JPH06309931A - Electrically insulative composition and electric wire/ cable - Google Patents

Abstract

PURPOSE:To prevent scorching of an electric wire/cable when it is formed through a fusion process and enable bridging when polyolefin having a high melting point is used by adding a specific bridging agent, to polyolefin. CONSTITUTION:An internal semiconductive layer 2, insulation layer 3, and external semiconductive layer 4 are as conductor shield layers put on a soft copper twisted wire 1 through extrusion, followed by a bridging process, and an electric wire/cable 5 is formed. The insulation layer 3 should be of an electric insulative compound prepared by adding 1-(2-tert-butylperoxyisopropyl)-4- isopropylbenzene and N,N'-m-phenylenebismaleimide as bridging age to polyolefin. This enables the prevention of scorching even though the shaping temp., is set high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical insulating composition mainly composed of polyolefin and an electric wire / cable.

[0002]

2. Description of the Related Art Polyolefin, particularly so-called cross-linked polyethylene obtained by cross-linking polyethylene, is widely used as an insulating material for electric wires and cables because of its excellent electric insulation and heat resistance.

Dicumyl peroxide (DCP) is generally used as a cross-linking agent used for molding the cross-linked polyethylene.
It is performed at around 0 ° C.

[0004]

However, if an attempt is made to increase the molding temperature, shorten the molding time, and increase the extrusion speed, this crosslinking agent alone will cause some crosslinking agents to decompose during molding. Because scorch is generated,
There is a problem that this lowers the AC breakdown voltage.

Furthermore, since the molding temperature also becomes high when a wire / cable is formed using medium-density polyethylene, high-density polyethylene having a high melting point, linear extremely low-density polyethylene, or linear low-density polyethylene, the scorch However, it was difficult to form an electric insulating composition containing a cross-linking agent therein, and it was difficult to cross-link electric wires and cables using these resins.

The present invention has been made based on the above, and prevents scorch when melt-molding an electric wire / cable with an electric insulating composition containing a cross-linking agent, and uses a polyolefin having a high melting point. The purpose of the present invention is to provide an electrical insulating composition and an electric wire / cable capable of cross-linking.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to add 1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene and N, N'-to polyolefin.
m-phenylene bismaleimide is added, and 1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene and N, N'-m-phenylene bismaleimide are added to polyolefin. It is an electric wire or cable obtained by coating a conductor or a conductor shielding layer with an electric insulating composition and crosslinking the same.

[0008]

In the present invention, the polyolefin is polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, linear very low density polyethylene, ethylene vinyl acetate copolymer, Ethylene-ethyl acrylate copolymer,
Examples thereof include ethylene-based main polymers containing ethylene in the majority, such as ethylene-propylene copolymers, which can be used alone or in combination of two or more.

1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene is a kind of organic peroxide and can be represented by the following chemical formula.

[0010]

[Chemical 1]

Although the amount of the organic peroxide added is not specified, it is 0.01 to 1 with respect to 100 parts by weight of the polyolefin.
A range of 0 parts by weight is preferred. If it is less than 0.01 part by weight, a sufficient degree of crosslinking cannot be achieved, and if it exceeds 10 parts by weight, scorch tends to occur. As a result of investigating the relationship between the degree of cross-linking and the cross-linked polyolefin insulated electric wire and the water-immersion voltage application characteristic of the cable, it has been confirmed that when the cross-linking degree (gel fraction) is 70% or more, the effect of improving the water-immersion voltage application characteristic is large. However, it is preferable to select the addition amount so that this degree of crosslinking can be achieved.

The organic peroxide of the present invention comprises dicumyl peroxide, 1,3-bis- (tert-butylperoxyisopropyl) benzene and 2,5-dimethyl-2, which have been conventionally used for crosslinking polyolefins. 5-di-
It is also possible to use it in combination with tert-butyl-hexyne-3 and the like, but in that case, it is desirable for the purpose of the present invention to add less than 1/2 of the organic peroxide specified in the present invention. .

N, N'-m-phenylene bismaleimide as an anti-scorch agent can be represented by the following chemical formula.

[0014]

[Chemical 2]

The present inventors have found that this compound has a function of preventing crosslinking of polyethylene during extrusion molding. That is, scorch at the time of extrusion molding can be prevented, and an electric wire / cable having a good appearance can be obtained. The addition amount of this compound is not particularly limited, but the polyolefin 100
The range of 0.01 to 10 parts by weight is preferable with respect to parts by weight. If it is less than 0.01 part by weight, there is no scorch preventing effect,
If the amount exceeds 10 parts by weight, crosslinking tends to be inhibited.

Additives such as antioxidants, lubricants and colorants may be added to the electrical insulation composition of the present invention.

[0017]

EXAMPLES The present invention will be described below together with comparative examples.

First, the electric wire / cable of the present invention will be described with reference to FIG.

In FIG. 1, 1 is an annealed copper stranded wire, and an inner semiconductive layer 2, an insulating layer 3 and an outer semiconductive layer 4 as conductor shield layers are extruded on the outer periphery of the stranded wire and then crosslinked to form an electric wire / cable 5. Become.

The compositions having the compositions shown in Tables 1 and 2 were kneaded with a 22-inch mixing roll to prepare a sheet, which was pelletized with a pelletizer. Then, the pellets were introduced into an extruder and, as explained in FIG. 1, a 4 mm thick insulating layer 3 was formed on a 60 mm ² annealed copper stranded wire 1 together with a 0.7 mm thick inner semiconductive layer 2 and an outer semiconductive layer 4. Was extruded as. Immediately thereafter, the cable 5 is cross-linked in a dry cross-linking tube using nitrogen gas as a heat medium, and then pressure-cooled.
Was completed and used as a sample.

[0021]

[Table 1]

[0022]

[Table 2]

The evaluation was performed based on the following.

Extrudability: The cable was evaluated by the appearance of extrusion at an extrusion temperature of 145 ° C., that is, the presence or absence of burning.

AC breakdown test method: Each sample was tested at room temperature for 17 hours.
After kV / 10 minutes, the voltage was increased at a rate of 5 kV / 10 minutes.

Gel fraction: Judged according to JIS C3005.

All of Examples 1 to 8 have good extrusion processability and large AC breakdown voltage. On the other hand, Comparative Examples 1 and 2 are not so good in extrusion processability,
The AC breakdown voltage is low. In Comparative Examples 3 to 5, extrusion processing was difficult, and it was impossible to measure the AC breakdown voltage.

[0028]

As described above, according to the present invention,
To provide an electric insulating composition and an electric wire / cable that prevent scorch when melt-molding an electric wire / cable with a resin composition containing a cross-linking agent and enable crosslinking when a polyolefin having a high melting point is used. It is possible and has an extremely high industrial value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electric wire / cable of the present invention.

[Explanation of symbols]

 1 Annealed copper stranded wire (conductor) 2 Internal semi-conductive layer (conductor shield layer) 3 Insulation layer

Claims (2)

[Claims] 1. A 1- (2-tert-
(Butylperoxyisopropyl) -4-isopropylbenzene and N, N'-m-phenylene bismaleimide are added, The electrical insulating composition characterized by the above-mentioned. 2. A polyolefin containing 1- (2-tert-)
Butyl peroxyisopropyl) -4-isopropylbenzene and N, N'-m-phenylene bismaleimide are added to the electric insulating composition to cover the conductor or the conductor shielding layer, and the electric wire is formed by crosslinking. ·cable.