A polyorganosilicon cyclotriphosphazene modified epoxy resin and a method for preparing the same

Abstract

The present application relates to a kind of polyorganosilicon cyclotriphosphazene modified epoxy resin and its preparation method, belong to flame-retardant material field, wherein the preparation method of polyorganosilicon cyclotriphosphazene flame retardant: with hexachlorotriphosphazene, p-hydroxy benzaldehyde, p-aminobenzoic acid, DOPO and diphenylsilanediol as raw material, by four-step reaction is made.Then the preparation method of epoxy resin with flame retardant as modifier: m-phenylenediamine is curing agent, add a series of gradient polyorganosilicon cyclotriphosphazene flame retardant to epoxy resin, after two times of curing, modified epoxy resin is obtained.The present application is mainly used for preparing polyorganosilicon cyclotriphosphazene flame retardant and polyorganosilicon cyclotriphosphazene modified epoxy resin.

Description

Technical Field

[0001] The invention relates to a polysilicone cyclophosphazene modified epoxy resin and a preparation method thereof, and belongs to the field of flame retardant materials. Background Art

[0002] Epoxy resin has been widely used in many fields such as electronics, aerospace, construction, and coatings due to its excellent mechanical properties, chemical stability, and electrical insulation properties. However, it is highly flammable and produces toxic fumes when burned, which greatly limits its application in high-temperature or flammable environments. This high flammability not only increases safety hazards during use, but also restricts its promotion and application in fields with strict flame retardancy requirements. In addition, the mechanical properties of epoxy resin are also a key factor in its use as a structural material, especially in situations with large loads, which require the material to have not only good mechanical strength but also good flame retardancy when exposed to fire. Therefore, how to improve the flame retardant effect of epoxy resin without significantly reducing the mechanical properties has become a technical problem that needs to be solved urgently.

[0003] At present, the conventional method to improve the flame retardant properties of epoxy resin is to add various flame retardants to it. Common flame retardants include phosphorus-containing, nitrogen-containing and other compounds. However, although the addition of a large amount of flame retardants can significantly improve the flame retardant properties of the material, this method often brings significant negative effects. First, the addition of a high proportion of flame retardants will significantly reduce the mechanical properties of the epoxy resin, such as tensile strength and toughness, causing the material to easily crack or deform when subjected to mechanical stress. Secondly, the flame retardant has poor compatibility with the epoxy resin matrix, and it is difficult for the flame retardant to be evenly dispersed in the resin, which in turn affects the molding and processing properties of the material and may cause its internal structure to be uneven. In addition, the addition of a large amount of flame retardants will also increase the cost of the material, affecting its application and promotion in industry. Therefore, how to balance the relationship between flame retardant effect and mechanical properties has become a huge challenge in current material modification.

[0004] The researchers further proposed a variety of improvement plans. For example, by reducing the particle size of the flame retardant, ultrafine or nano-processing is carried out in order to improve its dispersion and interface bonding performance with the matrix. However, in actual applications, it is found that it is often difficult to obtain the ideal effect through simple nano-processing alone. After the flame retardant reaches a certain mass or volume fraction, the performance improvement of the material tends to be saturated. In addition, adding reinforcing fibers is also considered to be one of the effective means to improve mechanical properties, but some reinforcing fibers themselves are flammable, which may aggravate the spread of flames and even cause a "wick effect", further reducing the flame retardant properties of epoxy resin. Therefore, optimizing the structure of the flame retardant, controlling its dispersibility, reducing the amount added, and improving the flame retardant efficiency on this basis have become the focus and difficulty in the research and development of epoxy resin composite materials. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a polysilicone cyclophosphazene-modified epoxy resin to solve the problem of incompatibility between flame retardancy and mechanical properties of existing modified epoxy resins. The invention mainly includes a method for preparing a polysilicone cyclophosphazene flame retardant and a method for preparing a polysilicone cyclophosphazene-modified epoxy resin.

[0006] Improving the mechanical properties of epoxy resin by adding nano flame retardants or doping with reinforcing fibers has many limitations. Therefore, the present invention proposes to design a flame retardant that contains special flame retardant elements such as N, P, and Si and has high stability and high flexibility. The flame retardant's own active groups are combined with the epoxy groups of the epoxy resin to achieve the purpose of modifying the molecular structure of the epoxy resin and optimizing the flame retardant and mechanical properties of the modified epoxy resin.

[0007] Advantage 1: To ensure that a dense carbon layer can be formed during the combustion process and to fully exert the flame retardant effect of the condensed phase, existing researchers often design flame retardants with relatively complex polymer chain structures. However, the complex flame retardant structure will further complicate the cross-linking network formed by the ring-opening cross-linking reaction between the flame retardant and the epoxy groups of the epoxy resin, resulting in a decrease in the uniformity of the corresponding modified epoxy resin phase system and the cross-linking density of the cured product, which in turn leads to a decrease in the mechanical properties of the modified epoxy resin. Therefore, the present invention designs the polysilicone cyclophosphazene flame retardant into a polymer structure with a certain number of active groups to better participate in the epoxy resin curing reaction and increase the cross-linking density between itself and the epoxy resin.

[0008] Advantage 2: Complex cross-linking networks and unevenly distributed cross-linking bonds may further lead to uneven stress distribution within the material, and even stress concentration, which may cause the epoxy resin product to break. Therefore, the polysilicone cyclophosphazene flame retardant proposed in the present invention is based on hexachlorotripolyphosphazene as the core skeleton. Its stable six-membered ring conjugated structure can be used to further enhance the structural stability of the flame retardant. In addition, the reactive anchor points participating in the curing reaction during the epoxy resin curing process are evenly distributed on the six branches of the six-membered ring, which can improve the interaction between the flame retardant and the epoxy resin and reduce the phenomenon of uneven stress distribution. In addition, the present invention further introduces a high-stability DOPO group on its side chain to increase its steric hindrance and increase the cross-linking density of the system during the actual curing process, so as to effectively improve the compatibility between the polysilicone cyclophosphazene flame retardant and the epoxy resin, thereby promoting the polysilicone cyclophosphazene-modified epoxy resin to have superior mechanical properties.

[0009] Advantage 3: The hexachlorotripolyphosphazene skeleton has a high content of N and P elements, and is also easy to derivatize with multiple side groups. This means that multiple flame retardant elements can be simultaneously incorporated into the flame retardant molecular structure, ensuring excellent mechanical properties of epoxy resin while also having good flame retardant properties.

[0010] Advantage 4: The polysilicone cyclophosphazene flame retardant proposed in this invention uses groups corresponding to high-energy chemical bonds, such as benzene rings, as the primary carbon structure extending the flame retardant's backbone branches. Diphenylsilanediol, a type of Si-O bond with long bond lengths, large bond angles, and excellent flexibility, is selected to provide the Si element in the flame retardant. By designing a highly stable flame retardant structure, the flame retardant maintains the epoxy resin's flame retardancy while minimizing its destructive effects on its mechanical properties.

[0011] The structural formula of polysilicone cyclophosphazene flame retardant is:

[0012]

[0013] The preparation method of the polysilicone cyclophosphazene flame retardant provided by the present invention is mainly completed according to the following steps: first, -OH in p-hydroxybenzaldehyde and -Cl in hexachlorotriphosphazene undergo a substitution reaction to obtain an intermediate 1; second, -CHO in the intermediate 1 reacts with -NH2 in p-aminobenzoic acid to generate an intermediate 2 containing a Schiff base structure; DOPO undergoes an addition reaction with the Schiff base structure in the intermediate 2 to obtain an intermediate 3; finally, diphenylsilanediol and the carboxylated intermediate 3 undergo an esterification reaction, and because diphenylsilanediol has two symmetrically positioned -OH reaction sites, the polysilicone cyclophosphazene flame retardant is finally synthesized.

[0014] The preparation method of the polyorganosilicon cyclophosphazene modified epoxy resin provided by the present invention is mainly completed according to the following steps: first, the epoxy resin (E-51) is heated to 100-120°C, a polyorganosilicon cyclophosphazene flame retardant is added, and the mixture is mixed evenly, and then the mixture is cooled to a temperature of 60-80°C, and then a curing agent (m-phenylenediamine) is added. After mixing evenly, vacuum degassing is performed, and then mold casting, double curing and natural cooling are performed in sequence to obtain the polyorganosilicon cyclophosphazene modified epoxy resin.

[0015] Technical effects of the present invention:

[0016] First, the polysilicone cyclophosphazene flame retardant prepared in this invention is a high-molecular-weight polymer with multiple active hydrogen species in its structure. This provides more active sites for the ring-opening reaction of epoxy groups in epoxy resins, allowing molecular chains to entangle with each other and increasing the crosslinking density of the epoxy resin. This results in a tighter system and superior mechanical properties. This invention successfully resolves the incompatibility between flame retardancy and mechanical properties of existing modified epoxy resins.

[0017] 2. The polysilicone cyclophosphazene-modified epoxy resins prepared by the present invention meet the test standards for flame-retardant materials. When the addition amount of the polysilicone cyclophosphazene flame retardant is 8% and 12%, respectively, the LOI values ​​of the corresponding modified epoxy resins are 32.3% and 30.4%, respectively. The UL-94 test reaches V-0 grade, that is, the polysilicone cyclophosphazene-modified epoxy resins have good flame retardant properties.

[0018] 3. The tensile properties and adhesive properties of the polysilicone cyclophosphazene modified epoxy resin prepared by the present invention are improved. When the addition amount of the polysilicone cyclophosphazene flame retardant is 4% and 8% respectively, the breaking strength of the corresponding modified epoxy resin is increased by 5.76 MPa and 3.79 MPa respectively compared with the unmodified epoxy resin, and the peel strength is increased by 0.2 kN / m and 0.12 kN / m respectively compared with the unmodified epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Infrared spectrum of the polysilicone cyclophosphazene flame retardant prepared in Example 5.

[0020] Figure 2 H-NMR spectrum of the polysilicone cyclophosphazene flame retardant prepared in Example 5.

[0021] Figure 3 NMR phosphorus spectrum of the polysilicone cyclophosphazene flame retardant prepared in Example 5.

[0022] Figure 4 Screenshot of the video of the vertical combustion experiment of the polysilicone cyclophosphazene-modified epoxy resin in Example 6.

[0023] Figure 5 Stress-strain curve of the polysilicone cyclophosphazene modified epoxy resin in Example 6.

[0024] Figure 6 Peel strength bar graph of the polysilicone cyclophosphazene modified epoxy resin in Example 6. DETAILED DESCRIPTION

[0025] The following examples are used to specifically describe the preparation method of the polysilicone cyclophosphazene flame retardant and the preparation method of the polysilicone cyclophosphazene modified epoxy resin proposed in the present invention, but the embodiment is not limited thereto and the examples should not be regarded as limiting the present invention.

[0026] Example 1

[0027] A method for preparing a polysilicone cyclophosphazene modified epoxy resin, the preparation steps of the resin are:

[0028] Step 1: p-Hydroxybenzaldehyde and hexachlorotriphosphazene undergo substitution reaction to obtain intermediate 1;

[0029] Step 2: intermediate 1 undergoes a dehydration condensation reaction with p-aminobenzoic acid to generate intermediate 2 containing a Schiff base structure;

[0030] Step 3: DOPO is reacted with intermediate 2 to obtain intermediate 3;

[0031] Step 4: Esterification reaction is carried out between diphenylsilanediol and intermediate 3, and due to the presence of two symmetrically positioned -OH reaction sites in diphenylsilanediol, polysilicone cyclophosphazene flame retardant 4 is obtained;

[0032] Step 5: Heat the E-51 epoxy resin to 100-120°C, add the polysilicone cyclophosphazene flame retardant 4, mix evenly, then cool to 60-80°C, add the curing agent, mix evenly and perform vacuum degassing, then pour into a preheated mold and cure at 60-80°C in a vacuum drying oven for 1.5-2h, then cure at 130-150°C for 1.5-2h, and cool to room temperature to obtain a polysilicone cyclophosphazene modified epoxy resin, wherein the mass fraction of the polysilicone cyclophosphazene flame retardant added to the modified epoxy resin is 4%-16%.

[0033] Example 2

[0034] This embodiment is substantially the same as embodiment 1, except that the substitution reaction in this embodiment is as follows: p-hydroxybenzaldehyde and anhydrous potassium carbonate are added to tetrahydrofuran solvent, wherein the molar ratio of p-hydroxybenzaldehyde to anhydrous potassium carbonate is 1:1 to 1:1.5, 100 mL of tetrahydrofuran solvent is required to dissolve every 0.01 to 0.02 mol of p-hydroxybenzaldehyde, and stirring is continued for 1 to 2 hours; hexachlorotrimer phosphazene is added to tetrahydrofuran, wherein 100 mL of tetrahydrofuran is required to dissolve every 0.06 to 0.07 mol of hexachlorotrimer phosphazene, and the mixture is stirred for 1 to 2 hours. After dissolution, the hexachlorotrimer phosphazene solution was slowly added dropwise to the p-hydroxybenzaldehyde and anhydrous potassium carbonate solution in a molar ratio of hexachlorotrimer phosphazene to p-hydroxybenzaldehyde of 1:6 to 1:7, and the mixture was heated in an oil bath with continuous stirring and reacted at 60-66°C for 20-24 hours. After the reaction, the mixture was cooled to room temperature and poured into a large amount of water. The precipitate was filtered and vacuum dried at 60-70°C for 10-12 hours. The crude product was recrystallized from ethyl acetate, allowed to cool, filtered, and vacuum dried at 70-85°C for 10-12 hours to obtain intermediate 1 as a light yellow solid.

[0035] Example 3

[0036] This example is basically the same as Example 2, except that the dehydration condensation reaction in this example is as follows: intermediate 1 and p-aminobenzoic acid are added to a dioxane solvent in a molar ratio of 1:6 to 1:7, wherein 100 mL of 1,4-dioxane is required to dissolve every 0.008 to 0.009 mol of intermediate 1, the mixture is evacuated and nitrogen is passed through, the mixture is heated in an oil bath with continuous stirring, the reaction is carried out at 90 to 101° C. for 20 to 24 hours, the reaction is completed and the mixture is cooled to room temperature, the reaction solution is poured into an ethanol diluent, the precipitate is filtered, washed twice with ethanol, and vacuum dried at 60 to 70° C. for 10 to 12 hours to obtain intermediate 2 as a white solid.

[0037] Example 4

[0038] This example is basically the same as Example 3, except that the addition reaction in this example is as follows: intermediate 2, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1,4-dioxane are added to a three-necked flask, wherein the molar ratio of intermediate 2 to DOPO is 1:6 to 1:7, 1,4-dioxane is used as a solvent, and 100 mL of 1,4-dioxane is required to dissolve every 0.0006 to 0.0007 mol of intermediate 2; under nitrogen protection, the mixture is heated in an oil bath with continuous stirring at 90 to 101° C. for 20 to 24 hours, and after the reaction is completed, the mixture is cooled to room temperature, and the reaction solution is poured into an ethanol diluent. The precipitate is filtered, washed twice with hot water and anhydrous ethanol, respectively, and dried in vacuo at 60 to 70° C. for 10 to 12 hours to obtain intermediate 3 as a white solid.

[0039] Example 5

[0040] This embodiment is basically the same as embodiment 5, except that the method for preparing a polysilicone cyclophosphazene modified epoxy resin described in this embodiment is characterized in that the esterification reaction is as follows: in a three-necked flask, the intermediate 3 and 1-hydroxybenzotriazole (HOBT) are dissolved in DMSO The mixture was stirred continuously for 1-2 hours until dissolved. 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI) and diphenylsilanediol were dissolved in DMSO. The molar ratios of intermediate 3 to HOBT, EDCI, and diphenylsilanediol were 10:1, 1:3-1:4, and 1:1, respectively. In addition, 100 mL of DMSO was required to dissolve every 0.0009-0.001 mol of intermediate 3. After complete dissolution, the EDCI solution and diphenylsilanediol solution were slowly added dropwise to the three-necked flask. The mixture was heated in an oil bath with continuous stirring and reacted at 115-125°C for 20-24 hours. After the reaction was completed, the mixture was cooled to room temperature and poured into a large amount of water. The precipitate was filtered, washed twice with ethanol, and dried under vacuum at 60-70°C for 10-12 hours to obtain a polysilicone cyclophosphazene flame retardant.

[0041] Example 6

[0042] This embodiment is basically the same as Example 5, except that the curing agent 2 in this embodiment is m-phenylenediamine, and the mass fraction of the polysilicone cyclophosphazene flame retardant added to the modified epoxy resin is 4%, 8%, 12%, or 16%, respectively. The sample with a polysilicone cyclophosphazene flame retardant added in an amount of 4% in the modified epoxy resin is marked as EP-1; the sample with a polysilicone cyclophosphazene flame retardant added in an amount of 8% in the modified epoxy resin is marked as EP-2; the sample with a polysilicone cyclophosphazene flame retardant added in an amount of 12% in the modified epoxy resin is marked as EP-3; the sample with a polysilicone cyclophosphazene flame retardant added in an amount of 16% in the modified epoxy resin is marked as EP-4; and the sample of the epoxy resin without the flame retardant added as a reference sample is marked as EP.

[0043] The structure of the polysilicone cyclophosphazene flame retardant prepared in Example 5 was characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and phosphorus spectrum. Figures 1-3 The flame retardancy and mechanical properties of the polysilicone cyclophosphazene modified epoxy resin were studied by subjecting the samples prepared in Example 6 to vertical combustion (UL-94), limiting oxygen index (LOI), and tensile properties tests, and by using the adhesive T peel strength test method. The relevant experimental data are recorded in Table 1, and the video screenshot of the modified epoxy resin during the vertical combustion test is shown in Figure 4 The corresponding stress-strain curves and peel strength test results are shown as Figure 5 、 Figure 6 The vertical burning, limiting oxygen index, tensile properties, and peel strength were determined in accordance with the following standards:

[0044] Vertical burning (UL-94) test: GB / T 2408-2021;

[0045] Limiting Oxygen Index (LOI) test: GB / T 2406.2-2009;

[0046] Tensile properties test: GB / T 1040.2-2006;

[0047] Peel strength test: GB / T 2791-1995.

[0048] Table 1 Flame retardant properties, breaking strength and bonding properties of samples in various embodiments

[0049]

[0050] From Table 1 and Figure 4It can be seen that the LOI value of pure epoxy resin is only 21.0%. It continues to burn in the UL-94 test, and the melting drop phenomenon occurs at the 33rd second of the combustion process, and fails the UL-94 test. The addition of polysilicone cyclophosphazene flame retardant increases the LOI value of the epoxy resin. The UL-94 test results also show that the polysilicone cyclophosphazene modified epoxy resins are self-extinguishing within a certain time range and have excellent flame retardancy. Among them, the polysilicone cyclophosphazene modified epoxy resins EP-2 and EP-3 obtained in Example 6 have the best flame retardancy, with LOI values ​​of 32.3% and 30.4% respectively, both reaching the UL-94 test V-0 grade. In addition, from Table 1, Figure 5 and Figure 6 It can be seen that compared with the polyorganosilicon cyclophosphazene-modified epoxy resins EP-1 and EP-2 obtained from pure epoxy resin EP and Example 6, the tensile properties and adhesive properties of the polyorganosilicon cyclophosphazene-modified epoxy resin are improved, that is, at the corresponding addition amount in this example, the polyorganosilicon cyclophosphazene-modified epoxy resin has excellent mechanical properties.

Claims

1. A method for preparing a polysilicone cyclophosphazene modified epoxy resin, the preparation steps of the resin are: Step 1: p-Hydroxybenzaldehyde and hexachlorotriphosphazene undergo substitution reaction to obtain intermediate 1; Step 2: intermediate 1 undergoes a dehydration condensation reaction with p-aminobenzoic acid to generate intermediate 2 containing a Schiff base structure; Step 3: DOPO is reacted with intermediate 2 to obtain intermediate 3; Step 4: Esterification reaction is carried out between diphenylsilanediol and intermediate 3, and due to the presence of two symmetrically positioned -OH reaction sites in diphenylsilanediol, polysilicone cyclophosphazene flame retardant 4 is obtained; Step 5: Heat the E-51 epoxy resin to 100-120°C, add the polysilicone cyclophosphazene flame retardant 4, mix well, then cool to 60-80°C, add the curing agent, mix well and vacuum degas, then pour into a preheated mold and cure at 60-80°C in a vacuum drying oven for 1.5-2h, then cure at 130-150°C for 1.5-2h, and cool to room temperature to obtain a polysilicone cyclophosphazene modified epoxy resin, wherein, The mass fraction of the polysilicone cyclophosphazene flame retardant added to the modified epoxy resin is 4% to 16%.

2. The method for preparing a polysilicone cyclophosphazene modified epoxy resin according to claim 1, wherein The substitution reaction described in step 1 is as follows: p-hydroxybenzaldehyde and anhydrous potassium carbonate are added to tetrahydrofuran solvent respectively, wherein the molar ratio of p-hydroxybenzaldehyde to anhydrous potassium carbonate is 1:1 to 1:1.5, 100 mL of tetrahydrofuran solvent is required for dissolving every 0.01 to 0.02 mol of p-hydroxybenzaldehyde, and stirring is continued for 1 to 2 hours; hexachlorotrimer phosphazene is added to tetrahydrofuran, 100 mL of tetrahydrofuran is required for dissolving every 0.06 to 0.07 mol of hexachlorotrimer phosphazene, and after complete dissolution, the mixture is stirred according to the following steps: The molar ratio of chlorotriphosphazene to p-hydroxybenzaldehyde is 1:6 to 1:

7. The hexachlorotriphosphazene solution is slowly added dropwise to the p-hydroxybenzaldehyde and anhydrous potassium carbonate solution, heated in an oil bath with continuous stirring, and reacted at 60-66° C. for 20-24 hours. After the reaction, the reaction solution is cooled to room temperature, poured into a large amount of water, and the precipitate is filtered and vacuum-dried at 60-70° C. for 10-12 hours. The crude product is recrystallized from ethyl acetate, allowed to cool, filtered, and vacuum-dried at 70-85° C. for 10-12 hours to obtain intermediate 1.

3. A method for preparing a polysilicone cyclophosphazene modified epoxy resin as claimed in claim 2, characterized in that The dehydration condensation reaction in step 2 is as follows: intermediate 1 and p-aminobenzoic acid are added to a dioxane solvent in a molar ratio of 1:6 to 1:7, wherein 100 mL of 1,4-dioxane is required for dissolving every 0.008 to 0.009 mol of intermediate 1, vacuuming with nitrogen, heating in an oil bath with continuous stirring, reacting at 90 to 101 ° C for 20 to 24 hours, cooling to room temperature after the reaction, pouring the reaction solution into an ethanol diluent, filtering the precipitate, washing twice with ethanol, and vacuum drying at 60 to 70 ° C for 10 to 12 hours to obtain intermediate 2.

4. The method for preparing a polysilicone cyclophosphazene modified epoxy resin according to claim 3, wherein The addition reaction in step 3 is as follows: intermediate 2, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1,4-dioxane are added to a three-necked flask, wherein the molar ratio of intermediate 2 to DOPO is 1:6 to 1:7, 1,4-dioxane is used as a solvent, and 100 mL of 1,4-dioxane is required to dissolve every 0.0006 to 0.0007 mol of intermediate 2; under nitrogen protection, the oil bath is heated with continuous stirring at 90 to 101° C. for 20 to 24 hours, the reaction is completed and cooled to room temperature, the reaction solution is poured into an ethanol diluent, the precipitate is filtered, washed twice with hot water and anhydrous ethanol, respectively, and vacuum dried at 60 to 70° C. for 10 to 12 hours to obtain intermediate 3.

5. The method for preparing a polysilicone cyclophosphazene modified epoxy resin according to claim 4, wherein The esterification reaction in step 4 is as follows: in a three-necked flask, the intermediate 3 and 1-hydroxybenzotriazole (HOBT) are dissolved in DMSO and stirred continuously for 1 to 2 hours until dissolved. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI) and diphenylsilanediol are dissolved in DMSO respectively. The molar ratios of intermediate 3 to HOBT, EDCI and diphenylsilanediol are 10:1, 1:3 to 1:4 and 1:1 respectively. In addition, 100 mL of DMSO is required for every 0.0009 to 0.001 mol of intermediate 3. The DMSO was dissolved, and after it was completely dissolved, the EDCI solution and the diphenylsilane diol solution were slowly added dropwise to the above three-necked flask in sequence, heated in an oil bath with continuous stirring, and reacted at 115-125° C. for 20-24 h. After the reaction was completed, the reaction solution was cooled to room temperature, poured into a large amount of water, and the precipitate was filtered, washed twice with ethanol, and vacuum dried at 60-70° C. for 10-12 h to obtain a polysilicone cyclophosphazene flame retardant.

6. The method for preparing a polysilicone cyclophosphazene modified epoxy resin according to claim 5, wherein The curing agent is m-phenylenediamine, and the mass fraction of the polysilicone cyclophosphazene flame retardant added to the modified epoxy resin is 4%, 8%, 12% or 16%.

7. A polyorganosilicon cyclophosphazene modified epoxy resin prepared by the method for preparing a polyorganosilicon cyclophosphazene modified epoxy resin according to claim 6, wherein the flame retardant contains N, P, and Si flame retardant elements, characterized in that The flame retardant uses hexachlorotripolyphosphazene as its core skeleton. The reactive anchor points participating in the curing reaction during the epoxy resin curing process are evenly distributed on the six branches of the six-membered ring, and DOPO groups are introduced into the six branches.

8. A polysilicone cyclophosphazene modified epoxy resin as claimed in claim 7, characterized in that The structural formula of polysilicone cyclophosphazene flame retardant is:

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