Insulated wire and wire harness

Abstract

Provided are: a cross-linkable polymer composition for providing a cross-linked body that is capable of realizing both heat resistance and re-moldability; a cross-linked polymer material that is capable of realizing both heat resistance and re-moldability; an insulated wire comprising such a cross-linked polymer material, and a wire harness.　The present invention provides a cross-linkable polymer composition comprising a component A in which metal ions are freed by heat, and a component B configured from an organic polymer having a side chain, wherein: the component B includes, in the side chain, an electron-accepting substituent which is capable of forming an ionic bond with a metal ion freed from the component A; and a cross-linked body in which the component B is cross-linked by the metal ion freed from the component A has a flow starting temperature in the range of 190°C to 300°C. Further, the present invention provides a cross-linked polymer material comprising a cross-linked body of the cross-linking polymer composition. The present invention also provides: an insulated wire having a wire conducting body and an insulation covering which is configured from the cross-linked polymer material and covers the outer periphery of the wire conducting body; and a wire harness comprising the insulated wire.

Description

Technical Field

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

Background Art

[0002] In insulated wires and wire harnesses, thermoplastic polymer compositions are widely used as insulating members such as insulating coatings that cover the outer periphery of wire conductors. When molding a thermoplastic polymer composition into a desired shape, a molding method such as extrusion molding is applied after bringing it into a state having fluidity by heating. In order to easily perform molding by heating, it is preferable that the polymer composition acquires fluidity without being heated to an extremely high temperature.

[0003] On the other hand, in insulated wires and wire harnesses, since the temperature rises due to energization, the polymer composition disposed in the vicinity of the energized portion, including the insulating coating, is required to have high heat resistance. That is, it is required that the polymer composition does not cause irreversible deformation due to heat generation during energization. For example, in the insulating coating of an automobile wire, it is desirable not to cause reversible deformation at a temperature of 190° C. or lower. In particular, in the case of an electric vehicle wire, a large current needs to flow through the wire conductor, and since the amount of heat generation during energization increases, a high heat resistance is required for the polymer composition constituting the insulating coating and the like.

[0004] Thus, in the polymer composition used for insulated wires and wire harnesses, it is required that the composition can be relatively easily formed into a moldable state by heating and that it has high heat resistance in the molded state. As a method for achieving both of these characteristics, it is conceivable to adjust the flow start temperature of the thermoplastic polymer material used. However, for polymer materials with a high flow start temperature, heating to a high temperature is required during molding, while polymer materials with a low flow start temperature are unlikely to have high heat resistance, and this method has limitations. Therefore, a method that utilizes crosslinking of polymer materials is also adopted. That is, an uncrosslinked polymer composition is formed into a desired shape by extrusion molding or the like, and then the molecular chains are crosslinked to improve the heat resistance. As crosslinking methods, electron beam crosslinking in which an electron beam is irradiated onto a material molded from polyolefin or the like to crosslink the molecular chains of the polymer into a three-dimensional network (for example, Patent Document 1), and silane crosslinking in which a thermoplastic resin into which an active silane group has been introduced is molded and then crosslinked by contact with moisture or the like (for example, Patent Document 2) are used. Further, when rubber is used as the polymer material, crosslinking by vulcanization can be utilized.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, a polymer composition crosslinked by electron beam crosslinking, silane crosslinking, or vulcanization is a material that acquires high heat resistance by undergoing crosslinking after being formed into a desired shape. However, it is difficult to reshape it into another shape after being formed into a predetermined shape. This is because strong covalent bonds are irreversibly formed by crosslinking, and while these crosslink bonds are effective in improving heat resistance, they prevent the fluidity of the molecular chains from being increased again to a state where reshaping is possible.

[0007] However, in the case of insulated electric wires and wire harnesses, there may be a requirement to reshape a polymer material that has once been formed into a predetermined shape. For example, in an insulated electric wire in which an insulating coating is formed on the outer periphery of an electric wire conductor composed of a stranded wire, due to restrictions on routing space, etc., the cross-sectional shape of the insulated electric wire may need to be deformed into a shape different from a circular shape, such as a flat shape. Conversely, there may also be a requirement to deform an insulated electric wire formed into a cross-sectional shape different from a circular shape, such as a flat shape, into a circular cross-section. In these cases, if the insulating coating can be made into a state where it can be reshaped by heating or the like, the insulating coating can also be deformed following the deformation of the electric wire conductor.

[0008] In view of the above, it is an object to provide a crosslinkable polymer composition that can give a crosslinked product having both heat resistance and reshaping properties, a crosslinked polymer material having both heat resistance and reshaping properties, an insulated electric wire and a wire harness provided with such a crosslinked polymer material.

Means for Solving the Problems

[0009] The crosslinkable polymer composition according to the present disclosure includes an A component in which metal ions are released by heat and a B component composed of an organic polymer having a side chain, and the B component includes, in the side chain, an electron-withdrawing substituent capable of forming an ionic bond with a metal ion released from the A component. A crosslinked product obtained by crosslinking the B component with a metal ion released from the A component has a flow start temperature in the range of 190°C or higher and 300°C or lower.

[0010] 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 B component with a metal ion released from the A component.

[0011] The insulated electric wire according to the present disclosure has an electric wire conductor and an insulation coating made of the crosslinked polymer material and covering the outer periphery of the electric wire conductor.

[0012] The wire harness according to the present disclosure includes the insulated electric wire.

Advantages of the Invention

[0013] The crosslinkable polymer composition according to the present disclosure provides a crosslinked product that can achieve both heat resistance and remoldability. The crosslinked polymer material according to the present disclosure can achieve both heat resistance and remoldability. Further, the insulated electric wire and the wire harness according to the present disclosure are provided with such a crosslinked polymer material.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0015] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0016] The crosslinkable polymer composition according to the present disclosure includes an A component in which metal ions are released by heat and a B component composed of an organic polymer having a side chain. The B component includes an electron-withdrawing substituent capable of forming an ionic bond with the metal ions released from the A component in the side chain. A crosslinked product obtained by crosslinking the B component with the metal ions released from the A component has a flow start temperature in the range of 190°C or higher and 300°C or lower.

[0017] The crosslinkable polymer composition according to the present disclosure can crosslink the B component through the metal ions released from the A component by heating. Therefore, in the state of the uncrosslinked composition, high moldability can be obtained when molding into a desired shape by extrusion molding or the like. On the other hand, by forming a crosslinked product through heating, it becomes a polymer material having high heat resistance. In particular, since the flow start temperature of the crosslinked product is 190°C or higher, it is ensured that the polymer material after crosslinking has high heat resistance. A material having high heat resistance with a flow start temperature of 190°C or higher can be suitably used particularly for forming the insulating coating of automotive wires.

[0018] Furthermore, in the crosslinked body composed of the crosslinkable polymer composition according to the present disclosure, since the crosslinked structure is formed through an ionic bond between a substituent of the organic polymer of component B and a metal ion, the crosslinked polymer material after crosslinking can be reshaped by utilizing the reversibility of the ionic bond. This is because by reheating the already formed crosslinked body, the movement of the crosslinking points due to the ionic bond occurs, causing the material to fluidize. Since 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. On the other hand, since the substituent is introduced into the side chain of the organic polymer, the degree of freedom of thermal motion at the crosslinked site increases, so that during heating, the movement of the crosslinking points is likely to occur, resulting in excellent reshaping properties and high flexibility of the crosslinked body. In particular, since the flow start temperature of the crosslinked body is suppressed to 300°C or lower, the reshaping property by heating at a temperature of 300°C or lower is ensured.

[0019] Here, the component B preferably has a flow start temperature in the range of 50°C or higher and 190°C or lower. Then, through crosslinking with metal ions derived from component A, it is easy to obtain a crosslinked body having a flow start temperature of 190°C or higher and 300°C or lower as described above. Also, when molding the uncrosslinked crosslinkable polymer composition into a desired shape by extrusion molding or the like, high moldability can be obtained.

[0020] The component B preferably has a Shore D hardness of less than 50. Then, through crosslinking of component B with metal ions derived from component A, it is easy to obtain a highly flexible crosslinked body that can be suitably used for applications involving bending, such as the insulation coating of insulated wires.

[0021] Further, the component A preferably has a decomposition point or a phase transition point at 50°C or higher and 300°C or lower. Then, during the preparation of the crosslinkable polymer composition or before using the crosslinkable polymer composition, the release of metal ions from the component A is suppressed, so that the progress of crosslinking is suppressed, and high storage stability is obtained in the crosslinkable polymer composition, such as suppressing the quality change of the crosslinkable polymer composition at a low temperature such as normal temperature. On the other hand, at an appropriate temperature, the component A decomposes or undergoes a phase transition, and metal ions are easily released from the component A, and the crosslinking reaction can proceed at a temperature at which the component B does not deteriorate.

[0022] The component A preferably has a decomposition point or a phase transition point at a temperature equal to or higher than the flow start temperature of the component B. Then, in a state where the component B has already acquired fluidity, the release of metal ions from the component A and the accompanying crosslinking of the component B occur. Therefore, by utilizing the flow of the component B, the dispersibility of the component A in the component B can be increased, and a crosslinked body with a high spatial uniformity of crosslinking points can be obtained. Further, during the preparation or molding of the crosslinkable polymer composition, a situation where the release of metal ions from the component A and the accompanying crosslinking of the component B proceed unintentionally is less likely to occur.

[0023] The component A is preferably a metal complex containing a ligand having the structure of the following formula (1).

Chemical formula

[0024] The β-diketonato ligand represented by the formula (1) is a bidentate ligand, and is superior to a monodentate ligand or a ligand forming a crosslinked coordination structure in the effect of stabilizing metal ions. During the preparation of the crosslinkable polymer composition or before using the crosslinkable polymer composition, the release of metal ions from the component A is suppressed, and particularly high storage stability is obtained.

[0025] The metal ions released from the component A are preferably at least one kind of ions among alkaline earth metals, aluminum, zinc, titanium, and zirconium. The ions of the above metals all have a valence of 2 or more and tend to form a stable crosslinked structure between the polymer chains of the component B. Furthermore, the above metal ions belong to hard acids in the HSAB principle and have a high ionization tendency, corresponding to forming a stable bond with the substituent of the component B. From this, it is also suitable as the metal for constituting the crosslinked body.

[0026] The metal ions released from the component A are preferably at least one kind of ions of aluminum and zirconium. When these metal ions are released from the component A, it becomes easier to form a particularly stable crosslinked structure with the component B. Also, in a relatively low-temperature state before crosslinking, it gives high storage stability.

[0027] The substituent of the component B is preferably at least one of a carboxylic acid group, an acid anhydride group, and a phosphate group. These substituents easily form an ionic bond with the metal ions released from the component A. Also, since they are relatively low-polarity acidic groups, it is difficult to cause phase separation with respect to the main chain and side chains of the component B, and a crosslinked structure with high spatial uniformity can be formed.

[0028] The substituent of the component B is preferably bonded to the main chain via an alkyl group or an alkylene group having 1 or more carbon atoms. Then, the degree of freedom of thermal motion at the crosslinked site becomes particularly high, and when heated, the movement of the crosslinked points is likely to occur, so particularly high reshaping properties can be obtained.

[0029] The component B preferably does not contain an electron-withdrawing group in the main chain. Then, a situation where the substituent of the side chain is prevented from forming an ionic bond with the metal ions derived from the component A due to competition with the electron-withdrawing group in the main chain does not occur. The substituent in the main chain is difficult to form a stable crosslinked structure with the metal ions due to steric hindrance. Moreover, even if a crosslinked structure is formed, the degree of freedom of movement of the crosslinked site becomes low, and it is difficult to obtain high reshaping properties in the crosslinked body, and the flexibility also tends to be low.

[0030] The main chain of the component B is preferably an olefin polymer or a styrene polymer. Then, it is difficult for the main chain to affect the formation of crosslinking points in the side chain of the component B and the movement of these crosslinking points, and the high heat resistance and re-moldability brought about by these phenomena in the side chain part are effectively exhibited as the characteristics of the whole material.

[0031] The crosslinkable polymer composition preferably contains 0.1 part by mass or more and 30 parts by mass or less of the component A, with the total of the component A and the component B being 100 parts by mass. Then, by containing a sufficient amount of the component A, the crosslinking density becomes high, and the crosslinkable polymer composition becomes excellent in crosslinkability. On the other hand, it is easy to avoid the influence of containing a large amount of the component A in the material before and after crosslinking.

[0032] The crosslinked polymer material according to the present disclosure includes a crosslinked body of the crosslinkable polymer composition according to the present disclosure, which is configured as a crosslinked body obtained by crosslinking the component B with metal ions released from the component A. The crosslinked body formed by crosslinking the component B via metal ions released from the component A has crosslinking points at the positions of the electron-withdrawing substituents introduced into the side chain of the component B, and has a flow start temperature in the range of 190°C or higher and 300°C or lower. Therefore, the crosslinked polymer material has both high heat resistance and re-moldability by heating. Also, it becomes a material having high flexibility.

[0033] The insulated electric wire according to the present disclosure has an electric wire conductor and an insulating coating made of the crosslinked polymer material according to the present disclosure, which coats the outer periphery of the electric wire conductor. In this insulated electric wire, since the insulating coating is made of the crosslinked polymer material according to the above-mentioned present disclosure, it exhibits high heat resistance, and even if the electric wire conductor generates heat due to energization, it is difficult to cause irreversible deformation. On the other hand, if the insulating coating is heated to a sufficient temperature, the insulating coating can be fluidized again to perform re-molding, and the shape of the insulating coating can be changed. For example, when deforming the electric wire conductor, the insulating coating also follows the shape of the electric wire conductor and is easily deformed.

[0034] Here, the electric wire conductor is formed by twisting a plurality of strands, and the insulated electric wire preferably has a flat portion where the cross-section of the electric wire conductor orthogonal to the axial direction is flat. An electric wire having a flat portion is required from the viewpoint of space saving and the like. The flat portion can be easily formed by applying a force to compress the insulation coating flat while heating the insulation coating on a normal insulated electric wire with a circular cross-section, utilizing the fact that the insulation coating has reworkability. Conversely, by applying a force in the direction of eliminating the flat shape to the electric wire with the flat portion while heating the insulation coating, the insulated electric wire can be deformed into a state having another cross-sectional shape such as a circular cross-section. In this way, by using an insulated electric wire including an electric wire conductor formed by twisting a plurality of strands and being easily deformed by the application of force, and an insulation coating that can be reversibly transitioned to a reworkable state by heating, deformation between a state with a low flatness such as a circular cross-section and a flat state can be easily performed in both directions. For example, by using a common insulated electric wire, various insulated electric wires with necessary portions deformed into necessary shapes such as a flat shape can be obtained according to the routing location and application.

[0035] The wire harness according to the present disclosure includes the insulated electric wire according to the present disclosure. Since the insulated electric wire according to the present disclosure has an insulation coating excellent in heat resistance and reworkability as described above, these characteristics can also be utilized in the wire harness.

[0036] [Details of Embodiments of the Present Disclosure] The crosslinkable polymer composition, crosslinked polymer material, insulated electric wire, and wire harness according to the embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these embodiments.

[0037] [1] Crosslinkable Polymer Composition and Crosslinked Polymer Material The crosslinkable polymer composition according to an embodiment of the present disclosure includes a component A in which metal ions are released by heat, and a component B composed of an organic polymer having an electron-withdrawing substituent capable of forming an ionic bond with the metal ions released from the component A on a side chain. The crosslinkable polymer composition according to the present embodiment constitutes a crosslinked polymer material according to an embodiment of the present disclosure by forming a crosslinked body in which the component B is crosslinked by metal ions released from the component A through heating. The crosslinked body has a flow start temperature of 190°C or higher and 300°C or lower.

[0038] (1) Characteristics of crosslinkable polymer composition and crosslinked polymer material Before explaining each component constituting the crosslinkable polymer composition in detail, first, the characteristics of the crosslinkable polymer composition and the crosslinked polymer material will be described. The crosslinkable polymer composition according to the present embodiment contains a component A in which metal ions are released by heat, and a component B having a substituent capable of forming an ionic bond with the metal ions. When the crosslinkable polymer composition containing these components is heated, metal ions are released from the component A. Then, as shown in FIG. 1A, the released metal ions form an ionic bond with the substituent of the component B, and the organic polymer chains of the component B are crosslinked through the ionic bond. In FIG. 1A and FIGS. 1B and 1C to be described later, a divalent metal ion M is assumed as the metal ion, and a carboxylate group (COO in anionic state) is assumed as the substituent of the component B. The polymer chain of the component B is shown by a broken line. 2+ is assumed, and as the substituent of the component B, a carboxylate group (COO - ) in anionic state is assumed. The polymer chain of the component B is shown by a broken line.

[0039] Component A releases metal ions upon heating. Until the temperature at which Component A releases metal ions due to decomposition or phase transition is reached, no metal ion release occurs from Component A, and the crosslinking of the organic polymer of Component B by the formation of ionic bonds does not proceed. Therefore, the crosslinkable polymer composition according to the present embodiment is in a relatively highly fluid state at a low temperature at which no metal ion release from Component A and no crosslinking of Component B thereby occur, and can be easily formed into a desired shape by extrusion molding or the like. Then, after forming the crosslinkable polymer composition into a desired shape, a crosslinked body can be formed by releasing metal ions from Component A by heating and crosslinking Component B. The crosslinked body has improved heat resistance compared to the state before crosslinking because adjacent polymer chains of Component B are crosslinked. In the crosslinked body, the organic polymer chains of Component B are crosslinked via ionic bonds, and the binding force is stronger than the van der Waals force, effectively improving the heat resistance and mechanical toughness of the crosslinked body.

[0040] In particular, the crosslinkable polymer composition according to the present embodiment forms a crosslinked polymer material having high heat resistance because the flow start temperature of the formed crosslinked body is 190°C or higher. That is, the crosslinked polymer material formed through crosslinking is less likely to experience an increase in fluidity and accompanying irreversible deformation at temperatures below 190°C. Here, the heat resistance temperature of 190°C is generally desired for the insulating coating of automotive insulated wires. As will be described in detail later, the crosslinkable polymer composition according to the present embodiment can be suitably used to form the insulating coating of automotive insulated wires. From the viewpoint of effectively enhancing the heat resistance of the crosslinked polymer material, it is more preferable that the flow start temperature of the crosslinked body is 200°C or higher, and further 220°C or higher. Note that the flow start temperature of the crosslinked body and Component B, which will be described later, refers to the temperature at which the solid material starts to exhibit fluidity when heated, and can be measured, for example, as the temperature at which a sheet-like material becomes penetrable by a indenter as shown in the later examples. Alternatively, the melting point or the flow point (the lower one if it has both) of the material can be regarded as the flow start temperature.

[0041] Furthermore, in the crosslinkable polymer composition according to the present embodiment, the crosslinked structure between the polymer chains of the component B is not an irreversible covalent bond formed in the case of electron beam crosslinking or silane crosslinking, but an ionic bond with a metal ion which is a reversible bond. Therefore, the formed crosslinked polymer material has reprocessability. That is, by heating the crosslinked polymer material once formed through crosslinking, the crosslinked polymer material becomes a state having fluidity again, and can be molded into a shape different from that before heating by applying an external force or the like.

[0042] The remoldability of the crosslinked polymer material can be explained by the following mechanism. In a state where the crosslinked body formed by crosslinking the polymer chains of component B with metal ions is not heated, at room temperature or near it, as shown in Fig. 1A, in the chain of component B, the crosslinking points by metal ions are localized at certain positions. However, when the crosslinked body is heated, the molecular motion of component B due to heat becomes active, and as shown in Fig. 1B, active thermal motion also occurs at the crosslinked sites where the substituents of component B and metal ions form ionic bonds and in the vicinity thereof. When the crosslinked body is heated to a higher temperature, the molecular motion of component B is further activated, and the crosslinking points via metal ions become movable to different sites (positions of other substituents) in the vicinity, and the crosslinking points become delocalized. By the delocalization of the crosslinking points, as shown in Fig. 1C, a state is formed in which a plurality of substituents in the same molecular chain of component B are simultaneously coordinated to one metal ion (multidentation). By such activation of the thermal motion in component B and subsequent movement of the crosslinking points, the crosslinked body becomes flowable. In these states, by appropriately applying an external force to the material, the crosslinked polymer material can be remolded. The activation of the thermal motion at the crosslinked sites and the delocalization of the crosslinking points are reversible phenomena. If the remolded crosslinked polymer material is cooled, the crosslinking points return to the localized state, and it returns to the state of a thermally stable crosslinked body. By repeating heating and cooling, the crosslinked polymer material can also be repeatedly remolded. Incidentally, the activation of the thermal motion at the crosslinked sites and the delocalization of the crosslinking points due to heating can be confirmed, for example, by infrared absorption spectrum. Typically, the activation of the thermal motion at the crosslinked sites appears as broadening of the absorption peak of the substituents forming the crosslinked structure in the spectrum, and the delocalization of the crosslinking points appears as the growth of new peaks corresponding to multidentation in the spectrum.

[0043] Furthermore, in the crosslinkable polymer composition according to the present embodiment, in component B, a substituent capable of forming an ionic bond with a metal ion is contained in the side chain rather than in the main polymer chain. Thus, when a crosslinked structure is formed via the metal ion, a high degree of freedom of movement can be obtained at the crosslinked sites. Therefore, in the crosslinked body, the thermal motion at the crosslinked sites and the movement of the crosslinking points are particularly likely to occur actively. As a result, the crosslinked polymer material exhibits high reprocessability when heated. Also, the crosslinked polymer material has high flexibility.

[0044] In particular, in the crosslinkable polymer composition according to the present embodiment, since the flow start temperature of the formed crosslinked body is suppressed to 300°C or lower, if the crosslinked polymer material is heated up to 300°C, reprocessing becomes possible and can be easily performed. From the viewpoint of effectively enhancing the reprocessability, it is more preferable that the flow start temperature of the crosslinked body is 280°C or lower, and further 250°C or lower.

[0045] As described above, the crosslinkable polymer composition according to the present embodiment contains component A in which metal ions are released by heat and component B containing a substituent capable of forming an ionic bond with the metal ion in the side chain. Further, the crosslinked body obtained by crosslinking component B with the metal ions released from component A has a flow start temperature in the range of 190°C or higher and 300°C or lower, thereby providing a crosslinked polymer material having both high heat resistance and reprocessability. Therefore, after molding the crosslinkable polymer composition into a desired shape by extrusion molding or the like and then undergoing crosslinking, a crosslinked polymer material having high heat resistance can be obtained. On the other hand, by reheating the crosslinked polymer material, the reprocessability can be utilized. The crosslinkable polymer composition according to the present embodiment has the above-described characteristics, and thus can be suitably used to form a member that requires high heat resistance, such as the insulating coating of an insulated wire, and is advantageous because of its reprocessability. Further, as another index indicating that the heat resistance improvement effect due to crosslinking is sufficiently exhibited in the crosslinked polymer material, it is preferable that the flow start temperature of the crosslinked polymer material is 5°C or higher, and further 10°C or higher than the flow start temperature of component B alone.

[0046] The movement of the crosslinked sites and the delocalization of the crosslinking points, which were described as the behavior when the crosslinked body was heated above, can occur to some extent even at relatively low temperatures such as room temperature. The movement of the crosslinked sites and the delocalization of the crosslinking points at these relatively low temperatures reduce the elastic modulus of the crosslinked polymer material and increase its flexibility. Therefore, unlike general crosslinked polymer materials that have undergone electron crosslinking or silane crosslinking, the crosslinked polymer material according to the present embodiment can maintain high flexibility even after crosslinking. Since the crosslinked polymer material obtained through crosslinking has high flexibility, it can be suitably used to form members that are frequently bent, such as the insulating coating of insulated wires. For example, the tensile elastic modulus of the crosslinked polymer material is preferably 30 MPa or less, and more preferably 20 MPa or less. Alternatively, it is preferable that the tensile elastic modulus of the crosslinked polymer material does not increase by more than 30%, and more preferably does not increase by more than 20%, compared to the tensile elastic modulus of the non-crosslinked Component B.

[0047] As described above, in the crosslinkable polymer composition according to the present embodiment, in order to obtain a crosslinked polymer material that achieves both high heat resistance and reprocessability through crosslinking, it is important that the crosslinked body has a flow start temperature within a predetermined range. The flow start temperature of the crosslinked body is determined by the type of metal ions released from Component A, the polymer main chain and side chains of Component B, the type and structure of the substituents, the ratio of Component A to Component B, and the like. The preferred structures and properties of each component will be described in order below.

[0048] (2) Component A Component A is a component from which metal ions are released by heat. By "by heat" is meant assuming heating, that is, assuming a temperature higher than room temperature. The release of metal ions means that metal ions are released from Component A due to the decomposition or phase transition of Component A. The metal ions released from Component A cause the crosslinking of Component B.

[0049] Component A preferably has a decomposition point or a phase transition point at 50°C or higher. Then, during the preparation of the crosslinkable polymer composition or before the use of the crosslinkable polymer composition (before crosslinking), the release of metal ions from Component A is likely to be suppressed, and the progress of crosslinking of Component B is suppressed, so that the crosslinkable polymer composition has excellent storage stability. That is, when preparing a crosslinkable polymer composition by mixing Component A and Component B at a low temperature such as less than 50°C, when storing the prepared crosslinkable polymer composition, or when shaping the crosslinkable polymer composition into a desired shape by extrusion molding or the like, quality deterioration of the crosslinkable polymer composition, such as the unintentional release of metal ions from Component A and the accompanying crosslinking of Component B, is less likely to occur. When Component A has a decomposition point or a phase transition point at 60°C or higher, and further at 70°C or higher, the effect of improving storage stability becomes even higher.

[0050] On the other hand, Component A preferably has a decomposition point or a phase transition point at 300°C or lower. Then, a situation where Component B deteriorates is less likely to occur at a temperature lower than when metal ions are released from Component A, and it becomes easier to crosslink Component B without deterioration with metal ions. Also, when Component A decomposes or undergoes a phase transition at an appropriate temperature, metal ions are likely to be released from Component A, and the crosslinkable polymer composition has excellent crosslinking speed. From these viewpoints, it is more preferable that Component A has a decomposition point or a phase transition point at 200°C or lower, further at 150°C or lower, and 120°C or lower.

[0051] Furthermore, the component A preferably has a decomposition point or a phase transition point at a temperature equal to or higher than the flow start temperature of the component B, which will be described later. Then, at the temperature at which the component A releases metal ions, the component B already has fluidity, and the crosslinking of the component B by the metal ions released from the component A can proceed. Therefore, by utilizing the fluidity of the component B, crosslinking can proceed in a state where metal ions are well dispersed in the component B, and it becomes easy to obtain a crosslinked polymer material with high tissue uniformity in which crosslinking points formed by metal ions are spatially distributed with high uniformity. In addition, during the preparation or molding of the crosslinkable polymer composition, a situation where metal ions are inadvertently released from the component A and the accompanying crosslinking of the component B is less likely to occur. More preferably, the component A preferably has a decomposition point or a phase transition point at a temperature higher than the flow start temperature of the component B, and further preferably, the component A has a decomposition point or a phase transition point at a temperature 10 °C or more higher than the flow start temperature of the component B. The decomposition point or phase transition point of the component A is represented by the starting temperature of the baseline change measured by differential scanning calorimetry (DSC) (measurement temperature range: 25 °C to 200 °C, measurement in air). The above phase transition point does not include the melting point, and the above phase transition does not include melting. When the component A has both a phase transition point and a decomposition point, or has a plurality of phase transition points, the lower one (the lowest one) of them shall be treated as the "decomposition point or phase transition point".

[0052] The metal species of the metal ions released from the component A is not particularly limited, but alkaline earth metals, aluminum, zinc, titanium, zirconium, etc. can be preferably used. The metal ions released from the component A are preferably ions of at least one of these metals. The ions of these metals have a valence of 2 or more, and by forming an ionic bond with the substituent of the component B, it is easy to form a stable crosslinked structure between the polymer chains of the component B. Furthermore, since the metals listed above belong to hard acids according to the HSAB rule and have a relatively high ionization tendency, they form a stable bond with the substituent of the component B and are suitable as metals for constituting the crosslinked body.

[0053] Among the metal species listed above, aluminum and zirconium are particularly suitable as the metal for forming the crosslinked body. Therefore, the metal ions released from the component A are preferably at least one kind of ions of aluminum and zirconium. The component A containing aluminum or zirconium has a certain degree of high stability and does not easily proceed with the formation of a crosslinked structure when mixed with the component B, and provides high storage stability in the crosslinkable polymer composition. On the other hand, when the component A is heated, metal ions are released relatively easily to form the crosslinked body. For example, as shown in the later examples, the phase transition start temperature of zirconium(IV) acetylacetonate (Zr-AA) is 180 °C, which is a high temperature among various acetylacetonate complexes. On the other hand, for aluminum(III) acetylacetonate, the phase transition start temperature (the start temperature of the baseline change by DSC) is not very high at 112 °C, but this compound has the characteristic that the change in the amount of heat from the start of the phase transition occurs gently, and a significant change in the amount of heat occurs around 170 °C. That is, when the temperature becomes relatively high around 170 °C, the phase transition proceeds significantly.

[0054] Furthermore, when at least one kind of ions of aluminum and zirconium is used as the metal ions released from the component A, the flow start temperature of the crosslinked body becomes higher than that when titanium is used, for example, and the crosslinked polymer material has excellent heat resistance. This is because aluminum and zirconium are not easily oxidized like titanium, so it is less likely that the efficiency of the crosslinking reaction will decrease due to the presence of the oxidation pathway. Also, compared with alkaline earth metals such as calcium, aluminum and zirconium are not as hard as acids as alkaline earth metals, so they are more likely to be uniformly dispersed in the component B. Furthermore, compared with zinc, aluminum and zirconium are more likely to have a higher decomposition temperature of the component A formed in the form of a metal complex or the like, and provide high storage stability.

[0055] In addition, when a member in contact with a metal member is formed using the crosslinkable polymer composition according to the present 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, at the interface between the metal member and the polymer material, the influence caused by the presence of the metal member on the formation and stable retention of the crosslinked structure can be easily reduced. For example, in an insulated wire, when forming an insulating coating that coats a wire conductor made of aluminum or an aluminum alloy using the crosslinkable polymer composition according to the present embodiment, the metal ions released from the A component may be aluminum.

[0056] Not limited to the metal species listed above as preferable ones such as aluminum and zirconium, any metal ion can be applied as the one released from the A component as long as it can crosslink the B component by forming an ionic bond with the substituent of the B component and can provide a crosslinked body having a flow start temperature of 190 ° C or higher and 300 ° C or lower. However, transition metals such as iron, nickel, and copper tend to give a crosslinked body having a higher flow start temperature than the above range. This is presumably because when a crosslinked body is formed using metal ions of a metal having many types of oxidation numbers that can be taken or a low ionization tendency, such as a transition metal, the movement of crosslinking points during heating (see Fig. 1C) tends not to occur. Further, the metal ions released from the A component may be not only monatomic ions of the metal but also polyatomic ions (including metal ions) formed by bonding a metal atom and other atoms. However, from the viewpoint of forming a stable ionic bond with the substituent of the B component, monatomic ions of the metal are preferable.

[0057] The component A can be any chemical species as long as it can release metal ions by heat, and a metal complex can be cited as a suitable chemical species. The metal complex is composed of a central metal ion coordinated with ligands having non-bonding electron pairs. When using a metal complex, it is excellent in the effect of stabilizing metal ions by ligands, and when preparing a crosslinkable polymer composition, before using the crosslinkable polymer composition, or when molding the crosslinkable polymer composition into a desired shape, the release of metal ions from the component A is suppressed. When crosslinking the crosslinkable polymer composition, metal ions are likely to be released from the component A by heat.

[0058] Examples of the ligands constituting the metal complex include monodentate ligands having one coordination site and polydentate ligands having two or more coordination sites. The metal complex formed by a polydentate ligand is more stable than the metal complex formed by a monodentate ligand or the metal complex formed by a ligand having a crosslinked coordination structure typified by an alkoxide ligand due to the chelate effect. Therefore, the component A is preferably a metal complex containing a polydentate ligand. Coordination by a polydentate ligand is superior in the effect of stabilizing metal ions compared to coordination by a monodentate ligand or coordination by a ligand having a crosslinked coordination structure, and the release of metal ions from the component A can be more effectively suppressed during the preparation of the crosslinkable polymer composition, before use, and during molding of the crosslinkable polymer composition.

[0059] Among the polydentate ligands, a bidentate ligand, β-diketonato ligand (1,3-diketonato ligand), can be preferably used. The β-diketonato ligand is particularly excellent in the effect of stabilizing metal ions. In addition, a metal complex having a β-diketonato ligand is easily well-dispersed in an organic polymer, so it is suitable for dispersing the component A in the component B and forming crosslinking points with high uniformity. The β-diketonato ligand is represented by the following general formula (1).

[0060]

Chemical formula

[0061] 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 an oxygen atom. Examples of the hydrocarbon groups constituting R1, R2, and R3 include an alkyl group, an alkoxy group, an aromatic group, and a condensed aromatic group. The number of carbon atoms of R1, R2, and R3 is not particularly limited, but is preferably 1 or more and 8 or less.

[0062] Specific β-diketonato ligands 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, and the like. Among these, from the viewpoint of simplicity of structure and the like, in the above formula (1), the acetylacetonato ligand in which R1 and R2 are methyl groups and R3 is a hydrogen atom is particularly preferred.

[0063] In the crosslinkable polymer composition, the content of component A is preferably 0.1 part by mass or more based on 100 parts by mass in total of component A and component B. Then, by containing a sufficient amount of component A with respect to component B, the crosslink density becomes high in the crosslinked body, and a high effect is exhibited in improving the heat resistance. From the viewpoint of enhancing the heat resistance improvement effect, the content of component A is more preferably 1.0 part by mass or more, and further preferably 2.0 part by mass or more, based on the above 100 parts by mass. On the other hand, the content of component A is preferably 30 parts by mass or less based on the above 100 parts by mass. Then, it is easy to avoid the influence of containing a large amount of component A, such as separation or precipitation of component A before crosslinking, embrittlement of the polymer material after crosslinking, or decrease in flexibility. From the viewpoint of enhancing these effects, the content of component A is more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less, based on the above 100 parts by mass.

[0064] (3) Component B Component B is a component composed of an organic polymer having a side chain, and contains an electron-withdrawing substituent capable of forming an ionic bond with a metal ion released from component A in the side chain. The substituent does not necessarily have to be an electron-withdrawing one, but can form an ionic bond with a metal ion released from component A. However, by being electron-withdrawing, a stable ionic bond can be formed with the metal ion. Therefore, when component B is crosslinked by a metal ion in the crosslinkable polymer composition, a crosslinked structure is stably formed, and the crosslinked body is likely to exhibit high heat resistance.

[0065] Examples of the electron-withdrawing substituents capable of forming an ionic bond with a metal ion include acidic groups other than a hydroxyl group, such as a carboxylic acid group, an acid anhydride group, and a phosphoric acid group. The substituent may be only one kind or two or more kinds, but it is preferably at least one kind of the substituents listed above. In particular, an acid anhydride group such as a maleic anhydride group can be preferably adopted. The substituents listed above are excellent in that they easily form an ionic bond with the metal ion released from the component A. Further, since all of the substituents listed above are acidic groups with relatively low polarity, phase separation is less likely to occur with respect to the main chain and side chain of the component B, and a high degree of uniformity can be achieved in the structure of the component B, and a crosslinked structure can be formed. For example, a sulfonic acid group is also an electron-withdrawing substituent that easily forms an ionic bond with a metal ion, but due to its high polarity, it is likely to cause phase separation and cannot be preferably adopted as a substituent of the component B as well as the substituents preferably listed above.

[0066] In the component B, as described above, since the substituent that forms an ionic bond with a metal ion is contained in the side chain rather than in the polymer main chain, when a crosslinked structure is formed, the crosslinked portion maintains a high degree of freedom of movement. As a result, the crosslinked polymer material has high reshaping properties and excellent flexibility. The structure and length of the side chain are not particularly limited, but from the viewpoint of enhancing their effects, it is preferable that the substituent is bonded to the main chain via an alkyl group or an alkylene group having 1 or more carbon atoms. Alternatively, the substituent may be bonded to the main chain via a heteroatom such as an oxygen atom. The substituent may be introduced at the end of the side chain or in the middle portion, but from the viewpoint of effectively enhancing the degree of freedom of movement of the crosslinked portion, it is preferably introduced at the end. The upper limit of the number of carbon atoms in the side chain is not particularly limited, but from the viewpoint of minimizing the influence on the physical properties of the main chain, the number of carbon atoms connecting the main chain and the substituent is preferably 4 or less. For the case where the substituent is a carboxylic acid group and a phosphoric acid group, particularly preferred structures of the side chain portion are represented by the following formulas (2) and (3), respectively.

[0067]

Chemical formula

[0068] In component B, as long as the electron-withdrawing substituent is included even in the side chain, it may or may not be included in the main chain, and it does not matter either way. However, it is preferable that the main chain does not contain an electron-withdrawing group. This is because if an electron-withdrawing group is contained in the main chain, it may prevent the electron-withdrawing group in the side chain from forming a crosslinked structure by ionic bonding with a metal ion. Since the electron-withdrawing group in the main chain is likely to receive a large steric hindrance, it is difficult to effectively contribute to crosslinking by forming an ionic bond with a metal ion, and the effect of improving heat resistance by crosslinking is poor. Also, even if a crosslinked structure is formed at the position of the electron-withdrawing group in the main chain, the degree of freedom of movement of the crosslinked position becomes small, and it is difficult to obtain high reshaping properties and flexibility. Examples of the electron-withdrawing group that is preferably not contained in the main chain of component B include a carbonyl group when the main chain is composed of a copolymer of (meth)acrylic acid, a hydrolyzable group when the main chain contains an ester structure such as vinyl acetate, and a halogen atom.

[0069] In component B, the content of the substituent contained in the side chain is not particularly limited, but from the viewpoint of ensuring physical properties by crosslinking, etc., it is preferably 0.01% by mass or more and 10% by mass or less with respect to the total mass of component B. More preferably, it is 0.1% by mass or more and 5% by mass or less, and even more preferably, it is 0.2% by mass or more and 3% by mass or less. The content of the above substituent in component B can be determined by comparing the magnitude of the substituent-specific peak in the infrared absorption spectrum with the magnitude of the spectral peak of a material with a known content.

[0070] The organic polymer of Component B is an organic polymer such as resin, rubber, or elastomer. Preferably, Component B may be composed of a resin or an elastomer having thermoplasticity. The main chain of Component B is preferably composed as 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. Alternatively, a form in which the main chain of Component B is composed as a styrene-based polymer such as a hydrogenated styrene-based thermoplastic elastomer (SEBS) is also preferable. Examples of the organic polymer applicable as Component B other than these include elastomers having a main chain of polyurethane-based, polyester-based, or polyamide-based. The main chain having these structures is less likely to affect the formation of crosslinking points in the side chain and the activation of molecular movement of the crosslinked portion and the movement of crosslinking points by heating, and in the side chain portion, the high heat resistance, reshaping property, and flexibility brought about by those phenomena are effectively exhibited as the characteristics of the entire crosslinked body of Component B. In particular, when the main chain of Component B is composed of an olefin-based polymer, those effects can be obtained highly.

[0071] Component B preferably has a flow start temperature in the range of 50°C or higher and 190°C or lower. Then, through crosslinking by metal ions released from Component A, it is easy to obtain a crosslinked body having a flow start temperature of 190°C or higher and 300°C or lower. Also, high moldability can be obtained when molding the crosslinkable polymer composition before crosslinking into a desired shape by extrusion molding or the like. If the flow start temperature of Component B is 80°C or higher and 160°C or lower, it is more preferable.

[0072] Furthermore, from the viewpoint of obtaining a crosslinked product exhibiting high flexibility through crosslinking by metal ions released from Component A, it is preferable that the hardness of Component B is kept low. For example, the Shore D hardness of Component B measured in accordance with JIS K6253 may be less than 50. Then, the crosslinked polymer material containing the crosslinked product can be suitably used to form members that require bending, such as the insulating coating of insulated wires. More preferably, the D hardness of Component B may be 45 or less, and further 40 or less. The lower limit of the D hardness of Component B is not particularly provided, but from the viewpoint of ensuring material strength, etc., it may be, for example, 10 or more, and further 20 or more.

[0073] The crosslinkable polymer composition according to the present embodiment may appropriately contain additives such as a flame retardant, a copper corrosion inhibitor, an antioxidant, and a colorant, in addition to the above-mentioned Component A and Component B, as long as the functions of the materials are not impaired. Further, as the polymer component, a polymer other than Component B may be contained, but the content thereof is preferably kept less than the content of Component B. More preferably, the crosslinkable polymer composition preferably contains only Component B as the polymer component. Further, compounds in the following groups (a) to (f) can be cited as components that are preferably not contained in the crosslinkable polymer composition. That is, (a) a silane coupling agent, (b) an epoxy compound, (c) an isocyanate, an isothiocyanate compound, (d) a photo radical generator, a thermal radical generator, (e) a chlorine compound, a bromine compound, (f) a volatile organic solvent can be cited. When the compounds in groups (a) to (d) are contained in the crosslinkable polymer composition, there is a possibility that unintended chemical reactions such as crosslinking of Component B by a reaction different from the crosslinking reaction via metal ions released from Component A during heating, or cleavage of the main chain of Component B may occur. Then, there is a possibility that the heat resistance and reprocessability of the crosslinkable polymer composition may not be sufficiently exhibited. Further, when the compounds in group (e) are contained in the crosslinkable polymer composition, coloring and generation of corrosive gases may occur due to heating. When the compounds in group (f) are contained in the crosslinkable polymer composition, ignition and generation of bubbles may occur when the composition is molded.

[0074] The crosslinkable polymer composition can be prepared by mixing component A, component B, and an additive component added as necessary. The mixing can be carried out, for example, by heat-kneading each component or by dissolving each component in an organic solvent and heating and stirring. When using the crosslinkable polymer composition, the crosslinkable polymer composition may be appropriately heated and then formed into an arbitrary shape by extrusion molding or the like. At this time, the heating temperature should be higher than the flow start temperature of component B and lower than the temperature at which component A dissociates metal ions due to decomposition or phase transition. Furthermore, by heating the crosslinkable polymer composition after molding to a temperature equal to or higher than the temperature at which component A dissociates metal ions due to decomposition or phase transition, the crosslinking of component B by the metal released from component A proceeds, resulting in a crosslinked polymer material containing a crosslinked body. Then, if the formed crosslinked polymer material is heated to a temperature equal to or higher than the flow start temperature of the crosslinked body, the crosslinked polymer material acquires fluidity and can be remolded. The remolding can be reversibly repeated. Since the crosslinkable polymer composition according to the present embodiment can form a crosslinked structure only by heating, compared with the case of using electron beam crosslinking or silane crosslinking, the crosslinking process can be carried out with simple equipment. The remolding process can also be carried out with simple equipment because it can be carried out by applying an external force as appropriate while heating.

[0075] [2] Insulated wires and wire harnesses The crosslinked polymer material formed from the crosslinkable polymer composition according to the present embodiment can be used for applications constituting any member. However, taking advantage of its high heat resistance, remoldability, and further flexibility, it can be suitably used as a constituent material for insulated wires and wire harnesses for automobiles and the like. In insulated wires and wire harnesses, heat generation easily occurs due to energization of metal members such as wire conductors, and high heat resistance such as not causing irreversible deformation during heat generation is also required for the polymer material disposed in the vicinity of these metal members. In addition, there may be a demand to remold the polymer material once formed into a predetermined shape due to requirements such as deformation of the insulated wire or change in the configuration of the wire harness.

[0076] In the case of an insulated wire and a wire harness, the specific location where 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 outer covering material that bundles a plurality of insulated wires in the wire harness, and a wire protection material. Among these, a form in which the insulating coating of the insulated wire is composed of the crosslinked polymer material according to the embodiment of the present disclosure is preferable.

[0077] Fig. 2 shows an example of an insulated wire according to the embodiment of the present disclosure in a cross section orthogonal to the axial direction. The insulated wire 1 shown in Fig. 2 has a wire conductor 2 and an insulating coating 3 that covers the outer periphery of the wire conductor 2. The configuration of the wire conductor 2 is not particularly limited, but it is configured as a stranded conductor in which a plurality of strands 21 are twisted together. Also, in the illustrated example, the insulated wire 1 is configured to have a flat portion, and the cross section of the wire conductor 2 has a flat shape (a shape that is long in the width direction). The insulating coating 3 is composed of the crosslinked polymer material according to the embodiment of the present disclosure described above. The insulating coating 3 also has a flat cross-sectional outer shape following the shape of the wire conductor 2.

[0078] In the insulated wire 1, when an electric current is passed through the wire conductor 2, heat generation occurs and the insulating coating 3 is also heated. However, the insulating coating 3 is composed of the crosslinked polymer material according to the embodiment of the present disclosure described above and has high heat resistance. Therefore, for example, if the temperature is 190°C or lower, even if the insulating coating 3 is heated, the influence of heat, such as irreversible deformation, is unlikely to occur.

[0079] Since the insulated wire 1 has a flat portion, the space required for routing can be reduced, and space savings can be enhanced. Here, by taking advantage of the fact that the crosslinked polymer material constituting the insulation coating 3 has reprocessability, the insulated wire 1 with a flat portion can be easily formed using a conventionally common insulated wire (round wire) having a substantially circular cross section. For example, with respect to a round wire having an insulation coating 3 made of a crosslinked polymer material that has been crosslinked according to an embodiment of the present disclosure, by applying a compressive force in one direction while heating the wire to a temperature equal to or higher than the flow start temperature of the crosslinked body, a flat portion can be easily formed. The wire conductor 2 is configured as a stranded conductor, so it can be easily deformed by the application of force, and the insulation coating 3 is also in a state of having fluidity by heating, so it can be easily deformed following the deformation of the wire conductor 2. After that, the insulation coating 3 may be allowed to cool and return to the state of the original stable crosslinked body. Alternatively, in the already formed flat portion, by applying a force so as to compress from both sides in the width direction while heating the insulation coating 3 to a temperature equal to or higher than the flow start temperature of the crosslinked body, the flat portion can be returned to the shape of a round wire or a shape with a low flatness close to it. Also in this case, following the deformation of the wire conductor 2, the insulation coating 3 will be deformed into a shape with a low flatness.

[0080] Thus, since the insulation coating 3 is composed of a material having reversible reprocessability, deformation of the insulated wire 1 into an arbitrary shape, such as bidirectional deformation between a cross-sectionally flat shape and a substantially circular cross section, can be easily performed while deforming the insulation coating 3 following the wire conductor 2. For example, in a routing path, changes in the cross-sectional shape of the insulated wire, such as forming a flat portion on a round wire only at locations where space savings are required, can be performed with a high degree of freedom. Then, for example, it becomes possible to produce various insulated wires having flat portions at different locations using a common wire as a raw material. The insulated wire may be used alone, or may be used in the form of a wire harness including the insulated wire by connecting members such as connection terminals or bundling it with another insulated wire.

Example

[0081] Examples are shown below. The present invention is not limited by the examples. Unless otherwise specified, sample preparation and evaluation were performed at room temperature in air.

[0082] <Sample Preparation> To prepare Samples A1 to A10 and Samples B1 to B13 respectively, the A component and the B component were put into xylene in an amount 5 times their total weight according to the composition (unit: parts by mass) shown in Tables 1 and 2, and vigorously stirred at 80 °C for 30 minutes for dispersion and mixing. Then, after vacuum drying the mixture, it was press-molded at 250 °C for 10 minutes to produce a sample sheet with a thickness of 2 mm. In at least Samples A1 to A10, crosslinking of the B component by metal ions derived from the A component occurred by heating at 250 °C. The progress of crosslinking was confirmed by infrared absorption spectrum. Specifically, the absorption of the C=O stretching vibration (around 1790 cm -1 -1) of the acid anhydride and the C=O stretching vibration (around 1720 cm -1 -1) of the carboxylic acid present in the infrared absorption spectrum of the B component before crosslinking was confirmed to disappear or decrease with crosslinking.

[0083] The materials used were as follows. (1) A component Below, together with the material type, the decomposition point or phase transition point obtained from DSC measurement is shown in parentheses. · 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(II) oxide (none (>300 °C)) ·stCa: Calcium stearate (93 °C)

[0084] (2) Component B Below, together with the material types, the flow start temperature (the measurement method is the same as the method described in the evaluation method section below), and the hardness (Shore D hardness measured according to JIS K6253) are shown together. ·MAH-SEBS: Maleic acid-modified hydrogenated styrene-based thermoplastic elastomer, "M1911" manufactured by Asahi Kasei Corporation, flow start temperature 142 °C, D hardness 36 ·MAH-EO: Maleic acid-modified ethylene-α-olefin copolymer, "MH5020" manufactured by Mitsui Chemicals, Inc., flow start temperature 132 °C, D hardness 15 ·MAHA-SBBS: Maleic acid·amine-modified hydrogenated styrene-based elastomer, "N502" manufactured by Asahi Kasei Corporation, flow start temperature 182 °C, D hardness 41 ·EMA: Ethylene-methacrylic acid copolymer, "N1110H" manufactured by Mitsui Dow Polychemical Co., Ltd., flow start temperature 109 °C, D hardness 49 ·SEBS: Hydrogenated styrene-based thermoplastic elastomer, "H1041" manufactured by Asahi Kasei Corporation, flow start temperature 137 °C, D hardness 36

[0085] <Evaluation Method> (1) Flow start temperature Using the above sample sheet, a test piece of 10 mm × 10 mm × 2 mm t was prepared. This test piece was placed on a hot plate with variable temperature, and a 2 mm φ cylindrical indenter with a dial gauge attached to the upper part was pressed against the center of the test piece with a force of 1 N. Then, while raising the temperature of the hot plate at a rate of 5 °C / min, the distance that the indenter penetrated into the sample was recorded.

[0086] When the penetration of the indenter reached 2.0 mm (when it penetrated), the temperature at that time was defined as the flow start temperature. Samples in which the flow start temperature was 5°C or more higher than that of the B component not containing the A component were considered to have improved heat resistance through crosslinking by metal ions.

[0087] (2) Elastic modulus The above sample sheet was cut into strips with a length of 50 mm × width of 5 mm × thickness of 2 mm. At room temperature and in the air, with a gripping width of 10 mm, a tensile test was carried out at a speed of 10 mm / min. Then, the elastic modulus (tensile elastic modulus) was obtained by converting from the strain between a tensile load of 1 N - 2 N. If the elastic modulus was within ±30% of the value of the B component not containing the A component (that is, the measured values of samples B1~B3, B12, B13), it could be considered that the influence of crosslinking on the elastic modulus was small. Note that the rate of change of the elastic modulus was defined as “+” for the direction in which the elastic modulus increased due to crosslinking and “-” for the decreasing direction. For samples B9 and B10, due to the low fluidity during press molding, a sample sheet large enough to evaluate the elastic modulus could not be obtained.

[0088] (3) Confirmation of chemical structure change during heating Regarding sample A1, during the preparation of the samples described above, a vacuum-dried product before press molding was taken out. Then, in the range of 100°C to 260°C, infrared absorption spectroscopic measurement was carried out by the total reflection measurement method (ATR method). The heating rate was 10°C / min. From the obtained spectrum, the change in the chemical structure of the crosslinked product due to heating was examined.

[0089] <Evaluation results> In the following Tables 1 and 2, for samples A1~A10, B1~B13, the content of each component (unit: parts by mass) is shown in the upper row, and the results of each evaluation are shown in the lower row.

[0090]

Table 1

Table 2

[0091] According to Table 1, all of Samples A1 to A10 contain, as raw materials, Component A in which metal ions are released by heat and Component B composed of an organic polymer containing an electron-withdrawing substituent capable of forming an ionic bond with a metal ion in the side chain. The sample sheet obtained through crosslinking during press molding has a flow start temperature of 190°C or higher and 300°C or lower. The flow start temperatures of these Samples A1 to A10 are each 5°C or higher than the flow start temperature of Component B, and it can be said that high heat resistance is obtained by crosslinking. Also, since the molding temperature of general thermoplastic resins is about 300°C and Samples A1 to A10 have a flow start temperature of 300°C or lower, it can be said that they have high remoldability. Furthermore, the elastic modulus is suppressed to 30 MPa or lower, and the increase rate with respect to the tensile elastic modulus of uncrosslinked Component B is also less than 30%. Each sample maintains high flexibility even after crosslinking.

[0092] In contrast, Samples B1 to B3, B12, and B13 do not contain Component A, and correspondingly, the flow start temperature is below 190°C because crosslinking of Component B by metal ions cannot proceed. In Samples B4 and B5, zinc oxide and calcium stearate are used as Component A instead of metal complexes. Since these compounds do not release metal ions even when heated, Component B cannot be crosslinked. Correspondingly, in Samples B4 and B5 as well, the flow start temperature is much lower than 190°C and is almost the same as that of Sample B1.

[0093] In Sample B6, Component B does not have a substituent capable of forming an ionic bond with a metal ion, and a crosslinked structure cannot be formed in Component B by metal ions derived from Component A. Correspondingly, the flow start temperature is much lower than 190°C and is almost the same as that of Sample B1.

[0094] In Sample B7, the polymer main chain of Component B has a carboxylic acid group, which is an electron-withdrawing group, but the side chain does not have an electron-withdrawing substituent. In the carboxylic acid group in the main chain, due to the steric hindrance of the adjacent methacryloyl group, a crosslinked structure via ionic bonding with metal ions cannot be effectively formed. Correspondingly, the flow start temperature is much lower than 190 °C. Also, even if a slight crosslinked structure is formed, it is considered that the degree of freedom of movement at the crosslinked sites is low, and correspondingly, the elastic modulus is also high.

[0095] In Sample B8 as well, the flow start temperature is below 190 °C. This is considered to be due to the fact that the metal contained in Component A is lithium, a monovalent metal, and a stable crosslinked structure cannot be formed in Component B. On the other hand, in Samples B9 and B10, the flow start temperature is above 300 °C. This is because copper and nickel, which are metals with a large number of possible oxidation states and a relatively low ionization tendency, are used as the metal in Component A, and when the crosslinked body is heated, it is considered that fluidization due to the movement of crosslinking points is less likely to occur. Furthermore, in these samples, due to the low fluidity of the crosslinked body, a sample sheet for measuring the elastic modulus could not be manufactured by press molding. When the temperature during press molding is further increased, partial decomposition of Component B starts, and discoloration and deterioration become significant.

[0096] In Sample B11, Component A is composed of a metal complex, but the titanium atom is in the state of TiO(II), and heat causes the release of TiO 2+ ions. Through ionic bonding with this metal ion-containing ion, the substituent on the side chain of Component B undergoes crosslinking. Correspondingly, since the ionic bond is not very strong, the flow start temperature of the crosslinked body remains below 190 °C. It is considered that the reason for the failure to form a strong ionic bond is that the three-dimensional structure of the metal coordination state at the crosslinked site becomes bulky and the molecular aggregation density at the crosslinked site decreases.

[0097] Here, Samples A1 to A10 are compared with each other. In Samples A1 to A4 and A9, the types of metals contained in Component A are different. Among these, when comparing the group of Samples A1 to A4 with Sample A9 in which Component A contains titanium, the flow start temperature of Sample A9 is lower than that of the other samples and is exactly 190°C. This is presumably because even if titanium ions are released from Component A, they are easily oxidized and become in a low-activity state, making it difficult to enhance the crosslinking efficiency. On the other hand, for calcium, zinc, aluminum, and zirconium contained in Component A in Samples A1 to A4, the released metal ions contribute to the formation of the crosslinked structure in Component B while maintaining high activity. Therefore, a high flow start temperature exceeding 190°C and even exceeding 200°C is obtained, and it has high heat resistance. Furthermore, among Samples A1 to A4, Samples A3 and A4 containing aluminum and zirconium in Component A have an extremely high flow start temperature exceeding 230°C. That is, it can be said that using a material that releases aluminum or zirconium ions as Component A can obtain particularly high heat resistance in the crosslinked body. In Sample A1 containing calcium, an alkaline earth metal, in Component A, some non-uniformity was observed during the kneading of Component A and Component B, and this is considered to be the reason why the flow start temperature does not become as high as that of Samples A3 and A4. Also, Sample A2 containing zinc in Component A is considered not to have as high a flow start temperature as Samples A3 and A4 due to the phase transition start temperature of Component A being lower than that of Samples A3 and A4 as shown above.

[0098] In each of the sets of Samples A1, A5, and A10, and the set of Samples A2 and A6, the types of Component B are different. When comparing the samples that make up each of these sets, in Samples A5 and A6, which use Component B with an olefin-based polymer as the main chain, the increase in the flow start temperature due to crosslinking is larger than that in Samples A1, A10, and A2, which use Component B with a styrene-based polymer as the main chain. That is, it can be seen that by using Component B with an olefin-based polymer as the main chain, a high effect of improving heat resistance can be obtained by forming a crosslinked structure via metal ions. When comparing Sample A1 and Sample A10, both of which use Component B with a styrene-based polymer as the main chain, the flow start temperature is higher in Sample A10. This is presumably because MAHA-SBBS used as Component B in Sample A10 is slightly amine-modified and contains domains of inner salts in the polymer chain.

[0099] Samples A1, A7, and A8 differ from each other in the content of Component A within the range of 0.1 to 30 parts by mass with respect to a total of 100 parts by mass of Component A and Component B. At any of these contents, a flow start temperature of 190°C or higher and 300°C or lower is obtained, and although the elastic modulus is suppressed to 30 MPa or lower, the flow start temperature increases as the content of Component A increases. On the other hand, the elastic modulus is suppressed to be lower as the content of Component A decreases, and high flexibility is exhibited.

[0100] Finally, taking Sample A1 as an example, the change in chemical structure when heating the crosslinked product obtained by crosslinking Component B with metal ions is examined. Fig. 3 shows the infrared absorption spectrum (ATR-IR spectrum) measured while raising the temperature of the vacuum-dried product of the composition for Sample A1. The measurement starts at 100°C, but in Sample A1, crosslinking of Component B by metal ions already released from Component A has progressed at 100°C, and the peak near 1600 cm -1 can be attributed to the C=O antisymmetric stretching of the carboxylic acid group in the state where the metal ions (calcium ions) released from Component A are ionically bonded to the carboxylic acid group of Component B in a monodentate manner, as shown in Fig. 1A.

[0101] The peak near 1600 cm -1 broadens with the increase in temperature. This broadening indicates that the molecular motion is activated in the vicinity of the carboxylic acid group. That is, as shown in Fig. 1B, it is suggested that the thermal motion is activated in the vicinity of the crosslinking site, including the side chain of component B.

[0102] Furthermore, in the spectrum at a temperature of 240 °C or higher, a new peak appears near 1540 cm -1 and the peak grows with further increase in temperature. According to past findings, this new peak can be attributed to the symmetric stretching of C=O in the state where the coordination of the carboxylic acid group to the metal ion is delocalized (multidentate). That is, as shown in Fig. 1C, it is suggested that the crosslinking structure is delocalized within the molecular chain of component B, resulting in a state where the crosslinking points are movable. It is considered that due to the movement of these crosslinking points, the already formed crosslinked body acquires fluidity and becomes in a state where it can be reshaped. The fact that the appearance of the new peak occurs between 220 °C and 240 °C also coincides with the flow start temperature of sample A1 being 225 °C located within this range, as shown in Table 1, supporting the above mechanism.

[0103] As described above, the embodiments of the present disclosure have been described in detail. However, the present invention is not limited to the above embodiments at all, and various modifications are possible without departing from the gist of the present invention.

Explanation of reference signs

[0104] 1 Insulated electric wire 2 Electric wire conductor 21 Strand 3 Insulation coating

Claims

1. An electric wire conductor and an insulating coating composed of a crosslinked polymer material formed as a crosslinked body of a crosslinkable polymer composition, covering the outer periphery of the electric wire conductor. The crosslinkable polymer composition includes a component A in which metal ions are released by heat, and a component B composed of an organic polymer having side chains. The component B includes, in the side chain, an electron-withdrawing substituent capable of forming an ionic bond with metal ions released from the component A. The crosslinked body is obtained by crosslinking the component B with metal ions released from the component A, and is an insulated electric wire having a flow start temperature in the range of 190°C or higher and 300°C or lower.

2. The component B has a flow start temperature in the range of 50°C or higher and 190°C or lower. The insulated electric wire according to Claim 1.

3. The component B has a Shore D hardness of less than 50. The insulated electric wire according to Claim 1 or Claim 2.

4. The component A has a decomposition point or a phase transition point in the range of 50°C or higher and 300°C or lower. The insulated electric wire according to any one of Claims 1 to 3.

5. The component A has a decomposition point or a phase transition point at a temperature equal to or higher than the flow start temperature of the component B. The insulated electric wire according to any one of Claims 1 to 4.

6. The component A is a metal complex containing a ligand having the structure of the following formula (1). The insulated electric wire according to any one of Claims 1 to 5. 【Chemical 1】 Here, R １ and R ２ each independently represents a hydrocarbon group having 1 to 8 carbon atoms, and R ３ represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. At least two of R １ , R ２ , R ３ include the case where they are interconnected by a ring structure.

7. The metal ions released from the component A are at least one kind of ions among alkaline earth metals, aluminum, zinc, titanium, and zirconium. The insulated electric wire according to any one of Claims 1 to 6.

8. The metal ions released from the component A are at least one kind of ions of aluminum and zirconium. The insulated electric wire according to Claim 7.

9. The substituent of the component B is at least one kind among carboxylic acid groups, acid anhydride groups, and phosphate groups. The insulated electric wire according to any one of Claims 1 to 8.

10. The substituent of the component B is bonded to the main chain via an alkyl group or an alkylene group having 1 or more carbon atoms. The insulated electric wire according to any one of Claims 1 to 9.

11. The component B does not contain an electron-withdrawing group in the main chain. The insulated electric wire according to any one of Claims 1 to 10.

12. The insulating electric wire according to claim 11, wherein the main chain of the component B is an olefin polymer or a styrene polymer.

13. The insulating electric wire according to any one of claims 1 to 12, wherein the crosslinkable polymer composition contains 0.1 part by mass or more and 30 parts by mass or less of the component A, with the total of the component A and the component B being 100 parts by mass.

14. The insulating electric wire according to any one of claims 1 to 13, wherein the wire conductor is formed by twisting a plurality of strands, and the insulating electric wire has a flat portion in which the cross section of the wire conductor orthogonal to the axial direction is flat.

15. A wire harness including the insulating electric wire according to any one of claims 1 to 14.

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