Phosphate intumescent flame retardant, preparation method and application of phosphate intumescent flame retardant in preparation of large shaving board

Abstract

The invention belongs to the technical field of flame retardant materials, and particularly relates to a phosphate intumescent flame retardant, a preparation method and application of the phosphate intumescent flame retardant in large wood shavings. The preparation method comprises the following steps: S1, uniformly mixing water and ethanol to prepare an ethanol solution, adding organic amine into the ethanol solution, and stirring, so that the organic amine is completely dissolved in the ethanol solution to obtain a mixed solution; s2, adding ammonium polyphosphate into the mixed solution, and then stirring in a nitrogen atmosphere to enable the organic amine and the ammonium polyphosphate to react to obtain a mixture; and S3, after the reaction is completed, filtering the mixture, washing white particles with ethanol, then drying, and sieving with a 80-mesh sieve to obtain the phosphate intumescent flame retardant. The ternary integrated intumescent flame retardant is prepared from different organic amines and ammonium polyphosphate through simple cation replacement reaction. The problems that an ammonium polyphosphate flame retardant is low in flame retardant efficiency and poor in compatibility with an artificial board are solved, and the prepared flame retardant is good in flame retardant performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant materials, and particularly relates to a phosphate intumescent flame retardant, a preparation method thereof, and an application thereof in the preparation of large-size particleboard. Background Art

[0002] Wood and its composite materials are increasingly used as carbon storage materials in buildings around the world. Large-size particleboard is one of the main materials for wood structure buildings. However, the fire extinguishing process of building structures is caused by multiple factors and largely depends on the flame retardant properties of building materials. Therefore, how to prepare a flame retardant with high flame retardant efficiency has important value.

[0003] In terms of improving the flame retardant efficiency, nitrogen element is introduced into the phosphorus-based flame retardant to form a complete and continuous carbon layer in the wood carbon layer, thereby improving the flame retardant efficiency. The N element usually exists in the flame retardant system in the form of amine or ammonium ion. Compared with ammonium ion, the organic amine has a similar polarity to wood or adhesive and has greater application potential. Although phosphorus-containing and phosphorus-nitrogen flame retardants are relatively effective in improving flame retardant properties and have low toxicity, their application in wood-based materials still faces some challenges. For example, the flame retardant efficiency of ammonium polyphosphate is low, ammonium polyphosphate causes great damage to the mechanical properties of wood-based panels, and the raw materials used in the single-component intumescent flame retardant prepared from multiple raw materials are toxic such as phosphorus oxychloride, the process is not green, and involves the release of harmful gases. Therefore, we propose a phosphate intumescent flame retardant, a preparation method thereof, and an application thereof in large-size particles. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention can be achieved by the following technical solutions:

[0005] A preparation method of a phosphate intumescent flame retardant, the preparation method comprising the following steps:

[0006] S1. Mix water and ethanol evenly to prepare an ethanol solution, add an organic amine to the ethanol solution and stir to completely dissolve the organic amine in the ethanol solution to obtain a mixed solution;

[0007] S2. Add ammonium polyphosphate to the mixed solution, and then stir in a nitrogen atmosphere to react the organic amine and ammonium polyphosphate to obtain a mixture;

[0008] S3. After the reaction is completed, filter the mixture, wash the white particles with ethanol, then dry and pass through an 80-mesh sieve to obtain the phosphate intumescent flame retardant.

[0009] Further, in step S1, the volume ratio of water to ethanol in the prepared ethanol solution is 600:36, and in step S2, when preparing the mixture, the mass ratio of the organic amine to ammonium polyphosphate is 86:100.

[0010] Furthermore, the organic amine is one or more of ethylenediamine, polyethyleneimine, piperazine, and 4,4'-diaminodiphenylmethane.

[0011] Furthermore, the reaction conditions in step S2 are as follows: the temperature is 90 - 100 °C, and the reaction time is 4 - 5 hours.

[0012] A kind of phosphate intumescent flame retardant is prepared by the preparation method of the above-mentioned phosphate intumescent flame retardant.

[0013] The above-mentioned phosphate intumescent flame retardant is applied to the preparation of large-size particleboards.

[0014] Furthermore, the specific steps of using the phosphate intumescent flame retardant to prepare large-size particleboards are as follows:

[0015] A1. Put the large-size wood shavings into a stirring barrel and spray with water; then add the phosphate intumescent flame retardant powder and spray water again, and then stir to obtain large-size wood shavings coated with the phosphate intumescent flame retardant;

[0016] A2. Put the large-size wood shavings coated with the phosphate intumescent flame retardant into an oven for drying, and then store them naturally to obtain flame-retardant wood shavings;

[0017] A3. Put the flame-retardant wood shavings into a glue mixer, add PMDI equivalent to 4 wt% of the oven-dry wood mass, and stir to obtain mixed wood shavings;

[0018] A4. Put the mixed wood shavings into a mold to form a board blank, and place polytetrafluoroethylene release paper and an iron plate on the top and bottom of the board blank; after removing the mold, move the board blank to a hot press and process it under different pressures at 170 °C to obtain a large-size particleboard.

[0019] Furthermore, the spraying time of water twice in step A1 is 14 - 17 s each time.

[0020] Furthermore, the specific steps of processing under different pressures at 170 °C in step A4 are as follows: First, process at a pressure of 10 MPa for 1 minute, then reduce the pressure to 5 MPa and hold for 3 minutes, and then reduce it to 2 MPa and hold for 6 minutes; 4 replicates are prepared for each board; the target board density is 800 kg / m 3 , and the size is 350 mm × 350 mm × 8 mm.

[0021] Advantages of the present invention: The present invention forms a ternary integrated intumescent flame retardant by a simple cation exchange reaction between different organic amines and ammonium polyphosphate. It not only solves the problems of low flame retardancy efficiency of ammonium polyphosphate flame retardant and poor compatibility with wood-based panels, but also solves the drawback of toxic gas release during the preparation of ammonium polyphosphate flame retardant; the flame retardant prepared by the present invention has good flame retardant performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 Infrared spectrum data of each flame retardant powder in the present invention;

[0024] Figure 2 SEM-EDS and 1H NMR data of APP and APP-EDA particles in the present invention, used to confirm the particle structure and the distribution of C and P elements in the particles. a is APP particles and b is APP-EDA particles;

[0025] Figure 3 SEM-EDS and 1H NMR images of APP-PEI particles in the present invention, used to confirm the particle structure and the distribution of C and P elements in the particles;

[0026] Figure 4 SEM-EDS and 1H NMR images of APP-PAz particles in the present invention, used to confirm the particle structure and the distribution of C and P elements in the particles;

[0027] Figure 5 SEM-EDS and 1H NMR images of APP-MDA particles in the present invention, used to confirm the particle structure and the distribution of C and P elements in the particles. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with several embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] Preparation of Flame Retardant

[0030] Mix water and ethanol in a volume ratio of 600:36 and pour them into a 1L three-necked flask equipped with a stirrer and a reflux condenser. Then, add 86g of organic amine to the flask and stir until the organic amine is completely dissolved in the ethanol solution. Next, add 100g of APP. Set the reaction temperature at 90°C and stir for 4 hours under a nitrogen atmosphere. After the reaction is completed, filter the mixture, wash the white particles with ethanol 3 times, and then dry them overnight in an 80°C oven. The dried powder is screened through an 80-mesh sieve to obtain the flame-retardant powder APP-PAz.

[0031] Preparation of large-sized particleboard

[0032] Put the large-sized particles into a stirring barrel and spray water for 15 seconds. Then add 10wt% (based on the mass of oven-dry wood) of the flame-retardant powder, spray water again for 15 seconds, and stir for 1 minute. The treated large-sized particles are dried in an 80°C oven for 40 minutes, and then stored naturally for 5 days until the moisture content is stable. After the moisture is stable, put the flame-retardant particles into a glue mixer, add PMDI equivalent to 4wt% of the mass of oven-dry wood, and stir for 2 minutes. Then put the mixture into a mold to form a slab, and place polytetrafluoroethylene release paper and an iron plate on the top and bottom of the slab. After removing the mold, move the slab to a hot press and process it at different pressures of 170°C for 10 minutes. The processing procedure is as follows: first process at a pressure of 10MPa for 1 minute, then reduce the pressure to 5MPa and hold for 3 minutes, and then reduce it to 2MPa and hold for 6 minutes. Four replicates are prepared for each board. The target board density is 800kg / m 3 , with dimensions of 350mm×350mm×8mm.

[0033] Table 1 Formulation and name of flame-retardant large-sized particleboard

[0034]

[0035] * represents the mass ratio of the flame retardant to oven-dry large-sized particles

[0036] Performance characterization:

[0037] Physical properties of large-sized particleboard

[0038] Evaluate the physical and mechanical properties of the particleboard by conducting a series of tests on a universal testing machine (Instron 5966, USA) according to the EN 310-1993 standard, and measure parameters such as the 24-hour thickness swelling rate (24h TS), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB). The three-point bending specimens are tested 6 times repeatedly, and the 24h TS and IB specimens are tested 10 times repeatedly.

[0039] Combustion performance

[0040] The limiting oxygen index (LOI) value was measured according to the ISO 4589-2 standard using an oxygen index meter (HC-2C, Jiangning Analytical Instrument Factory, China). The sample size was 100×100×10 mm 3 , and 15 samples were tested and their average value was calculated. The cone calorimeter test was carried out according to the ISO 5660 standard on a cone calorimeter (CONE FTTi-Cone 0402, Fire Testing Technology Limited Co., Ltd, London, UK), and the heat flux was set at 50 kW / m 2 .

[0041] Structural analysis of flame retardant powders

[0042] The infrared spectra of each flame retardant powder are as Figure 1 shown. Compared with APP, the phosphate products with organic amine substituting APP have some common characteristic peaks. In the range of 3400-3030 cm -1 , it corresponds to the asymmetric stretching vibration of NH 4+ ; at 2917 cm -1 and 2850 cm -1 are the new peaks of -CH2-CH2- groups. Among them, NH 4+ comes from the ammonium ions in the APP structure, and the alkyl characteristic peaks -CH2-CH2- (2917 cm -1 , 2850 cm -1 ) belong to the organic amine structure. This indicates that the organic amine structure exists in the newly formed phosphate, but the organic amine does not completely replace the ammonium ions.

[0043] The unmodified APP particles show an irregular blocky or granular structure. Due to high polymerization, the crystal growth of APP is uneven during synthesis, resulting in a relatively rough particle surface with obvious undulations and fine textures. Some larger particles may show agglomeration, where multiple small particles stick together to form larger aggregates, and the shape of the aggregates is not obviously regular. The 1H NMR (using D2O as the test solvent) of APP and APP-EDA is as Figure 1 shown. For APP, only a peak appears near δ = 3.38, which is attributed to -NH 4+ -. The NH 3+ -CH2-CH2-NH 3+ proton peak appears at 3.40 ppm for APP-EDA, further indicating successful cation replacement. Due to the small steric hindrance of the short-chain EDA, it is easy to replace NH4 in APP. Compared with APP particles, the distribution of C elements on the surface of APP-EDA is improved, resulting in many cracks in APP-EDA particles, which may lead to a decrease in the cohesion of APP-EDA flame retardant particles.

[0044] The 1H NMR measurement results of APP-PEI are as follows Figure 2 shown

[0045] After peak fitting and calculation of the corresponding peak areas, the primary average ratio was obtained. The ratio of primary amines to secondary amines in the APP-PEI structure is 1.3. Based on the structure of PEI and the calculation of the corresponding areas of each fitted peak, the deduced structure of PEI-APP was obtained, as shown Figure 2 shown. The average ratio of the remaining primary amines to secondary amines in the PEI structure is 0.8, indicating a decrease in the content of primary amines, which proves the existence of a cation exchange reaction between PEI and APP. When APP and PEI undergo cation exchange, due to the high degree of polymerization and long molecular chain of PEI, after the PEI molecules form anchor points on the surface of APP, a network structure is formed between the PEI molecules. And due to the high flexibility of the PEI molecules, APP-PEI forms a smooth surface. This obvious change in the microscopic morphology can also prove the successful modification of APP by PEI

[0046] The 1H-NMR test results of APP-PAz are as follows Figure 3 shown

[0047] APP-PAz has peaks at δ = 3.38 and δ = 2.78. The peak at δ = 3.38 is the ammonium ion peak, and δ = 2.78 corresponds to the "CH2" of PA [], indicating that there is no residual piperazine in the APP-PAz flame retardant and a cation displacement reaction has occurred between piperazine and APP. The distribution density of C elements on the surface of APP-PAz increases. Compared with APP particles, there is no obvious change in the microscopic morphology of APP-PAz

[0048] The peak at δ = 4.68 ppm of APP-MDA is the peak of H2O or D2O. The doublet appearing at 6.6 - 6.8 ppm is the H connected to CH2 on the benzene ring, and the doublet appearing at 7.0 - 7.2 ppm is the H connected to NH3+ on the benzene ring. These results indicate that MDA has been successfully incorporated into APP. After modification with MDA, the C element is widely distributed on the surface of APP, and there are crystalline undulations on the surface of the flame retardant particles, which further indicates the successful preparation of APP-MDA

[0049] By means of ICP-AES microwave digestion method, the content of P element in each flame retardant was accurately determined. The results showed that the content of P element in the modified flame retardants all decreased. However, there were differences in the decreasing trends among the flame retardant particles, and this differential distribution was closely related to the molecular structure characteristics of the modifier. Among them, the decrease amplitude of APP-PEI was the largest, because the interaction between the long-chain PEI and APP was different from the short-chain substitution of other flame retardants. After the long-chain PEI was anchored on the surface of APP, it would capture more PEI molecules and form a network structure on the surface of APP. As a result, the proportion of PEI in APP-PEI increased and the content of P element decreased. The decrease amplitude of the P element content in APP-EDA was also relatively obvious, indicating that EDA with small steric hindrance was prone to cation substitution reaction with the ammonium ions in APP and could provide more C elements for APP-EDA phosphate. Both PAz and MDA had rigid structures, and compared with PEI and EDA, their substitution degree with APP was lower.

[0050] Table Phosphorus element content measured by microwave digestion method for each flame retardant

[0051]

[0052] 2. Pyrolysis characteristics of flame-retarded wood powder

[0053] Among various organic amine-modified flame retardants, organic amines with weak thermal stability combined with phosphates, resulting in an earlier initial pyrolysis temperature (T10%) of each flame retardant. Before 521 °C, the pyrolysis process of each flame retardant was relatively slow. The temperature range of 521 °C - 637 °C was the main pyrolysis stage. During this period, the mass loss of each phosphate flame retardant was between 23% and 49%. Thus, it can be seen that the pyrolysis process in this stage was mainly dominated by phosphates rather than organic amines. However, organic amines could still intervene in this pyrolysis process, resulting in differences in the weight loss rate among different flame retardants. Among these flame retardants, the T10% of APP-PAz was the lowest, yet its remaining mass after pyrolysis was the highest. This phenomenon indicated that the pyrolysis intermediate products of APP-PAz gradually tended to a stable state during the pyrolysis process, and its final pyrolysis condensed-phase products had the highest thermal stability. The thermal stability of the pyrolysis condensed-phase products of APP-EDA was much lower than that of APP, showing a cliff-like difference. This was because the small-molecule organic amine in APP-EDA overly damaged the original high-polymer morphological structure of APP, making it difficult to jointly form condensed-phase products with good performance with phosphates.

[0054] Table Thermogravimetric data of each flame-retarded powder from room temperature to 800 °C under nitrogen atmosphere

[0055]

[0056] Note: a and b represent the temperatures corresponding to the weight loss of 10 wt% and 50 wt% respectively, and c represents the final residual mass ratio.

[0057] The flame-retardant wood flour exhibits more excellent thermal stability performance compared to the PMDIB powder. This difference indicates that the phosphate flame retardant plays a key role in enhancing the thermal stability of wood flour. By comparing the theoretical pyrolysis residual mass fraction with the actual pyrolysis residual mass fraction, a preliminary analysis was conducted on whether a chemical reaction that helps to improve the thermal stability of wood flour occurred with the phosphate flame retardant and the efficiency of the reaction. The higher the Vs value, the better the effect of the flame retardant on improving the thermal stability of the PMDIB powder. All phosphate flame retardants can effectively improve the thermal stability of PMDIB. Among them, APP-PEI is the most prominent in enhancing the thermal stability of the powder, followed by APP-PAz. This phenomenon reveals that a more efficient reaction that is beneficial to the construction of the carbon layer occurred between the wood flour components and APP-PEI.

[0058] Example 1: 10APP-PAz

[0059] Mix water and ethanol at a volume ratio of 600:36 and pour them into a 1 L three-necked flask equipped with a stirrer and a reflux condenser. Then, add 86 g of piperazine (PAz) to the flask and stir until the organic amine is completely dissolved in the ethanol solution. Next, add 100 g of APP. Set the reaction temperature to 90 °C and stir for 4 hours under a nitrogen atmosphere. After the reaction is completed, filter the mixture, wash the white particles with ethanol 3 times, and then dry them overnight in an 80 °C oven. The dried powder is sieved through an 80-mesh sieve to obtain the flame-retardant powder APP-PAz.

[0060] Next, place large flakes of wood shavings into a stirring bucket and spray water for 15 seconds. Then add 10 wt% (based on the mass of oven-dry wood) of the flame-retardant powder, spray water again for 15 seconds, and stir for 1 minute. The treated large flakes of wood shavings are placed in an 80 °C oven and dried for 40 minutes, and then stored naturally for 5 days until the moisture content is stable. After the moisture is stable, place the flame-retardant wood shavings into a glue mixer, add PMDI equivalent to 4 wt% of the mass of oven-dry wood, and stir for 2 minutes. Then place the mixture into a mold to form a slab, with polytetrafluoroethylene release paper and an iron plate placed on the top and bottom of the slab. After removing the mold, move the slab to a hot press and process it at 170 °C under different pressures for 10 minutes. The processing is carried out in the following order: first process at a pressure of 10 MPa for 1 minute, then reduce the pressure to 5 MPa and hold for 3 minutes, and then reduce it to 2 MPa and hold for 6 minutes. Four replicates are prepared for each board. The target board density is 800 kg / m 3 , and the size is 350 mm × 350 mm × 8 mm.

[0061] Table 2 Flame Retardant Properties of 10APP-PAz

[0062]

[0063] * indicates the standard deviation

[0064] Table 3 Mechanical properties of 10APP-PAz

[0065]

[0066] * indicates the standard deviation

[0067] Conclusion: Compared with the large-sized particleboard without adding flame retardant particles, the flame retardant performance of 10APP-PAz is improved. The limiting oxygen index reaches 41.32%, with an increase of 54.12%. The average heat release rate is reduced by 43.29%, and the total smoke release is reduced by 29.85%. The mechanical properties are significantly reduced, but they meet the national usage standard requirements.

[0068] Example 2: 10APP-PEI

[0069] Mix water and ethanol at a volume ratio of 600:36 and pour them into a 1L three-necked flask equipped with a stirrer and a reflux condenser. Then, add 86 g of polyethyleneimine (PEI) to the flask and stir until the organic amine is completely dissolved in the ethanol solution. Next, add 100 g of APP. Set the reaction temperature at 90 °C and stir for 4 hours under a nitrogen atmosphere. After the reaction is completed, filter the mixture, wash the white particles with ethanol 3 times, and then dry them overnight in an 80 °C oven. The dried powder is sieved through an 80-mesh sieve to obtain the flame retardant powder APP-PEI.

[0070] Next, put the large-sized particles into a stirring bucket and spray water for 15 seconds. Then add 10 wt% (based on the mass of oven-dry wood) of the flame retardant powder, spray water again for 15 seconds, and stir for 1 minute. The treated large-sized particles are dried in an 80 °C oven for 40 minutes, and then stored naturally for 5 days until the moisture content is stable. After the moisture is stable, put the flame retardant particles into a glue mixer, add PMDI equivalent to 4 wt% of the mass of oven-dry wood, and stir for 2 minutes. Then put the mixture into a mold to form a slab, and place polytetrafluoroethylene release paper and an iron plate on the top and bottom of the slab. After removing the mold, move the slab to a hot press and process it at different pressures of 170 °C for 10 minutes. The processing is carried out in the following order: first process at a pressure of 10 MPa for 1 minute, then reduce the pressure to 5 MPa and hold for 3 minutes, and then reduce it to 2 MPa and hold for 6 minutes. Four replicates are prepared for each board. The target board density is 800 kg / m 3 , with dimensions of 350 mm × 350 mm × 8 mm.

[0071] Table 4 Flame retardant properties of 10APP-PEI

[0072]

[0073] * indicates the standard deviation

[0074] Table 5 Mechanical properties of 10APP-PEI

[0075]

[0076] * indicates the standard deviation

[0077] Conclusion:

[0078] For the large particleboard without adding flame retardant particles, the limiting oxygen index of 10APP-PEI reaches 38.27%, with an increase of 42.74%, the average heat release rate decreases by 31.30%, and the total smoke release decreases by 9.6%. From the analysis of the morphological characteristics of the particles, the long-chain molecules of PEI wrap around the outer layer of the particles, which is beneficial to improving the compatibility between the flame retardant particles and the substrate. The mechanical properties of the board decrease, but the overall gap with the large particleboard without adding flame retardant is small. Especially in terms of the modulus of rupture and internal bond strength, the mechanical properties of 10APP-PEI meet the national use standard requirements.

[0079] Example 3: 10APP-MDA

[0080] Mix water and ethanol in a volume ratio of 600:36 and pour them into a 1L three-necked flask equipped with a stirrer and a reflux condenser. Then, add 86 g of 4,4`-diaminodiphenylmethane (MDA) to the flask and stir until the organic amine is completely dissolved in the ethanol solution. Then add 100 g of APP. Set the reaction temperature at 90 °C and stir for 4 hours under a nitrogen atmosphere. After the reaction is completed, filter the mixture, wash the white particles with ethanol 3 times, and then dry them overnight in an 80 °C oven. The dried powder is sieved through an 80-mesh sieve to obtain the flame retardant powder APP-MDA.

[0081] Next, large flakes are placed into a stirring barrel and sprayed with water for 15 seconds. Then, a flame retardant powder of 10 wt% (based on the mass of oven-dry wood) is added, and water is sprayed again for 15 seconds, followed by stirring for 1 minute. The treated large flakes are dried in an 80 °C oven for 40 minutes and then stored naturally for 5 days until the moisture content is stable. After the moisture is stable, the flame-retardant flakes are placed into a glue mixer, and PMDI equivalent to 4 wt% of the mass of oven-dry wood is added, and stirred for 2 minutes. Then, the mixture is placed into a mold to form a slab, with polytetrafluoroethylene release paper and an iron plate placed on the top and bottom of the slab. After removing the mold, the slab is moved to a hot press and treated at different pressures of 170 °C for 10 minutes. The treatment process is carried out in the following order: first, treated at a pressure of 10 MPa for 1 minute, then the pressure is reduced to 5 MPa and maintained for 3 minutes, and then reduced to 2 MPa and maintained for 6 minutes. Four replicates are prepared for each board. The target board density is 800 kg / m 3 , with dimensions of 350 mm × 350 mm × 8 mm.

[0082] Table 6 Flame Retardant Properties of 10APP-MDA

[0083]

[0084] * indicates standard deviation

[0085] Table 7 Mechanical Properties of 10APP-MDA

[0086]

[0087] * indicates standard deviation

[0088] Conclusion:

[0089] For the large flake board without adding flame retardant particles, the limiting oxygen index of 10APP-MDA reaches 36.97%, with an increase of 37.90%, the average heat release rate decreases by 15.89%, but the total smoke release increases by 60.94%, indicating that the gas-phase products generated during the thermal decomposition of the added MDA are not conducive to flame retardancy; at the same time, the internal bond strength of 10APP-MDA decreases, indicating a decline in the gluing performance of the plywood, but the bending performance is not affected, and even the stiffness increases. The overall mechanical properties meet the requirements of national use standards.

[0090] Example 4: 10APP-EDA

[0091] Mix water and ethanol in a volume ratio of 600:36 and pour them into a 1L three-necked flask equipped with a stirrer and a reflux condenser. Then, add 86 g of ethylenediamine (EDA) to the flask and stir until the organic amine is completely dissolved in the ethanol solution. Next, add 100 g of APP. Set the reaction temperature at 90 °C and stir for 4 hours under a nitrogen atmosphere. After the reaction is completed, filter the mixture, wash the white particles with ethanol three times, and then dry them overnight in an 80 °C oven. The dried powder is screened through an 80-mesh sieve to obtain the flame-retardant powder APP-EDA.

[0092] Next, place the large flakes into a stirring barrel and spray water for 15 seconds. Then add 10 wt% (based on the dry wood mass) of the flame-retardant powder, spray water again for 15 seconds, and stir for 1 minute. The treated large flakes are dried in an 80 °C oven for 40 minutes and then stored naturally for 5 days until the moisture content is stable. After the moisture is stable, place the flame-retardant flakes into a glue mixer, add PMDI equivalent to 4 wt% of the dry wood mass, and stir for 2 minutes. Then put the mixture into a mold to form a slab, with polytetrafluoroethylene release paper and an iron plate placed on the top and bottom of the slab. After removing the mold, move the slab to a hot press and process it at 170 °C under different pressures for 10 minutes. The processing is carried out in the following order: first process at a pressure of 10 MPa for 1 minute, then reduce the pressure to 5 MPa and hold for 3 minutes, and then reduce it to 2 MPa and hold for 6 minutes. Four replicates are prepared for each board. The target board density is 800 kg / m 3 , with dimensions of 350 mm × 350 mm × 8 mm.

[0093] Table 8 Flame-retardant properties of 10APP-EDA

[0094]

[0095] * indicates standard deviation

[0096] Table 9 Mechanical properties of 10APP-EDA

[0097]

[0098] * indicates standard deviation

[0099] Conclusion:

[0100] For the large-flake particleboard without added flame-retardant particles, the limiting oxygen index of 10APP-EDA reaches 43.60%, with an increase of 62.63%, the average heat release rate decreases by 23.80%, and the total smoke release decreases by 21.26%; the mechanical properties decrease significantly, which may be related to the decrease in cohesion during the formation of the particles. However, the mechanical properties of the flame-retardant large-flake particleboard still meet the national use standard requirements.

[0101] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0102] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A preparation method of a phosphate intumescent flame retardant, characterized in that, The preparation method includes the following steps: S1. Mix water and ethanol evenly to prepare an ethanol solution. Add organic amine to the ethanol solution and stir until the organic amine is completely dissolved in the ethanol solution to obtain a mixed solution. S2. Add ammonium polyphosphate to the mixed solution, and then stir in a nitrogen atmosphere to react the organic amine with ammonium polyphosphate to obtain a mixture. S3. After the reaction is completed, filter the mixture, wash the white particles with ethanol, then dry and pass through an 80-mesh sieve to obtain a phosphate intumescent flame retardant.

2. The preparation method of a phosphate intumescent flame retardant according to claim 1, characterized in that, In step S1, the volume ratio of water to ethanol in the prepared ethanol solution is 600:

36. In step S2, when preparing the mixture, the mass ratio of the organic amine to ammonium polyphosphate is 86:

100.

3. The preparation method of a phosphate intumescent flame retardant according to claim 1, characterized in that, The organic amine is one or more of ethylenediamine, polyethyleneimine, piperazine, and 4,4'-diaminodiphenylmethane.

4. The preparation method of a phosphate intumescent flame retardant according to claim 1, characterized in that, The reaction conditions in step S2 are: temperature is 90 - 100 °C, and reaction time is 4 - 5 hours.

5. A phosphate intumescent flame retardant is prepared by the preparation method of a phosphate intumescent flame retardant according to any one of claims 1 - 4.

6. A phosphate intumescent flame retardant as claimed in claim 5 is applied to the preparation of large-sized particleboards.

7. The application according to claim 6, characterized in that, The specific steps for using the phosphate intumescent flame retardant to prepare large-sized particleboards are as follows: A1. Put large-sized wood particles into a stirring barrel and spray with water; then add the phosphate intumescent flame retardant powder and spray water again, and then stir to obtain large-sized wood particles coated with the phosphate intumescent flame retardant. A2. Put the large-sized wood particles coated with the phosphate intumescent flame retardant into an oven for drying, and then let it stand naturally to obtain flame-retardant wood particles. A3. Put the flame-retardant wood particles into a glue mixer, add PMDI equivalent to 4 wt% of the oven-dry wood mass, and stir to obtain mixed wood particles. A4. Put the mixed wood particles into a mold to form a slab, and place polytetrafluoroethylene release paper and an iron plate on the upper and lower sides of the slab. After removing the mold, move the slab to a hot press and process it under different pressures at 170 °C to obtain a large-sized particleboard.

8. The application according to claim 7, wherein In step A1, the spraying time of water twice is 14 - 17 s each time.

9. The application according to claim 7, wherein The specific steps of the treatment at 170 °C under different pressures in step A4 are as follows: First, treat at a pressure of 10 MPa for 1 minute, then reduce the pressure to 5 MPa and hold for 3 minutes, and then reduce it to 2 MPa and hold for 6 minutes; 4 replicates are prepared for each board; the target board density is 800 kg / m 3 , with dimensions of 350 mm × 350 mm × 8 mm.

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