Cross-linked foaming polyethylene core wire coaxial cable

Abstract

The invention belongs to the field of coaxial cables, and particularly relates to a cross-linked foaming polyethylene core wire coaxial cable. The cross-linked foaming polyethylene core wire coaxial cable comprises an inner conductor, an insulating layer, an outer conductor layer and an outer sheath layer which are sequentially coated from inside to outside, the insulating layer is prepared by the following method: S1: performing foaming extrusion on a base material, a cross-linking agent and a nucleating agent to obtain an insulating core wire; during foaming extrusion, foaming gas is adopted for physical foaming; the base material is selected from high-density polyethylene; and S2, performing irradiation crosslinking on the insulating core wire through high-energy rays (such as gamma rays, alpha rays and electron rays) to obtain an insulating layer. The cross-linked foaming polyethylene core wire coaxial cable is suitable for high-temperature-resistant occasions including high-power high-frequency signal transmission occasions and coaxial cable frequent welding occasions, and can meet the requirements of a high-end communication system.

Description

Technical Field

[0001] The invention belongs to the field of coaxial cables, and in particular relates to a cross-linked foamed polyethylene core wire coaxial cable. Background Art

[0002] As an important transmission medium widely used in cable TV networks, TV broadcast transmission, wireless communication base stations, security monitoring systems, data communication networks and radar systems, the performance requirements of coaxial cable are increasing day by day.

[0003] Coaxial cable is a type of electrical wire and signal transmission line, generally made of four layers of material: the innermost is a conductive copper wire, the outside of the wire is surrounded by a layer of plastic (used as an insulator, dielectric), the outside of the insulator is covered with a thin mesh conductor (generally copper or alloy), and then the outside of the conductor is the outermost layer of insulating material as the outer sheath.

[0004] Coaxial cable can be used to transmit analog and digital signals for a wide variety of applications, the most important of which are cable television transmission, long-distance telephone transmission, short-distance connections between computer systems, and local area networks. Coaxial cable has developed rapidly as a means of transmitting television signals to thousands of households. This is cable television. A cable television system can carry dozens or even hundreds of television channels, and its transmission range can reach tens of kilometers. Coaxial cable has long been an important part of the long-distance telephone network. Today, it faces increasing competition from optical fiber, terrestrial microwave and satellite.

[0005] The development of coaxial cables can be divided into four generations: the first generation began to use polyethylene as a solid core insulating medium in the mid-19th century; the second generation used chemically foamed polyethylene as an insulating medium; the third generation used lotus-core longitudinal pore polyethylene as an insulating medium; and the fourth generation used physically foamed polyethylene as an insulating medium. Coaxial cables can be divided into leaky coaxial cables, multi-core coaxial cables, thin-diameter coaxial cables, and composite coaxial cables according to their structure.

[0006] The coaxial cable industry has undergone a series of changes since its development. As the global electronics industry entered its peak in 2000, the coaxial cable market, as part of the electronics industry, also reached its historical peak. In the following three years, as the global economic growth rate entered a trough, the coaxial cable industry also entered a downturn with the shrinking downstream demand, and did not show signs of recovery until the second half of 2003. Since 2004, the global coaxial cable industry has entered a new round of growth. With the continuous expansion of mobile communication signal coverage, the increase in the number of base stations, and the continuous improvement of mobile signal requirements in transportation, energy, medical and other fields, the market development prospects of the global RF coaxial cable industry remain promising.

[0007] Traditional coaxial cable cores are mostly made of physical foamed polyethylene material, which has a low dielectric constant and low attenuation for high-frequency signals, and can solve the transmission rate problem very well. However, since foamed polyethylene is not resistant to high temperatures, when the cable is running at high power, the cable itself heats up, and the foamed polyethylene becomes soft and plastic after heating. The polyethylene interface capacity decreases, and the gas in the pores expands due to heat, breaking through the pore wall and escaping, causing the polyethylene transmission performance to decline, which can no longer meet the needs of current high-end communication systems. On the other hand, the main feeder in the antenna requires frequent tin soldering, and the molten tin has a high temperature, which can easily damage the foamed polyethylene insulation layer. Therefore, it is urgent to develop a new type of high-temperature resistant coaxial cable to improve the efficiency and quality of signal transmission and expand the application scenarios of coaxial cables. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a cross-linked foamed polyethylene core coaxial cable, which comprises an inner conductor, a radiation cross-linked foamed high-density polyethylene insulation layer, an outer conductor layer and an outer sheath layer from inside to outside.

[0009] The present invention provides a cross-linked foamed polyethylene core wire coaxial cable, comprising an inner conductor, a cross-linked foamed insulation layer, an outer conductor layer and an outer sheath layer sequentially coated from the inside to the outside; the cross-linked foamed insulation layer comprises an inner skin layer, an intermediate foamed layer and an outer skin layer sequentially coated from the inside to the outside;

[0010] The cross-linked foamed insulation layer is prepared by the following method:

[0011] S1: In the extruder, after the inner conductor passes through the insulation extruder head, polyethylene is glued to the outer surface of the inner conductor to form an inner skin layer;

[0012] S2: performing double-layer co-extrusion outside the inner skin layer to form an intermediate foaming layer and an outer skin layer covering the outer layer of the intermediate foaming layer to obtain an insulated core wire;

[0013] Before double-layer co-extrusion, a base resin and a cross-linking agent are added to the feeding section of the middle foaming layer, and polyethylene is added to the feeding section of the outer skin layer, wherein the base resin is selected from high-density polyethylene (HDPE), and the cross-linking agent is selected from triallyl isocyanurate; during double-layer co-extrusion, a nucleating agent is added to the feeding section of the middle foaming layer, and a foaming gas is introduced for physical foaming;

[0014] S3: irradiating the insulating core wire with high-energy rays to cross-link the insulating core wire, thereby obtaining the cross-linked foamed insulating layer.

[0015] Preferably, the nucleating agent is selected from Dow DFNA-0078NT.

[0016] Preferably, the inner conductor is selected from silver-plated copper wire with a nominal diameter of 1.6-1.9 mm.

[0017] Preferably, the outer diameter of the insulating layer is 4.0-4.4 mm.

[0018] Preferably, the high-energy rays are selected from gamma rays, alpha rays or electron rays.

[0019] Preferably, the foaming gas is selected from nitrogen or carbon dioxide.

[0020] Preferably, the outer conductor layer is a spiral corrugated copper tube.

[0021] Furthermore, the thickness of the spiral corrugated copper tube is 0.12-0.23 mm.

[0022] Preferably, the material of the outer sheath layer is selected from low-smoke halogen-free flame-retardant polyolefin (LSZH); the low-smoke halogen-free flame-retardant polyolefin is provided by CGN Delta, and the brand is PT2935U.

[0023] Preferably, in step S1, the weight ratio of base resin: cross-linking agent: nucleating agent is 100:1.5-3.5:1-2.

[0024] Preferably, in step S1, 200-300 MPa of nitrogen is injected during foaming extrusion.

[0025] Preferably, in step S2, the radiation cross-linking dosage is 13-18 Mrd, and the speed is 50-65 m / min.

[0026] The technical solution of the present invention has the following advantages over the prior art:

[0027] 1. The inner conductor is made of silver-plated copper wire, which has the advantages of high conductivity and high temperature resistance. The conductor will not oxidize when used at high temperatures. It also has excellent mechanical properties and good transmission performance.

[0028] 2. The base material of the insulation layer is high-density polyethylene. The mechanical properties and temperature resistance of HDPE are better than those of low-density polyethylene (LDPE); the melting point of HDPE is 131-137℃, the tensile strength is 21-37MPa, the melting point of LDPE is 105-115℃, and the tensile strength is 7-15MPa;

[0029] 3. The insulation adopts a three-layer structure: crust layer-foaming layer-skin layer. The inner crust layer is used to increase the adhesion between the insulation and the inner conductor, and the outer crust layer is used to prevent moisture penetration;

[0030] 4. Preparation of cross-linked foamed insulation layer: polyethylene matrix resin + glue forms the inner insulation layer; polyethylene resin + cross-linking agent + nucleating agent forms the foaming layer, and the foaming layer and the outer polyethylene layer are co-extruded to form the foamed insulation layer. This preparation method is simple in process and has high insulation consistency;

[0031] 5. The polyethylene foam layer is added with a cross-linking agent, which has a higher degree of cross-linking than direct irradiation of polyethylene without a cross-linking agent, and the irradiation dose is low. The preparation method is simple and the cost is lower than that of purchased cross-linked foamed polyethylene insulation materials;

[0032] 6. It adopts the irradiation physical cross-linking method, which is simple to operate and can be widely used on cables that are difficult to extrude;

[0033] 7. The insulation is cross-linked to improve the mechanical properties of the cable, resistance to environmental stress cracking, chemical stability and the operating temperature of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the structural diagram of the cross-linked foamed high-density polyethylene core coaxial cable.

[0035] Figure 2 This is a diagram of the internal structure of a cross-linked foamed high-density polyethylene core coaxial cable.

[0036] Explanation of the reference numerals: 1-silver-plated copper wire inner conductor, 2-cross-linked foamed high-density polyethylene insulation layer, 3-spiral corrugated copper tube, 4-sheath. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0038] Example 1

[0039] (1) Insulation layer ingredients, the weight ratio of materials is: 100 parts of the base resin high-density polyethylene, 1.5 parts of the cross-linking agent triallyl isocyanate (TAIC), and 1 part of the nucleating agent Dow DFNA-0078NT;

[0040] (2) passing the inner conductor through an 80 / 100 insulation extruder head, firstly forming an insulating inner skin layer with polyethylene matrix resin and glue; secondly, injecting a high-density polyethylene base material and a cross-linking agent into a feeding barrel in a feeding section, adding a nucleating agent during the extrusion process for foaming extrusion, and co-extruding a middle foaming layer and an outer skin layer of polyethylene to form a polyethylene foam insulation core wire, and then injecting 300MPa of nitrogen with a nitrogen concentration of 99.99% to obtain an insulation core wire with a cross-linked foamed high-density polyethylene insulation layer containing a cross-linking agent;

[0041] (3) The insulating core wire is irradiated with high-energy gamma rays to crosslink the foamed high-density polyethylene insulation layer. The irradiation dose is 15 Mrd and the speed is 65 m / min, thereby obtaining the cross-linked foamed high-density polyethylene insulation layer 2.

[0042] Example 2

[0043] (1) Insulation layer ingredients, the weight ratio of materials is: 100 parts of the base resin high-density polyethylene, 2.5 parts of the cross-linking agent triallyl isocyanate (TAIC), and 1.5 parts of the nucleating agent Dow DFNA-0078NT;

[0044] (2) passing the inner conductor through an 80 / 100 insulation extruder head, firstly forming an insulating inner skin layer with polyethylene matrix resin and glue; secondly, injecting a high-density polyethylene base material and a cross-linking agent into a feeding barrel in a feeding section, adding a nucleating agent during the extrusion process for foaming extrusion, and co-extruding a middle foaming layer and an outer skin layer of polyethylene to form a polyethylene foam insulation core wire, and then injecting 300MPa of nitrogen with a nitrogen concentration of 99.99% to obtain an insulation core wire with a cross-linked foamed high-density polyethylene insulation layer containing a cross-linking agent;

[0045] (3) The insulating core wire is irradiated with high-energy gamma rays to crosslink the foamed high-density polyethylene insulation layer. The irradiation dose is 15 Mrd and the speed is 65 m / min, thereby obtaining the cross-linked foamed high-density polyethylene insulation layer 2.

[0046] Example 3

[0047] (1) Insulation layer ingredients, the weight ratio of materials is: 100 parts of the base resin high-density polyethylene, 3.5 parts of the cross-linking agent triallyl isocyanate (TAIC), and 2 parts of the nucleating agent Dow DFNA-0078NT;

[0048] (2) The inner conductor is passed through an 80 / 100 insulation extruder head, and polyethylene matrix resin and glue are firstly applied to the surface of the inner conductor to form an insulating inner skin layer; secondly, a high-density polyethylene base material and a cross-linking agent are injected into a feeding barrel in a feeding section, and a nucleating agent is added in the extrusion process for foaming and extrusion. The middle foaming layer and the outer skin layer of polyethylene are co-extruded to form a polyethylene foam insulation core wire, and 300 MPa of nitrogen is injected for foaming, and the nitrogen concentration is 99.99%, to obtain an insulation core wire containing a cross-linked foamed high-density polyethylene insulation layer containing a cross-linking agent;

[0049] (3) The insulating core wire is irradiated with high-energy gamma rays to crosslink the foamed high-density polyethylene insulation layer. The irradiation dose is 15 Mrd and the speed is 65 m / min, thereby obtaining the cross-linked foamed high-density polyethylene insulation layer 2.

[0050] Example 4

[0051] The inner conductor of the radio frequency coaxial cable adopts a silver-plated copper wire inner conductor 1 with a nominal diameter of 1.64mm; the foamed insulation layer of the radio frequency coaxial cable adopts a cross-linked foamed HDPE material, which is selected from the cross-linked foamed high-density polyethylene insulation layer 2 with an outer diameter of 4.1mm prepared in Example 1; the spiral corrugated copper tube 3 of the coaxial radio frequency cable adopts a 0.15mm copper corrugated tube coated on the outside of the cross-linked foamed high-density polyethylene insulation layer 2; the material of the sheath 4 is a low-smoke halogen-free flame-retardant polyolefin material. The structure of the cross-linked foamed HDPE core wire coaxial cable is shown in FIG. Figure 1 and Figure 2 .

[0052] Comparative Example 1

[0053] (1) Insulation layer preparation method According to the embodiment, the insulating material ratio is changed to: based on 100 parts by weight of the matrix resin high-density polyethylene, 4 parts by weight of the cross-linking agent triallyl isocyanate (TAIC) and 1 part by weight of the nucleating agent Dow DFNA-0078NT;

[0054] (2) Finished radio frequency coaxial cable: the inner conductor is a silver-plated copper wire inner conductor 1 with a nominal diameter of 1.64 mm; the foamed insulation layer of the radio frequency coaxial cable is a cross-linked foamed HDPE material, selected from the cross-linked foamed high-density polyethylene insulation layer 2 with an outer diameter of 4.1 mm prepared in (1); the spiral corrugated copper tube 3 of the coaxial radio frequency cable is a 0.15 mm copper corrugated tube coated on the outside of the cross-linked foamed high-density polyethylene insulation layer 2; the material of the sheath 4 is a low-smoke halogen-free polyolefin material.

[0055] Effect evaluation 1

[0056] The transmission performance of the cross-linked foamed high-density polyethylene core coaxial cables prepared in Example 4 and Comparative Example 1 was tested and compared, and the results are shown in Table 1 and Table 2. The results show that the transmission rate and attenuation of Comparative Example 1 are unqualified, and excessive addition of cross-linking agent is not conducive to signal transmission of the cable.

[0057] Table 1 Transmission performance test of the cross-linked foamed high-density polyethylene core wire coaxial cable prepared in Comparative Example 1

[0058]

[0059] Table 2 Transmission performance test of the cross-linked foamed high-density polyethylene core wire coaxial cable prepared in Example 4

[0060]

[0061] In summary, the cross-linked foamed polyethylene core wire coaxial cable provided by the present invention has the advantages of simple cable manufacturing process, increased temperature resistance to 150°C, increased insulation tensile strength by 1.5 times, fine insulation pores, excellent transmission performance, and wide application. The cross-linked foamed polyethylene core wire coaxial cable of the present invention is suitable for high temperature resistant occasions, including high-power and high-frequency signal transmission occasions, and occasions where coaxial cables are frequently welded, and can meet the needs of high-end communication systems.

[0062] The present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but is not limited to the embodiments. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements. The equivalent replacement of the selected components of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection required by the present invention.

Claims

1. A cross-linked foamed polyethylene core coaxial cable, It is characterized in that It includes an inner conductor, a cross-linked foamed insulation layer, an outer conductor layer and an outer sheath layer which are sequentially coated from the inside to the outside; the insulation layer includes an inner skin layer, an intermediate foamed layer and an outer skin layer which are sequentially coated from the inside to the outside; The cross-linked foamed insulation layer is prepared by the following method: S1: In the extruder, after the inner conductor passes through the insulation extruder head, polyethylene is glued to the outer surface of the inner conductor to form an inner skin layer; S2: performing double-layer co-extrusion outside the inner skin layer to form an intermediate foaming layer and an outer skin layer covering the outer layer of the intermediate foaming layer to obtain an insulated core wire; Before double-layer co-extrusion, a base resin and a cross-linking agent are added to the feeding section of the middle foaming layer, and polyethylene is added to the feeding section of the outer skin layer, wherein the base resin is selected from high-density polyethylene, and the cross-linking agent is selected from triallyl isocyanurate; during double-layer co-extrusion, a nucleating agent is added to the feeding section of the middle foaming layer, and a foaming gas is introduced for physical foaming; the weight ratio of the base resin, the cross-linking agent and the nucleating agent is 100:1.5-3.5:1-2; S3: cross-linking the insulating core wire by high-energy ray irradiation to obtain the cross-linked foamed insulating layer.

2. The cross-linked foamed polyethylene core coaxial cable according to claim 1, It is characterized in that The inner conductor is selected from silver-plated copper wire with a nominal diameter of 1.6-1.9 mm.

3. The cross-linked foamed polyethylene core coaxial cable according to claim 1, It is characterized in that The outer diameter of the insulating layer is 4.0-4.4 mm.

4. The cross-linked foamed polyethylene core coaxial cable according to claim 1, It is characterized in that The outer conductor layer is a spiral corrugated copper tube.

5. The cross-linked foamed polyethylene core coaxial cable as claimed in claim 4, It is characterized in that The thickness of the spiral corrugated copper tube is 0.12-0.23 mm.

6. The cross-linked foamed polyethylene core coaxial cable as claimed in claim 1, It is characterized in that The material of the outer sheath layer is selected from low-smoke halogen-free flame-retardant polyolefin.

7. The cross-linked foamed polyethylene core coaxial cable according to claim 1, It is characterized in that The foaming gas is selected from nitrogen or carbon dioxide.

8. The cross-linked foamed polyethylene core coaxial cable as claimed in claim 1, It is characterized in that In the step S1, during physical foaming, 200-300 MPa of foaming gas is injected.

9. The cross-linked foamed polyethylene core coaxial cable according to claim 1, It is characterized in that In the step S2, the radiation cross-linking dosage is 13-18 Mrd, and the speed is 50-65 m / min.

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