Pressure-resistant anti-bending superconducting cable and preparation process thereof

Abstract

The invention relates to the technical field of superconducting cables, and discloses a pressure-resistant and bending-resistant superconducting cable and a preparation process thereof. Comprising the following operation steps: step 1: (1) stranding a plurality of strands of superconducting filaments to obtain a stranded superconductor; (2) injecting the modified nitrile rubber compound into a mold, and performing vulcanization molding on the modified nitrile rubber compound and the stranded superconductor to form a stress buffer layer; (3) wrapping a polyimide film on the heated and softened stress buffer layer to form an insulating layer A and further obtain a cable core; step 2: (1) placing a plurality of groups of cable cores in a mold barrel, injecting a modified polyimide glue solution, and heating and curing to form a filling layer; wrapping a polyimide film on the surface of the superconducting cable to form an insulating layer B to obtain a superconducting cable A; and (2) injecting the modified nitrile rubber compound into a mold and carrying out vulcanization molding on the modified nitrile rubber compound and the superconducting cable A to form an outer sheath so as to obtain the pressure-resistant and bending-resistant superconducting cable.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting cables, in particular to a pressure-resistant and bending-resistant superconducting cable and a preparation process thereof. Background Art

[0002] With the rapid development of modern society, the power load in urban power grids continues to rise. Traditional cables have large power losses and occupy a large space when transmitting large amounts of power, making it difficult to meet demand. In some special application scenarios, such as aerospace and deep-sea exploration equipment, the equipment operating environment is complex, cables need to be bent frequently, and have to withstand high voltages, which places extremely high demands on the cable's pressure resistance and bending resistance. The materials and structures of traditional cables are not up to the task, and there is an urgent need for superconducting cables that are pressure-resistant and bending-resistant. Superconducting cables are designed and manufactured using the characteristics of superconducting materials that enter a superconducting state below a critical temperature, where resistance disappears and they can carry large currents. Compared with conventional cables, they have outstanding energy-saving effects and a stronger current-carrying capacity than conventional cables at the same cross-section. However, existing superconducting cables have poor bending resistance. During the bending process, the bonding force between the layers of material inside the cable is insufficient. When subjected to external forces, relative displacement between the layers is likely to occur, further reducing the overall performance of the superconducting cable.

[0003] In summary, it is of great significance to prepare a superconducting cable that is resistant to pressure and bending. Summary of the Invention

[0004] The object of the present invention is to provide a pressure-resistant and bending-resistant superconducting cable and a preparation process thereof, so as to solve the problems raised in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions: A process for preparing a pressure-resistant and bending-resistant superconducting cable comprises the following steps: Step 1: (1) Twisting multiple superconducting filaments to obtain a twisted superconductor; (2) Injecting a modified nitrile rubber compound into a mold and vulcanizing it with the twisted superconductor to form a stress buffer layer; (3) Wrapping a polyimide film around the heated and softened stress buffer layer to form an insulating layer A, thereby obtaining a cable core; Step 2: (1) Place multiple groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulating layer B to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath, thereby obtaining a pressure-resistant and bending-resistant superconducting cable.

[0006] More optimally, the thickness of the stress buffer layer is 0.35-0.55 mm; the thickness of the insulating layer A is 0.18-0.25 mm; the thickness of the insulating layer B is 0.18-0.25 mm; the thickness of the outer sheath is 0.9-2.2 mm; and the filling amount of the modified polyimide glue accounts for 50-60% of the volume of the mold barrel.

[0007] The preparation method of the modified nitrile rubber compound is more optimized as follows: (1) adding epoxidized hydrogenated nitrile rubber, aminopropyl-terminated polydimethylsiloxane, amino-silica, and potassium hydroxide ethanol solution to 1,4-dioxane, heating to 110-120°C and stirring for 3-4 hours under a nitrogen atmosphere to obtain a modified nitrile rubber; (2) kneading the modified nitrile rubber and silicone rubber at 100-115°C for 20-25 minutes, adding stearic acid and sulfur powder, kneading at 90-100°C for 15-20 minutes, discharging and placing in an open mill, adding an anti-aging agent, a vulcanizing aid, and an accelerator, and kneading at 60-80°C for 10-15 minutes to obtain a modified nitrile rubber compound.

[0008] More optimally, the raw materials of the modified nitrile rubber include the following components: 10 to 15 parts of epoxidized hydrogenated nitrile rubber, 2 to 4 parts of aminopropyl-terminated polydimethylsiloxane, 1 to 2 parts of amino-silica, and 12 to 16 parts of potassium hydroxide ethanol solution, by weight; the concentration of the potassium hydroxide ethanol solution is 30 to 40 wt%.

[0009] More optimally, the raw materials of the modified nitrile rubber compound include the following components: by mass, 15 to 20 parts of modified nitrile rubber, 30 to 40 parts of silicone rubber, 3 to 6 parts of stearic acid, 4 to 5 parts of sulfur powder, 0.5 to 0.6 parts of anti-aging agent, 1.5 to 1.8 parts of vulcanization aid, and 1 to 1.5 parts of accelerator.

[0010] In the scheme, the preparation method of epoxidized hydrogenated nitrile rubber is as follows: (1) formic acid (0.15 mol) and hydrogen peroxide (0.3 mol) are uniformly mixed to obtain a mixed solution; nitrile rubber is added to chlorobenzene to prepare an 8.5 wt% nitrile rubber solution, the mixed solution is added dropwise at 40°C (the addition time is 1 hour), the reaction is performed for 6 hours, the solution is cooled to room temperature, flocculated in an ethanol solution until the washing liquid is clear, and dried to obtain epoxidized nitrile rubber; (2) epoxidized nitrile rubber is added to chlorobenzene to prepare a 7.5 wt% epoxidized nitrile rubber solution; the solution and the catalyst are added to a reactor, nitrogen and hydrogen are filled and discharged three times in sequence, and finally hydrogen is filled and heated to 120°C at 3 MPa for reaction for 5 hours to obtain epoxidized hydrogenated nitrile rubber.

[0011] In the scheme, the preparation method of amino silica is as follows: 4 g of nano-silica is added to 20 mL of deionized water and mixed evenly, the temperature is raised to 80° C., the pH is adjusted to 3.5, 0.2 g of KH550 is added and mixed evenly, and stirred for 95 minutes to obtain amino silica.

[0012] The preparation method of the modified polyimide glue is as follows: (1) adding 3,5-diaminobenzoic acid to N-methylpyrrolidone and mixing uniformly, adding 4,4'-oxydiphthalic anhydride and stirring for 8-10 hours, drying and grinding, to obtain polyamic acid; (2) adding polyamic acid to DMF at 45-55°C and mixing uniformly, adding DCC and DMAP, adding amino carbon nanotubes under nitrogen protection, mixing uniformly for 20-24 hours, cooling to room temperature, adding Add n-hexane to precipitate, filter, wash and dry; then calcine it at 300-350°C for 6-8 hours to obtain carbon nanotube-modified polyimide; (3) add epoxidized hydrogenated nitrile rubber to DMF at 60-70°C, stir at 400-500 r / min for 2-3 hours, add carbon nanotube-modified polyimide under ultrasonic conditions of 200-500W for 40-60 minutes, add flame retardant, crosslinking agent, accelerator and plasticizer to obtain modified polyimide glue.

[0013] More optimally, the molar ratio of the 3,5-diaminobenzoic acid to 4,4'-oxydiphthalic anhydride is 1:1; the raw materials of the carbon nanotube-modified polyimide include the following components: by mass, 12 to 15 parts of polyamic acid, 0.25 to 0.4 parts of DCC, 0.07 to 0.13 parts of DMAP, 3 to 4 parts of amino-treated carbon nanotubes, and 30 to 40 parts of DMF.

[0014] More optimally, the raw materials of the modified polyimide glue include the following components: 30-50 parts of epoxidized hydrogenated nitrile rubber, 15-20 parts of carbon nanotube modified polyimide, 20-30 parts of DMF, 8-12 parts of flame retardant, 3-5 parts of cross-linking agent, 2.5-3 parts of accelerator, and 2-3 parts of plasticizer.

[0015] In the scheme, the preparation method of amino-treated carbon nanotubes is as follows: (1) 7 g of carbon nanotubes are added to 50 mL of 65 wt% concentrated nitric acid and ultrasonically treated for 30 minutes, stirred at 70 ° C for 60 minutes, filtered, washed with anhydrous ethanol, and dried to obtain acid-treated carbon nanotubes; (2) 13 g of KH550 are added to 60 mL of 80 wt% ethanol aqueous solution, the pH is adjusted to 3.5 with acetic acid, stirred for 40 minutes, 5 g of acid-treated carbon nanotubes are added, ultrasonicated for 30 minutes, reacted at 120 ° C for 5 hours, filtered, washed, and dried to obtain amino-treated carbon nanotubes.

[0016] More optimally, the superconducting filaments are composed of a superconducting core material and a copper or silver stabilization layer; the twisting pitch is 8~10mm, and the twisting tension is 3~4N; the vulcanization molding temperature is 170~180℃; the softening temperature of the stress buffer layer is 110~120℃; the wrapping pressure is 1~2MPa, and the winding angle is 45~60°.

[0017] Compared with the prior art, the present invention has the following beneficial effects: In this solution, multiple superconducting filaments are twisted together to ensure that the superconducting cable has stable and efficient superconducting properties when transmitting electric energy, thereby improving the overall power transmission efficiency and stability of the superconducting cable. At the same time, the contact area between the superconducting cable and the modified nitrile rubber compound can be increased to form a strong stress buffer layer. When the superconducting cable is bent or stretched by external force, the stress buffer layer can effectively disperse and absorb the stress, preventing the superconducting filaments from being damaged due to stress concentration, significantly enhancing the bending resistance of the superconducting cable, and thus extending the service life of the superconducting cable.

[0018] Among them, hydrogenated nitrile rubber can maintain its own mechanical properties and chemical stability under long-term low-temperature working conditions, ensuring the long-lasting and effective function of the buffer layer; silicone rubber, also known as silicone rubber, has excellent low-temperature resistance and can maintain stable performance in extremely low-temperature environments, thereby improving the performance of superconducting cables.

[0019] In order to improve the interface performance between the stress buffer layer and the twisted superconductor and polyimide film, in the scheme, aminosilica and aminopropyl-terminated polydimethylsiloxane are introduced into hydrogenated nitrile rubber to obtain modified nitrile rubber. Among them, aminopropyl-terminated polydimethylsiloxane can effectively improve the interface performance between it and silicone rubber; and the nano-silica on the modified nitrile rubber can enhance its bonding force with the twisted superconductor, thereby improving phase stability.

[0020] In the scheme, a polyimide film is wrapped around a heat-softened stress buffer layer to form an insulating layer to obtain a cable core; the polyimide film has excellent electrical insulation properties, low-temperature resistance and mechanical properties; when the stress buffer layer is heated and softened, the viscosity of its surface increases, allowing the polyimide film to better contact the buffer layer surface during wrapping, thereby improving the phase stability of the superconducting cable.

[0021] In the scheme, multiple groups of cable cores are placed in a mold barrel, modified polyimide glue is injected, and heated and cured to form a filling layer; a polyimide film is wrapped around its surface, and then a modified nitrile rubber compound is coated to form an outer sheath to obtain a pressure-resistant and bending-resistant superconducting cable; among them, the modified polyimide glue is beneficial to improving the interface bonding performance between the filling layer and the polyimide film, making the cable structure more compact, thereby enhancing the superconducting cable's ability to resist external pressure and deformation. DETAILED DESCRIPTION

[0022] 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 creative efforts are within the scope of protection of the present invention.

[0023] In the following specific embodiments, parts are by mass. In this embodiment, it should be noted that the purchase manufacturers of all raw materials involved in the present invention are not subject to any special restrictions. Examples include: aminopropyl-terminated polydimethylsiloxane with a CAS number of 99904-16-2, purchased from Hubei Rishengchang New Material Technology Co., Ltd.; KH550 (3-aminopropyltriethoxysilane) with a CAS number of 919-30-2; nano-silica is industrial grade, purchased from Hubei Fangde New Materials Co., Ltd.; carbon nanotubes with a CAS number of WD7632, purchased from Hubei Wonder Chemical Co., Ltd.; silicone rubber with a CAS number of JS3128, purchased from Hubei Jusheng Technology Co., Ltd.; nitrile rubber with a CAS number of A00724, purchased from Hubei Fangde New Materials Co., Ltd. From Wuhan Jiyesheng Chemical Co., Ltd.; the CAS number of octylated diphenylamine (anti-aging agent) is 4175-37-5; the CAS number of ethylene thiourea (vulcanization accelerator) is 96-45-7; the CAS number of stearic acid is 57-11-4; the CAS number of sulfur powder is 7704-34-9; the CAS number of accelerator DM (dibenzothiazyl disulfide) is 120-78-5; the CAS number of aluminum hydroxide (flame retardant) is 21645-51-2; the CAS number of magnesium hydroxide (flame retardant) is 1309-42-8; the CAS number of benzoyl peroxide (cross-linking agent) is 94-36-0; and the CAS number of dibutyl phthalate (plasticizer) is 84-74-2.

[0024] The preparation method of the modified nitrile rubber compound is as follows: (1) 12 parts of epoxidized hydrogenated nitrile rubber, 2.5 parts of aminopropyl-terminated polydimethylsiloxane, 1.4 parts of amino-silica, and 14 parts of potassium hydroxide ethanol solution (the concentration of potassium hydroxide ethanol solution is 35wt%) are added to 30 parts of 1,4-dioxane, heated to 115°C and stirred for 3 hours under a nitrogen atmosphere to obtain a modified nitrile rubber; (2) 20 parts of modified nitrile rubber and 30 parts of silicone rubber are kneaded at 110°C for 20 minutes, 5 parts of stearic acid and 4 parts of sulfur powder are added, and kneaded at 90°C for 15 minutes. After discharging, the mixture is placed in an open mill, 0.5 parts of an anti-aging agent, 1.6 parts of a vulcanizing aid, and 1.4 parts of an accelerator are added, and the mixture is kneaded at 70°C for 15 minutes to obtain a modified nitrile rubber compound.

[0025] The preparation method of the modified polyimide glue is as follows: (1) adding 3,5-diaminobenzoic acid to N-methylpyrrolidone and mixing evenly, adding 4,4'-oxydiphthalic anhydride, stirring for 8 hours (the molar ratio of 3,5-diaminobenzoic acid to 4,4'-oxydiphthalic anhydride is 1:1), drying and grinding to obtain polyamic acid; (2) adding 15 parts of polyamic acid to 30 parts of DMF at 50°C and mixing evenly, adding 0.3 parts of DCC and 0.08 parts of DMAP, adding 4 parts of amino-treated carbon nanotubes under nitrogen protection, mixing evenly for 22 hours, and cooling. The mixture was cooled to room temperature, and n-hexane was added to precipitate, filtered, washed, and dried; then calcined at 350°C for 8 hours to obtain carbon nanotube-modified polyimide; (3) 30 parts of epoxidized hydrogenated nitrile rubber were added to 30 parts of DMF at 60°C, stirred at 500 r / min for 2 hours, and 20 parts of carbon nanotube-modified polyimide were added under ultrasonic conditions of 400 W for 50 minutes, and 12 parts of flame retardant (magnesium hydroxide and aluminum hydroxide with a mass ratio of 1:1), 4 parts of cross-linking agent, 2.5 parts of accelerator, and 2 parts of plasticizer were added and mixed evenly to obtain modified polyimide glue. Example 1

[0026] A process for preparing a pressure-resistant and bending-resistant superconducting cable comprises the following steps: Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.42 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.2 mm, thereby obtaining a cable core; Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 0.9 mm to obtain a pressure-resistant and bending-resistant superconducting cable. Example 2

[0027] A process for preparing a pressure-resistant and bending-resistant superconducting cable comprises the following steps: Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.45 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.25 mm, thereby obtaining a cable core; Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 2.2 mm to obtain a pressure-resistant and bending-resistant superconducting cable. Example 3

[0028] A process for preparing a pressure-resistant and bending-resistant superconducting cable comprises the following steps: Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.4 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.2 mm, thereby obtaining a cable core; Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap the polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 1.5 mm to obtain a pressure-resistant and bending-resistant superconducting cable.

[0029] Comparative Example 1 is based on Example 2, except that no silica is added to the modified nitrile rubber compound; Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.45 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.25 mm, thereby obtaining a cable core; The preparation method of the modified nitrile rubber compound is as follows: (1) 12 parts of epoxidized hydrogenated nitrile rubber, 2.5 parts of aminopropyl-terminated polydimethylsiloxane, and 14 parts of potassium hydroxide ethanol solution (the concentration of potassium hydroxide ethanol solution is 35 wt%) are added to 30 parts of 1,4-dioxane, heated to 115 ° C and stirred for 3 hours under a nitrogen atmosphere to obtain a modified nitrile rubber; (2) 20 parts of modified nitrile rubber and 30 parts of silicone rubber are mixed at 110 ° C for 20 minutes, 5 parts of stearic acid and 4 parts of sulfur powder are added, and mixed at 90 ° C for 15 minutes. After discharging, the mixture is placed in an open mill, 0.5 parts of an anti-aging agent, 1.6 parts of a vulcanizing aid, and 1.4 parts of an accelerator are added, and mixed at 70 ° C for 15 minutes to obtain a modified nitrile rubber compound.

[0030] Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 2.2 mm to obtain a pressure-resistant and bending-resistant superconducting cable; Comparative Example 2 is based on Example 2, except that aminopropyl-terminated polydimethylsiloxane is not added to the modified nitrile rubber compound; Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.45 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.25 mm, thereby obtaining a cable core; Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm, and obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 2.2 mm, and obtain a pressure-resistant and bending-resistant superconducting cable; The preparation method of the modified nitrile rubber compound is as follows: (1) 12 parts of epoxidized hydrogenated nitrile rubber, 1.4 parts of amino-silica, and 14 parts of potassium hydroxide ethanol solution (the concentration of potassium hydroxide ethanol solution is 35 wt%) are added to 30 parts of 1,4-dioxane, heated to 115 ° C and stirred for 3 hours under a nitrogen atmosphere to obtain a modified nitrile rubber; (2) 20 parts of modified nitrile rubber and 30 parts of silicone rubber are mixed at 110 ° C for 20 minutes, 5 parts of stearic acid and 4 parts of sulfur powder are added, and mixed at 90 ° C for 15 minutes. After discharging, the mixture is placed in an open mill, 0.5 parts of an anti-aging agent, 1.6 parts of a vulcanizing aid, and 1.4 parts of an accelerator are added, and mixed at 70 ° C for 15 minutes to obtain a modified nitrile rubber compound.

[0031] Comparative Example 3 is based on Example 2, and the modified polyimide glue is directly prepared by mixing carbon nanotubes, polyimide, and epoxidized hydrogenated nitrile rubber; Step 1: (1) Set the twisting pitch to 10 mm and the twisting tension to 3 N; twist 35 superconducting filaments to obtain a twisted superconductor; (2) inject the modified nitrile rubber compound into the mold and vulcanize it with the twisted superconductor to form a stress buffer layer with a thickness of 0.45 mm; (3) wrap the polyimide film on the heated and softened stress buffer layer (the softening temperature of the stress buffer layer is 115 ° C, the wrapping pressure is 1.7 MPa, and the wrapping angle is 45°) to form an insulation layer A with a thickness of 0.25 mm, thereby obtaining a cable core; Step 2: (1) Place three groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulation layer B with a thickness of 0.25 mm to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath with a thickness of 2.2 mm to obtain a pressure-resistant and bending-resistant superconducting cable; Among them, the preparation method of the modified polyimide glue is: treat 30 parts of epoxidized hydrogenated nitrile rubber, 5 parts of amino carbon nanotubes, and 15 parts of polyimide for 50 minutes, add 12 parts of flame retardant (magnesium hydroxide and aluminum hydroxide with a mass ratio of 1:1), 4 parts of cross-linking agent, 2.5 parts of accelerator, and 2 parts of plasticizer, and mix them evenly to obtain modified polyimide glue.

[0032] Testing: (1) The superconducting cables prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in a -40°C environment for 5 days, and then placed in an impact device. A 1 kg hammer at a height of 2 m was used to impact the superconducting cables in Examples 1 to 3 and Comparative Examples 1 to 3. After 200 cycles, the tensile strength of the superconducting cables was tested. See Table 1. (2) The mechanical phase stability of Examples 1 to 3 and Comparative Examples 1 to 3 was tested according to IEC 60966-2-1; see Table 1; Table 1 Tensile strength (MPa) Change in standing wave after 20,000 bends / ° Example 1 228.6 1.24 Example 2 233.4 1.17 Example 3 230.6 1.20 Comparative Example 1 217.4 1.38 Comparative Example 2 220.7 1.29 Comparative Example 3 182.4 1.47 Conclusion: Comparative Example 1 is based on Example 2, except that silica is not added to the modified nitrile rubber compound; this results in reduced interface performance between the modified nitrile rubber compound and the twisted superconductor and polyimide film, thereby reducing the performance of the superconducting cable; Comparative Example 2 is based on Example 2, except that aminopropyl-terminated polydimethylsiloxane is not added to the modified nitrile rubber compound; this results in reduced interface performance between the nitrile rubber and the silicone rubber, thereby reducing the performance of the superconducting cable; Comparative Example 3 is based on Example 2, except that the modified polyimide glue is directly made by mixing carbon nanotubes, polyimide, and epoxidized hydrogenated nitrile rubber; this results in reduced performance of the superconducting cable.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A process for preparing a pressure-resistant and bending-resistant superconducting cable, characterized in that: The following steps are included: Step 1: (1) Twisting multiple superconducting filaments to obtain a twisted superconductor; (2) Injecting a modified nitrile rubber compound into a mold and vulcanizing it with the twisted superconductor to form a stress buffer layer; (3) Wrapping a polyimide film around the heated and softened stress buffer layer to form an insulating layer A, thereby obtaining a cable core; Step 2: (1) Place multiple groups of cable cores in a mold barrel, inject modified polyimide glue, heat and solidify to form a filling layer; wrap a polyimide film on its surface to form an insulating layer B to obtain a superconducting cable A; (2) Inject the modified nitrile rubber compound into the mold and vulcanize it with the superconducting cable A to form an outer sheath, thereby obtaining a pressure-resistant and bending-resistant superconducting cable.

2. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 1, characterized in that: The thickness of the stress buffer layer is 0.35-0.55 mm; the thickness of the insulating layer A is 0.18-0.25 mm; the thickness of the insulating layer B is 0.18-0.25 mm; the thickness of the outer sheath is 0.9-2.2 mm; and the filling amount of the modified polyimide glue accounts for 50-60% of the volume of the mold barrel.

3. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 1, characterized in that: The preparation method of the modified nitrile rubber compound is as follows: (1) adding epoxidized hydrogenated nitrile rubber, aminopropyl-terminated polydimethylsiloxane, amino-silica, and potassium hydroxide ethanol solution to 1,4-dioxane, heating to 110-120°C and stirring for 3-4 hours under a nitrogen atmosphere to obtain a modified nitrile rubber; (2) kneading the modified nitrile rubber and silicone rubber at 100-115°C for 20-25 minutes, adding stearic acid and sulfur powder, kneading at 90-100°C for 15-20 minutes, discharging and placing in an open mill, adding an anti-aging agent, a vulcanizing aid, and an accelerator, and kneading at 60-80°C for 10-15 minutes to obtain a modified nitrile rubber compound.

4. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 3, characterized in that: The raw materials of the modified nitrile rubber include the following components: 10-15 parts of epoxidized hydrogenated nitrile rubber, 2-4 parts of aminopropyl-terminated polydimethylsiloxane, 1-2 parts of amino-silica, and 12-16 parts of potassium hydroxide ethanol solution, in parts by mass; the concentration of the potassium hydroxide ethanol solution is 30-40 wt%.

5. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 3, characterized in that: The raw materials of the modified nitrile rubber compound include the following components: 15 to 20 parts of modified nitrile rubber, 30 to 40 parts of silicone rubber, 3 to 6 parts of stearic acid, 4 to 5 parts of sulfur powder, 0.5 to 0.6 parts of anti-aging agent, 1.5 to 1.8 parts of vulcanization aid, and 1 to 1.5 parts of accelerator, calculated by mass.

6. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 1, characterized in that: The preparation method of the modified polyimide glue is as follows: (1) adding 3,5-diaminobenzoic acid to N-methylpyrrolidone and mixing uniformly, adding 4,4'-oxydiphthalic anhydride and stirring for 8-10 hours, drying and grinding, to obtain polyamide acid; (2) adding polyamide acid to DMF at 45-55°C and mixing uniformly, adding DCC and DMAP, adding amino carbon nanotubes under nitrogen protection, mixing uniformly for 20-24 hours, cooling to room temperature, adding n-hexane to precipitate, filtering, washing, and drying; and then calcining at 300-350°C for 6-8 hours to obtain carbon nanotube-modified polyimide; (3) Add epoxidized hydrogenated nitrile rubber to DMF at 60-70°C, stir at 400-500 r / min for 2-3 hours, add carbon nanotube-modified polyimide under ultrasonic conditions of 200-500 W for 40-60 minutes, and add flame retardant, crosslinking agent, accelerator and plasticizer to obtain modified polyimide glue.

7. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 6, characterized in that: The molar ratio of the 3,5-diaminobenzoic acid to 4,4'-oxydiphthalic anhydride is 1:1; the raw materials of the carbon nanotube-modified polyimide include the following components: 12 to 15 parts of polyamic acid, 0.25 to 0.4 parts of DCC, 0.07 to 0.13 parts of DMAP, 3 to 4 parts of amino-treated carbon nanotubes, and 30 to 40 parts of DMF, calculated by mass.

8. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 6, characterized in that: The raw materials of the modified polyimide glue include the following components: 30-50 parts of epoxidized hydrogenated nitrile rubber, 15-20 parts of carbon nanotube modified polyimide, 20-30 parts of DMF, 8-12 parts of flame retardant, 3-5 parts of crosslinking agent, 2.5-3 parts of accelerator, and 2-3 parts of plasticizer.

9. The process for preparing a pressure-resistant and bending-resistant superconducting cable according to claim 1, characterized in that: The superconducting filaments are composed of a superconducting core material and a copper or silver stabilization layer; the twisting pitch is 8 to 10 mm, and the twisting tension is 3 to 4 N; the vulcanization molding temperature is 170 to 180° C.; the stress buffer layer softening temperature is 110 to 120° C.; the wrapping pressure is 1 to 2 MPa, and the winding angle is 45 to 60°.

10. A pressure-resistant and bending-resistant superconducting cable prepared by the process for preparing a pressure-resistant and bending-resistant superconducting cable according to any one of claims 1 to 9.