JPS58184206A - Wire and 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 The present invention relates to improvements in crosslinked polyethylene insulated wires and cables.

Cross-linked polyethylene is often used as an insulator for electric wires and cables due to its excellent insulation and heat resistance properties. -However, in recent years, it has been recognized that when electricity is applied in a flooded state, water trees occur and electrical deterioration progresses. Since cross-linked polyethylene cables will continue to be used in flooded environments, such as when buried underground, suppressing this water tree has become an important issue.

Various studies have already been conducted on this problem in various fields, and as countermeasures, for example, (1) methods using ethylene vinyl acetate copolymers alone or in combination, (2) methods containing special antioxidants or ester groups. Various methods of adding additives have been proposed. However, (1)
However, if the vinyl acetate content is increased in order to increase the water tree inhibiting effect, there is a problem in that the electrical characteristics deteriorate.

In addition, (2) was not so good that it could be said that the effect of inhibiting water tree generation was sufficient.

The present invention was made in view of the above situation, and provides an electric wire that can suppress the number of water trees that occur in an insulating composition that coats a conductor and prevent the progress of insulation deterioration of the insulating composition.
The purpose is to provide cables.

The electric wires and cables of the present invention include a mixture mainly made of polyethylene, which is produced by a high-pressure method, has a density (1/cd) in the range of 0.925 to 0.935, and has a melt index of 0.5 or more on a conductor. It is coated with a crosslinked insulating composition.

An embodiment of the electric wire and cable of the present invention will be described below. The high-pressure method used to produce the insulating composition for electric wires and cables in this example is a method conventionally used to produce low-density polyethylene, and involves a radical reaction using an organic peroxide under several thousand atmospheric pressures. This is a method of polymerizing ethylene. In addition, the density (97crJ) was limited to the range of 0.925 to 0.935 because below this value there is no effect of inhibiting the occurrence of water tree, and above this value it is practically difficult to synthesize. It is. The reason why the melt index is limited to 05 or more is that if it is less than 0.5, scorch will occur during extrusion molding, especially when extruding with the addition of organic peroxide, making it impossible to extrude smoothly. Although not particularly limited, if the number is too large, the degree of crosslinking may decrease, so it is desirable that the number is at most 10.
1 The most typical crosslinking mentioned here is a method of adding an organic peroxide such as dicumyl peroxide and heating after extrusion. In addition to this, crosslinking is carried out by irradiating radiation such as electron beams, or 'recently developed by a certain company, in which a silane compound with a hydrolyzable organic group is grafted onto polyethylene using an organic peroxide, and then There is no problem in crosslinking carried out by exposure to water in the presence of a silanol condensation catalyst. In addition, antioxidant,
It is possible to add compounding agents such as lubricants. Further, the water tree prevention property can be further improved by blending a compounding agent that prevents water tree, for example, a polymer having a polar group or adding an ester group-containing additive.

Next, the electric wire and cable of this example will be explained by making three samples of insulating compositions and comparing them with two comparative examples of insulating compositions. Evaluation of these insulators was carried out by creating a model cable as shown in the figure, which was produced by heating and crosslinking after extrusion. In the figure, 1 is a 1° conductor, and the outer periphery of the conductor 1 is coated with a semiconductive layer 2 with an insulating composition from a third company, and the outer diameter of the semiconductive layer 2 is 41111.
1. The outer diameter of the insulation composition 3 is 8 mm. Insulating composition 3 was prepared using the polyethylene manufacturing method shown in Table 1 using polyethylene 7100, dicumyl peroxide 25, and 4,4'-thiobis(6-tert-butyl-3-methylphenol) 0.2, Manufactured based on density and melt index. However, only in Example 3, lead stearate was added to 0.2
Added.

The test method in Table 1 is to immerse the model cable shown in the figure in water for 50 hours.
The test results shown in Table 2 were obtained using test conditions in which 3 KV was applied for 18 months.

As is clear from Table 2, the effect of inhibiting the occurrence of water trees in Examples 1, 2, and 3 is remarkable. Comparative Example 1 and Comparative Example 2, which are medium-density polyethylene obtained by a low-pressure method synthesized using a GRA and Natsuta catalyst, have a density as low as 0.920 even when manufactured by a high-pressure method. In both cases, water trees occur significantly.

In this way, the electric wires and cables of this example were manufactured by a high-pressure method, focusing on the polyethylene itself of the insulating composition, and pursuing the relationship between the water tree and the molecular structure of polyethylene. By coating the conductor with a polyethylene cross-linked insulating material having a melt index of 0.935 and 0.935 or more, the number of water tree occurrences can be significantly suppressed and electrical deterioration of the insulating coating can be prevented from progressing. In addition, at least 0.02 p h of fatty acid metal salt is added to 100 parts by weight of polyethylene in the insulating composition of the mixture.
By adding r or more, the occurrence of water trees can be further suppressed.

As described above, the electric wires and cables of the present invention have the effect of significantly suppressing the number of water trees that occur in the insulating composition that coats the conductor and preventing the progress of insulation deterioration of the insulating composition. It is.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a model cable of an embodiment of the electric wire and cable of the present invention. 1... Conductor, 2... Semiconductive layer, 3... Insulating composition. 1ζ 29-

Claims (1)

[Claims] (1) The density (g/cra) is manufactured using a high pressure method on a conductor.
) is in the range of 0.925 to 0.935 degrees and the melt intex is 0.5 or more. An electric wire or cable coated with an insulating composition made of a crosslinked mixture of polyethylene as a main component.