JP2001229732A - Semi-conductive resin composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-conductive resin composite available when used as a semi-conductive layer of plastic insulated power cable. SOLUTION: The semi-conductive resin composite of 100 parts in weight consisting of 50 to 90 parts in weight of ethylene-ethyl acrylate copolymer with vicat softening temperature above 55 deg.C and 50 to 10 parts in weight of polyolefin with m.p. above 100 deg.C is blended with 40 to 80 parts in weight of conductive carbon black. This gives a good smoothness and adhesion at the interface with an insulating body and, because its hardness at 90 deg.C is above 50, a hardly deformed power cable with excellent distortion resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive resin composition useful for a semiconductive layer of a plastic insulated power cable.

[0002]

BACKGROUND OF THE INVENTION Plastic insulated power cables, especially crosslinked polyethylene insulated power cables, have good smoothness at the interface between the semiconductive layer (usually having inner and outer semiconductive layers) and the insulator, and Having good adhesion is also an important factor for improving the reliability of the cable. In other words, if the interface irregularity exists, a high electric field is locally formed, corona discharge occurs, or, in a humid environment, water trees are generated when the cable is actually used, and the electrical insulation characteristics deteriorate.

[0003] As described above, the semiconductive layer is required to have good smoothness and adhesion at the interface with the insulator. On the other hand, the other properties are good shearing property during processing and heat resistance during use of the cable. Examples thereof include stable conductivity to heat such as a cycle, heat aging resistance, extrusion processability, and deformation resistance without being easily deformed.

[0004] Such a semiconductive layer is generally obtained by adding cambon black to a base resin. As this cambon black, acetylene black or furnace black is usually mainly used. As the base resin, an ethylene-vinyl acetate copolymer (EVA) or an ethylene-ethyl acrylate copolymer (EEA) is mainly used.

[0005]

However, EVA or EEA, which is the base resin of the above-mentioned semiconductive layer, has a low softening temperature of the resin itself when used alone. The danger of the outer semiconductive layer itself being deformed (crushed) is increased due to the tendency to increase and the weight of the cable itself due to the use of large conductors, and there is a concern that the reliability of the cable is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been made to have a resistance to deformation which is not easily deformed when used for a semiconductive layer of a power cable, particularly, an external semiconductive layer. It is intended to provide an excellent semiconductive resin composition.

[0007]

According to the present invention, there is provided a polyolefin having a Vicat softening temperature of not less than 55 ° C. and 50 to 90 parts by weight of an ethylene-ethyl acrylate copolymer (EEA) and a melting point of not less than 100 ° C. The semiconductive resin composition is obtained by mixing 40 to 80 parts by weight of conductive carbon black with 100 parts by weight of a mixture of 50 to 10 parts by weight.

According to a second aspect of the present invention, there is provided a semiconductive resin composition according to the first aspect, comprising 0.05 to 5 parts by weight of an antioxidant and 0.01 to 3 parts by weight of a crosslinking agent. In the conductive resin composition.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, EEA having a higher softening temperature than EVA is selected, and a mixture obtained by mixing a polyolefin having a relatively high melting point is used as a base resin.

More specifically, the Vicat softening temperature (JI
SK6731) using EEA having a temperature of 55 ° C. or higher, and a polyolefin having a melting point of 100 ° C. or higher mixed therein.
As a result, the actual operating temperature of the power cable (normal temperature to 90
In the range of about (° C.), the deformation resistance (crush resistance) of the semiconductive layer, in particular, the deformation resistance of the external semiconductive layer can be significantly improved.

Here, the reason why the Vicat softening temperature of the EEA used is 55 ° C. or higher is to improve the deformation resistance of the semiconductive layer. Because it cannot be obtained. Further, the reason why the melting point of the polyolefin to be mixed is set to 100 ° C. or higher is to reinforce the deformation resistance of the EEA-based semiconductive layer at the normal use temperature (normal temperature to about 90 ° C.) of the power cable. Examples of the polyolefin having a melting point of 100 ° C. or higher include low density polyethylene (LDPE) and linear low density polyethylene (L-LDPE).

Further, the mixing ratio of EEA and polyolefin is 50 to 90 parts by weight of EEA and 50 to 10 parts by weight of polyolefin is that EEA exceeds 90 parts by weight and 10 parts by weight of polyolefin is used. If it is less than 3, the reinforcing effect of the polyolefin at high temperatures is weakened, and sufficient deformation resistance of the semiconductive layer cannot be obtained.
If the EA is less than 50 parts by weight and the polyolefin exceeds 50 parts by weight, the characteristics due to the blending of the EEA are weakened, and good smoothness and good adhesion at the interface with the cable insulator cannot be expected. This is because the extrudability and the like are inferior depending on the characteristics of the polyolefin.

The object of the present invention is to add 40 to 80 parts by weight of acetylene black or furnace black as a conductive carbon black to 100 parts by weight of a base resin composed of such a mixture of EEA and polyolefin. A semiconductive resin composition is obtained.

If necessary, other additives such as an antioxidant, a crosslinking agent such as an organic peroxide, a crosslinking aid such as triisocyanurate, and a processing aid may be added to the semiconductive resin composition. Can be added. When an antioxidant is added, the amount is 0.05 to 5 parts by weight with respect to 100 parts by weight of the base resin. When a crosslinking agent is added, the amount of addition is 100 parts by weight of the base resin. 0.01 to 3 parts by weight with respect to Thereby, a semiconductive resin composition which is excellent in aging prevention and further excellent in properties due to crosslinking can be obtained.

Examples Tables 1 and 2 show examples (1 to 4) of the semiconductive resin composition according to the present invention and comparative examples (1) of the semiconductive resin composition lacking the requirements of the present invention. 4) shows the respective compounding ratios. Further, in the same table, each characteristic (hardness as a reference of deformation resistance, semiconducting volume resistivity, extrudability, overall properties) of these Examples (1 to 4) and Comparative Examples (1 to 4) is shown. Judgment) is also shown.

Here, the hardness is determined by JI at 90 ° C.
JISA described in S-K6253 (hardness test of vulcanized rubber)
Determined by The volume resistivity (Ω · cm) is 90 ° C
Was determined using the method of AEIC-CS5-82.

[0017]

[Table 1]

[0018]

[Table 2]

From Table 1 above, it can be seen that Examples (1 to 4) of the present invention are shown.
In each case, the hardness is 50 or more, and the deformation resistance is improved, and at the same time, there is no problem in terms of volume resistivity and extrudability, and it can be seen that excellent results are obtained overall. . On the other hand, in Comparative Examples (1 to 4) lacking the requirements of the present invention, properties such as hardness and extrudability are poor,
It turns out that good results were not obtained overall.

[0020]

As is apparent from the above description, according to the semiconductive resin composition of the present invention, the Vicat softening temperature is 5%.
Since conductive carbon black is blended with a mixture of EEA having a temperature of 5 ° C. or higher and a polyolefin having a melting point of 100 ° C. or higher, when a semiconductive layer of a plastic insulated power cable is formed using the mixture, an insulator and Good smoothness and good adhesion were obtained at the interface of
Since the hardness at 50 ° C. is 50 or more, the actual service temperature (normal temperature to 9
Within the range of about 0 ° C.), it is possible to obtain a highly reliable power cable that is not easily deformed, particularly in the outer semiconductive layer, and has excellent deformation resistance.

Claims (2)

[Claims] A conductive carbon black is added to 100 parts by weight of a mixture of 50 to 90 parts by weight of an ethylene-ethyl acrylate copolymer having a Vicat softening temperature of 55 ° C. or higher and 50 to 10 parts by weight of a polyolefin having a melting point of 100 ° C. or higher. A semiconductive resin composition comprising 40 to 80 parts by weight. 2. A semiconductive resin composition comprising the semiconductive resin composition according to claim 1 and 0.05 to 5 parts by weight of an antioxidant and 0.01 to 3 parts by weight of a crosslinking agent.