A PN flame retardant, its preparation method and application

Abstract

This invention belongs to the field of flame retardant materials technology, and particularly relates to a P-N flame retardant, its preparation method, and its application. The preparation method of the P-N flame retardant includes the following steps: (1) diluting aminotrimethylenephosphonic acid with a solvent; (2) adding 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione to the solution obtained in step (1), reacting in a constant temperature oil bath for 2-5 hours to obtain a P-N flame retardant precursor solution; (3) preparing an aqueous solution of an amino compound; (4) adding the P-N flame retardant precursor solution dropwise to the aqueous solution of the amino compound, reacting in a constant temperature oil bath for 5-10 minutes to produce a white precipitate, continuing the reaction for 0.5-1 h after the precipitate is produced, washing and filtering the precipitate, and drying to obtain the P-N flame retardant. The P-N flame retardant of this invention is a white solid that is almost insoluble in water at room temperature and has good flame retardant effect on bio-based materials.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, and particularly relates to a PN flame retardant, its preparation method, and its application. Background Technology

[0002] Since ancient times, wood has been closely related to human life. With its rich and beautiful grain and color, wood possesses environmental characteristics unmatched by building materials such as reinforced concrete. Living environments constructed from wood and its products provide people with a comfortable natural feel and a unique aesthetic enjoyment. As people's living standards improve and their pursuit of a better life increases, the use of wood products and materials in construction and home furnishings has surged. However, wood is a flammable biomass material, thus the potential fire hazard is rapidly increasing. Using flame-retardant treatments on wood materials is one of the strategic measures to prevent and reduce fires. Flame-retardant treatments for wood and wood materials to improve their combustion performance and reduce the incidence of fires have become an increasingly necessary research topic.

[0003] There are many types of wood flame retardants. With increasing environmental awareness, wood generally uses safe, smoke-suppressing, and non-toxic green flame retardants. Halogen-free flame retardants are a growing trend. Therefore, developing flame retardant systems containing phosphorus, nitrogen, boron, or phosphorus-nitrogen is the mainstream approach for wood flame retardants. Phosphorus and its compounds have a significant impact on the thermal decomposition process of oxygen-containing cellulose materials such as wood, mainly by lowering the thermal decomposition temperature of wood, increasing char formation, reducing the generation of combustible gases, and reducing heat release. For example, water-soluble ammonium polyphosphate (APP) is a highly efficient wood flame retardant containing PN. However, its drawback is that after APP enters the wood cells through the impregnation process, its hygroscopic nature causes it to seep out to the wood surface, reducing the APP content inside the wood and thus decreasing its flame retardant performance.

[0004] Chinese patent CN104072759B discloses a PN-based intumescent reactive flame retardant, p-(carboxyphenyl-amino)-(carboxyphenyl-amidoethyl)phenylphosphine oxide, and its preparation method: (a) p-aminobenzoic acid solution is added to glacial acetic acid; (b) triethylamine and the mixed solution obtained in step a are added to a 2-carboxyethylphenyl hypophosphite solution. After stirring at high speed for 2 hours, the temperature is raised to 80°C and reacted for 4 hours. The resulting white powder is obtained by cooling, hydrolysis, filtration, washing with water, and drying.

[0005] Chinese Patent CN 112358453 A discloses a PNC-type intumescent flame retardant, its preparation method, and its application in fire-retardant coatings. The preparation method of this intumescent flame retardant includes: (1) dissolving tris(hydroxymethyl)aminomethane and sodium hydroxide in deionized water, adding the resulting mixture to an acetone solution of cyanuric chloride, and reacting in an ice bath; (2) adding sodium carbonate and p-hydroxybenzaldehyde, reacting, filtering, washing with water, and drying; (3) adding a polyamine compound and the product from step (2) to ethanol, stirring and refluxing, evaporating the ethanol, washing three times with alcohol, and drying to obtain the product; (4) stirring the ethanol-water mixture under a nitrogen atmosphere, adding APP and the product obtained in step (3), refluxing, detecting no ammonia release, filtering, washing with ethanol and water, and drying. This method modifies all three components of the PNC-type intumescent flame retardant, improving its water resistance through chemical bonding, thus enhancing the water resistance of fire-retardant coatings.

[0006] Chinese Patent CN 114426701 B relates to the field of polymer flame retardant materials technology, disclosing the preparation of a PN compound synergistic graphene oxide flame retardant and its application in epoxy resin. First, under inert gas protection, p-aminoacetophenone, aniline, and p-toluenesulfonic acid are added to a three-necked flask and heated to melt. DOPO is then added and magnetically stirred. The mixture is filtered, washed, and dried to obtain solid powder I. Next, graphene oxide is dispersed in an organic solvent, and triethylamine and a chlorinated compound are added. The mixture is heated in an oil bath, and after the reaction, it is filtered under reduced pressure, washed, and dried to obtain solid powder II. Finally, II is dispersed in an organic solvent, and I and triethylamine are added. The mixture is heated to react, and after the reaction, it is filtered under reduced pressure, washed multiple times with ethanol and deionized water, and dried to obtain the final product. The product was applied to flame retardant studies of epoxy resin curing systems, confirming its excellent properties such as high flame retardancy, non-toxicity, and good compatibility.

[0007] All three patents involve the use of ethanol, glacial acetic acid, or other solvents or reaction media, or nitrogen protection, which undoubtedly increases the cost of solvent recovery, makes the process more complex, requires greater equipment investment, and increases the difficulty of industrial implementation.

[0008] It can be seen that phosphorus-nitrogen-based compounds are currently a promising class of flame-retardant additives for polymeric materials, and are applied to polymeric materials through physical blending. However, under normal circumstances, solid PN flame retardants are difficult to penetrate into the wood, or their solubility characteristics cause them to seep out onto the wood surface, making it impossible to maintain their flame-retardant properties stably over a long period. Therefore, the technical problems concerning the compatibility and anti-leakage properties of solid PN flame retardants still urgently need to be solved in this field. Summary of the Invention

[0009] The technical problem to be solved by the present invention is that wood flame retardants are easily soluble in water and easily lost. To overcome the shortcomings and defects mentioned in the background art, the present invention provides a PN flame retardant, its preparation method and application.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0011] A PN flame retardant has the following chemical structural formula:

[0012] .

[0013] The PN flame retardant of this invention is a white solid that is almost insoluble in water at room temperature and has a good synergistic flame retardant effect on bio-based materials. Compared with conventional PN flame retardants that are difficult to penetrate into the interior of bio-based materials or are easily permeable, the water-insoluble PN flame retardant of this invention can achieve high compatibility with bio-based materials and impart flame retardant and anti-leakage properties to wood.

[0014] Under the same technical concept, this application also provides a method for preparing PN flame retardant, comprising the following steps:

[0015] (1) Take aminotrimethylenephosphonic acid (ATMP), dilute it with solvent, and stir until homogeneous;

[0016] (2) 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione (THEIC) was added to the solution obtained by dilution in step (1) and reacted in a constant temperature oil bath to obtain a PN flame retardant precursor solution. The molar ratio of aminotrimethylenephosphonic acid to 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione was 1:1 to 3:1.

[0017] The high phosphorus and nitrogen content in the raw materials (ATMP) and (THEIC) results in a high phosphorus-to-nitrogen ratio in the synthesized target product, which is beneficial for achieving the goal of high flame retardancy with low loading of flame retardant. Since the 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione molecule has 3 hydroxyl groups, and 1 hydroxyl group undergoes a dehydration esterification reaction with 1 phosphonate group, 1 part of THEIC can react with 1~3 parts of ATMP to generate a phosphonate-containing PN flame retardant precursor, which is soluble in water. Therefore, the molar ratio of aminotrimethylenephosphonic acid to 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione should be controlled to be 1:1~3:1.

[0018] (3) Prepare an aqueous solution of an amino compound, wherein the molar ratio of amino group to aminotrimethylenephosphonic acid in the amino compound is 1:1 to 3:1;

[0019] (4) The PN flame retardant precursor solution from step (2) is added dropwise to the aqueous solution of the amino compound described in step (3), and the reaction is carried out in a constant temperature oil bath. After 5-10 min, a white precipitate is formed. After the precipitate is formed, the reaction continues for 0.5-1 h. Then, the precipitate is filtered and dried to obtain the PN flame retardant. The amino group reacts with the phosphonate group in the PN flame retardant precursor solution in an acid-base reaction to produce a salt, which further generates the water-insoluble PN flame retardant.

[0020] Preferably, the solvent in step (1) is water, and the concentration of aminotrimethylenephosphonic acid after dilution is 20%-50%. The reduced concentration of diluted aminotrimethylenephosphonic acid weakens its acidity, which is beneficial for the reaction.

[0021] Preferably, the constant temperature oil bath reaction in step (2) is 100-120℃, and the reaction time is 2-5h. This temperature and reaction time ensure that the reaction proceeds and generates a PN flame retardant precursor containing phosphonate.

[0022] Preferably, the method for preparing the aqueous solution of the amino compound in step (3) is as follows: add the solid amino compound to water, heat and stir at 95-105°C for 1-2 hours until the solid is completely dissolved to obtain a clear solution, wherein the aqueous solution of the amino compound is a saturated solution.

[0023] Preferably, the amino compound includes at least one of melamine, piperazine, guanine, or 1-(2-aminoethyl)piperazine.

[0024] Taking melamine (MEL) as an example, the chemical reaction mechanism of the preparation process in this application is as follows:

[0025]

[0026] During the preparation of PN flame retardants, intermediates containing PN bonds are generated. These PN bonds can enhance the reactivity of the carbonyl groups in fibers and their phosphorylation rate, further increasing the char yield. Simultaneously, nitrogen-containing compounds can release non-flammable gases such as ammonia, delaying the volatilization loss of phosphorus compounds and promoting the protective effect of the phosphide char layer.

[0027] Preferably, the constant temperature oil bath reaction temperature in step (4) is 100~105℃, the reaction time is 0.5-1 h; the filter is washed 1-3 times with hot water at 70~80℃, and the drying temperature is 80~100℃.

[0028] Under the same technical concept, this application also provides the application of PN flame retardant in flame retardant bio-based composite materials, wherein the PN flame retardant is constructed in situ in the flame retardant bio-based composite material.

[0029] This invention uses water-soluble precursors to construct an insoluble PN flame retardant in situ inside the wood, giving the wood flame retardancy while preventing leaching.

[0030] Preferably, the in-situ construction in the flame-retardant bio-based composite material specifically involves:

[0031] (1) Prepare bio-based materials;

[0032] (2) Dilute aminotrimethylenephosphonic acid with solvent and stir until homogeneous;

[0033] (3) Add 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione to the solution obtained by dilution in step (1) and carry out a constant temperature oil bath reaction to obtain a PN flame retardant precursor solution. The molar ratio of aminotrimethylenephosphonic acid to 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione is 1:1 to 3:1. The bio-based material is impregnated in the PN flame retardant precursor solution.

[0034] (4) Prepare an aqueous solution of an amino compound, wherein the molar ratio of amino group to aminotrimethylenephosphonic acid in the amino compound is 1:1 to 3:1;

[0035] (5) The bio-based material treated in step (3) is further immersed in an aqueous solution of amino compound and kept at 100~105℃ for 0.5-1 h. After the heat preservation is completed, the bio-based material is washed and dried to obtain a flame-retardant bio-based composite material in which PN flame retardant is constructed in situ in the bio-based material.

[0036] The flame retardant application scheme proposed in this paper is a two-step impregnation method. The bio-based material is impregnated in the PN flame retardant precursor solution obtained in step (2) and the aqueous solution of the amino compound prepared in step (3). It is particularly noted that the solution in step (3) needs to be kept at 100~105 ℃ for 0.5-1 h to ensure that the aqueous solution of the amino compound in step (3) enters the wood and reacts with the solution in step (2) impregnated in the bio-based material at 100~105 ℃, thereby constructing the PN flame retardant in situ in the cells of the bio-based material.

[0037] Preferably, the bio-based material includes one or more of wood, bamboo, wood-bamboo derived plywood, or recombinant materials;

[0038] The washing process includes washing with deionized water 1-3 times. The drying process includes air drying at room temperature for 24-48 hours, followed by drying in an oven at 80-105℃ for 24-48 hours. The impregnation process adopts a biomimetic breathing impregnation method and uses an impregnation device. The impregnation process specifically includes: evacuating the impregnation device to below 0.2 MPa and maintaining it for 0.5-1 hours; then using negative pressure to draw the impregnation solution into the impregnation device, pressurizing the impregnation device to 1.0-1.2 MPa, and maintaining it for 0.5-1.5 hours.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The PN flame retardant provided by the present invention contains two groups: phosphorus-containing and nitrogen-containing. The phosphorus-containing component decomposes into phosphoric acid, polyphosphoric acid, or phosphoric anhydride when heated, which phosphorylates the cellulose in the wood and dehydrates it to form char. Since the oxyacids of phosphorus are mostly viscous at high temperatures, they can form a liquid film covering the char layer on the surface of the wood, which helps to reduce the air permeability of the char layer and protect the char layer from further oxidation. When the flame retardant contains both phosphorus and nitrogen, the interaction between nitrogen and phosphorus forms many intermediates containing PN bonds, which can improve the carbonyl reaction activity of cellulose and the phosphorylation rate. The nitrogen-containing group also has a nucleophilic effect on the ROP bond in the phosphide, so that the phosphorus is in the form of a non-volatile salt. The formula is retained in the char layer, further improving the char formation rate and char layer quality, and giving the char layer excellent heat insulation and oxygen barrier capabilities; in addition to the synergistic solidification phase flame retardant effect of P and N, the P and N composite flame retardant decomposes upon heating to produce non-flammable gases such as NH3 and water vapor, which can dilute the air and play a role in gas phase flame retardancy; furthermore, the composite flame retardant of phosphorus and nitrogen not only increases the flame retardant effect but also reduces the amount used. In Example 2 of this application, wood is impregnated with 1% of the PN flame retardant precursor solution from step (2) and 1% of the aqueous solution of the amino compound from step (3), and the limiting oxygen index (LOI) of the impregnated wood can exceed 32%, and the combustion rating reaches B1 level;

[0041] (2) The preparation method of PN flame retardant provided by the present invention is green and environmentally friendly, does not use toxic solvents, has high flame retardant and smoke suppression efficiency, low energy consumption, and the scheme of first generating a soluble precursor and then generating a poorly soluble PN flame retardant is more conducive to the subsequent application in the in-situ construction of PN flame retardant in bio-based materials.

[0042] (3) The application of the PN flame retardant of the present invention can construct the PN flame retardant in situ within the cells of bio-based materials. On the one hand, the flame retardant obtained by in situ construction is itself insoluble in water and has good anti-leakage properties. On the other hand, the unreacted phosphonate on the ATMP molecule can undergo hydrogen bonding or esterification with the hydroxyl groups on the cellulose of the bio-based material to produce bonding and form rivets on the wood fiber to overcome the disadvantage of easy loss of flame retardant and give the wood material good flame retardant and smoke suppression properties. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a chemical synthesis route diagram of the PN flame retardant synthesized in Example 1;

[0045] Figure 2 This is the FTIR structural characterization spectrum of the PN flame retardant synthesized in Example 1;

[0046] Figure 3 This is the XPS structural characterization spectrum of the PN flame retardant synthesized in Example 1;

[0047] Figure 4 It is the PN flame retardant synthesized in Example 1. 1 H NMR analysis of structural characterization spectra;

[0048] Figure 5 It is the PN flame retardant synthesized in Example 1. 31 P NMR analysis of structural characterization spectra;

[0049] Figure 6 This is the CONE result of wood treated with the impregnation solution in Example 2;

[0050] Figure 7 The CONE results are for wood treated with the impregnation solution in Comparative Example 1.

[0051] Figure 8 The CONE results are for wood treated with the impregnation solution in Comparative Example 2;

[0052] Figure 9 The results of CONE for wood treated with the impregnation solution in Comparative Example 3 are shown.

[0053] Figure 10 This is the LOI result of the impregnation solution treated with wood in Example 2;

[0054] Figure 11 The results show the LOI of the wood treated with the impregnation solution in Comparative Example 1.

[0055] Figure 12 The results show the LOI of the wood treated with the impregnation solution in Comparative Example 2.

[0056] Figure 13 The results show the LOI of the wood treated with the impregnation solution in Comparative Example 3.

[0057] Figure 14 shows a digital photograph and SEM image of the char residue after a cone calorimetry experiment on ordinary wood.

[0058] Figure 15 is a digital photograph and SEM image of the char residue after the cone calorimetry experiment of wood treated with the slurry in Example 2.

[0059] Figure 16 shows a digital photograph and SEM image of the residual char after the cone calorimetry experiment of wood treated with the solution in Comparative Example 1.

[0060] Figure 17 shows a digital photograph and SEM image of the residual char after the cone calorimetry experiment of wood treated with the staining solution in Comparative Example 2.

[0061] Figure 18 shows a digital photograph and SEM image of the residual char after the cone calorimetry experiment of wood treated with the staining solution in Comparative Example 3.

[0062] Figure 19 This is the LOI result of the impregnation solution treated with wood in Example 3;

[0063] Figure 20 This is the LOI result of the impregnation solution treated with the wood in Comparative Example 4. Detailed Implementation

[0064] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0065] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0066] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0067] Example 1:

[0068] This embodiment provides a PN flame retardant, the chemical structure of which is shown below, and the chemical synthesis route is shown below. Figure 1 As shown:

[0069] ;

[0070] The preparation method of the above-mentioned PN flame retardant specifically includes the following steps:

[0071] (1) Take 400 mL of an aqueous solution of aminotrimethylene phosphonic acid (ATMP) with a phosphorus content of 31.63% and dilute it with 400 mL of water and stir well;

[0072] (2) Weigh 76.62 g of 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione (THEIC), add it to the solution obtained by dilution in step (1), and react it in a constant temperature oil bath at 120℃ for 4.0 h. Keep warm to obtain PN flame retardant precursor solution.

[0073] (3) To prepare an aqueous solution of melamine (MEL), add 12.4g of solid (MEL) to 450mL of water and stir at 100℃ for 1h until the solid is completely dissolved to obtain a clear solution;

[0074] (4) The PN flame retardant precursor solution was added dropwise to the MEL aqueous solution, heated and stirred at 100°C for 0.5 h, a precipitate was formed, and stirring was continued for 0.5 h. The precipitate was then filtered, washed three times with deionized water at 80°C, and dried at 80°C to obtain the PN flame retardant.

[0075] Structural characterization of the obtained PN flame retardant (hereinafter referred to as TAM): FTIR, XPS, 1 H NMR and 31 The chemical structure of TAM was analyzed by P NMR, and the resulting characterization spectrum is as follows: Figure 2-5 As shown. Figure 2 The FTIR spectra of flame retardant TAM and its reactants are shown, with the 1690 cm⁻¹ value being... -1 The absorption signal at this point is due to the stretching vibration of C=O caused by the isocyanuric acid ring skeleton vibration on the THEIC molecule. In addition to these characteristic peaks in the FTIR spectrum, the NC=O peak of THEIC corresponds to the 1470 cm⁻¹ peak. -1 The peak and the C=N corresponding to 1550 cm⁻¹ in MEL -1 The peaks all underwent superposition and displacement, and at 1510 cm⁻¹ -1 New absorption peaks are generated. In the TAM spectrum, due to NH... 4+ Tensile and deformation vibrations at 3120 cm -1 and 1400 cm -1 A new adsorption peak was discovered at 1250 cm⁻¹. -1 A new adsorption peak was found at 3468 cm⁻¹ (P=O). Simultaneously, a new adsorption peak was observed at 3468 cm⁻¹. -1 and 3418 cm -1 The characteristic stretching peaks of -NH2 on the MEL plate disappeared, which may be due to the formation of phosphate. The -OH peak at 3350 cm⁻¹... -1 The broad adsorption peak for THEIC at 3370 cm⁻¹ is also relatively weak. -1 A small peak forms there. Figure 3In XPS, the prepared TAM showed absorption peaks for P and N, and combined with absorption peaks for C and O, indicating the presence of P and N elements in TAM, and that the mass fraction ratio of C:O:N:P in the TAM flame retardant was 32.11%:26.45%:33.14%:8.30%. Figure 4 The TAM shown 1 In the 1H NMR spectrum, characteristic chemical shifts of H1 and H2 were found to be 2.93 ppm and 3.26 ppm, respectively, corresponding to two adjacent methylene groups in THEIC. The singlet signal at 7.50 ppm is attributed to the methylene H3 in ATMP. Figure 5 solid state of TAM 31 The P NMR spectrum shows three strong singlet signals at 6.2, 9.8, and 11.0 ppm. The signal at 11.0 ppm (label a) can be attributed to the P atom in the C-PO(OH)2 group, while the peaks at 9.8 ppm (label b) and 6.2 ppm (label c) can be attributed to -P=O(O-NH 4+ The peak areas of the MEL and COP=O groups were 1:0.85:1.1, indicating a molar ratio of MEL to THEIC to ATMP of 1:1.7:2.2. This provides a basis for the successful synthesis of TAM and is consistent with the expected chemical structure.

[0076] Example 2:

[0077] This embodiment provides a PN flame retardant, the chemical structure of which is shown below, and the chemical synthesis route is shown below. Figure 1 As shown:

[0078] ;

[0079] This embodiment provides an application of PN flame retardant in flame retardancy of wood materials, specifically including the following steps:

[0080] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it and record the mass.

[0081] (2) Weigh 800 mL of 50% aqueous solution of aminotrimethylenephosphonic acid (ATMP) with a phosphorus content of 31.63% and 152.2 g of THEIC. React at 120℃ for 4 h. Collect 900 mL of the reaction solution to obtain solution TA. Take 40 mL of the above-prepared solution TA, add 1960 mL of deionized water, stir evenly to obtain 1% TA solution.

[0082] (3) Place the fir sample obtained in (1) into the impregnation tank, evacuate to 0.15 MPa and maintain for 0.5 h; then use negative pressure to draw 2000 mL of 1% TA solution into the impregnation tank; next, pressurize the tank to 1.0 MPa and maintain it for 1 h with an air compressor, then depressurize and unload the solution from the impregnation tank and discharge it, and take out the treated sample;

[0083] (4) Weigh 50g of MEL and add it to 2000 mL of water. Stir at 100℃ for 1 hour until the solid is completely dissolved to obtain 2000 mL of MEL solution. Dilute the MEL solution to 1% MEL solution.

[0084] (5) Place the fir wood sample obtained in (3) into the impregnation tank, and replace the 1%TA solution with the 1%MEL solution obtained in step (4) according to the impregnation process in step (3), and keep the impregnation tank at 100 ℃ for 1 h; after depressurization, take out the treated sample, wash it with deionized water 3 times, dry it naturally at room temperature for 24 h, and then dry it in an oven at 105 ℃ for 48 h, weigh it, record the mass, and obtain the 1%TAM / wood sample.

[0085] Example 3:

[0086] This embodiment provides a PN flame retardant, the chemical structure of which is shown below, and the chemical synthesis route is shown below. Figure 1 As shown:

[0087] ;

[0088] This embodiment provides an application of PN flame retardant in flame retardant of fir wood, specifically including the following steps:

[0089] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it and record the mass.

[0090] (2) Take 800 mL of a 50% aqueous solution of aminotrimethylenephosphonic acid (ATMP) with a phosphorus content of 31.63% and 152.2 g of THEIC. React at 120℃ for 4 h. Collect 900 mL of the reaction solution to obtain solution TA. Take 200 mL of the above-prepared solution TA and add 1960 mL of deionized water. Stir well to obtain a 5% TA solution.

[0091] (3) Place the fir sample obtained in (1) into the impregnation tank, evacuate to 0.15 MPa and maintain for 0.5 h; then use negative pressure to draw 2000 mL of 5% TA solution into the impregnation tank; next, pressurize the tank to 1.0 MPa and maintain it for 1 h with an air compressor; after depressurization, unload and discharge the solution from the impregnation tank and take out the treated sample;

[0092] (4) Weigh 200g of MEL and disperse it in 4000mL of water. Stir at 100℃ for 1h until the solid is completely dissolved to obtain 4000mL of MEL solution. Dilute the MEL solution to 5% MEL solution.

[0093] (5) Place the fir wood sample obtained in (3) into the impregnation tank, and replace the solution (2) with the 1% MEL solution obtained in step (4) according to the impregnation process in step (3), and keep the impregnation tank at 100 ℃ for 1 h; after depressurization, take out the treated sample, wash it with deionized water 3 times, dry it naturally at room temperature for 24 h, and then dry it in an oven at 105 ℃ for 48 h, weigh it, record the mass, and obtain the 5% TAM / wood sample.

[0094] Example 4:

[0095] This embodiment provides a PN flame retardant, the chemical structure of which is shown below, and the chemical synthesis route is shown below. Figure 1 As shown:

[0096] ;

[0097] This embodiment provides an application of PN flame retardant in the flame retardancy of bamboo fiberboard, specifically including the following steps:

[0098] (1) Take 3000g of 200-mesh bamboo fiber sample and dry it in an oven at 70℃ for 24 h until constant weight;

[0099] (2) TAM / bamboo powder composite material was prepared according to the experimental steps of Example 2. The only difference was that in step (3), 5% TA solution was first drawn into the impregnation tank, and then the corresponding bamboo powder was added. The mixture was stirred at 100 °C for 1 h. In step (5), 5% MEL solution was first drawn into the impregnation tank, and then the corresponding bamboo powder was added. The mixture was stirred at 100 °C for 0.5-1 h. After depressurization, the treated sample was taken out, washed with deionized water 3 times, dried naturally at room temperature for 24 h, and then dried in an oven at 105 °C for 48 h. The sample was weighed and the mass was recorded to obtain 5% TAM / bamboo powder composite material.

[0100] (3) Weigh the TAM / bamboo powder composite material obtained in (2), weigh 10% of the mass of the TAM / bamboo powder composite material and mix it evenly with the 5% TAM / bamboo powder composite material obtained in (3). Then place the TAM / bamboo powder composite material with adhesive in an iron mold with a size of 300×300 mm and a thickness gauge of 1 cm. Hot press it for 8 min at 125℃ and 1.2 MPa to obtain the flame-retardant bamboo powder composite material treated with PN flame retardant.

[0101] Comparative Example 1:

[0102] This comparative example provides the application of melamine (MEL) flame retardant in flame retardancy of wood materials, specifically including the following steps:

[0103] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it, and record the mass;

[0104] (2) Weigh 50g of MEL and add it to 2000mL of water. Stir at 100℃ until the solid is completely dissolved to obtain MEL solution. Dilute the MEL solution to 1% MEL solution.

[0105] (3) Place the fir wood sample obtained in (1) into the impregnation tank and follow the impregnation process in step (3) of Example 2. Replace the 1% TA solution with the 1% MEL solution obtained in (2) above and add it into the impregnation tank. After the pressure is maintained, release the pressure and take out the treated sample. Wash it with deionized water, dry it naturally at room temperature for 24 h, dry it in an oven at 105℃ for 48 h, weigh it, record the mass, and obtain the 1% MEL / wood sample.

[0106] Comparative Example 2:

[0107] This comparative example provides an application of AM flame retardant in flame retardancy of wood materials, specifically including the following steps:

[0108] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it, and record the mass;

[0109] (2) Take 40 mL of ATMP solution and add it to 1960 mL of deionized water;

[0110] (3) Place the fir sample obtained in (1) into the impregnation tank, evacuate to 0.15 MPa and maintain for 0.5 h; then use negative pressure to draw 2000 mL of 1% ATMP solution (2) into the impregnation tank; next, pressurize the tank to 1.0 MPa and maintain for 1 h; after depressurization, unload and discharge the ATMP solution from the impregnation tank, and take out the treated sample and place it naturally for later use.

[0111] (4) Take 11.09g of MEL and add it to 2000 mL of deionized water. Heat to 100℃ and stir until a clear solution is obtained.

[0112] (5) Place the fir sample obtained in (3) into the impregnation tank, evacuate to -0.15 MPa, and maintain for 0.5 h; then use negative pressure to draw 2000 mL of a 1% MEL solution (4) into the impregnation tank; next, pressurize the tank to 1.0 MPa and maintain it for 1 h with an air compressor. After depressurization, unload and discharge the solution from the impregnation tank;

[0113] (6) Take out the treated sample, wash it with deionized water, place it in a natural environment for 24 h, and then dry it in an oven at 105℃ for 48 h. Weigh it, record the mass, and obtain a 1% AM / wood sample.

[0114] Comparative Example 3:

[0115] This comparative example provides an application of TA flame retardant in flame retardancy of wood materials, specifically including the following steps:

[0116] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it, and record the weight;

[0117] (2) The solution obtained in step (2) of Example 1 was used as the wood impregnation solution. The wood was impregnated according to the same scheme as step (3) of Example 2. The sample was left to stand naturally at room temperature for 24 h, dried in an oven at 105℃ for 48 h, weighed, and the mass was recorded. The obtained sample was a 1%TA / wood sample.

[0118] The combustion performance of wood samples treated with impregnation solutions from Examples 2, 1, 2, and 3 (with ordinary wood as the blank control group) was determined using an FTT cone calorimeter (CONE) and a JF-3 limiting oxygen index meter. The results are shown in Table 1. Figure 6-9 As shown:

[0119] Table 1. Cone calorimetric experimental data of wood materials impregnated with different 1% impregnation solutions

[0120]

[0121] Table 1 shows the cone calorimetric combustion performance test data of wood treated with different 1% impregnation solutions. As can be seen from Table 1, the peak maximum heat release rate of pure cedar wood is 255.2 kW / m³. 2 The average heat release rate, average effective heat of combustion, and total heat release were 94.1 kW / m³. 2 12.9 MJ / kg, 41.9 MJ / m 2 The total smoke emission (TSP) was 10.7 m³. 2 / m 2 The average heat release rate and total heat release of 1% TAM / wood with the addition of 1.0% novel PN flame retardant TAM were 64.2 kW / m³. 2 25.4 MJ / m 2 It was the lowest among all impregnated samples, reducing the yield by 29.9 kW / m compared to pure cedar. 2 16.5 MJ / m 2 Its total smoke production was also the lowest among all samples, at only 5.22 m³.2 / m 2 This accounts for less than half of the total smoke produced from logs. Combined with... Figure 3 It can be seen that the 1% TAM / wood sample was the first to extinguish, with the shortest flaming time. 1% TAM impregnation treatment of wood exhibited excellent flame retardant and smoke-suppressing effects.

[0122] Figure 10-13 The limiting oxygen index (LOI) results of Example 2 and Comparative Examples 1-3 were tested. From Figure 4 The LOI of different 1% impregnation solutions for fir wood can be seen as follows: the LOI of all impregnated wood samples is higher than that of untreated fir wood (17.4%). However, the LOI of the 1% TAM / wood sample is the highest at 34.2%, followed by the 1% AM / wood sample at 33.5%; the LOI of the 1% TA / wood and 1% MEL / wood samples decreases in that order.

[0123] Experimental data from CONE and LOI show that a 1% TAM solution can effectively suppress heat release and smoke generation in wood, demonstrating excellent flame retardant properties.

[0124] Figures 14-18 show digital photographs and SEM images of the char residue after cone calorimetry experiments on wood treated with the impregnation solution in Examples 2 and Comparative Examples 1-3, with ordinary wood as the blank control group; Figure 14(a) is a digital photograph of the char residue after the cone calorimetry experiment on ordinary wood, Figure 14(b) is the amount of char residue after the cone calorimetry experiment on ordinary wood, and Figure 14(c) is the SEM image of the char residue after the cone calorimetry experiment on ordinary wood; Figure 15(a) is a digital photograph of the char residue after the cone calorimetry experiment on wood treated with the impregnation solution, Figure 15(b) is the amount of char residue after the cone calorimetry experiment on wood treated with the impregnation solution, and Figure 15(c) is the SEM image of the char residue after the cone calorimetry experiment on wood treated with the impregnation solution; subsequent images are the same; in the figures, 1% The TAM-treated wood surface forms a molten carbon layer, which effectively prevents oxygen and radiant heat from entering the wood substrate below the carbon layer. This reduces the rate at which cellulose, hemicellulose, and lignin, among other hydrocarbons in the wood substrate, decompose and produce flammable gases, thus reducing the intensity of wood combustion.

[0125] Comparative Example 4:

[0126] This comparative example provides an application of APP flame retardant in flame retardancy of wood materials, specifically including the following steps:

[0127] (1) Dry the fir wood sample in an oven at 105℃ for 24 hours until constant weight, weigh it and record the mass.

[0128] (2) Weigh 105.3 g of APP and add it to 2000 mL of deionized water to prepare a 5% APP solution.

[0129] (3) Place the cedar wood sample obtained in (1) into an impregnation tank, evacuate to 0.15 MPa, and maintain for 0.5 h. Then, use negative pressure to draw 2000 mL of a 5% APP solution into the impregnation tank. Next, pressurize the tank to 1.0 MPa and maintain this pressure for 1 h using an air compressor. After depressurization, remove the solution from the impregnation tank and discharge it. Take out the treated sample.

[0130] (4) Take out the treated sample, wash it with deionized water, let it stand for 24 hours, and then dry it in an oven at 105℃ for 48 hours. Weigh it and record the mass. The resulting sample is a 5% APP / wood specimen.

[0131] The combustion performance of the impregnated samples in Example 3 and Comparative Example 4 was determined using an FTT cone calorimeter (CONE) and a JF-3 limiting oxygen index meter. The experimental data of CONE combustion performance are shown in Table 2.

[0132] Table 2. Cone calorimetry experimental data of 5% ATM and 5% APP impregnated cedar wood

[0133]

[0134] Table 2 shows the cone calorimetry data of 5% TAM and 5% APP impregnated cedar wood. The ignition time of the cedar wood sample treated with 5% TAM solution was 51 seconds later than that of pure cedar wood. The heat release parameters in the CONE experiment were significantly lower than those of pure cedar wood, with a total heat release of 12.32 MJ / m³. 2 It reduces emissions by 29.55 MJ / m compared to pure cedar. 2 The PHRR and average heat release rate were reduced by 57.02% and 56.74% respectively compared to the corresponding values ​​for pure cedar, and the total smoke emission and total smoke production were 2.83 m³. 2 / m 2 It was only 26.4% of that of pure cedar. Compared with the cedar sample impregnated with 5% APP solution in Comparative Example 4, except that the average heat release rate and peak heat release rate were slightly higher than those of 5% APP / wood, the ignition time was delayed by 11 seconds, and the flaming combustion time was 56-360 s (average 304 s), which was less than that of 44-410 s (average 366 s); other parameters such as average effective heat of combustion, total heat release, and total smoke production were all lower than those of 5% APP / wood, and the total heat release was 2.59 MJ / m³ lower than that of 5% APP / wood. 2The residual char rate was also 9 percentage points higher than that of the 5% APP sample; moreover, TAM was more effective than APP in suppressing smoke release, with its total smoke production being less than one-third of that of pure cedar and only 64.9% of that of 5% APP / wood. Therefore, TAM is an excellent flame retardant for wood materials, possessing the same high efficiency in suppressing wood combustion and reducing heat release as APP, and with a better smoke suppression effect than APP.

[0135] Figure 19 , 20 The limiting oxygen index (LOI) test results from Example 3 and Comparative Example 4 were tested. Figure 6 It can be seen that the limiting oxygen index (LOI) of pure cedar wood is 17.4%, while the LOI of the 5% APP / wood sample treated with 5% APP impregnation solution is 32.1%, and the LOI of the cedar wood sample treated with 5% ATM impregnation solution, 5% TAM / wood, is as high as 48.4%, which is 50.78% higher than that of 5% APP / wood. TAM exhibits good flame retardant and fireproof properties.

[0136] Comparative Example 5:

[0137] This comparative example provides a common bamboo fiberboard, and the preparation method of the bamboo fiberboard is as follows:

[0138] (1) After the bamboo fiber sample passes through a 200-mesh sieve, take 500g of bamboo fiber sample and dry it in an oven at 70℃ for 24h until constant weight.

[0139] (2) Weigh 10% of the mass of bamboo fiber urea-formaldehyde resin adhesive and mix it evenly with the bamboo fiber obtained by drying in (1). Then, heat press at 125℃ and 1.2MP for 8 minutes to form the product.

[0140] The oxygen index (LOI) of the bamboo fiberboard samples obtained in Example 4 and Comparative Example 5 was determined using an FTT cone calorimeter (CONE) and a JF-3 limiting oxygen index (LOI) meter. The results are listed in Table 3. The data in the table show that the LOI of the bamboo fiberboard increases with increasing TAM content. The LOI of the 20% TAM flame-retardant fiberboard is as high as 60.8%, indicating that TAM has excellent flame-retardant properties.

[0141] Table 3 Limiting Oxygen Index of Different TAM Flame-Retardant Bamboo Fiberboards

[0142]

Claims

1. A PN flame retardant, characterized in that, Its chemical structural formula is: 。 2. A method for preparing a PN flame retardant, characterized in that, Includes the following steps: (1) Dilute aminotrimethylenephosphonic acid with solvent and stir until homogeneous; (2) 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione is added to the solution obtained by dilution in step (1) and reacted in a constant temperature oil bath to obtain a PN flame retardant precursor solution. The molar ratio of aminotrimethylenephosphonic acid to 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione is 1:1 to 3:

1. (3) Prepare an aqueous solution of an amino compound, wherein the molar ratio of amino group to aminotrimethylenephosphonic acid in the amino compound is 1:1 to 3:1; (4) The PN flame retardant precursor solution in step (2) is added dropwise to the aqueous solution of the amino compound in step (3) and reacted in a constant temperature oil bath. After 5-10 min, a white precipitate is generated. After the precipitate is generated, the reaction continues for 0.5-1 h. Then the precipitate is filtered and dried to obtain the PN flame retardant.

3. The preparation method according to claim 2, characterized in that, The solvent in step (1) is water, and the concentration of aminotrimethylenephosphonic acid after dilution is 20%-50%.

4. The preparation method according to claim 2, characterized in that, The reaction temperature of the constant temperature oil bath reaction in step (2) is 100-120 ℃, and the reaction time is 2-5 h.

5. The preparation method according to claim 2, characterized in that, The method for preparing the aqueous solution of the amino compound in step (3) is as follows: add the solid amino compound to water, heat and stir at 95~105℃ for 1-2 hours until the solid is completely dissolved to obtain a clear solution. The aqueous solution of the amino compound is a saturated solution.

6. The preparation method according to claim 5, characterized in that, The amino compound includes at least one of melamine, piperazine, guanine, or 1-(2-aminoethyl)piperazine.

7. The preparation method according to claim 2, characterized in that, The temperature of the constant temperature oil bath reaction in step (4) is 100~105 ℃, and the reaction time is 0.5-1h; the filter is washed 1-3 times with hot water at 70~80℃, and the drying temperature is 80~100℃.

8. The application of a PN flame retardant as described in claim 1 or a PN flame retardant prepared by any one of claims 2-7 in flame-retardant bio-based composite materials, characterized in that, In-situ construction of PN flame retardant in the flame-retardant bio-based composite material.

9. The application as described in claim 8, characterized in that, The in-situ construction in flame-retardant bio-based composite materials specifically refers to: (1) Prepare bio-based materials; (2) Dilute aminotrimethylenephosphonic acid with solvent and stir until homogeneous; (3) Add 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione to the solution obtained by dilution in step (1) and carry out a constant temperature oil bath reaction to obtain a PN flame retardant precursor solution. The molar ratio of aminotrimethylenephosphonic acid to 1,3,5-tris(2-hydroxyethyl)1,3,5-triazine-2,4,6-trione is 1:1 to 3:

1. The bio-based material is impregnated in the PN flame retardant precursor solution. (4) Prepare an aqueous solution of an amino compound, wherein the molar ratio of amino group to aminotrimethylenephosphonic acid in the amino compound is 1:1 to 3:1; (5) The bio-based material treated in step (3) is further immersed in an aqueous solution of amino compound and kept at 100~105℃ for 0.5-1 h. After the heat preservation is completed, the bio-based material is washed and dried to obtain a flame-retardant bio-based composite material in which PN flame retardant is constructed in situ in the bio-based material.

10. The application as described in claim 9, characterized in that, The bio-based materials include one or more of wood, bamboo, wood-bamboo derived plywood, or recombinant materials; The washing includes washing with deionized water 1-3 times, and the drying includes air drying at room temperature for 24-48 hours, followed by drying in an oven at 80-105℃ for 24-48 hours. The impregnation is a biomimetic breathing impregnation method, using an impregnation device. The impregnation process specifically includes: evacuating the impregnation device to below 0.2 MPa and maintaining it for 0.5-1 h; then using negative pressure to draw the impregnation solution into the impregnation device, pressurizing the impregnation device to 1.0~1.2 MPa, and maintaining it for 0.5-1.5 h.

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