JP4951704B1 - Insulated wires for transmission cables and transmission cables - Google Patents

Abstract

To provide an insulated wire and a cable capable of achieving both excellent dielectric characteristics in the GHz band, excellent heat aging characteristics, and excellent flexibility.
SOLUTION: An insulated wire 5 comprising a conductor 1 and an insulating layer 2 covering the conductor 1, wherein the insulating layer 2 is obtained by synthesizing using a metallocene catalyst, and a hindered phenol structure. And an antioxidant having a different chemical structure, wherein the antioxidant is blended at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of polyethylene. Insulated wire 5.
[Selection] Figure 1

Description

The present invention relates to an insulated wire for a transmission cable and a transmission cable.

  In recent years, with the development of electronic devices that use frequencies in the GHz band, it is superior in the GHz band over high-speed transmission cables such as USB3.0 cables, HDMI cables, Infiniband cables, and micro USB cables that connect devices. It is required to have a dielectric property.

  As such a transmission cable, for example, a cable described in Patent Document 1 below is known. In the following Patent Document 1, an insulating layer covering a conductor is excellent by using a olefinic resin such as polyethylene and a phenolic antioxidant that does not have a hindered phenol structure as an antioxidant. It has been proposed to obtain good dielectric properties.

JP 2009-81132 A

  However, since the cable described in Patent Document 1 contains an antioxidant together with polyethylene in the insulating layer, it has excellent heat aging resistance and also exhibits good flexibility due to the flexibility of polyethylene itself. However, there is still room for improvement in the dielectric characteristics in the high frequency band.

The present invention has been made in view of the above circumstances, and provides an insulated wire for a transmission cable and a transmission cable that can achieve both excellent dielectric characteristics in the GHz band, excellent heat aging characteristics, and excellent flexibility. For the purpose.

  As a result of intensive studies to solve the above problems, the present inventor generally used polyethylene as an insulated wire is synthesized using a general-purpose catalyst such as a Ziegler-Natta catalyst. Polyethylene has a wide molecular weight distribution and includes a large amount of low molecular weight polyethylene, and this low molecular weight polyethylene tends to undergo molecular vibrations at high frequencies, thus easily causing thermal loss. I thought it would increase the tangent. Therefore, as a result of further earnest research, the present inventors made polyethylene synthesized using a metallocene catalyst, and blended an antioxidant having a specific structure with a predetermined ratio with respect to polyethylene. Thus, the present inventors have found that the above problem can be solved, and have completed the present invention.

That is, the present invention relates to an insulated wire for a transmission cable comprising a conductor and an insulating layer covering the conductor, wherein the insulating layer is obtained by synthesizing using a metallocene catalyst, and semi-hindered A phenolic antioxidant or a hindered phenolic antioxidant, and a metal deactivator having a chemical structure different from the hindered phenolic structure, and the antioxidant is added in an amount of 0. 01 parts by mass or more and less than 1.5 parts by mass, and the metal deactivator is 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of polyethylene. It is the insulated wire for transmission cables characterized by being mix | blended by the ratio .

According to this insulated cable for transmission cable, since the polyethylene contained in the insulating layer is synthesized by synthesizing using a metallocene catalyst, it was synthesized using a general-purpose catalyst such as a Ziegler-Natta catalyst. Compared to polyethylene, the molecular weight distribution can be narrowed. For this reason, in the insulating layer, since the molecular vibration is likely to occur with respect to the high frequency, the ratio of the low molecular weight polyethylene that causes a large dielectric loss tangent can be sufficiently reduced. In addition, polyethylene is easily oxidized and deteriorated by contact with a conductor, and molecules are easily cut. In that respect, in the present invention, the semi-hindered phenol antioxidant or the less hindered phenol antioxidant is blended at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of polyethylene. The Thereby, the thermal deterioration of polyethylene can be suppressed sufficiently. Furthermore, in this invention, the metal deactivator which has a chemical structure different from a hindered phenol structure is mix | blended in the ratio of 0.01 mass part or more and less than 1.5 mass parts with respect to 100 mass parts of polyethylene. Thereby, the heat aging resistance of an insulated wire improves more. Furthermore, since the base resin contained in the insulating layer is polyethylene, the flexibility of the insulated wire can be increased as compared with the propylene-based resin. Therefore, according to the insulated wire for a transmission cable of the present invention, it is possible to achieve both excellent dielectric characteristics in the GHz band, excellent heat aging characteristics, and excellent flexibility.

  In the insulated wire, the insulating layer is preferably cross-linked with an electron beam.

  In this case, since it is not necessary to add an additive for cross-linking in the insulating layer, a decrease in dielectric properties can be sufficiently suppressed, and the cross-linking can be used even in an environment higher than the melting point of polyethylene.

Moreover, this invention is a transmission cable which has the insulated wire for transmission cables mentioned above.

ADVANTAGE OF THE INVENTION According to this invention, the insulated wire for transmission cables and transmission cable which can make the outstanding dielectric characteristic in a GHz band, the outstanding heat aging characteristic, and the outstanding softness | flexibility compatible are provided.

It is a partial side view which shows one Embodiment of the transmission cable of this invention. It is sectional drawing along the II-II line of FIG. It is an end view which shows other embodiment of the transmission cable of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 is a partial side view showing an embodiment of a cable according to the present invention, and shows an example in which an electric wire is applied to a coaxial cable as a cable. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIG. 1, the cable 10 is a coaxial cable, and includes an insulated wire 5, an outer conductor 3 that surrounds the insulated wire 5, and a sheath 4 that covers the outer conductor 3. The insulated wire 5 includes an inner conductor 1 and an insulating layer 2 that covers the inner conductor 1.

  Here, the insulating layer 2 contains, as a base resin, polyethylene obtained by synthesis using a metallocene catalyst and an antioxidant having a chemical structure different from the hindered phenol structure. Here, antioxidant is mix | blended in the ratio of 0.01 mass part or more and less than 1.5 mass parts with respect to 100 mass parts of polyethylene.

  According to the cable 10, by using the insulated wire 5 using the insulating layer 2 having the above configuration, it is possible to realize excellent dielectric characteristics in the GHz band. The present inventor believes that the reason why the insulated wire 5 can realize excellent dielectric characteristics in the GHz band is as follows. That is, since the polyethylene contained in the insulating layer 2 is obtained by synthesis using a metallocene catalyst, it has a molecular weight distribution compared to polyethylene synthesized using a general-purpose catalyst such as a Ziegler-Natta catalyst. The width can be reduced. For this reason, in the insulating layer 2, it is possible to sufficiently reduce the proportion of low molecular weight polyethylene, which is likely to cause molecular vibration with respect to high frequencies in the GHz band and is considered to be a factor that increases the dielectric loss tangent. For this reason, according to the insulated wire 5, the inventor believes that excellent dielectric characteristics can be realized as described above.

  The insulating layer 2 contains an antioxidant having a chemical structure different from the hindered phenol structure, and the antioxidant is 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of polyethylene. Blended in proportions. Thereby, the thermal deterioration of polyethylene by the inner conductor 1 can be sufficiently suppressed, and the so-called Bloom phenomenon in which the antioxidant particles are floated on the surface of the insulating layer 2 can be sufficiently suppressed.

  Furthermore, since the base resin contained in the insulating layer 2 is polyethylene, the flexibility of the insulated wire 5 can be increased as compared with the propylene-based resin.

  For this reason, according to the cable 10, it is possible to achieve both excellent dielectric characteristics in the GHz band, excellent heat aging characteristics, and excellent flexibility.

  Next, a method for manufacturing the cable 10 will be described.

  First, a method for manufacturing the insulated wire 5 will be described.

<Inner conductor>
First, the inner conductor 1 is prepared. Examples of the inner conductor 1 include a metal wire made of a metal such as copper, a copper alloy, and aluminum. These metals can be used alone or in combination. Further, the internal conductor 1 may be formed by using the metal wire as a main body and plating the surface thereof with tin or silver to form a plating film. The inner conductor 1 can be a single wire or a stranded wire.

<Insulating layer>
Next, the insulating layer 2 is formed on the inner conductor 1.

  In order to form the insulating layer 2, polyethylene as a base resin and an antioxidant are prepared.

(Base resin)
Polyethylene is polyethylene obtained by synthesis using a metallocene catalyst. Examples of polyethylene that can be used include high-density polyethylene, medium-density polyethylene, and low-density polyethylene.

High density polyethylene usually has a density of 0.950 to 0.965 g / cm ³ . Medium density polyethylene usually has a density of 0.930 to 0.949 g / cm ³ . Low density polyethylene usually has a density of 0.90 to 0.929 g / cm ³ .

  The melting point of polyethylene is preferably 117 ° C to 129 ° C. Here, the melting point refers to the melting point measured according to the method of JIS-K7121. Specifically, with DSC (Perkin Elmer Diamond (input compensation type)), the amount of the sample is about 5 mg, and the sample is kept 1) isothermally at 200 ° C. for 10 minutes. 2) 10 ° C. from 200 ° C. to −60 ° C. 3) Keeping isothermal at -60 ° C for 10 minutes, 4) Heat of fusion observed under the conditions of 4) when the temperature is raised from -60 ° C to 200 ° C at 10 ° C / min. The melting heat peak temperature obtained as the apex of the peak portion is referred to as the melting point. When the melting point of polyethylene is within the above range, it is possible to obtain more sufficient heat resistance and higher crystallinity than when the melting point is less than 117 ° C. Can do. Moreover, compared with the case where melting | fusing point exceeds 129 degreeC, the softness | flexibility is excellent and the advantage that a chemical stress crack does not produce easily is acquired.

  The melting point of polyethylene is more preferably 120 to 128 ° C, still more preferably 122 to 127 ° C.

The polyethylene preferably has a crystallinity of 50 to 64%, and more preferably has a crystallinity of 55 to 63%. Here, the crystallinity is the following formula:
Xc = Hm / H _m0
(In the above formula, Xc represents crystallinity [%], Hm represents heat of fusion [J / g], and H _m0 represents 100% heat of crystallization [J / g].)
Is defined by Here, Hm is the melting heat of the melting heat peak observed in the above-described measurement of the melting point of polyethylene , and the value obtained by the method of JIS-K7122 is used as the heat of fusion. A value of 277.5 J / g is used as H _m0 . Here, the value of H _m0 is quoted from J. Brandup and EM Innergut: Polymer Handbook, Interscience New York (1965).

  In this case, when the crystallinity of polyethylene is within the above range, the ratio of amorphous components that are susceptible to molecular vibration in the high frequency band is further reduced as compared with the case where the crystallinity is less than 50%. Can be lowered. Further, more appropriate flexibility can be obtained as compared with the case where the crystallinity of polyethylene exceeds 64%.

(Antioxidant)
The antioxidant may be any as long as it is for preventing deterioration of the base resin due to contact with the inner conductor 1.

  As the antioxidant, for example, a phenolic antioxidant having a chemical structure different from the hindered phenol structure is used.

  Examples of the phenol-based antioxidant having a chemical structure different from the hindered phenol structure include semi-hindered phenol-based antioxidants and res-hindered phenol-based antioxidants.

As the semi-hindered phenol-based antioxidant, 3,9-bis [2- {3- (3-tertiarybutyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] is used. -2,4,8,10-tetraoxaspiro [5,5] undecane (e.g. ADEKA ADK STAB AO-80), ethylenebis ( oxyethylene ) bis [3- (5-tert-butyl-hydroxy-m -Tolyl) propionate] (for example, Irganox 245 from BASF), triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ] (for example, ADEKA STAB AO- from ADEKA) 70).

  As the hindered phenol-based antioxidant, 4,4′-thiobis (3-methyl-6-tertiarybutyl) phenol (for example, Nocrack 300 of Ouchi Shinsei Chemical Co., Ltd.), 1,1,3- Tris- (2-methyl-4-hydroxy-5-tertiarybutylphenyl) butane (for example, ADEKA ADEKA STAB AO-30), 4,4′-butylidenebis (3-methyl-6-tertiarybutyl) phenol ( For example, ADEKA Adeka Stub AO-40) may be mentioned.

  These antioxidants are relatively insensitive to frequency and can improve the dielectric characteristics in the GHz band.

  The antioxidant is added at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of the polyethylene. In this case, as compared with the case where the antioxidant is blended at a ratio of 1.5 parts by mass or more, the thermal deterioration of polyethylene due to the inner conductor 1 can be sufficiently suppressed, and the antioxidant on the surface of the insulating layer 2. The so-called bloom phenomenon in which the particles of the particles are lifted can be sufficiently suppressed. The antioxidant is more preferably blended at a ratio of 1 part by mass or less with respect to 100 parts by mass of the base resin. However, from the viewpoint of improving the heat aging characteristics by the antioxidant, it is blended at a ratio of 0.05 parts by mass or more with respect to 100 parts by mass of the base resin.

  The insulating layer 2 is made by introducing polyethylene as a base resin, an antioxidant, and if necessary, a metal deactivator into an extruder, melting and kneading the resin composition in the extruder, and extruding it. It is obtained by covering the inner conductor 1 with a material.

  The outer diameter of the insulating layer 2 is preferably 40 mm or less, more preferably 8 mm or less, and particularly preferably 1 mm or less.

  Furthermore, although the thickness of the insulating layer 2 is not particularly limited, it is preferably 0.3 mm or less and more preferably 0.2 mm or less because very excellent flexibility is obtained. . However, the thickness of the insulating layer 2 is usually 0.1 mm or more.

But the thickness of the insulating layer 2 may be larger than 0.3 mm. Even in this case, since the cable 10 has high flexibility, it is useful for applications that require frequent bending. However, the thickness of the insulating layer 2 is usually 6 mm or less because the workability (weight) at the time of laying deteriorates and it is not preferable to increase the amount of copper used unnecessarily.

In the insulated wire 5, the insulating layer 2 may be non-foamed or foamed, but is preferably non-foamed. In the case where the insulating layer 2 is a non-foamed body, the manufacture is easier than in the case of a foamed body. For this reason, it becomes difficult for the deterioration of skew, the deterioration of VSWR, and the accompanying increase in attenuation due to the outer diameter variation of the insulating layer 2 to occur. This becomes more conspicuous when the outer diameter of the insulating layer 2 becomes 0.7 mm or less, in particular, as the diameter of the insulating layer 2 is reduced. In addition, when the insulating layer 2 is a foam, it is preferable that the foaming degree is 30 to 60%. Here, the degree of foaming is calculated based on the following equation.

  In this case, even if a wire using polyethylene for the insulating layer 2 is used as an electric wire for a cable used in the GHz band, the foamed cell can be suppressed from being coarsened, and the foamed state having a fine and uniform foamed cell is used. The insulating layer 2 can be obtained. Further, the cable 10 using the insulated wire 5 has a small outer diameter variation, and even if the insulating layer 2 is made thin, there is little problem of crushing, and variations such as deterioration of attenuation are sufficiently suppressed.

  When the insulating layer 2 is a foamed insulating layer, the foamed insulating layer can be obtained by blending a foaming agent such as a chemical foaming agent in the resin composition.

  Moreover, it is preferable to interpose a thin layer made of unfoamed resin, a so-called inner layer, between the insulating layer 2 and the inner conductor 1. Thereby, the adhesiveness of the insulating layer 2 and the internal conductor 1 can be improved. In particular, when the unfoamed resin is made of polyethylene, the adhesion between the insulating layer 2 and the inner conductor 1 can be further improved. The inner layer may have a thickness of 0.01 to 0.1 mm, for example.

  Furthermore, it is preferable to interpose a thin layer, so-called outer layer, between the insulating layer 2 and the outer conductor 3. Transmission cables often need color. In this case, when an unfoamed resin is used as the thin layer, coloring can be easily performed without deteriorating electric characteristics as compared with the case where coloring is performed using a pigment. Further, when a thin layer made of foamed resin is interposed between the insulating layer 2 and the outer conductor 3, the appearance of the electric wire 5 is improved. That is, fluctuations in the outer diameter of the electric wire 5 are reduced, skew and VSWR are improved, crush resistance is improved, and the outer diameter of the electric wire 5 can be reduced. In addition, what is necessary is just to let the thickness of an outer layer be 0.02-0.2 mm, for example.

  Furthermore, the insulating layer 2 may be obtained by melt-kneading the resin composition and extrusion-coating the internal conductor 1 and then subjecting the extrudate to a crosslinking treatment. In this case, the crosslinking treatment can be performed, for example, by electron beam irradiation, but can also be performed by heating when the resin composition contains a crosslinking agent such as an organic peroxide or sulfur. However, from the viewpoint of improving electrical characteristics, it is preferable to perform the irradiation by electron beam irradiation.

<External conductor>
Next, the outer conductor 3 is formed so as to surround the insulated wire 5 obtained as described above. As the external conductor 3, a known one that has been conventionally used can be used. For example, the external conductor 3 can be formed by winding a conductive wire or a tape formed by sandwiching a conductive sheet between resin sheets along the outer periphery of the insulating layer 2. Further, the outer conductor 3 can be constituted by a corrugated metal tube, that is, a corrugated metal tube.

<Sheath>
Finally, the sheath 4 is formed. The sheath 4 protects the outer conductor 3 from physical or chemical damage. Examples of the material constituting the sheath 4 include resins such as fluororesin, polyethylene, and polyvinyl chloride. From the viewpoint of the above, a halogen-free material such as polyethylene resin is preferably used.

  The cable 10 is obtained as described above.

  FIG. 3 is a cross-sectional view showing a Twinax type cable having the insulated wire 5. As shown in FIG. 3, the Twinax type cable 20 is a laminate comprising two insulated wires 5, a drain wire 6, a laminate tape 7, two power lines 8, an aluminum tape layer and a knitted coarse layer. A layer 9 and a sheath 4 are provided. Here, the two insulated wires 5 are arranged in parallel to each other, and these are used as signal lines. The laminated tape 7 is wound around the insulated wire 5 and the drain wire 6, and the sheath 4 is formed on the laminated body layer 9 so as to surround the laminated body layer 9. The laminate tape 7 is composed of a laminate of, for example, an aluminum foil and a polyethylene terephthalate film, and the sheath 4 is composed of, for example, an olefin-based non-halo material such as ANA 9897N manufactured by Riken Technos. The insulated wire 5 and the insulating layer 2 are the same as those in the above embodiment.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, an example in which the insulated wire 5 is applied to a coaxial cable or a Twinax type cable as a cable is shown, but the insulated wire 5 is a USB 3.0 cable, an HDMI cable, an Infiniband cable, It can also be applied to a high-speed cable such as a micro USB cable.

  Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

( Reference Example 1)
First, 140HK (melting point: 126 ° C., density: 0.937 g / cm ³ ), which is polyethylene obtained by synthesis using a metallocene catalyst, was prepared as a base resin.

  The base resin and antioxidant are used in an extruder (product name: Laboplast Mill 4C150, twin screw segment extruder 2D30W2, screw diameter (D): diameter 25 mm, effective screw length (L): 750 mm, manufactured by Toyo Seiki Seisakusho). The agent was added and melt-kneaded to perform extrusion molding. At this time, the compounding amount of the antioxidant shown in Table 1 was an amount compounded with respect to 100 parts by mass of the base resin (unit: parts by mass), and the melt-kneading temperature was 170 ° C.

  Then, with an extruder (screw diameter (D): diameter 25 mm, effective screw length (L): 800 mm, manufactured by St. Seisakusho Co., Ltd.), the temperature was set to 170 ° C., and the extrudate was extruded into a tube shape. The object was covered with a tin-plated copper wire having a diameter of 0.172 mm. Thus, an insulated wire composed of a conductor and an insulating layer covering the conductor was produced. At this time, the extrudate was extruded so that the outer diameter of the insulating layer was 0.6 mm and the thickness was 0.215 mm.

  The insulated wire thus obtained was wound with a 25 μm thick laminate tape made of a laminate of an aluminum layer and a polyethylene terephthalate layer. Next, this was covered with a sheath made of PVC (polyvinyl chloride) having a thickness of 0.4 mm. Thus, a non-foamed and non-crosslinked coaxial cable having an impedance of 50Ω was produced.

( Reference Examples 2 to 9, Examples 1 to 9, Reference Examples 10 to 11 and Comparative Examples 1 to 6)
Except that the antioxidant and metal deactivator shown in Table 1 were blended in the proportions shown in Table 1 (units are parts by mass) with respect to 100 parts by mass of the base resin shown in Table 1, the same as in Reference Example 1 A coaxial cable was manufactured.

(Comparative Example 7)
The base resin shown in Table 1 was put into an extruder (screw diameter (D): diameter 25 mm, effective screw length (L): 800 mm, manufactured by Holy Seisakusho) at a temperature of 200 ° C., and the extrudate was tube-shaped. Extruded and coated with a tin-plated copper wire having a diameter of 0.172 mm with this tubular extrudate. Thus, an insulated wire composed of a conductor and an insulating layer covering the conductor was produced. At this time, the extrudate was extruded so that the outer diameter of the insulating layer was 0.6 mm and the thickness was 0.215 mm.

A coaxial cable was produced in the same manner as in Reference Example 1 using the insulated wire thus obtained.

In addition, the following were specifically used as the base resin, antioxidant and metal deactivator shown in Table 1.
(1) Base resin (1-1) 140HK (Umerit, manufactured by Ube Maruzen Polyethylene)
m-LLDPE
(1-2) 3540N (Umerit, Ube Maruzen Polyethylene)
m-LLDPE (melting point: 123 ° C., density: 0.931 g / cm ³ )
(1-3) B028 ("UBE polyethylene (registered trademark) B028", manufactured by Ube Maruzen Polyethylene)
Low density polyethylene (melting point 113 ° C., density: 0.928 g / cm ³ )
(1-4) DGDN3364 (Nihon Unicar)
Medium density polyethylene (melting point: 126 ° C., density: 0.945 g / cm ³ )
(1-5) 2070 (Ube Maruzen Polyethylene)
High density polyethylene (melting point: 134 ° C., density: 0.962 g / cm ³ )
(2) Antioxidant (2-1) Semi-hindered phenol antioxidant a) AO-80 (Adeka Stub AO-80, manufactured by ADEKA)
3,9-bis [2- {3- (3-tertiarybutyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane b) AO-70 (ADK STAB AO-70, manufactured by ADEKA)
Triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-
Methylphenyl) propionate]
(2-2) Resin hindered phenol antioxidant a) AO-40 (ADK STAB AO-40, manufactured by ADEKA)
4,4′-Butylidenebis (3-methyl-6-tertiarybutyl) phenol b) AO-30 (ADK STAB AO-30, manufactured by ADEKA)
1,1,3-tris- (2-methyl-4-hydroxy-5-tertiarybutylphenyl) butane c) Noc300 (Nocrack 300)
4,4′-thiobis (3-methyl-6-tertiarybutylphenol ) (Ouchi Shinsei Chemical Co., Ltd.)
(2-3) Hindered phenol antioxidant a) Ir3114 (Irganox 3114, manufactured by BASF)
1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl)-
1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione b) Ir1330 (Irganox 1330, manufactured by BASF)
3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(
Mesitylene-2,4,6-triyl) tri-p-cresol (3) metal deactivator (3-1) non-hindered phenolic metal deactivator a) CDA-1 (ADK STAB CDA-1, ADEKA (Made by company)
3- (N-salicyloyl) amino-1,2,4-triazole b) CDA-6 (ADK STAB CDA-6, manufactured by ADEKA)
Decamethylene dicarboxylic acid disalicyloyl hydrazide (3-2) hindered phenol-based metal deactivator a) IrMD1024 (Irganox MD1024, manufactured by BASF)
2 ′, 3-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl)
Propionyl] propionohydrazide

[Characteristic evaluation]
For the coaxial cables obtained in Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11 and Comparative Examples 1 to 7, the following characteristics were evaluated.

(1) Dielectric properties (tan δ)
Dielectric properties were examined by measuring the dielectric loss tangent (tan δ). Here, the dielectric loss tangent (tan δ) is the resin composition used for the production of the insulating layer in the coaxial cables of Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11 and Comparative Examples 1 to 7, The sheet was formed into a rod shape having a diameter of 2 mm and a length of 10 cm, and this sheet was measured with a microwave measurement system using a measurement program of SUM-TM0m0 manufactured by Samtec Co., Ltd., with measurement frequencies of 3.0 GHz, 6.9 GHz, 10.7 GHz and 14 Measured at each frequency of 6 GHz. The results are shown in Table 2. The acceptance criteria for tan δ for each frequency are as follows.

3.0 GHz ···· 1.90 × 10 ^-4 or less 6.9 GHz ··· 2.10 × 10 ^-4 or less 10.7 GHz ··· 2.30 × 10 ^-4 or less 14.6 GHz ··· 2.50 × 10 ⁻⁴ or less

(2) Attenuation amount
For the coaxial cables obtained in Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11 and Comparative Examples 1 to 7, using a network analyzer (manufactured by 8722ES Agilent Technologies), the frequency is 3.0 GHz, The attenuation was measured for each of 6.9 GHz, 10.7 GHz, and 14.6 GHz. The results are shown in Table 2.

(3) Heat resistance
Among the coaxial cables of Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11, and Comparative Examples 1 to 7, an insulated wire was cut at a length of 30 mm to prepare a test piece. About this test piece, using a heat deformation test ("Three-piece heat deformation tester model number W-3" manufactured by Toyo Seiki Seisakusho Co., Ltd.), the test piece is placed in the center of a sample stage having a diameter of 9 mm, a load of 250 g weight, The amount of deformation at 121 ° C. was measured at a loading time of 1 hour. The crushing rate (heating deformation rate) was calculated from the amount of deformation, and this crushing rate was used as an index of heat resistance. The results are shown in Table 2.

(4) Flexibility Flexibility was evaluated as follows for the coaxial cables obtained in Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11 and Comparative Examples 1 to 7.

That is, the flexibility of the coaxial cable was achieved by forming a sheet of the resin composition used for forming the insulating layer and evaluating the flexibility of the resin sheet. At this time, the flexibility of the resin sheet was evaluated using hardness (Shore D hardness) as an index. The hardness was measured according to JIS standard K7215 (load holding time 5 seconds). At this time, the hardness was measured on a resin sheet produced according to the ASTM D2240 standard. The results are shown in Table 2. The flexibility was evaluated according to the following criteria: “◯” and “◎” were accepted, and “x” was rejected.

Shore D hardness less than 55
Shore D hardness 55 to less than 65
Shore D hardness 65 or more

(5) Heat aging characteristics The heat aging characteristics were evaluated as follows. That is, first, a tensile test was performed on the coaxial cables obtained in Reference Examples 1 to 9, Examples 1 to 9, Reference Examples 10 to 11, and Comparative Examples 1 to 7, and tensile strength and elongation percentage were measured. Hereinafter, they are referred to as “initial tensile strength” and “initial elongation residual ratio”, respectively. Next, the coaxial cable was allowed to stand at 110 ° C. in a thermostatic bath, periodically taken out and subjected to a tensile test, and the tensile strength and the residual elongation rate were measured. Then, the number of years in which the tensile strength was 50% of the initial tensile strength or the residual elongation was 50% of the initial residual elongation was calculated as a relative value when the number of years in Comparative Example 7 was 100. . The results are shown in Table 2. In addition, the heat aging characteristic was set to pass if the relative value of the above years exceeded 110, and rejected if the relative value of 110 or less.

(6) Bloom (blooming)
Bloom removed the sheath and laminate tape from the coaxial cable cut to a length of 3 m, and left the surface of the insulating layer exposed at 50 ° C. for 3 months, and evaluated it according to the following criteria. The results are shown in Table 2.

◎ ... Magnified with a microscope at 100x and no foreign matter can be seen on the surface. ○ ... Magnified with a microscope at 100x and foreign matter can be seen on the surface.
△ ・ ・ ・ Magnified by a microscope with a magnification of 25 times and foreign matter can be confirmed on the surface × ・ ・ ・ Foreign matter can be clearly seen on the surface visually

From the results shown in Tables 1 and 2, each of Reference Examples 1 to 9, Examples 1 to 9, and Reference Examples 10 to 11 has a low dielectric loss tangent, a small attenuation amount, and a relative age that indicates heat aging resistance. It was high and had good flexibility, and passed the acceptance criteria for dielectric properties, heat aging properties and flexibility. On the other hand, Comparative Examples 1-7 did not reach the acceptance criteria in at least one of dielectric properties, heat aging properties and flexibility.

As described above, according to the insulated wire for transmission cable of the present invention, it was confirmed that excellent dielectric characteristics in the GHz band, excellent heat aging characteristics, and excellent flexibility can be achieved at the same time.

  DESCRIPTION OF SYMBOLS 1 ... Internal conductor (conductor), 2 ... Insulating layer, 5 ... Insulated electric wire, 10, 20 ... Cable.

Claims (3)

Conductors,
An insulated wire for a transmission cable comprising an insulating layer covering the conductor,
The insulating layer is
Polyethylene obtained by synthesis using a metallocene catalyst,
A semi-hindered phenolic antioxidant or a less hindered phenolic antioxidant ,
A metal deactivator having a chemical structure different from the hindered phenol structure ,
The antioxidant is blended at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of the polyethylene .
The metal deactivator is blended at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass with respect to 100 parts by mass of the polyethylene .
Insulated wires for transmission cables. The insulated wire for a transmission cable according to claim 1, wherein the insulating layer is cross-linked by an electron beam. Claim 1 or transmission cable having a transmission insulated wire cable according to 2.

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