Rubber jacketed flexible cable for coal mine and preparation method of rubber jacketed flexible cable

Abstract

The invention discloses a rubber jacketed flexible cable for a coal mine and a preparation method of the rubber jacketed flexible cable. The rubber jacketed flexible cable for the coal mine sequentially comprises a spiral space optimization cable core, a flexible shielding layer and a gradient hardness sheath from inside to outside, the spiral space optimization cable core is formed by spirally winding control wire cores on the periphery of power wire cores at equal pitches, the spiral direction of the control wire cores is opposite to the twisting direction of the power wire cores, and gaps of the cable core are filled with buffer layers; the control wire core is made of superfine tinned copper. The flexible shielding layer is formed by mixing and weaving tinned copper wires and aramid fibers. According to the rubber jacketed flexible cable for the coal mine, provided by the invention, the tensile strength, the wear resistance, the space utilization rate and the flexibility are synergistically improved, and the rubber jacketed flexible cable has a relatively good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of high-performance rubber-sheathed flexible cables, and particularly relates to a rubber-sheathed flexible cable for coal mines and its preparation method. Background Technology

[0002] Coal mine cables are special cables designed specifically for underground and surface areas in coal mines. They must meet the unique safety, mechanical, and electrical performance requirements of the coal mine environment. Coal mine rubber-sheathed flexible cables are special cables designed specifically for the harsh environment of mines. They are mainly made of chloroprene synthetic rubber, with a tear strength ≥12N / mm and abrasion resistance up to 3 times that of ordinary rubber. They can withstand rock friction and equipment compression.

[0003] Traditional rubber-sheathed flexible cables for coal mines have many problems in practical applications. Their conductors are mostly made of pure copper or ordinary alloys, with low tensile strength (≤220MPa), making them prone to breakage under the frequent dragging and stretching conditions in coal mines. At the same time, the parallel arrangement of the control cores results in a large cable outer diameter and a limited bending radius (≥6D), which seriously affects the flexible movement of equipment in the confined space of the mine, reducing space utilization and mining efficiency.

[0004] In summary, there is an urgent need to provide a high-performance rubber-sheathed flexible cable for coal mines that has high tensile strength and a compact structure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a rubber-sheathed flexible cable for coal mines and its preparation method, thereby solving the problems of traditional cables having easily broken conductors, large outer diameters, and large bending radii that restrict equipment movement and result in low mining efficiency.

[0006] The objective of this invention is achieved through the following technical solution: A rubber-sheathed flexible cable for coal mines comprises, from the inside out, a spiral space-optimized cable core, a flexible shielding layer, and a gradient hardness sheath. The spiral space optimized cable core is composed of a control wire core spirally wound around the power wire core with equal pitch. The spiral direction of the control wire core is opposite to the twisting direction of the power wire core, and the gap between the cable cores is filled with a buffer layer. The power core is composed of a high-strength flexible composite conductor covered with an insulating layer. The high-strength flexible composite conductor consists of a central layer, an outer layer, and a nanocrystalline layer from the inside out. The central layer is composed of multiple copper-tin alloy single wires concentrically twisted together. The outer layer is composed of multiple copper-tin alloy single wires and multiple aramid fibers alternately spirally wound together. The nanocrystalline layer is formed by depositing nanocrystalline copper on the surface of the outer layer and then undergoing impact treatment to form a nanocrystalline structure with a certain depth. The control wire core is made of ultra-fine tin-plated copper. The flexible shielding layer is woven from a mixture of tin-plated copper wire and aramid fiber.

[0007] Preferably, the spiral space-optimized cable core is composed of six control wires spirally wound around three power wires at equal pitch.

[0008] Preferably, the buffer layer is silicone rubber.

[0009] Preferably, the tensile strength of the insulating layer is ≥10.0 N / mm. 2 Elongation at break ≥250%.

[0010] Preferably, the insulating layer is high-strength ethylene propylene rubber.

[0011] Preferably, the central layer is composed of seven copper-tin alloy single wires concentrically twisted together; the outer layer is composed of twelve copper-tin alloy single wires and six aramid fibers alternately spirally wound together, with a pitch ratio of 10 to 12.

[0012] Preferably, the tensile strength of the copper-tin alloy single wire is ≥350MPa.

[0013] Preferably, the nanocrystalline layer is formed by physical vapor deposition of nanocrystalline copper on the outer surface, followed by laser shock peening to form a nanocrystalline structure with a depth of 0.3~0.35mm.

[0014] Preferably, the flexible shielding layer has a weave coverage of ≥95% and a shielding effectiveness of ≥95 dB.

[0015] Preferably, the gradient hardness sheath comprises, from the inside out, an inner layer, an interface coupling layer, and an outer layer. The inner layer is liquid silicone rubber, and the outer layer is chloroprene rubber. The interface coupling layer is a chemically bonded layer, which is formed by silanizing the inner layer, chlorinating and grafting the outer layer, and bridging with nano-silica.

[0016] Preferably, the outer layer is chloroprene rubber with added flame retardant, wherein the flame retardant is at least one of aluminum hydroxide and magnesium hydroxide.

[0017] Preferably, the outer surface is embossed with a diamond pattern.

[0018] The preparation method of the above-mentioned rubber-sheathed flexible cable for coal mines includes the following steps: S1. Electrolytic copper and tin are smelted at a mass ratio of 99.5:0.5, and then continuously cast, rolled, and drawn into copper-tin alloy single wires. Multiple strands of the copper-tin alloy single wires are concentrically twisted to form a core layer. Multiple strands of the copper-tin alloy single wires are alternately spirally wound with multiple aramid fibers to form an outer layer. After depositing nanocrystalline copper on the outer layer, an impact treatment is performed to form a nanocrystalline structure with a certain depth, thus obtaining a high-strength flexible composite conductor. S2. A high-strength flexible composite conductor is covered with an insulation layer to obtain a power core; the control core is wound around the power core with equal pitch in a spiral, the spiral direction of the control core is opposite to the twisting direction of the power core, and a buffer layer is filled in the gap between the cable cores to obtain a spiral space optimized cable core. S3. A flexible shielding layer is obtained by weaving a mixture of tin-plated copper wire and aramid fiber on the surface of the optimized cable core in the spiral space. S4. A gradient hardness sheath is prepared outside the flexible shielding layer using a double-layer co-extrusion coating method.

[0019] Preferably, in step S1, the melting temperature is 1100~1120℃, the holding time is 25~30min, the continuous casting speed is 2~2.2m / min, and the roll speed is 500~520r / min.

[0020] Preferably, in step S1, a three-dimensional stranding machine is used to strand the center layer and the outer layer. Preferably, in step S1, the rate of concentric twisting of the central layer is 10~12m / min; the winding tension is 5~6N.

[0021] Preferably, in step S1, nanocrystalline copper is deposited using physical vapor deposition, with a deposition vacuum degree ≤ 5 × 10⁻⁶. - 3 Pa, deposition rate of 0.5~0.6 nm / s; forming a nanocrystalline structure with a certain depth by laser shock peening, wherein the pulse energy of the laser shock peening is 10~12 J, the spot diameter is 3~3.5 mm, and the overlap rate is 50~55%.

[0022] Preferably, in step S2, a twin-screw extruder is used to coat the high-strength flexible composite conductor with an insulating layer.

[0023] Preferably, in step S2, a buffer layer is filled into the gap between the cable cores using high-pressure injection.

[0024] Preferably, in step S3, the weaving is done using a 32-spindle weaving machine with a weaving angle of 45~48°.

[0025] Preferably, the specific preparation steps of the gradient hardness sheath in step S4 are as follows: (1) Liquid silicone rubber is selected as the inner layer material and chloroprene rubber as the outer layer material. The inner and outer sheath materials are extruded simultaneously through a double-layer co-extrusion machine. (2) The inner layer material is immersed in γ-aminopropyltriethoxysilane solution and then dried; the outer layer material is subjected to chlorination grafting modification under Cl2 atmosphere; and finally, nano-silica is sprayed on the interface between the inner and outer layers to form an interface coupling layer.

[0026] Preferably, the concentration of the γ-aminopropyltriethoxysilane solution is 2~2.5wt%; the soaking temperature is 60~65℃, and the soaking time is 2~2.5h.

[0027] Preferably, the drying temperature is 100~105℃ and the soaking time is 0.5~0.6h.

[0028] Preferably, the flow rate of the Cl2 atmosphere is 50~55 mL / min, the temperature of the chlorination grafting modification treatment is 80~85℃, and the time is 10~12 min.

[0029] Preferably, the particle size of the nano-silica is 20-25 nm, and the coating amount is 5-6 g / m³. 2 The spraying air pressure is 0.2~0.25MPa, and the spraying distance is 10~12cm.

[0030] Preferably, after the outer layer material is subjected to chlorination grafting modification treatment, a diamond pattern is engraved on the surface of the outer layer material using laser engraving technology. The engraving depth is 0.1~0.12mm and the engraving speed is 10~12m / min.

[0031] Compared with the prior art, the beneficial effects of the present invention include: This invention achieves a synergistic improvement in tensile strength, wear resistance, space utilization, and flexibility. The introduction of a nanocrystalline layer and a gradient hardness sheath reduces the conductor creep strain rate, with a resistance change rate of ≤1.5%, completely eliminating the risk of local overheating. The spiral space-optimized cable core design reduces the cable diameter and compresses the bending radius to 3.3~3.5D, adapting to extreme environments from -20℃ to 90℃. Chemical bonding and nano-bridging technologies improve the sheath peel strength, and the interface moisture absorption rate is ≤0.05%, which is beneficial for improving adaptability to humid mining environments. Attached Figure Description

[0032] Figure 1 This is a schematic cross-sectional view of the high-strength flexible composite conductor described in the embodiment.

[0033] Figure 2 This is a schematic diagram of the overall structural cross-section of a rubber-sheathed flexible cable for coal mines prepared as an example. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Example 1 A method for preparing a rubber-sheathed flexible cable for coal mines, comprising the following specific steps: (1) Preparation of high-strength flexible composite conductor: Electrolytic copper and tin were selected as raw materials and accurately weighed at a mass ratio of 99.5:0.5 before being added to a smelting furnace. The furnace temperature was set to 1100℃ and held at this temperature for 30 minutes to ensure that the copper and tin were fully fused and the composition was uniform. A continuous casting and rolling process was adopted, with the continuous casting speed set at 2m / min and the roll speed at 500r / min, finally producing a copper-tin alloy rod with a diameter of 8.0mm. This rod was then drawn into a copper-tin alloy single wire with a diameter of 0.2mm. The stranding operation was performed using a three-dimensional stranding machine. The core layer consisted of 7 strands of the prepared copper-tin alloy monofilament, concentrically stranded, with each strand containing 26 copper-tin alloy monofilaments at a stranding speed of 10 m / min. For the outer layer stranding, 12 strands of copper-tin alloy monofilament and 6 strands of aramid fiber were alternately spirally wound, with each strand containing 26 copper-tin alloy monofilaments. The pitch accuracy was strictly controlled within ±0.5 mm, and the winding tension was 5 N to ensure the stability and uniformity of the outer layer structure. Nanocrystalline copper was deposited on the surface of the stranded conductor using physical vapor deposition (PVD). The vacuum level was controlled at ≤5×10⁻⁶. -3 The deposition rate was set to 0.5 nm / s, and the final deposition thickness reached 1.5 μm. After deposition, the conductor was strengthened using laser shock peening (LSP) technology. The pulse energy was set to 10 J, the spot diameter to 3 mm, and the overlap rate to 50%, forming a nanocrystalline structure with a depth of 0.3 mm on the conductor surface, thereby enhancing the mechanical properties of the conductor.

[0036] (2) Helical space optimization cable core forming Three of the prepared high-strength flexible composite conductors were selected as power wire cores. A twin-screw extruder was used to coat the power wire cores with high-strength ethylene propylene rubber. The insulation layer thickness was set to 1.5 mm, and the tensile strength of the insulation layer was ≥10.0 N / mm². 2 The elongation at break is ≥250%. During the extrusion process, the temperature is controlled at 60~85℃ and the linear speed is 16~20m / min to ensure the quality of the insulation layer.

[0037] The high-strength ethylene propylene rubber was manufactured in-house by the applicant. Ultrafine modified aluminum silicate was introduced into the ethylene propylene insulation formula. This ultrafine modified aluminum silicate was in-situ surface-modified with an average particle size of less than 2 micrometers. The selection and proportioning of each raw material were optimized, improving the tensile strength of the ethylene propylene insulation material while maintaining a high elongation at break. This improved the cable's tensile strength, bending resistance, winding resistance, and compression resistance, enhancing the mechanical strength and flexibility of the rubber-sheathed flexible cable and extending its service life.

[0038] The in-situ surface-modified ultrafine aluminum silicate was prepared according to the following steps: 1. Prepare the solution: Aluminum salt (Al2(SO4)3) was dissolved in deionized water to prepare a transparent solution with a concentration of 0.2 mol / L (denoted as solution A); sodium silicate was dissolved in deionized water (specific concentration is 0.2 mol / L) to prepare a solution (denoted as solution B); 2.0 g of surface modifier KH-550 was pre-hydrolyzed with 30 mL of ethanol or water (depending on its water solubility) and stirred for more than 30 min.

[0039] 2. Coprecipitation and in-situ modification: Add 100 mL of solution A to the reaction vessel, turn on the stirrer and control the temperature (usually 50~80℃). At the same time, add 100 mL of solution B and 32 mL of pre-hydrolyzed modifier solution dropwise to solution A through a dropping funnel. During the entire dropping process, strictly control the pH value of the reaction system by adding a precipitant (such as NaOH solution) dropwise to keep it within a stable range (generally pH=8~10). After the dropping is completed, continue to age at a constant temperature for 2~6 hours to ensure the reaction is complete, the particles grow and mature, and the modifier molecules fully react with the surface of the newly formed particles.

[0040] 3. Vacuum filtration: After the reaction is complete, the slurry is cooled to room temperature. It is then filtered using a vacuum filtration device, and the filter cake is washed with plenty of hot deionized water until no SO4 is detectable with BaCl2 solution. 2- To remove the salt produced as a byproduct.

[0041] 4. Drying and grinding: The washed filter cake is dried in an oven at 100~120℃ to obtain preliminarily modified ultrafine aluminum silicate powder; the dried powder is calcined at 500~700℃ to remove the physically adsorbed modifier, make the chemically bonded modified layer more stable, and adjust the crystal form of the product.

[0042] By mass parts, it includes the following components: EPDM rubber 100; Processing aids 4-8; Metal oxides 20-30; Ultrafine modified aluminum silicate 60-100; Softening aid 8-15; Vulcanizing aids 5-8; Anti-aging additives 2-4.

[0043] The ethylene propylene rubber is Dow 4725P.

[0044] The processing aids include one or more of stearic acid, microcrystalline wax, and paraffin.

[0045] The metal oxide includes one or more of zinc oxide, antimony trioxide, and titanium dioxide.

[0046] The softening agent is paraffin oil, and the flash point of the paraffin oil is 283~320℃.

[0047] The vulcanizing aids include DCP and TAIC, and the mass ratio of DCP to TAIC is (3~3.6):(3~4).

[0048] The anti-aging additives include RD and NBC, and the mass ratio of RD to NBC is (0.5~2):1.

[0049] The specific steps are as follows: Mix ethylene propylene rubber, processing aids, metal oxides, ultrafine modified aluminum silicate, softening agents and anti-aging agents for 6-8 minutes, and unload at 130-140℃; After cooling to 60~80℃, filter, roll and let stand for no less than 48 hours, then mix with vulcanizing aid, knead for 4~6 minutes, and unload at 110℃. After cooling and letting stand for no less than 48 hours, it is extruded to form ethylene propylene insulation material.

[0050] Six ultra-fine tin-plated soft copper conductors (self-made by the applicant, drawn from 8.0mm copper rods into 1.70mm copper monofilaments using a large copper wire drawing machine, then into 0.20mm copper monofilaments using a small copper wire drawing machine, and finally annealed and tin-plated using an annealing and tin-plating machine to produce tin-plated soft copper wires) were selected. Each ultra-fine tin-plated soft copper conductor was made by stranding 77 bundles of 0.20mm tin-plated soft copper wires, with a diameter of 2.0mm. These six ultra-fine tin-plated soft copper conductors were spirally wound around the power core with equal pitch, and the spiral direction was opposite to that of the power core. This design improved space utilization by 28%. Liquid silicone rubber was used to fill the gaps between the cable cores using high-pressure injection. The injection pressure was set at 10MPa, the vulcanization temperature at 120℃, and the vulcanization time at 10min to ensure that the liquid silicone rubber fully filled and cured, forming a good buffer layer.

[0051] (3) Flexible shielding layer weaving Tinned copper wire with a diameter of 0.10 mm (made by the applicant, drawn from an 8.0 mm copper rod into a 1.70 mm copper monofilament using a large copper wire drawing machine, then drawn into a 0.10 mm copper monofilament using a small copper wire drawing machine, and finally annealed and tinned using an annealing and tinning machine to produce tinned soft copper wire) is mixed with aramid fiber with a diameter of 0.08 mm in a 2:1 ratio. It is braided using a 32-spindle braiding machine with a braiding angle set at 45°, achieving a braiding coverage of 95% and a shielding effectiveness of 95 dB (1 MHz), effectively shielding against electromagnetic interference.

[0052] (4) Gradient hardness sheath co-extrusion The inner layer is made of liquid silicone rubber with a hardness of 50 Shore A (purchased from Hubei Zhengan New Materials Co., Ltd.) with a thickness of 1.0 mm; the outer layer is made of neoprene rubber with a hardness of 70 Shore A with a thickness of 3.0 mm. The inner and outer sheath materials are extruded simultaneously through a double-layer co-extrusion machine, with the extrusion temperatures set at 25℃ (inner layer) and 55℃ (outer layer) respectively to ensure the continuity and quality of the sheath.

[0053] The chloroprene rubber is manufactured in-house by the applicant and its components include chloroprene rubber, magnesium oxide, zinc oxide, stearic acid, antioxidants, softeners, fillers and reinforcing agents, pigments, coupling agents, etc., as detailed below: Chloroprene rubber: 100; Softener: 12-20; Magnesium oxide: 4-5; Reinforcing filler: 76-160; Zinc oxide: 6-8; Pigment: 0-2; Stearic acid: 1.5; Coupling agent: 2; Anti-aging agent: 2.5; The chloroprene rubber is a CR322 mixed and regulated chloroprene rubber.

[0054] The antioxidant is composed of antioxidant MB and antioxidant 1010.

[0055] The softener is composed of DOP and paraffin.

[0056] The reinforcing filler is composed of three or four of the following: calcined clay, calcium carbonate, talc, silica, and high abrasion-resistant carbon black.

[0057] The pigment is either Permanent Yellow or Lightfast Brilliant Red.

[0058] The coupling agent used is A-172.

[0059] (5) Interface coupling layer processing Inner layer silicone rubber silanization: The silicone rubber is immersed in a 2% γ-aminopropyltriethoxysilane solution at 60°C for 2 hours, and then dried at 100°C for 0.5 hours to enhance the interfacial bonding between the silicone rubber and other materials.

[0060] Chlorination grafting of outer chloroprene rubber: The chloroprene rubber was chlorinated and grafted at 80℃ for 10 min with a Cl2 flow rate of 50 mL / min to improve its performance.

[0061] Spraying nano-silica: Using a spraying device, nano-silica with a particle size of 20nm is sprayed onto the interface between the inner and outer layers. The spraying amount is 5g / m², the spraying air pressure is 0.2MPa, and the spraying distance is 10cm, which further enhances the interface performance.

[0062] (6) Laser engraving Laser engraving technology is used to engrave diamond patterns on the outer surface of the sheath, with an engraving depth of 0.1mm and an engraving speed of 10m / min, increasing the friction and aesthetics of the sheath surface.

[0063] Example 2 A method for preparing a rubber-sheathed flexible cable for coal mines, comprising the following specific steps: (1) Preparation of high-strength flexible composite conductor: Electrolytic copper and tin were selected as raw materials and accurately weighed at a mass ratio of 99.5:0.5 before being added to a smelting furnace. The furnace temperature was set at 1120℃ and held at this temperature for 25 minutes to ensure that the copper and tin were fully fused and the composition was uniform. A continuous casting and rolling process was adopted, with the continuous casting speed set at 2.2 m / min and the roll speed at 520 r / min, finally producing a copper-tin alloy rod with a diameter of 8.0 mm. This rod was then drawn into a copper-tin alloy single wire with a diameter of 0.22 mm. The stranding operation was performed using a three-dimensional stranding machine. The core layer consisted of 7 strands of the prepared copper-tin alloy monofilament, concentrically stranded, with each strand containing 26 copper-tin alloy monofilaments at a stranding speed of 12 m / min. For the outer layer stranding, 12 strands of copper-tin alloy monofilament and 6 strands of aramid fiber were alternately spirally wound, with each strand containing 26 copper-tin alloy monofilaments. The pitch accuracy was strictly controlled within ±0.4 mm, and the winding tension was 6 N to ensure the stability and uniformity of the outer layer structure. Nanocrystalline copper was deposited on the surface of the stranded conductor using physical vapor deposition (PVD). The vacuum level was controlled at ≤4×10⁻⁶. - The deposition rate was set to 0.6 nm / s at 3 Pa, resulting in a final deposition thickness of 1.8 μm. After deposition, the conductor was strengthened using laser shock peening (LSP) technology. The pulse energy was set to 12 J, the spot diameter to 3.5 mm, and the overlap ratio to 55%, forming a nanocrystalline structure with a depth of 0.35 mm on the conductor surface, thereby enhancing the conductor's mechanical properties.

[0064] (2) Helical space optimization cable core forming Three of the prepared high-strength flexible composite conductors were selected as power wire cores. A high-strength ethylene propylene rubber insulation layer was then coated onto the power wire cores using a twin-screw extruder. The insulation layer thickness was set to 1.8 mm, and the tensile strength of the insulation layer was ≥11.0 N / mm². 2 The elongation at break is ≥280%. During the extrusion process, the temperature is controlled at 65~90℃ and the linear speed is 12m / min to ensure the quality of the insulation layer.

[0065] The high-strength ethylene propylene rubber was prepared in-house by the applicant: ultrafine modified aluminum silicate was introduced into the ethylene propylene insulation formula. The ultrafine modified aluminum silicate was in-situ surface-modified ultrafine aluminum silicate (prepared according to the preparation method described in Example 1), with an average particle size of less than 2 micrometers. The selection and proportion of each raw material were optimized, improving the tensile strength of the ethylene propylene insulation material while maintaining a high elongation at break. This improved the cable's tensile strength, bending resistance, winding resistance, and compression resistance, enhancing the mechanical strength and flexibility of the rubber-sheathed flexible cable and extending its service life.

[0066] By mass parts, it includes the following components: EPDM rubber 100; Processing aids 4-8; Metal oxides 20-30; Ultrafine modified aluminum silicate 60-100; Softening aid 8-15; Vulcanizing aids 5-8; Anti-aging additives 2-4.

[0067] The ethylene propylene rubber is Dow 4725P.

[0068] The processing aids include one or more of stearic acid, microcrystalline wax, and paraffin.

[0069] The metal oxide includes one or more of zinc oxide, antimony trioxide, and titanium dioxide.

[0070] The softening agent is paraffin oil, and the flash point of the paraffin oil is 283~320℃.

[0071] The vulcanizing aids include DCP and TAIC, and the mass ratio of DCP to TAIC is (3~3.6):(3~4).

[0072] The anti-aging additives include RD and NBC, and the mass ratio of RD to NBC is (0.5~2):1.

[0073] The specific steps are as follows: Mix ethylene propylene rubber, processing aids, metal oxides, ultrafine modified aluminum silicate, softening agents and anti-aging agents for 6-8 minutes, and unload at 130-140℃; After cooling to 60~80℃, filter, roll and let stand for no less than 48 hours, then mix with vulcanizing aid, knead for 4~6 minutes, and unload at 110℃. After cooling and letting stand for no less than 48 hours, it is extruded to form ethylene propylene insulation material.

[0074] Six ultra-fine tin-plated soft copper conductors (self-made by the applicant, drawn from 8.0mm copper rods into 1.70mm copper monofilaments using a large copper wire drawing machine, then into 0.20mm copper monofilaments using a small copper wire drawing machine, and finally annealed and tin-plated using an annealing and tin-plating machine to produce tin-plated soft copper wires) were selected. Each ultra-fine tin-plated soft copper conductor was made by stranding 88 0.20mm tin-plated soft copper wires together, with a diameter of 2.2mm. These six ultra-fine tin-plated soft copper conductors were spirally wound around the power core with equal pitch, and the spiral direction was opposite to that of the power core. This design improved space utilization by 30%. Liquid silicone rubber (purchased from Hubei Zheng'an New Materials Co., Ltd.) was used to fill the gaps in the cable core using high-pressure injection. The injection pressure was set at 12MPa, the vulcanization temperature at 125℃, and the vulcanization time at 12min to ensure that the liquid silicone rubber fully filled and cured, forming a good buffer layer.

[0075] (3) Flexible shielding layer weaving Tin-plated copper wire with a diameter of 0.12 mm (made by the applicant, drawn from an 8.0 mm copper rod into a 1.70 mm copper monofilament using a large copper wire drawing machine, then drawn into a 0.12 mm copper monofilament using a small copper wire drawing machine, and finally annealed and tin-plated using an annealing and tin-plating machine to produce tin-plated soft copper wire) is mixed with aramid fiber with a diameter of 0.09 mm at a ratio of 2.5:1. A 32-spindle braiding machine is used for weaving, with a weaving angle set at 48°, achieving a weaving coverage of 97% and a shielding effectiveness of 97 dB (1 MHz), effectively shielding against electromagnetic interference.

[0076] (4) Gradient hardness sheath co-extrusion The inner layer is made of liquid silicone rubber with a hardness of 55 Shore A (purchased from Hubei Zhengan New Materials Co., Ltd.) with a thickness of 1.2 mm; the outer layer is made of neoprene rubber with a hardness of 75 Shore A with a thickness of 3.2 mm. The inner and outer sheath materials are extruded simultaneously through a double-layer co-extrusion machine, with the extrusion temperatures set at 30℃ (inner layer) and 60℃ (outer layer) respectively to ensure the continuity and quality of the sheath.

[0077] The chloroprene rubber is manufactured in-house by the applicant and its components include chloroprene rubber, magnesium oxide, zinc oxide, stearic acid, antioxidants, softeners, fillers and reinforcing agents, pigments, coupling agents, etc., as detailed below: Chloroprene rubber: 100; Softener: 12-20; Magnesium oxide: 4-5; Reinforcing filler: 76-160; Zinc oxide: 6-8; Pigment: 0-2; Stearic acid: 1.5; Coupling agent: 2; Anti-aging agent: 2.5; The chloroprene rubber is a CR322 mixed and regulated chloroprene rubber.

[0078] The antioxidant is composed of antioxidant MB and antioxidant 1010.

[0079] The softener is composed of DOP and paraffin.

[0080] The reinforcing filler is composed of three or four of the following: calcined clay, calcium carbonate, talc, silica, and high abrasion-resistant carbon black.

[0081] The pigment is either Permanent Yellow or Lightfast Brilliant Red.

[0082] The coupling agent used is A-172.

[0083] (5) Interface coupling layer processing Inner layer silicone rubber silanization: The silicone rubber is immersed in a 2.5% γ-aminopropyltriethoxysilane solution at 65°C for 2.5 hours, and then dried at 105°C for 0.6 hours to enhance the interfacial bonding between the silicone rubber and other materials.

[0084] Chlorination grafting of outer chloroprene rubber: The chloroprene rubber was chlorinated and grafted at 85℃ for 12 min with the Cl2 flow rate controlled at 55 mL / min to improve its performance.

[0085] Spraying nano-silica: Using a spraying device, nano-silica with a particle size of 25nm is sprayed onto the interface between the inner and outer layers. The spraying amount is 6g / m², the spraying air pressure is 0.25MPa, and the spraying distance is 12cm, which further enhances the interface performance.

[0086] (6) Laser engraving Laser engraving technology is used to engrave diamond patterns on the outer surface of the sheath, with an engraving depth of 0.12mm and an engraving speed of 12m / min, which increases the friction and aesthetics of the sheath surface.

[0087] Comparative Example 1 Traditional rubber-sheathed flexible cables for coal mines Traditional rubber-sheathed flexible cables for coal mines consist of multiple soft copper wires twisted together to form a soft conductor, ethylene propylene rubber insulation, control cores, and a chlorinated polyethylene sheath. The control cores and power cores are twisted together to form a cable.

[0088] Conductor: Made of 7 strands of pure copper single wire, each strand is made of 36 strands of pure copper single wire with a diameter of 0.3mm (tensile strength 220MPa). Insulation layer: XJ-30A type ordinary ethylene propylene rubber (purchased from Shandong Hongjian Polymer Materials Technology Co., Ltd., tensile strength ≥ 6.5 N / mm²) 2 (Elongation at break ≥200%, thickness 1.5mm); An insulating layer is prepared on the outside of the conductor to obtain the power wire core; Control conductor: It is composed of multiple soft copper wires twisted together to form a soft conductor, with ethylene propylene rubber insulation and chlorinated polyethylene sheath, etc. The conductor is made of 50 bundles of 0.25mm soft copper wires (the soft copper wires are made by the applicant, which are drawn from 8.0mm copper rods into 1.70mm copper monofilaments by a large copper wire drawing machine, and then drawn into 0.25mm copper monofilaments by a small copper wire drawing machine).

[0089] Outermost sheath: Made of XH-30A type ordinary chlorinated polyethylene (purchased from Shandong Hongjian Polymer Materials Technology Co., Ltd., tensile strength ≥11.0 N / mm²). 2 (Elongation at break ≥250%, thickness 2.5mm), without interface coupling layer; Structure: The control wire cores are arranged in parallel, with no buffer layer.

[0090] The products of Example 1, Example 2 and Comparative Example 1 were tested and the test results are shown in Table 1.

[0091] Table 1 Product Performance Test Results

[0092] Referring to Table 1, this invention achieves a synergistic improvement in tensile strength, wear resistance, space utilization, and flexibility. The introduction of the nanocrystalline layer and gradient hardness sheath reduces the conductor creep strain rate, with a resistance change rate ≤1.5%, completely eliminating the risk of local overheating. The spiral space optimized cable core design reduces the cable diameter and compresses the bending radius to 3.3~3.5D, adapting to extreme environments of -20℃~90℃. Chemical bonding and nano-bridging technology improve the sheath peel strength, and the interface moisture absorption rate is ≤0.05%, which is beneficial to improving the adaptability to the humid environment of mines.

[0093] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A rubber-sheathed flexible cable for coal mines, characterized in that, From the inside out, it consists of a spiral space-optimized cable core, a flexible shielding layer, and a gradient hardness sheath. The spiral space optimized cable core is composed of a control wire core spirally wound around the power wire core with equal pitch. The spiral direction of the control wire core is opposite to the twisting direction of the power wire core, and the gap between the cable cores is filled with a buffer layer. The power core is composed of a high-strength flexible composite conductor covered with an insulating layer. The high-strength flexible composite conductor consists of a central layer, an outer layer, and a nanocrystalline layer from the inside out. The central layer is composed of multiple copper-tin alloy single wires concentrically twisted together. The outer layer is composed of multiple copper-tin alloy single wires and multiple aramid fibers alternately spirally wound together. The nanocrystalline layer is formed by depositing nanocrystalline copper on the surface of the outer layer and then undergoing impact treatment to form a nanocrystalline structure with a certain depth. The control wire core is made of ultra-fine tin-plated copper. The flexible shielding layer is woven from a mixture of tin-plated copper wire and aramid fiber.

2. The rubber-sheathed flexible cable for coal mines according to claim 1, characterized in that, The spiral space-optimized cable core consists of six control wires spirally wound around three power wires at equal pitch; and / or The central layer is composed of seven copper-tin alloy single wires concentrically twisted together; the outer layer is composed of twelve copper-tin alloy single wires and six aramid fibers alternately spirally wound together, with a pitch ratio of 10~12.

3. The rubber-sheathed flexible cable for coal mines according to claim 1, characterized in that, The tensile strength of the insulation layer is ≥10.0 N / mm². 2 Elongation at break ≥250%; and / or The flexible shielding layer has a weave coverage of ≥95% and a shielding effectiveness of ≥95 dB.

4. The rubber-sheathed flexible cable for coal mines according to claim 1, characterized in that, The buffer layer is made of silicone rubber; and / or The nanocrystalline layer is formed by physical vapor deposition of nanocrystalline copper on the outer surface, followed by laser shock strengthening to form a nanocrystalline structure with a depth of 0.3~0.35mm.

5. The rubber-sheathed flexible cable for coal mines according to claim 1, characterized in that, The gradient hardness sheath comprises, from the inside out, an inner layer, an interface coupling layer, and an outer layer. The inner layer is liquid silicone rubber, and the outer layer is chloroprene rubber. The interface coupling layer is a chemically bonded layer, which is formed by silanizing the inner layer, chlorinating and grafting the outer layer, and bridging with nano-silica.

6. The method for preparing the rubber-sheathed flexible cable for coal mines according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Electrolytic copper and tin are smelted at a mass ratio of 99.5:0.5, and then continuously cast, rolled, and drawn into copper-tin alloy single wires. Multiple strands of the copper-tin alloy single wires are concentrically twisted to form a core layer. Multiple strands of the copper-tin alloy single wires are alternately spirally wound with multiple aramid fibers to form an outer layer. After depositing nanocrystalline copper on the outer layer, an impact treatment is performed to form a nanocrystalline structure with a certain depth, thus obtaining a high-strength flexible composite conductor. S2. A high-strength flexible composite conductor is covered with an insulation layer to obtain a power core; the control core is wound around the power core with equal pitch in a spiral, the spiral direction of the control core is opposite to the twisting direction of the power core, and a buffer layer is filled in the gap between the cable cores to obtain a spiral space optimized cable core. S3. A flexible shielding layer is obtained by weaving a mixture of tin-plated copper wire and aramid fiber on the surface of the optimized cable core in the spiral space. S4. A gradient hardness sheath is prepared outside the flexible shielding layer using a double-layer co-extrusion coating method.

7. The method for preparing the rubber-sheathed flexible cable for coal mines according to claim 6, characterized in that, The specific preparation steps for the gradient hardness sheath described in step S4 are as follows: (1) Liquid silicone rubber is selected as the inner layer material and chloroprene rubber as the outer layer material. The inner and outer sheath materials are extruded simultaneously through a double-layer co-extrusion machine. (2) The inner layer material is immersed in γ-aminopropyltriethoxysilane solution and then dried; the outer layer material is subjected to chlorination grafting modification under Cl2 atmosphere; and finally, nano-silica is sprayed on the interface between the inner and outer layers to form an interface coupling layer.

8. The method for preparing the rubber-sheathed flexible cable for coal mines according to claim 7, characterized in that, The concentration of the γ-aminopropyltriethoxysilane solution is 2-2.5 wt%; the soaking temperature is 60-65°C, and the soaking time is 2-2.5 h; and / or The drying temperature is 100~105℃, and the soaking time is 0.5~0.6h.

9. The method for preparing the rubber-sheathed flexible cable for coal mines according to claim 7, characterized in that, The flow rate of the Cl2 atmosphere is 50~55 mL / min, the temperature of the chlorination grafting modification treatment is 80~85℃, and the time is 10~12 min.

10. The method for preparing the rubber-sheathed flexible cable for coal mines according to claim 7, characterized in that, The nano-silica has a particle size of 20-25 nm and a coating amount of 5-6 g / m. 2 The spraying air pressure is 0.2~0.25MPa, and the spraying distance is 10~12cm.

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