JP2012087185A - Insulation resin composition, and insulated electric wire and cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation resin composition or the like achieving excellent heat aging resistance while sufficiently suppressing the reduction of dielectric characteristics in a GHz zone.SOLUTION: The insulation resin composition includes an olefin resin and an antioxidant regulated as follows. The antioxidant of 0.05-1.0 pt.mass is formulated with 100 pts.mass of the olefin resin, and the antioxidant is constituted of a primary antioxidant comprising a phenol-based antioxidant having a structure different from a hindered phenol structure, and a secondary antioxidant comprising at least one kind selected from the group consisting of a phosphorus-based antioxidant and a sulfur-based antioxidant, and the composition is regulated so that the content of the secondary antioxidant in the antioxidants may be 10-90 mass%.

Description

  The present invention relates to an insulating resin composition, an insulated wire, and a cable.

  In recent years, with the development of electronic devices using frequencies in the GHz band, it has been superior in the GHz band over high-speed coaxial cables, USB 3.0 cables, HDMI cables, Infiniband cables, micro USB cables, and other high-speed transmission cables. It is required to have dielectric properties.

  As such a transmission cable, in Patent Document 1 below, an insulating layer that covers a conductor is prepared by blending an olefin resin with a phenol-based antioxidant having no hindered phenol structure as an antioxidant. Thus, it has been proposed to obtain excellent dielectric properties.

JP 2009-81132 A

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

  That is, although the insulated wire described in Patent Document 1 has excellent dielectric characteristics in the GHz band, there is room for improvement in terms of heat aging resistance.

  Here, in order to improve the heat aging resistance, it is considered that an antioxidant may be further added. However, when the antioxidant is excessively added, the dielectric characteristics in the GHz band are deteriorated.

  Accordingly, there has been a demand for an insulated wire that can realize excellent heat aging resistance while sufficiently suppressing a decrease in dielectric characteristics in the GHz band.

  The present invention has been made in view of the above circumstances, and provides an insulating resin composition, an insulated wire, and a cable that can realize excellent heat aging resistance while sufficiently suppressing deterioration of dielectric properties in the GHz band. The purpose is to do.

  As a result of studying the above problems, the present inventor has added an antioxidant to the olefin resin at a predetermined blending ratio, and the antioxidant is a primary antioxidant composed of a phenolic antioxidant. And a secondary antioxidant such as a phosphorus-based and / or sulfur-based antioxidant, and by making the blending ratio of the secondary antioxidant in the antioxidant within a predetermined range, surprisingly, The present inventors have found that the above problems can be solved and have completed the present invention.

  That is, the present invention includes an olefin resin and an antioxidant, and the antioxidant is blended at a ratio of 0.05 to 1.0 part by mass with respect to 100 parts by mass of the olefin resin, and the oxidation 2 consisting of at least one selected from the group consisting of a primary antioxidant composed of a phenolic antioxidant having a structure different from the hindered phenol structure, and a phosphorous antioxidant and a sulfur antioxidant. It is comprised by secondary antioxidant, It is an insulating resin composition characterized by the compounding ratio of the said secondary antioxidant in the said antioxidant being 10-90 mass%.

  According to this insulating resin composition, excellent heat aging resistance can be realized while sufficiently suppressing a decrease in dielectric characteristics in the GHz band.

  The structure different from the hindered phenol structure is preferably a semi-hindered phenol structure or a less hindered phenol structure.

  In this case, compared to the case where the structure different from the hindered phenol structure is not a semi-hindered phenol structure or a less hindered phenol structure, it is less affected by the dielectric characteristics due to the frequency, and the deterioration of the dielectric characteristics is more sufficiently suppressed. can do.

  Furthermore, the present invention is an insulated wire comprising a conductor and an insulating layer covering the conductor, wherein the insulating layer is formed using the insulating resin composition. Or a cable having this insulated wire.

  ADVANTAGE OF THE INVENTION According to this invention, the insulated resin composition, the insulated wire, and cable which can implement | achieve the outstanding heat aging resistance, fully suppressing the fall of a dielectric property in a GHz band are provided.

It is a partial side view which shows one Embodiment of the 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 cable of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same or equivalent components are denoted by the same reference numerals.

  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 is formed using an insulating resin composition, and the insulating resin composition contains an olefin resin and an antioxidant. Here, antioxidant is mix | blended in the ratio of 0.05-1.0 mass part with respect to 100 mass parts of olefin resin. Further, the antioxidant is at least one selected from the group consisting of a primary antioxidant composed of a phenolic antioxidant having a structure different from the hindered phenol structure, and a phosphorus antioxidant and a sulfur antioxidant. The secondary antioxidant in the antioxidant is 10 to 90% by mass.

  According to the cable 10, by using the insulated wire 5 using the insulating layer 2 having the above-described configuration, it is possible to realize excellent heat aging resistance while sufficiently suppressing a decrease in dielectric characteristics in the GHz band.

  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, an insulating resin composition containing an olefin resin as a base resin and an antioxidant is prepared.

(Olefin resin)
Examples of the olefin resin include polyethylene and propylene resin. These can be used alone or in combination of two or more.

  The propylene-based resin refers to a resin containing propylene as a structural unit, and includes not only homopolypropylene but also a copolymer of propylene and another olefin. 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 these, ethylene and 1-butene are preferably used because they can lower the crystallinity and can efficiently lower the melting point with a small amount of addition, and more preferably ethylene.

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

(Antioxidant)
The antioxidant prevents the olefin resin from deteriorating due to contact with the inner conductor 1. An antioxidant is mix | blended in the ratio of 0.05 mass part-1.0 mass part with respect to 100 mass parts of said olefin resin. In this case, compared with the case where the antioxidant is blended at a ratio exceeding 1.0 part by mass, the so-called Bloom phenomenon in which the antioxidant particles are floated on the surface of the insulating layer 2 can be sufficiently suppressed. The antioxidant is more preferably blended at a rate of 0.1 to 0.7 parts by mass, and preferably at a rate of 0.2 to 0.5 parts by mass, with respect to 100 parts by mass of the olefin resin. More preferred.

  The antioxidant is composed of a primary antioxidant and a secondary antioxidant.

  The primary antioxidant is composed of a phenolic antioxidant having a structure different from the hindered phenol structure.

  Any primary antioxidant can be used as long as it is composed of a phenolic antioxidant having a structure different from the hindered phenol structure. Here, the use of a phenolic antioxidant having a chemical structure different from the hindered phenol structure reduces the dielectric characteristics in the GHz band compared to the case of a phenolic antioxidant having a hindered phenol structure. This is because it can be sufficiently suppressed.

  Examples of phenolic antioxidants that have a chemical structure different from the hindered phenol structure include semi-hindered phenolic antioxidants and res-hindered phenolic antioxidants, as well as semi-hindered phenolic and res-hindered phenols. Examples include antioxidants having a structure other than phenolic. Of these, semi-hindered phenol-based antioxidants and res-hindered phenol-based antioxidants are more preferable.

  In this case, the structure different from the hindered phenol structure is affected by the frequency-dependent dielectric properties due to the sterically hindered molecular structure as compared to the case where the structure is not a semi-hindered phenol structure or a less hindered phenol structure. It becomes difficult, and the deterioration of dielectric characteristics can be further sufficiently suppressed.

（上記一般式（１）式中、Ｒ^１〜Ｒ^４はメチル基を表し、Ｒ^５は置換基を表す。） The antioxidant having a semi-hindered phenol structure is represented by the following general formula (1).

(In the general formula (1), R ^{1 to} R ⁴ represent a methyl group, and R ⁵ represents a substituent.)

  As an antioxidant having a semi-hindered phenol structure, specifically, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1 , 1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane (for example, Adeka Stub AO-80 from Adeka), ethylenebis (oxyethylene) bis [3- (5- tert-butyl-hydroxy-m-tolyl) propionate] (for example, Irganox 245 from BASF Japan), triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] ( For example, Adeka Corporation's Adeka Stub AO-70) may be mentioned.

（上記一般式（２）式中、Ｒ^１〜Ｒ^４はメチル基を表し、Ｒ^５は置換基を表す。） The antioxidant having a hindered phenol structure is represented by the following general formula (2).

(In the general formula (2), R ^{1 to} R ⁴ represent a methyl group, and R ⁵ represents a substituent.)

  Specifically, as the antioxidant having a hindered phenol structure, 4,4′-thiobis (3-methyl-6-tert-butyl) phenol (for example, Nocrack 300 of Ouchi Shinsei Chemical Co., Ltd.), 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane (eg, Adeka Stub AO-30 from Adeka), 4,4′-butylidenebis (3-methyl-6- tert-butyl) phenol (for example, Adeka Stab AO-40 from Adeka).

In addition, as antioxidant which has structures other than a semi hindered phenol type and a res hindered phenol type, for example, antioxidant (1,3,5-tris [[4- (1,1-dimethylethyl) -3-hydroxy-2,6-dimethylphenyl] methyl] 1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione).
As the secondary antioxidant, a phosphorus-based antioxidant or a sulfur-based antioxidant can be used. These can be used alone or in combination of two or more.

  Examples of the phosphorus-based antioxidant include tris (2,4-di-tert-butylphenyl) phosphite and tris [2-[[2,4,8,10-tetra-tert-butyldibenzo [d, f]. [1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine. These can be used alone or in combination of two or more.

  Examples of the sulfur-based antioxidant include dioctadecyl 3,3'-thiodipropionate and didodecyl 3,3'-thiodipropionate. These can be used alone or in combination of two or more.

  The compounding ratio of the secondary antioxidant in the antioxidant is 10 to 90% by mass. When the mixing ratio of the secondary antioxidant in the antioxidant is less than 10% by mass, the heat aging resistance is poor. On the other hand, when the blending ratio of the secondary antioxidant in the antioxidant exceeds 90% by mass, excellent high frequency characteristics cannot be obtained.

  Here, the compounding ratio of the secondary antioxidant in the antioxidant is capable of efficiently decomposing peroxide (hydroperoxide) and excellent dielectric properties, and is in the range of 20 to 70% by mass. It is preferable that it is 30-60 mass%.

  The insulating layer 2 can be obtained by putting the above-described insulating resin composition into an extruder, melting and kneading the insulating resin composition in the extruder and extruding, and coating the inner conductor 1 with the 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 0.4 mm or less, more preferably 0.3 mm or less, and further preferably 0.2 mm or less. In particular, when the olefin resin is a propylene resin, the propylene resin is generally fragile and tends to be further fragile at a temperature lower than normal temperature. Therefore, when the cable 10 is bent, the insulating layer 2 is likely to be cracked. In this regard, when the thickness of the insulating layer 2 is 0.4 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 0.4 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 0.4 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, since the workability (weight) at the time of laying deteriorates and it is not preferable to increase the amount of copper used unnecessarily, the thickness of the insulating layer 2 is usually 6 mm or less.

  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, specifically as the insulating layer 2 is made thinner.

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 resin is used as the base resin of the insulating layer 2 as a cable wire used in the GHz band, and a fine and uniform foam cell. Thus, 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 insulating 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 heat aging characteristics 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 thickness of the thin layer may be 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, it is possible to easily perform coloring by suppressing deterioration of electrical characteristics due to the pigment as compared with the case of coloring without an outer layer. Further, when a thin layer made of foamed resin is interposed between the insulating layer 2 and the outer conductor 3, the appearance and characteristics of the electric wire 5 are 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. Note that the thickness of the thin layer may be 0.02 to 0.2 mm, for example.

  Further, the insulating layer 2 may be obtained by melt-kneading the insulating resin composition and extrusion-coating the inner conductor 1 and then subjecting the extrudate to a crosslinking treatment. In this case, the crosslinking treatment can be performed by, for example, electron beam irradiation, but can also be performed by heating when the insulating 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 includes a laminated body 9 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. 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. In addition, as the insulated wire 5 and the insulating layer 2, what was described in the said embodiment can be used.

  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, an olefin resin, a primary antioxidant, and a secondary antioxidant shown in Table 1 were mixed at a blending ratio shown in Table 1 to prepare an insulating resin composition. Next, this insulating resin composition was prepared by using an extruder (product name: Laboplast Mill 4C150, twin-screw segment extruder 2D30W2, screw diameter (D): φ25 mm, effective screw length (L): 750 mm, manufactured by Toyo Seiki Seisakusho Co., Ltd. ) And melt-kneaded to perform extrusion molding. At this time, the melt kneading temperature was 200 ° C. Further, in Table 1, the blending amounts of the primary antioxidant and the secondary antioxidant are amounts blended with respect to 100 parts by mass of the olefin-based resin (unit: parts by mass), and “secondary AO ratio” Means the blending ratio (mass ratio) of the secondary antioxidant in the antioxidant (AO) as a percentage.

  Then, the extrudate was extruded into a tube shape from the extruder, and a copper wire having a strand diameter of 0.60 mm was covered with the tube-shaped 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 2.1 mm and the thickness was 0.75 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 2-12 and Comparative Examples 1-4)
Example except that an insulating composition was prepared by blending the primary antioxidant and the secondary antioxidant shown in Table 1 with respect to 100 parts by mass of the olefin resin at a ratio (unit: parts by mass) shown in Table 1. In the same manner as in Example 1, a coaxial cable was produced.

In addition, the following were specifically used as the olefin resin, primary antioxidant and secondary antioxidant shown in Table 1.
(1) Olefin resin (1-1) Ethylene propylene random copolymer Trade name: WFW4 (manufactured by Nippon Polypro Co., Ltd.), melting point: 136 ° C.
(1-2) Ethylene propylene block copolymer Trade name: BC3RA (manufactured by Nippon Polypro Co., Ltd.), melting point: 165 ° C.
(1-3) Homopolypropylene trade name: MA3 (manufactured by Nippon Polypro Co., Ltd.), melting point: 165 ° C.
(1-4) Polyethylene (high density polyethylene)
Product name: 2070 (made by Ube Maruzen Polyethylene Co., Ltd.), melting point: 134 ° C
(2) Antioxidant (2-1) Primary antioxidant (semi-hindered phenol-based antioxidant)
Product Name: ADK STAB AO-80 (Adeka)
Generic name: 3,9-bis [2- {3- (3-tertiarybutyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10- Tetraoxaspiro [5,5] undecane (2-2) primary antioxidant (resin hindered phenolic antioxidant)
Product Name: ADK STAB AO-40 (Adeka)
General name: 4,4′-butylidenebis (3-methyl-6-tert-butyl) phenol (2-3) primary antioxidant (hindered phenol-based antioxidant)
Product name: Ir3114 (Irganox 3114) (manufactured by BASF Japan)
Generic name: (1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione )
(2-4) Secondary antioxidant (phosphorus antioxidant)
Product name: 168 (IRGAFOS 168) (manufactured by BASF Japan)
Generic name: Tris (2,4-di-tert-butylphenyl) phosphite (2-5) secondary antioxidant (sulfur-based antioxidant)
Product name: 802 FD (IRGANOX PS 802 FD) (manufactured by BASF Japan)
Generic name: didodecyl 3,3'-thiodipropionate

[Characteristic evaluation]
The following characteristics were evaluated about the coaxial cable obtained in Examples 1-12 and Comparative Examples 1-4.

(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 obtained by forming the insulating resin composition used for manufacturing the insulating layer of the coaxial cables of Examples 1 to 12 and Comparative Examples 1 to 4 into a rod shape having a diameter of 2 mm and a length of 10 cm. The sample was measured at a measurement frequency of 3.0 GHz, 6.9 GHz, 10.7 GHz, and 14.6 GHz with a microwave measurement system using a measurement program of SUM-TM0m0 manufactured by Samtec. The dielectric constant was also measured. The results are shown in Table 2. The acceptance criteria for tan δ for each frequency are as follows.
3.0 GHz ··· 1.30 × 10 ^-4 or less 6.9 GHz ··· 1.50 × 10 ^-4 or less 10.7 GHz ... 1.80 × 10 ^-4 or less 14.6 GHz ... 2.10 × 10 ⁻⁴ or less

(2) Cable attenuation and characteristic impedance For the coaxial cables obtained in Examples 1 to 12 and Comparative Examples 1 to 4, using a network analyzer (manufactured by Agilent Technologies 8722ES), the frequencies are 3.0 GHz and 6.9 GHz. The attenuation and characteristic impedance were measured for each of 10.7 GHz and 14.6 GHz. The results are shown in Table 2. The characteristic impedance was substantially constant regardless of the frequency in each of Examples 1 to 12 and Comparative Examples 1 to 4.

(3) Heat aging characteristics The heat aging characteristics were evaluated as follows. That is, first, the coaxial cable obtained in Examples 1 to 12 and Comparative Examples 1 to 4 was subjected to a tensile test, 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 120 ° 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 time when the tensile strength was 50% of the initial tensile strength or the residual elongation was 50% of the initial residual elongation was calculated as “120 ° C. life”. The results are shown in Table 2. In addition, about the heat aging characteristic, it was set as the pass if 120 degreeC lifetime was 7250 h or more, and it was set as unacceptable if less than 7250 h.

(4) Bloom (blooming)
Bloom removed the sheath and laminate tape from the coaxial cable cut to a length of 3 m, left it at 50 ° C. for 3 months, then observed the surface of the exposed insulating layer, 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 Table 2, all of Examples 1 to 12 reached the acceptance criteria in terms of dielectric properties and heat aging resistance. On the other hand, Comparative Example 1 did not reach the acceptance standard in terms of heat aging characteristics and dielectric characteristics at high frequencies. Moreover, although the comparative example 2 and the comparative example 3 reached the acceptance standard in terms of dielectric properties, they did not reach the acceptance standard in terms of heat aging resistance. Comparative Example 4 did not reach the acceptance standard in terms of hot water dielectric characteristics at high frequencies.

  From the above, according to the insulating resin composition of the present invention, it was confirmed that excellent heat aging resistance can be realized while sufficiently suppressing a decrease in dielectric properties in the GHz band.

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

Claims (4)

An olefin resin,
An antioxidant and
The antioxidant is blended at a ratio of 0.05 to 1.0 part by mass with respect to 100 parts by mass of the olefin resin,
The antioxidant is a primary antioxidant composed of a phenolic antioxidant having a structure different from the hindered phenol structure, and at least one selected from the group consisting of a phosphorus antioxidant and a sulfur antioxidant. A secondary antioxidant comprising
The blending ratio of the secondary antioxidant in the antioxidant is 10 to 90% by mass,
An insulating resin composition characterized by the above.   The insulating resin composition according to claim 1, wherein the structure different from the hindered phenol structure is a semi-hindered phenol structure or a less hindered phenol structure. Conductors,
An insulated wire comprising an insulating layer covering the conductor,
The insulating layer is formed using the insulating resin composition according to claim 1 or 2,
Insulated wire characterized by A cable having the insulated wire according to claim 3.

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