polymer's Tg, the polymer particles soften, and the melting and bonding of the polymer particles together, as well as the entanglement and interdiffusion of polymer chains, are promoted. Furthermore, through this heating and drying process, trace amounts of moisture and additives such as plasticizers remaining in the polymer evaporate, thereby forming a denser, continuous coating. Depending on the type of polymer, sometimes cross-linking of the polymer chains occurs through heating, resulting in a more robust film formation.

[0097] (Example 2) Except for diluting the emulsion by 2 times with distilled water, the same procedure as in Example 1 was followed to obtain the plant-based material of Example 2.

[0098] (Examples 3 to 5) Except for using the emulsions shown in Table 1, the plant-based materials of Examples 3 and 4 were obtained by operating in the same manner as in Example 1. Instead of cedar sapwood blocks, cypress sapwood blocks were used, and the emulsions shown in Table 1 were used; otherwise, the operation was the same as in Example 1 to obtain the plant-based material of Example 5. POLYSOL AP-4690N used in Example 3 and POLYSOL AP-3140 used in Examples 4 and 5 were manufactured by Resonac. The main components of each emulsion used are shown in Table 2.

[0099] (Comparative Example 1) Except for not performing heating and drying, the same procedure as in Example 1 was followed to obtain the plant-based material of Comparative Example 1.

[0100] [Table 1]

[0101] Table 2]

[0102] <Atomic Force Microscopy (AFM) Force Curves> The emulsions used in Examples 1 to 5 and Comparative Example 1 were coated onto a glass substrate (76 mm in length, 26 mm in width, and 1 mm in thickness) and dried at room temperature and pressure for 24 hours. Then, the emulsions used in Examples 1 to 5 were further heated and dried at 110°C for 20 hours. The resulting polymers were subjected to atomic force microscopy (AFM) force curve measurements under the following conditions to evaluate the polymer's spring constant.

[0103] • Measurement apparatus: Seiko Instruments SPI3800N-SPA300HV (AFM) atomic force microscope • Measurement mode: AFM mode (force curve measurement) • Probe: Olympus OMCL-AC200TR-R3 (Material: Si, Spring constant: 9 N / m, Front curvature radius R: 7 nm) • Measurement area: 1μm × 1μm • Atmosphere measurement: atmosphere • Measurement temperature: room temperature (23℃) The spring constants of the polymers are shown in Table 3.

[0104] <Compression Measurement> For the plant-based materials of Examples 1 to 5 and Comparative Example 1, the compressive strength in the radial direction of the untreated sample and the sample after polymer formation was measured under the following conditions to evaluate the increase in compressive strength in the radial direction caused by polymer formation. • Apparatus used: SVF-500N tensile and compression testing apparatus manufactured by Imada Manufacturing Co., Ltd. • Measurement mode: Compression • Fixture used: Flat compression fixture • Displacement speed: 1 mm / min • Load sensor: 2kN Each sample was compressed by 30% along the radial direction. The increase in compressive strength in the radial direction caused by polymer formation was calculated using the following formula. The results are shown in Table 3. Among them, the compressive strength in the radial direction of untreated cedar sapwood blocks was 2.5 MPa, and the compressive strength in the radial direction of untreated cypress sapwood blocks was 6.0 MPa.

[0105] Increase in compressive strength in the radial direction (MPa) = Compressive strength in the radial direction of the polymer-formed sample (MPa) - Compressive strength in the radial direction of the untreated sample (MPa)

[0106] <Polymer Filler Ratio> The wood cross-section of the modified plant-based material sample was ground using a microtome to create a cross-section for cell wall observation. As a pretreatment for observation, Pt-Pd was deposited onto the observation surface using an ion sputtering device E-1030 (manufactured by Hitachi High Technology). Scanning electron microscopy (SEM) images from one latewood to the next were obtained using a VE-8800 3D real-time viewing microscope (manufactured by KEYENCE).

[0107] Figure 8A It is a schematic cross-sectional view of the tubular cells of the plant material before modification (untreated), perpendicular to the fiber direction. Figure 8B A represents the area of ​​the cell wall in a cross-section perpendicular to the fiber direction of the tubular cells of the plant material before modification (untreated). 00 An example of a schematic cross-sectional view. Figure 8C A represents the area of ​​voids in the cross-section perpendicular to the fiber direction of the tubular cells of the untreated plant material. 01 An example of a schematic cross-sectional view. Figure 9A It is a schematic cross-sectional view showing the tubular cells of plant material perpendicular to the fiber direction. Figure 9B A represents the area A of the apparent cell wall, including the cell wall and polymer, in a cross-section perpendicular to the fiber direction of the tubular cells of the modified plant material. 10 An example of a schematic cross-sectional view. Figure 9C A represents the area of ​​residual voids in the cross-section of the tubular cells of the modified plant material perpendicular to the fiber direction. 11 An example of a schematic cross-sectional view.

[0108] The following describes an example of a method for calculating the polymer filling rate of the plant-based materials disclosed herein.

[0109] First, using image processing software, calculate the area A of the cell wall in the cross-section perpendicular to the fiber direction of the tubular cells of the plant material before modification (untreated). 00 ( Figure 8B ) and the area A of the gap 01 ( Figure 8C Second, for the modified plant-based materials, the area A of the apparent cell wall, including the cell wall and polymer, in the cross-section of the tubular cells perpendicular to the fiber direction was also calculated. 10 ( Figure 9B ) and the area A of the remaining void 11 ( Figure 9C Third, the polymer filling rate F of the plant material is calculated using the following formula (2).

[0110] [Mathematical Expression 1]

[0111] Equation (2) calculates the cross-sectional area of ​​the modified polymer relative to the cross-sectional area A of the intracellular cavity before modification (untreated). 01 The percentage (area %) is taken as the polymer filling rate F of the plant material. The cross-sectional area of ​​the modified polymer is, for example, the area A of the voids from the intracellular lumen of the untreated cell. 01 Subtract the cross-sectional area A of the intercellular cavity after modification. 11 To obtain. Before and after modification, the total cross-sectional area of ​​the pores and the cell wall (apparent cell wall) is the same (A). 00 +A 01 =A 10 +A 11 ).

[0112] <Determination of Polymer Film Thickness> The thickness of the polymer on the intracellular lumen side of the cell wall can be determined, for example, from a SEM image of the cell wall cross-section. Using image processing software, it is possible to study how many pixels constitute the scale bar in the image. This value can be used to convert the number of pixels representing the cell wall thickness in the image into the actual cell wall thickness. As an example, an SEM image of the earlywood portion of the sample from Example 4 is shown below. Figure 1A .according to Figure 1A It can be seen that a polymer membrane with a thickness of 0.1–10 μm forms along the inner lumen of the cell wall. The above method was used to determine the... Figure 1A The SEM images were able to confirm the thickness at any 10 points in the polymer, and the average thickness of the polymer film was found to be 5.3 μm.

[0113] <Density of plant-based materials> The volume (cm³) was calculated by measuring the lengths of the three sides of the sapwood of the plant-based materials obtained in the examples and comparative examples, respectively. 3 ), excluding the separately measured weight (g), calculate the density (g / cm³). 3 The results are shown in Table 3. [Table 3] As shown in Table 3, when the polymer's spring constant is 0.4 N / m or higher, the compressive strength of the material in the radial direction increases. This is because, with a stiffer polymer, the buckling and destruction of the cell walls of the tubular cells can be suppressed. Regarding the polymer filler content, it is also known that when it is in the range of 30% to 55%, voids exist within the material. Therefore, the plant-based materials of Examples 1 to 5 maintain the characteristic of being lightweight as plant structures containing tubular cells. The actual density of the obtained plant-based materials is 0.4 g / cm³. 3 Above and 0.6 g / cm 3 The following range is related to WPC (density 1 g / cm³). 3 Compared to the above, it has lower costs, achieving lightweight and high-strength plant-based materials. Industrial availability The plant-based material disclosed herein has high strength and can therefore be used as building interior materials and structural materials such as flooring materials. Explanation of reference numerals in the attached figures 1. Tubular cells 2. Cell wall 3 gaps 4. Intracellular lumen 5. Early-maturing wood 6. Late-blooming wood 7 Polymers 10. Plant-based materials 12 Emulsions 14 Polymer particles 15. Molten Adhesive 16 Solvent (water)

Claims

1. A plant-based material, comprising: Tubular cells, comprising an intracellular lumen and a cell wall surrounding the intracellular lumen; and The polymer is in contact with at least a portion of the surface belonging to the cell wall and in contact with the intracellular lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy, is greater than 0.4 N / m.

2. The plant-based material according to claim 1, wherein, The polymer is a thermoplastic resin.

3. The plant-based material according to claim 1, wherein, The polymer comprises one selected from the group consisting of vinyl acetate resin, acrylic resin, and styrene-acrylic copolymer resin.

4. The plant-based material according to claim 1, wherein, The average film thickness of the polymer is greater than 0.1 μm and less than 10 μm.

5. The plant-based material according to claim 1, wherein, In a cross section belonging to the plant material and orthogonal to the direction of extension of the tubular cells, the polymer area is expressed as a percentage relative to the area of ​​the cell cavity, i.e., the polymer filling rate is 30% or more and 55% or less.

6. The plant-based material according to claim 1, wherein, The tubular cells are plant cells of wood.

7. The plant-based material according to claim 6, wherein, The wood is coniferous.

8. A method for manufacturing a plant-based material, comprising: The step of injecting an emulsion containing water and polymer particles as a solvent into a plant structure containing tubular cells; and The step of removing the solvent from the plant structure by heating and drying.

9. The method for manufacturing plant-based materials according to claim 8, wherein, The step of injecting the emulsion into the plant structure includes: The step of immersing the plant structure in the emulsion; and The step of removing the plant structure immersed in the emulsion from the emulsion.

10. The plant-based material according to claim 1, wherein, In a cross-section belonging to the plant material and orthogonal to the direction in which the tubular cells extend, the cell lumen contains the polymer and voids.

11. The plant-based material according to claim 1, wherein, The spring constant of the polymer is 0.5 N / m or higher.

12. A plant-based material, comprising: Tubular cells, comprising an intracellular lumen and a cell wall surrounding the intracellular lumen; and The polymer is in contact with at least a portion of the surface belonging to the cell wall and in contact with the intracellular lumen. In a cross section belonging to the plant material and orthogonal to the direction of extension of the tubular cells, the polymer area is expressed as a percentage relative to the area of ​​the cell cavity, i.e., the polymer filling rate is 30% or more and 55% or less.

13. The plant-based material according to claim 1 or 12, wherein, The polymer was not impregnated in the cell wall.

14. A modified wood, comprising: Tubular cells, comprising an intracellular lumen and a cell wall surrounding the intracellular lumen; and The polymer is in contact with at least a portion of the surface belonging to the cell wall and in contact with the intracellular lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy, is greater than 0.4 N / m.

15. A cellulose molded article comprising: Tubular cells, comprising an intracellular lumen and a cell wall surrounding the intracellular lumen; and The polymer is in contact with at least a portion of the surface belonging to the cell wall and in contact with the intracellular lumen. The spring constant of the polymer, calculated by force curve determination using atomic force microscopy, is greater than 0.4 N / m.

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