JP2014096252A - Wire and cable using silane crosslinked polyethylene and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wires and cables using a silane crosslinked polyethylene that gives a smooth extrusion appearance and has a high crosslinking degree with an excellent crosslinking speed, and a method of producing the same.SOLUTION: In the wire and cable, the outer periphery of a conductor 1 is coated by extrusion with an inner layer 2 composed of a silane crosslinked polyethylene, and an external layer 3 composed of an ethylene polymer containing a silanol condensation catalyst.

Description

  The present invention relates to an electric wire / cable using a highly crosslinked silane-crosslinked polyethylene having a smooth extruded appearance and excellent crosslinking speed, and a method for producing the same.

  Polyethylene is widely used as a coating material for electric wires and cables because of its excellent electrical insulation. In particular, cross-linked polyethylene obtained by introducing a cross-linked structure into polyethylene can add heat resistance, and is therefore used in large quantities for coating materials such as power cables.

  The main crosslinking methods for polyethylene include organic peroxide crosslinking, electron beam irradiation crosslinking, and silane crosslinking. In silane cross-linking, after forming a polyethylene obtained by graft copolymerization of a silane compound, the cross-linking proceeds only by leaving it in the atmosphere where moisture exists or in a high-temperature and high-humidity environment. Therefore, there is a merit that the initial capital investment can be relatively reduced, and it is utilized as a method for manufacturing a low voltage power cable of about 600V.

  Generally, electric wires and cables using silane-crosslinked polyethylene are manufactured as follows.

  First, in order to graft copolymerize a silane compound with polyethylene, polyethylene, a silane compound, and a free radical generator are kneaded and reacted. Next, after adding a silanol condensation catalyst, a copper conductor or a cable core is extrusion coated. As a process at this time, a method of once preparing polyethylene obtained by graft copolymerization of a silane compound and kneading and extruding the silanol condensation catalyst and the polyethylene in a separate process, carrying out the entire kneading process with one extruder. In addition, there are methods such as extrusion coating.

  By the way, with the recent globalization of the market, there is an active movement to align domestic standards with international standards. In the field of low-voltage power cables, a JIS standard that conforms to the IEC standard is established, and cross-linked polyethylene used as an insulator is required to pass a hot set test at an air temperature of 200 ° C. The hot set test measures the ease of deformation of the insulating material at a high temperature, and even polyethylene that has been conventionally usable is rejected because it has a low degree of crosslinking and is greatly deformed. For this reason, it is necessary to develop a silane-crosslinked polyethylene having a high degree of crosslinking.

JP 2008-181754 A JP 11-320779 A

  Since silane-crosslinked polyethylene with a high degree of crosslinking is obtained by increasing the number of crosslinking points, the amount of the silane compound and free radical generator added is increased when the polyethylene obtained by graft copolymerization of the silane compound is increased. The amount needs to be increased. However, since a cross-linking reaction is likely to occur, the conventional production method in which the silanol condensation catalyst is kneaded in the extruder has a problem in that the reaction proceeds in the extruder, resulting in surface roughness or protrusion on the extrusion appearance.

  Moreover, when extruding a material containing a silane compound, there is a problem that die scum is likely to accumulate at the die outlet of the extruder and adheres to the surface of the extrudate to deteriorate the appearance.

  In order to solve these problems, as proposed in Patent Document 1, a method for forming a skin layer made of polyethylene having a melting point of 130 ° C. or more on the surface of a silane-crosslinked polyolefin is generally known. . However, since the inner layer contains a large amount of silanol condensation catalyst, the reaction in the extruder proceeds when the degree of crosslinking is increased, and the surface roughness of the inner layer becomes severe. Even if the skin layer was coated there, sufficient smoothness could not be obtained and the effect was limited. In addition, since polyethylene having a melting point of 130 ° C. or higher has high crystallinity and water hardly permeates, there is a problem that the water necessary for the cross-linking reaction of the inner layer is insufficient and the cross-linking speed is slow.

  Moreover, in patent document 2, the method of providing the outer layer which does not contain a silanol condensation catalyst which mix | blends a radical generator and an organic silane compound with an olefin resin and heats to the inner layer which consists of extrusion-molded crosslinked polyolefin resin. Proposed.

  In this Patent Document 2, since an extruded product of a silane-crosslinked polyolefin resin that crosslinks in the presence of a silanol condensation catalyst has a rough resin surface, the outer layer is made of a silane-crosslinked polyolefin resin that does not contain a silanol condensation catalyst. Is good.

  However, as described above, since the inner layer contains a large amount of silanol condensation catalyst, sufficient smoothness could not be obtained when the degree of crosslinking was increased. Furthermore, since the outer layer has a silane compound, the problem of die scum remains unsolved.

  Accordingly, an object of the present invention is to solve the above problems and provide an electric wire / cable using a highly crosslinked silane-crosslinked polyethylene having a smooth extruded appearance and a method for producing the same.

  In order to achieve the above object, the invention according to claim 1 is characterized in that an outer layer made of silane-crosslinked polyethylene and an outer layer made of an ethylene polymer containing a silanol condensation catalyst are extrusion coated on the outer periphery of the conductor.・ It is a cable.

  The invention according to claim 2 is characterized in that the silane-crosslinked polyethylene in the inner layer contains 0 to 0.4 parts by mass of silanol condensation catalyst with respect to 100 parts by mass of polyethylene obtained by graft copolymerization of a silane compound. Electric wire / cable.

  Invention of Claim 3 is an electric wire and cable of Claim 1 or 2 whose addition amount of the silanol condensation catalyst in the said outer layer is 0.4-6 mass parts with respect to 100 mass parts of ethylene-type polymers.

The invention according to claim 4 is characterized in that the ethylene polymer in the outer layer is polyethylene having a density of 0.885 to 0.915 g / cm ³ or an ethylene vinyl acetate copolymer having a vinyl acetate content of 30 mass% or less. It is an electric wire and cable in any one of Claims 1-3.

  A fifth aspect of the present invention is the electric wire / cable according to any one of the first to fourth aspects, wherein the outer layer has a thickness of 50 to 310 μm.

According to a sixth aspect of the present invention, in the hot set test shown in 9 of JIS C 3660-2-1, the insulator composed of the inner layer and the outer layer has an air temperature of 200 ° C., a load of 20 N / cm ² , and a load application time of 15 6. The electric wire / cable according to claim 1, wherein the elongation under load is 175% or less and the permanent elongation after cooling is 15% or less under the test conditions of 1 minute.

  In the invention of claim 7, an outer layer made of an ethylene-based polymer containing a silanol condensation catalyst is extrusion coated on the outer periphery of a conductor to form an inner layer by coating polyethylene obtained by graft copolymerization of a silane compound. Then, when crosslinking with normal temperature or water vapor, the inner layer polyethylene is crosslinked with a silanol condensation catalyst contained in the outer layer.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the electric wire and cable which coat | covered the silane bridge | crosslinking polyethylene of the high crosslinking degree whose extrusion external appearance is smooth.

It is a detailed sectional view of an electric wire to which the present invention is applied. It is a detailed sectional view of a cable to which the present invention is applied.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  An electric wire / cable coated with the silane-crosslinked polyethylene of the present invention will be described with reference to FIG.

  FIG. 1 shows an electric wire 10 in which a copper conductor 1 is coated with an inner layer 2 made of silane-crosslinked polyethylene and an outer layer 3 made of an ethylene-based polymer containing a silanol condensation catalyst.

  FIG. 2 shows a low-voltage power cable 20 in which the electric wire 10 shown in FIG. 1 is covered with a sheath 4 such as a vinyl chloride resin.

  The inner layer 2, the outer layer 3, and the sheath 4 shown in FIGS. 1 and 2 are covered by extrusion molding.

  The present invention uses a silane-crosslinked polyethylene that contains no or only a small amount of silanol condensation catalyst for the inner layer 2 that is extrusion coated on the copper conductor 1, and the silanol condensation catalyst is applied to the outer layer 3 that is extrusion coated on the surface of the inner layer 2. An ethylene polymer (low density polyethylene or ethylene vinyl acetate copolymer) is used. By doing so, the crosslinking reaction of the silane-crosslinked polyethylene of the inner layer 2 is suppressed during the extrusion of the inner layer 2, and in that state, the ethylene polymer containing the silanol condensation catalytic reaction is coated as the outer layer 3. Then, the liquid silanol condensation catalyst contained in the outer layer 3 permeates into the inner layer 2 and diffuses in the room temperature environment after the extrusion molding or in the saturated water vapor, so that the inner layer 2 contains a large amount of the silanol condensation catalyst. Since it acts as if contained, it can be crosslinked. Thereby, the silanol condensation catalyst contained in the inner layer 2 suppresses the silane crosslinking reaction in the extruder and promotes the crosslinking reaction with the silanol condensation catalyst contained in the outer layer 3 after the extrusion, so that the extrusion appearance is good. Highly bridging wires and cables can be obtained.

  In this way, the present inventors use the silane-crosslinked polyethylene containing no or only a small amount of silanol condensation catalyst for the inner layer 2 of the insulator, and coat the outer layer 3 with the ethylene-based polymer containing the silanol condensation catalyst. Thus, it was found that an electric wire / cable having a good extrusion appearance can be obtained. In other words, it is considered that the appearance is improved by suppressing the progress of the crosslinking reaction of polyethylene in the extruder. Further, the outer layer 3 does not contain a silane compound, and there is no generation of die scum during extrusion. The silanol condensation catalyst necessary for the crosslinking reaction is supplied by shifting from the outer layer 3 to the inner layer 2 after extrusion.

  Furthermore, the knowledge that cross-linking speed is improved by using low density polyethylene or an ethylene vinyl acetate copolymer having a polar group in the outer layer 3 was obtained, and the present invention was achieved. This is presumably because the moisture necessary for the silane crosslinking reaction is easily supplied to the inner layer 2 through the outer layer 3.

  As the polyethylene used as the raw material for the inner layer silane-crosslinked polyethylene in the present invention, general materials such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-low-density polyethylene can be used. Alternatively, two or more kinds can be blended and used. The melt index is not particularly limited.

  The silane compound that can be used in the present invention preferably has both a group capable of reacting with a polymer and an alkoxy group that forms a crosslink by silanol condensation. Specifically, vinyltrimethoxysilane, vinyltriethoxylane, Vinylsilane compounds such as vinyltris (β-methoxyethoxy) silane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, β- (aminoethyl) ) Aminosilane compounds such as γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ -Glycidoxypropyl methyl Epoxysilane compounds such as diethoxysilane, acrylic silane compounds such as γ-methacryloxypropyltrimethoxysilane, bis (3- (triethoxysilyl) propyl) disulfide, bis (3- (triethoxysilyl) propyl) tetrasulfide, etc. And a polycaptosilane compound such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

  Examples of free radical generators include dicumyl peroxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxyisopropyl carbonate, and t-butylperoxide. Oxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, methyl ethyl ketone peroxide, 2,2-bis (t-butylperoxy) butane, cumene hydroperoxide, etc. are decomposed and released by heat Organic peroxides that generate radicals can be mainly used.

  The amount of the silane compound and free radical generator added to polyethylene is arbitrary and is not particularly limited.

As the outer layer ethylene polymer in the present invention, a copolymer of ethylene and another monomer can be used in addition to polyethylene, such as ethylene vinyl acetate copolymer, ethylene methyl methacrylate copolymer, ethylene methyl acrylate copolymer. And generally known ones such as ethylene ethyl acrylate copolymer. Among them, a polyethylene having a density of 0.880 to 0.925 g / cm ³ , more preferably a polyethylene having a density of 0.885 to 0.915 g / cm ³ , or ethylene acetate having a vinyl acetate content of 35 mass% or less, more preferably 30 mass% or less. It is more preferable to use a vinyl copolymer.

Generally, polyethylene having a density of 0.880 to 0.925 g / cm ³ is produced by copolymerizing ethylene and an α-olefin. As the α-olefin, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like are used, and one or a combination of two or more is produced.

  In the present invention, these polyethylenes can be used alone or in combination of two or more. The melt index is not particularly limited.

When the density of the polyethylene is less than 0.880 g / cm ³ , the cable surface is highly tacky and handling properties are lowered. When the density exceeds 0.925 g / cm ³ , the moisture permeability decreases and the crosslinking speed of the inner layer becomes slow.

  The ethylene vinyl acetate copolymer preferably has a vinyl acetate content of 35 mass% or less. When vinyl acetate content exceeds 35 mass%, cable surface and adhesiveness will appear and handling property will fall. The melt index is not particularly limited.

  Silanol condensation catalysts that can be used in the present invention are dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, dioctyltin dioctate, dibutyltin dineodecanoate, dioctyltin dineodecanoate, acetic acid Examples include stannous, stannous caprylate, tin bisneodecanoate, zinc caprylate, zinc naphthenate, cobalt naphthenate, and tetra-i-propoxytitanium. In order to increase the condensation efficiency, acids such as carboxylic acid compounds and sulfonic acid compounds and alkalis such as amine compounds may be used, or they may be used in combination with the above-described tin and zinc compounds. The carboxylic acid compound can contain desorbed acetic acid derived from an ethylene vinyl acetate copolymer that can be used in the outer layer.

  The amount of silanol condensation catalyst added to the outer layer is preferably 0.4 to 6 parts by mass per 100 parts by mass of the ethylene polymer. Furthermore, it is more preferable in it being 0.5-5 mass parts per 100 mass parts of ethylene-type polymers. When the amount is less than 0.4 parts by mass, the degree of crosslinking of the inner layer silane-crosslinked polyethylene is lowered. When the amount is more than 6 parts by mass, there is a high possibility of bleeding or blooming on the surface, which causes a problem in use such as sticking.

  The silanol condensation catalyst may be added to the inner layer. The amount added is 0.4 parts by mass or less, preferably 0.3 parts by mass or less, with respect to 100 parts by mass of polyethylene obtained by graft copolymerization of a silane compound. If it exceeds 0.4 parts by mass, the cross-linking reaction in the extruder proceeds so much that the appearance of extrusion is remarkably deteriorated. The inner layer preferably has a degree of crosslinking (gel fraction) of less than 70 when left for 12 hours at 60 ° C. under saturated vapor pressure. Especially in the range of less than 60-70, the smoothness of the inner layer is high, the influence of extruding the outer layer is small, and an electric wire having a good appearance can be easily obtained.

  As an addition method, there is a method of using a masterbatch previously mixed with a polymer such as polyethylene in addition to the method of adding as it is.

  In addition to the above, process oil, processing aid, flame retardant, flame retardant aid, crosslinking agent, crosslinking aid, antioxidant, ultraviolet absorber, copper damage inhibitor, lubricant, inorganic filler, It is also possible to add additives such as compatibilizers, stabilizers, carbon black, and colorants.

  A method for producing an electric wire / cable coated with the silane-crosslinked polyethylene of the present invention will be described.

  An insulator consisting of an inner layer and an outer layer is coated on the copper conductor by known methods. In general, a multilayer extruder is used, and an inner layer of silane-crosslinked polyethylene is coated on the copper conductor from the main extruder, and at the same time, an outer layer made of an ethylene-based polymer containing a silanol condensation catalyst is coated on the inner layer from the sub-extruder. An electric wire is manufactured by covering with

  The thickness of the outer layer is preferably 50 to 310 μm. When the thickness is less than 50 μm, it is difficult to extrude to a uniform thickness, and when the appearance of the inner layer is extremely rough, the effect of smoothing the surface is insufficient. If the thickness exceeds 310 μm, the outer layer itself is an uncrosslinked component, and thus the crosslinking characteristics of the insulator may be deteriorated. In addition, moisture becomes difficult to be supplied to the inner layer, and the crosslinking speed may be reduced.

  In addition to the above, a method of forming a three-layer structure in which an innermost layer is provided on the inner side of the inner layer, and covering the innermost layer with an ethylene polymer containing a silanol condensation catalyst in the same manner as the outer layer can also be carried out. According to this method, since the silanol condensation catalyst can be transferred to the silane-crosslinked polyethylene of the inner layer from both the innermost layer and the outer layer, the crosslinking speed can be further increased.

  As a method of extruding the inner layer silane-crosslinked polyethylene, a known production method can be applied. For example, there is a method in which polyethylene is introduced from a hopper, a mixed solution of a silane compound and a free radical generator is injected from the middle of the hopper or an extruder, and the silane compound is graft copolymerized with polyethylene in the extruder to coat the copper conductor. Can be mentioned. There is also a method in which polyethylene obtained by graft copolymerization with a silane compound produced in a separate process in advance is directly coated by extrusion. When adding a silanol condensation catalyst, there are a method of feeding from a hopper, a side feed from the downstream side of the extruder, and the like. Moreover, when adding compounding agents, such as antioxidant and a coloring agent, it can throw in from a hopper or an extruder downstream.

  In order to crosslink the manufactured electric wire / cable, there are a method in which it is allowed to stand at room temperature and naturally crosslinks, and a method in which a temperature lower than the melting point of the ethylene polymer of the outer layer is applied to leave in a high humidity environment to promote crosslinking.

  Examples of the present invention will be specifically described below together with comparative examples.

First, polyethylene obtained by graft copolymerization with a silane compound was prepared. Using a single screw extruder (L / D = 25) with a screw diameter of 100 mm, linear low density polyethylene (d = 0.923 g / cm ³ , MI = 0.7 g / 10 min) is introduced from the hopper, and liquid-added. A solution in which dicumyl peroxide was dissolved in vinyltrimethoxysilane was injected from a pump, and a silane compound was graft copolymerized with polyethylene. 4 parts by mass and 0.08 parts by mass of vinyltrimethoxysilane and dicumyl peroxide were added to 100 parts by mass of linear low density polyethylene, respectively. The cylinder temperature was set to 200 ° C., and the inner layer material was produced by extruding so that the residence time in the extruder was 2 to 3 minutes.

  Next, an inner layer material and an outer layer material shown in Table 1 were coated on a 12 mmφ copper conductor so that the total thickness of the inner layer and the outer layer was 2.0 mm, thereby producing an electric wire. A single screw extruder (L / D = 28) having a screw diameter of 130 mm was used as an inner layer extruder, and polyethylene obtained by graft polymerization of a silane compound was introduced from a hopper. The cylinder temperature was set to 180 ° C. and the residence time in the extruder was 2 to 3 minutes. In the case of adding a silanol condensation catalyst, a master batch containing a silanol condensation catalyst previously blended at a ratio shown in Table 1 was charged from a hopper and extruded. A single screw extruder (L / D = 24) having a screw diameter of 40 mm was used as the outer layer extruder. The cylinder temperature was 160 ° C. The wire take-up speed was constant, and the thicknesses of the outer and inner layers were adjusted by changing the number of revolutions of both extruders.

  The produced electric wire was crosslinked at 60 ° C. under saturated vapor pressure for 12 hours.

  The electric wire produced by the above procedure was evaluated by the following method.

Extrusion appearance:
The smoothness of the surface, the presence / absence of protrusions, and the presence / absence of tackiness were evaluated visually and by hand. Those that were sufficiently smooth and non-sticky to give a gloss were used. Although it was not glossy, it was smooth and had no lips, or had a tackiness that did not cause a problem in use.

Outer layer thickness:
The cross section of the insulator was observed with an optical microscope, and the thickness of the outer layer was measured. A 5-point average value was calculated, and a value in the range of 50 to 310 μm was regarded as acceptable.

Gel fraction:
The copper conductor was removed and the gel fraction of the insulator was measured. Extraction in hot xylene at 130 ° C. for 24 hours,
(Mass of residual gel after extraction) / (Mass of insulator before extraction) x 100 (%)
Was the gel fraction.

  It measured and evaluated what was bridge | crosslinked for 12 hours under 60 degreeC and saturated vapor pressure after electric wire manufacture.

Hot set test:
The copper conductor was removed, the inside of the coating material was ground smoothly, and a hot set test based on 9 of JIS C 3660-2-1 was performed. A dumbbell-shaped sample is suspended in a thermostatic chamber having an air temperature of 200 ° C. A load of 20 N / cm ² was applied for 15 minutes, and the elongation under load was measured. Thereafter, the load was removed, and after 5 minutes, the sample was taken out and the permanent elongation after cooling was 15% or less was regarded as acceptable.

  As shown in Table 1, in Examples 1 to 15 of the present invention, the extrusion appearance is good, and in particular, all examples pass the hot set test when crosslinked at 60 ° C. under saturated vapor pressure. On the other hand, Comparative Examples 1 and 3 have a large elongation in the hot set test. In Comparative Example 2, the hot set test passes, but the extruded appearance is not possible.

  The reason for this will be described below together with examples and comparative examples.

  In Examples 1 and 2 and Comparative Examples 1 and 2, 0.05 parts by mass of the silanol condensation catalyst (dioctyltin dilaurate) to be contained in the inner layer is contained.

  As a result, Comparative Example 1 does not extrude the outer layer, so the appearance of extrusion is not possible, and Comparative Example 2 covers the outer layer, so that the appearance of extrusion is excellent, but the content of the silanol condensation catalyst in the inner layer is small. Therefore, the silane crosslinking reaction is not sufficiently performed and the hot set test is not passed.

  On the other hand, in Examples 1-4, since the silanol condensation catalyst was contained in the outer layer, the hot set test was passed. In this case, in Example 1, since the silanol condensation catalyst contained in the outer layer is as small as 0.4 parts by mass, the hot set test crosslinked at 60 ° C. under saturated vapor pressure passes, but as in Example 2. When the silanol condensation catalyst is 0.5 parts by mass, the properties when crosslinked under the same conditions are better. In Examples 3 and 4, the silanol condensation catalyst was increased to 5 parts by mass and 6 parts by mass. By passing a large amount of the silanol condensation catalyst in the outer layer, the hot set test was passed. Further, since 6 parts by mass of the silanol condensation catalyst was contained, a slight stickiness was felt on the surface, so that the extrusion appearance was good. Therefore, considering the properties after crosslinking under the same conditions and the appearance of extrusion, the silanol condensation catalyst contained in the outer layer is more preferably in the range of 0.5 to 6 parts by mass, particularly 0.5 to 5 parts by mass.

  Examples 5 to 8 show the influence of crosslinking due to the density of the ethylene-based polymer used in the outer layer. The inner layer does not contain a silanol condensation catalyst, but the outer layer contains 2 parts by mass of a silanol condensation catalyst. It is.

  As a result, it can be seen that the cross-linking reaction proceeds with the silanol condensation catalyst contained in the outer layer without containing the silanol condensation catalyst in the inner layer.

However, in Example 5, the density of the outer layer polyethylene is as high as 0.923 g / cm ³ . In Example 8, the density of the polyethylene used for the outer layer was as low as 0.880 g / cm ^3, and although the surface passed the hot set test, some tackiness was felt on the surface, and the extrusion appearance was good. Examples 6 and 7 on the other hand, density of 0.915 g / cm ^3, a 0.885 g / cm ^3, an extrusion appearance with excellent, hot set test was passed.

Therefore, the density of the polyethylene used in the outer layer, the range of 0.915g / cm ³ ~0.885g / cm ³ is more preferable.

  Examples 10 and 11 show the influence of the vinyl acetate content of the ethylene vinyl acetate copolymer used for the outer layer. In Example 10, the vinyl acetate content of the ethylene vinyl acetate copolymer used for the outer layer was 33 mass%, which was higher than the vinyl acetate content of 28 mass% in Example 9, so that some tackiness was felt on the surface.

  Therefore, the vinyl acetate content of the ethylene vinyl acetate copolymer is more preferably 30 mass% or less in view of the extrusion appearance.

  Moreover, in Example 11, the silanol condensation catalyst contained in the inner layer was 0.4 parts by mass, and compared with Example 9 of 0.3 parts by mass, the crosslinking reaction in the extruder progressed, and the inner layer Even if the outer layer is coated due to surface roughness, the degree of smoothness is lowered and the extrusion appearance is improved. In Comparative Example 3, the silanol condensation catalyst contained in the inner layer is 0.5 parts by mass, and this extrusion appearance is not possible. Considering this Comparative Example 3, the silanol condensation catalyst contained in the inner layer is preferably 0.4 parts by mass or less.

  In Examples 12 to 15, the inner layer contains 0.2 parts by mass of the silanol condensation catalyst, the outer layer contains 0.5 part by mass of the silanol condensation catalyst, and the thickness of the outer layer is changed in the range of 45 μm to 307 mm. is there.

  As a result, Example 12 with an outer layer thickness of 45 μm has a good extrusion appearance, and Example 15 with a thickness of 307 μm passes the hot set test.

  As described above, according to the present invention, the extrusion appearance is smooth, and an electric wire / cable using silane-crosslinked polyethylene having a high degree of crosslinking as a coating material can be obtained, and its industrial usefulness is extremely high. For example, it is suitable for a low-voltage power cable.

1 Copper conductor 2 Inner layer 3 Outer layer 4 Sheath 10 Electric wire 20 Cable

Claims (7)

  An electric wire / cable characterized in that an outer layer made of an ethylene polymer containing a silanol condensation catalyst and an outer layer made of an ethylene polymer containing a silanol condensation catalyst are extrusion coated on the outer periphery of the conductor.   The electric wire / cable according to claim 1, wherein the silane-crosslinked polyethylene in the inner layer contains more than 0 and 0.4 parts by mass of a silanol condensation catalyst with respect to 100 parts by mass of polyethylene obtained by graft copolymerization of a silane compound.   The electric wire / cable according to claim 1 or 2, wherein an addition amount of the silanol condensation catalyst in the outer layer is 0.4 to 6 parts by mass with respect to 100 parts by mass of the ethylene polymer. The ethylene polymer in the outer layer is polyethylene having a density of 0.885 to 0.915 g / cm ³ , or an ethylene vinyl acetate copolymer having a vinyl acetate content of 30 mass% or less. The electric wire / cable described in any one.   The electric wire / cable according to claim 1, wherein the outer layer has a thickness of 50 to 310 μm. In the hot set test shown in 9 of JIS C 3660-2-1, the insulator composed of the inner layer and the outer layer is loaded under the test conditions of an air temperature of 200 ° C., a load of 20 N / cm ² , and a load application time of 15 minutes. The wire / cable according to any one of claims 1 to 5, wherein an elongation of 175% or less and a permanent elongation after cooling is 15% or less.   The outer periphery of the conductor is coated with polyethylene obtained by graft copolymerization of a silane compound to form an inner layer, and the inner layer is coated with an outer layer made of an ethylene polymer containing a silanol condensation catalyst by extrusion coating at room temperature or with water vapor. A method for producing an electric wire / cable, wherein the inner layer polyethylene is crosslinked with a silanol condensation catalyst contained in the outer layer at the time of crosslinking.

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