KR20080074382A - Insulator for coaxial cable and method for preparing therof and low loss large diameter coaxial cable using the same - Google Patents

Abstract

An insulator for a coaxial cable is provided to realize a decreased dielectric constant, to reduce transmission loss, and to maximize transmission rate, thereby ensuring highly efficiency transmission in a coaxial cable. An insulator for a coaxial cable comprises foamed cells having a foaming ratio of at least 80%, a closed-cell shape, and a longer radius of 10-500 micrometers. A coaxial cable comprises: a cylindrical central conductor(10); an inner skin layer(20) surrounding the central conductor; the insulator layer(30) surrounding the inner skin layer in a layered form; an outer skin layer(40) surrounding the insulator layer; an external conductor(50) provided on the outer circumferential surface of the outer skin layer; and a coating layer(60) completely surrounding the external conductor.

Description

Insulator for coaxial cable, manufacturing method and low loss large diameter coaxial cable using the same {Insulator for coaxial cable and method for preparing therof and low loss large diameter coaxial cable using the same}

1 is a cross-sectional view showing a large diameter coaxial cable according to an embodiment of the present invention.

Figure 2 is a SEM photograph showing the foam cross section of the coaxial cable manufactured according to an embodiment of the present invention.

Figure 3 is a SEM photograph showing the foam cross section of the coaxial cable prepared according to the comparative example according to the prior art.

Figure 4 is a graph showing the loss characteristics of the coaxial cable manufactured according to an embodiment of the present invention.

5 is a graph showing the loss characteristics of a coaxial cable manufactured according to a comparative example according to the prior art.

Description of the main symbols in the drawings

10: center conductor 20: inner skin layer

30: insulator layer 40: outer skin layer

50: outer conductor 60: coating layer

The present invention relates to an insulator for a coaxial cable, a method for manufacturing the same, and a low loss large diameter coaxial cable using the same. More specifically, the foaming degree is 80% or more, and the closed-cell shape has a long radius of 10 to 500 μm. The present invention relates to an insulator for a coaxial cable capable of providing a coaxial cable having a low loss large diameter by manufacturing an coaxial cable having an insulator layer including a phosphor foam cell, a method of manufacturing the same, and a low loss large diameter coaxial cable using the same.

Until now, coaxial cable has been used for a long time, and a wide variety of products and types have been developed by size and type. Coaxial cable means a center conductor for transmitting a signal and an outer conductor disposed on the coaxial with the center conductor. The main development direction of the conventional coaxial cable is to improve the structural design or dielectric properties between the center conductor and the outer conductor or to give various functions to the outside conductor in order to reduce the loss of energy to be transmitted. It has been ongoing. Coaxial cable has been mainly used for the purpose of transmitting signals such as antennas or cable TVs in the basement of buildings, and as a measure for evaluating the signal transmission characteristics, a property called a characteristic impedance (Z) represented by Equation 1 below is important for structural design. Is reflected.

In Equation 1, ε _r represents the dielectric constant of the insulating material, d represents the diameter of the center conductor, D represents the inner diameter of the outer conductor.

Impedance matching is the most important factor in the coaxial cable, which is calculated as in Equation 1 above. The impedance of the energy wave having good power transmission characteristics is 33 Ω, and the impedance of the signal waveform is good. 75 Ω, the middle of which is 45 to 50 Ω is used as the international standard.

Conventional technologies for coaxial cables include U.S. Patent No. 6,130,385, U.S. Patent No. 4,965,412, U.S. Patent Application No.2003 / 0051897, and the like. It is a main content to provide the metal layer or the film layer in which the metal was excellent in the electromagnetic shielding characteristic inside or outside the shield layer.

Meanwhile, propagation velocity (V _f ), which is one of the main parameters of the coaxial cable, is calculated according to Equation 3 after calculating the dielectric constant ε _r according to Equation 2 below, and the higher the foaming degree, the higher the dielectric constant. This decrease in dielectric constant decreases the signal loss, thereby improving transmission speed.

In Equation 2, ε _{r, exp} represents the dielectric constant after foaming, ε _{r, solid} represents the dielectric constant before foaming, ρ _exp represents the density after foaming, and ρ _solid represents the density before foaming, respectively.

In Equation 3, V _p represents a transmission rate and is calculated as a permittivity ε _r calculated by Equation 2.

Meanwhile, the expansion ratio (V _f ) of the insulator used for the coaxial cable is calculated according to Equation 4 below, and the degree of foaming (D _f ) is calculated through Equation 5 below.

In Equation 4, P _v represents a polymer volume and G _v represents a gas volume (space volume).

The foaming degree (D _f ) shown in Equation (5) can be calculated directly from the foaming factor (V _f ) represented by Equation 4, and the unit is expressed as a percentage (%).

Each of the properties represented by the above equations is directly or indirectly correlated with the signal transmission speed of the coaxial cable. As a result of examining these relationships, the dielectric constant of the insulating layer is required to secure a high transmission speed and prevent loss during transmission. The key is to select a low resin, such as excellent flow characteristics, and adjust the blending ratio to increase the degree of foaming and to lower the dielectric constant value. In particular, in order to deliver more information due to the rapid development of information and communication technology in a shorter time, efforts have been made to use high frequency with the use frequency of several hundred MHz to several GHz, and the loss can be minimized. The need for technical supplementation is an important challenge.

Efforts to solve the technical problem as described above has been steadily progressed in the related art, and the present invention has been devised under such a technical background.

The technical problem to be achieved by the present invention based on the above-described problems, the material used in the coaxial cable for decreasing the dielectric constant, reducing the transmission loss and maximizing the transmission speed in order to secure a high efficiency transmission rate of the coaxial cable for high frequency transmission It is an object of the present invention to provide an insulator for a coaxial cable, a method for manufacturing the same, and a low loss large diameter coaxial cable using the same, which is in the development of the present invention.

The insulator for a coaxial cable provided to achieve the technical problem to be achieved by the present invention, the foaming degree is 80% or more, the closed-cell shape as a long radius of the foam cell containing 10 to 500 ㎛ It is characterized by.

The low-loss large-diameter coaxial cable provided for achieving the technical problem to be achieved by the present invention, the cylindrical center conductor; An inner skin layer surrounding the center conductor; An insulator layer surrounding the inner skin layer in a layered manner; An outer skin layer surrounding the dielectric layer; An outer conductor provided on an outer circumferential surface of the outer skin layer; And a coating layer completely surrounding the outer conductor, wherein the insulator layer has a foaming degree of 80% or more and a closed-cell shape, the long radius of which ranges from 10 to 500 It characterized in that it comprises a foam cell which is μm.

The insulator layer is preferably formed to a thickness of 60 to 170% of the inner diameter of the center conductor.

Insulator layer manufacturing method used in the low-loss large-diameter coaxial cable provided for achieving the technical problem to be achieved by the present invention, a cylindrical center conductor, an inner skin layer surrounding the center conductor, an insulator wrapping the inner skin layer in layers A method for manufacturing the insulator layer of a low loss large diameter coaxial cable comprising a layer, an outer skin layer surrounding the dielectric layer, an outer conductor provided on an outer circumferential surface of the outer skin layer, and a covering layer completely surrounding the outer conductor, (S1) ) Preparing a resin mixed with high density polyethylene (HDPE) and low density polyethylene (LDPE); (S2) adding a pyrogenic nucleating agent to the mixed resin; (S3) injecting a gas for securing a low dielectric constant to the mixed resin; (S4) foaming the prepared mixed resin; And (S5) extruding the foam to cover the inner skin layer upper surface in a layered manner.

The mixed resin of the step (S1) is preferably a mixed resin of 45 to 75% by weight of high density polyethylene (HDPE), 25 to 55% by weight of low density polyethylene (LDPE). The pyrogenic nucleating agent of step (S2) is preferably one or a mixture of two or more selected from azodicarbonamide, sulfonylhydrazides and 5-phenyltetrazole. In this case, the pyrogenic nucleating agent is preferably added in an amount of 150 to 750 ppm relative to the total weight of the mixed resin. The low dielectric constant securing gas of step (S3) is preferably carbon dioxide (CO2). The foaming in the step (S4) is preferably carried out so that the foaming degree is 80% or more. It is preferable that the insulator layer formed by extrusion in the step (S5) has a thickness of 60 to 170% of the inner diameter of the center conductor. The insulator layer extruded in the step (S5) has a closed-cell shape therein, and the foam layer has a long radius of 10 to 500 μm.

Hereinafter, the present invention will be described in detail with reference to examples, and detailed description will be made with reference to the accompanying drawings in order to help understanding of the present invention. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

The insulator used in the coaxial cable of the present invention has a foaming degree of 80% or more, a closed pore shape, and includes a foam cell having a long radius of 10 to 500 μm, and its manufacture is made of high density polyethylene (HDPE) and low density polyethylene (LDPE). The pyrogenic nucleating agent was added to the mixed resin (S1) (S2), a gas for securing a low dielectric constant was added to the mixture (S3) and foamed (S4), and then the foam was layered on the upper surface of the inner skin layer. It can be achieved by extrusion (S5) so as to wrap.

The mixed resin of the step (S1) is preferably a mixture of high density polyethylene (HDPE) and low density polyethylene (LDPE) to enable high foaming to secure a characteristic impedance and low dielectric constant. When only the high density polyethylene is used, the loss characteristics are excellent, but the foaming degree is not more than 80%, which is not preferable. When only the low density polyethylene is used, the foaming degree is high, but the transporting property is not secured, which is not preferable.

The mixed resin is preferably a high density polyethylene of 45 to 75% by weight, a low density polyethylene of 25 to 55% of the mixed resin, when the mixing ratio is within the range of 80% on average, up to 87% of the degree of foaming It is better to be able to secure. The foaming degree is closely related to the melt strength, but when the mixing ratio of the high density polyethylene and the low density polyethylene is outside the numerical range, at least 80% of the foaming degree cannot be obtained, which is not preferable.

The exothermic nucleating agent (CFA) of the step (S2) is used to optimize the cooling characteristics according to the large diameter.

In general, in the case of using an endothermic nucleating agent or a mixture of endothermic and exothermic nucleating agents, a foaming degree of 80% or more cannot be formed due to thermal balance problems such as cooling in manufacturing large diameter coaxial cables. Although it was impossible to obtain closed pores that can be suppressed, in the present invention, the foaming degree of 80% or more can be obtained by optimizing the cooling characteristics according to large diameter using only the pyrogenic nucleating agent.

The pyrogenic nucleating agent may be azodicarbonamide, sulfonylhydrazides, or 5-phenyltetrazole.

The pyrogenic nucleating agent is preferably added in an amount of 150 to 750 ppm based on the total weight of the mixed resin. In the numerical range of the pyrogenic nucleating agent, the desired foaming degree is not obtained when it is less than the lower limit, and when the upper limiting value is exceeded, since the reaction site is increased, the cell size is reduced and the foaming degree is also increased. It is lowered and is not preferable.

The thickness of the polymer insulating layer extruded on the loan coating layer was 6-14 mm, and the composition ratio was determined in consideration of loss characteristics (loss factor, tanδ).

The gas for securing the low dielectric constant of step (S3) is preferably CO ₂ . In this case, in order to mix the gas for securing the low dielectric constant to a supersaturated state, it is preferable to pressurize to 150 to 350 bar level. In the limited pressurization range, the mixing resin and the gas for securing the low dielectric constant are not preferable when the pressure is lower than the lower limit, and when the upper limit is exceeded, processing is difficult because it is different depending on the equipment process limit.

As described above, the mixture of the mixed resin, the pyrogenic nucleating agent, and the gas for securing the low dielectric constant is then foamed (S4). In this case, the foaming degree is preferably proceeded to be 80% or more.

In addition, the foamed foamed through the step (S4) may be formed to insulator layer by extruding to wrap the upper surface of the inner skin layer in a layered form (S5).

At this time, the insulator layer extruded in the step (S5) has a closed-cell shape therein, and includes a foam cell having a long radius of 10 to 500 ㎛. In the long radius value range of the foam cell, if it is less than the lower limit technically difficult to implement, due to the inter-foam dielectric constant between foam cells, the transmission rate is slow and the signal loss is likely to occur largely, if the upper limit is exceeded It is not desirable because the external appearance of the product is uneven or the spacing between cells is uneven.

Insulator layer formed through the step (S5) is preferably formed by extrusion so as to be 60 to 170% thickness of the inner diameter of the center conductor. In the limitation of the insulator layer thickness value, the capacitance is increased and the impedance is decreased when the thickness is less than the lower limit, and when the upper limit is exceeded, the impedance is greatly increased, which is not preferable.

The large-diameter coaxial cable including the insulator layer of the present invention having a foamed cell having a foamed cell having a foaming degree of 80% or more and a closed pore shape having a long pore size of 10 to 500 μm as described above is a cylindrical center conductor, the center conductor. It includes an inner skin layer to wrap, an insulator layer surrounding the inner skin layer in a layer, an outer skin layer surrounding the insulator layer, an outer conductor provided on the outer circumferential surface of the outer skin layer, and a covering layer completely surrounding the outer conductor. .

Hereinafter, a large diameter coaxial cable of the present invention will be described with reference to FIG. 1.

1 is a cross-sectional view showing a large diameter coaxial cable according to an embodiment of the present invention. As shown in FIG. 1, the structure of the large-diameter coaxial cable according to an embodiment of the present invention includes a center conductor 10, an inner skin layer 20 surrounding the center conductor 10, and the inner skin layer ( Insulator layer 30 surrounding the layer 20, outer skin layer 40 surrounding the insulator layer 30, outer conductor 50 provided on the outer circumferential surface of the outer skin layer 40, and the outside It consists of a coating layer 60 completely surrounding the conductor 50. That is, the large-diameter coaxial cable according to the embodiment of the present invention has a foamed degree of the insulation layer 30 of 80% or more in the large-diameter coaxial cable having the structure described above, and has a closed-cell shape. The long radius is characterized in that it comprises a foam cell of 10 to 500 ㎛.

The center conductor 10 has a diameter of about 9 to 10 mm, is manufactured using copper or a copper alloy having a thickness of about 0.5 mm, and has a hollow cylindrical structure in consideration of high frequency characteristics.

The inner skin layer 201 surrounding the center conductor 10 may be formed of polyethylene (PE) or the like.

The outer skin of the inner skin layer 20 is formed in the insulator layer 30 in order to improve the transmission characteristics, the insulator layer 30 is preferably formed so as to have a thickness of 60 to 166% of the inner diameter of the center conductor. Since the description of the insulator layer 30 is as described above, a detailed description thereof will be omitted.

The outer skin layer 40 surrounding the insulator layer 30 may be formed of polyethylene (PE) or the like.

The outer conductor 50 provided on the outer circumferential surface of the outer skin layer 40 is formed to suppress the loss of electromagnetic waves, and has a metal tube shape made of copper or a copper alloy to prevent loss of an electrical signal. The metal tube is in contact with the outer skin layer 40 and the coating layer 60 in the form of a corrugated tube having surface curvatures such that there is no change in properties even when repeated bending and no external moisture can penetrate.

The covering layer 60 completely surrounding the outer conductor 50 serves as a jacket to protect the coaxial cable of the present invention.

The coating layer 60 may be formed of polyethylene (PE) or the like.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

Example 1

Azodicarboamide was added in an amount of 200 ppm as a pyrogenic nucleating agent to a mixed resin obtained by mixing 55 wt% of high density polyethylene (HDPE) and 45 wt% of low density polyethylene (LDPE) as a resin for forming an insulator layer. The mixture was pressurized to 250 bar level by adding CO ₂ as a gas for securing a low dielectric constant.

The mixture was foamed and extruded to form an insulator layer by wrapping the upper surface of the inner layer layer surrounding the center conductor using the foamed foam. Then, an outer skin layer, an outer conductor, and a covering layer were formed on the insulator layer by a conventional method to produce a coaxial cable.

Example 2 and Comparative Examples 1-2

It carried out in the same manner as in Example 1 except that it was carried out under the conditions shown in Table 1.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Suzy HDPE / LDPE HDPE / LDPE MDPE / LDPE HDPE / LDPE Mixing ratio 55/45 70/30 50/50 50/50 Nuclear agent Azodicarboamides as pyrogenic nuclei Azodicarboamides as pyrogenic nuclei Sodium Carbonate As Endothermic Nucleating Agent Azodicarboamide as a pyrogenic nucleating agent + Sodium carbonate as an endothermic nucleating agent Low dielectric constant gas CO ₂ CO ₂ N ₂ Freon Pressurization (bar) 250 280 130 120

Using the coaxial cable prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the degree of foaming and the loss (dB / Km at 2 GHz) were respectively measured by the following method, and the results were measured. It is shown in Table 2 below.

First, the degree of foaming was measured by measuring the specific gravity of the foam, and the signal loss was measured by the network analyzer.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Firing degree 84% 85% 77% 75% Loss 3.4 dB 3.4 dB 3.9 dB 4.0 dB

As shown in Table 2, Examples 1 and 2 prepared according to the present invention was confirmed that the foaming degree is higher than 80%, and the signal loss is also excellent compared to Comparative Examples 1 and 2.

SEM images of each of the foamed cross-sections are shown in FIGS. 2 to 3 using the coaxial cables prepared in Example 2 and Comparative Examples 1 to 2. FIG.

2 shows that the coaxial cable of Example 2 manufactured according to the present invention is a uniform closed foam cell, in which a coating layer of the same composition and a foam cell adjacent to the foam cell are continuously formed on the interface of the foam cell. .

3 is a coaxial cable of Comparative Example 1 and Comparative Example 2, in the case of Comparative Example 1 foam cells are not formed in the neighboring and irregular foam cells are formed irregularly (Fig. 3a), or cooling conditions are not smooth foaming The cell burst (FIG. 3B), and in the case of Comparative Example 2, it could be confirmed that the cell became longer in association with the neighboring cell (FIG. 3C).

Through the above results, Examples 1 and 2 prepared according to the present invention was able to secure a foam size of a uniform size, unlike Comparative Examples 1 and 2, the locality of the dielectric constant due to bursting or partial aggregation of the foam Since the difference can be suppressed, signal degradation due to high frequency transmission can be suppressed and ultra high speed transmission is possible.

In addition, the loss characteristics (attenuation) of the coaxial cable manufactured in Example 2 and Comparative Example 2 was measured to a range of 30 MHz to 3 GHz using a network analyzer, and the results are shown in FIGS. 4 and 5.

Figure 4 shows the loss characteristics of the coaxial cable prepared according to Example 2, the coaxial cable of Example 2 is greatly improved in the dielectric properties by uniform foaming, the attenuation is about 5.4 dB at 2 GHz, about 3 GHz at about It was confirmed that it is 6.9 dB.

Figure 5 shows the loss characteristics of the coaxial cable prepared according to Comparative Example 2, the loss of the coaxial cable of Comparative Example 2 is greatly increased as the frequency is increased is about 6.15 dB at 2 GHz, about 8.03 dB at 3 GHz I could confirm it.

Through the above results, it can be seen that the coaxial cable of Example 2 according to the present invention has an average loss characteristic of about 10% compared with Comparative Example 2 according to the prior art.

Optimal embodiments of the present invention described above have been disclosed. Although specific terms have been used herein, they are used only for the purpose of describing the present invention in detail to those skilled in the art and are not intended to limit the scope of the present invention as defined in the claims or the claims.

The low-loss large-diameter coaxial cable insulator according to the present invention can minimize the signal loss by foaming the insulating material to a high level, the signal interference up to the high-speed signal transmission even in the ultra-high frequency transmission of the GHz band, uniform foaming characteristics It is possible to manufacture a very large coaxial cable with high speed and high-capacity signal transmission, and by suppressing abnormal association of foams, it does not cause a difference in dielectric properties between foamed and non-foamed, so that no group delay occurs. There is an effect that can ensure a good signal characteristics such as.

Claims (11)

Insulator used in coaxial cable, The insulator has a foaming degree of 80% or more, a closed-cell shape, the long radius of the insulator for coaxial cable, characterized in that it comprises a foam cell of 10 to 500 ㎛. Cylindrical center conductor; An inner skin layer surrounding the center conductor; An insulator layer surrounding the inner skin layer in a layered manner; An outer skin layer surrounding the insulator layer; An outer conductor provided on an outer circumferential surface of the outer skin layer; And In the low-loss large-diameter coaxial cable comprising a; covering layer completely surrounding the outer conductor; The insulator layer is a low-loss large-diameter coaxial cable, characterized in that the foaming degree is 80% or more, and a closed-cell shape, the long radius is 10 to 500 ㎛. The method of claim 2, The insulator layer is a low loss large diameter coaxial cable, characterized in that formed to a thickness of 60 to 170% of the inner diameter of the center conductor. A cylindrical center conductor, an inner skin layer surrounding the center conductor, an insulator layer surrounding the inner skin layer in layers, an outer skin layer surrounding the dielectric layer, an outer conductor provided on the outer circumferential surface of the outer skin layer and the outer conductor completely In the method of manufacturing the insulator layer of a low loss large diameter coaxial cable comprising a covering layer wrapped around, (S1) preparing a resin in which high density polyethylene (HDPE) and low density polyethylene (LDPE) are mixed; (S2) adding a pyrogenic nucleating agent to the mixed resin; (S3) injecting a gas for securing a low dielectric constant to the mixed resin; (S4) foaming the prepared mixed resin; And (S5) a step of extruding the foam so as to surround the upper surface of the inner skin layer in a layered; low loss large diameter coaxial cable insulator layer manufacturing method comprising the. The method of claim 4, wherein The mixed resin of step (S1) is a high-density polyethylene (HDPE) is 45 to 75% by weight, low-density polyethylene (LDPE) is a mixed resin of 25 to 55% by weight, low loss large diameter coaxial insulator layer production Way. The method of claim 4, wherein The pyrogenic nucleating agent of step (S2) is azodicarbonamide (Azodicarbonamide), sulfonylhydrazides (Sulfonylhydrazides) and 5-phenyltetrazole (Phenyltetrazole), characterized in that any one or a mixture of two or more selected from Insulation layer manufacturing method for low loss large diameter coaxial cable. The method of claim 6, The pyrogenic nucleating agent is a method of manufacturing an insulator layer for a low loss large diameter coaxial cable, characterized in that the content of 150 to 750 ppm relative to the total weight of the mixed resin. The method of claim 4, wherein The low dielectric constant securing gas of step (S3) is carbon dioxide (CO ₂ ), characterized in that the low-loss large-diameter coaxial cable insulator layer manufacturing method. The method of claim 4, wherein The foaming of the step (S4), the low-loss large-diameter coaxial cable insulator layer manufacturing method characterized in that the foaming to proceed to 80% or more. The method of claim 4, wherein The method of manufacturing an insulator layer for low-loss large-diameter coaxial cable, characterized in that the insulator layer extruded in the step (S5) has a thickness of 60 to 170% of the inner diameter of the center conductor. The method of claim 4, wherein The insulator layer extruded in the step (S5) has a closed-cell shape therein, the low-loss large-diameter coaxial cable insulator, characterized in that it comprises a foam cell having a long radius of 10 to 500 ㎛ Layer manufacturing method.

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