Smoke-suppression low-toxicity flame-retardant floor board and preparation method thereof

Abstract

The invention discloses a smoke-suppressing low-toxicity flame-retardant floor board and a preparation method thereof. The method comprises the steps that S1, wood is placed in a mixed solution of imidazole diethyl phosphate and a Lewis acid catalyst, vacuum impregnation and heating and pressurizing impregnation are sequentially conducted, and the wood is drained after impregnation; the wood is sequentially placed in a chitosan solution, a metal salt solution and an alkaline solution to be subjected to pressure dipping, and complexing flame retardant modified wood is obtained after draining and washing; and S2, the complex flame retardant modified wood is soaked in a water-soluble charring agent solution, drained after being pressurized and soaked, washed with water and dried, and the flame retardant modified wood is obtained. The imidazole diethyl phosphate is obtained by carrying out condensation reaction on 1-(3-aminopropyl) imidazole and (formyl methyl) diethyl phosphate in a mass ratio of (0.5-0.7): 1. The problems that a current floor board is poor in flame retardant property durability, high in smoke density and low in carbon residue amount can be effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame-retardant materials, in particular to a smoke-suppressing low-toxicity flame-retardant floor board and a preparation method thereof. BACKGROUND

[0002] Current flame-retardant floor boards generally use a mixed system of intumescent flame retardant (such as a compounded system of ammonium polyphosphate, pentaerythritol and melamine) or halogen-based flame retardant (such as decabromodiphenyl ethane) and a binder such as urea-formaldehyde resin or phenol-formaldehyde resin to form a flame-retardant coating, which is then coated on the surface of a wood veneer or particle board substrate as an intermediate layer to delay the spread of fire through the carbonization and expansion effect of the flame-retardant coating. However, this type of surface flame-retardant treatment technology causes the flame retardant to be distributed in a gradient within the board, and when the fire breaks through the surface layer, the core wood rapidly pyrolyzes and burns due to the lack of flame-retardant protection, resulting in limited improvement in overall flame-retardant performance. More seriously, halogen-based flame retardants release dioxin, hydrogen bromide and other toxic smoke at high temperatures, with high smoke density. The above defects make the existing flame-retardant floor boards still face the problems of poor flame-retardant durability, high smoke density and low residual carbon content in a fire. SUMMARY

[0003] To solve the problems of poor flame-retardant durability, high smoke density and low residual carbon content of current floor boards, the present application provides a smoke-suppressing low-toxicity flame-retardant floor board and a preparation method thereof.

[0004] In a first aspect, the present application provides a preparation method of a smoke-suppressing low-toxicity flame-retardant floor board, comprising the following steps: S1. Placing wood in a mixed solution of imidazole diethyl phosphate and a Lewis acid catalyst, sequentially performing vacuum impregnation and heating and pressure impregnation, and then draining the wood; then placing the wood in a chitosan solution, a metal salt solution and an alkaline solution for pressure impregnation, and then draining and washing to obtain a complex flame-retardant modified wood; S2. Immersing the complex flame-retardant modified wood in a water-soluble carbon-forming agent solution, pressure impregnating, draining, washing and drying to obtain the smoke-suppressing low-toxicity flame-retardant floor board. The imidazole diethyl phosphate is obtained by condensation reaction of 1-(3-aminopropyl)imidazole and (formylmethyl) diethyl phosphate in a mass ratio of 0.5-0.7:1.

[0005] In any of the above technical solutions, the preparation method of the imidazole diethyl phosphate is as follows: adding 1-(3-aminopropyl)imidazole and (formylmethyl) diethyl phosphate into an alcohol-water mixture, heating to 60-80℃, adding p-toluenesulfonic acid as a catalyst for condensation reaction, and then cooling, filtering and drying after the reaction is completed.

[0006]

[0007] In any of the above technical solutions, the metal salt is selected from any one or several of calcium salt, magnesium salt, aluminum salt.

[0008] In any of the above technical solutions, the calcium salt is selected from any one or several of calcium chloride, calcium sulfate, calcium nitrate.

[0009] In any of the above technical solutions, the magnesium salt is selected from any one or several of magnesium chloride, magnesium sulfate, magnesium nitrate.

[0010] In any of the above technical solutions, the aluminum salt is selected from any one or several of aluminum chloride, aluminum sulfate, aluminum nitrate.

[0011] In any of the above technical solutions, the temperature of the heating and pressurized impregnation is 100-110℃, and the pressure is 1.1-1.3 MPa.

[0012] In any of the above technical solutions, the concentrations of diethyl imidazole phosphate and Lewis acid catalyst in the mixed solution are 45-55wt% and 1-3wt%, respectively; the concentrations of the chitosan solution, the metal salt solution, and the alkaline solution are 8-15wt%, 15-25wt%, and 5-15wt%, respectively; and the concentration of the water-soluble carbonization agent solution is 5-10wt%.

[0013] In any of the above technical solutions, the Lewis acid catalyst is selected from any one or several of tetraisopropyl titanate, tetrabutyl titanate, tetrabutyl zirconate, and stannous octoate.

[0014] In any of the above technical solutions, the pressure of the vacuum impregnation is -0.08 to -0.1 MPa, and the impregnation duration is 0.5-1h.

[0015] In any of the above technical solutions, the impregnation duration of the heating and pressurized impregnation is 1-3h.

[0016] In any of the above technical solutions, the pressure of the pressurized impregnation of the wood in the chitosan solution, the metal salt solution, and the alkaline solution is 1.1-1.3 MPa, and the impregnation duration is 0.5-1h.

[0017] Illustratively, the solvent of the mixed solution is toluene.

[0018] Illustratively, the solvent of the chitosan solution is an acidic solvent with pH 3.0-5.0, including but not limited to hydrochloric acid, citric acid, or acetic acid aqueous solution.

[0019] In any of the above technical solutions, the solvent of the metal salt solution is water.

[0020] In any of the above technical solutions, the alkaline solution is an aqueous solution of sodium hydroxide and / or potassium hydroxide.

[0021] The present application makes imidazole diethyl phosphate, chitosan double ligand and metal ions gradually penetrate into the wood through a multi-step pressurized impregnation process, forming a flame retardant system combining chemical bonding and physical deposition. First, imidazole diethyl phosphate reacts with wood hydroxyl groups under Lewis acid catalysis to form stable phosphorus ester bonds (P-O-C), achieving firm combination of the flame retardant and wood, and fundamentally solving the gradient distribution problem of traditional coating flame retardants caused by physical adsorption. Second, chitosan, as a biomass ligand, forms a double ligand metal complex with metal ions through complexation of its abundant hydroxyl and amino groups in an alkaline environment. The double ligand structure significantly improves the charring rate and thermal stability. In addition, the introduction of imidazole groups enhances the metal-ligand crosslinking density, which, in combination with the synergistic effect of water-soluble charring agents, catalyzes the rapid dehydration and carbonization of wood during combustion, forming a continuous and dense carbon layer barrier. This carbon layer not only isolates oxygen and heat from spreading to the core layer, but also crosslinks with pyrolytic carbon chains through phosphorus-containing groups, allowing more carbon-containing substances to be retained and reducing the volatilization of flammable gases, thereby significantly improving flame retardant durability and suppressing smoke generation, reducing smoke density.

[0022] In any of the above technical solutions, after the wood is immersed in the alkaline solution, the wood is placed in a solution of 5-10 wt% copper tetraaminophenyl porphyrin modified graphite for pressurized impregnation.

[0023] In any of the above technical solutions, the copper tetraaminophenyl porphyrin modified graphite is prepared by blending graphite and copper tetraaminophenyl porphyrin in a mass ratio of 100:10-20.

[0024] In any of the above technical solutions, the particle size of the graphite is 1-50 μm, preferably 5-20 μm.

[0025] The copper tetraaminophenyl porphyrin modified graphite is stably attached to the surface of the graphite sheet layer through π-π stacking, and its copper ion metal center can form a coordination bond with the chitosan amino group or imidazole nitrogen atom in the double ligand flame retardant system, forming a three-dimensional network structure. This enhances the physical barrier, which expands at high temperatures through the sheet structure of the graphite, filling the pores of the carbon layer, and forms a dense heat barrier layer with the double ligand metal complex flame retardant, blocking the transfer of heat to the interior of the wood. In addition, the copper ions in the copper tetraaminophenyl porphyrin can catalyze the dehydrogenation reaction during the pyrolysis of wood, promoting the formation of aromatic carbon structures and improving the quality of residual carbon. At the same time, its large π conjugated system can capture free radicals, reducing the generation of smoke precursors and inhibiting the combustion chain reaction in the gas phase.

[0026] In any of the above technical solutions, the raw material of the water-soluble biological charring agent comprises vanillic acid-ethanolamine benzoxazine monomers, benzene phosphoric dichloride and acid-binding agent in a molar ratio of 1:0.45-0.55:1.1-1.2, and the vanillic acid-ethanolamine benzoxazine monomers are subjected to a substitution reaction with the benzene phosphoric dichloride.

[0027]

[0028] In any of the above technical solutions, the raw material of the vanillic acid-ethanolamine benzoxazine monomers comprises ethanolamine, paraformaldehyde and vanillic acid in a molar ratio of 1:2-2.2:1, and is prepared by reaction in a dioxane solvent.

[0029]

[0030] In any of the above technical solutions, the acid-binding agent is triethylamine.

[0031] In any of the above technical solutions, the reaction temperature of the ethanolamine, paraformaldehyde and vanillic acid in the dioxane solvent is 75-90℃.

[0032] The water-soluble charring agent (benzoxazine phosphate) of the present application releases phosphorus-containing free radicals when pyrolyzed at 200℃ or above, forming a polyphosphoric acid and a phosphoric acid salt aromatic carbon layer. On the one hand, the phosphorus-containing free radicals can effectively quench active H· and OH· free radicals, interrupting the combustion chain reaction. On the other hand, the generated polyphosphoric acid catalyzes the dehydration of wood to form carbon, and the phosphoric acid salt carbon layer forms a molten cover layer on the surface of the wood, effectively blocking the penetration of oxygen. It should be emphasized that the water-soluble nature ensures uniform penetration into the wood during the impregnation process, overcoming the early failure problem of traditional phosphorus-nitrogen flame retardants due to poor thermal stability (decomposition at 180℃).

[0033] In a second aspect, the present application provides a smoke-suppressing low-toxicity flame-retardant floor board prepared by any of the above preparation methods.

[0034] In summary, the present application has the following beneficial effects: The present application realizes chemical bonding of the flame retardant in the wood veneer through a pressurized impregnation process, integrates the bidentate metal complex, copper tetraaminophenyl porphyrin modified graphite and water-soluble charring agent into the wood, and constructs a multi-level flame-retardant smoke-suppressing system. Among them, the bidentate metal complex flame retardant realizes the synergistic cooperation of gas phase free radical capture and condensed phase charring, improving the residual carbon content and thermal resistance; the copper tetraaminophenyl porphyrin modified graphite enhances the compactness and thermal stability of the carbon layer through coordination bonding; the water-soluble charring agent generates a phosphoric acid salt barrier at high temperatures to inhibit the diffusion of oxygen. The synergistic effect of the three greatly improves the flame-retardant durability, significantly reduces the smoke density and toxicity release, and meets the requirements of green low-toxicity boards. DETAILED DESCRIPTION Preparation Example

[0035] Preparation Example 1-1, diethyl imidazole phosphate, was prepared as follows: 100 g of diethyl (formylmethyl) phosphate and 60 g of 1-(3- aminopropyl)imidazole were added to a mixed solvent of 200 mL of anhydrous ethanol and 50 mL of deionized water, and the temperature was raised to 70°C. 1.5 g of p-toluenesulfonic acid was added as a catalyst, and the reaction was stirred for 5 hours under nitrogen protection. After the reaction was completed, the temperature was lowered to 25°C, and solid impurities were removed by suction filtration. The filtrate was extracted three times with 100 mL of ethyl acetate, and the organic phases were combined and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and the product was dried in a vacuum oven at 60°C for 12 hours.

[0036] Preparation Example 1-2, diethyl imidazole phosphate, was prepared as follows: 100 g of diethyl (formylmethyl) phosphate and 50 g of 1-(3- aminopropyl)imidazole were added to a mixed solvent of 150 mL of anhydrous ethanol and 30 mL of deionized water, and the temperature was raised to 60°C. 1.0 g of p-toluenesulfonic acid was added as a catalyst, and the reaction was stirred for 4 hours under nitrogen protection. After the reaction was completed, the temperature was lowered to 20°C, and the filtrate was extracted three times with 80 mL of ethyl acetate. The organic phases were dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation, and the product was dried in a vacuum oven at 55°C for 16 hours.

[0037] Preparation Example 1-3, diethyl imidazole phosphate, was prepared as follows: 100 g of diethyl (formylmethyl) phosphate and 70 g of 1-(3- aminopropyl)imidazole were added to a mixed solvent of 250 mL of anhydrous ethanol and 70 mL of deionized water, and the temperature was raised to 80°C. 2.0 g of p-toluenesulfonic acid was added as a catalyst, and the reaction was stirred for 2.5 hours under nitrogen protection. After the reaction was completed, the temperature was lowered to 30°C, and the filtrate was extracted three times with 120 mL of ethyl acetate. The organic phases were combined and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and the product was dried in a vacuum oven at 65°C for 10 hours.

[0038] Preparation Example 2-1, copper tetraaminophenyl porphyrin modified graphite, was prepared as follows: 100 g of graphite powder with an average particle size of 10 μm and 15 g of copper tetraaminophenyl porphyrin powder were added to a ball mill tank, 300 mL of N-N dimethylformamide was added as a dispersion medium, zirconium oxide balls were used as a grinding medium (ball-to-material ratio of 10:1), and the mixture was ball-milled at 400 r / min for 4 hours under a nitrogen atmosphere. After the ball-milling, the slurry was filtered through a 200-mesh screen, the filter cake was washed three times with deionized water, and the product was dried in an oven at 80°C for 6 hours.

[0039] Preparation Example 2-2, copper tetraaminophenyl porphyrin modified graphite, was prepared as follows: Into a ball mill pot, 100 g of graphite powder with an average particle size of 5 μm and 10 g of tetraaminophenyl porphyrin copper powder were added, 300 mL of N-N dimethylformamide was added as a dispersion medium, zirconium oxide balls were used as a grinding medium (ball-to-material ratio of 10:1), and the mixture was ball-milled at 500 r / min for 3 hours under a nitrogen atmosphere. After the ball-milling, the slurry was filtered through a 200-mesh screen, the filter cake was washed with deionized water three times, and the cake was dried in an oven at 70°C for 9 hours to obtain the product.

[0040] Preparation Example 2-3, tetraaminophenyl porphyrin copper-modified graphite, was prepared by the following procedure: Into a ball mill pot, 100 g of graphite powder with an average particle size of 15 μm and 20 g of tetraaminophenyl porphyrin copper powder were added, 400 mL of dimethyl sulfoxide was added as a dispersion medium, zirconium oxide balls were used as a grinding medium (ball-to-material ratio of 10:1), and the mixture was ball-milled at 500 r / min for 3.5 hours under a nitrogen atmosphere. After the ball-milling, the slurry was filtered through a 200-mesh screen, the filter cake was washed with deionized water three times, and the cake was dried in an oven at 90°C for 5 hours to obtain the product.

[0041] Preparation Example 2-4, tetraaminophenyl porphyrin copper-modified graphite, was prepared by the following procedure:

[0042] Preparation Example 3-1, water-soluble biochar-forming agent, was prepared by the following procedure: Into a flask, 1 mol of ethanolamine and 2 mol of paraformaldehyde were dissolved in dioxane, 1 mol of vanillic acid was added dropwise, and the mixture was reacted at 80°C for 24 hours. After the reaction, the solvent was distilled off, and ethanol was added to the product to obtain a white powder, i.e., vanillic acid-ethanolamine benzoxazine monomer. Then, 1 mol of the vanillic acid-ethanolamine benzoxazine monomer and 1.1 mol of triethylamine were dissolved in dry N,N-dimethylformamide, 0.5 mol of phenylphosphoryl dichloride was added dropwise, the mixture was reacted in an ice water bath for 0.5 hours, and then the mixture was reacted at room temperature for 24 hours. After the reaction, the solvent was distilled off, and the product was dissolved in ethyl acetate to obtain a white powder, i.e., water-soluble biochar-forming agent.

[0043] Preparation Example 3-2, water-soluble biochar-forming agent, was prepared by the following procedure: Into a flask, 1 mol of ethanolamine and 2.1 mol of paraformaldehyde were dissolved in dioxane, 1 mol of vanillic acid was added dropwise, and the mixture was reacted at 85°C for 20 hours. After the reaction, the solvent was distilled off, and ethanol was added to the product to obtain a white powder, i.e., vanillic acid-ethanolamine benzoxazine monomer. Then, 1 mol of the vanillic acid-ethanolamine benzoxazine monomer and 1.1 mol of triethylamine were dissolved in dry N,N-dimethylformamide, 0.5 mol of phenylphosphoryl dichloride was added dropwise, the mixture was reacted in an ice water bath for 0.5 hours, and then the mixture was reacted at room temperature for 24 hours. After the reaction, the solvent was distilled off, and the product was dissolved in ethyl acetate to obtain a white powder, i.e., water-soluble biochar-forming agent.

[0044] Preparation Example 3-3, water-soluble biochar-forming agent, was prepared by the following procedure: Dissolve 1 mol of ethanolamine and 2.2 mol of paraformaldehyde in dioxane, and add 1 mol of vanillic acid dropwise. React at 90°C for 20 h. After the reaction is completed, spin off the solvent, and re-precipitate ethanol to obtain a white powder, which is a vanillic acid-ethanolamine benzoxazine monomer. Then, dissolve 1 mol of the vanillic acid-ethanolamine benzoxazine monomer and 1.2 mol of triethylamine in dry N,N-dimethylformamide, and add 0.55 mol of phenylphosphonic dichloride. React for 1 h in an ice water bath, and then react for 24 h at room temperature. After the reaction is completed, spin off the solvent, and finally, dissolve in dioxane and precipitate in ethyl acetate to obtain a white powder, which is a water-soluble biochar-forming agent. Example

[0045] Example 1, a smoke-suppressing low-toxicity flame-retardant flooring material, was prepared by the following procedure: Prepare a mixed solution (solvent: toluene) containing 50 wt% of imidazole diethyl phosphate of Preparation Example 1-1, 2 wt% of tetraisopropyl titanate, 10 wt% of a chitosan solution (pH = 5), 20 wt% of a magnesium chloride aqueous solution, 10 wt% of sodium hydroxide, 7.5 wt% of a water-soluble copper tetraaminophenyl porphyrin-modified graphite (Preparation Example 2-1) aqueous solution, and 8 wt% of a water-soluble biochar-forming agent (Preparation Example 3-1).

[0046] S1-1, place wood in a pressurized impregnation chamber filled with the above mixed solution, and maintain a constant pressure of -0.09 MPa for 0.5 h. Then, increase the temperature to 105°C, and increase the pressure to 1.2 MPa, and soak for 2 h. Drain the solution, and remove the wood and rinse the wood with tap water 3-5 times, and drain.

[0047] S1-2, immerse the wood (from step S1-1) in a chitosan solution, and pressurize to 1.2 MPa, and maintain for 1.5 hours, drain the solution, and remove the wood and drain.

[0048] S1-3, immerse the wood (from step S1-2) in a magnesium chloride solution, and pressurize to 1.2 MPa, and maintain for 1.5 hours, drain the solution, and remove the wood and drain.

[0049] S1-4, immerse the wood (from step S1-3) in a sodium hydroxide solution, and pressurize to 1.2 MPa, and maintain for 1.5 hours, drain the solution, and remove the wood and drain.

[0050] S1-5, immerse the wood (from step S1-4) in a water-soluble copper tetraaminophenyl porphyrin-modified graphite solution, and pressurize to 1.2 MPa, and maintain for 1.5 hours, drain the solution, and remove the wood and drain. Finally, rinse the wood with tap water 3-5 times to obtain a complex flame retardant-modified wood.

[0051] S2, the wood (from step S1-5) is immersed in the water-soluble charring agent solution, pressurized to 1.2 MPa, and kept for 1.5 hours, the solution is drained, and the wood is taken out and drained. Finally, the wood is washed with tap water for 3-5 times, and dried at 50°C to obtain the product.

[0052] Example 2, a smoke-suppressing and low-toxicity flame-retardant floor board is prepared as follows: A mixed solution containing 45wt% of the imidazole diethyl phosphate prepared in Preparation Example 1-2, 1.5wt% of tetrabutyl titanate, 8wt% of a chitosan solution (pH=5), 15wt% of an aluminum chloride aqueous solution, 5wt% of sodium hydroxide, 5wt% of a water-soluble copper tetraaminophenyl porphyrin modified graphite (Preparation Example 2-2) aqueous solution, and 10wt% of a water-soluble charring agent (Preparation Example 3-2) is prepared.

[0053] S1-1, the wood is placed in a pressurized impregnation chamber filled with the above mixed solution, and vacuumized at a constant pressure to -0.08 MPa for 1 h. Then, the temperature is increased to 100°C, the pressure is increased to 1.3 MPa, and the wood is soaked for 1.5 h. The solution is drained, and the wood is taken out and washed with tap water for 3-5 times, and drained.

[0054] S1-2, the wood (from step S1-1) is immersed in the chitosan solution, pressurized to 1.1 MPa, and kept for 1.5 hours, the solution is drained, and the wood is taken out and drained.

[0055] S1-3, the wood (from step S1-2) is immersed in the magnesium chloride solution, pressurized to 1.1 MPa, and kept for 2 hours, the solution is drained, and the wood is taken out and drained.

[0056] S1-4, the wood (from step S1-3) is immersed in the sodium hydroxide solution, pressurized to 1.1 MPa, and kept for 2 hours, the solution is drained, and the wood is taken out and drained.

[0057] S1-5, the wood (from step S1-4) is immersed in the water-soluble copper tetraaminophenyl porphyrin modified graphite solution, pressurized to 1.1 MPa, and kept for 2 hours, the solution is drained, and the wood is taken out and drained. Finally, the wood is washed with tap water for 3-5 times to obtain the complex flame retardant modified wood.

[0058] S2, the wood (from step S1-5) is immersed in the water-soluble charring agent solution, pressurized to 1.3 MPa, and kept for 2 hours, the solution is drained, and the wood is taken out and drained. Finally, the wood is washed with tap water for 3-5 times, and dried at 50°C to obtain the product.

[0059] Example 3, a smoke-suppressing and low-toxicity flame-retardant floor board is prepared as follows: A mixed solution (solvent: toluene) containing 55 wt% of imidazole diethyl phosphate prepared in Preparation Example 1-3, 3 wt% of tetraisopropyl titanate, 15 wt% of a chitosan solution (pH = 5), 25 wt% of a magnesium chloride aqueous solution, 15 wt% of a sodium hydroxide solution, 10 wt% of a water-soluble carbonization agent (Preparation Example 3-3) aqueous solution, and 5 wt% of water-soluble carbonization agent (Preparation Example 3-3) aqueous solution was prepared.

[0060] S1-1, wood was placed in a pressure impregnation chamber filled with the above mixed solution, and constant pressure vacuum was applied to -0.1 MPa for 0.5 h. Then the temperature was raised to 110°C, the pressure was increased to 1.1 MPa, and soaked for 3 h, the solution was drained, and the wood was taken out and washed with tap water for 3-5 times, and drained.

[0061] S1-2, the wood (from step S1-1) was immersed in a chitosan solution, pressurized to 1.3 MPa, and kept for 1.5 hours, the solution was drained, and the wood was taken out and drained.

[0062] S1-3, the wood (from step S1-2) was immersed in a magnesium chloride solution, pressurized to 1.3 MPa, and kept for 1.5 hours, the solution was drained, and the wood was taken out and drained.

[0063] S1-4, the wood (from step S1-3) was immersed in a sodium hydroxide solution, pressurized to 1.3 MPa, and kept for 1.5 hours, the solution was drained, and the wood was taken out and drained.

[0064] S1-5, the wood (from step S1-4) was immersed in a water-soluble carbonization agent solution, pressurized to 1.3 MPa, and kept for 1.5 hours, the solution was drained, and the wood was taken out and drained. Finally, the wood was washed with tap water for 3-5 times to obtain the complex flame retardant modified wood.

[0065] S2, the wood (from step S1-5) was immersed in a water-soluble carbonization agent solution, pressurized to 1.3 MPa, and kept for 2 hours, the solution was drained, and the wood was taken out and drained. Finally, the wood was washed with tap water for 3-5 times, and dried at 50°C to obtain the product.

[0066] Example 4, a smoke-suppressing and low-toxicity flame-retardant floor board, which is different from Example 1 in that an equal amount of tetraaminophenyl porphyrin copper modified graphite prepared in Preparation Example 2-4 is used to replace tetraaminophenyl porphyrin copper modified graphite prepared in Preparation Example 2-1 in the preparation process.

[0067] Example 5, a smoke-suppressing and low-toxicity flame-retardant floor board, which is different from Example 1 in that the step S1-5 is not performed after the step S1-4 in the preparation process, and the step S2 is directly performed (i.e., without immersing the water-soluble tetraaminophenyl porphyrin copper modified graphite solution).

[0068] Example 6, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 1 in that, in step S2, 8wt% of an aqueous solution of vanillic acid-ethanolamine benzoxazine monomer (prepared in Preparation Example 3-1) is used to replace the 8wt% of the aqueous solution of water-soluble char-forming agent (prepared in Preparation Example 3-1).

[0069] Example 7, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 1 in that, in step S2, 8wt% of an aqueous solution of carboxymethyl cellulose sodium is used to replace the 8wt% of the aqueous solution of water-soluble char-forming agent (prepared in Preparation Example 3-1). Comparative Example

[0070] Comparative Example 1, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 7 in that, in the operation of step S1-1, a 10wt% chitosan solution (pH = 5) is used to replace the mixed solution containing 50wt% of imidazole diethyl phosphate prepared in Preparation Example 1-1 and 2wt% of tetraisopropyl titanate.

[0071] Comparative Example 2, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 7 in that, in the operation of step S1-2, a mixed solution containing 50wt% of imidazole diethyl phosphate prepared in Preparation Example 1-1 and 2wt% of tetraisopropyl titanate is used to replace the 10wt% chitosan solution (pH = 5).

[0072] Comparative Example 3, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 7 in that, in the operation of step S1-1, a mixed solution containing 50wt% of (formylmethyl) diethyl phosphate and 2wt% of tetraisopropyl titanate (solvent: toluene) is used to replace the mixed solution containing 50wt% of imidazole diethyl phosphate prepared in Preparation Example 1-1 and 2wt% of tetraisopropyl titanate.

[0073] Comparative Example 4, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 7 in that, in the operation of step S1-1, a 50wt% aqueous solution of ammonium polyphosphate is used to replace the mixed solution containing 50wt% of imidazole diethyl phosphate prepared in Preparation Example 1-1 and 2wt% of tetraisopropyl titanate.

[0074] Comparative Example 5, a smoke-suppression low-toxicity flame-retardant flooring board, which is different from Example 7 in that, the step S1-4 of immersing in sodium hydroxide solution is not performed, and the operation of step S1-5 is directly performed after step S1-3.

[0075] Comparative Example 6, a smoke-suppression low-toxicity flame-retardant flooring board, which is prepared according to the following method: Complexing flame retardant preparation: the imidazole diethyl phosphate of preparation example 1 was dissolved in deionized water to prepare a 50wt% imidazole diethyl phosphate solution; the chitosan was dissolved in a hydrochloric acid aqueous solution with a pH of 5 to prepare a 10wt% ligand chitosan solution; the metal salt MgCl was dissolved in deionized water to prepare a 20wt% metal salt M solution; and the NaOH was dissolved in deionized water to prepare a 10wt% alkali solution. The imidazole diethyl phosphate solution and the chitosan solution were mixed in a mass ratio of 1:1, stirred at a speed of 500r / min at room temperature for 6min to obtain a ligand solution. Then the ligand solution and the metal salt M solution were blended in a mass ratio of 1:1, stirred at a speed of 300r / min at room temperature for 30min to facilitate the complexing reaction between the ligand and the metal ions. Finally, the alkali solution was slowly added to the mixed solution (the mass ratio of the alkali solution to the metal M solution was 2) to promote the complexing reaction and the precipitation of the complex. The precipitated complex was filtered and washed 3-5 times and dried in a blast drying oven to obtain the final complexing flame retardant.

[0076] The above complexing flame retardant and the water-soluble charring agent were mixed in a mass ratio of 1:1 to obtain a composite flame retardant, which was then uniformly mixed with starch in a mass ratio of 7:3 to obtain a flame-retardant powder. The flame-retardant powder was mixed with urea-formaldehyde adhesive in a mass ratio of 1:2, and then stirred at a speed of 800r / min for 15min to uniformly mix the flame-retardant powder and the urea-formaldehyde adhesive, thereby obtaining a flame-retardant adhesive.

[0077] The flame-retardant adhesive was coated on the upper surface of the finished plywood at a glue application amount of 200g / m 2 , and cured at a temperature of 125℃ for 4min to obtain a surface-layer flame-retardant plywood. Performance test

[0078] Test 1: Limiting oxygen index (LOI) test The test was performed in accordance with the provisions of GB / T 2406.2-2009 “Plastics-Determination of the burning behavior of plastics-Part 2: Guidance on the measurement of flame characteristics-Test flames 500 mm long”. Test specimens with dimensions of 125mm x 13mm x 3mm were cut from the finished panels of each example and the comparative example, with 5 parallel samples in each group. The test specimens were vertically fixed in the combustion cylinder of the oxygen index instrument, with an initial oxygen concentration of 30%, and a nitrogen-oxygen mixed gas was introduced (flow rate of 10L / min). The top end of the test specimen was ignited, and the lowest oxygen concentration required for the combustion length to reach 50mm was recorded (accurate to 0.1%). The test was repeated until a stable LOI value was obtained, and the average value was taken.

[0079] Test 2: Smoke density (specific optical density Ds) test Test according to GB / T 8625-2005 "Methods of testing the flammability of building materials". Cut 75mm x 75mm x 4mm samples, sandpaper the surface to smooth, 3 parallel samples per group. Place the sample on the sample holder of the NBS smoke density chamber, 25mm from the radiation cone. Set the radiation intensity to 50kW / m 2 Start the test in flame mode (with the igniter on), record the change in light transmittance over 10min, calculate the maximum specific optical density, take the average of three tests.

[0080] Test 3: Carbon residue rate and thermal stability (TGA) test Test according to GB / T 27761-2011 "Test method for weight loss and residual amount by thermogravimetric analyzer". Test with a thermogravimetric analyzer (TGA), nitrogen atmosphere, temperature range 50-800℃, rate 10℃ / min. Record the following parameters: T 5% (temperature at 5% weight loss, indicating thermal stability); T max (maximum weight loss rate temperature); Carbon residue rate (percentage of residual mass at 500℃); Take the average of three tests per group.

[0081] Test 4: Flame retardant durability (wet heat aging test) Test according to the wet heat cycle treatment clause of GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". Place the LOI sample in a constant temperature and humidity chamber (70℃, 95% humidity), cycle for 168 hours (7 days), then equilibrate the sample at 23℃ and 50% humidity for 24 hours.

[0082] Compare the change rate of LOI value before and after aging: ΔLOI = (LOI after aging - LOI before aging) / LOI before aging x 100%; The smaller the absolute value of ΔLOI, the better the flame retardant durability.

[0083] Table 1, performance test results

[0084] Test data analysis: Compared with Example 1, the LOI of Example 4 (graphite modified with aminosilane) decreased by 1.5%, and the ΔLOI decreased to -2.6%. The reason may be that the bridging effect and catalytic dehydrogenation of the copper metal site in the copper tetraaminophenyl porphyrin were absent, the carbon layer density decreased, and the oxygen and heat insulation ability was weakened. The LOI of Example 5 (graphite without the addition of copper tetraaminophenyl porphyrin) decreased by 3.2%, and the ΔLOI decreased to -3.4%. The reason may be that the graphite sheet layer expansion effect and copper ion bridging effect and catalytic dehydrogenation were absent, the carbon layer density decreased, and the oxygen and heat insulation ability was weakened.

[0085] Compared with Example 1, the smoke density of Example 6 (vanillic acid-ethanolamine benzoxazine monomer instead of char former) increased by 25%. The reason may be that the monomer did not form a phosphate structure, could not generate phosphorus-containing free radicals to quench free radicals, interrupt the combustion chain reaction, and the smoke suppression mechanism failed.

[0086] Compared with Example 1, the char yield of Example 7 (sodium carboxymethyl cellulose instead of char former) decreased by 12.4%, and the T5% decreased by 56℃. The reason may be that the phosphate salt carbon layer formed by the cross-linked structure of benzoxazine-phosphate was absent, resulting in a significant decrease in thermal stability.

[0087] Compared with Example 7, Comparative Examples 1 and 2 used only a single complexing agent, and the performance of LOI, smoke density, and char yield was further decreased. The reason may be that the phosphoric acid ester bonded to the wood hydroxyl group was absent, and the flame retardant volatilized in the early stage of combustion. Comparative Example 3 used (formylmethyl) diethyl phosphate instead of imidazole diethyl phosphate, and the LOI decreased by 4.0% and the char yield decreased by 5.9%. The reason may be that the absence of imidazole group caused the cross-linking performance of the bidentate metal to decrease, and the flame-retardant layer could not be formed on the wood. Comparative Example 4 (ammonium polyphosphate instead of imidazole diethyl phosphate) had an LOI decrease of 5.7% and a ΔLOI of -17.2%. The reason may be that the phosphoric acid ester bonded to the wood hydroxyl group was absent, and the flame retardant volatilized in the early stage of combustion. Moreover, the cross-linking degree of the ligand-metal network decreased. Comparative Example 5 (without alkali solution immersion) had a ΔLOI of -18.6%. The reason may be that the absence of an alkaline environment caused insufficient metal complexation, and the flame retardant was dissolved after wet heat aging. The performance of Comparative Example 6 was significantly deteriorated, and the flame retardant and char former were concentratedly distributed due to the coating process, resulting in poor flame-retardant durability, high smoke density, and low char yield.

[0088] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing a smoke-suppressing, low-toxicity, flame-retardant flooring material, characterized in that, The following steps are included in the preparation S1. Place the wood in a mixed solution of imidazole diethyl phosphate and Lewis acid catalyst, and perform vacuum impregnation and heated pressure impregnation in sequence. After impregnation, drain the wood. Then, place the wood in chitosan solution, metal salt solution and alkaline solution in sequence for pressure impregnation. After draining and washing, obtain the complex flame retardant modified wood. S2. The wood modified with complexed flame retardant is immersed in a water-soluble char-forming agent solution, impregnated under pressure, drained, washed with water and dried to obtain the final product. The imidazole diethyl phosphate is obtained by condensation reaction of 1-(3-aminopropyl)imidazole and (formylmethyl) phosphate in a mass ratio of 0.5 to 0.7:

1.

2. The preparation method according to claim 1, characterized in that, The preparation method of the imidazole diethyl phosphate is as follows: 1-(3-aminopropyl)imidazole and (formylmethyl) phosphate diethyl phosphate are added to an alcohol-water mixture, heated to 60-80℃, and p-toluenesulfonic acid catalyst is added to carry out a condensation reaction. After the reaction is completed, the mixture is cooled, filtered, and dried to obtain the final product.

3. The preparation method according to claim 1, characterized in that, The metal salt is selected from any one or more of calcium salts, magnesium salts, and aluminum salts.

4. The preparation method according to claim 1, characterized in that, The temperature for the heating and pressurizing impregnation is 100-110℃, and the pressure is 1.1-1.3MPa.

5. The preparation method according to claim 1, characterized in that, The concentrations of diethyl imidazole phosphate and Lewis acid catalyst in the mixed solution are 45-55 wt% and 1-3 wt%, respectively; the concentrations of chitosan solution, metal salt solution, and alkaline solution are 8-15 wt%, 15-25 wt%, and 5-15 wt%, respectively; and the concentration of water-soluble char-forming agent solution is 5-10 wt%.

6. The preparation method according to claim 1, characterized in that, In step S1, after impregnation in an alkaline solution, the wood is placed in a solution of 5-10 wt% tetraaminophenylporphyrin copper modified graphite for pressure impregnation.

7. The preparation method according to claim 6, characterized in that, The tetraaminophenylporphyrin copper-modified graphite was prepared by blending and modifying graphite with tetraaminophenylporphyrin copper in a mass ratio of 100:10 to 20.

8. The preparation method according to claim 1, characterized in that, The raw materials for the water-soluble biocharging agent include vanillic acid-ethanolamine benzoxazine monomer, phenylphosphodichloro and an acid-binding agent in a molar ratio of 1:0.45-0.55:1.1-1.2, wherein the vanillic acid-ethanolamine benzoxazine monomer and phenylphosphodichloro undergo a substitution reaction.

9. The preparation method according to claim 8, characterized in that, The vanillic acid-ethanolamine benzoxazine monomer is prepared by reacting ethanolamine, paraformaldehyde and vanillic acid in a dioxane solvent in a molar ratio of 1:2 to 2.2:

1.

10. A smoke-suppressing, low-toxicity, flame-retardant flooring material, characterized in that, Prepared according to the preparation method according to any one of claims 1 to 9.

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