JP6774735B2 - Polyolefin resin composition for coating electric wires and cables and electric wires and cables - Google Patents

Description

The present invention relates to a polyolefin resin composition for coating electric wires and cables, and electric wires and cables using the same.

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

As a resin composition for forming a coating of an electric wire or the like, Patent Document 1 describes an ethylene-α-olefin copolymer (I) satisfying all of the following requirements (b1) to (b4) and the following requirements (I). Described is a resin composition for wire coating or sheath, which contains high-density polyethylene (II) satisfying c1) to (c2) at a specific content and satisfies all of the following requirements (a1) to (a5). (Claim 1 of the same document).
(A1) Melt flow rate (MFR (2.16)) is 0.2 to 2 g / 10 minutes (a2) Density is 920 to 940 kg / m ³
(A3) The 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 to 2 g / 10 minutes (b2) Density is 905 to 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 minutes (c2) Density is 940 to 975 kg / m ³

Japanese Patent No. 5163237

By the way, an electric wire or the like having 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 it has been desired to solve them. That is, when a resin composition containing a film-grade polyolefin resin, which is in high demand and has good material supply, is used as the polyolefin resin composition for coating, the coating can be formed at low cost. However, the coating formed of such a polyolefin resin composition does not have a smooth surface and causes a rough appearance. This roughness in appearance may occur not only in film-grade polyolefin resin compositions but also in other polyolefin resin compositions conventionally used for coating. In particular, the appearance roughness of the coating becomes remarkable when the linear velocity in extrusion molding is increased in order to increase the manufacturing efficiency.
Further, in the conventional polyolefin resin composition, the load applied to the extrusion molding machine at the time of extrusion molding becomes large, which may make extrusion molding difficult (inferior in easy (low load) extrusion property). In particular, the extrudability decreases sharply when the linear velocity in extrusion molding is increased.
Further, 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, and electric wires having a thick coating have come to be used. However, if the extrudability of the polyolefin resin composition is increased in order to ensure the extrudability, the extruded polyolefin resin composition cannot maintain its shape immediately after extrusion (it is inferior in shape retention), and the polyolefin resin composition The shape of the wire collapses (drawdown), and as a result, it becomes impossible to manufacture an electric wire or the like having a predetermined shape.

INDUSTRIAL APPLICABILITY According to the present invention, the load on the extruder can be reduced, the shape can be maintained after extrusion molding, the wear resistance is high, and a coating having an excellent appearance can be formed. An object of the present invention is to provide a polyolefin resin composition for coating and an electric wire / cable using the same.

In the polyolefin resin composition used for coating electric wires and the like, the present inventors have a polyethylene resin (a1) having a specific density and melt flow rate (MFR), and a predetermined density higher than that of this resin (a1). When the resin (a2) having MFR and the polypropylene-based 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. It has been found that, despite being able to reduce the load on the machine, it also has high shape retention, high wear resistance, and can form a coating with excellent appearance. Based on this finding, the present invention has been further studied and completed.

The subject of the present invention has been achieved by the following means.
<1> Polyethylene resin (a1) having a density of 0.9000 to 0.935 g / cm ³ and a melt flow rate (190 ° C., 21.18 N) of 10 g / 10 minutes or less, 40 to 67 % by mass.
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 (melt flow rate). 190 ° C., 21.18N) is 0.2 to 10 g / 10 minutes, and the resin (a2) is 30 to 57 % by mass.
It contains 3 to 25% by mass of a polypropylene resin (a3) having a melt flow rate (230 ° C., 21.18N) of 0.8 to 50 g / 10 minutes .
A polyolefin resin composition for coating electric wires and cables having a melt flow rate (190 ° C., 21.18N) of 0.61 to 5.0 g / 10 minutes.
< 2 > The polyolefin resin composition for electric wire / cable coating according to <1> , which contains carbon black (b).
< 3 > The polyolefin resin composition for electric wire / cable coating according to <1> or <2> , wherein the polyethylene resin (a1) is a polyethylene resin synthesized by using a metallocene catalyst.
< 4 > The polypropylene-based resin (a3) is a homopolymer of propylene, a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, and a ternary polymer of propylene, ethylene and 1-butene. at least one containing polypropylene resins consisting of polymers <1> to wire and cable coatings for the polyolefin resin composition according to any one of <3> is selected from the group consisting of polymer.
< 5 > The content of the carbon black (b) is 1.5 to 5.0 mass with respect to 100 parts by mass of the total of the polyethylene resin (a1), the resin (a2) and the polypropylene resin (a3). The polyolefin resin composition for coating an electric wire / cable according to any one of < 2 > to < 4 >.
< 6 > The electric wire / cable according to any one of <1> to < 5 >, wherein the melt flow rate (190 ° C., 21.18N) of the polyethylene resin (a1) is 1.0 g / 10 minutes or more. Polyolefin resin composition for coating.
< 7 > An electric wire / cable having a coating formed by extruding the polyolefin resin composition for coating an electric wire / cable according to any one of <1> to < 6 > above.
The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

The polyolefin resin composition for coating electric wires and cables of the present invention can reduce the load on the extrusion molding machine (excellent extrudability) and can maintain the shape after extrusion molding (excellent shape retention). Further, the polyolefin resin composition for cable coating of the present invention can form a coating having high abrasion resistance, a smooth surface, and an excellent appearance. This polyolefin resin composition for coating electric wires and cables can maintain the above-mentioned excellent extrudability, shape retention and appearance even if the linear velocity in extrusion molding is increased to, for example, about 100 m / min.

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

<< Polyolefin resin composition for wire / cable coating >>
The polymer resin composition for coating electric wires and cables of the present invention (hereinafter, may be 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) is 10 g / 10 minutes or less of polyethylene resin (a1) 20 to 70% by mass, and at least one polymer selected from the group consisting of ethylene-α olefin copolymers and ethylene homopolymers. Resin (a2) 20 to 75 mass of resin 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 minutes. % And 3 to 25% by mass of the polypropylene-based resin (a3). The resin composition of the present invention containing these components has a melt flow rate (190 ° C., 21.18N) in the range of 0.61 to 5.0 g / 10 minutes.

Each component used in the present invention will be described.
The method for measuring the density, MFR (190 ° C., 21.18N), etc. of each component and the resin composition of the present invention will be described in detail in Examples.

<(A1) Polyethylene resin>
The polyethylene resin (a1) used in the present invention is not particularly limited as long as it has a predetermined density and MFR, 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 above-mentioned copolymer, the content of ethylene constituents is not particularly limited, but from the viewpoint of shape retention, 50 to 99.9% by mass is preferable, and 75 to 99.9% by mass, based on all the constituents of the copolymer. More preferably by mass. The content of ethylene constituents can be determined, for example, by infrared spectrophotometry.

The polyethylene resin (a1) is not particularly limited, but 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. Can be mentioned. The polyethylene resin synthesized in the presence of a metallocene catalyst is a resin obtained by copolymerizing ethylene and α-olefin in the presence of a metallocene catalyst. As the polyethylene resin (a1), a polyethylene resin synthesized in the presence of LLDPE or a metallocene catalyst is preferable in terms of tensile strength and environmental stress crack (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 Is. If the density is too low, it may not be possible to impart high wear resistance to the coating. On the other hand, if the density is too high, the extrudability will be inferior. Further, when the density is in the above range, it is possible to impart well-balanced flexibility and abrasion resistance to the electric wire and the like, and further to impart low temperature impact resistance.

The MFR (190 ° C., 21.18N) of the polyethylene resin (a1) is 10 g / 10 minutes or less, preferably 1.0 to 5.0 g / 10 minutes, and more preferably 1.0 to 3.0 g / 10 minutes. Minutes. If the MFR exceeds 10 g / 10 minutes, the shape of the polyolefin resin composition for coating electric wires / cables is deformed after extrusion molding, and the shape maintainability is lowered. In particular, when 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, is manufactured, the cross-sectional shape is liable to collapse.

As the polyethylene resin (a1), a commercially available product satisfying the above density and MFR may be used, or may be appropriately synthesized and used according to a conventional method.
Examples of commercially available products include "Kernel" (trade name, manufactured by Japan Polyethylene Corporation), "Evolu" (trade name, manufactured by Prime Polymer Co., Ltd.), "More Tech" (trade name, manufactured by Prime Polymer Co., Ltd.), and "NUC" (trade name, manufactured by Prime Polymer Co., Ltd.). Product name, manufactured by Nippon Unicar Co., Ltd.), "Novatec" (trade name, manufactured by Japan Polyethylene Corporation), etc. can be mentioned.

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

The polyethylene resin (a1) usually has a small melt viscosity, and is inferior in shape retention, especially when a deformed electric wire, a cable, or the like is manufactured. However, the polyethylene resin (a1) is used in combination with the resin (a2) and the polypropylene-based 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 value is 20 to 70% by mass, the resin composition has improved shape retention, has excellent extrudability, and can form a coating having high wear resistance and excellent appearance. Moreover, the above-mentioned excellent extrudability, shape retention and appearance can be obtained even if the linear velocity in extrusion molding is increased to, for example, about 100 m / min. If the content of the polyethylene resin (a1) is less than 20% by mass, the load on the extrusion molding machine increases, and in particular, if the linear velocity is increased, extrusion molding may not be possible. On the other hand, if it exceeds 70% by mass, the wear resistance becomes inferior.
The content of the polyethylene resin (a1) is preferably 40 to 67% by mass, preferably 40 to 60%, in that both extrudability and shape retention can be achieved, and high abrasion resistance and excellent appearance can be imparted to the coating. It is more preferably by mass%.

The polyethylene resin (a1) may be used alone or in combination of two or more. When two or more kinds are used in combination, the MFR, preferably the density, is preferably satisfied by each of the copolymers, but a blend of two or more kinds of copolymers may be satisfied as a 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 it has a predetermined density and MFR, 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 in terms of strength characteristics and shape retention, 95% by mass or more is preferable in the total constituent components of the copolymer, and 97 to 97 to 100% by mass is more preferable. The content of ethylene constituents can be determined by the above method.
The resin (a2) is preferably an ethylene homopolymer resin, among the ethylene homopolymer and ethylene-α-olefin copolymer resins.

The resin (a2) is not particularly limited, and examples thereof include HDPE (high density polyethylene) and ultra high molecular weight polyethylene (UHMWPE). 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 , and more preferably 0.948 to 0.958 g / cm ³ . is there. If the density is too low, mechanical strength and wear resistance may not be maintained. On the other hand, if the density is too high, the extrudability will be inferior.

The MFR (190 ° C., 21.18N) of the resin (a2) is less than 0.2 to 10 g / 10 minutes, preferably 0.8 to 5 g / 10 minutes, and more preferably 0.8 to 3 g / min. 10 minutes. If the MFR is less than 0.2 g / 10 minutes, the motor load applied to the extruder becomes high and the extrusion moldability is inferior. In particular, when the linear velocity in extrusion molding is increased, the extrusion moldability is significantly reduced (inferior in high speed moldability). On the other hand, if it exceeds 10 g / 10 minutes, the polyolefin resin composition for wire / cable coating draws down after extrusion molding, and the shape retention property deteriorates.

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 may be appropriately synthesized and used according to a conventional method.
Examples of commercially available products of ethylene-α-olefin copolymer resins include "Evolu H" (trade name, manufactured by Prime Polymer Co., Ltd.) and "SURPASS" (trade name, manufactured by NOVA Chemicals).
Commercially available products of ethylene homopolymer resins include, for example, "HIZEX" (trade name, manufactured by Prime Polymer Co., Ltd.), "Nipolon Hard" (trade name, manufactured by Tosoh Co., Ltd.), and "Novatec" (trade name, manufactured by Nippon Polyethylene). ) Etc. can be mentioned.

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

The content of the resin (a2) in the resin composition of the present invention is 20 to 75% by mass. If this content is less than 20% by mass, the wear resistance will be inferior. On the other hand, if it exceeds 75% by mass, the load on the extrusion molding machine increases, and in particular, if the linear velocity is increased, extrusion molding may not be possible.
The content of the resin (a2) is preferably 30 to 57% by mass, preferably 40 to 60% by mass, in that the load on the extrusion molding machine can be reduced without lowering the shape retention. More preferred.

The resin (a2) may be used alone or in combination of two or more. When two or more kinds are used together, it is preferable that each of them satisfies the density and MFR, but the polyethylene blend of two or more kinds may satisfy the density and MFR as a whole.

<(A3) Polypropylene resin>
In the present invention, polypropylene-based resin (a3) is used. By containing a specific amount of a polypropylene-based resin in the polyethylene resin (a1) and the resin (a2), it is possible to impart an excellent appearance to the coating while maintaining the characteristics of the polyethylene resin (a1) and the resin (a2).
The polypropylene-based 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 means that the content of the α-olefin component is about 1 to 10% by mass, and the α-olefin component is randomly incorporated into the propylene chain. To say. The ethylene-propylene block copolymer has a polyethylene or ethylene-propylene rubber (EPR) content of about 5 to 20% by mass, and has a sea-island structure in which polyethylene or EPR independently exists in polypropylene. It means something that is.
The propylene-α-olefin random copolymer is not particularly limited, and for example, a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, and a ternary copolymer of propylene, ethylene and 1-butene. Examples include copolymers.

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

The density of the polypropylene-based resin (a3) is not particularly limited, and is preferably 0.900 to 0.920 g / cm ³ , for example.

The MFR (230 ° C., 21.18N) of the polypropylene resin (a3) is not particularly limited, and is, for example, preferably 0.5 to 50 g / 10 minutes, more preferably 0.5 to 30 g / 10 minutes. Yes, more preferably 0.5-10 g / 10 minutes. By using a polypropylene-based resin having such 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 widened, and the appearance of electric wires and the like can be improved. be able to.

As the polypropylene-based resin (a3), a commercially available product satisfying the above characteristics may be used, or may be appropriately synthesized and used according to a conventional method.
Examples of commercially available products include "SunAllomer PP" (trade name, manufactured by SunAllomer Ltd.), "Prime Polypro" (trade name, manufactured by Prime Polymer Co., Ltd.), "Novatec PP" (trade name, manufactured by Japan Polypropylene Corporation), and the like. be able to.

When synthesizing a polypropylene-based resin, propylene, preferably an α-olefin, is 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 in a predetermined range in the same manner as the polyethylene resin (a1).

The content of the polypropylene-based resin (a3) in the resin composition of the present invention is 3 to 25% by mass, preferably 5 to 15% by mass. If this content is less than 3% by mass, the wear resistance and appearance will be inferior. On the other hand, if it exceeds 25% by mass, the load on the extrusion molding machine increases, and in particular, if the linear velocity is increased, extrusion molding may not be possible. In addition, the flexibility is impaired, and the wire or the like (coating) is inferior in cold resistance and weather resistance.

The polypropylene-based resin (a3) may be used alone or in combination of two or more. When two or more kinds are used in combination, it is preferable that each of them satisfies the density and MFR, but a blend of two or more kinds of polypropylene-based resins may satisfy 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 carbon blacks can be used. For example, reinforcing carbon black such as furnace black and thermal black, and conductive carbon black such as acetylene black and ketjen black can be mentioned. 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.
The carbon black (b) may be used alone or in combination of two or more.
Examples of the carbon black (b) include "Asahi Carbon" and "SUNBLACK" (trade names, both manufactured by Asahi Carbon Co., Ltd.).

The content of carbon black (b) in the resin composition of the present invention is not particularly limited. For example, 1.5 to 5.0 parts by mass is preferable, and 2.0 to 3.0 parts by mass is preferable with respect to a total of 100 parts by mass of the polyethylene resin (a1), the resin (a2) and the polypropylene resin (a3). More preferred. When this content is in the above range, the mechanical properties of the coating can be maintained for a long period of time 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 contains various additives generally used in electric wires, cables, cords, tubes, electric wire parts, sheets, etc., such as antioxidants, metal deactivators, flame retardants, and flame retardants. A fuel (auxiliary) agent, a filler, a lubricant and the like can be appropriately contained as long as the desired effect is not impaired. Further, the resin composition of the present invention can appropriately contain a resin other than the polyethylene resin (a1), the resin (a2) and the polypropylene-based resin (a3) as long as the desired effect is not impaired.

The antioxidant is preferably contained in the resin composition of the present invention.
The antioxidant that can be used in the present invention may be any one that is usually used for electric wires and the like, and examples thereof include phenolic antioxidants, phosphorus antioxidants, and other antioxidants. Of these, phenolic antioxidants and phosphorus antioxidants are preferable.
In the present invention, one type of antioxidant may be used alone, or two or more types may be used in combination.

The phenolic antioxidant is not particularly limited, but for example, pentaerythrityl-tetrax (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5-) Examples thereof include 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) and the like.
The content of the phenolic antioxidant in the resin composition of the present invention is not particularly limited, and is based on 100 parts by mass of the total of the polyethylene resin (a1), the resin (a2) and the polypropylene resin (a3). 0.01 to 1.0 parts by mass is preferable, 0.05 to 0.5 parts by mass is more preferable, and 0.1 to 0.3 parts by mass is further preferable.

The phosphorus-based antioxidant is not particularly limited, but is, for example, tris (2,4-di-tert-butylphenyl) dried fight, bis (2,4-di-tert-butyl-6-methylphenyl) -ethyl. − Examples include phosphite.
Examples of commercially available phenolic antioxidants include "Irgafos" (trade name, manufactured by BASF) and the like.
The content of the phosphorus-based antioxidant in the resin composition of the present invention is not particularly limited, and is based on 100 parts by mass of the total of the polyethylene resin (a1), the resin (a2) and the polypropylene-based resin (a3). 0.01 to 1.0 parts by mass is preferable, 0.05 to 0.5 parts by mass is more preferable, and 0.1 to 0.3 parts by mass is further preferable.

Other antioxidants include, for example, polymers of 4,4'-dioctyl-diphenylamine, N, N'-diphenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline and the like. Amine-based antioxidant, bis (2-methyl-4- (3-n-alkylthiopropionyloxy) -5-t-butylphenyl) sulfide, 2-mercaptobenzimidazole and its zinc salt, pentaerythritol-tetrakis (3) -Lauryl-thiopropionate) and other sulfur-based antioxidants can be mentioned.

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

<Characteristics of the resin composition of the present invention>
The resin composition of the present invention contains a polyethylene resin (a1), a resin (a2) and a polypropylene-based resin (a3) at the above contents. As a result, the resin composition of the present invention has an MFR (190 ° C., 21.18N) of 0.61 to 5.0 g / 10 min. Furthermore, the resin composition of the present invention preferably has the following properties. As a result, it is possible to form a coating that has both shape retention and extrusion properties, has high wear resistance, and has an excellent appearance. The resin composition of the present invention can preferably retain the above-mentioned excellent extrudability, shape retention and appearance even when the linear velocity in extrusion molding is increased to, for example, about 100 m / min. More preferably, it is possible to impart characteristics required for coating electric wires / cables (electric wires or cables), such as mechanical strength, flexibility, impact resistance, wear resistance, cold resistance, environmental stress crack resistance, and the like. ..

(MFR (190 ° C., 21.18N))
The resin composition of the present invention has an MFR (190 ° C., 21.18N) of 0.61 to 5.0 g / 10 minutes. If 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 retention property, particularly the extrudability when the linear velocity in extrusion molding is increased, is lowered. The MFR is 0.61 to 5 g / g in that it can form a coating with excellent shape retention and extrudability, high wear resistance and excellent appearance even when the linear velocity in extrusion molding is increased. 10 minutes is preferable, and 0.8 to 2.0 g / 10 minutes is more preferable.

(density)
The density of the resin composition of the present invention is not particularly limited, but is preferably 0.935 to 0.975 g / cm ^{3 from the} viewpoint of achieving both mechanical strength and flexibility as an electric wire / cable, and 0.940 to 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 rate or combination thereof of polyethylene resin (a1), resin (a2) and polypropylene-based resin (a3), or the type or content of additives. It can be set within a predetermined range depending on the amount and the like.

The resin composition of the present invention having the above-mentioned characteristics 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-walled electric wire / cable, or a self-supporting type, which will be described later. It is also preferably used as an electric wire / cable.

<Method for producing the resin composition of the present invention>
The resin composition of the present invention contains a polyethylene resin (a1), a resin (a2), a polypropylene-based resin (a3), and various additives as desired, in a proportion of the above content, using a mixer, a kneader, or the like. , Can be mixed (including melt kneading) to produce.
At this time, the mixing order at the time of mixing is not particularly limited, and the above components may be mixed in any order.

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

The mixing method may be any commonly used method, and a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, various kneaders, or the like is used as the mixer or kneader. Among them, a twin-screw extruder, a Banbury mixer, a kneader and the like are preferable in terms of dispersibility of carbon black and additives.

<< Electric wires / cables >>
The electric wire / cable of the present invention (hereinafter referred to as the electric wire or the like of the present invention) has an extruded coating formed by extrusion-molding the resin composition of the present invention on the outer periphery of a conductor or the like as an insulating layer or a 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, application, and the like of the electric wire and the like of the present invention. Further, as for the material, shape, size and the like of the conductor and the like, conventional ones can be appropriately selected and used.

The electric wires 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.
Further, as the cable, various cables can be applied without particular limitation, and includes a cable arranged indoors and a cable arranged outdoors. For example, a power cable, a communication cable, and the like are preferable.

Examples of the electric wire and the like of the present invention include electric wires and cables having a circular cross-sectional shape, 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, a cross-sectional shape other than a circle, for example, an elliptical shape, a rectangular shape (flat type), a shape having a notch (notch), or a deformed electric wire / cable having a shape obtained by combining these, the diameter is increased or the coating thickness is increased. Examples thereof include large-diameter, thick-walled electric wires and cables, and self-supporting electric wires and cables having a support wire portion in which a support wire is embedded.
The electric wire or the like of the present invention is preferably a deformed electric wire / cable, a large-diameter / thick-walled electric wire / cable, or a self-supporting electric wire / cable, which has been difficult to manufacture in the past. Examples of such electric wires / cables include twisted electric wires for electric power, tape core wires for communication cables, communication cables, and the like. 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, an indoor optical cable and the like. Among these, large-diameter, thick-walled, slot-type optical cables and leakage coaxial cables, which are required to maintain their shape, are preferable, and self-supporting electric wires and cables are also preferable.

Hereinafter, preferred electric wires and the like of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

A preferred electric wire or the like of the present invention is the slot type optical cable 1 shown in FIG. FIG. 1A is an end view showing the outline of the end face 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. It is the schematic end view which shows the end face of 11.

The slot-type optical cable 1 has the same shape and shape as the conventional slot-type optical cable, except that the coating, that is, the sheaths 12b, 19 and the neck portion 13 (see FIG. 1B) are formed of the resin composition of the present invention. It can be configured.
That is, the slot type optical cable 1 is a self-supporting type (SSW type) optical cable, and as shown in FIG. 1, a support wire portion 12 having a substantially circular end face (cross section) and a cable having a substantially circular cross section. It has a cross-sectional shape in which the portion 11 is connected by a plurality of neck portions (connecting portions) 13. As described above, 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 has a slot 15 coated on the peripheral surface of the tension member 14, and an optical fiber is formed in five storage grooves 15a formed along the axis of the slot 15. A predetermined number of core wires 16 are dropped, and they are embedded in a coating (also referred to as a sheath) 19 together with a tear cord 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 large. Although it cannot be said unconditionally, for 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, 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 thickness of the sheath 19 is thick, or even if the slot type optical cable 1 is a self-supporting type and has a support wire portion 12 and a neck portion 13, it has a complicated cross-sectional shape. The sheaths 12b, 19 and the neck 13 maintain a predetermined shape.
In the slot type optical cable 1, the support wire 12a, the tension member 14, the slot 15, the optical fiber core wire 16, the tear cord 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 or the like of the present invention is the 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, 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, a support wire portion 22 having a substantially circular end face (cross section) and a cable having a substantially circular cross section. The portion 21 has a cross-sectional shape in which the portions 21 are connected by a plurality of neck portions (connecting portions) 23. As described above, 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 insulating polyethylene string 25 and an insulating polyethylene pipe 26 on an inner conductor 24, has an outer conductor 27 on the inner conductor 24, and is collectively embedded in a coating (sheath) 28.
The support wire portion 22 has a plurality of support wires 22a and a coating (sheath) 22b that covers the support wires 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 be said unconditionally, for 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 is thick, even if the leaky coaxial cable 2 is a self-supporting type and has a support wire portion 22 and a neck portion 23, it has a complicated shape. , Sheaths 22b, 28 and neck 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, 21 and the support wire portions 12, 22 all have a substantially circular cross-sectional shape, but in addition to this, a substantially rectangular or elliptical shape is formed. There is also something like.

The electric wire or the like of the present invention can be produced by coating the outer periphery of a conductor or the like with the resin composition of the present invention while melting and mixing, for example, in an extrusion molding machine or an extrusion coating device.
At this time, if the resin composition of the present invention is extruded together with a conductor or the like, molding can be performed while maintaining this shape without breaking the complicated cross-sectional shape corresponding to the cross-sectional shape of the electric wire / cable. Further, even if the linear velocity in extrusion molding is increased to, for example, about 100 m / min, excellent extrusion property, shape retention and appearance can be maintained. Therefore, the electric wire or the like of the present invention can be manufactured with good shape reproducibility, high yield, and high structural efficiency.
Further, the resin composition of the present invention does not impose 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 a single wire or a stranded wire (also referred to as a conductor bundle) of annealed copper. As the conductor, in addition to the bare wire, a tin-plated conductor or a conductor having 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 of the resin composition of the present invention is appropriately determined according to the intended use and the like.
The thickness (maximum thickness) of the insulating layer is not particularly limited, but is usually about 0.15 to 5 mm. The thickness of the sheath is not particularly limited, but is usually about 0.15 to 30 mm.

The conditions for extrusion molding 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 extrusion molding machine can be reduced and the shape retention can be ensured. The extrusion temperature (head portion) is preferably 140 to 240 ° C, more preferably 160 to 210 ° C. Further, as another condition of extrusion molding, the screw rotation speed is preferably 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 100 m / min. It is 80 m / min.
The screw configuration of the extrusion molding machine is not particularly limited, and a normal full flight screw, double flight screw, tip double flight screw, Maddock screw and the like can be used.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. The numerical values of each formulation in Table 1 and Table 2 represent parts by mass.

The components used in each example are shown below.
The polyethylene resin (a1) and the resin (a2) each contain ethylene and, if necessary, an α-olefin at 70 to 150 ° C. in the presence of a Ziegler-Natta catalyst or a metallocene catalyst using a gas phase copolymerization device or a liquid phase polymerization device. It was copolymerized with and 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 contents of the polymerization reactor.

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

<(A2) resin>
Resin (a2-1)
Ethylene homopolymer, density 0.960 g / cm ³ , MFR (190 ° C., 21.18N) 0.70 g / 10 minutes Resin (a2-2)
Ethylene homopolymer, density 0.955 g / cm ³ , MFR (190 ° C, 21.18 N) 0.20 g / 10 minutes Resin (a2-3)
Ethylene homopolymer, density 0.958 g / cm ³ , MFR (190 ° C., 21.18N) 10.00 g / 10 minutes Resin (a2-4)
Ethylene homopolymer, density 0.940 g / cm ³ , MFR (190 ° C., 21.18N) 0.80 g / 10 minutes Resin (a2-5)
Ethylene homopolymer, density 0.965 g / cm ³ , MFR (190 ° C., 21.18 N) 5.50 g / 10 minutes Resin (a2-6)
Copolymer of ethylene and 1-hexene, content of ethylene components is 90% by mass, density 0.945g / cm ³ , MFR (190 ℃, 21.18N) 1.70g / 10 minutes Resin (a2-7) )
Ethylene homopolymer, density 0.970 g / cm ³ , MFR (190 ° C., 21.18N) 1.00 g / 10 minutes Resin (a2-8)
Ethylene homopolymer, density 0.958 g / cm ³ , MFR (190 ° C., 21.18 N) 0.10 g / 10 minutes 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 copolymerized with propylene and, if necessary, an α-olefin at 60 to 100 ° C. in the presence of a Ziegler-Natta catalyst or a metallocene catalyst using a gas phase polymerization apparatus or a liquid phase polymerization apparatus. , Synthesized. The catalyst concentration used may be a concentration at which the polymerization proceeds sufficiently, but 0.01 to 0.1% by mass was used based on the mass of the contents of the polymerization reactor.
Polypropylene resin (a3-1)
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 0.80g / 10 minutes Polypropylene resin (a3-2) )
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 0.50g / 10 minutes Polypropylene resin (a3-3) )
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 10.00g / 10 minutes Polypropylene resin (a3-4) )
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 50.00g / 10 minutes Polypropylene resin (a3-5) )
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 0.30g / 10 minutes Polypropylene resin (a3-6) )
Copolymer of propylene and ethylene, content of propylene component is 95% by mass, density 0.900g / cm ³ , MFR (230 ° C, 21.18N) 60.00g / 10 minutes

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

Examples 1-13 , Reference Examples 1-5 and Comparative Examples 1-11
In each example, a so-called "glasses-shaped" simple test cable having the end face contour 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, among the members constituting the simple test cable, those corresponding to the members constituting the slot type optical cable 1 shown in FIG. 1 are designated by the same reference numerals for convenience.

Polyethylene resin (a1), resin (a2), polypropylene resin (a3) and carbon black (b) shown in Tables 1 and 2 were mixed in the contents shown in Tables 1 and 2 using a 2L Banbury mixer. After melt-mixing at 200 ° C. for 20 minutes, pelletization was performed to obtain the polyolefin resin composition for coating electric wires and cables of the present invention.
Next, each of the obtained polyolefin resin compositions for coating electric wires and cables was extruded into an electric wire extrusion machine having an L / D (ratio of effective screw length L to diameter D) of 25 and a screw diameter of 40 mmφ. Using an extrusion die with a motor load limit of 80A) and a cross-sectional shape of eyeglasses, the following is placed on a 1.0 mmφ conductor (annealed copper wire) arranged in parallel under the following extrusion temperature conditions. In this way, they were integrally extruded and coated to produce a simple test cable.

As the cable portion 11, a polyolefin resin composition for wire / cable coating was extruded on the outer circumference of one of the conductors so as to have an outer diameter of 5.0 mmφ and a coating thickness of 2.0 mm. Further, the support wire portion 12 was extruded to the outer periphery of the other conductor so as to have an outer diameter of 2.0 mmφ and a coating thickness of 0.5 mm. Further, the polyolefin resin composition for electric wire / cable coating is formed so that 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. It was extruded as a connecting portion 13.

Further, on a conductor (annealed copper wire) of 0.8 mmφ, an electric wire for abrasion resistance test (cross-sectional shape is circular) having an outer diameter of 2.4 mmφ and a coating thickness of 0.8 mm is formed in the same manner as in the manufacture of a simple test cable. And made it.

Regarding the extrusion conditions (temperature), the temperature control in the cylinder part of the extrusion molding machine is divided into 3 zones C1, C2, and C3 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 divided into three zones. The temperature was set to 200 ° C. and the die temperature was set to 200 ° C.
The line speed was set to 10 m / min or 100 m / min.

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

<Measurement of MFR>
The MFR (190 ° C., 21.18N) was measured under the condition D of 190 ° C., 21.18N based on the "A method (manual cutting method)" specified in JIS K 7210.
The MFR (230 ° C., 21.18N) of the polypropylene resin (a3) was measured in the same manner as the MFR (190 ° C., 21.18N) except that the condition M was changed to a temperature of 230 ° C.

<Density>
The density was measured based on the "A method (underwater substitution method)" specified in JIS K 7112: 1999.

<Appearance test (surface roughness)>
The appearance of the simple test cable obtained by extrusion molding at each linear velocity was measured by measuring the arithmetic mean surface roughness (Ra) specified in JIS B 0601: 2013 under the following measurement conditions, and evaluated according to the following evaluation criteria. In the appearance test, the evaluation "B" is the passing level of this test, and it is desirable that the evaluation is "A" or higher.
-Measurement conditions-
The arithmetic mean surface roughness (Ra) of the prepared simple test cable was obtained by randomly sampling the coating of the simple test cable at five locations and based on JIS B 0601: 2013, a surface roughness measuring machine (manufactured by Mitutoyo, surf test). The arithmetic mean surface roughness (Ra, μm) was determined using SJ-301 (trade name)).
-Evaluation criteria-
AA: 1.5 μm or less A: 1.5 μm or more and 2.5 μm or less B: 2.5 μm or more and 3.5 μm or less C: 3.5 μm or less

<Abrasion resistance test>
A load of 15 N was applied onto the horizontally installed wear resistance test wire, and the coating was worn using a 0.25 mmφ piano wire. The piano wire was continuously reciprocated until it reached the conductor, and the number of reciprocations was measured. The portion to be abraded was carried out four times per sample at four locations of 90, 180, 270 and 360 ° in the circumferential direction, and the average value of the number of reciprocations of the four times was used as an index of wear resistance. Abrasion resistance was evaluated according to the following evaluation criteria based on the average number of round trips. In the wear resistance test, the evaluation "B" is the passing level of this test, and it is desirable that the evaluation is "A" or higher.
-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 retention (drawdown resistance) test>
In each example manufactured by extruding each simple test cable at a linear speed of 10 m / min, each electric wire / cable coating polyolefin resin composition extruded by the extrusion molding machine is not cooled with cold water or the like and is in the atmosphere. It was left inside for a maximum of 20 seconds, visually confirmed whether or not it maintained the predetermined shape, and evaluated according to the following evaluation criteria. In this test, maintaining the shape means that the shape is maintained after extrusion, which is connected with a polyolefin resin composition for cable coating by a predetermined time after extrusion molding (after being extruded from an extrusion molding machine). It means that the inclination angle of the simple electric wire connecting portion 13 is maintained within 5 degrees with respect to the shape of the extruded die. In the shape retention test, the evaluation "B" is the passing level of this test, and it is desirable that the evaluation is "A" or higher.
-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 and when the shape cannot be maintained after being left for 20 seconds B: When the shape is maintained even after being left for 5 seconds, If the shape cannot be maintained after leaving it for 10 seconds C: If the shape collapses in less than 5 seconds

<Extrusion test>
In each example manufactured by extruding a simple test cable at a linear velocity of 100 m / min, it acts on the motor of the extrusion molding machine when each wire / cable coating polyolefin resin composition is extruded by the above extrusion molding machine. The maximum value of the loaded load value was read.
The read value was divided by the motor load limit value to calculate the load factor (%) with respect to the motor load limit. The extrudability of the polyolefin resin composition for coating electric wires and cables was evaluated by the following evaluation criteria using the above load factor as an index. In the extrudability test, when the evaluation is "B", the load applied to the extruder can be tolerated, which is the passing level of this test, and when the evaluation is "A" or higher, it is at a desirable level.
-Evaluation criteria-
AA: 74% or less A: 74% or more and 85% or less B: 85% or more and 100% or less C: 100% or less

<Cold resistance test>
The embrittlement temperature was measured based on JIS C 3005 using a test piece obtained by molding the polyolefin resin composition for wire / cable coating prepared in each Example and each reference example into a sheet having a thickness of 2 mm. As a result, the test pieces prepared from the polyolefin resin compositions for wire / cable coating prepared in Examples 1 to 13 and Reference Examples 1 to 5 all had a crack generation temperature of −40 ° C. or lower and became cold-resistant. It was excellent.

The following can be seen from the results in Tables 1 and 2.
That is, the polyethylene resin (a1) having a specific density and MFR, the resin (a2) having a specific density and MFR, and the polypropylene resin (a3) are contained in a specific ratio, and the MFR is set to a specific value. All of the set polyolefin resin compositions for coating electric wires and cables were excellent in extrudability and shape retention even when the cross-sectional shape of the coating to be formed was spectacle-like. Further, with these polyolefin resin compositions for cable coating, it was possible to form a coating having high wear resistance, a smooth surface, and an excellent appearance. Moreover, even when the linear speed was set to a high speed of 100 m / min and extrusion molding was performed, the above-mentioned excellent extrudability, shape retention and appearance were maintained.

On the other hand, Comparative Example 1 in which the content of the polyethylene resin (a1) was high did not have sufficient wear resistance. On the other hand, in Comparative Example 2 in which the content of the polyethylene resin (a1) was low, the MFR was too small, the extrudability was not sufficient, and both the extrudability and the shape-retaining property could not be achieved. Comparative Example 3 in which the density of the polyethylene resin (a1) was too small did not have sufficient wear resistance. On the other hand, in Comparative Example 4 in which the density of the polyethylene resin (a1) was too high, the extrudability was not sufficient, and both the extrudability and the shape retention property could not be achieved. In Comparative Example 5 in which the MFR of the polyethylene resin (a1) was too large, the shape-retaining property was not sufficient, and both the extrudability and the shape-retaining property could not be achieved.
Further, in Comparative Example 6 in which the density of the resin (a2) was too large and Comparative Example 7 in which the MFR of the resin (a2) was too small, the extrudability was not sufficient, and both the extrudability and the shape retention property could not be achieved. In Comparative Example 8 in which the MFR of the resin (a2) was too large, the shape-retaining property was not sufficient, and both the extrudability and the shape-retaining property could not be achieved.
Further, Comparative Example 10 containing no polypropylene-based resin (a3) did not have sufficient appearance and abrasion resistance. On the other hand, Comparative Example 11 having a high content of the polypropylene-based resin (a3) did not have sufficient extrudability, and could not achieve both extrudability and shape retention. In Comparative Example 9 in which the MFR of the polyolefin resin composition for coating electric wires and cables was too small, the extrudability was not sufficient, and both the extrudability and the shape retention property could not be achieved.

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

Claims (7)

Polyethylene resin (a1) having a density of 0.9000 to 0.935 g / cm ³ and a melt flow rate (190 ° C., 21.18 N) of 10 g / 10 minutes or less, 40 to 67 % by mass.
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 (melt flow rate). 190 ° C., 21.18N) is 0.2 to 10 g / 10 minutes, and the resin (a2) is 30 to 57 % by mass.
It contains 3 to 25% by mass of a polypropylene resin (a3) having a melt flow rate (230 ° C., 21.18N) of 0.8 to 50 g / 10 minutes .
A polyolefin resin composition for coating electric wires and cables having a melt flow rate (190 ° C., 21.18N) of 0.61 to 5.0 g / 10 minutes. The polyolefin resin composition for coating an electric wire / cable according to claim 1, which contains carbon black (b) . The polyolefin resin composition for electric wire / cable coating according to claim 1 or 2, wherein the polyethylene resin (a1) is a polyethylene resin synthesized by using a metallocene catalyst . The polypropylene-based resin (a3) is made from a homopolymer of propylene, a copolymer of propylene and ethylene, a copolymer of propylene and 1-butene, and a ternary copolymer of propylene, ethylene and 1-butene. The polyolefin resin composition for coating an electric wire / cable according to any one of claims 1 to 3, which contains a polypropylene resin composed of at least one polymer selected from the above group . The content of the carbon black (b) is 1.5 to 5.0 parts by mass with respect to 100 parts by mass of the total of the polyethylene resin (a1), the resin (a2) and the polypropylene-based resin (a3). The polyolefin resin composition for coating an electric wire / cable according to any one of claims 2 to 4 . The polyolefin resin composition for electric wire / cable coating according to any one of claims 1 to 5, wherein the melt flow rate (190 ° C., 21.18N) of the polyethylene resin (a1) is 1.0 g / 10 minutes or more. Stuff. An electric wire / cable having a coating obtained by extruding the polyolefin resin composition for coating the electric wire / cable according to any one of claims 1 to 6 .

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