Halogen-free flame-retardant cable and method for producing the same

Abstract

This invention discloses a halogen-free flame-retardant cable and its preparation method, relating to the field of cable technology. The invention uses silica fiber as raw material, which undergoes gas-phase modification to generate phosphorus-containing silicon-rare earth ceramic fibers. These fibers are then modified with 5-hexenyltriethoxysilane. Sulfonate-based polystyrene microspheres are used as the core layer, and starch is used as an adhesive to bond the modified ceramic fibers to the surface of the microspheres, thus forming a core-shell flame retardant. The polystyrene's oxygen-barrier effect synergizes with the fiber's heat insulation properties to extinguish combustion and achieve a flame-retardant effect. Furthermore, the microspheres act as an acid source, and the starch as a carbon source, forming a continuous and dense carbon layer, thus improving the cable's flame-retardant performance.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a halogen-free flame-retardant cable and its preparation method. Background Technology

[0002] As a supporting industry to the power industry, one of the pillar industries of the national economy, the wire and cable industry plays an extremely important role and holds a significant position in the national economy.

[0003] Polyvinyl chloride (PVC) is commonly used as insulation and sheathing material for control cables. However, PVC contains chlorine, which increases smoke release and releases corrosive gases when burned, polluting the environment. Therefore, halogen-free plastics or rubber materials are required as insulation and sheathing materials. However, their flame retardancy is relatively low, so it is necessary to improve their flame retardancy. Summary of the Invention

[0004] The purpose of this invention is to provide a halogen-free flame-retardant cable and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a halogen-free flame-retardant cable, comprising a copper conductor, a polyethylene insulation layer, a copper braided shielding layer, and a flame-retardant layer, wherein the flame-retardant layer is composed of a core-shell flame retardant, polyethylene resin, a lubricant, and an antioxidant.

[0006] Furthermore, the polyethylene resin is a mixture of linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 40-50:10-20:20-35.

[0007] Furthermore, the linear low-density polyethylene has a density of 0.920 g / cm³. 3 The melt flow index is 2.0 g / 10 min.

[0008] Furthermore, the density of the high-density polyethylene is 0.953 g / cm³. 3 The melt flow index is 0.4 g / 10 min.

[0009] Furthermore, the lubricant is polyethylene wax or zinc stearate.

[0010] Furthermore, the antioxidant is dilaurate thiodipropionate or antioxidant 1010.

[0011] Furthermore, the preparation method of the core-shell flame retardant is as follows:

[0012] (1) Place the silica fiber in a reaction apparatus equipped with a stirring device, turn on the stirring, and stir at a speed of 100-150 rpm. The reaction apparatus has two vents. The first vent introduces argon at a rate of 80-100 mL / min, hydrogen at a rate of 150-280 mL / min, and vaporized 1.5 mol / L rare earth chloride aqueous solution at a rate of 22-31 mL / min. The second vent introduces argon at a rate of 80-100 mL / min, hydrogen at a rate of 150-280 mL / min, and vaporized 1.5 mol / L phosphate aqueous solution at a rate of 22-31 mL / min. The temperature is increased to 1050-1200℃ at a rate of 5-15℃ / min and held for 2 hours to obtain ceramic fiber. The rare earth chloride is lanthanum chloride or cerium chloride, and the phosphate is one of ammonium phosphate, sodium phosphate, or phosphoric acid.

[0013] (2) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:4 to 8:14 to 24, adjust the pH to 4, completely immerse the ceramic fiber in the mixture, react at 70°C for 1 to 2 hours, remove the mixture, wash it three times with ethanol at 3000 rpm, and then dry it at 60°C for 24 hours to obtain the modified ceramic fiber.

[0014] (3) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water. Stir evenly at 60°C, add sodium (4-vinylphenyl)methanesulfonate, with a volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water of 0.49–1.0:30–40, emulsify at 300–500 rpm for 20–25 min, add 60% potassium persulfate, and stir again at 75°C and 300–500 rpm for 10 min to obtain a pre-emulsion; mix 10 mL of deionized water with the remaining 20% ​​(4-vinylphenyl)methanesulfonate... Sodium (alkenylphenyl)methanesulfonate and the remaining 40% potassium persulfate were stirred at 300-500 rpm for 8 min, and then 30-40 mL of pre-emulsion was added. The mixture was heated to 75 °C, and then 10 mL of pre-emulsion was added. The mixture was stirred at 300-500 rpm for 6 h to obtain a microemulsion. Ethanol with a mass fraction of 95% was added at a volume equal to that of the microemulsion. The mixture was placed in an ice bath and allowed to separate into layers. The solid layer after centrifugation was taken out and washed three times with 95% ethanol. The mixture was then dried at 40 °C to constant weight to obtain sulfonated polystyrene microspheres.

[0015] (4) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer, and stir at a speed of 100-150 rpm. Add 1.5 wt% oxidized starch aqueous solution at a ratio of 1.0-1.1 times the mass of the sulfonated polystyrene microspheres. Heat to 90-95℃ and stir for 0.5-1 h. Then add 2-5 times the mass of the sulfonated polystyrene microspheres and stir for 44-66 min. Finally, freeze at -18℃ for 24 h to obtain a core-shell flame retardant.

[0016] Further, the preparation method of the silica fiber in step (1) is as follows: 1.2-2.0 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol are mixed and stirred at 30-60 rpm for 4-6 h to obtain a silica solution. 0.75-1.1 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide are mixed and stirred at 30-60 rpm for 8-12 h. The mixture is then added to the silica solution and stirred at 30-60 rpm for 2-5 h. Then, the silica precursor fiber with an aspect ratio of 10-20 is obtained by electrospinning at a voltage of 15-20 kV, a solution flow rate of 0.5-2 mL / h, and a working distance of 15-20 cm between the needle and the collecting plate. The silica fiber is then kept at a constant temperature of 520-600℃ for 3-5 h to obtain the silica fiber.

[0017] Furthermore, in step (3), the mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate is 5:0.4:90.

[0018] Furthermore, the mass ratio of the core-shell flame retardant, polyethylene resin, lubricant, and antioxidant is 10-20:100:1-5:1-5, and the flame retardant layer is obtained by extrusion using a single-screw extruder at an extrusion temperature of 180-188°C.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] This invention uses a core-shell structured flame retardant as a filler, which is co-extruded with polyethylene as a cable sheath material to achieve a highly efficient flame retardant effect for cables.

[0021] This invention uses silica fiber as raw material and rare earth chloride and phosphate as vaporization solutions to perform two-phase modification treatment on the silica fiber to generate phosphorus-containing silicon-rare earth ceramic fiber. This fiber is used as a heat insulation filler in cable sheath material to isolate heat transfer and interrupt combustion, thereby achieving a flame retardant effect. The presence of rare earth and phosphorus elements can promote char formation during the combustion process of the cable sheath. Then, 5-hexenyltriethoxysilane is used to modify the fiber to enhance the compatibility between the ceramic fiber and the polyethylene sheath material, thereby improving the dispersion in the sheath layer and thus better exerting the heat insulation and flame retardant effect.

[0022] This invention utilizes sodium (4-vinylphenyl)methanesulfonate as a monomer to polymerize and prepare sulfonic acid-based polystyrene microspheres. These microspheres then form a core layer, and modified ceramic fibers are adhered to the surface of the microspheres using starch as an adhesive, thus forming a core-shell flame retardant. Polystyrene has an oxygen-barrier effect, which synergistically works with the heat insulation properties of the fibers to interrupt combustion and improve the flame retardancy of the cable. Furthermore, the sulfonic acid groups of the microspheres act as an acid source, decomposing and releasing sulfuric acid substances during combustion. The generated acid combines with the starch carbon source to produce an esterification reaction, promoting the formation of char from the condensed phase, improving the quality and continuity of the char layer, and preventing secondary combustion caused by molten droplets. In addition, the presence of the core-shell structure promotes the uniform dispersion of the core layer, which is beneficial for optimizing the flame retardancy of the cable. At the same time, the heat insulation effect of the shell layer prevents premature decomposition of polystyrene, avoiding affecting the quality of the char layer. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Mix 1.2 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol, stir at 30 rpm for 4 h to obtain a silica solution. Mix 0.75 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide, stir at 30 rpm for 8 h, and then add all of them to the silica solution. Stir at 30 rpm for 2-5 h. Then, electrospin at a voltage of 15 kV, a solution flow rate of 0.5 mL / h, and a working distance of 15 cm between the needle and the collecting plate to obtain silica precursor fibers with an aspect ratio of 10. Keep at 520℃ for 3 h to obtain silica fibers.

[0026] (2) Place the silica fiber in a reaction apparatus equipped with a stirring device, turn on the stirring and the stirring speed is 100 rpm. The reaction apparatus has two vents. The first vent introduces argon gas at 80 mL / min, hydrogen gas at 150 mL / min, and vaporized 1.5 mol / L lanthanum chloride aqueous solution at 22 mL / min. The second vent introduces argon gas at 80 mL / min, hydrogen gas at 150 mL / min, and vaporized 1.5 mol / L ammonium phosphate aqueous solution at 22 mL / min. The temperature is increased to 1050℃ at 5℃ / min and kept at 2h to obtain ceramic fiber.

[0027] (3) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:4:14, adjust the pH to 4, completely immerse the ceramic fiber in it, react at 70°C for 1 h, take it out, wash it three times with ethanol at 3000 rpm, and then dry it at 60°C for 24 h to obtain modified ceramic fiber.

[0028] (4) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water. Stir evenly at 60°C, add sodium (4-vinylphenyl)methanesulfonate (volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water is 0.49:30), emulsify at 300 rpm for 20 min, add 60% potassium persulfate, and stir again at 75°C and 300 rpm for 10 min to obtain a pre-emulsion; then add 10 mL of deionized water, the remaining 20% ​​sodium (4-vinylphenyl)methanesulfonate, and the remaining 40% potassium persulfate, and stir at 300 rpm for 20 min. After stirring for 8 minutes, 30 mL of pre-emulsion was added, the temperature was raised to 75°C, 10 mL of pre-emulsion was added, and the mixture was stirred at 300 rpm for 6 hours to obtain a microemulsion. Ethanol with a mass fraction of 95% was added at a volume equal to that of the microemulsion, and the mixture was placed in an ice bath and allowed to separate into layers. The lower layer of solid was collected, centrifuged, washed three times with 95% ethanol, and dried at 40°C to constant weight to obtain sulfonated polystyrene microspheres. The mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate was 5:0.4:90.

[0029] (5) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer at a speed of 100 rpm, add 1.5 wt% oxidized starch aqueous solution with 1 times the mass of sulfonated polystyrene microspheres, heat to 90°C, stir for 0.5 h, then add modified ceramic fibers with 2 times the mass of sulfonated polystyrene microspheres, stir for 44 min, and then freeze at -18°C for 24 h to obtain a core-shell flame retardant;

[0030] (6) A polyethylene resin is prepared by mixing linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 40:10:20; a flame-retardant layer is extruded onto a copper braided shielded cable core in a mass ratio of 10:100:1:1 to obtain a cable.

[0031] Example 2

[0032] (1) Mix 1.8 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol, stir at 40 rpm for 5 h to obtain a silica solution. Mix 0.92 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide, stir at 40 rpm for 10 h, and then add all of them to the silica solution. Stir at 40 rpm for 3.5 h. Then, electrospin the silica precursor fiber with an aspect ratio of 15 at a voltage of 18 kV, a solution flow rate of 1.4 mL / h, and a working distance of 18 cm between the needle and the collecting plate. Keep the temperature at 570℃ for 4 h to obtain silica fiber.

[0033] (2) Place the silica fiber in a reaction apparatus equipped with a stirring device, turn on the stirring and the stirring speed is 120 rpm. The reaction apparatus has two vents. The first vent introduces argon gas at 90 mL / min, hydrogen gas at 210 mL / min, and vaporized 1.5 mol / L cerium chloride aqueous solution at 26 mL / min. The second vent introduces argon gas at 90 mL / min, hydrogen gas at 210 mL / min, and vaporized 1.5 mol / L sodium phosphate aqueous solution at 26 mL / min. The temperature is increased to 1100℃ at 10℃ / min and kept at the temperature for 2 hours to obtain ceramic fiber.

[0034] (3) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:6:20, adjust the pH to 4, completely immerse the ceramic fiber in it, react at 70℃ for 1.5h, take it out, wash it three times with ethanol at 3000rpm, and then dry it at 60℃ for 24h to obtain modified ceramic fiber.

[0035] (4) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water. Stir evenly at 60°C, add sodium (4-vinylphenyl)methanesulfonate (volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water is 0.72:35), emulsify at 400 rpm for 22 min, add 60% potassium persulfate, and stir again at 75°C and 400 rpm for 10 min to obtain a pre-emulsion; then add 10 mL of deionized water, the remaining 20% ​​sodium (4-vinylphenyl)methanesulfonate, and the remaining 40% potassium persulfate, and stir at 400 rpm for 22 min to obtain a pre-emulsion. After stirring for 8 minutes, 35 mL of pre-emulsion was added, the temperature was raised to 75°C, 10 mL of pre-emulsion was added, and the mixture was stirred at 400 rpm for 6 hours to obtain a microemulsion. Ethanol with a mass fraction of 95% was added at a volume equal to that of the microemulsion, and the mixture was placed in an ice bath and allowed to separate into layers. The lower layer of solid was collected, centrifuged, washed three times with 95% ethanol, and dried at 40°C to constant weight to obtain sulfonated polystyrene microspheres. The mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate was 5:0.4:90.

[0036] (5) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer at a speed of 120 rpm, add 1.5 wt% oxidized starch aqueous solution with a mass of 1.05 times that of the sulfonated polystyrene microspheres, heat to 92°C, stir for 0.8 h, then add 3.5 times that of the sulfonated polystyrene microspheres of modified ceramic fiber, stir for 53 min, and then freeze at -18°C for 24 h to obtain a core-shell flame retardant;

[0037] (6) A polyethylene resin is prepared by mixing linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 45:15:28; a flame-retardant layer is extruded onto a copper braided shielded cable core in a weight ratio of 15:100:3:3 to obtain a cable.

[0038] Example 3

[0039] (1) Mix 2.0 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol, stir at 60 rpm for 6 h to obtain a silica solution. Mix 1.1 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide, stir at 60 rpm for 12 h, and then add all of them to the silica solution. Stir at 60 rpm for 5 h. Then, electrospin the silica precursor fiber with an aspect ratio of 20 at a voltage of 20 kV, a solution flow rate of 2 mL / h, and a working distance of 20 cm between the needle and the collecting plate. Keep the temperature at 600℃ for 5 h to obtain silica fiber.

[0040] (2) Place the silica fiber in a reaction apparatus equipped with a stirring device, turn on the stirring and the stirring speed is 150 rpm. The reaction apparatus has two vents. The first vent introduces argon gas at 100 mL / min, hydrogen gas at 280 mL / min, and vaporized 1.5 mol / L lanthanum chloride aqueous solution at 31 mL / min. The second vent introduces argon gas at 100 mL / min, hydrogen gas at 280 mL / min, and vaporized 1.5 mol / L phosphoric acid aqueous solution at 31 mL / min. The temperature is increased to 1200℃ at 15℃ / min and kept at 2h to obtain ceramic fiber.

[0041] (3) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:8:24, adjust the pH to 4, completely immerse the ceramic fiber in it, react at 70°C for 2 hours, take it out, wash it three times with ethanol at 3000 rpm, and then dry it at 60°C for 24 hours to obtain modified ceramic fiber.

[0042] (4) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water. Stir evenly at 60°C, add sodium (4-vinylphenyl)methanesulfonate (volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water is 1.0:40), emulsify at 500 rpm for 25 min, add 60% potassium persulfate, and stir again at 75°C and 500 rpm for 10 min to obtain a pre-emulsion; combine 10 mL of deionized water with the remaining 20% ​​sodium (4-vinylphenyl)methanesulfonate and the remaining 40% potassium persulfate, and stir at 500 rpm... After stirring for 8 minutes, 40 mL of pre-emulsion was added, the temperature was raised to 75°C, 10 mL of pre-emulsion was added, and the mixture was stirred at 500 rpm for 6 hours to obtain a microemulsion. Ethanol with a mass fraction of 95% was added at a volume equal to that of the microemulsion, and the mixture was placed in an ice bath and allowed to separate into layers. The lower layer of solid was collected, centrifuged, washed three times with 95% ethanol, and dried at 40°C to constant weight to obtain sulfonated polystyrene microspheres. The mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate was 5:0.4:90.

[0043] (5) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer at a speed of 150 rpm, add 1.5 wt% oxidized starch aqueous solution with 1.1 times the mass of sulfonated polystyrene microspheres, heat to 95°C, stir for 1 h, then add 5 times the mass of sulfonated polystyrene microspheres of modified ceramic fiber, stir for 66 min, and then freeze at -18°C for 24 h to obtain a core-shell flame retardant;

[0044] (6) A polyethylene resin is prepared by mixing linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 50:20:35; a flame-retardant layer is extruded onto a copper braided shielded cable core in a weight ratio of 20:100:5:5 to obtain a cable.

[0045] Comparative Example 1

[0046] (1) Mix 1.8 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol, stir at 40 rpm for 5 h to obtain a silica solution. Mix 0.92 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide, stir at 40 rpm for 10 h, and then add all of them to the silica solution. Stir at 40 rpm for 3.5 h. Then, electrospin the silica precursor fiber with an aspect ratio of 15 at a voltage of 18 kV, a solution flow rate of 1.4 mL / h, and a working distance of 18 cm between the needle and the collecting plate. Keep the temperature at 570℃ for 4 h to obtain silica fiber.

[0047] (2) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:6:20, adjust the pH to 4, completely immerse the silica fiber in it, react at 70°C for 1.5 h, take it out, wash it three times with ethanol at 3000 rpm, and then dry it at 60°C for 24 h to obtain modified silica fiber.

[0048] (3) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water. Stir evenly at 60 °C, add sodium (4-vinylphenyl)methanesulfonate (volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water is 0.72:35), emulsify at 400 rpm for 22 min, add 60% potassium persulfate, and stir again at 75 °C and 400 rpm for 10 min to obtain a pre-emulsion; mix 10 mL of deionized water with the remaining 20% ​​sodium (4-vinylphenyl)methanesulfonate and the remaining 40% potassium persulfate at 400 rpm. After stirring for 8 minutes, 35 mL of pre-emulsion was added, the temperature was raised to 75°C, 10 mL of pre-emulsion was added, and the mixture was stirred at 400 rpm for 6 hours to obtain a microemulsion. Ethanol with a mass fraction of 95% was added at a volume equal to that of the microemulsion, and the mixture was placed in an ice bath and allowed to separate into layers. The lower layer of solid was collected, centrifuged, washed three times with 95% ethanol, and dried at 40°C to constant weight to obtain sulfonated polystyrene microspheres. The mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate was 5:0.4:90.

[0049] (4) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer at a speed of 120 rpm, add 1.5 wt% oxidized starch aqueous solution at 1.05 times the mass of the sulfonated polystyrene microspheres, heat to 92°C, stir for 0.8 h, then add 3.5 times the mass of the sulfonated polystyrene microspheres of modified silica fiber, stir for 53 min, and then freeze at -18°C for 24 h to obtain a core-shell flame retardant;

[0050] (5) A polyethylene resin is prepared by mixing linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 45:15:28; a flame-retardant layer is extruded onto a copper braided shielded cable core in a mass ratio of 15:100:3:3 to obtain a cable.

[0051] Comparative Example 2

[0052] The difference between Comparative Example 2 and Example 2 is that step (3) is omitted, and step (5) is changed to: placing sulfonated polystyrene microspheres in a reaction device with a stirring device, turning on the stirring, stirring at a speed of 120 rpm, adding 1.5 wt% oxidized starch aqueous solution with 1.05 times the mass of sulfonated polystyrene microspheres, heating to 92°C, stirring for 0.8 h, then adding ceramic fibers with 3.5 times the mass of sulfonated polystyrene microspheres, stirring for 53 min, and then freezing at -18°C for 24 h to obtain a core-shell flame retardant; the remaining steps are the same as in Example 2.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 2 is that step (4) is omitted, and step (5) is changed to: placing polystyrene microspheres in a reaction device equipped with a stirrer, turning on the stirrer at a speed of 120 rpm, adding 1.5 wt% oxidized starch aqueous solution at 1.05 times the mass of polystyrene microspheres, heating to 92°C, stirring for 0.8 h, then adding modified ceramic fibers at 3.5 times the mass of polystyrene microspheres, stirring for 53 min, and then freezing at -18°C for 24 h to obtain a core-shell flame retardant; the remaining steps are the same as in Example 2.

[0055] Comparative Example 4

[0056] The difference between Comparative Example 4 and Example 2 is that step (5) is omitted, and step (6) is changed to: mixing linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 45:15:28 to obtain polyethylene resin; extruding a flame-retardant layer of sulfonated polystyrene microspheres, modified ceramic fibers, polyethylene resin, zinc stearate, and antioxidant 1010 in a mass ratio of 15:15:100:3:3 onto a copper braided shielded cable core at 180-188°C to obtain a cable.

[0057] Example of effect

[0058] Table 1 below shows the performance analysis results of the cables using Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0059] Table 1

[0060]

[0061] This invention uses sulfonated polystyrene microspheres as the core layer and starch as an adhesive to adhere modified ceramic fibers to the surface of the microspheres, thereby forming a core-shell flame retardant. Polystyrene has an oxygen barrier effect, which works synergistically with the heat insulation properties of the fibers to interrupt combustion and improve the flame retardancy of the cable. Furthermore, the sulfonated groups of the microspheres act as an acid source, decomposing and releasing sulfuric acid substances during combustion. The generated acid combines with the starch carbon source to produce an esterification reaction, promoting the flame retardant carbonization of the condensed phase, improving the quality and continuity of the carbon layer, and preventing secondary combustion caused by molten droplets. In addition, the presence of the core-shell structure promotes the uniform dispersion of the core layer, which is beneficial to optimizing the flame retardancy of the cable. At the same time, the heat insulation effect of the shell layer prevents the premature decomposition of polystyrene and avoids affecting the quality of the carbon layer.

[0062] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A halogen-free flame-retardant cable, comprising a copper conductor, a polyethylene insulation layer, a copper braided shielding layer, and a flame-retardant layer, characterized in that, The flame retardant layer is composed of a core-shell flame retardant, polyethylene resin, lubricant, and antioxidant. The polyethylene resin is a mixture of linear low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer in a weight ratio of 40-50:10-20:20-35. The linear low-density polyethylene has a density of 0.920 g / cm³. 3 The melt flow index is 2.0 g / 10 min; The density of the high-density polyethylene is 0.953 g / cm³. 3 The melt flow index is 0.4 g / 10 min; The lubricant is polyethylene wax or zinc stearate; The antioxidant is dilaurate thiodipropionate or antioxidant 1010; The preparation method of the core-shell flame retardant is as follows: (1) Place the silica fiber in a reaction apparatus equipped with a stirring device, turn on the stirring, and stir at a speed of 100-150 rpm. The reaction apparatus has two vents. The first vent introduces argon at a rate of 80-100 mL / min, hydrogen at a rate of 150-280 mL / min, and vaporized 1.5 mol / L rare earth chloride aqueous solution at a rate of 22-31 mL / min. The second vent introduces argon at a rate of 80-100 mL / min, hydrogen at a rate of 150-280 mL / min, and vaporized 1.5 mol / L phosphate aqueous solution at a rate of 22-31 mL / min. The temperature is increased to 1050-1200℃ at a rate of 5-15℃ / min and held for 2 hours to obtain ceramic fiber. The rare earth chloride is lanthanum chloride or cerium chloride, and the phosphate is one of ammonium phosphate, sodium phosphate, or phosphoric acid. (2) Mix 5-hexenyltriethoxysilane, deionized water and ethanol in a mass ratio of 1:4 to 8:14 to 24, adjust the pH to 4, immerse the ceramic fiber completely in it, react at 70°C for 1 to 2 hours, take it out, wash it three times with ethanol at 3000 rpm, and then dry it at 60°C for 24 hours to obtain modified ceramic fiber. (3) Dissolve 80% sodium dodecylbenzenesulfonate in 100 mL of deionized water, stir evenly at 60 °C, add sodium (4-vinylphenyl)methanesulfonate, the volume ratio of sodium (4-vinylphenyl)methanesulfonate to deionized water is 0.49~1.0:30~40, emulsify at 300~500 rpm for 20~25 min, add 60% potassium persulfate, stir again at 75 °C and 300~500 rpm for 10 min to obtain a pre-emulsion; mix 10 mL of deionized water with the remaining 20% ​​sodium (4-vinylphenyl)methanesulfonate and the remaining 40% potassium persulfate, stir at 300~500 rpm for 8 min, add 30~40 mL of the pre-emulsion, heat to 75 °C, add 10 mL of the pre-emulsion, stir at 300~500 rpm for 6 min. h, to obtain microemulsion, add 95% ethanol with a mass fraction of 1 volume of microemulsion, place in an ice bath, allow to stand and separate into layers, take the lower layer of solid after centrifugation, wash 3 times with 95% ethanol with a mass fraction of 1, dry at 40℃ to constant weight, to obtain sulfonic acid polystyrene microspheres. (4) Place the sulfonated polystyrene microspheres in a reaction apparatus equipped with a stirrer, turn on the stirrer, and stir at a speed of 100-150 rpm. Add 1.5 wt% oxidized starch aqueous solution at a mass of 1.0-1.1 times that of the sulfonated polystyrene microspheres. Heat to 90-95°C and stir for 0.5-1 h. Then add modified ceramic fibers at a mass of 2-5 times that of the sulfonated polystyrene microspheres and stir for 44-66 min. Then freeze at -18°C for 24 h to obtain a core-shell flame retardant. The preparation method of the silica fiber in step (1) is as follows: 1.2-2.0 mL of tetraethyl orthosilicate and 10 mL of anhydrous ethanol are mixed and stirred at 30-60 rpm for 4-6 h to obtain a silica solution. 0.75-1.1 g of polyvinylpyrrolidone and 15 g of N,N-dimethylformamide are mixed and stirred at 30-60 rpm for 8-12 h. The mixture is then added to the silica solution and stirred at 30-60 rpm for 2-5 h. The silica precursor fiber with an aspect ratio of 10-20 is obtained by electrospinning at a voltage of 15-20 kV, a solution flow rate of 0.5-2 mL / h, and a working distance of 15-20 cm between the needle and the collecting plate. The silica fiber is then kept at 520-600℃ for 3-5 h to obtain the silica fiber. In step (3), the mass ratio of sodium dodecylbenzenesulfonate, potassium persulfate, and sodium (4-vinylphenyl)methanesulfonate is 5:0.4:

90.

2. The halogen-free flame-retardant cable according to claim 1, characterized in that, The mass ratio of the core-shell flame retardant, polyethylene resin, lubricant, and antioxidant is 10-20:100:1-5:1-5. The flame retardant layer is produced by extrusion using a single-screw extruder at an extrusion temperature of 180-188°C.

Images