JP2002164262A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrolytic capacitor from producing a gas inside raising the inner pressure of the capacitor containing laminated anode foils and cathode foils having an anode terminal and an cathode terminal, each of which at the end extends from a container containing an electrolyte. SOLUTION: A permeable film fullfils the three conditions (1) the contact angle of ethylene glycol is 85 deg. or larger, (2) the contact angle of water is 105 deg. or larger and (3) the hydrogen permeability is 5.0×10-6 mol.m-2.s-1.Pa-1 or larger. This film is mounted on an electrolytic capacitor, so that hydrogen gas produced in a container of the capacitor permeates the film and is exhausted out of the capacitor, this avoid damaging or breaking the container due to the inner pressure increase and losing the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel electrolytic capacitor capable of discharging hydrogen gas generated by electrolysis inside a container of an electrolytic capacitor to the outside of the container by using a hydrogen gas permeable membrane. The electrolytic capacitor of the present invention is an excellent one that can sufficiently extend the life of a conventionally known electrolytic capacitor that has been damaged by the pressure of hydrogen gas generated inside a sealed container, The capacitor can be suitably used for various applications requiring long-term life and safety of the capacitor.

[0002]

2. Description of the Related Art An electrolytic capacitor element in which an anode foil and a cathode foil are superimposed at a proper interval in a container,
A conventionally known electrolytic capacitor having an anode terminal and a cathode terminal provided on the element and having one end protruding outside the container, and an electrolytic solution is provided. As a result, the electrolytic solution undergoes electrolysis to generate mainly hydrogen gas, and the internal pressure of the electrolytic capacitor gradually increases, and finally the pressure of the hydrogen gas causes the container to be destroyed.

For this reason, the leakage current has been reduced by adding a hydrogen gas absorbent to the electrolyte or increasing the thickness of the anodic oxide film more than necessary. In addition, a porous ceramic plate is attached to a part of the container to discharge hydrogen gas to the outside, or a concave mark is formed on a part of the sealed container to reduce the influence on the surroundings due to damage of the electrolytic capacitor. The function of the opening plate is provided, or a thin portion is formed in the sealing member of the sealed container to operate it.

In Japanese Patent Application Laid-Open No. 62-112314 or Japanese Patent Application Laid-Open No. 62-272515, hydrogen gas generated in an electrolytic capacitor is formed by using a hollow fiber permeable membrane made of polyimide, Teflon (registered trademark) or polypropylene. A method of using the gas to discharge it to the outside has been proposed, but the effect of sufficiently discharging hydrogen gas to prevent the internal pressure from rising is still insufficient. In addition, since the electrolytic solution permeates from the capacitor as vapor, there is a major drawback in that the composition of the internal electrolytic solution changes and the characteristics of the capacitor change.

In recent years, hybrid vehicles and fuel cell vehicles have attracted attention from the viewpoint of environmental problems. Electric vehicles, including these, are always equipped with electrolytic capacitors. In automotive applications, electrolytic capacitors are used under more severe conditions. Under severe conditions, hydrogen is easily generated, and components of the electrolytic solution are easily evaporated. Therefore, a more advanced hydrogen permeable membrane is required, but cannot be achieved by conventional techniques.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and there is a concern that the electrolytic capacitor may be damaged or ruptured mainly by the pressure of hydrogen gas generated during use of the electrolytic capacitor. It is an object of the present invention to provide an electrolytic capacitor which does not have an endurance, is durable for a long period of time, and has excellent safety.

[0007]

The present invention has the following arrangement to achieve the above object. "In an electrolytic capacitor having an anode foil and a cathode foil superimposed in a container, an anode terminal and a cathode terminal having one end protruding outside the container, and an electrolytic solution, the electrolytic capacitor is (1) ethylene glycol Has a contact angle of 8
5 conditions or more, (2) water contact angle is 105 degrees or more, and (3) hydrogen permeability is 5.0X10 ^-6 mol · m ^-2 · s ^-1 · Pa ^-1 or more. An electrolytic capacitor having a permeable membrane. The present inventors have found that (1) the contact angle of ethylene glycol is 85 ° or more, (2) the contact angle of water is 105 ° or more, and (3) the hydrogen permeability is 5.0 × 10 ⁻⁶ mol.
・ M- ²・ s ^-1・ Pa ^-1 or more, and succeeded in making a permeable membrane which has three conditions, and this membrane is made of ethylene glycol which is a component of the electrolytic solution of the aluminum electrolytic capacitor. The inventors have found that it is difficult to transmit vapor, and have reached the present invention.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrolytic capacitor of the present invention will be described below in detail.

[0009] The permeable membrane provided in the electrolytic capacitor of the present invention has (1) a contact angle of ethylene glycol of 85 ° or more, (2) a contact angle of water of 105 ° or more, and (3) a hydrogen permeability of (3). 5.0X10 ^-6 mol ・ m ^-2・ s ^-1・ Pa ^-1 or more 3
It is necessary to satisfy two conditions.

In the present invention, the place where the permeable membrane is mounted is not particularly limited. In general, under use conditions, the temperature of the electrode portion is higher than that of the case or the sealing plate, and the vapor of the electrolytic solution condenses on the case or the sealing plate and adheres.
If these electrolyte components condense to form a liquid film on the hydrogen permeable film, hydrogen permeation will be significantly reduced. The permeable membrane of the present invention has (1) a contact angle of ethylene glycol of 85 ° or more, and (2) a contact angle of water of 105 ° or more. Is difficult to form. Further, the permeable membrane of the present invention,
(3) Hydrogen permeability is extremely high at 5.0X10 ^-6 mol · m ^-2 · s ^-1 · Pa ^-1 or more, and significantly higher hydrogen permeability than the conventionally proposed hydrogen permeable membrane for electrolytic capacitors. Have.
Further, they found that a permeable membrane having these properties permeated ethylene vapor and water vapor much less than hydrogen, and found that it was useful as a hydrogen permeable membrane for aluminum electrolytic capacitors.

The contact angle of ethylene glycol can be measured by a droplet method using, for example, an apparatus such as CA-D type manufactured by Kyowa Interface Science Co., Ltd. The permeable membrane of the present invention must have a contact angle of ethylene glycol of 85 degrees or more, more preferably 88 degrees or more. A larger contact angle is preferred because it has a property of repelling ethylene glycol. The membrane having such properties maintains hydrogen permeation even in the presence of electrolyte vapor.

The contact angle of water can also be measured by a droplet method using a device such as a CA-D type manufactured by Kyowa Interface Science Co., Ltd., similarly to the case of ethylene glycol. In the permeable membrane of the present invention, it is essential that the contact angle of water is 105 degrees or more, preferably 110 degrees or more, and more preferably 115 degrees or more. A larger contact angle is preferable because it has a property of easily repelling water. The membrane having such properties maintains hydrogen permeation even in the presence of electrolyte vapor.

Furthermore, the permeable membrane of the present invention has a hydrogen permeability of 5.0X.
It is essential that it be at least 10 ^-6 mol · m ^-2 · s ^-1 · Pa ^-1 .
This is the hydrogen permeability at room temperature, which can be measured and determined as follows. Hydrogen gas at 2 atm is supplied to one of the 1 cm ² permeable membranes at room temperature, and the amount of gas permeating from the opposite side of the membrane is measured with a soap membrane flow meter. By using this method, the transmittance when 1 ml of hydrogen gas per second permeates is 4.5 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ .

Next, a method for producing the film of the present invention will be described. The film of the present invention is preferably made of a porous material.
This is because the porous material has a higher hydrogen permeability than the dense membrane. Although a dense polymer film, for example, a silicone film does permeate hydrogen, it permeates by a dissolution-diffusion mechanism, and therefore has a low transmittance per unit area. Generally, a hollow fiber is used to increase the surface area to increase the permeation amount. However, in the case of a hydrogen permeable membrane for an electrolytic capacitor, a flat membrane is easier to use. Therefore, it is difficult to increase the surface area. That is, it is preferable that the transmittance per area is large. For this reason, the porous material is preferable because hydrogen permeates through the pores and has low resistance for permeation and a large transmittance per area. The material constituting the porous material may be any of organic polymers, metals and ceramics, but is preferably made of ceramics from the viewpoint of heat resistance and chemical resistance. The type of ceramics is not particularly limited,
Silica, alumina, zirconia, titania, silicon carbide,
Silicon nitride and the like can be given. These ceramics are excellent in chemical resistance and are preferably used. In particular, an alumina porous membrane is widely used and inexpensive, and is particularly preferably used.

The pore size of the porous membrane is not particularly limited,
It is preferably 1 nm or more and 1 μm or less. If it is less than 1 nm, a large hydrogen permeability cannot be obtained, which is insufficient for a hydrogen permeable film for an electrolytic capacitor. When it is larger than 1 μm, the permeation of the electrolyte vapor increases, and the composition of the electrolyte changes during use, so that it is difficult to obtain stable performance. The method of controlling the pore diameter of the porous membrane is not particularly limited, but usually, a method of laminating a porous membrane having a small pore diameter on a porous membrane having a relatively large pore diameter is adopted. For example, in the case of a ceramic porous film, relatively large ceramic particles are molded by a pressure molding method or a sheet molding method, and heated to about 1000 ° C. to obtain a porous film having a large pore diameter. Thereafter, ceramic particles having a small particle diameter are laminated to reduce the pore diameter. The materials of the porous membrane to be laminated and the porous membrane having a large pore diameter serving as a base may be different. The lamination may be any number of layers. Since the uppermost layer is in direct contact with the electrolyte vapor, a material having corrosion resistance as described above is preferable. The pore diameter of the support can be measured with a mercury porosimeter.

The permeable membrane of the present invention must have a contact angle of at least a certain angle with water and ethylene glycol. In the case of an organic film, even if it is not particularly treated, some have such properties.For example, even a silicone rubber having hydrophobicity has a contact angle of water of 100 degrees and a contact angle of ethylene glycol of 80 degrees. And does not satisfy the conditions of the present invention. For example, a porous organic film having fluorine can be suitably used as the film of the present invention. In the case of a porous film made of ceramics or metal, since it generally does not fall within the range of the contact angle of the present invention as it is, it is necessary to perform some treatment to obtain the permeable film of the present invention. By treating with a silane coupling agent or the like, the permeable membrane of the present invention can be obtained. The silane coupling agent is an organosilicon compound having both a group having an affinity for an organic group and a hydrolyzable group (an alkoxyl group such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, and a halogen hydrogen). . Particularly preferably the compound represented by the formula X-Si-Y _3, X is a group of organic affinity, Y is a hydrolyzable group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group Alkoxy group, halogen, hydrogen, etc.). Y may be one type or multiple types. Y in silane coupling agent
Reacts with the OH groups on the surface of the porous membrane to form a bond with the porous membrane and exposes X to the surface. Therefore, when X is a hydrophobic group, it shows hydrophobicity and the contact angle with hydrophilic water or ethylene glycol increases. Particularly, when X is an organic group having fluorine, it is particularly hydrophobic and is preferred. The actual method of treating the silane coupling agent is not particularly limited. For example, the treatment can be performed by bringing the film into contact with the silane coupling agent. It does not matter whether a solvent is used or not. Water or steam may be used to accelerate the reaction. Most preferably, the ceramic porous support is treated with a silane coupling agent to make it hydrophobic.

The present permeable membrane has a hydrogen permeability of 5.0 × 10 ⁻⁶ mol · m.
^-2 · s ^-1 · Pa ^-1 is essential. Usually, such a permeable membrane having a high hydrogen permeability easily permeates the electrolyte vapor of the electrolytic capacitor, and is not preferable as a permeable membrane mounted on the electrolytic capacitor. However, even if the hydrogen permeability is large, the membrane having (1) a contact angle of ethylene glycol of 85 ° or more and (2) a contact angle of water of 105 ° or more is surprisingly surprising because the ethylene glycol which is an electrolytic solution is used. And water vapor is difficult to permeate. As a result, the present invention has been achieved. The test tube containing ethylene glycol was covered with the permeable membrane, and the test tube was allowed to stand in an oven at 105 ° C., and the weight loss of ethylene glycol over time (weight loss rate) was measured. The transmission speed can be evaluated. This weight loss rate is 1.0X
It is preferably 10 ⁻³ g / h · cm ² or less. If the rate of weight loss is greater than this, the composition of the electrolyte changes due to the permeation of the electrolyte vapor, and the life of the electrolytic capacitor is not extended even if hydrogen passes sufficiently. This effect is particularly remarkable for a small capacitor having a small amount of electrolyte. The membrane of the present invention can suppress the permeation rate of ethylene glycol and water extremely low, although the reason is not known, although there are pores through which sufficient hydrogen can pass.

The present invention relates to an electrolytic capacitor having a permeable membrane. The permeable membrane is preferably mounted on a case or a sealing plug of the electrolytic capacitor, and particularly preferably mounted on a sealing plug. As a mounting method, it may be mounted with a sealing epoxy adhesive, or may be mounted using an O-ring or a spring.

Next, a preferred embodiment of the electrolytic capacitor of the present invention shown in the drawings will be specifically described.

An example which can be implemented in FIGS. 1 and 2 will be described below. FIG. 1 is a cross section of a general electrolytic capacitor. The electrolytic solution is impregnated in the capacitor element 2 wound with kraft paper interposed between the anode foil and the cathode foil, and the anode terminal 3 and the cathode terminal 4 are protruded from the through holes of the sealing plug 1 and housed in the aluminum container 5. It was done. FIG. 2 shows the sealing plug 1 as viewed from above. The permeable membrane of the present invention is, for example, installed at the position 6 in FIG. 2 with an adhesive or the like. This permeable membrane is permeable to hydrogen, but hard to permeate water and ethylene glycol, so it is difficult to transmit water vapor and ethylene glycol, which is a main component of the electrolyte. Can be escaped to the outside, so that bursting can be avoided and stable performance can be obtained for a long period of time. The form of the permeable membrane used in the present invention is preferably a flat plate. The shape is not particularly limited, and the size may be smaller than the size of the lid, and is preferably smaller than the radius of the lid. The thickness is not particularly limited, as long as it can maintain a mechanical strength that does not break at the time of setting.

The electrolytic capacitor of the present invention is configured similarly to a conventionally known electrolytic capacitor except for the hydrogen gas permeable membrane 1.

In the electrolytic capacitor of the present invention configured as described above, hydrogen gas generated in the container 5 during use passes through the permeable membrane 1 and is discharged out of the electrolytic capacitor.
Therefore, the hydrogen gas does not accumulate inside the container to be damaged or broken, and the electrolytic solution is prevented from evaporating as a liquid or vapor, so that a long-life capacitor can be obtained.

The present invention will be described in more detail by the following examples.

[0024]

[Example] (Example 1) [Coating of α-alumina pellet] n-C8F17C2H4S
i (OEt) 3 (Toray Dow Corning Silicone) approx. 10mg
Is a 2 mm thick porous α-alumina membrane with a diameter of 9.6 mm (ceramic film made by Nippon Insulators Co., Ltd. (100 mm x 100 mm)
X 3 mm) cut to this size: coated with alumina fine particles only on one side by a thickness of about 50 μm, and dropped as uniformly as possible onto the surface treated with alumina fine particles having an average pore diameter of 0.1 μm). . About 5 minutes after that, about 10 ml of distilled water was poured on the treated surface, left standing at 100 ° C. for 1 hour and heated to obtain a permeable membrane 1.

[Preparation of Cell for Transmission Measurement] The present apparatus will be described with reference to FIG. This device is made of stainless steel and supplies gas from a gas supply port. The permeable membrane is fixed to a union (manufactured by Swagelok) through an O-ring, and the treated surface of the permeable membrane faces the gas side shown at the gas supply port. In order to prevent gas from leaking from the gap between the O-ring and the permeable membrane, the surface opposite to the treated surface of the permeable membrane is connected to a reducer (Swagelok) through ferrule (manufactured by Swagelok).
(Made by the company).

[Measurement of hydrogen permeation rate using cell for permeation measurement] Using the cell for permeation measurement described above, the hydrogen permeation rate of the permeable membrane 1 was measured. The permeation apparatus was installed in an atmosphere of 20 ° C., and 2 atm of hydrogen was supplied to the gas supply side of the apparatus. The amount of hydrogen gas permeating the membrane was measured with a soap membrane flow meter, and was 19.8 × 10 ⁻⁶ (mol M ^-2 · s ^-1 · Pa ^-1 ).

[Ethylene Glycol Weight Loss Rate Ratio] About 10 g of ethylene glycol was placed in a test tube. Next, the permeable membrane 1 was fixed to the permeation measurement cell. The gas supply port of the permeation apparatus and the port of the test tube were connected by a rubber tube, and the total weight was measured. The entire apparatus was kept at 105 ° C. This device is 2
After a day, the device was taken out of the oven, allowed to cool at room temperature, and the weight of the entire device and ethylene glycol was measured. Weight loss rate is
5.19 x 10 ^-4 (g / h cm ² ).

[Measurement of Contact Angle of Water] The contact angle between the surface of the permeable membrane 1 and the water droplet is measured by an optical mirror type CA-D (manufactured by Kyowa Interface Science Co., Ltd.).
Was 116 ° to 118 ° (30 seconds after dropping of water).

[Measurement of Contact Angle of Ethylene Glycol] The contact angle between the surface of the permeable membrane 1 and the ethylene glycol droplet was measured using an optical mirror type CA-D (manufactured by Kyowa Interface Science Co., Ltd.). It was 90 ° (30 seconds after the dropwise addition of ethylene glycol).

[Preparation of permeable membrane electrolytic capacitor] permeable membrane 1
The large screw terminal type electrolytic capacitor 1 as shown in FIG. 1 was prepared by using a sealing plug having silicone rubber fixed at the position 6 in FIG. 2 and the silicone rubber at the position 7 in FIG. As shown in FIG. 4, the permeable membrane was fixed with an O-ring made of silicon rubber applied to the treated surface of the permeable membrane 1 and a spring applied to the non-treated surface.

[Electrolytic Capacitor Durability Test] The electrolytic capacitor 1 was placed in an oven at 85 ° C., and an applied voltage of 498 V was applied to the electrodes. After a lapse of 1000 hours, the state of the silicone rubber was visually checked, and the silicone rubber had not changed at all.

(Comparative Example 1) [Durability test of electrolytic capacitor without permeable membrane] A commercially available large screw terminal type electrolytic capacitor using a sealing plug fitted with only silicone rubber was heated to 85 ° C.
And placed in an oven maintained at a voltage of 498 V. After several tens of hours, the silicone rubber burst.

[0033]

The electrolytic capacitor of the present invention has a built-in hydrogen gas permeable element having a hydrogen gas permeable membrane having a specific performance. The hydrogen gas generated in the container is discharged to the outside of the electrolytic capacitor through the hydrogen gas permeable membrane, and there is no breakage or destruction of the container due to an increase in the internal pressure, and there is no loss of the electrolyte.

Therefore, the electrolytic capacitor of the present invention can maintain stable capacitor characteristics for a long time and can be used safely. In addition, since hydrogen can permeate high leakage current by permeating hydrogen, it leads to a reduction in the total cost of the aluminum electrolytic capacitor.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an electrolytic capacitor of the present invention.

FIG. 2 shows an example of a sealing plug of the condenser of the present invention.

FIG. 3 is an explanatory diagram of a transmission measurement cell.

FIG. 4 is a view showing a method of attaching a permeable membrane to a sealing plug of the electrolytic capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hydrogen gas permeable element 2 ... Electrolytic capacitor element 3 ... Anode terminal 4 ... Cathode terminal 5 ... Container 6 ... Permeation membrane mounting position 6 ... Silicone rubber membrane mounting position

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA41 HA41 MA03 MA22 MB04 MB10 MC03 MC03X MC09 MC09X NA48 PC80

Claims (2)

[Claims] An anode foil and a cathode superposed in a container.
Foil, anode terminal and cathode with one end protruding outside the container
Terminals and electrolytic capacitors with built-in electrolyte
And the electrolytic capacitor is (1) ethylene glycol
(2) Water contact angle is 105 degrees or more
Above, (3) Hydrogen permeability is 5.0X10^-6 mol ・ m^-2・ S ^-1・ Pa^-1Less than
With a permeable membrane that satisfies the three conditions of being above
An electrolytic capacitor, characterized in that: 2. The electrolytic capacitor according to claim 1, wherein the permeable membrane is mounted at a position through which gas generated in the container passes.