JPH0145186B2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Objectives of the Invention] The present invention relates to a method for cross-linking semiconductive polyolefin, particularly for mold connections of CV cables (cross-linked polyethylene insulated cables) of 154 KV or higher, polyolefin insulator parts, etc. The present invention relates to a method of crosslinking a semiconductive polyolefin layer onto a polyolefin insulator.

There are many products in which a semiconducting layer is cross-linked on polyolefin insulators, and in this case, the semi-conducting layer is often maintained at the cross-linking temperature using a heater, such as an electric heater (resistance heating due to electricity), but the cross-linking heating takes time. Therefore, there was a need for a method that could crosslink only the semiconductive layer using rapid heating.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a molding method capable of quickly thermally crosslinking a semiconductive polyolefin layer to a polyolefin insulator by eliminating the drawbacks of the prior art described above.

[Summary of the invention]

That is, the gist of the present invention is the use of dielectric heating to rapidly thermally crosslink a semiconductive polyolefin layer.

〔Example〕

FIG. 1 shows an embodiment of the invention, applied as a polyolefin insulator to a CV cable mold connection. A molded body 2 in which a CV cable 1 is provided with a semiconductive polyolefin layer (see FIG. 2) is placed in a mold 3. On the other hand, a pressurizing medium 5 is sealed in the mold 3 by a pressurizing device 4 .
The pressurized medium 5 is a gas (e.g. air, _N2 gas, _SF6
gas, etc.) or liquid (e.g. silicone oil, molten polyethylene, etc.). The mold 3 further includes a movable heating electrode 6 directly connected to a high frequency power oscillator, such as a magnetron 7, at a constant distance from the molded body 2. The heating electrode 6 applies dielectric heating uniformly to the dielectric material of the semiconductive polyolefin layer when high frequency power is applied from the high frequency power oscillator 7 while moving in the length direction or circumferential direction of the molded body 2. Only the semiconductive polyolefin layer can be crosslinked. The amount of heat generated by dielectric heating is P=k・E ² =5/9・f・ε・tanδ・E ²・10 ^-12 (W/cm ³ ) (where k is the equivalent conductivity of the dielectric material. where f is the frequency, ε is the dielectric constant, tan δ is the dielectric loss tangent, and E is the electric field strength. Therefore, like a semiconductive polyolefin layer, ε is large (10 ² ~ at a frequency of 50 Hz ~ 1 MHz).
10 ⁴ , but the ε of polyethylene insulation is 2.3
), the amount of heat generated is higher than that of polyolefin insulators when a constant power is applied, and for this reason, it is difficult to bring only the semiconductive polyolefin layer to the crosslinking temperature (usually 140°C to 200°C) in a short time. can. Moreover, the thickness of the semiconductive polyolefin layer is usually about 0.1 mm to 5 mm, and this also allows rapid thermal crosslinking of the semiconductive polyolefin layer. Note that the CV cable and the mold 3 are sealed at both ends of the mold 3 with pressurized seals 8.

FIG. 2 shows another embodiment of the invention, namely an embodiment applied to a polyolefin insulation component as a polyolefin insulation. In this example,
The molded body 2 comprises a polyolefin insulator component 9 and a semiconductive polyolefin layer 1 provided thereon.
0, is placed in the air, and is movable in its circumferential direction or lengthwise direction. Other than this,
Everything is as described in the embodiment of FIG.

〔Effect of the invention〕

According to this invention, (1) only the semiconductive polyolefin layer can reach the crosslinking temperature in a short period of time, thus reducing the working time, and (2) the semiconductive layer used in ordinary polyolefin insulators can be (3) cross-linking of semiconductive polyolefin layers is easy and reliable, and (4) high-performance mold connections or polyolefin parts can be obtained. be.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating another embodiment. 1: CV cable, 2: molded body, 3: mold,
4: Pressurizing device, 5: Pressurizing medium, 6: Mobile heating electrode, 7: High frequency power oscillator, 8: Pressurizing seal section,
9: Polyolefin insulator component, 10: Semiconductive polyolefin layer.

Claims (1)

[Scope of Claims] 1. A method of cross-linking only the semiconductive polyolefin layer on a molded article in which a semiconductive polyolefin layer is provided on a polyolefin insulator, in a mold containing a pressurized medium or in air. At the same time, a heating electrode is placed at a certain distance from the molded body, and the heating electrode is moved in the lengthwise or circumferential direction of the molded body, or the molded body is moved around the molded body. Applying high frequency power to the heating electrode while moving it in the lengthwise or circumferential direction,
A method for crosslinking and molding semiconductive polyolefin, characterized in that only the semiconductive polyolefin layer is dielectrically heated and crosslinked. 2. The crosslinking molding method of semiconductive polyolefin according to claim 1, wherein the molded body comprises a CV cable mold connection part and a semiconductive polyolefin layer provided thereon. 3. A method for crosslinking semiconductive polyolefin according to claim 1, wherein the molded body comprises a polyolefin insulator component and a semiconductive polyolefin layer provided thereon.