JPS6142117A - Oil-immersed capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an oil-impregnated capacitor in which a dielectric (insulator) layer using a polypropylene film (hereinafter abbreviated as PP film) is impregnated with insulating oil. .

[Background technology]

In recent years, plastic films have come to be used in the dielectric layers of various capacitors. Oil-impregnated capacitors are no exception, and among plastic films, PP film is particularly commonly used because of its excellent electrical properties. However, polypropylene (hereinafter referred to as P
Since a film containing only P) has extremely poor oil impregnation properties, it is usually used by roughening the surface or laminating an oil impregnating layer. As a PP film,
On at least one side of the base layer made of PP, a composite layer made of a mixture of PP and polyethylene, a polymer other than polyolefin, or a rubber, a propylene-ethylene random copolymer, a propylene-olefin block copolymer, etc. It is known what it has.

By the way, in order to extend the life of oil-impregnated capacitors under high-voltage charging, V- should be defined as voltage resistance (where ■: commercial frequency AC voltage, t: time required to reach dielectric breakdown). Improvement is essential. Conventionally, the capacitor with the best V- characteristic was an oil-impregnated capacitor that used an all-PP roughened film as the dielectric. Furthermore, the requirements for the dielectric to improve the V- characteristics are: ■ The impregnating oil (insulating oil) should flow smoothly through the film surface to completely eliminate air in the wound capacitor; ■ The dielectric The impregnating oil is absorbed into the film surface layer to reduce the electric field strength on the film surface layer, and the base layer, which bears the voltage under high voltage application, has a sufficiently high withstand voltage.

[Purpose of the invention]

The purpose of the present invention is to provide an oil-impregnated capacitor with a long life under high voltage application. [Disclosure of the Invention] In order to achieve the above object, the inventors focused on the point (2) above. I did a lot of research. In other words, one end of the capacitor (
The electric field strength Z of the surface layer of the dielectric film is expressed by the following formula: Surface leakage resistance Eo of the surface of the film
As can be seen from the above equation for applied voltage, it can be alleviated by lowering Rs. In order to reduce Rs, it is sufficient to increase the impregnation oil absorption rate of at least one surface layer of the dielectric. As a result of repeated research, the inventors have found that the impregnated oil absorption rate is expressed as the PXE oil absorption rate, and that the PXE oil absorption rate of oil-impregnated N (hereinafter referred to as a composite layer) is different from that of a layer made of PP (hereinafter referred to as a base layer). layer) PXE
They discovered that the oil absorption rate should be at least 1.2 times the oil absorption rate, and completed this invention. In addition, PXE means 1,1-phenylxylylethane.

Therefore, the present invention provides an oil-impregnated capacitor comprising an electrode, a dielectric layer, and an insulating oil, in which a base layer,
and a polypropylene film having a composite layer superimposed on one side thereof is used for at least a portion of the dielectric layer, and the PXE oil absorption rate of the composite layer is 1.2 times or more than the PXE oil absorption rate of the base layer. The gist of the invention is an oil-impregnated capacitor characterized by the following.Details of the invention will be described below.

Here, the P, P film is a mixture of PP and a polymer other than polyethylene or polyolefin, or rubber, on at least one side of a base layer made of PP, or
A composite layer made of a propylene-ethylene random copolymer, a block copolymer of propylene and other olefins, etc. is provided. The base layer does not necessarily need to be made of a PP homopolymer, and may be copolymerized with a small amount of other olefins within the scope of achieving the objectives of the present invention. Further, a small amount of other polyolefins may be mixed. Furthermore, it may contain various known additives, such as a stabilizer, a captivity agent, a curing inhibitor, a dielectric strength improver, and the like. In the mixture of PP and polyethylene, the polyethylene is preferably so-called medium-high density polyethylene with a density of 0.93 or more from the viewpoint of oil resistance, and polypropylene 80-5 wt%, medium-high density polyethylene 20-95 wt%
A blending composition range of -t% is more preferable because the surface becomes cloudy and rough, and the oil impregnation property increases significantly. Polymers other than polyolefins specifically mean polymers with poor compatibility with PP, and examples include polystyrene, straight-line polyesters, polyamides, polyacrylic esters, polymethacrylic esters, polycarbonates, Polyacetal, etc. Further, the rubbers include butyl rubber, 2-styrene-butadiene rubber, polybutadiene, polyisoprene, and ethylene-propylene rubber.

These include ethylene-propylene-diene ternary copolymer rubber or polyisobutylene rubber. It should be noted that as these polymers to be mixed with the PP, those which are melted by heat in the process of processing and blending the PP are preferably used. In this case, the block copolymer used in this invention is:
Propylene and olefins other than propylene, e.g.
It is a block copolymer with ethylene, butene-1,4-methyl-pentene-1, etc. Although the copolymerization ratio is not necessarily limited, the content of olefins other than propylene in the block copolymer is preferably 1 to 20 nt%, more preferably 5 to 15 wt%. As is well known, a block copolymer is one in which the copolymer components are not randomly distributed in the propylene chain, but are contained in a continuous manner to some extent.

The PXE oil absorption rate of the polypropylene film composite layer needs to be 1.2 times or more the PXE oil absorption rate of the base layer. In this case, the insulating oil penetrates well into the composite layer and the surface resistance Rs of the capacitor decreases, so the electric field strength Z at one end of the capacitor becomes less likely to occur, and the characteristic V- gets better. In other words, the life of the capacitor is extended.

Incidentally, the PXE oil absorption rate is a standard devised by the inventors in order to achieve the purpose of the present invention, and is measured by the test method described below.

(PXE oil absorption measurement method) (Al As pre-treatment, measurement sample (film)
is left for 12 hours (aging) in a constant temperature and humidity room maintained at 25° C. and 50% RH (relative humidity). All of the following work is also done in this constant temperature and humidity room.

(b) Cut the pretreated sample into 200 mm square pieces, place them in a 300 mm square flat vat, and conduct PXE.
Oil 1j! After filling it with water, put it in the oven and leave it at 80℃ for 24 hours.

The film was removed from the fclPXE oil, and the surface was lightly wiped with a cloth impregnated with xylene prior to measurement.

+dlFT-IR (Fourier transform infrared spectroscopy) is used to obtain the absorption spectrum of a portion of the film up to a thickness of 1 μm from the surface layer, and the difference spectrum from the absorption spectrum of the non-oil-impregnated film is obtained.

Regarding the absorbance I of the PXE characteristic absorption band, the absorbance difference Δ1 of each composite layer of oil-impregnated film and oil-unimpregnated film is
1 and the absorbance difference ΔI2 of the base layer.

However, Δ■! is the difference in absorbance between the characteristic absorption bands of the composite layer of the oil-impregnated and non-impregnated films, and ΔI2 is the difference in the absorbance of the characteristic absorption bands of the base layer of the oil-impregnated and non-impregnated films.

+a+ This absorbance difference ratio K pxe is 1μ from the surface layer.
At a thickness of up to m, this corresponds to the ratio of the amount of PXE oil contained in a unit volume.

The PP film used in this invention may contain other components to the extent that the characteristics of this invention are not impaired. Further, if necessary, electrical surface treatment using corona discharge, plasma, etc., or chemical surface treatment using antistatic agent, etc., may be performed in order to improve electrical performance, improve wetness, etc.

The method for producing the above PP film is, for example, as follows.

First, there is a method using coextrusion. In other words, two extruders are prepared, PP is supplied to one, and the material for the composite layer is supplied to the other, and the materials are melt-extruded, merged in one nozzle or near the exit, and then discharged as a laminated sheet. - Axial or two-wheel stretching. Alternatively, the composite layer material may be laminated by melt extrusion on a PP sheet prepared in advance (which may or may not be stretched), or may be bonded in a solidified state and then stretched as described above. . Alternatively, the base layer may be sandwiched between composite layers, other layers may be bonded together, the composite layer material may be dissolved in a solvent and coated on the base layer, or any other suitable method may be selected. The condition (roughness) of the surface of the composite layer side of the PP sheet may be rough, not so rough, or anywhere in between. The base layer and composite layer bond well without any special treatment, but if necessary, surface activation treatment (
(corona discharge treatment, etc.) or may be laminated after applying a suitable anchor coating agent.

The oil-impregnated capacitor according to the present invention is manufactured by the following method using the PP film obtained as described above.

A capacitor element is produced by overlapping and winding a PP film with a metal foil serving as an electrode. Metals such as aluminum, zinc, tin, copper, silver, and lead are used as electrodes. Alternatively, instead of forming the metals in the form of foils, these metals may be vapor-deposited or plated onto a film to form the electrodes. As the dielectric layer, one or more layers of the above PP film may be used alone, or it may be used in combination with other plastic films or thin paper for capacitors.

The capacitor element thus produced is subjected to treatments such as pressing or drying, then placed in a container and impregnated with insulating oil under reduced pressure.

As the insulating oil, any electrically insulating oil can be used, but examples include so-called mineral oils made of polychlorinated diphenyls, paraffinic, naphthenic, or aromatic hydrocarbons.

These include paraffin oil, polybutene, cottonseed oil, rapeseed oil, and silicone oil. These may be used alone or in combination. Furthermore, known additives such as epoxy compounds may be added to these oils.

Preferred insulating oils include phenylxylylethane and monoisopropylbiphenyl.

The oil-impregnated capacitor thus obtained is V-
The withstand voltage characteristics are improved and the lifespan is longer under high voltage application.

In addition, when a base layer of the PP film used in this invention is made of crystalline PP, PP
It is preferable that the crystal size of is 150 Å or less. The withstand voltage of the base layer becomes sufficiently high, and the capacitor
This is because the lifespan under high voltage application becomes longer. This satisfies (1) above. The crystal size is, for example,
Using the line wide-angle method and replacing the crystal size with the size of the 110 lattice plane, it can be determined from the following formula.

D: Crystal size and error constant (here = 1) λ: Wavelength of incident X-rays (1,5418 people) β: Half width θ: Beak angle (incident angle) Next, examples and comparative examples will be explained. (Examples 1 to 4 and Comparative Example 1.2) Electrical grade PP was used as a base layer, and a mixture of high density polyethylene and PP was coextruded as a composite layer through a T-die, and the base layer was 20 μm thick and the composite layer was 2 μm thick. A film was formed. By changing the mixing ratio of PP and polyethylene in the composite layer, PXE with different oil absorption rates were used (with the exception of Comparative Example 2). Two sheets of the PP film formed as described above were rolled together with Al foil to form a capacitor element. In parallel, PXE oil absorption was measured and the results are shown in Table 1. Table 1 also shows the crystal size of the base layer of the PP film. Next, the capacitor of the present invention was obtained by placing the above capacitor in a container and impregnating it with PXE under vacuum. Other manufacturing conditions are as shown below.

Thickness of PP film...22μm Width of PP film...100mm Number of stacked PP films...2 Al foil...Embossed Aβ grouper A7! Thickness of foil...10μm Width of Al1 foil...80ml11 Edge of Al foil...Clamp rate without bending...112% Insulating oil (impregnated oil)...PXE Impregnation conditions...80℃, 24 Time element capacitance: 0.1 μF 10 each of the capacitors of Examples 1 to 4 and Comparative Example 1.2
Each individual was tested at 4.0 kV (A
A forced charging test was conducted in which the voltage of C) was continuously applied, and the results are shown in Table 1 as the respective average values.

(Left below) As shown in Table 1, the PXE of the composite layer relative to the base layer
It can be seen that those with an oil absorption ratio of 1.2 or more have a longer energized life than those with an oil absorption ratio of 1.2 or more. In addition, among Examples 1 to 4, when comparing those using PP films with the same PXE oil supply ratio, that is, Examples 1 and 3.4, the crystal size of the base layer is 150 Å or less. In other words, it can be seen that Examples 3.4 have a longer lifespan than Example 1.

〔Effect of the invention〕

In the oil-impregnated capacitor according to the present invention, a polypropylene film having a base layer and a composite layer superimposed on at least one side of the base layer is used for at least a part of the dielectric layer, and the PXE oil absorption rate of the composite layer is higher than that of the base layer. Since the oil absorption rate of PX"E is more than 1.2 times the oil absorption rate of
Even when the capacitor of the present invention is used under high voltage application, dielectric breakdown is less likely to occur and the life of the capacitor is extended.

Agent: Patent Attorney Takehiko Matsumoto Procedural Amendment (August 10, 1982 2, Name of the invention: 泪搪 うまち p-capacitor 3, Relationship with the case of the person making the amendment: Patent applicant: Location: Nihonbashi, Chuo-ku, Tokyo) Muromachi 2-chome 2 Name Higashi Shi Co., Ltd. Company Representative Representative Director Masatoshi Ito 4, No representative 6 Subject of amendment: !F 7 Contents of amendment (11 Specification page 4) In the structural formula of Ll-phenylxylylethane in lines 19 and below, correct the text to read as follows.

(2) In the next line of formula (A) on page 9 of the specification, “However,
The 9th line counting from ``corresponds to the oil amount ratio. "In other words, this K pxe corresponds to the PXE oil absorption rate ratio of the composite layer to the PXE oil absorption rate of the base layer. This ratio is how many times the PXE oil absorption rate of the composite layer is that of the base layer. Insert "This indicates whether or not there is."

(3) In Table 1 on page 16 of the specification, rPXE oil supply rate oil color comparison is corrected to rPXB oil absorption rate ratio Kpxe, *.

(4) Under Table 1 on page 16 of the specification, “*...Chapter 8.
See PXE oil absorption measurement method on page 9. ” is inserted.

Claims (2)

[Claims] (1) In an oil-impregnated capacitor equipped with an electrode, a dielectric layer, and an insulating oil, a polypropylene film having a base layer and a composite layer superimposed on at least one side thereof is used for at least a portion of the dielectric layer. ,
An oil-impregnated capacitor characterized in that the PXE oil absorption rate of the composite layer is 1.2 times or more the PXE oil absorption rate of the base layer. (2) The oil-impregnated capacitor according to claim 1, wherein the polypropylene film base layer has a crystal size of 150 Å or less.