JP2017171700A - cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable suppressing transition of a plasticizer blended to a sheath to an insulator and having excellent flexibility even at low temperature.SOLUTION: There is provided a cable having an insulator 3 and a sheath 4 on an outer periphery of a conductor 2 in this order, the insulator 3 has an inner layer 31 covering the conductor 2 and an outer layer 32 positioned in outside of the inner layer 31 and contacting with the sheath 4, the inner layer 31 contains one or more kind of polyolefin resin having density of 0.880 to 0.950 g/cmor a polyolefin resin having density of 0.880 to 0.950 g/cmand an ethylene propylene non-conjugated diene copolymer rubber (EPDM) having ethylene content of 50 mass% or more with a percentage of 20:80 to 80:20 (mass ratio) as a base resin and the outer layer 32 contains one or more kind of polyolefin resin having density of 0.915 to 0.955 g/cmas a base resin and thickness of the outer layer 32 is 0.05 to 0.5 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cable, and more particularly, to a cable formed by covering an insulating wire core including a conductor and an insulator covering the conductor with a protective coating (sheath).

  Insulated electric wires with stranded conductors covered with an insulator, and cables with insulating wires covered with a protective sheath (sheath) can be used, for example, in low-voltage / high-voltage trunk lines, switchboards, railway vehicles, automobiles, electrical / electronic devices, etc. Used.

  For example, a polyvinyl chloride resin, a polyolefin resin, a fluorine resin, or the like is used as a resin constituting an electric wire or cable. Among them, a polyvinyl chloride resin composition using a vinyl chloride resin has good electrical insulation. It is generally used because it has excellent flame retardancy and mechanical properties. For example, Patent Document 1 proposes an electric wire / cable coated with a vinyl chloride resin composition in which 0.1 to 10 parts by weight of a specific synthetic aluminum silicate is added to 100 parts by weight of a vinyl chloride resin.

  It is known that the flexibility of a resin composition used for general electric wires and cables has temperature dependence, and decreases (hardens) as the temperature decreases. Therefore, in order to provide excellent flexibility even at low temperatures, low-density materials and rubber materials that are sufficiently flexible even at room temperature are used, or a large amount of material such as a plasticizer is added. Yes.

With respect to the insulator, for example, in Patent Document 2, an insulator having a multilayer structure is adopted, and the inner layer is made of a flexible ethylene / α-olefin copolymer, ethylene / α-olefin / polyene copolymer (α-olefin is C ₃ -C ₁₀ , polyene is a non-conjugated diene) and is composed of a polyolefin composition containing 20 to 80 parts by weight, and the outer layer is mainly composed of a heat-resistant resin containing no halogen, and polyamide, polyphenylene It has been proposed to be composed of one or two or more blends selected from sulfides or the like, or a polymer alloy mainly composed of these resins. According to Patent Document 2, the flexibility of the electric wire is enhanced by the inner layer of the insulator, and chemical resistance and the like are maintained by the outer layer.
Patent Document 3 proposes that the outer layer of an electric wire / cable is composed of two layers, an inner layer and an outer layer, and that a specific amount of a slipperiness imparting agent is blended only in the outer layer to improve the lubricity with the outside. Has been.

JP 2006-22252 A JP-A-5-12924 JP 2002-231067 A

In the polyvinyl chloride resin composition, the plasticizer tends to bleed depending on the use conditions and the environment, and when the polyvinyl chloride resin is used for the sheath, the plasticizer blended in the sheath is easily transferred to the insulator. In particular, when the flexibility is imparted to the insulator, it is necessary to reduce the density of the resin composition. For this reason, the plasticizer of the sheath is likely to be transferred to the insulator.
When the plasticizer blended in the sheath shifts to the insulator, there is a problem that the tensile elongation, tensile strength, heat deformation and the like of the cable deteriorate.

  Then, this invention makes it a subject to provide the cable which suppresses the transfer to the insulator of the plasticizer mix | blended with the sheath, and has the outstanding softness | flexibility also at the time of low temperature.

  As a result of intensive studies, the present inventor made the above-mentioned problem by forming the insulator into two or more layers and forming the outer layer and the inner layer of the insulator using a base resin having a specific density. The inventors have found that this can be solved, and have completed the present invention.

That is, the present invention is as follows (1) to (6).
(1) A cable provided with an insulator and a sheath in this order on the outer periphery of a conductor, wherein the insulator has an inner layer covering the conductor and an outer layer positioned outside the inner layer and in contact with the sheath. The inner layer contains at least one polyolefin resin having a density of 0.880 to 0.950 g / cm ³ as a base resin, or a polyolefin resin having a density of 0.880 to 0.950 g / cm ³ An ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) having an ethylene content of 50% by mass or more is contained in a ratio of 20:80 to 80:20 (mass ratio), and the outer layer has a density of 0 A cable comprising one or more polyolefin resins of .915 to 0.955 g / cm ³ and a thickness of the outer layer of 0.05 to 0.5 mm.
(2) The cable according to (1), wherein the resin composition constituting the inner layer has a cross-linking degree of 20 to 95%.
(3) The cable according to (1) or (2) above, wherein the polyolefin resin contained in the inner layer has a melt flow rate (MFR) of 0.1 to 10.0 g / 10 minutes.
(4) The melt flow rate (MFR) of the polyolefin-based resin contained in the outer layer is 0.1 to 10.0 g / 10 minutes, and any one of (1) to (3) above The described cable.
(5) The polyolefin resin contained in the inner layer is selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), and ethylene-vinyl acetate copolymer (EVA). The cable according to any one of (1) to (4), wherein the cable is at least one.
(6) The cable according to any one of (1) to (5), wherein the polyolefin resin contained in the outer layer is polyethylene (PE).

  The cable of the present invention has an insulator and a sheath provided in this order on the outer periphery of a conductor, and the insulator is composed of at least an inner layer and an outer layer. The density or composition of the base resin of the inner layer of the insulator, the base resin of the outer layer The density and thickness of the outer layer are specified. According to this configuration, the outer layer of the insulator mainly plays the role of suppressing the migration of the plasticizer from the sheath, and the inner layer mainly plays the role of imparting flexibility, and the synergistic effect of the multilayer structure of the inner layer and the outer layer. Thus, a cable having excellent flexibility even at low temperatures can be provided.

It is sectional drawing of one embodiment of the cable which concerns on this invention.

  The present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of one embodiment of a cable according to the present invention.
As shown in FIG. 1, a cable 1 according to an embodiment of the present invention includes a conductor 2 such as a copper wire, an insulator 3 that covers the outer periphery of the conductor 2, and a sheath 4 that covers the outer periphery of the insulator 3. . The insulator 3 includes an inner layer 31 that covers the conductor 2 and an outer layer 32 that covers the inner layer 31.

<Conductor>
The conductor 2 may be only one strand or may be formed by bundling a plurality of strands. As a material of the conductor 2, for example, conductive metal such as copper, plated copper, copper alloy, aluminum, aluminum alloy can be used.

<Insulator>
The insulator 3 is composed of at least two layers. That is, the insulator 3 includes an inner layer 31 that covers the conductor 2 directly or via another layer, and an outer layer 32 that is located outside the inner layer 31 and covers the inner layer 31 directly or via another layer. The outer layer 32 is in contact with the sheath 4.

<< Inner layer >>
In the present invention, the inner layer 31 of the insulator 3 includes any of the following forms (1) and (2) as a base resin.
Form (1): It contains one or more polyolefin resins having a density of 0.880 to 0.950 g / cm ³ .
Form (2): A polyolefin resin having a density of 0.880 to 0.950 g / cm ³ and an ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) having an ethylene content of 50% by mass or more from 20:80 to It is included at a ratio of 80:20 (mass ratio).

  In the above forms (1) and (2), as the polyolefin resin, polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene -A methyl acrylate copolymer (EMA), an ethylene propylene copolymer, etc. are mentioned. These polyolefin resins may be used alone or in combination of two or more. Among these, polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), and ethylene-vinyl acetate copolymer (EVA) are preferably used from the viewpoints of mechanical properties and electrical properties.

The density of the polyolefin resin is 0.880 to 0.950 g / cm ³ . When the density of the polyolefin resin is 0.880 g / cm ³ or more, sufficient heat deformation characteristics and heat resistance can be imparted to the insulator, and when it is 0.950 g / cm ³ or less, the insulator has a low temperature. Sufficient flexibility can be provided. The density of the polyolefin-based resin is preferably 0.880 to 0.940 g / cm ³ , and more preferably 0.880 to 0.925 g / cm ³ .

  Moreover, it is preferable that the melt flow rate (MFR) of polyolefin resin is 0.1-10.0 g / 10min. When the MFR is in the above range, there is an effect that coating extrusion is possible with a smooth appearance. The MFR is more preferably 0.3 to 3.0 g / 10 minutes.

  In addition, the density as used in the field of this invention is a value measured based on JISK7112, and MFR is a value measured based on JISK7210 at 190 degreeC and a 2.16kgf load.

In the form (2), an EPDM having an ethylene content of 50% by mass or more is used together with a polyolefin resin having a density of 0.880 to 0.950 g / cm ³ . By using EPDM in combination, flexibility can be imparted with a smaller amount of blending than polyolefin. The ethylene content of EPDM is preferably 50 to 90 mass%, more preferably 60 to 80 mass%, from the viewpoint of the balance between flexibility and heat deformation characteristics. Moreover, 2.0-8.0 mass% is preferable and, as for content of a nonconjugated diene compound in EPDM, 3.0-6.0 mass% is more preferable. Examples of non-conjugated dienes include 5-ethylidene-2-norbornene (ENB), 1,4-hexadiene, 5-methylene-2-norbornene (MNB), 1,6-octadiene, 5-methyl-1, Examples include 4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene, dicyclopentadiene, vinyl norbornene, dicyclooctadiene, methylene norbornene, and the like. .

  Moreover, in the said form (2), the compounding ratio of polyolefin-type resin and EPDM considers the balance of the softness | flexibility at the time of the low temperature of an insulator, and heat resistance, The former: The latter (mass ratio) 20: 80- The ratio is 80:20 (mass ratio), preferably 30:70 to 70:30, and more preferably 40:60 to 60:40.

  In order to crosslink the base resin in the inner layer 31, known means may be employed, and there is no particular limitation. However, a method using a composition in which a silane coupling agent, a crosslinking agent, and a crosslinking catalyst are blended with the base resin is preferable. Specifically, after introducing a silane coupling agent into the base resin using a crosslinking agent, the base resin is silane-crosslinked using a crosslinking catalyst. More specifically, it is preferable to form a crosslinked structure by grafting a silane coupling agent to the main chain of the base resin and then condensing the silane coupling agent.

  Examples of the silane coupling agent include vinyl silane compounds such as vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (β-methoxy ethoxy) silane, γ-aminopropyl trimethoxy silane, γ-aminopropyl triethoxy silane, N-β- Aminosilane compounds such as (aminoethyl) γ-aminopropyltrimethoxysilane, β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, β- (3,4 epoxy cyclohexyl) ) Epoxy silane compounds such as ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, acrylic silane compounds such as γ-methacryloxypropyltrimethoxysilane, bis Polysulfide silane compounds such as 3- (triethoxysilyl) propyl) disulfide and bis (3- (triethoxysilyl) propyl) tetrasulfide, mercaptosilane compounds such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane Etc. However, the silane coupling agent is not limited to these. Moreover, these can be used individually by 1 type or in combination of 2 or more types. Furthermore, it is preferable that the mixture ratio of a silane coupling agent is 0.5-3.0 mass parts with respect to 100 mass parts of base resins.

  Examples of the crosslinking agent (radical generator) include, but are not limited to, organic oxides. Specifically, as the crosslinking agent, dicumyl peroxide (DCP), di-tert-butyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane, 2,5 -Dimethyl-2,5-di- (tert-butylperoxy) hexyne-3, 1,3-bis (tert-butylperoxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3, 3,5-trimethylcyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperoxy Isopropyl carbonate, diacetyl peroxide, lauroyl peroxide, ert- butyl cumyl peroxide, and the like. These can be used individually by 1 type or in combination of 2 or more types. The blending ratio of the crosslinking agent is preferably 0.03 to 0.15 parts by mass with respect to 100 parts by mass of the base resin.

  Examples of the crosslinking catalyst include, but are not limited to, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, stannous acetate, stannous caprylate, zinc caprylate, lead naphthenate, and cobalt naphthenate. It is not a thing. Furthermore, in the case of dibutyltin dilaurate, the blending ratio of the crosslinking catalyst is preferably 0.03 to 0.20 parts by mass with respect to 100 parts by mass of the base resin, and 0.03 to 0.15 parts by mass. It is more preferable that

In the present invention, the degree of crosslinking of the resin composition constituting the inner layer 31 is preferably 20 to 95%, more preferably 30 to 70%, and further preferably 40 to 60% from the viewpoints of heat deformation characteristics and productivity. preferable.
In addition, a crosslinking degree shall comply with the test of 27 terms of JISC3005. Specifically, 5 g of a crosslinked base resin sample for forming the inner layer 31 is prepared, the sample is immersed in 100 g of solvent xylene, the temperature of the solvent is maintained at 120 ° C. for 24 hours, and The sample is taken out from the solvent, placed in a vacuum desiccator, and dried at a temperature of 100 ± 2 ° C. and a vacuum degree of 1.3 kPa (10 Torr) or less for 24 hours or more. After drying, the weight of the sample (mass after the test) is measured to the unit of mg and expressed as a percentage compared to the initial weight of the sample (mass before the test).

<< Outer layer >>
The base resin of the outer layer 32 of the insulator 3 includes at least one polyolefin resin having a density of 0.915 to 0.955 g / cm ³ .
The polyolefin resin of the outer layer 32 includes polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA). ), Ethylene-propylene copolymer and the like. These polyolefin resins may be used alone or in combination of two or more. Among these, polyethylene (PE) is preferably used from the viewpoint of a balance between mechanical properties and migration prevention properties.

The density of the polyolefin resin used as the base resin of the outer layer 32 is 0.915 to 0.955 g / cm ³ . When the density of the polyolefin resin is 0.915 g / cm ³ or more, the plasticizer migration from the sheath can be prevented, and when it is 0.955 g / cm ³ or less, the tensile elongation characteristic of the insulator can be maintained. it can. The density of the polyolefin resin is preferably 0.920 to 0.930 g / cm ³ .

  Moreover, it is preferable that the melt flow rate (MFR) of polyolefin resin is 0.1-10.0 g / 10min. When the MFR is in the above range, there is an effect that coating extrusion is possible with a smooth appearance. The MFR is more preferably 0.3 to 5.0 g / 10 minutes.

  The thickness of the outer layer 32 is 0.05 to 0.5 mm. When the thickness of the outer layer 32 is 0.05 mm or more, the tensile elongation of the insulator after migration of the plasticizer can be sufficiently maintained, and when it is 0.5 mm or less, the tensile elongation of the insulator can be maintained. The thickness of the outer layer 32 is preferably 0.05 to 0.35 mm, more preferably 0.05 to 0.20 mm.

  Further, the outer layer 32 may be subjected to silane crosslinking as described in the inner layer 31 as necessary.

  In the present invention, the insulator 3 may have one or more intermediate layers between the inner layer 31 and the outer layer 32. As the base resin constituting the intermediate layer, the same resin as that used for the inner layer and the outer layer can be used.

<Sheath>
The sheath 4 is not particularly limited, but a composition containing a polyvinyl chloride resin and a plasticizer is generally used from the viewpoints of flexibility and versatility.

  Examples of the polyvinyl chloride resin include, in addition to polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, alkyl (meth) acrylate, maleate, ethylene, propylene, styrene, vinylidene chloride, and the like. . These may be used individually by 1 type and may be used in combination of 2 or more type.

  The plasticizer can be appropriately selected from known plasticizers and is preferably an ester plasticizer from the viewpoint of the effects of the present invention. Examples of ester plasticizers include phthalate ester plasticizers, adipic acid ester plasticizers, phosphate ester plasticizers, azelaic acid ester plasticizers, sebacic acid ester plasticizers, and maleic acid ester plasticizers. And ester compounds such as fumaric acid ester plasticizer, trimellitic acid ester plasticizer, pyromellitic acid ester plasticizer, itaconic acid ester plasticizer, citric acid ester plasticizer, and polyester plasticizer.

In the present invention, since the migration of the plasticizer contained in the sheath 4 is suppressed by the outer layer 32, the amount of plasticizer contained in the sheath 4 can be increased, thereby further enhancing the flexibility of the cable.
For example, when the sheath 4 is made of a composition containing at least a polyvinyl chloride resin and a plasticizer, the blending amount of the plasticizer contained in the composition is 20 to 100 with respect to 100 parts by mass of the polyvinyl chloride resin. It is preferable that it is a mass part, More preferably, it is 20-60 mass parts.

  The inner layer 31, the outer layer 32, and the sheath 4 described above are provided with a flame retardant, a lubricant, a stabilizer, a filler, a foaming agent, an antioxidant, a processing aid, a neutralizing agent, and an ultraviolet absorber as necessary. Various known additives such as an agent, a pigment, an antistatic agent, a dispersant, a thickener, a metal deterioration preventing agent, an antifungal agent, and a flow modifier can also be blended.

  Examples of the flame retardant include a brominated flame retardant, an inorganic flame retardant, and a phosphoric acid flame retardant. Examples of brominated flame retardants include organic brominated flame retardants such as brominated ethylene bisphthalimide derivatives, bisbrominated phenylterephthalamide derivatives, brominated bisphenol derivatives, and 1,2-bis (bromophenyl) ethane. It is done. Examples of the inorganic flame retardant include magnesium hydroxide and aluminum hydroxide. Examples of the phosphoric acid flame retardant include aromatic condensed phosphate ester, ammonium polyphosphate, melamine phosphate and the like.

  Examples of the lubricant include hydrocarbon lubricants, fatty acid lubricants, ester lubricants and the like.

  As the foaming agent, a known chemical decomposition type foaming agent that generates carbon dioxide gas, nitrogen gas, or the like by chemical decomposition can be used. For example, an azo compound such as azodicarbonamide (ADCA), NN′— Examples thereof include nitroso compounds such as dinitrosopentamethylenetetramine, hydrazine derivatives such as 4,4′-oxybis (benzenesulfonylhydrazide) (OBSH) and hydrazodicarbonamide (HDCA), and sodium bicarbonate.

  Examples of the antioxidant include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, and the like.

  Examples of the processing aid include petroleum oils such as paraffinic oils, aromatic oils, and naphthenic oils added to resin materials and the like.

  Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylate compounds, substituted tolyl compounds, metal chelate compounds, and the like.

  As the colorant, general inorganic pigments and organic pigments described in “Handbook of Pigments (edited by Japan Pigment Technical Association)” can be used. Examples of inorganic pigments include (complex) metal oxides containing titanium such as titanium yellow, zinc oxide, iron oxide, zinc sulfide, and antimony trioxide. Examples of the organic pigment include phthalocyanine, anthraquinone, quinacridone, azo, isoindolinone, quinophthalone, perinone, and perylene pigments.

  Examples of the antistatic agent include alkyl phosphate esters and silicate compounds.

  Examples of the dispersant include acrylic dispersants, fatty acid ester dispersants, polyethylene glycol dispersants, nonionic surfactants, amphiphilic triphenylene derivatives, and pyrene derivatives.

  The cable of the present invention can be manufactured according to a known method. For example, a general extrusion molding method can be employed. As an extruder used in the extrusion molding method, for example, a single screw extruder or a twin screw extruder can be used.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example. It should be noted that simply “parts” means parts by mass.

The materials used for cable production in the following examples and comparative examples are as follows.
<Insulator layer>
Base resin (A1): Polyethylene (PE) (density 0.880 g / cm ³ , MFR 2.2 g / 10 min)
Base resin (A2): Polyethylene (PE) (density 0.901 g / cm ³ , MFR 2.0 g / 10 min)
Base resin (A3): Polyethylene (PE) (density 0.954 g / cm ³ , MFR 0.9 g / 10 min)
Base resin (A4): Polyethylene (PE) (density 0.957 g / cm ³ , MFR 0.2 g / 10 min)
Base resin (A5): ethylene-vinyl acetate copolymer (EVA) (density 0.920 g / cm ³ , MFR 2.0 g / 10 min)
Base resin (A6): Ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) (ethylene content 51%)
Base resin (A7): Ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) (ethylene content 77%)
Base resin (A8): Ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) (ethylene content 47%)
・ Crosslinking agent: Dicumyl peroxide ・ Crosslinking catalyst: Dibutyltin dilaurate ・ Silane coupling agent: Vinyltriethoxysilane

<Insulator outer layer>
Base resin (E1): Polyethylene (PE) (density 0.921 g / cm ³ , MFR 2.5 g / 10 min)
Base resin (E2): Polyethylene (PE) (density 0.953 g / cm ³ , MFR 5.0 g / 10 min)
Base resin (E3): Polyethylene (PE) (density 0.913 g / cm ³ , MFR 2.4 g / 10 min)
Base resin (E4): Polyethylene (PE) (density 0.960 g / cm ³ , MFR 1.0 g / 10 min)
Base resin (E5): Polyethylene (PE) (density 0.929 g / cm ³ , MFR 2.6 g / 10 min)

<Sheath>
・ Base resin: Polyvinyl chloride (PVC)
・ Plasticizer: Phthalate ester ・ Stabilizer: Ca / Zn stabilizer ・ Filler: Calcium carbonate

(Examples 1-9 and Comparative Examples 1-9)
First, according to the compounding quantity (mass part) shown in Table 1, 2, the resin composition used for the inner layer of an insulator was produced. Using a Henschel mixer, a crosslinking agent, a crosslinking catalyst, and a silane coupling agent were added to the base resin and reacted at 60 to 100 ° C. to obtain a resin composition. Moreover, according to the compounding quantity shown to Table 1, 2, each component was knead | mixed with the kneader set to about 140-180 degreeC of temperature, and the resin composition used for a sheath was prepared.

  Then, the cable 1 as shown in FIG. 1 was created. That is, using an extrusion molding machine ("Lab Station" (trade name) manufactured by Prabender Co., Ltd.), the outer periphery of a copper wire having a diameter of 14.0 mm was covered with an inner layer 31 having a thickness of 1.70 mm. After coating with the outer layer 32 having the thickness described in 2, the sheath 4 was coated with a thickness of 1.50 mm.

  Each cable obtained was evaluated as follows, and the results are shown in Tables 1 and 2.

<Twist angle at -15 ° C>
The insulator and the sheath were peeled from the cable, and the low-temperature flexibility at −15 ° C. was measured by the Crushberg flexibility temperature test. For the insulator, 30 ° or more, and for the sheath, 20 ° or more were evaluated as “good”, and less than that was evaluated as “failed”.

<Heating deformation>
The insulator and the sheath were peeled from the cable, and the degree of heat deformation was measured according to JIS K6723 6.5. For the insulator, 40% or less, and for the sheath, 25% or less were evaluated as acceptable “◯”, and those exceeding it were evaluated as rejected “x”.

<Degree of crosslinking>
The degree of cross-linking of the inner layer of the insulator was measured in accordance with the test of item 27 of JIS C 3005. 5 g of the resin composition forming the inner layer is immersed in 100 g of xylene as a solvent, the temperature of the solvent is kept at 120 ° C. for 24 hours, and a sample is taken out of the solvent and placed in a vacuum desiccator. And dried at a temperature of 100 ± 2 ° C. and a vacuum of 1.3 kPa (10 Torr) or less for 24 hours or more. The weight after drying was measured to the unit of mg, and the percentage compared with the initial weight of the resin composition was determined.

<Tensile elongation and tensile strength>
The insulator was peeled from the cable, and the tensile elongation and tensile strength were measured according to JIS C3005. About tensile elongation, 400% or more was set as the pass "(circle)", and less than 400% was evaluated as the rejection "x". Moreover, about tensile strength, 12 Mpa or more was set as the pass "(circle)", and less than 12 Mpa was evaluated as the rejection "x".

<Remaining strength ratio after transition>
In order to promote the migration of the plasticizer from the sheath to the insulator, the tensile elongation of the insulator after the cable was left in a 90 ° C. environment for 28 days was measured, and the ratio to the tensile elongation before the test was examined. 80% or more was evaluated as a pass “◯”, and less than 80% was evaluated as a fail “×”.

From the results of Tables 1 and 2, in Examples 1 to 9, the transition of the plasticizer contained in the sheath to the insulator is suppressed, and it has excellent flexibility even at low temperatures, as well as heat deformation, tensile elongation, and tension. It was found that it was excellent in various properties such as strength.
In contrast, Comparative Examples 1, 3, and 4 resulted in inferior twist angles at −15 ° C. of Insulators, Comparative Example 2 resulted in inferior tensile strengths of Insulators, and Comparative Examples 4 and 5 The results were inferior in the residual strength ratio, Comparative Examples 6 and 8 were inferior in tensile elongation, and Comparative Example 9 was inferior in heat deformation, and none of them could satisfy the acceptance criteria in all test items. .

1 Cable 2 Conductor 3 Insulator 31 Inner Layer 32 Outer Layer 4 Sheath

Claims (6)

A cable comprising an insulator and a sheath in this order on the outer periphery of a conductor,
The insulator has an inner layer covering the conductor, and an outer layer located outside the inner layer and in contact with the sheath;
The inner layer contains, as a base resin, one or more polyolefin resins having a density of 0.880 to 0.950 g / cm ³ , or contains a polyolefin resin having a density of 0.880 to 0.950 g / cm ³ and ethylene An amount of ethylene / propylene / non-conjugated diene copolymer rubber (EPDM) of 50% by mass or more in a ratio of 20:80 to 80:20 (mass ratio);
The outer layer includes at least one polyolefin resin having a density of 0.915 to 0.955 g / cm ³ as a base resin, and the outer layer has a thickness of 0.05 to 0.5 mm. cable.   The cable according to claim 1, wherein the resin composition constituting the inner layer has a degree of cross-linking of 20 to 95%.   The cable according to claim 1 or 2, wherein the polyolefin resin contained in the inner layer has a melt flow rate (MFR) of 0.1 to 10.0 g / 10 minutes.   The cable according to any one of claims 1 to 3, wherein the polyolefin resin contained in the outer layer has a melt flow rate (MFR) of 0.1 to 10.0 g / 10 minutes.   The polyolefin resin contained in the inner layer is at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), and ethylene-vinyl acetate copolymer (EVA). The cable according to claim 1, wherein the cable is one.   The cable according to any one of claims 1 to 5, wherein the polyolefin resin contained in the outer layer is polyethylene (PE).

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