JP4916574B1 - Insulated wires for transmission cables and transmission cables - Google Patents

Abstract

To provide an insulated wire and a cable capable of realizing excellent dielectric properties and heat aging resistance in the GHz band.
An insulated wire (5) comprising a conductor (1) and an insulating layer (2) covering the conductor (1), wherein the insulating layer (2) is synthesized by using a metallocene catalyst; An antioxidant having a chemical structure different from the hindered phenol structure, and the antioxidant is blended in an amount 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 propylene-based copolymer. The insulated wire 5 characterized by the above-mentioned.
[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 excellent dielectric property can be obtained by using an insulating layer covering a conductor, which is obtained by blending an olefin resin with a phenolic antioxidant having no hindered phenol structure. Proposed.

JP 2009-81132 A

  However, the cable described in Patent Document 1 has the following problems.

  That is, when polyethylene is used as the olefin resin of the insulating layer, there is a limit in obtaining excellent dielectric properties in the high frequency band with polyethylene. Therefore, in order to obtain excellent dielectric properties while using polyethylene as the olefin resin of the insulating layer, it has been practiced to use the insulating layer as a foam. However, when the insulating layer is made of a foam, the insulating layer must be thinned as the transmission cable diameter is reduced, the mechanical strength of the insulating layer is reduced, and the insulating layer is easily crushed against lateral pressure. . For this reason, it is difficult for polyethylene to impart heat resistance of about UL 90 ° C. to the insulating layer. Therefore, from the viewpoint of imparting heat resistance of about UL 90 ° C. to the insulating layer, it is conceivable to use a propylene resin having a high melting point instead of polyethylene as the olefin resin. However, in an insulating layer containing a propylene-based resin, the dielectric loss tangent in the GHz band may not be sufficiently small, and there is still room for improvement in terms of dielectric characteristics in the GHz band.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an insulated wire for a transmission cable and a transmission cable that have excellent dielectric characteristics in the GHz band and can realize excellent heat aging characteristics. To do.

  As a result of intensive studies to solve the above problems, the present inventor has found that propylene-based resins synthesized using general-purpose catalysts such as Ziegler-Natta catalysts have a wide molecular weight distribution and low molecular weight propylene. Since low-molecular-weight propylene-based resin easily oscillates with respect to high frequency, thermal loss is likely to occur, thereby increasing the dielectric loss tangent at high frequency. Therefore, as a result of further earnest research, the inventor made a propylene copolymer synthesized using a metallocene catalyst, and added an antioxidant having a specific structure to the propylene copolymer. Thus, the inventors have found that the above problem can be solved by blending at a predetermined ratio, and have completed the present invention.

That is, the present invention is an insulated electric 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, , Semi-hindered phenolic antioxidant or less hindered phenolic antioxidant, and the antioxidant is 0.01 parts by weight or more and 1.5 parts by weight with respect to 100 parts by weight of the propylene-based copolymer. It is the insulated wire for transmission cables characterized by being mix | blended in the ratio of less than a mass part.

According to this insulated cable for transmission cable, since the propylene copolymer contained in the insulating layer is obtained by synthesis using a metallocene catalyst, a general-purpose catalyst such as a Ziegler-Natta catalyst is used. Thus, the molecular weight distribution can be made narrower than that of the propylene copolymer synthesized. For this reason, in the insulating layer, the proportion of the low-molecular-weight propylene-based copolymer, which is likely to cause molecular vibration with respect to high frequencies and increase the dielectric loss tangent, can be sufficiently reduced. In general, the propylene-based copolymer is likely to be oxidized and deteriorated by contact with a conductor and includes tertiary carbon that is easily deteriorated. In that respect, in the present invention, the semi-hindered phenol-based antioxidant or the hindered phenol-based 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 the propylene-based copolymer. It is blended at a ratio of Therefore, deterioration of the propylene-based copolymer can be sufficiently suppressed. Therefore, according to the insulated wire for a transmission cable of the present invention, it has excellent dielectric characteristics in the GHz band and can realize excellent heat aging characteristics.

  In the insulated wire, the insulating layer further includes a metal deactivator having a chemical structure different from the hindered phenol structure, and the metal deactivator is based on 100 parts by mass of the propylene-based copolymer. It is preferably blended at a ratio of 0.01 parts by mass or more and less than 1.5 parts by mass.

  In this case, the heat aging resistance of the insulated wire is further improved.

  In the insulated wire, the propylene copolymer is specifically an ethylene-propylene copolymer.

  In this case, as compared with the case where a propylene copolymer other than the ethylene-propylene copolymer is used, in addition to obtaining superior strength and heat resistance, moderate flexibility can be obtained.

  In the said insulated wire, it is preferable that a propylene-type copolymer has 125-145 degreeC melting | fusing point.

  When the melting point of the propylene-based copolymer is within the above range, the melting point of the propylene-based copolymer can obtain more sufficient heat resistance as compared to less than 125 ° C., and the crystallinity becomes higher. More excellent dielectric properties can be obtained. Further, superior flexibility can be obtained as compared with the case where the melting point of the propylene-based copolymer exceeds 145 ° C.

  In the said insulated wire, it is preferable that the said insulating layer has a thickness of 0.3 mm or less.

  Propylene-based copolymers are generally brittle and tend to be more brittle at a temperature lower than room temperature, and therefore, when the cable is bent, cracks and the like are likely to occur in the insulating layer. In this regard, when the thickness of the insulating layer is 0.3 mm or less, the problem of embrittlement, particularly the problem of low temperature embrittlement, is significantly less likely to occur than when the thickness exceeds 0.3 mm.

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 have the outstanding dielectric characteristic in a GHz band and can implement | achieve the outstanding heat aging resistance 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, a propylene-based copolymer 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 propylene-type copolymers.

  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 propylene-based copolymer contained in the insulating layer 2 is obtained by synthesis using a metallocene catalyst, the propylene-based copolymer synthesized using a general-purpose catalyst such as a Ziegler-Natta catalyst. Compared to a polymer, the molecular weight distribution can be narrowed. For this reason, in the insulating layer 2, the proportion of the low molecular weight propylene-based copolymer, which is likely to cause molecular vibration with respect to high frequencies in the GHz band and increase the dielectric loss tangent, can be sufficiently reduced. For this reason, according to the insulated wire 5, the inventor believes that excellent dielectric characteristics can be realized as described above.

  In general, the propylene-based copolymer is likely to be oxidized and deteriorated by contact with the inner conductor 1 and includes tertiary carbon that is easily deteriorated, and thus the molecule is easily cleaved. In that respect, 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 with respect to 100 parts by mass of the propylene-based copolymer. It mix | blends in the ratio of less than 1.5 mass parts. Therefore, deterioration of the propylene-based copolymer due to the inner conductor 1 can be sufficiently suppressed. For this reason, the insulated wire 5 has excellent dielectric characteristics in the GHz band and can realize excellent heat aging characteristics.

  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 inner 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, a propylene-based copolymer as a base resin and an antioxidant are prepared.

(Base resin)
A propylene-based copolymer is a propylene-based copolymer obtained by synthesis using a metallocene catalyst. A propylene-based copolymer refers to a resin containing propylene as a structural unit, and only homopolypropylene It also includes copolymers of propylene and other olefins. Examples of other olefins include ethylene, 1-butene, 2-butene, 1-hexene, and 2-hexene. Other olefins can be used alone or in combination of two or more. Among them, ethylene and 1-butene are preferably used because they can lower the crystallinity and efficiently lower the melting point while suppressing deterioration of various properties as much as possible by adding a small amount, and more preferably ethylene.

  Specifically, as the propylene-based copolymer, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, propylene-butene copolymer, ethylene-propylene-butene-hexene copolymer, ethylene- Examples thereof include a propylene-hexene copolymer and a propylene-butene-hexene copolymer.

  The propylene-based copolymer may be a random copolymer or a block copolymer, but is preferably a random copolymer. In this case, compared with the case where a block copolymer is used, the melting point of the propylene-based copolymer is further lowered, and the flexibility of the insulated wire 5 can be further improved.

  The melting point of the propylene-based copolymer is preferably 125 ° C to 145 ° 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 the propylene copolymer 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 125 ° C. Can be obtained. Moreover, since the crystallinity does not become too high as compared with the case where the melting point of the propylene-based copolymer exceeds 145 ° C., the flexibility required for the cable can be obtained.

  The melting point of the propylene-based copolymer is more preferably 130 to 145 ° C, still more preferably 133 to 143 ° C.

  The total content of ethylene and butene in the propylene-based copolymer is 7% by mass or less, and the content of butene in the propylene-based copolymer preferably does not exceed 2% by mass.

The contents of ethylene and butene in the propylene-based copolymer can be determined by infrared spectroscopic analysis according to the calculation formula described in Polymer Analysis Handbook, p413-415 (2008). Specifically, the content of ethylene and butene in the propylene-based copolymer was tested by stripping the insulating layer 2 from the insulated wire and molding the insulating layer 2 to a thickness of 0.5 to 1 mm with a hydraulic press. Using the strip, the absorbance is measured with an infrared spectrophotometer (Perkin Elmer Spectrum One, FTIR) under the conditions of the transmission method, resolution 2 cm ⁻¹ , and number of integrations of 64 times. Here, ethylene means a structural unit of ethylene in the propylene-based copolymer, and does not mean an ethylene monomer. Similarly, butene means a structural unit of 1-butene in the propylene-based copolymer, and does not mean a butene monomer. In addition, the said calculation formula is represented by the following formula (1) to formula (3). Here, _Ak is the absorbance at k cm ⁻¹ , t is the thickness of the sample (cm), and ρ is the density (g / cm ³ ).
(1) Ethylene (% by mass) in random PP = (0.509A ₇₃₃ + 0.438A ₇₂₂ ) / tρ
(2) Ethylene (% by mass) in block PP = (1.10A ₇₂₂ -1.51A ₇₂₉ + 0.509A ₇₃₃ ) / tρ
(3) 1-butene (mass%) = 12.3 (A ₇₆₆ / t)

  The content of ethylene in the propylene-based copolymer is usually 5% by mass or less, preferably 4.5% by mass or less, and more preferably 3.0% by mass or less. However, from the viewpoint of improving flexibility, the ethylene content in the propylene-based copolymer is preferably 1.0% by mass or more, and more preferably 1.3% by mass or more. Further, the content of butene in the propylene-based copolymer may be in a range not exceeding 2.0 mass%, preferably 1.5 mass% or less, more preferably 1.0 mass% or less. . However, from the viewpoint of improving flexibility, the content of butene is preferably 0.5% by weight or more. However, when the crystallinity can be lowered efficiently only with ethylene, the propylene-based copolymer contains butene. More preferably it is not included.

  In addition, the content rate of ethylene and butene in a propylene-type copolymer can be adjusted by mixing the propylene-type copolymers synthesize | combined, for example using the metallocene catalyst.

The propylene copolymer has the following formula:
Melting point-crystallization peak temperature = 30-40 ° C.
It is preferable to satisfy. Here, the crystallization peak temperature refers to the crystallization peak temperature obtained from the apex of the crystallization heat peak portion observed under the condition 2). Melting | fusing point-crystallization peak temperature becomes like this. Preferably it is 30-35 degreeC, More preferably, it is 31-34 degreeC.

  In addition, the value of melting | fusing point-crystallization peak temperature of a propylene-type copolymer can be adjusted by mixing the propylene-type copolymers synthesize | combined using the metallocene catalyst.

The propylene-based copolymer preferably has a crystallinity of 50 to 60%. 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 heat of fusion of the melting heat peak observed when measuring the melting point of the above-mentioned propylene-based copolymer, and the value obtained by the method of JIS-K7122 is used as the heat of fusion. A value of 165 J / g is used as H _m0 . Here, the value of H _m0 is quoted from the polypropylene handbook (1998, P149) by Edward P. Moore Jr.

  When the crystallinity of the propylene-based copolymer is within the above range, the proportion of amorphous components that are susceptible to molecular vibration in the high-frequency band is further reduced as compared to the case where the crystallinity is less than 50%. The dielectric loss tangent can be reduced more sufficiently. Further, more appropriate flexibility can be obtained as compared with the case where the crystallinity of the propylene-based copolymer exceeds 60%.

(Antioxidant)
The antioxidant may prevent any deterioration of the base resin due to contact with the inner conductor 1 and may have any chemical structure as long as it has a chemical structure different from the hindered phenol structure.

  Examples of the 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. tetraoxaspiro [5,5] undecane (e.g., Adeka Stab AO-80 of ADEKA Corporation), 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 propylene-based copolymer. In this case, compared with the case where the antioxidant is blended at a ratio of 1.5 parts by mass or more, in addition to obtaining excellent dielectric properties, so-called blooms in which the particles of the antioxidant float on the surface of the insulating layer 2. The phenomenon can be sufficiently suppressed. Moreover, heat aging resistance improves notably compared with the case where an antioxidant is mix | blended in the ratio of less than 0.01 mass part. 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 propylene-based copolymer. However, from the viewpoint of improving the heat aging characteristics due to the antioxidant, it is preferably 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 prepared by introducing a propylene-based copolymer as a base resin, an antioxidant, and a metal deactivator as necessary into an extruder, and melt-kneading the resin composition in the extruder. It is obtained by extruding and coating the inner conductor 1 with this extrudate.

  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, the thickness of the insulating layer 2 is preferably 0.3 mm or less, and more preferably 0.2 mm or less. Since the propylene-based copolymer is generally brittle and tends to become brittle at a temperature lower than normal temperature, when the cable 10 is bent, the insulating layer 2 is likely to be cracked. In this respect, when the thickness of the insulating layer 2 is 0.3 mm or less, the problem of embrittlement, particularly the problem of low temperature embrittlement, is significantly less likely to occur than when the thickness exceeds 0.3 mm. 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, if the cable 10 is used for an application in which bending is hardly applied, for example, a fixed wiring material, the problem of low temperature embrittlement hardly occurs. 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, it is possible to suppress the foaming cell from becoming coarse even if a wire using a propylene-based copolymer is used for the insulating layer 2 as a cable electric wire used in the GHz band. The foamed 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 can also prevent deterioration (embrittlement) of the insulating layer 2 due to copper in the inner conductor 1. 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 an end view showing a Twinax type cable having the insulated wire 5. As shown in FIG. 3, the Twinax type cable 20 has a laminated body composed of two insulated wires 5, a drain wire 6, a laminate tape 7, two power lines 8, an aluminum tape layer and a braided layer. 9 and a sheath 4. 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.

Example 1
First, WMG03 (melting point: 142 ° C.), which is an ethylene-propylene random copolymer obtained by synthesis using a metallocene catalyst, was prepared as a base resin.

  Then, the above base resin is added to the extruder (product name: Labo Plast 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 antioxidant and metal deactivator shown in No. 1 were charged, melt-kneaded and extrusion molded. At this time, the blending amounts of the antioxidant and the metal deactivator shown in Table 1 are blended with respect to 100 parts by mass of the base resin (unit: parts by mass), and the melt-kneading temperature is 200 ° C. did.

  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 200 ° 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.

(Examples 2 to 22 and Comparative Examples 1 to 5)
As shown in Table 1, the antioxidant and the metal deactivator shown in Table 1 are 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. A coaxial cable was produced in the same manner as in Example 1 except that.

(Comparative Examples 6-9)
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 Example 1 using the insulated wire thus obtained.

(Examples 23 to 27)
A coaxial cable was produced in the same manner as in Example 1 except that the thickness of the insulating layer was as shown in Table 3.

In addition, the following were specifically used as the base resin, antioxidant and metal deactivator shown in Table 1.
(1) Base resin (1-1) WFX4 (Wintech, manufactured by Nippon Polypro)
Propylene ethylene random copolymer (melting point: 125 ° C)
(1-2) WFW4 (Wintech, manufactured by Nippon Polypro)
Propylene ethylene random copolymer (melting point: 136 ° C)
(1-3) WMG03 (Wintech, manufactured by Nippon Polypro)
Propylene ethylene random copolymer (melting point: 142 ° C)
(1-4) WFX6 (Wintech, manufactured by Nippon Polypro)
Propylene ethylene random copolymer (melting point: 125 ° C)
(1-5) FX4G (Novatech PP, manufactured by Nippon Polypro)
Propylene ethylene butene random copolymer (melting point: 126 ° C)
(1-6) FW4B (Novatech PP, manufactured by Nippon Polypro)
Propylene ethylene butene random copolymer (melting point: 138 ° C)
(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, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
4,4'-thiobis (3-methyl-6-tertiarybutyl) phenol (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]
The following characteristics were evaluated about the coaxial cable obtained in Examples 1-27 and Comparative Examples 1-9.

(1) Ethylene content and butene content rate The ethylene content rate and the butene content rate were measured for the test pieces after peeling off the insulating layer of the insulated wire from the coaxial cables of Examples 1 to 22 and Comparative Examples 1 to 9. Calculated from the IR spectrum. The results are shown in Table 1.

(2) Crystallization peak temperature and melting heat peak temperature (melting point), and crystallinity The crystallization peak temperature and melting heat peak temperature are the insulated wires among the coaxial cables of Examples 1 to 22 and Comparative Examples 1 to 9. The insulating layer was peeled off, and the test piece was measured by DSC and calculated. The results are shown in Table 1. The crystallinity was also calculated by measuring DSC for the same test piece. The results are shown in Table 1.

(3) Dielectric properties (tan δ)
Dielectric properties were examined by measuring the dielectric loss tangent (tan δ). Here, the dielectric loss tangent (tan δ) is obtained by molding the resin composition used for manufacturing the insulating layer in the coaxial cables of Examples 1 to 22 and Comparative Examples 1 to 9 into a rod shape having a diameter of 2 mm and a length of 10 cm. About this sheet | seat, it measured at each frequency of measurement frequency 3.0GHz, 6.9GHz, 10.7GHz, and 14.6GHz with the microwave measurement system using the measurement program of SUM-TM0m0 by Samtec. The results are shown in Table 2. The acceptance criteria for tan δ for each frequency are as follows.

3.0 GHz ····· 1.10 × 10 ^-4 or less 6.9 GHz · ··· 1.50 × 10 ^-4 or less 10.7 GHz ··· 2.00 × 10 ^-4 or less 14.6 GHz ··· 2.50 × 10 ⁻⁴ or less

(4) Attenuation For the coaxial cables obtained in Examples 1-22 and Comparative Examples 1-9, using a network analyzer (manufactured by 8722ES Agilent Technologies), the frequencies are 3.0 GHz, 6.9 GHz, 10.7 GHz. And the attenuation was measured for each of the cases of 14.6 GHz. The results are shown in Table 2.

(5) Heat resistance Among the coaxial cables of Examples 1 to 22 and Comparative Examples 1 to 9, 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.

(6) Crush resistance The Shore D hardness indicating the surface hardness was measured, and the Shore D hardness was used as an index of the crush resistance. Shore D hardness was measured according to JIS K7215 for the insulated wires of Examples 1 to 22 and Comparative Examples 1 to 9. Table 2 shows the measurement results at a load holding time of 5 seconds.

(7) Heat aging characteristics The heat aging characteristics were evaluated as follows. That is, first, tensile tests were performed on the coaxial cables obtained in Examples 1 to 22 and Comparative Examples 1 to 9, and the tensile strength and the residual elongation rate 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 days when this tensile strength is 50% of the initial tensile strength or the residual elongation percentage is 50% of the initial residual elongation ratio is the same as that of Comparative Example 6 using no antioxidant and no metal deactivator. The relative value was calculated when the number of days was 100. The results are shown in Table 2. If this relative value was 110 or more, it was judged as “pass” because it was excellent in heat aging resistance, and if it was less than 110, it was judged as “fail” because it was poor in heat aging resistance.

(8) Bloom (blooming)
Bloom removed the sheath and the laminate tape from the coaxial cable cut to a length of 3 m, and the surface of the insulating layer exposed by leaving at 50 ° C. for 3 months was visually observed and evaluated 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

(9) Low temperature embrittlement characteristics The low temperature embrittlement characteristics were evaluated by conducting a low temperature embrittlement test on the coaxial cables of Examples 1, 23 to 27. The low temperature embrittlement test was performed as follows.

That is, for the coaxial cables of Examples 1, 23 to 27, the embrittlement temperature was measured using an embrittlement temperature tester (product name: embrittlement tester TM-2110, manufactured by Ueshima Seisakusho). At this time, a specimen cut to about 60 mm was used as the test piece, and the test conditions were in accordance with ASTM D746, and the temperature at which the insulator was scratched or cracked was defined as the embrittlement temperature. The results are shown in Table 3.

  From the results shown in Tables 1 and 2, each of Examples 1 to 22 had a low dielectric loss tangent, a small amount of attenuation, and a high relative age indicating heat aging resistance. On the other hand, it was found that Comparative Examples 1 to 9 had a low relative age representing heat aging characteristics or a high dielectric loss tangent.

  In addition, from the results of Examples 23 to 27, it was confirmed that the embrittlement temperature was significantly lowered and the low temperature embrittlement was significantly improved by setting the thickness of the insulating layer to 0.3 mm or less. It was.

From the above, it was confirmed that the insulated wire for transmission cable of the present invention has excellent dielectric characteristics in the GHz band and can realize heat aging resistance.

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

Claims (6)

Conductors,
An insulated wire for a transmission cable comprising an insulating layer covering the conductor,
The insulating layer is
A propylene-based copolymer obtained by synthesis using a metallocene catalyst,
A semi-hindered phenolic antioxidant or a hindered phenolic antioxidant,
The antioxidant is blended in a proportion 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 propylene-based copolymer.
Insulated wires for transmission cables . The insulating layer further comprises a metal deactivator having a chemical structure different from the hindered phenol structure;
2. The transmission cable according to claim 1, wherein 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 propylene-based copolymer . Insulated wire. The insulated wire for transmission cables according to claim 1 or 2, wherein the propylene-based copolymer is an ethylene-propylene copolymer. The insulated wire for transmission cables according to any one of claims 1 to 3, wherein the propylene-based copolymer has a melting point of 125 to 145 ° C. The insulated wire for transmission cables according to any one of claims 1 to 4 , wherein the insulating layer has a thickness of 0.3 mm or less. Transmission cable having a transmission insulated wire cable according to any one of claims 1-5.

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