JPH08197632A - Method for crosslinking resin for power cable - Google Patents

Abstract

PURPOSE: To extinguish a void in a resin and prevent deterioration of insulating property of the resin by a method wherein an un-crosslinked resin is molded by extrusion in a crosslinking mold, pressed by a high temperature gas and crosslinked, and cooled by a gas having a specified pressure. CONSTITUTION: In a resin crosslinking process, a contractive tube 14 is attached instead of an extrusion mold. By a crosslinking mold 15 attached around the contractive tube 14, a resin around a conductor connecting pipe 5 is crosslinked. That is, a gas is charged in between the crosslinking mold 15 and the contractive tube 14 from a gas pressing opening 16. By heating the gas by a heater 17, the contractive tube 14 is heated in a pressed state and the resin is crosslinked. At this time, an output of the heater 17 is detected by a calorimeter 18 and the operation of the heater 17 is controlled by a controller 19 based on the detected result. Thereafter, the resin is cooled by gas. The pressure of the gas is set to above a difference between a pressure at the crosslinking of the resin and a pressure at the time when the gas melts with the resin into a saturated state at a room temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cross-linking a resin for power cables, which is suitable for use in electric wires, terminals of power cables, connecting portions and the like.

[0002]

2. Description of the Related Art In recent years, synthetic resins such as epoxy resins have been widely used in electrical equipment such as cable terminals and connecting portions. For example, as a resin molded product used in the field of cables, there is a molded connection part of a cross-linked polyethylene insulated PVC sheath cable (CV cable). In this mold-shaped connecting portion, the same kind of material is heat-molded and fused in order to firmly adhere the insulator of the CV cable and the insulating layer of the connecting portion. This mold type connection part is used for the connection part of the submarine cable because it has excellent electrical and mechanical properties and is compact.
It is used in the intermediate connection part of the class.

This mold type connection part has a TMJ (Tapi
ng Molded Joint) and EMJ (Extrusion Molded Join)
t) The TMJ is a connection part formed by winding a tape of polyethylene containing a crosslinking agent or irradiation polyethylene of the same type as that of the cable insulator to form an insulating layer, followed by heating and pressurizing and molding. Here, dicumyl peroxide (DCP) is used as the crosslinking agent. Further, the EMJ is a connection part formed by injecting the same material into a mold to form an insulating layer using an extruder and heating and pressurizing to mold. These T
The MJ and EMJ perform heating for crosslinking the resin in a pressurized state of gas such as nitrogen or air. At this time, a shrink tube made of silicon rubber or the like is attached to the outside of the resin to prevent the resin from being directly exposed to the hot gas.

When pressurizing the shrink tube with this gas,
Since gas permeates through the shrinkable tube, the gas dissolves in the resin to a saturated amount. Here, the temperature of the resin is 160
It is heated above ℃. Then, when the resin is cooled,
The gas in the supersaturated portion of the resin tends to generate voids because the saturated dissolution amount decreases. Here, if the cooling time is sufficiently long, the gas escapes due to diffusion.

[0005]

[Problems to be Solved by the Invention] However, EMJ
If you shorten the cooling time in order to shorten the assembly time, the gas diffusion will not be sufficient and the gas will not escape,
Voids are easy to form. There is a problem in that the insulation performance of the resin deteriorates because the voids remain in the resin.

Further, when the internal pressure of the void exceeds the rigidity of the surroundings, the void becomes large, and when the internal pressure of the void exceeds the yield stress of the resin near the temperature where the crystallization of the resin begins, the gas in the void Is not diffused and voids will not disappear. Therefore, the insulation performance of the resin is reduced.

The present invention effectively solves the above problems, and an object of the present invention is to provide a method for crosslinking a resin for a power cable, which can suppress the deterioration of the insulating performance of the resin by eliminating voids in the resin. .

[0008]

According to the method for crosslinking a resin for a power cable of the present invention, a bridge mold is arranged at a connection portion of a power cable, the resin is filled in the bridge mold, and the power for crosslinking the resin is provided. A method for cross-linking a resin for cables, in which a resin in an uncross-linked state is extruded and molded in the cross-linking mold, the resin is pressurized by hot gas to cross-link, and then, when the resin is cooled by gas, The pressure of this gas is set to be equal to or more than the difference between the pressure at which the resin is crosslinked and the pressure at which the gas is dissolved in the resin in a saturated state at room temperature, and the resin is cooled.

[0009]

According to the present invention, the resin is pressurized with a high temperature gas to be crosslinked, and then, when the resin is cooled, the pressure of the gas is the pressure at which the resin is crosslinked and the gas is saturated with the resin at room temperature. Since the pressure is set to be equal to or higher than the pressure at which the gas dissolves, the gas dissolves in the resin. Therefore, even if a void is generated in the resin, the void is dissolved in the resin and the void disappears. Since the resin is cooled in this state, a void-free resin molded product can be obtained.

[0010]

EXAMPLES An example of a method for crosslinking a resin for a power cable of the present invention will be described below with reference to FIGS. 1 to 4. As this resin, EMJ used for the connection part of the power cables connected to each other is used. This EMJ
The method of cross-linking includes a pretreatment step of connecting the conductors of the power cable, a resin extrusion step of covering the conductors of the power cable with a resin, and a resin cross-linking step of cross-linking the resin. Here, the power cable has a structure in which a conductor is an axis and an inner semiconductive layer, a cable insulator, an outer semiconductive layer, a metal shielding layer such as aluminum, and a sheath are sequentially arranged.

The pretreatment step is a pencil sharpening step of projecting a conductor from the end of the power cables connected to each other, a conductor connecting step of connecting the projected conductor, and an internal half around the connected conductor. An inner semiconductive layer attaching step of attaching the conductive layer. A power cable to which conductors are connected by this pretreatment step is shown in FIG. As shown in FIG. 2, in the power cable 1, the tip is shaved, the cable insulator 2, the outer semiconductive layer 3, and the metal shielding layer 4 are exposed, and the conductor at the tip is covered with the conductor connecting pipe 5. ing.
The conductor connecting pipe 5 connects the conductors of the power cable by abutting each other.

In the resin extruding step, as shown in FIG. 3, an extruding die 7 is attached around the conductor connecting pipe 5 to which the conductor is connected in the pretreatment step, and a reinforcing insulator is provided in the extruding die 7. The resin 8 is injected. In the extrusion die 7, resin is injected into the extrusion die 7 through the resin injection port 9 and the resin is heated by the heater 9.

Thereafter, in the resin cross-linking step, as shown in FIG. 4, a shrink tube 14 is attached instead of the extrusion die 10, a cross-link die 15 is attached around the shrink tube 14, and the cross-link die 15 is used. , The resin around the conductor connecting pipe 5 is cross-linked. In the bridging die 15,
A gas is filled from the gas pressurizing port 16 between the contracting tube 14 and the contracting tube 14, and the gas is heated by the heater 17, so that the contracting tube 14 is heated in a pressurized state to crosslink the resin. At this time, the output of the heater 17 is detected by the calorimeter 18, and the detection result is detected by the heater control 1
9 to the heater control 19 for the calorimeter 1
The operation of the heater 17 is controlled based on the detection result of No. 8.
By these heater 17 and heater control 19,
The crosslinking temperature of the resin 8 is maintained for a fixed time.

That is, as shown in FIG. 1, the temperature of the resin 8 is raised to about 300 ° C. in several hours, this is kept for about 7 to 8 hours, then rapidly cooled to about 100 ° C., and then from about 100 ° C. to room temperature. Then, the resin 8 is cooled. When the resin 8 is rapidly cooled, the operation of the heater 17 is stopped, the resin 8 is rapidly cooled, and
The resin is pressurized with a gas such as nitrogen. An inert gas is used as a gas for pressurizing the resin, for example, nitrogen,
Air, SF ₆ , He, Ar, etc. are available. The pressure of this gas is set to be equal to or more than the difference between the pressure when the resin 8 is cross-linked and the pressure when the gas is dissolved in the resin 8 in a saturated state at room temperature, and the resin is cooled.

According to such a method for crosslinking the resin for electric power cables, the resin 8 is pressurized with a high-temperature gas to be crosslinked, and then, when the resin 8 is cooled by the gas, the pressure of this gas is adjusted to the resin 8 Since the resin is cooled by setting the difference between the pressure at which the resin is cross-linked and the pressure at which the gas dissolves in the resin in a saturated state at room temperature to cool the resin, the gas melts into the resin by the pressure of this gas. Therefore, even if a void is generated in the resin 8, the void is dissolved in the resin 8 and the void disappears. Since the resin 8 is cooled in this state, the resin 8 without voids can be molded and the resin 8 having high insulation performance can be molded. Further, since the gas dissolves in the resin, the resin can be rapidly cooled, the crosslinking time of the resin can be shortened, and the molding workability of the resin can be improved.

[0016]

As described above, according to the method for cross-linking a resin for a power cable of the present invention, a cross-linking mold is arranged at the connecting portion of the power cable, and the cross-linking mold is filled with the resin. A method for cross-linking a resin for a power cable for cross-linking, wherein an uncross-linked resin is extruded and molded in the cross-linking mold, the resin is pressurized with a high-temperature gas to cross-link, and then the resin is cooled with a gas. In this case, the pressure of this gas is set to be equal to or more than the difference between the pressure at which the resin is cross-linked and the pressure at which the gas dissolves in the resin in a saturated state at room temperature, and the resin is cooled. Melts in. Therefore, even if a void is generated in the resin, the void is dissolved in the resin and the void disappears. Since the resin is cooled in this state, it is possible to mold a resin without voids,
A resin with high insulation performance can be molded. Further, since the resin is cooled in a state in which the gas is dissolved in the resin in a saturated state, it is possible to prevent the generation of voids even when the resin is cooled in a short time. Therefore, it is possible to reduce the cooling time of the resin after crosslinking.

[Brief description of drawings]

FIG. 1 is a graph showing a method for crosslinking a resin for a power cable of the present invention.

FIG. 2 is a configuration diagram showing a pretreatment process of the present invention.

FIG. 3 is a configuration diagram showing a resin extrusion process of the present invention.

FIG. 4 is a configuration diagram showing a resin crosslinking step of the present invention.

[Explanation of symbols]

 1 ... Power cable, 8 ... Resin, 15 ... Cross-linking mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kaneko 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Ltd.

Claims (1)

[Claims] 1. A method for cross-linking a resin for a power cable, wherein a cross-linking mold is arranged at a connection portion of a power cable, the cross-linking mold is filled with a resin, and the cross-linking is performed. An uncrosslinked resin is extruded and molded, and this resin is pressurized with a high-temperature gas to crosslink it. Then, when the resin is cooled with a gas, the pressure of this gas is the pressure at which the resin is crosslinked and the room temperature. In the method for crosslinking a resin for a power cable, the resin is cooled by setting the pressure to be equal to or higher than the pressure at which the gas is dissolved in the resin in a saturated state.