A self-repairing radio frequency coaxial cable, a leaky coaxial cable and a manufacturing method thereof

Abstract

The present application belongs to the field of wireless communication technology, and more specifically, it relates to a self-repairing radio frequency coaxial cable, a leaky coaxial cable and a method for making the same. On the basis of meeting the standards for communication cables, the present application further solves the technical problems of deterioration of electrical performance, reduced reliability and service life due to micro-damage to the foamed insulation layer of the cable during use. Tests show that the self-repairing technology provided by the present application is suitable for mobile communication radio frequency coaxial cables and leaky coaxial cables (frequency range 0.1 GHz~6GHz). The HLRCTYZ‑50‑22 leaky coaxial cable in the YD / T2491 standard and the HCTAYZ‑50‑22 radio frequency coaxial cable in the YD / T1092 standard involved in the present application have a voltage standing wave ratio of ≤1.20 and a characteristic impedance of 50±2Ω. Their MTBF (mean time between failures) can be increased by 20%~40% compared to before the improvement.

Description

Technical Field

[0001] The present application belongs to the field of wireless communication technology, and more specifically, relates to a self-repairing radio frequency coaxial cable, a leaky coaxial cable and a manufacturing method thereof. Background Art

[0002] RF coaxial cable is a cable used to transmit electromagnetic energy in the radio frequency range and is widely used in various radio communication systems and electronic equipment. It plays an important role in wireless communication, broadcasting, television, radar, navigation and other fields. Among them, coaxial cable is the most widely used type, mainly used as antenna feeder for radio transmitting or receiving equipment, as well as internal or interconnecting wires of various communication and electronic equipment.

[0003] The basic structure of the existing coaxial RF cable consists of a coaxial inner conductor, an insulating layer, an outer conductor and a sheath layer from the inside to the outside. The inner conductor is usually made of high-purity copper or silver and is responsible for transmitting RF signals. The inner conductor can be solid or hollow, and its diameter and surface roughness have an important impact on the signal quality. The insulating medium is located between the inner conductor and the outer conductor, which is used to isolate the inner and outer conductors while maintaining the cable structure. Common insulating materials include polyethylene, polytetrafluoroethylene (PTFE) or air-gap materials, and the dielectric constant and dielectric loss of these materials have a direct impact on the performance of the coaxial cable. The outer conductor is usually formed, welded, corrugated by copper strip, or adopts an aluminum tube structure or a braided structure. The main function of the outer conductor is to shield external electromagnetic interference and ensure stable signal transmission. The sheath is the outermost protective layer, usually made of polyvinyl chloride (PVC) or other weather-resistant materials, which mainly protects the cable from mechanical damage and environmental corrosion.

[0004] During use, the insulating material is subjected to huge electric field strength, which may cause damage such as partial discharge, surface flashover, and electrical breakdown. Long-term operation may also cause electrical aging phenomena such as electrical tree and water tree. These phenomena will cause the cable performance to deteriorate, the life to be shortened, and even failure. Therefore, research and development of insulating layer materials with self-healing properties is of great significance to improve the reliability and service life of RF coaxial cables. Summary of the invention

[0005] The existing technology mainly focuses on the self-repairing performance of the insulation layer on the outer sheath of the cable, and there is no self-repairing technology for the foam insulation material of the coaxial cable. In view of the defects of the existing technology, this application provides a self-repairing RF coaxial cable, a self-repairing leakage coaxial cable and a method for making the same. By adding a micro-foamed self-repairing insulation layer containing self-repairing materials to the insulation layer of the existing technology, on the basis of meeting the communication cable standard YDT 1092, the application further solves the technical problem of electrical performance deterioration, reliability and service life reduction caused by micro-damage to the foam insulation layer during use.

[0006] To achieve the above objectives, in a first aspect, the present application provides a self-repairing radio frequency coaxial cable, comprising an inner conductor, a composite insulation layer, an outer conductor and an outer sheath concentrically nested from inside to outside; wherein:

[0007] The composite insulation layer is coaxially arranged from inside to outside in sequence with a solid inner skin layer, a self-repairing micro-foam insulation layer, a solid middle isolation layer, a high-foam insulation layer and a solid outer skin layer;

[0008] The solid inner skin layer, the solid middle isolation layer and the solid outer skin layer are all solid polyolefin layers, and the thickness of each of them is independently 0.05 mm to 0.15 mm;

[0009] The thickness of the self-repairing micro-foamed insulation layer is 0.1 mm to 1 mm. The self-repairing micro-foamed insulation layer is a foamed polyolefin, and a self-repairing material is dispersed inside the self-repairing material, which comprises porous silica particles, ethylene-methacrylic acid copolymer attached to the surface or pores of some of the porous silica particles, and a mixture of epoxy resin and curing agent attached to the surface or inside another part of the porous silica particles;

[0010] The high foaming insulation layer is foamed polyolefin and has a thickness of 3 mm to 15 mm; the foaming degree of the high foaming insulation layer is higher than the foaming degree of the self-repairing micro-foaming insulation layer.

[0011] According to another aspect of the present invention, there is also provided a self-repairing leaky coaxial cable, comprising an inner conductor, a composite insulation layer, an outer conductor and an outer sheath which are concentrically nested from inside to outside; wherein:

[0012] The composite insulation layer is coaxially arranged from inside to outside in sequence with a solid inner skin layer, a self-repairing micro-foam insulation layer, a solid middle isolation layer, a high-foam insulation layer and a solid outer skin layer;

[0013] The solid inner skin layer, the solid middle isolation layer and the solid outer skin layer are all solid polyolefin layers, and the thickness of each of them is independently 0.05 mm to 0.15 mm;

[0014] The thickness of the self-repairing micro-foamed insulation layer is 0.1 mm to 1 mm. The self-repairing micro-foamed insulation layer is a foamed polyolefin, and a self-repairing material is dispersed inside the self-repairing material, which comprises porous silica particles, ethylene-methacrylic acid copolymer attached to the surface or pores of some of the porous silica particles, and a mixture of epoxy resin and curing agent attached to the surface or inside another part of the porous silica particles;

[0015] The high foaming insulation layer is foamed polyolefin and has a thickness of 3 mm to 15 mm; the foaming degree of the high foaming insulation layer is higher than the foaming degree of the self-repairing micro-foaming insulation layer.

[0016] Preferably, the specific surface area of ​​the porous silica particles is 200 m² / g to 400 m² / g, and the pore volume is 1.0 cm³ / g to 2.0 cm³ / g.

[0017] Further preferably, the loading amount of the ethylene-methacrylic acid copolymer in the self-healing micro-foamed insulation layer is 15wt%~25wt% of the mass of the porous silica, and the mass ratio of the ethylene-methacrylic acid copolymer attached to the porous silica to the mixture of the epoxy resin and the curing agent is 1~3:1.

[0018] Preferably, the mass percentage of the self-repairing material in the self-repairing micro-foamed insulation layer is 5% to 15%.

[0019] Preferably, the foaming material of the self-repairing micro-foamed insulation layer is foamed polyolefin, and its foaming degree is 25%~35%; the foaming material of the high-foamed insulation layer is foamed polyolefin, and its foaming degree is 40%~95%.

[0020] Preferably, the ethylene-methacrylic acid copolymer is attached to the surface or pores of the porous silica particles according to the following steps:

[0021] The ethylene-methacrylic acid copolymer is heated to a molten state and then mixed with the dried porous silica particles, and stirred so that the molten ethylene-methacrylic acid copolymer is impregnated into the pores of the porous silica particles; after cooling, the ethylene-methacrylic acid copolymer is solidified in the pores or on the surface, so that the ethylene-methacrylic acid copolymer is attached to the surface or in the pores of the porous silica particles; and the glass transition temperature of the ethylene-methacrylic acid copolymer is 80°C to 120°C.

[0022] Preferably, the mixture of epoxy resin and curing agent is attached to the surface or pores of the porous silica particles according to the following steps:

[0023] S1: drying the porous silica at 120°C to 150°C to remove adsorbed moisture and impurities;

[0024] S2: dissolving epoxy resin in a solvent to obtain an epoxy resin solution; immersing porous silica in the epoxy resin solution, and allowing the solution to fully enter the pores through vacuum assistance or ultrasonic treatment; volatilizing and removing the solvent at room temperature or under heating conditions, so that the epoxy resin remains in the pores;

[0025] S3: Dispersing a curing agent in an organic solvent to form a uniform curing agent suspension; immersing porous silica adsorbed with epoxy resin into the curing agent suspension, and allowing the curing agent to enter the pores not occupied by the epoxy resin through vacuum assistance or ultrasonic treatment; volatilizing and removing the organic solvent at room temperature or under heating conditions, leaving the curing agent in the pores, so that the epoxy resin and the curing agent are attached to the surface or pores of the porous silica particles.

[0026] According to another aspect of the present invention, there is provided a method for manufacturing the self-repairing RF coaxial cable or self-repairing leaky coaxial cable with optimized MTBF, comprising the following steps:

[0027] (1) The solid inner skin layer, the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the inner conductor by using the skin-foam-skin three-layer co-extrusion technology, or the solid inner skin layer is first extruded on the surface of the inner conductor, and then the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the solid inner skin layer by using the double-layer co-extrusion technology, wherein:

[0028] When preparing the self-repairing micro-foamed insulation layer by extrusion, the molten foaming material and the foaming gas are fully mixed in the screw to obtain an aerosol, and the aerosol is further mixed with a gas-solid mixture formed by mixing an inert gas and the self-repairing material at the inlet of the extruder head flow channel, and then extruded through the die mouth after mixing, the pressure is released to foam, and then cooled and shaped to form the self-repairing micro-foamed insulation layer with the self-repairing material dispersed inside;

[0029] (2) co-extruding the high foaming insulation layer and the solid outer skin layer on the surface of the intermediate isolation layer;

[0030] (3) An outer conductor and an outer sheath are sequentially prepared outside the outer skin layer.

[0031] Preferably, in step (1), a gas injection hole is provided at the inlet of the flow channel of the extruder head, and a gas-solid mixture formed by mixing an inert gas and the self-healing material is injected through the gas injection hole by a pneumatic sending device to mix with the aerosol; the diameter of the gas injection hole is 0.1 mm to 0.3 mm, and the gas injection pressure is 100 bar to 200 bar.

[0032] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0033] (1) The present invention provides a self-repairing radio frequency coaxial cable or a self-repairing leaky coaxial cable, which improves the structure and materials of the composite insulation layer. Specifically, a self-repairing micro-foamed insulation layer and a solid intermediate isolation layer are added between the solid inner skin layer and the foamed insulation layer in the composite insulation layer of the radio frequency coaxial cable or the leaky coaxial cable in the prior art, and a self-repairing material is provided in the self-repairing micro-foamed insulation layer. The self-repairing material comprises porous silica, and ethylene-methyl acrylate copolymer (EMAA) and epoxy resin attached to the surface or pores of the porous silica. The self-repairing material can melt or solidify and cross-link as the working temperature changes during the use of the cable, so as to flow, fill and repair the microcracks in the cable, thereby realizing the self-repair of the radio frequency coaxial cable or the leaky coaxial cable.

[0034] (2) The solid inner skin layer, the self-repairing micro-foaming insulation layer, and the solid middle isolation layer provided in the composite insulation layer of the self-repairing RF coaxial cable or the self-repairing leaky coaxial cable of the present invention form a closed body, so that the self-repairing material therein is better bound in the micro-foaming layer, and the self-repairing material is prevented from being affected by the foaming expansion process during the production of the high-foaming insulation layer and migrating to the high-foaming insulation layer along the radial direction of the cable, thereby affecting the subsequent self-repairing effect. In addition, the closed body design takes into account both mechanical support and heat conduction efficiency, and the self-repairing micro-foaming insulation layer acts as a heat buffer zone, which can absorb the heat generated by the inner conductor in a directional manner.

[0035] (3) The composite insulation layer of the self-repairing RF coaxial cable or the self-repairing leaky coaxial cable of the present invention contains a micro-foamed insulation layer and a high-foamed insulation layer. The foaming degree of the micro-foamed insulation layer is lower than that of the high-foamed insulation layer. The main purpose of the micro-foamed insulation layer is to introduce the self-repairing material and allow the self-repairing material to have a certain flow space during the repair process, so as to facilitate the occurrence of the self-repairing process. The foaming degree of the high-foamed insulation layer is in the same range as that of the existing foamed insulation layer, and its main purpose is to reduce the dielectric constant of the insulation layer.

[0036] (4) The self-repairing RF coaxial cable or self-repairing leaky coaxial cable proposed in the present invention has a micro-foamed insulation layer containing a self-repairing material, which contains a variety of repair materials with different repair response temperatures. The EMAA attached to the porous silica particles can be physically repaired at 80°C to 120°C to seal micron-sized cracks, and at 120°C to 200°C, the EMAA and epoxy resin EP blend system can form an interpenetrating network to improve the toughness of the repair layer; further, if the temperature is greater than 200°C, the epoxy resin is completely cured and chemically cross-linked to improve the insulation of the insulation layer.

[0037] (5) In the embodiment of the present invention, a self-repair simulation experiment of RF coaxial cable and leaky coaxial cable is designed. First, the cables that pass the standard voltage test are pressurized until the insulation layer breaks down. The cables that pass the dielectric strength test at the standard voltage after the breakdown test are considered damaged if they can pass the dielectric strength test at a voltage higher than the standard voltage. Then the damaged cable is connected to the simulation circuit and continues to run. The experiment found that the self-repairing RF coaxial cable or self-repairing leaky coaxial cable of the present invention can indeed achieve self-repair after continuing to run for a period of time after damage. The experiment found that 80% of the damaged cables have a degree of damage within the self-repairable range, and the thicker the thickness of the self-repairing micro-foam insulation layer, the shorter the time required for self-repair.

[0038] (6) The self-repairing RF coaxial cable or self-repairing leaky coaxial cable with optimized MTBF (Mean Time Between Failures) provided by the present invention is suitable for scenarios such as 5G base station high-frequency cables (frequency range 0.1GHz~6GHz), millimeter wave radar feeders, etc. Preliminary tests show that the cable MTBF (Mean Time Between Failures) can be increased by 20%~40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the side structure of the self-repairing radio frequency coaxial cable provided in Example 1 of the present application;

[0040] Figure 2 This is a schematic diagram of the end face structure of the self-repairing radio frequency coaxial cable provided in Example 1 of the present application;

[0041] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0042] 1-inner conductor; 2-composite insulation layer; 3-outer conductor; 4-outer sheath; 21-solid inner skin layer; 22-self-repairing micro-foam insulation layer; 23-solid middle isolation layer; 24-high foam insulation layer; 25-solid outer skin layer. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0045] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0046] The process parameters without specific conditions in the following examples are usually based on conventional conditions.

[0047] The present invention provides a self-repairing radio frequency coaxial cable, such as Figure 1 and Figure 2 As shown, it includes an inner conductor 1, a composite insulating layer 2, an outer conductor 3 and an outer sheath 4 which are concentrically nested from the inside to the outside; wherein:

[0048] The composite insulation layer 2 is coaxially provided with a solid inner skin layer 21, a self-repairing micro-foam insulation layer 22, a solid middle isolation layer 23, a high-foam insulation layer 24 and a solid outer skin layer 25 in sequence from inside to outside;

[0049] The solid inner skin layer 21, the solid middle isolation layer 23 and the solid outer skin layer 25 are all solid polyolefin layers, and the thickness of each of them is independently 0.05 mm to 0.15 mm;

[0050] The solid inner skin layer is used to bond the inner conductor and the self-repairing micro-foamed insulation layer; the solid middle isolation layer is used to play an isolation role to prevent the self-repairing material in the self-repairing micro-foamed insulation layer from escaping to the high-foamed insulation layer; specifically, the solid middle isolation layer wraps the self-repairing micro-foamed insulation layer so that the solid inner skin layer, the self-repairing micro-foamed insulation layer, and the solid middle isolation layer form a closed body (this design takes into account both mechanical support and heat conduction efficiency, and the self-repairing micro-foamed insulation layer acts as a heat buffer zone, which can absorb the heat generated by the inner conductor in a directional manner), and the self-repairing material is better bound in the micro-foamed layer to prevent the self-repairing material from being affected by the foaming expansion process during the production of the high-foamed insulation layer and migrating to the high-foamed insulation layer along the cable radius direction, affecting the subsequent self-repairing effect. The solid outer skin layer is used to protect the high-foamed insulation layer to isolate water and oxygen.

[0051] The thickness of the self-repairing micro-foamed insulation layer is 0.1mm~1mm, preferably 0.1mm~0.8mm. The self-repairing micro-foamed insulation layer is foamed polyolefin, and a self-repairing material is dispersed inside it. The self-repairing material includes porous silica particles, ethylene-methyl acrylic acid copolymer (EMAA) attached to the surface or pores of some of the porous silica particles, and a mixture of epoxy resin and curing agent attached to the surface or inside another part of the porous silica particles.

[0052] The high foaming insulation layer is foamed polyolefin and has a thickness of 3 mm to 15 mm. The foaming degree of the high foaming insulation layer is higher than the foaming degree of the self-repairing micro-foaming insulation layer.

[0053] The self-repairing RF coaxial cable and the self-repairing leaky coaxial cable of the present invention have the same nested structure. Unlike the RF coaxial cable, the leaky coaxial cable has periodic gaps or holes on its outer conductor, allowing signal leakage, and is used in a specific coverage area.

[0054] In some embodiments, the porous silica particles have a specific surface area of ​​200 m² / g to 400 m² / g, and a pore volume of 1.0 cm³ / g to 2.0 cm³ / g.

[0055] In some embodiments, the porous silica can be synthesized by a sol-gel method, a template method, and a hydrothermal synthesis method, or can be directly customized or purchased from the market.

[0056] In some embodiments, the loading amount of the ethylene-methacrylic acid copolymer in the self-repairing micro-foamed insulating layer is 15wt% to 25wt% of the mass of the porous silica, and the mass ratio of the ethylene-methacrylic acid copolymer attached to the porous silica to the mixture of the epoxy resin and the curing agent is 1 to 3: 1; and the mass ratio of the epoxy resin to the curing agent is 13 to 15: 1. The mass percentage of the self-repairing material in the self-repairing micro-foamed insulating layer is 5% to 15%.

[0057] The curing agent of the present invention is used for curing and cross-linking reaction with epoxy resin during the self-repairing process. The curing agent can be anhydrides (such as MTHPA, HHPA, etc.), aromatic amines (such as DDM, DDS, etc.), imidazoles (such as EMI, etc.) or dicyandiamide (DICY), etc., preferably a latent curing agent dicyandiamide.

[0058] In some embodiments, the self-repairing micro-foamed insulation layer is foamed polyolefin, such as polyethylene, polypropylene, etc., and its foaming degree is 25% to 35%. The purpose of micro-foaming is to accommodate the self-repairing material; the high-foamed insulation layer is foamed polyolefin, and its foaming degree is 40% to 95%.

[0059] The self-healing material of the present invention can be prepared by conventional methods. For example, in some embodiments, EMAA is attached to the surface or pores of the porous silica particles according to the following steps:

[0060] S1: drying the porous silica particles;

[0061] S2: EMAA is heated to a molten state, and dried porous silica particles are added, and stirred to allow the molten EMAA polymer to be impregnated into the pores of the porous silica particles; after cooling, the EMAA polymer solidifies in the pores or on the surface, so that EMAA (ethylene-methacrylic acid copolymer) is attached to the surface or in the pores of the porous silica particles.

[0062] The self-repairing material EMAA used in the self-repairing radio frequency coaxial cable or self-repairing leaky coaxial cable for optimizing MTBF of the present invention is a copolymer of ethylene and methacrylic acid, and its glass transition temperature can be adjusted between 80°C and 120°C by regulating the ratio and molecular structure of its comonomers ethylene and methacrylic acid. This temperature range forms a gradient response with the normal operating temperature of the cable (60°C to 80°C). When the local hot spot temperature of the cable exceeds 80°C, EMAA is released from the porous silica, and the molten EMAA penetrates into the microcracks (micron-level cracks) of the insulation layer through capillary action, and forms a tight sealing layer after cooling.

[0063] The high specific surface area of ​​porous silica (≥200m² / g) provides sufficient adsorption sites, and the pore volume of 1.0cm³ / g~2.0cm³ / g ensures that the EMAA loading reaches 15wt%~25wt%. The pore size distribution design is preferably a bimodal structure or a multimodal structure, with micropores used for stable storage of EMAA, and mesopores or macropores providing rapid release channels when thermally activated.

[0064] Further preferably, the epoxy resin curing temperature is higher than or equal to 200°C. When the operating temperature of the cable exceeds 200°C (for example, high temperature caused by partial discharge), the epoxy resin (EP) will be released from other porous silica particles, and a cross-linking curing reaction will occur after contacting with a curing agent such as dicyandiamide. During the curing process, its epoxy group may undergo a grafting reaction with the carboxyl group (derived from the thermal oxidation degradation product of EMAA) on the surface of the foamed polyolefin to form a C-O-C covalent bond, thereby improving the interface bonding strength.

[0065] The self-repairing RF coaxial cable or self-repairing leaky coaxial cable proposed by the present invention has a micro-foamed insulation layer containing a self-repairing material specially arranged in the insulation layer, which contains a variety of repair materials with different repair response temperatures. EMAA attached to some porous silica particles can be physically repaired between 80°C and 120°C to seal micron-level cracks, and at 120°C to 200°C, the EMAA and epoxy resin EP blend system can form an interpenetrating network to improve the toughness of the repair layer; further, if the temperature is greater than 200°C, the epoxy resin is completely cured and chemically cross-linked to improve the insulation of the insulation layer.

[0066] In other embodiments, the mixture of epoxy resin and curing agent is attached to the surface or pores of the porous silica particles according to the following steps:

[0067] S1: drying the porous silica at 120°C to 150°C to remove adsorbed moisture and impurities;

[0068] S2: As needed, the porous silica is surface modified (e.g., silanization treatment) to enhance its compatibility with epoxy resin or curing agent;

[0069] S3: dissolving epoxy resin in a low boiling point solvent (such as acetone or ethanol) to form a low viscosity solution; immersing porous silica in the epoxy resin solution, and allowing the solution to fully enter the pores through vacuum assistance or ultrasonic treatment; volatilizing the solvent at room temperature or under heating conditions to allow the epoxy resin to remain in the pores;

[0070] S4: Disperse a latent curing agent (such as dicyandiamide) in a solvent (ethanol, acetone, ethyl acetate, dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), etc.) to form a uniform suspension. Immerse porous silica adsorbed with epoxy resin in the curing agent suspension, and allow the curing agent to enter the pores not occupied by the epoxy resin through vacuum assistance or ultrasonic treatment; volatilize the solvent at room temperature or under heating conditions, so that the curing agent remains in the pores, so that the epoxy resin and the curing agent are attached to the surface or pores of the porous silica particles.

[0071] The present invention also provides a method for manufacturing a self-repairing radio frequency coaxial cable or a self-repairing leaky coaxial cable, comprising the following steps:

[0072] (1) The solid inner skin layer, the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the inner conductor by using the skin-foam-skin three-layer co-extrusion technology, or the solid inner skin layer is first extruded on the surface of the inner conductor, and then the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the solid inner skin layer by using the double-layer co-extrusion technology, wherein:

[0073] When preparing the self-repairing micro-foamed insulation layer by extrusion, the molten foaming material (polyolefin and nucleating agent, etc.) and the foaming gas (such as carbon dioxide, etc.) are fully mixed in the screw to obtain an aerosol, and the aerosol is further mixed with a gas-solid mixture formed by mixing an inert gas and the self-repairing material at the inlet of the extruder head flow channel, and then extruded through the die mouth after mixing, and the pressure is released to foam, and then cooled and shaped to form the self-repairing micro-foamed insulation layer with the self-repairing material dispersed inside;

[0074] (2) co-extruding the high foaming insulation layer and the solid outer skin layer on the surface of the intermediate isolation layer;

[0075] (3) An outer conductor and an outer sheath are sequentially prepared outside the outer skin layer.

[0076] In some embodiments, the diameter of the gas injection hole is 0.3 mm to 0.5 mm, and the gas injection pressure is 100 bar to 200 bar.

[0077] In the present invention, when the self-repairing micro-foamed insulation layer is prepared by extrusion, the molten foaming material is injected with high-pressure gas and fully mixed in the screw to form an aerosol, and before entering the die for high-pressure extrusion, in some embodiments, an inert gas such as argon and a high-pressure mixture of the self-repairing material are injected through the injection hole set at the inlet of the extruder die flow channel through a pneumatic sending device such as a pneumatic sending tank, and are uniformly mixed with the aerosol in the die flow channel and extruded through the die mouth, and the pressure is released for foaming, and then cooled and shaped to form the self-repairing micro-foamed insulation layer, and the self-repairing material is dispersed in the micro-foamed layer. The pneumatic sending tank, also known as a pneumatic conveying tank or a pneumatic conveying system, is a common device that uses airflow to transport powder or granular materials from one place to another. It is widely used in chemical, food, pharmaceutical, building materials and other industries for conveying materials such as flour, cement, plastic particles, and pharmaceutical powders. In other embodiments, nanoparticle or microparticle quantitative feeding technology may also be used, such as a micron-level powder particle ultrasonic precision feeding device disclosed in patent document CN112478787A, which realizes micro, continuous and precise feeding through ultrasonic transducer and pneumatic conveying pipeline. Another example is a small particle quantitative conveying mechanism disclosed in CN118323754A, which combines an air material transfer device and a quantitative feeding mechanism to realize rapid transportation and precise control of small particle materials through pneumatic conveying and a screw conveying shaft. After the material is mixed with compressed air, it is pneumatically conveyed to the storage box, and then evenly conveyed by the screw conveying shaft, ensuring the precise distribution of the material.

[0078] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0079] Example 1

[0080] 1. Preparation of self-healing materials:

[0081] EMAA (DuPont™ Nucrel® 0407HS, methacrylic acid content of about 4wt%, glass transition temperature of 80℃~120℃) was heated to a molten state, and dried porous silica particles (custom-made, with a specific surface area of ​​310m² / g and a pore volume of 1.6cm³ / g, the porous silica particles contained micropores of 2nm~5nm and macropores of 50nm~100nm) were added, and stirred to allow the molten EMAA polymer to be impregnated into the pores; after cooling, the EMAA polymer solidified in the pores or on the surface, so that EMAA adhered to the surface or pores of the porous silica particles, and the mass of the porous silica increased by 20% after attachment.

[0082] The dried porous silica particles obtained above were mixed with an ethanol solution of 3-aminopropyltriethoxysilane (KH550), and reacted in a constant temperature water bath at 55°C for 1 hour for surface modification to enhance their compatibility with epoxy resin and curing agent. After the reaction, the reacted solvent and unreacted silanization agent were removed by washing with ethanol, and the surface silanized porous silica particles were obtained after drying.

[0083] The epoxy resin (bisphenol A type epoxy resin E-44) was dissolved in ethanol to form a low viscosity solution with a viscosity of 20 mPa·s; the porous silica with the surface silanization modification was immersed in the epoxy resin solution, and the solution was fully entered into the pores by ultrasonic treatment; the solvent was volatilized under heating conditions at 40°C, so that the epoxy resin remained in the pores; then the latent curing agent dicyandiamide was dispersed in the solvent ethanol to form a uniform suspension. The porous silica adsorbed with epoxy resin was immersed in the curing agent suspension, and the curing agent was entered into the pores not occupied by the epoxy resin by ultrasonic treatment; the solvent was volatilized under room temperature conditions, so that the curing agent remained in the pores, so that the epoxy resin and the curing agent were attached to the surface or pores of the porous silica particles, the total mass ratio of the epoxy resin and the curing agent attached to the porous silica to the mass ratio of EMAA was 1:2, and the mass ratio of the epoxy resin and the curing agent was 14:1, and the self-healing material was obtained.

[0084] 2. Preparation of RF coaxial cable

[0085] The radio frequency coaxial cable provided in this embodiment is applied to the traditional cable of model HCTAYZ-50-22 in the YD / T1092 standard (cable specification is -22), and its end face and side face structure schematic diagrams are shown as follows: Figure 1 and Figure 2 As shown, an inner conductor 1, a composite insulation layer 2, an outer conductor 3 and an outer sheath 4 are coaxially arranged from the inside to the outside, wherein the composite insulation layer 2 includes a solid inner skin layer 21, a self-repairing micro-foamed insulation layer 22, a solid middle isolation layer 23, a high-foamed insulation layer 24 and a solid outer skin layer 25 from the inside to the outside, wherein the inner conductor is a solid copper-clad aluminum wire, the solid inner skin layer 21, the solid middle isolation layer 23 and the solid outer skin layer 25 are low-density polyethylene LDPE, the outer conductor is a copper tape, and the outer sheath is polyethylene. The preparation method of the radio frequency coaxial cable is carried out according to the following steps:

[0086] (1) Low-density polyethylene and glue (EVA resin) are mixed in a ratio of 3:1 and extruded at 130-220°C, and evenly coated on the surface of the inner conductor of a 9.0 mm diameter copper tube to form a solid inner skin layer with a thickness of 0.1 mm.

[0087] (2) High-density polyethylene, low-density polyethylene and a nucleating agent (a mixture of cyclodextrin nanosponge (NS) and vinyl triethoxysilane (VTES), mass ratio 1:1) are mixed in a mass ratio of 70:29:1, and after high-temperature plasticization at 130-195°C, high-pressure gas (carbon dioxide) is injected in a molten state and fully mixed in the screw; at the same time, a gas injection hole with a diameter of 0.2 mm is provided at the inlet of the extrusion flow channel, and argon gas is mixed with the self-healing material prepared in the above step to obtain a high-pressure gas-solid mixture, and then the high-pressure gas-solid mixture is injected through the above-mentioned gas injection hole (gas injection pressure is 150 bar) by using a pneumatic sending tank (customized, adapted to the size of the gas injection hole of 0.2 mm), and then mixed with the molten foaming aerosol and extruded at high pressure, attached to the solid inner skin layer for foaming and cooling to form a self-healing micro-foamed insulation layer with a thickness of 0.1 mm, the foaming degree of the micro-foamed insulation layer is 30%, and the mass percentage of the self-healing material in the self-healing micro-foamed insulation layer is 8%.

[0088] (3) At the same time as the self-repairing micro-foamed insulation layer in step (2), a solid intermediate isolation layer of low-density polyethylene with a thickness of 0.1 mm is extruded, which is evenly coated on the periphery of the self-repairing micro-foamed insulation layer, so that the solid inner skin layer, the self-repairing micro-foamed insulation layer and the solid intermediate isolation layer form a closed body, wherein the self-repairing material is better bound in the micro-foamed layer, thereby preventing the self-repairing material from being affected by the foaming expansion process during the production of the high-foamed insulation layer and migrating to the high-foamed insulation layer along the radial direction of the cable, thereby affecting the subsequent self-repairing effect.

[0089] (4) High-density polyethylene, low-density polyethylene and a nucleating agent (a mixture of cyclodextrin nanosponge (NS) and vinyl triethoxysilane (VTES), mass ratio 1:1) are mixed in a mass ratio of 70:29:1, and after high-temperature plasticization at 130-195°C, high-pressure gas (carbon dioxide) is injected into the molten state. After being fully mixed in the screw, the mixture is directly attached to the solid middle isolation layer by high-pressure extrusion for foaming and cooling to form an insulating foamed cable core with a diameter of 22.8 mm, thus obtaining a high-foaming insulation layer with a foaming degree of 75%.

[0090] (5) At the same time as the high foaming insulation layer in step (4), a low-density polyethylene solid outer skin layer with a thickness of 0.1 mm is extruded, which is evenly coated on the periphery of the foaming layer of the high foaming insulation layer, so that the insulation layer has better sealing properties.

[0091] (6) A 0.21 mm thick smooth copper strip is welded into a copper tube by forming argon arc welding and then inserted into the foam cable core for corrugation. The corrugation trough sinks into the cable core insulation layer, so that the outer conductor and the insulation layer fit tightly into a whole. The outer diameter of the corrugation peak is 24.95 mm.

[0092] (7) A layer of polyethylene sheath material is extruded on the surface of the outer conductor, and the sheath thickness is 1.1 mm.

[0093] Examples 2 to 10 are prepared in the same manner as Example 1, except that the thickness of the self-repairing foamed insulation layer is replaced from 0.1 mm in Example 1 to 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm and 0.6 mm, respectively. Table 1 lists the self-repairing simulation test results of the self-repairing RF coaxial cable of Examples 1 to 10. The specific experimental steps are as follows:

[0094] According to the thickness of the self-repairing foam insulation layer in item 4, 3 samples of 3 meters in length were taken for each thickness, and a total of 30 samples were taken and tested according to item 6 / 7 / 8 / 9. Among the 30 samples, 4 samples failed after the 8th test, and 2 samples failed after the 9th test. Among all the 24 samples that passed the 6 / 7 / 8 / 9 test items, one sample was taken for each thickness according to the thickness difference, and a total of 10 samples were tested for the 10th test in Table 1.

[0095] Experimental principle description:

[0096] Test 6: Standard dielectric strength of this type of cable. If the test passes, it proves that the samples meet the normal standard requirements.

[0097] Test 7: Simulate the insulation failure scenario when the cable is subjected to an instantaneous increase in power to find the minimum breakdown voltage;

[0098] Test 8: Tests whether the cable can temporarily operate at normal power after insulation damage caused by limited instantaneous high power. Pass means the test is passed, indicating that the cable can still temporarily operate at normal power after insulation damage caused by instantaneous high power.

[0099] Test 9: Use a voltage higher than the standard test voltage to check whether the insulation of the cable is partially damaged after being subjected to instantaneous high-power operation; NG means the test fails, indicating that the damage does exist;

[0100] Test 10: Test the effect of the thickness of the insulation repair layer on the repair time and confirm the insulation repair effect. NG means the test failed, indicating that the repair was not successful; pass means the test passed, indicating that the repair was successful. This test voltage is the same as the test voltage value of item 9, which is between the standard test voltage and the breakdown voltage to prevent other non-repaired locations from being broken down due to excessive test voltage, affecting the judgment of the repair effect.

[0101] Table 1

[0102]

[0103] It can be seen from Table 1 that for the 30 initial cable samples of different thicknesses that passed the standard voltage test in the embodiment of the present invention, after being pressurized to the breakdown voltage of the insulation layer, the proportion of those that cannot be repaired due to excessive damage is 6 / 30, or 20%. The remaining 80% of the optical cables can achieve self-repair after being damaged due to the role of the self-repairing materials therein, and the thicker the self-repairing micro-foam insulation layer, the shorter the time required to achieve self-repair.

[0104] In addition, through multiple cycles of breakdown-repair experiments (according to the order of item numbers in Table 1, 10-6-7-8-9-10, and so on), it was found that for cables with different thicknesses of self-repairing insulation layers, the mean time between failures (MTBF) can be increased by 20%~40% compared with cables without self-repairing micro-foam insulation layers, and the thicker the self-repairing micro-foam insulation layer, the higher the corresponding mean time between failures extension rate.

[0105] The self-repair technology provided in this application is applicable to mobile communication RF coaxial cables and leaky coaxial cables (frequency range 0.1GHz~6GHz). When the voltage standing wave ratio of the HLRCTYZ-50-22 leaky coaxial cable in the YD / T2491 standard and the HCTAYZ-50-22 RF coaxial cable in the YD / T1092 standard involved in this application is ≤1.20 and the characteristic impedance meets 50±2Ω, the MTBF (mean time between failures) can be increased by 20%~40% compared with before the improvement.

[0106] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A self-repairing radio frequency coaxial cable, characterized in that: It includes an inner conductor, a composite insulation layer, an outer conductor and an outer sheath which are concentrically nested from the inside to the outside; wherein: The composite insulation layer is coaxially arranged from inside to outside in sequence with a solid inner skin layer, a self-repairing micro-foam insulation layer, a solid middle isolation layer, a high-foam insulation layer and a solid outer skin layer; The solid inner skin layer, the solid middle isolation layer and the solid outer skin layer are all solid polyolefin layers, and the thickness of each of them is independently 0.05 mm to 0.15 mm; The thickness of the self-repairing micro-foamed insulation layer is 0.1 mm to 1 mm. The self-repairing micro-foamed insulation layer is a foamed polyolefin, and a self-repairing material is dispersed inside the self-repairing material, which comprises porous silica particles, ethylene-methacrylic acid copolymer attached to the surface or pores of some of the porous silica particles, and a mixture of epoxy resin and curing agent attached to the surface or inside another part of the porous silica particles; The high foaming insulation layer is foamed polyolefin and has a thickness of 3 mm to 15 mm; the foaming degree of the high foaming insulation layer is higher than the foaming degree of the self-repairing micro-foaming insulation layer.

2. A self-repairing leaky coaxial cable, characterized in that: It includes an inner conductor, a composite insulation layer, an outer conductor and an outer sheath which are concentrically nested from the inside to the outside; wherein: The composite insulation layer is coaxially arranged from inside to outside in sequence with a solid inner skin layer, a self-repairing micro-foam insulation layer, a solid middle isolation layer, a high-foam insulation layer and a solid outer skin layer; The solid inner skin layer, the solid middle isolation layer and the solid outer skin layer are all solid polyolefin layers, and the thickness of each of them is independently 0.05 mm to 0.15 mm; The thickness of the self-repairing micro-foamed insulation layer is 0.1 mm to 1 mm. The self-repairing micro-foamed insulation layer is a foamed polyolefin, and a self-repairing material is dispersed inside the self-repairing material, which comprises porous silica particles, ethylene-methacrylic acid copolymer attached to the surface or pores of some of the porous silica particles, and a mixture of epoxy resin and curing agent attached to the surface or inside another part of the porous silica particles; The high foaming insulation layer is foamed polyolefin and has a thickness of 3 mm to 15 mm; the foaming degree of the high foaming insulation layer is higher than the foaming degree of the self-repairing micro-foaming insulation layer.

3. The cable according to claim 1 or 2, characterized in that: The specific surface area of ​​the porous silica particles is 200 m² / g to 400 m² / g, and the pore volume is 1.0 cm³ / g to 2.0 cm³ / g.

4. The cable according to claim 1 or 2, characterized in that: The loading amount of the ethylene-methacrylic acid copolymer in the self-repairing micro-foamed insulating layer is 15% to 25wt% of the mass of the porous silica, and the mass ratio of the ethylene-methacrylic acid copolymer attached to the porous silica to the mixture of the epoxy resin and the curing agent is 1 to 3:

1.

5. The cable according to claim 1 or 2, characterized in that: The mass percentage of the self-repairing material in the self-repairing micro-foamed insulation layer is 5% to 15%.

6. The cable according to claim 1 or 2, characterized in that: The foaming degree of the self-repairing micro-foamed insulation layer is 25% to 35%; the foaming degree of the high-foamed insulation layer is 40% to 95%.

7. The cable according to claim 1 or 2, characterized in that: The ethylene-methacrylic acid copolymer is attached to the surface or the pores of the porous silica particles according to the following steps: The ethylene-methacrylic acid copolymer is heated to a molten state and then mixed with the dried porous silica particles, and stirred so that the molten ethylene-methacrylic acid copolymer is impregnated into the pores of the porous silica particles; after cooling, the ethylene-methacrylic acid copolymer is solidified in the pores or on the surface, so that the ethylene-methacrylic acid copolymer is attached to the surface or in the pores of the porous silica particles; and the glass transition temperature of the ethylene-methacrylic acid copolymer is 80°C to 120°C.

8. The cable according to claim 1 or 2, characterized in that: The mixture of epoxy resin and curing agent is attached to the surface or pores of the porous silica particles according to the following steps: S1: drying the porous silica at 120°C to 150°C to remove adsorbed moisture and impurities; S2: dissolving epoxy resin in a solvent to obtain an epoxy resin solution; immersing porous silica in the epoxy resin solution, and allowing the solution to fully enter the pores through vacuum assistance or ultrasonic treatment; volatilizing and removing the solvent at room temperature or under heating conditions, so that the epoxy resin remains in the pores; S3: Dispersing a curing agent in an organic solvent to form a uniform curing agent suspension; immersing porous silica adsorbed with epoxy resin into the curing agent suspension, and allowing the curing agent to enter the pores not occupied by the epoxy resin through vacuum assistance or ultrasonic treatment; volatilizing and removing the organic solvent at room temperature or under heating conditions, leaving the curing agent in the pores, so that the epoxy resin and the curing agent are attached to the surface or pores of the porous silica particles.

9. A method for preparing a cable as claimed in claim 1 or 2, characterized in that: The steps include: (1) The solid inner skin layer, the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the inner conductor by using the skin-foam-skin three-layer co-extrusion technology, or the solid inner skin layer is first extruded on the surface of the inner conductor, and then the self-repairing micro-foamed insulation layer and the solid middle isolation layer are sequentially prepared on the surface of the solid inner skin layer by using the double-layer co-extrusion technology, wherein: When the self-repairing micro-foamed insulation layer is prepared by extrusion, the molten foaming material and the foaming gas are fully mixed in the screw to obtain an aerosol, and the aerosol is further mixed with a gas-solid mixture formed by mixing an inert gas and the self-repairing material at the inlet of the extruder head flow channel, and then extruded through a die mouth after mixing, the pressure is released to foam, and then cooled and shaped to form the self-repairing micro-foamed insulation layer with the self-repairing material dispersed inside; (2) co-extruding the high foaming insulation layer and the solid outer skin layer on the surface of the solid intermediate isolation layer; (3) The outer conductor and the outer sheath are sequentially prepared outside the solid outer skin layer.

10. The method according to claim 9, characterized in that Step (1) An injection hole is provided at the inlet of the flow channel of the extruder head, and a gas-solid mixture formed by mixing an inert gas and the self-healing material is injected through the injection hole by using a pneumatic sending device to mix with the aerosol; the diameter of the injection hole is 0.1 mm to 0.3 mm, and the injection pressure is 100 bar to 200 bar.

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