In-vehicle busbar

Abstract

The objective of the present invention is to provide an in-vehicle busbar in which fire resistance performance and insulation performance are maintained even if a fire or the like occurs for an extended period of time. An in-vehicle busbar (10) that addresses the above includes a metal bar (20); a fire-resistant layer (30) covering the metal bar (20), and an insulator layer (40) covering the fire-resistant layer (30). The insulator layer (40) contains a dynamic crosslinked product of a polyolefin resin and a rubber component, and the gel fraction of the insulator layer (40) measured in accordance with JIS C 3005:2014 4.25 is 70% or more.

Description

Automotive Bus Bars

[0001] The present invention relates to a bus bar suitable for in-vehicle use.

[0002] In electric vehicles such as BEVs (Battery Electric Vehicles) and HEVs (Hybrid Electric Vehicles), bus bars are used to supply power between a battery unit and an inverter. In recent electric vehicles, not only the motor but also the brakes, steering wheel, doors, and window opening and closing mechanisms are electrically operated. Therefore, if a vehicle needs to leave the vehicle due to an accident or a fire caused by poor maintenance, the power supply system, including the battery unit and bus bars, must be able to maintain a power supply for a certain period of time and keep the electrical components running, ensuring time for evacuation and notification. Lithium-ion batteries, which are widely used as batteries, can deform and ignite due to external heating or self-heating. Therefore, lithium-ion batteries are protected as a unit in a robust, fire-resistant container. Furthermore, bus bars must be efficiently routed in the limited space around the battery, and therefore must also be fire-resistant.

[0003] Patent Document 1 describes a busbar wire having a flat conductor and an insulating coating covering the flat conductor. The insulating coating is made of a heat-shrinkable material such as polyolefin, polyvinyl chloride, or fluorine-based resin. The busbar wire is formed by placing the flat conductor inside the insulating coating and then thermally shrinking the insulating coating with a heat gun, iron, or the like.

[0004] Japanese Patent Application Laid-Open No. 2022-6856

[0005] However, in the busbar wire of Patent Document 1, if a fire caused by an accident or poor maintenance occurs over a long period of time, the insulating coating may melt due to heat. If the molten coating falls from the busbar wire, there is a risk of secondary fire spread. Furthermore, if the insulating layer burns and carbonizes, the insulating performance of the insulating layer may deteriorate, which may further exacerbate the damage.

[0006] Therefore, a main object of the present invention is to provide an in-vehicle bus bar that can maintain fire resistance and insulating performance even in the event of a fire or the like that lasts for a long period of time.

[0007] In order to solve the above problems, one aspect of the present invention provides the following vehicle busbars. [1] An vehicle busbar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulator layer covering the fire-resistant layer, wherein the insulator layer contains a dynamically cross-linked product of a polyolefin resin and a rubber component, and the insulator layer has a gel fraction of 70% or more as measured in accordance with JIS C 3005:2014 4.25. [2] The vehicle busbar described in [1] above, wherein the insulator layer has a minimum insulation resistance of 1 MΩ or more when heated at 500°C for 30 minutes. [3] The vehicle busbar described in [1] or [2] above, wherein the insulator layer has a gel fraction of 72 to 75%. [4] The on-vehicle busbar according to any one of the above [1] to [3], wherein the insulator layer further contains a flame retardant. [5] The on-vehicle busbar according to any one of the above [1] to [3], wherein the dynamically crosslinked product is obtained by dynamically crosslinking 100 parts by mass of the polyolefin resin and 20 parts by mass or more and 37.5 parts by mass or less of the rubber component in the presence of a crosslinking agent.

[0008] According to the present invention, it is possible to provide an in-vehicle bus bar that can maintain fire resistance and insulation performance even in the event of a fire or the like that lasts for a long time.

[0009] Fig. 1A is a perspective view showing the configuration of an on-board bus bar according to one embodiment of the present invention, and Fig. 1B is a cross-sectional view taken along line A-A in Fig. 1A. Fig. 2 is a flowchart showing a method for manufacturing an on-board bus bar according to one embodiment of the present invention. Fig. 3 is a graph showing the measurement results of the insulation resistance value of an insulator layer at 500°C measured in an example.

[0010] In-vehicle busbars according to preferred embodiments of the present invention will be described below. In this specification, the term "to" indicating a range of values ​​means that the range includes both the lower limit and the upper limit.

[0011] (Configuration of an Automotive Busbar) FIG. 1A is a perspective view showing the configuration of an automotive busbar 10 according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line A-A in FIG. 1A . As shown in FIGS. 1A and 1B , the automotive busbar 10 of this embodiment includes a metal bar 20, a fire-resistant layer 30 covering the metal bar 20, and an insulating layer 40 covering the fire-resistant layer 30. Heat-shrinkable polyolefins, polyvinyl chloride, fluorine-based resins, and silicones have also been used for the insulating layer 40 of conventional automotive busbars 10 having this configuration. However, insulating layers 40 made of these resins tend to melt and become more fluid when exposed to high temperatures in the event of a fire or other incident. The molten resin may then fall onto the surrounding area, potentially causing a secondary fire spread. On the other hand, if the molten resin penetrates into gaps in the fire-resistant layer 30, it may burn or carbonize. As a result, even if the insulating layer 40 and the fire-resistant layer 30 are provided, the insulating performance may be reduced, and there is a concern that the damage may become even greater.

[0012] In contrast, the insulator layer 40 of this embodiment contains a dynamically crosslinked product of a polyolefin resin and a rubber component. The insulator layer 40 has a gel fraction of 70% or more, as measured by the method described below. Even if such an insulator layer 40 reaches a high temperature and melts, the molten material has low fluidity. Therefore, even in the event of a fire or other disaster, the insulator layer 40 is not likely to fall off the vehicle bus bar 10 or penetrate into the fire-resistant layer 30. As a result, the vehicle bus bar can maintain its fire resistance and insulating performance even in the event of a prolonged fire. Each component of the vehicle bus bar is described below.

[0013] The metal bar 20 included in the vehicle bus bar 10 of this embodiment is a plate-shaped member made of a conductive metal material. The material of the metal bar 20 is not particularly limited as long as it is conductive. Examples of materials for the metal bar 20 include copper or a copper alloy. The metal bar 20 may be composed of a single metal plate or multiple laminated thin metal plates. The thickness and width of the metal bar 20 are determined appropriately depending on the magnitude of the current, the installation location, the installation conditions, and the like. When the metal bar 20 is composed of multiple laminated thin metal plates, the thickness of the metal plate is within a range of 0.1 to 0.3 mm. Furthermore, the metal bar 20 composed of multiple laminated thin metal plates may have both ends welded together, allowing it to be twisted or bent. For example, one end of the metal bar 20 is connected to one of the batteries, and the other end is connected to an inverter. If the battery terminals are bolt type, the connection between the battery and the vehicle bus bar 10 (metal bar 20) can be firmly fixed by fitting the terminals into the holes 21 formed at both ends of the metal bar 20 and fastening them with nuts.

[0014] The fire-resistant layer 30 is a layer disposed to cover the metal bar 20 except for the connection portion with the terminal. The fire-resistant layer 30 is, for example, composed of insulating fire-resistant tape wound horizontally to cover the metal bar 20. The insulating fire-resistant tape need only have insulating properties and may be composed of one layer or two layers. Examples of insulating fire-resistant tapes include mica tape and silicone tape. The mica (also called "mica") contained in mica tape is a natural mineral that has excellent electrical insulation and heat resistance. The mica tape may be a glass-mica tape in which mica is bonded to glass cloth. Alternatively, the mica tape may be a plastic-mica tape in which mica is bonded to a plastic film such as polyethylene. On the other hand, the silicone tape may be a tape composed of a single layer of silicone, or a tape composed of a laminate of a layer of silicone and a layer of glass cloth made of flat-woven glass fiber. If the insulating fire-resistant tape includes a glass cloth layer, the glass cloth layer is preferably disposed on the metal bar 20 side. The thickness of the fire-resistant layer 30 is preferably within a range of 0.1 to 0.5 mm. When the thickness of the fire-resistant layer 30 is 0.1 mm or more, the fire resistance and insulating properties are likely to be good. On the other hand, when the thickness of the fire-resistant layer 30 is 0.5 mm or less, the thickness of the fire-resistant layer is unlikely to be excessively thick.

[0015] The insulator layer 40 is a layer disposed so as to cover the fire-resistant layer 30. As described above, the insulator layer 40 contains at least a dynamically crosslinked product of a polyolefin resin and a rubber component. The gel fraction of the insulator layer 40 is 70% or more. Here, the dynamically crosslinked product of a polyolefin resin and a rubber component refers to a product in which a polyolefin resin and a rubber component are crosslinked by applying a shear force in the presence of a crosslinking agent. The dynamic crosslinking can be carried out when the insulator layer 40 is prepared as a compound or when the insulator layer 40 is formed by extrusion molding or the like.

[0016] The polyolefin resin used as the material for the dynamically crosslinked product may be any resin primarily containing olefin-derived structures. Specifically, the polyolefin resin may contain olefin-derived structural units in an amount of 50% by mass or more, preferably 80% by mass or more, of the total structural units constituting the polyolefin resin. Examples of polyolefin resins include olefin homopolymers, copolymers of two or more olefins, and copolymers of olefins with monomers other than olefins. The olefin preferably has 2 to 20 carbon atoms. Specific examples of olefins include ethylene, propylene, butylene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Examples of non-olefin monomers copolymerizable with olefins include vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. In this specification, the term "(meth)acrylate" includes methacrylate, acrylate, and mixtures thereof. Specific examples of polyolefin resins include polyethylene (ultra-low density polyethylene, low density polyethylene, high density polyethylene, etc.), polypropylene, polybutylene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-butylene-hexene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-butyl (meth)acrylate copolymer, etc. These can be used alone or in combination of two or more. Among the above, it is preferable that the polyolefin resin contains a structural unit derived from propylene, and polypropylene is preferred.

[0017] Examples of the rubber component include diene rubbers such as natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), and acrylonitrile butadiene rubber (NBR), as well as hydrogenated products thereof; olefin rubbers such as ethylene propylene rubber (EPDM, EPM) and butyl rubber (IIR); acrylic rubber (ACM); halogen-containing rubbers such as brominated butyl rubber, chlorinated butyl rubber, and halogenated isoolefin-para-alkylstyrene copolymer; silicone rubbers such as methyl vinyl silicone rubber and dimethyl silicone rubber; sulfur-containing rubbers such as polysulfide rubber; fluorine-containing rubbers such as vinylidene fluoride rubber and fluorine-containing vinyl ether rubber; and thermoplastic elastomers such as styrene elastomers, olefin elastomers, acid-modified olefin elastomers, ester elastomers, urethane elastomers, and polyamide elastomers. These may be used alone or in combination of two or more. Of the above, the rubber component is preferably an olefin-based elastomer or a styrene-based elastomer, and more preferably a styrene-based elastomer.

[0018] The crosslinking agent for dynamically crosslinking the polyolefin resin and the rubber component is not particularly limited, and examples thereof include sulfur, phenolic resins such as phenol-formaldehyde resins, peroxides, etc. Among these, peroxides are preferred in terms of reactivity, etc. Specific examples of peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl perbenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butylcumyl peroxide, etc. These may be used alone or in combination of two or more.

[0019] When obtaining a dynamically crosslinked product, the amount of rubber component is preferably 15 to 40 parts by mass, more preferably 17.5 to 37.5 parts by mass, and even more preferably 20.0 to 37.5 parts by mass, per 100 parts by mass of polyolefin resin. By adjusting the mass ratio of polyolefin resin to rubber component within this range, it becomes easier to satisfy the above-mentioned gel fraction. In this case, the amount of crosslinking agent is preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the polyolefin resin and rubber component combined. Within this range, dynamic crosslinking easily proceeds efficiently, and the gel fraction is easily increased.

[0020] Preferably, the insulator layer 40 further contains a flame retardant. The insulator layer 40 contains a flame retardant, which enhances the flame retardancy of the insulator layer 40. The insulator layer 40 may contain only one type of flame retardant, or may contain two or more types. Examples of flame retardants include magnesium hydroxide, aluminum hydroxide, halogen-based flame retardants, and phosphorus-based flame retardants. Among these, magnesium hydroxide is preferred from the viewpoint of ease of handling. When the insulator layer 40 contains a flame retardant, the amount of the flame retardant in the insulator layer 40 is preferably 30% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, relative to the total amount of the dynamically crosslinked product and the flame retardant.

[0021] The insulator layer 40 may further contain a copper inhibitor. When the metal bar 20 is made of copper or a copper alloy, copper ions from the metal bar 20 may deteriorate the insulator layer 40 (particularly the dynamically cross-linked product), resulting in a decrease in insulating performance. In contrast, when the insulator layer 40 contains a copper inhibitor, such a decrease in insulating performance is more easily suppressed. The insulator layer 40 may contain only one type of copper inhibitor, or may contain two or more types. The copper inhibitor may be any compound capable of capturing copper ions. Examples of copper inhibitors include hydrazides such as N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and isophthalic acid bis(2-phenoxypropionylhydrazine); 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzoamide; alcohol carboxylic acid esters, etc. When the insulator layer 40 contains a copper inhibitor, the amount of the copper inhibitor in the insulator layer 40 is, from the viewpoint of copper inhibition, preferably 0.1 parts by mass or more and 0.5 parts by mass or less, and more preferably 0.2 parts by mass or more and 0.4 parts by mass or less, relative to 100 parts by mass of the total amount of the dynamically crosslinked product and the flame retardant.

[0022] In addition to the dynamically crosslinked material, flame retardant, and copper inhibitor described above, the insulator layer 40 may further contain known additives, fillers, etc., within the scope that does not impair the purpose and effects of this embodiment.

[0023] The insulator layer 40 has a gel fraction of 70% or more, as measured by the following method. A gel fraction of 72% or more and 75% or less is more preferable. As described above, a high gel fraction makes the insulator layer 40 less likely to melt even at high temperatures, and even if it does melt, it is less likely to flow. Therefore, an automotive bus bar 10 with high fire resistance can be obtained. The gel fraction is largely dependent on the degree of crosslinking of the dynamically crosslinked product, but is also affected by the amount of the flame retardant. The gel fraction of the insulator layer 40 is a value measured in accordance with JIS C 3005:2014 4.25 (degree of crosslinking). Specifically, as described in the standard, the insulator layer alone is separated from the automotive bus bar and crushed to approximately 5 mm. 0.5 g of the sample is immersed in 50 g of xylene and heated to a temperature above the boiling point of xylene. The gel fraction (%) is the ratio of the mass of the sample after heating to the mass of the sample before heating, i.e., (mass of the sample after heating / mass of the sample before heating) × 100. The gel fraction in this specification is the average value of three measurements.

[0024] The minimum insulation resistance value of the insulator layer 40 during heating of the vehicle-mounted busbar 10 of this embodiment at 500°C for 30 minutes is preferably 1 MΩ or more, more preferably 10 MΩ or more, and even more preferably 40 MΩ or more. The higher the value, the better, so there is no particular upper limit. A high insulation resistance value means that when the insulator layer 40 is heated to 500°C, molten material of the insulator layer 40 is less likely to penetrate into the fire-resistant layer 30. The insulation resistance value of the insulator layer 40 can be measured, for example, by the following method. First, the vehicle-mounted busbar 10 is preheated to 500°C. Next, the insulator layer 40 is heated to 500°C for 30 minutes. During the 30-minute heating period, the insulation resistance value is measured multiple times using a mega-meter tester. For example, the insulation resistance value is measured every 5 minutes after the start of heating. The minimum insulation resistance value is then determined from the multiple measurements.

[0025] (Method of Manufacturing an On-Vehicle Busbar) Next, a method of manufacturing the above-described on-vehicle busbar 10 will be described. Fig. 2 is a flowchart of the method of manufacturing the on-vehicle busbar 10. As shown in Fig. 2, the method of manufacturing the on-vehicle busbar 10 includes a step (S110) of preparing a metal bar 20, a step (S120) of forming a fire-resistant layer 30 so as to cover the metal bar 20, and a step (S130) of forming an insulator layer 40 so as to cover the fire-resistant layer 30.

[0026] In the step (S110) of preparing a metal bar 20, a metal bar 20 is prepared. The metal bar 20 may be a commercially available product or may be manufactured.

[0027] In the step (S120) of forming the fire-resistant layer 30 of this embodiment, the fire-resistant tape is wound horizontally with a partial overlap to cover the metal bar 20. At this time, two pieces of insulating fire-resistant tape may be wound. For example, the first piece of insulating fire-resistant tape may be wound horizontally with a certain gap between them. Then, the second piece of insulating fire-resistant tape may be further wound horizontally with a predetermined overlap width over the first piece of insulating fire-resistant tape.

[0028] In the step (S120) of forming the insulator layer 40, the insulator layer 40 is formed so as to cover the fire-resistant layer 30. In this step, a resin composition containing the above-mentioned raw materials for the dynamically cross-linked product (a polyolefin resin, a rubber component, and a cross-linking agent), as well as a flame retardant, a copper inhibitor, and the like, as necessary, is prepared. The resin composition is then melt-extruded around the fire-resistant layer 30 to form the above-mentioned insulator layer 40.

[0029] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0030] 1. Preparation of an automotive bus bar (1) Example 1 A metal bar (width 20 to 30 mm × thickness 3 to 5 mm) made of rectangular copper was prepared. Two mica tapes (MAT-1PM18W, manufactured by Okabe Mica Industries Co., Ltd.) were wrapped horizontally around the metal bar with half of each tape overlapping, forming a fire-resistant layer.

[0031] As shown in Table 1 below, 100 parts by mass of polypropylene, which is the material for the dynamically crosslinked product, 27.5 parts by mass of a rubber component (styrene-based elastomer), and 0.3 parts by mass of a crosslinking agent (peroxide crosslinking agent), were charged into a kneading extruder. Furthermore, each component was further charged into the kneading extruder so that the amounts of the resulting dynamically crosslinked product and the flame retardant (magnesium hydroxide) would be the compositions shown in Table 2 below. A resin composition (compound) was then melt-kneaded and extruded around the fire-resistant layer to form an insulating layer. The insulating layer had a thickness of 1 mm.

[0032] (2) Examples 2 to 5 and Comparative Examples 1 and 2 Automotive bus bars were obtained in the same manner as in Example 1, except that the material of the dynamically cross-linked product was changed as shown in Table 1 below, and the composition of the insulator layer was changed as shown in Table 2 below. Irganox MD 1024 (manufactured by BASF) was used as the copper damage inhibitor. In Comparative Example 2, polyamide was used as the resin, and dynamic cross-linking was not performed.

[0033] 2. Evaluation (1) Identifying Gel Fraction The gel fraction of the insulator layer of the automotive busbars produced in the Examples and Comparative Examples was measured in accordance with JIS C 3005:2014 4.25 (degree of cross-linking). Specifically, as described in the standard, the insulator layer was separated from the automotive busbar and crushed to approximately 5 mm. 0.5 g of the sample was immersed in 50 g of xylene and heated to a temperature equal to or higher than the boiling point of xylene. The gel fraction (%) was calculated by dividing the mass of the sample after heating by the mass of the sample before heating (i.e., mass of the sample after heating / mass of the sample before heating × 100). The gel fraction was calculated by averaging three measurements taken using this method. The results are shown in Table 2.

[0034] (2) Measurement of Minimum Insulation Resistance at 500°C The insulation resistance of the insulator layer of the vehicle bus bars fabricated in the Examples and Comparative Examples was measured using the following method. First, the vehicle bus bars fabricated in the Examples and Comparative Examples were placed inside a heating furnace, and a load of 1 kg or more was applied to the vehicle bus bars. The vehicle bus bars were then preheated until the internal temperature reached 500°C. Then, the vehicle bus bars were subjected to main heating at 500°C for 30 minutes. During the main heating, specifically, the insulation resistance was measured using a mega tester immediately after the start of the main heating, and after 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes. The minimum insulation resistance during the main heating was determined. The measurement results of the insulation resistance values ​​are also shown in Figure 3. In Figure 3, the black circles indicate the results of Example 1, the white circles indicate the results of Example 2, and the black squares indicate the results of Example 3. The white squares indicate the results of Comparative Example 2. The dotted line in Figure 3 indicates the heating temperature. The minimum insulation resistance value at 500°C was evaluated according to the following criteria. The results are shown in Table 2. ◯: Minimum insulation resistance value at 500°C is 1 MΩ or more. ×: Minimum insulation resistance value at 500°C is less than 1 MΩ or burnt.

[0035] (3) Evaluation of Drooping The presence or absence of drooping of the insulator layer was evaluated as follows. It was visually evaluated whether the insulator layer melted and fell off due to heating during the measurement of the insulation resistance value. Drooping was evaluated according to the following criteria. The results are shown in Table 2. ◯: The molten insulator layer did not fall off. ×: The molten insulator layer fell off.

[0036] (4) Measurement of Brittle Temperature Only the insulator layer was peeled off from the vehicle bus bars produced in each Example and Comparative Example. Then, the brittle temperature of each layer was determined in accordance with JIS K7216 (1980). Evaluation was performed according to the following criteria. The results are shown in Table 2. ◯: Brittle temperature is -50°C or lower ×: Brittle temperature is above -50°C

[0037] (5) Evaluation of Heat Resistance on Vehicles The on-vehicle bus bars manufactured in each Example and Comparative Example were subjected to an on-vehicle heat resistance test based on ISO 19642-2 (2019). Evaluation was based on the following criteria. The results are shown in Table 2. ◎: 150°C or higher; ○: 125°C or higher but lower than 150°C; △: 105°C or higher but lower than 125°C.

[0038] 3. result

[0039]

[0040] As shown in Table 2 above, in Examples 1 to 5, in which the insulator layer contained a dynamically crosslinked product of a polyolefin resin and a rubber component and had a gel fraction of 70% or more, all had high insulation resistance values ​​and also good sagging evaluations. It is believed that with these insulator layers, even when the insulator layer reached high temperatures, the molten insulator layer was less likely to penetrate into the gaps in the fire-resistant tape layer, making it difficult for the insulation resistance value to decrease. Furthermore, it is believed that sagging was less likely to occur due to factors such as the low fluidity of the insulator layer when molten. Furthermore, the automotive bus bars of Examples 1 to 3 and 5 also had good brittle temperatures and in-vehicle heat resistance.

[0041] On the other hand, when the gel fraction of the insulator layer was less than 70%, sagging occurred and the insulation resistance value decreased (Comparative Examples 1 and 2). One of the reasons for this is thought to be the high fluidity of the molten insulator layer.

[0042] The vehicle-mounted bus bar of the present invention is useful, for example, as a bus bar for electrically connecting between a vehicle-mounted battery and an inverter.

[0043] 10: Vehicle bus bar 20: Metal bar 30: Fire-resistant layer 40: Insulator layer

Claims

1. An automotive busbar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulating layer covering the fire-resistant layer, wherein the insulating layer contains a dynamically cross-linked product of a polyolefin resin and a rubber component, and the gel fraction of the insulating layer measured in accordance with JIS C 3005:2014 4.25 is 70% or more.

2. The vehicle-mounted bus bar according to claim 1, wherein the minimum insulation resistance of the insulator layer is 1 MΩ or more when the vehicle-mounted bus bar is heated at 500°C for 30 minutes.

3. The vehicle-mounted bus bar according to claim 1, wherein the insulator layer has a gel fraction in the range of 72 to 75%.

4. The vehicle bus bar according to claim 1, wherein the insulating layer further contains a flame retardant.

5. An on-vehicle bus bar according to claim 1, wherein the dynamically crosslinked product is obtained by dynamically crosslinking 100 parts by mass of the polyolefin resin and 20 to 37.5 parts by mass of the rubber component in the presence of a crosslinking agent.

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