JPS6056313A - 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

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

In order to easily cover the peeling between the insulator and the outer semiconducting layer in the vulcanized EPR insulated cable, the outer semiconducting layer is made of an ethylene-vinyl acetate copolymer containing high vinyl acetate as a base polymer. It has been proposed that the composition be formed by a composition.

However, such a composition has the problem that acetic acid is released by heat during cable use and vulcanization, and this corrodes the copper tape for external shielding, greatly affecting the life of the cable.

In order to reduce the amount of acetic acid released during vulcanization, the vulcanization temperature may be set to about 200° C. or less, but this will reduce production efficiency.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to provide a vulcanized EP insulated electrical cable that prevents the adverse effects of desorbed acetic acid on the external shielding metal tape. It is something.

Summary of the Invention] The present invention mainly comprises an ethyl-1-non-vinyl acetate copolymer having a vinyl acetate content of 50 to 80% by weight, hydrotalcite, and a conductivity imparting agent as a composition for forming an external semiconductive layer. It is characterized in that it contains 0.5 to 30 parts by weight of hydrotalcite per 100 parts by weight of the ethylene-vinyl acetate copolymer.

In the composition, hydrotalcite selectively adsorbs acids because it has anion exchange properties, and forms a hydrotalcite compound with the desorbed acetic acid through the following reaction.

Mga, 5/lj! 2 (OH)13 CO3・3.5
+1-120+2CI-13cOOH -I M g4. s M2(OH) 13 (CI-I
s Coo) 2+ m H20+ H20+ G O
2 In the present invention, the ethylene-vinyl acetate copolymer includes not only those consisting of two components of ethylene and vinyl acetate, but also
Mainly ethylene and vinyl acetate, with propylene and
Refers to copolymerized or graphite-coated products of olefins such as butene, acrylates such as methyl acrylate, (2) tylacrylate 1 to 1, or aromatic polymers such as styrene.

It is necessary to use an ethylene-vinyl acetate copolymer with a vinyl acetate content of 60 to 80% by weight, and a 60% by weight non-vortexed copolymer has insufficient peelability from the insulator.
If it exceeds 80% by weight, the mechanical properties at low temperatures will be significantly reduced, making it unsuitable for practical use.

The amount of hydrotalcium 1- added to the ethylene-vinyl acetate copolymer must be within the range of 0.5 to 30 parts by weight of the latter to 100 parts by weight of the former, and less than 0.5 parts by weight. The metal tape has almost no effect in preventing corrosion,
Even if the amount exceeds 30 parts by weight, there is almost no improvement in the effect by increasing the amount, and an increase in volume resistivity and a decrease in tensile strength are observed.

As the conductivity imparting agent used in the present invention, carbon black such as acetylene black and 7-nes black is generally used. Department.

A vulcanizing agent, an anti-aging agent, a lubricant, etc. may be added to the composition comprising the ethylene-vinyl acetate copolymer, hydrotal 1 night, and a conductivity imparting agent.

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

[Embodiment j of the invention] Hydrotalcite was added in the proportions shown in Table 1 to 100 parts by weight of various ethylene-vinyl acetate copolymers, and furthermore, 1 part of an antiaging agent (trade name Nickrac 300) was added. 0 parts by weight, 1.0 parts by weight of stearin M zinc, 60 parts by weight of acetylene black, and ゛C2,5- as a crosslinking agent.
A semiconductive composition was obtained in which 1.0 parts by weight of dimethyl-2.5-di(t-butyl peroxy)-hexyne-3 and i and oim parts of triallylisocyanurate as a crosslinking aid were added. The obtained semiconductive composition was subjected to EP
The outer circumference of the R insulator was coated by extrusion to a thickness of 1M, and vulcanization was performed in a nitrogen gas atmosphere at 250°.

Next, a copper tape for external shielding was wrapped, and a vinyl sheath was coated around the outer periphery to create an electric cable.

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 predetermined length, sealing both ends, and energizing the conductor so that the conductor temperature reaches 105°C (4), and (4) at room temperature with the current turned off. Repeat the time heat cycle 100 times,
The corrosion status of the copper tape was determined by visual observation. In addition,
The surface temperature of the semiconducting layer was 75°C when the conductor temperature was 105°C.

The peel strength was determined by peeling off the semiconducting layer at an angle of 90° C. from the EPR insulator at 230° C. and a speed of 100 m/min, and measuring the resistance force <Kg/12, 7 m> at that time.

The volume resistivity was determined by measuring the value before and after the cable was heated to cycle 1.

Table 1 Examples 1 to 9 in Table 1 are within the scope of the present invention, and practically sufficient properties were obtained in all properties.

On the other hand, Comparative Examples 1, 3 to 5, in which the hydrotalcite content is less than 0.5 parts, have no corrosion-preventing effect on the copper tape, and Comparative Example 2, in which the hydrotalcite content exceeds 30 parts, has an increased volume resistivity for practical use. It becomes irrelevant.

[Effects of the invention j As explained above, the present invention provides an electric power cable in which a semiconductive composition prepared by adding hydrotalcite and a conductivity imparting agent to a specific ethylene-vinyl acetate copolymer is 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 released from the semiconductive layer.

Claims (1)

[Claims] In a power cable having a vulcanized EPR insulator, an outer semiconducting layer, and a metal tape sequentially on the outer periphery of the conductor, the outer semiconducting layer is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 50 to 80% by weight. , hydrotalcite and a conductivity-imparting agent as main components, and a composition comprising 015 to 30 parts by weight of a hydrotalcite compound based on 100 parts by weight of the ethylene-vinyl acetate copolymer. Sulfur EPR insulated electrical cable.