Bamboo-based reconstituted material and method for its production

Abstract

The application provides a bamboo-based recombination material and a preparation method thereof. The bamboo-based recombination material comprises a bamboo material unit with a porous structure and a formaldehyde-free adhesive, the bamboo material unit has cellulose, activated lignin and hemicellulose; wherein the activated lignin has activated active groups and active sites, and covalent bonding can occur between the active groups and the active sites to form ether bonds and / or carbon-carbon bonds; the bamboo material unit contains small molecule substances with fragrance releasing function, and the small molecule substances are derived from hemicellulose. The bamboo-based recombination material of the application not only breaks through the bottleneck of mild dissociation of the cell wall of the bamboo material unit, but also can synergistically activate the self-bonding potential of lignin and efficiently convert the hydrophilic groups and nutritional components of hemicellulose. The bamboo-based recombination material of the application has low water absorption thickness expansion rate, high physical and mechanical properties, can prevent mildew, and has certain fragrance releasing performance.

Description

Technical Field

[0001] This invention relates to a bamboo-based reconstituted material and its preparation method, specifically to a bamboo-based reconstituted material with low water absorption thickness swelling rate, high physical and mechanical properties, mildew resistance, and fragrance release, and its manufacturing method, belonging to the field of bamboo-based materials. Background Technology

[0002] Bamboo materials, as an important fast-growing biomass resource, play a significant role in alleviating the supply and demand imbalance of timber and promoting sustainable development through their high-value utilization. However, existing bamboo-based reconstituted materials still face several technical bottlenecks in practical applications. Because bamboo material units themselves contain a large number of hydrophilic components (such as hemicellulose and free hydroxyl groups), the materials are prone to moisture absorption and swelling in humid environments, with a 24-hour thickness swelling rate typically exceeding 16%, severely impacting the dimensional stability and service life of the products. Currently, this performance is mainly improved by increasing the amount of adhesive applied or adding hydrophobic agents; however, the former increases costs and environmental pressures, while the latter easily introduces chemical residues and reduces the mechanical properties of the material.

[0003] Reference 1 discloses a recombinant material and its preparation method, which improves the corrosion resistance and water resistance of the recombinant material by coating its surface with anti-corrosion and anti-mildew materials and / or hydrophobic materials containing nano-siloxane treatment agents. However, the chemical coating added to its surface not only increases the difficulty of environmental degradation, but also cannot guarantee long-term retention in outdoor application scenarios.

[0004] Reference 2 discloses a long-lasting, slightly odorous wood-based panel, which mainly achieves its odor-releasing properties by incorporating nanoparticles with fragrance-releasing functions. These nanoparticles are made from pepper shells and borates and also possess excellent flame-retardant properties. However, this panel relies on high-value chemicals (such as phenylboronic acid) during processing, and its long-lasting fragrance-releasing function depends on the nanoparticles being sprayed onto the panel substrate as an "external additive." There is a potential risk that the nanoparticles may not bond sufficiently to the substrate, leading to detachment during long-term use.

[0005] Therefore, there is an urgent need to develop a bamboo-based recombinant material that can simultaneously achieve formaldehyde-free bonding, low water absorption and swelling, long-lasting mildew prevention and self-driven functionalization, and to overcome the technical challenge of gentle dissociation of the cell walls of bamboo material units.

[0006] References:

[0007] Reference 1: CN 114290453A

[0008] Reference 2: CN 114772580A Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In view of the technical problems existing in the prior art, the present invention first provides a bamboo-based reconstituted material. The bamboo-based reconstituted material of the present invention not only overcomes the technical bottleneck of the inability of bamboo material unit cell walls to gently dissociate, but also synergistically activates the self-gelling potential of lignin and efficiently converts the hydrophilic groups and nutrient components of hemicellulose. The bamboo-based reconstituted material of the present invention has low water absorption thickness swelling rate, high physical and mechanical properties, mildew resistance, and a certain degree of fragrance release.

[0011] This invention also provides a method for preparing bamboo-based recombinant materials. This method is simple and easy to implement, the raw materials are readily available, and it is suitable for mass production.

[0012] Solution for solving the problem

[0013] This invention provides a bamboo-based reconstituted material, comprising bamboo material units with a porous structure and a formaldehyde-free adhesive, wherein the bamboo material units contain cellulose, activated lignin, and hemicellulose; wherein,

[0014] The activated lignin has activated active groups and active sites, and the active groups and active sites can undergo covalent bonding to form ether bonds and / or carbon-carbon bonds;

[0015] The bamboo material unit contains small molecule substances with fragrance-releasing function, and the small molecule substances are derived from hemicellulose.

[0016] According to the bamboo-based recombinant material of the present invention, the active groups include phenolic hydroxyl groups and / or alcoholic hydroxyl groups, and the active sites include α-carbon active sites;

[0017] The small molecule substances include one or more of aldehydes, furans, and aromatic hydrocarbons.

[0018] According to the bamboo-based reconstituted material of the present invention, the 2-hour water absorption thickness expansion rate of the bamboo-based reconstituted material is less than 8%, and the 24-hour water absorption thickness expansion rate is less than 16%; the three-point bending static strength of the bamboo-based reconstituted material is greater than 12 MPa, and the three-point bending elastic modulus is greater than 2100 MPa.

[0019] According to the bamboo-based reconstituted material of the present invention, the bamboo-based reconstituted material comprises two or more bamboo material units, and the bamboo material units are bonded together by a formaldehyde-free adhesive.

[0020] Preferably, the formaldehyde-free adhesive includes one or more of isocyanate adhesives, soybean protein-based adhesives, polyvinyl acetate emulsion adhesives, or bio-based epoxy resin adhesives.

[0021] The present invention also provides a method for preparing bamboo-based recombinant materials according to the present invention, which includes the following steps:

[0022] Pretreatment steps: The bamboo material is pretreated to obtain a pretreated product. The pretreatment includes physical crushing. Preferably, the pretreatment also includes a softening treatment of the physically crushed bamboo material.

[0023] Preliminary enzymatic hydrolysis step: The pretreated product is subjected to preliminary enzymatic hydrolysis using hemicellulase and cellulase to obtain preliminary enzymatic hydrolysis product;

[0024] Targeted enzymatic hydrolysis fermentation step: The preliminary enzymatic hydrolysis product is subjected to enzymatic hydrolysis fermentation treatment using Clostridium cellulose and / or Saccharomyces cerevisiae to obtain the enzymatic hydrolysis fermentation product.

[0025] According to the preparation method of the present invention, the average particle size of the bamboo material after physical crushing treatment is less than 50 mm;

[0026] The softening treatment temperature is 55-60℃, and the softening treatment time is 24-48h; the water content of the pretreated product is adjusted to 60-70%.

[0027] According to the preparation method of the present invention, the temperature of the preliminary enzymatic hydrolysis treatment is 30-40℃, and the time of the preliminary enzymatic hydrolysis treatment is 4-24h;

[0028] Preferably, on a dry basis, the total amount of cellulase and hemicellulase added is 0.1%-3.0% of the mass of the pretreated product;

[0029] More preferably, the mass ratio of cellulase to hemicellulase is 1:0.5-5.

[0030] According to the preparation method of the present invention, the temperature of the directional enzymatic hydrolysis fermentation step is 25-45℃, the pH value is 4.8-5.2, and the time of the directional enzymatic hydrolysis fermentation step is 12-72h.

[0031] On a dry basis, the amount of Clostridium cellulosum added is 0.05%-2.0% of the mass of the pretreated product; the amount of Saccharomyces cerevisiae added is 0.05%-2.0% of the mass of the pretreated product.

[0032] According to the preparation method of the present invention, the cellulose Clostridium includes one or more of the following: Clostridium thermocellum, Clostridium xantholyticum, Clostridium fibrinolyticum, and Clostridium difficile.

[0033] The brewing yeast includes one or more of the following: Pichia kudrica, Pichia tree, and Wickham yeast.

[0034] According to the preparation method of the present invention, the preparation method further includes a step of hot pressing the enzymatic fermentation product after assembling it with a formaldehyde-free adhesive;

[0035] Preferably, the concentration of the formaldehyde-free adhesive is 10%-20%; and / or, on a dry basis, the application rate of the formaldehyde-free adhesive is 3%-5%;

[0036] The hot pressing temperature is 130-190℃, the hot pressing pressure is 1-5MPa, and the hot pressing time is 0.2-2min / mm.

[0037] The effects of the invention

[0038] The bamboo-based recombinant material of this invention not only overcomes the bottleneck of mild dissociation of the cell walls of bamboo materials, but also synergistically activates the self-gelling potential of lignin and efficiently converts the hydrophilic groups and nutrient components of hemicellulose. The bamboo-based recombinant material of this invention has low water absorption and thickness swelling rate, high physical and mechanical properties, mildew resistance, and a certain degree of fragrance release.

[0039] The preparation method of the bamboo-based recombinant material of the present invention is simple and easy to implement, the raw materials are easy to obtain, and it is suitable for mass production. Attached Figure Description

[0040] Figure 1 Transmission electron microscope (TEM) and scanning electron microscope (SEM) images of the cell walls of bamboo material units are shown.

[0041] Figure 2 The results of nitrogen adsorption tests on bamboo material units are shown.

[0042] Figure 3 The TIC diagram of the odor components of bamboo material units is shown;

[0043] Figure 4 Diagram showing the connection mechanism of lignin self-gluing active functional groups;

[0044] Figure 5 Examples 1-3, and comparative example 1: schematic diagram of the fracture of the elastic modulus test specimen. Detailed Implementation

[0045] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0046] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0047] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0048] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0049] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0050] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0051] <First Aspect>

[0052] A first aspect of the present invention provides a bamboo-based reconstituted material, wherein the bamboo-based reconstituted material comprises bamboo material units having a porous structure and a formaldehyde-free adhesive, wherein the bamboo material units comprise cellulose, activated lignin, and hemicellulose; wherein,

[0053] The activated lignin has activated active groups and active sites, and the active groups and active sites can be covalently bonded to form ether bonds and / or carbon-carbon bonds;

[0054] The bamboo material unit contains small molecule substances with fragrance-releasing function, and the small molecule substances are derived from hemicellulose.

[0055] The bamboo-based recombinant material of this invention not only overcomes the bottleneck of mild dissociation of the cell walls of bamboo materials, but also synergistically activates the self-gelling potential of the original lignin to form activated lignin, and promotes the efficient conversion of hydrophilic groups and nutrient components of hemicellulose to form small molecules with aroma-releasing properties. The bamboo-based recombinant material of this invention has low water absorption thickness swelling rate, high physical and mechanical properties, mildew resistance, and certain aroma-releasing properties.

[0056] In this invention, the activated lignin of the bamboo material unit has activated active groups and active sites, thereby enabling self-gluing under hot-pressing conditions.

[0057] Specifically, the lignin in the bamboo material unit is mainly composed of three structural units: guaiacolyl (G), syringyl (S), and p-hydroxyphenyl (H), linked by ether bonds and carbon-carbon bonds, with the β-O-4 aryl ether bond being the most abundant. The inventors of this invention discovered that the bamboo-based recombinant material of this invention primarily works by acting on the naturally occurring lignin-carbohydrate complex (LCC) in the cell wall, causing the lignin macromolecules to expand and expose more active functional groups.

[0058] The inventors of this invention also discovered that the relatively unstable β-O-4 aryl ether bonds in lignin can undergo homolytic cleavage, generating highly reactive intermediates such as phenolic hydroxyl radicals, alcoholic hydroxyl radicals, and side-chain α-carbon radicals, thus forming active groups and active sites. Subsequently, these highly reactive intermediates undergo re-condensation through multiple pathways to form new, more stable chemical bonds, specifically carbon-carbon bonds and / or ether bonds. This process of breaking existing chemical bonds and forming new covalent bonds is known as lignin's "self-gluing." It reconnects separated bamboo material units at the molecular level, forming a synergistic gluing effect with added formaldehyde-free adhesives, significantly improving the material's mechanical properties and water resistance.

[0059] Specifically, the active group includes phenolic hydroxyl groups and / or alcoholic hydroxyl groups, and the active site includes a side chain α-carbon active site.

[0060] In this invention, the bamboo material unit contains small molecule substances that have fragrance-releasing functions. Specifically, the small molecule substances include one or more combinations of aldehydes, furans, and aromatic hydrocarbons.

[0061] In some specific implementations, the 24-hour water absorption thickness expansion rate of the bamboo-based reconstituted material is less than 16%, and the 2-hour water absorption thickness expansion rate is less than 8%; the three-point bending static strength of the bamboo-based reconstituted material is greater than 12 MPa, and the three-point bending elastic modulus is greater than 2100 MPa.

[0062] In some specific embodiments, the bamboo-based recombinant material comprises two or more bamboo material units bonded together by a formaldehyde-free adhesive; preferably, the formaldehyde-free adhesive comprises one or more combinations of isocyanate adhesives, soybean protein-based adhesives, polyvinyl acetate emulsion adhesives, or bio-based epoxy resin adhesives.

[0063] The raw materials for bamboo material units may include one or more of bamboo bundles, bamboo filaments, bamboo fibers, or bamboo-based solid residues.

[0064] The inventors of this invention have discovered that the formaldehyde-free adhesive, combined with the self-gluing effect of lignin and the enzymatic destruction of the bamboo cell wall layer, enables the reconstruction of the bamboo cell wall layer, thereby enhancing the bonding performance.

[0065] <Second aspect>

[0066] A second aspect of the present invention provides a method for preparing a bamboo-based recombinant material according to the first aspect of the present invention, comprising the following steps:

[0067] Pretreatment steps: The bamboo material is pretreated to obtain a pretreated product. The pretreatment includes physical crushing. Preferably, the pretreatment also includes a softening treatment of the physically crushed bamboo material.

[0068] Preliminary enzymatic hydrolysis step: The pretreated product is subjected to preliminary enzymatic hydrolysis using cellulase and hemicellulase to obtain preliminary enzymatic hydrolysis product;

[0069] Targeted enzymatic hydrolysis fermentation step: The preliminary enzymatic hydrolysis product is subjected to enzymatic hydrolysis fermentation treatment using Clostridium cellulose and / or Saccharomyces cerevisiae to obtain the enzymatic hydrolysis fermentation product.

[0070] This invention utilizes a three-step synergistic process—pretreatment, preliminary enzymatic hydrolysis, and targeted enzymatic fermentation—to gradually disintegrate the dense structure of the cell walls of bamboo material units. Pretreatment creates micropores through physical breaking and softening, laying the foundation for enzymatic hydrolysis. Preliminary enzymatic hydrolysis uses cellulase and hemicellulase to expand the pores and initially degrade hemicellulose into smaller molecules. Targeted enzymatic fermentation specifically activates lignin self-gelling (forming ether / carbon-carbon bonds) and further converts hemicellulose into aroma-releasing molecules. Finally, under hot-press curing, the bamboo-based reconstituted material exhibits low water absorption and swelling, high mechanical strength, and a lasting aroma. The entire process utilizes the bamboo material units' own components for "self-driven" functionalization, eliminating the need for external additives.

[0071] In this invention, the bamboo material is one or a combination of two or more of the following: moso bamboo, early-maturing bamboo, red-shelled bamboo, green-skinned bamboo, Ci bamboo, and pink bamboo.

[0072] In this invention, bamboo materials are pretreated to obtain a pretreated product. The pretreatment includes physical crushing. The physical crushing and softening processes in the pretreatment steps create initial pores, gradually disintegrating the dense structure of the cell walls of the bamboo material units. This invention utilizes physical crushing to create micro-damage channels and permeable pores, effectively disintegrating the degradation barrier of the bamboo material and improving cellulose accessibility.

[0073] In some specific implementation schemes, the average particle size of the bamboo material after physical crushing is less than 50 mm. When the average particle size of the bamboo material after physical crushing is less than 50 mm, it is beneficial for subsequent steps.

[0074] Furthermore, the pretreatment also includes a softening process for the physically crushed bamboo material. The softening process loosens the dense cell wall structure and increases intercellular spaces through gentle osmotic expansion, while efficiently dissolving soluble inhibitory components such as surface waxes, free silica, and tannins, and achieving uniform wetting of the material. This treatment can break down the natural barriers of bamboo material at low cost, improve the accessibility of substrates for subsequent fermentation microorganisms and enzymes, reduce fermentation inhibition, and ensure the uniformity and stability of the fermentation system, laying a key foundation for efficient fermentation and improved product quality.

[0075] In some specific embodiments, after physical crushing, the softening treatment includes immersion in a solvent for softening. The softening temperature is 55-60°C, and the softening time is 24-48 hours. Softening facilitates subsequent preliminary enzymatic hydrolysis steps. The solvent is not particularly limited in this invention and can be selected as needed. Generally, the solvent can be water.

[0076] In some specific implementations, the water content of the pretreated product is adjusted to 60-70%. Adjusting the water content of the pretreated product facilitates the subsequent preliminary enzymatic hydrolysis step.

[0077] Furthermore, the preliminary enzymatic hydrolysis step of this invention includes using cellulase and hemicellulase to perform preliminary enzymatic hydrolysis on the pretreated product to obtain a preliminary enzymatic hydrolysis product. This preliminary enzymatic hydrolysis step can expand pores and soften the structure. This preliminary enzymatic hydrolysis step requires no external additives; hemicellulose conversion directly produces aroma-releasing small molecules, and microbial activity naturally prevents mold growth. Through the synergistic effect of cellulase and hemicellulase, not only is the problem of cell wall dissociation in bamboo material units solved, but also multi-dimensional performance improvements are achieved through the reconstruction of the components of the bamboo material units themselves. It also reduces dependence on chemical reagents, has mild step conditions, is suitable for industrialization, has lower costs, and leaves no toxic residues.

[0078] The inventors of this invention have discovered that the monosaccharides produced during the preliminary enzymatic hydrolysis process can provide nutrients for microorganisms undergoing subsequent targeted enzymatic hydrolysis, enabling the microorganisms to multiply rapidly. Furthermore, this invention pre-hydrolyzes the cellulose and hemicellulose on the surface of bamboo cell walls through a preliminary enzymatic hydrolysis step, thereby breaking down the dense barrier of the bamboo cell walls, further increasing the porosity of the cell walls, and simultaneously opening channels for subsequent Clostridium cellulose and / or Saccharomyces cerevisiae to enter the bamboo cell walls.

[0079] Specifically, in this invention, the temperature of the preliminary enzymatic hydrolysis treatment is 30-50°C, and the time of the preliminary enzymatic hydrolysis treatment is 4-24 hours. When the temperature of the preliminary enzymatic hydrolysis treatment is 30-50°C, the activity of cellulose and / or hemicellulose is the highest, which is conducive to the preliminary enzymatic hydrolysis treatment.

[0080] Specifically, on a dry basis, the total amount of cellulase and hemicellulase added is 0.1%-3.0% of the mass of the pretreated product. When the total amount of cellulase and hemicellulase added is 0.1%-3.0% of the mass of the pretreated product, preliminary enzymatic hydrolysis can be achieved more effectively.

[0081] In some specific embodiments, the mass ratio of cellulase to hemicellulase is 1:0.5-5. When the mass ratio of cellulase to hemicellulase is 1:0.5-5, the synergistic effect between cellulase and hemicellulase can be exerted more effectively.

[0082] Furthermore, the preliminary enzymatic hydrolysis product is subjected to enzymatic fermentation treatment using *Clostridium cellulose* and / or *Saccharomyces cerevisiae* to obtain an enzymatic fermentation product. This invention, through targeted enzymatic fermentation treatment, further degrades the lignin-hemicellulose linkages, dissociates the cellulose, hemicellulose, and lignin structures of the bamboo cell wall, allowing the lignin to fully unfold and expose its active groups. Simultaneously, the hemicellulose is further enzymatically hydrolyzed to produce small molecules with aroma-releasing functions, thereby obtaining bamboo material units. Moreover, the targeted enzymatic fermentation step can gently act on the lignin-carbohydrate complex (LCC), allowing the lignin macromolecules to further unfold and expose more active functional groups. In this invention, *Clostridium cellulose* and *Saccharomyces cerevisiae* can have a synergistic effect; therefore, it is preferable to use *Clostridium cellulose* and / or *Saccharomyces cerevisiae* to perform enzymatic fermentation treatment on the preliminary enzymatic hydrolysis product.

[0083] In some specific embodiments, the cellulose-producing Clostridium includes one or more of the following: Clostridium thermophilum, Clostridium xantholyticum, Clostridium fibrinolyticum, and Clostridium difficile; the brewing yeast includes one or more of the following: Pichia kudrica, Pichia trunk, and Wickham's abnormal yeast. Both the cellulose-producing Clostridium and the brewing yeast can be purchased from Hangzhou Kenong Agricultural Technology Co., Ltd. This invention degrades hemicellulose into smaller molecules through preliminary enzymatic hydrolysis, and further converts it into aroma-releasing substances (such as hexanal and furfural) through targeted enzymatic fermentation, while simultaneously reducing hydrophilic groups. This directly results in low water absorption and swelling, and sustained aroma release.

[0084] In some specific embodiments, the temperature of the directed enzymatic hydrolysis fermentation step is 25-45℃, the pH value is 4.8-5.2, and the time of the directed enzymatic hydrolysis fermentation step is 12-72 hours. Specifically, the *Clostridium cellulose* exhibits the highest activity at 37℃, and *Saccharomyces cerevisiae* exhibits the highest activity at 30℃. In this invention, 25-45℃ is the optimal temperature range for the growth and enzyme production of *Clostridium cellulose* and *Saccharomyces cerevisiae*; if the temperature is too low, the reaction rate is slow, and if it is too high, it may lead to inactivation of the strains.

[0085] On a dry basis, the amount of Clostridium cellulosum added is 0.05%-2.0% of the mass of the pretreated product; the amount of Saccharomyces cerevisiae added is 0.05%-2.0% of the mass of the pretreated product.

[0086] Preferably, the present invention uses Clostridium cellulose and Saccharomyces cerevisiae to perform enzymatic hydrolysis and fermentation treatment on the preliminary enzymatic hydrolysis product to obtain the enzymatic fermentation product. Furthermore, when the amount of Clostridium cellulose added is 0.05%-2.0% of the mass of the pretreated product, and the amount of Saccharomyces cerevisiae added is 0.05%-2.0% of the mass of the pretreated product, Clostridium cellulose and Saccharomyces cerevisiae have a synergistic effect, which is beneficial to the enzymatic hydrolysis and fermentation.

[0087] In some specific embodiments, the preparation method further includes the steps of impregnating the enzymatic fermentation product, i.e., the bamboo material unit, with a formaldehyde-free adhesive, followed by assembly and hot pressing. The bamboo-based reconstituted material of the present invention does not require the addition of other functional chemical additives, especially aldehydes, thus fully realizing the intrinsic value of bamboo materials and is suitable for mass production.

[0088] In some specific implementations, the concentration of the formaldehyde-free adhesive is 10%-20%, and the application amount of the formaldehyde-free adhesive is 3%-5% on a dry basis.

[0089] Further, after drying the impregnated product, it is assembled into preforms. Further, the impregnated product is pre-dried at a temperature of 40-80°C until the moisture content is 5-15%, and then assembled into preforms using a mold.

[0090] In this invention, during the hot pressing process, the heat energy further induces the relatively unstable β-O-4 aryl ether bonds in the lignin structure to undergo homolytic cleavage, generating highly active intermediates such as phenolic hydroxyl radicals and side-chain α-carbon radicals, thus forming active groups such as phenolic hydroxyl and alcoholic hydroxyl groups, as well as side-chain α-carbon active sites.

[0091] Specifically, the hot pressing temperature is 130-190℃, the hot pressing pressure is 1-5MPa, and the hot pressing time is 0.2-2min / mm.

[0092] In this invention, pretreatment and enzymatic hydrolysis expose lignin, and targeted enzymatic fermentation further activates its active groups. Additionally, during hot pressing, the self-gluing of lignin (forming ether / carbon-carbon bonds) and the use of formaldehyde-free adhesives (such as isocyanate adhesives) create a "glue nail" effect, significantly improving mechanical properties.

[0093] Example

[0094] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0095] Cellulase and hemicellulase were purchased from Xiasheng (Beijing) Biotechnology Development Co., Ltd.

[0096] Clostridium cellulose strain and Saccharomyces cerevisiae were purchased from Hangzhou Kenong Agricultural Technology Co., Ltd.

[0097] Example 1

[0098] (1) Raw material pretreatment: Take moso bamboo raw material and crush it into bamboo-based solid residue with an average particle size of about 20 mm using a pulverizer. Then, soak the bamboo-based solid residue in hot water at 58°C for 40 h to soften it and dry it to a moisture content of 60% to obtain the pretreated product.

[0099] (2) Preliminary enzymatic hydrolysis: Take 1 kg of pretreated product, 5 L of acetate-sodium acetate buffer solution (pH 4.8), 6.5 g of cellulase, and 6.5 g of hemicellulase and mix them in a beaker. Use a magnetic stirrer with a speed of 200 rpm to ensure that the cellulase, hemicellulase and pretreated product are mixed evenly to avoid sedimentation. Place the mixture in a constant temperature shaker with an oscillation frequency of 100 rpm and a temperature of 37℃ for 12 h to obtain the preliminary enzymatic hydrolysis product.

[0100] (3) Targeted enzymatic hydrolysis: Add 10g of Clostridium difficile and 12g of Saccharomyces cerevisiae (the mass ratio of Pichia pastoris to Pichia kudriazine) to the preliminary enzymatic hydrolysis product, and continue fermentation in a constant temperature shaker for 24h at a temperature of 40℃ and a shaking frequency of 150rpm to obtain the enzymatic hydrolysis fermentation product. Through multiple cycles of preparation, collect no less than 5kg of enzymatic hydrolysis fermentation product in total.

[0101] (4) Adhesive impregnation and hot pressing: Naturally dried enzymatic fermentation products were impregnated in an isocyanate adhesive with a mass concentration of 20%. The amount of enzymatic fermentation products applied was controlled at 3% on a dry basis to obtain the impregnated product. The impregnated product was then pre-dried in a 60℃ oven until the moisture content was 10%, and then assembled using a mold. A flatbed hot press was used, with the hot pressing temperature set at 150℃, the hot pressing pressure at 5MPa, and the hot pressing time at 0.5min / mm. The impregnated product was then hot-pressed to obtain three pieces with dimensions of 380mm×360mm×16mm and a target density of 0.65g / cm³. 3 Bamboo-based reconstituted materials.

[0102] Example 2

[0103] (1) Raw material pretreatment: Take moso bamboo raw material and crush it into bamboo-based solid residue with an average particle size of about 20 mm using a pulverizer. Then, soak the bamboo-based solid residue in hot water at 58°C for 40 h to soften it and dry it to a moisture content of 60% to obtain the pretreated product.

[0104] (2) Preliminary enzymatic hydrolysis: Take 1 kg of pretreated product, 5 L of acetate-sodium acetate buffer solution (pH 4.8), 6.5 g of cellulase, and 13 g of hemicellulase and mix them in a beaker. Use a magnetic stirrer with a speed of 200 rpm to ensure that the cellulase, hemicellulase and pretreated product are mixed evenly to avoid sedimentation. Place the mixture in a constant temperature shaker with a shaking frequency of 100 rpm and a temperature of 37℃ for 12 h to maintain enzyme activity, thereby obtaining the preliminary enzymatic hydrolysis product.

[0105] (3) Targeted enzymatic hydrolysis: 10g of Clostridium difficile and 12g of Saccharomyces cerevisiae (the mass ratio of Pichia pastoris to Pichia kudriazine) were added to the preliminary enzymatic hydrolysis product, and fermentation was continued in a constant temperature shaker for 24h at a temperature of 40℃ and a shaking frequency of 150rpm to promote uniform distribution of cells and oxygen transport, thereby obtaining the enzymatic fermentation product. Through multiple cycles of preparation, a total of no less than 5 kg of enzymatic fermentation product was collected.

[0106] (4) Adhesive impregnation and hot pressing: Naturally dried enzymatic fermentation products were impregnated in an isocyanate adhesive with a mass concentration of 20%. The amount of enzymatic fermentation products applied was controlled at 3% on a dry basis to obtain the impregnated product. The impregnated product was then pre-dried in a 60℃ oven to a moisture content of 10%, and then assembled using molds. A flatbed hot press was used, with the hot pressing temperature set at 150℃, the hot pressing pressure at 5MPa, and the hot pressing time at 0.5min / mm. The impregnated product was hot-pressed to obtain three pieces with dimensions of 380mm×360mm×16mm and a target density of 0.65g / cm³. 3 Bamboo-based reconstituted materials.

[0107] Example 3

[0108] (1) Raw material pretreatment: Take moso bamboo raw material and crush it into bamboo-based solid residue with an average particle size of about 20 mm using a pulverizer. Then, soak the bamboo-based solid residue in hot water at 58°C for 40 h to soften it and dry it to a moisture content of 60% to obtain the pretreated product.

[0109] (2) Preliminary enzymatic hydrolysis: Take 1 kg of pretreated product, 5 L of acetate-sodium acetate buffer solution (pH 4.8), 6.5 g of cellulase, and 19.5 g of hemicellulase and mix them in a beaker. Use a magnetic stirrer with a speed of 200 rpm to ensure that the cellulase, hemicellulase and pretreated product are mixed evenly to avoid sedimentation. Place the mixture in a constant temperature shaker with an oscillation frequency of 100 rpm and a temperature of 37℃ for 12 h to obtain the preliminary enzymatic hydrolysis product.

[0110] (3) Targeted enzymatic hydrolysis: 10g of Clostridium difficile and 12g of Saccharomyces cerevisiae (the mass ratio of Pichia pastoris to Pichia kudriazine) were added to the preliminary enzymatic hydrolysis product, and fermentation was continued in a constant temperature shaker for 24h at a temperature of 40℃ and a shaking frequency of 150rpm to promote uniform distribution of cells and oxygen transport, thereby obtaining the enzymatic fermentation product. Through multiple cycles of preparation, a total of no less than 5 kg of enzymatic fermentation product was collected.

[0111] (4) Adhesive impregnation and hot pressing: Naturally dried enzymatic fermentation products were impregnated in an isocyanate adhesive with a mass concentration of 20%. The amount of enzymatic fermentation products applied was controlled at 3% on a dry basis to obtain the impregnated product. The impregnated product was then pre-dried in a 60℃ oven to a moisture content of 10%, and then assembled using molds. A flatbed hot press was used, with the hot pressing temperature set at 150℃, the hot pressing pressure at 5MPa, and the hot pressing time at 0.5min / mm. The impregnated product was hot-pressed to obtain three pieces with dimensions of 380mm×360mm×16mm and a target density of 0.65g / cm³. 3 Bamboo-based reconstituted materials.

[0112] Comparative Example 1

[0113] (1) Raw material pretreatment: Take moso bamboo raw material and crush it into bamboo-based solid residue with an average particle size of about 20 mm using a pulverizer. Then, soak the bamboo-based solid residue in hot water at 58°C for 40 h to soften it and dry it to a moisture content of 60% to obtain the pretreated product.

[0114] (2) Adhesive impregnation and hot pressing: The naturally dried pretreated product was impregnated in an isocyanate adhesive with a mass concentration of 20%. On a dry basis, the amount of adhesive applied to the pretreated product was controlled to be 3% to obtain the impregnated product. The impregnated product was then pre-dried in an oven at 60°C until the moisture content was 10%, and then assembled using a mold. A flatbed hot press was used, with the hot pressing temperature set at 150°C, the hot pressing pressure at 5MPa, and the hot pressing time at 0.5min / mm. The impregnated product was hot-pressed to obtain three pieces of bamboo-based reconstituted material with dimensions of 380mm×360mm×16mm and a target density of 0.65g / cm3.

[0115] Performance testing

[0116] 1. Physical and mechanical properties

[0117] The three-point bending performance test was conducted according to the national standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The test was performed on three 380×360×16mm panels prepared in Examples 1-3 and Comparative Example 1 with a bending strength of 0.65 g / cm³. 3 The bending performance of bamboo-based reconstituted materials was tested. Static bending strength is determined by the ratio of bending moment to section modulus under maximum load. This test primarily measures the static bending strength under three-point bending, where a load is applied to the midpoint of a two-point supported specimen. The elastic modulus is calculated based on the slope of the initial linear phase of the stress-strain curve. The internal bonding strength test, according to standard specifications, involves applying a tensile force perpendicular to the surface of the specimen until failure, recording the maximum failure strength. The results are shown in Table 1.

[0118] Table 1

[0119]

[0120] Table 1 shows that the bamboo-based reconstituted materials of Examples 1-3 exhibit significant differences in bending properties. Examples 1-3 show that as the hemicellulase content increased from 0.65% to 1.95%, the static bending strength increased from 12.58 MPa to 18.05 MPa, an increase of 43.5%; the internal bonding strength increased from 0.63 MPa to 0.90 MPa, an increase of 42.9%. Furthermore, as... Figure 5 As shown, in the tests of elastic modulus and static bending strength, Comparative Example 1 exhibits a rough fracture surface with obvious shavings and large-area delamination, corresponding to low elastic modulus and static bending strength, and weak internal bonding strength. In contrast, the specimens of Examples 1-3 show smooth fracture surfaces without obvious delamination, requiring greater loads to fail.

[0121] Furthermore, due to the lack of effective cell wall dissociation and enzymatic hydrolysis, the cell walls of the bamboo material units remained dense, and the degradation-resistant barriers of the cellulose microfibrils and hemicellulose-lignin network remained robust. This made it difficult for adhesives to penetrate into the cell walls, preventing the formation of a strong "glue nail" effect. The lack of a directional enzymatic hydrolysis step in the bamboo-based recombinant material of Comparative Example 1 resulted in the inactivation of the active groups (phenolic hydroxyl groups, alcoholic hydroxyl groups) and active sites (α-carbon) of lignin. During hot pressing, the self-adhesive reaction that forms ether bonds or carbon-carbon bonds could not occur, resulting in lower internal bonding strength of the bamboo-based recombinant material of Comparative Example 1 compared to Examples 1-3. Therefore, the mechanical strength of the bamboo-based recombinant material of Comparative Example 1 was significantly lower than that of Example 1.

[0122] 2. Water resistance test

[0123] The bamboo-based reconstituted materials prepared in Examples 1-3 and Comparative Example 1 were tested for 2-hour and 24-hour water absorption thickness swelling rates. The water absorption thickness swelling rate test of the bamboo-based reconstituted materials was conducted according to the method specified in the national standard GB / T17657–2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". Specifically, the water absorption thickness swelling rate test involved immersing a 50mm × 50mm × 16mm sample in a constant temperature water bath at a pH of 7±1 and a temperature of (63±3)℃ for 2 hours and 24 hours. The results are shown in Table 2 and... Figure 3 As shown.

[0124] Table 2

[0125]

[0126] As shown in Table 2, the 2-hour water absorption thickness swelling rate of the bamboo-based reconstituted materials prepared in Examples 1-3 of this invention is less than 4%, and the 24-hour water absorption thickness swelling rate is 11.1%-12.3%, which is far lower than the level of more than 16% in the prior art. Since Comparative Example 1 failed to change the inherent hydrophilic nature of bamboo and failed to construct an effective water-resistant barrier, the 2-hour and 24-hour water absorption thickness swelling rates of the bamboo-based reconstituted material in Comparative Example 1 are much higher than those in the examples.

[0127] In this invention, the enzymatic hydrolysis and fermentation processes not only remove hemicellulose but, more importantly, activate the self-healing ability of lignin. During hot pressing, the activated lignin forms ether bonds and carbon-carbon bonds, which, together with the formaldehyde-free adhesive, form a dense, hydrophobic cross-linked network that penetrates the entire material, effectively hindering the penetration and diffusion of moisture. Therefore, the bamboo-based reconstituted material of this invention exhibits excellent dimensional stability.

[0128] 3. Aroma release performance test

[0129] (200±10) g of the bamboo-based reconstituted material from Example 3 was placed in a 2500 mL wide-mouth bottle and incubated in an oven at (65±2) ℃ for 2 h±5 min, according to LY / T 3236-2020. After incubation, the sample was cooled at room temperature (20±2) ℃ for 1 h±5 min. The volatile organic compounds released from the sample were then captured using a dynamic headspace method, and the odor characteristics were analyzed using a thermal desorption-gas chromatography-mass spectrometry (GC-MS (GCMS-QP2020 NX)). The results are shown in Table 3.

[0130] Table 3. Results of Odor Characteristic Analysis

[0131]

[0132] The bamboo-based reconstituted material of this invention has a fresh bamboo fragrance, characterized by a greenish and slightly sweet aroma. The overall fragrance is a complex aroma profile dominated by fruity, baked sweetness, and plant-based notes, with an odor intensity level of 1, indicating a mild and pleasant scent. The aroma-releasing substances are mainly aldehydes, acids, and aromatic hydrocarbons. The main components are hexanal (fermented bread and fruity flavors), furfural (bitter almond flavor), isovaleraldehyde (chocolate and peach flavors), and 2-n-pentylfuran (fruity flavor).

[0133] 4. Formaldehyde emission test and total volatile organic compound (TVOC) emission test

[0134] The mildew resistance test of bamboo-based reconstituted materials was conducted according to the testing standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The formaldehyde emission test was conducted according to GB 18584-2024 "Limits of Hazardous Substances in Home Furnishings". The total volatile organic compound (TVOC) emission rate (72h) was conducted according to HJ571-2010 "Technical Requirements for Environmental Labeling Products - Wood-based Panels and Their Products", using the environmental testing chamber method. The test results are shown in Table 4.

[0135] Table 4

[0136]

[0137] As shown in Table 4, the bamboo-based reconstituted materials of Examples 1-3 of the present invention satisfy E NF Formaldehyde emission levels, grade 0 mildew resistance, and E1 formaldehyde emission levels. The preparation method of the bamboo-based reconstituted material of this invention consumes a large amount of nutrients within the bamboo material units during the preliminary and directional enzymatic hydrolysis processes. Simultaneously, the uniform penetration of the formaldehyde-free adhesive followed by hot-press curing results in a large number of dense cross-linked networks forming on the surface and inside of the bamboo-based reconstituted material, thereby significantly reducing mold invasion and limiting formaldehyde release.

[0138] In Comparative Example 1, the high temperature and pressure during hot pressing cause severe thermal degradation of organic components in the bamboo material unit, such as undegraded hemicellulose and sugars. This process is random and uncontrollable, producing a series of complex, low-molecular-weight volatile organic compounds, including various aldehydes (such as acetaldehyde and acrolein), ketones, and organic acids. This results in a total volatile organic compound content far exceeding that of the examples.

[0139] Furthermore, since all soluble sugars and starches are completely preserved inside the bamboo material unit of Comparative Example 1, these nutrients can promote mold growth when exposed to suitable temperature and humidity environments, leading to a decrease in the mold resistance level and the occurrence of mold growth.

[0140] 5. Microscopic pore structure analysis

[0141] To investigate the effect of the method of this invention on the microstructure of bamboo materials, nitrogen adsorption-desorption tests were performed on the dried enzymatic fermentation products from Examples 1-3 using a fully automated specific surface area and pore size analyzer (Micromeritics ASAP 2460). Before the tests, the samples were degassed under vacuum at 105°C for 12 hours. The specific surface area of ​​the samples was calculated using the BET (Brunauer-Emmett-Teller) method, and the pore size distribution was analyzed using the BJH (Barrett-Joyner-Halenda) model. The results are as follows: Figure 2 As shown.

[0142] like Figure 2 As shown, the nitrogen adsorption-desorption isotherms of Examples 1-3 all exhibit typical Type IV curves with H3-type hysteresis loops, indicating the presence of numerous mesoporous structures within the material. It is clearly visible in the figures that as the amount of hemicellulase added increases from 0.65% in Example 1 to 1.95% in Example 3, the nitrogen adsorption capacity of the samples increases sequentially. This indicates that the specific surface area and pore volume of the material also increase accordingly from Example 1 to Example 3. This is mainly because hemicellulase and cellulase have a synergistic effect; after hemicellulase degradation, the cellulose microfibrils are more exposed, facilitating further degradation of the amorphous region by cellulase and expanding the pore size.

[0143] Therefore, the directional enzymatic fermentation treatment employed in this invention can effectively open up the dense structure inside the cell walls of bamboo material units, forming a richer pore network and increasing the specific surface area. This porous structure not only facilitates the subsequent penetration and uniform distribution of formaldehyde-free adhesives, creating a stronger "glue anchoring" effect, but also provides a larger contact area and reaction space for the flow and self-gluing of lignin during hot pressing, thus strongly supporting the improvement of the mechanical properties and dimensional stability of the material of this invention.

[0144] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0145] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A bamboo-based reconstituted material, characterized in that, The bamboo-based recombinant material comprises bamboo material units with a porous structure and a formaldehyde-free adhesive. The bamboo material units contain cellulose, activated lignin, and hemicellulose. The activated lignin has activated active groups and active sites, and the active groups and active sites can undergo covalent bonding to form ether bonds and / or carbon-carbon bonds; The bamboo material unit contains small molecule substances with fragrance-releasing function, and the small molecule substances are derived from hemicellulose.

2. The bamboo-based reconstituted material according to claim 1, characterized in that, The active group includes phenolic hydroxyl and / or alcoholic hydroxyl, and the active site includes an α-carbon active site; The small molecule substances include one or more of aldehydes, furans, and aromatic hydrocarbons.

3. The bamboo-based reconstituted material according to claim 1 or 2, characterized in that, The thickness expansion rate of the bamboo-based reconstituted material after 2 hours of water absorption is less than 8%, and the thickness expansion rate after 24 hours of water absorption is less than 16%; the static bending strength of the bamboo-based reconstituted material at three points is greater than 12 MPa, and the elastic modulus at three points of bending is greater than 2100 MPa.

4. The bamboo-based reconstituted material according to any one of claims 1-3, characterized in that, The bamboo-based reconstituted material comprises two or more bamboo material units, which are bonded together by a formaldehyde-free adhesive. Preferably, the formaldehyde-free adhesive includes one or more of isocyanate adhesives, soybean protein-based adhesives, polyvinyl acetate emulsion adhesives, or bio-based epoxy resin adhesives.

5. A method for preparing a bamboo-based reconstituted material according to any one of claims 1-4, characterized in that, Includes the following steps: Pretreatment steps: The bamboo material is pretreated to obtain a pretreated product. The pretreatment includes physical crushing. Preferably, the pretreatment also includes a softening treatment of the physically crushed bamboo material. Preliminary enzymatic hydrolysis step: The pretreated product is subjected to preliminary enzymatic hydrolysis using hemicellulase and cellulase to obtain preliminary enzymatic hydrolysis product; Targeted enzymatic hydrolysis fermentation step: The preliminary enzymatic hydrolysis product is subjected to enzymatic hydrolysis fermentation treatment using Clostridium cellulose and / or Saccharomyces cerevisiae to obtain the enzymatic hydrolysis fermentation product.

6. The preparation method according to claim 5, characterized in that, The average particle size of bamboo material after physical crushing is less than 50mm; The softening treatment temperature is 55-60℃, and the softening treatment time is 24-48h; the water content of the pretreated product is adjusted to 60-70%.

7. The preparation method according to claim 5 or 6, characterized in that, The temperature of the preliminary enzymatic hydrolysis treatment is 30-40℃, and the time of the preliminary enzymatic hydrolysis treatment is 4-24h; Preferably, on a dry basis, the total amount of cellulase and hemicellulase added is 0.1%-3.0% of the mass of the pretreated product; More preferably, the mass ratio of cellulase to hemicellulase is 1:0.5-5.

8. The preparation method according to any one of claims 5-7, characterized in that, The temperature of the directional enzymatic hydrolysis fermentation step is 25-45℃, the pH value is 4.8-5.2, and the time of the directional enzymatic hydrolysis fermentation step is 12-72h; On a dry basis, the amount of Clostridium cellulosum added is 0.05%-2.0% of the mass of the pretreated product; the amount of Saccharomyces cerevisiae added is 0.05%-2.0% of the mass of the pretreated product.

9. The method according to claim 8, characterized in that, The cellulose-producing Clostridium includes one or more of the following: Clostridium thermocellum, Clostridium xantholyticum, Clostridium fibrinolyticum, and Clostridium difficileum. The brewing yeast includes one or more of the following: Pichia kudrica, Pichia tree, and Wickham yeast.

10. The preparation method according to any one of claims 5-9, characterized in that, The preparation method further includes a step of hot pressing the enzymatic fermentation product after assembling it with a formaldehyde-free adhesive. Preferably, the concentration of the formaldehyde-free adhesive is 10%-20%; and / or, on a dry basis, the application rate of the formaldehyde-free adhesive is 3%-5%; The hot pressing temperature is 130-190℃, the hot pressing pressure is 1-5MPa, and the hot pressing time is 0.2-2min / mm.

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