Fiber-reinforced flame-retardant plastic and preparation method thereof

Abstract

The invention relates to a fiber-reinforced flame-retardant plastic and a preparation method thereof, and belongs to the technical field of high polymer materials. The fiber-reinforced flame-retardant plastic comprises the following components in parts by weight: 60-80 parts of polycarbonate, 20-30 parts of titanium dioxide, 20-30 parts of glass fiber, 2-8 parts of a heat-resistant modifier, 0.1-2 parts of a modified flame retardant and 1-3 parts of a lubricant, a piperazine pyrophosphate compound in the modified flame retardant plays a role of a carbon source and cooperates with the phosphorus-nitrogen flame retardant to construct an expansive carbon layer, oxygen and a fire source are effectively blocked, and a phosphorus element of dimethyl chlorophosphate forms a phosphate protection layer to inhibit flame spreading; a maleimide group in the heat-resistant modifier enhances the interaction between molecules, improves the glass transition temperature and the melting point and improves the toughness, sulfonyl of an intermediate absorbs electrons and enhances the heat stability, and the sulfonyl cooperates with phosphite to improve the heat resistance; the fiber-reinforced flame-retardant plastic prepared by the invention not only has excellent flame retardance and high temperature resistance, but also has a good toughening effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a fiber-reinforced flame-retardant plastic and a preparation method thereof. Background Art

[0002] At present, a large number of electrical components are made of flame-retardant plastics. With the improvement of environmental awareness and the rapid progress of science and technology, the market demand for high-strength, flame-retardant and durable plastics is increasing day by day.

[0003] As a thermoplastic engineering plastic with excellent comprehensive properties, polycarbonate has high transparency, good toughness and weather resistance at room temperature due to the carbonate group structure in the molecular chain, and is widely used in the fields of automobile manufacturing, electronic equipment, medical devices, etc. However, when the temperature changes, the molecular chain activity of traditional polycarbonate materials is restricted, and it will change from a high elastic state to a glassy state, resulting in a significant decrease in toughness, easy embrittlement and cracking, thus limiting its application under high temperature conditions. In addition, although polycarbonate plastics have certain flame-retardant properties, with the improvement of actual application requirements, their own electrical conductivity can no longer meet the needs. Therefore, it is of great practical significance and application value to develop a fiber-reinforced flame-retardant plastic with excellent properties. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a fiber-reinforced flame-retardant plastic and a preparation method thereof.

[0005] The object of the present invention can be achieved by the following technical solutions: A fiber-reinforced flame-retardant plastic, comprising the following raw materials in parts by weight: 60-80 parts of polycarbonate, 20-30 parts of titanium dioxide, 20-30 parts of glass fiber, 2-8 parts of heat-resistant modifier, 0.1-2 parts of modified flame retardant, and 1-3 parts of lubricant; The lubricant is pentaerythritol stearate.

[0006] The modified flame retardant is prepared by the following method: Step A1: Stir anhydrous sodium carbonate and deionized water evenly, heat to 80 °C, then add anhydrous piperazine and dimethyl chlorophosphate and mix, react for 8 h, stand, filter, wash, vacuum dry, and in a nitrogen environment, add 1,3-propanediamine, stir at 100 °C for 30 min, condense and reflux at 140 °C for 8 h, and rotary evaporate to obtain a compound; Further, the dosage ratio of anhydrous sodium carbonate, deionized water, anhydrous piperazine, dimethyl chlorophosphate, and 1,3-propanediamine is 5.3-10.6 g: 20-50 mL: 2.15-4.3 g: 7.47-14.94 g: 7.41-14.82 g; First, react the chlorine atom of anhydrous piperazine with that of dimethyl chlorophosphate, and react the amino group of 1,3-propanediamine with dimethyl chlorophosphate to form a compound. Step A2: Mix 3-butenyltriethoxysilane and ethanol, stir at 80 °C for 10 h, then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir for 12 h, cool to room temperature, filter and wash to obtain a pre-product. Furthermore, the dosage ratio of 3-butenyltriethoxysilane, ethanol, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 0.04 - 0.08 mol : 100 - 200 mL : 0.04 - 0.08 mol. Secondly, react the carbon-carbon double bond of 3-butenyltriethoxysilane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to form a pre-product. Step A3: After mixing the pre-product and the ethanol-water mixed solution at 35 °C for 10 min, add the compound, react at 100 °C for 5 h, stop heating, and while stirring, naturally cool to room temperature, filter, wash, and dry to obtain a modified flame retardant. Furthermore, the dosage ratio of the pre-product, the ethanol-water mixed solution, and the compound is 0.04 - 0.08 mol : 150 mL : 0.03 - 0.06 mol, and the volume ratio of ethanol to water in the ethanol-water mixed solution is 4:1. Finally, react the silanol group after hydrolysis of the pre-product with the amino group of the compound to form a modified flame retardant.

[0007] The heat-resistant modifier is prepared by the following method: Step B1: Place maleic anhydride in a flask, seal it and introduce ammonia gas. When cooled to room temperature, stop introducing ammonia gas, then raise the temperature to 180 °C and react for 6 h. After cooling to room temperature, add tetrahydrofuran, formaldehyde, and sodium hydroxide and mix evenly, react at 30 °C for 4 h, perform rotary evaporation, wash and centrifuge, dry at 45 °C for 24 h, then adjust the temperature to 15 °C, dropwise add triethylamine, toluene, and diphenylphosphorus chloride. After dropping, slowly raise the temperature to 80 °C, keep the temperature for reaction for 3 h, cool and dry to obtain an intermediate. Furthermore, the dosage ratio of maleic anhydride, tetrahydrofuran, formaldehyde, sodium hydroxide, triethylamine, toluene, and diphenylphosphorus chloride is 0.164 - 0.328 g : 3.27 - 3.63 g : 0.05 - 0.1 g : 0.25 - 0.32 mL : 4.5 g : 50 g : 0.53 - 1.06 g. First, introduce ammonia gas to imidize maleic anhydride, then add formaldehyde to hydroxymethylate it, and then react with the chlorine atom of diphenylphosphorus chloride to form an intermediate. Step B2: 4-hydroxybenzyl sulfone, acryloyl chloride and tetrabutylammonium bromide were mixed, stirred for 20 min, heated to 80°C for reaction for 1 h, and after the temperature dropped to room temperature, washed, rotary evaporated, and dried at 60°C to obtain an intermediate product; Further, the mass ratio of 4-hydroxybenzyl sulfone, acryloyl chloride and tetrabutylammonium bromide is 0.86-1.72 g: 0.45-0.9 g: 0.001 g; Secondly, the hydroxyl group of 4-hydroxyphenyl sulfone is reacted with the acyl chloride of acryloyl chloride to generate an intermediate product; Step B3: Disperse the intermediate and benzoyl peroxide in xylene evenly, add the intermediate product and stir evenly, heat to 90°C under nitrogen protection and react for 4.5h, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a heat-resistant modifier; Further, the usage ratio of the intermediate, benzoyl peroxide, xylene, and intermediate product is 0.01-0.02 mol: 0.16 g: 70 mL: 0.01-0.02 mol; Finally, the heat-resistant modifier is generated by copolymerizing the carbon-carbon double bonds of the intermediate and the intermediate product.

[0008] A method for preparing a fiber-reinforced flame-retardant plastic comprises the following steps: S1. Fully mixing polycarbonate, titanium dioxide, heat-resistant modifier, modified flame retardant and lubricant in a mixer to prepare a premixed material; S2. The premixed material is added to a twin-screw extruder granulator for melting, the processing temperature is 200-280°C, the screw speed is 350-380r / min, and glass fiber is added. The premixed material is extruded and pelletized by the twin-screw extruder granulator to obtain uniform particles, thereby obtaining a fiber-reinforced flame-retardant plastic.

[0009] Beneficial effects of the present invention: The fiber-reinforced flame-retardant plastic of the present invention not only has good flame-retardant and high-temperature resistance properties, effectively prolonging the service life of the material, but also has excellent toughening effect and reduces brittleness.

[0010] In the modified flame retardant prepared by the present invention, the compound containing piperazine pyrophosphate plays an efficient carbon source role in polycarbonate plastics, synergistically acts with the phosphorus-nitrogen flame retardant to construct an expanded carbon layer, effectively blocks oxygen and the fire source, and realizes synergistic flame retardancy; during combustion, the nitrogen element is converted into inert gas to dilute oxygen and combustible gas, reducing the combustion intensity. At the same time, the phosphorus element in dimethyl chlorophosphate forms a phosphate protection layer to inhibit the spread of the flame, thereby achieving the flame retardant effect; in addition, the phosphorus-nitrogen flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the pre-product, as a phosphaphenanthrene compound with high thermal stability, can effectively retard the flame in the condensed phase and gas phase, promote the formation of a dense and continuous carbon layer, isolate oxygen and heat exchange, and further enhance the flame retardant effect; furthermore, the flame retardant prepared by the present invention is halogen-free, which helps to reduce environmental pollution and damage to the ecosystem, is harmless to human health, and realizes sustainable development.

[0011] The heat-resistant modifier prepared by the present invention, the maleimide group of the intermediate, has a dipole moment perpendicular to the main axis of the molecular chain, effectively enhancing the intermolecular interaction, significantly increasing the glass transition temperature and melting point of the material, improving the heat resistance, effectively preventing the embrittlement of the material in a high-temperature environment, and extending the service life. At the same time, due to the flexibility of this group, it enhances the flexibility of the plastic molecular chain, constructs an interpenetrating network structure, relieves stress concentration, and improves the toughness of the material; in addition, the phosphite compound of the intermediate can decompose hydroperoxides, prevent free radical oxidation, improve the stability of the plastic, and inhibit yellowing at high temperatures through its strong oxidation-reduction property, maintaining the good appearance of the plastic; the sulfone group of the intermediate product, as a strong electron-withdrawing group, can reduce the electron cloud density of the connected carbon atoms, enhance the molecular thermal stability, and further restrict the molecular chain movement through chain extension to improve the heat resistance; furthermore, this heat-resistant modifier is compatible with polycarbonate, effectively preventing migration. Specific embodiments

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0013] Example 1: A preparation method of a fiber-reinforced flame-retardant plastic specifically includes the following steps: S1. Weigh the raw materials by weight: 60 parts of polycarbonate, 20 parts of titanium dioxide, 20 parts of glass fiber, 2 parts of heat-resistant modifier (prepared by this example), 0.1 part of modified flame retardant (prepared by this example), and 1 part of lubricant; mix polycarbonate, titanium dioxide, heat-resistant modifier, modified flame retardant, and pentaerythritol stearate in a mixer to obtain a premixed material; S2. Add the premixed materials to a twin-screw extrusion granulation unit for melting. The processing temperature is 200 °C, the screw speed is 350 r / min. Then add glass fiber, and extrude and pelletize through a twin-screw extrusion granulator to make uniform pellets, thus obtaining fiber-reinforced flame-retardant plastics. The modified flame retardant is prepared by the following method: Step A1: Stir 5.3 g of anhydrous sodium carbonate and 20 mL of deionized water evenly. After heating to 80 °C, add 2.15 g of anhydrous piperazine and 7.47 g of dimethyl chlorophosphate and mix. React for 8 h, let it stand, filter, wash, and dry in vacuum. Under a nitrogen environment, add 7.41 g of 1,3-propanediamine, stir at 100 °C for 30 min, carry out condensation reflux at 140 °C for 8 h, and rotary evaporate to obtain a compound. Step A2: Mix 0.04 mol of 3-butene triethoxysilane and 100 mL of ethanol, stir at 80 °C for 10 h, then add 0.04 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and stir for 12 h. Cool to room temperature, filter and wash to obtain a pre-product. Step A3: Mix 0.04 mol of the pre-product and 150 mL of an ethanol-water mixed solution at 35 °C for 10 min, then add 0.03 mol of the compound, react at 100 °C for 5 h, stop heating, and under the state of stirring, naturally cool to room temperature, filter, wash and dry to obtain the modified flame retardant. The volume ratio of ethanol to water in the ethanol-water mixed solution is 4:1. The heat-resistant modifier is prepared by the following method: Step B1: Place 0.164 g of maleic anhydride in a flask, seal it and introduce ammonia gas. When cooled to room temperature, stop introducing ammonia gas, then heat to 180 °C and react for 6 h. After cooling to room temperature, add 3.27 g of tetrahydrofuran, 0.05 g of formaldehyde and 0.25 mL of sodium hydroxide and mix evenly. React at 30 °C for 4 h, rotary evaporate, wash and centrifuge, dry at 45 °C for 24 h, then adjust the temperature to 15 °C, dropwise add 4.5 g of triethylamine, 50 g of toluene and 0.53 g of diphenylphosphine chloride. After dropping, slowly heat to 80 °C, keep the temperature for reaction for 3 h, cool and dry to obtain an intermediate. Step B2: Mix 0.86 g of 4-hydroxybenzenesulfone, 0.45 g of acryloyl chloride and 0.001 g of tetrabutylammonium bromide, stir for 20 min, heat to 80 °C and react for 1 h. When the temperature drops to room temperature, wash and rotary evaporate, and dry at 60 °C to obtain an intermediate product. Step B3: Disperse 0.01 mol of the intermediate and 0.16 g of benzoyl peroxide evenly in 70 mL of xylene, then add 0.01 mol of the intermediate product and stir evenly. Under nitrogen protection, heat to 90 °C and react for 4.5 h, carry out vacuum distillation, cool down, wash, filter and dry in vacuum to obtain the heat-resistant modifier.

[0014] Embodiment 2: A method for preparing a fiber-reinforced flame-retardant plastic, comprising the following steps: S1. Weigh the raw materials by weight: 70 parts of polycarbonate, 25 parts of titanium dioxide, 25 parts of glass fiber, 6 parts of heat-resistant modifier (prepared in this embodiment), 1 part of modified flame retardant (prepared in this embodiment), and 2 parts of lubricant; fully mix the polycarbonate, titanium dioxide, heat-resistant modifier, modified flame retardant and pentaerythritol stearate in a mixer to obtain a premixed material; S2, adding the premixed material to a twin-screw extruder granulator for melting, with a processing temperature of 240°C and a screw speed of 365r / min, and then adding glass fiber, extruding and pelletizing the premixed material through a twin-screw extruder granulator to obtain uniform particles, thereby obtaining a fiber-reinforced flame-retardant plastic; The modified flame retardant is prepared by the following method: Step A1: 7.95 g of anhydrous sodium carbonate and 35 mL of deionized water were stirred evenly, and after heating to 80° C., 3.225 g of anhydrous piperazine and 12.7 g of dimethyl chlorophosphate were added and mixed, and the mixture was reacted for 8 h, allowed to stand, filtered, washed, and vacuum dried. Under a nitrogen environment, 11.12 g of 1,3-propylenediamine was added, and the mixture was stirred at 100° C. for 30 min, condensed and refluxed at 140° C. for 8 h, and rotary evaporated to obtain a compound; Step A2: 0.06 mol of 3-butylenetriethoxysilane and 150 mL of ethanol were mixed, stirred at 80° C. for 10 h, and then 0.06 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, stirred for 12 h, cooled to room temperature, filtered, and washed to obtain a pre-product; Step A3: 0.06 mol of the pre-product and 150 mL of an ethanol-water mixed solution were mixed at 35° C. for 10 min, and then 0.045 mol of the compound was added. After reacting at 100° C. for 5 h, heating was stopped, and the mixture was naturally cooled to room temperature under stirring, filtered, washed, and dried to obtain a modified flame retardant. The volume ratio of ethanol to water in the ethanol-water mixed solution was 4:1; The heat-resistant modifier is prepared by the following method: Step B1: 0.246 g of maleic anhydride was placed in a flask, and ammonia gas was introduced after sealing. When the flask was cooled to room temperature, the ammonia gas was stopped, and the temperature was raised to 180°C for reaction for 6 hours. After cooling to room temperature, 3.45 g of tetrahydrofuran, 0.075 g of formaldehyde and 0.285 mL of sodium hydroxide were added and mixed evenly, and the mixture was reacted at 30°C for 4 hours. The mixture was rotary evaporated, washed, centrifuged, and dried at 45°C for 24 hours. The temperature was then adjusted to 15°C, and 4.5 g of triethylamine, 50 g of toluene and 0.795 g of diphenylphosphine chloride were added dropwise. After the addition was completed, the temperature was slowly raised to 80°C, and the mixture was kept at this temperature for reaction for 3 hours. The mixture was cooled and dried to obtain an intermediate. Step B2: 1.29 g 4-hydroxyphenyl sulfone, 0.675 g acryloyl chloride and 0.001 g tetrabutylammonium bromide were mixed, stirred for 20 min, heated to 80°C for reaction for 1 h, and after the temperature dropped to room temperature, washed, rotary evaporated, and dried at 60°C to obtain an intermediate product; Step B3: Disperse 0.015 mol of the intermediate and 0.16 g of benzoyl peroxide in 70 mL of xylene, then add 0.015 mol of the intermediate and stir evenly. Under nitrogen protection, heat to 90 ° C to react for 4.5 hours, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a heat-resistant modifier.

[0015] Embodiment 3: A method for preparing a fiber-reinforced flame-retardant plastic, comprising the following steps: S1. Weigh the raw materials by weight: 80 parts of polycarbonate, 30 parts of titanium dioxide, 30 parts of glass fiber, 8 parts of heat-resistant modifier (prepared in this embodiment), 2 parts of modified flame retardant (prepared in this embodiment), and 3 parts of lubricant; fully mix the polycarbonate, titanium dioxide, heat-resistant modifier, modified flame retardant and pentaerythritol stearate in a mixer to obtain a premixed material; S2, adding the premixed material to a twin-screw extruder granulator for melting, with a processing temperature of 280°C and a screw speed of 380r / min, and then adding glass fiber, extruding and pelletizing the premixed material through a twin-screw extruder granulator to obtain uniform particles, thereby obtaining a fiber-reinforced flame-retardant plastic; The modified flame retardant is prepared by the following method: Step A1: 10.6 g of anhydrous sodium carbonate and 50 mL of deionized water were stirred evenly, and the mixture was heated to 80° C., and then 4.3 g of anhydrous piperazine and 14.94 g of dimethyl chlorophosphate were added and mixed, and the mixture was reacted for 8 h, and the mixture was allowed to stand, filtered, washed, and vacuum dried. Under a nitrogen environment, 14.82 g of 1,3-propylenediamine was added, and the mixture was stirred at 100° C. for 30 min, condensed and refluxed at 140° C. for 8 h, and rotary evaporated to obtain a compound; Step A2: 0.08 mol of 3-butylenetriethoxysilane and 200 mL of ethanol were mixed, stirred at 80° C. for 10 h, and then 0.08 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, stirred for 12 h, cooled to room temperature, filtered, and washed to obtain a pre-product; Step A3: 0.08 mol of the pre-product and 150 mL of an ethanol-water mixed solution were mixed at 35° C. for 10 min, and then 0.06 mol of the compound was added. After reacting at 100° C. for 5 h, heating was stopped, and the mixture was naturally cooled to room temperature under stirring, filtered, washed, and dried to obtain a modified flame retardant. The volume ratio of ethanol to water in the ethanol-water mixed solution was 4:1; The heat-resistant modifier is prepared by the following method: Step B1: Place 0.328 g of maleic anhydride in a flask. After sealing, introduce ammonia gas. When it is cooled to room temperature, stop introducing ammonia gas. Then raise the temperature to 180 °C and react for 6 h. After cooling to room temperature, add 3.63 g of tetrahydrofuran, 0.1 g of formaldehyde, and 0.32 mL of sodium hydroxide and mix evenly. React at 30 °C for 4 h. Carry out rotary evaporation, washing, and centrifugation, and dry at 45 °C for 24 h. Then adjust the temperature to 15 °C, and dropwise add 4.5 g of triethylamine, 50 g of toluene, and 1.06 g of diphenylphosphorus chloride. After dropping, slowly raise the temperature to 80 °C and keep the temperature for reaction for 3 h. Cool and dry to obtain an intermediate product; Step B2: Mix 1.72 g of 4 - hydroxybenzenesulfone, 0.9 g of acryloyl chloride, and 0.001 g of tetrabutylammonium bromide, stir for 20 min, raise the temperature to 80 °C and react for 1 h. Wait for the temperature to drop to room temperature, carry out washing and rotary evaporation, and dry at 60 °C to obtain an intermediate product; Step B3: Disperse 0.02 mol of the intermediate product and 0.16 g of benzoyl peroxide evenly in 70 mL of xylene, then add 0.02 mol of the intermediate product and stir evenly. Under the protection of nitrogen, heat to 90 °C and react for 4.5 h. Carry out vacuum distillation, cool down, wash, filter, and vacuum dry to obtain a heat - resistant modifier.

[0016] Comparative Example 1: This comparative example is a fiber - reinforced flame - retardant plastic. The difference from Example 3 is that magnesium hydroxide in equal amount is used to replace the modified flame - retardant prepared in Example 3, and the rest are the same.

[0017] Comparative Example 2: This comparative example is a fiber - reinforced flame - retardant plastic. The difference from Example 3 is that dibutyltin dilaurate in equal amount is used to replace the heat - resistant modifier prepared in Example 3, and the rest are the same.

[0018] Performance test: Cut the fiber - reinforced flame - retardant plastics prepared in Examples 1 - 3 and Comparative Examples 1 - 2 into standard test sizes, and use the vertical burning performance test method of GB / T 2048 - 1996 to test the vertical burning performance; test the heat distortion temperature according to the standard of GB / T 1634.2 - 2004; test the glass transition temperature according to the standard of GB / T 19466.2 - 2004; carry out the bending strength test using the standard of GB1042 - 79; the test results are shown in Table 1 below: Table 1

[0019] It can be seen from the data tested in Table 1 that the fiber - reinforced flame - retardant plastic prepared by the present invention has excellent flame - retardant and high - temperature resistance effects. It can also be seen from the above table that the fiber - reinforced flame - retardant plastic prepared by the present invention has good toughening performance.

[0020] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications, supplements, or use similar methods for substitution to the specific embodiments described. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a fiber-reinforced flame-retardant plastic, characterized in that: The specific steps include: S1. Weigh the raw materials by weight: 60-80 parts of polycarbonate, 20-30 parts of titanium dioxide, 20-30 parts of glass fiber, 2-8 parts of heat-resistant modifier, 0.1-2 parts of modified flame retardant, and 1-3 parts of lubricant; fully mix the polycarbonate, titanium dioxide, heat-resistant modifier, modified flame retardant and lubricant in a mixer to obtain a premixed material; S2, adding the premixed material to a twin-screw extruder granulator for melting, with a processing temperature of 200-280°C and a screw speed of 350-380r / min, and then adding glass fiber, extruding and pelletizing into uniform particles through a twin-screw extruder granulator to obtain a fiber-reinforced flame-retardant plastic; The modified flame retardant is prepared by the following method: Step A1: stir anhydrous sodium carbonate and deionized water evenly, heat to 80°C, add anhydrous piperazine and dimethyl chlorophosphate, react for 8 hours, let stand, filter, wash, vacuum dry, add 1,3-propylenediamine under nitrogen environment, stir at 100°C for 30 minutes, condense and reflux at 140°C for 8 hours, and rotary evaporate to obtain a compound; Step A2: 3-Butenetriethoxysilane and ethanol were mixed, stirred at 80° C. for 10 h, and then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, stirred for 12 h, cooled to room temperature, filtered, and washed to obtain a pre-product; Step A3: After mixing the pre-product and the ethanol-water mixed solution at 35° C. for 10 minutes, the compound is added, and the reaction is carried out at 100° C. for 5 hours. The heating is stopped, and the mixture is naturally cooled to room temperature under stirring, filtered, washed, and dried to obtain a modified flame retardant.

2. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 1, characterized in that: In step A1, the usage ratio of anhydrous sodium carbonate, deionized water, anhydrous piperazine, dimethyl chlorophosphate and 1,3-propylenediamine is 5.3-10.6 g: 20-50 mL: 2.15-4.3 g: 7.47-14.94 g: 7.41-14.82 g.

3. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 1, characterized in that: In step A2, the usage ratio of 3-butenetriethoxysilane, ethanol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 0.04-0.08 mol:100-200 mL:0.04-0.08 mol.

4. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 1, characterized in that: In step A3, the dosage ratio of the pre-product, the ethanol-water mixed solution, and the compound is 0.04-0.08 mol:150 mL:0.03-0.06 mol, and the volume ratio of ethanol to water in the ethanol-water mixed solution is 4:

1.

5. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 1, characterized in that: The heat-resistant modifier is prepared by the following method: Step B1: maleic anhydride is placed in a flask, sealed and ammonia is introduced, when cooled to room temperature, the introduction of ammonia is stopped, the temperature is raised to 180°C for reaction for 6 hours, after cooling to room temperature, tetrahydrofuran, formaldehyde and sodium hydroxide are added and mixed evenly, the reaction is carried out at 30°C for 4 hours, rotary evaporation is performed, washing and centrifugation are performed, drying is carried out at 45°C for 24 hours, the temperature is adjusted to 15°C, triethylamine, toluene and diphenylphosphine chloride are added dropwise, the temperature is slowly raised to 80°C after the addition is completed, the temperature is kept for reaction for 3 hours, cooling and drying are performed to obtain an intermediate; Step B2: 4-hydroxybenzyl sulfone, acryloyl chloride and tetrabutylammonium bromide were mixed, stirred for 20 min, heated to 80°C for reaction for 1 h, and after the temperature dropped to room temperature, washed, rotary evaporated, and dried at 60°C to obtain an intermediate product; Step B3: Disperse the intermediate and benzoyl peroxide evenly in xylene, then add the intermediate product and stir evenly, heat to 90°C under nitrogen protection for 4.5 hours, distill under reduced pressure, cool, wash, filter, and vacuum dry to obtain a heat-resistant modifier.

6. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 5, characterized in that: In step B1, the usage ratio of maleic anhydride, tetrahydrofuran, formaldehyde, sodium hydroxide, triethylamine, toluene and diphenylphosphine chloride is 0.164-0.328 g: 3.27-3.63 g: 0.05-0.1 g: 0.25-0.32 mL: 4.5 g: 50 g: 0.53-1.06 g.

7. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 5, characterized in that: The mass ratio of 4-hydroxybenzyl sulfone, acryloyl chloride and tetrabutylammonium bromide in step B2 is 0.86-1.72 g: 0.45-0.9 g: 0.001 g.

8. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 5, characterized in that: The usage ratio of the intermediate, benzoyl peroxide, xylene and intermediate product in step B3 is 0.01-0.02 mol: 0.16 g: 70 mL: 0.01-0.02 mol.

9. The method for preparing a fiber-reinforced flame-retardant plastic according to claim 1, characterized in that: The lubricant is pentaerythritol stearate.

10. A fiber-reinforced flame-retardant plastic, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

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