JP6329355B2 - Silane crosslinkable resin composition, insulated wire and method for producing the same - Google Patents

Description

  The present invention relates to a silane crosslinkable resin composition, an insulated wire, and a method for producing the same.

  Insulated wires that make up wiring harnesses for wiring of electrical equipment are generally composed of a conductor in which a plurality of metal wires made of copper, copper alloy, etc. are twisted, a resin insulating layer covering the conductor, and this insulation It is comprised from the sheath layer coat | covered on the surrounding surface of a layer. As a resin used for the insulating layer and the sheath layer, a polyvinyl chloride resin has been conventionally used. However, there is a concern about contamination with a halogen element at the time of disposal. Recently, polyethylene and ethylene-polar monomer copolymers are used. A synthetic resin in which heat resistance is improved by cross-linking with a silane compound is used (see Japanese Patent Application Laid-Open No. 2007-207638).

  This non-halogen insulated wire is excellent in heat resistance, flame retardancy, mechanical strength, etc. In recent years, as a cable (PV cable) used in the DC electric circuit of solar cell power generation equipment, connection between modules, connection between module and connection box, It is used for connection between a connection box and a power conditioner.

JP 2007-207638 A

  However, since the conventional non-halogen insulated wire is formed by grafting a silane compound onto polyethylene, ethylene-polar monomer copolymer or the like and forming a sheath layer containing this silane compound as a main component, the production unit price remains high. . In addition, the resin grafted with this silane compound has an increased melt viscosity compared to the ungrafted resin, and thus the torque during extrusion increases. However, the resin is extruded below the upper limit of torque determined by the extruder. And the linear speed of extrusion is regulated. Therefore, there is room for further improvement in the productivity of insulated wires.

  The present invention has been made based on the above-described circumstances, and is used for an insulated wire that can promote reduction in the manufacturing unit price while maintaining various characteristics such as heat resistance, a manufacturing method thereof, and a manufacturing method thereof. An object is to provide a silane crosslinkable resin composition.

The invention made to solve the above problems is
A silane crosslinkable resin composition for forming a sheath layer of an insulated wire,
A silane crosslinkable resin obtained by grafting at least one of polyethylene and ethylene-polar monomer copolymer with a silane compound;
A non-silane crosslinkable resin comprising at least one of polyethylene and ethylene-polar monomer copolymer;
Containing metal hydroxide,
The content of the non-silane crosslinkable resin with respect to a total of 100 parts by mass of the silane crosslinkable resin and the non-silane crosslinkable resin is 40 parts by mass or more and 90 parts by mass or less.

  Since the silane crosslinkable resin composition is a mixture of the silane crosslinkable resin and the non-silane crosslinkable resin in the above-mentioned range, the silane crosslinkable resin composition is non-silane crosslinkable while enjoying the advantages of containing the silane crosslinkable resin. The advantage by including resin can be enjoyed. That is, the silane crosslinkable resin composition has various properties such as heat resistance, flame retardancy, mechanical strength, etc., and is insulated by a relatively inexpensive non-silane crosslinkable resin so that the production cost is low. Can be manufactured. In addition, since the silane crosslinkable resin composition is blended in the above proportion of the non-silane crosslinkable resin, the promotion of silane crosslinking during extrusion molding is suppressed, so the extrusion linear velocity is increased and the productivity is improved. be able to.

  The silane crosslinkable resin is preferably ultra-low density polyethylene grafted with a silane compound. Thus, by using the silane crosslinkable resin based on ultra-low density polyethylene, the flexibility of the sheath layer formed with the silane crosslinkable resin composition can be increased, and the flexibility at low temperature can be improved. As a result, the wiring workability in a low-temperature environment of an insulated wire using the silane crosslinkable resin composition can be improved.

  The non-silane crosslinkable resin is preferably at least one selected from the group consisting of ultra-low density polyethylene, ethylene vinyl acetate copolymer (EVA), and ethylene ethyl acrylate copolymer. By using a non-silane crosslinkable resin that does not go through the mixing step of grafting silane in this way and does not increase the mixing fee, the unit price of the insulated wire using the silane crosslinkable resin composition is effectively reduced. it can.

  As content of the metal hydroxide with respect to 100 mass parts in total of the said silane crosslinkable resin and non-silane crosslinkable resin, 100 mass parts or more and 250 mass parts or less are preferable. Thus, the flame retardance of the said silane crosslinkable resin composition can be improved effectively by making content of a metal hydroxide into the said range.

  The melt flow rate of the non-silane crosslinkable resin is preferably 1 g / min to 10 g / min. When the melt flow rate of the non-silane crosslinkable resin is in the above range (by being reasonably large), the viscosity at the time of melting of the silane crosslinkable resin composition can be lowered. Therefore, the melt elongation when the sheath layer of the insulated wire is extruded from the silane crosslinkable resin composition can be increased appropriately. As a result, as a method for extruding the sheath layer, not only full extrusion molding but also drop extrusion molding can be employed.

  Here, in the case of solid extrusion molding, the insulation layer of the insulated wire and the molten sheath layer (silane crosslinkable resin composition) are in contact with each other in a pressurized state at a portion between the die and the point in the mold. In addition, the adhesion strength (peeling strength) between the sheath layer and the insulating layer may be excessively increased. On the other hand, in the case of pull-down extrusion, the insulating layer and the molten sheath layer (silane-crosslinkable resin composition) come into contact outside the mold after exiting the die. As described above, in the drop extrusion molding, the insulating layer and the sheath layer do not come into contact with each other in the pressurized mold, so that the adhesion strength (peeling strength) between the insulating layer and the sheath layer does not become too large. Easy to peel off later. Therefore, by setting the melt flow rate of the non-silane crosslinkable resin within the above range, the sheath layer can be formed by drop extrusion molding, and the sheath layer can be peeled off when connecting the connector to the end of the insulated wire. Since an easy insulated wire can be provided, workability, such as connector connection of an insulated wire, can be improved.

Moreover, another invention made in order to solve the said subject is:
An insulated wire comprising a conductor, an insulating layer covering the peripheral surface of the conductor, and a sheath layer covering the peripheral surface side of the insulating layer,
The sheath layer is formed from a crosslinked product of the silane crosslinkable resin composition.

  Since the sheath layer is formed from the silane crosslinkable resin composition, the insulated wire can be manufactured at a low unit price while having various properties such as heat resistance, flame retardancy, and mechanical strength. Further, since the sheath layer can be extruded at a high linear velocity, the productivity is excellent.

  The gel fraction of the sheath layer is preferably 50% or more and 80% or less. Thus, by setting the gel fraction of the sheath layer within the above range, it is possible to ensure a predetermined range of crosslinking of the silane crosslinkable resin composition, and to easily and reliably heat resistance, flame retardancy, machine of the insulated wire. The manufacturing unit price can be reduced while maintaining various properties such as strength.

Furthermore, another invention made to solve the above problems is
Preparing a silane crosslinkable resin, a non-silane crosslinkable resin and a metal hydroxide, and mixing them to obtain a silane crosslinkable resin composition;
A step of extruding the silane crosslinkable resin composition on the peripheral surface side of a linear body comprising a conductor and an insulating layer covering the peripheral surface;
And a step of crosslinking the extruded silane crosslinkable resin composition.

  Since the sheath layer is formed using the composition obtained by mixing the silane crosslinkable resin and the non-silane crosslinkable resin, the insulated wire manufacturing method can manufacture an insulated wire with a low manufacturing unit cost and excellent productivity. .

  Here, the “non-silane crosslinkable resin” means a resin having no crosslinkability by itself. “The melt flow rate of the non-silane crosslinkable resin” is an extrusion plastometer specified in JIS-K6760 (1995), in accordance with JIS-K7210 (1999), at a temperature of 190 ° C. and a load of 2.16 kgf. It is a measured value. “Gel fraction” means that the sheath layer before soaking in the solvent is W1 when the sheath layer is immersed in xylene, heated and dissolved at 120 ° C. for 24 hours, and then filtered to evaporate the filtrate to dryness. This is a value obtained from W1 / W2 × 100, where W2 is the mass of.

  As described above, the silane crosslinkable resin composition, the insulated wire and the method for producing the same according to the present invention can promote the reduction of the manufacturing unit cost while maintaining various characteristics such as the heat resistance of the insulated wire.

It is typical sectional drawing for demonstrating full extrusion molding. It is typical sectional drawing for demonstrating pulling extrusion molding. It is a typical perspective view for demonstrating the measuring method of sheath peeling force. It is a typical perspective view for demonstrating the measuring method of sheath peeling force.

  Hereinafter, embodiments of the silane crosslinkable resin composition of the present invention will be described in detail.

[Silane crosslinkable resin composition]
The silane crosslinkable resin composition includes a silane crosslinkable resin obtained by grafting a silane compound onto at least one of polyethylene and ethylene-polar monomer copolymer, and at least one of polyethylene and ethylene-polar monomer copolymer. The non-silane crosslinkable resin which consists of, and the metal hydroxide which is a non-halogen flame retardant.

  Among the polyethylene and ethylene-polar monomer copolymer (hereinafter sometimes referred to as graft target resin) used for the silane crosslinkable resin, as the ethylene-polar monomer copolymer, for example, ethylene vinyl acetate copolymer ( EVA) and ethylene acrylate copolymers such as ethylene ethyl acrylate copolymer (EEA). As the resin to be grafted, very low density polyethylene (VLDPE) having high flexibility even at a low temperature is particularly preferable. In addition, the graft target resin may contain a plurality of types of resins, and may contain a small amount of a resin other than polyethylene and an ethylene-polar monomer copolymer as a resin other than the main component.

The silane crosslinkable resin is obtained by grafting a silane compound onto a graft target resin. As the silane compound, a compound represented by the general formula RR′SiY ₂ can be used. Here, R is a monovalent olefinically unsaturated hydrocarbon group, R ′ is a monovalent hydrocarbon group other than aliphatic unsaturated hydrocarbon or a hydrolyzable organic group, and Y is hydrolyzed. It is a degradable organic group. Among the compounds represented by the above formula, preferred is an organic unsaturated silane represented by the general formula RSiY ₃ where R ′ is the same hydrolyzable organic group as Y. Examples of the organic unsaturated silane include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, allyltriethoxysilane, and oligomers thereof.

  As a minimum of content with respect to 100 mass parts of graft object resin of a silane compound, 0.01 mass part is preferred and 0.1 mass part is more preferred. On the other hand, as an upper limit of content with respect to 100 mass parts of graft target resin of a silane compound, 1.5 mass parts is preferable and 1.2 mass parts is more preferable. When the content of the silane compound is less than the above lower limit, grafting of the graft target resin becomes insufficient, and crosslinking of the graft target resin may not proceed sufficiently. On the contrary, when the content of the silane compound exceeds the above upper limit, the workability of the silane crosslinkable resin composition may be lowered, and the residual silane that is not grafted may increase, so that the sheath layer and the insulating layer may be formed when forming an insulated wire There is a risk that the adhesive strength with the lowering.

  A radical generator may be used for grafting the silane compound. Examples of the radical generator include dicumyl peroxide, α, α′-bis (t-butylperoxydiisopropyl) benzene, di-t-butyl peroxide, t-butylcumyl peroxide, di-benzoyl peroxide, Examples include 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, and the like.

  As a minimum of content with respect to 100 mass parts of graft object resin of a radical generating agent, 0.02 mass part is preferred and 0.05 mass part is more preferred. On the other hand, the upper limit of the content of the radical generator with respect to 100 parts by mass of the graft target resin is preferably 0.15 parts by mass, and more preferably 0.12 parts by mass. When content of a radical generating agent is less than the said minimum, there exists a possibility that the graft of graft object resin may become inadequate. On the contrary, when the content of the radical generator exceeds the above upper limit, the processability of the silane crosslinkable resin composition may be lowered, and local grafting may occur, which may deteriorate the molded appearance. .

  It is preferable to add a silane crosslinking catalyst to the silane crosslinkable resin in order to promote grafting of the silane compound. As the silane crosslinking catalyst, an organometallic compound-based crosslinking catalyst can be used. Specifically, for example, dioctyltin dilaurate, dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, zinc caprylate, tetrabutylester titanate, zinc stearate, calcium stearate and the like can be mentioned. .

  As a minimum of content to 100 mass parts of graft object resin of a silane crosslinking catalyst, 0.01 mass part is preferred and 0.03 mass part is more preferred. On the other hand, the upper limit of the content of the silane crosslinking catalyst with respect to 100 parts by mass of the graft target resin is preferably 0.15 parts by mass, and more preferably 0.12 parts by mass. When content of a silane crosslinking catalyst is less than the said minimum, there exists a possibility that the grafting of resin for grafting cannot fully be accelerated | stimulated. On the other hand, when the content of the silane crosslinking catalyst exceeds the above upper limit, local crosslinking may occur and the molded appearance may be deteriorated.

  The non-silane crosslinkable resin is composed of at least one of polyethylene and an ethylene-polar monomer copolymer. The polyethylene is preferably ultra-low density polyethylene, and the ethylene-polar monomer copolymer is preferably an ethylene vinyl acetate copolymer and an ethylene ethyl acrylate copolymer. Among these, as the non-silane crosslinkable resin, an ethylene ethyl acrylate copolymer that is inexpensive, excellent in heat resistance, and moldability is particularly preferable. The non-silane crosslinkable resin may contain a plurality of types of resins, and may contain a small amount of a resin other than polyethylene and ethylene-polar monomer copolymer as a resin other than the main component.

  The lower limit of the melt flow rate (hereinafter also referred to as “MFR”) of the non-silane crosslinkable resin is preferably 1 g / min, and more preferably 1.5 g / min. The upper limit of the MFR of the non-silane crosslinkable resin is preferably 10 g / min, and more preferably 8 g / min. If the MFR of the non-silane crosslinkable resin is less than the above lower limit, the melt elongation of the silane crosslinkable resin composition becomes high and the melt elongation becomes small, and the extrudability deteriorates (it is difficult to draw extrusion). There is a risk. On the other hand, if the MFR of the non-silane crosslinkable resin exceeds the above upper limit, the mechanical strength of the sheath layer formed from the silane crosslinkable resin composition is lowered, and the desired tensile strength may not be obtained. On the other hand, when the MFR of the non-silane crosslinkable resin is in a range between the above lower limit and the above upper limit (by being reasonably large), the viscosity at the time of melting of the silane crosslinkable resin composition is appropriately set. Can be lowered. Therefore, the melt elongation when extruding the sheath layer of the insulated wire from the silane crosslinkable resin composition can be appropriately increased, and the extrudability can be improved. As a result, as a method for extruding the sheath layer, not only full extrusion molding but also drop extrusion molding can be employed.

  In the silane crosslinkable resin composition, the content of the nonsilane crosslinkable resin with respect to a total of 100 parts by mass of the silane crosslinkable resin and the nonsilane crosslinkable resin is 40 parts by mass or more and 90 parts by mass or less. As a minimum of content of non-silane crosslinkable resin to 100 mass parts of total of silane crosslinkable resin and nonsilane crosslinkable resin, 50 mass parts is more preferred, and 70 mass parts is still more preferred. On the other hand, the upper limit of the content of the non-silane crosslinkable resin with respect to the total of 100 parts by mass of the silane crosslinkable resin and the non-silane crosslinkable resin is more preferably 85 parts by mass. When the content of the non-silane crosslinkable resin is less than the above lower limit, the effect of reducing the production unit cost of the insulated wire using the silane crosslinkable resin composition cannot be obtained, and the melt viscosity does not sufficiently decrease and the extrusion torque increases. As a result, the wire speed decreases, and the productivity of the insulated wire may be reduced. Conversely, when the content of the non-silane crosslinkable resin exceeds the above upper limit, the heat resistance and mechanical strength of the sheath layer formed of the silane crosslinkable resin composition may be reduced.

  As a metal hydroxide contained in the silane crosslinkable resin composition, for example, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, or the like can be used. Among these, it is preferable to use magnesium hydroxide, which has a high flame retarding effect, has a high decomposition temperature, and is difficult to decompose during extrusion molding.

  The metal hydroxide may be surface-treated in order to improve dispersibility. As this surface treatment, for example, a surface treatment using a silane coupling agent, a titanate coupling agent, a fatty acid, a fatty acid metal salt, or the like can be used. Among these, surface treatment using a silane coupling agent having an effect of improving the adhesion between the silane crosslinkable resin and the non-silane crosslinkable resin and the metal hydroxide is preferable.

  Examples of the silane coupling agent include vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris (β-methoxyethoxy) silane; γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, Aminosilane compounds such as N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane; β- (3 , 4 Epoxycyclohexyl) Epoxysilane compounds such as ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane; acrylic sila such as γ-methacryloxypropyltrimethoxysilane Compound: Polysulfide silane compounds such as bis (3- (triethoxysilyl) propyl) disulfide and bis (3- (triethoxysilyl) propyl) tetrasulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc. Mercaptosilane compounds, etc. can be used.

  As a surface treatment method of the metal hydroxide with the surface treatment agent, for example, a wet method, a dry method, a direct kneading method, or the like can be used. Further, the surface treatment amount for the metal hydroxide is preferably 0.1% by mass or more and 5% by mass or less. When the surface treatment amount is less than the lower limit, the effect of improving dispersibility may not be obtained. On the contrary, when the surface treatment amount exceeds the above upper limit, the processability and the like of the silane crosslinkable resin composition may be lowered.

  As a minimum of content with respect to 100 mass parts of total of the silane crosslinkable resin and non-silane crosslinkable resin of the said metal hydroxide, 100 mass parts is preferable and 140 mass parts is more preferable. On the other hand, the upper limit of the content of the metal hydroxide for the total of 100 parts by mass of the silane crosslinkable resin and the non-silane crosslinkable resin is preferably 250 parts by mass, and more preferably 180 parts by mass. When content of a metal hydroxide is less than the said minimum, there exists a possibility that the flame retardance of the said silane crosslinkable resin composition may not fully improve. On the contrary, when the content of the metal hydroxide exceeds the above upper limit, the melt viscosity of the silane crosslinkable resin composition increases. The speed may decrease and the productivity of the insulated wire may be deteriorated.

  In addition to the above additives, flame retardants such as melamine flame retardants and silicone flame retardants may be added to the silane crosslinkable resin composition. In addition, the silane crosslinkable resin composition includes inorganic fillers such as calcium carbonate, clay, talc, silica, and carbon, colorants, ultraviolet absorbers, hindered phenol antioxidants, sulfur antioxidants, phosphorus Additives such as lubricants such as system antioxidants, paraffin wax and silicone oil, and acrylic processing aids may be added as appropriate. In particular, an acrylic processing aid may be added to the silane crosslinkable resin composition in order to suppress sticking to the rotor or the like during mixing in a pressure kneader or the like.

  Next, an embodiment of the insulated wire of the present invention using the silane crosslinkable resin composition will be described in detail.

[Insulated wire]
The insulated wire includes a linear conductor, an insulating layer covering the peripheral surface of the conductor, and a sheath layer covering the peripheral surface of the insulating layer.

<Conductor>
The conductor used for the insulated wire is not particularly limited, and for example, a metal wire such as copper, copper alloy, aluminum, and aluminum alloy can be used.

  The cross-sectional shape of the metal wire forming the conductor is not particularly limited, and various shapes such as a circle, a rectangle, and a rectangle can be adopted. Further, the size of the cross section of the metal wire is not particularly limited. When the conductor is a round wire, one having a diameter of 100 μm to 5 mm is generally used, and when the conductor is a flat wire, one having a side length of 500 μm to 5 mm is generally used.

  The conductor can also be formed from a stranded wire obtained by twisting a plurality of metal wires. In this case, multiple types of metal wires may be combined. The number of twists is generally 7 or more.

<Insulating layer>
The insulating layer is coated on the peripheral surface of the conductor so as to cover the conductor. The insulating layer may be a single layer or a multilayer structure of two or more layers.

  The material of the insulating layer is not particularly limited as long as it has insulating properties. For example, the silane crosslinkable resin used in the silane crosslinkable resin composition (at least one of polyethylene and ethylene-polar monomer copolymer) is used. A resin obtained by grafting a silane compound to a resin can be used. When the silane crosslinkable resin is used, the insulating layer can be obtained by extruding the silane crosslinkable resin onto the conductor peripheral surface and crosslinking in an atmosphere with moisture. Further, a resin obtained by mixing a certain amount of a non-silane crosslinkable resin with a silane crosslinkable resin may be used as the material of the insulating layer. By using such a resin for the insulating layer, the manufacturing unit price of the insulated wire can be further reduced.

  Although it does not specifically limit as average thickness of an insulating layer, For example, it is 0.1 mm or more and 10 mm or less.

  The insulating layer may have a primer layer in contact with the conductor. As this primer layer, what hardened | cured crosslinkable resin, such as ethylene which does not contain a metal hydroxide, can be used conveniently. By providing such a primer layer, it is possible to prevent a decrease in peelability between the insulating layer and the conductor with time and prevent a reduction in efficiency of the wiring work.

<Sheath layer>
The sheath layer is coated on the peripheral surface of the insulating layer so as to cover the insulating layer. The sheath layer may be a single layer or a multilayer structure of two or more layers.

  The sheath layer can be obtained by extruding the silane crosslinkable resin composition described above on the peripheral surface of the insulating layer and crosslinking in a moisture atmosphere. A specific method for forming the sheath layer will be described in detail later in a method for manufacturing an insulated wire.

  The silane crosslinkable resin composition forming the sheath layer is preferably a non-silane crosslinkable resin having an MFR of 1 g / min to 10 g / min. As described above, when the MFR of the non-silane crosslinkable resin is within the above range, it is possible to employ the drop extrusion molding as the sheath layer extrusion molding method as described above.

  The MFR of the non-silane crosslinkable resin in the sheath layer can be specified by the following method. First, only the sheath layer is separated from the insulated wire, and this sheath layer is treated in xylene at 120 ° C. At this time, since the non-silane crosslinkable resin is not crosslinked, only the nonsilane crosslinkable resin can be extracted from the sheath layer. By measuring the MFR at a temperature of 190 ° C. and a load of 2.16 kgf in accordance with JIS-K7210 using an extrusion plastometer defined in JIS-K6760 for the non-silane crosslinkable resin thus extracted. The MFR of the non-silane crosslinkable resin blended in the sheath layer can be specified.

  Although it does not specifically limit as average thickness of a sheath layer, For example, they are 0.1 mm or more and 10 mm or less.

  The upper limit of the gel fraction of the sheath layer is preferably 50%, more preferably 55%, and even more preferably 60%. On the other hand, the lower limit of the gel fraction is preferably 80%, more preferably 70%, and even more preferably 65%. When the gel fraction of the sheath layer exceeds the above upper limit, it means that the degree of crosslinking of the sheath layer is high and the ratio of the silane crosslinkable resin is high. Therefore, there is a possibility that the extrusion linear velocity becomes low and the manufacturing cost becomes high. On the other hand, when the gel fraction of the sheath layer is less than the lower limit, the degree of crosslinking becomes too low, and the heat resistance and mechanical strength of the sheath layer may be reduced.

<Insulated wire>
The lower limit of the tensile strength of the insulated wire is preferably 8 MPa, and more preferably 9 MPa. When the tensile strength is less than the above lower limit, the insulated wire may be broken in the wiring work. The tensile strength is a value measured in accordance with the “rubber / plastic insulated wire test method” described in JIS-C3005 for the sheath layer from which the conductor and the insulating layer are removed from the insulated wire.

  The lower limit of the tensile elongation of the insulated wire is preferably 150%, and more preferably 180%. When tensile elongation is less than the said minimum, the flexibility of the said insulated wire may fall and it may be unsuitable for wiring. The tensile elongation is the elongation at the time of cutting an insulated wire measured in accordance with the “rubber / plastic insulated wire test method” described in JIS-C3005 for the sheath layer from which the conductor and the insulating layer are removed from the insulated wire. is there.

  The lower limit of the tensile strength (tensile strength remaining ratio) after heating the insulated wire at 150 ° C. for 168 hours is preferably 70% of the tensile strength at room temperature. When the tensile strength residual ratio is less than the lower limit, the sheath layer of the insulated wire may be broken under a high temperature environment, and may not serve as a protective layer for insulation.

  The lower limit of the tensile elongation (residual tensile elongation) after heating the insulated wire at 150 ° C. for 168 hours is preferably 70% of the tensile elongation at room temperature. On the other hand, the upper limit of the tensile elongation residual ratio is preferably 130% of the tensile elongation at room temperature. If the residual tensile elongation is less than the above lower limit, the flexibility of the sheath layer of the insulated wire may be reduced and broken under a high temperature environment. On the other hand, when the tensile elongation residual ratio exceeds the upper limit, sagging may occur in the insulated wire in a high temperature environment, which may cause defects in the wiring.

<Insulated wire manufacturing method>
The said insulated wire can be manufactured with the manufacturing method which has the following processes, for example.
(1) Conductor manufacturing process for manufacturing a conductor (2) Insulating layer coating process for covering an insulating layer on a conductor peripheral surface (3) Prepare a silane crosslinkable resin, a non-silane crosslinkable resin, and a metal hydroxide. Silane crosslinkable resin composition manufacturing step to be mixed (4) Step of manufacturing silane crosslinkable catalyst master batch (5) Sheath layer extrusion step of extruding silane crosslinkable resin composition on the peripheral surface of the insulating layer (6) Extruded silane Sheath layer crosslinking step for crosslinking a crosslinkable resin composition

<(1) Conductor manufacturing process>
In the conductor manufacturing process, first, copper or the like, which is a raw material for the conductor, is cast and rolled to obtain a rolled material. Next, this rolled material is subjected to wire drawing to form a wire drawing material having an arbitrary cross-sectional shape and wire diameter (short side width). As a method of wire drawing, for example, by using a wire drawing device equipped with a plurality of wire drawing dies, a rolled material coated with a lubricant is inserted into the wire drawing dies, thereby obtaining a desired cross-sectional shape and wire diameter (short side width). ) Can be used. Note that the cross-sectional processing can also be performed separately after softening described later.

  After the wire drawing, the wire drawing material is softened by heating to obtain a conductor metal wire. Since the crystal of the wire drawing material is recrystallized by performing the softening treatment, the toughness of the conductor can be improved. This softening treatment can be performed in an air atmosphere, but is preferably performed in a non-oxidizing atmosphere with a low oxygen content.

  When a stranded wire composed of a plurality of metal wires is used as a conductor, a conductor can be obtained by twisting a plurality of the metal wires.

<(2) Insulating layer coating process>
In the insulating layer coating step, a mixture obtained by mixing the composition forming the insulating layer at a predetermined ratio is put into a melt extruder, and then the outer peripheral surface of the conductor is extruded and coated, and further crosslinked to form the insulating layer. Form. The specific procedure of this extrusion molding can be the same as the sheath layer coating step described later.

<(3) Silane crosslinkable resin composition manufacturing process>
In the silane crosslinkable resin composition production process, a silane crosslinkable resin obtained by grafting a silane compound onto at least one resin (grafting target resin) of polyethylene and ethylene-polar monomer copolymer, polyethylene and ethylene-polar monomer copolymer. A silane crosslinkable resin composition in which a non-silane crosslinkable resin composed of at least one of polymers and a metal hydroxide is mixed is produced. Specifically, a silane crosslinkable resin, a non-silane crosslinkable resin, and a metal hydroxide can be introduced into a mixing device and melt kneaded. Examples of the mixing apparatus include an open roll mixer, a pressure kneader, a Banbury mixer, and a twin screw extruder.

  The silane crosslinkable resin is prepared by adding a silane compound and a radical generator within the above-mentioned number of parts to the resin to be grafted and stirring at room temperature with a super mixer or the like, and then applying a pressure kneader, Banbury mixer, biaxial or single. The silane crosslinkable resin can be produced by a method of kneading while heating to a temperature higher than the melting point of the resin to be grafted by a shaft extruder. After kneading is completed, when a pressure kneader or a Banbury mixer is used, a product extruded into a string shape (strand shape) with a feeder ruder is cooled with water, drained and then cut into pellets. When kneaded with a twin-screw or single-screw extruder, the mixture is originally extruded in a string shape (strand shape), so that it can be formed into a pellet shape by water cooling, draining and cutting. The temperature at the time of kneading can be appropriately determined in consideration of the melting point of the resin and the 10-hour half-life temperature of the radical generator, but is preferably 150 ° C. or higher and 200 ° C. or lower, for example.

<(4) Silane cross-linking catalyst master batch manufacturing process>
Using the same resin as that used for the silane crosslinkable resin composition, a silane crosslinking catalyst is added within the range of 0.1 to 10 parts, and the mixture is stirred at room temperature with a super mixer or the like. A silane cross-linking catalyst master batch can be produced by a method of kneading with a mixer, a twin screw or a single screw extruder while heating to a temperature higher than the melting point of the resin. After kneading is completed, when a pressure kneader or a Banbury mixer is used, a product extruded into a string shape (strand shape) with a feeder ruder is cooled with water, drained and then cut into pellets. When kneaded with a twin-screw or single-screw extruder, the mixture is originally extruded in a string shape (strand shape), so that it can be formed into a pellet shape by water cooling, draining and cutting.

<(5) Sheath layer extrusion process>
In the sheath layer extrusion step, the silane crosslinkable resin composition and the silane crosslinking catalyst master batch are put into a melt extruder, and are extruded and coated on the peripheral surface of the insulating layer.

  Examples of the extrusion molding method include solid extrusion molding and pull-down extrusion molding, and pull-down extrusion molding is preferable. Here, in the case of solid extrusion molding, as shown in FIG. 1A, a die 20 and a point where the insulating layer 10 of the insulated wire 1 and the molten sheath layer 11 (silane-crosslinkable resin composition) are in the mold 2 are provided. Since the contact is made in a pressurized state at the portion between the two layers 21, the adhesion strength (peeling strength) between the sheath layer 11 and the insulating layer 10 may be excessively increased. On the other hand, in the case of drop extrusion molding, as shown in FIG. 1B, the insulating layer 30 and the sheath layer 31 come into contact with each other outside the mold 4 after exiting the die 40 and the point 41. As described above, in the drop extrusion molding, the insulating layer 30 of the insulated wire 3 and the molten sheath layer 31 (silane-crosslinkable resin composition) do not come into contact with each other in the pressed mold 4. The adhesion strength (peeling strength) between the sheath layer 31 and the sheath layer 31 does not increase excessively, and the sheath layer 31 can be easily peeled later in the insulated wire 3. Therefore, if the sheath layer 31 can be formed by drop extrusion molding, the sheath layer 31 can be easily peeled off when the connector is connected to the end of the insulated wire 3, so that workability such as connector connection can be improved. .

  The sheath layer is formed from the silane crosslinkable resin composition, and the silane crosslinkable resin composition preferably contains a non-silane crosslinkable resin having an MFR of 1 g / min to 10 g / min. used. By containing such a non-silane crosslinkable resin having a moderately large MFR, the viscosity at the time of melting of the silane crosslinkable resin composition can be lowered. Therefore, the melt elongation when extruding the sheath layer of the insulated wire from the silane crosslinkable resin composition can be increased moderately, and as a result, pulling extrusion rather than full extrusion is preferable as the extrusion method of the sheath layer. Can be adopted. Thereby, the insulated wire in which the sheath layer can be easily peeled off can be provided.

  As extrusion temperature of a silane crosslinkable resin composition, it can be 160 degreeC or more and 210 degrees C or less, for example. When it is 160 ° C. or lower, the extrusion torque is not sufficiently lowered, the linear velocity is lowered, and the productivity is deteriorated. On the other hand, when the temperature is 200 ° C. or higher, crosslinking proceeds in the extruder and the appearance may be deteriorated.

  The lower limit of the extrusion linear velocity of the silane crosslinkable resin composition is preferably 105 m / min, and more preferably 180 m / min. On the other hand, the upper limit of the extrusion linear velocity is preferably 300 m / min. When extrusion line speed is less than the said minimum, there exists a possibility that productivity of the said insulated wire may fall. On the other hand, when the extrusion linear velocity exceeds the above upper limit, the load becomes excessive and damage such as cracks may occur on the surface of the sheath layer.

  In addition, it is good to dry with a thermostat etc. before throwing a silane crosslinkable resin composition into an extruder. By extruding after reducing the moisture content of the silane crosslinkable resin composition by drying, it is possible to prevent crosslinking during extrusion and to improve the appearance of the sheath layer.

<(6) Sheath layer cross-linking step>
In the sheath layer crosslinking step, the crosslinkable resin composition coated on the peripheral surface of the insulating layer is crosslinked. Specifically, the silane crosslinkable resin composition can be cured by silane crosslinking by supplying moisture by exposure to air, immersion in water, exposure to water vapor atmosphere, or the like. By this curing, the sheath layer of the insulated wire is completed.

  Since the insulated wire has excellent properties such as flame retardancy, it can be suitably used for outdoor wiring. Further, since the unit price of the insulated wire is low, for example, as a cable (PV cable) used in a DC power circuit of a solar cell power generation facility, connection between modules, connection between a module and a connection box, connection between a connection box and a power conditioner It can be used for the connection between. As such PV cable, the said insulated wire can also be used alone, and can also be used as a wire harness which combined the some insulated wire.

  Hereinafter, although an insulated wire of the present invention is explained still more concretely by an example, the present invention is not limited to the following manufacture examples.

[Production Example 1]
(Manufacture of silane crosslinkable resin)
A very low density polyethylene (VLDPE) having a density of 0.87 g / cm ³ as a resin to be grafted, a silane compound, and a radical generator were charged into a super mixer, and the rotor was rotated at 60 rpm at room temperature and stirred. Then, the mixture was put into a pressure kneader having a mixing capacity of 3 L, the rotor was rotated at 30 rpm, melt kneaded at a starting temperature of 100 ° C. and a kneading temperature of 200 ° C., and discharged. This was put into a feeder ruder having a set temperature of 140 ° C. and extruded into a strand to be cooled with water and cut into a pellet shape. The content of the silane compound with respect to 100 parts by mass of the ultra-low density polyethylene was 1 part by mass, and the content of the radical generator was 0.1 parts by mass.

(Manufacture of silane crosslinkable resin composition)
Mixing capacity of the above silane crosslinkable resin, ethylene ethyl acrylate copolymer (EEA3) with MFR of 5 g / min as non-silane crosslinkable resin, magnesium hydroxide as metal oxide (flame retardant), antioxidant and lubricant The mixture was put into a 3 L pressure kneader, melt-kneaded at a starting temperature of 100 ° C. and a kneading temperature of 160 ° C., and discharged. This was put into a feeder ruder having a set temperature of 140 ° C. and extruded into a strand shape, which was then cooled by water and cut into a pellet shape to produce a silane crosslinkable resin composition.

(Manufacture of insulated wires)
The silane crosslinkable resin composition and catalyst master batch (kneaded silane crosslinking catalyst in ultra-low density polyethylene) are charged into a melt extruder (screw diameter: 120 mmφ, L / D = 24) and 150 ° C. to 190 ° C. Then, the sheath layer was drawn and extruded on the peripheral surface of the insulating layer. The extrusion linear velocity was 200 m / min. This extrusion drawing speed is the maximum drawing speed at which a sheath layer having a smooth appearance with no defects such as irregularities on the surface can be formed by extrusion using the resin composition having the above blending ratio.

The extruded sheath layer was immersed in warm water at 60 ° C. for 12 hours to perform silane crosslinking, whereby an insulated wire of Production Example 1 was obtained. As the conductor, a conductor having a nominal cross-sectional area of 5.0 cm ^{2 obtained by} twisting 65 copper wires having a diameter of 0.32 mm was used. Moreover, the insulating layer was extrusion-molded on the same conditions as a sheath layer using the composition containing the ultra-low density polyethylene similar to a sheath layer, a silane compound, a radical generator, and a silane crosslinking catalyst.

  In the silane crosslinkable resin composition, the formulation was adjusted so that the mass mixing ratio of the silane crosslinkable resin and the non-silane crosslinkable resin was 20:80. Furthermore, with respect to a total of 100 parts by mass of the silane crosslinkable resin and the non-silane crosslinkable resin, the magnesium hydroxide content is 160 parts by mass, the silane crosslinking catalyst is 0.1 parts by mass, and the antioxidant content is 2 parts by mass. Part and lubricant content were adjusted to be 1 part by mass.

  Vinylsilane (“KBM-1003” from Shin-Etsu Chemical Co., Ltd.) as the silane compound, dicumyl peroxide (“Parkmill D” from NOF Corporation) as the radical generator, and dioctyltin (Nitto Kasei) as the silane crosslinking catalyst "Neostan U-810"), hindered phenol ("Irganox 1010" from BASF) and paraffin wax ("High Wax 420P" from Mitsui Chemicals) as the lubricant were used.

[Production Example 2]
As the non-silane crosslinkable resin, a very low density polyethylene (VLDPE) having an MFR of 5 g / min and a density of 0.87 g / cm ³ is used. And an insulated wire of Production Example 2 was produced by pull-out extrusion molding under the same conditions as in Production Example 1.

[Production Example 3]
An ethylene vinyl acetate copolymer (EVA) with an MFR of 2.5 g / min is used as a non-silane crosslinkable resin, and other materials and blends are prepared in the same manner as in Production Example 1 to prepare a silane crosslinkable resin composition. The insulated wire of Production Example 3 was produced by drop extrusion molding under the same conditions as in Example 1.

[Production Example 4 and Production Example 5]
Using the same material as in Production Example 1, insulated wires of Production Example 4 and Production Example 5 were produced. However, the formulation was adjusted such that the mass mixing ratio of the silane crosslinkable resin and the non-silane crosslinkable resin was 40:60 in Production Example 4 and 60:40 in Production Example 5. The content of other compounding agents (metal hydroxide, etc.) was the same as in Production Example 1.

[Production Example 6]
An ethylene ethyl acrylate copolymer (EEA2) having an MFR of 1.5 g / min as a non-silane crosslinkable resin was used, and other materials and blends were prepared in the same manner as in Production Example 1 to prepare a silane crosslinkable resin composition. The insulated wire of Production Example 6 was produced by drop extrusion molding under the same conditions as in Production Example 1.

[Production Example 7]
An insulated wire of Production Example 7 was produced in the same manner as Production Example 1 except that solid extrusion molding was employed instead of the drop extrusion molding.

  The solid extrusion molding was performed under the conditions of the drop extrusion molding of Production Example 1.

[Production Example 8]
An ethylene ethyl acrylate copolymer (EEA1) having an MFR of 0.8 g / min as a non-silane crosslinkable resin was used, and other materials and blends were prepared in the same manner as in Production Example 1 to prepare a silane crosslinkable resin composition. The insulated wire of Production Example 8 was produced by solid extrusion molding under the same conditions as in Production Example 7. In addition, although manufacture of the insulated wire was tried by pull-down extrusion molding, the sheath layer could not be formed.

[Production Example 9]
Using an ethylene ethyl acrylate copolymer (EEA4) having an MFR of 20 g / min as a non-silane crosslinkable resin, other materials and blends were prepared in the same manner as in Production Example 1 to prepare a silane crosslinkable resin composition. The insulated wire of Production Example 9 was produced by drop extrusion molding under the same conditions as in Example 1.

[Production Example 10]
Using the same material as in Production Example 1, the insulated wire of Production Example 10 was produced by adjusting the formulation so that the mass mixing ratio of the silane crosslinkable resin and the non-silane crosslinkable resin was 70:30. The content of other compounding agents (metal hydroxide, etc.) was the same as in Production Example 1.

[Production Example 11]
While the non-silane crosslinkable resin is not used, the same silane crosslinkable resin as in Production Example 1 is used, and other materials and blends are prepared in the same manner as in Production Example 1 to prepare a silane crosslinkable resin composition. Similarly, the insulated wire of Production Example 11 was produced.

[Production Example 12]
While not using a silane crosslinkable resin, an ethylene vinyl acetate copolymer not grafted with a silane compound as a non-silane crosslinkable resin was used, and other materials and blends were made in the same manner as in Production Example 1 to obtain a resin composition. The insulated wire of Production Example 12 was produced by pulling extrusion molding under the same conditions as in Production Example 1.

[Production Example 13]
While not using a non-silane crosslinkable resin, a silane-crosslinked ethylene vinyl acetate copolymer (EVA) grafted with a silane compound is used as the silane crosslinkable resin. An insulated wire of Production Example 13 was produced by pull-down extrusion molding under the same conditions as in Production Example 1.

  In Table 1, “-” means that the corresponding component was not used.

<Evaluation>
For the insulated wires of Production Examples 1 to 13, the sheath peeling force, gel fraction, tensile strength, tensile elongation, tensile strength residual rate, tensile elongation residual rate, maximum extrusion linear velocity, flame retardancy, and low-temperature flexibility are as follows: The method was evaluated. These evaluation results are shown in Table 2.

[Gel fraction (unit:%)]
10 parts by mass of a sheath layer of an insulated wire is immersed in 100 parts by mass of a solvent (component: xylene), heated and dissolved at 120 ° C. for 24 hours, and then filtered to evaporate the filtrate to dryness. The gel fraction was calculated by the following formula (1) using the mass W2 of the sheath layer before being immersed in the solvent.
Gel fraction = W1 / W2 × 100 (%) (1)

[Sheath peeling force (unit: N / 20 mm)]
As shown in FIG. 2A, an insulating wire 5 having a predetermined length in which the insulating layer 50 and the sheath layer 51 are peeled up to a portion 20 mm from the end to expose the conductor 52 is prepared. At the same time, an iron plate 6 is prepared in which a through hole 60 having a diameter larger than the outer diameter of the insulating layer 50 and smaller than the inner diameter of the sheath layer 51 is formed. As shown in FIG. 2B, the exposed conductor 52 in the insulated wire 5 is inserted into the through hole 60 of the iron plate 6. With the iron plate 6 fixed, the conductor 52 was pulled upward in the figure, the load when the sheath layer 51 was peeled off was measured, and this was used as the sheath peeling force.

[Tensile strength (unit: MPa)]
In accordance with “Rubber / Plastic Insulated Wire Test Method” described in JIS-C3005 (2000), the test piece of the sheath layer from which the conductor and the insulating layer were removed from the insulated wire was pulled at a tensile speed of 200 m / min. The maximum tensile load was measured and the tensile strength was calculated.

[Tensile elongation (unit:%)]
In accordance with “Rubber / Plastic Insulated Wire Test Method” described in JIS-C3005 (2000), the test piece of the sheath layer from which the conductor and the insulating layer were removed from the insulated wire was pulled at a tensile speed of 200 m / min. Then, the breaking length was measured, and the tensile elongation was calculated.

[Remaining tensile strength (unit:%)]
After the insulated wire is heated to 150 ° C. for 168 hours, the test piece of the sheath layer is obtained by removing the conductor and the insulating layer from the insulated wire in accordance with “Testing method for rubber / plastic insulated wire” described in JIS-C3005 (2000). Was pulled at a tensile speed of 200 m / min with a tensile tester, the maximum tensile load was measured, the tensile strength was calculated, and the ratio to the tensile strength at normal temperature was determined.

[Remaining tensile elongation (unit:%)]
After the insulated wire is heated to 150 ° C. for 168 hours, the test piece of the sheath layer is obtained by removing the conductor and the insulating layer from the insulated wire in accordance with “Testing method for rubber / plastic insulated wire” described in JIS-C3005 (2000). Was pulled at a tensile speed of 200 m / min with a tensile tester, the breaking length was measured, the tensile elongation was calculated, and the ratio to the tensile elongation at normal temperature was determined.

[Maximum extrusion linear velocity (unit: m / min)]
In the extrusion molding of the sheath layer, extrusion was performed at the maximum extrusion linear velocity at which a sheath layer having a smooth appearance without defects such as irregularities on the surface could be extruded. In Production Example 13, even when the linear velocity was minimized (3 m / min), a smooth sheath layer having no defects such as irregularities could not be formed on the surface.

[Flame retardance (vertical single-flammability)]
In accordance with EN60332-1-2 (IEC 603322-1 / JIS-C3665-1), the insulated wire is held vertically, the burner is placed at an angle of 45 degrees with respect to the insulated wire, and the flame of the burner is exposed to the surface of the insulated wire. The carbonization state of the insulated wire after a specified test time was observed. The case where the distance between the lower end of the upper support and the carbonization start point was 50 mm or more was designated as A (pass), and the case where the distance was less than 50 mm was designated as B (fail). Moreover, it was set as B (failure) also when combustion expanded below 540 mm from the lower end of the upper support material.

[Low temperature flexibility]
In accordance with EN60881-1-4, after being held for 16 hours in an environment of −40 ± 2 ° C., the cracks after being wound around the mandrel with the specified diameter at a rotation speed of 1/5 turns at the specified number of times. The presence or absence was examined. The case where there was no crack on the surface of the insulated wire was designated as A (pass), and the case where there was a crack was designated as B (fail).

  As shown from the results in Table 2, the insulated wires of Production Examples 1 to 9 are excellent in mechanical strength, heat resistance and flame retardancy while using a low-cost non-silane crosslinkable resin for the sheath layer, and even better. Excellent moldability. Among these Production Examples 1 to 9, the insulated wires of Production Examples 1 to 6 obtained an appropriate sheath peeling force (about 10 N / 20 mm or more and about 30 N / 20 mm or less) by pulling extrusion molding. This is considered that MFR of the non-silane crosslinkable resin contained in the silane crosslinkable resin composition for forming the sheath layer of the insulated wire of the manufacture examples 1-6 has influenced. That is, by setting the MFR of the non-silane crosslinkable resin within a predetermined range (1 g / min or more and about 10 g / min or less), it is considered that a sheath layer suitable for pull-out extrusion molding and having an appropriate peeling force can be obtained. It is done.

  As described above, the insulated wire using the silane crosslinkable resin composition of the present invention can promote the reduction of the manufacturing cost while maintaining various properties such as flame retardancy. Therefore, the said insulated wire can be used suitably as a cable (PV cable) used with the DC electric circuit of solar cell power generation equipment, for example.

DESCRIPTION OF SYMBOLS 1,3 Insulated electric wire 10,30 Insulating layer 11,31 Sheath layer 2,4 Die 20,40 Dice 21,41 Point 6 Iron plate 60 Through hole 5 Insulated electric wire 50 Insulating layer 51 Sheath layer 52 Conductor

Claims (6)

An insulated wire comprising a conductor, an insulating layer, and a sheath layer coated on the peripheral surface side of the insulating layer,
The silane crosslinkable resin composition forming the sheath layer is
A silane crosslinkable resin obtained by grafting at least one of polyethylene and ethylene-polar monomer copolymer with a silane compound;
A non-silane crosslinkable resin comprising at least one of polyethylene and ethylene-polar monomer copolymer;
Containing metal hydroxide,
The content of the non-silane crosslinkable resin with respect to a total of 100 parts by mass of the silane crosslinkable resin and the nonsilane crosslinkable resin is 40 parts by mass or more and 90 parts by mass or less,
The non-silane crosslinkable resin has a melt flow rate of 1 g / 10 min to 10 g / 10 min,
An insulated wire in which a sheath peeling force between the insulating layer and the sheath layer is more than 0 N / 20 mm and not more than 30 N / 20 mm.   The insulated wire according to claim 1, wherein a gel fraction of the sheath layer is 50% or more and 80% or less. A silane crosslinkable resin composition for pulling and extruding a sheath layer of an insulated wire,
A silane crosslinkable resin obtained by grafting at least one of polyethylene and ethylene-polar monomer copolymer with a silane compound;
A non-silane crosslinkable resin comprising at least one of polyethylene and ethylene-polar monomer copolymer;
Containing metal hydroxide,
The content of the non-silane crosslinkable resin with respect to a total of 100 parts by mass of the silane crosslinkable resin and the nonsilane crosslinkable resin is 40 parts by mass or more and 90 parts by mass or less,
The non-silane crosslinkable resin has a melt flow rate of 1 g / 10 min to 10 g / 10 min,
The silane crosslinkable resin composition whose content of the metal hydroxide is 100 parts by mass or more and 250 parts by mass or less with respect to a total of 100 parts by mass of the silane crosslinkable resin and the non-silane crosslinkable resin.   The silane crosslinkable resin composition according to claim 3, wherein the silane crosslinkable resin is an ultra-low density polyethylene grafted with a silane compound.   The silane cross-linking according to claim 3 or 4, wherein the non-silane cross-linking resin is at least one selected from the group consisting of ultra-low density polyethylene, ethylene vinyl acetate copolymer, and ethylene ethyl acrylate copolymer. Resin composition. A step of preparing a silane crosslinkable resin , a non-silane crosslinkable resin having a melt flow rate of 1 g / 10 min or more and 10 g / 10 min or less, and a metal hydroxide, and mixing them to obtain a silane crosslinkable resin composition When,
A step of extruding the silane crosslinkable resin composition by pull-down extrusion molding on the peripheral surface side of a linear body having a conductor and an insulating layer covering the peripheral surface;
And a step of crosslinking the extruded silane crosslinkable resin composition.

Images