JP4304183B2 - Foamed coaxial cable - Google Patents

Description

  The present invention relates to a foamed coaxial cable having a foamed insulating layer having a high foaming degree.

A high-frequency foamed coaxial cable is composed of an inner conductor made of copper or the like, a foamed insulator layer provided on the inner conductor, and an outer conductor provided on the outer periphery thereof. Recently, a foamed coaxial cable having a small attenuation is required even in the use frequency range of GHz, and therefore, it is desired to increase the degree of foaming of the insulating layer. For example, in Patent Document 1, in order to obtain a coaxial cable having a fine and uniform high foaming degree and a good appearance, a polyolefin resin that can be hot melt extruded and a fluorine resin powder as a nucleating agent are contained. A coaxial cable is described in which the composition is foam extruded in the presence of a blowing agent. However, only by improving the nucleating agent, when the degree of foaming is increased, huge air bubbles are formed in the foamed insulator layer, and it is difficult to stably and reliably form a foamed insulator layer having a high foaming degree. Patent Document 2 discloses a polymer composition for foam molding that is excellent in insulation characteristics such as dielectric loss tangent (tan δ) and foam moldability and suitable for forming an insulating layer of a coaxial cable. That is, as the base resin of the polymer composition, the above characteristics can be obtained by using a propylene / ethylene copolymer containing 0.5 to 20% by weight of an ethylene component. However, even when such a polymer composition is used, it has been difficult to stably and reliably increase the degree of foaming. This is presumably because the polymer composition does not have a sufficient balance between the melt tension at break and the extensibility at melt, so that the cell wall is broken at the time of foaming, and the foamed cells do not grow sufficiently. Further, in Patent Document 3, in order to solve the problem of decrease in the elongation of polypropylene in melt molding, any material of polypropylene, a block copolymer of polypropylene / polyethylene, and a block copolymer of polypropylene / ethylene / propylene rubber, and this material A foam insulated wire having an insulation coating made of a foam of a mixture with a high density polyethylene having a higher melt index and 10 g / 10 min or less is described. However, even if the above mixture is used, the melt tension at break or the extensibility at the time of melting is not sufficient, and it cannot be said that it is sufficient to obtain a foamed insulated wire having a high degree of foaming stably and reliably.
Japanese Patent No. 3227091 Japanese Patent No. 2668174 Japanese Patent No. 2618464

  Therefore, the problem to be solved by the present invention is to provide a foamed coaxial cable in which a foamed insulation layer having a foaming degree of 80% or more is stably and reliably formed and has a low attenuation in a high frequency band (1 MHz or more). It is in. Another object of the present invention is to provide a foamed coaxial cable having improved properties such as low-temperature bending properties, impact resistance and bending whitening in addition to the above properties.

The problem to be solved is a foamed coaxial cable in which a foamed insulation layer obtained by foaming an ethylene / propylene copolymer is provided on an inner conductor as defined in claim 1, wherein the ethylene・ Propylene copolymer was measured with a capillary rheometer at 190 ° C using a Φ2.095 mm × 8.03 mm capillary with a piston speed of 10 mm / min, furnace body diameter of 9.55 mm, take-up acceleration of 400 m / min ² The melt tension at break is 5.0 to 10.0 g, the melt mass flow rate at 190 ° C. and 2.16 kg is 1.0 g / 10 min or more, and the foamed insulating layer has a foaming degree of 80%. This is solved by using a foamed coaxial cable characterized by the above.

Moreover, as described in claim 2, a foamed coaxial cable in which a foamed insulator layer obtained by foaming a mixture of an ethylene / propylene copolymer and polyethylene is provided on an inner conductor, wherein the mixture is The ethylene / propylene copolymer content in the mixture is 20% by mass or more and less than 100% by mass, and the mixture uses a Φ2.095 mm × 8.03 mm capillary, the piston speed is 10 mm / min, the furnace Melt mass flow at a body diameter of 9.55 mm, take-up acceleration of 400 m / min ² , melt tension at break as measured with a capillary rheometer at 190 ° C. of 5.0 to 12.0 g, and 190 ° C. and 2.16 kg The rate is 1.0 g / 10 min or more, and the foamed insulating layer has a foaming degree of 80% or more. By the foam coaxial cable, it is solved.

The present invention described above is a foamed coaxial cable in which a foamed insulation layer obtained by foaming an ethylene / propylene copolymer is provided on an inner conductor, and the ethylene / propylene copolymer has a diameter of 2.095 mm × 8 A 0.03 mm capillary was used, the piston speed was 10 mm / min, the furnace body diameter was 9.55 mm, the take-up acceleration was 400 m / min ² , and the melt tension at break measured by a capillary rheometer at 190 ° C. was 5.0 to 10 A foamed coaxial cable having a melt mass flow rate at 190 ° C. and 2.16 kg of 1.0 g / 10 min or more, and the foamed insulating layer has a foaming degree of 80% or more. Therefore, it is possible to stably and reliably form the foamed insulating layer having a foaming degree of 80% or more on the inner conductor. The obtained foamed coaxial cable is excellent in that it has a small amount of attenuation in a high frequency band (1 MHz or more).

Further, the foamed insulation layer by foaming a mixture of ethylene-propylene copolymer and polyethylene, a foamed coaxial cable provided on the inner conductor, said mixture of ethylene-propylene copolymer in the mixture weight Content of coalescence is 20% by mass or more and less than 100% by mass, and the mixture uses a capillary of Φ2.095 mm × 8.03 mm, piston speed is 10 mm / min, furnace body diameter is 9.55 mm, take-up acceleration 400 m / min ² , the melt tension at break measured by a capillary rheometer at 190 ° C. is 5.0 to 12.0 g, and the melt mass flow rate at 190 ° C. and 2.16 kg is 1.0 g / 10 min or more. There, the foamed insulation layer, since the degree of foaming was Ru der least 80% possess the aforementioned properties, the foam coaxial Cold flexural properties of Buru, it is possible to further improve the impact resistance and bending whitening like.

The present invention is described in detail below. The invention described in claim 1 is a foamed coaxial cable in which a foamed insulating layer obtained by foaming an ethylene / propylene copolymer (hereinafter referred to as an EP copolymer) is provided on an inner conductor, The polymer is a Φ2.095 mm × 8.03 mm capillary, the piston speed is 10 mm / min, the furnace body diameter is 9.55 mm, the take-up acceleration is 400 m / min ² , and measured at 190 ° C. with a capillary rheometer The melt mass flow rate (hereinafter referred to as MFR) at 190 ° C. and 2.16 kg is 1.0 g / 10 min or more, and the foamed insulating layer has a foaming degree of 80 to 10.0 g. % Or more of the foamed coaxial cable.

  An example will be described with reference to FIG. For example, it comprises an inner conductor 1 made of a plated copper wire such as an oxygen-free copper wire or a silver-plated copper wire, a copper alloy wire, etc., and a foamed insulator layer 2 provided on the inner conductor 1, and further on the outer conductor 3 Usually, a sheath 4 made of a plastic material is provided as a protective layer. And as the internal conductor 1, the plated copper wire and copper alloy wire of a conductor diameter of about 0.5-20 mm are normally used, and the thickness of the foaming insulator layer 2 shall be about 0.5-15 mm. As shown in FIG. 1, it is preferable to form a corrugation in a spiral shape using, for example, a copper thin plate or the like as the external conductor 3, because flexibility can be further imparted. Such corrugating may be formed by a commonly performed method.

The foamed insulator layer 2 is a capillary rheometer at 190 ° C. using a Φ2.095 mm × 8.03 mm capillary with a piston speed of 10 mm / min, a furnace diameter of 9.55 mm, a take-up acceleration of 400 m / min ^2. An EP copolymer having a melt tension at break of 5.0 g or more as measured in (1) and an MFR of 1.0 g / 10 min or more at 190 ° C. and 2.16 kg is used. By using such an EP copolymer, the balance between the melt tension at the time of fracture and the extensibility at the time of melting is good, and the foam insulation layer 2 having a high foaming degree can be stably and reliably formed. That is, as EP copolymer, the melt tension at break is 5.0 g or more, and the cell wall is torn when foamed by setting MFR at 190 ° C. and 2.16 kg to 1.0 g / 10 min or more. In addition, since it has sufficient extensibility upon melting, the foamed cells can be sufficiently grown, and a high foaming degree can be obtained stably and reliably. This makes it possible to stably and reliably form a foamed insulator layer having a foaming degree of 80% or more (a foaming ratio of 5.0 or more). The obtained foamed coaxial cable is an excellent foamed coaxial cable with little attenuation in a high frequency band (1 MHz or more).
A preferred specific example of the EP copolymer is FB3312 manufactured by Nippon Polypro.

Moreover, as described in claim 2, a foamed coaxial cable in which a foamed insulator layer obtained by foaming a mixture of an ethylene / propylene copolymer and polyethylene is provided on an inner conductor , wherein the mixture is The ethylene / propylene copolymer content in the mixture is 20% by mass or more and less than 100% by mass, and the mixture uses a capillary of Φ2.095 mm × 8.03 mm, the piston speed is 10 mm / min, the furnace Melt mass flow at a body diameter of 9.55 mm, take-up acceleration of 400 m / min ² , melt tension at break as measured with a capillary rheometer at 190 ° C. of 5.0 to 12.0 g, and 190 ° C. and 2.16 kg rate is not less 1.0 g / 10min or more, the foamed insulation layer, characterized in that the foaming degree of 80% or more To the foam coaxial cable.

  The foamed insulator layer 2 can be formed by various foaming agents. For example, chemical blowing agents such as azodicarbonamide, 4,4'-oxybis (benzenesulfonylhydrazine), N, N'-dinitrosopentamethylenetetramine, and inert gases such as nitrogen gas, argon gas, freon gas, and carbon dioxide gas. Can be used alone or in combination. In particular, in the case of foaming with an inert gas, problems such as foaming residues having an adverse effect on dielectric properties as in the case of foaming with a chemical foaming agent and insufficient foaming are reduced. Moreover, it is preferable to add a foam nucleating agent. For example, fine powders such as talc, clay, boron nitride (BN), and silica, fine powders of azodicarbonamide and fluororesin, and fine powders of fluororubber. The addition amount is usually about 0.05 to 3.0 parts by mass with respect to 100 parts by mass of the base resin.

  Further, for example, 3- (N-salicyloyl) amino-1,2,4-triazole (trade name: CDA-1), 2 ′, 3-bis [3- (3,5-diazo) is used as the foamed insulating layer 2. -Tertiarybutyl-4-hydroxyphenyl) propionyl] propionohydrazide (trade name: Irganox MD1024) and other metal deactivators, N, N'-di-2-naphthyl-p-phenylenediamine (trade name: Nocrack) Hindered phenolic oxidations such as amine antioxidants such as White) and pentaerythritol tetrakis [3- (3,5-di-tertiarybutyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010). Inhibitors, 4,4'-thiobis (3-methyl-6-tertiarybutylphenol) (trade name NOCRACK 300), etc. It can be added o bisphenol-based antioxidant.

  The effects of the present invention are shown by the examples and comparative examples described in Table 1. In the second extruder of the two-stage extruder, the resin pellet material (resin material in the table) shown in Table 1 as the pellet material forming the foam insulation, and the talc differential powder (LMS) of Fuji Talc as the foam nucleating agent -300) is dry blended, supplied to a first extruder adjusted to 230 ° C., mixed and melted by injecting nitrogen gas from the middle of the first extruder, and heated to about 170 ° C. in the second extruder. A foamed coaxial cable was prepared by adjusting and extruding onto an inner conductor made of a copper wire with a diameter of 9 mm and simultaneously foaming.

For these foamed coaxial cables, the foaming degree (%) of the foamed insulating layer was calculated as [(specific gravity of base resin−specific gravity after foaming) / (specific gravity of base resin)] × 100. A foam having a foaming degree of 80% or more was regarded as acceptable. In addition, the expansion ratio was determined and described as [1 / (100-foaming degree)] × 100. 5 times or more is preferable. Moreover, the attenuation amount of the 20D size foam coaxial cable in 2.2 GHz was measured using the network analyzer. Attenuation was 62 dB / km or less as acceptable. As low-temperature bending characteristics, a 20D foam coaxial cable (outer diameter: 22 mm) was left in a thermostatic bath at -40 ° C. for 1 hour, and then wound around a mandrel of various diameters to examine the state of cracks in the foam insulation layer. . The minimum mandrel diameter (mm) at which no cracks occurred was described. Further, melt tension at break of the various resins (using a capillary of Φ2.095 mm × 8.03 mm, a piston speed of 10 mm / min, a furnace body diameter of 9.55 mm, and a take-up acceleration of 400 m / min ² at 190 ° C. Measured with a capillary rheometer) and MFR values. MFR is a value measured at 190 ° C. and 2.16 kg. Table 1 shows the results.

  As is clear from Table 1, as described in Examples 1 to 6, the foamed coaxial cable of the present invention had a foaming degree of 80% or more (a foaming ratio of 5.0 times or more). Moreover, it turns out that the attenuation amount in a high frequency band (1 GHz or more) is excellent with 60 dB / km or less. Furthermore, regarding the low temperature bending characteristics, it is sufficiently practical at 20 mm or more.

  That is, as shown in Example 1, the foamed coaxial cable formed by foaming an EP copolymer having a melt tension at break of 10.0 g and an MFR of 2.0 g / 10 min to form a foamed insulator layer has a foaming degree. It was as good as 89% (foaming ratio: 9.1 times), attenuation was 56 dB / km, and low-temperature bending characteristics were 80 mm. Further, as shown in Examples 2 to 6, also in the case of an EP copolymer mixture, the blending amount of the EP copolymer is 20% by mass or more and less than 99% by mass, and the melt tension at break is 5.0. ˜12.0 g, MFR of 1.0 to 8.0 g / 10 min, foaming degree is 82 to 88% (foaming ratio is also 5.6 to 8.3 times), attenuation is 56 to 60 dB / km It can be seen that a foamed coaxial cable having a low temperature bending characteristic of 20 to 80 mm can be obtained.

On the other hand, the foamed coaxial cable of the foamed insulator layer outside the scope of the present invention shown in Comparative Examples 1 to 7 has a problem in any of the degree of foaming (foaming ratio), the amount of attenuation, and the low-temperature bending characteristics. . That is, when the melt tension at break is as small as 2.0 g as in Comparative Example 1, the foaming degree is 68% (foaming ratio is 3.1 times) and the attenuation is as large as 72 dB / km. Also, as in Comparative Example 2, when the MFR is as small as 0.4 g / 10 min (and the density is 0.91 g / cm ³ at 230 ° C. and the 2.16 kg MFR is 0.5 g / 10 min), the melt tension at break Is 11.0 g, the foaming degree is 74% (foaming ratio is also 3.8 times), and the attenuation is as large as 67 dB / km. Furthermore, as shown in Comparative Example 6, even in the case of a mixture of an EP copolymer and PE, when the content of the EP copolymer is 10% by mass, the melt tension at break becomes as small as 4.0 g. The foaming degree was 79% (foaming ratio was 5.3 times), and the attenuation was 63 dB / km. Further, as shown in Comparative Example 7, even in the case of a mixture of EP copolymer and PE, when the content of the EP copolymer is 70% by mass, the melt tension at break becomes as small as 3.0 g. The foaming degree was 76% (foaming ratio was 4.2 times) and the attenuation was 67 dB / km. In addition, when PE having a low melt tension at break is used for the foamed insulator layer as in Comparative Examples 3 and 4, when the melt tension at break is as small as 0.5 g as in Comparative Example 4. The foaming degree is 52% (the foaming ratio is 2.1 times) and the damping amount is as large as 90 dB / km, and even when a mixture of PEs is used, the melt tension at the time of breaking as in Comparative Example 3 is high. In the case of 3.0 g, the foaming degree was 78% (foaming ratio was 4.5 times), and the attenuation was 64 dB / km. Furthermore, even if the melt tension at break is large as in Comparative Example 5, when PE with a small MFR of 0.2 g / 10 min is used, the foaming degree is 70% (the foaming ratio is 3.3 times), The amount of attenuation increases to 71 dB / km.

  The above foamed coaxial cable of the present invention is an EP copolymer in which the foamed insulator layer has a melt tension and MFR specified at break, or a mixture of an EP copolymer and polyethylene, and the melt tension at break and Since a mixture with MFR specified is used, it is possible to stably and surely form a foamed insulation layer having a high foaming degree, and to be used as a foamed coaxial cable for various applications with low attenuation in a high frequency band (1 GHz or more). it can.

It is a schematic sectional perspective view which shows an example of the foaming coaxial cable of this invention.

DESCRIPTION OF SYMBOLS 1 Inner conductor 2 Foam insulator layer 3 Corrugated structure outer conductor 4 Sheath

Claims (2)

A foamed insulation cable in which an ethylene / propylene copolymer is foamed is a foamed coaxial cable provided on an inner conductor,
The ethylene / propylene copolymer uses a capillary of Φ2.095 mm × 8.03 mm, has a piston speed of 10 mm / min, a furnace diameter of 9.55 mm, a take-up acceleration of 400 m / min ² , and a capillary rheometer at 190 ° C. The melt tension at the time of breaking as measured at 5.0 to 10.0 g, and the melt mass flow rate at 190 ° C. and 2.16 kg is 1.0 g / 10 min or more,
The foamed coaxial cable is characterized in that the foamed insulating layer has a foaming degree of 80% or more. A foamed coaxial cable in which a foamed insulation layer obtained by foaming a mixture of ethylene / propylene copolymer and polyethylene is provided on an inner conductor,
In the mixture, the content of the ethylene / propylene copolymer in the mixture is 20% by mass or more and less than 100% by mass,
The mixture used was a Φ2.095 mm × 8.03 mm capillary with a piston speed of 10 mm / min, a furnace diameter of 9.55 mm, a take-up acceleration of 400 m / min ² and a breakage measured with a capillary rheometer at 190 ° C. And melt mass flow rate at 190 ° C. and 2.16 kg is 1.0 g / 10 min or more,
The foamed coaxial cable is characterized in that the foamed insulating layer has a foaming degree of 80% or more.