Insulated cable and method for manufacturing the same

Abstract

This invention relates to the field of cable technology and proposes an insulated cable and its manufacturing method. An insulated cable includes an insulated core and, sequentially, a wrapping layer, an insulation layer, an armor layer, and a sheath layer disposed outside the insulated core. The insulated core includes several insulated conductors, each conductor consisting of a copper conductor and, sequentially, a mica tape layer, a shielding layer, and a fiberglass tape layer disposed outside the copper conductor. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20-30 parts polyethylene, 40-60 parts halogen-free flame retardant, 10-15 parts inorganic filler, 8-10 parts compatibilizer, and 3-5 parts polyethylene glycol. This technical solution solves the problem of insufficient mechanical properties in insulated cables in related technologies.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to an insulated cable and its manufacturing method. Background Technology

[0002] With the rapid development of new energy development, urban infrastructure upgrades, and intelligent industrial equipment, insulated cables, as the core carriers of power transmission and signal transmission, have been widely used in various scenarios such as rail transit, marine engineering, polar environments, industrial automation, and building wiring. Their service environments are becoming increasingly complex and demanding, placing higher requirements on the comprehensive performance of cables. The core structure of an insulated cable typically includes a conductor, an insulation layer, and a sheath layer. The sheath layer, as the outermost protective structure of the cable, needs to possess good mechanical properties to withstand the mechanical loads during laying and use, ensuring the long-term stable service of the cable.

[0003] Currently, most existing insulated cables are made of materials such as polyvinyl chloride (PVC), polyethylene (PE), rubber, or low-smoke halogen-free polyolefins. Although these materials can meet basic insulation and protection requirements, their mechanical properties are generally insufficient, making them difficult to adapt to the needs of complex working conditions. This has become a key issue restricting the service life and safety reliability of insulated cables.

[0004] Therefore, it is necessary to propose an insulated cable and its manufacturing method to improve the mechanical properties of the cable. Summary of the Invention

[0005] This invention proposes an insulated cable and its manufacturing method to solve or alleviate the problem of insufficient mechanical properties of the insulated cable mentioned above.

[0006] This invention proposes an insulated cable, comprising an insulated core and a wrapping layer, an insulation layer, an armor layer, and a sheath layer sequentially disposed on the outer layer of the insulated core. The insulated core comprises a plurality of insulated conductors, each insulated conductor comprising a copper conductor and a mica tape layer, a shielding layer, and a glass fiber tape layer sequentially disposed on the outer side of the copper conductor. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20-30 parts polyethylene, 40-60 parts halogen-free flame retardant, 10-15 parts inorganic filler, 8-10 parts compatibilizer, and 3-5 parts polyethylene glycol.

[0007] Preferably, the copper conductor is made of multiple strands of copper monofilaments twisted together.

[0008] Preferably, the space between the insulated wires is filled with a refractory material filling layer, which is a magnesium oxide filling layer.

[0009] Preferably, the shielding layer is a copper strip braided shielding layer.

[0010] Preferably, the armor layer is a copper strip interlocking armor layer.

[0011] Preferably, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 16wt%~28wt%, and the melt index is 1.5~150g / 10min under the test conditions of 190℃ and 2.16kg; the hydroxyl value of the polyethylene glycol is 127~156mgKOH / g.

[0012] Preferably, the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer A and ethylene-vinyl acetate copolymer B with the same vinyl acetate content but different melt indices.

[0013] Preferably, the ethylene-vinyl acetate copolymer A contains 28 wt% ethylene-vinyl acetate copolymer, and has a melt index of 150 g / 10 min under test conditions of 190°C and 2.16 kg; the ethylene-vinyl acetate copolymer B contains 28 wt% vinyl acetate, and has a melt index of 6 g / 10 min under test conditions of 190°C and 2.16 kg; the mass ratio of ethylene-vinyl acetate copolymer A to ethylene-vinyl acetate copolymer B is 1:4~6.

[0014] Preferably, by weight, the raw material of the sheath layer further includes 4 to 6 parts of a modifier, wherein the modifier comprises N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:2 to 3.

[0015] This invention also proposes a method for preparing an insulated cable, comprising the following steps: S1. A mica tape layer, a shielding layer, and a glass fiber tape layer are sequentially arranged on the outside of the copper conductor to obtain an insulated wire. S2. After twisting together several insulated wires, an insulated wire core is obtained; S3. After sequentially setting the wrapping layer, insulation layer and armor layer on the outside of the insulated wire core, a semi-finished insulated cable is obtained; S4. After the sheathing material is mixed evenly, it is extruded and wrapped on the outside of the semi-finished insulated cable to form a sheath layer, thus obtaining an insulated cable.

[0016] The beneficial effects of this invention are as follows: This invention employs a multi-layer composite structure of insulated core, wrapping layer, insulation layer, armor layer, and sheath layer in the insulated cable, thereby improving the overall service life of the cable. The wrapping layer tightens the insulated conductors, maintaining structural stability and reducing interlayer slippage and friction. The insulation layer enhances the main insulation performance and blocks leakage current. The armor layer possesses high mechanical compressive strength, preventing damage to the internal insulation caused by external pressure or bending. The outermost sheath layer uses a composite of ethylene-vinyl acetate copolymer and polyethylene as its matrix, giving it good mechanical properties. The insulated core comprises several insulated conductors, each consisting of a copper conductor and, sequentially, a mica tape layer, a shielding layer, and a fiberglass tape layer surrounding the copper conductor. The mica tape layer exhibits high temperature resistance and good electrical insulation. The shielding layer eliminates electric field concentration and reduces partial discharge. The fiberglass tape layer provides high mechanical strength and good heat resistance, enhancing the overall integrity of the insulated cable. Therefore, through the synergistic effect of the various layers of the insulated cable, the mechanical properties and structural stability of the cable are improved, extending its service life. Detailed Implementation

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0018] A specific embodiment of the first aspect of the present invention provides an insulated cable, including an insulated core and a wrapping layer, an insulation layer, an armor layer and a sheath layer sequentially disposed on the outer layer of the insulated core. The insulated core includes a plurality of insulated conductors, and the insulated conductors include a copper conductor and a mica tape layer, a shielding layer and a glass fiber tape layer sequentially disposed on the outer side of the copper conductor. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20-30 parts polyethylene, 40-60 parts halogen-free flame retardant, 10-15 parts inorganic filler, 8-10 parts compatibilizer, and 3-5 parts polyethylene glycol.

[0019] In one embodiment of the invention, the compatibilizer comprises maleic anhydride-grafted polyethylene.

[0020] In one embodiment of the present invention, the copper conductor is made of multiple strands of copper monofilaments twisted together.

[0021] In one embodiment of the present invention, a refractory material filling layer is filled between the insulated wires, and the refractory material filling layer is a magnesium oxide filling layer.

[0022] In one embodiment of the present invention, the shielding layer is a copper strip braided shielding layer.

[0023] In one embodiment of the present invention, the armor layer is a copper strip interlocking armor layer.

[0024] In one embodiment of the present invention, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 16wt%~28wt%, for example, it can be any point value or any range between any two point values ​​from 16wt%, 18wt%, 19wt%, 20wt%, 22wt%, 24wt%, 25wt%, 26wt%, 28wt%, etc. In a preferred embodiment, it can be 28wt%. The melt index under the test conditions of 190°C and 2.16kg is 1.5~150g / 10min, for example, it can be any point value or any range between any two point values ​​from 1.5g / 10min, 2.0g / 10min, 2.5g / 10min, 6g / 10min, 150g / 10min. The hydroxyl value of polyethylene glycol is 127~156mgKOH / g.

[0025] In one embodiment of the present invention, the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer A and ethylene-vinyl acetate copolymer B with the same vinyl acetate content but different melt indices.

[0026] In one embodiment of the present invention, the ethylene-vinyl acetate copolymer A contains 28 wt% ethylene-vinyl acetate copolymer, and has a melt index of 150 g / 10 min under test conditions of 190°C and 2.16 kg; the ethylene-vinyl acetate copolymer B contains 28 wt% vinyl acetate, and has a melt index of 6 g / 10 min under test conditions of 190°C and 2.16 kg; the mass ratio of ethylene-vinyl acetate copolymer A to ethylene-vinyl acetate copolymer B is 1:4 to 6, for example, any point value or range between any two point values ​​from 1:4, 1:4.5, 1:5, 1:5.5, 1:6. In a preferred embodiment, for example, it can be 1:4.5, 1:5, 1:5.5.

[0027] In this invention, the low melt index ethylene-vinyl acetate copolymer can provide long molecular chains, allowing the sheath layer to fully extend under stress. However, its high viscosity leads to poor dispersion performance of inorganic fillers and halogen-free flame retardants, and creates weak points under stress. On the other hand, the high melt index ethylene-vinyl acetate copolymer has better fluidity, which can improve the interfacial compatibility with inorganic fillers and halogen-free flame retardants, reduce porosity, and prevent the sheath layer from breaking prematurely due to local defects during stretching. By combining the two, the elongation at break of the sheath layer can be improved.

[0028] Furthermore, the ratio of low melt index ethylene-vinyl acetate copolymer (EVA) to high melt index EVA during the compounding process directly affects the elongation at break of the sheath layer. When the proportion of low melt index EVA is large, the viscosity is high, and the fluidity is poor, thus affecting the overall elongation at break of the sheath layer. When the proportion of low melt index EVA is small, the proportion of high melt index EVA increases, which leads to a decrease in the strength of the sheath layer matrix, thereby reducing the elongation at break of the sheath layer. Therefore, in order to further improve the elongation at break of the sheath layer, it is necessary to further limit the mass ratio of the two copolymers. This invention has found that when the mass ratio of EVA A to EVA B is 1:4~6, the elongation at break of the sheath layer can be further improved.

[0029] In one embodiment of the present invention, the raw material of the sheath layer further includes 4 to 6 parts by weight of a modifier, which includes N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:2 to 3. For example, the modifier can be any point value or the range between any two point values ​​from 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, and 1:3.

[0030] In this invention, N-phenylmaleimide can enhance the intermolecular forces between the ethylene-vinyl acetate copolymer and the polyethylene matrix, and polyester-modified acrylic resin can improve the dispersion of halogen-free flame retardants and inorganic fillers in the matrix, enhance the interfacial bonding force between inorganic fillers and halogen-free flame retardants and the sheath matrix, reduce interfacial defects and stress concentration, and improve the tensile strength of the sheath. By controlling the two in a specific ratio of 1:2 to 3, the synergistic effect of sheath matrix reinforcement and interfacial reinforcement of halogen-free flame retardants and inorganic fillers can be achieved, thereby improving the tensile strength of the cable sheath.

[0031] In one embodiment of the present invention, the raw material of the sheath layer further includes, by weight, 1 to 1.5 parts of antioxidant, for example, any value from 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, and 1.5 parts, and any range between any two values; and 0.5 to 1 part of ultraviolet absorber, for example, any value from 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, and 1 part, and any range between any two values.

[0032] In one embodiment of the present invention, the antioxidant is not particularly limited. As understood by those skilled in the art, the function of the antioxidant is to capture free radicals, rendering them inactive substances, thereby preventing oxidative degradation reactions and ensuring the long-term stable operation of the cable. The antioxidant includes one or more of antioxidants 1010, 164, 1076, TNP, and DNP.

[0033] In one embodiment of the present invention, the ultraviolet absorber is not particularly limited. As understood by those skilled in the art, the ultraviolet absorber can effectively absorb and convert the energy of ultraviolet rays, inhibit photo-oxidative aging, and ensure the long-term stable operation of the cable. The ultraviolet absorber includes at least one of ultraviolet absorber UV-531, ultraviolet absorber UV-327, and ultraviolet absorber UV-329.

[0034] A second aspect of the present invention provides a method for preparing an insulated cable, used to prepare the insulated cable provided in the first aspect of the present invention, comprising the following steps: S1. A mica tape layer, a shielding layer, and a glass fiber tape layer are sequentially arranged on the outside of the copper conductor to obtain an insulated wire. S2. After twisting together several insulated wires, an insulated wire core is obtained; S3. After sequentially setting the wrapping layer, insulation layer and armor layer on the outside of the insulated wire core, a semi-finished insulated cable is obtained; S4. After the sheathing material is mixed evenly, it is extruded and wrapped on the outside of the semi-finished insulated cable to form a sheath layer, thus obtaining an insulated cable.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through embodiments.

[0036] The present invention will now be described in detail with reference to preferred embodiments and comparative examples. The preferred embodiments of the invention described below can be modified in various ways, and therefore the scope of the invention should not be construed as limited to the preferred embodiments described in detail below. Preferred embodiments are provided to help those skilled in the art to more readily understand the invention.

[0037] In the following embodiments and comparative examples: Polyethylene: High-density polyethylene, grade HMA-016; Maleic anhydride grafted polyethylene: model TY 1053H; Magnesium hydroxide: particle size 325 mesh; Kaolin: particle size 325 mesh; Polyester modified acrylic resin SGR-2700, manufacturer Guangzhou Changhao Trading Co., Ltd. Ethylene-vinyl acetate copolymer UE629, vinyl acetate content 18wt%, melt index 2.5g / 10min (190℃, 2.16kg load); Ethylene-vinyl acetate copolymer UE659, VA content 25wt%, melt index 2.0g / 10min (190℃, 2.16kg load); Ethylene-vinyl acetate copolymer UE639-04, VA content 28wt%, melt index 150g / 10min (190℃, 2.16kg load); Ethylene-vinyl acetate copolymer UE630, VA content 16wt%, melt index 1.5g / 10min (190℃, 2.16kg load); Ethylene-vinyl acetate copolymer UE634-04, VA content 28wt%, melt index 6g / 10min (190℃, 2.16kg load). Manufacturer: Taiwan Polymer Chemicals Co., Ltd.

[0038] Example 1 A method for manufacturing an insulated cable includes the following steps: S1. A mica tape layer, a copper tape braided shielding layer, and a glass fiber tape layer are sequentially arranged on the outside of the copper conductor (which is made of 8 strands of copper monofilaments) to obtain an insulated wire; S2. After twisting 16 insulated wires together, an insulated core is obtained; the spaces between the insulated wires are filled with a magnesium oxide filler layer. S3. After sequentially setting the wrapping layer, insulation layer, and copper tape interlocking armor layer on the outside of the insulated wire core, a semi-finished insulated cable is obtained; S4. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20 parts polyethylene, 40 parts magnesium hydroxide, 10 parts kaolin, 8 parts maleic anhydride-grafted polyethylene, and 3 parts polyethylene glycol (number average molecular weight of 800, hydroxyl value of 127~156 mgKOH / g), wherein the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:4. After preparing the raw materials according to the above-mentioned weight proportions of each sheath layer, they are mixed evenly and then extruded through a twin-screw extruder to coat the outer layer of the semi-finished insulated cable, forming a sheath layer and obtaining an insulated cable.

[0039] Example 2 A method for manufacturing an insulated cable includes the following steps: S1. A mica tape layer, a copper tape braided shielding layer, and a glass fiber tape layer are sequentially arranged on the outside of the copper conductor (which is made of 8 strands of copper monofilaments) to obtain an insulated wire; S2. After twisting 16 insulated wires together, an insulated core is obtained; the spaces between the insulated wires are filled with a magnesium oxide filler layer. S3. After sequentially setting the wrapping layer, insulation layer, and copper tape interlocking armor layer on the outside of the insulated wire core, a semi-finished insulated cable is obtained; S4. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 30 parts polyethylene, 60 parts magnesium hydroxide, 15 parts kaolin, 10 parts maleic anhydride-grafted polyethylene, 5 parts polyethylene glycol (number average molecular weight of 800, hydroxyl value of 127~156 mgKOH / g), 1 part antioxidant 1010, and 0.5 parts ultraviolet absorber including UV-531, wherein the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:4; After preparing the raw materials according to the above-mentioned weight proportions of each sheath layer, they are mixed evenly and then extruded through a twin-screw extruder to coat the outer layer of the semi-finished insulated cable, forming a sheath layer and obtaining an insulated cable.

[0040] Example 3 In this embodiment, the only difference is that the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE659 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:4. Otherwise, it is the same as in Example 1.

[0041] Example 4 In this embodiment, the only difference is that the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE630 in a mass ratio of 1:4. Otherwise, it is the same as in Example 1.

[0042] Example 5 In this embodiment, the only difference from Example 1 is that the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:6.

[0043] Example 6 In this embodiment, the only difference is that the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:4.5.

[0044] Example 7 In this embodiment, the only difference is that the ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04 in a mass ratio of 1:5.5.

[0045] Example 8 In this embodiment, except that the raw material of the sheath layer also includes 5 parts (by weight) of modifier, which is N-phenylmaleimide, everything else is the same as in Example 1.

[0046] Example 9 In this embodiment, the modifier is the same as in Example 8, except that it is a polyester-modified acrylic resin.

[0047] Example 10 In this embodiment, the modifier is the same as in Example 8, except that it consists of N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:2.

[0048] Example 11 In this embodiment, the modifier is the same as in Example 8, except that it consists of N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:2.5.

[0049] Example 12 In this embodiment, the modifier is the same as in Example 8, except that it consists of N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:3.

[0050] Comparative Example 1 In this comparative example, except that the number average molecular weight of polyethylene glycol is 600 and the hydroxyl value is 170~208 mgKOH / g, everything else is the same as in Example 1.

[0051] Comparative Example 2 In this comparative example, except that the number average molecular weight of polyethylene glycol is 1000 and the hydroxyl value is 102~125 mgKOH / g, everything else is the same as in Example 1.

[0052] Comparative Example 3 In this comparative example, except that the ethylene-vinyl acetate copolymer is ethylene-vinyl acetate copolymer UE639-04, everything else is the same as in Example 1.

[0053] Comparative Example 4 In this comparative example, except that the ethylene-vinyl acetate copolymer is ethylene-vinyl acetate copolymer UE634-04, everything else is the same as in Example 1.

[0054] Comparative Example 5 In this comparative example, except that the raw material of the sheath layer does not contain polyethylene glycol, everything else is the same as in Example 1.

[0055] The insulation cable sheaths of Examples 1-12 and Comparative Examples 1-5 were subjected to the following performance tests: (1) The sheaths of the insulated cables of Examples 1 to 7 and Comparative Examples 1 to 5 were cut into dumbbell-shaped specimens (1.5 mm thick) according to the method in GB / T 2951.11-2008 and the elongation at break was determined. The test results are shown in Table 1 below.

[0056] Table 1 Results of Elongation at Break

[0057] Compared with Example 1, Examples 3-4 changed the type of ethylene-vinyl acetate copolymer compound, and Examples 5-7 changed the ratio of ethylene-vinyl acetate copolymer UE639-04 and ethylene-vinyl acetate copolymer UE634-04. As a result, the elongation at break of Example 1 was greater than that of Examples 3-4, and the elongation at break of Examples 6-7 was greater than that of Examples 1 and Example 5.

[0058] (2) The sheath layer of the insulated cables of Examples 1, 8 to 12 was cut into dumbbell samples (1.5 mm thick) according to the method in GB / T 2951.11-2008 and the tensile strength was determined. The test results are shown in Table 2 below.

[0059] Table 2 Tensile strength test results

[0060] As shown in Table 2, the addition of modifiers in Examples 8-12 improved the tensile strength compared to Example 1 without modifiers. Furthermore, compared to Examples 1 and 8, the modifiers in Examples 10-12 consisted of N-phenylmaleimide and polyester-modified acrylic resin, resulting in higher tensile strengths in Examples 10-12. This indicates that the modifiers consisting of N-phenylmaleimide and polyester-modified acrylic resin can further improve the tensile strength of the insulated cable sheath.

[0061] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An insulated electrical cable, characterized in that, It includes an insulated wire core and a wrapping layer, an insulation layer, an armor layer and a sheath layer sequentially disposed on the outer layer of the insulated wire core. The insulated wire core includes a plurality of insulated conductors. The insulated conductors include a copper conductor and a mica tape layer, a shielding layer and a glass fiber tape layer sequentially disposed on the outer side of the copper conductor. The sheath layer comprises the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20-30 parts polyethylene, 40-60 parts halogen-free flame retardant, 10-15 parts inorganic filler, 8-10 parts compatibilizer, and 3-5 parts polyethylene glycol.

2. An insulated electrical cable according to claim 1, characterized in that The copper conductor is made of multiple strands of copper monofilaments twisted together.

3. An insulated electrical cable according to claim 1, characterised in that The space between the insulated wires is filled with a refractory material filling layer, which is a magnesium oxide filling layer.

4. An insulated cable according to claim 1, characterized in that, The shielding layer is a copper strip braided shielding layer.

5. An insulated cable according to claim 1, characterized in that, The armor layer is a copper strip interlocking armor layer.

6. An insulated cable according to claim 1, characterized in that, The ethylene-vinyl acetate copolymer contains 16wt%~28wt% vinyl acetate and has a melt index of 1.5~150g / 10min under test conditions of 190℃ and 2.16kg; the polyethylene glycol has a hydroxyl value of 127~156mgKOH / g.

7. An insulated cable according to claim 6, characterized in that, The ethylene-vinyl acetate copolymer is composed of ethylene-vinyl acetate copolymer A and ethylene-vinyl acetate copolymer B with the same vinyl acetate content but different melt indices.

8. An insulated cable according to claim 7, characterized in that, The ethylene-vinyl acetate copolymer A contains 28 wt% ethylene-vinyl acetate copolymer, and its melt index is 150 g / 10 min under the test conditions of 190°C and 2.16 kg. The ethylene-vinyl acetate copolymer B contains 28 wt% vinyl acetate, and its melt index is 6 g / 10 min under the test conditions of 190°C and 2.16 kg. The mass ratio of ethylene-vinyl acetate copolymer A to ethylene-vinyl acetate copolymer B is 1:4~6.

9. An insulated cable according to claim 1, characterized in that, By weight, the raw material of the sheath layer also includes 4 to 6 parts of modifier, which includes N-phenylmaleimide and polyester-modified acrylic resin in a mass ratio of 1:2 to 3.

10. A method for preparing an insulated cable, characterized in that, The method for preparing the insulated cable according to any one of claims 1 to 9 comprises the following steps: S1. A mica tape layer, a shielding layer, and a glass fiber tape layer are sequentially arranged on the outside of the copper conductor to obtain an insulated wire. S2. After twisting together several insulated wires, an insulated wire core is obtained; S3. After sequentially setting the wrapping layer, insulation layer and armor layer on the outside of the insulated wire core, a semi-finished insulated cable is obtained; S4. After the sheathing material is mixed evenly, it is extruded and wrapped on the outside of the semi-finished insulated cable to form a sheath layer, thus obtaining an insulated cable.

Images