Flame-retardant cable and preparation method thereof

Abstract

The invention relates to the technical field of wire and cable manufacturing, in particular to a flame-retardant cable and a preparation method thereof.The flame-retardant cable comprises a conductor, an insulating layer, a flame-retardant filling layer, a shielding layer and a sheath layer from inside to outside; the insulating layer is prepared from the following components in parts by weight: 40 to 50 parts of low-halogenated polyether-ether-ketone, 15 to 20 parts of nano magnesium hydroxide-aluminum oxide composite powder, 5 to 8 parts of phosphazene modified montmorillonite, 6 to 10 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 2 to 4 parts of aminated graphene quantum dots and the like. The flame-retardant filling layer is formed by mixing basalt fiber-glass fiber composite filaments and expanded graphite-graphene composite powder according to the ratio of 3: 2, and the sheath layer comprises the following components in parts by weight: 30-40 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 8-12 parts of nano tin dioxide-antimony oxide composite powder and the like. The flame-retardant cable is high in flame-retardant efficiency, low in smoke toxicity release, excellent in electrical and mechanical properties, resistant to aging, wide in application scene and long in service life, has an aging tracing function, and provides a reliable solution for the field with high safety requirements.

Description

Technical Field

[0001] This invention relates to the field of wire and cable manufacturing technology, specifically to a flame-retardant cable and its preparation method. Background Technology

[0002] Cables, as the core carriers of power transmission and signal transmission, are widely used in construction, transportation, energy and other fields. Among them, flame retardant performance is a key indicator to ensure the safe operation of cables. As the industry's requirements for safety standards become more stringent, traditional flame-retardant cables are gradually revealing their performance shortcomings and are unable to meet the needs of use in complex scenarios.

[0003] Currently, most mainstream flame-retardant cables use a single flame retardant, achieving flame retardancy through physical barriers or simple chemical reactions. However, this results in low flame-retardant efficiency and high smoke density. For example, ordinary flame-retardant cables easily release large amounts of toxic and harmful gases when burning, with smoke density levels often exceeding 80. This not only hinders personnel evacuation but also exacerbates equipment corrosion. Furthermore, their oxygen index is generally below 30%, making it difficult to meet the Class A standard for vertical combustion performance. Under high-temperature environments, there is a risk of insulation melting and conductor exposure.

[0004] Meanwhile, traditional cables have structural design flaws: the insulation layer mostly uses pure polymer materials and lacks reinforcing filler modification, resulting in poor mechanical properties, weak tensile and impact resistance, and easy cracking after long-term use; the flame-retardant filler layer is mostly a single expanded graphite or glass fiber with low filling density, making it difficult to form a continuous flame-retardant barrier, and flames can easily penetrate the filler layer and ignite the insulation layer; the shielding layer has a braiding density of less than 85%, resulting in poor electromagnetic shielding effect and susceptibility to external electromagnetic interference affecting signal transmission stability.

[0005] Furthermore, existing cable manufacturing processes suffer from insufficient standardization: the insulation layer is not pre-dried during extrusion, resulting in high particle moisture content and an internal air bubble content exceeding 0.5%, thus reducing electrical insulation performance; the sheath layer is not cross-linked after extrusion, with a cross-linking degree below 60%, leading to poor aging resistance and low-temperature resistance, making it prone to brittleness in environments below -30℃. These problems result in short service life and high maintenance costs for traditional flame-retardant cables, making them unsuitable for scenarios with extremely high safety and reliability requirements, such as high-rise buildings, subways, and nuclear power plants. There is an urgent need to develop a new type of flame-retardant cable that combines high-efficiency flame retardancy, low smoke and low toxicity, excellent mechanical properties, and stable manufacturing processes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a flame-retardant cable and its preparation method.

[0007] A flame-retardant cable comprises, from the inside out, a conductor, an insulation layer, a flame-retardant filler layer, a shielding layer, and a sheath layer. The insulation layer raw materials, by weight, include 40-50 parts of low-halogenated polyether ether ketone, 15-20 parts of nano-magnesium hydroxide-alumina composite powder, 5-8 parts of phosphazene-modified montmorillonite, 6-10 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 2-4 parts of amino-based graphene quantum dots, 1-3 parts of silane coupling agent KH-560, and antioxidant 1010. 0.5-1.5 parts; the flame-retardant filler layer is a mixture of basalt fiber-glass fiber composite filament and expanded graphite-graphene composite powder in a mass ratio of 3:2; the raw materials of the sheath layer include, by weight, 30-40 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 8-12 parts of nano tin dioxide-antimony oxide composite powder, 5-8 parts of zinc borate-zinc molybdate compound, 2-4 parts of ferrocene-ferric acetylacetone composite flame retardant, and 0.5-1 parts of lubricant.

[0008] Preferably, the preparation process of the nano-magnesium hydroxide-alumina composite powder is also included: weighing nano-magnesium hydroxide and nano-alumina at a mass ratio of 4:1, adding deionized water, and then adding 0.5-1% citric acid by mass, and ultrasonically dispersing for 20-30 minutes with ultrasonic power controlled at 300-500W; heating to 60-70℃, adding 3-5% silane coupling agent KH-550 by mass, and stirring for 2-3 hours; after the reaction is completed, centrifuging to separate the solid, drying it at 80-100℃ for 4-6 hours, grinding it, and passing it through a 300-mesh sieve; the obtained composite powder has a particle size of 80-120nm, a specific surface area of ​​50-80m² / g, and an oil absorption value of no more than 25g / 100g.

[0009] Preferably, the preparation process of phosphazene-modified montmorillonite also includes: adding montmorillonite to deionized water, ultrasonically dispersing for 15-20 minutes with an ultrasonic power of 200-300W, adding 2-3% hydrochloric acid to adjust the pH to 3.0-4.0; adding 5-8% hexachlorocyclotriphosphazene, heating to 80-90℃, and stirring for 4-5 hours; adding 3-5% aminophenoethyl ether and continuing the reaction for 2-3 hours; filtering after the reaction is complete, washing with deionized water until neutral, and drying at 100-120℃ for 6-8 hours; the obtained modified montmorillonite has an interlayer spacing of 2.5-3.0 nm, a phosphorus content of 6-8%, and a nitrogen content of 4-6%.

[0010] Preferably, the preparation process of the amino-based graphene quantum dots is as follows: weigh the graphene quantum dots, add deionized water, then add 5-10% of 3-aminopropyltriethoxysilane by mass, and ultrasonically disperse for 15-20 minutes at an ultrasonic power of 250-350W; heat to 70-80℃ and stir for 3-4 hours; after the reaction is completed, dialyze using a dialysis bag with a molecular weight cutoff of 3000 Da for 24-36 hours, and then freeze-dry; the obtained product has an amino content of 2.0-2.8 mmol / g and a fluorescence quantum yield of 35-45%.

[0011] Preferably, the preparation process of the basalt fiber-glass fiber composite filament in the flame-retardant filler layer is as follows: weigh basalt fiber and glass fiber at a mass ratio of 2:1, perform hot stretching treatment at 200-220℃, and the stretching ratio is 1.2-1.5 times; soak in an ethanol solution containing 1-2% epoxy resin for 10-15 minutes, and dry at 80-100℃.

[0012] Preferably, the preparation process of the nano-tin dioxide-antimony oxide composite powder in the sheath layer is as follows: tin chloride and antimony chloride are weighed at a mass ratio of 3:1 and dissolved in deionized water to prepare a 0.5-1 mol / L solution; 1-2 mol / L sodium hydroxide solution is added dropwise to the solution to adjust the pH to 8.0-9.0, and the reaction is stirred at room temperature for 2-3 hours; after the reaction is completed, the precipitate is filtered, washed with deionized water until neutral, and calcined at 500-600℃ for 3-4 hours; the obtained composite powder has a particle size of 50-80 nm and an antimony doping content of 8-12%.

[0013] Preferably, the conductor is a multi-strand stranded tin-plated copper conductor; the purity of the single-strand copper conductor is not less than 99.95%, the tin plating layer thickness is 3-6μm; the conductor diameter is 0.8-2.5mm, the stranding pitch is 12-18 times the conductor diameter; the DC resistance of the stranded conductor at 20℃ is not greater than 0.017Ω / m, and the tensile strength is not less than 200MPa.

[0014] Preferably, the method for preparing the flame-retardant cable includes the following steps:

[0015] S1, Preparation of insulating layer material: Low-halogenated polyether ether ketone, nano-magnesium hydroxide-alumina composite powder, and other raw materials are mixed according to a specified ratio and added to a twin-screw extruder; the temperatures are set as follows: Zone 1 temperature 290-310℃, Zone 2 temperature 320-340℃, Zone 3 temperature 330-350℃, screw speed 350-450 r / min, and feeding rate 25-35 kg / h; after melt blending, the mixture is extruded and granulated, with a particle moisture content not exceeding 0.1%.

[0016] S2, Preparation of sheath layer material: Mix raw materials such as chlorinated polyvinyl chloride-ethylene acrylate copolymer and nano tin dioxide-antimony oxide composite powder, and add them to a twin-screw extruder; set the temperature of zone 1 to 140-150℃, zone 2 to 160-170℃, zone 3 to 170-180℃, screw speed to 300-400r / min, and feeding rate to 20-30kg / h; melt blend extrusion granulation, with a particle size of 2-4mm.

[0017] S3 Conductor Stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch. The stranding tension is controlled at 50-80N to ensure that the conductor roundness deviation is no more than 0.1mm.

[0018] S4 Extruded Insulation Layer: Insulation layer granules are added to the extruder, with a barrel temperature of 330-360℃, a die head temperature of 340-370℃, and a traction speed of 12-22m / min; the thickness of the extruded insulation layer is 1.0-2.2mm, and the eccentricity is no more than 5%.

[0019] S5 Flame-retardant wrapping filler layer: Basalt fiber-glass fiber composite filaments are mixed with expanded graphite-graphene composite powder and wrapped around the outside of the insulation layer at a speed of 50-80 r / min using a wrapping machine; the wrapping overlap rate is 15-20% and the filling density is not less than 1.2 g / cm³.

[0020] S6 braided shielding layer: Braided on a braiding machine with nickel-plated copper wire of 0.1-0.2mm in diameter, braiding density of 92-95%, braiding tension of 20-30N, and shielding layer thickness of 0.15-0.3mm;

[0021] S7 Extruded Sheath Layer: Sheath layer granules are added to the extruder, with a barrel temperature of 160-180℃, a die head temperature of 170-190℃, and a traction speed of 10-18m / min; the sheath layer thickness after extrusion is 1.2-3.2mm, the cooling water temperature is 20-30℃, and the cooling time is 5-10 minutes, resulting in a flame-retardant cable.

[0022] Preferably, in step S4, the insulating layer particles need to be pre-dried before extruding the insulating layer; dried in a hot air dryer at 80-100℃ for 4-6 hours, and the moisture content of the particles after drying is not greater than 0.05%; vacuum exhaust is used during the extrusion process, and the vacuum degree is -0.08 to -0.09 MPa.

[0023] Preferably, after extruding the sheath layer in step S7, a cross-linking treatment is required; the cable is placed in a cross-linking box and cross-linked for 2-3 hours at 120-140℃ and 0.8-1.2MPa pressure, with a cross-linking degree of not less than 70%; after cross-linking, performance testing is performed, and the cable's vertical combustion performance meets the Class A requirements of GB / T 18380.1-2008, with a smoke density level of not more than 50, an oxygen index of not less than 32%, and no cracks in the -40℃ low-temperature impact performance test.

[0024] (iii) Beneficial technical effects

[0025] Compared with existing technologies, the beneficial effects of this invention are:

[0026] 1. A synergistic system is formed by using low-halogenated polyetheretherketone (PEEK) as the matrix, combined with nano-magnesium hydroxide-alumina composite powder and phosphazene-modified montmorillonite. The former decomposes at high temperatures, absorbing heat and generating a dense magnesium-alumina oxide framework; the latter releases free radicals to quench the flame and catalyzes polymer crosslinking into a graphite-like carbon layer. The two intertwine to form a "ceramic-carbon layer" flame-retardant network, blocking heat and oxygen transfer. Furthermore, the amino groups in the amino-graphene quantum dots react with carboxyl groups during insulation aging, causing the fluorescence yield to decrease with aging. Monitoring the intensity with a fluorescence spectrometer allows for online aging warnings, solving the problem of tracelessness in traditional cables. 2. Using chlorinated polyvinyl chloride-ethylene acrylate copolymer as the matrix, nano-tin dioxide-antimony oxide composite powder can capture HCl produced during combustion, reducing toxic gases; zinc borate-zinc molybdate composites generate a glassy barrier layer at high temperatures, inhibiting dripping and smoldering; ferrocene-iron acetylacetone composite flame retardant releases iron-based free radicals, quenching flame-active groups. These three components work synergistically to achieve high flame retardancy and low smoke toxicity.

[0027] 2. The flame-retardant filler layer is made of basalt fiber-glass fiber composite filaments mixed with expanded graphite-graphene composite powder to form a continuous flame-retardant barrier to prevent flame penetration; the shielding layer increases the braiding density to enhance the electromagnetic shielding effect and ensure stable signal transmission; the conductor is made of high-purity tin-plated copper stranded to improve conductivity and corrosion resistance, solving the problems of weak protection and single function of traditional cable structure.

[0028] 3. Pre-drying of insulation particles and vacuum degassing reduce air bubbles and improve insulation performance; cross-linking treatment of the sheath layer enhances aging resistance and low-temperature resistance; precise control of parameters such as temperature and rotation speed at each stage ensures stable product quality. Overall, this flame-retardant cable has high flame-retardant efficiency, low smoke and toxicity release, excellent mechanical and electrical properties, and also has an aging tracing function. It is suitable for a wide range of scenarios, has a long service life, and provides a reliable cable solution for fields with high safety requirements, possessing significant practical value and promising prospects for promotion. Attached Figure Description

[0029] Figure 1This is a flowchart of the preparation method of a flame-retardant cable proposed in this invention;

[0030] Figure 2 This is a line graph comparing the smoke density level and oxygen index of the examples and comparative examples;

[0031] Figure 3 This is a graph comparing the tensile strength of the conductor and the eccentricity of the insulation layer in the examples and comparative examples;

[0032] Figure 4 This is a radar comparison chart created by standardizing the dimensions of the performance comparison data of the examples and comparative examples. Detailed Implementation

[0033] according to Figures 1 to 4 The specific embodiments of the present invention are as follows:

[0034] Example 1

[0035] Structural composition: From the inside out, it consists of tin-plated copper conductor, insulation layer, flame-retardant filler layer, shielding layer, and sheath layer.

[0036] Raw material proportions for each layer (by weight)

[0037] Conductor: Multi-strand stranded tin-plated copper conductor, single wire copper purity 99.96%, tin plating thickness 4μm, conductor diameter 1.5mm, stranding pitch 20mm.

[0038] Insulation layer: 45 parts of low-halogenated polyether ether ketone, 18 parts of nano magnesium hydroxide-alumina composite powder, 6 parts of phosphazene-modified montmorillonite, 8 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 3 parts of amino-graphene quantum dots, 2 parts of silane coupling agent KH-560, and 1 part of antioxidant 1010.

[0039] Flame-retardant filler layer: Basalt fiber-glass fiber composite filament and expanded graphite-graphene composite powder are mixed at a mass ratio of 3:2. The basalt fiber-glass fiber composite filament is weighed at a mass ratio of 2:1. After being hot-stretched 1.3 times at 210℃, it is soaked in an ethanol solution containing 1-2% epoxy resin for 12 minutes and then dried at 80-100℃.

[0040] Shielding layer: Nickel-plated copper wire with a diameter of 0.15mm.

[0041] Sheath layer: 35 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 10 parts of nano tin dioxide-antimony oxide composite powder, 6 parts of zinc borate-zinc molybdate compound, 3 parts of ferrocene-ferric acetylacetone composite flame retardant, and 0.8 parts of lubricant.

[0042] Preparation process parameters

[0043] S1 Preparation of insulating layer material: Mix the raw materials of the insulating layer according to the ratio and add them to a twin-screw extruder. Set the temperature of zone 1 to 300℃, zone 2 to 330℃, zone 3 to 340℃, screw speed to 400r / min, and feeding rate to 30kg / h. After melt blending, extrude and granulate. The moisture content of the granules is 0.08%.

[0044] S2 Preparation of Sheath Layer Material: Mix the raw materials for the sheath layer and add them to a twin-screw extruder. Set the temperature of Zone 1 to 145℃, Zone 2 to 165℃, Zone 3 to 175℃, screw speed to 350r / min, and feed rate to 25kg / h. Perform melt blending, extrusion, and granulation to achieve a particle size of 3mm.

[0045] S3 conductor stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch, with the stranding tension controlled at 65N and the conductor roundness deviation at 0.08mm.

[0046] S4 Extruded Insulation Layer: First, the insulation layer granules are dried in a 90℃ hot air dryer for 5 hours, and the moisture content of the granules after drying is 0.04%; then the insulation layer granules are added to the extruder, and the barrel temperature is set to 345℃, the die head temperature to 355℃, and the traction speed to 17m / min. Vacuum exhaust is used during the extrusion process, and the vacuum degree is -0.085MPa; the insulation layer thickness after extrusion is 1.6mm, and the eccentricity is 4%.

[0047] S5 Flame-retardant Filler Layer: Basalt fiber-glass fiber composite filaments are mixed with expanded graphite-graphene composite powder and wrapped around the insulation layer at a speed of 65 r / min using a wrapping machine. The wrapping overlap rate is 18% and the filling density is 1.3 g / cm³.

[0048] S6 braided shielding layer: Braided on a braiding machine with nickel-plated copper wire of 0.15mm diameter, braiding density of 93%, braiding tension of 25N, and shielding layer thickness of 0.2mm.

[0049] S7 Extruded Sheath Layer: The sheath layer granules are added to the extruder, the barrel temperature is set to 170℃, the die head temperature to 180℃, and the traction speed to 14m / min; the sheath layer thickness after extrusion is 2.2mm, and it is cooled with 25℃ cooling water for 8 minutes; then the cable is placed in the cross-linking box and cross-linked for 2.5 hours at 130℃ and 1.0MPa pressure, with a cross-linking degree of 75%.

[0050] Performance test results

[0051] The flame-retardant cable prepared in this embodiment meets the Class A requirements of GB / T 18380.1-2008 for vertical combustion performance, with a smoke density rating of 42, an oxygen index of 34%, no cracks in the -40℃ low-temperature impact performance test, a DC resistance of 0.015Ω / m at 20℃, and a conductor tensile strength of 215MPa.

[0052] Example 2

[0053] Structural composition: From the inside out, it consists of tin-plated copper conductor, insulation layer, flame-retardant filler layer, shielding layer, and sheath layer.

[0054] Raw material proportions for each layer (by weight)

[0055] Conductor: Multi-strand stranded tin-plated copper conductor, single wire copper purity 99.97%, tin plating thickness 3.5μm, conductor diameter 1.0mm, stranding pitch 15mm.

[0056] Insulation layer: 42 parts of low-halogenated polyether ether ketone, 16 parts of nano magnesium hydroxide-alumina composite powder, 5.5 parts of phosphazene-modified montmorillonite, 7 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 2.5 parts of amino-graphene quantum dots, 1.5 parts of silane coupling agent KH-560, and 0.8 parts of antioxidant 1010.

[0057] Flame-retardant filler layer: Basalt fiber-glass fiber composite filament and expanded graphite-graphene composite powder are mixed at a mass ratio of 3:2. The basalt fiber-glass fiber composite filament is weighed at a mass ratio of 2:1. After being hot-stretched 1.2 times at 205℃, it is soaked in an ethanol solution containing 1-2% epoxy resin for 10 minutes and then dried at 80-100℃.

[0058] Shielding layer: Nickel-plated copper wire with a diameter of 0.12mm.

[0059] Sheath layer: 32 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 9 parts of nano tin dioxide-antimony oxide composite powder, 5.5 parts of zinc borate-zinc molybdate compound, 2.5 parts of ferrocene-ferric acetylacetone composite flame retardant, and 0.6 parts of lubricant.

[0060] Preparation process parameters

[0061] S1 Preparation of insulating layer material: Mix the raw materials of the insulating layer according to the ratio and add them to a twin-screw extruder. Set the temperature of zone 1 to 295℃, zone 2 to 325℃, zone 3 to 335℃, screw speed to 380r / min, and feeding rate to 28kg / h. After melt blending, extrude and granulate. The moisture content of the granules is 0.07%.

[0062] S2 Preparation of Sheath Layer Material: Mix the raw materials for the sheath layer and add them to a twin-screw extruder. Set the temperature of Zone 1 to 142℃, Zone 2 to 162℃, Zone 3 to 172℃, screw speed to 320r / min, and feed rate to 22kg / h. Perform melt blending, extrusion, and granulation to achieve a particle size of 2.5mm.

[0063] S3 conductor stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch, with the stranding tension controlled at 60N and the conductor roundness deviation at 0.07mm.

[0064] S4 Extruded Insulation Layer: First, the insulation layer granules are dried in an 85℃ hot air dryer for 4.5 hours, and the moisture content of the granules after drying is 0.03%; then the insulation layer granules are added to the extruder, and the barrel temperature is set to 340℃, the die head temperature to 350℃, and the traction speed to 15m / min. Vacuum exhaust is used during the extrusion process, and the vacuum degree is -0.082MPa; the insulation layer thickness after extrusion is 1.3mm, and the eccentricity is 3.5%.

[0065] S5 Flame-retardant Wrapped Filler Layer: Basalt fiber-glass fiber composite filaments are mixed with expanded graphite-graphene composite powder and wrapped around the insulation layer at a speed of 60 r / min using a wrapping machine. The wrapping overlap rate is 16% and the filling density is 1.25 g / cm³.

[0066] S6 braided shielding layer: Braided on a braiding machine with nickel-plated copper wire of 0.12mm diameter, braiding density of 92%, braiding tension of 23N, and shielding layer thickness of 0.18mm.

[0067] S7 Extruded Sheath Layer: The sheath layer granules are added to the extruder, the barrel temperature is set to 165℃, the die head temperature to 175℃, and the traction speed to 12m / min; the sheath layer thickness after extrusion is 1.8mm, and it is cooled with 23℃ cooling water for 7 minutes; then the cable is placed in the cross-linking box and cross-linked for 2.2 hours at 125℃ and 0.9MPa pressure, with a cross-linking degree of 72%.

[0068] Performance test results

[0069] The flame-retardant cable prepared in this embodiment meets the Class A requirements of GB / T 18380.1-2008 for vertical combustion performance, with a smoke density rating of 45, an oxygen index of 33%, no cracks in the -40℃ low-temperature impact performance test, a DC resistance of 0.014Ω / m at 20℃, and a conductor tensile strength of 220MPa.

[0070] Example 3

[0071] Structural composition: From the inside out, it consists of tin-plated copper conductor, insulation layer, flame-retardant filler layer, shielding layer, and sheath layer.

[0072] Raw material proportions for each layer (by weight)

[0073] Conductor: Multi-strand stranded tin-plated copper conductor, single wire copper purity 99.98%, tin plating thickness 5μm, conductor diameter 2.0mm, stranding pitch 32mm.

[0074] Insulation layer: 48 parts of low-halogenated polyether ether ketone, 19 parts of nano magnesium hydroxide-alumina composite powder, 7.5 parts of phosphazene-modified montmorillonite, 9 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 3.5 parts of amino-graphene quantum dots, 2.5 parts of silane coupling agent KH-560, and 1.2 parts of antioxidant 1010.

[0075] Flame-retardant filler layer: Basalt fiber-glass fiber composite filament and expanded graphite-graphene composite powder are mixed at a mass ratio of 3:2. The basalt fiber-glass fiber composite filament is weighed at a mass ratio of 2:1. After being hot-stretched 1.4 times at 215℃, it is soaked in an ethanol solution containing 1-2% epoxy resin for 14 minutes and then dried at 80-100℃.

[0076] Shielding layer: Nickel-plated copper wire with a diameter of 0.18mm.

[0077] Sheath layer: 38 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 11 parts of nano tin dioxide-antimony oxide composite powder, 7.5 parts of zinc borate-zinc molybdate compound, 3.5 parts of ferrocene-ferric acetylacetone composite flame retardant, and 0.9 parts of lubricant.

[0078] Preparation process parameters

[0079] S1 Preparation of insulating layer material: Mix the raw materials of the insulating layer according to the ratio and add them to a twin-screw extruder. Set the temperature of zone 1 to 305℃, zone 2 to 335℃, zone 3 to 345℃, screw speed to 420r / min, and feed rate to 32kg / h. After melt blending, extrude and granulate. The moisture content of the granules is 0.09%.

[0080] S2 Preparation of Sheath Layer Material: Mix the raw materials for the sheath layer and add them to a twin-screw extruder. Set the temperature of Zone 1 to 148℃, Zone 2 to 168℃, Zone 3 to 178℃, screw speed to 380r / min, and feed rate to 28kg / h. Perform melt blending, extrusion, and granulation to achieve a particle size of 3.5mm.

[0081] S3 conductor stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch, with the stranding tension controlled at 70N and the conductor roundness deviation at 0.09mm.

[0082] S4 Extruded Insulation Layer: First, the insulation layer granules are dried in a 95℃ hot air dryer for 5.5 hours, and the moisture content of the granules after drying is 0.02%; then the insulation layer granules are added to the extruder, and the barrel temperature is set to 350℃, the die head temperature to 360℃, and the traction speed to 20m / min. Vacuum exhaust is used during the extrusion process, and the vacuum degree is -0.088MPa; the insulation layer thickness after extrusion is 2.0mm, and the eccentricity is 4.5%.

[0083] S5 Flame-retardant Filler Layer: Basalt fiber-glass fiber composite filaments are mixed with expanded graphite-graphene composite powder and wrapped around the insulation layer at a speed of 75 r / min using a wrapping machine. The wrapping overlap rate is 19% and the filling density is 1.35 g / cm³.

[0084] S6 braided shielding layer: Braided on a braiding machine with nickel-plated copper wire of 0.18mm diameter, braiding density of 94%, braiding tension of 28N, and shielding layer thickness of 0.22mm.

[0085] S7 Extruded Sheath Layer: The sheath layer granules are added to the extruder, the barrel temperature is set to 175℃, the die head temperature to 185℃, and the traction speed to 16m / min; the sheath layer thickness after extrusion is 3.0mm, and it is cooled with 28℃ cooling water for 9 minutes; then the cable is placed in the cross-linking box and cross-linked for 2.8 hours at 135℃ and 1.1MPa pressure, with a cross-linking degree of 78%.

[0086] Performance test results

[0087] The flame-retardant cable prepared in this embodiment meets the Class A requirements of GB / T 18380.1-2008 for vertical combustion performance, with a smoke density rating of 38, an oxygen index of 36%, no cracks in the -40℃ low-temperature impact performance test, a DC resistance of 0.013Ω / m at 20℃, and a conductor tensile strength of 225MPa.

[0088] Comparative example (traditional flame-retardant cable)

[0089] Structural composition: From the inside out, it consists of a tin-plated copper conductor, an insulating layer, and a sheath layer, but lacks a flame-retardant filler layer and a shielding layer.

[0090] Raw material proportions for each layer (by weight)

[0091] Conductor: Multi-strand stranded tin-plated copper conductor, single wire copper purity 99.9%, tin plating thickness 2μm, conductor diameter 1.5mm, stranding pitch 28mm.

[0092] Insulation layer: 45 parts of ordinary polyether ether ketone, 25 parts of single nano magnesium hydroxide, 2 parts of silane coupling agent KH-560, 1 part of antioxidant 1010, and phosphazene-free modified montmorillonite and amino graphene quantum dots.

[0093] Sheath layer: 35 parts ordinary polyvinyl chloride, 8 parts single chlorinated paraffin flame retardant, 0.8 parts lubricant, without nano tin dioxide-antimony oxide composite powder and zinc borate-zinc molybdate compound.

[0094] Preparation process parameters

[0095] S1 Preparation of insulating layer material: The raw materials for the insulating layer are mixed according to the ratio and then added to a twin-screw extruder. The temperature of zone 1 is set to 300℃, zone 2 to 330℃, zone 3 to 340℃, the screw speed is 400r / min, and the feeding rate is 30kg / h. After melt blending, the material is extruded and granulated. The granules are not dried and have a moisture content of 0.3%.

[0096] S2 Preparation of Sheath Layer Material: Mix the raw materials for the sheath layer and add them to a twin-screw extruder. Set the temperature of Zone 1 to 145℃, Zone 2 to 165℃, Zone 3 to 175℃, screw speed to 350r / min, and feed rate to 25kg / h. Perform melt blending, extrusion, and granulation to achieve a particle size of 3mm.

[0097] S3 conductor stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch, with the stranding tension controlled at 65N and the conductor roundness deviation at 0.12mm.

[0098] S4 Extrusion Insulation Layer: Undried insulation layer granules are directly added to the extruder without vacuum exhaust. The barrel temperature is set at 345℃, the die head temperature at 355℃, and the traction speed at 17m / min. The insulation layer thickness after extrusion is 1.6mm, and the eccentricity is 7%.

[0099] S5 Unwrapped Flame Retardant Filler Layer Process: Directly proceed to the Extrusion Sheath Layer Process.

[0100] S6 Non-woven Shielding Layer Process: Directly proceed to the Extrusion Sheath Layer Process.

[0101] S7 Extruded Sheath Layer: Sheath layer granules are added to the extruder, the barrel temperature is set to 170℃, the die head temperature to 180℃, and the traction speed to 14m / min; the sheath layer thickness after extrusion is 2.2mm, and it is cooled with 25℃ cooling water for 8 minutes; no cross-linking treatment is performed.

[0102] Performance test results

[0103] The flame-retardant cable prepared in this comparative example only meets the Class B requirements of GB / T 18380.1-2008 in terms of vertical combustion performance, with a smoke density rating of 75, an oxygen index of 28%, obvious cracks in the -40℃ low-temperature impact performance test, a DC resistance of 0.019Ω / m at 20℃, and a conductor tensile strength of 180MPa.

[0104] The flame retardant and safety performance of the examples and comparative examples are compared in the table below:

[0105] Table 1

[0106] Performance indicators Example 1 Example 2 Example 3 Comparative Example Vertical combustion performance Grade A Grade A Grade A Grade B Smoke density level 42 45 38 75 Oxygen index (%) 34 33 36 28 -40℃ low temperature impact performance No cracks No cracks No cracks Obvious cracks appeared

[0107] The mechanical, electrical, and process-related properties of the embodiments and comparative examples are compared in the table below:

[0108] Table 2

[0109] Performance indicators Example 1 Example 2 Example 3 Comparative Example DC resistance of a conductor at 20℃ (Ω / m) 0.015 0.014 0.013 0.019 Conductor tensile strength (MPa) 215 220 225 180 Insulation layer eccentricity (%) 4 3.5 4.5 7 Flame retardant filler layer filler density 1.3 1.25 1.35 none Shielding layer weave density (%) 93 92 94 none Degree of cross-linking of sheath layer (%) 75 72 78 none Moisture content (%) of the insulating layer particles after drying 0.04 0.03 0.02 0.3

[0110] As can be clearly seen from the two performance comparison tables, the vertical combustion performance of Examples 1-3 all meet the GB / T 18380.1-2008 Class A standard, with a smoke density rating of ≤45, an oxygen index of ≥33%, and no cracks after impact at -40℃. This is significantly better than the Class B combustion performance, smoke density rating of 75, oxygen index of 28%, and low-temperature cracking problem of the comparative example. This confirms that the design of the insulation layer, which is formed by compounding low-halogenated polyether ether ketone with composite powder to form a dense flame-retardant network, and the sheath layer, which is combined with composite flame retardant, effectively solves the defects of traditional cables such as low flame retardant efficiency, high smoke density, and poor low-temperature resistance, and achieves the beneficial effects of high-efficiency flame retardancy and low smoke and low toxicity.

[0111] The conductors in Examples 1-3 have a DC resistance of ≤0.015Ω / m at 20℃, a tensile strength of ≥215MPa, an insulation layer eccentricity of ≤4.5%, a flame-retardant filler layer with a fill density of ≥1.25g / cm³, a shielding layer with a braid density of ≥92%, a sheath layer crosslinking degree of ≥72%, and an insulation layer particle moisture content of ≤0.04% after drying. In contrast, the comparative examples lack a flame-retardant filler layer and a shielding layer, have substandard conductor performance, lack crosslinking treatment, and have high moisture content in the insulation particles. This demonstrates the advantages of this invention, which uses high-purity tin-plated copper conductors and precise process control. It solves the problems of weak protection, poor mechanical and electrical properties, and unstable processes in traditional cable structures, ultimately achieving the beneficial effects of excellent mechanical and electrical properties, stable quality, and wide applicability.

[0112] 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 flame-retardant cable, characterized in that, From the inside out, it includes a conductor, an insulating layer, a flame-retardant filler layer, a shielding layer, and a sheath layer; The insulating layer raw materials, by weight, include 40-50 parts of low-halogenated polyether ether ketone, 15-20 parts of nano-magnesium hydroxide-alumina composite powder, 5-8 parts of phosphazene-modified montmorillonite, 6-10 parts of melamine cyanuric acid-pentaerythritol phosphate compound, 2-4 parts of amino-based graphene quantum dots, 1-3 parts of silane coupling agent KH-560, and 0.5-1.5 parts of antioxidant 1010; The flame-retardant filler layer is a mixture of basalt fiber-glass fiber composite filament and expanded graphite-graphene composite powder in a mass ratio of 3:2; the raw materials of the sheath layer include, by weight, 30-40 parts of chlorinated polyvinyl chloride-ethylene acrylate copolymer, 8-12 parts of nano tin dioxide-antimony oxide composite powder, 5-8 parts of zinc borate-zinc molybdate compound, 2-4 parts of ferrocene-ferric acetylacetone composite flame retardant, and 0.5-1 parts of lubricant.

2. The flame-retardant cable according to claim 1, characterized in that, The process also includes the preparation of nano-magnesium hydroxide-alumina composite powder: weigh nano-magnesium hydroxide and nano-alumina at a mass ratio of 4:1, add deionized water, then add 0.5-1% citric acid by mass, and ultrasonically disperse for 20-30 minutes with ultrasonic power controlled at 300-500W; heat to 60-70℃, add 3-5% silane coupling agent KH-550 by mass, and stir for 2-3 hours; after the reaction is completed, centrifuge and separate, dry the obtained solid at 80-100℃ for 4-6 hours, grind and pass through a 300-mesh sieve; the obtained composite powder has a particle size of 80-120nm, a specific surface area of ​​50-80m² / g, and an oil absorption value of no more than 25g / 100g.

3. The flame-retardant cable according to claim 1, characterized in that, The process also includes the preparation of phosphazene-modified montmorillonite: montmorillonite is added to deionized water and ultrasonically dispersed for 15-20 minutes at an ultrasonic power of 200-300W. Hydrochloric acid (2-3% by mass) is added to adjust the pH to 3.0-4.

0. Hexachlorocyclotriphosphazene (5-8% by mass) is added, and the mixture is heated to 80-90℃ and stirred for 4-5 hours. Aminophene ether (3-5% by mass) is added, and the reaction continues for 2-3 hours. After the reaction is complete, the mixture is filtered, washed with deionized water until neutral, and dried at 100-120℃ for 6-8 hours. The resulting modified montmorillonite has an interlayer spacing of 2.5-3.0 nm, a phosphorus content of 6-8%, and a nitrogen content of 4-6%.

4. The flame-retardant cable according to claim 1, characterized in that, The preparation process of the amino-based graphene quantum dots is as follows: weigh the graphene quantum dots, add deionized water, and then add 5-10% of 3-aminopropyltriethoxysilane by mass. Disperse the mixture ultrasonically for 15-20 minutes at an ultrasonic power of 250-350W. Heat the mixture to 70-80℃ and stir for 3-4 hours. After the reaction is complete, dialyze the mixture using a dialysis bag with a molecular weight cutoff of 3000 Da for 24-36 hours, and then freeze-dry it. The obtained product has an amino content of 2.0-2.8 mmol / g and a fluorescence quantum yield of 35-45%.

5. The flame-retardant cable according to claim 1, characterized in that, The preparation process of the basalt fiber-glass fiber composite filament in the flame-retardant filler layer is as follows: weigh basalt fiber and glass fiber at a mass ratio of 2:1, perform hot stretching treatment at 200-220℃, and the stretching ratio is 1.2-1.5 times; soak in an ethanol solution containing 1-2% epoxy resin for 10-15 minutes, and dry at 80-100℃.

6. The flame-retardant cable according to claim 1, characterized in that, The preparation process of the nano-tin dioxide-antimony oxide composite powder in the sheath layer is as follows: tin chloride and antimony chloride are weighed at a mass ratio of 3:1 and dissolved in deionized water to prepare a 0.5-1 mol / L solution; 1-2 mol / L sodium hydroxide solution is added dropwise to the solution to adjust the pH to 8.0-9.0, and the reaction is stirred at room temperature for 2-3 hours; after the reaction is completed, the precipitate is filtered, washed with deionized water until neutral, and calcined at 500-600℃ for 3-4 hours; the obtained composite powder has a particle size of 50-80 nm and an antimony doping content of 8-12%.

7. The flame-retardant cable according to claim 1, characterized in that, The conductor is a multi-strand stranded tin-plated copper conductor; the purity of the single-strand copper conductor is not less than 99.95%, the tin plating layer thickness is 3-6μm; the conductor diameter is 0.8-2.5mm, the stranding pitch is 12-18 times the conductor diameter; the DC resistance of the stranded conductor at 20℃ is not greater than 0.017Ω / m, and the tensile strength is not less than 200MPa.

8. A method for preparing a flame-retardant cable as described in claim 1, characterized in that, Includes the following steps: S1, Preparation of insulating layer material: Low-halogenated polyether ether ketone, nano-magnesium hydroxide-alumina composite powder, and other raw materials are mixed according to a specified ratio and added to a twin-screw extruder; the temperatures are set as follows: Zone 1 temperature 290-310℃, Zone 2 temperature 320-340℃, Zone 3 temperature 330-350℃, screw speed 350-450 r / min, and feeding rate 25-35 kg / h; after melt blending, the mixture is extruded and granulated, with a particle moisture content not exceeding 0.1%. S2, Preparation of sheath layer material: Mix raw materials such as chlorinated polyvinyl chloride-ethylene acrylate copolymer and nano tin dioxide-antimony oxide composite powder, and add them to a twin-screw extruder; set the temperature of zone 1 to 140-150℃, zone 2 to 160-170℃, zone 3 to 170-180℃, screw speed to 300-400r / min, and feeding rate to 20-30kg / h; melt blend extrusion granulation, with a particle size of 2-4mm. S3 Conductor Stranding: The single-wire tin-plated copper conductor is stranded on a stranding machine at a set pitch. The stranding tension is controlled at 50-80N to ensure that the conductor roundness deviation is no more than 0.1mm. S4 Extruded Insulation Layer: Insulation layer granules are added to the extruder, with a barrel temperature of 330-360℃, a die head temperature of 340-370℃, and a traction speed of 12-22m / min; the thickness of the extruded insulation layer is 1.0-2.2mm, and the eccentricity is no more than 5%. S5 Flame-retardant wrapping filler layer: Basalt fiber-glass fiber composite filaments are mixed with expanded graphite-graphene composite powder and wrapped around the outside of the insulation layer at a speed of 50-80 r / min using a wrapping machine; the wrapping overlap rate is 15-20% and the filling density is not less than 1.2 g / cm³. S6 braided shielding layer: Braided on a braiding machine with nickel-plated copper wire of 0.1-0.2mm in diameter, braiding density of 92-95%, braiding tension of 20-30N, and shielding layer thickness of 0.15-0.3mm; S7 Extruded Sheath Layer: Sheath layer granules are added to the extruder, with a barrel temperature of 160-180℃, a die head temperature of 170-190℃, and a traction speed of 10-18m / min; the sheath layer thickness after extrusion is 1.2-3.2mm, the cooling water temperature is 20-30℃, and the cooling time is 5-10 minutes, resulting in a flame-retardant cable.

9. The method for preparing the flame-retardant cable according to claim 8, characterized in that, Before extruding the insulation layer in step S4, the insulation layer particles need to be pre-dried; they should be dried in a hot air dryer at 80-100℃ for 4-6 hours, and the moisture content of the particles after drying should not exceed 0.05%; vacuum exhaust is used during the extrusion process, and the vacuum degree is -0.08 to -0.09MPa.

10. The method for preparing the flame-retardant cable according to claim 8, characterized in that, After extruding the sheath layer in step S7, cross-linking treatment is required. The cable is placed in a cross-linking box and cross-linked for 2-3 hours at 120-140℃ and 0.8-1.2MPa pressure, with a cross-linking degree of not less than 70%. After cross-linking, performance testing is performed. The vertical combustion performance of the cable meets the Class A requirements of GB / T 18380.1-2008, with a smoke density level of not more than 50, an oxygen index of not less than 32%, and no cracks in the -40℃ low temperature impact performance test.

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