A freeze-resistant, crack-resistant, and cold-resistant cable

Abstract

This invention relates to the field of cable technology and discloses a freeze-resistant, crack-resistant, and cold-resistant cable, solving the problems of interlayer imbalance and complex processes in existing technologies. The cable comprises, from the inside out, a conductor layer, an insulation layer, and a sheath layer. The insulation layer uses cross-linked polyethylene as a matrix, combined with polyolefin elastomers, modified fillers, and antioxidants, with optional addition of dicumyl peroxide crosslinking agent. The sheath layer uses ethylene-vinyl acetate copolymer as a matrix, combined with polyolefin elastomers, thermoplastic polyurethane, modified fillers, and antioxidants, with optional addition of ethylene propylene diene monomer (EPDM) rubber. The insulation layer and sheath layer form a compositionally gradient transition layer through a co-extrusion process, followed by warm water crosslinking treatment. This invention, through the synergistic design of all layers, solves the problems of interlayer performance discontinuity, lack of a transition layer, and complex processes in existing technologies. It exhibits excellent cold resistance, crack resistance, and electrical stability in extremely cold environments, is suitable for continuous production, and is applicable to power transmission scenarios in cold regions.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a cold-resistant cable that is resistant to freezing and cracking. Background Technology

[0002] Cold-resistant cables are a type of special cable designed for stable operation in low-temperature environments. Their core feature is that they can maintain good electrical, mechanical, and structural stability at low temperatures, avoiding insulation or sheath cracking and embrittlement caused by low temperatures, thus ensuring reliable power and signal transmission. Traditional cold-resistant cables mainly improve low-temperature performance by modifying the material of a single sheath layer, but there are problems such as interlayer stress mismatch and insufficient long-term weather resistance, making it difficult to meet the comprehensive performance requirements in extremely cold environments.

[0003] Existing technology publication number CN120221177A discloses a cold-resistant and freeze-resistant cable and its preparation method, comprising, from the outside to the inside, a sheath layer, an insulation layer, and a conductive core layer; the sheath layer is prepared from a sheath material, which includes polyvinyl chloride resin, dioctyl terephthalate, modified polyurethane, epoxidized soybean oil, aluminum hydroxide, magnesium hydroxide, calcium-zinc stabilizer, and modified halloysite. The sheath material prepared by the prior art has good mechanical properties, antibacterial properties, and anti-aging properties, making it suitable for cold-resistant and freeze-resistant cables.

[0004] Regarding the aforementioned and existing related technologies, the inventors believe that the following defects often exist: 1. Existing technologies only improve the cold resistance of the sheath layer by modifying materials such as polyurethane and halloysite, but do not specifically optimize the cold resistance of the core functional layers of the cable. For example, the insulation layer, as a key layer to ensure electrical performance, does not have its material selection and low-temperature mechanical properties clearly specified in the documents. This single-layer optimization mode is prone to interlayer performance discontinuity. Although the sheath layer has a certain degree of flexibility, the insulation layer may lose its elasticity due to crystallization hardening in extremely cold environments, thus limiting the cable's antifreeze effect. 2. Existing technologies do not mention the interface treatment or transition layer design between the insulation layer and the sheath layer. In extremely cold environments, the difference in thermal expansion coefficients between different material layers will be significantly amplified due to sudden temperature changes. If there is no transition structure or interface modification between the layers, stress concentration is likely to occur. For example, if the sheath layer and the insulation layer are directly composited, inconsistent low-temperature shrinkage may cause interface peeling or microcracks. 3. Existing technologies for preparing sheath materials involve multiple complex chemical reactions. Modified porphyrins require a reaction at 65-70°C for 72 hours under anhydrous and oxygen-free conditions, modified polyurethanes require multiple nitrogen-protected reactions, and modified halloysite requires multiple organic synthesis steps. Such processes have stringent equipment requirements and long production cycles, making them difficult to adapt to the continuous production mode of existing cable production lines. At the same time, they lead to a significant increase in cost per ton, resulting in insufficient economic viability for enterprise-level mass production. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the existing technology has the disadvantages of interlayer imbalance and complicated process. To this end, we propose a cold-resistant cable that is frost-resistant and crack-resistant.

[0006] To achieve the above objectives, this application adopts the following technical solution: a freeze-resistant, crack-resistant, and cold-resistant cable, comprising, from the inside out, a conductor layer, an insulation layer, and a sheath layer. The insulation layer and the sheath layer are formed into a compositionally gradient transition layer through a co-extrusion process. The thickness of the transition layer is 0.1-0.3 mm. The insulation layer is made of the following materials in parts by weight: 90-100 parts cross-linked polyethylene, 17.6-25 parts polyolefin elastomer, 2-4 parts modified filler, 0.24-0.3 parts antioxidant 1010, 0.24-0.3 parts antioxidant 168, and 0-0.5 parts dicumyl peroxide cross-linking agent. The sheath layer is made of the following materials in parts by weight: 85-100 parts ethylene-vinyl acetate copolymer, 21.4-30 parts polyolefin elastomer, 15-21.4 parts thermoplastic polyurethane, 5-8 parts modified filler, 0.29 parts antioxidant 1010, and antioxidant 168. 0.29 parts, 0-5 parts of EPDM rubber, and the composite antioxidant system in the insulation layer and sheath layer is composed of antioxidant 1010 and antioxidant 168 in a 1:1 ratio.

[0007] Preferably, the modified filler of the insulating layer is one of spherical modified nano-calcium carbonate, halloysite nanotubes, or flake montmorillonite, and the modified filler of the sheath layer is one of modified nano-calcium carbonate, nano-calcium carbonate modified with a silane coupling agent containing epoxy groups, or carbon nanotubes.

[0008] Preferably, the raw materials for preparing the insulation layer and the sheath layer both include a polyolefin elastomer and a composite antioxidant system, and the polyolefin elastomer is an ethylene-octene copolymer with an octene monomer mass ratio of 20%-30%.

[0009] Preferably, the material composition of the transition layer includes the base material of the insulating layer and the sheath layer.

[0010] Preferably, the polyolefin elastomer in the insulation layer and the sheath layer is an ethylene-octene copolymer, and the thermoplastic polyurethane in the sheath layer is a polyether type, wherein the mass percentage of ether bonds is ≥50%.

[0011] A method for preparing a freeze-resistant, crack-resistant, and cold-resistant cable as described in any one of claims 1-5, characterized by comprising the following steps: C1: Selecting stranded conductors, after surface degreasing and plating thickness verification, installing them on a pay-off frame and adjusting the pay-off tension to 50N; C2: Setting the extrusion temperature and parameters for each section of the insulation layer and sheath layer, adding insulation layer granules and sheath layer granules after preheating; C3: Starting the insulation layer screw, inserting the conductor after the melt stabilizes, controlling the traction speed to ensure the thickness meets the standard; C4: Starting the sheath layer screw, so that the melt uniformly covers the insulation layer to form a transition layer, monitoring the thickness to 0.1-0.3mm and ensuring no delamination at the interface; C5: After cooling in a 25℃ cooling water bath, winding at an 80N winding tension to the set length; C6: Placing the entire cable in a warm water crosslinking bath, controlling the temperature, time, and water flow, and cooling to room temperature after completion.

[0012] Preferably, the preparation method of the insulating layer granules includes the following steps: S1-1: Weigh cross-linked polyethylene, polyolefin elastomer, modified filler and antioxidant according to the ratio to ensure that the raw material specifications meet the requirements; S1-2: Vacuum dry the cross-linked polyethylene and polyolefin elastomer granules, controlling the temperature, vacuum degree and time to ensure that the moisture content meets the standard; S1-3: Dry the modified filler by forced air drying, cool it and then sieve it to remove agglomerates, and seal it for storage; S1-4: Grind and mix antioxidants 1010 and 168 and sieve them to prepare a composite antioxidant; S1-5: Put the polymer, modified filler and antioxidant into a mixer in sequence, controlling the temperature, speed and time to make the materials melt and mix evenly; S1-6: Crush the melt after mixing, extrude it through a twin-screw extruder, cool it, granulate it, sieve it and then dry and seal it for storage.

[0013] Preferably, the preparation method of the sheath layer granules includes the following steps: S2-1: Weigh ethylene-vinyl acetate copolymer, polyolefin elastomer, thermoplastic polyurethane, modified filler and antioxidant according to the ratio, and confirm that the raw material specifications meet the requirements; S2-2: Vacuum dry the ethylene-vinyl acetate copolymer and polyolefin elastomer, controlling the temperature, vacuum degree and time to ensure that the moisture content meets the standard; S2-3: Vacuum dry the thermoplastic polyurethane separately, controlling the temperature to avoid softening, and ensuring that the granules are in good condition after drying; S2-4: Dry the modified filler with forced air, cool it and sieve it to remove agglomerates, and seal it for storage; S2-5: Grind, mix and sieve the antioxidant to verify its compatibility with the matrix material; S2-6: Add the polymer, modified filler and antioxidant in sequence, controlling the temperature, speed and time to make the materials melt and mix evenly; S2-7: Crush the melt after internal mixing, extrude it through a twin-screw extruder, cool it, granulate it, sieve it and dry it and seal it for storage.

[0014] Preferably, in the compatibility verification, antioxidant composite powder with a mass ratio of 1:10 and ethylene-vinyl acetate copolymer particles are melt-blended and stirred evenly at 120±5℃. After the blend is cooled, the cross-section is cut and observed to confirm that there are no antioxidant agglomerates.

[0015] Preferably, the basic temperature gradient between the insulation layer and the sheath layer in the extrusion process is as follows: for the insulation layer, the temperature in zone 1 of the extrusion section is 105-115℃, the temperature in zone 2 is 120-130℃, the temperature in zone 3 is 130-140℃, and the die temperature is 125-135℃; for the sheath layer, the temperature in zone 1 of the extrusion section is 95-105℃, the temperature in zone 2 is 110-120℃, the temperature in zone 3 is 120-130℃, and the die temperature is 125-135℃.

[0016] The technical effects and advantages of this invention are as follows: This invention achieves a balanced improvement in the overall cold resistance performance of the insulation and sheath layers through the synergistic design of the materials. The insulation layer uses cross-linked polyethylene as the matrix, combined with polyolefin elastomers and modified nanofillers to enhance low-temperature flexibility; the sheath layer uses ethylene-vinyl acetate copolymer as the base, combined with thermoplastic polyurethane and elastomers to optimize mechanical protection capabilities. Both share the core elastomer and additive system, avoiding the interlayer performance gaps caused by optimizing a single sheath layer in existing technologies. This ensures that the insulation and sheath layers maintain flexibility simultaneously in extremely cold environments, solving the problem of the sheath layer being flexible while the insulation layer becomes brittle. In this invention, a compositionally gradient transition layer is formed through a co-extrusion process, effectively alleviating interlayer stress concentration. The transition layer achieves a smooth transition from insulation material to sheath material through the natural mixing of the insulation and sheath layer melts, reducing the shrinkage stress caused by the difference in thermal expansion coefficients between different material layers during sudden temperature changes, avoiding interfacial peeling or microcracks, and significantly improving the structural stability of the cable under extreme temperature changes. In this invention, the preparation process is adapted to the continuous production mode of existing cable production lines, exhibiting excellent economic efficiency for mass production. Compared to existing technologies that require multiple complex chemical reactions, this invention uses conventional mixing and extrusion equipment, achieving material modification through precise control of parameters in drying, mixing, and granulation processes. This eliminates the need for special equipment investment, shortens the production cycle, reduces unit cost, and is more suitable for large-scale enterprise production. Attached Figure Description

[0017] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0018] Figure 1 This is a flowchart illustrating the preparation process of the insulating layer granules of the present invention. Figure 2 This is a flowchart illustrating the preparation process of the sheath layer granules of the present invention. Figure 3 This is a flowchart illustrating the fabrication process of the complete cable according to the present invention. Detailed Implementation

[0019] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0020] Preparation Example 1-1: Reference Figure 1 As shown in Table 1, a frost-resistant, crack-resistant, and cold-resistant cable insulation granule is provided. The raw materials and their proportions are shown in Table 1. The granules include 100 parts of cross-linked polyethylene, 17.6 parts of polyolefin elastomer, 3.5 parts of spherical modified nano calcium carbonate, 0.24 parts of antioxidant 1010, and 0.24 parts of antioxidant 168.

[0021] A method for preparing granular material for freeze-thaw resistant, crack-resistant, and cold-resistant cable insulation includes the following steps: S1-1: Raw material specification verification and weighing. Weigh 100 parts of high-density cross-linked polyethylene with a density range of 0.94-0.96 g / cm³. 3The polymer particles were heated to 230℃ to form a melt, and a pressure of 2.16 kg was applied. The melt flow rate was measured to be 2 g / min. 17.6 parts of polyolefin elastomer with an ethylene-octene copolymer chemical structure were weighed, wherein the octene monomer accounted for 20%-25% of the copolymer by mass, and the glass transition temperature was ≤-60℃. 3.5 parts of modified nano-calcium carbonate with a particle size of 50±5 nm were weighed, and the surface was modified with KH550 silane coupling agent with a grafting rate ≥90%. 0.24 parts of antioxidant 1010 with a purity ≥99% and a melting point range of 110-115℃ were weighed. 0.24 parts of antioxidant 168 with a purity ≥99% and a melting point range of 183-186℃ were weighed. S1-2: Drying of polymer particles. First, cross-linked polyethylene and polyolefin elastomer particles are passed through a 40-mesh sieve to remove lumps and impurities. The particles are then evenly spread on two trays that have been wiped and dried with anhydrous ethanol. Since polyolefin elastomers have a lower density, the spread thickness should be thinner to ensure uniform drying. The trays are placed in a DZF-6050 dual-chamber vacuum drying oven, and a vacuum of -0.09 MPa is applied. After maintaining this vacuum for 10 minutes to ensure no leaks, the temperature is increased to 60°C at a rate of 5°C / minute. The temperature is stabilized for 30 minutes after reaching the set temperature before starting the timer. Drying takes 8 hours, during which the particle condition is checked every 2 hours through the oven door. The particles should remain loose and not sticky. If the polyolefin elastomer softens, the temperature of the vacuum drying oven needs to be reduced to 58°C. After drying, the moisture content is measured using a Karl Fischer moisture analyzer and should be ≤0.05%. S1-3: Drying and dispersion of nano-calcium carbonate. Modified nano-calcium carbonate was poured into an evaporating dish, spread evenly, and then placed in a 101-2AB model forced-air dryer. The temperature was set to 80℃, and drying was carried out at a forced-air flow rate of 0.5 m / s for 4 hours. During this period, the chamber door was opened for 10 seconds every hour to replace the air and prevent moisture accumulation. After drying, the evaporating dish was removed and immediately placed into a desiccant dish containing molecular sieve desiccant. After cooling to room temperature, the mixture was passed through a 200-mesh sieve to remove agglomerates and collected in a sealed bottle. S1-4: Premixed antioxidant. Antioxidant 1010 and antioxidant 168 were poured into an agate mortar that had been cleaned and dried with anhydrous ethanol beforehand. After grinding for 5 minutes, the mixture was passed through a 100-mesh sieve, and the premixed powder was collected in a brown bottle for later use. S1-5: Intensive mixing. First, add the dried cross-linked polyethylene to the XM-150 internal mixer, tighten the top cover, and mix for 3 minutes until completely melted. Observe that the melt is transparent and without obvious particles. Add the dried polyolefin elastomer and continue mixing for 2 minutes. The melt turns into a milky white homogeneous phase, and the torque stabilizes at 40±2 N·m. Open the top cover and quickly add the dried and sieved nano-calcium carbonate. Tighten the top cover and mix for 5 minutes. During this period, the torque gradually increases to 50±3 N·m. If the torque fluctuation exceeds 5 N·m, the mixing time needs to be extended by 1 minute. Add the premixed antioxidant composite powder and mix for 5 minutes. The color of the melt should not change significantly and should remain milky white. The torque should stabilize at 48±2 N·m, indicating that the additives are evenly dispersed.Open the top bolt of the internal mixer, discharge the melt into a stainless steel tray lined with release agent, level the melt with a scraper, and cool to room temperature. S1-6: Extrusion granulation. The cooled, internally mixed melt was crushed into 1 cm × 1 cm pieces using a crusher and fed into an SHJ-35 twin-screw extruder. The extruder parameters were set as follows: zone 1 temperature 90℃, zone 2 temperature 105℃, zone 3 temperature 115℃, die temperature 110℃, zone 1 screw speed 100 rpm, vacuum degree -0.08 MPa, and water ring cooling water temperature 25℃±2℃. After the melt was continuously extruded from the die in strips, the pelletizer was started and set to a speed of 300 rpm to cut the strip melt into 3 mm × 3 mm cylindrical pellets. After being cooled by the water ring, the pellets were fed into a vibrating screen to remove excessively fine and sticky pellets. The qualified pellets were spread evenly and then placed in a 60℃ forced-air oven to dry for 4 hours, turning them over once an hour during the drying process. After cooling to room temperature, the insulating layer pellets were obtained and sealed in aluminum foil vacuum bags for storage.

[0022] Preparation Examples 1-2: Reference Figure 1 As shown, a frost-resistant, crack-resistant, and cold-resistant cable insulation granule is provided. The raw materials and their proportions are shown in Table 1. The difference between this granule and the preparation example 1-1 is that the proportion of polyolefin elastomer is significantly increased. The glass transition temperature of polyolefin elastomer is lower than that of cross-linked polyethylene. Increasing the content of polyolefin elastomer can reduce the glass transition temperature of the insulation layer, so that the molecular chains can still maintain a certain degree of mobility under extreme low temperature conditions.

[0023] It should be noted that, unlike Preparation Example 1-1, Preparation Example 1-2 uses 4 parts halloysite nanotubes as the modified filler. Halloysite nanotubes can be oriented along the stress direction at low temperatures to form a fiber-reinforced network. Compared with the spherical nano-calcium carbonate in Preparation Example 1, it can reduce the crack propagation rate. Since halloysite nanotubes are one-dimensional structures, they are slightly more difficult to disperse than spherical fillers, and the mixing time needs to be extended by 1-2 minutes.

[0024] Unlike Preparation Example 1-1, Preparation Example 1-2 is designed so that the oxidation aging of the material at extreme low temperatures is mainly a free radical chain reaction. The dosage of antioxidant 1010, the main antioxidant, and antioxidant 168, the auxiliary antioxidant, are both increased by 25%, which increases the number of free radicals that can be captured and improves the insulation resistance retention rate after freeze-thaw cycles at extreme low temperatures.

[0025] Preparation Examples 1-3: Reference Figure 1As shown, a frost-resistant, crack-resistant, and cold-resistant cable insulation granule is described in Table 1. The raw materials and their proportions are shown in Table 1. The difference between this granule and the preparation example 1-1 is that the polyolefin elastomer is replaced with a high melt strength polyolefin elastomer. The long-chain branched structure of the high melt strength polyolefin elastomer can enhance the molecular chain entanglement with cross-linked polyethylene and reduce cracks caused by repeated bending. Since the high melt strength polyolefin elastomer has a higher melt viscosity, the extruder parameters need to be modified: zone 1 temperature 95℃, zone 2 temperature 110℃, zone 3 temperature 120℃, die temperature 115℃, and screw speed 90 rpm.

[0026] It should be noted that, unlike Preparation Example 1-1, Preparation Example 1-3 uses two parts of flake montmorillonite as the modified filler. The montmorillonite is arranged parallel to the bending direction in the insulation layer, forming a physical barrier to block the crack propagation path.

[0027] Unlike Preparation Example 1-1, Preparation Example 1-3 newly added 0.5 parts of dicumyl peroxide crosslinking agent, which can initiate the crosslinking reaction of crosslinked polyethylene and polyolefin elastomer during the internal mixing process, forming a hybrid structure of crosslinking and elasticity. When bending, the stress can be dispersed through the crosslinking points, and the elastic chain segments absorb the deformation energy, improving the insulation resistance retention rate after repeated bending. Since the crosslinking agent must initiate the crosslinking reaction at a specific temperature, the internal mixing temperature needs to be increased. In the internal mixing process, after the crosslinked polyethylene is added and melted for 3 minutes, the high melt strength polyolefin elastomer is added and mixed for 3 minutes until the melt is homogeneous; then flake montmorillonite is added and mixed for 5 minutes until the torque is stable; the temperature is raised to 120-130℃, the dicumyl peroxide crosslinking agent is added, and the mixture is mixed for 4 minutes to ensure that the crosslinking agent is evenly dispersed.

[0028] Preparation Example 2-1: Reference Figure 2 As shown in Table 1, a granular material for frost-resistant, crack-resistant, and cold-resistant cable sheathing is provided, and its raw materials and proportions are listed below:

[0029]

[0030] A method for preparing granular material for frost-resistant, crack-resistant, and cold-resistant cable sheathing includes the following steps: S2-1: Raw material specification verification and weighing. Weigh 100 parts of ethylene-vinyl acetate copolymer, wherein the mass percentage of vinyl acetate monomer in the copolymer is 30%±2%, and the melt flow rate is 4-6 g / 10 minutes; weigh 21.4 parts of thermoplastic polyurethane, type polyether, Shore hardness A80; weigh 21.4 parts of polyolefin elastomer, 7.1 parts of modified nano-calcium carbonate, 0.29 parts of antioxidant 1010 and 0.29 parts of antioxidant 168, which are of the same type as those used in the insulation layer. S2-2: Polymer particle drying. Ethylene-vinyl acetate copolymer and polyolefin elastomer particles were evenly spread on trays and placed in a DZF-6050 dual-chamber vacuum drying oven. The oven was evacuated to -0.09 MPa and maintained for 10 minutes to check the seal. The temperature was then increased to 60°C at a rate of 5°C / minute. After reaching the set temperature and stabilizing for 30 minutes, the timer was started. Drying lasted for 8 hours, with the oven door opened every 2 hours to stir the particles and ensure the upper and lower layers were dry. After drying, the moisture content was measured using a Karl Fischer moisture analyzer; the moisture content should be ≤0.05%. S2-3: Drying of thermoplastic polyurethane. Thermoplastic polyurethane particles were spread evenly on aluminum trays and placed in a DZF-6020 small vacuum drying oven for 6 hours. The set temperature was 50°C and the vacuum degree was -0.09 MPa. The particle state was checked every hour through the observation window. Normally, the particles are dispersed and semi-transparent. If particles clump together, they should be dispersed with a plastic rod. After drying, the particles should be semi-transparent without yellowing or hardening. S2-4: Drying and dispersion of modified nano-calcium carbonate. Modified nano-calcium carbonate was spread evenly in an evaporating dish and placed in a 101-2AB forced-air drying oven. The oven was dried at 80℃ for 4 hours, with the door opened for 10 seconds every hour to replace the humid air. After drying, the evaporating dish was removed, cooled to room temperature, poured through a 200-mesh nylon sieve, and the agglomerates were removed and sealed in a glass desiccator containing molecular sieve desiccant. S2-5: Compatibility verification of premixed antioxidants. Antioxidant 1010 and antioxidant 168 were ground in a mortar for 5 minutes and then passed through a 100-mesh sieve to obtain an antioxidant composite powder. Take 1g of composite powder and 10g of ethylene-vinyl acetate copolymer particles and melt-blend them on a 120℃ hot plate. After stirring until uniform, cool and observe the cross-section with a stereomicroscope. Ensure that no white antioxidant particles precipitate out. Compatibility verification is performed during the pretreatment of the antioxidant composite powder to ensure that the antioxidant can be uniformly dispersed and stably coexist with the cable sheath matrix material and other additives. This avoids antioxidant agglomeration, precipitation, or delamination from the matrix due to polarity differences or solubility parameter mismatches. This ensures that the antioxidant does not decompose during processing and exerts a synergistic anti-aging effect during use, avoiding negative impacts on the material's mechanical properties, cold resistance, and interlayer adhesion. S2-6: Intensive mixing.Pour the dried ethylene-vinyl acetate copolymer into the XM-150 internal mixer, tighten the top cover, and start the rotor. Maintain a melting speed of 100 rpm for 4 minutes. During this time, the particles gradually soften, the torque increases to 25 N·m, and the melt becomes translucent with no obvious particles. After melting, the torque stabilizes at 35 ± 2 N·m. If the torque fluctuation exceeds 5 N·m, the mixing time needs to be extended by 1 minute. Add the polyolefin elastomer and thermoplastic polyurethane in stages, with a 30-second interval between additions to avoid rotor jamming caused by a single addition. After mixing, maintain the rotor speed at 100 rpm for 2 minutes. The melt will change from translucent to milky white, and the torque will rise to 40 N·m. After adding thermoplastic polyurethane, mix for 4 minutes. The melt will be uniformly pale yellow. Take a small amount of melt with a sampling spoon, and after cooling at room temperature, it should be elastic when stretched without delamination or breakage. After pausing the rotor, evenly sprinkle the dried and sieved modified nano-calcium carbonate on the surface of the melt, adding it in two batches with a 1-minute interval between each batch to avoid local accumulation. Restore the speed to 100 rpm and mix for 5 minutes. The torque will rise to 45 N·m. If the torque exceeds 50 N·m, it indicates that the filler has agglomerated. The speed should be reduced and the mixing time extended by 2 minutes. Pour the antioxidant composite powder into the feed port and mix quickly for 1 minute. During this time, the color of the melt should not change significantly. Open the top bolt of the internal mixer and discharge the melt into the tray of the demolding machine pre-coated with dimethyl silicone oil. Use a scraper to level the melt and cool it at room temperature for 30 minutes. After cooling, the hardness of the melt should reach Shore A 75. S2-7: Extrusion granulation. The cooled melt mixture was crushed into 2 cm × 2 cm pieces using a crusher. After passing through a 10-mesh sieve to remove impurities and lumps, the mixture was fed into an SHJ-35 twin-screw extruder. The extruder parameters were set as follows: zone 1 temperature 80℃, zone 2 temperature 95℃, zone 3 temperature 105℃, die temperature 110℃, zone 1 screw speed 90 rpm, vacuum degree -0.08 MPa, and water ring cooling water temperature 20±2℃. The state of the melt extruded from the die was observed. Normally, it should be a continuous, smooth, bubble-free cylinder. The extruded strip was immediately placed in a water ring cooling tank for 30 seconds. Then, the pelletizer was turned on and the speed was set to 250 rpm to cut the strip melt into 3 mm × 4 mm cylindrical pellets. The pellets were passed through a vibrating screen to remove large and broken particles. The qualified pellets were spread out and placed in a 50℃ forced-air drying oven to dry for 3 hours. Every hour, the pellets were turned over with a wooden rake to prevent clumping. After cooling to room temperature, the sheathed pellets were obtained and sealed in aluminum foil vacuum bags for storage.

[0031] Preparation Example 2-2: Reference Figure 2 As shown in Table 1, a granular material for a cold-resistant and crack-resistant cable sheath layer is provided. The raw materials and their proportions are shown in Table 1. The difference between this material and the material prepared in Example 2-1 is that the content of ethylene-vinyl acetate copolymer is reduced while the proportion of polyolefin elastomer is increased, which lowers the overall glass transition temperature of the sheath layer.

[0032] It should be noted that, unlike Preparation Example 2-1, Preparation Example 2-2 uses 8 parts of nano-calcium carbonate modified with KH560 silane coupling agent as the modified filler, which has better compatibility with polyolefin elastomers and enhances tear resistance and extrusion resistance.

[0033] Unlike Preparation Example 2-1, the thermoplastic polyurethane in Preparation Example 2-2 was replaced with a thermoplastic polyurethane with a high ether content, increasing the ether content from 50% to 70%. The low-temperature flexibility of ether bonds is better than that of ester bonds, which improves the elastic recovery rate under extreme low-temperature conditions and avoids permanent deformation after low-temperature bending. Since the thermoplastic polyurethane with high ether content has higher hygroscopicity, the drying time needs to be extended to 7 hours.

[0034] Preparation Examples 2-3: Reference Figure 2 As shown, a granular material for a freeze-resistant, crack-resistant, and cold-resistant cable sheath layer is provided. The raw materials and their proportions are shown in Table 1. The difference between this material and preparation example 2-1 is that thermoplastic polyurethane is replaced with polyether-type thermoplastic polyurethane. The ether bond structure is more resistant to bending fatigue than the ester bond, thereby reducing stress concentration during bending and improving the tear resistance of the cable.

[0035] It should be noted that, unlike Preparation Example 2-1, Preparation Example 2-3 uses 5 parts of carbon nanotubes as the modified filler. The carbon nanotubes form a three-dimensional conductive network in the sheath layer. Their high tensile strength can disperse local stress during bending, thereby improving the bending fatigue strength of the sheath layer. Since the melt strength of the carbon nanotube reinforced material is higher, the pelletizing speed needs to be reduced to 220 rpm to ensure that the strip melt is cut smoothly and the pellets are free of broken strips and burrs.

[0036] Unlike Preparation Example 2-1, Preparation Example 2-3 newly added 5 parts of ethylene propylene diene monomer (EPDM) rubber. The saturated main chain structure of EPDM rubber has strong resistance to dynamic oxidation and better compatibility with ethylene-vinyl acetate copolymer and thermoplastic polyurethane. It can absorb local stress during bending and extend the service life of the cable. Since EPDM rubber and ethylene-vinyl acetate copolymer have good compatibility but different melting rates, they need to be added after polyolefin elastomer and before thermoplastic polyurethane. In the internal mixing process, after the ethylene-vinyl acetate copolymer melts for 4 minutes, the polyolefin elastomer is added and mixed for 2 minutes, then EPDM rubber is added and mixed for 2 minutes, and finally polyether thermoplastic polyurethane is added and mixed for 4 minutes. Carbon nanotubes are added in three batches, with an interval of 1 minute each time, and mixed for 6 minutes until the melt is homogeneous.

[0037] Example 1: Refer to Figure 3 As shown, the present invention provides a technical solution: a freeze-resistant, crack-resistant, and cold-resistant cable, which includes a sheath layer, an insulation layer, and a conductor layer from the outside to the inside. The granules of the insulation layer are obtained by the method of Preparation Example 1-1, and the granules of the sheath layer are obtained by the method of Preparation Example 2-1.

[0038] A method for preparing a freeze-resistant, crack-resistant, and cold-resistant cable mainly includes the following steps: C1: Conductor preparation. A 10mm multi-strand stranded copper conductor is selected. The surface is wiped with alcohol to remove oil stains. The nickel plating layer thickness is checked with a film thickness gauge and found to be 5±1μm. The conductor is installed on a pay-off frame, and the tension is adjusted to 50N. Too loose a tension will cause the conductor to bend, while too tight a tension will stretch the conductor. C2: Co-extrusion unit commissioning. An SJ-65 / 65 type double-layer co-extrusion unit is used. The insulation extrusion section temperatures are set as follows: Zone 1: 110℃; Zone 2: 125℃; Zone 3: 135℃; Die head temperature: 130℃. The sheath extrusion section temperatures are set as follows: Zone 1: 100℃; Zone 2: 115℃; Zone 3: 125℃; Die head temperature: 130℃. Preheat for 40 minutes. After the temperatures of each section stabilize, add the corresponding granules to the insulation and sheath hoppers respectively. C3: Insulation extrusion. C3: Insulation Layer Screw. Start the insulation layer screw, maintaining a speed of 30 rpm. After the melt is stably extruded from the die, insert the conductor through the die core and adjust the traction speed to 5 m / min to achieve an insulation layer thickness of 1.5 mm. C4: Sheath Layer Covering. Start the sheath layer screw, maintaining a speed of 25 rpm. After the melt is evenly covered around the insulation layer to form a transition layer, use a diameter gauge to monitor the total diameter to ensure the transition layer thickness is 0.2 ± 0.1 mm. The transition layer should have no obvious interface. If delamination occurs, the sheath layer temperature needs to be reduced by 5℃. C5: Winding. After cooling the cable in a 25℃ cooling water bath, wind it into 20-meter coils with a winding tension of 80N to avoid stretching deformation. C6: Cross-linking Treatment. Immerse the entire cable in a 90±1℃ warm water cross-linking bath for 6 hours, keeping the water level submerged and the water flow rate maintained at 0.5 m / s. Record and adjust the water temperature every 30 minutes. After cross-linking is complete, remove the cable and allow it to cool naturally to room temperature to obtain the finished cable.

[0039] Example 2: A frost-resistant, crack-resistant, and cold-resistant cable, which differs from Example 1 in that the granules for the insulation layer and the sheath layer are from different sources, and the granules for the insulation layer are obtained by the method of Preparation Example 1-2, while the granules for the sheath layer are obtained by the method of Preparation Example 2-2.

[0040] Example 3: A frost-resistant, crack-resistant, and cold-resistant cable, which differs from Example 1 in that the granules for the insulation layer and the sheath layer are from different sources, and the granules for the insulation layer are obtained using the methods of Preparation Examples 1-3, while the granules for the sheath layer are obtained using the methods of Preparation Examples 2-3.

[0041] Comparative Example 1: A freeze-resistant, crack-resistant, and cold-resistant cable, which differs from Example 1 in that the insulation material retains only 100 parts of cross-linked polyethylene, and the granules of the sheath layer are obtained by the method of Preparation Example 2-1.

[0042] Comparative Example 2: A freeze-resistant, crack-resistant, and cold-resistant cable, which differs from Example 1 in that the granules of the insulation layer are obtained by the method of Preparation Example 1-1, but the drying pretreatment step is omitted, and the raw materials are used directly without drying; the granules of the sheath layer are obtained by the method of Preparation Example 2-1, but the antioxidant premixing and compatibility verification are omitted; no transition layer is set, and the insulation layer and sheath layer are directly extruded and compounded without a melt transition process.

[0043] Test Example 1: Low-Temperature Mechanical Performance Test; Elongation at Break of Insulation and Sheath Layers: Refer to standard GB / T1040.3-2006, unit: %, The test results of the freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 2. Tensile Strength Test: Refer to standard GB / T 1040.3-2006, unit: MPa, The test results of the freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 2. Tear Resistance Test: Refer to standard GB / T 1040.3-2006, unit: kN / m, The test results of the freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 2.

[0044]

[0045] Table 2 shows that in Example 2, the polyolefin elastomer content in the insulation layer increased from 17.6 parts to 25 parts, and halloysite nanotubes were used. The molecular chains maintained mobility at -50°C, resulting in a 36.8% increase in elongation at break compared to Example 1. The sheath layer used high-ether-bond thermoplastic polyurethane, which exhibited superior low-temperature resilience compared to conventional thermoplastic polyurethane, thus achieving an elongation at break of 600%. In Example 3, 0.5 parts of crosslinking agent were added, forming a hybrid structure with partial crosslinking and elasticity. The tensile strength reached 25 MPa, 13.6% higher than in Example 1. The sheath layer incorporated 5 parts of EPDM rubber, whose saturated main chain exhibited tear resistance, with a tear strength of 52 kN / m, 30% higher than in Example 1. In Comparative Example 1, the insulation layer lacked polyolefin elastomer and nanofillers. At -40°C, the crosslinked polyethylene crystallinity reached 65%, exhibiting high molecular chain rigidity and an elongation at break of only 150%, verifying that single-layer optimization could not resolve interlayer performance discontinuities. In Comparative Example 2, due to the raw materials not being dried, bubbles were generated during the mixing process, resulting in a decrease in the cohesiveness of the material and a 15%-20% lower mechanical properties compared to Example 1.

[0046] Test Example 2: Interlayer Performance and Interface Stability Test: Interlayer peel strength was tested according to standard GB / T2951.12-2008, unit: N / mm. A freeze-resistant, crack-resistant, and cold-resistant cable prepared in the test examples and comparative examples was used. The results are shown in Table 3. Difference in thermal expansion coefficient was tested according to standard GB / T 1036-2008, unit: ×10⁻⁶. -6 / ℃, the test examples and comparative examples of a freeze-thaw resistant and crack-resistant cold-resistant cable were tested, and the results are shown in Table 3. Interface state after freeze-thaw cycles: Referring to standard GB / T2951.41-2008, the test examples and comparative examples of a freeze-thaw resistant and crack-resistant cold-resistant cable were tested, and the results are shown in Table 3.

[0047]

[0048] Examples 1 to 3 use a co-extrusion process to form a compositionally gradient transition layer, combined with a shared polyolefin elastomer, with a difference in the coefficient of thermal expansion ≤ 1.8 × 10⁻⁶. -6 At low temperatures (℃), the shrinkage difference is small, therefore the peel strength is ≥2.3 N / mm. In Example 2, the polyolefin elastomer in the sheath layer is increased to 30 parts, which is close to the ratio of the insulation layer, and the difference in the coefficient of thermal expansion is reduced to 1.2 × 10⁻⁶. -6 At ℃, the highest peel strength is 2.5 N / mm. In Comparative Example 1, the insulation layer is pure cross-linked polyethylene, which has poor compatibility with the sheath layer, and the difference in the coefficient of thermal expansion is as high as 4.5 × 10⁻⁶. -6 At ℃, stress concentration during freeze-thaw cycles led to complete delamination. Comparative Example 2 did not form a transition layer, and the antioxidant was unevenly dispersed, making the interface prone to oxidation and aging, resulting in localized delamination after 300 cycles.

[0049] Test Example 3: Electrical Performance and Weather Resistance Tests: Insulation Resistance Test: Referencing standard GB / T 3048.5-2007, unit: Ω・cm, the test results of a freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 4. Insulation Resistance Retention Rate After Freeze-Thaw Test: The test results of a freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 4. Ultraviolet Aging Performance Test: Referencing standard GB / T 16422.3-2014, the test results of a freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples are shown in Table 4.

[0050]

[0051] In Example 3, the insulation layer was supplemented with flake montmorillonite and a crosslinking agent. After 300 freeze-thaw cycles, the insulation resistance retained 95%, and no cracks appeared after UV aging, making it suitable for long-term outdoor use. Although Example 2 had a slightly lower insulation resistance at room temperature due to its high polyolefin elastomer content, it still maintained 8.5 × 10⁻⁶ at -40°C. 13 Ω・cm, meeting the electrical requirements of extremely cold environments. In Comparative Example 1, the insulation layer lacked antioxidants, resulting in accelerated oxidation aging during freeze-thaw cycles and an insulation resistance retention rate of only 60%. After UV aging, the pure cross-linked polyethylene developed cracks due to the absence of polyolefin elastomer buffer.

[0052] Test Example 4: Dynamic Bending Performance Test: Low-Temperature Bending Fatigue Performance Test: Referring to standard GB / T 5470-2008, a freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples was tested. The results are shown in Table 5. Insulation Resistance Retention Rate Test after Bending: A freeze-resistant and crack-resistant cold-resistant cable prepared in the example and comparative examples was tested. The results are shown in Table 5.

[0053]

[0054] In Example 3, the insulation layer uses a high melt strength polyolefin elastomer, combined with 0.5 parts of crosslinking agent to form a three-dimensional network. After 1000 bends, the molecular chain slippage is only 8%, so there are no cracks. The carbon nanotubes in the sheath layer form a conductive network, which disperses the bending stress and makes the insulation resistance retention rate reach 94%, verifying the effectiveness of the bending resistance and crack prevention design.

[0055] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A freeze resistant, anti-cracking, cold resistant cable, characterized in that, From inside to outside, it includes conductor layer, insulation layer and sheath layer, the insulation layer and sheath layer form composition gradient transition layer through co-extrusion process, the thickness of the transition layer is 0.1-0.3mm; the insulation layer is made of the following materials by weight, including crosslinked polyethylene 90-100 parts, polyolefin elastomer 17.6-25 parts, modified filler 2-4 parts, antioxidant 1010 0.24-0.3 parts, antioxidant 168 0.24-0.3 parts, dicumyl peroxide crosslinking agent 0-0.5 parts; the sheath layer is made of the following materials by weight, including ethylene-vinyl acetate copolymer 85-100 parts, polyolefin elastomer 21.4-30 parts, thermoplastic polyurethane 15-21.4 parts, modified filler 5-8 parts, antioxidant 1010 0.29 parts, antioxidant 168 0.29 parts, ternary ethylene-propylene rubber 0-5 parts; the composite antioxidant system in the insulation layer and sheath layer is compounded by antioxidant 1010 and antioxidant 168 in a ratio of 1:

1.

2. A freeze resistant, anti-cracking cold-resistant cable according to claim 1, characterized in that: The modified filler of the insulation layer is one of spherical modified nano calcium carbonate, halloysite nanotube or flaky montmorillonite, and the modified filler of the sheath layer is one of modified nano calcium carbonate, nano calcium carbonate modified by silane coupling agent containing epoxy group or carbon nanotube.

3. A freeze resistant, anti-cracking cold-resistant cable according to claim 1, characterized in that: The raw materials for preparing the insulation layer and the sheath layer both contain polyolefin elastomer and composite antioxidant system, and the polyolefin elastomer is ethylene-octene copolymer with octene monomer mass ratio of 20%-30%.

4. A freeze resistant, anti-cracking cold-resistant cable according to claim 1, characterized in that: The material composition of the composition gradient transition layer contains the base materials of the insulation layer and the sheath layer.

5. A freeze resistant, anti-cracking cold-resistant cable according to claim 1, characterized in that: The polyolefin elastomer in the insulation layer and the sheath layer is ethylene-octene copolymer, and the thermoplastic polyurethane in the sheath layer is polyether type.

6. A process for the preparation of a frost resistant, crack resistant, cold resistant cable for the preparation of a frost resistant, crack resistant, cold resistant cable according to any one of claims 1 to 5, characterized in that, It comprises the following steps: C1: selecting stranded conductor, after surface oil removal and plating thickness verification, installing on the pay-off rack and adjusting the pay-off tension to 50N; C2: setting the extrusion temperature and parameters of each section of the insulation layer and the sheath layer, and adding the insulation layer granules and the sheath layer granules after preheating; C3: start the insulation layer screw, and after the melt is stable, pass through the conductor, control the traction speed to ensure the thickness meets the standard; C4: start the sheath layer screw, make the melt uniformly cover the insulation layer to form a transition layer, monitor the thickness of 0.1-0.3mm and the interface without delamination; C5: after cooling in a 25℃ cooling water tank, wind with 80N winding tension according to the set length; C6: place the whole cable in a warm water crosslinking tank, control the temperature, time and water flow, and cool to room temperature after completion.

7. A process for the preparation of a freeze resistant, anti-cracking, cold resistant cable as claimed in claim 6, wherein: The preparation method of the insulation layer granules comprises the following steps: S1-1: weighing cross-linked polyethylene, polyolefin elastomer, modified filler and antioxidant according to the proportion, and ensuring that the specifications of the raw materials meet the requirements; S1-2: vacuum drying the cross-linked polyethylene and polyolefin elastomer particles, controlling the temperature, vacuum degree and time, and ensuring that the moisture content meets the standards; S1-3: air-drying the modified filler, and screening the agglomerates after cooling and sealing for storage; S1-4: grinding and mixing the antioxidants 1010 and 168 and screening to prepare a composite antioxidant; S1-5: sequentially feeding the polymers, modified filler and antioxidant into a banbury mixer, controlling the temperature, rotating speed and time, and uniformly melting and blending the materials; S1-6: crushing the melt after banburying, extruding through a double-screw extruder, cooling, cutting and screening and drying and sealing for storage.

8. A process for the preparation of a freeze resistant, anti-cracking, cold resistant cable as claimed in claim 6, wherein: The preparation method of the sheath layer granules comprises the following steps: S2-1: weighing ethylene-vinyl acetate copolymer, polyolefin elastomer, thermoplastic polyurethane, modified filler and antioxidant according to the proportion, and confirming that the specifications of the raw materials meet the requirements; S2-2: vacuum drying the ethylene-vinyl acetate copolymer and polyolefin elastomer, controlling the temperature, vacuum degree and time, and ensuring that the moisture meets the standards; S2-3: separately vacuum drying the thermoplastic polyurethane, controlling the temperature to avoid softening, and ensuring that the particles are in good condition after drying; S2-4: air-drying the modified filler, screening the agglomerates after cooling and sealing for storage; S2-5: grinding and mixing the antioxidants and screening, and verifying the compatibility of the antioxidants with the matrix material; S2-6: sequentially feeding the polymers, modified filler and antioxidant, controlling the temperature, rotating speed and time, and uniformly melting and blending the materials; S2-7: crushing the melt after banburying, extruding through a double-screw extruder, cooling, cutting, screening and drying and sealing for storage.

9. A process for the preparation of a freeze resistant, anti-cracking, cold resistant cable as claimed in claim 8, characterized in that: In the compatibility verification, the antioxidant composite powder and ethylene-vinyl acetate copolymer particles with a mass ratio of 1:10 are melt-blended and stirred uniformly at 120±5℃, the blend is cooled and cut to observe the cross section, and it is confirmed that there are no antioxidant agglomerate particles.

10. A process for the preparation of a freeze resistant, anti-cracking, cold resistant cable as claimed in claim 6, wherein: In the extrusion process, the base temperature gradient of the insulation layer and the sheath layer is that the temperature of the first zone of the insulation layer extrusion section is 105-115℃, the temperature of the second zone is 120-130℃, the temperature of the third zone is 130-140℃, the die temperature is 125-135℃, the temperature of the first zone of the sheath layer extrusion section is 95-105℃, the temperature of the second zone is 110-120℃, the temperature of the third zone is 120-130℃, and the die temperature is 125-135℃.

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