Hyperbranched modifier containing benzoxazine phosphate structure, flame-retardant composite material and application of flame-retardant composite material

Abstract

The invention discloses a hyperbranched modifier containing a benzoxazine phosphate structure, a flame-retardant composite material and application of the hyperbranched modifier and the flame-retardant composite material, and belongs to the technical field of organic chemistry. Daidzein, alkanolamine, paraformaldehyde and an organic solvent are mixed and dissolved and then subjected to a Mannich reaction at 90-120 DEG C for 8-24 h, a polyhydroxy benzoxazine intermediate is prepared and obtained, and then the hyperbranched modifier containing the benzoxazine phosphate structure, the flame-retardant composite material containing the benzoxazine phosphate structure and the flame-retardant composite material containing the benzoxazine phosphate structure are prepared. And uniformly mixing the polyhydroxy benzoxazine intermediate, triethylamine and an organic solvent, adding phosphorus oxychloride, and reacting at 0-30 DEG C for 24-48 hours to obtain the hyperbranched modifier containing the benzoxazine phosphate structure, which can improve the flame retardant property of the epoxy resin. An epoxy resin precursor, a hyperbranched modifier containing a benzoxazine phosphate structure and a curing accelerator are subjected to heating gradient curing to obtain a flame-retardant composite material cured product with the flame-retardant grade reaching V-0 grade and excellent impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of organic chemistry technology, specifically relating to a hyperbranched modifier containing a benzoxazine phosphate ester structure, a flame-retardant composite material, and their applications. Background Technology

[0002] Epoxy resin, as one of the most widely used thermosetting resins, occupies an important position in aerospace, electronic packaging, coatings, and adhesives due to its excellent dimensional stability, mechanical properties, and chemical resistance. However, the inherent defect of poor flame retardancy in traditional epoxy resins severely restricts their application and promotion in scenarios with stringent flame retardancy requirements. Benzoxazine resin, as a novel thermosetting resin, has been gradually applied in high-end fields such as aerospace, electronic packaging, and rail transportation due to its almost non-shrinkage and lack of small molecule byproduct release during curing, combined with excellent chemical resistance, thermal stability, and flame retardancy. This provides a new direction for addressing the performance shortcomings of traditional thermosetting resins.

[0003] Given the increasing toxicity issues of halogenated flame retardants, highly efficient and environmentally friendly phosphorus-containing flame retardants have become a research focus. These flame retardants possess dual flame-retardant mechanisms in both the gas and condensed phases, effectively inhibiting flame spread and promoting the formation of a dense char layer to block combustion, while their thermal decomposition products are environmentally friendly. Among them, phosphate ester flame retardants derived from renewable resources show great application potential in the field of sustainable flame-retardant materials due to their green characteristics throughout their entire life cycle. For example, Chinese patent document CN113929968A discloses a resveratrol-based flame retardant and its preparation method and application. By reacting the bio-based raw material resveratrol with phosphorus-containing diphenylphosphine chloride, phosphorus is introduced, enabling rapid carbonization during heating or combustion, providing oxygen and heat insulation, reducing the release of combustible gases and toxic fumes, and thus improving flame-retardant performance. Therefore, developing benzoxazine flame-retardant monomers with phosphate ester structures and combining them with epoxy resins to improve flame-retardant performance is of great significance for expanding the application scenarios of epoxy resins.

[0004] Genistein is a natural, renewable compound widely found in soybeans and other legumes. Not only is it sustainably sourced and environmentally friendly, but the benzopyranone unit in its molecular structure endows it with excellent char-forming properties, a characteristic crucial for enhancing the thermal stability and smoke suppression of thermosetting resins. Chinese patent document CN110894274A discloses a bio-based main-chain benzoxazine resin based on genistein, its preparation method, and its applications. The preparation method includes: uniformly mixing genistein, furfurylamine, diamine compounds, and paraformaldehyde, followed by Mannich polymerization under heating conditions. This bio-based main-chain benzoxazine resin exhibits good thermodynamic properties; however, this invention does not involve research on flame retardant properties.

[0005] Currently, scholars both domestically and internationally have attempted to introduce benzoxazine phosphate into the crosslinking network of epoxy resin in order to prepare novel materials that possess both excellent flame retardant and mechanical properties. However, existing technologies still have significant shortcomings: firstly, a large amount of phosphorus needs to be added to ensure the flame retardant effect, which can easily lead to the deterioration of the material's thermal stability and limit its application range; secondly, some preparation processes have complex reaction routes, and some raw materials or intermediate products are highly toxic, making it difficult to meet the requirements of green and environmentally friendly production and application. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a hyperbranched modifier containing a benzoxazine phosphate structure, wherein the inherent daidzeinyl benzoxazine phosphate structural unit is beneficial to improving the flame retardant properties of epoxy resin.

[0007] The specific technical solution adopted is as follows: A hyperbranched modifier containing a benzoxazine phosphate structure, with the following general structural formula: R1 is a C2-C5 alkyl group. This indicates a repetitive branched structure; The number-average molecular weight of the hyperbranched modifier containing the benzoxazine phosphate structure is 1200-1500.

[0008] The hyperbranched modifier provided by this invention contains repeating daidzein benzoxazine phosphate structural units. Daidzein has a benzopyranone structure, exhibiting good char-forming properties, which can improve the flame retardant performance of the prepared thermosetting resin. Furthermore, the corresponding char-forming process can effectively adsorb toxic fumes generated during combustion, reducing the smoke toxicity during material combustion and achieving a synergistic effect of "flame retardancy, smoke suppression, and heat stabilization." During the curing process, the benzoxazine ring in the hyperbranched modifier undergoes a ring-opening polymerization reaction, forming a highly cross-linked network structure. This cross-linked structure endows the thermosetting resin with excellent thermal stability and mechanical properties. Simultaneously, it exerts a flame-retardant effect during combustion through a dual mechanism: on the one hand, the release of polyphosphate promotes the formation of a dense char layer, acting as a physical barrier; on the other hand, the generation of phosphorus-containing free radicals effectively quenches H• and OH• free radicals in the gas phase, thereby inhibiting the combustion chain reaction, jointly endowing the material with excellent flame-retardant properties.

[0009] The present invention also provides a method for preparing the hyperbranched modifier containing the benzoxazine phosphate structure, comprising the following steps: (1) After mixing and dissolving daidzein, alkanolamine, paraformaldehyde and organic solvent, the mixture was subjected to a Mannich reaction at 90-120°C for 8-24 h to prepare a polyhydroxybenzoxazine intermediate; The general structural formula of the polyhydroxybenzoxazine intermediate is: (2) After mixing the polyhydroxybenzoxazine intermediate, triethylamine and organic solvent evenly, phosphorus oxychloride is added and reacted at 0-30℃ for 24-48h to obtain the hyperbranched modifier containing benzoxazine phosphate ester structure.

[0010] The hyperbranched modifier containing benzoxazine phosphate structure can be used as an epoxy resin curing agent. Its preparation method is simple, the reaction conditions are controllable, it is easy to implement, and it is suitable for large-scale production.

[0011] Specifically, the daidzein is 4,7'-dihydroxyisoflavone, with the structural formula shown below. During the reaction, the amino group of the alkanolamine attacks the carbonyl group of paraformaldehyde, undergoing a nucleophilic addition reaction to give an imine ion intermediate. The imine ion acts as an electrophile, attacking the phenolic hydroxyl group of daidzein to give a polyhydroxybenzoxazine intermediate. In the polyhydroxybenzoxazine intermediate, the hydrogen on the hydroxyl group is replaced by the chlorine on phosphorus oxychloride, and finally polymerizes to form a hyperbranched benzoxazine phosphate.

[0012] Preferably, the alkanolamine is at least one of ethanolamine, propanolamine, butanolamine, and pentanolamine.

[0013] Preferably, in step (1), the molar ratio of daidzein, alkanolamine and paraformaldehyde is 1:2 to 2.5:4 to 5; in step (2), the molar ratio of polyhydroxybenzoxazine intermediate, phosphorus oxychloride and triethylamine is 3:1 to 3:3 to 4.

[0014] Preferably, the temperature of the Mannich reaction in step (1) is 90–120 °C and the time is 8–24 h; the temperature of the reaction in step (2) is 0–30 °C and the time is 24–48 h.

[0015] The present invention also provides the application of the hyperbranched modifier containing the benzoxazine phosphate structure in the preparation of flame retardant materials.

[0016] The present invention also provides a flame-retardant composite material composition comprising an epoxy resin precursor, a hyperbranched modifier containing a benzoxazine phosphate structure, and a curing accelerator.

[0017] Preferably, the mass of the curing accelerator is 0.05% to 0.5% of the total mass of the epoxy resin precursor and the hyperbranched modifier containing the benzoxazine phosphate structure; after curing, the phosphorus content of the flame-retardant composite material composition is 1.5-2 wt%.

[0018] The above composition can be cured by gradient curing to obtain an epoxy resin cured product with excellent flame retardancy and mechanical properties. Since the hyperbranched modifier contains a benzoxazine structure, the benzoxazine itself can be cured by heating to generate phenolic hydroxyl groups and produce active hydrogen. During the curing process, the benzoxazine ring undergoes a ring-opening polymerization reaction to form a highly cross-linked network structure, which can further improve the cross-linking density and thermodynamic properties of the cured epoxy resin.

[0019] The structure of epoxy resin precursors includes, but is not limited to, any of the following: ; Where X, Y, and Z are each independently selected from any of the following structures: R2, R3, R4, and R5 are each independently selected from hydrogen, C1-C6 alkyl, C1-C6 alkoxy, phenyl, phenoxy, or C3-C7 cycloalkyl. " is the connection position.

[0020] Preferably, the epoxy resin precursor is at least one of bisphenol A diglycidyl ether, tetramethylbisphenol A diglycidyl ether, 4,4'-dihydroxybenzophenone diglycidyl ether, tetraethylbisphenol F diglycidyl ether, diglycidyl terephthalate, p-phenylenediamine tetraglycidylamine, bisphenol A diglycidyl ether, bisphenol S diglycidyl ether, bisphenol S diglycidyl ether, bisphenol A epoxy resin, naphthylphenylenediamine tetraglycidylamine, and bisphenol F diglycidyl ether.

[0021] The curing accelerator can be selected from at least one of tertiary amines, tertiary amine salts, quaternary ammonium salts, imidazole compounds, organophosphorus compounds, metal salts of acetylacetone, metal salts of carboxylic acids, and boron trifluoride amine complexes.

[0022] Preferably, the curing accelerator is at least one selected from triethanolamine, dodecylamine, zinc acetylacetonate, triphenylphosphine, tetrabutylammonium iodide, 2-methylimidazole, dimethylphenylamine, 2-methylimidazole, boron trifluoride ethylamine, hexadecyl dimethyl benzylammonium, and manganese naphthenate.

[0023] The present invention also provides a flame-retardant composite material cured product, which is obtained by curing the flame-retardant composite material composition. Specifically, an epoxy resin precursor and a hyperbranched modifier containing a benzoxazine phosphate structure are mixed, and a curing accelerator is added. The mixture is then heated and cured in a gradient at 120-200°C to obtain the flame-retardant composite material cured product.

[0024] Compared with conventional epoxy resin cured products (cured with curing agents such as 4,4-diaminodiphenylmethane), this flame-retardant composite material has higher strength and thermal stability, and its flame retardancy rating reaches V-0, exhibiting excellent flame retardant properties. It also has excellent impact resistance, making it suitable for applications requiring high heat resistance, high strength, and flame retardancy.

[0025] Preferably, the gradient curing procedure is as follows: cure at 120 ℃ for 2 h, then at 140 ℃ for 2 h, then at 160 ℃ for 2 h, then at 180 ℃ for 2 h, and finally at 200 ℃ for 2 h to obtain the flame-retardant composite material cured product.

[0026] Preferably, the flame-retardant properties of the cured flame-retardant composite material reach V-0 level, and the impact strength is 3-6 kJ / m. 2 .

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention has obtained a series of hyperbranched modifiers containing benzopyranone, benzoxazine and phosphate ester structures through Mannich reaction, etc. The preparation method is simple, the reaction conditions are controllable and easy to implement, and it is suitable for large-scale industrial production.

[0028] (2) The hyperbranched modifier containing a benzoxazine phosphate structure synthesized in this invention can improve the flame retardant properties of epoxy resin. The benzoxazine structure itself can be cured by heating to generate phenolic hydroxyl groups and produce active hydrogen. During the curing process, the benzoxazine ring undergoes a ring-opening polymerization reaction to form a highly cross-linked network structure, which can further improve the cross-linking density and thermodynamic properties of the cured epoxy resin. Specifically, by using an epoxy resin precursor, a hyperbranched modifier containing a benzoxazine phosphate structure, and a curing accelerator, a flame-retardant composite material with a flame retardant rating of V-0 and excellent impact resistance can be obtained after gradient curing by heating. Attached Figure Description

[0029] Figure 1 The image shows the 1H NMR spectrum of the hyperbranched modifier containing the benzoxazine phosphate structure prepared in Example 1. Detailed Implementation

[0030] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0031] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0032] Example 1 (1) Synthesis of daidzein benzoxazine: Daidzein (0.01 mol, 2.542 g), ethanolamine (0.02 mol, 1.222 g), and paraformaldehyde (0.04 mol, 1.201 g) were placed in a single-necked flask with a magnetic stirrer and dissolved in 50 mL of chloroform at 50 °C. The mixture was heated under reflux at 110 °C for 14 hours. After the reaction was completed, the mixture was cooled at room temperature and then washed three times with deionized water to obtain a pale yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain polyhydroxybenzoxazine intermediate 1. The structural formula of polyhydroxybenzoxazine intermediate 1 is shown below: (2) Synthesis of hyperbranched modifier containing benzoxazine phosphate structure: Polyhydroxybenzoxazine intermediate 1 (0.03 mol, 12.734 g) and triethylamine (0.03 mol, 3.024 g) were placed in a single-necked flask with a magnetic stirrer and dissolved in 100 mL of dichloromethane at 0 °C. Then, phosphorus oxychloride (0.01 mol, 1.533 g) was added, and the mixture was magnetically stirred for 2 h. The mixture was then stirred at 25 °C for 36 h. After the reaction was complete, the mixture was washed three times with deionized water to obtain a yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain hyperbranched modifier 1 containing benzoxazine phosphate structure. Its 1H NMR spectrum is shown below. Figure 1 As shown, the number-average molecular weight is approximately 1300, and the structural formula is as follows: (3) Preparation of flame retardant composite material: Hyperbranched modifier 1 containing benzoxazine phosphate structure and bisphenol A diglycidyl ether are mixed evenly at a phosphorus content of 2% in the cured product. Then, the mixture is heated to 80 °C in a forced-air oven and mixed. Triethanolamine of 0.05% of the total mass of the mixture is added for pre-curing. Finally, the mixture is cured at 120 °C for 2 h, then at 140 °C for 2 h, then at 160 °C for 2 h, then at 180 °C for 2 h, and finally at 200 °C for 2 h to obtain the cured flame retardant composite material.

[0033] Tests showed that the impact strength of the cured flame-retardant composite material was 3.56 kJ / m.2 It has a flame retardant rating of V-0, making it suitable for flame retardant and impact-resistant applications.

[0034] Example 2 (1) Synthesis of daidzein benzoxazine: Daidzein (0.01 mol, 2.542 g), propanolamine (3-aminopropanol) (0.02 mol, 1.502 g) and paraformaldehyde (0.04 mol, 1.201 g) were placed in a single-necked flask with a magnetic stirrer and dissolved in 50 mL of 1,4-dioxane at 50 °C. The mixture was heated under reflux at 100 °C for 18 hours. After the reaction was completed, the mixture was cooled at room temperature and then washed three times with deionized water to obtain a pale yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain polyhydroxybenzoxazine intermediate 2. The structural formula of polyhydroxybenzoxazine intermediate 2 is shown below: (2) Synthesis of hyperbranched modifier containing benzoxazine phosphate structure: Polyhydroxybenzoxazine intermediate 2 (0.03 mol, 13.575 g) and triethylamine (0.03 mol, 3.024 g) were placed in a single-necked flask with magnetic stirring and dissolved in 100 mL DMF at 0 °C. Then, phosphorus oxychloride (0.01 mol, 1.533 g) was added, and the mixture was magnetically stirred for 2 h. Then, the mixture was stirred at 25 °C for 30 h. After the reaction was completed, the mixture was washed three times with deionized water to obtain a yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain hyperbranched modifier 2 containing benzoxazine phosphate structure. Its structural formula is shown below: (3) Preparation of flame retardant composite material: Hyperbranched modifier 2 containing benzoxazine phosphate structure and tetramethylbisphenol A diglycidyl ether are mixed evenly at a phosphorus content of 1.92% in the cured product. Then, the mixture is heated to 90 °C in a forced-air oven and mixed. 0.1% of dodecylamine is added to the mixture for pre-curing. Finally, the mixture is cured at 120 °C for 2 h, then at 140 °C for 2 h, then at 160 °C for 2 h, then at 180 °C for 2 h, and finally at 200 °C for 2 h to obtain the cured flame retardant composite material.

[0035] Tests showed that the impact strength of the cured flame-retardant composite material was 4.46 kJ / m. 2 It has a flame retardant rating of V-0, making it suitable for flame retardant and impact-resistant applications.

[0036] Example 3 (1) Synthesis of daidzein benzoxazine: Daidzein (0.01 mol, 2.542 g), butanolamine (2-aminobutanol) (0.02 mol, 1.783 g) and paraformaldehyde (0.04 mol, 1.201 g) were placed in a single-necked flask with a magnetic stirrer and dissolved in 50 mL of chloroform at 60 °C. The mixture was heated under reflux at 90 °C for 24 hours. After the reaction was completed, the mixture was cooled at room temperature and then washed three times with deionized water to obtain a pale yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain polyhydroxybenzoxazine intermediate 3. The structural formula of polyhydroxybenzoxazine intermediate 3 is shown below: (2) Synthesis of hyperbranched modifier containing benzoxazine phosphate structure: Polyhydroxybenzoxazine intermediate 3 (0.03 mol, 14.417 g) and triethylamine (0.03 mol, 3.024 g) were placed in a single-necked flask with magnetic stirring and dissolved in 100 mL DMF at 0 °C. Then, phosphorus oxychloride (0.01 mol, 1.533 g) was added, and the mixture was magnetically stirred for 3 h. Then, the mixture was stirred at 25 °C for 25 h. After the reaction was completed, the mixture was washed three times with deionized water to obtain a yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain hyperbranched modifier 3 containing benzoxazine phosphate structure. Its structural formula is shown below: (3) Preparation of flame retardant composite material: Hyperbranched modifier 3 containing benzoxazine phosphate structure and 4,4'-dihydroxybenzophenone diglycidyl ether were mixed evenly at a phosphorus content of 1.85% in the cured product. The mixture was then heated to 100 °C in a forced-air oven for mixing. Zinc acetylacetone of 0.05% of the total mass of the mixture was added for pre-curing. Finally, the mixture was cured at 120 °C for 2 h, then at 140 °C for 2 h, then at 160 °C for 2 h, then at 180 °C for 2 h, and finally at 200 °C for 2 h to obtain the cured flame retardant composite material.

[0037] Tests showed that the impact strength of the cured flame-retardant composite material was 5.31 kJ / m. 2 It has a flame retardant rating of V-0, making it suitable for flame retardant and impact-resistant applications.

[0038] Example 4 (1) Synthesis of daidzein benzoxazine: Daidzein (0.01 mol, 2.542 g), pentanolamine (5-amino-1-pentanol) (0.02 mol, 2.063 g) and paraformaldehyde (0.04 mol, 1.201 g) were placed in a single-necked flask with a magnetic stirrer and dissolved in 50 mL of 1,4-dioxane at 70 °C. The mixture was heated under reflux at 120 °C for 12 hours. After the reaction was completed, the mixture was cooled at room temperature and then washed three times with deionized water to obtain a pale yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain polyhydroxybenzoxazine intermediate 4. The structural formula of polyhydroxybenzoxazine intermediate 4 is shown below: (2) Synthesis of hyperbranched modifier containing benzoxazine phosphate structure: Polyhydroxybenzoxazine intermediate 4 (0.03 mol, 15.239 g) and triethylamine (0.03 mol, 3.024 g) were placed in a single-necked flask with magnetic stirring and dissolved in 100 mL of dichloromethane at 0 °C. Then, phosphorus oxychloride (0.01 mol, 1.533 g) was added, and the mixture was magnetically stirred for 4 h. Then, the mixture was stirred at 20 °C for 36 h. After the reaction was completed, the mixture was washed three times with deionized water to obtain a yellow precipitate. After filtration, the precipitate was washed two to three times with deionized water and dried at 60 °C to obtain hyperbranched modifier 4 containing benzoxazine phosphate structure. Its structural formula is shown below: (3) Preparation of flame retardant composite material: Hyperbranched modifier 4 containing benzoxazine phosphate structure and tetraethyl bisphenol F diglycidyl ether are mixed evenly at a phosphorus content of 1.78% in the cured product. Then, the mixture is heated to 90 °C in a forced-air oven and mixed. 0.1% of dodecylamine is added to the mixture for pre-curing. Finally, the mixture is cured at 120 °C for 2 h, then at 140 °C for 2 h, then at 160 °C for 2 h, then at 180 °C for 2 h, and finally at 200 °C for 2 h to obtain the cured flame retardant composite material.

[0039] Tests showed that the impact strength of the cured flame-retardant composite material was 5.98 kJ / m. 2 It has a flame retardant rating of V-0, making it suitable for flame retardant and impact-resistant applications.

[0040] Comparative Example 1 In this comparative example, the only difference between the preparation method of the epoxy resin cured product and the flame-retardant composite material of Example 1 is that the hyperbranched modifier 1 containing benzoxazine phosphate structure is replaced with the common curing agent 4,4-diaminodiphenylmethane. 4,4-diaminodiphenylmethane and bisphenol A diglycidyl ether are mixed evenly at a ratio of active hydrogen to epoxy group of 1:1. The remaining curing steps and parameters are the same as in Example 1, and the epoxy resin cured product is obtained.

[0041] Tests showed that the impact strength of the epoxy resin cured product prepared in Comparative Example 1 was 2.45 kJ / m. 2 It does not have flame-retardant properties and has no flame-retardant rating.

[0042] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hyperbranched modifier containing a benzoxazine phosphate structure, characterized in that, The general structural formula is: Wherein, R1 is a C2-C5 alkyl group; The number-average molecular weight of the hyperbranched modifier containing the benzoxazine phosphate structure is 1200-1500.

2. The method for preparing the hyperbranched modifier containing a benzoxazine phosphate structure according to claim 1, characterized in that, Includes the following steps: (1) After mixing and dissolving daidzein, alkanolamine, paraformaldehyde and organic solvent, the mixture was subjected to a Mannich reaction at 90-120°C for 8-24 h to prepare a polyhydroxybenzoxazine intermediate; The general structural formula of the polyhydroxybenzoxazine intermediate is: ； (2) After mixing the polyhydroxybenzoxazine intermediate, triethylamine and organic solvent evenly, phosphorus oxychloride is added and reacted at 0-30℃ for 24-48h to obtain the hyperbranched modifier containing benzoxazine phosphate ester structure.

3. The method for preparing the hyperbranched modifier containing a benzoxazine phosphate structure according to claim 2, characterized in that, Alkanolamines are at least one of ethanolamine, propanolamine, butanolamine, and pentanolamine.

4. The method for preparing the hyperbranched modifier containing a benzoxazine phosphate structure according to claim 2, characterized in that, In step (1), the molar ratio of daidzein, alkanolamine and paraformaldehyde is 1:2 to 2.5:4 to 5; in step (2), the molar ratio of polyhydroxybenzoxazine intermediate, phosphorus oxychloride and triethylamine is 3:1 to 3:3 to 4.

5. The method for preparing the hyperbranched modifier containing a benzoxazine phosphate structure according to claim 2, characterized in that, In step (1), the temperature of the Mannich reaction is 90–120 °C and the time is 8–24 h; in step (2), the temperature of the reaction is 0–30 °C and the time is 24–48 h.

6. The application of the hyperbranched modifier containing a benzoxazine phosphate structure according to claim 1 in the preparation of flame-retardant materials.

7. A flame-retardant composite material composition, characterized in that, The components include an epoxy resin precursor, a hyperbranched modifier containing a benzoxazine phosphate structure as described in claim 1, and a curing accelerator.

8. The flame-retardant composite material composition according to claim 7, characterized in that, The curing accelerator is 0.05% to 0.5% of the total mass of the epoxy resin precursor and the hyperbranched modifier containing benzoxazine phosphate ester structure; after curing, the phosphorus content of the flame-retardant composite material composition is 1.5-2 wt%.

9. The flame-retardant composite material composition according to claim 7, characterized in that, The structure of the epoxy resin precursor is any of the following: ； Where X, Y, and Z are each independently selected from any of the following structures: R2, R3, R4, and R5 are each independently selected from hydrogen, C1-C6 alkyl groups, C1-C6 alkoxy groups, phenyl groups, phenoxy groups, or C3-C7 cycloalkyl groups. " is the connection position; And / or, the curing accelerator is selected from at least one of tertiary amines, tertiary amine salts, quaternary ammonium salts, imidazole compounds, organophosphorus compounds, metal acetylacetone salts, metal carboxylic acid salts, and boron trifluoride amine complexes.

10. A flame-retardant composite material cured product, characterized in that, It is obtained by curing the flame-retardant composite material composition according to any one of claims 7-9.

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