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

Abstract

This plant-based material includes: a tubular cell which includes a cell lumen and a cell wall surrounding the cell lumen; and a polymer which is in contact with a part that is at least a part of the surface of the cell wall and is in contact with the cell lumen. The spring constant of the polymer as calculated by a force curve measurement by atomic force microscopy (AFM) is 0.4 N / m or more.

Description

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

[0001] The present disclosure relates to plant-based materials, methods for producing plant-based materials, modified wood, and cellulosic molded bodies.

[0002] Modified wood has been known in the past, in which properties such as strength and dimensional stability of wood have been changed by modifying the wood.

[0003] For example, Non-Patent Document 1 discloses modified eucalyptus wood in which styrene or methyl methacrylate is injected into the cell cavity of eucalyptus wood and polymerized to fill the cell cavity. Also, Non-Patent Document 2 discloses modified poplar wood in which the surface of the cell cavity of poplar wood is coated with a polymer.

[0004] Denise Ortigosa Stolf et al., "Wood-Polymer Composite: Physical and Mechanical Properties of Some Wood Species Impregnated with Styrene and Methyl Methacrylate", Materials Research, 2004, Vol. 7, No. 4, p.611-617.Denkang Guo et al., "Improving physical properties of wood-polymer composites by building stable interface structure between swelled cells walls and hydrophobic polymer", Wood Science and Technology, 2021, 55, p. 1401-1417.

[0005] The present disclosure aims to provide a plant-based material that has high strength.

[0006] The plant-based material according to the present disclosure comprises tubular cells each having an intracellular lumen and a cell wall surrounding the intracellular lumen, and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the intracellular lumen, the polymer having a spring constant of 0.4 N / m or greater as calculated by force curve measurement using atomic force microscopy (AFM).

[0007] The method for producing plant-based materials according to the present disclosure includes injecting an emulsion containing water as a solvent and polymer particles into a plant structure containing tubular cells, and removing the solvent from the plant structure by heat drying.

[0008] According to the plant-based material of the present disclosure, a plant-based material having high strength can be provided.

[0009] FIG. 1A is a SEM image of a cross section of a cell wall in a plant material according to embodiment 1, with a polymer in contact with the surface of the cell lumen of the cell wall. FIG. 1B is a schematic cross section showing a cross section of the cell lumen of a tubular cell in a plant material according to embodiment 1. FIG. 2A is a schematic cross section showing a cross section perpendicular to the fiber direction of a tubular cell in a plant material. FIG. 2B is a SEM image of a cross section of a cell wall in earlywood and latewood of a coniferous wood. FIG. 3A is a schematic see-through perspective view of a tubular cell, showing an untreated state before polymer injection. FIG. 3B is a cross section showing the cross section perpendicular to the fiber direction of a tubular cell, showing an untreated state before polymer injection. FIG. 3C is a cross section showing the cross section parallel to the fiber direction of a tubular cell, showing an untreated state before polymer injection. FIG. 3D is a cross section showing a portion of the cross section parallel to the fiber direction of a tubular cell, showing an untreated state before polymer injection. FIG. 4A is a schematic see-through perspective view of a tubular cell, showing a state in which a polymer is in contact with almost the entire inner surface of the cell wall. FIG. 4B is a cross-sectional view showing the cross-sectional structure perpendicular to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with almost the entire inner surface of the cell wall. FIG. 4C is a cross-sectional view showing the cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with almost the entire inner surface of the cell wall. FIG. 4D is a cross-sectional view showing a portion of the cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with almost the entire inner surface of the cell wall. FIG. 5A is a schematic see-through perspective view of a tubular cell, showing a state in which the polymer is in contact with approximately half of the inner surface of the cell wall. FIG. 5B is a cross-sectional view showing the cross-sectional structure perpendicular to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with approximately half of the inner surface of the cell wall. FIG. 5C is a cross-sectional view showing the cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with approximately half of the inner surface of the cell wall. FIG. 5D is a cross-sectional view showing a portion of the cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which the polymer is in contact with approximately half of the inner surface of the cell wall. FIG. 6A is a schematic see-through perspective view of a tubular cell, showing a state in which the polymer is in contact with a portion of the inner surface of the cell wall.FIG. 6B is a cross-sectional view showing a cross-sectional structure perpendicular to the fiber direction of a tubular cell, showing a state in which a polymer is in contact with a portion of the inner surface of the cell wall. FIG. 6C is a cross-sectional view showing a cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which a polymer is in contact with a portion of the inner surface of the cell wall. FIG. 6D is a cross-sectional view showing a portion of a cross-sectional structure parallel to the fiber direction of a tubular cell, showing a state in which a polymer is in contact with a portion of the inner surface of the cell wall. FIG. 7A is a schematic cross-sectional view showing an example of a step of immersing a plant material in the method for producing a plant material according to embodiment 1. FIG. 7B is a schematic cross-sectional view showing another example of the step of immersing a plant material in the method for producing a plant material according to embodiment 1. FIG. 7C is a schematic cross-sectional view showing a step of removing a solvent from a plant material in the method for producing a plant material according to embodiment 1. FIG. 8A is a schematic cross-sectional view showing a cross-section perpendicular to the fiber direction of a tubular cell of an untreated plant material. FIG. 8B is a schematic cross-sectional view showing the area of ​​the cell wall in a cross-section of the cell lumen of the plant material of FIG. 8A. FIG. 8C is a schematic cross-sectional view showing the area of ​​the void in a cross-section of the cell lumen of the plant material of FIG. 8A. Figure 9A is a schematic cross-sectional view showing a cross section perpendicular to the fiber direction of a tubular cell of the modified plant-based material. Figure 9B is a schematic cross-sectional view showing the area of ​​the apparent cell wall including the cell wall and polymer in a cross section of the cell lumen of the plant-based material of Figure 9A. Figure 9C is a schematic cross-sectional view showing the area of ​​the void in a cross section of the cell lumen of the plant-based material of Figure 9A.

[0010] (Knowledge that forms the basis of this disclosure) In order to curb global warming, curbing the increase in carbon dioxide, a greenhouse gas, has become an important issue shared worldwide. Therefore, in order to move towards a decarbonized society that aims to curb the increase in carbon dioxide, attention is being focused on plant-based resources that can absorb carbon dioxide, a greenhouse gas. In order to sustainably obtain the effects of plant-based resources as described above, it is necessary to cycle "cut, use, plant," and therefore there is a demand for the development of uses for plant-based resources and the creation of high added value.

[0011] Wood has various properties, such as strength, dimensional stability, weather resistance, and abrasion resistance, that vary depending on the tree species, so it is necessary to consider the appropriate use. Examples of uses include exterior building materials, interior building materials, furniture, and acoustic materials. High-strength wood has a wide range of potential uses, so depending on the tree species, excessive harvesting has progressed and depletion has become a problem. On the other hand, low-strength wood has become a problem due to the increase in stockpiles and the abandonment of artificial forests.

[0012] One major application requiring high-strength plant-based materials is building materials. Flooring materials, in particular, require numerous strength and durability characteristics. These include dent resistance to withstand heavy loads such as office furniture, surface hardness to resist scratches caused by falling objects, resistance to deterioration even when exposed to hot water, and resistance to peeling caused by repeated friction from furniture with casters. Among flooring materials, decorative materials, being exposed on the surface of the flooring, also require high designability. In addition, especially for interior building materials, it is desirable for them to be free of harmful substances. Furthermore, lightweight high-strength plant-based materials can reduce transportation costs and be easy to handle during construction, leading to the potential for expanded use. Given this background, there is a need for a safe method that uses little or no highly harmful VOCs and maintains the lightweight advantages of plant-based materials composed of plant structures containing tubular cells, while retaining their designability and improving their strength.

[0013] In recent years, modified wood, in which wood is chemically modified to alter properties such as strength and dimensional stability, has attracted attention. For example, Non-Patent Document 1 discloses modified wood in which styrene or methyl methacrylate is injected into the cell cavities of eucalyptus, a type of hardwood, and polymerized to fill the cell cavities. Wood modified in this manner and materials containing it are called WPC (Wood-Polymer Composites, or Wood-Plastic Composites). However, because WPC fills almost all of the intracellular voids, it suffers from the problem of losing the lightweight nature that is one of wood's advantages. Another issue is that the appearance of WPC is similar to that of resin products, and it loses the mellow luster characteristic of wood. This is due to the similar refractive indices of wood cells and resin. Designability is an essential factor for industrial use of wood.

[0014] Furthermore, for example, Non-Patent Document 2 discloses modified poplar wood, a type of hardwood, in which the cell lumen-side surface of the cell wall is coated with a polymer. Specifically, the proposed modification process includes Step 1, in which N-methylol acrylate and hydroxyethyl methacrylate are impregnated into the cell wall and a grafting reaction is carried out to introduce and fix carbon-carbon double bonds into the cell wall, and Step 2, in which the fixed carbon-carbon double bonds are used as active sites to carry out a polymerization reaction of vinyl monomers such as polystyrene. N-methylol acrylate and hydroxyethyl methacrylate, which contain OH groups, penetrate into the cell wall while cleaving hydrogen bonds derived from OH groups in components such as cellulose that make up the poplar cell wall. According to this method, the grafting reaction proceeds not only on the cell wall surface but throughout the entire cell wall, allowing for the introduction of numerous active sites. However, the formation of multipoint hydrogen bonds between wood components is the main reason for the high strength of wood. Therefore, impregnation of the wood components with chemicals and the resulting severance of hydrogen bonds is undesirable from the perspective of improving strength. Furthermore, Non-Patent Document 2 does not describe or suggest the spring constant of the polymer. Furthermore, since highly harmful volatile organic compounds (VOCs) are used to obtain the modified poplar wood described in Non-Patent Document 2, safety issues also remain when using modified poplar wood in industrial applications.

[0015] As a result of extensive research to achieve the above-mentioned object, the inventors discovered that by injecting an emulsion containing a water solvent and polymer particles into a plant structure and then removing the water solvent by heating and drying, a polymer can be formed that coats the lumen-side surface of the cell wall of tubular cells while leaving voids in the cell lumen. Furthermore, they discovered that when the spring constant of the polymer calculated by force curve measurement using atomic force microscopy is 0.4 N / m or greater, the plant-based material according to the present disclosure has high strength, leading to the development of a new plant-based material according to the present disclosure. Wood, bamboo, herbaceous plants, and the like can be used as plant structures.

[0016] Each aspect of the present disclosure will be described below.

[0017] A plant material according to a first aspect of the present disclosure includes tubular cells each having a cell lumen and a cell wall surrounding the cell lumen, and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the cell lumen. The polymer has a spring constant of 0.4 N / m or greater, as calculated by force curve measurement using atomic force microscopy (AFM).

[0018] According to the above configuration, the polymer that comes into contact with at least a portion of the surface of the cell wall of the tubular cells that is in contact with the cell lumen can suppress buckling failure of the tubular cells, resulting in a lightweight, high-strength material.

[0019] A plant-based material according to a second aspect is the plant-based material according to the first aspect, and in the second aspect, the polymer may be a thermoplastic resin.

[0020] The plant-based material of the third aspect is the plant-based material of the first or second aspect, and in the third aspect, the polymer may include one selected from the group consisting of vinyl acetate resin, acrylic resin, and styrene-acrylic copolymer resin.

[0021] The plant-based material having the above-mentioned structure can be easily prepared using an emulsion in which water is used as a dispersion medium.

[0022] The plant-based material of the fourth aspect is a plant-based material of any one of the first to third aspects, and in the fourth aspect, the average film thickness of the polymer may be 0.1 μm or more and 10 μm or less.

[0023] The plant-based material of the fifth aspect is a plant-based material of any one of the first to fourth aspects, and in the fifth aspect, in a cross section of the plant-based material that is perpendicular to the direction in which the tubular cells extend, the polymer filling rate, which is expressed as a percentage as the ratio of the area of ​​the polymer to the area of ​​the cell lumen, may be 30% or more and 55% or less.

[0024] The plant material according to the sixth aspect is the plant material according to any one of the first to fifth aspects, and in the sixth aspect, the tubular cells may be wood plant cells.

[0025] A plant-based material according to a seventh aspect is the plant-based material according to the sixth aspect, and in the seventh aspect, the wood may be softwood.

[0026] The method for producing a plant-based material according to the eighth aspect includes injecting an emulsion containing water as a solvent and polymer particles into a plant structure containing tubular cells, and removing the solvent from the plant structure by heat drying.

[0027] A ninth aspect of the method for producing a plant-based material is the same as the eighth aspect, and in the ninth aspect, injecting the emulsion into the plant structure may include immersing the plant structure in the emulsion and removing the plant structure immersed in the emulsion from the emulsion.

[0028] The plant-based material of the tenth aspect is a plant-based material of any one of the first to seventh aspects, and in the tenth aspect, in a cross section of the plant-based material that is perpendicular to the direction in which the tubular cells extend, the cell lumen may include the polymer and voids.

[0029] The plant-based material of the 11th aspect is a plant-based material of any one of the first to seventh and tenth aspects, and in the 11th aspect, the spring constant of the polymer may be 0.5 N / m or more.

[0030] A plant material according to a twelfth aspect comprises tubular cells each having an intracellular lumen and a cell wall surrounding the intracellular lumen, and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the intracellular lumen. In a cross section of the plant material perpendicular to the direction in which the tubular cells extend, the polymer filling rate, which is expressed as a percentage of the area of ​​the polymer relative to the area of ​​the intracellular lumen, is 30% to 55%.

[0031] A plant material according to a thirteenth aspect is the plant material according to the first or twelfth aspect, and in the thirteenth aspect, the polymer does not have to be impregnated into the cell wall.

[0032] Here, "the polymer is not impregnated into the cell wall" means that the polymer used for modification is not present between cell wall components such as cellulose, hemicellulose, and lignin, and the cell wall itself is not swollen compared to its state before modification.

[0033] A modified wood material according to a fourteenth aspect of the present invention comprises tubular cells each having a cell lumen and a cell wall surrounding the cell lumen, and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the cell lumen, the polymer having a spring constant of 0.4 N / m or more as calculated by force curve measurement using an atomic force microscope.

[0034] A cellulose shaped article according to a fifteenth aspect comprises tubular cells each having a cell lumen and a cell wall surrounding the cell lumen, and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the cell lumen, wherein the polymer has a spring constant of 0.4 N / m or more as calculated by force curve measurement using an atomic force microscope.

[0035] Hereinafter, a plant-based material and a method for producing the same 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] (Embodiment 1) Fig. 1A is a diagram showing an SEM image of a cross section of a cell wall of early wood of a cedar, which is a plant structure, having a polymer 7 in contact with the surface of the cell wall 2 facing the cell lumen 4 in a plant material 10 according to embodiment 1. Fig. 1B is a schematic cross section showing a cross section of the cell lumen 4 of a tubular cell of the plant material according to embodiment 1. Fig. 1B is a schematic diagram showing the state in which polymer 7 is provided on the surface of the cell wall 2 facing one of the cell lumen 4 in Fig. 1A.

[0037] As shown in FIGS. 1A and 1B , the plant-based material 10 according to the first embodiment comprises tubular cells including a cell wall 2 and a polymer 7 in contact with at least a portion of the surface of the cell wall 2 facing the cell lumen 4 of the tubular cells. The spring constant of the polymer 7, calculated by force curve measurement using atomic force microscopy, is 0.4 N / m or greater. The lattice-like cell walls 2 of the plant-based material 10 form a lattice-like arrangement of the cell lumen 4 surrounded by the cell walls 2. In this plant-based material 10, the polymer 7 provided on the surface of the cell wall 2 facing the cell lumen 4 forms a membrane. The formation of the polymer 7 membrane reduces the void space in the cell lumen 4 while leaving voids, suppressing an increase in density and maintaining the lightweight characteristic of plant-based materials. Furthermore, the polymer 7 suppresses buckling and cracking of the cell wall, resulting in a higher strength than the original plant-based material.

[0038] According to the plant-based material of embodiment 1, the polymer that comes into contact with at least a portion of the surface of the cell wall on the lumen side of the tubular cells can suppress buckling failure of the tubular cells, resulting in a lightweight, high-strength material.

[0039] The elements that make up this plant-based material are described below.

[0040] <Plant Structure> The plant material according to the first embodiment includes tubular cells.

[0041] Plant structures are made up of tubular cells, such as wood, bamboo, and herbaceous plants.

[0042] Examples of hardwoods include broad-leaved trees, such as ash, blue oak, red oak, asada, Distylium racemosum, silver maple, Chinese maple, Japanese linden, snowbell, Japanese walnut, persimmon, katsura, yellow bell, paulownia, camphor tree, chestnut, zelkova, Japanese zelkova, Chinese zelkova, cherry, Japanese walnut, hornbeam, linden, white oak, white birch, Machilus thunbergii, boxwood, horse chestnut, poplar, black locust, Japanese elm, Japanese elm, and alder. Oak, beech, magnolia, makamba, dogwood, oak, beech, mandarin ash, willows, mountain mulberry, Acacia mangium, azobe, apitong, African mahogany, albizia, yellow birch, yellow poplar, yellow meranti, ipe, iroko, erima, okoume, obeche, alder, kapoor, kapok, camelele, quince, calophyllum, gubas, Some of the woods that can be used include: Gelongan, Kempas, Cordia, Ebony, Coco Rojo, Coconut, Rubber, Sapele, Jelutong, Jara, Jongkong, Silver Beech, Spanish Cedar, Scepter, Soft Maples, Dark Red Meranti, Taung, Dao, Tagayasan, Teak, Nato, Hard Maple, Basswood, Balsa, Beech, Hickory, Bubinga, Ply, Black Walnut, Black Cherry, Black Bean, Perpok, White Ash, White Oak, White Meranti, Makore, Mahogany, Maras, Mansonia, Merina, Mersawa, Merbau, Mengelis, Monkey Pot, Light Red Meranti, Labra, Ramin, Lignum Vita, Red Oak, Rosewood, etc. Examples of coniferous wood include cedar, cypress, Japanese red pine, Japanese black pine, yew, ginkgo, Japanese holly, Siberian ash, Japanese kaya, larch, Japanese cedar, sawara, hemlock, Doga serrata, Sakhalin fir, Japanese juniper, hiba, Himekomatsu, fir, agathis, Scots pine, Caribbean pine, pine, Clinky pine, Southern yellow pine, Ponderosa pine, Radiata pine, lodgepole pine, spruce, Japanese holly, Western red cedar, Western hemlock, Japanese cypress, Japanese cypress, Douglas fir, Japanese fir, Beni pine, Honsun, Japanese larch, Mexican pine, Mexican cypress, and redwood.

[0043] Examples of bamboo include Madake, Moso bamboo, Hachiku bamboo, and Medake bamboo.

[0044] Examples of herbaceous plant materials include rice, wheat, sugarcane, reed, Japanese silver grass, corn, and kenaf. The cell walls of the tubular cells contain cellulose as a main component. Note that the above descriptions are merely examples and are not limiting.

[0045] Wood grows thicker and stronger than herbaceous plants, and has long been used as an important load-bearing component in buildings, furniture, and other structures. Indicators of wood's mechanical properties include compressive, tensile, and bending properties. Compressive properties can be evaluated from stress-strain curves obtained using commercially available autograph testing machines, universal testing machines, tension-compression testing devices, and compression testing machines. Compressive properties generally include compressive strength, compressive modulus, and buckling strain, which can be quantitatively compared and evaluated. Compressive strength can be calculated from the upper yield point of the stress-strain curve, and compressive modulus can be calculated from the slope of the stress-strain curve. Buckling strain is the magnitude of strain up to the upper yield point. Considering the practical use of wood as flooring, as described above, improving wood's compressive strength properties will greatly contribute to expanding its applications.

[0046] Among woods, softwoods in particular are soft and easily dented by impacts and easily damaged by friction. For this reason, hardwoods are sometimes called hardwoods and softwoods are called softwoods. This is because softwoods have a different cellular structure than hardwoods.

[0047] Fig. 2A is a schematic cross-sectional view showing a cross section perpendicular to the fiber direction of tubular cells constituting a plant structure. Fig. 2B is a view showing SEM images of cross sections perpendicular to the fiber direction of tubular cells in earlywood 5 and latewood 6 of a coniferous tree, Cryptomeria japonica.

[0048] As shown in Figure 2B, coniferous wood is a collection of various tubular cells approximately 1 to 6 mm in length. The relatively white-appearing portions of the grain that make up the annual rings of coniferous wood are called earlywood 5 (or summer grain, or early wood) and are composed of cells that grow rapidly from spring to early summer. On the other hand, the relatively dark brown portions of the grain are called latewood 6 (or winter grain, or late wood) and are composed of cells that grow rapidly from early summer to late summer. The cells that make up earlywood 5 and latewood 6 differ significantly. Earlywood 5 has a large cell outer diameter of up to approximately 70 μm, a thin cell wall, and a large void 3 formed in the cell lumen 4, with the thinnest cells being less than 1 μm thick. Therefore, high porosity and low density are thought to be the causes of its low strength. Latewood 6, on the other hand, has a small cell outer diameter of less than 10 μm and a thick cell wall, with the thickest cells being nearly 5 μm thick, resulting in low porosity. Compared to hardwoods, softwoods grow straighter and have fewer branches, making it easier to use industrially as it is possible to stably procure homogeneous raw materials. Furthermore, softwoods have the advantage of being lightweight and easy to handle due to their high porosity. Furthermore, softwoods have fewer cell types and a simple tissue structure, so the differences in properties between species are relatively small.

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

[0050] Figure 3A is a schematic perspective view of a tubular cell 1 when no polymer is in contact (i.e., when untreated), Figure 3B is a cross-sectional view showing the cross-sectional structure perpendicular to the fiber direction of the tubular cell 1 when no polymer is in contact, Figure 3C is a cross-sectional view showing the cross-sectional structure parallel to the fiber direction of the tubular cell 1 when no polymer is in contact, and Figure 3D is a cross-sectional view showing a portion of the cross-sectional structure parallel to the fiber direction of the tubular cell 1 when no polymer is in contact.

[0051] Figure 4A is a schematic perspective view of a tubular cell 1 when polymer 7 is in contact with almost the entire inner surface of the cell wall 2; Figure 4B is a cross-sectional view showing the cross-sectional structure perpendicular to the fiber direction of the tubular cell 1 when polymer 7 is in contact with almost the entire inner surface of the cell wall 2; Figure 4C is a cross-sectional view showing the cross-sectional structure parallel to the fiber direction of the tubular cell 1 when polymer 7 is in contact with almost the entire inner surface of the cell wall 2; and Figure 4D is a cross-sectional view showing a portion of the cross-sectional structure parallel to the fiber direction of the tubular cell 1 when polymer 7 is in contact with almost the entire inner surface of the cell wall 2.

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

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

[0054] The contact of the polymer with at least a portion of the surface of the cell lumen side of the cell wall of the plant material does not necessarily mean that the polymer 7 is in contact with almost the entire surface of the inner surface of the cell wall 2, as shown in Figures 4A to 4D. It may also be that the polymer 7 is in contact with about half of the inner surface of the cell wall 2, as shown in Figures 5A to 5D, or that the polymer 7 is in contact with only a portion of the inner surface of the cell wall 2, as shown in Figures 6A to 6D.

[0055] Furthermore, the polymer does not need to be in uniform contact with the surface of the cell wall facing the lumen; for example, as shown in Figures 5A to 5D, there may be areas where the polymer is locally abundant or sparse. The amount of polymer in contact with the surface of the cell wall facing the lumen also does not need to be uniform; for example, in multiple cross sections perpendicular to an arbitrary position in the fiber direction of a tubular cell, the polymer may be formed so as to completely fill the voids in some cross sections, while no polymer is formed at all in other cross sections. Furthermore, in a cross section perpendicular to the fiber direction of a tubular cell, some of the cell walls may have the polymer formed so as to completely fill the voids, some cell walls have the polymer formed on the surface facing the lumen, and some cell walls have no polymer formed at all.

[0056] In other words, the main structure of the cross-sections of the multiple tubular cells that make up the plant-based material should be a structure in which the cell wall has a hollow structure as shown in Figure 1B, and the polymer is in contact with the surface of the cell wall on the intracellular lumen side.

[0057] For example, the spring constant of the polymer calculated by measuring a force curve with an atomic force microscope (AFM) is 0.4 N / m or more and 0.8 N / m or less. The spring constant of the polymer will be described in detail later.

[0058] The polymer may be, for example, a thermoplastic resin. Examples of thermoplastic resins include vinyl acetate resin, acrylic resin, styrene-based resin, styrene-acrylic copolymer resin, polyolefin-based resin, polyvinyl chloride resin, polyurethane resin, ABS resin, polyamide resin, polyacetal resin, polycarbonate resin, polyester resin, polyvinyl alcohol, and polyethylene glycol. The thermoplastic resin may be a copolymer of multiple components or a mixture of multiple thermoplastic resins. It can be used as a dispersion of polymer particles such as an emulsion. From the viewpoint of film-forming properties and film hardness after impregnation, vinyl acetate resin, acrylic resin, and styrene-acrylic copolymer resin are particularly preferred. Furthermore, polymers made from thermoplastic resins are not dependent on the components that make up the polymer; if the strength of the polymer is equivalent, the strength of the plant-based material is also considered to be equivalent. On the other hand, the characteristics of the components that make up the polymer are considered to be 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 will also be enhanced.

[0059] <Density> For example, the length of each of the three sides of a rectangular sapwood of a plant-based material is measured to determine the volume (cm ３ ) and divided by the weight (g) of the plant-based material measured separately to obtain the density (g / cm ３ ) can be calculated.

[0060] The density of the plant-based material according to the first embodiment is 0.33 g / cm ３ Greater than 0.85 g / cm ３ The following is the result.

[0061] For example, when the plant structure is a cedar, the density of the plant-based material is preferably 0.34 g / cm ３ 0.85g / cm or more ３ More preferably, 0.35 g / cm ３0.85g / cm or more ３ The following is the result.

[0062] Furthermore, for example, when the plant structure is made of Japanese cypress, the density of the plant material is 0.49 g / cm ３ Greater than 0.85 g / cm ３ When the plant structure is a Japanese cypress, the density of the plant-based material is preferably 0.50 g / cm ３ 0.85g / cm or more ３ More preferably, it is 0.51 g / cm or less. ３ 0.85g / cm or more ３ The following is the result.

[0063] <Compressive strength in the radial direction (also called the radial direction or R direction) of the wood's annual rings, and its mechanical strength varies depending on the direction, with the tangential direction (T direction) and the fiber direction (L direction) of the wood's annual rings. Generally, the strength in the fiber direction is the highest. When utilizing the beauty of the wood grain as a flooring material, flat grain wood is used, so the compressive strength in the radial direction is important. The plant-based material according to the first embodiment has a compressive strength in the radial direction of greater than 2.5 MPa and equal to or less than 30 MPa.

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

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

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

[0067] Compressive strength can be evaluated from a stress-strain curve obtained using, for example, a commercially available autograph testing machine, universal testing machine, tension / compression testing device, or compression testing machine. Compressive strength may also be evaluated by measuring the strength using a micro-compression testing machine while observing the specimen under a microscope. Measurements using a micro-compression testing machine are particularly effective when the plant-based material specimen is thin, small, or has uneven grain orientation.

[0068] Furthermore, since compressive strength also varies depending on the size of the measurement sample, the ratio of early and late wood to the density of the measurement sample, and the inclination of the annual rings of the measurement sample, it is preferable to make evaluations using samples with the same size, density, and inclination of the annual rings as much as possible when measuring compressive strength. The measurement sample is, for example, a cubic block of 1 cm or 2 mm square.

[0069] The radial compressive strength of the plant-based material according to the first embodiment measured by the above-described method is, for example, an index representing the strength of the plant-based material. More specifically, the upper yield point in the stress-strain curve of the plant-based material indicates that the plant-based material has experienced damage such as buckling or cracking of the cell walls.

[0070] <Polymer filling ratio> The polymer filling ratio indicates the ratio of the area of ​​the polymer to the area of ​​the cell lumen in a cross section of the cell lumen. The polymer filling ratio is, for example, 10% or more and 60% or less.

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

[0072] <Polymer Content> The weight percentage (wt%) of the polymer after modification relative to the weight of the plant-based material after modification is calculated as the polymer content. The polymer content in the plant-based material is, for example, 5 wt% or more and 65 wt% or less. The polymer content in the plant-based material is preferably 7 wt% or more and 63 wt% or less, and more preferably 9 wt% or more and 60 wt% or less. The polymer content in the plant-based material can be adjusted by adjusting the concentration of polymer particles in the emulsion impregnated in the modification process. The polymer content in the plant-based material can also be adjusted by increasing the number of impregnations, such as impregnating the plant-based material with the emulsion, removing the solvent, and then impregnating the plant-based material with the emulsion again.

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

[0074] By using the spring constant, the longitudinal elastic modulus (Young's modulus) E (N / m ２ ) can be calculated as follows: E = kL / A (1) where A is the cross-sectional area (m ２ ), and L represents the length (m). The spring constant k (N / m) is an index of the hardness and resistance to deformation of a component. For example, when the same force (N) is applied, a component with a large spring constant is hard and resistant to deformation, while a component with a small spring constant is soft and easy to deform. In a heterogeneous composite material composed of multiple materials, the compressive strength measurement described above calculates the average value of the bulk of the composite material. On the other hand, the spring constant can be calculated locally using techniques such as force curve measurement with an atomic force microscope. Therefore, by calculating the spring constant of a specific material component of the composite material, the hardness of only that specific material component can be derived. In other words, in the present disclosure, the hardness of only the polymer of a plant-based material can be derived by calculating the spring constant.

[0075] For example, using an atomic force microscope probe, the spring constant k is 0.4 N / m and the thickness L is 1×10 －７ When measuring the force curve of a polymer film of 1.0 m, the contact cross-sectional area A between the probe and the polymer film is 1 × 10 －１７ m ２ Then, from equation (1), the Young's modulus of the polymer film is E = 4 × 10 ９ N / m ２ In reality, since the contact area between the probe and the polymer film cannot be measured, a theoretical calculation formula for a contact model (such as the JKR model) that assumes the shape of the probe tip is spherical is fitted to the force curve, and the elastic modulus can be calculated from the fitting parameters.

[0076] In addition, the local elastic modulus of the plant material can be measured by polishing a cross section perpendicular to the fiber direction of the tubular cells of the plant material and performing quantitative nanomechanical mapping (PF-QNM) measurements using a Bruker AXS MultiMode 8 scanning probe microscope. In this measurement, the elastic modulus of the cedar cell wall 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 ９ N / m ２ It was.

[0077] <Polymer Film Thickness> The polymer film thickness is not limited, but is, for example, 0.1 μm to 30 μm, preferably 0.1 μm to 10 μm. The polymer film thickness can be controlled by changing the solids concentration of the emulsion or the resin concentration in the solvent in the plant-based material production method described below.

[0078] <Method for manufacturing a plant-based material> The method for manufacturing a plant-based material according to the first embodiment includes the following steps. Figures 7A to 7C are schematic cross-sectional views showing the steps of the method for manufacturing a plant-based material according to the first embodiment. (1) A step of injecting an emulsion containing water as a solvent and polymer particles into a plant-based material. (2) A step of removing the solvent from the plant-based material by heating and drying.

[0079] (1) Step of injecting emulsion into plant-based material The step of injecting an emulsion containing water as a solvent and polymer particles into a plant-based material can be performed by various methods. For example, the emulsion may be applied to the plant-based material, and then injected into the plant-based material. Alternatively, the plant-based material may be immersed in the emulsion, and then injected into the plant-based material. The plant-based material immersed in the emulsion may be placed in a reduced pressure environment, and then the emulsion may be injected into the plant-based material. Alternatively, the plant-based material immersed in the emulsion may be degassed in a reduced pressure environment, and then the emulsion may be injected into the plant-based material in a pressurized environment. Furthermore, the emulsion may be injected into the plant-based material by combining these multiple methods.

[0080] Furthermore, the step of injecting the emulsion into the plant-based material may include, for example, as shown in Figures 7A and 7B, (1-1) a step of immersing the plant-based material in the emulsion (Figures 7A and 7B), and (1-2) a step of removing the immersed plant-based material from the emulsion.

[0081] 7A and 7B are schematic cross-sectional views showing an example of a step of immersing a plant-based material in the plant-based material manufacturing method according to embodiment 1. FIG.

[0082] <Emulsion> As shown in Fig. 7A, the emulsion 12 into which the plant-based material is immersed contains water as a solvent 16 and polymer particles 14. The polymer particles 14 are dispersed in the solvent 16, for example. The emulsion 12 is, for example, an oil-in-water (o / w) emulsion. By using water as the solvent 16, the possibility of the sustained release of highly harmful volatile organic compounds can be reduced. This reduces the possibility that industrial materials using plant-based materials will cause sick building syndrome.

[0083] It is known that in emulsions, polymer particles fuse together due to the evaporation of the dispersion medium, forming a continuous film. The fusion of polymer particles begins when the polymer particles deform at temperatures higher than the minimum film-forming temperature (MFT) of the emulsion. For emulsions that do not contain plasticizers, the MFT is often similar to the glass transition temperature (Tg) of the polymer particles. For emulsions that contain plasticizers, the MFT can be significantly reduced depending on the type of plasticizer. By exposing the formed polymer to a temperature higher than the MFT, the fusion of polymer particles is further promoted, polymer chains interdiffuse, and a dense, high-strength film is formed.

[0084] As shown in Figure 7B, only the solvent 16 penetrates the cell wall 2. The polymer particles 14 dispersed in the emulsion 12 increase in local concentration on the surface of the cell wall 2 facing the lumen, and fuse together on the surface of the cell wall facing the lumen, forming a fused product (specifically, partially fused polymer particles) 15.

[0085] It is known that solids do not penetrate the cell walls of plant structures (wood (coniferous wood), etc.), and the polymer particles contained in the emulsion do not penetrate the cell walls of the plant structures. Therefore, when the emulsion comes into contact with the cell walls in the cell lumen of the plant structures, only the dispersant water is absorbed into the cell walls, and the polymer particles contained in the locally concentrated emulsion fuse together.

[0086] The solvent used in the emulsion is a solvent capable of penetrating the cell wall. The use of a solvent can prevent the voids in the cell lumen from being completely filled with the polymer. Water is more preferably used as the solvent from the viewpoints of toxicity to the human body, environmental impact, and VOC reduction. From the same viewpoint, a green solvent may also be used. Specific examples of green solvents include ethanol obtained by saccharifying sugarcane, corn, cellulose materials, etc.; 1,3-butanediol and glycerin, which are extracts from natural products; biodegradable 3-methoxy-3-methyl-1-butanol; and ethylene glycol, propylene glycol, and their derivatives, which are used as regenerating solvents for various materials such as plastic products. When a water-soluble resin is used, the resin penetrates into the cell wall, which tends to increase the density and darken the material. When a highly polar green solvent is used, discoloration due to the elution of wood extractives and lignin leaching tends to occur. Therefore, it is more preferable to use an aqueous dispersion of the resin, such as an emulsion.

[0087] (2) Step of removing the solvent from the plant-based material by heat drying Figure 7C is a schematic cross-sectional view showing the step of removing the solvent from the plant-based material by heat drying. This removes the water solvent and forms polymer 7 from the fused material.

[0088] After the emulsion is poured into the plant-based material, the water solvent is dried by heating. Alternatively, a combination of drying methods, such as drying by blowing air with a fan or the like and drying under reduced pressure, may be used.

[0089] The upper limit of the heating temperature in the present disclosure may be any temperature at which the wood does not undergo significant changes such as carbonization, burning, or deterioration of appearance, and may be, for example, 300°C or lower.

[0090] The lower limit of the heating temperature in the present disclosure may be equal to or higher than the minimum film-forming temperature (MFT) of the emulsion. If the temperature of the environment in which the emulsion is injected is higher than the MFT, the heating step does not significantly promote fusion and film formation of the polymer particles, but it is desirable to perform the heating step to remove moisture. For example, the heating may be performed at 40°C or higher, 60°C or higher, or 110°C or higher. The heating temperature may be adjusted appropriately to develop the desired wood color.

[0091] Heating at a temperature higher than the Tg of the polymer softens the polymer particles, promoting fusion between the polymer particles and entanglement and interdiffusion of the polymer chains. In addition, this heat drying process volatilizes trace amounts of moisture and additives such as plasticizers remaining in the polymer, forming a denser, continuous coating. Depending on the type of polymer, heating may cause crosslinking of the polymer chains, resulting in the formation of a stronger film.

[0092] These processes can produce plant-based materials in which the polymer is in contact with the plant structure.

[0093] Emulsions are widely recognized as adhesives in the wood, construction, and wood research industries. However, the modification of plant structures by injecting an emulsion into the cell lumen and forming a polymer on the lumen-side surface of the cell wall, as disclosed herein, has not been reported and would not be easily conceived by even a person skilled in the art.

[0094] EXAMPLES The present disclosure will be described in more detail below with reference to examples. Note that the following examples are merely examples, and the present disclosure is not limited to the following examples.

[0095] (Example 1) <Impregnation> A cedar sapwood block was immersed in an emulsion, Polysol BX-8004 (manufactured by Resonac Co., Ltd.), and the pressure was reduced to 0.01 MPa (0.1 atm) or less at room temperature and held for 10 minutes. After returning to normal pressure, the pressure was increased to 0.85 MPa (8.5 atm) and held for 2 hours.

[0096] <Drying> The cedar sapwood block impregnated with the emulsion was removed, the excess emulsion was wiped off, and the block was dried at room temperature and atmospheric pressure for 24 hours, followed by heat drying at 110°C and atmospheric pressure for 60 hours to obtain the plant-based material of Example 1. The main components of the emulsion used are shown in Table 2. Heating at a temperature higher than the Tg of the polymer softens the polymer particles, promoting fusion between the polymer particles and entanglement and interdiffusion of the polymer chains. In addition, this heat drying process volatilizes traces of moisture and additives such as plasticizers remaining in the polymer, forming a denser, continuous coating. Depending on the type of polymer, heating may cause crosslinking of the polymer chains, resulting in the formation of a stronger film.

[0097] Example 2 A plant-based material according to Example 2 was obtained in the same manner as in Example 1, except that the emulsion was diluted two-fold with distilled water.

[0098] (Examples 3 to 5) Plant-based materials according to Examples 3 and 4 were obtained in the same manner as Example 1, except that the emulsions shown in Table 1 were used. Plant-based materials according to Example 5 were obtained in the same manner as Example 1, except that cypress sapwood blocks were used instead of cedar sapwood blocks, and that the emulsions shown in Table 1 were used. Polysol AP-4690N used in Example 3 and Polysol AP-3140 used in Examples 4 and 5 were manufactured by Resonac Co., Ltd. The main components of each emulsion used are shown in Table 2.

[0099] Comparative Example 1 A plant material according to Comparative Example 1 was obtained in the same manner as in Example 1, except that heat drying was not performed.

[0100]

[0101]

[0102] <Atomic Force Microscope (AFM) Force Curve> The emulsions used in Examples 1 to 5 and Comparative Example 1 were applied to a glass substrate (length 76 mm, width 26 mm, thickness 1 mm) and dried at room temperature and atmospheric pressure for 24 hours. Thereafter, the emulsions used in Examples 1 to 5 were heated and dried at 110°C for an additional 20 hours. The obtained polymers were subjected to atomic force microscope (AFM) force curve measurement under the following conditions to evaluate the spring constant of the polymers.

[0103] Measurement equipment: Atomic force microscope SPI3800N-SPA300HV (AFM) manufactured by Seiko Instruments Inc. Measurement mode: AFM mode (force curve measurement) Probe: Olympus OMCL-AC200TR-R3 (material: Si, spring constant: 9 N / m, tip curvature radius R: 7 nm) Measurement area: 1 μm × 1 μm Measurement atmosphere: air Measurement temperature: room temperature (23°C) 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 radial compressive strength of untreated samples and samples after polymer formation was measured under the following conditions to evaluate the increase in radial compressive strength due to polymer formation. - Equipment used: Tension / compression tester SVF-500N manufactured by Imada Seisakusho Co., Ltd. - Measurement mode: Compression - Jig used: Flat compression jig - Displacement rate: 1 mm / min - Load cell: 2 kN Each sample was compressed 30% in the radial direction. The increase in radial compressive strength due to polymer formation was calculated according to the following formula. The results are shown in Table 3. The radial compressive strength of the untreated cedar sapwood wood blocks was 2.5 MPa, and the radial compressive strength of the untreated cypress sapwood wood blocks was 6.0 MPa.

[0105] Increase in radial compressive strength (MPa) = radial compressive strength of sample after polymer formation (MPa) - radial compressive strength of untreated sample (MPa)

[0106] <Polymer filling rate> The end grain surface of the modified plant-based material sample was polished using a microtome to prepare a cross section for observation of the cell wall. As a pretreatment for observation, Pt-Pd was vapor-deposited on the observation surface using an ion sputtering device E-1030 (Hitachi High-Technologies Corporation). Scanning electron microscope (SEM) images from one latewood to the next were obtained using a 3D real surface view microscope VE-8800 (Keyence Corporation).

[0107] 8A is a schematic cross-sectional view showing a cross section perpendicular to the fiber direction of a tubular cell of a plant material before modification (untreated). FIG. 8B is a schematic cross-sectional view showing the cell wall area A of a tubular cell of a plant material before modification (untreated) in a cross section perpendicular to the fiber direction. ００ 8C is an example of a schematic cross-sectional view showing the area A of voids in a cross section perpendicular to the fiber direction of tubular cells of a plant-based material before modification (untreated). ０１ 9A is a schematic cross-sectional view showing a cross section perpendicular to the fiber direction of a tubular cell of the modified plant material. FIG. 9B is a schematic cross-sectional view showing the apparent cell wall area A of the modified plant material, including the cell wall and the polymer, in a cross section perpendicular to the fiber direction of the tubular cell of the modified plant material. １０ 9C is an example of a schematic cross-sectional view showing the area A of the remaining voids in a cross section perpendicular to the fiber direction of the tubular cells of the modified plant-based material. １１ 1 is an example of a schematic cross-sectional view showing the

[0108] An example of a method for calculating the polymer loading rate of the plant-based material of the present disclosure will be described below.

[0109] First, the area A 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 (Fig. 8B) and the area of ​​the gap A ０１ Secondly, for the modified plant material, the apparent cell wall area A, including the cell wall and polymer in a cross section perpendicular to the fiber direction of the tubular cells, is calculated using image processing software. １０ (FIG. 9B) and the area A of the remaining void １１ (FIG. 9C) is calculated. Third, the polymer filling rate F of the plant-based material is calculated using the following formula (2).

[0110]

[0111] Equation (2) is the cross-sectional area A of the void space of the cell lumen before modification (untreated). ０１ The proportion (area %) of the cross-sectional area of ​​the polymer after modification to the area of ​​the voids in the cell lumen before modification (untreated) is calculated as the polymer filling rate F of the plant-based material. ０１ Cross-sectional area A of the void space of the cell lumen after modification １１ The total cross-sectional area of ​​the voids and cell walls (apparent cell walls) is the same before and after modification (A ００ +A ０１ = A １０ +A １１ ).

[0112] <Measuring Polymer Thickness> The thickness of the polymer on the surface of the cell wall facing the lumen can be measured, for example, from an SEM image of the cell wall cross section. Image processing software can be used to determine the number of pixels represented by the scale bar in the image. Using this value, the number of pixels representing the cell wall thickness in the image can be converted into the actual cell wall thickness, allowing for measurement. As an example, Figure 1A shows an SEM image of the earlywood section of the sample in Example 4. Figure 1A reveals that a polymer with a thickness of 0.1 to 10 μm has formed along the lumen of the cell wall. The thickness of 10 randomly selected locations of the polymer visible in the SEM image of Figure 1A was measured using the method described above, and the average polymer thickness was 5.3 μm.

[0113] <Density of Plant-Derived Material> The lengths of the three sides of the sapwood of the plant-derived materials obtained in the Examples and Comparative Examples were measured to determine the volume (cm ３ ) and divided by the separately measured weight (g) to obtain the density (g / cm ３ The results are shown in Table 3.

[0114]

[0115] Table 3 shows that when the spring constant of the polymer is 0.4 N / m or more, the radial compressive strength of the material increases. This is because when the polymer is hard, buckling failure of the cell walls of the tubular cells can be suppressed. It can also be seen that the polymer filling rate is in the range of 30% to 55%, and there are voids within the material. As a result, the plant-based materials of Examples 1 to 5 maintain the light weight that is a feature of plant structures containing tubular cells. The density of the plant-based materials actually obtained was 0.4 g / cm ３ 0.6g / cm or more ３ The range is as follows: WPC (density 1 g / cm ３ This has resulted in the creation of a plant-based material that is both lightweight and strong, with lower carbon dioxide emissions than conventional materials (such as silicon dioxide).

[0116] The plant-based materials according to the present disclosure have high strength and can therefore be used as architectural interior materials such as flooring and structural materials.

[0117] 1 tubular cell 2 cell wall 3 cavity 4 cell lumen 5 early wood 6 late wood 7 polymer 10 plant-based material 12 emulsion 14 polymer particles 15 fusion product 16 solvent (water)

Claims

1. A plant-based material comprising: tubular cells including an intracellular lumen and a cell wall surrounding the intracellular lumen; and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the intracellular lumen, wherein the spring constant of the polymer calculated by force curve measurement using an atomic force microscope is 0.4 N / m or more.

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 0.1 μm or more and 10 μm or less.

5. The plant material according to claim 1, wherein in a cross section of the plant material perpendicular to the direction in which the tubular cells extend, the polymer filling rate, expressed as a percentage as the ratio of the area of ​​the polymer to the area of ​​the cell lumen, is 30% or more and 55% or less.

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

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

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

9. The method for producing a plant material according to claim 8, wherein injecting the emulsion into the plant structure comprises: immersing the plant structure in the emulsion; and 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 of the plant-based material perpendicular to the direction in which the tubular cells extend, the cell lumen comprises 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 more.

12. A plant-based material comprising: tubular cells including an intracellular lumen and a cell wall surrounding the intracellular lumen; and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the intracellular lumen, wherein in a cross-section of the plant-based material perpendicular to the direction in which the tubular cells extend, the polymer filling rate, expressed as a percentage as the ratio of the area of ​​the polymer to the area of ​​the intracellular lumen, is 30% or more and 55% or less.

13. The plant-based material of claim 1 or 12, wherein the polymer does not impregnate the cell walls.

14. Modified wood comprising: 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 of the cell wall that is in contact with the cell lumen, wherein the spring constant of the polymer calculated by force curve measurement using an atomic force microscope is 0.4 N / m or more.

15. A cellulose molded body comprising: a tubular cell including an intracellular lumen and a cell wall surrounding the intracellular lumen; and a polymer in contact with at least a portion of the surface of the cell wall that is in contact with the intracellular lumen, wherein the spring constant of the polymer calculated by force curve measurement using an atomic force microscope is 0.4 N / m or more.

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