High-fluidity phosphorus-nitrogen synergistic flame retardant and synthesis method thereof

Abstract

The invention provides a high-fluidity phosphorus-nitrogen synergistic flame retardant and a synthesis method thereof, and relates to the field of flame retardants. Comprising the following steps: S1, adding piperazine pyrophosphate into a metal salt solution, uniformly dispersing, then adding a weak base solution, adjusting the pH value to 8-9, stirring, filtering, drying and crushing to obtain a core material; s2, uniformly mixing the core material, melamine polyphosphate and ethanol, then adding the melamine formaldehyde resin liquid, uniformly stirring, adjusting the pH value to 3-5, heating to 50-60 DEG C in a water bath, and keeping the temperature for 1-2 hours; and S3, adding unsaturated oleic acid, a silane coupling agent and a melamine formaldehyde resin liquid, uniformly stirring, heating to 65-75 DEG C in a water bath, keeping the temperature for 1-2 hours, filtering, and drying to obtain the flame retardant. According to the synthesis method, through twice wrapping, the fluidity of the flame retardant in the resin can be fully improved, the dispersity of the flame retardant in the resin is improved, and the flame retardance of the resin is further improved.

Description

Technical Field

[0001] The invention relates to the field of flame retardants, and in particular to a high-fluidity phosphorus-nitrogen synergistic flame retardant and a synthesis method thereof. Background Art

[0002] Piperazine pyrophosphate (PAPP) is a highly efficient phosphorus-nitrogen synergistic, halogen-free, environmentally friendly intumescent flame retardant. Its flame retardant mechanism is mainly to form a dense carbonized layer during the combustion process to block oxygen and prevent the spread of flames. At the same time, the decomposition products of piperazine pyrophosphate can dilute the combustible gas and further improve the flame retardant effect. Due to its excellent water resistance, carbonization performance and flame retardant effect, it is increasingly used in resin materials.

[0003] The fluidity and dispersibility of flame retardants in resins are key factors affecting the flame retardant effect of finished resins. Among them, the type and properties of the resin matrix have a significant impact on the fluidity of piperazine pyrophosphate. For example, the viscosity, molecular structure and cross-linking density of resins such as epoxy resins and polyurethanes will affect the flow of flame retardants. On the other hand, as the amount of piperazine pyrophosphate added increases, the viscosity of the resin system gradually increases, and the fluidity of the flame retardant in the resin will also decrease accordingly. The size of piperazine pyrophosphate particles also directly affects its dispersibility in the resin. Smaller particles are easier to disperse evenly in the resin, improving the flame retardant effect.

[0004] Patent 202210729624.1 discloses a microencapsulated core-shell structure coated piperazine pyrophosphate flame retardant, which coats carbon nanotubes on the surface of piperazine pyrophosphate, improves the water resistance of piperazine pyrophosphate, and can effectively improve the compatibility of piperazine pyrophosphate in resin, thereby improving the fluidity of the flame retardant. Patent 202110088534.4 discloses a halogen-free flame retardant, which uses melamine formaldehyde resin to coat piperazine pyrophosphate, and embeds layered inorganic substances in the capsule material and the capsule core, and then surface treats the melamine formaldehyde resin capsule material to load alkoxy, vinyl and silicone oil long-chain groups. By encapsulating the capsule material and surface treating the capsule material, the fluidity of the flame retardant can be improved and its water solubility can be reduced. It is suitable for sealants. Adding the flame retardant to the sealant can improve the flame retardant properties of the sealant.

[0005] The fluidity of flame retardants in resins can be improved to a certain extent by coating and surface modification methods. However, the resin processing process is usually accompanied by high temperature and high-intensity stirring. Under high temperature and high-intensity stirring conditions, the bonding strength between the surface modifier and the flame retardant matrix is ​​low and easy to separate, or the coating structure is prone to rupture and failure, resulting in a decrease in the fluidity of the flame retardant. Summary of the invention

[0006] The object of the present invention is to provide a phosphorus-nitrogen synergistic flame retardant with high fluidity. Through two times of encapsulation, the fluidity of the flame retardant in the resin can be fully improved, the dispersibility of the flame retardant in the resin can be enhanced, and thus the flame retardancy of the resin can be improved.

[0007] Another object of the present invention is to provide a method for synthesizing a phosphorus-nitrogen synergistic flame retardant with high fluidity. By using the precipitation effect of a metal salt solution and the coating effect of melamine formaldehyde, piperazine pyrophosphate is coated inside to form a coated flame retardant, which has good hydrophobicity and good fluidity in the resin.

[0008] The present invention solves its technical problems by adopting the following technical solutions.

[0009] On the one hand, an embodiment of the present invention provides a method for synthesizing a phosphorus-nitrogen synergistic flame retardant with high fluidity, including the following steps:

[0010] S1, adding piperazine pyrophosphate into a metal salt solution, dispersing evenly, then adding a weak base solution, adjusting the pH value to 8-9, stirring, filtering, drying, and pulverizing to obtain a core material;

[0011] S2, mixing the core material, melamine polyphosphate, and ethanol evenly, then adding a melamine formaldehyde resin solution, stirring evenly, adjusting the pH value to 3-5, heating in a water bath to 50-60 °C, and keeping warm for 1-2 h;

[0012] S3, adding unsaturated oleic acid, a silane coupling agent, and a melamine formaldehyde resin solution, stirring evenly, heating the water bath to 65-75 °C, keeping warm for 1-2 h, filtering, and drying to obtain the flame retardant.

[0013] In some embodiments of the present invention, the metal salt solution is a mixture of one or more of zinc sulfate and magnesium sulfate.

[0014] In some embodiments of the present invention, the weak base solution is an ammonia water solution or a sodium carbonate solution.

[0015] In some embodiments of the present invention, the silane coupling agent is one of acetyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane.

[0016] In some embodiments of the present invention, in the step S1, the mass ratio of piperazine pyrophosphate to the metal salt is 1:(0.5-1).

[0017] In some embodiments of the present invention, in the step S2, the mass ratio of the core material, melamine polyphosphate, and the melamine formaldehyde resin solution is (0.5-1):(0.5-1):(1-1.5).

[0018] In some embodiments of the present invention, in step S3, the mass ratio of unsaturated oleic acid, silane coupling agent and melamine formaldehyde resin solution is (0.5 - 1):(0.1 - 0.5):(0.5 - 1).

[0019] In some embodiments of the present invention, the mass ratio of the melamine formaldehyde resin solution added in step S2 to the melamine formaldehyde resin solution added in step S3 is 1:(0.3 - 0.5).

[0020] In step S2, preliminary encapsulation is carried out with melamine formaldehyde resin, and the reaction is carried out at 50 - 60 °C to allow the encapsulation reaction to proceed slowly. Then, in step S3, unsaturated oleic acid and melamine formaldehyde resin are added for a second encapsulation. The unsaturated oleic acid molecules can enter the incompletely encapsulated wall material to form an embedded structure, improving the binding strength between the unsaturated oleic acid and the wall material. When using the flame retardant, the unsaturated oleic acid molecules can be embedded in the network structure of the resin to enhance the binding strength between the flame retardant and the resin matrix. In the present invention, more melamine formaldehyde resin is added in step S2 to fully encapsulate the core material, while a small amount of melamine formaldehyde resin is added in step S3. On the one hand, it is to supplement the encapsulation to improve the encapsulation rate of the core material; on the other hand, the small amount of melamine formaldehyde resin added for the second time can be used as a binder to fix the unsaturated oleic acid molecules on the wall material for surface modification.

[0021] In some embodiments of the present invention, in step S3, the unsaturated oleic acid is one or a mixture of linoleic acid, linolenic acid, oleic acid, etc. The unsaturated oleic acid molecules have active double bond structures and long carbon molecular chains. Grafting them on the surface of the flame retardant can, on the one hand, use the long carbon molecular chains to improve the hydrophobicity and lipophilicity of the flame retardant, that is, improve the fluidity of the flame retardant in the resin; on the other hand, the active double bonds can serve as reaction sites during the resin processing process to form chemical bond binding with the active sites in the resin matrix, thereby improving the binding strength between the flame retardant and the resin matrix and enhancing the migration resistance of the flame retardant.

[0022] On the other hand, the embodiments of the present invention provide a high-fluidity phosphorus-nitrogen synergistic flame retardant prepared by the above synthesis method.

[0023] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0024] The synthesis method of the high-fluidity phosphorus-nitrogen synergistic flame retardant provided by the present invention first mixes piperazine pyrophosphate with a metal salt solution. Under the action of a weak base, the metal salt forms a metal hydroxide precipitate that wraps around the surface of piperazine pyrophosphate to obtain a core material. The use of the metal hydroxide encapsulation can improve the flame retardant performance of piperazine pyrophosphate.

[0025] Then, use melamine formaldehyde resin to wrap the core material and melamine polyphosphate to form a double-layer wrapped structure of piperazine pyrophosphate-metal hydroxide-melamine polyphosphate-melamine formaldehyde resin. The outermost layer of melamine formaldehyde resin has good hydrophobicity, which can improve the fluidity of the flame retardant in the resin. Secondly, when the flame retardant is added to the resin for processing, after the outermost wall material of the double-layer wrapped structure is damaged, the metal hydroxide layer can still play a wrapping role and does not affect its fluidity in the resin. Thirdly, piperazine pyrophosphate, metal hydroxide, and melamine polyphosphate synergistically enhance the flame retardant performance of the flame retardant.

[0026] Then, use melamine formaldehyde resin, unsaturated oleic acid, and silane coupling agent for the third wrapping. The long-chain unsaturated oleic acid molecules can be embedded in the network structure formed by melamine formaldehyde resin, that is, unsaturated oleic acid molecules are loaded on the surface of the melamine formaldehyde resin wall material. When using this flame retardant, under the high temperature of resin processing, the double bonds in the unsaturated oleic acid molecules are activated and can further react with the molecular chains in the resin, which can improve the bonding strength between the flame retardant and the resin matrix and reduce the probability of the flame retardant migrating in the resin. Detailed implementation method

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0028] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0029] The features and properties of the present invention will be further described in detail below in conjunction with the embodiments.

[0030] Embodiment 1

[0031] Prepare the flame retardant of this embodiment according to the following method:

[0032] S1, add piperazine pyrophosphate to a zinc sulfate solution with a mass fraction of 10%, disperse evenly, then add ammonia water solution, adjust the pH value to 8, stir for 20 min, filter, dry, crush, and pass through a 100-mesh sieve to obtain the core material; the mass ratio of piperazine pyrophosphate to metal salt is 1:0.5.

[0033] S2. Mix the core material, melamine polyphosphate, and ethanol evenly, then add the melamine formaldehyde resin solution, stir evenly, adjust the pH value to 3, heat in a water bath to 55 °C, and keep warm for 2 h. The mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 1:1:1.5.

[0034] S3. Then add linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution, stir evenly, raise the temperature in the water bath to 70 °C, keep warm for 2 h, filter, and dry to obtain the flame retardant. The mass ratio of linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.5:1, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.3.

[0035] Example 2

[0036] Prepare the flame retardant of this example according to the following method:

[0037] S1. Add piperazine pyrophosphate to zinc sulfate with a mass fraction of 10%, disperse evenly, then add ammonia water solution, adjust the pH value to 8, stir for 20 min, filter, dry, crush, and pass through a 100-mesh sieve to obtain the core material. The mass ratio of piperazine pyrophosphate to the metal salt is 1:1.

[0038] S2. Mix the core material, melamine polyphosphate, and ethanol evenly, then add the melamine formaldehyde resin solution, stir evenly, adjust the pH value to 3, heat in a water bath to 60 °C, and keep warm for 1 h. The mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 1:1:1.

[0039] S3. Then add linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution, stir evenly, raise the temperature in the water bath to 75 °C, keep warm for 2 h, filter, and dry to obtain the flame retardant. The mass ratio of linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.3:1, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.5.

[0040] Example 3

[0041] Prepare the flame retardant of this example according to the following method:

[0042] S1. Add piperazine pyrophosphate to magnesium sulfate with a mass fraction of 10%, disperse evenly, then add ammonia water solution, adjust the pH value to 9, stir for 20 min, filter, dry, crush, and pass through a 100-mesh sieve to obtain the core material. The mass ratio of piperazine pyrophosphate to the metal salt is 1:0.8.

[0043] S2. Mix the core material, melamine polyphosphate, and ethanol evenly, then add the melamine formaldehyde resin solution, stir evenly, adjust the pH value to 5, heat in a water bath to 60 °C, and keep warm for 2 h; the mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 0.5:0.5:1.

[0044] S3. Then add linolenic acid, γ-aminopropyltriethoxysilane, and melamine formaldehyde resin solution, stir evenly, raise the temperature in a water bath to 65 °C, keep warm for 1.5 h, filter, and dry to obtain the flame retardant. The mass ratio of linolenic acid, γ-aminopropyltriethoxysilane, and melamine formaldehyde resin solution is 0.8:0.5:1, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.5.

[0045] Example 4

[0046] Prepare the flame retardant of this example according to the following method:

[0047] S1. Add piperazine pyrophosphate to zinc sulfate with a mass fraction of 10%, disperse evenly, then add ammonia water solution, adjust the pH value to 9, stir for 20 min, filter, dry, crush, and pass through a 100-mesh sieve to obtain the core material; the mass ratio of piperazine pyrophosphate to the metal salt is 1:0.8.

[0048] S2. Mix the core material, melamine polyphosphate, and ethanol evenly, then add the melamine formaldehyde resin solution, stir evenly, adjust the pH value to 5, heat in a water bath to 55 °C, and keep warm for 1.5 h; the mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 0.8:1:1.

[0049] S3. Then add oleic acid, γ-aminopropyltrimethoxysilane, and melamine formaldehyde resin solution, stir evenly, raise the temperature in a water bath to 70 °C, keep warm for 1.5 h, filter, and dry to obtain the said flame retardant. The mass ratio of oleic acid, γ-aminopropyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.5:0.8, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.5.

[0050] Example 5

[0051] Prepare the flame retardant of this example according to the following method:

[0052] S1. Add piperazine pyrophosphate to magnesium sulfate with a mass fraction of 10%, disperse evenly, then add ammonia water solution, adjust the pH value to 9, stir for 20 min, filter, dry, crush, and pass through a 100-mesh sieve to obtain the core material; the mass ratio of piperazine pyrophosphate to the metal salt is 1:1.

[0053] S2, Mix the core material, melamine polyphosphate, and ethanol evenly, then add the melamine formaldehyde resin solution, stir evenly, adjust the pH value to 5, heat in a water bath to 55 °C, and keep warm for 1.5 h; the mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 0.8:0.8:1.5.

[0054] S3, Then add oleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution, stir evenly, raise the temperature in the water bath to 70 °C, keep warm for 2 h, filter, and dry to obtain the flame retardant. The mass ratio of oleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.1:0.5, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.3.

[0055] Example 6

[0056] The difference from Example 1 is that in step S1 of this example, the mass ratio of piperazine pyrophosphate to metal salt is 1:0.8. In step S3, the mass ratio of linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.1:1, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.5. For the rest of the raw materials and ratios, they are the same as those in Example 1.

[0057] Example 7

[0058] The difference from Example 1 is that in step S1 of this example, the mass ratio of piperazine pyrophosphate to metal salt is 1:0.8. In step S3, the mass ratio of linoleic acid, acetyltrimethoxysilane, and melamine formaldehyde resin solution is 0.5:0.1:0.5, and the mass ratio of the melamine formaldehyde resin solution in step S2 to the melamine formaldehyde resin solution in step S3 is 1:0.3. For the rest of the raw materials and ratios, they are the same as those in Example 1.

[0059] Example 8

[0060] The difference from Example 1 is that in step S2 of this example, the mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 0.5:1:1.5. For the rest of the raw materials and ratios, they are the same as those in Example 1.

[0061] Example 9

[0062] The difference from Example 1 is that in step S2 of this example, the mass ratio of the core material, melamine polyphosphate, and melamine formaldehyde resin solution is 1:1:1. For the rest of the raw materials and ratios, they are the same as those in Example 1.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that in this comparative example, no metal salt solution is added in step S1, and the remaining raw materials and their ratios are the same as those in Example 1.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that in this comparative example, no melamine polyphosphate is added in step S2, and the remaining raw materials and their ratios are the same as those in Example 1.

[0067] Comparative Example 3

[0068] The difference from Example 1 is that in this comparative example, no linoleic acid and acetyltrimethoxysilane are added in step S3, and the remaining raw materials and their ratios are the same as those in Example 1.

[0069] Comparative Example 4

[0070] The difference from Example 1 is that in this comparative example, step S3 is not carried out. In step S2, the temperature is raised to 70 °C in a water bath, held for 2 h, filtered, and dried to obtain the flame retardant. The remaining raw materials and their ratios are the same as those in Example 1.

[0071] Experimental Example

[0072] 1. The flame retardants of Examples 1-5, Comparative Examples 1-4, and unmodified piperazine pyrophosphate were used to prepare flame-retardant polypropylene. The specific method is as follows: The polypropylene masterbatch and the flame retardant were added to a screw extrusion molding machine according to a mass ratio of 95:5 to obtain polypropylene resin.

[0073] The oxygen index performance and UL94 flame retardancy of each polypropylene resin were tested, and the results are shown in Table 1.

[0074] Table 1 Flame Retardant Properties of Each Resin

[0075]

[0076]

[0077] It can be concluded from Table 1 that the flame retardants in Examples 1-5 can effectively improve the flame retardancy of polypropylene, and the LOI is significantly improved compared with unmodified piperazine pyrophosphate. In Comparative Example 1, metal hydroxide was not used for coating, and the LOI value of the modified polypropylene resin decreased, and the flame retardancy also decreased, but it was still better than that of the single piperazine pyrophosphate polypropylene resin. In Comparative Example 2, melamine polyphosphate was not added, and the synergistic effect of the flame retardant was weakened, and the exhibited flame retardancy was also reduced. In Comparative Example 3, linoleic acid was not added, and its influence on the flame retardancy of the flame retardant was small. In Comparative Example 4, melamine formaldehyde resin was not used for coating, and the fluidity of the flame retardant was relatively poor, and its dispersion performance in the polypropylene resin was poor, resulting in poor flame retardancy.

[0078] 2. After aging treatment (ultraviolet light irradiation at 60 °C for 24 h) of the resins of Example 1 and Comparative Examples 3-4, the oxygen index performance and UL94 flame retardancy performance were tested, and the results are shown in Table 2.

[0079] Table 2

[0080] LOI(%) Flame retardancy Example 1 31.3 V0 Comparative Example 3 20.3 V2 Comparative Example 4 18.6 V2 Polypropylene + Piperazine pyrophosphate 15.3 V2

[0081] It can be concluded from Table 2 that after aging treatment, the flame retardancy of the polypropylene resin in Example 1 changed little. In the flame retardant of Comparative Example 3, due to the absence of linoleic acid and silane coupling agent, its binding strength with the resin matrix was poor. After aging treatment, the flame retardant migrated, thus affecting the flame retardancy of the polypropylene resin.

[0082] In summary, for the synthesis method of the high-fluidity phosphorus-nitrogen synergistic flame retardant provided by the embodiments of the present invention, first, piperazine pyrophosphate is mixed with a metal salt solution. Under the action of a weak base, the metal salt generates a metal hydroxide precipitate, which is coated on the surface of piperazine pyrophosphate to obtain a core material. The coating with metal hydroxide can improve the flame retardancy of piperazine pyrophosphate.

[0083] Then, melamine formaldehyde resin is used to coat the core material and melamine polyphosphate to form a double-layer coating structure of piperazine pyrophosphate-metal hydroxide-melamine polyphosphate-melamine formaldehyde resin. The outermost melamine formaldehyde resin has good hydrophobicity, which can improve the fluidity of the flame retardant in the resin; secondly, when the flame retardant is added to the resin for processing, for the flame retardant with a double-layer coating structure, after the outermost wall material is damaged, the metal hydroxide layer can still play a coating role and does not affect its fluidity in the resin. Thirdly, piperazine pyrophosphate, metal hydroxide, and melamine polyphosphate synergistically enhance the flame retardancy of the flame retardant.

[0084] For the third coating, melamine formaldehyde resin, unsaturated oleic acid and silane coupling agent are used. The long-chain unsaturated oleic acid molecules can be embedded into the network structure formed by melamine formaldehyde resin, that is, the unsaturated oleic acid molecules are loaded on the surface of the melamine formaldehyde resin wall material. When using this flame retardant, under the action of high temperature during resin processing, the double bonds in the unsaturated oleic acid molecules are activated, and can further react with the molecular chains in the resin, which can improve the bonding strength between the flame retardant and the resin matrix and reduce the probability of the flame retardant migrating in the resin.

[0085] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant, characterized in that: The following steps are involved: S1, adding piperazine pyrophosphate to a metal salt solution, dispersing it evenly, then adding a weak base solution, adjusting the pH value to 8-9, stirring, filtering, drying, and crushing to obtain a core material; S2, mixing the core material, melamine polyphosphate and ethanol evenly, then adding melamine formaldehyde resin liquid, stirring evenly, adjusting the pH value to 3-5, heating in a water bath to 50-60° C., and keeping warm for 1-2 hours; S3, adding unsaturated oleic acid, silane coupling agent and melamine formaldehyde resin liquid, stirring evenly, heating to 65-75° C. in a water bath, keeping the temperature for 1-2 hours, filtering, and drying to obtain the flame retardant.

2. The method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: The metal salt solution is a mixture of one or more of zinc sulfate and magnesium sulfate.

3. The method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: The weak alkaline solution is an aqueous ammonia solution or a sodium carbonate solution.

4. The method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: The silane coupling agent is one of acetyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane.

5. The method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: In the step S1, the mass ratio of piperazine pyrophosphate to metal salt is 1:(0.5-1).

6. The method for synthesizing a high-fluidity phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: In the step S2, the mass ratio of the core material, melamine polyphosphate and melamine formaldehyde resin liquid is (0.5-1):(0.5-1):(1-1.5).

7. The preparation method of the high-fluidity phosphorus-nitrogen synergistic flame retardant synthesis method according to claim 1, characterized in that: In step S3, the mass ratio of unsaturated oleic acid, silane coupling agent and melamine formaldehyde resin liquid is (0.5-1):(0.1-0.5):(0.5-1).

8. The preparation method of the high-fluidity phosphorus-nitrogen synergistic flame retardant synthesis method according to claim 1, characterized in that: The mass ratio of the melamine formaldehyde resin liquid added in step S2 to the melamine formaldehyde resin liquid added in step S3 is 1:(0.3-0.5).

9. The preparation method of the high-fluidity phosphorus-nitrogen synergistic flame retardant synthesis method according to claim 1, characterized in that: In step S3, the unsaturated oleic acid is a mixture of one or more of linoleic acid, linolenic acid and oleic acid.

10. A high-fluidity phosphorus-nitrogen synergistic flame retardant, characterized in that: Prepared by the synthesis method described in claims 1-9.

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