Modified PVC power cable protection pipe

Abstract

The present application relates to polyvinyl chloride pipe manufacturing technology field, disclose a kind of modified PVC power cable protection pipe, including polyvinyl chloride resin, heat stabilizer, pentaerythritol, stearic acid, calcium carbonate, polyolefin alloy ionomer masterbatch and liquid complexing agent.Polyolefin alloy ionomer masterbatch is composed of octene-1 and ethylene copolymer, high-density polyethylene, maleic anhydride grafted polyolefin elastomer and active zinc oxide.Liquid complexing agent is composed of isopropyl tri (dioctyl pyrophosphoric acyloxy) titanate and epoxy soybean oil.Polyvinyl chloride dry mix and polyolefin alloy ionomer masterbatch are melt extruded when preparing, and liquid complexing agent is injected laterally.The present application forms toughening phase by polyolefin alloy ionomer masterbatch to absorb and disperse impact stress, and liquid complexing agent improves compatibility of formula raw materials.Lateral injection process promotes liquid complexing agent to directly act on mixed interface, and improves the compactness of modified PVC power cable protection pipe.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl chloride pipe manufacturing technology, specifically a modified PVC power cable protection pipe. Background Technology

[0002] Polyvinyl chloride (PVC) pipes are commonly used in the manufacture of protective conduits for power cables. Due to the rigid structure of the PVC resin molecular chain, PVC power cable protective conduits are prone to brittle fracture at low temperatures. To address this issue, elastomers are typically added directly to the PVC resin as toughening materials during manufacturing. However, the inclusion of elastomers in the PVC resin reduces its modulus, resulting in a decrease in the overall rigidity of the PVC power cable protective conduit. During installation and use, the insufficient rigidity of the PVC power cable protective conduit can easily lead to compressive deformation, causing its overall mechanical properties to fail to meet the requirements of engineering construction.

[0003] Directly mixing toughening materials of different polarities with polyvinyl chloride (PVC) resin can lead to poor interfacial compatibility within the mixture. Poor interfacial compatibility increases internal friction during the extrusion process. This internal friction generates localized overheating, which accelerates the thermal degradation of PVC resin. The degradation products of PVC resin disrupt the material's internal molecular structure. Consequently, phase separation defects are prone to appear inside the molded PVC power cable protection pipe. These phase separation defects, when subjected to external impact stress, evolve into microcracks, and the propagation of these microcracks can cause the PVC power cable protection pipe to crack.

[0004] In the conventional manufacturing process of PVC power cable protection pipes, liquid additives are typically mixed directly with PVC dry mix at room temperature using a mixer. During the mixing stage, the liquid additives are easily and excessively absorbed by the pores within the PVC dry mix. This excessive absorption of liquid additives by the pores of the PVC dry mix results in the liquid additives being confined within the powder particles. When the material enters the extrusion equipment and undergoes the melting stage, the concentration of liquid additives at the mixing interface between the PVC phase and the toughening material phase decreases. The lack of coupling and plasticizing effects from the liquid additives at the mixing interface prevents the raw materials of different polarities from achieving a tight bond, reducing the overall density of the PVC power cable protection pipe. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a modified PVC power cable protection pipe, which solves the problems of poor low-temperature impact resistance of existing PVC power cable protection pipes and the tendency of directly adding toughening systems to lead to poor internal compatibility and reduced mechanical strength of the pipe.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a modified PVC power cable protection pipe, which is made from the following raw materials in parts by weight: 100 parts of polyvinyl chloride resin; 2.5-4.0 parts of calcium-zinc composite heat stabilizer; 0.3-0.8 parts of pentaerythritol; 0.3-0.8 parts of stearic acid; 5.0-15.0 parts of heavy calcium carbonate; 10.0-20.0 parts of octene-1 and ethylene copolymer; 3.0-8.0 parts of high-density polyethylene; 3.0-7.0 parts of maleic anhydride-grafted polyolefin elastomer; 1.0-2.5 parts of active zinc oxide; 0.5-1.5 parts of isopropyl tris(dioctyl pyrophosphate) titanate; and 1.0-3.0 parts of epoxidized soybean oil.

[0007] By adopting the above technical solution, and using a polyolefin blend system as the toughening phase, combined with a composite liquid plasticizing system, the following effects are achieved: First, octene-1 in the system combines with ethylene copolymer, high-density polyethylene, maleic anhydride-grafted polyolefin elastomer, and active zinc oxide to form an elastic toughening phase structure during processing. The maleic anhydride-grafted polyolefin elastomer reacts with the active zinc oxide to construct a stable network bonded system within the toughening phase. This network bonded system can absorb and disperse impact stress when the pipe is subjected to external impact; simultaneously, the high-density polyethylene distributed within the above structure maintains the required overall rigidity of the material, preventing excessive softening of the pipe and thus improving the overall mechanical properties of the pipe.

[0008] Secondly, isopropyl tris(dioctyl pyrophosphate)titanate and epoxidized soybean oil work synergistically in the formulation. Isopropyl tris(dioctyl pyrophosphate)titanate can improve the compatibility between polyvinyl chloride (PVC) and heavy calcium carbonate and polyolefin toughening phases, reducing internal friction when different materials are mixed. Epoxidized soybean oil, as an auxiliary heat stabilizer and plasticizer, can absorb the degradation products generated by PVC when heated and promote the uniform mixing and plasticizing of the above components during processing, preventing phase separation or cracking defects inside the pipe.

[0009] Preferably, the octene-1 copolymer with ethylene, the high-density polyethylene, the maleic anhydride-grafted polyolefin elastomer, and the active zinc oxide constitute a polyolefin alloy ionomer masterbatch.

[0010] By adopting the above technical solution, the four components are pre-mixed and extruded to form masterbatch, so that the toughening material can be mixed and reacted in an independent system in advance, avoiding the interference of polyvinyl chloride resin on the formation of the toughening system in subsequent processing, and ensuring that the toughening phase is uniformly distributed in the pipe matrix.

[0011] Preferably, the isopropyl tris(dioctyl pyrophosphate) titanate and the epoxidized soybean oil constitute a liquid composite additive.

[0012] By adopting the above technical solution, isopropyl tris(dioctyl pyrophosphate) titanate is dissolved and dispersed in epoxidized soybean oil, which reduces the overall viscosity of the mixed liquid and makes it reach a uniform liquid dispersion state, providing a basis for quantitative and rapid mixing in subsequent production processes.

[0013] Preferably, the preparation steps of the modified PVC power cable protection pipe are as follows: The octene-1 copolymer with ethylene, the high-density polyethylene, the maleic anhydride-grafted polyolefin elastomer and the active zinc oxide are mixed in a kneader and then directly fed into the main feed port of a co-rotating twin-screw extruder for extrusion pelleting to obtain the polyolefin alloy ionomer masterbatch. The polyvinyl chloride resin, the calcium-zinc composite heat stabilizer, the pentaerythritol, the stearic acid, and the heavy calcium carbonate are fed into a heated high-speed mixer for friction heating and heat preservation kneading, and then discharged into a cold mixer for cooling to obtain a dry polyvinyl chloride mixture. The isopropyl tris(dioctyl pyrophosphoryl oxy) titanate and the epoxidized soybean oil were added to a mixing tank and stirred to obtain the liquid composite additive. The PVC dry mix and the polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder. The metering pump is started, and the liquid composite additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through the metering pump. The internal material is extruded and formed through the die section and enters the vacuum setting box for cooling and setting. After being pulled and cut by the traction machine, the modified PVC power cable protection pipe is obtained.

[0014] By adopting the above technical solution, the preparation process employs a combination of feeding solid material through the main inlet and side-injecting liquid. The PVC dry mix and polyolefin alloy ionomer masterbatch undergo initial shear melting in an anti-rotating conical twin-screw extruder. While the material is in a molten state and enters the shear mixing section, a liquid composite additive is side-injected. This step prevents the liquid additive from being excessively absorbed by the dry powder pores during the mixing stage. The liquid composite additive directly enters the molten system, allowing it to act directly at the interface between the PVC and polyolefin phases, thus improving the overall density of the pipe.

[0015] Preferably, during the preparation of the modified PVC power cable protection pipe, the temperature of the mixing tank used to mix the isopropyl tris(dioctyl pyrophosphate) titanate and the epoxidized soybean oil is maintained at 40-50°C.

[0016] By adopting the above technical solution, the temperature of the mixing tank is controlled at 40-50℃, which can maintain the fluidity of the liquid, prevent the additives from agglomerating or separating at low temperatures, and maintain the consistency of the liquid composite additives.

[0017] Preferably, in the process of preparing the polyolefin alloy ionomer masterbatch, the kneader rotates at 500–800 rpm, and the mixing time is 3–5 min; the temperature of the feeding section of the co-rotating twin-screw extruder is controlled at 160–170°C, the melting section at 180–190°C, the reaction mixing section at 190–200°C, the homogenization section at 187–196°C, the die section at 185–194°C, and the screw speed is 150–250 rpm.

[0018] By adopting the above technical solution, the temperature from the feeding section to the die head section is controlled to be distributed in a gradient. Combined with the mechanical shearing action generated by the screw speed of 150-250 rpm, the energy required for the melting and mixing of each polyolefin component is provided, so that the components of the toughening phase are fully and evenly mixed, preventing the solid material from melting and bridging too early at the feeding port, and providing the stable extrusion pressure required for extrusion granulation.

[0019] Preferably, in the process of preparing the polyvinyl chloride dry mix, the speed of the heated high-speed mixer is 1000-1500 rpm and the friction heating is raised to 110-115°C, and the heat preservation kneading time is 5-8 min; the speed of the cold mixer is 100-200 rpm and the cooling temperature is lowered to 35-39°C.

[0020] By adopting the above technical solution, the frictional heat generated by high-speed operation raises the material temperature to 110-115°C, promoting the uniform dispersion and adhesion of powdered additives to the surface of polyvinyl chloride resin. The subsequent cold mixing and cooling step lowers the temperature to 35-39°C, preventing the dry mix from clumping or premature thermal degradation due to residual heat during storage or transportation.

[0021] Preferably, during the preparation of the liquid composite additive, the rotation speed of the mixing tank is 200-400 rpm, and the stirring time is 10-20 min.

[0022] By adopting the above technical solution, the uniform state of the liquid system is maintained under mechanical stirring, preventing differences in component concentration within the liquid and ensuring the stability of the pumped concentration in the subsequent lateral injection process.

[0023] Preferably, during the extrusion process in the counter-rotating conical twin-screw extruder, the temperature of the feeding section is controlled at 160–165°C, the temperature of the compression and melting section at 170–175°C, the temperature of the shearing and mixing section at 174–181°C, the temperature of the venting section at 176–183°C, the temperature of the homogenizing section at 180–186°C, and the temperature of the die section at 178–184°C; the screw speed is controlled at 20–40 rpm, and the vacuum degree of the venting section is -0.05 MPa to -0.08 MPa.

[0024] By adopting the above technical solution, the process temperature of each stage is controlled according to the melting characteristics of the mixed system, so that the polyvinyl chloride and polyolefin masterbatch have suitable flowability. At the same time, the exhaust section is controlled to be in a negative pressure state to extract the moisture and volatile gases released by the material when heated, and to prevent the formation of bubbles or micropore defects on the pipe wall after the pipe is extruded and formed.

[0025] Preferably, during the cooling and shaping process in the vacuum shaping chamber, the cooling water temperature of the vacuum shaping chamber is 15-20℃, and the vacuum degree is -0.02MPa to -0.04MPa.

[0026] By adopting the above technical solution, the high temperature of the extruded tube blank and the negative pressure vacuum environment are used to make the tube blank in a high temperature state adhere to the inner wall of the shaping sleeve for rapid cooling and solidification, thereby fixing the shape and outer diameter of the tube and preventing the tube from shrinking and deforming during the traction cutting process.

[0027] This invention provides a modified PVC power cable protection pipe. It has the following beneficial effects: 1. This invention comprises a polyolefin alloy ionomer masterbatch composed of octene-1-ethylene copolymer, high-density polyethylene, maleic anhydride-grafted polyolefin elastomer, and active zinc oxide. The polyolefin alloy ionomer masterbatch forms a toughening phase inside the modified PVC power cable protection pipe. The network-like bonding system within the polyolefin alloy ionomer masterbatch absorbs and disperses the impact stress experienced by the modified PVC power cable protection pipe. High-density polyethylene, distributed within the toughening phase, maintains the overall rigidity of the modified PVC power cable protection pipe, preventing excessive softening and improving its impact resistance and overall mechanical properties.

[0028] 2. This invention utilizes isopropyl tris(dioctyl pyrophosphate) titanate and epoxidized soybean oil to form a liquid composite additive. Isopropyl tris(dioctyl pyrophosphate) titanate improves the compatibility between polyvinyl chloride resin, heavy calcium carbonate, and polyolefin alloy ionomer masterbatch, reducing internal friction during raw material mixing. Epoxidized soybean oil absorbs the degradation products generated by the heating of polyvinyl chloride resin, promoting uniform mixing and plasticizing of all raw materials during processing, and preventing phase separation defects or cracking defects inside the modified PVC power cable protection pipe.

[0029] 3. This invention involves preliminary shearing and melting of PVC dry blend and polyolefin alloy ionomer masterbatch in an anti-rotating conical twin-screw extruder. Liquid composite additives are then laterally injected into the shearing and mixing section while the materials are in a molten state. This lateral injection process prevents excessive absorption of the liquid composite additives by the pores of the dry blend during the mixing stage. The liquid composite additives directly enter the molten system, allowing them to act directly at the interface between the PVC and polyolefin phases, thereby improving the density of the modified PVC power cable protection pipe. Attached Figure Description

[0030] Figure 1 Line graphs showing the static thermal stability time tests of Embodiments 1, 2, 3, and Comparative Example 1 of the present invention; Figure 2 These are melt pressure fluctuation diagrams for the homogenization section of Embodiments 1, 2, 3, and Comparative Example 2 of the present invention; Figure 3 Line graphs showing the radial compressive force test data of pipes in Embodiments 1, 2, and 3 of the present invention, as well as Comparative Examples 1 and 3; Figure 4 Line graphs showing the sample breakage rate test data of Examples 1, 2, and 3, and Comparative Examples 1 and 3 of the present invention; Figure 5 Line graphs showing the static sliding friction coefficient test results of the inner wall of the pipe in Embodiments 1, 2, and 3 of the present invention, as well as Comparative Examples 1 and 3. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Examples 1-3: Example 1: This embodiment provides a method for preparing a modified PVC power cable protection pipe, including the following steps: S1. 15.0 parts by weight of octene-1 copolymer with ethylene, 5.0 parts by weight of high-density polyethylene, 5.0 parts by weight of maleic anhydride grafted polyolefin elastomer, and 1.8 parts by weight of active zinc oxide were added to a kneader and mixed for 4 minutes at a speed of 650 rpm. The mixture was then directly fed into the main feed port of a co-rotating twin-screw extruder. The feeding section temperature of the co-rotating twin-screw extruder was controlled at 165℃, the melting section temperature at 185℃, the reaction mixing section temperature at 195℃, the homogenization section temperature at 192℃, and the die section temperature at 190℃. The screw speed of the co-rotating twin-screw extruder was controlled at 200 rpm. After extrusion and pelletizing by the co-rotating twin-screw extruder, polyolefin alloy ionomer masterbatch was obtained. S2. 100 parts by weight of polyvinyl chloride resin, 3.2 parts by weight of calcium-zinc composite heat stabilizer, 0.5 parts by weight of pentaerythritol, 0.5 parts by weight of stearic acid, and 10.0 parts by weight of heavy calcium carbonate are put into a heated high-speed mixer. The mixture is heated to 112°C by friction at 1250 rpm, and then kneaded at 112°C for 6 minutes before being discharged into a cold mixer. The mixture is cooled to 38°C at 150 rpm to obtain a dry polyvinyl chloride mixture. S3. 1.0 parts by weight of isopropyl tris(dioctyl pyrophosphoryloxy) titanate and 2.0 parts by weight of epoxidized soybean oil were added to the mixing tank and stirred for 15 minutes at 300 rpm while maintaining the temperature of the mixing tank at 45°C to obtain the liquid composite additive. S4. The obtained PVC dry mix and the obtained polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder. The temperature of the feeding section of the counter-rotating conical twin-screw extruder is controlled at 162℃, the temperature of the compression melting section is 172℃, the temperature of the shearing and mixing section is 177℃, the temperature of the exhaust section is 179℃, the temperature of the homogenization section is 182℃, and the temperature of the die section is 181℃. The screw speed of the counter-rotating conical twin-screw extruder is controlled at 30 rpm, and the vacuum degree of the exhaust section is controlled at -0.06 MPa. The metering pump is started, and the obtained liquid composite additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through the metering pump. The material inside the counter-rotating conical twin-screw extruder is extruded and formed through the die section and enters the vacuum shaping chamber. It is cooled and shaped under the conditions of cooling water temperature of 18℃ and vacuum degree of -0.03 MPa. After being pulled and cut by the traction machine, the modified PVC power cable protection pipe is obtained.

[0033] Example 2: This embodiment provides a method for preparing a modified PVC power cable protection pipe, including the following steps: S1. 20.0 parts by weight of octene-1 copolymer with ethylene, 8.0 parts by weight of high-density polyethylene, 7.0 parts by weight of maleic anhydride grafted polyolefin elastomer, and 2.5 parts by weight of active zinc oxide were added to a kneader and mixed for 5 minutes at 800 rpm. The mixture was then directly fed into the main feed port of a co-rotating twin-screw extruder. The feeding section temperature of the co-rotating twin-screw extruder was controlled at 170℃, the melting section temperature at 190℃, the reaction mixing section temperature at 200℃, the homogenization section temperature at 196℃, and the die section temperature at 194℃. The screw speed of the co-rotating twin-screw extruder was controlled at 250 rpm. After extrusion and pelletizing by the co-rotating twin-screw extruder, polyolefin alloy ionomer masterbatch was obtained. S2. 100 parts by weight of polyvinyl chloride resin, 4.0 parts by weight of calcium-zinc composite heat stabilizer, 0.8 parts by weight of pentaerythritol, 0.8 parts by weight of stearic acid, and 15.0 parts by weight of heavy calcium carbonate are put into a heated high-speed mixer. The mixture is heated to 115°C by friction at 1500 rpm, and then kneaded at 115°C for 8 minutes before being discharged into a cold mixer. The mixture is cooled to 35°C at 200 rpm to obtain a dry polyvinyl chloride mixture. S3. 1.5 parts by weight of isopropyl tris(dioctyl pyrophosphoryloxy) titanate and 3.0 parts by weight of epoxidized soybean oil were added to the mixing tank and stirred at 400 rpm for 20 min while maintaining the temperature of the mixing tank at 50°C to obtain the liquid composite additive. S4. The obtained PVC dry mix and the obtained polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder. The temperature of the feeding section of the counter-rotating conical twin-screw extruder is controlled at 165℃, the temperature of the compression melting section is 175℃, the temperature of the shearing and mixing section is 181℃, the temperature of the exhaust section is 183℃, the temperature of the homogenization section is 186℃, and the temperature of the die section is 184℃. The screw speed of the counter-rotating conical twin-screw extruder is controlled at 40 rpm, and the vacuum degree of the exhaust section is controlled at -0.08 MPa. The metering pump is started, and the obtained liquid composite additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through the metering pump. The material inside the counter-rotating conical twin-screw extruder is extruded and formed through the die section and enters the vacuum shaping chamber. It is cooled and shaped under the conditions of cooling water temperature of 20℃ and vacuum degree of -0.04 MPa. After being pulled and cut by the traction machine, the modified PVC power cable protection pipe is obtained.

[0034] Example 3: This embodiment provides a method for preparing a modified PVC power cable protection pipe, including the following steps: S1. 10.0 parts by weight of octene-1 copolymer with ethylene, 3.0 parts by weight of high-density polyethylene, 3.0 parts by weight of maleic anhydride grafted polyolefin elastomer, and 1.0 parts by weight of active zinc oxide are added to a kneader and mixed for 3 minutes at 500 rpm. The mixture is then directly fed into the main feed port of a co-rotating twin-screw extruder. The temperature of the feeding section of the co-rotating twin-screw extruder is controlled at 160℃, the melting section at 180℃, the reaction mixing section at 190℃, the homogenization section at 187℃, and the die section at 185℃. The screw speed of the co-rotating twin-screw extruder is controlled at 150 rpm. After extrusion and pelletizing by the co-rotating twin-screw extruder, polyolefin alloy ionomer masterbatch is obtained. S2. 100 parts by weight of polyvinyl chloride resin, 2.5 parts by weight of calcium-zinc composite heat stabilizer, 0.3 parts by weight of pentaerythritol, 0.3 parts by weight of stearic acid, and 5.0 parts by weight of heavy calcium carbonate are put into a heated high-speed mixer. The mixture is heated to 110°C by friction at 1000 rpm, and then kneaded at 110°C for 5 minutes before being discharged into a cold mixer. The mixture is cooled to 39°C at 100 rpm to obtain a dry polyvinyl chloride mixture. S3. 0.5 parts by weight of isopropyl tris(dioctyl pyrophosphoryloxy) titanate and 1.0 parts by weight of epoxidized soybean oil were added to the mixing tank and stirred for 10 minutes at 200 rpm while maintaining the temperature of the mixing tank at 40°C to obtain the liquid composite additive. S4. The obtained PVC dry mix and the obtained polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder. The temperature of the feeding section of the counter-rotating conical twin-screw extruder is controlled at 160℃, the temperature of the compression melting section is 170℃, the temperature of the shearing and mixing section is 174℃, the temperature of the exhaust section is 176℃, the temperature of the homogenization section is 180℃, and the temperature of the die section is 178℃. The screw speed of the counter-rotating conical twin-screw extruder is controlled at 20 rpm, and the vacuum degree of the exhaust section is controlled at -0.05 MPa. The metering pump is started, and the obtained liquid composite additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through the metering pump. The material inside the counter-rotating conical twin-screw extruder is extruded and formed through the die section and enters the vacuum shaping chamber. It is cooled and shaped under the conditions of cooling water temperature of 15℃ and vacuum degree of -0.02 MPa. After being pulled and cut by the traction machine, the modified PVC power cable protection pipe is obtained.

[0035] Comparative Examples 1-3: Comparative Example 1: Compared to Example 1, the difference lies in omitting steps S1 and S3, and instead using 15.0 parts by weight of octene-1 copolymer with ethylene, 5.0 parts by weight of high-density polyethylene, 5.0 parts by weight of maleic anhydride-grafted polyolefin elastomer, 1.8 parts by weight of active zinc oxide, 100 parts by weight of polyvinyl chloride resin, 3.2 parts by weight of calcium-zinc composite heat stabilizer, 0.5 parts by weight of pentaerythritol, 0.5 parts by weight of stearic acid, and 10.0 parts by weight of heavy calcium carbonate. 1.0 parts by weight of isopropyl tris(dioctyl pyrophosphoryloxy) titanate and 2.0 parts by weight of epoxidized soybean oil were fed into a heated high-speed mixer and heated to 112°C by friction at 1250 rpm. After being kneaded at 112°C for 6 minutes, the mixture was discharged into a cold mixer and cooled to 38°C at 150 rpm to obtain the total mixture. The total mixture was then fed into the main feed port of an anti-rotating conical twin-screw extruder for extrusion molding. All other steps were the same.

[0036] Comparative Example 2: Compared with Example 1, the difference lies in changing the addition position of the liquid composite additive. In step S4, the obtained liquid composite additive, the obtained polyvinyl chloride dry mix, and the obtained polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed port of the counter-rotating conical twin-screw extruder. The obtained liquid composite additive is not injected into the side of the shearing and mixing section of the counter-rotating conical twin-screw extruder. All other aspects are the same.

[0037] Comparative Example 3: Compared with Example 1, the difference is that isopropyl tris(dioctyl pyrophosphate) titanate in the formulation is removed. In step S3, only 2.0 parts by weight of epoxidized soybean oil is added to the mixing tank and stirred at 300 rpm for 15 min. The temperature of the mixing tank is maintained at 45°C to obtain liquid additive. In step S4, the liquid additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through a metering pump. All other steps are the same.

[0038] Test Examples 1-5: Test Example 1: The static thermal stability time test was used to determine the color change time of the sample under constant temperature conditions of 200℃, and to verify the anti-zinc burning effect of the preparation method of the example on the spatial isolation of active zinc oxide.

[0039] Experimental steps: The modified PVC power cable protection pipes prepared in Example 1, Example 2, Example 3 and Comparative Example 1 were cut into sample pieces with a size of approximately 5mm × 5mm.

[0040] Weigh 2.0g of the sample and place it at the bottom of the glass test tube.

[0041] Insert a rubber stopper with a glass tube into the top of the glass test tube. Moisten the Congo red test paper with deionized water and suspend it at the bottom of the glass tube. Adjust the vertical height of the bottom of the Congo red test paper from the top surface of the sample to 5 cm.

[0042] The glass test tube containing the sample and Congo red test paper was heated in a constant temperature oil bath at 200°C.

[0043] The time from when the glass test tube was placed in a 200°C constant temperature oil bath until the edge of the Congo red test paper began to change from red to blue was recorded as the static thermal stability time. Five independent parallel tests were performed on the samples of Example 1, Example 2, Example 3, and Comparative Example 1, and the test values ​​were recorded.

[0044] Table 1. Static thermal stability time test data ; Figure 1 This is a line graph of the static thermal stability time test of Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1 of the present invention, wherein the horizontal axis represents the number of tests and the vertical axis represents the static thermal stability time (min). The legend includes Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1.

[0045] in conclusion: According to Table 1 and Figure 1 The data shows that the static thermal stability time of Examples 1, 2, and 3 is longer than that of Comparative Example 1.

[0046] The preparation methods of Examples 1, 2, and 3 include step S1, which involves preparing polyolefin alloy ionomer masterbatch. During the preparation of the polyolefin alloy ionomer masterbatch, an active zinc oxide is encapsulated within a polyolefin matrix composed of octene-1-ethylene copolymer, high-density polyethylene, and maleic anhydride-grafted polyolefin elastomer. This encapsulation of the active zinc oxide by the polyolefin matrix spatially isolates the active zinc oxide from the polyvinyl chloride resin during the extrusion molding process in step S4. This spatial isolation cuts off the pathway for contact between the active zinc oxide and the hydrogen chloride released from the polyvinyl chloride resin upon heating, thus blocking the formation of zinc chloride. In the absence of zinc chloride as a Lewis acid catalyst in the system, the dehydrochlorination reaction of the polyvinyl chloride resin maintains its basic rate, resulting in a prolonged static thermal stability time in Examples 1, 2, and 3.

[0047] The preparation method of Comparative Example 1 omits the step of preparing the polyolefin alloy ionomer masterbatch, employing a one-time extrusion molding method by mixing 1.8 parts by mass of active zinc oxide with 100 parts by mass of polyvinyl chloride resin and other raw materials. During the heating, mixing, and extrusion process of Comparative Example 1, the active zinc oxide is directly exposed to the surface of the polyvinyl chloride resin. Under high temperature conditions, the active zinc oxide reacts with trace amounts of hydrogen chloride released by the thermal decomposition of the polyvinyl chloride resin to generate zinc chloride. The generated zinc chloride catalyzes a continuous dehydrochlorination reaction in the polyvinyl chloride resin, leading to zinc burning in the sample of Comparative Example 1, which is reflected in the fact that the static thermal stability time of the sample of Comparative Example 1 is shortened to less than 20 minutes in the test. The test data reflects that the step of separately pre-mixing to prepare the polyolefin alloy ionomer masterbatch eliminates the catalytic effect of active zinc oxide on the thermal degradation of polyvinyl chloride resin.

[0048] Test Example 2: The homogenization section melt pressure fluctuation test is used to verify the extrusion stability of the counter-rotating conical twin-screw extruder during continuous operation and to evaluate the impact of different liquid additive addition locations on material conveying and pressure build-up processes.

[0049] Experimental steps: Turn on the heating system of the counter-rotating conical twin-screw extruder, and set the control temperatures of the feeding section, compression melting section, shearing and mixing section, venting section, homogenization section and die section according to the corresponding requirements of Example 1, Example 2, Example 3 and Comparative Example 2. Maintain heating until the temperature of each temperature zone reaches the set value and is kept constant for 30 minutes.

[0050] Start the main drive motor of the counter-rotating conical twin-screw extruder and maintain the screw speed set in Examples 1, 2, 3 and Comparative Example 2 for 5 minutes under no-load operation.

[0051] For Examples 1, 2, and 3, the corresponding PVC dry mix and polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet. When the polymer melt enters the shearing and mixing section, the metering pump is started to inject the corresponding liquid composite additive through the side injection port.

[0052] For Comparative Example 2, the liquid composite additive, PVC dry mix, and polyolefin alloy ionomer masterbatch were mixed and simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder, without injecting the liquid composite additive into the side of the shearing and mixing section.

[0053] Once the die section of the counter-rotating conical twin-screw extruder has a continuous flow of polymer melt and is running smoothly, the operating time is recorded as zero. The melt pressure value is then extracted using a pressure sensor installed in the homogenization section of the counter-rotating conical twin-screw extruder.

[0054] The total test duration was 60 minutes. The melt pressure value in the homogenization section was recorded every 5 minutes. The recorded data were compiled and organized to analyze the stability of equipment operation.

[0055] Table 2. Continuous test data of melt pressure in the homogenization section ; Figure 2 This is a graph showing the melt pressure fluctuation in the homogenization section of Embodiments 1, 2, 3 and Comparative Example 2 of the present invention. The horizontal axis represents the time point (min) and the vertical axis represents the melt pressure in the homogenization section (MPa). The legend includes Embodiments 1, 2, 3 and Comparative Example 2.

[0056] in conclusion: According to Table 2 and Figure 2 The data shows that the melt pressure values ​​in the homogenization section of Examples 1, 2, and 3 remained stable during the 60-minute test cycle, while the melt pressure values ​​in the homogenization section of Comparative Example 2 showed a wide range of oscillations and were generally lower than the pressure levels of the Example group.

[0057] The preparation method of Comparative Example 2 changed the addition location of the liquid composite additive, simultaneously feeding the liquid composite additive, PVC dry mix, and polyolefin alloy ionomer masterbatch into the main feed inlet of a counter-rotating conical twin-screw extruder. The liquid composite additive is in a low-viscosity liquid state at the initial temperature of the feeding section. After entering the feeding and compression / melting sections of the counter-rotating conical twin-screw extruder, the free liquid composite additive coats the surface of the solid PVC dry mix particles. The liquid component generates excessive lubrication between the solid material and the screw surface, and between the solid material and the inner wall of the barrel. This excessive lubrication disrupts the mechanism of the counter-rotating conical twin-screw extruder in the solid conveying zone, which relies on friction to propel the material forward, causing the solid material to slip and stagnate in the feeding and compression / melting sections. The discontinuity of material delivery directly leads to periodic changes in the material filling degree inside the homogenization section, causing drastic fluctuations in the melt pressure of the homogenization section and making it difficult to establish a stable extrusion back pressure.

[0058] In Examples 1, 2, and 3, liquid composite additives were side-injected into the shearing and mixing section of an anti-rotating conical twin-screw extruder using a metering pump. When the material reached the shearing and mixing section, the solid particles had already undergone plasticization in the compression and melting section, transforming into a high-viscosity polymer melt. The side-injected liquid composite additive directly mixed into the polymer melt, participating in subsequent interfacial transesterification coupling reactions. This side-injection operation bypassed the solids conveying section of the anti-rotating conical twin-screw extruder, eliminating the negative interference of the liquid additive on the surface friction coefficient of the solid particles and ensuring continuous material conveying volume from the feeding section to the homogenization section. The stable performance of the test data in these examples demonstrates the engineering feasibility of the side-injection process in the continuous extrusion preparation of modified PVC power cable protection pipes.

[0059] Test Example 3: Radial compression testing of the pipe is used to verify how the preparation method changes the macroscopic mechanical load-bearing capacity of the modified PVC power cable protection pipe, and to evaluate the influence of different additives and process steps on the compatibility of the polymer system.

[0060] Experimental procedure: Cut the modified PVC power cable protection pipes prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 3 into 200mm long pipe segments as test samples.

[0061] Place the test specimen between the upper and lower pressure plates of the computer-controlled electronic universal testing machine, and adjust the central axis of the test specimen to be parallel to the upper and lower pressure plates of the computer-controlled electronic universal testing machine.

[0062] Set the compression speed of the microcomputer-controlled electronic universal testing machine to 10 mm / min, and start the test program to apply radial compression force to the test specimen.

[0063] When the inner diameter deformation rate of the test specimen reaches 1%, 2%, 3%, 4%, and 5%, the corresponding radial compressive force values ​​output by the microcomputer-controlled electronic universal testing machine are recorded.

[0064] Five independent parallel tests were conducted on the test samples of different groups, and the average value of the five tests was calculated as the final data for summary and comparison.

[0065] Table 3. Continuous test data of radial compressive force of pipes ; Figure 3 This is a line graph of radial compression force test data of pipes in Embodiments 1, 2, and 3 of the present invention, as well as Comparative Examples 1 and 3. The horizontal axis represents the inner diameter deformation rate (%), and the vertical axis represents the radial compression force (N). The legend includes Embodiments 1, 2, and 3, Comparative Examples 1 and 3.

[0066] in conclusion: According to Table 3 and Figure 3 The data shows that, under the same inner diameter deformation rate, the radial compressive force values ​​of Examples 1, 2, and 3 are all higher than those of Comparative Examples 1 and 3.

[0067] In Examples 1, 2, and 3, a liquid composite additive was used in the preparation process, formed by mixing isopropyltris(dioctylpyrophosphate)titanate with epoxidized soybean oil. Under the high-temperature shear environment of extrusion compounding, the hydrogen chloride released from the slight thermal degradation of polyvinyl chloride resin initiates ring-opening of the epoxy groups in the epoxidized soybean oil, generating hydroxyl structures. The generated hydroxyl structures and the polar groups on the surface of the polyvinyl chloride dry mix undergo transesterification with the centers of isopropyltris(dioctylpyrophosphate)titanate. This transesterification reaction constructs a chemically bonded network between the two phases of the polyvinyl chloride dry mix and the polyolefin alloy ionomer masterbatch. Externally applied radial loads are transferred and dispersed along this chemically bonded network between different continuous polymer phases, avoiding localized stress concentrations and improving the overall structural rigidity of the pipe, resulting in higher radial compressive force values ​​in macroscopic tests.

[0068] Comparative Example 1 employed a one-pot mixing process, eliminating the steps of separately preparing PVC dry mix and polyolefin alloy ionomer masterbatch. PVC resin is highly polar, while octene-1 copolymer and high-density polyethylene exhibit non-polarity. This polarity difference leads to severe macroscopic phase separation defects during extrusion. When radial compressive force is applied by a computer-controlled electronic universal testing machine, the internal phase separation interface cannot transmit mechanical stress, resulting in matrix slip yielding. This loss of structural continuity reduces the pipe's resistance to external deformation, ultimately causing Comparative Example 1 to have the lowest radial compressive force value among all test groups.

[0069] In step S3 of Comparative Example 3, the isopropyltris(dioctylpyrophosphate)titanate component was omitted. Although the test pipe contained epoxidized soybean oil for processing lubrication, it lacked a titanate center substance to provide coupling bridging. An interfacial crosslinking reaction could not be established between the PVC dry mix phase and the polyolefin alloy ionomer masterbatch phase; the polymer phases maintained their structure only through weak entanglement. When the test pipe was subjected to a compressive load applied by a computer-controlled electronic universal testing machine, slippage occurred at the interface between the two phases. Slippage cut off the stress transmission path resisting deformation, reducing the material's macroscopic compressive strength. This was reflected in the test data as the radial compressive force value of Comparative Example 3 being lower than that of Examples 1, 2, and 3.

[0070] Test Example 4: Low-temperature drop hammer impact test is used to verify the mechanical impact toughness of modified PVC power cable protection pipes under different low-temperature environments and to evaluate the ability of the polymer system phase structure to dissipate external instantaneous impact energy.

[0071] Experimental procedure: Cut the modified PVC power cable protection pipes prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 3 to obtain pipe sections with a length of 300 mm as test samples.

[0072] Adjust the internal test environment temperature of the low temperature constant temperature test chamber, and set the test environment temperature gradients to 0℃, -5℃, -10℃, -15℃, and -20℃.

[0073] The test samples of different groups were placed in a low-temperature constant temperature test chamber with the test environment temperature set for conditioning, and the conditioning time was 120 minutes.

[0074] Remove the test specimen after conditioning and place it on the V-shaped support frame of the drop hammer impact testing machine. Set the mass of the drop hammer to 1.0 kg and the vertical height of the drop hammer release to 2.0 m.

[0075] Start the drop hammer impact tester to apply a mechanical impact to the test specimen, and record the number of through cracks or complete fractures that occur on the surface of the test specimen.

[0076] For each test environment temperature condition, each group was subjected to 5 independent parallel tests, with 50 test specimens per test. The percentage of test specimens that developed through cracks or completely fractured in each test was calculated as the specimen breakage rate. Finally, the average value of the 5 test results was recorded and summarized.

[0077] Table 4. Test data on sample breakage rate under different test ambient temperatures ; Figure 4 This is a line graph of the sample breakage rate test data of Embodiments 1, 2, and 3, and Comparative Examples 1 and 3 of the present invention. The horizontal axis represents the test environment temperature (°C), and the vertical axis represents the sample breakage rate (%). The legend includes Embodiments 1, 2, and 3, Comparative Examples 1 and 3.

[0078] in conclusion: According to Table 4 and Figure 4The data shows that within the test environment temperature range of 0℃ to -20℃, the sample breakage rates of Examples 1, 2, and 3, as well as Comparative Examples 1 and 3, show an increasing trend as the test environment temperature decreases. At the same test environment temperature, the sample breakage rates of Examples 1, 2, and 3 are lower than those of Comparative Examples 1 and 3.

[0079] The preparation methods of Examples 1, 2, and 3 involve mixing 100 parts by weight of PVC dry mix containing PVC resin with polyolefin alloy ionomer masterbatch using a twin-screw extrusion process. The polyolefin alloy ionomer masterbatch contains octene-1 copolymer and maleic anhydride-grafted polyolefin elastomer components. Isopropyl tris(dioctyl pyrophosphate) titanate in the liquid composite additive promotes the formation of in-situ dispersed micro-regions of the polyolefin components within the PVC resin matrix. When the drop hammer of the drop hammer impact tester contacts the surface of the test specimen, the instantaneous mechanical impact energy is transferred into the PVC resin matrix. The polyolefin micro-regions undergo volume deformation upon receiving the mechanical impact energy. This volume deformation process consumes the impact energy transmitted into the material, preventing the formation and continuous expansion of destructive streaks within the PVC resin matrix. At a test environment temperature of -20°C, the molecular chain segments of the polyolefin micro-regions retain free space and possess yielding ability. The yield strength maintained the toughness of the modified PVC power cable protection pipe at low temperatures, resulting in lower sample breakage rates in Examples 1, 2, and 3.

[0080] Comparative Example 1 omitted the step of pre-mixing and preparing the polyolefin alloy ionomer masterbatch. All raw materials, including the octene-1 copolymer with ethylene and polyvinyl chloride resin, were directly extruded after being mixed in a one-pot process. A surface tension difference exists between the polar polyvinyl chloride resin matrix and the non-polar polyolefin component. This surface tension difference triggers large-scale macroscopic phase separation within the material system, forming agglomerated defect points. When mechanical impact energy is applied to the test specimen, stress concentration occurs at these defect points. This stress concentration leads to brittle fracture of the pipe wall. At test ambient temperatures below 0°C, the amorphous polymer matrix undergoes glass hardening, reducing its resistance to brittle fracture, resulting in the highest breakage rate for the sample in Comparative Example 1 among all test groups.

[0081] In Comparative Example 3, isopropyltris(dioctylpyrophosphate)titanate was not added in step S3. The test sample system lacked the chemical coupling structure constructed by interfacial transesterification. The polyolefin component and the polyvinyl chloride resin matrix maintained their bond solely through contact friction. When the drop hammer impact tester released a high-energy mechanical load, the molecular chain segments on both sides of the phase interface slid relative to each other and disengaged. This disengagement cut off the path for the mechanical impact energy to transfer from the polyvinyl chloride resin to the polyolefin microdomains for deformation dissipation. The accumulation of undissipated energy caused cracking in the macroscopic structure of the material, resulting in a higher breakage rate for the sample in Comparative Example 3 compared to those in Examples 1, 2, and 3.

[0082] Test Example 5: The static sliding friction coefficient test of the inner wall of the pipe is used to verify the reduction of the wire pulling resistance by the spontaneously formed slip layer inside the modified PVC power cable protection pipe, and to evaluate the influence of different production processes and formulations on the friction performance of the inner surface of the pipe.

[0083] Experimental procedure: Cut the modified PVC power cable protection pipes prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 3 along the axial direction to obtain a semi-circular pipe section with a length of 500 mm as a test sample.

[0084] Fix the test specimen on the horizontal test platform of the static sliding friction coefficient tester, keeping the inner wall surface of the test specimen facing upwards.

[0085] A cross-linked polyethylene insulated standard cable segment with an outer diameter of 50 mm was selected as the friction pair and placed on the inner wall of the test specimen.

[0086] Using the loading device of the static sliding friction coefficient tester, vertical normal loads of 50N, 100N, 150N, 200N, and 250N were applied to the friction pair respectively.

[0087] Start the static sliding friction coefficient tester and record the peak horizontal tension at the moment when the friction pair produces relative sliding on the inner wall of the test specimen.

[0088] The static sliding friction coefficient is calculated by dividing the peak horizontal tensile force by the corresponding vertical normal load value. Five independent parallel tests are performed for each vertical normal load condition, and the average value of the five test results is recorded and summarized.

[0089] Table 5. Static sliding friction coefficient test data ; Figure 5This is a line graph showing the static sliding friction coefficient test of the inner wall of the pipe in Embodiments 1, 2, and 3 of the present invention, as well as Comparative Examples 1 and 3. The horizontal axis represents the vertical normal load (N), and the vertical axis represents the static sliding friction coefficient. The legend includes Embodiments 1, 2, and 3, Comparative Examples 1 and 3.

[0090] in conclusion: According to Table 5 and Figure 5 The data shows that, within the vertical normal load range of 50N to 250N, the static sliding friction coefficient values ​​of Examples 1, 2, and 3 are lower than those of Comparative Examples 1 and 3.

[0091] In the preparation methods of Examples 1, 2, and 3, the polyolefin alloy ionomer masterbatch contains a high-density polyethylene (HDPE) component. During the high-temperature shear extrusion process in an anti-rotating conical twin-screw extruder, the molecular chain flexibility and melt viscosity of HDPE differ from those of polyvinyl chloride (PVC) resin. Driven by extrusion pressure, the HDPE melt migrates towards the outer surface of the polymer melt flow, i.e., the inner and outer walls of the pipe. After the HDPE that migrates to the inner wall of the pipe cools and solidifies, it forms a non-polar continuous slip layer. This continuous slip layer reduces the surface roughness of the inner wall of the pipe, thereby reducing the frictional resistance of the cross-linked polyethylene insulated standard cable segment sliding inside the pipe. Macroscopic test data show that Examples 1, 2, and 3 have low static sliding friction coefficients.

[0092] Comparative Example 1 employed a one-pot dry-mix extrusion process that omitted the preparation step of the polyolefin alloy ionomer masterbatch. High-density polyethylene granules were directly mixed with 100 parts by weight of polyvinyl chloride resin and other powder additives. Lacking pre-melted dispersion, the high-density polyethylene agglomerated within the polyvinyl chloride resin matrix, failing to migrate smoothly to the inner wall of the pipe during the extrusion molding stage to form a continuous sliding layer. The inner wall of the pipe directly exposed the polar polyvinyl chloride resin matrix and inorganic filler particles such as heavy calcium carbonate. The polar matrix and filler particles increased the frictional resistance of the inner wall surface, resulting in Comparative Example 1 having the highest static sliding friction coefficient among all test groups.

[0093] The preparation method of Comparative Example 3 removed isopropyltris(dioctylpyrophosphate)titanate. Due to the lack of transesterification coupling anchoring within the system, high-density polyethylene is prone to excessive aggregation during its migration to the polymer melt surface, making it impossible to form a uniformly thick, continuous sliding layer on the inner wall of the pipe. Some areas of the inner wall of the pipe exhibit rough protrusions caused by macroscopic phase separation. These rough protrusions hinder the smooth movement of the cross-linked polyethylene insulated standard cable segment, resulting in a higher static sliding friction coefficient in Comparative Example 3 compared to Examples 1, 2, and 3.

Claims

1. A modified PVC power cable protection pipe, characterized in that, The modified PVC power cable protection pipe is made from the following raw materials in parts by weight: Polyvinyl chloride resin: 100 parts; Calcium-zinc composite heat stabilizer: 2.5–4.0 parts; Pentaerythritol: 0.3–0.8 parts; Stearic acid: 0.3–0.8 parts; Heavy calcium carbonate: 5.0–15.0 parts; Octene-1 copolymer with ethylene: 10.0–20.0 parts; High-density polyethylene: 3.0–8.0 parts; Maleic anhydride-grafted polyolefin elastomer: 3.0–7.0 parts; Active zinc oxide: 1.0–2.5 parts; Isopropyl tris(dioctylpyrophosphoryloxy)titanate: 0.5–1.5 parts; Epoxidized soybean oil: 1.0 to 3.0 parts.

2. The modified PVC power cable protection pipe according to claim 1, characterized in that, The octene-1 and ethylene copolymer, the high-density polyethylene, the maleic anhydride-grafted polyolefin elastomer, and the active zinc oxide constitute a polyolefin alloy ionomer masterbatch.

3. The modified PVC power cable protection pipe according to claim 1, characterized in that, The isopropyl tris(dioctyl pyrophosphate) titanate and the epoxidized soybean oil constitute a liquid composite additive.

4. The modified PVC power cable protection pipe according to claim 1, characterized in that, The specific steps for preparing the modified PVC power cable protection pipe are as follows: The octene-1 copolymer with ethylene, the high-density polyethylene, the maleic anhydride-grafted polyolefin elastomer and the active zinc oxide are mixed in a kneader and then directly fed into the main feed port of a co-rotating twin-screw extruder for extrusion pelleting to obtain polyolefin alloy ionomer masterbatch. The polyvinyl chloride resin, the calcium-zinc composite heat stabilizer, the pentaerythritol, the stearic acid, and the heavy calcium carbonate are fed into a heated high-speed mixer for friction heating and heat preservation kneading, and then discharged into a cold mixer for cooling to obtain a dry polyvinyl chloride mixture. The isopropyl tris(dioctyl pyrophosphoryl oxy) titanate and the epoxidized soybean oil were added to a mixing tank and stirred to obtain a liquid composite additive. The PVC dry mix and the polyolefin alloy ionomer masterbatch are simultaneously fed into the main feed inlet of the counter-rotating conical twin-screw extruder. The metering pump is started, and the liquid composite additive is injected laterally into the shearing and mixing section of the counter-rotating conical twin-screw extruder through the metering pump. The internal material is extruded and formed through the die section and enters the vacuum setting box for cooling and setting. After being pulled and cut by the traction machine, the modified PVC power cable protection pipe is obtained.

5. The modified PVC power cable protection pipe according to claim 4, characterized in that, During the preparation of the modified PVC power cable protection pipe, the temperature of the mixing tank used to mix the isopropyl tris(dioctyl pyrophosphate) titanate and the epoxidized soybean oil is maintained at 40-50°C.

6. The modified PVC power cable protection pipe according to claim 4, characterized in that, In the process of preparing the polyolefin alloy ionomer masterbatch, the kneader rotates at 500-800 rpm, the mixing time is 3-5 min, and the temperature of the feeding section of the co-rotating twin-screw extruder is controlled at 160-170℃, the melting section temperature is 180-190℃, the reaction mixing section temperature is 190-200℃, the homogenization section temperature is 187-196℃, the die section temperature is 185-194℃, and the screw speed is 150-250 rpm.

7. The modified PVC power cable protection pipe according to claim 4, characterized in that, In the process of preparing the polyvinyl chloride dry mix, the speed of the heated high-speed mixer is 1000-1500 rpm and the friction heating is raised to 110-115°C, and the heat preservation kneading time is 5-8 min; the speed of the cold mixer is 100-200 rpm and the cooling temperature is lowered to 35-39°C.

8. The modified PVC power cable protection pipe according to claim 4, characterized in that, During the preparation of the liquid composite additive, the rotation speed of the mixing tank is 200-400 rpm, and the stirring time is 10-20 min.

9. The modified PVC power cable protection pipe according to claim 4, characterized in that, During the extrusion process in the counter-rotating conical twin-screw extruder, the temperature of the feeding section is controlled at 160–165°C, the temperature of the compression and melting section at 170–175°C, the temperature of the shearing and mixing section at 174–181°C, the temperature of the venting section at 176–183°C, the temperature of the homogenizing section at 180–186°C, and the temperature of the die section at 178–184°C; the screw speed is controlled at 20–40 rpm, and the vacuum degree of the venting section is -0.05 MPa to -0.08 MPa.

10. The modified PVC power cable protection pipe according to claim 4, characterized in that, During the cooling and shaping process in the vacuum shaping chamber, the cooling water temperature of the vacuum shaping chamber is 15-20℃, and the vacuum degree is -0.02MPa to -0.04MPa.

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