Preparation method of cross-linked polyolefin foaming insulating layer, cross-linked polyolefin foaming insulating layer and high-power feeder line

Abstract

The invention relates to the technical field of signal transmission in a high-power and high-temperature-resistant scene, and particularly discloses a preparation method of a cross-linked polyolefin foaming insulating layer, the cross-linked polyolefin foaming insulating layer and a high-power feeder line. The invention provides a preparation method of a cross-linked polyolefin foaming insulating layer, which specifically comprises the following steps: melting cross-linked polyolefin in a screw extruder, injecting a gas foaming agent, stirring to enable the cross-linked polyolefin to form aerosol, extruding the aerosol into a foaming mold to form a polyolefin foaming insulating layer, and carrying out extrusion molding on the polyolefin foaming insulating layer to obtain the cross-linked polyolefin foaming insulating layer. And finally, forming a cross-linked polyolefin foaming insulating layer by adopting electron beam irradiation cross-linking. And a corrugated metal tube outer conductor and a thermosetting sheath are coated outside the insulating layer to obtain a high-power feeder line. The preparation method provided by the invention is suitable for preparing a large-wire-diameter high-power high-temperature-resistant cross-linked foaming insulating layer. In addition, the high-power feeder line prepared by adopting the insulating layer is better in heat resistance, and can bear higher working power, working temperature and short-circuit temperature in actual work and application.

Description

Technical Field

[0001] The present application relates to a signal transmission technology for high-power, high-temperature resistant scenarios, and in particular to a method for preparing a cross-linked polyolefin foam insulation layer, a cross-linked polyolefin foam insulation layer, and a high-power feeder. Background Art

[0002] With the rapid development of mobile communication technology, the requirements for the performance and stability of communication equipment are constantly increasing. As an important component, the radio frequency (PF) feeder undertakes the key task of transmitting radio frequency signals.

[0003] Traditionally, RF feeders for mobile communications often use thermoplastic polyolefins or polyethylene materials as insulation or sheath materials for feeders because of their advantages such as good processing performance, high flexibility, low cost and recyclability. However, in some specific application scenarios, thermoplastic materials have been unable to meet the growing demand. For example, in high-frequency communication equipment signal connection occasions with high power and high temperature resistance requirements, thermoplastic materials have obvious limitations. Due to their physical properties (thermoplastic materials allow a maximum operating temperature of 85°C and a temperature resistance level of -55°C~85°C), thermoplastic polyolefins or polyethylene materials are prone to deformation in high temperature environments, which will have an adverse effect on the connection stability and signal transmission quality of communication equipment. In contrast, thermosetting polyolefins or polyethylene materials form a three-dimensional mesh structure after curing, showing excellent dimensional stability and strong resistance to deformation at high temperatures. This characteristic enables thermosetting materials to better adapt to the needs of such special scenarios and provide reliable protection for the connection of high-frequency communication equipment. At the same time, in harsh environments such as high corrosion, thermosetting materials also show better tolerance and good chemical corrosion resistance. They can maintain stable performance in extreme environments and ensure stable transmission of communication signals.

[0004] Therefore, in order to solve the prominent problem that traditional thermoplastic feeders generally have poor high temperature resistance and cannot be used in special occasions such as industrial plant communications in high temperature environments and outdoor communication base stations in high temperature climate areas, there is an urgent need for a high-power feeder that can adapt to extreme environments. Summary of the invention

[0005] In view of this, the purpose of the present application is to provide a method for preparing a cross-linked polyolefin foam insulation layer, a cross-linked polyolefin foam insulation layer and a high-power feeder, which are used to solve the problems of low working power and poor high temperature resistance of existing feeders.

[0006] In order to achieve the above technical objectives, the present application provides a method for preparing a cross-linked polyolefin foamed insulation layer, comprising the following steps:

[0007] Step S1, adding a cross-linked polyolefin into a screw extruder and heating the cross-linked polyolefin to melt the cross-linked polyolefin;

[0008] Step S2, injecting a gas foaming agent into the screw extruder through a gas injection needle with a diameter of 30-50 μm, so that the internal pressure of the screw extruder reaches a preset pressure;

[0009] Step S3, starting stirring, when the molten cross-linked polyolefin and the gas foaming agent are fully mixed to form an aerosol, causing the screw extruder to extrude the aerosol into the foaming mold at a first extrusion rate to form a polyolefin foaming insulation layer;

[0010] Step S4, using electron beam irradiation equipment to irradiate and crosslink the polyolefin foam insulation layer to obtain a cross-linked polyolefin foam insulation layer;

[0011] Cross-linked polyolefin, comprising the following components in percentage by weight:

[0012] High-density polyethylene 57.0%~78.90%;

[0013] Low-density polyethylene 18.5%~30%;

[0014] Elastomer 1%~5%;

[0015] Chemical foaming agent 0.1%~0.5%;

[0016] Nucleating agent 0.1%~0.5%;

[0017] Sensitizer 1%~5%;

[0018] Main antioxidant 0.1%~0.5%;

[0019] Auxiliary antioxidant 0.1%~0.5%;

[0020] Dispersant 0.1%~0.5%;

[0021] Lubricant 0.1%~0.5%.

[0022] Furthermore, the elastomer is one of ethylene-butene and ethylene-octene copolymers; the chemical foaming agent is one of bicarbonate and azodicarbonamide; the sensitizer is triallyl isocyanurate; the main antioxidant is 1010; the auxiliary antioxidant is one of phosphites and thioesters; the dispersant is precipitated silica; and the lubricant is polyethylene wax.

[0023] Furthermore, the preset pressure of step S2 is 160-250 bar; the stirring rate of step S3 is 10-30 r / min; and the first extrusion rate of step S3 is 10-30 r / min.

[0024] The present application provides a cross-linked polyolefin foamed insulation layer, which is prepared by adopting the above-mentioned preparation method of the cross-linked polyolefin foamed insulation layer.

[0025] The present application provides a high-power feeder, comprising the above-mentioned cross-linked polyolefin foamed insulation layer.

[0026] Furthermore, it comprises an inner conductor 1, a cross-linked polyolefin foam insulation layer 2, an outer conductor 3, and a sheath 4 which are arranged in sequence from the inside to the outside.

[0027] Furthermore, the outer conductor 3 is one of a spiral corrugated metal outer conductor and an annular corrugated metal outer conductor.

[0028] Furthermore, the sheath 4 is one of silane cross-linked polyethylene, radiation cross-linked polyethylene, and radiation cross-linked flame-retardant polyolefin.

[0029] In summary, the present application also provides a method for preparing an insulating layer using cross-linked polyolefin, comprising the following steps: step S1, adding the cross-linked polyolefin to a screw extruder, heating to melt the cross-linked polyolefin; step S2, injecting a gas foaming agent into the screw extruder, so that the internal pressure of the screw extruder reaches a preset pressure; step S3, starting stirring, when the molten cross-linked polyolefin and the gas foaming agent are fully mixed to form an aerosol, the screw extruder is made to extrude the aerosol into the foaming mold at a first extrusion rate to form polyolefin foam insulation; step S4, using an electron beam irradiation device to electron irradiate the polyolefin foam insulation layer to obtain a cross-linked polyolefin foam insulation layer. Compared with the prior art, the preparation method provided by the present invention is simple and clear, and does not require multiple program temperature control; at the same time, the method also has the advantage of preparing a large wire diameter insulation layer.

[0030] Finally, the present application provides a cross-linked polyolefin foam insulation layer and a high-power feeder including the cross-linked polyolefin foam insulation layer. Compared with the prior art, the high-power feeder provided by the present application has good heat resistance, a long-term operating temperature of up to 125°C, and a short-circuit temperature of up to 150°C. In actual work and application, it can withstand higher operating temperatures and short-circuit temperatures, further improving the safety of the line. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 A schematic diagram of the structure of a high-power feeder provided in an embodiment of the present application, wherein the metal outer conductor is a spirally corrugated metal outer conductor;

[0033] Figure 2A schematic diagram of the structure of a high-power feeder provided in an embodiment of the present application, wherein the metal outer conductor is an annular corrugated metal outer conductor;

[0034] Figure 3 A schematic diagram of the structure of a foaming mold provided in an embodiment of the present application;

[0035] Reference numerals: 1, inner conductor; 2, cross-linked polyolefin foam insulation layer; 3, outer conductor; 4, sheath. DETAILED DESCRIPTION

[0036] The technical solutions of the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the specification of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection requested by the present application.

[0037] The sources of all raw materials in the present invention are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0038] The present invention provides a method for preparing a cross-linked polyolefin foamed insulation layer, comprising the following steps:

[0039] Step S1, adding a cross-linked polyolefin into a screw extruder and heating the cross-linked polyolefin to melt the cross-linked polyolefin;

[0040] Step S2, injecting a gas foaming agent into the screw extruder through a gas injection needle with a diameter of 30-50 μm, so that the internal pressure of the screw extruder reaches a preset pressure;

[0041] Step S3, starting stirring, when the molten cross-linked polyolefin and the gas foaming agent are fully mixed to form an aerosol, causing the screw extruder to extrude the aerosol into the foaming mold at a first extrusion rate to form a polyolefin foaming insulation layer;

[0042] Step S4, using electron beam irradiation cross-linking equipment to irradiate and cross-link the polyolefin foam insulation layer, applying high-energy electron beams to the polymer molecular chains of the polyolefin foam insulation to generate free radicals to activate the molecular chains, and the activated molecular chains are cross-linked to form a network structure to obtain a cross-linked polyolefin foam insulation layer;

[0043] Cross-linked polyolefin, comprising the following components in percentage by weight:

[0044] High-density polyethylene 57.0%~78.90%;

[0045] Low-density polyethylene 18.5%~30%;

[0046] Elastomer 1%~5%;

[0047] Chemical foaming agent 0.1%~0.5%;

[0048] Nucleating agent 0.1%~0.5%;

[0049] Sensitizer 1%~5%;

[0050] Main antioxidant 0.1%~0.5%;

[0051] Auxiliary antioxidant 0.1%~0.5%;

[0052] Dispersant 0.1%~0.5%;

[0053] Lubricant 0.1%~0.5%.

[0054] It should be noted that in step S1, the cross-linked polyolefin can be mixed uniformly in advance before being added to the screw extruder. Compared with traditional cross-linked polyolefins, the cross-linked polyolefin used in the present invention has a small dielectric constant. The subsequent foaming method of step S2 can further reduce the dielectric constant and obtain a low-loss high-power feeder. Among them, in the gas injection process of step S2, a high-pressure gas injection device can be used for gas injection, and the nitrogen can be pressurized to a stable pressure that is 2 to 4 times greater than the gas injection pressure value required by the process, ensuring that the pressure of the nitrogen injection section of the barrel is maintained at more than 200 bar and the fluctuation range is stable at ±1 bar, forming a stable nitrogen flow; at the same time, the pressure control is implemented with the help of a flow control valve to increase the solubility of nitrogen in large wire diameters and ensure that a fine and uniform pore structure can be formed; it is also necessary to further explain step S2 that the present invention uses a micron-level gas injection needle to control the pressure inside the screw to maintain a stable gas injection rate, so that the bubbles are nucleated and form a fine and dense aerosol with pores that are not easy to break, and then it can maintain a stable shape in the later extrusion injection molding process, and solve the problem of pore collapse. . The foaming mold used in step S3 is as follows: Figure 3 As shown, by adjusting or increasing the wire diameter of the inner conductor, a cross-linked polyolefin foamed insulation layer with a large wire diameter can be prepared. In step S4, the foamed polyolefin is cross-linked and converted into a thermosetting plastic by electron irradiation, which can make the molecular structure more stable and help improve the temperature resistance level and mechanical strength of the insulation layer. In addition, the foaming mold provided by the present application is further explained: in order to ensure the adhesion of the large-diameter cross-linked foamed insulation layer, the foaming mold adopts an extrusion extrusion mold design, and by reasonably setting the extrusion pressure, accurately adjusting the distance between the mold core and the mold sleeve, and comprehensively considering the relationship between the screw speed, temperature, gear pump speed, and wire release speed and other factors, the foaming state is adjusted to a more ideal degree; at the same time, without damaging the quality of the bubble hole, the preheating degree of the inner conductor is improved, so that the foamed insulation can be tightly extruded on the inner conductor. Figure 3It is a schematic diagram of the tooling of the foaming mold, wherein A is the core of the foaming mold and B is the mold sleeve of the foaming mold.

[0055] It is also necessary to further explain that the present invention uses high-density polyethylene and low-density polyethylene as main materials, and uses elastomers, chemical foaming agents, nucleating agents, sensitizers, primary antioxidants, secondary antioxidants, dispersants, and lubricants as auxiliary materials. The cross-linked polyolefin obtained is a thermosetting material that can be cross-linked under specific physical and chemical conditions to form a network structure. After the cross-linking reaction, the cross-linked polyolefin provided in the present application exhibits the characteristics of high chemical resistance and high heat resistance; its structure has the characteristics of high strength and not easy to deform, and it can still show strong resistance to deformation even under high temperature conditions. Therefore, the cross-linked polyolefin can be used in harsh environments such as high temperature resistance and chemical corrosion resistance. At the same time, compared with other fluoroplastics with higher temperature resistance grades, the formula proposed by the present invention has significant advantages in terms of cost, and the material is a halogen-free and environmentally friendly material with environmentally friendly characteristics.

[0056] Specifically, the aspect ratio of the screw is 30 to 60, and the diameter of the screw is 80 mm. It should be noted that the cross-linked polyolefin used in the present invention has a relatively high viscosity, and a screw extruder with a large linear diameter ratio can increase the plasticizing time, make the material mix evenly, and improve the plasticizing effect, thereby obtaining an aerosol with tiny and dense pores and good mechanical properties; at the same time, a screw extruder with a large linear diameter can also provide a greater extrusion pressure, so that the aerosol can fully fill the foaming mold, thereby reducing the generation of defects such as pores and looseness inside the material.

[0057] In some embodiments, the elastomer is one of ethylene-butene and ethylene-octene copolymers; the chemical foaming agent is one of bicarbonate and azodicarbonamide; the sensitizer is triallyl isocyanurate; the primary antioxidant is 1010; the secondary antioxidant is one of phosphites and thioesters; the dispersant is precipitated silica; and the lubricant is polyethylene wax.

[0058] Specifically, the chemical foaming agent is an azodicarbonamide chemical foaming agent. Azodicarbonamide chemical foaming agents can be used as foaming gas nucleating agents. Under general treatment and processing conditions, they have a high decomposition temperature and good stability. At the same time, by means of physical foaming, they can form excellent foam structures and fine honeycomb network structures in the foaming process of cross-linked polyolefins.

[0059] Preferably, in step S2, the gas injection pressure is 160-250 bar.

[0060] Preferably, the heating temperature of step S3 is 150-200° C.; and the gas foaming agent is nitrogen.

[0061] Preferably, the electron beam irradiation intensity is 8 Mrad to 25 Mrad.

[0062] In some embodiments, the preset pressure of step S2 is 160-250 bar; the stirring rate of step S3 is 10-30 r / min; and the first extrusion rate of step S3 is 10-30 r / min.

[0063] It should be noted that setting the pressure inside the screw and the stirring rate helps to promote the formation of aerosol; in addition, the above extrusion rate does not easily cause the formed aerosol to break.

[0064] The present application provides a cross-linked polyolefin foamed insulation layer, which is prepared by adopting the above-mentioned preparation method of the cross-linked polyolefin foamed insulation layer.

[0065] The present application provides a high-power feeder, comprising the above-mentioned cross-linked polyolefin foamed insulation layer.

[0066] In some embodiments, the inner conductor 1, the cross-linked polyolefin foam insulation layer 2, the outer conductor 3, and the sheath 4 are sequentially arranged from the inside to the outside.

[0067] In some embodiments, the outer conductor 3 is one of a spiral corrugated metal outer conductor and an annular corrugated metal outer conductor.

[0068] Specifically, the metal outer conductor is a copper conductor or an aluminum conductor. It should be noted that the corrugated structure improves the bending, compression and other mechanical properties of the cable, and enables the feeder to have excellent mechanical protection characteristics; at the same time, the structure can also serve as an outer conductor shielding layer to play a role in resisting external electromagnetic interference.

[0069] In some embodiments, the sheath 4 is one of silane cross-linked polyethylene, radiation cross-linked polyethylene, and radiation cross-linked flame-retardant polyolefin.

[0070] It should be noted that the silane cross-linked polyethylene sheath can be prepared by natural cross-linking or warm water boiling cross-linking, and has the characteristics of halogen-free, wear-resistant, and high temperature resistant; the irradiated cross-linked polyethylene or irradiated flame-retardant cross-linked polyolefin is cross-linked by a high-energy electron beam generated by an electron accelerator, so that the polyethylene or flame-retardant polyolefin of the sheath layer changes from a linear molecular structure to a three-dimensional network structure, and finally forms a dense layer of a three-dimensional lattice, thereby improving the heat resistance, wear resistance or flame retardancy of the cable. The present invention uses one of silane cross-linked polyethylene, irradiated cross-linked polyethylene, and irradiated cross-linked flame-retardant polyolefin as the outer protective layer of the cable, further improving the high power resistance, temperature resistance level and service life of the cable.

[0071] The applicant further provides the following reference specific embodiments to describe the present invention. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0072] Example 1

[0073] This embodiment provides a cross-linked polyolefin, comprising the following components in percentage by weight:

[0074] High-density polyethylene 57.0%; low-density polyethylene 30%; elastomer 5%; chemical foaming agent 0.5%; nucleating agent 0.5%; sensitizer 5%; primary antioxidant 0.5%; secondary antioxidant 0.5%; dispersant 0.5%; lubricant 0.5%.

[0075] Among them, the elastomer is ethylene-butene; the chemical foaming agent is azodicarbonamide (CAS No.: 123-77-3); the sensitizer is triallyl isocyanurate (CAS No.: 1025-15-6); the main antioxidant is 1010 (CAS No.: 6683-19-8); the secondary antioxidant is pentaerythritol tetrakis (3-laurylthiopropionate) (CAS No.: 29598-76-3); the dispersant is precipitated silica (No.: 10279-57-9); and the lubricant is polyethylene wax (CAS No.: 1314-13-2).

[0076] Example 2

[0077] This embodiment provides a cross-linked polyolefin, comprising the following components:

[0078] High-density polyethylene 78.9%; low-density polyethylene 18.5%; elastomer 1%; chemical foaming agent 0.1%; nucleating agent 0.1%; sensitizer 1%; primary antioxidant 0.1%; secondary antioxidant 0.1%; dispersant 0.1%; lubricant 0.1%.

[0079] Among them, the elastomer is ethylene-butene; the chemical foaming agent is azodicarbonamide (CAS No.: 123-77-3); the sensitizer is triallyl isocyanurate (CAS No.: 1025-15-6); the main antioxidant is 1010 (CAS No.: 6683-19-8); the secondary antioxidant is pentaerythritol tetrakis (3-laurylthiopropionate) (CAS No.: 29598-76-3); the dispersant is precipitated silica (No.: 10279-57-9); and the lubricant is polyethylene wax (CAS No.: 1314-13-2).

[0080] Example 3

[0081] This embodiment provides a method for preparing a cross-linked polyolefin foam insulation layer, and the specific steps are as follows:

[0082] Step S1, adding the cross-linked polyolefin provided in Example 1 into a single screw extruder, heating the single screw to raise the internal temperature to 150° C., so that the cross-linked polyolefin inside the single screw is melted into a gel; wherein the single screw extruder has a diameter of 80 mm and an aspect ratio of 30;

[0083] Step S2, replacing the gas injection needle of the high-pressure gas injection device with a gas injection needle with a diameter of 40 μm, and injecting nitrogen into the single-screw extruder at a gas injection pressure of 200 bar through the gas injection needle, so that the internal pressure of the screw machine is always maintained at 200 bar;

[0084] Step S3, start stirring, and set the stirring speed of the single screw extruder to 20r / min, so that the nitrogen and the colloid in step S1 are fully mixed to form an aerosol; Figure 3 The foaming mold shown in the figure will Figure 3 The middle mold core A is connected to the mold sleeve B, so that the aerosol is extruded through the flow channel between the die head, the mold core A, and the mold sleeve B under the action of the single screw extrusion pressure and quickly released to normal pressure, forming a polyolefin foam insulation layer with a stable outer diameter and uniform foaming on the outer surface of the inner conductor;

[0085] Step S4, irradiating the polyolefin foamed insulation layer prepared in step 3 with an electron beam having an irradiation intensity of 15 Mrad to obtain a cross-linked polyolefin foamed insulation layer.

[0086] Example 4

[0087] This embodiment provides a high-power feeder, such as Figure 1 As shown, from the inside to the outside, an inner conductor, a cross-linked polyolefin insulation foam layer, an outer conductor, and a sheath are arranged in sequence. For specific parameters, see Table 1.

[0088] Testing: The high-power feeder prepared by the above method was tested for physical and chemical properties according to MIL-DTL-28830D and YD / T 1092. The test results are shown in Table 1.

[0089] Comparative Example 1

[0090] The comparative example of the present application provides a conventional feeder, and the details are shown in Table 1. The conventional feeder was tested for physical and chemical properties according to MIL-DTL-28830D and YD / T 1092, and the test results are shown in Table 1.

[0091] Table 1. Test results of Example 4 and Comparative Example 1

[0092]

[0093] According to the test results in this embodiment, the diameter of the cross-linked polyolefin foam insulation layer of the high-power feeder prepared by the scheme of the present application is 7.60±0.30mm, the temperature resistance level is -55℃~125℃, and the short-circuit temperature is 150℃; the temperature resistance level of the traditional feeder provided in Comparative Example 1 is -55℃~85℃. Based on the above experimental results, it can be obtained that the high-power feeder provided by the present invention has strong heat resistance and can operate for a long time in a high-temperature working environment; at the same time, the high-power feeder provided by the present invention can withstand a short-circuit temperature of up to 150℃. When a short short circuit occurs in the line, resulting in a local high temperature of the line, the integrity and stability of the feeder can still be maintained.

[0094] In summary, the solution of the present invention has the following beneficial effects:

[0095] (I) The thermosetting cross-linked polyolefin provided by the present invention can be based on high-density polyethylene or low-density polyethylene, and can be supplemented with ethylene-butene or ethylene-octene copolymer, triallyl isocyanurate, primary antioxidant 1010, phosphites or thioesters, precipitated silica, and polyethylene wax. Compared with the prior art, the thermosetting cross-linked polyolefin provided by the present invention has a simple formula and is easy to obtain, and can also be used to prepare high-power feeders with high heat resistance.

[0096] (ii) The method for preparing a cross-linked polyolefin foamed insulation layer provided by the present invention adopts melting, physical foaming, and electron irradiation to prepare the cross-linked polyolefin foamed insulation layer. Compared with the prior art, the method provided by the present invention has a simple and clear process and does not require multiple program temperature control; it can also be used to prepare a hollow cross-linked polyolefin foamed insulation layer with a large wire diameter.

[0097] (III) The high-power feeder provided by the present invention adopts an innovative structural design and process of combining a large-diameter cross-linked polyolefin foam insulation layer and a cross-linked polyethylene or cross-linked flame-retardant polyolefin sheath. The cross-linked polyolefin foam insulation layer is a cross-linked polyolefin that is transformed into an infusible thermosetting plastic by electron irradiation cross-linking. The molecular structure is more stable, which further improves the insulation's heat resistance and mechanical strength. The long-term operating temperature of the high-power feeder provided by the present invention can be as high as 125°C, and the short-circuit temperature can be increased to 150°C. Compared with other feeders prepared by traditional physical foaming polyolefin processing, it has better heat resistance and will not cause polymer degradation due to high temperature or unreacted catalysts. It can improve the product's thermal aging performance and high temperature stability, wear resistance, and soldering iron resistance. In addition, the present invention also uses cross-linked polyethylene or cross-linked flame-retardant polyolefin as the outer protective layer of the cable, which further improves the cable's high power resistance, temperature resistance and service life.

[0098] The above are only preferred embodiments of the present application and are not intended to limit the present invention. Although the present application has been described in detail with reference to the examples, those skilled in the art can still modify the technical solutions recorded in the aforementioned examples or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a cross-linked polyolefin foamed insulation layer, characterized in that: The preparation method comprises the following steps: Step S1, adding a cross-linked polyolefin into a screw extruder and heating the cross-linked polyolefin to melt the cross-linked polyolefin; Step S2, injecting a gas foaming agent into the screw extruder through a gas injection needle with a diameter of 30-50 μm, so that the internal pressure of the screw extruder reaches a preset pressure; Step S3, starting stirring, when the molten cross-linked polyolefin and the gas foaming agent are fully mixed to form an aerosol, causing the screw extruder to extrude the aerosol into the foaming mold at a first extrusion rate to obtain a polyolefin foamed insulation layer; Step S4, using electron beam irradiation equipment to irradiate and crosslink the polyolefin foam insulation layer to obtain a cross-linked polyolefin foam insulation layer; The cross-linked polyolefin comprises the following components in percentage by mass: High-density polyethylene 57.0%~78.90%; Low-density polyethylene 18.5%~30%; Elastomer 1%~5%; Chemical foaming agent 0.1%~0.5%; Nucleating agent 0.1%~0.5%; Sensitizer 1%~5%; Main antioxidant 0.1%~0.5%; Auxiliary antioxidant 0.1%~0.5%; Dispersant 0.1%~0.5%; Lubricant 0.1%~0.5%.

2. The method for preparing a cross-linked polyolefin foamed insulation layer according to claim 1, characterized in that: The elastomer is one of ethylene-butene and ethylene-octene copolymers; the chemical foaming agent is one of bicarbonate and azodicarbonamide; the sensitizer is triallyl isocyanurate; the main antioxidant is 1010; the auxiliary antioxidant is one of phosphites and thioesters; the dispersant is precipitated silica; and the lubricant is polyethylene wax.

3. The method for preparing a cross-linked polyolefin foamed insulation layer according to claim 1, characterized in that: The preset pressure of step S2 is 160-250 bar; the stirring rate of step S3 is 10-30 r / min; and the first extrusion rate of step S3 is 10-30 r / min.

4. A cross-linked polyolefin foamed insulation layer, characterized in that: The cross-linked polyolefin foamed insulation layer is prepared by the preparation method of any one of claims 1 to 3.

5. A high power feeder, characterized in that: The invention comprises the cross-linked polyolefin foamed insulation layer as claimed in claim 4.

6. The high power feeder according to claim 5, characterized in that: It comprises an inner conductor (1), a cross-linked polyolefin foam insulation layer (2), an outer conductor (3), and a sheath (4) which are arranged in sequence from the inside to the outside.

7. The high power feeder according to claim 6, characterized in that: The outer conductor (3) is one of a spiral corrugated metal outer conductor and an annular corrugated metal outer conductor.

8. The high power feeder according to claim 6, characterized in that: The sheath (4) is one of silane cross-linked polyethylene, radiation cross-linked polyethylene, and radiation cross-linked flame-retardant polyolefin.

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