Hydrophobic flame-retardant synergistic piperazine pyrophosphate and preparation method thereof

Abstract

The invention belongs to the technical field of flame-retardant materials, and particularly relates to hydrophobic flame-retardant synergistic piperazine pyrophosphate and a preparation method thereof. The preparation method comprises the following steps: diluting a polyfunctional group organosilicon compound containing P-N flame retardant elements by using absolute ethyl alcohol to obtain a diluent; uniformly spraying the diluent on the surface of the dried piperazine pyrophosphate, and then spraying deionized water; after heating and stirring, standing and preserving heat to obtain the piperazine pyrophosphate flame retardant. According to the invention, surface grafting modification is carried out through a specific polyfunctional group organosilicon compound, so that piperazine pyrophosphate with excellent hydrophobicity and flame-retardant synergistic characteristics is obtained.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, specifically relating to a high-performance piperazine pyrophosphate flame retardant and its preparation method. Background Technology

[0002] Piperazine pyrophosphate (PAPP), as a highly efficient intumescent flame retardant, is widely used in the flame-retardant modification of polyolefin materials such as polypropylene and polyethylene due to its environmentally friendly, low-smoke, and non-toxic properties. However, unmodified commercial piperazine pyrophosphate has two main drawbacks: first, its surface has a large number of polar groups, making it highly hydrophilic and incompatible with hydrophobic polymer matrices, resulting in uneven dispersion and easy agglomeration during processing, affecting the appearance and mechanical properties of the products; second, in humid and hot environments or during long-term use, the flame retardant is prone to migrate and precipitate from the matrix, causing permanent degradation of its flame-retardant performance.

[0003] Patent CN119331312A improves the hydrophobicity of piperazine pyrophosphate by utilizing the self-assembled structure resulting from the alcoholysis reaction of polysulfide silane compounds with piperazine pyrophosphate. Patent CN121159943A enhances the hydrophobicity of piperazine pyrophosphate by encapsulating it with a three-dimensional network structure of silicone resin. Existing technologies focus solely on improving hydrophobicity without addressing the trade-off between increased hydrophobicity and decreased flame retardant performance. This is because current products using silanes to enhance hydrophobicity introduce flammable alkane chains, leading to reduced flame retardant properties. Furthermore, commonly used silane coupling agents typically contain only 1-2 hydrolyzable alkoxy groups (such as triethoxy groups), limiting the grafting density with hydroxyl groups on the PAPP surface. This results in an insufficiently dense hydrophobic layer, which easily precipitates under high temperature and humidity, further reducing flame retardant efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a hydrophobic and flame-retardant piperazine pyrophosphate and its preparation method.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate, employing a dry grafting method, comprising the following steps: 1) Dry piperazine pyrophosphate (powder) (drying in a forced air at 110±20℃ for 1~3 hours) to obtain dried piperazine pyrophosphate; 2) The multifunctional organosilicon compound containing PN flame retardant element is diluted with anhydrous ethanol to obtain a diluted solution; 3) Set the mass ratio of the multifunctional organosilicon compound containing PN flame retardant elements to piperazine pyrophosphate to 1~5:100. Spray the diluted solution evenly (using the spray device on the high-speed mixer) onto the surface of the dried piperazine pyrophosphate, and then stir at 40~60℃ (stir at high speed for 20~40 minutes). 4) Set the mass ratio of deionized water to polyfunctional organosilicon compound containing PN flame retardant element = 1:5~10, spray (evenly spray) deionized water onto the surface of the material obtained in step 3); then raise the temperature to 90~110 ℃, stir (stir at high speed for 20~40 minutes), and then keep it at 90~110 ℃ for 2~4 hours to obtain piperazine pyrophosphate flame retardant (hydrophobic flame retardant enhanced piperazine pyrophosphate).

[0006] Note: Steps 3) and 4) can be performed in a high-speed mixer.

[0007] An improvement to the preparation method of the hydrophobic flame-retardant piperazine pyrophosphate of the present invention: The method for synthesizing the multifunctional organosilicon compound containing the PN flame-retardant element is as follows: under the protection of an inert gas (including nitrogen), bis-[3-(triethoxysilane)propyl]-amine and phenylphosphonodichloro react at 0~5℃ for 0.5~2 hours in an inert solvent and under the condition of an acid-binding agent, and then react at room temperature for 1.5~2.5 hours; the resulting reactants are post-treated to obtain the multifunctional organosilicon compound containing the PN flame-retardant element. The molar ratio of phenylphosphonodichloro to bis-[3-(triethoxysilyl)propyl]amine is 1:2 ± 0.1. The molar ratio of bis-[3-(triethoxysilyl)propyl]-amine to acid binder is 1:1 ± 0.1.

[0008] The acid-binding agent is triethylamine (anhydrous triethylamine).

[0009] The inert solvent is tetrahydrofuran (anhydrous tetrahydrofuran).

[0010] The specific method for synthesizing multifunctional organosilicon compounds containing PN flame-retardant elements is as follows: Under an inert gas atmosphere (including nitrogen), bis[3-(triethoxysilyl)propyl]amine and an acid-binding agent are placed in a reaction vessel containing an inert solvent. The temperature inside the reaction vessel is maintained at 0–5 °C, and stirring is started (stirring speed 400 ± 50 r / min). Then, a mixture of phenylphosphonic dichloride and the inert solvent is added dropwise (dropping time 20–40 minutes). After the dropwise addition is completed, the reaction is stirred for another 0.5–2 h (preferably 1 h). Then, the reaction is stirred for another 1.5–2.5 h (preferably 2 h) at room temperature. The resulting reactants are post-treated as follows: filtered, and the filtrate is rotary evaporated to remove the inert solvent, thus obtaining a multifunctional organosilicon compound containing the PN flame-retardant element, denoted as Si-PN-Si.

[0011] Note: Use 200-300 mL of inert solvent for every 2 mol of bis[3-(triethoxysilyl)propyl]amine.

[0012] In the mixture of phenylphosphonic dichloride and inert solvent, 40-60 mL of inert solvent is used for every 1 mol of phenylphosphonic dichloride.

[0013] As a further improvement to the preparation method of the hydrophobic flame-retardant and enhanced piperazine pyrophosphate of the present invention: In step 2), the mass ratio of the multifunctional organosilicon compound containing PN flame retardant element to anhydrous ethanol is 1:2~5 (preferably 1:2~4).

[0014] As a further improvement to the preparation method of the hydrophobic flame-retardant and enhanced piperazine pyrophosphate of the present invention: The stirring (high-speed stirring) speed in steps 3) and 4) is 600~1000 r / min (preferably 700~900 r / min).

[0015] This invention also provides a hydrophobic flame-retardant piperazine pyrophosphate prepared by any of the above methods, with the following structural formula: ; It belongs to a multifunctional organosilicon compound containing the PN flame-retardant element, which is chemically grafted onto the surface of piperazine pyrophosphate particles. This multifunctional organosilicon compound is preferably prepared by reacting 2 mol of bis-[3-(triethoxysilyl)propyl]-amine with 1 mol of phenylphosphonic dichloride, and its molecular structure contains four hydrolyzable triethoxysilyl groups and one phenylphosphonic diamine (PN) structural unit.

[0016] This invention utilizes surface grafting modification with specific multifunctional organosilicon compounds to obtain piperazine pyrophosphate products that possess both excellent hydrophobicity and flame retardant synergistic properties.

[0017] The method of this invention is a dry grafting process: a liquid multifunctional organosilicon compound is diluted with alcohol and then uniformly adhered to the surface of dry piperazine pyrophosphate powder by spraying. Subsequently, trace amounts of water molecules are introduced to initiate an in-situ hydrolysis-condensation reaction, and the grafting is finally completed through heat treatment. This process requires no large amounts of solvent, generates no wastewater, has a short process, and is suitable for industrial production. Therefore, the method of this invention has the advantages of high efficiency and environmental friendliness.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Flame retardant synergistic effect: The P and N flame retardant elements carried by the modifier molecule (a multifunctional organosilicon compound containing PN flame retardant elements) have a synergistic effect with the PN system in the piperazine pyrophosphate body. During combustion, it promotes the formation of a denser and more stable expanded char layer, thereby improving hydrophobicity while ensuring or even enhancing the flame retardant rating of the final composite material.

[0019] 2. Significant and long-lasting hydrophobic effect: The four triethoxysilane groups provide a high density of reaction sites, which can form a more cross-linked and stronger hydrophobic siloxane network on the surface of piperazine pyrophosphate, giving the product excellent hydrophobicity and resistance to water extraction.

[0020] 3. Green and efficient process: The dry grafting process avoids the steps of solvent use, filtration, washing and long drying time in the traditional wet process, which significantly reduces energy consumption and production costs, improves production efficiency and is more in line with the requirements of green chemical industry. Attached Figure Description

[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] Figure 1 A comparison diagram of the instantaneous water contact angles of piperazine pyrophosphate (used as a blank control) and piperazine pyrophosphate prepared in Example 1.

[0023] Figure 2 Thermogravimetric curves of piperazine pyrophosphate (as a blank control) and piperazine pyrophosphate prepared in Example 1 are compared. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] The raw materials used in the embodiments of the present invention are all commonly used in the art. For example: Piperazine pyrophosphate (PAPP) can be sourced from Shaoxing Xingxin New Materials Co., Ltd., with a moisture content ≤0.2%.

[0026] Bis[3-(triethoxysilyl)propyl]amine (Catalog No.: B833878), phenylphosphonodichloro (Catalog No.: P822213), triethylamine, tetrahydrofuran, vinyltriethoxysilane (Catalog No.: T742512), polymethylhydrosiloxane (hydrosilicone oil) (Catalog No.: P750098) and bis-[3-(triethoxysilyl)propyl]-disulfide (Catalog No.: B304016) are available from Shanghai Maclean Biochemical Technology Co., Ltd.

[0027] Example 1: Preparation of multifunctional organosilicon compounds (Si-PN-Si) containing PN flame retardant elements Under a nitrogen atmosphere, 2 mol of bis[3-(triethoxysilyl)propyl]amine and 2 mol of anhydrous triethylamine were weighed and placed in a three-necked flask containing 250 mL of anhydrous tetrahydrofuran. The temperature inside the flask was maintained at 0–5 °C using a cryogenic reactor, and stirring was started at 400 r / min. Then, a mixture of 1 mol of phenylphosphonodichloro and 50 mL of anhydrous tetrahydrofuran was added dropwise to the flask over approximately 30 minutes using a constant-pressure dropping funnel. After the addition was complete, the reaction was stirred for 1 hour. The cryogenic reactor was then removed, and the reaction was continued at room temperature for 2 hours. Finally, the mixture was filtered through a Buchner funnel to remove the triethylamine hydrochloride filter cake, and the filtrate was collected. The filtrate was then slowly evaporated at 30 °C using a rotary evaporator to remove excess tetrahydrofuran solvent, yielding the target product—a multifunctional organosilicon compound containing the PN flame-retardant element, denoted as Si-PN-Si.

[0028] Example 1: Preparation method of hydrophobic and flame-retardant piperazine pyrophosphate, comprising the following steps: 1) Place 1 kg of piperazine pyrophosphate in a forced-air drying oven and dry at 110℃ for 2 hours to obtain dried piperazine pyrophosphate (moisture content ≤0.2%). 2) Mix 10g of Si-PN-Si with 20g of anhydrous ethanol to obtain a diluted Si-PN-Si solution; 3) Place the dried piperazine pyrophosphate in a high-speed mixer and spray the Si-PN-Si diluent onto the surface of the dried piperazine pyrophosphate using the spray device on the high-speed mixer. Stir for 30 minutes at 50°C and 800 r / min.

[0029] 4) Continue to spray a small amount (2g) of deionized water onto the surface of the substance obtained in step 3) using a spraying device, and then raise the temperature from 50℃ to 100℃ (heating rate of 5℃ / min), stir for 30 minutes, and keep warm at 100℃ for 3 hours; to obtain hydrophobic flame retardant piperazine pyrophosphate.

[0030] Examples 2 and 3 differ from Example 1 in that the amounts of Si-PN-Si, anhydrous ethanol, and deionized water are changed (as shown in Table 1 below), while the rest are the same as in Example 1.

[0031] Table 1

[0032] Piperazine pyrophosphate was used as a blank control.

[0033] Comparative Example 1-1: The amount of Si-PN-Si in Example 1 was changed from 10g to 5g, and the rest was the same as in Example 1.

[0034] Comparative Examples 1-2: The amount of Si-PN-Si used in Example 3 was changed from 50g to 100g, and the rest was the same as in Example 3.

[0035] Comparative Example 2-1: The amount of deionized water used in Example 1 was changed from 2g to 0g, that is, the use of deionized water was cancelled, and the rest was the same as in Example 1.

[0036] Comparative Example 2-2: The amount of deionized water used in Example 1 was changed from 2g to 1g, and the rest was the same as in Example 1.

[0037] Comparative Examples 2-3: The amount of deionized water used in Example 1 was changed from 2g to 4g, and the rest was the same as in Example 1.

[0038] Comparative Example 3-1: Si-PN-Si in Example 1 was replaced with vinyltriethoxysilane, while the mass remained unchanged, and the rest was the same as in Example 1.

[0039] Comparative Example 3-2: In Example 1, Si-PN-Si was replaced with polymethylhydrosiloxane, while the mass remained unchanged, and the rest was the same as in Example 1.

[0040] Comparative Example 3-3: In Example 1, Si-PN-Si was replaced with bis-[3-(triethoxysilane)propyl]-disulfide, while the mass remained unchanged, and the rest was the same as in Example 1.

[0041] Comparative Examples 3-4: 2 mol of bis[3-(triethoxysilyl)propyl]amine and 1 mol of phenylphosphonic dichloride were simply stirred and mixed to obtain a mixture.

[0042] In Example 1, Si-PN-Si was replaced with a mixture, while the mass remained unchanged, and the rest was the same as in Example 1.

[0043] Comparative Examples 3-5: In Example 1, 1 mol of phenylphosphonic dichloride was replaced with 1 mol of methylphosphonic dichloride, while the rest remained the same as in Example 1. The resulting product was named SC.

[0044] In Example 1, Si-PN-Si was replaced with SC, while the quality remained unchanged; otherwise, the process was the same as in Example 1.

[0045] Experiment 1: Evaluation of the performance of piperazine pyrophosphate I. Water Contact Angle Test The water contact angle is measured using an optical contact angle meter OCA25. First, piperazine pyrophosphate powder is pressed into a uniformly thick disc (approximately 1 mm thick and 25 mm in diameter). Then, the disc is placed on a clean glass slide. Using the syringe provided with the OCA25 machine, a drop of deionized water is dropped onto the surface of the disc. The machine will then measure the instantaneous contact angle between the water droplet and the piperazine pyrophosphate powder.

[0046] II. UL 746C Water Resistance Test 25g of piperazine pyrophosphate (piperazine pyrophosphate flame retardant) and 75g of polypropylene were mixed and kneaded (at 80 r / min and 190℃ for 10 min), and then pressed into a size of 130×100×3.2 mm using a flat vulcanizing machine. 3 The sample was used to obtain piperazine pyrophosphate products.

[0047] Piperazine pyrophosphate products were soaked in distilled water at 70°C for 7 days, with the water changed daily for the first 5 days. After the 7-day soaking period, the products were placed in an environment of 23°C and 50% humidity for 2 weeks to obtain piperazine pyrophosphate products after high-temperature and high-humidity treatment.

[0048] Piperazine pyrophosphate products treated with high temperature and humidity were subjected to UL-94 vertical burning tests. The test specimen dimensions were 130×13×3.2 mm. 3 The testing standard is ASTM D3801.

[0049] The test results are shown in Table 2 below.

[0050] Table 2: Instantaneous water contact angle and flame retardant properties test results of several piperazine pyrophosphates

[0051] As shown in Table 2, the instantaneous water contact angle of piperazine pyrophosphate significantly improved after dry grafting with Si-PN-Si. When the mass ratio of Si-PN-Si to piperazine pyrophosphate was 1:100, the instantaneous water contact angle reached 145°. When the mass ratio was 3:100, it reached 155°. And when the mass ratio was 5:100, the water contact angle increased to 162°. Because the water resistance of the modified piperazine pyrophosphate was significantly improved, the sample still successfully passed the UL-94 V0 rating after the UL 746C water resistance test.

[0052] The blank control was pure piperazine pyrophosphate, which has many hydrophilic hydroxyl groups on its surface. In the water contact angle test, the instantaneous water contact angle was only about 20°, showing strong hydrophilicity. As a result, in the UL 746C test, piperazine pyrophosphate precipitates out of polypropylene and dissolves in deionized water, thus reducing its flame retardant performance to the non-flame retardant level.

[0053] Both Comparative Examples 1-1 and 1-2 altered the mass of Si-PN-Si, causing them to continue burning for more than 10 seconds after UL 746C testing, resulting in a flame retardant rating of only V1. Comparative Example 1-1 reduced the mass of Si-PN-Si, setting the Si-PN-Si to piperazine pyrophosphate mass ratio to 0.5:100. The instantaneous water contact angle was only 89°, indicating that the Si-PN-Si addition was too low, and much piperazine pyrophosphate was not grafted onto the Si-PN-Si. Therefore, during the water resistance test, the ungrafted piperazine pyrophosphate dissolved and leached out, leading to a decrease in flame retardant performance. Comparative Example 1-2 increased the mass of Si-PN-Si based on Example 3, setting the Si-PN-Si to piperazine pyrophosphate mass ratio to 1:10. Although the mass of Si-PN-Si was increased several times, the water contact angle did not change significantly, only increasing slightly from 162° to 170°. This is because when there is too much Si-PN-Si, Si-PN-Si is particularly prone to hydrolysis and self-polymerization, resulting in the modified piperazine pyrophosphate containing the self-polymerized products of Si-PN-Si after hydrolysis, which in turn reduces the overall flame retardant performance.

[0054] Comparative Examples 2-1, 2-2, and 2-3 all involved altering the quality of deionized water. Compared to Example 1, Comparative Example 2-1 did not use deionized water, preventing the siloxanes on the Si-PN-Si from undergoing hydrolysis; instead, they simply mixed physically with piperazine pyrophosphate. Therefore, the instantaneous water contact angle did not significantly improve, remaining at only 55°, resulting in no flame retardant rating in the high-temperature, high-humidity water resistance test. Comparative Example 2-2 reduced the deionized water from 2g to 1g; the low water content led to incomplete hydrolysis of Si-PN-Si, reducing the grafting rate of Si-PN-Si onto the piperazine pyrophosphate surface, resulting in an instantaneous water contact angle of only 109°. Comparative Example 2-3 increased the deionized water from 2g to 4g; the high water content caused Si-PN-Si to easily hydrolyze and self-polymerize, forming uneven "siloxane lumps" on the piperazine pyrophosphate surface and even causing powder agglomeration; therefore, the instantaneous water contact angle was also only 124°. Therefore, after the water resistance test, they can only reach the V1 level.

[0055] Comparative Examples 3-1, 3-2, and 3-3 replaced the Si-PN-Si modifier in Example 1 with several commonly used piperazine pyrophosphate modifiers in the prior art. Test results showed that vinyltriethoxysilane and polymethylhydrosiloxane did not have significant hydrophobic effects, with instantaneous water contact angles of only 75° and 98°, respectively. Both modifiers are flammable materials and did not contribute to improving flame retardant performance, achieving only a V1 rating before the water resistance test. Therefore, after the high-temperature and high-humidity water resistance test, they directly dropped to a non-flame retardant rating. Comparative Example 3-3 used bis-[3-(triethoxysilyl)propyl]-disulfide, which has two hydrolyzable triethoxysilyl groups, achieving an instantaneous water contact angle of 128°. While it also achieved a V1 rating after the water resistance test, an irritating odor was emitted during the mixing process with polypropylene, possibly due to the degradation of sulfur, posing a safety hazard.

[0056] Comparative Examples 3-4 involved directly using a mixture of 2 mol of bis[3-(triethoxysilyl)propyl]amine and 1 mol of phenylphosphonic dichloride to modify piperazine pyrophosphate. This addition disrupted the expansion and flame-retardant mechanism of piperazine pyrophosphate, resulting in a significant decrease in flame-retardant performance. Before the water resistance test, the flame retardant performance only reached a V2 rating. When the sample was ignited, a stable char layer did not form; instead, molten droplets ignited the absorbent cotton.

[0057] Comparative Examples 3-5 involved replacing phenylphosphonic dichloride with methylphosphonic dichloride. Although the molecular structure was simply a matter of replacing the phenyl group with a methyl group, significant changes were observed in water resistance and flame retardant properties. The hydrophobic mechanism of methyl groups relies primarily on the hydrophobic effect of alkane chains, but methyl chains are inherently short, offering limited improvement in the water contact angle. Phenyl groups, on the other hand, are inherently strong hydrophobic and can generate additional interactions with Si-O bonds through π-π interactions. Furthermore, the product corresponding to phenyl groups exhibits higher thermal stability and char-forming properties compared to methyl groups, making it more suitable for the intumescent flame-retardant mechanism of piperazine pyrophosphate. This aligns with experimental results: the modified piperazine pyrophosphate prepared with methylphosphonic dichloride only achieved a V1 rating before water resistance testing. When the sample was ignited, the resulting char layer was not dense enough, leading to a burning time exceeding 10 seconds. After water resistance testing, the char layer showed significant damage after combustion, allowing heat and combustible small molecules to easily penetrate the pores, causing the char layer to collapse and the molten droplets to ignite and degrease, resulting in a rating of only V2.

[0058] Experiment 2, Thermogravimetric Test To further investigate why the flame retardant properties of piperazine pyrophosphate improved after Si-PN-Si modification, thermogravimetric analysis (TGA) tests were conducted on pure piperazine pyrophosphate (blank comparative example) and piperazine pyrophosphate from Example 1 under a nitrogen atmosphere. Specifically, the TGA test involved heating from 50°C to 800°C under a nitrogen atmosphere at a heating rate of 10°C / min.

[0059] from Figure 2 The thermogravimetric curves show that pure piperazine pyrophosphate... T 1wt% The thermal decomposition temperature is 281 °C, and the char residue at 800 °C is 23.2%. The piperazine pyrophosphate prepared in Example 1... T 1wt% The thermal decomposition temperature increased to 295℃, and the char residue at 800℃ increased to 32.1%. The modified piperazine pyrophosphate showed significant improvements in thermal stability and expanded char layer. This is attributed to the hydrolytic condensation of Si-PN-Si with the hydroxyl groups on the surface of piperazine pyrophosphate, forming strong chemical bonds. This results in the construction of a functionalized coating layer on the surface of piperazine pyrophosphate particles containing both a hydrophobic siloxane network and PN synergistic flame-retardant elements.

[0060] In summary, the hydrophobic and flame-retardant enhanced piperazine pyrophosphate of this invention not only possesses excellent hydrophobicity and migration resistance, but also exhibits good flame-retardant properties, perfectly solving the industry problem of "mutual constraint between hydrophobicity and flame retardancy" faced by traditional products, and laying the foundation for the high-end application of piperazine pyrophosphate.

[0061] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate, characterized in that: The dry grafting method includes the following steps: 1) Dry piperazine pyrophosphate to obtain dried piperazine pyrophosphate; 2) Dilute the multifunctional organosilicon compound containing PN flame retardant element with anhydrous ethanol to obtain a diluted solution; 3) Set the mass ratio of the multifunctional organosilicon compound containing PN flame retardant element to piperazine pyrophosphate to 1~5:100, spray the diluted solution evenly on the surface of dried piperazine pyrophosphate, and then stir at 40~60℃. 4) Set the mass ratio of deionized water to polyfunctional organosilicon compound containing PN flame retardant element = 1:5~10, spray deionized water onto the surface of the substance obtained in step 3); then raise the temperature to 90~110 ℃, stir, and keep it at 90~110 ℃ for 2~4 hours to obtain piperazine pyrophosphate flame retardant.

2. The method for preparing the hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate according to claim 1, characterized in that: The method for synthesizing the multifunctional organosilicon compound containing PN flame retardant element is as follows: under inert gas protection, bis-[3-(triethoxysilyl)propyl]-amine and phenylphosphonodichloro react at 0~5℃ for 0.5~2 hours under inert solvent and acid-binding agent conditions, and then react at room temperature for 1.5~2.5 hours. The resulting reactants are post-treated to obtain the multifunctional organosilicon compound containing PN flame retardant element. The molar ratio of phenylphosphonodichloro to bis-[3-(triethoxysilyl)propyl]amine is 1:2 ± 0.

1. The molar ratio of bis-[3-(triethoxysilyl)propyl]-amine to acid binder is 1:1 ± 0.

1.

3. The method for preparing the hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate according to claim 2, characterized in that: The acid-binding agent is triethylamine.

4. The preparation method of the hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate according to claim 3, characterized in that: The inert solvent is tetrahydrofuran.

5. The method for preparing the hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate according to any one of claims 1 to 4, characterized in that: In step 2), the mass ratio of the multifunctional organosilicon compound containing PN flame retardant element to anhydrous ethanol is 1:2~5.

6. The method for preparing the hydrophobic, flame-retardant, and enhanced piperazine pyrophosphate according to claim 5, characterized in that: The stirring speed in steps 3) and 4) is 600~1000 r / min.

7. The hydrophobic flame-retardant piperazine pyrophosphate prepared by any one of claims 1 to 6.

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