Flexible mineral-insulated fire barrier cable

Abstract

The application discloses a kind of flexible mineral insulation isolation type fireproof cable, belong to fireproof cable processing technical field, for solving the technical problem that the surface of cable is prone to crack when bending in prior art fireproof cable, the flexibility and flame retardant performance of cable are poor, the mechanical strength of cable needs to be further improved, the present application includes filling strip and multiple cable cores wound outside the filling strip, the outside of multiple cable cores is provided with spiral-shaped covering aluminum cladding, the outside of aluminum cladding is covered with isolation layer, the outside of isolation layer is covered with oxygen barrier layer, the outside of oxygen barrier layer is covered with sheath layer, the present application not only effectively improves the flexibility of cable, facilitates bending during construction, further improves its flame retardant performance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of fire-resistant cable processing technology, specifically to a flexible mineral-insulated fire-resistant cable. Background Technology

[0002] With the development of society, higher requirements are being placed on the fire resistance of power cables. As an important energy and information transmission tool in modern society, cables can cause serious casualties and property damage in some high-fire-risk places, such as buildings and transportation facilities. Mineral insulation materials are widely used in power cables due to their good mechanical strength, insulation performance and flame-retardant and fire-resistant properties. Common mineral-insulated cables include rubber-impregnated magnetic powder insulated cables, aluminum silicate insulated cables, and magnesium silicate insulated cables.

[0003] Existing mineral-insulated cables typically use mineral insulating materials as the insulation layer, which have good insulation properties. However, their flexibility and flame retardant properties are poor, making it inconvenient to bend the cables during construction. In order to improve the flame retardant properties of the cables during the production process, halogen-free flame retardants are added to the cable material. However, the improvement of the flame retardant properties of cables by a single flame retardant is limited, and the flame retardant properties of cables need to be further improved. Furthermore, the flame retardant is mixed with the cable material through a material mixing method, resulting in a low degree of cross-linking between the flame retardant and the cable material. When bent, the cable surface is prone to cracking, and the mechanical strength of the cables needs to be further improved.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible mineral-insulated fireproof cable to address the technical deficiencies mentioned in the background art.

[0006] The objective of this invention can be achieved through the following technical solution: a flexible mineral-insulated fireproof cable, comprising a filler strip and multiple cable cores wound around the filler strip, wherein the multiple cable cores are provided with a spirally wrapped aluminum cladding, the aluminum cladding is covered with an insulating layer, the insulating layer is covered with an oxygen barrier layer, and the oxygen barrier layer is covered with a sheath layer.

[0007] The sheath layer is formed by the following steps:

[0008] Step 1: Add 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol, 4-p-chlorophenyl-1-butene, and N-methylpyrrolidone to a three-necked flask and stir until the system is dissolved. Add toluene and catalyst to the three-necked flask, raise the temperature of the three-necked flask to 140-150℃, and maintain the temperature for 4-6 hours. After post-processing, obtain intermediate I.

[0009] The principle of the synthesis reaction of intermediate I is as follows:

[0010]

[0011] Step 2: Add intermediate I, allyltriethoxysilane, polyethylene, 1-octene and N-methylpyrrolidone to a three-necked flask and stir until the system is dissolved. Then add an initiator to the three-necked flask, raise the temperature of the three-necked flask to 70-80℃, and keep the reaction at this temperature for 6-8 hours. Then lower the temperature of the three-necked flask to room temperature, add magnesium oxide dispersion to the three-necked flask, and keep the reaction at this temperature and stir for 2-3 hours. The post-treatment yields composite polyethylene.

[0012] The synthesis reaction principle of composite polyethylene is as follows:

[0013]

[0014] In the formula:

[0015]

[0016] Step 3: Add the composite polyethylene to the rollers of a plastic open mill at a temperature of 140-150℃, add the mixed additives, mix for 10-15 minutes, extrude the sheet, cool to room temperature, and granulate to obtain flexible mineral insulated cable material.

[0017] Step 4: Add the flexible mineral-insulated cable material into a twin-screw extruder, melt and extrude it, then coat it on the outside of the oxygen barrier layer, cool and shape it to form a coarse sheath layer with a thickness of 15-18mm on the outside of the oxygen barrier layer.

[0018] Step 5: Transfer the coarse sheath layer to a heating chamber, raise the temperature to 140-150℃, hot press for 5-8 minutes, and cool down to room temperature to form the sheath layer.

[0019] Furthermore, the cable core is made of several intertwined copper wires and an insulation layer covering the outside of the several copper wires, the insulation layer being extruded from rubber material;

[0020] The filler strip is a flame-retardant PP filler rope;

[0021] The isolation layer is made of PE material;

[0022] The oxygen barrier layer is formed by winding and covering a mica tape of model 5440-1 with a width of 35±1mm, and the thickness of the oxygen barrier layer is 5-7mm.

[0023] Furthermore, in step one, the ratio of 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol to 4-p-chlorophenyl-1-butene is 1 mol: 2 mol, the amount of N-methylpyrrolidone is 4 times the weight of 4-p-chlorophenyl-1-butene, the amount of toluene is 0.6 times the amount of N-methylpyrrolidone, the catalyst is potassium carbonate, and the amount of potassium carbonate is 1.5 times the weight of 4-p-chlorophenyl-1-butene. The post-treatment operation includes: after the reaction is complete, the temperature of the three-necked flask is lowered to room temperature, purified water is slowly added to the three-necked flask, stirred for 30-50 min, filtered, the filter cake is washed with purified water until neutral, and then transferred to a drying oven at a temperature of 75-85℃ and dried to constant weight to obtain intermediate I.

[0024] Furthermore, the preparation method of the magnesium oxide dispersion in step two is as follows: add nano magnesium oxide, 10wt% ammonia water and sodium dodecylbenzenesulfonate into a beaker at a ratio of 5g:20mL:1g, and ultrasonically disperse for 50-70min to obtain the magnesium oxide dispersion.

[0025] Furthermore, in step two, the ratio of intermediate I, allyltriethoxysilane, polyethylene, 1-octene, initiator, and N-methylpyrrolidone and magnesium oxide dispersion is 3g:2g:8g:4g:0.5g:60g:25g. The initiator is azobisisobutyronitrile. The post-treatment operation includes: after the reaction is complete, adding ethanol to a three-necked flask, stirring for 20-30 minutes, filtering, washing the filter cake three times with purified water and anhydrous ethanol, drying it under vacuum, transferring the filter cake to a drying oven at 70-80℃ and drying it to constant weight to obtain composite polyethylene.

[0026] Furthermore, in step three, the ratio of composite polyethylene to mixed additives is 11g:5g.

[0027] Furthermore, the mixed additive in step three consists of ammonium polyphosphate, pentaerythritol, polyvinyl alcohol, montmorillonite, and tetraethyl orthosilicate in a dosage ratio of 7g:2g:1g:2g:15g.

[0028] The present invention has the following beneficial effects:

[0029] 1. The flexible mineral-insulated fireproof cable of the present invention, in its manufacturing process, involves twisting multiple strands of fine copper wire together, then covering the outside of the fine copper wires with an insulating layer of rubber material to obtain the cable core. The cable core is then spirally wound around a flame-retardant filler strip. Using corrugated aluminum as the raw material, a spiral wrapping process is used to form an aluminum cladding layer. PE material is extruded and then wrapped around the aluminum cladding layer to form an insulating layer. Finally, mica tape is wound around the outside of the insulating layer to form an oxygen barrier layer. The flame-retardant PP filler rope contains flame retardant and glass fiber. The mica tape itself is made from mica, a naturally layered mineral. The cable boasts excellent fire resistance. Its main component, aluminum cladding, is alumina, which exhibits good high-temperature resistance. In combustion environments, the alumina and mica tape layers on the aluminum cladding work together to enhance the overall flame-retardant properties of the cable material. Both the aluminum cladding and the oxygen barrier are arranged in a layered structure, which prevents crack propagation during bending, thus increasing bending performance. The inter-strand cable cores effectively reduce the forces between them, making them a relatively complete unit. This prevents the cable cores from shifting during bending, which could damage the structure of the aluminum cladding and oxygen barrier, facilitating cable processing and improving the yield rate.

[0030] 2. In the preparation process of the flexible mineral-insulated fireproof cable of the present invention, 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol and 4-p-chlorophenyl-1-butene undergo a substitution addition reaction in a catalytic environment, where the silanol on 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol reacts with the halogen on 4-p-chlorophenyl-1-butene to prepare intermediate I with diolefin end-capping. Intermediate I reacts with allyltriethoxysilane, polyethylene, and 1-octene in the presence of an initiator via free radical polymerization to generate a polyolefin. After the reaction is complete, in an alkaline environment, the siloxane bond on allyltriethoxysilane breaks and binds to the active functional groups on the surface of nano-magnesium oxide. The reaction of energy groups generates composite polyolefins; 1-octene doping forms long-branched structures in the composite polyolefins, making it easier for the molecules of the composite polyolefins to crosslink; through the double-terminated olefins on intermediate I, a three-dimensional network crosslinked structure is formed in the linear polyolefin during the preparation of composite polyethylene, with intermediate I and magnesium oxide as bridges, which improves the degree of crosslinking of the composite polyolefin, thereby improving the tensile strength and stiffness of the composite polyolefin; the introduction of siloxane segments into intermediate I increases the flexibility of the composite polyethylene in terms of molecular structure, thereby improving its flexibility and ductility, making the material more able to withstand bending and deformation without breaking, and the siloxane segments have good oxidation resistance, and siloxane modification can slow down the aging rate of composite polyethylene and increase its service life.

[0031] 3. In the preparation process of the flexible mineral-insulated fireproof cable of the present invention, the composite additives and composite polyethylene are mixed by a compounding method. Tetraethyl orthosilicate is used as a lubricant and crosslinking agent to promote the uniform dispersion of ammonium polyphosphate, pentaerythritol, polyvinyl alcohol, and montmorillonite in the composite polyethylene. Simultaneously, under heating conditions, the siloxane bonds on the tetraethyl orthosilicate break, forming silanol and ethanol molecules. The silanol molecules can react with the active functional groups on the composite polyolefin, ammonium polyphosphate, pentaerythritol, polyvinyl alcohol, or montmorillonite, promoting intermolecular crosslinking and increasing the crosslinking degree between the mixed additives and the flexible mineral-insulated cable material. After the flexible mineral-insulated cable material is melt-extruded and coated onto the outside of the oxygen barrier layer, it undergoes hot pressing treatment to improve the crystallinity of the sheath layer, further enhancing the high-temperature resistance of the sheath layer. Temperature and mechanical properties; Ammonium polyphosphate is a commonly used nitrogen-phosphorus flame retardant that can inhibit flame propagation by forming a phosphorus oxide layer. Pentaerythritol is a charring agent that can promote the formation of a char layer when the material is heated, reducing the combustion rate. Polyvinyl alcohol may decompose to produce gas when heated, forming a gas barrier layer that reduces flame contact and combustion. Montmorillonite is an adsorbent material that may adsorb and stabilize other additives, helping to control the release and distribution of flame retardant components. By adjusting the composition ratio of ammonium polyphosphate, pentaerythritol, polyvinyl alcohol, and montmorillonite in the mixed additives, a char layer can be formed on the cable sheath during combustion, blocking oxygen while releasing non-flammable gases, forming a gas barrier on the outside of the cable, delaying combustion, and enhancing the flame retardant effect. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a cross-sectional structural diagram of the flexible mineral-insulated fireproof cable of the present invention.

[0034] In the diagram: 100, cable core; 101, copper wire; 102, insulation layer; 200, filler strip; 300, aluminum cladding; 400, isolation layer; 500, oxygen barrier layer; 600, sheath layer. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] Please see Figure 1 This embodiment describes a flexible mineral-insulated fire-resistant cable.

[0038] S1. Preparation of cable core

[0039] Several copper wires 101 with a diameter of 1.38 mm are twisted together to form a tightly bonded strand. An insulation layer 102 made of rubber material is then wrapped around the outside of the stranded wire to obtain the cable core 100.

[0040] S2, aluminum cladding, isolation layer and oxygen barrier layer coating molding

[0041] The brand name is Haoxinyuan, and the model is No. 9 flame-retardant PP filling rope, which is selected as the filling strip 200;

[0042] Multiple cable cores 100 are wound around the outside of the filler strip 200, and an aluminum cladding layer 300 is formed by using strip-shaped corrugated aluminum material to cover the outside of the multiple cable cores 100 in a spiral wrapping manner.

[0043] PE material is extruded onto the outside of the aluminum cladding 300 to form an isolation layer 400;

[0044] Select a mica tape of model 5440-1 with a width of 35±1mm and wrap it around the outside of the isolation layer 400 to form an oxygen barrier layer 500 with a thickness of 5-7mm.

[0045] S3. Preparation of composite polyethylene

[0046] Weigh out 166.3 g of 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol, 333.2 g of 4-p-chlorophenyl-1-butene, and 1332.8 g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 199.9 g of toluene and 499.8 g of potassium carbonate to the three-necked flask. Raise the temperature of the three-necked flask to 140 °C and keep it at that temperature for 4 h. Lower the temperature of the three-necked flask to room temperature and slowly add 1332.8 g of purified water to the three-necked flask. Stir for 30 min, filter, wash the filter cake with purified water until neutral, and then transfer it to a drying oven at 75 °C and dry it to constant weight to obtain intermediate I.

[0047] Nano magnesium oxide, 10wt% ammonia and sodium dodecylbenzenesulfonate were added to a beaker at a ratio of 5g:20mL:1g and ultrasonically dispersed for 50min to obtain magnesium oxide dispersion.

[0048] Weigh out 60g of intermediate I, 40g of allyltriethoxysilane, 160g of polyethylene, 80g of 1-octene, and 1200g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 10g of azobisisobutyronitrile to the three-necked flask. Raise the temperature of the three-necked flask to 70℃ and keep it at this temperature for 6 hours. Lower the temperature of the three-necked flask to room temperature and add 500g of magnesium oxide dispersion. Keep it at this temperature and stir for 2 hours. Add 700mL of ethanol to the three-necked flask and stir for 20 minutes. Filter the mixture. Wash the filter cake three times with purified water and anhydrous ethanol, and then dry it under vacuum. Transfer the filter cake to a drying oven at 70℃ and dry it to constant weight to obtain composite polyethylene.

[0049] S4. Preparation of flexible mineral-insulated cable material

[0050] Weigh out 140g of ammonium polyphosphate, 40g of pentaerythritol, 20g of polyvinyl alcohol, 40g of montmorillonite, and 300g of tetraethyl orthosilicate, add them to a beaker and mix well to obtain a mixed additive.

[0051] Weigh 1.1 kg of composite polyethylene and add it to the upper roller of a plastic open mill at a temperature of 140℃. Add 0.5 kg of mixed additives, mix for 10 min, extrude into sheets, cool to room temperature, and granulate to obtain flexible mineral insulated cable material.

[0052] S5, Sheath layer forming

[0053] Flexible mineral-insulated cable material is added to a twin-screw extruder, melt-extruded, and then coated on the outside of the oxygen barrier layer 500. After cooling and molding, a coarse sheath layer with a thickness of 15-18mm is formed on the outside of the oxygen barrier layer 500.

[0054] The cable containing the sheath layer is transferred to a heating box, where the temperature is raised to 140°C, hot-pressed for 5 minutes, and then cooled to room temperature, forming a sheath layer of 600 on the outside of the cable.

[0055] Example 2

[0056] Please see Figure 1 This embodiment describes a flexible mineral-insulated fire-resistant cable.

[0057] S1. Preparation of cable core

[0058] Several copper wires 101 with a diameter of 1.38 mm are twisted together to form a tightly bonded strand. An insulation layer 102 made of rubber material is then wrapped around the outside of the stranded wire to obtain the cable core 100.

[0059] S2, aluminum cladding, isolation layer and oxygen barrier layer coating molding

[0060] The brand name is Haoxinyuan, and the model is No. 9 flame-retardant PP filling rope, which is selected as the filling strip 200;

[0061] Multiple cable cores 100 are wound around the outside of the filler strip 200, and an aluminum cladding layer 300 is formed by using strip-shaped corrugated aluminum material to cover the outside of the multiple cable cores 100 in a spiral wrapping manner.

[0062] PE material is extruded onto the outside of the aluminum cladding 300 to form an isolation layer 400;

[0063] Select a mica tape of model 5440-1 with a width of 35±1mm and wrap it around the outside of the isolation layer 400 to form an oxygen barrier layer 500 with a thickness of 5-7mm.

[0064] S3. Preparation of composite polyethylene

[0065] Weigh out 166.3 g of 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol, 333.2 g of 4-p-chlorophenyl-1-butene, and 1332.8 g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 199.9 g of toluene and 499.8 g of potassium carbonate to the three-necked flask. Raise the temperature of the three-necked flask to 145 °C and keep it at that temperature for 5 h. Lower the temperature of the three-necked flask to room temperature and slowly add 1332.8 g of purified water to the three-necked flask. Stir for 40 min, filter, wash the filter cake with purified water until neutral, and then transfer it to a drying oven at 80 °C and dry it to constant weight to obtain intermediate I.

[0066] Nano magnesium oxide, 10wt% ammonia and sodium dodecylbenzenesulfonate were added to a beaker at a ratio of 5g:20mL:1g and ultrasonically dispersed for 60min to obtain magnesium oxide dispersion.

[0067] Weigh out 60g of intermediate I, 40g of allyltriethoxysilane, 160g of polyethylene, 80g of 1-octene, and 1200g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 10g of azobisisobutyronitrile to the three-necked flask. Raise the temperature of the three-necked flask to 75℃ and keep it at this temperature for 7h. Lower the temperature of the three-necked flask to room temperature and add 500g of magnesium oxide dispersion. Keep it at this temperature and stir for 2.5h. Add 700mL of ethanol to the three-necked flask and stir for 25min. Filter the mixture. Wash the filter cake three times with purified water and anhydrous ethanol, and then dry it under vacuum. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight to obtain composite polyethylene.

[0068] S4. Preparation of flexible mineral-insulated cable material

[0069] Weigh out 140g of ammonium polyphosphate, 40g of pentaerythritol, 20g of polyvinyl alcohol, 40g of montmorillonite, and 300g of tetraethyl orthosilicate, add them to a beaker and mix well to obtain a mixed additive.

[0070] Weigh out 1.1 kg of composite polyethylene and add it to the upper roller of a plastic open mill at a temperature of 145℃. Add 0.5 kg of mixed additives, mix for 13 min, extrude into sheets, cool to room temperature, and granulate to obtain flexible mineral insulated cable material.

[0071] S5, Sheath layer forming

[0072] Flexible mineral-insulated cable material is added to a twin-screw extruder, melt-extruded, and then coated on the outside of the oxygen barrier layer 500. After cooling and molding, a coarse sheath layer with a thickness of 15-18mm is formed on the outside of the oxygen barrier layer 500.

[0073] The cable containing the sheath layer is transferred to a heating box, where the temperature is raised to 145°C, hot-pressed for 7 minutes, and then cooled to room temperature, forming a sheath layer of 600 on the outside of the cable.

[0074] Example 3

[0075] Please see Figure 1 This embodiment describes a flexible mineral-insulated fire-resistant cable.

[0076] S1. Preparation of cable core

[0077] Several copper wires 101 with a diameter of 1.38 mm are twisted together to form a tightly bonded strand. An insulation layer 102 made of rubber material is then wrapped around the outside of the stranded wire to obtain the cable core 100.

[0078] S2, aluminum cladding, isolation layer and oxygen barrier layer coating molding

[0079] The brand name is Haoxinyuan, and the model is No. 9 flame-retardant PP filling rope, which is selected as the filling strip 200;

[0080] Multiple cable cores 100 are wound around the outside of the filler strip 200, and an aluminum cladding layer 300 is formed by using strip-shaped corrugated aluminum material to cover the outside of the multiple cable cores 100 in a spiral wrapping manner.

[0081] PE material is extruded onto the outside of the aluminum cladding 300 to form an isolation layer 400;

[0082] Select a mica tape of model 5440-1 with a width of 35±1mm and wrap it around the outside of the isolation layer 400 to form an oxygen barrier layer 500 with a thickness of 5-7mm.

[0083] S3. Preparation of composite polyethylene

[0084] Weigh out 166.3 g of 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol, 333.2 g of 4-p-chlorophenyl-1-butene, and 1332.8 g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 199.9 g of toluene and 499.8 g of potassium carbonate to the three-necked flask. Raise the temperature of the three-necked flask to 150 °C and keep it at that temperature for 6 h. Lower the temperature of the three-necked flask to room temperature and slowly add 1332.8 g of purified water to the three-necked flask. Stir for 50 min, filter, wash the filter cake with purified water until neutral, and then transfer it to a drying oven at 85 °C and dry it to constant weight to obtain intermediate I.

[0085] Nano magnesium oxide, 10wt% ammonia and sodium dodecylbenzenesulfonate were added to a beaker at a ratio of 5g:20mL:1g and ultrasonically dispersed for 70min to obtain magnesium oxide dispersion.

[0086] Weigh out 60g of intermediate I, 40g of allyltriethoxysilane, 160g of polyethylene, 80g of 1-octene, and 1200g of N-methylpyrrolidone and add them to a three-necked flask. Stir until the system is dissolved. Add 10g of azobisisobutyronitrile to the three-necked flask. Raise the temperature of the three-necked flask to 80℃ and keep it at this temperature for 8 hours. Lower the temperature of the three-necked flask to room temperature and add 500g of magnesium oxide dispersion. Keep it at this temperature and stir for 3 hours. Add 700mL of ethanol to the three-necked flask and stir for 30 minutes. Filter the mixture. Wash the filter cake three times with purified water and anhydrous ethanol, and then dry it under vacuum. Transfer the filter cake to a drying oven at 80℃ and dry it to constant weight to obtain composite polyethylene.

[0087] S4. Preparation of flexible mineral-insulated cable material

[0088] Weigh out 140g of ammonium polyphosphate, 40g of pentaerythritol, 20g of polyvinyl alcohol, 40g of montmorillonite, and 300g of tetraethyl orthosilicate, add them to a beaker and mix well to obtain a mixed additive.

[0089] Weigh 1.1 kg of composite polyethylene and add it to the upper roller of a plastic open mill at a temperature of 150℃. Add 0.5 kg of mixed additives, mix for 15 min, extrude into sheets, cool to room temperature, and granulate to obtain flexible mineral insulated cable material.

[0090] S5, Sheath layer forming

[0091] Flexible mineral-insulated cable material is added to a twin-screw extruder, melt-extruded, and then coated on the outside of the oxygen barrier layer 500. After cooling and molding, a coarse sheath layer with a thickness of 15-18mm is formed on the outside of the oxygen barrier layer 500.

[0092] The cable containing the sheath layer is transferred to a heating box, where the temperature is raised to 150°C, hot-pressed for 8 minutes, and then cooled to room temperature, forming a sheath layer of 600 on the outside of the cable.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 is that intermediate I was not added in step S3 when preparing the composite polyethylene.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 2 is that the mixed additive prepared in step S4 is obtained by adding 140g of ammonium polyphosphate, 40g of pentaerythritol, and 300g of tetraethyl orthosilicate into a beaker and mixing them evenly.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 1 is that the crude sheath product prepared in step S5 is used as the sheath layer.

[0099] Performance testing:

[0100] The flexibility, mechanical properties, and flame retardant properties of the cables prepared in Examples 1-3 and Comparative Examples 1-3 were tested. For flexibility, the bending wheel diameter of the sample was determined according to standard DB13 / T 2476-2017 "Specification for Flexible Copper Core Mineral Insulated Fire-Resistant Cables with Rated Voltage of 0.6 / 1KV". For mechanical properties, the elongation at break and tensile strength of the sample were determined according to standard GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods - Thickness and Dimensional Measurements - Mechanical Properties Tests". For flame retardant properties, the flame retardant level of the sample was determined according to standard XF 306.1-2007 "Flame-Retardant and Fire-Resistant Cables with Plastic Insulation - Classification and Requirements - Part 1: Flame-Retardant Cables". Specific test results are shown in the table below:

[0101]

[0102] Data Analysis:

[0103] This invention, through comparative analysis of the data in the table above, shows that introducing intermediate I with diene end-capping can effectively improve the flexibility, mechanical properties, and flame retardant properties of the cable; optimizing the ratio of the mixed additives, by adding polyvinyl alcohol and montmorillonite to the mixed additives, can improve the flame retardant properties of the cable; hot-pressing the cable sheath layer can further improve the mechanical properties of the cable, but correspondingly, the flexibility of the cable decreases after hot-pressing.

[0104] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0105] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0106] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flexible mineral-insulated fire-resistant cable, comprising a filler strip (200) and multiple cable cores (100) wound around the filler strip (200), characterized in that, The multiple cable cores (100) are provided with a spiral-shaped aluminum cladding (300) on the outside, the aluminum cladding (300) is covered with an isolation layer (400), the isolation layer (400) is covered with an oxygen barrier layer (500), and the oxygen barrier layer (500) is covered with a sheath layer (600). The sheath layer (600) is formed by the following steps: Step 1: Add 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol, 4-p-chlorophenyl-1-butene, and N-methylpyrrolidone to a three-necked flask and stir until the system is dissolved. Add toluene and catalyst to the three-necked flask, raise the temperature of the three-necked flask to 140-150℃, and maintain the temperature for 4-6 hours. After post-processing, obtain intermediate I. Step 2: Add intermediate I, allyltriethoxysilane, polyethylene, 1-octene and N-methylpyrrolidone to a three-necked flask and stir until the system is dissolved. Then add an initiator to the three-necked flask, raise the temperature of the three-necked flask to 70-80℃, and keep the reaction at this temperature for 6-8 hours. Then lower the temperature of the three-necked flask to room temperature, add magnesium oxide dispersion to the three-necked flask, and keep the reaction at this temperature and stir for 2-3 hours. The post-treatment yields composite polyethylene. Step 3: Add the composite polyethylene to the upper roller of a plastic open mill at a temperature of 140-150℃, add the mixed additives, mix for 10-15 minutes, extrude into sheets, cool to room temperature, and granulate to obtain flexible mineral insulated cable material. The mixed additives are composed of ammonium polyphosphate, pentaerythritol, polyvinyl alcohol, montmorillonite, and tetraethyl orthosilicate in a dosage ratio of 7g:2g:1g:2g:15g. Step 4: Add the flexible mineral insulated cable material into the twin-screw extruder, melt and extrude it, then coat it on the outside of the oxygen barrier layer (500), cool and shape it, and form a coarse sheath layer with a thickness of 15-18mm on the outside of the oxygen barrier layer (500). Step 5: Transfer the coarse sheath layer to a heating chamber, raise the temperature to 140-150℃, hot press for 5-8 minutes, cool down to room temperature, and form the sheath layer (600).

2. The flexible mineral-insulated fire-resistant cable according to claim 1, characterized in that, The cable core (100) is made of several intertwined copper wires (101) and an insulation layer (102) covering the outside of the several copper wires (101), wherein the insulation layer (102) is extruded from rubber material. The filler strip (200) is a flame-retardant PP filler rope; The isolation layer (400) is made of PE material; The oxygen barrier layer (500) is formed by winding and covering a mica tape of model 5440-1 with a width of 35±1mm, and the thickness of the oxygen barrier layer is 5-7mm.

3. The flexible mineral-insulated fire-resistant cable according to claim 1, characterized in that, In step one, the ratio of 1,1,3,3,5,5,7,7-octamethyl-1,7-tetrasiloxanediol to 4-p-chlorophenyl-1-butene is 1 mol: 2 mol. The amount of N-methylpyrrolidone is 4 times the weight of 4-p-chlorophenyl-1-butene. The amount of toluene is 0.6 times the amount of N-methylpyrrolidone. The catalyst is potassium carbonate, and its amount is 1.5 times the weight of 4-p-chlorophenyl-1-butene. The post-processing operation in step one includes: after the reaction is complete, the temperature of the three-necked flask is lowered to room temperature, purified water is slowly added to the three-necked flask, stirred for 30-50 min, filtered, the filter cake is washed with purified water until neutral, and then transferred to a drying oven at 75-85℃ and dried to constant weight to obtain intermediate I.

4. The flexible mineral-insulated fire-resistant cable according to claim 1, characterized in that, The preparation method of magnesium oxide dispersion in step two is as follows: add nano magnesium oxide, 10wt% ammonia water and sodium dodecylbenzenesulfonate into a beaker at a ratio of 5g:20mL:1g, and ultrasonically disperse for 50-70min to obtain magnesium oxide dispersion.

5. A flexible mineral-insulated fire-resistant cable according to claim 1, characterized in that, In step two, the ratio of intermediate I, allyltriethoxysilane, polyethylene, 1-octene, initiator, and N-methylpyrrolidone and magnesium oxide dispersion is 3g:2g:8g:4g:0.5g:60g:25g. The initiator is azobisisobutyronitrile. The post-processing operation in step two includes: after the reaction is complete, ethanol is added to a three-necked flask, stirred for 20-30 minutes, filtered, and the filter cake is washed three times with purified water and anhydrous ethanol in sequence and then dried. The filter cake is transferred to a drying oven at a temperature of 70-80℃ and dried to constant weight to obtain composite polyethylene.

6. A flexible mineral-insulated fire-resistant cable according to claim 1, characterized in that, In step three, the ratio of composite polyethylene to mixed additives is 11g:5g.

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