JPS6353654B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is concerned with the characteristics of composite electrical insulating paper in which kraft fiber paper is bonded under pressure to at least one side of a poly-4-methylpentene-1 film, and particularly the characteristics of the poly-4-methylpentene-1 film and kraft fibers in insulating oil. The present invention relates to a method for significantly improving adhesion and swelling properties. Composite electrical insulating paper, which is made by laminating kraft fiber paper on at least one side of poly-4-methylpentene-1 film, has features such as low dielectric loss and high withstand voltage, so it is suitable for insulation for ultra-high voltage OF cables. It is attracting attention worldwide as a body. Insulators for ultra-high voltage OF cables are required to have dielectric properties such as a dielectric constant ε of about 2.5 and a dielectric loss tangent tan δ of about 0.05 (%). 4-methylpentene-1
It is necessary to increase the ratio occupied by film to, for example, 60% or more. However, with composite electrical insulating paper in which poly-4-methylpentene-1 film accounts for 60% or more, the rate of increase in thickness in insulating oil, that is, the rate of swelling, becomes large, and for example, when a cable is bent, the insulating paper This causes problems such as wrinkles and cuts, which reduce the withstand voltage value of the cable. Conventionally, composite electrical insulating paper is produced by applying kraft fiber paper along at least one side of a poly-4-methylpentene-1 film extruded from an extruder equipped with a T-die, and then bonding and integrating the film with a pressurized water-cooled roll. Manufactured by. In this case, the poly-4-methylpentene-1 film extruded from the T-die is subjected to its own weight in a molten state before reaching the pressurized water-cooled roll, so that the formed film is oriented in the extrusion direction. Therefore, when the obtained composite electrical insulating paper is immersed in insulating oil, the poly-4-methylpentene-1 film layer exhibits swelling anisotropy, and the kraft fiber paper layer and the poly-4-methylpentene-1 film layer exhibit swelling anisotropy. It was found that it became easy to peel off. The present invention has been made to overcome these problems, and improves the properties of composite electrical insulating paper, particularly the adhesion and swelling properties of poly-4-methylpentene-1 film and kraft fiber paper in insulating oil. This provides a method for improving characteristics. In the method of the present invention, a composite electrically insulating paper obtained by adhering kraft fiber paper under pressure to one or both sides of a poly-4-methylpentene-1 film extruded using an extruder is used as the composite electrically insulating paper. The poly 4-methylpentene-1 film layer is
Apply it to a heated roll so that the temperature is higher than the crystal melting point of the methylpentene-1 film and the surface pressure applied to the composite electrical insulating paper is 10 g/cm ² or higher,
The film is then allowed to cool in air until the temperature reaches a temperature 30° C. or more lower than the crystalline melting point of the poly-4-methylpentene-1 film. In the present invention, poly-4-methylpentene-1 film is a film obtained by melt-extruding poly-4-methylpentene-1 pellets with excellent dielectric properties using an extruder using a T-die or the like. . In the present invention, first, by a conventional method, a composite electrically insulating paper is produced by overlapping and pressurizing kraft fiber paper on one or both sides of a poly-4-methylpentene-1 film extruded using an extruder. obtain. Next, the composite electrically insulating paper obtained in this way was placed on a heating roll to form the poly(4-methylpentene) used in the composite electrically insulating paper.
The temperature of one film layer is set to a temperature higher than the crystal melting point of the poly-4-methylpentene-1, and at this time, the surface pressure applied to the composite electrically insulating paper is set to 10 g/cm ² or more, preferably about 50 to 100 g/cm ² Hold. Poly 4-
The temperature of the methylpentene-1 film layer was
The reason for limiting the temperature to the crystal melting point of -methylpentene-1 is that the orientation imparted to the poly-4-methylpentene-1 film can be relaxed. At temperatures lower than the crystal melting point of poly-4-methylpentene-1, heating rolls have no effect on the adhesion between poly-4-methylpentene-1 film and kraft fiber paper in insulating oil. In addition, the surface pressure applied to the composite electrical insulating paper is 10g/
The reason why it is limited to cm ² or more is that by applying such surface pressure, the molten poly(4-methylpentene-1) sinks sufficiently between the fibers of the kraft fiber paper.
This is because the adhesion between the methylpentene-1 film and the kraft fiber paper is significantly improved. When the obtained composite electrically insulating paper is placed on a heating roll, the composite electrically insulating paper is pressed against the heating roll, so that the heat transfer from the heating roll to the composite electrically insulating paper is good, and therefore the surface of the heating roll is It is sufficient that the temperature is 10 to 20 DEG C. higher than the crystalline melting point of the poly-4-methylpentene-1 film. It is preferable to use two or more metal rolls as the heating rolls and to pass the composite electrically insulating paper through each roll while being in sufficient contact with the rolls, since a constant surface pressure can be applied. In the present invention, the composite electrically insulating paper is placed on a heated roll and then cooled. In this cooling step, it is necessary to allow the poly-4-methylpentene-1 film layer to cool in air until the temperature of the poly-4-methylpentene-1 film becomes at least 30°C lower than the crystal melting point of the poly4-methylpentene-1 film. be. The reason for this is that the crystallization temperature range of poly-4-methylpentene-1 film is
-The crystallinity of the poly-4-methylpentene-1 film is below the crystalline melting point of the poly-4-methylpentene-1 film and is 30°C lower than the crystalline melting point. This is because it is effective in increasing the thickness of the obtained composite electrically insulating paper, and accordingly, it is effective in reducing the rate of increase in thickness in insulating oil, that is, the rate of swelling of the obtained composite electrically insulating paper. When cooling in air, cooling is performed only by heat dissipation, resulting in poor heat transfer, and sufficient slow cooling is performed, resulting in a large effect of increasing the degree of crystallinity. Generally, from the viewpoint of productivity, it is preferable to let the material cool in the air for about 2 to 3 m after passing through the heating roll, and then cool it with a water-cooled roll or the like. The method of the present invention can be carried out immediately after the step of pressurizing and adhering kraft fiber paper to at least one side of a poly-4-methylpentene-1 film extruded by an extruder, resulting in good productivity and characteristics. This is particularly preferable because it can improve. Next, the present invention will be explained with reference to Examples and Comparative Examples. Comparative Example 1 Poly-4-methylpentene-1 (crystal melting point 235
℃) is extruded into a 90μ thick film using an extruder, and 30μ thick kraft fiber paper is layered on both sides of the film and bonded together using a pressure roll (surface temperature 15℃) to form composite electrical insulating paper. Obtained. Example 1 The composite electric insulating paper obtained in Comparative Example 1 was
The sample was passed between heating rolls at 250°C at a surface pressure of 50 to 70 g/cm ² and left to cool in the air up to a point 2 m away from the heating roll. The temperature of the composite electrically insulating paper at this time reached 200°C. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and further cooled. Comparative Example 2 The composite electrical insulating paper obtained in Comparative Example 1 was
The sample was passed between heating rolls at 230°C at a surface pressure of 50 to 70 g/cm ² and left to cool in the air up to a point 2 m away from the heating roll. At this time, the temperature of the composite electric insulating paper reached 180℃. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and further cooled. Comparative Example 3 The composite electrical insulating paper obtained in Comparative Example 1 was
The material was passed between 250° C. heating rolls to the extent that they were in slight contact with each other, and the material was left to cool in the air up to a point 2 m away from the heating rolls. The temperature of the composite electrical insulation paper at this time is
The temperature reached 200℃. Next, a water-cooled roll (surface temperature 15
℃) and further cooled. Comparative Example 4 The composite electrical insulating paper obtained in Comparative Example 1 was
The sample was passed between heating rolls at 250°C at a surface pressure of 50 to 70 g/cm ² and allowed to cool in the air up to a point 10 cm away from the heating roll. The temperature of the composite electrically insulating paper at this time reached 245°C. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and further cooled. Example 2 The surface temperature of the composite electrically insulating paper obtained in Comparative Example 1 was subsequently placed at a point 50 cm away from the pressure roll.
The sample was passed between heating rolls at 250°C at a surface pressure of 50 to 70 g/cm ² and left to cool in the air up to a point 2 m away from the heating roll. The temperature of the composite electrically insulating paper at this time reached 200°C. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and further cooled. Example 3 The composite electric insulating paper obtained in Comparative Example 1 was
The sample was passed between heating rolls at 240°C at a surface pressure of 50 to 70 g/cm ² and left to cool in the air up to a point 2 m away from the heating roll. The temperature of the composite electrically insulating paper at this time reached 190°C. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and further cooled. Example 4 The composite electrically insulating paper obtained in Comparative Example 1 was
The sample was passed between heating rolls at 250°C at a surface pressure of 100 to 150 g/cm ² and left to cool in the air up to a point 2 m away from the heating roll. The temperature of the composite electrically insulating paper at this time reached 200°C. Then, it was introduced into a water-cooled roll (surface temperature: 15°C) and cooled. The composite electrically insulating papers obtained in Examples 1 to 4 and Comparative Examples 1 to 4 described above were each dried at 100°C and 0.1 mmHg for 24 hours, and an oil obtained by impregnating them with dodecylbenzene (DDB). The dielectric properties of the soaked paper were measured. As a result, the dielectric constant ε is 2.45~
2.50, and the dielectric loss tangent tanδ at 80℃ is 0.045
It was good at ~0.055 (%). Further, the obtained composite electrically insulating paper was vacuum-dried in the same manner, then immersed in DDB at 100°C, and the rate of increase in thickness after being left for 240 hours was measured. The results are shown in Table 1. Furthermore, the obtained composite electric insulating paper was vacuum dried in the same way, then immersed in DDB at 100°C, and after being left for 24 hours, it was mixed with kraft fiber paper and poly-4-methylpentene.
The adhesive strength with one film layer was measured. The results are shown in Table 1.

[Table] As shown in Table 1, the composite electrical insulating paper produced by the method of the present invention has a small thickness increase rate after immersion in insulating oil, that is, a small swelling rate, and a high adhesive strength.
It had excellent physical properties. Next, a semiconducting layer was provided on the 2000 mm ² copper conductor, and the composite electrically insulating paper obtained in Example 1 and Comparative Example 1 was wrapped around this to a thickness of 15 mm, and the same external semiconducting layer and aluminum covering were applied. These cables were vacuum dried at 100°C and 0.1mmHg for 120 hours. After this, the conductor was impregnated with DDB, heated for 6 hours so that the conductor temperature reached 85℃ by energizing the conductor, cooled to room temperature, and after bending 20 times, the impact breakdown voltage was measured and shown in Table 2. Got the results.

[Table] Also, as a result of disassembling this cable, Example 1
In the cable using composite insulating paper, no paper wrinkles or cut parts were observed in the insulating paper layer, and the cable was in good condition. On the other hand, in the cable using the composite insulating paper of Comparative Example 1, the occurrence of paper wrinkles and the presence of cut portions in the insulating paper layer were observed, and dielectric breakdown occurred at the cut portions.

Claims (1)

[Claims] 1 Composite electrical insulating paper obtained by adhering kraft fiber paper under pressure to at least one side of a poly-4-methylpentene-1 film extruded using an extruder,
The poly-4-methylpentene-1 film layer used in the composite electrical insulating paper is
The poly4-methylpentene-1 film was heated to 30°C above the crystalline melting point of the poly4-methylpentene- ¹ film. A method for improving the characteristics of composite electrically insulating paper, characterized by cooling it in the air until the temperature reaches a temperature lower than that.