JPH02301903A - Manufacture of electric cable - Google Patents

Abstract

PURPOSE:To obtain electric cables with high bowtie-tree resistance by extrusion- coating a conductor with an insulating material prepared by adding an oxidation suppressing agent having 4-hydroxyphenyl propionate structure in a specified ratio and fatty acid amide to polyolefin. CONSTITUTION:After 0.05-3.0wt.% parts of an oxidation suppressing agent having 4-hydroxyphenyl propionate as molecular backbone and a fatty acid amide each and an organic peroxide as a crosslinking agent are previously fusion-mixed at a temperature at which they are decomposed, then added to 100wt. parts of polyolefine and a conductor is coated with the resultant insulating material by extrusion coating. The oxidation suppressing agent and fatty acid amide have relatively low melting point and are easy to dissolve in an organic peroxide and thus they are dissolved completely previously at a temperature at which the organic peroxide is not decomposed. In this way, raw materials can be mixed at relatively low temperature, influence of deterioration of the additives on is lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing electric wires and cables that can suppress the occurrence of bow tie tree.

[Prior Art] Cross-linked polyethylene has a high degree of electrical insulation and is therefore widely used as an electrical insulator for electric wires and cables.

However, when cross-linked polyethylene insulated wires and cables are used in a wet or flooded atmosphere, water leakage occurs and the electrical insulation performance is significantly reduced.

Water treeing is caused by water condensation in local high electric field areas such as voids, foreign matter, and irregularities at the interface between the insulator and the semiconducting layer in the crosslinked polyethylene insulator.

[Problem to be Solved by the Invention 1] Many efforts have been made to eliminate these defects in electrical insulators for wires and cables, and efforts have been made to improve resin quality control and wire and cable manufacturing technology. This has improved the effectiveness of preventing the occurrence of water trees.

However, it is not possible to completely eliminate these defects with the current technology, and measures to prevent the occurrence of water trees are being considered from various angles.

The present invention has been made based on the above, and is
An object of the present invention is to provide a method for manufacturing electric wires and cables with excellent tightness.

[Means for Solving the Problem] In order to achieve the above object, in the present invention, an antioxidant having a 4-hydroxyphenylpropionate structure as a molecular skeleton and a fatty acid amide are each added in an amount of 0.05 to 3.0 parts by weight. and an organic peroxide as a crosslinking agent are melt-mixed in advance at a temperature that does not cause a decomposition reaction, and then an insulating material made by adding the mixture to 100 parts by weight of polyolefin is extruded and coated on the conductor.

In the present invention, the polyolefin includes polyethylene such as low-density polyethylene and medium-density polyethylene, and ethylene such as ethylene-vinyl acetate copolymer, ethylene-ethylene acrylate copolymer, and ethylene-propylene copolymer. Examples include ethylene copolymers, which can be used alone or in combination of two or more.

The antioxidant added to the polyolefin is a compound having a 4-hydroxyphenylpropionate structure in its molecular skeleton, and has the following structural formula.

○ Specific examples of the antioxidant include triethylene glycol-bis[,1,13-t-butyl-5-
Methyl-4-hydroxyphenyl)propionate, 1
．． 6-Hexanediol-bis[3-(3,5-di-
t-butyl-4-hydroxyphenyl)'p[1pione-toko, pentaerythrityl-tetrakis[3-(3,
5-di-t,-butyl-4-hydroxyphenyl)propionate 1.2.2-thio-diethylenebis[3-(
3,5-di-t-butyl-4-human I]xifinyl)
propionate], octadecyl-3-(3,5-di-
Examples include t-butyl-4 to human 1-]xyphenylpropionate, which can be used alone or in combination of two or more.

Examples of fatty acid amides include lauric acid amide, valmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, N
-Stearyl stearamide, N, -oleyl oleate, N-stearyl oleate, N-oleyl stearamide, N-stearyl E "lucaic acid amide, N-oleyl balmitic acid amide, methylol stearic acid amide, Examples include methylolbehenic acid amide.

Since both the antioxidant and the fatty acid amide have relatively low melting points and dissolve in the organic peroxide, they can be completely dissolved in advance at a temperature at which the organic peroxide does not decompose.

Examples of the organic peroxide used as a crosslinking agent in the present invention include dicumyl peroxide, 1°3-bis=(t
-butyl peroxy-isopropyl)benzene, 2.
5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 and the like are suitable. In addition to the above-mentioned antioxidant and fatty acid amide, a lubricant, a coloring agent, a filler, a crosslinking accelerator, etc. may be added to these crosslinking agents as necessary.

In the present invention, the amounts of the antioxidant and fatty acid amide added are each 0.0 parts by weight per 100 parts by weight of the polyolefin.
The reason why the range is 3 to 3.0 parts by weight is that if it is less than 0.03 parts by weight, the bowtie resistance is insufficiently imparted.
This is because, if it exceeds the lt part, the bow tie resistance will decrease due to bloom.

[Function] In the present invention, the reason why the bow tie resistance is improved is not necessarily clear, but in the present invention, compounding agents other than the crosslinking agent and polyolefin are kneaded at a temperature equal to or higher than the melting point of the polyolefin, as in the prior art. It is presumed that no process is required, therefore the thermal history of the compounding agent is reduced, and the influence on the bow title tree due to deterioration of the compounding agent, etc. is reduced. or,
Since a liquid compounding agent melt-mixed with a cross-linking agent is added to the polyolefin, it is thought that the core of bow tie tree is not formed, and as a result, the bow tie tree resistance is improved.

The influence of moisture on bow ties is extremely large, and bow ties and trees have been found in cables that are energized in the air and cables that are water-shielded with metal sheaths. These are not caused by moisture penetrating from the outside, but by a trace amount of moisture contained inside the crosslinked polyethylene during cable manufacturing. It goes without saying that the composition of the present invention is also effective against such bow tit trees.

[Example] Next, examples of the present invention will be described together with comparative examples.

Examples 1 to 5 As shown in the table, an antioxidant having a 4-human[coxyphenylpropionate] structure as a molecular skeleton and a fatty acid amide were melt-mixed in dicumyl peroxide at 60°C. This was poured into a 60°C tumbler containing polyethylene pellets and stirred, allowing it to adhere (partially permeate) to the polyethylene pellets.

The pellets were introduced into an extruder, and coated on a copper conductor with an outer diameter of 3# with a polyethylene semiconducting material with a thickness of 0.5 m to a thickness of 2 m, and nitrogen gas was then used as a heat medium. An electric wire was manufactured by crosslinking in a dry crosslinking pipe.

Comparative Example 1 The above antioxidant and fatty acid amide were not melt-mixed with the organic peroxide in advance, but were individually added to a tumbler containing polyethylene pellets at 60°C, and after stirring, the pellets were used to conduct the example. Electric wires were manufactured in the same manner.

Comparative Example 2 A conventionally used antioxidant 4.4'-thiobis(6-t-butylphenol), a fatty acid amide, and dicumyl peroxide were each individually placed in a tumbler containing a polyethylene pellet at 60°C. After adding and stirring,
Using this pellet, an electric wire was manufactured in the same manner as in the example.

Comparative Examples 3 and 4 Electric wires were produced in the same manner as Examples 1 to 5, except that amounts of antioxidant and fatty acid amide outside the specified range were used.

(Evaluation method) The occurrence of bow tie tree was determined by immersing the insulated wire produced as described above in 90°C warm water, and adding A03 to the conductor-sluice gate.
This was done by applying KV for 500 days. This was sliced thinly and boiled and stained with a methylene blue aqueous solution, and the presence or absence and number of bow tit trees were examined using an optical microscope.

As is clear from the table, in Examples 1 to 5, the occurrence of bowtie trees was not sufficiently suppressed, whereas in Comparative Example 1,
- 4, the amount of bow tit trees generated is very large.

[Effect of the Invention 1] As explained above, according to the present invention, electric wires and cables with excellent bow tie resistance can be manufactured.

Claims (1)

[Claims] 1. An antioxidant having a 4-hydroxyphenylpropionate structure as a molecular skeleton and a fatty acid amide were each added at 0.0%.
After melt-mixing 05 to 3.0 parts by weight and an organic peroxide as a crosslinking agent at a temperature that does not cause a decomposition reaction,
A method for producing electric wires and cables, which comprises extruding and coating a conductor with an insulating material obtained by adding this to 100 parts by weight of polyolefin.