JPH01100803A - Electric insulator for wire and cable - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a water tree by bridging a composition obtained via the addition of the predetermined quantity of a hindered amine compound to the copolymer of polyethylene and ethylene or a mixture thereof. CONSTITUTION:A composition is formed via the addition of 0.05 to 3 weight parts of a hindered amine compound to 100 weight parts of base resin comprising polyethylene and/or ethylene copolymer. In this case, the hindered amine compound has a basic structure of 2,2,6,6-tetramethyl-4-biberzyl base or 1,2,2,6,6- pentamethyl-4-biberzyl. The added composition is subjected to bridging treatment like chemical bridging via organic peroxide and irradiation bridging via irradiation. In the aforesaid constitution, the occurrence of a water tree is seen less frequently than in other constitutions.

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.

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

However, when cross-linked polyethylene insulated electrical cables are used in a humid or waterlogged atmosphere, water trees will form in the insulator, significantly reducing the electrical insulation properties.

Wood tree is caused by water condensation in local high electric field areas such as voids in cross-linked polyethylene insulators, foreign matter, and irregularities at the interface between the insulator and the semiconducting layer. For this reason, 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 improved the effectiveness of suppressing water tree formation. There is.

[Problems to be Solved by the Invention] However, with the current technology, it is not possible to completely eliminate these defects, and measures to prevent the occurrence of water trees have been studied from various angles.

This invention was made in view of the above points, and is an electric wire/cable electric wire that can suppress the occurrence of water trees even if there are defects such as voids in the insulator, foreign matter, and irregularities at the interface between the insulator and the semiconducting layer. The purpose is to provide an insulator.

[Auxiliary actors and actions for solving the problem] In this invention, 1v, the gas insulator contains 0° of a hindered amine compound based on 10.0 parts by weight of polyethylene, polyethylene copolymer, or a mixture thereof. 05 to 3 parts by weight is crosslinked.

[Example] In this invention, conventionally known polyethylene or ethylene copolymer is used as the base resin,
Depending on the case, these may be used in combination. Ethylene-based copolymers include ethylene-vinyl acetate copolymers,
Examples include ethylene/ethyl acrylate copolymer, ethylene/butene-1 copolymer, ethylene proprene rubber, etc., and these are l! Use i or a mixture of two or more.

The hindered amine compound added to the above base range has a basic skeleton of 2,2,6°6-tetramethyl-4-piperidyl group or l.

It has a 2,2,6,6-bentamethyl-4-piperidyl group and is represented by the following structural formula.

The amount of such hindered amine compounds added to the base resin is 2100 parts by weight of the base resin! , 0.05 to 3.0 parts by weight per part.

This is because if the amount is less than 0.05 parts by weight, the effect of inhibiting water tree generation will be small, and if it exceeds 3.01 parts by weight, a phenomenon of precipitation from the inside of the insulator to the surface will be observed.

The composition thus obtained is crosslinked by chemical crosslinking using an organic peroxide, irradiation crosslinking using ionizing radiation, or silane water crosslinking using a silane compound.

Note that there is no problem in adding an antioxidant, a lubricant, a coloring agent, etc. to the above composition as necessary.

Examples of the present invention will be described below in comparison with comparative examples.

A sheet was prepared by kneading the composition shown in Table 1 using an 8-inch mixing roll, and this sheet was pelletized using a pelletizer. The pellets are then introduced into the extruder,
A 0.5 mm thick polyethylene semiconductive layer and an insulator were extruded and coated on a copper conductor with an outer diameter of 3 mm to a thickness of 2 mm.

This was followed by crosslinking in a dry crosslinking tube using nitrogen gas as a heating medium, followed by cooling under pressure to obtain an insulated wire.

The results of observing the occurrence of water trees and the precipitation of hindered amine compounds in the insulated wire thus obtained are shown in the lower column of Table 1. This observation was carried out as follows. .

An insulated wire is immersed in distilled water, and 3K is applied between the copper conductor and the water.
V, 50Hz AC voltage was applied for 18 months at room temperature.
After the electricity was applied, the insulator was sown into circular slices, boiled and stained with a methylene blue aqueous solution, and the number of water trees generated was observed using an optical microscope. In addition, the surface of the wire after energization was visually observed and analyzed by infrared absorption spectroscopy to investigate the precipitation of hindered amine compounds.

In Table 1, Examples 1 to 5 are bis(2,2,6,6-tetramethyl-4-
Separate (bepyridyl) was added in the amount specified in the present invention, and the occurrence of water trees was sufficiently suppressed, and no precipitation of hindered amine compounds on the surface of the insulator was observed.

On the other hand, Comparative Examples 1.2.3 are outside the scope of the present invention, and are insufficient in terms of water tree suppression effect or precipitation of hindered amine compounds on the surface of the insulator.

(The following is a blank space) [Effects of the Invention] As explained above, the electrical insulator of the present invention contains 0 parts by weight of a hindered amine compound based on 100 parts by weight of a base resin of polyethylene and/or ethylene copolymer.
．． 05 to 3 parts by weight is crosslinked.

It is possible to obtain an insulator which has an excellent water tree inhibiting effect and which does not cause precipitation of dirt amine compounds on the surface of electric wires and cables, greatly contributing to improving the reliability of electric wires and cables.

Claims (1)

[Claims] It is characterized by being constructed by crosslinking a composition obtained by adding 0.05 to 3.0 parts by weight of a hindered amine compound to 100 parts by weight of polyethylene, an ethylene copolymer, or a mixture thereof. Electrical insulator for wires and cables.