JPS5944756B2 - How to insulate the wiring part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for insulating the connection parts of plastic-coated conductive materials such as plastic electric wires and cables, and in particular to electrical insulation of the connection parts when the connection parts exist in an environment where the connection parts are exposed to water or steam. This relates to the simplification and reliability improvement of the treatment process of covering with a rubber mold etc. for the purpose of protecting the property.

Currently, there is a call for the development of deep-sea equipment or equipment that utilizes geothermal heat, and the development of equipment that is exposed to water or water vapor is increasing, and protection technology for the connection parts of electric wires and cables that are exposed to water or water vapor is also important. It's one of the things.

Protection of the connection part has a large effect on the characteristics of the equipment, and although various efforts have been made, there are many points that need improvement, and improvements in connection technology are required. Currently, rubber molding is commonly used to insulate wire connections that are exposed to water or steam. ), poly-4-methylpentene, silicone, butyl rubber, and other plastics have weak adhesion to butyl rubber, ethylene-propylene rubber, butadiene rubber, silicone rubber, Teflon rubber, and other mold materials, so water or steam may enter the adhesive layer. However, insulation failure is likely to occur. Therefore, various efforts have been made to improve adhesion, including a method of chemically and flame-treating the plastic surface that is used as the covering material for electric wires and cables to increase the adhesion with rubber molding materials. This is commonly done. In this method, for example, a putty-like solution of potassium dichromate dissolved in concentrated sulfuric acid is applied to the coating material, and then,
A method has been implemented in which the coated surface is treated with flame and washed with water.
In this method, the handling of processing chemicals requires, for example, the working environment,
There are issues with worker safety and health, as well as waste liquid treatment. Further, there were drawbacks such as insufficient uniformity of processing and problems in reliability of bonded parts. This invention was made in order to eliminate the drawbacks of the above-mentioned conventional methods, and by treating the surface of the plastic, which is the coating material of the plastic-coated conductive material, with corona discharge, the adhesion with the molding material is significantly improved. The object of the present invention is to provide a method for insulating wire connections, which simplifies the process and improves workability and reliability. Fig. 1 is a perspective view showing an example of a corona discharge device used in the present invention, Fig. 2 A is a cross-sectional view of an electrode section showing an example using a doughnut-shaped electrode, B is a cross-sectional view, and C is a separate one. FIG. 3A is a cross-sectional view of an electrode section showing an example with a protective insulator, B is a cross-sectional view, C is a cross-sectional view showing an example of
4A is a cross-sectional view of an electrode section showing an example using a square electrode, B is a cross-sectional view, and FIG.
The figure is a cross-sectional view of the electrode part showing an example equipped with a protective insulator, B
is a V-V sectional view, in which 1 is a high frequency and high voltage generator, 2 is a coated conductive material such as an electric wire or cable, and 3 is a sectional view taken along the line V-V.
is an electrode provided around the coated conductive material and connected to the high frequency and high voltage generator; 4 is the coated conductive material 2;
A ground electrode 5 is connected to the conductor portion of the electrode 3, and 5 is a protective insulator that covers the electrode 3.

In order to perform corona discharge treatment using the corona discharge device configured as described above, the covering conductive material 2 is arranged as shown in the figure, high frequency and high voltage are generated by the high frequency and high voltage generator 1, and the electrode 3 and generate a corona discharge between the coated conductive materials 2.

Corona discharge treatment is effective in improving the adhesion of film and sheet plastics. When corona discharge treatment is performed, the plastic surface is oxidized to form polar groups such as hydroxyl groups and carboxyl groups due to the effects of high-frequency alternating electric fields, ion bombardment, electron bombardment, and corona discharge. It is assumed that the synergistic effects of these phenomena, such as the formation of fine physical scratches on the surface and expansion of the surface area, and the washing away of dirt on the surface, lead to an improvement in adhesive strength. Ru. When treating wire and cable sheathing with corona discharge,
In order to confirm this effect, a sheet material of the same quality as the coating material was treated with corona discharge, and the results of examining the degree of improvement in adhesion will be described. The corona discharge device uses high frequency,
A high voltage generator and processing electrodes are required. Types of high frequency and high voltage generators include spark gap type,
There are vacuum tube oscillation methods, thyristor oscillation methods, etc., and the electrodes must have a structure that corresponds to the form of the object to be processed. Therefore, we output 2 the surface treatment of sheet plastic.
Corona discharge treatment was actually performed using a high-frequency, high-voltage generator with a frequency of 5 KHz. Polyethylene, polypropylene, Teflon, and 4-methylbenzene resin, which are commonly used as coating materials for electric wires and cables, were selected as the treatment materials, and the corona discharge treatment effect was determined by measuring the shear adhesive strength. A comparison was made with a method that combined acid treatment and flame treatment. As a sample, the width is 251
11 Using various types of plastic plates with a length of 100 mm and a thickness of 3 mm, the gap between the electrode and the plastic plate was set to 51.
Corona discharge treatment was performed for 10 seconds at 25K and 500Hz as t71L, and 10m7 with epoxy adhesive! The length of L was adhered and the shear adhesive strength was measured using a tensile tester. The results obtained are shown in Table 1. As is clear from Table 1, surface treatment significantly improves adhesive strength.
It is recognized that corona discharge treatment is more effective than dichromic acid or flame treatment. From the above results, it has been confirmed that corona discharge treatment significantly increases the adhesive strength of plastic plates, and by applying this method to insulating the connection parts of electric wires and cables, the reliability and workability of the connection parts can be significantly improved. It is clear that it can be done.

Therefore, based on the results of experiments on plastic plates, we created the electrodes shown in Figures 2 to 5, which were designed to uniformly treat the insulation coating surfaces of electric wires and cables, and used the high frequency and high voltage generator described above. Using the treatment equipment shown in Figure 1, the wire coating surface was subjected to corona discharge treatment, the wire connections were insulated using rubber molding material, and the treatment effect was examined by examining the insulation performance of the resulting product. . As the electrode 3 used for the corona discharge treatment of the coated surface of electric wires and cables, a flat plate electrode for ordinary film treatment may be used, but in consideration of the treatment effect and treatment time, the electrodes shown in Figs. 2 to 5 are used. Good results can be obtained using electrodes of the shape shown.

The most effective electrode 3 is a donut-shaped circular one as shown in FIGS. 2 and 3, but a square electrode 3 as shown in FIGS. 4 and 5 is also sufficiently effective. The discharge portion of the electrode may be either pointed as shown in FIGS. 2 and 3 B and C, or flat as shown in FIGS. 4 and 5 B. In order to treat the coating layer of electric wires and cables over a certain length, it is preferable to arrange the electrodes continuously as shown in FIG. When processing wire and cable sheathing materials, the conductor part of the wire and cable is used as the ground side electrode, so care must be taken to ensure the distance between the electrode and the conductor so that discharge does not leak directly to the ground side. , It is also necessary to consider protection of the conductor part.

For this purpose, dielectric breakdown of the insulation coating layer can be prevented by coating the electrode part with a protective insulator as shown in FIGS. 3 and 5. Especially when the insulation coating layer is thin,
The use of electrodes devised in this way is effective. In corona discharge, the closer the distance between the electrode and the insulating coating layer, the more efficiently it can be processed with less electric power.
Under the Hz condition, processing can be performed with a gap in the range of 1 to 3011, but preferably, processing with a gap of 1 to 10 m1 is preferable. Although FIGS. 2 to 5 show the case where electric wires and cables are processed one by one, it is also possible to process a plurality of wires and cables at the same time if a shorter processing time is required.

In this case, an electrode with a large inner diameter is fabricated and multiple objects can be treated simultaneously, and even areas that overlap each other can be treated uniformly by being exposed to corona discharge for a few seconds to more than ten seconds. It is. Comparing the treatment using the corona discharge method with the conventional dichromic acid and flame treatment methods, it can be seen that the treatment process is significantly simplified.

In the conventional method, a treatment chemical is first applied to the treated surface, then flame treatment is performed by roasting the coated surface with a burner, etc., and finally, the treatment chemical is thoroughly removed by washing with water, and then the water is wiped off and dried. However, in the method of the present invention, the treatment can be performed very easily in a short time of several seconds to several tens of seconds, and since it is a dry method, it is very easy to handle. Subsequently, the wire connection portion of the coated conductive material subjected to the corona discharge treatment is molded with a molding material.

An example of a molding method is to apply adhesive to the surface of the covering material, wrap it with rubber tape that becomes the rubber mold material, and vulcanize it. The materials will be in close contact. Further, when molding is performed using liquid rubber or the like to insulate the wire connection portion, the wire connection portion can be isolated from the outside air by molding without using an adhesive.
Furthermore, it can also be molded with epoxy resin. The following example shows the results of examining the insulation performance of the connecting portion by fabricating a prototype electric wire with the connecting portion protected by the method described above and actually degrading it under water.

The effectiveness of the present invention is clear from this example. Example 1. The terminal plastic coating surface, which is the connection part of a plastic wire having a copper wire of 911 and a polyethylene coating layer with a thickness of 250 μm, was set to output 2 w and a frequency of 5 KHz.
25KV500Hz using high frequency, high voltage generator
Corona discharge treatment was performed for about 10 seconds.

The ring-shaped electrodes shown in FIGS. 2A and 2B were used as electrodes. When connecting electric wires that have undergone corona discharge treatment at the terminal ends and wrapping butyl rubber-based rubber mold tape around the connection parts, apply epoxy adhesive to the plastic coating that comes into contact with the mold material, and then wrap the rubber mold tape. When vulcanization was performed by wrapping tape around the joint and heating it at about 130° C., it was possible to create a connection part that was sufficiently isolated from the outside air and unaffected by water or steam. In order to compare this performance, we fabricated a rubber mold with the plastic coating surface untreated and a rubber mold with conventional surface treatment using dichromic acid and flame treatment. Insulation performance was examined by conducting a voltage deterioration test. The test method for electrical deterioration was as follows: water and a test sample were placed in a tank, the tank was sealed, the tank was placed in an open tank at 100° C., a voltage of 450 V was applied to the sample, and the insulation resistance value was measured. The results obtained are shown in Table 2. As is clear from Table 2, it can be seen that the insulation treatment of the wire connection portion by the corona discharge method is excellent. As described above, according to the present invention, the treatment process is simplified and the workability is good, and the reliability of the molded portion is high, the shear strength is high, and the deterioration caused by the application of electricity is small.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the corona discharge device used in the present invention, Figs. 2 to 5 each show different electrode parts, A is a cross-sectional view, B is a 1, 1, 1 and V-V sectional view, C is a cross-sectional view showing another example. In the figures, the same symbols indicate the same or equivalent parts,
1 is a high frequency and high voltage generator, 2 is a covering conductive material, 3 is an electrode, 4 is a ground electrode, and 5 is a protective insulator.

Claims (1)

[Scope of Claims] 1. A method for insulating a wire connection portion of a plastic-coated conductive material, which comprises subjecting the plastic of the wire connection portion to corona discharge treatment and molding with a molding material. 2. The method for insulating a wire connection portion according to claim 1, wherein the corona discharge treatment is performed using a doughnut-shaped electrode. 3. A method for insulating a wire connection portion according to claim 1 or 2, wherein the corona discharge treatment is performed using an electrode covered with a protective insulator. 4. Any one of claims 1 to 3, characterized in that the mold is one in which an adhesive is applied to a corona discharge-treated plastic surface and a rubber mold tape is wrapped around the mold to proceed with vulcanization and curing. The method for insulating the wiring section described in . 5. The method for insulating a wire connection portion according to any one of claims 1 to 3, wherein the mold is a mold using liquid rubber. 6. The method for insulating a wire connection portion according to any one of claims 1 to 3, wherein the mold is an epoxy mold.