Fireproofing cable and method of manufacture

Abstract

This invention discloses a fire-resistant cementitious cable and its preparation method, belonging to the field of cable technology. It comprises, from the inside out, a conductor section, a filling layer, a fire-resistant layer, a shielding layer, and a protective layer. Three conductor sections are provided, bonded together. Each conductor section, from the inside out, includes a copper conductor, a wrapping layer, and an insulation layer. A filling layer is provided in the gap between adjacent conductor sections, and a fire-resistant layer, a shielding layer, and a protective layer are sequentially provided on the outside of the filling layer. The fire-resistant layer, from the inside out, includes fiberglass tape and fire-resistant cementitious material. The shielding layer, from the inside out, includes copper tape and fiberglass tape. The protective layer is formed by extrusion of cross-linked polyolefin material. Through this invention, the fire-resistant cementitious material uses ceramicized silica gel cement, which undergoes a ceramicization transformation at ≥300℃ to form a dense ceramic shell. This achieves a fire-resistant protective layer that transforms from a flexible state to a rigid ceramic state in the medium- and high-temperature range, preventing melting, dripping, and carbonization, thereby significantly extending the fire resistance time of the cable.

Description

Technical Field

[0001] This invention relates to a fireproof cement cable and its preparation method, belonging to the field of cable technology. Background Technology

[0002] In the main power distribution lines and critical emergency circuits of some large buildings, certain circuits need to maintain power supply to critical circuits for as long as possible under fire or high-temperature disaster conditions to ensure continuous power supply for personnel evacuation and fire rescue, as well as for critical loads such as fire-fighting equipment and elevators. Cables typically need to operate for extended periods in complex laying environments, and have high requirements for fire resistance, weather resistance, mechanical durability, low smoke and low toxicity, and construction adaptability.

[0003] Cables are made to meet usage requirements by applying fireproof sealant, but traditional fireproof sealant cables have certain problems: traditional organic fireproof sealants (such as asphalt-based and rubber-based sealants) will melt, drip or completely carbonize at temperatures above 600℃, failing to form a stable fire-resistant barrier. Flames can easily spread along the cable, and the fire resistance time is usually only 0.5-1h, which is difficult to meet the 1-3h fire resistance standard required by GB / T 19666; although inorganic rigid sealants are resistant to high temperatures, they have high thermal conductivity and are rigid structures, resulting in rapid temperature rise on the unexposed side, poor adaptability to cable bending and vibration, and easy water absorption, which affects insulation; existing structures often cannot simultaneously ensure the ability to be installed flexibly at room temperature.

[0004] Therefore, it is necessary to design a fireproof cement cable and its preparation method to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a fireproof cement cable and its preparation method, which solves the problems of traditional fireproof cement melting, high rigidity of the blockage material, poor adaptability to bending and vibration, and poor weather resistance.

[0006] The technical problem to be solved by this invention is achieved by the following technical solution: a fireproof mud cable, comprising... From the inside out, the layers are: conductor, filler, fireproof, shielding, and protective. The conductor portion is provided in three parts, and the conductor portions are attached to each other. Each conductor portion includes, from the inside to the outside, a copper conductor, a wrapping layer, and an insulating layer. A filling layer is provided in the gap between adjacent conductor portions, and a fireproof layer, a shielding layer, and a protective layer are sequentially provided on the outside of the filling layer; wherein the fireproof layer includes fiberglass tape and fireproof putty from the inside to the outside, the shielding layer includes copper tape and fiberglass tape from the inside to the outside, and the protective layer is formed by extrusion of cross-linked polyolefin material.

[0007] Preferably, the copper conductor is multi-stranded oxygen-free copper.

[0008] Preferably, the wrapping layer comprises synthetic mica tape, and the overlap rate of the wrapping layer is 20%-50%.

[0009] Preferably, the insulating layer comprises polyolefin, and the long-term temperature resistance of the insulating layer is 125°C.

[0010] Preferably, the filling layer includes a flame-retardant rope, which includes high-purity ceramic fiber, quartz fiber, carbon fiber, and boron fiber, and the filling layer fills the gaps between the conductor portions.

[0011] Preferably, the fiberglass tape is made by double-layer wrapping, and the fiberglass tape is made of high silica glass fiber.

[0012] Preferably, the fireproof putty has a thickness of 1.0-3.0 mm, and the fireproof putty includes ceramicized silica putty, which can be sintered into a ceramic shell at temperatures above 300°C.

[0013] Preferably, the copper strip in the shielding layer is 0.2 mm thick, overlaps circumferentially to form a continuous shield, and the overlap rate is 10%-20%.

[0014] A preferred method for preparing a fire-resistant cement cable includes the following steps: S1. Twist multiple oxygen-free copper wires together to form the copper conductor; S2. Wrap each of the copper conductors together to form a mica tape and then overlap and fix it; S3. Extruding a polyolefin insulating layer and cross-linking the insulating layer to form the conductor portion; S4. The three conductor sections are attached and twisted together, and a filling layer is provided between the conductor sections; S5. Wrap the fiberglass tape around the outside of the filling layer, and extrude ceramicized silica gel mud over the fiberglass tape and cure it to form the fireproof layer; S6. A 0.2mm thick copper strip is wrapped around the outside of the fireproof layer and overlapped for fixation. Then, a layer of fiberglass tape is wrapped around the copper strip as an isolation layer. S7. Polyolefin is extruded onto the outside of the fiberglass tape to form the protective layer, and then crosslinked.

[0015] Preferably, in S5, the mass fraction of the ceramicized silica paste includes 0.20-0.35 wt% silicone rubber matrix, 0.40-0.60 wt% inorganic refractory filler, 0.05-0.15 wt% low melting point flux, and 0.05-0.20 wt% inorganic binder.

[0016] The beneficial effects of this invention are: This invention employs a double-layer high-temperature resistant glass fiber tape as the base for fireproof putty, providing mechanical support and bonding interface for the ceramicized layer at high temperatures. This ensures the shape integrity and densification of the ceramicized silica putty during sintering, improving the stability of the high-temperature structure. The fireproof putty uses ceramicized silica putty, which allows it to undergo a ceramicization transformation at ≥300℃ to form a dense ceramic shell. This achieves a fire-resistant protective layer that transitions from a flexible state to a rigid ceramic state in the medium-high temperature range, preventing melting, dripping, and carbonization. It can block open flames and heat for a long time in the range of 800~1200℃, thereby significantly extending the fire resistance time of the cable to 1-3 hours.

[0017] Through this invention, a filling layer is provided between the conductor parts. The filling layer is made of high-temperature resistant inorganic flame-retardant filling rope, which can eliminate the gaps between the conductor parts and block the fire from spreading along the gaps between the cable cores. At the same time, it is non-flammable and non-melting at high temperatures, maintains structural stability, and extends the internal circuit holding time.

[0018] This invention provides a protective layer on the outside of the cable. The protective layer is made of cross-linked polyolefin, which can ensure the overall mechanical wear resistance, weather resistance, chemical resistance, and UV aging resistance of the cable at room temperature. At the same time, it can serve as an outer flame-retardant barrier in short-term fires, while also taking into account construction flexibility and on-site laying adaptability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] In the diagram: 11-copper conductor, 12-wrapping layer, 13-insulating layer, 2-filling layer, 31-fiberglass tape, 32-fireproof putty, 41-copper tape, 42-fiberglass tape, 5-protective layer. Detailed Implementation

[0021] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below in conjunction with specific embodiments. Example 1

[0022] like Figure 1 As shown, a fireproof cable includes, from the inside out, a conductor section, a filler layer 2, a fireproof layer, a shielding layer, and a protective layer 5. Three conductor sections 1 are provided, and they are bonded together. Each conductor section, from the inside out, includes a copper conductor 11, a wrapping layer 12, and an insulation layer 13. A filler layer 2 is provided in the gap between adjacent conductor sections. Outside the filler layer 2, a fireproof layer, a shielding layer, and a protective layer 5 are provided in sequence. The fireproof layer, from the inside out, includes fiberglass tape 31 and fireproof putty 32. The shielding layer, from the inside out, includes copper tape 41 and fiberglass tape 42. The protective layer 5 is formed by extrusion of cross-linked polyolefin.

[0023] In this embodiment, the conductor portion includes a copper conductor 11, a wrapping layer 12, and an insulating layer 13. The copper conductor 11 is a cylindrical multi-strand stranded conductor with a single copper wire diameter of 0.2-0.6 mm and the cross-section of the stranded conductor is nearly circular.

[0024] The wrapping layer 12 is a strip layer tightly wrapped around the surface of the copper conductor 11. The strip is narrow and long, and is wrapped in a spiral or coaxial circumferential manner. In this embodiment, a spiral manner is used. The wrapping layer 12 has a uniform thickness and stable overlap.

[0025] The insulating layer 13 is a ring-shaped cylindrical layer surrounding the wrapping layer, and its cross-section is a uniform ring layer.

[0026] The copper conductor 11 is formed by stranding multiple strands of oxygen-free copper, providing conductivity and ensuring the overall flexibility and mechanical strength of the cable. The wrapping layer 12 uses synthetic mica tape with a thickness of 0.05-0.20 mm and an overlap rate of 20%-50%. The synthetic mica tape is a strip-shaped inorganic roll material. The insulation layer 13 uses cross-linked polyolefin with a thickness of 0.8-1.5 mm.

[0027] The copper conductor 11 is formed by stranding multiple copper wires on a stranding machine. Synthetic mica tape is spirally wrapped and bonded to the surface of the copper conductor 11. An insulation layer 13 is applied to the outer surface of the wrapping layer 12 using an extruder, where polyolefin is extruded. After extrusion, the insulation layer 13 undergoes cross-linking to ensure its properties meet the overall cable requirements.

[0028] The conductor section is capable of conducting electricity and transmitting electrical energy; the wrapping layer 12 provided on the conductor section contacts the copper conductor 11 at high temperatures, preventing the insulation layer 13 from being directly heated; the insulation layer 13 can provide electrical insulation for the cable at normal temperature and under minor overload, and also provides a certain degree of mechanical protection.

[0029] In this embodiment, the three conductor sections are attached to each other, and a filling layer 2 is provided in the gap between the conductor sections. In this embodiment, the filling layer 2 is a filling rope, which is continuously arranged along the cable axis. The outer surface of the filling layer 2 is in close contact with the adjacent insulation layer 13 and fiberglass tape 31.

[0030] The filler rope is a high-temperature resistant inorganic flame-retardant rope, with its diameter and filler density determined by the cable core design. The flame-retardant rope is composed of 35% high-purity ceramic fiber, 25% quartz fiber, 10% carbon fiber, and 30% boron fiber. The long-term temperature resistance of the filler rope is ≥1000℃. In this embodiment, the high-purity ceramic fiber is zirconium-containing aluminosilicate fiber.

[0031] The filler layer 2 fills the gap between the conductors when the three conductors are twisted together. The filler layer 2 is mechanically shaped to make close contact with the surface of the conductors, and the filler layer 2 ensures that the cable is round overall.

[0032] The filler layer 2 can eliminate the gaps between the conductors and prevent flames or high-temperature airflows from rapidly burning through the gaps between the conductors; the filler layer 2 provides lateral support and structural shaping, reducing uneven stress on the insulation layer 13 during extrusion; the filler layer 2 is non-combustible and non-dripping at high temperatures and can maintain structural stability.

[0033] The fireproof layer is set on the outside of the filling layer 2. The fireproof layer includes fiberglass tape 31 and fireproof putty 32 from the inside to the outside. When the fireproof layer is exposed to fire, it can form a protective structure with a hard fire-resistant shell.

[0034] In this embodiment, the fiberglass tape 31 is disposed on the outside of the filling layer 2 in the form of a strip through double-layer wrapping. The fiberglass tape 31 is strip-shaped and is disposed in a spiral wrapping manner to form a continuous and uniform fiberglass tape 31. During the double-layer wrapping process, the layers of the fiberglass tape 31 can be staggered and overlapped.

[0035] The fiberglass tape 31 is made of high silica glass fiber, specifically with a SiO2 content of ≥98%. The thickness of a single layer is 0.1-0.3 mm, and the thickness of a double layer is 0.2-0.6 mm.

[0036] The fiberglass tape 31 is set in a circumferential spiral wrapping method with an overlap rate of 30%-35% to ensure the interlayer density of the fiberglass tape 31. After wrapping, fireproof putty is applied to the outside of the fiberglass tape 31.

[0037] Fiberglass tape 31 provides support for fireproof putty 32, ensuring the shape support and adhesion of fireproof putty 32 at high temperatures. Fiberglass tape 31 can improve the overall tensile and impact resistance of the cable and protect the conductor and filler layer 2 from damage under external forces.

[0038] Fireproof putty 32 is applied to the outside of the fiberglass tape 31 by extrusion. The fireproof putty 32 is made of ceramicized silica putty. The cross-section of the fireproof putty 32 is annular, and the thickness is 1.0-3.0mm. At room temperature, it is a flexible paste layer. At high temperature, the fireproof putty 32 can be ceramicized and transformed into a hard ceramic shell.

[0039] In this embodiment, the fireproof putty 32 comprises 0.20-0.35 wt% silicone rubber matrix, 0.40-0.60 wt% inorganic refractory filler, 0.05-0.15 wt% low-melting-point flux, and 0.05-0.20 wt% inorganic binder. In this embodiment, the inorganic refractory filler is preferably alumina, mica, or glass powder.

[0040] After the fiberglass tape 31 is wound around the cable, ceramicized silica gel putty is evenly extruded onto the outer surface of the fiberglass tape 31 using an extrusion device. The fireproof putty 32 can sinter into a dense ceramic layer when exposed to a temperature of 300°C or higher, forming a hard fireproof shell.

[0041] Under fire conditions, fire-retardant putty 32 will not melt and drip. It begins to sinter at ≥300℃ and eventually forms a dense ceramic shell that can withstand temperatures of 800-1200℃. This shell can effectively block open flames and high-temperature gases for a long time, significantly extending the lifespan of the conductors and insulation inside the cable. The fire-retardant putty produces low smoke and low toxicity during the firing process.

[0042] A shielding layer is provided on the outside of the fireproof layer. The shielding layer is used for electromagnetic shielding and lateral heat dissipation. At the same time, a fiberglass tape 42 is provided on the outer layer to prevent the copper tape 41 from directly contacting the protective layer 5.

[0043] The inner side of the shielding layer uses copper strip 41. In this embodiment, the copper strip 41 is a narrow and long metal strip that is arranged around the perimeter. The cross-section of the copper strip 41 is a thin strip with a thickness of 0.2 mm. After the copper strip 41 is overlapped in the perimeter, a continuous metal layer is formed, with an overlap rate of 10%-20%.

[0044] The copper strip 41 is made of pure copper and is fixed by mechanical compression at the overlap. The ends of the copper strip 41 can be led out to achieve shielding grounding.

[0045] Copper tape 41 can reduce external electromagnetic interference and limit the electromagnetic radiation of the cable to the outside, ensuring the overall electromagnetic shielding effect of the cable. Utilizing the high thermal conductivity of copper, it can laterally disperse the heat of the outer layer under fire conditions, slowing down the rate of temperature rise of the internal structure of the cable.

[0046] A fiberglass tape 42 is provided on the outside of the copper strip 41. The fiberglass tape 42 is wrapped around the outside of the copper strip 41 to isolate the copper strip 41 from the protective layer 5 and prevent the metal edges or overlapping areas of the copper strip 41 from damaging the plastic sheath. The fiberglass tape 42 is a single layer of fiberglass tape, and the thickness is preferably 0.1-0.3 mm.

[0047] By setting a fiberglass tape 42 on the outside of the copper tape 41, the copper tape 41 is prevented from causing wear to the protective layer 5, which helps with heat insulation protection and ensures the overall wear resistance of the cable.

[0048] A protective layer 5 is provided on the outside of the shielding layer. The protective layer 5 is a cross-linked polyolefin formed by extrusion, with a thickness of 1.5-3.0 mm. The protective layer 5 is formed by extrusion, and cross-linking is performed after extrusion to ensure the long-term performance of the protective layer 5.

[0049] The protective layer 5 provides mechanical abrasion resistance, weather resistance, chemical corrosion resistance and ultraviolet protection, protecting the internal multi-layer structure from damage by external factors in different environments. In addition, the protective layer 5 can work with the fireproof layer to achieve overall fire resistance of the cable.

[0050] In this embodiment, one end of the copper strip 41 can be led out separately as a shielding ground terminal to ensure that the overall shielding function of the copper strip 41 can be used normally.

[0051] When a fire occurs, the fireproof putty 32 can begin to ceramicize at ≥300℃. The fiberglass tape 31 provides initial structural support. After the ceramic shell is formed, it can provide long-term heat insulation protection for the inner copper conductor 11 and insulation layer 13. The copper tape 41 disperses heat laterally on the outside and acts as a shield. The protective layer 5 prevents the outer flame from directly contacting the conductor in the short term. The overall cooperation extends the maintenance time of the electrical circuit inside the cable.

[0052] A method for preparing a fire-resistant cement cable includes the following steps: S1. Multiple oxygen-free copper wires are twisted together to form a copper conductor 11. Specifically, qualified oxygen-free copper wires are selected and twisted into multiple strands on a stranding machine. The stranding pitch is set according to the conductor specifications to ensure that the copper conductor 11 is round and not loose.

[0053] S2. Wrap synthetic mica tape around the outside of each copper conductor 11 and secure it by overlapping, forming a wrapping layer 12. Tightly wrap the synthetic mica tape around the surface of each copper conductor 11 in a spiral manner, ensuring an overlap rate between 20% and 50%. The wrapping direction and subsequent stranding direction can be selectively set to reduce stress. After wrapping, secure the start and end ends of the overlap by short-term hot pressing or mechanical pressing.

[0054] S3. A polyolefin insulation layer 13 is formed by extrusion and cross-linking the insulation layer 13 to form a conductor portion. A copper conductor 11 with a wrapping layer 12 is extruded with the polyolefin insulation layer 13 and cross-linked to form the insulation layer 13.

[0055] S4. The three conductor sections are attached and twisted together, and a filler layer 2 is placed between the conductor sections for filling. Specifically, the three conductor sections are placed at the vertices of an equilateral triangle, adjacent conductor sections are attached together, and the filler layer 2 is placed axially in the gaps between the conductor sections to form a round structure during the twisting process.

[0056] S5. Fiberglass tape 31 is wrapped around the outside of the filling layer 2, and ceramicized silica gel putty is extruded and cured on the outside of the fiberglass tape 31 to form a fireproof layer. Specifically, high-silica fiberglass tape 31 is wrapped in a double layer in a circumferential manner around the outside of the filling layer 2, with an overlap rate preferably of 30%-35%, and the layers can be staggered. An inorganic adhesive is applied to the fiberglass tape 31 before wrapping and pre-cured to enhance the interfacial adhesion.

[0057] Fireproof putty 32 is prepared and applied to the outside of fiberglass tape 31 by extrusion.

[0058] S6. Wrap a 0.2mm thick copper strip 41 around the outside of the fireproof layer and secure it by overlapping. Then wrap a layer of fiberglass tape 42 around the outside of the copper strip 41 as an insulation. The copper strip 41 can form a circumferential continuous shielding layer and achieve heat dissipation and electromagnetic shielding, while the fiberglass tape 42 isolates the copper strip from the outer sheath.

[0059] After the fireproof putty 32 has cured, a copper strip 41 with a thickness of 0.2mm is wrapped around it in the circumferential direction with an overlap rate of 10%-20%, and the overlap is mechanically pressed and fixed; then a layer of fiberglass tape 42 is wrapped around the outside of the copper strip 41 as an isolation.

[0060] In this embodiment, one end of the copper strip 41 extends and is grounded, and the extension can serve as a shielded grounding terminal.

[0061] S7. Extrude polyolefin onto the outside of the fiberglass tape 42 to form a protective layer 5, and cross-link the protective layer 5. Feed the cable with the shielding layer into the extruder, and extrude the protective layer 5 through the extruder. The thickness of the protective layer 5 is 1.5-3.0 mm.

[0062] Offline crosslinking was used during the crosslinking process, and the product was completed after quality inspection.

[0063] 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, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fireproof cable, comprising: From the inside out, the layers are: conductor, filler, fireproof, shielding, and protective. Its features are: The conductor portion is provided in three parts, and the conductor portions are attached to each other. Each conductor portion includes, from the inside to the outside, a copper conductor, a wrapping layer, and an insulating layer. A filling layer is provided in the gap between adjacent conductor portions, and a fireproof layer, a shielding layer, and a protective layer are sequentially provided on the outside of the filling layer; wherein the fireproof layer includes fiberglass tape and fireproof putty from the inside to the outside, the shielding layer includes copper tape and fiberglass tape from the inside to the outside, and the protective layer is formed by extrusion of cross-linked polyolefin material.

2. A fireclay cable as claimed in claim 1, characterised in that: The copper conductor is multi-stranded oxygen-free copper.

3. A fireclay cable as claimed in claim 1, characterised in that: The wrapping layer includes a synthetic mica tape, and the overlap rate of the wrapping layer is 20%-50%.

4. A fireclay cable as claimed in claim 1, characterised in that: The insulating layer comprises polyolefin, and the long-term temperature resistance of the insulating layer is 125°C.

5. A fireclay cable as claimed in claim 1, characterised in that: The filling layer includes a flame-retardant rope, which comprises high-purity ceramic fiber, quartz fiber, carbon fiber, and boron fiber, and the filling layer fills the gaps between the conductor portions.

6. A fireclay cable as claimed in claim 1, characterised in that: The fiberglass tape is made by double-layer wrapping and is made of high-silica glass fiber.

7. A fireclay cable as claimed in claim 1, characterised in that: The fireproof putty has a thickness of 1.0-3.0 mm, and includes ceramicized silica putty. The fireproof putty can be sintered into a ceramic shell at temperatures above 300°C.

8. A fireclay cable as claimed in claim 1, characterised in that: The copper strip in the shielding layer is 0.2 mm thick, and it overlaps circumferentially to form a continuous shield with an overlap rate of 10%-20%.

9. A process for the production of a fireclay cable, characterized in that: The method for preparing a fire-resistant mud cable as described in any one of claims 1-8 comprises the following steps: S1. Twist multiple oxygen-free copper wires together to form the copper conductor; S2. Wrap each of the copper conductors together to form a mica tape and then overlap and fix them; S3. Extruding a polyolefin insulating layer and cross-linking the insulating layer to form the conductor portion; S4. The three conductor sections are attached and twisted together, and a filling layer is provided between the conductor sections; S5. Wrap the fiberglass tape around the outside of the filling layer, and extrude ceramicized silica gel mud over the fiberglass tape and cure it to form the fireproof layer; S6. A copper strip with a thickness of 0.2mm is wrapped around the outside of the fireproof layer and overlapped and fixed. Then, a layer of fiberglass tape is wrapped around the copper strip as an isolation layer. S7. Polyolefin is extruded onto the outside of the fiberglass tape to form the protective layer, and then crosslinked.

10. A method for preparing a fireproof cement cable according to claim 9, characterized in that: In S5, the mass fraction of the ceramicized silica paste includes 0.20-0.35 wt% silicone rubber matrix, 0.40-0.60 wt% inorganic refractory filler, 0.05-0.15 wt% low melting point flux, and 0.05-0.20 wt% inorganic binder.

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