JP2666543B2 - Electric wires and cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric wire / cable having a crosslinked coating layer made of polyolefin around a conductor.

[Prior Art] Polyolefins such as polyethylene are widely used as insulating materials for electric wires and cables. Polyethylene has excellent electrical insulation properties and is roughly classified into low-density polyethylene, medium-density polyethylene, and high-density polyethylene. High-density polyethylene has a higher molding temperature than low-density and medium-density polyethylene, at 145 ° C or higher. The low-density polyethylene includes linear low-density polyethylene and linear low-density polyethylene, which have a relatively high molding temperature (140 ° C. or higher) despite their low density.

Crosslinked polyethylene obtained by crosslinking these polyethylenes is more excellent in heat resistance than uncrosslinked polyethylene and is useful. As a cross-linking agent for cross-linking polyethylene, dicumyl peroxide is generally used, and molding is usually performed at about 130 ° C.

[Problems to be solved by the invention] However, dicumyl peroxide (DCP) is used as a crosslinking agent.
If the molding temperature is increased to shorten the molding time or to speed up the extrusion molding, there is a problem that scorch (burn) occurs and the AC breakdown voltage decreases. Furthermore, when DCP is used to crosslink medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, or linear ultra-low-density polyethylene, which originally have a high molding temperature, scorch is remarkably generated, making it difficult to form a crosslinked coating layer. Met.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric wire / cable capable of suppressing the occurrence of scorch when the extrusion molding temperature is increased to increase the molding speed, and preventing a decrease in AC breakdown voltage.

Another object of the present invention is to provide an electric wire or cable having a crosslinked coating layer made of a polyolefin having a high molding temperature.

[Means for Solving the Problems] The first invention of the present invention provides a polyolefin having 1- (2-te
(rt-butylperoxyisopropyl) -4-isopropylbenzene, wherein a crosslinked coating layer made of a resin composition is formed on the outer periphery of the conductor.
Cable.

Further, the second invention relates to 1- (2-tert.
A crosslinked coating layer composed of a resin composition obtained by adding an unsaturated dimer of -butylperoxyisopropyl) -4-isopropylbenzene and α-aromatic-substituted α-methylalkene is formed on the outer periphery of the conductor. Wires characterized by
Cable.

That is, the first feature of the present invention is to use 1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene, which is a kind of organic peroxide, as a crosslinking agent. -Tert-butylperoxyisopropyl) -4-isopropylbenzene and the addition of an unsaturated dimer of α-aromatic-substituted-α-methylalkene as a second feature.

As the polyolefin used in the present invention, low-density polyethylene, medium-density polyethylene, high-density polyethylene,
Linear low-density polyethylene and linear ultra-low-density polyethylene are typical. Copolymers containing 50% or more of ethylene, for example, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene -Ethyl methacrylate copolymer, ethylene-propylene copolymer, etc., and these may be used alone or in combination of two or more.

1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene, which is a crosslinking agent, has the following structural formula I
It is a compound represented by these.

[Structural formula I] The unsaturated dimer of α-aromatic substituted-α-methylalkene is a compound represented by the following structural formula II.

[Structural formula II] In the formula, R represents an aryl group, an alkaryl group or a methyl group, R ¹ and R ² represent an aryl group or an alkaryl group, and these aryl group and alkaryl group may be halogen-substituted, respectively.

Compounds represented by Structural Formula II include α-methylstyrene, p-methyl-α-methylstyrene, p-ethyl-
α-methylstyrene, p-isopropyl-α-methylstyrene, m-ethyl-α-methylstyrene, m-methyl-α-methylstyrene, ar-dimethyl-α-methylstyrene, ar-chloro-α-methylstyrene, ar-chlor-
ar-methyl-α-methylstyrene, ar-diethyl-α-
Methylstyrene, ar-methyl-ar-isopropyl-α-
And unsaturated dimers such as methylstyrene. Specific examples of the compound include 2,4-diphenyl-4-methyl-1-pentene which is an unsaturated dimer of α-methylstyrene. These unsaturated dimers may be used alone or in combination of two or more.

The amount of the crosslinking agent to be added is not particularly limited, but is selected so that the degree of crosslinking is preferably 60% or more, particularly 70% or more. As a result, the flooding characteristics of the electric wires and cables are improved.
Crosslinking of conventionally used dicumyl peroxide, 1,3-bis- (t-butylperoxyisopropyl) -4-isopropylbenzene, 2,5-dimethyl-2,5-di-tert-butylhexyne-3, etc. Can be used in combination, but the amount added is 1/2 that of the compound represented by the structural formula I.
Preferably, the amount is less than.

In the present invention, an antioxidant, a lubricant, a coloring agent and the like may be added in addition to the above components.

[Function] In the present invention, since the polyolefin is cross-linked by using the compound represented by the above structural formula I, it is possible to suppress the occurrence of scorch when the extrusion molding temperature is increased and the molding speed is increased, and the AC breakdown is prevented. Voltage drop can be prevented. In addition, low-density polyethylene, medium-density polyethylene with high molding temperature, high-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, etc. can suppress the occurrence of scorch even when crosslinked, and have excellent properties. Electric wires and cables can be realized. Further, the gel fraction can be improved by adding the compound represented by the structural formula II in addition to the compound represented by the structural formula I.

[Embodiment] The accompanying drawings are sectional explanatory views of an embodiment of the present invention, and show an application example to a power cable. The cable 1 has an inner semiconductive layer 3 having a thickness of 0.7 mm, an insulating layer 4 having a thickness of 4 mm, and an outer semiconductive layer 5 having a thickness of 0.7 mm on the outer periphery of the conductor ² . The soft copper stranded wire and the insulating layer 4 are made of a crosslinked polyethylene described below.

The six compositions shown in Table 1 were kneaded with a 22-inch mixing roll to form a sheet, and pelletized with a pelletizer. Next, the pellets were introduced into an extruder, and 145 ° C.
And extruded together with the inner semiconductive layer 3 and the outer semiconductive layer 5. Thereafter, the cable 1 was immediately cross-linked in a dry cross-linking tube using a nitrogen gas as a heat medium, and then pressurized and cooled to complete the cable 1.

 These cables were evaluated as follows.

Extrusion processability: The appearance of the cable after extrusion, that is, the occurrence of scorch (burn) was observed.

AC breakdown voltage: Apply a voltage to the test cable at room temperature,
The breakdown voltage when the voltage was increased at a rate of kV / 10 min was measured.

 The test results are shown in Table 1.

As is clear from Table 1, the power cables of Examples 1 to 6 have a gel fraction of the insulator of 70% or more, have good extrusion workability, and have a high AC breakdown voltage of 240 kV or more.

[Examples 7 to 12] The extruded compositions in Examples 1 to 6 are represented by α shown in Table 2.
A cable was manufactured and evaluated in the same manner as in Examples 1 to 6, except that the composition contained a methylstyrene dimer.

 The evaluation results are shown in Table 2.

As is clear from Table 2, the power cables of Examples 7 to 12 have a gel fraction of the insulator of 70% or more, have good extrusion workability, and have a high AC breakdown voltage of 210 kV or more.

[Examples 13 to 14] The extruded compositions in Examples 1 to 6 were used as the compositions shown in Table 3, except that cables were manufactured and evaluated in the same manner as in Examples 1 to 6.

The evaluation results are shown in Table 3. Example 8 is also shown for comparison.

As is clear from Table 3, the power cables of Examples 13 and 14 have a gel fraction of the insulator of 70% or more, have good extrusion workability, and have a high AC breakdown voltage of 230 kV or more.

[Comparative Examples 1 to 4] The extruded compositions in Examples 1 to 6 were used as the compositions shown in Table 4, except that cables were manufactured and evaluated in the same manner as in Examples 1 to 6.

 The evaluation results are shown in Table 4.

As shown in Table 4, all of the power cables of Comparative Examples 1 to 4 had a gel fraction of 70% or more, but were difficult to extrude, and the AC voltage could not be measured.

[Effects of the Invention] As described above, according to the present invention, it is possible to prevent the occurrence of scorch when extruding an insulator of an electric wire / cable with a composition containing a crosslinking agent, so that production efficiency can be improved, In addition, wires and cables having a high AC breakdown voltage can be realized.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are sectional explanatory views of an embodiment of the electric wire / cable of the present invention. 1: cable, 2: conductor 3: inner semiconductive layer, 4: insulating layer 5: outer semiconductive layer

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-236516 (JP, A) JP-A-4-212207 (JP, A) JP-A-4-82108 (JP, A)

Claims (2)

(57) [Claims] 1. A crosslinked coating layer comprising a resin composition obtained by adding 1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene to a polyolefin is formed on the outer periphery of a conductor. Electric wires and cables. 2. A resin composition obtained by adding an unsaturated dimer of 1- (2-tert-butylperoxyisopropyl) -4-isopropylbenzene and α-aromatic-substituted α-methylalkene to a polyolefin. An electric wire / cable, characterized in that a cross-linking coating layer is formed on the outer periphery of a conductor.