JPS5827091B2 - plastic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glasstic film that has good electrical insulation properties, particularly good partial discharge resistance in air, and excellent insulating oil impregnation properties.

Plastic film oil-immersed insulators are a high-voltage insulator that can replace oil-impregnated cellulose paper as a high-performance electrical insulator used in cables, capacitors, etc., but it is difficult to impregnate film laminates with insulating oil. However, there are problems such as the fact that the film is hard to clean and is prone to deterioration due to crazing in oil, so it is used as a composite with cellulose paper, with the inherent low loss property of the film being somewhat compromised.

In addition, dry-type small capacitors are manufactured by wrapping aluminum foil around a plastic film, or by wrapping a film with a metalized surface, but the operating voltage of these is limited to a value significantly lower than the withstand voltage of the film. ing.

This is because partial discharge deterioration of the film in the air is taken into consideration, and if the partial discharge characteristics are improved, use at even higher voltages becomes possible.

The present inventors have conducted repeated research to improve the above-mentioned problems, and as a result, they have arrived at the present invention.

That is, the present invention relates to a plastic film having annular or fibril-like fine irregularities on its surface obtained by biaxially stretching a mixed material containing 0.01 to 20 parts by weight of silicone oil per 100 parts by weight of a thermoplastic resin.

Thermoplastic resins used in the present invention include polyolefins such as polyethylene, polypropylene, poly-4-methylpentene-1, and polybutene-1, polystyrene, polycarbonate, polysulfone, polyethylene terephthalate, polyvinyl chloride, polyvinylidene fluoride, etc. Those that can be stretched are suitable, and these can be used alone, as a mixture, or as a copolymer of these together or with other components.

Silicone oil generally refers to ganopolysiloxanes, such as those in which R is a methyl group, and those in which R is partly a methyl group and the rest is hydrogen, an ethyl group, a phenyl group, a halogenated phenyl group, etc. There is.

High molecular weight is particularly desirable, with a viscosity of about 5 at 25°C.
A value of 0 cs or more is particularly good.

Silicone oil is added to the thermoplastic resin and kneaded using an extruder, kneading roll, etc., and then formed into a sheet using a die, calender roll, etc., and then biaxially stretched by a conventional method.

That is, stretching is carried out by a combination of longitudinal stretching using speed difference rolls and transverse stretching using tenter clips, simultaneous biaxial stretching using accelerated tenter, inflation, or the like.

Two types of films can be obtained by selecting the stretching temperature.

When stretching starts at a relatively low temperature, the sheet becomes cloudy at first.

After that, it becomes translucent.

The film thus obtained has a porous structure in which the insulating oil can easily penetrate from the film surface into the inside.

In addition, such a state can also be obtained by deforming the sheet before stretching, such as bending or twisting, to make the sheet cloudy, and then stretching it at a normal stretching temperature. If stretching is carried out at a stretching temperature range of It has a structure that is suitable for winding and impregnating the interlayers with insulating oil.

The stretching ratio can be within the range normally used for sheets that do not contain silicone oil, and it is also possible to thermally stabilize the sheet by heat setting by a conventional method after stretching.

Next, examples of the present invention will be described.

Example 1 Some of the experimental examples are summarized in the table below.

In this experiment, a mixture of polymer pellets or powder and silicone oil was kneaded using an extruder, formed into a sheet using a T-die, and then biaxially stretched using an experimental biaxial stretching device to produce a film.

The main conditions are listed in the table.

The resulting film was examined for insulating oil impregnation and aerial partial discharge resistance.

The impregnability was determined by inserting three pieces of film between 100mmφ metal flat disk electrodes, vacuum impregnating them with insulating oil while tightly tightening the electrodes, and then measuring the corona onset voltage between the electrodes.
The quality was determined based on the value.

Partial discharge resistance in air is 4 by concentration method using IEC electrode.
Accelerated deterioration occurred at 00 Hz, and the lifespan at that time was expressed as a ratio to the lifespan of a sample of the same polymer that did not contain silicone oil.

/I66 to /I68 in the table are conventionally known films that do not contain silicone oil.

As is clear from the above explanation, the film of the present invention is
Because it has good insulating oil impregnation properties and air partial discharge resistance, it is useful as a material for electric cables, oil-immersed capacitors, dry type capacitors, etc., and also has characteristics as an oil-impregnated film, such as wastewater resistance, water resistance, moisture resistance, It has good surface smoothness, so it can be used for various packaging materials, rust prevention materials, etc.
It is industrially very useful.

Claims (1)

[Claims] 1 A plastic film having an annular or fibril-like fine unevenness on its surface obtained by biaxially stretching a kneaded material containing 0.01 to 20 parts by weight of silicone oil based on 100 parts by weight of a thermoplastic resin.