Heat-resistant polypropylene power sheath pipe and its production process

Abstract

This invention relates to the field of polymer composite materials, specifically heat-resistant polypropylene power sheathing pipes and their manufacturing process. The pipes comprise a polypropylene (PP) matrix, cage-type polysilsesquioxane (POSS) nanocomponents, and a micro-crosslinked network building block. POSS is uniformly anchored to the PP matrix via chemical bonds through a reactive extrusion process, utilizing its rigid framework to restrict the thermal movement of molecular chains. The core principle is to enhance the thermal stability of the matrix through the micro-crosslinked network, resulting in a ring stiffness of the pipe material that is more than 40% higher than that of pure PP under various environmental conditions. This invention abandons the traditional method of adding macroscopic inorganic fillers, ensuring excellent elongation at break and low-temperature impact resistance of the pipe material while improving high-temperature mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and pipe processing technology, and more specifically, to heat-resistant polypropylene power sheath pipes and their manufacturing process. Background Technology

[0002] High-voltage power cables generate excessive Joule heat during operation, and their sheathing pipes are subjected to high temperature, high humidity, and complex stress environments underground for extended periods. Currently, ordinary polypropylene (PP) pipes are prone to softening and deformation under high-temperature conditions exceeding predetermined temperature thresholds, leading to a significant decrease in ring stiffness, pipe deformation, and even collapse. Simultaneously, the polypropylene molecular chain contains a large number of tertiary carbon atoms, which tend to undergo thermo-oxidative degradation under high temperature and oxygen conditions, resulting in embrittlement and cracking of the pipes.

[0003] Existing technologies typically employ two approaches for modification: one is to physically add inorganic fillers to improve heat resistance and rigidity, but this can lead to pipe flexibility parameters falling below the baseline threshold, reduced low-temperature impact resistance, and accelerated wear on extrusion equipment; the other is to physically blend small-molecule antioxidants, but under long-term high temperatures and groundwater erosion, small-molecule antioxidants are prone to migrate to and precipitate on the pipe surface, causing the pipe's long-term resistance to thermo-oxidative aging to fail. Summary of the Invention

[0004] The purpose of this invention is to provide heat-resistant polypropylene power sheathing pipes and their manufacturing process, aiming to improve the problems of ordinary polypropylene pipes in the prior art, such as easy softening and deformation at high temperatures, easy thermo-oxidative degradation, loss of low-temperature toughness due to physical modification, and easy migration and precipitation failure of small molecule antioxidants. By preparing and grafting a multifunctional modifier containing a rigid cage-like skeleton, hindered phenolic groups and active terminal alkenyl groups, the micro-crosslinking structure of the pipe and the covalent anchoring of antioxidant sites are realized, thereby synergistically improving the high-temperature ring stiffness, long-term thermo-oxidative aging resistance and low-temperature impact toughness of the pipe.

[0005] To achieve the above objectives, the present invention provides a heat-resistant polypropylene power sheath pipe, the technical solution of which is that the pipe is made by reactive extrusion of a raw material composition comprising the following parts by weight: polypropylene resin: 100 parts; multifunctional reactive modifier: 3-10 parts; compatibilizer: 2-5 parts; free radical initiator: 0.05-0.2 parts; processing aid: 0.1-0.5 parts; The molecular structure of the multifunctional reactive modifier is characterized by a cage-like polysilsesquioxane (POSS) core skeleton, with hindered phenolic antioxidant groups and terminal alkenyl active groups connected to the apex of the skeleton by chemical bonds. The preparation method of the multifunctional reactive modifier includes the following steps: 1. Pretreatment and first-step grafting: Under nitrogen protection, octaamino-cage-type polysilsesquioxane was dissolved in anhydrous tetrahydrofuran, and triethylamine, an acid-binding agent, was added; under ice-water bath conditions of 0~5℃, anhydrous tetrahydrofuran solution of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride was slowly added dropwise (the molar ratio of octaamino-cage-type polysilsesquioxane to acyl chloride was controlled at 1:2~1:3); after the addition was completed, the temperature was raised to room temperature and the reaction was carried out for 12~24h to convert some amino groups into hindered phenol-modified amide structures; 2. Second grafting step: Cool the above reaction system back to 0~5℃, slowly add methacrylamide chloride, the amount added is 1.1~1.5 times the molar number of the remaining amino group; after the addition is complete, react at room temperature for 12h. 3. Purification treatment: After the reaction is completed, the reaction solution is filtered to remove the byproduct triethylamine hydrochloride; the filtrate is slowly added dropwise to excess ice water or methanol for precipitation, and the precipitate is collected after filtration. After washing several times, it is vacuum dried at 40~50℃ to constant weight to obtain the multifunctional reactive modifier. The manufacturing process of the heat-resistant polypropylene power sheath pipe includes the following steps: 1. Premixing: Polypropylene resin, multifunctional reactive modifier, compatibilizer, free radical initiator and processing aid are mixed evenly in a high-speed mixer; 2. Reactive extrusion and molding: The premixed material is fed into a co-rotating twin-screw extruder; the temperature of each zone of the extruder is set in a stepped manner from 170℃ to 220℃; under this high temperature and strong shear, the initiator decomposes to generate free radicals, which take away tertiary carbon and hydrogen atoms on the PP macromolecular chain to form macromolecular free radicals; at the same time, the terminal alkenyl groups on the periphery of the multifunctional modifier are opened and undergo in-situ grafting reaction with the PP macromolecular free radicals to form a micro-crosslinked topological network with a cage-type polysilsesquioxane nanoscale rigid skeleton as the crosslinking nodes; 3. The melt is extruded through the pipe die, shaped by the vacuum sizing sleeve, cooled by the cooling water tank, and pulled by the track, and then cut to obtain the final pipe.

[0006] The present invention has the following beneficial effects: This invention uses reactive extrusion to uniformly disperse and anchor POSS in the PP matrix in the form of chemical bonds, forming a micro-crosslinked network. POSS restricts the thermal motion of PP molecular chains at high temperatures through steric hindrance, thereby increasing the glass transition temperature of the pipe. The high-temperature ring stiffness of the pipe at 90℃ and 110℃ is increased by more than 40% compared with pure PP pipe. The elongation at break and low-temperature drop hammer impact performance of the pipe are maintained in an excellent manner. The hindered phenolic antioxidant groups are covalently linked to the POSS backbone and grafted onto the PP macromolecular chain along with the POSS. This macromolecularization and chemical bonding effectively inhibits the migration, volatilization, and extraction of small molecule antioxidants in long-term high-temperature and water-vapor environments. After the pipe is soaked in 90℃ hot water for 1000 hours, the oxidation induction time (OIT) reaches more than 95%, achieving long-term anti-aging. Characterization evidence supports this: the multifunctional modifier was detected by Fourier transform infrared spectroscopy (FT-IR) at 1650 cm⁻¹. -1 A characteristic peak of amide bond appears at 3500 cm⁻¹. -1 The presence of a hindered phenolic hydroxyl characteristic peak nearby confirms the successful introduction of the group; Soxhlet extraction of the reactive extruded tubing yielded a gelation rate of 5%–15%, confirming the formation of in-situ grafting and micro-crosslinked networks. Attached Figure Description

[0007] Figure 1 This is a flowchart of the heat-resistant polypropylene power sheath pipe and its production process according to the present invention. Detailed Implementation

[0008] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0009] Example 1: Please see Figure 1 This embodiment provides a heat-resistant polypropylene power sheath pipe and its manufacturing process, specifically including the following steps: S1. Preparation of multifunctional reactive modifier: 11.5 g of octaamino-cage-type polysilsesquioxane and 150 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a nitrogen introduction device. After stirring until evenly dispersed, 4.0 g of triethylamine was added. The system was cooled to 2 °C, and 7.7 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride in 50 mL of anhydrous tetrahydrofuran solution was added dropwise, with the addition time controlled at 40 min. After the addition was completed, the temperature was raised to 25 °C, and the reaction was maintained at this temperature for 12 h. The reaction system was cooled to 2℃ again, and 9.5g of methacryloyl chloride was added dropwise over a period of 30min. After the addition was complete, the reaction was continued at 25℃ for 12h. The reaction solution was filtered through diatomaceous earth to remove triethylamine hydrochloride. The filtrate was slowly added dropwise to 1000mL of ice water to precipitate the precipitate. After filtration, the precipitate was washed successively with deionized water and ethanol, and then dried under vacuum at 50℃ for 24h to obtain a pale yellow multifunctional reactive modifier. The molar ratio of octaamino-cage-type polysilsesquioxane to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride was 1:2, and the amount of methacryloyl chloride added was 1.17 times the molar amount of the remaining amino group. The yield of the obtained multifunctional reactive modifier was 86%, and the purity was 98% (high performance liquid chromatography). Using FT-IR and nuclear magnetic resonance hydrogen spectroscopy (FT-IR and nuclear magnetic resonance hydrogen spectroscopy) 1 The product was characterized by ¹H NMR: In the FT-IR spectrum, the original octaamino-cage polysilsesquioxane showed a peak density of 3300 cm⁻¹. -1 The characteristic absorption peak of the primary amine group disappears near the 1650 cm⁻¹. -1 and 1530cm -1 A distinct characteristic absorption peak of amide bonds (amide I and II bands) appears at 3640 cm⁻¹, along with a peak at 3640 cm⁻¹. -1 The characteristic absorption peak of the hindered phenolic hydroxyl group appears at 1630 cm⁻¹. -1 The characteristic absorption peak of a carbon-carbon double bond appears at this location; 1 In the 1H NMR (CDCl3, 400MHz) spectrum, the proton peak at δ1.43ppm is the proton peak of the hindered phenol tert-butyl group, and the proton peaks at δ5.3ppm and 5.7ppm are the proton peaks of the terminal alkenyl group in the methacryloyl group. The integral area ratio of the terminal alkenyl matrix proton peak to the hindered phenol tert-butyl matrix proton peak was calculated to show that each cage-like polysilsesquioxane core skeleton is connected to an average of 2.1 hindered phenol antioxidant groups and 5.9 terminal alkenyl active groups, thus confirming the product structure. S2. Raw material premixing: Weigh the following raw materials according to the following weight parts: 100 parts polypropylene resin; 5 parts multifunctional reactive modifier; 3 parts maleic anhydride grafted polypropylene; 0.1 parts dicumyl peroxide; 0.2 parts calcium stearate; wherein, the polypropylene resin is block copolymer polypropylene with a melt flow rate of 0.8 g / 10 min; add the above raw materials to a high-speed mixer and mix at room temperature for 5 min to obtain the premix. S3. Reactive Extrusion and Pipe Forming: The premixed material is added to a co-rotating twin-screw extruder with a length-to-diameter ratio of 40. The temperatures of each zone are set to 170℃, 185℃, 195℃, 210℃, 210℃, and 210℃, the die head temperature is 200℃, and the screw speed is 150r / min. The melt is extruded through a pipe die with an outer diameter of 110mm, enters a vacuum sizing sleeve for shaping, the vacuum degree is -0.05MPa, the cooling water temperature is 20℃, and the pipe is obtained after being pulled by a crawler and cut.

[0010] Example 2: The process steps in this embodiment are the same as those in Example 1, except that the formulation and the synthesis parameters of the modifier are adjusted as follows.

[0011] In S1, the molar ratio of octaamino-cage-type polysilsesquioxane to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride is 1:2, and the amount of methacryloyl chloride added is 1.10 times the molar amount of the remaining amino group. Specifically, the dosage is 11.5 g of octaamino-cage-type polysilsesquioxane (specifically octa(3-aminopropyl)polysilsesquioxane, purchased from Hybrid Plastics, brand name AM0265), 7.7 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and 9.0 g of methacryloyl chloride. Simultaneously, 150 mL of anhydrous tetrahydrofuran and 4.0 g of triethylamine are added. When adding the 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride solution, 50 mL of anhydrous tetrahydrofuran is used, and the adding time is adjusted to 45 min. After the addition was completed, the reaction time at room temperature was adjusted to 16 hours; the addition time of methacryloyl chloride was adjusted to 35 minutes; the yield of the obtained multifunctional reactive modifier was 88% after weighing. 1 H NMR testing showed that, calculated by the integral area ratio of the terminal olefin matrix sub-peak to the hindered phenol tert-butyl matrix sub-peak, each cage-type polysilsesquioxane core skeleton is connected to an average of 2.0 hindered phenol antioxidant groups and 6.0 terminal olefin active groups. In S2, the weight parts of each raw material are as follows: 100 parts of polypropylene resin; 3 parts of multifunctional reactive modifier; 2 parts of maleic anhydride-grafted polypropylene; 0.05 parts of dicumyl peroxide; 0.1 parts of calcium stearate; the mixing time of the above raw materials in the high-speed mixer is adjusted to 6 minutes. In S3, the twin-screw extruder temperature is set to 170℃, 180℃, 190℃, 205℃, 205℃, and 210℃, the die head temperature is 198℃, and the screw speed is 140 r / min.

[0012] Example 3: The process steps in this embodiment are the same as those in Example 1, except that the formulation and the synthesis parameters of the modifier are adjusted as follows.

[0013] In S1, the molar ratio of octaamino-cage-type polysilsesquioxane to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride is 1:2.5, and the amount of methacryloyl chloride added is 1.30 times the molar amount of the remaining amino group; specifically, the amounts used are 11.5 g of octaamino-cage-type polysilsesquioxane, 9.7 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and 9.7 g of methacryloyl chloride, and simultaneously 160 mL of anhydrous tetrahydrofuran and 4.5 g of triethylamine are added. When adding the 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride solution, 55 mL of anhydrous tetrahydrofuran is used, and the adding time is adjusted to 50 min. After the adding is completed, the reaction time at room temperature is adjusted to 20 h; the adding time of methacryloyl chloride is adjusted to 40 min. The yield of the obtained multifunctional reactive modifier was 85% upon weighing. 1 H NMR tests showed that, calculated by the integral area ratio of the terminal olefin matrix sub-peak to the hindered phenol tert-butyl matrix sub-peak, each cage-type polysilsesquioxane core skeleton was connected to an average of 2.4 hindered phenol antioxidant groups and 5.6 terminal olefin active groups. In S2, the weight parts of each raw material are as follows: 100 parts of polypropylene resin; 8 parts of multifunctional reactive modifier; 4 parts of maleic anhydride-grafted polypropylene; 0.15 parts of dicumyl peroxide; and 0.3 parts of calcium stearate. The mixing time of the above raw materials in the high-speed mixer is adjusted to 8 minutes. In S3, the twin-screw extruder temperature is set to 172℃, 185℃, 195℃, 210℃, 212℃, and 215℃, the die head temperature is 202℃, and the screw speed is 155 r / min.

[0014] Example 4: The process steps in this embodiment are the same as those in Example 1, except that the formulation and the synthesis parameters of the modifier are adjusted as follows.

[0015] In S1, the molar ratio of octaamino-cage-type polysilsesquioxane to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride is 1:3, and the amount of methacryloyl chloride added is 1.50 times the molar amount of the remaining amino group; specifically, the amounts used are 11.5 g of octaamino-cage-type polysilsesquioxane, 11.6 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and 10.2 g of methacryloyl chloride, and simultaneously 180 mL of anhydrous tetrahydrofuran and 5.0 g of triethylamine are added. When adding the 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride solution, 60 mL of anhydrous tetrahydrofuran is used, and the adding time is adjusted to 60 min. After the adding is completed, the reaction time at room temperature is adjusted to 24 h; the adding time of methacryloyl chloride is adjusted to 45 min. In S2, the weight parts of each raw material are as follows: 100 parts of polypropylene resin; 10 parts of multifunctional reactive modifier; 5 parts of maleic anhydride-grafted polypropylene; 0.2 parts of dicumyl peroxide; 0.5 parts of calcium stearate; the mixing time of the above raw materials in the high-speed mixer is adjusted to 10 minutes. In S3, the twin-screw extruder temperature is set to 175℃, 188℃, 198℃, 212℃, 215℃, and 220℃, the die head temperature is 205℃, and the screw speed is 160r / min.

[0016] Comparative Example 1: The difference between this comparative example and Example 1 is that: no multifunctional reactive modifier is added in S2, and an equal amount of polypropylene resin is used to make up the difference; other operating steps and process parameters are exactly the same as in Example 1. Comparative Example 2: The difference between this comparative example and Example 1 is that the methacryloyl chloride grafting step is omitted in S1, and only a cage-type polysilsesquioxane modifier with hindered phenolic groups but without terminal alkenyl active groups is obtained; the modifier is still added in 5 parts in S2, and the other operation steps and process parameters are exactly the same as in Example 1. Comparative Example 3: The difference between this comparative example and Example 1 is that: in S1, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride is not added, and the octaamino-cage-type polysilsesquioxane is modified only by methacryloyl chloride to obtain a cage-type polysilsesquioxane modifier containing terminal alkenyl groups but not hindered phenolic antioxidant groups; in S2, the modifier is still added in 5 parts, and other operating steps and process parameters are exactly the same as in Example 1; Comparative Example 4: The difference between this comparative example and Example 1 is that maleic anhydride-grafted polypropylene is not added in S2, while the other operating steps and process parameters are exactly the same as in Example 1. Comparative Example 5: The difference between this comparative example and Example 1 is that dicumyl peroxide is not added in S2, while the other operating steps and process parameters are exactly the same as in Example 1. Performance Testing and Datasheets High-temperature ring stiffness was tested according to GB / T9647 at 90℃ and 110℃; OIT was determined by differential scanning calorimetry at 200℃ in a pure oxygen atmosphere; hot water aging was performed by soaking at 90℃ for 1000h, and OIT was measured and retention rate was calculated after aging; low-temperature drop hammer impact was tested at -5℃ according to GB / T14152, and the true impact rate (TIR) ​​was recorded; gelation rate was determined after xylene reflux extraction for 24h. Comparison table of sample performance test data Comparing the test results of Example 1 and Comparative Example 1 in the table, it can be seen that after omitting the multifunctional reactive modifier, the ring stiffness at 90℃, the ring stiffness at 110℃, the initial OIT, the OIT after hot water aging, and the gel rate all showed a decreasing trend. The underlying mechanism is that: the lack of a cage-like polysilsesquioxane rigid skeleton weakens the restriction on the movement of polypropylene chain segments at high temperatures, reducing the pipe's ability to withstand compression deformation; at the same time, the lack of covalently fixed hindered phenolic groups means that the material can only rely on the basic stability of the polypropylene matrix, making it more prone to chain breakage under the combined action of oxygen and hot water, thus resulting in a decreasing trend in OIT and its retention rate; the gel rate being close to zero also indicates that a measurable grafted micro-crosslinked structure has not been formed in the system. As can be seen from the comparison of the test results of Example 1 and Comparative Example 2 in the table, after omitting the terminal alkenyl active group in the multifunctional reactive modifier, the high-temperature ring stiffness and gel rate are substantially reduced, while the initial OIT and the OIT after aging remain at a high level. The underlying mechanism is that the modifier in this comparative example still has hindered phenolic groups, and therefore still has an inhibitory effect on thermo-oxidative degradation; however, due to the lack of terminal alkenyl groups, the modifier cannot effectively graft with polypropylene free radicals during extrusion, and the cage-type polysilsesquioxane is difficult to be fixed on the polypropylene chain as a crosslinking node. The system only exists in physical dispersion and cannot form a continuous micro-crosslinked topology, so the gel rate and high-temperature ring stiffness decrease. Comparing the test results of Example 1 and Comparative Example 3 in the table, it can be seen that after omitting the hindered phenolic antioxidant group in the multifunctional reactive modifier, the ring stiffness at 90℃ and the ring stiffness at 110℃ still remain at a high level, but the initial OIT, the OIT after hot water aging and its retention rate show a downward trend. The underlying mechanism is as follows: the modifier in this comparative example still has terminal alkenyl groups, which can be grafted onto the polypropylene chain under free radical initiation and form a certain micro-crosslinked structure. Therefore, the high-temperature ring stiffness and gel rate are still relatively high. However, due to the lack of hindered phenolic groups, there is a lack of effective free radical termination sites in the material. The peroxide free radicals generated by the thermo-oxidative degradation of polypropylene cannot be eliminated in time, the chain breakage rate is accelerated, and the OIT and its aging retention rate show a deterioration trend. This result shows that the rigid skeleton and antioxidant groups correspond to different performance contributions in this invention, and both need to exist simultaneously. Comparing the test results of Example 1 and Comparative Example 4 in the table, it can be seen that after omitting maleic anhydride-grafted polypropylene, the high-temperature ring stiffness, OIT retention rate and low-temperature impact performance all decreased. The underlying mechanism is that after the compatibilizer is missing, the interfacial bonding between the modifier and the polypropylene matrix is ​​weakened, the uniformity of the cage-type polysilsesquioxane modifier in the melt decreases, and local enrichment areas are easily formed. Insufficient interfacial bonding weakens stress transfer efficiency and reduces structural stability under high temperature and pressure; local phase separation can also create impact weak points, increasing the probability of low temperature impact failure; the decrease in OIT retention rate after hot water aging indicates that unevenly dispersed modifiers are difficult to form a uniform protective layer throughout the material, and local areas are more prone to oxidative degradation. As can be seen from the comparison of the test results of Example 1 and Comparative Example 5 in the table, the high-temperature ring stiffness, gelation rate, OIT retention rate and low-temperature impact performance all decreased after omitting the free radical initiator. The underlying mechanism is as follows: when the initiator is insufficient, the number of active free radicals on the polypropylene backbone is significantly reduced, the degree of grafting reaction between the terminal alkenyl modifier and polypropylene decreases, the cage-type polysilsesquioxane and hindered phenolic groups cannot be fully anchored on the polypropylene chain, the formation of micro-crosslinked structures is restricted, and the gel rate shows a downward trend; due to insufficient grafting fixation, the modifier is more likely to undergo interfacial detachment or migration loss under long-term hot water action, thus the OIT retention rate after hot water aging decreases; insufficient grafting degree also leads to local structural inhomogeneity, increasing the probability of low-temperature impact failure. The test results from Examples 1 to 4 show that adjusting the amount of modifier, compatibilizer, and initiator within the limits defined in these examples can yield pipes with good heat resistance and resistance to thermo-oxidative aging. Among them, Example 2 is near the lower limit of each component, with relatively low gelation rate and high-temperature ring stiffness. Example 3 maintains a good balance between heat resistance and anti-aging performance. In Example 4, the amount of modifier and initiator added is relatively high, the gelation rate increases further, and the ring stiffness at 110℃ is still relatively high, but the low-temperature impact performance decreases, indicating that excessive crosslinking weakens some toughness. Considering the ring stiffness, OIT retention rate, and low-temperature impact results, the formulation and process parameters corresponding to Example 1 have better overall performance.

[0017] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any conventional modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. Heat-resistant polypropylene power sheathing pipe, characterized in that: The pipe is made by reactive extrusion of a raw material composition comprising the following parts by weight: polypropylene resin: 100 parts; multifunctional reactive modifier: 3 to 10 parts; Compatibilizer: 2 to 5 parts; Free radical initiator: 0.05 to 0.2 parts; Processing aid: 0.1 to 0.5 parts; The multifunctional reactive modifier uses a cage-like polysilsesquioxane with eight vertices as its core skeleton. Two to three vertices of the core skeleton are connected to hindered phenolic antioxidant groups by chemical bonds, and the remaining vertices are connected to terminal alkenyl active groups by chemical bonds.

2. The heat-resistant polypropylene power sheathing pipe according to claim 1, characterized in that: The compatibilizer is maleic anhydride-grafted polypropylene.

3. The heat-resistant polypropylene power sheathing pipe according to claim 1, characterized in that: The multifunctional reactive modifier is prepared by the following steps: (1) Under nitrogen protection, dissolve octaamino-cage-type polysilsesquioxane in anhydrous tetrahydrofuran and add triethylamine; under ice-water bath conditions of 0℃~5℃, slowly add anhydrous tetrahydrofuran solution of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride; after the addition is completed, raise the temperature to room temperature and react for 12h~24h. (2) Cool the reaction system after step (1) to 0℃~5℃ again, and slowly add methacryloyl chloride; after the addition is complete, react at room temperature for 12h. (3) After the reaction in step (2) is completed, the reaction solution is filtered; the filtrate is slowly dripped into ice water or methanol to precipitate, and the precipitate is collected after filtration. The precipitate is washed multiple times and then vacuum dried at 40℃~50℃ to constant weight to obtain the multifunctional reactive modifier.

4. The heat-resistant polypropylene power sheathing pipe according to claim 3, characterized in that: In step (1), the molar ratio of the octaamino-cage-type polysilsesquioxane to 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride is 1:2 to 1:

3.

5. The heat-resistant polypropylene power sheathing pipe according to claim 3, characterized in that: In step (2), the amount of methacryloyl chloride added is 1.1 to 1.5 times the remaining molar number of amino groups.

6. The heat-resistant polypropylene power sheathing pipe according to claim 1, characterized in that: The free radical initiator is dicumyl peroxide or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

7. The heat-resistant polypropylene power sheathing pipe according to claim 1, characterized in that: The processing aid is calcium stearate.

8. A manufacturing process for heat-resistant polypropylene power sheathing tubing as described in any one of claims 1-7, characterized in that: Includes the following steps: Step 1: Mix polypropylene resin, multifunctional reactive modifier, compatibilizer, free radical initiator and processing aid in a high-speed mixer to obtain a premix; Step 2: The premixed material is fed into a co-rotating twin-screw extruder. The temperature of each zone of the co-rotating twin-screw extruder is set in a stepped manner from 170°C to 220°C to carry out reactive extrusion and obtain the reacted melt. Step 3: The reacted melt is extruded through a pipe die, shaped by a vacuum sizing sleeve, cooled by a cooling water tank, and pulled by a track. After cutting, heat-resistant polypropylene power sheath pipe is obtained.

9. The manufacturing process of the heat-resistant polypropylene power sheath pipe according to claim 8, characterized in that: In step two, the length-to-diameter ratio of the co-rotating twin-screw extruder is 40.

10. The manufacturing process of the heat-resistant polypropylene power sheath pipe according to claim 8, characterized in that: In step three, the vacuum degree of the vacuum sizing sleeve is -0.05MPa, and the water temperature is 20℃.

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