JPH0370113A - Roll-in type capacitor - Google Patents

Abstract

PURPOSE:To prevent characteristic deterioration due to electrode corrosion by providing terminals on a capacitor body formed through rolling in particular polypropylene based resin films, each being impregnated with an impregnate containing water content not more than 15ppm and having a metal film layer on one side thereof and having a roughened surface. CONSTITUTION:Polypropylene based films 2, each being impregnated with an impregnate and having a metal film layer at least on one side thereof and having a roughened surface, are rolled in to form a capacitor body and terminals are provided thereon. As the impregnate, any one, which does not cause change in the metal film such as cracking, swelling and falling out etc., and has good electric characteristics, can be used. However, one with large viscosity is preferably avoided because it has low handling property and low impregnating ability. The water content in the impregnate is not more than 15ppm (preferably not more than 10ppm). If the water content is more than 15ppm, the corrosion speed of the metal film layer becomes large suddenly, and characteristic deteriorations such as capacity decrease due to electrode disappearance, increase of dielectric loss, dielectric breakdown, etc., are liable to take place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to capacitors, particularly wound type capacitors.

[Conventional technology]

Wrapped-type capacitors have conventionally been made by laminating a roughened resin film and metal foil such as aluminum, or by wrapping paper and metal foil together and impregnating them with an impregnating agent. provided. Also,
Recently, wound-type capacitors have been provided in which a metallized film having a metal thin film layer formed on the surface of the film is wound and impregnated with an impregnating agent. In these wound type capacitors, film or paper serves as the dielectric;
A metal foil or thin metal film layer serves as an electrode.

[Problems to be Solved by the Invention] In the conventional wound type capacitors described above, the metal layer does not corrode and disappear because the thickness of the metal layer is large in those using metal foil. In contrast, in wound capacitors using metallized films, the thickness of the metal thin film layer is 100 to 3
Since the film is as thin as 0.00 mm, the film is likely to disappear due to metal corrosion due to moisture contained in the impregnating agent. For this reason, wound type capacitors using metallized films have problems in that they tend to suffer from poor characteristics such as a decrease in capacity due to loss of electrodes, an increase in dielectric loss (tan δ), and dielectric breakdown.

The inventor investigated what kind of correlation exists between electrode corrosion and the moisture content in the impregnating agent.

As a result, they found that the corrosion rate suddenly increases when the moisture content exceeds a certain level.

An object of the present invention is to provide a wound type capacitor that is less likely to suffer from poor characteristics due to electrode corrosion.

[Means to solve the problem]

The wound type capacitor of the present invention includes a capacitor body wound with a roughened polypropylene film impregnated with an impregnating agent and having a metal thin film layer on at least one side, and terminals provided on the capacitor body. The amount of water contained in the impregnating agent is 15 ppm or less.

＊＊＊＊＊＊＊ Examples of the polypropylene resin used in the present invention include isotactic polypropylene, ethylene-propylene copolymer, butene-propylene copolymer, ethylene-butene-propylene copolymer, etc. . The polypropylene copolymer resin may be either a random copolymer or a block copolymer.

The polypropylene resins may be used alone or in combination of two or more. Also,
Other polymers, nucleating agents, antioxidants, other 3e,
may be added.

In addition, in the polypropylene resin used in the present invention,
It is desirable that the proportion of polypropylene is 80% by weight or more.

The polypropylene resin film used in the present invention is
The polypropylene resin is molded into a film. Desirable polypropylene resin films used in the present invention include, for example, a polypropylene resin film (A) with an isotactic degree of 96 to 99.6%, and an ethylene resin film (A) with an ethylene content of 10.7 to 2.5% by weight. Propylene random copolymer 70-85ffii1
Ethylene-propylene block copolymerization with an isotactic degree of 85-95% obtained by copolymerizing ethylene with 15-30% by weight
After biaxially stretching the laminated layer of B), the wetting tension on one side was reduced to 37 to 46 dyne by corona discharge treatment.
/ cm. In this case, it is desirable that the thickness of A and B be 80/20 to 9515 in terms of weight ratio (A/B).

A rough surface is formed on one or both sides of the polypropylene resin film used in the present invention.

These rough surfaces include, for example, those formed by a network structure due to α-product transformation of β crystal spherulites, those formed by utilizing the difference in melt tension between polypropylene resin and polyethylene resin, and those formed by using organic or inorganic materials in polypropylene resin. These include those formed by adding a pigment of the same type, cooling it into a film, and then biaxially stretching it. A method for forming such a rough surface is described in, for example, Japanese Patent Laid-Open No. 61-42116.

For example, a large number of independent granular protrusions are formed on the rough surface. In this case, among the independent granular protrusions, the height is 0.
．． 7 protrusions/mm or more of 4μm or more, plus 10
It is desirable that the number of particles/mm or more is formed. height 0
．． If the number of granular protrusions of 4 μm or more is less than 7/mm, the surface roughness may be insufficient and the impregnating property of the impregnating agent may not be sufficient.

The height and number of such granular protrusions can be measured using a three-dimensional surface profile measuring device with an analyzer (for example, manufactured by Koita Institute ■: 5E).
-3FKS). Note that the measurement conditions are as follows.

Measurement length: 1 mm Vertical magnification: 5000 times Lateral magnification = 200 times Feed speed: Q, 1 mm/sec Filter: 0.25 mm Measurement interval: 10 um Number of measurements: 20 Measurement direction: Longitudinal direction of the film Granular shape obtained under the above conditions The number of protrusions with a height of 0.4 μm or more is counted from the number of protrusions (PC-1). Note that the number of granular protrusions (PC-1) herein refers to the number of granular protrusions having a height of 0.2 μm or more from the center line of the unevenness of the rough surface.

A thin metal film is formed on at least one side of the polypropylene resin film used in the present invention.

The metal thin film used in the present invention is a thin film layer made of zinc, aluminum, a mixture of zinc and aluminum, a mixture of zinc or other metals (eg, silver, copper, etc.). Such a metal thin film can be formed by vapor deposition using a known method.

The thickness of the metal thin film must be adjusted to provide a film resistance depending on the purpose of use, but is generally 100 to 300. If the thickness is less than 100 mm, the film strength may become weak. On the other hand, if it exceeds 300 Å, self-healing properties may deteriorate. Note that the film thickness can be measured by obtaining correlation data with the film resistance value in advance and converting it from the film resistance value. The membrane resistance is O
It can be measured using HMH-ta (for example, manufactured by Toyo Metallizing ■) under the following conditions.

Measurement length: 20 cm in the length direction of the film Measurement width: arbitrarily set to 10 cm or less in the width direction of the film.

Note that it is preferable to measure the membrane resistance value of three or more pieces and express it as the average value.

The impregnating agent used in the present invention prevents cracks, blisters, and
Any material may be used as long as it does not cause decarburization such as decarburization and has good electrical properties. However, it is preferable to avoid the use of highly viscous materials, as they impair handling and impregnating properties.

Preferred impregnating agents include, for example, vegetable oils such as rapeseed oil and cottonseed oil, and aromatic compounds containing these as main components (
For example, mixed oils with alkylbenzenes) can be mentioned. The water content in the impregnation agent is 15 ppm or less (preferably 10 ppm or less). When the water content exceeds 15 ppm, the corrosion rate of the metal thin film layer increases rapidly, resulting in a decrease in capacity due to loss of electrodes, an increase in dielectric loss (tan δ),
Characteristic defects such as insulation breakdown are more likely to occur. Note that the water content in the impregnating agent is a value measured by the Karl Fischer method.

Next, an example of a wound type capacitor according to the present invention is shown in FIG. The wound type capacitor 1 is made by stacking two polypropylene films (metalized polypropylene films) 2 having the metal thin film layer described above so that the metal thin films H2a do not face each other and rolling them to a desired hardness, and metallicon 3 at both ends. After drying the element, the terminal 4 is connected, and then the element is impregnated with dehydrated and purified insulating oil.

Next, an example of a method for manufacturing a wound type capacitor according to the present invention will be described.

First, a capacitor body is created by cutting a metalized polypropylene film into a predetermined shape, and rolling up two sheets of the same. Next, metals such as zinc, aluminum, lead, tin, or alloys thereof are coated on both ends of the capacitor body, and terminals are attached to the metallicon parts. The capacitor element with terminals attached is placed in an impregnation tank and vacuum dried. Next, insulating oil that has been dehydrated and purified by vacuum evaporation or adsorption is placed in an impregnating tank and impregnated for at least 24 hours at 50 to 90°C, 1mmHgabs or less, to produce a wound capacitor. .

〔Effect of the invention〕

In the present invention, the amount of water contained in the impregnating agent is 15 ppm.
It is as follows. Therefore, according to the present invention, it is possible to obtain a wound type capacitor that is unlikely to suffer from characteristic defects due to electrode corrosion.

〔Example〕

1 to 3 and 12 The base layer is a polypropylene resin with an isotactic degree of 99.4%, the composite layer is an ethylene-propylene random copolymer with an ethylene content of 1.4% by weight, 85% by weight, and ethylene 15% by weight. % and an ethylene-propylene block copolymer with an isotactic degree of 92.4%, respectively, were melted in an extruder at 260°C. Then, both melts were coextruded into a sheet through a T-die with a width of 630 mm and a gap of 1.0 mm, and this was cooled on a casting drum to create a laminated polypropylene resin film. At this time, the thickness of the base layer is 13μ
The extruder was adjusted so that the thickness of the composite layer was 1.3 μm. Also, the temperature of the casting drum is 30'
It was set as C.

Next, the obtained polypropylene resin film was
Stretched 5.0 times in the length direction at 175°C and 9.0 times in the width direction at 175°C, then subjected to relaxation heat treatment at 155°C to create a biaxially stretched film, and the rough side was stretched by corona discharge treatment. 4
The wetting tension was 2 dyne/cm. In addition, the wetting tension was measured according to the method of JIS-6788.

Next, the biaxially stretched film was slit into a width of 75 mm, and zinc was vapor-deposited using a known method to produce a vapor-deposited film. At this time, the membrane resistance of zinc was set to 6Ω/mouth.

The thus obtained vapor-deposited film was rolled with a hardness of 92 to 94.
A capacitor was created by winding the capacitor under conditions of 2 μF of shore and capacitance, applying metallization treatment to both ends, and attaching terminals.

Next, put the capacitor in a specified can, seal it except for the liquid inlet, and then put it in an impregnation tank and heat it at 80°C 10.5mm.
Drying was performed for 24 hours under conditions of Hgabs or less. Thereafter, commercially available rapeseed salad oil, which had been dehydrated and purified in advance, was quickly supplied into the impregnation tank, and impregnation was carried out for 48 hours.

In addition, for dehydration and purification of rapeseed salad oil, a diameter of 10 cm,
Synthetic zeolite (product name: Mizuriki Sheeps 4A) dried from the bottom of a column with a height of 70 cm to the height shown in Table 1.
-C8B (manufactured by Mizusawa Kagaku ■)), and rapeseed salad oil was passed from the top of the column at the speed shown in Table 1. Note that such dehydration and purification operations were repeated twice for Example 1, and once for Examples 2 and 3 and Comparative Examples 1.2.

Table 1 The water content after dehydration was measured by the Karl Fischer method.

The results are shown in Table 2. For the measurement, a trace moisture measuring device CA-02 manufactured by Mitsubishi Kasei ■ was used. In addition, as reagents for coulometric titration, Aquamicron Yakutubishi (trade name, manufactured by Mitsubishi Kasei ■) was used for the generated liquid layer, and Aqua≧Cron C Mitsubishi (trade name, manufactured by Mitsubishi Kasei ■) was used for the counter electrode layer. . The results in Table 2 are the average values of the measurements for two samples.

Next, an AC withstand voltage characteristic test was conducted on the capacitor impregnated with rapeseed salad oil. The test sample includes
A sealed can containing a capacitor was used. This sample was aged at 80° C. for 48 hours, and after measuring the capacitance (C) and dielectric loss (tan δ) of the capacitor at room temperature, an AC withstand voltage characteristic test was conducted. Measurements and tests were carried out as follows.

Measurements were made at room temperature using an LCR meter manufactured by Ando Electric, type AC-4311.

Automatic cylinder bridge made by Souken Electric ■, D
60Hz using AC-DSC-20W.

Measured at 400v.

ΔDankori Pressure Toyosumi ■Using a capacitor-resistant power supply made by Sashito Electric Seisakusho,
The test was conducted under the following conditions.

Measurement atmosphere: 280°C Applied voltage: 1500V The results are shown in Table 2. In addition, in the table, ΔC (capacitance change rate)
The values of tan δ and tan δ are the average values of 5 measurements.

Table 2 After 400 hours of testing, the capacitors were disassembled and observed, and in Comparative Examples 1 and 2, considerable film loss was observed. On the other hand, such a phenomenon was not observed in Examples 1 to 3. These results show that in wound type capacitors using metallized films, slight differences in trace water content have a significant effect on capacitor characteristics.

[Brief explanation of drawings]

FIG. 1 is a partially exploded perspective view of a wound type capacitor according to an example of the present invention. 1...-wound type capacitor,...metal thin film, 4...terminal. 2...Film 1a

Claims (1)

[Claims] (1) A capacitor body impregnated with an impregnating agent and wrapped with a roughened polypropylene film having a metal thin film layer on at least one side, and a terminal provided on the capacitor body, the capacitor body being impregnated with an impregnating agent, the capacitor body is provided with a terminal provided on the capacitor body, and the moisture contained in the impregnating agent is The amount is less than 15 ppm, wound type capacitor.