Preparation method and use of a ferrocene-phosphazene flame retardant nanosheet

Abstract

The present invention discloses a preparation method and use of a ferrocene-phosphazene flame retardant nanosheet, which is characterized in that: N,N-dimethylformamide, phosphorus oxychloride, and ferrocene are added to dichloromethane, and first stirred and reacted at a low temperature for a certain period of time, then heated and stirred, and then extracted, recrystallized and purified, and dried to obtain ferrocene formaldehyde; hexakis(4-aminophenoxy)cyclotriphosphazene, ferrocene formaldehyde, and a solvent are added to a reactor, and stirred and reacted at 20-100 °C. After removing water through a water separator, it is recrystallized and purified and then dried to obtain a ferrocene-phosphazene flame retardant nanosheet, namely: hexakis(4-imino)cyclotriphosphazene-ferrocene. Due to the organic characteristics and nano-scale advantages of the ferrocene-phosphazene flame retardant nanosheet, it has good compatibility in the polymer matrix, can endow the polymer with good flame retardancy at a low addition amount, and improve the mechanical properties of the polymer material.

Description

Technical Field

[0001] The present invention belongs to the preparation of organic compound flame retardants, and relates to a preparation method and use of ferrocene-phosphazene flame retardant nanosheets. The ferrocene-phosphazene flame retardant nanosheets prepared by the present invention are an additive flame retardant, which can be added to polymer materials and applied to flame-retardant epoxy resins, polypropylenes, polyethylenes, polylactic acids, polystyrenes, etc. to improve the flame retardant properties of polymer materials. It can also be used as a synergist for other types of flame retardants for compounding. Background Art

[0002] Organic polymer materials are widely used in various fields of the national economy and people's lives, and have become one of the main varieties with the largest production quantity. Unfortunately, organic polymer materials mainly composed of hydrogen and carbon elements are one of the most typical combustible materials, and exhibit a large fire load. During the combustion process, a large amount of heat and smoke are released, accompanied by melting and dripping phenomena, posing a great fire hazard, which greatly restricts the use of polymer materials in some scientific and technological fields with high flame retardant requirements. Therefore, it is of great significance to flame-retardant polymer materials to improve fire safety performance.

[0003] In the prior art, the application of ferrocene-based compounds in flame-retardant polymer materials has attracted extensive attention. It is usually used as a flame retardant synergist and smoke suppressant in polymer materials such as epoxy resins, polystyrenes, polypropylenes, and waterborne polyurethanes. On the other hand, phosphazenes are an important class of organic phosphorus flame retardants. Phosphorus-based flame retardants have low corrosivity, good flame retardant and smoke suppression performance, and belong to environmentally friendly materials. They have the characteristics of a large phosphorus content, strong thermal stability, and high flame retardant efficiency. Among them, cyclotriphosphazene, as a new phosphorus-nitrogen flame retardant backbone material, is one of the most representative compounds in phosphazenes. It has a stable six-membered ring conjugated structure, good thermal stability, and a unique molecular structure with alternating phosphorus and nitrogen atoms (-P=N-), and is widely used in the field of flame retardants. However, the disadvantages and deficiencies are that when ferrocene metal-based derivatives are added alone, the flame retardant effect will be weakened due to their own sublimation and excessive catalytic degradation, while when P / N type flame retardants are added alone, their compatibility with the polymer matrix is poor, the flame retardant efficiency is low, and a large loading amount is required to meet the flame retardant performance requirements, which makes the flame retardant performance and mechanical properties of polymer materials conflict with each other. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies in the prior art and provide a preparation method and use of a ferrocene-phosphazene flame retardant nanosheet, so as to solve the problem that the high addition amount and poor compatibility of the flame retardant in the polymer material matrix affect the flame retardancy and other properties of the matrix. The present invention mainly combines ferrocene and a phosphazene material with high stability, and obtains an organic macromolecular nanosheet hexakis(4-imino)cyclotriphosphazene-ferrocene with a microporous structure through an organic synthesis method; at the same time, by improving and optimizing the reaction conditions, the purity and yield of one of the reactants, ferrocene formaldehyde, are increased. The hexakis(4-imino)cyclotriphosphazene-ferrocene obtained in the present invention, which contains phosphorus, nitrogen and a metal group in one body, is a novel macromolecular nanosheet flame retardant; the microporous structure, high specific surface area and organic characteristics of hexakis(4-imino)cyclotriphosphazene-ferrocene help to improve the compatibility in the polymer matrix and increase the flame retardancy efficiency; in addition, the reinforcing effect of the flame retardant nanosheet can enable the polymer material to maintain or even improve its mechanical properties.

[0005] The content of the present invention is: a preparation method of a ferrocene-phosphazene flame retardant nanosheet, characterized in that the steps are as follows:

[0006] a. Preparation of ferrocene formaldehyde: The first-step reaction is the reaction of ferrocene to form ferrocene formaldehyde, and the main reaction mechanism is cyclization nucleophilic addition reaction. The reaction steps are as follows: Add 0.8 g to 4.5 Kg of N,N-dimethylformamide to 30 mL to 20 L of the solvent dichloromethane, and carry out mechanical stirring reaction in a low-temperature reaction bath at a temperature of -5 to 5 °C until uniformly dispersed; then, add 0.5 g to 3 Kg of phosphorus oxychloride to the above reaction solution, and after the addition is completed, continue mechanical stirring reaction for 0.5 to 24 hours; continue to add 0.4 g to 5 Kg of ferrocene, and stir the reactant solution at a temperature of 40 to 60 °C (the reactant can be transferred to an oil bath at a temperature of 40 to 60 °C) for 2 to 48 hours; after the reaction is completed, slowly drip the reaction solution into ice deionized water, and after the dripping is completed, continue to slowly drip a NaOH aqueous solution with a mass percentage concentration of 15 to 30% to keep the pH value of the system at 6 to 9; subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the moisture in the extract is removed with anhydrous sodium sulfate, and the collected extract is placed in a rotary evaporator at a temperature of 40 to 60 °C for rotary evaporation to collect the crude product; the crude product is recrystallized with a mixed solution of dichloromethane and n-hexane with a volume ratio of 1:6 to 3:1. The collected product is placed in a vacuum drying oven and dried at a temperature of 50 to 70 °C for 24 to 48 hours to obtain (reddish-brown solid) ferrocene formaldehyde (abbreviation: Fc-CHO);

[0007] b. Preparation of ferrocene-phosphazene flame retardant nanosheets: The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviated as HACP) and ferrocene formaldehyde. The reaction steps are as follows: 0.1 g to 5 kg of hexakis(4-aminophenoxy)cyclotriphosphazene, 1 g to 10 kg of ferrocene formaldehyde, and 30.5 mL to 10 L of solvent are mixed and added to a reaction vessel, and stirred at a temperature of 40 to 90 °C for 0.5 to 48 hours. The by-product water is removed in a timely manner through a water separator. After the reaction is completed, it is naturally cooled to room temperature to obtain a crude product; a mixed solution of ethanol and dichloromethane with a volume ratio of 1:6 to 9:1 is prepared for recrystallization (purification) of the crude product to obtain the product; the product is placed in a vacuum drying oven and dried at a temperature of 60 to 80 °C for 24 to 48 hours to obtain ferrocene-phosphazene flame retardant nanosheets (purple-red powder), namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH).

[0008] The solvent is any one of ethanol, acetone, and dichloromethane.

[0009] The prepared ferrocene-phosphazene flame retardant nanosheets, namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH) has the chemical structural formula shown in (I):

[0010]

[0011] In the content of the present invention: In step b, the molar ratio of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviated as HACP) to ferrocene formaldehyde (abbreviated as Fc-CHO) (i.e., the molar ratio of the amounts used in the two reactions) is preferably 6:1 to 1:9.

[0012] In the content of the present invention: In step b, the molar ratio of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviated as HACP) to ferrocene formaldehyde (abbreviated as Fc-CHO) (i.e., the molar ratio of the amounts used in the two reactions) is preferably 6:1 to 1:6.

[0013] In the content of the present invention: The prepared ferrocene-phosphazene flame retardant nanosheets, namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH) has a size of 50 to 100 nm, a thickness (up to) of 3 to 50 nm, a pore volume between 0.091 and 0.25 cc / g, and a pore size distribution between 1.9 and 5.6 nm.

[0014] In the content of the present invention: The prepared ferrocene-phosphazene flame retardant nanosheets, namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH) can be used in flame-retardant polymer composites;

[0015] The flame-retardant polymer composites are flame-retardant epoxy resins, flame-retardant polypropylenes, flame-retardant polylactic acid composites, etc.

[0016] In the content of the present invention, the hexakis(4-aminophenoxy)cyclotriphosphazene is prepared by the preparation method disclosed in the patent application with the applicant being "Southwest University of Science and Technology", application number 202110451629.8, publication number CN115246860A, and title "Preparation Method and Use of a Phosphorus-Nitrogen Intumescent Flame Retardant Nanoplate", or it can also be obtained by other existing technologies or purchased as a commercially available product.

[0017] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0018] (1) By adopting the present invention, the ferrocene metal-based derivative is utilized for its role in suppressing smoke and catalyzing carbonization in flame retardancy. During the combustion process, the ferrocene derivative generates substances such as iron oxide and iron atoms, which have the effects of catalyzing carbonization, capturing free radicals, and suppressing smoke on the polymer material. With the assistance of iron atoms and iron oxide, carbon monoxide is converted into carbon dioxide, thereby reducing the emission of toxic gases.

[0019] (2) By adopting the present invention, the phosphazene containing phosphorus and nitrogen flame retardant elements and its high thermal stability have a positive effect on flame retardancy. Phosphazene is an important class of organic phosphorus flame retardants. Phosphorus-based flame retardants have low corrosiveness and excellent flame retardant and smoke suppression performance, belonging to environmentally friendly materials. It has the characteristics of a large phosphorus content and strong thermal stability. Among them, cyclotriphosphazene, as a new phosphorus-nitrogen flame retardant skeleton material, is one of the most representative compounds in phosphazenes. It has a stable six-membered ring conjugated structure, good thermal stability, and a unique molecular structure with alternating phosphorus and nitrogen atoms (-P=N-). Each phosphorus atom in cyclotriphosphazene has two active P-Cl bonds, with good designability, and different phosphazene structures can be synthesized. The formed cyclic cross-linked phosphazene compounds have various morphologies such as nanofibers, hollow spheres, and layered structures. The main flame retardant function of cyclotriphosphazene is to generate a high-quality carbon layer containing phosphorus oxides or phosphoric acid at high temperatures, and some undegraded cyclotriphosphazene can act as a rigid skeleton to prevent the collapse of the carbon layer. It can also generate non-combustible gases such as carbon dioxide, ammonia, and nitrogen.

[0020] (3) By adopting the present invention, the ferrocene metal-based group and cyclotriphosphazene are formed into a macromolecular organic compound through a simple organic reaction, exerting the flame retardant synergistic effect of the two. Moreover, by using a cyclotriphosphazene derivative containing an active amino group and ferrocene formaldehyde through a nucleophilic addition reaction to introduce a rigid Schiff base (-C=N-) structure, the Schiff base (-C=N-) group will participate in the cross-linking reaction at high temperatures to form a thermally stable six-membered ring structure with alternating C and N, which can produce multiple effects to flame retard the polymer material and improve the flame retardant efficiency.

[0021] (4) By adopting the present invention, a macromolecular organic compound is formed by a simple organic reaction of a ferrocene metal group and cyclotriphosphazene; the aldehyde groups in ferrocene formaldehyde and the amino groups in HACP have very high reaction activities, and the reaction conditions are simple. The only by-product of the reaction is water, which is convenient for subsequent treatment; due to the presence of benzene rings, cyclopentadienyl rings, carbon-carbon double bonds, cyclotriphosphazene, and Schiff bases (-C=N-) in the obtained FH after the reaction, there is a π-π stacking effect between them, thereby obtaining a nanosheet morphology with a microporous structure. Nanosheets have more advantages in improving the properties in the polymer matrix;

[0022] (5) By adopting the present invention, due to the nanosheet structure of FH, it has a relatively high specific surface area, and combined with the organic characteristics of FH, the compatibility of FH nanosheets in the polymer matrix is improved; during the combustion process, the ferrocene metal group, cyclotriphosphazene, Schiff base structure, and nanosheet structure in FH have positive multiple effects on flame retardancy, such as free radical capture, release of non-combustible gases such as ammonia and nitrogen, catalytic carbonization of the metal group, catalytic crosslinking of the Schiff base, and catalytic dehydration carbonization of cyclotriphosphazene, significantly improving the flame retardancy of the polymer composite; therefore, only when 2 wt.% of the flame retardant FH is added to the epoxy resin, the vertical burning V-0 level can be achieved. Compared with pure epoxy resin, the peak heat release rate in the cone calorimeter test decreased by 30.2%, and the total heat release decreased by 14.6%;

[0023] Through literature retrieval, it is known that in the same epoxy resin curing system, the addition amount of the same type of flame retardant needs to reach 5 wt.% - 15 wt.% to achieve the UL-94 V-0 level; while adopting the present invention, only 2 wt.% needs to be added to achieve UL-94 V-0, and the oxygen index reaches 31.3%;

[0024] (6) By adopting the present invention, the FH nanosheet flame retardant can achieve excellent flame retardancy at a low addition amount in the matrix, and due to the structural advantages of the FH nanosheets themselves (high specific surface area, organic characteristics), good dispersibility and the strengthening effect of the nanosheets effectively improve the mechanical properties of the flame-retardant polymer material. Therefore, when 2 wt.% of the flame retardant FH is added to the epoxy resin, compared with pure epoxy resin, the tensile strength is increased by 9.1%, and the elongation at break is increased by 37%, which has a significant strengthening and toughening effect on the flame-retardant polymer material;

[0025] In composite materials, an excessive addition amount will deteriorate the mechanical properties; through literature retrieval, it is known that in the same epoxy resin curing system, when using the existing same type of flame retardant, the addition amount is 8wt.% - 10wt.%, the tensile strength reaches about 65.0MPa, and the elongation at break reaches about 7.3%; while for the present invention, only 2wt.% (wt.% means mass percentage, weight percentage) needs to be added, and the tensile strength of the epoxy resin composite material system can reach 70.0MPa, and the elongation at break reaches 9.5%.

[0026] (7) The synthesis process of the product of the present invention is simple, easy to operate, and the product treatment is simple, with strong practical value. Description of the Drawings

[0027] Figure 1 It is the infrared diagram of Fc-CHO and flame retardant FH synthesized in Example 1 of the present invention, which proves the successful synthesis of Fc-CHO and flame retardant FH;

[0028] Figure 2 It is the scanning electron microscope diagram of FH synthesized by the present invention, and it can be observed that FH has a nano-sheet structure;

[0029] Figure 3 It is the transmission electron microscope diagram of the microporous nano-sheet of FH synthesized by the present invention, with a size of 50 - 100nm and a thickness of up to 30 - 50nm;

[0030] Figure 4 and Figure 5 They are the nitrogen adsorption - desorption isotherm curve and pore size distribution diagram of FH nano-sheets. It can be found that the pore volume of FH nano-sheets is between 0.091 - 0.25 cc / g, and the pore size distribution is between 1.9 - 5.6nm;

[0031] Figure 6 It is the heat release rate diagram of pure epoxy resin and epoxy resin composite material with 2wt.% of FH flame retardant nano-sheets added by weight percentage. Compared with pure epoxy resin, the peak heat release rate of the epoxy resin composite material with the added flame retardant is reduced by about 30.2%;

[0032] Figure 7 It is the total heat release diagram of pure epoxy resin and epoxy resin composite material with 2wt.% of FH flame retardant nano-sheets added by weight percentage. Compared with pure epoxy resin, the total heat release of the epoxy resin composite material with the added flame retardant is reduced by about 14.6%;

[0033] Figure 8 It is the carbon monoxide release amount diagram of pure epoxy resin and epoxy resin composite material with 2wt.% of FH flame retardant nano-sheets added by weight percentage. It can be observed that the release of carbon monoxide in the epoxy resin composite material with the added flame retardant has a significant decrease. Detailed implementation manners

[0034] The following embodiments are intended to further illustrate the present invention, but should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the above content of the present invention still fall within the protection scope of the present invention.

[0035] Embodiment 1:

[0036] A preparation method of a ferrocene-phosphazene flame retardant nanosheet is as follows:

[0037] a. The first-step reaction is the reaction of ferrocene to form ferrocene formaldehyde. The main reaction mechanism is cyclization nucleophilic addition reaction, as shown in Route A. The reaction steps are as follows: Add 4.0 Kg (54.7 mol) of N,N-dimethylformamide to 20 L of the solvent dichloromethane, and carry out mechanical stirring reaction in a low-temperature reaction bath at 5 °C until uniformly dispersed. Then, add 2.5 Kg (16.3 mol) of phosphorus oxychloride to the above reaction solution. After the addition is completed, continue mechanical stirring for 24 hours. During the reaction, continue to add 5 Kg (26.9 mol) of ferrocene, and transfer the reaction solution to an oil bath at 60 °C and stir for 48 hours. After the reaction is completed, slowly drop the reaction solution into ice deionized water. After the dropping is completed, continue to slowly drop a 30% NaOH solution by mass to keep the pH value of the system at 9. Subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the moisture in the extract is removed with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 60 °C for rotary evaporation, and the crude product is collected. The crude product is recrystallized with a mixed solution of dichloromethane and n-hexane with a volume ratio of 3:1. The product is collected and dried in a vacuum drying oven at 70 °C for 48 hours to obtain a red-brown solid ferrocene formaldehyde (abbreviated as Fc-CHO), and the yield is 81%;

[0038]

[0039] b. The second step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene and ferrocene formaldehyde, as shown in Route B. The reaction procedure is to add 4.5 Kg (5.75 mol) of hexakis(4-aminophenoxy)cyclotriphosphazene, 9.5 Kg (44.3 mol) of ferrocene formaldehyde, and 9 L of the solvent acetone into a reaction vessel, stir and react at 90 °C for 48 hours, timely remove the by-product water through a water separator, naturally cool to room temperature after the reaction ends, and recrystallize and purify the crude product with a mixed solution of ethanol and dichloromethane with a volume ratio of 8.5:1 to obtain the product. Place the collected product in a vacuum drying oven and dry it at 80 °C for 48 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH), with a yield of 90%;

[0040]

[0041] In this example, the infrared spectra of the synthesized ferrocene formaldehyde (Fc-CHO) and hexakis(4-imino)cyclotriphosphazene-ferrocene (FH) are as Figure 1 shown: The characteristic absorption peaks of C═C, C-H, and the cyclopentene ring of ferrocene derivatives are mainly at 1480 cm- 1 、3100 cm- 1 and 490 cm- 1 . Compared with Fc, Fc-CHO shows a characteristic infrared absorption peak of C═O at 1680 cm- 1 . When HACP reacts with Fc-CHO to form FH, the characteristic peaks of -NH2 at 3430 cm- 1 and 3340 cm- 1 and the C═O group at 1680 cm- 1 almost disappear, and the characteristic infrared absorption peak of the aromatic ring is at 1505 cm- 1 . The disappearance of the characteristic peak value of the C═O group and the appearance of the characteristic peak value of C═N at 1640 cm- 1 verify the successful synthesis of FH.

[0042] Example 2:

[0043] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows:

[0044] a. The first-step reaction is the formation of ferrocene formaldehyde from ferrocene, and the main reaction mechanism is cyclization nucleophilic addition reaction. The reaction procedure is as follows: Add 0.8 g (0.01 mol) of N,N-dimethylformamide to 30 mL of dichloromethane as the solvent, and carry out mechanical stirring reaction in a low-temperature reaction bath at 0 °C until it is evenly dispersed. Then, add 0.5 g (3.26 mmol) of phosphorus oxychloride to the above reaction solution. After the addition, continue mechanical stirring for 0.5 h. During the reaction, continue to add 0.4 g (2.1 mmol) of ferrocene, and transfer the reaction solution to an oil bath at 40 °C and stir for 2 h. After the reaction is completed, slowly drop the reaction solution into ice deionized water. After the dropping is completed, continue to slowly drop a 15% NaOH solution by mass to keep the pH value of the system at 6. Subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the extract is dehydrated with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 40 °C for rotary evaporation to collect the crude product. The crude product is recrystallized with a mixed solution of dichloromethane and n-hexane with a volume ratio of 1:6. The collected product is placed in a vacuum drying oven and dried at 50 °C for 24 h to obtain red-brown solid ferrocene formaldehyde (abbreviated as Fc-CHO) with a yield of 80%;

[0045] b. The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene and ferrocene formaldehyde. The reaction procedure is as follows: Mix 0.1 g (0.13 mmol) of hexakis(4-aminophenoxy)cyclotriphosphazene, 1 g (4.67 mmol) of ferrocene formaldehyde, and 30.5 mL of acetone as the solvent and add them to the reaction vessel. Stir and react at 40 °C for 2 h, and timely remove the by-product water through a water separator. After the reaction ends, naturally cool to room temperature, and recrystallize and purify with a mixed solution of ethanol and dichloromethane with a volume ratio of 1:6 to obtain the product. The collected product is placed in a vacuum drying oven and dried at 60 °C for 24 h to obtain purple-red powder of ferrocene-phosphazene flame retardant nanosheet - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH) with a yield of 85%;

[0046] Example 3:

[0047] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows:

[0048] a. The first-step reaction is the formation of ferrocene formaldehyde from ferrocene. The main reaction mechanism is cyclization nucleophilic addition reaction. The reaction procedure is as follows: Add 20 g (0.27 mol) of N,N-dimethylformamide to 200 mL of dichloromethane as the solvent, and carry out mechanical stirring reaction in a low-temperature reaction bath at -5 °C until evenly dispersed. Then, add 20 g (0.13 mol) of phosphorus oxychloride to the above reaction solution. After the addition is completed, continue mechanical stirring for 12 hours. During the reaction, continue to add 10 g (0.05 mol) of ferrocene, and transfer the reaction solution to an oil bath at 50 °C and stir for 24 hours. After the reaction is completed, slowly drip the reaction solution into ice deionized water. After the dripping is completed, continue to slowly drip 25% NaOH solution by mass to keep the pH value of the system at 7. Subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and anhydrous sodium sulfate is used to remove the water from the extract. The collected extract is placed in a rotary evaporator at 50 °C for rotary evaporation, and the crude product is collected. The crude product is recrystallized with a mixed solution of dichloromethane and n-hexane with a volume ratio of 2:1. The collected product is placed in a vacuum drying oven and dried at 60 °C for 36 hours to obtain red-brown solid ferrocene formaldehyde (abbreviated as Fc-CHO) (reactant 2), and the yield is 80%;

[0049] b. The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene and ferrocene formaldehyde. The reaction procedure is as follows: Mix 5 g (6.4 mmol) of hexakis(4-aminophenoxy)cyclotriphosphazene, 10 g (46.7 mmol) of ferrocene formaldehyde, and 200 mL of acetone as the solvent and add them to the reaction vessel. Stir and react at 65 °C for 36 hours, and timely remove the by-product water through a water separator. After the reaction ends, naturally cool to room temperature, and recrystallize and purify with a mixed solution of ethanol and dichloromethane with a volume ratio of 5:2 to obtain the product. The collected product is placed in a vacuum drying oven and dried at 70 °C for 36 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheet - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH), and the yield is 86%.

[0050] The following invention is an application example of FH in a polymer matrix.

[0051] Application Examples 1-4:

[0052] The application examples in this group are prepared according to the formula in Table 1, and the FH used is from Example 1. The epoxy resin composite is prepared by a casting method using a polytetrafluoroethylene mold, and the flame retardancy and mechanical properties of the composite are tested by vertical burning (UL-94), limiting oxygen index (LOI), cone calorimeter test (CC), tensile strength, etc. The results are shown in Table 1.

[0053] Table 1:

[0054]

[0055] Wherein: FH / wt.% represents the weight percentage of FH contained, and pHRR is the peak heat release rate.

[0056] Table 2 lists the flame retardancy performance test and mechanical property test data of some epoxy resin flame retardant systems of the same type according to the addition amount of the flame retardant. It shows that the synthesized ferrocene-phosphazene flame retardant nanosheets of the present invention can achieve high flame retardancy performance and excellent mechanical properties of epoxy resin under the lowest addition amount (2 wt.%).

[0057] Table 2:

[0058]

[0059] Application Examples 5 - 7:

[0060] This group of application examples was prepared according to the formula in Table 3. The product FH obtained in Example 2, ammonium polyphosphate (referred to as APP), pentaerythritol (referred to as PER), and polypropylene (referred to as PP) were dried at 70°C for 5 hours for standby. According to the formula shown in Table 2, PER, APP, FH, and PP were weighed, and PER, APP, and FH were placed in a mortar and ground and mixed evenly. Among them, the intumescent flame retardant composed of APP / PER has a mass ratio of 3:1, and FH is used as a flame retardant synergist. After mixing PP and the flame retardant evenly, it was slowly placed in a mixer and melt-blended for 15 minutes, and the temperature settings of the three zones of the mixer were maintained at 180°C and the rotation speed was 50 rpm. After the mixing was completed, a PP composite material was obtained. After the PP composite material was cooled to room temperature, it was crushed by a powerful plastic crusher to obtain PP composite material particles. The crushed PP composite material particles were placed on molds of different sizes and subjected to molding treatment on a flat vulcanizing machine at 190°C. The specific molding treatment was to cover the pre-prepared PP composite material particle mold with a PET film, hot press at 8 MPa for 3 minutes, then reduce to 0 MPa and hold for 1 minute, continue hot press at 10 MPa for 5 minutes, and finally cold press at 10 MPa for 5 minutes. After cooling to room temperature, the sample bars were taken out to obtain standard sample bars that meet the size requirements for different tests. The flame retardancy performance and mechanical properties of the composite material were tested by vertical burning (UL-94), limiting oxygen index (LOI), tensile strength, etc., and the results are shown in Table 3.

[0061] Table 3:

[0062]

[0063] Table 4 lists the flame retardancy test and mechanical property test data of some polypropylene flame retardant systems of the same type according to the addition amount of the flame retardant, indicating that the ferrocene-phosphazene flame retardant nanosheets synthesized in the present invention can meet the requirements of high-efficiency flame retardancy and excellent mechanical properties in the polypropylene system with the lowest addition amount.

[0064] Table 4:

[0065]

[0066] Application Examples 8 - 10:

[0067] This group of application examples was prepared according to the formula in Table 5. The product FH obtained in Example 3, ammonium polyphosphate (referred to as APP), pentaerythritol (referred to as PER), and polyethylene (referred to as PE) were dried at 70 °C for 5 hours for standby. According to the formula shown in Table 2, PER, APP, FH, and PE were weighed, and PER, APP, and FH were placed in a mortar and ground and mixed evenly. Among them, the intumescent flame retardant composed of APP / PER has a mass ratio of 3:1, and FH is used as a flame retardant synergist. After mixing PE with the flame retardant evenly, it was slowly placed in a mixer and melt-blended for 15 minutes, keeping the temperature settings of the three zones of the mixer at 180 °C and the rotation speed at 50 rpm. After the mixing was completed, a PE composite material was obtained. After the PE composite material was cooled to room temperature, it was crushed with a powerful plastic crusher to obtain PE composite material particles. The crushed PE composite material particles were placed on molds of different sizes and subjected to molding treatment on a flat vulcanizing machine at 180 °C. The specific molding treatment was to cover the mold of the prepared PP composite material particles with a PET film paper, hot press at 8 MPa for 3 minutes, then reduce to 0 MPa and hold for 1 minute, continue hot press at 10 MPa for 5 minutes, and finally cold press at 10 MPa for 5 minutes. After cooling to room temperature, the sample bars were taken out to obtain standard sample bars that met the size requirements for different tests. The flame retardancy and mechanical properties of the composite material were tested by vertical burning (UL-94), limiting oxygen index (LOI), tensile strength, and elongation at break, and the results are shown in Table 5.

[0068] Table 5:

[0069]

[0070] In the previous flame retardancy research on polyethylene by the present applicant, when 30 wt.% of the flame retardant was added, the UL-94 V-0 level could be achieved, but the mechanical properties decreased significantly; while in the present invention, when 30 wt.% of the flame retardant was added, with FH being 1 wt.%, the UL-94 V-0 level was achieved, and the mechanical properties were well maintained.

[0071] Example 4:

[0072] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows: 4.5 Kg of hexakis(4-aminophenoxy)cyclotriphosphazene, 9 Kg of ferrocene formaldehyde, and 8 L of solvent ethanol are mixed and added to a reaction vessel, and stirred at 90 °C for 48 hours. By means of a water separator, the by-product water is removed in time. After the reaction is completed, it is naturally cooled to room temperature, and the product is obtained after recrystallization purification with a mixed solution of ethanol and dichloromethane. The collected product is placed in a vacuum drying oven and dried at 80 °C for 48 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH). The others are the same as any one of Examples 1-3, which are omitted.

[0073] Example 5:

[0074] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows: 0.1 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 1 g of ferrocene formaldehyde, and 35 mL of solvent ethanol are mixed and added to a reaction vessel, and stirred at 40 °C for 0.5 hour. By means of a water separator, the by-product water is removed in time. After the reaction is completed, it is naturally cooled to room temperature, and the product is obtained after recrystallization purification with a mixed solution of ethanol and dichloromethane with a volume ratio of 1:1. The collected product is placed in a vacuum drying oven and dried at 60 °C for 24 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH). The others are the same as any one of Examples 1-3, which are omitted.

[0075] Example 6:

[0076] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows: 200 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 500 g of ferrocene formaldehyde, and 500 mL of solvent dichloromethane are mixed and added to a reaction vessel, and stirred at 90 °C for 48 hours. By means of a water separator, the by-product water is removed in time. After the reaction is completed, it is naturally cooled to room temperature, and the product is obtained after recrystallization purification with a mixed solution of ethanol and dichloromethane with a volume ratio of 2:1. The collected product is placed in a vacuum drying oven and dried at 80 °C for 48 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH). The others are the same as any one of Examples 1-3, which are omitted.

[0077] Example 7:

[0078] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows: 0.5 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 1.5 g of ferrocene formaldehyde, and 35 mL of solvent acetone are mixed and added to a reaction vessel, and stirred at 40 °C for 0.5 hours. The by-product water is removed in time through a water separator. After the reaction is completed, it is naturally cooled to room temperature, and the product is obtained after recrystallization and purification with a mixed solution of ethanol and dichloromethane with a volume ratio of 1:7. The collected product is placed in a vacuum drying oven and dried at 60 °C for 24 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH). Others are the same as any one of Examples 1-3, which are omitted.

[0079] Examples 8-11:

[0080] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows: Take HACP, Fc-CHO and a solvent, where the molar ratio of HACP to Fc-CHO is 6:1 to 1:9. The molar ratios of HACP to Fc-CHO in Examples 8-11 are 1:2, 1:4, 1:6, and 1:8 respectively. The dosage of the solvent is 50 mL, 100 mL, 150 mL, and 200 mL for every 1.0 mmol of HACP. Stir at any temperature between 40 and 90 °C, and react for any reaction time between 0.5 and 48 hours. The by-product water is removed in time through a water separator. After the reaction is completed, it is naturally cooled to room temperature, and the product is obtained after recrystallization and purification with a mixed solution of ethanol and dichloromethane in any ratio with a volume ratio of 1:6 to 9:1. The collected product is placed in a vacuum drying oven and dried at any temperature between 60 and 80 °C for any time between 24 and 48 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH). Others are the same as any one of Examples 1-3, which are omitted.

[0081] Example 12:

[0082] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows:

[0083] a. The first-step reaction is the formation of ferrocene formaldehyde from ferrocene. The main reaction mechanism is cyclization nucleophilic addition reaction. The reaction procedure is as follows: Add 0.8 g of N,N-dimethylformamide to 30 mL of dichloromethane as the solvent, and conduct mechanical stirring reaction in a low-temperature reaction bath at -5 °C until it is evenly dispersed. Then, add 0.5 g of phosphorus oxychloride to the above reaction solution. After the addition, continue mechanical stirring for 0.5 hour. During the reaction, continue to add 0.4 g of ferrocene, and transfer the reaction solution to an oil bath at 40 °C and stir for 2 hours. After the reaction is completed, slowly drop the reaction solution into ice deionized water. After the dropping is completed, continue to slowly drop the 15% (by mass) NaOH solution to keep the pH value of the system at 8. Subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the extract is dehydrated with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 50 °C for rotary evaporation to collect the crude product. Recrystallize the crude product with a mixed solution of dichloromethane and n-hexane with a volume ratio of 1:1. Collect the product and place it in a vacuum drying oven to dry at 50 °C for 48 hours to obtain red-brown solid ferrocene formaldehyde (abbreviation: Fc-CHO) (reactant 2);

[0084] b. The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene and ferrocene formaldehyde. The reaction procedure is as follows: Mix 10 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 20 g of ferrocene formaldehyde, and 30.5 mL of the solvent and add them to the reaction vessel. Stir and react at 40 °C for 0.5 hour, and timely remove the by-product water through a water separator. After the reaction ends, naturally cool to room temperature, and recrystallize and purify with a mixed solution of ethanol and dichloromethane with a volume ratio of 3:1 to obtain the product. Place the collected product in a vacuum drying oven to dry at 60 °C for 48 hours to obtain purple-red powder of ferrocene-phosphazene flame retardant nanosheet - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviation: FH);

[0085] Example 13:

[0086] A preparation method of ferrocene-phosphazene flame retardant nanosheet, the steps are as follows:

[0087] a. The first-step reaction is the formation of ferrocene formaldehyde from ferrocene, and the main reaction mechanism is cyclization nucleophilic addition reaction. The reaction procedure is as follows: Add 2 Kg of N,N-dimethylformamide to 10 L of the solvent dichloromethane, and conduct mechanical stirring reaction in a low-temperature reaction bath at 0 °C until uniformly dispersed. Then, add 1.5 Kg of phosphorus oxychloride to the above reaction solution. After the addition is completed, continue mechanical stirring for 124 hours. During the reaction, continue to add 2 Kg of ferrocene, and transfer the reaction solution to an oil bath at 50 °C and stir for 24 hours. After the reaction is completed, slowly drop the reaction solution into ice deionized water. After the dropping is completed, continue to slowly drop a 20% NaOH solution by mass to keep the pH value of the system at 7. Subsequently, the reaction mixture is extracted with dichloromethane and deionized water respectively, and the extract is dehydrated with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 50 °C for rotary evaporation to collect the crude product. Recrystallize the crude product with a mixed solution of dichloromethane and n-hexane with a volume ratio of 2:1. Collect the product and place it in a vacuum drying oven to dry at 70 °C for 36 hours to obtain a red-brown solid ferrocene formaldehyde (abbreviation: Fc-CHO) (reactant 2);

[0088] b. The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene and ferrocene formaldehyde. The reaction procedure is as follows: Mix 6 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 40 g of ferrocene formaldehyde, and 500 mL of the solvent and add them to a reaction vessel. Stir and react at 85 °C for 36 hours, and timely remove the by-product water through a water separator. After the reaction is completed, naturally cool to room temperature, and recrystallize and purify with a mixed solution of ethanol and dichloromethane with a volume ratio of 1:4 to obtain the product. Place the collected product in a vacuum drying oven to dry at 70 °C for 36 hours to obtain a purple-red powder of ferrocene-phosphazene flame retardant nanosheet - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviation: FH);

[0089] Example 14:

[0090] A preparation method of ferrocene-phosphazene flame retardant nanosheet, the steps are as follows:

[0091] a. Preparation of ferrocene formaldehyde: The first-step reaction is the formation of ferrocene formaldehyde from ferrocene. The main reaction mechanism is cyclization nucleophilic addition reaction. The reaction steps are as follows: Add 0.8 g of N,N-dimethylformamide to 30 mL of dichloromethane as the solvent, and carry out mechanical stirring reaction in a low-temperature reaction bath at -5 °C until evenly dispersed. Then, add 0.5 g of phosphorus oxychloride to the above reaction solution. After the addition is completed, continue mechanical stirring reaction for 0.5 hour. Then add 0.4 g of ferrocene, and stir the reactant (solution) at 40 °C (the reactant can be transferred to an oil bath at 40 °C) for 2 hours. After the reaction is completed, slowly drip the reaction solution into ice deionized water. After the dripping is completed, continue to slowly drip a 15% NaOH aqueous solution by mass percentage to keep the pH value of the system at 6. Subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the extract is dehydrated with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 40 °C for rotary evaporation to collect the crude product. Recrystallize the crude product with a mixed solution of dichloromethane and n-hexane with a volume ratio of 1:6. Collect the product and place it in a vacuum drying oven to dry at 50 °C for 24 hours to obtain ferrocene formaldehyde (abbreviation: Fc-CHO) as a red-brown solid;

[0092] b. Preparation of ferrocene-phosphazene flame retardant nanosheets: The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviation: HACP) and ferrocene formaldehyde. The reaction steps are as follows: Mix 0.1 g of hexakis(4-aminophenoxy)cyclotriphosphazene, 1 g of ferrocene formaldehyde, and 30.5 ml of the solvent and add them to the reaction vessel. Stir and react at 40 °C for 0.5 hour, and timely remove the by-product water through a water separator. After the reaction ends, naturally cool to room temperature to obtain the crude product. Prepare a mixed solution of ethanol and dichloromethane with a volume ratio of 1:6 to recrystallize (purify) the crude product to obtain the product. Place the product in a vacuum drying oven to dry at 60 °C for 24 hours to obtain ferrocene-phosphazene flame retardant nanosheets (purple-red powder), namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviation: FH);

[0093] The solvent is any one of ethanol, acetone, and dichloromethane.

[0094] Example 15:

[0095] A preparation method of ferrocene-phosphazene flame retardant nanosheets, the steps are as follows:

[0096] a. Preparation of ferrocene formaldehyde: The first-step reaction is the formation of ferrocene formaldehyde from ferrocene. The main reaction mechanism is cyclization nucleophilic addition reaction. The reaction steps are as follows: Add 4.5 Kg of N,N-dimethylformamide to 20 L of the solvent dichloromethane, and carry out mechanical stirring reaction in a low-temperature reaction bath at 5 °C until evenly dispersed; then, add 3 Kg of phosphorus oxychloride to the above reaction solution, and continue mechanical stirring reaction for 24 hours after the addition; continue to add 5 Kg of ferrocene, and stir the reactant (solution) at 60 °C (the reactant can be transferred to an oil bath at 60 °C) for 48 hours; after the reaction is completed, slowly drip the reaction solution into ice deionized water, and after the dripping is completed, continue to slowly drip a 30% NaOH aqueous solution by mass percentage concentration to keep the pH value of the system at 9; subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the moisture in the extract is removed with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 60 °C for rotary evaporation to collect the crude product; recrystallize the crude product with a mixed solution of dichloromethane and n-hexane with a volume ratio of 3:1. Collect the product and place it in a vacuum drying oven to dry at 70 °C for 48 hours to obtain ferrocene formaldehyde (abbreviated as Fc-CHO), a red-brown solid;

[0097] b. Preparation of ferrocene-phosphazene flame retardant nanosheets: The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviated as HACP) and ferrocene formaldehyde. The reaction steps are as follows: Mix 5 Kg of hexakis(4-aminophenoxy)cyclotriphosphazene, 10 Kg of ferrocene formaldehyde, and 10 L of the solvent and add them to a reaction vessel, and stir the reaction at 90 °C for 48 hours. Remove the by-product water in time through a water separator. After the reaction is completed, naturally cool to room temperature to obtain the crude product; prepare a mixed solution of ethanol and dichloromethane with a volume ratio of 9:1 to recrystallize (purify) the crude product to obtain the product; place the product in a vacuum drying oven to dry at 80 °C for 48 hours to obtain ferrocene-phosphazene flame retardant nanosheets (purple-red powder), that is, hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH);

[0098] The solvent is any one of ethanol, acetone, and dichloromethane.

[0099] Example 16:

[0100] A preparation method of ferrocene-phosphazene flame retardant nanosheets, and the steps are as follows:

[0101] a. Preparation of ferrocene formaldehyde: The first-step reaction is the reaction of ferrocene to form ferrocene formaldehyde. The main reaction mechanism is cyclization nucleophilic addition reaction. The reaction steps are as follows: Add 2.2 Kg of N,N-dimethylformamide to 10 L of the solvent dichloromethane, and carry out mechanical stirring reaction in a low-temperature reaction bath at 2 °C until evenly dispersed; then, add 1.5 Kg of phosphorus oxychloride to the above reaction solution. After the addition is completed, continue mechanical stirring reaction for 12 hours; continue to add 2.5 Kg of ferrocene, and stir the reactant solution at 50 °C (the reactant can be transferred to an oil bath at 50 °C) for 25 hours; after the reaction is completed, slowly drip the reaction solution into ice deionized water. After the dripping is completed, continue to slowly drip a NaOH aqueous solution with a mass percentage concentration of 22% to keep the pH value of the system at 7.5; subsequently, the reaction mixture solution is extracted with dichloromethane and deionized water respectively, and the extract is dehydrated with anhydrous sodium sulfate. The collected extract is placed in a rotary evaporator at 50 °C for rotary evaporation to collect the crude product; the crude product is recrystallized with a mixed solution of dichloromethane and n-hexane with a volume ratio of 2:3. The collected product is placed in a vacuum drying oven and dried at 60 °C for 36 hours to obtain ferrocene formaldehyde (abbreviation: Fc-CHO), a red-brown solid;

[0102] b. Preparation of ferrocene-phosphazene flame retardant nanosheets: The second-step reaction is the aldehyde-amine dehydration condensation (nucleophilic addition reaction) of hexakis(4-aminophenoxy)cyclotriphosphazene (abbreviation: HACP) and ferrocene formaldehyde. The reaction steps are as follows: Add 2.5 Kg of hexakis(4-aminophenoxy)cyclotriphosphazene, 5 Kg of ferrocene formaldehyde, and 5 L of the solvent to the reaction vessel, and stir the reaction at 65 °C for 24 hours. Remove the by-product water in time through a water separator. After the reaction is completed, naturally cool to room temperature to obtain the crude product; prepare a mixed solution of ethanol and dichloromethane with a volume ratio of 5:3 to recrystallize (purify) the crude product to obtain the product; place the product in a vacuum drying oven and dry at 70 °C for 36 hours to obtain ferrocene-phosphazene flame retardant nanosheets (a purple-red powder), namely: hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviation: FH);

[0103] The solvent is any one of ethanol, acetone, and dichloromethane.

[0104] Example 17:

[0105] The ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviation: FH) prepared in the above example can be used in flame-retardant polymer composites. For example, it can be used in flame-retarding epoxy resins, polypropylenes, polyethylenes, etc. The flame retardant effect is good, and it can also maintain or even improve the mechanical properties of the composites.

[0106] The size of the ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (abbreviated as FH) prepared in the above embodiments is between 50 and 100 nm, and the thickness can reach between 30 and 50 nm; the pore volume is between 0.091 and 0.25 cc / g, and the pore size distribution is between 1.9 and 5.6 nm.

[0107] In the above examples, the solvent described in step d is any one of ethanol, acetone, and dichloromethane.

[0108] The ferrocene-phosphazene flame retardant nanosheets - hexakis(4-imino)cyclotriphosphazene-ferrocene (FH) prepared in the above examples have the chemical structural formula shown in (I):

[0109]

[0110] In the above embodiments: all raw materials used are commercially available products.

[0111] In the above embodiments: in the percentage ratios used, unless otherwise specified, they are all mass (weight) percentage ratios or percentage ratios well-known to those skilled in the art; the mass (weight) parts can all be grams or kilograms.

[0112] In the above embodiments: for the process parameters (temperature, time, concentration, etc.) and the numerical values of the amounts of each component in each step that are in a range, any point can be applicable.

[0113] The technical content not specifically described in the content of the present invention and the above embodiments is the same as the prior art.

[0114] The present invention is not limited to the above embodiments, and all the contents described in the present invention can be implemented and have the said good effects.

Claims

1. A preparation method of a ferrocene-phosphazene flame retardant nanosheet, characterized in that The steps are as follows: a. Preparation of ferrocene formaldehyde: Add 0.8 g to 4.5 Kg of N, N-dimethylformamide to 30 mL to 20 L of the solvent dichloromethane, and stir and react at a temperature of -5 to 5 °C until uniformly dispersed; then, add 0.5 g to 3 Kg of phosphorus oxychloride to the above reaction solution, and continue to stir and react for 0.5 to 24 hours; continue to add 0.4 g to 5 Kg of ferrocene, and stir and react the reactants at a temperature of 40 to 60 °C for 2 to 48 hours; after the reaction is completed, drop the reaction solution into ice deionized water, and continue to drop a NaOH aqueous solution with a mass percentage concentration of 15 to 30% to keep the pH value of the system at 6 to 9; subsequently, extract the reaction mixture solution with dichloromethane and deionized water respectively, and use anhydrous sodium sulfate to remove the moisture from the extract. Place the collected extract in a rotary evaporator at a temperature of 40 to 60 °C for rotary evaporation, and collect the crude product; recrystallize the crude product with a mixed solution of dichloromethane and n-hexane with a volume ratio of 1:6 to 3:1; collect the product and place it in a vacuum drying oven to dry at a temperature of 50 to 70 °C for 24 to 48 hours to obtain ferrocene formaldehyde; b. Preparation of ferrocene-phosphazene flame retardant nanosheets: Add 0.1 g to 5 Kg of hexakis(4-aminophenoxy)cyclotriphosphazene, 1 g to 10 Kg of ferrocene formaldehyde, and 30.5 mL to 10 L of the solvent to a reaction vessel, and stir and react at a temperature of 40 to 90 °C for 0.5 to 48 hours. Remove the by-product water in time through a water separator. After the reaction is completed, naturally cool to room temperature to obtain the crude product; prepare a mixed solution of ethanol and dichloromethane with a volume ratio of 1:6 to 9:1 to recrystallize the crude product to obtain the product; place the product in a vacuum drying oven to dry at a temperature of 60 to 80 °C for 24 to 48 hours to obtain ferrocene-phosphazene flame retardant nanosheets; The molar ratio of the hexakis(4-aminophenoxy)cyclotriphosphazene to the ferrocene formaldehyde is 1:6; The solvent is any one of ethanol, acetone, and dichloromethane.

2. The preparation method of the ferrocene-phosphazene flame retardant nanosheet according to claim 1, characterized in that: The size of the ferrocene-phosphazene flame retardant nanosheets is 50 to 100 nm, the thickness is 3 to 50 nm, the pore volume is between 0.091 and 0.25 cc / g, and the pore size distribution is between 1.9 and 5.6 nm.

3. Use of the ferrocene-phosphazene flame retardant nanosheets obtained by the preparation method according to claim 1, characterized in that: The ferrocene-phosphazene flame retardant nanosheets are used in flame retardant polymer composites.

4. The use of the ferrocene-phosphazene flame retardant nanosheet according to claim 3, characterized in that: The flame retardant polymer composites are flame retardant epoxy resin, flame retardant polypropylene, and flame retardant polylactic acid composites.

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