JP2003068152A - High foaming and high frequency coaxial cable and method of manufacturing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high foaming and high frequency coaxial cable with a less damping amount and a less voltage standing-wave ratio. SOLUTION: A high foaming insulation layer 3 around an inner conductor 2 is formed of a compound manufactured by adding low density polyethylene of 0.925 to 0.930 g/cm<3> in density, to which foaming core agent is added beforehand, to a high density polyethylene of 0.94 g/cm<3> or more in density synthesized through a metallocene catalyst at a ratio of 45 to 5 pts.wt. to 55 to 95 pts.wt. Thus, since the damping amount can be reduced and the occurrence of pin holes are suppressed, the high foaming and high frequency coaxial cable 1 with a less voltage standing-wave ratio can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-foaming high-frequency coaxial cable used in mobile communication facilities, microwave communication facilities and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, as a foam insulating layer of a high frequency high foam coaxial cable used in a mobile communication facility, a microwave communication facility, etc., conventionally, a high melt tension (MS) and Based on low density polyethylene (LDPE), which is easy to foam, the dielectric loss tangent (t
LDPE obtained by blending high density polyethylene (HDPE) with low an δ) and low attenuation, and foaming this
A rich mixed resin is used.

Recently, however, the frequency of use of the high-frequency high-foam coaxial cable has tended to increase for the purpose of increasing the communication speed and capacity, and accordingly, a cable with less transmission loss, that is, less attenuation is required. However, the conventional L
The DPE-rich mixed resin is no longer able to deal with it.

Therefore, it is conceivable to use a HDPE-rich mixed resin in which the ratio of HDPE having a smaller attenuation amount is increased. However, if the ratio of HDPE is simply increased, cavities are formed in the foam insulating layer due to the breakage of the bubble wall. It may occur. That is, the nest is generated by the voltage standing wave ratio (V
Since the SWR is increased, it becomes a fatal defect as a high frequency cable.

Therefore, the present invention has been devised in order to effectively solve such a problem, and its purpose is to provide a novel high-foaming high-frequency coaxial cable having a small amount of attenuation and a small voltage standing wave ratio. It provides a cable.

[0006]

In order to solve the above problems, the present invention provides a high-foaming high-frequency coaxial cable in which the periphery of an inner conductor is covered with a high-foaming insulating layer, wherein the foamed insulating layer is
A density of 0.925 to 0.930 g / in which a foaming nucleating agent was added in advance to 55 to 95 parts by weight of high density polyethylene synthesized with a metallocene catalyst and having a density of 0.94 g / cm ³ or more
It is made by foaming a compound in which 45 to 5 parts by weight of low-density polyethylene of ³ cm ³ is added, and this reduces the amount of attenuation and suppresses the generation of cavities, so that the voltage standing wave ratio is small and high. A foamed high frequency coaxial cable is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a high-foaming high-frequency coaxial cable (hereinafter referred to as a coaxial cable) 1 according to the present invention.

As shown in the figure, this coaxial cable 1 integrally covers the periphery of an inner conductor 2 made of annealed copper wire or the like with a foam insulating layer 3, and surrounds the outer conductor 4 made of a copper tape, a copper waveguide or the like. And a surrounding portion thereof is covered with a sheath 5 made of polyethylene or the like.

The foamed insulating layer 3 used in the present invention
Is a density of 0.94 g / cm synthesized with a metallocene catalyst.
^{As a} foaming nucleating agent, a mixed resin obtained by adding 45 to 5 parts by weight of low density polyethylene (LDPE) having a density of 0.925 to 0.930 g / cm ³ to 55 to 95 parts by weight of high density polyethylene (HDPE) of ³ or more is used. It is foamed using a foaming agent (gas), and its melt flow rate (MFR)
Is in the range of 1 to 5 g / 10 minutes.

The HDPE-rich resin is used here for the purpose of reducing the dielectric loss tangent (tan δ) in the high frequency band. This dielectric loss tangent is closely related to the density of polyethylene and if the impurities are the same. This is because the higher the density, the smaller the density. In addition, H synthesized with a metallocene catalyst
The reason why DPE is used is that the dielectric loss tangent is smaller than that using a conventional Ziegler catalyst or Phillips catalyst, because the amount of catalyst, residue and the like during synthesis are small.

Blending with LDPE is also because HDPE synthesized by a metallocene catalyst has a narrow molecular weight distribution, and thus has a small melt tension (MS) alone, but when blended with LDPE, the molecular weight distribution becomes broad and melt tension increases. Because it does. The melt tension (MS) is the strength when the resin is melted, and the larger this value, the more difficult it is to form cavities during cable production.

The LDPE used in the present invention must have a density of 0.925 to 0.930 g / cm ^{3 in} terms of dielectric loss tangent. That is, as a conventional LDPE,
While density is of the order of 0.920 g / cm ³ is used, by way of a density less than 0.925 g / cm ³ dielectric loss tangent (tan [delta) is large, the items exceeding 0.930 g / cm ³ to melt back This is because the tension (MS) is lowered and the nests are easily generated.

The melt flow rate (MFR) of this mixed resin is defined as 1 to 5 g / 10 minutes by 1 g / min.
This is because if the time is less than 10 minutes, the heat of the resin during manufacturing is large and temperature unevenness inside and outside the insulating layer 3 is likely to occur, resulting in the formation of cavities. Conversely, if it exceeds 5 g / 10 minutes, the melt tension (MS)
This is due to a decrease in the number of nests and the likelihood of nest formation.
The melt flow rate (MFR) referred to here is JI
It is a value measured at 190 ° C. and 21.18 N based on S-K7210.

The gas used as the foaming agent is not particularly limited, and for example, non-regulated fluorocarbon gas, nitrogen gas, carbon dioxide gas, and a mixed gas of these inert gases may be used.

The reason for adding the foam nucleating agent is to form uniform cells, which are conventionally used.
For example, azodicarbonamide (ADCA), BN, silica, talc, etc. can be used, but among them, phthalic acid hydrazide which has a high decomposition temperature of 300 ° C. or higher and does not affect the dielectric loss tangent (tan δ) is most suitable. is there.

The amount of the foam nucleating agent added is preferably 0.02 to 3.0 parts by weight with respect to 100 parts by weight of the mixed resin. That is, if the amount is less than 0.02 parts by weight, uniform bubbles cannot be obtained. On the contrary, if the amount exceeds 3.0 parts by weight, not only the attenuation amount is deteriorated, but also the particles are aggregated or the obtained bubble diameter becomes nonuniform. This is because it will end up.

In the coaxial cable 1 of the present invention having the foamed insulating layer 3 as described above, as will be demonstrated from the following examples, for example, the amount of 2 GHz attenuation is small and the voltage standing wave ratio is small. It is possible to exhibit excellent transmission characteristics with a small (VSWR).

[0019]

EXAMPLES Example 1 First, as shown in the column of Example 1 in Table 1 below, HDP synthesized by a metallocene catalyst was used.
E (density 0.943 g / cm ³ , MFR 4.0 g / 10
Min) 70 parts by weight, and density 0.928 g / cm ³ , MF
(R 0.5 g / 10 min) LDPE 30 parts by weight of 100 parts by weight of a mixed resin was blended with 1 part by weight of phthalic acid hydrazide as a foam nucleating agent to form a compound. After injecting an appropriate amount of nitrogen gas, which is a foaming agent, with the gas injecting device 7 in the extruder 6,
After kneading well with the resin, the temperature is lowered to a temperature suitable for foaming by the second extruder 8, the foaming resin is coated on the conductor by the extrusion head 9 and is cooled by the cooling water tank 10 to produce a foamed insulator, and thereafter. , The characteristics of this cable, specifically 2GHz
The amount of attenuation, the voltage standing ratio (VSWR), and the presence or absence of nests were evaluated.

As a method of producing this compound, a nucleating agent masterbatch is prepared by previously kneading the LDPE with a foaming nucleating agent 10 times, and the remaining resin is added to this LDPE at a concentration of 0.02 to 0.02. It was prepared by dry blending so as to be between 3 parts by weight.

(Examples 2 to 5) Examples 2 to 1 shown in Table 1 below.
As shown in the column of 5, the density of each LDPE is 0.
928 g / cm ³ , MFR 1.0 g / 10 min, density 0.
928 g / cm ³ , MFR 2.0 g / 10 min, density 0.
925 g / cm ³ , MFR 3.3 g / 10 min, density 0.
A cable was produced in the same manner as in Example 1 except that 930 g / cm ³ and MFR 2.0 g / 10 min were used, and the respective cable characteristics were evaluated.

Example 6 Similar to Example 2, except that 0.1 part by weight of ADCA (azodicarbonamide) was used as a foam nucleating agent as shown in the column of Example 6 of Table 1 below. A cable was produced by the method and its cable characteristics were evaluated.

(Examples 7 and 8) LDPE having a density of 0.
928 g / cm ³ , MFR 1.0 g / 10 min, H
DPE (density 0.943 g / cm ³ , MFR 4.0 g /
Cables were produced in the same manner as in Example 1 except that the compounding ratio with 10 minutes) was changed, and the respective cable characteristics were evaluated.

(Comparative Example 1) As shown in the column of Comparative Example 1 in Table 1 below, the density of LDPE was 0.919 g / c.
Example ³ except that m ³ , MFR 4.0 g / 10 min was used.
A cable was produced in the same manner as in (1) and the cable characteristics were evaluated.

Comparative Example 2 HDPE synthesized with a Ziegler catalyst as shown in the column of Comparative Example 2 in Table 1 below.
A cable was produced in the same manner as in Example 2 except that was used, and the cable characteristics were evaluated.

Comparative Example 3 As shown in the column of Comparative Example 3 in Table 1 below, the blending ratio of HDPE and LDPE is 40: 6.
A cable was produced in the same manner as in Example 2 except that the value was 0, and the cable characteristics were evaluated.

Comparative Example 4 As shown in the column of Comparative Example 4 in Table 1 below, a cable was prepared in the same manner as in Example 1 except that HDPE was used alone and a resin containing no LDPE was used. It was produced and its cable characteristics were evaluated.

(Comparative Examples 5 and 6) As shown in the columns of Comparative Examples 5 and 6 in Table 1 below, resins in which no foam nucleating agent was added and when the amount of the foam nucleating agent was 5 parts by weight. A cable was produced in the same manner as in Example 2 except that was used, and the cable characteristics were evaluated.

[0029]

[Table 1]

As a result, as shown in the lower column of Table 1, in the cables of Examples 1 to 8 according to the present invention, 2 GHz was used.
Is standard (6.5 dB / 100 m or less)
Satisfied. In addition, all cables have no nests, and the voltage standing ratio (VSWR) standard (1.1 or less)
Was also satisfied.

On the other hand, in Comparative Example 1 in which the LDPE used was outside the specified value of the present invention, the amount of attenuation was large and it was rejected. Further, in Comparative Example 2 using HDPE other than the metallocene type, not only the amount of attenuation but also the voltage standing ratio became large, and all failed. Further, in Comparative Example 3 in which the compounding ratio of HDPE and LDPE was outside the specified value of the present invention, that is, in Comparative Example 3 in which the LDPE-rich compound was used, the amount of attenuation increased and the test failed. In addition, in Comparative Example 4 in which HDPE was used alone, a large nest was generated, and it was not possible to form a cable. Further, in Comparative Example 5 in which the amount of the foam nucleating agent added is within the range of the present invention, it is impossible to form a cable, and in contrast, in Comparative Example 6 in which the amount exceeds the range, the amount of attenuation becomes large, which is unsatisfactory. It has passed.

[0032]

In summary, according to the present invention, it is easy to provide a high-performance high-foaming high-frequency coaxial cable which has a small amount of attenuation at 2 GHz which is a high frequency band, suppresses the generation of nests, and has a small voltage standing wave ratio. Can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of a high-foaming high-frequency coaxial cable according to the present invention.

FIG. 2 is a conceptual diagram showing a manufacturing apparatus and a manufacturing method of a high-foaming high-frequency coaxial cable according to the present invention.

[Explanation of symbols]

1 High-foam high-frequency coaxial cable 2 inner conductor 3 Foam insulation layer 4 outer conductor 5 sheath 6 First extruder 7 gas injector 8 Second extruder 9 Extrusion head 10 cooling water tank

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01B 13/00 553 H01B 13/00 553Z // B29K 23:00 B29K 23:00 105: 04 105: 04 105 : 22 105: 22 B29L 31:34 B29L 31:34 (72) Inventor Akira Shoji 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Kimihiro Yokoyama Ibaraki Prefecture 880, Sunazawa-machi, Hitachi City F-term in Takasago Plant, Hitachi Cable Co., Ltd. (reference) 4F074 AA18A AA20A AD13 AG20 BA20 BA33 CA22 4F207 AA05 AA07 AB02 AD03 AD15 AG20 AH35 KA01 KA11 KB18 KF02 KF04 KF04 K204BB02 05F1 KB04 EQ0 FD326 GQ00 5G323 HA03

Claims (5)

[Claims] 1. A high-foam high-frequency coaxial cable in which the periphery of an inner conductor is covered with a high-foam insulation layer, wherein the foam insulation layer is synthesized with a metallocene catalyst and has a density of 0.94 g / cm.
^For 55 to 95 parts by weight of ³ or more high density polyethylene,
Density 0.925 to 0.930 with foam nucleating agent added in advance
A high-foaming high-frequency coaxial cable, which is obtained by foaming a compound to which 45 to 5 parts by weight of low-density polyethylene of g / cm ³ is added. 2. The high-foaming high-frequency coaxial cable according to claim 1, wherein the melt flow rate (MFR) of the compound is in the range of 1 to 5 g / 10 minutes. 3. A method for producing a high-foaming high-frequency coaxial cable in which the periphery of an inner conductor is covered with a foaming insulating layer, relative to 55 to 95 parts by weight of high-density polyethylene having a density of 0.94 g / cm ³ or more synthesized with a metallocene catalyst. After compounding 45 to 5 parts by weight of low density polyethylene having a density of 0.925 to 0.930 g / cm ³ to which a foam nucleating agent has been added in advance, a compound is obtained and then extruded onto the inner conductor while foaming the compound. A method of manufacturing a high-foaming high-frequency coaxial cable, which comprises covering and forming the foamed insulating layer. 4. The foam nucleating agent is added to the compound 100.
The method for producing a high-foaming high-frequency coaxial cable according to claim 3, wherein 0.02 to 3 parts by weight is added per part by weight. 5. The method for producing a high-foaming high-frequency coaxial cable according to claim 3, wherein phthalic acid hydrazide is used as the foam nucleating agent.