A corrosion-resistant and flame-retardant cross-linked polyolefin cable

Abstract

The present invention discloses a corrosion-resistant and flame-retardant cross-linked polyolefin cable, belonging to the technical field of polyolefin cable manufacturing. The corrosion-resistant and flame-retardant cross-linked polyolefin cable of the present invention includes a conductor wrapped with an isolation layer, an oxygen barrier layer, an insulating layer are extruded in sequence outside the isolation layer, then a tape layer is wrapped around, and then a polyolefin composite shielding material inner shielding layer containing ferrite and a ceramicized flame-retardant polyolefin composite material flame-retardant layer are extruded in sequence. The outer shielding layer is formed by wrapping an aluminum foil mylar tape, and finally a halogen-free, low-smoke, flame-retardant, corrosion-resistant polyolefin mixture outer sheath is coated, and a protective coating is applied. The corrosion-resistant and flame-retardant cross-linked polyolefin cable of the present invention has a simple structure and is easy to manufacture, and has excellent mechanical properties, high voltage resistance, tensile and bending resistance, flame retardancy, waterproofness, corrosion resistance, aging resistance, anti-interference, radiation resistance and high and low temperature impact resistance, and prolongs the high-temperature service life of the cable.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyolefin cable manufacturing, and particularly relates to a corrosion-resistant and flame-retardant cross-linked polyolefin cable and a manufacturing method thereof. Background Art

[0002] With the acceleration of the urbanization and industrialization construction paces in China, high-voltage, extra-high-voltage and ultra-high-voltage power transmissions with advantages such as long distance and large capacity have developed rapidly. High-voltage direct-current power transmission has characteristics of low loss, long distance, large capacity, convenient power connection and control, and simple regulation. Therefore, high-voltage direct-current cables need to have good electrical insulation, corrosion resistance, flame retardancy, withstand voltage, low dielectric loss, light weight, high and low temperature stability, anti-aging property and mechanical properties, etc.

[0003] At present, the main problems encountered by high-voltage direct-current cable insulation materials are the problems of conductivity temperature characteristics and space charge accumulation. The voids between the conductor and the insulation layer are likely to cause the accumulation of space charges, resulting in material aging and cracking, and ultimately leading to the breakdown of the material. The operating temperature of high-voltage cables is relatively high, and the real-time temperature under unstable conditions can exceed 110°C, which further accelerates the aging of the insulation layer and causes it to be broken down. Therefore, high-voltage direct-current cables require better high-temperature stability and flame retardancy. Most high-voltage direct-current cables work in harsh environments, such as mines, deep seas, aerospace, nuclear power and other environments. They are easily corroded or damaged by the environment after long-term use, which is likely to cause short circuits of high-voltage cables, affect the normal use of the cables, and shorten the service life of the cables. In fields such as nuclear power plants, marine communications, electronic communications, railway transportation, and aerospace transportation, at present, domestic high-voltage cables generally cannot simultaneously meet the performances of high voltage resistance, electrical insulation, high flame retardancy, corrosion resistance, anti-interference, high and low temperature resistance, anti-aging, and long service life. This is also the problem that the technical personnel of the present invention strive to solve, in order to reach the foreign technical level and break the technical monopoly of foreign enterprises.

[0004] The invention patent CN201911309331.2 discloses an anti-interference, highly flame-retardant and environmentally friendly transponder data transmission cable, which adopts a double composite high electromagnetic shielding layer to form a three-level shielding, with strong anti-interference ability and the amount of smoke and toxic gases generated during combustion reduced to the lowest level. However, the insulating layer of this patent uses high-temperature-resistant fluoroplastics, which does not belong to the development trend of halogen-free cables; the semiconductor nylon tape wrapped outside the cable core is prone to electrostatic accumulation during long-term operation, which affects the insulation of the cable, and its elongation performance is average. In a low-temperature environment, it is prone to cracking, which in turn affects the quality and service life of high-voltage cables. The invention patent CN201911116173.9 discloses a high-voltage soft polyolefin wire material for new energy vehicles, which is prepared by irradiating and cross-linking raw materials such as elastomer rubber, elastomer polyethylene, and olefin copolymer, and has the characteristics of good comprehensive performance, good flame retardancy and high-temperature resistance, and sufficient toughness. However, the corrosion resistance of this polyolefin material is not good, and it is not mentioned in this solution. The invention patent CN202311194403.X discloses a medium- and high-voltage cable for smart grid, including a cable core wire, an inner insulating layer, and a protective outer layer. The protective outer layer uses PVC, chloroprene rubber, and ethylene-vinyl acetate copolymer as the main raw materials, and has high surface strength, waterproofness, abrasion resistance, flame retardancy, and corrosion resistance. However, the protective outer layer raw material of this high-voltage cable contains PVC, which does not conform to the current development trend of halogen-free cables. At the same time, this cable does not include a shielding layer, so this cable does not have anti-interference, radiation resistance and other properties, which limits its scope of use. Summary of the Invention

[0005] The main object of the present invention is to provide a corrosion-resistant and flame-retardant cross-linked polyolefin cable, which has a simple structure, is easy to manufacture, and has excellent mechanical properties, high voltage resistance, tensile and bending resistance, waterproofness, corrosion resistance, aging resistance, anti-interference, radiation resistance, and high and low temperature impact resistance. At the same time, the combustion performance of this polyolefin cable is halogen-free low-smoke flame-retardant type A, and the grade can reach B1 level. At the same time, it can withstand cold down to -40°C, ensuring that the high-voltage cable of the present invention still has better use effect and longer service life in harsh environments.

[0006] To achieve the object of the present invention, the present invention provides a corrosion-resistant and flame-retardant cross-linked polyolefin cable, including a cable core, a tape layer, an inner shielding layer, a flame-retardant layer, an outer shielding layer, an outer protective layer, and a protective coating. The cable core is one or more wire cores, and each wire core includes a conductor, an isolation layer, an insulating layer, and an oxygen isolation layer. The isolation layer is wound around the conductor, the oxygen isolation layer is extruded outside the isolation layer, and the insulating layer is extruded outside the oxygen isolation layer;

[0007] The insulating layer is wound with a tape layer, the inner shielding layer is extruded outside the tape layer, the flame-retardant layer is extruded outside the inner shielding layer, the outer shielding layer is wound with an aluminum foil mylar tape outside the flame-retardant layer, the outer protective layer is coated outside the outer shielding layer, and the protective coating is applied outside the outer protective layer;

[0008] The inner shielding layer is a polyolefin composite shielding material containing ferrite;

[0009] The flame retardant layer is a ceramized flame retardant polyolefin composite material;

[0010] The outer protective layer is a halogen-free, low-smoke, flame retardant and corrosion-resistant polyolefin mixture.

[0011] Furthermore, when the cable core consists of one conductor, the tape layer is directly wound around the insulating layer; when the cable core consists of two or more conductors, the multiple conductors are stranded to form the cable core, then a filling cord is filled in the gaps of the cable core, and then the tape layer is wound.

[0012] Furthermore, the polyolefin composite shielding material is composed of the following raw materials in parts by mass: 40 - 60 parts of polypropylene resin, 25 - 35 parts of ethylene-vinyl acetate copolymer, 15 - 25 parts of ethylene-butyl acrylate copolymer, 5 - 10 parts of PP grafted maleic anhydride, 5 - 15 parts of carbon black, 3 - 6 parts of barium ferrite, 10 - 20 parts of flame retardant, 0.1 - 0.5 part of initiator DCP, 0.5 - 2 parts of the first silane coupling agent, 0.3 - 0.5 part of antioxidant, and 1 - 3 parts of lubricant.

[0013] Furthermore, the preparation method of the barium ferrite is as follows:

[0014] S1. Appropriate proportions of ferrous nitrate, ferric nitrate and polyethylene glycol are added to an appropriate amount of deionized water and continuously stirred until dissolved, then ammonia water is added to adjust the pH value to 10 - 11, the temperature is raised to 50 - 70 °C and reacted for 2 - 4 h, filtered by suction, washed and dried to obtain an iron oxide precursor;

[0015] S2. The iron oxide precursor prepared above and barium carbonate are added to glacial acetic acid and stirred until dissolved to form a mixed solution;

[0016] S3. An appropriate amount of dilute nitric acid is added to the above mixed solution, stirred for 5 - 10 min, then the temperature is raised to 200 - 220 °C and reacted for 3 - 5 h, cooled to room temperature, filtered by suction, and then washed 2 - 3 times successively with deionized water and absolute ethanol, and then vacuum dried at 80 °C for 2 - 5 h to obtain barium ferrite.

[0017] Furthermore, the molar ratio of ferrous nitrate to ferric nitrate is (0.4 - 0.6):1;

[0018] The molar ratio of iron in the iron oxide precursor to barium carbonate is (9 - 10):1.

[0019] Furthermore, the flame retardant is composed of microencapsulated red phosphorus and organic montmorillonite with a mass ratio of 1:4.

[0020] Furthermore, the ceramizable flame-retardant polyolefin composite material is composed of the following raw materials in parts by mass: 30-50 parts of low-density polyethylene, 15-30 parts of ethylene-methyl acrylate copolymer, 25-40 parts of ethylene propylene diene terpolymer, 30-50 parts of amino-silane-coated wollastonite, 10-20 parts of low-melting-point glass powder, 15-25 parts of phlogopite powder, 5-10 parts of lithium borate salt, 6-12 parts of halogen-free flame retardant, 0.2-0.4 part of initiator DCP, and 1-3 parts of second silane coupling agent.

[0021] Furthermore, the amino-silane-coated wollastonite is obtained by surface modification of wollastonite with aminopropyltriethoxysilane, and the coating rate is ≥70%;

[0022] The lithium borate salt is composed of lithium tetraborate, lithium metaborate, and zinc borate with a mass ratio of 1:2:4;

[0023] The halogen-free flame retardant is composed of nano-magnesium hydroxide, magnesium stearate, and silicone oil with a mass ratio of (0.2-0.5):1:1;

[0024] The second silane coupling agent is composed of vinyltrimethoxysilane and aminopropyltriethoxysilane.

[0025] Furthermore, the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture is composed of the following raw materials in parts by mass: 30-50 parts of linear low-density polyethylene, 10-15 parts of ultra-high molecular weight polyethylene, 30-50 parts of ethylene-ethyl acrylate copolymer, 15-30 parts of metallocene ethylene-octene copolymer, 15-30 parts of methyl vinyl silicone rubber, 20-40 parts of low-melting-point glass powder, 15-25 parts of plasticizer, 30-50 parts of composite flame retardant, 10-15 parts of titanium-aluminum oxide, 20-40 parts of filler, 0.3-0.5 part of antioxidant, 0.2-0.4 part of initiator DCP, and 3-5 parts of third silane coupling agent.

[0026] Furthermore, the composite flame retardant is composed of the following raw materials in parts by mass: 40-60 parts of nano-magnesium hydroxide, 30-40 parts of aluminum hydroxide, and 10-20 parts of zinc borate.

[0027] Furthermore, the titanium-aluminum oxide is formed by mixing titanium dioxide and aluminum oxide with a mass ratio of 3:2;

[0028] The filler is composed of calcined kaolin, phlogopite powder, and calcium carbonate with a mass ratio of 1:2:1;

[0029] The third silane coupling agent is vinyltrimethoxysilane.

[0030] Furthermore, the isolation layer is a halogen-free and non-corrosive non-woven fabric made of polyester fiber or polyester fiber;

[0031] The insulating layer is a radiation-crosslinked flame-retardant polyolefin insulating material that can withstand high temperatures of 150°C;

[0032] The oxygen barrier layer is a low-smoke and halogen-free flame-retardant cable material with an oxygen index greater than or equal to 40;

[0033] The tape layer is a halogen-free, low-smoke, and highly flame-retardant tape made of non-woven fabric or fiberglass fabric, which is overlapped and wrapped around the outside of the insulating layer with an overlapping rate of 15-20%;

[0034] The outer shielding layer is an aluminum foil mylar tape;

[0035] The protective coating is a flame-retardant and corrosion-resistant waterborne polyurethane coating.

[0036] The present invention has achieved the following beneficial effects:

[0037] 1. The present invention uses a halogen-free, low-smoke, flame-retardant, and corrosion-resistant polyolefin mixture as the outer sheath, with a composite polyolefin (i.e., linear low-density polyethylene, ultra-high molecular weight polyethylene, ethylene-ethyl acrylate copolymer, and metallocene ethylene-octene copolymer) as the matrix, ensuring that the present invention has excellent electrical insulation, mechanical strength, and bending and tensile resistance, while also having excellent comprehensive properties such as corrosion resistance, waterproofness, wear resistance, and low-temperature resistance; the addition of methyl vinyl silicone rubber has good compatibility with the polyolefin resin, significantly improving the corrosion resistance, flame retardancy, electrical insulation, aging resistance, high-temperature resistance, waterproofness, etc. of the outer sheath, and further extending the high-temperature service life of the cable; the addition of titanium-aluminum oxide significantly improves the high-temperature resistance and flame retardancy of the cable, making the present invention have better mechanical strength, wear resistance, corrosion resistance, radiation resistance, etc.

[0038] 2. The present invention uses a ceramized flame-retardant polyolefin composite material as the flame-retardant layer, which not only improves the flame retardancy of the polyolefin cable but also enhances the mechanical strength, tensile and bending resistance, wear resistance, and corrosion resistance of the cable, effectively playing the roles of fire prevention, flame retardancy, and anti-aging.

[0039] 3. The present invention uses a polyolefin composite shielding material containing ferrite as the inner shielding layer, which improves the electromagnetic shielding performance of the cable, while also playing a role in radiation resistance, and reducing the resistivity and cost, thereby extending the service life of the polyolefin cable. At the same time, the inner shielding layer of the polyolefin composite shielding material containing ferrite and the outer shielding layer of aluminum foil mylar tape form a double-layer electromagnetic shielding, reducing the signal interference and space charge accumulation problems of the polyolefin cable, while improving the radiation resistance, high-temperature resistance, and flame retardancy of the cable.

[0040] 4. The present invention sprays a protective coating on the outside of the outer sheath, which can effectively play the roles of fire prevention, flame retardancy, anti-aging, wear resistance, etc., thereby improving the overall outer layer protection ability of the cable and extending its service life.

[0041] 5. The base materials of the insulating layer, oxygen barrier layer, flame retardant layer and outer protective layer of the present invention are all polyolefins, halogen-free, environmentally friendly, ensuring that the polyolefin cable still has excellent mechanical strength, electrical insulation, tensile and bending resistance, waterproofness, corrosion resistance, aging resistance and high and low temperature stability under high voltage conditions, and has a long service life; the combustion performance of the polyolefin cable is non-halogen low-smoke flame retardant class A, and the grade can reach B1 level.

[0042] 6. The corrosion-resistant and flame-retardant cross-linked polyolefin cable prepared by the present invention has a smooth surface, simple structure, convenient production, excellent flame retardant and corrosion resistance performance, wide application range and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic structural diagram of a single-core cable of the corrosion-resistant and flame-retardant cross-linked polyolefin cable of the present invention;

[0044] Figure 2 is a schematic structural diagram of a three-core cable of the corrosion-resistant and flame-retardant cross-linked polyolefin cable of the present invention.

[0045] REFERENCE SIGNS IN THE DRAWINGS: 1, conductor; 2, isolation layer; 3, oxygen barrier layer; 4, insulating layer; 5, tape layer; 6, inner shielding layer; 7, flame retardant layer; 8, outer shielding layer; 9, outer protective layer; 10, protective coating; 11, filling cord. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] As Figure 1 shown, the present invention provides a corrosion-resistant and flame-retardant cross-linked polyolefin cable, including a cable core, a tape layer 5, an inner shielding layer 6, a flame retardant layer 7, an outer shielding layer 8, an outer protective layer 9 and a protective coating 10. Among them, the cable core is one or more wire cores, and the wire core includes a conductor 1, an isolation layer 2, an insulating layer 4 and an oxygen barrier layer 3.

[0048] When the cable core is a single wire core (as Figure 1 shown), the conductor 1 is wrapped with an isolation layer 2, the isolation layer 2 is extruded with an oxygen barrier layer 3, the oxygen barrier layer 3 is extruded with an insulating layer 4, the insulating layer 4 is wrapped with a tape layer 5, the tape layer 5 is extruded with an inner shielding layer 6, the inner shielding layer 6 is extruded with a flame retardant layer 7, the flame retardant layer 7 is wrapped with an aluminum foil mylar tape as the outer shielding layer 8, the outer shielding layer 8 is coated with an outer protective layer 9, and the outer protective layer 9 is coated with a protective coating 10. The embodiments of the present invention mainly describe the cross-linked polyolefin cable with a single wire core.

[0049] When the cable core consists of two or more cores (as shown in Figure 2 , for example, 3 cores), the 3 cores are stranded to form a cable core, then filling cords 11 are filled in the gaps of the cable core, and then a tape layer 5 is wound around.

[0050] Preferably, the isolation layer 2 is a halogen-free and non-corrosive non-woven fabric such as polyester fiber and polyester fiber. The setting of the isolation layer 2 is to protect the electrical performance of the conductor 1 of the present invention, prevent water and fire, and can effectively prevent problems such as corrosion, aging or short circuit of the conductor 1, and facilitate the peeling of the insulating layer 4 from the conductor 1 during the installation process, and at the same time has good insulation and flame retardant properties. In the embodiment of the present invention, the isolation layer 2 selected is a polyester halogen-free and non-corrosive non-woven fabric (Jiangsu Yilong Textile), with a thickness of 0.1 - 0.3 mm.

[0051] Preferably, the oxygen isolation layer 3 is a low-smoke and halogen-free flame retardant cable material with an oxygen index greater than or equal to 40. The oxygen isolation layer 3 is used to protect the isolation layer 2. In case of a fire, it delays the ignition time of the conductor 1, reduces losses, and ensures that the present invention has good insulation and electrical performance. In the embodiment of the present invention, the low-smoke and halogen-free flame retardant cable material is selected from EPC6909 of Yangzhong Oubo Chemical Industry.

[0052] Preferably, the insulating layer 4 is a 150 °C high-temperature resistant irradiated cross-linked flame retardant polyolefin insulating material, which is halogen-free and environmentally friendly, can effectively protect the electrical performance of the conductor 1, ensure that the polyolefin cable has excellent insulation and flame retardant properties, and improve the mechanical properties, aging resistance, corrosion resistance and temperature resistance grade of the cable. In the embodiment of the present invention, the 150 °C high-temperature resistant irradiated cross-linked flame retardant polyolefin insulating material is selected from those produced by China Guangdong Nuclear High-Tech Materials.

[0053] Preferably, the tape layer 5 is a halogen-free, low-smoke and high-flame retardant tape made of non-woven fabric or fiberglass fabric, which is overlapped and wound around the outside of the insulating layer 4, and the lapping rate is 15 - 20%. In order to further ensure that the product meets the national standard for halogen-free, low-smoke and flame retardant Class A, and the combustion performance grade reaches the national standard B1 level, in the embodiment of the present invention, the preferably selected tape layer 5 is a halogen-free, low-smoke and high-flame retardant fiberglass tape of Shuangxiong Cable, with a thickness of 0.2 mm, which can withstand a temperature of 300 °C, and is wound in a double-layer overlapping manner, with a lapping rate of 20%. Using the halogen-free, low-smoke and high-flame retardant fiberglass tape of the present invention as the tape layer 5 not only improves the flame retardant effect of the cable of the present invention, but also improves the high and low temperature resistance, chemical corrosion resistance, insulation and anti-static properties of the present invention, and further ensures the insulation and service life of the cable of the present invention.

[0054] Preferably, the inner shielding layer 6 is a polyolefin composite shielding material containing ferrite, which can significantly improve the anti-interference and radiation resistance of the cable of the present invention, and reduce the resistivity and cost, ensure the smooth surface of the inner shielding layer 6, and further prevent the electric field distortion from damaging the insulating layer 4, thereby extending the service life of the cable of the present invention.

[0055] The polyolefin composite shielding material is composed of the following raw materials in parts by weight: 40-60 parts of polypropylene resin, 25-35 parts of ethylene-vinyl acetate copolymer, 15-25 parts of ethylene-butyl acrylic acid copolymer, 5-10 parts of PP grafted maleic anhydride, 5-15 parts of carbon black, 3-6 parts of barium ferrite, 10-20 parts of flame retardant, 0.1-0.5 parts of initiator DCP, 0.5-2 parts of first silane coupling agent, 0.3-0.5 parts of antioxidant, and 1-3 parts of lubricant. The raw material combination and proportion of the polyolefin composite shielding material ensure that the present invention has good anti-interference, mechanical properties and combustion performance, and interacts with each component of the cable to ensure that it has excellent comprehensive performance.

[0056] Polypropylene resin (selected from Korean Lotte's polypropylene JI-320), ethylene-vinyl acetate copolymer (selected from Japan Mitsui's EVA 45X) and ethylene-butyl acrylic acid copolymer (selected from Dow's EBA 3217) are selected and combined in appropriate proportions to ensure that the polyolefin composite shielding material has easy processing, better mechanical properties and ductility, and improves the crosslinking density and temperature resistance level. PP grafted maleic anhydride (selected from SK Chemical's The addition of carbon black improves the compatibility between PP and other components, making the components closely bonded, thereby improving the mechanical properties and tensile and bending properties of the inner shielding layer 6. The use of carbon black (acetylene carbon black selected from Tianjin Huacai Chemical) improves the conductivity of the polyolefin composite shielding material and reduces the cost; however, if the amount of carbon black added is too much, the inner shielding layer 6 prepared is brittle, has poor ductility, low elongation at break, and affects the smoothness of the surface of the inner shielding layer 6, thereby affecting the mechanical properties and flexibility of the cable, and easily causing electric field distortion to damage the insulating layer 4, reducing the service life of the cable; if the amount of carbon black is too little, the conductivity of the inner shielding layer 6 cannot be guaranteed, reducing the anti-interference performance of the cable, etc.

[0057] The present invention uses carbon black and barium ferrite in appropriate proportions, which not only improves the conductivity of the inner shielding layer 6, but also improves the high temperature resistance and wear resistance of the cable of the present invention, so that the cable has better anti-interference, radiation resistance and corrosion resistance, but also ensures that the inner shielding layer 6 has excellent mechanical strength, flexibility, and surface smoothness, thereby extending the high temperature service life of the cable.

[0058] Preferably, barium ferrite BaFe 12 O 19 Commercially available or homemade ones can be selected, wherein the commercially available barium ferrite is selected from Wuhan Langbowan Biomedicine Company.

[0059] Homemade barium ferrite BaFe 12 O 19 The specific preparation process is:

[0060] S1. Add 371.8 g of ferrous nitrate, 1 kg of ferric nitrate (i.e., the molar ratio of ferrous nitrate to ferric nitrate is 1:2), and 96 g of PEG8000 to 1.2 L of deionized water, and continuously stir until dissolved. Then add ammonia water to adjust the pH value to 11, heat up to 60 °C, react for 4 h, carry out suction filtration, washing, and drying to obtain an iron oxide precursor;

[0061] S2. Add the above-prepared iron oxide precursor and 122.4 g of barium carbonate (i.e., the molar ratio of iron in the iron oxide precursor to barium carbonate is 10:1) to 1 L of glacial acetic acid, and stir until dissolved to form a mixed solution;

[0062] S3. Add 700 mL of 4 mol / L dilute nitric acid to the above mixed solution, stir for 10 min, then heat up to 220 °C, react for 4 h, cool to room temperature, carry out suction filtration, and then wash 3 times successively with deionized water and absolute ethanol, and then dry in vacuum at 80 °C for 3 h to obtain barium ferrite.

[0063] The barium ferrite BaFe 12 O 19 prepared by the present invention has an easy-to-operate preparation method, and the obtained barium ferrite has small grain size, good dispersion, and few impurities, which can significantly improve the conductivity and anti-interference performance of the inner shielding layer 6, and can also significantly improve the radiation resistance and corrosion resistance of the present invention, and ensure that the mechanical strength, flexibility, surface smoothness, etc. of the inner shielding layer 6 meet the requirements of the cable.

[0064] Preferably, the flame retardant is composed of microencapsulated red phosphorus (2000-mesh coated red phosphorus flame retardant YMRP-90 from Yimin Chemical Industry) and organic montmorillonite (nano-montmorillonite from Longchuan) with a mass ratio of 1:4. This flame retardant combination has good compatibility with components such as polyolefin, can significantly improve the flame retardancy, corrosion resistance, and wear resistance of the present invention, and ensure that the present invention has good mechanical properties and electrical properties.

[0065] Preferably, the first silane coupling agent is vinyltrimethoxysilane. On the one hand, it is to improve the bonding force between the organic and inorganic components in the polyolefin composite shielding material, thereby improving the mechanical strength of the inner shielding layer 6; on the other hand, it increases the crosslinking density between polyolefin resins, further improving the mechanical properties, water resistance, and high-temperature resistance of the polyolefin composite shielding material.

[0066] Preferably, the antioxidant is antioxidant 1010, which improves the heat-oxygen aging resistance of the polyolefin composite shielding material, is not easy to migrate, and has high thermal stability. The lubricant is CYD-P214, which improves the processing fluidity and dimensional stability of the polyolefin composite shielding material.

[0067] Preferably, the flame retardant layer 7 is a ceramifiable flame retardant polyolefin composite material, which has high mechanical strength and chemical stability, can be used for a long time at 150 °C, and can form a ceramic body during the combustion process in a flame, significantly improving the fire retardancy, smoke suppression and heat insulation properties. The oxygen index is ≥35. At the same time, it also has a supporting effect, improving the abrasion resistance and corrosion resistance of the cable, and having good thermal shock resistance and electrical properties.

[0068] The ceramifiable flame retardant polyolefin composite material is composed of the following raw materials in parts by mass: 30-50 parts of low-density polyethylene, 15-30 parts of ethylene-methyl acrylate copolymer, 40-60 parts of ethylene propylene diene terpolymer, 30-50 parts of amino-silane-coated wollastonite, 10-20 parts of low-melting-point glass powder, 15-25 parts of phlogopite powder, 5-10 parts of lithium borate salt, 0.2-0.4 part of initiator DCP, 6-12 parts of halogen-free flame retardant, and 1-3 parts of second silane coupling agent.

[0069] In order to ensure that the present invention has excellent mechanical properties, combustion properties and no corrosiveness, preferably, the melt index of the low-density polyethylene at 190 °C under a load of 2.16 Kg is 1.5-4 g / 10 min (DJ210 from Shanghai Petrochemical is selected in the examples of the present invention); the melt index of the ethylene-methyl acrylate copolymer at 190 °C under a load of 2.16 Kg is 5-10 g / 10 min (LOTADER AX8900 from Arkema is selected in the examples of the present invention); the ethylene content in the ethylene propylene diene terpolymer is 40-55 wt%, and the propylene content is 40-50 wt% (EPDM565 from Dow Chemical of the United States is selected in the examples of the present invention). The performance settings and combinations of the low-density polyethylene, ethylene-methyl acrylate copolymer and EPDM can enable the present invention to have no any dripping objects during 20 minutes of combustion under a fire source with a power of 20.5 kW; when the present invention burns at 935 °C, the conductivity ≤10 μs / mm and pH ≥4.

[0070] The amino-silane-coated wollastonite, low-melting-point glass powder and phlogopite powder are added as ceramic-forming fillers for the ceramic material, which not only have good bonding force with the polyolefin material, but also improve the mechanical strength, electrical insulation, high temperature resistance and corrosion resistance of the cable of the present invention.

[0071] The addition of low-melting glass powder improves the mechanical strength, corrosion resistance, wear resistance, high-temperature resistance and combustion performance of the ceramized flame-retardant polyolefin composite, and further ensures that the cable of the present invention meets the requirements of halogen-free, low-smoke and flame-retardant Class A, and the combustion performance level reaches the national standard B1 level. At the same time, it also improves the electrical insulation and arc resistance of high-voltage cables. In order to improve the use effect of low-melting glass powder in the ceramized flame-retardant polyolefin composite, preferably, the melting temperature of the low-melting glass powder is 350°C - 550°C, and the average particle size is not more than 10μm. In the examples of the present invention, the melting temperature of the selected low-melting glass powder is 350°C, and it is sieved through 2000 meshes.

[0072] The wollastonite coated with amino silane is surface-modified with aminopropyltriethoxysilane on wollastonite (selected from 400-mesh acicular wollastonite powder of Jiangxi Kete Fine Chemicals), and the coating rate is ≥70%, which improves the bonding force between wollastonite and other components, and further ensures that the ceramized flame-retardant polyolefin composite can achieve the mechanical strength and combustion performance required by the present invention. The addition of phlogopite powder can form an integral body with the outer sheath 9 during combustion, forming a non-dripping ceramic body and improving the fire and flame retardant performance.

[0073] Preferably, the lithium borate salt is composed of lithium tetraborate, lithium metaborate and zinc borate with a mass ratio of 1:2:4. Using this combination of lithium borate salts can not only reduce the ceramization transition temperature of the ceramized flame-retardant polyolefin composite and improve the processing performance, but also significantly improve the mechanical strength and flame retardancy of the ceramized flame-retardant polyolefin composite.

[0074] Preferably, the halogen-free flame retardant is composed of nano magnesium hydroxide, magnesium stearate and silicone oil with a mass ratio of (0.2 - 0.5):1:1. Using this combination of halogen-free flame retardants not only has excellent flame retardancy, but also ensures that the ceramized flame-retardant polyolefin composite has excellent mechanical strength and processing performance. In the examples of the present invention, the selected halogen-free flame retardant is a mixture of nano magnesium hydroxide, magnesium stearate and silicone oil with a mass ratio of 1:2:2.

[0075] Preferably, the second silane coupling agent is composed of vinyltrimethoxysilane and aminopropyltriethoxysilane with a mass ratio of 3:2. This combination of silane coupling agents increases the crosslinking density between polyolefin resins and improves the mechanical properties, water resistance and high-temperature resistance of the ceramized flame-retardant polyolefin composite.

[0076] Preferably, the outer shielding layer 8 is an aluminum foil mylar tape, which provides double protection with the inner shielding layer 6, further improving the anti-interference, radiation resistance and other performance of the cable of the present invention, and at the same time improving the high-temperature resistance and fire and flame retardancy of the present invention.

[0077] Preferably, the outer protective layer 9 is a halogen-free, low-smoke, flame-retardant, corrosion-resistant polyolefin mixture, which can withstand high temperatures of 150 °C, low temperatures of -40 °C, has an oxygen index ≥ 35, and has excellent mechanical properties, combustion properties, corrosion resistance, radiation resistance, and electrical insulation properties.

[0078] The halogen-free, low-smoke, flame-retardant, corrosion-resistant polyolefin mixture is composed of the following raw materials in parts by mass: 30-50 parts of linear low-density polyethylene, 10-15 parts of ultra-high molecular weight polyethylene, 25-40 parts of ethylene-ethyl acrylate copolymer, 15-30 parts of metallocene ethylene-octene copolymer, 15-30 parts of methyl vinyl silicone rubber, 20-40 parts of low-melting point glass powder, 15-25 parts of plasticizer, 30-50 parts of compound flame retardant, 10-15 parts of titanium aluminum oxide, 20-40 parts of filler, 0.3-0.5 parts of antioxidant, 0.2-0.4 parts of initiator DCP, and 3-5 parts of the third silane coupling agent.

[0079] To ensure that the present invention has excellent mechanical properties, combustion properties, and corrosion resistance, preferably, the linear low-density polyethylene has a melt index of 1.5-3 g / 10 min at 190 °C under a load of 2.16 Kg (DFDA-7042 from Maoming Petrochemical is selected in the examples of the present invention); the molecular weight of the ultra-high molecular weight polyethylene UHMWPE ≥ 4.5 million (GUR 4150 from Celanese, USA is selected in the examples of the present invention); the ethylene-ethyl acrylate copolymer has a melt index of 5-10 g / 10 min at 190 °C under a load of 2.16 Kg (AC 2618 from DuPont, USA is selected in the examples of the present invention); the metallocene ethylene-octene copolymer has a melt index of 4-8 g / 10 min at 190 °C under a load of 2.16 Kg (C5070D from Sabic is selected in the examples of the present invention). By setting the performance and ratio of these components, the comprehensive performance of the outer sheath of the present invention can be ensured to be excellent, and it has better mechanical strength, flame retardancy, and corrosion resistance.

[0080] The addition of methyl vinyl silicone rubber increases the crosslinking density of the polyolefin mixture, further improves the mechanical strength and toughness of the halogen-free, low-smoke, flame-retardant, corrosion-resistant polyolefin mixture, and at the same time improves the water resistance and corrosion resistance of the polyolefin mixture. In the examples of the present invention, preferably, vinyl-terminated methyl vinyl silicone rubber with a vinyl content of 0.21-0.24 wt% from Nanjing Dongjue's 110-3S is selected.

[0081] The addition of low-melting point glass powder improves the mechanical strength, corrosion resistance, wear resistance, high-temperature resistance, and combustion properties of the halogen-free, low-smoke, flame-retardant, corrosion-resistant polyolefin mixture. In the examples of the present invention, preferably, the low-melting point glass powder is selected from Hebei Jinghang, with a melting temperature of 350 °C and sieved through 2000 meshes.

[0082] Preferably, the plasticizer is any one or two of trioctyl trimellitate, diisononyl phthalate, dipentaerythritol ester or glycol ester. This plasticizer has good compatibility with polyolefin, high plasticizing efficiency, low volatility, and excellent heat resistance, chemical corrosion resistance and electrical insulation, improving the processing performance and flame retardancy of the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture. In the embodiment of the present invention, the plasticizer is trioctyl trimellitate, which is from Jinan Shengchen Chemical Industry.

[0083] Preferably, the composite flame retardant is composed of the following raw materials in parts by mass: 40-60 parts of nano magnesium hydroxide, 30-40 parts of aluminum hydroxide and 10-20 parts of zinc borate. This composite flame retardant can ensure that the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture has excellent low-smoke flame retardancy, and can form a non-dripping hard shell-like substance during combustion. It can also ensure that the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture has excellent mechanical strength, corrosion resistance and processing performance. In the embodiment of the present invention, the formula of the composite flame retardant is: 50 parts of nano magnesium hydroxide (in the embodiment, it is selected from the 5000-mesh nano magnesium hydroxide of Jiuzhuo Chemical Industry), 35 parts of aluminum hydroxide (in the embodiment, it is selected from FR3801 of Zhongke Flame Retardant, with a particle size of 8000 mesh) and 15 parts of zinc borate (in the embodiment, it is selected from zinc borate HT-207 of Taixing New Materials).

[0084] Preferably, the titanium-aluminum oxide is formed by mixing titanium dioxide and aluminum oxide in a mass ratio of 3:2, which can improve the corrosion resistance and aging resistance of the outer sheath 9, and enable the outer sheath 9 to achieve the mechanical strength, high temperature resistance, wear resistance and flame retardancy required by the present invention.

[0085] Preferably, the filler is composed of calcined kaolin (i.e., calcined kaolin YF-4000), mica powder (selected from the calcined mica powder of Deqian Mineral Products) and calcium carbonate (selected from the heavy calcium carbonate GS2500A of Kerna New Materials) in a mass ratio of 1:2:1, improving the mechanical strength, flame retardancy, corrosion resistance and wear resistance of the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture.

[0086] Preferably, the antioxidant is antioxidant 1010, which improves the heat-oxygen aging of the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture, is not easy to migrate, and has high thermal stability.

[0087] Preferably, the third silane coupling agent is composed of vinyltrimethoxysilane and vinyltri(2-methoxyethoxy)silane in a mass ratio of 2:1, which improves the crosslinking density between polyolefin resins and simultaneously improves the mechanical properties, water resistance and high temperature resistance of the halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture.

[0088] Preferably, a flame-retardant and corrosion-resistant polyurethane waterborne coating is sprayed on the outer sheath 9 to form an outer protective coating, so that the outer sheath of the cable forms a double protection, further improving the flame-retardant and corrosion-resistant properties of the cable. The polyurethane waterborne coating selected in the embodiment of the present invention is Akade UR-36, and it also has excellent waterproof, insulating, anti-aging and other properties.

[0089] The present invention also provides a method for preparing a corrosion-resistant and flame-retardant crosslinked polyolefin cable (hereinafter a single-core cable), which specifically includes the following steps:

[0090] P1. Stranding the tinned copper wire through a cantilever single-twist machine to form a single conductor 1;

[0091] P2. Wrapping a halogen-free and non-corrosive non-woven fabric around the conductor 1 to form an isolation layer 2;

[0092] P3. Coating a low-smoke and halogen-free flame-retardant cable material with an oxygen index greater than or equal to 40 outside the isolation layer 2 to form an oxygen isolation layer 3;

[0093] P4. Extruding and coating the 150 °C high-temperature radiation-crosslinked flame-retardant polyolefin insulating material through an extruder on the oxygen isolation layer 3 to form an insulating layer 4;

[0094] P5. Wrapping a halogen-free, low-smoke and high-flame-retardant tape made of non-woven fabric or fiberglass fabric around the insulating layer 4 to form a tape layer 5;

[0095] P6. Weighing the raw materials in the above-mentioned polyolefin composite shielding material containing ferrite according to the mass parts, adding them to a high-speed mixer, mixing at 480 r / min and 110-120 °C for 8-10 min, cooling to below 50 °C, and then transporting them to a twin-screw extruder for granulation to obtain a polyolefin composite shielding material; then using an extruder under the condition of a temperature of 130-150 °C, extruding and coating the above-mentioned prepared polyolefin composite shielding material on the tape layer 5 to form an inner shielding layer 6;

[0096] P7. Weighing the raw materials in the above-mentioned ceramizable flame-retardant polyolefin composite material according to the mass parts, adding them to a high-speed mixer, mixing at 480 r / min and 100-110 °C for 10-15 min, cooling to below 70 °C, and then transporting them to a twin-screw extruder for granulation to obtain a ceramizable flame-retardant polyolefin composite material; then using an extruder under the condition of a temperature of 125-135 °C, extruding and coating the above-mentioned prepared ceramizable flame-retardant polyolefin composite material on the inner shielding layer 6 to form a flame-retardant layer 7;

[0097] P8. Wrapping an aluminum foil mylar tape around the flame-retardant layer 7 to form an outer shielding layer 8;

[0098] P9. Weigh the above halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture according to parts by mass, add it to a high-speed mixer, mix it for 8 - 10 min at 480 r / min and 110 - 120 °C, cool it to below 70 °C, and then transport it to a twin-screw extruder for granulation to obtain a halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture; then, using an extruder under the condition of a temperature of 120 - 140 °C, extrude and coat the above-prepared halogen-free low-smoke flame-retardant and corrosion-resistant polyolefin mixture on the outer shielding layer 8 to form an outer protective layer 9;

[0099] P10. Spray 2 - 4 layers of flame-retardant and corrosion-resistant polyurethane waterborne coating on the outer surface of the outer protective layer 9 to form a protective coating 10.

[0100] The corrosion-resistant and flame-retardant crosslinked polyolefin cable of the present invention will be described below in conjunction with specific embodiments.

[0101] Inner shielding layer 6: Polyolefin composite shielding material containing ferrite

[0102] Example 1

[0103] The polyolefin composite shielding material containing ferrite is composed of the following raw materials in parts by mass: 50 parts of polypropylene resin, 32 parts of ethylene-vinyl acetate copolymer, 18 parts of ethylene-butyl acrylate copolymer, 8 parts of PP grafted maleic anhydride, 10 parts of carbon black, 5 parts of barium ferrite, 15 parts of flame retardant, 0.4 part of initiator DCP, 1.5 parts of the first silane coupling agent, 0.4 part of antioxidant 1010, and 1.5 parts of lubricant CYD-P214.

[0104] The raw materials, raw material models, and preparation processes of the polyolefin composite shielding material containing ferrite are all described in the above specific embodiments. For details, please refer to the above description. In addition, in this Example 1, the barium ferrite is selected from Wuhan Langbowan Biomedical Co., Ltd. on the market.

[0105] After testing, the tensile strength of Example 1 is 23.4 MPa, the elongation at break is 378.5%, the volume resistivity at 20 °C is 6.8 Ω·cm, the volume resistivity at 90 °C is 20.4 Ω·cm, and the melt index is 6.8 g / 10 min.

[0106] Example 2

[0107] The raw materials, components, and preparation processes of the polyolefin composite shielding material containing ferrite in this Example 2 are the same as those in Example 1. For details, please refer to Example 1. The difference is that the barium ferrite in this Example 2 is self-made. For the specific preparation method, please refer to the description in the above specific embodiments.

[0108] After testing, the tensile strength of Example 2 was 26.9 MPa, the elongation at break was 425.6%, the volume resistivity at 20 °C was 4.3 Ω·cm, the volume resistivity at 90 °C was 12.5 Ω·cm, and the melt index was 8.2 g / 10 min.

[0109] Comparative Example 1

[0110] The polyolefin composite shielding material of Comparative Example 1 was prepared in the same manner as in Example 2, specifically referring to Example 1. The difference was that barium ferrite was not added in Comparative Example 1, and the addition amount of carbon black was 15 parts.

[0111] After testing, the tensile strength of Comparative Example 1 was 21.6 MPa, the elongation at break was 327.5%, the volume resistivity at 20 °C was 15.3 Ω·cm, the volume resistivity at 90 °C was 42.8 Ω·cm, and the melt index was 5.6 g / 10 min.

[0112] Comparative Example 2

[0113] The polyolefin composite shielding material of Comparative Example 2 was prepared in the same manner as in Example 2, specifically referring to Example 1. The difference was that barium ferrite was not added in Comparative Example 2, and the addition amount of carbon black was 25 parts.

[0114] After testing, the tensile strength of Comparative Example 2 was 12.8 MPa, the elongation at break was 185.4%, the volume resistivity at 20 °C was 9.5 Ω·cm, the volume resistivity at 90 °C was 25.8 Ω·cm, and the melt index was 4.5 g / 10 min.

[0115] Comparative Example 3

[0116] The polyolefin composite shielding material of Comparative Example 3 was prepared in the same manner as in Example 2, specifically referring to Example 1. The difference was that the flame retardant in Comparative Example 3 was composed of microencapsulated red phosphorus and magnesium hydroxide with a mass ratio of 1:9.

[0117] After testing, the tensile strength of Comparative Example 3 was 22.5 MPa, the elongation at break was 368.5%, the volume resistivity at 20 °C was 5.2 Ω·cm, the volume resistivity at 90 °C was 15.9 Ω·cm, and the melt index was 6.5 g / 10 min.

[0118] Flame retardant layer 7: Ceramicized flame retardant polyolefin composite material

[0119] Example 3

[0120] The ceramifiable flame-retardant polyolefin composite material is composed of the following raw materials in parts by mass: 38 parts of low-density polyethylene, 25 parts of ethylene-methyl acrylate copolymer, 37 parts of ethylene-propylene-diene terpolymer, 40 parts of amino-silane-coated wollastonite, 16 parts of low-melting-point glass powder, 18 parts of phlogopite powder, 8 parts of lithium borate, 0.3 part of initiator DCP, 10 parts of halogen-free flame retardant, and 1.8 parts of second silane coupling agent.

[0121] The raw materials, raw material models, and preparation process of the ceramifiable flame-retardant polyolefin composite material are described in the above specific embodiments. For details, please refer to the above description.

[0122] Comparative Example 4

[0123] The preparation method of the ceramifiable flame-retardant polyolefin composite material in Comparative Example 4 is the same as that in Example 3. Specifically, refer to Example 3. The difference is that the wollastonite in Comparative Example 4 is not coated with amino-silane, that is, 400-mesh acicular wollastonite powder from Jiangxi Kete Fine Chemicals is directly added.

[0124] Comparative Example 5

[0125] The preparation method of the ceramifiable flame-retardant polyolefin composite material in Comparative Example 5 is the same as that in Example 3. Specifically, refer to Example 3. The difference is that phlogopite powder is not added in Comparative Example 6, and the addition amount of low-melting-point glass powder is 34 parts.

[0126] Comparative Example 6

[0127] The preparation method of the ceramifiable flame-retardant polyolefin composite material in Comparative Example 6 is the same as that in Example 3. Specifically, refer to Example 3. The difference is that zinc borate is not added in Comparative Example 5, and the mass ratio of lithium tetraborate to lithium metaborate is 1:2.

[0128] The ceramifiable flame-retardant polyolefin composite materials prepared in Example 3 and Comparative Examples 4-6 above were made into specimens for performance testing, as shown in Table 1 below.

[0129] Table 1 Performance test results of the ceramifiable flame-retardant polyolefin composite material

[0130]

[0131]

[0132] It can be seen from the experimental results in Table 1 above that the ceramifiable flame-retardant polyolefin composite material of the present invention has high mechanical strength, chemical stability, and flame retardancy, and can be used for a long time at 150 °C.

[0133] Outer sheath 9: halogen-free, low-smoke, flame-retardant, and corrosion-resistant polyolefin mixture

[0134] Example 4

[0135] The halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture is composed of the following raw materials in parts by mass: 40 parts of linear low-density polyethylene, 12 parts of ultra-high molecular weight polyethylene, 30 parts of ethylene-ethyl acrylate copolymer, 18 parts of metallocene ethylene-octene copolymer, 22 parts of methyl vinyl silicone rubber, 32 parts of low-melting glass powder, 20 parts of plasticizer, 36 parts of composite flame retardant, 12 parts of titanium-aluminum oxide, 35 parts of filler, 0.4 part of antioxidant 1010, 0.3 part of initiator DCP, and 3.6 parts of third silane coupling agent.

[0136] The raw materials, raw material models, and preparation processes of the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture are described in the above specific embodiments. For details, please refer to the above description.

[0137] Comparative Example 7

[0138] The preparation method of the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture in Comparative Example 7 is the same as that in Example 4. Specifically, refer to Example 4. The difference is that methyl vinyl silicone rubber is not added in Comparative Example 7, and 22 parts of hydrogenated nitrile rubber are added instead.

[0139] Comparative Example 8

[0140] The preparation method of the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture in Comparative Example 8 is the same as that in Example 4. Specifically, refer to Example 4. The difference is that titanium-aluminum oxide is not added in Comparative Example 8, and 12 parts of iron-tin oxide are added instead. The iron-tin oxide is composed of iron oxide and tin oxide mixed in a mass ratio of 2:1.

[0141] Comparative Example 9

[0142] The preparation method of the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture in Comparative Example 9 is the same as that in Example 4. Specifically, refer to Example 4. The difference is that the composite flame retardant in Comparative Example 9 is composed of 50 parts of nano magnesium hydroxide, 35 parts of aluminum hydroxide, and 15 parts of charring agent CFA (triazine charring agent CFA selected from Xijia Chemical Industry).

[0143] The halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixtures prepared in Example 4 and Comparative Examples 7-9 above were made into specimens for performance testing, as shown in Table 2 below.

[0144] Table 2 Performance test results of halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixtures

[0145]

[0146]

[0147] As can be seen from the experimental results in Table 2 above, the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture of the present invention can withstand high and low temperatures, and has high mechanical strength, combustion performance, corrosion resistance, radiation resistance and electrical insulation.

[0148] Application Example 1

[0149] A corrosion-resistant and flame-retardant cross-linked polyolefin cable is manufactured using the preparation method in the above specific embodiment. The raw materials and structure are as described in the specific embodiment. The cable core is a single conductor. Conductor 1 is 1 piece with a diameter of 18.00 mm. The thickness of the isolation layer 2 is 0.2 mm. The thickness of the insulation layer 4 is 2.2 mm. The thickness of the oxygen barrier layer 3 is 2.1 mm. The thickness of the tape layer 5 is 0.2 mm. The thickness of the inner shielding layer 6 is 0.5 mm. The thickness of the flame-retardant layer 7 is 1.5 mm. The thickness of the outer shielding layer 8 is 0.3 mm. The thickness of the outer sheath 9 is 2.5 mm. The thickness of the protective coating 10 is 0.02 mm. Among them, the preparation methods of the polyolefin composite shielding material containing ferrite, the ceramizable flame-retardant polyolefin composite material and the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture refer to Example 1, Example 3 and Example 4 respectively.

[0150] Application Example 2

[0151] A corrosion-resistant and flame-retardant cross-linked polyolefin cable is manufactured using the preparation method in the above specific embodiment. The raw materials and structure are as described in the specific embodiment. The cable core is a single conductor. Conductor 1 is 1 piece with a diameter of 18.00 mm. The thickness of the isolation layer 2 is 0.2 mm. The thickness of the insulation layer 4 is 2.2 mm. The thickness of the oxygen barrier layer 3 is 2.1 mm. The thickness of the tape layer 5 is 0.2 mm. The thickness of the inner shielding layer 6 is 0.5 mm. The thickness of the flame-retardant layer 7 is 1.5 mm. The thickness of the outer shielding layer 8 is 0.3 mm. The thickness of the outer sheath 9 is 2.5 mm. The thickness of the protective coating 10 is 0.02 mm. Among them, the preparation methods of the polyolefin composite shielding material containing ferrite, the ceramizable flame-retardant polyolefin composite material and the halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture refer to Example 2, Example 3 and Example 4 respectively. It should be noted that the thickness differences of each layer in Application Example 1 and Application Example 2 are within a reasonable range.

[0152] The properties of the corrosion-resistant and flame-retardant cross-linked polyolefin cables manufactured in the above Application Examples 1-2 are tested, and the test results are shown in Table 3.

[0153] Table 3 Performance Test Results of the Cable

[0154]

[0155] As can be seen from Application Examples 1-2, for the corrosion-resistant and flame-retardant cross-linked polyolefin cable and its manufacturing method of the present invention, starting from the perspective of optimizing the formulas of each cable component, inner shielding layer 6, flame-retardant outer sheath, etc., making full use of the synergistic effect between each component and each component, the deficiencies described in the background art are overcome, ensuring that the combustion performance of the cable of the present invention reaches Class A for flame retardancy and the combustion performance level reaches B1 level, and the product has a simple structure, is easy to manufacture, has a wide range of applications, and low cost, and has excellent flame retardancy, excellent electrical properties, good mechanical properties, strong corrosion resistance and other characteristics.

[0156] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0157] The above embodiments only represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A cross-linked polyolefin cable with corrosion resistance and flame retardancy, comprising a cable core, a tape layer, an inner shielding layer, a flame retardant layer, an outer shielding layer, an outer sheath layer and a protective coating. The cable core is one or more wire cores, and each wire core includes a conductor, an isolation layer, an insulating layer and an oxygen isolation layer. The isolation layer is wound around the conductor, the oxygen isolation layer is extruded on the outer side of the isolation layer, and the insulating layer is extruded on the outer side of the oxygen isolation layer; An insulating layer is wrapped with a tape layer, an inner shielding layer is extruded outside the tape layer, a flame-retardant layer is extruded outside the inner shielding layer, an outer shielding layer is wrapped outside the flame-retardant layer, an outer sheath is wrapped outside the outer shielding layer, and a protective coating is applied outside the outer sheath, characterized in that The inner shielding layer is a polyolefin composite shielding material containing barium ferrite; The polyolefin composite shielding material is composed of the following raw materials in parts by mass: 40 - 60 parts of polypropylene resin, 25 - 35 parts of ethylene-vinyl acetate copolymer, 15 - 25 parts of ethylene-butyl acrylate copolymer, 5 - 10 parts of PP grafted maleic anhydride, 5 - 15 parts of carbon black, 3 - 6 parts of barium ferrite, 10 - 20 parts of flame retardant, 0.5 - 2 parts of the first silane coupling agent, 0.1 - 0.5 parts of initiator DCP, 0.3 - 0.5 parts of antioxidant, and 1 - 3 parts of lubricant; The flame retardant layer is a ceramized flame retardant polyolefin composite material; The outer shielding layer is an aluminum foil mylar tape; The outer sheath layer is a halogen-free, low-smoke, flame retardant and corrosion-resistant polyolefin mixture.

2. The corrosion-resistant and flame-retardant cross-linked polyolefin cable according to claim 1, wherein, The preparation method of the barium ferrite is as follows: S1. Add appropriate proportions of ferrous nitrate, ferric nitrate and polyethylene glycol to an appropriate amount of deionized water, stir continuously until dissolved, then add ammonia water to adjust the pH value to 10 - 11, raise the temperature to 50 - 70 °C and react for 2 - 4 h, then carry out suction filtration, washing and drying to obtain an iron oxide precursor; S2. Add the iron oxide precursor prepared above and barium carbonate to glacial acetic acid, stir until dissolved to form a mixed solution; S3. Add an appropriate amount of dilute nitric acid to the above mixed solution, stir for 5 - 10 min, then raise the temperature to 200 - 220 °C and react for 3 - 5 h, cool to room temperature, carry out suction filtration, then wash with deionized water and absolute ethanol successively for 2 - 3 times, and then dry in vacuum at 80 °C for 2 - 5 h to obtain barium ferrite.

3. The corrosion-resistant and flame-retardant cross-linked polyolefin cable according to claim 2, wherein, The molar ratio of ferrous nitrate to ferric nitrate is (0.4 - 0.6):1; The molar ratio of iron in the iron oxide precursor to barium carbonate is (9 - 10):

1.

4. The corrosion-resistant and flame-retardant crosslinked polyolefin cable according to claim 1, wherein The ceramized flame retardant polyolefin composite material is composed of the following raw materials in parts by mass: 30 - 50 parts of low-density polyethylene, 15 - 30 parts of ethylene-methyl acrylate copolymer, 25 - 40 parts of ethylene propylene diene terpolymer, 30 - 50 parts of amino-silane-coated wollastonite, 10 - 20 parts of low-melting glass powder, 15 - 25 parts of phlogopite powder, 5 - 10 parts of lithium borate salt, 6 - 12 parts of halogen-free flame retardant, 0.2 - 0.4 parts of initiator DCP and 1 - 3 parts of the second silane coupling agent.

5. The corrosion-resistant and flame-retardant crosslinked polyolefin cable according to claim 4, wherein, The amino-silane-coated wollastonite is obtained by surface modification of wollastonite with aminopropyltriethoxysilane, and the coating rate is ≥70%; The lithium borate salt is composed of lithium tetraborate, lithium metaborate and zinc borate with a mass ratio of 1:2:4; The halogen-free flame retardant is composed of nano-magnesium hydroxide, magnesium stearate and silicone oil with a mass ratio of (0.2 - 0.5):1:1; The second silane coupling agent is composed of vinyltrimethoxysilane and aminopropyltriethoxysilane.

6. The corrosion-resistant and flame-retardant crosslinked polyolefin cable according to claim 1, wherein, The halogen-free, low-smoke, flame-retardant and corrosion-resistant polyolefin mixture is composed of the following raw materials in parts by mass: Linear low-density polyethylene: 30 - 50 parts, Ultra-high molecular weight polyethylene: 10 - 15 parts, Ethylene-ethyl acrylate copolymer: 30 - 50 parts, Metallocene ethylene-octene copolymer: 15 - 30 parts, Methyl vinyl silicone rubber: 15 - 30 parts, Low-melting glass powder: 20 - 40 parts, Plasticizer: 15 - 25 parts, Compound flame retardant: 30 - 50 parts, Titanium-aluminum oxide: 10 - 15 parts, Filler: 20 - 40 parts, Antioxidant: 0.3 - 0.5 part, Initiator DCP: 0.2 - 0.4 part, Third silane coupling agent: 3 - 5 parts.

7. The corrosion-resistant and flame-retardant crosslinked polyolefin cable according to claim 6, characterized in that, The compound flame retardant is composed of the following raw materials in parts by mass: 40 - 60 parts of nano magnesium hydroxide, 30 - 40 parts of aluminum hydroxide, and 10 - 20 parts of zinc borate.

8. The corrosion-resistant and flame-retardant crosslinked polyolefin cable according to claim 6, wherein The titanium-aluminum oxide is formed by mixing titanium dioxide and aluminum oxide in a mass ratio of 3:2; The filler is composed of calcined kaolin, phlogopite powder, and calcium carbonate in a mass ratio of 1:2:1; The third silane coupling agent is vinyltrimethoxysilane.

9. The cross-linked polyolefin cable with corrosion resistance and flame retardancy according to claim 1, characterized in that, The isolation layer is a halogen-free and non-corrosive non-woven fabric made of polyester fiber or polyester fiber; The insulating layer is a radiation-crosslinked flame-retardant polyolefin insulating material with a high temperature resistance of 150 °C; The oxygen barrier layer is a low-smoke and halogen-free flame-retardant cable material with an oxygen index greater than or equal to 40; The tape layer is a halogen-free, low-smoke, and high-flame-retardant tape made of non-woven fabric or fiberglass cloth, which is overlapped and wound around the outside of the insulating layer, and the overlapping rate is 15 - 20%; The outer shielding layer is an aluminum foil mylar tape; The protective coating is a flame-retardant and corrosion-resistant waterborne polyurethane coating.

Images