PP pipe and preparation method thereof

Abstract

The invention belongs to the technical field of pipes, and particularly relates to a PP pipe and a preparation method thereof. The pipe is prepared from the following raw materials in parts by mass: 70-90 parts of polypropylene resin, 5-10 parts of modified aramid fiber, 2-5 parts of nano titanium dioxide, 1-5 parts of polybutadiene, 0.5-2 parts of an antioxidant, 0.5-1 part of a lubricant and 0.2-0.8 part of a coupling agent. The PP pipe prepared by the invention has excellent tensile strength, impact strength and other mechanical properties, and also has good thermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of pipes, and in particular relates to a PP pipe and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is a low-cost, high-performance polymer material with excellent corrosion resistance and good mechanical properties. Therefore, it has been greatly developed in the fields of new building pipelines and industrial pipelines. However, PP has poor impact resistance and low toughness, which limits its application in the field of pipes.

[0003] A Chinese patent application document with publication number CN113372651A discloses a high-strength and high-toughness polypropylene injection molding compound; the polypropylene injection molding compound comprises the following mass fractions of raw material polypropylene: 50-70 parts, inorganic whiskers: 10-40 parts, fluorine-containing polymer: 10-30 parts, ultrafine wollastonite: 10-20 parts, toughening agent: 10-30 parts, and antioxidant: 1-5 parts; the application document uses inorganic whiskers and fluorine-containing compounds to increase the strength of polypropylene, uses toughening agent acrylonitrile-butadiene-styrene copolymer to increase the toughness of polypropylene injection molding compound, and uses ultrafine wollastonite and antioxidant to obtain a polypropylene injection molding compound with high strength and high toughness, and good antioxidant properties.

[0004] However, the polypropylene injection molding material includes a large amount of ultrafine wollastonite and inorganic whiskers, which are easy to agglomerate in polypropylene and have poor dispersion. Therefore, the toughening modification effect cannot meet the high performance requirements of PP. Summary of the invention

[0005] The existing PP pipe has the problem of unsatisfactory toughening effect; in order to solve this problem, the present invention provides a PP pipe and a preparation method thereof.

[0006] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a PP pipe, wherein the pipe is made of the following raw materials in parts by weight: 70-90 parts of polypropylene resin, 5-10 parts of modified aramid fiber, 2-5 parts of nano titanium dioxide, 1-5 parts of polybutadiene, 0.5-2 parts of antioxidant, 0.5-1 parts of lubricant, and 0.2-0.8 parts of coupling agent.

[0007] Preferably, the method for preparing the modified aramid fiber comprises the following steps: (1) subjecting the aramid fiber to ultrasonic treatment with an acetone aqueous solution having a mass fraction of 60% to 80%, washing, drying and setting aside; (2) mixing the aramid fiber obtained in step (1) with a 1% to 3% by mass aqueous solution of hexadecyltrimethylammonium bromide, washing, drying and setting aside; (3) Evenly mixing the nucleating agent and anhydrous ethanol to obtain a nucleating agent suspension; (4) The aramid fiber obtained in step (2) is evenly mixed with the nucleating agent suspension, washed, and dried to obtain modified aramid fiber.

[0008] Preferably, in step (1), the ratio of aramid fiber to acetone aqueous solution is 1 g: 300-450 mL; the temperature of ultrasonic treatment is 20-30° C., and the time of ultrasonic treatment is 2-4 h.

[0009] Preferably, in step (1), the aramid fiber is selected from one or more of poly(p-phenylene terephthalamide) fiber, poly(m-phenylene isophthalamide) fiber and poly(p-phenylene terephthalamide) fiber.

[0010] Preferably, in step (2), the mass ratio of the aramid fiber to the aqueous solution of hexadecyltrimethylammonium bromide is 1:(10-40); the mixing temperature is 40-60° C., and the mixing time is 1-4 h.

[0011] Preferably, in step (3), the ratio of the nucleating agent to anhydrous ethanol is 1 g: 0.5-4 L.

[0012] Preferably, in step (3), the method for preparing the nucleating agent comprises the following steps: The 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid is uniformly mixed with an ethanol aqueous solution with a mass fraction of 30%-50%, the pH is adjusted to 5-7, and then scandium nitrate is added, the temperature is increased for reaction, and the solution is cooled, washed, and dried to obtain a nucleating agent.

[0013] Preferably, the molar ratio of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid to scandium nitrate is (3-4.5):1.

[0014] By adopting the above technical solution, under this ratio, the coordination environment around the scandium ions is relatively simple, which is conducive to forming a stable structure.

[0015] Preferably, the reaction temperature is 60°C-80°C, and the reaction time is 8-14h.

[0016] Preferably, the mass ratio of the aramid fiber to the nucleating agent is 1:(0.4-0.8).

[0017] By adopting the above technical solution, within the ratio range, the toughness and impact resistance of the pipe are optimized, and excessive crystallization that causes the material to become brittle can be avoided.

[0018] In a second aspect, the present invention provides a method for preparing the above-mentioned PP pipe, comprising the following steps: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer and stir evenly, transfer to a twin-screw extruder for melting, extrusion and drying to obtain pellets; S2: Add the pellets into a single screw extruder for extrusion to obtain a PP pipe.

[0019] Preferably, in step S1, the stirring speed is 350-550 r / min, and the stirring time is 5-10 min; the temperatures of the four sections of the twin-screw extruder are 185-190°C, 190-195°C, 195-200°C and 190-195°C respectively.

[0020] By adopting the above technical solution, the nucleating agent can better play its role within this temperature range; if the temperature is too low, the fluidity of PP is poor, the nucleating agent is difficult to disperse evenly, and it is not conducive to nucleation; and if the temperature is too high, it may cause the β-crystal of PP to transform into the α-crystal.

[0021] In summary, the beneficial effects of the present invention are: (1) The present invention tightly combines the nucleating agent with the aramid fiber through the effect of electrostatic adsorption; the electrostatic adsorption between the two can form a relatively strong bond between the nucleating agent and the aramid fiber, which helps to improve the mechanical properties of PP; at the same time, the interaction between the two is conducive to the uniform dispersion of the nucleating agent on the surface of the aramid fiber to avoid agglomeration; (2) The present invention prepares a rare earth carboxylate nucleating agent, which helps to improve the crystallinity and crystallization rate of polypropylene, refine the crystal size, effectively prevent crack propagation, and cooperate with aramid fiber to improve the toughness and impact resistance of PP; (3) The PP pipe prepared by the present invention with polypropylene resin and modified aramid fiber as main components and compounded with polybutadiene, nano-titanium dioxide and other components has excellent mechanical properties such as tensile strength and impact strength, and also has good thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a scanning electron microscope image of the poly(p-phenylene terephthalamide) fiber in Example 1; Figure 2 is a scanning electron microscope image of the modified aramid fiber in Example 1; Figure 3 This is the infrared spectrum of the modified aramid fiber in Example 1. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is explained in detail below with reference to several representative embodiments of the present invention.

[0024] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0025] In the present invention, the antioxidant can be selected from commonly used antioxidants without special restrictions. In the following embodiments, the antioxidant is 2,2-methylene-bis(4-methyl-6-tert-butylphenol); in the present invention, the lubricant can be selected from commonly used lubricants without special restrictions. In the following embodiments, the lubricant is polyethylene wax; in the present invention, the coupling agent can be selected from commonly used coupling agents without special restrictions. In the following embodiments, the coupling agent is isopropyl tri(isostearoyl) titanate.

[0026] The average diameter of the aramid fibers in the following examples is 5 μm, and the average length is 2 mm.

[0027] In the following examples, the average particle size of nano-titanium dioxide is 80 nm.

[0028] Example 1 A PP pipe in this embodiment is made of the following raw materials in parts by weight: 85kg of polypropylene resin, 6kg of modified aramid fiber, 5kg of nano titanium dioxide, 3kg of polybutadiene, 1.5kg of antioxidant, 1kg of lubricant, and 0.5kg of coupling agent.

[0029] The preparation method of the modified aramid fiber of this embodiment comprises the following specific steps: (1) Add 10 g of poly(p-phenylene terephthalamide) fiber and 3 L of 70% acetone aqueous solution into a beaker, ultrasonically treat at 20 °C for 3 h, wash with water 10 times, dry at 80 °C for 12 h, and set aside; (2) 8 g of the poly(p-phenylene terephthalamide) fiber prepared in step (1) and 200 g of a 2% by mass aqueous solution of hexadecyltrimethylammonium bromide were added to a beaker, stirred at 50° C. for 3 h, washed with water 10 times, dried at 80° C. for 12 h, and set aside; (3) Add 3 g of nucleating agent and 9 L of anhydrous ethanol into a three-necked flask and stir for 45 min to obtain a nucleating agent suspension; (4) 5 g of the poly(p-phenylene terephthalamide) fiber prepared in step (2) was stirred with the nucleating agent suspension for 2 h, washed with water 10 times, and dried at 65° C. for 12 h to obtain modified aramid fiber; The scanning electron microscope image of poly(p-phenylene terephthalamide) fiber is shown in Figure 1 , the scanning electron microscope image of the modified aramid fiber is shown in Figure 2 ; Figure 3 is the infrared spectrum of modified aramid fiber. Figure 3It can be seen that 3207, 1687, 1246, 1021, 719 cm -1 The characteristic absorption peaks of the amide bond and benzene ring of poly(p-phenylene terephthalamide) fiber are at 1541 cm -1 The absorption peak of the C=N bond on the pyridine ring in the nucleating agent is 1450-1610 cm -1 The absorption peaks in the range are the vibration peaks of the benzene ring skeleton, 964-1264cm -1 The absorption peaks in the range are the in-plane bending vibration peaks of the CH bonds on the benzene ring, 648-833cm -1 The absorption peak in the range is the out-of-plane bending vibration peak of the CH bond on the benzene ring, at 558 cm -1 is the stretching vibration peak of Sc-O; Figure 1 , Figure 2 and Figure 3 It can be seen that the nucleating agent is successfully electrostatically adsorbed on the poly(p-phenylene terephthalamide) fiber.

[0030] The preparation method of the nucleating agent of this embodiment comprises the following specific steps: Add 114.88g of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid and 1L of 50% ethanol aqueous solution into a three-necked flask, stir for 10 minutes, adjust the pH to 7, then add 10.8g of scandium nitrate, heat to 60°C to react for 10 hours, cool, wash with water 3 times, and dry at 65°C for 8 hours to obtain a nucleating agent.

[0031] The preparation method of a PP pipe in this embodiment comprises the following specific steps: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer, stir at a stirring speed of 500r / min for 8min, transfer to a twin-screw extruder for melting, extrusion and drying to obtain pellets; the four-stage temperatures of the twin-screw extruder are 185℃, 192℃, 195℃ and 190℃ respectively; S2: Add the pellets into a single screw extruder and extrude at 195°C to obtain a PP pipe.

[0032] Example 2 A PP pipe in this embodiment is made of the following raw materials in parts by weight: 75kg polypropylene resin, 8kg modified aramid fiber, 5kg nano titanium dioxide, 1kg polybutadiene, 0.5kg antioxidant, 0.8kg lubricant, and 0.2kg coupling agent.

[0033] The preparation method of the modified aramid fiber of this embodiment comprises the following specific steps: (1) Add 10 g of poly(p-phenylene terephthalamide) fiber and 4 L of 80% acetone aqueous solution into a beaker, ultrasonically treat at 25 °C for 4 h, wash with water 10 times, dry at 80 °C for 12 h, and set aside; (2) 8 g of the poly(p-phenylene terephthalamide) fiber prepared in step (1) and 150 g of a 3% by mass aqueous solution of hexadecyltrimethylammonium bromide were added to a beaker, stirred at 400° C. for 4 h, washed with water 10 times, dried at 80° C. for 12 h, and set aside; (3) Add 2 g of nucleating agent and 8 L of anhydrous ethanol into a three-necked flask and stir for 45 min to obtain a nucleating agent suspension; (4) 5 g of the poly(p-phenylene terephthalamide) fiber prepared in step (2) was stirred with the nucleating agent suspension for 2 h, washed with water 10 times, and dried at 65° C. for 12 h to obtain modified aramid fiber.

[0034] The preparation method of the nucleating agent of this embodiment comprises the following specific steps: Add 86.17g of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid and 1L of 30% ethanol aqueous solution into a three-necked flask, stir for 10 minutes, adjust the pH to 7, then add 10.8g of scandium nitrate, heat to 70°C and react for 14 hours, cool, wash with water 3 times, and dry at 65°C for 8 hours to obtain a nucleating agent.

[0035] The preparation method of a PP pipe in this embodiment comprises the following specific steps: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer, stir at a stirring speed of 350r / min for 5 minutes, transfer to a twin-screw extruder for melting, extrusion, and drying to obtain pellets; the four-stage temperatures of the twin-screw extruder are 187°C, 195°C, 198°C and 192°C respectively; S2: Add the pellets into a single screw extruder and extrude at 195°C to obtain a PP pipe.

[0036] Example 3 A PP pipe in this embodiment is made of the following raw materials in parts by weight: 90kg polypropylene resin, 5kg modified aramid fiber, 3kg nano titanium dioxide, 2kg polybutadiene, 2kg antioxidant, 0.8kg lubricant, and 0.8kg coupling agent.

[0037] The preparation method of the modified aramid fiber of this embodiment comprises the following specific steps: (1) Add 10 g of poly(m-phenylene isophthalamide) and 4.5 L of 60% acetone aqueous solution into a beaker, ultrasonically treat at 25 °C for 2 h, wash with water 10 times, dry at 80 °C for 12 h, and set aside; (2) 8 g of the poly(m-phenylene isophthalamide) fiber prepared in step (1) and 320 g of a 1% by mass aqueous solution of hexadecyltrimethylammonium bromide were added to a beaker, stirred at 60° C. for 4 h, washed with water 10 times, dried at 80° C. for 12 h, and set aside; (3) Add 2 g of nucleating agent and 1 L of anhydrous ethanol into a three-necked flask and stir for 45 min to obtain a nucleating agent suspension; (4) 5 g of the poly(m-phenylene isophthalamide) fiber prepared in step (2) was stirred with the nucleating agent suspension for 2 h, washed with water 10 times, and dried at 65° C. for 12 h to obtain modified aramid fiber.

[0038] The preparation method of the nucleating agent of this embodiment comprises the following specific steps: Add 129.2g of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid and 1L of 40% ethanol aqueous solution into a three-necked flask, stir for 10 minutes, adjust the pH to 6, then add 10.8g of scandium nitrate, heat to 80°C and react for 8h, cool, wash with water 3 times, and dry at 65°C for 8h to obtain a nucleating agent.

[0039] The preparation method of a PP pipe in this embodiment comprises the following specific steps: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer, stir at a stirring speed of 550r / min for 6min, transfer to a twin-screw extruder for melting, extrusion and drying to obtain pellets; the four-stage temperatures of the twin-screw extruder are 190℃, 193℃, 200℃ and 195℃ respectively; S2: Add the pellets into a single screw extruder and extrude at 195°C to obtain a PP pipe.

[0040] Example 4 A PP pipe in this embodiment is made of the following raw materials in parts by weight: 70kg polypropylene resin, 10kg modified aramid fiber, 2kg nano titanium dioxide, 2kg polybutadiene, 1kg antioxidant, 0.5kg lubricant, and 0.5kg coupling agent.

[0041] The preparation method of the modified aramid fiber of this embodiment comprises the following specific steps: (1) Add 10 g of poly(p-phenylene amide) fiber and 3.5 L of 65% acetone aqueous solution into a beaker, ultrasonically treat at 30 °C for 2 h, wash with water 10 times, and dry at 80 °C for 12 h for later use; (2) 8 g of the poly(p-phenylene amide) fiber obtained in step (1) and 80 g of a 2.5% by mass aqueous solution of hexadecyltrimethylammonium bromide were added to a beaker, stirred at 50° C. for 1 h, washed with water 10 times, dried at 80° C. for 12 h, and set aside; (3) Add 4 g of nucleating agent and 6 L of anhydrous ethanol into a three-necked flask and stir for 45 min to obtain a nucleating agent suspension; (4) 5 g of the poly(p-phenylene amide) fiber obtained in step (2) was stirred with the nucleating agent suspension for 2 h, washed with water 10 times, and dried at 65° C. for 12 h to obtain modified aramid fiber.

[0042] The preparation method of the nucleating agent of this embodiment comprises the following specific steps: Add 100.53g of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid and 1L of 40% ethanol aqueous solution into a three-necked flask, stir for 10 minutes, adjust the pH to 5, then add 10.8g of scandium nitrate, heat to 80°C, react for 12 hours, cool, wash with water 3 times, and dry at 65°C for 8 hours to obtain a nucleating agent.

[0043] The preparation method of a PP pipe in this embodiment comprises the following specific steps: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer, stir at a stirring speed of 450r / min for 10min, transfer to a twin-screw extruder for melting, extrusion and drying to obtain pellets; the four-stage temperatures of the twin-screw extruder are 190℃, 195℃, 200℃ and 195℃ respectively; S2: Add the pellets into a single screw extruder and extrude at 195°C to obtain a PP pipe.

[0044] Comparative Example 1 Compared with Example 1, the difference is that the amount of polybutadiene used in this comparative example is adjusted, as shown in Table 1 for details.

[0045] Table 1 Amount of polybutadiene

[0046] Comparative Example 2 Compared with Example 1, the difference is that the amount of nano titanium dioxide is adjusted in this comparative example, as shown in Table 2 for details.

[0047] Table 2 Amount of nano titanium dioxide

[0048] Comparative Example 3 Compared with Example 1, the difference is that the amount of modified aramid fiber is adjusted in this comparative example, as shown in Table 3 for details.

[0049] Table 3 Dosage of modified aramid fiber

[0050] Comparative Example 4 Compared with Example 1, the difference is that in the preparation method of the nucleating agent in this comparative example, the molar ratio of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid to scandium nitrate is 1:1.

[0051] Comparative Example 5 Compared with Example 1, the difference is that the PP pipe of this comparative example is made of the following raw materials in parts by weight: 85 kg of polypropylene resin, 5.5 kg of poly(p-phenylene terephthalamide) fiber, 0.5 kg of nucleating agent, 5 kg of nano-titanium dioxide, 3 kg of polybutadiene, 1.5 kg of antioxidant, 1 kg of lubricant, and 0.5 kg of coupling agent.

[0052] Related tests The pipes prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to relevant tests, and the test results are shown in Table 4.

[0053] Table 4 Test results

[0054] By comparing Comparative Example 1 with Example 1, it can be seen that the toughness of the pipe with the addition of polybutadiene is improved; polybutadiene can absorb and buffer impact energy and improve toughness; excessive addition of polybutadiene can easily interfere with the crystallization process of polypropylene, affect the growth of β-crystal, cause crystal structure defects, and affect the performance of the pipe.

[0055] From the comparison between Comparative Example 2 and Example 1, it can be seen that nano-titanium dioxide can synergistically act with the nucleating agent to improve the nucleation activity and promote the growth of β-crystal; however, excessive addition of nano-titanium dioxide is prone to agglomeration, affecting the nucleation sites and resulting in a decrease in the proportion of β-crystal.

[0056] By comparing Comparative Example 3 with Example 1, it can be seen that with the increase in the amount of modified aramid fiber added, the tensile properties and impact resistance of the pipe are relatively enhanced; when the amount of modified aramid fiber added is too much, fiber agglomeration is likely to occur, resulting in uneven stress transfer between fibers, reducing the tensile strength and other properties of the pipe. Excessive addition of modified aramid fiber increases the viscosity of polypropylene, affecting the processing performance of the pipe.

[0057] By comparing Comparative Example 4 with Example 1, it can be seen that during the crystallization process of polypropylene, the molecular chains can be orderly arranged and stacked on the benzene ring plane to promote the formation of crystal nuclei; the nitrogen atoms on the pyridine ring can also form hydrogen bonds and other interactions with the hydrogen atoms in the polypropylene molecular chain, thereby enhancing the affinity between the nucleating agent and the polypropylene, so that the nucleating agent can better play the role of inducing crystallization and improve the nucleation efficiency. When the amount of 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid added is too small, it may not be able to fully coordinate with scandium nitrate to form a complete nucleating agent structure, the active sites of the nucleating agent are reduced, the size of the spherulites is uneven, and the tensile strength, impact strength and other properties of the pipe are reduced.

[0058] By comparing Comparative Example 5 with Example 1, it can be seen that compared with the separate addition of aramid fiber and nucleating agent, on the one hand, the aramid fiber combined with the nucleating agent and then added to the polypropylene can effectively induce the orderly growth of polypropylene around the aramid fiber-polypropylene interface, thereby improving the crystallization performance of polypropylene and improving the interface bonding between the aramid fiber and polypropylene; on the other hand, the overall structure after electrostatic adsorption is relatively stable, which is conducive to its dispersion in the polypropylene.

[0059] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or equivalent replacement that can be made by other persons skilled in the art without incurring any creative effort may be made.

Claims

1. A PP pipe, characterized in that: The pipe is made of the following raw materials in parts by weight: 70-90 parts of polypropylene resin, 5-10 parts of modified aramid fiber, 2-5 parts of nano titanium dioxide, 1-3 parts of polybutadiene, 0.5-2 parts of antioxidant, 0.5-1 parts of lubricant, 0.2-0.8 parts of coupling agent; The preparation method of the modified aramid fiber comprises the following steps: (1) subjecting the aramid fiber to ultrasonic treatment with an acetone aqueous solution having a mass fraction of 60% to 80%, washing, drying and setting aside; (2) mixing the aramid fiber obtained in step (1) with a 1% to 3% by mass aqueous solution of hexadecyltrimethylammonium bromide, washing, drying and setting aside; (3) Evenly mixing the nucleating agent and anhydrous ethanol to obtain a nucleating agent suspension; (4) uniformly mixing the aramid fiber obtained in step (2) with the nucleating agent suspension, washing, and drying to obtain modified aramid fiber; In the step (3), the preparation method of the nucleating agent comprises the following steps: The 4-(4-carboxyphenyl)-2,6-pyridinedicarboxylic acid is uniformly mixed with an ethanol aqueous solution with a mass fraction of 30%-50%, the pH is adjusted to 5-7, and then scandium nitrate is added, the temperature is increased for reaction, and the solution is cooled, washed, and dried to obtain a nucleating agent.

2. A PP pipe according to claim 1, characterized in that: In the step (1), the ratio of aramid fiber to acetone aqueous solution is 1 g: 300-450 mL; the temperature of ultrasonic treatment is 20-30° C., and the time of ultrasonic treatment is 2-4 h.

3. A PP pipe according to claim 1, characterized in that: In the step (2), the mass ratio of the aramid fiber to the aqueous solution of hexadecyltrimethylammonium bromide is 1:(10-40); the mixing temperature is 40-60° C., and the mixing time is 1-4 hours.

4. A PP pipe according to claim 1, characterized in that: In the preparation method of the nucleating agent, the molar ratio of 4-(4-carboxylphenyl)-2,6-pyridinedicarboxylic acid to scandium nitrate is (3-4.5):

1.

5. A PP pipe according to claim 1, characterized in that: In the preparation method of the nucleating agent, the reaction temperature is 60° C.-80° C., and the reaction time is 8-14 hours.

6. A PP pipe according to claim 1, characterized in that: The mass ratio of the aramid fiber to the nucleating agent is 1:(0.4-0.8).

7. A method for preparing a PP pipe according to any one of claims 1 to 6, characterized in that: The steps include: S1: Add polypropylene resin, modified aramid fiber, nano titanium dioxide, polybutadiene, antioxidant, lubricant and coupling agent into a mixer and stir evenly, transfer to a twin-screw extruder for melting, extrusion and drying to obtain pellets; S2: Add the pellets into a single screw extruder for extrusion to obtain a PP pipe.

8. The method for preparing a PP pipe according to claim 7, characterized in that: In the step S1, the stirring speed is 350-550 r / min, and the stirring time is 5-10 min; the temperatures of the four sections of the twin-screw extruder are 185-190° C., 190-195° C., 195-200° C. and 190-195° C. respectively.

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