High-temperature-resistant PP bar and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant PP bar and a preparation method thereof, and belongs to the technical field of polypropylene materials. The preparation method comprises the following steps: weighing 150-200 parts by weight of PP resin, 30-45 parts by weight of modified hollow glass beads, 2-5 parts by weight of a lubricant, 0.5-1.5 parts by weight of an ultraviolet light absorber and 0.01-0.1 part by weight of an initiator, uniformly mixing in a high-speed mixer, carrying out melt extrusion in a double-screw machine, cooling, shaping, and carrying out traction cutting to obtain the high-temperature-resistant PP bar. The modified hollow glass beads have good compatibility with PP resin and other raw materials, and have chemical action with the PP resin, so that the modified hollow glass beads containing POSS, phosphorus element, hindered phenol structure and hindered amine structure can be dispersed and stabilized in a PP bar, and play the role to the greatest extent, and the service life of the modified hollow glass beads is prolonged. And the high temperature resistance, flame retardance, oxidation resistance, mechanical properties and the like of the PP bar are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene materials, and specifically relates to a high-temperature resistant PP rod and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is a non-toxic, odorless, milky white highly crystalline polymer with a density of only 0.90 - 0.91 g / cm 3 , and it is one of the lightest varieties among all plastics currently. It is particularly stable in water, with a water absorption rate in water of only 0.01%. Its molecular weight is about 80,000 - 150,000. Its strength, stiffness, hardness, and heat resistance are all superior to low-pressure polyethylene, and it can be used at about 100°C. Polypropylene resin is one of the most widely used and largest-consumed organic synthetic high-molecular resins, and is widely used in fields such as electrical insulation switches, plastic encapsulation materials, electrical appliance shells, drinking water pipes, cable pipelines, sewage pipes, etc.

[0003] However, since polypropylene is a hydrocarbon-based high-molecular material, it is not resistant to high temperatures and is prone to softening and losing its original functions when heated. In addition, polypropylene materials are prone to aging under the action of light, heat, and oxygen during use, which not only reduces the aesthetics but also greatly limits its practical applications. At the same time, polypropylene is flammable, with an oxygen index of only about 18. When burning, it is accompanied by a melting drop phenomenon, which is likely to cause a fire and has certain potential safety hazards. Chinese Patent CN1872909A discloses a general high-temperature resistant polypropylene and a preparation method thereof. The components of the high-temperature resistant polypropylene include 67.9 - 85 parts by weight of copolymerized polypropylene, 2 - 10 parts of calcium carbonate, 30 - 40 parts of talcum powder, and 0.1 - 1 part of antioxidant. This invention improves the heat distortion temperature of the polypropylene material by modifying polypropylene with inorganic fillers, overcomes the defect of its easy heat deformation, but the dispersion degree of the inorganic powder is poor, and the high-temperature resistance performance of the polypropylene material still needs to be improved. At the same time, the flame retardancy and anti-aging properties also need to be improved.

[0004] Therefore, how to improve the high-temperature resistance performance of polypropylene rods and also have high flame retardancy and anti-aging properties has become an urgent problem to be solved in the development of such materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a high-temperature resistant PP rod and a preparation method thereof.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A high-temperature resistant PP rod, comprising the following raw materials in parts by weight: 150 - 200 parts of PP resin, 30 - 45 parts of modified hollow glass microspheres, 2 - 5 parts of lubricant, 0.5 - 1.5 parts of ultraviolet absorber, and 0.01 - 0.1 part of initiator.

[0007] Further, the modified hollow glass microspheres are prepared through the following steps: S1. Add 3,5 - di - tert - butyl - 4 - hydroxycinnamic acid, pentaerythritol phosphate ester, and 1,4 - dioxane into a sufficiently dried three - necked flask. After stirring evenly, slowly add concentrated sulfuric acid. After the addition, slowly raise the temperature to 110 °C and keep the reaction for 5 h. After the reaction is completed, first cool to room temperature, then add deionized water. After oscillation, let it stand for liquid - liquid separation until the pH of the aqueous phase is neutral. Take the organic phase, first dry it with anhydrous magnesium sulfate, then filter it. Distill the filtrate under reduced pressure and purify it by column chromatography (the eluent is a mixed solvent of cyclohexane and ethyl acetate, and the volume ratio of cyclohexane to ethyl acetate is 1:1). Finally, distill it under reduced pressure again to obtain intermediate 1. The dosage ratio of 3,5 - di - tert - butyl - 4 - hydroxycinnamic acid, pentaerythritol phosphate ester, concentrated sulfuric acid, and 1,4 - dioxane is 28 g:23 g:0.2 mL:240 mL; Under the heating condition and the catalytic condition of concentrated sulfuric acid, control the molar ratio of 3,5 - di - tert - butyl - 4 - hydroxycinnamic acid to pentaerythritol phosphate ester to be 1:1.2 - 1.3, then 3,5 - di - tert - butyl - 4 - hydroxycinnamic acid and pentaerythritol phosphate ester undergo an esterification reaction, and the reaction process is as follows:

[0008] S2. Add intermediate 1, 2,2,6,6 - tetramethyl - 4 - piperidinol, DBU (1,8 - diazabicyclo[5.4.0]undec - 7 - ene), and 1,4 - dioxane into a sufficiently dried three - necked flask. After stirring evenly, raise the temperature to 60 °C and react for 48 h. After the reaction is completed, first cool to room temperature, then distill it under reduced pressure and purify it by column chromatography (the eluent is a mixed solvent of chloroform and ether, and the volume ratio of chloroform to ether is 8:2). Finally, distill it under reduced pressure again to obtain intermediate 2. The dosage ratio of intermediate 1, 2,2,6,6 - tetramethyl - 4 - piperidinol, DBU, and 1,4 - dioxane is 39 g:16.4 g:0.4 mL:240 mL; Under the catalytic action of DBU, control the molar ratio of intermediate 1 to 2,2,6,6 - tetramethyl - 4 - piperidinol to be 1:1.1 - 1.2, then intermediate 1 and 2,2,6,6 - tetramethyl - 4 - piperidinol undergo a Michael addition reaction, and the reaction process is as follows:

[0009] S3. Purge the dry three-necked flask with nitrogen for 30 min to expel the air and moisture inside the flask. Then add octavinyl-POSS, 3-mercaptopropyltriethoxysilane, 2-tert-butylanthraquinone, and dimethyl sulfoxide. After mixing evenly and stirring until dissolved, irradiate it under a 365 nm ultraviolet lamp for 0.5 h under nitrogen protection. After the irradiation ends, perform vacuum distillation to obtain intermediate 3. The dosage ratio of octavinyl-POSS, 3-mercaptopropyltriethoxysilane, 2-tert-butylanthraquinone, and dimethyl sulfoxide is 50 g: 21 mL: 0.06 g: 200 mL; Under the action of ultraviolet irradiation and the photoinitiator 2-tert-butylanthraquinone, control the molar ratio of octavinyl-POSS and 3-mercaptopropyltriethoxysilane to be 1: 1.05 - 1.15, then the thiol-ene click reaction occurs between octavinyl-POSS and 3-mercaptopropyltriethoxysilane, and the reaction process is as follows:

[0010] S4. Purge the dry three-necked flask with nitrogen for 30 min to expel the air and moisture inside the flask. Then add intermediate 2, intermediate 3, titanium tetraisopropoxide, and dimethyl sulfoxide. After stirring evenly, heat up to 90 °C and keep the temperature for reaction for 26 h. After the reaction ends, cool to room temperature, perform vacuum distillation, and purify by column chromatography (select a mixed solvent of benzene and methanol as the eluent, and the volume ratio of benzene to methanol is 9:1). Finally, perform vacuum distillation to remove the eluent to obtain intermediate 4. The dosage ratio of intermediate 2, intermediate 3, titanium tetraisopropoxide, and dimethyl sulfoxide is 30 g: 47 g: 0.5 mL: 250 mL; Control the molar ratio of intermediate 2 and intermediate 3 to be 1: 1.05 - 1.1. Intermediate 2 and intermediate 3 undergo the following chemical reaction under the catalysis of titanium tetraisopropoxide, and the reaction process is as follows:

[0011] S5. Add hollow glass microspheres and absolute ethanol to a three-necked flask. After stirring evenly, add acetic acid to adjust the pH to 4. Under nitrogen protection, disperse intermediate 4 in DMF (N,N-dimethylformamide), stir until dissolved, then transfer it into the above three-necked flask. After the transfer is completed, stir and heat up to 65 °C, keep the temperature for reaction for 1 h. After the reaction ends, cool to room temperature, centrifuge, take the precipitate, ultrasonically disperse it in DMF, and finally dry it at 110 °C for 12 h to obtain modified hollow glass microspheres. The mass ratio of hollow glass microspheres to intermediate 4 is 4:1.

[0012] The main component of the hollow glass microspheres is borosilicate, and the surface is rich in silanol groups. While intermediate 4 contains silaneoxy groups on the surface. Under acidic conditions, the silaneoxy groups will hydrolyze to form silanol groups, which can form chemical bonds with the hydroxyl groups on the surface of the hollow glass microspheres, thereby preparing the modified hollow glass microspheres.

[0013] The modified hollow glass microspheres contain cage-like polyhedral oligomeric silsesquioxane (POSS). The POSS framework has a regular cage structure, with a silicon-oxygen framework structure, which has a certain rigidity, relatively high thermal stability and mechanical properties. When heated, it will form a more dense and stable protective layer containing Si-O bonds and Si-C bonds than the conventional carbon layer, isolating the heat transfer and the escape of combustibles generated by the decomposition of polymer materials. At the same time, it blocks the supply of oxygen, enhancing the flame retardancy, heat resistance and mechanical properties of the polymer materials. At the same time, the modified glass microspheres also contain the halogen-free flame retardant element phosphorus. The phosphorus-containing flame retardants coexist and interact with the gas-phase and condensed-phase flame retardant mechanisms, thus exerting the flame retardant effect. Therefore, adding the modified hollow glass microspheres containing POSS and phosphorus can effectively improve the flame retardancy, heat resistance and mechanical properties of PP rods.

[0014] In addition, the modified hollow glass microspheres also contain hindered phenols and hindered amines. Among them, the hindered phenols can provide active hydrogen atoms to capture peroxy radicals, enhancing the antioxidant performance of the modified hollow glass microspheres. The hindered amines are a class of organic amine compounds with steric hindrance, which have a good inhibitory effect on the photo-oxidative degradation reaction of polymer materials. Acting synergistically with ultraviolet absorbers can effectively protect PP rods from ultraviolet damage. Therefore, adding the modified hollow glass microspheres containing hindered phenols and hindered amines can effectively improve the antioxidant performance and anti-ultraviolet performance of PP rods.

[0015] The main component of the hollow glass microspheres in the modified hollow glass microspheres is borosilicate, which has the advantages of light weight, low thermal conductivity, high strength and good chemical stability. The modified hollow glass microspheres prepared by the present invention have lipophilic ester groups, heterocycles, benzene rings, etc. on the surface, which makes the modified hollow glass microspheres very easy to disperse in organic materials such as PP resin. In addition, the surface of the modified hollow glass microspheres contains abundant terminal carbon-carbon double bonds, which can chemically react with the unreacted carbon-carbon double bonds at the end of the PP resin under the action of an initiator. Furthermore, the modified hollow glass microspheres can be further dispersed and stabilized in the PP resin, thus effectively improving the high-temperature resistance, flame retardancy, antioxidant performance and mechanical properties of PP rods.

[0016] Further, the lubricant is one or more of calcium stearate, magnesium stearate, zinc stearate, and polyethylene wax.

[0017] Further, the ultraviolet absorber is one or more of ultraviolet absorber UV-P, ultraviolet absorber UV-531, ultraviolet absorber UVP-327, and ultraviolet absorber UV-9.

[0018] Further, the initiator is one or more of dicumyl peroxide, azobisisobutyronitrile, and 2,3-dimethyl-2,3-diphenylbutane.

[0019] A preparation method of a high-temperature resistant PP rod, comprising the following steps: Weigh each raw material by weight parts and place them in a high-speed mixer to mix evenly, then place them in a twin-screw extruder for melt extrusion, and then cool, shape, draw and cut to obtain the high-temperature resistant PP rod.

[0020] Advantages of the present invention: The modified hollow glass microspheres of the present invention have good compatibility with raw materials such as PP resin, and there is a chemical interaction with the PP resin. Therefore, the modified hollow glass microspheres containing POSS, phosphorus element, hindered phenol structure and hindered amine structure can be dispersed and stabilized in the PP rod, maximizing their own functions, and effectively improving the high-temperature resistance, flame retardancy, antioxidant performance and mechanical properties of the PP rod, etc. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0022] Example 1, preparation of modified hollow glass microspheres, the specific steps are as follows: S1. Add 28 g of 3,5-di-tert-butyl-4-hydroxycinnamic acid, 23 g of pentaerythritol phosphate and 240 mL of 1,4-dioxane into a 500 mL fully dried three-necked flask, stir evenly, then slowly add 0.2 mL of concentrated sulfuric acid. After adding, slowly raise the temperature to 110 °C, keep the temperature for reaction for 5 h. After the reaction is completed, first cool to room temperature, then add deionized water, shake and let it stand for stratification until the pH of the aqueous phase is neutral. Take the organic phase, first dry it with anhydrous magnesium sulfate, then filter, distill the filtrate under reduced pressure, and purify it by column chromatography (the eluent is a mixed solvent of cyclohexane and ethyl acetate, and the volume ratio of cyclohexane to ethyl acetate is 1:1). Finally, distill under reduced pressure again to obtain intermediate 1; S2. Add 39 g of intermediate 1, 16.4 g of 2,2,6,6-tetramethyl-4-piperidinol, 0.4 mL of DBU and 240 mL of 1,4-dioxane into a 500 mL fully dried three-necked flask, stir evenly, then raise the temperature to 60 °C for reaction for 48 h. After the reaction is completed, first cool to room temperature, then distill under reduced pressure, and purify it by column chromatography (the eluent is a mixed solvent of chloroform and ether, and the volume ratio of chloroform to ether is 8:2). Finally, distill under reduced pressure again to obtain intermediate 2; S3. Flush a 500 mL dry three-necked flask with nitrogen for 30 min to expel the air and moisture inside the flask. Then add 50 g of octavinyl-POSS, 21 mL of 3-mercaptopropyltriethoxysilane, 0.06 g of 2-tert-butylanthraquinone, and 200 mL of dimethyl sulfoxide. After mixing evenly and stirring until dissolved, irradiate it under a 365 nm ultraviolet lamp for 0.5 h under nitrogen protection. After the irradiation, perform vacuum distillation to obtain intermediate 3; S4. Flush a 500 mL dry three-necked flask with nitrogen for 30 min to expel the air and moisture inside the flask. Then add 30 g of intermediate 2, 47 g of intermediate 3, 0.5 mL of tetra-isopropyl titanate, and 250 mL of dimethyl sulfoxide. After stirring evenly, heat up to 90 °C and keep the temperature for 26 h. After the reaction, cool to room temperature and perform vacuum distillation. Purify by column chromatography (select a mixed solvent of benzene and methanol as the eluent, and the volume ratio of benzene to methanol is 9:1). Finally, perform vacuum distillation to remove the eluent to obtain intermediate 4; S5. Add 28 g of hollow glass microspheres and 250 mL of absolute ethanol to a 500 mL three-necked flask. After stirring evenly, add acetic acid to adjust the pH to 4. Under nitrogen protection, disperse 7 g of intermediate 4 in 25 mL of DMF. After stirring until dissolved, transfer it to the above three-necked flask. After the transfer, stir and heat up to 65 °C and keep the temperature for 1 h. After the reaction, cool to room temperature, centrifuge, take the precipitate, ultrasonically disperse it in DMF, and finally dry it at 110 °C for 12 h to obtain modified hollow glass microspheres.

[0023] Example 2. To prepare a PP rod, the specific steps are as follows: Weigh 150 parts of PP resin, 30 parts of the modified hollow glass microspheres prepared in Example 1, 2 parts of calcium stearate, 0.5 part of ultraviolet absorber UV-P, and 0.01 part of azobisisobutyronitrile by weight and place them in a high-speed mixer to mix evenly. Then place them in a twin-screw extruder for melt extrusion, and then cool, shape, and cut by traction to obtain a PP rod.

[0024] Example 3. To prepare a PP rod, the specific steps are as follows: Weigh 180 parts of PP resin, 40 parts of the modified hollow glass microspheres prepared in Example 1, 2 parts of calcium stearate, 1 part of magnesium stearate, 0.5 part of ultraviolet absorber UV-531, 0.5 part of ultraviolet absorber UVP-327, and 0.05 part of 2,3-dimethyl-2,3-diphenylbutane by weight and place them in a high-speed mixer to mix evenly. Then place them in a twin-screw extruder for melt extrusion, and then cool, shape, and cut by traction to obtain a PP rod.

[0025] Example 4. To prepare a PP rod, the specific steps are as follows: Weigh 200 parts of PP resin, 45 parts of the modified hollow glass microspheres prepared in Example 1, 3 parts of zinc stearate, 2 parts of polyethylene wax, 1 part of ultraviolet absorber UVP-327, 0.5 part of ultraviolet absorber UV-9, and 0.1 part of dicumyl peroxide, and place them in a high-speed mixer to mix evenly. Then, place them in a twin-screw extruder for melt extrusion, followed by cooling and shaping, and traction cutting to obtain PP rods.

[0026] Comparative Example 1, preparing PP rods, the specific steps are as follows: Keep the remaining steps unchanged, and only replace the modified hollow glass microspheres in Example 2 with hollow glass microspheres without any treatment to prepare PP rods.

[0027] Comparative Example 2, preparing PP rods, the specific steps are as follows: Keep the remaining steps unchanged, and only replace the modified hollow glass microspheres in Example 2 with 24 parts of hollow glass microspheres without any treatment, 2 parts of flame retardant poly(silsesquioxane), 2 parts of flame retardant FRC-2, 1 part of antioxidant 1010, and 1 part of light stabilizer 622 to prepare PP rods.

[0028] Comparative Example 3, preparing PP rods, the specific steps are as follows: Keep the remaining steps unchanged, and only remove the modified hollow glass microspheres in Example 2 to prepare PP rods.

[0029] Make specimens from the PP rods prepared in Examples 2-4 and Comparative Examples 1-3 according to the corresponding standards, and conduct the following performance tests: Tensile strength test: The tensile strength test standard is in accordance with GB / T 1040.1-2018; Anti-aging performance test: After making standard specimens from the PP rods prepared in Examples 2-4 and Comparative Examples 1-3, place them in a dry heat and ultraviolet aging chamber for 120 h of aging respectively, and measure the tensile strength retention rate of the specimens before and after aging (the tensile strength test standard is in accordance with GB / T 1040.1-2018, tensile strength retention rate = (tensile strength after aging / initial tensile strength) × 100%). The test conditions are as follows: dry heat aging at 105 °C for 120 h; ultraviolet aging under a 30 W ultraviolet lamp at room temperature with a vertical irradiation distance of 20 cm for 120 h; Heat resistance test: According to the standard GB / T 1634, test the heat distortion temperature of the material. The specimen size is 80 × 10 × 4 mm, the specimen is placed flat, and the load is 0.45 MPa; Flame retardant performance test: According to the standard GB / T 2406.2-2009, test the oxygen index of the material; The test results of all items are shown in the following table:

[0030] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0031] The above content is only an example and illustration of the present invention. Those skilled in the art to which the present technology pertains may make various modifications or supplements to the described specific embodiments or use similar ways to substitute them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A high temperature resistant PP rod, characterized in that: The invention comprises the following raw materials in parts by weight: 150-200 parts of PP resin, 30-45 parts of modified hollow glass microspheres, 2-5 parts of lubricant, 0.5-1.5 parts of ultraviolet absorber, and 0.01-0.1 parts of initiator; Wherein, the modified hollow glass microspheres are prepared by the following steps: S1. Add 3,5-di-tert-butyl-4-hydroxycinnamic acid, pentaerythritol phosphate and 1,4-dioxane into a flask, add concentrated sulfuric acid after stirring, heat to 110°C for reaction for 5 hours, cool to room temperature, add deionized water, stand for stratification until the pH of the aqueous phase is neutral, take the organic phase, dry it, filter it, distill the filtrate under reduced pressure, purify it by column chromatography, and distill it under reduced pressure to obtain intermediate 1; S2, adding intermediate 1, 2,2,6,6-tetramethyl-4-piperidinol, DBU and 1,4-dioxane into a flask, stirring and heating to 60°C for 48 hours, cooling to room temperature, distilling under reduced pressure, purifying by column chromatography, and distilling under reduced pressure to obtain intermediate 2; S3, nitrogen was blown into the flask, octavinyl-POSS, 3-mercaptopropyltriethoxysilane, 2-tert-butylanthraquinone and dimethyl sulfoxide were added, stirred, irradiated under a 365 nm ultraviolet lamp for 0.5 h under nitrogen protection, and distilled under reduced pressure to obtain intermediate 3; S4, nitrogen purged the flask, added intermediate 2, intermediate 3, tetraisopropyl titanate and dimethyl sulfoxide, stirred and heated to 90°C for 26 hours, cooled to room temperature, distilled under reduced pressure, purified by column chromatography, and distilled under reduced pressure to obtain intermediate 4; S5. Add hollow glass microspheres and anhydrous ethanol into a flask, stir and then add acetic acid to adjust the pH to 4; disperse the intermediate 4 in DMF under nitrogen protection, stir and then transfer to the above flask, heat to 65°C for reaction for 1 hour, cool to room temperature, centrifuge, take the precipitate and ultrasonically disperse it in DMF, dry at 110°C for 12 hours to obtain modified hollow glass microspheres.

2. A high temperature resistant PP rod according to claim 1, characterized in that: The usage ratio of 3,5-di-tert-butyl-4-hydroxycinnamic acid, pentaerythritol phosphate, concentrated sulfuric acid and 1,4-dioxane in step S1 is 28 g:23 g:0.2 mL:240 mL.

3. A high temperature resistant PP rod according to claim 1, characterized in that: The usage ratio of the intermediate 1, 2,2,6,6-tetramethyl-4-piperidinol, DBU and 1,4-dioxane in step S2 is 39 g:16.4 g:0.4 mL:240 mL.

4. A high temperature resistant PP rod according to claim 1, characterized in that: The usage ratio of octavinyl-POSS, 3-mercaptopropyltriethoxysilane, 2-tert-butylanthraquinone and dimethyl sulfoxide in step S3 is 50 g:21 mL:0.06 g:200 mL.

5. The high temperature resistant PP rod according to claim 1, characterized in that: The usage ratio of intermediate 2, intermediate 3, tetraisopropyl titanate and dimethyl sulfoxide in step S4 is 30 g:47 g:0.5 mL:250 mL.

6. The high temperature resistant PP rod according to claim 1, characterized in that: The mass ratio of the hollow glass microspheres in step S5 to the intermediate 4 is 4:

1.

7. The high temperature resistant PP rod according to claim 1, characterized in that: The lubricant is one or more of calcium stearate, magnesium stearate, zinc stearate and polyethylene wax.

8. The high temperature resistant PP rod according to claim 1, characterized in that: The ultraviolet absorber is one or more of the ultraviolet absorber UV-P, ultraviolet absorber UV-531, ultraviolet absorber UVP-327, and ultraviolet absorber UV-9.

9. The high temperature resistant PP rod according to claim 1, characterized in that: The initiator is one or more of dicumyl peroxide, azobisisobutyronitrile and 2,3-dimethyl-2,3-diphenylbutane.

10. A method for preparing a high temperature resistant PP rod, applied to a high temperature resistant PP rod according to any one of claims 1 to 9, characterized in that: The following steps are involved: The raw materials are weighed by weight and mixed evenly in a high-speed mixer, then melt-extruded in a twin-screw machine, cooled to shape, and pulled and cut to obtain high-temperature resistant PP rods.

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