Flame-retardant optical cable capable of passively extinguishing fire and preparation method thereof

Abstract

The invention discloses a flame-retardant optical cable capable of passively extinguishing fire and a preparation method of the flame-retardant optical cable. The optical cable comprises a cable core, a water-blocking tape, a first metal tape, an LSZH inner sheath, a flat water tape, a second metal tape and an LSZH outer sheath which are sequentially arranged from inside to outside. The optical cable provided by the invention has excellent passive fire extinguishing capability, and changes passive flame retardance into active suppression: by arranging the flat water hose and placing the fire extinguishing medium in the flat water hose, when the temperature reaches 80-150 DEG C, the flat water hose is broken to release the fire extinguishing medium, so that the fire extinguishing effect is improved; open fire in a local area of the optical cable can be quickly and effectively extinguished or inhibited through mechanisms of heat absorption cooling, suffocation isolation, chemical inhibition and the like, and fire is prevented from spreading along the cable; the survival time of the optical cable in a fire environment is greatly prolonged, and the optical cable is not easy to collapse and melt down at a high temperature, so that the transmission characteristic of an optical signal is ensured not to be rapidly deteriorated, and the optical cable is particularly suitable for scenes with extremely high requirements on safety and reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical cables, and particularly relates to a flame-retardant optical cable capable of passive fire extinguishing and a preparation method thereof. BACKGROUND

[0002] With the rapid development of communication networks, optical cables, as the key carriers of information transmission, are widely used in various complex environments, such as high-rise buildings, underground pipe galleries, data centers and the like. However, the flame-retardant performance and fire extinguishing capacity of conventional optical cables are often difficult to meet the safety requirements in the event of a fire. The outer sheath and inner sheath of the existing optical cables are mostly made of conventional flame-retardant materials, which can delay the spread of fire, but lack active or passive fire extinguishing functions, and are prone to structural damage due to high temperature in a fire, causing communication interruption and even secondary disasters. In addition, the components such as the optical fiber paste and the loose tube inside the optical cable may release toxic gases at high temperatures, threatening personnel safety and the environment. Therefore, it is of great significance to develop an optical cable with excellent flame-retardant performance and passive fire extinguishing function for improving the fire safety of communication networks. SUMMARY

[0003] To solve the problems in the prior art, the purpose of the present application is to provide a flame-retardant optical cable capable of passive fire extinguishing and a preparation method thereof.

[0004] To achieve the above-mentioned purposes and achieve the above-mentioned technical effects, the technical solution adopted by the present application is as follows: A flame-retardant optical cable capable of passive fire extinguishing comprises, from inside to outside, a cable core, a water-blocking tape, a first metal tape, an LSZH inner sheath, a flat water tape, a second metal tape and an LSZH outer sheath.

[0005] Further, the cable core comprises a central reinforcing member located at the center position and a plurality of optical fiber units and a plurality of fillers stranded around the periphery of the central reinforcing member, each optical fiber unit comprising a PBT loose tube and a plurality of optical fibers arranged in the PBT loose tube and an optical fiber paste filled in the gap between the optical fibers.

[0006] Further, the outer surface of the PBT loose tube is coated with a nano flame-retardant coating with a thickness of 5-20 microns.

[0007] Further, the central reinforcing member is a glass fiber reinforced plastic rod, and a heat-sensitive wire is embedded in the interior, and the heat-sensitive wire is connected to an external monitoring system, and when the temperature exceeds 150 DEG C, the heat-sensitive wire triggers an alarm signal.

[0008] Further, the first metal tape and the second metal tape are both galvanized steel tapes or stainless steel tapes with a thickness of 0.1-0.3 mm, and a fireproof coating is provided on the surface.

[0009] Further, the material of the LSZH inner sheath and the LSZH outer sheath is low-smoke halogen-free flame-retardant polyolefin, the oxygen index is greater than or equal to 32%, and magnesium hydroxide or aluminum hydroxide flame retardant is added.

[0010] Further, a heat reflection layer is arranged between the LSZH inner sheath and the flat water hose, the heat reflection layer is aluminum foil or ceramic coating, and the thickness is 0.05-0.2mm.

[0011] Further, the flat water hose is in a ring structure, a plurality of independent sealed cavities are arranged on the flat water hose, each cavity is filled with different or same fire extinguishing medium, the material of the flat water hose is temperature-breakable high polymer material, the flat water hose breaks and releases the internal fire extinguishing medium when the temperature reaches 80-150℃, and the fire extinguishing medium is at least one of water-based extinguishing agent, inert gas and ultra-fine dry powder extinguishing agent.

[0012] Further, the outer surface of the LSZH outer sheath is provided with a concave-convex structure, the concave-convex structure is annular corrugation or grid, and the depth is 0.5-2mm.

[0013] The application further discloses a preparation method of the passive fire extinguishing flame-retardant optical cable. 1) preparing a cable core: Preparation of the optical fiber unit, a plurality of optical fiber units and a plurality of fillers are stranded around the periphery of the central reinforcing member, the stranding pitch is 150-300mm, and SZ stranding is adopted; 2) after stranding, the water-blocking hose is longitudinally wrapped or spirally wrapped outside the cable core to ensure that the overlapping parts are tightly attached; 3) after the water-blocking hose, a first metal belt is longitudinally wrapped, and the sealed tubular structure is formed by welding or overlapping after the longitudinal wrapping; 4) after the longitudinal wrapping of the first metal belt, the LSZH inner sheath is obtained by extruding through an extruder, and after extrusion, the LSZH inner sheath is cooled and shaped in a cooling water tank; 5) an aluminum foil is wrapped outside the LSZH inner sheath as a heat reflection layer by longitudinal wrapping, or a ceramic coating is prepared on the outer surface of the LSZH inner sheath as a heat reflection layer by using plasma spraying technology; 6) the temperature-breakable high polymer material is used to prepare the flat water hose with a plurality of independent sealed cavities by co-extrusion; The prepared ring-shaped flat water hose is tightly wrapped outside the heat reflection layer or the LSZH inner sheath; 7) a second metal belt is longitudinally wrapped outside the flat water hose; 8) the LSZH outer sheath is extruded outside the second metal belt; 9) cooling and shaping to obtain the passive fire extinguishing flame-retardant optical cable.

[0014] Compared with the prior art, the present application has the following advantages: 1) Excellent passive fire extinguishing capability, changing "passive fire retardation" to "active suppression": by setting a flat water hose and placing fire extinguishing medium inside, when the temperature reaches 80-150℃, the flat water hose breaks and releases the fire extinguishing medium, which can quickly and effectively extinguish or suppress the open fire in the local area of the optical cable through heat absorption cooling, suffocation isolation, chemical inhibition, etc. mechanism, preventing the spread of fire along the cable; 2) Extreme fire resistance and heat management performance: the heat reflecting layer between the LSZH inner sheath and the flat water hose can effectively reflect radiant heat, significantly delay the transfer of heat to the cable core, and together with the double-layer LSZH sheath (LSZH inner sheath, LSZH outer sheath) and double-layer metal belt (first and second metal belts) form a multi-layer efficient heat barrier and physical fireproof layer; by setting a nano flame-retardant coating, the fire resistance level of the first protective tube of the optical fiber is directly improved, preventing it from melting, decomposing and releasing toxic gases at high temperatures, ensuring the integrity of the optical cable structure at high temperatures; achieving temperature control from the outside to the inside of the optical cable, providing the possibility for the core optical fiber communication function to maintain longer uninterrupted in a fire; 3) Significantly improved safety, protecting life and property safety: the materials of LSZH inner sheath and LSZH outer sheath are low-smoke halogen-free flame-retardant polyolefin, with oxygen index ≥32%, and adding magnesium hydroxide or aluminum hydroxide flame retardant, the flame retardation effect is good, which can minimize the release of toxic and corrosive smoke, creating a valuable "safety window period" for personnel evacuation and fire rescue; the heat-sensitive wire is embedded in the center reinforcing member, which is connected to the external monitoring system, when the temperature exceeds 150℃, the heat-sensitive wire triggers an alarm signal, realizing early detection of fire and gaining valuable time for emergency measures; 4) Double water blocking protection: the water blocking belt and the double-layer metal belt longitudinal wrapping structure provide reliable longitudinal water blocking performance, suitable for underground pipe gallery, humid environment and other application scenarios; 5) The concave-convex structure of the LSZH outer sheath not only increases the heat dissipation area, but also improves the surface friction and scratch resistance, facilitating installation and extending the service life; 6) The fire extinguishing function is integrated into the optical cable itself, eliminating or reducing the need for additional installation of expensive fire protection facilities on the communication route, reducing the overall system engineering cost; Through the above protective measures, the optical cable of the present application has excellent flame-retardant performance and passive fire extinguishing function, the survival time in fire environment is greatly prolonged, the optical cable is not easy to collapse and melt under high temperature, thereby ensuring that the transmission characteristics (such as attenuation) of the optical signal will not deteriorate sharply, which is crucial for emergency command and communication in fire, can maximize the protection of the smoothness of the communication lifeline and the safety of the personnel environment under extreme fire conditions, and is particularly suitable for scenes with extremely high safety and reliability requirements, such as data centers, high-rise buildings, nuclear power plants, rail transit, etc. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The present application is a structural schematic diagram. DETAILED DESCRIPTION

[0016] The present application will be described in detail below to make the advantages and features of the present application more easily understood by those skilled in the art, so as to define the protection scope of the present application more clearly and explicitly.

[0017] The following gives a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an extensive overview of all contemplated aspects, and is neither intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is given later.

[0018] As shown in Figure 1 The present application discloses a flame-retardant optical cable that can be passively extinguished, comprising a cable core, a water-blocking tape 5, a first metal tape 6, an LSZH inner sheath 7, a flat water tape 8, a second metal tape 9 and an LSZH outer sheath 10 arranged in turn from inside to outside, wherein the cable core comprises a central reinforcing member 4 located at the center position and a plurality of optical fiber units and a plurality of fillers 11 (such as filler ropes, etc.) stranded around the periphery of the central reinforcing member 4, each optical fiber unit comprises a PBT loose tube 3 and a plurality of optical fibers 1 arranged therein and fiber paste 2 filled in the gap between the optical fibers, the fiber paste 2 is a flame-retardant type, the drop point is ≥120℃, and does not contain halogen components.

[0019] In some embodiments, the outer surface of the PBT loose tube 3 is coated with a nano flame-retardant coating, which is made of silicon dioxide and carbon nanotubes, and the coating thickness is 5-20μm, which directly improves the fire resistance level of the first protection tube of the optical fiber, prevents it from melting, decomposing and releasing toxic gas under high temperature, and ensures the integrity of the optical cable structure under high temperature.

[0020] In some embodiments, the central reinforcing member 4 is a glass fiber reinforced plastic rod, and a thermosensitive wire is embedded inside, the thermosensitive wire is connected to an external monitoring system, and when the temperature exceeds 150℃, the thermosensitive wire triggers an alarm signal.

[0021] In some embodiments, the water-blocking tape 5 is a composite water-blocking tape, which is composed of a non-woven fabric layer and a water-absorbing expansion layer, and the water-absorbing expansion ratio is greater than or equal to 200%.

[0022] In some embodiments, the first metal tape 6 and the second metal tape 9 are both galvanized steel tapes or stainless steel tapes, the thickness is 0.1-0.3mm, and the surface is provided with a fireproof coating.

[0023] In some embodiments, the material of the LSZH inner sheath 7 and the LSZH outer sheath 10 is low-smoke halogen-free flame-retardant polyolefin, the oxygen index is greater than or equal to 32%, and magnesium hydroxide or aluminum hydroxide flame retardant is added, and the addition amount is 30-50wt%.

[0024] In some embodiments, a heat reflecting layer is arranged between the LSZH inner sheath 7 and the flat water tape 8, the heat reflecting layer is aluminum foil or ceramic coating, and the thickness is 0.05-0.2mm.

[0025] In some embodiments, the flat water tape 8 is in a ring structure, which is wrapped between the LSZH inner sheath 7 and the second metal tape 9, a plurality of independent sealed cavities are arranged on the flat water tape 8, each cavity is filled with different or same fire extinguishing medium, and the fire extinguishing medium is at least one of water-based extinguishing agent (used for cooling and extinguishing fire), inert gas (used for suffocation and isolation for extinguishing fire), and ultra-fine dry powder extinguishing agent (used for chemical inhibition for extinguishing fire). The material of the flat water tape 8 is a temperature-breakable polymer material, which breaks and releases the internal fire extinguishing medium when the temperature reaches 80-150℃, so as to achieve fire extinguishing.

[0026] In some embodiments, the particle size of the ultra-fine dry powder extinguishing agent is less than 10μm, and the ultra-fine dry powder extinguishing agent accounts for 20-50% of the total mass of the fire extinguishing medium.

[0027] In some embodiments, the outer surface of the LSZH outer sheath 10 is provided with a concave-convex structure, the concave-convex structure is annular corrugation or grid, and the depth is 0.5-2mm, so as to increase the heat dissipation area and the anti-friction performance.

[0028] The application also discloses a preparation method of the flame-retardant optical cable which can be passively extinguished. 1) Preparation of the cable core: Preparation of the optical fiber unit, a plurality of optical fiber units and a plurality of fillers 11 are stranded around the periphery of the central reinforcing member 4, the stranding pitch is 150-300mm, and SZ stranding is adopted; 2) The water-blocking tape 5 is longitudinally wrapped or spirally wrapped outside the stranded cable core, so as to ensure that the overlapping parts are tightly fitted; 3) Outside the water-blocking tape 5, the first metal tape 6 is formed by longitudinal wrapping, which is a galvanized steel tape or a stainless steel tape, and the surface can be pre-coated with a fireproof coating. After longitudinal wrapping, a sealed tubular structure is formed by welding or lapping; 4) Outside the first metal tape 6 after longitudinal wrapping, an LSZH inner sheath 7 is obtained by extrusion. The extrusion material is low-smoke halogen-free flame-retardant polyolefin with 30-50wt% magnesium hydroxide or aluminum hydroxide added. After extrusion, it immediately enters the cooling tank for cooling and shaping; In this step, the temperature of the extruder is set as follows: feeding zone (Zone 1): 120-140℃; compression zone (Zone 2): 140-160℃; metering zone (Zone 3): 160-180℃; head (die): 170-190℃; The cooling water temperature is: the first stage cooling water tank (quenching) water temperature is 10-25℃; the subsequent water tanks can be gradually increased to room temperature to avoid internal stress due to rapid cooling; 5) Outside the LSZH inner sheath 7, a layer of aluminum foil is wrapped as a heat reflective layer by longitudinal wrapping, or a ceramic coating is prepared on the outer surface of the LSZH inner sheath 7 as a heat reflective layer by plasma spraying technology. The plasma spraying power is 30-50kW, the spraying distance is 80-150mm, the powder feeding rate is 20-40g / min, and the LSZH inner sheath 7 preheating temperature is 50-80℃ to enhance the coating adhesion; 6) A flat water hose 8 with multiple independent sealed cavities is made by co-extrusion using temperature-sensitive high polymer materials. During the preparation process, different or the same extinguishing medium can be filled into each cavity through different injection ports; The prepared annular flat water hose 8 is tightly wrapped outside the heat reflective layer or LSZH inner sheath 7, and temporary binding is used to fix it in the center without twisting. A slight tension of 10-20N is applied during installation to ensure that the flat water hose 8 is flat and adheres to the heat reflective layer or LSZH inner sheath 7 without wrinkles, but it should not be too tight to avoid premature damage; 7) Outside the flat water hose 8, a second metal tape 9 is wrapped longitudinally to provide additional mechanical protection and fireproof barrier, and to help fix the flat water hose 8; 8) Outside the second metal tape 9, an LSZH outer sheath 10 is extruded. When the molten LSZH extrusion material passes through the extruder head die (the inner wall of the die has a pattern corresponding to the concave-convex structure, with a concave-convex depth of 0.5-2mm and a pitch of 2-8mm), the outer surface forms an annular corrugated or grid-like concave-convex structure; In this step, the temperature of the extruder is set as follows: feeding zone (Zone 1): 130-150℃; compression zone (Zone 2): 150-170℃; metering zone (Zone 3): 170-190℃; head (die): 180-200℃; 9) Cooling and winding: The extruded optical cable enters the cooling water tank (the water temperature of the first cooling water tank is 30-50℃ for 10-30s to prevent rapid cooling from causing deformation of the concave and convex structure or excessive shrinkage of the sheath; the water temperature of the subsequent water tanks is 10-25℃) for cooling, and is finally pulled by a tracked traction machine and wound onto a large tooling tray.

[0029] Example 1 like Figure 1 As shown, a passive fire-retardant optical cable includes, from the inside out, a cable core, a water-blocking tape 5, a first metal tape 6, an LSZH inner sheath 7, a flat water tape 8, a second metal tape 9, and an LSZH outer sheath 10. The cable core includes a central reinforcing member 4 located at the center, two optical fiber units twisted around the central reinforcing member 4, and three fillers 11 (filler ropes). Each optical fiber unit includes a PBT loose tube 3 and several optical fibers 1 disposed therein, and fiber paste 2 filling the gaps between the optical fibers. The fiber paste 2 is a flame-retardant fiber paste with a dropping point ≥120℃ and does not contain halogen components.

[0030] In this embodiment, the outer surface of the PBT loose tube 3 is coated with a nano flame-retardant coating. The nano flame-retardant coating is made of silicon dioxide and carbon nanotubes, and the coating thickness is 10μm. This directly improves the fire resistance of the first protective tube of the optical fiber, prevents it from melting, decomposing and releasing toxic gases at high temperatures, and ensures the integrity of the optical cable structure at high temperatures.

[0031] The central reinforcing member 4 is a glass fiber reinforced plastic rod with an embedded thermal wire. The thermal wire is connected to an external monitoring system, and when the temperature exceeds 150°C, the thermal wire triggers an alarm signal.

[0032] Water-blocking tape 5 is a composite water-blocking tape, consisting of a non-woven fabric layer and a water-absorbing and swelling layer, with a water absorption and swelling ratio ≥200%.

[0033] Both the first metal strip 6 and the second metal strip 9 are galvanized steel strips with a thickness of 0.1 mm and a fireproof coating on the surface.

[0034] The inner sheath 7 and outer sheath 10 of LSZH are made of low-smoke halogen-free flame-retardant polyolefin with an oxygen index ≥32% and contain magnesium hydroxide flame retardant at a dosage of 30wt%.

[0035] A heat-reflective layer is provided between the inner sheath 7 of the LSZH and the flat water hose 8. The heat-reflective layer is made of aluminum foil with a thickness of 0.2mm.

[0036] The flat hose 8 has a ring-shaped structure, wrapped between the inner sheath 7 of the LSZH and the second metal belt 9. The flat hose 8 has multiple independently sealed cavities, each filled with a different or identical extinguishing medium. The extinguishing medium is a water-based extinguishing agent (used for cooling and extinguishing fires) or an inert gas (used for asphyxiation and isolation). The flat hose 8 is made of a heat-sensitive polymer material that ruptures at temperatures between 80-150℃, releasing the internal extinguishing medium to extinguish the fire.

[0037] The outer surface of the LSZH outer sheath 10 is provided with a concave-convex structure, which is a ring-shaped corrugation with a depth of 1mm, to increase the heat dissipation area and anti-friction performance.

[0038] This embodiment also discloses a method for preparing a flame-retardant optical cable capable of passive fire extinguishing, comprising the following steps: 1) Preparation of cable core: To prepare fiber optic units, two fiber optic units and three fillers 11 are twisted together around the central reinforcing member 4 with a twisting pitch of 150 mm and SZ twisting is used. 2) After stranding, water-blocking tape 5 is wrapped longitudinally in a spiral around the outside of the cable core to ensure that the overlapping parts fit tightly; 3) Outside the water-blocking strip 5, a first metal strip 6 is formed longitudinally. This metal strip is made of galvanized steel and pre-coated with a conventional fire-retardant coating. After longitudinal wrapping, a sealed tubular shape is formed by welding or overlapping. 4) After longitudinal wrapping, the first metal strip 6 is extruded using an extruder to obtain the LSZH inner sheath 7. The extrusion material is a low-smoke, halogen-free, flame-retardant polyolefin with added magnesium hydroxide. Immediately after extrusion, it enters a cooling water bath for cooling and shaping. In this step, the extruder temperature settings are as follows: feeding zone (zone 1): 120℃; compression zone (zone 2): 140℃; metering zone (zone 3): 160℃; die head (mold head): 170℃. Cooling water temperature: The temperature of the first cooling water tank (rapid cooling) is 15℃; the temperature of subsequent water tanks can be gradually increased to room temperature to avoid internal stress caused by excessive cooling. 5) An aluminum foil layer is wrapped around the outer sheath 7 of the LSZH in a longitudinal wrapping manner as a heat reflective layer; 6) A flat water hose 8 with multiple independent sealed cavities inside is made by co-extrusion using a heat-sensitive polymer material. During the preparation process, different or the same extinguishing medium can be filled into each cavity through different injection ports. The prepared annular flat water strip 8 is tightly wrapped around the outside of the heat reflective layer and fixed with temporary straps to ensure that it is centered and not twisted. When installing, apply a slight tension of 10N to ensure that the flat water strip 8 is flat on the heat reflective layer without wrinkles, but it should not be too tight to avoid premature damage. 7) A second metal strip 9 is longitudinally wrapped around the flat hose 8 to provide additional mechanical protection and fire barrier, and to help secure the flat hose 8; 8) Extruding an LSZH outer sheath 10 outside the second metal strip 9. When the molten LSZH extruded material passes through the extruder die (the inner wall of the die has a texture corresponding to the concave and convex structure, with a concave and convex depth of 1 mm and a texture spacing (pitch) of 2 mm), the outer surface forms a concave and convex structure with annular ripples. In this step, the extruder temperature settings are as follows: feeding zone (zone 1): 130℃; compression zone (zone 2): 150℃; metering zone (zone 3): 170℃; die head (die head): 180℃. 9) Cooling and winding: The extruded optical cable enters the cooling water tank (the water temperature of the first cooling water tank is 30℃ for 20s to prevent the deformation of the concave and convex structure or excessive shrinkage of the sheath due to rapid cooling; the water temperature of the subsequent water tank is 15℃) for cooling, and is finally pulled by the tracked traction machine and wound onto the large tooling tray.

[0039] Example 2 like Figure 1 As shown, a passive fire-retardant optical cable includes, from the inside out, a cable core, a water-blocking tape 5, a first metal tape 6, an LSZH inner sheath 7, a flat water tape 8, a second metal tape 9, and an LSZH outer sheath 10. The cable core includes a central reinforcing member 4 located at the center, two optical fiber units twisted around the central reinforcing member 4, and three fillers 11 (such as filler ropes). Each optical fiber unit includes a PBT loose tube 3 and several optical fibers 1 disposed therein, and fiber paste 2 filling the gaps between the optical fibers. The fiber paste 2 is a flame-retardant fiber paste with a dropping point ≥120℃ and does not contain halogen components.

[0040] The outer surface of the PBT loose tube 3 is coated with a nano flame-retardant coating, which is made of silicon dioxide and carbon nanotubes. The coating thickness is 20μm, which directly improves the fire resistance of the first protective tube of the optical fiber, prevents it from melting, decomposing and releasing toxic gases at high temperatures, and ensures the integrity of the optical cable structure at high temperatures.

[0041] The central reinforcing member 4 is a glass fiber reinforced plastic rod with an embedded thermal wire. The thermal wire is connected to an external monitoring system, and when the temperature exceeds 150°C, the thermal wire triggers an alarm signal.

[0042] Water-blocking tape 5 is a composite water-blocking tape, consisting of a non-woven fabric layer and a water-absorbing and swelling layer, with a water absorption and swelling ratio ≥200%.

[0043] Both the first metal strip 6 and the second metal strip 9 are stainless steel strips with a thickness of 0.3 mm and a fire-retardant coating on the surface.

[0044] The material of the LSZH inner sheath 7 and the LSZH outer sheath 10 is low-smoke halogen-free flame-retardant polyolefin, with an oxygen index of greater than or equal to 32%, and an added amount of 50 wt% of an aluminum hydroxide flame retardant.

[0045] A heat-reflecting layer is arranged between the LSZH inner sheath 7 and the flat water hose 8, and the heat-reflecting layer is an aluminum foil with a thickness of 0.2 mm.

[0046] The flat water hose 8 has a ring structure and is wrapped between the LSZH inner sheath 7 and the second metal belt 9. The flat water hose 8 is provided with a plurality of independently sealed cavities, each of which is filled with different or the same fire extinguishing medium. The fire extinguishing medium is at least one of a water-based extinguishing agent (for cooling and extinguishing) and a superfine dry powder extinguishing agent (for chemical suppression and extinguishing). The material of the flat water hose 8 is a temperature-sensitive high polymer material that ruptures and releases the internal fire extinguishing medium when the temperature reaches 80-150°C, thereby achieving fire extinguishing.

[0047] The particle size of the superfine dry powder extinguishing agent is 8 μm, and the superfine dry powder extinguishing agent accounts for 20% of the total mass of the fire extinguishing medium, and the rest is the water-based extinguishing agent.

[0048] The outer surface of the LSZH outer sheath 10 is provided with a concave-convex structure, which is a grid-shaped structure with a depth of 2 mm, to increase the heat dissipation area and the anti-friction performance.

[0049] A preparation method of a flame-retardant optical cable capable of passive fire extinguishing, comprising the following steps: 1) Preparing a cable core: Preparation of an optical fiber unit, two optical fiber units and three fillers 11 are twisted together around the periphery of the central reinforcing member 4, with a twisting pitch of 300 mm, and SZ twisting is adopted; 2) After twisting the cable core, longitudinally wrap the water-blocking belt 5 to ensure that the overlapping part is tightly attached; 3) After the water-blocking belt 5, longitudinally wrap to form a first metal belt 6, which is a stainless steel belt, and the surface can be pre-coated with a fireproof coating. After longitudinal wrapping, a sealed tubular structure is formed by welding; 4) After the longitudinal wrapping of the first metal belt 6, an LSZH inner sheath 7 is obtained by extrusion with an extruder, and the extrusion material is low-smoke halogen-free flame-retardant polyolefin with an added amount of 50 wt% of aluminum hydroxide. After extrusion, immediately enter the cooling water tank for cooling and shaping; In this step, the temperature of the extruder is set as follows: feeding area (first zone): 140°C; compression area (second zone): 160°C; metering area (third zone): 180°C; head (die): 190°C; The cooling water temperature is: the first stage cooling water tank (quenching) water temperature is 20°C; the subsequent water tanks can be gradually increased to room temperature to avoid internal stress due to rapid cooling; 5) Outside the LSZH inner sheath 7, wrap a layer of aluminum foil as a heat-reflecting layer by longitudinal wrapping; 6) Use warm-broken type high molecular material, by co-extrusion method to make flat water hose 8 with multiple independent sealed cavities, in the preparation process, different injection ports can be used to fill different or same fire extinguishing medium into each cavity; The prepared annular flat water hose 8 is tightly wrapped outside the heat reflecting layer, and temporary bandages are used to fix it, to ensure that it is centered and not twisted, and a slight tension of 20N is applied during installation to ensure that the flat water hose 8 is flat and adheres to the heat reflecting layer without wrinkles, but it should not be too tight to avoid premature damage; 7) A second metal strip 9 is longitudinally wrapped outside the flat water hose 8 to provide additional mechanical protection and fireproof barrier, and to help fix the flat water hose 8; 8) An LSZH outer sheath 10 is extruded outside the second metal strip 9. When the molten LSZH extruded material passes through the extruder head die (the inner wall of the die has a pattern corresponding to the concave-convex structure, the inner wall pattern: concave-convex depth 2mm, pitch 2mm), the outer surface forms a grid-like concave-convex structure; In this step, the extruder temperature is set as follows: feeding area (zone 1): 150℃; compression area (zone 2): 170℃; metering area (zone 3): 190℃; head (die): 200℃; 9) Cooling and take-up: the extruded optical cable enters the cooling water tank (the first section of the cooling water tank has a water temperature of 50℃ for 10s to prevent deformation of the concave-convex structure or excessive shrinkage of the sheath due to rapid cooling; the subsequent water tank has a water temperature of 25℃) for cooling, and finally pulled by a track-type tractor and wound onto a large tooling disc.

[0050] The rest is the same as example 1.

[0051] Parts or structures not specifically described in the present application can use existing technology or existing products, which are not described here.

[0052] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A fire resistant optical cable which can be extinguished passively, characterized in that, The cable core, the water-blocking tape, the first metal tape, the LSZH inner sheath, the flat water tape, the second metal tape and the LSZH outer sheath are sequentially arranged from inside to outside.

2. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The cable core comprises a central reinforcing member at a central position and a plurality of optical fiber units and a plurality of fillers stranded around the central reinforcing member, each optical fiber unit comprising a PBT loose sleeve and a plurality of optical fibers and optical fiber paste filled in the gaps between the optical fibers.

3. A fire-retardant optical cable which can be passively extinguished according to claim 2, wherein The outer surface of the PBT loose sleeve is coated with a nano flame-retardant coating with a thickness of 5-20 μm.

4. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The central reinforcing member is a glass fiber reinforced plastic rod, and a heat-sensitive wire is embedded in the central reinforcing member, the heat-sensitive wire being connected to an external monitoring system, and when the temperature exceeds 150℃, the heat-sensitive wire triggers an alarm signal.

5. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The first metal tape and the second metal tape are both galvanized steel tapes or stainless steel tapes with a thickness of 0.1-0.3 mm and a fireproof coating on the surface.

6. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The LSZH inner sheath and the LSZH outer sheath are made of low-smoke halogen-free flame-retardant polyolefin with an oxygen index of ≥32% and added magnesium hydroxide or aluminum hydroxide flame retardant.

7. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein A heat-reflecting layer is arranged between the LSZH inner sheath and the flat water tape, the heat-reflecting layer being an aluminum foil or a ceramic coating with a thickness of 0.05-0.2 mm.

8. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The flat water tape has a ring structure, and a plurality of independently sealed cavities are arranged on the flat water tape, each cavity being filled with different or same fire extinguishing medium, the flat water tape being made of a temperature-sensitive high polymer material, which ruptures and releases the internal fire extinguishing medium when the temperature reaches 80-150℃, the fire extinguishing medium being at least one of water-based extinguishing agent, inert gas and ultra-fine dry powder extinguishing agent.

9. A fire-retardant optical cable which can be passively extinguished according to claim 1, wherein The outer surface of the LSZH outer sheath is provided with a concave-convex structure, which is an annular corrugation or a grid, with a depth of 0.5-2 mm.

10. A process for the production of a flame-retardant optical cable which is self-extinguishing according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: 1) preparing the cable core: Preparation of optical fiber units, a plurality of optical fiber units and a plurality of fillers are stranded around the central reinforcing member, the stranding pitch is 150-300 mm, and SZ stranding is adopted; 2) longitudinally wrapping or spirally wrapping the water-blocking tape outside the stranded cable core to ensure that the overlapping parts are tightly fitted; 3) longitudinally wrapping the first metal tape outside the water-blocking tape to form a sealed tubular shape by welding or lapping after longitudinal wrapping; 4) extruding the LSZH inner sheath outside the first metal tape after longitudinal wrapping by using an extruder, and then cooling and shaping in a cooling water tank after extrusion; 5) wrapping an aluminum foil layer as a heat-reflecting layer outside the LSZH inner sheath by longitudinal wrapping, or preparing a ceramic coating layer as a heat-reflecting layer on the outer surface of the LSZH inner sheath by using plasma spraying technology; 6) using temperature-sensitive high polymer material to prepare a flat water tape with a plurality of independently sealed cavities by co-extrusion method; Tightly wrapping the prepared ring-shaped flat water tape outside the heat-reflecting layer or the LSZH inner sheath; 7) longitudinally wrapping the second metal tape outside the flat water tape; 8) extruding the LSZH outer sheath outside the second metal tape; 9) cooling and shaping to obtain the required passive fire extinguishing flame-retardant optical cable.

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