JP2012113888A - Covering material and communication cable using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covering material for a metal communication wire which can sufficiently suppress an increase in the attenuation factor during communication transmission and which is used for obtaining a communication cable having flexibility, and to provide the communication cable which can sufficiently suppress the increase in the attenuation factor during the communication transmission and which has flexibility.SOLUTION: A communication cable 1 is formed by covering a plurality of metal communication wires 10 composed of conductors 11a, 11b and insulators 12a, 12b covering the conductors 11a, 11b, with the covering material 20 containing an ethylene propylene polymer resin having an ethylene content which is 10 to 15 mass%, a melt flow rate which is 2 to 8 g for 10 minutes, the dielectric constant at 25°C which is 2.50 or lower, and the dielectric tangent at 25°C, 1 GHz which is 0.00024 or below.

Description

  The present invention relates to a covering material and a communication cable using the same.

  In general, a communication cable such as an industrial LAN cable used when constructing a network (LAN) in a factory or the like often has a long wiring unlike a home LAN cable. Therefore, particularly when transmitting high-density information at high frequencies, the attenuation rate during communication transmission increases due to mutual interference between a plurality of metal communication lines (electric wires) arranged in the LAN cable. As a result, transmission efficiency was hindered, and communication performance was likely to be reduced.

Therefore, in order to reduce mutual interference between metal communication lines, communication cables in which metal communication lines are individually shielded with metal and communication cables in which metal communication lines are covered with a thermoplastic resin have been proposed.
As a thermoplastic resin suitable for coating a metal communication line, a propylene / ethylene copolymer containing at least 60% by mass of propylene-derived units and 0.1% by mass of ethylene-derived units (Patent Document 1), ethylene -A thermoplastic elastomer composition (Patent Document 2) containing propylene-nonconjugated diene copolymer rubber (EPDM), polypropylene (PP), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS) Are known.

JP 2005-508415 A JP 2009-13428 A

However, a communication cable in which metal communication lines are individually shielded with metal is likely to be less flexible, and as a result, is difficult to bend and difficult to wire.
Moreover, in the communication cable which coat | covered the metal communication line with the thermoplastic resin as described in patent document 1, 2, it was not necessarily enough to suppress the increase in an attenuation factor.

  The present invention has been made in view of the above circumstances, and it is possible to sufficiently suppress an increase in attenuation rate during communication transmission, and to provide a flexible communication cable for a metal communication line, and during communication transmission. An object of the present invention is to provide a flexible communication cable that can sufficiently suppress an increase in the attenuation factor of the cable.

The coating material of the present invention is a coating material for coating a plurality of metal communication lines, having an ethylene content of 10 to 15% by mass, a melt flow rate of 2 to 8 g / 10 min, and a dielectric constant at 25 ° C. of 2. It is characterized by comprising an ethylene / propylene copolymer resin having a dielectric loss tangent of 50 or less, 25 ° C. and 1 GHz of 0.00024 or less.
Moreover, the communication cable of this invention has a some metal communication wire which consists of a conductor and the insulator which coat | covers this conductor, and the said coating | covering material which coat | covers a some metal communication wire.

The covering material of the present invention is for a metal communication line, and an increase in attenuation rate during communication transmission can be sufficiently suppressed, and a flexible communication cable can be obtained.
The communication cable of the present invention can sufficiently suppress an increase in attenuation rate during communication transmission and has flexibility.

It is sectional drawing which shows an example of the communication cable of this invention. It is sectional drawing which shows the other example of the communication cable of this invention.

[Coating material]
The coating material of the present invention covers a metal communication line of a communication cable having a plurality of metal communication lines, and includes an ethylene / propylene copolymer resin.
Hereinafter, the ethylene / propylene copolymer resin will be described.

  The ethylene content (ethylene unit) of the ethylene / propylene copolymer resin is 10 to 15% by mass. The ethylene content tends to affect the electrical properties (particularly the dielectric constant) of the ethylene / propylene copolymer resin, and the dielectric constant tends to decrease as the ethylene content increases. If the ethylene content is within the above range, the electrical properties of the ethylene / propylene copolymer resin can be maintained well.

The melt flow rate (MFR) of the ethylene / propylene copolymer resin is 2 to 8 g / 10 min. When the MFR is within the above range, a coating material having excellent workability when coating a metal communication line can be obtained. The term “workability” as used herein means that, in addition to coating the metal communication line uniformly, for example, when the metal communication line is coated by simultaneously extruding a plurality of metal communication lines and a coating material, It is covering so that communication lines are arranged at equal distances. If the metal communication line is uniformly coated, mutual interference between the metal communication lines is reduced, and thus an increase in the attenuation factor during communication transmission can be suppressed. Moreover, if it coat | covers so that metal communication lines may be arrange | positioned equidistantly, it is hard to receive the influence of noise and can suppress the increase in an attenuation factor.
The MFR is a value measured under the conditions of a temperature of 190 ° C. and a load of 21.2 N by the method specified in JIS K 7210.

The dielectric constant of the ethylene / propylene copolymer resin is 2.50 or less, preferably 2.35 or less. If the dielectric constant is 2.50 or less, the mutual interference between the metal communication lines coated with the coating material of the present invention is reduced, so that a communication cable that can sufficiently suppress an increase in the attenuation factor during communication transmission can be obtained. . The lower limit of the dielectric constant is not particularly limited, but is usually 2.00 or more.
The dielectric constant is a value measured at a temperature of 25 ° C. by the “cavity resonance method” defined in JIS C 2565.

The dielectric loss tangent of the ethylene / propylene copolymer resin is 0.00024 or less. If the dielectric loss tangent is 0.00024 or less, the mutual interference between the metal communication lines coated with the coating material of the present invention is reduced, so that a communication cable that can sufficiently suppress an increase in the attenuation factor during communication transmission can be obtained. . The lower limit of the dielectric loss tangent is not particularly limited, but is usually 0.00010 or more.
The dielectric loss tangent is a value measured under the conditions of a temperature of 25 ° C. and a frequency of 1 GHz by the “cavity resonance method” defined in JIS C 2565.

The ethylene / propylene copolymer resin preferably has a density of 0.860 to 0.870 g / cm ³ . The density tends to affect the electrical characteristics (particularly dielectric loss tangent) of the ethylene / propylene copolymer resin, and the dielectric loss tangent tends to decrease as the density value increases. When the density is 0.860 g / cm ³ or more, the dielectric loss tangent of the ethylene / propylene copolymer resin can be maintained well. However, if the value of the density becomes too large, the workability when covering the metal communication line may be deteriorated. Therefore, the density is preferably 0.870 g / cm ³ or less.
The density is a value measured under conditions of a temperature of 25 ° C. according to the “underwater substitution method” defined in JIS K7112.

The ethylene / propylene copolymer resin preferably has a crystallinity of 10.0 to 20.0%. Crystallinity is derived from the density of the ethylene / propylene copolymer resin. Therefore, the electrical characteristics (especially the dielectric loss tangent) are likely to be influenced similarly to the density, and the dielectric loss tangent tends to decrease as the crystallinity value increases. If the crystallinity is 10.0% or more, the dielectric loss tangent of the ethylene / propylene copolymer resin can be maintained well. However, if the crystallinity value becomes too large, the workability when coating the metal communication line may be lowered. Therefore, the crystallinity is preferably 20.0% or less.
The crystallinity is a value measured by an X-ray diffraction method.

The ethylene / propylene copolymer resin preferably has a hardness of 70 to 90, and preferably has an elastic modulus of 10 to 50 MPa. If the hardness and elastic modulus are within the above ranges, the dielectric loss tangent of the ethylene / propylene copolymer resin can be maintained well.
The hardness is a value measured by a method defined in JIS K 6253.
On the other hand, the elastic modulus is a value measured by a method defined in JIS K 7203-1982.

The ethylene / propylene copolymer resin preferably has a number average molecular weight (Mw) of 150,000 to 300,000, and more preferably a mass average molecular weight (Mn) of 50,000 to 100,000. If Mw and Mn are within the above ranges, better workability can be obtained.
Mw and Mn are values converted to styrene using gel permeation chromatography (GPC).

The ethylene / propylene copolymer resin preferably has a glass transition temperature (Tg) of −25.0 to −35.0 ° C. and a melting point (Tm) of 5 to 80 ° C. If Tg and Tm are within the above ranges, better workability can be obtained.
Tg and Tm are values measured by differential scanning calorimetry at a heating rate of 10 ° C./min by the method defined in JIS K7121.

The ethylene / propylene copolymer resin preferably has a heat of crystallization (ΔHc) of 10.0 J / g or less. If ΔHc is 10.0 J / g or less, better workability can be obtained.
Note that ΔHc is a value measured by differential scanning calorimetry at a heating rate of 10 ° C./min by the method defined in JIS K7122.

  The ethylene / propylene copolymer resin is not particularly limited as long as it has an ethylene content, MFR, dielectric constant, and dielectric loss tangent within the above ranges, and has at least an ethylene unit and a propylene unit. The propylene unit) is preferably 70 to 90% by mass. If the propylene content is within the above range, the electrical properties of the ethylene / propylene copolymer resin can be maintained well.

The ethylene / propylene copolymer resin may be a copolymer of ethylene and propylene, or may be a copolymer of ethylene, propylene and another monomer.
The other monomer is not particularly limited as long as it is a monomer copolymerizable with ethylene and propylene. For example, α-olefin such as 1-butene, 1-pentene, 1-hexane; 5-methylene-2 -Norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclo Non-conjugated dienes such as pentadiene, 1,4-cyclohexadiene, tetrahydroindene, methyltetrahydroindene, dicyclopentadiene, 5-isopropylidene-2-norbornene, 5-vinyl-norbornene, dicyclooctadiene, methylene norbornene, etc. It is done.

  The content of the ethylene / propylene copolymer resin is preferably 50% by mass or more and more preferably 70% by mass or more in 100% by mass of the coating material. When the content of the ethylene / propylene copolymer resin is 50% by mass or more, an increase in attenuation rate during communication transmission can be sufficiently suppressed, and a flexible communication cable can be obtained.

The coating material of the present invention is preferably made of an ethylene / propylene copolymer resin, but may contain other resins and additives as long as the effects of the present invention are not impaired.
Examples of other resins include polyethylene, polypropylene, ethylene-α olefin copolymer, and ethylene-cycloolefin copolymer.
When it contains other resin, it is preferable that the content is 50 mass% or less in 100 mass% of coating materials.

Examples of additives include stabilizers such as antioxidants, light stabilizers, heavy metal deactivators, processing aids such as lubricants and waxes, and pigments.
When an additive is contained, the content is preferably 50% by mass or less in 100% by mass of the coating material.

  As described above, according to the present invention, by defining the ethylene content, MFR, dielectric constant and dielectric loss tangent of the ethylene / propylene copolymer resin contained in the coating material, the metal communication coated with the coating material of the present invention. Mutual interference between lines can be reduced. Therefore, a communication cable that can sufficiently suppress an increase in the attenuation rate during communication transmission can be obtained.

Moreover, since the coating material of this invention is excellent also in workability, it is easy to coat | cover a metal communication line uniformly. In particular, when covering in a state where a plurality of metal communication lines are twisted together, each metal communication line can be covered while maintaining a twisted state, so that the metal communication lines can be arranged at equal distances. Therefore, it is possible to obtain a communication cable that is not easily affected by noise and that can suppress an increase in attenuation rate.
The coating | covering material of this invention can be used for the various types of communication cable provided with the some metal communication line.

[communication cable]
Hereinafter, the communication cable of the present invention will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing an example of a communication cable of the present invention. The communication cable 1 of this example includes four metal communication lines 10 and a covering material 20 that covers the metal communication lines 10, and further covers the four metal communication lines 10 that are covered with the covering material 20. And a sheath layer 40 formed on the shield layer 30.

The metal communication line 10 in FIG. 1 is composed of two wire cores A and B including conductors 11a and 11b and insulators 12a and 12b covering the conductors 11a and 11b.
Examples of the conductors 11a and 11b include copper wire, aluminum alloy, steel core aluminum, and hard copper.
Examples of the insulators 12a and 12b include polyethylene (particularly foamed polyethylene), ethylene propylene rubber, cross-linked polyethylene, polyolefins such as ethylene-α olefin copolymer, and vinyl resins.

The wire cores A and B are twisted together to form a twisted pair wire, and the surface of the twisted pair wire (that is, the surface of the metal communication line 10) is covered with the coating material 20 (20a) of the present invention.
Further, the four metal communication lines 10 each covered with the covering material 20a are twisted together, and the surface thereof is further covered with the covering material 20 (20b) of the present invention.
Hereinafter, in this specification, a metal communication line covered with a covering material may be referred to as a “covered wire”.

The shield layer 30 is provided on the outer periphery of the covering material 20b.
The shield layer 30 may be any material that can shield noise, and examples thereof include aluminum tape, aluminum braid, and metal foil such as aluminum.
The thickness of the shield layer 30 is preferably 0.001 to 0.100 mm.

The sheath layer 40 is provided on the outer periphery of the shield layer 30.
Examples of the material of the sheath layer 40 include polyethylene, vinyl chloride, styrene elastomer (styrene butadiene rubber (SBR), styrene ethylene butylene styrene block copolymer (SEBS), etc.), thermoplastic resin such as polypropylene, and the like.
The thickness of the sheath layer 40 is preferably 0.010 to 0.100 mm.

The communication cable 1 of FIG. 1 can be manufactured as follows, for example.
First, the wire cores A and B are twisted at a predetermined pitch to produce a metal communication line (twisted pair wire) 10.
Next, the metal communication line 10 and the covering material 20a are coextruded by a coextrusion method, and the surface of the metal communication line 10 is covered with the covering material 20a. Similarly, a total of four covered wires are produced.
Four coated wires are twisted at a predetermined pitch and coextruded together with the coating material 20b by a coextrusion method, and the surfaces of the four twisted coated wires are further coated with the coating material 20b.
Next, the surface of the covering material 20 b is covered with the shield layer 30, and the sheath layer 40 is formed on the shield layer 30 to obtain the communication cable 1.

In the communication cable 1 thus obtained, since the surface of the metal communication line 10 is covered with the coating material 20 of the present invention, mutual interference between the metal communication lines is reduced, and the attenuation factor during communication transmission is increased. Can be sufficiently suppressed.
Further, since the metal communication line 10 is coated with resin, the metal communication line 10 is more flexible than a communication cable in which the metal communication line is covered with metal. Therefore, the communication cable 1 of the present invention is easy to bend and wire.

  In addition, since the communication cable 1 uses the coating material 20 of the present invention that is excellent in workability, the surface of the metal communication line 10 can be covered while maintaining the twisted state of the wire cores A and B well. In addition, the surface of the coated wire can be coated while maintaining a good twisted state of the four coated wires. Therefore, the communication cable 1 of the present invention is not easily affected by noise, and can sufficiently suppress an increase in attenuation rate during communication transmission.

In addition, the communication cable of this invention is not limited to the communication cable 1 of the example of illustration.
For example, in the communication cable 1 of FIG. 1, the metal communication line 10 including the two wire cores A and B is illustrated as the metal communication line, but the metal communication line may be formed of one wire core. It may consist of more than a book core. Moreover, when a metal communication line consists of a some core, the cores which comprise a metal communication line may be twisted together, and do not need to be twisted.

  Further, although the communication cable 1 of FIG. 1 includes four metal communication lines 10, the number of metal communication lines is not particularly limited, and may be any number such as 2, 6, 8, and the like. . Furthermore, the metal communication lines do not have to be twisted together.

  In addition, when four covered wires are twisted together as shown in FIG. 1, these covered wires may not be further covered with the covering material 20b, or may be covered with a covering material other than the covering material of the present invention. However, it is preferably coated with the coating material of the present invention.

Moreover, when manufacturing a communication cable in which a plurality of metal communication lines are not twisted together, a plurality of metal communication lines coated with the coating material of the present invention may be packaged together and covered with a shield layer. Alternatively, a plurality of metal communication lines coated with the coating material of the present invention or other coating materials are extruded in a tubular shape at equal intervals, and at the same time, the coating material of the present invention is coextruded to form a plurality of metal communication lines of the present invention. After covering with a covering material, it may be covered with a shield layer.
Further, for example, like the communication cable 2 shown in FIG. 2, a plurality of metal communication wires 10 before coating are extruded into a tube at equal intervals, and at the same time, the coating material 20 of the present invention is coextruded to produce a plurality of metal communication wires After covering 10 with the covering material 20 of the present invention, it may be covered with a shield layer 30. The metal communication line 10 shown in FIG. 2 is composed of a single wire core A. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  1 is a category 5, 5e (CAT5, CAT5e) type, for example, a category 6, 6e, 6a (CAT6, CAT6e, CAT6a) type is covered with the coating material of the present invention A plurality of metal communication lines may be partitioned by a spacer.

Hereinafter, the present invention will be specifically described with reference to examples.
Various measurement / evaluation methods and ethylene / propylene copolymer resins used in each example are as follows.

[Measurement and evaluation method]
(Measurement of MFR)
The MFR of the ethylene / propylene copolymer resin was measured under the conditions of a temperature of 190 ° C. and a load of 21.2 N by the method defined in JIS K 7210.

(Measurement of dielectric constant)
The dielectric constant of the ethylene / propylene copolymer resin was measured at a temperature of 25 ° C. according to the “cavity resonance method” defined in JIS C 2565.

(Measurement of dielectric loss tangent)
The dielectric loss tangent of the ethylene / propylene copolymer resin was measured under the conditions of a temperature of 25 ° C. and a frequency of 1 GHz according to the “cavity resonance method” defined in JIS C 2565.

(Density measurement)
The density of the ethylene / propylene copolymer resin was measured under the condition of a temperature of 25 ° C. according to the “in-water substitution method” defined in JIS K7112.

(Measurement of crystallinity)
The crystallinity of the ethylene / propylene copolymer resin was measured by an X-ray diffraction method.

(Measurement of hardness and elastic modulus)
The hardness of the ethylene / propylene copolymer resin was measured by a method defined in JIS K 6253, and the elastic modulus was measured by a method defined in JIS K 7203-1982.

(Measurement of Mw and Mn)
Mw and Mn of the ethylene / propylene copolymer resin were determined by styrene conversion using GPC.

(Measurement of Tg and Tm)
Tg and Tm of the ethylene / propylene copolymer resin were measured by differential scanning calorimetry at a heating rate of 10 ° C./min by the method defined in JIS K7121.

(Measurement of ΔHc)
ΔHc of the ethylene / propylene copolymer resin was measured by differential scanning calorimetry at a heating rate of 10 ° C./min by the method defined in JIS K7122.

(Evaluation of workability 1)
A metal communication line formed by twisting two wire cores at a predetermined pitch and a coating material are coextruded, and the state of the metal communication line when the metal communication line is covered with the coating material is visually observed. Evaluation was made based on evaluation criteria.
○: The metal communication line could be uniformly covered with the covering material while maintaining the twisted state.
X: The twisted state cannot be maintained, or the metal communication line cannot be uniformly coated with the covering material.

(Processability evaluation 2)
The four coated wires twisted at a predetermined pitch and the coating material are coextruded, and the state of the coated wire when the four coated wires are coated with the coating material is visually observed. evaluated.
○: The twisted state can be maintained, and the respective covered wires are arranged at equal intervals.
(Triangle | delta): Although the state of a twist can be substantially maintained, each coated wire may shift from equidistant arrangement.
X: The twisted state cannot be maintained, and the respective covered wires are not arranged at equal intervals.

(Evaluation of attenuation)
The attenuation of the communication cable was measured using a network analyzer (“E5071B” manufactured by Agilent Technologies, Inc.) under the conditions of a temperature of 20 ° C. and a frequency of 100.00 MHz by the method specified in TIA / EIA568B2.

[Ethylene / propylene copolymer resin]
Copolymer resins A to F having physical properties and electrical properties shown in Table 1 were used. The copolymer resins A to F are copolymers of ethylene and propylene.

[Example 1]
Based on the TIA / EIA568B2 standard, a communication cable was produced as follows.
First, a co-extrusion machine is used to co-extrude a metal communication line formed by twisting two wire cores coated with foamed polyethylene on a conductor (cross-sectional area 0.34 mm ² ) made of copper wire and a copolymer resin A as a coating material. Thus, a coated wire in which the metal communication line was coated with the copolymer resin A was obtained. Similarly, four coated wires were produced.
Next, the four coated wires were twisted and coextruded with the copolymer resin A by a coextrusion machine, and the four coated wires twisted were coated with the copolymer resin A to obtain a coated body.
The outer peripheral surface of the obtained covering was covered with an aluminum foil to form a shield layer (thickness 0.05 mm). Further, a sheath layer (thickness: 0.2 mm) made of polyethylene was formed on the shield layer to obtain a communication cable as shown in FIG.
The obtained communication cable was cut, the state of the metal communication line and the covered wire was confirmed, and the workability was evaluated. The results are shown in Table 2.
Moreover, the attenuation amount was measured about the obtained communication cable. The results are shown in Table 2.

[Examples 2-3, Comparative Examples 1-3]
A communication cable was produced in the same manner as in Example 1 except that the covering material shown in Table 2 was used, and each evaluation was performed. The results are shown in Table 2.

  As is clear from Table 2, in Examples 1 to 3, the processability was excellent. Therefore, it has been shown that the covering material used in each example can cover the surface while maintaining the twisted state of the wire core and the covered wire, and the communication cable obtained in each example is affected by noise. Hateful. Further, these communication cables have small attenuation values, and can suppress an increase in attenuation rate during communication transmission at a high frequency of 100.00 MHz. Moreover, since the metal communication line is covered with resin, it has flexibility.

On the other hand, the communication cables obtained from Comparative Examples 1 and 2 using the copolymer resins D and E having a dielectric loss tangent greater than 0.00024 as the covering material have large attenuation values and attenuation at a frequency of 100.00 MHz. Was big. That is, these communication cables have a large attenuation rate of transmitted signals. In particular, the communication cable of Comparative Example 2 using the copolymer resin E having a low ethylene content of 5% by mass has a large attenuation value and could not suppress an increase in the attenuation factor.
In the case of Comparative Example 3 using the copolymer resin F having a low ethylene content of 9% by mass and a large MFR of 25.0 g / 10 min, the evaluation result of workability is poor and the function as a communication cable can be achieved. The attenuation was not measured because it was clearly difficult.

[Example 4]
A communication cable was obtained in the same manner as in Example 1. About the obtained communication cable, the attenuation amount in each frequency shown in Table 3 was measured. The results are shown in Table 3.

[Reference Example 1]
A metal communication line formed by twisting two wire cores in which a conductor made of copper wire is coated with foamed polyethylene has an ethylene content of 10 to 15% by mass, an MFR of 2 to 8 g / 10 min, and a dielectric constant of 2.50. Table 3 below shows commercially available communication cables having a coated body in which four coated wires coated with copolymer resin G whose dielectric loss tangent does not satisfy 0.00024 or less are twisted and coated with copolymer resin G. The attenuation at each frequency shown was measured. The results are shown in Table 3.

As is clear from Table 3, the communication cable obtained in Example 4 is 1.00-100. At the frequency of MHz, the attenuation value was smaller than that of the current product communication cable used in Reference Example 1. It can be presumed that such a tendency also applies to the communication cables obtained in Examples 2-3.
Therefore, according to the present invention, a higher quality communication cable can be manufactured.

1, 2: communication cable,
10: Metal communication line,
11a, 11b: conductors
12a, 12b: insulator,
20, 20a, 20b: coating material,
30: shield layer,
40: sheath layer,
A, B: Wire core.

Claims (2)

A covering material for covering a plurality of metal communication lines,
An ethylene / propylene copolymer having an ethylene content of 10 to 15% by mass, a melt flow rate of 2 to 8 g / 10 min, a dielectric constant at 25 ° C. of 2.50 or less, and a dielectric loss tangent at 25 ° C. and 1 GHz of 0.00024 or less. A covering material comprising a resin.   A communication cable comprising: a plurality of metal communication lines made of a conductor and an insulator covering the conductor; and the covering material according to claim 1 that covers the plurality of metal communication lines.

Images