A phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant and its preparation method and application

Abstract

The present invention belongs to the technical field of flame retardant materials, and specifically relates to a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and a preparation method and application thereof. The preparation method of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant of the present invention comprises the following steps: S1, mixing aluminum hydroxide and phosphoric acid to obtain a prepolymer; S2, adding a nitrogen-containing compound, and condensing the reaction to obtain the halogen-free intumescent flame retardant. The present invention uses phosphoric acid and aluminum hydroxide to undergo an acid-base neutralization reaction to generate aluminum dihydrogen phosphate, and then adds a nitrogen-containing compound for condensation reaction to obtain a halogen-free intumescent flame retardant. The prepared flame retardant is a high-efficiency halogen-free and environmentally friendly flame retardant that contains phosphorus, nitrogen, and aluminum at the same time, and has excellent heat resistance and excellent flame retardant synergy. The introduction of aluminum element increases the initial decomposition temperature of the flame retardant, and at the same time can promote the carbonization of the matrix, improve the flame retardant carbonization efficiency; improve the smoke suppression effect, and improve the flame retardant synergy of phosphorus, nitrogen, and aluminum.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant materials, and in particular relates to a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant and a preparation method and application thereof. Background Art

[0002] Since the 1990s, halogen-free, environmentally friendly flame retardants have become a research hotspot in the flame retardant field. Primarily used in chemically synthesized materials and natural polymers, they primarily prevent ignition and suppress the spread of flames. In particular, large-scale use of flammable materials such as plastics, rubber, textiles, and fibers poses a significant fire hazard. Treating these flammable materials with flame retardants can significantly reduce their fire hazard. Furthermore, while improving the flame retardant properties of materials, it is also necessary to minimize the toxic gases or smoke produced during combustion or decomposition. Halogen-free, environmentally friendly flame retardants pose less risk to human health and are more environmentally compatible, making them more in line with current flame retardant development trends.

[0003] With the development of flame retardants, people have higher requirements for the manufacturing cost, flame retardancy, and heat resistance of halogen-free and environmentally friendly flame retardants. However, existing halogen-free flame retardants generally have problems such as insufficient heat resistance, low initial thermal decomposition temperature (1% decomposition temperature ≤ 200°C), and the discharge of waste gas, wastewater, and waste residue during the production process, which causes significant environmental pollution. Summary of the Invention

[0004] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a method for preparing a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant. This method eliminates the discharge of three wastes during the preparation process, making it environmentally friendly. The resulting flame retardant contains phosphorus, nitrogen, and aluminum, and exhibits excellent heat resistance and synergistic flame retardancy.

[0005] The present invention also provides a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant prepared by the preparation method and application thereof.

[0006] In a first aspect of the present invention, a method for preparing a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is provided, comprising the following steps:

[0007] S1, mixing aluminum hydroxide and phosphoric acid to react to obtain a prepolymer;

[0008] S2, adding a nitrogen-containing compound and subjecting it to a condensation reaction to obtain the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant.

[0009] According to the first aspect of the present invention, there are at least the following beneficial effects:

[0010] The present invention utilizes phosphoric acid and aluminum hydroxide to undergo an acid-base neutralization reaction to generate aluminum dihydrogen phosphate (prepolymer), followed by a condensation reaction with a nitrogen-containing compound to produce a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant. The resulting flame retardant is a highly efficient, halogen-free, environmentally friendly flame retardant containing phosphorus, nitrogen, and aluminum, exhibiting excellent heat resistance and flame retardant synergy. The introduction of aluminum increases the initial decomposition temperature of the flame retardant, while also promoting carbonization of the matrix and increasing the flame retardant carbonization efficiency. This improves smoke suppression and enhances the flame retardant synergy of phosphorus, nitrogen, and aluminum.

[0011] Preferably, the reaction temperature of step S1 is 50-100° C., more preferably 60-95° C.; the reaction time is 1-4 h, more preferably 1-2.5 h.

[0012] Preferably, in step S1, the molar ratio of the aluminum hydroxide to the phosphoric acid is 1:1-5, more preferably 1:2-4; further preferably 1:2.5-3.8.

[0013] Preferably, the step S1 further comprises a solvent, and the solvent comprises water; the mass ratio of the solvent to the nitrogen-containing compound is 8 to 25:1, more preferably 10 to 23:1.

[0014] Preferably, after the reaction in step S1 is completed, the temperature is further lowered to 40-55° C., more preferably 45-50° C.; and then the nitrogen-containing compound is added.

[0015] When nitrogen-containing compounds are added at higher temperatures, the materials will form hydrogen bonds before they are fully and evenly mixed, consuming a large amount of solvent (such as water). This will lead to a sharp increase in the viscosity of the system, making it more difficult to disperse the materials within the system, affecting subsequent reactions or even preventing them from proceeding. Moreover, directly adding nitrogen-containing compounds at high temperatures requires more solvent, affecting production efficiency and generating more wastewater, which is more polluting to the environment. The present invention, which adds nitrogen-containing compounds after cooling, is more conducive to the dispersion of the materials and also to the integrity of the subsequent temperature-raising reaction.

[0016] Preferably, the temperature of the condensation reaction in step S2 is 60 to 140° C., more preferably 80 to 120° C.; the time of the condensation reaction is 1 to 7 hours, more preferably 2 to 6 hours.

[0017] Preferably, the nitrogen-containing compound in step S2 is a compound containing an amino group (-NH2) or an imino group (-NH-), specifically including at least one of piperazine, dicyandiamide, melamine, and urea. Compared to the prior art using ammonium dihydrogen phosphate as a nitrogen source, since the ammonium dihydrogen phosphate contains -NH4, there is no chemical reaction between it and aluminum dihydrogen phosphate. The resulting phosphorus-nitrogen-aluminum flame retardant is actually a mixture of ammonium dihydrogen phosphate and aluminum dihydrogen phosphate, which has poor heat resistance and an initial decomposition temperature of ≤200°C. The present invention uses a compound containing an amino group or imino group as a nitrogen source, which can undergo a condensation reaction with aluminum dihydrogen phosphate to obtain a flame retardant with a high decomposition temperature and excellent flame retardant properties.

[0018] Preferably, the molar ratio of the nitrogen-containing compound to the phosphoric acid is 1:1-4, more preferably 1:2-3.

[0019] Preferably, the method for preparing the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant further comprises cooling, centrifugation, washing, and drying steps. More preferably, the liquid produced after the centrifugation and washing can be used as a solvent for the next production.

[0020] Preferably, the drying temperature is 80 to 150° C., more preferably 100 to 130° C.; and the drying time is 1 to 5 hours, more preferably 2 to 3.5 hours.

[0021] Preferably, the preparation method of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant further includes a dehydration condensation treatment; specifically, after the reaction in step S2 is completed, the temperature is lowered to below 50°C, the material is centrifuged, washed, and dried to obtain a crude product, and then the temperature is increased to dehydrate and condense the crude product to obtain the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant.

[0022] Preferably, the dehydration condensation is carried out in an inert gas atmosphere or a vacuum environment, the temperature of the dehydration condensation is 230-300°C, more preferably 250-280°C, and the time is 1-8 hours, more preferably 2-6 hours. More preferably, the dehydration condensation process is carried out in a kneader.

[0023] Preferably, after the dehydration condensation, the process further comprises the following steps: placing the dehydration condensed material in a kneader, cooling the temperature to 40-50° C., discharging the material, and obtaining a finished product.

[0024] In a second aspect of the present invention, a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant prepared by the above preparation method is provided.

[0025] Preferably, the phosphorus content (mass percentage) of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is 10-20%, more preferably 15-20%, further preferably 16-16.5%; the phosphorus content (mass percentage) is 25-35%, more preferably 25-30%, further preferably 28-30%; the aluminum content (mass percentage) is 3-6%, more preferably 4-5%, further preferably 4.5-5%.

[0026] Preferably, the moisture content (mass percentage) of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is less than 1%, more preferably less than 0.5%, and further preferably less than 0.4%.

[0027] Preferably, the water solubility of the halogen-free intumescent flame retardant is less than 1 g / 100 mL H2O, more preferably less than 0.5 g / 100 mL H2O. The water solubility refers to the mass of the sample dissolved in 100 mL of water.

[0028] Preferably, the particle size D50 of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is less than 5 μm, and more preferably the particle size D50 is 3.9 to 4.3 μm.

[0029] Preferably, the temperature of 1% thermal weight loss of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is greater than 300°C, and more preferably, the temperature of 1% thermal weight loss is greater than or equal to 315°C.

[0030] Preferably, the pH value of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant is 5 to 7, more preferably 5 to 6, and further preferably 5 to 5.5.

[0031] The third aspect of the present invention is the use of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant in the preparation of flame retardant materials.

[0032] Preferably, the flame retardant material includes at least one of nylon, polypropylene, fire retardant coating, rubber, paper, wood, fabric, and fiber.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] 1. The present invention uses phosphoric acid and aluminum hydroxide to undergo an acid-base neutralization reaction to generate aluminum dihydrogen phosphate; then a nitrogen-containing compound is added to undergo a condensation reaction to obtain a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant with excellent heat resistance and flame retardancy; and the addition of aluminum can improve the heat resistance of the flame retardant, promote carbonization of the matrix, and increase the carbonization rate; improve the smoke suppression effect, and promote the synergistic flame retardancy of phosphorus, nitrogen, and aluminum.

[0035] 2. The preparation method of the present invention is simple, and the production process does not discharge three wastes (waste gas, waste water, and waste residue), which is environmentally friendly.

[0036] 3. The phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant of the present invention can be used to prepare flame-retardant materials and has a wide range of applications, such as in the flame retardant fields of nylon, polypropylene, high-grade fire-retardant coatings, rubber, paper, wood, fabrics, fibers, etc. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0038] Unless otherwise specified, the raw materials used in the following examples can be obtained from conventional commercial sources; the processes used, unless otherwise specified, are conventional processes in the art; and the operating temperatures used, unless otherwise specified, are room temperature (20±5°C).

[0039] Example 1

[0040] This example prepares a high-efficiency phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and the specific process is as follows:

[0041] 18 kg (230.8 mol) of aluminum hydroxide, 85 kg (867.3 mol) of phosphoric acid, and 500 kg of solvent water were added to a 1.0 m 3 The mixture was placed in a reactor, stirred, and allowed to react at 60°C for 1 hour. The reactor temperature was then lowered to 45°C, and 37.35 kg (433.6 mol) of piperazine was slowly added and dispersed evenly. Heating was initiated, and the reactor temperature was rapidly raised to 80°C, where it was maintained for 2 hours. After the reaction, the reactor temperature was lowered to below 50°C, and the contents were centrifuged and washed. The centrifugation and washing liquid was stored in the reactor as solvent for the next batch. The centrifuged material was dried in a 100°C oven for 2 hours to obtain a crude product. This crude product was transferred to an electric kneader and dehydrated and condensed at 250°C under a nitrogen atmosphere for 2 hours. The kneader temperature was then slowly lowered to 50°C and the product was discharged to obtain the finished product. The results of the whiteness, phosphorus content, nitrogen content, aluminum content, moisture content, pH value, water solubility, particle size D50, and 1% heat loss of the finished product are shown in Table 1.

[0042] Example 2

[0043] This example prepares a high-efficiency phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and the specific process is as follows:

[0044] 20kg (256.4mol) aluminum hydroxide, 90kg (918.4mol) phosphoric acid, and 550kg solvent water were added to a 1.0m 3 The mixture was placed in a reactor, stirred, and allowed to react at 70°C for 1.5 hours. The reactor temperature was then lowered to 50°C, and 38.61 kg (459.2 mol) of dicyandiamide was slowly added and dispersed evenly. Heating was initiated, and the reactor temperature was rapidly raised to 80°C, where it was maintained for 3 hours. After the reaction, the reactor temperature was lowered to below 50°C, and the contents were centrifuged and washed. The centrifugation and washing liquid was stored in the reactor as solvent for the next batch. The centrifuged contents were oven-dried at 110°C for 3 hours to obtain a crude product. This crude product was transferred to an electric kneader and dehydrated and condensed at 260°C under a nitrogen atmosphere for 2 hours. The kneader contents were then slowly cooled to 50°C and discharged to obtain the finished product. The results of the whiteness, phosphorus content, nitrogen content, aluminum content, moisture content, pH value, water solubility, particle size D50, and 1% heat loss of the finished product are shown in Table 1.

[0045] Example 3

[0046] This example prepares a high-efficiency phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and the specific process is as follows:

[0047] 25kg (320.5mol) aluminum hydroxide, 90kg (918.4mol) phosphoric acid, and 600kg solvent water were added to a 1.0m 3 The reaction kettle was stirred and allowed to react at 80°C for 2.0 hours. The temperature of the reactor contents was then lowered to 50°C, and 57.9 kg (459.0 mol) of melamine was slowly added and dispersed evenly. Heating was initiated, and the reactor temperature was rapidly raised to 90°C, where the reaction was maintained for 4 hours. After the reaction, the contents were cooled to below 50°C, and the contents were centrifuged and washed. The centrifugation and washing liquid was stored in the reactor as solvent for the next batch. The centrifuged contents were dried in a 120°C oven for 3.5 hours to obtain a crude product. This crude product was transferred to an electric kneader and dehydrated and condensed at 270°C under a nitrogen atmosphere for 4 hours. The contents of the kneader were then slowly cooled to 50°C and discharged to obtain the finished product. The results of the whiteness, phosphorus content, nitrogen content, aluminum content, moisture content, pH value, water solubility, particle size D50, and 1% heat loss of the finished product are shown in Table 1.

[0048] Example 4

[0049] This example prepares a high-efficiency phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and the specific process is as follows:

[0050] 27 kg (356.2 mol) of aluminum hydroxide, 90 kg (918.4 mol) of phosphoric acid, and 620 kg of solvent water were added to a 1.0 m 3 The mixture was placed in a reactor, stirred, and allowed to react at 95°C for 2.5 hours. The reactor temperature was then lowered to 50°C, and 38.6 kg (306.0 mol) of melamine was slowly added and dispersed evenly. Heating was initiated, and the reactor temperature was rapidly raised to 100°C, where it was maintained for 6 hours. After the reaction, the reactor temperature was lowered to below 50°C, and the contents were centrifuged and washed. The centrifugation and washing liquid was stored in the reactor as solvent for the next batch. The centrifuged material was oven-dried at 130°C for 3.5 hours to obtain a crude product. This crude product was transferred to an electric kneader and dehydrated and condensed at 275°C under a nitrogen atmosphere for 5 hours. The kneader contents were then slowly cooled to 50°C and discharged to obtain the finished product. The results of the whiteness, phosphorus content, nitrogen content, aluminum content, moisture content, pH value, water solubility, particle size D50, and 1% heat loss of the finished product are shown in Table 1.

[0051] Example 5

[0052] This example prepares a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, and the specific process is as follows:

[0053] 30kg (384.6mol) aluminum hydroxide, 100kg (1020.4mol) phosphoric acid, and 680kg solvent water were added to a 1.0m 3 The mixture was stirred in a reactor and allowed to react at 100°C for 3 hours. The reactor temperature was then lowered to 50°C, and 30.6 kg (509.4 mol) of urea was slowly added and dispersed evenly. Heating was initiated, and the reactor temperature was rapidly raised to 120°C, where it was maintained for 6 hours. After the reaction, the reactor temperature was lowered to below 50°C, and the contents were centrifuged and washed. The centrifugation and washing liquid was stored in the reactor as solvent for the next batch. The centrifuged material was oven-dried at 150°C for 4 hours to obtain a crude product. This crude product was transferred to an electric kneader and dehydrated and condensed at 280°C under vacuum for 6 hours. The kneader contents were then slowly cooled to 50°C and discharged to obtain the finished product. The results of the whiteness, phosphorus content, nitrogen content, aluminum content, moisture content, pH value, water solubility, particle size D50, and 1% heat loss of the finished product are shown in Table 1.

[0054] Test example

[0055] This test example tests the performance of the flame retardant prepared in the example.

[0056] Test method for phosphorus content:

[0057] In an acidic medium, phosphate reacts with sodium molybdate and quinoline to form a quinoline phosphomolybdate precipitate. After filtration, drying, and weighing, the phosphorus content of the sample is calculated. Specifically, weigh 0.2g of the sample (accurate to 0.0002g) using an analytical balance. Weigh the sample with a small amount of pure water. Slowly add 3mL of a 1:1 nitric acid-sulfuric acid mixture and heat over low heat until white smoke appears. Rinse the sides of the flask with approximately 20mL of pure water and bring to a slight boil. After cooling, add 10mL of a 1:1 nitric acid solution, dilute 100mL with water, preheat to near boiling, add 170mL of quinomolybdate solution, cover the flask with a watch glass, and continue heating to boiling for 1 minute. During cooling, rotate the flask 3-4 times. Filter by decantation using a glass fritted funnel that has been previously dried to constant weight at 160°C ± 5°C. Wash the precipitate in the flask 3-4 times with 20mL of water each time. Finally, transfer the entire precipitate to a glass fritted funnel and wash it 3-4 times with water. Place the glass frit funnel and the precipitate in a dry place at 160°C ± 5°C for 45 minutes. Remove and cool in a desiccator. Weigh the precipitate. Perform a blank test at the same time. Calculate the phosphorus content using Formula I:

[0058]

[0059] In the formula: m1 is the mass of quinoline phosphomolybdate precipitate generated in the test solution, in grams (g); m2 is the mass of quinoline phosphomolybdate precipitate generated in the blank test solution, in grams (g); m is the numerical value of the mass of the sample, in grams (g); 0.01400 is the coefficient for converting quinoline phosphomolybdate to phosphorus; the arithmetic mean of the parallel determination results is taken as the determination result, and the absolute value of the two parallel determination results shall not exceed 0.2%.

[0060] Nitrogen content test method:

[0061] Weigh 1g of sample to the nearest 0.0002g. Place in a 250mL beaker, moisten with calcined water, add 10mL of sulfuric acid solution, cover with a watch glass, and heat until white sulfur trioxide smoke appears. Cool to room temperature. Carefully dilute with water and transfer the entire amount to a 1000mL round-bottom flask (with a small amount of explosion-proof zeolite). Add water to approximately 350mL. Use a pipette to transfer 50.0mL of sulfuric acid solution (0.5mol / L) to an absorption flask and add 4-5 drops of methyl red-methylene blue ethanol solution (indicator). Fill with water to a level slightly above the end of the double-Ryukyu tube receiver (approximately 120mL) to prevent ammonia loss. Connect the receiver to the lower end of the straight condenser. Connect the distilling flask and add 25mL of sodium hydroxide solution (400g / L) through the dropping funnel. When the solution is almost gone, add 20-30mL of water to flush the funnel. Close the stopcock when 3-5mL of water remain. Turn on the cooling water and begin heating. When at least 150 mL of distillate is collected, move the receiver slightly away, place the lower end of the condenser against the wall of the receiver, and test the distillate at the lower end of the condenser with pH test paper. After confirming that the ammonia has been completely evaporated, remove the heat source. Titrate the solution with a standard sodium hydroxide solution (0.5 mol / L) until the indicator turns gray-green. At the same time as the determination, perform a blank test using the same reagent but without adding the sample. The nitrogen content is expressed as the mass fraction (W2) of nitrogen (N), and the value is expressed in %, and is calculated according to the following formula II:

[0062]

[0063] Wherein, c is the accurate value of the concentration of the sodium hydroxide standard titration solution, in moles per liter (mol / L); V0 is the volume of the sodium hydroxide standard titration solution consumed in the titration of the blank test solution, in milliliters (mL); V1 is the volume of the sodium hydroxide standard titration solution consumed in the titration of the sample solution, in milliliters (mL); M is the molar mass of nitrogen (N), in grams per mole (g / mol) (M=14.01), and m is the mass of the sample, (g).

[0064] Test method for aluminum content:

[0065] Weigh approximately 5g of solid sample or approximately 13g of liquid sample to the nearest 0.0001g and place in a 250mL beaker. Add 100mL of water and 2mL of hydrochloric acid solution. Heat to dissolve and boil for 5 minutes (filter if necessary). After cooling, transfer the entire amount to a 500mL volumetric flask, dilute to the mark with water, and shake well. Simultaneously prepare a blank test solution.

[0066] Use a pipette to transfer 20 mL of the test solution into a 250 mL conical flask. Use a pipette to add 20 mL of EDTA (ethylenediaminetetraacetic acid) solution. Boil for 1 minute. After cooling, add 5 mL of sodium acetate solution and 2 drops of xylenol orange indicator solution. Titrate with zinc chloride standard solution until a light pink color appears. Simultaneously perform a blank test. The aluminum oxide content is expressed as mass fraction ω, expressed in %, and calculated according to the following formula III:

[0067]

[0068] In the formula: c is the exact value of the concentration of the zinc chloride standard titrant, in moles per liter (mol / L); V0 is the volume of the zinc chloride standard titrant consumed in the titration of the blank test solution, in milliliters (mL); V is the volume of the zinc chloride standard titrant consumed in the titration of the test solution, in milliliters (mL); m is the mass of the sample, in grams (g); M1 is the molar mass of aluminum oxide (Al2O3), in grams per mole (g / mol) (M1=101.96); M2 is the molar mass of iron (Fe), in grams per mole (g / mol) (M2=55.85); ω2 is the iron (Fe) content measured in the sample, in %. The arithmetic mean of the parallel determination results is taken as the measurement result, and the absolute difference between the two parallel determination results is not greater than 0.20%.

[0069] Water solubility test method:

[0070] Prepare a solution with a sample:pure water ratio of 1:10. Stir, centrifuge, and filter. Place 10 mL of the supernatant in a beaker and dry. The mass fraction of water-soluble matter is W%, expressed in grams per 100 mL (g / 100 mL), and calculated using Formula IV:

[0071] W%= (m1-m2) / n1×100% Formula IV

[0072] Where: n1 is the volume of the supernatant transferred to the beaker, in milliliters (mL); m is the total mass of the aqueous solution and the beaker, in grams (g); m2 is the mass of the beaker, in grams (g).

[0073] The pH test method is to weigh 5g of sample (accurate to 0.02g), dissolve it in 45mL of pure water, let it stand for 1min, and then test it with a pH meter. The test results are shown in Table 1.

[0074] The whiteness was tested using a WSB-3 digital whiteness meter. The test results are shown in Table 1.

[0075] The particle size D50 was measured using a MS2000 laser particle size analyzer. The test results are shown in Table 1.

[0076] The 1% thermal weight loss was tested using a Q500 TGA instrument. The test results are shown in Table 1.

[0077] Table 1 Properties of phosphorus-nitrogen-aluminum halogen-free intumescent flame retardants prepared in Examples 1 to 5

[0078]

[0079]

[0080] As can be seen from Table 1, the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant produced by the present invention has the characteristics of uniform particle size, good water solubility, good heat resistance and high content of effective flame retardant elements.

[0081] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant, characterized in that: The steps include: S1, mixing aluminum hydroxide and phosphoric acid, and reacting them at 95° C. for 2.5 hours to obtain a prepolymer; the molar ratio of the aluminum hydroxide to the phosphoric acid is 356.2:918.4; S2, adding a nitrogen-containing compound and carrying out a condensation reaction at 100° C. for 6 hours to obtain the halogen-free intumescent flame retardant; The molar ratio of the nitrogen-containing compound to the phosphoric acid is 1:3; The nitrogen-containing compound is melamine; The preparation method of the phosphorus-nitrogen-aluminum halogen-free intumescent flame retardant also includes a dehydration condensation treatment; specifically, after the reaction in step S2 is completed, the temperature is lowered to below 50°C, the material is centrifuged, washed, and dried to obtain a crude product, and then the temperature is increased to dehydrate and condense the crude product to obtain the flame retardant; the dehydration condensation temperature is 275°C and the time is 5 hours.

Images