Method of Preparing High-Strength, High-Toughness, and Recyclable Fiberboard with Bionic Structure

Abstract

A method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure and its recycling treatment method. The present invention relates to a method for preparing a fiberboard and a recycling method thereof, which solves the problem that the current technologies fail to prepare a green, environmentally friendly, high-strength, high-toughness and recyclable fiberboard with bionic structure. The method includes (1) pretreatment; (2) swelling treatment, (3) dissociation and dispersion treatment; (4) centrifugation; (5) hydrogel construction; and (6) densification treatment. The recycling treatment is: the high-strength, high-toughness, and recyclable fiberboard with bionic structure is placed in a crusher for crushing treatment, and then swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment are repeated. The present invention is applied in manufacturing of the high-strength, high-toughness, and recyclable fiberboard with bionic structure and its recycling treatment.

Description

BACKGROUND OF THE PRESENT INVENTION

Field of Invention

The present invention relates to a fiberboard manufacturing method and its recycling method.

Description of Related Arts

After millions of years of evolution and development, the exquisite structural design and excellent mechanical properties of animals and plants in nature have gradually achieved perfect unity. Among many natural materials, organisms such as shells, bones, and teeth use complex and orderly multi-scale hierarchical structures to obtain higher strength, hardness, and toughness than their own components, wherein the nacre in the shell has become a structural model for high-strength and ultra-tough layered composite materials. The aragonite layer and the organic matrix are stacked layer by layer through complex interactions, forming the “brick and mortar” structure commonly used in construction. This unique assembly method and multi-layered structural characteristics make the tensile strength of the nacre 3,000 times higher than that of natural aragonite, and at the same time have a good toughening effect. During the fracture process, the aragonite layer induced cracks frequently deflect, triggering organic bridging. The slip resistance between aragonite layers and fiber pull-out under the action of a strong interface are used to effectively transfer stress and consume energy, providing design inspiration for the research and development of new lightweight and high-strength composite materials and promoting the rapid development of bionic materials.

Cellulose fiber is one of the most abundant natural renewable polymers in plant cell walls. It has the advantages of wide sources, high mechanical properties, low thermal expansion rate, easy modification, good biocompatibility, and low density. In recent years, the use of natural fibers from wood processing residues as reinforcement phases to prepare environmentally friendly high-performance composite materials has shown an increasing trend and has been widely used in aerospace, industrial construction, home decoration, product packaging and other fields. However, currently, high-strength all-cellulose structural materials are mostly processed by physical or chemical methods to grind or oxidize cellulose raw materials into nanocellulose. Not only is the process complicated and energy-intensive, but also due to the low-concentration gelation behavior of nanocellulose, it is difficult to expand the preparation of large-scale bulk structural materials, and is limited to the preparation of large fibers or film materials. The other production process of fiber-reinforced composite materials that can be prepared in large sizes includes two types: adhesive-free type and adhesive-containing type. Fiberboard produced with formaldehyde adhesives has the risk of releasing harmful gases, while inorganic fiberboard produced by cross-linking and bonding inorganic salts, inorganic acids, inorganic bases, metal oxides and hydroxides is difficult to apply on a large scale due to high density and high processing difficulty. In addition, both two types generally lack the microscopic and macroscopic structural and functional design of the fibers, and have the disadvantages of weak interfacial bonding between cellulose fibers and adhesives (reinforcement phase and matrix material) and low mechanical strength of fiberboard. At the same time, because of their complex composition and difficulty in separation and recycling, both two types cannot be recycled.

In summary, the existing technology cannot produce green, environmentally friendly, high-strength, high-toughness, and recyclable fiberboard with bionic structure.

Summary of the Present Invention

In order to solve the problems of failing prepare a green, environmentally friendly, high-strength, high-toughness and recyclable bionic structural fiberboard in the existing technologies, the present invention provides a method of preparing a high-strength, high-toughness, and recyclable fiberboard with bionic structure and its recycling treatment method.

A preparation method of high-strength, high-toughness, and recyclable fiberboard with bionic structure and the recycling treatment method thereof, the method is carried out by the following steps:

• • (1) Pretreatment:

Sequentially process removal of some lignin from wood processing residues and drying treatment to obtain wood processing residues with partial lignin removal.

• • (2) Swelling Treatment:

Under room temperature conditions, immerse the wood processing residues with partial lignin removal in an activation solution for 30 minutes ~3 hours, then replace the activation solution and repeat the step of immersion for 1~5 times to obtain swollen wood processing residues.

• • (3) Dissociation and Dispersion Treatment:

Add the swollen wood processing residues into a cellulose solvent, stir continuously for 5~30 minutes at a temperature of −20° C.~150° C., then finally stand for reaction for 5~10 minutes to obtain a high-viscosity, milky white, multi-scale cellulose mixed solution.

The high-viscosity, milky white, multi-scale cellulose mixed solution has a density of 0.8 g/cm³~3 g/cm³.

• • 4) Centrifugation:

Place the high-viscosity, milky white, multi-scale cellulose mixed solution in a centrifuge and process centrifugation to remove bottom sediments, and then obtain a high-viscosity, uniformly dispersed multi-scale cellulose solution.

The high-viscosity, uniformly dispersed multi-scale cellulose solution has a density of 0.5 g/cm³~2 g/cm³.

• • (5) Hydrogen Construction:

Pour the high-viscosity, uniformly dispersed multi-scale cellulose solution into a mold, and stand for 2 hours~10 hours for solidification and molding, after solidification and molding, immerse in a regeneration solution for 5~20 hours and finally wash to obtain a uniform multi-scale cellulose hydrogel.

• • (6) Densification Treatment:

Put the uniform multi-scale cellulose hydrogel in a hot press machine and process hot-pressing to obtain a high-strength, high-toughness, and recyclable fiberboard with bionic structure.

A recycling treatment method of the high-strength, high-toughness, and recyclable fiberboard with bionic structure, the method is carried out by the following steps:

Place the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeat the steps of swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment to complete the recycling treatment method.

The advantages of the present invention are as follows:

The present invention utilizes the method of dissolution and regeneration of cellulose fibers to fully dissociate the cellulose skeleton in the wood processing residues in the form of cellulose fibers, and disperses them evenly in the cellulose solution with the help of external force. This process not only avoids the high-energy mechanical grinding and homogenization process used for the same purpose, but also solves the problem of uneven sizing in the traditional fiberboard manufacturing process.

After being placed in the regeneration liquid, the dissociated and dispersed cellulose fibers are reassembled under the connection of the regenerated nanocellulose network, interweaving to form a multi-scale cellulose hydrogel, realizing an ingenious and reasonable micro/nanostructure design. By utilizing the high contact area, high-density hydrogen bonds and van der Waals forces between the fibers, the multi-scale cellulose hydrogel forms a shell-like “brick and mortar” structure during the hot-pressing process.

With the cellulose fibers dissolved on the surface as the hard phase material and the regenerated nanocellulose network as the soft phase material, this strong and delicate multi-scale micro/nanocellulose network structure replaces the bonding effect of traditional organic and inorganic adhesives, provides ultra-high interface strength between cellulose fibers, avoids the use of additives and modifiers, simplifies the preparation process, and obtains environmentally friendly, biodegradable, lightweight, high-strength and high-toughness cellulose board. In addition, since the fiberboard is a full cellulose material, it can be recycled and crushed after it loses its use function and be used as raw material again for producing new fiberboard. This bottom-up scalable preparation method has good application prospects and use value in the fields of aircraft, construction, automobiles, etc.

The present invention is applicable in a manufacturing method of a high-strength, high-toughness, recyclable fiberboard with bionic structure and a recycling treatment method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of a high-viscosity, uniformly dispersed multi-scale cellulose solution prepared in step 4 of Exemplary Embodiment 1.

FIG. 2 is a photograph of a uniform multi-scale cellulose hydrogel after pouring a high-viscosity, uniformly dispersed multi-scale cellulose solution into different molds in step 5 of Exemplary Embodiment 1.

FIG. 3 is an electron microscope image of the internal network structure of the uniform multi-scale cellulose hydrogel prepared in step 5 of Exemplary Embodiment 1.

FIG. 4 is an actual photograph of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1.

FIG. 5 is a scanning electron microscope image of the cross section of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, where 1 refers to cellulose fiber and 2 refers to regenerated nanocellulose.

FIG. 6 is a flexural stress-strain curve diagram, 1-1 refers to the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, 1-2 refers to a pure fiberboard prepared in Comparative Experiment 1, and 1-3 refers to a regenerated fiberboard without cellulose fiber prepared in Comparative Experiment 2.

FIG. 7 is a cross-sectional fracture electron microscope image of a high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1.

FIG. 8 is a fracture toughness bar graph, 1-1 refers to the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, 1-2 refers to a pure fiberboard prepared in Comparative Experiment 1, and 1-3 refers to a regenerated fiberboard without cellulose fiber prepared in Comparative Experiment 2.

FIG. 9 is a tensile stress-strain curve of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1.

FIG. 10 is a photograph of the fiber pieces that are used as raw material again in Exemplary Embodiment 2, which are obtained from crushing the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1.

FIG. 11 is an actual photograph of the uniform multi-scale cellulose hydrogel prepared in step 5 of Exemplary Embodiment 2.

FIG. 12 is a scanning electron microscope image of a cross section of a high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling treatment in Exemplary Embodiment 2, where 1 refers to cellulose fiber and 2 refers to regenerated nanocellulose.

FIG. 13 is a flexural stress-strain curve of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling treatment in Exemplary Embodiment 2.

FIG. 14 is a photograph of a high-strength, high-toughness, recyclable fiber cups or bowls with bionic structure prepared in Exemplary Embodiment 3.

FIG. 15 is a photograph of load-bearing the high-strength, high-toughness, recyclable fiber bowl with bionic structure prepared in Exemplary Embodiment 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiment 1: According to this embodiment, a method of preparing a high-strength, high-toughness, and recyclable fiberboard with bionic structure and a recycling treatment method thereof, the method is carried out according to the following steps:

• • (1) Pretreatment:

Sequentially process removal of some lignin from wood processing residues (to remove some lignin from the wood processing residues) and drying treatment to obtain wood processing residues with partial lignin removal.

• • (2) Swelling Treatment:

Under room temperature conditions, immerse the wood processing residues with partial lignin removal in an activation solution for 30 minutes~3 hours, then replace the activation solution and repeat the step of immersion for 1~5 times to obtain swollen wood processing residues.

• • (3) Dissociation and Dispersion Treatment:

Add the swollen wood processing residues into a cellulose solvent, stir continuously for 5~30 minutes at a temperature of −20° C.~150° C., then finally stand for reaction for 5~10 minutes to obtain a high-viscosity, milky white, multi-scale cellulose mixed solution.

The high-viscosity, milky white, multi-scale cellulose mixed solution has a density of 0.8 g/cm³~3 g/cm³.

• • (4) Centrifugation:

Place the high-viscosity, milky white, multi-scale cellulose mixed solution in a centrifuge and carry out centrifugation to remove bottom sediments, then a high-viscosity, uniformly dispersed multi-scale cellulose solution is obtained.

The high-viscosity, uniformly dispersed multi-scale cellulose solution has a density of 0.5 g/cm³~2 g/cm³.

• • (5) Hydrogel Construction:

Pour the high-viscosity, uniformly dispersed multi-scale cellulose solution into a mold, and stand for 2 hours~10 hours for solidification and molding, after solidification and molding, immerse in a regeneration solution for 5 hours~20 hours and finally wash to obtain a uniform multi-scale cellulose hydrogel.

• • (6) Densification Treatment:

Put the uniform multi-scale cellulose hydrogel in a hot press machine and process hot-pressing to obtain a high-strength, high-toughness, and recyclable fiberboard with bionic structure.

In step (2), the wood processing residues with partial lignin removal is soaked in the activation liquid. After soaking for a period of time, the agglomerates therein are crushed with a glass rod so that they can fully absorb the activation liquid. When the activation liquid is replaced, the wood processing residue is appropriately squeezed to discharge the previously absorbed activation liquid, and then re-immersed to absorb the newly replaced activation liquid to fully weaken the interaction between the cellulose fibers in the wood processing residues.

The purpose of step (2) is mainly to fully swell the cellulose fibers in the wood processing residues with partial lignin removal and to weaken the hydrogen bonding between the cellulose fibers.

Principle of step (2): Although the macroscopic size and shape of wood processing residues vary, they are consistent with the microstructure of natural wood. They are mainly composed of three macromolecular polymers: cellulose, hemicellulose and lignin, and are porous, hierarchical and anisotropic. The basic skeleton of its cell wall is mainly composed of cellulose molecular chains that are aggregated and arranged in an orderly manner. The strong hydrogen bonds within and between cellulose molecules hinder the contact between cellulose solvent and cellulose molecules. After treatment with the activation liquid, some hydrogen bonds between cellulose microfibrils exposed on the surface of cellulose fibers in wood processing residues are opened, and the molecular chains obtain a more relaxed configuration, which can increase their chances of contact with cellulose solvents, thereby promoting the dissociation of the cellulose skeleton of wood processing residues and the dissolution process of the cellulose fiber surface after dissociation.

In step (3), the swollen wood processing residues are added into the cellulose solvent and stirred continuously, so that the wood processing residues precipitated at the bottom are redispersed in the solvent to participate in the dissolution reaction.

The purpose of step (3) is to promote the surface dissolution process of the partially delignified wood processing residues.

Principle of step (3): the swollen wood processing residues still maintain an orderly arranged cellulose fiber skeleton. Under the action of external stirring, partially delignified wood processing residues are fully in contact with the cellulose solvent. Benefited from the partial delignification treatment in the early stage, some cellulose microfibrils are exposed on the surface of the wood processing residues. After being dispersed in the cellulose solvent, a cellulose dissolution reaction occurs on the surface, and the hydrogen bonds between the cellulose fibers in the cellulose skeleton of the wood processing residues are broken, and the cellulose is dissolved, which promotes the dissociation of the cellulose skeleton of the wood processing residues. At the same time, due to the presence of a small amount of lignin, the cellulose fibers in the cellulose skeleton of the wood processing residues are prevented from being excessively dissolved. Under the action of external force stirring and solvent dissolution, cellulose fibers with surface dissolution and relatively complete cell wall structure are obtained. After regeneration, cellulose fibers with nanosized surface which have a large amount of nanocellulose distributed on the surface can be obtained to increase the contact area and interaction between interfaces and improve the interface strength.

In step (4), after placing the milky white multi-scale cellulose into the centrifuge, the large undissolved and dispersed fibers are precipitated to the bottom, and the upper uniform and slightly transparent cellulose solution is taken to ensure that all cellulose fibers in the solution participate in the dissolution reaction and are dissociated and dispersed.

The purpose of step (4) is mainly to obtain a uniformly dispersed surface-dissolved multi-scale cellulose solution.

Principle of step (4): The milky white cellulose mixed solution obtained after dissolution and dissociation contains some undecomposed aggregates, which makes it difficult to form a reasonable and effective structural design, and it is very easy to form holes during the densification process, resulting in structural defects, stress concentration, and thus reducing the strength of the fiberboard. The cellulose mixed solution is placed in a centrifuge. Under the action of external force, the difference in gravity can be used to precipitate and remove the heavy, undispersed fiber blocks, while retaining the cross-linked and entangled cellulose fibers with natural crystalline cellulose (providing reinforcement for the fiberboard), thereby obtaining a uniformly dispersed multi-scale cellulose solution.

In step (5), the multi-scale cellulose hydrogel solidified in the mold is immersed in the regeneration liquid, and a multi-scale micro/nanocellulose network structure formed by interweaving and entanglement of cellulose fibers with nanosized surface and regenerated nanocellulose networks is formed inside the multi-scale cellulose hydrogel.

The purpose of step (5) is to form a cellulose hydrogel with a multi-scale micro/nanocellulose network structure.

Principle of step (5): The multi-scale cellulose hydrogel is prepared based on the dissociation and dispersion of the cellulose skeleton of the wood processing residue in the early stage, and the cellulose fibers that are exposed to cellulose microfibrils after the delignification process and then dissolved on the surface. After soaking in the regeneration liquid, the hydrogen bonds within and between cellulose molecules are reconnected to form a dense nanoscale regenerated cellulose network structure, while the cellulose fibers with nanosized surface, that uniformly dispersed in the interior and retaining the natural cellulose crystal structure, are connected to each other by utilizing the good biocompatibility, large specific surface area, van der Waals force and hydrogen bond network between cellulose fibers, and reassembly to form a cellulose hydrogel with multi-scale micro/nanocellulose network structure, wherein cellulose fibers play a mechanical supporting role as a skeleton structure, while the regenerated nanocellulose network plays an adhesive effect, laying the foundation for the strong interface between the two phases in the fiberboard with shell-like structure.

In step (6), the multi-scale cellulose hydrogel shrinks and aggregates continuously during the hot-pressing process as the water evaporates, and under the action of external force, a high-strength, high-toughness, recyclable fiberboard with bionic structure is formed.

The purpose of step (6) is to densify the multi-scale cellulose hydrogel by hot-pressing to obtain a fiberboard with a shell-like “brick and mortar” structure having high flexural strength and high fracture toughness.

Principle of step (6): During the hot-pressing process, as the water evaporates, the fibers continue to shrink and aggregate, wherein the regenerated nanocellulose has a large specific surface area and shrinks violently, forming a dense bonding layer with high hydrogen bond density between cellulose fibers. On the other hand, the cellulose fibers that retain natural crystalline cellulose are under the action of external forces and regenerated nanocellulose, the internal lumen are compressed and a reinforcement similar to a brick structure is formed, which is intertwined and stacked with the bonding layer formed by the regenerated nanocellulose network. This multi-scale layered structure can produce effective strengthening and toughening mechanisms during the fracture process, which can not only realize the effective transmission of external loads, but also dissipate a large amount of energy through crack deflection, branching, bridging and fiber pull-out, change the direction of crack propagation, inhibit crack propagation, delay the fracture process, and obtain higher mechanical strength and toughness.

The beneficial effects of this specific embodiment are:

This embodiment utilizes the dissolution and regeneration of cellulose fibers to fully dissociate the cellulose skeleton in the wood processing residues in the form of cellulose fibers, and disperses them evenly in the cellulose solution with the help of external force. This process not only avoids the high-energy mechanical grinding and homogenization process used for the same purpose, but also solves the problem of uneven sizing in the traditional fiberboard manufacturing process. After being placed in the regeneration liquid, the dissociated and dispersed cellulose fibers are reassembled under the connection of the regenerated nanocellulose network, interweaving to form a multi-scale cellulose hydrogel, realizing an ingenious and reasonable micro/nanostructure design. By utilizing the high contact area, high-density hydrogen bonds and van der Waals forces between the fibers, the multi-scale cellulose hydrogel forms a shell-like “brick and mortar” structure during the hot-pressing process. With the cellulose fibers dissolved on the surface as the hard phase material and the regenerated nanocellulose network as the soft phase material, this strong and delicate multi-scale micro/nanocellulose network structure replaces the bonding effect of traditional organic and inorganic adhesives, provides ultra-high interface strength between cellulose fibers, avoids the use of additives and modifiers, simplifies the preparation process, and obtains environmentally friendly, biodegradable, lightweight, high-strength and high-toughness cellulose board. In addition, since the fiberboard is a full cellulose material, it can be recycled and crushed after it loses its use function and used as raw material again for producing new fiberboard. This bottom-up scalable preparation method has good application prospects and use value in the fields of aircraft, construction, automobiles, etc.

Embodiment 2: This embodiment is different from Embodiment 1 in that: a size of the wood processing residue (raw material) in step 1 is 0.3 mm~2.5 cm. Others are the same as the Embodiment 1.

According to this embodiment, the wood processing residue (raw material) are coniferous wood material or broadleaved wood material, from which wood powder of 60 mesh and above is removed.

Embodiment 3: This embodiment is different from Embodiment 1 or 2 in that: the process of removing some lignin from the wood processing residues is specifically carried out according to the following steps: immersing the raw wood processing residues in a delignification solution, heating in a water bath at a temperature of 60° C.~90° C. for 10 hours~15 hours, then immersing in deionized water for 1 hour-3 hours at a temperature of 20° C.~50° C., and repeating the step of immersing in deionized water for 2 ~4 times to obtain the wood processing residues with partial lignin removal. Others are the same as the Embodiment 1 or 2.

Embodiment 4: This embodiment is different from one of Embodiments 1-3 in that: the delignification solution is a mixed solution of sodium chlorite solution and acetate buffer solution, 1%~30% by mass of hydrogen peroxide, 1%~30% by mass of sodium hypochlorite solution or 1%~30% by mass of anthraquinone solution; wherein the mixed solution of sodium chlorite solution and acetate buffer solution is a mixture of 5% sodium chlorite solution by mass and acetate buffer solution with a pH of 4.6 in a volume ratio of 30:1. Others are the same as the Embodiment 1-3.

Embodiment 5: This embodiment is different from one of Embodiments 1-4 in that: in step (1), the drying treatment is specifically referred to heating for 5~15 hours at a temperature of 40° C.~110° C. Others are the same as the Embodiment 1-4.

Embodiment 6: This embodiment is different from one of Embodiments 1-5 in that: in step (2), the activation solution is dimethylacetamide, dimethylformamide or lithium chloride/dimethylacetamide solution with a lithium chloride mass fraction of 1%~6%. Others are the same as the Embodiment 1-5.

Embodiment 7: This embodiment is different from one of Embodiments 1-6 in that: in step (3), the cellulose solvent is selected from one or a mixture of two or more of: N-methylmorpholine-N-oxide solution with 85% mass fraction, 1-allyl -3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, dimethylacetamide/lithium chloride solution with a lithium chloride mass fraction of 8%~10%, sodium hydroxide/urea mixed aqueous solution, zinc chloride/calcium chloride mixed aqueous solution, and zinc chloride/aluminum chloride mixed aqueous solution; wherein the mass fraction of sodium hydroxide in the sodium hydroxide/urea mixed aqueous solution is 7%, and a mass fraction of urea is 12%; a mass fraction of zinc chloride in the zinc chloride/calcium chloride mixed aqueous solution is 72%, and a mass fraction of calcium chloride is 2.2%; a mass fraction of zinc chloride in the zinc chloride/aluminum chloride mixed aqueous solution is 59%, and a mass fraction of aluminum chloride is 6.4%. Others are the same as the Embodiment 1-6.

Embodiment 8: This embodiment is different from one of Embodiments 1-7 in that: in step (5), wherein the regeneration solution is anhydrous ethanol, acetone, distilled water or deionized water. Others are the same as the Embodiment 1-7.

Embodiment 9: This embodiment is different from one of Embodiments 1-8 in that: in step (6), the process of hot-pressing is specifically referring to: hot-pressing at a temperature of 30° C.~150° C. and a pressure of 1 MPa~10 MPa for 5 hours~50 hours Others are the same as the Embodiment 1-8.

Embodiment 10: According to this embodiment, a method of recycling treatment of the high-strength, high-toughness, and recyclable fiberboard with bionic structure is carried out according to the following steps:

• • placing the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeating the steps of swelling treatment dissociation and dispersion treatment, hydrogel construction, and densification treatment to complete the recycling treatment.

The fiberboard is placed in a crusher to make small-sized fiber pieces, wherein the fiber pieces should not be too large. If there are larger block particles, they need to be placed in the crusher again to process crushing to obtain fiber pieces.

The purpose of crushing is to increase the contact area of the fiber fragment pieces, improve their swelling, dissociation and dispersion effects, obtain a uniform and viscous multi-scale cellulose mixed solution, form a multi-scale cellulose hydrogel, and also form a high-strength fiberboard with bionic structure after hot-pressing.

Principle: Fiberboard is a fully cellulose material, consisting of cellulose fibers and regenerated nanocellulose. Cellulose fibers retain some lignin and have a short reaction time in cellulose solvents, so they retain the natural fiber cell wall structure and have a large amount of type I crystalline cellulose. With the high theoretical mechanical strength of type I crystalline cellulose, cellulose fibers play a role of mechanical reinforcement as a reinforcing phase in fiberboard. Similarly, regenerated nanocellulose and the large amount of cellulose microfibrils exposed on the surface of wood processing residues after partial delignification can be dissolved again with the help of cellulose solvent to obtain a viscous cellulose solution, which is placed in the regeneration liquid to form a dense regenerated nanocellulose network. Due to its huge specific surface area and high chemical reactivity, the regenerated nanocellulose network acts as a soft phase in the fiberboard to bind the fiberboard. Therefore, the crushed fiberboard can be used as raw material again for the preparation of fiberboard with bionic structure.

The following exemplary embodiments are used to verify the beneficial effects of the present invention:

Exemplary Embodiment 1

A preparation method of high-strength, high-toughness, and recyclable fiberboard with bionic structure, the preparation method is carried out according to the following steps:

• • (1) Pretreatment:

Sequentially process removal of some lignin from wood processing residues and drying treatment to obtain wood processing residues with partial lignin removal.

• • (2) Swelling Treatment:

Under room temperature conditions, immerse the wood processing residues with partial lignin removal in an activation solution for 30 minutes, then replace the activation solution and repeat the step of immersion for 3 times to obtain swollen wood processing residues.

• • (3) Dissociation and Dispersion Treatment:

Add the swollen wood processing residues into a cellulose solvent, stir continuously for 20 minutes at a temperature of 28° C., then finally stand for reaction for 6 minutes to obtain a high-viscosity, milky white, multi-scale cellulose mixed solution.

The high-viscosity, milky white, multi-scale cellulose mixed solution has a density of 1.02 g/cm³.

• • (4) Centrifugation:

Place the high-viscosity, milky white, multi-scale cellulose mixed solution in a centrifuge and carry out centrifugation for 5 minutes at a rotational speed of 2000 r/min, remove bottom sediments to obtain a high-viscosity, uniformly dispersed multi-scale cellulose solution having a density of 0.99 g/cm³.

• • (5) Hydrogel Construction:

Pour the high-viscosity, uniformly dispersed multi-scale cellulose solution into a mold, and stand for 8 hours, after solidification and molding, immerse in a regeneration solution for 10 hours and finally wash to obtain a uniform multi-scale cellulose hydrogel.

• • (6) Densification Treatment:

Put the uniform multi-scale cellulose hydrogel in a hot press machine and process hot-pressing to obtain a high-strength, high-toughness, and recyclable fiberboard with bionic structure of which its length, width and thickness are 20 cm, 7 cm, and 0.3 cm respectively.

In step (1), the wood processing residues refer to poplar wood shavings with a size of 0.3 mm~2.5 cm.

In step (1), the process of removing some lignin from the wood processing residues is specifically carried out according to the following steps: immersing the wood processing residues (raw materials) in a delignification solution, heating in a water bath at a temperature of 80° C. for 12 hours, then immersing in deionized water for 1 hour at a temperature of 30° C., and repeating the step of immersing in deionized water for 3 times to obtain the wood processing residues with partial lignin removal.

The delignification solution is a mixed solution of sodium chlorite solution and acetate buffer solution, wherein the mixed solution of sodium chlorite solution and acetate buffer solution is a mixture of 5% sodium chlorite solution by mass and acetate buffer solution with a pH of 4.6 in a volume ratio of 30:1.

In step (1), the drying treatment is specifically referred to heating for 8 hours at a temperature of 60° C.

In step (2), the activation solution is lithium chloride/dimethylacetamide solution, wherein the lithium chloride/dimethylacetamide solution has a lithium chloride mass fraction of 2%.

In step (3), the cellulose solvent is dimethylacetamide/lithium chloride solution; the mass percentage of lithium chloride in the dimethylacetamide/lithium chloride solution is 8%.

In step (5), the regeneration solution is anhydrous ethanol.

In step (6), the process of hot-pressing is specifically referring to: hot-pressing at a temperature of 80° C. and a pressure of 5 MPa for 15 hours.

Exemplary Embodiment 2

The difference between this embodiment and the Exemplary Embodiment 1 is that the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in step 6 of the Exemplary Embodiment 1 is broken into cellulose pieces with a size of less than 0.8 mm, and then the cellulose pieces are repeatedly processed according to steps (2) to step (6) of the Exemplary Embodiment 1 to obtain the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling. Others are the same as the Exemplary Embodiment 1.

Exemplary Embodiment 3: The difference between this embodiment and the Exemplary Embodiment 1 is that: in step (5), the high-viscosity, uniformly dispersed multi-scale cellulose solution is poured into a cup-shaped or a bowl-shaped mold, and is allowed to stand for 8 hours. After solidification and molding, it is immersed in a regeneration solution for 10 hours and finally is washed to obtain a uniform multi-scale cellulose hydrogel. Finally, the cup or bowl is dried and formed under room temperature conditions to obtain a high-strength, high-toughness, recyclable cup or bowl with bionic structure. Others are the same as the Exemplary Embodiment 1.

Comparative Experiment 1: This comparative experiment is different from Exemplary Embodiment 1 in that the wood processing residues with partial lignin removal prepared in step (1) of Exemplary Embodiment 1 is directly subjected to hot-pressing in step (6) to obtain a pure fiberboard. Others are the same as the Exemplary Embodiment 1.

Comparative Experiment 1 lacks regenerated nanocellulose and structural design, the interface strength between wood processing residues is low, and the cellulose fibers are unevenly distributed, which easily causes structural defects, resulting in low flexural performance.

Comparative Experiment 2: This comparative experiment is different from Exemplary Embodiment 1 in that: in step (1), the wood processing residue is poplar wood powder with a size of 60 meshes or above, and a regenerated fiberboard without cellulose fiber is obtained. Others are the same as the Exemplary Embodiment 1.

In Comparative Experiment 2, the flexural strength of the regenerated fiberboard is relatively low due to the lack of cellulose fiber reinforcement phase containing natural crystalline cellulose.

FIG. 1 illustrates a photo of a high-viscosity, uniformly dispersed multi-scale cellulose solution prepared in step (4) of Exemplary Embodiment 1. It can be seen from the figure that the cellulose solution has a certain viscosity and is relatively uniform without obvious stratification, and the wood processing residues can be processed into a uniform cellulose mixed solution.

In Exemplary Embodiment 1, a high-viscosity, uniformly dispersed multi-scale cellulose solution is poured into different molds in step (5). FIG. 2 is a photo of a uniform multi-scale cellulose hydrogel after pouring a high-viscosity, uniformly dispersed multi-scale cellulose solution into different molds in step 5 of Exemplary Embodiment 1. It can be seen from the figure that the hydrogel can be used to prepare products of different shapes according to different molds, and has good plasticity.

FIG. 3 illustrates an electron microscope image of the internal network structure of the uniform multi-scale cellulose hydrogel prepared in step 5 of Exemplary Embodiment 1. It can be seen from the figure that the hydrogel has a densely packed multi-scale micro/nanofiber network structure, and the regenerated cellulose nanofibers are densely packed on the surface of cellulose fibers, resulting in a higher specific surface area.

FIG. 4 illustrates a photo of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1. It can be seen from the figure that the fiberboard has a smooth and dense appearance, and the fibers are closely arranged.

FIG. 5 illustrates a scanning electron microscope image of the cross section of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, where 1 refers to cellulose fiber and 2 refers to regenerated nanocellulose. It can be seen from the figure that the partially dissolved cellulose microfibers act as a reinforcing phase, with regenerated nanocellulose providing bonding, and assemble into a shell-like ‘brick and mortar’ structure, presenting a dense layered structure.

The flexural test of the high-strength, high-toughness, recyclable fiberboard with bionic structure is carried out according to the method under the national standard GB/T 9341-2008, Plastic—Determination of flexural properties. FIG. 6 is a flexural stress-strain curve diagram, 1-1 refers to the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, 1-2 refers to a pure fiberboard prepared in Comparative Experiment 1, and 1-3 refers to a regenerated fiberboard without cellulose fiber prepared in Comparative Experiment 2. It can be seen from the figure that the high-strength, high-toughness, recyclable bionic structural fiberboard prepared in Exemplary Embodiment 1 has good mechanical strength, a flexural strength of up to 222 MPa, and a strain of 5.2%, which has a good toughening effect.

FIG. 7 illustrates a cross-sectional fracture electron microscope image of a high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1. It can be seen from the figure that the fracture cracks of the fiberboard show toughening fracture mechanisms such as crack deflection, branching, and bridging.

The fracture toughness test of the high-strength, high-toughness, recyclable fiberboard with bionic structure is carried out according to the method under national standard GB/T 4161-2007, Metallic materials—Determination of plane-strain fracture toughness K_IC. FIG. 8 illustrates a fracture toughness bar graph, 1-1 refers to the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1, 1-2 refers to a pure fiberboard prepared in Comparative Experiment 1, and 1-3 refers to a regenerated fiberboard without cellulose fiber prepared in Comparative Experiment 2. It can be seen from the figure that by means of the shell-like bionic “brick and mortar” structure and the high interface strength between multi-scale fibers, the fiberboard prepared in Exemplary Embodiment 1 shows relatively excellent fracture toughness compared with pure fiberboard and regenerated fiberboard, and the fracture toughness can reach 4.4 MPa·m^0.5.

The tensile test of high-strength, high-toughness, recyclable fiberboard with bionic structure is carried out according to the method under national standard GB/T 22.1-2010, Metallic materials—Tensile testing. FIG. 9 is a tensile stress-strain curve of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1. It can be seen from the figure that the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1 has good mechanical strength, and the tensile strength is as high as 208 MPa.

FIG. 10 is an actual photograph of the fiber pieces that are used as raw material again in Exemplary Embodiment 2, which are obtained from crushing the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1. It can be seen from the figure that the fiberboard can be broken down into smaller fiber pieces and reused as cellulose-rich raw material for fiberboard production.

FIG. 11 is an actual photograph of the uniform multi-scale cellulose hydrogel prepared in step 5 of Exemplary Embodiment 2. It can be seen from the figure that the fiber fragment pieces obtained after being broken into pieces in Exemplary Embodiment 1 can be cross-linked and reorganized among the fibers by the same treatment method to obtain a cellulose hydrogel having the same effect as that in Exemplary Embodiment 1.

FIG. 12 is a scanning electron microscope image of a cross section of a high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling treatment in Exemplary Embodiment 2, where 1 refers to cellulose fiber and 2 refers to regenerated nanocellulose. It can be seen from the figure that the uniform multi-scale cellulose hydrogel prepared in step 5 of Exemplary Embodiment 2 can be hot-pressed in step (6) to obtain a fiberboard with the same bionic “brick and mortar” structure.

The high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling in Exemplary Embodiment 2 is subjected to a flexural test according to the national standard GB/T 9341-2008, Plastic—Determination of flexural properties. FIG. 13 is a flexural stress-strain curve of the high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling treatment in Exemplary Embodiment 2. It can be seen from the figure that high-strength, high-toughness, recyclable fiberboard with bionic structure prepared by recycling in Exemplary Embodiment 2 has good mechanical strength and a flexural strength of up to 218 MPa.

FIG. 14 is a photo of a high-strength, high-toughness, recyclable fiber cup or bowl with bionic structure prepared in Exemplary Embodiment 3. It can be seen from the figure that the hydrogel has good plasticity.

FIG. 15 is a photograph showing load bearing of the high-strength, high-toughness, recyclable fiber bowl with bionic structure prepared in Exemplary Embodiment 3. It can be seen from the figure that the two air-dried fiber bowls can withstand the weight of a 50 kg adult standing on one foot, and have good mechanical strength.

Comparative Experiment 3: This experiment is carried out by repeating the experiment according to Embodiment 1 of the inventive patent with application number 202110396379.2, authorization publication number CN 113001696 B, and title of invention “A method for forming high-strength, formaldehyde-free plywood by self-adhesion without adhesive”.

Benefited from the bottom-up preparation method, Exemplary Embodiment 1 (of the present invention) is mainly aimed at the preparation of load-bearing block materials. Also, benefited from the dispersion of the raw materials and the bionic design of the structure, the pretreatment process, reaction time and process of Embodiment 1 are further shortened and improved, and the resulting samples are larger in size, more diverse in shape, better in mechanical strength, and more uniform in structure. Therefore, its application range is wider and its industrial production potential is higher. On the other hand, Comparison Experiment 3 is limited by the natural size and defects of the wood (knots, insect bites, diagonal grain, etc.). the resulting products are prone to uneven and reduced structure and mechanical properties.

Based on the high interface interaction formed by the physical entanglement, van der Waals force and strong hydrogen bond between highly dense multi-scale fibers, the high-strength, high-toughness and recyclable fiberboard with bionic structure prepared in Exemplary Embodiment 1 has a Shore D hardness of 90.8, while the Shore D hardness of the plywood in Comparative Experiment 3 is 85. Also, the fiberboard of Exemplary Embodiment 1 exhibits a comparable tensile strength, which is 208 MPa, while the tensile strength of the plywood of Comparative Experiment 3 is 200 MPa.

With the help of a simple and efficient preparation process and a high cellulose fiber content, the fiberboard obtained in Exemplary Embodiment 1 can be fully prepared into a (recycled) fiberboard with the same bionic structure and mechanical properties through a simple crushing process, while the plywood obtained in the Comparative Experiment 3 cannot achieve the same cycle process and failed to repeatedly obtain the resulting plywood with the same performance.

Claims

1. A method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure, characterized in that, the method is carried out according to the following steps:

(1) Pretreatment:

obtaining wood processing residues and sequentially removing lignin portion partially from the wood processing residues and processing drying treatment; then obtaining wood processing residues with partial lignin removal;

(2) Swelling Treatment:

under room temperature conditions, immersing the wood processing residues with partial lignin removal in an activation solution for 30 minutes to 3 hours, then replacing the activation solution and repeating the step of immersing the wood processing residues with partial lignin removal in the activation solution for 30 minutes to 3 hours for 1-5 times to obtain swollen wood processing residues;

(3) Dissociation and Dispersion Treatment:

adding the swollen wood processing residues into a cellulose solvent, stirring continuously for 5-30 minutes at a temperature of −20C.-150C., then finally allowing to stand and react for 5-10 minutes to obtain a high-viscosity, milky white, multi-scale cellulose mixed solution,

wherein the high-viscosity, milky white, multi-scale cellulose mixed solution has a density of 0.8 g/cm3-3 g/cm3;

(4) Centrifugation:

placing the high-viscosity, milky white, multi-scale cellulose mixed solution in a centrifuge and processing centrifugation to remove bottom sediments and then to obtain a high-viscosity, uniformly dispersed multi-scale cellulose solution,

wherein the high-viscosity, uniformly dispersed multi-scale cellulose solution has a density of 0.5 g/cm3-2 g/cm3;

(5) Hydrogel Construction:

pouring the high-viscosity, uniformly dispersed multi-scale cellulose solution into a mold, and standing for 2-10 hours for solidification, then immersing in a regeneration solution for 5-20 hours and finally washing to obtain a uniform multi-scale cellulose hydrogel;

(6) Densification Treatment:

putting the uniform multi-scale cellulose hydrogel in a hot press machine and processing hot-pressing to obtain a high-strength, high-toughness, and recyclable fiberboard with bionic structure.

2. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (1), a size of the wood processing residues is 0.3 mm-2.5 cm.

3. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (1), the process of removing lignin portion partially from the wood processing residues is specifically carried out according to the following steps: immersing the wood processing residues in a delignification solution, heating in a water bath for 10 hours-15 hours at a temperature of 60° C.-90° C., then immersing in deionized water for 1 hour-3 hours at a temperature of 20° C.-50° C., and repeating the step of immersing in deionized water for 2-4 times to obtain the wood processing residues with partial lignin removal.

4. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 3, characterized in that, the delignification solution is a mixed solution of sodium chlorite solution and acetate buffer solution, 1% to 30% by mass of hydrogen peroxide, 1% to 30% by mass of sodium hypochlorite solution or 1% to 30% by mass of anthraquinone solution; wherein the mixed solution of sodium chlorite solution and acetate buffer solution is a mixture of 5% sodium chlorite solution by mass and acetate buffer solution with a pH of 4.6 in a volume ratio of 30:1.

5. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (1), the drying treatment is specifically referred to heating for 5 hours-15 hours at a temperature of 40° C.-110° C.

6. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (2), the activation solution is dimethylacetamide, dimethylformamide or lithium chloride/dimethylacetamide solution with a lithium chloride mass fraction of 1%-6%.

7. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (3), the cellulose solvent is selected from one or a mixture of two or more of: N-methylmorpholine-N-oxide solution with 85% mass fraction, 1-allyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, dimethylacetamide/lithium chloride solution with a lithium chloride mass fraction of 8% to 10%, sodium hydroxide/urea mixed aqueous solution, zinc chloride/calcium chloride mixed aqueous solution, and zinc chloride/aluminum chloride mixed aqueous solution; wherein a mass fraction of sodium hydroxide in the sodium hydroxide/urea mixed aqueous solution is 7%, and a mass fraction of urea is 12%; a mass fraction of zinc chloride in the zinc chloride/calcium chloride mixed aqueous solution is 72%, and a mass fraction of calcium chloride is 2.2%; a mass fraction of zinc chloride in the zinc chloride/aluminum chloride mixed aqueous solution is 59%, and a mass fraction of aluminum chloride is 6.4%.

8. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (5), the regeneration solution is anhydrous ethanol, acetone, distilled water or deionized water.

9. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 1, characterized in that, in step (6), the process of hot-pressing is specifically referring to: hot-pressing at a temperature of 30° C.-150° C. and a pressure of 1 MPa-10 MPa for 5 hours-50 hours.

10. A method of recycling treatment of the high-strength, high-toughness, and recyclable fiberboard with bionic structure prepared by the method according to claim 1, characterized in that, the method is carried out according to the following steps:

placing the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeating the steps of swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment to complete the recycling treatment method.

11. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 3, characterized in that, in step (1), the process of removing lignin portion partially from the wood processing residues is specifically carried out according to the following steps: immersing the wood processing residues in a delignification solution, heating in a water bath for 10 hours-15 hours at a temperature of 60° C.-90° C., then immersing in deionized water for 1 hour-3 hours at a temperature of 20° C.-50° C., and repeating the step of immersing in deionized water for 2-4 times to obtain the wood processing residues with partial lignin removal.

12. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 11, characterized in that, the delignification solution is a mixed solution of sodium chlorite solution and acetate buffer solution, 1% to 30% by mass of hydrogen peroxide, 1% to 30% by mass of sodium hypochlorite solution or 1% to 30% by mass of anthraquinone solution; wherein the mixed solution of sodium chlorite solution and acetate buffer solution is a mixture of 5% sodium chlorite solution by mass and acetate buffer solution with a pH of 4.6 in a volume ratio of 30:1.

13. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 12, characterized in that, in step (1), the drying treatment is specifically referred to heating for 5 hours-15 hours at a temperature of 40° C.-110° C.

14. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 13, characterized in that, in step (2), the activation solution is dimethylacetamide, dimethylformamide or lithium chloride/dimethylacetamide solution with a lithium chloride mass fraction of 1%-6%.

15. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 14, characterized in that, in step (3), the cellulose solvent is selected from one or a mixture of two or more of: N-methylmorpholine-N-oxide solution with 85% mass fraction, 1-allyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, dimethylacetamide/lithium chloride solution with a lithium chloride mass fraction of 8% to 10%, sodium hydroxide/urea mixed aqueous solution, zinc chloride/calcium chloride mixed aqueous solution, and zinc chloride/aluminum chloride mixed aqueous solution; wherein a mass fraction of sodium hydroxide in the sodium hydroxide/urea mixed aqueous solution is 7%, and a mass fraction of urea is 12%; a mass fraction of zinc chloride in the zinc chloride/calcium chloride mixed aqueous solution is 72%, and a mass fraction of calcium chloride is 2.2%; a mass fraction of zinc chloride in the zinc chloride/aluminum chloride mixed aqueous solution is 59%, and a mass fraction of aluminum chloride is 6.4%.

16. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 15, characterized in that, in step (5), the regeneration solution is anhydrous ethanol, acetone, distilled water or deionized water.

17. The method of preparing high-strength, high-toughness, and recyclable fiberboard with bionic structure according to claim 16, characterized in that, in step (6), the process of hot-pressing is specifically referring to: hot-pressing at a temperature of 30° C.-150° C. and a pressure of 1 MPa-10 MPa for 5 hours-50 hours.

18. A method of recycling treatment of the high-strength, high-toughness, and recyclable fiberboard with bionic structure prepared by the method according to claim 11, characterized in that, the method is carried out according to the following steps:

placing the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeating the steps of swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment to complete the recycling treatment method.

19. A method of recycling treatment of the high-strength, high-toughness, and recyclable fiberboard with bionic structure prepared by the method according to claim 13, characterized in that, the method is carried out according to the following steps:

placing the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeating the steps of swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment to complete the recycling treatment method.

20. A method of recycling treatment of the high-strength, high-toughness, and recyclable fiberboard with bionic structure prepared by the method according to claim 17, characterized in that, the method is carried out according to the following steps:

placing the high-strength, high-toughness, and recyclable fiberboard with bionic structure in a crusher to process crushing, then repeating the steps of swelling treatment, dissociation and dispersion treatment, centrifugation, hydrogel construction, and densification treatment to complete the recycling treatment method.