Bamboo-based biomass foaming material and preparation method thereof

Abstract

The invention provides a bamboo-based biomass foaming material and a preparation method thereof. The bamboo-based biomass foaming material is derived from bamboo cellulose; wherein the bamboo-based biomass foaming material is of a three-dimensional network structure, and the three-dimensional network structure is formed by stacking micro-scale polyhedral cell walls; in addition, pore structures are formed among at least part of the polyhedral cell walls. The three-dimensional network structure of the bamboo-based biomass foaming material is mainly composed of micro-scale polyhedral cell walls, pore structures are arranged among at least part of the polyhedral cell walls, and the bamboo-based biomass foaming material which is excellent in performance and environmentally friendly is obtained.

Description

Technical Field

[0001] This invention relates to a bamboo-based biomass foaming material and its preparation method, belonging to the field of bamboo material application. Background Technology

[0002] The efficient utilization of bamboo materials is a key issue for green development. However, traditional utilization paradigms (such as bamboo plywood and reconstituted bamboo materials) essentially densify bamboo materials for use as structural building materials. This paradigm fails to fully leverage the inherent characteristics of bamboo as a natural polymer composite material—lightweight, high-strength, and porous—limiting its value enhancement potential. Therefore, transforming bamboo materials into high-performance foam materials to replace petroleum-based foam plastics represents a higher-value utilization direction that better aligns with its inherent properties, and is a significant breakthrough in achieving a green and low-carbon transformation.

[0003] However, the naturally dense composite structure of bamboo (cellulose, hemicellulose, and lignin tightly interwoven) is the source of its high strength, but it is also an obstacle to its direct foaming. To prepare foamed materials, this natural structure must first be deconstructed to expose active groups and create foamable conditions. However, traditional chemical or physical deconstruction methods (such as strong acids and bases, high temperature and high pressure) often severely damage the strength of cellulose itself while destroying hemicellulose and lignin, or cause environmental pollution, resulting in a "one-for-all" dilemma.

[0004] Existing technologies, represented by CN120570928A and CN120700074A, introduce a green method of eutectic solvent (DES) pretreatment. DES effectively breaks down the encapsulation of lignin and hemicellulose, reduces cellulose crystallinity, and significantly improves the efficiency of subsequent enzymatic hydrolysis and component separation. However, the intensive DES treatment typically causes bamboo materials to completely disintegrate from a "fiber-reinforced composite material" state into a "solution of active small molecules" at the molecular or oligomer level. While this deep, homogeneous dissociation is beneficial for chemical transformation (such as saccharification and small molecule extraction), it causes the material system to lose its fibrous network framework, which forms its structural basis. Subsequent "reconstruction" can only be achieved through chemical repolymerization (such as synthetic resins), which essentially abandons the naturally excellent mechanical properties of bamboo cellulose, and the reconstruction process is complex and poorly controllable. In short, "over-deconstruction" leads to the loss of the foundation for "high-performance reconstruction."

[0005] Therefore, how to achieve a "controllable, heterogeneous" deconstruction of bamboo materials under green and mild conditions, that is, to effectively break the binding of lignin and other substances and fully expose the active sites of cellulose while maximizing the preservation of the structural integrity and network skeleton of cellulose micro / nanofibers, so as to lay the foundation for the subsequent direct construction of foamed networks with inherent fiber reinforcement effects through physical interactions, has become an urgent technical problem to be solved. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In view of the technical problems existing in the prior art, the present invention first provides a bamboo-based biomass foaming material. The bamboo-based biomass foaming material of the present invention forms a unique three-dimensional network structure through the stacking of microscale polyhedral cell walls. The three-dimensional network structure is mainly composed of microscale polyhedral cell walls, and at least some of the polyhedral cell walls have porous structures, resulting in a high-performance and environmentally friendly bamboo-based biomass foaming material.

[0008] This invention utilizes the cellulose in bamboo materials to form bamboo-based biomass foaming materials with excellent performance through controllable physical interactions.

[0009] Solution for solving the problem

[0010] This invention provides a bamboo-based biomass foaming material, wherein the bamboo-based biomass foaming material is derived from bamboo cellulose; wherein,

[0011] The bamboo-based biomass foaming material has a three-dimensional network structure, which is formed by the stacking of microscale polyhedral cell walls; and...

[0012] At least some of the polyhedral cell walls have a porous structure.

[0013] According to the bamboo-based biomass foaming material of the present invention, the average diameter of the polyhedral cell wall is 50-200 μm.

[0014] According to the bamboo-based biomass foaming material of the present invention, the pore volume of the bamboo-based biomass foaming material is greater than 1.5 cm³. 3 / g, the specific surface area of ​​the bamboo-based biomass foaming material is greater than 1500m². 2 / g, the Zeta potential value of the bamboo-based biomass foaming material is below -10mV.

[0015] The present invention also provides a method for preparing a bamboo-based biomass foaming material according to the present invention, which includes the following steps:

[0016] Steps for obtaining bamboo-based solid residue;

[0017] The bamboo-based solid residue was modified using a eutectic solvent to obtain modified bamboo pulp.

[0018] The modified bamboo pulp was gelled to obtain bamboo-based nanocellulose gel.

[0019] After pre-freezing the bamboo-based nanocellulose gel, moisture was removed by freeze-drying to obtain a porous bamboo-based foam material.

[0020] According to the preparation method of the present invention, the step of obtaining bamboo-based solid residue includes:

[0021] Pretreatment steps: The biomass material is pretreated to obtain a pretreated product. The pretreatment includes mechanical crushing and softening.

[0022] Enzymatic hydrolysis step: The pretreated product is enzymatically hydrolyzed using cellulase and / or hemicellulase to obtain the enzymatic hydrolysate;

[0023] Separation step: The enzymatic hydrolysis product is separated to obtain bamboo-based solid residue.

[0024] According to the preparation method of the present invention, the bamboo bundles or bamboo filaments in the mechanically crushed bamboo material have a length of 10-100 mm, a width of 0.5-5 mm, and a thickness of 0.1-1 mm; the bamboo fibers or bamboo chips have a length of less than 10 mm.

[0025] The softening treatment is performed at a temperature of 55-65℃ for 24-48 hours.

[0026] According to the preparation method of the present invention, the temperature of the enzymatic hydrolysis treatment is 30-50℃, and the time of the enzymatic hydrolysis treatment is 4-12h;

[0027] On a dry basis, the amount of cellulase and / or hemicellulase added is 0.1%-3.0% of the mass of the pretreated product.

[0028] According to the preparation method of the present invention, the eutectic solvent includes choline chloride, urea and aminosulfonic acid; preferably, the molar ratio of choline chloride, urea and aminosulfonic acid is 1:1.5-2.0:0.5-1.0.

[0029] The mass ratio of the bamboo-based solid residue to the eutectic solvent is 1:30-80;

[0030] The modification treatment is performed at a temperature of 60-130℃ for 3-7 hours.

[0031] According to the preparation method of the present invention, the gelation includes diluting the modified bamboo pulp and then subjecting it to ultrafine pulverization to obtain bamboo-based nanocellulose gel.

[0032] Preferably, the particle size after ultrafine pulverization is less than 50 μm;

[0033] According to the preparation method of the present invention, the pre-freezing temperature is below -20°C, and the pre-freezing time is 3-5 hours.

[0034] The effects of the invention

[0035] The three-dimensional network structure of the bamboo-based biomass foaming material of the present invention is mainly composed of microscale polyhedral cell walls, and at least some of the polyhedral cell walls have a porous structure, thereby obtaining a bamboo-based biomass foaming material with excellent performance and environmental friendliness.

[0036] Unlike existing foaming systems that rely on eutectic solvents to completely dissolve biomass components and then chemical resins to reconstruct the network, the material obtained in this invention can form a stable self-supporting structure without the introduction of external polymeric binders, indicating that the cellulose network skeleton is effectively preserved during the processing. Furthermore, the bamboo-based biomass foam material is biodegradable and has high thermal insulation properties. Attached Figure Description

[0037] Figure 1 A schematic diagram of the preparation process of bamboo-based biomass foaming material according to one embodiment of the present invention is shown;

[0038] Figure 2 A comparison diagram of pore volume and specific surface area of ​​bamboo-based biomass foam materials in Examples 1-3 and the comparative examples is shown.

[0039] Figure 3 The thermal insulation effect of the bamboo-based biomass foam material in Example 1 is shown;

[0040] Figure 4 A comparison graph showing the Zeta potential test results of bamboo-based biomass foam materials in Examples 1-3 and the comparative example is shown.

[0041] Figure 5 A comparison chart of the compression performance test results of bamboo-based biomass foam materials in Examples 1-3 is shown;

[0042] Figure 6 The photographs shown are of the bamboo-based biomass foaming material of Embodiment 1 of the present invention from different angles;

[0043] Figure 7 A scanning electron microscope image of the bamboo-based biomass foaming material in Embodiment 1 of the present invention is shown. Detailed Implementation

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0048] 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.

[0049] 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.

[0050] <First Aspect>

[0051] A first aspect of the present invention provides a bamboo-based biomass foaming material, wherein the bamboo-based biomass foaming material is derived from bamboo cellulose; wherein,

[0052] The bamboo-based biomass foaming material has a three-dimensional network structure, which is formed by the stacking of microscale polyhedral cell walls; and...

[0053] At least some of the polyhedral cell walls have a porous structure.

[0054] This invention utilizes the stacking of microscale polyhedral cell walls to form a unique three-dimensional network structure. The three-dimensional network structure is primarily composed of microscale polyhedral cell walls, and at least some of these cell walls have porous structures between them.

[0055] In some specific embodiments, the average diameter of the polyhedral cell wall is 50-200 μm. The bamboo-based biomass foaming material of the present invention retains most of the cell wall structure, which is the main reason why the bamboo-based biomass foaming material has a large specific surface area and pore structure. At the same time, these high aspect ratio nanofibers also give the overall material good compressibility.

[0056] The bamboo-based biomass foaming material of this invention uses bamboo-based solid residue as raw material, thus turning waste into treasure. Furthermore, the prepared bamboo-based biomass foaming material is biodegradable and has high thermal insulation properties, therefore this invention can be used for packaging, thermal insulation layers, and other applications.

[0057] In some specific embodiments, the pore volume of the biomass foaming material is greater than 1.5 cm³. 3 / g, preferably 1.7 cm 3 / g or more; the specific surface area of ​​the bamboo-based biomass foaming material is greater than 1500m². 2 / g, preferably 1800 m 2 / g or more; the zeta potential value of the bamboo-based biomass foaming material is below -10mV, preferably below -15mV.

[0058] This invention not only solves the problem of low resource utilization, but also provides a feasible path for the mass production of bamboo-based foamed materials, supporting the expansion of green material applications.

[0059] <Second aspect>

[0060] A second aspect of the present invention provides a method for preparing a bamboo-based biomass foaming material according to the first aspect of the present invention, comprising the following steps:

[0061] Steps for obtaining bamboo-based solid residue;

[0062] The bamboo-based solid residue was modified using a eutectic solvent (DES) to obtain modified bamboo pulp.

[0063] The modified bamboo pulp was gelled to obtain bamboo-based nanocellulose gel.

[0064] The bamboo-based nanocellulose gel was freeze-dried to remove moisture, resulting in a porous bamboo-based foam material.

[0065] In this invention, the bamboo material is not specifically limited, and may include various bamboo species such as *Phyllostachys edulis*, *Phyllostachys pubescens*, *Phyllostachys liangshanensis*, *Phyllostachys nanmu*, *Phyllostachys pubescens*, *Phyllostachys nigra ... The bamboo species include: silver bamboo, human-faced bamboo, moso bamboo, flowery moso bamboo, flowery bamboo, purple bamboo, spotted bamboo, tortoise-shell bamboo, light bamboo, rigid bamboo, bitter bamboo, golden bamboo, tortoise-patterned bamboo, silver-chain bamboo, jade-edged bamboo, tea-stalk bamboo, arrow bamboo, bubble bamboo, Luohan bamboo, seedling bamboo, goose-feather bamboo, thorny bamboo, yellow bamboo, Chinese bamboo, black bamboo, stone bamboo, lucky bamboo, red bamboo, red-shelled bamboo, early-growing bamboo, large bamboo, water bamboo, bitter bamboo, yellow-stalked black-breasted chicken bamboo, melon bamboo, *Bambusa* species, *Bambusa* species, large green hedge bamboo, *Bambusa* species, and *Bambusa* species. Specifically, the bamboo material of this invention is preferably moso bamboo.

[0066] Furthermore, the method of the present invention can also be applied to other biomass materials besides bamboo, specifically any feasible biomass material in the art. The biomass material can be woody materials (such as various types of wood chips, particleboard, sawdust), switchgrass, miscanthus, rope grass, reeds, rice husks, oat husks, wheat bran, barley husks, rapeseed straw, wheat straw, barley straw, oat straw, rice straw, jute, flax, sisal, abaca, corn cobs, corn stalks, soybean stalks, corn fiber, alfalfa, hay, coconut fiber, sugarcane bagasse, buckwheat, kudzu vine, sorghum, and any mixture of these substances.

[0067] Steps for obtaining bamboo-based solid residue

[0068] In this invention, enzymatic hydrolysis can be performed before obtaining the bamboo-based solid residue. The inventors of this invention discovered that enzymatic hydrolysis can preferentially destroy the anti-degradation barrier of bamboo materials, creating micro-damage channels and laying the foundation for further processing.

[0069] In some specific implementations, the step of obtaining bamboo-based solid residue includes:

[0070] Pretreatment steps: The biomass material is pretreated to obtain a pretreated product. The pretreatment includes mechanical crushing and softening.

[0071] Enzymatic hydrolysis step: The pretreated product is enzymatically hydrolyzed using cellulase and / or hemicellulose to obtain the enzymatic hydrolysate;

[0072] Separation step: The enzymatic hydrolysis product is separated to obtain bamboo-based solid residue.

[0073] In this invention, bamboo materials are pretreated to obtain pretreated products. The pretreatment includes mechanical crushing and softening.

[0074] This invention utilizes mechanical crushing to create micro-damage channels and permeable pores, and effectively dissociates the anti-degradation barrier of bamboo materials. This also increases the channels for subsequent enzymatic hydrolysis and modification steps, greatly improving the efficiency of subsequent steps.

[0075] In some specific implementations, the average length of the bamboo shreds after mechanical crushing is less than 10 mm.

[0076] The softening treatment of biomass materials in this invention is mainly to improve enzymatic hydrolysis efficiency. Softened biomass materials can come into more thorough contact with cellulase, hemicellulase, and other enzymes involved in the hydrolysis process, and it also facilitates the growth and reproduction of microorganisms. The softening treatment provides a suitable moist environment for the microorganisms participating in the hydrolysis, which is beneficial for them to attach to the surface of the cellulose biomass material and penetrate deep into its interior, accelerating metabolic activity.

[0077] In some specific embodiments, after mechanical pulverization, the softening treatment includes immersion in a solvent for softening. The solvent is not particularly limited in this invention and can be selected as needed. Generally, the solvent can be water.

[0078] Specifically, in this invention, the softening treatment temperature is 55-65°C, and the softening treatment time is 24-48 hours.

[0079] Furthermore, this invention utilizes cellulase and / or hemicellulase to enzymatically hydrolyze the pretreated product, obtaining an enzymatic hydrolysate. The inventors of this invention have discovered that the specific degradation by cellulase and hemicellulase can effectively disrupt the degradation barrier of bamboo materials, creating abundant micro-damage channels and permeable pores. Moreover, the enzymatic hydrolysis step can also degrade some of the crystalline regions of hemicellulose and cellulose, loosening the overall structure.

[0080] Preferably, the present invention utilizes cellulase and hemicellulase to enzymatically hydrolyze the pretreated product, wherein the mass ratio of cellulase to hemicellulase is 1:1-2:1. By using cellulase and hemicellulase for treatment, cellulose and hemicellulose can be effectively initially exposed, significantly improving the efficiency of the active components in the eutectic solvent.

[0081] In some specific implementations, the enzymatic hydrolysis treatment is carried out at a temperature of 30-50°C for 4-12 hours. When the enzymatic hydrolysis treatment temperature is 30-50°C and the treatment time is 4-12 hours, the enzymatic hydrolysis is complete, which is beneficial for subsequent processing.

[0082] Specifically, on a dry basis, the amount of cellulase and / or hemicellulase added is 0.1%-3.0% of the mass of the pretreated product. When the amount of cellulase and / or hemicellulase added is 0.1%-3.0% of the mass of the pretreated product, its function can be effectively exerted.

[0083] Finally, the enzymatic hydrolysis product is separated to obtain bamboo-based solid residue, which is used for subsequent processing.

[0084] Modification treatment

[0085] Modified bamboo pulp is obtained by modifying the bamboo-based solid residue using a eutectic solvent. This invention enables the eutectic solvent to penetrate deeper into the bamboo material, allowing it to fully contact and react with the components, thereby modifying and activating the remaining bamboo-based solid residue, which is mainly composed of cellulose.

[0086] In some specific embodiments, the eutectic solvent includes choline chloride, urea, and sulfamic acid. The eutectic solvent system (such as choline chloride-urea-sulfamic acid) specifically removes lignin and reduces the crystallinity of cellulose after enzymatic hydrolysis, thereby synergistically constructing the three-dimensional network structure of the bamboo-based foam material. This invention does not inhibit enzymatic hydrolysis during the preparation process, fully utilizing the synergistic effect of chemical and physical processes to give the foam material a high specific surface area and large pore volume. It should be noted that in this invention, the target of the eutectic solvent treatment is bamboo-based solid residue, which already has multi-scale micro-damage channels formed inside. The eutectic solvent can selectively modify and activate the cellulose surface, rather than dissolving the intact cell wall as a whole, thus avoiding the complete disintegration of the cellulose skeleton.

[0087] In this invention, the protons (H+) provided by aminosulfonic acid in the eutectic solvent + The modification process disrupts the ether and carbon-carbon bonds of the phenylpropane units in lignin, reducing them to soluble fragments. Simultaneously, the quaternary ammonium salt structure of choline chloride exfoliates lignin fragments through ionic interactions, resulting in efficient lignin removal. Furthermore, urea disrupts the hydrogen bond network between cellulose molecular chains, reducing crystallinity and promoting the nanostructuring and reconstruction of cellulose. Moreover, the modification exposes a large number of hydroxyl groups in cellulose. Simultaneously, the eutectic solvent modification creates conditions for the subsequent gelation process, as the exposed cellulose hydroxyl groups facilitate hydrogen bond formation. The lignin removal solves the problems of hydrophilic swelling and mold growth in bamboo materials, ensuring the stability of the gelation step. Through this modification process, the lignin removal rate can reach over 92%, and the cellulose crystallinity can be reduced by approximately 40%.

[0088] Preferably, the molar ratio of choline chloride, urea, and sulfamic acid can be 1:1.5-2.0:0.5-1.0. When the molar ratio of choline chloride, urea, and sulfamic acid is 1:1.5-2.0:0.5-1.0, the eutectic solvent has better thermal and chemical stability, and it is not easily decomposed or deteriorated under high temperature or long-term storage.

[0089] The present invention does not impose any particular limitation on the total amount of eutectic solvent used; it is sufficient to completely soak the bamboo-based solid residue.

[0090] Preferably, the modification treatment temperature is 60-130℃, and the modification treatment time is 3-7 hours. When the modification treatment temperature is 60-130℃ and the modification treatment time is 3-7 hours, the modification treatment is complete, which is beneficial for obtaining the desired porous bamboo-based foamed material. The present invention does not particularly limit the heating method; an oil bath method can be used.

[0091] Furthermore, after modification, water is used to terminate the excessive aggregation of the hydrogen bond network, thereby ending the reaction.

[0092] gelation

[0093] The modified bamboo pulp is gelled to obtain a bamboo-based nanocellulose gel. Through gelation, the numerous hydroxyl groups exposed by the cellulose can form a three-dimensional network structure through hydrogen bonds. Furthermore, the inventors of this invention have discovered that gelation can effectively prevent the formation of a dense, brittle solid due to excessively strong and rapid cross-linking of hydrogen bonds, and instead guide the formation of a bamboo-based nanocellulose gel that is transportable, rich in moisture, and has a three-dimensional network structure.

[0094] In some specific embodiments, the gelation involves diluting the modified bamboo pulp and then subjecting it to ultrafine grinding to obtain bamboo-based nanocellulose gel. During the dilution process, as the eutectic solvent system is gradually diluted, the original strong solvent-cellulose interactions between cellulose molecules are weakened, and the exposed hydroxyl groups re-establish intermolecular interactions dominated by hydrogen bonds, causing the system to spontaneously transform from a fluid slurry into a physical gel structure with a certain yield stress.

[0095] Specifically, the particle size after ultrafine pulverization is less than 50 μm. After ultrafine pulverization, the system gradually changes from a flowing state to a homogeneous and stable gel state during the static process, indicating that a hydrogen bond network between cellulose molecules has been formed.

[0096] Preferably, in this invention, the degree of dilution of the modified bamboo pulp is not particularly limited, and it can generally be diluted to a mass concentration of 0.1-5wt%.

[0097] Finally, the bamboo-based nanocellulose gel is pre-frozen and then freeze-dried to remove moisture, yielding a porous bamboo-based foamed material. Preferably, the pre-freezing temperature is below -20°C, and the pre-freezing time is 3-5 hours.

[0098] Specifically, the bamboo-based nanocellulose gel is pre-frozen and then stored in a freeze dryer for more than 24 hours to achieve complete de-icing and obtain the bamboo-based nanocellulose gel.

[0099] This invention achieves partial degradation of hemicellulose and loosens its structure through enzymatic hydrolysis of biomass materials. The eutectic solvent modification process involves modifying and activating bamboo-based solid residues, primarily composed of cellulose. By gelling the modified bamboo pulp, excessive aggregation of the hydrogen bond network is terminated, and the formation of a dense, brittle solid due to excessively strong and rapid cross-linking of hydrogen bonds is prevented. Instead, it guides the formation of a loose, water-rich nanocellulose gel with a three-dimensional network structure. Further, by pre-freezing and freeze-drying this precursor gel, the aqueous phase (ice crystals) in the gel sublimates, thereby transforming the gel network structure into a porous solid material.

[0100] Example

[0101] 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.

[0102] Cellulase and hemicellulase were purchased from Xiasheng (Beijing) Biotechnology Development Co., Ltd.

[0103] Example 1

[0104] like Figure 1 As shown, using moso bamboo as raw material, the moso bamboo is mechanically crushed into bamboo fragments with an average length of less than 10mm using a crusher; the bamboo fragments are soaked in water at 60℃ for 24 hours to soften them, and then taken out and drained to obtain the pre-treated product.

[0105] 100g of the pretreated product was mixed with 500ml of acetate-sodium acetate buffer (pH 4.8) in a reactor. Then, 0.65g of cellulase and 0.65g of hemicellulase were added, and the mixture was stirred evenly at 200rpm for 10min using a magnetic stirrer. The reactor was then transferred to a constant-temperature water bath and soaked at 37℃ for 12h to obtain the enzymatic hydrolysis product. The enzymatic hydrolysis product was then separated using a filtration separator to obtain bamboo-based solid residue.

[0106] 1174g of choline chloride, 1010g of urea, and 816g of aminosulfonic acid were weighed and mixed to obtain a eutectic solvent. 60g of bamboo-based solid residue was then placed in the eutectic solvent and heated in an oil bath at 110℃ for 6 hours. Deionized water was then added to terminate the reaction, yielding modified bamboo pulp.

[0107] 60g of modified bamboo pulp was diluted with 5940g of deionized water to a mass concentration of 1wt%. The diluted bamboo pulp was then pulverized using an ultrafine pulverizer to an average particle size of less than 50μm to obtain bamboo-based nanocellulose gel.

[0108] Bamboo-based nanocellulose gel was pre-frozen in a freezer at -20°C for 4 hours, and then stored in a freeze dryer for 48 hours to completely remove the ice, yielding bamboo-based biomass foaming material (e.g. Figure 5 and Figure 6 (As shown).

[0109] Example 2

[0110] like Figure 1 As shown, using moso bamboo as raw material, the moso bamboo is mechanically crushed into bamboo fragments with an average length of less than 10mm using a crusher; the bamboo fragments are soaked in water at 60℃ for 24 hours to soften them, and then taken out and drained to obtain the pre-treated product.

[0111] 100g of the pretreated product was mixed with 500ml of acetate-sodium acetate buffer (pH 4.8) in a reactor. Then, 0.65g of cellulase and 0.65g of hemicellulase were added, and the mixture was stirred evenly at 200rpm for 10min using a magnetic stirrer. The reactor was then transferred to a constant-temperature water bath and soaked at 37℃ for 12h to obtain the enzymatic hydrolysis product. The enzymatic hydrolysis product was then separated using a filtration separator to obtain bamboo-based solid residue.

[0112] 1359g of choline chloride, 1168g of urea, and 472g of aminosulfonic acid were weighed and mixed to obtain a eutectic solvent. 60g of bamboo-based solid residue was then placed in the eutectic solvent and heated in an oil bath at 110°C for 6 hours. Deionized water was then added to terminate the reaction, yielding modified bamboo pulp.

[0113] 60g of modified bamboo pulp was diluted with 5940g of deionized water to a mass concentration of 1wt%. The diluted bamboo pulp was then pulverized using an ultrafine pulverizer to an average particle size of less than 50μm to obtain bamboo-based nanocellulose gel.

[0114] Bamboo-based nanocellulose gel was pre-frozen in a freezer at -20°C for 4 hours, and then stored in a freeze dryer for 48 hours to completely remove the ice, thus obtaining bamboo-based biomass foam material.

[0115] Example 3

[0116] like Figure 1 As shown, using moso bamboo as raw material, the moso bamboo is mechanically crushed into bamboo fragments with an average length of less than 10mm using a crusher; the bamboo fragments are soaked in water at 60℃ for 24 hours to soften them, and then taken out and drained to obtain the pre-treated product.

[0117] 100g of the pretreated product was mixed with 500ml of acetate-sodium acetate buffer (pH 4.8) in a reactor. Then, 0.65g of cellulase and 0.65g of hemicellulase were added, and the mixture was stirred evenly at 200rpm for 10min using a magnetic stirrer. The reactor was then transferred to a constant-temperature water bath and soaked at 37℃ for 12h to obtain the enzymatic hydrolysis product. The enzymatic hydrolysis product was then separated using a filtration separator to obtain bamboo-based solid residue.

[0118] 1281g of choline chloride, 826g of urea, and 891g of aminosulfonic acid were weighed and mixed to obtain a eutectic solvent. 60g of bamboo-based solid residue was then placed in the eutectic solvent and heated in an oil bath at 110°C for 6 hours. Deionized water was then added to terminate the reaction, yielding modified bamboo pulp.

[0119] 60g of modified bamboo pulp was diluted with 5940g of deionized water to a mass concentration of 1wt%. The diluted bamboo pulp was then pulverized using an ultrafine pulverizer to an average particle size of less than 50μm to obtain bamboo-based nanocellulose gel.

[0120] Bamboo-based nanocellulose gel was pre-frozen in a freezer at -20°C for 4 hours, and then stored in a freeze dryer for 48 hours to completely remove the ice, thus obtaining bamboo-based biomass foam material.

[0121] Comparative Example 1

[0122] Using moso bamboo as raw material, the moso bamboo is mechanically crushed into bamboo fragments with an average length of less than 10mm using a crusher; the bamboo fragments are soaked in water at 60℃ for 24 hours to soften them, and then taken out and drained to obtain the pre-treated product.

[0123] 100g of the pretreated product was mixed with 500ml of acetate-sodium acetate buffer (pH 4.8) in a reactor. Then, 0.65g of cellulase and 0.65g of hemicellulase were added, and the mixture was stirred evenly at 200rpm for 10min using a magnetic stirrer. The reactor was then transferred to a constant-temperature water bath and soaked at 37℃ for 12h to obtain the enzymatic hydrolysis product. The enzymatic hydrolysis product was then separated using a filtration separator to obtain bamboo-based solid residue.

[0124] 60g of bamboo-based solid residue was diluted with 5940g of deionized water to a mass concentration of 1wt%. The diluted bamboo pulp was then pulverized using an ultrafine pulverizer to an average particle size of less than 50μm to obtain bamboo-based nanocellulose gel.

[0125] Bamboo-based nanocellulose gel was pre-frozen in a freezer at -20°C for 4 hours, and then stored in a freeze dryer for 48 hours to completely remove the ice, thus obtaining bamboo-based biomass foam material.

[0126] Comparative Example 2

[0127] Using moso bamboo as raw material, the moso bamboo is mechanically crushed into bamboo fragments with an average length of less than 10mm using a crusher; the bamboo fragments are soaked in water at 60℃ for 24 hours to soften them, and then taken out and drained to obtain the pre-treated product.

[0128] 1174g of choline chloride, 1010g of urea, and 816g of aminosulfonic acid were weighed and mixed to obtain a eutectic solvent. 60g of the pretreated product was then placed in the eutectic solvent and heated in an oil bath at 110°C for 6 hours. Deionized water was then added to terminate the reaction, yielding modified bamboo pulp.

[0129] 60g of modified bamboo pulp was diluted with 5940g of deionized water to a mass concentration of 1wt%. The diluted bamboo pulp was then pulverized using an ultrafine pulverizer to an average particle size of less than 50μm to obtain bamboo-based nanocellulose gel.

[0130] Bamboo-based nanocellulose gel was pre-frozen in a freezer at -20°C for 4 hours, and then stored in a freeze dryer for 48 hours to completely remove the ice, thus obtaining bamboo-based biomass foam material.

[0131] Performance testing

[0132] 1. Pore volume and specific surface area test

[0133] The pore volume and specific surface area of ​​the bamboo-based biomass foam materials in Examples 1-3 and Comparative Examples 1-2 were tested using a Micron Autopore 9520 mercury porosimeter. The results are as follows: Figure 2 As shown.

[0134] Depend on Figure 2It can be seen that the synergistic treatment with enzymatic hydrolysis and eutectic solvent (DES) significantly improved the pore volume and specific surface area, achieving partial degradation of hemicellulose and loosening the cell wall structure, thus allowing for better utilization of the subsequent DES. Furthermore, the DES treatment efficiently removed lignin from the bamboo material and dissolved some hemicellulose, effectively separating the main framework cellulose of the bamboo cells, resulting in a bamboo-based biomass foam material with a good pore structure.

[0135] 2. Thermal insulation performance test

[0136] The thermal insulation performance of the bamboo-based biomass foam material in Example 1 was measured using a handheld thermal imager in a liquid nitrogen environment at -196.56℃. The temperature of the foam material was observed at 0 minutes, 5 minutes, 10 minutes, and 30 minutes, and the imaging results are as follows. Figure 3 As shown.

[0137] Depend on Figure 3 It can be seen that after being kept in a liquid nitrogen environment at -196.56℃ for 30 minutes, the surface temperature of the bamboo-based biomass foam material only decreased from 13.3℃ to 11.7℃. The large space formed inside the bamboo-based biomass foam material gives it a low thermal conductivity, thus exhibiting excellent thermal insulation performance.

[0138] 3. Zeta potential test

[0139] The zeta potential of bamboo-based biomass foam materials treated with eutectic solvent was tested using a laser particle size analyzer (Zetasizer Nano ZS90) manufactured by Malvern Instruments, UK. The testing method is as follows: 20.0 mg of each of the bamboo-based biomass foam material samples prepared in Examples 1-3 and Comparative Examples 1-2 were weighed and placed in separate 50 mL beakers. 40 mL of ultrapure water (resistivity ≥18.2 MΩ·cm) was added to each beaker to prepare a suspension with a concentration of 0.5 mg / mL. The suspension was placed in an ultrasonic cell disruptor and ultrasonically treated at 300 W for 10 minutes under ice-water bath conditions to ensure thorough and uniform dispersion of the sample, forming a stable suspension for testing. The zeta potential was then measured using a zeta potential analyzer. During testing, approximately 1 mL of the ultrasonically treated homogeneous suspension was drawn using a sterile syringe and slowly injected into a disposable folded capillary sample cell, avoiding the introduction of air bubbles. Each sample was measured three times consecutively. The instrument software (Zetasizer Software) automatically calculated and provided the Zeta potential value and its average value for each measurement. The detection results are as follows: Figure 4 As shown.

[0140] Depend on Figure 4It can be seen that the bamboo-based biomass foam material prepared by the combined process of enzymatic hydrolysis and eutectic solvent (DES) has a higher absolute value of Zeta potential. At this time, the repulsive force between the fiber units due to the same charge is much greater than the van der Waals attraction, which can effectively prevent the fiber units from agglomerating and the colloidal system maintains a stable dispersion state. On the other hand, the bamboo-based foam material prepared by enzymatic hydrolysis only without eutectic solvent treatment (Comparative Example 1) and the bamboo-based foam material prepared by eutectic solvent treatment only without enzymatic hydrolysis treatment (Comparative Example 2) have lower absolute values ​​of Zeta potential, the charge repulsive force is weakened, the particles are prone to agglomeration and sedimentation due to attraction, and the colloidal system becomes unstable.

[0141] 4. Compression Test

[0142] The compressive strength of bamboo-based biomass foamed materials was tested using a universal mechanical testing machine (MWD-W10) and in accordance with GB / T 8813-2020 "Determination of compressive properties of rigid foamed plastics". The results are as follows: Figure 5 As shown.

[0143] Depend on Figure 5 It can be seen that by further analyzing the mechanical strength of the foamed material through compression experiments, the three-stage stress-strain behavior of rigid porous foam is revealed: (i) before reaching the yield limit, it is an elastic deformation zone, which is characterized by a linear stress-strain curve; (ii) after reaching the yield limit, it is a plastic deformation zone, where a stress-strain plateau appears; and then it gradually transitions to (iii) the material densification stage, where the stress value increases rapidly.

[0144] Although no statistically significant differences were observed in the compression response among the samples from different embodiments, the bamboo-based biomass foam material prepared by treatment with the low eutectic solvent ratio of Example 1 showed little variation in experimental replicates.

[0145] 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.

[0146] 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 biomass foaming material, characterized in that, The bamboo-based biomass foaming material is derived from bamboo cellulose; wherein... The bamboo-based biomass foaming material has a three-dimensional network structure, which is formed by the stacking of microscale polyhedral cell walls; and... At least some of the polyhedral cell walls have a porous structure.

2. The bamboo-based biomass foaming material according to claim 1, characterized in that, The average diameter of the polyhedral cell wall is 50-200 μm.

3. The bamboo-based biomass foaming material according to claim 1 or 2, characterized in that, The pore volume of the bamboo-based biomass foam material is greater than 1.5 cm³. 3 / g, the specific surface area of ​​the bamboo-based biomass foaming material is greater than 1500m². 2 / g, the Zeta potential value of the bamboo-based biomass foaming material is below -10mV.

4. A method for preparing a bamboo-based biomass foaming material according to any one of claims 1-3, characterized in that, Includes the following steps: Steps for obtaining bamboo-based solid residue; The bamboo-based solid residue was modified using a eutectic solvent to obtain modified bamboo pulp. The modified bamboo pulp was gelled to obtain bamboo-based nanocellulose gel. After pre-freezing the bamboo-based nanocellulose gel, moisture was removed by freeze-drying to obtain a porous bamboo-based foam material.

5. The preparation method according to claim 4, characterized in that, The steps for obtaining bamboo-based solid residue include: Pretreatment steps: The biomass material is pretreated to obtain a pretreated product. The pretreatment includes mechanical crushing and softening. Enzymatic hydrolysis step: The pretreated product is enzymatically hydrolyzed using cellulase and / or hemicellulase to obtain the enzymatic hydrolysate; Separation step: The enzymatic hydrolysis product is separated to obtain bamboo-based solid residue.

6. The preparation method according to claim 5, characterized in that, The bamboo bundles or bamboo filaments in the mechanically crushed bamboo material have a length of 10-100mm, a width of 0.5-5mm, and a thickness of 0.1-1mm; the bamboo fibers or bamboo chips have a length of less than 10mm. The softening treatment is performed at a temperature of 55-65℃ for 24-48 hours.

7. The preparation method according to claim 5 or 6, characterized in that, The enzymatic hydrolysis treatment is performed at a temperature of 30-50℃ for 4-12 hours. On a dry basis, the amount of cellulase and / or hemicellulase added is 0.1%-3.0% of the mass of the pretreated product.

8. The preparation method according to any one of claims 4-7, characterized in that, The eutectic solvent includes choline chloride, urea, and aminosulfonic acid; preferably, the molar ratio of choline chloride, urea, and aminosulfonic acid is 1:1.5-2.0:0.5-1.

0. The mass ratio of the bamboo-based solid residue to the eutectic solvent is 1:30-80; The modification treatment is performed at a temperature of 60-130℃ for 3-7 hours.

9. The preparation method according to any one of claims 4-8, characterized in that, The gelation process involves diluting the modified bamboo pulp and then subjecting it to ultrafine pulverization to obtain bamboo-based nanocellulose gel. Preferably, the particle size after ultrafine pulverization is less than 50 μm.

10. The preparation method according to any one of claims 4-9, characterized in that, The pre-freezing temperature is below -20°C, and the pre-freezing time is 3-5 hours.

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