JPS61225715A - Heatproof crosslinked polyolefin insulation cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-resistant crosslinked polyolefin insulated cable.

[Conventional technology]

Conventionally, the structure of heat-resistant cross-linked polyolefin insulated cables is as follows:
In order to increase the heat resistance, an internal semiconducting layer is coated on the conductor, and a crosslinked polyolefin insulator is coated on top of the internal semiconducting layer.

The crosslinked polyolefin insulator can be formed by using well-known organic peroxides such as dicumyl oxide, t-butyl cumyl oxide, and t-butyl cumyl oxide on medium density polyethylene having a melting point of 120 DEG C. or higher.

1.3-bis(1-butylperoxide-isopropylene)-benzene, 2.5-dimethyl-2゜5-di(
It is formed by extrusion coating a mixture to which a desired amount of 1-purutyl peroxide)-hexyne-3 is added onto the internal semiconductive layer, and crosslinking the mixture by heating.

[Problem that the invention seeks to solve]

However, since the cross-linking temperature of the organic peroxide is low, cables with the above-mentioned structure require extrusion molding to form the insulator at a temperature of, for example, 135°C or lower, and the wax must be extruded before the cross-linking process. There is a problem that early crosslinking, so-called scorch, occurs at this stage. Considering this point, the resin temperature when extruding the insulator is set to a low temperature of 135°C or less, and
When extrusion molding is performed at low speed rotation, the polyolefin mixture is not sufficiently kneaded, resulting in a rough appearance of the extruded insulator. As a result, there was a problem in that the electrical properties of the cable, particularly the withstand voltage properties, were deteriorated.

The present invention has been made in view of these points, and is a heat-resistant cross-linked material with good electrical properties. This is a lyolefin insulated electrical cable developed.

[Means for solving problems]

The present invention is to extrusion coat a conductor with a composition containing 0.5 to 5 parts by weight of an azo compound mixed with 100 parts by weight of 4-diolefin having a melting point of 120°C or higher, and crosslink it by heating to form an insulating layer. This is a heat-resistant cross-linked I-lyolefin insulated cable characterized by:

The heat-resistant cross-linked polyolefin insulated cable of the present invention is manufactured by forming an inner semiconducting layer 2 on a stranded conductor 1, as shown in the figure. The crosslinkable polyolefin insulator 3 and the external semiconductive layer 4 are sequentially extruded, crosslinked by heating, and then cooled.
5. Metal shielding layer such as copper tape around its outer periphery. This is done by forming a sheath 6 such as a vinyl sheath.

Here, the crosslinkable polyolefin insulator has a melting point of 120
It is formed by extrusion coating of a mixture in which 0.5 to 5 parts by weight of an azo compound represented by the following general formula is added to 100 parts by weight of polyolefin having a temperature of 100 parts by weight or higher.

(Formula) (However, R1, R2"'!5IR4 are alkyl groups) Examples of polyolefins having a melting point of 120°C or higher include linear low density polyethylene and medium density polyethylene.

High-density polyethylene, a mixture thereof, and a polyolefin obtained by adding a copolymer such as ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer to these polyolefins can be used. The melting point refers to the peak of the endothermic curve of the sample measured by differential scanning calorimeter (DSC), and is 10'c/r111.
This is the value at a temperature increase rate of n. Also, the melting point is 120
Cables made of polyolefin, such as low-density polyethylene, whose temperature is less than 120 degrees Celsius, have thermal deformation in their insulators when the conductor temperature reaches about 120 degrees Celsius, making them unusable as heat-resistant cables.

The reason for using an azo compound as a crosslinking agent is that the crosslinking temperature is about 50°C higher than that of conventional organic peroxides, so the extrusion temperature of the composition can be made sufficiently high, for example about 160°C. This is because even if the insulator is extruded at a temperature of 100 to 100 mL, no scorch will occur, and the molded product will have a good appearance by eliminating rough skin and the like, as well as improving its electrical properties.

If the amount of the azo compound added is less than 0.5 parts by weight, a sufficient degree of crosslinking will not be obtained, and if it exceeds 5 parts by weight, the degree of crosslinking will not change. It is set.

In the present invention, the crosslinked polyolefin insulator may contain small amounts of well-known antioxidants, inorganic fillers, pigments, and the like. Moreover, the internal semiconducting layer 2. Of course, the above-mentioned azo compound may be added to the outer semiconductive layer 4 as a crosslinking agent instead of the conventional organic peroxide.

[Function and effect of the invention]

The heat-resistant crosslinked/IJ olefin insulated cable of the present invention has a crosslinked polyolefin insulating layer coated by extrusion with a composition containing 100 parts by weight of a polyolefin with a melting point of 120°C or higher and 0.5 to 5 parts by weight of an azo compound, and then crosslinked by heating. This prevents the composition from scorching during extrusion molding of the insulator, prevents rough skin, provides a good appearance, and improves electrical properties such as withstand voltage properties.

[Example/Comparative example]

Examples 1 to 4 of heat-resistant crosslinked polyolefin insulated cables according to the present invention and Comparative Examples 1 to 5, which were carried out for comparison, will be described below.

An internal semiconductive layer with a thickness of 1 m was formed on a stranded conductor with a cross section of 60 m'', and a crosslinkable polyolefin composition having the composition shown in the table below was extruded on the surface at an extrusion temperature of 160°C. This insulator was then coated with an external semiconducting layer of 0.5 m thick and heated at 250°C.
After heating and crosslinking in a heating and pressurizing tube, and cooling, a cable core was obtained. Thereafter, a copper tape was wrapped around the cable core, and a vinyl sheath was further formed to form Examples 1 to 4. Comparative example 1
~5 cables were obtained.

Each of the cables thus obtained has five cable cores.
Length l) When a load of 5 kg was applied for 10 minutes at a temperature of 135°C, the insulators of all cables of Comparative Examples 1 to 30 were deformed by about 50%, indicating that they could not be used as heat-resistant crosslinked polyolefin insulated cables. understood. In the cables of Examples 1 to 4 and Comparative Examples 4 and 50 other than these, the deformation of the insulator was slight. Furthermore, since the degree of deformation of the insulators of the cables of Example 2 and Comparative Example 40 was almost the same, it was found that the amount of the azo compound in Example 2 was sufficient. On the other hand, the cables of Comparative Example 2 and Comparative Example 5 are
Scorch occurred in the composition during extrusion molding to form the insulator, and the resulting insulator had irregularities on its surface and had a poor appearance, making it unusable.

Next, a cable of Comparative Example 5 was manufactured in the same manner as described above except that the extrusion temperature was 120°C. Roughness was observed on the surface of the crosslinked polyethylene insulator of the obtained cable. When this cable was subjected to an Inno9Rs destruction test, it was destroyed at 80 kV. On the other hand, when the cable obtained in Example 2 was subjected to a similar in-A pulse breakdown test, the breakdown value was 180 kV, indicating that the dielectric strength voltage was sufficiently improved.

[Brief explanation of drawings]

The figure is a sectional view of one embodiment of the present invention. 1...Twisted wire conductor, 2...Inner semiconducting layer, 3...Bridging? Lyolefin insulator, 4... External semiconducting layer, 5.
...metal shielding layer, 6... sheath.

Claims (1)

[Scope of Claims] A composition prepared by blending 0.5 to 5 parts by weight of an azo compound represented by the following formula with 100 parts by weight of a polyolefin having a melting point of 120°C or higher is extrusion coated onto a conductor, and crosslinked by heating to form a crosslinked polyolefin. A heat-resistant cross-linked polyolefin insulated cable characterized by having an insulating layer. (Formula) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R_1, R_2, R_3, R_4 are alkyl groups)