JPS6356650B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a power cable using a crosslinked rubber or plastic composition as an insulator. In general, in the production of crosslinked rubber or plastic insulated power cables, the rubber or plastic composition that forms the insulator extruded on the conductor is crosslinked to improve the heat resistance, mechanical strength and mechanical strength of the insulator.
Improved physical properties such as weather resistance and moisture resistance.
This crosslinking is carried out by extrusion coating a conductor in an uncrosslinked state with a composition made by blending a vulcanizing agent, a crosslinking agent, and a vulcanization accelerator with the rubber or plastic composition that forms the insulator, and then using a continuous vulcanization device or the like. This is generally done by heating. The thermal energy required for this heating is mostly supplied from outside the power cable in the form of heated steam, high temperature gas, heated silicone oil, radiant heat, etc. In this method, the temperature rise in the inner part of the insulator (the center side of the cable) is slower than the temperature rise in the outer part (the outer circumferential side of the cable), so the progress of crosslinking in the inner part of the insulator is slowed down.
As a result, the degree of crosslinking differs between the inner and outer portions of the insulator, resulting in the inconvenience of having different physical properties. For this reason, the heating time is increased so that the temperature of the inner portion of the insulator rises sufficiently, but this method has low manufacturing efficiency and is not a preferred method. Another possibility is to uniformly heat and raise the temperature of the entire insulator using ultrasonic irradiation or high-frequency dielectric heating, but this method requires the installation and modification of cross-linking equipment and is not suitable for use in actual production lines. is subject to various restrictions. This invention was made in view of the above circumstances,
Manufacture of crosslinked rubber and plastic insulated power gales that can be manufactured using existing crosslinking equipment, can crosslink the entire insulator uniformly, can obtain an insulator with homogeneous physical properties, and can increase manufacturing speed. The purpose of this method is to provide rubber with a faster cross-linking speed sequentially from the outer periphery of the insulator inward.
It is characterized by being composed of a plastic composition. Hereinafter, the present invention will be explained in detail with reference to the drawings. The drawing shows an example of a power cable obtained by the present invention. This power cable 1
From inside to outside, conductor 2, inner semiconductor 3, insulator 4, outer semiconductor 5, sheath 6
It consists of In a power cable 1 having this structure, an internal semiconductor 3 made of an EVA copolymer composition blended with conductive carbon is first provided on a conductor 2 by a conventional extrusion coating method. Next, an inner layer 4a of the insulator 4 made of an uncrosslinked polyethylene composition is provided on the internal semiconductor 3, and an outer layer 4b of the insulator 4 made of an uncrosslinked polyethylene composition is then provided, and the inner layer 4a is further provided with an outer layer 4b of the insulator 4 made of an uncrosslinked polyethylene composition. An insulator 4 is formed by the outer layer portion 4b and the outer layer portion 4b. The crosslinking speed of the polyethylene composition forming the inner layer portion 4a is higher than the crosslinking speed of the polyethylene composition forming the outer layer portion 4b. Generally, the crosslinking rate of polyethylene compositions is
The concentration of the crosslinking agent added to this, the type of crosslinking agent,
Since it is affected by the presence or absence of a crosslinking accelerator and temperature, the polyethylene composition forming the inner layer 4a has
A larger amount of crosslinking agent is blended than the polyethylene composition forming the outer layer 4b, or the inner layer 4a
By blending a crosslinking accelerator that is not blended into the outer layer portion 4b with the polyethylene composition, or blending a low temperature activated crosslinking agent into the inner layer portion 4a,
The crosslinking speed of the polyethylene composition forming the inner layer portion 4a can be made faster than the crosslinking speed of the polyethylene composition forming the outer layer portion 4b. However, if a low temperature activated crosslinking agent is used, the polyethylene composition may be crosslinked in the extrusion coating step before the crosslinking step, so this is not a very preferable method. In addition,
As a crosslinking agent to be added to the polyethylene composition, known organic peroxides such as dicumyl peroxide (DCP) are used, and as crosslinking accelerators, triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC) are used. ) etc. are used. After the insulator 4 is formed, conductive carbon-containing EVA is coated on the insulator 4 by a similar extrusion coating.
An outer semiconductor 5 made of a copolymer composition and a sheath 6 made of a polyvinyl chloride composition are sequentially formed on the outer semiconductor 5 to produce an uncrosslinked polyethylene insulated power cable. This uncrosslinked polyethylene insulated power cable 1 is obtained by crosslinking the uncrosslinked polyethylene composition forming the insulator 4 at a predetermined temperature for a predetermined time using a continuous crosslinking device. According to the manufacturing method of the power cable 1 explained above, when forming the insulator 4, the inner layer 4a and the outer layer 4b are
Since the crosslinking speed of the polyethylene composition forming the inner layer 4a was made higher than the crosslinking speed of the polyethylene composition forming the outer layer 4b, the degree of crosslinking of the polyethylene composition of the inner layer 4a and the outer layer 4b
The degree of crosslinking of the polyethylene compositions becomes approximately equal, and the entire insulator 4 is formed of a homogeneous crosslinked polyethylene product. Although this example uses a polyethylene composition for the insulator 4, the insulator 4 is not limited to this, but a butyl rubber composition, an ethylene propylene rubber composition, etc. can be used. In this case, it goes without saying that a crosslinking agent suitable for each composition should be selected. In addition, in this example, the insulator 4 is divided into two layers, the inner layer 4a and the outer layer 4b, but it is not limited to this and may be divided into three or more layers. Body 4 is obtained and is preferred. Hereinafter, this invention will be specifically explained based on Examples. Example 1 On an annealed copper stranded wire with a cross-sectional area of 100 ^mm2 , an internal semiconductor layer with a thickness of 1 mm, an insulator layer with a thickness of 4.5 mm, and an insulator layer with a thickness of 4.5 mm are sequentially formed.
An insulating outer layer of 0.5 mm thick was coated with an outer semiconducting layer of 0.5 mm thick. Both the inner and outer layers of the insulator are made of low-density polyethylene with a melt index of 3, dicumyl peroxide (DCP) as a crosslinking agent, and triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC) as crosslinking accelerators. Contains the amount shown in Table 1, and also contains Suntonox as an anti-aging agent.
A polyethylene composition containing 0.2 parts by weight of R (trade name) was used. This uncrosslinked polyethylene insulated power cable was introduced into a continuous vulcanizer, and the crosslinking temperature was raised to 300°C.
A cross-linked polyethylene insulated power cable was manufactured by cross-linking the power cable at different wire speeds. The crosslinked gel fraction of the crosslinked polyethylene composition forming the insulator inner layer and outer layer of this power cable was measured by a heated xylene method. The results are also shown in Table 1.

[Table] Parts by weight.
As is clear from Table 1, when the polyethylene composition of the insulating inner layer contains a larger amount of crosslinking agent than the polyethylene composition of the outer layer, or when a crosslinking accelerator is added, the polyethylene composition of the inner layer can be cross-linked. It can be seen that even if the crosslinking speed is increased and crosslinking is performed at a high linear speed, the gel fractions of the outer layer and the inner layer are approximately equal, and a uniform crosslinked composition can be obtained. Example 2 In Example 1, the compositions forming the insulator inner layer and outer layer were changed to ethylene propylene rubber compositions, and DCP as a crosslinking agent and TAC as a crosslinking aid were added in the amounts shown in Table 2, and the same procedure was carried out. A cross-linked ethylene propylene rubber insulated power cable was manufactured.
The degree of crosslinking of the inner and outer layers of the insulator of the obtained power cable was measured in terms of permanent deformation rate. The results are shown in Table 2.

[Table] As explained above, in the method of manufacturing the crosslinked rubber/plastic insulated power cable of the present invention, the insulator is composed of a composition whose crosslinking speed is sequentially increased from the outer periphery of the insulator toward the inside. , the crosslinking speed of the inner part of the insulator is faster than that of the outer part, and the entire insulator can be crosslinked in a short crosslinking time. Furthermore, the degree of crosslinking between the inner and outer portions is approximately equal, resulting in a homogeneous insulator. Furthermore, since the crosslinking time can be shortened by using the conventional crosslinking equipment as is, there is an advantage that the manufacturing cost can be significantly reduced.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of a crosslinked rubber, plastic insulated power cable obtained by the power cable manufacturing method of the present invention. 4...Insulator, 4a...Inner layer, 4b...Outer layer.

Claims (1)

[Claims] 1. When manufacturing a crosslinked rubber or plastic insulated power cable, it is recommended that an insulator made of an uncrosslinked rubber or plastic composition be crosslinked by sequentially constructing a composition with a faster crosslinking speed inward from the outer periphery of the insulator. A manufacturing method for cross-linked rubber and plastic insulated power cables.