Novel high-temperature self-cracking curing agent and preparation method thereof, and application of curing agent in preparation of active flame-retardant epoxy resin

Abstract

The invention belongs to the technical field of flame retardants, and particularly relates to a novel high-temperature self-cracking curing agent and a preparation method thereof, and application of the curing agent in preparation of active flame-retardant epoxy resin. The high-temperature self-cracking curing agent is prepared by taking organic aliphatic diamine, organic aliphatic amine, di-tert-butyl dicarbonate ester, cyanuric chloride and triethylamine as raw materials through a three-step reaction. The curing agent has two triazine structures and a polyamine structure, the triazine structure has double functions, on one hand, the triazine structure has a flame retardant function and can be decomposed at high temperature to release inert gas to dilute oxygen concentration to suffocate flame, and on the other hand, the curing agent is self-cracked before the self-combustion of an epoxy resin material, so that the self-combustion performance of the epoxy resin material is improved. The three-dimensional network structure of the polymer is decomposed, so that the combusted part of the polymer is separated from a matrix under the action of inert gas, and active flame retardance and fire prevention are realized. Limit oxygen index (LOI) and vertical combustion UL-94 experiment results show that the curing agent can endow an epoxy resin material with good flame retardant property, and the LOI value can be up to 33.8% and passes the UL-94V-0 level; a cone calorimeter test shows that the curing agent can significantly reduce the total smoke generation amount of the epoxy resin material. In addition, the curing agent belongs to an environment-friendly halogen-free flame retardant, the preparation process is simple, the yield is 90% or above, and industrial production is easy.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and specifically relates to a novel high-temperature self-decomposition curing agent and a preparation method thereof, and application in preparing active flame-retardant epoxy resin. Background Art

[0002] As an important class of thermosetting polymers, epoxy resins are widely used as coatings, adhesives, insulation materials, and structural composite materials due to their low shrinkage, high thermal and mechanical stability, excellent bonding properties, and excellent chemical corrosion resistance. However, the high flammability of epoxy resins and the large amount of toxic gases and smoke produced during combustion have greatly limited their further application in areas requiring flame retardancy, especially in the aerospace, electrical, and electronics industries.

[0003] The traditional method of enhancing the flame retardant properties of polymers is to add flame retardants containing elements such as phosphorus, nitrogen, halogens, and boron to the matrix, which is generally achieved through the following flame retardant mechanisms: 1. After the flame retardant decomposes, it forms highly active free radicals, which can quench the free radicals generated by the combustion of the polymer and terminate the combustion chain reaction; 2. The flame retardant decomposes at high temperature to generate inert gases such as nitrogen, ammonia, and carbon dioxide, which can dilute the oxygen concentration and slow down the combustion rate; 3. The flame retardant decomposes at high temperature to generate acidic substances, which can catalyze the polymer matrix or carbonizing agent to form a carbon layer with barrier substances and energy exchange. However, the passive flame retardant method based on the decomposition products of flame retardants to enhance the flame retardant properties of polymers generally requires the addition of a large amount of flame retardants, which often leads to the deterioration of the mechanical properties of the polymer and even causes an increase in the release of toxic gases.

[0004] Therefore, how to optimize the molecular structure of epoxy resin or curing agent through molecular design, construct intrinsic epoxy resin materials, and reduce the use of traditional flame retardants through active flame retardant mechanism, while ensuring the high flame retardant performance and low smoke toxicity of epoxy resin materials. Fire safety is of great significance to the development of environmentally friendly high-performance epoxy resin materials. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a new type of high-temperature self-decomposition curing agent, which can solve the problems faced by the passive flame retardant mechanism of epoxy resin materials, such as large amount of flame retardant added and easy deterioration of mechanical properties.

[0006] The present invention is based on molecular structure design and synthesizes a high-temperature self-decomposing curing agent through synthetic chemistry. The specific curing agent molecular construction strategy is: using the three highly reactive C-Cl bonds in cyanuric chloride as sites, C-Cl sequentially reacts with the amino group not protected by tert-butyloxycarbonyl (Boc) and the organic fatty diamine in the organic fatty diamine through nucleophilic substitution reaction, to generate a parallel molecular structure with a melamine derivative as the core, and further add a strong acid for deprotection, and finally a melamine derivative containing a polyamine structure can be prepared as an epoxy resin curing agent. It is worth noting that the three reactive sites of cyanuric chloride have different reaction conditions, and organic diamines of different structures can be sequentially introduced by controlling the reaction temperature. This feature not only brings convenience for the precise construction of curing agents with different structures / functions, but also provides more possibilities for the functional regulation of epoxy resin materials.

[0007] The curing agent provided by the present invention has two triazine structures and a polyamine structure, wherein the triazine structure has dual functions. On the one hand, it has a flame retardant function. It decomposes at about 250°C to generate inert gas (ammonia, carbon dioxide) to dilute the oxygen concentration and suffocate the flame; on the other hand, the triazine structure is the core of the curing agent structure. After the curing reaction, it serves as a key node in the three-dimensional network structure of the epoxy resin. The high-temperature decomposition will cause the epoxy resin material to self-cleave through the curing agent before self-combustion, causing the disintegration of the three-dimensional network structure of the polymer, thereby causing the burned part of the matrix to be separated from the polymer body under the action of the inert gas, thereby realizing an active flame retardant strategy. The intrinsic epoxy resin material generated by the curing agent solves the problem of large amount of flame retardant added and easy deterioration of the mechanical properties of the matrix brought about by the traditional flame retardant method, and enhances the comprehensive performance of the epoxy resin material. Finally, the preparation process of the flame retardant is simple, green and environmentally friendly, without complicated post-processing, and the raw materials are easily available. The synthesis yield can reach 90%, which is easy to industrialize.

[0008] The present invention further provides a method for preparing the novel high-temperature self-decomposition curing agent.

[0009] Another object of the present invention is to provide the use of the novel high-temperature self-decomposition curing agent in the preparation of active flame-retardant epoxy resin.

[0010] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: The present invention provides a novel high-temperature self-decomposition curing agent, the structural formula of which is: .

[0011] The present invention also provides a method for preparing the novel high-temperature self-decomposition curing agent, comprising the following steps: (1) Add an organic fatty diamine to chloroform, mix well, then add a chloroform solution of di-tert-butyl dicarbonate dropwise at low temperature, return to room temperature and continue stirring for a certain period of time; after the reaction is completed, wash with deionized water, dry, evaporate to remove the solvent, and separate and purify by column chromatography to obtain an intermediate product I; (2) Add cyanuric chloride and triethylamine to the solvent in proportion, mix well, slowly add the intermediate product I and organic fatty monoamine at low temperature, return to room temperature and react for a certain period of time to obtain a mixed reaction liquid; (3) Then, triethylamine and organic fatty diamine are added to the mixed reaction liquid, and the mixture is reacted at 70°C for a certain period of time. After the reaction is completed, the mixture is filtered, washed with water, dried, and the solvent is evaporated to obtain the intermediate product II. (4) Add the intermediate product II to the solvent, mix well, slowly add trifluoroacetic acid at low temperature, and carry out the third reaction for a certain period of time after returning to room temperature; after the reaction is completed, wash with alkaline sodium bicarbonate, extract and dry, and evaporate and remove the solvent to obtain the product HMEL.

[0012] Furthermore, in step (1), the molar ratio of the organic fatty diamine to di-tert-butyl dicarbonate is 5-10:1; the dropping time is controlled at 3 hours; the stirring time is 16 hours; the organic fatty diamine is one or two of ethylenediamine, butanediamine, 6-hexanediamine, 7-heptanediamine and 10-decanediamine; when there are two organic fatty diamines, the intermediate product I is prepared according to the method in step (1) respectively.

[0013] Furthermore, in step (1), the intermediate product I has the following chemical structure: .

[0014] Furthermore, in step (2), the molar ratio of the intermediate product I to cyanuric chloride is 1-2:1; the molar ratio of the organic fatty monoamine to cyanuric chloride is 0-1:1; the molar ratio of triethylamine to cyanuric chloride is 2-3:1; the solvent is dioxane; and the reaction time is 6 hours.

[0015] Furthermore, in step (3), the molar ratio of triethylamine to organic fatty diamine is 2:1; the molar ratio of cyanuric chloride to organic fatty diamine is 1.5-2.5:1; and the reaction is carried out at 70° C. for 12 hours.

[0016] Furthermore, in step (3), the intermediate product II has the following chemical structure: .

[0017] Furthermore, the molar ratio of melamine to trifluoroacetic acid is 2-3:1; and the reaction is stirred in an ice bath for 2 hours.

[0018] The present invention also provides an active flame retardant epoxy resin prepared by using the high-temperature self-decomposition curing agent.

[0019] The curing agent provided by the present invention has the following preparation reaction process: .

[0020] The present invention also provides an epoxy resin prepared by using a high-temperature self-decomposition curing agent, and the preparation method thereof comprises the following steps: (1) Weigh the epoxy resin and the prepared curing agent in proportion; (2) Add HMEL curing agent to epoxy resin, stir evenly at room temperature, and evacuate to remove bubbles to obtain a mixture.

[0021] In some embodiments, the method further includes injecting the mixed material into a mold and curing the mixed material at room temperature to prepare a target component.

[0022] The beneficial effects achieved by one or more embodiments of the present invention are as follows: (1) The present invention aims to develop an intrinsic flame retardant / curing agent that can fix the flame retardant unit of the triazine structure in the epoxy resin material through covalent bonds, thereby avoiding the precipitation of the additive flame retardant and the deterioration of the mechanical properties of the polymer.

[0023] (2) The curing agent provided by the present invention can achieve "active" flame retardancy. The high-temperature cleavable curing agent serves as the core node in the three-dimensional cross-linked network structure of the epoxy resin. At high temperatures, the triazine structure of the curing agent will decompose and release inert gases such as ammonia and carbon dioxide, which dilute the oxygen in the air to achieve polymer combustion suffocation. More importantly, the cleavage of the curing agent structure causes the polymer body to disintegrate, thereby delaying or even preventing the spread of flames, thereby avoiding the problems of large amounts of flame retardants and high smoke toxicity brought about by the traditional passive flame retardant mechanism.

[0024] (3) The curing agent provided by the present invention can give epoxy resin materials good flame retardant properties. The results of the limiting oxygen index (LOI) and vertical combustion UL-94 test show that the maximum LOI value can reach 33.8%, UL-94 V-0 level; the cone calorimeter test shows that the curing agent can significantly reduce the total amount of smoke generated by epoxy resin materials. In addition, the curing agent is an environmentally friendly halogen-free flame retardant, the preparation process is simple, the yield is above 90%, and it is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1This is the total smoke generation diagram of epoxy resin material; Figure 2 This is the CO generation rate diagram of epoxy resin material. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0029] In some embodiments, in the preparation process of the intermediate product I of the present invention, the organic fatty diamines used include but are not limited to: ethylenediamine, butanediamine, 6-hexanediamine, 7-heptanediamine, and 10-decanediamine.

[0030] In some embodiments, the organic aliphatic monoamines used in the present invention include, but are not limited to, butylamine, heptylamine, and decylamine.

[0031] Example 1 (1) Preparation of intermediate product I 30.05 g of ethylenediamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 97%.

[0032] The chemical structure of intermediate product I is as follows: (2) Preparation of intermediate II 9.2g of cyanuric chloride and 10.12g of triethylamine were added to 300ml of dioxane and stirred evenly. 16g of intermediate product I was slowly added dropwise in an ice-water bath. After returning to room temperature, the reaction was continued for 6h. Then 5.06g of triethylamine and 1.5g of ethylenediamine were added to the reaction system and reacted at 70°C for 12h. After the reaction was completed, the mixture was filtered, washed with water, and dried. After the solvent was removed by rotary evaporation under reduced pressure, the intermediate product II was obtained with a yield of 98%.

[0033] The chemical structure of intermediate II is as follows: (3) Preparation of product HMEL-1 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-1 with a yield of 92%.

[0034] The chemical structure of the product HMEL-1 is as follows: The product HMEL-1 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ 1.90, 2.74, 2.89, 2.90, 2.96, 3.50, 3.52, 3.53, 3.58,3.63, 3.64, 3.68, 4.21, 6.00, 6.33, 6.39, 6.45, which is consistent with the chemical environment of H in the product HMEL-1.

[0035] Example 2 (1) Preparation of intermediate product I 44.07g of dibutylamine was added to 500ml of chloroform and stirred evenly, then 10.91g of di-tert-butyl dicarbonate was dissolved in 250ml of chloroform and slowly added to the reaction system. The addition time was controlled within 3h and the reaction system was always kept in an ice bath. After the addition was completed, the room temperature was restored and the stirring was continued for 16h. Then, deionized water (250ml) was added to wash 6 times. After drying with anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After column chromatography separation and purification (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 98%. The chemical structure of intermediate product I is as follows: (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 18.8g of intermediate product I in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 2.2g of diaminobutane to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 98%.

[0036] (3) Preparation of product HMEL-2 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-2 with a yield of 93%.

[0037] The chemical structure of the product HMEL-2 is as follows: The product HMEL-2 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponded to the following: δ 1.49, 1.51, 1.62, 1.65, 1.71, 2.74, 2.81, 3.38, 3.41,3.42, 3.49, 3.61, 3.99, 6.39, which is consistent with the chemical environment of H in the product HMEL-2.

[0038] Example 3 (1) Preparation of intermediate product I 58g of 1,6-hexanediamine was added to 500ml of chloroform and stirred evenly. Then, 10.91g of di-tert-butyl dicarbonate was dissolved in 250ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3h and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16h. Then, deionized water (250ml) was added for 6 times for washing. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 98%.

[0039] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly add 21.6g of intermediate product I in an ice-water bath. After returning to room temperature, continue to react for 6h. Then add 5.06g of triethylamine and 2.9g of hexamethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 98%.

[0040] (3) Preparation of product HMEL-3 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-3 with a yield of 92%.

[0041] The chemical structure of the product HMEL-3 is as follows: The product HMEL-3 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak values ​​δ (ppm) correspond to the following: δ 1.22, 1.23, 1.26, 1.27, 1.37, 1.43, 1.56, 2.66, 2.75,3.14, 3.40, 3.61, 3.88, 3.89, 6.39, which is consistent with the chemical environment of H in the product HMEL-3.

[0042] Example 4 (1) Preparation of intermediate product I 86g of 1,10-decanediamine was added to 500ml of chloroform and stirred evenly. Then, 10.91g of di-tert-butyl dicarbonate was dissolved in 250ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3h and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16h. Then, deionized water (250ml) was added for 6 times for washing. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (the eluent was chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 98%.

[0043] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 27.2g of intermediate product I in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 4.3g of decanediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 97%.

[0044] (3) Preparation of product HMEL-4 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-4 with a yield of 92%.

[0045] The chemical structure of the product HMEL-4 is as follows: The product HMEL-4 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ 1.16, 1.17, 1.18, 1.20, 1.22, 1.26, 1.37, 1.43, 1.56,2.66, 2.75, 3.14, 3.40, 3.61, 3.88, 3.89, 6.39, which is consistent with the chemical environment of H in the product HMEL-4.

[0046] Example 5 (1) Preparation of intermediate product I 30.05 g of ethylenediamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 97%.

[0047] (2) Preparation of intermediate II 9.2g of cyanuric chloride and 10.12g of triethylamine were added to 300ml of dioxane and stirred evenly. 8g of intermediate product I and 2.25g of ethylamine were slowly added dropwise in an ice-water bath. After returning to room temperature, the reaction was continued for 6h. Then 5.06g of triethylamine and 1.5g of ethylenediamine were added to the reaction system and reacted at 70°C for 12h. After the reaction was completed, the product was filtered, washed with water, and dried. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II was obtained with a yield of 98%.

[0048] (3) Preparation of product HMEL-5 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-5 with a yield of 93%.

[0049] The chemical structure of the product HMEL-5 is as follows: The product HMEL-5 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ 1.14, 2.90, 2.95, 3.38, 3.39, 3.50, 3.58, 3.64, 3.66,3.77, 3.84, 4.21, 4.65, 5.24, 5.87, 6.39, 6.75, 6.76, 6.86, 7.10, which is consistent with the chemical environment of H in the product HMEL-5.

[0050] Example 6 (1) Preparation of intermediate product I 44.07 g of dibutyleneamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 98%.

[0051] (2) Preparation of intermediate II 9.2g of cyanuric chloride and 10.12g of triethylamine were added to 300ml of dioxane and stirred evenly. 9.4g of intermediate product I and 3.65g of butylamine were slowly added dropwise in an ice-water bath. After returning to room temperature, the reaction was continued for 6h. Then 5.06g of triethylamine and 2.2g of dibutylamine were added to the reaction system and reacted at 70°C for 12h. After the reaction was completed, the product was filtered, washed with water, and dried. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II was obtained with a yield of 96%.

[0052] (3) Preparation of product HMEL-6 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-6 with a yield of 94%.

[0053] The chemical structure of the product HMEL-6 is as follows: The product HMEL-6 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ 0.79, 1.26, 1.49, 1.51, 1.54, 1.62, 1.65, 1.71, 2.74, 2.75, 2.81, 3.38, 3.41, 3.42, 3.43, 3.49, 3.49, 3.61, 3.99, 6.01, 6.39, which is consistent with the chemical environment of H in the product HMEL-6.

[0054] Example 7 (1) Preparation of intermediate product I 58g of 1,6-hexanediamine was added to 500ml of chloroform and stirred evenly. Then, 10.91g of di-tert-butyl dicarbonate was dissolved in 250ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3h and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16h. Then, deionized water (250ml) was added for 6 times for washing. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 98%.

[0055] (2) Preparation of intermediate II 9.2g of cyanuric chloride and 10.12g of triethylamine were added to 300ml of dioxane and stirred evenly. 10.8g of intermediate product I and 5.05g of hexylamine were slowly added dropwise in an ice-water bath. After returning to room temperature, the reaction was continued for 6h. Then 5.06g of triethylamine and 2.9g of hexamethylenediamine were added to the reaction system and reacted at 70°C for 12h. After the reaction was completed, the product was filtered, washed with water, and dried. After the solvent was removed by rotary evaporation under reduced pressure, the intermediate product II was obtained with a yield of 95%.

[0056] (3) Preparation of product HMEL-7 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-7 with a yield of 93%.

[0057] The chemical structure of the product HMEL-7 is as follows: The product HMEL-7 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ0.76, 1.17, 1.19, 1.22, 1.23, 1.26, 1.27, 1.37, 1.43, 1.56, 2.66, 2.75, 3.14, 3.40, 3.61, 3.88, 6.39, which is consistent with the chemical environment of H in the product HMEL-7.

[0058] Example 8 (1) Preparation of intermediate product I 30.05 g of ethylenediamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 97%.

[0059] (2) Preparation of intermediate II 9.2g of cyanuric chloride and 10.12g of triethylamine were added to 300ml of dioxane and stirred evenly. 8g of intermediate product I and 3.65g of butylamine were slowly added dropwise in an ice-water bath. After returning to room temperature, the reaction was continued for 6h. Then 5.06g of triethylamine and 1.5g of ethylenediamine were added to the reaction system and reacted at 70°C for 12h. After the reaction was completed, the product was filtered, washed with water, and dried. After the solvent was removed by rotary evaporation under reduced pressure, the intermediate product II was obtained with a yield of 98%.

[0060] (3) Preparation of product HMEL-8 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-8 with a yield of 93%.

[0061] The chemical structure of the product HMEL-8 is as follows: The product HMEL-8 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ0.79, 1.26, 1.54, 2.90, 2.96, 3.43, 3.50, 3.58, 3.64,3.68, 3.69, 3.84, 4.20, 6.01, 6.39, 6.56, 6.57, 6.64, which is consistent with the chemical environment of H in the product HMEL-8.

[0062] Example 9 (1) Preparation of intermediate product I 30.05 g of ethylenediamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 97%.

[0063] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 8g of intermediate product I and 5.05g of hexylamine in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 1.5g of ethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 98%.

[0064] (3) Preparation of product HMEL-9 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-9 with a yield of 93%.

[0065] The chemical structure of the product HMEL-9 is as follows: The product HMEL-9 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ0.76, 1.17, 1.19, 1.26, 1.56, 2.90, 2.96, 3.40, 3.50,3.58, 3.64, 3.68, 3.69, 3.84, 4.20, 4.21, 6.39, 6.56, 6.57, 6.63, 6.64, which is consistent with the chemical environment of H in the product HMEL-9.

[0066] Example 10 (1) Preparation of intermediate product I 30.05 g of ethylenediamine was added to 500 ml of chloroform and stirred evenly. Then, 10.91 g of di-tert-butyl dicarbonate was dissolved in 250 ml of chloroform and slowly added dropwise to the reaction system. The dropping time was controlled within 3 hours and the reaction system was always kept in an ice bath. After the dropping was completed, the room temperature was restored and stirring was continued for 16 hours. Then, deionized water (250 ml) was added for washing 6 times. After drying over anhydrous sodium sulfate, the chloroform solution was subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent: chloroform / methanol = 2:1), intermediate product I was obtained with a yield of 97%.

[0067] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 8g of intermediate product I and 7.85g of decylamine in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 1.5g of ethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 98%.

[0068] (3) Preparation of product HMEL-10 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 2 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-10 with a yield of 93%.

[0069] The chemical structure of the product HMEL-10 is as follows: The product HMEL-10 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ0.76, 1.15, 1.17, 1.18, 1.26, 1.56, 2.90, 2.96, 3.40,3.50, 3.58, 3.64, 3.68, 3.69, 3.84, 4.21, 6.39, 6.56, 6.57, 6.63, 6.64, which is consistent with the chemical environment of H in the product HMEL-10.

[0070] Embodiment 11 (1) Preparation of intermediate product I Add 30.05g of ethylenediamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, return to room temperature and continue stirring for 16h. Then add deionized water (250ml) to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-1 can be obtained with a yield of 97%.

[0071] Add 44.07g of dibutyleneamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, return to room temperature and continue stirring for 16h. Then add deionized water (250ml) to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-2 can be obtained with a yield of 98%.

[0072] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 8g of intermediate product I-1 and 9.4g of intermediate product I-2 in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 1.5g of ethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the intermediate product II can be obtained with a yield of 96%.

[0073] (3) Preparation of product HMEL-11 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-11 with a yield of 92%.

[0074] The chemical structure of the product HMEL-11 is as follows: The product HMEL-11 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ 1.51, 1.62, 2.74, 2.75, 2.90, 2.96, 3.38, 3.49, 3.50,3.58, 3.64, 3.68, 3.69, 3.84, 4.21, 6.39, 6.56, 6.57, 6.63, 6.64, which is consistent with the chemical environment of H in the product HMEL-11.

[0075] Example 12 (1) Preparation of intermediate product I Add 30.05g of ethylenediamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, return to room temperature and continue stirring for 16h. Then add deionized water (250ml) to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-1 can be obtained with a yield of 98%.

[0076] Add 58g of 1,6-hexanediamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, the room temperature is restored and stirring is continued for 16h. Then, deionized water (250ml) is added to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-2 can be obtained with a yield of 95%.

[0077] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 8g of intermediate product I-1 and 10.8g of intermediate product I-2 in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 1.5g of ethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the product intermediate product II can be obtained with a yield of 96%.

[0078] (3) Preparation of product HMEL-12 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with a saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-12 with a yield of 93%.

[0079] The chemical structure of the product HMEL-12 is as follows: The product HMEL-12 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ1.22, 1.26, 1.43, 1.56, 2.66, 2.90, 2.96, 3.14, 3.40,3.50, 3.58, 3.64, 3.68, 3.69, 3.84, 4.21, 6.39, 6.56, 6.57, 6.63, 6.64, which is consistent with the chemical environment of H in the product HMEL-12.

[0080] Example 13 (1) Preparation of intermediate product I Add 30.05g of ethylenediamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, return to room temperature and continue stirring for 16h. Then add deionized water (250ml) to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-1 can be obtained with a yield of 97%.

[0081] Add 86g of 1,10-decanediamine to 500ml of chloroform and stir evenly, then dissolve 10.91g of di-tert-butyl dicarbonate in 250ml of chloroform and slowly add it dropwise to the reaction system. The addition time is controlled to 3h and the reaction system is always kept in an ice bath. After the addition is completed, the room temperature is restored and stirring is continued for 16h. Then, deionized water (250ml) is added to wash 6 times. After drying over anhydrous sodium sulfate, the chloroform solution is subjected to rotary evaporation to remove the solvent under reduced pressure to obtain a crude product. After separation and purification by column chromatography (eluent is chloroform / methanol = 2:1), intermediate product Ⅰ-2 can be obtained with a yield of 98%.

[0082] (2) Preparation of intermediate II Add 9.2g of cyanuric chloride and 10.12g of triethylamine to 300ml of dioxane and stir evenly. Slowly drop 8g of intermediate product I-1 and 13.6g of intermediate product I-2 in an ice-water bath. After returning to room temperature, continue the reaction for 6h. Then add 5.06g of triethylamine and 1.5g of ethylenediamine to the reaction system and react at 70℃ for 12h. After the reaction is completed, filter, wash with water, and dry. After removing the solvent by rotary evaporation under reduced pressure, the product intermediate product II can be obtained with a yield of 97%. (3) Preparation of product HMEL-13 All the intermediate product II in step (2) was dissolved in 200 ml of ethyl acetate, and 4 g of trifluoroacetic acid (TFA) was added dropwise under ice bath conditions. After stirring for 2 h, the mixture was washed three times with saturated sodium bicarbonate solution and extracted to obtain an ethyl acetate solution. The solvent was removed by rotary evaporation under reduced pressure to obtain the product HMEL-13 with a yield of 91%.

[0083] The chemical structure of the product HMEL-13 is as follows: The product HMEL-13 prepared in this example was subjected to 1H NMR (400 MHz, DMSO-d6) nuclear magnetic spectrum analysis. The peak δ (ppm) corresponds to the following: δ1.16, 1.17, 1.20, 1.26, 1.43, 1.56, 2.66, 2.90, 2.96,3.14, 3.40, 3.50, 3.58, 3.64, 3.68, 3.69, 3.84, 4.21, 6.39, 6.56, 6.57, 6.63,6.64, which is consistent with the chemical environment of H in the product HMEL-13.

[0084] Examples 14-26 1) Weigh epoxy resin and HMEL curing agent, the amount is shown in the formula in Table 1; 2) Add HMEL curing agent to epoxy resin, stir evenly at room temperature, and vacuum to remove bubbles to obtain a mixture; 3) The mixture is injected into a mold and cured at room temperature for 24 hours until the coating is completely dry to obtain a flame retardant modified epoxy resin material.

[0085] Comparative Example 1 1) Weigh 75g epoxy resin and 22g T31 curing agent; 2) Add T31 curing agent to epoxy resin, stir evenly at room temperature, and vacuum to remove bubbles to obtain a mixture; 3) Inject the mixture into a mold and cure it at room temperature for 24 hours until the coating is completely dry to obtain an epoxy resin material.

[0086] Performance Testing: The flame retardant modified epoxy resins obtained in Examples 14-26 and Comparative Example 1 were subjected to LOI test and UL-94 vertical burning test, and the results are shown in Table 1. The LOI test was conducted in accordance with ASTM D2863-19 standard, and the sample size was 130×6.5×3 mm2. The UL-94 vertical burning test was conducted in accordance with GBT2408-2008 standard, and the sample size was 130×13×3 mm2.

[0087] Table 1 Flame retardant modified epoxy resin material formula and flame retardant performance test results It should be pointed out that the T31 curing agent has a structure composed of hydroxyl, amine, secondary group, benzene ring, etc. Compared with the high temperature self-cleaving curing agent HMEL of the present invention, it has excellent thermal stability and no flame retardant performance. Figure 1 and Figure 2 The results show that compared with the epoxy resin material prepared by traditional T31, the high-temperature cleavable curing agent can significantly enhance the flame retardant properties of the epoxy resin material, reduce the total amount of smoke and CO generation rate, and achieve a maximum LOI value of 33.8% and pass the UL-94 V-0 grade. This is attributed to the high-temperature cleavage of the triazine structure in the curing agent, which not only releases inert gas to suffocate the combustion, but also causes the disintegration of the polymer matrix to prevent the spread of combustion.

[0088] In addition, the molecular structure of the curing agent has a direct impact on the performance of the epoxy resin material. With the increase of the organic fatty diamine or organic fatty amine molecular chain, the molecular weight of the curing agent gradually increases, resulting in a decrease in the "amine value" of the curing agent. In order to ensure that the "amine value" required for curing with a fixed amount of epoxy resin remains unchanged, the amount of the corresponding curing agent is also increased from 17g of the lowest HMEL-1 to 52g of the maximum HMEL-7. The flame retardant performance of the corresponding EP composite material decreases and the total amount of smoke increases. This may be attributed to the increase in the organic fatty diamine or organic fatty amine molecular chain, which not only reduces the "amine value" of the curing agent, causing an increase in the amount of curing agent used and a decrease in the content of flame retardant nitrogen, but also the curing agent itself is a combustible structure, and the increase in the amount added also contributes to the fuel used for combustion to a certain extent.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A novel high temperature self-decomposition curing agent, characterized in that: Its structural formula is: 。 2. A method for preparing the novel high-temperature self-decomposing curing agent according to claim 1, characterized in that: The following steps are involved: (1) Add an organic fatty diamine to chloroform, mix well, then add a chloroform solution of di-tert-butyl dicarbonate dropwise at low temperature, return to room temperature and continue stirring for a certain period of time; after the reaction is completed, wash with deionized water, dry, evaporate to remove the solvent, and separate and purify by column chromatography to obtain an intermediate product I; (2) Add cyanuric chloride and triethylamine to the solvent in proportion, mix well, slowly add the intermediate product I and organic fatty monoamine at low temperature, return to room temperature and react for a certain period of time to obtain a mixed reaction liquid; (3) Then, triethylamine and organic fatty diamine are added to the mixed reaction liquid, and the mixture is reacted at 70°C for a certain period of time. After the reaction is completed, the mixture is filtered, washed with water, dried, and the solvent is evaporated to obtain the intermediate product II. (4) Add the intermediate product II to the solvent, mix well, slowly add trifluoroacetic acid at low temperature, and carry out the third reaction for a certain period of time after returning to room temperature; after the reaction is completed, wash with alkaline sodium bicarbonate, extract and dry, and evaporate and remove the solvent to obtain the product HMEL.

3. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of the organic fatty diamine to di-tert-butyl dicarbonate is 5-10:1; the dropping time is controlled at 3 hours; the stirring time is 16 hours; the organic fatty diamine is one or two of ethylenediamine, butanediamine, 6-hexanediamine, 7-heptanediamine and 10-decanediamine; when there are two organic fatty diamines, the intermediate product I is prepared according to the method in step (1).

4. The preparation method according to claim 2 or 3, characterized in that: In step (1), the intermediate product I has the following chemical structure: 。 5. The preparation method according to any one of claims 2 to 4, characterized in that: In step (2), the molar ratio of the intermediate product I to cyanuric chloride is 1-2:1; the molar ratio of the organic fatty monoamine to cyanuric chloride is 0-1:1; the molar ratio of triethylamine to cyanuric chloride is 2-3:1; the solvent is dioxane; and the reaction time is 6 hours.

6. The preparation method according to claim 1 or 5, characterized in that: In step (3), the molar ratio of triethylamine to organic fatty diamine is 2:1; the molar ratio of cyanuric chloride to organic fatty diamine is 1.5-2.5:1; and the reaction is carried out at 70° C. for 12 hours.

7. The preparation method according to claim 1 or 6, characterized in that: In step (3), the intermediate product II has the following chemical structure: 。 8. The preparation method according to any one of claims 1 to 7, characterized in that: The molar ratio of melamine to trifluoroacetic acid is 2-3:1; and the reaction is stirred for 2 hours in an ice bath.

9. An active flame retardant epoxy resin, characterized in that: The high-temperature self-decomposition curing agent is prepared using the high-temperature self-decomposition curing agent described in claim 1.

10. A method for preparing the active flame retardant modified epoxy resin according to claim 9, characterized in that: The steps include: (1) Add the high-temperature self-decomposing curing agent to the epoxy resin, mix well at room temperature, and vacuum to remove bubbles to obtain a mixture; (2) The mixture is injected into a mold and cured at room temperature for 24 hours until the coating is completely dry to obtain a flame retardant modified epoxy resin material.

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