Insulated wire, wiring harness, and method for manufacturing insulated wire

Abstract

To provide an insulated wire having an insulation coating which is composed of a material containing a silicone resin and has high oil resistance, a wire harness including the insulated wire, and a method for manufacturing the insulated wire.SOLUTION: An insulated wire 1 has a wire conductor 2 and an insulation coating 3 which is composed of a crosslinked polymer material and coats the outer periphery of the wire conductor 2, wherein the crosslinked polymer material contains a metal ion and a silicone resin including a substituent capable of forming an ion bond with the metal ion at a side chain, and the silicone resin constitutes a crosslinked body by an ion bond between the substituent and the metal ion. The insulated wire 1 is manufactured by arranging a crosslinkable polymer composition containing a metal compound where the metal ion is isolated by heat and the silicone resin on the outer periphery of the wire conductor 2, forming the crosslinked body from the crosslinkable polymer composition by heating, and preparing the insulation coating 3 composed of the crosslinked polymer material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an insulated wire, a wire harness, and a method for manufacturing an insulated wire. [Background technology]

[0002] In insulated wires, silicone resins are sometimes used as insulating coatings that cover the wire conductors. Silicone resins are often used by cross-linking polymer chains, which gives them excellent properties such as heat resistance and flexibility. For example, Patent Document 1 listed below discloses an insulated wire with excellent properties such as heat resistance, which has an insulating coating made of a material containing cross-linked silicone resin. Here, the cross-linking of the silicone resin is formed using a cross-linking agent such as an organic peroxide. High heat resistance in the insulating coating is important, particularly for insulated wires that are placed in environments prone to high temperatures, such as the interior of an automobile. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-65777 [Patent Document 2] International Publication No. 2011 / 074620 [Patent Document 3] Japanese Patent Application Publication No. 6-41436 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-256253 [Patent Document 5] Japanese Patent Application Publication No. 7-11139 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, by forming an insulating coating from a material containing a cross-linked silicone resin, it is possible to achieve the desired properties of insulated wires for automobiles and other uses, such as heat resistance and flexibility. However, conventional silicone resins cross-linked with organic compounds such as organic peroxides do not have very high oil resistance and are prone to swelling when in contact with oils such as oil and gasoline. For insulated wires used in locations where contact with oils such as oil and gasoline is expected, such as inside automobiles, high oil resistance is desirable, along with heat resistance.

[0005] In view of the above, an object of the present invention is to provide an insulated wire that is made of a material containing a silicone resin and has an insulating coating that has high oil resistance, a wire harness that includes such an insulated wire, and a method for manufacturing such an insulated wire. [Means for solving the problem]

[0006] The insulated wire according to the present disclosure includes a wire conductor and an insulating coating made of a cross-linked polymer material that covers the outer periphery of the wire conductor. The cross-linked polymer material includes a metal ion and a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with the metal ion. The silicone resin forms a cross-linked body through the ionic bond between the substituent and the metal ion.

[0007] A wire harness according to the present disclosure includes the insulated wire.

[0008] The method for producing an insulated wire according to the present disclosure includes placing a crosslinkable polymer composition containing the silicone resin and a metal compound that liberates metal ions when heated around the outer periphery of the wire conductor, and then heating the crosslinkable polymer composition to form the crosslinked body, thereby producing the insulating coating made of the crosslinked polymer material, and producing the insulated wire. [Effects of the Invention]

[0009] The insulated wire, wire harness, and method for manufacturing an insulated wire according to the present disclosure provide an insulated wire made of a material containing a silicone resin and having an insulating coating with high oil resistance, a wire harness including such an insulated wire, and a method for manufacturing such an insulated wire. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing the structure of an insulated wire according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a side view showing a structure of a wire harness according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] The insulated wire according to the present disclosure includes a wire conductor and an insulating coating made of a cross-linked polymer material that covers the outer periphery of the wire conductor. The cross-linked polymer material includes a metal ion and a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with the metal ion. The silicone resin forms a cross-linked body through the ionic bond between the substituent and the metal ion.

[0013] In the insulated wire according to the present disclosure, the insulating coating is made of a crosslinked polymer material including a crosslinked silicone resin. In conventional crosslinked silicone resins, the polymer chains of the silicone resin are crosslinked by a crosslinking agent composed of an organic substance such as an organic peroxide, resulting in high affinity with oil and easy absorption of oil components into the network of the crosslinked silicone resin. In contrast, in the insulated wire according to the present embodiment, the silicone resin constituting the insulating coating contains substituents in its side chains capable of forming ionic bonds with metal ions, and the silicone resin is crosslinked by ionic bonds between the substituents and the metal ions. Therefore, the crosslinked sites have inorganic properties and low affinity with oil. As a result, oil components are less likely to be absorbed into the network of the crosslinked silicone resin, resulting in high oil resistance of the insulating coating. The insulating coating made of this crosslinked polymer material can be easily produced by extruding or otherwise disposing a composition containing a silicone resin and a metal compound that liberates metal ions upon heating around the outer periphery of a wire conductor, and then heating the composition to liberate the metal ions, forming ionic bonds with the substituents of the silicone resin to form a crosslinked silicone resin.

[0014] Here, the crosslinked polymer material preferably contains polar fine particles in addition to the crosslinked product. By adding polar fine particles to a non-crosslinked silicone resin, the fine particles function as a molding aid. As a result, even if the non-crosslinked silicone resin has a low viscosity, adding the fine particles increases the viscosity or imparts thixotropy, making it easier to arrange the silicone resin around the outer periphery of the electric wire conductor by extrusion molding or the like.

[0015] In this case, the fine particles preferably contain at least one of silica, metal oxide, clay mineral, cellulose, fluororesin, and carbon, which exhibit high functionality as a molding aid.

[0016] In particular, the fine particles are preferably fumed silica fine particles, which are highly effective in improving the viscosity of compositions containing silicone resins as molding aids.

[0017] The average particle size of the fine particles is preferably 5 nm or more and 100 nm or less, which makes it easier for the fine particles to give the silicone resin-containing composition a viscosity suitable for molding around the outer periphery of the electric wire conductor by extrusion molding or the like.

[0018] The crosslinked polymer material preferably contains 1 part by mass or more and 100 parts by mass or less of the microparticles per 100 parts by mass of the silicone resin, so that the microparticles are highly effective in improving the viscosity of the composition, and the crosslinked polymer material obtained by crosslinking the silicone resin is less likely to have an effect on the material properties due to the inclusion of a large amount of microparticles.

[0019] The silicone resin preferably has a flow-start temperature of 150° C. or less. This allows the silicone resin to be kneaded with a metal compound or the like that serves as a metal ion source and then extruded or otherwise processed to be in a state that allows it to be disposed on the outer periphery of the electric wire conductor, without having to be heated to a high temperature.

[0020] The substituents contained in the silicone resin are preferably anionic groups derived from at least one of a carboxylic acid group, an acid anhydride group, and a phosphate group. These substituents readily form ionic bonds with metal ions. Furthermore, because the substituents are acidic groups with relatively low polarity, they are less likely to cause phase separation in the main chain or side chain of the silicone resin, allowing for the formation of a highly spatially uniform crosslinked structure.

[0021] In the silicone resin, the substituent may be bonded to the main chain via an alkyl or alkylene group having one or more carbon atoms, which reduces the influence of the main chain on the formation of the crosslinked product and makes it easier to form a sufficient and uniform crosslinked structure.

[0022] The silicone resin preferably does not contain a moiety capable of forming an ionic bond with a metal ion in the main chain, which prevents the side chain substituents from being prevented from forming an ionic bond with the metal ion due to competition with the moiety capable of forming an ionic bond in the main chain. The substituents in the main chain are unlikely to form a stable crosslinked structure with the metal ion.

[0023] The main chain of the silicone resin is preferably an organopolysiloxane chain, which makes it less likely that the main chain will affect the crosslinking in the side chains of the silicone resin.

[0024] The metal ions can form a metal complex with a β-diketonato ligand or an alkoxide ligand in a state in which they can be released as metal ions by heat. β-diketonato ligands and alkoxide ligands are effective in stabilizing metal ions. Therefore, before the silicone resin is crosslinked, the metal complex can be stably maintained in a state in which the metal ions are not released, thereby preventing unintended crosslinking.

[0025] In this case, it is preferable that the metal ions can be liberated as metal ions from the metal complex by heating at 50°C or higher and 300°C or lower. In this way, in a composition containing a silicone resin and a metal complex, before the silicone resin is crosslinked, the metal complex can be stably maintained in a state in which no metal ions are liberated, and the progress of unintended crosslinking can be suppressed. On the other hand, when intentionally crosslinking the silicone resin, the metal ions can be liberated and the silicone resin can be crosslinked without heating to such a high temperature.

[0026] The metal ion is preferably at least one of alkaline earth metal, aluminum, zinc, titanium, and zirconium ions, all of which readily form stable crosslinked structures between polymer chains of silicone resins and are therefore suitable as metals for forming crosslinked bodies.

[0027] The metal ions are preferably at least one of aluminum and zirconium ions. These metal ions tend to form particularly stable crosslinked structures with the substituents of the silicone resin. Furthermore, at relatively low temperatures before crosslinking, they tend to be stably maintained in the form of metal compounds that are not liberated as metal ions.

[0028] The crosslinked polymer material preferably contains 0.03 to 10 parts by mass of the metal ions per 100 parts by mass of the silicone resin. This allows for a sufficient amount of metal ions to be contained, resulting in a high crosslink density and enhanced heat resistance and other improvements in properties due to the crosslinking of the silicone resin. Meanwhile, the effects of containing a large amount of metal components in the material before and after crosslinking can be easily avoided.

[0029] The crosslinked polymer material preferably does not contain, except for unavoidable components, any component in which the silicone resin is crosslinked without an ionic bond between the substituent and the metal ion, thereby significantly improving the oil resistance of the crosslinked polymer material by forming crosslinks between polymer chains of the silicone resin through ionic bonds with the metal ions.

[0030] A wire harness according to the present disclosure includes the insulated wire. The insulating coating of the insulated wire constituting the wire harness is made of a crosslinked polymer material including a crosslinked product formed by ionic bonding between a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with a metal ion and the silicone resin being crosslinked by the ionic bond between the substituent and the metal ion. Therefore, the wire harness can utilize the high oil resistance as a characteristic of the wire harness.

[0031] In a method for producing an insulated wire according to the present disclosure, a crosslinkable polymer composition containing a silicone resin and a metal compound that liberates metal ions upon heating is applied to the outer periphery of the wire conductor, and then the crosslinkable polymer composition is heated to form the crosslinked body, thereby producing the insulating coating made of the crosslinked polymer material, thereby producing the insulated wire. In this method, a silicone resin having a side chain with a substituent capable of forming an ionic bond with a metal ion is crosslinked via an ionic bond with the metal ion, so that the crosslinked site has inorganic properties and does not exhibit high affinity for oil, thereby forming an insulating coating with high oil resistance. Furthermore, in this method, the metal ions for crosslinking are supplied by being liberated from the metal compound upon heating, so that the series of steps of preparing the uncrosslinkable polymer composition, applying the crosslinkable polymer composition to the outer periphery of the wire conductor, and forming the crosslinked body can be easily performed.

[0032] [Details of the embodiments of the present disclosure] An insulated wire, a wire harness, and a method for manufacturing an insulated wire according to embodiments of the present disclosure will be described below with reference to the drawings. However, the present disclosure is not limited to these embodiments.

[0033] <Outline of insulated wires and wire harnesses> 1 shows the structure of an insulated wire 1 according to one embodiment of the present disclosure. The insulated wire 1 includes a conductor 2 and an insulating coating 3 that covers the outer periphery of the conductor 2. The insulating coating 3 is made of a cross-linked polymer material, which will be described later.

[0034] The conductor diameter and material of the wire conductor 2 of the insulated wire 1 are not particularly limited and can be appropriately selected depending on the application of the insulated wire 1. Examples of materials that can be used to form the wire conductor 2 include metal materials such as copper, copper alloys, aluminum, and aluminum alloys. The wire conductor 2 may be made of a single wire, but is preferably made of a stranded wire in which multiple wires are twisted together in order to ensure flexibility.

[0035] The wire harness according to the embodiment of the present disclosure is not particularly limited in its specific configuration as long as it includes the insulated wire 1 according to the embodiment of the present disclosure. FIG. 2 shows the structure of an example wire harness 5. As shown in FIG. 2, the wire harness 5 has a connector 52 including a connection terminal (not shown) provided at the end of an insulated wire 51. In the wire harness 5, a plurality of insulated wires 51 may be bundled together, and in this case, a tape 53 may be used as an exterior material for bundling the insulated wires 51. At least one, and preferably all, of the insulated wires 51 constituting the wire harness 5 are formed from the insulated wire 1 according to the embodiment of the present disclosure.

[0036] The insulated wire 1 and the wiring harness 5 according to the embodiments of the present disclosure are not particularly limited in their applications, but are preferably used inside an automobile. As will be described later, the cross-linked polymer material constituting the insulating coating 3 of the insulated wire 1 according to the present embodiment contains a cross-linked product in which silicone resin is cross-linked with metal ions, and has excellent heat resistance, flexibility, and oil resistance. Many parts inside an automobile become hot, and contact with gasoline and oil is also expected. By placing the insulated wire 1 and the wiring harness 5 according to the present embodiment in such an environment, the properties of the cross-linked polymer material constituting the insulating coating 3 can be effectively utilized.

[0037] <Insulating coating materials> Next, the crosslinked polymer material constituting the insulating coating 3 of the insulated wire 1 according to the embodiment of the present disclosure will be described. The crosslinked polymer material constituting the insulating coating 3 includes a silicone resin and a metal ion. The silicone resin includes a substituent in its side chain that can form an ionic bond with the metal ion. In this crosslinked polymer material, an ionic bond is formed between the substituent in the side chain of the silicone resin and the metal ion, and the silicone resin is crosslinked by this ionic bond to form a crosslinked body. In other words, the polymer chains of the silicone resin are crosslinked via the metal ion. Note that, in this specification, the term "metal ion" refers not only to a free metal ion but also to a state in which a metal ion forms an ionic bond with a negatively charged structure. In addition to the crosslinked body composed of the silicone resin and the metal ion, the crosslinked polymer material may appropriately include additive components such as polar fine particles, which will be described later.

[0038] In this embodiment, the crosslinked polymer material constituting the insulating coating 3 is formed by crosslinking silicone resin to form a three-dimensional network structure. Therefore, similar to conventional crosslinked silicone resins, it has excellent properties such as heat resistance and flexibility. In this crosslinked polymer material, the crosslinked structure is formed via ionic bonds rather than covalent bonds. However, the bonding strength of the ionic bonds is sufficient to improve the heat resistance and mechanical toughness of the crosslinked body and also impart high flexibility. Meanwhile, the crosslinked polymer material exhibits high oil resistance, unlike conventional crosslinked silicone resins, because the crosslinked structure in the silicone resin is formed by ionic bonds mediated by metal ions. In conventional crosslinked silicone resins, in which the polymer chains of the silicone resin are crosslinked using a crosslinking agent made of an organic compound such as an organic peroxide, the highly organic nature of the crosslinked sites increases their affinity for oils, such as gasoline and oil, which are also organic substances. Prolonged contact with these substances easily traps oil molecules in the crosslinked network structure. In contrast, the crosslinked sites of the present crosslinked polymer material are composed of ionic bonds containing metal ions, and have a strong inorganic nature, which reduces the affinity for oils such as gasoline and oil, making it difficult for oil components to be trapped in the network structure. As a result, the present crosslinked polymer material exhibits high oil resistance.

[0039] In order to ensure sufficient oil resistance, the crosslinked polymer material preferably has an oil-resistant volumetric expansion coefficient of 60% or less, more preferably 40% or less, or even 20% or less. Furthermore, the fuel-resistant volumetric expansion coefficient is preferably 40% or less, even more preferably 20% or less. Here, the oil-resistant volumetric expansion coefficient and the fuel-resistant volumetric expansion coefficient are evaluated by a fluid resistance test in accordance with JIS K 6258. The oil-resistant volumetric expansion coefficient is evaluated by immersing the material in ATF oil (automatic transmission oil) at 150°C for 72 hours, and the fuel-resistant volumetric expansion coefficient is evaluated by immersing the material in isooctane for 24 hours. While there are no specific lower limits for the oil-resistant volumetric expansion coefficient and the fuel-resistant volumetric expansion coefficient, practically obtainable crosslinked polymer materials generally have a volumetric expansion coefficient of 1% or more.

[0040] The physical properties of the crosslinked polymer material are not particularly specified, and can be appropriately set depending on the application of the insulated wire by selecting the type and content of the silicone resin, metal ions, and other additives used. For example, from the viewpoint of ensuring sufficient mechanical strength as an insulating coating, the crosslinked polymer material should have a durometer A hardness of 10 or more, or even 20 or more, and a tensile modulus of 0.1 MPa or more, or even 0.5 MPa or more. On the other hand, from the viewpoint of ensuring sufficiently high flexibility as an insulated wire, the crosslinked polymer material should have a durometer A hardness of 90 or less, or even 80 or less, and a tensile modulus of 50 MPa or less, or even 15 MPa or less.

[0041] Generally, ionic bonds are reversible, and when this crosslinked polymer material in which a crosslinked structure is formed via ionic bonds is heated to a high temperature, the ionic bond points delocalize, causing the crosslinked polymer material to soften or flow, potentially making it impossible to maintain the desired physical properties and shape of the insulating coating 3. To avoid this situation and improve the heat resistance of the insulating coating 3, it is preferable that the flow initiation temperature (melting point or flow point) of the crosslinked body be 150°C or higher, or even 180°C or higher. On the other hand, if it is desired to actively utilize the softening and flow of the crosslinked polymer material, such as for remolding the insulating coating 3, the flow initiation temperature of the crosslinked body should be set to 300°C or lower, or even 250°C or lower.

[0042] The insulated wire 1 having the insulating coating 3 according to this embodiment can be manufactured by disposing a crosslinkable polymer composition containing a metal compound serving as a metal ion source and a silicone resin having a substituent in its side chain capable of forming an ionic bond with the metal ion around the outer periphery of the wire conductor 2, and then crosslinking the silicone resin with the metal ions to form a crosslinked body from the crosslinkable polymer composition, thereby producing the insulating coating 3 made of a crosslinked polymer. If a metal compound that liberates desired metal ions upon heating, such as a metal complex described below, is used as the metal compound, crosslinking can be easily promoted by heating the crosslinkable polymer composition to liberate the metal ions, thereby forming the insulating coating 3. In this specification, the polymer material after crosslinking is referred to as the crosslinked polymer material, and the raw material composition before crosslinking is referred to as the crosslinkable polymer composition, to distinguish them from each other.

[0043] The crosslinking of the crosslinkable polymer composition by heating can be carried out in parallel with the process of disposing the crosslinkable polymer composition, which is a mixture of the components, around the periphery of the electric wire conductor 2 by extrusion molding or the like, or can be carried out after disposing the crosslinkable polymer composition in an uncrosslinked state around the periphery of the electric wire conductor 2. From the perspective of simplifying the process of forming the insulating coating 3, it is preferable to proceed with crosslinking in parallel with disposing the crosslinkable polymer composition around the periphery of the electric wire conductor 2. Since the crosslinking reaction does not proceed unless metal ions are liberated by heating, handling the crosslinkable polymer composition containing a metal compound and a silicone resin without heating allows for stable preparation and storage of the composition while avoiding unintended crosslinking. Below, each component of the crosslinkable polymer material is described in detail.

[0044] (1) Silicone resin First, the silicone resin that serves as the base resin in the present crosslinked polymer material will be described.

[0045] In this embodiment, the main material of the cross-linked polymer material constituting the insulating coating 3 is a silicone resin containing a substituent in its side chain that can form an ionic bond with a metal ion. The type of substituent is not particularly limited as long as it can form an ionic bond with the metal ion contained in the cross-linked polymer material. The substituent is preferably a neutral group in the silicone resin before cross-linking, and a negatively charged anionic group in the cross-linked product. It is particularly preferable that the substituent is a neutral electron-withdrawing group in the silicone resin before cross-linking, and an anionic group generated by releasing a proton from the electron-withdrawing group in the cross-linked product. The electron-withdrawing group (hereinafter, including an anionic group) can form a stable ionic bond with a metal ion. When the silicone resin is cross-linked with the metal ion, a stable cross-linked structure is formed, and the cross-linked product is likely to exhibit high heat resistance and oil resistance.

[0046] Suitable examples of electron-withdrawing substituents capable of forming ionic bonds with metal ions include acidic groups other than hydroxyl groups, such as carboxylic acid groups, acid anhydride groups, and phosphate groups. Carboxylic acid groups and acid anhydride groups are particularly suitable. The substituent may be one type or two or more types, preferably at least one of the substituents listed above. The substituents listed above are advantageous in that they easily form ionic bonds with metal ions. Furthermore, since all of the substituents listed above are acidic groups with relatively low polarity, they are less likely to undergo phase separation in the main chain or side chain of the silicone resin, allowing for the formation of highly uniform crosslinked structures within the silicone resin structure. For example, sulfonic acid groups are also electron-withdrawing substituents that easily form ionic bonds with metal ions, but due to their high polarity, they are prone to phase separation, and therefore are not as suitable as the substituents listed above as suitable substituents for silicone resins.

[0047] As explained above, in silicone resins, the substituents that form ionic bonds with metal ions are contained in the side chains rather than the polymer backbone. This allows for the stable formation of a crosslinked structure with strong inorganic properties while suppressing the influence of the backbone, making it easier to obtain high oil resistance in crosslinked polymer materials. Furthermore, the formation of crosslinked structures in the side chains allows the crosslinked sites to maintain a high degree of freedom of movement, resulting in a crosslinked material with excellent flexibility. While the type and length of the side chains are not particularly limited, to enhance their effects, it is preferable for the silicone resin to have a substituent introduced into the organic side chain. In other words, it is preferable for the silicone resin to be an organopolysiloxane having a substituent in the side chain that can form an ionic bond with metal ions. It is particularly preferable for the substituent to be bonded to the backbone via an alkyl or alkylene group having one or more carbon atoms. Alternatively, the substituent may be bonded to the backbone via a heteroatom such as an oxygen atom. The substituent may be introduced at the end or the middle of the side chain, but it is preferable for it to be introduced at the end to effectively enhance the stability and freedom of movement of the crosslinked sites. There is no particular upper limit to the number of carbon atoms in the side chain, but from the viewpoint of minimizing the influence of the main chain on the crosslinking sites, it is preferable that the number of carbon atoms connecting the main chain and the substituent be 4 or less.

[0048] In silicone resins, moieties capable of forming ionic bonds with metal ions, such as electron-withdrawing substituents, may be contained in the main chain (including terminal portions; the same applies below) or not, as long as they are contained in the side chain. A suitable example of a main chain that does not contain such moieties is a polysiloxane chain containing only an -Si-O- structure. Examples of main chains that contain such moieties include block copolymers containing a unit made of a polysiloxane chain and a unit made of a polymer containing a monomer having an electron-withdrawing group, and structures containing an electron-withdrawing substituent at the end of a polysiloxane chain. However, it is preferable that the main chain does not contain moieties capable of forming ionic bonds with metal ions. This is because the presence of such moieties in the main chain may prevent the side chain substituents from forming a crosslinked structure through ionic bonding with the metal ion. Even if the main chain contains a moiety capable of forming an ionic bond, it is susceptible to large steric hindrance and therefore does not effectively contribute to crosslinking by forming an ionic bond with a metal ion, and crosslinking is not effective in improving material properties such as heat resistance while maintaining high oil resistance. Furthermore, if the moiety capable of forming an ionic bond with a metal ion is one that can form a resonance structure, such as a carbonyl group, the presence of such a moiety in the main chain will involve the main chain in the resonance, and the uniformity of the crosslinked body will likely be reduced.

[0049] It is most preferable to use a polysiloxane chain containing only an -Si-O- structure as the main chain, and the most preferable silicone resin is an organopolysiloxane in which organic groups are bonded as side chains to such a polysiloxane chain, and in which substituents capable of forming ionic bonds with metal ions are further introduced into the side chains. When the main chain is a polysiloxane chain, the main chain is less likely to affect the formation of crosslinking points in the side chains, and the high heat resistance and oil resistance brought about by the crosslinking in the side chains become prominent properties of the entire crosslinked product.

[0050] In the silicone resin, the content of the substituent capable of forming an ionic bond with a metal ion is not particularly limited, but from the viewpoint of ensuring physical properties through crosslinking, it is preferably 0.05% by mass or more and 10% by mass or less relative to the total mass of the silicone resin. More preferably, it is 0.1% by mass or more and 5% by mass or less. The content of the above-mentioned substituent in the silicone resin can be determined by comparing the magnitude of the peak characteristic of the substituent in the infrared absorption spectrum with the magnitude of the spectral peak of a material with a known content.

[0051] The silicone resin preferably has a flow initiation temperature (melting point or pour point) of 150°C or lower. In other words, it is preferably liquid at 150°C or lower. Furthermore, it is preferably liquid at room temperature. This allows for easy mixing, kneading, and molding of the components without heating to high temperatures when preparing a crosslinkable polymer composition containing a silicone resin and a metal compound as a metal ion source and disposing the composition on the outer periphery of the electric wire conductor 2 by extrusion molding or the like. Furthermore, by mixing the silicone resin in a highly fluid state in the crosslinkable polymer composition with the metal compound as a metal ion source, the metal compound is well dispersed in the silicone resin, and crosslinking by heating can form a crosslinked body with a highly uniform distribution of crosslinking points. Note that a silicone resin with a relatively low flow initiation temperature may result in a low viscosity of the composition, which may hinder smooth molding when the composition is molded by extrusion molding or the like. In such cases, the viscosity of the composition can be increased by adding polar fine particles, as described below.

[0052] (2) Metallic components Next, the metal ions that crosslink the silicone resin in the present crosslinked polymer material and the metal compounds that are contained in the crosslinkable polymer composition before crosslinking and serve as the source of the metal ions will be described.

[0053] The metal species of the metal ions used for crosslinking the silicone resin are not particularly limited, but alkaline earth metals, aluminum, zinc, titanium, zirconium, etc. can be suitably used. The metal ions used should be at least one of these metal ions. These metal ions have a valence of 2 or more, and form ionic bonds with the substituents of the silicone resin, making it easy to form a stable crosslinked structure between the polymer chains of the silicone resin. Furthermore, the metals listed above belong to hard acids according to the HSAB rule and are metals with a relatively high ionization tendency, so they form stable bonds with the substituents of the silicone resin and are suitable as metals for constituting a crosslinked body.

[0054] Among the metal species listed above, aluminum and zirconium are particularly suitable as metals for forming crosslinked bodies. Therefore, it is preferable that the metal ions used be at least one of aluminum and zirconium ions. Metal compounds, such as metal complexes containing aluminum or zirconium, have a relatively high degree of stability. When mixed with a silicone resin as a metal ion source in a pre-crosslinked composition, the formation of a crosslinked structure does not proceed easily, resulting in a pre-crosslinked composition with high stability during preparation and storage. On the other hand, when these metal compounds are heated, the metal ions are relatively easily liberated, forming a crosslinked body with the silicone resin. The liberation of the metal from the metal compound occurs accompanied by decomposition or phase transition of the metal compound. For example, as shown in the examples below, the phase transition onset temperature (the temperature at which the baseline change in differential scanning calorimetry (DSC) begins) of zirconium(IV) acetylacetonate (Zr-AA) is 180°C, which is higher than that of various acetylacetonate complexes. On the other hand, the phase transition onset temperature for aluminum(III) acetylacetonate is not so high at 112°C, but this compound is characterized by a gradual change in heat quantity from the onset of the phase transition, with a significant change in heat quantity occurring around 170°C. In other words, at relatively high temperatures around 170°C, the phase transition and the accompanying release of metal ions progress significantly.

[0055] Furthermore, when aluminum and zirconium ions are used as metal ions, the flow initiation temperature of the crosslinked body becomes higher than when titanium is used, for example, and the crosslinked polymer material becomes excellent in heat resistance. This is because aluminum and zirconium are not easily oxidized like titanium, and therefore the efficiency of forming and maintaining the crosslinked structure is less likely to decrease due to the existence of an oxidation pathway. Furthermore, when aluminum and zirconium are used, unlike titanium, which is significantly stabilized by oxidation, ionic bonds that can participate in crosslinking are less likely to occur. The point Since the amount of aluminum and zirconium is increased, the polarity of the crosslinked product is increased, and higher oil resistance can be obtained than when titanium is used. Furthermore, compared to alkaline earth metals such as calcium, aluminum and zirconium do not have as high an acid hardness as alkaline earth metals, so they are easily dispersed uniformly in silicone resins. Furthermore, compared to zinc, aluminum and zirconium tend to have higher decomposition temperatures of metal compounds such as metal complexes, which improves the stability of the composition during preparation and storage.

[0056] Furthermore, in the insulated wire 1, if the metal species contained in the cross-linked polymer material constituting the insulating coating 3 is the same as the metal species that is the main component of the wire conductor 2, it is easy to minimize the effect of the presence of the wire conductor 2 on the formation and stable maintenance of a cross-linked structure in the insulating coating 3 at the interface between the wire conductor 2 and the insulating coating 3. For example, when the wire conductor 2 is made of aluminum or an aluminum alloy, the metal ions used for cross-linking the silicone resin in the insulating coating 3 may be aluminum.

[0057] The metal species is not limited to the metal species listed above as preferred, including aluminum and zirconium, and any metal species can be used as long as it can crosslink the silicone resin by forming an ionic bond with the substituent contained in the side chain of the silicone resin. Furthermore, the metal ion used to crosslink the silicone resin may not only be a monoatomic ion of the metal, but also a polyatomic ion (metal-containing ion) formed by bonding a metal atom to another atom. However, from the viewpoint of forming a stable ionic bond with the substituent on the side chain of the silicone resin, a monoatomic ion of the metal is preferred. Among polyatomic ions, those containing an organic moiety are not preferred from the viewpoint of improving the oil resistance of the crosslinked product.

[0058] The metal ions that crosslink the silicone resin may be introduced into the crosslinked polymer material in any form and from any source, but it is preferable that the metal ion source be contained in the crosslinkable polymer composition before crosslinking in the form of a metal compound that liberates metal ions when heated. Here, "by heat" refers to heating, and is intended to be at a temperature higher than room temperature. "Liberating metal ions" refers to the release of metal ions from a metal compound due to decomposition or phase transition of the metal compound.

[0059] The metal compound serving as the metal ion source preferably liberates metal ions upon heating at 50°C or higher. In other words, it is preferable that the metal compound have a decomposition point or phase transition point at 50°C or higher. This suppresses the liberation of metal ions from the metal compound during preparation of the crosslinkable polymer composition or before use (before crosslinking) of the crosslinkable polymer composition, thereby suppressing the progress of crosslinking of the silicone resin, resulting in excellent storage stability of the crosslinkable polymer composition. In other words, when preparing the crosslinkable polymer composition by mixing the metal compound and the silicone resin at low temperatures (e.g., below 50°C), when storing the prepared crosslinkable polymer composition, or when disposing the crosslinkable polymer composition on the outer periphery of the electric wire conductor 2 by extrusion molding or the like, the quality degradation of the crosslinkable polymer composition, such as unintended liberation of metal ions from the metal compound and the resulting crosslinking of the silicone resin, is unlikely to occur. When the metal compound has a decomposition point or phase transition point at 60°C or higher, or even 70°C or higher, the effect of improving storage stability is further enhanced.

[0060] On the other hand, the metal compound preferably liberates metal ions when heated at 300°C or below. In other words, it is preferable that the metal compound has a decomposition point or phase transition point at 300°C or below. This makes it difficult for the silicone resin to degrade at temperatures lower than those at which metal ions are liberated from the metal compound, making it easier to crosslink unaltered silicone resins with metal ions. Furthermore, liberating metal ions by heating at a moderate temperature results in a crosslinkable polymer composition with an excellent crosslinking rate. From these perspectives, it is more preferable that the metal compound has a decomposition point or phase transition point at 250°C or below, more preferably 150°C or below, or even 120°C or below. The decomposition point or phase transition point of the metal compound is expressed as the baseline change onset temperature measured by differential scanning calorimetry (DSC) (measurement temperature range: 25°C to 200°C, measured in air). The phase transition point does not include the melting point, and the phase transition does not include melting. In addition, when a metal compound has both a phase transition point and a decomposition point, or when it has multiple phase transition points, the lower of these (the lowest) is treated as the "decomposition point or phase transition point."

[0061] The metal compound serving as the metal ion source may be any chemical species as long as it liberates metal ions by heat, but a suitable chemical species is a metal complex. A metal complex is composed of a central metal ion to which a ligand having an unshared electron pair is coordinately bonded. When a metal complex is used, the ligand has an excellent effect of stabilizing the metal ion, suppressing the liberation of metal ions during the preparation of the crosslinkable polymer composition or before use of the crosslinkable polymer composition, and also making it easy to liberate metal ions by heat when crosslinking a silicone resin.

[0062] Ligands that make up metal complexes include monodentate ligands, which have one coordination site, and multidentate ligands, which have two or more coordination sites. Metal complexes formed with multidentate ligands are more stable than those formed with monodentate ligands due to the chelating effect. Ligands can be non-bridging ligands, in which one ligand coordinates to one metal ion, or bridging ligands, in which one ligand coordinates to two or more metal ions. Bridging ligands can be monodentate or multidentate.

[0063] The metal compound serving as the metal ion source is preferably a metal complex containing a polydentate ligand or a bridging ligand, because coordination with a polydentate ligand or a bridging ligand is more effective in stabilizing metal ions than non-bridging coordination with a monodentate ligand, and therefore liberation of metal ions can be more effectively suppressed during preparation of the crosslinkable polymer composition or before use of the crosslinkable polymer composition.

[0064] Among various metal complexes, metal complexes containing β-diketonato ligands (1,3-diketonato ligands) or alkoxide ligands are preferably used as metal ion sources. β-diketonato ligands and alkoxide ligands are likely to form multidentate or bridging ligands, and are more effective at stabilizing metal ions than non-bridging ligands formed by monodentate ligands. This effectively suppresses the liberation of metal ions during the preparation of a crosslinkable polymer composition or before use of the crosslinkable polymer composition. In particular, metal complexes containing β-diketonato ligands are preferred.

[0065] The β-diketonato ligand is represented by the following general formula (1). [ka] In formula (1), R1 and R2 each independently represent a hydrocarbon group, and R3 represents a hydrogen atom or a hydrocarbon group. At least two of R1, R2, and R3 may be connected to each other via a ring structure. The ligand may also have the structure of formula (1) due to a resonance structure.

[0066] In formula (1), R1, R2, and R3 may be aliphatic hydrocarbon groups or hydrocarbon groups containing an aromatic ring. They may also contain heteroatoms such as oxygen atoms. Examples of hydrocarbon groups constituting R1, R2, and R3 include alkyl groups, alkoxy groups, aromatic groups, and condensed aromatic groups. The number of carbon atoms in R1, R2, and R3 is not particularly limited, but is preferably 1 to 8.

[0067] Specific examples of the β-diketonato ligand include acetylacetonato ligand (acac), 2,2,6,6-tetramethyl-3,5-heptanedionato ligand (dpm), 3-methyl-2,4-pentanedionato ligand, 3-ethyl-2,4-pentanedionato ligand, 3,5-heptanedionato ligand, 2,6-dimethyl-3,5-heptanedionato ligand, 1,3-diphenyl-1,3-propanedionato ligand, etc. Among these, from the viewpoint of structural simplicity, etc., an acetylacetonato ligand in which R1 and R2 are methyl groups and R3 is a hydrogen atom in the above formula (1) is particularly preferred.

[0068] The alkoxide ligand is represented by the following general formula (2). [ka] In formula (2), R4 represents a hydrocarbon group. R4 may be an aliphatic hydrocarbon group or a hydrocarbon group containing an aromatic ring. R4 is preferably a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of the alkoxide ligand include a methoxide ligand, an ethoxide ligand, an isopropoxide ligand, an n-propoxide ligand, and an n-butoxide ligand.

[0069] The content of metal components that can participate in the crosslinking of silicone resins is preferably 0.03 parts by mass or more, or even 0.1 parts by mass or more, based on 100 parts by mass of silicone resin, in terms of the metal ion content in the crosslinked polymer material after crosslinking. Furthermore, the content of metal compounds in the crosslinkable polymer composition before crosslinking is preferably 0.1 parts by mass or more, or even 1.0 parts by mass or more. By incorporating a sufficiently large amount of metal ions relative to the silicone resin, the crosslinked product has a high crosslink density, which is highly effective in improving heat resistance and oil resistance. Meanwhile, the content of the metal components is preferably 10 parts by mass or less, or even 5 parts by mass or less, in terms of the metal ion content in the crosslinkable polymer composition before crosslinking. Furthermore, the content of metal compounds in the crosslinkable polymer composition before crosslinking is preferably 20 parts by mass or less, or even 10 parts by mass or less. This makes it easier to avoid the effects of incorporating a large amount of metal components, such as separation or precipitation of metal components before crosslinking, and embrittlement and reduced flexibility of the insulating coating 3 after crosslinking.

[0070] (3) Polar fine particles The crosslinked polymer material constituting the insulating coating 3 of the insulated wire 1 preferably contains polar microparticles in addition to a crosslinked silicone resin crosslinked with metal ions, especially when the silicone resin used as the raw material has a low viscosity before crosslinking. The polar microparticles serve as a molding aid in the crosslinkable polymer composition before crosslinking, providing thickening and thixotropy. When the silicone resin is in a low-viscosity liquid state, it is difficult to stably position the crosslinkable polymer composition around the outer periphery of the conductor 2. Furthermore, even when molding by extrusion molding or the like while heating to promote crosslinking via metal ions, problems such as insufficient torque applied to molding equipment such as screws and leakage of the composition from the equipment can occur, particularly in the early stages of the crosslinking reaction, making molding difficult. Therefore, adding polar microparticles as a molding aid to increase the viscosity of the composition allows for stable molding. Furthermore, the polar microparticles added exhibit substantially no oil absorption, thereby less compromising the oil resistance of the crosslinked silicone resin.

[0071] The type of polar fine particles is not particularly limited, and may be entirely composed of a polar material, or may be non-polar material particles surface-treated with a polar material. Specific examples of polar fine particles include fine particles made of silica, metal oxides such as aluminum oxide and zinc oxide, clay minerals such as montmorillonite and sepiolite, cellulose, fluororesins such as Teflon (registered trademark), and carbon. One type of fine particle or two or more types of fine particles may be used. Fumed silica fine particles are particularly preferred as polar fine particles. Fumed silica is easily available as fine particles with excellent particle size uniformity, and the hydrogen bridge bonding effect of surface silanol groups provides a high viscosity-increasing effect and a thixotropic effect.

[0072] The particle size of the polar fine particles is not particularly limited, but a smaller particle size results in a larger specific surface area, which results in a higher uniformity throughout the composition and a thickening effect and thixotropy-imparting effect. From this perspective, the particle size of the polar fine particles is preferably an average particle size of 100 nm or less, more preferably 50 nm or less. On the other hand, if the particle size is too small, higher-order aggregates are formed, resulting in an uneven apparent particle size distribution. Therefore, the average particle size of the polar fine particles is preferably 5 nm or more, more preferably 7 nm or more. Furthermore, the particle shape of the polar fine particles is not particularly limited, but a spherical shape is a preferred example.

[0073] The content of polar fine particles is preferably 1 part by mass or more, and even 10 parts by mass or more, per 100 parts by mass of silicone resin. This enhances the thickening effect and thixotropy-imparting effect of adding polar fine particles. On the other hand, the content of polar fine particles is preferably kept to 100 parts by mass or less, and even 60 parts by mass or less, per 100 parts by mass of silicone resin. This makes it easier to disperse the polar fine particles well in the silicone resin.

[0074] (4) Other ingredients The crosslinked polymer material constituting the insulating coating 3 may contain additives such as flame retardants, copper inhibitors, antioxidants, and colorants in addition to the crosslinked silicone resin crosslinked with metal ions described above and optionally added polar microparticles, as long as the functionality of the material is not impaired. Furthermore, the polymer component may contain polymers other than the crosslinked silicone resin crosslinked with metal ions, but the content of such polymers is preferably kept lower than the content of the crosslinked silicone resin. More preferably, the crosslinked polymer material contains only the crosslinked silicone resin as the polymer component, excluding unavoidable components such as uncrosslinked silicone resins having the substituents.

[0075] Examples of polymer components that should not be included in crosslinked polymer materials, except for unavoidable components, include silicone resins crosslinked by crosslinking structures other than those mediated by metal ions. That is, examples include silicone resins having side chains with substituents capable of forming ionic bonds with metal ions, or other silicone resins crosslinked without ionic bonds between the substituents and metal ions. Examples of crosslinking structures other than those mediated by metal ions include crosslinking structures formed by organic crosslinking agents such as organic peroxides, epoxy compounds, and amine compounds. The inclusion of crosslinking structures mediated by organic crosslinking agents in crosslinked polymer materials leads to reduced oil resistance. Furthermore, regardless of whether crosslinking occurs, it is preferable to avoid silicone resins other than those having side chains with substituents capable of forming ionic bonds with metal ions in crosslinked polymer materials. Furthermore, while silicone rubber and other resin materials can function as molding aids, these organic molding aids are preferably not included because they may reduce the oil resistance of crosslinked polymer materials. Furthermore, it is preferable to avoid polymer components that have a higher flow initiation temperature in an uncrosslinked state than the silicone resins having side chains with substituents capable of forming ionic bonds with metal ions.

[0076] In addition to polymer components, fillers for improving oil resistance are another component that should not be included in crosslinked polymer materials. While fillers such as flame retardants may be included in crosslinked polymer materials, fillers primarily intended to improve oil resistance are not necessary. Because crosslinked silicone resins crosslinked via metal ions exhibit high oil resistance, the addition of fillers for improving oil resistance is unnecessary. Furthermore, additives that should not be included in crosslinkable polymer compositions prior to crosslinking include (a) photoradical generators, thermal radical generators, and (b) chlorine compounds and bromine compounds. If compounds in group (a) are included in a crosslinkable polymer composition, unintended chemical reactions, such as crosslinking of silicone resins through reactions separate from the crosslinking reaction mediated by metal ions liberated from metal compounds, may occur upon heating. This may prevent the production of crosslinked polymer materials that fully exhibit properties such as heat resistance and oil resistance. Furthermore, if compounds in group (b) are included in a crosslinkable polymer composition, coloration and the generation of corrosive gases may occur upon heating. [Example]

[0077] Examples are shown below. The present invention is not limited to these examples. Unless otherwise specified, the preparation and evaluation of samples were carried out at room temperature in the atmosphere.

[0078] [1] Characteristics of cross-linked silicone resin First, the relationship between the composition and properties of cross-linked silicone resin was investigated.

[0079] <Sample preparation> (1) Preparation of silicone resin The following four types of silicone resins were prepared. All four types of silicone resins are liquid at room temperature.

[0080] Modified silicone A 10 g (epoxy group 2.86 mmol) of epoxy-modified silicone ("KF-1001" manufactured by Shin-Etsu Silicones Co., Ltd.; epoxy equivalent 3500 g / mol) was dissolved in 500 mL of diethyl ether, and 0.4 g (2.92 mmol) of 4-aminobenzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added in small portions while vigorously stirring at 30°C or below. Stirring was continued at 30°C or below for 3 hours. After that, insoluble matter was removed by filtration, and the diethyl ether in the filtrate was distilled off using an evaporator at a bath temperature of 40°C or below, yielding a clear, pale yellow oil. This product was a carboxylic acid-modified silicone resin in which the epoxy groups in the silicone had been converted to benzoic acid (carboxylic acid group equivalent 3500 g / mol). This was designated Modified Silicone A.

[0081] Modified silicone B 10 g (epoxy group 2.86 mmol) of epoxy-modified silicone (KF-1001 manufactured by Shin-Etsu Silicone Co., Ltd.; epoxy equivalent 3500 g / mol) was dissolved in 500 mL of diethyl ether, and the mixture was stirred at 30°C or less with 5-aminoisophthalic acid. acid 0.55 g (3.04 mmol) of ethanol (Tokyo Chemical Industry Co., Ltd.) was added in small portions. Stirring was continued at 30°C or below for 48 hours. After that, insoluble matter was removed by filtration, and the diethyl ether in the filtrate was distilled off using an evaporator at a bath temperature of 40°C or below, yielding a pale yellow, clear oil. This product was a carboxylic acid-modified silicone resin in which the epoxy groups in the silicone had been converted to isophthalic acid (carboxylic acid group equivalent: 1750 g / mol). This was designated Modified Silicone B.

[0082] Modified Silicone C A clear, pale yellow oil was obtained by carrying out the same synthesis method as for Modified Silicone B, except that 0.8 g (3.21 mmol) of 4-amino-1-hydroxybutane-1,1-diphosphonic acid (Tokyo Chemical Industry Co., Ltd.) was used instead of 0.55 g of 5-aminoisophthalic acid. This product was a phosphate-modified silicone resin in which the epoxy groups in the silicone had been converted to diphosphonic groups (phosphate group equivalent: 1750 g / mol). This was designated Modified Silicone C.

[0083] Unmodified silicone Unmodified silicone ("KF-96-30,000cs" manufactured by Shin-Etsu Chemical Co., Ltd.) was also prepared.

[0084] (2) Sample preparation The silicone resin prepared above and various metal compounds or other crosslinkers shown below were added to xylene in an amount five times their total mass (unit: parts by mass) in the amounts shown in Table 1, and dispersed and mixed by vigorously stirring at 80°C for 30 minutes. The mixture was then vacuum dried and press-molded at 250°C for 10 minutes to prepare 2 mm thick sample sheets, designated as Samples A1 to A9 and B2 to B7.

[0085] Silicone rubber was also prepared as sample B1. Specifically, "ELASTOSIL EL 4500" manufactured by Wacker Asahi Kasei Corporation was mixed with a predetermined curing agent, molded into a sample sheet with a thickness of 2 mm, and then heated and cured under predetermined conditions to obtain silicone rubber.

[0086] The materials used as metal compounds or other crosslinking agents in the preparation of Samples A1 to A9 and B2 to B7 are as follows. Below, the decomposition points or phase transition points obtained by DSC measurement are shown in parentheses along with the material types. (metal compound) Zn-AA: Zinc(II) acetylacetonate (105°C) Al-AA: Aluminum(III) acetylacetonate (112°C) Zr-AA: Zirconium(IV) acetylacetonate (180°C) Al-IP: Aluminum(III) triisopropoxide (94°C) Ti-IP: Titanium(IV) tetraisopropoxide (85°C) ZnO: Zinc oxide (II) (None (>300°C)) Al-st: Aluminum stearate (125°C) (Other crosslinkers) Epoxy compound: Hydrogenated bisphenol A diglycidyl ether (epoxy equivalent: 215-245) "Epolite 4000" manufactured by Kyoeisha Chemical Amine compound (long-chain tertiary amine): 1,6-bis(dimethylamino)hexane (Tokyo Chemical Industry Co., Ltd.)

[0087] <Evaluation method> (1) Hardening In the sample preparation process, after press molding, samples that were visually observed to have no flow or stringiness were deemed to have hardened and were rated "A." On the other hand, samples that showed flow or stringiness were deemed to have not hardened and were rated "B."

[0088] (2) Oil-resistant volume expansion rate The oil resistance volumetric expansion rate of each sample was evaluated using a fluid resistance test in accordance with JIS K 6258. The volumetric expansion rate was measured after immersion in ATF oil (automatic transmission oil) at 150°C for 72 hours. The higher this oil resistance volumetric expansion rate, the higher the oil resistance of the material.

[0089] (3) Fuel volume expansion resistance The fuel volume expansion resistance of each sample was evaluated using a liquid resistance test in accordance with JIS K 6258. 2,2,4-trimethylpentane (isooctane) was used as the test fuel oil, and the volume expansion resistance was measured after immersion for 24 hours at 40°C. The higher this fuel volume expansion resistance, the higher the oil resistance of the material.

[0090] (4)Hardness The hardness of each sample was evaluated based on JIS K6253-3. Hardness was measured as Durometer Type A hardness. The lower the hardness, the higher the flexibility of the material.

[0091] (5) Elastic modulus The sample sheet of each sample was cut into a strip measuring 50 mm long x 5 mm wide x 2 mm thick, and a tensile test was performed with a grip width of 10 mm at a speed of 10 mm / min. The elastic modulus (tensile modulus) was calculated from the strain between 1N and 2N tensile loads. The lower the elastic modulus, the higher the flexibility of the material.

[0092] <Evaluation results> In Table 1 below, the content of each component (unit: parts by mass) for Samples A1 to A9 and B1 to B7 is shown in the upper row, and the results of each evaluation are shown in the lower row.

[0093] [Table 1]

[0094] According to Table 1, samples A1 to A9 were all obtained using modified silicone resin and metal complex as raw materials. These samples were fully cured after press molding (a cure rating of "A"). This corresponds to the fact that the heat generated during press molding liberated metal ions from the metal complex, forming ionic bonds with the substituents of the modified silicone resin, thereby promoting crosslinking. These samples exhibited high oil resistance, with both the oil-resistant volumetric expansion coefficient and fuel-resistant volumetric expansion coefficient of the crosslinked bodies kept below 20%. This is likely due to the reduced affinity for oil components at the crosslinked sites via metal ions. Furthermore, compared to the silicone rubber of sample B1, each sample exhibited Type A hardness of 1.5 times or less and elastic modulus of 2 times or less. While inferior to silicone rubber, these samples exhibited relatively high flexibility. This suggests that even though the crosslinked structure in the silicone resin was formed by ionic bonds via metal ions, the inherent flexibility of crosslinked silicone resin was exhibited, providing oil resistance.

[0095] Next, we will examine samples B1 to B7. Sample B1 is made of silicone rubber in which silicone polymer chains are cross-linked by organic chains. Correspondingly, the oil-resistant volumetric expansion coefficient and fuel-resistant volumetric expansion coefficient are both high, exceeding 50%, and the oil resistance is low.

[0096] In sample B2, the silicone resin used was unmodified and did not contain any substituents capable of forming ionic bonds with metal ions. Sample B3 did not contain any components capable of forming crosslinked structures with the silicone resin. Furthermore, samples B4 and B5 used zinc oxide and aluminum stearate, respectively, rather than metal complexes as the metal compounds. These compounds do not liberate metal ions even when heated. In other words, none of samples B3 to B5 contained a metal ion source. In samples B2 to B5, the absence of substituents capable of forming ionic bonds with metal ions or metal ions resulted in the silicone resin not being crosslinked, and the composition not being sufficiently cured (cure evaluation: "B"). Because no cured samples were obtained, evaluation of various properties was not possible.

[0097] Samples B6 and B7 use organic compounds rather than metal compounds as crosslinkers. Consequently, their oil and fuel volumic expansion coefficients are comparable to or even higher than those of the silicone rubber in sample B1, resulting in poor oil resistance. This is due to the highly organic nature of the crosslinked sites, which causes swelling in response to oil and fuel. Sample B7, in particular, uses a basic amine compound as a crosslinker. The basicity of the amino groups crosslinks the carboxylic acid groups in the modified silicone. However, compared to crosslinked structures via metal ions, this highly organic nature makes it difficult to suppress swelling in response to oil and fuel. Furthermore, due to the basicity of the amine compound, mixing it with the silicone resin immediately leads to gelation, resulting in an inconsistent cured product.

[0098] Here, samples A1 to A9 are compared with one another. Samples A1 to A5 use different types of metal complexes, but all of them combine high oil resistance and flexibility. In particular, samples A2 and A3, which use β-diketonato complexes of aluminum and zirconium, exhibit particularly high oil resistance and flexibility. On the other hand, sample A5, which uses an alkoxide complex of titanium, exhibits slightly lower oil resistance.

[0099] Samples A1, A6, and A7 use different types of modified silicone resin. Comparing these, samples A1 and A6, which use carboxylic acid-modified silicone resin, have particularly high flexibility.

[0100] Samples A1, A8, and A9 differ in the amount of metal complex added. Comparing these evaluation results, the oil resistance increases as the amount of metal complex added increases, while the flexibility increases as the amount of metal complex added decreases. This is interpreted as being because the crosslink density in the silicone resin increases as the amount of metal complex added increases.

[0101] [2] Compactibility when polar fine particles are added Next, moldability was evaluated when polar fine particles were added to a composition containing a silicone resin and a metal compound.

[0102] <Sample preparation> 95 parts by mass of the modified silicone A synthesized in the above test [1] was added with 40 parts by mass of fumed silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.; average particle size 12 nm) as polar fine particles and 5 parts by mass of Al-AA, and mixed and kneaded at room temperature in a mixer kneader (manufactured by Primix Corporation) to prepare a molding raw material.

[0103] <Evaluation method> The molding raw material obtained above was loaded into the barrel of a Capillograph (manufactured by Toyo Seiki Seisakusho), and the piston was pushed down to extrude it through a die with a 1 mm hole. The temperatures of the barrel and die were set to 40°C, and other conditions were based on JIS K 7199. The formability was evaluated by observing the state of the extruded strand.

[0104] Furthermore, a portion of the strand obtained above was cut off and left in a thermostatic bath at 80°C for 5 hours. It was then left in a thermostatic bath at 200°C for another 20 minutes to complete the crosslinking reaction. Thereafter, the presence or absence of deformation of the sample was evaluated visually compared with the state before leaving it in the thermostatic bath. Furthermore, the sample was placed on a hot plate at 190°C and visually confirmed for melting.

[0105] <Evaluation results> Observation of the strands during the extrusion process revealed that the extruded strands were continuously extruded without sagging or breakage. Furthermore, the extruded strands maintained their shape well. This confirms that the molding material containing polar fine particles exhibits high moldability.

[0106] Furthermore, observations after the crosslinking reaction were as follows: permanent It was confirmed that no deformation had occurred compared to before crosslinking by leaving it in a warm bath. Furthermore, visual observation when the sample was placed on a hot plate showed that it had not melted. These results confirm that the addition of polar microparticles does not hinder the progress of crosslinking of the silicone resin by metal ions, and furthermore, does not impair the heat resistance of the crosslinked polymer material obtained by crosslinking.

[0107] Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0108] 1. Insulated wire 2. Wire conductor 3. Insulation coating 5. Wire harness 51 Insulated wire 52 connectors 53 Tape

Claims

1. A wire conductor; an insulating coating made of a cross-linked polymer material and covering the outer periphery of the electric wire conductor; the cross-linked polymer material includes a metal ion and a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with the metal ion; the silicone resin forms a crosslinked body by an ionic bond between the substituent and the metal ion, The insulated wire of claim 1, wherein the crosslinked polymer material contains only the crosslinked body as a polymer component, excluding unavoidable components.

2. 2. The insulated wire according to claim 1, wherein the substituent contained in the silicone resin is an anionic group derived from at least one of a carboxylic acid group, an acid anhydride group, and a phosphate group.

3. A wire conductor; an insulating coating made of a cross-linked polymer material and covering the outer periphery of the electric wire conductor; the crosslinked polymer material comprises a metal ion and a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with the metal ion, the substituent being an anionic group derived from at least one of a carboxylic acid group, an acid anhydride group, and a phosphate group; The silicone resin forms a crosslinked body by an ionic bond between the substituent and the metal ion.

4. 4. The insulated wire according to claim 1, wherein in the silicone resin, the substituent is bonded to a main chain via an alkyl group or an alkylene group having one or more carbon atoms.

5. A wire conductor; an insulating coating made of a cross-linked polymer material and covering the outer periphery of the electric wire conductor; the crosslinked polymer material includes a metal ion and a silicone resin having a substituent capable of forming an ionic bond with the metal ion, the substituent being attached to a main chain via an alkyl group or alkylene group having one or more carbon atoms and having, in a side chain, The silicone resin forms a crosslinked body by an ionic bond between the substituent and the metal ion.

6. 6. The insulated wire according to claim 1, wherein the metal ion can form a metal complex with a β-diketonato ligand or an alkoxide ligand in a state in which the metal ion can be released as a metal ion by heat.

7. A wire conductor; an insulating coating made of a cross-linked polymer material and covering the outer periphery of the electric wire conductor; the cross-linked polymer material includes a metal ion and a silicone resin having, in a side chain, a substituent capable of forming an ionic bond with the metal ion; the silicone resin forms a crosslinked body by an ionic bond between the substituent and the metal ion, The insulated wire is one in which the metal ion can form a metal complex with a β-diketonato ligand or an alkoxide ligand in a state in which the metal ion can be liberated as a metal ion by heat.

8. 8. The insulated wire according to claim 6, wherein the metal ions can be liberated from the metal complex as metal ions by heating at a temperature of 50°C or higher and 300°C or lower.

9. The insulated wire according to claim 1 , wherein the crosslinked polymer material contains polar fine particles in addition to the crosslinked body.

10. 10. The insulated wire according to claim 9, wherein the fine particles contain at least one of silica, metal oxide, clay mineral, cellulose, fluororesin, and carbon.

11. 11. The insulated wire according to claim 9, wherein the fine particles are fumed silica fine particles.

12. 12. The insulated wire according to claim 9, wherein the fine particles have an average particle size of 5 nm or more and 100 nm or less.

13. 13. The insulated wire according to claim 9, wherein the cross-linked polymer material contains the fine particles in an amount of 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the silicone resin.

14. The insulated wire according to claim 1 , wherein the silicone resin has a flow start temperature of 150° C. or less.

15. The insulated wire according to claim 1 , wherein the silicone resin does not contain a moiety capable of forming an ionic bond with a metal ion in a main chain.

16. 16. The insulated wire according to claim 15, wherein the main chain of the silicone resin is an organopolysiloxane chain.

17. 17. The insulated wire according to claim 1, wherein the metal ions are ions of at least one of alkaline earth metals, aluminum, zinc, titanium, and zirconium.

18. 18. The insulated wire of claim 17, wherein the metal ions are ions of at least one of aluminum and zirconium.

19. 19. The insulated wire according to claim 1, wherein the cross-linked polymer material contains the metal ions in an amount of 0.03 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the silicone resin.

20. 20. The insulated wire according to claim 1, wherein the crosslinked polymer material does not contain, except for unavoidable components, a component in which the silicone resin is crosslinked without an ionic bond between the substituent and the metal ion.

21. An insulated wire described in any one of claims 1 to 20, wherein the cross-linked polymer material does not contain a photoradical generator, a thermal radical generator, or components derived therefrom.

22. A wire harness comprising the insulated wire according to any one of claims 1 to 21.

23. a crosslinkable polymer composition containing a metal compound from which metal ions are liberated by heat and the silicone resin, disposed around the outer periphery of the electric wire conductor; forming the crosslinked body from the crosslinkable polymer composition by heating, thereby producing the insulating coating made of the crosslinked polymer material; A method for producing an insulated wire, comprising producing the insulated wire according to any one of claims 1 to 21.

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