JPH07288039A - Electrical insulating resin composition and electric wire / cable - Google Patents

Abstract

(57) [Summary] [Object] The object of the present invention is to inevitably have defects that cause water trees, such as voids, foreign matters, and irregularities at the interface between the insulator and the semiconductive layer, in the insulator. Another object of the present invention is to provide a novel electric insulating composition and a wire / cable that can significantly suppress the generation of water trees. [Structure] The present invention comprises a base resin 10 made of polyethylene, an ethylene copolymer, or a mixture thereof.
For 0 parts by weight, the following formula: (Wherein R ¹ and R ² are hydrogen or a hydrocarbon group,
In addition, 0.005 of an acrylate having an oxygen atom, a nitrogen atom, a sulfur atom, an atom atom such as silicon, or an atomic group consisting of these atoms may be contained in the structure of R ¹ and R ^2.
It is characterized by adding 1.5 parts by weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically insulating resin composition capable of greatly suppressing the generation of water trees, especially bow tie tree, generated in insulators such as cross-linked polyethylene insulated power cables and the like, and a coating thereof. It relates to electric wires and cables.

[0002]

2. Description of the Related Art Generally, as a material for electric insulators for electric wires / cables, polyolefin, particularly so-called cross-linked polyethylene obtained by cross-linking polyethylene is widely used. Insulated wires and cables coated with this crosslinked polyethylene have excellent electrical insulation and heat resistance, but when used in a humid environment or in a flooded atmosphere, electrochemical deterioration called water tree occurs in the insulator, It has the drawback that the electrical insulation performance is significantly reduced.

For example, the general structure of an insulated cable for high voltage is that an insulating layer 3 is provided on a conductor 1 via an inner semiconductive layer 2 as shown in FIG. The conductive layer 4 is provided, and when a bowtie-shaped water tree is generated inside the insulating layer 3 or an interfacial water tree is generated at the interface of the inner semiconductive layer 2 or the outer semiconductive layer 4, In the worst case, it may even penetrate the insulating layer 3 and cause dielectric breakdown.

The water tree is a void in the insulator, foreign matter,
In addition, non-polar cross-linked polyethylene, which has a low affinity for water, is generated around the local high electric field part such as irregularity of the interface between the insulator and the semiconductive layer due to the increase in pressure of the condensed water. Caused by mechanical strain.

Therefore, in order to prevent the generation of this water tree, in order to reduce the voids, foreign matters, and protrusions that cause the generation, meticulous quality control of the resin and the use of electric wires and cables for making the production line a clean room, etc. Measures have been taken to improve the manufacturing technique or improve the hydrophilicity by introducing a polar group into the insulator.

[0006]

However, in spite of efforts to be made in various fields, it is not possible to completely eliminate the defect that causes the generation of the water tree by the above-mentioned technique alone. The current situation is not.

The present invention has been devised in order to effectively solve the above-mentioned problems, and its purpose is to eliminate voids, foreign matters, and irregularities at the interface between the insulator and the semiconductive layer in the insulator. It is intended to provide a novel electrical insulating composition and a wire / cable capable of significantly suppressing the generation of a water tree even if the causative defect is unavoidably present.

[0008]

In order to solve the above problems, the present invention provides the following formula based on 100 parts by weight of a base resin made of polyethylene, an ethylene copolymer or a mixture thereof.

[0009]

[Chemical 1]

(Here, R ¹ and R ² are hydrogen or a hydrocarbon group, and in the structure of R ¹ and R ² , atoms such as oxygen, nitrogen, sulfur, silicon, etc., or atoms composed of these atoms are partially contained. An electrically insulating resin composition containing 0.005 to 1.5 parts by weight of an acrylate having a group), and a conductor is coated with the electrically insulating resin composition and crosslinked. It is a wire or cable that has been processed.

Examples of the base resin which can be used in the present invention include low density polyethylene, medium density polyethylene and ethylene-propylene copolymer, as well as ethylene-ethyl acrylate copolymer and ethylene-vinyl acetate copolymer. A polyolefin containing a majority of ethylene is applicable, and these may be used alone or in combination of two or more, if necessary.

Examples of the acrylate added to the base resin include 2,2,6,6, -tetramethylpiperidinyl methacrylate and N-methyl-2,2,6,6-tetramethylpiperidinyl methacrylate. The
These may be used alone or in combination of two or more.

Further, in the present invention, this addition amount is 0.
The amount of 005 to 1.5 parts by weight means that if the amount is less than 0.005 parts by weight, the desired effect of suppressing the formation of boutite trie is insufficient, and if the amount exceeds 1.5 parts by weight, the compatibility is higher than the upper limit of the insulator. Deposited on the surface (this phenomenon is called bloom),
This is because it deteriorates the quality of the product.

As a cross-linking agent for cross-linking the electrically insulating resin composition, dicumyl peroxide, 1,3-bis- (tert-butylperoxy-isopropyl) benzene, and 2,5-dimethyl, which are commonly used, are used. -2
5- (t-butylperoxy) -hexyne 3 and the like can be mentioned. Then, as the cross-linking method, in addition to the chemical cross-linking with an organic peroxide, an organic silane such as vinyltriethoxysilane is grafted to a polymer, and the silane is condensed by contacting with a silanol condensation catalyst to cross-link, There are so-called silane water crosslinks or ionizing radiation.

Incidentally, it is possible to add a lubricant, a coloring agent, a filler, a crosslinking accelerator, etc. to the composition, if necessary.

[0016]

As described above, the present invention provides an electrical insulating composition obtained by mixing the above acrylate with a base resin made of polyethylene, an ethylene copolymer or a mixture thereof, and the electrical insulating composition on a conductor. Since it is coated with and cross-linked, it exhibits sufficient bowtley characteristics. Therefore, even if a defect such as a void, a foreign substance, or a protrusion that causes a water tree is generated in the insulator, the generation of the water tree is greatly suppressed.

[0017]

EXAMPLES Hereinafter, specific examples of the present invention will be described in detail.

First, each composition consisting of the compounding ingredients shown in Table 1 was kneaded by a hot roll heated to 120 ° C. and formed into a sheet, which was then pelletized using a pelletizer. On the conductor 1 having an outer diameter of 3 mm, together with the inner semi-conductive layer 2 and the outer semi-conductive layer 4 having a thickness of 0.5 mm by extrusion extrusion coating so as to form the insulating layer 3 having a thickness of 2 mm. Immediately thereafter, continuous cross-linking was performed in a cross-linking tube by a dry cross-linking method using nitrogen gas as a heating medium, and then pressure cooling was performed to produce 9 types of sample electric wires. Then, with respect to each of these sample electric wires, the number of occurrence of boutrite and the presence or absence of occurrence of bloom were examined, and the results are shown in the lower column of Table 1.

For the evaluation of the number of occurrence of bow tie tree, each sample electric wire was immersed in warm water at 90 ° C.
After applying AC3kV AC voltage between water and water for 500 days, thinly slice this and boil it with methylene blue aqueous solution. Counted. on the other hand,
The presence or absence of bloom was evaluated by visually observing the surface of the pellet after holding it in a thermostat at 80 ° C. for 10 days before producing the electric wire.

[0020]

[Table 1]

As a result, as is clear from Table 1, in Examples 1 to 8 which consisted of the compounding components defined in the present invention, the occurrence of boutite tree was sufficiently suppressed and the occurrence of bloom was observed. There wasn't.

On the other hand, Comparative Example 1 in which no methacrylate such as 2,2,6,6-tetramethylpiperidinyl methacrylate was added, and Comparative Examples 2, 4 in which the amount of these methacrylates was less than the specified amount of the present invention. In each case, a large amount of boutite tree was generated. In addition, Comparative Example 3 in which the amount of addition of these methacrylates exceeds the specified amount of the present invention
Bloom was seen in all of No. 5.

As described above, according to the present invention, by adding a predetermined amount of the above-mentioned methacrylate to the base resin made of polyethylene or the like, the number of generation of the bow tie tree is greatly reduced, so that generation of water tree in the insulator is caused. Even if defects such as voids, foreign matter, and protrusions that cause the problem occur, the generation of water trees is greatly suppressed.

The influence of water on the bow tie tree is extremely large, and the vault tie tree is also found in a cable charged in the air or a cable shielded by a metal sheath. It is considered that these are not due to water permeating from the outside, but due to a small amount of water contained inside the cross-linked polyethylene during cable production. It is needless to say that the insulator according to the present invention also exerts an effective water tree suppressing effect against such a bowtie tree.

[0025]

In summary, according to the present invention, the generation of water trees is greatly suppressed even if defects such as voids, foreign matters, and protrusions that cause water trees are generated in the insulator. The durability in a wet environment is improved, and excellent effects such as obtaining highly reliable electric wires and cables can be exhibited.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 conductor 2 inner semiconductive layer 3 insulating layer 4 outer semiconductive layer

Claims (2)

[Claims] 1. To 100 parts by weight of a base resin composed of polyethylene, an ethylene copolymer or a mixture thereof, the following formula: (Wherein R ¹ and R ² are hydrogen or a hydrocarbon group,
In addition, 0.005 of an acrylate having an oxygen atom, a nitrogen atom, a sulfur atom, an atom atom such as silicon, or an atomic group consisting of these atoms may be contained in the structure of R ¹ and R ^2.
An electrically insulating resin composition comprising 1.5 parts by weight. 2. An electric wire / cable comprising a conductor coated with the electrically insulating resin composition according to claim 1 and crosslinked.