Preparation method of photo-thermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation

Abstract

The invention discloses a preparation method of photo-thermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation, which comprises the following steps: introducing a polydopamine (PDA) / MXene material into polyurethane foam through a simple one-step foaming method, then introducing a nitrogen-phosphorus-silicon hybrid flame retardant N3P3 [NH (CH2) 3Si (OEt) 3] 6 through dip-coating and a sol-gel method, and finally preparing the photo-thermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation. The preparation method of the flame-retardant photo-thermal super-hydrophobic polyurethane sponge for oil-water separation is obtained. The polyurethane sponge prepared by the method not only has stable super-hydrophobicity, excellent photo-thermal conversion performance and excellent adsorption capacity to oil products, but also has better thermal stability.

Description

Technical Field

[0001] The invention relates to the technical field of sponges for oil-water separation, and more specifically, to a method for preparing a photothermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation. Background Art

[0002] Porous materials with special wettability can achieve oil-water separation by selectively adsorbing oil / water, which provides ideas for separating oil-water mixtures. Polyurethane foam is a three-dimensional porous material with the advantages of light weight, high porosity, large specific surface area, good elasticity, and large-scale production. It is a good base material for preparing oil-water separation materials.

[0003] However, conventional polyurethane foam still has the following problems: (1) poor selectivity for oil-water separation; (2) low adsorption efficiency of polyurethane foam for high viscosity oil at room temperature; (3) the limiting oxygen index (LOI) of polyurethane foam is only 19%, which is highly flammable, burns quickly, and releases a large amount of heat and thick black smoke as well as toxic gases such as CO, NO, HCN, etc., which can easily cause suffocation, poisoning and death of people in fires, resulting in serious loss of life and property. Therefore, it is of great significance to develop a new polyurethane foam adsorption material with both hydrophobic and oleophilic properties, flame retardant properties and photothermal conversion properties in the practical application field of oil-water separation. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art, and to provide a method for preparing a photothermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation, wherein a polydopamine / MXene material is introduced by a one-step foaming method, and then a nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6 is introduced by a sol-gel method, thereby obtaining a method for preparing a flame-retardant photothermal super-hydrophobic polyurethane sponge for oil-water separation. The obtained polyurethane sponge not only has stable super-hydrophobicity, excellent photothermal conversion performance and excellent adsorption capacity for oil products, but also has good thermal stability.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing a photothermal super-hydrophobic flame-retardant polyurethane sponge for oil-water separation, the method comprising the following steps:

[0007] (1) Mixing polydopamine-modified MXene powder, polyether polyol, deionized water, Maitu L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate to form a mixture, and allowing the mixture to stand at room temperature until the foam shape is stable, and then fully ripening the polyurethane foam to obtain a PDA / MXene-modified polyurethane foam;

[0008] (2) Synthesis of nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6

[0009] 3-aminopropyltriethoxysilane and triethylamine are dissolved in toluene, and a toluene solution of hexachlorocyclotriphosphazene is added dropwise, mixed evenly, and then heated under reflux for reaction, and a white solid is precipitated after the reaction; after the reaction is completed, the reaction liquid is filtered, and then the residual 3-aminopropyltriethoxysilane and triethylamine in the filtrate are removed to obtain a colorless transparent liquid, which is the nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6;

[0010] (3) dissolving the nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6 in a mixed solution of deionized water and ethanol to obtain a N3P3[NH(CH2)3Si(OEt)3]6 solution, adding dopamine, and adjusting the pH value of the solution to 8-9 with Tris-HCl buffer to obtain a nitrogen-phosphorus-silicon flame retardant / PDA solution;

[0011] (4) The PDA / MXene modified polyurethane foam is immersed in a nitrogen-phosphorus-silicon flame retardant / PDA solution, taken out after the immersion is completed, and the excess liquid is squeezed out and then washed and dried to obtain a photothermal superhydrophobic flame retardant polyurethane sponge.

[0012] Furthermore, in step (1), the dosage ratio of polydopamine-modified MXene powder to polyether polyol, deionized water, Maitu L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate is (0.4-1): (25-35): (0.7-1): (0.2-0.32): (0.01-0.05): (0.01-0.03): (10-15).

[0013] Furthermore, in step (1), the mixture is foamed at room temperature; after standing at room temperature, the foam is placed in an oven at 80-85° C. for maturation.

[0014] Furthermore, in step (2), the molar ratio of 3-aminopropyltriethoxysilane to triethylamine and hexachlorocyclotriphosphazene is (65-70): (75-80) mmol: (10-11) mmol.

[0015] Furthermore, in step (2), the heating reflux temperature is 110° C. and the reaction time is 3-5 h.

[0016] Furthermore, in step (3), the concentration of N3P3[NH(CH2)3Si(OEt)3]6 in the N3P3[NH(CH2)3Si(OEt)3]6 solution is 10-60 g / L, the mass ratio of deionized water to ethanol is 1:1; and the concentration of dopamine is 2 g / L.

[0017] Furthermore, in step (4), the ratio of PDA / MXene modified polyurethane foam to nitrogen-phosphorus-silicon flame retardant / PDA solution is 1 g:30 mL; the immersion temperature is 30-50° C., and the immersion time is 2-4 h.

[0018] Furthermore, polydopamine-modified MXene powders were prepared by the following steps:

[0019] (a) dissolving lithium fluoride powder in hydrochloric acid solution, adding Ti3AlC2 powder to react; after the reaction, washing the reaction product with water by ultrasonic centrifugation for multiple times until the pH value is 7; collecting the centrifuge liquid for multiple times, centrifuging, collecting the centrifuge liquid for freeze drying, and obtaining a single-layer or few-layer MXene powder;

[0020] (b) adding the prepared MXene powder to a Tris buffer, mixing well, and then adding dopamine hydrochloride to react; after the reaction, centrifuging and washing the obtained precipitate until it is neutral, and vacuum drying to obtain a polydopamine-modified MXene powder;

[0021] Furthermore, in step (a), the hydrochloric acid solution is prepared by mixing 6 mol / L concentrated hydrochloric acid and deionized water in a volume ratio of 1:1, and the amount ratio of lithium fluoride powder to hydrochloric acid solution and Ti3AlC2 powder is 1g:16-25mL:1g; the reaction temperature is 30-40°C, and the reaction time is 20-28h.

[0022] Furthermore, in step (b), the mass ratio of MXene powder to dopamine hydrochloride is 1:0.5-1.

[0023] The beneficial effects of the present invention are:

[0024] 1) The highly chemically active polydopamine (PDA) layer in the present invention provides active sites for the adsorption of MXene nanosheets, and strengthens the interfacial bonding ability between the MXene layer and the polyurethane sponge. The abundant active hydrophilic functional groups on the MXene surface can form hydrogen bonds with the hydroxyl groups on the PDA, so that the MXene nanosheets can be firmly adsorbed on the surface of the modified polyurethane sponge, and PDA can also prevent the restacking of MXene.

[0025] 2) In the present invention, N3P3[NH(CH2)3Si(OEt)3]6 is applied to polyurethane by a sol-gel method, which hydrolyzes to form silanol groups and polymerizes to form polysilsesquioxane, which can reduce the surface energy of the polyurethane. At the same time, under alkaline conditions, dopamine hydrochloric acid is oxidized to form polydopamine, and the granular coating formed by polydopamine, PDA, can strengthen the interface between N3P3[NH(CH2)3Si(OEt)3]6 and polyurethane, and increase the roughness of the polyurethane surface. In addition, the silicon of polysilsesquioxane and the nitrogen and phosphorus in cyclotriphosphazene can improve the thermal stability of the material.

[0026] 3) The MXene in the present invention has good light absorption properties, which makes the sponge have good photothermal conversion ability and promotes the material's absorption of high-viscosity crude oil.

[0027] 4) The production process of the present invention is simple, does not require complicated equipment, is conducive to industrial production, and has broad application prospects. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The preparation method of the photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation of the present invention is mainly divided into 4 processes, process 1 is the preparation of polydopamine modified MXene powder; process 2 is the preparation of PDA / MXene modified polyurethane by a simple one-step foaming method; process 3 is the preparation of nitrogen-phosphorus-silicon flame retardant / PDA solution; process 4 is to immerse the PDA / MXene modified polyurethane in the nitrogen-phosphorus-silicon flame retardant / PDA solution, perform hydrolysis and polycondensation reaction, and then wash and dry the sponge to obtain a flame retardant super hydrophobic photothermal polyurethane foam. The specific steps are as follows:

[0030] (1) dissolving lithium fluoride powder in a hydrochloric acid solution (the hydrochloric acid solution is prepared by mixing 6 mol / L concentrated hydrochloric acid and deionized water in a volume ratio of 1:1), adding Ti3AlC2 powder several times and mixing evenly, and then reacting at 30-40°C for 20-28h, wherein the amount ratio of lithium fluoride powder to hydrochloric acid solution and Ti3AlC2 powder is 1g:16-25mL:1g; after the reaction, washing the reaction product with water by ultrasonic centrifugation for multiple times until the pH value is 7; collecting the centrifugal solution for multiple times, centrifuging, collecting the centrifugal solution for freeze drying, and obtaining a single-layer or few-layer MXene powder;

[0031] (2) Add MXene powder to Tris buffer (pH = 8.5), stir mechanically and disperse ultrasonically for 1-2 hours to mix evenly, then add dopamine hydrochloride and react at room temperature for 8-10 hours, wherein the mass ratio of MXene powder to dopamine hydrochloride is 1:0.5-1, and the amount ratio of MXene powder to Tris buffer is 1:350-450mL; after the reaction, the obtained precipitate is centrifuged and washed to neutrality, and vacuum dried to obtain polydopamine-modified MXene powder;

[0032] (3) Mix polydopamine-modified MXene powder, polyether polyol, deionized water, Momentive L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate for foaming, and let stand at room temperature until the foam shape is stable, and then mature the polyurethane foam completely to obtain PDA / MXene modified polyurethane foam. The mass ratio of polydopamine-modified MXene powder to polyether polyol, deionized water, Momentive L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate is (0.4-1): (25-35): (0.7-1): (0.2-0.32): (0.01-0.05): (0.01-0.03): (10-15).

[0033] The specific steps are as follows: add polydopamine-modified MXene powder to polyether polyol, mechanically stir and ultrasonically disperse for 2-4 hours to fully mix the three; then add deionized water, Maitu L-580 silicone oil, dibutyltin disilicate, and triethylenediamine successively, and stir vigorously to mix evenly. Then add polymethylene polyphenyl isocyanate (PAPI) and quickly mix and stir evenly, pour the mixed solution into the mold for foaming reaction at room temperature, let it stand at room temperature for 3-8 minutes after the reaction until the foam shape is stable, then put it into the oven, bake it at 80-85°C for 3-5 hours to fully mature the polyurethane foam, and obtain PDA / MXene modified polyurethane foam.

[0034] (4) Synthesis of nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6

[0035] 3-aminopropyltriethoxysilane and triethylamine are dissolved in toluene in a ratio of (65-70) mmol: (75-80) mmol: 50 mL, a toluene solution of hexachlorocyclotriphosphazene (the concentration of hexachlorocyclotriphosphazene in the solution is 0.5 mol / L) is added dropwise at room temperature, mixed evenly, heated under reflux at 110° C. for 3-5 h, and a white solid is precipitated after the reaction. The molar ratio of 3-aminopropyltriethoxysilane to triethylamine and hexachlorocyclotriphosphazene in the reaction system is (65-70): (75-80) mmol: (10-11) mmol. After the reaction is completed, the reaction solution is filtered to remove the white solid, and then the residual 3-aminopropyltriethoxysilane and triethylamine in the filtrate are removed by rotary evaporation to obtain a colorless transparent liquid, which is a nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6.

[0036] (5) dissolving N3P3[NH(CH2)3Si(OEt)3]6 in a mixed solution of deionized water and ethanol (the mass ratio of deionized water to ethanol is 1:1) to obtain a mixed solution with a concentration of N3P3[NH(CH2)3Si(OEt)3]6 of 10-60 g / L, adding dopamine (PDA) so that the dopamine concentration in the system is 2 g / L, and adjusting the pH value of the solution to 8-9 with Tris-HCl buffer to obtain a nitrogen-phosphorus-silicon flame retardant / PDA solution;

[0037] (6) The PDA / MXene modified polyurethane foam was immersed in nitrogen-phosphorus-silicon flame retardant / PDA solution at 30-50°C for 2-4 h (the dosage ratio of PDA / MXene modified polyurethane foam to nitrogen-phosphorus-silicon flame retardant / PDA solution was 1 g:30 mL). After the immersion was completed, the foam was taken out, the excess liquid was squeezed out, and it was washed with ethanol and deionized water. Finally, it was placed in an oven and dried at 100°C for 30-40 min to obtain a photothermal superhydrophobic flame-retardant polyurethane sponge.

[0038] The preferred embodiments are as follows:

[0039] Example 1

[0040] (1) Preparation of MXene powder: LiF powder was dissolved in hydrochloric acid solution, Ti3AlC2 powder was added several times and mixed evenly, and then the reaction was carried out at 35°C for 24 h. The amount ratio of lithium fluoride powder to hydrochloric acid solution and Ti3AlC2 powder was 1 g: 20 mL: 1 g. After the reaction, the reaction product was washed with water by ultrasonic centrifugation several times until the pH value was 7. The centrifuge liquid was collected several times, centrifuged, and the centrifuge liquid was collected and freeze-dried to obtain a single-layer or few-layer MXene powder.

[0041] (2) Preparation of PDA / MXene: 1.0 g of the MXene powder prepared above was added to 400 mL of Tris buffer (pH = 8.5), mechanically stirred and ultrasonically dispersed for 1 hour to mix evenly, and 0.8 g of dopamine hydrochloride was added to react at room temperature for 9 hours. The obtained precipitate was then centrifuged and washed to neutrality, and vacuum dried to obtain polydopamine-modified MXene powder (PDA / MXene).

[0042] (3) Preparation of polyurethane by one-step foaming method: 0.6g PDA / MXene powder was added to 30g polyether polyol N330 (PDA / MXene powder accounted for 2wt% of the mass of polyether polyol N330), mechanically stirred and ultrasonically dispersed for 3 hours to make the three fully mixed. Then 0.9g deionized water, 0.27g Maitu L-580 silicone oil, 0.03g dibutyltin disilicate, and 0.024g triethylenediamine were added successively, and the mixture was stirred vigorously and mixed evenly. Then polymethylene polyphenyl isocyanate (PAPI, 13g) was added and quickly mixed and stirred evenly, and the mixed solution was poured into a mold for foaming reaction at room temperature. After the reaction, it was allowed to stand at room temperature for 5 minutes until the foam shape was stable, and then put into an oven and baked at 80°C for 4 hours to fully mature the polyurethane foam, that is, PDA / MXene modified polyurethane foam was obtained.

[0043] (4) First, 3-aminopropyltriethoxysilane (15.32 g, 69 mmol) and triethylamine (8.46 g, 76 mmol) were dissolved in 50 mL of toluene. Then, at room temperature, a toluene (20 mL) solution of hexachlorocyclotriphosphazene (HCCP) (3.61 g, 10.4 mmol) was added dropwise to the above solution. The mixture was heated to reflux at 110°C for 4 h, and a white solid precipitated. After the reaction was completed, the reaction solution was filtered to remove the white solid, and then a rotary evaporator was used to remove 3-aminopropyltriethoxysilane and triethylamine in the filtrate to obtain a colorless and transparent liquid, which was the nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6. 1 H NMR (ppm, CDCl3) δ: 3.8-3.85(36H), 2.91(12H), 1.61(12H), 1.22(54H), 0.63(12H). 31 P NMR (ppm,CDCl3)δ:18.0.

[0044] (5) N3P3[NH(CH2)3Si(OEt)3]6 was dissolved in a solution of deionized water and ethanol (30 g / L, the mass ratio of deionized water to ethanol was 1:1) to obtain a mixed solution with a concentration of N3P3[NH(CH2)3Si(OEt)3]6 of 10 g / L. A certain amount of dopamine hydrochloride was then added to the mixed solution, the dopamine concentration in the system was 2 g / L, and the pH value of the solution was adjusted to 8.5 with Tris-HCl buffer to obtain a nitrogen-phosphorus-silicon flame retardant / PDA solution.

[0045] (6) The prepared PDA / MXene modified polyurethane foam was immersed in the above nitrogen-phosphorus-silicon flame retardant / PDA solution at 30°C for 3 h (the ratio of PDA / MXene modified polyurethane foam to nitrogen-phosphorus-silicon flame retardant / PDA solution was 1 g:30 mL), then taken out, the excess liquid was squeezed out, and then washed with ethanol and deionized water, and finally placed in an oven and baked at 100°C for 30 min.

[0046] Example 2

[0047] A photothermal superhydrophobic flame-retardant polyurethane sponge for oil-water separation was prepared according to the method of Example 1, except that when the PDA / MXene powder was mixed with 30 g of polyether polyol N330 in step (3), the PDA / MXene powder accounted for 1 wt % of the mass of the polyether polyol N330.

[0048] Example 3

[0049] A photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation was prepared according to the method of Example 1, except that when the PDA / MXene powder was mixed with 30 g of polyether polyol N330 in step (3), the PDA / MXene powder accounted for 3 wt % of the mass of the polyether polyol N330.

[0050] Example 4

[0051] A photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation was prepared according to the method of Example 1, except that: in step (6), the immersion temperature was 40°C.

[0052] Example 5

[0053] A photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation was prepared according to the method of Example 1, except that: in step (6), the immersion temperature was 50°C.

[0054] Comparative Example 1

[0055] According to the method of Example 1, unmodified polyurethane sponge was prepared, that is, 0.9g of deionized water, 0.27g of Maitu L-580 silicone oil, 0.03g of dibutyltin disilicate, and 0.024g of triethylene diamine were successively added to 30g of polyether polyol N330, and the mixture was vigorously stirred and mixed evenly. Then, polymethylene polyphenyl isocyanate (PAPI, 13g) was added and quickly mixed and stirred evenly, and the mixed solution was poured into a mold for foaming reaction at room temperature. After the reaction, it was allowed to stand at room temperature for 5 minutes until the foam shape was stable, and then put into an oven and baked at 80°C for 4 hours to fully mature the polyurethane foam.

[0056] Comparative Example 2

[0057] A polyurethane sponge was prepared according to the method of Example 1, except that the immersion of the PDA / MXene-modified polyurethane sponge in the nitrogen-phosphorus-silicon flame retardant / PDA solution was not performed, i.e., step (6) was omitted.

[0058] Comparative Example 3

[0059] A polyurethane sponge was prepared according to the method of Example 1, except that no PDA / MXene powder was added when the polyurethane was prepared by the one-step foaming method.

[0060] The performance of the polyurethane sponges prepared in each embodiment and each comparative example was tested, and the results are as follows:

[0061] (1) Photothermal performance test

[0062] Table 1

[0063]

[0064] It can be seen from Table 1 that the addition of MXene effectively improves the photothermal conversion performance of polyurethane foam.

[0065] (2) Hydrophobic performance test

[0066] The contact angle test was performed on the photothermal super hydrophobic flame retardant polyurethane obtained in the examples and comparative examples, and the test results are shown in the following table. As can be seen from Table 2, only Example 1 exhibits super hydrophobic properties.

[0067] Table 2

[0068]

[0069] (3) Flame retardant performance test

[0070] Table 3

[0071]

[0072] It can be seen from the test results in Table 3 that, compared with Comparative Example 1, the limiting oxygen index and thermal decomposition temperature of the modified polyurethane foam are increased; the limiting oxygen index and thermal decomposition temperature of Example 1 are the highest.

[0073] It was also found through experiments that the contact angles of the products prepared in Examples 1 to 5 to paraffin oil, gasoline, diesel, n-hexane, and acetone were all 0°.

[0074] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation, characterized in that: The method comprises the following steps: (1) Mixing polydopamine-modified MXene powder, polyether polyol, deionized water, Maitu L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate to form a mixture, and allowing the mixture to stand at room temperature until the foam shape is stable, and then fully ripening the polyurethane foam to obtain a PDA / MXene-modified polyurethane foam; (2) Synthesis of nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6 3-aminopropyltriethoxysilane and triethylamine are dissolved in toluene, and a toluene solution of hexachlorocyclotriphosphazene is added dropwise, mixed evenly, and then heated under reflux for reaction, and a white solid is precipitated after the reaction; after the reaction is completed, the reaction liquid is filtered, and then the residual 3-aminopropyltriethoxysilane and triethylamine in the filtrate are removed to obtain a colorless transparent liquid, which is the nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6; (3) dissolving the nitrogen-phosphorus-silicon hybrid flame retardant N3P3[NH(CH2)3Si(OEt)3]6 in a mixed solution of deionized water and ethanol to obtain a N3P3[NH(CH2)3Si(OEt)3]6 solution, adding dopamine, and adjusting the pH value of the solution to 8-9 with Tris-HCl buffer to obtain a nitrogen-phosphorus-silicon flame retardant / PDA solution; (4) The PDA / MXene modified polyurethane foam is immersed in a nitrogen-phosphorus-silicon flame retardant / PDA solution, taken out after the immersion is completed, and the excess liquid is squeezed out and then washed and dried to obtain a photothermal superhydrophobic flame retardant polyurethane sponge.

2. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (1), the dosage ratio of polydopamine-modified MXene powder to polyether polyol, deionized water, Maitu L-580 silicone oil, dibutyltin dilaurate, triethylenediamine, and polymethylene polyphenyl isocyanate is (0.4-1): (25-35): (0.7-1): (0.2-0.32): (0.01-0.05): (0.01-0.03): (10-15).

3. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (1), the mixture is foamed at room temperature; after standing at room temperature, the foam is placed in an oven at 80-85° C. for maturation.

4. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (2), the molar ratio of 3-aminopropyltriethoxysilane to triethylamine and hexachlorocyclotriphosphazene is (65-70): (75-80) mmol: (10-11) mmol.

5. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (2), the heating reflux temperature is 110° C. and the reaction time is 3-5 h.

6. The method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (3), the concentration of N3P3[NH(CH2)3Si(OEt)3]6 in the N3P3[NH(CH2)3Si(OEt)3]6 solution is 10-60 g / L, the mass ratio of deionized water to ethanol is 1:1; and the dopamine concentration is 2 g / L.

7. The method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (4), the ratio of PDA / MXene modified polyurethane foam to nitrogen-phosphorus-silicon flame retardant / PDA solution is 1 g:30 mL; the immersion temperature is 30-50° C., and the immersion time is 2-4 h.

8. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to any one of claims 1 to 7, characterized in that: Polydopamine-modified MXene powders were prepared by the following steps: (a) dissolving lithium fluoride powder in hydrochloric acid solution, adding Ti3AlC2 powder to react; after the reaction, washing the reaction product with water by ultrasonic centrifugation for multiple times until the pH value is 7; collecting the centrifuge liquid for multiple times, centrifuging, collecting the centrifuge liquid for freeze drying, and obtaining a single-layer or few-layer MXene powder; (b) The prepared MXene powder is added to Tris buffer, mixed evenly, and then dopamine hydrochloride is added to react; after the reaction, the obtained precipitate is centrifuged and washed to neutrality, and vacuum dried to obtain polydopamine-modified MXene powder.

9. A method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 8, characterized in that: In step (a), the hydrochloric acid solution is prepared by mixing 6 mol / L concentrated hydrochloric acid and deionized water in a volume ratio of 1:1, and the amount ratio of lithium fluoride powder to hydrochloric acid solution and Ti3AlC2 powder is 1g:16-25mL:1g; the reaction temperature is 30-40°C, and the reaction time is 20-28h.

10. The method for preparing a photothermal super hydrophobic flame retardant polyurethane sponge for oil-water separation according to claim 1, characterized in that: In step (b), the mass ratio of MXene powder to dopamine hydrochloride is 1:0.5-1.

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