A flame-retardant cable and its preparation method

Abstract

This invention discloses a flame-retardant cable, comprising an insulated core, a first flame-retardant layer disposed on the outside of the insulated core, a gap filler between the insulated core and the first flame-retardant layer, an isolation sleeve disposed on the outside of the first flame-retardant layer, a fire-resistant layer disposed on the outside of the isolation sleeve, a skeleton sleeve disposed on the outside of the fire-resistant layer, a seepage-proof layer disposed on the outside of the skeleton sleeve, a second flame-retardant layer disposed on the outside of the seepage-proof layer, a protective layer disposed on the outside of the second flame-retardant layer, a metal armor layer disposed on the outside of the protective layer, and an outer sheath disposed on the outside of the metal armor layer. This invention overcomes the shortcomings of the prior art and improves the fire resistance and flame retardancy of the flame-retardant cable.

Description

Technical Field

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

[0002] With the development of the industrial sector, conventional wires and cables are gradually failing to meet higher application requirements. When wires experience short circuits or current overloads, the resulting high temperatures can easily cause cable fires, especially for the 8.7 / 15kV medium-voltage power cables most commonly used in substations before the low-voltage end. The requirements for maintaining power supply in the event of a fire are becoming increasingly stringent. Currently, in large and medium-sized cities in China, high-rise buildings, offshore oil platforms, mines, metallurgical plants, ships, power plants, subways, tunnels, and other locations with high population density and stringent fire safety requirements, flame-retardant cables are widely used to prevent the spread of fire through cables and maintain power supply during a fire. However, existing flame-retardant cables generally have low fire resistance and flame retardancy, resulting in a short period of time they can maintain power supply during a fire. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a flame-retardant cable and its preparation method, which can overcome the shortcomings of the prior art and improve the fire resistance and flame retardancy of the flame-retardant cable.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0005] A flame-retardant cable includes an insulated core, a first flame-retardant layer on the outside of the insulated core, a gap filler between the insulated core and the first flame-retardant layer, an isolation sleeve on the outside of the first flame-retardant layer, a fire-resistant layer on the outside of the isolation sleeve, a skeleton sleeve on the outside of the fire-resistant layer, a seepage-proof layer on the outside of the skeleton sleeve, a second flame-retardant layer on the outside of the seepage-proof layer, a protective layer on the outside of the second flame-retardant layer, a metal armor layer on the outside of the protective layer, and an outer sheath on the outside of the metal armor layer.

[0006] Preferably, the insulated core includes a conductor core, and the outer side of the conductor core is provided with an inner shielding layer, an insulation layer, an outer shielding layer, and a metal shielding layer in sequence from the inside to the outside.

[0007] Preferably, the inner shielding layer is a semi-conductive inner shielding thermoplastic material, the insulating layer is a chemically cross-linked polyethylene insulating material, and the outer shielding layer is a semi-conductive outer shielding thermoplastic material.

[0008] Preferably, the gap filler is a flame-retardant filling rope, the first flame-retardant layer and the second flame-retardant layer are fiberglass tape, the isolation sleeve is flame-retardant PE material, the fire-resistant layer is a mixture of aluminum hydroxide and sodium silicate, the seepage-proof layer is a polyester film, the protective layer is a flame-retardant oxygen-barrier material, the metal armor layer is formed by two layers of galvanized steel strips overlapping each other, and the outer protective layer is flame-retardant PVC material.

[0009] Preferably, the flame-retardant PVC material is composed of the following raw materials in parts by weight: 100 parts S-70 resin powder, 40 parts DOTP, 5 parts epoxidized soybean oil, 20 parts aluminum hydroxide, 20 parts magnesium hydroxide, 5 parts calcium zinc stabilizer, 0.5 parts each of polyethylene wax and stearic acid, and 10 parts tetrabromophthalic anhydride ester.

[0010] Preferably, the skeleton sleeve includes a skeleton sleeve body, on which a plurality of through grooves are evenly arranged, and spring pieces are fixed in the through grooves. The angle between the spring pieces and the refractory layer is 65° to 50°, and the surface of the refractory layer is pre-formed with grooves that engage with the spring pieces.

[0011] Preferably, the outer end of the spring sheet is provided with a slot, and when the polyester film is wrapped around it, the polyester film is located in the slot.

[0012] Preferably, pressure plates are connected to both sides of the slot via flexible connection points. The pressure plates include an upper rubber pressure plate and a lower hard pressure plate connected together. The upper rubber pressure plate is arc-shaped, and the lower hard pressure plate is planar. The rotation planes of the two pressure plates are parallel to each other. When the polyester film presses down on the lower hard pressure plate, the upper rubber pressure plate applies pressure to the polyester film simultaneously.

[0013] Preferably, the spring is provided with an arc-shaped extrusion piece on the side wall inside the main body of the skeleton sleeve, and the arc-shaped extrusion piece is in extrusion contact with the surface of the refractory layer.

[0014] A method for preparing the above-mentioned flame-retardant cable includes the following steps:

[0015] Flame-retardant filler rope is filled around the insulated wire core to form a gap filler. Fiberglass tape is wrapped around the insulated wire core to form a first flame-retardant layer. Flame-retardant PE material is extruded around the first flame-retardant layer to form an isolation sleeve. A mixture of aluminum hydroxide and sodium silicate is extruded around the isolation sleeve to form a fire-resistant layer. A pre-formed skeleton sleeve is fitted over the fire-resistant layer. Polyester film is wrapped around the skeleton sleeve to form a seepage-proof layer. Fiberglass tape is wrapped around the seepage-proof layer to form a second flame-retardant layer. Flame-retardant oxygen-barrier material is extruded around the second flame-retardant layer to form a protective layer. Galvanized steel strip is wrapped around the protective layer to form a metal armor layer. Flame-retardant PVC material is extruded around the metal armor layer to form an outer protective layer.

[0016] The beneficial effects of adopting the above technical solution are as follows: By setting an outer sheath, the present invention protects the cable from being burned in a short time. It uses high oxygen index flame-retardant PVC material, which has excellent physical properties, dimensional stability, low shrinkage rate, strong tensile strength and tear strength, and good heat resistance, flame resistance, sunlight resistance and chemical reagent resistance. The modified filler of the present invention has good dispersibility and low surface tension, which further improves the tensile strength of the cable material. It not only slows down the aging rate of the cable material, but also improves the chemical reagent resistance, reduces production costs, and has strong flame retardant and fire resistance. The gap filler prevents the insulation core from overheating and short-circuiting during a fire, thus preventing spontaneous combustion. The insulating sleeve serves both as an oxygen barrier and ensures the inorganic mineral flame-retardant and fire-resistant layer reaches the standard thickness. The fire-resistant layer, extruded from a mixture of aluminum hydroxide and sodium silicate, forms a flame-retardant and fire-resistant shell at high temperatures, effectively isolating heat and preventing the diffusion of combustion heat into the cable core, further reducing the possibility of cable combustion and effectively protecting the insulation core. The effective protection during the initial extrusion of the anti-seepage layer and fire-resistant layer further improves the forming quality. Installing a prefabricated skeleton sleeve between the anti-seepage layer and the fire-resistant layer improves the surface tension uniformity during the polyester film wrapping process, enhances the relative stability of the wrapping between the polyester film and the fire-resistant layer, and improves the overall bending toughness of the cable. Multiple layers of protection—the first flame-retardant layer, the second flame-retardant layer, and the metal armor layer—prevent the insulation core from burning. The triple shielding design of the insulation core further enhances the cable's resistance to electromagnetic induction and power line conduction interference. The insulation layer is used for insulation to prevent cable leakage. The cable of this invention has strong flame retardancy and fire resistance, and can maintain power supply for several hours after a fire, which helps to reduce the difficulty of personnel evacuation and fire rescue, and reduce personnel safety risks and property losses. Attached Figure Description

[0017] Figure 1 This is a structural diagram of a specific embodiment of the present invention.

[0018] Figure 2 This is a partial enlarged view of the through groove portion of the skeleton sleeve in a specific embodiment of the present invention.

[0019] Figure 3 This is a structural diagram of the pressure plate inside the slot in a specific embodiment of the present invention. Detailed Implementation

[0020] Reference Figure 1One specific embodiment of the present invention includes an insulated core 1, of which three insulated cores 1 are provided to improve the power transmission capacity of the cable. The three insulated cores 1 are twisted together to form a cable core. The insulated core 1 includes a conductor core 1a. From the inside out, an inner shielding layer 1b, an insulation layer 1c, an outer shielding layer 1d, and a metallic shielding layer 1e are arranged sequentially on the outside of the conductor core 1a. The inner shielding layer 1b is a semi-conductive thermoplastic inner shielding material, the insulation layer 1c is a chemically cross-linked polyethylene insulation material, and the outer shielding layer 1d is a semi-conductive thermoplastic outer shielding material.

[0021] A first flame-retardant layer 2 is provided on the outside of the insulated core 1. A gap filler 3 is filled between the insulated core 1 and the first flame-retardant layer 2. An isolation sleeve 4 is provided on the outside of the first flame-retardant layer 2. A fire-resistant layer 5 is provided on the outside of the isolation sleeve 4. A skeleton sleeve 6 is provided on the outside of the fire-resistant layer 5. A seepage-proof layer 7 is provided on the outside of the skeleton sleeve 6. A second flame-retardant layer 8 is provided on the outside of the seepage-proof layer 7. A protective layer 9 is provided on the outside of the second flame-retardant layer 8. A metal armor layer 10 is provided on the outside of the protective layer 9. An outer sheath 11 is provided on the outside of the metal armor layer 10.

[0022] The gap filler 3 is a flame-retardant filling rope; the first flame-retardant layer 2 and the second flame-retardant layer 8 are fiberglass tapes; the isolation sleeve 4 is a flame-retardant PE material (the flame-retardant PVC material is composed of 100 parts of S-70 resin powder, 40 parts of DOTP, 5 parts of epoxidized soybean oil, 20 parts of aluminum hydroxide, 20 parts of magnesium hydroxide, 5 parts of calcium zinc stabilizer, 0.5 parts each of polyethylene wax and stearic acid, and 10 parts of tetrabromophthalic anhydride ester); the fire-resistant layer 5 is a mixture of aluminum hydroxide and sodium silicate; the seepage-proof layer 7 is a polyester film; the protective layer 9 is a flame-retardant oxygen barrier material; the metal armor layer 10 is formed by two layers of galvanized steel strips overlapping each other; and the outer protective layer 11 is a flame-retardant PVC material.

[0023] During the wrapping of the polyester film, due to the inherent properties of the polyester film and limitations of existing wrapping equipment, the coating stability between the polyester film and the fire-resistant layer 5 is poor. This can lead to separation between the waterproof layer 7 and the fire-resistant layer 5 after prolonged cable use. To address this issue, without altering the existing polyester film and wrapping process, we designed a dedicated skeleton sleeve 6 to improve the coating stability between the polyester film and the fire-resistant layer 5. (Refer to...) Figure 2-3The skeleton sleeve 6 includes a skeleton sleeve body 12, on which several through slots 13 are evenly arranged. Spring pieces 14 are fixed within the through slots 13, with the angle between the spring pieces 14 and the refractory layer 5 being 55°. The surface of the refractory layer 5 has pre-formed grooves for engaging with the spring pieces 14. A slot 15 is provided at the outer end of the spring piece 14, and when wrapping the polyester film, the polyester film is located within the slot 15. Pressure plates are connected to both sides of the slot 15 via flexible connection points 16. The pressure plates include an upper rubber pressure plate 17 and a lower rigid pressure plate 18 connected together. The upper rubber pressure plate 17 is arc-shaped, and the lower rigid pressure plate 18 is planar. The rotation planes of the two pressure plates are parallel to each other. When the polyester film presses down on the lower rigid pressure plate 18, the upper rubber pressure plate 17 simultaneously applies pressure to the polyester film. An arc-shaped extrusion piece 19 is provided on the inner side wall of the spring piece 14 within the skeleton sleeve body 12, and the arc-shaped extrusion piece 19 is in contact with the surface of the refractory layer 5. When the polyester film is wrapped around the skeleton sleeve 6, it snaps into the slot 15 and presses down on the spring sheet 14, causing it to elastically deform. The spring sheet 14 provides ample elastic buffer space for the polyester film. Simultaneously, the pressure plate rotates slightly downwards during the pressing of the polyester film, causing the rubber pressure plate 17 to apply pressure to the polyester film synchronously. Since the rotation planes of the two pressure plates within the same slot 15 are parallel, the polyester film is subjected to a tensile force parallel to its surface, thereby improving the surface tension uniformity of the polyester film. Furthermore, the protection provided by the skeleton sleeve body 12 reduces the localized stress changes in each functional material layer when the cable is bent, thus enhancing the cable's toughness and durability.

[0024] A method for preparing the above-mentioned flame-retardant cable includes the following steps:

[0025] Flame-retardant filler rope is filled around the insulated core 1 to form gap filler 3. Fiberglass tape is wrapped around the insulated core 1 to form the first flame-retardant layer 2. Flame-retardant PE material is extruded around the first flame-retardant layer 2 to form an isolation sleeve 4. A mixture of aluminum hydroxide and sodium silicate is extruded around the isolation sleeve 4 to form a fire-resistant layer 5. A pre-formed skeleton sleeve 6 is fitted over the fire-resistant layer 5. Polyester film is wrapped around the skeleton sleeve 6 to form a seepage-proof layer 7. Fiberglass tape is wrapped around the seepage-proof layer 7 to form the second flame-retardant layer 8. Flame-retardant oxygen-barrier material is extruded around the second flame-retardant layer 8 to form a protective layer 9. Galvanized steel strip is wrapped around the protective layer 9 to form a metal armor layer 10. Flame-retardant PVC material is extruded around the metal armor layer 10 to form an outer protective layer 11.

[0026] When the outer sheath 11 is burned, the flame and heat can be isolated by the dual protection of the metal armor layer 10 and the second flame-retardant layer 8 and protective layer 9 disposed between the metal armor layer 10 and the fire-resistant layer 5. When heat penetrates the second flame-retardant layer 8 and protective layer 9 and continues to transfer inward, the heat is further isolated, and oxygen is isolated by the isolation sleeve 4, the fire-resistant layer 5, and the first flame-retardant layer 2 to prevent the insulated core 1 from burning. The flame-retardant cable sheath material and cable of the present invention can still maintain power supply for several hours after a fire, which helps to reduce the difficulty of personnel evacuation and fire rescue, and reduce personnel safety risks and property losses.

[0027] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0028] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A flame-retardant cable, comprising an insulated core (1), characterized in that: A first flame-retardant layer (2) is provided on the outside of the insulated wire core (1), and a gap filler (3) is filled between the insulated wire core (1) and the first flame-retardant layer (2). An isolation sleeve (4) is provided on the outside of the first flame-retardant layer (2), a fire-resistant layer (5) is provided on the outside of the isolation sleeve (4), a skeleton sleeve (6) is provided on the outside of the fire-resistant layer (5), a seepage-proof layer (7) is provided on the outside of the skeleton sleeve (6), and a second flame-retardant layer (8) is provided on the outside of the seepage-proof layer (7). A protective layer (9) is provided, a metal armor layer (10) is provided on the outside of the protective layer (9), and an outer protective layer (11) is provided on the outside of the metal armor layer (10); the gap filler (3) is a flame-retardant filling rope, the first flame-retardant layer (2) and the second flame-retardant layer (8) are fiberglass tapes, the isolation sleeve (4) is a flame-retardant PE material, the fire-resistant layer (5) is a mixture of aluminum hydroxide and sodium silicate, the seepage-proof layer (7) is a polyester film, the protective layer (9) is a flame-retardant oxygen barrier material, and the metal armor layer (10) consists of two The outer protective layer (11) is made of flame-retardant PVC material, and the frame sleeve (6) includes the frame sleeve body (12). Several through grooves (13) are evenly arranged on the frame sleeve body (12). A spring piece (14) is fixed in the through groove (13). The angle between the spring piece (14) and the fire-resistant layer (5) is 65° to 50°. The surface of the fire-resistant layer (5) is pre-made with a groove that engages with the spring piece (14). A slot (15) is provided on the outer end of the spring piece (14). When wrapping the polyester film, the polyester film is located in the slot (15); the two sides of the slot (15) are connected to the pressure plate through the flexible connection point (16). The pressure plate includes a rubber upper pressure plate (17) and a hard lower pressure plate (18) connected together. The rubber upper pressure plate (17) is arc-shaped and the hard lower pressure plate (18) is planar. The rotation planes of the two pressure plates are parallel to each other. When the polyester film presses down on the hard lower pressure plate (18), the rubber upper pressure plate (17) applies pressure to the polyester film simultaneously.

2. The flame-retardant cable according to claim 1, characterized in that: The insulated core (1) includes a conductor core (1a), and an inner shielding layer (1b), an insulation layer (1c), an outer shielding layer (1d), and a metal shielding layer (1e) are arranged sequentially from the inside to the outside of the conductor core (1a).

3. The flame-retardant cable according to claim 2, characterized in that: The inner shielding layer (1b) is a semi-conductive inner shielding thermoplastic material, the insulation layer (1c) is a chemically cross-linked polyethylene insulation material, and the outer shielding layer (1d) is a semi-conductive outer shielding thermoplastic material.

4. The flame-retardant cable according to claim 1, characterized in that: The flame-retardant PVC material is composed of the following raw materials in parts by weight: 100 parts S-70 resin powder, 40 parts DOTP, 5 parts epoxidized soybean oil, 20 parts aluminum hydroxide, 20 parts magnesium hydroxide, 5 parts calcium zinc stabilizer, 0.5 parts each of polyethylene wax and stearic acid, and 10 parts tetrabromophthalic anhydride ester.

5. The flame-retardant cable according to claim 1, characterized in that: The spring piece (14) is provided with an arc-shaped extrusion piece (19) on the side wall inside the skeleton sleeve body (12), and the arc-shaped extrusion piece (19) is in extrusion contact with the surface of the fire-resistant layer (5).

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