JPH10144141A - Semi-conductive material for insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-conductive material in which a plastic component as a hard segment acts as a cross-linking point, heat resistance is superior, and mechanical characteristics are excellent by using polyolefine thermoplastic elastomer composed of a rubber component and a plastic component together with carbon black. SOLUTION: Semi-conductive material is composed of 100 parts by weight of a base resin, polyolefine thermoplastic elastomer and 25 to 70 parts by weight of carbon black. As the rubber component of the used elastomer EPDM or NBR is cited, and as a plastic component polypropylene or polyethylene is cited. These are hydrocarbon compounds, no polar group is contained so that the electric dependency of electric characteristics is little. These are non-cross- linking type so as to be superior in extrusion workability. Such a case where the rubber component is the EPDM, and the plastic component is the polypropylene is particularly preferable combination. Acetylene black is preferable as the carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive material used as a semiconductive layer in insulated wires (including cables).

[0002]

2. Description of the Related Art Conventionally, semiconductive materials for insulated wires include:
A material in which EVA, polyethylene, or the like is used as a base resin and carbon black as a conductivity-imparting agent, for example, acetylene black, is used. And
At the time of its concrete use, it is used as a crosslinked type or a non-crosslinked type.

[0003]

However, the above-mentioned conventional non-crosslinked or crosslinked semiconductive materials have the following disadvantages. (1) In the case of a non-crosslinked semiconductive material, the mechanical properties at high temperatures (temperatures near the melting point of the base resin) are inferior, and a special solution (such as a 10% solution of alkyl allyl polyoxyethylene) is required. There is also a problem that stress cracks (cracks) are liable to occur due to the contact of. (2) In the case of a cross-linkable semiconductive material There is a problem that appearance defects are likely to occur due to the occurrence of scorch and the like due to the addition of a cross-linking agent, and there is also a problem that extrusion workability is poor.

Therefore, the present inventors have proposed that, while being non-crosslinked, they have the same mechanical properties as a crosslinked semiconductive material, and can be plastically deformed by increasing the processing temperature. As a result of various studies as being excellent in extrusion processability, it has been found that a polyolefin-based thermoplastic elastomer is optimal as a base resin material of a semiconductive material. In particular, it has been found that a polyolefin-based thermoplastic elastomer obtained by mixing a rubber component and a plastic component, that is, a rubber component such as EPDM or NBR, and a plastic component such as PP or PE is preferable.

[0005]

Means for Solving the Problems The present invention has been made in view of the above point of view, and a characteristic feature (structure) of the present invention is a polyolefin-based thermoplastic elastomer obtained by mixing rubber and plastic components. It is a semiconductive material for an insulated wire consisting of 100 parts by weight and 25 to 70 parts by weight of carbon black.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the polyolefin-based thermoplastic elastomer used in the present invention, EPDM and NBR are mentioned as rubber components as described above.
Examples of the plastic component also include PP and PE as described above. As a particularly preferred combination, the rubber component is EPDM and the plastic component is PDM.
P is preferred. These are hydrocarbon compounds,
This is because a polar group is not contained, so that the electrical characteristics are good and the electrical dependence of the electrical characteristics is small. Specific examples thereof include Mirastomer M4400N (trade name, manufactured by Mitsui Chemicals, Inc.) and Sumitomo TPE (trade name, manufactured by Sumitomo Chemical Co., Ltd.).

As the carbon black used in the present invention, acetylene black is preferable, and specific examples thereof include Denka Black (trade name, manufactured by Denki Kagaku Kogyo KK) and ENASCO-200 GRAN (MM.
M. Carbon Corporation), ENASCO-250 GRANU
LAR (manufactured by MMM Carbon), P1250 (SKW
And the like). The reason why the addition amount is set to 25 to 70 parts by weight with respect to 100 parts by weight of the polyolefin-based thermoplastic elastomer is that if less than 20 parts by weight, a predetermined semiconductivity cannot be obtained, and conversely, 70 parts by weight. Is exceeded, the amount of carbon becomes too large, and the tensile elongation properties, flexibility, embrittlement properties, mechanical properties (strength, viscosity, etc.), extrudability, etc., deteriorate.

In the extrusion of the semiconductive material of the present invention having such a composition (blending), the processing temperature is raised (about 160 to 230 ° C.), and the polyolefin thermoplastic elastomer of the base resin is plastically deformed. If it is extruded in a possible state, it can be extruded smoothly and good extrusion processability can be obtained.

[0009]

Next, a semi-conductive material of the present invention having the composition shown in Table 1 (Examples 1 to 3) and a semi-conductive material lacking the conditions of the present invention (Comparative Examples 1 to 3) were used to reduce the half of the electric wire. The conductive layer was extruded and examined for various characteristics (volume resistivity, Mooney viscosity, occurrence of stress crack). These characteristics are also shown in Table 1. Here, the volume resistivity is determined by a Whiston bridge and is 10 ⁶ Ω · cm.
In the following cases, it was indicated by ○, and when it exceeded this, it was indicated by ×. The Mooney viscosity was determined using a Mooney viscometer, and was indicated as ○ when it was 50 or less, and as X when exceeding it. The occurrence of stress cracks was visually determined.

[0010]

[Table 1]

From the above Table 1, it was found that the semiconductive material of the present invention (Examples 1 to 3) exhibited good results in all characteristics. In contrast, the semiconductive materials lacking the conditions of the present invention (Comparative Examples 1 to 3) were found to be inferior in any of the characteristics.

[0012]

As described above, according to the semiconductive material for an insulated wire according to the present invention, the following excellent effects can be obtained. (1) Since a polyolefin-based thermoplastic elastomer obtained by mixing a rubber component and a plastic component is used as the base resin, the plastic (resin) component as a hard segment acts as a cross-linking point. Excellent heat resistance and good mechanical properties. (2) Since the polyolefin-based thermoplastic elastomer is a non-crosslinked type, it has excellent extrudability. (3) The material has excellent electrical properties because the base resin is a polyolefin-based resin, does not contain a polar group, and does not contain any other filler. For the same reason,
Temperature dependence of electrical characteristics can be suppressed.

Claims (1)

[Claims] 1. A semiconductive material for an insulated wire, comprising 100 parts by weight of a polyolefin-based thermoplastic elastomer obtained by mixing a rubber component and a plastic component, and 25 to 70 parts by weight of carbon black.