Phosphazene hyperbranched metal porous ionic liquid flame retardant, preparation, application and recovery method thereof

Abstract

The invention relates to a phosphazene hyperbranched metal porous ionic liquid flame retardant as well as preparation, application and a recovery method thereof, and belongs to the technical field of flame-retardant materials. The flame retardant is formed by compounding a phosphazene hyperbranched ionic liquid and a metal organic framework NH2-UiO-66. The flame retardant is a metal porous phosphazene intumescent flame retardant integrating an intumescent system. When the flame retardant is added into the polyurethane foam, the flame retardance of the polyurethane foam can be obviously improved, the flame retardant has a self-extinguishing effect when being away from fire during indoor combustion, the grade reaches V-2 from no grade in a UL-94 test, and the LOI is effectively improved.

Description

Technical Field

[0001] The invention relates to a phosphazene hyperbranched metal porous ionic liquid flame retardant, a preparation method, an application method and a recovery method thereof, and belongs to the technical field of flame retardant materials. Background Art

[0002] Polyurethane foam is a polymer material produced by the reaction of polyols, isocyanates, and additives such as blowing agents. It is widely used in building insulation (such as wall insulation), transportation (refrigerated truck insulation, car seat filling), and daily life (mattresses, packaging cushioning). It also plays a role in the military industry and electromagnetic shielding technology. However, due to its low flash point (260°C), polyurethane foam burns very quickly when exposed to open flames, with a burning speed of 1.5-2.0 mm / s. During combustion, it decomposes and produces toxic gases such as hydrogen cyanide (HCN) and carbon monoxide (CO), which can cause asphyxiation within seconds after inhalation. Flame temperatures can reach as high as 2000°C, and the resulting thick smoke can rapidly reduce visibility, hindering fire escape. In recent years, tragic fires caused by accidental ignition of polyurethane foam due to operational errors have occurred repeatedly. Therefore, improving the flame retardancy of polyurethane foam is an urgent issue that is of great significance to the well-being of the people and the healthy development of the economy.

[0003] In recent years, ionic liquids (ILs) have become a research hotspot for high-efficiency flame retardants due to their inclusion of flame-retardant elements such as phosphorus, fluorine, and nitrogen, their high thermal stability, environmental friendliness, and designability. They enhance flame retardancy through a dual mechanism: catalytic carbonization (promoting the formation of an expanded carbon layer within the PUF, insulating it from heat and oxygen) and gas-phase free radical quenching (releasing PO· / PO2· to capture active free radicals). Elements such as phosphorus and nitrogen complement each other in flame retardants, not only enhancing flame retardancy but also enabling better hydrogen bonding between the flame retardant and the matrix. This, by strengthening the π-π stacking interaction between the flame retardant and the macromolecular chains in the matrix, improves the mechanical properties of the polymer and increases compatibility with the polymer while maintaining flame retardancy. Furthermore, in recent years, both domestic and international research has begun to incorporate metal elements into flame retardants, further enhancing their flame retardancy through their catalytic carbonization. Among them, metal organic frameworks (MOFs) have attracted widespread attention due to their large specific surface area, ultra-high porosity and rich active adsorption properties, which can be flexibly controlled through different reaction conditions to obtain different performance advantages.

[0004] At present, the research areas of ionic liquid and MOF composite materials at home and abroad are mainly gas adsorption and separation, energy-efficient storage, and catalytic conversion. In the field of flame retardancy, it is still in the initial research stage. Domestic research focuses on synergistic systems (such as ILs / expanded graphite composites) and green synthesis processes (solvent-free catalytic foaming), which have certain applications in flame retardancy in textiles, electronic materials, etc. Internationally, they are exploring the combination of bio-based PUFs and multifunctionalization (such as flame retardant-conductive dual-functional materials). By adding 15% or more of ionic liquid flame retardants, the LOI of polyurethane foam can be increased from 18% to approximately 26%. However, the ionic liquids currently used are still relatively high in cost, have complex synthesis methods, and may also change the transparency of the material. In addition, traditional flame retardants are mostly powder flame retardants, which are prone to uneven distribution in the matrix, resulting in uneven distribution of flame retardant properties. At the same time, both traditional flame retardants and ionic liquid flame retardants are currently facing serious waste problems. The recycling rate is generally less than 20% (the recycling rate of fluoropolymers is even less than 10%). A large amount of waste flame retardant materials are disposed of by incineration or landfill, which not only releases toxic gases such as dioxins and hydrogen fluoride, but also leads to the loss of high value-added resources.

[0005] To address these issues, it is particularly meaningful to design an ionic liquid flame retardant containing MOFs to improve the flame retardancy of polyurethane foam. Furthermore, while improving the flame retardancy of the material, it is also important to consider the potential problems caused by the flame retardant. By using a liquid flame retardant and immersion coating method to obtain a polyurethane foam flame retardant material, while also imparting recyclability, this approach explores a more effective, environmentally friendly, economical, and versatile option. This has important reference value for the flame retardancy of polyurethane foam and even other systems, as well as the recycling of flame retardants. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a phosphazene hyperbranched metal porous ionic liquid flame retardant, and its preparation, application and recovery method.

[0007] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0008] A phosphazene hyperbranched metal porous ionic liquid flame retardant, wherein the flame retardant is composited with a phosphazene hyperbranched ionic liquid and a metal organic framework NH2-UiO-66. The structural formula of the phosphazene hyperbranched ionic liquid is as follows:

[0009]

[0010] Preferably, the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 5 to 15: 1. More preferably, the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 8 to 12: 1.

[0011] The preparation method of a phosphazene hyperbranched metal porous ionic liquid flame retardant according to the present invention comprises the following steps:

[0012] (1) dissolving 2-methylimidazole in an organic solvent, mixing uniformly, and heating to 20-70° C., adding hexachlorocyclotriphosphazene solution, and continuously heating, stirring, and reflux for 8-24 hours. After the reaction is completed, rotary evaporation, washing, and vacuum drying are performed to obtain a phosphazene hyperbranched ionic liquid;

[0013] (2) The metal organic framework NH2-UiO-66 is dissolved in an organic solvent and mixed evenly, and then heated to 30-80°C, and the phosphazene hyperbranched ionic liquid is added, and the reaction is continuously heated, stirred and refluxed for 8-24 hours. After the reaction is completed, rotary evaporation, washing, and vacuum drying are performed to obtain a phosphazene hyperbranched metal porous ionic liquid flame retardant.

[0014] Preferably, in step (1), the molar ratio of hexachlorocyclotriphosphazene to 2-methylimidazole is 1:6 to 9. More preferably, the molar ratio of hexachlorocyclotriphosphazene to 2-methylimidazole is 1:6.5 to 7.5.

[0015] Preferably, in step (1), the reaction temperature is 30-40° C., and the reaction time is 12-18 h.

[0016] Preferably, in step (1), the stirring rate is 300-400 rpm.

[0017] Preferably, in step (1), the rotary evaporation temperature is 55-70° C. and the time is 0.5-2 h.

[0018] Preferably, in step (1), the organic solvent is one or more of tetrahydrofuran, anhydrous ethanol and acetone.

[0019] Preferably, in step (2), the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 5 to 15: 1. More preferably, the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 8 to 12: 1.

[0020] Preferably, in step (2), the metal organic framework NH2-UiO-66 is prepared by the following method, which comprises: dissolving 2-aminoterephthalic acid in an organic solvent and mixing uniformly, adding zirconium tetrachloride solution, continuously stirring and reacting for 0.5 to 2 hours, then placing the mixed solution in a hydrothermal reactor, reacting at 100 to 150°C for 12 to 36 hours, filtering, washing, and vacuum drying to obtain a yellow-brown metal organic framework NH2-UiO-66. More preferably, the organic solvent is a mixed solution of N,N-dimethylformamide and acetic acid in a volume ratio of 10 to 4:1. More preferably, the organic solvent is a mixed solution of N,N-dimethylformamide and acetic acid in a volume ratio of 8 to 6:1; the solvent of the zirconium tetrachloride solution is N,N-dimethylformamide; the vacuum drying temperature is 90 to 110°C and the time is 3 to 6 hours.

[0021] Preferably, in step (2), the stirring rate is 300-400 rpm.

[0022] Preferably, in step (2), the organic solvent is one or more of tetrahydrofuran, anhydrous ethanol and acetone.

[0023] Preferably, in step (2), the rotary evaporation temperature is 55-70° C. and the time is 0.5-2 h.

[0024] The invention discloses an application of a phosphazene hyperbranched metal porous ionic liquid flame retardant, wherein the flame retardant is used as a flame retardant for polyurethane foam.

[0025] Preferably, the added amount of the flame retardant is 5% to 20% of the mass of the polyurethane foam.

[0026] The method for recovering a phosphazene hyperbranched metal porous ionic liquid flame retardant according to the present invention comprises the following steps:

[0027] The polyurethane foam containing the flame retardant is added to ethanol for full soaking and extrusion, the recovered solution is subjected to rotary evaporation at 40-60° C. for 20-60 minutes, and then vacuum dried to recover the phosphazene hyperbranched metal porous ionic liquid flame retardant;

[0028] The recovered phosphazene hyperbranched metal porous ionic liquid flame retardant is filtered and washed with ethanol to recover the solid to obtain the metal organic framework NH2-UiO-66; the recovered liquid is rotary evaporated at 40-60°C for 20-60 minutes, and then vacuum dried to obtain the phosphazene hyperbranched ionic liquid.

[0029] Beneficial effects

[0030] The flame retardant provided by the present invention is a metal porous phosphazene intumescent flame retardant that integrates an expansion system (including an acid source, a gas source, and a carbon source). Through simple reaction steps, the flame retardant contains high nitrogen and phosphorus contents and has higher flame retardant efficiency. At the same time, the addition of the metal organic framework NH2-UiO-66 and the imidazole ring in the flame retardant cooperate with each other to more efficiently adsorb toxic gases generated during the combustion process. The presence of zirconium ions can better catalyze the formation of the flame retardant carbon layer, thereby better exerting the synergistic effect between different flame retardant elements and improving the flame retardant effect. At the same time, with the help of the hydrogen bond formed by the amino group and the ionic liquid, the ionic liquid can be more evenly and more strongly loaded on the metal organic framework, thereby promoting the uniformity of the distribution of the metal organic framework in the ionic liquid. At the same time, the flame retardant in the form of an ionic liquid has good flame retardancy, high thermal stability and appropriate viscosity, and can be more evenly distributed on the polyurethane foam. At the same time, the flame retardant is synthesized through the design of a multi-ring structure, which increases the stability of the coating formed by the flame retardant on the surface of the polyurethane foam. Furthermore, because the flame retardant can be dissolved in specific solvents, it can be recycled multiple times through these solvents. Furthermore, thanks to the high stability of NH2-UiO-66, the NH2-UiO-66 in the ionic liquid can also be recovered, thus achieving dual recycling, better meeting environmental and economic requirements. Compared to existing single-chain or branched phosphorus / nitrogen flame retardants, this phosphazene hyperbranched metal porous ionic liquid flame retardant not only has excellent flame retardancy but is also recyclable.

[0031] Adding the flame retardant described in the present invention to polyurethane foam significantly improves its flame retardancy, achieving self-extinguishing properties when burning indoors. The UL-94 test results in a V-2 rating, significantly improving the LOI. The prepared polyurethane foam composite material is recycled, yielding up to 70% flame retardant. Furthermore, secondary recovery of the flame retardant can recover the NH2-UiO-66 contained in the flame retardant. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the H NMR spectrum of the phosphazene hyperbranched ionic liquid synthesized in Example 1 of the present invention.

[0033] Figure 2 This is the infrared spectrum of the phosphazene hyperbranched ionic liquid synthesized in Example 1 of the present invention.

[0034] Figure 3 This is a scanning electron microscope image of the metal organic framework NH2-UiO-66 synthesized in Example 1 of the present invention.

[0035] Figure 4 This is the infrared spectrum of the phosphazene hyperbranched metal porous ionic liquid flame retardant synthesized in Example 1 of the present invention.

[0036] Figure 5 This is a scanning electron microscope image of the phosphazene hyperbranched metal porous ionic liquid flame retardant synthesized in Example 1 of the present invention.

[0037] Figure 6 1 is the XRD pattern of the metal organic framework NH2-UiO-66 synthesized in Example 1 of the present invention and its recovered state. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to specific embodiments.

[0039] Example 1

[0040] 20 g of 2-methylimidazole was weighed and dissolved in 200 mL of anhydrous ethanol solution, and stirred until the solution was clear and free of precipitation, which was referred to as solution A. Solution A was then added to a 500 mL three-necked flask, which was connected to a 100 mL constant pressure dropping funnel, a magnetic stirrer, a 24-mouth serpentine condenser, and an exhaust gas receiving and treatment device, and the temperature was stirred and raised at 70° C. 15 g of hexachlorocyclotriphosphazene was dissolved in 100 mL of tetrahydrofuran solution and stirred at room temperature and pressure until the solution was clear and transparent, which was referred to as solution B. Solution B was then added to a constant pressure funnel, the flow rate was adjusted to drip over 30 minutes, and the reaction was continued with stirring for 24 hours. The reacted solution was subjected to rotary evaporation at 45° C. and 1 kPa for 30 minutes, and then dried in a vacuum oven at 80° C. and 1 kPa for 12 hours to obtain a yellow transparent phosphazene hyperbranched ionic liquid.

[0041] The nuclear magnetic hydrogen spectrum and infrared spectrum of the yellow transparent phosphazene hyperbranched ionic liquid are as follows Figure 1-2 As shown, the structural formula is:

[0042]

[0043] Weigh 1.08g of zirconium tetrachloride and dissolve it in 100mL of N,N-dimethylformamide, stir until it is clear without precipitation as solution C; then add solution A to a 500mL beaker and stir magnetically; dissolve 0.82g of 2-aminoterephthalic acid in a mixed solution of 120mL of N,N-dimethylformamide and 20mL of acetic acid, stir until it is clear without precipitation and pour it into a beaker, and the mixed solution in the beaker is called solution D; after stirring for 30min, add solution D to a hydrothermal reactor and react at 120℃ for 24h, then cool, filter the precipitate, and wash it alternately with 10mL of ethanol and 10mL of acetone three times, and then dry it in a vacuum oven at 80℃ and 1KPa for 12h to obtain a yellow-brown metal organic framework NH2-UiO-66. The scanning electron microscopy results of NH2-UiO-66 are shown as follows: Figure 3 shown.

[0044] Weigh 1 g of the metal organic framework NH2-UiO-66, add it to 10 mL of anhydrous ethanol, stir evenly, and pour it into a 100 mL beaker as solution E; weigh 10 g of the phosphazene hyperbranched ionic liquid in 50 mL of anhydrous ethanol, stir until clear and without precipitate, then pour it into a 100 mL beaker, and then stir it with solution E at 40 ° C for 6 h. The reacted solution is rotary evaporated at 45 ° C and 1 KPa for 30 min, and then dried in a vacuum oven at 80 ° C and 1 KPa for 12 h to obtain a phosphazene hyperbranched metal porous ionic liquid flame retardant.

[0045] The infrared spectrum results of phosphazene hyperbranched metal porous ionic liquid flame retardant are as follows Figure 4 As shown, located at 767 and 663cm -1 The characteristic peak near 1440 cm corresponds to the coordination of Zr-O bond. -1 The characteristic peaks near the symmetric stretching vibration peaks of carboxyl groups are located at 3358 and 3450 cm -1 The characteristic peaks near 1580 cm correspond to the stretching vibration peaks of NH. -1 There is a bending vibration peak of NH. At the same time, the scanning electron microscopy results are as follows Figure 5 As shown, it can be clearly seen that the Figure 3 Medium single particle NH2-UiO-66, Figure 5 The surface of NH2-UiO-66 is covered with a layer of ionic liquid, but the original morphology of NH2-UiO-66 is always maintained, which proves the successful synthesis of phosphazene hyperbranched metal porous ionic liquid flame retardant

[0046] Weigh 10 mL of phosphazene hyperbranched metal porous ionic liquid flame retardant, add it to 100 mL of anhydrous ethanol and stir evenly, pour it into a 250 mL beaker, use 30×30×30 mm soft polyurethane foam as the matrix, put it into the above solution to soak and squeeze it 5 times, and then dry it at 80°C and 1 kPa for 12 hours to obtain a polyurethane foam composite material.

[0047] The obtained polyurethane foam composite material was subjected to a limiting oxygen index test (LOI), and the measured limiting oxygen index value was 26.2%, which was an increase of 85.8% compared to the original LOI value (14.1%). It has a self-extinguishing effect when burning at room temperature and reaches V-2 grade in the UL-94 test.

[0048] The resulting polyurethane foam composite material was completely immersed and squeezed in ethanol 10 times. The resulting solution was rotary evaporated at 45°C and 1 kPa for 30 minutes and then dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered phosphazene hyperbranched metal porous ionic liquid flame retardant. The recovered phosphazene hyperbranched metal porous ionic liquid flame retardant was further filtered and washed with ethanol to obtain a double-recovered metal-organic framework NH2-UiO-66. The filtered solution was rotary evaporated at 45°C and 1 kPa for 30 minutes and then dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered phosphazene hyperbranched ionic liquid. The soaked polyurethane foam was dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered polyurethane foam.

[0049] The recovered polyurethane foam was weighed and the recovery rate was 75.6%. The metal organic framework UiO-66 obtained by double recovery was subjected to XRD test, and the results were the same as those of the original UiO-66, such as Figure 6 shown.

[0050] Example 2

[0051] 10 g of 2-methylimidazole was weighed and dissolved in 100 mL of anhydrous ethanol solution, and stirred until clear and free of precipitate, which was referred to as solution A. Solution A was then added to a 250 mL three-necked flask, which was connected to a 100 mL constant pressure dropping funnel, a magnetic stirrer, a 24-mouth serpentine condenser, and an exhaust gas receiving and treatment device, and the mixture was stirred and heated at 40° C. 7 g of hexachlorocyclotriphosphazene was dissolved in 100 mL of tetrahydrofuran solution and stirred at room temperature and pressure until clear and transparent, which was referred to as solution B. Solution B was then added to a constant pressure funnel, the flow rate was adjusted to drip over 30 minutes, and the reaction was continued with stirring for 12 hours. The resulting solution was subjected to rotary evaporation at 45° C. and 1 kPa for 30 minutes, and then dried in a vacuum oven at 80° C. and 1 kPa for 12 hours to obtain a yellow transparent phosphazene hyperbranched ionic liquid.

[0052] The results of H NMR and IR spectra of the transparent phosphazene hyperbranched ionic liquid show that the structural formula of the flame retardant is the same as that of Example 1.

[0053] Weigh 1 g of the metal organic framework NH2-UiO-66, add it to 10 mL of anhydrous ethanol, stir evenly, and pour it into a 100 mL beaker as solution E; weigh 10 g of the phosphazene hyperbranched ionic liquid in 50 mL of anhydrous ethanol, stir until clear and without precipitate, then pour it into a 100 mL beaker, and then stir it with solution E at 40 ° C for 6 h. The reacted solution is rotary evaporated at 45 ° C and 1 KPa for 30 min, and then dried in a vacuum oven at 80 ° C and 1 KPa for 12 h to obtain a phosphazene hyperbranched metal porous ionic liquid flame retardant.

[0054] Weigh 10 mL of phosphazene hyperbranched metal porous ionic liquid flame retardant, add it to 100 mL of anhydrous ethanol and stir evenly, pour it into a 250 mL beaker, use 30×30×30 mm polyurethane foam as the matrix, put it into the above solution to soak and squeeze it 5 times, and then dry it at 80°C and 1 kPa for 12 h to obtain a polyurethane foam composite material.

[0055] The obtained polyurethane foam composite material was subjected to a limiting oxygen index test (LOI), and the measured limiting oxygen index value was 25.8%, which was an increase of 83.0% compared to the original LOI value (14.1%). It has a self-extinguishing effect when burning at room temperature and reaches V-2 grade in the UL-94 test.

[0056] The resulting polyurethane foam composite material was completely immersed and squeezed in ethanol 10 times. The resulting solution was rotary evaporated at 45°C and 1 kPa for 30 minutes and then dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered phosphazene hyperbranched metal porous ionic liquid flame retardant. The recovered ionic liquid flame retardant was further filtered and washed with ethanol to obtain a double-recovered metal-organic framework NH2-UiO-66. The filtered solution was rotary evaporated at 45°C and 1 kPa for 30 minutes and then dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered phosphazene hyperbranched ionic liquid. The soaked polyurethane foam was dried in a vacuum oven at 80°C and 1 kPa for 12 hours to obtain a recovered polyurethane foam.

[0057] The recovered polyurethane foam was weighed and the recovery rate was 73.3%. The metal organic framework NH2-UiO-66 obtained by double recovery was tested by XRD, and the results were the same as those of the original UiO-66.

[0058] Example 3

[0059] 30 g of 2-methylimidazole was weighed and dissolved in 200 mL of anhydrous ethanol solution, and stirred until the solution was clear and free of precipitation, which was referred to as solution A. Solution A was then added to a 500 mL three-necked flask, which was connected to a 100 mL constant pressure dropping funnel, a magnetic stirrer, a 24-mouth serpentine condenser, and an exhaust gas receiving and treatment device, and the temperature was stirred and increased at 40° C. 20 g of hexachlorocyclotriphosphazene was dissolved in 100 mL of tetrahydrofuran solution and stirred at room temperature and pressure until the solution was clear and transparent, which was referred to as solution B. Solution B was then added to a constant pressure funnel, the flow rate was adjusted to drip over 30 minutes, and the reaction was continued with stirring for 8 hours. The reacted solution was subjected to rotary evaporation at 45° C. and 1 kPa for 30 minutes, and then dried in a vacuum oven at 80° C. and 1 kPa for 12 hours to obtain a light yellow transparent phosphazene hyperbranched ionic liquid.

[0060] The results of H NMR and IR spectra of the transparent phosphazene hyperbranched ionic liquid show that the structural formula of the flame retardant is the same as that of Example 1.

[0061] Weigh 1 g of the metal organic framework NH2-UiO-66, add it to 10 mL of anhydrous ethanol, stir evenly, and pour it into a 100 mL beaker as solution E; weigh 10 g of the phosphazene hyperbranched ionic liquid in 50 mL of anhydrous ethanol, stir until clear and without precipitate, then pour it into a 100 mL beaker, and then stir it with solution E at 40 ° C for 6 h. The reacted solution is rotary evaporated at 45 ° C and 1 KPa for 30 min, and then dried in a vacuum oven at 80 ° C and 1 KPa for 12 h to obtain a phosphazene hyperbranched metal porous ionic liquid flame retardant.

[0062] Weigh 10 mL of phosphazene hyperbranched metal porous ionic liquid flame retardant, add it to 100 mL of anhydrous ethanol and stir evenly, pour it into a 250 mL beaker, use 30×30×30 mm polyurethane foam as the matrix, put it into the above solution to soak and squeeze it 5 times, and then dry it at 80°C and 1 kPa for 12 h to obtain a polyurethane foam composite material.

[0063] The obtained polyurethane foam composite material was subjected to a limiting oxygen index test (LOI), and the measured limiting oxygen index value was 26.7%, which was an increase of 89.4% compared to the original LOI value (14.1%). It has a self-extinguishing effect when burning at room temperature and reaches V-2 grade in the UL-94 test.

[0064] After the obtained polyurethane foam composite is subjected to 10 times of complete immersion extrusion in ethanol, the obtained solution is rotary evaporated at 45℃ and 1KPa for 30min, and then dried in a vacuum oven at 80℃ and 1KPa for 12h to obtain the recovered phosphazene hyperbranched metal porous ionic liquid flame retardant, and the recovered phosphazene hyperbranched metal porous ionic liquid flame retardant is further cleaned by filtration with ethanol to obtain the doubly recovered metal organic framework NH2-UiO-66, and the solution after filtration is rotary evaporated at 45℃ and 1KPa for 30min, and then dried in a vacuum oven at 80℃ and 1KPa for 12h to obtain the recovered phosphazene hyperbranched ionic liquid. The polyurethane foam after immersion is dried in a vacuum oven at 80℃ and 1KPa for 12h to obtain the recovered polyurethane foam.

[0065] The recovered polyurethane foam is subjected to weighing treatment to obtain a recovery rate of 72.8%, and the doubly recovered metal organic framework NH2-UiO-66 is subjected to XRD test, and the obtained result is the same as that of the original NH2-UiO-66.

[0066] In summary, the application includes but is not limited to the above embodiments, and any equivalent replacement or partial improvement made within the spirit and principles of the application shall be considered within the protection scope of the application.

Claims

1. A phosphazene hyperbranched metal porous ionic liquid flame retardant, characterized in that: The flame retardant is composed of a composite of a phosphazene hyperbranched ionic liquid and a metal organic framework NH2-UiO-66. The structural formula of the phosphazene hyperbranched ionic liquid is as follows:

2. A phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 1, characterized in that: The mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 5 to 15:1; preferably, the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 8 to 12:

1.

3. A method for preparing the phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 1 or 2, characterized in that: The method steps include: (1) dissolving 2-methylimidazole in an organic solvent, mixing uniformly, and heating to 20-70° C., adding hexachlorocyclotriphosphazene solution, and continuously heating, stirring, and reflux for 8-24 hours. After the reaction is completed, rotary evaporation, washing, and vacuum drying are performed to obtain a phosphazene hyperbranched ionic liquid; (2) The metal organic framework NH2-UiO-66 is dissolved in an organic solvent and mixed evenly, and then heated to 30-80°C, and the phosphazene hyperbranched ionic liquid is added, and the reaction is continuously heated, stirred and refluxed for 8-24 hours. After the reaction is completed, rotary evaporation, washing, and vacuum drying are performed to obtain a phosphazene hyperbranched metal porous ionic liquid flame retardant.

4. The method for preparing a phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 3, wherein: In step (1), the molar ratio of the hexachlorocyclotriphosphazene to 2-methylimidazole is 1:6-9; preferably, the molar ratio of the hexachlorocyclotriphosphazene to 2-methylimidazole is 1:6.5-7.

5.

5. The method for preparing a phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 3, wherein: In step (1), the reaction temperature is 30-40° C., and the reaction time is 12-18 h.

6. The method for preparing a phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 3, wherein: In step (2), the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 5 to 15:1; preferably, the mass ratio of the phosphazene hyperbranched ionic liquid to the metal organic framework NH2-UiO-66 is 8 to 12:

1.

7. The method for preparing a phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 3, wherein: In step (2), the metal organic framework NH2-UiO-66 is prepared by the following method, which includes: dissolving 2-aminoterephthalic acid in an organic solvent and mixing evenly, adding zirconium tetrachloride solution, continuously stirring and reacting for 0.5 to 2 hours, then placing the mixed solution in a hydrothermal reactor, reacting at 100 to 150°C for 12 to 36 hours, filtering, washing, and vacuum drying to obtain a yellow-brown metal organic framework NH2-UiO-66; preferably, the organic solvent is a mixed solution of N,N-dimethylformamide and acetic acid in a volume ratio of 10 to 4:1; more preferably, the organic solvent is a mixed solution of N,N-dimethylformamide and acetic acid in a volume ratio of 8 to 6:1; the solvent of the zirconium tetrachloride solution is N,N-dimethylformamide; the vacuum drying temperature is 90 to 110°C, and the time is 3 to 6 hours.

8. The method for preparing a phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 3, wherein: In steps (1) and (2), the stirring rate is 300-400 rpm respectively; The organic solvents are one or more of tetrahydrofuran, anhydrous ethanol and acetone; The rotary evaporation temperature is 55 to 70°C, and the time is 0.5 to 2 h.

9. Use of the phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 1 or 2, wherein the flame retardant is used as a flame retardant for polyurethane foam; preferably, the addition amount of the flame retardant is 5% to 20% of the mass of the polyurethane foam.

10. A method for recovering the phosphazene hyperbranched metal porous ionic liquid flame retardant according to claim 1 or 2, the method comprising the steps of: The polyurethane foam containing the flame retardant is added to ethanol for full soaking and extrusion, the recovered solution is subjected to rotary evaporation at 40-60° C. for 20-60 minutes, and then vacuum dried to recover the phosphazene hyperbranched metal porous ionic liquid flame retardant; The recovered phosphazene hyperbranched metal porous ionic liquid flame retardant is filtered and washed with ethanol to recover the solid to obtain the metal organic framework NH2-UiO-66; the recovered liquid is rotary evaporated at 40-60°C for 20-60 minutes, and then vacuum dried to obtain the phosphazene hyperbranched ionic liquid.

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