Plant material with improved water stability and method for producing the same.

Abstract

Plant materials can be impregnated with a solution containing a stabilizer and / or a stabilizer precursor. The stabilizer and / or precursor can be absorbed into the amorphous cellulose and / or hemicellulose regions of the cell walls of the plant material. After impregnation, the amorphous cellulose and / or hemicellulose can be crosslinked with the stabilizer. The stabilizer precursor may contain a nucleophile and an electrophile, and the stabilizer may contain the reaction product of the nucleophile and the electrophile. During impregnation, each of the stabilizer and / or precursor may have a molecular weight of 500 g / mol or less. After crosslinking, the stabilizer can impart improved water resistance to the plant material, and in particular, the swelling of the plant material can be limited regardless of the exposure time to water and / or the amount of water absorbed by the plant material.

Description

Cross-reference of related applications

[0001] This application claims the benefits and priority of U.S. Provisional Application No. 63 / 460,736 (filed April 20, 2023, title "High Density Wood Compositions Made with Methylolated Phenol for Improved Water Resistance"), which has an earlier filing date, and the entire contents of said application are incorporated herein by reference. [Technical Field]

[0002] This disclosure relates to structures generally formed from plant materials (e.g., wood, bamboo, etc.), and more specifically to a method for producing plant materials with improved water stability. [Background technology]

[0003] Conventional wood products (including solid wood and laminated veneer) have a density of approximately 300-800 kg / m³ 3 In some cases, the tensile strength (axial) is approximately 100 MPa, the elastic modulus (axial) is approximately 11 GPa, and the compressive strength (axial) is approximately 50 MPa. Conventional wood products are readily available and commonly used in construction, especially in residential construction. Steel is also used in construction. Compared to wood, steel has a density of approximately 7,800 to 8,000 kg / m³. 3 In some cases, the tensile strength at the yield point is approximately 400 MPa, the modulus of elasticity is approximately 200 GPa, and the compressive strength is approximately 170 MPa.

[0004] While steel is stronger than conventional wood, producing one cubic meter of wood results in approximately 110 kg of carbon emissions, compared to approximately 12,000 kg of carbon emissions for one cubic meter of steel. Therefore, replacing steel with wood is desirable. This substitution strategy becomes more feasible by using novel modification technologies such as densification to increase the strength of wood.

[0005] In addition to strength, dimensional stability is also important for building materials. Steel has higher dimensional stability than conventional wood in the event of water exposure such as rainfall or flooding. Steel does not absorb water and does not swell when exposed to water. Unfortunately, structures made from conventional plant materials such as wood may absorb large amounts of water (e.g., as much as the dry weight of the plant material) when exposed to water. Most conventional plant material products also show significant swelling (e.g., more than 20%) as they absorb water. In some cases (e.g., high-density plant material products), the amount of swelling can prevent proper fitting between adjacent members in a building structure. This can increase the effort and complexity of the construction process. For example, if conventional wood building materials in an existing building are exposed to water (e.g., flooding), the resulting swelling can sometimes be irreversible and may require repair.

[0006] Various coatings and sealants exist to improve the water resistance of wood and other plant materials. These coatings and sealants generally function by forming a layer on the outer surface of the material. Often, these coatings are hydrophobic, effectively slowing the rate of water absorption into the treated material. However, if water exposure is long enough, the plant material will fully hydrate and swell. Furthermore, swelling can cause the applied coating to crack and / or peel off from the surface of the plant material. Oils (e.g., tung oil, alkyd resins, etc.) have been used to improve the water resistance of wood, but their hydrophobic nature limits their ability to effectively penetrate critical areas of the plant material that cause swelling. In fact, absorbed oil can slow water absorption, but if the treated plant material is exposed to water for a long time, it will eventually fully hydrate and swell.

[0007] The aspects of the disclosed subject matter may, in particular, address one or more of the above-mentioned problems and disadvantages. [Overview of the Initiative]

[0008] Aspects of this disclosure provide a compressed plant material with improved resistance to swelling in the presence of water and a method for producing the plant material. The plant material can be modified by uniformly absorbing a stabilizer precursor that penetrates the cross-section of the plant material. In some embodiments, the stabilizer precursor can be moved to a specific region of the plant material that can swell with water (e.g., amorphous cellulose and / or hemicellulose). Upon reaching the specific region, the precursor can react to form a stabilizer. In some embodiments, the stabilizer formed from such stabilizer precursor reacts with components in the specific region (e.g., crosslinks) and the plant material reaches a target density (e.g., 900 kg / m³). 3 The water-swelling capacity after being compressed to an extreme degree can be significantly reduced. In some embodiments, the compressed plant material mainly consists of an array of oriented, collapsed cells, with specific regions of the cells being cross-linked, and the cells being distributed within a matrix of lignin (e.g., natural and / or degraded lignin), which is also cross-linked. In some embodiments, the water-stabilized plant material may have outstanding strength and exhibit a unique combination of high water absorption capacity and relatively low thickness-direction swelling capacity (e.g., <10%, e.g., ≤5%).

[0009] In some embodiments, water-stabilized plant materials can be formed by a multi-step process. For example, in the first step of some embodiments, the plant material (e.g., wood such as timber or veneer) can be modified by impregnating the plant material with a loading solution in a portion where the thickness direction of the plant material roughly coincides with the radial, tangential, or mixed radial and tangential directions of the plant material. In some embodiments, the lignin in the plant material is partially degraded by the loading solution. This degradation can facilitate subsequent compression processing without destroying cells or rupturing lignin (or at least reducing destruction or rupture). In some embodiments, some of the lignin can also be removed from the plant material in the first step. Alternatively, in some embodiments, the loading solution contains water, and the plant material is heated to over approximately 50°C after treatment with the loading solution.

[0010] In some embodiments, the second step may include partially drying the treated plant material, for example, so that the moisture content of the dried treated plant material is about 1-10% of the dry weight of the treated plant material. In some embodiments, the third step may include impregnating the treated plant material with the stabilizer and / or its precursor under conditions suitable for the stabilizer and / or its precursor to migrate into the amorphous cellulose and / or hemicellulose regions of the treated plant material, where the selective absorption process occurs throughout the entire cross-section (or at least 90%) of the plant material. In some embodiments, the time required for the impregnation process may be sufficient for the concentration gradient of the stabilizer and / or its precursor in the plant material to reach equilibrium. In some embodiments, the impregnation is carried out under conditions that the stabilizer formed by the reaction of the precursor does not crosslink the cellulose and / or hemicellulose.

[0011] In some embodiments, the fourth step may include partially drying the treated plant material so that the moisture content of the dried treated plant material is about 1-25% of the dry weight of the treated plant material, while ensuring that the stabilizer and / or its precursor does not crosslink the cellulose and / or hemicellulose. In some embodiments, the fifth step may include drying the plant material along an axis parallel to the thickness direction of the plant material until the density of the plant material increases, for example (e.g., about 900 kg / m³). 3 This may include applying pressure (e.g., sustained pressure) to the treated plant material (up to a value greater than 1). In some embodiments, the compression of the plant material in the fifth step is carried out so that the stabilizer and / or its precursors do not crosslink the plant material, and / or the water content of the partially compressed plant material is in the range of about 1–20%.

[0012] In some embodiments, the sixth stage may include further drying the plant material while preventing the stabilizer and / or its precursor from crosslinking the plant material, for example, to a value where the moisture content of the treated plant material is less than 10%. In some embodiments, the seventh stage may include applying pressure (e.g., continuous pressure) to the treated plant material along an axis parallel to the thickness direction of the treated plant material, for example, until the density of the plant material increases (e.g., to a value greater than about 1200 kg / m 3 to a value in the range of, for example, about 1,250 to 1,450 kg / m 3 ). In some embodiments, the stabilizer may crosslink specific regions of the plant material, such as amorphous cellulose, hemicellulose, and / or lignin (e.g., degraded or native lignin) after the plant material has been compressed to the target density range (e.g., during or after the seventh stage). Alternatively or additionally, in some embodiments, the fifth and sixth stages may be omitted.

[0013] In some embodiments, the densified plant material crosslinked by the stabilizer at specific sites has a density value in the range of about 900 to 1,450 kg / m 3 and may exhibit the ability to absorb about 10 - 30% of the dry weight of the densified plant material in water, for example, in a range where the swelling along the compression direction does not exceed about 10%.

[0014] In one or more embodiments, the method may include impregnating the plant material with a solution containing a stabilizer and / or a stabilizer precursor such that the stabilizer and / or the stabilizer precursor is absorbed within the amorphous cellulose and / or hemicellulose regions of the cell wall of the plant material. The method may further include crosslinking the amorphous cellulose and / or hemicellulose with the stabilizer after impregnation. The stabilizer precursor may include a nucleophile and an electrophile. The stabilizer may include the reaction product of a nucleophile and an electrophile or, in some embodiments, may simply be the reaction product of a nucleophile and an electrophile. At the time of impregnation, each of the stabilizer and its precursor may have a molecular weight of 500 g / mol or less.

[0015] In one or more embodiments, the structure may comprise a plant material and a stabilizer. The plant material may have cell walls having amorphous cellulose and / or hemicellulose regions. The stabilizer may crosslink the amorphous cellulose and / or hemicellulose regions of the cell walls of the plant material. The stabilizer may be a reaction product of a nucleophile and an electrophile. Each of the nucleophile, electrophile, and stabilizer may have a molecular weight of 500 g / mol or less before crosslinking.

[0016] The various technological innovations of this disclosure can be used in combination or individually. This summary is intended to provide a simplified introduction to a selection of concepts that will be further described in the following detailed description. This summary is not intended to identify any important or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The aforementioned and other purposes, features and advantages of the disclosed technology will become more apparent from the following detailed description with reference to the accompanying drawings.

[0017] Aspects of this disclosure are described below with reference to the accompanying drawings. The drawings are not necessarily drawn to scale. Where applicable, some elements may be simplified or omitted to aid in the description and illustration of basic features. Throughout the drawings, the same reference numerals indicate the same element. [Brief explanation of the drawing]

[0018] [Figure 1] This is a simplified process flow diagram illustrating a method for producing a plant material with improved water stability, relating to one or more aspects of the subject matter of this disclosure. [Figure 2] This figure shows radial cuts, longitudinal cuts, rotary cuts, and radial-tangential cross-sections of natural wood that may be subject to water stabilization treatment according to one or more embodiments of the subject matter of this disclosure. [Figure 3] Figures 3A and 3B are graphs showing the thickness swelling rate (%) versus water absorption rate (%) of compressed poplar wood samples with and without a stabilizer. [Modes for carrying out the invention]

[0019] General matters For the purposes of this explanation, specific aspects, advantages, and novel features of the disclosed subject matter are described herein. The disclosed methods and systems are not intended to be limited in any way. Rather, this disclosure is directed toward all novel and non-obvious features and aspects disclosed herein, including those alone or in various combinations and partial combinations thereof. The methods and systems are not limited to specific aspects or features or combinations thereof, and the disclosed aspects are not required to have one or more specific advantages or to solve a problem. Any aspect or example of the technology may be combined with one or more of the other aspects or examples described herein. Given the many possible ways in which the principles of the disclosed technology may be applied, it should be recognized that the aspects described in this disclosure are illustrative and not intended to limit the scope of the disclosed technology.

[0020] While some operations of the disclosed methods are described in a specific order for convenience, this description should be understood to be interchangeable unless a specific order is required by the specific descriptions below. For example, operations described sequentially may be performed in a different order or simultaneously. Furthermore, for simplicity, the accompanying drawings may not show various embodiments in which the disclosed methods are used in combination with other methods. In addition, terms such as “provide” or “achieve” may be used in the description to explain the disclosed methods. These terms are higher-level abstractions of the actual operations performed. The actual operations corresponding to these terms may vary depending on the specific embodiment and will be readily understood by those skilled in the art.

[0021] Unless otherwise specified, disclosures of numerical ranges should be understood to refer to each discrete point (including endpoints) within that range. Unless otherwise explicitly stated, all numerical values ​​used herein or in claims to represent component amounts, molecular weights, percentages, temperatures, times, etc., should be understood to be modified by "approximately". Thus, unless explicitly or implicitly indicated, or unless the context is appropriately understood to be more restrictively interpreted by those skilled in the art, the numerical parameters described are approximations that may depend on the desired properties and / or detection limits under standard test conditions / methods. Where differences from the prior art are directly and explicitly distinguished, numerical values ​​are not approximations unless words such as "approximately," "substantially," or "about" are used. Where words such as "substantially," "about," or "approximately" are explicitly used in combination with a specific value, a variation of up to 10% of that value is intended unless otherwise specified.

[0022] Directions and other relative references are used to facilitate the explanation of drawings and principles, but are not intended to be limiting. For example, terms such as “inside,” “outside,” “top,” “bottom,” “upper part,” “lower part,” “internal,” “external,” “left,” “right,” “front,” “back,” and “rear” may be used. These terms are used, where applicable, to clarify the explanation of relative relationships, particularly with respect to the illustrated aspects. However, these terms are not intended to imply absolute relationships, positions, and / or orientations. For example, what is called the “top” of an object may become the “bottom” simply by turning the object inside out. It is still the same part, and the object itself is the same.

[0023] As used herein, “includes” means “contains,” and the singular forms “a,” “an,” or “the” include the plural unless the context clearly indicates otherwise. The term “or” refers to a single element or a combination of two or more elements of the listed options unless the context clearly indicates otherwise.

[0024] Where alternatives exist for any of the components, parameters, operating conditions, etc., described herein, this does not necessarily mean that they are equivalent and / or function equivalently. Furthermore, unless otherwise specified, it does not mean that the alternatives are listed in order of priority. Unless otherwise specified, any of the groups defined below may be substitutable or non-substitutable.

[0025] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of this disclosure. Methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this disclosure, but suitable methods and materials are listed below. Materials, methods, and examples are illustrative and not intended to limit the scope. The characteristics of the subject matter of this disclosure will become apparent from the following detailed description and appended claims. Overview of Terms

[0026] Overview of Terms The following is provided to facilitate the description of each aspect of the disclosed subject matter and to guide those skilled in the art in carrying out the subject matter of this disclosure.

[0027] Plant material: A portion of a photosynthetic eukaryote belonging to the plant kingdom, in its growing state (e.g., a portion cut by mechanical or other means). In some embodiments, plant material includes wood (e.g., broad-leaved or coniferous trees) or bamboo (e.g., any of the Bambusoideae, such as Moso, Phyllostachys vivax, Phyllostachys viridis, Phyllostachys bambusoides, Phyllostachys nigra, Guadua angustifolia, Bambusa emeiensis, Arundinaria gigantea, Chusquea culeou, Bambusa vulgaris Vittata, etc.). For example, natural wood may be either hardwood (e.g., with a natural lignin content in the range of 18-25% by weight) or softwood (e.g., with a natural lignin content in the range of 25-35% by weight), and is not limited to such types, but includes basswood, poplar, ash, alder, aspen, balsa, beech, birch, cherry, butternut, chestnut, cocobolo, elm, hickory, maple, oak, padauk, plum, walnut, willow, yellow poplar, bald cypress, cedar, cypress, Douglas fir, fir, hemlock, larch, pine, redwood, spruce, tamarak, juniper, yew, etc. In other embodiments, the plant material includes reeds (e.g., common reed (Phragmites australis), giant reed (Arundo donax), vermal reed (Neyraudia reynaudiana), reed canarygrass (Phalaris arundinacea), reed sweetgrass (Glyceria maxima), small reed (Calamagrostis), paper reed (Cyperus papyrus), barn reed (Sparganium), reed mace (Typha), cape thatched reed (Elegia tectorum), and thatched reed (Thamnochortus insignis)), hemp (Cannabis sativa), or grasses (species selected from the orders Poales or the family Poaceae).Alternatively, in some embodiments, the plant material may be any fibrous plant composed of lignin and cellulose. For example, the plant material may be bagasse (e.g., formed from the processing residue of sugarcane or sorghum stalks) or straw (e.g., formed from the processing residue of cereal plants such as rice, wheat, millet, or maize).

[0028] Lignin-degraded plant materials are plant materials modified by one or more chemical treatments, which (a) modify natural lignin and / or (b) partially remove natural lignin (i.e., partially lignin-degraded). In some embodiments, ligin-degraded plant materials may substantially retain the natural microstructure formed by the cellulosic cell walls of natural plant materials.

[0029] Partial lignin removal: Removal of some (e.g., at least 5%) of the natural lignin from plant material, but not all (e.g., 95% or less) (e.g., by weight percentage). In some embodiments, partial lignin removal can be carried out by subjecting the plant material to one or more chemical treatments. In some embodiments, the lignin content after partial lignin removal may range from 0.9 to 23.8% by weight for hardwoods or bamboo, and from 1.25 to 33.25% by weight for conifers. The lignin content before and after partial lignin removal can be evaluated using techniques known to those skilled in the art, such as Laboratory Analytical Procedure (LAP) TP-510-42618 "Determination of Structural Carbohydrates and Lignin in Biomass" (August 3, 2012 edition) published by the National Renewable Energy Laboratory (NREL), and ASTM E1758-01 (2020) "Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography" published by ASTM International, which are incorporated herein by reference. In some embodiments, the partial lignin removal process may be as described, for example, in U.S. Patent Application Publication No. 2020 / 0223091 (published July 16, 2020, titled "Strong and Tough Structural Wood Materials, and Methods for Fabricating and Use Thereof") and U.S. Patent Application Publication No. 2022 / 0412002 (published December 29, 2022, titled "Bamboo Structures, and Methods for Fabrication and Use Thereof"), and these lignin removal and densification processes are incorporated herein by reference.

[0030] Lignin modification: The process of altering one or more properties of natural lignin in plant material while retaining at least a portion (e.g., most) of the lignin within the plant material. In some embodiments, the lignin content of the plant material before and after in-situ modification is substantially the same; for example, the in-situ modified plant material retains at least 90% of the natural lignin content (e.g., removal of 10% or less of the natural lignin content, or 1% or less). In some embodiments, the plant material is modified in situ (e.g., OH -Through a chemical reaction, lignin is depolymerized, and the depolymerized lignin is retained within the microstructure of the plant material. In some embodiments, the modified lignin has shorter polymer chains than the natural lignin in the natural plant material piece, and / or has more functional groups exposed on its surface compared to the natural lignin in the corresponding natural plant material. Alternatively, lignin modification reduces the molecular weight of lignin (compared to natural lignin), but not to the extent that the lignin becomes water-soluble (e.g., at temperatures involved in lignin modification, such as 20-200°C). The lignin content in plant materials before and after lignin modification can be evaluated using techniques known to those skilled in the art, such as Laboratory Analytical Procedure (LAP) TP-510-42618 "Determination of Structural Carbohydrates and Lignin in Biomass" (August 3, 2012 edition) published by the National Renewable Energy Laboratory (NREL), ASTM E1758-01 (2020) "Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography" published by ASTM International, and / or Standard T 222-om-83 "Standard Test Method for Acid-Insoluble Lignin in Wood" published by the Technical Association of Pulp and Paper Industry (TAPPI), all of which are incorporated herein by reference.In some embodiments, the lignin modification process may be as described, for example, in U.S. Patent Application Publication No. 2024 / 0083067 (published on March 14, 2024, titled "Waste-free Processing for Lignin Modification of Fibrous Plant Materials, and Lignin-modified Fibrous Plant Materials"), which is hereby incorporated by reference into this specification.

[0031] Consolidated or compressed plant material: Plant material that has been compressed until its thickness is reduced. In some embodiments, the thickness is reduced by at least one-half. In some embodiments, the consolidated plant material has a higher density than the starting plant material (e.g., at least 0.9 g / cm 3 , for example, at least 1.1 g / cm 3 , or even at least 1.2 g / cm 3 (e.g., 1.2 - 1.4 g / cm 3) etc.) may have. For example, compacted plant materials may be formed as described in U.S. Patent No. 1,1130256 (published September 28, 2021, titled "Strong and Tough Structural Wood Materials, and Methods for Fabricating and Use Thereof") and U.S. Patent Application Publication No. 2022 / 0412002 (published December 29, 2022, titled "Bamboo Structures, and Methods for Fabrication and Use Thereof"), which are incorporated herein by reference, respectively. In some embodiments, compacted plant material is a component of an engineered plant material structure in which multiple components (e.g., layers or chips) are bonded together with an adhesive or other binder (e.g., a filler such as carboxymethylcellulose (CMC)), and includes, but is not limited to, cross-laminated timber (CLT), glue-laminated timber (Glue-laminated timber) or bamboo glue-laminated timber (Glue-laminated timber), laminated veneer lumber (LVL), oriented strand board (OSB), parallel strand lumber (PSL), and / or oriented structural strawboard (OSSB).

[0032] Fiber direction: This is the direction in which a plant grows from its roots or stem, and the cellulose fibers that form the cell walls of a plant are generally oriented in this direction. In some cases, the fiber direction is generally perpendicular or corresponds to the direction of water transpiration. This is in contrast to the radial direction, which extends outward from the center of the plant stem and is perpendicular to the fiber direction.

[0033] Polymerization: A chemical process in which monomers and / or oligomers react to form polymers.

[0034] Crosslinking: A chemical process in which small reactive molecules (e.g., less than 500 g / mol) react with polymers or macromolecules (e.g., amorphous cellulose and / or hemicellulose in the cell walls of plant materials, and / or lignin in plant materials) to reduce the degrees of freedom of movement of the polymer or macromolecule at the molecular level. In some embodiments, crosslinking of amorphous cellulose and / or hemicellulose (e.g., by stabilizers) can prevent volume expansion when the polymer absorbs water. Alternatively, in some embodiments, crosslinking can make lignin molecules (e.g., decomposed lignin) water-insoluble.

[0035] Reaction product: The reaction product between at least two reactants. In some embodiments, the reaction product is the product of a chemical reaction between a nucleophile (e.g., a Lewis base) and an electrophile (e.g., a Lewis acid). In some embodiments, the reaction product may be the product of a reaction in which all atoms present in the reactants are retained in the reaction product. In other embodiments, the reaction product may be the product of a reaction in which not all atoms present in the reactants are present in the reaction product. In some embodiments, the reaction product may be an adduct. In some embodiments, the reaction product has a molecular weight of 500 g / mol or less.

[0036] Thickness: The cross-sectional dimension of a plant material piece that coincides with the compression direction of this disclosure. In some embodiments, the thickness dimension is less than 25.4 mm (1.0 inch), for example, 6.4 mm (0.25 inch) or less, for example, greater than 0 inch and up to 6.4 mm (0.25 inch). In some embodiments, the thickness dimension coincides with the radial direction of the plant material. In other embodiments, the thickness dimension coincides with the tangential direction of the plant material. In yet another embodiment, the thickness dimension coincides with a mixed direction of the tangential and radial directions of the plant material. Alternatively, in some embodiments, the direction of the thickness dimension is at a non-orthogonal angle to either or both the fiber direction and the radial direction. In some embodiments, the thickness direction corresponds to the minimum cross-sectional dimension of the plant material piece.

[0037] Stabilizers: Reaction products of nucleophiles and electrophile precursors. In some embodiments, stabilizers are formed by the reaction of nucleophiles and electrophiles and have the ability to crosslink specific polysaccharides (e.g., amorphous cellulose and / or hemicellulose) in specific regions within plant cell walls. In some embodiments, stabilizers are small molecules (e.g., less than 500 g / mol) and hydrophilic. In certain embodiments, stabilizers may have high water solubility. In some embodiments, stabilizers have the ability to crosslink lignin (e.g., decomposed lignin) in plant material.

[0038] Stabilizer precursor: A chemical species that can react to form a stabilizer. In some embodiments, the stabilizer precursor includes electrophiles and nucleophiles. In certain embodiments, the stabilizer precursor is a small molecule (e.g., molecular weight less than 500 g / mol, e.g., having a molecular weight greater than 0 g / mol and up to 500 g / mol).

[0039] Introduction Disclosed herein are compressed plant materials with improved resistance to swelling in the presence of water, and methods for producing such plant materials. This disclosure is based on a counterintuitive approach of conferring resistance to the swelling effect of water by treating plant materials (e.g., wood) with compounds that have some properties similar to water. Most techniques designed to reduce wood swelling involve coating the wood with hydrophobic substances, but aspects of this disclosure provide a more effective solution by treating the wood (or other plant materials) with hydrophilic substances. The aspects of the disclosed subject matter are particularly effective in controlling excessive swelling in compressed plant material products. Because wood and many other plant materials exhibit "shape memory" properties, their swelling ability is particularly high when compressed during the manufacturing process. Plant materials, including wood, typically swell by about 2-8% radially or tangentially when the moisture level changes from a dry state to a fully saturated state, but compressed plant materials can swell by more than 30% when changing from a dry state to a fully saturated state. Generally, the higher the degree of compression of the plant material, the greater the swelling value. To increase the strength of the wood, the density value (for example, 900-1450 kg / m³) is increased. 3When compressing to a certain extent (within a certain range), the ability to suppress or at least reduce swelling in the presence of water can be important.

[0040] While not intended to be constrained by theory, it is useful to note that when water is absorbed into conventional wood (or other plant materials), the water is first absorbed into the cell wall tissue. Specifically, water is absorbed into the regions of the cell wall that contain amorphous cellulose and / or hemicellulose. Water absorption into the lignin-based regions of wood is relatively small. Similarly, water absorption into the crystalline cellulose regions of wood is also very small. Furthermore, water does not move into the cell cavity until the cell wall is saturated (in conventional wood, this is about 28-30% of the water absorption mass of dry wood), but after the cell wall is saturated, water can be absorbed into the cavity as well. More than 90% of the swelling that occurs when conventional solid wood gets wet is due to swelling of the cell wall. Even when the cavities of wood (or other plant materials) are filled with water, the dimensional change of solid wood is generally very small.

[0041] The stabilizers and stabilizer precursors described herein are unique, at least in the context of their use in the methods of the embodiments of this disclosure. The stabilizers and stabilizer precursors of the embodiments of this disclosure are generally small, hydrophilic, and / or have a desired water solubility (e.g., high water solubility as described herein). These properties, alone or in combination, allow these compounds to be moved to specific areas of plant material responsible for most of the swelling under water exposure conditions. In some embodiments, the stabilizer and / or precursor is diffused to the most active sites within the plant tissue, the material is compressed, and after compression (or during the final compression stage in some embodiments), the stabilizer crosslinks amorphous cellulose and / or hemicellulose, preventing volume expansion of these polysaccharides. Thus, the reaction kinetics and process conditions of the stabilizer are controlled so that the stabilizer is activated (e.g., crosslinked) only after the wood (or other plant material) has reached the final compressed state.

[0042] In some embodiments, the compression of plant materials can be facilitated by partially decomposing lignin before compression. In such embodiments, the secondary function of the stabilizer may be to crosslink the decomposed lignin remaining after compression. This crosslinking of decomposed lignin may help reduce the presence of extractives in the final product.

[0043] In some embodiments, compressed plant materials containing amorphous cellulose and / or hemicellulose, impregnated with a stabilizer before compression and crosslinked with the stabilizer after compression, have significantly reduced swelling capacity, for example, in the compression direction (parallel to the thickness dimension), while maintaining a certain water absorption capacity. For example, the thickness-direction swelling of plant materials treated with a stabilizer according to embodiments of this disclosure can be limited to 10% or less (e.g., ≤5%), regardless of the amount of water absorbed or water exposure time of the plant material. This property, coupled with the very small size of the stabilizer and stabilizer precursors, promotes the spontaneous movement of these molecules to sites within the microstructure of the plant material that preferentially absorb and retain water.

[0044] Manufacturing method example Figure 1 shows various embodiments of Method 100 for producing plant material or structures containing plant material with improved water stability. Method 100 can begin with a process block 102, which may be provided with one or more pieces of plant material. In some embodiments, providing the process block 102 may involve cutting, removing, or otherwise separating the piece from a parent plant. In some embodiments, the parent plant may be small-diameter or young plant material (e.g., trees, bamboo stalks, etc.). In some embodiments, cutting may form the plant material into veneers, strips, pieces, or strands, etc., for example, with a thickness of 25.4 mm or less (e.g., <6.4 mm). Optionally, in some embodiments, preparation may include pretreatment of the natural plant material piece, for example, washing to remove unwanted substances or contaminants in preparation for subsequent processing, shaping the natural plant material into a specific form (e.g., slicing into smaller strips) in preparation for subsequent processing, or any combination thereof. In some embodiments, the plant material has a natural lignin content of 15% by weight or less.

[0045] In some embodiments, the plant material is natural wood, which contains various interconnected cells and / or has its own three-dimensional porous microstructure defined thereby. For example, Figure 2 shows the microstructure 210 of a hardwood, in which vessels 212 are arranged within a hexagonal arrangement of wood fiber cells 216 in longitudinally extending cellular regions. The vessels and fiber cells may extend along the longitudinal direction L of the wood. Thus, the lumen of each vessel 212 may have an extending axis 214 substantially parallel to the longitudinal direction L, and the lumen of each fiber cell 216 may have an extending axis 218 substantially parallel to the longitudinal direction L. Between adjacent regions along the tangential direction T, there are radially extending cellular regions, in which a plurality of radiating cells 220 are located. The radiating cells 220 may extend along the radial direction R of the wood. Thus, the lumen of each radiating cell 220 may have an extending axis 222 substantially parallel to the radial direction R of the wood. Intercellular lamellae are arranged between the vessels 212, fibrous cells 216, and radiating cells 220, serving to connect the cells to each other. Conifers can have a similar microstructure to broad-leaved trees, but the vessels and wood fibers are replaced by tracheids that extend along the longitudinal direction L of the wood.

[0046] The cutting direction of the original wood piece can determine the orientation of the cell lumens in the final structure. For example, in some embodiments, by cutting the natural wood piece perpendicularly or longitudinally (e.g., parallel to the longitudinal growth direction L of the wood) from the trunk 202 of the tree 200, the lumens of longitudinally extending cells can be oriented substantially parallel to the main surface (e.g., maximum surface area) of the longitudinally cut wood piece 206. In the longitudinally cut wood piece 206, the tangential direction T may be substantially perpendicular to the main surface. Alternatively, in some embodiments, by cutting the natural wood piece horizontally or radially (e.g., perpendicular to the longitudinal growth direction L of the wood), the lumens of longitudinally extending cells can be oriented substantially perpendicular to the main surface of the radially cut wood piece 204. Alternatively, in some embodiments, by cutting the natural wood piece in a rotational direction (e.g., perpendicular to the longitudinal direction L and along the circumferential direction of the trunk 202), the lumens of longitudinal cells can be oriented substantially parallel to the main surface of the rotationally cut wood piece 208. In some embodiments, natural wood pieces can be cut in any orientation between longitudinal, radial, and curvilinear cuts. In some embodiments, the cutting orientation of the wood pieces may affect the mechanical properties of the final structure.

[0047] Returning to Figure 1, method 100 proceeds to decision block 104, where it is determined whether the lignin in the plant material should be decomposed (for example, by using partial lignin removal (e.g., a lignin removal process disclosed in either U.S. Patent Application Publication No. 2020 / 0223091 or No. 2022 / 0412002, the relevant portion of which is incorporated herein by reference) and / or lignin modification (e.g., a lignin modification process described in U.S. Patent Application Publication No. 2024 / 0083067, the relevant portion of which is incorporated herein by reference)).

[0048] If decomposition by modification is desired, method 100 proceeds to process block 106, where the plant material can be impregnated with the loading solution. The loading solution may contain an aqueous sodium hydroxide solution (e.g., a concentration of 0-15.0%). Alternatively, the loading solution may also contain sodium sulfite and / or an oxidizing agent such as ozone, oxygen, hydrogen peroxide, or organic peroxide. In some embodiments, the loading solution may be an aqueous system. In some embodiments, the plant material can be immersed in the loading solution. For example, the immersed plant material can be subjected to one or more vacuum cycles to promote the absorption of the loading solution into the plant material. Alternatively, positive pressure can be applied to the system to promote a faster absorption rate. The absorption of the loading solution may occur at a temperature of about 20-100°C. The absorption of the loading solution can be carried out for a sufficient period of time for the loading solution to be uniformly distributed within the plant material. During this process, the water content of the plant material may increase from about 1-20% of the first water content to about 15-100% of the second water content. As used herein, the term "moisture content" is defined as the value obtained by dividing the mass of water in the sample by the mass of dry wood and multiplying by 100%.

[0049] Alternatively, or further, in some embodiments, the loading solution is OH - Having ions, or in solution, OH - It may contain at least one chemical component capable of generating ions. In some embodiments, one, some, or all of the chemicals in the loading solution may be alkaline. In some embodiments, the loading solution used in embodiments of the methods described herein may be sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium sulfite (Na2SO3), sodium sulfide (Na2S), Na n S (n is an integer), urea (CH4N2O), sulfur dioxide (SO2), anthraquinone (AQ) (C 14This may include H8O2), methanol (CH3OH), ethanol (C2H5OH), butanol (C4H9OH), formic acid (CH2O2), hydrogen peroxide (H2O2), acetic acid (CH3COOH), butyric acid (C4H8O2), performic acid (CH2O3), peracetic acid (C2H4O3), ammonia (NH3), tosylic acid (p-TsOH), sodium hypochlorite (NaClO), sodium chlorite (NaClO2), chlorine dioxide (ClO2), chlorine (Cl2), or any combination thereof. Exemplary combinations of chemicals for chemical treatment include NaOH + Na2SO3, NaOH + Na2S, NaOH + urea, NaOH + Na2SO3, NaOH + AQ, NaOH + Na2S + AQ, NaOH + Na2SO3 + AQ, Na2SO3 + AQ, NaOH + Na2S + Na n This includes, but is not limited to, S (where n is an integer), Na2SO3 + NaOH + CH3OH + AQ, C2H5OH + NaOH, CH3OH + HCOOH, NH3 + H2O, and NaClO2 + acetic acid. In some embodiments, the loading solution contains NaHSO3 and / or Na2SO3. For example, the first and second chemical solutions may be ≤2 wt% NaOH and Na2SO3 (e.g., formed by adding H2SO3 acid to NaOH). In some specific embodiments, the loading solution contains NaOH, LiOH, KOH, Na2O, or any combination thereof. Additional exemplary combinations of chemicals in specific embodiments of the methods of this disclosure include, but are not limited to, NaOH, NaOH + Na2SO3 / Na2SO4, NaOH + Na2S, NaOH + Na2SO3, NaOH / NaH2O 3+The following are included: AQ, NaOH / Na2S+AQ, NaOH+Na2SO3+AQ, Na2SO3+NaOH+CH3OH+AQ, NaOH+Na2Sx, any of the above in which NaOH is substituted with LiOH or KOH, or any combination thereof. In some embodiments, the loading solution may contain NaHSO3 and / or Na2SO3, which may be formed by a specific loading solution chemical. In some embodiments, the concentration of the chemical for lignin modification may be 5% by weight or less, for example, in the range of 1-4% by weight. In some embodiments, immersion of plant material in the loading solution can be carried out without heating, for example at room temperature (20-30°C, for example about 22-23°C). In some embodiments, the loading solution is not stirred in order to avoid disturbance of the natural cellulosic microstructure of the plant material pieces.

[0050] For example, in some embodiments, plant material pieces can be immersed in a chemical solution (e.g., 2-5% NaOH) in a container. The container can then be placed in a vacuum box and subjected to reduced pressure (e.g., 0.1 MPa). This allows air to be drawn out from within the plant material, and the absorption of the solution into the plant material pieces proceeds more rapidly. This process can be repeated multiple times (e.g., three times), thereby filling the tubes inside the plant material pieces with the chemical solution (e.g., for about two hours). After this treatment, the moisture content can increase (e.g., from about 10% to over 70% in natural wood).

[0051] Method 100 proceeds to process block 108, where the impregnated plant material piece can be subjected to heating and / or pressurization. For example, after absorbing the loading solution, the treated plant material can be heated and pressurized to promote the reaction between the absorbed loading solution and the lignin in the plant material. The temperature associated with this process may be in the range of 20 to 200°C. The gauge pressure may be in the range of 100 to 1200 MPa. In some embodiments, higher pressures can prevent or at least reduce the evaporation of water in the plant material, even when the temperature exceeds about 100°C.

[0052] For example, treated wood can be subjected to a pressure of approximately 700–850 MPa and a temperature of approximately 150–200°C for approximately 1–5 hours. Under these conditions, the lignin in the wood may be partially decomposed or modified to promote wood softening (especially at high temperatures). Partial decomposition generally reduces the molecular weight of lignin, but not to the extent that the lignin becomes water-soluble. In some embodiments, the temperature of the wood impregnated with the loading solution can be adjusted to increase or decrease the degree of lignin decomposition in the wood. After decomposition, the wood may be cooled to approximately 20°C, and the gauge pressure on the wood may be reduced to approximately 0 MPa.

[0053] In some embodiments, heating may be achieved by steam heating, for example, by steam generated in a closed reactor (e.g., a pressurized reactor), a steam flow in a flow-through reactor, and / or steam from a superheated steam generator. Alternatively, or further, in some embodiments, heating of the process block 108 can be achieved by dry heating, i.e., by conduction and / or radiation of thermal energy from one or more heating elements, without the use of steam.

[0054] In some embodiments, the impregnated plant material pieces can be subjected to a heating state for a first period, for example, 1 to 10 hours (for example, depending on the size of the plant material piece, with thicker pieces requiring longer heating times). In some embodiments, after the first period, the steam generated by heating the impregnated plant material pieces can be released, for example, by opening the reactor pressure release (e.g., a safety valve). For example, in some embodiments, pressure release can remove about 50% of the moisture in the modified plant material pieces. For example, in some embodiments, the softened plant material pieces may have a moisture content in the range of 30 to 50% by weight.

[0055] In some embodiments, impregnation and heating of plant material fragments are effective in modifying the internal lignin, for example, hydroxide ions can hydrolyze ether bonds, shortening the lignin polymer chains and softening the plant material fragments. Furthermore, hydroxide ions can also hydrolyze hemicellulose. This process generates acidic decomposition products that can react with alkaline solutions (e.g., NaOH) to form neutral salts. In some embodiments, black liquor is not observed during the lignin modification process, and the decomposition products from hemicellulose and lignin are completely immobilized within the tubes of the softened plant material fragments. In some embodiments, since all chemicals are consumed during the process, the softened plant material fragments may exhibit a neutral pH.

[0056] Method 100 can proceed to a decision block 110, where it is determined whether washing is necessary. If washing is necessary, Method 100 can proceed to a process block 114, where the treated plant material can be washed with a solvent, for example, deionized (DI) water, alcohol (e.g., ethanol, methanol, isopropanol, etc.), or any combination thereof. In some embodiments, the treated plant material can then be immersed or washed in water to remove some of the lignin that has been broken down until it is water-soluble.

[0057] If, in decision block 104, partial lignin removal is preferred instead, method 100 can proceed to process block 112, where the plant material is subjected to one or more chemical treatments, for example, by immersing a piece of plant material (or a portion thereof) in a chemical solution related to the treatment, thereby removing at least some of the lignin. In some embodiments, each or some of the chemical treatments may be carried out under reduced pressure, thereby promoting complete penetration of the solution related to the treatment into the cell walls and lumens of the plant material. Alternatively, in some embodiments, the chemical treatments may be carried out under atmospheric pressure or pressurized conditions (e.g., about 6–8 bar). In some embodiments, each or some of the chemical treatments may be carried out at any temperature from room temperature (e.g., about 23°C) to a temperature at which the solution related to the chemical treatment boils (e.g., about 100–160°C). In some embodiments, the solution is not stirred in order to minimize disruption of the natural cellulosic microstructure of the plant material piece.

[0058] In some embodiments, the immersion time may be in the range of 0.1 to 96 hours, for example, in the range of 1 to 12 hours. The immersion time in the solution may be a function of the amount of lignin to be removed, the type of plant material, the size of the plant material pieces, the temperature of the solution, the pressure of the treatment, and / or stirring. For example, if the amount of lignin to be removed is small, the size of the plant material pieces (e.g., cross-sectional thickness) is small, the solution temperature is high, the treatment pressure is high, and there is stirring, the immersion time tends to be shorter. On the other hand, if the amount of lignin to be removed is large, the size of the plant material pieces is large, the solution temperature is low, the treatment pressure is low, and there is no stirring, the immersion time tends to be longer.

[0059] The chemical treatment can be continued (or repeated with subsequent solutions) until the lignin content in the plant material pieces is reduced to a desired degree. In some embodiments, the lignin content can be reduced by 5% (95% of the original lignin content in the natural plant material) to 95% (5% of the original lignin content in the natural plant material). In some embodiments, the chemical treatment can reduce the hemicellulose content simultaneously with the lignin content (e.g., to the same extent as or less than the reduction in lignin content).

[0060] Method 100 can proceed to process block 114, where the treated plant material can be washed with a solvent, for example, deionized (DI) water, alcohol (e.g., ethanol, methanol, isopropanol, etc.), or any combination thereof. In some embodiments, washing can be used to remove residual chemicals or particles remaining after the chemical treatment. For example, partially lignin-removed plant material pieces can be partially or completely immersed in one or more washing solutions. In some embodiments, the washing solution can be formed with equal parts water and ethanol. In some embodiments, washing can be carried out without stirring, for example, to avoid disturbance of the microstructure. In some embodiments, washing can be carried out with a fresh mixed washing solution each time, or can be repeated multiple times (e.g., at least three times) until the pH of the chemically treated plant material pieces becomes substantially neutral.

[0061] If lignin degradation is not required in decision block 104, method 100 can proceed to process block 116, where the plant material can be impregnated with water. In some embodiments, lignin degradation may not be required if the initial plant material already has a low lignin content (e.g., 15% by weight or less). Method 100 then proceeds from process block 116 to process block 118, where the hydrated plant material can be heated to a temperature. For example, after impregnation with water, the plant material may be heated to a temperature above approximately 50°C.

[0062] If washing is not required in the decision block 110 or after either the process block 114 or 118, the method 100 proceeds to the process block 120, where the plant material pieces may be dried to reduce their moisture content (e.g., without removing excessive moisture to the point where the plant material pieces lose their softened properties (e.g., so that the moisture content is about 15% by weight or more)). In some embodiments, drying the process block 120 may be effective in reducing the moisture content of the plant material to a range of over 30% by weight (e.g., 30-50% by weight) to less than 25% by weight, e.g., 10-20% by weight.

[0063] In some embodiments, the moisture content of the treated plant material can be reduced to about 10-20% under mild drying conditions before the subsequent processing step. Drying can be achieved using a kiln. Alternatively, drying can also be achieved by reducing the pressure inside the chamber after the treated plant material has been placed inside the chamber. In some embodiments, the treated plant material can be constrained to prevent dimensional deformation during the drying process. For example, the treated plant material can be sandwiched between metal screens and hot-press dried under low pressure to effectively dry the material while preventing or at least reducing dimensional deformation of the plant material. In some embodiments, drying the treated plant material can facilitate the absorption of stabilizers and / or precursors in the subsequent processing step.

[0064] Alternatively, the drying of process block 120 may include any or a combination thereof of conduction, convection, and / or radiation heating processes (including, but not limited to, air drying processes, vacuum-assisted drying processes, oven drying processes, freeze-drying processes, critical point drying processes, and microwave drying processes). For example, an air drying process may include air-drying the processed plant material pieces in stationary or moving air, where the air may be at any temperature (e.g., room temperature (e.g., 23°C) or heated (e.g., above 23°C)). For example, a vacuum-assisted drying process may include exposing the processed plant material pieces to reduced pressure (e.g., less than 0.1 MPa) in, for example, a vacuum chamber or vacuum oven. For example, an oven drying process may include heating the processed plant material pieces to a heated temperature (e.g., above 23°C), for example, 70°C or higher, using an oven, hot plate, or other conduction, convection, or radiation heating device. For example, a freeze-drying process may involve lowering the temperature of a processed plant material piece to below the freezing point of the internal fluid (e.g., below 0°C), then reducing the pressure (e.g., below a few millibars) to sublimate the internal frozen fluid. For example, a critical point drying process may involve immersing a processed plant material piece in a fluid (e.g., liquid carbon dioxide), raising the temperature and pressure of the plant material piece above the critical point of the fluid (e.g., 7.39 MPa, 31.1°C in the case of carbon dioxide), then gradually releasing the pressure to remove the vaporized fluid. For example, a microwave drying process may involve exposing a processed plant material piece to electromagnetic waves in the microwave region (e.g., 300 MHz to 300 GHz), for example, about 915 MHz or about 2.45 GHz, using a microwave oven or other microwave generator to induce dielectric heating.

[0065] Method 100 proceeds to process block 122, where the plant material can be impregnated with a solution of a stabilizer precursor and / or stabilizer. The stabilizer precursor may contain a nucleophile and an electrophile, and the stabilizer may contain a reaction product of the nucleophile and the electrophile. Each stabilizer precursor has a molecular weight of 500 g / mol or less, and upon impregnation, the stabilizer precursor is absorbed into the amorphous cellulose and / or hemicellulose regions of the cell walls of the plant material. Alternatively, or further, in some embodiments, the solution impregnated into the plant material in process block 122 contains a stabilizer, the stabilizer also has a molecular weight of 500 g / mol or less, and upon impregnation, the stabilizer is absorbed into the amorphous cellulose and / or hemicellulose regions of the cell walls of the plant material. In some embodiments, the nucleophile comprises an aromatic nucleophile (e.g., phenol or cresol), and the electrophile comprises an aldehyde (e.g., formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, or glutaraldehyde), an oxirane, an oxazolidine, or a bisoxazolidine, or any combination of an aldehyde and an oxirane, an oxazolidine, or a bisoxazolidine.

[0066] In some embodiments, the nucleophile is phenol, the electrophile is formaldehyde, and the stabilizer is methylolated phenol. For example, in some embodiments, the stabilizer precursor may include an aqueous solution with a viscosity of less than about 40 cPs (20°C). In some embodiments, the solution includes water as the solvent and contains solute molecules dissolved in water. In some embodiments, all (or at least 90%) of the solute molecules in the solution have a molecular weight of less than 500 g / mol. In some embodiments, all (or at least 90%) of the solute molecules in the solution have a molecular weight of less than 300 g / mol. In some embodiments, all (or at least 90%) of the solute molecules are even smaller, for example, with a molecular weight of less than 150 g / mol.

[0067] The combination of a low-viscosity solution and a very low molecular weight solute may offer certain advantages over conventional water stabilization processes. For example, large solute molecules cannot diffuse into certain regions of plant material tissue that have the highest affinity for water molecules, and into regions that cause most of the swelling when water is absorbed into the plant material. Such regions include amorphous cellulose and amorphous hemicellulose. Alternatively, or furthermore, stabilizers may dissolve very well in water, thereby promoting the spontaneous migration of these compounds to amorphous cellulose and / or hemicellulose regions of the cell wall during the impregnation process.

[0068] In some embodiments of the disclosure of the present invention, the stabilizer is highly hydrophilic. In some embodiments, the stabilizer may be water-soluble under alkaline conditions, neutral conditions, or both. In certain embodiments, the stabilizer has a water solubility value of 2 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, for example, 5 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, or 10 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, or 15 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, or 20 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, or 25 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C, or 30 g or more of the compound dissolved in 100 mL of water at a temperature of 20°C. In some embodiments of the disclosure, the stabilizer has a high water solubility value of 30 g or more per 100 mL of water at a temperature of 20°C.

[0069] As used herein, the term “dissolved solute” is intended to exclude “dispersed compounds,” “suspended compounds,” or “emulsified compounds.” The latter compositions generally cannot diffuse into the amorphous cellulose and / or hemicellulose regions of plant cell walls. Therefore, crosslinking of the amorphous cellulose and / or hemicellulose regions of plant cell walls cannot be achieved using dispersed, suspended, or emulsified compounds.

[0070] In some embodiments, stabilizers have the ability to crosslink plant material tissues (amorphous cellulose and / or hemicellulose). The selection of stabilizers is such that the crosslinking reaction does not occur rapidly at low temperatures (e.g., 20-50°C). Rather, the crosslinking reaction is intended to occur relatively slowly at high temperatures (e.g., ≥130°C). This combination of reaction rate characteristics can facilitate a process in which the plant material is first compacted at high temperatures (e.g., around 130°C) (e.g., compaction by compression), and then crosslinked at even higher temperatures (e.g., ≥150°C). Effectively crosslinked amorphous cellulose and / or hemicellulose have some water absorption capacity, but their volume expansion capacity is very limited.

[0071] In some embodiments, the stabilizer precursor may be (i) a mixture of a nucleophile and an electrophile, (ii) a reaction product of a nucleophile and an electrophile, or (iii) a mixture of a nucleophile, an electrophile, and a reaction product. At the time of impregnation, the molecular weights of the electrophile, nucleophile, and reaction product may be independently less than 500 g / mol, for example, greater than 0 g / mol to less than 500 g / mol, greater than 0 g / mol to less than 300 g / mol, or greater than 0 g / mol to 150 g / mol. Techniques for verifying that all solute molecules are low molecular weight include, but are not limited to, gel electrophoresis and mass spectrometry.

[0072] In some aspects of this disclosure, the stabilizer precursor is highly hydrophilic. In certain aspects disclosed in the specification, the stabilizer precursor may be water-soluble under alkaline conditions, neutral conditions, or both. In certain aspects, the stabilizer precursor has a water solubility value of 2 g or more of the compound dissolved in 100 mL of water at 20°C, for example, 5 g or more of the compound dissolved in 100 mL of water at 20°C, or 10 g or more of the compound dissolved in 100 mL of water at 20°C, or 15 g or more of the compound dissolved in 100 mL of water at 20°C, or 20 g or more of the compound dissolved in 100 mL of water at 20°C, or 25 g or more of the compound dissolved in 100 mL of water at 20°C, or 30 g or more of the compound dissolved in 100 mL of water at 20°C. In some aspects of this disclosure, the stabilizer precursor has a high water solubility of 30 g or more of the compound dissolved in 100 mL of water at 20°C.

[0073] In some embodiments, the nucleophile may include aromatic nucleophiles such as phenol, cresol, aniline, resorcinol, aminophenol, metaphenylenediamine, etc. Alternatively, the nucleophile may also include non-aromatic nucleophiles such as urea, morpholine, etc. For some of these nucleophiles, the required water solubility level can be obtained by adjusting the pH of the stabilizer solution.

[0074] In some embodiments, the electrophile may include aldehydes, oxiranes, and oxazolidines (including bisoxazolidines). Aldehydes may include formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, acrolein, and glutaraldehyde. Oxazolidines and bisoxazolidines can provide stabilizers with low volatility. An example of a suitable bisoxazolidine is hydroxymethyl dioxoazabicyclooctane with a molecular weight of 145 g / mol. In another example, a suitable bisoxazolidine is 5-hydroxymethyl-1-aza-3,7-dioxabicyclo[3,3,0]octane.

[0075] In some embodiments, the stabilizer may include a low molecular weight reaction product obtained by reacting the nucleophile with the electrophile. Examples of suitable reaction products include methylolated phenol with a molecular weight of 124 g / mol, or methylolated cresol with a molecular weight of 138 g / mol.

[0076] In some embodiments, a solution of the stabilizer precursor can be prepared by combining a nucleophile, an electrophile, and water in a mixing vessel. The resulting solution can then be used as the stabilizer precursor solution. The ratio of nucleophile to electrophile may be about 1:0.9 to 1:3 in molar ratio (e.g., 1 mole of nucleophile to 2 moles of electrophile). In some embodiments, the stabilizer may contain multiple nucleophiles and / or multiple electrophiles. The water content of the solution containing the stabilizer precursor and / or stabilizer may be in the range of 20 to 95%. In some embodiments, the water content may substantially affect the amount of active solute carried in the plant material during the impregnation process, for example, when the stabilizer is incorporated into the plant material using an immersion treatment. In this type of process, a lower water content results in a higher amount of solute in the plant material.

[0077] In some embodiments, stabilizers can be prepared by reacting a nucleophile with an electrophile to form a low molecular weight reaction product. For example, methylolated phenol can be prepared by reacting phenol with formaldehyde in an aqueous medium. Phenol and, optionally, water, sodium hydroxide, and / or a catalyst can be added to a mixing tank equipped with a heating and cooling system. In some embodiments, sodium carbonate can be used as a catalyst and can be added at a level of about 0.0001 to 0.01% of the mass of phenol in the initial stages of the production process. Formaldehyde can be added to the mixing tank at a predetermined rate or in portions over a certain period of time while continuously stirring. In some embodiments, formaldehyde may be in the form of formalin, such as a 50% formalin solution. In some embodiments, formaldehyde may be in the form of paraformaldehyde. Formaldehyde can be added at a slow rate so as not to overheat the mixture when an exothermic reaction occurs between phenol and formaldehyde. In some embodiments, the temperature of the mixture can be maintained in the range of approximately 50–80°C during this process. The molar ratio of formaldehyde to phenol may be approximately 3.0–1.0. The water content in the mixture may be approximately 30–80%. The sodium hydroxide content (solids) may be approximately 1–15% of the amount of phenol added (mass / mass basis). In some embodiments, it may be desirable to use a sodium hydroxide level of 0.1–3.0% of the mass of the amount of phenol added until almost all of the formaldehyde has reacted with the phenol. This approach helps to avoid formaldehyde disproportionation, which is likely to occur when the pH value exceeds approximately 9. Once all the formaldehyde has been added, the temperature of the mixture can be maintained in the range of approximately 50–80°C, and the mixture can be stirred and heated until a sample of the mixture has a viscosity of approximately 20–35 cPs at a temperature of 20°C. Such a determination can be made using a Gardner-Holt bubble tube or other viscometery. In the final stage of this reaction, formaldehyde can be subsequently added to phenol as a methylol group.Furthermore, a moderate level of oligomer formation may occur during this heating period. The oligomers formed in the mixture may contain two or three substituted phenol groups linked via ether bonds. Oligomer formation should not proceed to the stage where a reaction product with a molecular weight of 500 g / mol or more is formed. Once the viscosity target is reached, the mixture can be rapidly cooled to room temperature. In some embodiments, urea can be added to the mixture in a later stage of the manufacturing process (after or immediately before cooling) to reduce the release of residual formaldehyde that may be present in the mixture. In some embodiments, additional sodium hydroxide can be added to the mixture in a later stage of the manufacturing process to improve the water solubility of the reaction product. In some embodiments, the level of sodium hydroxide in the formulation may be low or may be omitted entirely from the formulation. In some embodiments, the resulting mixture can be used directly as a stabilizer. In other embodiments, the resulting mixture can be further formulated with water, a nucleophile, or an electrophile to obtain a stabilized solution.

[0078] In some embodiments, a high proportion of phenolic molecules in a methylolated phenol composition may exist as single phenol molecules with approximately 1 to 3 methylol groups attached to the ortho and para positions of the phenol ring. These compounds exhibit excellent absorption into plant tissues, particularly cell wall regions based on amorphous cellulose and / or hemicellulose. Oligomers formed by the condensation of approximately 2 to 3 molecules of methylolated phenol compounds can also be absorbed into plant tissues, including cell wall regions based on amorphous cellulose and / or hemicellulose. While oligomers may be absorbed more slowly into plant tissues than monomeric methylolated phenol compounds, smaller oligomers have the advantage of lower vapor pressure than methylolated phenol monomers, which can improve the health and safety of the manufacturing process.

[0079] Compositions containing high molecular weight condensates of methylolated phenol compounds, such as those commonly used as adhesive resins for plywood, oriented strand board, or other wood composite materials, are readily absorbed into cracks and vessels on the surface of plant materials, but generally not into the cell walls of plant material tissue. A commercial example of a high molecular weight condensate of methylolated phenol compounds is the trade name 70CR66 phenolic adhesive resin (manufactured by Bakelite Synthetics, Atlanta, Georgia). High molecular weight phenolic resins are commonly used as wood adhesives and include compositions such as 70CR66, but they do not yield the desired product or performance attributes and are unsuitable for the applications of the embodiments assumed in the subject matter of this disclosure. The average molecular weight of molecules in these phenolic resins can be approximately 1,500 to 5,000 Da. Similarly, the molecular weight in "green phenolic resins" is also typically around 800 to 1,500 Da. Therefore, the molecules in green phenolic resins are also too large to effectively diffuse into the critical areas of plant tissue most relevant to swelling in the presence of water.

[0080] In some embodiments, one or more sections of the treated plant material can be immersed in an aqueous solution containing a stabilizer and / or a stabilizer precursor. The system can be subjected to one or more depressurization cycles to facilitate the absorption of the solution into specific target regions of the plant tissue across the entire cross-section of the plant material. In another embodiment, the treated plant material and aqueous solution are placed in a pressurized vessel, the mixture is brought to positive pressure (gauge pressure about 100 to 4,500 MPa), and the temperature is maintained at about 20 to 50°C.

[0081] The absorption process is continued for a sufficient period to achieve distribution of the stabilizer (and / or its precursor) across the entire cross-section of the treated plant material. In contrast, merely absorbing the stabilizer (and / or its precursor) onto the outer surface of the treated plant material is insufficient, and procedures resulting under such conditions are outside the scope of this disclosure. The immersion time required to achieve absorption of the stabilizer and / or its precursor into the entire cross-section of the plant material can depend on several factors, including the thickness and width dimensions of the plant material, the specific formulation of the stabilizer and / or stabilizer precursor, the temperature, and the pressure applied to the system. For example, a wood section 17 mm thick, 180 mm wide, and 244 cm long may require an immersion time of approximately 3 hours at a temperature of 25°C and a gauge pressure of 725 MPa when using methylolated phenol as the stabilizer.

[0082] During the immersion process with the stabilizer, the moisture content of the treated plant material can increase from a primary moisture content of approximately 1-20% to a secondary moisture content of approximately 10-80%. The amount of absorbed stabilizer solute or absorbed stabilizer precursor solute may be approximately 1-30% of the dry mass of the wood.

[0083] Method 100 can proceed to decision block 124, where it is determined whether to dry the plant material impregnated with the stabilizer precursor or stabilizer solution. If drying is desired, Method 100 can proceed to process block 126, where the plant material is dried in the same manner as described in process block 120 above, for example. For example, the treated and impregnated plant material can be dried to a moisture content of about 1-25% before subsequent processing steps. In some embodiments, this drying step can be carried out in such a manner that the absorbed stabilizer solute does not prematurely crosslink amorphous cellulose and / or hemicellulose before the plant material is compressed to the target level. Appropriate drying conditions depend on the specific stabilizer composition or stabilizer precursor composition and the dimensions of the plant material. In some embodiments, the treated and impregnated plant material can be dried at a temperature of about 60-80°C for about 6-10 hours. During this period, drying the plant material without crosslinking amorphous cellulose and / or hemicellulose can be achieved by selecting a stabilizer with a relatively high activation energy value. For example, stabilizing compositions based on less reactive nucleophiles such as phenol and cresol can help achieve this condition. Alternatively, or further, in some embodiments, a faster drying rate can be promoted without the risk of premature crosslinking by carrying out the drying process under reduced pressure. Suitable equipment for carrying out the drying process includes, but is not limited to, ovens, kilns, and drying presses. In some embodiments, the treated (lignin-degraded) and impregnated plant material can be mechanically restrained to prevent dimensional deformation during the drying process. After the drying process, the treated and impregnated plant material may have a moisture content of about 1-20%.

[0084] After drying process block 126, or if drying is undesirable in determination block 124, method 100 may proceed to determination block 128, where it is determined whether partial compression (e.g., partial compaction) is desirable. If partial compression is desirable, method 100 may proceed to process block 130, where the plant material has a first density of at least 900 kg / m³ 3For example, 900-1200 kg / m 3 It is compressed (for example, at least along its thickness direction) to be within a certain range. In some embodiments, the compression of the process block 130 is controlled to avoid premature crosslinking of either amorphous cellulose and / or hemicellulose (or at least the majority, e.g., 90%) by stabilizers and / or precursors in the plant material.

[0085] In some embodiments, the plant material can be compressed in a direction transverse to the fiber direction. Alternatively, in some embodiments, the compression may be substantially perpendicular to the fiber direction, and in other embodiments, the compression may have a component perpendicular to the fiber direction. In any case, partial compression of process block 128 can be effective in reducing the thickness of the plant material and thereby increasing its density, as well as crushing (at least partially) natural lumens (e.g., xylem vessels, lumens of each fiber, parenchyma cells, etc.), voids and / or gaps within the cross-section of the plant material. In some embodiments, the compression can be performed in a single direction (e.g., along the radial direction R) to reduce the thickness of the plant material piece, for example, by degrading the lignin (e.g., a dimensional reduction of at least 50% compared to the plant material piece before compression). Alternatively, in some embodiments, the plant material piece can be compressed simultaneously in two orthogonal directions (e.g., both perpendicular to the fiber direction) to reduce the cross-sectional area of ​​the plant material piece (e.g., to produce a high-density rectangular strip). Alternatively, in some embodiments, the plant material piece can be compressed sequentially in different orthogonal directions.

[0086] In some embodiments, pressurization can be carried out without pre-drying the plant material pieces or while the plant material pieces retain at least some water or other fluids internally. The pressure and time of pressurization may depend on the size of the plant material pieces before pressurization, the desired size after pressurization, the water or fluid content within the plant material pieces (if any), the temperature at which pressurization is performed, the relative humidity, and / or other factors. For example, plant material pieces can be held under pressure for 1 minute to several hours (e.g., 1 to 180 minutes). In some embodiments, plant material pieces can be held under pressure for 3 to 72 hours. In some embodiments, pressurization can be carried out at a pressure of 0.5 MPa to 20 MPa, e.g., 5 MPa. In some embodiments, pressurization can be carried out without heating (e.g., cold pressurization), and in other embodiments, it can be carried out with heating (e.g., hot pressurization). For example, pressurization can be carried out at a temperature of 20°C to about 160°C, e.g., above 100°C. When plant material is pressurized at a relatively high temperature (e.g., 160°C), the time of the pressurization process can be kept short enough so that the impregnated stabilizer does not prematurely crosslink the amorphous cellulose and / or hemicellulose within the cell walls of the plant material. In some embodiments, pressurization is effective in completely crushing the cavities of the natural cellulosic microstructure of the plant material and / or the density of the compressed plant material is at least 0.9 g / cm³. 3 (For example, >1.1 g / cm³) 3 or greater than 1.2 g / cm³ 3 For example, 1.3~1.5 g / cm³ 3 (This range) can be

[0087] For example, processed, impregnated, and dried plant material can be placed in a press where the temperature of the upper and lower platens of the press is in the range of approximately 20-150°C. The processed, impregnated, and dried plant material can be positioned in the press so that the thickness axis of the plant material is perpendicular to the contact surface of the platen. The pressure applied to the processed, impregnated, and dried plant material can be increased from 0 to approximately 3-8 MPa over 0-10 minutes. The applied pressure can then be maintained until the processed, impregnated, and dried plant material is compressed to approximately 40-60% of its original thickness. At this point, the density of the processed, impregnated, and dried plant material is approximately 900-1,250 kg / m³. 3 This is possible. This compression process may take approximately 15 to 100 minutes, depending on factors such as the original thickness of the plant material, the pressure applied, the platen temperature, the wood species, and other factors including those related to the lignin decomposition process (first step) during the process. While there are economic advantages to performing the compression process as quickly as possible, slowing the compression rate may result in a finished product with improved surface quality (less cracking). In some embodiments, plasticization compression can be achieved without destroying the plant material by partial modification of lignin (and / or hemicellulose) by process blocks 106-108, for example, and / or partial removal of lignin by process blocks 112-114, for example. Once the desired compression level is reached, the pressure applied to the compressed plant material can be released, and then the compressed plant material can be removed from the press. As described above, partial compression can prevent the absorbed stabilizer solute molecules from prematurely crosslinking the amorphous cellulose and / or hemicellulose in the plant material after removal from the press. Alternatively, or further, in some embodiments, the treated, impregnated, and dried plant material is partially compressed in a first compression step, and the density of the compressed plant material is approximately 900-1,250 kg / m³. 3 The water content is approximately 10% or more, and the absorbed stabilizer solute molecules (or their precursors) do not crosslink amorphous cellulose and / or hemicellulose.

[0088] After partial compression in process block 130, or if partial compression is undesirable in decision block 128, the method may proceed to decision block 132, where it is determined whether drying is desirable. If drying is desirable, method 100 may proceed to process block 134, where the plant material is dried in the same manner as described in process block 120, for example. For example, partially compressed plant material can be subjected to an additional drying step, where the moisture content of the plant material is reduced to less than about 10%, for example, in the range of 1-10%. In some embodiments, drying can be carried out using a kiln, or drying can be carried out in a chamber operating under reduced pressure. In some embodiments, the treated, impregnated, and partially compressed plant material can be constrained to prevent dimensional deformation (warping or twisting) during the drying process. Low-temperature, reduced-pressure drying may help prevent stabilizers (or their precursors) absorbed during this process from prematurely crosslinking amorphous cellulose and / or hemicellulose.

[0089] After drying process block 134, or if drying is undesirable in determination block 132, method 100 may proceed to determination block 136, where it is determined whether complete compression (e.g., complete consolidation) is desirable. If complete compression is desirable, method 100 may proceed to process block 138, where the plant material is compressed (e.g., at least along its thickness) to a second density greater than the first density. For example, the second density is at least 1,200 kg / m³ 3 For example, 1,200-1,450 kg / m 3 The range may also be . In some embodiments, the compression of process block 138 can be carried out in the same manner as described above for process block 130. In some embodiments, the dried plant material from process block 134 can be subjected to a final hot pressing step, where the density of the plant material is approximately 1,250 to 1,450 kg / m³. 3The value increases to within the range of [value]. After reaching the target compression level, the absorbed stabilizer solute molecules can crosslink amorphous cellulose and / or hemicellulose to significantly prevent volume expansion in the presence of water.

[0090] For example, processed, impregnated, partially compressed, and dried plant material can be placed in a press where the temperature of the upper and lower platens is in the range of approximately 100-200°C. The plant material can be positioned in the press so that its thickness axis is perpendicular to the contact surface of the platen. The pressure applied to the processed, impregnated, partially compressed, and dried plant material can be increased from 0 to approximately 3-10 MPa in 0-10 minutes. Subsequently, the applied pressure is such that the processed, impregnated, partially compressed, and dried plant material is approximately 1,200-1,450 kg / m³. 3 It can be maintained until it is compressed to a level equivalent to the density of . Alternatively, or further, in some embodiments, the density of the treated, impregnated, partially compressed, and dried plant material can be reduced to approximately 1,300 kg / m³. 3 Values ​​exceeding a certain threshold, for example, at least 1,350 kg / m³ 3 It can be increased up to that point. In some embodiments, the full compression process may take about 2 to 40 minutes, depending on the original thickness of the plant material, the pressure applied, the temperature of the platen, the type of plant material, and other factors (e.g., those related to the partial compression of process block 130).

[0091] In some embodiments, the manufacturing process may utilize only a single compression step (e.g., process block 138 only, without pre-compression by process block 130). In such embodiments, the pressure and associated time of compression (e.g., hot pressurization) can be selected to obtain a desired compression level, and the heating and associated time can be selected to crosslink amorphous cellulose and / or hemicellulose (and optionally lignin) after the target compression level has been reached. In some embodiments, single-step complete compression can be performed on treated, impregnated, and dried plant material with a moisture content of less than about 12%.

[0092] In some embodiments, the compression of process block 138 can be controlled so that amorphous cellulose and / or hemicellulose are not crosslinked before reaching a desired compression level. In such embodiments, after process block 138, method 100 can proceed to process block 140, where amorphous cellulose and / or hemicellulose can be crosslinked with a stabilizer within the plant material. For example, after complete compression of the plant material is achieved, amorphous cellulose and / or hemicellulose can be crosslinked with a stabilizer to prevent significant volume expansion in the presence of water. In some embodiments, after reaching a target compression level, the plant material can be further heated until crosslinking of amorphous cellulose and / or hemicellulose occurs. Alternatively, crosslinking of decomposed lignin can also occur during this step of the process. For example, decomposed lignin in highly compressed plant material can be crosslinked so that previously decomposed lignin is no longer soluble in water. Alternatively, in some embodiments, amorphous cellulose and / or hemicellulose can be crosslinked during at least part of process block 138 (e.g., before the pressure on the plant material is released in the press).

[0093] For example, processed, impregnated, partially compressed, and dried plant material at approximately 1,200-1,450 kg / m³ 3 The plant material, fully compressed to a certain density, is removed from the press and transferred to a kiln, where amorphous cellulose, hemicellulose, and decomposed lignin can be crosslinked. In some embodiments, the plant material can be confined within the kiln to prevent or at least reduce the occurrence of geometric defects such as twisting or warping.

[0094] After crosslinking, method 100 can proceed to process block 142, where the water-stabilized plant material may optionally be machined, cut, transported, assembled, and / or otherwise operated in preparation for final use. Machining processes include, but are not limited to, cutting (e.g., sawing), drilling, woodturning, tapping, boring, carving, routering, polishing, grinding, polishing tumbling, etc. Operating processes include, but are not limited to, bending, forming, and other forming techniques. In some embodiments, one or more pieces (e.g., flakes) of the resulting dimensionally stable, high-density plant material can be laminated to each other or with other pieces or composite materials. For example, laminated veneer or other composite materials can be produced by laminating one or more sections of the resulting dimensionally stable, high-density wood. Lamination can be carried out using, for example, phenolic, isocyanate, polyurethane, or epoxy adhesives.

[0095] In some embodiments, process block 142 also includes using the plant material as a structural member (e.g., load-bearing or non-load-bearing member), such as a building component. For example, a laminate or composite material containing water-stabilized plant material can be used as a beam or other structural member in a residential or commercial building. When used in environments exposed to water, the swelling of plant materials having internally crosslinked amorphous cellulose and / or hemicellulose can be limited to 10% (in the thickness direction of the plant material), regardless of the exposure time to water or the amount of water absorbed. Those skilled in the art will readily understand that the high-density water-stabilized plant materials disclosed herein can be readily applied to a variety of uses based on the teachings of this disclosure.

[0096] Modified plant material products prepared according to this disclosure have much higher density and strength values ​​than the original plant starting material. Furthermore, the water content behavior of the modified product is substantially different from that obtained by simply compressing sections of plant material by hot pressing without the stabilizing treatment described herein. Specifically, the preparation method of this disclosure yields high-density plant material products with significantly reduced swelling capacity, but with retained water absorption capacity. Due to the latter property, the modified plant material products can interact well with water-based adhesives, paints, and other coatings, for example, by absorbing water from paints, coatings, or adhesives. Alternatively, composite materials such as laminated veneers can be manufactured using modified veneers manufactured according to this disclosure, and the composite materials can be manufactured using conventional water-based phenolic adhesives.

[0097] Although blocks 102-142 of Method 100 have been described as being performed only once, in some embodiments, a particular process block may be repeated multiple times before proceeding to the next decision block or process block. Furthermore, although blocks 102-142 of Method 100 have been illustrated and described separately, in some embodiments, process blocks may be performed in combination (simultaneously or sequentially). Moreover, although Figure 1 shows a specific order of blocks 102-142, the embodiments of the subject matter of this disclosure are not limited thereto. In fact, in certain embodiments, blocks may be performed in a different order than that shown, or simultaneously with other blocks. In some embodiments, Method 100 may include steps or other embodiments not specifically shown in Figure 1. Or, or further, in some embodiments, Method 100 may include only a portion of blocks 102-142 of Figure 1.

[0098] Examples of fabrication and experimental results Comparative example: Compressed wood without stabilizers High-density wood was prepared without stabilizers, and the resulting product was subjected to a water immersion test. The results are shown in Figure 3A.

[0099] Two sections of poplar wood (19.1 mm thick x 127 mm wide x 305 mm long), with a dry specific gravity of approximately 0.45 and a moisture content of approximately 8%, were immersed in a 5.0% sodium hydroxide aqueous solution at 20°C and a gauge pressure of 19.3 bar for 18 hours. The immersed wood sections were then heated at 170°C and a gauge pressure of 4 bar for 3 hours. The treated wood sections were then dried at room temperature (20°C, gauge pressure 0) for approximately 10 days until the moisture content was approximately 7%. Subsequently, the sections were placed in a hot press with a platen temperature of 132°C. The press was closed for the first 14 minutes, with a pressure of less than 10 psi. After this initial heating period, the pressure was increased to 2.07 MPa per minute. The sections were held under this pressure for 24 minutes. Subsequently, the pressure was increased to 5.10 MPa per minute. The sections were held under this pressure for 5 minutes. Furthermore, the pressure was increased to 5.56 MPa over 44 minutes. The pressure on the section was then completely released over 1 minute. The section was then removed from the hot press and transferred to a cold press. The section was then cold-pressed at 40°C and 1 MPa for 15 minutes.

[0100] The density of compressed wood is approximately 1.13 kg / m³ 3 The thickness was 7.7 mm. Three test specimens (each 7.7 mm thick × 15.5 mm wide × 100.5 mm long) were cut from the compressed wood section. Initial measurements of mass and dimensions (thickness, width, length) were taken for each specimen. Thickness measurements were taken at the midpoint of the four sides of each specimen. The specimens were then immersed in 1 inch of water for 168 hours. After intermediate immersion periods of 4 hours and 24 hours, the specimens were removed from the water and their mass and dimensions were measured after another 168 hours. The immersion solution at the end of the test was dark purple. The water absorption rate and thickness swelling rate were calculated using the following formulas:

number

number

[0101] [Table 1]

[0102] Example of production: Compressed wood with stabilizers High-density wood was prepared using a stabilizer, and the resulting product was subjected to a water immersion test. The results are shown in Figure 3B.

[0103] Two sections of poplar wood (19.1 mm thick x 127 mm wide x 305 mm long) with a dry specific gravity of approximately 0.45 and a moisture content of approximately 8% were immersed in a 5.0% sodium hydroxide aqueous solution at 20°C and a gauge pressure of 19.3 bar for 18 hours. The immersed wood sections were then heated at 170°C and a gauge pressure of 4 bar for 3 hours. The treated wood sections were then dried at room temperature (20°C, 0 gauge pressure) for approximately 10 days until the moisture content reached approximately 7%.

[0104] From a large section of treated poplar wood, I cut out 16 subsections (17.0mm thick x 20mm wide x 100mm long).

[0105] The stabilizer solution was prepared by the following method: 18 polyethylene bottles (500 mL each) were each filled with 110.0 g of 89% phenol aqueous solution and 1.0 g of 0.10% sodium carbonate aqueous solution. The bottles were tightly sealed and shaken for 15 seconds. Next, 60.0 g of 37% formaldehyde aqueous solution was added to each bottle. The bottles were tightly sealed and shaken for 30 seconds. The sealed bottles were stored at 20°C for 6 hours. A second 60.0 g of 37% formaldehyde aqueous solution was added to each bottle. The bottles were tightly sealed and shaken for 30 seconds. The sealed bottles were stored at 20°C for 15 hours. A third 60.0 g of 37% formaldehyde aqueous solution was added to each bottle. The bottles were tightly sealed and shaken for 30 seconds. The sealed bottles were stored at 20°C for 6 hours. The fourth 37% formaldehyde aqueous solution (60.0 g) was added to each bottle. The bottles were tightly sealed and shaken for 30 seconds. The sealed bottles were stored at 20°C for 15 hours. The calculated solid content of the resulting solution was 53.2%. The viscosity of the solution was less than 20 cPs at 20°C.

[0106] All subsections of treated poplar wood were selected for stabilizer treatment. Each subsection was wrapped in metal mesh and placed in a steel beaker (capacity 10L). Stabilizer was then added to the beaker so that the entire wrapped treated poplar wood subsection was submerged. The beaker was placed in a pressurized container and subjected to positive pressure (gauge pressure 5 bar) at 25°C for 30 minutes. Under these conditions, the treated wood section absorbed approximately the same amount of stabilizer as its own weight. One of the treated subsections was cut transversely to obtain two pieces (each 17.0 mm thick × 20 mm wide × 50 mm long). Observation of the cut surface revealed that the stabilizer had penetrated the entire cross-section of the wood.

[0107] The subsection was placed in a hot press at a platen temperature of 132°C. The press was closed for the first 14 minutes, but the pressure was less than 10 psi. After this initial heating period, the pressure was increased to 2.07 MPa in 1 minute. The subsection was held at this pressure for 24 minutes. Then the pressure was increased to 5.10 MPa in 1 minute. The subsection was held at this pressure for 5 minutes. Further, the pressure was increased to 5.56 MPa in 44 minutes. Then the pressure was completely released in 1 minute. Further, the pressure was increased to 5.56 MPa in 1 minute. The subsection was held at this pressure for 179 minutes. Then the pressure was completely released in 1 minute. The subsection was removed from the hot press and transferred to a cold press. The subsection was cold-pressed at 40°C and 1 MPa for 15 minutes.

[0108] The density of compressed wood is approximately 1.34 kg / m³ 3 The thickness was 8.0 mm. Ten duplicate test specimens (each 8.0 mm thick × 24 mm wide × 81 mm long) were cut from the compressed wood section. Initial measurements of mass and dimensions (thickness, width, length) were taken for each specimen. Thickness measurements were taken at the midpoint of the four sides of each specimen. The specimens were immersed in 1 inch of water for 168 hours. After intermediate immersion periods of 4 hours and 24 hours, the specimens were removed from the water and their mass and dimensions were measured after another 168 hours. The immersion solution at the end of the test was clear and pale yellow. The water absorption rate and thickness swelling rate were calculated using the following formulas.

number

number

[0109] [Table 2]

[0110] Dry, unmodified poplar wood has a swelling capacity of approximately 4.6% radially and 8.2% tangentially. Therefore, compressed poplar wood without stabilizers showed a much larger thickness swelling value (32.0%) than the unmodified material. In contrast, compressed poplar wood prepared with stabilizers had a thickness swelling value of only 8.6%, which was only slightly higher than the value of the unmodified poplar wood.

[0111] Both compressed wood types demonstrated the ability to absorb water, but the water absorption rate of the sample type prepared with a stabilizer was approximately 50% slower than that of the sample type prepared without a stabilizer.

[0112] When the relationship between water absorption and thickness swelling was investigated in compressed wood prepared without the use of stabilizers, a strong linear correlation (R) was found between these two parameters at immersion times of 4, 24, and 168 hours. 2 A relationship of 0.985 was observed. The slope associated with this relationship is approximately 1.01 (see Figure 3B).

[0113] For comparison, compressed wood prepared with a stabilizer showed an almost linear relationship between water absorption and thickness swelling after only immersion times of 4 or 24 hours (R 2A relationship exists (=0.810). The slope of this relationship is approximately 1.04, which is very similar to the slope associated with compressed wood prepared without stabilizers. When compressed wood prepared with stabilizers was immersed for 168 hours, the water absorption value exceeded 9%. When the water absorption value for this type of wood was between 9.4% and 16.8%, the average thickness swelling was only 8.6%. Therefore, it is considered that the maximum thickness swelling value (average) for this type of modified wood is approximately 8.6%. The thickness swelling value of compressed wood prepared without stabilizers was 32.0% after 168 hours of immersion. The maximum swelling value of compressed wood prepared without stabilizers may actually exceed 32.0%, which may have been observed when the water immersion test was conducted for a longer period than 168 hours.

[0114] The compressed timber described herein has a density of approximately 900-1,450 kg / m³. 3 The material has a density range and contains crushed wood cells based on cellulose and / or hemicellulose, with the cell wall regions, particularly those containing amorphous cellulose and / or hemicellulose, being crosslinked to significantly reduce their ability to undergo volume swelling in the presence of water. Decomposed, molded, and further crosslinked lignin exists as a continuous phase between the modified cells. Cell walls impregnated with the stabilizer have a significantly darker hue than cells before treatment. Evidence of the stabilizer treatment is most evident in the changes in the hydration and swelling behavior of the modified plant material, which has the ability to absorb approximately 10–30% of the dry weight of the plant material in water without swelling more than approximately 10% in the compression axis direction. This combination of properties has significant commercial value and has not been previously demonstrated.

[0115] Additional examples of disclosure techniques In consideration of embodiments of the subject matter of the above disclosure, the Application discloses additional examples in the clauses listed below. Note that a single feature of a clause, a combination of features of a clause, and optionally a combination of features of one or more clauses are also further examples included in the disclosure.

[0116] Clause 1. Impregnate the first plant material with a solution containing a stabilizer and / or stabilizer precursor so that the stabilizer and / or stabilizer precursor is absorbed into the amorphous cellulose and / or hemicellulose regions of one or more cell walls of the first plant material; After impregnating the first plant material with the solution, the amorphous cellulose and / or hemicellulose regions are crosslinked with the stabilizer, A method including, (i) The stabilizer precursor comprises a nucleophile and an electrophile, the stabilizer is a reaction product of the nucleophile and the electrophile, and (ii) each of the stabilizer and the stabilizer precursor has a molecular weight of 500 g / mol or less when impregnating the first plant material with the solution.

[0117] Clause 2. The method according to Clause 1, wherein the degree of swelling in the thickness direction of the first plant material containing the stabilizer is 10% or less, regardless of the exposure time to water and / or the amount of water absorbed by the first plant material.

[0118] Clause 3. The nucleophile includes an aromatic nucleophile; The method according to either of Clause 1 or 2, wherein the electrophile comprises (i) an aldehyde, oxirane, oxazolidine, or bisoxazolidine; (ii) both an aldehyde and an oxazolidine; (iii) both an aldehyde and an oxirane; or (iv) both an aldehyde and a bisoxazolidine.

[0119] Clause 4. (i) The aromatic nucleophile includes phenol or cresol; (ii) The electrophile is soluble in water; (iii) The aldehyde includes formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, or glutaraldehyde; or (iv) Any combination of two or more of (i), (ii), and (iii), The method described in any one of the clauses 1 to 3.

[0120] Clause 5. The method according to any one of Clauses 1 to 4, wherein the nucleophile is phenol, the electrophile is formaldehyde, the stabilizer precursor is a monomer and / or oligomer of methylolated phenol, and, if present, the molecular weight of each oligomer is 500 g / mol or less.

[0121] Clause 6. The method according to any one of Clauses 1 to 5, wherein the molar ratio of formaldehyde to phenol in the stabilizer precursor is in the range of 1:1 to 3:1.

[0122] Clause 7.(i) The solution containing the stabilizer precursor is an aqueous solution; (ii) The viscosity of the solution is in the range of 1 to 40 cPs at 20°C; (iii) The stabilizer and / or the stabilizer precursor are present in an amount of 1 to 70% of the mass of the solution; or (iv) Any combination of two or more of (i), (ii), and (iii), The method described in any of clauses 1 to 6.

[0123] Clause 8. The method according to any one of Clauses 1 to 7, further comprising breaking down the natural lignin of an initial plant material to form the first plant material before impregnating the first plant material with the solution, wherein the breakdown of the natural lignin includes modifying the natural lignin in the initial plant material and / or removing at least some of the natural lignin from the initial plant material.

[0124] Article 9. The decomposition of the aforementioned natural lignin, The initial plant material is impregnated with the loading solution; The initial plant material containing the aforementioned loading solution is exposed to a first temperature and a first pressure to modify the natural lignin and obtain modified lignin. Includes, The method according to any one of the claims 1 to 8, wherein the first temperature is in the range of 20 to 200°C and the first pressure is in the range of 1 to 8 bar.

[0125] Clause 10. The method according to any one of Clauses 1 to 9, wherein the loading solution comprises sodium hydroxide, sodium sulfite, an oxidizing agent, or any combination thereof.

[0126] Clause 11. The method according to any one of Clauses 1 to 10, wherein the oxidizing agent comprises ozone, oxygen, hydrogen peroxide, or an organic peroxide.

[0127] Clause 12. The method according to any one of Clauses 1 to 11, wherein the loading solution contains water.

[0128] Clause 13. The moisture content of the initial plant material before impregnation with the loading solution is within the range of 1 to 20% by weight; The method according to any one of the claims 1 to 12, wherein the moisture content of the initial plant material after impregnation with the loading solution and before exposure of the initial plant material containing the loading solution to the first temperature and pressure is in the range of 20 to 100% by weight.

[0129] Clause 14. The method according to any one of Clauses 1 to 13, wherein the molecular weight of the modified lignin is reduced compared to the molecular weight of the natural lignin in the initial plant material, and the modified lignin is insoluble in water at room temperature.

[0130] Clause 15. The method according to any one of Clauses 1 to 14, wherein the decomposition of the natural lignin comprises subjecting the initial plant material to a chemical lignin removal treatment to remove some, but not all, of the natural lignin from the initial plant material.

[0131] Clause 16. The chemical lignin removal treatment of the initial plant material includes partially or completely immersing the initial plant material in one or more chemical solutions at a temperature of at least 100°C. The aforementioned one or more chemical solutions include alkaline solutions. The method described in any one of the clauses 1 through 15.

[0132] Clause 17. The one or more chemical solutions mentioned above include sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium sulfite (Na2SO3), sodium sulfate (Na2SO4), sodium sulfide (Na2S), urea (CH4N2O), NaH2O3, sulfur dioxide (SO2), and anthraquinone (C). 14 The method according to any one of clauses 1 to 16, comprising H8O2), methanol (CH3OH), ethanol (C2H5OH), butanol (C4H9OH), formic acid (CH2O2), hydrogen peroxide (H2O2), acetic acid (CH3COOH), butyric acid (C4H8O2), performic acid (CH2O3), peracetic acid (C2H4O3), ammonia (NH3), tosylic acid (p-TsOH), sodium hypochlorite (NaClO), sodium chlorite (NaClO2), chlorine dioxide (ClO2), chlorine (Cl2), ozone (O3), or any combination thereof.

[0133] Clause 18. The method according to any one of Clauses 1 to 17, wherein the lignin content of the first plant material after decomposition of the natural lignin of the initial plant material is 5% to 95% of the lignin content of the initial plant material.

[0134] Clause 19. The method according to any one of Clauses 1 to 18, further comprising drying the first plant material to a moisture content of 1 to 20% by weight after decomposing the natural lignin and before impregnating the first plant material with the solution.

[0135] Clause 20. Before impregnating the first plant material with the solution, the initial plant material shall be impregnated with a water-containing liquid; Exposing the initial plant material containing the aforementioned liquid to a temperature of at least 50°C, The method described in any one of the provisions 1 to 19, further including the method described in any one of the provisions 1 to 19.

[0136] Clause 21. The method according to any one of Clauses 1 to 20, further comprising impregnating the first plant material with the solution, and then compressing the first plant material containing the stabilizer and / or stabilizer precursor.

[0137] Clause 22. The first plant material containing the stabilizer and / or stabilizer precursor contains at least 900 kg / m³ 3 The method according to any one of the clauses 1 to 21, wherein the result is compressed to a first density.

[0138] Clause 23. The method according to any one of Clauses 1 to 21, wherein the compression of the first plant material containing the stabilizer and / or stabilizer precursor is carried out along the thickness direction of the first plant material, and the thickness of the first plant material after compression is 50% or less of the thickness of the first plant material before compression.

[0139] Clause 24. The above first density is 900-1200 kg / m³ 3 The method described in any one of the clauses 1 to 23, which falls within the scope of the above.

[0140] Clause 25. The method according to any one of Clauses 1 to 24, wherein compression is performed at a temperature in the range of 20 to 150°C and a pressure in the range of 3 to 8 MPa.

[0141] Clause 26. The method according to any one of Clauses 1 to 25, wherein the compression is carried out at a temperature in the range of 20 to 60°C.

[0142] Clause 27. The method according to any one of Clauses 1 to 26, wherein the compression is carried out so that the stabilizer and / or stabilizer precursor in the first plant material does not crosslink the amorphous cellulose and / or hemicellulose regions.

[0143] Clause 28. The method according to any one of Clauses 1 to 27, further comprising drying the first plant material to a water content of 15 to 25% by weight after impregnating the first plant material with the solution and before compressing the first plant material.

[0144] Clause 29. The method according to any one of Clauses 1 to 28, further comprising compressing the first plant material and then drying the first plant material to a moisture content of 1 to 10% by weight.

[0145] Clause 30. The method according to any one of Clauses 1 to 29, wherein the moisture content of the first plant material after drying is approximately 5% by weight.

[0146] Clause 31. The method according to any one of Clauses 1 to 30, further comprising drying the first plant material and then further compressing the first plant material.

[0147] Clause 32. The first plant material described above is at least 1200 kg / m³ 3 The method according to any one of clauses 1 to 31, wherein the result is further compressed to a second density.

[0148] Clause 33. The method according to any one of Clauses 1 to 32, wherein the amorphous cellulose and / or hemicellulose regions are crosslinked by the stabilizer while the first plant material is further compressed.

[0149] Clause 34. The method according to any one of Clauses 1 to 33, wherein the amorphous cellulose and / or hemicellulose regions are crosslinked by the stabilizer after further compression of the first plant material.

[0150] Clause 35. The second density is 1200-1450 kg / m³ 3 The method described in any one of the clauses 1 to 34, which falls within the scope of the above.

[0151] Clause 36. The method according to any one of Clauses 1 to 35, wherein the further compression of the first plant material is carried out at a temperature in the range of 20 to 200°C and a pressure in the range of 3 to 10 MPa.

[0152] Clause 37. While impregnating the first plant material with the solution, (i) The stabilizer is hydrophilic and has a water solubility such that at least 30 g dissolves in 100 mL of water at 20°C; (ii) The stabilizer precursor is hydrophilic and has a water solubility such that at least 2 g dissolves in 100 mL of water at 20°C; or (iii) A combination of (i) and (ii), The method described in any one of the clauses 1 to 36.

[0153] Clause 38. The method according to any one of Clauses 1 to 37, wherein the amorphous cellulose and / or hemicellulose region maintains hydrophilicity after crosslinking.

[0154] Clause 39. The method according to any one of Clauses 1 to 38, wherein the amount of stabilizer and / or stabilizer precursor absorbed into the cell walls of the first plant material after impregnation of the first plant material with the solution is within the range of 1 to 25% by weight of the first plant material in its dry state before impregnation.

[0155] Clause 40. The method according to any one of Clauses 1 to 39, wherein the impregnation of the first plant material with the solution is carried out at a temperature in the range of 20 to 50°C.

[0156] Clause 41. The method according to any one of Clauses 1 to 40, further comprising impregnating the initial plant material with a loading solution before impregnating the first plant material with a solution containing the stabilizer and / or stabilizer precursor.

[0157] Clause 42. The method according to any one of Clauses 1 to 41, wherein the loading solution and / or the solution containing the stabilizer or stabilizer precursor comprises water, sodium hydroxide, a catalyst, or any combination thereof.

[0158] Clause 43. The method according to any one of Clauses 1 to 42, wherein the nucleophile is phenol or cresol and the electrophile is oxazolidine or bisoxazolidine.

[0159] Clause 44. The method according to any one of Clauses 1 to 43, wherein the first plant material is wood.

[0160] Article 45. The method according to any one of Articles 1 to 44, wherein the first plant material is bamboo.

[0161] Clause 46. A structure formed by any one of the methods described in Clauses 1 to 45.

[0162] Clause 47. Plant materials having one or more cell walls including amorphous cellulose regions and hemicellulose regions; A stabilizer that crosslinks amorphous cellulose regions and / or hemicellulose regions of one or more cell walls of the plant material to form a crosslinked plant material, A structure that includes, The aforementioned stabilizer is a reaction product of a nucleophile and an electrophile, A structure in which each of the nucleophile, electrophile, and stabilizer has a molecular weight of 500 g / mol or less before crosslinking.

[0163] Clause 48. The structure according to Clause 47, wherein the degree of swelling of the plant material containing the stabilizer is 10% or less in the thickness direction of the plant material, regardless of the exposure time to water and / or the amount of water absorbed by the plant material.

[0164] Article 49. The nucleophile includes an aromatic nucleophile; The structure according to any one of the clauses 47 to 48, wherein the electrophile comprises (i) an aldehyde, oxirane, oxazolidine, or bisoxazolidine; (ii) both an aldehyde and an oxazolidine; (iii) both an aldehyde and an oxirane; or (iv) both an aldehyde and a bisoxazolidine.

[0165] Clause 50.(i) The aromatic nucleophile comprises phenol or cresol; (ii) The electrophile is soluble in water and contains formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, or glutaraldehyde; or (iii) A combination of (i) and (ii), A structure as described in any one of the clauses 49-49.

[0166] Clause 51. The structure according to any one of Clauses 47 to 50, wherein the nucleophile is phenol or cresol and the electrophile is oxazolidine or bisoxazolidine.

[0167] Clause 52. The structure according to any one of Clauses 47 to 51, wherein at least a portion of the lignin in the plant material is modified compared to the lignin in the natural plant material.

[0168] Clause 53. The structure according to any one of Clauses 47 to 52, wherein the molecular weight of the modified lignin is reduced compared to the molecular weight of lignin in natural plant material, and the modified lignin is insoluble in water at room temperature.

[0169] Clause 54. A structure according to any one of Clauses 47 to 53, wherein the lignin content of the plant material is less than the lignin content of natural plant material.

[0170] Clause 55. The density of the cross-linked plant material is at least 900 kg / m³. 3 A structure as described in any one of clauses 47 to 54.

[0171] Clause 56. The density of the crosslinked plant material is at least 1200 kg / m³. 3 A structure as described in any one of clauses 47 to 55.

[0172] Clause 57. The density of the cross-linked plant material is 1200-1450 kg / m³. 3 A structure described in any one of clauses 47 to 56, which falls within the scope of the above.

[0173] Clause 58. The structure according to any one of Clauses 47 to 57, wherein the plant material is a compacted piece in which the original cavities formed by one or more cell walls of the plant material are substantially collapsed and the cell walls are formed by cell fibers oriented in a common direction.

[0174] The structure according to any one of the clauses 47 to 58, wherein (i) the stabilizer is hydrophilic, and / or (ii) the amorphous cellulose region and / or hemicellulose region crosslinked with the stabilizer is hydrophilic.

[0175] Clause 60. The structure according to any one of Clauses 47 to 59, wherein the stabilizer has a water solubility such that at least 2 g dissolves in 100 mL of water at 20°C.

[0176] Clause 61. The structure according to any one of Clauses 47 to 60, wherein the stabilizer has a water solubility such that at least 30 g dissolves in 100 mL of water at 20°C.

[0177] Clause 62. A structure according to any one of Clauses 47 to 61, wherein the plant material is wood.

[0178] Article 63. A structure according to any one of Articles 47 to 62, wherein the plant material is bamboo.

[0179] conclusion For example, any of the features illustrated or described herein with respect to Figures 1-3B and Clauses 1-63 can be combined with any other features illustrated or described herein with respect to Figures 1-3B and Clauses 1-63 to provide materials, systems, apparatus, structures, methods, and embodiments not illustrated or specifically described herein. All features described herein are independent of each other and can be used in combination with any other features described herein, unless structurally impossible. Given the many possible embodiments to which the principles of the disclosed art may be applied, it should be recognized that the illustrated embodiments are merely examples and do not limit the scope of the disclosed art. Rather, the scope is defined by the following claims. Accordingly, we claim all that is included in the scope and spirit of these claims.

Claims

1. Impregnating a first plant material with a solution containing a stabilizer and / or stabilizer precursor so that the stabilizer and / or stabilizer precursor is absorbed into the amorphous cellulose and / or hemicellulose regions of one or more cell walls of the first plant material; After impregnating the first plant material with the solution, the amorphous cellulose and / or hemicellulose regions are crosslinked with the stabilizer, A method including, (i) The stabilizer precursor comprises a nucleophile and an electrophile, the stabilizer is a reaction product of the nucleophile and the electrophile, and (ii) each of the stabilizer and the stabilizer precursor has a molecular weight of 500 g / mol or less when impregnating the first plant material with the solution.

2. The method according to claim 1, wherein the degree of swelling in the thickness direction of the first plant material containing the stabilizer is 10% or less, regardless of the exposure time to water and / or the amount of water absorbed by the first plant material.

3. The nucleophile includes an aromatic nucleophile; The method according to claim 1, wherein the electrophile comprises (i) an aldehyde, oxirane, oxazolidine, or bisoxazolidine; (ii) both an aldehyde and an oxazolidine; (iii) both an aldehyde and an oxirane; or (iv) both an aldehyde and a bisoxazolidine.

4. (i) The aromatic nucleophile comprises phenol or cresol; (ii) The electrophile is soluble in water; (iii) The aldehyde includes formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, or glutaraldehyde; or (iv) Any combination of two or more of (i), (ii), and (iii), The method according to claim 3.

5. The method according to claim 1, wherein the nucleophile is phenol, the electrophile is formaldehyde, the stabilizer precursor is a monomer and / or oligomer of methylolated phenol, and, if present, the molecular weight of each oligomer is 500 g / mol or less.

6. The method according to claim 5, wherein the molar ratio of formaldehyde to phenol in the stabilizer precursor is in the range of 1:1 to 3:

1.

7. (i) The solution containing the stabilizer precursor is an aqueous solution; (ii) The viscosity of the solution is in the range of 1 to 40 cPs at 20°C; (iii) The stabilizer and / or the stabilizer precursor is present in an amount of 1 to 70% of the mass of the solution; or (iv) Any combination of two or more of (i), (ii), and (iii), The method according to claim 1.

8. The method according to claim 1, further comprising breaking down the natural lignin of an initial plant material to form the first plant material before impregnating the first plant material with the solution, wherein the breakdown of the natural lignin includes modifying the natural lignin in the initial plant material and / or removing at least some of the natural lignin from the initial plant material.

9. The decomposition of the aforementioned natural lignin Impregnating the aforementioned initial plant material with the loading solution; The initial plant material containing the loading solution is exposed to a first temperature and a first pressure to modify the natural lignin and obtain modified lignin. Includes, The method according to claim 8, wherein the first temperature is in the range of 20 to 200°C and the first pressure is in the range of 1 to 8 bar.

10. The method according to claim 9, wherein the loading solution comprises sodium hydroxide, sodium sulfite, an oxidizing agent, or any combination thereof.

11. The method according to claim 10, wherein the oxidizing agent comprises ozone, oxygen, hydrogen peroxide, or an organic peroxide.

12. The method according to claim 9, wherein the loading solution contains water.

13. The moisture content of the initial plant material before impregnation with the loading solution is in the range of 1 to 20% by weight; The method according to claim 9, wherein the moisture content of the initial plant material after impregnation with the loading solution and before exposure of the initial plant material containing the loading solution to the first temperature and pressure is in the range of 20 to 100% by weight.

14. The method according to claim 9, wherein the molecular weight of the modified lignin is reduced compared to the molecular weight of the natural lignin in the initial plant material, and the modified lignin is insoluble in water at room temperature.

15. The method according to claim 8, wherein the decomposition of the natural lignin includes subjecting the initial plant material to a chemical lignin removal treatment to remove some, but not all, of the natural lignin from the initial plant material.

16. The chemical lignin removal treatment of the initial plant material includes partially or completely immersing the initial plant material in one or more chemical solutions at a temperature of at least 100°C. The aforementioned one or more chemical solutions include an alkaline solution. The method according to claim 15.

17. The one or more chemical solutions are sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium sulfite (Na ２ SO ３ ), sodium sulfate (Na ２ SO ４ ), sodium sulfide (Na ２ S), urea (CH ４ N ２ O), NaH ２ O ３ , sulfur dioxide (SO ２ ), anthraquinone (C １４ H ８ O ２ ), methanol (CH ３ OH), ethanol (C ２ H ５ OH), butanol (C ４ H ９ OH), formic acid (CH ２ O ２ ), hydrogen peroxide (H ２ O ２ ), acetic acid (CH ３ COOH), butyric acid (C ４ H ８ O ２ ), performic acid (CH ２ O ３ ), peracetic acid (C ２ H ４ O ３ ), ammonia (NH ３ ), p-toluenesulfonic acid (p-TsOH), sodium hypochlorite (NaClO), sodium chlorite (NaClO ２ ), chlorine dioxide (ClO ２ ), chlorine (Cl ２ ), ozone (O ３ ), or any combination thereof, the method according to claim 16.

18. The method according to claim 15, wherein the lignin content of the first plant material after decomposing the natural lignin of the initial plant material is 5% to 95% of the lignin content of the initial plant material.

19. The method according to claim 8, further comprising drying the first plant material to a moisture content of 1 to 20% by weight after decomposing the natural lignin and before impregnating the first plant material with the solution.

20. Before impregnating the first plant material with the solution, the initial plant material is impregnated with a water-containing liquid; Exposing the initial plant material containing the aforementioned liquid to a temperature of at least 50°C, The method according to claim 1, further comprising:

21. The method according to any one of claims 1, 8, or 20, further comprising impregnating the first plant material with the solution, and then compressing the first plant material containing the stabilizer and / or stabilizer precursor.

22. The first plant material containing the stabilizer and / or stabilizer precursor contains at least 900 kg / m³ ３ The method according to claim 21, wherein the material is compressed to a first density.

23. The method according to claim 21, wherein the compression of the first plant material containing the stabilizer and / or stabilizer precursor is carried out along the thickness direction of the first plant material, and the thickness of the first plant material after compression is 50% or less of the thickness of the first plant material before compression.

24. The first density is 900 to 1200 kg / m³ ３ The method according to claim 22, which is within the range.

25. The method according to claim 21, wherein the compression is performed at a temperature in the range of 20 to 150°C and a pressure in the range of 3 to 8 MPa.

26. The method according to claim 25, wherein the compression is performed at a temperature in the range of 20 to 60°C.

27. The method according to claim 21, wherein the compression is carried out such that the stabilizer and / or stabilizer precursor in the first plant material does not crosslink the amorphous cellulose and / or hemicellulose regions.

28. The method according to claim 21, further comprising drying the first plant material to a water content of 15 to 25% by weight after impregnating the first plant material with the solution and before compressing the first plant material.

29. The method according to claim 21, further comprising compressing the first plant material and then drying the first plant material to a moisture content of 1 to 10% by weight.

30. The method according to claim 29, wherein the moisture content of the first plant material after drying is about 5% by weight.

31. The method according to claim 29, further comprising drying the first plant material and then further compressing the first plant material.

32. The first plant material is at least 1200 kg / m³ ３ The method according to claim 31, wherein the material is further compressed to a second density.

33. The method according to claim 31, wherein the amorphous cellulose and / or hemicellulose regions are crosslinked by the stabilizer while the first plant material is further compressed.

34. The method according to claim 31, wherein the amorphous cellulose and / or hemicellulose regions are crosslinked with the stabilizer after further compression of the first plant material.

35. The second density is 1200 to 1450 kg / m³ ３ The method according to claim 32, which is within the range.

36. The method according to claim 31, wherein the further compression of the first plant material is carried out at a temperature in the range of 20 to 200°C and a pressure in the range of 3 to 10 MPa.

37. While the first plant material is impregnated with the solution, (i) The stabilizer is hydrophilic and has a water solubility such that at least 30 g dissolves in 100 mL of water at 20°C; (ii) The stabilizer precursor is hydrophilic and has a water solubility such that at least 2 g dissolves in 100 mL of water at 20°C; or (iii)(i) and (ii) are combinations The method according to claim 1.

38. The method according to claim 1, wherein the amorphous cellulose and / or hemicellulose region maintains hydrophilicity even after crosslinking.

39. The method according to claim 1, wherein the amount of stabilizer and / or stabilizer precursor absorbed into the cell wall of the first plant material after impregnation of the first plant material with the solution is within the range of 1 to 25% by weight of the first plant material in its dry state before impregnation.

40. The method according to claim 1, wherein the impregnation of the first plant material with the solution is carried out at a temperature in the range of 20 to 50°C.

41. The method according to claim 1, further comprising impregnating an initial plant material with a loading solution before impregnating the first plant material with a solution containing the stabilizer and / or stabilizer precursor.

42. The method according to claim 41, wherein the load solution and / or the stabilizer or stabilizer precursor solution comprises water, sodium hydroxide, a catalyst, or any combination thereof.

43. The method according to claim 1, wherein the nucleophile is phenol or cresol, and the electrophile is oxazolidine or bisoxazolidine.

44. The method according to claim 1, wherein the first plant material is wood.

45. The method according to claim 1, wherein the first plant material is bamboo.

46. A structure formed by the method described in any one of claims 1 to 45.

47. Plant material having one or more cell walls including amorphous cellulose regions and hemicellulose regions; A stabilizer that crosslinks amorphous cellulose regions and / or hemicellulose regions of one or more cell walls of the plant material to form a crosslinked plant material, A structure that includes, The aforementioned stabilizer is a reaction product of a nucleophile and an electrophile, A structure in which each of the nucleophile, electrophile, and stabilizer has a molecular weight of 500 g / mol or less before crosslinking.

48. The structure according to claim 47, wherein the degree of swelling of the plant material containing the stabilizer is 10% or less in the thickness direction of the plant material, regardless of the exposure time to water and / or the amount of water absorbed by the plant material.

49. The nucleophile includes an aromatic nucleophile; The structure according to claim 47, wherein the electrophile comprises (i) an aldehyde, oxirane, oxazolidine, or bisoxazolidine; (ii) both an aldehyde and an oxazolidine; (iii) both an aldehyde and an oxirane; or (iv) both an aldehyde and a bisoxazolidine.

50. (i) The aromatic nucleophile comprises phenol or cresol; (ii) The electrophile is soluble in water and contains formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, or glutaraldehyde; or (iii)(i) and (ii) are combinations The structure according to claim 49.

51. The structure according to claim 47, wherein the nucleophile is phenol or cresol, and the electrophile is oxazolidine or bisoxazolidine.

52. The structure according to claim 47, wherein at least a portion of the lignin in the plant material is modified compared to lignin in natural plant material.

53. The structure according to claim 52, wherein the molecular weight of the modified lignin is reduced compared to the molecular weight of lignin in natural plant materials, and the modified lignin is insoluble in water at room temperature.

54. The structure according to claim 47, wherein the lignin content of the plant material is less than the lignin content in natural plant material.

55. The density of the crosslinked plant material is at least 900 kg / m³ ３ The structure according to claim 47.

56. The density of the crosslinked plant material is at least 1200 kg / m³ ３ The structure according to claim 47.

57. The density of the cross-linked plant material is 1200 to 1450 kg / m³. ３ The structure according to claim 47, which is within the range.

58. The structure according to claim 47, wherein the plant material is a compacted piece in which the original cavities formed by one or more cell walls of the plant material are substantially crushed, and the cellulosic fibers forming the cell walls are oriented in a common direction.

59. (i) The stabilizer is hydrophilic, and / or (ii) the amorphous cellulose region and / or hemicellulose region crosslinked with the stabilizer is hydrophilic, the structure according to claim 47.

60. The structure according to claim 47, wherein the stabilizer has a water solubility such that at least 2 g dissolves in 100 mL of water at 20°C.

61. The structure according to claim 47, wherein the stabilizer has a water solubility such that at least 30 g dissolves in 100 mL of water at 20°C.

62. The structure according to claim 47, wherein the plant material is wood.

63. The structure according to claim 47, wherein the plant material is bamboo.

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