Halogen-free environmentally-friendly fireproof flame-retardant cable and preparation method thereof

Abstract

This invention relates to the field of cable manufacturing technology, specifically to a halogen-free, environmentally friendly, fire-retardant cable and its manufacturing method. The cable includes a conductor, an insulation layer, and a sheath layer. The insulation layer and sheath layer use the same halogen-free flame-retardant substrate. The halogen-free flame-retardant substrate, by weight, comprises: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 15 to 28 parts aluminum diethyl phosphite, 6 to 10 parts piperazine pyrophosphate, 3 to 5 parts boron nitride, 1.5 to 3.0 parts silane coupling agent KH-570, 0.6 to 1.2 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide. This invention uses halogen-free flame-retardant components, fundamentally avoiding pollution problems caused by halogen-containing substances, and releases no toxic or corrosive gases during combustion.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, specifically to a halogen-free, environmentally friendly, fire-retardant cable and its manufacturing method. Background Technology

[0002] As the core carrier of power and signal transmission, cables are widely used in many fields such as construction, transportation, and industry. Their fire resistance and flame retardant performance are directly related to the safety and stability of the application scenarios. Currently, most flame-retardant cables use halogen-containing flame-retardant systems, which have a certain flame-retardant effect, but release a large amount of corrosive gases and toxic fumes when burning, polluting the environment and endangering human health, making it difficult to meet the dual requirements of modern environmental protection and safety.

[0003] With increasingly stringent environmental standards, halogen-free flame-retardant cables have become an industry trend. However, existing halogen-free flame-retardant cables still have many technical shortcomings. Most halogen-free flame retardants have poor compatibility with the matrix resin, easily leading to uneven dispersion, sedimentation, and stratification, resulting in unstable flame-retardant performance and difficulty in meeting stringent fire protection standards.

[0004] Meanwhile, the addition of flame retardants can damage the structural integrity of the substrate, leading to a significant decrease in the mechanical and electrical insulation properties of the cable, making it impossible to simultaneously achieve flame retardancy, environmental friendliness, and performance. Some halogen-free flame-retardant cables have complex manufacturing processes, unreasonable flame retardant system combinations, and insufficient flame retardant persistence and smoke suppression performance, still posing safety hazards in high-temperature combustion scenarios.

[0005] Existing technologies struggle to achieve synergistic optimization of flame retardant, environmental, mechanical, and electrical properties, making them unsuitable for the stringent requirements of high-end applications for cables. Summary of the Invention

[0006] The primary objective of this invention is to provide a halogen-free, environmentally friendly, fire-resistant, and flame-retardant cable and its preparation method.

[0007] A further objective of this invention is to provide a halogen-free, environmentally friendly, fire-retardant cable, comprising a conductor, an insulation layer, and a sheath layer, wherein the insulation layer and the sheath layer use the same halogen-free flame-retardant substrate; the halogen-free flame-retardant substrate comprises, by weight: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 15 to 28 parts aluminum diethyl phosphite, 6 to 10 parts piperazine pyrophosphate, 3 to 5 parts boron nitride, 1.5 to 3.0 parts silane coupling agent KH-570, 0.6 to 1.2 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide.

[0008] Preferably, the conductor is an oxygen-free copper wire with a conductivity of 99.96%, a diameter of 0.5 mm, and is formed by twisting 19 oxygen-free copper wires together with a twisting pitch of 7.5 mm.

[0009] Preferably, the vinyl acetate content of the ethylene-vinyl acetate copolymer is 25% to 35%.

[0010] Preferably, the insulation layer has a thickness of 1.0 mm and the sheath layer has a thickness of 1.5 mm.

[0011] A method for preparing a halogen-free, environmentally friendly, fire-retardant cable includes, in sequence, a halogen-free compound flame retardant pretreatment, a substrate mixing and granulation, a conductor preparation, insulation coating, sheath coating, and cross-linking curing steps; wherein the halogen-free compound flame retardant is a compound mixture of diethylaluminum hypophosphite, piperazine pyrophosphate, boron nitride, and magnesium hydroxide.

[0012] Preferably, the pretreatment of the halogen-free compound flame retardant is as follows: the halogen-free compound flame retardant is dried at 110°C for 12 min; the silane coupling agent KH-570 is mixed with ethanol and water at a mass ratio of 1:4:0.8 to 1:6:1.2 and stirred for 8 min to complete hydrolysis; the dried halogen-free compound flame retardant is fluidized at 1000 r / min and sprayed with the hydrolyzed silane coupling agent KH-570, stirred for 20 min, and then heated to 110°C to react for 12 min.

[0013] Preferably, the matrix compounding and granulation is performed as follows: the matrix resin, modified halogen-free compound flame retardant, and additives are fed into a mixer for segmented compounding. The first segment is compounded at 130°C and 600 r / min for 4 min, and the second segment is compounded at 170°C and 900 r / min for 6 min. The mixture is then granulated using a twin-screw extruder at a speed of 200 r / min and an extrusion temperature of 170°C.

[0014] Preferably, the conductor is prepared by: stranding 19 oxygen-free copper wires together with a stranding pitch of 7.5 mm and polishing at 800 r / min for 3 min.

[0015] Preferably, the insulation coating is performed by melting halogen-free flame-retardant substrate particles at 170°C, coating the conductor at a speed of 10 m / min to form an insulation layer, and applying a head pressure of 18 MPa; the sheath coating is performed by melting halogen-free flame-retardant substrate particles at 180°C, coating the insulated wire core at a speed of 8 m / min to form a sheath layer, and applying a head pressure of 20 MPa.

[0016] Preferably, the crosslinking curing is performed as follows: electron beam irradiation dose of 100 kGy, irradiation rate of 5 m / min, followed by heat treatment at 90°C for 3 h, and cooling to room temperature at a rate of 5°C / min.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses halogen-free flame retardant components, which avoids pollution problems caused by halogen-containing substances from the source, and releases no toxic or corrosive gases during combustion. This invention significantly improves the compatibility between flame retardants and matrix resins by compounding flame retardant components and performing surface modification treatment, so that the flame retardant is evenly dispersed in the substrate to form a stable flame retardant barrier, effectively improving the flame retardant performance of cables. It has excellent self-extinguishing properties during combustion, low flame spread, and outstanding smoke suppression effect.

[0018] 2. The flame retardant pretreatment and anti-settling component addition of this invention solve the problems of uneven dispersion and sedimentation of flame retardants, ensure the uniform and complete structure of the substrate, significantly improve the mechanical properties of the cable, and enable it to maintain good service condition under tensile, bending and other working conditions.

[0019] 3. The electron beam irradiation crosslinking and isothermal aging process of this invention further solidifies the substrate structure, enhances material stability, and gives the cable excellent electrical insulation performance, ensuring safe and reliable power transmission.

[0020] 4. This invention achieves a synergistic improvement in flame retardant performance, environmental performance, mechanical performance and electrical performance. The preparation process is simple and controllable, the product performance is stable, and it can meet the requirements of various high-end scenarios for fire prevention, flame retardancy and environmental safety of cables. Detailed Implementation

[0021] 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. 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] Example 1: This embodiment provides a halogen-free, environmentally friendly, fire-retardant cable, comprising a conductor, an insulation layer, and a sheath layer. The insulation layer and the sheath layer use the same halogen-free, flame-retardant substrate. Specific implementation details are as follows: The following raw materials were selected: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 20 parts aluminum diethyl phosphite, 8 parts piperazine pyrophosphate, 4 parts boron nitride, 1.5 parts KH-570, 0.6 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide. The ethylene-vinyl acetate copolymer contained 25% vinyl acetate. The oxygen-free copper wire had a conductivity of 99.96% and a diameter of 0.5 mm. The butyl stearate had a purity of 99.5%. The magnesium hydroxide had a particle size of 2 μm. The hydrophobic fumed silica had a specific surface area of ​​200 m². 2 / g.

[0023] In the preparation process, the halogen-free compound flame retardant is first placed in a drying device and dried at 110℃ for 12 minutes to remove surface adsorbed water. At the same time, the silane coupling agent is mixed with ethanol and trace amounts of water at a mass ratio of 1:4:0.8 and stirred for 8 minutes to complete hydrolysis. The dried halogen-free compound flame retardant is then placed in a high-speed mixer, fluidized at 1000 r / min, and the hydrolyzed silane coupling agent is sprayed evenly. After spraying, high-speed stirring is continued for 20 minutes, and then the temperature is raised to 110℃ and reacted for 12 minutes to complete surface modification. The mixture is then cooled to room temperature for later use.

[0024] Subsequently, the matrix resin, modified halogen-free compound flame retardant, anti-settling agent, antioxidant, lubricant, and smoke suppressant were put into a mixer and mixed in stages. First, they were mixed at 130°C and 600 r / min for 4 minutes, and then at 170°C and 900 r / min for 6 minutes. After the mixing was completed, the mixture was granulated by a twin-screw extruder at a speed of 200 r / min and an extrusion temperature of 170°C to obtain halogen-free flame retardant matrix granules.

[0025] For conductor preparation, oxygen-free copper wire with a conductivity of 99.96% was selected and stranded in groups of 19 with a stranding pitch of 7.5 mm. Uniform tension was maintained during stranding. After completion, the surface was polished at 800 r / min for 3 minutes to remove the oxide layer. For insulation coating, halogen-free flame-retardant substrate granules were fed into an extruder and melted at 170℃. The conductor was fed into the die head at a speed of 10 m / min and coated through a die to form an insulation layer with a thickness of 1.0 mm. The extruder die head pressure was 18 MPa.

[0026] The same halogen-free flame-retardant base material particles are fed into another extruder and melted at 180°C. The insulated wire core is fed into the die head at a speed of 8 m / min to form a sheath layer with a thickness of 1.5 mm and a die head pressure of 20 MPa.

[0027] Cross-linking and curing: The coated cable is sent to an electron beam irradiation device with an irradiation dose of 100 kGy and an irradiation rate of 5 m / min to complete the cross-linking. Then it is placed in a constant temperature aging chamber, kept at 90℃ for 3 hours, and cooled to room temperature at a rate of 5℃ / min. Finally, the cable is tested for appearance, dimensions, electrical performance, mechanical performance, flame retardancy, and environmental performance. If it passes the tests, it is considered a finished product.

[0028] Example 2: This embodiment is based on Example 1, with the single variable being the dosage of each component of the halogen-free compound flame retardant. The specific implementation details are as follows: The following raw materials were selected: 35 parts of polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 28 parts of aluminum diethyl phosphite, 6 parts of piperazine pyrophosphate, 3 parts of boron nitride, 1.5 parts of KH-570, 0.6 parts of hydrophobic fumed silica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 1.0 part of butyl stearate, and 2 parts of magnesium hydroxide.

[0029] The product contains 25% vinyl acetate copolymer, 99.96% oxygen-free copper wire with a diameter of 0.5 mm, 99.5% butyl stearate, 2 μm magnesium hydroxide particles, and 200 m² hydrophobic fumed silica. 2 / g.

[0030] The preparation steps are exactly the same as in Example 1, ensuring that the single variable is the amount of each component of the halogen-free compound flame retardant.

[0031] Example 3: This embodiment is based on Example 1, with the single variable being the amount of silane coupling agent and the hydrolysis ratio. The specific implementation details are as follows: The following raw materials were selected: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 20 parts aluminum diethyl phosphite, 8 parts piperazine pyrophosphate, 4 parts boron nitride, 3.0 parts KH-570, 0.6 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide. The ethylene-vinyl acetate copolymer contained 25% vinyl acetate. The oxygen-free copper wire had a conductivity of 99.96% and a diameter of 0.5 mm. The butyl stearate had a purity of 99.5%. The magnesium hydroxide had a particle size of 2 μm, and the hydrophobic fumed silica had a specific surface area of ​​200 m². 2 / g.

[0032] The preparation steps are basically the same as in Example 1, except that the pretreatment hydrolysis ratio of the flame retardant is adjusted to 1:6:1.2, the speed of the high-speed mixer is kept at 1000 r / min, and the other process parameters are the same as in Example 1.

[0033] Example 4: This embodiment provides a halogen-free, environmentally friendly, fire-retardant cable. Based on Embodiment 1, the single variable is adjusted to the mixing and extrusion process parameters. The specific implementation details are as follows: the raw materials and key raw material parameters are completely consistent with those in Embodiment 1.

[0034] The preparation steps are basically the same as in Example 1. The base material mixing parameters are adjusted as follows: first stage 145℃, 800r / min, 6min; second stage 185℃, 1100r / min, 9min; twin-screw extruder speed 220r / min; extrusion temperature 185℃; insulation coating temperature 185℃; extrusion speed 16m / min; sheath coating temperature 195℃; die head pressure 26MPa; and other process parameters are the same as in Example 1.

[0035] Example 5: This embodiment is based on Example 1, with the single variable being the type of matrix resin and the blending ratio. The specific implementation details are as follows: The following raw materials were selected: 30 parts polypropylene, 25 parts polyethylene, 20 parts aluminum diethyl phosphite, 8 parts piperazine pyrophosphate, 4 parts boron nitride, 1.5 parts KH-570, 0.6 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide.

[0036] The polypropylene has a melt index of 2.5 g / 10 min, the oxygen-free copper wire has a conductivity of 99.96% and a diameter of 0.5 mm, the butyl stearate has a purity of 99.5%, the magnesium hydroxide has a particle size of 2 μm, and the hydrophobic fumed silica has a specific surface area of ​​200 m². 2 / g.

[0037] The preparation steps are basically the same as in Example 1, except that the base material mixing temperature is adjusted to 135°C for the first stage and 175°C for the second stage, the twin-screw extruder speed is 210 r / min and the extrusion temperature is 175°C, and the other process parameters are the same as in Example 1.

[0038] Example 6: This embodiment provides a halogen-free, environmentally friendly, fire-retardant cable. Based on Embodiment 1, the single variable is adjusted to be the total amount and proportion of each component of the halogen-free compound flame retardant. Specific implementation details are as follows: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 15 parts aluminum diethyl phosphite, 10 parts piperazine pyrophosphate, 5 parts boron nitride, 1.5 parts KH-570, 0.6 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide are selected as raw materials. The ethylene-vinyl acetate copolymer contains 25% vinyl acetate, the oxygen-free copper wire has a conductivity of 99.96% and a diameter of 0.5 mm, the butyl stearate has a purity of 99.5%, the magnesium hydroxide has a particle size of 2 μm, and the hydrophobic fumed silica has a specific surface area of ​​200 m². 2 / g.

[0039] The preparation steps are completely consistent with those in Example 1, ensuring that the only variables are the total amount of halogen-free compound flame retardant and the proportion of each component.

[0040] Example 7: This embodiment provides a halogen-free, environmentally friendly, fire-retardant cable. Based on Example 1, the single variable is adjusted to be the blending ratio of the matrix resin and the vinyl acetate content of the ethylene-vinyl acetate copolymer. Specific implementation details are as follows: The following raw materials were selected: 25 parts of polyethylene, 30 parts of ethylene-vinyl acetate copolymer, 20 parts of aluminum diethyl phosphite, 8 parts of piperazine pyrophosphate, 4 parts of boron nitride, 1.5 parts of KH-570, 0.6 parts of hydrophobic fumed silica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 1.0 part of butyl stearate, and 2 parts of magnesium hydroxide.

[0041] The product contains 35% vinyl acetate copolymer, 99.96% oxygen-free copper wire with a diameter of 0.5 mm, 99.5% butyl stearate, 2 μm magnesium hydroxide particles, and 200 m² hydrophobic fumed silica. 2 / g.

[0042] The preparation steps are basically the same as in Example 1, except that the temperature of the first stage of substrate mixing is adjusted to 125°C, the twin-screw extruder speed is 190 r / min and the extrusion temperature is 165°C, and the other process parameters are the same as in Example 1.

[0043] Example 8: This embodiment provides a halogen-free, environmentally friendly, fire-retardant cable. Based on Example 1, the single variable is adjusted to be the amount of anti-settling additive. The specific implementation details are as follows: 35 parts of polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 20 parts of aluminum diethyl phosphite, 8 parts of piperazine pyrophosphate, 4 parts of boron nitride, 1.5 parts of KH-570, 1.2 parts of hydrophobic fumed silica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 1.0 part of butyl stearate, and 2 parts of magnesium hydroxide are selected as raw materials.

[0044] The product contains 25% vinyl acetate copolymer, 99.96% oxygen-free copper wire with a diameter of 0.5 mm, 99.5% butyl stearate, 2 μm magnesium hydroxide particles, and 200 m² hydrophobic fumed silica. 2 / g.

[0045] The preparation steps are exactly the same as in Example 1, ensuring that the single variable is the amount of anti-settling agent.

[0046] Comparative Example 1: This comparative example is based on Example 1, but omits the flame retardant pretreatment step. The specific implementation details are as follows: The raw materials and key parameters of the raw materials were selected in complete accordance with those in Example 1.

[0047] The preparation steps are basically the same as in Example 1, except that the flame retardant pretreatment step is omitted. The unmodified halogen-free compound flame retardant is directly added to the internal mixer to mix with other raw materials. The remaining process parameters are the same as in Example 1, namely, the base material is first mixed at 130°C and 600 r / min for 4 min, and then mixed at 170°C and 900 r / min for 6 min. The twin-screw extruder speed is 200 r / min and the extrusion temperature is 170°C. The conductor is prepared by stranding 19 copper wires with a stranding pitch of 7.5 mm. The polishing speed is 800 r / min and the polishing time is 3 min. The insulation coating is 170°C, the extrusion speed is 10 m / min, the insulation layer thickness is 1.0 mm, and the die head pressure is 18 MPa. The sheath coating is 180°C, the extrusion speed is 8 m / min, the sheath layer thickness is 1.5 mm, and the die head pressure is 20 MPa. The irradiation dose is 100 kGy, the irradiation rate is 5 m / min, the constant temperature aging is 90°C for 3 h, and the cooling rate is 5°C / min.

[0048] Comparative Example 2: This comparative example is based on Example 1, with the single variable adjusted to be the total amount of halogen-free compound flame retardant and the proportion of each component. The specific implementation details are as follows: The following raw materials were selected: 35 parts of polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 12 parts of aluminum diethyl phosphite, 4 parts of piperazine pyrophosphate, 2 parts of boron nitride, 1.5 parts of KH-570, 0.6 parts of hydrophobic fumed silica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 1.0 part of butyl stearate, and 2 parts of magnesium hydroxide.

[0049] The key parameters of the raw materials are the same as those in Example 1, and the preparation steps are exactly the same as those in Example 1.

[0050] Comparative Example 3: This comparative example is based on Example 1, but the flame retardant is replaced with a halogenated flame retardant. The specific implementation details are as follows: The following raw materials were selected: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 25 parts polyvinyl chloride, 1.5 parts KH-570, 0.6 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide. Key parameters for the raw materials included: ethylene-vinyl acetate copolymer with a vinyl acetate content of 25%; oxygen-free copper wire with a conductivity of 99.96% and a diameter of 0.5 mm; butyl stearate with a purity of 99.5%; magnesium hydroxide with a particle size of 2 μm; and hydrophobic fumed silica with a specific surface area of ​​200 m². 2 / g.

[0051] The preparation steps are exactly the same as in Example 1.

[0052] Comparative Example 4: This comparative example is based on Example 1, but without the anti-settling additive. The specific implementation details are as follows: the raw materials selected are exactly the same as those in Example 1, except that the hydrophobic fumed silica is omitted.

[0053] The key parameters of the raw materials are the same as those in Example 1, and the preparation steps are exactly the same as those in Example 1.

[0054] Comparative Example 5: This comparative example is based on Example 1, but omits the crosslinking and curing step. The specific implementation details are as follows: the raw materials and key parameters of the raw materials are completely consistent with those in Example 1.

[0055] The preparation steps are basically the same as in Example 1, except that the cross-linking and curing steps are omitted. After the sheath is coated, it is directly cooled to room temperature at a rate of 5℃ / min. The remaining process parameters are the same as in Example 1, namely, flame retardant pretreatment: drying at 110℃ for 12 min, hydrolysis ratio of 1:4:0.8 and stirring for 8 min, modification: stirring at 1000 r / min for 20 min and reacting at 110℃ for 12 min; substrate mixing: first mixing at 130℃ and 600 r / min for 4 min, then mixing at 170℃ and 900 r / min for 6 min; conductor preparation: stranding 19 copper wires with a stranding pitch of 7.5 mm, polishing speed of 800 r / min and polishing time of 3 min; insulation coating: 170℃, extrusion speed of 10 m / min, insulation layer thickness of 1.0 mm, die head pressure of 18 MPa; sheath coating: 180℃, extrusion speed of 8 m / min, sheath layer thickness of 1.5 mm, die head pressure of 20 MPa.

[0056] Comparative Example 6: This comparative example provides a cable based on Example 1, employing a binary composite flame-retardant system. Specific implementation details are as follows: The following raw materials were selected: 35 parts of polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 28 parts of aluminum diethyl phosphite, 12 parts of piperazine pyrophosphate, 1.5 parts of KH-570, 0.6 parts of hydrophobic fumed silica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 1.0 part of butyl stearate, and 2 parts of magnesium hydroxide.

[0057] The key parameters of the raw materials are the same as those in Example 1, and the preparation steps are exactly the same as those in Example 1.

[0058] Comparative Example 7: This comparative example provides a cable based on Example 1, with the addition of an anti-settling additive but without flame retardant modification. Specific implementation details are as follows: The raw materials and key parameters of the raw materials were selected in complete accordance with those in Example 1.

[0059] The preparation steps are basically the same as in Example 1, except that the flame retardant pretreatment step is omitted. The unmodified halogen-free compound flame retardant is directly put into the internal mixer to mix with other raw materials. The remaining process parameters are the same as in Example 1.

[0060] The halogen-free compound flame retardant of this invention is a compound mixture of aluminum diethylphosphite, piperazine pyrophosphate, boron nitride, and magnesium hydroxide. All components are commercially available industrial-grade raw materials used in cable processing. The aluminum diethylphosphite has a purity ≥98%, the piperazine pyrophosphate has a purity ≥99%, the boron nitride is hexagonal boron nitride with a particle size of 1-5 μm, and the magnesium hydroxide is active magnesium hydroxide with a particle size of 2 μm. The silane coupling agent KH-570, hydrophobic fumed silica, antioxidant 1010, antioxidant 168, and butyl stearate are all conventional processing aids for polyolefin cable materials. The hydrophobic fumed silica has a specific surface area of ​​200 m². 2 / g, butyl stearate purity 99.5%.

[0061] The internal mixer, twin-screw extruder, high-speed mixer, electron beam irradiation equipment, and constant temperature aging chamber used in this invention are all conventional equipment in the cable manufacturing field, and those skilled in the art can adapt and operate them according to conventional process parameters. The performance test samples are all finished cable products prepared according to the method of this invention. Sample preparation and testing environments comply with relevant national / industry standards, and the test data are stable and repeatable.

[0062] Performance testing and results analysis: Performance testing standards: The finished cables prepared in the eight examples and seven comparative examples were subjected to comprehensive performance tests according to the following standards. The test items covered flame retardancy, halogen-free environmental protection performance, mechanical performance, and electrical performance to ensure that the test results were authoritative and comparable. The specific test standards are as follows: (1) Flame retardant performance: The vertical burning rating, bundled burning flame spread length and self-extinguishing time were tested according to GB / T18380-2008 "Cables under flame conditions"; the oxygen index was tested according to GB / T2406-2008 "Plastics burning performance test method oxygen index method"; and the smoke density and toxic gas (CO) yield were tested according to EN50268-2 standard.

[0063] (2) Halogen-free environmental performance: Halogen content was tested according to GB / T17650-1998 Test method for gases released during combustion of materials derived from cables or optical cables; Heavy metal content was tested according to RoHS directive (the heavy metal content of all samples complies with the requirements of RoHS directive, and specific data are not listed).

[0064] (3) Mechanical properties: The tensile strength and elongation at break were tested in accordance with GB / T2951.11-2008 General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables Part 11: General Test Methods for Thickness and Dimensional Measurement and Mechanical Properties Test; the peel strength between the insulation layer and the conductor, and between the sheath layer and the insulation layer were tested (the peel strengths all meet the industry standards, and specific data are not listed).

[0065] (4) Electrical performance: Conductor resistance, insulation resistance and finished cable voltage test were conducted in accordance with T / GDAQIXX.2—2022 "Halogen-free polyolefin insulated cables with rated voltage of 450 / 750V and below - Part 2: Test methods" (all samples passed the 450 / 750V, 5min no breakdown test, and the conductor resistance met the standard, but specific data were not listed).

[0066] The test results are shown in Table 1 below: Table 1:

[0067] Results analysis: (1) Flame retardant performance analysis: All embodiments achieved a vertical combustion rating of V-0, with an oxygen index above 31.5%, a flame spread length not exceeding 1.2m, a self-extinguishing time within 30s, a smoke density below 46, and a CO yield not exceeding 0.052kg / kg. Overall, the flame retardant performance was excellent and stable, meeting the stringent requirements for fire resistance and flame retardancy in high-end applications. Embodiments 2 and 6 exhibited the best flame retardant performance. In Embodiment 2, by adjusting the dosage of each component of the halogen-free compound flame retardant, increasing the dosage of aluminum diethyl phosphite to 28 parts, the oxygen index reached 34%, the flame spread length was only 0.9m, and the self-extinguishing time was 24s. Embodiment 6 optimized the total dosage and component ratio of the halogen-free compound flame retardant, achieving an oxygen index of 33.5%, a smoke density of 41, and a toxic gas yield as low as 0.044kg / kg. This demonstrates that rationally adjusting the composition and dosage of the halogen-free compound flame retardant can significantly improve flame retardant efficiency while reducing the release of smoke and toxic gases.

[0068] As can be seen from the comparison of the examples and comparative examples, the absence or unreasonable use of key technical features can lead to a significant decrease in flame retardant performance. Comparative Example 1, lacking a flame retardant pretreatment step, saw its vertical burning rating drop to V-1, oxygen index to only 28%, self-extinguishing time extended to 55s, and smoke density increase to 62. This was because the unmodified flame retardant had poor compatibility and uneven dispersion with the matrix resin, failing to form a continuous flame retardant barrier. Comparative Example 2, due to insufficient total amount of halogen-free compound flame retardant and an unreasonable component ratio, had a vertical burning rating of only V-2, oxygen index of 26%, a bundled flame spread length of 2.1m, and a self-extinguishing time of 78s, indicating that insufficient flame retardant directly leads to the failure of the flame retardant effect. Comparative Example 6 used a binary compound flame retardant system, lacking nitriding... The boron component showed an oxygen index of 31%, a flame spread length of 1.3 m, and a smoke density of 48, indicating that the synergistic flame-retardant effect of the ternary composite flame-retardant system (diethylaluminum hypophosphite, piperazine pyrophosphate, and boron nitride) was better than that of the binary system, effectively improving flame-retardant stability. Comparative Example 7, although it had an anti-settling additive added, did not undergo flame-retardant modification, and its flame-retardant performance was close to that of Comparative Example 1, further verifying the necessity of the flame-retardant pretreatment step for improving flame-retardant performance. Comparative Example 5, lacking the cross-linking curing step, had an oxygen index of 27% and a self-extinguishing time of 62 s, indicating that cross-linking curing can improve the structural stability of the substrate and enhance the flame-retardant persistence.

[0069] (2) Halogen-free environmental performance analysis: The halogen content in all embodiments was controlled between 2.6 mg / g and 2.8 mg / g, far below the industry standard for halogen-free cables (≤5 mg / g), and the heavy metal content complied with RoHS directive requirements. There was no release of toxic or harmful gases, truly achieving halogen-free environmental protection. Comparative Example 3, where the flame retardant was replaced with a halogen-containing flame retardant (polyvinyl chloride), saw the halogen content soar to 12.5 mg / g. During combustion, it released a large amount of toxic and harmful gases and corrosive fumes, failing to meet environmental requirements. This highlights the environmental advantages of the halogen-free compound flame retardant system used in this invention. The halogen content in the other comparative examples was close to that of the embodiments, indicating that the halogen-free environmental performance is mainly determined by the type of flame retardant. The halogen-free compound flame retardant selected in this invention ensures the environmental friendliness of the cable.

[0070] (3) Mechanical performance analysis: All examples exhibit tensile strengths exceeding 17.8 MPa and elongation at break exceeding 365%, demonstrating excellent mechanical properties that meet the tensile and bending requirements of cables during long-term use. Example 5, by adjusting the type and blending ratio of the matrix resin and using a polypropylene-polyethylene blend system, achieved a tensile strength of 19.5 MPa and an elongation at break of 370%, indicating that proper selection of the matrix resin and blending ratio can improve the mechanical strength of the cable. Example 3, with optimized silane coupling agent dosage and hydrolysis ratio, achieved a tensile strength of 19.2 MPa and an elongation at break of 400%, demonstrating that the modification effect of the silane coupling agent can improve the compatibility between the flame retardant and the matrix resin, thereby enhancing the mechanical properties of the material.

[0071] The mechanical properties of the comparative examples were significantly inferior to those of the examples: Comparative Example 1, lacking the flame retardant pretreatment step, had a tensile strength of only 14.2 MPa and an elongation at break of 300%. This was due to uneven dispersion of the flame retardant, resulting in defects within the substrate and a decline in mechanical properties. Comparative Example 5, lacking the crosslinking and curing step, had a tensile strength of 13.5 MPa and an elongation at break of 280%, indicating that crosslinking and curing can enhance the structural integrity and toughness of the substrate. Comparative Example 4, lacking the anti-settling agent, had a tensile strength of 14.8 MPa and an elongation at break of 310%, demonstrating that the anti-settling agent can prevent the flame retardant from settling, avoiding uneven internal structure of the substrate and ensuring stable mechanical properties. Comparative Example 7, without flame retardant modification, had a tensile strength of 14.5 MPa and an elongation at break of 305%, further verifying the important role of flame retardant pretreatment in improving mechanical properties.

[0072] (4) Electrical performance analysis: All embodiments exhibited insulation resistances above 11500 MΩ·km and passed a 450 / 750V, 5-minute no-breakdown test. Conductor resistance met standards, demonstrating stable electrical performance and ensuring the safety and reliability of power transmission. Embodiments 3 and 6 showed the best insulation resistances at 12500 MΩ·km and 12300 MΩ·km respectively. This was attributed to the modification effect of the silane coupling agent and the appropriate ratio of flame retardant, which improved the insulation performance of the substrate. Embodiment 4, with optimized mixing and extrusion process parameters, achieved an insulation resistance of 12200 MΩ·km, demonstrating that appropriate process parameters can reduce internal porosity in the substrate and improve insulation stability.

[0073] The insulation resistance of the comparative examples was lower than that of the examples: the insulation resistance of comparative examples 1, 4, 5 and 7 was all lower than 9000 MΩ·km, with comparative example 5 having the lowest at only 7800 MΩ·km. This was mainly due to the lack of key technical features (crosslinking curing, flame retardant pretreatment, anti-settling additives) which led to uneven substrate structure and defects, thus affecting the insulation performance. Comparative example 3, which used a halogen-containing flame retardant, had an insulation resistance of 9200 MΩ·km, lower than that of the examples, indicating that the insulation performance of the halogen-free flame retardant system was better than that of the halogen-containing system and was more suitable for scenarios with high electrical performance requirements.

[0074] Based on the comprehensive performance test results, this invention achieves a synergistic improvement in the flame retardant performance, halogen-free environmental performance, mechanical performance, and electrical performance of cables through key technical means such as reasonable proportioning of halogen-free compound flame retardants, pretreatment and modification of flame retardants, addition of anti-settling additives, optimization of the blending ratio and process parameters of matrix resin, and addition of cross-linking and curing steps.

[0075] As can be seen from the above performance test results and analysis, the design of using the same halogen-free flame-retardant substrate for the insulation layer and the sheath layer in the halogen-free environmentally friendly fire-retardant cable of the present invention has sufficient technical rationality and practical application feasibility.

[0076] In the conventional understanding of this field, the core requirement for cable insulation is electrical insulation performance, while the sheath layer focuses on mechanical strength, abrasion resistance, and external weather resistance. The two are usually made of different base materials to match their functional differences. However, this invention modifies the surface of the halogen-free compound flame retardant with silane coupling agent, adds hydrophobic fumed silica to optimize filler dispersion and anti-settling effect, and combines electron beam irradiation crosslinking curing process. This enables the halogen-free flame retardant base material to simultaneously possess high electrical insulation, high mechanical strength, excellent flame retardancy, and low smoke, low toxicity, and environmentally friendly characteristics, breaking through the conventional design concept in the industry that insulation and sheath layers must use different base materials.

[0077] Based on actual performance data, when this substrate is used as an insulation layer, its insulation resistance can reach over 11,500 MΩ·km, fully meeting the electrical safety standards for power transmission; when used as a sheath layer, its tensile strength is not less than 17.8 MPa, its vertical burning rating consistently reaches V-0, and it also possesses good toughness and smoke suppression effects, fully meeting the mechanical protection, flame retardant and fireproof requirements of the sheath layer, with no functional compatibility shortcomings.

[0078] Meanwhile, the use of the same base material for insulation and sheath simplifies the production process of material preparation and extrusion coating, reduces the need for raw material allocation and equipment debugging, improves production efficiency and batch stability, and enhances the interlayer compatibility of the same material, effectively strengthening the bond between the insulation layer and the sheath layer. This avoids interlayer peeling and separation failures under operating conditions such as high temperature, bending, and tension, further improving the overall structural stability and long-term reliability of the cable. This fully demonstrates the rationality and superiority of the design in terms of technical principles, process implementation, and application effects.

[0079] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A halogen-free, environmentally friendly, fire-retardant cable, characterized in that, It includes a conductor, an insulating layer, and a sheath layer, wherein the insulating layer and the sheath layer use the same halogen-free flame-retardant substrate; the halogen-free flame-retardant substrate comprises, by weight: 35 parts polyethylene, 20 parts ethylene-vinyl acetate copolymer, 15 to 28 parts aluminum diethyl phosphite, 6 to 10 parts piperazine pyrophosphate, 3 to 5 parts boron nitride, 1.5 to 3.0 parts silane coupling agent KH-570, 0.6 to 1.2 parts hydrophobic fumed silica, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 1.0 part butyl stearate, and 2 parts magnesium hydroxide.

2. The halogen-free, environmentally friendly, fire-retardant cable according to claim 1, characterized in that, The conductor is an oxygen-free copper wire with a conductivity of 99.96% and a diameter of 0.5 mm. It is formed by twisting 19 oxygen-free copper wires together with a twist pitch of 7.5 mm.

3. The halogen-free, environmentally friendly, fire-retardant cable according to claim 1, characterized in that, The vinyl acetate content of the ethylene-vinyl acetate copolymer is 25% to 35%.

4. The halogen-free, environmentally friendly, fire-retardant cable according to claim 1, characterized in that, The insulation layer has a thickness of 1.0 mm, and the sheath layer has a thickness of 1.5 mm.

5. A method for preparing a halogen-free, environmentally friendly, fire-retardant cable, used to prepare the cable according to any one of claims 1 to 4, characterized in that, The process includes, in sequence, a halogen-free compound flame retardant pretreatment, a substrate mixing and granulation process, a conductor preparation process, an insulation coating process, a sheath coating process, and a cross-linking and curing process; the halogen-free compound flame retardant is a compound mixture of diethylaluminum hypophosphite, piperazine pyrophosphate, boron nitride, and magnesium hydroxide.

6. The preparation method according to claim 5, characterized in that, The pretreatment of the halogen-free compound flame retardant is as follows: the halogen-free compound flame retardant is dried at 110℃ for 12 min; the silane coupling agent KH-570 is mixed with ethanol and water at a mass ratio of 1:4:0.8 to 1:6:1.2 and stirred for 8 min to complete hydrolysis; the dried halogen-free compound flame retardant is fluidized at 1000 r / min and sprayed with the hydrolyzed silane coupling agent KH-570, stirred for 20 min, and then heated to 110℃ to react for 12 min.

7. The preparation method according to claim 5, characterized in that, The substrate compounding and granulation process involves: mixing the matrix resin, modified halogen-free compound flame retardant, and additives in a mixer in stages. The first stage is mixed at 130°C and 600 r / min for 4 minutes, and the second stage is mixed at 170°C and 900 r / min for 6 minutes. The mixture is then granulated using a twin-screw extruder at a speed of 200 r / min and an extrusion temperature of 170°C.

8. The preparation method according to claim 5, characterized in that, The conductor is prepared by stranding 19 oxygen-free copper wires together with a stranding pitch of 7.5 mm and polishing them at 800 r / min for 3 min.

9. The preparation method according to claim 5, characterized in that, The insulation coating is as follows: halogen-free flame-retardant substrate particles are melted at 170℃, and the conductor is coated at a speed of 10m / min to form an insulation layer, with a head pressure of 18MPa; the sheath coating is as follows: halogen-free flame-retardant substrate particles are melted at 180℃, and the insulated wire core is coated at a speed of 8m / min to form a sheath layer, with a head pressure of 20MPa.

10. The preparation method according to claim 5, characterized in that, The crosslinking and curing process involves an electron beam irradiation dose of 100 kGy, an irradiation rate of 5 m / min, followed by heat treatment at 90°C for 3 hours and cooling to room temperature at a rate of 5°C / min.

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