JPH01267905A - Extruded type semiconductive resin compound for electric power cable - Google Patents

Abstract

PURPOSE:To improve a water tree-resistant property by adding 0.01 to 3.0 weight part of fatty acid which includes a hydroxyl group in its molecules or metallic salt thereof and conductivity actuator agent to the 100 weight part of ethylene polymer. CONSTITUTION:0.01 to 3.0 weight part of fatty acid which includes a hydroxyl group in its molecules or a metallic salt thereof is added to the 100 weight part of ethylene polymer. The amounts of the compounds to be added are deter mined as 0.01 to 3.0 weight part, because the inhibition effect of a water tree is not sufficient when it is less than 0.01 weight part, while the compounds are deposited to the surface of an semiconductive layer due to the limit of compatibility when it is more than 3.0 weight part. As for polymers to which these compounds are to be added, there are polyolefin such as polyethylene, polypropylene, polybutene and so forth, or ethylene copolymer such as ethylen- vinyl acetate copolymer, ethylene-ethylacrilate copolymer, ethylene- methylmethacrylate copolymer, ethylene-propylene copolymer and so forth. Thus a water tree resistant property of electric cable power can improve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a semiconductive resin composition suitable for being provided on the outer periphery of a conductor or insulator of a power cable.

[Prior art] The smoothness and adhesion of the interface between the semiconducting layer and the insulator in a cross-linked polyethylene insulated power cable are important for improving the reliability of the cable, and the presence of irregularities at the interface can result in the formation of a locally high electric field. , water tree deterioration occurs during corona discharge or flooding, leading to a decline in the electrical properties of the cable.

To address this issue, studies have been conducted from both the structural and material aspects of semiconducting layers, and extruded semiconducting layers have been developed to replace semiconductive cloth tapes, which tend to have a lot of fuzz. . As the material for the extruded semiconductive layer, materials based on polar ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer are mainly used.

Problem to be Solved by the Invention 1 However, although the cross-linked polyethylene power cable with such a semiconductive layer has a significantly improved breakdown current, If long-term energization is performed, water trees occur frequently and the breakdown voltage becomes low.

The present invention has been made based on the above, and its main purpose is to provide an extruded semiconductive resin composition for power cables that can improve water resistance.

[Means for Solving the Problems] The extruded semiconductive resin composition for power cables of the present invention has the following features:
Water H in the molecule based on 100 parts by weight of ethylene polymer
0.01 to 3.0 parts by weight of a fatty acid containing M or a metal salt thereof is added.

In the present invention, fatty acids or metal salts thereof containing water am in the molecule include those having the following structures.

R-(Coo to 1), 1! M(R
-Coo)nI or 1 (Of-1>k
(ON) m (in the formula, 1 or m contains a hydroxyl group in the molecule (O to Ink /: A indicates a hydrocarbon), and some atoms such as oxygen, nitrogen, and sulfur are present in the structure of R. Or, there is no problem even if an atomic group consisting of these is included. k and j are each an integer of 3 or less. M represents a metal.
Group 1 of the periodic table, such as Mq.

Group Ⅰ such as Ca, Ba, Cd, Zn, Group Ⅰ such as A1,
Group 1V such as Sn, Pb, Group V1 such as Mn, Co, N
Examples include Group 1 metals such as i, but are not particularly limited. n is an integer of 4 or less that varies depending on the valence of the metal, and rTl is an integer of 3 or less. ) As a specific example, CH(C1-1) -CH(C11,,) 1
o-,OH OH0HOH (CI-1) -CI-1(CH2)5-CI-1
- OH C to I C1” C-(CH2) 7
-1, CH(CF+ 2 ) 5 Cl
-1cH, , = 01+ CH(CH2) 7-, etc. can be mentioned.

The reason for specifying the amount of these compounds to be added is 0.01 to 3.0 parts by weight, because if it is less than 0.01 parts by weight, the desired water tree inhibiting effect is insufficient, so 3.0 parts by weight is specified. This is because if it exceeds the limit, the compound will precipitate on the surface of the semiconducting layer due to compatibility limitations.

Polymers to which these compounds are added include polyolefins such as polyethylene, polypro, pyrene, and polybutene, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers, and ethylene-vinyl acetate copolymers. Examples include ethylene copolymers such as propylene copolymers. These may be used alone or may be blended as necessary.

As the conductivity imparting agent, conductive carbon black is most suitable, and acetylene black and furnace black can also be used. From the viewpoint of imparting conductivity, it is preferable that the conductivity imparting agent is blended in an amount of 40 parts by weight or more, 8 parts or more per 100 parts by weight of the resin.

In the present invention, antioxidants and other additives may be blended as appropriate.

In the present invention, the semiconductor 1'8 hlJ of the power cable may be non-crosslinked or crosslinked. When crosslinking, dicumyl peroxide, 2,5-dimethyl-2,
It is common to heat the mixture using a peroxide such as 5-di(tert-butylperoxy)hexyne-3. In addition, so-called silane water cross-linking, in which an organic silane such as vinyltrimethoxysilane is grafted onto a polymer and then brought into contact with water to bond and cross-link the silane using a silanol condensation catalyst, or the ionizing radiation of Ichiko Line Kasa Crosslinking by irradiation may also be used.

[Example] Semiconductive resin compositions having the formulations shown in the table were prepared.

Forming an internal semiconductive layer by extrusion coating the above semiconductive resin composition to a thickness of 1M on a stranded copper conductor with a cross-sectional area of 80 mm2,
Next, low-density polyethylene (density 0.920
1 Melt index 1.0) A resin composition consisting of 8 parts of 100 parts, 2.5 parts of dicumyl peroxinide, and 0.25 parts of antioxidant was extruded and coated to a thickness of 4 mm.
Furthermore, the above-mentioned semiconductive resin composition was extrusion coated on the outer periphery to form an external semiconductive layer, and heat crosslinking was performed to produce a crosslinked polyethylene insulated lightning cable.

Next, after injecting water into the conductor of the power cable to submerge the cable, an AC voltage of 5011z, 15kV was applied between the conductor and the water electrode, and the water dia was kept at 90°C and the cable was heated for 18 hours. I charged a monthly charge.

After the voltage application was completed, the insulator was spirally cut to a thickness of 0.5 mm, boiled and stained with a methylene blue aqueous solution, and the number of water trees generated at the interface between the insulator and the internal semiconducting layer was observed using a microscope. . The results are shown in Table 1. As is clear from the table, it can be seen that the number of water trees after adding the hydroxyl group-containing fatty acids or metal salts of Examples 1 to 5 was small.

On the other hand, it can be seen that the number of occurrences is large in cases such as Comparative Example 1, in which this is not added, and in Comparative Example 2, in which the amount added is less than the specified range. Further, in cases where the addition 1fi exceeds the specified range as in Comparative Example 3, the additive is deposited on the surface of the semiconducting layer. In general, it can be seen that those containing no hydroxyl groups, such as Comparative Examples 4 and 5, have no water tree inhibiting effect.

``Effects of the Invention'' As is clear from the above description, the present invention can significantly improve the water resistance of city pulls.

Claims (1)

[Claims] 1. An extruded semiconducting material for power cables, characterized in that 0.01 to 3.0 parts by weight of a fatty acid containing a hydroxyl group in the molecule or a metal salt thereof and a conductivity imparting agent are added to 100 parts by weight of an ethylene polymer. Resin composition.