Fire-resistant cable protective sleeve material, preparation method thereof and fire-resistant cable

Abstract

The invention relates to the technical field of cables, in particular to a fire-resistant cable protection sleeve material, a preparation method of the fire-resistant cable protection sleeve material and a fire-resistant cable. 25 to 40 parts of a flame retardant; 10 to 20 parts of high-temperature-resistant filler; 3-8 parts of a plasticizer; 0.5 to 2 parts of an antioxidant; and 1-3 parts of a coupling agent. According to the embodiment of the invention, through the synergistic effect of the ethylene-vinyl acetate copolymer, the low-density polyethylene and the regenerated rubber, the flexibility and the mechanical strength of the material are remarkably enhanced; novel flame retardants such as boron nitride nanotubes, bio-based iron phytate and nano aluminum hydroxide are used and matched with a temperature-sensitive polymer, so that efficient and environment-friendly flame retardance is realized; meanwhile, the high-temperature-resistant filler is introduced, so that the fire-resistant temperature and the stability of the material are greatly improved. Therefore, the problems of low flame retardant efficiency, no environmental protection, contradiction between mechanical properties and high temperature resistance, performance reduction caused by addition of regenerated materials, poor processing technology compatibility, high cost and the like in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and particularly relates to a refractory cable sheath material, a preparation method thereof, and a refractory cable. Background Art

[0002] As an important part of cables, the performance of cable sheaths directly affects the fire resistance performance of cables. Existing refractory cable sheath materials have some deficiencies in practical applications. For example, the fire resistance performance of some sheath materials is limited, and they are prone to decomposition and deformation in high-temperature environments, unable to maintain the normal operation of cables for a long time; some sheath materials have low mechanical strength and are easily damaged by external forces during installation and use, resulting in a decline in the insulation performance of cables; there are also some sheath materials with complex processing processes and high costs, which are not conducive to large-scale popularization and application. Summary of the Invention

[0003] The present application provides a refractory cable sheath material, a preparation method thereof, and a refractory cable to solve the problems of low flame retardancy efficiency, environmental unfriendliness, contradiction between mechanical properties and high-temperature resistance performance, performance decline caused by the addition of recycled materials, poor processing process compatibility, and high costs in the prior art.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a refractory cable sheath material, and the sheath material comprises the following components by weight: Matrix resin: 40 - 60 parts; Flame retardant: 25 - 40 parts; High-temperature resistant filler: 10 - 20 parts; Plasticizer: 3 - 8 parts; Antioxidant: 0.5 - 2 parts; Coupling agent: 1 - 3 parts; Among them, the flame retardant comprises the following components by weight: Boron nitride nanotubes: 5 - 8 parts; Mica powder: 10 - 15 parts; Bio-based iron phytate: 8 - 12 parts; Thermosensitive polymer: 3 - 5 parts; Nanometer aluminum hydroxide: 20 - 30 parts; Among them, the bio-based iron phytate is prepared by mixing phytate extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.2 - 1:1.5; The thermosensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.3 - 1:0.5 and adding an initiator.

[0005] It should be noted that the preparation method of bio-based ferric phytate includes: preparing the phytate extracted from biomass into an aqueous solution with a concentration of 15-20 wt%, mixing it with ferrous sulfate heptahydrate under nitrogen protection in a molar ratio of phytate to ferrous sulfate heptahydrate of 1:1.2 - 1:1.5, stirring and reacting at 40-50 °C and 200-300 rpm for 2-3 hours; after the reaction mixture is concentrated under reduced pressure at 80-90 °C until the solid content is ≥80%, then vacuum dried at 60-70 °C for 12-15 hours, and ground through an 80-100 mesh sieve to obtain bio-based ferric phytate; The preparation method of the thermosensitive polymer includes: adding polyvinyl butyral to N,N-dimethylformamide, stirring and dissolving it at 60-70 °C to obtain a polyvinyl butyral solution with a mass fraction of 10-15%; adding N-isopropylacrylamide to the polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.3 - 1:0.5; then adding an initiator, under nitrogen protection, heating the reaction system to 70-80 °C, stirring and reacting at a speed of 150-200 rpm for 4-6 hours to carry out graft polymerization reaction; after the reaction is completed, washing and dehydrating to obtain the thermosensitive polymer; Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 0.5%-1% of the mass of N-isopropylacrylamide.

[0006] Furthermore, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 50-60 parts; Low-density polyethylene: 20-30 parts; Recycled rubber: 5-20 parts.

[0007] Furthermore, the purity of the boron nitride nanotubes is 95%, and the phase transition temperature of the thermosensitive polymer is 80-100 °C.

[0008] Furthermore, the high-temperature resistant filler includes the following components by weight: Transition metal nitride: 50-70 parts; Zinc borate: 20-30 parts; Nanoscale silicon carbide: 10-20 parts; Fumed silica: 5-10 parts.

[0009] Furthermore, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0010] Furthermore, the plasticizer is composed of triphenyl phosphate, epoxidized soybean oil and adipic acid polyester in a mass ratio of 2:2:1.

[0011] Furthermore, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0012] The present application also provides a method for preparing a refractory cable sheath material, which is characterized by including the following steps: S1. Pretreat the raw materials. Among them, the pretreatment includes modifying the flame retardant and high-temperature resistant filler and preparing the thermosensitive polymer. Among them, the modification treatment is to place boron nitride nanotubes, mica powder, nano-aluminum hydroxide, transition metal nitrides, nano-silicon carbide, and fumed silica in a vacuum drying oven, dry at 110-130°C for 2-4 hours, with a moisture content ≤ 0.1%. Add the dried flame retardant and high-temperature resistant filler to a high-speed mixer, spray silane coupling agent, and mix at 50-70°C for 12-16 minutes to complete surface modification; the preparation treatment is to vacuum dehydrate polyvinyl butyral grafted with thermosensitive groups at 40-60°C for 1-3 hours to avoid moisture absorption during processing; S2. Blend the raw materials. Add ethylene-vinyl acetate copolymer, low-density polyethylene, and recycled rubber to a mixer, heat up to 110-130°C and premix for 4-6 minutes; then add triphenyl phosphate, epoxy soybean oil, and adipic acid polyester in the plasticizer, and antioxidant 1010, and continue to knead for 2-4 minutes; at the same time, add the modified flame retardant and high-temperature resistant filler in stages; control the kneading temperature at 140-150°C, the rotation speed at 40-60 rpm, and dynamically vulcanize for 10-20 minutes in the atmosphere of a peroxide vulcanization system to form a micro-crosslinked network; then add the thermosensitive polymer to the mixer, cool down to 70-90°C, and knead at a low speed for 4-6 minutes to obtain a mixture; S3. Extrude and pelletize the mixture. Use a co-rotating twin-screw extruder, set the temperature gradient, where zone 1 is 150-160°C, zone 2 is 160-170°C, zone 3 is 170-175°C, zone 4 is 175-180°C, and the die head is 170°C; after melting and extruding, cool and pelletize with water to prepare sheath material pellets with a particle size of 3-5 mm; S4. Feed the sheath material pellets into a double-layer co-extrusion extruder, where the inner layer extrusion temperature is 160-170°C; the outer layer extrusion temperature is 160-170°C to form a sheath with a thickness of 1.5-3.0 mm.

[0013] The present application also provides a refractory cable, which includes a conductor, an insulating layer, a refractory mica tape wrapping layer, a metal shielding layer arranged in sequence from inside to outside, and an outer sheath made of the above-mentioned sheath material.

[0014] The beneficial effects obtained by adopting the above-mentioned invention of the present application are as follows: 1. The present invention prepares a refractory cable sheath material. The matrix resin composed of ethylene-vinyl acetate copolymer, low-density polyethylene and recycled rubber has a significant synergistic effect. Among them, the ethylene-vinyl acetate copolymer has good flexibility and processing performance, the low-density polyethylene provides rigidity and stability, and the macromolecular chains of the recycled rubber penetrate between the molecular chains of the ethylene-vinyl acetate copolymer and the low-density polyethylene, forming a stable network through physical entanglement and chemical crosslinking. This not only enhances the flexibility of the material, increasing the elongation at break to more than 280%, but also effectively improves the problem that the traditional single-polymer matrix is prone to brittle fracture at low temperatures. At the same time, due to the support of the network, the impact resistance and tensile strength of the material are greatly improved, meeting the requirements of mechanical strength in complex use environments. 2. The present application prepares a novel flame retardant. Among them, boron nitride nanotubes have extremely high thermal conductivity. When the material is heated, heat is quickly conducted and diffused through the boron nitride nanotubes, effectively reducing the surface temperature of the material and inhibiting local overheating. Secondly, the phosphorus element contained in bio-based ferric phytate pyrolyzes at high temperatures to generate phosphoric acid, and the phosphoric acid further dehydrates to form polyphosphoric acid with strong dehydrating effects, promoting the dehydration and carbonization of the matrix resin to form a carbonaceous layer with heat insulation and oxygen isolation functions. At the same time, iron ions can catalyze the carbonization reaction, improving the graphitization degree of the carbon layer and enhancing the stability and strength of the carbon layer. Bio-based ferric phytate synergizes with nano-aluminum hydroxide. The water vapor generated by the thermal decomposition absorbs a large amount of heat to reduce the system temperature while diluting the concentration of combustible gases, and cooperates with the catalytic carbonization effect of bio-based ferric phytate to inhibit combustion from both the gas phase and the condensed phase. Its combustion products are non-toxic and harmless. The thermosensitive polymer is polyvinyl butyral grafted with thermosensitive groups. At the phase transition temperature of 80 - 100 °C, its molecular structure changes, and the microcapsules rupture to release the encapsulated nano-aluminum hydroxide. When the temperature rises to the phase transition temperature during the normal operation of the cable, the thermosensitive polymer quickly releases nano-aluminum hydroxide, increasing the concentration of the flame retardant and strengthening the flame retardant effect, realizing preventive flame retardancy. Compared with traditional flame retardant systems, it can inhibit the occurrence and spread of fires at an earlier stage, significantly improving the flame retardant efficiency. 3. High-temperature resistant fillers are also added. Among them, titanium nitride in transition metal nitrides undergoes a solid-phase reaction with zinc borate to form a TiB 2 ceramic phase. TiB 2The ceramic phase has a high melting point, high hardness, and good chemical stability. It can form a strong ceramic barrier on the material surface, effectively blocking heat transfer and raising the refractory temperature of the material to over 1200°C. At the same time, the transition metal nitride itself has a relatively high thermal conductivity, which cooperates with the heat insulation performance of zinc borate to build an efficient heat conduction - heat insulation dual - function network inside the material, further improving the stability of the material at high temperatures. Secondly, nano - silicon carbide has high hardness, high thermal conductivity, and good chemical stability. On the one hand, it can fill the voids in the matrix resin, enhancing the denseness of the material and improving its mechanical strength. On the other hand, its high thermal conductivity helps the rapid conduction of heat inside the material, synergistically optimizing the thermal management performance of the material with the transition metal nitride. While ensuring the mechanical properties of the material, it significantly improves the high - temperature resistance performance and solves the contradiction between the two; 4. In addition, antioxidant 1010 can effectively inhibit the oxidative degradation of the material during long - term use and delay the aging process. At the same time, the strong interfacial interaction formed by fumed silica and the matrix resin enhances the denseness of the material and reduces the erosion of the internal structure of the material by external environmental factors such as water vapor and ultraviolet rays. This enables the cable protective sleeve to maintain its performance stability for a long time even in harsh outdoor environments, extends the service life of the cable, and reduces maintenance and replacement costs; 5. During the preparation process of the present invention, parameters such as temperature and rotation speed at each stage are precisely controlled, and combined with specific raw material pretreatment and blending methods, the material has good fluidity during processing. For example, in the extrusion granulation stage, by setting a temperature gradient, it is ensured that the material can be uniformly melted and extruded, and in the subsequent double - layer co - extrusion process, it can be stably coated outside the cable conductor. This not only improves production efficiency but also ensures the stability of product quality, reduces the defective rate, and lowers production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above - mentioned and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where: Figure 1 is a flow chart of the preparation method of the fire - resistant cable protective sleeve material provided in Embodiment 1 of the present invention; Figure 2 is a structural schematic diagram of a fire - resistant cable provided in an embodiment of the present invention; Figure 3 is a microscopic schematic diagram of the fire - resistant cable protective sleeve material provided in Embodiment 1 of the present invention; Figure 4 is a microscopic schematic diagram of the fire - resistant cable protective sleeve material provided in Embodiment 2 of the present invention; Figure 5 is a microscopic schematic diagram of the fire - resistant cable protective sleeve material provided in Embodiment 3 of the present invention; Figure 6 Microscopic diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention; Figure 7 Microscopic diagram of the fire-resistant cable sheath material provided in Embodiment 5 of the present invention Figure 8 EDS carbon composition analysis diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention; Figure 9 EDS hydrogen composition analysis diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention; Figure 10 EDS nitrogen composition analysis diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention; Figure 11 EDS titanium composition analysis diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention; Figure 12 EDS aluminum composition analysis diagram of the fire-resistant cable sheath material provided in Embodiment 4 of the present invention. Detailed implementation manners

[0016] The technical solutions of the present invention are illustrated below through specific specific examples. It should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination steps or the insertion of other method steps between these clearly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Moreover, unless otherwise specified, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0017] In order to better understand the above technical solutions, the exemplary embodiments of the present invention are described in more detail below. Although the exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0018] The following describes a fire-resistant cable sheath material, its preparation method, and a fire-resistant cable according to embodiments of the present application with reference to the accompanying drawings. In view of the problem of the contradiction between mechanical properties and high-temperature resistance mentioned in the above background art, the present application provides a fire-resistant cable sheath material. In this method, through the synergistic effect of ethylene-vinyl acetate copolymer, low-density polyethylene, and recycled rubber, the flexibility and mechanical strength of the material are significantly enhanced; new flame retardants such as boron nitride nanotubes, bio-based ferric phytate, and nano-aluminum hydroxide are used, and in combination with a temperature-sensitive polymer, efficient and environmentally friendly flame retardant performance is achieved; at the same time, high-temperature resistant fillers such as titanium nitride, nano-silicon carbide, and fumed silica are introduced, greatly improving the fire-resistant temperature and stability of the material. In addition, the addition of antioxidant 1010 and precise processing control ensure the stable performance of the material during long-term use and in harsh outdoor environments. Thus, the problems in the prior art such as low flame retardant efficiency, environmental unfriendliness, contradiction between mechanical properties and high-temperature resistance, performance degradation caused by the addition of recycled materials, poor processing technology compatibility, and high cost are solved.

[0019] The present invention will be further described in conjunction with the following embodiments.

[0020] Example 1 A fire-resistant cable sheath material, and the sheath material includes the following components by weight: Matrix resin: 40 parts; Flame retardant: 25 parts; High-temperature resistant filler: 10 parts; Plasticizer: 3 parts; Antioxidant: 0.5 part; Coupling agent: 1 part; Among them, the flame retardant includes the following components by weight: Boron nitride nanotubes: 5 parts; Mica powder: 10 parts; Bio-based ferric phytate: 8 parts; Temperature-sensitive polymer: 3 parts; Nano-aluminum hydroxide: 20 parts; Among them, bio-based ferric phytate is prepared by mixing phytate extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.2; the temperature-sensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.3 and adding an initiator.

[0021] Specifically, the preparation method of bio-based ferric phytate includes: preparing phytate extracted from biomass into a 15wt% aqueous solution, mixing it with ferrous sulfate heptahydrate in a molar ratio of 1:1.2 under nitrogen protection, stirring and reacting at 40°C and 200 rpm for 2 hours; after the reaction mixture is concentrated under reduced pressure at 80°C to a solid content of ≥80%, then vacuum dried at 60°C for 12 hours, ground through an 80-mesh sieve to obtain bio-based ferric phytate; The preparation method of the temperature-sensitive polymer includes: adding polyvinyl butyral to N,N-dimethylformamide, stirring and dissolving at 60 °C to obtain a 10% polyvinyl butyral solution by mass fraction; adding N-isopropylacrylamide to the above polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.3; then adding an initiator, under nitrogen protection, heating the reaction system to 70 °C, stirring and reacting at a speed of 150 rpm for 4 hours to carry out graft polymerization reaction; after the reaction is completed, washing and dehydrating to obtain the temperature-sensitive polymer.

[0022] Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 0.5% of the mass of N-isopropylacrylamide.

[0023] In the embodiment of the present application, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 50 parts; Low-density polyethylene: 20 parts; Recycled rubber: 5 parts.

[0024] Among them, the recycled rubber is ethylene propylene diene monomer recycled rubber.

[0025] Among them, the purity of the boron nitride nanotubes is 95%, and the phase transition temperature of the temperature-sensitive polymer is 80-100 °C.

[0026] In the embodiment of the present application, the high-temperature resistant filler includes the following components by weight: Transition metal nitride: 50 parts; Zinc borate: 20 parts; Nanoscale silicon carbide: 10 parts; Fumed silica: 5 parts.

[0027] Among them, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0028] Among them, the plasticizer is composed of triphenyl phosphate, epoxidized soybean oil and adipic acid polyester according to the mass ratio of 2:2:1.

[0029] Among them, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0030] The present application also proposes a preparation method of a refractory cable sheath material, as Figure 1 shown, including the following steps: S1. Pretreat the raw materials. The pretreatment includes modifying the flame retardant and high-temperature resistant filler and preparing the thermosensitive polymer. The modification treatment is to place boron nitride nanotubes, mica powder, nano-aluminum hydroxide, transition metal nitride, nano-silicon carbide, and fumed silica in a vacuum drying oven, dry at 120°C for 3 hours, with the moisture content ≤ 0.1%. Add the dried flame retardant and high-temperature resistant filler to a high-speed mixer, spray silane coupling agent, and mix at 60°C for 15 minutes to complete surface modification. The preparation treatment is to graft thermosensitive groups onto polyvinyl butyral and dehydrate it under vacuum at 50°C for 2 hours to avoid moisture absorption during processing. S2. Blend the raw materials. Add ethylene-vinyl acetate copolymer, low-density polyethylene, and recycled rubber to a mixer, heat up to 120°C and premix for 5 minutes. Then add triphenyl phosphate, epoxy soybean oil, and adipic acid polyester in the plasticizer, and antioxidant 1010, and continue mixing for 3 minutes. At the same time, add the modified flame retardant and high-temperature resistant filler in stages. Control the mixing temperature at 140 - 150°C, the rotation speed at 40 - 60 rpm, and dynamically vulcanize for 15 minutes in a peroxide vulcanization system atmosphere to form a micro-crosslinked network. Then add the thermosensitive polymer to the mixer, cool down to 80°C, and mix at low speed for 5 minutes to obtain a mixture. S3. Extrude and pelletize the mixture. Use a co-rotating twin-screw extruder, set the temperature gradient, where zone 1 is 150°C, zone 2 is 160°C, zone 3 is 170°C, zone 4 is 175°C, and the die head is 170°C. After melting and extruding, cool and pelletize with water to prepare protective sleeve material pellets with a particle size of 3 - 5 mm. S4. Feed the protective sleeve material pellets into a double-layer co-extrusion extruder, where the inner layer extrusion temperature is 170°C and the outer layer extrusion temperature is 160°C to form a protective sleeve with a thickness of 1.5 - 3.0 mm.

[0031] This application also proposes a fire-resistant cable, as Figure 2 shown, including a conductor, an insulating layer, a fire-resistant mica tape wrapping layer, a metal shielding layer, and an outer sheath made of the protective sleeve material, which are arranged in sequence from the inside to the outside.

[0032] Example 2 A fire-resistant cable protective sleeve material, and the protective sleeve material includes the following components by weight: Matrix resin: 45 parts; Flame retardant: 28 parts; High-temperature resistant filler: 12 parts; Plasticizer: 4 parts; Antioxidant: 0.8 part; Coupling agent: 1.5 parts; Among them, the flame retardant includes the following components by weight: Boron nitride nanotubes: 6 parts; Mica powder: 11 parts; Bio-based iron phytate: 9 parts; Thermosensitive polymer: 3.5 parts; Nanometer aluminum hydroxide: 22 parts; Among them, the bio-based iron phytate is prepared by mixing phytate extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.3; the thermosensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.4 and adding an initiator.

[0033] Specifically, the preparation method of the bio-based iron phytate includes: preparing the phytate extracted from biomass into a 16wt% aqueous solution, mixing it with ferrous sulfate heptahydrate in a molar ratio of 1:1.3 under nitrogen protection, and stirring and reacting at 42°C and 220 rpm for 2 hours; after the reaction mixture is concentrated under reduced pressure at 82°C until the solid content ≥ 80%, then vacuum dried at 62°C for 13 hours, ground through an 80-mesh sieve to obtain the bio-based iron phytate; The preparation method of the thermosensitive polymer includes: adding polyvinyl butyral to N,N-dimethylformamide, stirring and dissolving at 62°C to obtain a 11% polyvinyl butyral solution by mass; adding N-isopropylacrylamide to the above polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.4; then adding an initiator, under nitrogen protection, heating the reaction system to 72°C, stirring and reacting at a speed of 160 rpm for 5 hours to carry out graft polymerization reaction; after the reaction is completed, washing and dehydrating to obtain the thermosensitive polymer.

[0034] Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 0.6% of the mass of N-isopropylacrylamide.

[0035] In the embodiment of the present application, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 52 parts; Low-density polyethylene: 22 parts; Recycled rubber: 8 parts.

[0036] Among them, the recycled rubber is ethylene propylene diene monomer recycled rubber.

[0037] Among them, the purity of the boron nitride nanotubes is 95%, and the phase transition temperature of the thermosensitive polymer is 80 - 100°C.

[0038] In the embodiment of the present application, the high-temperature resistant filler includes the following components by weight: Transition metal nitride: 55 parts; Zinc borate: 22 parts; Nanometer silicon carbide: 12 parts; Fumed silica: 6 parts.

[0039] Among them, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0040] Among them, the plasticizer is composed of triphenyl phosphate, epoxy soybean oil and adipic acid polyester in a mass ratio of 2:2:1.

[0041] Among them, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0042] This application also provides a preparation process of a refractory cable sheath material. Among them, the preparation process is the same as that in Example 1.

[0043] Example 3 A refractory cable sheath material, the sheath material comprises the following components by weight: Matrix resin: 50 parts; Flame retardant: 32 parts; High temperature resistant filler: 15 parts; Plasticizer: 5 parts; Antioxidant: 1.2 parts; Coupling agent: 2 parts; Among them, the flame retardant comprises the following components by weight: Boron nitride nanotubes: 7 parts; Mica powder: 12 parts; Bio-based phytic acid iron: 10 parts; Thermosensitive polymer: 4 parts; Nano aluminum hydroxide: 25 parts; Among them, the bio-based phytic acid iron is prepared by mixing phytic acid extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.4; the thermosensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.4 and adding an initiator.

[0044] Specifically, the preparation method of the bio-based phytic acid iron includes: preparing phytic acid extracted from biomass into a 17wt% aqueous solution, mixing it with ferrous sulfate heptahydrate in a molar ratio of 1:1.4 under nitrogen protection, and stirring and reacting at 45°C and 250 rpm for 3 hours; after the reaction mixture is concentrated under reduced pressure at 85°C to a solid content ≥80%, then vacuum dried at 65°C for 14 hours, ground through an 80-mesh sieve to obtain bio-based phytic acid iron; The preparation method of the temperature-sensitive polymer includes: adding polyvinyl butyral into N,N-dimethylformamide, stirring and dissolving at 65 °C to obtain a polyvinyl butyral solution with a mass fraction of 13%; adding N-isopropylacrylamide into the above polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.4; then adding an initiator, under nitrogen protection, heating the reaction system to 75 °C, stirring and reacting at a speed of 170 rpm for 5 hours to carry out graft polymerization reaction; after the reaction is completed, washing and dehydrating to obtain the temperature-sensitive polymer.

[0045] Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 0.7% of the mass of N-isopropylacrylamide.

[0046] In the embodiment of the present application, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 55 parts; Low-density polyethylene: 25 parts; Recycled rubber: 12 parts.

[0047] Among them, the recycled rubber is ethylene propylene diene monomer recycled rubber.

[0048] Among them, the purity of boron nitride nanotubes is 95%, and the phase transition temperature of the temperature-sensitive polymer is 80-100 °C.

[0049] In the embodiment of the present application, the high-temperature resistant filler includes the following components by weight: Transition metal nitride: 60 parts; Zinc borate: 25 parts; Nanoscale silicon carbide: 15 parts; Fumed silica: 7 parts.

[0050] Among them, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0051] Among them, the plasticizer is composed of triphenyl phosphate, epoxy soybean oil and adipic acid polyester in a mass ratio of 2:2:1.

[0052] Among them, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0053] The present application also proposes a preparation process of a fire-resistant cable sheath material, wherein the preparation process is the same as that in Example 1.

[0054] Example 4 A fire-resistant cable sheath material, the sheath material includes the following components by weight: Matrix resin: 55 parts; Flame retardant: 37 parts; High-temperature resistant filler: 18 parts; Plasticizer: 7 parts; Antioxidant: 1.7 parts; Coupling agent: 2.5 parts; Among them, the flame retardant includes the following components by weight: Boron nitride nanotubes: 7 parts; Mica powder: 14 parts; Bio-based ferric phytate: 11 parts; Thermosensitive polymer: 4.5 parts; Nano aluminum hydroxide: 28 parts; Among them, the bio-based ferric phytate is prepared by mixing phytic acid extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.5; the thermosensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.5 and adding an initiator.

[0055] Specifically, the preparation method of the bio-based ferric phytate includes: preparing phytic acid extracted from biomass into a 19wt% aqueous solution, mixing it with ferrous sulfate heptahydrate in a molar ratio of 1:1.5 under nitrogen protection, and stirring and reacting at 48°C and 280 rpm for 3 hours; after the reaction mixture is concentrated under reduced pressure at 88°C to a solid content of ≥80%, then vacuum dried at 68°C for 14 hours, ground through an 80-mesh sieve to obtain the bio-based ferric phytate; The preparation method of the thermosensitive polymer includes: adding polyvinyl butyral to N,N-dimethylformamide and stirring to dissolve at 68°C to obtain a 14% polyvinyl butyral solution by mass; adding N-isopropylacrylamide to the above polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.5; then adding an initiator, under nitrogen protection, raising the temperature of the reaction system to 78°C, stirring and reacting at a speed of 180 rpm for 6 hours to carry out graft polymerization; after the reaction is completed, washing and dehydrating to obtain the thermosensitive polymer.

[0056] Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 0.8% of the mass of N-isopropylacrylamide.

[0057] In the embodiments of the present application, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 58 parts; Low-density polyethylene: 28 parts; Recycled rubber: 17 parts.

[0058] Among them, the recycled rubber is ethylene propylene diene monomer recycled rubber.

[0059] Among them, the purity of the boron nitride nanotubes is 95%, and the phase transition temperature of the thermosensitive polymer is 80-100°C.

[0060] In the embodiments of the present application, the high-temperature resistant filler comprises the following components by weight: Transition metal nitride: 65 parts; Zinc borate: 28 parts; Nanoscale silicon carbide: 18 parts; Fumed silica: 9 parts.

[0061] Among them, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0062] Among them, the plasticizer is composed of triphenyl phosphate, epoxy soybean oil and adipic acid polyester in a mass ratio of 2:2:1.

[0063] Among them, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0064] The present application also proposes a preparation process of a refractory cable sheath material, wherein the preparation process is the same as that in Example 1.

[0065] Example 5 A refractory cable sheath material, the sheath material comprises the following components by weight: Matrix resin: 60 parts; Flame retardant: 40 parts; High-temperature resistant filler: 20 parts; Plasticizer: 8 parts; Antioxidant: 2 parts; Coupling agent: 3 parts; Among them, the flame retardant comprises the following components by weight: Boron nitride nanotubes: 8 parts; Mica powder: 15 parts; Bio-based ferric phytate: 12 parts; Thermosensitive polymer: 5 parts; Nanoscale aluminum hydroxide: 30 parts; Among them, the bio-based ferric phytate is prepared by mixing phytate extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.5; the thermosensitive polymer is prepared by mixing polyvinyl butyral and N-isopropylacrylamide in a mass ratio of 1:0.5 and adding an initiator.

[0066] Specifically, the preparation method of the bio-based ferric phytate includes: preparing phytate extracted from biomass into a 20wt% aqueous solution, mixing it with ferrous sulfate heptahydrate in a molar ratio of 1:1.5 under nitrogen protection, stirring and reacting at 50°C and 300 rpm for 3 hours; after the reaction mixture is concentrated under reduced pressure at 90°C to a solid content of ≥80%, then vacuum drying at 70°C for 15 hours, grinding and passing through an 80-mesh sieve to obtain the bio-based ferric phytate; The preparation method of the temperature-sensitive polymer includes: adding polyvinyl butyral to N,N-dimethylformamide, stirring and dissolving at 70 °C to obtain a 15% polyvinyl butyral solution by mass fraction; adding N-isopropylacrylamide to the above polyvinyl butyral solution according to the mass ratio of polyvinyl butyral to N-isopropylacrylamide of 1:0.5; then adding an initiator, under nitrogen protection, heating the reaction system to 80 °C, stirring and reacting at a speed of 200 rpm for 6 hours to carry out graft polymerization reaction; after the reaction is completed, washing and dehydrating to obtain the temperature-sensitive polymer.

[0067] Among them, the initiator is azobisisobutyronitrile, and the dosage of the initiator is 1% of the mass of N-isopropylacrylamide.

[0068] In the embodiment of the present application, the matrix resin includes the following components by weight: Ethylene-vinyl acetate copolymer: 60 parts; Low-density polyethylene: 30 parts; Recycled rubber: 20 parts.

[0069] Among them, the recycled rubber is ethylene propylene diene monomer recycled rubber.

[0070] Among them, the purity of the boron nitride nanotubes is 95%, and the phase transition temperature of the temperature-sensitive polymer is 80-100 °C.

[0071] In the embodiment of the present application, the high-temperature resistant filler includes the following components by weight: Transition metal nitride: 70 parts; Zinc borate: 30 parts; Nanoscale silicon carbide: 20 parts; Fumed silica: 10 parts.

[0072] Among them, the transition metal nitride is one of titanium nitride and aluminum nitride.

[0073] Among them, the plasticizer is composed of triphenyl phosphate, epoxy soybean oil and adipic acid polyester in a mass ratio of 2:2:1.

[0074] Among them, the antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

[0075] The present application also proposes a preparation process of a fire-resistant cable sheath material, wherein the preparation process is the same as that in Example 1.

[0076] Comparative Example 1 A fire-resistant cable sheath material, which is different from that in Example 1 only in that recycled rubber is not added to the matrix resin, and the reduced amount of recycled rubber is evenly distributed to low-density polyethylene, and the other materials and preparation methods are the same as those in Example 1.

[0077] Comparative Example 2 A refractory cable sheath material, which is different from Example 1 only in that the flame retardant does not add bio-based ferric phytate and thermosensitive polymer, and the reduced amounts of bio-based ferric phytate and thermosensitive polymer are apportioned to mica powder. The remaining materials and preparation method are the same as those in Example 1.

[0078] Comparative Example 3 A refractory cable sheath material, which is different from Example 1 only in that the high-temperature resistant filler does not add transition metal nitride, and the reduced amount of transition metal nitride is apportioned to zinc borate. The remaining materials and preparation method are the same as those in Example 1.

[0079] Comparative Example 4 A refractory cable sheath material, which is different from Example 1 in that the matrix resin does not add recycled rubber, the flame retardant does not add bio-based ferric phytate and thermosensitive polymer, and the high-temperature resistant filler does not add transition metal nitride. The reduced amount of recycled rubber is apportioned to low-density polyethylene, the reduced amounts of bio-based ferric phytate and thermosensitive polymer are apportioned to mica powder, and the reduced amount of transition metal nitride is apportioned to zinc borate. The remaining materials and preparation method are the same as those in Example 1.

[0080] Performance Test According to GB / T528-2009 "Rubber, vulcanized or thermoplastic - Determination of tensile stress-strain properties", use an electronic universal testing machine for testing, and synchronously record the elongation at break during the tensile test; use a cantilever beam impact testing machine and conduct the test according to GB / T1043.1-2008 "Plastics - Determination of Charpy impact properties - Part 1: Non-instrumented impact test"; according to GB / T1408.1-2016 "Test method for electrical strength of insulating materials - Part 1: Tests at power frequency", place the specimen between the specified electrodes, raise the voltage at a specified rate until breakdown, and divide the breakdown voltage value by the specimen thickness to obtain the dielectric strength; place the samples of Examples 1-5 and Comparative Examples 1-4 in a high-temperature furnace, heat at a certain heating rate, and observe the temperature when obvious damage starts to occur. The results are shown in Table 1 below.

[0081] Table 1 Performance Test of Refractory Cable Sheath Materials

[0082] As Figures 3 - 7 shown in Table 1, the elongation at break, tensile strength, fire resistance temperature, impact resistance, dielectric strength and flame retardant effect of the refractory cable sheath materials in the examples of the present invention are significantly higher than those of the comparative examples, and the density is significantly improved, indicating that the refractory cable sheath materials of the present invention have excellent properties such as high elongation at break, tensile strength, fire resistance temperature, impact resistance, dielectric strength and flame retardant effect, and can achieve large-scale production at low cost.

[0083] As Figures 8 - 11 shown, in the refractory cable sheath material, elements such as carbon and hydrogen from the matrix resin, nitrogen from the flame retardant boron nitride nanotubes, and titanium and aluminum from the transition metal nitrides are detected. It can be observed whether components such as flame retardants and high-temperature resistant fillers are evenly dispersed in the matrix resin.

[0084] Using the preparation method of the refractory cable sheath material provided by the present invention, the elongation, tensile strength, refractory temperature, impact resistance, dielectric strength, and flame retardant effect of Example 4 are the best. Among them, the elongation reaches 308%, the tensile strength reaches 25 MPa, the refractory temperature reaches 1330 °C, the impact resistance reaches 17 kJ / m², the dielectric strength reaches 25 kV / mm, and the flame retardant effect is the best. It can be seen that the introduced materials need to be within a certain quantity, adding too much or too little will affect the performance; while the performance of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 is relatively poor and there is no obvious difference. Therefore, considering the comprehensive performance impact of the refractory cable sheath material, the refractory cable sheath material of the present invention can achieve strong tensile strength, improve excellent properties such as the thermal decomposition temperature, etc. under the conditions of environmental protection and low cost, while reducing the cost, and the preparation process is simple and operable.

[0085] The embodiments of the present application provide a refractory cable sheath material. In this method, through the synergistic effect of ethylene-vinyl acetate copolymer, low-density polyethylene, and recycled rubber, the flexibility and mechanical strength of the material are significantly enhanced; new flame retardants such as boron nitride nanotubes, bio-based ferric phytate, and nano-aluminum hydroxide are used, and in combination with temperature-sensitive polymers, efficient and environmentally friendly flame retardant performance is achieved; at the same time, high-temperature resistant fillers such as titanium nitride, nano-silicon carbide, and fumed silica are introduced, greatly improving the refractory temperature and stability of the material. In addition, the addition of antioxidant 1010 and precise processing control ensure the stable performance of the material during long-term use and in harsh outdoor environments. Thus, the problems in the prior art such as low flame retardant efficiency, non-environmental protection, contradiction between mechanical properties and high-temperature resistance, performance degradation caused by the addition of recycled materials, poor processing technology compatibility, and high cost are solved.

[0086] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A fire-resistant cable protective sheath material, characterized in that: The protective cover material comprises the following components by weight: Base resin: 40-60 parts; Flame retardant: 25-40 parts; High temperature resistant filler: 10-20 parts; Plasticizer: 3-8 parts; Antioxidant: 0.5-2 parts; Coupling agent: 1-3 parts; Wherein, the flame retardant comprises the following components by weight: Boron nitride nanotubes: 5-8 parts; Mica powder: 10-15 parts; Bio-based phytic iron: 8-12 parts; Thermosensitive polymer: 3-5 parts; Nano aluminum hydroxide: 20-30 parts; The bio-based phytic acid iron is prepared by mixing phytic acid extracted from biomass with ferrous sulfate heptahydrate in a molar ratio of 1:1.2-1:1.5; The temperature-sensitive polymer is prepared by mixing polyvinyl butyral and N-isopropyl acrylamide in a mass ratio of 1:0.3-1:0.5 and adding an initiator.

2. A fire-resistant cable protective sheath material according to claim 1, characterized in that: The base resin comprises the following components by weight: Ethylene-vinyl acetate copolymer: 50-60 parts; Low density polyethylene: 20-30 parts; Recycled rubber: 5-20 parts.

3. A fire-resistant cable protective sheath material according to claim 1, characterized in that: The purity of the boron nitride nanotubes is 95%.

4. A fire-resistant cable protective sheath material according to claim 1, characterized in that: The high temperature resistant filler comprises the following components by weight: Transition metal nitride: 50-70 parts; Zinc borate: 20-30 parts; Nano silicon carbide: 10-20 parts; Fumed silica: 5-10 parts.

5. A fire-resistant cable protective sheath material according to claim 4, characterized in that: The transition metal nitride is one of titanium nitride and aluminum nitride.

6. A fire-resistant cable protective sheath material according to claim 1, characterized in that: The plasticizer is composed of triphenyl phosphate, epoxy soybean oil and adipic acid polyester in a mass ratio of 2:2:

1.

7. A fire-resistant cable protective sheath material according to claim 1, characterized in that: The antioxidant is antioxidant 1010, and the coupling agent is silane coupling agent KH-550.

8. A method for preparing the fire-resistant cable protective sheath material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Pre-treat the raw materials, wherein the pre-treatment includes modifying the flame retardant and the high temperature resistant filler and preparing the temperature sensitive polymer, wherein the modification treatment is to place the boron nitride nanotubes, mica powder, nano aluminum hydroxide, transition metal nitride, nano silicon carbide, and fumed silica in a vacuum drying oven, and dry them at 110-130°C for 2-4 hours, with a moisture content of ≤0.1%, add the dried flame retardant and high temperature resistant filler into a high-speed mixer, spray silane coupling agent, and mix at 50-70°C for 12-16 minutes to complete the surface modification; the preparation treatment is to vacuum dehydrate the polyvinyl butyral grafted temperature sensitive group at 40-60°C for 1-3 hours to avoid moisture absorption during processing; S2, blending the raw materials, adding ethylene-vinyl acetate copolymer, low-density polyethylene, and recycled rubber into an internal mixer, heating to 110-130°C for premixing for 4-6 minutes; then adding triphenyl phosphate, epoxy soybean oil, adipic acid polyester, and antioxidant 1010 in the plasticizer, and continuing to mix for 2-4 minutes; at the same time, adding the modified flame retardant and high-temperature resistant filler in stages; controlling the internal mixing temperature to 140-150°C and the rotation speed to 40-60rpm, and dynamically vulcanizing for 10-20 minutes in the atmosphere of a peroxide vulcanization system to form a micro-crosslinked network; then adding the temperature-sensitive polymer into the internal mixer, cooling to 70-90°C, and mixing at a low speed for 4-6 minutes to obtain a mixture; S3, extruding the mixture into granules, using a co-rotating twin-screw extruder, setting a temperature gradient, wherein the first zone is 150-160°C, the second zone is 160-170°C, the third zone is 170-175°C, the fourth zone is 175-180°C, and the die head is 160-170°C; after melt extrusion, water cooling and pelletizing are performed to prepare protective cover material particles with a particle size of 3-5 mm; S4, feeding the protective cover material particles into a double-layer co-extrusion extruder, wherein the inner layer extrusion temperature is 160-170°C; the outer layer extrusion temperature is 160-170°C, to form a protective cover with a thickness of 1.5-3.0 mm.

9. A fire-resistant cable, characterized in that: The invention comprises a conductor, an insulating layer, a fire-resistant mica tape wrapping layer, a metal shielding layer, and an outer sheath made of the protective sheath material as described in any one of claims 1 to 7, which are arranged in sequence from the inside to the outside.

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