JP2000030532A - Power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scavenge and neutralize acetic acid produced from an EVA resin (ethylene-vinyl acetate copolymer) and prevent the discoloring and corrosion of a conductor and a metallic shield layer, when a semiconducting layer made of a semiconductor composition using the EVA resin is used as a base polymer. SOLUTION: An internal semiconducting layer 2 or an external semiconducting layer 4 is formed out of semiconducting composition blended with fatty acid amide such as amide stearate as an acid receiving agent for scavenging and neutralizing acetic acid. The semiconducting composition contains the EVA resin as a part or the whole of the base polymer, and further contains 0.01 to 3 pts.wt. of fatty acid amid for 100 pts.wt. of the base polymer. Also, an insulation composition for forming an insulator 3 may as well be blended with fatty acid amide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power cable such as a crosslinked polyethylene insulated power cable (CV cable).

[0002]

2. Description of the Related Art FIG. 1 shows an example of a CV cable, in which reference numeral 1 denotes a conductor. On the conductor 1, an inner semiconductive layer 2, an insulator 3 made of cross-linked polyethylene, an outer semiconductive layer 4, a metal shielding layer 5 wound by a copper tape or the like, and a sheath 6 made of polyethylene, polyvinyl chloride, or the like. They are provided sequentially. Both the inner semiconductive layer 2 and the outer semiconductive layer 3 are composed of a semiconductive composition. The semiconductive composition is prepared by adding a conductive carbon black, an antioxidant, an organic compound to a base polymer composed of an ethylene-vinyl acetate copolymer (referred to as EVA resin) alone or a base polymer composed of an EVA resin and another olefin polymer such as polyethylene. It contains a peroxide crosslinking agent and the like.

[0003] By the way, the EVA resin constituting a part or all of the base polymer of the semiconductive composition decomposes when heated and generates acetic acid. Therefore, when such a power cable is used in a high-temperature environment, acetic acid is generated in the inner semiconductive layer 2 and the outer semiconductive layer 4, and the acetic acid discolors the conductor 1 and the metal shielding layer 5, May corrode.

In order to prevent this phenomenon, an acid acceptor composed of an inorganic filler such as calcium carbonate or aluminum hydroxide is blended with the semiconductive composition to capture the generated acetic acid.
Neutralization methods have been proposed. However, in the semiconductive composition containing the acid acceptor composed of the inorganic filler, the inorganic filler agglomerates to form coarse particles, which appear on the surfaces of the semiconductive layers 2 and 4 as protrusions, bumps, and the like. However, there is a drawback that the electric field is concentrated, resulting in an electrical defect. In addition, cations and anions are generated from the inorganic filler, and these ions may cause water trees.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to use an acid acceptor instead of an inorganic filler to capture and neutralize acetic acid generated, and to generate projections and bumps on the surface of the semiconductive layer. Is to prevent

[0006]

This problem can be solved by using a fatty acid amide as an acid acceptor. The fatty acid amide may be blended not only in the semiconductive composition forming the semiconductive layer but also in the insulating composition forming the insulator in some cases.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
A first example of the power cable of the present invention is a semiconductive composition that forms one or both, preferably both, of the inner semiconductive layer 2 and the outer semiconductive layer 4 of the power cable having the structure shown in FIG. It is characterized in that a fatty acid amide is blended as an acid acceptor. That is, the semiconductive composition contains 30 to 70 parts by weight of a conductive carbon black based on 100 parts by weight of a base polymer composed of an EVA resin alone or a blend polymer of an EVA resin and another olefin polymer such as polyethylene. Inhibitor 0.1-1
Parts by weight and 0.01 to 3 parts by weight of fatty acid amide.

The above-mentioned EVA resin is not particularly limited, and those having a vinyl acetate content of 25 to 50% by weight and a melt flow rate of about 0.5 to 20 are used. Low-density polyethylene is mainly used as the other olefin-based polymer. When the EVA resin is used in combination with another olefin-based polymer, the amount of the other olefin-based polymer is about 5 to 40% by weight of the total amount of the base polymer. It is said.

The conductive carbon black is preferably a conductive carbon black, such as conductive acetylene black or conductive furnace black, which has good dispersibility and does not agglomerate. The amount of the conductive carbon black depends on the conductivity required for the inner and outer semiconductive layers 2 and 4. And usually 30 to 7 parts per 100 parts by weight of the base polymer.
It is in the range of 0 parts by weight. Anti-aging agents include 4,4'-
Phenolics such as thiobis-6-t-butyl-3-methylphenol are used.
It is blended in an amount of 0.1 to 2 parts by weight with respect to 0 parts by weight.

Examples of the fatty acid amide functioning as an acid acceptor include one or more amides of higher fatty acids having 11 to 17 carbon atoms, such as stearic acid amide, oleic acid amide, palmitic acid amide, rawanic acid amide, and myristic acid amide. A mixture of two or more is used. The amount of the fatty acid amide is 0.01 to 3 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the base polymer. , 3
Exceeding parts by weight causes bloom.

The semiconductive composition may further comprise a crosslinking agent comprising an organic peroxide such as 1.3-bis (t-butylperoxyisopropyl) benzene.
The inner and outer semiconductive layers 2 and 4 can be made into a crosslinked system by mixing 0.2 to 1 part by weight with respect to part by weight. The formation of the inner semiconductive layer 2 and the outer semiconductive layer 4 from such a semiconductive composition can be carried out by extrusion coating as in the prior art.

In a power cable having such a structure, even if acetic acid is generated from the EVA resin as a base polymer of the inner semiconductive layer 2 and the outer semiconductive layer 4 under a high temperature environment, the fatty acid amide is immediately converted to the fatty acid amide. The conductor 1 is neutralized by the reaction, and the conductor 1 or the metal shielding layer 5 does not discolor or corrode. Also,
Unlike the inorganic filler, no protrusions or bumps are generated on the surfaces of the semiconductive layers 2 and 4.

The fatty acid amide generally has poor compatibility with the polymer, and the compounded fatty acid amide has a large tendency to bloom on the surfaces of the inner and outer semiconductive layers 2 and 4. Therefore, the amount of the fatty acid amide depends on the amount of acetic acid generated. When a fatty acid amide cannot be compounded, for example, the base polymer of the semiconductive composition may be entirely composed of an EVA resin. In such a case, as a second example of the power cable of the present invention, a fatty acid amide is also blended in the insulating composition forming the insulator 3, and
The fatty acid amide can be transferred from the inner semiconductive layer 2 and the outer semiconductive layer 4 to compensate for the shortage.

Such an insulating composition has a base polymer of polyethylene or the like.
Crosslinking composed of 0.01 to 1 part by weight of fatty acid amide, preferably 0.03 to 0.5 part by weight, 0.1 to 2 parts by weight of an antioxidant, and an organic peroxide such as dicumyl peroxide based on parts by weight. It is a crosslinked system containing 0.5 to 2 parts by weight of an agent. The same fatty acid amide as described above is used as the fatty acid amide. If the compounding amount is less than 0.01 part by weight, an acid-receiving effect cannot be obtained, and if it exceeds 1 part by weight, bloom occurs. As the anti-aging agent, the same phenolic anti-aging agent as described above is used.

In the power cable having such a structure, since not only the inner semiconductive layer 2 and the outer semiconductive layer 4 but also the insulator 3 contains fatty acid amide, the insulator 3
The fatty acid amide therein gradually migrates to the semiconductive layers 2 and 4, and functions as an acid acceptor in the semiconductive layers 2 and 4, and the semiconductive layers 2 and 4
The shortage of the acid acceptor can be compensated for, so that even if the amount of acetic acid generated increases, the conductor 1, the metal barrier layer 5 discolors,
Does not corrode. Since the fatty acid amide is well dispersed in the polymer, the surfaces of the semiconductive layers 2 and 4 become smooth.

Hereinafter, specific examples will be described. A semiconductive composition having a composition shown in Table 1 and an insulating composition having a composition shown in Table 2 were prepared, and each was extruded to produce a test sheet. This test sheet was measured for volume resistivity and subjected to a copper plate discoloration test. The copper plate discoloration test is a test sheet (1 m thick) made of a semiconductive composition.
m) and a test sheet (5 m thick) composed of an insulating composition
m) and a copper foil (0.1 m thick)
m) at about 250 ° C. to form a sample. This sample was subjected to a heat cycle test under a temperature condition of room temperature to 60 ° C. at a humidity of 70% RH for 2 weeks, and the discoloration of the copper foil was visually observed.

The extrudability of each composition was evaluated by torque fluctuation using a Brabender plastograph (trade name, manufactured by Brabender). That is, the temperature of Brabender Plus and the graph was set to 120 ° C., kneading and extrusion were performed for about 1 hour, and the torque fluctuation of the screw during that time was investigated. The results are shown in Tables 1 and 2.

[0018]

[Table 1]

[0019]

[Table 2]

In Tables 1 and 2, the composition is all parts by weight, and the EVA resin has a vinyl acetate content of 28 parts.
%, Melt flow rate 15; low-density polyethylene, density 0.92 g / cm ³ ; melt flow rate 7.2; carbon black, conductive acetylene black; 3-Bis (t-butylperoxyisopropyl) benzene was used, and 4,4'-thiobis-6-t-butyl-3-methylphenol was used as an antioxidant.

In the copper plate discoloration test, test sheets made of the semiconductive composition and the insulating composition were bonded together with the same test numbers in Tables 1 and 2.

From the results shown in Tables 1 and 2, it can be seen that the addition of the fatty acid amide has the same electrical properties and workability as the conventional ones, and can prevent copper discoloration.

[0023]

As described above, in the power cable of the present invention, one or both of the inner semi-conductive layer, the outer semi-conductive layer, and the outer semi-conductive layer are connected to the E cable.
Since it is composed of a semiconductive composition in which a VA resin is used as a base polymer and a fatty acid amide is blended as an acid acceptor with the VA polymer, even if acetic acid is generated from the EVA resin in a high-temperature environment, it is converted into a fatty acid amide. Captured and neutralized. Therefore, the conductor and the metal shielding layer are not discolored or corroded.

In the case where not only each semiconductive layer but also the insulator is composed of an insulating composition containing a fatty acid amide, the fatty acid amide transfers from the insulator to the inner semiconductive layer and the outer semiconductive layer, This also functions as an acid acceptor,
A large amount of acetic acid is generated in the inner semiconducting layer or the outer semiconducting layer, and even if the fatty acid amide in the inner semiconducting layer or the outer semiconducting layer is insufficient and cannot be completely neutralized, acetic acid is compensated for by this insufficient amount. Neutralize, as well as discoloration of conductors, metal barrier layers,
Prevent corrosion.

Further, since the fatty acid amide is quickly melted and dispersed in the base polymer, no projections or bumps are formed on the surface of the semiconductive layer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a power cable according to the present invention.

[Explanation of symbols]

 2: Internal semiconductive layer 3: Insulator 4: External semiconductive layer

Claims (2)

[Claims] 1. A power cable in which an inner semiconductive layer, an insulator, and an outer semiconductive layer are provided on a conductor, and a semiconductive composition constituting one or both of the inner semiconductive layer and the outer semiconductive layer. Is a power cable characterized in that part or all of the base polymer is an ethylene-vinyl acetate copolymer and contains 0.01 to 3 parts by weight of fatty acid amide per 100 parts by weight of the base polymer. 2. In a power cable having an inner semiconductive layer, an insulator, and an outer semiconductive layer provided on a conductor, a semiconductive composition constituting one or both of the inner semiconductive layer and the outer semiconductive layer. A part or all of the base polymer is an ethylene-vinyl acetate copolymer, and contains 0.01 to 3 parts by weight of a fatty acid amide per 100 parts by weight of the base polymer; A power cable comprising 0.01 to 1 part by weight of a fatty acid amide per 100 parts by weight of a base polymer.