Crosslinkable polymer composition, crosslinkable polymer material, insulated wire and wiring harness

Abstract

The present invention provides: a crosslinkable polymer composition which enables the achievement of a crosslinked body that has both heat resistance and re-formability, while exhibiting high wear resistance; a crosslinked polymer material which has both heat resistance and re-formability, while exhibiting high wear resistance; and an insulated wire and a wiring harness, each of which comprises this crosslinked polymer material.　The present invention provides a crosslinkable polymer composition which contains a component A that releases metal ions by means of heat and a component B that is composed of an organic polymer having a side chain and a Shore D hardness of 50 or more, wherein: the component B comprises, in the side chain, an electron-withdrawing substituent that is capable of forming an ion bond with a metal ion that is released from the component A; and a crosslinked body, which is obtained by crosslinking the component B by means of metal ions that are released from the component A, has a flow starting temperature within the range from 190°C to 300°C. The present invention also provides a crosslinked polymer material which comprises a crosslinked body of the crosslinkable polymer composition.

Description

[Technical Field]

[0001] The present disclosure relates to a crosslinkable polymer composition, a crosslinked polymer material, an insulated wire, and a wiring harness. [Background technology]

[0002] In insulated wires and wiring harnesses, thermoplastic polymer compositions are often used as insulating materials, such as insulating coatings that cover the outer periphery of wire conductors. Polyolefins are particularly popular for their cost-saving and chemical resistance. When molding a thermoplastic polymer composition into a desired shape, it is heated to a flowable state, and then a molding method such as extrusion molding is applied. To easily perform molding by heating, it is preferable that the polymer composition acquires flowability without being heated to an extremely high temperature.

[0003] On the other hand, in insulated electric wires and wiring harnesses, the temperature rises when current is applied, so the polymer compositions arranged near the current-carrying points, including the insulating coating, are required to have high heat resistance. In other words, the polymer composition is required to not undergo irreversible deformation due to heat generated when current is applied. For example, it is desirable that the insulating coating of electric wires for automobiles does not undergo reversible deformation at temperatures of 190°C or less. In particular, electric wires for electric vehicles require the flow of a large current through the wire conductor, which generates a large amount of heat when current is applied, so the polymer composition constituting the insulating coating, etc. is required to have high heat resistance.

[0004] Thus, polymer compositions used in insulated wires and wiring harnesses are required to be relatively easily moldable by heating and to have high heat resistance after molding. One approach to achieving both of these properties is to adjust the flow initiation temperature of the thermoplastic polymer material used. However, this approach has limitations, as polymer materials with high flow initiation temperatures require high heating during molding, while polymer materials with low flow initiation temperatures are unlikely to have high heat resistance. Therefore, a method utilizing crosslinking of polymer materials has also been adopted. Specifically, an uncrosslinked polymer composition is molded into a desired shape by extrusion molding or the like, and then the molecular chains are crosslinked to improve heat resistance. Examples of crosslinking methods include electron beam crosslinking, in which a material molded from polyolefin or the like is irradiated with an electron beam to crosslink the molecular chains into a three-dimensional network (see, for example, Patent Document 1), and silane crosslinking, in which a thermoplastic resin containing activated silane groups is molded and then crosslinked upon contact with moisture or the like (see, for example, Patent Document 2). Furthermore, when rubber is used as the polymer material, crosslinking by vulcanization can be used. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-176257 [Patent Document 2] Japanese Patent Application Publication No. 2020-161398 [Patent Document 3] International Publication No. 2014 / 57858 [Patent Document 4] Japanese Patent Application Publication No. 7-41636 [Patent Document 5] Japanese Patent Application Laid-Open No. 2011-162673 [Patent Document 6] Japanese Patent Application Laid-Open No. 2010-96416 [Patent Document 7] Japanese Patent Application Publication No. 5-239292 [Patent Document 8] Japanese Patent Application Laid-Open No. 2001-342305 [Patent Document 9] Patent Publication No. 2021-8613 [Patent Document 10] Japanese Patent Publication No. 2020-164837 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, polymer compositions crosslinked by electron beam crosslinking, silane crosslinking, or vulcanization are materials that acquire high heat resistance by undergoing crosslinking after being molded into a desired shape, but it is difficult to remold them into a different shape after they have been molded into a predetermined shape. This is because strong covalent bonds are irreversibly formed by crosslinking, and while these crosslinks are effective in improving heat resistance, they also increase the fluidity of the molecular chains again, preventing them from becoming remoldable.

[0007] However, in the case of insulated wires and wire harnesses, it is sometimes necessary to reshape a polymeric material that has been molded into a predetermined shape. For example, in an insulated wire in which an insulating coating is formed on the outer periphery of a stranded wire conductor, the cross-sectional shape of the insulated wire may be deformed into a shape other than circular, such as a flattened shape, due to restrictions on routing space. Conversely, it may be necessary to deform an insulated wire that has been molded into a cross-sectional shape other than circular, such as a flattened shape, into a circular cross-section. In these cases, if the insulating coating can be made reshapeable by heating or other means, it can be deformed to follow the deformation of the wire conductor.

[0008] Furthermore, polymeric materials often require mechanical strength, such as abrasion resistance. For example, insulated electric wires and wiring harnesses, where contact with other components, such as surrounding devices or adjacent electric wires, is anticipated, insulating coatings with high abrasion resistance are desirable. However, when crosslinking organic polymers by electron beam crosslinking, the organic polymer may be denatured by electron beam irradiation, resulting in a decrease in mechanical strength. In particular, when the organic polymer is polypropylene, electron beam irradiation is likely to cause a decrease in surface hardness. Furthermore, when crosslinking organic polymers by silane crosslinking, active silane groups must be introduced into the organic polymer in advance, and the introduction of these active silane groups may change the mechanical properties of the organic polymer.

[0009] In view of the above, an object of the present invention is to provide a crosslinkable polymer composition that can provide a crosslinked product having both heat resistance and remoldability and high abrasion resistance, a crosslinked polymer material that can provide both heat resistance and remoldability and high abrasion resistance, and an insulated wire and a wire harness that include such a crosslinked polymer material. [Means for solving the problem]

[0010] The crosslinkable polymer composition according to the present disclosure comprises a component A that liberates metal ions when heated, and a component B that is composed of an organic polymer having side chains and a Shore D hardness of 50 or more, wherein the component B contains, in the side chains, electron-withdrawing substituents that are capable of forming ionic bonds with the metal ions liberated from the component A, and a crosslinked product formed by crosslinking the component B with the metal ions liberated from the component A has a flow-initiation temperature in the range of 190°C or higher and 300°C or lower.

[0011] The crosslinked polymer material according to the present disclosure includes a crosslinked product of the crosslinkable polymer composition, which is configured as a crosslinked product obtained by crosslinking the component B with metal ions liberated from the component A.

[0012] The insulated wire according to the present disclosure includes a conductor and an insulating coating made of the cross-linked polymer material and covering the outer periphery of the conductor.

[0013] A wire harness according to the present disclosure includes the insulated wire. [Effects of the Invention]

[0014] The crosslinkable polymer composition according to the present disclosure provides a crosslinked product that is both heat-resistant and remoldable and has high abrasion resistance. The crosslinked polymer material according to the present disclosure is both heat-resistant and remoldable and has high abrasion resistance. Furthermore, the insulated wire and wiring harness according to the present disclosure include such a crosslinked polymer material. [Brief explanation of the drawings]

[0015] [Figure 1] 1A to 1C are diagrams illustrating the behavior of a crosslinked body contained in a crosslinked polymer material according to an embodiment of the present disclosure when heated, showing states in which the temperature increases in the order of Fig. 1A, Fig. 1B, and Fig. 1C. M2+ represents a metal ion, and R represents a side chain. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of an insulated wire according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0017] The crosslinkable polymer composition according to the present disclosure comprises a component A that liberates metal ions when heated, and a component B that is composed of an organic polymer having side chains and a Shore D hardness of 50 or more, wherein the component B contains, in the side chains, electron-withdrawing substituents that are capable of forming ionic bonds with the metal ions liberated from the component A, and a crosslinked product formed by crosslinking the component B with the metal ions liberated from the component A has a flow-initiation temperature in the range of 190°C or higher and 300°C or lower.

[0018] When the crosslinkable polymer composition according to the present disclosure is heated, component B can be crosslinked via metal ions liberated from component A. Therefore, in the uncrosslinked state, the composition exhibits high moldability when molded into a desired shape by extrusion molding or the like, while when heated to form a crosslinked product, it becomes a polymer material with high heat resistance. In particular, a crosslinked product with a flow initiation temperature of 190°C or higher ensures that the crosslinked polymer material has high heat resistance. Highly heat-resistant materials with a flow initiation temperature of 190°C or higher are particularly suitable for use in forming insulating coatings for automotive electric wires.

[0019] Furthermore, in a crosslinked body composed of the crosslinkable polymer composition according to the present disclosure, the crosslinked structure is formed via an ionic bond between a substituent of the organic polymer of component B and a metal ion. Therefore, the reversibility of the ionic bond can be utilized to reshape the crosslinked polymer material. Reheating an already formed crosslinked body causes the crosslinking points to migrate due to the ionic bond, resulting in fluidization of the material. Because the substituent introduced into the organic polymer of component B is an electron-withdrawing group, the crosslinked structure is stably formed, and the crosslinked body exhibits high heat resistance. Meanwhile, because the substituent is introduced into the side chain of the organic polymer, the degree of freedom of thermal motion at the crosslinked site is increased, facilitating migration of the crosslinking points upon heating, resulting in excellent reshapeability. In particular, because the flow initiation temperature of the crosslinked body is kept below 300°C, reshapeability by heating at temperatures below 300°C is ensured.

[0020] Furthermore, Component B contained in the crosslinkable polymer composition according to the present disclosure has a high hardness of at least 50 Shore D hardness, resulting in a crosslinked body with excellent mechanical strength and high abrasion resistance. Component B is crosslinked by ionic bonds mediated by metal ions, but the formation of ionic bonds is unlikely to significantly impair the properties of the organic polymer, and the properties obtained by the high hardness of Component B are more likely to be inherited as properties of the crosslinked body compared to electron beam crosslinking or silane crosslinking.

[0021] Here, the main chain of the component B is preferably polypropylene. Because polypropylene has high crystallinity, the component B tends to have a Shore D hardness of 50 or more and high mechanical properties. Furthermore, the crosslinked product tends to have a flow initiation temperature in the range of 190°C to 300°C. As a result, the crosslinked product has excellent remoldability, heat resistance, and abrasion resistance.

[0022] The component B preferably has a flow initiation temperature in the range of 50° C. to 190° C. In this case, a crosslinked product having a flow initiation temperature of 190° C. to 300° C. as described above can be easily obtained through crosslinking by metal ions derived from component A. Furthermore, high moldability can be obtained when the uncrosslinked crosslinkable polymer composition is molded into a desired shape by extrusion molding or the like.

[0023] Furthermore, it is preferable that the component A has a decomposition point or phase transition point between 50°C and 300°C. This suppresses the release of metal ions from component A during preparation of the crosslinkable polymer composition or before use, thereby suppressing the progress of crosslinking and achieving high storage stability for the crosslinkable polymer composition, such as suppressing changes in the quality of the crosslinkable polymer composition at low temperatures such as room temperature. On the other hand, component A undergoes decomposition or phase transition at a moderate temperature, facilitating the release of metal ions from component A, and the crosslinking reaction can proceed at a temperature at which component B does not deteriorate.

[0024] The component A preferably has a decomposition point or phase transition point at a temperature equal to or higher than the flow initiation temperature of the component B. This allows the release of metal ions from the component A and the resulting crosslinking of the component B to occur while the component B has already acquired fluidity. Therefore, the flow of the component B can be utilized to enhance the dispersibility of the component A in the component B, resulting in a crosslinked product in which crosslinking points are formed with high spatial uniformity. Furthermore, during the preparation or molding of the crosslinkable polymer composition, the release of metal ions from the component A and the resulting crosslinking of the component B are unlikely to occur unintentionally.

[0025] The component A is preferably a metal complex containing a ligand having the structure of the following formula (1). [ka] Here, R1 and R2 each independently represent a hydrocarbon group having 1 to 8 carbon atoms, and R3 represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. This also includes cases where at least two of R1, R2, and R3 are connected to each other by a ring structure.

[0026] The β-diketonato ligand represented by formula (1) is a bidentate ligand, and has a superior effect of stabilizing metal ions compared to monodentate ligands or ligands that form a crosslinked coordination structure. This suppresses the release of metal ions from component A during the preparation of the crosslinkable polymer composition or before use of the crosslinkable polymer composition, thereby achieving particularly high storage stability.

[0027] The metal ions liberated from the A component are preferably ions of at least one of alkaline earth metals, aluminum, zinc, titanium, and zirconium. The ions of the above metals all have a valence of 2 or more, and are likely to form stable crosslinked structures between the polymer chains of the B component. Furthermore, the above metal ions belong to the hard acids in the HSAB rule and have a high ionization tendency, forming stable bonds with the substituents of the B component. For these reasons, they are suitable as metals for forming crosslinked bodies.

[0028] The metal ions liberated from Component A are preferably ions of at least one of aluminum and zirconium. When these metal ions are liberated from Component A, they facilitate the formation of a particularly stable crosslinked structure with Component B. Furthermore, this provides high storage stability at relatively low temperatures before crosslinking.

[0029] The substituent of the component B may be at least one of a carboxylic acid group, an acid anhydride group, and a phosphate group. These substituents are likely to form ionic bonds with metal ions released from the component A. Furthermore, since the substituent is an acidic group with relatively low polarity, it is less likely to cause phase separation in the main chain or side chain of the component B, and a crosslinked structure with high spatial uniformity can be formed.

[0030] The substituent of component B is preferably bonded to the main chain via an alkyl or alkylene group having one or more carbon atoms, which increases the degree of freedom of thermal movement at the crosslinked sites and makes the crosslinked points more likely to move when heated, resulting in particularly high remoldability.

[0031] Preferably, the component B does not contain an electron-withdrawing group in the main chain. This prevents the side chain substituents from forming ionic bonds with the metal ions derived from the component A due to competition with the electron-withdrawing group in the main chain. The substituents in the main chain are unlikely to form stable crosslinked structures with metal ions due to steric hindrance. Even if a crosslinked structure is formed, the degree of freedom of movement of the crosslinked sites is reduced, making it difficult to obtain high remoldability in the crosslinked product.

[0032] The crosslinkable polymer composition preferably contains 0.1 to 30 parts by mass of the A component, with the total of the A and B components being 100 parts by mass. By including a sufficient amount of the A component, the crosslink density increases, and the crosslinkable polymer composition exhibits excellent crosslinkability. Meanwhile, the effects of including a large amount of the A component in the material before and after crosslinking can be easily avoided.

[0033] The crosslinked polymer material according to the present disclosure includes a crosslinked product of the crosslinkable polymer composition according to the present disclosure, which is configured as a crosslinked product obtained by crosslinking the B component with a metal ion liberated from the A component. The crosslinked product formed by crosslinking the B component via the metal ion liberated from the A component has a crosslinking point at the position of the electron-withdrawing substituent introduced into the side chain of the B component, and has a flow initiation temperature in the range of 190°C to 300°C. Therefore, the crosslinked polymer material has both high heat resistance and remoldability by heating. Furthermore, the B component has a high hardness of 50 or more Shore D, which makes the crosslinked polymer material highly wear-resistant.

[0034] The insulated wire according to the present disclosure includes a conductor and an insulating coating made of the cross-linked polymer material according to the present disclosure and covering the outer periphery of the conductor. Because the insulating coating is made of the cross-linked polymer material according to the present disclosure, this insulated wire exhibits high heat resistance and is less likely to undergo irreversible deformation even if the conductor generates heat due to current flow. Meanwhile, by heating the insulating coating to a sufficient temperature, the insulating coating can be re-fluidized and reshaped, allowing for a change in shape of the insulating coating. For example, when the conductor is deformed, the insulating coating can easily be deformed to follow the shape of the conductor. Furthermore, the insulating coating has high abrasion resistance, making the insulated wire suitable for use in locations where it comes into contact with other components.

[0035] Here, the conductor may be formed by twisting together a plurality of strands of wire, and the insulated wire may have a flattened portion where the cross section of the conductor perpendicular to the axial direction is flattened. A wire having a flattened portion is required from the viewpoint of space saving, etc. The flattened portion can be easily formed by applying a compressive force to a circular cross section of a normal insulated wire by heating the insulating coating, taking advantage of the reshapeability of the insulating coating. Conversely, by applying a force to a wire with a flattened portion while heating the insulating coating in a direction that eliminates the flattened shape, the insulated wire can be deformed to a state having a different cross section, such as a circular cross section. Thus, by using an insulated wire having a conductor formed by twisting together a plurality of strands of wire and that is easily deformed by applying a force, and an insulating coating that can be reversibly transformed into a reshapeable state by heating, deformation between a state with low flatness, such as a circular cross section, and a flat state can be easily performed in both directions. For example, a variety of insulated wires can be obtained by using a common insulated wire and deforming necessary portions into a required shape, such as a flat shape, depending on the installation location and application.

[0036] A wire harness according to the present disclosure includes the insulated wire according to the present disclosure. Since the insulated wire according to the present disclosure has an insulating coating that is excellent in heat resistance, remoldability, and abrasion resistance as described above, these properties can also be utilized in the wire harness.

[0037] [Details of the embodiments of the present disclosure] A crosslinkable polymer composition, a crosslinked polymer material, an insulated wire, and a wire harness 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.

[0038] [1] Crosslinkable polymer composition and crosslinked polymer material A crosslinkable polymer composition according to an embodiment of the present disclosure includes a component A from which metal ions are liberated by heat, and a component B composed of an organic polymer having a Shore D hardness of 50 or greater and having electron-withdrawing substituents on its side chains capable of forming ionic bonds with the metal ions liberated from the component A. The crosslinkable polymer composition according to this embodiment is heated to form a crosslinked product in which the metal ions liberated from the component A crosslink the component B, thereby constituting a crosslinked polymer material according to an embodiment of the present disclosure. The crosslinked product has a flow initiation temperature of 190°C or higher and 300°C or lower.

[0039] (1) Properties of crosslinkable polymer compositions and crosslinked polymer materials Before describing in detail each component constituting the crosslinkable polymer composition, the properties of the crosslinkable polymer composition and crosslinked polymer material will first be described. The crosslinkable polymer composition according to this embodiment contains component A, which liberates metal ions when heated, and component B, which has a substituent capable of forming an ionic bond with the metal ion. When the crosslinkable polymer composition containing these components is heated, metal ions are liberated from component A. As shown in FIG. 1A, the liberated metal ions then form ionic bonds with the substituents of component B, and the organic polymer chains of component B are crosslinked via these ionic bonds. Note that in FIG. 1A and in FIGS. 1B and 1C, which will be described later, divalent metal ions M are used as the metal ions. 2+Assuming that the substituent of component B is a carboxylic acid group in an anionic state (COO - ) is assumed. The polymer chain of component B is shown as a broken line.

[0040] Component A liberates metal ions upon heating. Until the temperature at which component A liberates metal ions due to decomposition or phase transition is reached, the liberation of metal ions from component A does not occur, and crosslinking of the organic polymer in component B due to the formation of ionic bonds does not proceed. Therefore, the crosslinkable polymer composition according to this embodiment is in a relatively fluid state at low temperatures at which the liberation of metal ions from component A and the resulting crosslinking of component B do not occur, and can be easily molded into a desired shape by extrusion molding or the like. After molding the crosslinkable polymer composition into a desired shape, a crosslinked body can be formed by heating to liberate metal ions from component A and crosslinking component B. The crosslinked body has improved heat resistance compared to the state before crosslinking due to the crosslinking of adjacent polymer chains in component B. In the crosslinked body, the organic polymer chains of component B are crosslinked via ionic bonds, and the bonding force is stronger than van der Waals forces, effectively improving the heat resistance and mechanical toughness of the crosslinked body.

[0041] In particular, the crosslinkable polymer composition according to this embodiment forms a crosslinked polymer material with high heat resistance because the crosslinked product has a flow initiation temperature of 190°C or higher. In other words, the crosslinked polymer material formed through crosslinking is less likely to experience increased fluidity and associated irreversible deformation at temperatures below 190°C. A heat resistance temperature of 190°C is generally desired for insulating coatings for insulated electric wires for automobiles, and the crosslinkable polymer composition according to this embodiment can be suitably used to form insulating coatings for insulated electric wires for automobiles, as described in detail below. From the perspective of effectively enhancing the heat resistance of the crosslinked polymer material, the flow initiation temperature of the crosslinked product is preferably 200°C or higher, and even more preferably 220°C or higher. The flow initiation temperature of the crosslinked product and of component B, which will be described later, refers to the temperature at which a solid material begins to exhibit fluidity when heated. For example, as shown in the examples below, it can be measured as the temperature at which an indenter can penetrate a sheet-like material. Alternatively, the melting point or flow point of the material (the lower of the two, if both exist) can be considered the flow initiation temperature.

[0042] Furthermore, in the crosslinkable polymer composition according to this embodiment, the crosslinked structure between the polymer chains of component B is formed by a reversible ionic bond with a metal ion, rather than an irreversible covalent bond formed in the case of electron beam crosslinking or silane crosslinking, and therefore the crosslinked polymer material formed is remoldable. In other words, by heating a crosslinked polymer material formed through crosslinking, the crosslinked polymer material regains its fluidity and can be molded into a shape different from that before heating by applying an external force, etc.

[0043] The reshapeability of crosslinked polymer materials can be explained by the following mechanism. When a crosslinked polymer, in which the polymer chains of component B are crosslinked with metal ions, is not heated and is kept at room temperature or near room temperature, the crosslinking points of the metal ions are localized at certain positions within the chains of component B, as shown in Figure 1A. However, when the crosslinked polymer is heated, the molecular motion of component B becomes active due to heat, and as shown in Figure 1B, active thermal motion occurs at the crosslinked sites where the substituents of component B form ionic bonds with the metal ions, as well as in their vicinity. When the crosslinked polymer is heated to a higher temperature, the molecular motion of component B becomes even more active, allowing the crosslinking points mediated by the metal ions to migrate to nearby sites (the positions of other substituents), resulting in delocalization of the crosslinking points. This delocalization of the crosslinking points results in the formation of a state in which multiple substituents within the same molecular chain of component B simultaneously coordinate to a single metal ion (multidentate structure), as shown in Figure 1C. This increased thermal motion in component B and the subsequent migration of the crosslinking points make the crosslinked polymer flowable. In these states, the crosslinked polymer material can be reshaped by applying an appropriate external force to the material. The activation of thermal motion at crosslinking sites and the delocalization of crosslinking sites are reversible phenomena; cooling the reshaped crosslinked polymer material returns it to a localized state of crosslinking sites, returning it to a thermally stable crosslinked state. Repeated heating and cooling also allows the crosslinked polymer material to be repeatedly reshaped. The activation of thermal motion at crosslinking sites and the delocalization of crosslinking sites due to heating can be confirmed, for example, by infrared absorption spectroscopy. Typically, the activation of thermal motion at crosslinking sites appears in the spectrum as a broadening of the absorption peak of the substituents forming the crosslinked structure, and the delocalization of crosslinking sites appears in the spectrum as the growth of a new peak corresponding to multidentate crosslinking.

[0044] Furthermore, in the crosslinkable polymer composition according to this embodiment, the substituent capable of forming an ionic bond with a metal ion is contained in the side chain of component B, rather than in the polymer main chain. This allows for high freedom of movement at the crosslinked sites when a crosslinked structure is formed via the metal ion. Therefore, in the crosslinked product, thermal movement at the crosslinked sites and migration of the crosslinking points are particularly likely to occur. This allows the crosslinked polymer material to exhibit high remoldability when heated.

[0045] In particular, in the crosslinkable polymer composition according to this embodiment, the flow initiation temperature of the crosslinked body formed is suppressed to 300° C. or less, and therefore remolding can be easily performed by heating the crosslinked polymer material up to 300° C. From the viewpoint of effectively enhancing remoldability, the flow initiation temperature of the crosslinked body is preferably 280° C. or less, and more preferably 250° C. or less.

[0046] As described above, the crosslinkable polymer composition according to this embodiment contains component A, which liberates metal ions upon heating, and component B, which contains a substituent in its side chain capable of forming an ionic bond with the metal ion. Furthermore, the crosslinked product obtained by crosslinking component B with the metal ions liberated from component A has a flow initiation temperature in the range of 190°C to 300°C, thereby providing a crosslinked polymer material that combines high heat resistance and remoldability. Therefore, by molding the crosslinkable polymer composition into a desired shape by extrusion molding or the like and then crosslinking, a crosslinked polymer material with high heat resistance can be obtained, and the crosslinked polymer material can be reheated to utilize its remoldability. Because of these properties, the crosslinkable polymer composition according to this embodiment can be suitably used to construct components that require high heat resistance and are advantageously remoldable, such as insulating coatings for insulated electric wires. Furthermore, as another indicator of the sufficient heat resistance improvement effect of crosslinking in a crosslinked polymer material, the flow initiation temperature of the crosslinked polymer material is preferably at least 5°C, or even at least 10°C, higher than the flow initiation temperature of component B alone.

[0047] Furthermore, in the crosslinkable polymer composition according to this embodiment, component B has a high hardness of 50 or more Shore D. Therefore, the crosslinked material obtained by crosslinking component B via metal ions also has high material strength and exhibits high abrasion resistance. Unlike electron beam crosslinking or silane crosslinking, which requires the introduction of silane groups, crosslinking by ionic bonds with metal ions does not significantly impair the mechanical properties of component B, and the high mechanical strength of component B is fully exhibited as a characteristic of the crosslinked material. Furthermore, crosslinking via metal ions further improves abrasion resistance compared to an uncrosslinked component B. If component B has a Shore D hardness of 50 or more, the crosslinked polymer material obtained by crosslinking component B is likely to have high mechanical strength, such as a Shore D hardness of 50 or more, or even 55 or more, and a tensile modulus of elasticity of 800 MPa or more. Although there are no particular restrictions on the upper limits of the hardness and tensile modulus of the crosslinked polymer material, from the viewpoint of ensuring the desired flexibility in components made of polymer materials, such as insulating coatings for insulated electric wires, it is desirable that the Shore D hardness be 90 or less and the tensile modulus be 1600 MPa or less. Furthermore, as mentioned above, crosslinking by ionic bonding via metal ions does not significantly impair the mechanical properties of Component B, and the hardness and tensile modulus of the crosslinked polymer material preferably do not increase by more than 30% compared to those of the uncrosslinked Component B. Furthermore, it is more desirable that they do not increase by more than 20%.

[0048] As described above, in the crosslinkable polymer composition according to this embodiment, in order to obtain a crosslinked polymer material that combines high heat resistance and remoldability through crosslinking, it is important that the crosslinked product has a flow initiation temperature within a predetermined range. The flow initiation temperature of the crosslinked product is determined by the type of metal ion released from component A, the polymer main chain and side chain of component B, the type and structure of the substituents, the ratio of components A and B, and other factors. Furthermore, in order to ensure that the crosslinked polymer material obtained through crosslinking has high abrasion resistance, it is important that component B contained in the crosslinkable polymer composition has a high hardness equal to or greater than a predetermined level. The hardness of component B is also determined by the structure of component B. The preferred structures and properties of each component are described below in order.

[0049] (2) Component A Component A is a component that releases metal ions when heated. "When heated" refers to heating, and is assumed to be at temperatures higher than room temperature. "Metal ions are released" refers to the decomposition or phase transition of component A, which causes the metal ions to be released from component A. The metal ions released from component A cause crosslinking of component B.

[0050] Component A preferably has a decomposition point or phase transition point of 50°C or higher. This helps to suppress the release of metal ions from component A during preparation of the crosslinkable polymer composition or before use (before crosslinking) of the crosslinkable polymer composition, thereby inhibiting the progress of crosslinking of component B, resulting in excellent storage stability of the crosslinkable polymer composition. In other words, when mixing components A and B at low temperatures (e.g., below 50°C) to prepare the crosslinkable polymer composition, when storing the prepared crosslinkable polymer composition, or when molding the crosslinkable polymer composition into a desired shape by extrusion molding or the like, unintended release of metal ions from component A and the resulting crosslinking of component B are unlikely to occur, leading to quality degradation of the crosslinkable polymer composition. Having a decomposition point or phase transition point of component A of 60°C or higher, or even 70°C or higher, further enhances the effect of improving storage stability.

[0051] On the other hand, it is preferable that Component A has a decomposition point or phase transition point of 300°C or less. This makes it difficult for Component B to degrade at a temperature lower than that at which metal ions are liberated from Component A, and makes it easier to crosslink unaltered Component B with metal ions. Furthermore, decomposition or phase transition of Component A at a moderate temperature facilitates the liberation of metal ions from Component A, resulting in a crosslinkable polymer composition with an excellent crosslinking rate. From these perspectives, it is more preferable that Component A has a decomposition point or phase transition point of 200°C or less, more preferably 150°C or less, or even 120°C or less.

[0052] Furthermore, it is preferable that component A has a decomposition point or phase transition point at a temperature equal to or higher than the flow initiation temperature of component B, which will be described later. This allows crosslinking of component B by the metal ions liberated from component A to proceed while component B has already acquired fluidity at the temperature at which component A liberates metal ions. Therefore, by utilizing the flow of component B, crosslinking can proceed while the metal ions are well dispersed in component B, making it easier to obtain a crosslinked polymer material with a highly uniform structure in which crosslinking points by metal ions are spatially distributed with high uniformity. Furthermore, unintended liberation of metal ions from component A and the resulting crosslinking of component B during preparation or molding of the crosslinkable polymer composition are unlikely to occur. More preferably, component A has a decomposition point or phase transition point higher than the flow initiation temperature of component B, and even more preferably, component A has a decomposition point or phase transition point at a temperature 10°C or higher than the flow initiation temperature of component B. The decomposition point or phase transition point of component A is represented by 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. When component A has both a phase transition point and a decomposition point, or when it has multiple phase transition points, the lowest of these (the lowest) is treated as the "decomposition point or phase transition point."

[0053] The metal species of the metal ions liberated from component A is not particularly limited, but alkaline earth metals, aluminum, zinc, titanium, zirconium, etc. can be suitably used. The metal ions liberated from component A are preferably ions of at least one of these metals. These metal ions have a valence of 2 or more, and form ionic bonds with the substituents of component B, which facilitates the formation of a stable crosslinked structure between the polymer chains of component B. Furthermore, the metals listed above are classified as hard acids according to the HSAB rule and are metals with a relatively high ionization tendency, and therefore form stable bonds with the substituents of component B, making them 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 the crosslinked product. Therefore, it is preferable that the metal ions liberated from Component A be at least one of aluminum and zirconium ions. Component A containing aluminum or zirconium has a relatively high stability, and when mixed with Component B, the formation of a crosslinked structure does not proceed easily, providing high storage stability to the crosslinkable polymer composition. On the other hand, when Component A is heated, the metal ions are relatively easily liberated, forming a crosslinked product. For example, as shown in the examples below, the phase transition onset temperature of zirconium(IV) acetylacetonate (Zr-AA) is 180°C, which is high among various acetylacetonate complexes. On the other hand, the phase transition onset temperature (the temperature at which the baseline change in DSC is initiated) of aluminum(III) acetylacetonate is not particularly 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 progresses significantly.

[0055] Furthermore, when at least one of aluminum and zirconium ions is used as the metal ion liberated from Component A, the flow initiation temperature of the crosslinked body is higher than when, for example, titanium is used, resulting in a crosslinked polymer material with excellent heat resistance. Because aluminum and zirconium are not as easily oxidized as titanium, the efficiency of the crosslinking reaction is less likely to decrease due to the presence of an oxidation pathway. Furthermore, compared to alkaline earth metals such as calcium, aluminum and zirconium are not as hard as alkaline earth metals, so they are more easily dispersed uniformly in Component B. Furthermore, compared to zinc, aluminum and zirconium tend to have a higher decomposition temperature for Component A formed in the form of a metal complex, etc., resulting in high storage stability.

[0056] Furthermore, when a member that comes into contact with a metal member is constructed using the crosslinkable polymer composition according to this embodiment, if the metal species contained in the crosslinkable polymer composition is the same as the metal species that is the main component of the metal member, the influence of the presence of the metal member on the formation and stability of the crosslinked structure at the interface between the metal member and the polymer material can be easily minimized. For example, when an insulating coating that covers an aluminum or aluminum alloy wire conductor in an insulated wire is formed using the crosslinkable polymer composition according to this embodiment, the metal ions liberated from Component A can be aluminum.

[0057] Ions of any metal, including aluminum and zirconium, not limited to the metal species listed above as preferred, can be used as the metal to be liberated from component A, as long as they can form ionic bonds with the substituents of component B to crosslink component B and provide a crosslinked product with a flow initiation temperature of 190°C or higher and 300°C or lower. However, transition metals such as iron, nickel, and copper tend to provide crosslinked products with a flow initiation temperature higher than the above range. This is thought to be because when crosslinked products are formed using ions of metals with a wide range of oxidation states or low ionization tendency, such as transition metals, the crosslinking points tend to be less likely to migrate when heated (see Figure 1C). Furthermore, the metal ions liberated from component A may be monoatomic ions of the metal or polyatomic ions (metal-containing ions) formed by bonding a metal atom to another atom. However, monoatomic ions of the metal are preferred from the viewpoint of forming stable ionic bonds with the substituents of component B.

[0058] Component A 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, and liberation of metal ions from component A is suppressed during preparation of the crosslinkable polymer composition, before use of the crosslinkable polymer composition, and when molding the crosslinkable polymer composition into a desired shape. At the same time, when crosslinking the crosslinkable polymer composition, metal ions are easily liberated from component A by heat.

[0059] Ligands constituting the metal complex include monodentate ligands with one coordination site and multidentate ligands with two or more coordination sites. Due to the chelating effect, metal complexes formed with multidentate ligands are more stable than metal complexes formed with monodentate ligands or metal complexes formed with ligands having a bridged coordination structure, such as alkoxide ligands. Therefore, it is preferable that component A is a metal complex containing a multidentate ligand. Coordination with a multidentate ligand is more effective at stabilizing metal ions than coordination with a monodentate ligand or coordination with a ligand having a bridged coordination structure, and more effectively suppresses the release of metal ions from component A during the preparation of the crosslinkable polymer composition, before use, and during molding of the crosslinkable polymer composition.

[0060] Among polydentate ligands, bidentate β-diketonato ligands (1,3-diketonato ligands) can be preferably used. β-diketonato ligands are particularly effective in stabilizing metal ions. Furthermore, metal complexes having β-diketonato ligands are easily dispersed in organic polymers, making them suitable for dispersing component A in component B and forming highly uniform crosslinking points. β-diketonato ligands are represented by the following general formula (1):

[0061] [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 a resonance structure, resulting in the structure of formula (1).

[0062] 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.

[0063] 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.

[0064] In the crosslinkable polymer composition, the content of component A is preferably 0.1 parts by mass or more, based on 100 parts by mass of the total of components A and B. By incorporating a sufficiently large amount of component A relative to component B, the crosslink density in the crosslinked product is increased, thereby effectively improving heat resistance and abrasion resistance. From the perspective of enhancing the heat resistance improvement effect, the content of component A is preferably 1.0 parts by mass or more, and even more preferably 2.0 parts by mass or more, based on the 100 parts by mass. On the other hand, the content of component A is preferably 30 parts by mass or less, based on the 100 parts by mass. This makes it easier to avoid the effects of incorporating a large amount of component A, such as separation or precipitation of component A before crosslinking and embrittlement of the polymer material after crosslinking. Furthermore, by not incorporating an excessive amount of component A in the crosslinkable polymer composition, the high mechanical strength of component B can be more easily exhibited as a property of the entire crosslinked polymer material. From the viewpoint of enhancing these effects, the content of component A is more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass.

[0065] (3)B component Component B is a component composed of an organic polymer having a side chain and a Shore D hardness of 50 or more, and the side chain contains an electron-withdrawing substituent that can form an ionic bond with a metal ion released from Component A. The substituent does not necessarily have to be electron-withdrawing to form an ionic bond with a metal ion released from Component A, but being electron-withdrawing allows for the formation of a stable ionic bond with the metal ion. Therefore, when Component B is crosslinked with a metal ion in the crosslinkable polymer composition, a stable crosslinked structure is formed, and the crosslinked product is likely to exhibit high heat resistance.

[0066] 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. The substituents may be one type or two or more types, but at least one of the substituents listed above is preferred. Acid anhydride groups, such as maleic anhydride groups, are particularly suitable. The substituents listed above are advantageous in that they easily form ionic bonds with metal ions released from component A. Furthermore, all of the substituents listed above are acidic groups with relatively low polarity, making them less likely to undergo phase separation with respect to the main chain or side chain of component B, and allowing for the formation of highly uniform crosslinked structures within the structure of component B. 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, making them less suitable as substituents for component B than the substituents listed above as being suitable.

[0067] As explained above, in component B, the substituents that form ionic bonds with metal ions are contained in the side chains rather than the polymer main chain, thereby maintaining high freedom of movement at the crosslinked sites when a crosslinked structure is formed. As a result, the crosslinked polymer material has high reshapeability. The structure and length of the side chains are not particularly limited, but to enhance their effectiveness, it is preferable for the substituents to be attached to the main chain via an alkyl or alkylene group having one or more carbon atoms. Alternatively, the substituents may be attached to the main chain via a heteroatom such as an oxygen atom. The substituents may be introduced at the terminal or middle of the side chain, but to effectively increase the freedom of movement at the crosslinked sites, it is preferable for them to be introduced at the terminal. There is no particular upper limit on the number of carbon atoms in the side chain, but to minimize the impact on the physical properties of the main chain, it is preferable for the number of carbon atoms connecting the main chain and the substituent to be four or less. When the substituents are carboxylic acid groups and phosphate groups, particularly preferred side chain structures are represented by the following formulas (2) and (3), respectively.

[0068] [ka] [ka] Here, R4 is the main chain, R5 is an oxygen atom or an alkyl or alkylene group having one or more carbon atoms, and R6 is an alkyl or alkylene group having one or more carbon atoms. Multiple electron-withdrawing substituents may be bonded to the main chain via a common R5 or R6. Furthermore, multiple electron-withdrawing substituents may form an anhydride together.

[0069] In Component B, the electron-withdrawing substituent may be present in either the main chain or the side chain, as long as it is present in the side chain. However, it is preferable that the main chain does not contain electron-withdrawing groups. This is because the presence of electron-withdrawing groups in the main chain may prevent the electron-withdrawing groups in the side chain from forming a crosslinked structure through ionic bonding with metal ions. Because electron-withdrawing groups in the main chain are susceptible to significant steric hindrance, they are less likely to effectively contribute to crosslinking through the formation of ionic bonds with metal ions, and crosslinking is less effective in improving heat resistance. Furthermore, even if a crosslinked structure is formed at the electron-withdrawing group in the main chain, the degree of freedom of movement at the crosslinked site is reduced, making it difficult to achieve high remoldability. Examples of electron-withdrawing groups that should not be present in the main chain of Component B include carbonyl groups when the main chain is composed of a copolymer of (meth)acrylic acid, hydrolyzable groups when the main chain contains an ester structure such as vinyl acetate, and halogen atoms.

[0070] In Component B, the content of the substituents contained in the side chains is not particularly limited, but from the viewpoint of ensuring physical properties through crosslinking, it is preferably 0.01% by mass to 10% by mass relative to the total mass of Component B. It is more preferably 0.1% by mass to 5% by mass, and even more preferably 0.2% by mass to 3% by mass. The content of the above-mentioned substituents in Component B 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 of the substituent.

[0071] The organic polymer of Component B is an organic polymer such as a resin, rubber, or elastomer. From the viewpoints of moldability and mechanical strength, Component B is preferably composed of a thermoplastic resin. In particular, from the viewpoint of obtaining excellent mechanical strength, such as high hardness, it is preferable that the main chain of Component B is composed of an olefin-based polymer. The olefin-based polymer may be a homopolymer such as polyethylene or polypropylene, or a copolymer such as an ethylene-α-olefin copolymer. A configuration in which the main chain of Component B is composed of polypropylene is particularly preferable. Because polypropylene has high crystallinity, Component B tends to have high mechanical properties, such as a Shore D hardness of 50 or more. A main chain composed of an olefin-based polymer not only has high mechanical properties, such as high hardness, but also is less likely to affect the formation of crosslinking points in the side chains, the activation of molecular motion at the crosslinked sites due to heating, or the movement of the crosslinking points. The high heat resistance and remoldability brought about by these phenomena in the side chains are effectively exhibited as properties of the entire crosslinked product of Component B. These effects are particularly pronounced when the main chain of Component B is composed of an olefin-based polymer.

[0072] As described above, Component B has a high Shore D hardness of 50 or more. As a result, crosslinking occurs via ionic bonds with the metal ions derived from Component A, resulting in a crosslinked polymer material with excellent mechanical strength, such as abrasion resistance. From the perspective of further increasing the mechanical strength of the crosslinked polymer material, it is more preferable for Component B to have a Shore D hardness of 60 or more, 70 or more, or 80 or more. From the perspective of the mechanical strength of the resulting crosslinked polymer material, there is no particular upper limit to the hardness of Component B. However, to ensure the flexibility required for products requiring bending, such as insulating coatings for insulated electric wires, it is preferable to keep the Shore D hardness at 95 or less. The Shore D hardness of Component B and the crosslinked polymer material can be measured in accordance with JIS K 6253.

[0073] Component B preferably has a flow initiation temperature in the range of 50°C or higher and 190°C or lower. This makes it easy to obtain a crosslinked product having a flow initiation temperature of 190°C or higher and 300°C or lower through crosslinking with metal ions liberated from component A. Furthermore, when the crosslinkable polymer composition before crosslinking is molded into a desired shape by extrusion molding or the like, high moldability is obtained. The flow initiation temperature of component B is more preferably 80°C or higher and 160°C or lower.

[0074] The crosslinkable polymer composition according to this embodiment may contain additives such as flame retardants, copper inhibitors, antioxidants, and colorants in addition to the above-described components A and B, as long as they do not impair the functionality of the material. Furthermore, the polymer component may contain polymers other than component B, but the content of these polymers is preferably kept lower than the content of component B. Even when the polymer component contains polymers other than component B, the overall hardness of the polymer components is preferably 50 or higher in Shore D. Furthermore, each polymer component other than component B should also have a Shore D hardness of 50 or higher. More preferably, the crosslinkable polymer composition contains only component B as the polymer component. Furthermore, compounds in the following groups (a) to (f) can be listed as components that should not be included in the crosslinkable polymer composition. These include (a) silane coupling agents, (b) epoxy compounds, (c) isocyanates and isothiocyanate compounds, (d) photoradical generators and thermal radical generators, (e) chlorine compounds and bromine compounds, and (f) volatile organic solvents. When a crosslinkable polymer composition contains compounds from groups (a) to (d), unintended chemical reactions, such as crosslinking of component B through a reaction separate from the crosslinking reaction mediated by metal ions liberated from component A, or cleavage of the main chain of component B, may occur upon heating. This may result in insufficient heat resistance and remoldability of the crosslinkable polymer composition. Furthermore, when a crosslinkable polymer composition contains a compound from group (e), heating may result in coloration or the generation of corrosive gases. When a crosslinkable polymer composition contains a compound from group (f), ignition or the generation of bubbles may occur during molding of the composition.

[0075] The crosslinkable polymer composition can be prepared by mixing component A, component B, and any additional components that are added as needed. Mixing can be performed, for example, by heating and kneading the components, or by dissolving the components in an organic solvent and heating and stirring. Furthermore, when using the crosslinkable polymer composition, the crosslinkable polymer composition can be appropriately heated and then molded into any desired shape by extrusion molding or other methods. The heating temperature should be higher than the flow initiation temperature of component B but lower than the temperature at which component A liberates metal ions through decomposition or phase transition. Furthermore, by heating the molded crosslinkable polymer composition to a temperature above the temperature at which component A liberates metal ions through decomposition or phase transition, crosslinking of component B by the metal liberated from component A progresses, resulting in a crosslinked polymer material containing a crosslinked product. The formed crosslinked polymer material can then be heated above the flow initiation temperature of the crosslinked product, allowing the crosslinked polymer material to acquire fluidity and become remoldable. Remolding can be repeated reversibly. The crosslinkable polymer composition according to the present embodiment can form a crosslinked structure simply by heating, and therefore the crosslinking process can be carried out with simpler equipment than when electron beam crosslinking or silane crosslinking is used. The remolding process can also be carried out by applying an appropriate external force while heating, and therefore can be carried out with similarly simple equipment.

[0076] [2] Insulated wires and wiring harnesses The crosslinked polymer material formed from the crosslinkable polymer composition according to this embodiment can be used to construct any desired component. However, by taking advantage of its high heat resistance, remoldability, and high abrasion resistance, it can be suitably used as a constituent material for insulated wires and wiring harnesses for automobiles and the like. Insulated wires and wiring harnesses are prone to heat generation when current is passed through metal components, such as wire conductors. Therefore, polymer materials placed near these metal components are required to have high heat resistance, such as not undergoing irreversible deformation when heated. Furthermore, when contact is expected between the polymer material constituting the insulated wire and other components, such as devices placed near the insulated wire or other insulated wires bundled together, the polymer material is desired to have high abrasion resistance. On the other hand, there are also cases where a polymer material once molded into a predetermined shape needs to be remolded due to deformation of the insulated wire or changes in the configuration of the wiring harness.

[0077] In the insulated wire and the wire harness, the specific portion to which the crosslinked polymer material according to the embodiment of the present disclosure is applied is not particularly limited, and examples thereof include an insulating coating that covers the outer periphery of the wire conductor of the insulated wire, an exterior material that bundles a plurality of insulated wires in the wire harness, a wire protection material, etc. Among these, it is preferable that the insulating coating of the insulated wire be made of the crosslinked polymer material according to the embodiment of the present disclosure.

[0078] FIG. 2 shows an example of an insulated wire according to an embodiment of the present disclosure in a cross section perpendicular to the axial direction. The insulated wire 1 shown in FIG. 2 includes a conductor 2 and an insulating coating 3 that covers the outer periphery of the conductor 2. The configuration of the conductor 2 is not particularly limited, but it is configured as a stranded conductor in which a plurality of wires 21 are twisted together. In the example shown, the insulated wire 1 is configured to have a flat portion, and the cross section of the conductor 2 has a flat shape (a shape elongated in the width direction). The insulating coating 3 is made of the cross-linked polymer material according to the embodiment of the present disclosure described above. The insulating coating 3 also has a flat cross-sectional outer shape that follows the shape of the conductor 2.

[0079] In the insulated wire 1, heat is generated when a current is applied to the conductor 2, and the insulating coating 3 also heats up. However, the insulating coating 3 is made of the cross-linked polymer material according to the embodiment of the present disclosure described above and has high heat resistance. Therefore, even if the insulating coating 3 is heated to a temperature of, for example, 190°C or less, it is unlikely to be affected by heat, such as irreversible deformation. Furthermore, because the cross-linked polymer material has high abrasion resistance, the insulating coating 3 is unlikely to be damaged by abrasion even if it comes into contact with other components.

[0080] The insulated wire 1 has a flat portion, which reduces the space required for wiring and improves space-saving performance. The remoldability of the cross-linked polymer material constituting the insulating coating 3 allows the insulated wire 1 to be easily formed using a conventional, generally circular insulated wire (round wire). For example, the flat portion can be easily formed by applying a compressive force in one direction to a round wire having an insulating coating 3 made of a cross-linked cross-linked polymer material according to an embodiment of the present disclosure while heating the round wire to a temperature above the flow temperature of the cross-linked body. The wire conductor 2 is configured as a stranded conductor, so it can be easily deformed by the application of force. The insulating coating 3, which is in a fluid state upon heating, can also be easily deformed following the deformation of the wire conductor 2. The insulating coating 3 is then allowed to cool and return to its original, stable cross-linked state. Alternatively, in the already formed flattened portion, by applying a compressive force from both sides in the width direction while heating the insulating coating 3 to a temperature equal to or higher than the flow temperature of the cross-linked body, the flattened portion can be returned to the shape of a round electric wire or a similar shape with a low degree of flatness. In this case, too, the insulating coating 3 deforms to a shape with a low degree of flatness in accordance with the deformation of the electric wire conductor 2.

[0081] In this way, since the insulating coating 3 is made of a material having reversible reshapeability, deformation of the insulated electric wire 1 into any shape, such as bidirectional deformation between a flat cross-sectional shape and a substantially circular cross-sectional shape, can be easily achieved by deforming the insulating coating 3 in accordance with the wire conductor 2. For example, the cross-sectional shape of the insulated electric wire can be changed with a high degree of freedom, such as by forming flat portions on a round electric wire only in areas where space saving is required in the wiring path. This makes it possible to produce a variety of insulated electric wires having flat portions in different locations using a common electric wire as raw material. The insulated electric wire may be used alone, or may be used in the form of a wire harness including the insulated electric wire by connecting components such as connecting terminals or bundling it with other insulated electric wires. [Example]

[0082] Examples are shown below. The present invention is not limited to these examples. Unless otherwise specified, sample preparation and evaluation were carried out at room temperature in the atmosphere.

[0083] <Sample preparation> To prepare samples A1 to A8 and samples B1 to B12, the components A and B were added to xylene in an amount five times their total weight according to the blending compositions (units: parts by mass) shown in Tables 1 and 2, and dispersed and mixed under vigorous stirring at 80°C for 30 minutes. The mixture was then vacuum dried and press-molded at 250°C for 10 minutes to prepare sample sheets 2 mm thick. At least in samples A1 to A8, crosslinking of component B by metal ions derived from component A occurred upon heating to 250°C. The progress of crosslinking was confirmed by infrared absorption spectroscopy. Specifically, the C=O stretching vibration (1790 cm) of the acid anhydride present in the infrared absorption spectrum of component B before crosslinking was detected. -1 around 1720cm) and the C=O stretching vibration of carboxylic acids -1 It was confirmed that the absorption of α-glucan (near α-glucan) disappeared or decreased with crosslinking.

[0084] The materials used are as follows: (1) Component A Below, the material types are listed in parentheses, along with the decomposition points or phase transition points obtained by DSC measurement. Ca-AA: Calcium(II) acetylacetonate (110°C) Zn-AA: Zinc(II) acetylacetonate (105°C) Al-AA: Aluminum(III) acetylacetonate (112°C) Zr-AA: Zirconium(IV) acetylacetonate (180°C) Ti-AA: Titanium(IV) acetylacetonate (125°C) TiO-AA: Titanium(IV) oxyacetylacetonate (158°C) Cu-AA: Copper(II) acetylacetonate (205°C) Ni-AA: Nickel(II) acetylacetonate (200°C) Li-AA: Lithium acetylacetonate (225°C) ZnO: Zinc oxide (II) (None (>300°C)) stCa: Calcium stearate (93°C)

[0085] (2)B component Below, the material type is listed along with the flow initiation temperature (measured using the same method as in the evaluation method section below) and hardness (Shore D hardness measured in accordance with JIS K6253). MAH-PP1: Maleic acid modified polypropylene, "Admer QB550" manufactured by Mitsui Chemicals, flow temperature 142°C, D hardness 58 MAH-PP2: Maleic acid modified polypropylene, "Admer QF500" manufactured by Mitsui Chemicals, flow temperature 167°C, D hardness 66 MAH-PE: Maleic acid modified polyethylene, "Admer NF539" manufactured by Mitsui Chemicals, flow starting temperature 110°C, D hardness 41 EMA: Ethylene-methacrylic acid copolymer, Mitsui Dow Polychemicals "N035C", flow temperature 65°C, D hardness 41 PP: Polypropylene, Prime Polymer "E111G", flow temperature 160°C, D hardness 70 PE: Polyethylene, Tosoh Corporation "LUMITAC 54-1", flow temperature 113°C, D hardness 47

[0086] <Evaluation method> (1) Flow start temperature A 10mm x 10mm x 2mm test piece was prepared using the sample sheet. This test piece was placed on a temperature-variable hot plate, and a 2mm diameter cylindrical indenter with a dial gauge attached to the top was pressed against the center of the test piece with a force of 1N. The temperature of the hot plate was then increased at a rate of 5°C / min, and the distance the indenter penetrated into the sample was recorded.

[0087] The temperature at which the indenter penetrated 2.0 mm was taken as the flow initiation temperature. Samples with a flow initiation temperature 5°C or higher than that of component B, which does not contain component A, can be considered to have undergone cross-linking by metal ions, resulting in improved heat resistance.

[0088] (2) Wear resistance (wear mass) Abrasion resistance was evaluated using the abrasion mass as an index in accordance with JIS K 7204. Specifically, the sample sheet was punched into a predetermined test shape, and an abrasion test was performed using a CS-17 abrasion wheel under conditions of 9.8 N, 72 rpm, and 1,000 revolutions. The abrasion mass was evaluated from the amount of mass loss of the test piece due to the abrasion test. Abrasion mass of 5.0 mg or less can be considered to have high abrasion resistance.

[0089] (3) Elastic modulus The sample sheets were cut into strips measuring 50 mm long, 5 mm wide, and 2 mm thick, and subjected to tensile tests at room temperature in air with a grip width of 10 mm and a rate of 10 mm / min. The modulus of elasticity (tensile modulus) was calculated from the strain between 1 N and 2 N tensile loads. For samples B6 and B7, due to poor fluidity during press molding, it was not possible to obtain sample sheets large enough to evaluate the modulus of elasticity.

[0090] (4)Hardness The Shore D hardness (Durometer D hardness) of the sample sheet obtained above was measured in accordance with JIS K6253.

[0091] <Evaluation results> In Tables 1 and 2 below, the content of each component (unit: parts by mass) for Samples A1 to A8 and B1 to B12 is shown in the upper row, and the results of each evaluation are shown in the lower row.

[0092] [Table 1] [Table 2]

[0093] According to Table 1, samples A1–A8 all contain a raw material, component A, which releases metal ions when heated, and component B, an organic polymer containing electron-withdrawing substituents in its side chains capable of forming ionic bonds with metal ions. The sample sheets obtained through crosslinking during press molding have flow initiation temperatures between 190°C and 300°C. The flow initiation temperatures of samples A1–A8 are each 5°C higher than the flow initiation temperature of component B, demonstrating high heat resistance through crosslinking. Furthermore, while the molding temperature of typical thermoplastic resins is around 300°C, samples A1–A8 have flow initiation temperatures below 300°C, demonstrating high remoldability. Furthermore, because component B has a Shore D hardness of 50 or higher, each of samples A1–A8 obtained through crosslinking exhibited high wear resistance, with wear masses kept below 5.0 mg. Furthermore, each sample has an elastic modulus of 800 MPa or higher and a Shore D hardness of 55 or higher, demonstrating excellent mechanical strength, including wear resistance.

[0094] In contrast to the above, samples B1 and B2 do not contain component A, and crosslinking of component B by metal ions cannot proceed. Therefore, the flow initiation temperature is below 190°C. The lack of crosslinking of component B also results in a large wear mass. In samples B3 and B4, component B does not have a substituent capable of forming an ionic bond with a metal ion, and metal ions derived from component A cannot form a crosslinked structure in component B. Therefore, the flow initiation temperature is below 190°C. The lack of crosslinking of component B also results in a large wear mass.

[0095] In sample B5, component A is composed of a metal complex, but the titanium atom is in the state of TiO(II), and when heated, TiO 2+ The substituents on the side chains of component B undergo crosslinking through ionic bonds with these metal-containing ions, but the flow initiation temperature of the crosslinked body remains below 190°C, corresponding to the fact that the ionic bonds are not very strong. The reason why strong ionic bonds are not formed is thought to be because the three-dimensional structure of the metal coordination state at the crosslinked site becomes bulky, lowering the molecular aggregation density at the crosslinked site.

[0096] For samples B6 and B7, the flow initiation temperature exceeded 300°C. This is likely due to the use of copper and nickel as the metals in component A, which have a wide range of oxidation states and a relatively low ionization tendency. Therefore, when the crosslinked body is heated, the crosslinked body is less likely to undergo flow due to migration of crosslinking points. Furthermore, the low fluidity of the crosslinked body in these samples precluded the production of sample sheets suitable for measuring the elastic modulus through press molding. Furthermore, if the press molding temperature were to be further increased, partial decomposition of component B would begin, resulting in significant discoloration and deterioration. On the other hand, for sample B8, the flow initiation temperature was below 190°C. This is likely due to the fact that the metal contained in component A is lithium, a monovalent metal, which is unable to form a stable crosslinked structure in component B. The lack of crosslinking in component B also corresponds to the large wear mass.

[0097] Samples B9 and B10 use zinc oxide and calcium stearate, respectively, as component A, rather than a metal complex. These compounds do not liberate metal ions even when heated, so they cannot crosslink component B. Corresponding to this, the flow initiation temperature of samples B9 and B10 is well below 190°C, almost the same as that of sample B1. The wear mass is also larger.

[0098] Samples B11 and B12 used a B component with a Shore D hardness of less than 50. Therefore, even after crosslinking via metal ions, only low-wear-resistant materials were obtained, with a wear mass significantly exceeding 5.0 mg. Furthermore, sample B12 used EMA as B component, which contains electron-withdrawing carboxylic acid groups in the polymer backbone but lacks electron-withdrawing substituents in the side chains. Due to steric hindrance from the adjacent methacryloyl groups, the carboxylic acid groups in the backbone cannot effectively form crosslinked structures via ionic bonds with metal ions. Correspondingly, the flow initiation temperature was significantly below 190°C.

[0099] Here, samples A1 to A8 are compared. Samples A1 to A5 differ in the type of metal contained in the A component. Comparing samples A1 to A4 with sample A5, whose A component contains titanium, the flow initiation temperature of sample A5 is lower than that of the other samples. This is thought to be because even if titanium ions are liberated from the A component, they are easily oxidized, resulting in a low activity state and making it difficult to improve crosslinking efficiency. In contrast, the calcium, zinc, aluminum, and zirconium contained in the A component of samples A1 to A4 contribute to the formation of crosslinked structures in the B component while retaining their high activity. As a result, high flow initiation temperatures exceeding 190°C and even 200°C are achieved, demonstrating high heat resistance. Furthermore, among samples A1 to A4, samples A3 and A4, which contain aluminum and zirconium in the A component, have particularly high flow initiation temperatures exceeding 240°C. In other words, if Component A is used, which liberates aluminum or zirconium ions, it can be said that the crosslinked body will have particularly high heat resistance. Sample A1, which contains calcium, an alkaline earth metal, in Component A, showed some non-uniformity when mixing Components A and B, which is thought to be the reason why the flow initiation temperature was not as high as that of Samples A3 and A4. Furthermore, Sample A2, which contains zinc in Component A, does not have as high a flow initiation temperature as Samples A3 and A4, likely due to the fact that the phase transition initiation temperature of Component A is lower than that of Samples A3 and A4, as shown above.

[0100] The pair of samples A3 and A6 differs in the type of B component. However, both samples have a B component with a Shore D hardness of 50 or greater, which corresponds to high wear resistance resulting in a small wear mass of 5.0 mg or less, a high elastic modulus exceeding 900 MPa, and a high hardness exceeding Shore D hardness of 60. However, sample A6, which uses a harder B component, has a small wear mass and a high elastic modulus and hardness. This shows that increasing the hardness of B component results in high mechanical strength.

[0101] Samples A3, A7, and A8 have different contents of component A, ranging from 0.1 to 30 parts by mass, relative to 100 parts by mass of the total of components A and B. At all contents, a flow initiation temperature of 190°C or higher and 300°C or lower was obtained. The abrasion mass was kept below 5.0 mg for all samples, but sample A3, which has an intermediate content of component A at 5.0 parts by mass, had an especially small abrasion mass, indicating that it had high abrasion resistance.

[0102] 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]

[0103] 1. Insulated wire 2. Wire conductor 21 Wire 3. Insulation coating

Claims

1. Component A, which liberates metal ions when heated; The composition includes a main chain constituted as an olefin-based polymer which is a homopolymer, and a component B which has side chains and is constituted by an organic polymer having a Shore D hardness of 50 or more, Contains only the component B as a polymer component, the component B includes, in the side chain, an electron-withdrawing substituent capable of forming an ionic bond with a metal ion released from the component A; A crosslinkable polymer composition in which the component B is crosslinked by the metal ions liberated from the component A, has a flow-initiation temperature in the range of 190°C or higher and 300°C or lower.

2. The crosslinkable polymer composition according to claim 1 , wherein the main chain of the component B is polypropylene.

3. The crosslinkable polymer composition according to claim 1, wherein the component B has a flow starting temperature in the range of 50°C or higher and 190°C or lower.

4. The crosslinkable polymer composition according to claim 1 , wherein the component A has a decomposition point or a phase transition point of 50° C. or higher and 300° C. or lower.

5. The crosslinkable polymer composition according to claim 1 , wherein the component A has a decomposition point or a phase transition point at a temperature equal to or higher than the flow-initiation temperature of the component B.

6. 2. The crosslinkable polymer composition according to claim 1, wherein the component A is a metal complex containing a ligand having a structure of the following formula (1): 【Chemistry 1】 Here, R １ and R ２ each independently represents a hydrocarbon group having 1 to 8 carbon atoms; R ３ represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. １ , R ２ , R ３ The present invention also includes a case where at least two of the groups are connected to each other by a ring structure.

7. 2. The crosslinkable polymer composition according to claim 1, wherein the metal ions liberated from said component A are ions of at least one of alkaline earth metals, aluminum, zinc, titanium, and zirconium.

8. 8. The crosslinkable polymer composition according to claim 7, wherein the metal ions liberated from said component A are ions of at least one of aluminum and zirconium.

9. 2. The crosslinkable polymer composition according to claim 1, wherein the substituent of the component B is at least one of a carboxylic acid group, an acid anhydride group, and a phosphoric acid group.

10. 2. The crosslinkable polymer composition according to claim 1, wherein the substituent of the component B is bonded to the main chain via an alkyl group or alkylene group having one or more carbon atoms.

11. The crosslinkable polymer composition according to claim 1 , wherein the component B does not contain an electron-withdrawing group in the main chain.

12. The crosslinkable polymer composition according to claim 1 , wherein the component A is contained in an amount of 0.1 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the total of the components A and B.

13. A crosslinked polymer material comprising a crosslinked product of the crosslinkable polymer composition according to any one of claims 1 to 12, wherein the crosslinked product is formed by crosslinking the B component with metal ions liberated from the A component.

14. A wire conductor; An insulated wire comprising: an insulating coating made of the crosslinked polymer material according to claim 13 and covering the outer periphery of the wire conductor.

15. The electric wire conductor is formed by twisting together a plurality of wires, The insulated wire according to claim 14 , wherein the insulated wire has a flat portion where a cross section of the wire conductor perpendicular to the axial direction has a flat shape.

16. A wire harness comprising the insulated wire according to claim 14.

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