Low temperature resistant wear-resistant cable protection pipe and preparation method thereof

Abstract

The application discloses a low-temperature wear-resistant cable protection pipe and a preparation method thereof. The method comprises the following steps: first, making maleic anhydride grafted polyethylene selectively soften and adhere to the surface of ultra-high molecular weight polyethylene micro powder, and then adding polyethylene carrier silicone master batch for second stage hot mixing after cooling and crystallization setting, so as to prepare a coated wear-resistant master batch; subsequently, melt-mixing high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, inorganic rigid filler and antioxidant, and then adding the wear-resistant master batch by a rear-stage side feeder after forming a continuous polyethylene melt of the three kinds of matrix resins, and finally, extruding, granulating and pipe forming to obtain the cable protection pipe. The method is beneficial to improving the interface bonding and dispersion state of the ultra-high molecular weight polyethylene micro powder, and the obtained pipe has low-temperature toughness, wear resistance, rigidity and forming stability.

Description

Technical Field

[0001] This invention relates to the technical field of cable protection pipes, and in particular to a low-temperature wear-resistant cable protection pipe and its preparation method. Background Technology

[0002] Cable protection pipes are mainly used for the laying and protection of power cables and communication cables. During transportation, installation, and service, they need to withstand soil loads, external impacts, and friction generated by cable laying and traction. Polyethylene material has the characteristics of corrosion resistance, good electrical insulation, convenient molding and processing, and strong construction adaptability, and is therefore used to manufacture cable protection pipes. With the increase in cable laying distance and the increasing frequency of low-temperature construction environments, in addition to the necessary circumferential load-bearing capacity and dimensional stability, the pipe material also needs to maintain good low-temperature toughness and inner wall wear resistance.

[0003] Existing polyethylene pipes typically improve their mechanical and performance properties by adding components such as elastomers, inorganic fillers, lubricants, or wear-resistant resins. Chinese patent CN1322773A discloses a special material for modifying optical cable sheathing tubes with inorganic nanoparticles and its preparation method. This method improves the low-temperature toughness, rigidity, and processing performance of the sheathing tube material by mixing polyethylene, rubber elastomers, activated inorganic nanoparticles, and other additives and then extruding and granulating the mixture. While this type of modification can adjust the toughness and rigidity of polyethylene pipes, the dispersion state of different modifying components in the polyethylene matrix still affects the stability of the material's properties.

[0004] Ultra-high molecular weight polyethylene (UHMWPE) possesses a low coefficient of friction and good wear resistance. Adding it as a wear-resistant component to the polyethylene matrix is ​​a technical approach to improve the friction resistance of pipes. Chinese patent CN101003651A discloses a blend of high-density polyethylene (HDPE) and UHMWPE, its preparation method, and its application. The method involves first modifying UHMWPE with a composite dispersant composed of a low-melting-point, low-viscosity resin and a lubricant, and then co-extruding it with an elastomer and HDPE. The patent also points out that UHMWPE powder may form large particles in HDPE due to incomplete melting, and its high melt viscosity can easily increase the extrusion processing load.

[0005] Due to the high molecular weight, high melt viscosity, and low flowability of ultra-high molecular weight polyethylene (UHMWPE), its micropowder is difficult to fully plasticize and uniformly disperse under conventional polyethylene melt processing conditions. When UHMWPE micropowder is melt-blended with matrix resin and other modifying components, micropowder agglomeration, insufficient interfacial wetting, and uneven local dispersion are prone to occur, making it difficult for the wear-resistant components to be stably distributed in the continuous polyethylene phase. This dispersion not only affects the full realization of wear resistance but may also form local structural defects and adversely affect the low-temperature toughness, rigidity, melt processing performance, and pipe forming stability of the composite material.

[0006] Therefore, the technical problem that needs to be solved at present is how to improve the dispersion stability of ultra-high molecular weight polyethylene micropowder in polyethylene cable protection pipe materials, so that it can play a wear-resistant role while reducing the adverse effects on the processing performance of composite materials and the comprehensive mechanical properties of pipe materials. Summary of the Invention

[0007] To address the challenge of plasticizing and dispersing ultra-high molecular weight polyethylene (UHMWPE) micropowder in polyethylene cable protection pipe processing due to its high molecular weight and poor melt flowability, this invention provides a low-temperature wear-resistant cable protection pipe and its preparation method. The method involves a first stage of selective softening and adhesion followed by cooling and shaping, a second stage of selective softening of the silicone masterbatch carrier, and a subsequent stage of side feeding combined with continuous polyethylene melt. This approach helps maintain the main morphology of the UHMWPE micropowder particles while promoting compatibility and lubrication / dispersion at the appropriate stages, achieving a good balance between low-temperature toughness, rigidity, processability, and dimensional stability in the pipe material.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a low-temperature wear-resistant cable protection tube, comprising the following steps: S1 provides ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, inorganic rigid filler and antioxidant.

[0009] S2. The ultra-high molecular weight polyethylene micro powder and the maleic anhydride-grafted polyethylene are subjected to a first-stage hot mixing, so that the maleic anhydride-grafted polyethylene softens and adheres to the surface of the ultra-high molecular weight polyethylene micro powder, thereby obtaining wear-resistant particles after primary treatment.

[0010] S3. After the first stage of hot mixing is completed, the primary-treated wear-resistant particles are cooled to a temperature 5-20°C lower than the differential scanning calorimetry crystallization peak temperature of the maleic anhydride-grafted polyethylene and held at that temperature for 3-10 minutes to allow the maleic anhydride-grafted polyethylene adhering to the surface of the ultra-high molecular weight polyethylene micro powder to crystallize and solidify. Then, the polyethylene carrier silicone masterbatch is added to the cooled and held-temperature primary-treated wear-resistant particles for the second stage of hot mixing. After cooling and crushing, a coated wear-resistant masterbatch is obtained.

[0011] S4. The high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, inorganic rigid filler and antioxidant are added to a twin-screw extruder and melt-plasticized. After the high-density polyethylene, linear low-density polyethylene and ethylene-octene copolymer elastomer form a continuous polyethylene melt, the coated wear-resistant masterbatch is added through the side feed port of the twin-screw extruder, so that the coated wear-resistant masterbatch is dispersed in the continuous polyethylene melt. After extrusion granulation, a low-temperature wear-resistant polyethylene composite material is obtained.

[0012] S5. The low-temperature wear-resistant polyethylene composite material is extruded into a pipe, vacuum sizing, cooled and traction-cut to obtain the low-temperature wear-resistant cable protection pipe.

[0013] Based on 100 parts by weight of the ultra-high molecular weight polyethylene micro powder, the amount of maleic anhydride-grafted polyethylene is 6 to 12 parts by weight, and the amount of polyethylene carrier silicone masterbatch is 3 to 7 parts by weight.

[0014] Based on 100 parts by weight of the high-density polyethylene, the amount of linear low-density polyethylene is 8 to 18 parts by weight, the amount of ethylene-octene copolymer elastomer is 6 to 14 parts by weight, the amount of ultra-high molecular weight polyethylene micro powder is 20 to 36 parts by weight, the amount of inorganic rigid filler is 3 to 8 parts by weight, and the amount of antioxidant is 0.3 to 0.8 parts by weight.

[0015] This invention utilizes the differences in thermal transition temperatures of various polyethylene materials to sequentially process ultra-high molecular weight polyethylene (UHMWPE) micropowder, maleic anhydride-grafted polyethylene (MAGPE), and polyethylene-carrier silicone masterbatch according to different process stages. First, the MAGPE is selectively softened and adheres to the surface of the UHMWPE micropowder. After cooling and crystallization, the carrier resin in the polyethylene-carrier silicone masterbatch is selectively softened. Subsequently, the resulting wear-resistant masterbatch is added to a continuous polyethylene melt for subsequent dispersion. This sequential processing facilitates the compatibility of the MAGPE, the lubricating and dispersing effect of the polyethylene-carrier silicone masterbatch, and the dispersion of the wear-resistant masterbatch within the polyethylene matrix, allowing each process stage to function effectively and improving the matching degree between each processing stage and the corresponding material state.

[0016] The above preparation method first processes ultra-high molecular weight polyethylene (UHMWPE) micropowder in two sequential stages, then adds the resulting wear-resistant masterbatch to continuous polyethylene melt in the latter stage. In the first stage of hot mixing, maleic anhydride-grafted polyethylene (MAG) is used as the processing component. Under the condition that the main particle morphology of the UHMWPE micropowder is relatively maintained, MAG selectively softens and wets and adheres to the surface of the micropowder under the mixing action. After the first stage of hot mixing, cooling and heat preservation are performed, which helps to improve the crystallinity of the attached MAG, ensuring that the formed adhesion remains relatively stable under the conditions of the second stage processing.

[0017] The second-stage hot mixing uses polyethylene-carrier silicone masterbatch as the treatment component. This is carried out at a relatively stable temperature under conditions where the carrier resin has preferentially softened or melted and the maleic anhydride-grafted polyethylene has already crystallized and solidified. This facilitates the dispersion of the polyethylene-carrier silicone masterbatch among the wear-resistant particles treated in the first stage and on their surface. Based on temperature control and experimental results, it is speculated that the first stage is beneficial for improving the wetting and compatibility between ultra-high molecular weight polyethylene micropowder and polyethylene materials; the second stage is beneficial for improving the sliding state between the treated particles and promoting their flowability and subsequent dispersion performance.

[0018] The wear-resistant masterbatch refers to a mixture obtained by sequentially processing ultra-high molecular weight polyethylene micropowder through the first stage of treatment, cooling and heat preservation, and the second stage of treatment. This application defines the above name based on the preparation sequence and usage state; its microstructure may include discrete adhesion, partial coverage, and other states that can reflect relative encapsulation relationships.

[0019] Based on the two-stage temperature control relationship, particle dispersion results, and wear resistance results, it is speculated that maleic anhydride-grafted polyethylene may be mainly distributed between ultra-high molecular weight polyethylene micropowder and continuous polyethylene melt, which is beneficial to improving the compatibility and interfacial bonding between wear-resistant particles and polyethylene matrix; polyethylene carrier silicone masterbatch may be mainly distributed on the outer side of the primary-processed wear-resistant particles, which is beneficial to improving the sliding state between particles and promoting the dispersion of coated wear-resistant masterbatch in continuous polyethylene melt. The terms "inner side" and "outer side" are used to describe possible relative distribution relationships; specific micromorphologies may manifest as discrete adhesion, local coverage, etc., and the actual characterization results shall prevail.

[0020] Preferably, the maleic anhydride grafting rate of the maleic anhydride-grafted polyethylene is 0.6% to 1.5%, and the melt mass flow rate under conditions of 190°C and 2.16 kg load is 10 to 50 g / 10 min; the differential scanning calorimetry melting peak temperature of the maleic anhydride-grafted polyethylene is 5 to 25°C lower than that of the ultra-high molecular weight polyethylene micropowder.

[0021] The maleic anhydride grafting rate is used to limit the content of polar groups in grafted polyethylene, and the melt mass flow rate is used to limit its flow and spreading ability at the hot mixing temperature. Making the differential scanning calorimetry (DSC) melting peak temperature of maleic anhydride-grafted polyethylene lower than that of ultra-high molecular weight polyethylene (UHMWPE) micropowder is beneficial for establishing selective softening conditions during the first stage of hot mixing, promoting the softening and adhesion of maleic anhydride-grafted polyethylene, and better maintaining the morphology of the main UHMWPE micropowder particles, thereby helping to maintain the dispersion state of the micropowder.

[0022] Preferably, in step S2, the temperature of the first-stage hot mixing is 5–20°C higher than the differential scanning calorimetry melting peak temperature of the maleic anhydride-grafted polyethylene and 3–15°C lower than the differential scanning calorimetry melting peak temperature of the ultra-high molecular weight polyethylene micropowder; the first-stage hot mixing time is 5–15 min, and the mixing speed is 500–1000 r / min. The first-stage hot mixing temperature is the material temperature measured by the material temperature probe.

[0023] The first-stage hot-mixing temperature is higher than the melting peak temperature of maleic anhydride-grafted polyethylene, which is beneficial for it to achieve the softening degree required for adhesion and spreading. Simultaneously, the hot-mixing temperature is lower than the melting peak temperature of ultra-high molecular weight polyethylene micropowder, which is beneficial for maintaining the morphology of the main micropowder particles. Limiting the hot-mixing time and mixing speed within the above range is conducive to the distribution and adhesion of the softened maleic anhydride-grafted polyethylene to the micropowder surface under mechanical mixing, resulting in a relatively stable particle dispersion.

[0024] Preferably, the carrier resin of the polyethylene carrier silicone masterbatch is one or both of low-density polyethylene and linear low-density polyethylene. The differential scanning calorimetry (DSC) melting peak temperature of the maleic anhydride-grafted polyethylene is denoted as Tm1, and the DSC melting peak temperature of the carrier resin is denoted as Tm2, ​​where Tm1–Tm2 ranges from 10 to 22°C. When the carrier resin contains two resins and the DSC curve shows more than two melting peaks, the dominant melting peak temperature on the lower temperature side is taken as Tm2. This range matches the second-stage thermal mixing temperature relationship described below, ensuring that each temperature condition has a compatible operating range.

[0025] After the first stage of hot mixing in step S2 is completed, the wear-resistant particles of the first treatment are cooled to Tc1-20℃ to Tc1-5℃ and kept at that temperature for 3 to 10 minutes to allow the maleic anhydride-grafted polyethylene attached to the surface of the ultra-high molecular weight polyethylene micro powder to crystallize and solidify, wherein Tc1 is the differential scanning calorimetry crystallization peak temperature of the maleic anhydride-grafted polyethylene.

[0026] The second stage of hot mixing, step S3, is then performed. The temperature of this second stage is denoted as T2, where T2–Tm2 is 3–10°C, and Tm1–T2 is 3–12°C. The mixing time for this second stage is 3–8 minutes, and the mixing speed is 300–700 r / min. Tm1 and Tm2 are both taken as the melting endothermic peak temperature from the second heating curve, and Tc1 is taken as the crystallization exothermic peak temperature from the cooling curve. Both are measured under a nitrogen atmosphere at a heating or cooling rate of 10°C / min. The temperature of the second stage hot mixing is the material temperature measured by a material temperature probe.

[0027] After the first-stage hot mixing, the primary-treated wear-resistant particles are cooled to a specified range below the peak crystallization temperature of maleic anhydride-grafted polyethylene and held at that temperature. This helps to increase the crystallinity of the already attached maleic anhydride-grafted polyethylene and maintain its relative stability in the subsequent second-stage hot mixing. The term "crystallization shaping" or "crystallization locking" used in this paper is a process description of the relatively stable state of the attached structure based on DSC temperature relationships. It is used to characterize the relative stability of the attached structure under specified subsequent process conditions. Its actual deformation, local flow, and coating morphology can vary with temperature, shear conditions, and material state, and the actual characterization results shall prevail.

[0028] The second-stage thermal mixing temperature is higher than the melting peak temperature of the carrier resin but lower than that of maleic anhydride-grafted polyethylene. This facilitates the preferential softening or melting of the carrier resin in the polyethylene carrier silicone masterbatch and maintains the relative stability of the already crystallized and stabilized maleic anhydride-grafted polyethylene attachment structure in the second stage. This mechanism is based on the relative thermal response relationship of the materials and can serve as a reasonable explanation for the process phenomena. The melting peak temperature obtained by differential scanning calorimetry reflects the overall thermal response of the material. The local softening state of different crystalline regions of the carrier resin and the maleic anhydride-grafted polyethylene may differ; the specific state can be determined by actual characterization.

[0029] Treating the material under the prescribed cooling and heat preservation conditions is beneficial for achieving sufficient crystallization and shaping of the maleic anhydride-grafted polyethylene (MPPE) attachment structure. Controlling the second-stage hot-mixing temperature within a range where the relative thermal responses of the carrier resin and MPPE match is conducive to maintaining the relative stability of the formed attachment state. Allowing the silicone masterbatch carrier resin to reach the required softened or molten state is beneficial for the silicone components to form a more uniform relative distribution on the outer surface of the wear-resistant particles after primary treatment. The above-mentioned relationships are speculations based on temperature conditions and experimental results; the specific microscopic processes may vary depending on the state of the raw materials and actual processing conditions.

[0030] The mixing speed in the second-stage hot mixing is lower than that used in the first-stage hot mixing. This facilitates the softening of the carrier resin and its distribution on the outer surface of the primary-processed wear-resistant particles, while maintaining the relative stability of the already crystallized and stabilized maleic anhydride-grafted polyethylene adhesion state. The material after the second-stage hot mixing is cooled and crushed to form a coated wear-resistant masterbatch with a particle size and flowability suitable for side feeding. This facilitates metering and improves the continuity and stability of the ultra-high molecular weight polyethylene micropowder side feeding process.

[0031] Preferably, in step S4, the high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer form the continuous polyethylene melt at or before a position 40% to 60% of the effective screw length from the main feed port of the twin-screw extruder. The effective screw length, as referred to in this invention, is the axial length from the centerline of the main feed port to the end of the screw. The actual formation position of the continuous polyethylene melt is determined according to the sampling method described in Example 1, using the absence of solid matrix resin particles in three consecutive samples and the sample exhibiting a continuous, homogeneous melt state as the criterion.

[0032] The coated abrasion-resistant masterbatch is added at a position 55%–75% of the effective screw length from the main feed port of the twin-screw extruder, ensuring that the actual side feed position is downstream of the actual formation position of the continuous polyethylene melt, with a distance of not less than 5% of the effective screw length. The peak residence time from the addition of the coated abrasion-resistant masterbatch to the extrusion die is 20–60 seconds. The peak residence time refers to the time from the pulsed addition of tracer particles from the side feed port to the tracer signal reaching its peak value at the die exit.

[0033] First, a continuous polyethylene melt is formed from high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer. Then, a coated abrasion-resistant masterbatch is added from the rear side-feeding position. This facilitates the reception and wetting of the side-feeded abrasion-resistant masterbatch by the continuous melt and maintains good dispersion of the ultra-high molecular weight polyethylene powder. Limiting the side-feeding position and the peak residence time after side-feeding within the above range helps provide a suitable mixing stroke for the dispersion of the coated abrasion-resistant masterbatch in the continuous melt and helps maintain the relative structural state of the coated abrasion-resistant masterbatch and the segmental state of the ultra-high molecular weight polyethylene.

[0034] Inorganic rigid fillers and antioxidants can be added together with high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer through the main feed inlet, and their wetting and initial dispersion are completed during the formation of the continuous polyethylene melt. The coated wear-resistant masterbatch is added after the continuous polyethylene melt has formed. This segmented feeding relationship facilitates better matching of the plasticization of the matrix resin, the dispersion of the inorganic fillers, and the subsequent dispersion of the wear-resistant masterbatch with the corresponding screw sections.

[0035] Preferably, in step S4, the measured melt temperature at the die outlet of the twin-screw extruder is 170–195°C, and the screw speed of the twin-screw extruder is 180–350 r / min. The measured melt temperature characterizes the actual temperature of the composite melt before entering the die, distinct from the set temperatures of each barrel zone; the screw speed is coordinated with the peak residence time after side feeding, which helps to maintain harmony between dispersion and shear strength.

[0036] Preferably, in step S5, the measured melt temperature at the die outlet of the single-screw pipe extruder is 175-195°C. The extruded pipe blank is first vacuum-sized on its outer surface using circulating water at 15-25°C, and then dry air at 45-65°C is introduced into the pipe blank. The initial sizing cooling section is 1.5m long. Subsequently, the internal cooling air is switched to dry air at 15-25°C to continue cooling the inner and outer surfaces of the pipe blank simultaneously until the inner and outer surface temperatures of the pipe blank are both reduced to below 45°C.

[0037] As soon as the tube blank leaves the extrusion die, it is first vacuum-sized using circulating water to form the outer diameter and outer surface profile of the tube. Simultaneously, dry air at a temperature higher than the external circulating water is introduced into the tube blank. This ensures a more coordinated initial cooling process between the inner and outer surfaces and promotes a more uniform temperature field within the tube wall. After the outer surface has achieved initial shaping, both the inner and outer surfaces of the tube blank are simultaneously cooled to below 45°C. This further promotes uniform cooling of the tube wall, improving dimensional stability and forming quality. The dry air also helps maintain a stable forming environment within the tube blank.

[0038] A second aspect of the present invention provides a low-temperature wear-resistant cable protection pipe, wherein the low-temperature wear-resistant cable protection pipe is extruded from a low-temperature wear-resistant polyethylene composite material. The low-temperature wear-resistant polyethylene composite material comprises the following raw materials in parts by weight: 100 parts high-density polyethylene; 8-18 parts linear low-density polyethylene; 6-14 parts ethylene-octene copolymer elastomer; 20-36 parts ultra-high molecular weight polyethylene micro powder; 1.2-4.32 parts maleic anhydride grafted polyethylene; 0.6-2.52 parts polyethylene carrier silicone masterbatch; 3-8 parts inorganic rigid filler; and 0.3-0.8 parts antioxidant.

[0039] Based on 100 parts by weight of the ultra-high molecular weight polyethylene (UHMWPE) micropowder, the maleic anhydride-grafted polyethylene comprises 6-12 parts by weight, and the polyethylene carrier silicone masterbatch comprises 3-7 parts by weight. The UHMWPE micropowder is first thermally mixed with the maleic anhydride-grafted polyethylene in a first-stage process. The resulting primary-treated wear-resistant particles are then cooled to a temperature 5-20°C lower than the differential scanning calorimetry (DSC) crystallization peak temperature of the maleic anhydride-grafted polyethylene and held at this temperature for 3-10 minutes. They are then thermally mixed with the polyethylene carrier silicone masterbatch in a second-stage process to form a coated wear-resistant masterbatch. This coated wear-resistant masterbatch is added to the continuous polyethylene melt after the high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer have formed a continuous polyethylene melt.

[0040] The aforementioned 1.2–4.32 parts by weight of maleic anhydride-grafted polyethylene and 0.6–2.52 parts by weight of polyethylene carrier silicone masterbatch are overall extreme values ​​calculated based on the usage range of 20–36 parts by weight of ultra-high molecular weight polyethylene micropowder. To ensure that the dosage of each component corresponds to the actual ratio of the wear-resistant masterbatch, the composite material also satisfies the following: based on 100 parts by weight of ultra-high molecular weight polyethylene micropowder, maleic anhydride-grafted polyethylene is 6–12 parts by weight, and polyethylene carrier silicone masterbatch is 3–7 parts by weight. Therefore, the wear-resistant masterbatch ratio in the preparation method corresponds to the overall raw material ratio of the low-temperature wear-resistant polyethylene composite material.

[0041] In the composite material, high-density polyethylene (HDPE) helps to form a continuous bulk phase with high rigidity and circumferential load-bearing capacity; linear low-density polyethylene (LDPE) can be used to adjust melt toughness and molding performance; ethylene-octene copolymer elastomer is beneficial to improving the deformation and energy absorption capacity of the polyethylene matrix under low-temperature conditions; ultra-high molecular weight polyethylene (UHMWPE) micropowder is dispersed in the continuous polyethylene phase as a wear-resistant component; maleic anhydride-grafted polyethylene and polyethylene carrier silicone masterbatch help to improve interfacial compatibility and lubrication dispersion, respectively; inorganic rigid filler helps to improve rigidity and dimensional stability; antioxidants help to maintain the stability of the polyethylene material during melt processing. The combination of components within the above ranges is beneficial to achieving a balance between wear resistance, low-temperature toughness, melt flowability, rigidity, and pipe molding stability.

[0042] Preferably, the low-temperature wear-resistant polyethylene composite material comprises the following raw materials in parts by weight: 100 parts high-density polyethylene; 10-15 parts linear low-density polyethylene; 8-12 parts ethylene-octene copolymer elastomer; 24-32 parts ultra-high molecular weight polyethylene micro powder; 1.92-3.20 parts maleic anhydride-grafted polyethylene; 0.96-1.92 parts polyethylene carrier silicone masterbatch; 4-6 parts inorganic rigid filler; and 0.4-0.6 parts antioxidant. The preferred proportions also satisfy: based on 100 parts by weight of ultra-high molecular weight polyethylene micro powder, maleic anhydride-grafted polyethylene comprises 8-10 parts by weight, and polyethylene carrier silicone masterbatch comprises 4-6 parts by weight.

[0043] Preferably, the ultra-high molecular weight polyethylene (UHMWPE) micropowder has a viscosity-average molecular weight of 2.5 million to 5 million and a particle size D50 of 30 to 80 μm. This viscosity-average molecular weight range is beneficial for UHMWPE to maintain the long molecular chain characteristics suitable for its wear-resistant properties; the particle size range is beneficial for balancing the load-bearing capacity of wear-resistant particles, staged surface treatment, and side-feed dispersion requirements.

[0044] The high-density polyethylene exhibits a melt flow rate of 0.2–0.8 g / 10 min and a density of 0.945–0.960 g / cm³ under conditions of 190°C and 2.16 kg load. 3 The density of the ethylene-octene copolymer elastomer is 0.860–0.890 g / cm³. 3 The glass transition temperature is not higher than -45℃. The melt flow rate and density of high-density polyethylene are used to characterize the melt processing capability and rigidity of the main resin, while the density and glass transition temperature of ethylene-octene copolymer elastomer are used to characterize its flexible segments and low-temperature elastic characteristics, which are beneficial for the elastomer to exert deformation and energy absorption effects in low-temperature environments.

[0045] Preferably, the polysiloxane content in the polyethylene carrier silicone masterbatch is 40% to 55% by mass. Adding polysiloxane in the form of polyethylene carrier masterbatch is beneficial to improving its metering and dispersion stability; within the temperature window of the second stage hot mixing, the softened or molten state of the carrier resin is conducive to the distribution of silicone components on the outer side of the wear-resistant particles in the primary treatment.

[0046] Preferably, the inorganic rigid filler is one or more of talc, wollastonite, and calcium carbonate surface-treated with a silane coupling agent or a titanate coupling agent. The particle size D50 of the inorganic rigid filler is 2–8 μm, and the aspect ratio is not greater than 8. Surface treatment is used to improve the wetting and dispersion state between the inorganic rigid filler and the polyethylene phase; limiting the particle size and aspect ratio within the above range is beneficial to maintaining a more uniform local stress distribution and to leveraging the role of the inorganic filler in improving the rigidity and dimensional stability of the composite material.

[0047] Preferably, the melt flow rate of the low-temperature wear-resistant polyethylene composite material under 190℃ and 5kg load conditions is 0.10~1.00g / 10min, and the Shore D hardness is 58~68. When tested according to the method described in this specification, the impact failure rate of the low-temperature wear-resistant cable protection pipe at -40℃ is not higher than 10%, the 2-hour mass wear amount tested with reference to GB / T 3960—2016 and using the pipe inner wall sample conditions described in this specification is not higher than 4.4mg, and the arithmetic mean of the maximum depth of cable reciprocating wear at -20℃ for five samples is not higher than 0.13mm. The above performance parameters characterize the low-temperature wear-resistant performance of the pipe from three aspects: low-temperature impact, sliding wear, and simulated low-temperature cable threading.

[0048] The present invention, by adopting the above technical solution, has the following beneficial effects: (1) The present invention sequentially performs selective softening and adhesion of maleic anhydride-grafted polyethylene, cooling and heat preservation for crystallization and shaping, and preferential softening or melting of silicone masterbatch carrier resin. Based on particle dispersion and wear resistance results, it is speculated that this sequential treatment is beneficial for the silicone masterbatch to form a relative distribution on the outside of the particles in the first treatment, promotes the stability of the adhesion state between grafted polyethylene and micro powder, and improves the micro powder dispersion, interface wetting, and interface stability of wear-resistant particles during repeated friction.

[0049] (2) This invention utilizes the thermal transition temperature difference between maleic anhydride-grafted polyethylene, silicone masterbatch carrier resin, and ultra-high molecular weight polyethylene micropowder to establish a first-stage selective softening and adhesion, a cooling crystallization and shaping below Tc1, and a second-stage selective thermal mixing condition above Tm2 and below Tm1. The aforementioned "selective softening" and "crystallization and shaping" are used to characterize the relative thermal response of each material at a specified temperature; the specific micromorphology can be manifested as discrete adhesion, local coverage, or other states that can reflect the relative coating relationship, and the actual characterization results shall prevail. The temperature relationship jointly defines the two-stage processing process, which is beneficial to improving the controllability and batch repeatability of the wear-resistant masterbatch processing state.

[0050] (3) In this invention, after forming a continuous polyethylene melt from high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer, a coated abrasion-resistant masterbatch is fed into the rear section of a twin-screw extruder. The continuous melt facilitates the reception and wetting of the side-feed particles. The side-feeding position and the subsequent peak residence time of 20-60 seconds are conducive to providing a suitable mixing stroke for the dispersion of the abrasion-resistant masterbatch, and help maintain the relative structural state, micro-powder dispersion state, and chain segment state of the coated abrasion-resistant masterbatch.

[0051] (4) In this invention, high-density polyethylene plays a major role in rigidity, linear low-density polyethylene and ethylene-octene copolymer elastomer are used to adjust low-temperature toughness and processing performance, ultra-high molecular weight polyethylene micro powder with coating treatment plays a wear-resistant role, and inorganic rigid fillers are used to improve rigidity and dimensional stability. The components and their dosages are coordinated to ensure that the pipe extrusion processing capacity, rigidity, low-temperature toughness and wear resistance are kept in harmony.

[0052] (5) In this invention, after the pipe is extruded, low-temperature circulating water is first used to vacuum-size the outer surface, while high-temperature dry air is introduced into the pipe blank, and then the inner and outer surfaces of the pipe blank are cooled simultaneously. This step-by-step cooling method is beneficial to coordinate the initial cooling process of the inner and outer surfaces, and promotes further uniform cooling of the pipe wall after the outer diameter is initially shaped, thereby improving the dimensional stability and forming quality of the pipe.

[0053] (6) By limiting the raw material ratio, material thermal transformation temperature, two-stage thermal mixing conditions, twin-screw feeding position and residence time, pipe step-by-step cooling conditions, and melt mass flow rate and Shore D hardness of composite material, this invention enables the formation of a detectable and adjustable process parameter system for each stage of wear-resistant masterbatch preparation, composite material granulation and pipe extrusion. This is beneficial to improving the repeatability of the preparation process and provides support for the obtained low-temperature wear-resistant cable protection pipe to obtain continuous processing adaptability, wear-resistant use basis and low-temperature impact resistance basis. Detailed Implementation

[0054] The present invention will be further described below with reference to the embodiments. Unless otherwise specified, all raw materials can be obtained commercially, and all percentages are by weight. Except for the internal proportion of the wear-resistant masterbatch based on ultra-high molecular weight polyethylene micropowder, all other weight parts are based on 100 parts of high-density polyethylene. The melt mixing temperature in step S4 and the pipe extrusion temperature in step S5 mentioned in Examples 2-6 refer to the actual melt temperature measured by an insertion melt temperature probe at the corresponding extruder die head or die outlet. Each temperature control zone follows the gradient setting method of Example 1 and is adjusted overall to ensure that the measured melt temperature reaches the specified value.

[0055] The viscosity of dilute solutions of ultra-high molecular weight polyethylene (UHMWPE) micropowder was determined according to GB / T 1632.3—2010, and the viscosity-average molecular weight was calculated using the same solvent system, test temperature, and Mark-Houwink conversion parameters. Particle size D50 was determined using laser diffraction dry method, and all samples used the same dispersion pressure and optical parameters. The density of the polyethylene material was determined according to the impregnation method of GB / T 1033.1—2008, and the melt mass flow rate was determined according to GB / T 3682.1—2018. The melting peak temperature and crystallization peak temperature of the polyethylene material were determined according to GB / T 19466.3—2025: nitrogen flow rate 50 mL / min, heating from 25℃ to 180℃ at 10℃ / min and holding for 3 min, then cooling to 25℃ at 10℃ / min; the endothermic peak temperature of the second heating curve was recorded as the melting peak temperature, and the exothermic peak temperature of the cooling curve was recorded as the crystallization peak temperature. The glass transition temperature of the ethylene-octene copolymer elastomer was determined by the second heating curve according to GB / T 19466.2—2025. The maleic anhydride grafting rate was verified by acid-base titration calibrated with standard samples; the polydimethylsiloxane content and number-average molecular weight were based on the corresponding batch of raw material factory inspection reports, and the same batch of raw materials was used in the examples and comparative examples.

[0056] To avoid deviations in implementation results due to differences in polymer grades, comonomers, molecular weights, particle sizes, grafting degrees, or surface treatment states when raw materials are disclosed using only generic names, all formulation raw materials actually used in the examples and comparative examples are further specified according to Table 1. The CAS number of the polymer is only used to confirm the basic chemical category and cannot be used as the sole basis for raw material selection; the actual selection should simultaneously meet the structural and performance parameters listed in Table 1 and the aforementioned unified testing caliber, without limiting specific manufacturers or product models. Unless otherwise stated in each example, only the formulation dosage and process conditions are listed below, and the raw material grades and fixed selection parameters already specified in Table 1 will not be repeated.

[0057] In Table 1, MFR refers to the melt mass flow rate measured at 190℃ and 2.16kg load; Tm and Tc are both determined by differential scanning calorimetry at a heating / cooling rate of 10℃ / min, where Tm is the melting endothermic peak temperature of the second heating curve and Tc is the crystallization exothermic peak temperature of the cooling curve; D50 is determined by laser diffraction; the content of comonomer structural units is determined by Fourier transform infrared spectroscopy calibration method.

[0058] Table 1 Raw material information for the examples and comparative formulations Example 1 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. The low-temperature wear-resistant polyethylene composite material comprises 100 parts of high-density polyethylene, 12 parts of linear low-density polyethylene, 10 parts of ethylene-octene copolymer elastomer, 28 parts of ultra-high molecular weight polyethylene micropowder, 2.52 parts of maleic anhydride-grafted polyethylene, 1.40 parts of polyethylene carrier silicone masterbatch, 5 parts of inorganic rigid filler, and 0.50 parts of antioxidant. Based on 100 parts of ultra-high molecular weight polyethylene micropowder, 9 parts of maleic anhydride-grafted polyethylene and 5 parts of polyethylene carrier silicone masterbatch are used.

[0059] S1. Dry ultra-high molecular weight polyethylene micropowder, maleic anhydride-grafted polyethylene powder, and polyethylene carrier silicone masterbatch separately at 55℃ for 3 hours; dry talc powder at 105℃ for 2 hours; dry high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, and antioxidants at 60℃ for 2 hours. After drying, seal and cool to 25℃. When weighing, first weigh each raw material separately, then premix the two antioxidants for 3 minutes to ensure uniform distribution of the hindered phenolic antioxidant and phosphite antioxidant.

[0060] S2. Add 28 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) micropowder to a high-speed mixer equipped with a jacketed temperature control and a material temperature probe, and premix at 300 rpm for 2 minutes. Then, uniformly add 2.52 parts by weight of maleic anhydride-grafted polyethylene powder within 2 minutes, increase the speed to 800 rpm, and raise the material temperature to 132°C through the jacket and mixing friction heat. After the material temperature reaches 132°C, maintain the temperature and hot mix for 10 minutes. 132°C is 8°C higher than Tm1 and 5°C lower than the melting peak temperature of UHMWPE micropowder, which softens and spreads the grafted polyethylene while the micropowder body maintains its granular shape, resulting in primary processed wear-resistant particles.

[0061] Immediately after steps S3 and S2, reduce the rotation speed to 150 r / min and introduce 15°C circulating water into the jacket to lower the temperature of the primary-treated wear-resistant particles to 92°C within 8 minutes; 92°C is 12°C lower than Tc1. Maintain this temperature at 92°C for 6 minutes to complete crystallization and solidification, then raise the temperature to 114°C. Once the material temperature stabilizes at 114°C, add 1.4 parts by weight of polyethylene carrier silicone masterbatch within 1 minute and hot mix at 500 r / min for 5 minutes. 114°C is 6°C higher than Tm2 and 10°C lower than Tm1, softening the carrier resin and carrying polydimethylsiloxane to the outer side of the primary-treated wear-resistant particles, while simultaneously preventing the inner grafted polyethylene attachment structure from remelting. After hot mixing, discharge the material into a 20°C water-cooled cold mixer, cool it to 40°C at 100 r / min, then crush it using a low-speed shear crusher and pass it through an 8-mesh sieve to obtain coated wear-resistant masterbatch with a particle size of 1.0–2.5 mm.

[0062] S4. A co-rotating parallel twin-screw extruder with a screw diameter of 50 mm and a length-to-diameter ratio of 48:1 was used. 100 parts by weight of high-density polyethylene, 12 parts by weight of linear low-density polyethylene, 10 parts by weight of ethylene-octene copolymer elastomer, 5 parts by weight of talc, and 0.5 parts by weight of antioxidant were premixed for 5 minutes and then added through the main feed inlet. The temperature control zones from the main feed end to the die were sequentially set to 170℃, 175℃, 180℃, 185℃, 190℃, 190℃, 185℃, 185℃, 180℃, and 180℃, with a screw speed of 260 r / min. A sampling port was set at 50% of the effective screw length. No solid particles of high-density polyethylene, linear low-density polyethylene, or ethylene-octene copolymer elastomer were observed in three consecutive samples, and the samples were in a continuous, homogeneous melt state. This confirmed that the three matrix resins formed a continuous polyethylene melt before this location. 31.92 parts by weight of coated wear-resistant masterbatch were metered and added from a side feed port located 65% of the effective screw length from the main feed port. The side feed position was 15% of the effective screw length downstream of the continuous melt confirmation position. The peak residence time was determined by pulsed addition of 0.5g of blue polyethylene tracer particles from the side feed port, continuously recording the color intensity of the material exiting the die, and using the time it took for the color intensity to reach its peak value. In this embodiment, the peak residence time was 40s. The melt was then subjected to vacuum degassing, die extrusion, water-cooled stripping, and pelletizing to obtain a low-temperature wear-resistant polyethylene composite material. The pellets were dried at 70°C for 3 hours for later use.

[0063] S5. A single-screw pipe extruder with a screw diameter of 65mm and a length-to-diameter ratio of 30:1 is used to extrude the composite material into a tube blank with a nominal outer diameter of 110mm and a wall thickness of 5.0mm. The barrel temperatures are 175℃, 180℃, 185℃, 190℃, and 190℃ respectively, while the die and die head temperatures are both 188℃. The screw speed is 55r / min, and the traction speed is 1.20m / min. After the tube blank leaves the die, it is first vacuum-sized using 20℃ circulating water at a vacuum degree of -0.035MPa. Simultaneously, dry air at 55℃ with a dew point below -20℃ is introduced into the inner surface through an internal cooling air duct located at the center of the tube blank, with an air flow rate of 35m³ / min. 3 / h; the initial sizing cooling section is 1.5m long. Subsequently, the outer surface continues to be cooled with 20℃ circulating water, while the internal cooling air is switched to 25℃ and a flow rate of 45m³ / h. 3 Dry air is supplied at a rate of / h to cool both the inner and outer surfaces simultaneously until the outer surface temperature measured by infrared thermography and the inner surface temperature measured by insertion thermocouple are both below 45℃. Finally, the tube is cut to a fixed length of 6m and placed at 23℃ for 24 hours to obtain a low-temperature wear-resistant cable protection tube.

[0064] Example 2 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. Compared with Embodiment 1, the difference is that the high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, talc powder and antioxidant are 100 parts, 8 parts, 6 parts, 20 parts, 1.2 parts, 0.6 parts, 3 parts and 0.3 parts respectively.

[0065] The hot mixing temperature of S2 is 118℃, the time is 5 min, and the rotation speed is 500 r / min; 118℃ is 5℃ higher than Tm1 and 15℃ lower than the melting peak temperature of the micronized powder. S2 is then cooled to 77℃ and held for 3 min; 77℃ is 20℃ lower than Tc1. The hot mixing temperature of S3 is 106℃, the time is 3 min, and the rotation speed is 300 r / min; 106℃ is 3℃ higher than Tm2 and 7℃ lower than Tm1. The melt mixing temperature of S4 is 170℃, the screw rotation speed is 180 r / min, the matrix resin forms a continuous melt at 40% of the effective screw length, the masterbatch is side-fed from 55% of the length, and the peak residence time after side-feeding is 60 s. The pipe extrusion temperature of S5 is 175℃, the initial external cooling circulating water temperature is 15℃, and the internal drying air temperature is 45℃. Other operations are the same as in Example 1.

[0066] Example 3 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. Compared with Embodiment 1, the difference is that the raw materials are, in order: 100 parts of high-density polyethylene, 18 parts of linear low-density polyethylene, 14 parts of ethylene-octene copolymer elastomer, 36 parts of ultra-high molecular weight polyethylene micro powder, 4.32 parts of maleic anhydride grafted polyethylene, 2.52 parts of polyethylene carrier silicone masterbatch, 8 parts of talc powder, and 0.80 parts of antioxidant.

[0067] The hot mixing temperature of S2 is 136℃, the time is 15 min, and the rotation speed is 1000 r / min; 136℃ is 20℃ higher than Tm1 and 3℃ lower than the melting peak temperature of the micronized powder. S2 is then cooled to 94℃ and held for 10 min; 94℃ is 5℃ lower than Tc1. The hot mixing temperature of S3 is 104℃, the time is 8 min, and the rotation speed is 700 r / min; 104℃ is 10℃ higher than Tm2 and 12℃ lower than Tm1. The melt mixing temperature of S4 is 195℃, the screw rotation speed is 350 r / min, the matrix resin forms a continuous melt at 60% of the effective screw length, the masterbatch is side-fed from 75% of the length, and the peak residence time after side-feeding is 20 s. The pipe extrusion temperature of S5 is 195℃, the initial external cooling circulating water temperature is 25℃, and the internal drying air temperature is 65℃. Other operations are the same as in Example 1.

[0068] Example 4 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. Compared with Embodiment 1, the difference is that the high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, inorganic rigid filler and antioxidant are 100 parts, 10 parts, 8 parts, 24 parts, 1.92 parts, 0.96 parts, 4 parts and 0.40 parts respectively.

[0069] S2 involves hot mixing at 126°C and 650 rpm for 7 minutes, followed by cooling to 90°C and holding for 5 minutes; S3 involves hot mixing at 109°C and 400 rpm for 4 minutes; S4 involves side feeding at 180°C and 220 rpm at 60% of the effective screw length, with a peak residence time of 50 seconds after side feeding; S5 involves extrusion at 180°C, external cooling water at 18°C, and internal dry air circulation at 50°C. Other operations are the same as in Example 1.

[0070] Example 5 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. Compared with Embodiment 1, the difference is that the high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, inorganic rigid filler and antioxidant are 100 parts, 15 parts, 12 parts, 32 parts, 3.20 parts, 1.92 parts, 6 parts and 0.60 parts respectively.

[0071] S2 involves hot mixing at 134°C and 900 rpm for 12 min, followed by cooling to 96°C and holding for 8 min; S3 involves hot mixing at 113°C and 600 rpm for 6 min; S4 involves side feeding at 190°C and 300 rpm at 70% of the effective screw length, with a peak residence time of 30 s after side feeding; S5 involves extrusion at 190°C, external cooling water at 23°C, and internal dry air circulation at 60°C. Other operations are the same as in Example 1.

[0072] Example 6 This embodiment discloses a low-temperature wear-resistant cable protection pipe and its preparation method. Compared with Embodiment 1, the difference is that the high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, inorganic rigid filler and antioxidant are 100 parts, 13 parts, 11 parts, 30 parts, 3.00 parts, 1.80 parts, 5.5 parts and 0.50 parts respectively.

[0073] S2 involves hot mixing at 129°C and 750 rpm for 9 minutes, followed by cooling to 92°C and holding for 7 minutes; S3 involves hot mixing at 112°C and 550 rpm for 5 minutes; S4 involves side feeding at 185°C and 270 rpm at 65% of the effective screw length, with a peak residence time of 40 seconds after side feeding; S5 involves extrusion at 185°C, external cooling water at 20°C, and internal dry air circulation at 55°C. Other operations are the same as in Example 1.

[0074] Comparative Example 1 This comparative example differs from Example 1 in that steps S2 and S3 are omitted, and no coated wear-resistant masterbatch is prepared. Ultra-high molecular weight polyethylene micropowder, maleic anhydride-grafted polyethylene powder, and polyethylene carrier silicone masterbatch are added together with the matrix resin, talc, and antioxidant from the main feed port of a twin-screw extruder. Other formulations, twin-screw temperature, screw speed, and pipe forming conditions are the same as in Example 1.

[0075] Comparative Example 2 The difference between this comparative example and Example 1 is that after S2, cooling and heat preservation below Tc1 is not performed. The material is directly reduced from 132°C to 114°C, and then polyethylene carrier silicone masterbatch is added and hot-mixed according to the speed and time of S3. Other operations are the same as in Example 1.

[0076] Comparative Example 3 The difference between this comparative example and Example 1 lies in the order in which the two treatment components were added. First, the polyethylene carrier silicone masterbatch was added to the ultra-high molecular weight polyethylene micropowder and hot-mixed at 114°C and 500 rpm for 5 min; then the temperature was raised to 132°C, and maleic anhydride-grafted polyethylene was added and hot-mixed at 800 rpm for 10 min, followed by cooling and crushing. Other operations were the same as in Example 1.

[0077] Comparative Example 4 Compared with Example 1, the difference in this comparative example is that after the cooling and heat preservation after S2, the second stage hot mixing temperature is set to 126°C, which is 2°C higher than Tm1; the second stage is still hot mixed at 500r / min for 5min, and other operations are the same as in Example 1.

[0078] Comparative Example 5 The difference between this comparative example and Example 1 is that the coated wear-resistant masterbatch prepared in S2 and S3 is that it is not added from the rear side feed port, but is added from the main feed port together with the matrix resin, talc, and antioxidant. The peak residence time of the coated wear-resistant masterbatch from the main feed port to the die head is 85s, and other operations are the same as in Example 1.

[0079] Comparative Example 6 The difference between this comparative example and Example 1 is that step-by-step cooling is omitted in step S5. Immediately after the tube blank leaves the die, the outer surface is cooled with 20°C circulating water, while 20°C dry air is introduced into the inner surface. This condition is maintained until the temperature of both the inner and outer surfaces is below 45°C. Other operations are the same as in Example 1.

[0080] Comparative Example 7 The difference between this comparative example and Example 1 is that maleic anhydride-grafted polyethylene is not added. Ultra-high molecular weight polyethylene micropowder is directly thermally mixed with polyethylene carrier silicone masterbatch at 114°C, then cooled and crushed, and fed from the side at 65% of the effective screw length. Other formulations and operations are the same as in Example 1.

[0081] Comparative Example 8 The difference between this comparative example and Example 1 is that no polyethylene carrier silicone masterbatch is added. The wear-resistant particles obtained in S2 are directly cooled and crushed after being kept at 92°C for 6 minutes, and then fed from the side at 65% of the effective length of the screw. Other formulations and operations are the same as in Example 1.

[0082] Comparative Example 9 The difference between this comparative example and Example 1 is that ethylene-octene copolymer elastomer is not added, and the amount of high-density polyethylene is increased from 100 parts by weight to 110 parts by weight, so that the total feed mass remains unchanged. Other formulations and operations are the same as in Example 1.

[0083] To verify the effects of two-stage processing, post-stage side feeding, and step-by-step cooling on material processability, particle dispersion, low-temperature toughness, dimensional stability, and wear resistance, the following methods were used to test Examples 1-6 and Comparative Examples 1-9. Unless otherwise stated, each result is based on five independent parallel samples: for items with multiple measurement points or fields of view, the results for each individual sample were calculated first, and then the arithmetic mean of the results for the five samples was calculated; the arithmetic mean is listed in the table. The -40℃ impact failure rate was calculated based on a total of 100 impact points across five pipe sections; the maximum equivalent diameter of agglomerates in Table 2 is the arithmetic mean of the maximum values ​​for each of the five samples.

[0084] 1. Melt flow rate, Shore D hardness, and particle dispersion state detection Melt flow rate was determined according to GB / T 3682.1—2018 "Determination of melt flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method", with a test temperature of 190℃ and a load of 5 parts by weight. Continuously extruded granules were used as samples. Shore D hardness was determined according to GB / T 2411—2008 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester". Cut pieces of the tube wall were stacked with the inner surface facing the indenter, and each layer was stacked in the same direction to a thickness of 6 mm. After conditioning at 23℃ for 24 hours, the sample was tested. Five measurements were taken at intervals of not less than 6 mm for each sample, and the average value was taken.

[0085] The particle dispersion was examined using a transmission optical microscope. Samples were taken from the pipe wall at four positions along the circumference: 0°, 90°, 180°, and 270°. These samples were then cryostated at -80°C to prepare 20 μm thick sections along the pipe's axial direction. Ten 1.00 mm² sections were randomly collected from each position. 2 The field of view was determined. All images were acquired using the same light source, exposure time, magnification, and 8-bit grayscale conditions. First, a matrix control sample without ultra-high molecular weight polyethylene (UHMWPE) powder was used for calibration and a fixed grayscale threshold. Subsequently, the same threshold was applied to all images in the same batch, without manual adjustment for each image. Image analysis software was used to classify dark connected regions with an equivalent circle diameter greater than 100 μm but lower than the fixed grayscale threshold as agglomeration areas, excluding areas overlapping with slice edges, bubbles, or identifiable inorganic filler particles. The agglomeration area ratio was calculated by dividing the total area of ​​the agglomeration areas by the total area of ​​the field of view; simultaneously, the equivalent circle diameter of the largest agglomeration area within the entire field of view for each sample was recorded.

[0086] The test results for material processability and particle dispersion are shown in Table 2.

[0087] Table 2. Results of material processability and particle dispersion testing 2. Testing of pipe ring stiffness, low-temperature impact, ellipticity, and longitudinal shrinkage rate. Ring stiffness was determined according to GB / T 9647—2015 "Determination of Ring Stiffness of Thermoplastic Pipes". Low-temperature external impact was conducted according to GB / T 14152—2001 "Test Method for External Impact Resistance of Thermoplastic Pipes - Clockwise Rotation Method": A 200mm long pipe section was conditioned at -40℃ for 4 hours, and then impacted from a height of 1.0m using a 5.0kg drop hammer with a 50mm radius. Twenty impact points were set for each parallel pipe section, totaling 100 impact points for five sections. Visible through-cracks or fissures were considered failures, and the total failure rate was calculated by dividing the total number of failure points by 100 and multiplying by 100%. The -40℃ temperature was used to directly evaluate the low-temperature cable laying environment; apart from temperature conditions, the impact positions and conditioning were arranged according to this standard.

[0088] Pipe dimensions were determined according to GB / T 8806—2008 "Determination of Dimensions of Plastic Components in Plastic Piping Systems". The maximum and minimum outer diameters were measured at three cross-sections 100mm, 1000mm, and 2000mm from the pipe end. Ovality was calculated by dividing (maximum outer diameter - minimum outer diameter) by the nominal outer diameter and multiplying by 100%. Longitudinal shrinkage rate was determined according to GB / T 6671—2001 "Determination of Longitudinal Shrinkage Rate of Thermoplastic Pipes" using the oven method, with a test temperature of 100℃ and a holding time of 1 hour.

[0089] The test results of the mechanical properties and dimensional stability of the pipe are shown in Table 3.

[0090] Table 3. Test results of mechanical properties and dimensional stability of the pipes 3. Sliding friction wear and low-temperature cable reciprocating wear detection Sliding friction and wear tests were conducted according to GB / T 3960—2016 "Test Method for Sliding Friction and Wear of Plastics". Samples with a length of 30 mm, a width of 7 mm, and a thickness equal to the actual wall thickness of the pipe were cut axially from the inner wall of the pipe, with the inner surface used as the friction test surface. The friction pair consisted of a 45 steel ring with a surface roughness Ra of 0.4 μm. The load was 196 N, the sliding speed was 0.42 m / s, and the test duration was 2 hours. Before and after the test, the samples were placed at 23℃ and 50% relative humidity for 24 hours and weighed to calculate the mass wear. The coefficient of friction was taken as the average value of the last 30 minutes of the stable test phase.

[0091] To simulate the low-temperature cable threading process, a reciprocating abrasion test was also conducted. A complete pipe section with a length of 1000 mm was placed in an environmental chamber at -20°C for 6 hours, and the temperature of the environmental chamber was maintained at -20°C throughout the reciprocating test. Round cables from the same batch, with an outer diameter of 20 mm and an outer sheath of cross-linked polyethylene, were selected, and a new cable contact section was used for each pipe section. The natural curvature of the pipe's inner wall was used as the contact curvature, and the cable was positioned against the inner wall of the pipe at a 90° wrap angle using a positioning clamp. One end of the cable was connected to a reciprocating drive mechanism, and the other end was subjected to a constant tension device with a tension of 200 N, reciprocating 2000 times at a stroke of 600 mm and a speed of 0.20 m / s. After the test, the pipe section was cut along the deepest wear mark. The difference between the wall thickness of the adjacent unworn area and the minimum wall thickness of the wear mark area was measured using a wall thickness micrometer with a resolution of 0.01 mm. This difference was taken as the maximum wear depth. Five locations were measured at equal intervals for each pipe section. The maximum value among the five measurements was taken as the maximum wear depth of the sample. The arithmetic mean of the maximum wear depth of the five samples was then calculated.

[0092] The results of the wear resistance test are shown in Table 4.

[0093] Table 4. Test results of wear resistance As can be seen from Examples 1-6, under the listed formulation and process parameter combinations, the melt flow rate of the composite material is 0.11-0.82 g / 10 min, the Shore D hardness is 58-68, and the agglomeration area ratio is not higher than 1.9%; the ring stiffness of the resulting pipe is 8.1-11.8 kN / m. 2 The impact failure rate at -40℃ was 0–10%, the mass wear amount over 2 hours was 1.9–4.4 mg, and the arithmetic mean of the maximum depth of reciprocating wear at -20℃ was 0.06–0.13 mm. These results indicate that the parameter combination used in the listed examples can balance continuous extrusion, low-temperature toughness, rigidity, and wear resistance.

[0094] A comparison of Example 1 and Comparative Example 1 shows that when the three abrasion-resistant treatment components are blended with the matrix resin in a single step, the agglomeration area ratio increases from 0.7% to 6.8%, and the 2-hour mass abrasion amount increases from 2.8 mg to 7.9 mg. A comparison of Example 1 and Comparative Example 2 shows that if the temperature is not lowered below Tc1 after the first stage and heat preservation is performed, the agglomeration area ratio and mass abrasion amount increase to 4.1% and 6.2 mg, respectively. These results indicate that cooling heat preservation is beneficial for improving the relative stability of the grafted polyethylene adhesion state.

[0095] A comparison of Example 1 with Comparative Examples 3 and 4 shows that adding silicone masterbatch before adding maleic anhydride-grafted polyethylene, or raising the second-stage temperature above Tm1, significantly increases the agglomeration area ratio and wear rate. These results indicate that the process sequence of first performing compatibility adhesion, then cooling and crystallizing for shaping, followed by the second-stage hot mixing, is superior. Furthermore, the second-stage temperature window above Tm2 and below Tm1, when combined with this sequence, is beneficial for improving dispersion and wear resistance.

[0096] A comparison of Example 1 and Comparative Example 5 shows that even with the same pre-prepared masterbatch, adding the masterbatch from the main feed port and subjecting it to 85 seconds of high-temperature, high-shear treatment resulted in a decrease in MFR to 0.27 g / 10 min, an increase in agglomeration area ratio to 5.9%, and an increase in mass attrition to 7.3 mg. This indicates that subsequent side feeding after the formation of the continuous polyethylene melt and limiting the subsequent residence time are more effective. A comparison of Example 1 and Comparative Example 6 shows that after eliminating the initial sizing stage involving external cooling water and high-temperature internally circulated dry air, the ellipticity increased from 0.6% to 2.7%, the longitudinal shrinkage rate increased from 1.1% to 3.4%, and the -40°C impact failure rate increased to 25%. These results indicate that step-by-step cooling is beneficial for improving the dimensional stability and low-temperature impact performance of the pipe.

[0097] The results of Example 1, Comparative Examples 7 and 8 collectively demonstrate that when maleic anhydride-grafted polyethylene or polyethylene-carrier silicone masterbatch were removed and the processing steps were changed accordingly, agglomeration and wear significantly increased. A comparison of Example 1 and Comparative Example 9 shows that replacing the ethylene-octene copolymer elastomer with an equal mass of high-density polyethylene increased the ring stiffness, but the impact failure rate at -40°C reached 55%, indicating that in this formulation system, the amount of elastomer is related to the low-temperature impact performance. Example 1, even with the elastomer present, still maintained 9.4 kN / m. 2 The ring stiffness indicates that the overall formulation of this embodiment can balance ring stiffness and low-temperature impact performance.

[0098] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-temperature wear-resistant cable protection tube, characterized in that, Includes the following steps: S1. Provides ultra-high molecular weight polyethylene micro powder, maleic anhydride grafted polyethylene, polyethylene carrier silicone masterbatch, high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, inorganic rigid filler and antioxidant. S2. The ultra-high molecular weight polyethylene micro powder and the maleic anhydride grafted polyethylene are thermally mixed in the first stage to soften the maleic anhydride grafted polyethylene and attach it to the surface of the ultra-high molecular weight polyethylene micro powder to obtain wear-resistant particles after one treatment. S3. After the first stage of hot mixing is completed, the primary-treated wear-resistant particles are cooled to 5-20°C lower than the differential scanning calorimetry crystallization peak temperature of the maleic anhydride-grafted polyethylene and held at that temperature for 3-10 minutes to allow the maleic anhydride-grafted polyethylene adhering to the surface of the ultra-high molecular weight polyethylene micro powder to crystallize and solidify. Then, the polyethylene carrier silicone masterbatch is added to the cooled and held-temperature primary-treated wear-resistant particles for the second stage of hot mixing. After cooling and crushing, a coated wear-resistant masterbatch is obtained. S4. The high-density polyethylene, linear low-density polyethylene, ethylene-octene copolymer elastomer, inorganic rigid filler and antioxidant are added to a twin-screw extruder and melt-plasticized. After the high-density polyethylene, linear low-density polyethylene and ethylene-octene copolymer elastomer form a continuous polyethylene melt, the coated wear-resistant masterbatch is added through the side feed port of the twin-screw extruder, so that the coated wear-resistant masterbatch is dispersed in the continuous polyethylene melt. After extrusion granulation, a low-temperature wear-resistant polyethylene composite material is obtained. S5. The low-temperature wear-resistant polyethylene composite material is extruded into a pipe, vacuum sizing, cooled and traction-cut to obtain the low-temperature wear-resistant cable protection pipe. Based on 100 parts by weight of the ultra-high molecular weight polyethylene micro powder, the amount of maleic anhydride grafted polyethylene is 6 to 12 parts by weight, and the amount of polyethylene carrier silicone masterbatch is 3 to 7 parts by weight. Based on 100 parts by weight of the high-density polyethylene, the amount of linear low-density polyethylene is 8 to 18 parts by weight, the amount of ethylene-octene copolymer elastomer is 6 to 14 parts by weight, the amount of ultra-high molecular weight polyethylene micro powder is 20 to 36 parts by weight, the amount of inorganic rigid filler is 3 to 8 parts by weight, and the amount of antioxidant is 0.3 to 0.8 parts by weight.

2. The preparation method according to claim 1, characterized in that, The maleic anhydride grafting rate of the maleic anhydride-grafted polyethylene is 0.6% to 1.5%, and the melt mass flow rate under the conditions of 190℃ and 2.16kg load is 10 to 50g / 10min; the differential scanning calorimetry melting peak temperature of the maleic anhydride-grafted polyethylene is 5 to 25℃ lower than that of the ultra-high molecular weight polyethylene micropowder.

3. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the first-stage hot mixing is 5–20°C higher than the differential scanning calorimetry melting peak temperature of the maleic anhydride-grafted polyethylene and 3–15°C lower than the differential scanning calorimetry melting peak temperature of the ultra-high molecular weight polyethylene micropowder; the first-stage hot mixing time is 5–15 min, and the mixing speed is 500–1000 r / min. The first-stage hot mixing temperature is the material temperature measured by the material temperature probe.

4. The preparation method according to claim 3, characterized in that, The carrier resin of the polyethylene carrier silicone masterbatch is one or both of low-density polyethylene and linear low-density polyethylene. The differential scanning calorimetry (DSC) melting peak temperature of the maleic anhydride-grafted polyethylene is denoted as Tm1, and the differential scanning calorimetry melting peak temperature of the carrier resin is denoted as Tm2, ​​with Tm1-Tm2 ranging from 10 to 22°C. When the carrier resin contains two resins and the differential scanning calorimetry curve shows more than two melting peaks, the main melting peak temperature on the low-temperature side is taken as Tm2. The cooling and heat preservation in step S3 specifically involves cooling the wear-resistant particles processed in the first step to Tc1-20℃ to Tc1-5℃ and keeping them warm for 3 to 10 minutes, so that the maleic anhydride-grafted polyethylene attached to the surface of the ultra-high molecular weight polyethylene micro powder crystallizes and solidifies, wherein Tc1 is the differential scanning calorimetry crystallization peak temperature of the maleic anhydride-grafted polyethylene. The second stage of hot mixing is then carried out, and the temperature of the second stage of hot mixing is denoted as T2. T2-Tm2 is 3-10℃, Tm1-T2 is 3-12℃, the time of the second stage of hot mixing is 3-8 minutes, and the mixing speed is 300-700 r / min. The temperature of the second stage of hot mixing is the material temperature measured by the material temperature probe. Tm1 and Tm2 are both taken from the melting endothermic peak temperature of the second heating curve, and Tc1 is taken from the crystallization exothermic peak temperature of the cooling curve. Both are measured under nitrogen atmosphere at a heating rate or cooling rate of 10℃ / min.

5. The preparation method according to claim 1, characterized in that, In step S4, the high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer form the continuous polyethylene melt at or before a position 40% to 60% of the effective screw length from the main feed port of the twin-screw extruder. The coated wear-resistant masterbatch is added at a position 55% to 75% of the effective screw length from the main feed port of the twin-screw extruder, and the actual side feeding position is located downstream of the actual formation position of the continuous polyethylene melt, with a distance of not less than 5% of the effective screw length; the peak residence time from the addition of the coated wear-resistant masterbatch to the extrusion die is 20 to 60 seconds.

6. The preparation method according to claim 1, characterized in that, In step S4, the measured melt temperature at the die outlet of the twin-screw extruder is 170–195°C, and the screw speed of the twin-screw extruder is 180–350 r / min. In step S5, the measured melt temperature at the die outlet of the single-screw pipe extruder is 175-195℃. The extruded pipe blank is first vacuum-sized on its outer surface using circulating water at 15-25℃, and then dry air at 45-65℃ is introduced into the pipe blank. The initial sizing cooling section is 1.5m long. Subsequently, the internal cooling air is switched to dry air at 15-25℃ to continue cooling the inner and outer surfaces of the pipe blank simultaneously until the inner and outer surface temperatures of the pipe blank are both reduced to below 45℃.

7. A low-temperature wear-resistant cable protection pipe, characterized in that, The low-temperature wear-resistant cable protection tube is extruded from low-temperature wear-resistant polyethylene composite material; The low-temperature wear-resistant polyethylene composite material comprises the following raw materials in parts by weight: 100 parts of high-density polyethylene; 8-18 parts of linear low-density polyethylene; 6-14 parts of ethylene-octene copolymer elastomer; 20-36 parts of ultra-high molecular weight polyethylene micro powder; Maleic anhydride-grafted polyethylene: 1.2–4.32 parts; 0.6–2.52 parts of polyethylene carrier silicone masterbatch; 3-8 parts of inorganic rigid filler; Antioxidant 0.3–0.8 parts; In this process, based on 100 parts by weight of the ultra-high molecular weight polyethylene micro powder, the maleic anhydride-grafted polyethylene comprises 6-12 parts by weight, and the polyethylene carrier silicone masterbatch comprises 3-7 parts by weight. The ultra-high molecular weight polyethylene micro powder is first thermally mixed with the maleic anhydride-grafted polyethylene in a first stage. Then, the resulting primary-treated wear-resistant particles are cooled to a temperature 5-20°C lower than the differential scanning calorimetry crystallization peak temperature of the maleic anhydride-grafted polyethylene and held at that temperature for 3-10 minutes. Then, they are thermally mixed with the polyethylene carrier silicone masterbatch in a second stage to form a coated wear-resistant masterbatch. The coated wear-resistant masterbatch is added to the continuous polyethylene melt after the high-density polyethylene, linear low-density polyethylene, and ethylene-octene copolymer elastomer form a continuous polyethylene melt.

8. The low-temperature wear-resistant cable protection pipe according to claim 7, characterized in that, The low-temperature wear-resistant polyethylene composite material comprises the following raw materials in parts by weight: 100 parts of high-density polyethylene; 10-15 parts of linear low-density polyethylene; 8-12 parts of ethylene-octene copolymer elastomer; 24-32 parts of ultra-high molecular weight polyethylene micro powder; Maleic anhydride-grafted polyethylene: 1.92–3.20 parts; 0.96–1.92 parts of polyethylene carrier silicone masterbatch; 4-6 parts of inorganic rigid packing; Antioxidant 0.4-0.6 parts; wherein, based on 100 parts by weight of the ultra-high molecular weight polyethylene micro powder, the maleic anhydride grafted polyethylene is 8-10 parts by weight, and the polyethylene carrier silicone masterbatch is 4-6 parts by weight.

9. The low-temperature wear-resistant cable protection pipe according to claim 7, characterized in that, The ultra-high molecular weight polyethylene micro powder has a viscosity-average molecular weight of 2.5 million to 5 million and a particle size D50 of 30 to 80 μm. The high-density polyethylene exhibits a melt flow rate of 0.2–0.8 g / 10 min and a density of 0.945–0.960 g / cm³ under conditions of 190°C and 2.16 kg load. 3 ; The density of the ethylene-octene copolymer elastomer is 0.860–0.890 g / cm³. 3 The glass transition temperature is not higher than -45℃.

10. The low-temperature wear-resistant cable protection pipe according to claim 7, characterized in that, The polysiloxane content in the polyethylene carrier silicone masterbatch is 40% to 55% by mass. The inorganic rigid filler is one or more of talc, wollastonite and calcium carbonate that have been surface-treated with silane coupling agent or titanate coupling agent. The particle size D50 of the inorganic rigid filler is 2 to 8 μm and the aspect ratio is not greater than 8. The low-temperature wear-resistant polyethylene composite material exhibits a melt flow rate of 0.10–1.00 g / 10 min at 190°C and a 5 kg load, and a Shore D hardness of 58–68. The low-temperature wear-resistant cable protection pipe, after being conditioned at -40°C for 4 hours, shows a damage rate of no more than 10% when impacted from a height of 1.0 m by a 5.0 kg drop hammer with a 50 mm radius, in accordance with GB / T standards. 3960—2016, a sample with a length of 30 mm, a width of 7 mm, and a thickness equal to the actual wall thickness of the pipe was cut axially from the inner wall of the pipe. The inner surface was used as the friction test surface, and a 45 steel ring with a surface roughness Ra of 0.4 μm was used as the friction pair. The test was conducted for 2 hours under a load of 196 N and a sliding speed of 0.42 m / s. The mass wear amount obtained was not higher than 4.4 mg. Furthermore, after 2000 cycles of cross-linked polyethylene sheathed cable with an outer diameter of 20 mm at -20℃ with a 90° wrap angle, a constant tension of 200 N, a stroke of 600 mm, and a speed of 0.20 m / s, the arithmetic mean of the maximum wear depth of the five samples was not higher than 0.13 mm.

Images