JPS6046497B2 - composite electrical insulation paper - Google Patents

Description

[Detailed description of the invention] This invention relates to improvements in composite electrically insulating paper.

For example, in oil-immersed insulated power cables, insulating kraft paper used to reduce dielectric loss of oil-immersed insulators has E.
It is effective to combine plastics with small tan δ, and known methods include mixing short fibers of the plastic during paper making, or laminating kraft paper and the plastic film. . The inventors have identified the above-mentioned E as such plastic.
Polymethylpentene has been found to be very promising in terms of tan δ value, heat resistance, etc., and various tests have been conducted.
It was confirmed that this polymethylpentene actually exhibits excellent properties. However, this laminate of polymethylpentene film and kraft paper is impregnated with dodecylbenzene, a hydrocarbon-based synthetic insulating oil widely used as an insulating oil, and this is used to obtain an N-sheathed OF cable. Contrary to expectations, when we performed a bending test of about 2 reciprocations on a diameter of 2, bending wrinkles that were not observed in the oil-immersed insulator layer, which were not observed when using only kraft paper, were found, and the withstand voltage characteristics of the cable deteriorated. A shortcoming occurred. As a result of various investigations into the causes of these wrinkles, we found that the polymethylpentene swelled due to the dodecylbenzene impregnated into the laminate of the polymethylpentene and kraft paper, increasing its thickness by approximately 10%. It has been found that this is caused by the fact that when the composite electrically insulating paper is wrapped in several layers and is in contact with each other, the pressing force between them increases significantly and the mutual slippage decreases. The inventors have made intensive studies to solve the drawbacks of composite electrical insulating paper made of polymethylpentene, and as a result, among polymethylpentene resins, the inventors have developed a polymethylpentene resin that has stable crystals with a 7-f2 helical structure. They found that methylpentene has a significantly low swelling property with the above-mentioned hydrocarbon insulating oil, and that products using this are surprisingly effective.That is, this invention has been completed by combining cellulose fiber paper layer and 7-2. This is a composite electrically insulating paper consisting of at least one polymethylpentene film layer each having stable crystals having a helical structure.

In this invention, the above-mentioned polymethylpentene film having stable crystals having a 7-2 helical structure can be obtained by heat-treating a normal polymethylpentene resin at a temperature range of 160 to 220°C for at least 15 seconds. .

Therefore, a composite electrically insulating paper having a polymethylpentene layer with stable crystals having a 7-2 helical structure is
Specifically, a laminate of a paper layer made of cellulose such as kraft paper and a normal polymethylpentene layer is obtained using a conventional method, and this is heated in an atmosphere of 160 to 220°C for at least 1 hour.
It can be easily obtained by heating the mixture for 5 seconds or more.
Of course, such heat treatment may be performed with the object to be treated stationary. In this case, it is desirable to uniformly heat the object from above and below. The composite electrically insulating paper of the present invention, as shown in FIG.
As shown in the figure, polymethylpentene film 2 is placed on both sides of paper layer 1.
Furthermore, as shown in FIG. 3, a film in which paper layers 1 are laminated on both sides of the polymethylpentene film 2 is selected as appropriate depending on the purpose of use. Figure 4 shows an ordinary polymethylpentene film l and a polymethylpentene film with stable crystals having a 7-2 helical structure obtained by heat-treating the film at 200°C for 30 seconds. ．． The line diffraction diagram is shown by a solid line, and the X-ray diffraction diagram of the sample without any heat treatment is also shown by a dotted line.

The present invention will be specifically explained below with reference to Examples. Example Polymethylpentene laminated paper consisting of kraft paper on both sides was obtained by melt extruding polymethylpentene and pressing kraft paper on both sides (weight ratio with polymethylpentene paper: 50
:50).

The resulting laminated paper was heat treated as described below using the method described above. These Examples and Comparative Example products were heated at 100°C.
2 under 0.1TwtHg? After vacuum drying for 100
After impregnating dodecylbenzene at 0C and holding at 1000C for 240 hours, the increase in thickness was determined as a percentage.

Next, these were wound 5 times thickly around a 1x2000d copper conductor to obtain an 0F cable, which was 15 times the outer diameter of the core and 2@
Two reciprocating bending tests and an impulse breakdown test were conducted on the diameter to investigate the occurrence of wrinkles in the oil-immersed insulating paper layer and the effect on the withstand voltage characteristics.

These results are shown in the table below. According to the results in the above table, the composite insulating paper using polymethylpentene with a stable crystal with a 7-2 helical structure in the example is different from the composite insulating paper using polymethylpentene with a different crystal morphology. Compared to composite insulating paper, the increase in thickness due to insulating oil was significantly smaller, and as a result, the bending test of cables formed using this resulted in good results with no wrinkles occurring in the oil-immersed insulating paper layer.

As described above, this invention achieves the excellent properties inherent in polymethylpentene by laminating at least one layer each of a special polymethylpentene film layer with stable crystals having a 7-2 helical structure and a cellulose fiber paper layer. In addition to these properties, we have obtained a composite electrical insulating paper that has very excellent oil resistance properties, and the above-mentioned drawbacks have been overcome, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are cross-sectional views of a composite electrically insulating paper according to the present invention, and FIG. 4 is an X-ray diffraction diagram of a polymethylpentene film. 1...Paper layer, 2...Polymethylpentene layer.

Claims (1)

[Claims] 1. A composite electrically insulating paper comprising at least one cellulose fiber paper layer and a polymethylpentene film layer having stable crystals having a 7-2 helical structure.