JPH0582006B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of manufacturing a resistance wire for preventing noise radio waves used in an ignition circuit of an internal combustion engine such as an automobile. (Prior art) High-frequency radio waves generated from the ignition system of internal combustion engines in automobiles, etc.
FM radio) and other wireless devices are subject to noise interference. Various resistance wires are used as one method of suppressing noise current to eliminate this interference. Resistance wires have a predetermined conductor resistance, and are required to have heat resistance and ozone resistance in order to withstand the environment in which they are used. Resistance wires with various structures have been considered in response to these demands, but in recent years, resistance wires in particular have been made of tension members made of highly heat-resistant materials, semiconducting layers, and insulating layers because they need to withstand harsh usage conditions. Many of them have a structure with a concentric circular cross section. The material for the semiconductive layer is generally a carbonaceous conductive filler mixed with matrix resin or rubber, and since resistance wires are required to have high withstand voltage,
The thickness of the insulating layer is large compared to the outer diameter of the resistance conductor including the tension member, so ethylene is used as the insulating layer to improve the flexibility of the wire and to ensure heat resistance and ozone resistance. Many use propylene rubber, and as is well known, vulcanization is performed to bring out the properties of the rubber. (Problems to be Solved by the Invention) As mentioned above, tension is applied to the wire in the process of insulating the resistance wire and vulcanizing it, but this tension is borne by the dimensionally small tension member. The tension member also undergoes flexure. Therefore, the semiconducting layer that is in close contact with the tension member is exposed to tensile stress and bending stress, which often causes fluctuations (variations and level deviations) in the resistance value of the resistance conductor made of the above-mentioned materials. .
As a method to eliminate such fluctuations in resistance value, there is a method of increasing the degree of crosslinking of the semiconducting layer matrix polymer.
Alternatively, there has been a method of providing a non-adhesive intervening material between the semiconducting layer and the insulating layer, but these methods have not necessarily stabilized the quality sufficiently. Incidentally, for this type of resistance wire for automobiles, for example, in Japanese Patent Publication No. 48-25589, a solidified carbonaceous silicon conductive layer is fixed on the outer periphery of a carbonaceous fiber conductive rubber string, and an insulating layer and an outer layer are fixed on the outer periphery of a carbonaceous fiber conductive rubber string. In noise prevention resistance wires with sequential coating layers, 120~
Although it is stated that the carbonaceous silicon conductive layer is cross-linked and bonded to the conductive rubber surface by air heating at 180°C for 2 to 10 minutes, the conductive layer is subjected to stress during this vulcanization process, and the conductive filler is A disconnection occurs;
Electrical resistance increases, which is undesirable. Also, JP-A-60
Publication No. 208009 describes a method for manufacturing a conductor for a resistance wire, in which a plurality of fiber bundles are twisted together to form a tow-like tension member, and a semiconductive resin layer is provided on the tension member. In this example, the process of drying at 150℃ for 10 minutes is a process for drying the paint, and the process of drying at 200℃ for 24 hours is just drying before vulcanization. Internal influences such as an increase in electrical resistance due to cutting of the conductive filler due to vulcanization cannot be prevented. (Means for Solving the Problems) The present invention is an attempt to solve the problems of the conventional technology as described above.The present invention is intended to solve the problems of the conventional technology as described above. This aims to stabilize the resistance value of the layer. A resistor made of a rubber matrix and a carbonaceous conductive filler compounded on the surface of a tension member in which the fibers inside the resistance wire of the present invention are twisted or bundled, or filled between the fibers. Simply put, a resistance conductor is a semi-conductive material, that is, a rubber matrix mixed with a carbonaceous conductive filler, which is coated directly on the tension member by extrusion, or by coating it in a solvent. It is formed by impregnating and coating the tension member with a paint, or by using a combination of these. In particular, when extruding a semiconducting material, it can be formed by a co-extrusion method with the extrusion of the outer insulating layer. Further, when forming the semiconducting layer and forming the insulating layer separately, the matrix rubber of the semiconductor layer may be vulcanized in advance. In the present invention, since stabilization heat treatment is performed, the semiconducting layer is materially stable, and therefore, even if it is subjected to tension and bending during the insulation/vulcanization process, fluctuations in resistance value are reduced. Further, cross-linking of the matrix polymer of the semiconducting layer or post-curing of the insulating layer can be simultaneously achieved by performing stabilizing heat treatment. (Function) In the present invention, at least after coating the insulating layer, that is, immediately after coating the insulating layer or after coating the sheath thereon, stabilization heat treatment is performed at 100°C or more for 10 hours or more. The mechanism behind this is that when a semiconductive layer is formed on a tension member by coating or extrusion, the characteristic values of the semiconductive layer vary under high temperatures during the coating or vulcanization process with an insulating layer applied to the outside. When exposed to such stress, the chain structure of the carbonaceous conductive filler in the semiconducting layer is broken, so if the characteristic value of electrical resistance changes to the large side, stabilization treatment (heat treatment) is required. The chain structure is regenerated and repaired by the cohesive force of the carbonaceous conductive filler while the viscosity of the matrix polymer is lowered by temperature, and the regeneration and repair process of the chain structure includes the following steps:
It takes quite a long time, and the relationship between time t and change in characteristic value R is approximately expressed as R=A logt. And for the same matrix polymer material, the higher the temperature, the shorter the time required. However, unnecessarily high-temperature heat treatment causes thermal deterioration of the material, which is undesirable. In this sense, it can be said that the lower the temperature, the more preferable the heat treatment for stabilization is, but the lower the temperature, the longer it takes in an exponential manner, which is not preferable from an industrial production technology point of view.
Both of these were determined empirically as a stabilization treatment of 100°C or more for 10 hours or more, which takes into consideration the heat-resistant temperature of the polymer material used in resistance wires and the heat treatment time that can be applied in industrial production. . (Example) Example 1 Figure 1 shows the structure up to the insulator coating according to the present invention, using 1500 denier Kevlar tow (tow using Dupont's aromatic polyamide trade name Kevlar) as the tension member material. As a material for the conductive layer, 100 parts by weight of chlorosulfonated polyethylene rubber, 70 parts by weight of conductive carbon black (acetylene black), and other vulcanizing agents, anti-aging agents, etc. are mixed, and the mixture is made into a paint using an aromatic solvent and impregnated. - The resistive conductor 1 was formed by coating. Therefore, vulcanization was carried out under different conditions to form groups No. 1, No. 2 and No. 3 in Table 1 shown below. Furthermore, an ethylene propylene rubber mixture was extruded and coated on top of these as an insulating layer 2, and continuously vulcanized in an atmosphere of 200°C.
The line tension at this time was 12Kgf at the end.
Then, each of these was cut to a predetermined length, and the lead terminals were attached and caps were mounted.The resistance values were measured for 10 samples in each group, and the results were used as a comparative example for No. 1 in Table 1. , No. 2 and No. 3. Next, 10 pieces each of groups No. 1, No. 2, and No. 3 were heated at 140°C.
After heat treatment (stabilization) for 15 hours, the resistance values were measured, and the results were used as examples and No. 1 in Table 1.
4, No. 5 and No. 6.

[Table] Example 2 According to Fig. 1, a twisted glass fiber string with an outer diameter of 0.5 mm was used as the tension member, and a silicone rubber-carbon black type mixture (vulcanized... peroxide type) was used as the material for the semiconductive layer. A semiconductive layer and an insulating layer were formed by coextrusion using an ethylene propylene rubber mixture as the material for the insulating layer 2, and vulcanization was performed. The degree of vulcanization was kept within a range that would not cause deformation in the next step. A sample was prepared in the same manner as in Example 1, and then heat treated at 160°C for 12 hours.
The resistance value before heat treatment is average 29.8kΩ/m, standard deviation
It was 5.7kΩ/m. Resistance value after heat treatment is average
The resistance was 16.4kΩ/m, with a standard deviation of 0.83kΩ/m. (Effects of the invention) By performing stabilization heat treatment at 100°C or more for 10 hours or more (even within these temperature and time ranges, the actual heat treatment temperature and time vary depending on the composition of the semiconducting layer material) according to the present invention. Example 1 and Example 2
As shown in Figure 2, the standard deviation or fluctuation of the resistance value is significantly reduced, and the effect of the stabilizing heat treatment is obvious. In Example 2, even if the degree of pre-vulcanization of the semiconducting layer and the insulating layer is kept within a range that does not cause deformation in the next step, the semiconducting layer and the insulating layer may be damaged by the heat of the stabilization heat treatment. It has been found that the matrix rubber used in this invention is sufficiently vulcanized.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an embodiment up to coating the resistance wire with an insulating layer. 1: Resistance conductor consisting of a tension member and a semiconducting layer, 2: Insulating layer.

Claims (1)

[Claims] 1. A semiconductive layer comprising a tension member made of twisted or bundled fibers and a carbonaceous conductive filler with a rubber matrix on the surface of the tension member or between the fibers. In the method of manufacturing a resistance wire, the resistance conductor is formed by forming a resistance conductor, an insulating layer is coated on top of the resistance conductor, and a sheath made of a synthetic rubber mixture is further applied on top of the resistance conductor, and the temperature is at least 100°C or higher for 10 hours or more after the insulation layer is coated. A method for manufacturing a resistance wire, characterized by performing a stabilization treatment.