Super-flexible low-smoke flame-retardant cable and preparation method thereof

Abstract

The application discloses a kind of superflexible low smoke flame retardant cable and preparation method thereof, the superflexible low smoke flame retardant cable is by internal multiple strand twisted copper conductor and protective layer, protective layer is coated in the multiple strand twisted copper conductor outer surface, from inside to outside successively include: inner sheath layer, thickness is 0.5mm-1.5mm, is made of first polymer composite material;Outer sheath layer, thickness is 0.8mm-2.0mm, is made of second polymer composite material;Inner protective layer is tightly coated multiple strand twisted copper conductor outer surface, outer sheath layer is coated in the outer surface of inner sheath layer, and outer sheath layer inside is coated with several groups of coated inner sheath layer multiple strand twisted copper conductor;The first polymer composite material and second polymer composite material are prepared by 100-120 parts of organic silicon modified polyolefin resin, 12-25 parts of modified nanometer montmorillonite, 40-70 parts of halogen-free flame-retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent and 8-20 parts of superflexible plasticizer by mass fraction.

Description

Technical Field

[0001] This invention belongs to the field of cable materials and preparation technology, specifically relating to an ultra-flexible, low-smoke, flame-retardant cable; and more particularly to a method for preparing an ultra-flexible, low-smoke, flame-retardant cable. Background Technology

[0002] Traditional flexible flame-retardant cables typically use multi-strand fine copper wire stranded conductors combined with polyvinyl chloride (PVC), ethylene-vinyl acetate copolymer (EVA), or cross-linked polyolefin sheath materials to improve flexibility. To meet flame-retardant requirements, halogen-free flame retardants such as aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are often added to the sheath, and the IEC60332 flame-retardant rating is achieved through high filler content (>60 phr).

[0003] However, existing technologies have two significant drawbacks: a contradiction between flexibility and flame retardancy. High levels of flame retardant filler increase the rigidity of the sheath material, resulting in bending radii often exceeding eight times the cable diameter. Repeated bending easily leads to interface cracks, making it difficult to meet the 10,000+ bending life requirements of dynamic applications such as robots and automotive wiring harnesses. Simultaneously, conventional plasticizers have poor compatibility with halogen-free flame retardants, easily migrating and precipitating, accelerating material aging.

[0004] Insufficient smoke density control, even with montmorillonite modification, results in uneven dispersion of nanoparticles and a single smoke-blocking path due to the lack of a functional gradient distribution structure. Consequently, the light transmittance of smoke density during combustion is generally below 45%. Therefore, we propose an ultra-flexible low-smoke flame-retardant cable and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide an ultra-flexible, low-smoke, flame-retardant cable and its preparation method. Molecular-level flexibility is achieved through an organosilicon resin skeleton and a synergistic compound plasticizing system, while the star-shaped split structure and expanded silicone gel eliminate the risk of dynamic bending fatigue.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An ultra-flexible, low-smoke, flame-retardant cable, comprising an inner multi-strand stranded copper conductor and a protective layer, wherein the protective layer covers the outer surface of the multi-strand stranded copper conductor and comprises, from the inside out:

[0008] The inner sheath layer, with a thickness of 0.5mm-1.5mm, is made of a first polymer composite material;

[0009] The outer sheath layer, with a thickness of 0.8mm-2.0mm, is made of a second polymer composite material;

[0010] The inner protective layer tightly covers the outer surface of the multi-stranded copper conductor, the outer sheath layer covers the outer surface of the inner sheath layer, and the outer sheath layer contains several sets of multi-stranded copper conductors that cover the inner sheath layer.

[0011] By mass fraction, both the first polymer composite material and the second polymer composite material are prepared from 100-120 parts of organosilicon modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer.

[0012] The ultra-flexible plasticizer is selected from phthalates or polyether polyol esters;

[0013] The platinum complex catalytic crosslinking agent is a compound system of [(1,5-cyclooctadiene)Pt(OSiMe3)2] and dicumyl peroxide in a mass ratio of (1:0.3) to (1:0.5). It achieves rapid gelation in 2-5 minutes at a vulcanization temperature of 130℃-150℃, and inhibits the migration and precipitation of plasticizer.

[0014] The modified nano-montmorillonite is obtained by intercalation modification of montmorillonite with long-chain alkyl quaternary ammonium salt, and the particle size D90≤500nm.

[0015] The organosilicon-modified polyolefin resin is an ethylene-octene copolymer grafted with polysiloxane blocks, and the siloxane segment content is ≥15wt%.

[0016] The halogen-free flame retardant synergist combination contains magnesium hydroxide and aluminum hydroxide in a mass ratio of (2:1) to (3:1).

[0017] Preferably, the multi-strand stranded copper conductor is composed of 150-220 annealed copper wires with a diameter of 0.08mm-0.12mm, which are stranded in a layered reverse stranding manner, with a stranding pitch ratio of 14-18 times, and the conductor surface is pre-coated with a nano-alumina insulating layer with a coating thickness of 0.03μm-0.1μm.

[0018] Preferably, a spirally wound aramid fiber reinforcing tape is provided between the inner sheath layer and the multi-stranded copper conductor. This reinforcing tape wraps around the conductor at an angle of 45°±5°, has a width of 0.5mm-2mm, and a basis weight of 30-60g / m³. 2 .

[0019] Preferably, in the first polymer composite material and the second polymer composite material, the modified nano-montmorillonite is distributed in a gradient: the montmorillonite content in the inner sheath layer is 15-18 parts, and in the outer sheath layer it is 20-25 parts. The distribution of dense outer layer and sparse inner layer achieves directional control of smoke blocking performance and flexibility requirements.

[0020] Preferably, the halogen-free flame retardant synergist combination further comprises zinc borate-coated carbon nanotubes, the amount of which is 5%-12% of the total mass of magnesium hydroxide / aluminum hydroxide, the coating thickness is 5-50nm, and the mass ratio of the zinc borate-coated carbon nanotubes to the modified nano-montmorillonite is (1:2)-(1:3), the two synergistically constructing a hierarchical barrier channel.

[0021] Preferably, the super-flexible plasticizer is composed of diisononyl phthalate (DINP) and epoxidized soybean oil in a mass ratio of (7:3) to (8:2), and the compounding system reduces the cold bending brittleness point of the polymer composite material at -50°C.

[0022] A method for preparing an ultra-flexible, low-smoke, flame-retardant cable, the method comprising the following steps:

[0023] S1. Conductor pretreatment: Annealed copper wire with a diameter of 0.08mm-0.12mm is made into a multi-strand stranded copper conductor by layered reverse stranding with a stranding pitch ratio of 14-18 times. Then, a nano-alumina insulating layer with a thickness of 0.03μm-0.1μm is formed on the conductor surface by vapor deposition.

[0024] S2. Preparation of sheath material: Preparation of the first polymer composite material: By mass, 100-120 parts of organosilicon modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer are put into an internal mixer and mixed at 120℃-140℃ for 15-25 minutes, and then granulated by twin-screw extrusion.

[0025] Preparation of the second polymer composite material: The composition is the same as that of the first polymer composite material, except that the content of modified nano-montmorillonite is adjusted to 20-25 parts;

[0026] S3, double-layer co-extrusion: The first polymer composite material obtained in S2 is extruded through a 35mm single-screw extruder at 105℃-125℃ to form an inner sheath layer. At the same time, the second polymer composite material is extruded through a 45mm single-screw extruder at 110℃-130℃ to form an outer sheath layer. The two extruders are extruded synchronously using a common die head, so that the inner sheath layer directly covers the multi-stranded copper conductor treated in S1, and the outer sheath layer covers the inner sheath layer. The co-extrusion thickness is controlled to be 0.5mm-1.5mm and 0.8mm-2.0mm, respectively.

[0027] S4. Dynamic cross-linking and cooling: The cable formed in S3 is passed through the cross-linking pipe at a speed of 8-12m / min, nitrogen gas is introduced for protection and radiation heating to 150℃-170℃, and the temperature is held for 2-5min to activate the platinum complex to catalyze cross-linking; then two-stage cooling is performed, first by spraying with 40℃-60℃ warm water for 20-30s, and then by circulating cold air at 5℃-10℃ to cure.

[0028] S5. Structural Integration: The four sets of single-core cables obtained from S4 are arranged symmetrically at 90°. Expandable flame-retardant silicone gel is injected into the gaps between the conductors, with a filling rate of 85%-95%. Finally, the cables are wound into a cable using a rotating traction device.

[0029] Preferably, before the vapor deposition described in S1, the multi-stranded copper conductor is first subjected to plasma activation treatment: the conductor is placed in a 0.5-1.5 kPa vacuum reaction chamber, an argon-oxygen mixture is introduced at a volume ratio of 4:1, and 100-150 W radio frequency power is applied for 2-5 minutes; this treatment increases the bonding strength of the nano-alumina layer by 50% and reduces the interfacial resistance to <10 Ω·cm. -6 Ω·cm.

[0030] Preferably, before S3 co-extrusion, an aramid fiber reinforcing tape spiral winding process is set between the multi-strand stranded copper conductor and the outer sheath layer: a servo motor is used to control the reinforcing tape to continuously wind the conductor at an inclination angle of 45°±5°, the tensile tension is kept constant at 1.5-2.5N, and the winding pitch is 1.2-1.8 times the conductor diameter; after winding, a silane coupling agent (concentration 15wt%-25wt%) is sprayed on the surface of the reinforcing tape, with a spraying amount of 0.8-1.2g / m.

[0031] The technical effects and advantages of this invention are as follows:

[0032] Using silicone-modified polyolefin resin as the matrix, a molecular-level flexible network is constructed through polysiloxane block synthesis. It is compounded with a phthalate / polyether polyol ester ultra-flexible plasticizing system, and flame retardants are uniformly dispersed in the matrix. Combined with a star-shaped four-part structure and expanded silicone gel filling, the mechanical stress distribution is transformed from concentrated to dispersed, thereby improving the dynamic bending life while maintaining a flame retardant rating of limiting oxygen index >38%.

[0033] Gradient-distribution modified nano-montmorillonite, with 12-18 parts inner sheath and 20-25 parts outer sheath, forms a hierarchical barrier from sparse to dense; the introduction of zinc borate-coated carbon nanotube synergistic system, which reacts with magnesium hydroxide / aluminum at high temperature to generate a three-dimensional ceramic barrier; synergistically improves smoke transmittance and increases the visible distance of combustion.

[0034] Platinum-catalyzed composite crosslinking technology achieves a fracture elongation of >350% at -50℃, avoiding the embrittlement risk of traditional peroxide crosslinking; pre-coated nano-alumina conductor layer inhibits electrochemical corrosion. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. 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.

[0036] This invention proposes an ultra-flexible, low-smoke, flame-retardant cable and its preparation method. Molecular-level flexibility is achieved through an organosilicon resin skeleton and a synergistic compound plasticizing system. The star-shaped split structure and expanded silica gel are combined to eliminate the risk of dynamic bending fatigue. Gradiently distributed modified nano-montmorillonite and zinc borate-coated carbon nanotubes construct a hierarchical smoke barrier, breaking through the bottleneck of smoke density suppression and significantly improving visibility. Platinum-catalyzed crosslinking and aramid reinforcing tape winding ensure reliability under extreme working conditions.

[0037] Specifically, the ultra-flexible low-smoke flame-retardant cable consists of an internal multi-strand stranded copper conductor and a protective layer. The protective layer covers the outer surface of the multi-strand stranded copper conductor and includes, from the inside out:

[0038] The inner sheath layer, with a thickness of 0.5mm-1.5mm, is made of a first polymer composite material;

[0039] The outer sheath layer, with a thickness of 0.8mm-2.0mm, is made of a second polymer composite material;

[0040] The inner protective layer tightly covers the outer surface of the multi-stranded copper conductor, and the outer sheath layer covers the outer surface of the inner sheath layer. The outer sheath layer contains several sets of multi-stranded copper conductors that cover the inner sheath layer. A spirally wound aramid fiber reinforcing tape is placed between the inner sheath layer and the multi-stranded copper conductor. This reinforcing tape wraps around the conductor at a 45°±5° angle, has a width of 0.5mm-2mm, and a basis weight of 30-60g / m². 2 By limiting the axial displacement between the conductor and the sheath, the conductivity stability of the cable under repeated bending conditions is improved by more than 20%.

[0041] As an optional feature of this embodiment, the outer surface of the outer sheath layer is provided with an equally spaced annular groove structure. The groove depth is 20%-40% of the thickness of the outer sheath layer, the width is 0.8mm-1.5mm, and the center distance between adjacent grooves is 3mm-8mm. This microstructure design reduces the overall weight of the cable by 15%-25% and significantly improves heat dissipation efficiency (temperature rise / fall ≥10℃).

[0042] A heat-reflective metallized polyester film is provided between the inner and outer sheath layers. The film thickness is 0.05mm-0.15mm, the aluminum layer deposition rate is ≥85%, and its reflectivity is >90% (wavelength 2.5-25μm). By blocking the internal heat conduction path, the peak heat release rate (ISO 5660-1) of the cable in the initial stage of combustion is reduced by 40%.

[0043] The outer sheath layer is co-extruded to form a flame-retardant marking embossed pattern. The embossed pattern has a height of 0.1mm-0.3mm and a width of 1mm-3mm. It is prepared using fluorescent masterbatch with a refractive index difference of >0.25 from the matrix material. It can achieve visual recognition within 500mm in a fire smoke environment.

[0044] By mass fraction, both the first polymer composite material and the second polymer composite material are prepared from 100-120 parts of organosilicon-modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer. Furthermore, in the first polymer composite material and the second polymer composite material, the modified nano-montmorillonite is distributed in a gradient: the montmorillonite content in the inner sheath layer is 15-18 parts, and in the outer sheath layer it is 20-25 parts. The distribution of dense outer layer and sparse inner layer achieves directional control of smoke blocking performance and flexibility requirements.

[0045] The super-flexible plasticizer is composed of diisononyl phthalate (DINP) and epoxidized soybean oil in a mass ratio of (7:3) to (8:2). The compound system reduces the cold bending brittleness point of the polymer composite material at -50℃ by more than 25℃ (ASTM D746 test).

[0046] The platinum complex catalytic crosslinking agent is a compound system of [(1,5-cyclooctadiene)Pt(OSiMe3)2] and dicumyl peroxide in a mass ratio of (1:0.3)-(1:0.5). It achieves rapid gelation in 2-5 minutes at a vulcanization temperature of 130℃-150℃, and inhibits the migration and precipitation of plasticizer.

[0047] Modified nano-montmorillonite was obtained by intercalation modification of montmorillonite with long-chain alkyl quaternary ammonium salts, and the particle size D90≤500nm.

[0048] The organosilicon-modified polyolefin resin is composed of ethylene-octene copolymer grafted polysiloxane blocks, with a siloxane segment content of ≥15wt%.

[0049] The multi-strand stranded copper conductor is composed of 150-220 annealed copper wires with a diameter of 0.08mm-0.12mm, which are stranded in a layered reverse stranding manner. The stranding pitch ratio is controlled at 14-18 times, and the conductor surface is pre-coated with a nano-alumina insulating layer with a coating thickness of 0.03μm-0.1μm. While maintaining ultra-flexibility, this structure improves the dynamic bending fatigue life to >10,000 cycles (IEC 60228 standard test) by reducing the diameter of the single wire and optimizing the stranding tension distribution.

[0050] The halogen-free flame retardant synergist combination further includes zinc borate-coated carbon nanotubes, which are added at 5%-12% of the total mass of magnesium hydroxide / aluminum hydroxide, with a coating thickness of 5-50 nm. This structure forms a three-dimensional network ceramic barrier layer at high temperature, increasing the limiting oxygen index (LOI) to >38%. The mass ratio of zinc borate-coated carbon nanotubes to modified nano-montmorillonite is (1:2)-(1:3), and the two work together to construct a hierarchical barrier channel, reducing the smoke density grade (GB / T 8627) to ≤5 while maintaining an elongation at break of >350%.

[0051] In addition, this embodiment also proposes a method for preparing an ultra-flexible low-smoke flame-retardant cable. The method is used to prepare the above-mentioned ultra-flexible low-smoke flame-retardant cable and includes the following steps:

[0052] S1. Conductor pretreatment: Annealed copper wire with a diameter of 0.08mm-0.12mm is made into a multi-strand stranded copper conductor by layered reverse stranding with a stranding pitch ratio of 14-18 times. Then, a nano-alumina insulating layer with a thickness of 0.03μm-0.1μm is formed on the conductor surface by vapor deposition.

[0053] Before S1 vapor deposition, the multi-stranded copper conductor is first subjected to plasma activation treatment: the conductor is placed in a 0.5-1.5 kPa vacuum reaction chamber, an argon-oxygen mixture (volume ratio 4:1) is introduced, and 100-150 W radio frequency power is applied for 2-5 min; this treatment increases the bonding strength of the nano-alumina layer by 50% and reduces the interfacial resistance to <10 Ω·cm. -6 Ω·cm;

[0054] S2. Preparation of sheath material: Preparation of the first polymer composite material: By mass, 100-120 parts of organosilicon modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer are put into an internal mixer and mixed at 120℃-140℃ for 15-25 minutes, and then granulated by twin-screw extrusion.

[0055] Preparation of the second polymer composite material: The composition is the same as that of the first polymer composite material, except that the content of modified nano-montmorillonite is adjusted to 20-25 parts;

[0056] S3, Double-layer co-extrusion: The first polymer composite material obtained in S2 is extruded through a 35mm single-screw extruder at 105℃-125℃ to form an inner sheath layer. Simultaneously, the second polymer composite material is extruded through a 45mm single-screw extruder at 110℃-130℃ to form an outer sheath layer. The two extruders use a common die for synchronous extrusion, so that the inner sheath layer directly covers the multi-stranded copper conductor treated in S1, and the outer sheath layer covers the inner sheath layer. The co-extrusion thickness is controlled to be 0.5mm-1mm respectively. 5mm and 0.8mm-2.0mm; Before S3 co-extrusion, an aramid fiber reinforcing tape is spirally wound between the multi-stranded copper conductor and the outer sheath layer: a servo motor is used to control the reinforcing tape to continuously wind the conductor at an angle of 45°±5°, the tensile tension is kept constant at 1.5-2.5N, and the winding pitch is 1.2-1.8 times the conductor diameter; after winding, a silane coupling agent (concentration 15wt%-25wt%) is sprayed on the surface of the reinforcing tape, with a spraying amount of 0.8-1.2g / m.

[0057] S4. Dynamic Crosslinking and Cooling: The cable formed in S3 is passed through the crosslinking pipe at a speed of 8-12 m / min, protected by nitrogen gas and radiantly heated to 150℃-170℃, and held at this temperature for 2-5 min to activate the platinum complex for catalytic crosslinking. Then, two-stage cooling is performed: first, the cable is cooled by spraying with warm water at 40℃-60℃ for 20-30 s, and then cured by circulating cold air at 5℃-10℃. After S4 cooling, the outer sheath layer is laser micro-processed: a 355nm ultraviolet laser with a pulse width ≤100ns is used to etch annular grooves on the sheath surface at a frequency of 15-25kHz. The groove depth is 20%-40% of the outer sheath layer thickness, and the width is 0.8mm-1.5mm. Immediately after etching, hot air at 40℃-50℃ is introduced to eliminate residual stress, so that the surface roughness Ra≤0.8μm.

[0058] S5. Structural Integration: The four sets of single-core cables obtained from S4 are arranged symmetrically at 90°. Expandable flame-retardant silicone gel is injected into the conductor gaps, with a filling rate of 85%-95%. Finally, the cables are wound into a cable using a rotary traction device. Before the S5 structural integration, a metallized polyester film lamination process is added: A 0.05mm-0.15mm thick polyester film is deposited with an aluminum layer by magnetron sputtering (deposition rate ≥85%), and then hot-pressed onto the surface of the inner sheath layer at a pressure of 0.6-0.8MPa. The hot-pressing temperature is controlled at 110℃-130℃ and the speed at 5-10m / min to ensure that the film reflectivity is >90%.

[0059] The S5 expandable flame-retardant silicone gel injection process employs multi-needle ultrasonic-assisted injection: four needles are simultaneously inserted into the gap of the star-shaped four-split cable, and the gel is injected under ultrasonic oscillation at 30-50kHz; the injection pressure is controlled at 0.2-0.5MPa, the needle temperature at 80℃-90℃, and the ultrasonic amplitude at 10-20μm, so that the gel filling uniformity is >98%.

[0060] The above methods, plasma activation + vapor deposition: solve the problem of interfacial bonding between nanolayers and conductors; servo winding + coupling agent spraying: achieve precise positioning of reinforcing strips and interface strengthening; ultraviolet laser micromachining + hot air stress relief: break through the limitations of traditional extrusion dies on groove structure;

[0061] Magnetron sputtering of aluminum layer + low temperature hot pressing: avoids high temperature damage to the sheath layer and ensures the reflective function of the thin film; ultrasound-assisted gel injection: eliminates bubble defects in the gaps between split conductors.

[0062] Based on the above, the following table compares the effects:

[0063] Table 1 Comparison of Results

[0064]

[0065] The performance evaluation system establishes a closed-loop logic linking background technology deficiencies → innovative technical solutions → ultimate performance breakthroughs. Addressing the two core pain points explicitly identified in the background technology (the contradiction between flexibility and flame retardancy, and insufficient smoke transmittance), a fundamental breakthrough is achieved through material design and structural innovation.

[0066] Flexibility-Flame Retardant Synergistic Optimization – Breakthrough adoption of silicone-modified polyolefin resin + compounded ultra-flexible plasticizing system to replace traditional high-filler sheath, balancing mechanical properties and flame retardant efficiency at the molecular level; combined with star-shaped four-split conductor topology, enabling the cable to withstand >10,000 dynamic bends without cracking, completely solving the risk of fracture failure of high-rigidity sheath under bending conditions.

[0067] The smoke suppression mechanism has been upgraded with a dual-layer gradient montmorillonite smoke-blocking distribution strategy (low content in the inner sheath to ensure flexibility → high content in the outer sheath to enhance barrier properties). Combined with the catalytic carbonization effect of zinc borate-coated carbon nanotubes, a continuous ceramic barrier is formed in the early stage of combustion. The smoke density transmittance has jumped from the industry average of <45% to >60%, meeting the strict visual escape requirements of high-risk places such as nuclear power plants.

[0068] In summary, this invention uses silicone-modified polyolefin resin as the matrix, constructs a molecular-level flexible network through polysiloxane block synthesis, and combines it with a phthalate / polyether polyol ester ultra-flexible plasticizing system. The flame retardant is uniformly dispersed in the matrix, and combined with a star-shaped tetrasplit structure and expanded silicone gel filling, the mechanical stress distribution is transformed from concentrated to dispersed, thereby improving the dynamic bending life while maintaining a flame retardant rating of limiting oxygen index >38%.

[0069] Gradient-distribution modified nano-montmorillonite, with 12-18 parts inner sheath and 20-25 parts outer sheath, forms a hierarchical barrier from sparse to dense; the introduction of zinc borate-coated carbon nanotube synergistic system, which reacts with magnesium hydroxide / aluminum at high temperature to generate a three-dimensional ceramic barrier; synergistically improves smoke transmittance and increases the visible distance of combustion.

[0070] Platinum-catalyzed composite crosslinking technology achieves a fracture elongation of >350% at -50℃, avoiding the embrittlement risk of traditional peroxide crosslinking; pre-coated nano-alumina conductor layer inhibits electrochemical corrosion.

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ultra-flexible, low-smoke, flame-retardant cable, characterized in that, The ultra-flexible low-smoke flame-retardant cable consists of an internal multi-strand stranded copper conductor and a protective layer. The protective layer covers the outer surface of the multi-strand stranded copper conductor and comprises, from the inside to the outside: The inner sheath layer, with a thickness of 0.5mm-1.5mm, is made of a first polymer composite material; The outer sheath layer, with a thickness of 0.8mm-2.0mm, is made of a second polymer composite material; The inner protective layer tightly covers the outer surface of the multi-stranded copper conductor, the outer sheath layer covers the outer surface of the inner sheath layer, and the outer sheath layer contains several sets of multi-stranded copper conductors that cover the inner sheath layer. By mass fraction, both the first polymer composite material and the second polymer composite material are prepared from 100-120 parts of organosilicon modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer. The ultra-flexible plasticizer is selected from phthalates or polyether polyol esters; The platinum complex catalytic crosslinking agent is a compound system of [(1,5-cyclooctadiene)Pt(OSiMe3)2] and dicumyl peroxide in a mass ratio of 1:0.3~0.

5. It achieves rapid gelation in 2-5 minutes at a vulcanization temperature of 130℃-150℃, and inhibits the migration and precipitation of plasticizer. The modified nano-montmorillonite is obtained by intercalation modification of montmorillonite with long-chain alkyl quaternary ammonium salt, and the particle size D90≤500nm. The organosilicon-modified polyolefin resin is an ethylene-octene copolymer grafted with polysiloxane blocks, and the siloxane segment content is ≥15wt%. The halogen-free flame retardant synergist combination contains magnesium hydroxide and aluminum hydroxide in a mass ratio of 2~3:

1.

2. The ultra-flexible low-smoke flame-retardant cable according to claim 1, characterized in that, The multi-strand stranded copper conductor is composed of 150-220 annealed copper wires with a diameter of 0.08mm-0.12mm, which are stranded in a layered reverse stranding manner. The stranding pitch ratio is 14-18 times, and the conductor surface is pre-coated with a nano-alumina insulating layer with a coating thickness of 0.03μm-0.1μm.

3. The ultra-flexible low-smoke flame-retardant cable according to claim 1, characterized in that, A spirally wound aramid fiber reinforcing tape is provided between the inner sheath layer and the multi-stranded copper conductor. This reinforcing tape wraps around the conductor at an angle of 45°±5°, has a width of 0.5mm-2mm, and a basis weight of 30-60g / m². 2 .

4. The ultra-flexible low-smoke flame-retardant cable according to claim 1, characterized in that, In the first polymer composite material and the second polymer composite material, the modified nano-montmorillonite is distributed in a gradient: the montmorillonite content in the inner sheath layer is 15-18 parts, and the content in the outer sheath layer is 20-25 parts. The distribution of dense outer layer and sparse inner layer achieves directional control of smoke blocking performance and flexibility requirements.

5. The ultra-flexible low-smoke flame-retardant cable according to claim 1, characterized in that, The halogen-free flame retardant synergist combination further comprises zinc borate-coated carbon nanotubes, which are added at 5%-12% of the total mass of magnesium hydroxide / aluminum hydroxide, with a coating thickness of 5-50 nm. The mass ratio of the zinc borate-coated carbon nanotubes to the modified nano-montmorillonite is 1:2-3, and the two work together to construct a hierarchical barrier channel.

6. The ultra-flexible low-smoke flame-retardant cable according to claim 1, characterized in that, The super-flexible plasticizer is composed of diisononyl phthalate and epoxidized soybean oil in a mass ratio of 7:

3. The compound system reduces the cold bending brittleness point of the polymer composite material at -50℃.

7. A method for preparing an ultra-flexible, low-smoke, flame-retardant cable, the method being used to prepare the ultra-flexible, low-smoke, flame-retardant cable according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Conductor pretreatment: Annealed copper wire with a diameter of 0.08mm-0.12mm is made into a multi-strand stranded copper conductor by layered reverse stranding with a stranding pitch ratio of 14-18 times. Then, a nano-alumina insulating layer with a thickness of 0.03μm-0.1μm is formed on the conductor surface by vapor deposition. S2. Preparation of sheath material: Preparation of the first polymer composite material: By mass, 100-120 parts of organosilicon modified polyolefin resin, 12-25 parts of modified nano-montmorillonite, 40-70 parts of halogen-free flame retardant synergist combination, 0.5-3 parts of platinum complex catalytic crosslinking agent, and 8-20 parts of ultra-flexible plasticizer are put into an internal mixer and mixed at 120℃-140℃ for 15-25 minutes, and then granulated by twin-screw extrusion. Preparation of the second polymer composite material: The composition is the same as that of the first polymer composite material, except that the content of modified nano-montmorillonite is adjusted to 20-25 parts; S3, double-layer co-extrusion: The first polymer composite material obtained in S2 is extruded through a 35mm single-screw extruder at 105℃-125℃ to form an inner sheath layer. At the same time, the second polymer composite material is extruded through a 45mm single-screw extruder at 110℃-130℃ to form an outer sheath layer. The two extruders are extruded synchronously using a common die head, so that the inner sheath layer directly covers the multi-stranded copper conductor treated in S1, and the outer sheath layer covers the inner sheath layer. The co-extrusion thickness is controlled to be 0.5mm-1.5mm and 0.8mm-2.0mm, respectively. S4. Dynamic cross-linking and cooling: The cable formed in S3 is passed through the cross-linking pipe at a speed of 8-12m / min, nitrogen gas is introduced for protection and radiation heating to 150℃-170℃, and the temperature is held for 2-5min to activate the platinum complex to catalyze cross-linking; then two-stage cooling is performed, first by spraying with 40℃-60℃ warm water for 20-30s, and then by circulating cold air at 5℃-10℃ to cure. S5. Structural Integration: The four sets of single-core cables obtained from S4 are arranged symmetrically at 90°. Expandable flame-retardant silicone gel is injected into the gaps between the conductors, with a filling rate of 85%-95%. Finally, the cables are wound into a cable using a rotating traction device.

8. The method for preparing an ultra-flexible, low-smoke, flame-retardant cable according to claim 7, characterized in that, Prior to the vapor deposition described in S1, the multi-stranded copper conductor undergoes plasma activation treatment: the conductor is placed in a 0.5-1.5 kPa vacuum reaction chamber, an argon-oxygen mixture (volume ratio 4:1) is introduced, and 100-150 W of radio frequency power is applied for 2-5 minutes; this treatment increases the bonding strength of the nano-alumina layer by 50% and reduces the interfacial resistance to <10 Ω·cm. -6 Ω·cm.

9. The method for preparing an ultra-flexible, low-smoke, flame-retardant cable according to claim 7, characterized in that, Before S3 co-extrusion, an aramid fiber reinforcing tape spiral winding process is set between the multi-strand stranded copper conductor and the outer sheath layer: a servo motor is used to control the reinforcing tape to continuously wind the conductor at an inclination angle of 45°±5°, the tensile tension is kept constant at 1.5-2.5N, and the winding pitch is 1.2-1.8 times the conductor diameter; after winding, a silane coupling agent is sprayed on the surface of the reinforcing tape with a concentration of 15wt%-25wt% and a spraying amount of 0.8-1.2g / m.

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