Nitrogen-phosphorus high flame-retardant high-strength pet composite material and preparation method thereof

Abstract

The application belongs to the technical field of high polymer materials, and particularly discloses a nitrogen-phosphorus high-flame-retardant high-strength PET composite material and a preparation method thereof. The high-flame-retardant high-strength PET composite material comprises the following components: 100 parts of PET granules, 5-25 parts of polyester, 1-5 parts of a toughening agent, 0.1-0.5 parts of an antioxidant, 2-15 parts of a smoke suppressant, 5-25 parts of a compounded flame retardant, and 5-30 parts of a fiber material. The preparation method comprises the following steps: taking the PET granules as the main raw material, and adding the polyester, the toughening agent, the antioxidant, the smoke suppressant, the compounded flame retardant and the fiber material as the functional additives; and mixing the components by means of a high-speed mixer. The high-flame-retardant high-strength PET composite material has the advantages of high strength, excellent flame-retardant performance and the like, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and specifically discloses a nitrogen-phosphorus high-flame-retardant high-strength PET composite material and a preparation method thereof. BACKGROUND

[0002] Ethylene terephthalate (PET) is widely used, and has excellent mechanical properties under static and dynamic load, and can be generally used for manufacturing daily necessities such as fibers, films and plastic containers. Although PET has excellent comprehensive performance, its limiting oxygen index is relatively low, and because the carbonization effect on the surface during combustion is weak, it cannot effectively isolate the transmission of oxygen and heat, so a large amount of molten droplets with flames and harmful smoke will be generated during combustion. The molten droplets will cause secondary disasters, and the smoke is not only harmful to the human body, but also brings visual obstacles to fire fighting and escape. Its flammability seriously limits its application field. Therefore, the flame-retardant research of polyester fibers has attracted worldwide attention.

[0003] Patents CN108164935A and CN104672817A mention the preparation method of high-glow-wire high-strength reinforced flame-retardant PET material, and both involve bromine-based flame retardants, but the bromine-based flame retardants will produce toxic and corrosive gases and a large amount of smoke during combustion, and have been banned in recent years. Therefore, it is necessary to develop a halogen-free flame-retardant PET composite material. SUMMARY

[0004] In view of the defects or deficiencies of the prior art, the technical problem to be solved by the application is to provide a high-flame-retardant high-strength PET composite material and a preparation method thereof.

[0005] To solve the above technical problems, the application realizes the technical scheme as follows:

[0006] The application provides a high-flame-retardant high-strength PET composite material, which comprises the following formula components: 100 parts of PET granules, 5-25 parts of thermoplastic polyester, 1-5 parts of toughening agent, 0.1-0.5 parts of antioxidant, 2-15 parts of smoke suppressant, 5-25 parts of compound flame retardant and 5-30 parts of fiber material.

[0007] The thermoplastic polyester is one or more of polybutylene terephthalate, polyarylate and thermoplastic polyester elastomer (TPEE).

[0008] The toughening agent is one or more of polyolefin elastomer (POE), methyl propyl glycidyl methacrylate (GMA) grafted polyolefin elastomer (POE-g-GMA), ethylene-glycidyl methacrylate copolymer (E-GMA) and ethylene butyl acrylate (EBA).

[0009] The antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris[2,4-di-tert-butylphenyl]phosphite, or bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0010] The smoke suppressant is one or more of molybdenum compounds, iron compounds, metal oxides, or zinc-magnesium complexes.

[0011] Among them, the molybdenum compound is molybdenum trioxide or ammonium octamolate; the iron compound is ferrocene.

[0012] The metal oxide is one or more of magnesium oxide, zinc oxide, nickel oxide or zirconium oxide; the zinc-magnesium complex is a complex of magnesium oxide and zinc oxide.

[0013] The compound flame retardant is composed of nitrogen and phosphorus macromolecular flame retardants and antimony trioxide, magnesium hydroxide, aluminum hydroxide or zinc compounds.

[0014] The zinc compound is one or more of zinc borate, zinc aluminate, or zinc stannate.

[0015] The fibrous material is one or more of asbestos, glass fiber, or carbon fiber.

[0016] The preparation method of high flame retardant and high strength PET composite material includes the following steps:

[0017] (1) Dry the PET granules thoroughly to ensure that the moisture content is less than 100 ppm;

[0018] (2) Dry the compound flame retardant thoroughly to ensure that the moisture content is less than 100 ppm;

[0019] (3) Pretreatment of fiber materials: First, prepare a polyacrylonitrile solution, then immerse the fiber material in the polyacrylonitrile solution, and then pre-oxidize the immersed fiber material in an oven at 50℃~300℃ for 0.1~100 hours and dry it to obtain surface-modified pretreated fiber material for later use;

[0020] (4) Thoroughly mix PET granules, thermoplastic polyester, toughening agent, antioxidant, smoke suppressant, compound flame retardant and fiber material. The compound flame retardant is added by side feeding or main feeding after being weighed by a loss-in-weight weigher, preferably by side feeding. PET granules and other ingredients are added by main feeding after being weighed by a loss-in-weight weigher. According to the set extrusion process, the mixture is then blended, extruded and granulated by a twin-screw extruder to obtain the required PET composite material.

[0021] The specific process of extruder blending extrusion granulation is as follows: Zone 1 temperature 180±5℃, Zone 2 temperature 260±5℃, Zone 3 temperature 280±5℃, Zone 4 temperature 280±5℃, Zone 5 temperature 280±5℃, Zone 6 temperature 280±5℃, Zone 7 temperature 280±5℃, Zone 8 temperature 260±5℃, Zone 9 temperature 250±5℃, Die head temperature 270±5℃, and screw speed 360-400r / min.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] The high flame-retardant, high-strength PET of this invention exhibits significantly higher oxygen index and vertical flammability rating than common flame-retardant PET, substantially improving both its flame-retardant and mechanical properties. This further expands the application range of flame-retardant PET. The added compound flame retardant further enhances the flame-retardant properties of the composite material; the added fiber material further improves the toughness and tensile strength of the composite material. The preparation method of this invention has advantages such as simple process, convenient operation, and easy industrial implementation. Attached Figure Description

[0024] Figure 1 The image shows the infrared spectrum of a nitrogen-phosphorus macromolecular flame retardant.

[0025] Figure 2 The heat release rate curves are used to compare Examples 1-3 and Example 2.

[0026] Figure 3 The total exothermic curves are shown for comparison between Examples 1-3 and Example 2.

[0027] Figure 4 The temperature rise curves in the differential scanning calorimetry curves of Examples 1-3 and Example 2 are shown for comparison.

[0028] Figure 5 The cooling curves in the differential scanning calorimetry curves of Examples 1-3 and Example 2 are used for comparison.

[0029] Figure 6 The images shown are digital photographs and SEM images of the char layer surface after high-temperature combustion in Example 2. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments.

[0031] Example 1: Synthesis of reactive nitrogen-phosphorus flame retardants. The synthesis reaction equation is as follows:

[0032]

[0033] Add 5.969 g of hexamethylenediamine and 200 ml of ethanol solution to a 500 ml Erlenmeyer flask. Place the flask in an ice bath at 0 °C and stir. Once the liquid temperature in the flask has dropped to 0 °C and the hexamethylenediamine is completely dissolved in the ethanol solution, add 16.17 g of [(6-oxo-6H-dibenzo[C,E][1,2]oxophosphazenecyclo-6-yl)methyl]succinic acid (DDP). React in a water bath at 70 °C for 5 h. After the reaction is complete, cool to room temperature. Filter the product using a Buchner funnel. Wash the filter cake with 100 ml of ethanol to remove excess hexamethylenediamine and dry it in a vacuum oven at 50 °C for 4 h.

[0034] The synthesis reaction equation for nitrogen-phosphorus macromolecular flame retardants is as follows:

[0035]

[0036] Terephthalic acid (0.19 mol, 31 g), isophthalic acid (0.19 mol, 31 g), ethylene glycol (0.29 mol, 18 g), neopentyl glycol (0.19 mol, 20 g), reactive nitrogen-phosphorus flame retardant (0.04 mol, 20 g), and tetrabutyl titanate catalyst (0.0001 mol, 0.035 g) were added to a three-necked flask and stirred with a mechanical stirrer until homogeneous. A vacuum distillation apparatus was set up, and a thermometer was inserted at the top of the distillation column. Nitrogen was used to purge the air from the three-necked flask. The temperature was increased to 195°C using a stepwise heating method (50°C per hour). By controlling the stirring rate (120 r / min) and preventing alcohol loss from the distillation column, when the distillate reached the theoretical value (13.69 g) and the column top temperature dropped to 50-60°C, the calculated esterification rate exceeded 96%. After the esterification reaction, the distillation column was removed and replaced with a three-way valve. The remaining water in the system was slowly evaporated using a water pump. Finally, a vacuum was slowly drawn using an oil pump to remove any remaining water. The vacuum was then stopped, and tetrabutyl titanate (0.00001 mol, 0.0035 g) was added. The temperature was increased to 250 °C using a stepwise heating method (30 °C per hour). A pre-polymerization reaction was carried out for 30 minutes while maintaining a low vacuum. Finally, the temperature was increased to 260 °C, and the reaction continued under a high vacuum of 100 Pa. When the system reached a certain viscosity and the rod climbed, the reaction ended. The mixture was then discharged after being purged with nitrogen, placed in cold water, and pelletized to obtain the nitrogen-phosphorus flame-retardant copolymer.

[0037] Figure 1 This is the infrared spectrum of a nitrogen-phosphorus macromolecular flame retardant. The infrared spectrum shows that at 2965 cm⁻¹... -1 and 2878 cm -1 The peak at 1714 cm⁻¹ represents the stretching vibration absorption peak of the methylene group (CH₂) in ethylene glycol and neopentyl glycol. -1The peak at 1067 cm⁻¹ represents the C=O carbonyl stretching vibration. -1 1167 cm -1 The peak at 1714 cm⁻¹ corresponds to the COC stretching vibration absorption peak. -1 and 1167cm -1 The characteristic absorption peak at 1440 cm⁻¹ indicates the presence of ester groups in the sample. -1 A new stretching vibration peak of P=O was observed, indicating the successful preparation of a nitrogen-phosphorus macromolecular flame retardant.

[0038] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts polybutylene terephthalate (PBT) granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 5 parts compound flame retardant, and 30 parts carbon fiber, of which 2.5 parts are nitrogen-phosphorus macromolecular flame retardant and 2.5 parts are antimony trioxide.

[0039] The preparation method of high flame retardant and high strength PET composite material includes the following steps:

[0040] A. Dry the PET granules thoroughly to ensure that the moisture content is less than 100ppm;

[0041] B. Thoroughly dry the compounded flame retardant to ensure that the moisture content is less than 100 ppm;

[0042] C. Carbon fiber pretreatment: First, prepare a polyacrylonitrile solution (concentration of 10%), immerse the carbon fiber in the polyacrylonitrile solution for 60 minutes, then pre-oxidize the immersed carbon fiber in a 300℃ oven for 70 minutes and dry it to obtain surface-modified pretreated carbon fiber for later use.

[0043] C. Thoroughly mix PET granules, PBT granules, toughening agent, antioxidant, smoke suppressant, compound flame retardant and carbon fiber. The compound flame retardant is added through the fifth side feed port of the twin-screw extruder after being weighed by a loss-in-weight weigher. PET granules and other ingredients are added through the main feed port after being weighed by a loss-in-weight weigher. According to the set extrusion process, the mixture is then blended, extruded and granulated through the twin-screw extruder to obtain the desired PET composite material.

[0044] The specific extrusion process is as follows: Zone 1 temperature 175℃, Zone 2 temperature 255℃, Zone 3 temperature 275℃, Zone 4 temperature 275℃, Zone 5 temperature 275℃, Zone 6 temperature 275℃, Zone 7 temperature 275℃, Zone 8 temperature 255℃, Zone 9 temperature 245℃, die head temperature 265℃, and screw speed 360r / min.

[0045] Example 2: The preparation of nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0046] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compound flame retardant, and 30 parts carbon fiber, of which 7.5 parts are nitrogen and phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0047] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0048] Example 3: The preparation of nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0049] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 25 parts compound flame retardant, and 30 parts carbon fiber, of which 12.5 parts are nitrogen and phosphorus macromolecular flame retardant and 12.5 parts are antimony trioxide.

[0050] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0051] Example 4: The preparation of nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0052] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts polyester elastomer (TPEE), 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compound flame retardant, and 30 parts carbon fiber, of which 7.5 parts are nitrogen and phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0053] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0054] Example 5: The preparation of the nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0055] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts glycidyl methacrylate (GMA) grafted polyolefin elastomer (POE-g-GMA) toughening agent, 0.3 parts phosphite-based antioxidant 168 antioxidant, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compounded flame retardant, and 30 parts fiber material, of which 7.5 parts are nitrogen-phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0056] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0057] Example 6: The preparation of nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0058] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compound flame retardant, and 30 parts glass fiber, of which 7.5 parts are nitrogen and phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0059] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0060] Example 7: The preparation of nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0061] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compound flame retardant, and 10 parts glass fiber, of which 7.5 parts are nitrogen-phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0062] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0063] Example 8: The preparation of the nitrogen-phosphorus macromolecular flame retardant is the same as in Example 1.

[0064] The high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 0.3 parts antioxidant phosphite-based antioxidant 168, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts compound flame retardant, and 20 parts glass fiber, of which 7.5 parts are nitrogen and phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0065] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0066] Comparative Example 1: The flame-retardant high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 1680.3 parts antioxidant phosphite-based antioxidant, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), and 30 parts carbon fiber.

[0067] The preparation method of the flame-retardant high-strength PET composite material is the same as in Example 1.

[0068] Comparative Example 2, the flame-retardant high-strength PET composite material comprises the following weight percentage formulation: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 1680.3 parts antioxidant phosphite-based antioxidant, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts antimony trioxide, and 30 parts carbon fiber.

[0069] The preparation method of the flame-retardant high-strength PET composite material is the same as in Example 1.

[0070] Comparative Example 3: The flame-retardant high-strength PET composite material comprises the following weight percentages of the following formulation: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent polyolefin elastomer (POE), 1680.3 parts antioxidant phosphite-based antioxidant, 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), 15 parts nitrogen and phosphorus macromolecular flame retardant, and 30 parts carbon fiber.

[0071] The preparation method of the flame-retardant high-strength PET composite material is the same as in Example 1.

[0072] Comparative Example 4 shows that the high flame-retardant and high-strength PET composite material comprises the following weight percentages: 100 parts PET granules, 15 parts PBT granules, 2 parts toughening agent (polyolefin elastomer (POE), 1680.3 parts antioxidant (phosphite-based antioxidant), 4 parts smoke suppressant (0.5 parts molybdenum trioxide, 0.5 parts ferrocene, 1 part magnesium oxide, 1 part zinc oxide, 1 part zinc borate), and 15 parts compounded flame retardant. Among these, 7.5 parts are nitrogen-phosphorus macromolecular flame retardant and 7.5 parts are antimony trioxide.

[0073] The preparation method of the high flame retardant and high strength PET composite material is the same as in Example 1.

[0074] Experimental example: The composite materials prepared using the various embodiments of the present invention were tested.

[0075] Tensile property testing: Tensile specimens with a gauge length of 20 mm, a width of 5 mm, and a thickness of 2 mm were prepared according to GB / T1040-2006 standard. Tests were conducted at a tensile speed of 50 mm / min. A total of 5 tests were performed, and the data were calculated as the average value.

[0076] Impact performance test: According to GB / T1843—2008, a cantilever beam pendulum impact test was used, with a V-shaped notch on the spline and a pendulum energy of 2.75 J. A total of five sets of splines were tested, and the data obtained were calculated as average values.

[0077] Limiting Oxygen Index (LOI) Test: The test is conducted according to the national standard GB / T2406.2-2009. The test specimen dimensions are 130 mm in length, 6.5 mm in width, and 3 mm in thickness. The limiting oxygen index refers to the minimum oxygen volume fraction concentration required for the specimen to burn in an N2 and O2 atmosphere.

[0078] Vertical burning test: The test was conducted according to the ASTM D3801 national standard. The test specimen was 130 mm long, 13 mm wide, and 3 mm thick. Based on the burning behavior of the specimen, the material was classified into three levels: V-0, V-1, and V-2 (V = vertical burning).

[0079] Table 1. Performance Comparison of PET Composite Materials

[0080] .

[0081] The high flame-retardant, high-strength PET composite material of this invention exhibits significantly higher oxygen index and vertical burning rating than common PET, substantially improving the flame-retardant properties and mechanical properties of PET. This further expands the application fields of flame-retardant PET. The added compound flame retardant possesses excellent high-temperature resistance and flame-retardant properties, further enhancing the flame-retardant performance of the composite material. The added fiber material further improves the toughness and tensile strength of the composite material, while the added antimony trioxide lowers the combustion temperature. The preparation method of this invention has advantages such as simple process, convenient operation, and easy industrial implementation.

Claims

1. A nitrogen-phosphorus high flame-retardant and high-strength PET composite material, characterized in that, The composite material is composed of the following components by weight: 100 parts PET granules, 5-25 parts thermoplastic polyester, 1-5 parts toughening agent, 0.1-0.5 parts antioxidant, 2-15 parts smoke suppressant, 15-25 parts compound flame retardant, and 5-30 parts fiber material. The compound flame retardant is composed of nitrogen-phosphorus macromolecular flame retardant and antimony trioxide. The toughening agent is polyolefin elastomer POE or glycidyl methacrylate GMA grafted polyolefin elastomer POE-g-GMA. The synthesis of nitrogen-phosphorus macromolecular flame retardants is as follows: (1) Synthesis of reactive nitrogen-phosphorus flame retardants Add 5.969 g of hexamethylenediamine and 200 ml of ethanol solution to a 500 ml Erlenmeyer flask. Place the Erlenmeyer flask in an ice bath at 0 °C and stir. When the temperature of the liquid in the Erlenmeyer flask drops to 0 °C and the hexamethylenediamine is completely dissolved in the ethanol solution, add 16.17 g of [(6-oxo-6H-dibenzo[C,E][1,2]oxophosphazenecyclo-6-yl)methyl]succinic acid and react in a water bath at 70 °C for 5 h. After the reaction is complete, cool to room temperature, filter the product using a Buchner funnel, wash the filter cake with 100 ml of ethanol to remove excess hexamethylenediamine, and dry it in a vacuum oven at 50 °C for 4 h. (2) Synthesis of nitrogen-phosphorus macromolecular flame retardants 31 g of terephthalic acid, 31 g of isophthalic acid, 18 g of ethylene glycol, 20 g of neopentyl glycol, 20 g of reactive nitrogen-phosphorus flame retardant, and 0.035 g of tetrabutyl titanate catalyst were added to a three-necked flask and stirred until homogeneous using a mechanical stirrer. A vacuum distillation apparatus was set up, and a thermometer was inserted at the top of the distillation column. Nitrogen was used to purge the air from the three-necked flask. The temperature was increased by 50°C per hour to 195°C using a stepwise heating method. By controlling the stirring rate at 120 r / min and preventing alcohol loss through the distillation column, the esterification rate was calculated to exceed 96% when the amount of distillate reached the theoretical value and the column top temperature dropped to 50-60°C. After the esterification reaction was completed, the distillation column was removed and replaced with a three-way valve. The residual water in the system was slowly evaporated using a water pump. Finally, a vacuum was slowly drawn using an oil pump to remove the residual water in the system again. The vacuum was then stopped, and 0.0035 g of catalyst was added. Tetrabutyl titanate; The temperature is increased in a stepwise manner, from 30°C to 250°C per hour, and a pre-condensation reaction is carried out for 30 minutes while maintaining a low vacuum. Finally, the temperature is increased to 260°C, and the reaction continues under a high vacuum of 100 Pa. When the system reaches a certain viscosity and the rod-climbing phenomenon occurs, the reaction ends. After purging with nitrogen, the material is discharged, placed in cold water, and then pelletized to obtain the final product.

2. The nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 1, characterized in that, The thermoplastic polyester is one or more of polybutylene terephthalate, polyarylate, and polyester elastomer TPEE.

3. The nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 1, characterized in that, The antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris[2,4-di-tert-butylphenyl]phosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

4. The nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 1, characterized in that, The smoke suppressant is one or more of molybdenum compounds, iron compounds, metal oxides, or zinc-magnesium complexes.

5. The nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 4, characterized in that, The molybdenum compound is molybdenum trioxide or ammonium octamolate, the iron compound is ferrocene, the metal oxide is one or more of magnesium oxide, zinc oxide, nickel oxide or zirconium oxide, and the magnesium-zinc complex is a complex of magnesium oxide and zinc oxide.

6. The nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 1, characterized in that, The fiber material is one or more of asbestos, glass fiber, or carbon fiber.

7. A method for preparing a nitrogen-phosphorus high flame-retardant and high-strength PET composite material as described in any one of claims 1-6, characterized in that, The preparation method steps are as follows: (1) Dry the PET granules thoroughly to ensure that the moisture content is less than 100 ppm; (2) Dry the compound flame retardant thoroughly to ensure that the moisture content is less than 100 ppm; (3) Pretreatment of fiber materials: First, prepare a polyacrylonitrile solution, then immerse the fiber material in the polyacrylonitrile solution, and then pre-oxidize the immersed fiber material in an oven at 50℃~300℃ for 0.1~100 hours and dry it to obtain surface-modified pretreated fiber material for later use; (4) Thoroughly mix PET granules, thermoplastic polyester, toughening agent, antioxidant, smoke suppressant, compound flame retardant and fiber material. The compound flame retardant is added from the fifth section side feed of the twin-screw extruder or from the main feed after being weighed by a loss-in-weight weigher. The PET granules and other ingredients are added from the main feed after being weighed by a loss-in-weight weigher. Then, the mixture is blended, extruded and granulated by the twin-screw extruder to obtain the PET composite material.

8. The method for preparing the nitrogen-phosphorus high flame-retardant and high-strength PET composite material according to claim 7, characterized in that: The extruder blending extrusion granulation process in step (4) is as follows: Zone 1 temperature 180±5℃, Zone 2 temperature 260±5℃, Zone 3 temperature 280±5℃, Zone 4 temperature 280±5℃, Zone 5 temperature 280±5℃, Zone 6 temperature 280±5℃, Zone 7 temperature 280±5℃, Zone 8 temperature 260±5℃, Zone 9 temperature 250±5℃, Die head temperature 270±5℃, and screw speed 360-400r / min.

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