A highly flame retardant cable and a method for producing the same

Abstract

The application provides a high-flame-retardant cable and a preparation method thereof, and belongs to the technical field of cables. The method comprises the following steps: S1, preparing an insulation layer-conductor material; S2, preparing an insulation layer-conductor filling composite material; S3, putting ethylene-vinyl acetate copolymer, ethylene-octene copolymer, a flame retardant and montmorillonite into a banburying machine, banburying, extruding, and obtaining a sheath material; and coating the insulation layer-conductor filling composite material, a semi-conductive layer, a shielding layer and the sheath along the conductor axis in sequence to obtain the high-flame-retardant cable. The technical scheme provided by the application achieves the purposes of good flame retardancy and good smoke suppression of the cable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable, in particular to a high flame-retardant cable and a preparation method thereof. BACKGROUND

[0002] With the development of power system to high voltage and large capacity, and the strict requirements of rail transit, nuclear power facilities and other special scenes on cable safety, the flame retardant performance of traditional cable has been difficult to meet the modern engineering demand. According to statistics, the limiting oxygen index of conventional flame-retardant cable under high temperature and open flame condition is generally lower than 28%, the heat release rate is generally high, and a large amount of toxic smoke is accompanied during combustion, which exists significant safety hazard. Traditional flame-retardant system mainly depends on the endothermic decomposition of aluminum / magnesium hydroxide or the gas phase quenching effect of halogen-based flame retardant. Although the halogen-based flame retardant has high efficiency, it releases toxic gases such as HBr and dioxin during combustion, causing environmental pollution.

[0003] The patent application file with publication number CN103093873A discloses a halogen-free high flame-retardant cable. The insulating layer of the cable includes an outer insulating layer and an inner insulating layer formed by double-layer co-extrusion. The tensile strength of the outer insulating layer is greater than or equal to 13.8 MPa, and the elongation at break is greater than or equal to 300%. The material of the inner insulating layer is high flame-retardant adhesive. The outer insulating layer includes 100 parts of ethylene copolymer and / or ternary ethylene propylene rubber, 60-150 parts of halogen-free flame retardant, 1-10 parts of compatibilizer, 0.1-5 parts of antioxidant, 0.1-5 parts of lubricant, 0-20 parts of polymer elastomer, and 0-3 parts of coupling agent. The inner insulating layer includes 100 parts of ethylene copolymer and / or ternary ethylene propylene rubber, 80-250 parts of halogen-free flame retardant, 1-10 parts of compatibilizer, 0.1-5 parts of antioxidant, 0.1-5 parts of lubricant, 0-20 parts of polymer elastomer, and 0-3 parts of coupling agent. The patent only improves the flame retardant performance of the insulating layer, and the overall flame retardant performance of the cable is still insufficient.

[0004] Therefore, it is necessary to provide a high flame-retardant cable and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0005] Therefore, the present application provides a high flame-retardant cable and a preparation method thereof, which realizes good flame retardant and smoke suppression performance.

[0006] The specific scheme of the present application is as follows. A preparation method of a high flame-retardant cable includes the following steps:

[0007] Step S1. Mix and knead methyl vinyl silicone rubber and KH-550 (γ-aminopropyl triethoxysilane), then add boron nitride, aluminum hydroxide and composite powder, continue to knead, deaerate, obtain a kneaded adhesive, inject into a conductor outer layer mold for extrusion molding, vulcanize, and form an insulating layer coated conductor after demolding to obtain an insulating layer-conductor material;

[0008] Step S2. Add the rice powder to the deionized water, gelatinize, then add the expanded graphite powder, magnesium hydroxide and azodicarbonamide, mix uniformly, knead to obtain a filling material, inject into the core gap of the insulation-conductor material, foam to obtain an insulation-conductor filling composite material;

[0009] Step S3. Put the ethylene-vinyl acetate copolymer, ethylene-octene copolymer, flame retardant and montmorillonite into a banbury mixer, mix and extrude to obtain a sheath material, then sequentially coat the insulation-conductor filling composite material, the semi-conductive layer and the shielding layer along the conductor axis to obtain a high-flame-retardant cable;

[0010] The raw material of the composite powder comprises rice powder and cerium oxide.

[0011] The methyl vinyl silicone rubber is used as the base material to prepare the cable insulation layer, which has a high Si-O bond energy, can endow the insulation layer with high temperature stability, and as an elastomer, can increase the flexibility of the cable. Boron nitride has a unique two-dimensional layered structure, and through molding, it promotes the directional arrangement of boron nitride, forming an efficient heat transfer channel, thereby significantly improving the heat conduction capacity of the insulation layer. Meanwhile, boron nitride also has insulation and stability, which can make the insulation performance and high temperature stability of the insulation layer better. The cerium oxide in the composite powder can provide thermal stability at high temperatures, and together with boron nitride and aluminum hydroxide, it forms an inorganic framework to provide structural support, prevent collapse and enhance the mechanical properties of the cable. The cerium oxide can also enhance the strength of the carbon layer after the silicon rubber is ceramicized, and promote the improvement of the flame retardant performance of the cable. Aluminum hydroxide as a flame retardant, decomposes into aluminum oxide at high temperatures, which can block oxygen and inhibit combustion.

[0012] At high combustion temperatures, the interlayer sulfuric acid molecules of expanded graphite can vaporize, allowing it to expand rapidly and form a porous structure. Meanwhile, the three-dimensional gel network formed by the gelatinization of rice powder can carbonize to form a porous carbon layer when the cable is in a combustion environment, further cooperating with the porous structure formed by the expanded graphite to adsorb smoke particles and play a role in smoke suppression. Magnesium hydroxide will absorb heat and decompose at high temperatures, forming MgO and releasing water vapor. MgO can adsorb acidic smoke to reduce smoke density, play a role in flame retardation and smoke suppression, and improve the flame retardant performance of the cable.

[0013] The ethylene-vinyl acetate copolymer has good flexibility and impact resistance, can provide good adhesion, and helps to enhance the bonding force between the sheath layer and other layers. The ethylene-octene copolymer has excellent flexibility and resilience, significantly improves the bending performance of the cable, and also helps to improve the wear resistance and tear resistance of the cable. Montmorillonite has good thermal stability, compressive strength and swelling properties, and can improve the flame retardant performance of the sheath layer when combined with the flame retardant.

[0014] The sheath layer, insulation layer and conductor filling material of the cable all have flame-retardant properties from outside to inside, the carbon layer formed by the sheath can block oxygen, the composite carbon layer formed by the expanded graphite powder and the sesbania powder can seal the gap and absorb smoke, and the ceramic insulation layer can further block oxygen and quickly conduct heat to reduce the temperature, so that the three effects synergistically inhibit combustion to achieve the purpose of flame-retardant and smoke-suppressing.

[0015] Preferably, in the step S1, the mixing and mixing time is 5-10 min; the temperature for continuing mixing is 85-95℃, and the time is 15-20 min; and the conductor is twisted from a copper core.

[0016] Preferably, the preparation of the composite powder comprises the following steps: adding the sesbania powder and cerium oxide into a ball mill tank for ball milling, sieving, and drying to obtain the composite powder.

[0017] Preferably, the rotation speed of the ball milling is 200-400 rpm, and the time is 1.5-3 h.

[0018] Preferably, in the step S2, the temperature for gelation is 55-65℃, and the time is 20-30 min.

[0019] The sesbania powder is a natural high-molecular polysaccharide, and the hydroxyl groups thereof can form hydrogen bonds with the surface hydroxyl groups of cerium oxide, so as to promote the dispersion of cerium oxide in the base material and avoid agglomeration. Moreover, the sesbania powder can form a three-dimensional gel network after gelation, so as to play a role of adhesive.

[0020] Preferably, in the step S3, the montmorillonite is modified montmorillonite, and the modification step is as follows: adding 30-40 parts of 1,8-eucalyptol and 500-600 parts of montmorillonite into a mixer, and heating and mixing to obtain the modified montmorillonite.

[0021] The 1,8-eucalyptol is non-polar and has strong lipophilicity, can penetrate the lipid bilayer structure of the cell membrane of microorganisms, interfere with the permeability of the membrane, and cause the death of microorganisms, so as to achieve the effect of inhibiting bacteria. The introduction of 1,8-eucalyptol intercalation modification of montmorillonite can realize the slow release of 1,8-eucalyptol, so as to enhance the antibacterial and mildew-proof performance of the cable.

[0022] Preferably, the temperature for heating and mixing is 50-60℃, and the time is 30-60 min.

[0023] Preferably, in the step S3, the temperature for internal mixing is 135-150℃, and the time is 20-40 min.

[0024] Preferably, in the step S3, the semi-conductive layer is a ternary ethylene-propylene rubber; and the shielding layer is a copper wire woven shielding layer.

[0025] To achieve the above object, the application further provides a high flame-retardant cable prepared by the preparation method of the high flame-retardant cable.

[0026] Preferably, the high flame-retardant cable is obtained by sequentially coating an insulation layer-conductor filling composite material, a semi-conductive layer, a shielding layer and a sheath along the conductor axis.

[0027] Preferably, the insulation layer-conductor filling composite material is obtained by compounding an insulation layer-conductor material and a filling material.

[0028] Preferably, the insulation layer in the insulation layer-conductor material comprises the following raw materials in parts by weight: methyl vinyl silicone rubber 50-60 parts, KH-550 2-4 parts, boron nitride 10-15 parts, aluminum hydroxide 18-23 parts and composite powder 8-12 parts.

[0029] Preferably, the filling material comprises the following raw materials in parts by weight: sesbania powder 9-11 parts, deionized water 90-110 parts, expanded graphite powder 28-32 parts, magnesium hydroxide 45-55 parts and azodicarbonamide 4-5 parts.

[0030] Preferably, the sheath material comprises the following raw materials in parts by weight: ethylene-vinyl acetate copolymer 35-45 parts, ethylene-octene copolymer 35-45 parts, flame retardant 10-20 parts and montmorillonite 10-15 parts.

[0031] The cable with the best flame-retardant performance can be obtained by using the above components in parts by weight, so as to achieve the purposes of good flame-retardant performance and good smoke suppression performance of the cable.

[0032] The above technical solution of the application at least has the following beneficial effects:

[0033] (1) The methyl vinyl silicone rubber can endow the insulation layer with high-temperature stability, and as an elastomer, it can increase the flexibility of the cable. The boron nitride has a unique two-dimensional layered structure, can form an efficient heat transfer channel, and can improve the heat conduction capacity of the insulation layer, and at the same time, can make the insulation performance and high-temperature stability of the insulation layer better. The aluminum hydroxide as a flame retardant can absorb heat and decompose into aluminum oxide at high temperature, which can block oxygen and inhibit combustion.

[0034] (2) At high combustion temperature, the expanded graphite forms a porous structure and the sesbania powder forms a porous carbon layer, which produce a synergistic effect, adsorb smoke particles, and play a role in smoke suppression. The magnesium hydroxide will absorb heat and decompose to form MgO and release water vapor at high temperature, the MgO can adsorb acidic smoke and reduce smoke density, play a role in flame retardation and smoke suppression, and improve the flame-retardant performance of the cable.

[0035] (3) The carbon layer formed by the cable sheath can block oxygen, the composite carbon layer formed by the filling layer can close the gap and absorb smoke, and the insulating layer can further block oxygen and quickly conduct heat to reduce the temperature, so that the three effects synergistically inhibit combustion, achieving the purpose of flame retardation and smoke suppression. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. The described embodiments are part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present application belong to the scope of protection of the present application.

[0037] In the following embodiments, the semi-conductive layer uses terpolymer, and the shielding layer uses copper wire braided shielding layer.

[0038] Embodiment 1

[0039] 50 g of sesbania powder and 40 g of cerium oxide were added to a ball mill tank, and ball milling was performed at a speed of 300 rpm for 2 h, sieved through a 200 mesh sieve, and dried to obtain a composite powder. 55 g of methylvinyl silicone rubber and 3 g of KH-550 were added to a mixer, heated to 80℃, and mixed for 10 min. Then, 12 g of boron nitride, 20 g of aluminum hydroxide and 10 g of the composite powder were added, heated to 90℃, and mixed for 15 min. After degassing, a mixing compound was obtained, which was injected into a conductor outer layer mold and extruded into a shape. After vulcanization and demolding, an insulating layer-coated conductor was formed, and an insulating layer-conductor material was obtained.

[0040] 10 g of sesbania powder was added to 100 ml of deionized water, heated to 65℃, and stirred at a speed of 200 rpm for 20 min. Then, 30 g of expanded graphite powder, 50 g of magnesium hydroxide and 5 g of azodicarbonamide were added, and a filling material was obtained after kneading. The filling material was injected into the gap between the cable core of the insulating layer-conductor material, and foaming was performed to obtain an insulating layer-conductor filling composite material.

[0041] 35 g of 1,8-eucalyptol and 500 g of montmorillonite were added to a mixer, heated to 55℃, and mixed at a speed of 700 rpm for 50 min to obtain modified montmorillonite.

[0042] 40 g of ethylene-vinyl acetate copolymer, 40 g of ethylene-octene copolymer, 15 g of flame retardant and 10 g of modified montmorillonite were put into a banbury mixer, fully stirred and uniformly mixed, heated to 150℃, and banbury mixed for 20 min. Extrusion granulation was performed to obtain a sheath material. The insulating layer-conductor filling composite material, the semi-conductive layer, the copper wire braided shielding layer and the sheath were sequentially coated along the conductor axis, and cooled to obtain a high-flame-retardant cable.

[0043] Embodiment 2

[0044] 50 g of sesbania powder and 40 g of cerium oxide were added to a ball mill tank, and ball milling was performed at a speed of 200 rpm for 3 h, sieved through a 200 mesh screen, and dried to obtain a composite powder. 50 g of methyl vinyl silicone rubber and 4 g of KH-550 were added to a mixer, heated to 80°C, and mixed for 5 min, and then 15 g of boron nitride, 18 g of aluminum hydroxide, and 12 g of the composite powder were added, heated to 90°C, and mixed for 15 min to obtain a mixed rubber, which was injected into a conductor outer layer mold to be extrusion molded, vulcanized, and then removed to form an insulating layer-coated conductor, thereby obtaining an insulating layer-conductor material.

[0045] 9 g of sesbania powder was added to 90 ml of deionized water, heated to 55°C, and stirred at a speed of 200 rpm for 25 min, and then 30 g of expanded graphite powder, 55 g of magnesium hydroxide, and 4 g of azodicarbonamide were added to obtain a filling material after kneading, which was injected into the gap between the cores of the insulating layer-conductor material, and foamed to obtain an insulating layer-conductor filling composite material.

[0046] 30 g of 1,8-eucalyptol and 550 g of montmorillonite were added to a mixer, heated to 60°C, and mixed at a speed of 650 rpm for 60 min to obtain modified montmorillonite.

[0047] 35 g of ethylene-vinyl acetate copolymer, 45 g of ethylene-octene copolymer, 10 g of a flame retardant, and 10 g of modified montmorillonite were put into a mixer, stirred well and uniformly, heated to 140°C, and mixed for 35 min to obtain a sheath material, which was coated on the insulating layer-conductor filling composite material, the semi-conductive layer, the copper wire braided shielding layer, and the sheath along the conductor axis in sequence to obtain a high-flame-retardant cable.

[0048] Example 3

[0049] 50 g of sesbania powder and 40 g of cerium oxide were added to a ball mill tank, and ball milling was performed at a speed of 400 rpm for 2 h, sieved through a 200 mesh screen, and dried to obtain a composite powder. 60 g of methyl vinyl silicone rubber and 2 g of KH-550 were added to a mixer, heated to 80°C, and mixed for 8 min, and then 10 g of boron nitride, 23 g of aluminum hydroxide, and 8 g of the composite powder were added, heated to 90°C, and mixed for 20 min to obtain a mixed rubber, which was injected into a conductor outer layer mold to be extrusion molded, vulcanized, and then removed to form an insulating layer-coated conductor, thereby obtaining an insulating layer-conductor material.

[0050] 11 g of sesbania powder was added to 110 ml of deionized water, heated to 60°C, and stirred at a speed of 200 rpm for 25 min, and then 32 g of expanded graphite powder, 50 g of magnesium hydroxide, and 5 g of azodicarbonamide were added to obtain a filling material after kneading, which was injected into the gap between the cores of the insulating layer-conductor material, and foamed to obtain an insulating layer-conductor filling composite material.

[0051] Put 40 g of 1,8-cineole and 500 g of montmorillonite into a mixer, heat to 50℃, mix at 800 rpm for 30 min, to obtain modified montmorillonite.

[0052] Put 45 g of ethylene-vinyl acetate copolymer, 40 g of ethylene-octene copolymer, 10 g of flame retardant, and 15 g of modified montmorillonite into an internal mixer, mix well, heat to 135℃, and mix for 40 min, then extrude and granulate to obtain a sheath material. The insulating layer-conductor filling composite material, the semi-conductive layer, the copper wire braided shielding layer, and the sheath are sequentially coated along the conductor axis to obtain a high-flame-retardant cable.

[0053] Example 4

[0054] Put 50 g of sesbania powder and 40 g of cerium oxide into a ball mill tank, and ball mill at 400 rpm for 1.5 h, then sieve through a 200-mesh sieve and dry to obtain a composite powder. Put 55 g of methylvinyl silicone rubber and 4 g of KH-550 into a mixer, heat to 80℃, and mix for 5 min. Then add 10 g of boron nitride, 23 g of aluminum hydroxide, and 8 g of the composite powder, heat to 90℃, and mix for 20 min. Defoam to obtain a mixed rubber, which is injected into a conductor outer layer mold to be extruded and molded, vulcanized, and demolded to form an insulating layer-coated conductor to obtain an insulating layer-conductor material.

[0055] Put 10 g of sesbania powder into 100 ml of deionized water, heat to 60℃, and stir at 200 rpm for 20 min. Then add 32 g of expanded graphite powder, 45 g of magnesium hydroxide, and 5 g of azodicarbonamide, and knead to obtain a filling material, which is injected into the gap between the cable cores of the insulating layer-conductor material to be foamed to obtain an insulating layer-conductor filling composite material.

[0056] Put 35 g of 1,8-cineole and 600 g of montmorillonite into a mixer, heat to 55℃, and mix at 750 rpm for 40 min to obtain modified montmorillonite.

[0057] Put 40 g of ethylene-vinyl acetate copolymer, 45 g of ethylene-octene copolymer, 15 g of flame retardant, and 15 g of modified montmorillonite into an internal mixer, mix well, heat to 140℃, and mix for 30 min, then extrude and granulate to obtain a sheath material. The insulating layer-conductor filling composite material, the semi-conductive layer, the copper wire braided shielding layer, and the sheath are sequentially coated along the conductor axis to obtain a high-flame-retardant cable.

[0058] Example 5

[0059] Put 50 g of sesbania powder and 40 g of cerium oxide into a ball mill tank, and mill at 350 rpm for 2 h, sieve through a 200 mesh screen, and dry to obtain a composite powder. Put 60 g of methyl vinyl silicone rubber and 2 g of KH-550 into a mixer, heat to 80 °C, and mix for 10 min, then add 15 g of boron nitride, 18 g of aluminum hydroxide, and 12 g of the composite powder, heat to 90 °C, and mix for 15 min, and then deaerate to obtain a mixed rubber, which is injected into a conductor outer layer mold to be extruded into shape, vulcanized, and then removed from the mold to form an insulating layer-coated conductor, thereby obtaining an insulating layer-conductor material.

[0060] Put 11 g of sesbania powder into 110 ml of deionized water, heat to 55 °C, and stir at 200 rpm for 30 min, then add 30 g of expanded graphite powder, 45 g of magnesium hydroxide, and 5 g of azodicarbonamide, and knead to obtain a filling material, which is injected into the gap between the cores of the insulating layer-conductor material, and foamed to obtain an insulating layer-conductor filling composite material.

[0061] Put 30 g of 1,8-eucalyptol and 600 g of montmorillonite into a mixer, heat to 50 °C, and mix at 700 rpm for 45 min to obtain modified montmorillonite.

[0062] Put 35 g of ethylene-vinyl acetate copolymer, 35 g of ethylene-octene copolymer, 20 g of a flame retardant, and 15 g of modified montmorillonite into a mixer, mix well, heat to 135 °C, and mix for 40 min, and then extrude and granulate to obtain a sheath material, which is used to coat the insulating layer-conductor filling composite material, the semiconductive layer, the copper wire braided shielding layer, and the sheath along the conductor axis in sequence to obtain a high-flame-retardant cable.

[0063] Example 6

[0064] Put 50 g of sesbania powder and 40 g of cerium oxide into a ball mill tank, and mill at 250 rpm for 2.5 h, sieve through a 200 mesh screen, and dry to obtain a composite powder. Put 50 g of methyl vinyl silicone rubber and 3 g of KH-550 into a mixer, heat to 80 °C, and mix for 8 min, then add 15 g of boron nitride, 21 g of aluminum hydroxide, and 12 g of the composite powder, heat to 90 °C, and mix for 17 min, and then deaerate to obtain a mixed rubber, which is injected into a conductor outer layer mold to be extruded into shape, vulcanized, and then removed from the mold to form an insulating layer-coated conductor, thereby obtaining an insulating layer-conductor material.

[0065] Put 10 g of sesbania powder into 100 ml of deionized water, heat to 55 °C, and stir at 200 rpm for 25 min, then add 28 g of expanded graphite powder, 50 g of magnesium hydroxide, and 4 g of azodicarbonamide, and knead to obtain a filling material, which is injected into the gap between the cores of the insulating layer-conductor material, and foamed to obtain an insulating layer-conductor filling composite material.

[0066] Put 40g ethylene-vinyl acetate copolymer, 35g ethylene-octene copolymer, 15g flame retardant and 10g montmorillonite into a banbury mixer, fully stir evenly, heat to 150℃, banbury time 30min, extrusion granulation, get the sheath material, the insulating layer-conductor filling composite material, the semiconductive layer, the copper wire braid shielding layer and the sheath are coated along the conductor axis in turn, get the high flame retardant cable.

[0067] The present application also carries out comparative examples and related tests

[0068] Comparative example 1

[0069] Comparative example 1 and example 1 are different in that the preparation of composite powder is not carried out, and the other components and preparation methods are the same as example 1, and the high flame retardant cable is prepared.

[0070] Comparative example 2

[0071] Comparative example 2 and example 1 are different in that the preparation of insulating layer-conductor filling composite material is not used with the use of sesbania powder, and the other components and preparation methods are the same as example 1, and the high flame retardant cable is prepared.

[0072] Comparative example 3

[0073] Comparative example 3 and example 1 are different in that the expanded graphite powder is not used, and the other components and preparation methods are the same as example 1, and the high flame retardant cable is prepared.

[0074] Performance test

[0075] According to the test standard of GB / T 31248-2014, the high flame retardant cables prepared by example 1-6 and comparative example 1-3 are tested for flame retardant performance, and the results are shown in table 1.

[0076] Table 1 flame retardant performance test results

[0077]

[0078] From the results in table 1, it can be seen that the flame retardant performance of comparative example 1 is obviously different from that of example 1, which shows that the addition of composite powder can effectively improve the flame retardant performance of the insulating layer, thereby improving the flame retardant property of the cable; the smoke suppression performance of comparative example 2 is obviously lower than that of example 1, which shows that sesbania powder helps to improve the density of carbon layer and promote the improvement of cable smoke suppression performance; the flame retardant performance of comparative example 3 is decreased to a certain extent compared with example 1, and the difference in smoke suppression performance is the largest, which shows that expanded graphite powder can improve the flame retardant performance of the cable and greatly improve the smoke suppression performance of the cable.

[0079] The high flame-retardant cables prepared by the examples 1-6 and the comparative examples 1-3 were subjected to toughness test and antibacterial test, the toughness performance test was conducted according to GB / T 2951-2008, and the antibacterial test was conducted according to ISO 22196-2011, and the test results are shown in Table 2.

[0080] Table 2: Test results of toughness and antibacterial performance

[0081]

[0082] According to the test results of the comparative examples 1-3 and the examples 1-6, it can be seen from the test results in Table 2 that the toughness of the comparative example 2 decreases obviously, which indicates that the three-dimensional gel network formed by the amaranth powder promotes the toughness of the cable; the antibacterial rate of the example 6 decreases obviously compared with the examples 1-5, which indicates that the 1,8 cineole modified montmorillonite helps to improve the antibacterial performance of the cable.

[0083] The above is the preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing a highly flame-retardant cable, characterized in that: The following steps are involved: Step S1. Methyl vinyl silicone rubber and KH-550 are mixed and kneaded, and then boron nitride, aluminum hydroxide and composite powder are added, and the mixing is continued and degassed to obtain a mixed rubber material, which is injected into a conductor outer layer mold for extrusion molding, vulcanized, and demolded to form an insulating layer covering the conductor to obtain an insulating layer-conductor material; Step S2. The sesbania powder is added to deionized water, gelled, and then expanded graphite powder, magnesium hydroxide and azodicarbonamide are added, mixed evenly, and kneaded to obtain a filling material, which is injected into the gap between the insulating layer and the conductor material of the cable core and foamed to obtain an insulating layer-conductor filled composite material; Step S3. Ethylene-vinyl acetate copolymer, ethylene-octene copolymer, flame retardant, and montmorillonite are placed in an internal mixer, mixed, and extruded to obtain a sheath material. The insulating layer-conductor filling composite material, the semiconductive layer, the shielding layer, and the sheath are sequentially coated along the axial direction of the conductor to obtain a highly flame-retardant cable; The raw materials of the composite powder include sesbania powder and cerium oxide.

2. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: In step S1, the mixing and kneading time is 5-10 minutes; the mixing temperature is continued at 85-95° C. for 15-20 minutes; and the conductor is formed by twisting the copper core.

3. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: The preparation of the composite powder comprises the following steps: adding sesbania powder and cerium oxide into a ball mill, performing ball milling, sieving, and drying to obtain the composite powder.

4. The method for preparing a highly flame-retardant cable according to claim 3, characterized in that: The ball milling speed is 200-400 rpm, and the time is 1.5-3 hours.

5. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: In step S2, the gelling temperature is 55-65° C. and the gelling time is 20-30 minutes.

6. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: In step S3, the montmorillonite is modified montmorillonite, and the modification steps are as follows: 30-40 parts of 1,8-cineole and 500-600 parts of montmorillonite are added into a mixer, heated and mixed to obtain the modified montmorillonite.

7. The method for preparing a highly flame-retardant cable according to claim 6, characterized in that: The temperature of the heating and mixing is 50-60° C., and the time is 30-60 minutes.

8. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: In step S3, the mixing temperature is 135-150° C. and the mixing time is 20-40 minutes.

9. The method for preparing a highly flame-retardant cable according to claim 1, characterized in that: In step S3, the semi-conductive layer is EPDM rubber; and the shielding layer is a copper wire braided shielding layer.

10. A highly flame-retardant cable, characterized in that: The highly flame-retardant cable is prepared by the method for preparing the highly flame-retardant cable according to any one of claims 1 to 9.

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