Flat wall reinforced spiral corrugated power protection pipe

Abstract

This invention relates to the field of power protection equipment technology, and discloses a flat-walled reinforced spiral corrugated power protection tube, comprising an inner layer and an outer layer arranged sequentially from the inside out. The inner and outer layers are co-extruded to form a composite tube strip, which is then spirally wound. The inner layer comprises high-density polyethylene, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, and hydrotalcite. The outer layer comprises high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, hindered amine light stabilizer, and benzotriazole UV absorber. This invention improves the contact stability between the inner wall of the sheath and the guy wire through the inner layer composite system, reducing micro-slippage, repeated friction, and localized impacts, and reduces fading through the outer layer weather-resistant system.

Description

Technical Field

[0001] This invention relates to the field of power protection equipment technology, specifically to a flat-walled reinforced spiral corrugated power protection pipe. Background Technology

[0002] Power protection pipes are tubular structural components used to cover cables or conductors. Their main function is to provide mechanical protection and environmental isolation for cables during power transmission or distribution, preventing damage to the cables from external loads, friction, and environmental factors, thereby ensuring the safe operation of the power system. In practical engineering applications, power protection pipes are usually used in conjunction with guy wires or cables and operate under long-term conditions of vibration, wind load, or external disturbance. Therefore, they need to have a stable structural form and a continuous interface contact state to maintain the reliability of the cable during operation.

[0003] In existing technologies, power protection pipes are mostly made of polyolefin materials through extrusion or winding molding. The inner layer is usually made of materials such as high-density polyethylene. The strength of the material itself provides support and protection for the cable. However, during use, the inner wall is prone to unstable contact with the cable under vibration or stress disturbance conditions, which can cause slight slippage and repeated friction, affecting the structural stability of the power protection pipe during long-term use. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a flat-walled reinforced spiral corrugated power protection pipe, which solves the problem of unstable contact between the pipe and the guy wire, affecting the structural stability of the power protection pipe during long-term use.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a flat-walled reinforced spiral corrugated power protection pipe, comprising an inner layer and an outer layer arranged sequentially from the inside to the outside, wherein the inner layer and the outer layer are co-extruded to form a composite tube strip, and then spirally wound to form the tube.

[0006] By adopting the above technical solution, the inner and outer layers are co-extruded to form a composite tube strip, so that the inner and outer layers form a continuous interface in the molten state. The inner layer provides the structural basis for contact with the draw wire, and the outer layer provides an external environmental protection layer, thereby achieving the synergistic effect of the inner and outer layers during use. On this basis, the composite tube strip is arranged in a continuous spiral structure along the axial direction by spiral winding molding, so that when the tube body is subjected to external force, a stress dispersion path is generated along the spiral direction, thereby reducing the degree of local stress concentration in the inner layer interface area and keeping the contact state between the inner layer and the draw wire continuous and stable.

[0007] Preferably, the inner layer comprises the following raw materials in parts by weight: 20-30 parts high-density polyethylene, 20-30 parts ethylene-octene copolymer, 8-15 parts ethylene-vinyl acetate copolymer, 3-6 parts maleic anhydride-grafted polyethylene, 2-4 parts maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts ethylene-propylene random copolymer, 6-12 parts talc, 0.1-0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1-0.3 parts tris(2,4-di-tert-butylphenyl) phosphite, 0.3-0.8 parts polyethylene wax, and 0.1-0.5 parts hydrotalcite.

[0008] By adopting the above technical solution, high-density polyethylene serves as the continuous phase, providing basic structural support. Ethylene-octene copolymer, ethylene-vinyl acetate copolymer, and ethylene-propylene random copolymer form dispersed phases with elastic response characteristics within the system, enabling the material to undergo reversible deformation and maintain continuous contact with the wire surface under external vibration or stress. Simultaneously, maleic anhydride-grafted polyethylene and maleic anhydride-grafted ethylene-octene copolymer form interfacial bonding structures between the components, creating stable interfaces between components of different polarities, thereby reducing interfacial separation and localized slippage during stress. Furthermore, talc and hydrotalcite are dispersed in the matrix, further enhancing the material's properties. The deformation process of the material under stress creates constraints, allowing stress to diffuse along the volume distribution path in the inner layer structure, reducing the impact of local stress concentration on the inner wall structure; pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite inhibit the thermo-oxidative reaction of the material during processing and use; polyethylene wax participates in the flow regulation of the system in the molten state, so that each component forms a uniform distribution structure during the molding process. This ensures that the inner layer maintains a stable structure during long-term use and reduces wear and local impact caused by micro-slippage and repeated friction during contact with the wire.

[0009] Preferably, the outer layer comprises the following raw materials in parts by weight: 40-55 parts high-density polyethylene, 8-15 parts ethylene-methyl methacrylate copolymer, 5-10 parts rutile titanium dioxide, 2-6 parts iron oxide red, 0.2-0.6 parts bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 0.2-0.8 parts 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 0.5-1.5 parts triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 0.1-0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1-0.3 parts tris(2,4-di-tert-butylphenyl) phosphite, and 0.3-0.8 parts polydimethylsiloxane-modified polyolefin additive.

[0010] By employing the above technical solution, high-density polyethylene serves as the continuous phase forming the outer structural matrix, while ethylene-methyl methacrylate copolymer provides polar components in the system, enabling a stable dispersion structure between the inorganic components and the matrix. Rutile titanium dioxide and iron oxide red are distributed within the matrix, scattering and absorbing incident light, reducing light transmission within the material. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole participate in the absorption of ultraviolet radiation and the inhibition of free radical reactions under illumination, allowing the material's molecular chains to remain stable under illumination. The fracture reaction is restricted; triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] ester, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester and tris(2,4-di-tert-butylphenyl) phosphite participate in the control of thermo-oxidative reactions during processing and use, thus restricting the structural changes of the material under the action of heat and oxygen; polydimethylsiloxane modified polyolefin additives participate in the flow regulation of the system in the molten state, so that the outer layer forms a continuous and dense structure during the molding process, thereby maintaining the structural stability of the outer layer under the action of light and environment, thereby reducing the degree of material fading and maintaining the stability of the surface state.

[0011] Preferably, a method for preparing a flat-walled reinforced spiral corrugated power protection tube includes the following steps: S1. Weigh high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix them and then perform melt grafting pretreatment to obtain inner layer pretreated grafted material. S2. Weigh the inner layer pretreated grafted material, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, polyethylene wax and hydrotalcite, melt mix and extrude to obtain the inner layer functional masterbatch; S3. Weigh out high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix and melt them, then add bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives and melt-blend to obtain the outer functional masterbatch; S4. The inner functional masterbatch and the outer functional masterbatch are melted and plasticized separately and then co-extruded to obtain a composite tube strip; S5. The composite tube strip is introduced into the spiral winding forming device, spirally wound on the outer surface of the rotating mandrel, and adjacent composite tube strips are heated and fused to obtain a tubular structure. S6. The tubular structure is segmented and cooled for shaping, and then subjected to thermal stabilization treatment to obtain the flat-walled reinforced spiral corrugated power protection tube.

[0012] By adopting the above technical solution, high-density polyethylene, ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene are premixed and melt grafting pretreatment is carried out through step S1 to form a stable grafting structure in the system, thereby forming a continuous interface between different components in the subsequent processing. In step S2, the inner layer pretreated grafted material is melt-mixed and extruded together with ethylene-octene copolymer, ethylene-propylene random copolymer and maleic anhydride grafted ethylene-octene copolymer, so that the elastic component is dispersed in the matrix on the basis of the grafted structure, and forms a composite distribution structure with talc and hydrotalcite. This allows the inner layer to undergo reversible deformation and disperse stress during the stress process, reducing the occurrence of local stress concentration and interface separation on the inner wall. In step S3, rutile titanium dioxide, iron oxide red, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole and an antioxidant system are melt-blended to form a composite system in the outer layer that includes light absorption, free radical inhibition and thermo-oxidative reaction control. In step S4, the inner functional masterbatch and the outer functional masterbatch are melted and plasticized and co-extruded separately, so that the two layers form a continuous bonding interface in the molten state. In step S5, the composite tube strips are spirally wound and heated and fused together to form a continuous structure in the axial direction and maintain the continuity of interlayer bonding. In step S6, segmented cooling and thermal stabilization treatments are used to enable the material to form a stable structural state during the cooling process. This ensures that the inner layer of the resulting flat-walled reinforced spiral corrugated power protection pipe maintains continuous contact with the pull wire during use, reducing micro-slippage and repeated friction. At the same time, the outer layer maintains a stable structural state under light conditions, thereby reducing the degree of fading.

[0013] Preferably, in step S1, during premixing, the mixing speed is 600-900 rpm and the mixing time is 5-10 min. During melt grafting pretreatment, the premixed high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a twin-screw extruder and extruded under conditions of screw speed of 180-300 rpm and vacuum exhaust degree of -0.04 to -0.08 MPa. After extrusion, the material is cooled by water stripping and pelletized.

[0014] By adopting the above technical solution, high-density polyethylene, ethylene-vinyl acetate copolymer, and maleic anhydride-grafted polyethylene are premixed to ensure that each component is uniformly dispersed before entering the molten state. Based on this, a twin-screw extruder is used for melt grafting pretreatment. Under the action of dicumyl peroxide, a grafted structure is formed between maleic anhydride-grafted polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer. Simultaneously, during extrusion, low-molecular-weight volatiles and reaction byproducts are discharged through vacuum degassing, ensuring the grafting reaction proceeds under stable conditions. Furthermore, the thermo-oxidative reaction in the molten system is controlled under the action of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite. This results in an inner layer pretreated grafted material forming a matrix with a continuous interface structure, enabling the inner layer to maintain structural continuity under stress and reducing micro-slippage and repeated friction caused by interface separation.

[0015] Preferably, in step S2, during melt mixing and extrusion, the inner layer pretreated graft material, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, and hydrotalcite are added to the twin-screw extruder through the main hopper. The ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through a side feeder. The ethylene-propylene random copolymer is added in the middle section, and the maleic anhydride-grafted ethylene-octene copolymer and polyethylene wax are added in the rear section. After melt mixing and extrusion at 145-195°C, the mixture is cooled and pelletized.

[0016] By adopting the above technical solution, the pre-treated grafted material, talc, hydrotalcite, and antioxidant system are fed into the twin-screw extruder through the main hopper, allowing the grafted matrix and inorganic components to form an initial dispersed structure after entering the melting section. Based on this, ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through a side feeder, allowing the elastic component to disperse into the continuous matrix phase in the molten state and form a dispersed phase structure under shear. Ethylene-propylene random copolymer is added in the middle section, further participating in phase structure construction within the already formed molten system. Maleic anhydride-grafted ethylene-octene copolymer and polyethylene wax are added in the rear section, allowing the grafted component to form an interfacial bond with the elastic and matrix phases in the molten system. Simultaneously, the polyethylene wax participates in regulating the melt flow process, ensuring a continuous distribution of components during extrusion. During extrusion and cooling pelletizing, the structure solidifies, forming a state where dispersed and continuous phases coexist. This allows the inner layer to disperse and transfer stress within the structure through elastic phase deformation and inorganic component constraint during stress, reducing slippage and friction caused by interfacial separation.

[0017] Preferably, in step S3, during premixing, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a mixer and mixed for 800-1200 rpm for 8-15 minutes. Then, the mixture is fed into a twin-screw extruder for melt mixing, and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane-modified polyolefin additives are added. The mixture is then melt-mixed at 180-200°C, cooled, and pelletized.

[0018] By employing the above technical solution, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, and iron oxide red are premixed in a mixer to ensure that each component forms a uniform dispersion before entering the molten state. The ethylene-methyl methacrylate copolymer provides a polar phase in the system, enabling the inorganic components to form a stable dispersion structure with the matrix during subsequent melting. Subsequently, melt mixing is performed in a twin-screw extruder, and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, and an antioxidant system are added. This allows the components to participate in controlling the light and thermo-oxidative reaction process in the molten state. The rutile titanium dioxide and iron oxide red, in particular, form a uniform dispersion in the matrix. A structure for scattering and absorbing light is formed. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole participate in the absorption of ultraviolet radiation and the inhibition of free radical reactions. Triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] ester, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester and tris(2,4-di-tert-butylphenyl) phosphite control the thermo-oxidative reaction. Polydimethylsiloxane-modified polyolefin additives participate in the flow regulation of the system during the melting process, so that each component forms a continuous and dense distribution structure after cooling and pelletizing. This limits the change of molecular structure of the outer layer under the action of light environment and reduces the degree of fading.

[0019] Preferably, in step S4, when co-extruding after melting and plasticizing, the inner functional masterbatch is added to the first extruder and melted and plasticized at 180-195°C, and the outer functional masterbatch is added to the second extruder and melted and plasticized at 190-210°C. Then, they are added together to a composite die at a temperature of 190-215°C and extruded to form a composite tube / strip.

[0020] By employing the above technical solution, the inner and outer functional masterbatches are melt-plasticized separately in different extruders, allowing both materials to form stable molten flow states before entering the composite die, and completing the plasticization process in their respective extrusion channels. Subsequently, they converge in the composite die, forming a continuous interface between the inner and outer functional masterbatches in a molten state and extruding synchronously to form a composite tube with an inner and outer layered structure. The inner layer retains its composition of ethylene-octene copolymer, ethylene-vinyl acetate copolymer, and maleic anhydride grafted components. The elastic and grafted structure of the outer layer maintains a light-stable structure composed of rutile titanium dioxide, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole. This ensures a continuous interface between the inner and outer layers during the formation of the composite tube and maintains the distribution of their respective components. This allows the inner layer to maintain continuous contact with the wire during subsequent use and reduces slippage and friction, while the outer layer maintains structural stability and reduces fading under light conditions.

[0021] Preferably, in step S5, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel at a speed of 1 to 5 m / min, and adjacent composite tube strips are heated and welded at 120 to 170°C.

[0022] By adopting the above technical solution, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel, so that the composite tube strip forms a continuous spiral structure along the axial direction. During the winding process, adjacent composite tube strips are heated and fused together, so that the adjacent layers form a continuous bonding interface in the molten state, thereby forming an integrated structure in the circumferential and axial directions of the tubular structure. During the formation of this structure, the inner layer is continuously distributed on the inner side of the tubular structure along the composite tube strip, so that the inner layer forms a continuous contact area along the spiral path in subsequent use. When subjected to vibration or force disturbance, the contact state with the tension wire is maintained through structural continuity, reducing slippage and repeated friction caused by local interface separation. At the same time, the fusion interface between adjacent composite tube strips forms a stress dispersion path for the overall structure during the stress process, thereby reducing the impact of local stress concentration on the inner layer contact interface.

[0023] Preferably, in step S6, when performing segmented cooling, the tubular structure is first cooled in the first stage at 10-25°C for 30-120 seconds, then cooled in the second stage at 40-80°C for 5-20 minutes, and then subjected to thermal stabilization treatment at 45-65°C for 10-24 hours.

[0024] By adopting the above technical solution, the composite tube strip is cooled in stages during the transition from a molten state to a solid state, thus completing the structural shaping in stages. The first stage of cooling quickly fixes the material's shape and restricts overall deformation. The second stage of cooling gradually equalizes the internal temperature of the material and releases some internal stress. Subsequently, thermal stabilization treatment further adjusts the internal structure of the material, allowing each component to form a stable distribution structure in the solid state. This ensures that the inner layer maintains structural continuity and contact with the tension wire during subsequent use, reducing interface separation and slight slippage caused by residual stress. At the same time, it ensures that the overall tubular structure maintains dimensional stability during long-term use, reducing performance degradation caused by structural changes.

[0025] This invention provides a flat-walled reinforced spiral corrugated power protection pipe. It has the following beneficial effects: 1. This invention constructs a composite system with good compatibility and flexibility by introducing ethylene-octene copolymer, maleic anhydride-grafted polyethylene and maleic anhydride-grafted ethylene-octene copolymer into the inner layer. This allows the inner wall of the sheath to maintain a continuous fit with the pull wire when subjected to vibration or force disturbance, thereby effectively suppressing micro-slippage caused by interface instability, reducing axial movement and local impact phenomena caused by repeated friction, and improving the structural stability during use.

[0026] 2. This invention forms a stable anti-UV aging and light-shielding system by synergistically setting rutile titanium dioxide, hindered amine light stabilizer and benzotriazole UV absorber in the outer layer. This effectively slows down the molecular chain degradation and pigment decomposition of the material under light exposure, thereby significantly reducing the degree of fading of the sheath and maintaining surface gloss, and improving the appearance stability under long-term service conditions.

[0027] 3. This invention utilizes the combined effect of various elastomers and grafted compatibilizers in the inner layer to enable the material to have good stress dispersion and recovery capabilities after being subjected to force. This can reduce the damage to the inner wall structure caused by local stress concentration, reduce wear and fatigue damage, and thus extend the service life of the power protection tube.

[0028] 4. This invention improves the dimensional stability and thermo-oxidative stability of the material by introducing talc and hydrotalcite into the inner layer system and combining them with an antioxidant system. This makes the composite pipe less prone to deformation or performance degradation during processing and long-term use, thus ensuring the reliability of the structural performance. Attached Figure Description

[0029] Figure 1 This is a cross-sectional schematic diagram of the internal structure of the power protection pipe of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention.

[0030] Among them, 1 is the outer layer; 2 is the inner layer. Detailed Implementation

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0032] The following are the main raw materials and reagents used in the preparation examples, embodiments, and comparative examples, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products: 1. High-density polyethylene, purchased from Shanghai Pengyue New Materials Co., Ltd., brand name: HYA-600.

[0033] 2. Ethylene-vinyl acetate copolymer, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S45075.

[0034] 3. Ethylene-methyl methacrylate copolymer, purchased from Shanghai Saikerui Biotechnology Co., Ltd., CAS: 25053-53-6.

[0035] 4. Ethylene-octene copolymer, purchased from Dongguan Yucheng Plastics Co., Ltd., grade: 8999.

[0036] 5. Ethylene-propylene random copolymer, purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd., CAS: 9010-79-1.

[0037] 6. Maleic anhydride-grafted polyethylene, purchased from Dongguan Shenghao Plastic Raw Materials Co., Ltd., item number: 5541254.

[0038] 7. Dicumyl peroxide, purchased from Merck Group Darmstadt, Germany, CAS: 80-43-3.

[0039] 8. Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S67391.

[0040] 9. Tris(2,4-di-tert-butylphenyl) phosphite, purchased from Shanghai Jieshikai Biotechnology Co., Ltd., CAS: 31570-04-4.

[0041] 10. Triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid] ester, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S64859.

[0042] 11. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 52829-07-9.

[0043] 12. 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S65077.

[0044] 13. Polyethylene wax, purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: Y45330.

[0045] Example 1 This embodiment provides a flat-walled reinforced spiral corrugated power protection pipe, which includes an inner layer 2 and an outer layer 1 arranged sequentially from the inside to the outside. The inner layer 2 and the outer layer 1 are co-extruded to form a composite tube strip, and then spirally wound to form the tube.

[0046] The inner layer 2 comprises the following raw materials in parts by weight: 20 parts high-density polyethylene, 20 parts ethylene-octene copolymer, 8 parts ethylene-vinyl acetate copolymer, 3 parts maleic anhydride-grafted polyethylene, 2 parts maleic anhydride-grafted ethylene-octene copolymer, 3 parts ethylene-propylene random copolymer, 6 parts talc, 0.1 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1 parts tris(2,4-di-tert-butylphenyl) phosphite, 0.3 parts polyethylene wax, and 0.1 parts hydrotalcite.

[0047] The outer layer 1 comprises the following raw materials in parts by weight: 40 parts high-density polyethylene, 8 parts ethylene-methyl methacrylate copolymer, 5 parts rutile titanium dioxide, 2 parts iron oxide red, 0.2 parts bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 0.2 parts 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 0.5 parts triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] ester, 0.1 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester, 0.1 parts tris(2,4-di-tert-butylphenyl) phosphite, and 0.3 parts polydimethylsiloxane-modified polyolefin additive.

[0048] The preparation method of the above-mentioned flat-walled reinforced spiral corrugated power protection pipe includes the following steps: S1. Weigh high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix them, and then perform melt grafting pretreatment to obtain inner layer 2 pretreated grafted material. During premixing, the mixing speed is 600 rpm and the mixing time is 5 min. During melt grafting pretreatment, the premixed high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a twin-screw extruder and extruded under the conditions of screw speed of 180 rpm and vacuum exhaust degree of -0.04 MPa. After that, the mixture is cooled by water stripping and pelletized.

[0049] S2. Weigh out the inner layer 2 pretreated grafted material, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, polyethylene wax and hydrotalcite, melt mix and extrude to obtain the inner layer 2 functional masterbatch; In the melt-mixing extrusion process, the inner layer 2 pretreated grafted material, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, and hydrotalcite are fed into the twin-screw extruder through the main hopper. The ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through the side feeder. The ethylene-propylene random copolymer is added in the middle section, and the maleic anhydride-grafted ethylene-octene copolymer and polyethylene wax are added in the rear section. After melt-mixing extrusion at 145°C, the mixture is cooled and pelletized.

[0050] S3. Weigh high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix and melt them, then add bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives and melt-blend to obtain outer layer 1 functional masterbatch; During premixing, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a mixer and mixed at 800 rpm for 8 minutes. Then, the mixture is fed into a twin-screw extruder for melt mixing. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives are added and melt-mixed at 180°C, followed by cooling and pelletizing.

[0051] S4. The inner layer 2 functional masterbatch and the outer layer 1 functional masterbatch are melted and plasticized separately and then co-extruded to obtain a composite tube strip; In the process of co-extrusion after separate melting and plasticization, the inner layer 2 functional masterbatch is added to the first extruder and melted and plasticized at 180°C, while the outer layer 1 functional masterbatch is added to the second extruder and melted and plasticized at 190°C. The two parts are then added together to a composite die at 190°C and extruded to form a composite tube and strip.

[0052] S5. Introduce the composite tube strip into the spiral winding forming device, spirally wind it on the outer surface of the rotating mandrel, and heat and weld adjacent composite tube strips to obtain a tubular structure. Among them, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel at a speed of 1m / min, and adjacent composite tube strips are heated and fused at 120℃.

[0053] S6. The tubular structure is segmented and cooled to shape, and then subjected to thermal stabilization treatment to obtain a flat-walled reinforced spiral corrugated power protection tube. During the segmented cooling process, the tubular structure is first cooled at 10℃ for 30 seconds, then cooled at 40℃ for 5 minutes, and finally subjected to thermal stabilization treatment at 45℃ for 10 hours.

[0054] Example 2 This embodiment provides a flat-walled reinforced spiral corrugated power protection pipe, which includes an inner layer 2 and an outer layer 1 arranged sequentially from the inside to the outside. The inner layer 2 and the outer layer 1 are co-extruded to form a composite tube strip, and then spirally wound to form the tube.

[0055] The inner layer 2 comprises the following raw materials in parts by weight: 25 parts high-density polyethylene, 25 parts ethylene-octene copolymer, 11 parts ethylene-vinyl acetate copolymer, 4 parts maleic anhydride-grafted polyethylene, 3 parts maleic anhydride-grafted ethylene-octene copolymer, 5 parts ethylene-propylene random copolymer, 9 parts talc, 0.2 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.2 parts tris(2,4-di-tert-butylphenyl) phosphite, 0.5 parts polyethylene wax, and 0.3 parts hydrotalcite.

[0056] The outer layer 1 comprises the following raw materials in parts by weight: 47 parts high-density polyethylene, 11 parts ethylene-methyl methacrylate copolymer, 7 parts rutile titanium dioxide, 4 parts iron oxide red, 0.4 parts bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 0.5 parts 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 1.0 part triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 0.2 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.2 parts tris(2,4-di-tert-butylphenyl) phosphite, and 0.5 parts polydimethylsiloxane-modified polyolefin additive.

[0057] The preparation method of the above-mentioned flat-walled reinforced spiral corrugated power protection pipe includes the following steps: S1. Weigh high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix them, and then perform melt grafting pretreatment to obtain inner layer 2 pretreated grafted material. During premixing, the mixing speed was 750 rpm and the mixing time was 7 min. During melt grafting pretreatment, the premixed high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite were added to a twin-screw extruder and extruded under the conditions of screw speed of 240 rpm and vacuum exhaust degree of -0.06 MPa. After that, the mixture was cooled by water stripping and pelletized.

[0058] S2. Weigh out the inner layer 2 pretreated grafted material, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, polyethylene wax and hydrotalcite, melt mix and extrude to obtain the inner layer 2 functional masterbatch; In the melt-mixing extrusion process, the inner layer 2 pretreated grafted material, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, and hydrotalcite are fed into the twin-screw extruder through the main hopper. The ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through the side feeder. The ethylene-propylene random copolymer is added in the middle section, and the maleic anhydride-grafted ethylene-octene copolymer and polyethylene wax are added in the rear section. After melt-mixing extrusion at 170°C, the mixture is cooled and pelletized.

[0059] S3. Weigh high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix and melt them, then add bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives and melt-blend to obtain outer layer 1 functional masterbatch; During premixing, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a mixer and mixed at 1000 rpm for 11 minutes. Then, the mixture is fed into a twin-screw extruder for melt mixing. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives are added and melt-mixed at 190°C, followed by cooling and pelletizing.

[0060] S4. The inner layer 2 functional masterbatch and the outer layer 1 functional masterbatch are melted and plasticized separately and then co-extruded to obtain a composite tube strip; In the process of co-extrusion after separate melting and plasticization, the inner layer 2 functional masterbatch is added to the first extruder and melted and plasticized at 187°C, while the outer layer 1 functional masterbatch is added to the second extruder and melted and plasticized at 200°C. The two parts are then added together to a composite die at 202°C and extruded to form a composite tube and strip.

[0061] S5. Introduce the composite tube strip into the spiral winding forming device, spirally wind it on the outer surface of the rotating mandrel, and heat and weld adjacent composite tube strips to obtain a tubular structure. Among them, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel at a speed of 3m / min, and adjacent composite tube strips are heated and welded at 145℃.

[0062] S6. The tubular structure is segmented and cooled to shape, and then subjected to thermal stabilization treatment to obtain a flat-walled reinforced spiral corrugated power protection tube. During the segmented cooling process, the tubular structure was first cooled at 17°C for 75 seconds, then cooled at 60°C for 12 minutes, and finally thermally stabilized at 55°C for 17 hours.

[0063] Example 3 This embodiment of a flat-walled reinforced spiral corrugated power protection pipe includes an inner layer 2 and an outer layer 1 arranged sequentially from the inside to the outside. The inner layer 2 and the outer layer 1 are co-extruded to form a composite tube strip, and then spirally wound to form the tube.

[0064] The inner layer 2 comprises the following raw materials in parts by weight: 30 parts high-density polyethylene, 30 parts ethylene-octene copolymer, 15 parts ethylene-vinyl acetate copolymer, 6 parts maleic anhydride-grafted polyethylene, 4 parts maleic anhydride-grafted ethylene-octene copolymer, 8 parts ethylene-propylene random copolymer, 12 parts talc, 0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.3 parts tris(2,4-di-tert-butylphenyl) phosphite, 0.8 parts polyethylene wax, and 0.5 parts hydrotalcite.

[0065] The outer layer 1 comprises the following raw materials in parts by weight: 55 parts high-density polyethylene, 15 parts ethylene-methyl methacrylate copolymer, 10 parts rutile titanium dioxide, 6 parts iron oxide red, 0.6 parts bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 0.8 parts 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 1.5 parts triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.3 parts tris(2,4-di-tert-butylphenyl) phosphite, and 0.8 parts polydimethylsiloxane-modified polyolefin additive.

[0066] The preparation method of the above-mentioned flat-walled reinforced spiral corrugated power protection pipe includes the following steps: S1. Weigh high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix them, and then perform melt grafting pretreatment to obtain inner layer 2 pretreated grafted material. During premixing, the mixing speed is 900 rpm and the mixing time is 10 min. During melt grafting pretreatment, the premixed high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a twin-screw extruder and extruded under the conditions of screw speed of 300 rpm and vacuum exhaust degree of -0.08 MPa. After that, the mixture is cooled by water stripping and pelletized.

[0067] S2. Weigh out the inner layer 2 pretreated grafted material, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, polyethylene wax and hydrotalcite, melt mix and extrude to obtain the inner layer 2 functional masterbatch; In the melt-mixing extrusion process, the inner layer 2 pretreated grafted material, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, and hydrotalcite are fed into the twin-screw extruder through the main hopper. The ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through the side feeder. The ethylene-propylene random copolymer is added in the middle section, and the maleic anhydride-grafted ethylene-octene copolymer and polyethylene wax are added in the rear section. After melt-mixing extrusion at 195°C, the mixture is cooled and pelletized.

[0068] S3. Weigh high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix and melt them, then add bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives and melt-blend to obtain outer layer 1 functional masterbatch; In the premixing process, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a mixer and mixed at 1200 rpm for 15 minutes. Then, the mixture is fed into a twin-screw extruder for melt mixing. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives are added and melt-mixed at 200°C, followed by cooling and pelletizing.

[0069] S4. The inner layer 2 functional masterbatch and the outer layer 1 functional masterbatch are melted and plasticized separately and then co-extruded to obtain a composite tube strip; In the process of co-extrusion after separate melting and plasticization, the inner layer 2 functional masterbatch is added to the first extruder and melted and plasticized at 195°C, while the outer layer 1 functional masterbatch is added to the second extruder and melted and plasticized at 210°C. The two parts are then added together to a composite die at 215°C and extruded to form a composite tube and strip.

[0070] S5. Introduce the composite tube strip into the spiral winding forming device, spirally wind it on the outer surface of the rotating mandrel, and heat and weld adjacent composite tube strips to obtain a tubular structure. Among them, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel at a speed of 5m / min, and adjacent composite tube strips are heated and fused at 170℃.

[0071] S6. The tubular structure is segmented and cooled to shape, and then subjected to thermal stabilization treatment to obtain a flat-walled reinforced spiral corrugated power protection tube. During the segmented cooling process, the tubular structure is first cooled at 25°C for 120 seconds, then cooled at 80°C for 20 minutes, and finally subjected to thermal stabilization treatment at 65°C for 24 hours.

[0072] Comparative Example 1 The only difference from Example 2 is that the maleic anhydride-grafted ethylene-octene copolymer is missing from the raw material of inner layer 2.

[0073] Comparative Example 2 The only difference from Example 2 is that the outer layer 1 raw material lacks 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole.

[0074] Comparative Example 3 The only difference from Example 2 is that the ethylene-octene copolymer in the inner layer 2 raw material is replaced with an equal amount of high-density polyethylene.

[0075] Comparative Example 4 The only difference from Example 2 is that the bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate in the outer layer 1 raw material is replaced with an equal amount of talc.

[0076] Comparative Example 5 The only difference from Example 2 is that the outer layer 1 material lacks rutile titanium dioxide.

[0077] Experiment 1: Dynamic Fretting Wear and Axial Movement Test Flat-walled reinforced spiral corrugated power protection pipes prepared in Examples 1, 2, 3, and Comparative Examples 1-5 were used to cut samples with a length of 300 mm. Each sample was placed on the outside of a galvanized steel strand simulation component with a diameter of 12 mm. The two ends of the steel strand were fixed with clamps, and the samples were subjected to a reciprocating fretting test in an environment of 25°C and 50% relative humidity. The test conditions were set as follows: axial displacement amplitude of 3 mm, frequency of 2 Hz, normal clamping load of 30 N, and a cumulative number of cycles of 100,000. The axial displacement, inner wall wear, and mass loss of the sample were recorded every 25,000 cycles. The axial displacement was taken as the maximum displacement value of the sample relative to the initial position. The inner wall wear was expressed as the difference in the average thickness of the inner wall before and after the test. The mass loss rate was calculated as [(mass before test - mass after test) / mass before test] × 100%.

[0078] Experiment 2: Contact-Separation-Recontact and Local Impact Stability Test Five samples each from Examples 1, 2, 3, and Comparative Examples 1-5 were taken, each sample measuring 300 mm. These samples were fitted onto galvanized steel strands of the same specification, and the steel strands were installed in a combined vibration and impact device. First, transverse sinusoidal vibration was applied, followed by intermittent impact loads to simulate the contact-separation-re-contact condition between the sheath and the guy wire under the combined effects of wind vibration and external force disturbance. The sinusoidal vibration frequency was set to 8 Hz, the peak displacement to 10 mm, and the duration to 60 min. A 10 N impact load was applied every 5 min, with each impact lasting 1 s, for a total test duration of 2 h. During the test, the peak vibration value of the outer wall of the sample was recorded using a displacement sensor, the number of interface contact failures was recorded using a pressure sensing diaphragm, and the maximum instantaneous noise generated by localized impacts was measured using a sound level meter. The number of interface contact failures was defined as the number of times the interface pressure dropped below 20% of the initial stable contact pressure within a unit test duration.

[0079] Experiment 3: Correlation Test between Accelerated Weathering Fading and Interface Retention After Weathering Three samples each from Examples 1, 2, 3 and Comparative Examples 1-5 were taken, with a sample size of 300 mm. The initial color parameters L, a, and b* were measured first, and then the samples were placed in a xenon lamp aging chamber for accelerated weathering test. The irradiation intensity was set to 0.51 W / m² (340 nm), the blackboard temperature to 65 °C, the relative humidity to 50%, and the light / condensation cycle to be 102 min of light followed by 18 min of spraying. The cumulative aging time was 500 h. After aging, the comprehensive color difference ΔE was measured, and the gloss retention rate of the outer surface at 60° was measured. At the same time, the aged samples were subjected to 50,000 micro-motion tests as described in Test 1, and the axial movement after weathering was recorded to evaluate the correlation between the weather resistance of the outer layer 1 and the stable contact capability of the inner layer 2 after aging.

[0080] Table 1. Test data of dynamic fretting wear and axial movement

[0081] Table 2. Data from contact-separation-re-contact and localized impact stability tests

[0082] Table 3. Correlation test data between accelerated weathering fading and post-weathering interface retention

[0083] By comparing the experimental data of the examples and the comparative examples, it can be seen that: As can be seen from Example 2 and Comparative Example 1, and Table 1, the introduction of maleic anhydride-grafted ethylene-octene copolymer into the inner layer 2 can significantly improve the interfacial compatibility between the components, enabling the material to have better compliant adhesion and stress buffering ability under stress, thereby effectively reducing the unstable contact state between the inner wall of the sheath and the pull wire; while without this grafted elastomer, the interfacial compatibility decreases, and the inner wall and pull wire are more prone to micro-slippage and repeated friction, resulting in a significant increase in axial movement and wear.

[0084] As can be seen from Example 2 and Comparative Example 3, and Table 1, the ethylene-octene copolymer in the inner layer 2 system can impart appropriate elasticity and resilience to the material, enabling the inner wall of the sheath to promptly adhere to the surface of the drawstring after vibration or stress, thus reducing the generation of contact gaps. When replaced with an equal amount of high-density polyethylene, the material rigidity increases while its elasticity is insufficient, making it more prone to contact-separation-re-contact processes when disturbed, thereby exacerbating local impact and friction damage, manifested as a significant increase in the amount of movement, wear, and mass loss rate.

[0085] As can be seen from Example 2, Comparative Examples 2 and 4, and Table 2, the inclusion of hindered amine light stabilizer and UV absorber in outer layer 1, along with rutile titanium dioxide, can form a stable anti-UV aging system on the pipe surface. Under long-term light exposure, this system effectively inhibits molecular chain degradation and pigment decomposition, thereby significantly reducing fading and maintaining surface gloss. When the UV absorber is missing or inorganic fillers are used to replace the light stabilizer system, the absorption and shielding ability of outer layer 1 for UV radiation decreases, resulting in a significant increase in color difference and a decrease in gloss retention.

[0086] As can be seen from Example 2 and Comparative Example 5 and Table 2, rutile titanium dioxide in the outer layer 1 system not only plays a coloring role, but also works synergistically with the light-stabilizing system to provide excellent light-shielding and anti-aging properties, so that the outer layer 1 maintains good structural stability and color stability during weathering. When this component is missing, the outer layer 1 is more prone to photodegradation and fading, and the degradation of surface properties will further affect the overall stability of the sheath during long-term use.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flat-walled reinforced spiral corrugated power protection pipe, characterized in that, It includes an inner layer (2) and an outer layer (1) arranged sequentially from the inside to the outside. The inner layer (2) and the outer layer (1) are formed into a composite tube by co-extrusion and then spirally wound.

2. The flat-walled reinforced spiral corrugated power protection pipe according to claim 1, characterized in that, The inner layer (2) comprises the following raw materials in parts by weight: 20-30 parts of high-density polyethylene, 20-30 parts of ethylene-octene copolymer, 8-15 parts of ethylene-vinyl acetate copolymer, 3-6 parts of maleic anhydride-grafted polyethylene, 2-4 parts of maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts of ethylene-propylene random copolymer, 6-12 parts of talc, 0.1-0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1-0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.3-0.8 parts of polyethylene wax, and 0.1-0.5 parts of hydrotalcite.

3. The flat-walled reinforced spiral corrugated power protection pipe according to claim 1, characterized in that, The outer layer (1) comprises the following raw materials in parts by weight: 40-55 parts of high-density polyethylene, 8-15 parts of ethylene-methyl methacrylate copolymer, 5-10 parts of rutile titanium dioxide, 2-6 parts of iron oxide red, 0.2-0.6 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 0.2-0.8 parts of 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 0.5-1.5 parts of triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 0.1-0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1-0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, and 0.3-0.8 parts of polydimethylsiloxane-modified polyolefin additive.

4. A method for preparing a flat-walled reinforced spiral corrugated power protection pipe, characterized in that, The flat-walled reinforced spiral corrugated power protection tube according to any one of claims 1-3 comprises the following steps: S1. Weigh high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix them and then perform melt grafting pretreatment to obtain inner layer (2) pretreated grafted material. S2. Weigh the pretreated grafted material of the inner layer (2), ethylene-octene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-octene copolymer, ethylene-propylene random copolymer, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, polyethylene wax and hydrotalcite, melt mix and extrude to obtain the functional masterbatch of the inner layer (2); S3. Weigh high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite, premix and melt them, then add bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane modified polyolefin additives for melt mixing to obtain the outer layer (1) functional masterbatch; S4. The inner layer (2) functional masterbatch and the outer layer (1) functional masterbatch are melted and plasticized respectively and then co-extruded to obtain a composite tube strip; S5. The composite tube strip is introduced into the spiral winding forming device, spirally wound on the outer surface of the rotating mandrel, and adjacent composite tube strips are heated and fused to obtain a tubular structure. S6. The tubular structure is segmented and cooled for shaping, and then subjected to thermal stabilization treatment to obtain the flat-walled reinforced spiral corrugated power protection tube.

5. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S1, during premixing, the mixing speed is 600-900 rpm and the mixing time is 5-10 min. During melt grafting pretreatment, the premixed high-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, dicumyl peroxide, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a twin-screw extruder and extruded under conditions of screw speed of 180-300 rpm and vacuum exhaust degree of -0.04 to -0.08 MPa. Afterwards, the mixture is cooled by water stretching and pelletized.

6. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S2, during melt mixing and extrusion, the inner layer (2) pretreated graft material, talc, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite and hydrotalcite are added to the twin-screw extruder through the main hopper. The ethylene-octene copolymer and ethylene-vinyl acetate copolymer are added through the side feeder. The ethylene-propylene random copolymer is added in the middle section. The maleic anhydride grafted ethylene-octene copolymer and polyethylene wax are added in the rear section. After melt mixing and extrusion at 145-195°C, the mixture is cooled and pelletized.

7. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S3, during premixing, high-density polyethylene, ethylene-methyl methacrylate copolymer, rutile titanium dioxide, iron oxide red, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added to a mixer and mixed for 800-1200 rpm for 8-15 minutes. Then, the mixture is fed into a twin-screw extruder for melt mixing. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and polydimethylsiloxane-modified polyolefin additives are added and melt-mixed at 180-200°C, followed by cooling and pelletizing.

8. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S4, when co-extruding after melting and plasticizing, the inner layer (2) functional masterbatch is added to the first extruder and melted and plasticized at 180-195°C. The outer layer (1) functional masterbatch is added to the second extruder and melted and plasticized at 190-210°C. Then, they are added together to a composite die head at a temperature of 190-215°C and extruded to form a composite tube and strip.

9. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S5, after the composite tube strip is introduced into the spiral winding forming device, it is spirally wound on the outer surface of the rotating mandrel at a speed of 1 to 5 m / min, and adjacent composite tube strips are heated and welded at 120 to 170°C.

10. The method for preparing a flat-walled reinforced spiral corrugated power protection tube according to claim 4, characterized in that, In step S6, when performing segmented cooling, the tubular structure is first cooled in the first stage at 10-25°C for 30-120 seconds, then cooled in the second stage at 40-80°C for 5-20 minutes, and then subjected to thermal stabilization treatment at 45-65°C for 10-24 hours.

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