Ammonium polyphosphate-based flame retardant as well as preparation method and application thereof

Abstract

The invention provides an ammonium polyphosphate-based flame retardant as well as a preparation method and application thereof, and belongs to the technical field of flame retardants. The preparation method comprises the following steps: by taking an amino benzimidazole compound, ammonium polyphosphate and transition metal salt as reactants, modifying ammonium polyphosphate with amino benzimidazole, carrying out ion exchange reaction to generate active sites, and complexing transition metal ions on the basis of the modified ammonium polyphosphate to obtain the modified ammonium polyphosphate. The ammonium polyphosphate-based flame retardant modified by the benzimidazole substances and the transition metal ions is obtained. The flame retardant can be applied to materials such as soft polyurethane foam or fiber fabrics and the like through an adhesion effect, so that recycling is realized, and excellent flame-retardant and smoke-suppressing effects are realized at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardants, and in particular to an ammonium polyphosphate-based flame retardant and a preparation method and application thereof. Background Art

[0002] Fiber fabrics and soft polyurethane foams are indispensable materials in human life, but they are flammable. Once they come into contact with flames, they will burn rapidly, accompanied by the generation of a large amount of droplets and smoke, which seriously hinders the further application and development of fiber fabrics and soft polyurethane foams.

[0003] At present, various surface treatment strategies have been gradually used to prepare flame-retardant soft polyurethane foams or fiber fabrics. Surface treatment can position flame retardants on the surface of polymer materials without compromising their properties. Introducing flame retardant coatings on the surface is a simple and common method. However, flame retardants applied to coatings can usually only be used once, which inevitably leads to a waste of resources.

[0004] Among the common flame retardant systems, the intumescent flame retardant system has attracted much attention due to its green, high efficiency and low cost. Ammonium polyphosphate has been found to be an excellent intumescent flame retardant with the advantages of high flame retardant efficiency and low price. It can not only be used as a flame retardant alone, but also in conjunction with other flame retardants. The most common method is to use ammonium polyphosphate in conjunction with a carbon-forming agent to form an intumescent flame retardant system, and act as an acid source and gas source in the system. However, ammonium polyphosphate cannot be grafted onto the surface of soft polyurethane foam or fiber fabric through chemical reaction, and can only be loaded by coprecipitation, which also causes ammonium polyphosphate to fall off easily, resulting in low flame retardant efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide an ammonium polyphosphate-based flame retardant and a preparation method and application thereof. The ammonium polyphosphate-based flame retardant has excellent flame retardant properties and is recyclable.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an ammonium polyphosphate-based flame retardant, comprising the following steps:

[0008] The aminobenzimidazole compound, ammonium polyphosphate and a dispersing solvent are mixed and modified in a protective gas to obtain modified ammonium polyphosphate;

[0009] The modified ammonium polyphosphate, transition metal salt and alcohol solvent are mixed to carry out complex reaction to obtain an ammonium polyphosphate-based flame retardant;

[0010] The metal elements in the transition metal salt include one or more of cobalt, nickel and copper.

[0011] Preferably, the aminobenzimidazole compound includes 2-aminobenzimidazole, 4-aminobenzimidazole, 5-aminobenzimidazole, 6-aminobenzimidazole, 1,7-dimethyl-2-aminobenzimidazole or 2-(3-aminophenyl)-5-aminobenzimidazole; the mass ratio of the aminobenzimidazole compound to ammonium polyphosphate is 1:(2-6).

[0012] Preferably, the protective gas includes nitrogen, helium, argon or neon; the modification temperature is 70 to 95° C., and the modification time is 2 to 12 hours.

[0013] Preferably, the transition metal salt includes one or more of cobalt chloride, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel nitrate, nickel chloride, copper sulfate, copper chloride, copper nitrate and copper acetate.

[0014] Preferably, the molar ratio of the aminobenzimidazole compound to the metal element in the transition metal salt is 1:(0.5-1.2).

[0015] Preferably, the temperature of the complex reaction is room temperature, and the time is 6 to 24 hours.

[0016] The present invention provides an ammonium polyphosphate-based flame retardant prepared by the preparation method described in the above technical solution.

[0017] The present invention provides application of the ammonium polyphosphate-based flame retardant described in the above technical solution in soft polyurethane foam or fiber fabric.

[0018] Preferably, the mass ratio of the ammonium polyphosphate-based flame retardant to the soft polyurethane foam is 1 to 20:100; the mass ratio of the ammonium polyphosphate-based flame retardant to the fiber fabric is 1 to 20:100.

[0019] Preferably, after the ammonium polyphosphate-based flame retardant is applied to the soft polyurethane foam or fiber fabric, the ammonium polyphosphate-based flame retardant adhering to the surface of the soft polyurethane foam or fiber fabric is washed with water or alcohol, and then filtered and dried in sequence to obtain a recovered flame retardant.

[0020] The present invention provides a method for preparing an ammonium polyphosphate-based flame retardant. The present invention uses an aminobenzimidazole compound, ammonium polyphosphate and a transition metal salt as reactants, firstly modifies the ammonium polyphosphate with aminobenzimidazole, generates active sites through an ion exchange reaction, and then complexes transition metal ions such as cobalt ions or copper ions on the basis of the modified ammonium polyphosphate to obtain an ammonium polyphosphate-based flame retardant modified by benzimidazole substances and metal ions. The introduction of metal ions not only improves the smoke suppression performance of the flame retardant, but also the complexation of metal ions strengthens the ion aggregation effect, and at the same time gives the flame retardant adhesion in the mixed solution, so that it can firmly adhere to foam or fabric.

[0021] The ammonium polyphosphate-based flame retardant is added to polymers such as epoxy resin, thermoplastic polyurethane, polyurethane foam and cotton fabric to achieve excellent flame retardant effect. When applied to soft polyurethane foam or fiber fabric, since the ammonium polyphosphate-based flame retardant has the physical property of being insoluble in water and alcohol, it can be effectively recycled and reused by washing and filtering. When applied to soft polyurethane foam plastics, the flame retardant can not only provide an ideal flame retardant effect, but also be recycled and reused. When the recycled ammonium polyphosphate-based flame retardant is applied to thermoplastic polyurethane, the compatibility between the ammonium polyphosphate-based flame retardant and the matrix after metal ion surface modification is significantly improved, thereby achieving excellent flame retardant and smoke suppression effects.

[0022] The preparation method of the invention is simple, the reaction process is safe and stable, it can be recycled and reused, it complies with the sustainable development strategy, and is convenient for industrial production.

[0023] The ammonium polyphosphate-based flame retardant of the present invention uses aminobenzimidazole substances as carbon sources and ammonium polyphosphate as acid sources and gas sources to form an intumescent flame retardant system, which can be applied to most foams or fabrics (such as soft polyurethane foams or fiber fabrics) as a flame retardant coating to provide excellent flame retardant effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The ammonium polyphosphate-based flame retardant prepared in Example 1 and the scanning electron microscope images of ammonium polyphosphate; wherein (a1) and (a2) are scanning electron microscope images of ammonium polyphosphate; (b1) and (b2) are scanning electron microscope images of the ammonium polyphosphate-based flame retardant;

[0025] Figure 2 In the figure, (a) is a scanning electron microscope image of the raw material soft polyurethane foam in Example 2, (b) is a scanning electron microscope image of the soft polyurethane foam in Comparative Example 1, (c) is a scanning electron microscope image of the ammonium polyphosphate-based flame retardant loaded on the surface of the soft polyurethane foam skeleton in Example 2, (d) and (e) are the distribution of each element after the ammonium polyphosphate-based flame retardant is loaded on the surface of the soft polyurethane foam frame in Example 2;

[0026] Figure 3 Cone calorimeter test results for flexible polyurethane foam and its composites;

[0027] Figure 4 Cone calorimeter test results for thermoplastic polyurethane and its composites;

[0028] Figure 5 The recovery rates of the ammonium polyphosphate-based flame retardant in the flexible polyurethane foam containing a flame retardant coating in Example 2 were measured using water and ethanol, respectively. DETAILED DESCRIPTION

[0029] In the present invention, unless otherwise specified, the raw materials or reagents used are commercially available products well known in the art.

[0030] The present invention provides a method for preparing an ammonium polyphosphate-based flame retardant, comprising the following steps:

[0031] The aminobenzimidazole compound, ammonium polyphosphate and a dispersing solvent are mixed and modified in a protective gas to obtain modified ammonium polyphosphate;

[0032] The modified ammonium polyphosphate, transition metal salt and alcohol solvent are mixed to carry out complex reaction to obtain an ammonium polyphosphate-based flame retardant;

[0033] The metal elements in the transition metal salt include one or more of cobalt, nickel and copper.

[0034] In the present invention, the aminobenzimidazole compound preferably includes 2-aminobenzimidazole, 4-aminobenzimidazole, 5-aminobenzimidazole, 6-aminobenzimidazole, 1,7-dimethyl-2-aminobenzimidazole or 2-(3-aminophenyl)-5-aminobenzimidazole; the mass ratio of the aminobenzimidazole compound to ammonium polyphosphate is preferably 1:(2-2.5), more preferably 1:(2-2.5).

[0035] The present invention has no particular limitation on the order of mixing the aminobenzimidazole compound, ammonium polyphosphate and the dispersing solvent. The materials can be mixed uniformly according to a process well known in the art.

[0036] In the present invention, the dispersion solvent is preferably a mixture of water and alcohol; the alcohol preferably includes methanol, ethanol or propanol; the volume ratio of water to alcohol is preferably 4 to 20:1, more preferably 10 to 20:1. The present invention has no special limitation on the amount of the dispersion solvent, which can be adjusted according to actual needs to ensure uniform dispersion of the material.

[0037] In the present invention, the protective gas preferably includes nitrogen, helium, argon or neon.

[0038] In the present invention, the modification temperature is preferably 70-95°C, more preferably 80-90°C, and the modification time is preferably 2-12 hours, more preferably 4-6 hours. In the modification process, the amino group (NH2) of benzimidazole partially replaces the ammonium ion (NH4 + ), generating O=PO-NH3 + The nitrogen in benzimidazole and the oxygen in polyphosphoric acid provide active sites for the coordination reaction of transition metal ions.

[0039] After the modification is completed, the present invention preferably cools the obtained suspension to room temperature, adds a transition metal salt solution, and performs a complex reaction; the transition metal salt solution is formed by mixing a transition metal salt with an alcohol solvent. In the present invention, the alcohol solvent preferably includes methanol, ethanol or propanol. The present invention has no special limitation on the concentration of the transition metal salt solution, and the concentration can be adjusted according to the needs to ensure the required molar ratio of the metal elements.

[0040] In the present invention, the transition metal salt preferably includes one or more of cobalt chloride, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel nitrate, nickel chloride, copper sulfate, copper chloride, copper nitrate and copper acetate. When the transition metal salt is two or more of the above, the present invention has no special limitation on the ratio of different types of transition metal salts, and any ratio can be mixed.

[0041] In the present invention, the molar ratio of the aminobenzimidazole compound to the metal element in the transition metal salt is preferably 1:(0.5-1.2), more preferably 1:(0.57-1.07), and further preferably 1:0.9.

[0042] In the present invention, the temperature of the complex reaction is preferably room temperature, and the time is preferably 6 to 24 hours, more preferably 12 to 18 hours; during the complex reaction, the O=PO-NH4 of the modified ammonium polyphosphate + Coordinates with metal ions and becomes O=PO-NH3 + , and finally form a metal complex modified ammonium polyphosphate based flame retardant.

[0043] After the complexation reaction is completed, the product is filtered, washed with distilled water, methanol and ethanol in turn, dried and ground to obtain an ammonium polyphosphate-based flame retardant. The present invention has no special restrictions on the washing, drying and grinding, and can be carried out according to processes well known in the art.

[0044] The present invention provides an ammonium polyphosphate-based flame retardant prepared by the preparation method described in the above technical solution.

[0045] The present invention provides application of the ammonium polyphosphate-based flame retardant described in the above technical solution in soft polyurethane foam or fiber fabric.

[0046] In the present invention, the mass ratio of the ammonium polyphosphate-based flame retardant to the soft polyurethane foam is preferably 1-20:100, more preferably 10:100; the mass ratio of the ammonium polyphosphate-based flame retardant to the fiber fabric is preferably 1-20:100, more preferably 10:100.

[0047] In the present invention, the ammonium polyphosphate-based flame retardant is preferably applied to the soft polyurethane foam or fiber fabric by an impregnation method; the impregnation method preferably includes dispersing the ammonium polyphosphate-based flame retardant in water to obtain a flame retardant aqueous dispersion, immersing the soft polyurethane foam or fiber fabric in the aqueous dispersion, and uniformly adhering the flame retardant to the soft polyurethane foam or fiber fabric under stirring conditions. When the aqueous dispersion is completely clear and transparent, the soft polyurethane foam or fiber fabric is taken out and dried.

[0048] As another embodiment of the present invention, the present invention sequentially immerses the soft polyurethane foam or fiber fabric into a mixed suspension of an aminobenzimidazole compound, ammonium polyphosphate and a dispersing solvent, reacts under the above-mentioned modified conditions, and then immerses the mixture in an alcohol solvent of a transition metal salt to carry out a complexation reaction under the above-mentioned conditions, thereby achieving direct adhesion of the flame retardant on the soft polyurethane foam or fiber fabric.

[0049] After the ammonium polyphosphate-based flame retardant of the present invention is applied to soft polyurethane foam or fiber fabric, the ammonium polyphosphate-based flame retardant adhering to the surface of the soft polyurethane foam or fiber fabric is washed with water or alcohol (preferably ethanol), and then filtered and dried in sequence to obtain a recovered flame retardant.

[0050] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but it should be noted that these embodiments should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] 50 g (0.33 mol) of ammonium polyphosphate and 25 g (0.188 mol) of 5-aminobenzimidazole were added to a mixed liquid of 400 mL of deionized water and 20 mL of methanol and stirred for 10 min to form a suspension, the suspension was placed in a helium atmosphere, heated to 80° C. for reaction for 6 h, and then cooled to room temperature, 14 g (0.108 mol) of anhydrous cobalt chloride was dissolved in 150 mL of ethanol, and the obtained metal salt solution was added to the suspension, stirred at room temperature for 18 h, filtered, washed with deionized water, methanol and ethanol in turn, dried and ground to obtain an ammonium polyphosphate-based flame retardant;

[0053] The 3 g ammonium polyphosphate-based flame retardant is dispersed in 150 mL water to obtain a flame retardant aqueous dispersion, and the soft polyurethane foam is immersed in the flame retardant aqueous dispersion and mechanically stirred for 12 hours. Under stirring conditions, the flame retardant is uniformly adhered to the soft polyurethane foam. After the stirring is completed, the soft polyurethane foam is dried to obtain the adhered polyurethane.

[0054] Example 2

[0055] 20 g (0.13 mol) of ammonium polyphosphate was dispersed in 200 mL of a mixed solution of deionized water and ethanol (the volume ratio of water to ethanol was 4:1), and stirred at a speed of 200 r / min for 10 min to obtain an ammonium polyphosphate dispersion; then 8 g (0.06 mol) of 2-aminobenzimidazole was added to the ammonium polyphosphate dispersion, and 10 g of soft polyurethane foam was completely immersed in the mixed liquid, and reacted for 4 h under a nitrogen atmosphere at 90 ° C; after the reaction was completed, the foam was taken out and completely immersed in an ethanol solution containing 16 g (0.064 mol) of cobalt chloride hexahydrate, and reacted at room temperature for 24 h. After the reaction was completed, the foam was taken out and placed in an oven at 80 ° C for drying to obtain a soft polyurethane foam containing a flame retardant coating, which was recorded as PU@PN@Co.

[0056] Example 3

[0057] like Figure 5 As shown, the soft polyurethane foam containing the flame retardant coating prepared in Example 2 is evenly divided into two parts, respectively put into ethanol and deionized water, and washed by repeated pressing, and then filtered, dried and ground in sequence to obtain the recovered ammonium polyphosphate-based flame retardant.

[0058] Calculations show that the recovery rates of ethanol and deionized water for ammonium polyphosphate-based flame retardant are 94.1% and 79.4%, respectively.

[0059] Three portions of 55g thermoplastic polyurethane particles were placed in a mixing torque rheometer and melted at 175°C, and 2wt% (1.1g) of ammonium polyphosphate and 2wt% (1.1g) of the above-mentioned recycled ammonium polyphosphate-based flame retardant were added and mixed evenly for 10 minutes, and the mixture was transferred to a flat vulcanizer and pressed at 180°C to obtain 100mm*100mm*5mm thermoplastic polyurethane composite materials, which were recorded as TPU / 2APP and TPU / 2P-N@Co. The remaining portion was used as a TPU pure sample control group, recorded as TPU / 0.

[0060] Comparative Example 1

[0061] The only difference from Example 2 is that 2-aminobenzimidazole is not added and the foam is not immersed in the ethanol solution of cobalt chloride hexahydrate, and a soft polyurethane composite foam loaded with only ammonium polyphosphate is obtained, which is recorded as PU@APP.

[0062] Comparative Example 2

[0063] The only difference from Example 2 is that the foam was not immersed in the ethanol solution of cobalt chloride hexahydrate, and a soft polyurethane composite foam loaded with 2-aminobenzimidazole-modified ammonium polyphosphate was obtained, which was recorded as PU@PN.

[0064] Characterization and performance testing

[0065] 1) Figure 1 The scanning electron microscope images of the ammonium polyphosphate-based flame retardant and ammonium polyphosphate prepared in Example 1. Among them, (a1) and (a2) are scanning electron microscope images of ammonium polyphosphate, showing a block structure with a smooth surface. (b1) and (b2) are scanning electron microscope images of the ammonium polyphosphate-based flame retardant, and the morphology is significantly changed compared with ammonium polyphosphate, and the surface becomes rough and irregular, indicating that the introduction of the cobalt ion complex causes a change in the morphology.

[0066] 2) Figure 2 In the figure, (a) is the scanning electron microscope image of the raw material soft polyurethane foam in Example 2 at different magnifications, showing the smooth surface of the pure soft polyurethane sponge skeleton and its loose pore structure. (b) is the scanning electron microscope image of the surface of the soft polyurethane foam skeleton in Comparative Example 1 at different magnifications. It can be clearly found that a block structure similar to ammonium polyphosphate appears on the surface of the soft polyurethane sponge skeleton, confirming that ammonium polyphosphate is deposited on the soft polyurethane foam. (c) is the scanning electron microscope image of the surface of the soft polyurethane foam skeleton loaded with ammonium polyphosphate-based flame retardant in Example 2 at different magnifications. Adhesion causes more ammonium polyphosphate-based flame retardant to be loaded on the skeleton surface, causing more micron particles to appear on the skeleton surface, making it rougher. (d) and (e) are the distribution of each element after the ammonium polyphosphate-based flame retardant is loaded on the surface of the soft polyurethane foam frame in Example 2; from Figure 2 From the EDS of (e), we can see that only C, N, and O elements exist on the foam frame. On the contrary, P and Co appear on the film formed by the flame retardant between the frames. Figure 2 As can be seen in (d), the film formed by the flame retardant adheres to the surface of the film frame, so that C, N, O, P and Co elements appear on the foam frame at the same time.

[0067] 3) Combustion performance test was carried out using cone calorimeter, and the heat flux during the test was 35kW·m -2 , the sample size is 100mm*100mm*5mm, the results are shown in Figures 3-4 .

[0068] Figure 3 The cone calorimeter test results of soft polyurethane foam and its composite materials (PU represents pure soft polyurethane foam, PU@APP represents the soft polyurethane composite foam loaded with ammonium polyphosphate in comparative example 1, PU@PN represents the soft polyurethane composite foam loaded with 2-aminobenzimidazole-modified ammonium polyphosphate in comparative example 2, and PU@PN@Co represents the soft polyurethane composite foam loaded with ammonium polyphosphate-based flame retardant in Example 2); wherein, (a) is the instantaneous heat release rate, (b) is the total heat release, (c) is the instantaneous smoke release rate, and (d) is the total smoke release. Figure 3It can be seen from (a) that ammonium polyphosphate and ammonium polyphosphate-based flame retardant reduce the combustion intensity of soft polyurethane foam, and the ammonium polyphosphate-based flame retardant of the present invention has a better inhibitory effect on combustion intensity. (b) shows that the ammonium polyphosphate-based flame retardant of the present invention can better reduce the release of heat during the combustion of soft polyurethane foam than ammonium polyphosphate, and has better fire safety. (c) and (d) reflect the smoke release inhibitory effect of the ammonium polyphosphate-based flame retardant of the present invention on the combustion of soft polyurethane foam.

[0069] Figure 4 The cone calorimeter test results of thermoplastic polyurethane and its composite materials (TPU / 0 represents pure thermoplastic polyurethane, TPU / 2APP represents the thermoplastic polyurethane composite material containing 2wt% ammonium polyphosphate in Example 3, and TPU / 2P-N@Co represents the thermoplastic polyurethane composite material containing 2wt% recycled ammonium polyphosphate-based flame retardant in Example 3); wherein, (a) is the instantaneous heat release rate, (b) is the total heat release, (c) is the instantaneous smoke release rate, and (d) is the total smoke release. (a) and (b) show that pure thermoplastic polyurethane burns rapidly and releases a large amount of heat during combustion, while ammonium polyphosphate and ammonium polyphosphate-based flame retardant can effectively reduce the heat release during combustion of thermoplastic polyurethane, and the ammonium polyphosphate-based flame retardant has better control over heat under the synergistic effect of metal ions. (c) and (d) show that ammonium polyphosphate-based flame retardant can also effectively inhibit the smoke release of thermoplastic polyurethane. The above results show that the recycled ammonium polyphosphate-based flame retardant can still effectively improve the fire safety of the material.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an ammonium polyphosphate-based flame retardant, characterized in that: The following steps are involved: The aminobenzimidazole compound, ammonium polyphosphate and a dispersing solvent are mixed and modified in a protective gas to obtain modified ammonium polyphosphate; The modified ammonium polyphosphate, transition metal salt and alcohol solvent are mixed to carry out complex reaction to obtain an ammonium polyphosphate-based flame retardant; The metal elements in the transition metal salt include one or more of cobalt, nickel and copper.

2. The preparation method according to claim 1, characterized in that: The aminobenzimidazole compound includes 2-aminobenzimidazole, 4-aminobenzimidazole, 5-aminobenzimidazole, 6-aminobenzimidazole, 1,7-dimethyl-2-aminobenzimidazole or 2-(3-aminophenyl)-5-aminobenzimidazole; the mass ratio of the aminobenzimidazole compound to ammonium polyphosphate is 1:(2-6).

3. The preparation method according to claim 1, characterized in that: The protective gas includes nitrogen, helium, argon or neon; the modification temperature is 70-95° C. and the modification time is 2-12 hours.

4. The preparation method according to claim 1, characterized in that: The transition metal salt includes one or more of cobalt chloride, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel nitrate, nickel chloride, copper sulfate, copper chloride, copper nitrate and copper acetate.

5. The preparation method according to claim 1 or 4, characterized in that: The molar ratio of the aminobenzimidazole compound to the metal element in the transition metal salt is 1:(0.5-1.2).

6. The preparation method according to claim 5, characterized in that: The temperature of the complex reaction is room temperature, and the time is 6 to 24 hours.

7. The ammonium polyphosphate-based flame retardant prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the ammonium polyphosphate-based flame retardant according to claim 7 in soft polyurethane foam or fiber fabric.

9. The use according to claim 8, characterized in that: The mass ratio of the ammonium polyphosphate-based flame retardant to the soft polyurethane foam is 1 to 20:100; the mass ratio of the ammonium polyphosphate-based flame retardant to the fiber fabric is 1 to 20:

100.

10. The use according to claim 9, characterized in that: After the ammonium polyphosphate-based flame retardant is applied to the soft polyurethane foam or fiber fabric, the ammonium polyphosphate-based flame retardant adhering to the surface of the soft polyurethane foam or fiber fabric is washed with water or alcohol, and then filtered and dried in sequence to obtain the recovered flame retardant.

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