JP7596595B2 - Insulated wire and automotive cables - Google Patents

Description

The present invention relates to insulated electric wires and automotive cables.

Due to growing interest in environmental protection, hybrid electric vehicles (HEVs) that also use motors are becoming more common, and in the future, the shift to electric vehicles (EVs) will accelerate with the advent of advanced driver-assistance systems (ADAS) and autonomous driving.

Automotive cables contain insulated wires in which the conductor is covered with an insulator, and the insulator (covering material) is required to have high heat resistance. Specifically, the heat resistance must meet the required characteristics of Class D or higher of ISO 6722, the automotive wire standard. Conventionally, polyethylene with enhanced heat resistance due to cross-linking has generally been used for the insulator of such automotive cables, which require high heat resistance (see, for example, Patent Document 1).

On the other hand, the standard for electric wires for automobiles has been shifted from ISO 6722 to ISO 19642, and it has become necessary to select an insulator that can be applied to this. Class B requires heat resistance of -40 to 100°C, while Class C requires heat resistance of -40 to 125°C.

JP 2013-155269 A

Generally, materials with low dielectric constant such as polyethylene are used as the insulator, but polyethylene needs to be cross-linked to increase heat resistance, which leads to an increase in mass production costs due to the introduction of cross-linking equipment. Fluorine resins are also expected to be used as an alternative material with high heat resistance, but this has the problem of high material costs.
In this regard, there is the option of using polypropylene, which is inexpensive and has high heat resistance, but polypropylene deteriorates rapidly when it comes into contact with copper, a conductor (a phenomenon known as "copper poisoning" occurs), and its use as an insulator has been avoided.
Therefore, a main object of the present invention is to provide an insulated wire that is suitable for an in-vehicle cable and satisfies at least the requirements of Class B of ISO 19642, and that has heat resistance and can suppress the occurrence of copper damage even when polypropylene is used as the base resin.

In order to solve the above problems, the present invention provides:
Insulated wires used in automotive cables
A conductor made of soft copper wire;
and an insulator covering the conductor.
The base resin of the insulator is polypropylene,
The insulator contains a primary antioxidant, a secondary antioxidant and a copper inhibitor .
The primary antioxidant is a phenolic antioxidant, and the amount of the primary antioxidant added to the insulator is 0.15 to 0.50% by weight,
The secondary antioxidant is a phosphorus-based antioxidant, and the amount of the secondary antioxidant added to the insulator is 0.20 to 0.66 wt %;
The copper inhibitor is a heavy metal deactivator, and the amount of the heavy metal deactivator added to the insulator is 0.10 to 0.34% by weight.
The insulated wire is characterized in that the amount of the secondary antioxidant added is greater than the amount of the primary antioxidant added .

According to the present invention, even when polypropylene is used as the base resin, it is possible to obtain heat resistance and suppress the occurrence of copper damage.

FIG. 2 is a cross-sectional view showing a schematic configuration of an in-vehicle cable. FIG. 1 is a diagram illustrating the relationship between the autoxidation mechanism of a polymer and an antioxidant. FIG. 1 is a diagram illustrating the chemical action of a phenolic antioxidant. FIG. 1 is a diagram illustrating the chemical action of a phosphorus-based antioxidant. FIG. 2 is a diagram illustrating the chemical action of a copper inhibitor.

Hereinafter, a vehicle-mounted cable according to a preferred embodiment of the present invention will be described.
In this specification, the term "to" indicating a range of values means that the range includes the lower limit and the upper limit.

FIG. 1 is a cross-sectional view showing a schematic configuration of an in-vehicle cable 1. As shown in FIG.
As shown in FIG. 1 , the vehicle-mounted cable 1 has a twisted pair 10, a pressed winding 20, an inner sheath 30, a first shielding layer 40, a second shielding layer 50 and an outer sheath 60, and the outer circumference of the twisted pair 10 is wound and covered with the pressed winding 20, the inner sheath 30, the first shielding layer 40, the second shielding layer 50 and the outer sheath 60 in this order.

The twisted pair 10 is composed of two insulated electric wires 12, with a first type core 10A and a second type core 10B used as a pair. A third type core and a fourth type core may be added as a second twisted pair and used as a pair (it may be composed of four cores), or subsequent pairs of cores may be added and used. When adding a pair of cores, the insulated electric wires 12 are quad twisted.

The insulated wire 12 is composed of a conductor 14 and an insulator 16 , and has a configuration in which the outer circumference of the conductor 14 is covered with the insulator 16 .
The conductor 14 has a circular cross section and is a stranded wire formed by twisting together a plurality of wires. The conductor 14 may be a solid wire as long as it has a circular cross section, or may be a compressed stranded wire formed by twisting together a plurality of wires and compressing them.
The conductor 14 (including wire) is preferably a soft copper wire, and the outer periphery may be coated with a plating layer (not shown) of tin, nickel, or silver.
The outer diameter of the conductor 14 is preferably 0.4 to 0.6 mm.

The insulator 16 is made of insulating resin and is formed by extruding the insulating resin through a die of an extruder. The thickness of the insulator 16 is preferably 0.2 to 0.4 mm.
The insulating resin has polypropylene (PP) as a base resin, and a primary antioxidant, a secondary antioxidant, and a copper inhibitor are added to the insulating resin.
The "base resin" is the main component in the insulating resin, and is the component that is present in the largest amount among the components that make up the insulating resin.

The primary antioxidant and the secondary antioxidant are so-called antioxidants, and have the function of preventing aging (oxidative deterioration) of the base resin.
FIG. 2 is a diagram for explaining this function.
As shown in cycle I of Figure 2, when a polymer (RH) receives thermal or mechanical energy, it generates radicals (R.) and is automatically oxidized (ROO.). The primary antioxidant reacts with a substance that has oxygen radicals (ROO.), capturing the oxygen radicals and transforming the substance into a metastable substance (ROOH).
As shown in FIG. 2, the secondary antioxidant reacts with the metastable material (ROOH) and converts it to a stable material (ROH).
As shown in cycle II in Figure 2, the metastable substance (ROOH) is automatically oxidized to generate radicals (RO.+.OH). The primary antioxidant reacts again with the substance (RO.+.OH) that has oxygen radicals, capturing the oxygen radicals and turning the substance into an inactive substance (ROH+ _H2O ).
In this way, the primary antioxidant and the secondary antioxidant act as stabilizers in two stages against the autoxidation mechanism of the polymer, thereby preventing aging of the polymer.

The primary antioxidant according to this embodiment is preferably a phenolic antioxidant.
As shown in FIG. 3, the phenolic antioxidant captures the peroxide radical (ROO.) in the first stage of autoxidation, converting it to a metastable peroxide (ROOH).
As the phenol-based antioxidant, for example, pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) can be used, and Irganox 1010 manufactured by BASF Japan is commercially available.

The secondary antioxidant according to this embodiment is preferably a phosphorus-based antioxidant.
As shown in FIG. 4, a trivalent phosphite, which is an example of a phosphorus-based antioxidant, converts a metastable peroxide (ROOH) into a stable alcohol (ROH) in the second stage of autoxidation, and then becomes a pentavalent phosphate and is stabilized.
As the phosphorus-based antioxidant, for example, tris(2,4-di-tert-butylphenyl)phosphite can be used, and Irgafos 168 manufactured by BASF Japan is commercially available.

The amount of the primary antioxidant added to the insulating resin is preferably 0.15 to 0.50% by weight, and the amount of the secondary antioxidant added to the insulating resin is preferably 0.20 to 0.66% by weight. When comparing the amounts added, the amount of the secondary antioxidant added is greater than the amount of the primary antioxidant. This is for the following reason. In cycle I, the primary antioxidant captures peroxide radicals (ROO.) and turns them into a metastable substance (ROOH), which automatically oxidizes in cycle II to generate radicals (RO.+.OH). If the amount of the secondary antioxidant added is greater than the amount of the primary antioxidant added, the circulation of this cycle can be prevented.

The copper inhibitor is a so-called heavy metal deactivator, and has the function of forming a stable complex with heavy metal ions to prevent oxidation-reduction reactions.
FIG. 5 is a diagram for explaining this function.
As shown in FIG. 5, the copper inhibitor forms a stable complex by coordinating OH and CO with the copper ion, thereby blocking the copper ion (FIG. 5 shows salicyloylaminotriazole as an example of the copper inhibitor).
As the copper inhibitor according to the present embodiment, for example, 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide can be used, and Irganox MD 1024 manufactured by BASF Japan is commercially available.
The amount of the copper inhibitor added to the insulating resin is preferably 0.10 to 0.34% by weight.

In this embodiment, since the conductor 14 is made of soft copper wire, the copper damage inhibitor in the insulator 16 forms a stable complex with the copper ions to prevent copper damage.

The winding 20 is made of tape-shaped polyethylene terephthalate (PET) or polypropylene (PP). The winding 20 may be made of tape-shaped nonwoven fabric.

The inner jacket 30 is formed by extruding an inner jacket resin through a die of an extruder. The inner jacket resin is preferably made of polyvinyl chloride (PVC) or thermoplastic elastomers (TPE).
The inner jacket 30 is not essential and may be omitted.

The first shielding layer 40 is constructed by overlappingly winding metal tape.
The metal tape is a tape formed by laminating a metal foil and a resin tape, and is preferably formed by laminating an aluminum foil and a polyethylene terephthalate tape (PET tape). In the first shielding layer 40, the metal foil is wound in an overlapping manner so that the outer periphery is exposed.
On the other hand, the second shielding layer 50 is formed by braiding a plurality of metal wires. The second shielding layer 50 may be formed by horizontally winding a plurality of metal wires at a certain pitch or less. Each of the metal wires is preferably a so-called tin-plated annealed copper wire (TA; Tinned Annealed copper) in which a tin-plated layer is coated on a annealed copper wire.
The shielding layer according to this embodiment is composed of the first shielding layer 40 and the second shielding layer 50, and is adapted to block electromagnetic waves.

The outer jacket 60 is a so-called sheath, and is formed by extruding the resin for the jacket from the die of an extruder. The resin for the jacket is preferably made of polyvinyl chloride (PVC), polyolefin (PO), or thermoplastic elastomers (TPE).

Next, we will explain the manufacturing method of the vehicle cable 1.

First, a solid wire or compressed stranded wire having a circular cross section is prepared as the conductor 14, and an insulating resin is extrusion-coated onto the conductor 14 to form the insulator 16, thereby producing the insulated wire 12.
Thereafter, the two insulated wires 12 are twisted together at a constant pitch (pair twisted).

Thereafter, polyethylene terephthalate tape (PET tape) is wound around the twisted pair 10 in an overlapping manner to form a roll 20 .
Thereafter, the inner sheath resin is extruded onto the roll 20 to form the inner sheath 30 .
Thereafter, a metal tape is wound around the inner sheath 30 to form a first shielding layer 40, and a plurality of metal wires are braided to form a second shielding layer 50.

Finally, the second shielding layer 50 is extruded with a resin for the outer sheath to form the outer sheath 60, thereby manufacturing the vehicle cable 1.

According to the above-described in-vehicle cable 1, the primary and secondary anti-aging agents act effectively against the auto-oxidation mechanism of the base resin in the insulator 16, and the copper damage inhibitor acts effectively against copper damage in the conductor 14, so that even if polypropylene is used as the base resin, it has heat resistance and can suppress the occurrence of copper damage (see the examples below).

The in-vehicle cable 1 is preferably used for in-vehicle communication applications, and more preferably for transmitting images or video signals from an in-vehicle camera. In other words, the in-vehicle cable 1 is suitable as a cable that complies with the ISO-6722 standard or the ISO-19642 standard.

(1) Preparation of Samples (1.1) Preparation of Insulated Wire Samples First, seven soft copper wires with a diameter of 0.16 mm were twisted together to form a conductor with an outer diameter of 0.48 mm. The conductor was extrusion-coated with an insulating resin having the composition shown in Table 1 to form an insulator with a thickness of 0.225 mm, and an insulated wire with an outer diameter of 0.93 mm was formed.

(1.2) Preparation of Vehicle Cable Sample Two of the above-mentioned insulated electric wires were twisted together (twisted in a pair) at a constant pitch to form a twisted pair.
Thereafter, a 0.025 mm thick polyethylene terephthalate tape (PET tape) was wound around the twisted pair in a 1/4 overlapping manner (the PET tape was wound while overlapping by 1/4 of its width). The winding was then extrusion-coated with a thermoplastic elastomer (TPE) to form an inner jacket having an outer diameter of 2.76 mm.

Thereafter, a metal tape made by bonding aluminum foil and polyethylene terephthalate tape (PET tape) was prepared as the first shielding layer, and the metal tape was wrapped around the inner jacket in a 1/4 overlap to form a first shielding layer with an outer diameter of 2.92 mm.
Then, 85 pieces of tin-plated soft copper wire (TA) having a diameter of 0.1 mm were prepared as a second shielding layer, and the tin-plated soft copper wire was braided with the first shielding layer to form a second shielding layer having an outer diameter of 3.42 mm.
Finally, the second shielding layer was extrusion-coated with polyvinyl chloride (PVC) to produce an in-vehicle cable having an outer diameter of 4.12 mm.

(2) Evaluation of Samples According to ISO 19642 Class B and Class C, the heat resistance and the occurrence of copper damage at 105° C. and the heat resistance and the occurrence of copper damage at 125° C. were evaluated.
The evaluation results are shown in Table 1. In Table 1, "◯" indicates that the standard is met, and "×" indicates that the standard is not met.
Since the evaluation results were the same for the insulated wire sample and the in-vehicle cable sample, the same sample number is given to them in Table 1 and the evaluation results are shown therefor.

(3) Summary As shown in Table 1, in Sample 1, although an excessive amount of primary antioxidant was added (no secondary antioxidant was added), the sample lacked heat resistance and suffered from copper damage.
In sample 2, a secondary antioxidant was added (the amount added was less than that of the primary antioxidant), and it had heat resistance at 105°C and was able to prevent copper damage at 105°C.
In contrast, Samples 11-15 had heat resistance and were able to prevent copper damage at both 105° C. and 125° C. From these results, it was found that when a polypropylene resin is used as the base resin, adding a primary antioxidant and a secondary antioxidant, preferably adding a larger amount of the secondary antioxidant than the amount of the primary antioxidant, is effective in improving heat resistance at 105° C. and 125° C. and preventing copper damage.

This application claims priority from Japanese Patent Application No. 2022-024801, filed February 21, 2022. The contents of the specification and drawings of that application are incorporated herein by reference in their entirety.

The present invention relates to insulated electric wires and automotive cables, and is particularly useful for providing heat resistance and suppressing the occurrence of copper damage even when polypropylene is used as the base resin.

REFERENCE SIGNS LIST 1 In-vehicle cable 10 Twisted pair 10A to 10B First and second type wire cores 12 Insulated wire 14 Conductor 16 Insulator 20 Winding 30 Inner sheath 40 First shielding layer 50 Second shielding layer 60 Outer sheath

Claims (2)

Insulated wires used in automotive cables,
A conductor made of soft copper wire;
and an insulator covering the conductor.
The base resin of the insulator is polypropylene,
The insulator contains a primary antioxidant, a secondary antioxidant and a copper inhibitor .
The primary antioxidant is a phenolic antioxidant, and the amount of the primary antioxidant added to the insulator is 0.15 to 0.50% by weight,
The secondary antioxidant is a phosphorus-based antioxidant, and the amount of the secondary antioxidant added to the insulator is 0.20 to 0.66 wt %;
The copper inhibitor is a heavy metal deactivator, and the amount of the heavy metal deactivator added to the insulator is 0.10 to 0.34% by weight.
An insulated wire, wherein the amount of the secondary antioxidant added is greater than the amount of the primary antioxidant added . An insulated wire in which a conductor is covered with an insulator;
A shielding layer that blocks electromagnetic waves;
an outer jacket that covers the insulated wire and the shielding layer,
The conductor is a annealed copper wire,
The base resin of the insulator is polypropylene,
The insulator contains a primary antioxidant, a secondary antioxidant and a copper inhibitor .
The primary antioxidant is a phenolic antioxidant, and the amount of the primary antioxidant added to the insulator is 0.15 to 0.50% by weight,
The secondary antioxidant is a phosphorus-based antioxidant, and the amount of the secondary antioxidant added to the insulator is 0.20 to 0.66 wt %;
The copper inhibitor is a heavy metal deactivator, and the amount of the heavy metal deactivator added to the insulator is 0.10 to 0.34% by weight.
An in-vehicle cable, wherein the amount of the secondary antioxidant added is greater than the amount of the primary antioxidant added .

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