Flame-retardant composite material and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant materials, and the flame-retardant material is prepared from the following components in percentage by mass: 35 to 45 percent of ethylene-vinyl acetate copolymer, 4 to 6 percent of compatilizer, 0.05 to 0.2 percent of antioxidant, 23 to 31 percent of modified magnesium aluminum hydrotalcite, 8 to 16 percent of magnesium hydroxide, 4 to 12 percent of ammonium polyphosphate and 4 to 12 percent of nano silicon dioxide. The modified magnesium aluminum hydrotalcite, the magnesium hydroxide, the ammonium polyphosphate and the nano silicon dioxide are combined to form a compound flame-retardant system, and the compound flame-retardant system is combined with the ethylene-vinyl acetate copolymer through the compatilizer, so that the flame-retardant composite material with excellent char forming property, flame retardant property and mechanical property is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardant materials, and particularly to a flame retardant composite material and a preparation method thereof. Background Art

[0002] Ethylene-vinyl acetate copolymer (EVA) is widely used in fields such as wire and cable, toys, and adhesives due to its good flexibility, transparency, chemical stability, electrical insulation, easy processability, and non-toxicity. However, EVA itself does not have flame retardant properties. Therefore, flame retardants are generally added to improve the flame retardant properties of EVA. However, when a single flame retardant is added to improve the flame retardant properties, the mechanical properties of the polymer will decrease simultaneously.

[0003] Therefore, how to improve a composite material with excellent mechanical properties and flame retardant properties at the same time is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a flame retardant composite material to solve the problem that the flame retardant properties and mechanical properties of the existing ethylene-vinyl acetate copolymer cannot be effectively balanced.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a flame retardant composite material, which includes the following components by mass percentage: 35-45% of ethylene-vinyl acetate copolymer, 4-6% of compatibilizer, 0.05-0.2% of antioxidant, 23-31% of modified magnesium aluminum hydrotalcite, 8-16% of magnesium hydroxide, 4-12% of ammonium polyphosphate, and 4-12% of nano-silica.

[0007] Preferably, the modified magnesium aluminum hydrotalcite is composed of a silane coupling agent and magnesium aluminum hydrotalcite.

[0008] Preferably, the mass ratio of the silane coupling agent to the magnesium aluminum hydrotalcite is 0.5-2.5:1.

[0009] Preferably, the silane coupling agent includes one or more of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-methacryloxypropyltrimethoxysilane.

[0010] Preferably, the compatibilizer includes one or more of maleic anhydride grafted EVA, compatibilizer MC226, compatibilizer MC218, and compatibilizer MC328.

[0011] Preferably, the antioxidant includes one or more of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (antioxidant 1010), tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), n-octadecyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate (antioxidant 1076), and antioxidant B215.

[0012] On the other hand, the present invention also provides a method for preparing the flame-retardant composite material described in any one of the above, comprising the following steps:

[0013] (1) Melting and blending ethylene-vinyl acetate copolymer and a compatibilizer to obtain a blend;

[0014] (2) Kneading the first blend, antioxidant, modified magnesium-aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica to obtain a kneaded product;

[0015] (3) Thermally pressing and molding the kneaded product to obtain a flame-retardant composite material.

[0016] Preferably, in step (1), the temperature of the melting and blending is 130-160°C, and the time is 2-5 min.

[0017] Preferably, in step (2), the temperature of the kneading is 130-160°C, and the time is 10-15 min.

[0018] Preferably, in step (3), the temperature of the thermally pressing and molding is 170-190°C, the pre-pressing time is 1-3 min, and the pressing time is 4-10 min.

[0019] Preferably, the modified magnesium-aluminum hydrotalcite is obtained by mixing and stirring magnesium-aluminum hydrotalcite and a silane coupling agent.

[0020] Preferably, the temperature of the mixing and stirring is 80-100°C, the time is 8-15 min, and the rotation speed is 1000-1500 rpm.

[0021] The present invention provides a flame-retardant composite material. Compared with the prior art, its beneficial effects are as follows:

[0022] In the present invention, the modified magnesium-aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica combine to form a compound flame-retardant system. The compound flame-retardant system combines with the ethylene-vinyl acetate copolymer through a compatibilizer, thereby preparing a flame-retardant composite material with excellent char-forming property, flame-retardant property, and mechanical property. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0024] Figure 1 Schematic diagram of the test results of the charring performance of the flame-retardant composite materials of Examples 1-7 and Comparative Examples 1-5 of the present invention Detailed implementation manners

[0025] The present invention will be described below through specific embodiments. Those skilled in the art can understand that the following specific embodiments are only for the purpose of illustration and do not limit the scope of the present invention in any way. Additionally, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and methods are not clearly described in the subsequent embodiments, the conditions and methods well known in the art can be used for processing.

[0026] In one aspect of the present invention, the present invention provides a flame-retardant composite material, which includes the following components by mass percentage: ethylene-vinyl acetate copolymer 35-45%, compatibilizer 4-6%, antioxidant 0.05-0.2%, modified magnesium aluminum hydrotalcite 23-31%, magnesium hydroxide 8-16%, ammonium polyphosphate 4-12%, and nano-silica 4-12%.

[0027] In the present invention, the modified magnesium aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica combine to form a compound flame-retardant system. The compound flame-retardant system combines with the ethylene-vinyl acetate copolymer through the compatibilizer, thereby preparing a flame-retardant composite material with excellent charring performance, flame-retardant performance, and mechanical properties.

[0028] Among them, when magnesium aluminum hydrotalcite is thermally decomposed, water and carbon dioxide gases are released. The release of water and carbon dioxide gases can dilute the concentration of combustible gases, thereby reducing the intensity of combustion.

[0029] Magnesium hydroxide can be decomposed into magnesium oxide and water. Water can dilute combustible gases, and magnesium oxide will form a dense carbon layer on the surface of the composite material. The shielding and insulating effects of the carbon layer can isolate oxygen and heat, thereby assisting the flame retardancy of magnesium aluminum hydrotalcite.

[0030] Ammonium polyphosphate can play a role in flame retardancy and toughening. When burning, ammonium polyphosphate releases inert gases such as ammonia upon heating, and at the same time decomposes to produce substances with dehydration effects such as phosphoric acid and hypophosphorous acid, accelerating the dehydration and carbonization of the polymer, forming a dense carbon layer on the surface of EVA, hindering the heat transfer between the environment and EVA, and thus achieving a better synergistic flame retardant effect. At the same time, ammonium polyphosphate can make magnesium aluminum hydrotalcite disperse more uniformly in EVA, thereby improving the mechanical properties of the composite material.

[0031] Nano-silica will form a uniformly dispersed barrier network structure inside the composite material, thereby hindering the heat transfer and the contact between oxygen and the material during combustion, inhibiting the combustion reaction. At the same time, nano-silica can promote the formation of a denser carbon layer during the combustion of the composite material, improving the protection effect on the internal material; there are active sites on the surface of nano-silica, which can capture the highly active free radicals generated during the combustion process, thereby interrupting the combustion reaction and achieving a flame retardant effect.

[0032] In some embodiments of the present invention, the modified magnesium aluminum hydrotalcite is composed of a silane coupling agent and magnesium aluminum hydrotalcite, and the mass ratio of the silane coupling agent to the magnesium aluminum hydrotalcite is 0.5 - 2.5:1, for example, it can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, etc. Within this range, the modification of magnesium aluminum hydrotalcite can be completed. The silane coupling agent includes one or more of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane.

[0033] In some embodiments of the present invention, the compatibilizer includes one or more of maleic anhydride grafted EVA, compatibilizer MC226, compatibilizer MC218, and compatibilizer MC328.

[0034] In some embodiments of the present invention, the antioxidant includes one or more of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), and antioxidant B215.

[0035] In another aspect of the present invention, the present invention also provides a preparation method of the flame retardant composite material described in any one of the above, including the following steps:

[0036] (1) Melting and blending ethylene-vinyl acetate copolymer and a compatibilizer to obtain a blend;

[0037] (2) Kneading the first blend, antioxidant, modified magnesium aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica to obtain a kneaded product;

[0038] (3) Hot press the mixture to obtain a flame-retardant composite material.

[0039] In some embodiments of the present invention, ethylene-vinyl acetate copolymer and a compatibilizer are melt-blended to obtain a blend. Among them, the melt-blending can be carried out in a mixer. The temperature of the melt-blending is 130-160 °C, for example, it can be 130 °C, 140 °C, 150 °C, 160 °C, etc.; the time of the melt-blending is 2-5 min, for example, it can be 2 min, 3 min, 4 min, 5 min, etc.

[0040] In some embodiments of the present invention, the first blend, an antioxidant, modified magnesium aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica are kneaded to obtain a kneaded product. Among them, the kneading can be carried out in a mixer. The temperature of the kneading is 130-160 °C, for example, it can be 130 °C, 140 °C, 150 °C, 160 °C, etc.; the time of the kneading is 10-15 min, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc.

[0041] It should be noted that if the melt-blending temperature in step (1) and the kneading temperature in step (2) are too low, the flame retardant and the polymer cannot be effectively fused, and if the temperature is too high, the composite material will be charred. Therefore, the temperature is limited to 130-160 °C.

[0042] In some embodiments of the present invention, the kneaded product is hot press-molded to obtain a flame-retardant composite material. Among them, the hot press molding can be carried out in a flat vulcanizer. The temperature of the hot press molding is 170-190 °C, for example, it can be 170 °C, 180 °C, 190 °C, etc. The pre-pressing time is 1-3 min, for example, it can be 1 min, 2 min, 3 min, etc., and the pressing time is 4-10 min, for example, it can be 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0043] In some embodiments of the present invention, the modified magnesium aluminum hydrotalcite is obtained by mixing and stirring magnesium aluminum hydrotalcite and a silane coupling agent. Among them, the temperature of the mixing and stirring is 80 - 100 °C, for example, it can be 80 °C, 90 °C, 100 °C, etc., the time of the mixing and stirring is 8 - 15 min, for example, it can be 8 min, 9 min, 10 min, 12 min, 15 min, etc., and the rotation speed of the mixing and stirring is 1000 - 1500 rpm, for example, it can be 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, etc. The mixing and stirring process can be carried out in a high-speed mixer. Preferably, before adding the silane coupling agent for mixing and stirring, the magnesium aluminum hydrotalcite is pre-stirred in the high-speed mixer for 3 - 6 min, and the temperature and rotation speed of the pre-stirring are the same as those of the subsequent mixing and stirring process.

[0044] The technical solutions in the present invention will be clearly and completely described below with reference to specific embodiments. The embodiments of this application are only for illustration, and all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0045] Example 1

[0046] This example provides a method for preparing a flame-retardant composite material, and the specific steps are as follows:

[0047] (1) Put magnesium aluminum hydrotalcite into a high-speed mixer, stir for 5 min under the conditions of a rotation speed of 1300 rpm and a temperature of 90 °C, then add a silane coupling agent accounting for 2% of the mass of the magnesium aluminum hydrotalcite, and continue to stir for 10 min to obtain modified magnesium aluminum hydrotalcite;

[0048] (2) Mix 40% EVA polymer and 5% compatibilizer MC226 and add them to an internal mixer, and carry out melt blending at 140 °C for 3 min to obtain a blend, where the content of vinyl acetate in the EVA polymer is 18%;

[0049] (3) Add 0.1% antioxidant 1010, 31% modified magnesium aluminum hydrotalcite, 8% magnesium hydroxide, 8% ammonium polyphosphate, and 8% nano-silica to the internal mixer, and knead at 140 °C for 10 min to obtain a kneaded product;

[0050] (4) Put the kneaded product into a flat vulcanizer for hot pressing and forming, the hot pressing temperature is 180 °C, the pre-pressing time is 2 min, and the pressing time is 7 min to obtain a flame-retardant composite material.

[0051] Example 2

[0052] (1) Put the magnesium aluminum hydrotalcite into a high-speed blender, stir for 5 min under the conditions of a rotation speed of 1300 rpm and a temperature of 90 °C, then add a silane coupling agent accounting for 2% of the mass of the magnesium aluminum hydrotalcite, and continue to stir for 10 min to obtain modified magnesium aluminum hydrotalcite;

[0053] (2) Mix 40% EVA polymer and 5% compatibilizer MC226, then add them to an internal mixer, and carry out melt blending at 140 °C for 3 min to obtain a blend, where the content of vinyl acetate in the EVA polymer is 18%;

[0054] (3) Add 0.2% antioxidant 1010, 31% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 4% ammonium polyphosphate, and 8% nano-silica into the internal mixer, and carry out mixing at 140 °C for 10 min to obtain a mixture;

[0055] (4) Put the mixture into a flat vulcanizer for hot pressing molding. The hot pressing temperature is 180 °C, the pre-pressing time is 2 min, and the pressing time is 7 min to obtain a flame-retardant composite material.

[0056] Example 3

[0057] (1) Put the magnesium aluminum hydrotalcite into a high-speed blender, stir for 5 min under the conditions of a rotation speed of 1300 rpm and a temperature of 90 °C, then add a silane coupling agent accounting for 2% of the mass of the magnesium aluminum hydrotalcite, and continue to stir for 10 min to obtain modified magnesium aluminum hydrotalcite;

[0058] (2) Mix 39% EVA polymer and 6% compatibilizer MC226, then add them to an internal mixer, and carry out melt blending at 140 °C for 3 min to obtain a blend, where the content of vinyl acetate in the EVA polymer is 18%;

[0059] (3) Add 0.1% antioxidant 1010, 31% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 8% ammonium polyphosphate, and 4% nano-silica into the internal mixer, and carry out mixing at 140 °C for 10 min to obtain a mixture;

[0060] (4) Put the mixture into a flat vulcanizer for hot pressing molding. The hot pressing temperature is 180 °C, the pre-pressing time is 2 min, and the pressing time is 7 min to obtain a flame-retardant composite material.

[0061] Example 4

[0062] This example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010, 27% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 8% ammonium polyphosphate, and 8% nano-silica are added into the internal mixer, and mixing is carried out at 140 °C for 10 min to obtain a mixture.

[0063] Example 5

[0064] (1) Put magnesium aluminum hydrotalcite into a high-speed blender, stir for 5 min under the conditions of a rotation speed of 1300 rpm and a temperature of 90 °C, then add a silane coupling agent accounting for 2% of the mass of magnesium aluminum hydrotalcite, and continue to stir for 10 min to obtain modified magnesium aluminum hydrotalcite;

[0065] (2) Mix 41% EVA polymer and 4% compatibilizer MC226 and add them to an internal mixer, and carry out melt blending at 140 °C for 3 min to obtain a blend, wherein the content of vinyl acetate in the EVA polymer is 18%;

[0066] (3) Add 0.1% antioxidant 1010, 23% modified magnesium aluminum hydrotalcite, 16% magnesium hydroxide, 8% ammonium polyphosphate, and 8% nano-silica into an internal mixer, and carry out mixing at 140 °C for 10 min to obtain a mixture;

[0067] (4) Put the mixture into a flat vulcanizer for hot pressing and forming, the hot pressing temperature is 180 °C, the pre-pressing time is 2 min, and the pressing time is 7 min to obtain a flame-retardant composite material.

[0068] Example 6

[0069] This example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010, 23% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 12% ammonium polyphosphate, and 8% nano-silica are added into an internal mixer, and carry out mixing at 140 °C for 10 min to obtain a mixture.

[0070] Example 7

[0071] This example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010, 23% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 8% ammonium polyphosphate, and 12% nano-silica are added into an internal mixer, and carry out mixing at 140 °C for 10 min to obtain a mixture.

[0072] Comparative Example 1

[0073] This comparative example is basically the same as Example 4, and the only difference is that step (1) is omitted, and the modified magnesium aluminum hydrotalcite is replaced with magnesium aluminum hydrotalcite.

[0074] Comparative Example 2

[0075] This comparative example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010 and 55% modified magnesium aluminum hydrotalcite are added to an internal mixer and kneaded at 140 °C for 10 min to obtain a kneaded product.

[0076] Comparative Example 3

[0077] This comparative example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010 and 55% magnesium hydroxide are added to an internal mixer and kneaded at 140 °C for 10 min to obtain a kneaded product.

[0078] Comparative Example 4

[0079] This comparative example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010 and 55% ammonium polyphosphate are added to an internal mixer and kneaded at 140 °C for 10 min to obtain a kneaded product.

[0080] Comparative Example 5

[0081] This comparative example is basically the same as Example 1, and the only difference is that in step (3), 0.1% antioxidant 1010 and 55% nano-silica are added to an internal mixer and kneaded at 140 °C for 10 min to obtain a kneaded product.

[0082] The flame-retardant composite materials prepared in Examples 1-7 and Comparative Examples 1-5 were tested for mechanical properties, flame-retardant properties, and limiting oxygen index. The test results are shown in Table 1.

[0083] Mechanical property test: Referring to the standard GB / T 528-2009, through a universal testing machine of Shenzhen SANS Technology Co., Ltd., the test option is the determination of the tensile properties of molded and extruded plastics. The sample size is 115 mm × 6 mm × 1.6 mm (dumbbell shape), the testing machine speed is 50 mm / min, and the extensometer scale is 25 mm.

[0084] Flame-retardant property test: Referring to the standard GB / T 2408, through a UL-94 horizontal and vertical burning tester of Motis Technology Co., Ltd., the UL-94 flame-retardant grade of the sample was tested. The sample size is: 125 mm × 13 mm × 3 mm.

[0085] Limiting oxygen index test: Referring to the standard ISO 4589-2:2017, through an oxygen index combustion tester of Motis Technology Co., Ltd., the sample size is: 150 mm × 6.5 mm × 1.6 mm.

[0086] Table 1

[0087]

[0088]

[0089] As can be seen from Table 1, in Example 4, when 27% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 8% ammonium polyphosphate, and 8% nano-silica are added, the mechanical properties, flame retardancy, and limiting oxygen index of the composite material are all relatively excellent; Example 6 shows that although adding more ammonium polyphosphate can increase the elongation at break of the composite material, its tensile strength will also decrease. Therefore, the flame retardant compounding system of 27% modified magnesium aluminum hydrotalcite, 12% magnesium hydroxide, 8% ammonium polyphosphate, and 8% nano-silica in the present invention is the best solution for the flame retardant composite material.

[0090] It can be seen from Example 1 and Comparative Examples 2-5 that the synergistic effect of modified magnesium aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate, and nano-silica can effectively balance the flame retardancy of the flame retardant composite material and mechanical properties such as elongation at break and tensile strength, and obtain a flame retardant composite material with relatively excellent comprehensive performance.

[0091] In addition, the present invention has carried out charring performance tests on the flame retardant composite materials of Examples 1-7 and Comparative Example 5. From Figure 1 it can be seen that after combustion, the surfaces of the flame retardant composite materials are all covered with a thick carbon layer, indicating that the flame retardant composite materials of the present invention have excellent charring performance.

[0092] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A flame retardant composite material, characterized in that: The invention comprises the following components by mass percentage: 35-45% of ethylene-vinyl acetate copolymer, 4-6% of compatibilizer, 0.05-0.2% of antioxidant, 23-31% of modified magnesium aluminum hydrotalcite, 8-16% of magnesium hydroxide, 4-12% of ammonium polyphosphate and 4-12% of nano silicon dioxide.

2. The flame retardant composite material according to claim 1, characterized in that: The modified magnesium aluminum hydrotalcite is composed of a silane coupling agent and magnesium aluminum hydrotalcite; The mass ratio of the silane coupling agent to the magnesium aluminum hydrotalcite is 0.5-2.5:

1.

3. The flame retardant composite material according to claim 2, characterized in that: The silane coupling agent includes one or more of 3-aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane.

4. The flame retardant composite material according to claim 1, characterized in that: The compatibilizer includes one or more of maleic anhydride grafted EVA, compatibilizer MC226, compatibilizer MC218 and compatibilizer MC328.

5. The flame retardant composite material according to any one of claims 1 to 4, characterized in that: The antioxidant includes one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris[2,4-di-tert-butylphenyl]phosphite, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and antioxidant B215.

6. A method for preparing the flame retardant composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) melt-blending an ethylene-vinyl acetate copolymer and a compatibilizer to obtain a blend; (2) mixing the first blend, an antioxidant, modified magnesium aluminum hydrotalcite, magnesium hydroxide, ammonium polyphosphate and nano silicon dioxide to obtain a mixture; (3) hot pressing the mixed material to obtain a flame retardant composite material.

7. The method for preparing a flame retardant composite material according to claim 6, characterized in that: The temperature of the melt blending in step (1) is 130-160° C. and the time is 2-5 min.

8. The method for preparing a flame retardant composite material according to claim 6, characterized in that: The mixing temperature in step (2) is 130-160° C. and the mixing time is 10-15 min.

9. The method for preparing a flame retardant composite material according to claim 6, characterized in that: The temperature of the hot pressing molding in step (3) is 170-190° C., the pre-pressing time is 1-3 min, and the pressing time is 4-10 min.

10. The method for preparing a flame retardant composite material according to any one of claims 6 to 9, characterized in that: The modified magnesium aluminum hydrotalcite is obtained by mixing and stirring magnesium aluminum hydrotalcite and a silane coupling agent; The mixing and stirring is performed at a temperature of 80-100° C., a time of 8-15 min, and a rotation speed of 1000-1500 rpm.

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