Oxygen-proof and fire-resistant medium-voltage hoisting cable for high-rise buildings and preparation method thereof

Abstract

The application discloses a high-rise building oxygen-isolating and temperature-reducing fire-resistant medium-voltage hoisting cable and a preparation method thereof. The cable comprises, from inside to outside, a conductor, a conductor shield, an insulation layer, an insulation shield, a metal shield, a phase change energy storage ceramic filling layer, a high-strength oxygen-isolating inner lining layer, a mechanical interlocking load-bearing armor layer and an outer sheath. The phase change energy storage ceramic filling layer comprises a silicone rubber matrix and phase change microcapsules and ceramic forming auxiliaries dispersed in the silicone rubber matrix, can generate a dense ceramic hard shell in situ through endothermic phase change under high temperature in a fire, effectively blocks a chimney effect and reduces the temperature of a wire core. The mechanical interlocking load-bearing armor layer adopts an S-shaped double-hook interlocking structure and provides strong axial tensile force. The application combines active temperature reduction and passive oxygen isolation, cooperates with a special mechanical load-bearing structure, solves the problems of easy slippage of vertical laying of the high-rise building cable and too fast temperature rise in a vertical shaft in a fire, and significantly improves power supply reliability.

Description

Technical Field

[0001] This invention relates to the field of wire and cable manufacturing technology, specifically to a fire-resistant medium-voltage hoisting cable with active cooling and oxygen isolation functions, specifically designed for vertical installation in high-rise and super high-rise buildings, and its preparation method. Background Technology

[0002] With the acceleration of urbanization, the number of high-rise and super high-rise buildings is increasing, making the safety and reliability of their power supply systems crucial. High-rise building power supply faces two main challenges: First, there is the issue of mechanical stress during vertical laying. Medium-voltage cables are heavy, and when laid vertically in shafts hundreds of meters long, the cable's own weight generates enormous axial tensile force. During long-term suspension, the insulated cores of traditional steel wire armored cables are prone to creep and slippage within the sheath, leading to thinning or even breakage of the insulation layer and causing electrical faults.

[0003] Secondly, there's the "chimney effect" and fire resistance challenges within cable shafts. Cable shafts act as natural chimneys during fires. Once a fire breaks out, flames and smoke spread rapidly upwards along the cables, reaching extremely high temperatures with a fast temperature rise. Traditional mica-lined fire-resistant cables rely solely on the fire-resistant insulation of the mica layer, which is insufficient to reduce the ambient temperature. At temperatures exceeding 1000 degrees Celsius, even if the mica layer doesn't burn, the internal copper conductors will experience a surge in resistance and heat accumulation, leading to carbonization of the insulation layer. Furthermore, the loose ash formed after ordinary cables burn cannot block oxygen supply, thus contributing to the spread of the fire.

[0004] While existing technologies utilize ceramicized silicone rubber as a fire-resistant layer, its mechanical strength is low, and it lacks an active heat absorption and cooling mechanism, making it unsuitable for the extremely harsh fire environment inside the vertical shafts of high-rise buildings. Therefore, developing a cable that can both solve the problem of hoisting slippage through mechanical self-locking and actively cool and isolate oxygen through material phase change is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an oxygen-barrier, cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings and its preparation method, so as to solve the problems of existing cables being prone to slippage during vertical laying and being unable to actively cool down and have poor oxygen barrier effect in fire.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a medium-voltage hoisting cable for high-rise buildings with oxygen-barrier cooling and fire resistance, characterized in that it comprises three insulated cores, the insulated cores being stranded around a central reinforcing member, and a phase change energy storage ceramicized filling layer being provided in the gaps after stranding; a high-strength oxygen-barrier inner lining layer, a mechanically interlocking load-bearing armor layer, and an outer sheath are sequentially wrapped around the stranded cores from the inside out; the insulated cores, from the inside out, are a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, and a metal shielding layer; the phase change energy storage ceramicized filling layer is made of the following raw materials in parts by weight: 100 parts silicone rubber matrix, 20-30 parts reinforcing filler, 15-25 parts ceramicizing agent, 30-50 parts phase change microcapsules, 20-40 parts metal hydroxide flame retardant, and 0.5-1 parts platinum catalyst.

[0007] Preferably, the silicone rubber matrix is ​​methyl vinyl silicone rubber; the reinforcing filler is fumed silica; the ceramic-forming aid is low-melting-point glass powder with a softening point of 400-500℃; and the metal hydroxide flame retardant is magnesium hydroxide.

[0008] Preferably, the phase change microcapsules have melamine-formaldehyde resin as the capsule wall, n-octadecane, paraffin or high-carbon alkanes as the core, a particle size of 5-20 μm, and a phase change temperature of 50-80℃.

[0009] Preferably, the mechanically interlocking load-bearing armor layer is made of aluminum alloy strip or stainless steel strip spirally wound, the strip cross section is "S" shaped, and a mechanical interlocking structure is formed between two adjacent strips, with an interlocking depth of 1.5-2.5mm.

[0010] Preferably, the high-strength oxygen-barrier inner liner is an extruded low-smoke halogen-free, highly flame-retardant polyolefin material with a thickness of 1.0-1.5 mm.

[0011] Preferably, the central reinforcing member is a galvanized steel wire rope with an extruded EPDM rubber layer and anti-slip protrusions on the surface.

[0012] This invention also provides a method for preparing the oxygen-barrier, cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings as described above, comprising the following steps: S1: Preparation of insulated wire core: The conductor shield, insulation layer and insulation shield are extruded on the outside of the conductor through a three-layer co-extrusion process, and then a metal shield layer is wrapped around it; S2: Preparation of phase change energy storage ceramic filler: Silicone rubber matrix, reinforcing filler, ceramic additive, phase change microcapsule, and metal hydroxide flame retardant are mixed at low temperature in an internal mixer, and platinum catalyst is added and mixed evenly to obtain filler rubber. S3: Cable making and filling: Three insulated wire cores are twisted around the central reinforcing member. At the same time, during the twisting process, the filling rubber material prepared in S2 is extruded into the gap between the wire cores through an extruder to form a phase change energy storage ceramic filling layer. S4: Sheath preparation: A high-strength oxygen-barrier inner liner, a mechanically interlocking load-bearing armor layer, and an outer sheath are sequentially extruded over the filler layer.

[0013] 8. The preparation method according to claim 7, characterized in that, in step S2, the mixing temperature of the internal mixer is controlled within a range of 5-10°C below the phase change temperature of the phase change microcapsules, and not exceeding 60°C, to prevent the phase change microcapsules from being damaged or undergoing premature phase change during processing.

[0014] Preferably, in step S3, the extrusion pressure of the filler compound is 5-10 MPa to ensure that the filler layer is dense and free of air bubbles.

[0015] Preferably, in step S4, the winding pitch multiple of the mechanical interlocking load-bearing armor layer is 5-8 times.

[0016] The beneficial effects of this invention are as follows: 1) Active cooling and oxygen barrier mechanism: This invention creatively introduces phase change microcapsules into a ceramicized silicone rubber matrix. In the early stage of a fire (50-80℃), the microcapsules undergo a phase change to absorb a large amount of heat, delaying the temperature rise inside the cable; in the middle and later stages of a fire (>500℃), the silicone rubber and ceramicizing additives rapidly undergo a ceramicization reaction under the action of a platinum catalyst, forming a hard and dense ceramic shell. Combined with a high-strength oxygen barrier inner lining, this effectively prevents oxygen from entering the interior, cutting off the combustion-supporting path of the "chimney effect".

[0017] 2) No slippage during vertical installation: The S-shaped mechanical interlocking load-bearing armor layer is adopted. Compared with the traditional steel wire armor, this structure not only provides extremely high radial compressive strength, but also converts the axial tensile force into radial clamping force on the inner lining layer. Combined with the anti-slip protrusions on the surface of the central reinforcement, it realizes the overall mechanical locking from the inside out, and completely solves the problem of cable core slippage during vertical laying. 3) Excellent fire resistance and reliability: Combining passive ceramic fire isolation with active phase change heat absorption, it significantly improves the cable's survivability in extreme fire environments, making it particularly suitable for important locations such as high-rise buildings, hospitals, and data centers. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of a medium-voltage hoisting cable for high-rise buildings with oxygen-barrier cooling and fire resistance according to the present invention.

[0019] Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of the corrugated interlocking load-bearing armor layer in this invention (showing the S-type interlock).

[0020] Figure 3 This is a schematic diagram of the mechanism of the ceramicized filler layer for phase change energy storage in this invention during the heating process (a is the room temperature state, b is the phase change endothermic state, and c is the ceramicized oxygen barrier state).

[0021] Figure reference numerals: 1. Conductor; 2. Conductor shielding layer; 3. Cross-linked polyethylene insulation layer; 4. Insulation shielding layer; 5. Copper tape shielding layer; 6. Central reinforcement (steel wire rope core); 61. Anti-slip protrusion (rubber layer protrusion on the surface of the central reinforcement); 7. Phase change energy storage ceramicized filler layer; 71. Phase change microcapsule (granular); 72. Ceramic forming aid / glass powder (granular); 8. High-strength oxygen-barrier inner lining layer; 9. Corrugated interlocking load-bearing armor layer; 91. Interlocking engagement point ( Figure 2 (as shown in the image); 10. Outer sheath. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] Example 1 A medium-voltage hoisting cable for high-rise buildings with oxygen-barrier cooling and fire resistance, voltage rating 8.7 / 15kV, conductor cross-section 3×240mm². For example... Figure 1 As shown, the cable comprises, from the inside out, a central reinforcing member, three insulated cores, a phase change energy storage ceramicized filling layer, a high-strength oxygen-barrier inner lining layer, a mechanically interlocked load-bearing armor layer, and an outer sheath.

[0024] Material preparation: The ceramicized filler layer for phase change energy storage is formulated as follows: 100 parts of methyl vinyl silicone rubber, 25 parts of fumed silica, 20 parts of low melting point glass powder with a softening point of 450℃, 40 parts of phase change microcapsules (with melamine-formaldehyde resin as the wall and sliced ​​paraffin as the core, phase change point of 55℃), 30 parts of magnesium hydroxide, and 0.8 parts of platinum catalyst.

[0025] Cable Manufacturing Process: S1: Insulated cores are prepared using a catenary three-layer co-extrusion production line. S2: The above-mentioned filler layer raw materials are thoroughly mixed at temperatures below 50℃ (below the phase change point to ensure the microcapsules do not break). S3: The three insulated cores are twisted around a 10mm outer diameter steel wire rope (with an outer EPDM rubber strip protrusion), with a twisting pitch 20 times the cable's outer diameter. Simultaneously, filler rubber is extruded into the gaps using an extruder to ensure full filling without voids. S4: A 1.2mm thick low-smoke halogen-free polyolefin inner liner is extruded. S5: S-type interlocking armor is applied using 0.8mm thick aluminum alloy strip, with an interlocking depth of 1.8mm and a pitch multiple of 6. S6: A black PE outer sheath is extruded.

[0026] Performance Testing: The prepared cable underwent a BS 6387 CWZ fire resistance test. Under the combined effects of a flame temperature of 950℃, spraying, and mechanical vibration, the cable maintained continuous power supply for 180 minutes, far exceeding the standard requirement of 15 minutes. Dissection of the burned cable revealed that the filler layer had transformed into a hard, grayish-white ceramic body, and the surface of the internal insulation core showed only slight discoloration without carbonization, demonstrating the significant role of the phase change material's heat absorption and the ceramic layer's heat and oxygen insulation.

[0027] Example 2 This example focuses on improving the mechanical performance of vertically laid structures in super high-rise buildings (such as those over 300 meters).

[0028] Material Preparation: The formulation for the ceramicized filler layer of phase change energy storage consists of: 100 parts methyl vinyl silicone rubber, 30 parts fumed silica, 15 parts glass powder, 30 parts phase change microcapsules (high-melting-point paraffin core, phase change point 60℃), 40 parts magnesium hydroxide, and 1.0 part platinum catalyst. The increased amount of reinforcing fumed silica improves the strength of the raw rubber filler layer.

[0029] Cable manufacturing process: Structural adjustment: The mechanical interlocking load-bearing armor layer is made of 0.8mm thick 304 stainless steel strip, and the interlocking depth is increased to 2.2mm.

[0030] Performance Testing and Beneficial Effects: A vertical laying simulation test was conducted. A 100-meter section of cable was vertically suspended with a weight 2.5 times its own weight applied to the lower end and left to stand for 48 hours. Post-test measurements showed that the relative displacement between the conductor and the armor layer was 0 mm. This indicates that the mechanical interlocking force generated by the S-shaped stainless steel interlocking structure, combined with the support of the high-hardness filler layer, successfully locked the internal structure of the cable, preventing slippage caused by gravity. Simultaneously, the cable passed the GB / T 19216.21 fire resistance test, maintaining power supply for over 120 minutes.

[0031] Example 3 This example focuses on oxygen isolation and cooling performance under extreme fire conditions.

[0032] Material preparation: The ceramicized filler layer formulation for phase change energy storage consists of 100 parts methyl vinyl silicone rubber, 20 parts fumed silica, 25 parts glass powder, 50 parts phase change microcapsules, 20 parts magnesium hydroxide, and 0.5 parts platinum catalyst. The microcapsule and glass powder contents are at the highest possible ratio.

[0033] Cable manufacturing process: The process parameters are the same as in Example 1, but the die head temperature is strictly controlled not to exceed 45°C during the extrusion of the filler layer to prevent microcapsule rupture.

[0034] Performance Testing: In a simulated vertical shaft combustion test, the cable was placed in a vertical combustion furnace. Due to the presence of up to 50 parts of phase change microcapsules in the filler layer, the cable surface temperature rose rapidly within the first 15 minutes of heating, but the core temperature rose extremely slowly (due to latent heat absorption of phase change). As the temperature continued to rise, 25 parts of glass powder melted and formed a smooth glaze layer (similar to ceramic glaze) on the surface of the ceramicized skeleton, exhibiting excellent airtightness. Testing showed that the total amount of smoke released during combustion was 40% lower than that of conventional fire-resistant cables, demonstrating its effective blocking of internal smoke channels (chimney effect) and significantly improving the fire safety of high-rise buildings.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A medium-voltage hoisting cable for high-rise buildings with oxygen-barrier cooling and fire resistance, characterized in that, The cable includes three insulated cores, which are stranded around a central reinforcing member. A phase-change energy storage ceramic filling layer is placed in the gaps after cabling. The central reinforcing member is a galvanized steel wire rope with an extruded EPDM rubber layer and anti-slip protrusions on its surface. From the inside out, the cable cores are sequentially covered with a high-strength oxygen-barrier inner lining, a mechanically interlocking load-bearing armor layer, and an outer sheath. The mechanically interlocking load-bearing armor layer is made of aluminum alloy or stainless steel strip spirally wound in an "S"-shaped cross-section. Adjacent turns of the strip... The components form a mechanical interlocking structure with an interlocking depth of 1.5-2.5 mm. The insulated core consists of a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, and a metal shielding layer, from the inside out. The phase change energy storage ceramicized filler layer is made from the following raw materials in parts by weight: 100 parts silicone rubber matrix, 20-30 parts reinforcing filler, 15-25 parts ceramicizing agent, 30-50 parts phase change microcapsules, 20-40 parts metal hydroxide flame retardant, and 0.5-1 parts platinum catalyst.

2. The oxygen-barrier, heat-cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings according to claim 1, characterized in that, The silicone rubber matrix is ​​methyl vinyl silicone rubber; the reinforcing filler is fumed silica; the ceramic-forming aid is low-melting-point glass powder with a softening point of 400-500℃; and the metal hydroxide flame retardant is magnesium hydroxide.

3. The oxygen-barrier, cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings according to claim 1, characterized in that, The phase change microcapsules have melamine-formaldehyde resin as the capsule wall and n-octadecane, paraffin or high-carbon alkanes as the core, with a particle size of 5-20 μm and a phase change temperature of 50-80℃.

4. The oxygen-barrier, cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings according to claim 1, characterized in that, The high-strength oxygen-barrier inner lining is made of extruded low-smoke halogen-free, highly flame-retardant polyolefin material with a thickness of 1.0-1.5 mm.

5. A method for preparing an oxygen-barrier, cooling, fire-resistant, medium-voltage hoisting cable for high-rise buildings as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Preparation of insulated wire core: The conductor shield, insulation layer and insulation shield are extruded on the outside of the conductor through a three-layer co-extrusion process, and then a metal shield layer is wrapped around it; S2: Preparation of phase change energy storage ceramic filler: Silicone rubber matrix, reinforcing filler, ceramic additive, phase change microcapsule, and metal hydroxide flame retardant are mixed at low temperature in an internal mixer, and platinum catalyst is added and mixed evenly to obtain filler rubber. S3: Cable making and filling: Three insulated wire cores are twisted around the central reinforcing member. At the same time, during the twisting process, the filling rubber material prepared in S2 is extruded into the gap between the wire cores through an extruder to form a phase change energy storage ceramic filling layer. S4: Sheath preparation: A high-strength oxygen-barrier inner liner, a mechanically interlocking load-bearing armor layer, and an outer sheath are sequentially extruded over the filler layer.

6. The preparation method according to claim 5, characterized in that, In step S2, the mixing temperature of the internal mixer is controlled within a range of 5-10°C below the phase change temperature of the phase change microcapsules, and the maximum temperature shall not exceed 60°C, to prevent the phase change microcapsules from being damaged or undergoing premature phase change during processing.

7. The preparation method according to claim 5, characterized in that, In step S3, the extrusion pressure of the filler compound is 5-10 MPa to ensure that the filler layer is dense and free of air bubbles.

8. The preparation method according to claim 5, characterized in that, In step S4, the winding pitch multiple of the mechanical interlocking load-bearing armor layer is 5-8 times.

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