Fire resistant cable with self-sealing and fire resistant structure and method of manufacturing

Abstract

The application belongs to the technical field of electric wire and cable, and further relates to a fire-resistant cable with a self-sealing and fire-resistant structure and a manufacturing method thereof. The fire-resistant cable comprises a conductor and, from inside to outside, a fire-resistant tape wrapping layer, an insulation layer, a ceramicized silicone rubber tape wrapping layer, a self-sealing layer, a metal shielding layer and a sheath layer wrapped on the outer periphery of the conductor. The insulation layer forms a self-supporting inorganic framework under the condition of heat. The self-sealing layer expands to fill the interlayer gap and forms sealing to cracks or gaps when heated, and the expansion trigger temperature is 150-450 DEG C. The metal shielding layer is used for electromagnetic shielding and equipotential wrapping. The application can improve the loop integrity maintenance ability and stability of the cable under the conditions of high temperature in a fire, accompanied by mechanical disturbance, and optional water spraying / humidity, solve the problems of traditional fire-resistant cables under the complex disaster scene of fire, especially the fire superimposed mechanical physical damage, and improve the active repair and function maintenance ability of the cable under extreme conditions.

Description

Technical Field

[0001] This invention belongs to the field of wire and cable technology, and further relates to a fire-resistant cable with a self-sealing synergistic fire-resistant structure and its manufacturing method. Background Technology

[0002] Building fire protection and emergency power supply systems are crucial for ensuring personnel evacuation, fire rescue, and the operation of critical equipment during fires, placing extremely high demands on power and signal continuity. Currently, the industry commonly uses cable structures with mica tape or inorganic fire-resistant tape wrapped around the conductor insulation layer as the primary fire-resistant layer, and a metallic shielding layer added according to electromagnetic compatibility (EMC) requirements. This type of structure can meet basic fire resistance requirements under standard fire resistance test conditions.

[0003] However, in real-world fire disaster scenarios, these conventional fire-resistant cables expose a series of technical bottlenecks and reliability risks: fire scenes are often accompanied by building component collapses, impacts from falling objects, crushing, and potential cutting risks during fire rescue. Under such conditions of mechanical stress combined with high temperatures, the interlayer structure of the cable (such as the mica tape wrapping layer, the shielding layer, and the outer sheath) is prone to cracking and delamination due to differences in material thermal deformation coefficients and bonding failure, forming physical gaps. These defects not only directly damage the integrity of the structure but may also cause local short circuits between conductors or to ground, or lead to conductor open circuits, resulting in an instantaneous loss of power supply and signal transmission functions. The large amount of sprayed water generated during fire fighting or the high temperature and humidity environment of the fire scene makes it extremely easy for moisture or water vapor to migrate and penetrate along the aforementioned interlayer micro-cracks and gaps. Moisture infiltration will directly reduce the electrical performance of the insulation material, leading to a decrease in insulation resistance, and even causing leakage or breakdown. Meanwhile, moisture at high temperatures accelerates the oxidation and hydrolysis of material interfaces (such as mica tape and conductor, shielding layer and sheath), further weakening the mechanical strength of the structure and the stability of its fire-resistant and heat-insulating effects, seriously threatening the ability of the circuit to maintain integrity throughout the entire fire cycle.

[0004] To address these issues, a common solution is to enhance the mechanical protection of the cable, such as by adding rigid armor or thickening the structure. However, this often comes at the cost of sacrificing the cable's necessary flexibility, resulting in increased bending radius and weight. This poses significant challenges to laying and installing the cable in complex building structures, increasing installation costs and time, and sometimes even failing to meet the requirements of the actual wiring path. Summary of the Invention

[0005] The purpose of this invention is to provide a fire-resistant cable with a self-sealing and synergistic fire-resistant structure and its manufacturing method, so as to solve the systemic problems of the protection system of traditional fire-resistant cables in fire, especially in complex disaster scenarios where fire is superimposed with mechanical and physical damage, and improve the cable's ability to actively repair and maintain its function under extreme conditions.

[0006] In a first aspect, the present invention provides a fire-resistant cable with a self-sealing and synergistic fire-resistant structure, comprising a conductor and, from the inside out, a fire-resistant tape wrapping layer, an insulation layer, a ceramicized silicone rubber tape wrapping layer, a self-sealing layer, a metal shielding layer, and a sheath layer, which are sequentially wrapped around the outer periphery of the conductor from the inside out. The self-sealing layer consists of a bonding matrix and a component that expands when heated; The adhesive matrix is ​​composed of silicone rubber, halogen-free polymer, and inorganic silicate adhesive; The component that expands upon heating consists of expanded graphite, inorganic hydrated salts, and foamed inorganic materials. The expansion trigger temperature of the self-sealing layer is 150–450℃.

[0007] The fire-resistant cable with a self-sealing synergistic fire-resistant structure constructed in this invention achieves excellent comprehensive fire resistance and protection performance through the synergistic cooperation of its various structural layers. In the event of a fire, the fire-resistant tape wrapping layer, the insulation layer, and the ceramicized silicone rubber tape wrapping layer located outside the conductor together form the initial first line of fire resistance. The ceramicized silicone rubber tape wrapping layer can rapidly ceramicize at high temperatures, forming a rigid, self-supporting insulation skeleton, effectively preventing short-circuit risks caused by insulation softening, collapse, or carbonization. The self-sealing layer expands in volume when heated, forming a continuous porous / dense isolation structure that fills interlayer gaps, cracks, and gaps, improving the cable's ability to maintain circuit integrity and stability under high fire temperatures and accompanying mechanical disturbances, water spray / humid conditions. Simultaneously, it forms a synergistic constraint with the outer metal shielding layer and outer sheath layer, enhancing the overall structural stability. Furthermore, the self-sealing layer's reaction process absorbs a large amount of heat and isolates flames, reducing the internal temperature of the cable and slowing down the aging process of the insulation.

[0008] Furthermore, the mass ratio of the adhesive matrix to the heat-expanding component is (40-50):(50-60); The mass ratio of silicone rubber, halogen-free polymer and inorganic silicate binder in the adhesive matrix is ​​(3-5):(1-3):(3-5); The mass ratio of expanded graphite, inorganic hydrated salt and foamed inorganic material in the heat-expanding component is (6-8):1:(2-3).

[0009] Furthermore, the silicone rubber includes polydimethylsiloxane RTV / HTV; its repeating unit is [ Si(CH3)2 O ] n The repeating unit has a molecular weight of approximately 74.15; among them, the number-average molecular weight of RTV-type polydimethylsiloxane is 2.0 × 10⁻⁶. 4 ~8.0×10 4 The corresponding degree of polymerization is approximately 270–1080; the number average molecular weight of HTV-type polydimethylsiloxane is 3.0 × 10⁻⁶.5 ~8.0×10 5 The corresponding degree of polymerization is approximately 4000 to 10800.

[0010] Halogen-free polymers include polypropylene-polyethylene blends; the repeating unit of polyethylene is [-CH2-CH(CH3)-]. n The repeating unit has a molecular weight of approximately 28.05 and a number-average molecular weight of 3.0 × 10⁻⁶. 4 ~2.0×10 5 The mass ratio of polypropylene to polyethylene is (3-7):(7-3), and even more specifically (4-6):(6-4).

[0011] The inorganic silicate binder includes an aluminum hydroxide-silicate composite system; wherein the aluminum hydroxide has the chemical formula Al(OH)3 and a relative molecular mass of 78.00; the silicate is sodium silicate, silica sol or a combination thereof, and the silicate modulus is 2.5-3.5, more specifically 2.8-3.3; the mass ratio of aluminum hydroxide to silicate is (3-7):(7-3), more specifically (4-6):(6-4), and the molar ratio of SiO2 / Al2O3 in the composite system is 2-6.

[0012] Inorganic hydrated salts include sodium sulfate decahydrate; its chemical formula is Na₂SO₄·10H₂O, and its relative molecular mass is approximately 322.20. The purity of sodium sulfate decahydrate is not less than 95 wt%, with an average particle size of 1–100 μm, and further, an average particle size of 5–50 μm; the water of crystallization content is 50–60 wt%, and further, 53–56 wt%. During heating, sodium sulfate decahydrate can release water of crystallization and absorb some heat, thus playing a role in cooling, diluting flammable volatiles, and assisting in expansion and sealing to a certain extent. Furthermore, sodium sulfate decahydrate is pre-dried at 80–120℃ for 2–6 h before being added to the mixing system to reduce the impact of surface free water on subsequent extrusion stability.

[0013] The foamed inorganic material includes aluminosilicate foam. The aluminosilicate foam preferably comprises an Al2O3-SiO2 porous inorganic material, wherein the Al2O3 content is 30–60 wt%, and the SiO2 content is preferably 40–70 wt%; further, the molar ratio of SiO2 / Al2O3 is 1.5–4.5, and even more preferably 2.0–3.5. The aluminosilicate foam has a bulk density of 0.2–0.8 g / cm³, more preferably 0.3–0.6 g / cm³; an average particle size of 10–200 μm, more preferably 20–100 μm; and a porosity of 40%–85%, and even more preferably 50%–75%.

[0014] By using the aforementioned aluminum silicate foam, a lightweight porous support structure can be formed after heating. This structure works synergistically with the volume expansion of expanded graphite and the skeletal consolidation of inorganic silicate binders, thereby improving the sealing integrity and structural stability of the self-sealing layer under high-temperature fire conditions, accompanied by mechanical disturbances, and optional water spray / humid conditions.

[0015] Furthermore, the self-sealing layer is composed of a binder matrix and a heat-expanding component mixed in a mass ratio of 45:55, which are then compounded, extruded, and coated onto the surface of the wire core. The binder matrix is ​​composed of silicone rubber (polydimethylsiloxane RTV / HTV), a halogen-free polymer (polypropylene-polyethylene blend), and an inorganic silicate binder (aluminum hydroxide-silicate composite system) mixed in a mass ratio of 40:20:40. The heat-expanding component is composed of expanded graphite, an inorganic hydrated salt (sodium sulfate decahydrate), and a foamed inorganic material (aluminum silicate foam) mixed in a mass ratio of 70:10:20.

[0016] The self-sealing layer expands when heated to fill interlayer voids and seal cracks / notches. Optionally, the expansion trigger temperature of the self-sealing layer is 180–380°C; further, the expansion trigger temperature of the self-sealing layer is 200–350°C.

[0017] Furthermore, the conductor has 1-5 cores and a nominal cross-sectional area of ​​16–630 mm². 2 .

[0018] The conductor configuration of this cable design offers excellent engineering adaptability and application flexibility, meeting the power distribution needs of both small and large equipment, thus achieving versatility in various scenarios such as industrial automation, building electrical systems, and infrastructure. Simultaneously, it reduces the need for customized special cable specifications, simplifies engineering design selection, on-site installation, and subsequent spare parts inventory management, significantly improving the overall performance and large-scale application of this fire-resistant cable technology solution.

[0019] Furthermore, the overlap rate of the refractory tape wrapping is 15%–50%, and the material of the refractory tape wrapping is synthetic phlogopite tape, more preferably synthetic fluorophlogopite tape. Before wrapping, the tape is heated to 500°C in a drying oven, causing the hydroxyl groups in the mica tape to be released in the form of water molecules in advance, avoiding the influence of water molecule aggregation on the circuit continuity during the refractory test. Optionally, the overlap rate of the refractory tape wrapping is 20%–40%, and more specifically, 25%–35%. The refractory tape wrapping possesses both refractory performance and structural stability through its material and structure.

[0020] Furthermore, the insulation layer has a thickness of 0.8–3.0 mm and is made of cross-linked polyolefin material, more specifically cross-linked polyolefin insulation material X-HF-1101, with an insulation performance reaching 110℃. Optionally, the insulation layer has a thickness of 1.2–2.5 mm; further, it has a thickness of 1.5–2.2 mm. The structural design of the insulation layer achieves a dynamic synergy between structural stability and electrical safety at high temperatures. Under normal operating temperatures, this layer provides reliable flexible insulation and physical protection; however, when a fire is triggered by high temperatures, its material can quickly transform into a hard, dense, and self-supporting ceramic skeleton. This in-situ phase change characteristic effectively prevents the insulation layer from softening, melting, or carbonizing and collapsing, thereby actively resisting the risk of short circuits between conductors or to ground caused by insulation failure.

[0021] The overlap rate of the ceramicized silicone rubber tape wrapping layer is 15%–50%, and the reinforcing material in the ceramicized silicone rubber tape wrapping layer is basalt fiber; optionally, the overlap rate is 20%–40%, and further, 25%–35%. Basalt fiber is used to replace the glass fiber reinforcement layer in traditional ceramicized silicone rubber tapes. Basalt fiber has non-combustible properties and can effectively prevent the spread of flames in the cable. In addition, the ceramicized silicone rubber tape wrapping can achieve a ceramicized shell at high temperatures of 300~500℃, possessing flame-retardant and heat-insulating properties. Tests show that the tensile strength of the ceramicized silicone rubber tape is ≥30MPa, and the tear strength is ≥140kN·m. -1 The water absorption rate is ≥0.18%. The ceramicized silicone rubber tape has a ceramicized silicone rubber coating on the surface, providing fire resistance and erosion resistance on the outer side. Basalt fiber tape serves as the load-bearing skeleton in the middle, resisting cracking and providing flame retardancy. The bottom layer is also ceramicized silicone rubber coated and bonded to the covered material. The density of the basalt fiber cloth is 180 g / m². 2 The thickness is 0.16mm.

[0022] Further, the thickness of the self-sealing layer is 0.10–0.80 mm, and the volume expansion ratio is 2–10 times; optionally, the thickness of the self-sealing layer is 0.15–0.60 mm, and the volume expansion ratio is 3–8 times; further, the thickness of the self-sealing layer is 0.20–0.5 mm, and the volume expansion ratio is 4–6 times.

[0023] The self-sealing layer actively fills and seals interlayer gaps and cracks or gaps caused by impact / cutting, improving the circuit integrity under fire and mechanical disturbance conditions. At the same time, the reaction process can absorb a large amount of heat and isolate flames, reduce the internal temperature of the cable, and slow down the aging process of the insulation.

[0024] The metallic shielding layer is a copper strip wrapped and overlapped structure, with a copper strip thickness of 0.05–0.30 mm and an overlap rate of 10%–35%. The metallic shielding layer is used for electromagnetic shielding. Optionally, the copper strip thickness is 0.08–0.20 mm with an overlap rate of 10%–15%; further, the copper strip thickness is 0.10–0.15 mm. The loose wrapping of the copper strip provides space for the expansion of the self-sealing layer. Simultaneously, the copper strip itself, as a shielding layer, effectively solves the problem of electric field distortion caused by rough conductor surfaces and poor contact with the insulation layer, confining the electric field within the insulation layer.

[0025] Furthermore, the sheath layer is a 110°C halogen-free low-smoke polyolefin, model HFS-110-TP. The thickness of the sheath layer is 1.2–4.0 mm. Optionally, the thickness of the sheath layer is 1.5–3.2 mm; further, the thickness of the sheath layer is 1.8–2.8 mm.

[0026] Furthermore, when the number of conductor cores is ≥2, a filler layer is also included; The filler layer is disposed between the insulating layer and the ceramicized silicone rubber tape wrapping layer.

[0027] When the number of conductor cores is two or more, the added filler layer significantly improves the overall integrity, stability, and independent protection capability between each core of the cable structure. The filler layer effectively eliminates the gaps between the cable cores after cabling, ensures the roundness of the cable cross-section, and provides uniform mechanical support for the internal structure, enhancing its compressive and impact resistance.

[0028] Furthermore, the filler layer is made of filler rope (halogen-free, low-smoke, flame-retardant glass fiber filler rope); the filler rope has a temperature resistance rating of 280℃ and is not prone to molten dripping and burning at high temperatures; the oxygen index of the filler rope is greater than 35%, which can prevent the spread of flames during combustion and allows for rapid self-extinguishing when combustion ceases. The tensile strength of the filler rope should be ≥280N, and the elongation at break should be ≥25%. The mass fraction of halogen acid gas is <0.5%. The separator layer is made of halogen-free, low-smoke, flame-retardant polyolefin material, requiring an oxygen index >34%.

[0029] In a second aspect, the present invention provides a method for manufacturing a fire-resistant cable with a self-sealing synergistic fire-resistant structure as described in the first aspect, comprising the following steps: Copper wires are twisted together to form a conductor; Inorganic fire-resistant strips are wrapped around the conductor to form a fire-resistant strip wrapping layer, with the overlap rate controlled at 15% to 50%. Cross-linked polyolefin material is extruded over the refractory tape wrapping layer to form an insulating layer, which is then cured or cross-linked. A ceramicized silicone rubber tape is wrapped around the outside of the insulation layer to form a ceramicized silicone rubber tape wrapping layer; A self-sealing layer is formed by wrapping or coating a mixture of adhesive matrix and heat-expanding components around or coating the ceramicized silicone rubber tape wrapping layer, followed by drying or shaping treatment. A copper strip is wrapped around the self-sealing layer to form an overlapping metal shielding layer; Extruding sheath material at the metal shielding layer to form a sheath layer; The cable is cooled, printed, and inspected to obtain the finished cable.

[0030] The manufacturing method strictly follows the functional layer structure of the cable from the inside out, starting with the stranding of the inner conductor, followed by the sequential construction of the core functional layers (fire-resistant wrapping layer, ceramicized insulation layer, and self-sealing layer), and then the application of the outer shielding and protective layers (copper tape shielding and outer sheath). By precisely controlling the overlap rate of the fire-resistant tape, the uniformity and reliability of the first fire-resistant barrier are ensured. Special curing or cross-linking treatment of the ceramicized silicone rubber pre-imparts its high-temperature ceramicization capability. Drying or shaping treatment of the self-sealing layer stabilizes its room-temperature form and thermal expansion characteristics. This standardized and controllable manufacturing process not only efficiently and stably reproduces the synergistic structure integrating passive fire resistance, active sealing, electromagnetic shielding, and mechanical protection, but also facilitates large-scale industrial production and full-process quality monitoring, thereby ensuring the consistency and reliability of the final product performance.

[0031] Furthermore, when the number of conductor cores is ≥2, before forming the ceramicized silicone rubber tape wrapping layer, a flame-retardant material is filled around the outer periphery of the insulation layer to form a filler layer.

[0032] The manufacturing method of this multi-core cable significantly optimizes process adaptability and the structural integrity of the final product by adding two steps at key process nodes: filling the cable with flame-retardant material to form a filler layer after cabling and wrapping polyester tape / non-woven fabric around the self-sealing layer to form another filler layer. Filling immediately after stranding the conductors ensures the roundness and compactness of the cable core, providing a stable foundation for the uniform coverage of subsequent functional layers. The separator layer outside the self-sealing layer establishes a flexible physical barrier between it and the subsequent metal shielding layer. This design not only facilitates the wrapping of the subsequent metal shielding layer and prevents adhesion, but also ensures, at the process level, that the self-sealing layer can expand orderly in a fire without being disturbed by external structural compression. These two added steps precisely address the structural requirements of multi-core cables, allowing the manufacturing process to flexibly adapt to different core counts and ensuring that the supporting role of the filler layer and the coordinating function of the separator layer are reliably realized in the finished product, thereby systematically improving the structural consistency and overall performance of the multi-core cable product.

[0033] The beneficial effects of this invention are: The self-sealing synergistic fire-resistant cable provided by this invention achieves a synergistic upgrade from "passive fire resistance" to "active repair sealing + passive fire resistance + comprehensive protection" through a synergistic design of functional layers from the inside out, ensuring that the cable can operate more safely and for longer in extreme environments. Specifically, the fire-resistant tape wrapping layer and the ceramicized insulation layer constitute the first rigid fire-resistant skeleton that does not melt or collapse at high temperatures, preventing short circuits caused by insulation failure. Furthermore, the ceramicized silicone rubber tape wrapping layer can rapidly ceramicize at high temperatures, forming a hard, self-supporting insulation skeleton, effectively preventing short circuit risks caused by insulation softening, collapse, or carbonization. More importantly, the self-sealing layer can actively expand when heated, sealing the interlayer gaps and cracks in its inner ceramicized silicone rubber tape wrapping layer caused by high temperatures or mechanical damage in real time, forming a dynamic seal and significantly improving the circuit's integrity maintenance capability under complex disasters. The outer metal shielding layer and sheath layer together provide electromagnetic shielding equipotential bonding and dual protection against external mechanical and environmental factors. It systematically solves the problem that traditional fire-resistant cables are passive in protection and prone to failure due to structural weaknesses under the harsh conditions of fire, especially fire combined with physical impact.

[0034] The manufacturing method provided by this invention ensures that the core characteristics of each functional layer (such as wrapping uniformity, high-temperature ceramization capability, and thermal expansion characteristics) are precisely assigned and fixed during the manufacturing process through a strict process sequence (building layer by layer from the inside out) and key process control points (such as controlling the overlap rate of the fire-resistant tape wrapping, curing / crosslinking the ceramicized silicone rubber insulation layer, and drying and shaping the self-sealing layer). This method not only achieves repeatable production of complex functional structures, but also ensures from the source of the process that the finished cable can sequentially activate multiple mechanisms such as the fire-resistant skeleton, active sealing, and external protection in a fire, as designed, thereby solving the process problem of how to stably and reliably manufacture cables with synergistic functions of "active sealing" and "passive fire resistance". Attached Figure Description

[0035] The accompanying drawings, which form part of the embodiments of the present invention, are used to provide a further understanding of the embodiments of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the embodiments of the present invention and do not constitute an improper limitation of the embodiments of the present invention.

[0036] Figure 1 It is the single-core 0.6 / 1kV 630 mm in Embodiment 1 of the present invention. 2 Schematic diagram of the structure of a fire-resistant power cable; Figure 2 It is the 3-core 0.6 / 1kV 185 mm in Embodiment 2 of the present invention. 2 Schematic diagram of the structure of a fire-resistant power cable; Figure 3 It is the single-core 0.6 / 1kV 630 mm in Embodiment 1 of the present invention.2 A flowchart of the manufacturing method for fire-resistant power cables; Figure 4 It is the 3-core 0.6 / 1kV 185 mm in Embodiment 2 of the present invention. 2 A flowchart of the manufacturing method for fire-resistant power cables; Among them, 1. conductor, 2. fire-resistant tape wrapping layer, 3. insulation layer, 4. ceramicized silicone rubber tape wrapping layer, 5. self-sealing layer, 6. metal shielding layer, 7. sheath layer and 8. filler layer. Detailed Implementation

[0037] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components used, unless otherwise stated, are commercially available conventional products.

[0038] As an example, the conductor can be a purchased T1 copper rod, which is drawn and stranded into a conductor using in-house equipment. The fire-resistant tape uses synthetic mica tape, the insulation layer can be 110℃ halogen-free, low-smoke, flame-retardant irradiated cross-linked polyolefin insulation material X-HF-110, and the filler rope can be halogen-free, low-smoke, flame-retardant glass fiber filler rope; the cabling wrapping tape can be ceramicized silicone rubber fire-resistant tape, followed by the extrusion of a self-sealing layer comprising a bonding matrix and a heat-expanding component, mixed at a total mass ratio of 45:55. The bonding matrix (total 45%) includes: silicone rubber (polydimethylsiloxane RTV / HTV) 18%; halogen-free polymer (polypropylene-polyethylene blend) 9%; and inorganic silicate binder (aluminum hydroxide-silicate composite system) 18%. The heat-expanding component (total 55%) includes: high expansion ratio graphite sheets 38.5%; hydrated salt system (sodium sulfate decahydrate, 53-56 wt%) 5.5%; and foamable inorganic system (aluminum silicate foam) 11%. The shielding layer can be made of brass tape; the outer sheath is made of 110℃ halogen-free low-smoke polyolefin, model HFS-110-TP.

[0039] The structural design of conventional fire-resistant cables in existing technologies has significant shortcomings in dealing with the extreme conditions of "high temperature, mechanical stress, and water erosion" coupled in real fires. This invention provides a fire-resistant cable with "ceramic self-support + thermal expansion self-sealing + copper tape shielding". This invention produces a fire-resistant cable with a self-sealing synergistic fire-resistant structure and copper tape shielding, improving the cable's circuit integrity maintenance capability under high-temperature fire conditions and accompanying mechanical disturbances, and enhancing its stability under water spray / humid conditions, while also meeting electromagnetic shielding and engineering laying requirements.

[0040] This invention first provides a fire-resistant cable with a self-sealing and synergistic fire-resistant structure, including a conductor and, from the inside out, a fire-resistant tape wrapping layer, an insulation layer, a ceramicized silicone rubber tape wrapping layer, a self-sealing layer, a metal shielding layer, and a sheath layer, which are sequentially wrapped around the outer periphery of the conductor. The self-sealing layer consists of a bonding matrix and a component that expands when heated; The adhesive matrix is ​​composed of silicone rubber, halogen-free polymer, and inorganic silicate adhesive; The component that expands upon heating consists of expanded graphite, inorganic hydrated salts, and foamed inorganic materials. The expansion trigger temperature of the self-sealing layer is 150–450℃.

[0041] Secondly, the present invention provides a method for manufacturing a fire-resistant cable with a self-sealing synergistic fire-resistant structure, comprising the following steps: twisting copper wires to form a conductor; Inorganic fire-resistant strips are wrapped around the conductor to form a fire-resistant strip wrapping layer, with the overlap rate controlled at 15% to 50%. Cross-linked polyolefin material is extruded over the refractory tape wrapping layer to form an insulating layer, which is then cured or cross-linked. A ceramicized silicone rubber tape is wrapped around the outside of the insulation layer to form a ceramicized silicone rubber tape wrapping layer; A self-sealing layer is formed by wrapping or coating a mixture of adhesive matrix and heat-expanding components around or coating the ceramicized silicone rubber tape wrapping layer, followed by drying or shaping treatment. A copper strip is wrapped around the self-sealing layer to form an overlapping metal shielding layer; Extruding sheath material at the metal shielding layer to form a sheath layer; The cable is cooled, printed, and inspected to obtain the finished cable.

[0042] To better illustrate the effects of the present invention, the structure and manufacturing method of the fire-resistant cable are described below with reference to further embodiments and comparative examples: Example 1 This embodiment provides a fire-resistant cable with a self-sealing and synergistic fire-resistant structure and its manufacturing method, further as follows: 1. Single-core 0.6 / 1kV 630 mm 2 Taking fire-resistant power cables as an example, Figure 1 As shown, the fire-resistant cable includes a conductor 1 and, sequentially, a fire-resistant tape wrapping layer 2, an insulation layer 3, a ceramicized silicone rubber tape wrapping layer 4, a self-sealing layer 5, a metallic shielding layer 6, and a sheath layer 7, all wrapped around the conductor 1. Further structural details are as follows: Conductor 1 is a stranded copper conductor with a nominal cross-sectional area of ​​630 mm². 2Conductor 1 is wrapped with fire-resistant tape to form a wrapping layer 2, with an overlap rate of 25%. An insulating layer 3 and a ceramicized silicone rubber tape wrapping layer 4 are extruded onto the outside of the fire-resistant tape wrapping layer 2. The insulation layer 3 has a thickness of 2.4 mm. A self-sealing layer 5 with a thickness of 0.50 mm, an expansion ratio of 5, and a triggering temperature preferably of 200–350℃ is provided outside the ceramicized silicone rubber tape wrapping layer 4.

[0043] A metal shielding layer 6 is formed outside the self-sealing layer 5, using longitudinally overlapping copper tape with a thickness of 0.08 mm and an overlap rate of 20%. The outermost extruded sheath layer 7 has a thickness of 2.4 mm. Its working mechanism is as follows: the insulation layer 3 forms a self-supporting skeleton. When impact, compression, or cutting causes local gaps in the outer layer, the self-sealing layer 5 expands and fills and seals the gaps / cracks; the metal shielding layer 6 and the sheath layer 7 form a protective covering for the inner structure, improving the circuit integrity and stability.

[0044] 2. The manufacturing method of the fire-resistant cable in this embodiment, such as... Figure 3 As shown, it includes the following steps: S1 Conductor manufacturing: Copper wires are stranded together to form conductor 1; S2 Fire-resistant wrapping tape: Inorganic fire-resistant tape is wrapped around the conductor 1 to form fire-resistant wrapping layer 2, and the overlap rate is controlled; S3 Extruded insulation: Polyethylene is extruded over the refractory tape wrapping layer 2 to form an insulation layer 3, which is then cured / crosslinked; S4 Forming a wrapping layer: A ceramicized silicone rubber tape is wrapped around the insulating layer 3 to form a ceramicized silicone rubber tape wrapping layer 4; S5 Forming a self-sealing layer: A self-sealing layer 5 (wrapping or coating) is set outside the ceramicized silicone rubber tape wrapping layer 4 and shaped; S6 Forming a metallic shield: A metallic shielding layer 6 (such as copper strip, wrapped and overlapped) is formed outside the self-sealing layer 5. S7 Extruded outer sheath: The sheath layer 7 is extruded outside the metal shielding layer 6, completing the cooling, printing and finished product inspection.

[0045] Example 2 This embodiment provides a fire-resistant cable with a self-sealing and synergistic fire-resistant structure and its manufacturing method, using a 3-core 0.6 / 1kV 185 mm... 2 Taking fire-resistant power cables as an example, Figure 2 As shown, the fire-resistant cable includes a 3-core conductor 1 and, sequentially, a fire-resistant tape wrapping layer 2, an insulation layer 3, a filler layer 8, a ceramicized silicone rubber tape wrapping layer 4, a self-sealing layer 5, a metallic shielding layer 6, and a sheath layer 7, all wrapped around the 3-core conductor 1. Further structural details are as follows: Each of the three conductors in conductor 1 has a nominal cross-sectional area of ​​185 mm². 2The cable has 3 cores. Each conductor is wrapped with a fire-resistant tape wrapping layer with an overlap rate of 25%. An insulation layer 3 with a thickness of 1.6 mm is extruded outside the fire-resistant tape wrapping layer 2. A filler layer 8 is set in the three-core stranded cable to improve roundness. A self-sealing layer 5 with a thickness of 0.5 mm and an expansion ratio of 5 is set outside the cable. A metal shielding layer 6 with a copper tape thickness of 0.08 mm and an overlap rate of 20% is formed outside the self-sealing layer 5. A sheath layer 7 with a thickness of 2.8 mm is extruded outside the metal shielding layer 6.

[0046] 2. The manufacturing method of the fire-resistant cable in this embodiment, such as... Figure 4 As shown, it includes the following steps: S1 Conductor manufacturing: Copper wires are stranded together to form conductor 1; S2 Refractory Wrapping Tape: Inorganic refractory tape is wrapped around the outside of conductor 1 to form wrapping layer 2, controlling the overlap rate; S3 Extruded insulation: Polyethylene is extruded over the refractory tape wrapping layer 2 to form an insulation layer 3, which is then cured / crosslinked. S4 cabling (for multi-core cables): Twist 1 to 5 cores into a cable according to the pitch and add a filler layer 8; S5 Forming a wrapping layer: A ceramicized silicone rubber tape is wrapped around the insulating layer 3 to form a ceramicized silicone rubber tape wrapping layer 4; S6 Forming a self-sealing layer: A self-sealing layer 5 (wrapping or coating) is set outside the ceramicized silicone rubber tape wrapping layer 4 and shaped; S7 Forming a metal shield: A metal shielding layer 6 (overlapping) is formed outside the self-sealing layer 5. S8 Extruded outer sheath: The sheath layer 7 is extruded outside the metal shielding layer 6, completing the cooling, printing and finished product inspection.

[0047] Example 3 This embodiment provides a fire-resistant cable with a self-sealing and synergistic fire-resistant structure and its manufacturing method, using a 5-core 0.6 / 1kV 16–50 mm² cable. 2 Taking the fire-resistant power cable as an example, the structure and manufacturing method of each core are the same as in Example 2. The self-sealing layer 5 is preferably made of wrapping expansion tape to improve the uniformity of coverage; the sheath layer 7 is preferably made of low-smoke halogen-free material to improve the overall safety performance in a fire environment.

[0048] The manufacturing method of the fire-resistant cable in this embodiment is the same as that in Embodiment 2.

[0049] Comparative Example 1 Unlike Example 1, the fire-resistant cable structure omits the fire-resistant wrapping layer 2, while the other structures and manufacturing methods are the same as in Example 1.

[0050] Comparative Example 2 Unlike Example 1, the ceramicized silicone rubber tape wrapping layer 4 is omitted in the fire-resistant cable structure, while the other structures and manufacturing methods are the same as in Example 1.

[0051] Comparative Example 3 Unlike Example 1, the self-sealing layer 5 is omitted in the fire-resistant cable structure, while the other structures and manufacturing methods are the same as in Example 1.

[0052] Comparative Example 4 Unlike Example 1, in the fire-resistant cable structure, the material of the self-sealing layer 5 is replaced with expanded graphite, while the other structures and manufacturing methods are the same as in Example 1.

[0053] The cables prepared in the examples and comparative examples were subjected to performance tests, and the results are shown in Table 1. The test methods are as follows: (1) Fire Resistance Test: The cable sample is placed in a heat-preserving furnace controlled by a standard time-temperature curve and mounted on a cable tray. A specific gas torch (usually a strip torch or a tubular torch) is placed under the cable tray and aimed at the cable sample at a standardized distance and angle for combustion. The flame temperature must be maintained at 750°C throughout the test. At one end of the cable sample, all conductors are electrically connected together. At the other end of the cable sample, each conductor is connected to a three-phase star-connected (or similar) transformer, and the rated voltage of the cable (0.6 / 1kV) is applied between the conductors. At the same time, a fault current monitoring device is connected to the neutral point to detect whether insulation breakdown occurs during combustion and continuous heating of the furnace.

[0054] (2) Spray test: The cable sample was taken out of the heat preservation furnace, installed on the tray, and the tray was installed horizontally on the bracket of the water spray test equipment. The spray equipment sprayed the cable for 180 s without interruption of the circuit.

[0055] (3) Impact resistance test: The cable sample is installed on the impactor, and the impact force of 15 J is set through the fault current monitoring device. Three impacts are completed within 300 s.

[0056] Table 1. Cable performance of the examples and comparative examples

[0057] As shown in Table 1, the present invention provides a fire-resistant cable that can form a stable support structure under high temperature in a fire and actively seal cracks / gaps when they occur, while also taking into account water resistance and shielding. This solves the problem that the structural design of conventional fire-resistant cables is significantly insufficient when dealing with the extreme working conditions of multiple factors such as high temperature, mechanical stress and water erosion in real fires.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the embodiments of the present invention. For those skilled in the art, the present invention can have various modifications and variations. 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. A fire-resistant cable with a self-sealing synergistic fire-resistant structure, characterized in that, It includes a conductor and, from the inside out, a fire-resistant tape wrapping layer, an insulating layer, a ceramicized silicone rubber tape wrapping layer, a self-sealing layer, a metal shielding layer, and a sheath layer that are sequentially wrapped around the outer periphery of the conductor; The self-sealing layer is made of a bonding matrix and a heat-expanding component. The adhesive matrix is ​​composed of silicone rubber, halogen-free polymer and inorganic silicate adhesive; The heat-expanding component is composed of expanded graphite, inorganic hydrated salt, and foamed inorganic material; The expansion trigger temperature of the self-sealing layer is 150–450°C.

2. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 1, characterized in that, The mass ratio of the adhesive matrix to the heat-expanding component is (40-50):(50-60); The mass ratio of the silicone rubber, halogen-free polymer, and inorganic silicate binder is (3-5):(1-3):(3-5); The mass ratio of the expanded graphite, inorganic hydrated salt and foamed inorganic material is (6-8):1:(2-3).

3. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 2, characterized in that, The silicone rubber includes polydimethylsiloxane RTV / HTV; The halogen-free polymer includes polypropylene-polyethylene blends; The inorganic silicate binder includes an aluminum hydroxide-silicate composite system; The inorganic hydrated salt includes sodium sulfate decahydrate; The foamed inorganic material includes aluminum silicate foam.

4. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 1, characterized in that, The conductor has 1-5 cores and a nominal cross-sectional area of ​​16–630 mm². 2 ; The overlap rate of the refractory tape wrapping layer is 15%–50%, and the material is synthetic phlogopite tape. The insulation layer has a thickness of 0.8–3.0 mm and is made of cross-linked polyolefin material.

5. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 1, characterized in that, The overlap rate of the ceramicized silicone rubber tape wrapping layer is 15%–50%, and the reinforcing material in the ceramicized silicone rubber tape wrapping layer is basalt fiber. The thickness of the self-sealing layer is 0.10–0.80 mm, and the volume expansion ratio is 2–10 times; The metal shielding layer is a copper strip shielding layer with a wrapping and overlapping structure. The copper strip thickness is 0.05–0.30 mm and the overlap rate is 10%–35%.

6. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 1, characterized in that, The sheath layer is made of halogen-free low-smoke polyolefin, and the sheath thickness is 1.2–4.0 mm.

7. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 1, characterized in that, When the number of conductor cores is ≥2, a filler layer is also included; The filler layer is disposed between the insulating layer and the ceramicized silicone rubber tape wrapping layer.

8. The fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 7, characterized in that, The filling layer is made of filling rope with a tensile strength ≥280 N, an elongation at break ≥25%, and a halogen acid gas mass fraction <0.5%.

9. A method for manufacturing a fire-resistant cable with a self-sealing synergistic fire-resistant structure as described in any one of claims 1-8, characterized in that, Includes the following steps: Copper wires are twisted together to form a conductor; Inorganic fire-resistant strips are wrapped around the conductor to form a fire-resistant strip wrapping layer, with the overlap rate controlled at 15%–50%. Cross-linked polyolefin material is extruded over the refractory tape wrapping layer to form an insulating layer, which is then cured or cross-linked. A ceramicized silicone rubber tape is wrapped around the outside of the insulation layer to form a ceramicized silicone rubber tape wrapping layer; A self-sealing layer is formed by wrapping or coating a mixture of adhesive matrix and heat-expanding components around or coating the ceramicized silicone rubber tape wrapping layer, followed by drying or shaping treatment. A copper strip is wrapped around the self-sealing layer to form an overlapping metal shielding layer; Extruding sheath material at the metal shielding layer to form a sheath layer; The cable is cooled, printed, and inspected to obtain the finished cable.

10. A method for manufacturing a fire-resistant cable with a self-sealing synergistic fire-resistant structure according to claim 9, characterized in that, When the number of conductor cores is ≥2, before forming the ceramicized silicone rubber tape wrapping layer, a flame-retardant material is filled around the outer periphery of the insulation layer to form a filler layer.

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