JPH0268809A - Electrical insulators for wires and cables - Google Patents

Abstract

PURPOSE:To prevent generation of water tree by cross-linking a compound where 0.01-3.0 parts by weight of diamine with total carbon number 8-70 is added to polyethylene or ethylene copolymer or to 100 parts by weight of these mixture. CONSTITUTION:A compound where 0.01-3.0 parts by weight of diamine having total carbon number 8-70 is added to polyethylene or to ethylene copolymer, or 100 parts by weight of these mixture is cross-linked. As the cross-linking method, chemical cross-linking by organic peroxide, silane water cross-linking, or ionized radial ray method is used. It is thus possible to obtain an electrical insulator for wire and cable excellent in its water tree resistivity, especially in bow tie water tree resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrical insulator for electric wires and cables that can suppress the occurrence of water trees, particularly bow tree trees.

1. 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 treeing occurs, significantly reducing electrical insulation performance.

Water tree is caused by voids, foreign matter, etc. in cross-linked polyethylene insulation.
It also occurs when water condenses in local high electric field areas such as irregularities at the interface between the insulator and the peninsular layer.

[Problem to be solved by the invention] Many efforts have been made to eliminate these defects in wire and cable insulation, and improvements in resin quality control and wire and cable manufacturing technology have led to The effectiveness of preventing the occurrence of water trees is improving.

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

The present invention has been made based on the above, and its purpose is to prevent water retardation even when defects such as voids, foreign matter, and irregularities at the interface between the insulator and the semiconducting layer exist in the insulator. An object of the present invention is to provide an electrical insulator for cables that can suppress the occurrence of II.

[Means and effects for solving the problem J Electric wire of the present invention
The electrical insulator for cables is made by adding 0.01 to 3.0 ml of diamine having a total carbon number of 8 to 70 to 100 parts by weight of polyethylene, ethylene copolymer, or a mixture thereof.
The composition is cross-linked, and as a result, the water resistance, especially the bow tie resistance, is greatly improved.

In the present invention, diamine has the following structure.

(Total number of carbon atoms in R1 and R2 is 8 to 70) Among those having such a structure, stearylbutyl [
] Pyrene diamine and beef tallow propylene diamine are common, but others include oleylpropylene diamine, lauryl propylene diamine, octymyl bropylene diamine, palmityl bropylene diamine, myristyl propylene diamine, decyl propylene diamine, co-nutpropylene diamine, and montane propylene diamine. Nylbrobylene diamine, tetracontanyl propylene diamine, hydroxystearyl propylene diamine, hydroxyoleyl propylene diamine, pentanyl butylene diamine, stearyl butylene diamine, oleyl ethylene diamine, lauryl butylene diamine, octymyl butylene diamine, valmityl butylene diamine Examples include amine, myristyl butylene diamine, stearyl ethylene diamine, oleyl ethylene diamine, lauryl butylene diamine, octymyl ethylene diamine, valmityl ethylene diamine, hydroxystearyl ethylene diamine, and the like.

In the above formula, there is no problem even if the structure of R contains an atom such as oxygen, nitrogen, sulfur, or an atomic group thereof.

Moreover, several kinds of the above-mentioned compounds may be used in combination.

The reason why the total carbon number of the diamine is set to 8 to 70 is because if it is less than 8, it is not compatible with polyethylene, an ethylene copolymer, or a mixture thereof, and will precipitate on the surface. In addition, when it exceeds 70, the amine inherently has
This is because the effect of suppressing the occurrence of bow tit tree will be significantly reduced.

The reason why the amount of diamine added is limited to 0.01 to 3.0 parts by weight is that if it is less than 0.011 parts by weight, the desired effect of suppressing the occurrence of bowthorn tree is insufficient; This is because, if the diamine exceeds 50%, the diamine will precipitate on the surface of the insulator due to compatibility limitations.

Suitable base resins include polyolefins containing a majority of ethylene, such as low-density polyethylene, medium-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, and ethylene-bu-O-pyrene copolymer. You may use 1 type or a combination of 2 or more types among these.

As the crosslinking agent, commonly used dicumyl peroxide, 1,3-bis-(t-butyl peroxy-isopropyl)benzene, 2,5-dimethyl-2,5-(t
-butylperoxy)-hexyne-3 and the like.

Crosslinking methods include chemical crosslinking using organic peroxides, silane water crosslinking, and ionizing radiation.

There is no problem in adding other lubricants, coloring agents, fillers, crosslinking accelerators, etc. as necessary.

The influence of moisture on bow tree is extremely large, and bow tree is also 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 lactation.

[Example] (Preparation of electric wire) A sheet prepared by kneading each composition shown in the table with a hot roll at 120°C was knotted using a pelletizer. This was extruded and coated on a conductor with an outer diameter of 3 shoes with a polyethylene internal semiconductive layer of 0.5 # thickness to an insulator thickness of 2M, and then cross-linked in a dry cross-linking pipe using nitrogen gas as a heating medium. Then, an insulated wire was obtained by cooling under pressure.

(Evaluation method) To determine the occurrence of bow tree, the electric wire prepared as described above is immersed in 90°C warm water, and the conductor-sluice gate is exposed to AC3KV.
was applied 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.

Bloom made Belen 1-8 before making the electric wire.
After storing it in a constant temperature bath at 0°C for 10 days, the surface was
I observed and evaluated it.

As is clear from the table, in Examples 1 to 6 in which only a limited amount of the diamine according to the present invention was added, the occurrence of bow tree was sufficiently suppressed, and no bloom was observed.

On the other hand, Comparative Example 1 in which the diamine according to the present invention was not added and Comparative Example 2 in which the amount of addition m was less than the limited amount had a very large number of ends where bow tite trees were generated. In addition, in Comparative Example 3, in which the amount was added in excess of the limited amount, although there were few ends of bowtery,
Bloom was seen.

[Effects of the Invention] As explained above, according to the present invention, water resistance,
In particular, an electrical insulator for wires and cables with significantly improved bow tightness can be obtained.

Claims (1)

[Claims] 1. A composition obtained by adding 0.01 to 3.0 parts by weight of a diamine having a total carbon number of 8 to 70 to 100 parts by weight of polyethylene or ethylene copolymer or a mixture thereof is subjected to crosslinking treatment. Electrical insulator for wires and cables.