Modified piperazine pyrophosphate, composite flame retardant as well as preparation method and application of modified piperazine pyrophosphate and composite flame retardant

Abstract

The invention belongs to the technical field of flame-retardant materials, and particularly relates to modified piperazine pyrophosphate, a composite flame retardant and a preparation method and application of the modified piperazine pyrophosphate and the composite flame retardant. The modified piperazine pyrophosphate provided by the invention is obtained by modifying piperazine pyrophosphate with a modifier; the modifier comprises silicon resin. According to the preparation method, the piperazine pyrophosphate is modified by adopting a specific type of silicon resin as a modifier, and the piperazine pyrophosphate is coated by utilizing a three-dimensional network structure of the silicon resin, so that the hydrophobicity and the flowability of the piperazine pyrophosphate powder can be improved, and the piperazine pyrophosphate powder has good dispersity in a high polymer material; and the paint has good flame retardance, water resistance, acid resistance and alkali resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flame-retardant materials, and particularly relates to a modified piperazine pyrophosphate, a composite flame retardant, and a preparation method and application thereof. BACKGROUND

[0002] Piperazine pyrophosphate (PAPP) is a nitrogen-phosphorus synergistic halogen-free environmentally friendly high-efficiency flame retardant, which integrates acid source, gas source and carbon source, has excellent carbonization and flame retardant performance, and is white powder without odor and taste. The piperazine pyrophosphate flame retardant has the advantages of environmental protection and high efficiency, and can be used for flame-retardant polypropylene, polyethylene, acrylonitrile-butadiene-styrene, epoxy resin and polyurethane materials, and is a halogen-free flame retardant with great development potential.

[0003] However, due to the existence of hydroxyl and hydrogen bonds in the piperazine pyrophosphate molecule, the piperazine pyrophosphate is hydrophilic and easy to agglomerate, and has poor dispersibility in macromolecular materials such as polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), epoxy resin (EP) and polyurethane (PU), and polyamide (PA). In order to improve the dispersibility of piperazine pyrophosphate in these high molecular materials, silicon oil is currently mainly used to modify piperazine pyrophosphate, such as dimethyl silicone oil and hydrogen-containing silicone oil. Although this kind of modifier can improve the water resistance of piperazine pyrophosphate to a certain extent, the acid resistance and alkali resistance are basically not improved.

[0004] Therefore, it is of great significance to improve the dispersibility, flame retardancy, water resistance, acid resistance and alkali resistance of piperazine pyrophosphate in high molecular materials. SUMMARY

[0005] The present application aims to solve one or more problems existing in the prior art, and at least provide a beneficial alternative. Specifically, the present application provides a modified piperazine pyrophosphate which has good hydrophobicity and fluidity, and thus has good dispersibility in high molecular materials, and has good flame retardancy, water resistance, acid resistance and alkali resistance.

[0006] The inventive concept of the present application is that the modified piperazine pyrophosphate is obtained by modifying piperazine pyrophosphate with a modifier; and the modifier comprises a silicone resin. The present application uses a specific kind of modifier to modify piperazine pyrophosphate, and uses the three-dimensional network structure of the silicone resin to coat the piperazine pyrophosphate, so as to improve the hydrophobicity and fluidity of the piperazine pyrophosphate powder, and thus improve the dispersibility of the piperazine pyrophosphate in high molecular materials, and improve the flame retardancy, water resistance, acid resistance and alkali resistance of the piperazine pyrophosphate.

[0007] Therefore, the first aspect of the present application provides a modified piperazine pyrophosphate.

[0008] Specifically, the modified pyrophosphoryl piperazine is obtained by modifying pyrophosphoryl piperazine with a modifier.

[0009] The modifier comprises a silicone resin.

[0010] Preferably, the silicone resin comprises at least one of a methyl silicone resin, a methyl phenyl silicone resin, and a phenyl silicone resin.

[0011] Preferably, the mass ratio of the pyrophosphoryl piperazine to the modifier is 1:(0.001-0.1).

[0012] Further preferably, the mass ratio of the pyrophosphoryl piperazine to the modifier is 1:(0.01-0.05).

[0013] Preferably, the particle size D50 of the pyrophosphoryl piperazine is ≤10 μm.

[0014] The second aspect of the present application provides a preparation method of the modified pyrophosphoryl piperazine according to the first aspect of the present application.

[0015] Specifically, the preparation method of the modified pyrophosphoryl piperazine comprises the following steps:

[0016] Mixing pyrophosphoryl piperazine and a modifier in a solvent, and heating to obtain the modified pyrophosphoryl piperazine.

[0017] Preferably, the solvent comprises at least one of toluene, aliphatic hydrocarbon solvent oil, octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane.

[0018] Further preferably, the aliphatic hydrocarbon solvent oil comprises at least one of D40 and D80.

[0019] Preferably, the mass ratio of the pyrophosphoryl piperazine to the modifier is 1:(0.001-0.1).

[0020] Further preferably, the mass ratio of the pyrophosphoryl piperazine to the modifier is 1:(0.01-0.05).

[0021] Preferably, the mass ratio of the modifier to the solvent is (0.1-10):1.

[0022] Further preferably, the mass ratio of the modifier to the solvent is (0.5-5):1.

[0023] Preferably, the heating temperature is 100-500 ℃.

[0024] Further preferably, the heating temperature is 200-400 ℃.

[0025] Preferably, the heating time is 1-10 h.

[0026] Further preferably, the heating time is 2-8h.

[0027] Preferably, stirring is performed during the heating, and the stirring speed is 100-1000rpm.

[0028] Further preferably, stirring is performed during the heating, and the stirring speed is 200-600rpm.

[0029] The third aspect of the present application provides a composite flame retardant.

[0030] Specifically, the composite flame retardant comprises the modified piperazine pyrophosphate according to the first aspect of the present application.

[0031] Preferably, the composite flame retardant further comprises at least one of a phosphorus-nitrogen synergistic halogen-free flame retardant, an antioxidant, and a lubricant.

[0032] Further preferably, the composite flame retardant further comprises a phosphorus-nitrogen synergistic halogen-free flame retardant, an antioxidant, and a lubricant.

[0033] Preferably, the composite flame retardant comprises 27-65 parts of the modified piperazine pyrophosphate, 27-65 parts of the phosphorus-nitrogen synergistic halogen-free flame retardant, 0.9-11 parts of the antioxidant, and 0.9-11 parts of the lubricant by mass fraction.

[0034] Further preferably, the composite flame retardant comprises 30-60 parts of the modified piperazine pyrophosphate, 30-60 parts of the phosphorus-nitrogen synergistic halogen-free flame retardant, 1-10 parts of the antioxidant, and 1-10 parts of the lubricant by mass fraction.

[0035] Preferably, the phosphorus-nitrogen synergistic halogen-free flame retardant comprises at least one of melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate.

[0036] Preferably, the antioxidant comprises at least one of 2,6-di-tert-butyl-p-cresol, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis-(4-methyl-6-tert-butylphenol), tris[2.4-di-tert-butylphenyl]phosphite, tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0037] Preferably, the lubricant comprises at least one of zinc oxide, zinc stearate, and calcium stearate.

[0038] The fourth aspect of the present application provides a preparation method of the composite flame retardant according to the third aspect of the present application.

[0039] Specifically, the preparation method of the composite flame retardant comprises the following steps:

[0040] Mixing the components of the composite flame retardant to obtain the composite flame retardant.

[0041] The fifth aspect of the present application provides a modified piperazine pyrophosphate according to the first aspect of the present application or a composite flame retardant according to the third aspect of the present application for use in the field of flame retardation.

[0042] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0043] (1) The present application uses a specific type of silicone resin as a modifier to modify piperazine pyrophosphate. The three-dimensional network structure of the silicone resin is used to coat the piperazine pyrophosphate, which can improve the hydrophobicity and flowability of the piperazine pyrophosphate powder, thereby improving the dispersibility of the piperazine pyrophosphate in high polymer materials, and improving the flame retardancy, water resistance, acid resistance and alkali resistance.

[0044] (2) The preparation process of the present application is simple and convenient for large-scale industrial application. DETAILED DESCRIPTION

[0045] In order to make the skilled in the art more clearly understand the technical scheme of the present application, the following examples are given for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0046] The raw materials, reagents or devices used in the following examples, if not specifically stated, can be obtained from conventional commercial channels, or can be obtained by existing known methods.

[0047] Example 1

[0048] A modified piperazine pyrophosphate is obtained by modifying piperazine pyrophosphate with methyl silicone resin.

[0049] The preparation method of the modified piperazine pyrophosphate comprises the following steps:

[0050] Dissolve 10g of methyl silicone resin in 10g of toluene to obtain a methyl silicone resin toluene solution; add 1kg of piperazine pyrophosphate powder to a high-speed stirrer, and under the condition of 300rpm stirring, add 20g of methyl silicone resin toluene solution dropwise, and add dropwise for 10 minutes. After the solution is added dropwise, open the condensation reflux device, heat to 200℃, evaporate the toluene, and gradually solidify the methyl silicone resin. The piperazine pyrophosphate powder is coated, and after 4h of heat preservation, the temperature is lowered, and the stirring is stopped to obtain the modified piperazine pyrophosphate powder.

[0051] A composite flame retardant is prepared from the following raw materials by mass fraction: 30 parts of the modified pyrazophosphoric acid powder of Example 1, 60 parts of melamine polyphosphate, 1 part of 2,6-di-tert-butyl-p-cresol, and 9 parts of zinc oxide.

[0052] A preparation method of the composite flame retardant, comprising the following steps:

[0053] The raw materials of the composite flame retardant are mixed to obtain the composite flame retardant.

[0054] Example 2

[0055] A modified pyrazophosphoric acid is obtained by modifying pyrazophosphoric acid with methylphenyl silicone resin.

[0056] A preparation method of the modified pyrazophosphoric acid, comprising the following steps:

[0057] 20 g of methylphenyl silicone resin is dissolved in 10 g of Shell D40 solvent to obtain a methylphenyl silicone resin D40 solution; 1 kg of pyrazophosphoric acid powder is added to a high-speed stirrer, and 30 g of the methylphenyl silicone resin D40 solution is added dropwise under the condition of 400 rpm stirring, and the dropping is completed in 12 minutes; after the solution is added dropwise, the condensation reflux device is opened, the temperature is raised to 250°C, the D40 solvent is evaporated, the methylphenyl silicone resin is gradually solidified, the pyrazophosphoric acid powder is coated, and the temperature is maintained for 3 h, then the temperature is lowered, the stirring is stopped, and the modified pyrazophosphoric acid powder is obtained.

[0058] A composite flame retardant is prepared from the following raw materials by mass fraction: 30 parts of the modified pyrazophosphoric acid powder of Example 1, 60 parts of melamine polyphosphate, 1 part of 2,6-di-tert-butyl-p-cresol, and 9 parts of zinc oxide.

[0059] A preparation method of the composite flame retardant, comprising the following steps:

[0060] The raw materials of the composite flame retardant are mixed to obtain the composite flame retardant.

[0061] Example 3

[0062] A modified pyrazophosphoric acid is obtained by modifying pyrazophosphoric acid with methylphenyl silicone resin.

[0063] A preparation method of the modified pyrazophosphoric acid, comprising the following steps:

[0064] 10g phenyl silicone resin is dissolved in 20g octamethylcyclotetrasiloxane to obtain a phenyl silicone resin octamethylcyclotetrasiloxane solution; 1kg piperazine pyrophosphate powder is added to a high-speed stirrer, 30g phenyl silicone resin octamethylcyclotetrasiloxane solution is added dropwise under the condition of 400rpm stirring, and the dropping is completed in 15 minutes; after the solution is added dropwise, the condensation reflux device is opened, the temperature is raised to 300℃, the octamethylcyclotetrasiloxane is evaporated, the phenyl silicone resin is gradually solidified, and the piperazine pyrophosphate powder is coated; after being heated for 2h, the temperature is lowered, the stirring is stopped, and the modified piperazine pyrophosphate powder is obtained.

[0065] A composite flame retardant is prepared from the following raw materials in mass fraction: 60 parts of the modified piperazine pyrophosphate powder of Example 3, 30 parts of melamine polyphosphate, 9 parts of bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, and 1 part of calcium stearate.

[0066] The preparation method of the composite flame retardant comprises the following steps:

[0067] The raw materials of the composite flame retardant are mixed to obtain the composite flame retardant.

[0068] Comparative Example 1

[0069] The difference between the modified piperazine pyrophosphate of Comparative Example 1 and Example 1 is that the methyl silicone oil is used to replace the methyl silicone resin of Example 1 in the same amount, and the others are the same as Example 1.

[0070] Specifically, the preparation process of the modified piperazine pyrophosphate powder of Comparative Example 1 methyl silicone oil comprises the following steps:

[0071] 10g methyl silicone oil is dissolved in 10g toluene to obtain a methyl silicone oil toluene solution; 1kg piperazine pyrophosphate powder is added to a high-speed stirrer, 20g methyl silicone oil toluene solution is added dropwise under the condition of 300rpm stirring, and the dropping is completed in 10 minutes; after the methyl silicone oil toluene solution is added dropwise, the condensation reflux device is opened, the temperature is raised to 200℃, the toluene is evaporated, the silicone oil coats the piperazine pyrophosphate powder, the temperature is raised for 4h, the temperature is lowered, the stirring is stopped, and the modified piperazine pyrophosphate powder is obtained.

[0072] The difference between the composite flame retardant of Comparative Example 1 and the preparation method thereof and Example 1 is that the modified piperazine pyrophosphate prepared in Comparative Example 1 is used in the composite flame retardant of Comparative Example 1, and the others are the same as Example 1.

[0073] Comparative Example 2

[0074] The difference between the modified piperazine pyrophosphate of Comparative Example 2 and Example 1 is that the hydrogen-containing silicone oil is used to replace the methyl silicone resin of Example 1 in the same amount, and the others are the same as Example 1.

[0075] Specifically, the preparation process of the modified pyrophosphoryl piperazine powder prepared by the hydrogen-containing silicone oil of Comparative Example 2 includes the following steps:

[0076] 10 g of the hydrogen-containing silicone oil was dissolved in 10 g of toluene to obtain a hydrogen-containing silicone oil toluene solution; 1 kg of the pyrophosphoryl piperazine powder was added into a high-speed stirrer, and 20 g of the hydrogen-containing silicone oil toluene solution was added dropwise under the condition of 300 rpm stirring, and the dropping was completed in 10 minutes; after the dropping of the solution was completed, the condensation reflux device was opened, and the temperature was increased to 200 °C to evaporate the toluene, and the silicone oil coated the pyrophosphoryl piperazine powder; after the temperature was increased for 4 hours, the temperature was decreased, and the stirring was stopped to obtain the modified pyrophosphoryl piperazine powder.

[0077] The difference between the composite flame retardant of Comparative Example 2 and the preparation method thereof and Example 1 is only that the modified pyrophosphoryl piperazine prepared by Comparative Example 2 is used in the composite flame retardant of Comparative Example 2, and the others are the same as Example 1.

[0078] Comparative Example 3

[0079] The difference between Comparative Example 3 and Example 1 is that the pyrophosphoryl piperazine powder is not modified by using a modifier in Comparative Example 3, that is, the unmodified pyrophosphoryl piperazine powder is used.

[0080] The difference between the composite flame retardant of Comparative Example 3 and the preparation method thereof and Example 1 is only that the unmodified pyrophosphoryl piperazine powder of Comparative Example 3 is used in the composite flame retardant of Comparative Example 3, and the others are the same as Example 1.

[0081] Performance test

[0082] 1. Moisture and rest angle test

[0083] The moisture and rest angle tests were performed on the modified pyrophosphoryl piperazines prepared by Example 1-3 and Comparative Example 1-2, and the unmodified pyrophosphoryl piperazine of Comparative Example 3, and the test items and test methods were as follows:

[0084] Moisture test: tested according to GB / T 6284-2006;

[0085] Rest angle test: tested according to GB / T 11986-1989.

[0086] The moisture and rest angle test results of the modified pyrophosphoryl piperazines of Example 1-3 and Comparative Example 1-2, and the unmodified pyrophosphoryl piperazine of Comparative Example 3 are shown in Table 1.

[0087] Table 1: Moisture and rest angle of the modified pyrophosphoryl piperazines of Example 1-3 and Comparative Example 1-2, and the unmodified pyrophosphoryl piperazine of Comparative Example 3

[0088] Group Moisture content (%) Repose angle (°) Example 1 0.01 22 Example 2 0.01 25 Example 3 0.01 24 Comparative Example 1 0.09 42 Comparative Example 2 0.07 40 Comparative Example 3 0.18 58

[0089] From Table 1, it can be seen that the modified pyrophosphoric acid piperazine prepared by the application has lower water content and repose angle, indicating that it has good hydrophobicity and flowability.

[0090] Comparative Example 1 and Comparative Example 2 respectively use methyl silicone oil and hydrogen-containing silicone oil to modify the pyrophosphoric acid piperazine powder, so that the water content and repose angle of the prepared modified pyrophosphoric acid piperazine are higher than those of Example 1. It is indicated that after the pyrophosphoric acid piperazine powder is modified by using methyl silicone oil and hydrogen-containing silicone oil, the hydrophobicity and flowability of the flame retardant are poorer than those of the modification by using silicone resin.

[0091] Comparative Example 3 does not use a modifier for modification, so that the water content and repose angle of the pyrophosphoric acid piperazine are significantly greater than those of the modified pyrophosphoric acid piperazine of Example 1.

[0092] 2. Dispersion, flame retardancy, water resistance, acid resistance, and alkali resistance test

[0093] In 79.8 parts by mass of PP, polycarbonate (PC), and PA particles, 20 parts by mass of the composite flame retardant of Example 1-3 and Comparative Example 1-3, and 0.2 parts by mass of Eucleron carbon black are added, respectively, and a double-screw extruder is used for melt extrusion and granulation to obtain flame-retardant particles, i.e., flame-retardant resin materials. Finally, the flame-retardant particles are injection molded in a horizontal injection molding machine under the conditions of a plasticizing temperature of 200°C, a screw rotation speed of 50 r / min, an injection pressure of 45%, and a pressure maintaining time of 8 s to obtain test bars with a length of 127 mm, a width of 12.7 mm, and a thickness of 3.2 mm. The white point condition of the surface of the test bar and the flame retardancy, water resistance, acid resistance, and alkali resistance of the test bar are observed.

[0094] The dispersion of the modified pyrophosphoric acid piperazine powder in PP, PC, and PA is determined by the white point condition of the surface of the test bar. The fewer the white points, the better the dispersion.

[0095] The white point condition of the test bar prepared by the composite flame retardant of Example 1-3 and Comparative Example 1-3 is shown in Table 2.

[0096] Table 2: White point condition of the test bar prepared by the composite flame retardant of Example 1-3 and Comparative Example 1-3

[0097]

[0098] As can be seen from Table 2, the number of white points in the test bar prepared by the composite flame retardant of Example 1-3 and PP, PC, and PA is significantly less than that in the test bar prepared by the composite flame retardant of Comparative Example 1-3 and PP, PC, and PA. It is indicated that the surface modification of the pyrophosphoric acid piperazine powder by using silicone resin in the application can make the pyrophosphoric acid piperazine powder have better dispersion in PP, PC, and PA.

[0099] Each group of 5 samples was taken from Examples 1-3 and Comparative Examples 1-3, and flame retardant tests were carried out according to the UL94 standard to evaluate the flame retardant performance, and the combustion conditions are shown in Table 3 below.

[0100] Table 3: Combustion conditions of composite flame retardants of Examples 1-3 and Comparative Examples 1-3

[0101]

[0102] As can be seen from Table 3, the afterflame time of the composite flame retardants of Examples 1-3 in PP / PC / PA is significantly less than that of Comparative Examples 1-3, and the shorter the afterflame time, the better the flame retardant performance, which shows that the pyrophosphoric acid piperazine powder modified by the silicon resin has better flame retardant performance.

[0103] The samples prepared by the composite flame retardants of Examples 1-3 and Comparative Examples 1-2 were respectively placed in pure water, hydrochloric acid solution with pH=3, and sodium hydroxide solution with pH=10, and soaked for 24h, and then the white spot conditions of the samples were observed to evaluate the water resistance, acid resistance and alkali resistance of each group of samples.

[0104] The statistical results of the white spot conditions of the samples prepared by the composite flame retardants of Examples 1-3 and Comparative Examples 1-2 after soaking test are shown in Table 4.

[0105] Table 4: White spot conditions of samples prepared by the composite flame retardants of Examples 1-3 and Comparative Examples 1-2 after soaking test

[0106]

[0107] As can be seen from Table 4, the number of white spots of the samples prepared by the composite flame retardants of Examples 1-3 and PP, PC, and PA respectively after soaking in pure water, acid solution, and alkali solution is less, because the structure of the modifier is not damaged by pure water, acid solution, and alkali solution. This shows that the pyrophosphoric acid piperazine powder modified by the silicon resin has excellent water resistance, acid resistance and alkali resistance.

[0108] The number of white spots of the samples prepared by the composite flame retardants of Comparative Examples 1-2 and PP, PC, and PA respectively after soaking in pure water, acid solution, and alkali solution is significantly more than that of Examples 1. This is because the modifier in Comparative Examples 1-2 is damaged by pure water, acid solution, and alkali solution, which makes the pyrophosphoric acid piperazine powder flame retardant migrate to the surface of the sample, and the number of white spots on the surface of the sample increases. That is, the water resistance, acid resistance and alkali resistance of the modified pyrophosphoric acid piperazine powder of Comparative Examples 1-2 are poorer than those of Examples 1.

[0109] To sum up, the pyrophosphoric acid piperazine is modified by adopting the specific kind of silicone resin as the modifier, the pyrophosphoric acid piperazine is coated by the three-dimensional network structure of the silicone resin, the hydrophobicity and flowability of the pyrophosphoric acid piperazine powder can be improved, and the pyrophosphoric acid piperazine has good dispersibility in the high polymer material, and has good flame retardancy, water resistance, acid resistance and alkali resistance.

[0110] The above examples are only used to illustrate the technical solutions of the present application, but not limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A modified pyrrolizine diphosphate, characterized in that, The modified pyrophosphorpiperazine is obtained by modifying pyrophosphorpiperazine with a modifier; The modifier comprises a silicone resin.

2. The modified piperazine pyrophosphates according to claim 1, characterized in that, The silicone resin comprises at least one of a methyl silicone resin, a methylphenyl silicone resin, and a phenyl silicone resin; and / or, the mass ratio of the pyrophosphorpiperazine to the modifier is 1:(0.001-0.1).

3. Process for the preparation of modified pyrrolizine pyrophosphates according to any one of claims 1-2, characterized in that, The method comprises the following steps: The pyrophosphorpiperazine, the modifier, and a solvent are mixed and heated to obtain the modified pyrophosphorpiperazine.

4. The production method according to claim 3, characterized by, The solvent comprises at least one of toluene, aliphatic hydrocarbon solvent oil, octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane; and / or, the mass ratio of the modifier to the solvent is (0.1-10):

1.

5. The preparation method according to claim 3, characterized in that, The heating temperature is 100-500℃; and / or, the heating time is 1-10h; and / or, stirring is performed during the heating, and the stirring speed is 100-1000rpm.

6. A composite flame retardant characterized by comprising: The modified pyrophosphorpiperazine of any one of claims 1-2.

7. The composite flame retardant according to claim 6, wherein The composite flame retardant further comprises at least one of a phosphorus-nitrogen synergistic halogen-free flame retardant, an antioxidant, and a lubricant.

8. The composite flame retardant according to claim 7, wherein The composite flame retardant comprises 27-65 parts of the modified pyrophosphorpiperazine, 27-65 parts of the phosphorus-nitrogen synergistic halogen-free flame retardant, 0.9-11 parts of the antioxidant, and 0.9-11 parts of the lubricant by mass fraction.

9. Process for the preparation of the complex flame retardant according to any one of claims 6-8, characterized in that, The method comprises the following steps: The components of the composite flame retardant are mixed to obtain the composite flame retardant.

10. Use of the modified pyrophosphorpiperazine of any one of claims 1-2, or the composite flame retardant of any one of claims 6-8 in the field of flame retardation.

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