JP4232223B2 - Electrolytic capacitor sealing body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolytic capacitor sealing body for sealing an opening of a case containing a capacitor element in an electrolytic capacitor.
[0002]
[Prior art]
In general, as shown in FIG. 1, an electrolytic capacitor accommodates a capacitor element 2 impregnated with a paste-like electrolyte (electrolytic solution) in a bottomed cylindrical case 1 made of aluminum or the like. The opening is sealed by the sealing body 3. The capacitor element 2 is formed by winding an anode foil and a cathode foil through a separator, and lead wires 4 and 5 connected to the capacitor element 2 are inserted into lead holes 6 and 7 provided in the sealing body 3. And pulled out of the case 1. A safety valve is provided at the end of the case 1 opposite to the sealing body 3 by intentionally providing a mechanically weak portion such as a groove 8 in a part of the end. When the pressure in the case 1 exceeds a predetermined level due to some abnormal situation, the safety valve is operated in such a manner that the case 1 is broken at a mechanically weak portion such as the groove 8 and the internal pressure of the case 1 is released, and explosion-proof. Is designed.
[0003]
Conventionally, as the constituent material of the sealing body 3, the sealing solution and the gas barrier property are higher than those of other rubbers, and the electrolytic solution that prevents the electrolytic solution from escaping to the outside of the case 1 and holds the electrolytic solution in the case 1 is used. Because of its high retention, rubbers mainly composed of regular butyl rubber have been frequently used (for example, JP-A-55-158621, JP-A-1-114030).
[0004]
On the other hand, in recent years, there has been an increasing demand for longer life of electronic components, and longer life of electrolytic capacitors is also required. However, in the electrolytic capacitor using the sealing body 3 made of the rubber mainly composed of the regular butyl rubber, the rubber mainly composed of the regular butyl rubber has insufficient heat resistance, so that the rubber deteriorates when exposed to a high temperature for a long time. As a result, the electrolytic solution inside the capacitor escapes through the sealing body 3, and the life of the capacitor is reduced.
[0005]
In addition, in the sealing body 3 made of rubber mainly composed of regular butyl rubber, dirt adheres to the mold during molding, it takes a long time for cleaning, and workability is poor, and high temperature and long time crosslinking is required. There was also a problem that.
[0006]
Therefore, a sealing body 3 made of rubber obtained by crosslinking partially crosslinked butyl rubber having good heat resistance with a peroxide has been recently developed. The sealing body 3 has good heat resistance and is free from mold contamination, and can be crosslinked at a low temperature in a short time.
[0007]
[Problems to be solved by the invention]
However, the sealing body made of rubber obtained by crosslinking the partially crosslinked butyl rubber with a peroxide has the following various problems.
[0008]
Although the rubber obtained by crosslinking the partially crosslinked butyl rubber with a peroxide has good properties such as heat resistance, the partially crosslinked butyl rubber that has already been partially crosslinked is used as a raw material rubber. There was a problem that the property and the like were poor and further poor fusion occurred. For this reason, the workability in the kneading process is poor, the process conditions are complicated, and when the sealing body 3 is formed, variations in dimensional accuracy and internal defects are likely to occur. There was a problem that the rate of occurrence of defective products was high. There is also a problem that the heat distortion resistance is insufficient.
[0009]
Further, when the thickness of the sealing body 3 is reduced, the sealing body 3 tends to swell with respect to the pressure in the thickness direction, and when the internal pressure rises due to gas generation at the time of abnormality such as reverse voltage application, before the safety valve operates, Cracks are generated from defective portions and the like, and problems such as discharge of the electrolyte in the case 1 occur. For this reason, since the thickness of the sealing body 3 had to be increased to some extent, there was a problem that the substantial volume of the case 1 was reduced, and consequently the capacity of the electrolytic capacitor was reduced.
[0010]
Further, recently, the chip formation and downsizing associated with the surface mounting of electronic components have been progressed, but the sealing body 3 made of rubber obtained by crosslinking the partially crosslinked butyl rubber is described above in detail. Therefore, there is a problem that it cannot be applied to a chip-shaped electrolytic capacitor and there is a limit to application to a miniaturized electrolytic capacitor.
[0011]
That is, in the electrolytic capacitor formed into a chip, since it goes through a solder reflow process, it becomes a high temperature state in this process, and the gas pressure inside the capacitor rises, but at that time, cracking occurs from an internal defect part or the like, Since the heat-resistant deformation property is not sufficient, the sealing body may come off from the case, thereby causing problems such as discharge of the electrolyte solution inside the case. Furthermore, since the hardness is not sufficient, there is a problem that the sealing body swells due to an increase in internal pressure during reflow, and the capacitor rises from the substrate. Therefore, a sealing body made of rubber obtained by crosslinking the partially crosslinked butyl rubber cannot be applied to a chip electrolytic capacitor.
[0012]
In addition, the following problems occur when applying to miniaturized electrolytic capacitors. First, when the opening of the case 1 is sealed with the sealing body 3, generally, as shown in FIG. 1, the drawing process is performed over the entire circumference in the vicinity of the opening of the case 1 (in FIG. 1). , 9 indicates the drawn portion by this drawing process). However, when the diameter of the sealing body 3 is reduced, the compression rate of the rubber by the drawing process is increased and the applied pressure is increased, and the applied pressure causes cracking of the rubber. Further, when the thickness of the sealing body 3 is reduced, as described above, it tends to swell with respect to the pressure in the thickness direction, and when the internal pressure rises due to gas generation at the time of abnormality such as reverse voltage application, the case 1 side Before the safety valve is activated, a crack is generated from an internal defect portion, and a problem such as discharge of the electrolyte in the case 1 occurs. Therefore, the sealing body 3 made of rubber obtained by crosslinking the partially crosslinked butyl rubber has a limit in application to a miniaturized electrolytic capacitor.
[0013]
In addition, since the rubber obtained by crosslinking the partially crosslinked butyl rubber with peroxide has a large surface frictional resistance, when the lead wires 4 and 5 of the capacitor element 2 are inserted into the lead holes 6 and 7 of the sealing body 3, Since a large resistance acts on the capacitor element 2 via the lead wires 6 and 7, the insertion work becomes difficult and the wound electrode foil and the separator are displaced or wrinkled. There was a problem that the rubber on the peripheral surface 7 was scraped off by the lead wires 4 and 5.
[0014]
Moreover, since the gas barrier property was insufficient, there was a problem that the life of the electrolytic capacitor was shortened by the evaporation of the electrolytic solution through the sealing body 3.
[0015]
In addition, the rubber obtained by crosslinking the partially crosslinked butyl rubber with a peroxide had to be mixed with a large amount of carbon having a low electrical resistance as a filler.
[0016]
The present invention has been made in view of such circumstances, and one of the objects of the present invention is that kneading of raw materials can be performed very easily, and molding defects are hardly caused, and dimensional accuracy is high. It is an object of the present invention to provide an electrolytic capacitor sealing body that can be molded and has very good workability.
[0017]
Another object of the present invention is to provide a sealing body for an electrolytic capacitor that can prevent internal defects due to poor fusion.
[0018]
Another object of the present invention is to provide a sealing body for an electrolytic capacitor that can improve heat resistance and heat aging resistance.
[0019]
Another object of the present invention is to provide a sealing body for an electrolytic capacitor that can easily have high hardness and high modulus.
[0020]
Another object of the present invention is to provide a sealing body for an electrolytic capacitor that can be crosslinked and molded at a low temperature in a short time.
[0021]
Another object of the present invention is to provide an electrolytic capacitor sealing body having a small surface frictional resistance (good surface slipping).
[0022]
Another object of the present invention is to provide an electrolytic capacitor sealing body having excellent gas barrier properties.
[0023]
Still other objects of the present invention will become apparent from the following description.
[0024]
[Means for Solving the Problems]
The sealing body of the electrolytic capacitor according to the present invention is a sealing body of an electrolytic capacitor that seals the opening of a case containing a capacitor element in the electrolytic capacitor, and is 100 parts by weight of an elastomeric polymer that can be crosslinked with a peroxide. A diallyl isophthalate initial polymer, which is an initial polymer of a thermosetting resin curable with a peroxide, is mixed with 5 to 300 parts by weight, and then the polymer is crosslinked with the peroxide and the thermosetting resin. It consists of a rubber elastic body obtained by curing the initial polymer.
[0025]
When the blending amount of the thermosetting resin is less than 5 parts by weight with respect to 100 parts by weight of the elastomeric polymer, the following effects cannot be obtained sufficiently, while when it exceeds 300 parts by weight, rubber elasticity is increased. descend. A particularly preferable blending amount of the thermosetting resin with respect to 100 parts by weight of the elastomeric polymer is 10 to 200 parts by weight.
[0026]
The initial polymer of the thermosetting resin is solid at room temperature, but softens at a relatively low temperature of 40 to 100 ° C., and cures by reacting with a peroxide at a certain temperature or higher, and is hard and has good heat resistance. It becomes resin. The reason for curing in this way is considered to be that the initial polymer is polymerized and crosslinked. In the rubber elastic body according to the present invention, the polymer and the thermosetting resin are cured by crosslinking the elastomeric polymer and curing the thermosetting resin in a state where the elastomeric polymer and the thermosetting resin are mixed. It is considered that a bond with the functional resin also occurs.
[0027]
As described above, the initial polymer of the thermosetting resin softens at a relatively low temperature. Therefore, when the initial polymer and the elastomeric polymer are mixed at a temperature at which the initial polymer softens, both of them are very easy. Therefore, the workability in the kneading process is greatly improved, and the process conditions can be simplified. In addition, since the initial polymer of the thermosetting resin is softened at a relatively low temperature, the mixture of the elastomeric polymer and the initial polymer of the thermosetting resin easily flows during heat molding. As a result, a molded product (sealing body) with good dimensional accuracy is obtained, and internal defects are not generated. Therefore, the rubber elastic body according to the present invention has very good processability.
[0028]
Moreover, since the initial polymer of the elastomeric polymer and the thermosetting resin can be crosslinked and cured in a short time, the molding time of the sealing body can be shortened.
[0029]
Further, as described above, the initial polymer of the thermosetting resin is cured with a peroxide and becomes a hard and heat-resistant resin. Therefore, the initial polymer of the elastomeric polymer and the thermosetting resin is crosslinked / The cured rubber elastic body according to the present invention is also excellent in heat resistance, and can have high hardness and high modulus.
[0030]
In addition, as described above, high hardness and high modulus can be obtained, and internal defects can be eliminated. Therefore, even if the thickness of the sealing body is reduced to some extent, the internal pressure due to gas generation during abnormalities such as reverse voltage application When the rise occurs, the crack does not occur before the safety valve operates, and problems such as discharge of the electrolytic solution inside the case do not occur. Furthermore, since the dimensionality is improved, the variation in the thickness of the sealing body is reduced, so that the lower limit of the thickness tolerance can be increased, and the thickness setting value (the median value of the standard) can be increased accordingly. Can be small. For this reason, even if the size of the case 1 is the same as the conventional size, the thickness of the sealing body can be reduced to increase the substantial volume of the case, and the capacity of the electrolytic capacitor can be increased. The effect of increasing the capacity of the electrolytic capacitor due to the thinning of the sealing body 3 is extremely great.
[0031]
In addition, as described above, internal defects can be prevented from occurring, and the heat resistance of the sealing body can be improved. Then, the sealing body does not come off from the case, and problems such as discharge of the electrolyte do not occur. In addition, since the sealing body can be made to have high hardness, even if there is an increase in internal pressure during reflow, swelling of the sealing body is suppressed, and lifting of the capacitor from the substrate is suppressed. It will be applicable to.
[0032]
Further, as described above, since the hardness and modulus can be high and internal defects can be eliminated, even when the diameter of the sealing body is reduced, the aperture when the opening of the case is sealed with the sealing body. Rubber cracking due to processing does not occur. Furthermore, as already described, the thickness of the sealing body can be reduced. Therefore, it is possible to reduce the size of the electrolytic capacitor.
[0033]
Moreover, since the frictional resistance of the surface of the sealing body is reduced by blending the thermosetting resin, when inserting the lead wire of the capacitor element into the lead hole of the sealing body, Since a large resistance force does not act on the capacitor element, this insertion work is facilitated, the wound electrode foil and separator are displaced and wrinkled, and the rubber on the peripheral surface of the lead hole is caused by the lead wire. It will not be scraped off. In addition, by reducing the thickness of the sealing body, it is possible to reduce the resistance when inserting the lead wire, and to further easily insert the lead wire of the capacitor element into the lead hole of the sealing body.
[0034]
Further, when the thermosetting resin is blended, and further when the initial polymer of the elastomeric polymer and the thermosetting resin is crosslinked and cured, the thermosetting resin is connected to the crosslinking component of the elastomeric polymer. Since the cross-linking structure is involved and the cross-linking structure is complicated, the gas barrier property of the sealing body is improved, so that the electrolyte solution that evaporates through the sealing body is reduced, thereby extending the life of the electrolytic capacitor. Can be planned.
[0035]
Moreover, since it is not necessary to mix a large amount of carbon having a low electrical resistance as a filler, the electrical insulation of the sealing body can be increased.
[0036]
In addition, when the internal pressure rises due to gas generation at the time of abnormality such as reverse voltage application due to the improved hardness, the swelling of rubber is suppressed and the pressure to the safety valve of the capacitor case increases, and the safety valve This improves the operability of the system and improves safety in the event of an abnormality.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
As the elastomeric polymer crosslinkable with peroxide in the present invention, various raw rubbers, thermoplastic elastomers and the like can be used. From the viewpoint of high gas barrier property, partially crosslinked butyl rubber, butyl rubber, EPDM, EPM Among them, partially crosslinked butyl rubber having the highest gas barrier property is particularly preferable.
[0038]
The curable thermoset resin with a peroxide in the present invention, (preferably from polymerization rate 5-25%) diallyl isophthalate prepolymer thereof can be used, in that the thermal deformation temperature is high, Jiariruiso A phthalate prepolymer is particularly preferred.
[0039]
Conventionally, diallyl phthalate is sometimes added to the raw rubber, but this is not in the state of the initial polymer as in the present invention, but in the monomer state, the co-crosslinking agent (crosslinking aid) for the rubber. The amount of addition is small (about 1 to 5 parts by weight with respect to 100 parts by weight of rubber), which is essentially different from the usage in the present invention.
[0040]
In the present invention, as the peroxide for crosslinking and curing the initial polymer of the elastomeric polymer and the thermosetting resin, many of the peroxides usually used as a crosslinking agent can be used. Those that begin to cure are not suitable because crosslinking and curing begin in the process of mixing the polymer and the thermosetting resin. Therefore, the one where the temperature at which the half-life is 1 minute is 120 ° C. or more is preferable.
[0041]
【Example】
Hereinafter, the present invention will be described based on examples.
[0042]
Partially crosslinked butyl rubber: 70 parts by weight Diallyl isophthalate initial polymer: 30 parts by weight
(For 100 parts by weight of partially crosslinked butyl rubber
42.9 parts by weight)
Zinc stearate ... 1 part by weight Dicumyl peroxide ... 2 parts by weight Calcined clay ... 100 parts by weight Carbon ... 1 part by weight Acid adsorbent ... 5 parts by weight Anti-aging agent ... 1 part by weight of diallyl isophthalate initial polymerization by Banbury mixer A sealing body 3 is formed by kneading at a temperature at which the product is softened, at 60 to 80 ° C., and by cross-linking and curing at 170 ° C. for 5 minutes by compression molding to form a sealing body 3. An electrolytic capacitor having the same mechanical configuration as 1 was constructed.
[0043]
In this example, zinc oxide (MgO) was used as the acid adsorbent. For example, Al (OH) ₃ · xH ₂ O, 1.25Mg (OH) ₂ · Al (OH) ₃ · xCO ₃ · Other species such as yH ₂ O, Al (OH) ₃ .NaHCO ₃ , Mg ₅ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O An acid adsorbent or an acid alkali adsorbent such as 2MgO.6SiO ₂ .xH ₂ O may be used.
[0044]
If an acid adsorbent or an acid-alkali adsorbent is added to the sealing body 3 as in this embodiment, leakage of the electrolyte solution to the outside of the case 1, particularly between the sealing body 3 and the lead wires 4, 5, especially on the negative side. The leakage of the electrolytic solution from between the lead wires 5 can be effectively prevented, and this can further increase the life of the electrolytic capacitor. Although the mechanism of action for obtaining such an effect is still unclear, the following two different inferences have been considered.
[0045]
(Inference 1) When an acid adsorbent or an acid alkali adsorbent is added, a phenomenon in which a portion of the sealing body 3 in contact with the electrolytic solution swells is observed. From this, the acid or base in the electrolyte is adsorbed by the acid adsorbent or the acid-alkali adsorbent in the sealing body 3 to swell the sealing body 3, and the seal between the sealing body 3 and the lead wires 4 and 5 is sealed. As a result, the leakage of the electrolyte solution from between the sealing body 3 and the lead wires 4 and 5 is prevented.
[0046]
(Inference 2) Since the reaction between the rubber component constituting the sealing body 3 and the electrolytic solution is suppressed by the acid adsorbent or the acid-alkaline adsorbent, the deterioration of the sealing body 3 due to the reaction with the electrolytic solution is suppressed. Leakage of the electrolyte solution outside the case 1 is prevented.
[0047]
【The invention's effect】
As described above, the sealing body of the electrolytic capacitor according to the present invention is as follows.
(A) The raw materials can be mixed very easily.
(B) It is possible to obtain a sealing body that is less prone to molding defects and is molded with high dimensional accuracy.
(C) Internal defects due to poor fusion can be prevented from occurring,
(D) heat resistance, heat aging resistance can be improved,
(E) high hardness and high modulus;
(F) From the above (c), (d) and (e), even if the case has the same size as the conventional case, the thickness of the sealing body can be reduced and the capacity of the electrolytic capacitor can be increased.
(G) From the above (c), (d) and (e), it becomes possible to chip electrolytic capacitors.
(H) From the above (c), (d) and (e), the diameter and thickness of the sealing body can be reduced, and the electrolytic capacitor can be miniaturized.
(I) It can be crosslinked and molded at a low temperature in a short time.
(J) The frictional resistance of the surface can be reduced, which facilitates the lead wire insertion work, and the electrode foil and separator are misaligned and wrinkled. Will not be scraped off by
(K) The gas barrier property can be improved and the life of the electrolytic capacitor can be extended.
(L) Since it is not necessary to mix a large amount of carbon having a low electrical resistance as a filler, electrical insulation can be increased.
(M) From the above (e), when the internal pressure rises due to gas generation at the time of abnormality such as reverse voltage application, rubber bulge is suppressed and the operability of the safety valve of the electrolytic capacitor case is improved. , Safety at the time of abnormality is improved,
It is possible to obtain excellent effects such as.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a mechanical structure of an electrolytic capacitor.
[Explanation of symbols]
1 Case 2 Capacitor element 3 Sealing body

Claims (3)

An electrolytic capacitor sealing body for sealing an opening of a case containing a capacitor element in an electrolytic capacitor,
To 100 parts by weight of an elastomeric polymer crosslinkable with peroxide , 5 to 300 parts by weight of diallyl isophthalate initial polymer, which is an initial polymer of a thermosetting resin curable with peroxide, is mixed, An electrolytic capacitor sealing body comprising a rubber elastic body obtained by crosslinking the polymer with a peroxide and curing an initial polymer of the thermosetting resin. The rubber elastic body is prepared by mixing the elastomeric polymer, the diallyl isophthalate initial polymer and a peroxide at a temperature at which the diallyl isophthalate initial polymer is softened, and then mixing the mixture with the peroxide. The polymer is cross-linked and heated to a temperature at which the diallyl isophthalate initial polymer is cured with the peroxide to cross-link the polymer and simultaneously cure the diallyl isophthalate initial polymer . Item 14. An electrolytic capacitor sealing body according to Item 1.   The sealing body for an electrolytic capacitor according to claim 1, wherein the elastomeric polymer is partially crosslinked butyl rubber.

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