High-load flame-retardant steel wire rope and preparation method thereof

Abstract

The invention discloses a high-load flame-retardant steel wire rope which comprises a composite rope core and rope strands, the composite rope core is composed of seven sets of combined wires, and the invention relates to the technical field of steel wire ropes. According to the high-load flame-retardant steel wire rope and the preparation method thereof, the aramid fibers and the ultra-high molecular weight polyethylene fibers are combined through a specific structure to prepare the composite rope core of the steel wire rope, the high polymer material rope core can further improve the load capacity of the steel wire rope, and the high-load flame-retardant steel wire rope has good tensile capacity and toughness; the flame-retardant layer is arranged outside the steel wire rope strands, the internal structure of the steel wire rope can be protected, open fire combustion of the rope core and breakage caused by change of the internal structure of the rope under the high-temperature flammable condition are avoided, and the high-temperature stability and flame-retardant performance of the steel wire rope can be further improved through the flame retardant and the flame-retardant lubricant in the flame-retardant layer. The steel wire rope has high strength, high load bearing capacity and excellent flame retardant property, and is suitable for high-temperature flammable occasions.

Description

Technical Field

[0001] The present invention relates to the technical field of wire ropes, and particularly to a high-load flame-retardant wire rope and a preparation method thereof. Background Art

[0002] As an important mechanical transmission and load-bearing component, wire ropes are widely used in various fields such as hoisting, towing, transportation, and fixing. With the development of modern industry, the application environment of wire ropes has become more and more complex, and the requirements for their performance have also become higher and higher. In some special occasions, such as high-temperature, flammable and explosive environments, wire ropes not only need to have sufficient strength and load-bearing capacity, but also need to have good flame-retardant performance to prevent accidents caused by combustion.

[0003] Traditional wire ropes usually use natural fibers or synthetic fibers as the rope core to provide support and reduce the pressure between strands. However, these materials are prone to combustion in high-temperature and flammable environments, resulting in changes in the overall structure of the wire rope, which in turn affects its performance and safety. Therefore, it is particularly important to develop a high-load wire rope with excellent flame-retardant performance. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a high-load flame-retardant wire rope and a preparation method thereof, which solve the problems mentioned in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-load flame-retardant wire rope includes a composite rope core and rope strands. The composite rope core is composed of seven groups of combined wires, among which six groups of combined wires are helically twisted around another group of combined wires. Each group of combined wires includes a ultra-high molecular weight polyethylene fiber wire and several aramid fiber wires. The rope strands include a sub-outer layer strand and an outer layer strand. A nylon fiber layer is provided between the outside of the composite rope core and the rope strands, and a flame-retardant layer is provided on the outside of the rope strands, and a wear-resistant synthetic resin layer is provided on the outside of the flame-retardant layer.

[0006] Preferably, the aramid fiber wires are helically twisted around the ultra-high molecular weight polyethylene fiber wire, the sub-outer layer strand is helically twisted around the composite rope core in a specific manner, and the outer layer strand is helically twisted around the sub-outer layer strand in another specific manner.

[0007] Preferably, the raw materials of the flame-retardant layer and their mass fractions are: ethylene propylene diene monomer (EPDM) 50% - 60%, acrylonitrile grafted EPDM 5% - 10%, chloroprene rubber 10% - 17%, stearic acid 1% - 2%, accelerator 1% - 2%, vulcanizing agent 2% - 3%, antioxidant 1% - 2%, flame-retardant lubricant 3% - 5% and flame retardant 8% - 13%.

[0008] Preferably, the second outer layer strands are wrapped around the composite rope core in a left regular lay, and the outer layer strands are wrapped around the second outer layer strands in a right regular lay.

[0009] Preferably, the diameter of the outer layer strand wires is 2 to 3 times that of the second outer layer strand wires.

[0010] Preferably, the thickness of the wear-resistant synthetic resin layer is 0.3 mm, and the wear-resistant synthetic resin layer is made of one of epoxy resin and polyurethane resin.

[0011] The present invention also discloses a preparation method of a high-load flame-retardant steel wire rope, which specifically includes the following steps:

[0012] S1. Spinning ultra-high molecular weight polyethylene fibers into ultra-high molecular weight polyethylene fiber yarns through a machine, and then spinning the ultra-high molecular weight polyethylene fiber yarns into ultra-high molecular weight polyethylene filaments. Spinning aramid fibers into aramid fiber yarns through a machine, and then spinning the aramid fiber yarns into aramid filaments. Then, combining the ultra-high molecular weight polyethylene filaments and the aramid filaments into a combined filament by a spiral regular lay method, wherein the aramid filaments are spirally wrapped around the ultra-high molecular weight polyethylene filaments. Then, six groups of combined filaments are spirally wrapped around another group of combined filaments to form a composite rope core;

[0013] S2. Phosphating a number of steel wires with two diameters to obtain phosphated coated steel wires, wherein the diameter of the outer layer strand wires is 2 to 3 times that of the second outer layer strand wires. Then, wrapping the second outer layer strands around the composite rope core in a left regular lay, and then wrapping the outer layer strands around the second outer layer strands in a right regular lay. The structure of the second outer layer strands is 1×3, that is, each strand is composed of three steel wires; the structure of the outer layer strands is 1×7, that is, each strand is composed of seven steel wires;

[0014] S3. Setting a nylon fiber layer between the composite rope core and the second outer layer strands, and adding a brominated styrene polymer to the nylon fiber layer;

[0015] S4. Preparing the raw materials for the flame-retardant layer, mixing 50% - 60% of ethylene propylene diene monomer rubber, 5% - 10% of acrylonitrile-grafted ethylene propylene diene monomer rubber, 10% - 17% of chloroprene rubber, 1% - 2% of stearic acid, 1% - 2% of accelerator, 2% - 3% of vulcanizing agent, 1% - 2% of antioxidant, 3% - 5% of flame-retardant lubricant and 8% - 13% of flame retardant evenly, controlling the stirring temperature at 200°C - 280°C, the stirring time at 50 - 80 minutes, and the stirring rate of the mixer at 150 - 200 revolutions per minute. Coating the evenly mixed raw materials for the flame-retardant layer on the outer surface of the outer layer strands, and curing them through specific process means to form a flame-retardant layer;

[0016] S5. Setting a wear-resistant synthetic resin layer outside the flame-retardant layer, and the wear-resistant synthetic resin layer is set outside the flame-retardant layer by spraying, dipping or coating.

[0017] Beneficial effects

[0018] The present invention provides a high-load flame-retardant steel wire rope and a preparation method thereof. Compared with the prior art, the following beneficial effects are achieved. For the high-load flame-retardant steel wire rope and its preparation method, a composite rope core of the steel wire rope is prepared by combining aramid and ultra-high molecular weight polyethylene fibers in a specific structure. The high-molecular material rope core can further improve the load-bearing capacity of the steel wire rope, and has good tensile strength and toughness. A flame-retardant layer is provided outside the wire strands of the steel wire rope, which can protect the internal structure of the steel wire rope and prevent the rope core from catching fire under high-temperature and flammable conditions, and avoid the internal structure of the rope from changing and breaking. The flame retardant and flame-retardant lubricant in the flame-retardant layer can further improve the high-temperature stability and flame-retardant performance of the steel wire rope. The steel wire rope has high strength, high load-bearing capacity and excellent flame-retardant performance, and is suitable for high-temperature and flammable occasions, which can not only improve work efficiency but also enhance the safety of construction. By adding a nylon fiber layer modified with brominated styrene polymer, the flame-retardant performance and stability of the steel wire rope are further improved. The nylon fiber layer can stabilize the structure of the composite rope core and improve the oil storage effect of the rope core. Phosphated coated steel wires are used as the outer strands and the sub-outer strands, which improves the wear resistance and corrosion resistance of the steel wire rope and extends its service life. The phosphating treatment can also improve the bonding force between the steel wire and the flame-retardant layer, making the steel wire rope more firm and durable. The preparation method is simple and feasible, and is easy to realize industrial production. By precisely controlling the ratio of each raw material and the process parameters, a high-load flame-retardant steel wire rope with excellent performance can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional view of the structure of the present invention;

[0020] Figure 2 is a schematic structural view of the wire strands of the present invention;

[0021] Figure 3 is a schematic structural view of the composite rope core of the present invention.

[0022] In the figure: 1 - composite rope core, 2 - wire strands, 21 - sub-outer strands, 22 - outer strands, 3 - ultra-high molecular weight polyethylene fiber filaments, 4 - aramid fiber filaments, 5 - nylon fiber layer, 6 - flame-retardant layer, 7 - wear-resistant synthetic resin layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Please refer to Figures 1-3 Figures 1-3 , the present invention provides a technical solution: a high-load flame-retardant steel wire rope, which includes a composite rope core 1 and rope strands 2. The composite rope core 1 is composed of seven groups of combined wires, among which six groups of combined wires are helically twisted around another group of combined wires in a specific manner. Each group of combined wires includes a ultra-high molecular weight polyethylene fiber wire 3 and several aramid fiber wires 4. The rope strands 2 include a sub-outer layer strand 21 and an outer layer strand 22. A nylon fiber layer 5 is provided between the outside of the composite rope core 1 and the rope strands 2, and a flame-retardant layer 6 is provided on the outside of the rope strands 2, and a wear-resistant synthetic resin layer 7 is provided on the outside of the flame-retardant layer 6.

[0025] In the present invention, the aramid fiber wires 4 are helically twisted around the ultra-high molecular weight polyethylene fiber wire 3, the sub-outer layer strand 21 is helically twisted around the composite rope core 1 in a specific manner, and the outer layer strand 22 is helically twisted around the sub-outer layer strand 21 in another helical manner.

[0026] In the present invention, the raw materials of the flame-retardant layer 6 and their mass fractions are: ethylene-propylene-diene monomer 50% - 60%, acrylonitrile-grafted ethylene-propylene-diene monomer 5% - 10%, chloroprene rubber 10% - 17%, stearic acid 1% - 2%, accelerator 1% - 2%, vulcanizing agent 2% - 3%, antioxidant 1% - 2%, flame-retardant lubricant 3% - 5% and flame retardant 8% - 13%.

[0027] In the present invention, the sub-outer layer strand 21 is twisted around the composite rope core 1 in a left regular lay manner, and the outer layer strand 22 is twisted around the sub-outer layer strand 21 in a right regular lay manner.

[0028] In the present invention, the wire diameter of the outer layer strand 22 is 2 - 3 times that of the wire diameter of the sub-outer layer strand 21.

[0029] In the present invention, the thickness of the wear-resistant synthetic resin layer 7 is 0.3 mm, and the wear-resistant synthetic resin layer 7 is made of one of epoxy resin and polyurethane resin.

[0030] The present invention also discloses a preparation method of a high-load flame-retardant steel wire rope, which specifically includes the following embodiments:

[0031] Example 1

[0032] S1. Spin the ultra-high molecular weight polyethylene fiber into ultra-high molecular weight polyethylene fiber yarn through a machine, and then spin the ultra-high molecular weight polyethylene fiber yarn into ultra-high molecular weight polyethylene fiber wire 3. Spin the aramid fiber into aramid fiber yarn through a machine, and then spin the aramid fiber yarn into aramid fiber wire 4. Then, combine the ultra-high molecular weight polyethylene fiber wire 3 and the aramid fiber wire 4 into combined wires by using a helical alternating twist method, where the aramid fiber wire 4 is helically twisted around the ultra-high molecular weight polyethylene fiber wire 3. Next, helically twist six groups of combined wires around another group of combined wires to form the composite rope core 1;

[0033] S2. Phosphatize several steel wires of two diameters to obtain phosphatized coated steel wires. Among them, the diameter of the steel wires in the outer layer strand 22 is 2.5 times that of the steel wires in the sub-outer layer strand 21. Then, wrap the sub-outer layer strand 21 around the composite rope core 1 in a left regular lay manner, and then wrap the outer layer strand 22 around the sub-outer layer strand 21 in a right regular lay manner. The structure of the sub-outer layer strand 21 is 1×3, that is, each strand is composed of three steel wires; the structure of the outer layer strand 22 is 1×7, that is, each strand is composed of seven steel wires.

[0034] S3. Set a nylon fiber layer 5 between the composite rope core 1 and the sub-outer layer strand 21, and a brominated styrene polymer is added to the nylon fiber layer 5.

[0035] S4. Prepare the raw materials for the flame retardant layer 6. Mix 55% of ethylene propylene diene monomer rubber, 7% of acrylonitrile grafted ethylene propylene diene monomer rubber, 13% of chloroprene rubber, 2% of stearic acid, 1% of accelerator, 2% of vulcanizing agent, 1% of antioxidant, 4% of flame retardant lubricant and 10% of flame retardant evenly. Control the stirring temperature at 240°C, the stirring time at 65 minutes, and the stirring rate of the mixer at 175 revolutions per minute. Coat the evenly mixed raw materials for the flame retardant layer 6 on the outer surface of the outer layer strand 22, and cure it through specific process means to form a flame retardant layer 6.

[0036] S5. Set a wear-resistant synthetic resin layer 7 outside the flame retardant layer 6. The wear-resistant synthetic resin layer is set outside the flame retardant layer 6 by spraying, dipping or coating.

[0037] Example 2

[0038] S1. Spin ultra-high molecular weight polyethylene fibers into ultra-high molecular weight polyethylene fiber yarns through a machine, and then spin the ultra-high molecular weight polyethylene fiber yarns into ultra-high molecular weight polyethylene filaments 3. Spin aramid fibers into aramid fiber yarns through a machine, and then spin the aramid fiber yarns into aramid filaments 4. Then, combine the ultra-high molecular weight polyethylene filaments 3 and the aramid filaments 4 into a combined filament by means of spiral regular lay, where the aramid filaments 4 are spirally wrapped around the ultra-high molecular weight polyethylene filaments 3. Then, wrap six groups of combined filaments around another group of combined filaments to form a composite rope core 1.

[0039] S2. Phosphatize several steel wires of two diameters to obtain phosphatized coated steel wires. Among them, the diameter of the steel wires in the outer layer strand 22 is 2 times that of the steel wires in the sub-outer layer strand 21. Then, wrap the sub-outer layer strand 21 around the composite rope core 1 in a left regular lay manner, and then wrap the outer layer strand 22 around the sub-outer layer strand 21 in a right regular lay manner. The structure of the sub-outer layer strand 21 is 1×3, that is, each strand is composed of three steel wires; the structure of the outer layer strand 22 is 1×7, that is, each strand is composed of seven steel wires.

[0040] S3. A nylon fiber layer 5 is provided between the composite rope core 1 and the sub - outer layer strands 21, and a brominated styrene polymer is added to the nylon fiber layer 5;

[0041] S4. Prepare the raw materials for the flame - retardant layer 6. Mix 50% ethylene propylene diene monomer rubber, 5% acrylonitrile - grafted ethylene propylene diene monomer rubber, 10% chloroprene rubber, 1% stearic acid, 1% accelerator, 2% vulcanizing agent, 1% antioxidant, 3% flame - retardant lubricant, and 8% flame - retardant evenly. Control the stirring temperature at 200 °C, the stirring time at 50 minutes, and the stirring rate of the mixer at 150 revolutions per minute. Coat the outer surface of the outer layer strands 22 with the evenly - mixed raw materials for the flame - retardant layer 6 and cure it through specific technological means to form a flame - retardant layer 6;

[0042] S5. An abrasion - resistant synthetic resin layer 7 is provided outside the flame - retardant layer 6, and the abrasion - resistant synthetic resin layer is provided outside the flame - retardant layer 6 by spraying, impregnating, or coating.

[0043] Example 3

[0044] S1. Spun ultra - high - molecular - weight polyethylene fibers into ultra - high - molecular - weight polyethylene fiber yarns through a machine, and then spun the ultra - high - molecular - weight polyethylene fiber yarns into ultra - high - molecular - weight polyethylene filaments 3. Spun aramid fibers into aramid fiber yarns through a machine, and then spun the aramid fiber yarns into aramid filaments 4. Then, combine the ultra - high - molecular - weight polyethylene filaments 3 and aramid filaments 4 in a spiral cross - twist manner, where the aramid filaments 4 are spirally wrapped around the ultra - high - molecular - weight polyethylene filaments 3. Next, twist six groups of combined filaments around another group of combined filaments to form a composite rope core 1;

[0045] S2. Phosphatize several steel wires of two diameters to obtain phosphatized - coated steel wires. Among them, the diameter of the steel wires in the outer layer strands 22 is 3 times that of the steel wires in the sub - outer layer strands 21. Then, wrap the sub - outer layer strands 21 around the composite rope core 1 in a left - regular lay manner, and then wrap the outer layer strands 22 around the sub - outer layer strands 21 in a right - regular lay manner. The structure of the sub - outer layer strands 21 is 1×3, that is, each strand is composed of three steel wires; the structure of the outer layer strands 22 is 1×7, that is, each strand is composed of seven steel wires;

[0046] S3. A nylon fiber layer 5 is provided between the composite rope core 1 and the sub - outer layer strands 21, and a brominated styrene polymer is added to the nylon fiber layer 5;

[0047] S4. Prepare the raw materials for the flame retardant layer 6. Mix 60% ethylene propylene diene monomer rubber, 10% acrylonitrile grafted ethylene propylene diene monomer rubber, 17% chloroprene rubber, 2% stearic acid, 2% accelerator, 3% vulcanizing agent, 2% antioxidant, 5% flame retardant lubricant, and 13% flame retardant evenly. Control the stirring temperature at 280 °C, the stirring time at 50 - 80 minutes, and the stirring rate of the mixer at 200 revolutions per minute. Coat the evenly mixed raw materials of the flame retardant layer 6 on the outer surface of the outer layer strands 22, and cure it through specific process means to form a flame retardant layer 6.

[0048] S5. Set a wear-resistant synthetic resin layer 7 outside the flame retardant layer 6. The wear-resistant synthetic resin layer is set outside the flame retardant layer 6 by spraying, dipping, or coating.

[0049] Meanwhile, the content not described in detail in this specification belongs to the well-known prior art in the art.

[0050] Comparative experiment

[0051] A wire rope production factory conducts tensile strength, wear resistance, and alcohol blowtorch combustion tests on the cables made from Example 1, Example 2, and Example 3 respectively and the general wire ropes on the market simultaneously, and operates under the same time and conditions. During the detection process, data is statistically analyzed and a statistical table graph is made.

[0052]

[0053] As can be seen from the above table: By combining aramid and ultra-high molecular weight polyethylene fiber in a specific structure to produce the composite rope core of the wire rope, its high molecular material rope core can further improve the load-bearing capacity of the wire rope, and has good tensile strength and toughness; Setting a flame retardant layer outside the wire rope strands can protect the internal structure of the wire rope, avoid open flame combustion of the rope core under high-temperature flammable conditions, and prevent the internal structure of the rope from changing and breaking. The flame retardant and flame retardant lubricant in the flame retardant layer can further improve the high-temperature stability and flame retardant performance of the wire rope; The wire rope has high strength, high load-bearing capacity, and excellent flame retardant performance, and is suitable for high-temperature flammable occasions, which can not only improve work efficiency but also enhance construction safety; By adding a nylon fiber layer modified with brominated styrene polymer, the flame retardant performance and stability of the wire rope are further improved. The nylon fiber layer can stabilize the composite rope core structure and improve the oil storage effect of the rope core; Using phosphated coated steel wires as the outer layer strands and the sub-outer layer strands improves the wear resistance and corrosion resistance of the wire rope, extends its service life, and the phosphating treatment can also improve the bonding force between the steel wire and the flame retardant layer, making the wire rope more firm and durable; The preparation method is simple and feasible, easy to realize industrial production. By precisely controlling the ratio of each raw material and the process parameters, a high-load flame retardant wire rope with excellent performance can be prepared.

[0054] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0055] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-load flame-retardant steel wire rope, comprising a composite rope core (1) and rope strands (2), characterized in that: The composite rope core (1) is composed of seven groups of combined filaments, six of which are wrapped around another group of combined filaments in a specific spiral manner, each group of combined filaments includes an ultra-high molecular weight polyethylene fiber filament (3) and a plurality of aramid fiber filaments (4), the rope strands (2) include sub-outer strands (21) and outer strands (22), a nylon fiber layer (5) is arranged between the outside of the composite rope core (1) and the rope strands (2), and a flame retardant layer (6) is arranged outside the rope strands (2), and a wear-resistant synthetic resin layer (7) is arranged outside the flame retardant layer (6).

2. A high-load flame-retardant steel wire rope according to claim 1, characterized in that: The aramid fiber filaments (4) are twisted around the ultra-high molecular weight polyethylene fiber filaments (3) in a spiral manner, the sub-outer strands (21) are twisted around the composite rope core (1) in a specific spiral manner, and the outer strands (22) are twisted around the sub-outer strands (21) in another spiral manner.

3. The high-load flame-retardant steel wire rope according to claim 1, characterized in that: The raw materials of the flame retardant layer (6) and their mass fractions are: 50% to 60% of EPDM rubber, 5% to 10% of acrylonitrile-grafted EPDM rubber, 10% to 17% of chloroprene rubber, 1% to 2% of stearic acid, 1% to 2% of accelerator, 2% to 3% of vulcanizer, 1% to 2% of antioxidant, 3% to 5% of flame retardant lubricant and 8% to 13% of flame retardant.

4. The high-load flame-retardant steel wire rope according to claim 1, characterized in that: The sub-outer strands (21) are twisted around the composite rope core (1) in a left-hand alternating twist mode, and the outer strands (22) are twisted around the sub-outer strands (21) in a right-hand alternating twist mode.

5. The high-load flame-retardant steel wire rope according to claim 1, characterized in that: The diameter of the steel wire of the outer layer strand (22) is 2 to 3 times the diameter of the steel wire of the sub-outer layer strand (21).

6. The high-load flame-retardant steel wire rope according to claim 1, characterized in that: The thickness of the wear-resistant synthetic resin layer (7) is 0.3 mm, and the wear-resistant synthetic resin layer (7) is made of one of epoxy resin and polyurethane resin.

7. A method for preparing a high-load flame-retardant steel wire rope, characterized in that: The specific steps include: S1, spinning ultra-high molecular weight polyethylene fibers into ultra-high molecular weight polyethylene fiber yarns by a machine, then spinning the ultra-high molecular weight polyethylene fiber yarns into ultra-high molecular weight polyethylene fiber filaments (3), spinning aramid fibers into aramid fiber yarns by a machine, then spinning the aramid fiber yarns into aramid fiber filaments (4), then combining the ultra-high molecular weight polyethylene fiber filaments (3) and the aramid fiber filaments (4) into combined filaments by a spiral twisting method, wherein the aramid fiber filaments (4) spirally wrap around the ultra-high molecular weight polyethylene fiber filaments (3), then, spirally wrap around another group of combined filaments, and form a composite rope core (1); S2, phosphating a plurality of steel wires of two diameters to obtain phosphating coated steel wires, wherein the diameter of the outer strand (22) is 2 to 3 times the diameter of the sub-outer strand (21), and then the sub-outer strand (21) is twisted around the composite rope core (1) in a left-hand alternating twisting manner, and then the outer strand (22) is twisted around the sub-outer strand (21) in a right-hand alternating twisting manner, the sub-outer strand (21) has a structure of 1×3, i.e., each strand is composed of three steel wires; the outer strand (22) has a structure of 1×7, i.e., each strand is composed of seven steel wires; S3, a nylon fiber layer (5) is provided between the composite rope core (1) and the secondary outer strand (21), wherein a brominated styrene polymer is added to the nylon fiber layer (5); S4, prepare the raw materials of the flame retardant layer (6), mix 50%-60% of EPDM rubber, 5%-10% of acrylonitrile-grafted EPDM rubber, 10%-17% of chloroprene rubber, 1%-2% of stearic acid, 1%-2% of accelerator, 2%-3% of vulcanizer, 1%-2% of antioxidant, 3%-5% of flame retardant lubricant and 8%-13% of flame retardant evenly, control the stirring temperature at 200° C.-280° C., the stirring time at 50-80 minutes, and the stirring speed of the mixer at 150-200 rpm, apply the evenly mixed raw materials of the flame retardant layer (6) on the outer surface of the outer layer strand (22), and solidify them by specific process means to form a flame retardant layer (6); S5. Arrange a wear-resistant synthetic resin layer (7) outside the flame-retardant layer (6). The wear-resistant synthetic resin layer is arranged outside the flame-retardant layer (6) by spraying, dipping or coating.

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