Ceramic polyolefin insulating fire-resistant cable and preparation method thereof

Abstract

The invention relates to a ceramic polyolefin insulating fire-resistant cable and a preparation method thereof. The cable comprises a conductor, a ceramic polyolefin insulating layer and an outer sheath. The conductor is coated with the ceramic polyolefin insulating layer, the ceramic polyolefin insulating layer is made of matrix resin and a ceramic additive, and the ceramic additive is a mixture of silicate filler, aluminate filler and borate filler. The mass ratio of the silicate filler to the aluminate filler to the borate filler in the ceramization auxiliary agent is (70-80): (15-25): (5-10). And the outer sheath is coated on the ceramic polyolefin insulating layer. The single-layer structure of the ceramic polyolefin insulating layer has the functions of insulation and fire resistance, a traditional mica tape wrapping process is omitted, the production process is greatly simplified, the efficiency is improved, meanwhile, the problems that due to the fact that inorganic materials such as mica tapes are high in hardness, the overall flexibility of the cable is poor, and installation and laying are not facilitated are solved, and the material cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cable preparation, and in particular to a ceramic polyolefin insulated fire-resistant cable and a preparation method thereof. Background Art

[0002] Traditional polyolefin insulated cables, due to their insufficient high-temperature resistance, are susceptible to softening, melting, and even burning in fires or high-temperature environments, leading to insulation failure and the risk of fire spread. To address this issue, existing technologies generally use inorganic materials such as mica tape and ceramic fiber as a fire-resistant layer, covering the conductor surface through a wrapping or braiding process to improve fire resistance. However, these methods have significant drawbacks: First, mica tape or ceramic fiber must be processed through a complex multi-pass wrapping process, resulting in a cumbersome and inefficient production process; second, inorganic materials have high hardness and poor ductility, resulting in insufficient cable flexibility, making it difficult to adapt to the requirements of laying in small spaces or complex paths; in addition, materials such as mica tape are expensive, and the energy consumption during processing is high, further increasing the cost of cable manufacturing; finally, some inorganic materials may release dust or silicon-containing pollutants during production and use, posing an environmental risk. Summary of the Invention

[0003] The purpose of the present invention is to provide a ceramic polyolefin insulated fire-resistant cable and a preparation method thereof, which can

[0004] To achieve the above object, according to a first aspect of the present invention, there is provided a ceramic polyolefin insulated fire-resistant cable, comprising:

[0005] conductor;

[0006] A ceramic polyolefin insulation layer is coated on the conductor, wherein the material of the ceramic polyolefin insulation layer includes a base resin and a ceramic additive, wherein the ceramic additive is a mixture of silicate fillers, aluminate fillers, and borate fillers, and the mass ratio of the silicate fillers, aluminate fillers, and borate fillers in the ceramic additive is 70-80:15-25:5-10;

[0007] The outer sheath is coated on the ceramicized polyolefin insulation layer.

[0008] Optionally, the ceramic polyolefin insulation layer comprises the following components in parts by weight:

[0009] 50-70 parts of base resin;

[0010] 15-30 parts of silicate filler;

[0011]

[0012] Optionally, the matrix resin is any one or more of polyethylene and polypropylene, the silicate filler is any one or more of mica powder, kaolin, talc powder, glass powder, wollastonite, the aluminate filler is any one or more of calcium aluminate, spinel, boehmite, and the borate filler is any one or more of zinc borate, borosilicate glass powder, aluminum borate.

[0013] Optionally, the flame retardant synergist is any one or more of inorganic flame retardants and phosphorus-nitrogen based flame retardants, the crosslinking agent and the co-crosslinking agent are any one or more of peroxide crosslinking agents and silane coupling agents, the processing aid is any one or more of lubricants, antioxidants, plasticizers, and the other functional additives are any one or more of carbon fiber, glass fiber, expanded graphite.

[0014] Optionally, the outer sheath is any one of flame retardant polyvinyl chloride or low-smoke zero-halogen material.

[0015] According to the second aspect of the present invention, there is provided a method for preparing a ceramized polyolefin insulated fire-resistant cable, comprising the following steps:

[0016] Mixing various components of the ceramized polyolefin insulating layer by a high-speed mixer;

[0017] Extruding and molding the mixed material through a twin-screw extruder to coat on a conductor to form a ceramized polyolefin insulating layer;

[0018] Extruding an outer sheath outside the ceramized polyolefin insulating layer through a twin-screw extruder to complete the cable preparation.

[0019] Optionally, the mixing of various components of the ceramized polyolefin insulating layer by a high-speed mixer comprises the following steps:

[0020] Putting the matrix resin and the processing aid into the high-speed mixer and mixing for 2 - 3 minutes;

[0021] Adding the ceramization aid and the flame retardant synergist and mixing for 5 - 10 minutes within a temperature of 80 °C;

[0022] Finally, adding the crosslinking agent and the co-crosslinking agent and mixing for 1 - 2 minutes for a short time.

[0023] Optionally, before mixing various components of the ceramized polyolefin insulating layer by a high-speed mixer, the following steps are included:

[0024] Performing surface coupling modification treatment on the ceramization aid;

[0025] Drying the flame retardant synergist.

[0026] Optionally, the temperature range of the first zone of the twin-screw extruder is 120°C - 140°C, the temperature range of the second to third zones of the twin-screw extruder is 150°C - 170°C, the temperature range of the fourth to fifth zones of the twin-screw extruder is 160°C - 180°C, and the temperature range of the head of the twin-screw extruder is 170°C - 190°C.

[0027] The beneficial effects of the present invention are as follows: By directly using the ceramized polyolefin material as the insulating layer, a dense ceramized protective layer is formed at high temperature to replace the traditional fire-resistant structure. The single-layer structure of the ceramized polyolefin insulating layer combines the functions of insulation and fire resistance, eliminating the traditional mica tape wrapping process, greatly simplifying the production process and improving efficiency. At the same time, it avoids the problem that the overall flexibility of the cable is poor due to the high hardness of inorganic materials such as mica tape, which is not conducive to installation and laying, and also reduces the material cost; the introduction of the ceramization additive forms a stable ceramic barrier through chemical reactions at high temperature to ensure that the fire resistance performance meets the standards; in addition, the ceramized polyolefin material is non-toxic and harmless, and there is no pollution discharge during the production process, with prominent environmental protection advantages.

[0028] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a ceramized polyolefin insulated fire-resistant cable shown in an embodiment of the present invention;

[0030] Figure 2 It is a schematic flow chart of a preparation method of a ceramized polyolefin insulated fire-resistant cable shown in an embodiment of the present invention;

[0031] Figure 3 For Figure 2 It is a schematic flow chart of step S10 in

[0032] In the figure: 1, conductor; 2, ceramized polyolefin insulating layer; 3, outer sheath. Detailed Embodiments

[0033] Next, the technical solution of the present invention will be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Please refer to Figure 1 , a ceramizable polyolefin insulated fire-resistant cable shown in a preferred embodiment of the present application includes a conductor 1, a ceramizable polyolefin insulation layer 2, and an outer sheath 3. The ceramizable polyolefin insulation layer 2 is coated on the conductor 1. The material of the ceramizable polyolefin insulation layer 2 includes a matrix resin and a ceramization aid. The ceramization aid is a mixture of silicate fillers, aluminate fillers, and borate fillers. The mass ratio of silicate fillers, aluminate fillers, and borate fillers in the ceramization aid is 70-80:15-25:5-10. The outer sheath 3 is coated on the ceramizable polyolefin insulation layer 2.

[0037] It should be noted that silicate, as the main refractory framework, generates a SiO2-Al2O3 network structure through a dehydroxylation reaction at high temperature (>750 °C), forming a continuous ceramic framework and providing a basic refractory barrier. However, the pure silicate has a high sintering temperature (>1000 °C), and the ceramic layer is brittle, making it difficult to adapt to the low-temperature thermal decomposition characteristics of the matrix resin. After introducing aluminate, the aluminate melts to form a liquid phase at 800-900 °C, filling the pores of the silicate framework, significantly improving the density and mechanical strength of the ceramic layer, and at the same time reducing the sintering temperature to match the decomposition temperature of the matrix resin. However, an excessive amount of aluminate (>25%) will result in too much high-temperature liquid phase, and the ceramic layer is prone to flow failure. Borate decomposes at 300-500 °C, wrapping the silicate / aluminate particles in advance, reducing the system viscosity, promoting pre-sintering at low temperature (<750 °C), and avoiding the risk of flame penetration caused by the failure to form the ceramic layer before the complete decomposition of the matrix resin. However, when the addition amount of borate >10%, the refractoriness of the ceramic layer will be excessively reduced. That is to say, borate forms an initial protective layer through low-temperature pre-sintering, silicate constructs the framework at medium temperature, and aluminate is densified by high-temperature melting, finally forming a ceramized polyolefin insulating layer 2 with high density, low porosity and matching expansion coefficient with the matrix. On the basis of retaining the insulation performance, it has excellent fire resistance.

[0038] In one embodiment, the ceramized polyolefin insulating layer 2 comprises the following components in parts by weight:

[0039]

[0040] In this embodiment, the matrix resin ensures processability as a continuous phase, the silicate provides a refractory framework, the aluminate optimizes the strength of the ceramic layer, the borate promotes low-temperature sintering, the flame retardant synergist absorbs heat and has flame retardancy, the crosslinking agent and co-crosslinking agent improve the heat resistance, the processing aid improves the extrusion performance, and other functional additives enhance the mechanical properties. The overall formula balances fire resistance, flexibility and cost. The parts by weight of the matrix resin can be, for example, 50 parts, 60 parts or 70 parts, the parts by weight of the silicate filler can be, for example, 15 parts, 20 parts, 25 parts or 30 parts, the parts by weight of the aluminate filler can be, for example, 4 parts, 6 parts or 8 parts, the parts by weight of the borate filler can be, for example, 1 part or 2 parts, the parts by weight of the flame retardant synergist can be, for example, 5 parts, 10 parts or 15 parts, the parts by weight of the crosslinking agent and co-crosslinking agent can be, for example, 1 part, 3 parts or 5 parts, the parts by weight of the processing aid can be, for example, 1 part, 2 parts or 3 parts, and the parts by weight of other functional additives can be, for example, 3 parts, 6 parts or 9 parts.

[0041] In one embodiment, the matrix resin is any one or more of polyethylene and polypropylene, the silicate filler is any one or more of mica powder, kaolin, talc powder, glass powder, and wollastonite, the aluminate filler is any one or more of calcium aluminate, spinel, and boehmite, and the borate filler is any one or more of zinc borate, borosilicate glass powder, and aluminum borate. In this embodiment, the matrix resin is selected as polyethylene, such as LDPE (low-density polyethylene) or LLDPE (linear low-density polyethylene), which can provide basic flexibility and electrical insulation; polypropylene is selected, and its heat resistance is slightly higher than that of polyethylene, which is suitable for higher-temperature environments. Mica powder is selected as the silicate, which can form a ceramic skeleton at high temperatures; kaolin is selected, and high-temperature-resistant Al2O3 and SiO2 can be generated after dehydration; talc powder, such as borosilicate glass, promotes ceramization during high-temperature melting; wollastonite can provide a calcium source to enhance the strength of the ceramic layer. Calcium aluminate is selected as the aluminate, which can melt at low temperatures and promote the densification of the ceramic layer; spinel is selected, which is stable at high temperatures and reduces cracking of the ceramic layer; boehmite can be dehydrated and transformed into γ-Al2O3 to increase the porosity of the ceramic layer. Zinc borate is selected as the borate, which releases crystal water above 300°C to generate a B2O3 glass phase to coat the filler particles; borosilicate glass powder can be used as a bonding phase to connect ceramic particles; aluminum borate can generate an Al2O3-B2O3 composite phase at high temperatures to improve thermal shock resistance.

[0042] In one embodiment, the flame-retardant synergist is any one or more of inorganic flame retardants and phosphorus-nitrogen flame retardants, the crosslinking agent and the co-crosslinking agent are any one or more of peroxide crosslinking agents and silane coupling agents, the processing aids are any one or more of lubricants, antioxidants, and plasticizers, and the other functional additives are any one or more of carbon fiber, glass fiber, and expanded graphite. In this embodiment, aluminum hydroxide or magnesium hydroxide is selected as the inorganic flame retardant, which can decompose endothermically and release water vapor to inhibit combustion; ammonium polyphosphate is selected as the phosphorus-nitrogen flame retardant, which can promote carbonization and ceramization. Dicumyl peroxide is selected as the peroxide crosslinking agent, which can improve the heat resistance of the material; KH-550 is selected as the silane coupling agent, which can improve the interfacial bonding between the filler and the resin. Zinc stearate is selected as the lubricant, which can improve the processing fluidity; 1010 and 168 are selected as the antioxidants, which can prevent thermal oxidative degradation during processing; DOA is selected as the plasticizer, which can adjust the flexibility of the material. Carbon fiber or glass fiber is selected as the other functional additives, which can enhance the mechanical strength; expanded graphite is selected, which has a synergistic flame-retardant and ceramization effect.

[0043] In one embodiment, the outer sheath 3 is any one of flame-retardant polyvinyl chloride or low-smoke halogen-free material. Flame-retardant polyvinyl chloride has low cost and good flame retardancy, and low-smoke halogen-free material is low-toxic and environmentally friendly, which can meet the different requirements for smoke toxicity, cost, and flame retardancy in different scenarios.

[0044] Please refer to Figure 2, this application also provides a method for preparing a ceramizable polyolefin insulated fire-resistant cable, which includes the following steps:

[0045] Step S10: Mix various components of the ceramizable polyolefin insulation layer 2 through a high-speed mixer;

[0046] Step S20: Extrude the mixed material through a twin-screw extruder and coat it on the conductor 1 to form the ceramizable polyolefin insulation layer 2;

[0047] Step S30: Extrude the outer sheath 3 outside the ceramizable polyolefin insulation layer 2 through a twin-screw extruder to complete the cable preparation.

[0048] Please refer to Figure 3 , and this step S10 includes the following steps:

[0049] Step S101: Put the matrix resin and processing aids into a high-speed mixer and mix for 2 - 3 minutes;

[0050] Step S102: Add the ceramization aid and flame retardant synergist and mix for 5 - 10 minutes within the temperature of 80°C;

[0051] Step S103: Finally, add the crosslinking agent and co-crosslinking agent and mix for 1 - 2 minutes for a short time.

[0052] In this step S10, first mix the matrix resin and processing aids to avoid high-temperature degradation, then add the ceramization aid and flame retardant synergist for sufficient dispersion, and finally add the crosslinking agent and co-crosslinking agent to prevent premature decomposition, ensure material uniformity and crosslinking efficiency, and avoid scorching or uneven dispersion.

[0053] Before this step S10, the following steps are included:

[0054] Conduct surface coupling modification treatment on the ceramization aid;

[0055] Dry the flame retardant synergist.

[0056] In an embodiment, the surface coupling treatment of the glass powder is carried out by the silane coupling agent KH-550 to enhance its interfacial bonding force and compatibility with the matrix resin. By drying aluminum hydroxide at 80°C for 4 hours to remove moisture, avoid the generation of bubbles during processing and improve the material density, and ensure the continuity of ceramization of the insulation layer at high temperatures.

[0057] In one embodiment, the temperature range of the first zone of the twin-screw extruder is 120°C - 140°C, the temperature range of the second to third zones of the twin-screw extruder is 150°C - 170°C, the temperature range of the fourth to fifth zones of the twin-screw extruder is 160°C - 180°C, and the temperature range of the head of the twin-screw extruder is 170°C - 190°C. Setting the temperature of the first zone of the twin-screw extruder at 120°C - 140°C can prevent premature melting and blocking of the resin; setting the second to third zones at 150°C - 170°C can achieve melting and plasticization; setting the fourth to fifth zones at 160°C - 180°C can strengthen the shear dispersion of the ceramicizing agent; setting the head at 170°C - 190°C can ensure the stability of extrusion molding, and control the filler dispersion quality and the fire resistance of the insulating layer through the temperature gradient. At the same time, the screw speed of the twin-screw extruder is 200 - 400 rpm.

[0058] To illustrate the performance effects of the embodiments of the present invention, the following specific examples are used for detailed description:

[0059] Example 1:

[0060] A ceramifiable polyolefin insulated fire-resistant cable according to an embodiment of the present invention includes a conductor 1, a ceramifiable polyolefin insulating layer 2, and an outer sheath 3. The ceramifiable polyolefin insulating layer 2 includes the following components in parts by weight:

[0061]

[0062] The method for preparing the ceramifiable polyolefin insulated fire-resistant cable includes the following steps:

[0063] Mix various components of the ceramifiable polyolefin insulating layer 2 through a high-speed mixer. Put the matrix resin and processing aids into the high-speed mixer, mix for 2 minutes, then add the ceramicizing agent and flame retardant synergist, mix for 7 minutes within a temperature of 80°C, and finally add the crosslinking agent and co-crosslinking agent, and mix for 2 minutes for a short time;

[0064] Extrude the mixed material through a twin-screw extruder and coat it on the conductor 1 to form a ceramifiable polyolefin insulating layer 2;

[0065] Extrude the outer sheath 3 outside the ceramifiable polyolefin insulating layer 2 through a twin-screw extruder to complete the preparation of the cable.

[0066] In this example, for the components of the ceramifiable polyolefin insulating layer 2, the matrix resin is polyethylene, the silicate filler is glass powder, the aluminate filler is calcium aluminate, the borate filler is zinc borate, the flame retardant synergist is aluminum hydroxide, the crosslinking agent and co-crosslinking agent are diisopropylbenzene peroxide, the processing aids are zinc stearate and antioxidant 1010, and the other functional additives are expanded graphite.

[0067] Example 2:

[0068] The difference between Example 2 and Example 1 lies only in the different weight parts of each component of the ceramizable polyolefin insulating layer 2. The ceramizable polyolefin insulating layer 2 comprises the following components in weight parts:

[0069]

[0070] Example 3:

[0071] The difference between Example 3 and Example 1 lies only in the different categories of each component of the ceramizable polyolefin insulating layer 2. In this example, for the components of the ceramizable polyolefin insulating layer 2, the matrix resin is polypropylene, the silicate filler is kaolin, the aluminate filler is spinel, the borate filler is aluminum borate, the flame retardant synergist is aluminum hydroxide, the crosslinking agent and the co-crosslinking agent are silane coupling agent KH-550, the processing aids are zinc stearate and antioxidant 1010, and the other functional additives are expanded graphite.

[0072] The ceramizable polyolefin insulating layers 2 prepared in Examples 1 to 3 were tested for insulation resistance in accordance with GB / T 1410 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials", and three conventional insulating materials, namely ordinary polyethylene, silicone rubber, and ceramizable silicone rubber, were selected as Comparative Example 1, Comparative Example 2, and Comparative Example 3 respectively for testing. The test results are shown in Table 1. During the test, at a normal temperature of 23°C or a high temperature of 150°C, the humidity was controlled at 50RH. The insulating material samples to be tested were cut into a size of 100×100×2 mm 3 specification, placed in the electrode system, and after 24 hours of environmental pretreatment, a test voltage of 500V DC at atmospheric pressure or 1000V DC at high voltage was applied. After 1 minute of power-on to eliminate the polarization effect, a high resistance meter HP 4339B was used to directly read the volume resistivity and surface resistivity. When performing high temperature tests, the target temperature needed to be maintained in the constant temperature box for 30 minutes before measurement. Each group of samples was tested 3 times and the average value was taken to ensure the accuracy of the data.

[0073] Table 1

[0074]

[0075] Please refer to Table 1. The ceramizable polyolefin insulating layers 2 prepared in Examples 1 to 3 have higher resistivity compared with the conventional insulating materials in the comparative examples, and have better stability in high temperature environments. Among the comparative examples, the resistivity of ordinary polyethylene is lower than that of the ceramizable polyolefin insulating layer 2 prepared in the examples, and the resistivity drops significantly in high temperature environments, resulting in poor insulation performance. Although silicone rubber has good flexibility, its resistivity is relatively low, and the insulation performance of ceramizable silicone rubber is between that of silicone rubber and the ceramizable polyolefin insulating layer 2.

[0076] The cables prepared in Examples 1 to 3 and the cables made of conventional insulating materials in Comparative Examples 1 to 3 were subjected to a fire resistance test in accordance with the BS 6387 standard. Before the test, at least 1.2 m of the cable was fixed horizontally or vertically, the effective test section was 600 mm, the rated voltage was applied and a fault monitoring circuit was connected, and a combustion furnace, a water spraying system and an impact device were used. The test was divided into three categories: (1) Class C fire resistance test: the combustion furnace was heated to 950 °C and burned continuously for 3 hours, and the current continuity was monitored throughout the process; (2) Class W fire resistance + water spraying test: after burning at 650 for 15 minutes, water was sprayed synchronously for 15 minutes; (3) Class Z fire resistance + impact test: during the 15-minute burning at 950, a mechanical impact was applied every 30 seconds (3 times in total). When the current was not interrupted during all test stages (the fault circuit was not triggered) and the insulation resistance was ≥0.1 MΩ after the test, the test was considered to have passed; if the cable melted, the conductor 1 was exposed, the insulation carbonized and short-circuited, or the voltage dropped to zero, the test was considered to have failed. After the test, the cables prepared in Examples 1 to 3 passed the fire resistance test, while the cables prepared in Comparative Examples 1 to 3 did not pass the test.

[0077] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0078] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A ceramized polyolefin insulated fire-resistant cable, characterized in that, Comprising: A conductor; A ceramized polyolefin insulating layer, coated on the conductor, the material of the ceramized polyolefin insulating layer comprising a matrix resin and a ceramization aid, the ceramization aid being a mixture of a silicate filler, an aluminate filler and a borate filler, and the mass ratio of the silicate filler, the aluminate filler and the borate filler in the ceramization aid being 70 - 80:15 - 25:5 - 10; An outer sheath, coated on the ceramized polyolefin insulating layer.

2. The ceramifiable polyolefin insulated fire-resistant cable according to claim 1, characterized in that, The ceramized polyolefin insulating layer comprises the following components in parts by weight:

3. The ceramizable polyolefin insulated fire-resistant cable according to claim 2, wherein, The matrix resin is any one or more of polyethylene and polypropylene, the silicate filler is any one or more of mica powder, kaolin, talc powder, glass powder, wollastonite, the aluminate filler is any one or more of calcium aluminate, spinel, boehmite, and the borate filler is any one or more of zinc borate, borosilicate glass powder, aluminum borate.

4. The ceramifiable polyolefin insulated fire-resistant cable according to claim 3, characterized in that, The flame retardant synergist is any one or more of inorganic flame retardants and phosphorus-nitrogen based flame retardants, the crosslinking agent and the co-crosslinking agent are any one or more of peroxide crosslinking agents and silane coupling agents, the processing aid is any one or more of lubricants, antioxidants, plasticizers, and the other functional additives are any one or more of carbon fibers, glass fibers, and expanded graphite.

5. The ceramifiable polyolefin insulated fire-resistant cable according to claim 1, wherein, The outer sheath is any one of flame retardant polyvinyl chloride or low-smoke and halogen-free materials.

6. A method for preparing a ceramized polyolefin insulated fire-resistant cable according to any one of claims 1 to 5, characterized in that, Including the following steps: Mixing various components of the ceramized polyolefin insulating layer by a high-speed mixer; Extruding and molding the mixed material through a twin-screw extruder and coating it on the conductor to form a ceramized polyolefin insulating layer; Extruding an outer sheath outside the ceramized polyolefin insulating layer through a twin-screw extruder to complete the preparation of the cable.

7. The preparation method of the ceramized polyolefin insulated fire-resistant cable according to claim 6, characterized in that, The mixing of various components of the ceramized polyolefin insulating layer by a high-speed mixer includes the following steps: Putting the matrix resin and the processing aid into the high-speed mixer and mixing for 2 - 3 minutes; Adding the ceramization aid and the flame retardant synergist and mixing for 5 - 10 minutes within a temperature of 80°C; Finally adding the crosslinking agent and the co-crosslinking agent and mixing for 1 - 2 minutes for a short time.

8. The preparation method of the ceramifiable polyolefin insulated fire-resistant cable according to claim 6, characterized in that, Before mixing various components of the ceramized polyolefin insulating layer by a high-speed mixer, the following steps are included: Performing surface coupling modification treatment on the ceramization aid; Drying the flame retardant synergist.

9. The preparation method of the ceramifiable polyolefin insulated fire-resistant cable according to claim 6, wherein, The temperature range of the first zone of the twin-screw extruder is 120°C - 140°C, the temperature range of the second to third zones of the twin-screw extruder is 150°C - 170°C, the temperature range of the fourth to fifth zones of the twin-screw extruder is 160°C - 180°C, and the temperature range of the head of the twin-screw extruder is 170°C - 190°C.

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