A kind of electric wire and cable resistant to extremely low temperature

Abstract

The present invention discloses a wire and cable resistant to extremely low temperatures, which belongs to the technical field of cable manufacturing, and is used to solve the technical problem that the low temperature resistance and anti-electromagnetic interference performance of the cable in the prior art need to be further improved; a wire and cable resistant to extremely low temperatures, characterized in that it comprises a cable conductor, a buffer shielding layer, a sheath layer and a low temperature resistant coating layer arranged in sequence from the inside to the outside. The present invention prepares an inorganic buffer material with a rigid skeleton and a flexible surface structure, and while its rigid structure provides support for the cable, its honeycomb material significantly improves the electromagnetic interference resistance of the cable, and the flexible surface improves the low temperature shrinkage resistance of the cable; its surface modified amino hybridizes the organic chain segment of the low temperature resistant material, and cooperates with its annular structure to significantly enhance the mechanical properties of the material, and the extremely low thermal conductivity of the inorganic buffer material ensures the stable operation of the internal conductor of the cable, thereby preparing a cable resistant to ultra-low temperature liquefied gas.

Description

Technical Field

[0001] The invention relates to the technical field of cable manufacturing, and in particular to an electric wire and cable resistant to extremely low temperatures. Background Art

[0002] The technical development of extremely low temperature resistant cables mainly focuses on improving their performance at liquid nitrogen temperatures and their ability to resist electromagnetic interference. In the early days, cables mostly used polytetrafluoroethylene or silicone rubber as insulation materials. With technological advances, new materials such as fluororubber have been used to improve the physical and chemical stability of cables in extreme low temperature environments. In order to further enhance its resistance to electromagnetic interference, a metal shielding layer is introduced into the cable design. Commonly used shielding materials include copper tape, aluminum foil and copper wire braid. These shielding measures effectively isolate external electromagnetic interference and limit the electromagnetic radiation of the cable itself; these technological improvements not only enhance the practicality of the cable, but also expand its application in high-tech fields such as aerospace and deep-sea exploration.

[0003] The prior art CN114628065B discloses a low-temperature resistant shielded control cable, comprising a cable core, a cushion layer is arranged outside the cable core, a total shielding layer is arranged outside the cushion layer, a wrapped shielding layer is arranged outside the total shielding layer, and a sheath layer is arranged outside the wrapped shielding layer; the raw material of the sheath layer is low-temperature resistant silicone rubber; the cable of this invention can withstand ultra-low temperatures, and has high mechanical strength and strong shielding effect. It is a low-temperature resistant shielded control cable suitable for vehicles or equipment in special ultra-low temperature environments.

[0004] However, the above invention is to obtain low-temperature resistant silicone rubber by preparing silicone-modified polyimide resin powder and then mixing it with methylphenylvinyl silicone rubber raw rubber and auxiliary materials, and wrapping a shielding tape inside the cable to improve the cable's low-temperature resistance and anti-electromagnetic shielding effectiveness. However, since there is no buffering substance inside the low-temperature resistant silicone rubber, its anti-shrinkage performance at low temperatures needs to be further improved, which will cause the material to pulverize and crack. During the shrinkage and cracking process, changes in the cable structure will affect the covering property of the shielding tape, so that the cable's anti-electromagnetic interference performance needs to be further improved.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0006] The object of the present invention is to provide an extremely low temperature resistant wire and cable, so as to solve the technical problem in the prior art that the low temperature resistance and anti-electromagnetic interference performance of the cable need to be further improved.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] An extremely low temperature resistant wire and cable, comprising a plurality of cable conductors, a buffer shielding layer, a sheath layer and a low temperature resistant coating layer arranged in sequence from the inside to the outside;

[0009] The cable conductor is composed of a core composed of multiple silver-plated copper conductors twisted together and a polytetrafluoroethylene insulation layer coated on the surface;

[0010] The buffer shielding layer is obtained by filling the inorganic buffer material between the cable conductor and the sheath layer;

[0011] The sheath layer is composed of a sheath tube formed by melt-extruding a composite polytetrafluoroethylene material into a mold;

[0012] The method for preparing the low temperature resistant coating layer comprises the following steps:

[0013] A1. Evenly mix the low temperature resistant material, antistatic agent, defoaming agent, coupling agent and dimethylacetamide to obtain a low temperature resistant coating;

[0014] A2. Spin-coating the low-temperature resistant coating onto the surface of the sheath layer to obtain a coating precursor, and post-treating the coating precursor to obtain a low-temperature resistant coating layer.

[0015] Furthermore, in step A1, the amount ratio of low-temperature resistant material, antistatic agent, defoaming agent, coupling agent and dimethylacetamide is 20-30g:1-2g:0.5-0.8g:2-3g:60-80mL; in step A2, the low-temperature resistant coating is spin-coated with a thickness of 30-50μm, and the post-treatment includes: transferring the material to a drying oven at a temperature of 100-150°C for vacuum drying for 4-6h, then raising the temperature of the drying oven to 300-360°C, and heat-insulating for 12-16h to obtain a low-temperature resistant coating layer.

[0016] Furthermore, the antistatic agent is one or more of conductive carbon black, graphene and multi-walled carbon nanotubes; the defoaming agent is polydimethylsiloxane; and the coupling agent is one or more of trimethoxysilane, triethoxysilane and 3-(2,3-epoxypropyloxy)propyltrimethoxysilane.

[0017] Furthermore, the preparation method of the low temperature resistant material comprises the following steps:

[0018] B1. Add 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2'-diaminoethylene glycol diphenyl ether, triethylamine and N,N-dimethylformamide into a reactor, raise the temperature of the reactor to 40-60°C, keep the temperature for 1-2 hours, add an inorganic buffer into the reactor, keep the temperature for 20-40 minutes, and post-treat to obtain a low-temperature resistant material precursor;

[0019] B2. Add the cryogenic material precursor and dimethylacetamide into the reactor, stir at room temperature for 10-15 minutes, and after the temperature of the reactor rises to 70-80°C, add acetic anhydride and triethylamine into the reactor, keep the temperature for 10-12 hours, and post-treat to obtain the cryogenic material.

[0020] The reaction equation for preparing low temperature resistant material is:

[0021]

[0022] Where:

[0023] ;

[0024] ;

[0025] “ " indicates inorganic buffer;

[0026] “*” indicates the active linking site of the organic chain segment.

[0027] The reaction principle for preparing low-temperature-resistant materials is as follows: under the catalysis of catalysts and heating conditions, by controlling the dosage ratio of reaction monomers, the anhydride groups on 4,4'-(hexafluoroisopropylene) diphthalic anhydride and the amino groups on 2,2'-diaminoethylene glycol diphenyl ether react to form a long-chain structure with anhydride groups as end groups, and then an inorganic buffer material with a large number of amino groups on the surface of the filler is added to the reaction system. The amino groups on the surface of the inorganic buffer material further react with the end-capping anhydride groups to form a cross-linked structure to obtain a low-temperature-resistant material precursor; the low-temperature-resistant material precursor is catalyzed by triethylamine and assisted by acetic anhydride, and a cyclization reaction occurs inside the low-temperature-resistant material precursor, and finally a cyclic polyimide structure is formed, thereby preparing the low-temperature-resistant material.

[0028] Furthermore, in step B1, the dosage ratio of 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2'-diaminoethylene glycol diphenyl ether, triethylamine, N,N-dimethylformamide and inorganic buffer is 5.3-5.5g:2.5-2.7g:0.3-0.5g:20-30mL:2-3g, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 60-80°C, and the solvent is evaporated under reduced pressure to obtain a low-temperature resistant material precursor.

[0029] Furthermore, in step B2, the stirring rate of the reactor is 80-120rpm, the amount ratio of the cryogenic material precursor, dimethylacetamide, acetic anhydride and triethylamine is 4.0-4.2g:18-20mL:1.0-1.2g:0.3-0.5g, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 60-80°C, and the solvent is evaporated under reduced pressure to obtain the cryogenic material.

[0030] Furthermore, the preparation method of the inorganic buffer comprises the following steps:

[0031] C1. Add modified foamed metal, hexadecyltrimethylammonium bromide, deionized water and acetic acid into a reactor and stir for 8-10 minutes, then raise the temperature of the reactor to 40-60°C, add a composite silicon source into the reactor, keep the temperature for 2-3 hours, then add silica sol into the reactor, keep the temperature for 1-2 hours, and obtain a buffer material precursor;

[0032] C2. The buffer precursor is transferred to a hydrothermal reactor, the temperature of the hydrothermal reactor is increased to 60-80°C, and after keeping the temperature for 20-24 hours, the gel is taken out and washed 3-5 times with anhydrous ethanol and deionized water, and then the inorganic buffer is obtained by post-treatment.

[0033] The reaction principle for preparing inorganic buffer materials is as follows: a large amount of siloxane structures on the surface of modified foam metal modified by silane coupling agent are co-hydrolyzed with the composite silicon source to form a silica gel structure, and the silica particles in the silica sol are used as the nucleation center in the gel process, and the hydroxyl groups on the surface of the silica particles are the nucleation sites. The size of the aerogel secondary particles is refined and the degree of cross-linking is increased, thereby obtaining a flexible silica aerogel structure and finally preparing the inorganic buffer material.

[0034] Furthermore, in step C1, the amount ratio of modified foam metal, hexadecyltrimethylammonium bromide, deionized water, acetic acid, composite silicon source and silica sol is 3-5g:0.3-0.5g:80-100mL:5-8mL:20-30g:2-3mL, the composite silicon source is obtained by mixing methyltriethoxysilane, tetraethoxysilane and 3-aminopropyltriethoxysilane in an amount ratio of 3-4g:3-4g:1-2g, and the stirring rate of the reactor is 80-120rpm; in step C2, the post-treatment includes: transferring the gel to a drying oven at a temperature of 60°C, drying at room temperature and pressure for 6-8h to obtain an inorganic buffer material.

[0035] Furthermore, the preparation method of the modified foam metal comprises the following steps:

[0036] D1. Add the modified pore-forming agent and copper powder into a ball mill to grind the mixture. After ball milling for 10-15 minutes, add calcium stearate into the ball mill, continue ball milling for 5-8 minutes to obtain a mixture, and post-treat to obtain a mixed body;

[0037] D2. calcining the mixed green body to obtain a porous material, and post-treating the porous material to obtain a foamed metal green body;

[0038] D3. Add the foam metal body, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol into the reactor, increase the temperature of the reactor to 50-70°C, keep the reaction temperature for 2-4 hours, and post-treat to obtain the modified foam metal.

[0039] The reaction principle for preparing modified foam metal is as follows: copper powder is lubricated and cross-linked by calcium stearate to form a uniform system with the modified pore-forming agent. During the calcination process, the calcium hydride component first decomposes to produce a pre-foam structure, which promotes the outflow of calcium chloride after melting, thereby forming a more uniform foam structure. After high-temperature activation by water vapor and oxygen, the active free radicals on its surface react with 3-(2,3-epoxypropoxy)propyltrimethoxysilane, thereby introducing a siloxane structure into the material structure, and finally preparing the modified foam metal.

[0040] Furthermore, in step D1, the modified pore-forming agent, copper powder and calcium stearate are used in a ratio of 4-6g:3-4g:0.3-0.5g, and the modified pore-forming agent is obtained by mixing calcium chloride and calcium hydride in a ratio of 1g:1-1.5g. The post-processing includes: transferring the mixture to a punching machine, punching at a pressure of 200-300Mpa for 3-4min, and obtaining a mixed green body.

[0041] Furthermore, in step D2, the calcination operation is as follows: the mixed green body is transferred to a tubular furnace, nitrogen is introduced for protection, the temperature of the tubular furnace is increased to 600-620°C at a heating rate of 3-5°C / min, and the temperature is kept at 840-860°C at a heating rate of 3-5°C / min for 2-4 hours, and the temperature is continued to be increased to 100-150°C at a heating rate of 3-5°C / min. After being kept at 1-2 hours, the reactor is naturally cooled to 100-150°C, the nitrogen is disconnected, and an equal volume of mixed gas of water vapor and oxygen is introduced at a flow rate of 1-2L / min, and the temperature is kept at 1-2 hours to obtain a porous material; post-treatment includes: after the porous material is soaked and rinsed with anhydrous ethanol and deionized water for 3-5 times, the porous material is ground and passed through a 100-200 mesh sieve to obtain a foam metal green body.

[0042] Furthermore, in step D3, the usage ratio of the foam metal body, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol is 8-10g:2-3g:0.2-0.4g:30-40mL, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is transferred to a drying oven at a temperature of 60-80°C and vacuum dried to constant weight to obtain a modified foam metal.

[0043] Furthermore, the preparation method of the sheath tube comprises the following steps:

[0044] The composite polytetrafluoroethylene material is added into a twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 300°C, 325°C, 325°C, 350°C, 350°C, 370°C, 370°C, and 380°C, respectively, the main engine speed of the twin-screw extruder is 80-120rpm, the pressure is 100-150 bar, the material is melted and extruded into a mold, and cooled to obtain a sheath tube.

[0045] Furthermore, the composite polytetrafluoroethylene material comprises the following raw materials in parts by weight: 80-100 parts of polytetrafluoroethylene, 15-20 parts of inorganic buffer material, 5-8 parts of glass fiber and 20-30 parts of plasticizer, wherein the plasticizer is one or more of dioctyl phthalate, diisononyl phthalate and trimethyl phosphate.

[0046] Furthermore, the preparation method of the buffer shielding layer and the sheath layer comprises the following steps:

[0047] After the sheath tube is put on the outside of the cable conductor, the inorganic buffer material is filled into the gap, and the material is vibrated and compacted and added until the gap between the sheath tube and the cable conductor is completely filled to obtain a buffer shielding layer and a sheath layer.

[0048] The present invention has the following beneficial effects:

[0049] 1. The present invention prepares an inorganic buffer material with a rigid skeleton and a flexible surface structure. While its rigid structure provides support for the cable, its honeycomb material significantly improves the cable's resistance to electromagnetic interference, and the flexible surface improves the cable's resistance to low-temperature shrinkage. The surface-modified amino groups hybridize the organic chain segments of the low-temperature resistant material, and cooperate with its annular structure to significantly enhance the material's mechanical properties. The extremely low thermal conductivity of the inorganic buffer material ensures the stable operation of the cable's internal conductor, thereby preparing a cable resistant to ultra-low temperature liquefied gas.

[0050] 2. The inorganic buffer prepared by the present invention has a modified foam metal as a skeleton and a flexible silica aerogel as a modification, and the active group amino is modified in the flexible silica aerogel layer. In the process of preparing the low-temperature resistant material precursor, the modified buffer is used as a cross-linking agent, and a large number of amino groups on its surface react with the anhydride at the end of the polyamide segment to hybridize the organic segment. The large number of fluorine groups inside it reduce the surface energy of the coating. The two cooperate to improve the wear resistance of the coating, and the lower surface energy makes it difficult for liquid nitrogen to adhere to the cable surface, thereby improving the safety of cable maintenance. After the hybrid polyamide segment is cyclized, it has more excellent low-temperature resistance. The cyclized structure cooperates with the flexible aerogel layer to significantly improve the tensile strength of the material.

[0051] The modified foam metal and silica aerogel layer of the inorganic buffer prepared by the present invention not only have extremely low thermal conductivity to protect the inside of the cable, but also have the modified foam metal inside as a skeleton and the flexible silica aerogel layer as a buffer, so that the organic material components of the extremely low temperature resistant cable have extremely high low temperature shrinkage resistance. The two properties work together to significantly improve the low temperature resistance of the cable, providing a basis for the extremely low temperature resistant cable to not pulverize or crack inside ultra-low temperature liquefied gas. The internal foam metal copper structure has a porous structure that captures and scatters incoming electromagnetic waves, and the unique porosity and continuous metal network provide a good shielding effect, and improve the material's anti-electromagnetic interference performance through reflection, absorption and multiple scattering mechanisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0053] Figure 1 It is a cross-sectional schematic diagram of the entire extremely low temperature resistant cable;

[0054] Figure 2 A schematic cross-sectional view of a cable conductor.

[0055] In the figure: 1. Cable conductor; 2. Buffer shielding layer; 3. Sheath layer; 4. Low-temperature resistant coating layer; 11. Silver-plated copper conductor; 12. Polytetrafluoroethylene insulation layer. DETAILED DESCRIPTION

[0056] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Embodiment 1, this embodiment provides a method for preparing a modified foam metal for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0058] Step 1: preparing a mixed green body;

[0059] Weigh: 100.0 g of calcium chloride and 100.0 g of calcium hydride and mix to obtain a modified pore-forming agent;

[0060] Weigh: 400.0g of modified pore-forming agent and 300.0g of copper powder are added to a ball mill to grind the mixture. After ball milling for 10 minutes, 30.0g of calcium stearate is added to the ball mill. After continuing ball milling for 5 minutes, a mixture is obtained. The mixture is transferred to a punch press and punched at a pressure of 200Mpa for 3 minutes to obtain a mixed green body.

[0061] Step ②, preparing a foam metal blank;

[0062] The mixed body was transferred to a tubular furnace, and nitrogen was introduced for protection. The temperature of the tubular furnace was increased to 600°C at a heating rate of 3°C / min, and the temperature was kept at that temperature for 2 hours. The temperature was then increased to 840°C at a heating rate of 3°C / min, and the temperature was kept at that temperature for 1 hour. The reactor was naturally cooled to 100°C, the nitrogen was disconnected, and a mixed gas of equal volumes of water vapor and oxygen was introduced at a flow rate of 1L / min. The temperature was kept at that temperature for 1 hour to obtain a porous material.

[0063] After the porous material was soaked and rinsed with anhydrous ethanol and deionized water for three times, the porous material was ground and passed through a 100-mesh sieve to obtain a foam metal blank.

[0064] Step 3, preparing modified foam metal;

[0065] Weigh: 800.0g of foam metal blank, 200.0g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 20.0g of triethylamine and 3.0L of anhydrous ethanol are added into a reactor, the temperature of the reactor is raised to 50°C, and the reaction is kept warm for 2h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is transferred to a drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain a modified foam metal.

[0066] Embodiment 2, this embodiment provides a method for preparing a modified foam metal for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0067] Step 1: preparing a mixed green body;

[0068] Weigh: 100.0 g of calcium chloride and 150.0 g of calcium hydride are mixed to obtain a modified pore-forming agent;

[0069] Weigh: 600.0g of modified pore-forming agent and 400.0g of copper powder are added to a ball mill to grind the mixture. After ball milling for 15 minutes, 50.0g of calcium stearate is added to the ball mill. After continuing ball milling for 8 minutes, a mixture is obtained. The mixture is transferred to a punch press and punched at a pressure of 300Mpa for 4 minutes to obtain a mixed green body.

[0070] Step ②, preparing a foam metal blank;

[0071] The mixed body was transferred to a tubular furnace, and nitrogen was introduced for protection. The temperature of the tubular furnace was increased to 620°C at a heating rate of 5°C / min, and the temperature was kept for 4 hours. Then, the temperature was increased to 860°C at a heating rate of 5°C / min, and the temperature was kept for 2 hours. The reactor was naturally cooled to 150°C, the nitrogen was disconnected, and a mixed gas of equal volumes of water vapor and oxygen was introduced at a flow rate of 2L / min. The temperature was kept for 2 hours to obtain a porous material.

[0072] After the porous material was soaked and rinsed with anhydrous ethanol and deionized water for 5 times, the porous material was ground and passed through a 200-mesh sieve to obtain a foam metal blank.

[0073] Step 3, preparing modified foam metal;

[0074] Weigh: 1000.0g of foam metal blank, 300.0g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 40.0g of triethylamine and 4.0L of anhydrous ethanol are added into a reactor, the temperature of the reactor is raised to 70°C, and the reaction is kept warm for 4 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is transferred to a drying oven at a temperature of 80°C and vacuum dried to constant weight to obtain a modified foam metal.

[0075] Embodiment 3, this embodiment provides a method for preparing a modified foam metal for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0076] Step 1: preparing a mixed green body;

[0077] Weigh: 100.0 g of calcium chloride and 125.0 g of calcium hydride are mixed to obtain a modified pore-forming agent;

[0078] Weigh: 500.0g of modified pore-forming agent and 350.0g of copper powder are added to a ball mill to grind the mixture. After ball milling for 12 minutes, 40.0g of calcium stearate is added to the ball mill. After continuing ball milling for 6 minutes, a mixture is obtained. The mixture is transferred to a punch press and punched at a pressure of 250Mpa for 4 minutes to obtain a mixed body.

[0079] Step ②, preparing a foam metal blank;

[0080] The mixed body was transferred to a tubular furnace, and nitrogen was introduced for protection. The temperature of the tubular furnace was increased to 610°C at a heating rate of 4°C / min, and the temperature was kept at that temperature for 3 hours. Then, the temperature was increased to 850°C at a heating rate of 4°C / min, and the temperature was kept at that temperature for 2 hours. The reactor was naturally cooled to 125°C, the nitrogen was disconnected, and a mixed gas of equal volumes of water vapor and oxygen was introduced at a flow rate of 1.5L / min. The temperature was kept at that temperature for 2 hours to obtain a porous material.

[0081] After the porous material was soaked and rinsed with anhydrous ethanol and deionized water for 4 times, the porous material was ground and passed through a 150-mesh sieve to obtain a foam metal blank.

[0082] Step 3, preparing modified foam metal;

[0083] Weigh: 900.0g of foam metal blank, 250.0g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 30.0g of triethylamine and 3.5L of anhydrous ethanol are added into a reactor, the temperature of the reactor is raised to 60°C, and the reaction is kept warm for 3 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain a modified foam metal.

[0084] Embodiment 4, this embodiment provides a method for preparing an inorganic buffer material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0085] Step (1), preparing a buffer material precursor;

[0086] Weigh: 300.0 g of methyltriethoxysilane, 400.0 g of tetraethoxysilane and 100.0 g of 3-aminopropyltriethoxysilane and mix to obtain a composite silicon source;

[0087] Weigh: 300.0 g of the modified foam metal prepared in Example 1, 30.0 g of hexadecyltrimethylammonium bromide, 8.0 L of deionized water and 500.0 L of acetic acid, add them into a reactor and stir for 8 min. The stirring rate is 80 rpm, the temperature of the reactor is increased to 40°C, 2000.0 g of the composite silicon source is added to the reactor, and the reaction is kept warm for 2 h. Then, 200.0 L of silica sol is added to the reactor and the reaction is kept warm for 1 h to obtain a buffer material precursor.

[0088] Step (2), preparing an inorganic buffer material;

[0089] The buffer precursor was transferred to a hydrothermal autoclave, the temperature of the hydrothermal autoclave was raised to 60°C, and after keeping warm for 20 hours, the gel was taken out and washed three times with anhydrous ethanol and deionized water, and the gel was transferred to a drying oven at a temperature of 60°C, and dried at room temperature and pressure for 6 hours to obtain an inorganic buffer.

[0090] Embodiment 5, this embodiment provides a method for preparing an inorganic buffer material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0091] Step (1), preparing a buffer material precursor;

[0092] Weigh: 400.0 g of methyltriethoxysilane, 400.0 g of tetraethoxysilane and 200.0 g of 3-aminopropyltriethoxysilane and mix to obtain a composite silicon source;

[0093] Weigh: 500.0 g of the modified foam metal prepared in Example 2, 50.0 g of hexadecyltrimethylammonium bromide, 10.0 L of deionized water and 800.0 mL of acetic acid, add them into a reactor and stir for 10 min. The stirring rate is 120 rpm, the temperature of the reactor is increased to 60°C, 3000.0 g of the composite silicon source is added to the reactor, and the reaction is kept warm for 3 h. Then, 300.0 L of silica sol is added to the reactor and the reaction is kept warm for 2 h to obtain a buffer material precursor.

[0094] Step (2), preparing an inorganic buffer material;

[0095] The buffer precursor was transferred to a hydrothermal autoclave, the temperature of the hydrothermal autoclave was raised to 80°C, and after keeping warm for 24 hours, the gel was taken out and washed 5 times with anhydrous ethanol and deionized water, and the gel was transferred to a drying oven at a temperature of 60°C, and dried at room temperature and pressure for 8 hours to obtain an inorganic buffer.

[0096] Embodiment 6, this embodiment provides a method for preparing an inorganic buffer material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0097] Step (1), preparing a buffer material precursor;

[0098] Weigh: 350.0 g of methyltriethoxysilane, 350.0 g of tetraethoxysilane and 150.0 g of 3-aminopropyltriethoxysilane and mix to obtain a composite silicon source;

[0099] Weigh: 400.0 g of the modified foam metal prepared in Example 3, 40.0 g of hexadecyltrimethylammonium bromide, 9.0 L of deionized water and 750.0 mL of acetic acid, add them into a reactor and stir for 9 minutes. The stirring rate is 100 rpm, the temperature of the reactor is increased to 50°C, 2500.0 g of the composite silicon source is added to the reactor, and the reaction is kept warm for 3 hours. Then, 250.0 mL of silica sol is added to the reactor and the reaction is kept warm for 2 hours to obtain a buffer material precursor.

[0100] Step (2), preparing an inorganic buffer material;

[0101] The buffer precursor was transferred to a hydrothermal autoclave, the temperature of the hydrothermal autoclave was raised to 70°C, and after keeping warm for 21 hours, the gel was taken out and washed 4 times with anhydrous ethanol and deionized water, and the gel was transferred to a drying oven at a temperature of 60°C, and dried at room temperature and pressure for 7 hours to obtain an inorganic buffer.

[0102] Embodiment 7, this embodiment provides a method for preparing a low temperature resistant material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0103] Step I: preparing a low temperature resistant material precursor;

[0104] Weigh: 530.0g 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 250.0g 2,2'-diaminoethylene glycol diphenyl ether, 30.0g triethylamine and 2.0L N,N-dimethylformamide and add them into a reactor. The temperature of the reactor is raised to 40°C. After the reaction is kept warm for 1h, 200.0g of the inorganic buffer prepared in Example 4 is added to the reactor. The reaction is kept warm for 20min. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction solution is transferred to a rotary evaporator at a temperature of 60°C. The solvent is evaporated under reduced pressure to obtain a low-temperature resistant material precursor.

[0105] Step II, preparing low temperature resistant material;

[0106] Weigh: 400.0g of low-temperature resistant material precursor and 1.8L of dimethylacetamide are added to the reactor, stirred at room temperature for 10min, the stirring rate is 80rpm, after the temperature of the reactor is raised to 70°C, 100.0g of acetic anhydride and 30.0g of triethylamine are added to the reactor, and the reaction is kept warm for 10h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator at a temperature of 60°C, and the solvent is evaporated under reduced pressure to obtain the low-temperature resistant material.

[0107] Embodiment 8, this embodiment provides a method for preparing a low temperature resistant material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0108] Step I: preparing a low temperature resistant material precursor;

[0109] Weigh: 550.0g 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 270.0g 2,2'-diaminoethylene glycol diphenyl ether, 50.0g triethylamine and 3.0L N,N-dimethylformamide and add them into a reactor. The temperature of the reactor is raised to 60°C. After the reaction is kept warm for 2h, 300.0g of the inorganic buffer prepared in Example 5 is added to the reactor. The reaction is kept warm for 20min. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction solution is transferred to a rotary evaporator at a temperature of 60°C. The solvent is evaporated under reduced pressure to obtain a low-temperature resistant material precursor.

[0110] Step II, preparing low temperature resistant material;

[0111] Weigh: 420.0g of low-temperature resistant material precursor and 2.0L of dimethylacetamide are added to the reactor, stirred at room temperature for 15min, the stirring rate is 120rpm, after the temperature of the reactor is raised to 80°C, 120.0g of acetic anhydride and 50.0g of triethylamine are added to the reactor, and the reaction is kept warm for 12h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator at a temperature of 80°C, and the solvent is evaporated under reduced pressure to obtain the low-temperature resistant material.

[0112] Embodiment 9, this embodiment provides a method for preparing a low temperature resistant material for electric wires and cables resistant to extremely low temperatures, comprising the following steps:

[0113] Step I: preparing a low temperature resistant material precursor;

[0114] Weigh: 540.0g 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 260.0g 2,2'-diaminoethylene glycol diphenyl ether, 40.0g triethylamine and 2.5L N,N-dimethylformamide and add them into the reactor, the temperature of the reactor is raised to 50°C, and after the reaction is kept warm for 2h, 250.0g of the inorganic buffer prepared in Example 6 is added to the reactor, and the reaction is kept warm for 30min. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 70°C, and the solvent is evaporated under reduced pressure to obtain a low-temperature resistant material precursor.

[0115] Step II, preparing low temperature resistant material;

[0116] Weigh: 410.0g of low-temperature resistant material precursor and 1.9L of dimethylacetamide are added to the reactor, stirred at room temperature for 12min, the stirring rate is 100rpm, after the temperature of the reactor is raised to 75°C, 110.0g of acetic anhydride and 40.0g of triethylamine are added to the reactor, and the reaction is kept warm for 11h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 70°C, and the solvent is evaporated under reduced pressure to obtain the low-temperature resistant material.

[0117] Example 10, please refer to Figure 1-2This embodiment provides a method for preparing an extremely low temperature resistant wire and cable, comprising the following steps:

[0118] Step 1, preparing the sheath tube;

[0119] Weigh: 8.0 kg of polytetrafluoroethylene, 1.5 kg of the inorganic buffer prepared in Example 4, 500.0 g of glass fiber and 2.0 kg of dioctyl phthalate and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port toward the discharge port are 300° C., 325° C., 325° C., 350° C., 350° C., 370° C., 370° C., 380° C., the main engine speed of the twin-screw extruder is 80 rpm, the pressure is 100 bar, and the melt is extruded into a mold and cooled to obtain a sheath tube.

[0120] Step 2: preparing a buffer shielding layer and a sheath layer;

[0121] After the sheath tube is sleeved on the outside of the cable conductor, the inorganic buffer material prepared in Example 4 is filled into the gap, and the material is vibrated and compacted and added until the gap between the sheath tube and the cable conductor is completely filled, thereby obtaining a buffer shielding layer (2) and a sheath layer (3).

[0122] Step 3: preparing extremely low temperature resistant cables;

[0123] Weigh: 2000.0 g of the low-temperature resistant material prepared in Example 7, 100.0 g of multi-walled carbon nanotubes, 50.0 g of polydimethylsiloxane, 200.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 6.0 L of dimethylacetamide, and mix them evenly to obtain a low-temperature resistant coating;

[0124] The low-temperature resistant coating is spin-coated on the surface of the sheath layer (3) to obtain a coating precursor with a thickness of 30 μm. The material is transferred to a drying oven at a temperature of 100° C. and vacuum dried for 4 hours. The temperature of the drying oven is then increased to 300° C. and heat-insulated for 12 hours to obtain a low-temperature resistant coating layer (4), thereby obtaining an extremely low-temperature resistant cable.

[0125] Example 11, please refer to Figure 1-2 This embodiment provides a method for preparing an extremely low temperature resistant wire and cable, comprising the following steps:

[0126] Step 1, preparing the sheath tube;

[0127] Weigh: 10.0 kg of polytetrafluoroethylene, 2.0 kg of the inorganic buffer prepared in Example 5, 500.0 g of glass fiber and 2.0 kg of dioctyl phthalate and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port toward the discharge port are 300° C., 325° C., 325° C., 350° C., 350° C., 370° C., 370° C., 380° C., the main engine speed of the twin-screw extruder is 120 rpm, the pressure is 150 bar, and the extruder is melt-extruded into a mold and cooled to obtain a sheath tube.

[0128] Step 2: preparing a buffer shielding layer and a sheath layer;

[0129] After the sheath tube is sleeved on the outside of the cable conductor, the inorganic buffer material prepared in Example 5 is filled into the gap, and the material is vibrated and compacted and added until the gap between the sheath tube and the cable conductor is completely filled, thereby obtaining a buffer shielding layer (2) and a sheath layer (3).

[0130] Step 3: preparing extremely low temperature resistant cables;

[0131] Weigh: 3000.0 g of the low-temperature resistant material prepared in Example 9, 200.0 g of multi-walled carbon nanotubes, 80.0 g of polydimethylsiloxane, 300.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 8.0 L of dimethylacetamide, and mix them evenly to obtain a low-temperature resistant coating;

[0132] The low-temperature resistant coating is spin-coated on the surface of the sheath layer (3) to obtain a coating precursor with a thickness of 50 μm. The material is transferred to a drying oven at a temperature of 150° C. and vacuum dried for 6 hours. The temperature of the drying oven is then increased to 360° C. and heat-insulated for 16 hours to obtain a low-temperature resistant coating layer (4), thereby obtaining an extremely low-temperature resistant cable.

[0133] Example 12, please refer to Figure 1-2 This embodiment provides a method for preparing an extremely low temperature resistant wire and cable, comprising the following steps:

[0134] Step 1, preparing the sheath tube;

[0135] Weigh: 9.0 kg of polytetrafluoroethylene, 1.8 kg of the inorganic buffer prepared in Example 6, 720.0 g of glass fiber and 2.5 kg of dioctyl phthalate and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port toward the discharge port are 300°C, 325°C, 325°C, 350°C, 350°C, 370°C, 370°C, and 380°C, respectively. The main engine speed of the twin-screw extruder is 100 rpm, the pressure is 125 bar, and the melt is extruded into a mold and cooled to obtain a sheath tube.

[0136] Step 2: preparing a buffer shielding layer and a sheath layer;

[0137] After the sheath tube is sleeved on the outside of the cable conductor, the inorganic buffer material prepared in Example 6 is filled into the gap, and the material is vibrated and compacted and added until the gap between the sheath tube and the cable conductor is completely filled, thereby obtaining a buffer shielding layer (2) and a sheath layer (3).

[0138] Step 3: preparing extremely low temperature resistant cables;

[0139] Weigh: 2.5 kg of the low-temperature resistant material prepared in Example 9, 150.0 g of multi-walled carbon nanotubes, 75.0 g of polydimethylsiloxane, 250.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 7.2 L of dimethylacetamide, and mix them evenly to obtain a low-temperature resistant coating;

[0140] The low-temperature resistant coating is spin-coated on the surface of the sheath layer (3) to obtain a coating precursor with a thickness of 40 μm. The material is transferred to a drying oven at a temperature of 125° C. and vacuum dried for 5 hours. The temperature of the drying oven is then increased to 320° C. and heat-insulated for 12 hours to obtain a low-temperature resistant coating layer (4), thereby obtaining an extremely low-temperature resistant cable.

[0141] Comparative Example 1: The difference between this comparative example and Example 12 is that, in the preparation process of the inorganic buffer material used in step 1 and step 2, the use of modified foam metal is eliminated.

[0142] Comparative Example 2: The difference between this comparative example and Example 12 is that step three is eliminated.

[0143] Comparative Example 3: The difference between this comparative example and Example 12 is that, during the preparation of the low-temperature resistant material used in step 3, the addition of inorganic buffer material is omitted.

[0144] Performance Test:

[0145] According to the standard GB / T 2951.14-2008 "General test methods for insulation and sheath materials of electric and optical cables Part 14: General test methods for low temperature test", the extremely low temperature resistant cables prepared in Examples 10-12 and Comparative Examples 1-3 were immersed in liquid nitrogen for low temperature treatment for 8-10 days, and the coating and cable conditions were observed;

[0146] The wear resistance of the extremely low temperature resistant cables prepared in Examples 10-12 and Comparative Examples 1-4 was tested with reference to the standard GB / T 3960-2016 "Test Methods for Sliding Friction and Wear of Plastics";

[0147] The anti-electromagnetic interference level of the extremely low temperature resistant cables prepared in Examples 10-12 and Comparative Examples 1-4 was tested with reference to the standard GB / T 19666-2019 "General Technical Requirements for Electromagnetic Shielding Films";

[0148] The tensile strength of the sheath tube coated with the low-temperature resistant coating of the extremely low-temperature resistant cable prepared in Examples 7-9 and Comparative Examples 1-3 was measured with reference to the standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0149] See Table 1 for specific data;

[0150] The thermal conductivity of the inorganic buffer prepared in Example 6 was tested according to the standard GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials - hot wire method", and the thermal conductivity of the inorganic buffer was 0.003 W·(m·K). -1 .

[0151] Table 1-Performance test data of each sample

[0152] Project Category Example 10 Embodiment 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 Coating conditions No cracking or powdering No cracking or powdering No cracking or powdering Cracking, powdering - Cracking, powdering Cable situation No cracking or powdering No cracking or powdering No cracking or powdering Cracking, powdering Cracking, powdering Cracking, powdering Wear amount / mg 36 35 32 42 43 68 Anti-electromagnetic interference grade / level SE-1 SE-1 SE-1 SE-3 SE-2 SE-2 Tensile strength / MPa 42.3 44.5 45.6 38.3 36.3 28.9

[0153] Data Analysis:

[0154] Comparative analysis of the data in Table 1 above shows that the coating of the extremely low temperature resistant cable prepared by the present invention and the coating and cable after long-term immersion in liquid nitrogen are free of cracking and powdering, the wear amount is 32 mg, the anti-electromagnetic interference level is SE-1, and the tensile strength is 45.6 MPa. All data are better than the comparative example, and "-" means that the embodiment has not been subjected to coating modification treatment, so the coating situation is not counted;

[0155] It is explained that the inorganic buffer prepared by the present invention has a modified foam metal as a skeleton and a flexible silica aerogel as a modification, and the active group amino group is modified in the flexible silica aerogel layer. In the process of preparing the low-temperature resistant material precursor, the modified buffer is used as a cross-linking agent, and a large number of amino groups on its surface react with the anhydride at the end of the polyamide segment to hybridize the organic segment. The large number of fluorine groups inside it reduce the surface energy of the coating. The two cooperate to improve the wear resistance of the coating, and the lower surface energy makes it difficult for liquid nitrogen to adhere to the cable surface, thereby improving the safety of cable maintenance. After the hybrid polyamide segment is cyclized, it has more excellent low-temperature resistance. The cyclized structure cooperates with the flexible aerogel layer to significantly improve the tensile strength of the material.

[0156] The modified foam metal and silica aerogel layer of the inorganic buffer prepared by the present invention not only have extremely low thermal conductivity to protect the inside of the cable, but also have the modified foam metal inside as a skeleton and the flexible silica aerogel layer as a buffer, so that the organic material component of the extremely low temperature resistant cable has extremely high low temperature shrinkage resistance. The two properties work together to significantly improve the low temperature resistance of the cable, providing a basis for the extremely low temperature resistant cable to not pulverize or crack inside ultra-low temperature liquefied gas. The internal foam metal copper structure has a porous structure that captures and scatters incoming electromagnetic waves, and the unique porosity and continuous metal network provide a good shielding effect, and improve the material's anti-electromagnetic interference performance through reflection, absorption and multiple scattering mechanisms.

[0157] It is explained that the present invention prepares an inorganic buffer material with a rigid skeleton and a flexible surface structure. While the rigid structure provides support for the cable, the flexible surface improves the cable's resistance to low-temperature shrinkage. The surface-modified amino groups hybridize the organic chain segments of the low-temperature resistant material, which cooperates with its annular structure to significantly enhance the mechanical properties of the material. The extremely low thermal conductivity of the inorganic buffer material ensures the stable operation of the internal conductor of the cable, thereby preparing a cable resistant to ultra-low temperature liquefied gas.

[0158] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0159] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0160] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A wire and cable resistant to extremely low temperatures, characterized in that: It comprises a cable conductor (1), a buffer shielding layer (2), a sheath layer (3) and a low-temperature resistant coating layer (4) which are arranged in sequence from the inside to the outside; The cable conductor (1) is composed of a core composed of a plurality of silver-plated copper conductors (11) twisted together and a polytetrafluoroethylene insulation layer (12) coated on the surface; The buffer shielding layer (2) is obtained by filling an inorganic buffer material between the cable conductor (1) and the sheath layer (3); The sheath layer (3) is composed of a sheath tube formed by melt-extruding a composite polytetrafluoroethylene material into a mold; The method for preparing the low-temperature resistant coating layer (4) comprises the following steps: A1. Evenly mix the low temperature resistant material, antistatic agent, defoaming agent, coupling agent and dimethylacetamide to obtain a low temperature resistant coating; A2, spin coating a low-temperature resistant coating on the surface of the sheath layer (3) to obtain a coating precursor, and post-treating the coating precursor to obtain a low-temperature resistant coating layer (4); The preparation method of the low temperature resistant material comprises the following steps: B1. Add 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2'-diaminoethylene glycol diphenyl ether, triethylamine and N,N-dimethylformamide into a reactor, raise the temperature of the reactor to 40-60°C, keep the temperature for 1-2 hours, add an inorganic buffer into the reactor, keep the temperature for 20-40 minutes, and post-treat to obtain a low-temperature resistant material precursor; B2. Add the low-temperature resistant material precursor and dimethylacetamide to the reactor, stir at room temperature for 10-15 minutes, raise the temperature of the reactor to 70-80°C, add acetic anhydride and triethylamine to the reactor, keep the temperature for 10-12 hours, and post-treat to obtain the low-temperature resistant material; The preparation method of the inorganic buffer comprises the following steps: C1. Add modified foamed metal, hexadecyltrimethylammonium bromide, deionized water and acetic acid into a reactor and stir for 8-10 minutes, then raise the temperature of the reactor to 40-60°C, add a composite silicon source into the reactor, keep the temperature for 2-3 hours, then add silica sol into the reactor, keep the temperature for 1-2 hours, and obtain a buffer material precursor; C2. The buffer precursor is transferred to a hydrothermal reactor, the temperature of the hydrothermal reactor is increased to 60-80°C, and after keeping the temperature for 20-24 hours, the gel is taken out and washed 3-5 times with anhydrous ethanol and deionized water, and then the inorganic buffer is obtained by post-treatment.

2. The extremely low temperature resistant wire and cable according to claim 1, characterized in that: In step A1, the usage ratio of low temperature resistant material, antistatic agent, defoaming agent, coupling agent and dimethylacetamide is 20-30g:1-2g:0.5-0.8g:2-3g:60-80mL; In step A2, the low-temperature resistant coating is spin-coated to a thickness of 30-50 μm, and the post-treatment includes: transferring the material to a drying oven at a temperature of 100-150° C. and vacuum drying for 4-6 hours, then raising the temperature of the drying oven to 300-360° C. and heat-insulating for 12-16 hours to obtain a low-temperature resistant coating layer (4).

3. The extremely low temperature resistant wire and cable according to claim 1, characterized in that: In step B1, the amount ratio of 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2'-diaminoethylene glycol diphenyl ether, triethylamine, N,N-dimethylformamide and inorganic buffer is 5.3-5.5g:2.5-2.7g:0.3-0.5g:20-30mL:2-3g; in step B2, the stirring rate of the reactor is 80-120rpm, and the amount ratio of the low-temperature resistant material precursor, dimethylacetamide, acetic anhydride and triethylamine is 4.0-4.2g:18-20mL:1.0-1.2g:0.3-0.5g.

4. The extremely low temperature resistant wire and cable according to claim 1, characterized in that: In step C1, the amount ratio of modified foam metal, hexadecyltrimethylammonium bromide, deionized water, acetic acid, composite silicon source and silica sol is 3-5g:0.3-0.5g:80-100mL:5-8mL:20-30g:2-3mL, the composite silicon source is obtained by mixing methyltriethoxysilane, tetraethoxysilane and 3-aminopropyltriethoxysilane in a ratio of 3-4g:3-4g:1-2g, and the stirring rate of the reactor is 80-120rpm.

5. The extremely low temperature resistant wire and cable according to claim 1, characterized in that: The preparation method of the modified foam metal comprises the following steps: D1. Add the modified pore-forming agent and copper powder into a ball mill to grind the mixture. After ball milling for 10-15 minutes, add calcium stearate into the ball mill, continue ball milling for 5-8 minutes to obtain a mixture, and post-treat to obtain a mixed body; D2. calcining the mixed green body to obtain a porous material, and post-treating the porous material to obtain a foamed metal green body; D3. Add the foam metal body, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol into the reactor, increase the temperature of the reactor to 50-70°C, keep the reaction temperature for 2-4 hours, and post-treat to obtain the modified foam metal.

6. The extremely low temperature resistant wire and cable according to claim 5, characterized in that: In step D1, the modified pore-forming agent, copper powder and calcium stearate are used in a ratio of 4-6g:3-4g:0.3-0.5g, and the modified pore-forming agent is obtained by mixing calcium chloride and calcium hydride in a ratio of 1g:1-1.5g; in step D3, the foam metal blank, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol are used in a ratio of 8-10g:2-3g:0.2-0.4g:30-40mL.

7. The extremely low temperature resistant wire and cable according to claim 5, characterized in that: In step D2, the calcination operation is as follows: the mixed green body is transferred to a tubular furnace, nitrogen is introduced for protection, the tubular furnace is heated to 600-620°C at a heating rate of 3-5°C / min, and after being kept warm for 2-4 hours, the temperature is further increased to 840-860°C at a heating rate of 3-5°C / min, and after being kept warm for 1-2 hours, the reactor is naturally cooled to 100-150°C, the nitrogen is disconnected, and an equal volume mixed gas of water vapor and oxygen is introduced at a flow rate of 1-2L / min, and the temperature is kept warm for 1-2 hours to obtain a porous material.

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