JPH07312328A - Separator for capacitor - Google Patents

Abstract

PURPOSE:To provide a separator which has a heat-resistant property and an affinity with an electrolytic solution by a method wherein a polymer film which has been impregnated with a fluorine-based surface-active agent by making use of pores in a fluorine-based polymer porous film is manufactured as a fluorine-based porous polymer film and a multilayer body in which a paper base material or a sheet of manufactured paper has been laminated is used for the polymer film. CONSTITUTION:A separator 7 for a capacitor is composed of a multilayer body obtained by using a paper base material or a sheet of manufactured paper and a special polymer film. The special polymer film is a polymer film A which has been impregnated with a fluorine-based surface-active agent by making use of pores in a fluorine-based polymer porous film. Then, the separator is manufactured in such a way that an adhesive layer is formed on the surface of the paper base material and that the polymer film A is bonded to, and formed in multilayer, the face of the adhesive layer so as to be integrated. The separator 7 for the capacitor is sandwiched between, and held by, both electrode foils as an anode foil 1 and a cathode foil 2. Then, this assembly is wound to be a tubular shape, lead wires 3 are connected respectively to the anode foil 1 and the cathode foil 2, and a capacitor element 4 is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator suitable for capacitors, for example, having sufficient electrophilicity and stable heat resistance for a long period of time, and excellent in workability of separator winding in a capacitor manufacturing process. It also relates to separators for electrolytic capacitors and electric double layer capacitors.

[0002]

2. Description of the Related Art Conventionally, as a separator for capacitors,
Paper base materials such as kraft paper and Manila paper, and polyethylene or polypropylene porous membranes that have been subjected to treatment such as graft polymerization of hydrophilic monomers are used. Further, a porous film obtained by treating a fluororesin with alcohol (Japanese Patent Laid-Open No. 62-263624) or a porous fluororesin film formed by coating a substance having an affinity for a polar organic solvent (Japanese Laid-Open Patent Publication No. 2-241013). ) Etc. have been proposed. Further, a hydrophilization film (Japanese Patent Publication No. 5-21009, Japanese Patent Publication No. 5-21010) in which a fluororesin porous film is impregnated with a fluorosurfactant and crosslinked and fixed is proposed.

[0003]

However, in the case of the above-mentioned kraft paper and manila paper, they are deteriorated by being exposed to a high temperature in the electrolytic solution and are embrittled by an acidic electrolytic solution such as sulfuric acid. There was a problem that I could not. Further, in the case of the polyethylene or polypropylene porous film, since it has poor heat resistance, when it is used at a high temperature for a long time or when it is heated in a short time of 200 ° C. or more during the capacitor manufacturing process, it is melted to form pores. There was a problem of being blocked. Further, in the case of the porous membrane obtained by treating the fluororesin with alcohol, there is a problem that the membrane is dried and the amount of the absorbing liquid is reduced as a result of long-term use. Further, in the case of a fluororesin porous membrane formed by coating a specific perfluoro ion exchange polymer as a substance having an affinity for the polar organic solvent, this polymer has only one --CF ₃ end which is a hydrophobic part, Since it has a weak affinity for, it was not sufficiently hydrophilized depending on the selection of the above polymer, and the obtained separator was not satisfactory. Then, the fluororesin porous film is impregnated with a fluorosurfactant, and the crosslinked and fixed hydrophilic film is a soft porous film, so the porous film is impregnated with a fluorosurfactant, Even if fixed by cross-linking
The film was weak, and wrinkles were easily formed during the capacitor manufacturing process, resulting in extremely poor workability.

The present invention has been made in view of the above circumstances, and provides a capacitor separator having not only excellent heat resistance but also sufficient electrophilicity and excellent workability in the capacitor manufacturing process. Is its purpose.

[0005]

In order to achieve the above-mentioned object, the capacitor separator of the present invention is composed of a polymer film (A) and a paper base material laminated or paper-made. Take composition. (A) A polymer film obtained by impregnating a fluorine-based porous polymer film with a fluorine-based surfactant by utilizing the porosity of the fluorine-based polymer porous film.

[0006]

In other words, the present inventors not only have heat resistance,
A series of studies have been conducted in order to obtain a separator which has sufficient electrophilicity and does not cause wrinkles during the capacitor manufacturing process and has excellent workability. As a result, a fluorocarbon polymer membrane is laminated with a polymer membrane (A) in which a fluorosurfactant is impregnated by utilizing its porosity and a paper base material, or a papermaking laminate. When used, the polymer film (A) has heat resistance and lyophilic property, and since the paper base material or papermaking has a reinforcing effect, the capacitor using this separator has desired capacitor characteristics. The present invention has been accomplished, and at the same time, the inventors have found that wrinkles and the like are not formed at the time of manufacturing a capacitor and workability is improved, and the present invention has been reached.

Next, the present invention will be described in detail.

The capacitor separator of the present invention comprises a laminate obtained by using a paper base material or papermaking and a special polymer film.

The above-mentioned paper base material is not particularly limited, and conventionally known ones may be used, and examples thereof include paper made of natural cellulose, that is, paper produced from wood pulp or Manila hemp.

The above-mentioned special polymer film is a polymer film (A) obtained by impregnating a fluorine-based porous polymer film with a fluorine-based surfactant by utilizing the porosity of the fluorine-based polymer porous film. .

As the above-mentioned fluorine-based porous polymer film, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) And a hydrophobic porous film made of tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (CTFE), or the like. In particular, the above PTFE is preferable from the viewpoint of chemical resistance, heat resistance and the like. The pore size of these membranes is preferably 0.01 to 20 μm, particularly 0.0
A membrane having a pore size of 5 to 5 μm is preferably used.

Utilizing the porosity of the above-mentioned fluorine-based porous polymer membrane, the fluorine-based surfactant to be impregnated into the membrane is as follows:
The following (a) anionic, (b) cationic,
(C) Nonionic fluorine-based surfactants may be mentioned.
These may be used alone or in combination of two or more. Above all, it is preferable to use a fluorine-containing surfactant containing no metal because it is used as a separator for capacitors.

(A) Anionic Fluorine-based Surfactant Perfluoroalkylcarboxylic acid salt, perfluoroalkylsulfonic acid salt, perfluoroalkylphosphoric acid salt and the like can be mentioned. The positive component for salt formation includes Na ⁺ , K ⁺ , Li ⁺ and NH ₄ ⁺ , and the perfluoroalkyl group preferably has 4 to 20 carbon atoms.

(B) Cationic Fluorine Surfactant Perfluoroalkyl quaternary ammonium salt such as perfluoroalkyl trimethyl ammonium salt can be used. The negative component for the salt formation is C
l ⁻ and NO ₃ ⁻ are included, and the perfluoroalkyl group preferably has 4 to 20 carbon atoms. (C) Nonionic Fluorosurfactant Examples include perfluoroalkylethylene oxide adducts and perfluoroalkylamine oxide adducts represented by the following general formulas and. The perfluoroalkyl group of the perfluoroalkylamine oxide adduct preferably has 4 to 20 carbon atoms.

[0015]

[Chemical 1]

The method for impregnating the porous fine pores of the fluorine-containing porous polymer membrane with the fluorine-containing surfactant is not particularly limited, but, for example, the fluorine-containing surfactant may be mixed with an organic solvent. 1-10% by weight (hereinafter "%"
Is abbreviated), preferably after diluting to 1 to 5%, the fluorine-based porous polymer membrane is immersed in the above-mentioned fluorine-based surfactant solution, or the solution is applied, and the membrane is dried. Can be given. The organic solvent used for the above dilution is not particularly limited, but for example, acetone, ethanol, isopropyl alcohol, etc. are preferably used.

According to the above method, the coating layer made of the above-mentioned fluorine-containing surfactant is formed on at least the surface of the fine pores of the fluorine-containing porous polymer membrane, and the porous membrane which has been made electrophilic solution is easily obtained. Here, the fine pore surface means a fiber surface that constitutes porosity, and the coating layer is at least the fine pore surface, that is, it may be formed inside the thickness direction of the polymer film, Furthermore, a coating layer may be formed on the surface of the porous polymer film.

The degree of formation of the coating layer formed by impregnating the above-mentioned fluorine-containing surfactant can be appropriately controlled by the concentration of the fluorine-containing surfactant, the dipping time and the coating amount. In order to use it as a constituent element of, the weight ratio before and after coating is preferably set to be in the range of after coating layer formation / before coating layer formation = 1.040 / 1 to 1.070 / 1, and particularly preferably. 1.045 /
It is 1 to 1.060 / 1. That is, when the weight after forming the coating layer is less than 1.040 based on the weight before coating, it is difficult to obtain a satisfactory lyophilic property. On the contrary, when the weight exceeds 1.070, the coating layer falls off after forming the coating layer. The capacitor characteristic (loss tangent of loss angle, impedance)
This is because there is a tendency to decrease.

The capacitor separator of the present invention can be manufactured, for example, as follows. That is, first, a polymer film (A) in which a coating layer made of the above-mentioned fluorine-based surfactant is formed on the surface of the fine pores of the fluorine-based porous polymer film is produced by the above method. Then, an adhesive layer is formed on the surface of the paper base material, and the polymer film (A) is adhered and laminated on the adhesive layer surface to be integrated.

Examples of the adhesive layer forming material include a conductive adhesive, and the adhesive layer is formed by applying the conductive adhesive. Thus, the adhesive is used to integrate the polymer film (A) and the paper base material in the capacitor manufacturing process. Then, as the characteristics of the conductive adhesive, for example, at the time when the winding of the electrode foil and the separator in the capacitor manufacturing process using the capacitor separator of the present invention is completed, it is dissolved in the electrolytic solution after being injected. The adhesive function may disappear. further,
The properties required of the above conductive adhesive include such conductivity, and specifically, polyvinyl alcohol (PVA), starch, carboxymethyl cellulose (CMC), polyethylene oxide (PE).
O), polyvinylpyrrolidone (PNVP), sodium polyacrylate (PAANA), and the like. These may be used alone or in combination of two or more.

The separator for capacitors produced as described above is a laminate having a two-layer structure of the polymer film (A) and the paper base material, but in the present invention, it is limited to the two-layer structure. Instead, the polymer film (A) and the paper base material may be used in plural to form a multi-layer structure of three or more layers. At this time, the stacking order is not particularly limited. For example, a laminated body using a plurality of paper base materials may be used in order to make the separator more elastic.

Further, the formation of the laminated body is not limited to the lamination of the polymer film (A) and the paper base material, but the polymer film (A) is combined with pulp fibers or the like to produce the polymer film. It is possible to obtain the same effect as that of the laminate of (A) and the paper base material.

Examples of capacitors using the capacitor separator of the present invention include electrolytic capacitors and electric double layer capacitors in which the separator is impregnated with an electrolytic solution and the electrolytic solution is placed between a pair of electrodes. Examples of the electrolytic solution in the electrolytic capacitor include those containing an electrolyte such as adipate or phthalate in a solvent such as ethylene glycol, γ-butyrolactone or dimethylformamide (DMF). Then, an anode foil and a cathode foil are used for the electrodes. Examples of the anode foil include those obtained by forming a dielectric coating on the surface of a metal foil such as aluminum or tantalum having a coating forming ability by anodic oxidation or the like. As the cathode foil, the same metal foil as the anode foil is used. As these metal foils, those subjected to etching treatment are preferably used in order to increase the surface area per volume.

As the electrolytic solution in the electric double layer capacitor, an aqueous solution system using an aqueous solution of sulfuric acid, an aqueous solution of potassium hydroxide or the like, or an electrolyte such as perchlorate of alkylammonium, γ-butyrolactone, dimethylformamide, dimethyl is used. Examples include non-aqueous solutions dissolved in an organic solvent such as fluroxide and propylene carbonate. Further, the electrode is not particularly limited, and examples thereof include activated carbon fiber cloth, or activated carbon fiber cloth having a conductive layer formed on one surface thereof.

[0025]

As described above, the separator for capacitors of the present invention comprises a laminate in which a paper base material is laminated or paper-made on the special polymer film (A). Therefore, it has excellent heat resistance due to the polymer film (A) and sufficient electrophilicity, and further, is laminated with a paper base material,
Alternatively, papermaking improves the weakness of the waist, and wrinkles are not formed in the capacitor manufacturing process to improve the manufacturing workability. Therefore, by using the separator of the present invention, it is possible to improve the quality and production efficiency of the capacitor.

Next, examples will be described together with comparative examples.

First, prior to the examples, three kinds of fluorochemical surfactants shown in Table 1 below were prepared.

[0028]

[Table 1]

[0029]

Example 1 A 15 μm-thick PTFE porous membrane (pore size: 3 μm) was dipped in a 2% by weight isopropyl alcohol solution in which an anionic fluorosurfactant a (described in Table 1) was dissolved for 10 minutes. Then, pull up and hold at 40 ° C for 3
By performing drying for 0 minutes, a polymer film having fine pores impregnated with the above-mentioned fluorine-containing surfactant was obtained. On the other hand, as a manila paper, a 25 μm thick electrolytic capacitor paper (ME3.5 made by Nippon Koshigami Kogyo Co., Ltd.) was prepared.
A 3% aqueous solution of polyvinyl alcohol is applied, and the above polymer film is attached to this applied surface in a semi-dried state, and then applied at 80 ° C.
A target capacitor separator was obtained by drying for 0 minutes.

[0030]

Examples 2 to 8 The fluorine-based porous polymer film, the fluorine-based surfactant and the conductive adhesive shown in Table 2 below were used. Otherwise, in the same manner as in Example 1, a target capacitor separator was obtained.

[0031]

[Table 2]

[0032]

[Comparative Example 1] Two sheets of electrolytic capacitor paper (PEDH60 manufactured by Nippon Koshigami Kogyo Co., Ltd.), which is kraft paper, were prepared, and these two kraft paper sheets were used as capacitor separators.

[0033]

[Comparative Example 2] Two electrolytic capacitor papers (manufactured by Nippon Kogyo Kogyo Co., Ltd., ME3.5), which are manila papers, were prepared, and these two manila papers were used as capacitor separators.

The capacitor separators of Examples and Comparative Examples thus obtained were sandwiched between the anode foil and the cathode foil. Then, as shown in FIG. 1, a capacitor element 4 was produced by winding it in a tubular shape and connecting the lead wires 3 to the anode foil 1 and the cathode foil 2, respectively. In the figure, 5 and 6 are materials constituting the separator 7 (the example product is a single-layer product having a two-layer structure, and the comparative example product is composed of two independent sheets as shown). Next, as shown in FIG. 2, the capacitor element 4 was loaded in the aluminum case 8 to produce an electrolytic capacitor. As a result, Examples 1 to 8
Also, there was no problem in the manufacturing process of the electrolytic capacitor using the separator of the comparative example.

Further, the tangent of the loss angle and the impedance of each electrolytic capacitor were measured and evaluated. The results are shown in Table 3 below. The method for evaluating the capacitor characteristics (tangent of loss angle and impedance) was according to the following method.

[Method for Evaluating Capacitor Characteristics] As shown in FIG. 1, the specifications of the produced electrolytic capacitor were such that a high-purity aluminum foil having a thickness of 70 μm was used as the anode foil 1, and the lead wire 3 was connected thereto. On the other hand, the cathode foil 2 has a thickness of 40 μm.
Using the aluminum foil of
Connected. The separator 7 was impregnated with a low-voltage low-voltage electrolytic solution and then housed in an aluminum case 8 (see FIG. 2). The outer shape of this electrolytic capacitor has a diameter of 10 mm and a length of 20 mm. After aging the obtained electrolytic capacitor, the tangent (120 Hz) of the initial loss angle was measured. Similarly, the impedance (100 kHz) was measured. All show the characteristics of the examples and comparative examples at 20 ° C.

[0037]

[Table 3]

From the results shown in Table 3 above, it can be seen that the electrolytic capacitors using the separators of Examples 1 to 8 are superior in characteristics to the electrolytic capacitors using the separator of the comparative example. The polymer membrane obtained in Example 1 was combined with pulp fibers to produce a capacitor separator.
Then, an electrolytic capacitor was manufactured in the same manner as above, and the capacitor characteristics were evaluated. As a result, Examples 1 to 8 above
The same excellent effect as the electrolytic capacitor using the separator of 1 was obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a capacitor element manufactured by sandwiching a separator.

FIG. 2 is a cross-sectional view showing an electrolytic capacitor incorporating the above capacitor element.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuji Okei 1-2-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Kozaburo Okubo Ichidori Karasuma Higashiirisuji, Nakagyo-ku, Kyoto Prefecture Eye 4th Uehara Bldg., 191, Nakaboricho Nichicon Co., Ltd. (72) Inventor, Kazumi Fujisawa Oike Dori, Kaikemaru Higashiiri, Nakagyo-ku, Kyoto, Kyoto Prefecture 4th Uehara Bldg., 191, Nakaboricho Nichicon Co., Ltd. Within

Claims (1)

[Claims] 1. A separator for a capacitor, which comprises a polymer film (A) described below and a paper-made substrate laminated or paper-made. (A) A polymer film obtained by impregnating a fluorine-based porous polymer film with a fluorine-based surfactant by utilizing the porosity of the fluorine-based polymer porous film.