Phosphorylated bamboo wood composite chitosan plate product and preparation method thereof

Abstract

The invention provides a phosphorylated bamboo wood composite chitosan plate product and a preparation method thereof. The plate product is a plate product with high hardness, high density, degradability, flame retardance and high mechanical property, which is obtained by performing hot press molding on one or more phosphorylated bamboo wood impregnated with a protonated chitosan solution in a mold, wherein the interfaces of the bamboo materials are tightly combined through chemical bond crosslinking, hydrogen bond interaction and / or physical winding, so that the flame retardant property and the mechanical property are improved at the same time. Based on the regulation and control strategy of the interface of the bamboo material, the preparation method of the plate product is simple, easy to operate and expandable in size, is more suitable for large-scale production and popularization, and has great application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bamboo processing technology and bamboo products, and more particularly to a phosphated bamboo composite chitosan board product and a method for preparing the same. BACKGROUND

[0002] At present, many studies focus on partially removing lignin and hemicellulose to obtain a bamboo framework with excellent mechanical properties and renewable characteristics, and then a series of treatments including bamboo framework densification, bamboo framework modification or polymer filling are performed to prepare high-strength bamboo-based materials. Traditional bamboo integrated wood, reconstituted bamboo and other products will produce pollutant emissions during resin impregnation processing and use, and the use of thermosetting resins is also difficult to degrade, recycle and reuse.

[0003] At present, there are few studies on fully bio-based bamboo-based structural materials, and most studies focus on the processing and modification of whole bamboo, and the materials prepared are limited by the size of the original bamboo. At the same time, there are few studies on the preparation of fully bio-based bamboo-based structural materials based on the interface regulation of bamboo materials. Therefore, it is of great practical significance to develop fully bio-based materials based on the interface regulation of bamboo. In addition, untreated bamboo materials may be easily ignited, which poses a safety hazard. Therefore, how to improve the flame retardant performance of engineering bamboo has also attracted widespread attention. The commonly used flame retardant treatment is to add flame retardants to the product to achieve the effect of flame retardation, but this method lacks effective combination between the flame retardant and the product, which will adversely affect the mechanical properties of the product, and also cause the loss of flame retardant during use, resulting in a decrease in the flame retardant effect.

[0004] Therefore, it is of great application value to develop a bamboo-based product with both mechanical properties and flame retardant effect. SUMMARY

[0005] Therefore, it is of great application value to develop a bamboo-based product with both mechanical properties and flame retardant effect.

[0006] In view of the above, one aspect of the present application provides a phosphonated bamboo composite chitosan board product, which is a naturally degradable bio-based product obtained by hot-pressing one or more phosphonated bamboos impregnated with a protonated chitosan solution in a mold, wherein the weight ratio of the phosphonated bamboo to the protonated chitosan in the board product is 1:0.1 to 1:0.4, the phosphonated bamboo is obtained by phosphonating modification of etched bamboo so that one or more of cellulose, hemicellulose and lignin of the bamboo is grafted with phosphonic groups, thereby obtaining a phosphonated bamboo having a multi-dimensional bamboo fiber network composed of macro bamboo fiber structures and micro-nano bamboo fiber networks; the protonated chitosan solution is obtained by dissolving chitosan with a deacetylation degree of 60% or more in an acidic solution capable of protonating the chitosan, and after impregnation, the protonated chitosan is filled in the multi-dimensional bamboo fiber network of the phosphonated bamboo; and wherein the board product has the following properties: (1) a bending strength of 100 MPa or more by three-point bending test; (2) a Shore D hardness value greater than 70 by Shore hardness test; (3) a limiting oxygen index greater than 30% according to ISO4589; and (4) optionally a density greater than 1.0 g / cm 3 .

[0007] In preferred embodiments, the bamboo used is derived from natural bamboo and is in one or more forms selected from bamboo splints, bamboo blocks, bamboo boards, flattened bamboo and bamboo fibers obtained by processing natural bamboo.

[0008] In preferred embodiments, the board product is a decorative board, a packaging board or a structural board.

[0009] In another aspect, the present application provides a method for preparing the above-mentioned board product, which comprises: etching treatment of bamboo; phosphonating modification of the etched bamboo to obtain a phosphonated bamboo; impregnating the phosphonated bamboo with a protonated chitosan solution so that the protonated chitosan is filled into the multi-dimensional bamboo fiber network of the phosphonated bamboo; hot-pressing one or more phosphonated bamboos impregnated with the protonated chitosan solution in a mold to obtain a preformed product; and after taking out the preformed product from the mold, drying it to obtain the desired board product.

[0010] In preferred embodiments, the etching treatment comprises soaking the bamboo with one or more etching solutions selected from aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous sodium sulfite solution, aqueous hydrogen peroxide solution, aqueous acetic acid solution and aqueous sodium carbonate solution, preferably the etching treatment is carried out at a temperature of 50-95°C.

[0011] In a preferred embodiment, the phosphorylation modification comprises treating the etched bamboo with a solution containing urea-phosphate, urea-phosphoric acid or urea-phosphoric acid-phosphate, so as to graft one or more of cellulose, hemicellulose and lignin of the bamboo with phosphoric acid groups, preferably the phosphorylation modification is carried out at a temperature of 100-170 °C.

[0012] In a preferred embodiment, the mass concentration of chitosan in the protonated chitosan solution is 2-10 %, preferably the acidic solution used to protonate the chitosan is aqueous acetic acid, preferably the impregnation is carried out under reduced pressure.

[0013] In a preferred embodiment, the hot-pressing is carried out at a temperature of 90-170 °C, a pressure of 1-800 MPa and a time of 1-20 h; preferably the hot-pressing is carried out at a temperature of 90-150 °C, a pressure of 20-200 MPa and a time of 5-20 h.

[0014] In a preferred embodiment, the drying is carried out at a temperature of 50-170 °C and a time of 1-100 h, preferably the drying is carried out at a temperature of 60-150 °C and a time of 5-50 h.

[0015] In a preferred embodiment, before the hot-pressing, the plurality of phosphorylated bamboos impregnated with the protonated chitosan solution are assembled and laid into a mold in a regular manner, such as but not limited to side-by-side laying, orthogonal laying, layer-by-layer laying, spiral laying at a non-right angle or a combination thereof.

[0016] The board product of the present application is a phosphorylated bamboo due to the chemical etching (which can be used to remove impurities and expose the fiber structure of the bamboo) and the phosphorylation modification, and the bamboo is composed of a multi-dimensional bamboo fiber network of macro bamboo fiber structure and micro-nano bamboo fiber network. The interface between the phosphorylated bamboos is tightly combined by the chemical bond crosslinking, hydrogen bonding and / or physical entanglement after the impregnation of the protonated chitosan and the hot-pressing, so that a high mechanical strength can be obtained without adding other adhesives such as polymer adhesives; at the same time, due to the presence of a large amount of phosphorus and / or nitrogen elements in the bamboo product, the resulting composite bamboo product has good flame retardant performance, and since the raw materials used are derived from biomass, the resulting composite bamboo product is safe, non-toxic and harmless and can be naturally degraded.

[0017] The plate product of the present application is a bio-based material product with high strength, high modulus, degradability, excellent flame retardancy and high impact resistance, and thus can meet the growing demand for lightweight high-strength structural materials and environmentally friendly materials. In addition, the composite plate product of the present application is prepared based on the interface regulation strategy of bamboo materials, and thus its size is expandable. Moreover, the preparation method of the composite plate product of the present application is simple and easy to operate, and is more suitable for large-scale production.

[0018] In addition, the advantages of the plate product of the present application also include but are not limited to the following aspects: the plate product of the present application is a high-performance environmentally friendly bio-based plate, which has many significant differences compared with the artificial plate widely used in the current market. For example, A) the artificial plate and wood-plastic product widely used in the current market both contain phenolic resin and other adhesives, which are non-degradable components and have a serious risk of polluting the environment. In contrast, the plate product of the present application is a full-biomass structure and does not contain any petroleum-based polymer adhesive, and is compostable and naturally degradable; B) the plate product of the present application has better mechanical properties, including bending strength and hardness; C) the plate product of the present application prepared based on the bamboo interface regulation has the expandability of size and thus has practicality in the engineering field; D) the plate product of the present application retains part of the lignin and the high-strength bamboo cellulose component, and contains a large amount of phosphorus and nitrogen elements, and has good flame retardant performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 and Figure 2 respectively show scanning electron microscope photos of phosphated bamboo splints prepared according to Example 1 at different scales;

[0020] Figure 3 shows a 2p electron test result graph of the phosphorus element of the X-ray photoelectron spectroscopy of the plate product prepared according to Example 1;

[0021] Figure 4 shows a digital photo of the plate product prepared according to Example 1;

[0022] Figure 5 shows a scanning electron microscope photo of the plate product prepared according to Example 1;

[0023] Figure 6 shows the Shore D value of each plate product prepared according to Examples 1-5;

[0024] Figure 7 shows the density value of each plate product prepared according to Examples 1-5;

[0025] Figure 8A scanning electron microscope photograph of a fracture surface of a board product prepared according to Example 1 after three-point bending test;

[0026] Figure 9 Results of the bending strength of each board product prepared according to Examples 1-5 are shown;

[0027] Figure 10 Results of the 1s electron test of the nitrogen element of the X-ray photoelectron spectroscopy of the board product prepared according to Example 1 are shown;

[0028] Figure 11 Results of the limiting oxygen index of each board product prepared according to Examples 1-5 are shown;

[0029] Figure 12 and Figure 13 Scanning electron microscope photographs of phosphorylated bamboo splints prepared according to Example 2 are shown at different scales, respectively;

[0030] Figure 14 A scanning electron microscope photograph of a board product prepared according to Example 2 is shown;

[0031] Figure 15 A scanning electron microscope photograph of a board product prepared according to Example 3 is shown;

[0032] Figure 16 A scanning electron microscope photograph of a board product prepared according to Example 4 is shown; and

[0033] Figure 17 A scanning electron microscope photograph of a board product prepared according to Example 5 is shown. DETAILED DESCRIPTION

[0034] The present application provides a board product of phosphorylated bamboo composite chitosan, which is a naturally degradable bio-based product obtained by hot-pressing one or more phosphorylated bamboo materials impregnated with a protonated chitosan solution in a mold.

[0035] Specifically, the present application is modified by chemical etching and phosphorylation, then the bamboo material modified by chemical etching and phosphorylation is impregnated with a protonated chitosan solution, so that the protonated chitosan is fully filled in the multi-dimensional bamboo fiber network of the phosphorylated bamboo material, and finally the desired composite bamboo product is obtained by hot-pressing one or more phosphorylated bamboo materials impregnated with a protonated chitosan solution in a mold.

[0036] In the present application, the weight ratio of the phosphorylated bamboo material to the protonated chitosan in the board product is 1:0.1-1:0.4, preferably 1:0.1-1:0.3.

[0037] In the present application, the bamboo material is first subjected to chemical etching, then modified by phosphating, and then subjected to filling treatment with protonated chitosan. The obtained composite bamboo product has a multi-dimensional phosphated bamboo fiber network composed of macro bamboo fiber structure and micro-nano bamboo fiber network, and protonated chitosan filled therebetween. The interface between the bamboo materials forms a chemical bond crosslinking, hydrogen bonding and / or physical entanglement to achieve close combination. Thus, the flame retardant performance and mechanical performance are simultaneously improved, and the obtained board product has at least the following properties:

[0038] (1) The bending strength by three-point bending test is 100 MPa or more, preferably 200 MPa or more, and more preferably 300 MPa or more;

[0039] (2) The Shore D value by Shore hardness test is greater than 70; preferably greater than 80;

[0040] (3) The limiting oxygen index measured according to ISO 4589 is greater than 30%, preferably greater than 40%, and more preferably greater than 45%; and

[0041] (4) Optionally, the density of the obtained board product is greater than 1.0 g / cm 3 , preferably greater than 1.2 g / cm 3 .

[0042] In the present application, the bamboo material used is not particularly limited. Preferably, it can be at least one of natural bamboo and parts thereof such as bamboo green (i.e. the outer part of the bamboo material) or bamboo yellow (i.e. the inner part of the bamboo material) processed after bamboo splints, bamboo blocks, bamboo boards, flat bamboo, bamboo fibers from different producing areas, different varieties.

[0043] In the present application, the specific application of the board product is not particularly limited, which mainly depends on the mold selected according to the required application. Preferably, for example, the board product of the present application can be a decorative board, a packaging board or a structural board, for example but not limited to, which can be used for automobile floor, wind turbine blade, space shuttle and other special application scenarios.

[0044] The present application provides a method for preparing the above-mentioned board product, comprising: etching the bamboo material; phosphating the etched bamboo material to obtain a phosphated bamboo material; immersing the phosphated bamboo material in a protonated chitosan solution to fill the protonated chitosan into the multi-dimensional bamboo fiber network of the phosphated bamboo material; assembling one or more phosphated bamboo materials immersed in the protonated chitosan solution in a mold for hot pressing to obtain a preformed product; and after taking the preformed product out of the mold, drying it to obtain the desired board product.

[0045] In the present application, the etching treatment can also be referred to as a pretreatment, which is mainly used for removing impurities on the surface of the bamboo material and part of the biological macromolecules present in the bamboo tissue, including but not limited to proteins, sugars, cellulose, etc., so that the etched bamboo material exposes a rich micro-nano fiber network (i.e., has a multi-dimensional bamboo fiber network composed of macro bamboo fiber structure and micro-nano bamboo fiber network) while retaining the excellent performance of the macro fiber structure, thereby providing a filling space for the protonated chitosan in the subsequent impregnation process.

[0046] In the present application, preferably, the etching treatment includes soaking the bamboo material in one or more etching solutions selected from aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous sodium sulfite solution, aqueous hydrogen peroxide solution, aqueous acetic acid solution, and aqueous sodium carbonate solution, and other solutions capable of dissolving biological macromolecules. More preferably, the etching treatment can be carried out in a hot etching solution, for example, at a temperature of 50-95 ℃. The present application does not have a particular limitation on the time of etching or impregnation, which can be preferably 10 min to 4 h, for example, 1 h.

[0047] In the present application, the composition and concentration of the etching solution used are not particularly limited and can be prepared as needed. For example, in one specific embodiment, the etching solution can be a 0.1 mol / L sodium hydroxide solution. In another specific embodiment, the etching solution can be a mixed solution of hydrogen peroxide (30% content) and acetic acid in a volume ratio of 1:1.

[0048] In the present application, preferably, the phosphorylation modification includes treating the etched bamboo material with a solution containing urea-phosphate, urea-phosphoric acid, or urea-phosphoric acid-phosphate, so that one or more of cellulose, hemicellulose, and lignin of the bamboo are grafted with phosphoric acid groups. In the present application, the phosphating agent used can contain phosphorus elements, and the phosphate used therein can be, for example, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, etc. More preferably, the phosphating agent used can be, for example, one or more selected from aqueous urea-ammonium dihydrogen phosphate solution, aqueous urea-sodium dihydrogen phosphate solution, aqueous urea-disodium hydrogen phosphate solution, aqueous urea-diammonium hydrogen phosphate solution, aqueous urea-phosphoric acid-diammonium hydrogen phosphate solution, or aqueous urea-phosphoric acid-ammonium dihydrogen phosphate solution.

[0049] More preferably, the phosphorylation modification can be performed in a hot phosphorylating solution, for example at a temperature of 100-170 °C, more preferably 110-150 °C. The present application does not have a particular limitation on the time for phosphorylation, which can be preferably 5 min to 2 h, more preferably 30-90 min, for example 30 min. For example, in one specific embodiment, the phosphorylation can be achieved by immersing 10 g of etched bamboo (for example in the form of bamboo splints) (if necessary, cleaned with water in advance and dried) in a mixed solution of 40 g of urea and 15 g of ammonium dihydrogen phosphate dissolved in water, drying the water, and then keeping at 150 °C for 10 min to react (so that one or more of cellulose, hemicellulose and lignin of the bamboo is grafted with phosphoric acid groups, which can be confirmed by successful grafting of phosphoric acid groups based on test results of X-ray photoelectron spectroscopy (XPS) of the phosphorylated bamboo, for example), thereby preparing phosphorylated bamboo splints.

[0050] In the present application, the protonated chitosan solution used is obtained by dissolving chitosan having a degree of deacetylation of 60% or more (preferably 70% or more, more preferably 80% or more) in an acidic solution capable of protonating the chitosan.

[0051] In the present application, the mass concentration of chitosan in the protonated chitosan solution used is not particularly limited and can be preferably 2-10%. In the present application, the kind and concentration of the acidic solution used to protonate the chitosan are not particularly limited. For example, the acidic solution can be an aqueous solution of a common inorganic acid such as hydrochloric acid, sulfuric acid, etc., or an aqueous solution of an organic acid such as formic acid, acetic acid, propionic acid, etc. In one preferred embodiment, the acidic solution used to protonate the chitosan is an aqueous acetic acid solution, preferably having a mass concentration of 2-10%. As a non-limiting example, the protonated chitosan solution used can be a solution formed by dissolving 2 g of chitosan and 2 g of acetic acid in 96 g of water. As another non-limiting example, the protonated chitosan solution used can be a solution formed by dissolving 4 g of chitosan and 4 g of acetic acid in 92 g of water.

[0052] In the present application, preferably, the impregnation of the phosphorylated bamboo with the protonated chitosan solution can be performed under normal pressure or reduced pressure.

[0053] In the present application, preferably, one or more of the phosphorylated bamboo impregnated with the protonated chitosan solution can be assembled and laid in the mold in a regular pattern before hot press molding, which includes, for example, laying in parallel in the longitudinal direction of the bamboo, laying orthogonally, laying in layers, laying in a spiral at a non-right angle, or a combination thereof.

[0054] In the present application, the mold type, shape, and size specifications for hot press molding are not particularly limited, and can be selected or designed as needed for the intended application. For example, the mold for hot press molding can be a mold of a material such as stainless steel, aluminum alloy, etc. commonly used in the art, and the shape and / or size thereof can be selected or designed as needed.

[0055] In the present application, preferably, the temperature for hot press molding can be 90-170 °C, the pressure can be 1-800 MPa, and the time can be 1-20 h. More preferably, the temperature for hot press molding can be 90-150 °C, the pressure can be 20-200 MPa, and the time can be 5-20 h. Hot pressing can also be achieved by multi-stage hot pressing at different temperatures, for example, by first holding at a lower temperature for a longer time and then holding at a higher temperature for a shorter time.

[0056] In the present application, preferably, after the hot press is completed, pressure holding and cooling (i.e., normal temperature standing) can be performed, the pressure is released after cooling to room temperature, and then the preform is removed for subsequent drying.

[0057] In the present application, the equipment for drying is not particularly limited, and can be performed in a dryer or drying chamber as needed, for example. Preferably, the temperature for drying the preform can be 50-170 °C, and the time can be 1-100 h. More preferably, the temperature for drying can be 60-150 °C, and the time can be 5-50 h.

[0058] In the present application, preferably, after the drying is completed, the obtained plate product can be cut and / or polished as needed.

[0059] As used herein, the term "macroscopic bamboo fiber structure" refers to a structure in a bamboo material formed by fibers having a diameter of about 50 μm or more and a length of about 1 mm or more. As used herein, the term "micro-nano bamboo fiber network" refers to an intertangled network structure in a bamboo material formed by fibers having a diameter of 50 μm or less (typically 10 μm or less).

[0060] As used herein, the term "phosphorylation modification" refers to a phosphorylation reaction of a bamboo material using a phosphorylation reagent to graft phosphate groups to one or more of cellulose, hemicellulose, and lignin in the bamboo material. More specifically, in the present application, the phosphorylation modification includes treating an etched bamboo raw material using a solution containing urea-phosphate, urea-phosphoric acid, or urea-phosphoric acid-phosphate to graft phosphate groups to one or more of cellulose, hemicellulose, and lignin therein.

[0061] As used herein, the expression "without the addition of other binders such as polymer binders" means that, in the process of hot-pressing the plurality of phosphatized bamboo materials impregnated with the protonated chitosan solution in a mold, since the protonated chitosan solution used for the impregnation treatment itself can play the role of a binder, additional binders such as polymer binders can not be required to be added. Although a conventional binder such as a polymer binder can be additionally added in certain cases, it is preferred in the present application that no binder other than the protonated chitosan solution, such as a polymer binder, is added, from the viewpoint of environmental protection, cost, etc. As used herein, the term "polymer binder" refers to a polymer binder (also referred to as a high-molecular-weight binder) added in the wood-based panel industry in order to form and achieve a certain strength of bamboo, wood, etc. as a raw material, which includes, but is not limited to, phenol formaldehyde resin, urea formaldehyde resin, melamine formaldehyde resin, epoxy resin, polyurethane, neoprene, and acrylic resin, etc. that are generally used as binders.

[0062] Without being bound by any theory, it is believed that, after impregnation with the protonated chitosan solution, the phosphatized modified bamboo material (i.e., the phosphatized bamboo material) can form physical entanglement between the materials, and at the same time, strong cross-linking can be achieved through chemical cross-linking such as chemical bonds and hydrogen bonds, so that the final board product can have excellent mechanical properties such as high bending strength and high hardness, thereby eliminating the environmental pollution caused by the use of polymer binders such as phenol formaldehyde resin, urea formaldehyde resin, and epoxy resin, etc. in the prior art, so that the industrial application prospect of the present application is very broad. In fact, the present application can completely avoid the use of high-cost and high-environmental-pollution polymer binders such as phenol formaldehyde resin, and at the same time, can achieve the improvement of various properties of the phosphatized bamboo-chitosan composite board product, including the significant improvement of strength, hardness, fire resistance, and environmental protection.

[0063] In order to further illustrate the present application, the preferred embodiments of the present application are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not intended to limit the scope of the present application.

[0064] Example 1

[0065] Newly cut natural bamboo was taken from the inside of the bamboo yellow part with a bamboo knife to process into a bamboo splint piece with a thickness of about 0.5 mm, a width of about 1 cm, and a length of about 5.9 cm. 30 such bamboo splint pieces were placed in a beaker containing 0.1 mol / L sodium hydroxide aqueous solution (sodium hydroxide was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.) and placed in an oven at 80°C for 1 h, then taken out and washed with deionized water, and the pH of the washing solution was detected with pH paper until the pH of the washing solution was neutral, to obtain etched bamboo splint pieces. Then, 30 etched bamboo splint pieces were placed in a beaker containing a water solution dissolved with 40 g urea and 15 g ammonium dihydrogen phosphate (urea and ammonium dihydrogen phosphate were both purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.) and soaked thoroughly, then placed in an oven at 80°C for drying, and after drying, heated to 150°C and kept at 150°C for 10 minutes. Then the heating was turned off, the reaction product was washed with deionized water, and the pH of the washing solution was detected with pH paper until the pH of the washing solution was neutral, to obtain phosphated bamboo splint pieces. The multi-dimensional bamboo fiber network composed of macro bamboo fiber structure and micro-nano bamboo fiber network. The prepared phosphated bamboo splint pieces were observed using a scanning electron microscope (Gemini SEM 500), and Figure 1 and Figure 2 show the scanning electron microscope photos of the phosphated bamboo splint pieces at different scales, respectively. From Figure 1 and Figure 2 it can be observed that the prepared phosphated bamboo splint pieces have macro bamboo fiber structure and micro-nano bamboo fiber network structure, and it can also be observed that the prepared phosphated bamboo splint pieces have a multi-dimensional bamboo fiber network composed of macro bamboo fiber structure and micro-nano bamboo fiber network. The prepared phosphated bamboo splint pieces were tested using X-ray photoelectron spectroscopy (Kratos AXIS SUPRA+), and Figure 3 show the XPS P2P test result graph of the phosphorus element (P) of the phosphated bamboo splint pieces. From Figure 3 it can be seen that the signal peak of the phosphorus element appears in the P2P test result of the prepared phosphated bamboo splint pieces, which confirms the success of the phosphating modification.

[0066] Next, in a beaker, 2 g of chitosan powder (85% degree of deacetylation, purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.) and 2 g of acetic acid (purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.) were dissolved into 96 g of water to prepare a protonated chitosan solution with a chitosan mass concentration of 2%. 30 obtained phosphated bamboo splint pieces were immersed in the prepared protonated chitosan solution with a chitosan mass concentration of 2%, and then immersed in a vacuum oven under reduced pressure using a pressure of -0.5 MPa.

[0067] The phosphorylated bamboo strips, which have been impregnated with protonated chitosan solution, are evenly laid out in a 6*6 cm area along the grain of the bamboo. 2 In a custom stainless steel mold, hot pressing is performed using a hot press (Tianjin Keqi 150F): First, cold pressing is performed at room temperature to remove excess water. Then, under a pressure of 90 MPa, the temperature is first raised to 90 ℃ and held for 3 hours, and then held at 140 ℃ for 0.5 hours, thus completing the hot pressing process.

[0068] Finally, turn off the heating, depressurize the mold after cooling to room temperature, remove the preform, and dry it in an oven at 80°C for 10 hours. Then, remove the burrs with a cutting blade and sand it to obtain the final sheet product.

[0069] The resulting board products were photographed using a Redmi K50 mobile phone, and Figure 4 A photograph of the sheet material is shown. From Figure 4 It can be seen that the resulting board products are bamboo boards, which can be used for decorative boards / packaging boards or structural boards such as automobile floorboards, wind turbine blades, and space shuttles.

[0070] The obtained sheet metal products were observed using a scanning electron microscope (Gemini SEM 500), and Figure 5 A scanning electron microscope image of the sheet material is shown. From Figure 5 As can be seen, the resulting sheet material is very dense at the micrometer scale and has no porous structure.

[0071] The obtained sheet metal products were tested for Shore hardness D value using a digital Shore hardness tester (HS-A), and the results were within... Figure 6 As shown in the image. From Figure 6 The results show that the Shore hardness D value of the sheet material prepared according to Example 1 is about 89, indicating that the surface of the prepared sheet material has a very high hardness.

[0072] The mass and dimensions of the obtained sheet metal products were measured using a precision electronic scale and vernier calipers, and their density was calculated. The results were then... Figure 7 As shown in the image. From Figure 7 The results show that the density of the sheet material prepared according to Example 1 is 1.321 g / cm³. 3 This indicates that the prepared sheet material has a dense structure.

[0073] The obtained sheet metal products were tested for bending strength or bending fracture strength using a universal mechanical testing machine (AGX-V 20KN). Figure 8A scanning electron microscope image of the cross-section of a sheet metal article prepared according to Example 1 after fracture under a three-point bend test is shown, and from this... Figure 8 It can be observed that the sheet material exhibits broken fiber structures at the fracture surface. Furthermore, the measured flexural strength is... Figure 9 As shown in, and from that Figure 9 The results show that the prepared board products have a bending strength of 377 MPa perpendicular to the bamboo fiber arrangement direction.

[0074] The obtained sheet products were subjected to XPS testing using an X-ray photoelectron spectroscopy (XPS) instrument. Figure 10 The graph shows the 1s electron (N1s) test results for nitrogen (N) in XPS of this sheet material. From... Figure 10 As can be seen, an NP signal peak appeared in the measured N1s spectrum, which confirms that a chemical bond was formed between the phosphorylated bamboo strips prepared according to the present invention and the protonated chitosan.

[0075] The resulting board products were tested using a limiting oxygen index tester (VOUCH 5801A) according to ISO 4589, and the results are shown below. Figure 11 From Figure 11 The results show that the limiting oxygen index of the board product prepared according to Example 1 is 53.2%, indicating that it has excellent flame retardant properties.

[0076] Example 2

[0077] Freshly cut natural bamboo, using the pith, is processed into bamboo strips approximately 0.5 mm thick, 1 cm wide, and 5.9 cm long. Thirty such bamboo strips are placed in a beaker containing a 0.1 mol / L sodium hydroxide aqueous solution and left to stand in an oven at 80°C for 1 hour. They are then removed and rinsed with deionized water, with the pH of the rinsing solution checked using pH paper until the pH of the solution is neutral, resulting in etched bamboo strips. Next, the etched bamboo strips are placed in a beaker containing a 1:1 volume ratio of hydrogen peroxide (30% concentration, purchased from Sinopharm Chemical Reagent Co., Ltd.) to acetic acid and left to stand in an oven at 80°C for 1.5 hours. They are then removed and rinsed with deionized water, with the pH of the rinsing solution checked using pH paper until the pH of the solution is neutral, resulting in pretreated bamboo strips.

[0078] After that, 30 pretreated bamboo splints were put into a beaker in which 5 g of urea and 1.875 g of ammonium dihydrogen phosphate were dissolved in an aqueous solution, and were soaked thoroughly, and then were placed in an oven at 80 °C for drying. After drying, heating was performed to 150 °C, and was maintained at 150 °C for 10 minutes. Then, heating was turned off, the reaction product was taken out and was soaked in deionized water, and the pH of the soaking solution was detected using pH paper until the pH of the soaking solution was neutral, and thus phosphated bamboo splints were obtained. The prepared phosphated bamboo splints were observed using a scanning electron microscope, and Figure 12 and Figure 13 show scanning electron microscope photographs of the phosphated bamboo splints at different scales, respectively. From Figure 12 and Figure 13 it can be observed that the prepared phosphated bamboo splints have a macro bamboo fiber structure and a micro-nano bamboo fiber network structure, and it can also be observed that the prepared phosphated bamboo splints have a multi-dimensional bamboo fiber network composed of the macro bamboo fiber structure and the micro-nano bamboo fiber network. In addition, it was also confirmed that the phosphating modification was successful by XPS testing (not shown) using an X-ray photoelectron spectrometer.

[0079] Next, in a beaker, 2 g of chitosan powder and 2 g of acetic acid were dissolved in 96 g of water to prepare a 2% mass concentration of protonated chitosan solution. The 30 obtained phosphated bamboo splints were immersed in the prepared 2% mass concentration of protonated chitosan solution, and then were impregnated under reduced pressure using a vacuum oven at a pressure of -0.5 MPa.

[0080] The above phosphated bamboo splints impregnated with the protonated chitosan solution were uniformly laid in a stainless steel mold with a size of 6*6 cm 2 in the bamboo wood direction, and hot pressing was completed using a hot press: first, cold pressing was performed at room temperature to remove excess water. Then, under a pressure of 90 MPa, the temperature was first increased to 90 °C and maintained for 3 hours, and then the temperature was maintained at 140 °C for 0.5 hours, and thus hot pressing was completed.

[0081] Finally, heating was turned off, the mold was depressurized after cooling to room temperature, and then the preform was taken out and was dried in an oven at 80 °C for 10 hours, and then burrs were removed by using a cutting blade and were polished by using sandpaper, and thus the final board product was obtained.

[0082] The obtained board product was observed using a scanning electron microscope, and Figure 14 showed a scanning electron microscope photograph of the board product. From Figure 14 it can be seen that the obtained board product is very dense on a micron scale.

[0083] The obtained board product was subjected to Shore D hardness value test using a digital Shore hardness tester, and the results are shown in Table 2. Figure 6 As can be seen from the results shown in Table 2, the board product prepared according to Example 2 had a Shore D hardness value of 85, indicating that the surface of the obtained board product had a very high hardness. Figure 6

[0084] The mass and size of the obtained board product were detected using a precision electronic scale and a vernier caliper, and its density was calculated, and the results are shown in Table 3. Figure 7 As can be seen from the results shown in Table 3, the board product prepared according to Example 2 had a density value of 1.305 g / cm 3 , indicating that the structure of the prepared board product was dense. Figure 7

[0085] The obtained board product was subjected to flexural strength or flexural fracture strength test using a universal mechanical testing machine, and the measured flexural strength is shown in Table 4. Figure 9 As can be seen from the results shown in Table 4, the prepared board product had a flexural strength of 330 MPa in the direction perpendicular to the arrangement direction of the bamboo fibers. In addition, similar to Example 1, the board product had a fiber structure pulled apart on the fracture surface. Figure 9

[0086] The obtained board product was subjected to XPS test using an X-ray photoelectron spectrometer, and similar to Example 1, the results (not shown) confirmed that a chemical bond was formed between the phosphonated bamboo splints and the protonated chitosan prepared according to the present application.

[0087] The obtained board product was subjected to test according to ISO 4589 using a limiting oxygen index tester, and the results are shown in Table 5. Figure 11 As can be seen from the results shown in Table 5, the board product prepared according to Example 2 had a limiting oxygen index of 49.6 %, indicating that it had excellent flame retardant properties. Figure 11 Example 3

[0088]

[0089] ​​​​A freshly cut natural bamboo (including bamboo green and bamboo yellow) was processed with a bamboo knife into a bamboo block having a thickness of about 3 mm, a width of about 5.9 cm, and a length of about 5.9 cm. One such bamboo block was placed in a beaker containing 0.1 mol / L aqueous sodium hydroxide solution and left in an oven at 80°C for 1 h. It was then removed and soaked with deionized water, and the pH of the soaking solution was tested with pH paper until the pH of the soaked solution was neutral, to obtain an etched bamboo block. The etched bamboo block was then placed in a beaker containing a mixed aqueous solution of hydrogen peroxide:acetic acid in a volume ratio of 1:1 and left in an oven at 80°C for 1.5 h. It was then removed and soaked with deionized water, and the pH of the soaking solution was tested with pH paper until the pH of the soaked solution was neutral, to obtain a pretreated bamboo block.

[0090] After that, one bamboo block was placed in a beaker containing an aqueous solution in which 5 g of urea and 1.875 g of ammonium dihydrogen phosphate were dissolved, and was soaked thoroughly, and then was placed in an oven at 80°C to dry. After drying, it was heated to 150°C and maintained at 150°C for 10 minutes. Then the heating was turned off, the reaction product was removed and soaked with deionized water, and the pH of the soaking solution was tested with pH paper until the pH of the soaked solution was neutral, to obtain a phosphated bamboo block. The prepared phosphated bamboo block was observed using a scanning electron microscope, and as a result (not shown), it was also observed that the phosphated bamboo block prepared according to Example 3 had a macro bamboo fiber structure and a micro-nano bamboo fiber network structure similar to those of the phosphated bamboo splint prepared in Example 1, and it was also observed that the prepared phosphated bamboo block had a multi-dimensional bamboo fiber network composed of the macro bamboo fiber structure and the micro-nano bamboo fiber network. In addition, it was also confirmed that the phosphating modification was successful through XPS testing (not shown) using an X-ray photoelectron spectrometer.

[0091] Next, in a beaker, 2 g of chitosan powder and 2 g of acetic acid were dissolved in 96 g of water to prepare a protonated chitosan solution having a chitosan mass concentration of 2%. The resulting one phosphated bamboo splint was immersed in the prepared protonated chitosan solution having a chitosan mass concentration of 2%, and then was impregnated under reduced pressure using a vacuum oven at a pressure of -0.5 MPa.

[0092] The phosphated bamboo block impregnated with the above protonated chitosan solution was placed in a stainless steel mold having a size of 6*6 cm 2 , and hot pressing was completed using a hot press: first, cold pressing was performed at room temperature to remove excess water. Then, at a pressure of 90 MPa, the temperature was first increased to 90°C and maintained for 3 hours, and then the temperature was increased to 140°C and maintained for 0.5 hours, thereby completing the hot pressing.

[0093] Finally, turn off the heating, depressurize the mold after cooling to room temperature, remove the preform, and dry it in an oven at 80°C for 10 hours. Then, remove the burrs with a cutting blade and sand it with sandpaper to obtain the final sheet product.

[0094] The obtained sheet metal products were observed using a scanning electron microscope, and Figure 15 A scanning electron microscope image of the sheet material is shown. From Figure 15 As can be seen, the resulting sheet material is very dense in most areas at the micrometer scale.

[0095] The obtained sheet metal products were tested for Shore hardness D value using a digital display Shore hardness tester, and the results were within... Figure 6 As shown in the image. From Figure 6 The results show that the Shore hardness D value of the sheet material prepared according to Example 3 is 90, indicating that the surface of Example 3 has a very high hardness.

[0096] The mass and dimensions of the obtained sheet metal products were measured using a precision electronic scale and vernier calipers, and their density was calculated. The results were then... Figure 7 As shown in the image. From Figure 7 The results show that the density of the sheet material prepared according to Example 3 is 1.265 g / cm³. 3 This indicates that the structure of the sheet material prepared in Example 3 is dense.

[0097] The obtained sheet metal products were tested for flexural strength or flexural fracture strength using a universal testing machine, and the measured flexural strength was within... Figure 9 As shown in the image. Figure 9 The results show that the prepared board product has a bending strength of 351 MPa perpendicular to the bamboo fiber arrangement direction. Furthermore, similar to Example 1, this board product exhibits a broken fiber structure at the fracture surface.

[0098] The obtained board products were tested using an X-ray photoelectron spectroscopy (XPS) instrument, and similar to Example 1, the results (not shown) confirmed that a chemical bond was formed between the phosphorylated bamboo strips prepared according to the present invention and the protonated chitosan.

[0099] The resulting board products were tested using a limiting oxygen index tester according to ISO 4589, and the results are shown in [the table / formula]. Figure 11 From Figure 11 The results show that the limiting oxygen index of the board product prepared according to Example 3 is 50.7%, indicating that it has excellent flame retardant properties.

[0100] Example 4

[0101] Freshly cut natural bamboo is processed using a bamboo knife, taking the inner yellow part of the bamboo and cutting it into bamboo strips approximately 0.5 mm thick, 1 cm wide, and 5.9 cm long. Thirty such bamboo strips are placed in a beaker containing a 0.1 mol / L sodium hydroxide aqueous solution and left to stand in an oven at 80 °C for 1 hour. They are then removed and rinsed with deionized water, and the pH value of the rinsing solution is tested with pH paper until the pH of the rinsing solution is neutral, resulting in etched bamboo strips.

[0102] Next, 30 etched bamboo strips were thoroughly immersed in an aqueous solution containing 40 g of urea and 15 g of ammonium dihydrogen phosphate, and then dried in an oven at 80 °C. After drying, the temperature was raised to 150 °C and maintained at 150 °C for 10 minutes. The heating was then turned off, and the reactants were removed and rinsed with deionized water. The pH of the rinsing solution was measured using pH paper until the pH of the rinsing solution was neutral, yielding phosphorylated bamboo strips. The prepared phosphorylated bamboo strips were observed using a scanning electron microscope, and as a result (not shown), it was also observed that the phosphorylated bamboo strips prepared according to Example 4 had a similar macroscopic bamboo fiber structure and micro / nano bamboo fiber network structure as those prepared in Example 1. Furthermore, the prepared phosphorylated bamboo blocks exhibited a multidimensional bamboo fiber network composed of macroscopic bamboo fiber structures and micro / nano bamboo fiber networks. In addition, XPS testing using X-ray photoelectron spectroscopy (not shown) also confirmed the success of the phosphorylation modification.

[0103] Next, in a beaker, 4 g of chitosan powder and 4 g of acetic acid were dissolved in 92 g of water to prepare a protonated chitosan solution with a chitosan mass concentration of 4%. 10 g of the obtained phosphorylated bamboo strips were then impregnated in the prepared protonated chitosan solution with a chitosan mass concentration of 4%, and then impregnated in a vacuum oven under reduced pressure of -0.5 MPa to allow penetration.

[0104] The phosphorylated bamboo strips, which have been impregnated with protonated chitosan solution, are evenly laid out in a 6*6 cm area along the grain of the bamboo. 2 In the stainless steel mold, hot pressing is performed using a hot press: first, cold pressing is performed at room temperature to remove excess water. Then, under a pressure of 90 MPa, the temperature is first raised to 90 ℃ and held for 3 hours, and then held at 140 ℃ for 0.5 hours, thus completing the hot pressing process.

[0105] Finally, turn off the heating, depressurize the mold after cooling to room temperature, remove the preform, and dry it in an oven at 80°C for 10 hours. Then, remove the burrs with a cutting blade and sand it with sandpaper to obtain the final sheet product.

[0106] The obtained sheet metal products were observed using a scanning electron microscope, and Figure 16 A scanning electron microscope image of the sheet material is shown. From Figure 16 As can be seen, the resulting sheet material is very dense at the micrometer scale.

[0107] The obtained sheet metal products were tested for Shore hardness D value using a digital display Shore hardness tester, and the results were within... Figure 6 As shown in the image. From Figure 6 The results show that the Shore hardness D value of the sheet material prepared according to Example 4 is 88.5, indicating that the surface of the obtained sheet material has a very high hardness.

[0108] The mass and dimensions of the obtained sheet metal products were measured using a precision electronic scale and vernier calipers, and their density was calculated. The results were then... Figure 7 As shown in the image. From Figure 7 The results show that the density of the sheet material prepared according to Example 4 is 1.384 g / cm³. 3 This indicates that the prepared sheet material has a dense structure.

[0109] The obtained sheet metal products were tested for flexural strength or flexural fracture strength using a universal testing machine, and the measured flexural strength was within... Figure 9 As shown in the image. Figure 9 The results show that the prepared board product has a bending strength of 337 MPa perpendicular to the bamboo fiber arrangement direction. Furthermore, similar to Example 1, this board product exhibits a broken fiber structure at the fracture surface.

[0110] The obtained board products were tested using an X-ray photoelectron spectroscopy (XPS) instrument, and similar to Example 1, the results (not shown) confirmed that a chemical bond was formed between the phosphorylated bamboo strips prepared according to the present invention and the protonated chitosan.

[0111] The resulting board products were tested using a limiting oxygen index tester according to ISO 4589, and the results are shown in [the table / formula]. Figure 11 From Figure 11 The results show that the limiting oxygen index of the board product prepared according to Example 4 is 52.7%, indicating that it has excellent flame retardant properties.

[0112] Example 5

[0113] Freshly cut natural bamboo is processed using a bamboo knife, taking the inner yellow part of the bamboo and cutting it into bamboo strips approximately 0.5 mm thick, 1 cm wide, and 15.9 cm long. Ninety such bamboo strips are placed in a beaker containing a 0.1 mol / L sodium hydroxide aqueous solution and left to stand in an oven at 80°C for 1 hour. They are then removed and rinsed with deionized water, with the pH value of the rinsing solution being tested using pH paper until the pH of the rinsing solution is neutral, thus obtaining etched bamboo strips.

[0114] Next, 90 etched bamboo strips were thoroughly soaked in an aqueous solution containing 400 g of urea and 150 g of ammonium dihydrogen phosphate. They were then dried in an oven at 80 °C, followed by heating to 150 °C and maintaining this temperature for 10 minutes. The heating was then turned off, and the reactants were removed and rinsed with deionized water. The pH of the rinsing solution was checked with pH paper until it reached neutral, yielding phosphorylated bamboo strips. The prepared phosphorylated bamboo strips were observed using a scanning electron microscope (not shown). It was also observed that the phosphorylated bamboo strips prepared according to Example 5 possessed a similar macroscopic bamboo fiber structure and micro / nano bamboo fiber network structure as those prepared in Example 1. Furthermore, the prepared phosphorylated bamboo blocks exhibited a multidimensional bamboo fiber network composed of macroscopic bamboo fiber structures and micro / nano bamboo fiber networks. In addition, XPS testing using X-ray photoelectron spectroscopy (not shown) confirmed the successful phosphorylation modification.

[0115] Next, in a beaker, 20 g of chitosan powder and 20 g of acetic acid were dissolved in 960 g of water to prepare a protonated chitosan solution with a chitosan mass concentration of 2%. Ninety phosphorylated bamboo strips were then immersed in the prepared protonated chitosan solution with a chitosan mass concentration of 2%, and then impregnated in a vacuum oven under reduced pressure of -0.5 MPa to allow penetration.

[0116] The phosphorylated bamboo strips, which have been impregnated with protonated chitosan solution, are laid out orthogonally in a 16*16 cm area. 2 In the stainless steel mold, hot pressing is performed using a hot press: first, cold pressing is performed at room temperature to remove excess water. Then, under a pressure of 20 MPa, the temperature is first raised to 60 ℃ and held for 2 hours, then raised to 80 ℃ and held for 1 hour, then raised to 90 ℃ and held for 3 hours, and finally held at 140 ℃ for 1 hour, thus completing the hot pressing process.

[0117] Finally, turn off the heating, depressurize the mold after cooling to room temperature, remove the preform, and dry it in an oven at 80°C for 10 hours. Then, remove the burrs with a cutting blade and sand it with sandpaper to obtain the final sheet product.

[0118] The obtained sheet metal products were observed using a scanning electron microscope, and Figure 17 A scanning electron microscope image of the sheet material is shown. From Figure 17 As can be seen, the resulting sheet material is very dense at the micrometer scale.

[0119] The obtained sheet metal products were tested for Shore hardness D value using a digital display Shore hardness tester, and the results were within... Figure 6 As shown in the image. From Figure 6 The results show that the Shore hardness D value of the sheet material prepared according to Example 4 is 84.5, indicating that the surface of the obtained sheet material has a very high hardness.

[0120] The mass and dimensions of the obtained sheet metal products were measured using a precision electronic scale and vernier calipers, and their density was calculated. The results were then... Figure 7 As shown in the image. From Figure 7 The results show that the density of the sheet material prepared according to Example 5 is 1.287 g / cm³. 3 This indicates that the prepared sheet material has a dense structure.

[0121] The obtained sheet metal products were tested for flexural strength or flexural fracture strength using a universal testing machine, and the measured flexural strength was within... Figure 9 As shown in the image. Figure 9 The results show that the prepared board product has a bending strength of 182 MPa perpendicular to the bamboo fiber arrangement direction. Furthermore, similar to Example 1, this board product exhibits a broken fiber structure at the fracture surface.

[0122] The obtained board products were tested using an X-ray photoelectron spectroscopy (XPS) instrument, and similar to Example 1, the results (not shown) confirmed that a chemical bond was formed between the phosphorylated bamboo strips prepared according to the present invention and the protonated chitosan.

[0123] The resulting board products were tested using a limiting oxygen index tester according to ISO 4589, and the results are shown in [the table / formula]. Figure 11 From Figure 11 The results show that the limiting oxygen index of the sheet product prepared according to Example 5 is 51.9%, indicating that it has excellent flame retardant properties.

[0124] The above embodiments and examples are only used to help understand the inventive concept of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from the principles and spirit of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A board product made of phosphorylated bamboo composite chitosan, characterized in that, The aforementioned board product is a biodegradable bio-based product obtained by hot-pressing one or more phosphorylated bamboo materials impregnated with protonated chitosan solution in a mold. The weight ratio of phosphorylated bamboo to protonated chitosan in the board product is 1:0.1 to 1:0.

4. The phosphorylated bamboo material is obtained by phosphorylating the etched bamboo material, so that one or more of the cellulose, hemicellulose and lignin of the bamboo material are grafted with phosphate groups, thereby obtaining phosphorylated bamboo material with a multi-dimensional bamboo fiber network composed of macroscopic bamboo fiber structure and micro-nano bamboo fiber network. The protonated chitosan solution is obtained by dissolving chitosan with a deacetylation degree of 60% or more in an acidic solution that can protonate the chitosan, and after impregnation, the protonated chitosan fills the multidimensional bamboo fiber network of the phosphorylated bamboo. Furthermore, the sheet material product possesses the following properties: (1) The bending strength through the three-point bending test is above 100 MPa; (2) The Shore hardness D value obtained by the Shore hardness test is greater than 70; (3) The limiting oxygen index, as measured by ISO 4589, is greater than 30%; and (4) The density of the land is selected to be greater than 1.0 g / cm³. 3 .

2. The sheet material product according to claim 1, characterized in that, The bamboo used is derived from natural bamboo and is selected from one or more forms of bamboo strips, bamboo blocks, bamboo boards, flattened bamboo, and bamboo fibers obtained through processing natural bamboo.

3. The sheet metal product according to claim 1, characterized in that, The board products mentioned are decorative boards, packaging boards, or structural boards.

4. A method for preparing sheet metal articles according to any one of claims 1-3, characterized in that, The method includes: The bamboo is etched. Phosphorylation modification was performed on etched bamboo to obtain phosphorylated bamboo. The phosphorylated bamboo is impregnated with a protonated chitosan solution so that the protonated chitosan fills the multidimensional bamboo fiber network of the phosphorylated bamboo. One or more phosphorylated bamboo materials impregnated with protonated chitosan solution are hot-pressed in a mold to obtain a preform; and After the preform is removed from the mold, it is dried to obtain the desired sheet product.

5. The method according to claim 4, characterized in that, The etching process includes immersing the bamboo in one or more etching solutions selected from aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous sodium sulfite solution, aqueous hydrogen peroxide solution, aqueous acetic acid solution, and aqueous sodium carbonate solution. Preferably, the etching process is carried out at a temperature of 50-95°C.

6. The method according to claim 4, characterized in that, The phosphorylation modification involves treating the etched bamboo with a solution containing urea-phosphate, urea-phosphoric acid, or urea-phosphoric acid-phosphate, so that one or more of the cellulose, hemicellulose, and lignin of the bamboo are grafted with phosphate groups. Preferably, the phosphorylation modification is carried out at a temperature of 100~170°C.

7. The method according to claim 4, characterized in that, The chitosan concentration in the protonated chitosan solution is 2-10%, and preferably the acidic solution used to protonate the chitosan is an aqueous acetic acid solution. Preferably, the impregnation is carried out under reduced pressure.

8. The method according to claim 4, characterized in that, The hot pressing temperature is 90-170℃, the pressure is 1-800MPa, and the time is 1-20h; preferably, the hot pressing temperature is 90-150℃, the pressure is 20-200MPa, and the time is 5-20h.

9. The method according to claim 4, characterized in that, The drying temperature is 50-170℃ and the time is 1-100h, preferably the drying temperature is 60-150℃ and the time is 5-50h.

10. The method according to claim 4, characterized in that, Before the hot pressing, the plurality of phosphorylated bamboo materials impregnated with protonated chitosan solution are laid in the mold in the direction of grain, in parallel, orthogonal, layered, spirally at a non-right angle, or a combination thereof.

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