Flame retardant, preparation method thereof and polyurethane material

Abstract

The invention relates to the technical field of flame-retardant materials, in particular to a flame retardant, a preparation method thereof and a polyurethane material. The preparation method of the flame retardant provided by the invention comprises the following step: reacting benzimidazole, metal nitrate, aluminum hypophosphite, a surfactant and a solvent in a microwave reactor to obtain the flame retardant. According to the preparation method of the flame retardant, the synthesized metal organic framework material is used for coating the modified aluminum hypophosphite flame retardant, so that the compatibility with a matrix material is greatly improved, the problems of easiness in hydrophilicity, difficulty in dispersion, easiness in migration and the like during use are solved, and the flame-retardant effect and the processability are improved; the flame retardant can be independently used and does not need to be compounded with other flame retardants, and the flame retardant effect can still reach the V-0 level; when the flame retardant is used in a polyurethane material, the flame retardant property and the mechanical property of the material can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, in particular to a flame retardant and a preparation method thereof and a polyurethane material. Background Art

[0002] Thermoplastic polyurethane (TPU) has the characteristics of good wear resistance, wide hardness range, high strength and long pull-up rate, good shock absorption effect, good oil resistance, etc. It is widely used in the automotive industry, aerospace electronics, electronic communications, textile industry and other industries. The disadvantage of thermoplastic polyurethane is that it is very easy to burn. After burning, it releases toxic gases such as HCN and CO, which can easily cause suffocation and death. Therefore, it is more urgent to improve the flame retardant properties of thermoplastic polyurethane materials.

[0003] Aluminum hypophosphite (AHP) flame retardant, as a low-smoke, non-toxic, high-phosphorus content, high flame retardant efficiency, and good thermal stability, is widely used in the flame retardancy of thermoplastic polyurethane materials. However, it also has a series of problems: (1) poor dispersibility in the matrix polymer and easy agglomeration; (2) it has strong polarity, poor compatibility with organic polymers, and easy precipitation; (3) it needs to be used in combination with organic flame retardants (MCA, ADP, TPP, etc.), which reduces the flame retardant effect and increases the processing cost. The above problems greatly limit the application of aluminum hypophosphite flame retardant in thermoplastic polyurethane materials.

[0004] In view of this, this invention is proposed. Summary of the invention

[0005] The first purpose of the present invention is to provide a method for preparing a flame retardant, which utilizes a synthetic metal organic framework material to coat a modified aluminum hypophosphite flame retardant, thereby greatly improving the compatibility with a base material, solving the problems of easy hydrophilicity, difficult dispersion, and easy migration during use, and improving the flame retardant effect and processing performance; it can be used alone in a polyurethane material, which is beneficial to improving the flame retardant properties and mechanical properties of the material.

[0006] The second object of the present invention is to provide a flame retardant.

[0007] The third object of the present invention is to provide a polyurethane material.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] In a first aspect, the present invention provides a method for preparing a flame retardant, comprising the following steps:

[0010] The flame retardant is obtained after benzimidazole, metal nitrate, aluminum hypophosphite, a surfactant and a solvent react in a microwave reactor.

[0011] Further, it includes at least one of the following features (1) to (3);

[0012] (1) The microwave power of the reaction is 60 to 90 Hz;

[0013] (2) The reaction temperature is 100-150° C.;

[0014] (3) The reaction time is 0.5 to 2 hours.

[0015] Furthermore, the mass ratio of the benzimidazole, the metal nitrate and the aluminum hypophosphite is (10-20): (15-25): (20-30);

[0016] And / or, the mass ratio of the aluminum hypophosphite to the surfactant is (20-30):(3-8).

[0017] Furthermore, the metal nitrate includes at least one of copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, zirconium nitrate, chromium nitrate and calcium nitrate.

[0018] And / or, the particle size D98 of the aluminum hypophosphite is 5 to 15 μm.

[0019] Furthermore, the surfactant includes at least one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium carboxymethyl cellulose and polyvinyl pyrrolidone.

[0020] Further, it includes at least one of the following features (1) to (3);

[0021] (1) The solvent includes an organic solvent and water;

[0022] (2) The mass ratio of the organic solvent to the water is (50-80): (90-140)

[0023] (3) The organic solvent includes methanol and / or ethanol.

[0024] Furthermore, the method for preparing the flame retardant comprises the following steps:

[0025] The benzimidazole and the organic solvent are mixed to obtain a benzimidazole solution; the metal nitrate and water are mixed to obtain a metal nitrate solution; the aluminum hypophosphite, the surfactant and water are mixed to obtain an aluminum hypophosphite dispersion;

[0026] The aluminum hypophosphite dispersion and the benzimidazole solution are mixed to obtain a mixed solution; the mixed solution is mixed with the metal nitrate solution and reacted in a microwave reactor to obtain the flame retardant.

[0027] In a second aspect, the present invention further provides a flame retardant, which is prepared by the flame retardant preparation method as described above.

[0028] In a third aspect, the present invention further provides a polyurethane material comprising the flame retardant as described above.

[0029] Furthermore, in the polyurethane material, the mass percentage of the flame retardant is 5% to 15%.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The flame retardant preparation method of the invention adopts benzimidazole as an organic ligand for synthesizing MOFs material, and adopts a microwave-assisted method as a synthesis method. The synthesized MOFs material has a higher specific surface area, a finer pore size, a more regular crystal form, a higher thermal stability and a more efficient flame retardant effect. The characteristics of the synthesized MOFs material are fully utilized to coat and modify the aluminum hypophosphite flame retardant to obtain the MOFs@AHP flame retardant, which greatly improves the compatibility with the matrix material, solves the problems of easy hydrophilicity, difficult dispersion, easy migration, etc. during use, and improves the flame retardant effect and processing performance.

[0032] AHP flame retardant can only achieve a better flame retardant effect when used in combination with flame retardants such as MCA; and the MOFs@AHP flame retardant of the present invention can be used alone as a flame retardant without being used in combination with other flame retardants, and its flame retardant effect can still reach V-0 level.

[0033] The MOFs@AHP flame retardant of the present invention is added to a polyurethane material, especially a thermoplastic polyurethane material. The modified flame retardant burns and decomposes to produce substances such as phosphoric acid, which can accelerate the dehydration and carbonization of the polyurethane material to form a dense carbon layer, thereby improving the strength and rigidity of the material; at the same time, it blocks heat transfer and oxygen diffusion, thereby improving the flame retardant effect and mechanical properties of the material. DETAILED DESCRIPTION

[0034] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0035] The flame retardant and its preparation method and polyurethane material of the present invention are described in detail below.

[0036] In some embodiments of the present invention, a method for preparing a flame retardant is provided, comprising the following steps:

[0037] The flame retardant is obtained after benzimidazole, metal nitrate, aluminum hypophosphite, surfactant and solvent react in a microwave reactor.

[0038] The flame retardant preparation method of the present invention generates a metal organic framework (MOFs) material during the reaction process, and encapsulates and modifies aluminum hypophosphite (AHP) to obtain a metal organic framework (MOFs)-encapsulated modified aluminum hypophosphite (AHP) flame retardant (MOF@AHP).

[0039] MOFs have abundant transition metal species, flame retardant elements and potential carbon sources, and their structures and properties are easily adjustable. Compared with other inorganic flame retardants, the organic part of MOFs enhances the compatibility of fillers and polymer chains and reduces the burden of additional organic modifications. At the same time, their organic structure helps to carry flame retardant groups such as phosphorus, nitrogen and aromatic compounds through appropriate modification, thus improving their flame retardant properties.

[0040] The present invention utilizes the MOFs material synthesized by the above method to coat and modify aluminum hypophosphite, and the MOFs@AHP flame retardant obtained after the modification greatly improves the compatibility with the base material, solves the problems of easy hydrophilicity, difficult dispersion, easy migration, etc. during use, and improves the flame retardant effect and processing performance; the MOF@AHP flame retardant greatly improves the precipitation problem, dispersion and migration problem of the AHP flame retardant; the AHP flame retardant and the MCA flame retardant can only have a better flame retardant effect when used in combination, and the MOFs@AHP flame retardant of the present invention can be used alone in polymer materials without being used in combination with other flame retardants, and its flame retardant effect can reach the V-0 level; it is beneficial to improve the flame retardant effect and mechanical properties of polymer materials (such as thermoplastic polyurethane materials); and the preparation method of the present invention is simple and easy to operate, with low production cost, and is suitable for large-scale production.

[0041] The MOFs@AHP flame retardant of the present invention is added to a polyurethane material, especially a thermoplastic polyurethane material. The modified flame retardant burns and decomposes to produce substances such as phosphoric acid, which can accelerate the dehydration and carbonization of the polyurethane material to form a dense carbon layer, thereby improving the strength and rigidity of the material; at the same time, it blocks heat transfer and oxygen diffusion, thereby improving the flame retardant effect and mechanical properties of the material.

[0042] The present invention starts from the perspective of the organic ligand and synthesis method of MOFs materials, and uses benzimidazole as the organic ligand. The benzene ring structure in the benzimidazole improves the stability of the material and the compactness after the flame retardant carbonization, greatly improving the flame retardant effect and stability of the MOFs material itself; thereby improving the flame retardant effect of the flame retardant. At the same time, the microwave-assisted method is used to synthesize MOFs materials under higher temperature and pressure conditions, and the MOFs materials have a higher specific surface area, finer pore size, more regular crystal form and higher thermal stability.

[0043] In some embodiments of the present invention, the microwave power of the reaction is 60-90 Hz; typically but not limitatively, for example, the microwave power of the reaction can be 60 Hz, 65 Hz, 70 Hz, 75 Hz, 80 Hz, 85 Hz, 90 Hz or a range consisting of any two of them.

[0044] In some embodiments of the present invention, the reaction temperature is 100-150°C; typically but not limiting, for example, the reaction temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or a range of any two thereof; preferably 120-150°C.

[0045] In some embodiments of the present invention, the reaction time is 0.5 to 2 h; typically but not limiting, for example, the reaction time can be 0.5 h, 1 h, 1.5 h, 2 h or a range consisting of any two thereof.

[0046] In some embodiments of the present invention, the mass ratio of benzimidazole, metal nitrate and aluminum hypophosphite is (10-20): (15-25): (20-30); typically but not limitatively, for example, the mass ratio of benzimidazole and metal nitrate can be 10:15, 10:25, 15:15, 15:20, 20:25 or a range consisting of any two thereof; the mass ratio of benzimidazole and aluminum hypophosphite can be 10:20, 10:25, 10:30, 15:20, 15:25, 15:30, 20:20, 20:25, 20:30 or a range consisting of any two thereof.

[0047] In some embodiments of the present invention, the mass ratio of aluminum hypophosphite to the surfactant is (20-30):(3-8); typically but not limitatively, for example, the mass ratio of aluminum hypophosphite to the surfactant can be 20:3, 20:5, 20:8, 25:3, 25:5, 25:8, 30:3, 30:5, 30:8 or a range of any two thereof.

[0048] In some embodiments of the present invention, the mass ratio of benzimidazole to solvent is (10-20):(140-220); typically but not limiting, for example, the mass ratio of benzimidazole to solvent can be 10:140, 10:220, 15:180, 20:140, 20:220 or any range of two values.

[0049] In some embodiments of the present invention, the metal nitrate includes at least one of copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, zirconium nitrate, chromium nitrate and calcium nitrate.

[0050] In some embodiments of the present invention, the particle size D98 of aluminum hypophosphite is 5 to 15 μm; typically but not limiting, for example, the particle size D98 of aluminum hypophosphite can be 5 μm, 7 μm, 10 μm, 12 μm, 15 μm or a range of any two thereof.

[0051] In some embodiments of the present invention, the surfactant includes at least one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium carboxymethyl cellulose and polyvinyl pyrrolidone.

[0052] In some embodiments of the present invention, the solvent includes an organic solvent and water.

[0053] In some embodiments of the present invention, the mass ratio of the organic solvent to water is (50-80):(90-140).

[0054] In some embodiments of the present invention, the organic solvent comprises methanol and / or ethanol.

[0055] In some embodiments of the present invention, the method for preparing a flame retardant specifically comprises the following steps:

[0056] Mixing benzimidazole and an organic solvent to obtain a benzimidazole solution; mixing metal nitrate and water to obtain a metal nitrate solution; mixing aluminum hypophosphite, a surfactant and water to obtain an aluminum hypophosphite dispersion; preferably, mixing 10 to 20 parts of benzimidazole and 50 to 80 parts of an organic solvent at 50 to 70° C. to obtain a benzimidazole solution; mixing 15 to 25 parts of a metal nitrate and 50 to 80 parts of water at 60 to 70° C. to obtain a metal nitrate solution; mixing 20 to 30 parts of aluminum hypophosphite, 3 to 8 parts of a surfactant and 40 to 60 parts of water at 50 to 70° C. to obtain an aluminum hypophosphite dispersion;

[0057] After the aluminum hypophosphite dispersion and the benzimidazole solution are mixed, a mixed solution is obtained; after the mixed solution is mixed with the metal nitrate solution, the mixture is reacted in a microwave reactor to obtain a flame retardant. During the reaction process, under the conditions of high temperature and high pressure in the microwave reactor, the metal organic framework precursor undergoes an in-situ polymerization reaction on the surface of the aluminum hypophosphite flame retardant, and the reaction equation is: M(NO3)2+2C7H6N2→[M(C7H6N2)2](NO3)2, thereby achieving surface coating modification of the aluminum hypophosphite flame retardant.

[0058] In some embodiments of the present invention, the reaction further comprises: centrifugation, washing and drying in sequence.

[0059] In some embodiments of the present invention, a flame retardant is also provided, which is prepared by the above-mentioned method for preparing the flame retardant.

[0060] In some embodiments of the present invention, a polyurethane material is further provided, comprising the flame retardant mentioned above; preferably, the polyurethane material comprises thermoplastic polyurethane elastomer (TPU) and the flame retardant.

[0061] By adding the flame retardant of the present invention to thermoplastic polyurethane elastomer (TPU), an excellent flame retardant effect can be achieved at a relatively low addition amount, and the combustion level can reach V-0 level; moreover, the mechanical properties such as tensile strength of the material are also improved.

[0062] In some embodiments of the present invention, the mass percentage of the flame retardant in the polyurethane material is 5% to 15%; typically but not limiting, for example, in the thermoplastic polyurethane material, the mass percentage of the flame retardant can be 5%, 7%, 10%, 12%, 15% or a range of any two thereof; preferably 5% to 10%.

[0063] In some embodiments of the present invention, a method for preparing the above-mentioned polyurethane material is also provided, comprising the following steps:

[0064] The flame retardant and thermoplastic polyurethane elastomer (TPU) are mixed, and then extruded and injection molded in sequence to obtain a polyurethane material.

[0065] In some embodiments of the present invention, the extrusion comprises: extruding the modified material using a twin-screw extruder, the twin-screw extruder No. 30 extruder, the feeding speed is 20 rpm, and the temperature is 150-200°C.

[0066] In some embodiments of the present invention, injection molding includes: injection molding the modified material using an injection molding machine, the processing temperature of the injection molding machine is: the temperature of the first section is 210°C, the temperature of the second section is 210°C, and the temperature of the unloading section is 215°C.

[0067] Example 1

[0068] The method for preparing the flame retardant provided in this embodiment comprises the following steps:

[0069] 15 parts of benzimidazole are added to 60 parts of methanol, heated to 60°C, stirred to dissolve, and a benzimidazole solution is obtained; 18 parts of cobalt nitrate are added to 50 parts of water, heated to 62°C, stirred to dissolve, and a cobalt nitrate solution is obtained; 25 parts of aluminum hypophosphite with a particle size D98 of 10 μm are added to 40 parts of water, heated to 50°C, 4 parts of sodium dodecyl sulfate are added, and stirred to disperse uniformly to obtain an aluminum hypophosphite dispersion;

[0070] The aluminum hypophosphite dispersion is slowly added dropwise to the benzimidazole solution, stirred and dispersed, and mixed evenly to form a mixed solution; the cobalt nitrate solution is slowly added dropwise to the above mixed solution under stirring conditions, and then the mixed solution is transferred to a microwave reaction container. Under stirring conditions, the microwave power is set to 80HZ, and the reaction is carried out at 135°C for 1h. After the reaction is completed, centrifugation, washing, and drying are performed in sequence to obtain a metal organic framework (MOFs)-encapsulated modified aluminum hypophosphite (AHP) flame retardant, which is recorded as A1.

[0071] The method for preparing the polyurethane material provided in this embodiment comprises the following steps:

[0072] 5 parts of A1 and 95 parts of thermoplastic polyurethane elastomer (TPU) were added to a high-speed mixer and mixed at high speed. The modified material was extruded using a twin-screw extruder. The twin-screw extruder No. was 30 extruder, the feeding speed was 20 rpm, and the temperature was 150-200°C. The modified material was then injection molded using an injection molding machine. The processing temperature of the injection molding machine was: the temperature of the first section was 210°C, the temperature of the second section was 210°C, and the temperature of the unloading section was 215°C. A polyurethane material sample was obtained, which was recorded as M1.

[0073] Example 2

[0074] The method for preparing the flame retardant provided in this embodiment comprises the following steps:

[0075] 18 parts of benzimidazole are added to 65 parts of methanol, heated to 65°C, stirred to dissolve, and a benzimidazole solution is obtained; 20 parts of zinc nitrate are added to 60 parts of water, heated to 65°C, stirred to dissolve, and a zinc nitrate solution is obtained; 30 parts of aluminum hypophosphite with a particle size D98 of 10 μm are added to 55 parts of water, heated to 60°C, 6 parts of polyvinyl pyrrolidone are added, stirred and dispersed evenly, and an aluminum hypophosphite dispersion is obtained;

[0076] The aluminum hypophosphite dispersion is slowly added dropwise to the benzimidazole solution, stirred and dispersed, and mixed evenly to form a mixed solution; the zinc nitrate solution is slowly added dropwise to the above mixed solution under stirring conditions, and then the mixed solution is transferred to a microwave reaction container. Under stirring conditions, the microwave power is set to 85HZ, and the reaction is carried out at 120°C for 1.2h. After the reaction is completed, centrifugation, washing, and drying are performed in sequence to obtain a metal organic framework (MOFs)-encapsulated modified aluminum hypophosphite (AHP) flame retardant, which is recorded as A2.

[0077] The method for preparing the polyurethane material provided in this embodiment comprises the following steps:

[0078] 10 parts of A2 and 90 parts of thermoplastic polyurethane elastomer (TPU) were added into a high-speed mixer and mixed at high speed. The modified material was extruded by a twin-screw extruder. The twin-screw extruder No. 30 extruder had a feeding speed of 20 rpm and a temperature of 150-200°C. The modified material was then injection molded by an injection molding machine. The processing temperature of the injection molding machine was: the temperature of the first section was 210°C, the temperature of the second section was 210°C, and the temperature of the unloading section was 215°C. A polyurethane material sample was obtained, which was recorded as M2.

[0079] Example 3

[0080] The method for preparing the flame retardant provided in this embodiment comprises the following steps:

[0081] Take 10 parts of benzimidazole and add it to 50 parts of methanol, heat it to 55°C, stir it to dissolve it, and obtain a benzimidazole solution; take 15 parts of copper nitrate and add it to 50 parts of water, heat it to 60°C, stir it to dissolve it, and obtain a copper nitrate solution; take 20 parts of aluminum hypophosphite with a particle size D98 of 5 μm and add it to 40 parts of water, heat it to 60°C, add 3 parts of sodium dodecylbenzene sulfonate, stir and disperse it evenly, and obtain an aluminum hypophosphite dispersion;

[0082] The aluminum hypophosphite dispersion is slowly added dropwise to the benzimidazole solution, stirred and dispersed, and mixed evenly to form a mixed solution; the cobalt nitrate solution is slowly added dropwise to the above mixed solution under stirring conditions, and then the mixed solution is transferred to a microwave reaction container. Under stirring conditions, the microwave power is set to 75HZ, and the reaction is carried out at 145°C for 0.8h. After the reaction is completed, centrifugation, washing, and drying are performed in sequence to obtain a metal organic framework (MOFs)-encapsulated modified aluminum hypophosphite (AHP) flame retardant, which is recorded as A3.

[0083] The method for preparing the polyurethane material provided in this embodiment comprises the following steps:

[0084] 15 parts of A3 and 85 parts of thermoplastic polyurethane elastomer (TPU) were added to a high-speed mixer and mixed at high speed. The modified material was extruded using a twin-screw extruder. The twin-screw extruder number was No. 30 extruder, the feeding speed was 20 rpm, and the temperature was 150-200°C. The modified material was then injection molded using an injection molding machine. The processing temperature of the injection molding machine was: the temperature of the first section was 210°C, the temperature of the second section was 210°C, and the temperature of the unloading section was 215°C. A polyurethane material sample was obtained, which was recorded as M3.

[0085] Example 4

[0086] The preparation method of the flame retardant provided in this embodiment refers to Example 1, except that 3 parts of benzimidazole are added to 60 parts of methanol, heated to 60°C, and stirred to dissolve to obtain a benzimidazole solution; 18 parts of cobalt nitrate are added to 50 parts of water, heated to 62°C, and stirred to dissolve to obtain a cobalt nitrate solution; 25 parts of aluminum hypophosphite with a particle size D98 of 10 μm are added to 40 parts of water, heated to 50°C, 4 parts of sodium dodecyl sulfate are added, and stirred to disperse evenly to obtain an aluminum hypophosphite dispersion; the obtained flame retardant is recorded as A4.

[0087] The preparation method of the polyurethane material provided in this embodiment refers to that in Embodiment 1, the only difference is that the flame retardant A1 is replaced by A4; the obtained polyurethane material sample is recorded as M4.

[0088] Example 5

[0089] The preparation method of the flame retardant provided in this embodiment refers to Example 1, except that 30 parts of benzimidazole are added to 60 parts of methanol, heated to 60°C, and stirred to dissolve to obtain a benzimidazole solution; 18 parts of cobalt nitrate are added to 50 parts of water, heated to 62°C, and stirred to dissolve to obtain a cobalt nitrate solution; 25 parts of aluminum hypophosphite with a particle size D98 of 10 μm are added to 40 parts of water, heated to 50°C, 4 parts of sodium dodecyl sulfate are added, and stirred to disperse evenly to obtain an aluminum hypophosphite dispersion; the obtained flame retardant is recorded as A5.

[0090] The preparation method of the polyurethane material provided in this embodiment refers to Example 1, except that the flame retardant A1 is replaced by A5; the obtained polyurethane material sample is recorded as M5.

[0091] Comparative Example 1

[0092] The preparation method of the polyurethane material provided in this comparative example refers to Example 1, except that the flame retardant A1 is replaced by aluminum hypophosphite (AHP); the obtained polyurethane material sample is recorded as M6.

[0093] Comparative Example 2

[0094] The preparation method of the polyurethane material provided in this comparative example refers to Example 1, except that the flame retardant A1 is replaced by a composite flame retardant of aluminum hypophosphite (AHP) and melamine cyanurate (MCA) in a mass ratio of 1:2; the obtained polyurethane material sample is recorded as M7.

[0095] Comparative Example 3

[0096] The preparation method of the flame retardant provided in this comparative example comprises the following steps:

[0097] 15 parts of 2-methylimidazole were added to 60 parts of methanol, heated to 60°C, stirred to dissolve, and a 2-methylimidazole solution was obtained; 18 parts of cobalt nitrate were added to 50 parts of water, heated to 62°C, stirred to dissolve, and a cobalt nitrate solution was obtained; 25 parts of aluminum hypophosphite with a particle size D98 of 10 μm were added to 40 parts of water, heated to 50°C, stirred and dispersed uniformly, and an aluminum hypophosphite dispersion was obtained;

[0098] The aluminum hypophosphite dispersion is slowly dropped into 2-methylimidazole, stirred and dispersed, and mixed evenly to form a mixed solution; the cobalt nitrate solution is slowly dropped into the above mixed solution under stirring conditions, and reacted at 25°C for 1 hour. After the reaction is completed, centrifugation, washing, and drying are performed in sequence to obtain a metal organic framework-encapsulated modified aluminum hypophosphite flame retardant, which is recorded as A6.

[0099] The preparation method of the polyurethane material provided in this comparative example refers to Example 1, except that the flame retardant A1 is replaced by A6; the obtained polyurethane material sample is recorded as M8.

[0100] Test example

[0101] The flame retardant properties and mechanical properties of the polyurethane material samples M1, M2, M3, M4, M5, M6, M7, and M8 of Examples 1 to 5 and Comparative Examples 1 to 3 were tested, and the results are shown in Table 1.

[0102] Vertical burning test (UL94): tested in accordance with GB / 2408-2008 standard, sample size is 130mm×13mm×4mm.

[0103] Limiting oxygen index test: Tested in accordance with ISO 4589-2 standard, sample size is 100mm×10mm×4mm.

[0104] Tensile strength test: According to GB / T 1040-2006 standard test, the sample size is 75mm×5mm×2mm, the tensile rate is 40mm / min, and 5 samples are tested in each group to take the average value.

[0105] Precipitation test: Place the sample at 85°C, 85RH for 7 days and observe the precipitation on the surface.

[0106] Table 1

[0107]

[0108] As can be seen from Table 1, when the MOFs-coated modified AHP flame retardant of the present invention is applied to thermoplastic polyurethane elastomer, when its mass fraction exceeds 15 parts, the transparency of the material will be reduced; compared with the compound flame retardant, when a lower amount (5wt%) of MOFs@AHP flame retardant is added to the material, its combustion level can also reach the V-0 level, the limiting oxygen index can reach 29.5%, the tensile strength of the material is also enhanced, and the material has no precipitation; when AHP is used alone, its combustion level does not reach the V-0 level, and the mechanical properties of the material are poor, and the precipitation of the thermoplastic polyurethane elastomer is serious. This shows that the MOFs-coated modified AHP flame retardant can greatly improve the precipitation problem, dispersion and migration problem of the AHP flame retardant, and can improve the mechanical properties and flame retardant effect of the material.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a flame retardant, characterized in that: The steps include: The flame retardant is obtained after benzimidazole, metal nitrate, aluminum hypophosphite, a surfactant and a solvent react in a microwave reactor.

2. The method for preparing a flame retardant according to claim 1, characterized in that: The method comprises at least one of the following features (1) to (3); (1) The microwave power of the reaction is 60 to 90 Hz; (2) The reaction temperature is 100-150° C.; (3) The reaction time is 0.5 to 2 hours.

3. The method for preparing a flame retardant according to claim 1, characterized in that: The mass ratio of the benzimidazole, the metal nitrate and the aluminum hypophosphite is (10-20): (15-25): (20-30); And / or, the mass ratio of the aluminum hypophosphite to the surfactant is (20-30):(3-8).

4. The method for preparing a flame retardant according to claim 1, characterized in that: The metal nitrate comprises at least one of copper nitrate, iron nitrate, zinc nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, zirconium nitrate, chromium nitrate and calcium nitrate; And / or, the particle size D98 of the aluminum hypophosphite is 5 to 15 μm.

5. The method for preparing a flame retardant according to claim 1, characterized in that: The surfactant includes at least one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium carboxymethyl cellulose and polyvinyl pyrrolidone.

6. The method for preparing a flame retardant according to claim 1, characterized in that: The method comprises at least one of the following features (1) to (3); (1) The solvent includes an organic solvent and water; (2) The mass ratio of the organic solvent to the water is (50-80):(90-140); (3) The organic solvent includes methanol and / or ethanol.

7. The method for preparing a flame retardant according to claim 1, characterized in that: The steps include: The benzimidazole and the organic solvent are mixed to obtain a benzimidazole solution; the metal nitrate and water are mixed to obtain a metal nitrate solution; the aluminum hypophosphite, the surfactant and water are mixed to obtain an aluminum hypophosphite dispersion; The aluminum hypophosphite dispersion and the benzimidazole solution are mixed to obtain a mixed solution; the mixed solution is mixed with the metal nitrate solution and reacted in a microwave reactor to obtain the flame retardant.

8. A flame retardant, characterized in that: The flame retardant is prepared by the method for preparing the flame retardant according to any one of claims 1 to 7.

9. A polyurethane material, characterized in that: Comprising the flame retardant according to claim 8.

10. The polyurethane material according to claim 9, characterized in that: In the polyurethane material, the mass percentage of the flame retardant is 5% to 15%.

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