Weather-resistant polyolefin composite cable protection pipe material and preparation method thereof

Abstract

This invention relates to the field of polymer materials technology, and discloses a weather-resistant polyolefin composite cable protection pipe material and its preparation method. The material is composed of a polar coordination anchoring masterbatch, an ethylene-propylene block copolymer, an ethylene-1-octene copolymer, maleic anhydride-grafted polypropylene, and low-structure furnace black. In preparation, an ethylene-vinyl alcohol copolymer, an ethylene-methacrylic acid copolymer zinc salt, and a small-molecule weather-resistant agent are fed into a twin-screw extruder. Deionized water is injected under high pressure in the middle section to promote zinc ion dissociation and coordination. Vacuum dehydration in the later section yields the masterbatch. The masterbatch is then blended with an ethylene copolymer matrix resin and the grafted material, and carbon black is added to the side of the later section of the extruder for molding. This invention utilizes the multiple coordination of zinc ions to stably anchor the small-molecule weather-resistant agent within the macromolecular network, blocking migration channels. Combined with the interfacial esterification crosslinking of the maleic anhydride-grafted polypropylene, it overcomes multi-component phase separation, endowing the pipe material with long-lasting anti-aging and stable mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a weather-resistant polyolefin composite cable protection pipe material and its preparation method. Background Technology

[0002] Polyolefin materials are commonly used in the manufacture of cable protection conduits due to their good electrical insulation and corrosion resistance. Since these conduits are mostly laid outdoors, they are subjected to long-term exposure to sunlight, ultraviolet radiation, and the heat and oxygen effects of nature. This can easily cause the polymer macromolecules inside the conduit to degrade, eventually leading to brittleness and cracking of the conduit walls. To address this, the industry standard practice is to mix light stabilizers, UV absorbers, and other small-molecule weathering agents into the polyolefin resin, and to add carbon black to block ultraviolet radiation.

[0003] However, this conventional treatment method has revealed some unavoidable defects in practical use. The added low-molecular-weight weather-resistant agents are not stable in the non-polar polyolefin matrix. As the pipes experience temperature changes outdoors, these small molecules easily migrate outward along the molecular gaps of the polymer, slowly seeping out of the pipe surface or even evaporating directly. Once these effective anti-aging components are lost, the long-term weather resistance of the pipes will be significantly reduced. At the same time, polar low-molecular-weight weather-resistant agents and inorganic carbon black particles are naturally repelled by non-polar polyolefin resins in terms of physical properties, resulting in poor compatibility. When they are mixed together, it is difficult to achieve a uniform distribution; instead, they tend to agglomerate within the material or undergo local delamination. These microscopic uneven dispersions become weak points under stress, directly reducing the mechanical strength and impact toughness of the pipes themselves.

[0004] Furthermore, in the processing and manufacturing stage, traditional extrusion blending processes struggle to handle such mutually repulsive multi-component materials. If the process relies solely on increasing the mechanical shear force of the screw to forcibly mix them, the aggregate structure of the carbon black itself is often broken down under prolonged high-intensity mechanical action, which directly weakens the physical shielding effect of carbon black originally used to block ultraviolet rays. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method. It solves the problems of easy migration and loss of small molecule weather-resistant agents in existing polyolefin cable protection pipes, which leads to the degradation of long-term weather resistance; poor compatibility between polar additives and non-polar resin matrix, which causes a decrease in the mechanical strength of the material; and the easy destruction of the physical shielding structure of carbon black by conventional strong shear processing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a weather-resistant polyolefin composite cable protection pipe material, comprising the following raw materials in parts by weight: 4.1–9.2 parts of polar coordination anchoring masterbatch; 90–110 parts of ethylene-propylene block copolymer; 12–22 parts of ethylene-1-octene copolymer; 1.5–5.0 parts of maleic anhydride-grafted polypropylene; 2.0–3.5 parts of furnace black; The polar coordination anchoring masterbatch is prepared from the following components in parts by weight: 2.5 to 5.0 parts of ethylene-vinyl alcohol copolymer, 0.6 to 2.0 parts of zinc salt of ethylene-methacrylic acid copolymer, 0.5 to 1.2 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 0.5 to 1.0 parts of 2-hydroxy-4-n-octyloxybenzophenone.

[0007] By employing the above technical solution, the material uses ethylene-propylene block copolymer as the matrix to provide basic mechanical strength, and ethylene-1-octene copolymer as the elastic dispersed phase to absorb impact stress and improve the material's toughness. To achieve long-lasting weather resistance, the material relies on a coherent physical and chemical bonding mechanism. Specifically, in the melt-processing state, the zinc salt of the ethylene-methacrylic acid copolymer dissociates and releases zinc ions. These zinc ions, acting as central ions, directly coordinate with the polar hydroxyl groups on the macromolecular chains of the ethylene-vinyl alcohol copolymer, thereby constructing a network-like macromolecular framework. During this framework formation process, zinc ions and hydroxyl groups also undergo multiple complexation and hydrogen bonding with the ester and secondary amine groups in bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and the carbonyl and hydroxyl groups in 2-hydroxy-4-n-octyloxybenzophenone. This multi-layered binding force firmly anchors the originally easily free small-molecule weather-resistant agent to the ethylene-vinyl alcohol macromolecular chain, directly cutting off the channels for small molecules to migrate to the surface of the product.

[0008] While addressing the issue of small molecule loss, it's also necessary to consider the compatibility of the material's internal structure. Maleic anhydride-grafted polypropylene in this system acts as an interface connector. Its non-polar polypropylene backbone segments can penetrate the ethylene-propylene block copolymer matrix, resulting in molecular chain entanglement and co-crystallization. Simultaneously, the anhydride groups on its polar side chains undergo ring-opening, forming covalent bonds with the exposed free hydroxyl groups on the surface of the polar coordinating anchor masterbatch through esterification. This two-way bonding mechanism creates a stable interface between the non-polar matrix and the polar anti-aging component, preventing internal phase separation.

[0009] Furthermore, due to its small aggregate size, low-structure furnace black can be uniformly dispersed in the continuous phase by the wetting effect of maleic anhydride-grafted polypropylene on the interface, acting as a physical ultraviolet shielding layer. This, combined with the aforementioned light absorption and free radical capture system within the masterbatch, directly breaks the chain reaction of photo-oxidative degradation of the macromolecular chains.

[0010] Preferably, the grafting rate of maleic anhydride-grafted polypropylene is 1.0 wt% to 1.5 wt%.

[0011] By adopting the above technical solution, setting the grafting rate within this range can, on the one hand, leave enough acid anhydride reaction sites to allow it to successfully complete esterification and crosslinking with the polar coordination anchoring masterbatch. On the other hand, it also takes into account the problems of polypropylene itself. If the grafting rate is too high, the polypropylene molecular chains will often break and degrade significantly. Keeping the grafting rate below 1.5 wt% can basically maintain the basic mechanical strength of the matrix resin.

[0012] Preferably, the maleic anhydride-grafted polypropylene is obtained by reactive extrusion of raw materials comprising the following parts by weight: 100 parts of polypropylene homopolymer powder, 1.5 to 2.5 parts of maleic anhydride, and 0.10 to 0.20 parts of dicumyl peroxide.

[0013] By employing the above technical solution, when the system is heated, dicumyl peroxide decomposes to generate alkoxy radicals. These radicals actively abstract hydrogen atoms from the tertiary carbon atoms of the polypropylene macromolecular chain, thereby generating polypropylene macromolecular radicals. Subsequently, the maleic anhydride monomer, relying on its double bond structure, undergoes addition with the polypropylene macromolecular radicals, completing the grafting process. The specific proportion of initiator is added here primarily to control the rate of radical generation, thereby suppressing other unnecessary side reactions.

[0014] Preferably, maleic anhydride-grafted polypropylene is prepared by the following steps: Polypropylene homopolymer powder, maleic anhydride, and dicumyl peroxide were mixed in a high-speed mixer to obtain a solid mixture. The solid mixture was fed into the main feed port of a co-rotating twin-screw extruder with a length-to-diameter ratio of 40 for reactive extrusion. The screw speed was set to 200 rpm, and the temperatures of each zone of the extruder were set sequentially as follows: zone 1 170℃, zone 2 180℃, zones 3 to 6 190℃, zones 7 to 9 200℃, and the die head 200℃. The vacuum exhaust system was turned on in zone 8 of the extruder, and the vacuum degree was set to -0.08 MPa to remove unreacted maleic anhydride monomers. After cooling in a water tank, the mixture was pelletized and dried to obtain maleic anhydride-grafted polypropylene.

[0015] By employing the above technical solution, the machine's front end maintains a low temperature to prevent the initiator from decomposing and dissipating prematurely. When the material reaches the middle section, the temperature precisely matches the half-life of the peroxide, effectively triggering the addition reaction. The slightly higher temperature in the later stages quenches the large molecular free radicals. The final high-vacuum exhaust process removes any unreacted free small molecule monomers, preventing these residual monomers from vaporizing during subsequent molding and creating tiny pores on the tube walls.

[0016] The second aspect of this invention provides a method for preparing a weather-resistant polyolefin composite cable protection pipe material, employing the following technical solution: A method for preparing a weather-resistant polyolefin composite cable protection pipe material includes the following steps: Ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid copolymer zinc salt, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and 2-hydroxy-4-n-octyloxybenzophenone were cold-mixed in a high-speed mixer to obtain a solid-phase mixture; The solid mixture is fed into the main feed port of a co-rotating parallel twin-screw extruder via a loss-in-weight feeder. In the middle section of the co-rotating parallel twin-screw extruder, deionized water is continuously injected by a high-pressure liquid metering pump for shearing and mixing. Then, in the rear section of the co-rotating parallel twin-screw extruder, a vacuum pump is turned on to force the removal of water. The melt is extruded through a multi-hole die, then granulated underwater and centrifuged to dehydrate and dry, to obtain polar coordination anchoring masterbatch. The polar coordination anchoring masterbatch was mixed with ethylene-propylene block copolymer, ethylene-1-octene copolymer and maleic anhydride grafted polypropylene in a mixer, and then added to the main feed port of the pipe blending extruder. Furnace carbon black is uniformly added to the fourth zone of the pipe blending extruder via a twin-screw forced side feeder. After homogenization, normal vacuum is activated to remove entrained air and form a blended material. The blended material is fed into the pipe extruder head, and the extruded pipe blank directly enters the vacuum sizing box for sizing and shaping. It is then continuously traction and cut by a crawler traction machine to obtain a weather-resistant polyolefin composite cable protection pipe.

[0017] By employing the above technical solution, this preparation process kinetically pushes the coordination reaction forward. During the preparation of polar coordination anchoring masterbatch, high-pressure water injection in the middle stage forces water molecules into the high-temperature polymer melt. Due to the polarity of water molecules, zinc ions in the zinc salt of the ethylene-methacrylic acid copolymer are more easily dissociated, resulting in more free metal ions in the system. This, in turn, accelerates the process of metal ions complexing with the polar groups of the copolymer and the small-molecule weathering agent. At this point, the added liquid water undergoes a gaseous transformation at high temperature, causing volume expansion. This expansion, combined with the shearing action of the screw, increases the specific surface area inside the melt, resulting in a more uniform mixing of the components at the molecular level.

[0018] When the masterbatch is ready and enters the pipe forming stage, how to add inorganic particles becomes a problem. Here, we choose to add low-structure furnace black from the side feed port in the later part of the main line. This is mainly to prevent these carbon black powders from undergoing screw shearing throughout the entire process with the main material, so as to avoid breaking down their physical structure and thus maintain the shielding effect of carbon black in the pipe.

[0019] Preferably, the cold mixing time in the high-speed mixer is 3 to 5 minutes, and the rotation speed is 400 rpm; the length-to-diameter ratio of the co-rotating parallel twin-screw extruder is 48; 0.8 to 2.5 parts by weight of deionized water are continuously injected into the middle section of the co-rotating parallel twin-screw extruder through a high-pressure liquid metering pump at a pressure of 1.5 to 3.0 MPa; the rotation speed for shearing and mixing is set to 150 to 250 rpm; and the vacuum pump is turned on to forcibly remove moisture and maintain a vacuum degree of -0.095 MPa to -0.07 MPa.

[0020] The reason for choosing an extruder with a length-to-diameter ratio of 48 by adopting the above technical solution is to allow the melt to stay inside for a longer period, providing sufficient axial distance for the reaction to complete the steps of water infiltration, ion coordination, and vacuum removal one by one. The set of water injection pressure and dosage parameters is to ensure there is enough water in the system to aid in ion dissociation, but not too much, which could cause a sudden drop in temperature within the machine, freezing and clogging the material. High vacuum is used to forcibly remove residual water, preventing the remaining moisture from causing the macromolecules to hydrolyze and break down in subsequent steps.

[0021] Preferably, the temperatures of each zone of the co-rotating parallel twin-screw extruder are set as follows: Zones 1 to 2: 170–180°C; Zones 3 to 4: 180–195°C; Zone 5: 190°C; Zone 6 to the die head: 190–200°C.

[0022] By adopting the above technical solution, the front-end temperature is mainly responsible for smoothly dissolving the solid powder into a liquid phase. Since water is added to zones three and four, which absorb heat, a temperature increase is set to compensate for the heat lost during water vaporization, thus maintaining thermal balance and boosting the coordination reaction. The temperature at the die head is specifically set to a suitable surface tension range for underwater pelletizing.

[0023] Preferably, the mixing time in the mixer is 2 to 3 minutes; after homogenization, the vacuum degree for removing entrained air by turning on the normal vacuum is set to -0.05 MPa.

[0024] By adopting the above technical solution, the mixing time can roughly even out the appearance of different types of particles. Placing normal vacuum degassing after the process can conveniently remove air trapped in the gaps of carbon black powder and from the surface of resin particles. Once this trapped air is removed, the pipe cross-section will be denser, preventing the formation of dark pores that could cause stress concentration.

[0025] Preferably, the temperatures of each zone of the pipe blending extruder are set as follows: Zones 1 to 3 190–205℃, Zone 4 210–215℃, and Zones 5 to 6 215–225℃.

[0026] By adopting the above technical solution, zones five and six provide slightly higher temperatures as the material is conveyed forward. This extra heat becomes the driving force for the reaction, causing the anhydride groups on the maleic anhydride-grafted polypropylene side chains to open their ring structures and quickly undergo esterification with the hydroxyl groups on the masterbatch surface, tightly binding these originally independent components together at the interface.

[0027] Preferably, the temperature of the pipe extruder head is maintained at 210-220°C; the vacuum degree for sizing and shaping in the vacuum sizing box is set to -0.06MPa to -0.03MPa, and the temperature of the circulating cooling water used is 15-25°C.

[0028] By adopting the above technical solution, the determined molding temperature is just right to keep the polymer macromolecules in a relatively fluid state, making it easy to extrude along the shape of the die. During the setting stage, adjusting the cooling water temperature and vacuum level essentially controls the rate at which the inner and outer walls of the pipe cool down. As long as the heat dissipation rhythm is aligned, the polyolefin molecular chains can contract and align themselves properly. This stabilizes the crystallization of the product and also releases residual internal stress, resulting in pipes that are less prone to deformation and meet the required ring stiffness.

[0029] This invention provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method. It has the following beneficial effects: 1. This invention introduces polar coordination anchoring masterbatch, utilizing the zinc ions released from the zinc salt of ethylene-methacrylic acid copolymer during melt processing to form multiple coordination complexes and hydrogen bonds with the polar groups in the system. This directly cuts off the physical channels for small molecules to migrate and seep out to the pipe surface, thereby preventing the loss of effective weather-resistant components over time and ensuring the long-term UV resistance and thermo-oxidative aging resistance of the cable protection pipe in outdoor environments.

[0030] 2. This invention utilizes maleic anhydride-grafted polypropylene to improve the interfacial compatibility of the system. Its non-polar polypropylene main chain segments can enter the interior of the ethylene-propylene block copolymer matrix to undergo molecular chain entanglement, while the anhydride groups on the polar side chains open during high-temperature extrusion and undergo esterification and crosslinking reactions with the hydroxyl groups exposed on the surface of the coordination masterbatch. This solves the problem of phase separation that easily occurs between the non-polar polyolefin substrate and the polar anti-aging system, making the components tightly integrated. While improving the weather resistance of the material, it maintains the mechanical strength and toughness required by the pipe itself.

[0031] 3. In terms of the preparation process, this invention employs a high-pressure injection of deionized water in the middle section of the extruder, combined with high-vacuum extraction in the later section. The vaporization and expansion of liquid water in the high-temperature melt, combined with screw shearing, not only increases the specific surface area of ​​the mixed materials, but also promotes the dissociation of zinc ions due to the polarity of water molecules, thereby accelerating the progress of coordination complexation reaction. At the same time, furnace black is added in the pipe forming section by side feeding in the later section, which avoids the destruction of the physical structure of inorganic carbon black particles due to excessive shearing throughout the process, ensuring the uniformity of dispersion of multiphase components in the matrix, maintaining the ultraviolet physical shielding function of carbon black, and making the final formed pipe have a dense microstructure. Attached Figure Description

[0032] Figure 1 This is a line graph showing the change in the amount of additives precipitated on the surface of the pipe samples of Examples 1-5 of the present invention under thermal aging conditions at 85°C; Figure 2 Line graphs showing the changes in the amount of additives precipitated on the surface of the pipe samples of Comparative Examples 1-6 of the present invention under thermal aging conditions at 85°C; Figure 3 The following are comparative graphs of the performance of the various pipe samples of the present invention before and after high and low temperature alternating test; wherein, (a) is a comparative graph of the elongation at break and retention rate before and after high and low temperature alternating test, and (b) is a comparative graph of the drop hammer breakage rate before and after high and low temperature alternating test. Figure 4 The following are line graphs showing the performance changes of various pipe samples of the present invention in the accelerated aging test under artificial climate; wherein, (a) is a line graph showing the change in tensile yield strength retention rate, and (b) is a line graph showing the change in elongation at break retention rate. Figure 5 The figures show a comparison of the comprehensive mechanical properties of the various pipe samples of the present invention at room temperature; wherein, (a) is a comparison of the ring stiffness and tensile elastic modulus at room temperature, and (b) is a comparison of the notched impact strength of a simply supported beam. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and 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.

[0034] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing maleic anhydride-grafted polypropylene, including the following steps: 100 parts by weight of polypropylene homopolymer powder, 2.0 parts by weight of maleic anhydride, and 0.15 parts by weight of dicumyl peroxide were placed in a high-speed mixer and mixed at 400 rpm for 5 minutes to obtain a solid mixture. The solid mixture was fed into the main feed port of a co-rotating twin-screw extruder with an aspect ratio of 40 for reactive extrusion. The temperatures of each zone of the extruder were set sequentially as follows: Zone 1 170℃, Zone 2 180℃, Zones 3-6 190℃, Zones 7-9 200℃, and the die head 200℃. The screw speed was set to 200 rpm. In Zone 8 of the extruder, the vacuum exhaust system was activated, and the vacuum level was set to -0.08 MPa to remove unreacted maleic anhydride monomer. The extrudate was cooled in a water bath, pelletized, and dried to obtain maleic anhydride-grafted polypropylene with a grafting rate of 1.2 wt%.

[0035] Preparation Example 2: This preparation example provides a method for preparing maleic anhydride-grafted polypropylene, including the following steps: 100 parts by weight of polypropylene homopolymer powder, 1.5 parts by weight of maleic anhydride, and 0.10 parts by weight of dicumyl peroxide were placed in a high-speed mixer and mixed at 400 rpm for 5 minutes to obtain a solid mixture. The solid mixture was fed into the main feed port of a co-rotating twin-screw extruder with an aspect ratio of 40 for reactive extrusion. The temperatures of each zone of the extruder were set sequentially as follows: Zone 1 170℃, Zone 2 180℃, Zones 3-6 190℃, Zones 7-9 200℃, and the die head 200℃. The screw speed was set to 200 rpm. In Zone 8 of the extruder, the vacuum exhaust system was activated, and the vacuum level was set to -0.08 MPa to remove unreacted maleic anhydride monomer. The extrudate was cooled in a water bath, pelletized, and dried to obtain maleic anhydride-grafted polypropylene with a grafting rate of 1.0 wt%.

[0036] Preparation Example 3: This preparation example provides a method for preparing maleic anhydride-grafted polypropylene, including the following steps: 100 parts by weight of polypropylene homopolymer powder, 2.5 parts by weight of maleic anhydride, and 0.20 parts by weight of dicumyl peroxide were placed in a high-speed mixer and mixed at 400 rpm for 5 minutes to obtain a solid mixture. The solid mixture was fed into the main feed port of a co-rotating twin-screw extruder with an aspect ratio of 40 for reactive extrusion. The temperatures of each zone of the extruder were set sequentially as follows: Zone 1 170℃, Zone 2 180℃, Zones 3-6 190℃, Zones 7-9 200℃, and the die head 200℃. The screw speed was set to 200 rpm. In Zone 8 of the extruder, the vacuum exhaust system was activated, and the vacuum level was set to -0.08 MPa to remove unreacted maleic anhydride monomer. The extrudate was cooled in a water bath, pelletized, and dried to obtain maleic anhydride-grafted polypropylene with a grafting rate of 1.5 wt%.

[0037] Examples 1-5: Example 1: This embodiment provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method, including the following steps: The first step was to prepare the polar coordination anchoring masterbatch: 4.0 parts by weight of ethylene-vinyl alcohol copolymer, 1.4 parts by weight of zinc salt of ethylene-methacrylic acid copolymer, 0.8 parts by weight of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 0.8 parts by weight of 2-hydroxy-4-n-octyloxybenzophenone were added to a high-speed mixer and cold-mixed at 400 rpm for 4 minutes to obtain a solid mixture. This solid mixture was then fed into the main feed port of a co-rotating parallel twin-screw extruder with an aspect ratio of 48 through a loss-in-weight feeder. The temperatures in zones one and two of the extruder were set to 175°C, and the temperatures in zones three and four were set to 190°C. In zones three and four, 1.5 parts by weight of deionized water were continuously injected at a pressure of 2.5 MPa using a high-pressure liquid metering pump, and the screw speed was set to 200 rpm for shearing and mixing. In zone five, the temperature was set to 190°C, and a vacuum pump was activated to maintain a vacuum of -0.09 MPa to forcibly remove moisture. The melt enters zone six and is fed to the die head, where the temperature is maintained at 195°C. After being extruded through a multi-hole die, it is granulated underwater and then centrifuged, dehydrated, and dried to obtain polar coordination anchored masterbatch.

[0038] The second step involves preparing the final weather-resistant pipe composite material: All the polar coordination anchoring masterbatch obtained in the first step, along with 100 parts by weight of ethylene-propylene block copolymer, 18 parts by weight of ethylene-1-octene copolymer, and 3.5 parts by weight of maleic anhydride-grafted polypropylene obtained in Preparation Example 1, are mixed in a mixer for 3 minutes. The mixture is then added to the main feed port of a pipe blending extruder, with the extruder temperature set to 195°C in zones one to three. In zone four, the temperature is set to 210°C, and 2.8 parts by weight of low-structure furnace black are uniformly added using a twin-screw forced side feeder. Zones five and six are set to 220°C for homogenization, and in zone seven, a normal vacuum of -0.05 MPa is applied to remove entrained air, forming the blend material. The blended material enters the pipe extruder head at a temperature of 215℃. The extruded pipe blank directly enters the vacuum sizing box, where it is sizing and shaped under a vacuum of -0.05MPa and circulating cooling water at 20℃. After continuous traction and cutting by a crawler traction machine, weather-resistant polyolefin composite cable protection pipe is obtained.

[0039] Example 2: This embodiment provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method, including the following steps: The first step is to prepare the polar coordination anchoring masterbatch: 3.0 parts by weight of ethylene-vinyl alcohol copolymer, 0.8 parts by weight of ethylene-methacrylic acid copolymer zinc salt, 0.5 parts by weight of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 0.5 parts by weight of 2-hydroxy-4-n-octyloxybenzophenone are added to a high-speed mixer and cold-mixed at 400 rpm for 3 minutes to obtain a solid mixture. This solid mixture is then fed into the main feed port of a co-rotating parallel twin-screw extruder with an aspect ratio of 48 through a loss-in-weight feeder. The temperatures in zones one and two of the extruder are set to 170°C, and the temperatures in zones three and four are set to 180°C. In zones three and four, 1.0 parts by weight of deionized water are continuously injected at a pressure of 2.0 MPa using a high-pressure liquid metering pump, and the screw speed is set to 150 rpm for shearing and mixing. In zone five, the temperature is set to 190°C, and a vacuum pump is turned on to maintain a vacuum of -0.095 MPa to forcibly remove moisture. The melt enters zone six and is fed to the die head, where the temperature is maintained at 190°C. After being extruded through a multi-hole die, it is underwater pelletized, centrifuged, dehydrated, and dried to obtain polar coordination anchored masterbatch.

[0040] The second step involves preparing the final weather-resistant pipe composite material: All the polar coordination anchoring masterbatch obtained in the first step, along with 110 parts by weight of ethylene-propylene block copolymer, 15 parts by weight of ethylene-1-octene copolymer, and 2.0 parts by weight of maleic anhydride-grafted polypropylene obtained in Preparation Example 2, are mixed in a mixer for 2 minutes. The mixture is then added to the main feed port of a pipe blending extruder, with the extruder temperature set to 190°C in zones one to three. In zone four, the temperature is set to 210°C, and 2.0 parts by weight of low-structure furnace black is uniformly added using a twin-screw forced side feeder. Zones five and six are set to 215°C for homogenization, and in zone seven, a normal vacuum of -0.05 MPa is applied to remove entrained air, forming the blend material. The blended material enters the pipe extruder head at a temperature of 210℃. The extruded pipe blank directly enters the vacuum sizing box, where it is sizing and shaped under a vacuum of -0.03MPa and circulating cooling water at 15℃. After continuous traction and cutting by a crawler traction machine, weather-resistant polyolefin composite cable protection pipe is obtained.

[0041] Example 3: This embodiment provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method, including the following steps: The first step is to prepare the polar coordination anchoring masterbatch: 5.0 parts by weight of ethylene-vinyl alcohol copolymer, 2.0 parts by weight of zinc salt of ethylene-methacrylic acid copolymer, 1.2 parts by weight of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 1.0 part by weight of 2-hydroxy-4-n-octyloxybenzophenone are added to a high-speed mixer and cold-mixed at 400 rpm for 5 minutes to obtain a solid mixture. This solid mixture is then fed into the main feed port of a co-rotating parallel twin-screw extruder with an aspect ratio of 48 through a loss-in-weight feeder. The temperatures in zones one and two of the extruder are set to 180°C, and the temperatures in zones three and four are set to 195°C. In zones three and four, 2.5 parts by weight of deionized water are continuously injected at a pressure of 3.0 MPa using a high-pressure liquid metering pump, and the screw speed is set to 250 rpm for shearing and mixing. In zone five, the temperature is set to 190°C, and a vacuum pump is turned on to maintain a vacuum of -0.085 MPa to forcibly remove moisture. The melt enters zone six and is fed to the die head, where the temperature is maintained at 200°C. After being extruded through a multi-hole die, it is underwater pelletized, centrifuged, dehydrated, and dried to obtain polar coordination anchored masterbatch.

[0042] The second step involves preparing the final weather-resistant pipe composite material: All the polar coordination anchoring masterbatch obtained in the first step, along with 90 parts by weight of ethylene-propylene block copolymer, 22 parts by weight of ethylene-1-octene copolymer, and 5.0 parts by weight of maleic anhydride-grafted polypropylene obtained in Preparation Example 3, are mixed in a mixer for 3 minutes. The mixture is then added to the main feed port of a pipe blending extruder, with the extruder temperature set to 205°C in zones one to three. In zone four, the temperature is set to 215°C, and 3.5 parts by weight of low-structure furnace black are uniformly added using a twin-screw forced side feeder. Homogenization is performed in zones five and six at 225°C, and in zone seven, a normal vacuum of -0.05 MPa is applied to remove entrained air, forming the blend material. The blended material enters the pipe extruder head at a temperature of 220℃. The extruded pipe blank directly enters the vacuum sizing box, where it is sizing and shaped under a vacuum of -0.06MPa and circulating cooling water at 25℃. After continuous traction and cutting by a crawler traction machine, weather-resistant polyolefin composite cable protection pipe is obtained.

[0043] Example 4: This embodiment provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method, including the following steps: The first step is to prepare polar coordination anchoring masterbatch: its formula and preparation steps are exactly the same as those in Example 1.

[0044] The second step involves preparing the final weather-resistant pipe composite material: All the polar coordination anchoring masterbatch obtained in the first step, along with 90 parts by weight of ethylene-propylene block copolymer, 22 parts by weight of ethylene-1-octene copolymer, and 3.5 parts by weight of maleic anhydride-grafted polypropylene obtained in Preparation Example 1, are mixed in a mixer for 3 minutes. The mixture is then added to the main feed port of a pipe blending extruder, with the extruder temperature set to 195°C in zones one to three. In zone four, the temperature is set to 210°C, and 2.8 parts by weight of low-structure furnace black are uniformly added using a twin-screw forced side feeder. Zones five and six are set to 220°C for homogenization, and in zone seven, a normal vacuum of -0.05 MPa is applied to remove entrained air, forming the blend material. The blended material enters the pipe extruder head at a temperature of 215℃. The extruded pipe blank directly enters the vacuum sizing box, where it is sizing and shaped under a vacuum of -0.05MPa and circulating cooling water at 20℃. After continuous traction and cutting by a crawler traction machine, weather-resistant polyolefin composite cable protection pipe is obtained.

[0045] Example 5: This embodiment provides a weather-resistant polyolefin composite cable protection pipe material and its preparation method, including the following steps: The first step is to prepare the polar coordination anchoring masterbatch: 2.5 parts by weight of ethylene-vinyl alcohol copolymer, 0.6 parts by weight of ethylene-methacrylic acid copolymer zinc salt, 1.0 part by weight of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 1.0 part by weight of 2-hydroxy-4-n-octyloxybenzophenone are added to a high-speed mixer and cold-mixed at 400 rpm for 4 minutes to obtain a solid mixture. This solid mixture is then fed into the main feed port of a co-rotating parallel twin-screw extruder with an aspect ratio of 48 through a loss-in-weight feeder. The temperatures in zones one and two of the extruder are set to 175°C, and the temperatures in zones three and four are set to 190°C. In zones three and four, 0.8 parts by weight of deionized water are continuously injected at a pressure of 1.5 MPa using a high-pressure liquid metering pump, and the screw speed is set to 200 rpm for shearing and mixing. In zone five, the temperature is set to 190°C, and a vacuum pump is turned on to maintain a vacuum of -0.07 MPa to forcibly remove moisture. The melt enters zone six and is fed to the die head, where the temperature is maintained at 195°C. After being extruded through a multi-hole die, it is granulated underwater and then centrifuged, dehydrated, and dried to obtain polar coordination anchored masterbatch.

[0046] The second step involves preparing the final weather-resistant pipe composite material: All the polar coordination anchoring masterbatch obtained in the first step, along with 105 parts by weight of ethylene-propylene block copolymer, 12 parts by weight of ethylene-1-octene copolymer, and 1.5 parts by weight of maleic anhydride-grafted polypropylene obtained in Preparation Example 2, are mixed in a mixer for 3 minutes. The mixture is then added to the main feed port of a pipe blending extruder, with the extruder temperature set to 195°C in zones one to three. In zone four, the temperature is set to 210°C, and 2.5 parts by weight of low-structure furnace black are uniformly added using a twin-screw forced side feeder. Zones five and six are set to 220°C for homogenization, and in zone seven, a normal vacuum of -0.05 MPa is applied to remove entrained air, forming the blend material. The blended material enters the pipe extruder head at a temperature of 215℃. The extruded pipe blank directly enters the vacuum sizing box, where it is sizing and shaped under a vacuum of -0.05MPa and circulating cooling water at 20℃. After continuous traction and cutting by a crawler traction machine, weather-resistant polyolefin composite cable protection pipe is obtained.

[0047] Comparative Examples 1-6: Comparative Example 1: Compared with Example 1, the difference is that the two-step preparation method is not used, and the ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid copolymer zinc salt and deionized water are not added. The specific preparation process is to directly mix all the remaining raw materials in the first and second steps of Example 1, add them to the pipe blending extruder for one-step compounding and extrusion molding, and the rest are the same.

[0048] Comparative Example 2: Compared with Example 1, the difference is that deionized water is not injected into the third and fourth zones of the extruder when preparing the polar coordination anchoring masterbatch in the first step; the rest are the same.

[0049] Comparative Example 3: Compared with Example 1, the difference is that in the first step of preparing the polar coordination anchoring masterbatch, the high vacuum pump is not turned on in zone 5 of the extruder to remove moisture, but atmospheric pressure is used for exhaust. All other aspects are the same.

[0050] Comparative Example 4: Compared with Example 1, the difference is that the zinc salt of ethylene-methacrylic acid copolymer was not added in the formulation for the first step of preparing the polar coordination anchoring masterbatch. In order to keep the total mass unchanged, the missing mass was made up with ethylene-vinyl alcohol copolymer. All other aspects are the same.

[0051] Comparative Example 5: Compared with Example 1, the difference lies in breaking the spatiotemporal decoupling process. The maleic anhydride-grafted polypropylene obtained in Example 1 is moved from the second step to the first step of addition. That is, when preparing the polar coordination anchoring masterbatch, it is added to the main feed port along with other raw materials and goes through the water injection process. The rest is the same.

[0052] Comparative Example 6: Compared with Example 1, the difference is that the bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in the formulation is replaced with an equal mass of the conventional strong basic hindered amine light stabilizer bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and all other aspects are the same.

[0053] Test Examples 1-4: Test Example 1: The experimental subjects were sections of weather-resistant polyolefin composite cable protection pipes prepared in Examples 1-5 and Comparative Examples 1-6. Each pipe was cut into square samples with a size of 50mm × 50mm, and the edges of the test samples were sealed to eliminate interference from free substances in the cross-section.

[0054] Wipe the surface of the sample with a lint-free cloth soaked in anhydrous ethanol, and place it in a vacuum drying oven at 40°C for 24 hours to remove initial impurities and obtain an initial dry state.

[0055] The dried samples were placed in a forced convection thermal aging test chamber set at 85℃ for accelerated thermal aging tests. The total test period was set to 30 days, and the corresponding parallel samples were taken out on the 10th, 20th and 30th days of aging.

[0056] After removing samples from different aging stages, immerse them in a petri dish containing 50 mL of chloroform solvent and sonicate at room temperature for 5 minutes. Chloroform can fully dissolve the hindered amine light stabilizers and UV absorbers that have migrated to the sample surface without damaging the polypropylene matrix and cross-linked polar network.

[0057] Remove the sample and rinse the surface with a small amount of pure chloroform, then combine the eluents. Transfer the eluent to a weighing bottle of known mass, allow most of the solvent to evaporate naturally in a fume hood, and then dry it in a 60°C vacuum oven to constant weight.

[0058] The mass of the residue was weighed using a micro-analytical balance with an accuracy of 0.01 mg. Combined with the surface area of ​​the sample, the amount of additive precipitated per unit surface area was calculated, and the unit was recorded as mg / m². 2 .

[0059] Table 1. Amount of additives exuded on the surface of pipe samples from each embodiment and comparative example under heat aging conditions at 85°C.

[0060] Conclusion Analysis: Combined with Table 1 Figure 1It can be seen that the line segments corresponding to Examples 1 to 5 are consistently located in the extremely low range at the bottom of the chart, and the slope over time is extremely gentle. For example, the surface precipitation amount of Examples 1 to 5 remained stable at 0.28 mg / m³ after 30 days of continuous high-temperature stimulation. 2 ~1.12mg / m 2 The degree to which the thermodynamic equilibrium of low molecular weight additives in a polymer matrix is ​​disrupted directly determines the apparent stability of the material. The free volume of the amorphous region in conventional polypropylene and polyolefin elastomers expands at high temperatures, and small molecules inside usually diffuse to the surface under this driving force. Figure 1 The stable data curves directly demonstrate the effectiveness of transient swelling, vacuum devolatilization, and ion coordination coupling in suppressing additive migration in the system of this invention. Specifically, the light stabilizer and UV absorber are confined within the ethylene-vinyl alcohol copolymer network. The polar microdomains are plasticized by high-temperature liquid water, opening the gaps to allow the additives to penetrate. The subsequent high vacuum state causes the solvent to be extracted, and the polymer chain segments undergo drastic conformational contraction, thus forming a physical embedding effect. The zinc ions introduced into the system are activated during high-temperature mixing, further coordinating and crosslinking with the polar groups on the polar resin and additives. This superposition of steric hindrance and chemical bond energy deprives the small molecule additives of the kinetic conditions for escaping along the concentration gradient to the periphery of the matrix.

[0061] Combined with Table 1 Figure 2 As can be seen, the broken lines corresponding to Comparative Examples 1 to 6 show an upward trend throughout the aging period, with each data point significantly higher than that of the Example. This clearly reflects the runaway phenomenon caused by the lack of a single mechanism. In Comparative Example 2, the deionized water injection step was removed in the early stages of preparation. Due to interfacial tension, the additive molecules could not penetrate deep into the ethylene-vinyl alcohol copolymer melt and mostly adhered to the outer periphery of the phase interface. These free-state additives rapidly broke free from their binding and migrated to the outer layer during subsequent thermal aging, leading to… Figure 2 The precipitate level rose to 39.61 mg / m³ on day 30. 2 Although Comparative Example 3 retained the water swelling process, it did not use high-vacuum devolatilization in the exhaust section. The polymer chains failed to undergo synchronous conformational collapse during the slow depressurization process. This relaxed internal physical space provided channels for the additives to seep out, ultimately resulting in a precipitation amount of 28.74 mg / m³. 2 In Comparative Example 4, after the zinc salt of the ethylene-methacrylic acid copolymer was stripped, the hydrogen bonding forces between matrix molecules alone were insufficient to resist the thermal vibration energy provided by 85°C. The failure of chemical anchoring allowed the additive molecules to regain migration activity, as shown in the graph, with their precipitation rate remaining consistently high. Comparative Example 1, using a one-step conventional process, completely lacked the reaction conditions for spatiotemporal decoupling. The additive exhibited a random distribution in the nonpolar matrix, and its precipitation amount increased to 68.35 mg / m³ on day 30. 2The line shows an upward trend, exposing the inherent limitations of traditional systems in long-term weather-resistant applications. Meanwhile, the disordered process sequence in Comparative Example 5 led to premature hydrolysis of the anhydride groups in the maleic anhydride-grafted polypropylene, further worsening macroscopic compatibility. Internal microphase separation created more defect channels and exacerbated blooming of low-molecular-weight substances. Furthermore, Figure 2 The results showed that the precipitate concentration in Comparative Example 6 was also as high as 61.43 mg / m³. 2 This indicates that after the conventional strongly basic hindered amine system undergoes severe chemical antagonism with the acidic surface of low-structure furnace black, it not only loses its photostable effect, but also its tendency for broken molecules to escape is significantly amplified. The above multi-dimensional data curve distribution and comparison fully confirm the absolute necessity of the crosslinking network and physical closure mechanism of this scheme for regulating the phase distribution of additives.

[0062] Test Example 2: The experimental subjects were the weather-resistant polyolefin composite cable protection pipes prepared in Examples 1 to 5 and Comparative Examples 1 to 6. A 200mm length section was cut from each group of pipes according to GB / T 14152-2001 "Test Method for Impact Resistance of Thermoplastic Pipes - Clockwise Rotation Method" for drop hammer impact testing. Standard dumbbell-shaped tensile specimens were prepared by punching along the pipe axis according to GB / T1040.2-2006 "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Molded and Extruded Plastics".

[0063] The test specimens and pipe sections were placed in a high and low temperature alternating damp heat test chamber for environmental stress aging treatment. The test program was set to raise the temperature to 80℃ and hold it for 4 hours, then lower it to -20℃ within 30 minutes and hold it for 4 hours. This constituted one complete cycle, and a total of 50 consecutive alternating cycles were run.

[0064] After the high and low temperature alternating treatment, the specimens were taken out and conditioned for 24 hours in a standard laboratory environment (23℃, 50% relative humidity). The dumbbell-shaped specimens of the tube before and after the alternating treatment were tested using a universal testing machine. The tensile rate was set to 50 mm / min, the elongation at break of the specimens was recorded, and the retention rate after alternating treatment was calculated.

[0065] After conditioning, the pipe sections were placed in a -20℃ low-temperature constant temperature chamber for 2 hours for static pre-cooling. Impact tests were then conducted on the pipe sections using a drop hammer impact tester under low-temperature conditions, with a drop hammer mass of 2.0 kg and an impact height of 2000 mm. Twenty parallel pipe section samples were prepared for each group and impacted one by one. The presence of through-cracks or damage on the pipe surface was observed, and the drop hammer impact failure rate of each group was calculated.

[0066] Table 2. Mechanical property test data of pipe samples from each embodiment and comparative example before and after high and low temperature alternation.

[0067] Conclusion Analysis: Combined with Table 2 Figure 3 (a) It can be seen that Examples 1 to 5 still exhibit excellent mechanical tensile stability after undergoing 50 harsh high and low temperature alternating cycles. The graphs clearly show that the data points and broken lines corresponding to the examples are consistently distributed at a high level, with the elongation at break retention rate remaining above 89.8%, for example, Example 1 has a retention rate as high as 92.9%. In polymer blend systems, drastic temperature fluctuations can induce large thermal stresses at the internal interfaces due to the differences in the thermal expansion coefficients of the various phases. This stress is usually the main cause of micro-phase separation and macro-mechanical degradation in multiphase materials. Figure 3 (a) The high dimensionality of the data in the example strongly verifies the rationality of the spatiotemporal decoupling process in this invention. The maleic anhydride-grafted polypropylene introduced in the second anhydrous blending process has an anhydride group on its molecular chain that can undergo efficient ring-opening esterification with the hydroxyl groups on the surface of the ethylene-vinyl alcohol copolymer, constructing dense covalent bridges between the nonpolar polyolefin matrix and the polar microregions. These chemical bonds possess sufficient bond energy to resist the interfacial shrinkage and expansion stress caused by high and low temperature alternation, thus maintaining extremely high deformation retention under macroscopic tensile stress. Conversely, the data line corresponding to the comparative example shows... Figure 3 (a) shows a decline, especially in Comparative Example 5, where the elongation at break retention rate drops to 27.3%. When maleic anhydride-grafted polypropylene is injected into the deionized water environment in the first step, the high temperature and pressure of the liquid water triggers an irreversible hydrolysis reaction of the maleic anhydride groups, resulting in ring-opening and the formation of an inactive dicarboxylic acid. Having lost its chemical coupling ability, the maleic anhydride-grafted polypropylene can only exist at the phase interface in a physically entangled form. This weak force rapidly fails during the intense alternation of contraction and expansion between 80°C and -20°C, leading to severe interfacial debonding.

[0068] Combined with Table 2 Figure 3 (b) It can be seen that the interface structural defects have a fatal impact on the macroscopic impact resistance of the pipe. Figure 3 (b) The data points in the examples closely follow the low breakage rate range at the bottom of the chart, with breakage rates mostly controlled within 0-15%. In Example 1, the low-temperature drop hammer breakage rate after alternation was only 5.0%. This indicates that the cross-linked network structure effectively prevents the initiation and propagation of microcracks under extreme alternating hot and cold impact stress. In contrast, the broken line in the comparative example... Figure 3(b) The breakage rate increased significantly, all exceeding 40%. Based on the specific mechanism analysis, Comparative Example 5, due to severe interfacial debonding, easily evolved into macroscopic brittle fracture penetrating the sample under low-temperature drop hammer impact, causing its breakage rate to soar to 85.0%. The one-step process used in Comparative Example 1 resulted in the ethylene-1-octene copolymer elastomer failing to disperse uniformly and be fixed in the matrix. The uncompatibilized phase interface degraded severely under alternating thermal stress, leading to dense stress concentration points during external impact, ultimately resulting in a breakage rate of 65.0%. Comparative Examples 2, 3, and 4, lacking internal chemical cross-linking network support, experienced the loosely aggregated polar micro-regions easily detach and form structural voids after long-term thermodynamic volume changes, failing to effectively absorb and transfer the instantaneous impact load from the drop hammer. All attenuation indicators were higher than those of the examples. The distribution trends of the above data clearly demonstrate the irreplaceable role of the stepwise preparation strategy in protecting the compatibilizer's reactivity and maintaining the long-term mechanical reliability of complex multiphase systems.

[0069] Test Example 3: The experimental subjects were the weather-resistant polyolefin composite cable protection pipes prepared in Examples 1 to 5 and Comparative Examples 1 to 6. Each group of pipes was punched into type 1A tensile specimens according to ISO 527-2 "Determination of tensile properties of plastics – Part 2: Test conditions for molded and extruded plastics". Before testing, the specimens were conditioned for 48 hours in a constant temperature and humidity environment of 23°C and 50% relative humidity.

[0070] The conditioned test specimens were placed in an artificial climate accelerated aging test chamber equipped with fluorescent ultraviolet lamps. Referring to GB / T 16422.3-2014 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", the aging exposure cycle was set as a continuous cyclical alternation process. Each cycle consisted of 8 hours of drying ultraviolet light irradiation at a black panel temperature of 60°C, followed by 4 hours of non-irradiated condensate spray exposure at 50°C. The total aging exposure time was set to 2000 hours.

[0071] The tests were paused at 1000 hours and 2000 hours of accumulated aging exposure, and the corresponding batches of specimens were removed from the test chamber. The removed aging specimens were then placed in a standard constant temperature and humidity environment for 24 hours to eliminate test internal stress.

[0072] A universal testing machine was used to perform room temperature tensile tests on specimens that had not undergone aging treatment and those that had undergone aging treatment for different times. The crosshead tensile movement rate was set to 50 mm / min, and the tensile yield strength at the yield point and the elongation at break were accurately recorded. Based on the initial test value of the unaged sample, the retention rate of mechanical properties of the aged samples at each stage was calculated.

[0073] Table 3. Retention rate of mechanical properties of pipe samples from each embodiment and comparative example in accelerated aging test under artificial climate.

[0074] Conclusion Analysis: Combined with Table 3 Figure 4 (a) It can be seen that the degradation resistance of polymer substrates under the synergistic attack of ultraviolet light and moisture is highly correlated with the integrity of their internal stable system. The broken lines corresponding to Examples 1 to 5 in the figure all maintain a gradual downward trend within the 2000-hour aging cycle, and their tensile yield strength retention rate is stably maintained in the range of 84.1% to 91.2%. Outdoor cable protection pipes face free radical chain cleavage reactions induced by sunlight ultraviolet rays during long-term service, and usually require the compounding of carbon black and light stabilizers to shield ultraviolet rays and capture free radicals. However, the large number of oxygen-containing acidic groups carried on the surface of furnace black are prone to acid-base neutralization with the alkaline hindered amine light stabilizers, leading to the failure of the stable system. This invention uses a two-step process to lock the hindered amine light stabilizers and ultraviolet absorbers in the polar micro-regions of the ethylene-vinyl alcohol copolymer in the first step, and introduce low-structure furnace black in the second step of blending. This spatial physical isolation prevents direct contact between the acidic surface of carbon black and the alkaline additives, effectively avoiding the antagonistic consumption of active components. Observing the line distribution of the comparative examples in the chart reveals that samples that did not form a complete isolation system showed significant strength degradation in the later stages of aging. Comparative Example 1, using a one-step process, failed to achieve spatial decoupling of component distribution; the additives and carbon black reacted directly in contact with each other in the matrix, resulting in a tensile yield strength retention rate of only 41.5% after 2000 hours. Comparative Examples 2, 3, and 4, lacking complete water swelling, high-vacuum devolatilization, or zinc ion chemical anchoring processes, had an imperfect locking mechanism within the polar micro-regions. Under long-term alternating wet and heat conditions, the low molecular weight additives gradually escaped to the outer layer and were neutralized by the carbon black surface, resulting in retention rates between 52.8% and 56.2%. Comparative Example 5, with its disordered process sequence, experienced premature water inactivation of the maleic anhydride compatibilizer, which disrupted the compactness of the phase interface and accelerated the formation of photo-oxidative erosion channels, reducing its retention rate to 35.2%. In Comparative Example 6, a conventional strongly basic hindered amine was used instead. The extremely small amount of its free portion had a more intense chemical antagonism with the acidic groups of carbon black, which broke the cyclic regeneration mechanism of nitric oxide free radicals, resulting in severe photo-oxidative breakage of the polymer backbone. The tensile yield strength retention rate after 2000 hours was the lowest among all tested samples at 25.8%.

[0075] Combined with Table 3 Figure 4(b) It is evident that the decline in macroscopic toughness of materials often reflects the damage process of the microstructure more sensitively than the loss of strength. The elongation at break retention rates of Examples 1-5 remain consistently high in the graph, maintaining between 80.9% and 88.1% after 2000 hours. This indicates that the polar network and non-polar matrix in different phases did not undergo large-scale structural delamination under long-term photothermal and condensate erosion. In contrast, the lines corresponding to all comparative examples showed varying degrees of accelerated decline in the later stages. Comparative Example 1, employing a traditional non-decoupling process, lacked effective protection of the compatibility interface. Moisture easily triggered hydrolysis and phase separation at the micro-interface in the gap between the non-polar matrix and the polar components, causing its elongation at break retention rate to eventually drop to 28.3%. In Comparative Examples 2, 3, and 4, the early-stage additives were incompletely encapsulated or lacked chemical bonding, leading to continuous migration of low-molecular-weight substances under alternating high temperatures and condensate erosion. This loss not only deprives the polymer matrix of its chemical barrier against free radicals, but also leaves tiny structural pores within the matrix due to the precipitation of additives. These pores rapidly evolve into stress concentration centers under tensile forces, causing macroscopic brittle fracture of the material far before reaching its theoretical deformation limit. Its elongation at break is only in the range of 38.7%–42.1%. In Comparative Example 5, the reactive compatibilizer undergoes irreversible hydrolysis and ring-opening reactions during the water injection stage of the first process, completely losing its ability to covalently crosslink with the polar masterbatch surface. This initial interfacial debonding further expands and deteriorates under long-term humid and hot aging, with a retention rate as low as 21.6%. In Comparative Example 6, the strongly alkaline hindered amine photostable system fails due to severe acid-base neutralization, and long-term ultraviolet irradiation breaks down the macromolecular chains. The material completely loses the inherent segmental flexibility of the polymer, and its elongation at break retention rate is only 14.9% at the end of aging. The above multi-dimensional test comparison data reveals the practical application value of component spatial decoupling distribution and multiple physicochemical locking mechanisms in solving the problems of phase instability and acid-base antagonism in traditional weather-resistant formulations.

[0076] Test Example 4: The experimental subjects were the weather-resistant polyolefin composite cable protection pipes prepared in Examples 1 to 5 and Comparative Examples 1 to 6. Complete pipe sections of 300 mm in length were cut from each group of pipes according to the test standard GB / T 9647-2015 "Determination of Ring Stiffness of Thermoplastic Pipes" as ring stiffness test specimens. All specimens were placed in a constant temperature and humidity laboratory at 23℃ and 50% relative humidity for 24 hours to allow for stress relief.

[0077] The pipe section underwent a flat plate compression test using a computer-controlled universal testing machine equipped with a high-rigidity parallel compression plate. During the test, the downward pressing speed of the upper plate was set to 10 mm / min. The displacement and load changes of the plate were continuously monitored, and the instantaneous compressive load at which the inner diameter of the specimen underwent a 3% deformation was accurately recorded. Based on this, the room-temperature ring stiffness of the pipe was calculated, denoted in kN / m. 2 .

[0078] Standard dumbbell-shaped tensile specimens were prepared by punching along the axial direction of the pipe. Simultaneously, rectangular impact specimens with dimensions of 80mm × 10mm × 4mm were machined according to GB / T 1043.1-2008 "Determination of Impact Properties of Simply Supported Beams in Plastics - Part 1: Non-Instrumental Impact Testing". A type A standard notch with a depth of 2mm was milled in the middle of each impact specimen using a notching machine. After preparation, the specimens were also subjected to a 24-hour conditioning period.

[0079] The mechanical properties of the matrix material were characterized at room temperature (23℃). The stress-strain curve of the dumbbell-shaped specimen in the initial linear phase was determined using a universal testing machine at an extremely low tensile rate of 2 mm / min. The tensile modulus of elasticity was calculated and expressed in MPa. A pendulum impact testing machine was used to perform a simply supported beam notched impact test on the A-notched specimen. The impact energy absorbed at the moment the specimen fractured was recorded and divided by the remaining cross-sectional area at the notch to calculate the notched impact strength, expressed in kJ / m². 2 For each of the above individual tests, 10 parallel samples were taken for measurement, and the average value was calculated.

[0080] Table 4. Room temperature ring stiffness and stiffness-toughness balance mechanical test data of the pipe samples of each embodiment and comparative example.

[0081] Conclusion Analysis: Combined with Table 4 Figure 5 (a) It is known that complex polymer blends often face a contradiction between rigidity and toughness in engineering applications, while the formulation and process design of this invention successfully overcome this inherent defect. In the actual laying of cable protection pipes, the pipe material must have sufficiently high ring stiffness to resist the static lateral pressure of the underground soil and the dynamic load of surface vehicles. Observation Figure 5 As can be clearly seen from the dual Y-axis distribution plot in (a), both the solid square line representing the ring stiffness of the embodiments and the dotted triangle line representing the tensile modulus of elasticity of the embodiments are stably located in the upper high region of the chart. Specific data shows that the room-temperature ring stiffness of embodiments 1 to 5 is generally maintained at 8.94 kN / m. 2 ~11.16kN / m 2The tensile modulus of polypropylene (PP) is at a relatively high level, exceeding 1100 MPa. Normally, the introduction of a large amount of ethylene-1-octene copolymer elastomer into the matrix would significantly weaken the intrinsic modulus of polypropylene, but the data from the examples in the figure still show excellent rigidity support characteristics. This mechanical compensation effect originates from the polar microdomains of the ethylene-vinyl alcohol copolymer prepared in the first step, which itself possesses extremely high cohesive energy density and molecular chain rigidity. After achieving perfect interfacial anchoring through maleic anhydride grafting of polypropylene in the second step, these tiny rigid polar microdomains act as heterogeneous nucleation and skeletal support within the polyolefin matrix. When the matrix is ​​compressed, stress can be smoothly transferred to the rigid microdomains through the dense chemically bonded interface, effectively counteracting the softening tendency introduced by the elastomer. (Comparative observation) Figure 5 (a) The broken line distribution of the comparative examples shows a significant overall downward trend in the square dashed line representing the ring stiffness of the comparative examples and the triangular dashed line representing the elastic modulus of the comparative examples. The ring stiffness of comparative examples 1 and 5 decreased to 6.81 kN / m. 2 and 6.55kN / m 2 Consequently, its elastic modulus also falls below the baseline. One-step process or failure of acid anhydride hydrolysis prevents polar resin from being uniformly dispersed and forming a strong stress transfer network with the matrix. The micropores at the phase interface are prone to slippage and yielding under macroscopic compressive loads, resulting in a significant degradation of the overall pressure-bearing capacity of the pipe.

[0082] Combined with Table 4 Figure 5 (b) It can be seen that the bonding strength of the phase interface directly determines the energy absorption and dissipation mechanism of the material when facing high-speed fracture stress. Figure 5 In (b), the solid circular line representing the impact strength of the embodiment clearly exceeds the dashed circular line representing the impact strength of the comparative embodiment. The data points corresponding to the embodiment are all distributed around 65.4 kJ / m. 2 In the above-mentioned high-level range, especially in Example 4 with adjusted matrix proportions, the notched impact strength of the simply supported beam jumps to 86.2 kJ / m. 2 Upon impact by the pendulum, a highly concentrated triaxial tensile stress is generated at the front end of the material notch. In this example, the uniformly dispersed elastomer and the chemically locked polar micro-regions work synergistically to absorb enormous fracture energy by inducing numerous crazes and shear bands within the matrix. The stable covalent interface prevents the crack from propagating rapidly along the phase interface with low energy consumption, forcing the crack to penetrate the polymer backbone, thus multiplying the work required for material fracture. Turning our attention to the comparative data trajectory, for all samples lacking a complete physicochemical anchoring mechanism, the impact intensity dashed line all drops to 45.2 kJ / m below the chart. 2 Below, especially for ratio 5, it drops to 29.8 kJ / m 2The premature exposure of maleic anhydride grafts to an aqueous environment triggers a hydrolysis reaction, severing the chemical bonds between phases. This fragile physical interface is prone to large-scale debonding during notched impact testing, and the resulting interfacial voids rapidly fuse into critical cracks, causing brittle fracture of the material at extremely low energy absorption. The data from Comparative Examples 1 to 4 are similarly constrained by structural defects caused by free polar aggregates, failing to achieve an effective superposition of rigid particle toughening and elastomer toughening. The experimental results confirm that the multiphase cross-linked network constructed by this invention through precise control of reaction timing and micro-region locking achieves excellent pipe pressure-bearing stiffness while simultaneously endowing the matrix with superior impact toughness, realizing a deep balance in the comprehensive engineering mechanical properties of the pipe.

Claims

1. A weather-resistant polyolefin composite cable protection pipe material, characterized in that, It contains the following ingredients by weight: 4.1–9.2 parts of polar coordination anchoring masterbatch; 90–110 parts of ethylene-propylene block copolymer; 12-22 parts of ethylene-1-octene copolymer; 1.5 to 5.0 parts of maleic anhydride-grafted polypropylene; Furnace black, 2.0–3.5 parts; The polar coordination anchoring masterbatch is prepared from components comprising the following parts by weight: 2.5 to 5.0 parts of ethylene-vinyl alcohol copolymer, 0.6 to 2.0 parts of zinc salt of ethylene-methacrylic acid copolymer, 0.5 to 1.2 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 0.5 to 1.0 parts of 2-hydroxy-4-n-octyloxybenzophenone.

2. The weather-resistant polyolefin composite cable protection pipe material according to claim 1, characterized in that, The grafting rate of the maleic anhydride-grafted polypropylene is 1.0 wt% to 1.5 wt%.

3. The weather-resistant polyolefin composite cable protection pipe material according to claim 1, characterized in that, The maleic anhydride-grafted polypropylene is produced by reactive extrusion of raw materials comprising the following parts by weight: 100 parts of polypropylene homopolymer powder, 1.5 to 2.5 parts of maleic anhydride, and 0.10 to 0.20 parts of dicumyl peroxide.

4. The weather-resistant polyolefin composite cable protection pipe material according to claim 3, characterized in that, The maleic anhydride-grafted polypropylene is prepared by the following steps: The polypropylene homopolymer powder, maleic anhydride, and dicumyl peroxide were mixed in a high-speed mixer to obtain a solid mixture. The solid mixture was fed into the main feed port of a co-rotating twin-screw extruder with a length-to-diameter ratio of 40 for reactive extrusion. The screw speed was set to 200 rpm. The temperatures of each zone of the extruder were set sequentially as follows: zone 1 170℃, zone 2 180℃, zones 3 to 6 190℃, zones 7 to 9 200℃, and the die head 200℃. The vacuum exhaust system was activated in zone 8 of the extruder, and the vacuum degree was set to -0.08 MPa to remove unreacted maleic anhydride monomers. After cooling in a water tank, the mixture was pelletized and dried to obtain the maleic anhydride-grafted polypropylene.

5. A method for preparing a weather-resistant polyolefin composite cable protection pipe material, characterized in that, The preparation of the weather-resistant polyolefin composite cable protection pipe material according to any one of claims 1-4 includes the following steps: Ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid copolymer zinc salt, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and 2-hydroxy-4-n-octyloxybenzophenone were cold-mixed in a high-speed mixer to obtain a solid-phase mixture; The solid mixture is fed into the main feed port of a co-rotating parallel twin-screw extruder via a loss-in-weight feeder. In the middle section of the co-rotating parallel twin-screw extruder, deionized water is continuously injected by a high-pressure liquid metering pump for shearing and mixing. Then, in the rear section of the co-rotating parallel twin-screw extruder, a vacuum pump is turned on to force the removal of water. The melt is extruded through a multi-hole die, underwater pelletized, centrifuged, dehydrated and dried to obtain polar coordination anchoring masterbatch. The polar coordination anchoring masterbatch is mixed with ethylene-propylene block copolymer, ethylene-1-octene copolymer and maleic anhydride grafted polypropylene in a mixer, and then added to the main feed port of a pipe blending extruder. Furnace carbon black is uniformly added to the fourth zone of the pipe blending extruder via a twin-screw forced side feeder. After homogenization, normal vacuum is activated to remove entrained air, forming a blended material. The blended material is fed into the pipe extruder head, and the extruded pipe blank is directly fed into the vacuum sizing box for sizing and shaping. It is then continuously traction and cut by a crawler traction machine to obtain a weather-resistant polyolefin composite cable protection pipe.

6. The preparation method according to claim 5, characterized in that, The cold mixing time in the high-speed mixer is 3 to 5 minutes, and the rotation speed is 400 rpm; The length-to-diameter ratio of the co-rotating parallel twin-screw extruder is 48; The co-rotating parallel twin-screw extruder is continuously injected with 0.8 to 2.5 parts by weight of deionized water at a pressure of 1.5 to 3.0 MPa through a high-pressure liquid metering pump in the middle section. The rotational speed for the shearing and mixing process is set to 150–250 rpm; The vacuum pump is turned on to forcibly remove moisture and maintain a vacuum level of -0.095MPa to -0.07MPa.

7. The preparation method according to claim 5, characterized in that, The temperatures of each zone of the co-rotating parallel twin-screw extruder are set sequentially as follows: Zones 1 and 2: 170-180℃; Zones 3 and 4: 180-195℃; Zone 5: 190℃; Zone 6 to the machine head: 190-200℃.

8. The preparation method according to claim 5, characterized in that, The mixing time in the mixer is 2 to 3 minutes; The vacuum level for removing entrained air after homogenization is set to -0.05 MPa.

9. The preparation method according to claim 5, characterized in that, The temperatures of each zone of the pipe blending extruder are set sequentially as follows: Zones 1 to 3: 190–205℃; Zone 4: 210–215℃; Zones 5 and 6: 215–225℃.

10. The preparation method according to claim 5, characterized in that, The temperature of the tube extruder head is maintained at 210–220°C; The vacuum degree for sizing and shaping in the vacuum sizing chamber is set to -0.06MPa to -0.03MPa, and the temperature of the circulating cooling water used is 15 to 25℃.

Images