A high-voltage flexible cable for shield machine and its preparation process

Abstract

The present invention relates to the field of cable technology, and more specifically, it relates to a high-voltage flexible cable for a shield machine and a preparation process thereof. A high-voltage flexible cable for a shield machine comprises a cable core, an inner sheath, a tensile reinforcement braided layer and an outer sheath arranged in sequence from the inside to the outside, wherein the raw material of the tensile reinforcement braided layer is tensile toughened aramid yarn, and the raw material of the outer sheath is wear-resistant flexible sheath material. The tensile toughened aramid yarn has good tensile and bending resistance, can effectively withstand the tensile force to which the cable is subjected during use, and adapt to the frequent bending of the cable; the flexible and wear-resistant composite filler in the wear-resistant flexible sheath material combines the flame retardancy and wear resistance of hydroxyapatite with the flexibility and tensile strength of reed fiber, which can improve the tensile strength, flame retardancy and wear resistance of the sheath of the flexible cable for the shield machine.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and in particular to a high-voltage flexible cable for a shield machine and a preparation process thereof. Background Art

[0002] A shield machine is a mechanical device used for underground tunneling, suitable for modern transportation, underground engineering, mining, water conservancy projects, municipal construction, and electrical communications. Shield machines excavate tunnels in harsh environments such as high temperature, humidity, and gravel. As a core component of these machines, shield machine cables must not only exhibit excellent insulation physical and mechanical properties, as well as electrical performance, but also possess superior physical and mechanical properties and crack resistance. Existing technologies typically utilize high-performance sheath materials and incorporate a fiber braid reinforcement layer embedded within the extruded outer sheath to improve the overall performance of the cable sheath.

[0003] At present, the commonly used fiber braiding reinforcement material is mainly aramid yarn. Although aramid yarn has high strength and heat resistance, it is composed of a highly conjugated rigid structure, with a smooth surface and high inertness. It has poor interfacial adhesion with the inner sheath, outer sheath and other sheath materials of the cable, which can easily lead to delamination and debonding between the fiber braiding reinforcement layer and other sheath layers during the use of the cable, affecting the overall structural stability and mechanical properties such as tensile strength and bending resistance of the cable.

[0004] Existing high-performance sheath materials are primarily made by adding fillers (such as kaolin, zinc oxide, hydroxylated apatite, and silica), flame retardants, antioxidants, and other additives to a rubber base material (such as polyvinyl chloride, butyl rubber, and ethylene propylene rubber), imparting wear resistance, flame retardancy, and aging resistance to the rubber base material. Hydroxylated apatite, while possessing high hardness, strength, and flame retardancy, can improve the wear resistance and flame retardancy of cable sheath materials. However, hydroxylated apatite is inherently brittle, and excessive addition can reduce the toughness of the sheath material. Furthermore, the presence of hydroxyl groups in hydroxylated apatite results in poor compatibility with the rubber base material of the sheath material. Consequently, cracks can easily form at the interface between the hydroxylated apatite particles and the rubber base material when the cable is subjected to deformation, such as bending or stretching. These cracks can then expand and damage the sheath material, impacting the reliability and service life of the cable.

[0005] In addition, reed is a widely distributed natural plant, a renewable resource, and has certain strength and modulus, which can improve the tensile strength and flexibility of cable sheath materials to a certain extent. However, reed fiber has poor flame retardancy and contains a large amount of hydroxyl groups, which are hydrophilic, reducing the interfacial bonding strength between reed fiber and rubber substrate, affecting the overall performance of the sheath material, and thus the safety of cable use. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a high-voltage flexible cable for a shield machine and a preparation process thereof.

[0007] A high-voltage flexible cable for a shield machine comprises a cable core, an inner sheath, a tensile reinforcement braided layer, and an outer sheath, which are arranged in sequence from the inside out. The cable core consists of three main cores and three ground cores. The centers of the three main cores are arranged in an equilateral triangle, and the three ground cores are respectively arranged in the gap between every two adjacent main cores.

[0008] The raw material of the tensile reinforcement braided layer is tensile toughened aramid yarn, and the raw material of the outer sheath is wear-resistant flexible sheath material;

[0009] The tensile toughening aramid yarn is prepared by using silica particle grafted aramid yarn and methyl methacrylate as raw materials, using azobisisobutyronitrile as an initiator, and grafting polymethyl methacrylate on the surface of the silica particle grafted aramid yarn;

[0010] The silica particle grafted aramid yarn is obtained by modifying the aramid yarn with a silane coupling agent and then loading silica particles on the surface of the modified aramid yarn.

[0011] The raw materials of the wear-resistant flexible sheath material are 80-120 parts by weight of rubber base material, 10-30 parts by weight of flexible and wear-resistant composite filler, 1-5 parts by weight of plasticizer, 2-6 parts by weight of vulcanizing agent, 2-5 parts by weight of antioxidant, 1-7 parts by weight of coupling agent KH-550, 1-3 parts by weight of antioxidant and 1-3 parts by weight of accelerator;

[0012] The flexible and wear-resistant composite filler is obtained by hydrophobically modifying hydroxyapatite-loaded reed fiber with a silane coupling agent KH-550. The hydroxyapatite-loaded reed fiber is obtained by forming hydroxyapatite crystals on the surface of the reed fiber using soluble calcium salt and soluble phosphate as raw materials.

[0013] Furthermore, the raw material of the inner protective layer is the inner sheath material, and the inner sheath material includes a rubber base material, silicon dioxide, a vulcanizing agent, an antioxidant, a silane coupling agent KH-550 and an antioxidant.

[0014] Furthermore, the rubber base material is at least one of chloroprene rubber, styrene-butadiene rubber or chlorinated polyethylene.

[0015] Furthermore, the preparation of silica particle grafted aramid fibers specifically includes the following steps:

[0016] The aramid yarn is soaked in anhydrous ethanol and ultrasonically cleaned for 20 to 30 minutes, and then dried to obtain the aramid yarn with surface oil and impurities removed. The aramid yarn with surface oil and impurities removed is placed in a sodium hydroxide solution with a mass fraction of 5 to 10%, and soaked at 60 to 70° C. for 1 to 2 hours. Subsequently, the soaked aramid yarn is rinsed with deionized water until it is neutral, and dried to obtain the pretreated aramid yarn.

[0017] The pretreated aramid yarn is immersed in the modification solution, ultrasonically dispersed for 10 to 30 minutes, the pH is adjusted to 4 to 5, and the reaction is carried out at 56 to 72° C. for 1 to 2 hours. After the reaction is completed, the reacted aramid yarn is washed with ethanol and dried to obtain a modified aramid yarn;

[0018] 1 to 3 parts by weight of modified aramid yarn are immersed in a reactor filled with 150 to 360 parts by weight of anhydrous ethanol, ammonia water is added to the reactor, the pH is adjusted to 9 to 10, ultrasonic dispersion is carried out for 10 to 20 minutes, and then magnetic stirring is carried out at 50 to 60° C. During the stirring process, 50 to 80 parts by weight of reaction liquid are slowly added dropwise. After the reaction liquid is added dropwise, stirring is continued for 4 to 6 hours. After the reaction is completed, the modified aramid yarn is washed with ethanol. Finally, curing is carried out at 90 to 105° C. for 1 to 2 hours to obtain silica particle grafted aramid yarn.

[0019] Furthermore, the modified solution is prepared by mixing a silane coupling agent KH-550 and an ethanol solution with a volume fraction of 90% in a mass ratio of (2-5):100.

[0020] Furthermore, the reaction liquid is prepared by mixing ethyl orthosilicate and 70% ethanol solution by volume in a mass ratio of (5-10):100.

[0021] Furthermore, the preparation of the tensile toughened aramid yarn specifically includes the following steps:

[0022] 1 to 5 parts by weight of silica particle grafted aramid yarn, 4 to 9 parts by weight of methyl methacrylate and 0.02 to 0.05 parts by weight of azobisisobutyronitrile are added to 200 to 400 parts by weight of toluene, the pH is adjusted to 5 to 7, and the mixture is stirred and reacted in an oil bath at 60 to 80° C. under a nitrogen atmosphere for 3 to 6 hours. After the reaction is completed, the mixture is cooled to room temperature. The treated silica particle grafted aramid yarn is filtered, washed with toluene, washed with ethanol and dried in sequence to obtain a tensile toughened aramid yarn.

[0023] Furthermore, the preparation of the flexible and wear-resistant composite filler specifically includes the following steps:

[0024] The reed fiber is immersed in a sodium hydroxide solution with a mass fraction of 5 to 10% for alkalization treatment, and then washed with deionized water and dried to obtain the alkalized reed fiber;

[0025] A soluble calcium salt and a soluble phosphate are respectively dissolved in deionized water to prepare a calcium salt solution with a concentration of 0.05-0.1 mol / L and a phosphate solution with a concentration of 0.3-1 mol / L; 1-3 parts by weight of alkalized reed fiber are added to 200-600 parts by weight of the calcium salt solution, and stirred evenly; 20-60 parts by weight of the phosphate solution are slowly added dropwise under stirring; after the addition of the phosphate solution is completed, the pH value of the solution is adjusted to 8-10 with ammonia water, and stirred in a water bath at 30-75° C. for 1-3 hours. After the stirring is completed, the solution is aged for 24-36 hours, and then washed, filtered, dried and crushed to obtain hydroxylated apatite-loaded reed fiber;

[0026] Hydroxylated apatite-loaded reed fiber is added to an ethanol solution with a volume fraction of 70% to prepare a hydroxylated apatite-loaded reed fiber dispersion solution with a hydroxylated apatite-loaded reed fiber concentration of 1 to 3 g / L. Silane coupling agent KH-550 is added to the hydroxylated apatite-loaded reed fiber dispersion solution in an amount of 3 to 5% of the mass of the hydroxylated apatite-loaded reed fiber dispersion solution. The mixture is stirred and reacted at 40 to 70° C. for 1 to 3 hours. Subsequently, the mixture is filtered and dried to obtain a flexible and wear-resistant composite filler.

[0027] Furthermore, the plasticizer is at least one of dioctyl phthalate, dibutyl phthalate, and diisononyl phthalate; the vulcanizing agent is at least one of tert-butyl perbenzoate, diisopropyl benzene peroxide, and tert-butyl isopropyl benzene peroxide; the antioxidant is at least one of antioxidant A, antioxidant H, antioxidant ODA, or antioxidant 4020; the antioxidant is at least one of antioxidant TPP, antioxidant 1010, antioxidant 1076, or antioxidant 168; and the accelerator is at least one of accelerator D, accelerator M, or accelerator PZ.

[0028] A process for preparing a high-voltage flexible cable for a shield machine comprises the following steps:

[0029] S1: uniformly mixing the raw materials for the inner sheath material, kneading, extruding, and granulating to obtain the inner sheath material;

[0030] S2: uniformly mixing the raw materials for the wear-resistant flexible sheath material, kneading, extruding, and granulating to obtain the wear-resistant flexible sheath material;

[0031] S3: Extrude a layer of inner sheath material outside the cable core to form an inner sheath. Then, weave a tensile reinforcement braid layer with tensile toughening aramid yarn outside the inner sheath. The braiding density is 20-35%, and the braiding pitch ratio is 2-4.5.

[0032] S4: A layer of wear-resistant flexible sheath material is extruded outside the tensile reinforcement braided layer to form an outer sheath to obtain a high-voltage flexible cable for a shield machine.

[0033] The present invention has the following advantages:

[0034] 1. In the present invention, by loading silica particles on the surface of aramid yarn, the obtained silica particle grafted aramid yarn can not only utilize the silica particles to increase the surface area and roughness of the aramid yarn surface, which is beneficial to improving the interface bonding performance between the aramid yarn and the rubber substrate in the sheath, but also the silica particles in the silica particle grafted aramid yarn can enhance the tensile properties of the aramid yarn, thereby improving the tensile strength and bending resistance of the high-voltage flexible cable for shield machines.

[0035] 2. In the present invention, azobisisobutyronitrile is used as an initiator to trigger a free radical polymerization reaction of methyl methacrylate on the surface of the silica particles grafted onto the aramid fiber, and polymethyl methacrylate is grafted onto the surface of the aramid fiber to obtain a tensile toughened aramid fiber. The flexibility and elasticity of polymethyl methacrylate can further enhance the tensile strength and bending resistance of the silica particle grafted aramid fiber, so that the high-voltage flexible cable for the shield machine can effectively withstand the tensile force to which the high-voltage flexible cable for the shield machine is subjected during use when subjected to external force, adapt to frequent bending, reduce the risk of damage to the high-voltage flexible cable for the shield machine due to stretching, and improve the reliability and service life of the high-voltage flexible cable for the shield machine.

[0036] 3. In the present invention, the active groups on the surface of reed fiber, such as carboxyl and hydroxyl groups, are used as nucleation sites to allow hydroxylated apatite to grow and load on the fiber surface of the reed fiber. The obtained hydroxylated apatite-loaded reed fiber combines the wear resistance and flame retardancy of hydroxylated apatite with the flexibility and tensile strength of reed fiber, and has good mechanical properties, wear resistance and flame retardant properties. In addition, the hydrophobic modification treatment of silane coupling agent KH-550 is used to allow the hydroxyl groups on the surface of the hydroxylated apatite-loaded reed fiber to undergo condensation reaction with the silanol groups generated after the hydrolysis of the silane coupling agent KH-550. The obtained flexible and wear-resistant composite filler is better dispersed in the rubber matrix after surface hydrophobization, thereby improving the tensile strength, flame retardancy and wear resistance of the high-voltage flexible cable for shield machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a structural diagram of a high-voltage flexible cable for a shield machine prepared according to an embodiment of the present invention and a comparative example. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1

[0040] A process for preparing a high-voltage flexible cable for a shield machine comprises the following steps:

[0041] S1: 100 parts by weight of chlorinated polyethylene, 20 parts by weight of silicon dioxide, 5 parts by weight of dibutyl phthalate, 3 parts by weight of antioxidant A, 5 parts by weight of silane coupling agent KH-550 and 3 parts by weight of antioxidant 1010 are mixed uniformly, kneaded, extruded and granulated at an extrusion temperature of 200° C. to obtain an inner sheath material;

[0042] S2: 100 parts by weight of chlorinated polyethylene, 30 parts by weight of flexible and wear-resistant composite filler, 5 parts by weight of dibutyl phthalate, 6 parts by weight of dicumyl peroxide, 2 parts by weight of antioxidant A, 2 parts by weight of antioxidant H, 7 parts by weight of coupling agent KH-550, 3 parts by weight of antioxidant 1010, and 3 parts by weight of accelerator M are mixed uniformly, kneaded, extruded, and granulated at an extrusion temperature of 200° C. to obtain a wear-resistant flexible sheath material;

[0043] S3: Extrude a layer of inner sheath material outside the cable core to form an inner sheath with a nominal thickness of 3mm. Then, weave a tensile reinforcement braid layer with tensile toughening aramid yarn outside the inner sheath with a braiding density of 30% and a braiding pitch ratio of 3;

[0044] S4: A layer of wear-resistant flexible sheath material is extruded outside the tensile reinforcement braided layer to form an outer sheath with a nominal thickness of 6mm to obtain a high-voltage flexible cable for shield machines, such as Figure 1 shown.

[0045] Among them, the preparation of tensile toughened aramid yarn is as follows: 5 parts by weight of silica particle grafted aramid yarn, 9 parts by weight of methyl methacrylate and 0.05 parts by weight of azobisisobutyronitrile are added to 400 parts by weight of toluene, the pH is adjusted to 5, and the reaction is stirred in a 70°C oil bath under a nitrogen atmosphere for 6 hours. After the reaction is completed, the temperature is cooled to room temperature. The treated silica particle grafted aramid yarn is filtered, washed with toluene, washed with ethanol and dried in sequence to obtain tensile toughened aramid yarn.

[0046] The preparation of silica particle-grafted aramid fibers is as follows: the aramid fibers are immersed in anhydrous ethanol and ultrasonically cleaned for 30 minutes, followed by drying to obtain aramid fibers with surface oil and impurities removed; the aramid fibers with surface oil and impurities removed are placed in a 10% by mass sodium hydroxide solution at 60°C for 2 hours; the immersed aramid fibers are then rinsed with deionized water until neutral, and dried to obtain pretreated aramid fibers;

[0047] The pretreated aramid yarn was immersed in a modification solution composed of a silane coupling agent KH-550 and a 90% ethanol solution in a mass ratio of 5:100, ultrasonically dispersed for 30 minutes, and the pH was adjusted to 5. The solution was reacted at 60°C for 2 hours. After the reaction was completed, the reacted aramid yarn was washed with ethanol and dried to obtain a modified aramid yarn.

[0048] 3 parts by weight of modified aramid yarn was immersed in a reactor filled with 360 parts by weight of anhydrous ethanol, ammonia water was added to the reactor, the pH was adjusted to 10, and ultrasonic dispersion was carried out for 20 minutes. Subsequently, magnetic stirring was carried out at 60°C, and 80 parts by weight of reaction liquid was slowly added dropwise during the stirring process. The reaction liquid was composed of ethyl orthosilicate and 70% ethanol solution in a mass ratio of 8:100. After the reaction liquid was added dropwise, the reaction was continued with stirring for 6 hours. After the reaction was completed, the modified aramid yarn after the reaction was washed with ethanol. Finally, it was cured at 100°C for 2 hours to obtain silica particle grafted aramid yarn.

[0049] The flexible and wear-resistant composite filler is prepared by immersing the reed fiber in a sodium hydroxide solution with a mass fraction of 10% for alkalization treatment, and then washing with deionized water and drying to obtain the alkalized reed fiber;

[0050] Calcium chloride and diammonium hydrogen phosphate were dissolved in deionized water to prepare a calcium chloride solution with a concentration of 0.05 mol / L and a diammonium hydrogen phosphate solution with a concentration of 0.3 mol / L, 3 parts by weight of alkalized reed fiber were added to 500 parts by weight of the calcium chloride solution and stirred evenly, and then 60 parts by weight of the diammonium hydrogen phosphate solution were slowly added dropwise under stirring. After the diammonium hydrogen phosphate solution was added dropwise, the pH of the solution was adjusted to 10 with ammonia water, and stirred in a water bath at 60°C for 3 hours. After the stirring was completed, the solution was aged for 36 hours, and then washed, filtered, dried and pulverized to obtain hydroxylated apatite-loaded reed fiber;

[0051] Hydroxylated apatite-loaded reed fiber was added to an ethanol solution with a volume fraction of 70% to prepare a hydroxylated apatite-loaded reed fiber dispersion solution with a hydroxylated apatite-loaded reed fiber concentration of 3 g / L. Silane coupling agent KH-550 was added to the hydroxylated apatite-loaded reed fiber dispersion solution. The amount of silane coupling agent KH-550 added was 5% of the mass of the hydroxylated apatite-loaded reed fiber dispersion solution. The mixture was stirred and reacted at 70°C for 3 hours. Subsequently, the mixture was filtered and dried to obtain a flexible and wear-resistant composite filler.

[0052] Example 2

[0053] A process for preparing a high-voltage flexible cable for a shield machine comprises the following steps:

[0054] S1: 100 parts by weight of chlorinated polyethylene, 20 parts by weight of silicon dioxide, 5 parts by weight of dibutyl phthalate, 3 parts by weight of antioxidant A, 5 parts by weight of silane coupling agent KH-550 and 3 parts by weight of antioxidant 1010 are mixed uniformly, kneaded, extruded and granulated at an extrusion temperature of 180° C. to obtain an inner sheath material;

[0055] S2: 100 parts by weight of chlorinated polyethylene, 30 parts by weight of flexible and wear-resistant composite filler, 5 parts by weight of dibutyl phthalate, 6 parts by weight of dicumyl peroxide, 2 parts by weight of antioxidant A, 2 parts by weight of antioxidant H, 7 parts by weight of coupling agent KH-550, 3 parts by weight of antioxidant 1010, and 3 parts by weight of accelerator M are mixed uniformly, kneaded, extruded, and granulated at an extrusion temperature of 180° C. to obtain a wear-resistant flexible sheath material;

[0056] S3: Extrude a layer of inner sheath material outside the cable core to form an inner sheath with a nominal thickness of 3mm. Then, weave a tensile reinforcement braid layer with tensile toughening aramid yarn outside the inner sheath with a braiding density of 30% and a braiding pitch ratio of 3;

[0057] S4: A layer of wear-resistant flexible sheath material is extruded outside the tensile reinforcement braided layer to form an outer sheath with a nominal thickness of 6mm to obtain a high-voltage flexible cable for shield machines, such as Figure 1 shown.

[0058] Among them, the preparation of tensile toughened aramid yarn is as follows: 5 parts by weight of silica particle grafted aramid yarn, 9 parts by weight of methyl methacrylate and 0.05 parts by weight of azobisisobutyronitrile are added to 400 parts by weight of toluene, the pH is adjusted to 7, and the reaction is stirred in a 60°C oil bath under a nitrogen atmosphere for 6 hours. After the reaction is completed, the temperature is cooled to room temperature. The treated silica particle grafted aramid yarn is filtered, washed with toluene, washed with ethanol and dried in sequence to obtain tensile toughened aramid yarn.

[0059] The preparation of silica particle-grafted aramid fibers is as follows: the aramid fibers are immersed in anhydrous ethanol and ultrasonically cleaned for 30 minutes, followed by drying to obtain aramid fibers with surface oil and impurities removed; the aramid fibers with surface oil and impurities removed are then immersed in a 10% by mass sodium hydroxide solution at 60°C for 1 hour; the immersed aramid fibers are then rinsed with deionized water until neutral, and dried to obtain pretreated aramid fibers;

[0060] The pretreated aramid yarn was immersed in a modification solution prepared by mixing a silane coupling agent KH-550 with a 90% ethanol solution in a mass ratio of 5:100, and ultrasonically dispersed for 30 minutes. The pH was adjusted to 4, and the mixture was reacted at 72°C for 1 hour. After the reaction, the aramid yarn was washed with ethanol and dried to obtain a modified aramid yarn.

[0061] 3 parts by weight of modified aramid yarn was immersed in a reactor filled with 360 parts by weight of anhydrous ethanol, ammonia water was added to the reactor, the pH was adjusted to 10, and ultrasonic dispersion was carried out for 20 minutes. Subsequently, magnetic stirring was carried out at 60°C, and 80 parts by weight of reaction liquid was slowly added dropwise during the stirring process. The reaction liquid was composed of ethyl orthosilicate and 70% ethanol solution in a mass ratio of 8:100. After the reaction liquid was added dropwise, the reaction was continued with stirring for 4 hours. After the reaction was completed, the modified aramid yarn was washed with ethanol. Finally, it was cured at 105°C for 2 hours to obtain silica particle grafted aramid yarn.

[0062] The flexible and wear-resistant composite filler is prepared by immersing the reed fiber in a sodium hydroxide solution with a mass fraction of 10% for alkalization treatment, and then washing with deionized water and drying to obtain the alkalized reed fiber;

[0063] Calcium chloride and diammonium hydrogen phosphate were dissolved in deionized water to prepare a calcium chloride solution with a concentration of 0.05 mol / L and a diammonium hydrogen phosphate solution with a concentration of 0.3 mol / L, 3 parts by weight of alkalized reed fiber were added to 500 parts by weight of the calcium chloride solution and stirred evenly, and then 60 parts by weight of the diammonium hydrogen phosphate solution were slowly added dropwise under stirring. After the diammonium hydrogen phosphate solution was added dropwise, the pH of the solution was adjusted to 9 with ammonia water, and stirred in a water bath at 40°C for 3 hours. After the stirring was completed, the solution was aged for 36 hours, and then washed, filtered, dried and crushed to obtain hydroxylated apatite-loaded reed fiber;

[0064] Hydroxylated apatite-loaded reed fiber was added to an ethanol solution with a volume fraction of 70% to prepare a hydroxylated apatite-loaded reed fiber dispersion solution with a hydroxylated apatite-loaded reed fiber concentration of 3 g / L. Silane coupling agent KH-550 was added to the hydroxylated apatite-loaded reed fiber dispersion solution, and the amount of silane coupling agent KH-550 added was 5% of the mass of the hydroxylated apatite-loaded reed fiber dispersion solution. The mixture was stirred and reacted at 50°C for 3 hours. Subsequently, the mixture was filtered and dried to obtain a flexible and wear-resistant composite filler.

[0065] Example 3

[0066] A process for preparing a high-voltage flexible cable for a shield machine comprises the following steps:

[0067] S1: 100 parts by weight of chlorinated polyethylene, 20 parts by weight of silicon dioxide, 5 parts by weight of dibutyl phthalate, 3 parts by weight of antioxidant A, 5 parts by weight of silane coupling agent KH-550 and 3 parts by weight of antioxidant 1010 are mixed uniformly, kneaded, extruded and granulated at an extrusion temperature of 200° C. to obtain an inner sheath material;

[0068] S2: 100 parts by weight of chlorinated polyethylene, 10 parts by weight of flexible and wear-resistant composite filler, 5 parts by weight of dibutyl phthalate, 6 parts by weight of dicumyl peroxide, 2 parts by weight of antioxidant A, 2 parts by weight of antioxidant H, 7 parts by weight of coupling agent KH-550, 3 parts by weight of antioxidant 1010, and 3 parts by weight of accelerator M are mixed uniformly, kneaded, extruded, and granulated at an extrusion temperature of 200° C. to obtain a wear-resistant flexible sheath material;

[0069] S3: Extrude a layer of inner sheath material outside the cable core to form an inner sheath with a nominal thickness of 3mm. Then, weave a tensile reinforcement braid layer with tensile toughening aramid yarn outside the inner sheath with a braiding density of 30% and a braiding pitch ratio of 3;

[0070] S4: A layer of wear-resistant flexible sheath material is extruded outside the tensile reinforcement braided layer to form an outer sheath with a nominal thickness of 6mm to obtain a high-voltage flexible cable for shield machines, such as Figure 1 shown.

[0071] Among them, the preparation of tensile toughened aramid yarn is as follows: 5 parts by weight of silica particle grafted aramid yarn, 5 parts by weight of methyl methacrylate and 0.05 parts by weight of azobisisobutyronitrile are added to 400 parts by weight of toluene, the pH is adjusted to 5, and the reaction is stirred in a 70°C oil bath under a nitrogen atmosphere for 6 hours. After the reaction is completed, the temperature is cooled to room temperature. The treated silica particle grafted aramid yarn is filtered, washed with toluene, washed with ethanol and dried in sequence to obtain tensile toughened aramid yarn.

[0072] The preparation of silica particle-grafted aramid fibers is as follows: the aramid fibers are immersed in anhydrous ethanol and ultrasonically cleaned for 30 minutes, followed by drying to obtain aramid fibers with surface oil and impurities removed; the aramid fibers with surface oil and impurities removed are placed in a 10% by mass sodium hydroxide solution at 60°C for 2 hours; the immersed aramid fibers are then rinsed with deionized water until neutral, and dried to obtain pretreated aramid fibers;

[0073] The pretreated aramid yarn was immersed in a modification solution composed of a silane coupling agent KH-550 and a 90% ethanol solution in a mass ratio of 5:100, ultrasonically dispersed for 30 minutes, and the pH was adjusted to 5. The solution was reacted at 60°C for 2 hours. After the reaction was completed, the reacted aramid yarn was washed with ethanol and dried to obtain a modified aramid yarn.

[0074] 2 parts by weight of modified aramid yarn was immersed in a reactor containing 200 parts by weight of anhydrous ethanol, ammonia water was added to the reactor, the pH was adjusted to 10, and ultrasonic dispersion was carried out for 20 minutes. Subsequently, magnetic stirring was carried out at 60°C, and 50 parts by weight of reaction liquid was slowly added dropwise during the stirring process. The reaction liquid was composed of ethyl orthosilicate and 70% ethanol solution in a mass ratio of 10:100. After the reaction liquid was added dropwise, the reaction was continued with stirring for 6 hours. After the reaction was completed, the modified aramid yarn after the reaction was washed with ethanol. Finally, it was cured at 100°C for 2 hours to obtain silica particle grafted aramid yarn.

[0075] The flexible and wear-resistant composite filler is prepared by immersing the reed fiber in a sodium hydroxide solution with a mass fraction of 10% for alkalization treatment, and then washing with deionized water and drying to obtain the alkalized reed fiber;

[0076] Calcium chloride and diammonium hydrogen phosphate were dissolved in deionized water to prepare a calcium chloride solution with a concentration of 0.05 mol / L and a diammonium hydrogen phosphate solution with a concentration of 0.3 mol / L, 3 parts by weight of alkalized reed fiber were added to 500 parts by weight of the calcium chloride solution and stirred evenly, and then 60 parts by weight of the diammonium hydrogen phosphate solution were slowly added dropwise under stirring. After the diammonium hydrogen phosphate solution was added dropwise, the pH of the solution was adjusted to 10 with ammonia water, and stirred in a water bath at 60°C for 3 hours. After the stirring was completed, the solution was aged for 36 hours, and then washed, filtered, dried and pulverized to obtain hydroxylated apatite-loaded reed fiber;

[0077] Hydroxylated apatite-loaded reed fiber was added to an ethanol solution with a volume fraction of 70% to prepare a hydroxylated apatite-loaded reed fiber dispersion solution with a hydroxylated apatite-loaded reed fiber concentration of 3 g / L. Silane coupling agent KH-550 was added to the hydroxylated apatite-loaded reed fiber dispersion solution. The amount of silane coupling agent KH-550 added was 5% of the mass of the hydroxylated apatite-loaded reed fiber dispersion solution. The mixture was stirred and reacted at 70°C for 3 hours. Subsequently, the mixture was filtered and dried to obtain a flexible and wear-resistant composite filler.

[0078] Comparative Example 1

[0079] Compared with Example 1, the difference of Comparative Example 1 is that, in the preparation process of the high-voltage flexible cable for the shield machine, the tensile toughened aramid yarn used in step S3 is replaced by the silica particle grafted aramid yarn, and the other steps and components remain unchanged. The cable core is processed and prepared into a high-voltage flexible cable for the shield machine using the same cable core as in Example 1, which is recorded as Comparative Example 1.

[0080] Comparative Example 2

[0081] Compared with Example 1, the difference of Comparative Example 2 is that, in the preparation process of the high-voltage flexible cable for the shield machine, the tensile toughened aramid yarn used in step S3 is replaced by an aramid yarn that has not been treated in any way, and the other steps and components remain unchanged. The cable core is processed and prepared into a high-voltage flexible cable for the shield machine using the same cable core as in Example 1, which is recorded as Comparative Example 2.

[0082] Comparative Example 3

[0083] Compared with Example 1, the difference of Comparative Example 3 is that in the preparation process of the high-voltage flexible cable for the shield machine, the flexible and wear-resistant composite filler in step S2 is replaced by hydroxylated apatite-loaded reed fiber, and the other steps and components remain unchanged. The cable core is processed and prepared into a high-voltage flexible cable for the shield machine using the same cable core as in Example 1, which is recorded as Comparative Example 3.

[0084] Comparative Example 4

[0085] Compared with Example 1, the difference of Comparative Example 4 is that, in the preparation process of the high-voltage flexible cable for the shield machine, the flexible and wear-resistant composite filler in step S2 is replaced with reed fiber that has not been treated in any way, and the other steps and components remain unchanged. The cable core is processed and prepared into a high-voltage flexible cable for the shield machine using the same cable core as in Example 1, which is recorded as Comparative Example 4.

[0086] Comparative Example 5

[0087] Compared with Example 1, the difference of Comparative Example 5 is that in the preparation process of the high-voltage flexible cable for the shield machine, the flexible and wear-resistant composite filler in step S2 is replaced with hydroxylated apatite, and the other steps and components remain unchanged. The cable core is processed and prepared into a high-voltage flexible cable for the shield machine using the same cable core as in Example 1, which is recorded as Comparative Example 5.

[0088] Mechanical Properties: Three cables from each of Examples 1-3 and Comparative Examples 1-5 were selected as test samples. Tensile strength and elongation at break were tested according to GB / T2951-2008. The average tensile strength and elongation at break values for each group of test samples were taken as the test results. The results are shown in Table 1.

[0089] Table 1:

[0090]

[0091] As can be seen from Table 1, the tensile strength and elongation at break test results of the high-voltage flexible cables for shield machines in Examples 1-3 are better than those of the high-voltage flexible cables for shield machines in Comparative Examples 1-5, indicating that the mechanical properties of the high-voltage flexible cables for shield machines can be effectively improved by weaving a tensile-reinforced braided layer with tensile-toughened aramid yarns and adding a flexible, wear-resistant composite filler as a filler in the outer sheath, thereby improving the tensile strength of the high-voltage flexible cables for shield machines and effectively withstanding the tensile force to which the high-voltage flexible cables for shield machines are subjected during use.

[0092] Bending Resistance: Three cables from each of Examples 1-3 and Comparative Examples 1-5 were selected as test samples. These cables were subjected to a bending test using a bending machine. The number of times each group of test samples broke after bending was recorded, and the average number of times these cables broke after bending was taken as the test result. The results are shown in Table 2.

[0093] Table 2:

[0094]

[0095] As can be seen from Table 2, the bending and fracture test results of the high-voltage flexible cables for shield machines in Examples 1-3 are better than those of the high-voltage flexible cables for shield machines in Comparative Examples 1-5, indicating that the use of tensile-toughened aramid yarns to weave a tensile-reinforced braided layer and the addition of flexible and wear-resistant composite fillers as fillers in the outer sheath can effectively improve the flexibility and bending resistance of the high-voltage flexible cables for shield machines, enhance the bending resistance of the high-voltage flexible cables for shield machines, and adapt to frequent bending.

[0096] Wear resistance: Three cables from each of Examples 1-3 and Comparative Examples 3-5 were selected as test samples. Friction and wear tests were performed on these cables according to GB / T3960-2016. The wear loss of each cable in each group of Examples and Comparative Examples was calculated, and the average wear rate for each group was calculated as the test result. Wear rate (%) = wear loss / cable mass before wear * 100%. The results are shown in Table 3.

[0097] Table 3:

[0098]

[0099] As can be seen from Table 3, the high-voltage flexible cables for shield machines in Examples 1-3, after the friction and wear test, have wear rates of less than 1.5%, and the friction loss is lighter than that of the high-voltage flexible cables for shield machines in Comparative Examples 3-5. This shows that by adding a flexible and wear-resistant composite filler as a filler in the outer sheath, the wear resistance of the high-voltage flexible cable for shield machines can be effectively improved, and the hydroxylated apatite in the flexible and wear-resistant composite filler mainly plays a wear-resistant role.

[0100] Flame retardancy: The wear-resistant flexible sheath materials used in Examples 1-3 and Comparative Examples 3-5 were tested according to GB / T 2406.1-2008. Each group was tested three times, and the average value of the test results for each group of examples and comparative examples was calculated as the test results. The results are shown in Table 4.

[0101] Table 4:

[0102]

[0103] As can be seen from Table 4, the flame retardant properties of the high-voltage flexible cables for shield machines in Examples 1-3 are better than those of the high-voltage flexible cables for shield machines in Comparative Examples 3-5, indicating that the flame retardant properties of the high-voltage flexible cables for shield machines can be effectively improved by adding a flexible and wear-resistant composite filler as a filler in the outer sheath, wherein the hydroxylated apatite in the flexible and wear-resistant composite filler mainly plays a flame retardant effect.

[0104] It should be understood that those skilled in the art may make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the scope of protection of the appended claims. Any portion of this specification not described in detail is prior art known to those skilled in the art.

Claims

1. A high-voltage flexible cable for a shield machine, comprising a cable core, an inner sheath, a tensile reinforcement braid, and an outer sheath, arranged sequentially from the inside out. The cable core consists of three main cores and three ground cores, the centers of the three main cores being arranged in an equilateral triangle, and the three ground cores being arranged in the gap between every two adjacent main cores. It is characterized in that The raw material of the tensile reinforcement braided layer is tensile toughened aramid yarn, and the raw material of the outer sheath is wear-resistant flexible sheath material; The tensile toughening aramid yarn is prepared by using silica particle grafted aramid yarn and methyl methacrylate as raw materials, using azobisisobutyronitrile as an initiator, and grafting polymethyl methacrylate on the surface of the silica particle grafted aramid yarn; The silica particle grafted aramid yarn is obtained by modifying the aramid yarn with a silane coupling agent and then loading silica particles on the surface of the modified aramid yarn. The raw materials of the wear-resistant flexible sheath material are 80-120 parts by weight of rubber base material, 10-30 parts by weight of flexible and wear-resistant composite filler, 1-5 parts by weight of plasticizer, 2-6 parts by weight of vulcanizing agent, 2-5 parts by weight of antioxidant, 1-7 parts by weight of coupling agent KH-550, 1-3 parts by weight of antioxidant and 1-3 parts by weight of accelerator; The flexible and wear-resistant composite filler is obtained by hydrophobically modifying hydroxyapatite-loaded reed fiber with a silane coupling agent KH-550. The hydroxyapatite-loaded reed fiber is obtained by forming hydroxyapatite crystals on the surface of the reed fiber using soluble calcium salt and soluble phosphate as raw materials.

2. The high-voltage flexible cable for a shield machine according to claim 1, characterized in that: The raw materials of the inner protective layer are the inner sheath materials, and the inner sheath materials include rubber base material, silicon dioxide, vulcanizing agent, antioxidant, silane coupling agent KH-550 and antioxidant.

3. The high-voltage flexible cable for a shield machine according to claim 1 or 2, characterized in that: The rubber base material is at least one of chloroprene rubber, styrene-butadiene rubber or chlorinated polyethylene.

4. The high-voltage flexible cable for a shield machine according to claim 1, characterized in that: The preparation of silica particle grafted aramid yarn specifically includes the following steps: The aramid yarn is soaked in anhydrous ethanol and ultrasonically cleaned for 20 to 30 minutes, and then dried to obtain the aramid yarn with surface oil and impurities removed. The aramid yarn with surface oil and impurities removed is placed in a sodium hydroxide solution with a mass fraction of 5 to 10%, and soaked at 60 to 70° C. for 1 to 2 hours. Subsequently, the soaked aramid yarn is rinsed with deionized water until it is neutral, and dried to obtain the pretreated aramid yarn. The pretreated aramid yarn is immersed in the modification solution, ultrasonically dispersed for 10 to 30 minutes, the pH is adjusted to 4 to 5, and the reaction is carried out at 56 to 72° C. for 1 to 2 hours. After the reaction is completed, the reacted aramid yarn is washed with ethanol and dried to obtain a modified aramid yarn; 1 to 3 parts by weight of modified aramid yarn are immersed in a reactor containing 150 to 360 parts by weight of anhydrous ethanol, ammonia water is added to the reactor, the pH is adjusted to 9 to 10, and ultrasonic dispersion is performed for 10 to 20 minutes. Subsequently, magnetic stirring is performed at 50 to 60° C., and 50 to 80 parts by weight of reaction liquid is slowly added dropwise during the stirring process. After the reaction liquid is added dropwise, stirring is continued for 4 to 6 hours. After the reaction is completed, the modified aramid yarn is washed with ethanol. Finally, the modified aramid yarn is cured at 90 to 105° C. for 1 to 2 hours to obtain silica particle grafted aramid yarn; the modified solution is prepared by a silane coupling agent KH-550 and a 90% by volume ethanol solution in a mass ratio of (2 to 5):100; the reaction liquid is prepared by a ethyl orthosilicate and a 70% by volume ethanol solution in a mass ratio of (5 to 10):

100.

5. The high-voltage flexible cable for a shield machine according to claim 1, characterized in that: The preparation of tensile toughened aramid yarn specifically includes the following steps: 1 to 5 parts by weight of silica particle grafted aramid yarn, 4 to 9 parts by weight of methyl methacrylate and 0.02 to 0.05 parts by weight of azobisisobutyronitrile are added to 200 to 400 parts by weight of toluene, the pH is adjusted to 5 to 7, and the mixture is stirred and reacted in an oil bath at 60 to 80° C. under a nitrogen atmosphere for 3 to 6 hours. After the reaction is completed, the mixture is cooled to room temperature. The treated silica particle grafted aramid yarn is filtered, washed with toluene, washed with ethanol and dried in sequence to obtain a tensile toughened aramid yarn.

6. The high-voltage flexible cable for a shield machine according to claim 1, characterized in that: The preparation of the flexible and wear-resistant composite filler specifically includes the following steps: The reed fiber is immersed in a sodium hydroxide solution with a mass fraction of 5 to 10% for alkalization treatment, and then washed with deionized water and dried to obtain the alkalized reed fiber; A soluble calcium salt and a soluble phosphate are respectively dissolved in deionized water to prepare a calcium salt solution with a concentration of 0.05-0.1 mol / L and a phosphate solution with a concentration of 0.3-1 mol / L; 1-3 parts by weight of alkalized reed fiber are added to 200-600 parts by weight of the calcium salt solution, and stirred evenly; 20-60 parts by weight of the phosphate solution are slowly added dropwise under stirring; after the addition of the phosphate solution is completed, the pH value of the solution is adjusted to 8-10 with ammonia water, and stirred in a water bath at 30-75° C. for 1-3 hours. After the stirring is completed, the solution is aged for 24-36 hours, and then washed, filtered, dried and crushed to obtain hydroxylated apatite-loaded reed fiber; Hydroxylated apatite-loaded reed fiber is added to an ethanol solution with a volume fraction of 70% to prepare a hydroxylated apatite-loaded reed fiber dispersion solution with a hydroxylated apatite-loaded reed fiber concentration of 1 to 3 g / L. Silane coupling agent KH-550 is added to the hydroxylated apatite-loaded reed fiber dispersion solution in an amount of 3 to 5% of the mass of the hydroxylated apatite-loaded reed fiber dispersion solution. The mixture is stirred and reacted at 40 to 70° C. for 1 to 3 hours. Subsequently, the mixture is filtered and dried to obtain a flexible and wear-resistant composite filler.

7. The high-voltage flexible cable for a shield machine according to claim 2, characterized in that: The plasticizer is at least one of dioctyl phthalate, dibutyl phthalate, and diisononyl phthalate; the vulcanizing agent is at least one of tert-butyl perbenzoate, diisopropyl benzene peroxide, and tert-butyl isopropyl benzene peroxide; the antioxidant is at least one of antioxidant A, antioxidant H, antioxidant ODA, or antioxidant 4020; the antioxidant is at least one of antioxidant TPP, antioxidant 1010, antioxidant 1076, or antioxidant 168; and the accelerator is at least one of accelerator D, accelerator M, or accelerator PZ.

8. A process for preparing a high-voltage flexible cable for a shield machine according to claim 2, characterized in that: The steps include: S1: uniformly mixing the raw materials for the inner sheath material, kneading, extruding, and granulating to obtain the inner sheath material; S2: uniformly mixing the raw materials for the wear-resistant flexible sheath material, kneading, extruding, and granulating to obtain the wear-resistant flexible sheath material; S3: Extrude a layer of inner sheath material outside the cable core to form an inner sheath. Then, weave a tensile reinforcement braid layer with tensile toughening aramid yarn outside the inner sheath. The braiding density is 20-35%, and the braiding pitch ratio is 2-4.

5. S4: A layer of wear-resistant flexible sheath material is extruded outside the tensile reinforcement braided layer to form an outer sheath to obtain a high-voltage flexible cable for a shield machine.

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