JPS628514A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Ribuki 225 Months Above! The present invention relates to an electrolytic capacitor sealed with a crosslinked mixture of two types of ethylene copolymers. More specifically, the synthetic resin for sealing the electrolytic capacitor is (A) ethylene having at least an ethylene unit and at least one unit selected from the group consisting of a carboxylic acid unit, a dicarboxylic acid unit, an anhydride unit thereof, and a halfester unit thereof. and (B) an uncrosslinked mixture of an ethylene copolymer having at least an ethylene unit and at least one unit selected from the group consisting of a hydroxyl unit, an amino unit, and a glycidyl unit, or a crosslinked product thereof. This relates to electrolytic capacitors, which are characterized by not only sufficient resistance to electrolytes and heat resistance to withstand nozzle, but also relatively easy crosslinking, and the ability to easily form a case. Another object of the present invention is to provide an electrolytic capacitor sealed with a synthetic resin that has excellent adhesion to lead wires.

With the development of the electronics industry, various types of capacitors have been developed, and the growth of capacitors for electronic devices is particularly remarkable. Recently, especially miniaturization.

Electrolytic capacitors are growing rapidly due to their increased capacity and lower prices. A typical electrolytic capacitor uses high-purity aluminum as an anode, and by electrolyzing it in an electrolytic solution, a layer of aluminum oxide with a uniform thickness is formed on the surface of the anode as a dielectric material. aluminum electrolytic capacitors, dry electrolytic capacitors that use sherry-like liquid for the cathode, and solid semiconductors and conductors.In terms of capacitance, there are tube-type capacitors of about 0.05 cc, which are widely used mainly in transistor radios, etc. A metal case type of about 1,000 cc is also used. Recently, solid electrolytic capacitors
With progress in miniaturization, tube-shaped devices have been developed that do not require the use of cathode electrolytic capacitors, but instead use manganese dioxide, carbon bander, etc., and the electrodes are taken out from the seal.

Conventionally, these electrolytic capacitors have been sealed with thermosetting resin, room temperature curing resin, or photocuring resin to prevent moisture from entering and to ensure internal airtightness. However, these curable resins not only have poor manufacturing efficiency due to the relatively long curing time, but also
Due to insufficient adhesion with the condenser case,
If the liquid leaks or the cathode liquid (e.g. glycerin,
It is immersed in an electrolytic solution (based on ethylene glycol, fluoric acid, ammonia, etc.), and because it is hygroscopic, it absorbs moisture through the sealing opening, causing a change in the concentration of the electrolytic solution inside.

It was shortening lifespan. In addition, with the recent trend towards miniaturization, solder is used when fixing devices to printed circuit boards, etc., resulting in problems such as the solder heat being transmitted through the lead wires and melting the sealing portion.

But −. From the above, the present invention does not have these drawbacks (problems), can be crosslinked in a short time, has sufficient resistance to electrolytes, and has sufficient resistance to solder. To obtain an electrolytic capacitor sealed with a synthetic resin having heat resistance and excellent adhesion to a case and lead wires.

. According to the present invention, these problems can be solved if the synthetic resin sealing the electrolytic capacitor is composed of (A) "at least ethylene, carboxylic acid units, dicarboxylic acid units, anhydride units thereof, and halfester units thereof; at least one type of unit selected from the group consisting of
0 to 99.5% by weight of an ethylene copolymer" [hereinafter referred to as "ethylene copolymer (A)]" 1 to 99% by weight; and (B) "at least an ethylene unit, a hydroxyl unit, an amino unit and ``Ethylene copolymer consisting of at least one unit selected from the group consisting of glycidyl units and having an ethylene unit content of 30 to 99.5% by weight'' [hereinafter referred to as ``ethylene copolymer (
B) An electrolytic capacitor characterized in that it is a crosslinked product of a mixture having a content of 99 to 1% by weight. The present invention will be specifically explained below.

(A) Ethylene copolymer (A) The ethylene copolymer (A) used in the present invention contains at least ethylene units and a group consisting of carboxylic acid units, dicarboxylic acid units, anhydride units thereof, and halfester units thereof. It is an ethylene copolymer containing 30 to 99.5% by weight of the ethylene units.

This ethylene copolymer (A) contains at least the second component (
A) Copolymers that can be obtained by copolymerizing the following quinomers, multi-component copolymers of these and other monomers, and acid anhydride groups in these copolymers. Examples include those obtained by hydrolysis and/or alcohol denaturation.

Representative examples of these 7-mers include acrylic acid, methacrylic acid, and ethacrylic acid, which have at most 25 carbon atoms.
unsaturated monocarboxylic acids as well as maleic anhydride, tetrahydrophthalic anhydride, maleopimaric anhydride, 4-methylcyclohexan-4-ene-1,2-carboxylic anhydride and bicyclo(2,2,1)-hebutyric anhydride. -5-en-
4-50 carbon atoms such as 2,3-dicarboxylic anhydride
unsaturated dicarboxylic acid anhydrides.

Other monomers having at most 30 carbon atoms ([1 (preferably 10 or less)] such as methyl (meth)acrylate, ethyl (meth)acrylate, hydroxymethyl (meth)acrylate and diethyl fumarate Mention may be made of unsaturated carboxylic acid esters and vinyl esters having at most 30 carbon atoms, such as vinyl acetate and vinyl propionate.

Among the above ethylene copolymers (A), copolymers of ethylene and unsaturated dicarboxylic anhydrides or multicomponent copolymers of these and unsaturated dicarboxylic esters and/or vinyl esters are hydrolyzed and The dicarboxylic acid anhydride units of these copolymers can be converted to dicarboxylic acid units or Hafester units by modification with alcohol. Ethylene copolymers (A) obtained by replacing part or all of the acid anhydride units with dicarboxylic acid units or halfester units can also be preferably used.

To carry out the hydrolysis, the ethylene copolymer (A
) in the presence of a catalyst (e.g. tertiary amino) in an organic solvent (e.g. toluene) that dissolves the copolymer.
It can be obtained by reacting with water at a temperature of ~100° C. for 0.5 to 10 hours (preferably 2 to B hours, preferably 3 to 8 hours), followed by neutralization with an acid.

To carry out the alcohol modification, the ethylene copolymer (A) can be obtained by the solution method or crosslink method described below.

The solution method is similar to the case of hydrolysis, in which the reaction is carried out in an organic solvent in the presence or absence of the above-mentioned catalyst (the reaction is slow in its absence).
2 minutes to 5 hours at the reflux temperature of the alcohol used in
Preferably from 2 minutes to 2 hours, preferably from 15 minutes to 1 hour.
time).

On the other hand, in the cross-wire method, tertiary amino and Generally 0.1 per dicarboxylic acid unit' in the copolymer.
~3.0 times mole (preferably 1.0 to 2.0 times mole) of saturated alcohol is added to the ethylene copolymer (A) at a temperature above the melting point of the ethylene copolymer (A) but below the boiling point of the alcohol used. A few minutes to several tens of minutes (preferably 10 to 30 minutes) using a mixing machine such as the Banbury Mixer 1 extruder used in the field of synthetic resins.
This method involves reacting while kneading.

The saturated alcohol used in the above modification with alcohol is a linear or branched saturated alcohol having 1 to 12 carbon atoms, and includes methyl alcohol, ethyl alcohol, and -butyl alcohol.

In the case of the above hydrolysis and in the case of denaturation with alcohol, the conversion rate to dicarboxylic acid and the rate of hafestation are both 0., 5 to 100%, and 10.0%.
~100% is desirable.

The ethylene units in this ethylene copolymer (A) are 30
-99.5% by weight, preferably 30-99.0% by weight, particularly preferably 35-99.0% by weight. Further, the proportion of carboxylic acid units, their anhydride units, and halfester units in the copolymer is 0.1 to 70% by weight as a total amount thereof, and 0.5 to 70% by weight.
is desirable, and 0.5 to BO weight % is especially suitable. If an ethylene-based polymer in which the proportion of carboxylic acid units, anhydride units, and halfester units in this ethylene-based copolymer (A) is 0.1% by weight is used, the ethylene-based copolymer described below When cross-linking with the composite (B) by heating, not only is the cross-linking incomplete, but also the adhesion to the metal layer is poor.On the other hand, even if the amount exceeds 70% by weight, the characteristics of the present invention are expressed. , it is not necessary to exceed 70% by weight, which is unfavorable from the viewpoint of manufacturing and economics.

In addition, when using a multicomponent copolymer containing the unsaturated carboxylic acid ester and/or vinyl ester, the total amount thereof is usually at most 70% by weight, and 8% by weight.
When using an ethylene copolymer in which the copolymerization ratio of unsaturated dicarboxylic acid ester and/or vinyl ester exceeds 70% by weight, which is preferably 0% by weight or less, the softening point of the copolymer becomes high, and the softening point is 150°C. The temperature below is not only undesirable because fluidity is impaired, but also economically unfavorable.

(B) Ethylene copolymer (B) In addition, the ethylene copolymer (B) used in the present invention (
B) contains at least ethylene units and hydroxyl units,
At least one unit selected from the group consisting of amino units and glycidyl units" [hereinafter referred to as "second component (B)]", and the ethylene units thereof are 30 to 86.5
It is an ethylene copolymer containing % by weight.

This ethylene copolymer (B) is a multi-component copolymer obtained by copolymerizing at least ethylene with the following monomers to constitute the second component (B), and a multicomponent system of these and other monomers. Examples include saponified products obtained by saponifying copolymers and copolymers of ethylene and vinyl esters (especially vinyl acetate).

Examples of this monomer include glycidyl alkyl (meth)acrylate and hydroxyalkyl (meth)acrylate represented by the following general formula (the number of carbon atoms in the alkyl group is usually 1).
~25 carbon atoms), α-fulkenyl alcohol having 3 to 25 carbon atoms, and α-amino and primary or secondary aminoalkyl (meth)acrylates having 2 to 25 carbon atoms (the number of carbon atoms in the alkyl group is usually 1 to 25 ([l).

CH2= C-R1 小C=0 龜0- R2-CH-CH2 (Here, R1 is H or a methyl group, R2 has 1 to 1 carbon atoms
Representative examples of this monomer (12 linear or branched alkyl groups) include butene tricarboxylic acid monoglycidyl ester, glycidyl methacrylate, glycidyl acrylate, glycidyl methacrylate, itaconate glycidyl ester, hydroxymethyl (meth)
Acrylate, Hydroxymethyl (meth)acrylate, Hydroxypropyl (meth)acrylate, L-Droxybutyl (meth)acrylate, Hydroxyhexyl (
Mention may be made of meth)acrylate, allyl alcohol, allyl amino and aminoethyl (meth)acrylate.

Moreover, examples of other monomers include the unsaturated carboxylic acid esters and vinyl esters.

The ethylene unit in this ethylene copolymer (B) is 30
-99.5% by weight, preferably 30-93.0% by weight, particularly preferably 35-99.0% by weight. Further, the proportion of hydroxyl units, amino units and glycidyl units in the copolymer is 0.1 to 70% by weight for the same reason as in the case of the ethylene copolymer (A), and is 0.5 to 0.5% by weight. 70% by weight is preferred, especially 0.5-BO
% by weight is preferred. Furthermore, when using a multicomponent copolymer containing the unsaturated carboxylic acid ester and/or vinyl ester, the total amount thereof is generally at most 70 copolymers for the same reason as in the case of the ethylene copolymer (A). The amount of strain is preferably 60% by weight or less.

Melt index (JIS K-721) of the ethylene copolymer (A) and ethylene copolymer (B)
Measured under 1 condition 4 according to 0, hereinafter rM, 1. J) is generally o, oot to 1000 g/10 min, preferably 0.05 to 500 g/10 min, particularly preferably 0.1 to 500 g/10 min. M, 1.
When these ethylene-based copolymers having a weight ratio of less than 0.01 g/10 minutes are used, it is not only difficult to mix these copolymers uniformly, but also the moldability is poor.

Among these ethylene copolymers, when produced by copolymerization method, the amount is usually 500 to 2500 kg/c.
ethylene and the second component (A) or the second component (B) or these and other components in the presence of a fast chain transfer agent (e.g. an organic peroxide) at a temperature of 120 to 2 EiO'O under high pressure of m' They can be obtained by copolymerizing the components, and their production methods are well known. Furthermore, the method of manufacturing the ethylene copolymer (A) by hydrolysis and/or modification with alcohol and the method of manufacturing the ethylene copolymer (B) by saponification are also well-known methods. be.

(C) Production of mixture (1) Mixing ratio In producing the mixture of the present invention, ethylene copolymer (A) and ethylene copolymer (B
) Ethylene copolymer (A) in the total amount (total)
The mixing ratio of the ethylene copolymer (B) is 1 to 99% by weight [that is, the mixing ratio of the ethylene copolymer (B) is 98 to 1% by weight], and the mixing ratio is 5 to 9% by weight.
5% by weight is desirable, and 10 to 80% by weight is particularly preferred. Ethylene copolymer (A) in the total amount of ethylene copolymer (A) and ethylene copolymer (B)
Even if the mixing ratio is less than 1% by weight or more than 99% by weight, the crosslinking of the mixture by the method described later will be insufficient, and for example, adhesion with the electrolytic capacitor described later will be poor.

(2) Mixing method To produce this mixture, it is sufficient to uniformly mix the ethylene copolymer (A) and the ethylene copolymer (B). Triblending may be carried out using a commonly used mixer such as a Henschel mixer, or melt kneading may be carried out using a mixer such as a Banbury, extruder, or roll mill. At this time, a more uniform mixture can be obtained by triblending in advance and melt-kneading the resulting mixture. When melt-mixing, it is necessary that the ethylene copolymer (A) and the ethylene copolymer (B) do not substantially undergo crosslinking reaction (
If the resulting mixture is crosslinked, it will not only deteriorate the moldability when molding the resulting mixture as described below, but also cause a decrease in the shape of the intended molded product and the heat resistance when crosslinking the molded product. Therefore, the melt-kneading temperature is desirably room temperature (20°C) to 150°C, and preferably 140°C or lower, although it depends on the type and viscosity of the ethylene polymer used.

As a guideline for this "substantially no crosslinking", rmlll
) After extraction treatment in toluene for 3 hours, the amount of residue having a diameter of 0.1 micron or more (hereinafter referred to as "extraction residue") is generally preferably 15% by weight or less, and 10% by weight or less. is preferable, and 5% by weight or less is optimal.

(D) Sealing of electrolytic capacitors In order to seal electrolytic capacitors using the mixture obtained as described above, injection molding or stamping is commonly used in the field of thermoplastic resins or thermosetting resins. This can be achieved by applying a molding method, press molding method, dipping method, injection method, low pressure transfer method, etc. At this time, in the case of the present invention, it is important to perform the molding at a temperature at which the ethylene copolymer (A) and the ethylene copolymer (8) are not substantially crosslinked.
It is best to carry out at a temperature of the mixture below 250°C, 1
The temperature is preferably 80°C or lower. However, temperatures below 80°C are not preferred because the mixture does not melt sufficiently. At this point, the extraction residue of the mixture is preferably 15% or less, and 10% by weight.
The following is preferable, and in particular, 5% by weight or less is optimal. From the above, in order to seal by injection molding method, low pressure transfer molding method, etc., 9 is obtained by press-fitting a molten mixture into a mold at a temperature range of 80 to 180 ° C.
A feature of the present invention is that the integrally molded product is maintained at a temperature at which the mixture crosslinks (usually 12°C to 280°C) for a certain period of time. 0, 1~ while holding
20Kg/c rrr, (gauge pressure) It is preferable to apply pressure with a saw and a hoe.The higher the temperature, the shorter the holding time is.At 200°C or higher, it is usually 10 seconds to 10 minutes, and at 120-200°C, it is 1 minute to 30 minutes. For the same reason as above, in the case of press molding, 8 minutes is preferable.
A substantially non-crosslinked sheet material molded at 0 to 180°C is pressurized at a pressure of 1 to 40 kg/cm' (gauge pressure) in a mold preset at a temperature range of 180 to 280°C. It is possible to simultaneously manufacture an electrolytic capacitor sealed in a desired mold while molding it.

Further, as shown in Fig. 1, lead wires are set in the case in advance, and the mixture is poured into a predetermined mold under pressure in a molten state.
surrounding container by heating at temperatures ranging from 280°C to
Furthermore, it can also be crosslinked while being bonded to the lead wire.

The crosslinked mixture in the electrolytic capacitor obtained as described above desirably has an extracted afterflame of 70% or more, particularly preferably 75% or more.

In the present invention, in order to impart heat resistance to the mixture in the electrolytic capacitor thus obtained, 120-2
It is important to heat and pressurize in a temperature range of 80°C. In this temperature range, a crosslinking reaction takes place within the mixture, resulting in a marked improvement in adhesion and heat resistance. Furthermore, in order to obtain uniform adhesion, a method of applying pressure under reduced pressure and a slight load may be used.

A typical electrolytic capacitor of the present invention will be briefly explained with reference to the drawings. FIG. 1 is a partially enlarged sectional view of this electrolytic capacitor. In this drawing, l is a case, and 2 is the sealing material of the present invention (sealing port, crosslinked mixture)
3 is an electrolytic capacitor, which is made up of lead wire terminals Φ and e. The sealing material is molded in advance to a size 1 to 5% larger than the predetermined size,
After being sealed in a case, it can be heated and pressurized in the above-mentioned temperature range to bond the case and lead wire simultaneously with crosslinking. Furthermore, it is also possible to inject the electrolyte etc. later through the sealing port.

The present invention will now be explained in more detail with reference to Examples.

In addition, in Examples and Comparative Examples, the peel strength was measured by the force with which the sealing material was pulled out from the case. Furthermore, the solder heat resistance of the encapsulant is 90. /1
G (weight ratio) for 20 seconds in a solder bath for evaluation.

The mixture of ethylene copolymer (A) and ethylene copolymer (B) used in Examples and Comparative Examples is shown below.

Ethylene copolymer (A) and ethylene copolymer (B)
As a mixture with ethylene-acrylic acid copolymer (density 0.954
g/cm″, acrylic acid copolymerization ratio 20% by weight,
rEAA J) and vinyl acetate copolymerization ratio is 2.
Saponified product obtained by saponifying 8% by weight of ethylene-vinyl acetate copolymer (saponification degree 87
．． 5%, 1. 75g 710 minutes, density 0.951
g/crn", hereinafter referred to as "saponified material") (mixing ratio 50:50 (weight ratio),
(hereinafter referred to as "mixture (1)"), M, 1. is 200
A mixture of an ethylene-methacrylic acid copolymer (density: 0.950 g/crn', methacrylic acid copolymerization ratio: 25% by weight) and the saponification degree described above [mixing ratio: 50:50 (weight ratio), Hereinafter referred to as "mixture (■)"].

An ethylene-ethyl acrylate-maleic anhydride ternary copolymer (ethyl acrylate copolymerization ratio: 30.7% by weight, maleic anhydride copolymerization ratio: 1.7% by weight) with M, r, of 212 g/10 min. M, 1. is 123g/
A mixture of ethylene-methyl methacrylate-hydroxymethacrylate ternary copolymer (copolymerization ratio of methyl methacrylate: 20.7% by weight, copolymerization ratio of hydroxymethacrylate: 11.7% by weight) (
A terpolymer of ethylene-methyl methacrylate-maleic anhydride (copolymer of methyl methacrylate) with a mixing ratio of 50:5G (weight ratio), hereinafter referred to as "mixture (■)" and (■) is 105g710 minutes. Proportion: 20.5% by weight, copolymerization ratio of maleic anhydride: 3.
1% by weight) and a terpolymer of ethylene-methyl methacrylate-glycidyl methacrylate (copolymerization ratio of methyl methacrylate: 18.6% by weight, copolymerization ratio of glycidyl methacrylate: 12.7% by weight) [
A mixture ratio of 30:70 (weight ratio), hereinafter referred to as "mixture (■)" was used. Note that these mixtures were produced by tri-blending the respective copolymers or terpolymers for 5 minutes using a Henschel mixer.

Mixture (I) to IV) obtained as described above
In addition, EAA and saponified materials were each made into a 100 micron thick extruder with a T-die (diameter 40+em, die width 30 cam, rotation speed 85 rpm) under the conditions of the cylinder temperature shown in Table 1. A film was formed. The extracted residual aroma of the obtained film was measured. In both cases it was 0%.

(Margins below) Table 1 Examples 1 to 4, Comparative Examples 1.2 Each of the sheets thus obtained was heated to 20 kg/kg using a heat press for 10 minutes at the temperature shown in Table 2.
Under pressure of c m' (gauge pressure), the diameter becomes f (1 mm,
A cylindrical encapsulation with a height of 5 layers was produced.

In addition, the cylindrical sealant was inserted into the entrance of the case shown in Fig. 1 (made of aluminum, inner diameter 10 m, depth 30 II, aluminum thickness 0.5 mm), and the surrounding area was heated to 240°C. An electrolytic capacitor was manufactured by sealing the capacitor.

Example 5, Comparative Example 3 Each sheet used in Example 1 and Comparative Example 2 was cut out into a cylindrical seal with a diameter of 5 rirs and a height of 3 sm, and the diameter was 5 mm, the inner diameter thickness was lam, and the height was 15+++
The container was heated to 300° C. and inserted into the inlet of a cylindrical aluminum container as shown in FIG.

After cooling, it was taken out.

The solder heat resistance of each cylindrical seal obtained as described above, the stress when the seal was pulled out from an electrolytic capacitor through a screw inserted at right angles at a pulling speed of 50 μ/min, and the stress of each electrolytic capacitor. The extracted residual odor of the crosslinked product of the mixture in the condenser was measured.

These are shown in Table 2. In the column of ``Solder heat resistance'' in this table, rOJ means that no deformation is observed, and ``x'' means that it melts and does not retain its original shape. .

(Left below) From the results of the above examples and comparative examples, the ethylene copolymer (A) used for manufacturing the electrolytic capacitor of the present invention
The cross-linked mixture of ethylene copolymer (B) and ethylene copolymer (B) not only has excellent solder heat resistance but also has strong adhesion to the case, so it can be used with thermosetting resins such as commonly used epoxy resins. It is clear that this method is cheaper and easier to manufacture than encapsulation using resin, and also eliminates the drawbacks of the conventional method.

11.] The electrolytic capacitor of the present invention and the crosslinked mixture used for its production exhibit the following effects (characteristics), including the production process.

(1) Excellent adhesion to the capacitor case reduces evaporation of electrolyte and infiltration of impurities such as moisture.
Therefore, the electrical characteristics of the electrolytic capacitor do not deteriorate,
It can be used in a stable state for a long time.

(2) Since it has good solvent resistance, it can also be cleaned with solvents such as trichlene and freon.

(3) Since it has excellent flexibility and heat resistance, it has good thermal shock resistance and impact resistance.

(4) Since sealing and sealing can be performed simultaneously, it is advantageous in terms of cost.

(5) Since the solder heat resistance is excellent, it is possible to directly solder the lead wires during mounting.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged sectional view of the electrolytic capacitor of the present invention. l...Case

Claims (1)

[Claims] The synthetic resin for sealing the electrolytic capacitor (A) consists of at least ethylene and at least one unit selected from the group consisting of carboxylic acid units, dicarboxylic acid units, anhydride units thereof, and half ester units, and contains ethylene units; 1 to 99% by weight of an ethylene copolymer in an amount of 30 to 99.5% by weight; and (B) at least ethylene units and at least one unit selected from the group consisting of hydroxyl units, amino units and glycidyl units. and the content of ethylene units is 30 to 9
99-1% by weight of ethylene-based copolymer which is 9.5% by weight
An electrolytic capacitor characterized by being a crosslinked product of a mixture.