Environment-friendly green halogen-free flame-retardant cable and preparation method thereof

Abstract

This invention discloses an environmentally friendly, green, halogen-free flame-retardant cable and its preparation method, relating to the field of cable technology. The cable includes a tin-plated copper conductor at its center. An inner shielding layer, an insulation layer, and an outer shielding layer are extruded onto the conductor using a three-layer co-extrusion process to form an insulated core. The insulated core is then wrapped with an oxygen-free soft copper strip as a metallic shielding layer, followed by a semi-conductive water-resistant tape pad, then longitudinally wrapped with an aluminum-plastic composite tape and extruded with polyethylene. A waterproof layer is wrapped with a double-layer high-strength corrosion-resistant alloy tape as an armor layer. The outermost layer of the cable is extruded with a flame-retardant outer sheath. This sheath uses polyethylene as a base material, adding maleic anhydride-modified oleic acid and peroxide, and incorporating zinc oxide and magnesium oxide to form an ion network structure, while also incorporating flame-retardant fillers. This invention exhibits good tensile strength, electrical insulation performance, compressive and tensile strength, and bending performance, while also possessing excellent elongation at break, low-temperature crack resistance, and halogen-free flame-retardant characteristics.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to an environmentally friendly, green, halogen-free flame-retardant cable and its preparation method. Background Technology

[0002] Currently, in the technical solutions for halogen-free flame-retardant polyolefin cable materials, the common approach to achieve the specified flame-retardant rating is to add inorganic hydroxides or phosphorus-nitrogen-based flame-retardant fillers. This approach results in a high filler content within the polyethylene matrix, leading to disruption of the matrix's continuity. This manifests as reduced elongation at break, decreased low-temperature impact resistance, and increased tendency to crack under bending conditions. Simultaneously, the interfacial compatibility between the flame-retardant filler and the polyethylene matrix is ​​poor; unmodified filler particles easily agglomerate, forming stress concentration points and further deteriorating the material's mechanical toughness.

[0003] Surface treatment agents or compatibilizers introduced to improve compatibility often have limited effect on improving the dispersion of flame-retardant fillers and may interfere with crosslinking or grafting reactions. On the other hand, existing technologies use peroxide-crosslinked polyethylene to improve heat resistance and mechanical strength, but excessively high crosslinking densities can exacerbate material brittleness, causing cable sheaths to crack under repeated bending or vibration. Reducing the degree of crosslinking or the amount of filler to maintain toughness fails to pass corresponding flame-retardant tests. Some approaches attempt to introduce elastomer toughening components into polyethylene, but the modulus difference between the elastomer and the matrix leads to uneven filler distribution in each phase, reduced flame-retardant efficiency, and significant interfacial debonding after long-term thermal aging.

[0004] For halogen-free flame-retardant cable sheaths, existing products struggle to strike a balance between environmental friendliness and high toughness. They either sacrifice some flame-retardant properties for acceptable flexibility or prioritize high flame-retardant ratings at the expense of stringent requirements for low-temperature brittleness and crack resistance. This contradiction is particularly pronounced in laying environments requiring frequent movement or experiencing significant temperature variations. Furthermore, traditional blending processes struggle to establish a stable internal structure to support high proportions of inorganic fillers. The lack of chemical bonding or ionic cross-linking between the filler and the matrix leads to filler migration or precipitation during processing and service, affecting the durability of the flame-retardant effect. Therefore, there is an urgent need to develop a cable material that, without relying on halogens, constructs a stable network through ionic bonding within the polyethylene matrix, achieving a balance between high-filling flame-retardant properties and good toughness. Summary of the Invention

[0005] The purpose of this invention is to provide an environmentally friendly, green, halogen-free flame-retardant cable and its preparation method, so as to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an environmentally friendly green halogen-free flame-retardant cable, comprising a tin-plated copper conductor located at the very center of the cable, wherein the tin-plated copper conductor is made of 37 tin-plated soft copper wires with a diameter of 2.30mm through layered stranding and compaction annealing treatment, with an outer diameter of 14.2mm and a cross-section of 150mm². An insulated wire core is formed by extruding a conductor shielding layer with a thickness of 0.9 mm made of low-resistance thermally stable semi-conductive shielding material, an insulation layer with a thickness of 5.2 mm, and an insulation shielding layer with a thickness of 0.8 mm and an outer diameter of 26.8 mm made of low-resistance thermally stable semi-conductive shielding material onto a tin-plated copper conductor using a three-layer co-extrusion method. The insulated wire core is wrapped with a metal shielding layer consisting of oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm in a gap-overlap manner. The outer diameter after wrapping is 27.2 mm. The metal shielding layer is wrapped with a semi-conductive water-blocking tape pad with a thickness of 0.25 mm and a width of 40 mm, and the outer diameter of the pad is 27.9 mm. The water-blocking tape pad is first wrapped with an aluminum-plastic composite tape layer with a thickness of 0.25 mm and a width of 90 mm, and then a polyethylene layer with a thickness of 1.5 mm is extruded. The moisture barrier layer is wrapped with a double-layer armor layer consisting of high-strength corrosion-resistant alloy strips with a thickness of 0.25mm; the outermost layer of the cable is extruded with an outer sheath with a thickness of 2.5mm.

[0007] Furthermore, the outer sheath is composed of the following raw materials in parts by weight: 120 parts polyethylene, 10-15 parts maleic anhydride modified oleic acid, 0.8-1.2 parts peroxide, 6-10 parts zinc oxide, 5-8 parts magnesium oxide, 10-12 parts zinc borate, 6-9 parts hydrotalcite, 4-7 parts zinc stannate, 0.5-2 parts lubricant, and 0.3-1 parts antioxidant.

[0008] Furthermore, the tin-plated copper conductor is made of 37 tin-plated soft copper wires with a diameter of 2.30 mm through layered stranding and compaction annealing. The conductor surface is round and smooth, and the stranding pitch ratio is 14-18 times.

[0009] Furthermore, the oxygen-free soft copper strip is wrapped in a gap-overlapping manner with an overlap rate of 18%-22%, which provides a path for capacitive current and short-circuit current, and also confines the main electric field inside the insulation layer.

[0010] Furthermore, the high-strength corrosion-resistant alloy strip is a tantalum steel alloy strip with a melting point of 2700℃, a tensile strength of 900MPa, and a wrapping gap of 35%-45% of the width.

[0011] Furthermore, a method for preparing an environmentally friendly, green, halogen-free flame-retardant cable includes the following preparation steps: S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to make a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted and annealed. The stranding pitch ratio is 14-18 times to make a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm². S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 165-185℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 18%-22%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the outside of the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 35%-45% of the width of the strip, to form an armor layer; S7. Preparation of the outer sheath: Weigh 120 parts of polyethylene, 10-15 parts of maleic anhydride modified oleic acid, 0.8-1.2 parts of peroxide, 6-10 parts of zinc oxide, 5-8 parts of magnesium oxide, 10-12 parts of zinc borate, 6-9 parts of hydrotalcite, 4-7 parts of zinc stannate, 0.5-2 parts of lubricant, and 0.3-1 parts of antioxidant according to the weight ratio. Put them into a high-speed mixer and stir for 12-18 minutes until they are evenly mixed. Then feed the mixture into an internal mixer and knead it at 145-155℃ for 10-15 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 155-175℃ and the die head temperature is 165-180℃. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0012] Furthermore, in step S1, the tin-plated copper conductor is pressed in layers in a compaction mold with a compaction coefficient of 0.86-0.90, then annealed at 320-360℃ under a protective atmosphere for 1.5-2.5 hours, and finally cooled to room temperature by water.

[0013] Furthermore, the extrusion temperature in step S5 is 185-205℃.

[0014] Furthermore, the lubricant in step S7 is stearic acid.

[0015] Furthermore, the antioxidant in step S7 is antioxidant 1010.

[0016] This invention uses polyethylene as its base material, incorporating maleic anhydride-modified oleic acid and peroxide. During the mixing process, the peroxide initiates grafting points in the polyethylene, allowing the maleic anhydride-modified oleic acid to bond to the molecular chain. Simultaneously, zinc oxide and magnesium oxide are introduced, forming ionic complexes with carboxyl groups and creating an in-situ ionic network, significantly improving the material's thermal stability and mechanical consistency. It employs a halogen-free flame-retardant design, containing no halogenated flame retardants, resulting in low smoke density and minimal toxic gases during combustion. Zinc oxide and magnesium oxide promote charring on the polyethylene surface upon heating, and the ionic network itself possesses high-temperature stability. Compared with the prior art, the beneficial effects achieved by the present invention are: 1. The conductor of this invention is made of tin-plated copper single wire that has been layered, tightly stranded, and annealed to improve tensile strength and corrosion resistance.

[0017] 2. The insulation layer of this invention is formed by three-layer co-extrusion. Both the inner and outer shielding layers are made of low-resistance thermally stable semi-conductive shielding material with low volume resistivity and small change at high temperature, which makes the electric field distribution at the insulation interface more uniform and suppresses the occurrence of partial discharge.

[0018] 3. The metal shielding layer of this invention uses oxygen-free soft copper strip wrapped in a gap-overlapping manner, which serves as a path for the flow of capacitive current and short-circuit current, and can also confine the electric field inside the insulated core wire, thus weakening external magnetic field interference.

[0019] 4. The present invention wraps a semi-conductive resistive water tape around the metal shielding layer, then longitudinally wraps an aluminum-plastic composite tape and extrudes a layer of polyethylene, so that the aluminum-plastic tape and polyethylene are fused and bonded together to form a continuous and dense waterproof and moisture-proof barrier, which has a good mechanical isolation effect and can reduce the impact of external vibration on insulation.

[0020] 5. The armor layer of this invention uses a double-layer high-strength corrosion-resistant alloy strip with a high melting point, radiation resistance, and impact resistance. After wrapping, the cable still maintains good flexibility, taking into account the compressive, tensile, and bending performance, making it suitable for long-term laying in harsh environments.

[0021] 6. The flame-retardant outer sheath of this invention uses polyethylene as the base material, adds maleic anhydride-modified oleic acid and peroxide, and adds zinc oxide and magnesium oxide to form a stable ion network structure through ion complexation. At the same time, it is compounded with three halogen-free flame-retardant fillers: zinc borate, hydrotalcite and zinc stannate, to optimize the sheath's elongation at break and low-temperature brittleness, while also taking into account crack resistance.

[0022] 7. The present invention features a compact multi-layer structure and a wide process window, allowing for production using conventional extrusion and wrapping equipment. This results in short production cycles, high output, and low overall cost. It achieves green manufacturing of halogen-free flame-retardant cables, with a reasonable structure that is practical, energy-efficient, and highly effective. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] To more clearly illustrate the method provided by this invention, the following embodiments are provided in detail. The testing method for various indicators of an environmentally friendly, green, halogen-free flame-retardant cable produced in the following embodiments refers to patent CN118824623B, the specific content of which is as follows: Insulation: The 1kV cable was tested according to GB / T3048.5-2007 "Test Methods for Electrical Properties of Wires and Cables - Part 5: Determination of Insulation Resistance"; Tensile property test: According to GB / T 2951.11-2008: "General Test Methods for Cable Insulation and Sheath Materials", the rate of change of tensile strength was calculated. Tensile strength change rate = (initial strength - final strength) / initial strength × 100%; Flexibility: According to GB / T 2951.14-2017 "Insulating materials and processed products - Test methods for wires and cables - Part 14: Bending test", the tensile strength of the cable after 1000 repeated bending is tested; Flame retardancy: The flame retardancy performance of the cable is evaluated according to the international standard IEC60332, and a vertical burning test is conducted. According to the flame retardancy ratings: A (IEC 60332-3-21): The cable does not exhibit sustained vertical burning within 60 minutes; B (IEC 60332-3-22): Within a 40-minute test time, the cable bundle must not spread more than 3.5 meters, and no burning residue should fall; C (IEC 60332-3-23): Within 20 minutes, the cable can burn, but the vertical spread distance must not exceed 2.5 meters, and no residue falling is acceptable; D (IEC 60332-3-24): The cable, once ignited individually, does not exhibit sustained burning, with no restrictions on vertical spread distance or time.

[0025] Heat aging resistance: According to GB / T2951.12-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers, Part 12: General Test Methods - Heat Aging Test Method", the cable was aged in hot air at 300℃ for 72 hours, and the change rate of its elongation at break was calculated. Example 1 S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to produce a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted in a compaction mold with a compaction coefficient of 0.86. Then, they are annealed at 320℃ under a protective atmosphere for 1.5 hours. Finally, they are water-cooled to room temperature. The stranding pitch ratio is 14 times, and a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm² is produced. S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 165℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 18%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer at an extrusion temperature of 185℃. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 35% of the width of the strip, to form an armor layer; S7. Preparation of outer sheath: Weigh 120 parts of polyethylene, 10 parts of maleic anhydride modified oleic acid, 0.8 parts of peroxide, 6 parts of zinc oxide, 5 parts of magnesium oxide, 10 parts of zinc borate, 6 parts of hydrotalcite, 4 parts of zinc stannate, 0.5 parts of lubricant stearic acid, and 0.3 parts of antioxidant 1010 according to the weight ratio. Put them into a high-speed mixer and stir for 12 minutes to mix evenly. Then feed the mixture into an internal mixer and mix at 145℃ for 10 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 155℃ and the die head temperature is 165℃. After extrusion, cool to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0026] Example 2 S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to produce a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted in a compaction mold with a compaction coefficient of 0.87. Then, they are annealed at 330℃ in a protective atmosphere for 1.75 h. Finally, they are water-cooled to room temperature with a stranding pitch ratio of 15 to produce a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm². S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 170℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 19%, to form a metal shielding layer with an outer diameter of 27.2 mm. S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer at an extrusion temperature of 190℃. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 37.5% of the width of the strip, to form an armor layer; S7. Preparation of outer sheath: Weigh 120 parts of polyethylene, 11.25 parts of maleic anhydride modified oleic acid, 0.9 parts of peroxide, 7 parts of zinc oxide, 5.75 parts of magnesium oxide, 10.5 parts of zinc borate, 6.75 parts of hydrotalcite, 4.75 parts of zinc stannate, 0.85 parts of lubricant stearic acid, and 0.5 parts of antioxidant 1010 according to the weight ratio. Put them into a high-speed mixer and stir for 15 minutes to mix evenly. Then feed the mixture into an internal mixer and mix at 150°C for 12 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 160°C and the die head temperature is 170°C. After extrusion, cool to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0027] Example 3 S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to produce a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted in a compaction mold with a compaction coefficient of 0.88. Then, they are annealed at 340℃ under a protective atmosphere for 2.0 h. Finally, they are water-cooled to room temperature. The stranding pitch ratio is 16 times, and a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm² is produced. S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 175℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 20%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer at an extrusion temperature of 195℃. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 40% of the width of the strip, to form an armor layer; S7. Preparation of outer sheath: Weigh 120 parts by weight of polyethylene, 12.5 parts by weight of maleic anhydride modified oleic acid, 1.0 part by weight of peroxide, 8 parts by weight of zinc oxide, 6.5 parts by weight of magnesium oxide, 11 parts by weight of zinc borate, 7.5 parts by weight of hydrotalcite, 5.5 parts by weight of zinc stannate, 1.25 parts by weight of lubricant stearic acid, and 0.65 parts by weight of antioxidant 1010. Put them into a high-speed mixer and stir for 15 minutes until they are evenly mixed. Then feed the mixture into an internal mixer and knead it at 150°C for 12.5 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 165°C and the die head temperature is 172.5°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0028] Example 4 S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to produce a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted in a compaction mold with a compaction coefficient of 0.89. Then, they are annealed at 350°C under a protective atmosphere for 2.25 h. Finally, they are water-cooled to room temperature. The stranding pitch ratio is 17 times, and a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm² is produced. S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 180℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 21%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer at an extrusion temperature of 200℃. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 42.5% of the width of the strip, to form an armor layer; S7. Preparation of the outer sheath: Weigh 120 parts of polyethylene, 13.75 parts of maleic anhydride modified oleic acid, 1.1 parts of peroxide, 9 parts of zinc oxide, 7.25 parts of magnesium oxide, 11.5 parts of zinc borate, 8.25 parts of hydrotalcite, 6.25 parts of zinc stannate, 1.6 parts of stearic acid lubricant, and 0.8 parts of antioxidant 1010 according to the weight ratio. Put them into a high-speed mixer and stir for 18 minutes until they are evenly mixed. Then feed the mixture into an internal mixer and knead it at 155°C for 15 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 170°C and the die head temperature is 180°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0029] Example 5 S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to produce a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted in a compaction mold with a compaction coefficient of 0.90. Then, they are annealed at 360°C under a protective atmosphere for 2.5 hours. Finally, they are water-cooled to room temperature. The stranding pitch ratio is 18 times, and a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm² is produced. S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 185℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 22%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer at an extrusion temperature of 205℃. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 45% of the width of the strip, to form an armor layer; S7. Preparation of outer sheath: Weigh 120 parts of polyethylene, 15 parts of maleic anhydride modified oleic acid, 1.2 parts of peroxide, 10 parts of zinc oxide, 8 parts of magnesium oxide, 12 parts of zinc borate, 9 parts of hydrotalcite, 7 parts of zinc stannate, 2 parts of lubricant stearic acid, and 1 part of antioxidant 1010 according to the weight ratio. Put them into a high-speed mixer and stir for 18 minutes until they are evenly mixed. Then feed the mixture into an internal mixer and knead it at 155°C for 15 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 175°C and the die head temperature is 180°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

[0030] Comparative Example 1 The difference between Comparative Example 1 and Example 3 lies in step S7. Step S7 is changed to: preparing the outer sheath: weigh 120 parts of polyethylene, 8 parts of zinc oxide, 6.5 parts of magnesium oxide, 11 parts of zinc borate, 7.5 parts of hydrotalcite, 5.5 parts of zinc stannate, 1.25 parts of stearic acid lubricant, and 0.65 parts of antioxidant 1010 according to the weight, put them into a high-speed mixer and stir for 15 minutes to mix evenly; then feed the mixture into an internal mixer and mix at 150°C for 12.5 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 165°C and the die head temperature is 172.5°C. After extrusion, cool to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm; the remaining steps are the same as in Example 3.

[0031] Comparative Example 2 The difference between Comparative Example 2 and Example 3 lies in step S7. Step S7 is changed to: preparing the outer sheath: weigh 120 parts by weight of polyethylene, 12.5 parts by weight of maleic anhydride modified oleic acid, 1.0 part by weight of peroxide, 8 parts by weight of zinc oxide, 6.5 parts by weight of magnesium oxide, 1.25 parts by weight of lubricant stearic acid, and 0.65 parts by weight of antioxidant 1010, and put them into a high-speed mixer and stir for 15 minutes to mix evenly; then feed the mixture into an internal mixer and knead it at 150°C for 12.5 minutes; granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 165°C and the die head temperature is 172.5°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm; the remaining steps are the same as in Example 3.

[0032] Comparative Example 3 The difference between Comparative Example 3 and Example 3 lies in step S7. Step S7 is changed to: preparing the outer sheath: weigh 120 parts of polyethylene, 12.5 parts of maleic anhydride modified oleic acid, 1.0 part of peroxide, 8 parts of zinc oxide, 6.5 parts of magnesium oxide, 30 parts of aluminum hydroxide, 1.25 parts of lubricant stearic acid, and 0.65 parts of antioxidant 1010, and put them into a high-speed mixer and stir for 15 minutes to mix evenly; then feed the mixture into an internal mixer and knead it at 150°C for 12.5 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 165°C and the die head temperature is 172.5°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm; the remaining steps are the same as in Example 3.

[0033] Comparative Example 4 The difference between Comparative Example 4 and Example 3 lies in step S7. Step S7 is changed to: preparing the outer sheath: weigh 120 parts of polyethylene, 12.5 parts of maleic anhydride modified oleic acid, 1.0 part of peroxide, 11 parts of zinc borate, 7.5 parts of hydrotalcite, 5.5 parts of zinc stannate, 1.25 parts of lubricant stearic acid, and 0.65 parts of antioxidant 1010, and put them into a high-speed mixer and stir for 15 minutes to mix evenly; then feed the mixture into an internal mixer and knead it at 150°C for 12.5 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 165°C and the die head temperature is 172.5°C. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5 mm; the remaining steps are the same as in Example 3.

[0034] Example of effect Table 1 below presents the performance analysis results of an environmentally friendly, green, halogen-free flame-retardant cable using Examples 1 to 5 and Comparative Examples 1 to 4 of the present invention.

[0035] Table 1 It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. An environmentally friendly, green, halogen-free flame-retardant cable, characterized in that, It includes a tinned copper conductor located at the very center of the cable. The tinned copper conductor is made of 37 tinned soft copper wires with a diameter of 2.30 mm, which are stranded in layers and subjected to compaction and annealing. Its outer diameter is 14.2 mm and its cross-section is 150 mm². An insulated wire core is formed by extruding a conductor shielding layer with a thickness of 0.9 mm made of low-resistance thermally stable semi-conductive shielding material, an insulation layer with a thickness of 5.2 mm, and an insulation shielding layer with a thickness of 0.8 mm and an outer diameter of 26.8 mm made of low-resistance thermally stable semi-conductive shielding material onto a tin-plated copper conductor using a three-layer co-extrusion method. The insulated wire core is wrapped with a metal shielding layer consisting of oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm in a gap-overlap manner. The outer diameter after wrapping is 27.2 mm. The metal shielding layer is wrapped with a semi-conductive water-blocking tape pad with a thickness of 0.25 mm and a width of 40 mm, and the outer diameter of the pad is 27.9 mm. The water-blocking tape pad is first wrapped with an aluminum-plastic composite tape layer with a thickness of 0.25 mm and a width of 90 mm, and then a polyethylene layer with a thickness of 1.5 mm is extruded. The moisture barrier layer is wrapped with a double-layer armor layer consisting of high-strength corrosion-resistant alloy strips with a thickness of 0.25mm; the outermost layer of the cable is extruded with an outer sheath with a thickness of 2.5mm.

2. The environmentally friendly, green, halogen-free flame-retardant cable according to claim 1, characterized in that, The outer sheath is composed of the following raw materials in parts by weight: 120 parts polyethylene, 10-15 parts maleic anhydride modified oleic acid, 0.8-1.2 parts peroxide, 6-10 parts zinc oxide, 5-8 parts magnesium oxide, 10-12 parts zinc borate, 6-9 parts hydrotalcite, 4-7 parts zinc stannate, 0.5-2 parts lubricant, and 0.3-1 parts antioxidant.

3. The environmentally friendly, green, halogen-free flame-retardant cable according to claim 1, characterized in that, The tin-plated copper conductor is made of 37 tin-plated soft copper wires with a diameter of 2.30 mm through layered stranding and compaction annealing. The conductor surface is round and smooth, and the stranding pitch ratio is 14-18 times.

4. The environmentally friendly, green, halogen-free flame-retardant cable according to claim 1, characterized in that, The oxygen-free soft copper strip is wrapped in a gap-overlapping manner with an overlap rate of 18%-22%, which provides a path for capacitive current and short-circuit current, and confines the main electric field inside the insulation layer.

5. The environmentally friendly, green, halogen-free flame-retardant cable according to claim 1, characterized in that, The high-strength corrosion-resistant alloy strip is a tantalum steel alloy strip with a melting point of 2700℃, a tensile strength of 900MPa, and a wrapping gap of 35%-45% of the strip width.

6. A method for preparing an environmentally friendly, green, halogen-free flame-retardant cable, characterized in that, The preparation steps include the following: S1. An electrolytic copper rod with a diameter of 8.0 mm is drawn, annealed, and tin-plated to make a tin-plated soft copper wire with a diameter of 2.30 mm. Then, 37 tin-plated soft copper wires are layered, bundled, and compacted and annealed. The stranding pitch ratio is 14-18 times to make a tin-plated copper conductor with an outer diameter of 14.2 mm and a cross-section of 150 mm². S2. A three-layer co-extrusion method is used on the tin-plated copper conductor to extrude a 0.9mm thick low-resistance thermally stable semi-conductive shielding material as the conductor shielding layer, a 5.2mm thick insulating layer, and a 0.8mm thick low-resistance thermally stable semi-conductive shielding material as the insulating shielding layer. The extrusion temperature is 165-185℃ to form an insulated wire core. The outer diameter of the insulating shielding layer is 26.8mm. S3. Wrap an oxygen-free soft copper strip with a thickness of 0.12 mm and a width of 40 mm around the outside of the insulating shielding layer in a gap-overlap manner, with an overlap rate of 18%-22%, to form a metal shielding layer with an outer diameter of 27.2 mm; S4. Wrap a semi-conductive resistive water tape with a thickness of 0.25 mm and a width of 40 mm around the metal shielding layer to form a pad with an outer diameter of 27.9 mm; S5. A 0.25mm thick and 90mm wide aluminum-plastic composite strip is longitudinally wrapped around the outside of the water-blocking strip pad, and then a 1.5mm thick polyethylene is extruded to form a moisture barrier layer. S6. Wrap a double layer of high-strength corrosion-resistant alloy strip with a thickness of 0.25mm around the outside of the moisture barrier layer, with the wrapping gap being 35%-45% of the width of the strip, to form an armor layer; S7. Preparation of the outer sheath: Weigh 120 parts of polyethylene, 10-15 parts of maleic anhydride modified oleic acid, 0.8-1.2 parts of peroxide, 6-10 parts of zinc oxide, 5-8 parts of magnesium oxide, 10-12 parts of zinc borate, 6-9 parts of hydrotalcite, 4-7 parts of zinc stannate, 0.5-2 parts of lubricant, and 0.3-1 parts of antioxidant according to the weight ratio. Put them into a high-speed mixer and stir for 12-18 minutes until they are evenly mixed. Then feed the mixture into an internal mixer and knead it at 145-155℃ for 10-15 minutes. Granulate the mixture through a twin-screw extruder, and then extrude the outer sheath over the armor layer through a single-screw extruder. The extruder body temperature is 155-175℃ and the die head temperature is 165-180℃. After extrusion, cool it to room temperature in a water cooling tank to form an outer sheath with a thickness of 2.5mm. S8. Conduct withstand voltage and flame retardant tests on the finished cables, and put them into storage after passing the inspection.

7. The method for preparing an environmentally friendly, green, halogen-free flame-retardant cable according to claim 6, characterized in that, In step S1, the tin-plated copper conductor is pressed in layers in a compaction mold with a compaction coefficient of 0.86-0.90, then annealed at 320-360℃ under a protective atmosphere for 1.5-2.5 hours, and finally cooled to room temperature by water.

8. The method for preparing an environmentally friendly, green, halogen-free flame-retardant cable according to claim 6, characterized in that, The extrusion temperature in step S5 is 185-205℃.

9. The method for preparing an environmentally friendly, green, halogen-free flame-retardant cable according to claim 6, characterized in that, The lubricant used in step S7 is stearic acid.

10. The method for preparing an environmentally friendly, green, halogen-free flame-retardant cable according to claim 6, characterized in that, The antioxidant in step S7 is antioxidant 1010.

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