JP2016162634A - Polyolefin resin composition for electric wire / cable coating and electric wire / cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin composition for covering a wire and a cable, the polyolefin resin composition allowing for reduction of load to an extrusion molding machine, excellent in shape maintainability after extrusion-molded and further allowing for formation of a cover having high wear resistance and excellent in appearance, and to provide a wire and a cable each employing the polyolefin resin composition.SOLUTION: The polyolefin resin composition for covering a wire and a cable is provided that contains: 20 to 70 mass% of a polyethylene resin (a1) having a specific density and a specific MFR (Melt Flow Rate,190°C, 21.18 N); 20 to 75 mass% of a resin (a2) of at least one kind of polymer selected from an ethylene-α olefin copolymer and an ethylene single polymer and having a specific density and a specific MFR (190°C, 21.18 N); and 3 o 25 mass% of a polypropylene resin (a3) and that has an MFR (190°C, 21.18 N) of 0.61 to 5.0 g/10 min. The wire and the cable having an extrude cover obtained by extrusion-molding the polyolefin resin composition are also provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyolefin resin composition for covering an electric wire / cable, and an electric wire / cable using the same.

Various cables such as electric wires (also called insulated wires), power cables and communication cables used in electrical and electronic equipment (the above electric wires and various cables are collectively referred to as electric wires) are conductors, core wires, conductor bundles, fiber core wires, etc. Those having a coating made of a polyolefin resin on the outer periphery of (sometimes referred to as a conductor or the like) are widely used.
An insulation coating of an insulated wire or a sheath of various cables (sometimes referred to as a coating) is required to have excellent strength characteristics and high wear resistance.

As a resin composition for forming a coating such as an electric wire, Patent Document 1 includes an ethylene-α-olefin copolymer (I) satisfying all of the following requirements (b1) to (b4) and the following requirements ( A resin composition for covering an electric wire or a sheath that contains high-density polyethylene (II) that satisfies c1) to (c2) at a specific content and satisfies all of the following requirements (a1) to (a5) is described. (Claim 1 of the same document).
(A1) Melt flow rate (MFR (2.16)) is 0.2-2 g / 10 minutes (a2) Density is 920-940 kg / m ³
(A3) Melting component ratio (HL110) of 110 ° C. or lower is 30 to 75%
(A4) Flow activation energy (Ea) is 40 kJ / mol or more (a5) Molecular weight distribution (Mw / Mn) is 6 to 25
(B1) Melt flow rate (MFR) is 0.05-2 g / 10 min (b2) Density is 905-935 kg / m ³
(B3) Flow activation energy (Ea) is 40 kJ / mol or more (b4) Molecular weight distribution (Mw / Mn) is 6 to 25
(C1) Melt flow rate (MFR) is 0.2 to 20 g / 10 min (c2) Density is 940 to 975 kg / m ³

Japanese Patent No. 5163237

Incidentally, an electric wire or the like provided with a coating is usually manufactured by extruding a polyolefin resin composition on the outer periphery of a conductor or the like.
However, the conventional polyolefin resin composition has the following problems, and the solution has been desired. That is, when a resin composition containing a film grade polyolefin resin, which is in high demand and has good material supply properties, is used as the coating polyolefin resin composition, the coating can be formed at low cost. However, the coating formed with such a polyolefin resin composition causes a rough appearance without smoothing the surface. This rough appearance is not limited to the film grade polyolefin resin composition, and may occur even with other polyolefin resin compositions conventionally used for coating. In particular, the rough appearance of the coating is prominent when the linear velocity in extrusion is increased in order to increase the production efficiency.
Moreover, in the conventional polyolefin resin composition, the load applied to the extruder during extrusion molding becomes large, and extrusion molding becomes difficult (it is inferior in easy (low load) extrudability). In particular, extrudability decreases rapidly when the linear velocity in extrusion molding is increased.
Furthermore, in recent years, due to the diversification of electric wires and the like, electric wires having a complicated cross-sectional shape, electric wires having a large diameter, electric wires having a thick coating, and the like have been used. However, if the extrudability of the polyolefin resin composition is increased to ensure extrudability, the extruded polyolefin resin composition cannot maintain the shape immediately after extrusion (inferior in shape maintainability), and the polyolefin resin composition As a result, the electric wire having a predetermined shape cannot be manufactured.

  INDUSTRIAL APPLICABILITY The present invention is an electric wire / cable that can reduce the load on the extrusion molding machine, has excellent shape maintenance after extrusion molding, and has a high wear resistance and can form a coating with excellent appearance. An object is to provide a polyolefin resin composition for coating, and an electric wire / cable using the composition.

  In the polyolefin resin composition used for coating such as an electric wire, the present inventors have a polyethylene resin (a1) having a specific density and a melt flow rate (MFR), a density higher than the resin (a1), and a predetermined density. When the resin (a2) having MFR and the polypropylene resin (a3) are contained in a specific ratio, and the MFR of the obtained resin composition is set to a specific value, the fluidity of the resin composition is increased and extrusion molding is performed. Although the load on the machine can be reduced, the present inventors have found that it is possible to form a coating having high shape maintenance, high wear resistance and excellent appearance. The present invention has been further studied based on this finding and has been completed.

The object of the present invention has been achieved by the following means.
<1> 20 to 70% by mass of a polyethylene resin (a1) having a density of 0.900 to 0.935 g / cm ³ and a melt flow rate (190 ° C., 21.18 N) of 10 g / 10 min or less;
A resin of at least one polymer selected from the group consisting of an ethylene-α-olefin copolymer and an ethylene homopolymer, having a density of 0.940 to 0.965 g / cm ³ and a melt flow rate ( 190 ° C., 21.18 N) is 0.2 to 10 g / 10 min of resin (a2) 20 to 75% by mass,
Containing 3 to 25% by mass of a polypropylene resin (a3),
A polyolefin resin composition for covering electric wires and cables having a melt flow rate (190 ° C., 21.18 N) of 0.61 to 5.0 g / 10 min.
<2> 40% to 67% by mass of the polyethylene resin (a1), 30% to 57% by mass of the resin (a2), and 3% to 25% by mass of the polypropylene resin (a3). Polyolefin resin composition for covering electric wires and cables.
<3> The polyolefin resin composition for covering electric wires and cables according to <1> or <2>, which contains carbon black (b).
<4> The polyolefin resin composition for covering an electric wire / cable according to any one of <1> to <3>, wherein the polyethylene resin (a1) is a polyethylene resin synthesized using a metallocene catalyst.
<5> The polypropylene resin (a3) is a homopolymer of propylene, a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, a ternary copolymer of propylene, ethylene and 1-butene. A polypropylene resin comprising a polypropylene resin comprising at least one polymer selected from the group consisting of polymers and having a melt flow rate (230 ° C., 21.18 N) of 0.5 to 50 g / 10 min. The polyolefin resin composition for electric wire / cable coating according to any one of <1> to <4>.
<6> The content of the carbon black (b) is 1.5 to 5.0 mass with respect to a total of 100 mass parts of the polyethylene resin (a1), the resin (a2), and the polypropylene resin (a3). The polyolefin resin composition for covering electric wires and cables according to any one of <3> to <5>, which is a part.
<7> An electric wire / cable having a coating formed by extruding the polyolefin resin composition for electric wire / cable coating according to any one of <1> to <6> above.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The polyolefin resin composition for covering electric wires and cables of the present invention can reduce the load on the extruder (excellent extrudability) and can maintain the shape after extrusion (excellent shape maintainability). Further, the polyolefin resin composition for cable coating of the present invention has high abrasion resistance, can form a coating with a smooth surface and excellent appearance. The polyolefin resin composition for covering electric wires / cables can maintain the above-described excellent extrudability, shape maintenance and appearance even when the linear velocity in extrusion molding is increased to, for example, about 100 m / min.

It is the schematic which shows the slot type | mold optical cable as a preferable electric wire and cable of this invention. It is a schematic explanatory drawing which shows the shape and structure of the leaky coaxial cable as another preferable electric wire and cable of this invention.

<< Polyolefin resin composition for covering electric wires and cables >>
The polyolefin resin composition for covering electric wires and cables of the present invention (hereinafter sometimes referred to as the resin composition of the present invention) has a density of 0.900 to 0.935 g / cm ³ and a melt flow rate (190 ° C., 21.18N) of at least one polymer selected from the group consisting of 20 to 70% by mass of a polyethylene resin (a1) having an amount of 10 g / 10 min or less, and an ethylene-α-olefin copolymer and an ethylene homopolymer. Resin (a2) having a density of 0.940 to 0.965 g / cm ³ and a melt flow rate (190 ° C., 21.18 N) of 0.2 to 10 g / 10 min, 20 to 75 mass % And polypropylene resin (a3) 3 to 25% by mass. The resin composition of the present invention containing these components has a melt flow rate (190 ° C., 21.18 N) in the range of 0.61 to 5.0 g / 10 minutes.

Each component used in the present invention will be described.
In addition, in each component and the resin composition of this invention, measuring methods, such as a density and MFR (190 degreeC, 21.18N), are demonstrated in detail in an Example.

<(A1) Polyethylene resin>
The polyethylene resin (a1) used for this invention will not be specifically limited if a density and MFR are a predetermined thing, For example, the copolymer of ethylene and C4-C12 alpha olefin is mentioned. The α-olefin is not particularly limited, and examples thereof include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like.

  In the above copolymer, the content of the ethylene component is not particularly limited, but 50 to 99.9% by mass is preferable, and 75 to 99.9% of all the components of the copolymer from the viewpoint of shape maintenance. The mass% is more preferable. The content rate of an ethylene structural component can be calculated | required, for example with an infrared spectrophotometry.

  The polyethylene resin (a1) is not particularly limited. For example, LDPE (low density polyethylene), LLDPE (linear low density polyethylene), MDPE (medium density polyethylene), polyethylene resin synthesized in the presence of a metallocene catalyst, and the like. Is mentioned. The polyethylene resin synthesized in the presence of a metallocene catalyst is a resin obtained by copolymerizing ethylene and an α-olefin in the presence of a metallocene catalyst. The polyethylene resin (a1) is preferably a polyethylene resin synthesized in the presence of LLDPE or a metallocene catalyst in terms of tensile strength and environmental stress cracking (ESCR).

The density of the polyethylene resin (a1) is a 0.900~0.935g / cm ^3, preferably 0.910~0.925g / cm ^3, more preferably 0.912~0.923g / cm ³ It is. If the density is too small, high abrasion resistance may not be imparted to the coating. On the other hand, if the density is too high, the extrudability is poor. Moreover, when the density is in the above range, the electric wire or the like can be provided with a well-balanced flexibility and wear resistance, and further can be imparted with low temperature impact resistance.

  MFR (190 degreeC, 21.18N) of polyethylene resin (a1) is 10 g / 10min or less, Preferably it is 1.0-5.0 g / 10min, More preferably, it is 1.0-3.0 g / 10. Minutes. If the MFR exceeds 10 g / 10 min, the shape of the polyolefin resin composition for covering electric wires / cables is destroyed after extrusion, and the shape maintainability is lowered. In particular, when manufacturing a deformed electric wire / cable, a large-diameter thick-walled electric wire / cable, or a self-supporting electric wire / cable, which will be described later, the cross-sectional shape tends to collapse.

As the polyethylene resin (a1), a commercially available product satisfying the above-mentioned density and MFR may be used, or it may be appropriately synthesized based on a conventional method.
Examples of commercially available products include “Kernel” (trade name, manufactured by Nippon Polyethylene Co., Ltd.), “Evolue” (trade name, manufactured by Prime Polymer Co., Ltd.), “Moretec” (trade name, manufactured by Prime Polymer Co., Ltd.), “NUC” ( Product name, manufactured by Nippon Unicar Co., Ltd.), “NOVATEC” (trade name, manufactured by Nippon Polyethylene Co., Ltd.), and the like.

  When the polyethylene resin (a1) is synthesized, ethylene and α-olefin are copolymerized in the presence of a Ziegler-Natta catalyst or a metallocene catalyst using, for example, a gas phase polymerization apparatus or a liquid phase polymerization apparatus. At this time, the density can be set within a predetermined range depending on, for example, the type of α-olefin and the amount of introduction. Further, the MFR can be set in a predetermined range by, for example, the average molecular weight.

The polyethylene resin (a1) usually has a low melt viscosity, and is inferior in shape maintainability particularly when producing a deformed electric wire or cable. However, the polyethylene resin (a1) is used in combination with the resin (a2) and the polypropylene resin (a3) having a content in the range described later, and the content of the polyethylene resin (a1) in the resin composition of the present invention. When the content is 20 to 70% by mass, the shape maintaining property is improved, and the resin composition has excellent extrudability and can form a coating with high wear resistance and excellent appearance. Moreover, the above-described excellent extrudability, shape maintainability and appearance can be obtained even when the linear velocity in extrusion molding is increased to, for example, about 100 m / min. When the content of the polyethylene resin (a1) is less than 20% by mass, the load on the extrusion molding machine increases. In particular, when the linear velocity is increased, extrusion molding may not be possible. On the other hand, when it exceeds 70 mass%, it will be inferior to abrasion resistance.
The content of the polyethylene resin (a1) is preferably 40 to 67% by mass in terms of achieving both extrudability and shape maintainability and imparting high abrasion resistance and excellent appearance to the coating, and 40 to 60% by mass. More preferably, it is mass%.

  A polyethylene resin (a1) may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, it is good for each copolymer to satisfy | fill MFR, Preferably a density, but the blend of 2 or more types of copolymers may satisfy | fill the whole.

<Resin (a2)>
The resin (a2) used in the present invention is a resin of at least one polymer selected from the group consisting of an ethylene-α olefin copolymer and an ethylene homopolymer. The ethylene-α olefin copolymer is not particularly limited as long as the density and MFR are predetermined, and examples thereof include a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. The α-olefin is not particularly limited, and examples thereof include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like.

In the ethylene-α olefin copolymer, the content of the ethylene constituent component is not particularly limited, but is preferably 95% by mass or more in the total constituent components of the copolymer in terms of strength characteristics and shape maintainability. 100 mass% is more preferable. The content rate of an ethylene structural component can be calculated | required by the said method.
The resin (a2) is preferably an ethylene homopolymer resin among ethylene homopolymers and ethylene-α-olefin copolymer resins.

Although it does not specifically limit as resin (a2), For example, HDPE (high density polyethylene), ultra high molecular weight polyethylene (UHMWPE), etc. are mentioned. Of these, HDPE is preferable.
The density of the resin (a2) is 0.940 to 0.965 g / cm ³ , preferably 0.945 to 0.960 g / cm ³ , more preferably 0.948 to 0.958 g / cm ³ . is there. If the density is too small, the mechanical strength and wear resistance may not be maintained. On the other hand, if the density is too high, the extrudability is poor.

  MFR (190 degreeC, 21.18N) of resin (a2) is less than 0.2-10 g / 10min, Preferably it is 0.8-5 g / 10min, More preferably, it is 0.8-3g / 10 minutes. When the MFR is less than 0.2 g / 10 minutes, the motor load applied to the extruder becomes high and the extrusion moldability is poor. In particular, when the linear velocity in extrusion molding is increased, the extrusion moldability is greatly lowered (inferior to the high-speed moldability). On the other hand, if it exceeds 10 g / 10 minutes, the polyolefin resin composition for covering electric wires / cables is drawn down after extrusion molding, and the shape maintainability is lowered.

As the resin (a2) having a density and MFR in the above range, a commercially available product satisfying the above characteristics may be used, or it may be appropriately synthesized based on a conventional method.
Examples of commercially available ethylene-α-olefin copolymer resins include “Evolue H” (trade name, manufactured by Prime Polymer Co., Ltd.), “SURPASS” (trade name, manufactured by NOVA Chemicals Co., Ltd.), and the like.
Commercially available ethylene homopolymer resins include, for example, “Hi-Zex” (trade name, manufactured by Prime Polymer Co., Ltd.), “Nipolon Hard” (trade name, manufactured by Tosoh Corporation), “Novatech” (trade name, manufactured by Nippon Polyethylene Co., Ltd.) And the like.

  When synthesizing the resin (a2), ethylene and optionally α-olefin are polymerized or copolymerized by, for example, a low pressure method using a Ziegler-Natta catalyst or an intermediate pressure method. At this time, the density and MFR can be set within a predetermined range in the same manner as in the polyethylene resin (a1).

The content rate of resin (a2) in the resin composition of this invention is 20-75 mass%. When the content is less than 20% by mass, the wear resistance is inferior. On the other hand, when it exceeds 75% by mass, the load on the extrusion molding machine increases. In particular, when the linear velocity is increased, extrusion molding may not be possible.
The content of the resin (a2) is preferably 30 to 57% by mass and 40 to 60% by mass in that the load on the extrusion molding machine can be reduced without reducing the shape maintainability. Further preferred.

  Resin (a2) may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, it is good for each to satisfy | fill density and MFR, but 2 or more types of polyethylene blends may satisfy | fill density and MFR as a whole.

<(A3) Polypropylene resin>
In the present invention, a polypropylene resin (a3) is used. By including a specific amount of polypropylene resin in the polyethylene resin (a1) and the resin (a2), an excellent appearance can be imparted to the coating while maintaining the properties of the polyethylene resin (a1) and the resin (a2).
The polypropylene resin (a3) used in the present invention is not particularly limited, and is a propylene homopolymer resin (homopolypropylene resin), a propylene-α olefin random copolymer resin, or an ethylene-propylene block copolymer resin. Etc. can be used. Here, the resin of the propylene-α-olefin random copolymer has a content of the α-olefin constituent component of about 1 to 10% by mass, and the α-olefin constituent component is randomly incorporated in the propylene chain. Say. The ethylene-propylene block copolymer has a polyethylene or ethylene-propylene rubber (EPR) content of about 5 to 20% by mass, and is a sea-island structure in which polyethylene and EPR exist independently in polypropylene. It means what is.
The propylene-α-olefin random copolymer is not particularly limited, and examples thereof include a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, and a ternary copolymer of propylene, ethylene and 1-butene. A polymer etc. are mentioned.

  The polypropylene resin (a3) is preferably a propylene homopolymer resin or a propylene-α-olefin random copolymer resin from the viewpoint of appearance after extrusion molding, and a propylene homopolymer, a copolymer of propylene and ethylene. More preferable is a resin of at least one polymer selected from the group consisting of a polymer, a copolymer of propylene and 1-butene, and a terpolymer of propylene, ethylene and 1-butene.

The density of polypropylene resin (a3) is not specifically limited, For example, 0.900-0.920 g / cm < ³ > is preferable.

  MFR (230 degreeC, 21.18N) of polypropylene resin (a3) is not specifically limited, For example, Preferably it is 0.5-50 g / 10min, More preferably, it is 0.5-30 g / 10min. Yes, more preferably 0.5 to 10 g / 10 min. By using such a polypropylene resin having an MFR value, the molecular weight distribution of both the polyethylene resin (a1) and the resin (a2) that can be used in the present invention can be broadened, and the appearance of electric wires and the like is improved. be able to.

As the polypropylene resin (a3), a commercially available product satisfying the above characteristics may be used, or it may be appropriately synthesized based on a conventional method.
Examples of commercially available products include “Sun Allomer PP” (trade name, manufactured by Sun Allomer), “Prime Polypro” (trade name, manufactured by Prime Polymer), “Novatech PP” (trade name, manufactured by Nippon Polypro), and the like. be able to.

  When synthesizing a polypropylene resin, propylene and optionally α-olefin are copolymerized in the presence of various catalysts using, for example, a gas phase polymerization apparatus or a liquid phase polymerization apparatus. At this time, the density and MFR can be set within a predetermined range in the same manner as in the polyethylene resin (a1).

  The content rate in the resin composition of this invention of a polypropylene resin (a3) is 3-25 mass%, Preferably it is 5-15 mass%. When the content is less than 3% by mass, the wear resistance and the appearance are inferior. On the other hand, if it exceeds 25% by mass, the load on the extrusion molding machine increases. In particular, if the linear velocity is increased, extrusion molding may not be possible. In addition, the flexibility is impaired, and an electric wire or the like (coating) having poor cold resistance and weather resistance is obtained.

  A polypropylene resin (a3) may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, it is good for each to satisfy | fill density and MFR, but the blend of 2 or more types of polypropylene resin may satisfy | fill the density and MFR as a whole.

<(B) Carbon black>
The type of carbon black (b) used in the present invention is not particularly limited, and various types can be used. Examples thereof include carbon black for reinforcement such as furnace black and thermal black, and conductive carbon black such as acetylene black and ketjen black. Of these, furnace black is preferable.
The average particle size of the carbon black (b) is not particularly limited, but is preferably 10 to 500 nm.
Carbon black (b) may be used individually by 1 type, and may use 2 or more types together.
Examples of carbon black (b) include “Asahi Carbon”, “SUNBLACK” (trade names, both manufactured by Asahi Carbon Co., Ltd.), and the like.

  The content of carbon black (b) in the resin composition of the present invention is not particularly limited. For example, with respect to a total of 100 parts by mass of the polyethylene resin (a1), the resin (a2), and the polypropylene resin (a3), 1.5 to 5.0 parts by mass is preferable, and 2.0 to 3.0 parts by mass is preferable. Further preferred. When this content is in the above range, mechanical properties over a long period of time can be maintained even when used outdoors and exposed to ultraviolet rays without impairing the mechanical properties and appearance of the coating.

<Other ingredients>
The resin composition of the present invention includes various additives generally used in electric wires, cables, cords, tubes, electric wire parts, sheets, etc., such as antioxidants, metal deactivators, flame retardants, flame retardants, etc. A fuel (auxiliary) agent, a filler, a lubricant, and the like can be appropriately contained as long as the intended effects are not impaired. Moreover, the resin composition of this invention can contain suitably resin other than a polyethylene resin (a1), resin (a2), and a polypropylene resin (a3) in the range which does not impair the target effect.

The antioxidant is preferably contained in the resin composition of the present invention.
Antioxidants that can be used in the present invention are usually those used for electric wires and the like, and examples thereof include phenol-based antioxidants, phosphorus-based antioxidants, and other antioxidants. Of these, phenol-based antioxidants and phosphorus-based antioxidants are preferable.
In this invention, antioxidant may be used individually by 1 type and may use 2 or more types together.

Although it does not specifically limit as a phenolic antioxidant, For example, pentaerythrityl-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5- And di-t-butyl-4-hydroxyphenyl) propionate and 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene.
Examples of commercially available phenolic antioxidants include “Irganox” (trade name, manufactured by BASF).
The content of the phenolic antioxidant in the resin composition of the present invention is not particularly limited, and is 100 parts by mass in total of the polyethylene resin (a1), the resin (a2), and the polypropylene resin (a3). 0.01-1.0 mass part is preferable, 0.05-0.5 mass part is more preferable, 0.1-0.3 mass part is further more preferable.

Although it does not specifically limit as phosphorus antioxidant, For example, tris (2, 4- di-tert- butylphenyl) dried phyto, bis (2, 4- di-tert- butyl-6-methylphenyl) -ethyl -Phosphite etc. are mentioned.
Examples of commercially available phenolic antioxidants include “Irgaphos” (trade name, manufactured by BASF).
Content in the resin composition of this invention of phosphorus antioxidant is not specifically limited, With respect to a total of 100 mass parts of polyethylene resin (a1), resin (a2), and polypropylene resin (a3), 0.01-1.0 mass part is preferable, 0.05-0.5 mass part is more preferable, 0.1-0.3 mass part is further more preferable.

  Examples of other antioxidants include 4,4′-dioctyl diphenylamine, N, N′-diphenyl-p-phenylenediamine, and a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline. Amine-based antioxidants, bis (2-methyl-4- (3-n-alkylthiopropionyloxy) -5-tert-butylphenyl) sulfide, 2-mercaptoben ヅ imidazole and its zinc salt, pentaerythritol-tetrakis (3 -Lauryl-thiopropionate) and other sulfur-based antioxidants.

  The lubricant is not particularly limited, and examples thereof include hydrocarbon lubricants, fatty acid lubricants, fatty acid amide lubricants, ester lubricants, alcohol lubricants, metal soap lubricants, and silicone gums.

<Characteristics of Resin Composition of the Present Invention>
The resin composition of the present invention contains a polyethylene resin (a1), a resin (a2), and a polypropylene resin (a3) at the above-described content. Thereby, the resin composition of this invention has MFR (190 degreeC, 21.18N) of 0.61-5.0 g / 10min. Furthermore, the resin composition of the present invention preferably has the following characteristics. As a result, it is possible to form a coating having both shape maintenance and extrudability, high wear resistance, and excellent appearance. Preferably, the resin composition of the present invention can maintain the above-described excellent extrudability, shape maintenance, and appearance even when the linear velocity in extrusion molding is increased to, for example, about 100 m / min. More preferably, the properties required for the coating of electric wires / cables (electric wires or cables), for example, mechanical strength, flexibility, impact resistance, wear resistance, cold resistance, environmental stress cracking characteristics, etc. can be imparted. .

(MFR (190 ° C., 21.18 N))
The resin composition of the present invention has an MFR (190 ° C., 21.18 N) of 0.61 to 5.0 g / 10 min. When the MFR is less than 0.61 g / 10 minutes, the extrudability, particularly the extrudability when the linear velocity in extrusion molding is increased is lowered. On the other hand, if it exceeds 5.0 g / 10 minutes, the shape maintainability, particularly the extrudability when the linear velocity in extrusion molding is increased is lowered. Even when the linear velocity in extrusion molding is increased, the MFR is 0.61 to 5 g / in that it exhibits excellent shape maintenance and extrudability and can form a coating having high wear resistance and excellent appearance. 10 minutes is preferable, and 0.8 to 2.0 g / 10 minutes is more preferable.

(density)
Although the density of the resin composition of this invention is not specifically limited, 0.935-0.975 g / cm < ³ > is preferable at the point which can make mechanical strength and a softness | flexibility as an electric wire and a cable compatible, 0.940-0. 973 g / cm ³ is more preferable.

  In the resin composition of the present invention, the MFR and density are, for example, the type, content, or combination of polyethylene resin (a1), resin (a2) and polypropylene resin (a3), or the type or content of additives. The predetermined range can be set depending on the amount or the like.

  The resin composition of the present invention having the above properties is preferably used as a coating for electric wires and cables. As will be described later, the form of the electric wire / cable is not particularly limited, and may be a conventional electric wire or the like, but in particular, a deformed electric wire / cable, a large diameter / thick electric wire / cable, or a self-supporting type described later. It is also preferably used as an electric wire / cable.

<The manufacturing method of the resin composition of this invention>
The resin composition of the present invention comprises a polyethylene resin (a1), a resin (a2), a polypropylene resin (a3), and various additives as required, in a proportion of the above content, using a mixer, a kneader, or the like. , Mixing (including melt-kneading).
At this time, the mixing order in mixing is not particularly limited, and the above components may be mixed in any order.

The mixing temperature for mixing the above-described components is not particularly limited as long as it is at least the temperature at which the polyethylene resin (a1), the resin (a2) and the polypropylene resin (a3) are melted. For example, 160-250 degreeC is preferable and 180-220 degreeC is more preferable.
Also, the mixing conditions such as the mixing time are not particularly limited, and may be determined as appropriate as long as the above components are mixed. For example, it can be 5 to 30 minutes.

  Any mixing method may be used, and a single-screw extruder, twin-screw extruder, roll, Banbury mixer, or various kneaders may be used as a mixer or kneader. Of these, a twin screw extruder, a Banbury mixer, a kneader and the like are preferable from the viewpoint of dispersibility of carbon black and additives.

<< Wire / Cable >>
The electric wire / cable of the present invention (hereinafter referred to as the electric wire of the present invention) has an extrusion coating formed by extruding the resin composition of the present invention on the outer periphery of a conductor or the like as an insulating layer or sheath.
The conductor or the like from which the resin composition of the present invention is extruded is not particularly limited, and is appropriately selected according to the type and use of the electric wire of the present invention. Further, the material, shape, dimensions, etc. of the conductor can be appropriately selected and used.

The electric wire and the like are not particularly limited as long as they are used for electric / electronic devices, and include those used for internal and external wiring of electric / electronic devices.
Moreover, as a cable, various cables can be applied without being specifically limited, and include a cable disposed indoors and a cable disposed outdoors. For example, a power cable, a communication cable, etc. are mentioned preferably.

Examples of the electric wire and the like of the present invention include electric wires and cables having a circular cross section, electric wires and cables having an outer diameter of 30 mm or less, and electric wires and cables having a coating thickness of 5 mm or less. In addition, cross-sectional shapes other than circular, for example, elliptical shapes, rectangular shapes (flat shapes), shapes having notches, or combinations of these, modified wires / cables, increased diameter or increased coating thickness Examples thereof include a large-diameter / thick-walled electric wire / cable, or a self-supporting electric wire / cable provided with a support line portion in which a support line is embedded.
The electric wire of the present invention is preferably a deformed electric wire / cable, a large-diameter / thick electric wire / cable, or a self-supporting electric wire / cable, which has been difficult to manufacture. Examples of such electric wires and cables include power twisted electric wires, communication cable tape core wires, and communication cables. Examples of the communication cable include a slot type optical cable, a leaky coaxial cable, a slotless optical cable, an intermediate branch type aerial optical cable, an optical drop cable, and an indoor optical cable. Among these, a large-diameter / thick slot optical cable and a leaky coaxial cable, which require shape maintenance, are preferable, and self-supporting electric wires / cables are also preferable.

  Below, although the preferable electric wire etc. of this invention are demonstrated with reference to drawings, this invention is not limited to these.

  A preferred example of the electric wire of the present invention is the slot type optical cable 1 shown in FIG. FIG. 1A is an end view showing an end face profile of the slot type optical cable 1, FIG. 1B is a schematic perspective view of the slot type optical cable 1, and FIG. 1C is a cable portion of the slot type optical cable 1. 11 is a schematic end view showing an end face of No. 11. FIG.

The slot-type optical cable 1 has the same shape as that of the conventional slot-type optical cable except that the sheaths, ie, the sheaths 12b and 19 and the neck portion 13 (see FIG. 1B) are formed of the resin composition of the present invention. The configuration can be taken.
That is, the slot type optical cable 1 is a self-supporting type (SSW type) optical cable, and as shown in FIG. 1, the end face (cross section) shape is a substantially circular support line portion 12 and the cross section shape is a substantially circular cable. The portion 11 has a cross-sectional shape connected by a plurality of neck portions (connecting portions) 13. Thus, the cross-sectional shape of the slot-type optical cable 1 is not a simple shape but a complicated shape.

As shown in FIG. 1 (c), the cable portion 11 is coated with a slot 15 on the peripheral surface of the tension member 14, and an optical fiber is inserted into five housing grooves 15 a formed along the axis of the slot 15. A predetermined number of core wires 16 are dropped, and are embedded in a covering (also referred to as a sheath) 19 together with a tear string 17 and a presser winding tape 18.
As shown in FIG. 1B, the support wire portion 12 has a plurality of support wires 12a and a coating (sheath) 12b that covers the support wires 12a.

  In the slot type optical cable 1, the outer diameter of the cable portion 11 is large and the thickness of the sheath 19 is thick. Although it cannot generally be said, as an example, the outer diameter of the cable portion 11 is 8 to 35 mm. The thickness of the sheath 19 will be described later.

The sheaths 12b and 19 and the neck 13 are all formed of the resin composition of the present invention. Therefore, even if the outer diameter of the cable portion 11 is large and the sheath 19 is thick, or the slot-type optical cable 1 is a self-supporting type and has a complicated cross-sectional shape having the support line portion 12 and the neck portion 13, The sheaths 12b and 19 and the neck 13 maintain a predetermined shape.
In the slot type optical cable 1, the support wire 12 a, the tension member 14, the slot 15, the optical fiber core wire 16, the tear string 17, and the presser winding tape 18 are not particularly limited as long as they are used for a normal optical cable. Can be used.

  Another preferred electric wire of the present invention is a leaky coaxial cable 2 shown in FIG. FIG. 2 shows the end face shape and structure of the leaky coaxial cable 2.

The leaky coaxial cable 2 can have the same shape and configuration as the conventional leaky coaxial cable except that the sheath, that is, the sheaths 22b and 28 and the neck portion 23 are formed of the resin composition of the present invention. .
That is, the leaky coaxial cable 2 is a self-supporting type (SSW type) cable, and as shown in FIG. 2, the end face (cross-sectional) shape is a substantially circular support line portion 22 and the cross-sectional shape is a substantially circular cable. The portion 21 has a cross-sectional shape connected by a plurality of neck portions (connecting portions) 23. Thus, the cross-sectional shape of the leaky coaxial cable 2 is not a simple shape but a complicated shape.

The cable portion 21 is covered with an insulator polyethylene string 25 and an insulator polyethylene pipe 26 on the inner conductor 24, and has an outer conductor 27 thereon, and is buried in a cover (sheath) 28 at a time.
The support line portion 22 includes a plurality of support lines 22a and a covering (sheath) 22b that covers the support lines 22a.

  In the leaky coaxial cable 2, the outer diameter of the cable portion 21 is large, and the thickness of the sheath 28 is large. Although it cannot generally be said, as an example, the outer diameter of the cable portion 21 is 20 to 60 mm. The thickness of the sheath 28 will be described later.

The sheaths 22b and 28 and the neck portion 23 are all formed of the resin composition of the present invention. Therefore, even if the outer diameter of the cable portion 21 is large and the thickness of the sheath 28 may be increased, or the leaky coaxial cable 2 is a self-supporting type and has a complicated shape having the support wire portion 22 and the neck portion 23. The sheaths 22b and 28 and the neck portion 23 maintain a predetermined shape.
In the leaky coaxial cable 2, the support wire 22a, the inner conductor 24, the insulator polyethylene string 25, the insulator polyethylene pipe 26, and the outer conductor 27 are not particularly limited as long as they are used for a normal leaky coaxial cable. Can be used.

  In the slot type optical cable 1 and the leaky coaxial cable 2, the cable portions 11 and 21 and the support wire portions 12 and 22 are all substantially circular in cross section. There is something like this.

The electric wire or the like of the present invention can be produced by coating the outer periphery of a conductor or the like while melting and mixing the resin composition of the present invention in an extruder or an extrusion coating apparatus, for example.
At this time, when the resin composition of the present invention is extruded together with a conductor or the like, the resin composition of the present invention can be molded while maintaining its shape without breaking the complicated cross-sectional shape corresponding to the cross-sectional shape of the electric wire / cable. Moreover, even if the linear velocity in extrusion molding is increased to, for example, about 100 m / min, excellent extrudability, shape maintenance, and appearance can be maintained. Accordingly, the electric wire of the present invention can be manufactured with good shape reproducibility, high yield, and high structural efficiency.
Furthermore, the resin composition of the present invention does not put an excessive load on the extrusion molding machine and has good productivity.

  The conductor that can be used in the present invention is not particularly limited as long as it can be a conductor of an electric wire, and examples thereof include an annealed copper single wire or a stranded wire (also referred to as a conductor bundle). As the conductor, in addition to the bare wire, a tin-plated one or an enamel-coated insulating layer (also referred to as a core wire) can be used. The fiber core wire, tension member, and support wire that can be used in the present invention are as described above.

The thickness of the coating formed with the resin composition of the present invention is appropriately determined according to the application and the like.
Although the thickness (maximum thickness) of an insulating layer is not specifically limited, Usually, it is about 0.15-5 mm. The thickness of the sheath is not particularly limited, but is usually about 0.15 to 30 mm.

The conditions for extruding the resin composition of the present invention are not particularly limited as long as the resin composition of the present invention can be extruded, but the load on the extruder can be reduced and shape maintainability can be secured. And it is preferable that extrusion temperature (head part) is 140-240 degreeC, and it is more preferable that it is 160-210 degreeC. Further, as other conditions of extrusion molding, the screw rotation speed is 2 to 80 rpm, the linear velocity is preferably 2 to 120 m / min, preferably 2 to 100 m / min, and more preferably 2 to 2 m / min. 80 m / min.
The screw configuration of the extruder is not particularly limited, and a normal full flight screw, a double flight screw, a tip double flight screw, a Maddock screw, or the like can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these. The numerical values of the respective formulations in Table 1 and Table 2 represent parts by mass.

The components used in each example are shown below.
Each of the polyethylene resin (a1) and the resin (a2) is ethylene and, if necessary, α-olefin, in the presence of a Ziegler-Natta catalyst or a metallocene catalyst, using a gas phase polymerization apparatus or a liquid phase polymerization apparatus at 70 to 150 ° C. And then synthesized. The catalyst concentration used may be a concentration at which the polymerization proceeds sufficiently, but 0.0001 to 5% by mass was used based on the mass of the content of the polymerization reactor.

<(A1) Polyethylene resin>
Polyethylene resin (a1-1):
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.920 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min polyethylene resin (a1- 2)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.920 g / cm ³ , MFR (190 ° C., 21.18 N) 10.00 g / 10 min polyethylene resin (a1- 3)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.900 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min polyethylene resin (a1- 4)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.935 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min polyethylene resin (a1- 5)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.890 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min polyethylene resin (a1- 6)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.940 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min polyethylene resin (a1- 7)
Copolymer of ethylene and 1-butene, content of ethylene component is 90% by mass, density is 0.920 g / cm ³ , MFR (190 ° C., 21.18 N) is 12.00 g / 10 min.

<(A2) resin>
Resin (a2-1)
Ethylene homopolymer, density 0.960 g / cm ³ , MFR (190 ° C., 21.18 N) 0.70 g / 10 min Resin (a2-2)
Ethylene homopolymer, density 0.955 g / cm ³ , MFR (190 ° C., 21.18 N) 0.20 g / 10 min Resin (a2-3)
Ethylene homopolymer, density 0.958 g / cm ³ , MFR (190 ° C., 21.18 N) 10.00 g / 10 min Resin (a2-4)
Ethylene homopolymer, density 0.940 g / cm ³ , MFR (190 ° C., 21.18 N) 0.80 g / 10 min Resin (a2-5)
Ethylene homopolymer, density 0.965 g / cm ³ , MFR (190 ° C., 21.18 N) 5.50 g / 10 min Resin (a2-6)
Copolymer of ethylene and 1-hexene, content of ethylene component is 90% by mass, density is 0.945 g / cm ³ , MFR (190 ° C., 21.18 N) 1.70 g / 10 min Resin (a2-7 )
Ethylene homopolymer, density 0.970 g / cm ³ , MFR (190 ° C., 21.18 N) 1.00 g / 10 min Resin (a2-8)
Ethylene homopolymer, density 0.958 g / cm ³ , MFR (190 ° C., 21.18 N) 0.10 g / 10 min Resin (a2-9)
Ethylene homopolymer, density 0.950 g / cm ³ , MFR (190 ° C., 21.18 N) 13.00 g / 10 min

<(A3) Polypropylene resin>
The polypropylene resin (a3) is obtained by copolymerizing propylene and, if necessary, α-olefin at 60 to 100 ° C. using a gas phase polymerization apparatus or a liquid phase polymerization apparatus in the presence of a Ziegler-Natta catalyst or a metallocene catalyst. And synthesized. The catalyst concentration used may be a concentration at which the polymerization proceeds sufficiently, but was used in an amount of 0.01 to 0.1% by mass based on the mass of the contents of the polymerization reactor.
Polypropylene resin (a3-1)
Copolymer of propylene and ethylene, content of propylene constituent component is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18N) 0.80 g / 10 min. Polypropylene resin (a3-2 )
Copolymer of propylene and ethylene, content of propylene constituent component is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18N) 0.50 g / 10 min. Polypropylene resin (a3-3 )
Copolymer of propylene and ethylene, content of propylene constituent component is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18N) is 10.00 g / 10 min. Polypropylene resin (a3-4 )
Copolymer of propylene and ethylene, content of propylene constituent component is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18N) 50.00 g / 10 min. Polypropylene resin (a3-5 )
Copolymer of propylene and ethylene, content of propylene constituent component is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18N) 0.30 g / 10 min. Polypropylene resin (a3-6 )
Copolymer of propylene and ethylene, content of propylene constituents is 95% by mass, density is 0.900 g / cm ³ , MFR (230 ° C., 21.18 N) 60.00 g / 10 minutes

<Carbon black (b)>
“Asahi Carbon # 70” (trade name, manufactured by Asahi Carbon Co., Ltd., average particle size 28 nm)

Examples 1-13 and Comparative Examples 1-11
In each example, a so-called “glasses-like” simple test cable having an end face profile shown in FIG. 1A was manufactured, and the following items were evaluated. This simple test cable is a simple test piece of a slot type optical cable. Hereinafter, of the members constituting the simple test cable, those corresponding to the members constituting the slot type optical cable 1 shown in FIG. 1 are denoted by the same reference numerals for convenience.

Using the 2L Banbury mixer, the polyethylene resin (a1), resin (a2), polypropylene resin (a3) and carbon black (b) shown in Table 1 and Table 2 at the contents shown in Table 1 and Table 2. After being melt-mixed at 200 ° C. for 20 minutes, pelletized to obtain a polyolefin resin composition for covering electric wires and cables of the present invention.
Next, each of the obtained polyolefin resin compositions for covering electric wires / cables is an extrusion molding machine for electric wires having an L / D (ratio of effective screw length L to diameter D) of 25 and a screw diameter of 40 mmφ (Holy Manufacturing Co., Ltd.) By using an extrusion die having a motor load limit of 80A) and a cross-sectional shape of glasses, the following extrusion temperature conditions are used on a 1.0 mmφ conductor (an annealed copper wire) arranged in parallel. In this way, a simple test cable was produced by integrally extruding and coating.

  As the cable part 11, the polyolefin resin composition for electric wire and cable coating was extruded on the outer periphery of one conductor so that the outer diameter was 5.0 mmφ and the coating thickness was 2.0 mm. Further, the support wire portion 12 was extruded to the outer periphery of the other conductor so that the outer diameter was 2.0 mmφ and the coating thickness was 0.5 mm. Furthermore, the polyolefin resin composition for electric wire / cable coating is connected so that each of the polyolefin resin composition for electric wire / cable coating extruded as the cable portion 11 and the support wire portion 12 is connected by the connecting portion 13 having a thickness of 1.0 mm. Extruded as a connecting portion 13.

  In addition, an abrasion resistance test wire (cross-sectional shape is circular) having an outer diameter of 2.4 mmφ and a coating thickness of 0.8 mm on a 0.8 mmφ conductor (an annealed copper wire) is the same as the manufacture of a simple test cable. Thus, it was produced.

Extrusion conditions (temperature) are divided into three zones C1, C2, and C3, with the temperature control in the cylinder part of the extruder from the feeder side to the die side. The C1 zone is 170 ° C, the C2 zone is 190 ° C, and the C3 zone is It was set to 200 ° C. and a die temperature of 200 ° C.
The linear velocity was set to 10 m / min or 100 m / min.

  The density and MFR of each resin and the obtained polyolefin resin composition for covering electric wires and cables were measured by the following methods. The results are shown in Tables 1 and 2.

<Measurement of MFR>
MFR (190 ° C., 21.18 N) was measured under the condition D of 190 ° C. and 21.18 N based on “Method A (manual cut-off method)” defined in JIS K 7210.
The MFR (230 ° C., 21.18 N) of the polypropylene resin (a3) was measured in the same manner as MFR (190 ° C., 21.18 N) except that the condition M was changed to 230 ° C.

<Density>
The density was measured based on “Method A (underwater substitution method)” defined in JIS K 7112: 1999.

<Appearance test (surface roughness)>
The appearance of a simple test cable obtained by extrusion molding at each linear velocity was measured according to the following evaluation criteria by measuring the arithmetic average surface roughness (Ra) defined in JIS B 0601: 2013 under the following measurement conditions. In the appearance test, the evaluation “B” is a pass level of this test, and it is at a desirable level when “A” or more.
-Measurement conditions-
The arithmetic average surface roughness (Ra) of the prepared simple test cable was obtained by sampling the coating of the simple test cable at five random locations, based on JIS B 0601: 2013, a surface roughness measuring machine (manufactured by MITUTOYO, Surf Test) The arithmetic average surface roughness (Ra, μm) was determined using SJ-301 (trade name)).
-Evaluation criteria-
A: 1.5 μm or less A: More than 1.5 μm and 2.5 μm or less B: More than 2.5 μm and 3.5 μm or less C: More than 3.5 μm

<Abrasion resistance test>
A 15N load was applied on the abrasion resistance test wire installed horizontally, and the coating was worn using a piano wire of 0.25 mmφ. The piano wire was continuously reciprocated until reaching the conductor, and the number of reciprocations was measured. The part to be worn was carried out four times at 90, 180, 270 and 360 ° in the circumferential direction for each sample, and the average value of the four round-trip times was used as an index of wear resistance. The wear resistance was evaluated according to the following evaluation criteria based on the average number of reciprocations. In the abrasion resistance test, the evaluation “B” is a pass level of this test, and it is a desirable level when it is “A” or more.
-Evaluation criteria-
AA: 300 times or more A: 200 times or more and less than 300 times B: 100 times or more and less than 200 times C: Less than 100 times

<Shape maintenance (draw-down resistance) test>
In each example where each simple test cable was manufactured by extrusion molding at a linear speed of 10 m / min, the polyolefin resin composition for covering electric wires / cables extruded by the extruder was not cooled with cold water or the like. It was allowed to stand for a maximum of 20 seconds and visually confirmed whether or not the predetermined shape was maintained, and evaluated according to the following evaluation criteria. In this test, maintaining the shape means that after extrusion (after being extruded from the extruder) and after the extrusion connected by the polyolefin resin composition for cable coating, after a predetermined time elapses. It means that the inclination angle of the simplified electric wire connecting portion 13 is kept within 5 degrees with respect to the shape of the extrusion die. In the shape maintenance test, the evaluation “B” is a pass level of this test, and it is a desirable level when it is “A” or more.
-Evaluation criteria-
AA: When the shape is maintained even after being left for 20 seconds A: When the shape is maintained even after being left for 10 seconds, the shape cannot be maintained when left for 20 seconds B: The shape is maintained even after being left for 5 seconds, When the shape cannot be maintained after being left for 10 seconds C: When the shape collapses in less than 5 seconds

<Extrudability test>
In each example where a simple test cable was manufactured by extrusion molding at a line speed of 100 m / min, it acted on the motor of the extrusion molding machine when the polyolefin resin composition for covering each wire / cable was extruded by the above extruder. The maximum load value was read.
The read value was divided by the motor load limit value to calculate the load ratio (%) with respect to the motor load limit. The extrudability of the polyolefin resin composition for covering electric wires and cables was evaluated according to the following evaluation criteria using the load factor as an index. In the extrudability test, when the evaluation is “B”, the load applied to the extruder can be tolerated.
-Evaluation criteria-
AA: 74% or less A: Over 74% and 85% or less B: Over 85% and 100% or less C: Over 100%

<Cold resistance test>
The embrittlement temperature was measured based on JIS C 3005 using a test piece prepared by molding the polyolefin resin composition for covering electric wires / cables in each Example into a sheet shape having a thickness of 2 mm. As a result, all the test pieces prepared with the polyolefin resin composition for covering electric wires and cables prepared in Examples 1 to 13 had a crack generation temperature of −40 ° C. or less and excellent cold resistance.

The following can be understood from the results of Tables 1 and 2.
That is, a polyethylene resin (a1) having a specific density and MFR, a resin (a2) having a specific density and MFR, and a polypropylene resin (a3) are contained in a specific ratio, and MFR is set to a specific value. The set polyolefin resin composition for electric wire / cable coating of the present invention was excellent in extrudability and shape maintainability even when the cross-sectional shape of the coating to be formed was glasses. In addition, these polyolefin resin compositions for cable coating were able to form a coating having high wear resistance, a smooth surface and excellent appearance. In addition, even when the linear velocity was set at a high speed of 100 m / min and extrusion molding was performed, the above-described excellent extrudability, shape maintainability and appearance were maintained.

On the other hand, Comparative Example 1 having a high content of the polyethylene resin (a1) did not have sufficient wear resistance. On the other hand, Comparative Example 2 having a low content of the polyethylene resin (a1) had an MFR that was too small, and the extrudability was not sufficient, and the extrudability and the shape maintainability were not compatible. In Comparative Example 3 in which the density of the polyethylene resin (a1) is too small, the abrasion resistance was not sufficient. On the other hand, Comparative Example 4 in which the density of the polyethylene resin (a1) was too high was not sufficiently extrudable and could not achieve both extrudability and shape maintainability. In Comparative Example 5 in which the MFR of the polyethylene resin (a1) was too large, the shape maintainability was not sufficient, and the extrudability and the shape maintainability were not compatible.
Moreover, the comparative example 6 in which the density of the resin (a2) is too large and the comparative example 7 in which the MFR of the resin (a2) is too small have insufficient extrudability, and the extrudability and the shape maintainability cannot be achieved at the same time. In Comparative Example 8 in which the MFR of the resin (a2) was too large, the shape maintainability was not sufficient, and both the extrudability and the shape maintainability were not compatible.
Furthermore, the comparative example 10 which does not contain a polypropylene resin (a3) was not sufficient in appearance and wear resistance. On the other hand, Comparative Example 11 having a high content of the polypropylene resin (a3) was not sufficiently extrudable and could not achieve both extrudability and shape maintainability. Comparative Example 9 in which the MFR of the polyolefin resin composition for covering electric wires / cables was too small was not sufficiently extrudable and could not achieve both extrudability and shape maintainability.

DESCRIPTION OF SYMBOLS 1 Slot type optical cable 2 Leaky coaxial cable 11, 21 Cable part 12, 22 Support line part 12a, 22a Support line 12b, 22b Cover (sheath)
13, 23 Neck part 14 Tension member 15 Slot 15a Storage groove 16 Optical fiber core wire 17 Tear string 18 Holding tape 19, 28 Cover (sheath)
24 Inner conductor 25 Insulator polyethylene string 26 Insulator polyethylene pipe 27 Outer conductor

Claims (7)

20 to 70% by mass of a polyethylene resin (a1) having a density of 0.900 to 0.935 g / cm ³ and a melt flow rate (190 ° C., 21.18 N) of 10 g / 10 min or less,
A resin of at least one polymer selected from the group consisting of an ethylene-α-olefin copolymer and an ethylene homopolymer, having a density of 0.940 to 0.965 g / cm ³ and a melt flow rate ( 190 ° C., 21.18 N) is 0.2 to 10 g / 10 min of resin (a2) 20 to 75% by mass,
Containing 3 to 25% by mass of a polypropylene resin (a3),
A polyolefin resin composition for covering electric wires and cables having a melt flow rate (190 ° C., 21.18 N) of 0.61 to 5.0 g / 10 min.   The electric wire / cable according to claim 1, comprising 40 to 67% by mass of the polyethylene resin (a1), 30 to 57% by mass of the resin (a2), and 3 to 25% by mass of the polypropylene resin (a3). Polyolefin resin composition for coating.   The polyolefin resin composition for covering electric wires and cables according to claim 1 or 2, containing carbon black (b).   The polyolefin resin composition for covering electric wires and cables according to any one of claims 1 to 3, wherein the polyethylene resin (a1) is a polyethylene resin synthesized using a metallocene catalyst.   The polypropylene resin (a3) is composed of a homopolymer of propylene, a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, and a terpolymer of propylene, ethylene and 1-butene. A polypropylene resin comprising at least one polymer selected from the group consisting of a polypropylene resin having a melt flow rate (230 ° C., 21.18 N) of 0.5 to 50 g / 10 min. Item 5. The polyolefin resin composition for covering electric wires / cables according to item 1 to item 4.   Content of the said carbon black (b) is 1.5-5.0 mass parts with respect to a total of 100 mass parts of the said polyethylene resin (a1), the said resin (a2), and the said polypropylene resin (a3). The polyolefin resin composition for electric wire / cable coating according to any one of claims 3 to 5.   An electric wire / cable having a coating formed by extruding the polyolefin resin composition for coating an electric wire / cable according to claim 1.

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