JP2586006B2 - Oil immersion capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oil immersion capacitor using a metal deposition layer as an electrode.

[Conventional technology]

BACKGROUND ART Conventionally, an oil immersion capacitor using a plastic film, particularly a polypropylene film as a dielectric, and using a metal deposited on the film as an electrode has been known (for example, JP-A-59-39017).

[Problems to be solved by the invention]

However, in such a conventional technique, although the impregnating property of the electrical insulating oil is improved, when the dielectric material swells significantly by changing the oil type according to the required characteristics of the capacitor,
Alternatively, there has been a problem that when the dielectric material swells significantly due to long-term use in a high-temperature state, cracks occur in the metal deposited film formed as an electrode.

The present invention eliminates the problems of the prior art, that is, the life when dioctyl phthalate or diisononyl phthalate, etc., which have conventionally been used as an electrical insulating oil of a fully impregnated vapor-deposited polypropylene film capacitor, are used. It is an object of the present invention to provide an oil immersion capacitor that is long and hardly causes cracks in a metal deposition layer even when a dielectric expands.

[Means for solving the problem]

The present invention relates to an oil immersion capacitor in which a film is a dielectric mainly composed of polypropylene, and a metal layer deposited on at least one surface of the film is an electrode, wherein the film has a surface length index on the deposited metal layer side. 1-7 is a rough surface, moreover, the film, oil-immersion condenser and wherein the M value obtained by the following formula is 3-50 [g / 100in ² /24hr/0.001in].

M = (- log P) × L However, L: a surface length index P: is the oil permeation coefficient [g / 100in ² /24hr/0.001in] that the gist.

The polypropylene-based film of the present invention is a film obtained by roughening at least one surface by the following method. That is, inorganic or organic particles are added to polypropylene, cast and biaxially stretched, those having surface irregularities caused by a change in form from β crystals to α crystals, and at least two components mixed in the surface layer. It has a rough surface caused by a difference in melt tension.

To describe a specific example of the film of the present invention, for example, the isotacticity (hereinafter abbreviated as II) is 96 to 99.5%.
A film obtained by roughening a polypropylene homopolymer by shape transformation, or a polypropylene (A) having II of 96 to 99.6% and a random copolymer of ethylene and propylene having an ethylene content of 0.7 to 2.5% by weight of 70 to 85% by weight And an ethylene-propylene block copolymer (B) containing 85 to 95% of II obtained by polymerizing 15 to 30% by weight of ethylene.
A typical example is an axially stretched film. In the latter case, the thickness of the polypropylene (A) and the thickness of the copolymer (B) are 80 / 20-95 / in the polymerization ratio (A / B). A value of 5 is preferred. In this film, other polymers may be copolymerized or mixed as long as the effects of the present invention are not impaired, but the content of the polypropylene in the film is preferably 80% by weight or more. Further, it is preferable to use a film in which the wetting tension is adjusted to 40 to 46 dyne / cm by corona discharge treatment on the rough side.

The film of the present invention may be either surface-roughened or both surfaces may be roughened, or both may be roughened, but a composite roughened film is better than a single-layer roughened film. preferable.

On the metal deposition side of the film of the present invention, the surface length index is 1
７7, preferably 2-5. Further, M value obtained by the following formula is 3~50g / 100in ² /24hr/0.001i
Must be n.

M = (− log P) × L where L: surface length index P: penetration coefficient [g / 100in ² /24hr/0.001in] The surface length index L is a unit of film obtained by the following equation It is an approximate index of the ratio of the length of the surface to be deposited to the length.

L = 100H × N / l, where H: average height of projections (mm) N: number of projections in length l (pieces / mm) l: length of film (mm) average height of projections , The number measurement method is as described below.

When the above surface length index (hereinafter simply referred to as L value) is less than 1, the oil impregnating property and the stability of the deposited film are inferior.

The permeation coefficient P is a coefficient derived by the following equation, and a value of 23 ° C. is used in the present invention.

log P = K-Rπ However, P: permeability coefficient [g / 100in ² /24hr/0.001in] K: temperature correction constant [g / 100in ² /24hr/0.001in] R: Plastic characteristic value [g / 100in ² / 24hr / 0.001in] π: Value determined by molecule or group The above formula is described in PLASTICS, MAY1965, and P has a good correlation with membrane stability and is preferably less than 0.1, more preferably 0.1 or more Is unfavorable because cracks in the deposited film are likely to occur. In the case of polypropylene, the temperature correction constant K has the following relationship with temperature.

K = 0.0286 t + 3.532 where, t: temperature [° C.] (23 ° C. is used in the present invention) The plastic characteristic value R is 0.26 in the case of polypropylene. π is called PERMACHOR VALUE and is determined by molecule or group. The main ones are shown in Table 1.

In the case of the film of the present invention, the values of K and R are the same as those of the polypropylene.

In the present invention, the L, M value calculated based on P (unit: g / 100in ² /24hr/0.001in) is of less than 3, tends to occur a deposited film cracks, those exceeding 50 The M value is 3 because the impregnating property deteriorates due to the high viscosity.
Must be ~ 50.

The thickness of the film in the present invention is not particularly limited, but is preferably 6 to 30 μm. Further, the film in the present invention is preferably biaxially stretched in the case of a single layer,
In the case of lamination, it is preferable that at least the polypropylene (A) layer is biaxially stretched.

The dielectric of the present invention may be only the above film,
It may be a laminate with another film or paper.

The metal layer deposited according to the present invention is a layer formed of various metals, preferably Zn or Al, deposited by a known method. The thickness of the layer is not particularly limited, but is preferably 100 to 300 °. When the thickness is less than 100 mm, the film strength becomes weak, and when the thickness exceeds 300 mm, the self-healing property deteriorates, which is not preferable.

The electrical insulating oil used in the present invention may be any as long as it has the above-mentioned insulating properties, and may be a mixture thereof, but it is necessary to select an oil having an M value within a predetermined range. Preferred insulating oils include dioctyl phthalate, tricresyl phosphate, vegetable oil (a mixture of fatty acids such as behenic acid and oleic acid).

Next, a method of manufacturing a film on which a metal vapor-deposited layer of the present invention is formed and an oil immersion capacitor using the film will be described.
An example will be described.

First, a film is manufactured as follows. II is 98 ~
99.6% of PP was fed to an extruder heated to 240 to 280 ° C and dissolved.

On the other hand, an ethylene-propylene block copolymer having an 85-95% II obtained by polymerizing 15-30% by weight of ethylene to 70-85% by weight of an ethylene-propylene random copolymer having an ethylene content of 0.7-2.5% by weight is 240-270%. Dissolved at ° C.

These two polymers were extruded from one T-die into a sheet having a size of 400 to 800 µm, wound around a chill roll having a surface temperature of 20 to 40 ° C, and solidified by cooling. 130 to 155
After stretching 4.0 to 5.5 times in the length direction at a temperature of ° C.
After stretching at a temperature of 155 to 175 ° C in a perpendicular direction at a temperature of 7.0 to 11.0 times 145
Heat treatment at a temperature of ~ 160 ° C while slightly relaxing to obtain a film having a rough surface formed on the copolymer layer side, and performing corona discharge treatment on the rough surface side of this film to reduce the surface wetting tension to 40 ~.
After adjusting to 46 dyne / cm, wind up.

The film may be made as follows.

II-96-99.5% PP homopolymer with a small amount of organic nucleating agent added and melted at an extrusion temperature of 250-270 ° C, 80-90 ° C
After contacting the heated chill roll to solidify it into a sheet of 400 to 800 μm and relaxing and heat-treating at a temperature of 150 to 160 ° C. to obtain a roughened film, the film surface is subjected to 40 to 46 by corona discharge.
Take up dyne / cm wetting tension and wind.

Al or Zn is adhered to the rough surface side of the film formed as described above in a thickness of 100 to 300 ° to obtain a film on which a metal layer is formed.

Next, two films on which the metal layer is formed are stacked and wound to obtain an element capacitor. Metallicon of Zn, Al, Pb, Sn or their alloys on both ends of this element capacitor, and after attaching terminals on both sides of the metallikon part,
Place in a container and perform vacuum drying.Insulated oil impregnated by vacuum or adsorption, etc., into the unimpregnated condenser thus formed, at 50 to 90 ° C, at a pressure of 0.1 mmHg abs or less, for 24 hours or more. After impregnation, sealing is performed in oil to obtain an oil immersion condenser.

The method for measuring and evaluating the characteristic values of the present invention are as follows.

(1) Number of protrusions, height of protrusions The surface of the film is measured under the following conditions using a three-dimensional universal surface shape measuring instrument MODEL SE-3FKS with an analyzer of Kosaka Laboratory Co., Ltd.

Measuring length: 1mm Vertical magnification: 5000 times Horizontal magnification: 200 times Feeding speed: 0.1mm / sec Filter: 0.25mm Measurement interval: 10μ Number of measurements: 20 Height of the peak from the number of peaks Pc-1 obtained under the above conditions The number of protrusions of 0.2 μ or more is called the number of protrusions. Here, Pc-1 refers to the number of protrusions having a height of 0.2 μ or more from the center line of the irregularities on the surface. The average height H is determined by incrementing the projection height by 0.2 μ
~ 0.4μ, all the center value, for example, counted as a height of 0.3μ, the number of protrusions corresponding to the center value divided by the total number of protrusions measured under the above conditions, It refers to the sum of values multiplied by the height (center value) of the protrusion.

(2) Membrane resistance change It was measured by the following method using a portal tuple and a Hoytstone bridge manufactured by Yokogawa Electric Corporation. Cut one side of the deposited film to 25cm and the other to 3cm length.
Assuming that the resistance of 0 cm is R ₁ and the middle point thereof, that is, the resistance of 10 cm is R ₂ , the resistance value _RT of the deposition surface is R _T (Ω / □) = [(R ₁ −R ₂ ) / (20−10) ] × W where W is determined by the film width (here, 3 cm). Similarly, the film resistance after the oil immersion treatment was measured, and the value obtained by dividing the film resistance after the oil immersion treatment by the film resistance before the oil immersion treatment was defined as the film resistance change. The measurement was performed three times, and the average value was obtained.

(3) Stability of evaporated film in oil 80% in insulating oil such as phenylxylylethane, dioctyl phthalate, tricresyl phosphate, vegetable oil (a mixture of fatty acids such as behenic acid and oleic acid), alkylbenzene and monoisopropyl biphenyl. ~ 100 ℃, 2
The deposited film was immersed for 4 to 72 hours, and examined by observing the rate of change in the film resistance after immersion and the change in the deposited film using a microscope. The criteria for the stability evaluation of the deposited film are:
An enlarged photograph having a film resistance change rate of 10% or less and no crack in a 125-times magnification was regarded as stable.

〔Example〕

 Next, embodiments of the present invention will be described based on examples.

Examples 1, 2 and Comparative Example 1 At an extruder temperature of 250 ° C., a 99.2% PP homopolymer was melted and an ethylene propylene random copolymer having an ethylene content of 1.2% by weight was polymerized in a blending ratio of 85% by weight and 15% by weight of ethylene. A block copolymer of ethylene propylene (92% II) obtained by melting was melted at an extruder temperature of 250 ° C., and both melts were extruded into a sheet form from a T-die having a width of 660 mm and a gap of 1 mm, and then heated at 30 ° C. After being cooled and solidified by a chill roll cooled at a temperature of 5.0 ° C., the film is stretched 5.0 times in the length direction at a temperature of 140 ° C., and at a right angle, 175 ° C. in Example 1;
Was stretched 9.0-fold at a temperature of 156 ° C., and then subjected to a relaxation heat treatment at 155 ° C., and then wound up by corona discharge to a wetting tension of 43 dyne / cm on the rough side. After slitting this film,
Al having a thickness of 150 to 200 ° was vacuum-deposited on the rough surface side.

Comparative Example 1 was prepared in the same manner as described above, and the stretching temperature in the perpendicular direction was 149 ° C. Table 2 shows the characteristic values and M values of the metal-deposited polypropylene film obtained by the above method.

 In addition, the calculation example of the M value of Table 2 is shown.

In the case of phenylxylylethane and an L value of 4.5, when π is determined from Table 1, a phenyl group of 5.4 × 2 = 10.8 carbon group 1.0 × 4 = 4.0 branches 2.0 × 1 = 2.0 π = 16.8 is obtained. At 23 ° C, the K value was 4.2 and R was 0.26.
By substituting into the equation for obtaining, log P = 4.2−0.26 × 16.8 = −0.168 = −0.17 is obtained.

 From this value and L value, M = −log P × L = 0.17 × 4.5 = 0.765 = 0.8 is obtained.

All the M values in Table 2 were determined in this way.

The capacitors having the respective M values shown in Table 2 were immersed in insulating oil at 80 ° C. for 24 hours, and the resistance change of the metal deposited film was measured. The results are shown in FIG. As is clear from the figure,
Those having an M value of 3 or more do not cause any change in the film resistance, indicating that the film has excellent film stability. In the figure, ND indicates that the rate of change was too large to be measured. In the figure, ○ indicates Example 1, □ indicates Example 2, and Δ indicates Comparative Example 1.

Examples of the surface state of the metal-deposited film used in the measurement of the change in resistance of the metal-deposited film are shown in FIGS. (1) and (3) use vegetable oil, (2) and (4) use phenylxylylethane, and those having L of 0.5 cause cracks in the deposited film even in vegetable oil having a relatively small permeability coefficient. An insulating oil having an extremely small P, that is, an insulating oil composed of macromolecules, does not cause cracks in a deposited film even when combined with an oil having a small L. (Figure 2 shows a photograph of the deposited film taken at 125x magnification and sketched it).

Example 3 and Comparative Example 2 At an extrusion temperature of 260 ° C., 97% of II containing 0.03% of quinacridone was added.
5% PP homopolymer is melted and the melt is 620m wide.
m, extruded into a sheet from a T-die with a gap of 1.2 mm, contacted with a chill roll heated to 90 ° C., and cooled and solidified a 750 μ sheet, and then at a temperature of 155 ° C., 5.0 times in the length direction. At the same time as stretching, stretching was performed 10.0 times at a temperature of 165 ° C. at a temperature of 165 ° C., and then subjected to a relaxation heat treatment at 160 ° C., and then the film surface on the non-contact surface side of the chill roll was wound by corona discharge to a null tension of 43 dyne / cm. . After slitting the film, Al having a thickness of 150 to 200 ° was vacuum-deposited.

In Comparative Example 2, the chill roll temperature was changed to 50 ° C. with II of 97.5%, and the other conditions were the same as in the above method. Table 3 shows the L value and the M value of the metal-deposited polypropylene film obtained by the above method.

These metallized films were prepared at 80 ° C for 24 hours.
As a result of the oil resistance test, the results indicated by ３, Δ, and × in Table 3 were obtained. In Table 3, ○ indicates that the film did not undergo any film change or film cracking, Δ indicates that the film had almost the same state as (1) in FIG. 2, and X indicates that the film cracked violently as shown in (2) in FIG. The results indicate that the resulting film resistance cannot be measured. As is clear from the above, no matter how the PP film is produced, those having an M value of 3 or more have excellent film stability in oil,
It can be seen that the smaller the value, the more easily the film cracks.

[Effect of the Invention] The present invention, as described above, the surface length index of the dielectric,
Further, since the M value determined from the dielectric and the insulating oil was set to a specific value, the range of applicable oil types was widened, and an oil immersion capacitor in which cracks were unlikely to occur in the metal deposition layer could be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the M value and the resistance of a metal deposition film, FIG.
The figure is a diagram showing the state of occurrence of cracks in the metal deposition film.

Claims (1)

(57) [Claims] 1. An oil immersion capacitor comprising a polypropylene-based film as a dielectric and a metal layer deposited on at least one side of the film as an electrode, wherein the film has a surface length on the side of the deposited metal layer. index is rough 1-7, moreover, the film, oil-immersion condenser and wherein the M value obtained by the following formula is 3-50 [g / 100in ² /24hr/0.001in] . M = (-log P) × L where L: surface length index P: oil permeability coefficient [g / 100in ² /24hr/0.001in]