Preparation process of green fire-retardant plywood

Abstract

The present application relates to a kind of preparation process of green fire-retardant plywood, it includes: the preparation of dioxane, the preparation of vanillic acid-furfuryl benzoxazine (VF), the preparation of binary benzoxazine derivative monomer, the preparation of refined carboxymethyl cellulose sodium (CMC), the preparation of water-soluble bio-based charring agent, the preparation of smoke suppression low-toxicity fire-retardant liquid PAP-Mg-Na, the preparation of complex type flame retardant PAP-Ly-Mg, the preparation of MOF (metal organic framework) fire-retardant composite material and other steps, the present application creatively combines Diels-Alder reaction method, high-temperature heating method and other preparation methods, the green fire-retardant plywood prepared has the advantages of smoke suppression, low toxicity, green, fire-retardant, etc., can be used in building, decoration, home and other fields.

Description

Technical Field

[0001] This invention relates to the preparation of a new material, and more particularly to a process for preparing a green flame-retardant plywood. Background Technology

[0002] With increasing environmental awareness, the environmental performance of engineered wood products has become a crucial factor for consumers when making purchasing decisions. However, wood is flammable, posing a fire hazard when using engineered wood in building decoration. With the implementation of relevant regulations and standards for flame-retardant materials in my country, higher requirements have been placed on these materials, making the flame-retardant performance of engineered wood products a primary factor for consumers. While traditional synthetic resin adhesives based on petrochemical products perform well in terms of bonding and water resistance, the formaldehyde, phenol, and other harmful substances they release pose a potential threat to the environment and human health. Therefore, developing safe, environmentally friendly, and green flame-retardant plywood has become a key direction for the industry's transformation and upgrading.

[0003] At the same time, as the main raw material of wood-based panels, the flammability of wood-based panels poses certain safety hazards in the application of wood-based panels in the fields of construction and decoration. With the continuous improvement of national regulations and standards on flame-retardant materials, stricter requirements have been put forward for the flame-retardant performance of wood-based panels. By creatively combining advanced preparation technologies such as the Diels-Alder reaction method and high-temperature heating method, and with the characteristics of (1) smoke suppression, (2) low toxicity, (3) environmental protection and excellent flame-retardant performance, it provides strong support for the widespread application in multiple fields such as construction, decoration and home furnishing. Summary of the Invention

[0004] To address the above problems, this invention provides a process for preparing green flame-retardant plywood.

[0005] This invention provides a preparation process for green flame-retardant plywood, comprising the following steps: preparation of dioxane, preparation of vanillic acid-furfurylamine benzoxazine (VF), preparation of dibenzoxazine derivative monomers, preparation of refined sodium carboxymethyl cellulose (CMC), preparation of water-soluble bio-based charring agent, preparation of smoke-suppressing and low-toxicity flame-retardant liquid PAP-Mg-Na, preparation of complexed flame retardant PAP-Ly-Mg, and preparation of MOF (metal-organic framework) flame-retardant composite material.

[0006] Among them, step (3) preparation of the binary benzoxazine derivative monomer

[0007] First, a certain amount of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, a small amount of furfuryl alcohol resin and a small amount of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at high temperature to obtain a binary benzoxazine derivative monomer.

[0008] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0009] First, water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) was used as an organic ligand to prepare a ligand solution. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a metal solution. The two solutions were then mixed in a certain mass ratio and stirred at room temperature. Then, the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction between the ligand and the metal ions Mg. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution while stirring to obtain smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na.

[0010] As a preferred option, step (1) involves the preparation of dioxane.

[0011] In a round-bottom flask, a certain amount of diethylene glycol and anhydrous copper sulfate were added. The mixture was heated to keep the reaction flask boiling and the heating was controlled for a period of time. After the reaction was completed, the mixture was cooled to room temperature. A large amount of diethylene glycol was then added to the reaction flask and the mixture was heated again. The distillate was collected, and a small amount of concentrated hydrochloric acid was added to the distillate. Then the mixture was refluxed to remove acetal impurities. The aqueous layer was separated by post-treatment, the oil layer was dried, and the distillate was collected by distillation to obtain dioxane.

[0012] Step (2) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0013] Take a small amount of dioxane, furfurylamine and a small amount of paraformaldehyde from step (1) and add them in sequence to a three-necked flask. Then add a certain amount of toluene / ethanol mixed solution, stir to mix the raw materials evenly, and then reflux at high temperature for a period of time to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0014] Step (3) Preparation of binary benzoxazine-derived monomers

[0015] A small amount of phenyl phosphate bismaleimide was dissolved in a certain amount of methyl sulfoxide and subjected to the Diels-Alder reaction. After cooling to room temperature, it was placed in a three-necked flask equipped with an N, inlet and outlet, magnetic stirring and water separation condenser and slowly dissolved in vanillic acid-furfuryl benzoxazine (VF) at high temperature to obtain a binary benzoxazine derivative monomer.

[0016] Step (4) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0017] The concentration of concentrated nitric acid was diluted with anhydrous ethanol to obtain a nitric acid ethanol solution. A small amount of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After the reaction, the solution was filtered. The insoluble substance obtained at this time was CMC-H. CMC-H was washed with deionized water several times. The above CMC-H was added to a high concentration of sodium hydroxide solution and stirred thoroughly to obtain a viscous transparent liquid. At this time, CMC-H and sodium oxide reacted to generate CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) was viscous in water. A large amount of the dibenzoxazine derivative monomer from step (3) was added to obtain a white flocculent substance, which was CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) was washed with ethanol solution several times until the pH was neutral. It was then dried in a vacuum oven to constant weight and pulverized to obtain refined sodium carboxymethyl cellulose (CMC).

[0018] Step (5) Preparation of water-soluble bio-based charring agent

[0019] Melamine (MA) and vanillin were added to a flask in a certain proportion, and dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). The refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) was added and stirred thoroughly. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0020] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0021] First, water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) was used as an organic ligand to prepare a ligand solution. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a metal solution. The two solutions were then mixed in a certain mass ratio and stirred at room temperature. Then, the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction between the ligand and the metal ions Mg. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution while stirring to obtain smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na.

[0022] Step (7) Preparation of complexed flame retardant PAP-Ly-Mg

[0023] Lysine, ammonium polyphosphate (APP) and melamine are added to a four-necked flask in a certain molar ratio, mixed and stirred, heated to high temperature by a constant temperature digital display heating mantle, a small amount of smoke-suppressing and low-toxicity flame-retardant liquid PAP-Mg-Na from step (6) is added, followed by chitosan and vitamin B. After solidification and aging reaction, the mixture is crushed to obtain the complexed flame retardant PAP-Ly-Mg.

[0024] Step (8) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0025] A small amount of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in an ethanol solution, and then the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. After standing, it was added to the cellulose dispersion and stirred vigorously at room temperature. The mixture was drained of water through a Buchner funnel and then dried in a vacuum oven to obtain the MOF (metal-organic framework) flame retardant composite material.

[0026] As a preferred option, step (1) involves the preparation of dioxane.

[0027] In a 250-500 mL round-bottom flask, add 100-200 g of diethylene glycol and 2-5 g of anhydrous copper sulfate. Heat the flask to a boil for 1-5 hours. After the reaction is complete, cool to room temperature and add another 105-200 g of diethylene glycol. Continue heating and collect the distillate. Add 10-20 mL of concentrated hydrochloric acid to the distillate and reflux to remove acetal impurities. After post-treatment, separate the aqueous layer and dry the oil layer. Distill and collect the distillate with a boiling point of 100-200 °C to obtain dioxane.

[0028] The advantages of this invention are that it uses diethylene glycol as a starting material and performs dehydration condensation under the catalysis of anhydrous copper sulfate to generate an intermediate containing an epoxy group, which further reacts to form the target product dioxane. This changes the more dangerous and expensive reagents used in traditional synthetic routes, and effectively removes by-product impurities through distillation, improving the purity of the product and providing an excellent foundation for subsequent modification steps.

[0029] Preferably, step (2) involves the preparation of vanillic acid-furfurylamine benzoxazine (VF).

[0030] Take 16-20g of dioxane from step (1), 9-15g of furfurylamine (0.1-1mol), and 6-10g of paraformaldehyde and add them in sequence to a three-necked flask. Then add 90-100mL of toluene / ethanol mixed solution and stir to mix the raw materials evenly. Then reflux at 80-100℃ for 8-15h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0031] The advantages of this invention are that by selecting dioxane, furfurylamine, and paraformaldehyde as starting materials and conducting a long-term reflux reaction at high temperature, the synthetic route of vanillic acid-furfurylamine benzoxazine (VF) is simplified, improving the yield and product purity. Moreover, by using a toluene / ethanol mixed solvent system, a more environmentally friendly and economically efficient production process is achieved, the reaction conditions are optimized, and the occurrence of side reactions is reduced. This invention is of great significance for the research and development and industrial application of new materials.

[0032] Preferably, step (3) involves the preparation of the binary benzoxazine-derived monomer.

[0033] First, weigh 1-5g of phenyl phosphate bismaleimide using an electronic analytical balance and perform the Diels-Alder reaction. Then, weigh 2-6g of furfuryl alcohol resin and 1-5g of vanillic acid-furfurylamine benzoxazine (VF) from step (2), mix them together in a transparent glass vial and sonicate. Place the vial in an oven at 70-90℃ for 24-48h to obtain a binary benzoxazine derivative monomer.

[0034] The advantages of this invention are that it utilizes high-temperature heat preservation treatment, which helps to form a stable six-membered ring structure, providing better thermal stability and mechanical strength, while reducing the occurrence of side reactions, ensuring the purity and quality of the product, and the Diels-Alder reaction helps to generate cis-addition products.

[0035] Preferably, step (4) involves the preparation of refined sodium carboxymethyl cellulose (CMC).

[0036] Dilute concentrated nitric acid to a concentration of 25-35% with anhydrous ethanol to obtain a nitric acid ethanol solution. Weigh 10-20g of CMC powder (sodium carboxymethyl cellulose) and dissolve it in the nitric acid ethanol solution. React for 2-5 hours and then filter. The insoluble residue obtained is CMC-H. Wash CMC-H repeatedly with deionized water until its pH is 6-10. Add the above CMC-H to a 40-50% sodium hydroxide solution and stir thoroughly to obtain a viscous, transparent liquid. At this point, CMC-H... The reaction with sodium oxide produces CMC (sodium carboxymethyl cellulose). CMC is viscous in water. 100-200 mL of the dibenzoxazine derivative monomer from step (3) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed 1-5 times with a 70-85% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 100-150℃ to constant weight for about 4-10 hours. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0037] The advantages of this invention are that it introduces nitric acid ethanol pretreatment and dibenzoxazine derivative monomer posttreatment steps, which optimizes the purification process of CMC (sodium carboxymethyl cellulose). Through chemical modification, its molecular structure is changed, enhancing its physicochemical properties. Nitric acid ethanol treatment helps to remove impurities and adjust the functional group distribution of CMC (sodium carboxymethyl cellulose), while the combination with dibenzoxazine derivative monomers endows CMC (sodium carboxymethyl cellulose) with a new cross-linking structure, improving the mechanical strength and thermal stability of the material.

[0038] Preferably, step (5) involves the preparation of the water-soluble bio-based charring agent.

[0039] Melamine (MA) and vanillin were added to a flask in a ratio of 1-5:2-5, and then 10-20g of dimethylformamide (DMF) solvent was added. The mixture was stirred for 2-5 hours. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 10-20g of refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a ratio of 1-5:1-5 was added and stirred thoroughly for 1-5 hours. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0040] The advantages of this invention are that it combines organic synthesis and physical mixing techniques to construct a composite material with excellent thermal stability and char-forming properties through chemical reactions. The reaction of melamine (MA) with vanillin generates a char-coated body with rich aromatic structure and three-dimensional network, which enhances the thermal stability of the material. The introduction of refined sodium carboxymethyl cellulose (CMC) and ammonium polyphosphate (APP) improves the water solubility and processing performance of the material.

[0041] As a preferred option, step (6) involves the preparation of the smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na.

[0042] First, using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as an organic ligand, a 50-70 wt% ligand solution was prepared. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 20-50 wt% metal solution. The two solutions were then mixed at a mass ratio of 1-5:1-5 and stirred at room temperature for 30-60 minutes. Then, 10-20 g of the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction of the ligand with the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to obtain a complexation solution. Then, NaOH accelerator solution is added and slowly added to the complexation solution. Stirring for 10-60 minutes yields smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na.

[0043] The advantages of this invention are that it utilizes the unique molecular structure of PAPEMP (polyaminopolyether methylenephosphonic acid) to form a stable complex with magnesium ions, and combines it with a bio-based charring agent to enhance the charring and smoke suppression properties of the material, improve the thermal stability and flame retardant efficiency of the product, ensure the occurrence of efficient complexation reaction, reduce the product's excellent water solubility and low toxicity, and help develop high-performance, environmentally friendly flame retardant materials that are suitable for the fire-retardant modification and smoke suppression needs of various polymer systems.

[0044] Preferably, step (7) involves the preparation of the complexed flame retardant PAP-Ly-Mg.

[0045] Lysine, ammonium polyphosphate (APP), and melamine are added to a four-necked flask in a molar ratio of 1-5:2-5:3-5. The mixture is stirred and heated to 300-600℃ using a constant temperature digital display heating mantle. 10-50mL of the smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na from step (6) is added, followed by 10-50g of chitosan and vitamin B. After solidification, the mixture is allowed to mature for 60-120min. The mixture is then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0046] The advantages of this invention are that it utilizes the synergistic effect of lysine with ammonium polyphosphate (APP) and melamine, combined with the complexing properties of PAP-Mg-Na, to construct a composite material with excellent thermal stability and flame retardant effect. Through high-temperature treatment and chemical cross-linking between components, the mechanical strength and heat resistance of the material are enhanced. The introduction of bio-based components such as chitosan and vitamin B improves the biocompatibility and environmental protection characteristics of the material, which helps to develop high-performance, multifunctional flame retardant materials suitable for application fields with high requirements for safety and environmental protection.

[0047] Preferably, step (8) involves the preparation of the MOF (metal-organic framework) flame-retardant composite material.

[0048] 0.1-0.5g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 30-60mL of ethanol solution, and then 10-50mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 30-60min, and then added to 150-300mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 4-10h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 80-100℃ for 24-48h to obtain MOF (metal-organic framework) flame retardant composite material.

[0049] The advantages of this invention are that it utilizes the high specific surface area and porosity characteristics of MOFs, combined with the excellent flame retardant properties of PAP-Ly-Mg, to construct a composite material with efficient flame retardant and smoke suppression functions. This invention changes the traditional preparation method of composite materials. Ultrasonic dispersion and vigorous stirring ensure the uniform distribution and close contact between the components, enhancing the overall stability and mechanical strength of the material. The introduction of PAP-Ly-Mg as a functional filler improves the thermal stability and flame retardant effect of the composite material.

[0050] In summary, the present invention has the following beneficial effects:

[0051] 1. The advantages of this invention are that it uses diethylene glycol as a starting material and performs dehydration condensation under the catalysis of anhydrous copper sulfate to generate an intermediate containing an epoxy group, which further reacts to form the target product dioxane. This changes the more dangerous and expensive reagents used in traditional synthetic routes, and effectively removes by-product impurities through distillation, improving the purity of the product and providing an excellent foundation for subsequent modification steps.

[0052] 2. The advantages of this invention are that by selecting dioxane, furfurylamine, and paraformaldehyde as starting materials and refluxing at high temperature for a long time, the synthetic route of vanillic acid-furfurylamine benzoxazine (VF) is simplified, the yield and product purity are improved, and a more environmentally friendly and economically efficient production process is achieved by using a toluene / ethanol mixed solvent system. The reaction conditions are optimized and the occurrence of side reactions is reduced, which is of great significance for the research and development and industrial application of new materials.

[0053] 3. The advantages of using this invention are that it utilizes high temperature for heat preservation, which helps to form a stable six-membered ring structure, providing better thermal stability and mechanical strength, while reducing the occurrence of side reactions, ensuring the purity and quality of the product, and the Diels-Alder reaction helps to generate cis-addition products.

[0054] 4. The advantages of this invention are that it introduces nitric acid ethanol pretreatment and dibenzoxazine derivative monomer posttreatment steps, which optimizes the purification process of CMC (sodium carboxymethyl cellulose). Through chemical modification, its molecular structure is changed, enhancing its physicochemical properties. Nitric acid ethanol treatment helps to remove impurities and adjust the functional group distribution of CMC (sodium carboxymethyl cellulose), while the combination with dibenzoxazine derivative monomers endows CMC (sodium carboxymethyl cellulose) with a new cross-linking structure, improving the mechanical strength and thermal stability of the material.

[0055] 5. The advantages of this invention are that it combines organic synthesis and physical mixing techniques to construct a composite material with excellent thermal stability and char-forming properties through chemical reaction. The reaction of melamine (MA) with vanillin generates a char coating with rich aromatic structure and three-dimensional network, which enhances the thermal stability of the material. The introduction of refined sodium carboxymethyl cellulose (CMC) and ammonium polyphosphate (APP) improves the water solubility and processing performance of the material.

[0056] 6. The advantages of this invention are that it utilizes the unique molecular structure of PAPEMP (polyaminopolyether methylenephosphonic acid) to form a stable complex with magnesium ions, and combines it with a bio-based charring agent to enhance the charring and smoke suppression properties of the material, improve the thermal stability and flame retardant efficiency of the product, ensure the occurrence of efficient complexation reaction, reduce the product's excellent water solubility and low toxicity, and help develop high-performance, environmentally friendly flame retardant materials that are suitable for the fire-retardant modification and smoke suppression needs of various polymer systems.

[0057] 7. The advantages of this invention are that it utilizes the synergistic effect of lysine with ammonium polyphosphate (APP) and melamine, combined with the complexing properties of PAP-Mg-Na, to construct a composite material with excellent thermal stability and flame retardant effect. Through high-temperature treatment and chemical cross-linking between components, the mechanical strength and heat resistance of the material are enhanced. The introduction of bio-based components such as chitosan and vitamin B improves the biocompatibility and environmental protection characteristics of the material, which helps to develop high-performance, multifunctional flame retardant materials suitable for application fields with high requirements for safety and environmental protection.

[0058] 8. The advantages of this invention are that it utilizes the high specific surface area and porosity of MOFs (metal-organic frameworks) and combines them with the excellent flame retardant properties of PAP-Ly-Mg to construct a composite material with efficient flame retardant and smoke suppression functions. This invention changes the traditional method of preparing composite materials. Ultrasonic dispersion and vigorous stirring ensure the uniform distribution and close contact between the components, enhancing the overall stability and mechanical strength of the material. The introduction of PAP-Ly-Mg as a functional filler improves the thermal stability and flame retardant effect of the composite material. Attached Figure Description

[0059] Figure 1 This is a process flow diagram for the preparation of a green flame-retardant plywood. Detailed Implementation

[0060] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0061] Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art. Furthermore, all component raw materials used in the embodiments are known commercially available products.

[0062] Example 1

[0063] Step (1) Preparation of dioxane

[0064] In a 250 mL round-bottom flask, add 100 g of diethylene glycol and 2 g of anhydrous copper sulfate. Heat the flask to keep it boiling and control the heating for 1 hour. After the reaction is complete, cool to room temperature, add 105 g of diethylene glycol to the flask, continue heating, collect the distillate, add 10 mL of concentrated hydrochloric acid to the distillate, and then reflux to remove acetal impurities. After post-treatment, separate the aqueous layer, dry the oil layer, and distill to collect the distillate with a boiling point of 100 °C to obtain dioxane.

[0065] Step (2) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0066] Take 16g of dioxane from step (1), 9g of furfurylamine (0.1mol) and 6g of paraformaldehyde and add them in sequence to a three-necked flask. Then add 90mL of toluene / ethanol mixed solution and stir to mix the raw materials evenly. Then reflux at 80℃ for 8h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0067] Step (3) Preparation of binary benzoxazine-derived monomers

[0068] First, 1g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 2g of furfuryl alcohol resin and 1g of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 70°C for 24 hours to obtain a binary benzoxazine derivative monomer.

[0069] Step (4) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0070] Concentrated nitric acid was diluted to a concentration of 25% with anhydrous ethanol to obtain a nitric acid ethanol solution. 10g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After reacting for 2 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 6. This CMC-H was then added to a 40% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 100 mL of the dibenzoxazine derivative monomer from step (3) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed once with a 70% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 100°C to constant weight for about 4 hours. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0071] Step (5) Preparation of water-soluble bio-based charring agent

[0072] Melamine (MA) and vanillin were added to a flask at a ratio of 1:2, and then 10g of dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted for 2 hours. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal-coated carbon body (MV). 10g of refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) was added at a ratio of 1:1 and stirred thoroughly for 1 hour. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal-coated carbon.

[0073] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0074] First, a 50 wt% ligand solution was prepared using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as the organic ligand. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 20 wt% metal solution. The two solutions were then mixed at a 1:1 mass ratio and stirred at room temperature for 30 minutes. Finally, 10 g of the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 10 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0075] Step (7) Preparation of complexed flame retardant PAP-Ly-Mg

[0076] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 1:2:3. The mixture was stirred and heated to 300°C with a constant temperature digital display heating mantle. 10 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (6) was added, followed by 10 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 60 min and then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0077] Step (8) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0078] 0.1 g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 30 mL of ethanol solution, and then 10 mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 30 min, and then added to 150 mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 4 h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 80 °C for 24 h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0079] Example 2

[0080] Step (1) Preparation of dioxane

[0081] In a 270 mL round-bottom flask, add 120 g of diethylene glycol and 2.5 g of anhydrous copper sulfate. Heat the flask to keep it boiling and control the heating for 2 hours. After the reaction is complete, cool to room temperature, add 110 g of diethylene glycol to the flask, continue heating, collect the distillate, add 15 mL of concentrated hydrochloric acid to the distillate, and then reflux to remove acetal impurities. After post-treatment, separate the aqueous layer, dry the oil layer, and distill to collect the distillate with a boiling point of 110 °C to obtain dioxane.

[0082] Step (2) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0083] Take 17g of dioxane from step (1), 10g of furfurylamine (0.13mol) and 7g of paraformaldehyde and add them in sequence to a three-necked flask. Then add 92mL of toluene / ethanol mixed solution and stir to mix the raw materials evenly. Then reflux at 83℃ for 9h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0084] Step (3) Preparation of binary benzoxazine-derived monomers

[0085] First, 2g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 4g of furfuryl alcohol resin and 2g of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 75°C for 29 hours to obtain a binary benzoxazine derivative monomer.

[0086] Step (4) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0087] Concentrated nitric acid was diluted to a concentration of 27% with anhydrous ethanol to obtain a nitric acid ethanol solution. 13g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After reacting for 2.5 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 6.5. The CMC-H was then added to a 43% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. At this point, CMC... -H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 120 mL of the dibenzoxazine derivative monomer from step (3) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed twice with a 72% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 120°C to constant weight for about 4.5 h. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0088] Step (5) Preparation of water-soluble bio-based charring agent

[0089] Melamine (MA) and vanillin were added to a flask in a ratio of 2:3, and then 13g of dimethylformamide (DMF) solvent was added. The mixture was stirred for 2.6h. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 15g of refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a ratio of 2:2 was added and stirred thoroughly for 2h. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal agent.

[0090] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0091] First, using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as an organic ligand, a 60wt% ligand solution was prepared. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 25wt% metal solution. The two solutions were then mixed at a 2:2 mass ratio and stirred at room temperature for 34 minutes. Finally, 14g of the water-soluble bio-based char-forming agent from step (5) was added to promote the interaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 19 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0092] Step (7) Preparation of complexed flame retardant PAP-Ly-Mg

[0093] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 2:3:4. The mixture was stirred and heated to 350°C with a constant temperature digital display heating mantle. 19 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (6) was added, followed by 19 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 69 min. The mixture was then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0094] Step (8) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0095] 0.19 g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 37 mL of ethanol solution, and then 18 mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 40 min, and then added to 200 mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 5 h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 88 °C for 29 h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0096] Example 3

[0097] Step (1) Preparation of dioxane

[0098] In a 200 mL round-bottom flask, add 139 g of diethylene glycol and 3 g of anhydrous copper sulfate. Heat the flask to keep it boiling for 3 hours. After the reaction is complete, cool to room temperature and add 120 g of diethylene glycol to the flask. Continue heating and collect the distillate. Add 18 mL of concentrated hydrochloric acid to the distillate and then reflux to remove acetal impurities. After post-treatment, separate the aqueous layer and dry the oil layer. Distill and collect the distillate with a boiling point of 139 °C to obtain dioxane.

[0099] Step (2) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0100] Take 19g of dioxane from step (1), 13g of furfurylamine (0.13mol) and 9g of paraformaldehyde and add them in sequence to a three-necked flask. Then add 98mL of toluene / ethanol mixed solution and stir to mix the raw materials evenly. Then reflux at 89℃ for 13h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0101] Step (3) Preparation of binary benzoxazine-derived monomers

[0102] First, 4g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 4g of furfuryl alcohol resin and 4g of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 85°C for 35 hours to obtain a binary benzoxazine derivative monomer.

[0103] Step (4) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0104] Concentrated nitric acid was diluted to a concentration of 30% with anhydrous ethanol to obtain a nitric acid ethanol solution. 16g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After reacting for 3 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 8. This CMC-H was then added to a 49% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 140 mL of the dibenzoxazine derivative monomer from step (3) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed 4 times with a 75% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 130°C to constant weight for about 5 hours. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0105] Step (5) Preparation of water-soluble bio-based charring agent

[0106] Melamine (MA) and vanillin were added to a flask in a ratio of 3:4, and then 16g of dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted for 4 hours. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 18g of refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a ratio of 4:4 was added and stirred thoroughly for 4 hours. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0107] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0108] First, a 62 wt% ligand solution was prepared using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as the organic ligand. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 30 wt% metal solution. The two solutions were then mixed at a 3:3 mass ratio and stirred at room temperature for 50 minutes. Finally, 19 g of the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 30 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0109] Step (7) Preparation of complexed flame retardant PAP-Ly-Mg

[0110] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 3:4:5. The mixture was stirred and heated to 400°C with a constant temperature digital display heating mantle. 23 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (6) was added, followed by 39 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 80 min and then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0111] Step (8) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0112] 0.4 g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 40 mL of ethanol solution, and then 31 mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 48 min, and then added to 210 mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 7 h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 94 °C for 36 h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0113] Example 4

[0114] Step (1) Preparation of dioxane

[0115] In a 500 mL round-bottom flask, add 200 g of diethylene glycol and 5 g of anhydrous copper sulfate. Heat the flask to keep it boiling and control the heating for 5 hours. After the reaction is complete, cool to room temperature, add another 200 g of diethylene glycol to the flask, continue heating, collect the distillate, add 20 mL of concentrated hydrochloric acid to the distillate, and then reflux to remove acetal impurities. After post-treatment, separate the aqueous layer, dry the oil layer, and distill to collect the distillate with a boiling point of 200 °C to obtain dioxane.

[0116] Step (2) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0117] Take 20g of dioxane from step (1), 15g of furfurylamine (1mol) and 10g of paraformaldehyde and add them in sequence to a three-necked flask. Then add 100mL of toluene / ethanol mixed solution and stir to mix the raw materials evenly. Then reflux at 100℃ for 15h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0118] Step (3) Preparation of binary benzoxazine-derived monomers

[0119] First, 5g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 6g of furfuryl alcohol resin and 5g of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 90°C for 48 hours to obtain a binary benzoxazine derivative monomer.

[0120] Step (4) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0121] Concentrated nitric acid was diluted to 35% with anhydrous ethanol to obtain a nitric acid ethanol solution. 20g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After reacting for 5 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 10. This CMC-H was then added to a 50% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 200 mL of the dibenzoxazine derivative monomer from step (3) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed 5 times with an 81% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 150°C to constant weight for about 10 h. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0122] Step (5) Preparation of water-soluble bio-based charring agent

[0123] Melamine (MA) and vanillin were added to a flask in a 5:5 ratio, and 20g of dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted for 5h. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 20g of refined sodium carboxymethyl cellulose (CMC) from step (4) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a 5:5 ratio was added and stirred thoroughly for 5h. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0124] Step (6) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0125] First, a 69 wt% ligand solution was prepared using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as the organic ligand. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 50 wt% metal solution. The two solutions were then mixed at a 5:5 mass ratio and stirred at room temperature for 60 minutes. Finally, 20 g of the water-soluble bio-based char-forming agent from step (5) was added to promote the reaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to obtain a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 60 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0126] Step (7) Preparation of complexed flame retardant PAP-Ly-Mg

[0127] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 5:5:5. The mixture was stirred and heated to 600°C with a constant temperature digital display heating mantle. 50 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (6) was added, followed by 50 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 120 min and then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0128] Step (8) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0129] 0.5g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 60mL of ethanol solution, and then 50mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 60min, and then added to 300mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 10h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 100℃ for 48h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0130] Comparative Example 1

[0131] Step (1) Preparation of binary benzoxazine-derived monomers

[0132] First, 8g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 8g of furfuryl alcohol resin and 9g of vanillic acid-furfurylamine benzoxazine (VF) were weighed and mixed together in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 99°C for 46 hours to obtain a binary benzoxazine derivative monomer.

[0133] Step (2) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0134] Concentrated nitric acid was diluted to 70% with anhydrous ethanol to obtain a nitric acid-ethanol solution. 90g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid-ethanol solution. After reacting for 8 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 16. This CMC-H was then added to a 120% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 210 mL of the dibenzoxazine derivative monomer from step (1) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed 6 times with a 93% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 190°C to constant weight for about 11 hours. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0135] Step (3) Preparation of water-soluble bio-based charring agent

[0136] Melamine (MA) and vanillin were added to a flask in a ratio of 9:5, and then 28g of dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted for 7 hours. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 23g of refined sodium carboxymethyl cellulose (CMC) from step (2) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a ratio of 6:9 was added and stirred thoroughly for 8 hours. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0137] Step (4) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0138] First, using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as an organic ligand, an 85wt% ligand solution was prepared. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 50wt% metal solution. The two solutions were then mixed at a mass ratio of 9:5 and stirred at room temperature for 66 minutes. Finally, 20g of the water-soluble bio-based char-forming agent from step (3) was added to promote the reaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to obtain a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 60 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0139] Step (5) Preparation of complexed flame retardant PAP-Ly-Mg

[0140] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 6:5:7. The mixture was stirred and heated to 670°C with a constant temperature digital display heating mantle. 50 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (4) was added, followed by 57 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 135 min and then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0141] Step (6) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0142] 0.7 g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 89 mL of ethanol solution, and then 50 mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 69 min, and then added to 390 mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 16 h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 180 °C for 49 h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0143] Comparative Example 2

[0144] Step (1) Preparation of vanillic acid-furfurylamine benzoxazine (VF)

[0145] 24g of dioxane, 18g of furfurylamine (1mol) and 16g of paraformaldehyde were added to a three-necked flask in sequence, followed by 109mL of toluene / ethanol mixed solution. The raw materials were mixed evenly by stirring, and then refluxed at 121℃ for 16h to obtain vanillic acid-furfurylamine benzoxazine (VF).

[0146] Step (2) Preparation of binary benzoxazine-derived monomers

[0147] First, 9g of phenyl phosphate bismaleimide was weighed using an electronic analytical balance and subjected to the Diels-Alder reaction. Then, 11g of furfuryl alcohol resin and 14g of vanillic acid-furfurylamine benzoxazine (VF) from step (2) were weighed together and mixed in a transparent glass vial and ultrasonically stirred. The mixture was then placed in an oven at 103°C for 60h to obtain a binary benzoxazine derivative monomer.

[0148] Step (3) Preparation of refined sodium carboxymethyl cellulose (CMC)

[0149] Concentrated nitric acid was diluted to 39% with anhydrous ethanol to obtain a nitric acid ethanol solution. 29g of CMC powder (sodium carboxymethyl cellulose) was weighed and dissolved in the nitric acid ethanol solution. After reacting for 9 hours, the solution was filtered. The insoluble residue obtained was CMC-H. CMC-H was washed repeatedly with deionized water until its pH reached 19. This CMC-H was then added to a 190% sodium hydroxide solution and stirred thoroughly to obtain a viscous, transparent liquid. H reacts with sodium oxide to produce CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is viscous in water. 220 mL of the dibenzoxazine derivative monomer from step (2) is added to obtain a white flocculent substance, which is CMC (sodium carboxymethyl cellulose). CMC (sodium carboxymethyl cellulose) is washed 8 times with a 95% ethanol solution until the pH is neutral. Then it is dried in a vacuum oven at 200°C to constant weight for about 13 hours. After pulverization, refined sodium carboxymethyl cellulose (CMC) is obtained.

[0150] Step (4) Preparation of water-soluble bio-based charring agent

[0151] Melamine (MA) and vanillin were added to a flask in a ratio of 7:9, and then 70g of dimethylformamide (DMF) solvent was added. The mixture was stirred and reacted for 9 hours. After the reaction was complete, the reaction temperature was raised until the dimethylformamide (DMF) evaporated. The solution after the reaction was poured out and dried to obtain a bio-based charcoal coating (MV). 29g of refined sodium carboxymethyl cellulose (CMC) from step (3) was added to a beaker and stirred to mix the solution evenly. Ammonium polyphosphate (APP) in a ratio of 7:7 was added and stirred thoroughly for 9 hours. Finally, the resulting solution was dried and pulverized to obtain a water-soluble bio-based charcoal.

[0152] Step (5) Preparation of smoke-suppressing, low-toxicity, flame-retardant liquid PAP-Mg-Na

[0153] First, using water treatment PAPEMP (polyaminopolyether methylenephosphonic acid) as an organic ligand, an 87wt% ligand solution was prepared. The metal salt MgCl2·6H2O was dissolved in tap water to obtain a 59wt% metal solution. The two solutions were then mixed at a mass ratio of 8:9 and stirred at room temperature for 78 minutes. Finally, 28g of the water-soluble bio-based char-forming agent from step (4) was added to promote the reaction between the ligand and the metal ions MgCl2·6H2O. 2+ A complexation reaction occurs to prepare a complexation solution. Then, NaOH promoting solution is added and slowly added to the complexation solution. After stirring for 89 minutes, smoke-suppressing, low-toxicity, and flame-retardant liquid PAP-Mg-Na is obtained.

[0154] Step (6) Preparation of complexed flame retardant PAP-Ly-Mg

[0155] Lysine, ammonium polyphosphate (APP) and melamine were added to a four-necked flask in a molar ratio of 9:5:7. The mixture was stirred and heated to 690°C with a constant temperature digital display heating mantle. 52 mL of the smoke-suppressing, low-toxicity flame-retardant liquid PAP-Mg-Na from step (5) was added, followed by 57 g of chitosan and vitamin B. After solidification, the mixture was allowed to mature for 190 min and then pulverized to obtain the complexed flame retardant PAP-Ly-Mg.

[0156] Step (7) Preparation of MOF (Metal-Organic Framework) Flame-Retardant Composite Material

[0157] 0.9 g of dried MOF (metal-organic framework) nanoparticles were ultrasonically dispersed in 90 mL of ethanol solution, and then 59 mL of the complexed flame retardant PAP-Ly-Mg from step (7) was added to the above liquid. The mixture was allowed to stand for 69 min, and then added to 300 mL of cellulose dispersion. The mixture was stirred vigorously at room temperature for 19 h. The water in the mixture was removed through a Buchner funnel, and then dried in a vacuum oven at 190 °C for 49 h to obtain the MOF (metal-organic framework) flame retardant composite material.

[0158] Comparison of detection experiments:

[0159] The green flame-retardant plywood obtained in Examples 1 to 4 and comparative products 1 and 2 were tested. The specific testing methods are as follows:

[0160] Oxygen Index Test

[0161] The oxygen index refers to the minimum volume concentration of oxygen required to sustain combustion of a prepared material during combustion. It is usually expressed as a percentage. If the oxygen index of the prepared material is greater than 21% in the test, it is not easy to spontaneously combust in air. The higher the oxygen index, the more difficult the material is to burn, exhibiting excellent flame retardancy. If it is lower than 21%, the opposite is true.

[0162] Moisture content test method

[0163] When the moisture content of the plywood is too high, the moisture in the wood will dilute the adhesive, reduce the curing effect of the adhesive, and lead to a decrease in the bonding strength of the adhesive layer. When the moisture content is too low, the water absorption capacity of its internal fibers will be enhanced, and the adhesive will be quickly absorbed into the wood, resulting in uneven distribution of adhesive on the wood surface and insufficient adhesive on the bonding surface. The international standard for the optimal moisture content range is 7%-12%. Within this range, the flexibility of the wood can be guaranteed, and a good environment can be provided for the adhesion and curing of the adhesive.

[0164] Table 1. Results of oxygen index test

[0165] Example Oxygen Index / % 1 27 2 24 3 23 4 22 Comparative Example 1 10 Comparative Example 2 5

[0166] As shown in Table 1, Example 1 is the best, while Comparative Example 2 is the worst. The oxygen index of Example 1 is 27%, which shows the best flame retardant performance. This is because melamine forms a dense expanded char layer during the thermal decomposition process, which effectively blocks heat conduction and oxygen entry, thereby delaying the thermal degradation of the matrix and inhibiting the generation of volatile free formaldehyde. In contrast, the oxygen index of Comparative Example 2 is only 5%, indicating that an effective flame retardant protective layer is not formed. This is because it lacks the key char-forming and foaming components in the intumescent flame retardant system, which makes it unable to effectively block heat and oxygen when heated, resulting in the worst flame retardant performance.

[0167] Table 2. Results of Moisture Content Test Method

[0168] Example Moisture content / % 1 10 2 9 3 8 4 7 Comparative Example 1 4 Comparative Example 2 3

[0169] As shown in Table 2, Example 1 is the best and Comparative Example 2 is the worst. The moisture content of Example 1 is 10%, which is in the middle of the international standard optimal moisture content range (7%-12%). The wood has moderate flexibility, the adhesive is evenly distributed and has the best curing effect, and the adhesive layer has high bonding strength, so the adhesive performance is the best. The moisture content of Comparative Example 2 is 3%, which is far below the standard range. The wood is too dry, the fiber's water absorption capacity is enhanced, which leads to the rapid absorption of adhesive. The adhesive layer is unevenly distributed and there is insufficient adhesive on the bonding surface, resulting in a significant decrease in bonding strength, so the performance is poor.

[0170] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A process for the preparation of green fire-retardant plywood, characterized by, Comprise: Preparation of dioxane, preparation of vanillic acid-furfurylamine benzoxazine, preparation of binary benzoxazine derivative monomer, preparation of refined sodium carboxymethyl cellulose, preparation of water-soluble bio-based charring agent, preparation of smoke suppression low-toxicity flame-retardant liquid PAP-Mg-Na, preparation of complex flame retardant PAP-Ly-Mg, preparation of metal organic framework flame-retardant composite material; Step (1) preparation of dioxane In a round-bottom flask, add a certain amount of diethylene glycol and anhydrous copper sulfate, heat to keep the reaction bottle boiling, control the heating time, after the reaction is completed, cool to room temperature, then add a large amount of diethylene glycol to the reaction bottle, continue to heat, collect the distillate, add a small amount of concentrated hydrochloric acid to the distillate, then reflux to remove acetal impurities, separate the water layer after post-treatment, dry the oil layer, distill the distillate, and obtain dioxane; Step (2) preparation of vanillic acid-furfurylamine benzoxazine Take a small amount of dioxane in step (1), furfurylamine and a small amount of paraformaldehyde, add them to a three-necked flask in order, then add a certain amount of toluene / ethanol mixed solution, mix the raw materials uniformly by stirring, then reflux at high temperature for a period of time to obtain vanillic acid-furfurylamine benzoxazine; Step (3) preparation of binary benzoxazine derivative monomer First, weigh a certain amount of benzophosphonate bismaleimide after Diels-Alder reaction, then take a small amount of furfuryl alcohol resin and a small amount of vanillic acid-furfurylamine benzoxazine in step (2), mix them together in a transparent glass vial and stir uniformly under ultrasonic, then place it in an oven at high temperature for heat preservation to obtain binary benzoxazine derivative monomer; Step (4) preparation of refined sodium carboxymethyl cellulose Dilute concentrated nitric acid with anhydrous ethanol to obtain nitric acid ethanol solution, take a small amount of carboxymethyl cellulose powder, dissolve it in nitric acid ethanol solution after reaction and filtration, at this time the insoluble substance is CMC-H, wash CMC-H with deionized water several times, add the above CMC-H to a high-concentration sodium hydroxide solution, stir well to obtain a viscous transparent liquid, at this time CMC-H reacts with sodium hydroxide to obtain sodium carboxymethyl cellulose, which is viscous in water, add a large amount of binary benzoxazine derivative monomer in step (3) to obtain white flocculent material, which is sodium carboxymethyl cellulose, wash sodium carboxymethyl cellulose with ethanol solution several times until the pH is neutral, then dry it to constant weight in a vacuum oven, crush it to obtain refined sodium carboxymethyl cellulose; Step (5) preparation of water-soluble bio-based charring agent Add melamine and vanillin in a certain proportion into a flask, then add dimethylformamide solvent, stir and react, then increase the reaction temperature to volatilize dimethylformamide, pour out the reacted solution and dry it to obtain bio-based charring agent carbon coating body, take refined sodium carboxymethyl cellulose in step (4), stir to mix the solution uniformly, add ammonium polyphosphate, stir thoroughly, and finally dry the obtained solution, then crush it to obtain water-soluble bio-based charring agent; Step (6) preparation of smoke suppression low-toxicity flame-retardant liquid PAP-Mg-Na First, using water treatment polyamino polyether-based methylene phosphonic acid PAPEMP as an organic ligand, a ligand solution is prepared, a metal salt MgCl2·6H20 is dissolved in tap water to obtain a metal solution, and then the two solutions are mixed in a certain mass ratio, stirred at room temperature, and then a water-soluble bio-based carbonization agent prepared in step (5) is added to promote the complexation of the ligand and metal ions Mg 2+ The complexation reaction occurs to obtain a complex solution, then NaOH is added to promote the solution, and it is slowly added to the complex solution, stirred to obtain a smoke suppression low-toxicity flame-retardant liquid PAP-Mg-Na; Step (7) Preparation of complex flame retardant PAP-Ly-Mg Lysine, ammonium polyphosphate APP and melamine are added into a four-necked flask in a certain molar ratio, mixed and stirred, heated to high temperature by a constant-temperature digital heating jacket, a small amount of smoke suppression low-toxicity flame retardant liquid PAP-Mg-Na of step (6) is added, then chitosan and vitamin B are added, and after solidification and maturation reaction, crushing is performed to obtain the complex flame retardant PAP-Ly-Mg. Step (8) Preparation of metal-organic framework flame-retardant composite material A small amount of dried metal-organic framework nanoparticles is ultrasonically dispersed in an ethanol solution, and then the complex flame retardant PAP-Ly-Mg of step (7) is added to the above liquid, which is then placed in a cellulose dispersion liquid and stirred vigorously at room temperature. The mixed liquid is drained of water through a Buchner funnel, and then dried in a vacuum oven to obtain the metal-organic framework flame-retardant composite material.

2. The preparation process of the green flame-retardant plywood according to claim 1, characterized in that: Step (1) Preparation of dioxane In a 250-500 mL round-bottom flask, 100-200 g of diethylene glycol and 2-5 g of anhydrous copper sulfate are added, the reaction bottle is kept boiling by heating, and the heating is controlled for 1-5 h. After the reaction is completed, the reaction bottle is cooled to room temperature, 105-200 g of diethylene glycol is added to the reaction bottle, and heating is continued. The distillate is collected, 10-20 mL of concentrated hydrochloric acid is added to the distillate, and then the acetal impurities are removed by reflux. After post-treatment, the water layer is separated, the oil layer is dried, and the distillate with a boiling point of 100-200 ℃ is collected by distillation to obtain dioxane.

3. The preparation process of the green flame-retardant plywood according to claim 2, characterized in that: Step (2) Preparation of vanillic acid-furfuryl amine benzoxazine (VF) 16-20 g of dioxane of step (1), 9-15 g of furfuryl amine, and 6-10 g of paraformaldehyde are sequentially added to a three-necked flask, then 90-100 mL of a toluene / ethanol mixed solution is added, the raw materials are uniformly mixed by stirring, and then vanillic acid-furfuryl amine benzoxazine (VF) is obtained by refluxing at 80-100 ℃ for 8-15 h.

4. The preparation process of the green flame-retardant plywood according to claim 3, characterized in that: Step (3) Preparation of binary benzoxazine derivative monomer First, 1-5 g of benzophospholipid bismaleimide after Diels-Alder reaction is weighed using an electronic analytical balance, then 2-6 g of furfuryl alcohol resin and 1-5 g of vanillic acid-furfuryl amine benzoxazine (VF) of step (2) are weighed, and they are mixed and ultrasonically stirred in a transparent glass vial. The mixture is placed in an oven at 70-90 ℃ for 24-48 h to obtain the binary benzoxazine derivative monomer.

5. The preparation process of the green flame-retardant plywood according to claim 4, characterized in that: Step (4) Preparation of refined sodium carboxymethyl cellulose Dilute concentrated nitric acid with anhydrous ethanol to a concentration of 25-35% to obtain a nitric acid ethanol solution, weigh 10-20 g of carboxymethyl cellulose, dissolve the carboxymethyl cellulose in the nitric acid ethanol solution and react for 2-5 h, then filter, at this time the insoluble material is CMC-H, wash the CMC-H with deionized water multiple times until the pH of the CMC-H is 6-10, add the above CMC-H to a 40-50% concentration sodium hydroxide solution and stir thoroughly to obtain a viscous transparent liquid, at this time the CMC-H and sodium hydroxide react to form sodium carboxymethyl cellulose, which is viscous in water, add 100-200 mL of the binary benzoxazine derivative monomer of step (3) to obtain white flocculent material, which is sodium carboxymethyl cellulose, wash the sodium carboxymethyl cellulose with a 70-85% volume fraction ethanol solution 1-5 times until the pH is neutral, then dry in a vacuum oven at 100-150°C to constant weight, 4-10 h, and pulverize to obtain refined sodium carboxymethyl cellulose.

6. The preparation process of the green flame-retardant plywood according to claim 5, characterized in that: Step (6) preparation of smoke-suppressing low-toxicity flame-retardant liquid PAP-Mg-Na First, use water to treat polyamino polyether-based methylene phosphonic acid as an organic ligand, prepare a 50-70wt% ligand solution, dissolve metal salt MgCl2·6H20 in tap water to obtain a 20-50w% metal solution, then mix the two solutions in a 1-5:1-5 mass ratio, stir at room temperature for 30-60min, then add 10-20g of the water-soluble bio-based carbonization agent of step (5) to promote the ligand to react with the metal ion Mg 2+ complexation reaction to obtain a complex solution, then add NaOH to promote the solution, slowly add it to the complex solution, stir for 10-60min, and obtain the smoke suppression low toxicity flame retardant liquid PAP-Mg-Na.

7. The preparation process of the green flame-retardant plywood according to claim 6, characterized in that: Step (7) preparation of complex flame retardant PAP-Ly-Mg Add lysine, ammonium polyphosphate and melamine into a four-necked flask in a molar ratio of 1-5:2-5:3-5, mix and stir, heat to 300-600°C with a constant-temperature digital heating jacket, add 10-50 mL of the smoke-suppressing low-toxicity flame-retardant liquid PAP-Mg-Na of step (6), then add 10-50 g of chitosan and vitamin B, after solidification, mature the reaction for 60-120 min, and pulverize to obtain the complex flame retardant PAP-Ly-Mg.

8. The preparation process of the green flame-retardant plywood according to claim 7, characterized in that: Step (8) preparation of metal-organic framework flame-retardant composite material Ultrasonic and disperse 0.1-0.5 g of dried metal-organic framework nanoparticles in 30-60 mL of an ethanol solution, then add 10-50 mL of the complex flame retardant PAP-Ly-Mg of step (7) to the above liquid, stand for 30-60 min, then add it to 150-300 mL of a cellulose dispersion liquid, stir vigorously at room temperature for 4-10 h, remove the water from the mixed liquid through a Buchner funnel, then dry in a vacuum oven at 80-100°C for 24-48 h to obtain the metal-organic framework flame-retardant composite material.

Images