A highly flexible, low-smoke, halogen-free insulated shielded cable and its preparation method

Abstract

This invention discloses a highly flexible, low-smoke, halogen-free insulated shielded cable and its preparation method. The conductor is manufactured using a layered staggered stranding process and filled with flexible fiber bundles, combined with low-temperature annealing under inert gas protection, which eliminates the internal stress of stranding and enhances the bending resistance of the conductor core. The insulation material uses a multi-resin compound as the matrix, and the composite flame retardant is surface modified and a compound toughening agent is added to optimize the compatibility between the flame retardant and the matrix, avoiding material embrittlement. The three-layer co-extruded insulation layer structure further improves the flexibility and buffering performance of the insulation part. The composite shielding structure, which combines aluminum-plastic composite tape wrapping with tin-plated ultrafine copper wire double oblique braiding, ensures effective shielding against external electromagnetic interference and guarantees signal transmission quality. Furthermore, the application of flexible adhesive and the filling of flame-retardant sealant alleviate the problem of increased rigidity caused by high-density shielding.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically a highly flexible, low-smoke, halogen-free insulated shielded cable and its preparation method. Background Technology

[0002] Low-smoke halogen-free cables release no toxic halogen gases and produce low smoke concentrations during combustion, effectively reducing secondary fire hazards. They have gradually replaced traditional halogen-containing cables as the mainstream choice. However, existing low-smoke halogen-free insulated shielded cables still have the following technical problems in practical applications: The insulation layer of existing low-smoke halogen-free insulated cables is mostly made of polyolefin-based materials. To achieve flame retardant performance, a high proportion of inorganic flame retardants, such as aluminum hydroxide and magnesium hydroxide, are often added. High filler content will cause material embrittlement, decrease elongation at break, and significantly reduce cable flexibility. The bending radius is difficult to meet the requirements for laying in narrow spaces. During bending, problems such as insulation layer cracking and shielding layer peeling are likely to occur, which will affect the service life and electrical safety of the cable.

[0003] Secondly, traditional shielding layers mostly use a single metal wire braid or metal strip wrapping structure. There is a trade-off between braiding density and flexibility. High-density braiding can improve shielding effectiveness, but it will significantly increase the rigidity of the cable. Low-density braiding cannot effectively shield external electromagnetic interference, thus affecting the signal transmission quality.

[0004] In addition, under the existing manufacturing process, the interface bonding between the insulation layer and the shielding layer is not good, and delamination is prone to occur, which will further reduce the flexibility and structural stability of the cable. Summary of the Invention

[0005] The purpose of this invention is to provide a highly flexible, low-smoke, halogen-free insulated shielded cable and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable, comprising: Preferably, in the conductor preparation stage, industrial-grade oxygen-free soft copper wire with a purity ≥99.99% is selected, free from defects such as oxidation, inclusions, and peeling. It is drawn into ultra-fine monofilaments with a diameter of 0.10-0.13mm by a wire drawing equipment. The diameter tolerance of the ultra-fine monofilaments is controlled at ±0.002mm. After drawing, the surface of the monofilaments is free from defects such as burrs and oxide layers. The wire drawing equipment is a high-speed wet continuous wire drawing machine, and the wire drawing die is a polycrystalline diamond die to ensure the dimensional accuracy and surface quality of the monofilaments.

[0007] The conductor core is formed by twisting ultra-fine copper wires in three layers: two wires in the inner layer, three wires in the middle layer, and five wires in the outer layer. The twisting pitch ratio of each layer is controlled to be 12.5-13.5 times. The twisting direction is left-handed for the inner layer, right-handed for the middle layer, and left-handed for the outer layer. Flexible fiber bundles with a diameter of 0.01-0.02 mm are filled in the gaps between each layer. The flexible fiber bundles are polyester flexible fiber bundles, made of polyester filaments with a melting point of 250-260℃ and a breaking strength ≥5cN / dtex. The fiber bundles are free from twisting and fraying. After stranding, the conductor core is placed in an inert gas protective atmosphere for low-temperature continuous annealing. The inert gas is a mixture of argon and nitrogen in a volume ratio of 2:1, and the inert gas introduction rate is 2-3 L / min to ensure that the annealing atmosphere is an oxygen-free environment. The annealing temperature is controlled at 285-295℃, the holding time is 16-18 min, and the cooling rate is controlled at 5℃ / min. The internal stress of stranding is eliminated by low-temperature annealing, and finally the conductor core is obtained.

[0008] Preferably, the insulation material modification stage uses ethylene-vinyl acetate copolymer, polyolefin elastomer, and thermoplastic polyurethane as the base resin, mixed in a mass ratio of 4:3:3. The ethylene-vinyl acetate copolymer contains 28% vinyl acetate, the polyolefin elastomer has a melt index of 1.5 g / 10 min (190℃ / 2.16 kg), and the thermoplastic polyurethane has a Shore hardness of 85A. All three are granular raw materials with a particle size of 2-3 mm and no agglomeration. The total mass of the added base resin... The composite flame retardant comprises 27-29% by weight, wherein the composite flame retardant is composed of aluminum hydroxide and magnesium hydroxide in a mass ratio of 2:1, the particle size of the composite flame retardant is 1-3μm, the particle size distribution is uniform, and there is no large particle agglomeration. Both aluminum hydroxide and magnesium hydroxide are ultrafine powders that have undergone surface pretreatment. In addition, 3.5-4.5% by weight of the matrix resin is added, along with 2.5-3% by weight of the composite silane coupling agent, 1.2-1.8% by weight of the composite antioxidant, and 0.3-0.5% by weight of the compatibilizer. First, the composite flame retardant is placed in a high-speed mixer and pretreated for 10 minutes at 85-88℃ and 800r / min. Then, a compound silane coupling agent is added for surface modification, and an inert gas is introduced for protection. The modified composite flame retardant is then mixed with the matrix resin, compound toughening agent, compound antioxidant and compatibilizer, and fed into an internal mixer. The mixture is then internally mixed for 22-24 minutes at 135-138℃ and 600r / min. The discharge temperature of the internally mixed material is controlled at 140-145℃. After internal mixing, the material is in a uniform molten state and there is no raw rubber or clumping. The material is then extruded and granulated using a twin-screw extruder to obtain a highly flexible, low-smoke, halogen-free insulating material. The high-speed mixer is a vertical high-speed mixer, and the internal mixer is a meshing rotor internal mixer. The twin-screw extruder has a screw length-to-diameter ratio of 40:1, and the extruder die temperature is controlled at 135-138℃. After pelleting, the insulating material particles have a particle size of 3-4mm and a moisture content of ≤0.05%.

[0009] Preferably, the insulation layer extrusion stage employs a three-layer co-extrusion extruder, where the insulation material prepared in the insulation material modification stage is used as the inner insulation layer, intermediate buffer layer, and outer insulation layer, respectively, and simultaneously extruded and coated onto the surface of the conductor core; the thickness of the inner insulation layer is controlled to be 0.32-0.38 mm, the thickness of the intermediate buffer layer is 0.12-0.14 mm, 5% of a flexible toughening agent is added separately, the thickness of the outer insulation layer is 0.32-0.38 mm, and the total insulation layer thickness is 0.76-0.9 mm; The extrusion process employs a gradient temperature control technology. The barrel temperature is controlled sequentially from the feed inlet to the die head at 122℃, 132℃, 136℃, and 140℃, with the die head temperature controlled at 138℃. The extrusion speed is controlled at 8.5-9.5 m / min. The eccentricity of the insulation layer is controlled to ≤3.5% through a precision mold. The precision mold is a cemented carbide mold with a dimensional accuracy of ±0.01 mm and a concentricity error between the mold core and the mold sleeve of ≤0.005 mm. After extrusion, air cooling and water cooling are used in combination. The cooling water temperature is controlled at 26-29℃, and the cooling time is 10-12 min to obtain the insulation layer. The air speed in the air cooling section is controlled at 3-5 m / s, and the air cooling distance is 1.5-2 m. The material first undergoes preliminary cooling by air cooling before entering the water cooling section.

[0010] Preferably, in the shielding layer preparation stage, the surface of the insulation layer obtained in the insulation layer extrusion stage is first wrapped with an ultra-thin aluminum-plastic composite tape with a thickness of 0.03-0.04 mm. The thickness tolerance of the ultra-thin aluminum-plastic composite tape is ±0.002 mm, wherein the aluminum layer has a thickness of 0.01 mm and a tolerance of ±0.001 mm, the flame-retardant PE plastic layer has a thickness of 0.02-0.03 mm and a tolerance of ±0.002 mm, the aluminum layer is pure aluminum foil with a purity ≥99.9%, and the PE plastic layer is halogen-free flame-retardant polyethylene. Grade V-0; the wrapping overlap rate is controlled at 27-29%, the wrapping tension is uniformly controlled at 6-7N, a spiral wrapping method is adopted, the wrapping angle is 45°±1° with the cable axis, and a 0.01-0.015mm thick flexible adhesive is sprayed simultaneously during the wrapping process; the flexible adhesive is a water-based polyurethane adhesive with a solid content of 30-35%, a viscosity of 500-800mPa·s (25℃), and a drying film-forming temperature of 60-70℃, and no embrittlement or cracking after film formation; Subsequently, tin-plated ultrafine copper wire with a diameter of 0.08-0.09 mm was used. The tin-plated ultrafine copper wire had a tensile strength ≥200 MPa, an elongation at break ≥15%, and a bonding force between the tin plating layer and the copper wire substrate ≥5 N, exhibiting no tin detachment during bending. The copper wire substrate was oxygen-free copper with a purity ≥99.99%, and the tin plating layer was pure tin with a thickness tolerance of ±0.001 mm. The tin plating layer adhesion was ≥5 N, and no tin detachment was observed during bending tests. Double oblique braiding was then performed on the surface of the aluminum-plastic composite tape, with a braiding density controlled at 93-94%, a braiding angle of 35-38° to the cable axis, and controlled braiding tension. The material has a strength of 3.5-4.5N and is produced using a four-spindle synchronous braiding process. This process employs a high-speed braiding machine with a rotation speed of 300-350 r / min. During the braiding process, the tension fluctuation of the copper wire is ≤0.5N, ensuring a smooth surface of the braided layer without skipped or broken wires. Simultaneously, a small amount of flexible flame-retardant sealant is filled into the braiding gaps. This flexible flame-retardant sealant is a halogen-free flame-retardant silicone sealant with a flame retardant rating of V-0, a Shore hardness of 20-30A, and a solid content ≥95%. After filling, it is free of bubbles and shrinkage cavities, exhibits good compatibility with tin-plated ultrafine copper wire and aluminum-plastic composite tape, and has no corrosive effect. After weaving, a modified flexible adhesive with a thickness of 0.025-0.03mm is coated on the surface of the shielding layer to form a flexible composite shielding layer.

[0011] Preferably, in the interface activation stage, the cable core covered with a flexible composite shielding layer is fed into a plasma surface treatment device. A mixture of argon and oxygen is used as the plasma gas source, and nitrogen is added as an auxiliary gas source at a volume ratio of 0.5-1% of the mixed gas source. The volume ratio of argon to oxygen is 3:1. The plasma device is an atmospheric pressure plasma treatment device. The cable traction speed during treatment is consistent with the insulation extrusion speed, which is 8.5-9.5 m / min. The plasma glow uniformly covers the surface of the cable core, with no untreated areas. The treatment power is controlled at 160-190W, the treatment time is 3.5-4.5 min, and the treatment distance is controlled at 6-7 mm. During the treatment, uniform traction synchronized with the insulation extrusion speed is used. The plasma activation treatment removes impurities and oil stains from the interface between the insulation layer and the shielding layer. After treatment, immediately spray a layer of modified flexible adhesive onto the interface, with the spraying amount controlled at 0.012-0.018 g / cm². After spraying, the modified flexible adhesive forms a continuous and uniform film on the surface of the cable core, without any exposed substrate or dripping. The film thickness is controlled at 0.01-0.015 mm, providing a good interfacial bonding foundation for subsequent curing. Then, it is placed in a constant temperature curing oven and cured in sections at 85-88℃, first at 85℃ for 6 minutes, and then at 88℃ for 8 minutes.

[0012] Preferably, in the outer sheath extrusion stage, a low-smoke halogen-free elastomer of the same system as the insulating material in the insulation modification stage is selected, and 4.5-5.5% of abrasion-resistant agent, 3.2-3.8% of UV stabilizer, and 0.4-0.6% of anti-aging agent are added according to the total mass of the matrix resin. The anti-aging agent is 2-mercaptobenzimidazole (MB), industrial grade pure product, with an effective content ≥99%. The polytetrafluoroethylene microparticles in the abrasion-resistant agent have a particle size of 1-3μm, and the nano-silica particles have a particle size of 20-30nm. The UV stabilizer UV-531 is 2-hydroxy-4-n-octyloxybenzophenone, and UV-327 is 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, both of which are industrial grade pure products with an effective content ≥98%. After being uniformly mixed in a high-speed mixer, the material is fed into a single-screw extruder and extruded onto the surface of the cable core to form an outer sheath. The extrusion temperature is controlled at 130-133℃, and the extrusion speed is synchronized with the insulation extrusion speed. An online thickness closed-loop control system is used to monitor the outer sheath thickness in real time, controlling the thickness to 0.85-0.95mm, with a core eccentricity ≤2.5%. The online thickness closed-loop control system uses a laser thickness gauge with a detection accuracy of ±0.001mm and a detection frequency of 10 times / second. When the detected thickness exceeds the set range, the system automatically adjusts the screw speed and traction speed of the extruder to achieve real-time thickness feedback adjustment.

[0013] After extrusion, the material is placed in a shaping and cooling tank and cooled with gradient water temperature for 22-24 minutes. After cooling and shaping, the material is pulled at a constant speed by a traction machine to obtain the finished cable to be tested.

[0014] The specific steps of the gradient water temperature cooling are as follows: the cooling tank is divided into three sections from the inlet to the outlet. The water temperature of the first section is 40±2℃, the water temperature of the second section is 31±2℃, and the water temperature of the third section is 25±2℃. The cooling time of each section is 7-8 minutes. The water temperature gradually decreases from the first section to the third section, and the cooling rate is 3℃ / 5min to avoid the outer sheath from generating internal stress due to sudden cooling.

[0015] Preferably, in the finished product testing stage, the finished cable to be tested obtained in the outer sheath extrusion stage is sent into a constant temperature and humidity aging treatment chamber for gradient temperature and humidity aging treatment. First, it is kept warm and moist at 40°C and 60% humidity for 24 hours, then kept warm and moist at 25°C and 50% humidity for 48 hours, and finally kept warm and moist at 15°C and 45% humidity for 24 hours, through three stages of gradient aging treatment. After the aging process is completed, the cable undergoes a full-performance integrated test, which includes flexibility testing, low-smoke halogen-free testing, shielding effectiveness testing, electrical performance testing, mechanical performance testing, and additional testing. Defective products are reworked, while qualified products are cut, rolled up, and packaged to finally obtain a high-flexibility, low-smoke halogen-free insulated shielded cable.

[0016] This invention also provides a highly flexible, low-smoke, halogen-free insulated shielded cable, prepared using the above-described method, comprising, based on 1000 parts by weight: Conductor core: 490-530 parts by weight; Three-layer co-extruded insulation layer: 180-200 parts by weight; Flexible composite shielding layer: 60-70 parts by weight; Interface adhesive layer: 2-3 parts by weight; Outer sheath: 145-167 parts by weight; The conductor core adopts a layered staggered stranded structure, and its components and weight parts are as follows: Oxygen-free soft copper wire: 488-526 parts by weight; Flexible fiber bundles: 2-4 parts by weight, made of polyester fiber; The insulation layer is made of a highly flexible, low-smoke, halogen-free insulating material, and the specific components and their weight parts are as follows: Matrix resin: 100 parts by weight, of which 40 parts by weight of ethylene-vinyl acetate copolymer, 30 parts by weight of polyolefin elastomer POE, and 30 parts by weight of thermoplastic polyurethane TPU; Composite flame retardant: 27-29 parts by weight, of which aluminum hydroxide (ATH) is 18-19.3 parts by weight and magnesium hydroxide (MDH) is 9-9.7 parts by weight, with a mass ratio of 2:1; the composition and proportions are completely consistent with those of the composite flame retardant for the insulation layer (ATH:MDH=2:1); Silane coupling agent: 3.5-4.5 parts by weight, of which KH-550 is 1.75-2.25 parts by weight and KH-560 is 1.75-2.25 parts by weight, in a mass ratio of 1:1; wherein KH-550 is γ-aminopropyltriethoxysilane and KH-560 is γ-glycidoxypropyltrimethoxysilane, both of which are industrial grade pure products with an effective content ≥98%; Flexible toughening agent: 2.5-3 parts by weight, of which 1.875-2.25 parts by weight of polybutene PB and 0.625-0.75 parts by weight of hydroxyl-terminated liquid nitrile rubber HTBN are compounded in a mass ratio of 3:1. Antioxidant: 1.2-1.8 parts by weight, of which antioxidant 1010 is 0.8-1.2 parts by weight and antioxidant 168 is 0.4-0.6 parts by weight, in a mass ratio of 2:1. Compatibilizer: 0.3-0.5 parts by weight, using maleic anhydride-grafted polyolefin PO-g-MAH; Additional addition: 5 parts by weight of flexible toughening agent, consistent with the above-mentioned flexible toughening agent composition, calculated based on the weight of the intermediate buffer layer insulation material; The inner insulation layer and the outer insulation layer each account for 40% of the total weight of the insulation layer, and the intermediate buffer layer accounts for 20%. The shielding layer is composed of aluminum-plastic composite tape, tin-plated ultrafine copper wire, flexible adhesive, and flame-retardant sealant. The components and their weight parts are as follows: Ultra-thin aluminum-plastic composite belt: 15-18 parts by weight, of which aluminum layer is 4.5-5.4 parts by weight and flame-retardant PE plastic layer is 10.5-12.6 parts by weight; Tin-plated ultrafine copper wire: 35-40 parts by weight, of which copper wire accounts for 34.8-39.8 parts by weight and tin plating is the remaining parts by weight, with a tin plating thickness of 0.005-0.008 mm; Flexible adhesive: 2-3 parts by weight; Modified flexible adhesive for shielding layer: 4-5 parts by weight, of which 3.2-4 parts by weight of polyurethane adhesive and 0.8-1 parts by weight of neoprene rubber, in a mass ratio of 4:1, and 0.02-0.025 parts by weight of micronized silica gel, accounting for 0.5% of the total weight of modified adhesive; Flexible flame retardant sealant: 4 parts by weight; The interface bonding layer is used for the tight bonding between the insulation layer and the shielding layer. Its composition is the same as that of the modified flexible adhesive used in the shielding layer coating stage. The components and their weight parts are as follows: Modified flexible adhesive for the interface bonding layer: 2-3 parts by weight, of which 1.6-2.4 parts by weight of polyurethane adhesive and 0.4-0.6 parts by weight of neoprene rubber, in a mass ratio of 4:1, and 0.01-0.015 parts by weight of micronized silica gel, accounting for 0.5% of the total weight of the modified adhesive; The outer sheath is made of a low-smoke halogen-free elastomer of the same system as the insulation material. The components and their weight proportions are based on the total weight of the sheath material, as follows: Matrix resin: 100 parts by weight, consistent with the matrix resin composition of the insulating layer: 40 parts by weight of EVA, 30 parts by weight of POE, and 30 parts by weight of TPU; Wear-resistant agent: 4.5-5.5 parts by weight, of which 3.375-4.125 parts by weight of polytetrafluoroethylene micro powder and 1.125-1.375 parts by weight of nano-silica, in a mass ratio of 3:1. UV protectant: 3.2-3.8 parts by weight, of which UV-531 is 2.13-2.53 parts by weight and UV-327 is 1.07-1.27 parts by weight, in a mass ratio of 2:1. Anti-aging agent: 0.4-0.6 parts by weight; Composite flame retardant: 27-29 parts by weight; Silane coupling agent: 3.5-4.5 parts by weight; Flexible toughening agent: 2.5-3 parts by weight; Compatibilizer: 0.3-0.5 parts by weight.

[0017] The beneficial effects of this invention are as follows: 1. The conductor of this invention adopts a layered staggered stranding process and is filled with flexible fiber bundles. Combined with low-temperature annealing under inert gas protection, the internal stress of stranding is eliminated while enhancing the bending resistance of the conductor core. The insulation material uses a variety of resins as the matrix, the composite flame retardant is surface modified and a compound toughening agent is added to optimize the compatibility between the flame retardant and the matrix, avoid material embrittlement, and the three-layer co-extruded insulation layer structure further improves the flexibility and buffer performance of the insulation part, so that the cable can adapt to the laying requirements of narrow spaces and is less prone to insulation layer cracking when bent.

[0018] 2. This invention adopts a composite shielding structure that combines aluminum-plastic composite tape wrapping with double oblique braiding of tin-plated ultra-fine copper wire. This ensures effective shielding against external electromagnetic interference and guarantees signal transmission quality. Furthermore, the application of flexible adhesive and the filling of flame-retardant sealant alleviate the problem of increased rigidity caused by high-density shielding. This makes the composite shielding layer both flexible and airtight, preventing the shielding layer from falling off or the shielding effectiveness from decreasing during cable bending. It is suitable for various complex application scenarios.

[0019] 3. This invention removes interface impurities and improves interface roughness through plasma interface activation treatment. Combined with the spraying and segmented curing of modified flexible adhesive, the insulation layer and shielding layer are tightly bonded, avoiding interlayer delamination caused by bending and vibration during use. The outer sheath uses a low-smoke halogen-free elastomer of the same system as the insulation material. Combined with gradient cooling process, the compatibility of each layer material is enhanced. The gradient temperature and humidity aging treatment of the finished product further eliminates the internal stress of each layer, making the overall cable structure more stable, while improving mechanical properties and environmental adaptability. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the overall manufacturing process of the high-flexibility, low-smoke, halogen-free insulated shielded cable of this invention. Figure 2 This is a flowchart of the insulation material modification stage of the present invention. Figure 3 This is a flowchart of the shielding layer preparation stage of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figures 1 to 3 As shown in the figure, this invention provides a method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable, the process steps and parameters of which are as follows: In the conductor preparation stage, oxygen-free soft copper wire with a purity of 99.99% was drawn into an ultra-fine monofilament with a diameter of 0.12 mm. It was then stranded in a 2+3+5 layered staggered manner with a stranding pitch ratio of 13 times and filled with a 0.015 mm polyester flexible fiber bundle. The conductor was then annealed at a low temperature of 290℃ under inert gas (argon-nitrogen 2:1) protection for 17 min at a cooling rate of 5℃ / min.

[0023] In the insulation material modification stage, EVA (VA 28%), POE, and TPU were used as the matrix in a ratio of 4:3:3. A composite flame retardant (ATH:MDH=2:1, particle size 2μm) was added at 28% of the total mass of the matrix. 4% silane coupling agent, 2.8% flexible toughening agent, 1.5% antioxidant, and 0.4% compatibilizer were also added. After pretreatment of the flame retardant at 86℃, the silane coupling agent was modified, and the mixture was internally mixed at 136℃ for 23 minutes and then granulated by twin-screw extrusion.

[0024] The insulation layer is co-extruded in three layers during the extrusion stage. The inner / outer insulation layer is 0.35mm thick, the middle buffer layer is 0.13mm (with an additional 5% flexible toughening agent), and the total thickness is 0.83mm. The barrel temperature gradient is controlled at 122 / 132 / 136 / 140℃, the die head at 138℃, the extrusion speed is 9m / min, the eccentricity is controlled by precision die control at ≤3%, and air cooling + water cooling are used for synergistic cooling (water temperature 28℃, time 11min).

[0025] During the shielding layer preparation stage, a 0.035mm ultra-thin aluminum-plastic composite tape is wrapped with an overlap rate of 28% and a wrapping tension of 6.5N. A 0.012mm flexible adhesive is then sprayed on. 0.085mm tin-plated ultra-fine copper wire is double-obliquely woven with a density of 93.5% and a weaving tension of 4N. After filling with a flexible flame-retardant sealant, a 0.028mm modified flexible adhesive is applied.

[0026] The interface activation stage uses an argon-oxygen 3:1 mixed gas source with 0.8% nitrogen assistance, a processing power of 175W, a time of 4min, a processing distance of 6.5mm, and a traction speed of 9m / min; after spraying 0.015mm of modified flexible adhesive, it is cured in stages by holding at 85℃ for 6min and then at 88℃ for 8min.

[0027] The outer sheath is extruded using a low-smoke halogen-free elastomer of the same system, with 5% wear-resistant agent, 3.5% UV stabilizer, and 0.5% anti-aging agent MB added. The extrusion temperature is 132℃, the extrusion speed is 9m / min, the thickness of the outer sheath is controlled online with a closed loop to 0.9mm, and the eccentricity is ≤2%. Gradient water cooling (40→31→25℃) is used, with a total cooling time of 23min.

[0028] The finished product undergoes a gradient temperature and humidity aging treatment at 40℃ / 60%RH×24h→25℃ / 50%RH×48h→15℃ / 45%RH×24h, followed by full-performance linkage testing. Example

[0029] The parameters selected in this embodiment are the lower limit of the range, which is suitable for the manufacturing requirements of small and medium-sized cables. The specific process parameters are as follows: Conductor preparation stage: 99.99% pure oxygen-free soft copper wire is selected and drawn into ultra-fine monofilaments with a diameter of 0.10 mm using a high-speed wet continuous drawing machine, with a diameter tolerance of ±0.002 mm; the conductor core is formed by a 2+3+5 layered staggered stranding process, with a stranding pitch ratio of 12.5 times, and the stranding direction is left-handed for the inner layer, right-handed for the middle layer, and left-handed for the outer layer. Each layer gap is filled with a 0.01 mm polyester flexible fiber bundle; after stranding, it is placed under the protection of argon and nitrogen 2:1 inert gas (introduction rate 2 L / min) and continuously annealed at a low temperature of 285℃ for 16 min, with a cooling rate of 5℃ / min to eliminate the internal stress of stranding.

[0030] Insulation material modification stage: Using EVA (VA 28%), POE (melt index 1.5 g / 10 min), and TPU (Shore 85A) in a 4:3:3 ratio as the matrix resin, 27% of a composite flame retardant (ATH:MDH = 2:1, particle size 1 μm) by weight of the matrix resin was added. Simultaneously, 3.5% of a compounded silane coupling agent (KH-550:KH-560 = 1:1), 2.5% of a compounded flexible toughening agent (PB:HTBN = 3:1), and 1.2% of the same agent by weight of the matrix resin were added. The compound antioxidant (1010:168=2:1) ​​and compatibilizer PO-g-MAH were added. The composite flame retardant was pretreated at 85℃ and 800r / min for 10min, and then surface modified under inert gas protection with the addition of silane coupling agent. It was then mixed with the remaining components and kneaded at 135℃ and 600r / min for 22min. The mixture was then extruded and granulated through a twin-screw extruder with a length-to-diameter ratio of 40:1 (die temperature 135℃) to obtain an insulating material with a particle size of 3mm and a moisture content of ≤0.05%.

[0031] Insulation layer extrusion stage: The conductor core is coated by a three-layer co-extrusion process, with an inner insulation layer of 0.32mm, an intermediate buffer layer of 0.12mm (with an additional 5% flexible toughening agent), and an outer insulation layer of 0.32mm, for a total thickness of 0.76mm; the barrel temperature gradient is controlled at 122℃, 132℃, 136℃, and 140℃, the die head at 138℃, and the extrusion speed is 8.5m / min; the insulation layer eccentricity is controlled at 2.8% using a hard alloy precision die (accuracy ±0.01mm); after extrusion, the insulation layer is obtained by combined air cooling (air speed 3m / s, distance 1.5m) and water cooling (water temperature 26℃) for 10min.

[0032] Shielding layer preparation stage: A 0.03mm ultra-thin aluminum-plastic composite tape (0.01mm aluminum layer, 0.02mm flame-retardant PE plastic layer) is spirally wrapped around the surface of the insulation layer, with a wrapping overlap rate of 27%, tension of 6N, and wrapping angle of 45°±1°. Simultaneously, a 0.01mm water-based polyurethane flexible adhesive is sprayed. 0.08mm tin-plated ultra-fine copper wire is used for double oblique weaving, with a weaving density of 93%, a weaving angle of 35°, tension of 3.5N, and four spindles are simultaneously woven (speed 300r / min). The weaving gaps are filled with flexible flame-retardant silicone sealant. After weaving, a 0.025mm modified flexible adhesive (polyurethane: neoprene rubber = 4:1 + 0.5% micro powder silicone) is applied to form a composite shielding layer.

[0033] Interface activation stage: The cable core is sent into an atmospheric pressure plasma device, using an argon-oxygen 3:1 mixed gas source + 0.5% nitrogen assistance, a processing power of 160W, a processing time of 3.5min, a processing distance of 6mm, and a traction speed of 8.5m / min; after processing, 0.01mm of modified flexible adhesive is sprayed (spraying amount 0.012g / cm²), and then sent into a constant temperature curing chamber for segmented curing at 85℃ for 6min + 88℃ for 8min, with an interface adhesion ≥8N / 15mm.

[0034] Outer sheath extrusion stage: Low-smoke halogen-free elastomer of the same system is selected, and 4.5% wear-resistant agent (PTFE micro powder: nano SiO2=3:1), 3.2% UV stabilizer (UV-531:UV-327=2:1), and 0.4% anti-aging agent MB are added to the matrix by weight. After mixing in a high-speed mixer, it is fed into a single-screw extruder. The extrusion temperature is 130℃ and the extrusion speed is 8.5m / min. The thickness is controlled online by a laser thickness gauge in a closed loop. The outer sheath thickness is 0.85mm and the eccentricity is 2.0%. After extrusion, it is cooled by gradient water temperature (40±2℃→31±2℃→25±2℃, 7min per stage), with a total cooling time of 22min, a traction speed of 8.5m / min, and a tension of 8N.

[0035] Finished product testing stage: The cable to be tested was sent into a constant temperature and humidity chamber and subjected to gradient temperature and humidity aging treatment at 40℃ / 60%RH×24h→25℃ / 50%RH×48h→15℃ / 45%RH×24h (total duration 96h); then a full-performance linkage test was carried out, and all test items met the standards, with no rework required. Example

[0036] This embodiment uses the upper limit of the parameter range to meet the manufacturing requirements of large-diameter, high-protection cables. The specific process parameters are as follows: Conductor preparation stage: 99.99% pure oxygen-free soft copper wire is selected and drawn into an ultra-fine monofilament with a diameter of 0.13 mm and a diameter tolerance of ±0.002 mm; it is stranded in 2+3+5 layers with staggered twisting, with a twisting pitch ratio of 13.5 times, and the gaps are filled with 0.02 mm polyester flexible fiber bundles; under the protection of argon and nitrogen 2:1 inert gas (introduction rate 3 L / min), it is annealed at 295℃ for 18 min, with a cooling rate of 5℃ / min.

[0037] Insulation material modification stage: The matrix resin is a mixture of EVA, POE, and TPU in a 4:3:3 ratio. 29% of the total matrix mass of a composite flame retardant (ATH:MDH=2:1, particle size 3μm) is added, along with 4.5% of a compound silane coupling agent, 3.0% of a compound flexible toughening agent, 1.8% of a compound antioxidant, and 0.5% of a compatibilizer. After pretreatment of the composite flame retardant at 88℃, the silane coupling agent is modified, and the mixture is then internally mixed at 138℃ for 24 minutes. Granulation is performed using a twin-screw extruder (die temperature 138℃). The insulation material has a particle size of 4mm and a moisture content of ≤0.05%.

[0038] Insulation layer extrusion stage: The three-layer co-extrusion parameters are: inner insulation layer 0.38mm, middle buffer layer 0.14mm (with an additional 5% flexible toughening agent), outer insulation layer 0.38mm, and total thickness 0.90mm; extrusion speed 9.5m / min, precision die control insulation layer eccentricity 3.2%; air cooling (wind speed 5m / s, distance 2m) + water cooling (water temperature 29℃) synergistic cooling for 12min.

[0039] Shielding layer preparation stage: Wrap 0.04mm ultra-thin aluminum-plastic composite tape (0.01mm aluminum layer, 0.03mm flame-retardant PE plastic layer) with an overlap rate of 29% and a tension of 7N; spray 0.015mm flexible adhesive; use 0.09mm tin-plated ultra-fine copper wire for double oblique weaving, with a weaving density of 94%, a weaving angle of 38°, a tension of 4.5N, and four spindles for synchronous weaving (speed 350r / min); after weaving, coat with 0.03mm modified flexible adhesive to form a composite shielding layer.

[0040] Interface activation stage: Argon-oxygen 3:1 mixed gas source + 1.0% nitrogen assistance, processing power 190W, processing time 4.5min, processing distance 7mm, traction speed 9.5m / min; after processing, 0.015mm modified flexible adhesive is sprayed (spraying amount 0.018g / cm²), and the curing is carried out in stages by holding at 85℃ for 6min + holding at 88℃ for 8min.

[0041] Outer sheath extrusion stage: 5.5% wear-resistant agent, 3.8% UV stabilizer, and 0.6% anti-aging agent MB were added by the total mass of the matrix; extrusion temperature was 133℃, and extrusion speed was 9.5m / min; online thickness closed-loop control was used to control the outer sheath thickness to 0.95mm and the eccentricity rate to 2.4%; gradient water temperature cooling was used for 8min per stage, with a total cooling time of 24min, traction speed of 9.5m / min, and tension of 10N.

[0042] Finished product testing stage: After undergoing aging treatment with gradient temperature and humidity (96h) according to the same standard, full performance linkage testing was carried out. All test items met the standards and there was no rework.

[0043] Performance Testing and Results Analysis The high-flexibility, low-smoke, halogen-free insulated shielded cables prepared in Examples 1 and 2 were subjected to full-performance linkage testing. The testing methods followed the relevant national standards for wires and cables. The test items, standard requirements, and test results of Examples 1 and 2 are shown in the table below.

[0044]

[0045] Test Result Analysis The finished cables from Examples 1 and 2 showed that all test results were far superior to the standard requirements, proving that the manufacturing process of the present invention can produce high-performance products with different parameter values ​​within the range, and that the process has good stability and adaptability. Because Example 2 uses the upper limit parameters, its shielding effectiveness, electrical performance, and mechanical performance are slightly better than Example 1, making it suitable for high protection and high transmission quality application scenarios. Example 1 has a slightly better number of bends and better flexibility, making it suitable for laying scenarios with confined spaces and frequent bends. Both embodiments have low smoke and halogen-free indicators that are significantly lower than the standard limit, with extremely low secondary hazards during combustion. At the same time, the composite shielding layer achieves a braiding density of over 93% and a shielding effectiveness of over 92dB, solving the problem of mutual constraints between high flame retardancy and high flexibility, and high shielding density and low rigidity in traditional cables. After aging tests, the mechanical properties of both embodiments were maintained at a rate higher than the standard requirements. Combined with the additional test results for UV resistance and abrasion resistance, this demonstrates that the products have excellent environmental adaptability and service life.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable, characterized in that, include: Conductor preparation stage: oxygen-free soft copper wire is selected to make single wires, which are then processed by layered staggered stranding process and filled with flexible fiber bundles. After low-temperature annealing under inert gas protection, the conductor core is prepared. Insulation material modification stage: Using ethylene-vinyl acetate copolymer, polyolefin elastomer, and thermoplastic polyurethane as the base resin, they are mixed in a set ratio, and composite flame retardants and various compound additives are added. The flame retardant is first surface modified, and then mixed, kneaded, extruded and granulated to prepare a highly flexible, low-smoke, halogen-free insulation material. Insulation layer extrusion stage: A three-layer co-extrusion process is used to coat the modified insulating material onto the surface of the conductor core. The insulation layer is prepared through temperature control, precision mold control and coordinated cooling. Shielding layer preparation stage: First, wrap ultra-thin flame-retardant aluminum-plastic composite tape around the surface of the insulation layer and spray flexible adhesive. Then, double oblique weaving is carried out using tin-plated ultra-fine copper wire, and after filling with flexible flame-retardant sealant, modified flexible adhesive is coated to prepare the composite shielding layer. Interface activation stage: The cable core covered with composite shielding layer is sent into the plasma equipment and the interface is activated by a mixed gas source of argon, oxygen and nitrogen to remove interface impurities and improve roughness. After spraying modified flexible adhesive, it is cured in sections. Outer sheath extrusion stage: Low-smoke halogen-free elastomers of the same system as the insulation material are selected, functional additives are added, and after mixing and extrusion coating on the surface of the cable core, the outer sheath is prepared through temperature control, gradient cooling and traction control, and the finished cable to be tested is obtained. Finished product testing stage: The finished cable to be tested is subjected to gradient temperature and humidity aging treatment to eliminate internal stress in each layer, and then full-performance linkage testing is carried out. Defective products are reworked, and qualified products are cut, rolled and packaged to obtain the final finished cable.

2. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 1, characterized in that, In the conductor preparation stage, oxygen-free soft copper wire is drawn into ultra-fine monofilaments. The ultra-fine copper wires are twisted in three layers in a staggered manner to form a conductor core. The twisting pitch ratio of each layer is controlled to be 12.5-13.5 times, and the twisting direction is set alternately. The gap between each layer of twisting is filled with flexible fiber bundles. After the twisting is completed, the conductor core is subjected to low-temperature continuous annealing under inert gas protection. The annealing temperature is controlled at 285-295℃ to eliminate the internal stress of the twisting.

3. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 2, characterized in that, In the insulation material modification stage, the matrix resin is mixed with ethylene-vinyl acetate copolymer, polyolefin elastomer, and thermoplastic polyurethane in a mass ratio of 4:3:

3. The amount of composite flame retardant added is 27-29% of the total mass of the matrix resin, which is composed of aluminum hydroxide and magnesium hydroxide in a mass ratio of 2:

1. The compound additives include 3.5-4.5% of the total mass of the matrix resin, 2.5-3% of the total mass of the matrix resin, 1.2-1.8% of the total mass of the matrix resin, and 0.3-0.5% of the total mass of the matrix resin, and compatibilizer. After surface modification, the composite flame retardant is mixed with the remaining components, kneaded, extruded and granulated to obtain a high-flexibility, low-smoke, halogen-free insulation material.

4. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 3, characterized in that, In the extrusion stage of the insulation layer, the three-layer co-extruded insulation layer includes an inner insulation layer, an intermediate buffer layer, and an outer insulation layer. The total insulation layer thickness is controlled to be 0.76-0.9 mm. The thickness of the inner insulation layer is the same as that of the outer insulation layer, and a flexible toughening agent is added separately to the intermediate buffer layer. The extrusion process adopts a gradient temperature control process, and the core eccentricity of the insulation layer is controlled to be ≤3.5% through a precision mold. After extrusion, it is cooled and shaped.

5. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 4, characterized in that, In the shielding layer preparation stage, the ultra-thin flame-retardant aluminum-plastic composite tape is spirally wrapped with a wrapping overlap rate of 27-29%, and a flexible adhesive is sprayed after wrapping. The density of the double oblique braiding of the tin-plated ultra-fine copper wire is controlled at 93-94%, and the braiding gaps are filled with a flexible flame-retardant sealant. After the braiding is completed, a modified flexible adhesive is applied to form a flexible composite shielding layer.

6. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 5, characterized in that, During the interface activation stage, the mixed gas source is mainly composed of argon and oxygen, with nitrogen added at a volume ratio of 0.5-1% as an auxiliary gas source. The plasma treatment power, time, and distance are controlled according to preset parameters. After the treatment is completed, a modified flexible adhesive is sprayed on and sent to a constant temperature curing chamber for segmented curing to ensure tight interface bonding.

7. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 6, characterized in that, During the extrusion stage of the outer sheath, the functional additives include wear-resistant agents, UV inhibitors, and anti-aging agents, and the amount added is controlled according to a preset ratio; the extrusion temperature is controlled at 130-133℃, and an online thickness closed-loop control system is adopted to control the thickness of the outer sheath to 0.85-0.95mm, with an eccentricity rate ≤2.5%, and the sheath is cooled and shaped after extrusion.

8. The method for preparing a highly flexible, low-smoke, halogen-free insulated shielded cable according to claim 7, characterized in that, In the finished product testing stage, the gradient temperature and humidity aging treatment is divided into three stages, which are kept warm and moist according to different temperature and humidity parameters in sequence, with a total aging treatment time of not less than 96 hours. The comprehensive performance testing includes tests for flexibility, low smoke and halogen-free properties, shielding effectiveness, electrical and mechanical performance. Non-conforming products are reworked and retested.

9. A highly flexible, low-smoke, halogen-free insulated shielded cable, prepared using the method described in claim 8, characterized in that, Based on a total of 1000 parts by weight, the product includes 490-530 parts by weight of conductor core, 180-200 parts by weight of three-layer co-extruded insulation layer, 60-70 parts by weight of flexible composite shielding layer, 2-3 parts by weight of interface bonding layer and 145-167 parts by weight of outer sheath. The conductor core has a layered staggered stranded structure, composed of oxygen-free soft copper wire and polyester flexible fiber bundles. The flexible fiber bundles account for 0.4-0.8% of the total weight of the conductor core. The insulation layer uses the highly flexible, low-smoke, halogen-free insulation material as described in claim 3, with the inner insulation layer and outer insulation layer each accounting for 40% of the total weight of the insulation layer, and the intermediate buffer layer accounting for 20%. The flexible composite shielding layer is composed of ultra-thin aluminum-plastic composite tape, tin-plated ultra-fine copper wire, flexible adhesive, modified flexible adhesive and flexible flame-retardant sealant, with each component matched according to a preset weight ratio. The interface bonding layer uses the same material as the modified flexible adhesive of the shielding layer to ensure a tight bond between the insulation layer and the shielding layer. The outer sheath is made of a low-smoke halogen-free elastomer of the same system as the insulation material, and functional additives including wear-resistant agents, UV stabilizers, anti-aging agents and composite flame retardants are added to match the performance of the insulation layer.

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