JPS6056314A - Vulcanized epr-insulated power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to a power cable having an outer semiconductive layer around the outer periphery of a vulcanized EPR (ethylene-propylene rubber) insulator.

In order to facilitate peeling between the insulator applied to the vulcanized EPR lightning cable and the outer semiconducting layer, the outer semiconducting N layer is made of a high vinyl acetate-containing ethylene-vinyl acetate copolymer as a base polymer. It has been proposed that the composition be formed using

However, when using such a composition, l13
There is also the problem that acetic acid is eliminated by the heat during vulcanization, which corrodes the copper tape for external shielding, greatly affecting the life of the cable.

In order to reduce the amount of desorbed vinegar Mffi during vulcanization,
It is possible to reduce the temperature to about 200° C. or lower, but this will result in a decrease in production efficiency.

The present invention was made in order to solve the problems of the prior art described above, and aims to provide a vulcanized EPR insulated lightning horn cable that can prevent the adverse effects of desorbed acetic acid on the external shielding metal tape. It is.

[Summary of the Invention] The present invention uses an ethylene-vinyl acetate copolymer having a vinyl acetate content of 50 to 80% by weight and a metal oxide having a water immersion liquid pH of 9 or more as a composition for forming an outer semiconductive layer. It is characterized in that it contains a conductivity-imparting agent as a main component.

In the present invention, the ethylene-vinyl acetate copolymer may not only be composed of two components, ethylene and vinyl acetate, but also be composed mainly of ethylene and vinyl acetate, in addition to olefins such as propylene and butene, methyl acrylate, ethyl acrylate, etc. acrylate, or a copolymer of aromatic monomers such as styrene or graph 1.

■ It is necessary to use a dylene-vinyl acetate copolymer with a vinyl acetate content of 60 to 80% by weight; if it is less than 60% by weight, the peelability from the insulator will be insufficient.
If the content exceeds 80% by weight, the mechanical properties at low temperatures will be significantly reduced and it cannot be put to practical use.

In the present invention, the pH of the immersion liquid is 9 for metal oxides.
It is necessary to use the above-mentioned metal oxides, and examples of metal oxides that can be used include magnesium oxide, magnesium hydroxide, and magnesium carbonate.

The mechanism by which metal oxides have a corrosion-preventing effect on metal tapes is that they chemically combine with the released acetic acid.
From this point of view, the desired purpose cannot be achieved unless the water immersion liquid PH is 9 or higher.If the water immersion liquid PH is less than 9, the effect of neutralizing acidic substances will be small, and the metal tape will be corroded. The prevention effect is insufficient.

The amount of the metal oxide added is not particularly limited, but in consideration of the corrosion prevention effect of the metal tape, it is necessary to add 0.5 parts by weight or more to 100 parts by weight of the ethylene-vinyl acetate copolymer.

Further, the upper limit is 50 parts by weight, and even if the amount exceeds this, there is almost no improvement in the effect by increasing the amount, and an increase in volume resistivity and a decrease in extrusion processability are observed.

As the conductivity-imparting agent used in the present invention, carbon black such as acetylene black and furnace black is generally used. Department.

The above composition comprising an ethylene-vinyl acetate copolymer, a metal oxide, and a conductivity imparting agent includes a vulcanizing agent, an anti-aging agent,
A lubricant or the like may be added.

As a vulcanizing agent, dicumyl peroxide, 1゜3-bis-(t-butyl peroxy-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butyl peroxynohexane-3) etc.

[Examples of the invention] As shown in Table 1, ethylene-vinyl acetate copolymer 1
Various metal oxides were added to 00 parts by weight, and furthermore, 1.0 parts by weight of an anti-aging agent (trade name Nicklac 300), 1.0 parts by weight of zinc stearate, 60 parts by weight of acetylene black, 2,5-dimethyl-2, as a crosslinking agent
5-di(butyl peroxy)-hexyne-3 to 1
．． A semiconductive composition was obtained in which 1.0 parts by weight of triallyl isocyanurate 1 to 1 was added as a crosslinking auxiliary agent.

The obtained semiconductive composition was applied to the outer circumference of the EPR insulator for 1 m.
It was extruded and sealed to a thickness of m, and vulcanization was performed in a nitrogen gas atmosphere at 250°C.

Next, a copper tape for external shielding was wrapped, and the outer periphery was covered with a vinyl sheath to create an electric knock couple.

Table 1 shows various characteristics of the electric power cable thus obtained.

Corrosion of the copper tape can be determined by cutting the cable to a specified length, sealing both ends, and keeping the conductor energized for 4 hours so that the conductor temperature reaches 105°C, and then cutting off the current and leaving it at room temperature. The 4-hour heating cycle was repeated 100 times, and the corrosion status of the copper tape was determined by visual observation. Furthermore, when the conductor temperature is 105°C, the surface temperature of the semiconducting layer is 75°C.
It was ℃.

Peel strength was determined by making a shallow circumferential scratch with a width of 12.7 m and q in the outer semiconducting layer, and pulling the semiconducting layer at a 90° angle to the EPR insulator at 23°C and a speed of 100 mm/min. Peeling resistance (K"il/12, 7mm)
Examples 1 to 4 in Table 1 are within the range of the present invention, and practically sufficient properties were obtained in all properties.

On the other hand, in Comparative Examples 1 and 2 in which the water immersion liquid P)-1 was less than 9, there was no effect of preventing corrosion of the copper tape.

[Effects of the Invention] As explained above, the present invention provides a semiconductive composition in which a metal oxide having a water immersion liquid pH of 9 or more and a conductivity imparting agent are added to a specific ethylene-vinyl acetate copolymer. This relates to an electric cable provided on the outer periphery of an insulator. This makes it possible to prevent corrosion of the external shielding metal tape caused by acetic acid removed from the semiconductive layer.

Claims (1)

[Claims] (1) In a power cable having a vulcanized EPR insulator, an outer semiconducting layer, and a metal tape on the outer periphery of the conductor, the outer semiconducting layer is made of ethylene-vinyl acetate with a vinyl acetate content of 60 to 80% by weight. Copolymer and water immersion liquid pH is 9
A vulcanized EPR insulated electrical cable comprising a composition containing the above-mentioned metal oxidation and a conductivity imparting agent as main components.