Mildew-proof water-resistant bamboo-based artificial board and preparation method thereof

Abstract

The present application relates to the field of artificial board, and discloses a mildew-proof and water-resistant bamboo-based artificial board and a preparation method thereof, wherein the board blank of the artificial board is formed by bamboo shaving glue mixing and paving; the components for glue application include melamine, formaldehyde, modified bamboo powder, modified nano silicon dioxide, plant oil acid and water; the modified bamboo powder is made by grafting modified silane coupling agent with bamboo powder; the modified silane coupling agent is made by reacting functional modifier obtained by the reaction of 3-chloro-2-hydrazine pyridine intermediate made from 3-chloro-2-hydrazine pyridine and carbon disulfide, hydrophobic modified ultraviolet absorber made from 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole and glycidyl ester tertiary carbonic acid, and p-phenylenediamine, and then reacting with vinyl trimethoxysilane; the modified nano silicon dioxide is made by modifying with silicon-phosphorus coupling modifier obtained from DOPO and vinyl triethoxysilane and tetraethyl orthosilicate, so as to prepare the artificial board with good ultraviolet resistance, antibacterial and mildew-proof property, water resistance and flame retardance.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood products technology, specifically relating to a mildew-resistant and water-resistant bamboo-based engineered wood product and its preparation method. Background Technology

[0002] Both bamboo and wood are renewable, low-carbon biomass materials. Compared to wood, bamboo has natural advantages such as a shorter growth cycle and higher yield. Bamboo-based engineered wood products are engineering bamboo products with fixed dimensions that can be mass-produced. They not only preserve the physical and mechanical properties of bamboo but also have high in-plane strength and stiffness, and offer advantages such as continuous and efficient production. They demonstrate enormous application potential and development prospects in the field of modern bamboo and wood structure construction engineering.

[0003] Because bamboo contains more nutrients such as hemicellulose, starch, protein, and soluble sugars than wood, its resistance to mold is not as good as that of wood. Bamboo is also prone to absorbing moisture, which can cause mold and bacterial growth. The antibacterial and anti-mold properties of existing engineered wood products are mainly achieved by adding antibacterial and anti-mold additives to the adhesive used for gluing. However, simple physical mixing can easily lead to the precipitation of antibacterial agents, resulting in poor dimensional stability, weakened bonding ability, and quality problems such as surface cracking. In addition, existing engineered wood products have poor UV resistance and flame retardant properties, which further reduces their durability. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a mildew-resistant and water-resistant bamboo-based engineered wood panel and its preparation method. By adding modified bamboo powder and modified nano-silica, the bamboo-based engineered wood panel is endowed with good UV resistance, antibacterial and mildew-resistant properties, water resistance, and flame retardant properties.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A mildew-resistant and water-resistant bamboo-based engineered wood panel includes upper and lower surface layers and a middle core layer. The surface layers are made of fine bamboo shavings mixed with adhesive and laid out. The core layer is made of coarse bamboo shavings mixed with adhesive and laid out.

[0007] The sizing components include the following raw materials in parts by weight: 65-80 parts melamine, 55-75 parts formaldehyde, 5-10 parts modified bamboo powder, 2-5 parts modified nano silica, 1-3 parts vegetable oleic acid, and 40-60 parts deionized water.

[0008] The modified bamboo powder is prepared by grafting a modified silane coupling agent onto the surface of bamboo powder; the modified silane coupling agent is prepared by simultaneously reacting a triazolopyridine intermediate and a hydrophobic modified UV absorber with p-phenylenediamine to obtain a functional modifier, and then reacting the functional modifier with vinyltrimethoxysilane in a thiol-ene click reaction; the triazolopyridine intermediate is prepared by reacting 3-chloro-2-hydrazidopyridine and carbon disulfide under alkaline conditions; the hydrophobic modified UV absorber is prepared by reacting 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole and glycidyl tert-carbonate in a ring-opening reaction;

[0009] The modified nano-silica was prepared by an addition reaction of DOPO and vinyltriethoxysilane to obtain a silicon-phosphorus coupling modifier, and then the nano-silica was coated and modified using the silicon-phosphorus coupling modifier and tetraethyl orthosilicate as precursors via a sol-gel method.

[0010] Preferably, the method for preparing the modified bamboo powder includes the following steps:

[0011] A. Take 3-chloro-2-hydrazinopyridine, potassium hydroxide, and ethanol in a reactor, stir and mix them evenly, then slowly add carbon disulfide, heat to 55-65℃, stir and react for 7-9 hours, cool to room temperature after the reaction is completed, place the reaction product in an ice-water bath and stir until a large amount of solid precipitates, filter and dry to prepare triazolidine intermediate;

[0012] B. Take 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole, sodium hydroxide, and glycidyl tert-carbonate in a reactor and react them in a nitrogen atmosphere at 75-85℃ for 6-8 hours. After the reaction is completed, cool to room temperature and adjust the pH of the solution to 6-7 with dilute hydrochloric acid. After the reaction is completed, extract with benzene, filter out the insoluble residue and wash with water to prepare a hydrophobic modified ultraviolet absorber.

[0013] C. Take triazolidine intermediate, hydrophobically modified UV absorber and triethylamine in a reactor, add acetonitrile solvent, heat to 50-60℃, then add p-phenylenediamine and stir for 4-6 hours. After the reaction is completed, the functional modifier is prepared by rotary evaporation, filtration and drying.

[0014] D. Take the functional modifier, vinyltrimethoxysilane and tetrahydrofuran into a reactor, heat to 55-70°C under a nitrogen atmosphere, then add triethylamine and stir for 3-5 hours. After the reaction is completed, filter, wash and dry to prepare the modified silane coupling agent.

[0015] E. Take bamboo powder and ultrasonically disperse it in a mixed solution of anhydrous ethanol and deionized water. Then add a modified silane coupling agent and stir the mixture at 60-85℃ for 4-7 hours. After the reaction is completed, filter, wash and dry the mixture to obtain modified bamboo powder.

[0016] Preferably, the preparation method of 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole in step B includes the following steps:

[0017] B1. Under ice bath conditions, 4-chloro-2-nitroaniline, deionized water, and hydrochloric acid were placed in a reactor, stirred and mixed, and then sodium nitrite aqueous solution was added. The mixture was stirred and reacted for 25-40 minutes. Then urea was added to decompose excess nitrite to prepare a diazonium salt solution.

[0018] B2. Add a mixed solution of resorcinol, anhydrous ethanol, and deionized water to the diazonium salt solution, stir the reaction for 3 to 3.5 hours, filter, and recrystallize the solid product using ethanol-deionized water to prepare the azo product.

[0019] B3. Take the azo product, anhydrous ethanol, and sodium hydroxide solution into a reactor, heat to 60-75℃, add thiourea dioxide and stir for 1-1.5 h. After the reaction is completed, the filtrate is stirred in an ice bath while adding hydrochloric acid to neutralize the pH to 2-3. Filter out the solid and recrystallize it with ethanol-deionized water to prepare 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole.

[0020] Preferably, in step C, the molar ratio of the triazolidine intermediate, the hydrophobically modified UV absorber, and p-phenylenediamine is 1:1:1 to 1.2.

[0021] Preferably, the molar ratio of the functional modifier and vinyltrimethoxysilane in step D is 1:1 to 1.2.

[0022] Preferably, the method for preparing the modified nano-silica includes the following steps:

[0023] (1) Take DOPO and diethylene glycol dimethyl ether in a reactor, stir evenly and heat to 70-85℃, then add a mixed solution of vinyltriethoxysilane, azobisisobutyronitrile and diethylene glycol dimethyl ether, stir and react for 20-24h, and after the reaction is completed, prepare the silicon-phosphorus coupling modifier.

[0024] (2) Take nano-silica and ultrasonically disperse it in a mixed solution of ethanol and deionized water. Heat it to 40-50℃, add polyethylene glycol octylphenyl ether, ammonia and tetraethyl orthosilicate in sequence, stir and react for 0.5-1h, then add silicon-phosphorus coupling modifier and continue stirring and reacting for 4-5h. After the reaction is completed, filter, wash and dry to prepare modified nano-silica.

[0025] Preferably, the preparation method of the sizing component includes the following steps:

[0026] ① Weigh each raw material according to the weight proportions, mix formaldehyde and deionized water to obtain mixture one;

[0027] ② Adjust the pH of mixture one to 8-9.5, heat it to 70-85℃ and keep it at that temperature for 20-30 minutes, add melamine, stir and mix for 20-30 minutes to obtain mixture two;

[0028] ③ Add vegetable oleic acid, modified bamboo powder and modified nano silica to mixture 2, stir and mix for 2-4 hours to obtain the sizing component.

[0029] Preferably, the coarse bamboo shavings are 8-18 mm long, 2-6 mm wide, and 0.3-1.1 mm thick; the fine bamboo shavings are 2-8 mm long, 0.3-1.2 mm wide, and 0.1-0.3 mm thick.

[0030] A method for preparing a mildew-resistant and water-resistant bamboo-based engineered wood panel includes the following steps:

[0031] S1. Bamboo shavings are made by shaving and ring planing bamboo.

[0032] S2. The dried bamboo shavings are graded and screened to obtain coarse bamboo shavings and fine bamboo shavings;

[0033] S3. The fine bamboo shavings and coarse bamboo shavings obtained are mixed and laid out using adhesive components to prepare surface slabs and core slabs.

[0034] S4. Through pre-pressing, hot-pressing, and cooling molding, a mildew-resistant and water-resistant bamboo-based artificial board is prepared by combining two surface layers and a core layer.

[0035] Preferably, the pre-pressing pressure is controlled at 0.5-0.8 MPa, and then the material is fed into a continuous press. During hot pressing, the pressure is controlled at 1.2-2.5 MPa, the temperature is controlled at 180-220°C, and the hot pressing time is 6-9 s / mm.

[0036] The beneficial effects of this invention are:

[0037] This invention utilizes 3-chloro-2-hydrazinopyridine and carbon disulfide under alkaline conditions, with ethanol as a solvent, to prepare a triazolidine intermediate containing chlorine atoms and mercapto groups via heating. Simultaneously, this invention utilizes the ring-opening reaction between the hydroxyl group in 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole and the epoxy group in tert-butyl carbonate to prepare a hydrophobically modified UV absorber containing a hydrophobic group of tert-butyl carbonate. Then, using p-phenylenediamine as a bridging agent, the chlorine atoms in both the triazolidine intermediate and the hydrophobically modified UV absorber undergo substitution reactions with the amino groups at both ends of p-phenylenediamine to prepare a functional modifier. Subsequently, the mercapto group introduced in the functional modifier is reacted with ethylene... Modified silane coupling agents are prepared by undergoing a thiol-ene click reaction with trimethoxysilane. These agents are then used to modify bamboo powder, which contains a significant amount of cellulose. As a natural polymer, the hydroxyl groups on the surface of cellulose undergo a dehydration condensation reaction with the silanol groups in the modified silane coupling agent, resulting in modified bamboo powder. This process grafts hydrophobic groups of tert-carbonate, benzotriazole UV absorbers, and triazolidine antibacterial and antifungal agents onto the surface of the bamboo powder through strong chemical bonds, endowing the material with excellent UV resistance, antibacterial and antifungal properties, and water resistance. Furthermore, the grafting reaction enhances the oleophilicity of the bamboo powder surface, allowing it to be relatively uniformly dispersed in the matrix material, thus effectively maximizing its overall performance.

[0038] This invention utilizes the addition reaction between the PH bond in DOPO and the double bond in vinyltriethoxysilane to prepare a silicon-phosphorus coupling modifier. Then, using the silicon-phosphorus coupling modifier and tetraethyl orthosilicate as precursors, the nano-silica is coated and modified using the sol-gel method to prepare modified nano-silica, which improves the water resistance of the material. Phosphorus and silicon elements have a synergistic flame-retardant effect, and the silicon-phosphorus coupling modifier and tetraethyl orthosilicate form a protective shell at high temperatures, protecting the material from further thermal decomposition. At the same time, the coating modification helps to improve the dispersion uniformity of nano-silica, allowing its mechanical properties to be fully utilized. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1: A method for preparing 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole includes the following steps:

[0041] B1. Under ice bath conditions, 10.4 g of 4-chloro-2-nitroaniline, 100 mL of deionized water, and 17.2 mL of hydrochloric acid were placed in a reactor. After stirring and mixing, a mixed solution of 4.4 g of sodium nitrite and 10 mL of water was added. The mixture was stirred and reacted for 30 min. Then, urea was added to decompose excess nitrite to prepare a diazonium salt solution.

[0042] B2. Add a mixed solution of 10g resorcinol, 200mL anhydrous ethanol and 180mL deionized water to the obtained diazonium salt solution, stir for 3h and filter. The solid product is recrystallized from ethanol-deionized water in a volume ratio of 1:1 to prepare the azo product.

[0043] B3. Take 17.7g of azo product, 200mL of anhydrous ethanol, and 200mL of 0.16wt% sodium hydroxide solution in a reactor, heat to 70℃, add thiourea dioxide and stir for 1h. After the reaction is complete, the filtrate is stirred in an ice bath and the pH is neutralized to 2 with hydrochloric acid. Filter out the solid and recrystallize it using ethanol-deionized water at a volume ratio of 1:1 to prepare 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole.

[0044] Example 2: A method for preparing modified bamboo powder includes the following steps:

[0045] A. Take 1g of 3-chloro-2-hydrazinopyridine, 0.4g of potassium hydroxide, and 50mL of ethanol in a reactor, stir and mix evenly, then slowly add 0.84mL of carbon disulfide, heat to 60℃, stir and react for 8h, cool to room temperature after the reaction is complete, place the reaction product in an ice-water bath and stir until a large amount of solid precipitates, filter and dry to prepare triazolidine intermediate;

[0046] B. Take 13.1g of 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole, 0.15g of sodium hydroxide, and 11.4g of glycidyl tert-carbonate in a reactor and react them in a nitrogen atmosphere at 80℃ for 8h. After the reaction is completed, cool to room temperature and adjust the pH of the solution to 7 with dilute hydrochloric acid. After the reaction is completed, extract with benzene, filter out the insoluble residue and wash with water to prepare a hydrophobic modified ultraviolet absorber.

[0047] C. Take 1.7g of triazolidine intermediate, 4.9g of hydrophobic modified UV absorber and 2g of triethylamine into a reactor, add 50mL of acetonitrile solvent, heat to 55℃, then add 1.1g of p-phenylenediamine and stir for 6h. After the reaction is completed, the functional modifier is prepared by rotary evaporation, filtration and drying.

[0048] D. Take 6.9g of functional modifier, 1.5g of vinyltrimethoxysilane and 50mL of tetrahydrofuran into a reactor, heat to 65℃ under a nitrogen atmosphere, then add 0.5g of triethylamine and stir for 4h. After the reaction is completed, filter, wash and dry to prepare the modified silane coupling agent.

[0049] E. Take 10g of bamboo powder (1200 mesh, produced by Lu'an Xingzhu New Material Technology Co., Ltd.) and ultrasonically disperse it in a mixed solution of 90mL anhydrous ethanol and 10mL deionized water. Then add 5.5g of modified silane coupling agent and stir at 75℃ for 6h. After the reaction is completed, filter, wash and dry to prepare modified bamboo powder.

[0050] Example 3: A method for preparing modified nano-silica includes the following steps:

[0051] (1) Take 45g DOPO and 70mL diethylene glycol dimethyl ether in a reactor, stir evenly and heat to 80℃, then add a mixed solution of 28g vinyltriethoxysilane, 0.3g azobisisobutyronitrile and 20mL diethylene glycol dimethyl ether, stir and react for 24h, and after the reaction is completed, prepare the silicon-phosphorus coupling modifier.

[0052] (2) Take 5g of nano silica and ultrasonically disperse it in a mixed solution of 90mL ethanol and 10mL deionized water. Heat it to 45℃ and add 1mL polyethylene glycol octylphenyl ether, 1.5mL ammonia and 1g tetraethyl orthosilicate in sequence. After stirring for 1h, add 0.3g of silicon-phosphorus coupling modifier and continue stirring for 4h. After the reaction is completed, filter, wash and dry to prepare modified nano silica.

[0053] Example 4: A component for sizing includes the following raw materials in parts by weight: 67 parts melamine, 55 parts formaldehyde, 5.5 parts modified bamboo powder prepared in Example 2, 2 parts modified nano silica prepared in Example 3, 1 part vegetable oleic acid, and 44 parts deionized water.

[0054] The preparation method of the above-mentioned sizing component includes the following steps:

[0055] ① Weigh each raw material according to the weight proportions, mix formaldehyde and deionized water to obtain mixture one;

[0056] ② Adjust the pH of mixture one to 9, heat it to 80℃ and keep it at that temperature for 30 minutes, add melamine, stir and mix for 30 minutes to obtain mixture two;

[0057] ③ Add vegetable oleic acid, modified bamboo powder and modified nano silica to mixture 2, stir and mix for 3 hours to obtain the sizing component.

[0058] A method for preparing a mildew-resistant and water-resistant bamboo-based engineered wood panel includes the following steps:

[0059] S1. Bamboo shavings are made by shaving and ring planing bamboo.

[0060] S2. The dried bamboo shavings are graded and screened to obtain coarse bamboo shavings and fine bamboo shavings. The coarse bamboo shavings are 8-18 mm long, 2-6 mm wide, and 0.3-1.1 mm thick. The fine bamboo shavings are 2-8 mm long, 0.3-1.2 mm wide, and 0.1-0.3 mm thick.

[0061] S3. The fine bamboo shavings and coarse bamboo shavings obtained are mixed and laid out using adhesive components to prepare surface slabs and core slabs.

[0062] S4. The upper and lower surface slab blanks and the middle core slab blank are combined and pre-pressed, hot-pressed and cooled to form the product. The pressure is controlled at 0.7MPa during pre-pressing and then fed into a continuous press. During hot pressing, the pressure is controlled at 2MPa, the temperature is controlled at 185℃ and the hot pressing time is 7s / mm to prepare a mildew-resistant and water-resistant bamboo-based artificial board.

[0063] Example 5: A component for sizing includes the following raw materials in parts by weight: 72 parts melamine, 66 parts formaldehyde, 7 parts modified bamboo powder prepared in Example 2, 3 parts modified nano silica prepared in Example 3, 2 parts vegetable oleic acid, and 50 parts deionized water.

[0064] The preparation method of the above-mentioned sizing components is the same as that in Example 4.

[0065] The preparation method of a mildew-resistant and water-resistant bamboo-based artificial board is the same as in Example 4.

[0066] Example 6: A component for sizing includes the following raw materials in parts by weight: 77 parts melamine, 72 parts formaldehyde, 9 parts modified bamboo powder prepared in Example 2, 4.5 parts modified nano silica prepared in Example 3, 3 parts vegetable oleic acid, and 55 parts deionized water.

[0067] The preparation method of the above-mentioned sizing components is the same as that in Example 4.

[0068] The preparation method of a mildew-resistant and water-resistant bamboo-based artificial board is the same as in Example 4.

[0069] Comparative Example 1: A method for preparing modified bamboo powder includes the following steps:

[0070] A. Take 1g of 3-chloro-2-hydrazinopyridine, 0.4g of potassium hydroxide, and 50mL of ethanol in a reactor, stir and mix evenly, then slowly add 0.84mL of carbon disulfide, heat to 60℃, stir and react for 8h, cool to room temperature after the reaction is complete, place the reaction product in an ice-water bath and stir until a large amount of solid precipitates, filter and dry to prepare triazolidine intermediate;

[0071] B. Take 1.7g of triazolidine intermediate, 2.6g of 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole and 2g of triethylamine into a reactor, add 50mL of acetonitrile solvent, heat to 55℃, then add 1.1g of p-phenylenediamine and stir for 6h. After the reaction is completed, the product is prepared by rotary evaporation, filtration and drying.

[0072] C. Take 4.7g of functional modifier, 1.5g of vinyltrimethoxysilane and 50mL of tetrahydrofuran into a reactor, heat to 65℃ under a nitrogen atmosphere, then add 0.5g of triethylamine and stir for 4h. After the reaction is completed, filter, wash and dry to prepare the modified silane coupling agent.

[0073] D. Take 10g of bamboo powder (1200 mesh, produced by Lu'an Xingzhu New Material Technology Co., Ltd.) and ultrasonically disperse it in a mixed solution of 90mL anhydrous ethanol and 10mL deionized water. Then add 5.5g of modified silane coupling agent and stir at 75℃ for 6h. After the reaction is completed, filter, wash and dry to prepare modified bamboo powder.

[0074] Comparative Example 2: A sizing component includes the following raw materials in parts by weight: 77 parts melamine, 72 parts formaldehyde, 9 parts modified bamboo powder prepared in Comparative Example 1, 4.5 parts modified nano silica prepared in Example 3, 3 parts vegetable oleic acid, and 55 parts deionized water.

[0075] The preparation method of the above-mentioned sizing components is the same as that in Example 4.

[0076] The preparation method of a mildew-resistant and water-resistant bamboo-based artificial board is the same as in Example 4.

[0077] Comparative Example 3: A sizing component includes the following raw materials in parts by weight: 77 parts melamine, 72 parts formaldehyde, 9 parts bamboo powder (1200 mesh, produced by Lu'an Xingzhu New Material Technology Co., Ltd.), 4.5 parts modified nano silica prepared in Example 3, 3 parts vegetable oleic acid, and 55 parts deionized water.

[0078] The preparation method of the above-mentioned sizing components is the same as that in Example 4.

[0079] The preparation method of a mildew-resistant and water-resistant bamboo-based artificial board is the same as in Example 4.

[0080] Comparative Example 4: A sizing component includes the following raw materials in parts by weight: 77 parts melamine, 72 parts formaldehyde, 9 parts modified bamboo powder prepared in Example 2, 4.5 parts nano silica, 3 parts vegetable oleic acid, and 55 parts deionized water.

[0081] The preparation method of the above-mentioned sizing components is the same as that in Example 4.

[0082] The preparation method of a mildew-resistant and water-resistant bamboo-based artificial board is the same as in Example 4.

[0083] Performance testing

[0084] The mildew-resistant and water-resistant bamboo-based engineered wood panels prepared in Examples 4-6 and Comparative Examples 2-4 were subjected to performance testing: Physicochemical properties were tested according to GB / T17657-2022; limiting oxygen index was tested according to GB / T 2406.2-2009 to evaluate the flame retardant properties of the samples; the engineered wood panels were tested in an ultraviolet aging test chamber under ultraviolet light at 270-380 nm, with an irradiation distance (distance between sample and lamp) of 50 mm and a test time of 12 h. The static bending strength retention rate was then tested to evaluate the ultraviolet aging resistance of the samples; a concentration of 10... 7 A solution of Staphylococcus aureus and Aspergillus niger at CFU / mL was applied to the surface of the artificial board and covered with a sterile PE film. After 1 hour, the pipe was rinsed with phosphate buffer and the rinsing solution was applied to the culture medium and incubated for 24 hours. The number of colonies was counted, the antibacterial rate was calculated, and the antibacterial performance of the sample was evaluated. The data results are shown in Table 1.

[0085] Table 1. Test results of sample performance

[0086]

[0087] As can be seen from the data results in Table 1, the bamboo-based artificial boards prepared in Examples 4-6 of the present invention have excellent physical and mechanical properties, and also possess good UV resistance, antibacterial and antifungal properties, water resistance and flame retardant properties. In Comparative Example 2, the modified bamboo powder without glycidyl tert-carbonate grafting showed poorer water resistance than Examples 4-6. This was because no hydrophobic groups of glycidyl tert-carbonate were introduced. In Comparative Example 3, the bamboo powder was not modified, and its mechanical properties were slightly worse than those of Examples 4-6. This may be due to the agglomeration of bamboo powder leading to reduced mechanical properties. Furthermore, the static bending strength retention rate, Staphylococcus aureus antibacterial rate, and Aspergillus niger antifungal rate were lower than those of Examples 4-6, while the 24-hour water absorption thickness swelling rate was higher. This indicates that modifying the bamboo powder can improve the material's UV resistance, antibacterial and antifungal properties, and water resistance. In Comparative Example 4, the nano-silica was not modified, and its mechanical properties were slightly worse than those of Examples 4-6. The 24-hour water absorption thickness swelling rate was higher than that of Examples 4-6, and the limiting oxygen index was significantly lower than that of Examples 4-6. This indicates that modifying the nano-silica improved the material's water resistance and flame retardant properties to some extent.

[0088] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A mildew-resistant and water-resistant bamboo-based engineered wood panel, characterized in that, It includes upper and lower surface slabs and a middle core slab. The surface slabs are made of fine bamboo shavings mixed with glue and laid out. The core slabs are made of coarse bamboo shavings mixed with glue and laid out. The sizing components include the following raw materials in parts by weight: 65-80 parts melamine, 55-75 parts formaldehyde, 5-10 parts modified bamboo powder, 2-5 parts modified nano silica, 1-3 parts vegetable oleic acid, and 40-60 parts deionized water. The modified bamboo powder is prepared by grafting a modified silane coupling agent onto the surface of bamboo powder; the modified silane coupling agent is prepared by simultaneously reacting a triazolopyridine intermediate and a hydrophobic modified UV absorber with p-phenylenediamine to obtain a functional modifier, and then reacting the functional modifier with vinyltrimethoxysilane in a thiol-ene click reaction; the triazolopyridine intermediate is prepared by reacting 3-chloro-2-hydrazidopyridine and carbon disulfide under alkaline conditions; the hydrophobic modified UV absorber is prepared by reacting 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole and glycidyl tert-carbonate in a ring-opening reaction; The modified nano-silica was prepared by an addition reaction of DOPO and vinyltriethoxysilane to obtain a silicon-phosphorus coupling modifier, and then the nano-silica was coated and modified using the silicon-phosphorus coupling modifier and tetraethyl orthosilicate as precursors via a sol-gel method.

2. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 1, characterized in that, The preparation method of the modified bamboo powder includes the following steps: A. Take 3-chloro-2-hydrazinopyridine, potassium hydroxide, and ethanol in a reactor, stir and mix them evenly, then slowly add carbon disulfide, heat to 55-65℃, stir and react for 7-9 hours, cool to room temperature after the reaction is completed, place the reaction product in an ice-water bath and stir until a large amount of solid precipitates, filter and dry to prepare triazolidine intermediate; B. Take 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole, sodium hydroxide, and glycidyl tert-carbonate in a reactor and react them in a nitrogen atmosphere at 75-85℃ for 6-8 hours. After the reaction is completed, cool to room temperature and adjust the pH of the solution to 6-7 with dilute hydrochloric acid. After the reaction is completed, extract with benzene, filter out the insoluble residue and wash with water to prepare a hydrophobic modified ultraviolet absorber. C. Take triazolidine intermediate, hydrophobically modified UV absorber and triethylamine in a reactor, add acetonitrile solvent, heat to 50-60℃, then add p-phenylenediamine and stir for 4-6 hours. After the reaction is completed, the functional modifier is prepared by rotary evaporation, filtration and drying. D. Take the functional modifier, vinyltrimethoxysilane and tetrahydrofuran into a reactor, heat to 55-70°C under a nitrogen atmosphere, then add triethylamine and stir for 3-5 hours. After the reaction is completed, filter, wash and dry to prepare the modified silane coupling agent. E. Take bamboo powder and ultrasonically disperse it in a mixed solution of anhydrous ethanol and deionized water. Then add a modified silane coupling agent and stir the mixture at 60-85℃ for 4-7 hours. After the reaction is completed, filter, wash and dry the mixture to obtain modified bamboo powder.

3. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 2, characterized in that, The preparation method of 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole in step B includes the following steps: B1. Under ice bath conditions, 4-chloro-2-nitroaniline, deionized water, and hydrochloric acid were placed in a reactor, stirred and mixed, and then sodium nitrite aqueous solution was added. The mixture was stirred and reacted for 25-40 minutes. Then urea was added to decompose excess nitrite to prepare a diazonium salt solution. B2. Add a mixed solution of resorcinol, anhydrous ethanol, and deionized water to the diazonium salt solution, stir the reaction for 3 to 3.5 hours, filter, and recrystallize the solid product using ethanol-deionized water to prepare the azo product. B3. Take the azo product, anhydrous ethanol, and sodium hydroxide solution into a reactor, heat to 60-75℃, add thiourea dioxide and stir for 1-1.5 h. After the reaction is completed, the filtrate is stirred in an ice bath while adding hydrochloric acid to neutralize the pH to 2-3. Filter out the solid and recrystallize it with ethanol-deionized water to prepare 5-chloro-2-(2',4'-dihydroxyphenyl)-2H-benzotriazole.

4. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 2, characterized in that, In step C, the molar ratio of the triazolidine intermediate, the hydrophobically modified UV absorber, and p-phenylenediamine is 1:1:1 to 1.

2.

5. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 2, characterized in that, In step D, the molar ratio of the functional modifier to vinyltrimethoxysilane is 1:1 to 1.

2.

6. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 1, characterized in that, The method for preparing the modified nano-silica includes the following steps: (1) Take DOPO and diethylene glycol dimethyl ether in a reactor, stir evenly and heat to 70-85℃, then add a mixed solution of vinyltriethoxysilane, azobisisobutyronitrile and diethylene glycol dimethyl ether, stir and react for 20-24h, and after the reaction is completed, prepare the silicon-phosphorus coupling modifier. (2) Take nano-silica and ultrasonically disperse it in a mixed solution of ethanol and deionized water. Heat it to 40-50℃, add polyethylene glycol octylphenyl ether, ammonia and tetraethyl orthosilicate in sequence, stir and react for 0.5-1h, then add silicon-phosphorus coupling modifier and continue stirring and reacting for 4-5h. After the reaction is completed, filter, wash and dry to prepare modified nano-silica.

7. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 1, characterized in that, The preparation method of the sizing component includes the following steps: ① Weigh each raw material according to the weight proportions, mix formaldehyde and deionized water to obtain mixture one; ② Adjust the pH of mixture one to 8-9.5, heat it to 70-85℃ and keep it at that temperature for 20-30 minutes, add melamine, stir and mix for 20-30 minutes to obtain mixture two; ③ Add vegetable oleic acid, modified bamboo powder and modified nano silica to mixture 2, stir and mix for 2-4 hours to obtain the sizing component.

8. The mildew-resistant and water-resistant bamboo-based engineered wood panel according to claim 1, characterized in that, The coarse bamboo shavings are 8–18 mm long, 2–6 mm wide, and 0.3–1.1 mm thick; the fine bamboo shavings are 2–8 mm long, 0.3–1.2 mm wide, and 0.1–0.3 mm thick.

9. A method for preparing a mildew-resistant and water-resistant bamboo-based engineered wood panel according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Bamboo shavings are made by shaving and ring planing bamboo. S2. The dried bamboo shavings are graded and screened to obtain coarse bamboo shavings and fine bamboo shavings. S3. The fine bamboo shavings and coarse bamboo shavings obtained are mixed and laid out using adhesive components to prepare surface slabs and core slabs. S4. Through pre-pressing, hot-pressing, and cooling molding, a mildew-resistant and water-resistant bamboo-based artificial board is prepared by combining two surface layers and a core layer.

10. The method for preparing mildew-resistant and water-resistant bamboo-based engineered wood panels according to claim 9, characterized in that, The pre-pressing pressure is controlled at 0.5–0.8 MPa, and then the material is fed into a continuous press. During hot pressing, the pressure is controlled at 1.2–2.5 MPa, the temperature is controlled at 180–220°C, and the hot pressing time is 6–9 s / mm.

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