JP3677128B2 - Sealing body and manufacturing method thereof - Google Patents

Description

（脚注）
ＰＰＳ（１）：溶融粘度（３１０℃、剪断速度１２００／秒）２１０Ｐａ・ｓ
ＰＰＳ（２）：溶融粘度（３１０℃、剪断速度１２００／秒）１２０Ｐａ・ｓ
ＰＰＳ（３）：溶融粘度（３１０℃、剪断速度１２００／秒）２０Ｐａ・ｓ
【００３０】
【発明の効果】
本発明によれば、半田耐熱性に優れたＰＰＳ製の封口体が提供される。本発明の封口体は、収縮率が小さく、かつ、適度な引張伸度を有しているため、電気二重層コンデンサ、リチウムイオン電池、ポリアセン電池など、電荷蓄積を行う素子や電源素子などであって、特に表面実装用の素子に好適に使用される。
【図面の簡単な説明】
【図１】図１は、リチウムイオン電池の一例の構造を示す断面図である。
【符号の説明】
１：正極（ＭｎＯ₂）
２：負極（Ｌｉ）
３：有機電解液を含浸させたセパレータ
４：集電層
５：皿状の金属ケース（正極缶）
６：金属蓋（負極キャップ）
７：封口体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sealing body made of polyphenylene sulfide, and more specifically, an element formed by enclosing a liquid or solid electrolyte inside a metal container such as an electric double layer capacitor, a lithium ion battery, or a polyacene battery. It is related with the sealing body for sealing an opening part, and its manufacturing method. Among these elements, the sealing body of the present invention is particularly suitable for a surface mounting element.
[0002]
[Prior art]
As electronic devices become smaller and mobile communication devices develop, elements that store charge, such as electric double layer capacitors, and batteries (power supply elements) such as lithium ion batteries and polyacene batteries, in addition to demands for miniaturization, Response to surface mounting is now required. In surface mounting, since these elements are soldered to the substrate, the sealing body is also required to have solder heat resistance.
Conventionally, these elements have a metal container composed of two parts constituting a counter electrode or a positive and negative electrode, a liquid or solid electrolyte enclosed therein, and two parts of the metal container that is each electrode. It consists of a sealing body that interposes and encloses the internal electrolyte together with electrical insulation. The sealing body is also called a non-conductive gasket or insulating packing.
[0003]
A lithium ion battery will be described as an example with reference to FIG. FIG. 1 shows an example of a button-type (flat type) lithium-manganese dioxide battery. This lithium ion battery has a positive electrode 1 (MnO ₂ ), a negative electrode 2 (Li), and a separator 3 impregnated with an organic electrolyte therebetween. The positive electrode 1, the negative electrode 2, and the separator 3 are enclosed between a dish-shaped metal case 5 (positive electrode can) and a metal lid 6 (negative electrode cap), and a current collecting layer is disposed between the negative electrode 2 and the metal lid 6. 4 is arranged. The opening of the metal case 5 is sealed with a metal lid 6 via a sealing body 7. Depending on the type of battery, the internal structure and the pole material used differ, but the metal case has a substantially common structure in that the opening of the metal case is sealed with a metal lid via a sealing body.
The electric double layer capacitor comprises (1) a pair of polarizable electrodes, (2) a separator interposed between the pair of polarizable electrodes, (3) an electrolyte solution impregnated in each polarizable electrode and the separator, and (4) A structure having current collecting layers disposed between a pair of polarizable electrodes, a dish-shaped metal case and a metal lid, and the opening of the dish-shaped metal case being sealed with a metal lid via a sealing body have.
[0004]
Conventionally, polypropylene is used as the material of the sealing body, but the heat resistance is not sufficient, and when exposed to a high temperature of 160 ° C. or higher, the sealing body deforms due to instantaneous stress relaxation, and the electrolyte solution There was a problem of leaking. When the device is mounted on the surface, a soldering process at a high temperature of about 240 ° C. is necessary. However, since the polypropylene sealing body is inferior in solder heat resistance, the sealing is broken in the soldering process and the liquid leaks. During subsequent use, the battery may be shocked and leaked.
[0005]
In order to solve this problem, Japanese Patent Application Laid-Open No. 8-64484 discloses any one of polyamide, polyphenylene sulfide, polyethylene terephthalate, polybutylene terephthalate, polyamideimide, polyimide, and liquid crystal polymer as a sealing body for an electric double layer capacitor. Is proposed. Among these, polyphenylene sulfide is particularly preferable because it is excellent in heat resistance, chemical resistance, moisture resistance, flame retardancy, electrical characteristics, and the like.
However, even if the sealing body is simply formed using polyphenylene sulfide, the element exposed to a high temperature during surface mounting may cause leakage of the electrolyte solution if continued to be used.
[0006]
[Problem to be Solved by the Invention]
An object of the present invention is to seal an opening of an element formed by using a metal container as an electrode and enclosing a liquid or solid electrolyte therein, such as an electric double layer capacitor suitable for surface mounting, a lithium battery, or a polyacene battery. It is to provide a sealing body.
Another object of the present invention is to provide a method of manufacturing a sealing body that does not cause liquid leakage even after a soldering process at a high temperature during surface mounting of an element.
[0007]
As a result of diligent research to solve the leakage problem of the sealing body made of polyphenylene sulfide, the present inventor uses polyphenylene sulfide having a specific melt viscosity and performs heat treatment at a high temperature after forming the sealing body. It was found that a sealing body having an extremely small shrinkage rate and a tensile elongation in an appropriate range as compared with a conventional product was obtained. The shrinkage rate can also be reduced by maintaining the mold temperature at a high temperature during injection molding of the sealing body. Further, by using a resin material in which glass fibers are blended with polyphenylene sulfide at a specific ratio, the shrinkage rate can be further reduced without excessively reducing the tensile elongation. The sealing body of the present invention has an extremely small shrinkage rate at 200 ° C. of 0.1% or less, and the element in which the sealing body is disposed causes liquid leakage even after a high temperature soldering process during surface mounting. There is nothing.
The present invention has been completed based on these findings.
[0008]
[Means for Solving the Problems]
According to the present invention, a resin material containing 80 to 100% by weight of polyphenylene sulfide having a melt viscosity of 40 to 600 Pa · s measured at 310 ° C. and a shear rate of 1200 / sec and 0 to 20% by weight of glass fiber is molded. Thus, a sealing body having a shrinkage rate at 200 ° C. of 0.1% or less is provided.
Moreover, according to the present invention, a resin material containing 80 to 100% by weight of polyphenylene sulfide having a melt viscosity of 40 to 600 Pa · s measured at 310 ° C. and a shear rate of 1200 / second and 0 to 20% by weight of glass fiber is sealed. There is provided a method for producing a sealing body, which is heat-treated at a temperature of 200 to 280 ° C for 1 minute to 72 hours after being formed into a body shape.
In the present invention, the shrinkage at 200 ° C. means the shrinkage when the sealing body is heated to 200 ° C. and then returned to room temperature (23 ° C.).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The polyphenylene sulfide (hereinafter abbreviated as PPS) used in the present invention is preferably a linear polymer. The linear PPS is generally a substantially linear polymer obtained by polymerizing a monomer mainly composed of a bifunctional monomer in the presence of a polymerization assistant such as sodium acetate or water. On the other hand, the cross-linked PPS is generally polymerized without using a polymerization aid, and the resulting low-polymerization degree polymer is oxidized and crosslinked to increase the viscosity (curing). Such a cross-linking type PPS is not preferable because it is inferior in flexibility, rigidity, strength, and the like.
[0010]
The PPS used in the present invention can be obtained, for example, by a known method disclosed in Japanese Patent Publication No. Sho 63-33775, Japanese Patent Publication No. 53-25589, and the like. For example, as disclosed in Japanese Patent Publication No. 63-33775, an alkali metal sulfide and a dihaloaromatic compound are heated in a specific two-step process in a polar solvent such as N-methylpyrrolidone in the presence of water. It can be suitably obtained by warm polymerization.
Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Sodium sulfide produced by reacting NaSH and NaOH in the reaction system can also be used.
[0011]
Examples of the dihaloaromatic compound include p-dichlorobenzene, m-dichlorobenzene, 2,5-dichlorotoluene, p-dibromobenzene, 2,6-dichloronaphthalene, 1-methoxy-2,5. -Dichlorobenzene, 4,4'-dichlorobiphenyl, 3,5-dichlorobenzoic acid, p, p'-dichlorodiphenyl ether, 4,4'-dichlorodiphenyl sulfone, 4,4'-dichlorodiphenyl sulfoxide 4,4'-dichlorodiphenyl ketone, and a mixture of two or more thereof.
[0012]
The PPS used in the present invention preferably contains p-phenylene sulfide units in an amount of 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, especially poly (p-phenylene sulfide), And a poly (p-phenylene sulfide / m-phenylene sulfide) copolymer containing m-phenylene sulfide units as a minor component. When PPS having too few p-phenylene sulfide units is used, the physical properties of the sealing body at high temperatures may be deteriorated.
As long as the linear PPS used in the present invention is substantially linear, it may contain some branched structure or a crosslinked structure. A slightly branched structure may be introduced by allowing a small amount of an aromatic halogen compound having 3 or more halogen substituents per molecule such as 3,5-trichlorobenzene.
[0013]
The PPS used in the present invention has a melt viscosity measured at 310 ° C. and a shear rate of 1200 / sec in the range of 40 to 600 Pa · s. If the melt viscosity of PPS is too small, the strength and tensile elongation of the sealing body will be low, and in the process of mounting the sealing body on a metal container, for example, when the end of a dish-shaped metal case is caulked, It is not preferable because a problem occurs. If the melt viscosity of PPS is too high, it is not preferable because it becomes difficult to form a sealing body having a thin portion. The melt viscosity of PPS is preferably 100 to 300 Pa · s.
[0014]
In the present invention, PPS can be used alone as the resin material, but a resin composition in which glass fibers are blended with PPS can be used in order to reduce the shrinkage rate. The glass fiber is not particularly limited, and short fibers generally used as a filler can be used, but those having a diameter of 15 μm or less are preferable from the viewpoint of elongation. The glass fiber may be surface-treated with various surface treatment agents. An antioxidant can be surface-treated on the surface of the glass fiber.
[0015]
The ratio of PPS and glass fiber in the resin material is 80 to 100% by weight of PPS and 0 to 20% by weight of glass fiber. By blending the glass fiber, the shrinkage rate of the sealing body can be made smaller. However, if the blending ratio of the glass fiber is too large, the tensile elongation of the sealing body is too low. If the tensile elongation of the sealing body is too small, the end of the metal container is bent in the process of attaching the sealing body to the metal container, and cracking occurs when the sealing body is caulked, or adhesion to the metal container Lowers and causes leakage. The blending ratio of the glass fiber is preferably 0.1 to 20% by weight, more preferably 5 to 15% by weight.
[0016]
Resin materials used in the present invention include, in addition to glass fibers, other fillers, mold release agents, colorants, heat stabilizers, UV stabilizers, rust preventives, flame retardants, lubricants, cups, as desired. Additives such as ring agents can be blended. Further, the resin material includes polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylene within the range not impairing the object of the present invention. , Polyether nitrile, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, ABS resin, epoxy resin, phenol resin, urethane resin, liquid crystal polymer, etc .; polyolefin rubber, styrene rubber, fluoro rubber, silicon Elastomers such as rubber: etc. can be blended. However, these compounding agents are desirably used in a small proportion of usually 10 parts by weight or less, preferably 5 parts by weight or less, based on 100 parts by weight of the resin material (PPS + glass fiber).
The resin material may be supplied to the molding machine as it is, or may be supplied to the molding machine after being melt-kneaded in advance using an extruder to form a pellet that is easy to handle. The resin material is supplied to various molding machines and molded into a desired sealing body shape. Usually, it is desirable to mold the sealing body by injection molding.
[0017]
After the resin material is molded into the shape of the sealing body, heat treatment is performed at a temperature of 200 to 280 ° C. (dry heat condition) for 1 minute to 72 hours. By this heat treatment, it is possible to obtain a sealing body having a low shrinkage rate of 0.1% or less at 200 ° C. By holding the mold temperature at a high temperature during injection molding, it is possible to obtain a sealing body with a low shrinkage rate, but shortening the molding time, preventing deterioration during molding of the resin material, and further heat treatment effect In order to increase, for example, a molten resin material is injected into a mold maintained at a temperature of about 120 to 160 ° C., and the resulting molded product is heated at a temperature of 200 to 280 ° C. for 1 minute to 72 hours, It is preferable to perform a heat treatment. In general, it is desirable that the heat treatment time is longer as the heat treatment temperature is lower, and the heat treatment time is shorter as the heat treatment temperature is higher. However, if the heat treatment time is too short, it is difficult to sufficiently reduce the shrinkage rate. Conversely, if it exceeds 72 hours, it is difficult to obtain a desired sealing body industrially and economically, which is not preferable. If the heat treatment temperature is too low, it will be difficult to obtain a sufficient effect, and if it is too high, it will be deformed or start to melt, which is not preferable. Heat treatment is preferably performed at a temperature of 220 to 260 ° C. within a range of about 30 minutes to 2 hours.
[0018]
The sealing body of the present invention has an extremely small shrinkage ratio at 200 ° C. of 0.1% or less and a tensile elongation of usually 2% or more, and thus is suitable for surface mounting. According to the study by the present inventors, when solder reflow is performed at a temperature of about 240 ° C., the inside of the device rises to about 200 ° C. For this reason, crystallization of PPS constituting the sealing body proceeds, and as a result, shrinkage occurs, and adhesion with the metal container surface is impaired. Under high temperature conditions, leakage of the internal electrolyte solution can be prevented due to thermal expansion, but when used by returning to around room temperature, a defect in which the internal electrolyte solution leaks occurs. On the other hand, when the sealing body of the present invention is used, an element that does not cause liquid leakage during use can be obtained because the shrinkage rate is small even when receiving a heat history at a high temperature of soldering.
[0019]
The sealing body of the present invention preferably has a tensile elongation of 2% or more. After the sealing body is mounted on the metal container, a part of the metal container is bent and the sealing body is caulked. At this time, if the elongation of the sealing body is low, the adhesion with the metal is lowered and the sealing body itself is broken. For this reason, in the present invention, the tensile elongation is preferably 2% or more. The tensile elongation referred to in the present invention refers to a tensile elongation obtained by measurement after adding a thermal history similar to the step of obtaining a sealing body using a sample for a tensile test obtained from the same composition. Say degree.
The sealing body of the present invention is useful as a sealing body for sealing an opening of an element formed by using a metal container as an electrode and enclosing a liquid or solid electrolyte therein. Examples of such an element include an element that accumulates charges such as an electric double layer capacitor, or a battery (power supply element) such as a lithium ion battery or a polyacene battery.
[0020]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further in detail, this invention is not limited only to this Example.
[0021]
[Example 1]
Polyphenylene sulfide (manufactured by Kureha Chemical Industry; 310 ° C., melt viscosity at a shear rate of 1200 / sec of 210 Pa · s) was supplied to a twin screw extruder adjusted to a cylinder temperature of 280 to 310 ° C. to produce pellets. The obtained pellets were supplied to an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., PS-10E), the mold temperature was 150 ° C., the cylinder temperature was 280 to 300 ° C., the outer diameter was 19.4 mm, the inner diameter was 17 mm, the height was 1. A 1 mm sealing body was formed. The sealing body thus obtained was heat-treated at 240 ° C. for 1 hour and then cooled to room temperature (23 ° C.).
Measurement of shrinkage rate After the temperature of the obtained sealing body was raised to 200C and then returned to room temperature, the shrinkage rate was 0.08%.
Measurement of tensile elongation A test piece for a tensile test (JIS K7113) was formed from the pellets obtained above, placed at 240 ° C for 1 hour, returned to room temperature, and then measured for tensile elongation. It was 8.0%.
Leakage test The obtained sealing body was attached to a metal container, and 10 lithium ion batteries using an electrolytic solution in which LiClO ₄ was dissolved in propylene carbonate were prepared. A solder paste was applied to the back surface of the prepared lithium ion battery, preheated to 180 ° C., heated to 240 ° C., and soldered to a glass epoxy substrate. After soldering, it was placed at room temperature for 7 days and the presence or absence of electrolyte leakage was observed. There was no sample in which leakage was observed in one sample.
[0022]
[Example 2]
The same PPS 9 kg as in Example 1 and 1 kg of glass fiber (manufactured by JEOL Glass, diameter 13 μm) were mixed and supplied to a twin screw extruder adjusted to a cylinder temperature of 280 to 310 ° C. to produce pellets. The obtained pellets were supplied to an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., PS-10E), the mold temperature was 150 ° C., the cylinder temperature was 280 to 300 ° C., the outer diameter was 19.4 mm, the inner diameter was 17 mm, the height was 1. A 1 mm sealing body was formed. The obtained sealing body was subjected to heat treatment at 240 ° C. for 1 hour, and then cooled to room temperature.
Measurement of shrinkage rate When the obtained sealing body was heated to 200C and returned to room temperature, the shrinkage rate was measured and found to be 0.04%.
Measurement of tensile elongation A tensile test piece was molded from the obtained pellets, placed at 240C for 1 hour, returned to room temperature, and measured for tensile elongation, which was 3.2%.
Leakage test The obtained sealing body was attached to a metal container, and 10 lithium ion batteries using an electrolytic solution in which LiClO ₄ was dissolved in propylene carbonate were prepared. A solder paste was applied to the back surface of the prepared lithium ion battery, preheated to 180 ° C., heated to 240 ° C., and soldered to a glass epoxy substrate. After soldering, it was placed at room temperature for 7 days and the presence or absence of electrolyte leakage was observed. There was no sample in which leakage was observed in one sample.
[0023]
[Example 3]
The same operation as in Example 2 was performed except that 8.5 kg of PPS and 1.5 kg of glass fiber were mixed. The results are shown in Table 1.
[0024]
[Comparative Example 1]
The same operation as in Example 1 was performed except that the obtained sealing body was not heat-treated. The results are shown in Table 1.
[0025]
[Comparative Example 2]
The same operation as in Example 2 was performed except that the obtained sealing body was not heat-treated. The results are shown in Table 1.
[0026]
[Comparative Example 3]
The same operation as in Example 2 was performed except that 7 kg of PPS and 3 kg of glass fiber were used. The results are shown in Table 1.
[0027]
[Example 4]
The same operation as in Example 2 was performed, except that PPS having a melt viscosity of 210 Pa · s was replaced with PPS (manufactured by Kureha Chemical Industry; 310 ° C., melt viscosity of 120 Pa · s at a shear rate of 1200 / sec). The results are shown in Table 1.
[0028]
[Comparative Example 4]
The same operation as in Example 2 was performed except that PPS having a melt viscosity of 210 Pa · s was replaced with PPS (manufactured by Kureha Chemical Industry; 310 ° C., melt viscosity at 1200 / sec shear rate of 20 Pa · s). The results are shown in Table 1.
[0029]
[Table 1]

(footnote)
PPS (1): Melt viscosity (310 ° C., shear rate 1200 / sec) 210 Pa · s
PPS (2): Melt viscosity (310 ° C., shear rate 1200 / sec) 120 Pa · s
PPS (3): Melt viscosity (310 ° C., shear rate 1200 / sec) 20 Pa · s
[0030]
【The invention's effect】
According to the present invention, a PPS sealing body excellent in solder heat resistance is provided. Since the sealing body of the present invention has a small shrinkage ratio and an appropriate tensile elongation, it is an element such as an electric double layer capacitor, a lithium ion battery, or a polyacene battery, a power storage element, and the like. In particular, it is preferably used for a surface mounting element.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a structure of an example of a lithium ion battery.
[Explanation of symbols]
1: Positive electrode (MnO ₂ )
2: Negative electrode (Li)
3: Separator impregnated with organic electrolyte 4: Current collecting layer 5: Dish-shaped metal case (positive electrode can)
6: Metal lid (negative electrode cap)
7: Sealing body

Claims (4)

A resin material containing 80 to 100% by weight of polyphenylene sulfide having a melt viscosity of 40 to 600 Pa · s measured at 310 ° C. and a shear rate of 1200 / sec and 0 to 20% by weight of glass fiber is molded at 200 ° C. A sealing body having a shrinkage ratio of 0.1% or less. The sealing body according to claim 1, which is heat-treated at a temperature of 200 to 280 ° C. after molding. The sealing body according to claim 1 or 2, wherein the tensile elongation is 2% or more. A resin material containing 80 to 100% by weight of polyphenylene sulfide having a melt viscosity of 40 to 600 Pa · s and a glass fiber of 0 to 20% by weight measured at 310 ° C. and a shear rate of 1200 / sec. A method for producing a sealing body, characterized by heat-treating at a temperature of 280 ° C for 1 minute to 72 hours.

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