Multi-layer composite special cable and preparation method thereof

Abstract

The invention discloses a multi-layer composite special cable and a preparation method thereof, and relates to the technical field of cables, the multi-layer composite special cable comprises a conductive layer, a semi-conductive nylon layer, an insulating layer, a flame retardant layer, an anti-freezing layer, a buffer layer and an outer sheath which are sequentially arranged from inside to outside, and a plurality of wear-resistant bulges are uniformly distributed on the outer layer of the outer sheath. Compared with a common cable in the prior art, the cable provided by the invention has excellent wear resistance, can resist mechanical wear in laying and service processes, can adapt to extreme service conditions such as cold regions and the like, effectively resists the damage of a low-temperature environment to a material structure, has excellent flame-retardant efficiency, and is suitable for popularization and application. Flame spreading can be inhibited in a fire risk scene, and use safety is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and more specifically, to a multilayer composite special cable and its preparation method. Background Technology

[0002] As the core carrier of power transmission and signal transmission, wires and cables are widely used in many fields such as industrial production, civil buildings, and infrastructure. With the accelerated advancement of new urbanization, the laying scenarios and usage environments of cables have undergone significant changes, including not only cables laid in the open air, but also various forms of cables such as underground direct burial and pipeline laying, and their service environment is becoming increasingly complex and harsh.

[0003] For example, in low-temperature environments, cable materials are susceptible to embrittlement, deformation, and even breakage due to freeze-thaw cycles. In cold regions, the economic losses and power outages caused by such faults each year are considerable. Furthermore, fires caused by short circuits and overloads are frequent occurrences in electrical systems, requiring cables to possess excellent flame-retardant properties to suppress flame spread, reduce the release of toxic fumes, and prevent the expansion of safety hazards due to cable damage and cracking. Simultaneously, when cables are laid underground, they come into contact with and rub against hard objects such as soil, gravel, and pipes. When installed outdoors, they may be subject to friction under wind loads or collisions with external objects. Long-term wear can easily lead to damage to the cable insulation and sheath layers, resulting in serious faults such as leakage and short circuits. Therefore, abrasion resistance is one of the key indicators for ensuring the structural integrity and long-term service stability of cables.

[0004] Ordinary cables can no longer meet the high standards required for use in today's complex environments in terms of core properties such as freeze resistance, flame retardancy, and abrasion resistance. The research and development and application of high-performance special cables have become an inevitable trend in the industry. Summary of the Invention

[0005] To address the shortcomings of existing cables in terms of core properties such as flame retardancy, freeze resistance, and abrasion resistance, this invention provides a multi-layer composite special cable and its preparation method. This cable possesses excellent abrasion resistance, which can withstand mechanical wear during laying and service, and is suitable for extreme service conditions such as cold regions, effectively resisting the damage to the material structure caused by low temperature environments. At the same time, it has excellent flame retardant performance, which can suppress the spread of flames and ensure safe use in fire risk scenarios.

[0006] The specific plan is as follows: The present invention provides a multi-layer composite special cable, comprising: a conductive layer, a semi-conductive nylon layer, an insulating layer, a flame-retardant layer, an antifreeze layer, a buffer layer, and an outer sheath arranged sequentially from the inside to the outside; The conductive layer is formed by spirally twisting together multiple sets of oxygen-free copper wires. The semi-conductive nylon layer is made by wrapping semi-conductive nylon tape around the outer layer of each group of conductive layers; The insulating layer is extruded onto the outer layer of the semi-conductive nylon layer; The flame-retardant layer is made by wrapping flame-retardant rubber tape around the outer layer of the insulation layer; The antifreeze layer is made by wrapping antifreeze rubber tape around the outer layer of the flame retardant layer; The buffer layer is made of sponge tape wrapped around the outer layer of the antifreeze layer; The outer layer of the outer sheath has multiple wear-resistant protrusions evenly distributed on its outer surface. The wear-resistant protrusions are either wear-resistant protrusion one or wear-resistant protrusion two. Wear-resistant protrusion one is hemispherical. The center of wear-resistant protrusion two has multiple evenly distributed hemispherical protrusions. The outer periphery of wear-resistant protrusion two is surrounded by multiple semi-rotary protrusions. The height of the hemispherical protrusions of wear-resistant protrusion two is lower than that of the semi-rotary protrusions.

[0007] Preferably, the flame-retardant rubber tape of the flame-retardant layer is composed of the following raw materials by weight percentage: 31.5% ethylene propylene rubber, 14.3% urea-formaldehyde melamine resin, 12.6% chloroprene rubber, 15% aluminum hydroxide, 8.9% phosphate ester, 8% polystyrene, 7.18% zinc borate, 1.26% nano zinc oxide, and 1.26% corundum.

[0008] Preferably, the antifreeze rubber strip of the antifreeze layer is composed of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate.

[0009] Preferably, the center of the wear-resistant protrusion two has three hemispherical protrusions evenly distributed, and the outer periphery of the wear-resistant protrusion two is formed by a circumferential array of six semi-rotary protrusions, with the outer arcs of the six semi-rotary protrusions forming a complete circle.

[0010] A second aspect of this invention provides a method for preparing a multilayer composite special cable, the method comprising the following steps: S1, Preparation of conductive layer: Multiple oxygen-free copper wires are spirally twisted together to form a set of oxygen-free copper wires, and then multiple sets of oxygen-free copper wires are spirally twisted together to form a conductive layer. S2, Preparation of semi-conductive nylon layer: uniformly wrap semi-conductive nylon tape around the outer layer of each group of conductive layers; S3, Preparation of insulating layer: Cross-linked polyethylene is extruded onto the outer layer of semi-conductive nylon layer, and degassed in hot air environment to remove cross-linking byproducts; S4, Preparation of flame retardant layer: The pre-made flame retardant rubber tape is spirally wound around the outer layer of the insulation layer. After winding, it is cured at a constant temperature and then cooled to room temperature. S5, Preparation of antifreeze layer: The pre-made antifreeze rubber strip is spirally wound around the outer layer of the flame retardant layer. After winding, it is cured at a constant temperature and then cooled to room temperature. S6, Preparation of buffer layer: Closed-cell sponge tape is spirally wound around the outer layer of the antifreeze layer; S7, Preparation of outer sheath: Chlorinated polyethylene is used as the base material and filled into the mold cavity. The mold cavity wall is evenly distributed with pits of the same shape as wear-resistant protrusion one or wear-resistant protrusion two. After molding, an outer sheath with wear-resistant protrusion one or wear-resistant protrusion two is obtained. Then it is placed in a flat vulcanizing machine for vulcanization. After cooling to room temperature, it is covered on the outer layer of the buffer layer through a hot-fitting process. After natural cooling, it is tightly bonded.

[0011] Preferably, the flame-retardant rubber tape in step S4 is composed of the following raw materials by weight percentage: 31.5% ethylene propylene rubber, 14.3% urea-formaldehyde melamine resin, 12.6% chloroprene rubber, 15% aluminum hydroxide, 8.9% phosphate ester, 8% polystyrene, 7.18% zinc borate, 1.26% nano zinc oxide, and 1.26% corundum. Its preparation method is as follows: Aluminum hydroxide and zinc borate are dried to remove surface adsorbed water. Nano zinc oxide is premixed with 1% by weight of dispersant and stirred to disperse agglomerated particles. Ethylene propylene rubber and chloroprene rubber are added to a mixer and mixed to soften and plasticize the rubber. Then, urea-formaldehyde melamine resin is added and mixing continues to allow the resin to initially bond with the rubber matrix. Then, pretreated aluminum hydroxide, zinc borate, and corundum are added in sequence and mixing continues to disperse the inorganic filler evenly in the rubber matrix. Finally, phosphate ester, polystyrene, and pre-dispersed nano zinc oxide are added and mixed to obtain a uniform flame-retardant compound. The flame-retardant compound is transferred to a two-roll mill, fed into the rollers, and repeatedly turned over three times to produce a uniformly thick flame-retardant sheet. The sheet is then cooled to room temperature for later use. Finally, the flame-retardant sheet is calendered into rubber belts.

[0012] Preferably, the antifreeze rubber strip in step S5 is composed of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate. Its preparation method is as follows: Short-cut glass fibers and ramie fibers are dried to remove the moisture adsorbed on the fiber surface. Micronized polytetrafluoroethylene, 2% by weight of maleic anhydride-grafted POE, mica powder and 1% by weight of stearic acid are premixed and stirred. Dioctyl adipate is preheated to 40°C. Nitrile rubber and chloroprene rubber are added to a mixer and mixed to soften and plasticize the rubber to form a continuous rubber matrix. Then, oxidized polyethylene, maleic anhydride-grafted POE and polystyrene are added and mixed again. Then, pre-dispersed micronized polytetrafluoroethylene masterbatch, dried chopped glass fiber, ramie fiber and activated mica powder are added in sequence and mixed. Finally, preheated dioctyl adipate is added and mixed. After the rubber compound is evenly mixed, the rubber is discharged to obtain the antifreeze compound. The internally mixed antifreeze compound is transferred to an open mill and repeatedly turned three times to produce an antifreeze sheet of uniform thickness. The antifreeze sheet is then calendered into an antifreeze rubber strip using a calender.

[0013] Preferably, the overlap rate of the flame-retardant rubber tape is not less than 40%, and the total thickness of the flame-retardant layer is not less than 1.5 mm.

[0014] Preferably, the semiconductive nylon tape has a thickness of 0.2 mm, a width of 10 mm, and a volume resistivity of 1 × 10⁻⁶. 5 Ω·cm.

[0015] Preferably, the buffer layer is made of closed-cell sponge tape with a density of 0.2 g / cm³ and an overlap rate of not less than 30%.

[0016] The beneficial effects of this invention are as follows: The multi-layer composite cable structure established by this invention achieves complementary and synergistic functions of each layer, forming a continuous protective barrier. This composite system enables the cable to adapt to complex environments with high temperature, low temperature (-55℃ to 70℃), humidity, high friction, and flame retardant requirements. This invention solves the problems of traditional cables, such as skin effect under high current carrying capacity, contradiction between flame retardancy and environmental protection, embrittlement and cracking at extreme low temperatures, and easy wear of outer sheath, while also being environmentally friendly in terms of materials. Inspired by the wear-resistant characteristics of organisms in nature, this invention features two types of wear-resistant protrusions that not only significantly improve the wear resistance of cables, but also increase the gripping force during installation and reduce the risk of construction damage. This invention, through its multi-dimensional innovations in materials science, structural design, and composite system construction, significantly improves the electrical performance, environmental adaptability, and service life of cables, driving the cable industry towards high efficiency, safety, greenness, and durability, and has significant value for technology promotion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the multilayer composite special cable of the present invention.

[0018] Figure 2 This is a schematic diagram and a partial enlarged view of the design of the outer sheath and wear-resistant protrusion in this invention.

[0019] Figure 3 This is a schematic diagram and a partial enlarged view of the outer sheath and the second wear-resistant protrusion in this invention.

[0020] Figure 4 This is a schematic diagram of the structure of the conductive layer and the semi-conductive nylon layer in this invention.

[0021] The reference numerals in the appendix of this invention are as follows: 1. Conductive layer; 2. Semi-conductive nylon layer; 3. Insulating layer; 4. Flame retardant layer; 5. Antifreeze layer; 6. Buffer layer; 7. Outer sheath; 71. Wear-resistant protrusion one; 72. Wear-resistant protrusion two. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Please see Figures 1 to 4 This embodiment discloses a multilayer composite special cable, comprising: a conductive layer 1, a semi-conductive nylon layer 2, an insulating layer 3, a flame-retardant layer 4, an antifreeze layer 5, a buffer layer 6, and an outer sheath 7 arranged sequentially from the inside to the outside.

[0024] The outer sheath 7 has multiple wear-resistant protrusions evenly distributed on its outer layer. The wear-resistant protrusions include two types: wear-resistant protrusion 1 71 or wear-resistant protrusion 2 72.

[0025] Please see Figure 2 The wear-resistant protrusion 71 is hemispherical, inspired by the environmental adaptations of the desert horned lizard's skin. The desert horned lizard inhabits a sandy, high-friction desert environment, and its skin naturally features hemispherical protrusions (such as...) Figure 2 As shown on the left (the circled area in the image represents the typical morphology of the horned lizard's skin protrusions), this is the core adaptive structure that helps it resist sand abrasion and reduce surface wear. Inspired by the protrusion morphology of the horned lizard's skin, wear-resistant protrusions 71 are set on the surface of the outer sheath 7, which is a biomimetic replication of this biological structure. The wear-resistant protrusions 71 on the surface of the outer sheath 7 highly simulate the protrusions on the horned lizard's skin surface in terms of morphology and distribution logic.

[0026] Please see Figure 3Wear-resistant protrusion 2 72 is a redesign based on the design concept of wear-resistant protrusion 1 71. The overall shape of wear-resistant protrusion 2 72 is as follows: the center consists of multiple evenly distributed hemispherical protrusions, surrounded by a ring of multiple semi-rotary protrusions. The hemispherical protrusions of wear-resistant protrusion 2 72 are lower in height than the semi-rotary protrusions. In this embodiment, the center of wear-resistant protrusion 2 72 consists of 3 spherical protrusions, and the outer ring consists of 6 semi-rotary protrusions.

[0027] The construction process of wear-resistant protrusion 272 is as follows: Using the center of the unit cell as the center, a 60° circumferential angle is selected to draw an arc. Then, symmetry is performed using the straight line connecting the two endpoints of the arc as the axis to form a near-elliptical shape. This near-elliptical shape is stretched to form a semi-fusiform protrusion. Then, using the center of the unit cell as the axis, the semi-fusiform protrusion is arranged in a circular array to form six closed semi-fusiform protrusions. The edges of the semi-fusiform protrusions are rounded. Subsequently, within the area enclosed by the six semi-fusiform protrusions, three small hemispherical protrusions are evenly distributed along the circumferential direction of the frame, with the center of the unit cell as the symmetry point. The vertices of these three hemispherical protrusions do not exceed the highest point of the semi-fusiform frame, and their bottoms are completely connected to the substrate surface of the outer sheath 7.

[0028] The single hemispherical protrusion of wear-resistant protrusion 71 is a point contact, and the concentrated contact stress easily leads to protrusion deformation and wear. In contrast, the semi-fusiform protrusion of wear-resistant protrusion 72 is a line contact, where contact stress can be dispersed along a gradually curvature surface. Simultaneously, the semi-fusiform surface guides the abrasive (such as sand) to slide along the surface, reducing abrasive "embedding and scraping" and lowering the friction and wear rate. Since the contact area of ​​the semi-fusiform is slightly larger than that of a single sphere, three small spherical protrusions are added within the frame, forming a composite contact mode of "line contact (semi-fusiform protrusion) + point contact (hemispherical protrusion)". This not only disperses stress through the semi-fusiform but also further refines the contact points through the hemispherical protrusions, preventing excessive wear of the frame.

[0029] Among them, the flame retardant layer 4 is made of flame retardant rubber tape wrapped around the outer layer of the insulation layer 3. The flame retardant rubber tape is composed of the following raw materials by weight percentage: ethylene propylene rubber 31.5%, urea-formaldehyde melamine resin 14.3%, chloroprene rubber 12.6%, aluminum hydroxide 15%, phosphate ester 8.9%, polystyrene 8%, zinc borate 7.18%, nano zinc oxide 1.26%, and corundum 1.26%.

[0030] The antifreeze layer 5 is made of antifreeze rubber tape wrapped around the outer layer of the flame retardant layer 4. The antifreeze rubber tape is composed of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate.

[0031] This embodiment also discloses a method for preparing a multilayer composite special cable, including the following steps: S1, Preparation of conductive layer 1: Conductive layer 1 uses oxygen-free copper rod as raw material, which is drawn into oxygen-free copper wire with a diameter of 0.5mm. Multiple oxygen-free copper wires are spirally twisted together to form a group of oxygen-free copper wires. Then, multiple groups of oxygen-free copper wires are spirally twisted together using a spiral binding machine. The number of oxygen-free copper wires can be determined according to the actual situation and is not limited to... Figure 4 Five groups of oxygen-free copper wires.

[0032] S2, Preparation of semiconductive nylon layer 2: The semiconductive nylon layer 2 has a volume resistivity of 1×10⁻⁶. 5 A semi-conductive nylon tape with an Ω·cm thickness, a thickness of 0.2mm, and a width of 10mm is used to uniformly wind each group of conductive layers 1 using a winding machine. This winding method can effectively homogenize the electric field of the electric layer and reduce the skin effect.

[0033] S3, Preparation of insulating layer 3: The insulation layer 3 is formed by extruding cross-linked polyethylene on the outer layer of the semi-conductive nylon layer 2 using a φ65mm extruder, and the molding quality is measured with a polarization meter. Then, it is degassed in a 70℃ hot air environment for 10 days to remove cross-linking byproducts, avoid later aging and cracking, and extend the insulation life.

[0034] S4, Preparation of flame retardant layer 4: The flame-retardant layer 4 is made by spirally winding pre-made flame-retardant rubber tape around the outer layer of the insulation layer 3 using a winding machine. The winding overlap rate is 40%, and the winding tension is controlled at 30N to ensure that the flame-retardant layer 4 is tightly attached to the insulation layer 3, preventing the flame from spreading longitudinally along the gaps between the layers. The total thickness of the flame-retardant layer 4 reaches 1.5mm, ensuring sufficient content of flame-retardant components, extending the duration of the flame-retardant reaction, and ensuring the rapid formation of a complete char layer barrier system in the early stages of a fire.

[0035] The flame-retardant rubber tape is composed of the following raw materials by weight percentage: ethylene propylene rubber 31.5%, urea-formaldehyde melamine resin 14.3%, chloroprene rubber 12.6%, aluminum hydroxide 15%, phosphate ester 8.9%, polystyrene 8%, zinc borate 7.18%, nano zinc oxide 1.26%, and corundum 1.26%. Its preparation method is as follows: (1) Place aluminum hydroxide and zinc borate in an 80℃ forced-air drying oven for 2 hours to remove surface adsorbed water. Premix nano zinc oxide with 1% by weight of dispersant and break up agglomerated particles by high-speed stirring (1500r / min for 5min) to avoid generating bubbles or uneven dispersion during the mixing process.

[0036] (2) Add ethylene propylene rubber and chloroprene rubber to the internal mixer and mix for 3 minutes to soften and plasticize the rubber. Then add urea-formaldehyde melamine resin and continue mixing for 2 minutes to allow the resin to initially combine with the rubber matrix. Then add pretreated aluminum hydroxide, zinc borate and carborundum in sequence and mix for 4 minutes (the chamber temperature rises to 80°C) to evenly disperse the inorganic filler in the rubber matrix. Finally add phosphate ester, polystyrene, pre-dispersed nano zinc oxide and other small molecule components and mix for 2 minutes (the chamber temperature does not exceed 90°C) to obtain a uniform flame retardant compound.

[0037] (3) Transfer the internally mixed flame retardant compound to the open mill, put the compound into the rollers, and repeatedly turn it three times to get a uniform flame retardant sheet (2mm thick). Cool it to room temperature for later use. Finally, use a calender to make the sheet into a rubber tape that meets the winding requirements, and use a fully automatic winding machine to attach the rubber tape to the outer layer of the insulation layer 3.

[0038] (4) Place the wound cable in an 80°C oven and cure it at a constant temperature for 4 hours. After curing, cool it to room temperature. Finally, the total thickness of the flame retardant layer 4 reaches the target thickness.

[0039] When the cable is ignited, during the heating stage, the flame-retardant layer 4 absorbs external heat. Phosphate esters and urea-formaldehyde melamine resin decompose first, initiating a carbonization reaction. Aluminum hydroxide decomposes simultaneously and absorbs heat, significantly reducing the surface temperature of the flame-retardant layer 4 and slowing down the pyrolysis rate of the matrix. At the same time, it releases water vapor to dilute the surrounding gas, initially reducing the risk of combustion. The Al2O3 generated by its decomposition is a high-temperature resistant oxide that deposits on the surface of the carbon layer, further enhancing the heat resistance of the carbon layer. In the early stage of combustion, chloroprene rubber decomposes and releases HCl, which efficiently captures active free radicals of the flame and interrupts the combustion chain reaction. Zinc borate decomposes to generate boron anhydride, which fills the micropores of the carbon layer to form a glassy sealing layer. The carbon-nitrogen-phosphorus composite carbon layer is initially formed and begins to play a barrier role. During the high-temperature combustion stage, the dense carbon-nitrogen-phosphorus composite carbon layer completely blocks the transfer of oxygen and heat. The internal insulation layer 3 stops pyrolysis due to lack of oxygen and heat. Inorganic fillers such as corundum, alumina, and zinc oxide form a high-temperature resistant barrier, maintaining the stability of the carbon layer structure. The flame gradually extinguishes due to the lack of combustible components and oxygen, thus achieving flame-retardant protection for the cable.

[0040] S5, Prepare antifreeze layer 5: The antifreeze layer 5 is made by spirally winding a pre-made antifreeze rubber strip around the outer layer of the flame-retardant layer 4 using a winding machine. The antifreeze rubber strip is composed of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate. Its preparation method is as follows: (1) Place short glass fibers (3-5 mm in length) and ramie fibers in an 80°C forced-air drying oven for 2 hours to remove the moisture adsorbed on the fiber surface, prevent air bubbles from being generated during the mixing process, and avoid the material from becoming brittle due to fiber water absorption at low temperature; premix micro-powdered polytetrafluoroethylene, 2% by weight of maleic anhydride-grafted POE, mica powder and 1% by weight of stearic acid (stearic acid accounts for 1% of the total weight of the antifreeze rubber belt main material) and stir at high speed for 5 minutes; preheat dioctyl adipate (DOA) to 40°C to reduce viscosity and facilitate rapid and uniform integration into the rubber matrix.

[0041] (2) Add nitrile rubber and chloroprene rubber to the internal mixer (initial chamber temperature 60℃, rotor speed 50r / min) and mix for 3min to soften and plasticize the rubber and form a continuous rubber matrix. Then add oxidized polyethylene, maleic anhydride grafted POE and polystyrene and continue mixing for 2min. Then add pre-dispersed micronized polytetrafluoroethylene masterbatch, dried chopped glass fiber, ramie fiber and activated mica powder in sequence and mix for 4min. Finally add preheated dioctyl adipate and mix for 1min. After the rubber compound is mixed evenly, discharge the rubber to obtain the antifreeze compound.

[0042] (3) Transfer the mixed rubber after internal mixing to the open mill, repeatedly turn it 3 times, and get a uniform thickness antifreeze sheet. Then, use a calender to calender the sheet into an antifreeze rubber strip with a width of 50mm and a thickness of 0.9mm. Finally, use the same winding process as the flame retardant layer 4 to ensure that the antifreeze layer 5 and the flame retardant layer 4 are tightly bonded.

[0043] (4) Place the wound cable in an 85°C oven and cure it at a constant temperature for 3 hours to allow the antifreeze compound to fully crosslink and form a stable three-dimensional network structure. After curing, cool it to room temperature with the oven, and the total thickness of the antifreeze layer 5 finally reaches the target thickness.

[0044] The antifreeze principle of this antifreeze layer 5 is to maintain the flexibility of the material through the combination of components, avoiding brittleness and preventing interlayer delamination. When the cable is at a low temperature of -40℃, dioctyl adipate and maleic anhydride-grafted POE weaken the intermolecular forces, allowing the rubber molecular chains to remain flexible at low temperatures, further reducing the glass transition temperature of the matrix from -40℃ for pure nitrile rubber to below -55℃, keeping the matrix in a highly elastic state without hardening or brittleness; micronized polytetrafluoroethylene hinders the orderly arrangement of rubber molecular chains, destroying the "crystal nucleus growth environment" for crystallization, reducing the low-temperature crystallinity of the rubber from 25% for pure rubber to below 8%, preventing the material from becoming hard and brittle due to crystallization; chopped glass fiber, ramie fiber, and mica powder disperse low-temperature stress, preventing brittleness / delamination; oxidized polyethylene ensures the stability of the interfaces of each component, eliminating the risk of delamination; ultimately, the antifreeze layer 5 achieves "flexibility, crack resistance, and structural stability" at low temperatures, protecting the internal flame-retardant layer 4 and insulation layer 3 from low-temperature damage.

[0045] S6, Prepare buffer layer 6: The buffer layer 6 uses a closed-cell sponge tape with a density of 0.2g / cm³, a thickness of 2.0mm, and a width of 30mm. It is spirally wound onto the outer layer of the antifreeze layer 5 using a winding machine. The winding overlap rate is 30%, and the winding tension is 15N (to avoid excessive compression of the sponge). The elastic buffering properties of the sponge are used to absorb external impacts.

[0046] S7, Preparation of outer sheath 7: The outer sheath 7 is made of chlorinated polyethylene (CPE, chlorine content 35%) as the base material. The rubber material is filled into the mold cavity. The mold cavity wall is evenly distributed with pits of the same shape as the wear-resistant protrusion 71 or the wear-resistant protrusion 72. It is placed in a flat vulcanizing machine and vulcanized at 160℃ and 10MPa pressure for 15 minutes. After molding, the outer sheath 7 with wear-resistant protrusion 71 or the wear-resistant protrusion 72 (thickness 3.0mm) is obtained. After cooling to room temperature, it is covered on the outer layer of the buffer layer 6 by a hot-fitting process (heating the outer sheath 7 to 80℃ to make it slightly expand). After natural cooling, it is tightly bonded.

[0047] The above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Various modifications, alterations, equivalent substitutions and improvements made by those skilled in the art within the scope of the claims should be included within the scope of protection of the present invention.

Claims

1. A multi-layer composite special cable, characterized in that, include: The conductive layer (1), semi-conductive nylon layer (2), insulating layer (3), flame retardant layer (4), antifreeze layer (5), buffer layer (6), and outer sheath (7) are arranged sequentially from the inside to the outside. The conductive layer (1) is formed by spirally twisting multiple sets of oxygen-free copper wires; The semi-conductive nylon layer (2) is made by wrapping semi-conductive nylon tape around the outer layer of each set of conductive layers (1); The insulating layer (3) is extruded onto the outer layer of the semi-conductive nylon layer (2); The flame-retardant layer (4) is made by wrapping flame-retardant rubber tape around the outer layer of the insulating layer (3); The antifreeze layer (5) is made by wrapping antifreeze rubber tape around the outer layer of the flame retardant layer (4); The buffer layer (6) is made by wrapping a sponge strip around the outer layer of the antifreeze layer (5); The outer sheath (7) has multiple wear-resistant protrusions evenly distributed on its outer layer. The wear-resistant protrusions are wear-resistant protrusion one (71) or wear-resistant protrusion two (72). Wear-resistant protrusion one (71) is hemispherical. The center of wear-resistant protrusion two (72) has multiple evenly distributed hemispherical protrusions. The outer periphery of wear-resistant protrusion two (72) is surrounded by multiple semi-rotary protrusions. The height of the hemispherical protrusions of wear-resistant protrusion two (72) is lower than that of the semi-rotary protrusions.

2. The multi-layer composite special cable according to claim 1, characterized in that, The flame-retardant rubber strip of the flame-retardant layer (4) is composed of the following raw materials by weight percentage: 31.5% ethylene propylene rubber, 14.3% urea-formaldehyde melamine resin, 12.6% chloroprene rubber, 15% aluminum hydroxide, 8.9% phosphate ester, 8% polystyrene, 7.18% zinc borate, 1.26% nano zinc oxide, and 1.26% corundum.

3. The multi-layer composite special cable according to claim 1, characterized in that, The antifreeze layer (5) consists of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate.

4. The multi-layer composite special cable according to claim 1, characterized in that, The wear-resistant protrusion 2 (72) has 3 hemispherical protrusions evenly distributed in the center, and the outer periphery of the wear-resistant protrusion 2 (72) is formed by 6 semi-rotary protrusions arranged in a circular array, with the outer arcs of the 6 semi-rotary protrusions forming a complete circle.

5. A method for preparing a multilayer composite special cable, characterized in that, The preparation method includes the following steps: S1, Prepare conductive layer (1): Spiral twist multiple oxygen-free copper wires to form a group of oxygen-free copper wires, and then spiral twist multiple groups of oxygen-free copper wires to form conductive layer (1). S2, Prepare a semi-conductive nylon layer (2): Wrap a semi-conductive nylon strip evenly around the outer layer of each set of conductive layers (1); S3, Preparation of insulating layer (3): Cross-linked polyethylene is extruded onto the outer layer of semi-conductive nylon layer (2), and degassed in hot air environment to remove cross-linking byproducts; S4, Prepare the flame retardant layer (4): The flame retardant rubber tape is spirally wound around the outer layer of the insulation layer (3) after the winding is completed and cured at a constant temperature. After curing, it is cooled to room temperature. S5, Prepare the antifreeze layer (5): The pre-made antifreeze rubber strip is spirally wound around the outer layer of the flame retardant layer (4). After the winding is completed, it is cured at a constant temperature and then cooled to room temperature. S6, Prepare the buffer layer (6): Use closed-cell sponge tape spirally wound on the outer layer of the antifreeze layer (5); S7, Preparation of outer sheath (7): Chlorinated polyethylene is used as the base material and is filled into the mold cavity. The mold cavity wall is evenly distributed with pits of the same shape as wear-resistant protrusion one (71) or wear-resistant protrusion two (72). After molding, an outer sheath (7) with wear-resistant protrusion one (71) or wear-resistant protrusion two (72) is obtained. Then it is placed in a flat vulcanizing machine for vulcanization. After cooling to room temperature, it is covered on the outer layer of the buffer layer (6) through a hot-fitting process. After natural cooling, it is tightly bonded.

6. The method for preparing the multilayer composite special cable according to claim 5, characterized in that, The flame-retardant rubber tape in step S4 is composed of the following raw materials by weight percentage: ethylene propylene rubber 31.5%, urea-formaldehyde melamine resin 14.3%, chloroprene rubber 12.6%, aluminum hydroxide 15%, phosphate ester 8.9%, polystyrene 8%, zinc borate 7.18%, nano zinc oxide 1.26%, and corundum 1.26%. Its preparation method is as follows: Aluminum hydroxide and zinc borate are dried to remove surface adsorbed water. Nano zinc oxide is premixed with 1% by weight of dispersant and stirred to disperse agglomerated particles. Ethylene propylene rubber and chloroprene rubber are added to a mixer and mixed to soften and plasticize the rubber. Then, urea-formaldehyde melamine resin is added and mixing continues to allow the resin to initially bond with the rubber matrix. Then, pretreated aluminum hydroxide, zinc borate, and corundum are added in sequence and mixing continues to disperse the inorganic filler evenly in the rubber matrix. Finally, phosphate ester, polystyrene, and pre-dispersed nano zinc oxide are added and mixed to obtain a uniform flame-retardant compound. The flame-retardant compound is transferred to a two-roll mill, fed into the rollers, and repeatedly turned over three times to produce a uniformly thick flame-retardant sheet. The sheet is then cooled to room temperature for later use. Finally, the flame-retardant sheet is calendered into rubber belts.

7. The method for preparing the multilayer composite special cable according to claim 5, characterized in that, The antifreeze rubber strip in step S5 is composed of the following raw materials by weight percentage: 31.5% nitrile rubber, 14.7% oxidized polyethylene, 10% chloroprene rubber, 15% micronized polytetrafluoroethylene, 4% maleic anhydride-grafted POE, 8% polystyrene, 7.1% chopped glass fiber, 1.3% ramie fiber, 1.3% mica powder, and 7.1% dioctyl adipate. Its preparation method is as follows: Short-cut glass fibers and ramie fibers are dried to remove the moisture adsorbed on the fiber surface. Micronized polytetrafluoroethylene, 2% by weight of maleic anhydride-grafted POE, mica powder and 1% by weight of stearic acid are premixed and stirred. Dioctyl adipate is preheated to 40°C. Nitrile rubber and chloroprene rubber are added to a mixer and mixed to soften and plasticize the rubber to form a continuous rubber matrix. Then, oxidized polyethylene, maleic anhydride-grafted POE and polystyrene are added and mixed again. Then, pre-dispersed micronized polytetrafluoroethylene masterbatch, dried chopped glass fiber, ramie fiber and activated mica powder are added in sequence and mixed. Finally, preheated dioctyl adipate is added and mixed. After the rubber compound is evenly mixed, the rubber is discharged to obtain the antifreeze compound. The internally mixed antifreeze compound is transferred to an open mill and repeatedly turned three times to produce an antifreeze sheet of uniform thickness. The antifreeze sheet is then calendered into an antifreeze rubber strip using a calender.

8. The method for preparing the multilayer composite special cable according to claim 5, characterized in that, The overlap rate of the flame-retardant rubber tape is not less than 40%, and the total thickness of the flame-retardant layer (4) is not less than 1.5 mm.

9. The method for preparing the multilayer composite special cable according to claim 5, characterized in that, The volume resistivity of the semiconductive nylon tape is 1×10⁻⁶. 5 Ω·cm, thickness 0.2mm, width 10mm.

10. The method for preparing the multilayer composite special cable according to claim 5, characterized in that, The buffer layer (6) is made of closed-cell sponge tape with a density of 0.2 g / cm³ and the wrapping overlap rate is not less than 30%.

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