Fireproof power cable and preparation method and application thereof

Abstract

The invention relates to a fire-resistant cable and a preparation method and application thereof. The fire-resistant cable comprises a conductor core layer, a silicone rubber insulating layer, a fire-resistant mica filling layer, a shielding layer and a fire-resistant flame-retardant sheath layer. When the magnesium hydroxide flame retardant is prepared, piperazine phytate is added and is adsorbed on the surface of magnesium hydroxide to form electrostatic repulsion or steric hindrance, so that a protective layer is constructed on the surface of a particle, and particle aggregation is prevented. In addition, after the piperazine phytate modified magnesium hydroxide is compounded with the expanded graphite and the zinc stannate, a remarkable synergistic flame-retardant effect is shown, and efficient flame-retardant and fire-resistant performance of the cable material is achieved. The fireproof filler is added in the polypropylene cable sheath layer, so that the flame retardance and fire resistance of the cable are further improved, and it is ensured that the cable does not drip in the combustion process; therefore, the cable can still keep safe and reliable performance under extreme conditions such as fire disasters and the like, and powerful guarantee is provided for personnel safety and fire rescue.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and more specifically, it relates to a fire-resistant cable and its preparation method and application. Background Art

[0002] A fire-resistant cable is a specially designed cable product that can maintain normal operation for a certain period of time even when an external fire is still burning during a fire accident, ensuring the integrity of the line and the normal operation of equipment. With its excellent fire-resistant performance and reliability, this cable is widely used in key places such as high-rise buildings, railways, airports, large power stations, and important industrial and mining enterprises. These fields are closely related to fire safety and fire rescue. Therefore, fire-resistant cables play a crucial role in ensuring personnel safety, maintaining system operation, and reducing fire losses.

[0003] Currently, the fire-resistant and flame-retardant sheaths of ordinary power cables are mainly composed of flame-retardant polyolefins, and the flame-retardant effect is achieved by adding organic or inorganic flame retardants to polyolefin materials. Organic flame retardants mainly include phosphate esters, ammonium polyphosphate, melamine, etc. Their characteristics are small addition amounts, high prices, and limited smoke suppression effects. In contrast, inorganic flame retardants have been widely used in cable sheath materials due to their good thermal stability, environmental friendliness, and low production costs. Common inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, antimony-based, zinc stannate, etc. Among them, the advantages of aluminum hydroxide and magnesium hydroxide are non-toxicity and low cost, but the disadvantages are that large addition amounts are required and they will have an obvious impact on the mechanical strength of the material. Zinc stannate, as an inorganic flame retardant, is considered an efficient, green, and environmentally friendly flame retardant because of its environmental friendliness, non-toxicity, good smoke suppression performance, and high flame-retardant efficiency. In addition, phytic acid (PA), as a biomass renewable resource widely present in plant seeds, is also used as a renewable and environmentally friendly flame retardant due to its wide source and environmental friendliness. In the research of cable flame retardants, compounding or modification methods are usually adopted to further improve the flame-retardant efficiency. For example, by compounding different types of flame retardants or modifying the surface of the flame retardant, the flame-retardant performance and mechanical properties of the material can be significantly improved.

[0004] In view of the problems existing in current flame retardants, such as poor flame retardancy, large addition amount, and serious environmental pollution, the inventor has developed a green, low-toxic, and highly efficient functional flame retardant, which is specifically used for the sheath material of fire-resistant cables. While ensuring the safe operation of the cables, this new type of flame retardant can minimize the emission of toxic components and smoke during a fire, thereby reducing environmental pollution and damage to human health. In the event of a fire, when the cable burns, only a small amount of smoke is released, effectively reducing the smoke density and the emission of toxic gases, and significantly improving the fire safety. By optimizing the formula and production process, this flame retardant reduces the addition amount of traditional flame retardants, while enhancing the flame retardancy of the cable sheath material and the fire resistance of the cable. In addition, the new type of flame retardant also uses the environmentally friendly material magnesium hydroxide, which is not only non-toxic and environmentally friendly, but also can form a protective layer during combustion to further reduce the generation of smoke. This innovative flame retardant technology not only meets modern environmental protection and safety standards, but also provides an efficient and sustainable solution for the cable industry, helping to promote the development of cable materials towards low-smoke, halogen-free, fire-resistant, and environmentally friendly directions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a green and environmentally friendly functional flame retardant for the sheath layer of fire-resistant power cables. The sheath layer prepared by this flame retardant for fire-resistant cable materials not only has low smoke, high flame retardancy, and excellent fire resistance, but also does not drip during the combustion process, which enables the cable to still maintain safe and reliable performance under extreme conditions such as fires, providing strong protection for personnel safety and fire rescue.

[0006] The present invention provides a fire-resistant power cable, including a conductor core layer, a silicone rubber insulation layer, a fire-resistant mica filling layer, a shielding layer, and a fire-resistant flame-retardant sheath layer.

[0007] The fire-resistant flame-retardant sheath layer includes the following raw materials: 80-100 parts of polypropylene, 20-35 parts of functional flame retardant, 10-20 parts of compatibilizer, 15-25 parts of fire-resistant filler, 1-3 parts of silane coupling agent, 1-5 parts of antioxidant, and 1-5 parts of lubricant.

[0008] The preparation method of the functional flame retardant includes the following steps:

[0009] Step S1: Dissolve 5-10 parts of phytic acid in 20-50 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 0.5-5 parts of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 6-8 with ammonia water, heat and react, cool to room temperature, and filter to obtain phytic acid piperazine;

[0010] Step S2: Dissolve 20 - 30 parts of soluble magnesium salt in deionized water to prepare a magnesium salt solution with a concentration of 1 - 5 mol / L. Add 2 - 5 parts of the piperazine phytate from Step S1, and slowly drop the alkali solution into the magnesium salt solution under stirring. Stir and react, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of the soluble magnesium salt to the alkali solution is 1:2.1 - 3.5;

[0011] Step S3: Extrude 30 - 50 parts of the modified magnesium hydroxide from Step S2, 8 - 10 parts of expanded graphite, 5 - 8 parts of zinc stannate, and 60 - 100 parts of polypropylene through a screw for melt extrusion, and then pelletize to obtain a functional flame retardant.

[0012] The soluble magnesium salt is any one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate; the alkali solution is a solution of any one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0013] The refractory filler includes at least one of mica powder, zirconia, alumina, expanded perlite, and silicon nitride.

[0014] The D50 particle size of the refractory filler is 50 - 100 μm.

[0015] The temperature of the heating reaction in Step S1 is 50 - 80°C, and the reaction time is 3 - 6 h.

[0016] The temperature of the stirring reaction in Step S2 is 40 - 80°C, and the reaction time is 1 - 5 h.

[0017] The melt extrusion temperature in Step S3 is 180 - 230°C, the screw speed is 300 - 450 r / min, and the screw length - diameter ratio is 48:1.

[0018] The polypropylene is homopolypropylene or propylene - ethylene copolymer, and the melt index of the polypropylene resin under the test conditions of 230°C and 2.16 KG is 10 - 150 g / 10 min.

[0019] The compatibilizer is at least one of maleic anhydride - grafted polypropylene and maleic anhydride - grafted polyethylene.

[0020] The silane coupling agent is at least one of γ - aminopropyltriethoxysilane, vinyltriethoxysilane, γ - glycidyletheroxypropyltrimethoxysilane, and γ - methacryloxypropyltrimethoxysilane.

[0021] The antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0022] The lubricant is at least one of stearate, PE wax, and oleic amide.

[0023] The principle of the present invention using aminopiperazine to react with phytic acid is mainly based on the amino group (-NH 2 ) in aminopiperazine and the phosphate group (-PO 3 H 2 ) in phytic acid. Phytic acid (PA) is a polyphosphoric acid compound containing multiple phosphate groups, while aminopiperazine has a basic amino group that can react with the acidic phosphate groups in phytic acid to form piperazine phytate (PA-Pi). During the reaction, the phosphate groups of phytic acid combine with the amino groups of aminopiperazine to form ionic bonds, generating a bio-based flame retardant containing nitrogen and phosphorus. The resulting piperazine phytate has good thermal stability and flame retardancy, and can form a protective carbon layer during combustion to inhibit the release of heat and smoke. In addition, as a bio-based flame retardant, piperazine phytate has the advantages of environmental protection, low toxicity, and high flame retardancy efficiency.

[0024] In the preparation of magnesium hydroxide flame retardant in the present invention, piperazine phytate is added and adsorbed on the surface of magnesium hydroxide to form an electrostatic repulsion or steric hindrance, forming a protective layer on the particle surface to prevent particle contact and prevent the aggregation of magnesium hydroxide particles. It can be used as a stabilizer for magnesium hydroxide, improving the compatibility between magnesium hydroxide and the polypropylene matrix, and enhancing the dispersibility and flame retardancy efficiency, thereby improving the comprehensive performance of the fire-resistant cable.

[0025] The functional flame retardant of the present invention also includes expanded graphite and zinc stannate, which show obvious synergistic flame retardant effects in the composite material with the modified magnesium hydroxide. Expanded graphite will rapidly expand when heated, forming a dense carbon layer covering the surface of the material, playing a role in heat insulation and oxygen isolation. Magnesium hydroxide reduces the material temperature and delays combustion through an endothermic dehydration reaction. When zinc stannate is used in combination with magnesium hydroxide, it can significantly improve the flame retardancy efficiency and smoke suppression effect of the material. Zinc stannate promotes the endothermic dehydration reaction of magnesium hydroxide by catalyzing the carbonization of the polymer surface, enhancing the flame retardant effect. The addition of expanded graphite can significantly improve the flame retardancy and mechanical properties of the composite material, while reducing the dosage of magnesium hydroxide. When expanded graphite, zinc stannate, and magnesium hydroxide are used together, a denser and continuous carbon layer can be formed, further improving the flame retardancy of the material, achieving a better flame retardant effect at a lower dosage of the flame retardant, and reducing the impact on the mechanical properties of the material.

[0026] The present invention selects high-quality refractory fillers such as mica powder, zirconia, alumina, expanded perlite, and silicon nitride to fill the polypropylene cable sheath layer. On the one hand, refractory materials such as mica powder and alumina can significantly improve the charring and crusting properties of the cable sheath, making it have no dripping substances during combustion, thereby reducing the risk of fire spread and increasing the anti-dripping performance of the cable material. During combustion, these materials will form a strong ceramic structure, enhancing the fire resistance of the sheath and effectively reducing the heat release rate. On the other hand, materials such as mica powder, zirconia, and alumina can also significantly improve the mechanical strength and toughness of the cable sheath, reducing wear. Therefore, using these refractory materials to fill polypropylene as the cable sheath layer can significantly improve the flame retardancy, fire resistance, smoke density, and anti-dripping performance of the cable, enabling it to maintain safe and reliable performance under extreme conditions such as fire.

[0027] The present invention also provides a method for preparing a fire-resistant power cable, comprising the following steps:

[0028] (1) Conductor core layer preparation: Drawing the conductor material to obtain a wire, and preparing the conductor core layer;

[0029] (2) Preparing a silicone rubber insulation layer: Using an extrusion die to coat the silicone rubber insulation layer on the surface of the conductor core in step (1) to obtain the silicone rubber insulation layer;

[0030] (3) Preparing a fire-resistant mica filling layer: Wrapping a fire-resistant mica filling layer on the surface of the silicone rubber insulation layer in step (2) to obtain the fire-resistant mica filling layer;

[0031] (4) Preparing a shielding layer: Coating a shielding layer on the surface of the fire-resistant mica filling layer in step (3) to obtain the shielding layer;

[0032] (5) Preparing a fire-resistant and flame-retardant sheath layer: Extruding a fire-resistant and flame-retardant sheath layer on the surface of the shielding layer in step (4) to obtain the fire-resistant cable.

[0033] The present invention also provides an application of the fire-resistant power cable in the fields of high-rise buildings, subways, and airports.

[0034] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0035] 1) When preparing the magnesium hydroxide flame retardant in the present invention, phytic acid piperazine is added as a stabilizer. Phytic acid piperazine can adsorb on the surface of magnesium hydroxide particles, and by forming an electrostatic repulsion or steric hindrance, a protective film is constructed on the particle surface. This protective film can effectively prevent the contact between magnesium hydroxide particles, thereby preventing particle agglomeration. Therefore, phytic acid piperazine can not only be used as a stabilizer for magnesium hydroxide, but also significantly improve the compatibility between magnesium hydroxide and the polypropylene matrix, improve its dispersion in the matrix, and further improve the flame retardancy efficiency. This modification method can significantly improve the comprehensive performance of the fire-resistant cable.

[0036] 2) The flame retardant of the present invention is composed of piperazine phytate modified magnesium hydroxide, expanded graphite and zinc stannate, realizing the high-efficiency flame retardancy and fire resistance of cable materials. Among them, piperazine phytate modified magnesium hydroxide contains phytic acid and piperazine and can be used as an acid source. During combustion, phytic acid decomposes and promotes the formation of a carbon layer by the composite flame retardant. At the same time, zinc stannate forms a glass-like substance at high temperature, coating the surface of the carbon layer, sealing the pores, forming a dense layer, and effectively preventing the escape of internal combustible gases and the entry of external oxygen. Expanded graphite will rapidly expand when heated, forming a dense carbon layer covering the surface of the material, playing a role in heat insulation and oxygen isolation. The synergistic effect of these three flame retardant materials significantly improves the flame retardancy and fire resistance of cable materials. After testing, the oxygen index of the fire-resistant cable sheath material can reach 41%, and the fire-resistant cable line lasts for 180 minutes at a fire supply temperature of 1400 °C without obvious damage, showing excellent fire resistance.

[0037] 3) By adding fire-resistant fillers to the polypropylene cable sheath layer, the present invention significantly improves the flame retardancy, fire resistance and other properties of the cable compared with fillers such as talc and glass fiber, enabling it to maintain safe and reliable performance under extreme conditions such as fire. Detailed implementation mode

[0038] The technical solution of the present invention will be further described below through specific implementation modes. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the rights of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0039] Experimental materials:

[0040] Homopolypropylene resin 1#: PPH-Y26, with a melt flow rate of 30 g / 10 min at 230 °C under a load of 2.16 kg, purchased from the East China Branch of Sinopec Sales Co., Ltd.

[0041] Homopolypropylene resin 2#: PP M60T, with a melt flow rate of 56 g / 10 min at 230 °C under a load of 2.16 kg, purchased from the East China Branch of Sinopec Chemical Sales Co., Ltd.

[0042] Random copolymer polypropylene resin 3#: PP K9930H, with a melt flow rate of 30 g / 10 min at 230 °C under a load of 2.16 kg and an ethylene-propylene rubber content of 29.1 wt%, purchased from Maoming Petrochemical.

[0043] Random copolymer polypropylene resin 4#: PP SP179 (Zhenhai), with a melt flow rate of 10 g / 10 min at 230 °C under a load of 2.16 kg and an ethylene-propylene rubber content of 25 wt%, purchased from Sinopec Zhenhai Petrochemical.

[0044] Compatibilizer 1#: maleic anhydride grafted polypropylene, commercially available.

[0045] Compatibilizer 2#: maleic anhydride grafted polyethylene, commercially available.

[0046] Refractory fillers, coupling agents, antioxidant 1010, antioxidant 168, lubricants, 2-aminopiperazine, phytic acid, expanded graphite, zinc stannate, etc. are all commercially available. Unless otherwise specified, a certain component (such as lubricant) in the parallel examples and comparative examples of the present invention is the same commercially available product; the parts of each component in the examples of the present invention are equivalent to grams or kilograms under the same conditions.

[0047] I. Preparation examples of functional flame retardants are as follows:

[0048] Example 1 Preparation of functional flame retardant 1#

[0049] Step S1: Dissolve 5 parts of phytic acid in 30 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 0.5 part of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 7 with ammonia water, heat to 50 °C and react for 6 h, cool to room temperature, and filter to obtain phytic acid piperazine;

[0050] Step S2: Dissolve 20 parts of magnesium chloride in deionized water to prepare a 2 mol / L magnesium salt solution, add 2 parts of the phytic acid piperazine obtained in Step S1, slowly drop 1 mol / L sodium hydroxide into the magnesium chloride solution with stirring, stir and react at 40 °C for 5 h, filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.5;

[0051] Step S3: Extrude 30 parts of the modified magnesium hydroxide obtained in Step S2, 8 parts of expanded graphite, 6 parts of zinc stannate, and 70 parts of polypropylene at 190 °C through a screw, and pelletize to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0052] Example 2 Preparation of functional flame retardant 2#

[0053] Step S1: Dissolve 10 parts of phytic acid in 50 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 4 parts of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 8 with ammonia water, heat to 70 °C and react for 3 h, cool to room temperature, and filter to obtain phytic acid piperazine;

[0054] Step S2: Dissolve 25 parts of magnesium nitrate in deionized water to prepare a 5 mol / L magnesium salt solution. Add 5 parts of the phytic acid piperazine from Step S1, and slowly drop 2 mol / L potassium hydroxide into the magnesium nitrate solution under stirring. Stir and react at 60 °C for 2.5 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium nitrate to potassium hydroxide solution is 1:3.

[0055] Step S3: Extrude 50 parts of the modified magnesium hydroxide from Step S2, 10 parts of expanded graphite, 5 parts of zinc stannate, and 100 parts of polypropylene through a screw for melt extrusion and granulation to obtain a functional flame retardant; the screw speed is 350 r / min, the screw melt temperature is 210 °C, and the screw length-diameter ratio is 48:1.

[0056] Example 3: Preparation of functional flame retardant 3#

[0057] Step S1: Dissolve 8 parts of phytic acid in 40 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 4 parts of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 7 with ammonia water, heat to 60 °C and react for 3.5 h, cool to room temperature, and filter to obtain phytic acid piperazine.

[0058] Step S2: Dissolve 20 parts of magnesium sulfate in deionized water to prepare a 3 mol / L magnesium salt solution. Add 4 parts of the phytic acid piperazine from Step S1, and slowly drop 1 mol / L potassium hydroxide into the magnesium salt solution under stirring. Stir and react at 70 °C for 2 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium sulfate to potassium hydroxide solution is 1:2.4.

[0059] Step S3: Extrude 40 parts of the modified magnesium hydroxide from Step S2, 8 parts of expanded graphite, 8 parts of zinc stannate, and 70 parts of polypropylene through a screw for melt extrusion and granulation to obtain a functional flame retardant; the screw speed is 400 r / min, the screw melt temperature is 220 °C, and the screw length-diameter ratio is 48:1.

[0060] Example 4: Preparation of functional flame retardant 4#

[0061] Step S1: Dissolve 10 parts of phytic acid in 35 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 3.5 parts of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 6 with ammonia water, heat to 80 °C and react for 3 h, cool to room temperature, and filter to obtain phytic acid piperazine.

[0062] Step S2: Dissolve 35 parts of magnesium sulfate in deionized water to prepare a 2 mol / L magnesium salt solution. Add 5 parts of the piperazine phytate from Step S1, and slowly dropwise add 1.5 mol / L sodium hydroxide to the magnesium salt solution under stirring. Stir and react at 80 °C for 1.5 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium sulfate to potassium hydroxide solution is 1:2.5;

[0063] Step S3: Extrude 35 parts of the modified magnesium hydroxide from Step S2, 9 parts of expanded graphite, 7 parts of zinc stannate, and 60 parts of polypropylene through a screw for melt extrusion and granulation to obtain a functional flame retardant; the screw speed is 450 r / min, the screw melt temperature is 200 °C, and the screw length-diameter ratio is 48:1.

[0064] Example 5: Preparation of functional flame retardant 5#

[0065] Step S1: Dissolve 7 parts of phytic acid in 35 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 2 parts of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 7 with ammonia water, heat to 50 °C and react for 4 h, cool to room temperature, and filter to obtain piperazine phytate;

[0066] Step S2: Dissolve 25 parts of magnesium chloride in deionized water to prepare a 1.5 mol / L magnesium salt solution. Add 3 parts of the piperazine phytate from Step S1, and slowly dropwise add 1 mol / L sodium hydroxide to the magnesium salt solution under stirring. Stir and react at 50 °C for 4.5 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.3;

[0067] Step S3: Extrude 40 parts of the modified magnesium hydroxide from Step S2, 10 parts of expanded graphite, 7 parts of zinc stannate, and 90 parts of polypropylene at 220 °C through a screw for melt extrusion and granulation to obtain a functional flame retardant; the screw speed is 380 r / min, and the screw length-diameter ratio is 48:1.

[0068] Example 6: Preparation of functional flame retardant 6#

[0069] Step S1: Dissolve 20 parts of magnesium chloride in deionized water to prepare a 2 mol / L magnesium salt solution. Slowly dropwise add 1 mol / L sodium hydroxide to the magnesium chloride solution under stirring. Stir and react at 40 °C for 5 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.5;

[0070] Step S2: Extrude 30 parts of the modified magnesium hydroxide from Step S2, 8 parts of expanded graphite, 6 parts of zinc stannate, and 70 parts of polypropylene at 190 °C through a screw for melt extrusion and granulation to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0071] Example 7 Preparation of Functional Flame Retardant 7#

[0072] Step S1: Dissolve 20 parts of magnesium chloride in deionized water to prepare a magnesium salt solution with a concentration of 2 mol / L. Add 2 parts of phytic acid, and slowly drop 1 mol / L sodium hydroxide into the magnesium chloride solution under stirring. Stir and react at 40°C for 5 h, filter, and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.5;

[0073] Step S2: Extrude 30 parts of the modified magnesium hydroxide obtained in Step S1, 8 parts of expanded graphite, 6 parts of zinc stannate, and 70 parts of polypropylene through a screw at 190°C, and pelletize to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0074] Example 8 Preparation of Functional Flame Retardant 8#

[0075] Step S1: Dissolve 5 parts of phytic acid in 30 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 0.5 part of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 7 with ammonia water, heat to 50°C and react for 6 h, cool to room temperature, and filter to obtain phytic acid piperazine;

[0076] Step S2: Dissolve 20 parts of magnesium chloride in deionized water to prepare a magnesium salt solution with a concentration of 2 mol / L. Add 2 parts of the phytic acid piperazine obtained in Step S1, and slowly drop 1 mol / L sodium hydroxide into the magnesium salt solution under stirring. Stir and react at 40°C for 5 h, filter, and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.5;

[0077] Step S3: Extrude 30 parts of the modified magnesium hydroxide obtained in Step S2, 6 parts of zinc stannate, and 78 parts of polypropylene through a screw at 190°C, and pelletize to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0078] Example 9 Preparation of Functional Flame Retardant 9#

[0079] Step S1: Dissolve 5 parts of phytic acid in 30 parts of deionized water, stir until completely dissolved to form a transparent solution, then add 0.5 part of 2-aminopiperazine to the above solution, stir until completely dissolved, adjust the pH of the solution system to 7 with ammonia water, heat to 50°C and react for 6 h, cool to room temperature, and filter to obtain phytic acid piperazine;

[0080] Step S2: Dissolve 20 parts of magnesium chloride in deionized water to prepare a 2 mol / L magnesium salt solution. Add 2 parts of the piperazine phytate from Step S1, and slowly drop 1 mol / L sodium hydroxide into the magnesium chloride solution under stirring. Stir and react at 40 °C for 5 h, then filter and wash to obtain modified magnesium hydroxide; the molar ratio of magnesium chloride to sodium hydroxide is 1:2.5.

[0081] Step S3: Extrude 30 parts of the modified magnesium hydroxide from Step S2, 8 parts of expanded graphite, 76 parts of polypropylene through a screw at 190 °C, and pelletize to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0082] Example 10 Preparation of Functional Flame Retardant 10#

[0083] Extrude 30 parts of magnesium hydroxide, 8 parts of expanded graphite, 6 parts of zinc stannate, 70 parts of polypropylene through a screw at 190 °C, and pelletize to obtain a functional flame retardant; the screw speed is 300 r / min, and the screw length-diameter ratio is 48:1.

[0084] Second, the present invention also includes a fire-resistant power cable prepared with the functional flame retardants 1# - 10# for a fire-resistant and flame-retardant sheath layer, including the following steps:

[0085] (1) Conductor core layer preparation: Draw the conductor material to obtain a wire, and prepare the conductor core layer;

[0086] (2) Preparation of silicone rubber insulation layer: Use an extrusion die to coat the silicone rubber insulation layer on the surface of the conductor core in step (1) to obtain the silicone rubber insulation layer;

[0087] (3) Preparation of fire-resistant mica filling layer: Wrap the fire-resistant mica filling layer on the surface of the silicone rubber insulation layer in step (2) to obtain the fire-resistant mica filling layer;

[0088] (4) Preparation of shielding layer: Coat the shielding layer on the surface of the fire-resistant mica filling layer in step (3) to obtain the shielding layer;

[0089] (5) Preparation of fire-resistant and flame-retardant sheath layer: Extrude the fire-resistant and flame-retardant sheath layer on the surface of the shielding layer in step (4) to obtain the fire-resistant cable.

[0090] In the application examples and comparative application examples, the diameter of the conductor core layer of the fire-resistant cable is 1.5 cm, the thickness of the silicone rubber insulation layer is 2.0 mm, the thickness of the fire-resistant mica filling layer is 1.5 mm, the thickness of the shielding layer is 1.5 mm, and the thickness of the fire-resistant and flame-retardant sheath layer is 3.5 mm.

[0091] The difference between Application Examples 1 - 10 and Comparative Application Examples 1 - 10 lies in the different fire-resistant and flame-retardant sheath layers, as shown in Tables 1 and 2 specifically.

[0092] Table 1 Allocation ratios (parts by weight) of each group in Application Examples 1-10

[0093]

[0094] Table 2 Allocation ratios (parts by weight) of each group in Comparative Application Examples 1-10

[0095]

[0096] Performance test

[0097] Perform relevant performance tests on the fire-resistant power cables prepared in Application Examples 1-10 and Comparative Application Examples 1-10. The specific test methods are as follows:

[0098] (1) Fire resistance: Refer to GBT19216.21-2003 "Line Integrity of Cables or Optical Fibre Cables under Fire Conditions" to detect the fire resistance of the cable. The fire supply temperatures are 1200°C and 1400°C respectively, and the duration is 180 min. Check whether the line is damaged. The results are divided into different grades: A - The line has no obvious damage; B - The line has obvious loss; C - The line is open circuit.

[0099] (2) Smoke density (minimum light transmittance): Test the smoke density of the cable according to the standard of "GB / T 17651.2-2021 Determination of Smoke Density of Cables or Optical Fibre Cables when Burning under Specific Conditions".

[0100] (3) Oxygen index: Determine the oxygen index of the test sample according to the method of GB / T 2406.2-2009 "Determination of Combustion Behavior of Plastics by the Oxygen Index Method".

[0101] (4) Dripping performance: Take a 10-cm-long cable material, burn it with a blowtorch with a thermal power of 500 W for 20 s, the flame height is 150 mm, then stop for 15 s, and burn it repeatedly five times. Calculate the content of the dripping substances during the combustion process to measure the degree of cable damage. The dripping rate = (weight before burning - weight after burning) / weight before burning × 100%. The test results are shown in Table 3.

[0102] (5) Flame retardancy: UL94 vertical burning grade. Detect the UL94 vertical burning grade of the shielded cable according to GB / T 2408-2008.

[0103] The test results are shown in Table 3.

[0104] Table 3

[0105]

[0106] According to the test results in Table 3, the fire-resistant cable of the present invention exhibits excellent flame retardant properties. Its oxygen index is higher than 41%, and it reaches the UL94 vertical burning rating V0. In addition, the smoke density (minimum light transmittance) of this cable exceeds 80%, meaning that it produces less smoke during combustion, which is beneficial to personnel safety and fire rescue. In terms of fire resistance, the fire-resistant cable of the present invention lasts for 180 minutes at a fire supply temperature of 1200 °C without obvious damage to the line; at a fire supply temperature of 1400 °C for 180 minutes, the line is also without obvious damage. At the same time, its dripping rate (burning rate) is lower than 2.65%, further demonstrating its excellent fire resistance.

[0107] By comparing the results of Application Example 1 with those of Comparative Application Examples 1 and 2, it can be seen that adding piperazine phytate as a stabilizer for magnesium hydroxide flame retardant can significantly improve the performance of the fire-resistant cable. Piperazine phytate adsorbs on the surface of magnesium hydroxide to form an electrostatic repulsion or steric hindrance, thus constructing a protective layer on the particle surface and effectively preventing particle agglomeration. This not only improves the compatibility between magnesium hydroxide and the polypropylene matrix, but also improves its dispersibility and flame retardant efficiency, and then significantly enhances the flame retardancy, fire resistance and smoke density performance of the fire-resistant cable. In addition, piperazine phytate itself has good thermal stability and flame retardant properties, and can form a protective carbon layer during combustion to inhibit the release of heat and smoke, further improving the flame retardant and fire resistance of the cable. In contrast, Comparative Application Example 1 did not add piperazine phytate as a magnesium hydroxide stabilizer, while Comparative Application Example 2 only used phytic acid as a stabilizer, and the cables prepared were inferior to Application Example 1 in terms of flame retardancy and fire resistance.

[0108] By comparing the results of Application Example 1 with those of Comparative Application Examples 3 - 5, it can be found that the flame retardant composed of piperazine phytate - modified magnesium hydroxide, expanded graphite, and zinc stannate in Application Example 1 has a significant synergistic effect, achieving high - efficiency flame retardancy and fire - resistance performance of cable materials. Among them, piperazine phytate - modified magnesium hydroxide contains phytic acid and piperazine and can serve as an acid source. During combustion, phytic acid decomposes and promotes the formation of a carbon layer by the composite flame retardant. At the same time, zinc stannate forms a glass - like substance at high temperatures, which coats the surface of the carbon layer, seals the pores, forms a dense layer, and effectively prevents the escape of internal combustible gases and the entry of external oxygen. Expanded graphite expands rapidly when heated, forming a dense carbon layer covering the material surface, playing a role in heat insulation and oxygen isolation. The synergistic effect of these three flame - retardant materials significantly improves the flame retardancy and fire - resistance performance of cable materials. After testing, the oxygen index of the fire - resistant cable sheath material in Application Example 1 can reach over 41%. The fire - resistant cable line lasts for 180 minutes at a fire - supplying temperature of 1400 °C without obvious damage, the smoke density is greater than 80%, and the dripping rate is less than 3%, demonstrating excellent flame retardancy and fire - resistance performance. In contrast, Comparative Application Example 3 does not add expanded graphite, Comparative Application Example 4 does not add zinc stannate, and the magnesium hydroxide in Comparative Application Example 5 is not modified with piperazine phytate, and their flame retardancy and fire - resistance performance are significantly lower than that of Application Example 1.

[0109] By comparing Application Example 1 with Comparative Application Examples 6 - 9, it can be found that the absence of a functional flame retardant in Comparative Application Example 6 leads to a significant decline in the flame retardancy, smoke density, and fire - resistance performance of the prepared fire - resistant cable. While Comparative Application Examples 7 - 9 use talc powder, calcium carbonate, and glass fiber as fillers respectively, and the fire - resistance performance of the cable materials prepared by them is significantly lower than that of the mica powder fire - resistant filler used in Application Example 1. Thus, it can be seen that the present invention selects mica powder with excellent fire - resistance performance as the filler, significantly improving the flame retardancy and fire - resistance of the cable, enabling it to maintain safe and reliable performance under extreme conditions such as fire.

[0110] By comparing Application Example 1 with Comparative Application Example 10, it can be found that the silane coupling agent added in the present invention contains two groups with different properties: one is a hydrolyzable inorganic group (such as methoxy, ethoxy, etc.), which can chemically react with the hydroxyl groups on the surface of inorganic fillers to form strong chemical bonds; the other is an organic functional group (such as amino, epoxy, vinyl, etc.), which can interact with organic polymers such as polypropylene. When the silane coupling agent acts on the fire - resistant filler, its inorganic group reacts with the hydroxyl groups on the filler surface, reducing the polarity and enhancing the hydrophobicity of the filler surface, thus significantly improving the compatibility between the filler and polypropylene, reducing the agglomeration phenomenon between filler particles, and further improving the dispersion of the filler in the polypropylene matrix. This improvement in dispersion ultimately enhances the comprehensive performance of the cable, such as flame retardancy, fire - resistance, and smoke density.

[0111] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, and any modifications, equivalent substitutions, or improvements made within the basic principles and scope of the present invention shall be considered to fall within the protection scope of the present invention.

Claims

1. A fire-resistant power cable, characterized in that: It includes a conductor core layer, a silicone rubber insulation layer, a fire-resistant mica filling layer, a shielding layer, and a fire-resistant flame-retardant sheath layer; The fire-resistant flame-retardant sheath layer comprises the following raw materials: 80-100 parts of polypropylene, 20-35 parts of functional flame retardant, 10-20 parts of compatibilizer, 15-25 parts of fire-resistant filler, 1-3 parts of silane coupling agent, 1-5 parts of antioxidant, and 1-5 parts of lubricant; The preparation method of the functional flame retardant comprises the following steps: Step S1, dissolving 5-10 parts of phytic acid in 20-50 parts of deionized water, stirring until completely dissolved to form a transparent solution, then adding 0.5-5 parts of 2-aminopiperazine to the above solution, stirring until completely dissolved, adjusting the pH of the solution system to 6-8 with ammonia water, heating for reaction, cooling to room temperature, filtering, and obtaining phytic acid piperazine; Step S2, dissolving 20-30 parts of a soluble magnesium salt in deionized water to prepare a 1-5 mol / L magnesium salt solution, adding 2-5 parts of the phytic acid piperazine of step S1, slowly dripping the alkaline solution into the magnesium salt solution under stirring, stirring to react, filtering, washing, and obtaining modified magnesium hydroxide; Step S3, melt-extrude 30-50 parts of the modified magnesium hydroxide of step S2, 8-10 parts of expanded graphite, 5-8 parts of zinc stannate, and 60-100 parts of polypropylene through a screw, and granulate to obtain a functional flame retardant; The refractory filler includes at least one of mica powder, zirconium oxide, aluminum oxide, expanded perlite and silicon nitride.

2. The fire-resistant power cable according to claim 1, characterized in that: The soluble magnesium salt in step S2 is any one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate; the alkaline solution is any one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide; and the molar ratio of the soluble magnesium salt to the alkaline solution is 1:2.1-3.

5.

3. The fire-resistant power cable according to claim 1, characterized in that: The D50 particle size of the refractory filler is 50-100 μm.

4. The fire-resistant power cable according to claim 1, characterized in that: The temperature of the heating reaction in step S1 is 50-80°C, and the reaction time is 3-6h; the temperature of the stirring reaction in step S2 is 40-80°C, and the reaction time is 1-5h.

5. The fire-resistant power cable according to claim 1, characterized in that: The melt extrusion temperature in step S3 is 180-230° C., the screw speed is 300-450 r / min, and the screw aspect ratio is 48:

1.

6. The fire-resistant power cable according to claim 1, characterized in that: The polypropylene is homopolymer polypropylene or propylene-ethylene copolymer, and the melting index of the polypropylene resin under the test conditions of 230° C. and 2.16 kg is 10-150 g / 10 min.

7. The fire-resistant power cable according to claim 1, characterized in that: The compatibilizer is at least one of maleic anhydride grafted polypropylene and maleic anhydride grafted polyethylene; the antioxidant is at least one of antioxidant 1010 and antioxidant 168; and the lubricant is at least one of stearate, PE wax and oleamide.

8. The fire-resistant power cable according to claim 1, characterized in that: The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

9. A method for preparing a fire-resistant power cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Preparation of conductor core layer: The conductor material is subjected to wire drawing to obtain a conductor to prepare a conductor core layer; (2) preparing a silicone rubber insulation layer: using an extrusion die to coat the silicone rubber insulation layer on the surface of the conductor core in step (1) to obtain a silicone rubber insulation layer; (3) preparing a refractory mica filling layer: wrapping the refractory mica filling layer on the surface of the silicone rubber insulation layer in step (2) to obtain a refractory mica filling layer; (4) preparing a shielding layer: coating the shielding layer on the surface of the refractory mica filling layer in step (3) to obtain a shielding layer; (5) Preparing a fire-resistant flame-retardant sheath layer: Extruding a fire-resistant flame-retardant sheath layer on the surface of the shielding layer in step (4) to obtain a fire-resistant cable.

10. Use of the fire-resistant power cable according to any one of claims 1 to 8 in the fields of high-rise buildings, subways and airports.

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