JPH07201648A - Film for oil-immersion condenser and oil-immersion film condenser - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a highly reliable oil-immersed film capacitor and a film used for the same. [Structure] An oil-immersed film capacitor obtained by impregnating a capacitor film with an element formed by winding a polypropylene film and an aluminum foil or winding a polypropylene film on which a metal vapor deposition film is formed, wherein the polypropylene film is Melt flow value 1-1
A polypropylene composition obtained by adding 500 to 1500 ppm of an antioxidant to a polypropylene resin having 0 g / 10 minutes, isotacticity of 93% or more, chlorine content of 10 ppm or less, and ash content of 30 ppm or less is formed by heating.
And the haze value of the surface irregularities is 10 to 60%, the crystallinity is 60 to 80%, and the rate of change of the polypropylene film when impregnated with the oil for capacitors is 3 to 15% in the thickness direction of the film, It is characterized in that it is adjusted to 3% or less in each of the longitudinal and lateral directions of the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for an oil-immersed film capacitor having a polypropylene film as a dielectric and an oil-immersed film capacitor.

[0002]

2. Description of the Related Art Currently,
Polypropylene film (PPF) is widely used as a dielectric for high voltage capacitors. In particular, a biaxially stretched PPF (Japanese Patent Publication No. 60-12217) having excellent electrical performance has been adopted for an oil-immersed all-film capacitor for power applications, and has become the mainstream in the industry.

However, in an oil-immersed film capacitor for electric power, the frequency of dielectric breakdown due to the film itself, the frequency of dielectric breakdown due to swelling of the film caused by impregnating the film with the capacitor oil, or the destruction of the container itself due to thermal expansion. The frequency is still high, and therefore there is a strong demand for improved reliability of oil-immersed film capacitors.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide a film for an oil-immersed film capacitor having high reliability and an oil-immersed film capacitor.

[0005]

Means and Actions for Solving the Problems The inventors of the present invention have made extensive studies on the factors contributing to the improvement of the reliability of the oil-immersed film capacitor, and as a result, a polypropylene film is wound around an aluminum foil or a metal vapor deposition film is formed. The polypropylene film is wound up and assembled into a capacitor element, impregnated with the oil for the capacitor, and in the process of manufacturing the capacitor by aging, the polypropylene film is impregnated with the oil for the capacitor, and the polypropylene film is swollen. By maintaining the predetermined conditions, that is, by determining the swelling degree and the rate of change of the film in the aging step, the dielectric breakdown frequency of the polypropylene film itself is reduced, and the element is pressed in the container. Things that happen Reduction of breakdown frequency by damage, can also be suppressed container breakage due to thermal expansion of the element and the oil, as a result, have found that excellent condenser life.

That is, the melt flow value is preferably 1 to 10
g / 10 min, isotacticity 93% or more, chlorine content 10 ppm or less, ash content 30 ppm or less polypropylene resin composition in which 500 to 1500 ppm of antioxidant is added to a polypropylene resin, and inflation is preferable in this case. To prepare a polypropylene film having a haze value of 10 to 60% and a crystallinity of 60 to 80% as the haze film on one side by the method, and the polypropylene film preferably has a haze value of 40 to 40%.
The film was impregnated with a condenser oil heated to 70 ° C. and then immersed in a condenser oil preferably kept at 50 to 95 ° C. to change the rate of change in the thickness direction of the film to 3
It was found that an oil-immersed film capacitor with improved reliability can be obtained by adjusting the characteristics of the film so that the rate of change in the lengthwise and crosswise directions of the film is 3% or less, respectively. It was the eggplant.

Therefore, the present invention provides an oil-immersed film capacitor obtained by winding a polypropylene film and an aluminum foil, or by winding a polypropylene film having a metal evaporated film formed thereon, and impregnating the device with a capacitor oil. In polypropylene, the haze value of the surface irregularities of the polypropylene film is 10 to 60%, and the crystallinity is 60 to 80%, and when the polypropylene film is impregnated with oil for capacitors, A film for an oil-immersed condenser and a film for oil-immersed film using the film, wherein the rate of change is adjusted to 3 to 15% in the thickness direction of the film, and 3% or less in the longitudinal and transverse directions of the film. Provide a condenser.

The present invention will be described in more detail below. The polypropylene film used for the oil-immersed film capacitor of the present invention (film for oil-immersed capacitor) has a melt flow value of 1 to 10 g / 10 minutes, preferably 2 to 6 g / 1.
0 minutes, isotacticity of 93% or more, preferably 9
5% or more, chlorine content 10ppm or less, ash content 30ppm
The following polypropylene resin is 500-1500p
It is preferable that the polypropylene composition to which a pm antioxidant is added is heat-molded, and the haze value of the surface irregularities is 10 to 60%, and the crystallinity is 60 to 80%.
Is.

When the polypropylene resin has a melt flow value of less than 1 g / 10 min, it becomes difficult to mold the polypropylene composition into a film and obtain a film having desired properties, and the melt flow is also reduced. If the value is larger than 10 g / 10 min, the amount of low-molecular-weight polypropylene component eluted into the capacitor oil (insulating oil) increases, which is not preferable.

When the degree of isotacticity is less than 93%, the PPF formed by thermoforming the polypropylene composition has a large amount of non-crystalline portion, and therefore the PPF due to the oil is increased.
The degree of swelling is large, and it becomes difficult to control the degree of swelling.

Both the chlorine content and the ash content affect the withstand voltage performance of PPF. Since the withstand voltage of PPF decreases with any increase in the content, the chlorine content is 10 pp.
m or less, and ash content should be 30 ppm or less.

When the amount of the antioxidant in the polypropylene composition is less than 500 ppm, heat deterioration of the polypropylene occurs when the polypropylene composition is heat-formed into a film, and when the amount of the antioxidant exceeds 1500 ppm. Since the dielectric loss tangent (tan δ) of PPF becomes large, internal heat generation becomes large when this PPF is used as a capacitor, which is not preferable.

The haze value of the PPF obtained by film-forming the above polypropylene composition is 10 to 60%, but it is particularly preferably 20 to 50%. If the haze value is less than 10%, the roughness of the PPF surface is not sufficient. Therefore, for example, when a capacitor element produced by alternately winding PPF and an aluminum foil is impregnated with insulating oil under vacuum, the insulating oil is PPF. Between or P
The PF-aluminum is not sufficiently impregnated, which causes dielectric breakdown. Further, when the haze value exceeds 60%, microscopically complex and deep concave portions are formed on the surface of the PPF, and the PPF locally becomes thin at this portion, so that the withstand voltage is reduced. The haze value is PP
It is expressed by the amount of light passing through F, that is, the ratio (percentage) of transmitted light intensity to incident light intensity, and the unevenness ratio of the PPF surface is determined based on the degree of haze or haze of the film. .

Further, the crystallinity of PPF varies depending on film forming conditions such as film forming temperature and draw ratio during film forming, but is strongly influenced by the isotactic degree. In the present invention, the crystallinity of PPF is 60 to 80%, preferably 65 to 75%. When the crystallinity is less than 60%, the amorphous portion in PPF increases,
A decrease in the ratio of crystal regions in the thickness direction lowers the withstand voltage, and it becomes difficult to control the degree of swelling, resulting in lower reliability. If the crystallinity exceeds 80%, PP
The amount of oil permeating into F is small, and therefore PPF
Withstand voltage is reduced.

Therefore, in order to manufacture the oil-immersed film capacitor of the present invention, first, a melt flow value of 1 to 10 g /
10 minutes, isotacticity 93% or more, chlorine content 10ppm or less, ash content of 30ppm or less polypropylene resin composition was added by adding 500 to 1500ppm of antioxidant to polypropylene resin, the haze value of the surface unevenness is 10. A PPF having a crystallinity of -60% and a crystallinity of 60-80% is prepared.

Although various forms of PPF are known depending on the molding method, those molded by the inflation method (simultaneous biaxial stretching method) are preferably used in terms of shape and heat shrinkage. In particular, it is preferable that at least one surface of the PPF is a cloudy rough surface film having minute irregularities, for example, a film (haze film) prepared by the method disclosed in Japanese Patent Publication No. 60-12217.
Is preferably adopted.

There are two types of haze films, a double-sided haze film having the same degree of unevenness on both sides and a single-sided haze film having only one side smaller than the other side and gentle unevenness. The PPF used in the invention is preferably a single-sided haze film.

On the other hand, a forming method called a tenter method (sequential biaxial stretching method) is also known, which is generally suitable for producing a smooth film. In this case, in the tenter method, it is possible to produce a haze film in the same manner as in the inflation method by sacrificing the productivity, but as will be described later, a change in size caused by shrinkage by heating and swelling by oil. However, since it is difficult to adjust to the above-mentioned predetermined range, it is preferable to use the PPF molded by the inflation method rather than the tenter method.

Explaining this point in more detail, in the case of a film having no uneven density and a uniform thickness, the withstand voltage of the film at any given position is the same. However, since the film used in the present invention is a haze film, microscopically, there may occur a case where the recesses on the front surface and the recesses on the back surface coincide with each other. In this case, the thickness of the film at that portion is small. Therefore, the higher the probability of coincidence, the lower the withstand voltage of the film, and the higher the risk of dielectric breakdown when used as a capacitor. This risk is greater in double-sided haze products than in single-sided haze products. In addition, since the haze film obtained by the inflation method is obtained in a tubular shape due to its manufacturing method, the degree of haze value is different between the inner surface and the outer surface. Usually, unevenness is large on the slowly cooled side with low cooling efficiency, and conversely is small on the rapidly cooled side. Such a film is usually called single-sided haze.

On the other hand, the value obtained by calculating the ratio of the thickness occupied by the irregularities on the surface to the total thickness of the film is called the space factor (SF), and the thickness (t) measured by a micrometer or the like. On the other hand, the ratio of the thickness (w) calculated from the weight of the film is represented by SF = [(t−w) ÷ t] × 100.

For example, when the SF value is large, the surface irregularities are large. Here, the SF value of the single-sided haze PPF obtained by the inflation method is kept constant at about 8.5 to 10%, and the degree of unevenness on the surface at this time is determined by the surface roughness (R
As shown in a), Ra = 0.1 for a film having a thickness of 9 μm.
6, and as the film becomes thicker, the value becomes larger, and Ra = 0.72 for a film having a thickness of 30 μm. At this time, the value of the back surface Ra of the film is 50 to 60% of the Ra of the front surface, and the back surface is in a state where there are not as many irregularities as the front surface as shown in FIG. R of the surface when the SF value is 10% in a single-sided haze film with a thickness of 15 μm
a is 0.22, and Ra on the back surface is 0.14. Also, S
When the F value increases to 15%, the surface Ra is 0.44,
Ra on the back surface is 0.32, and the unevenness is large on both the front surface and the back surface, and the haze value also increases in proportion to the SF value.
In this case, the ratio of Ra on the front surface to Ra on the front surface is 75%.
If it is above, the unevenness | corrugation will be large and will increase in both a front surface and a back surface. Such a film is called a double-sided haze film.

In the tenter method, since the PPF is manufactured in a flat plate shape rather than a tubular shape, both sides of the PPF are at the same temperature, and haze is likely to occur on both sides. The double-sided haze product has excellent oil permeability between the films and into the PPF-aluminum foil, but since the number of establishments where the recessed part on the front surface and the recessed part on the back surface are coincident with each other increases, the withstand voltage performance is not only inferior to that of the one-sided haze PPF, but also as oil Even in the combination, the improvement in withstand voltage cannot be expected for the reason described later.

The tenter method can also be used to produce a single-sided haze film by appropriately adjusting the cooling rates on both sides of the film. However, the PPF produced by the tenter method is the PP produced by the inflation method.
Compared with F, the degree of heat shrinkage and the degree of swelling with oil are small. It is necessary that the thickness of PPF and the rate of change in the length and width when impregnated with oil for condensers fall within the ranges described below, but the tenter method has a small shrinkage rate due to heating, and the overall size with swelling due to oil added. The rate of change is greater in the vertical and horizontal directions and smaller in the thickness than in the inflation method. That is, when aging is carried out in the oil for condensers, there is a disadvantage that the dimensional change rates of length and width and thickness exceed the range of the present invention.

On the other hand, when a capacitor element is made of a film having a smooth surface, there are few gaps where oil permeates between the films and between the PPF and the aluminum foil, so that bubbles and the like remain and the electric charge is locally concentrated due to the residual. It happens and leads to dielectric breakdown. Therefore, in general, sandblasting, etching, a combination of rolling and embossing,
Or same or different film with rough surface and PPF
PPF with a smooth surface by laminating with
Is being roughened. However, when the roughening method or the method using the laminating step is adopted, deterioration of the withstand voltage performance cannot be avoided due to mixing of impurities, damage to the PPF, and the like. Further, when different kinds of films are stuck together, a difference occurs in the distribution ratio of the voltage between the different films, and the withstand voltage performance deteriorates.

From these points, the PPF produced by the above inflation method should utilize only the physical crystal structure change of polypropylene in the resin film forming step to make the surface rough at the same time as the film formation. Therefore, the withstand voltage characteristic of PPF can be obtained without impairing it.

Therefore, as described above, the PPF includes a plain film having a smooth surface and a haze film having minute unevenness, and the haze film is a double-sided hazy film having both surfaces having the same degree of unevenness. There is a single-sided haze film in which only one surface is smaller than the other surface and has gentle unevenness.
The PF is preferably a single-sided haze film.

The oil-immersed film capacitor of the present invention is manufactured by winding the above polypropylene film with an aluminum foil, or by winding a polypropylene film having a vapor deposited metal film of aluminum, zinc, aluminum-zinc alloy or the like. It can be obtained by forming it and impregnating it with oil for capacitors.

The capacitor oil serves to complement the withstand voltage of the capacitor element. The oil for capacitors is basically an electrically insulating oil,
The standard is shown at -2320. These are exemplified by mineral oil, alkylbenzene, polybutene, alkylnaphthene, alkyldiphenylethane, and silicone oil.
Other than JIS, plant-based oils and other synthetic hydrocarbon-based oils are used. Examples of plant-based condenser oils include soybean oil, rapeseed oil, cottonseed oil, castor oil, and the like, and synthetic hydrocarbon-based oils include long-chain alcohols, phosphate esters, sulfonic oils, and the like. These may be used alone or in combination of two or more.

The characteristics required for the oil for capacitors are that no ionic impurities are mixed in, the dielectric loss tangent is small,
It is excellent in H ₂ gas absorption and has a high withstand voltage. Aromatic synthetic oils have been frequently used for many years to satisfy these requirements, and PXE or SAS40 (both manufactured by Nippon Petrochemical Co., Ltd.) are known as typical examples. PXE contains phenylxylylethane as a main component, and SAS40 contains m-benzyltoluene (32%) and o-benzyltoluene (5%).
%), P-benzyltoluene (22%) and diphenylethane (38%). For the purpose of improving low temperature characteristics, diphenyltoluene in which a part of diphenylethane is replaced with dibenzyltoluene and phenylxylylmethane have been investigated, and these oils have particularly excellent H ₂ gas absorption.

In recent years, capacitors have tended to increase in size (capacity of a single unit increases). Therefore, particularly flammable oil,
The amount of PPF used is increasing. Therefore, the capacitor fire caused by dielectric breakdown is a big social problem. Although the route leading to the fire has not been clarified yet, the generation of H ₂ gas, which is thought to be generated by the abstraction of hydrogen atoms from hydrocarbon compounds at the start of the dielectric breakdown, has been confirmed, which is considered to be the main cause of the fire. There is. That is, when H ₂ gas is generated, that portion is ionized under the application of electricity, and corona discharge occurs. When this discharge continues, it is assumed that the PPF, which is an insulator, is sequentially eroded, eventually leading to damage to the capacitor and igniting H ₂ gas. Therefore, it is preferable to use a synthetic hydrocarbon condenser oil containing an aromatic ring as one having a high H ₂ gas absorption performance.

Thus, in the present invention, the rate of change in the thickness direction of the film is in the range of 3 to 15% due to the swelling of the film when the polypropylene film is impregnated with the oil for capacitors, and Is adjusted so that the rate of change due to swelling is 3% or less. That is, a film is assembled as a capacitor element, and a capacitor oil is filled, impregnated, and aged to manufacture a capacitor.In this process, the film shrinks due to temperature rise and swells due to the oil, especially during the aging process. The degree of swelling and the rate of change are determined, and as a result, a capacitor having an excellent life can be obtained.

Here, the rate of change in thickness due to swelling of PPF in oil is preferably 3 to 15%, particularly 5 to 13%. That is, as the rate of change in thickness increases, the breakdown voltage of the film rises significantly, but when the rate of change exceeds 15%, the capacity of the entire capacitor element increases due to swelling, so that the container is destroyed or It is not preferable because the capacitor element may be pressed even if it is not destroyed, causing physical damage to the PPF and deforming the aluminum foil. On the other hand, when the rate of change in thickness is less than 3%, the oil is not sufficiently permeated and impregnated into the film, which is not sufficient to compensate for the above defects and the withstand voltage is not improved.

The rate of change of PPF in the vertical and horizontal directions is 3%.
Although it is below, it is particularly preferably set to 2% or less. P
If the PF stretches or shrinks excessively in the vertical and horizontal directions, the PPF may have a moving scratch or wrinkles on the aluminum foil, which may cause a charge concentration phenomenon and reduce the reliability of the capacitor. Therefore, it is desirable that the rate of change in the vertical and horizontal directions is small.

To further elaborate on this point, the element of the high-voltage condenser is usually made by alternately winding aluminum foil on a plurality of (2 to 3) PPFs. This is put in a container and a lid is closed, and the oil inlet and the vacuum suction port are left and sealed. By sufficiently vacuuming and removing water that adversely affects the dielectric loss tangent and then injecting oil,
Capacitors are manufactured. In order to fill the oil between the films or between the film and the aluminum foil reliably, quickly, and without air traps, it is preferable that the viscosity of the oil is low, so the oil injection is usually performed under heating / decompression. . After filling with oil, by keeping it under heating, the capacitor element is sufficiently impregnated with oil,
The swelling into the film, which is a main constituent of the present invention, is achieved by allowing the material to spread, and then maintaining it at a predetermined temperature for a predetermined time. This is called an aging step, and is a step that greatly affects the film characteristics described above, particularly the relationship between the degree of swelling and the withstand voltage, in the capacitor manufacturing process.

The PPF expands or contracts (mainly contracts) only by heating, but in the heated oil to which oil is added, the oil permeates into the film and swells. The former depends on the PPF molding method, and the latter depends on the mutual relationship between the film and oil properties in the aging step.

That is, when the film is put in oil and heated, the film becomes thick due to contraction due to heating and swelling due to penetration of oil. The withstand voltage of the film increases in proportion to the increase in thickness. The heat shrinkage of the film depends on the ambient temperature where the film is placed, but the temperature in the capacitor manufacturing process is 100 ° C. or less at the maximum. At this time, since the heat shrinkage ratio due to only heat is 3% or less, the film becomes thick due to the shrinkage, but the increase in withstand voltage is not remarkable because the ratio is small. Therefore, thermal contraction due to simple heating does not pose a big problem to the withstand voltage. On the other hand, swelling occurs as the oil penetrates into the film. Oil is poured into a container containing an element made of PPF and aluminum foil, the element is impregnated with the oil, and then aging is performed, but this aging step has a great influence on the swelling degree of the film, and finally the condenser. Will determine the lifespan of. That is, the conditions for obtaining the preferred degree of swelling in the thickness direction and the vertical and horizontal directions are:
The temperature and time of the impregnation process and the aging process are important factors. The temperature of the impregnation process is affected by the reduced pressure,
The temperature is in the range of 40 to 70 ° C. If the temperature is lower than 40 ° C., the viscosity of the oil is high, so that the impregnation requires a long time, and if the temperature exceeds 70 ° C., the vapor pressure of the oil becomes high and it becomes difficult to maintain the vacuum system, which is economically disadvantageous. is there.

The aging temperature is 60 to 95 ° C., preferably 70 to 90 ° C. If the temperature is lower than 60 ° C., it takes a lot of time to reach the predetermined degree of swelling, and if it exceeds 95 ° C., it becomes difficult to adjust the degree of swelling. The aging time varies depending on the capacity of the condenser and the properties of the oil, but it is usually several hours
It can be a few days.

When manufacturing the device, the PPF and the aluminum foil are wound to form the device. However, if the device is too stiff in this step, the device is rolled and squeezed due to the shrinkage and swelling of the film in the impregnation process. It becomes the state of. It is considered that the penetration of oil between the wound inner layers of the element becomes difficult and a portion (air pocket) where the element surface does not get wet with oil is generated. The voltage is concentrated in such air pockets, corona discharge occurs, and the PPF is destroyed. Although it is possible to loosely wind it as a measure to avoid this, in this case, winding deviation and winding wrinkles occur. In the wrinkle portion generated on the aluminum foil, the electric field strength becomes non-uniform, and excessive electrical stress is generated in the film, which may lead to dielectric breakdown. The same problem occurs when the film has pinholes or microscopic pores exist in the film. Therefore, it is preferable that the degree of the above-mentioned winding is performed in consideration of this point.

[0039]

According to the present invention, by using a PPF manufactured so as to be suitable for an oil-immersed film capacitor, the element made of the film is put in a container, and the capacitor oil is impregnated and aged. By controlling the conditions at that time, a capacitor having a large dielectric breakdown voltage can be manufactured. Further, since excessive swelling of PPF due to oil can be avoided, it is possible to suppress dielectric breakdown and container breakdown due to thermal expansion of the polypropylene film, and it is possible to obtain an oil-immersed film capacitor having an excellent life.

[0040]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] Melt flow value 3.7 g / 1
0 minutes, isotacticity 95.7%, chlorine content 6
A polypropylene resin having an ash content of 20 ppm and an ash content of 20 ppm (antioxidant (Irganox) 950 ppm) was used to produce a single-sided haze PPF having a thickness of 15 μm by the inflation method so as to have the following properties. Among the characteristic values, the haze value was 35%, the SF value was 10.6%, and the Ra of the front surface and the back surface were 0.27 μm and 0.14 μm, respectively. In addition, this film is used in the following method in PXE 80
As a result of obtaining the change rates of the vertical and horizontal directions and the thickness after immersion at 24 ° C. for 24 hours, -0.5% (minus shrinkage),
It was 0.0% and + 6.3% (plus means elongation or swelling).

Two sheets of this film and one sheet of aluminum foil (manufactured by Toyo Aluminum Co., Ltd.) having a thickness of 7 μm were wound as a pair to prepare a capacitor element of 2.2 μF. A plurality of these elements are pressed and fixed with a band, put in a container, degassed under vacuum at 80 ° C for 30 hours, then cooled to 50 ° C, and used as insulating oil according to JIS C-2320, type 5 oil (Japan Petroleum PXE manufactured by Kagaku Co., Ltd. was charged for 3 hours.

Then, after carrying out 7 cycles of a cycle of vacuum (decompression) and normal pressure (decompression) at 50 ° C. for 3 hours / cycle, the system is heated to 80 ° C. under atmospheric pressure and kept at this temperature for 4 hours. Then, the device was aged. After that, the element was disassembled, and the degree of impregnation of the PXE oil into the inner layer of the element was observed. As a result, it was confirmed that the element was evenly distributed over the entire surface.

When the withstand voltage (AC) of this film was measured, the minimum was 9,210 V and the maximum was 13,110.
V, the average was 9,700 V (initial value 7,650 V).

Measurement of Dimensional Change Rate The swelling degree of a polypropylene film is usually measured by immersing the film in oil at a predetermined temperature for a predetermined time and measuring the weight change rate. According to this method, Since it is determined only from the weight change before and after the immersion, it is not possible to obtain information on the behavior of the dimensional change of the PPF when the capacitor element is used. Therefore, the present inventors decided to capture the process of swelling that occurs at the same time as contraction by the change in the thickness direction and the change in the vertical and horizontal directions. Further, when measuring the change in the thickness of the film, since the film is extremely thin and lacks in accuracy, the measurement was performed using PPF in which a large number of sheets were stacked.

Specifically, the dimensional change rate in the vertical and horizontal directions is determined by marking the film with a mark at 100 mm intervals.
After the treatment under the conditions of temperature and time, a method of reading the change in the reference point was adopted. Further, the change in the thickness direction was measured in a state where 10 films were stacked because the film itself was very thin.

[Examples 2 to 5, Comparative Example 1] A single-sided haze PPF (Shin-Etsu PP film 15R, manufactured by Shin-Etsu Film Co., Ltd.) having a thickness of 18 μm and a haze value of 44% obtained by an inflation method was heated at 60 ° C. under atmospheric pressure ( Example 2), 80
After dipping for 24 hours in PXE oil at 0 ° C. (Example 3) and 100 ° C. (Comparative Example 1), the elongation rate (swelling rate) of the PPF in the longitudinal direction, the lateral direction, and the thickness direction was measured. The results are shown in Table 1.

The breakdown voltage values of this film are 10,703 V at 60 ° C. and 11,558 V at 80 ° C., which are 7% and 1% of the initial value of 10,010 V, respectively.
It showed an increase in withstand voltage of 5%. Further, in Comparative Example 1, the rate of change in thickness was as large as about 30%, and it was impossible to apply it to a capacitor.

The rate of change and the withstand voltage were measured in the same manner as in Example 2 except that rapeseed oil (Example 4) and dioctyl phthalate (DOP) (Example 5) were used as oils. The results are also shown in Table 1.

[0050]

[Table 1]

[Examples 6 and 7] One-sided haze PPF (slit width 10 obtained by the inflation method shown in Table 2
0 mm) and a 7 μm thick aluminum foil (manufactured by Toyo Aluminum Co., Ltd.) were used as one electrode to prepare a capacitor element having a capacity before impregnation of 0.93 μF.

[0052]

[Table 2]

The device was kept under a vacuum of 10 ^-2 Torr, dried at 90 ° C for 24 hours, and then cooled to 60 ° C. Then, JIS was separately degassed in vacuum and adjusted to 60 ℃
C-2320 type 5 oil was vacuum impregnated. Subsequently, the same temperature was maintained for 30 hours to stabilize the device.

The system was returned to atmospheric pressure, heated to 80 ° C., and kept at the same temperature for 4 hours for aging. After cooling to room temperature, the container was sealed to manufacture a test model capacitor (rated voltage 1900V). The results of measuring the electrostatic capacitance of this product before and after aging are shown in Table 3.

[0055]

[Table 3]

The voltage shown in Table 4 was continuously applied to the model capacitor at a temperature of 60 ° C. from a power source of 60 Hz, and the condition after 200 days was observed at each voltage. The results are shown in Table 4.

[0057]

[Table 4]

From the results shown in Table 4, it can be seen that the oil-immersed film capacitor of the present invention can be operated for a long time even at an applied voltage that greatly exceeds the rated voltage.

[Comparative Examples 2 to 4] Capacitor elements prepared by using the three types of PPF shown in Table 5 having different film surface characteristics were impregnated with oil in the same manner as in Example 1, and the degree of oil impregnation was observed. However, in Comparative Example 2, the oil did not spread all over the film.

[0060]

[Table 5]

Then, these films were subjected to a film behavior test at 80 ° C. in the same manner as in Example 1. The results are shown in Table 6, which were all positive (elongate or swell).

[0062]

[Table 6]

Also, model capacitors were prepared in the same manner as in Examples 6 and 7 and subjected to a long-term life test. The results are shown in Table 7.

[0064]

[Table 7]

From the above results, it can be seen that the plane and haze films formed by the tenter method have a large vertical and horizontal change rate (elongation) and a small thickness change rate in the combination of the temperature and the oil during the production of the capacitor. On the other hand, it can be understood that the inflation haze film obtained by the method of the present inventors exhibits appropriate shrinkage and swelling in the opposite. That is, it is recognized that the PPF obtained by the inflation method contracts in the vertical and horizontal directions in combination with oil and the thickness direction increases with temperature, resulting in an improvement in withstand voltage and a long-life capacitor.

[Embodiment 8] A single-sided haze PP having a thickness of 16 μm and a haze value of 37% obtained by an inflation method.
F is a vapor deposition machine (TYPE A-650 manufactured by Leibold in West Germany).
B 2 KAZS) was used to deposit an alloy of Zn—Al (Al content 7%) to obtain a metallized film having the following characteristics. Film width 150 mm, margin width 5.0 mm, active part resistance 25 Ω / □, heavy edge part resistance 4 Ω / □.

Two vapor-deposited films were wound as a pair (so that the edges are on the opposite side) to form an element, and Zn was metallikoned to form an electrode, and then rapeseed oil (white clay treated product; tan δ0). 0.06) and 32.
A 6 μF oil immersion metallized film capacitor was produced. A DC voltage of 5,500 V was applied to this product, and charging / discharging (charging 60 seconds, discharging 60 seconds) was repeated 500 times. As a result, no reduction in capacity was observed.

On the other hand, an oil-immersed metallized film capacitor (capacity: 34 μF) was manufactured using a tenter method PPF film (haze value: 0.3%, film thickness: 16 μm), and the same test as above was conducted. After a large number of shots (charging / discharging), a large decrease in capacitance of 22.5 μF was recognized.

[Brief description of drawings]

FIG. 1 is an explanatory view of a concavo-convex state on a front surface and a back surface of a haze film according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Uesaka Kenichi Uesaka 2-1-5 Kitafu, Fukui Prefecture Shinetsu Film Co., Ltd. (72) Inventor Akira Hayashida 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa Shin-Etsu Chemical Co., Ltd. Corporate Research Center

Claims (4)

[Claims] 1. An oil-immersed film capacitor obtained by impregnating an element formed by winding a polypropylene film and an aluminum foil or winding a polypropylene film having a metal evaporated film formed thereon with a capacitor oil. The polypropylene film has a haze value of 10 to 6 on the surface irregularities.
0%, the degree of crystallinity is 60 to 80%, and when the polypropylene film is impregnated with oil for capacitors, the rate of change of the polypropylene film is 3 to 15% in the thickness direction of the film. A film for an oil-immersed condenser, which is adjusted to 3% or less in each direction. 2. The film for oil-immersed capacitors according to claim 1, wherein the polypropylene film is a single-sided haze film formed by an inflation method. 3. A polypropylene film having a melt flow value of 1 to 10 g / 10 minutes and an isotacticity of 93%.
Above, 500-1500ppm for polypropylene resin with chlorine content of 10ppm or less and ash content of 30ppm or less
The film for oil-immersed condensers according to claim 1 or 2, which is formed by heat-molding the polypropylene composition containing the antioxidant. 4. An oil-immersed film capacitor using the film for oil-immersed capacitor according to claim 1, 2, or 3.