Smoke-suppression flame-retardant ecological board and preparation method thereof

Abstract

The invention discloses a smoke-suppression flame-retardant ecological board and a preparation method thereof. The ecological board comprises a base material, a flame-retardant adhesive layer and a facing layer which are sequentially stacked, wherein the flame-retardant adhesive layer is prepared from the following raw materials: 100 parts of urea-formaldehyde resin, 10-15 parts of a phosphorus-nitrogen composite flame retardant and 5-10 parts of flame-retardant filler; the preparation method of the phosphorus-nitrogen composite flame retardant comprises the following steps: carrying out an aminomethylation reaction on p-hydroxybenzoic acid, ethanolamine and paraformaldehyde which are used as raw materials in a molar ratio of 1: (1-1.2): (2-2.2) to prepare a Mannich base intermediate; and carrying out substitution reaction on the Mannich base intermediate and phosphonitrilic chloride trimer serving as raw materials according to the molar ratio of (3-7): 1. The phosphorus-nitrogen flame retardant disclosed by the invention is high in content of phosphorus and nitrogen elements and uniform in distribution ratio, and has more excellent synergistic smoke suppression and flame retardant effects compared with an existing physical compound system.

Description

Technical Field

[0001] This application relates to the field of flame-retardant building materials, and in particular to a smoke-suppressing and flame-retardant ecological board and its preparation method. Background Technology

[0002] Ecological boards, a commonly used material for interior decoration and furniture manufacturing, have always been a fire safety hazard due to their flammability and the large amount of smoke they produce during combustion. The industry generally uses a physical compound system of phosphorus-based and nitrogen-based flame retardants to improve their flame-retardant performance. In this system, phosphorus-based flame retardants mainly function in the solidified phase, decomposing through thermal decomposition to generate highly dehydrating substances such as phosphoric acid and polymetaphosphoric acid, catalyzing the dehydration of polymer components such as cellulose into char, forming a char layer with certain heat insulation and oxygen barrier properties. This slows down the combustion process and reduces the volatilization of combustibles, achieving smoke suppression and flame retardancy to a certain extent. Nitrogen-based flame retardants, on the other hand, mainly function in the gas phase, decomposing upon heating to release non-flammable gases such as ammonia and nitrogen, diluting the concentration of combustible gases and oxygen, while simultaneously promoting the expansion of the char layer, enhancing its heat insulation effect.

[0003] However, this phosphorus-nitrogen composite flame retardant system based on physical mixing has significant limitations. First, the uniform dispersion of the two flame retardants in the matrix is ​​difficult to guarantee, easily leading to local agglomeration or uneven distribution. This results in an imbalance in the phosphorus-nitrogen ratio in some areas during combustion, preventing the timely and efficient formation of a complete expanded char layer and weakening the synergistic flame retardant effect. Second, the single phosphorus or nitrogen flame retardants used in existing technologies generally have low effective phosphorus or nitrogen atom content in their molecules. To meet the specified flame retardant standards, large amounts often need to be added, which inevitably deteriorates the physical and mechanical properties and processing performance of the eco-board, and may lead to problems such as precipitation and migration. More importantly, these traditional flame retardants may not achieve the expected smoke suppression effect during combustion due to insufficient synergy, resulting in relatively dense smoke. Summary of the Invention

[0004] This application provides a smoke-suppressing and flame-retardant ecological board and its preparation method. The phosphorus and nitrogen elements used in the board are high in content and uniformly distributed, which has a better synergistic smoke-suppressing and flame-retardant effect than the existing physical compound system.

[0005] In a first aspect, this application provides a smoke-suppressing and flame-retardant ecological board, comprising a substrate, a flame-retardant adhesive layer, and a decorative layer stacked sequentially. The raw materials of the flame-retardant adhesive layer include: 100 parts of urea-formaldehyde resin, 10-15 parts of phosphorus-nitrogen composite flame retardant, and 5-10 parts of flame-retardant filler. The phosphorus-nitrogen composite flame retardant is first prepared by amine methylation reaction of p-hydroxybenzoic acid, ethanolamine, and paraformaldehyde in a molar ratio of 1:1-1.2:2-2.2 to obtain a Mannich base intermediate; then, it is prepared by substitution reaction of the Mannich base intermediate in a molar ratio of 3-7:1 with hexachlorocyclotriphosphazene.

[0006] In any of the above technical solutions, the preparation method of the phosphorus-nitrogen composite flame retardant is as follows: Ethanolamine and paraformaldehyde were mixed and dissolved in dioxane, and then p-hydroxybenzoic acid was added dropwise to the system to carry out an aminomethylation reaction. After the reaction was completed, the solvent was removed by vacuum distillation, and the residue was recrystallized from ethanol to obtain the Mannich base intermediate. Mannich base intermediate and acid-binding agent are dissolved in dry solvent, and hexachlorocyclotriphosphazene is added dropwise at low temperature and reacted for 0.5-1 h. Then the reaction is carried out at room temperature for 20-30 h. After the reaction is completed, the solvent is removed by vacuum distillation, the residue is dissolved in dioxane, and the resulting solution is added to ethyl acetate to precipitate solid product. After filtration and drying, phosphorus-nitrogen composite flame retardant is obtained.

[0007] The reaction process of the above aminomethylation reaction is shown below:

[0008] Theoretically, when the molar ratio of the Mannich base intermediate to hexachlorocyclotriphosphazene is 3:1, the reaction process of the above amine substitution reaction is as follows:

[0009] In any of the above technical solutions, the solvent is N,N-dimethylformamide or tetrahydrofuran.

[0010] In any of the above technical solutions, the acid-binding agent is triethylamine.

[0011] In any of the above technical solutions, the reaction temperature of the aminomethylation reaction is 70-90℃; the low temperature is 0±2℃.

[0012] The phosphorus-nitrogen composite flame retardant synthesized in this application uses a highly symmetrical rigid phosphazene ring core with hexachlorocyclotriphosphazene as its core. Through nucleophilic substitution reactions between its six active chlorine atoms and Mannich base intermediates in a specific molar ratio, a three-dimensional molecular structure is generated. This structure achieves a high-density, uniform distribution of phosphorus and nitrogen elements at the molecular level. Its P / N atomic ratio can be precisely controlled by the molar ratio of the feed, thus exhibiting optimal intramolecular synergistic flame retardant effect during thermal degradation. In the initial stage of combustion, the nitrogen element rapidly decomposes, releasing non-combustible gases, diluting the concentration of oxygen and combustible gases in the gas phase, and promoting the expansion of the char layer. Simultaneously, phosphorus-containing groups such as the phosphazene ring efficiently catalyze the dehydration of the polymer matrix into char in the condensed phase, and synergistically with the foaming effect of the nitrogen source, promoting the formation of a dense, robust, and porous expanded char layer. This char layer not only effectively isolates heat and oxygen transfer, slowing down the combustion process, but also significantly adsorbs and fixes smoke particles generated during pyrolysis, thereby inhibiting smoke generation at the source and exhibiting a superior synergistic smoke suppression and flame retardant effect compared to physical compound systems. Furthermore, the flame retardant molecule incorporates multiple carboxyl functional groups derived from p-hydroxybenzoic acid. These carboxyl groups can chemically react with the amino or hydroxymethyl groups on the urea-formaldehyde resin molecular chain to form chemical bonds, thereby firmly binding the flame retardant molecule to the cross-linked network of the urea-formaldehyde resin. This chemical bonding fundamentally solves the problem of easy migration and precipitation of additive flame retardants, ensuring not only the long-term durability of the smoke-suppressing and flame-retardant properties of the eco-board but also greatly reducing the risk of corrosion to metal components in furniture or building structures caused by flame retardant precipitation.

[0013] In any of the above technical solutions, the urea-formaldehyde resin is a boron-modified urea-formaldehyde resin, which is obtained by reacting urea, formaldehyde, and boron-containing aminosilane in a molar ratio of 1:1 to 1.4:0.3 to 0.5.

[0014] In any of the above technical solutions, the boron-containing aminosilane is prepared by de-alcoholization condensation under the catalysis of an aminosilane coupling agent and a borate ester with a molar ratio of 1 to 1.2:1.

[0015] In any of the above technical solutions, the reaction time of the aminomethylation reaction is 3 to 5 hours.

[0016] In any of the above technical solutions, the aminosilane coupling agent is selected from any one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, and γ-aminopropylmethyldimethoxysilane.

[0017] In any of the above technical solutions, the borate ester is selected from any one or more of trimethyl borate, triethyl borate, n-propyl borate, isopropyl borate, and butyl borate.

[0018] In any of the above technical solutions, the method for preparing the boron-modified urea-formaldehyde resin is as follows: Formaldehyde is added to water and mixed to prepare a formaldehyde aqueous solution. The temperature is raised to 40-50°C, the pH is adjusted to 8.0-9.0, 50%-70% of the total urea is added, and the mixture is stirred to dissolve. The temperature is then raised to 80-90°C and the reaction is maintained. The pH is adjusted to 4-5, 20%-30% of the total urea and boron-containing aminosilane are added, and the reaction is maintained at 80-90°C. The remaining urea is added, the temperature is lowered to below 60°C, and the pH is adjusted to 7.0-8.0. The mixture is then cooled and discharged to obtain the final product.

[0019] In any of the above technical solutions, the heat preservation reaction time after the first addition of urea is 0.5 to 1.5 hours.

[0020] In any of the above technical solutions, the heat preservation reaction after the first addition of urea is stopped when the turbidity point of the sample reaches 20-30℃ (measured at 25±1℃).

[0021] The boron-modified urea-formaldehyde resin used in this application incorporates boron and organosilicon segments into the resin's molecular backbone through a co-condensation reaction involving boron-containing aminosilanes during resin synthesis. The introduction of boron provides excellent smoke suppression and flame retardancy. Specifically, boron compounds, as excellent flame retardants and char-forming promoters, generate a glassy borate protective layer covering the substrate surface during combustion, enhancing overall flame retardancy and smoke suppression performance, and exhibiting a positive synergistic effect with the phosphorus-nitrogen composite flame retardant. More importantly, the introduction of flexible organosilicon segments effectively compensates for the increased brittleness that may result from the extensive cross-linking of carboxyl groups in the phosphorus-nitrogen composite flame retardant with the resin. The silicon-oxygen bond (Si-O) has low bond energy and good rotational freedom; its introduction is like adding flexible segments to a rigid resin network, helping to disperse stress, improve the flexibility and toughness of the adhesive layer, thereby ensuring the internal bonding strength of the ecological board and balancing the flame retardant and mechanical properties of the board.

[0022] It should be noted that the boron-containing aminosilane in this application is not added all at once with all the urea, but rather during the second addition of urea. This process has a significant impact on the mechanical properties of the resin. If the boron-containing aminosilane is added during the first addition of urea, i.e., during the stage of forming hydroxymethylurea under alkaline conditions, it will participate in the reaction prematurely, competing for formaldehyde and interfering with the full formation of hydroxymethylurea, thus leading to a decrease in the molecular weight and insufficient cross-linking of the final resin, and deterioration of the resin's mechanical properties. Conversely, if it is added during the third addition of urea (i.e., in the later stage of the reaction), by which time the resin has already formed a certain prepolymer network, the viscosity increases, and the boron-containing aminosilane is difficult to disperse uniformly in the system, failing to effectively embed itself into the resin network structure through chemical bonding. Its excellent toughening effect and flame-retardant synergistic effect cannot be fully realized. Therefore, introducing it during the second addition, precisely at the stage when the resin chains begin to condense but before the network is formed, ensures that the boron-containing aminosilane can be uniformly distributed and fully participate in the reaction, introducing boron and silicon segments into a uniform and dense resin cross-linking network.

[0023] The boron-containing aminosilane in this application needs to be added together with the second addition of urea. After the first addition of urea and the formation of hydroxymethylurea, it participates in the polycondensation reaction to generate a network structure. If added in the first addition, it will affect the formation of hydroxymethylurea in the resin and reduce its mechanical properties; if added in the third addition of urea, it will be difficult to distribute evenly in the resin network and will not achieve a good toughening effect.

[0024] In any of the above technical solutions, the flame-retardant filler is selected from any one or more of magnesium hydroxide, aluminum hydroxide, antimony trioxide, molybdenum oxide, ammonium molybdate, zinc borate, expandable graphite, zinc hydroxystannate, and zirconium phosphate.

[0025] In any of the above technical solutions, the D50 particle size of the flame retardant filler is 1 to 10 µm.

[0026] Secondly, this application provides a method for preparing a smoke-suppressing and flame-retardant ecological board, characterized in that it includes: According to any of the above-mentioned composition ratios for smoke-suppressing and flame-retardant ecological boards, the phosphorus-nitrogen composite flame retardant is mixed with urea-formaldehyde resin adhesive and stirred until homogeneous to obtain a flame-retardant adhesive. The flame-retardant adhesive is applied to the surface of the finished plywood, then the finishing material is attached, and the plywood is hot-pressed in a press at a temperature of 115-135℃ and a pressure of 0.6-1MPa for 2-5 minutes to obtain the final product.

[0027] In any of the above technical solutions, the substrate is prepared by uniformly applying a resin adhesive to the veneer to form a resin layer, stacking the adhesive-coated veneers into a blank, and then subjecting it to cold pressing and hot pressing in sequence. The cold pressing temperature is 20-30℃, the pressure is 0.6-1.0MPa, and the time is 1-2h. The hot pressing temperature is 100-120℃, the pressure is 0.8-1.2MPa, and the time is 5-15min.

[0028] In any of the above technical solutions, the number of single boards of the substrate can be stacked and composited according to actual needs, preferably 3-7 single boards.

[0029] In any of the above technical solutions, the veneer is eucalyptus veneer or birch veneer.

[0030] In any of the above technical solutions, the finishing material is selected from high-temperature decorative film, engineered wood, or calcium silicate board.

[0031] In summary, this application has the following beneficial effects: This application employs a reactive phosphorus-nitrogen composite flame retardant, which is effectively anchored in a boron-silicon synergistically modified urea-formaldehyde resin network through chemical bonding, resulting in a novel eco-board with multiple flame-retardant and smoke-suppressing effects while maintaining good mechanical properties. This board not only overcomes the inherent defects of traditional physically compounded flame retardants, such as uneven dispersion, weak synergistic effect, large addition amount, and easy migration and precipitation, but also achieves an organic combination of condensed phase and gas-phase flame-retardant mechanisms through the synergistic effect of multiple elements including boron, phosphorus, nitrogen, and silicon. Ultimately, the resulting eco-board exhibits excellent and durable smoke-suppressing and flame-retardant performance, significantly improved internal bonding strength, and lower risk of metal corrosion. Detailed Implementation Preparation Example

[0032] Preparation Example 1-1: A phosphorus-nitrogen composite flame retardant was prepared by the following steps: 74.1 g (1.2 mol) of ethanolamine was dissolved in 200 mL of 1,4-dioxane, and 72.1 g (2.2 mol, based on formaldehyde) of paraformaldehyde was added. The mixture was heated to 80 °C with stirring to dissolve the formaldehyde. Then, 500 mL of a suspension of 1,4-dioxane containing 138.1 g (1.0 mol) of p-hydroxybenzoic acid was slowly added dropwise to the system. After the addition was complete, the mixture was kept at 80 °C for 4 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and the solvent 1,4-dioxane was removed by vacuum distillation. The resulting viscous residue was added to 400 mL of anhydrous ethanol, heated to dissolve, recrystallized, filtered, and dried under vacuum to obtain the Mannich base intermediate.

[0033] 2.5 mol of the Mannich base intermediate prepared according to the above method and 381.6 mL (2.75 mol) of triethylamine were dissolved in 1000 mL of N,N-dimethylformamide (DMF) dried through a 4A molecular sieve. The solution was placed in a three-necked flask equipped with a mechanical stirrer, thermometer, and constant-pressure dropping funnel. Under nitrogen protection, the system was cooled to 0°C in an ice-water bath. Then, 500 mL of dry DMF solution containing 173.8 g (0.5 mol) of hexachlorocyclotriphosphazene was slowly added dropwise, controlling the dropping rate to maintain the reaction temperature at 0 ± 2°C. The addition was completed in about 1 hour. After the addition was complete, the reaction was continued at this low temperature for another hour. Then, the ice bath was removed, and the reaction system was allowed to warm naturally to room temperature (25 ± 2°C), and the reaction was continued with stirring for 24 hours. After the reaction was completed, most of the DMF was removed by vacuum distillation, and the resulting viscous substance was dissolved in 500 mL of 1,4-dioxane. Under vigorous stirring, this solution was slowly poured into 4000 mL of ethyl acetate, resulting in the precipitation of a large amount of solid. The solid was filtered, washed three times with a small amount of ethyl acetate, and then dried under vacuum at 60°C for 24 hours to obtain a phosphorus-nitrogen composite flame retardant.

[0034] Preparation Examples 1-2: A phosphorus-nitrogen composite flame retardant was prepared by the following steps: 61.8 g (1.0 mol) of ethanolamine was dissolved in 180 mL of 1,4-dioxane, and 65.5 g (2.0 mol, based on formaldehyde) of paraformaldehyde was added. The mixture was heated to 70 °C with stirring to dissolve the formaldehyde. Then, 500 mL of a suspension of 1,4-dioxane containing 138.1 g (1.0 mol) of p-hydroxybenzoic acid was slowly added dropwise to the system. After the addition was complete, the mixture was kept at 70 °C for 5 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and the solvent 1,4-dioxane was removed by vacuum distillation. The resulting viscous residue was added to 350 mL of anhydrous ethanol, heated to dissolve, recrystallized, filtered, and dried under vacuum to obtain the Mannich base intermediate.

[0035] 1.5 mol of the Mannich base intermediate prepared according to the above method and 222.4 mL (1.6 mol) of triethylamine were dissolved in 800 mL of tetrahydrofuran (THF) dried through a 4A molecular sieve and placed in a three-necked flask equipped with a mechanical stirrer, thermometer, and constant-pressure dropping funnel. Under nitrogen protection, the system was cooled to 0°C in an ice-water bath. Then, 400 mL of dry THF solution containing 173.8 g (0.5 mol) of hexachlorocyclotriphosphazene was slowly added dropwise, controlling the dropping rate to maintain the reaction temperature at 0 ± 2°C, and the addition was completed in about 1.5 hours. After the addition was complete, the reaction was continued at this low temperature for another 0.5 hours. Then, the ice bath was removed, and the reaction system was allowed to warm naturally to room temperature (25 ± 2°C), and the reaction was continued with stirring for 26 hours. After the reaction was completed, most of the THF was removed by vacuum distillation, and the resulting viscous substance was dissolved in 500 mL of 1,4-dioxane. Under vigorous stirring, the solution was slowly poured into 3500 mL of ethyl acetate, resulting in the precipitation of a large amount of solid. The solid was filtered, washed three times with a small amount of ethyl acetate, and then dried under vacuum at 60°C for 24 hours to obtain a phosphorus-nitrogen composite flame retardant.

[0036] Preparation Examples 1-3: A phosphorus-nitrogen composite flame retardant was prepared by the following steps: 86.5 g (1.4 mol) of ethanolamine was dissolved in 220 mL of 1,4-dioxane, and 78.8 g (2.4 mol, based on formaldehyde) of paraformaldehyde was added. The mixture was heated to 90 °C with stirring to dissolve the formaldehyde. Then, 500 mL of a suspension of 1,4-dioxane containing 138.1 g (1.0 mol) of p-hydroxybenzoic acid was slowly added dropwise to the system. After the addition was complete, the mixture was kept at 90 °C for 3 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and the solvent 1,4-dioxane was removed by vacuum distillation. The resulting viscous residue was added to 500 mL of anhydrous ethanol, heated to dissolve, recrystallized, filtered, and dried under vacuum to obtain the Mannich base intermediate.

[0037] 3.5 mol of the Mannich base intermediate prepared according to the above method and 528.8 mL (3.8 mol) of triethylamine were dissolved in 1200 mL of N,N-dimethylformamide (DMF) dried through a 4A molecular sieve. The solution was placed in a three-necked flask equipped with a mechanical stirrer, a thermometer, and a constant-pressure dropping funnel. Under nitrogen protection, the system was cooled to 0°C in an ice-water bath. Then, 600 mL of dry DMF solution containing 173.8 g (0.5 mol) of hexachlorocyclotriphosphazene was slowly added dropwise, controlling the dropping rate to maintain the reaction temperature at 0 ± 2°C. The addition was completed in about 1 hour. After the addition was complete, the reaction was continued at this low temperature for another hour. Then, the ice bath was removed, and the reaction system was allowed to warm naturally to room temperature (25 ± 2°C), and the reaction was continued with stirring for 20 hours. After the reaction was completed, most of the DMF was removed by vacuum distillation, and the resulting viscous substance was dissolved in 500 mL of 1,4-dioxane. Under vigorous stirring, this solution was slowly poured into 5000 mL of ethyl acetate, resulting in the precipitation of a large amount of solid. The solid was filtered, washed three times with a small amount of ethyl acetate, and then dried under vacuum at 60°C for 24 hours to obtain a phosphorus-nitrogen composite flame retardant.

[0038] Preparation Examples 1-4, a phosphorus-nitrogen composite flame retardant, differ from Preparation Example 1-1 in that equimolar amounts of phenylphosphine dichloride are used instead of hexachlorocyclotriphosphazene.

[0039] Preparation Example 2-1: A boron-modified urea-formaldehyde resin was prepared by the following method: Step 1: Add 221.4 g (1.0 mol) of γ-aminopropyltriethoxysilane and 104.0 g (1.1 mol) of trimethyl borate to a 500 mL three-necked flask equipped with a stirrer, a fractionating column, and a condenser. Under nitrogen protection, add 2.2 g of tetraisopropyl titanate as a catalyst. Slowly raise the temperature to 120 °C and react at this temperature. Distill off the methanol produced in the reaction through the fractionating column until the distillation temperature rises above 64 °C and no more fraction flows out, yielding boron-containing aminosilane.

[0040] Step 2: Add 1200g of deionized water and 973.4g (12.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 8.5 with 10% sodium hydroxide solution, raise the temperature to 45℃, add 360.4g (6.0mol) of urea (60% of the total amount), stir to dissolve, and then raise the temperature to 85℃ and maintain the reaction at this temperature for 1 hour. Then adjust the pH of the reaction solution to 4.5 with 20% formic acid solution, add 180.2g (3.0mol) of urea (30% of the total amount) and 4.0mol of boron-containing aminosilane, and continue the reaction at 85℃, periodically sampling and measuring the turbidity point until the required level is reached. Finally, add the remaining 60.1g (1.0mol) of urea (10% of the total amount), and maintain the reaction at 65℃ for 20 minutes. The mixture was allowed to cool naturally to below 60°C, and the pH was adjusted to 7.5 using a 10% sodium hydroxide solution. The temperature was then further reduced to below 40°C, and the material was discharged to obtain boron-modified urea-formaldehyde resin.

[0041] Preparation Example 2-2: A boron-modified urea-formaldehyde resin was prepared by the following method: Step 1: Add 179.3 g (1.0 mol) of γ-aminopropyltrimethoxysilane and 146.0 g (1.0 mol) of triethyl borate to a 500 mL three-necked flask equipped with a stirrer, a fractionating column, and a condenser. Under nitrogen protection, add 2.2 g of tetrabutyl titanate as a catalyst. Slowly raise the temperature to 130 °C and react at this temperature. Distill off the ethanol produced in the reaction through the fractionating column until the distillation temperature rises above 78 °C and no more fraction flows out, yielding boron-containing aminosilane.

[0042] Step 2: Add 1100g of deionized water and 892.3g (11.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 8.0 with 10% sodium hydroxide solution, raise the temperature to 40℃, add 300.3g (5.0mol) of urea (50% of the total amount), stir to dissolve, raise the temperature to 80℃, and maintain the reaction at this temperature for 1.5 hours. Then adjust the pH of the reaction solution to 5.0 with 20% formic acid solution, add 180.2g (3.0mol) of urea (30% of the total amount) and 3.0mol of boron-containing aminosilane, and continue the reaction at 80℃, periodically sampling and measuring the turbidity point until the required level is reached. Finally, add the remaining 120.1g (2.0mol) of urea (20% of the total amount), and maintain the reaction at 65℃ for 15 minutes. The mixture was allowed to cool naturally to below 60°C, and the pH was adjusted to 8.0 using a 10% sodium hydroxide solution. The temperature was then further reduced to below 40°C, and the material was discharged to obtain boron-modified urea-formaldehyde resin.

[0043] Preparation Examples 2-3: A boron-modified urea-formaldehyde resin was prepared by the following method: Step 1: Add 265.5 g (1.2 mol) of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 146.0 g (1.0 mol) of triethyl borate to a 500 mL three-necked flask equipped with a stirrer, a fractionating column, and a condenser. Under nitrogen protection, add 2.6 g of tetraisopropyl titanate as a catalyst. Slowly raise the temperature to 125 °C and react at this temperature. Distill off the ethanol produced in the reaction through the fractionating column until no more distillate flows out, yielding boron-containing aminosilane.

[0044] Step 2: Add 1300g of deionized water and 1135.6g (14.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 9.0 with 10% sodium hydroxide solution, raise the temperature to 50°C, add 420.4g (7.0mol) of urea (70% of the total amount), stir to dissolve, and then raise the temperature to 90°C and maintain the reaction at this temperature for 0.5 hours. Then adjust the pH of the reaction solution to 4.0 with 20% formic acid solution, add 120.1g (2.0mol) of urea (30% of the total amount) and 5.0mol of boron-containing aminosilane, and continue the reaction at 90°C, periodically sampling and measuring the turbidity point until the required level is reached. Finally, add the remaining 60.1g (1.0mol) of urea (10% of the total amount), and maintain the reaction at 65°C for 30 minutes. The mixture was allowed to cool naturally to below 55°C, and the pH was adjusted to 7.0 using a 10% sodium hydroxide solution. The temperature was then further reduced to below 40°C, and the material was discharged to obtain boron-modified urea-formaldehyde resin.

[0045] Preparation Example 2-4, a boron-modified urea-formaldehyde resin, differs from Preparation Example 2-1 in that, in step 2, a boron-containing aminosilane is added during the first addition of urea, as detailed below: Add 1200g of deionized water and 973.4g (12.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 8.5 with 10% sodium hydroxide solution, raise the temperature to 45℃, add 360.4g (6.0mol) of urea (60% of the total) and 4.0mol of boron-containing aminosilane, stir to dissolve, and then raise the temperature to 85℃ and maintain the reaction at this temperature for 1 hour. Then adjust the pH of the reaction solution to 4.5 with 20% formic acid solution, add 180.2g (3.0mol) of urea (30% of the total), and continue the reaction at 85℃, periodically sampling and measuring the turbidity point until the required level is reached. Finally, add the remaining 60.1g (1.0mol) of urea (10% of the total), and maintain the reaction at 65℃ for 20 minutes. The mixture was allowed to cool naturally to below 60°C, and the pH was adjusted to 7.5 using a 10% sodium hydroxide solution. The temperature was then further reduced to below 40°C, and the material was discharged to obtain boron-modified urea-formaldehyde resin.

[0046] Preparation Example 2-5, a boron-modified urea-formaldehyde resin, differs from Preparation Example 2-1 in that, in step 2, a boron-containing aminosilane is added during the third addition of urea, as detailed below: Add 1200g of deionized water and 973.4g (12.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 8.5 with 10% sodium hydroxide solution, raise the temperature to 45℃, add 360.4g (6.0mol) of urea (60% of the total amount), stir to dissolve, raise the temperature to 85℃, and maintain the reaction at this temperature for 1 hour. Then adjust the pH of the reaction solution to 4.5 with 20% formic acid solution, add 180.2g (3.0mol) of urea (30% of the total amount), and continue the reaction at 85℃, periodically sampling and measuring the turbidity point until the required level is reached. Finally, add the remaining 60.1g (1.0mol) of urea (10% of the total amount) and 4.0mol of boron-containing aminosilane, and maintain the reaction at 65℃ for 30 minutes. The mixture was allowed to cool naturally to below 60°C, and the pH was adjusted to 7.5 using a 10% sodium hydroxide solution. The temperature was then further reduced to below 40°C, and the material was discharged to obtain boron-modified urea-formaldehyde resin.

[0047] Preparation Example 2-6, a boron-modified urea-formaldehyde resin, differs from Preparation Example 2-1 in that, in step 2, boron-containing aminosilane is replaced with an equimolar mass of urea, as detailed below: Add 1200g of deionized water and 973.4g (12.0mol, based on formaldehyde) of 37% formaldehyde aqueous solution to a 2000mL three-necked flask equipped with a reflux condenser, stirrer, and thermometer, and stir until homogeneous. Adjust the pH to 8.5 with 10% sodium hydroxide solution, raise the temperature to 45℃, add 360.4g (6.0mol) of urea (60% of the total amount), stir to dissolve, and raise the temperature to 85℃. Maintain the reaction at this temperature for 1 hour. Then adjust the pH of the reaction solution to 4.5 with 20% formic acid solution, add 420.5g (7.0mol) of urea, and continue the reaction at 85℃, periodically sampling and measuring the turbidity point until the desired result is achieved. Finally, add the remaining 60.1g (1.0mol) of urea (10% of the total amount), and maintain the reaction at 65℃ for 30 minutes. Allow the mixture to cool naturally to below 60℃, and adjust the pH to 7.5 with 10% sodium hydroxide solution. Continue cooling to below 40℃, then discharge the material to obtain boron-modified urea-formaldehyde resin. Example

[0048] Example 1: A smoke-suppressing and flame-retardant ecological board, the preparation steps are as follows: The boron-modified urea-formaldehyde resin used in Preparation Example 2-1 was used to uniformly apply glue to eucalyptus veneer (2.6 mm thick), with a glue application rate of 200 g / m² on both sides. 2 (Based on dry glue) After gluing, the grain direction of the veneer wood is crisscrossed. Three veneers are combined into one board. After cold pressing (pressure 0.9MPa, time 80min) and hot pressing (temperature 120℃, pressure 1.0MPa, time 10min), the substrate is obtained.

[0049] Take 130g of the phosphorus-nitrogen composite flame retardant of Preparation Example 1-1, 70g of aluminum hydroxide and 1000g of the boron-modified urea-formaldehyde resin of Preparation Example 2-1 and mix them. Then use a high-speed mixer to stir at 800r / min for 10 minutes to obtain a flame retardant adhesive.

[0050] Flame retardant adhesive at 180g / m 2 The appropriate amount of adhesive is applied to the surface of the substrate, and then a 1.0mm thick layer of engineered wood (poplar) is attached. After that, it is hot-pressed in a press at 130℃ and 0.9MPa for 3 minutes to obtain a smoke-suppressing and flame-retardant ecological board.

[0051] Example 2, a smoke-suppressing and flame-retardant ecological board, the preparation steps are as follows: The boron-modified urea-formaldehyde resin used in Preparation Example 2-2 was used to uniformly apply glue to eucalyptus veneer (2.6 mm thick), with a glue application rate of 200 g / m² on both sides. 2 After gluing, the grain direction of the veneer wood is crisscrossed. Three veneers are combined to form a board. After cold pressing (pressure 1.0MPa, time 70min) and hot pressing (temperature 120℃, pressure 1.0MPa, time 15min), the substrate is obtained.

[0052] Take 100g of phosphorus-nitrogen composite flame retardant from Preparation Example 1-2, 50g of magnesium hydroxide, 50g of ammonium molybdate, and 1000g of boron-modified urea-formaldehyde resin from Preparation Example 2-2 and mix them. Then, use a high-speed mixer to stir at 900r / min for 10 minutes until the mixture is uniform to obtain a flame-retardant adhesive.

[0053] Flame retardant adhesive at 180g / m 2 The appropriate amount of adhesive is applied to the surface of the substrate, and then a 1.0mm thick layer of engineered wood (poplar) is attached. After that, it is hot-pressed in a press at 130℃ and 0.9MPa for 3 minutes to obtain a smoke-suppressing and flame-retardant ecological board.

[0054] Example 3, a smoke-suppressing and flame-retardant ecological board, the preparation steps are as follows: The boron-modified urea-formaldehyde resin used in Preparation Examples 2-3 was used to uniformly apply glue to eucalyptus veneer (2.6 mm thick), with a glue application rate of 200 g / m² on both sides. 2 After gluing, the grain direction of the veneer wood is crisscrossed. Three veneers are combined to form a board. After cold pressing (pressure 1.0MPa, time 90min) and hot pressing (temperature 110℃, pressure 1.0MPa, time 15min), the substrate is obtained.

[0055] Take 150g of phosphorus-nitrogen composite flame retardant from Preparation Examples 1-3, 50g of aluminum hydroxide, and 1000g of boron-modified urea-formaldehyde resin from Preparation Examples 2-3 and mix them. Then, use a high-speed mixer to stir at 600r / min for 15 minutes to obtain a flame-retardant adhesive.

[0056] Flame retardant adhesive at 180g / m 2 The appropriate amount of adhesive is applied to the surface of the substrate, and then a 1.0mm thick layer of engineered wood (poplar) is attached. After that, it is hot-pressed in a press at 120℃ and 1.0MPa for 5 minutes to obtain a smoke-suppressing and flame-retardant ecological board.

[0057] Example 4, a smoke-suppressing and flame-retardant ecological board, differs from Example 1 in that the boron-modified urea-formaldehyde resin of Example 2-1 is replaced with an equal amount of boron-modified urea-formaldehyde resin prepared in Example 2-4.

[0058] Example 5, a smoke-suppressing and flame-retardant ecological board, differs from Example 1 in that the boron-modified urea-formaldehyde resin used in Preparation Examples 2-5 is replaced with an equal amount of boron-modified urea-formaldehyde resin used in Preparation Example 2-1.

[0059] Example 6, a smoke-suppressing and flame-retardant ecological board, differs from Example 1 in that the boron-modified urea-formaldehyde resin of Example 2-1 is replaced with an equal amount of boron-modified urea-formaldehyde resin prepared in Example 2-6. Comparative Example

[0060] Comparative Example 1, a smoke-suppressing and flame-retardant ecological board, differs from Example 1 in that an equal amount of the phosphorus-nitrogen composite flame retardant of Preparation Examples 1-4 is used to replace the phosphorus-nitrogen composite flame retardant of Preparation Example 1-1.

[0061] Comparative Example 2, a smoke-suppressing and flame-retardant ecological board, differs from Example 1 in that an equal amount of a composition of ammonium polyphosphate and guanidine carbonate (mass ratio 1:1) replaces the phosphorus-nitrogen composite flame retardant of Preparation Example 1-1.

[0062] Comparative Example 3: An ecological board was prepared according to the following method: Melamine-modified urea-formaldehyde resin (MUF-230, 50% solids content) was applied evenly to the surface of eucalyptus veneer (2.6mm thick), with an application rate of 200g / m² on both sides. 2 After gluing, the grain direction of the veneer wood is crisscrossed. Three veneers are combined to form a board blank. After cold pressing (pressure 1.0MPa, time 90min) and hot pressing (temperature 110℃, pressure 1.0MPa, time 15min), the substrate is obtained. Melamine-modified urea-formaldehyde resin (MUF-230, solid content 50%) was used at 180 g / m³. 2 The appropriate amount of adhesive is applied to the surface of the substrate, and then a 1.0mm thick layer of engineered wood (poplar) is applied. After that, it is hot-pressed in a press at 120℃ and 1.0MPa for 5 minutes to obtain a regular ecological board. Performance testing

[0063] Test 1: Flame Retardant Performance (LOI) Test The test was conducted according to GB / T 2406.2-2009, "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". Samples measuring 100mm × 10mm were cut from the ecological boards used in the examples and comparative examples. The samples were vertically fixed in the combustion chamber of the oxygen indexer, and a nitrogen-oxygen mixture (flow rate 10 L / min) was introduced. The top of the sample was ignited, and the minimum oxygen concentration (accurate to 0.1%) required for a combustion damage length of 50mm was recorded. The test was repeated until a stable LOI value was obtained, which was recorded as the initial LOI. Five parallel samples were tested in each group, and the average value was taken.

[0064] Experiment 2: Smoke Suppression Performance Test Experiment 2: Smoke density (specific optical density Ds) test The tests were conducted according to the specifications in GB / T 8625-2005, "Test Methods for Flame Retardancy of Building Materials". 75mm × 75mm specimens were cut from the smoke-suppressing and flame-retardant ecological boards used in the examples and comparative examples. The surfaces were sanded smooth, with three parallel samples per group. The specimens were placed on the sample rack of the NBS smoke density chamber, 25mm from the radiation cone. The radiation intensity was set to 50kW / m². 2The test was started in flameless mode (igniter off), and the change in transmittance was recorded within 10 minutes. The maximum specific light density was calculated, and the average value of three tests was taken.

[0065] Experiment 3: Internal Bond Strength Test The test was conducted according to the provisions of "4.11 Determination of Internal Bond Strength" in GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". 50 mm × 50 mm specimens were cut from the ecological boards of each embodiment and comparative example, with no fewer than 5 specimens per group. The specimens were conditioned to constant mass at (20±2)℃ and (65±5)% relative humidity. A water-resistant adhesive (such as epoxy resin) was uniformly coated on the upper and lower surfaces of the specimens. The specimens were then adhered to a special clamp and pressed firmly to ensure a strong bond. The prepared specimens were mounted on a universal testing machine, and a tensile force perpendicular to the board surface was applied at a constant loading rate (0.5 mm / min) until the specimen failed. The maximum failure load was recorded, and the actual bonded area was measured. The internal bond strength was calculated using the formula σ=P / (a×b), where σ is the internal bond strength (MPa), P is the maximum failure load (N), and a and b are the length and width of the specimen (mm). The average value of each group of samples was taken as the test result.

[0066] Experiment 4: Metal Corrosion Rate Test Experimental steps: (1) Specimen preparation Samples measuring 80×40mm and metal sheets measuring 50×25×1.5mm were cut from the smoke-suppressing and flame-retardant ecological boards of the various embodiments and comparative examples. The metal sheets were made of carbon steel (Q235). The metal sheets were cleaned of grease with a mixture of ethanol and acetone (volume ratio 1:1) and wiped clean with paper towels. The metal sheets were then dried at 40℃ for 1 hour, weighed, and recorded as m1. They were then placed in a desiccator for later use.

[0067] (2) Corrosion test Plywood was kept in a constant temperature and humidity chamber (50℃, 90% humidity) for 3 days. A metal sheet was placed between two pieces of plywood and fixed with screws to prepare a rust sample. The samples were then treated in a constant temperature and humidity chamber (50℃, 90% humidity), with one group exposed for 360 hours and the other for 720 hours. The metal samples were then removed, rinsed with clean water, and gently brushed with a nylon brush to remove loose corrosion products from the sample surface. The metal sheet was chemically cleaned with a metal cleaning solution, and then gently scrubbed with a nylon brush until no corrosion products were left on the metal surface. The metal sheet was rinsed with pure water 3–6 times, and then dried in a 40℃ oven for 12 hours. The mass of the metal sheet was measured and recorded as m2'.

[0068] (3) Control group experiment Clean the metal sheet with a 1:1 mixture of ethanol and acetone to remove grease, then wipe it clean with paper towels. Dry the metal sheet at 40°C for 1 hour, weigh it, and record its mass as m3. Place it in a desiccator for later use. Chemically clean the metal sheet with a metal cleaning solution, then gently scrub with a nylon brush until no corrosion products remain on the metal surface. Rinse the metal sheet 3-6 times with pure water, then dry it in a 40°C oven for 12 hours. Weigh the metal sheet and record its mass as m4.

[0069] Calculate the mass loss of the control group: Δm = m3 - m4.

[0070] (4) Corrosion rate calculation Mass of the metal sheet after corrosion: m2 = m2' + Δm Corrosion rate of metal sample: R = C × (m1 - m2) / (A × T × D) R—corrosion rate, in micrometers per year (μm / a), accurate to 0.01 μm / a; C—Conversion constant, C=8.76×10 7 (h·μm) / (a·cm); The mass of the metal sample before corrosion, expressed in grams (g). m2—The mass of the metal sample after corrosion, in grams (g); A—Metal contact surface area, in square centimeters (cm²) 2 ); T—Exposure time, in hours (h); D—Metal density, measured in grams per cubic centimeter (g / cm³) 3 ).

[0071] Table 1. Performance Test Results

[0072] Analysis of experimental results: Compared to Example 1, Example 4 (where boron-containing aminosilane was added during the first addition of urea) showed poorer performance in terms of LOI, smoke suppression, internal bond strength, and resistance to metal corrosion, indicating that the premature addition of boron-containing aminosilane deteriorated the overall performance of the resin. This may be because, under alkaline conditions, the premature introduction of boron-containing aminosilane causes its active groups to compete with urea for formaldehyde, interfering with the complete formation of hydroxymethyl urea. This results in a lower molecular weight and insufficient cross-linking of the final resin, thus affecting char formation efficiency and the mechanical properties of the adhesive layer. Furthermore, the incompletely reacted silane may also affect the fixation effect of the flame retardant.

[0073] Example 5 (where boron-containing aminosilane was added during the third addition of urea) also showed a decline in various properties, indicating that adding it too late also degrades product performance. This may be because the viscosity of the system increases in the later stages of the reaction, forming a certain network structure. The boron-containing aminosilane is difficult to disperse uniformly and cannot effectively participate in the resin's polycondensation network, resulting in its toughening and flame-retardant synergistic effects not being fully realized, and the boron and silicon elements are unevenly distributed in the resin.

[0074] All performance indicators of Example 6 (without boron-containing aminosilane) were worse than those of the other examples. This is because the lack of boron in enhancing the char formation of the condensed phase and the lack of siloxane chains in toughening the resin network prevented the system from compensating for the brittleness caused by the high cross-linking of phosphorus and nitrogen flame retardants, thus deteriorating its internal bonding strength and weakening the synergistic effect of flame retardancy and smoke suppression.

[0075] Compared to Example 1, Comparative Example 1 (using phenylphosphonate dichloride instead of hexachlorocyclotriphosphazene) showed a significant decrease in flame retardancy, smoke suppression, and mechanical properties, indicating that phenylphosphonate dichloride cannot form a similar intramolecular synergistic structure. This may be because phenylphosphonate dichloride has low functionality, only generating linear or low-branched molecules, and cannot form a three-dimensional molecular structure with hexachlorocyclotriphosphazene as the core. This results in an imbalance in the phosphorus-nitrogen ratio, low effective content, and a weakened synergistic effect of smoke suppression and flame retardancy.

[0076] Compared to Example 1, Comparative Example 2 (using a mixture of ammonium polyphosphate and guanidine carbonate) showed significantly worse performance across all aspects, especially an extremely high metal corrosion rate, reflecting the inherent defects of physically compounded systems. This is because physically mixed flame retardants exhibit poor dispersion uniformity and weak synergistic effects, and the large amount of added acidic ammonium polyphosphate is highly hygroscopic and prone to leaching, causing severe corrosion to metal components.

[0077] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A smoke-suppressing and flame-retardant ecological board, characterized in that, The product comprises a substrate, a flame-retardant adhesive layer, and a finishing layer stacked sequentially. The raw materials for the flame-retardant adhesive layer include: 100 parts of urea-formaldehyde resin, 10-15 parts of phosphorus-nitrogen composite flame retardant, and 5-10 parts of flame-retardant filler. The phosphorus-nitrogen composite flame retardant is first prepared by amine methylation reaction of p-hydroxybenzoic acid, ethanolamine, and paraformaldehyde in a molar ratio of 1:1-1.2:2-2.2 to obtain a Mannich base intermediate. Then, the Mannich base intermediate in a molar ratio of 3-7:1 is reacted with hexachlorocyclotriphosphazene as a raw material by a substitution reaction to obtain the final product.

2. The smoke-suppressing and flame-retardant ecological board according to claim 1, characterized in that, The preparation method of the phosphorus-nitrogen composite flame retardant is as follows: Ethanolamine and paraformaldehyde were mixed and dissolved in dioxane, and then p-hydroxybenzoic acid was added dropwise to the system to carry out an aminomethylation reaction. After the reaction was completed, the solvent was removed by vacuum distillation, and the residue was recrystallized from ethanol to obtain the Mannich base intermediate. Mannich base intermediate and acid-binding agent are dissolved in dry solvent, and hexachlorocyclotriphosphazene is added dropwise at low temperature and reacted for 0.5-1 h. Then the reaction is carried out at room temperature for 20-30 h. After the reaction is completed, the solvent is removed by vacuum distillation, the residue is dissolved in dioxane, and the resulting solution is added to ethyl acetate to precipitate solid product. After filtration and drying, phosphorus-nitrogen composite flame retardant is obtained.

3. The smoke-suppressing and flame-retardant ecological board according to claim 2, characterized in that, The reaction temperature for the aminomethylation reaction is 70–90°C; the low temperature is 0 ± 2°C.

4. The smoke-suppressing and flame-retardant ecological board according to claim 1, characterized in that, The urea-formaldehyde resin is a boron-modified urea-formaldehyde resin, which is obtained by reacting urea, formaldehyde, and boron-containing aminosilane in a molar ratio of 1:1 to 1.4:0.3 to 0.

5.

5. The smoke-suppressing and flame-retardant ecological board according to claim 4, characterized in that, The boron-containing aminosilane is prepared by de-alcoholization condensation of an aminosilane coupling agent and a borate ester in a molar ratio of 1 to 1.2:1 under the catalysis of a titanate ester.

6. The smoke-suppressing and flame-retardant ecological board according to claim 5, characterized in that, The aminosilane coupling agent is selected from any one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, and γ-aminopropylmethyldimethoxysilane.

7. The smoke-suppressing and flame-retardant ecological board according to claim 5, characterized in that, The borate ester is selected from any one or more of trimethyl borate, triethyl borate, n-propyl borate, isopropyl borate, and butyl borate.

8. The smoke-suppressing and flame-retardant ecological board according to claim 4, characterized in that, The boron-modified urea-formaldehyde resin is prepared as follows: Formaldehyde is added to water and mixed to prepare a formaldehyde aqueous solution. The temperature is raised to 40-50°C, the pH is adjusted to 8.0-9.0, 50%-70% of the total urea is added, and the mixture is stirred to dissolve. The temperature is then raised to 80-90°C and the reaction is maintained. The pH is adjusted to 4-5, 20%-30% of the total urea and boron-containing aminosilane are added, and the reaction is maintained at 80-90°C. The remaining urea is added, the temperature is lowered to below 60°C, and the pH is adjusted to 7.0-8.

0. The mixture is then cooled and discharged to obtain the final product.

9. The smoke-suppressing and flame-retardant ecological board according to claim 1, characterized in that, The flame-retardant filler is selected from any one or more of magnesium hydroxide, aluminum hydroxide, antimony trioxide, molybdenum oxide, ammonium molybdate, zinc borate, expandable graphite, zinc hydroxystannate, and zirconium phosphate.

10. A method for preparing a smoke-suppressing and flame-retardant ecological board, characterized in that, include: According to the composition ratio of the smoke-suppressing and flame-retardant ecological board according to any one of claims 1 to 9, the phosphorus-nitrogen composite flame retardant is mixed with urea-formaldehyde resin glue and stirred until homogeneous to obtain a flame-retardant adhesive. The flame-retardant adhesive is applied to the surface of the finished plywood, then the finishing material is attached, and the plywood is hot-pressed in a press at a temperature of 115-135℃ and a pressure of 0.6-1MPa for 2-5 minutes to obtain the final product.

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