A nitrogen-phosphorus flame-retardant epoxy resin curing agent, an epoxy resin prepreg and a carbon fiber composite material

Abstract

The present invention discloses a nitrogen-phosphorus flame-retardant epoxy resin curing agent, an epoxy resin prepreg and a carbon fiber composite material. The nitrogen-phosphorus flame-retardant epoxy resin curing agent contains benzene ring groups, nitrogen and phosphorus elements. By using a curing agent with a specific structure, the present invention enables the epoxy resin to cure for a longer time at room temperature, and can rapidly cure the epoxy resin at high temperature, thereby prolonging the operability time for preparing the carbon fiber composite material. Moreover, the nitrogen and phosphorus elements in the molecular structure of the curing agent can improve the flame-retardant performance of the epoxy resin, making the prepared epoxy resin prepreg have high fire resistance.

Description

Technical Field

[0001] The present invention belongs to the field of epoxy resin curing agents, and particularly relates to a nitrogen-phosphorus flame-retardant epoxy resin curing agent, an epoxy resin prepreg, and a carbon fiber composite material. Background Art

[0002] The power batteries of new energy vehicles have the risk of spontaneous combustion, which is characterized by rapid combustion, high heat, difficulty in prediction, and difficulty in extinguishing. The fire prevention of new energy vehicle battery packs mainly relies on fireproof felt materials such as heat insulation blankets and mica plates. Although these materials can effectively insulate heat and control the fire, they also have problems such as increasing vehicle weight, poor heat dissipation, and construction limitations. Therefore, in order to meet the safety and lightweight requirements of power batteries, prepregs with excellent flame retardant performance are becoming the first choice.

[0003] Traditional prepregs use halogenated flame retardants, which have the characteristics of good flame retardant effect, low dosage, and little impact on mechanical properties, and have always been the main flame retardants for flame retardant materials. However, halogenated flame retardants are prone to produce thick smoke, dioxins, and hydrogen halides when burning, which limits their application in new energy vehicles. Therefore, it is an urgent problem to develop an environmentally friendly and highly fireproof prepreg for the upper cover of the battery box and the energy storage battery box of electric vehicles to meet the growing safety requirements. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a nitrogen-phosphorus flame-retardant epoxy resin curing agent, an epoxy resin prepreg, and a carbon fiber composite material. By using a curing agent with a specific structure, the curing agent has a longer curing time for epoxy resin at room temperature and can quickly cure epoxy resin at high temperature, extending the operable time for preparing carbon fiber composite materials. Moreover, the molecular structure of the curing agent contains nitrogen and phosphorus elements, which can improve the flame retardant performance of epoxy resin and make the prepared epoxy resin prepreg have high fire resistance.

[0005] The purpose of the present invention is to provide a nitrogen-phosphorus flame-retardant epoxy resin curing agent, and the structure of the nitrogen-phosphorus flame-retardant epoxy resin curing agent is as follows:

[0006] 。

[0007] Another purpose of the present invention is to provide a preparation method of the nitrogen-phosphorus flame-retardant epoxy resin curing agent, including the following steps:

[0008] Amidate 3-dimethoxyphosphorylbenzoic acid, and then react with 4-aminophthalic anhydride to obtain the nitrogen-phosphorus flame-retardant epoxy resin curing agent.

[0009] In some embodiments of the present invention, the reagent for acyl chlorination is SOCl2.

[0010] In some embodiments of the present invention, the mass ratio of 3-dimethoxyphosphorylbenzoic acid to SOCl2 is 1:1.1 to 1.5.

[0011] In some embodiments of the present invention, the temperature of the acyl chlorination is 80 to 100 °C, and the time is 15 to 20 h.

[0012] In some embodiments of the present invention, the mass ratio of 3-dimethoxyphosphorylbenzoic acid to 4-aminophthalic anhydride is 1:1 to 1.2.

[0013] In some embodiments of the present invention, the temperature of the reaction is 100 to 120 °C, and the time is 10 to 15 h.

[0014] Another object of the present invention is a method for preparing an epoxy resin prepreg, comprising the following steps:

[0015] Add the carbon fiber fabric to an acetone mixture of epoxy resin and the nitrogen-phosphorus flame-retardant epoxy resin curing agent, soak it, and remove acetone to obtain the epoxy resin prepreg.

[0016] In some embodiments of the present invention, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin.

[0017] In some embodiments of the present invention, the mass ratio of the carbon fiber fabric to the epoxy resin is 1.2 to 1.7:1.

[0018] In some embodiments of the present invention, the mass ratio of the epoxy resin to the nitrogen-phosphorus flame-retardant epoxy resin curing agent is 8 to 12:1.

[0019] Another object of the present invention is to provide a method for preparing an epoxy resin prepreg, comprising the following steps:

[0020] Add the carbon fiber fabric to an acetone mixture of epoxy resin, the nitrogen-phosphorus flame-retardant epoxy resin curing agent, inorganic flame-retardant filler, and synergistic intumescent flame retardant, soak it, and remove acetone to obtain the epoxy resin prepreg.

[0021] In some embodiments of the present invention, the mass ratio of the epoxy resin to the inorganic flame-retardant filler and the synergistic intumescent flame retardant is 8 to 12:0.2 to 0.5:0.3 to 0.5.

[0022] In some embodiments of the present invention, the mass ratio of the carbon fiber fabric to the epoxy resin is 1.2 to 1.7:1.

[0023] In some embodiments of the present invention, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin.

[0024] In some embodiments of the present invention, the inorganic flame retardant filler is selected from at least one of aluminum hydroxide, magnesium hydroxide, kaolin, clay, montmorillonite, and diatomite.

[0025] In some preferred embodiments of the present invention, the inorganic flame retardant filler is selected from montmorillonite.

[0026] In some embodiments of the present invention, the synergistic intumescent flame retardant is selected from melamine.

[0027] Another object of the present invention is to provide a method for preparing a carbon fiber composite material, comprising the following steps:

[0028] Lay up the prepregs prepared by the method for preparing the epoxy prepregs of multiple layers, and perform hot pressing and molding to obtain a carbon fiber composite material.

[0029] In some embodiments of the present invention, the temperature of the hot pressing and molding is 160 - 200 °C, the pressure is 0.2 - 0.6 MPa, and the time is 0.5 - 2 hours.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The epoxy prepreg of the present invention has high fire resistance. When subjected to heat, it can rapidly expand on the surface and absorb heat, effectively preventing high temperature from invading the interior of the battery, thereby achieving the purpose of fire prevention.

[0032] (2) The curing agent of the present invention plays a role in forming carbon. When burning, a carbon layer covering the substrate is formed on the surface. This carbon layer is flame - resistant and plays a role in isolating oxygen, isolating heat transfer, and preventing the volatilization of combustible gases, thereby achieving the purpose of flame retardancy; the inorganic flame retardant filler plays an endothermic role. The flame retardant undergoes an endothermic reaction at high temperature, reducing the temperature of the combustion area and achieving the effect of flame retardancy; the curing agent and the synergistic intumescent flame retardant can generate free - radical scavengers to capture free radicals in the air and terminate the combustion chain reaction, playing a flame - retardant role in the condensed phase and the gas phase; the curing agent and the inorganic flame retardant filler play an endothermic role, reducing the temperature of the combustion area; the curing agent, the inorganic flame retardant filler, and the synergistic intumescent flame retardant cooperate with each other. The inorganic filler absorbs heat and dehydrates to dilute the combustible gas, the curing agent undergoes a reaction when heated, and the three - source integrated intumescent flame retardancy occurs. The synergistic intumescent flame retardant provides part of the carbon source and gas source to the curing agent during the combustion process, improving the expansion efficiency, increasing the expansion height, and forming a more solid expansion layer, thereby achieving excellent flame - retardant effects. Description of the Drawings

[0033] Figure 1 . Flame - retardant effect of the carbon fiber composite material of Example 12.

[0034] Figure 2 . Flame - retardant effect of the carbon fiber composite material of Example 14. Detailed implementation mode

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will, in conjunction with the embodiments of the present invention, clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0036] The structure of 3-dimethoxyphosphorylbenzoic acid is shown as follows:

[0037] ;

[0038] The structure of 4-aminophthalic anhydride is shown as follows:

[0039] ;

[0040] Bisphenol A epoxy resin is from SM828, Mitsui Chemicals Group;

[0041] All raw materials of the present invention are commercially available as normal.

[0042] Example 1

[0043] This example provides a nitrogen-phosphorus flame retardant epoxy resin curing agent, and the specific preparation process is as follows:

[0044] Add 10 parts by mass of 3-dimethoxyphosphorylbenzoic acid and 13 parts by mass of SOCl2 into a reaction flask, add 50 parts by mass of N,N-dimethylformamide, react at 90 °C for 18 h, then add 11 parts by mass of 4-aminophthalic anhydride, stir for 1 hour, add 1 mL of triethylamine, and react at 110 °C for 12 h to obtain a nitrogen-phosphorus flame retardant epoxy resin curing agent.

[0045] The nuclear magnetic structure of the nitrogen-phosphorus flame retardant epoxy resin curing agent is as follows:

[0046] 1 H NMR (400 MHz, CDCl3) δ 10.05 (s, 1H, NH), 8.57 (s, 1H, Ar), 8.43(s, 1H, Ar), 8.45 (s, 1H, Ar), 8.20 - 8.16 (m, 2H, Ar), 7.97(s, 1H, Ar), 7.69(m, 1H, Ar), 3.82 (s, 6H, CH3).

[0047] Example 2

[0048] This embodiment provides a preparation method of epoxy resin, and the specific preparation process is as follows:

[0049] Mix 80 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, and 40 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0050] Example 3

[0051] This embodiment provides a preparation method of epoxy resin, and the specific preparation process is as follows:

[0052] Mix 120 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, and 60 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0053] Example 4

[0054] This embodiment provides a preparation method of epoxy resin, and the specific preparation process is as follows:

[0055] Mix 80 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, 5 parts by mass of aluminum hydroxide, 3 parts by mass of melamine, and 40 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0056] Example 5

[0057] This embodiment provides a preparation method of epoxy resin, and the specific preparation process is as follows:

[0058] Mix 120 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, 2 parts by mass of diatomite, 5 parts by mass of melamine, and 60 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0059] Example 6

[0060] This embodiment provides a preparation method of epoxy resin, and the specific preparation process is as follows:

[0061] Mix 120 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, 2 parts by mass of montmorillonite, 5 parts by mass of melamine, and 60 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0062] Example 7

[0063] This example provides a formulation of epoxy resin, which is only different from Example 5 in that it does not contain melamine. The specific preparation process is as follows:

[0064] Mix 120 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, 7 parts by mass of diatomaceous earth, and 60 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0065] Example 8

[0066] This example provides a formulation of epoxy resin, which is only different from Example 5 in that it does not contain diatomaceous earth. The specific preparation process is as follows:

[0067] Mix 120 parts by mass of bisphenol A epoxy resin, 10 parts by mass of the nitrogen-phosphorus flame-retardant epoxy resin curing agent prepared in Example 1, 7 parts by mass of melamine, and 60 parts by mass of acetone, stir evenly, remove acetone by vacuum distillation, and test the pot life of the obtained epoxy resin at room temperature. The results are shown in Table 1.

[0068] Example 9

[0069] This example provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0070] Add T700 carbon fiber fabric to the epoxy resin-acetone mixture in Example 2 for soaking, remove acetone to obtain an epoxy resin prepreg. Lay 5 layers of the epoxy resin prepreg, and perform hot pressing. The pressure for hot pressing is 0.6 MPa, the temperature for hot pressing is 160 °C, and the time for hot pressing is 2 hours to obtain a carbon fiber composite material; the mass ratio of epoxy resin to T700 carbon fiber fabric is 1.2:1 to obtain the carbon fiber composite material.

[0071] Example 10

[0072] This example provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0073] Add T700 carbon fiber fabric to the epoxy resin-acetone mixture in Example 3 for soaking, remove acetone to obtain an epoxy resin prepreg. Lay 5 layers of the epoxy resin prepreg, and perform hot pressing. The pressure for hot pressing is 0.2 MPa, the temperature for hot pressing is 200 °C, and the time for hot pressing is 0.5 hours to obtain a carbon fiber composite material; the mass ratio of epoxy resin to T700 carbon fiber fabric is 1.7:1 to obtain the carbon fiber composite material.

[0074] Example 11

[0075] This embodiment provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0076] The T700 carbon fiber fabric was added to the epoxy resin acetone mixture of Example 4 for soaking, and the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot-pressed. The pressure for hot-pressing was 0.6 MPa, the temperature for hot-pressing was 160 °C, and the time for hot-pressing was 2 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.2:1 to obtain a carbon fiber composite material.

[0077] Example 12

[0078] This embodiment provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0079] The T700 carbon fiber fabric was added to the epoxy resin acetone mixture of Example 5 for soaking, and the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot-pressed. The pressure for hot-pressing was 0.2 MPa, the temperature for hot-pressing was 200 °C, and the time for hot-pressing was 0.5 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.7:1 to obtain a carbon fiber composite material.

[0080] Example 13

[0081] This embodiment provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0082] The T700 carbon fiber fabric was added to the epoxy resin acetone mixture of Example 6 for soaking, and the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot-pressed. The pressure for hot-pressing was 0.2 MPa, the temperature for hot-pressing was 200 °C, and the time for hot-pressing was 0.5 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.7:1 to obtain a carbon fiber composite material.

[0083] Example 14

[0084] This embodiment provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0085] The T700 carbon fiber fabric was added to the epoxy resin - acetone mixture of Example 7 for soaking, and then the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot - pressed. The pressure for hot - pressing was 0.2 MPa, the temperature for hot - pressing was 200 °C, and the time for hot - pressing was 0.5 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.7:1 to obtain the carbon fiber composite material.

[0086] Example 15

[0087] This example provides an epoxy resin prepreg and a carbon fiber composite material. The specific preparation process is as follows:

[0088] The T700 carbon fiber fabric was added to the epoxy resin - acetone mixture of Example 8 for soaking, and then the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot - pressed. The pressure for hot - pressing was 0.2 MPa, the temperature for hot - pressing was 200 °C, and the time for hot - pressing was 0.5 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.7:1 to obtain the carbon fiber composite material.

[0089] Comparative Example 1

[0090] This comparative example provides a preparation of an epoxy resin, which is only different from that of Example 3 in the curing agent. The specific preparation process is as follows:

[0091] 120 parts by mass of bisphenol A - type epoxy resin, 10 parts by mass of 4 - aminophthalic anhydride, and 60 parts by mass of acetone were mixed and stirred evenly. Then, the acetone was removed by vacuum distillation, and the pot life of the obtained epoxy resin at room temperature was tested. The results are shown in Table 1.

[0092] Comparative Example 2

[0093] This comparative example provides an epoxy resin prepreg and a carbon fiber composite material, which is only different from that of Example 8 in the epoxy resin - acetone mixture used. The specific preparation process is as follows:

[0094] The T700 carbon fiber fabric was added to the epoxy resin - acetone mixture of Comparative Example 1 for soaking, and then the acetone was removed to obtain an epoxy resin prepreg. Five layers of the epoxy resin prepreg were laid and hot - pressed. The pressure for hot - pressing was 0.2 MPa, the temperature for hot - pressing was 200 °C, and the time for hot - pressing was 0.5 hours to obtain a carbon fiber composite material; the mass ratio of the epoxy resin to the T700 carbon fiber fabric was 1.7:1 to obtain the carbon fiber composite material.

[0095] Performance test:

[0096] The reference standard for the limiting oxygen index (LOI) performance test is ASTM D2863-2012. The standard size of the test spline is 130 mm × 6.5 mm × 3.2 mm, and the ignition method is ignition from the top center.

[0097] The reference standard for the vertical burning test (UL-94) performance test is ASTM D3801-2010. There are 5 vertical burning test splines in each group, and the standard size is 130 mm × 12.7 mm × 3.2 mm. During the test, a 10-second flame is applied to each specimen twice.

[0098] The reference standard for the flexural performance test is the three-point bending test in ASTM D7264.

[0099] The tensile strength test is carried out with reference to the standard GB / T 1447-2005.

[0100] Table 1. Pot life of the epoxy resins of Examples 2 to 8 and Comparative Example 1 at room temperature.

[0101] Sample Pot life (days) at room temperature Example 2 25 Example 3 24 Example 4 23 Example 5 26 Example 6 24 Example 7 24 Example 8 25 Comparative Example 1 5

[0102] As can be seen from Table 1, the epoxy resin of the present invention has a long pot life at room temperature.

[0103] Table 2. Performance test results of the carbon fiber composites of Examples 9 to 15 and Comparative Example 2.

[0104] Sample Limiting oxygen index (%) UL-94 flame retardant rating Flexural strength (Mpa) Tensile strength (Mpa) Example 9 30.5 V-0 998.4 561 Example 10 30.8 V-0 100.1 556 Example 11 39.2 V-0 1260.5 622 Example 12 39.4 V-0 1261.2 619 Example 13 39.5 V-0 1261.6 685 Example 14 36.7 V-0 1112.3 620 Example 15 36.9 V-0 1113.8 612 Comparative Example 2 20.8 No rating 993.7 557

[0105] As can be seen from Table 2, the curing agent of the present invention can improve the flame retardant performance of the epoxy resin, making the prepared epoxy resin prepreg have high fire resistance; by comparing Examples 11 to 12 and Examples 14 to 15, it can be seen that the inorganic flame retardant filler and the synergistic intumescent flame retardant can synergistically improve the flame retardant effect of the curing agent. The three cooperate with each other, making the epoxy resin prepreg of the present invention have high fire resistance.

[0106] From Figure 1 it can be seen that after adding the synergistic intumescent flame retardant, the surface expands fully. According to the proportion of the compounding system, the expansion height can reach 30 - 50 mm. The carbon layer fully protects the main structure, and the back temperature is about 200 °C.

[0107] From Figure 2 it can be seen that without adding the synergistic intumescent flame retardant, the surface expands slightly, the height < 10 mm, high-efficiency fire prevention cannot be achieved, the carbon layer cannot protect, it is easy to burn through, and the back temperature > 400 °C.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that after reading the specification of this application, they can still modify the specific implementation manners of the present invention or make equivalent substitutions, but these modifications or changes do not depart from the protection scope of the pending claims of this invention application.

Claims

1. A nitrogen and phosphorus flame retardant epoxy resin curing agent, characterized in that, The structure of the nitrogen-phosphorus flame-retardant epoxy resin curing agent is as follows: 。 2. The preparation method of the nitrogen-phosphorus flame retardant epoxy resin curing agent according to claim 1, wherein It includes the following steps: Mix 3-dimethoxyphosphorylbenzoic acid with SOCl2 for reaction, and then react with 4-aminophthalic anhydride to obtain the nitrogen-phosphorus flame-retardant epoxy resin curing agent.

3. The preparation method of the nitrogen-phosphorus flame retardant epoxy resin curing agent according to claim 2, wherein, The mass ratio of the 3-dimethoxyphosphorylbenzoic acid to SOCl2 is 1:1.1 - 1.5; The temperature of the mixing reaction is 80 - 100 °C, and the time is 15 - 20 h; The mass ratio of the 3-dimethoxyphosphorylbenzoic acid to 4-aminophthalic anhydride is 1:1 - 1.2; The temperature of the reaction is 100 - 120 °C, and the time is 10 - 15 h.

4. A method for preparing an epoxy resin prepreg, characterized in that, It includes the following steps: Immerse the carbon fiber fabric in the acetone mixture of epoxy resin and the nitrogen-phosphorus flame-retardant epoxy resin curing agent described in claim 1, and remove the acetone to obtain the epoxy resin prepreg.

5. The preparation method of the epoxy resin prepreg according to claim 4, characterized in that, The epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin.

6. The preparation method of the epoxy resin prepreg according to claim 4, characterized in that, The mass ratio of the epoxy resin to the nitrogen-phosphorus flame-retardant epoxy resin curing agent is 8 - 12:

1.

7. A method for preparing an epoxy resin prepreg, characterized in that, It includes the following steps: Immerse the carbon fiber fabric in the acetone mixture of epoxy resin, the nitrogen-phosphorus flame-retardant epoxy resin curing agent described in claim 1, inorganic flame retardant filler, and synergistic intumescent flame retardant, and remove the acetone to obtain the epoxy resin prepreg.

8. The preparation method of the epoxy resin prepreg according to claim 7, wherein, The mass ratio of the epoxy resin to the inorganic flame retardant filler and the synergistic intumescent flame retardant is 8 - 12:0.2 - 0.5:0.3 - 0.

5.

9. The method for preparing the epoxy resin prepreg according to claim 7, characterized in that, The epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and phenolic epoxy resin; The inorganic flame retardant filler is selected from at least one of aluminum hydroxide, magnesium hydroxide, kaolin, clay, montmorillonite, and diatomite; The synergistic intumescent flame retardant is selected from melamine.

10. A method for preparing a carbon fiber composite material, characterized in that, It includes the following steps: Lay up the prepregs prepared by the preparation method of the epoxy resin prepreg according to any one of claims 4 - 9, and hot press them into shape to obtain the carbon fiber composite material.

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