JPH06215752A - Alkaline battery separator - Google Patents

Abstract

PURPOSE:To improve the preservability of an electrolyte and prolong a use life by adopting a sheet, composed of specific components 1 and 2 respectively and including a composite fiber in which the component 2 is partially positioned on a fiber surface, as an alkaline battery separator. CONSTITUTION:A composite fiber 3 used for a separator is composed of mainly an alkali-proof resin component l and an ethylene-vinylalcohol copolymer component 2, and the copolymer component 2 is positioned partially on a fiber surface, consequently is excellent in affinity with an electrolyte and also in liquid- preservability. Even the copolymer component 2 is eluted in an electrolyte, the electrolyte can be preserved in a space occupied by the copolymer component 2, eliminating the lowering of the preservability. Since ethylene-vinylalcohol copolymer is not causing self-discharge like polyamide resin, a separator using the composite fiber 3 can prolong a use life.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an alkaline battery separator.

[0002]

2. Description of the Related Art Conventionally, a separator has been used to separate a positive electrode and a negative electrode of a battery to prevent a short circuit, hold an electrolytic solution, and smoothly carry out an electromotive reaction. This separator is generally provided in the form of a woven fabric or a non-woven fabric, and various proposals have been made to improve the retention of the electrolytic solution.

For example, JP-A-59-101763 and JP-A-55-25921 disclose separators using composite fibers obtained by mixing and spinning a polyolefin resin and a polyamide resin, and JP-A-3-93154. Japanese Patent Publication discloses a separator using a fiber having a sea component made of polyamide and an island component made of polyolefin as a first component and a polyolefin as a second component,
Japanese Patent Laid-Open No. 59-196556 discloses a separator using a composite fiber in which a mixed resin of polypropylene and polyamide is used as a core portion, and a mixed resin having the same composition is used as a sheath portion foamed by a foaming agent, and Fair 4-706
Japanese Patent Publication No. 6 and Japanese Patent Publication No. 4-7067 disclose a separator using fibers obtained by dividing polypropylene resin by radially extending polyamide resin in the fiber cross section. However, it is pointed out that the polyamide resin used in these separators may cause self-discharge due to oxidative deterioration due to charge and discharge in the case of alkaline electrolyte or secondary battery. There was a problem in terms of service life.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a separator for an alkaline battery, which has excellent electrolyte retention and long service life. And

[0005]

The alkaline battery separator of the present invention (hereinafter referred to as "separator") is mainly composed of an alkali resistant resin component 1 and an ethylene-vinyl alcohol copolymer component 2. A vinyl sheet comprising a composite fiber 3 in which the vinyl alcohol copolymer component 2 is partially located on the fiber surface.

In the fiber cross section of the composite fiber 3, an internal island region composed of the ethylene-vinyl alcohol copolymer component 2 located inside and a sea composed of the alkali-resistant resin component 1 located around the internal island region. Area and
To connect the inner island region and the fiber surface, ethylene-
When the island region of the vinyl alcohol copolymer component 2 is located, the liquid retaining property is more excellent.

Further, in the fiber cross section of the composite fiber 3, even if the region of the alkali-resistant resin component 1 is divided by the region of the ethylene-vinyl alcohol copolymer component 2 extending radially from the center, the liquid retaining property is further improved. Is excellent.

[0008]

The composite fiber 3 used in the separator of the present invention is
It is mainly composed of an alkali-resistant resin component 1 and an ethylene-vinyl alcohol copolymer component 2, and since this ethylene-vinyl alcohol copolymer component 2 is partially located on the fiber surface, it has an affinity with the electrolytic solution. It has excellent properties and liquid retention. Further, even if the ethylene-vinyl alcohol copolymer component 2 is eluted into the electrolytic solution, the electrolytic solution can be retained in the space occupied by the ethylene-vinyl alcohol copolymer component 2, so that the electrolytic solution retainability is lowered. do not do. Further, since the resin to be eluted is the ethylene-vinyl alcohol copolymer component 2 and does not cause self-discharge unlike the polyamide resin, the separator using the composite fiber 3 has a long service life.

Composite fiber 3 used in the separator of the present invention
Will be described with reference to FIGS. 1 to 4, which are cross-sectional views of fibers. The composite fiber 3 usable in the present invention is shown in FIG.
As shown in (a), the ethylene-vinyl alcohol copolymer component 2 may be located only on the fiber surface portion, or as shown in FIG. 1 (b), it may be located over the entire fiber. Is also good.

Further, as shown in FIG. 2 and FIG. 3, from the internal island region composed of the ethylene-vinyl alcohol copolymer component 2 located inside and the alkali-resistant resin component 1 located around the internal island region. When the composite fiber 3 has the sea area and the island area of the ethylene-vinyl alcohol copolymer component 2 is located so as to connect the internal island area and the fiber surface, the ethylene-vinyl alcohol is used during battery use. Since the electrolytic solution can be held in the space where the copolymer component 2 is eluted, the electrolytic solution is excellent in holding property. Further, as shown in FIG. 2B and FIG. 3, the number of internal island regions may be two or more,
The cross-sectional shape may be a circle, an ellipse, an oval, a polygon such as a triangle or a quadrangle, or a fan shape, and is not particularly limited. If you have multiple internal island regions like this,
The island region composed of the ethylene-vinyl alcohol copolymer component 2 not only connects the fiber surface and the internal island region,
When the inner island regions are not connected to each other, the retention of the electrolytic solution is more excellent when the ethylene-vinyl alcohol copolymer component 2 in the inner island regions is eluted.

Further, as shown in FIG. 4, when the composite fiber 3 in which the region of the alkali-resistant resin component 1 is divided by the region of the ethylene-vinyl alcohol copolymer component 2 extending radially from the center is used, a battery is obtained. Ethylene during use
The vinyl alcohol copolymer component 2 is eluted and the composite fiber 3
Even if it is divided into fine fibers, it retains electrolyte well due to the capillary effect. As shown in FIG. 4 (b), if an island region composed of the ethylene-vinyl alcohol copolymer component 2 is also located on the fiber surface portion of the region of the alkali-resistant resin component 1, the electrolyte retaining property is further improved. Is excellent.

Such a composite fiber 3 can be easily obtained by a composite spinning method or a mixed spinning method. For example, the composite fiber 3 as shown in FIG. 2 (a) includes an ethylene-vinyl alcohol copolymer which becomes an inner island region, an alkali resistant resin which becomes a sea region and an ethylene-vinyl alcohol copolymer which becomes an island region. It can be obtained by composite spinning with a resin mixed with.

Examples of the alkali-resistant resin component 1 of the present invention include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyester copolymers, and polystyrene resins. No. 3 is excellent in alkali resistance, and polypropylene resin is particularly excellent in alkali resistance, oxidation resistance, and strength, and it is not very compatible with the electrolytic solution and has excellent gas permeability. Therefore, it can be preferably used.

On the other hand, as the ethylene-vinyl alcohol copolymer component 2, it is preferable to use one having a molar ratio of ethylene part to vinyl alcohol part of 20:80 to 40:60. When the ethylene portion is less than 20 mol%,
This is because the oxidation resistance and alkali resistance due to the ethylene part are poor, and when the ethylene part exceeds 40 mol%, the hydrophilicity due to the vinyl alcohol part is poor. Further, the ethylene-vinyl alcohol copolymer component 2 has a characteristic that it does not cause self-discharge unlike polyamide, even if it is eluted in the electrolytic solution.

The content of the ethylene-vinyl alcohol copolymer component 2 in the composite fiber 3 of the present invention is preferably 10% by weight or more from the viewpoint of affinity with the electrolytic solution when the battery is used, and it is eluted in the electrolytic solution. From the viewpoint of strength retention, it is preferably 90% by weight or less.

Further, as shown in FIGS. 2, 3 and 4 (b), when the ethylene-vinyl alcohol copolymer component 2 forms an island region in the sea region of the alkali resistant resin component, ethylene is used. -The amount of vinyl alcohol copolymer component is 3
It is preferably from 0 to 70% by weight. This is because if it is less than 30% by weight, the affinity with the electrolytic solution is poor, and if it exceeds 70% by weight, the strength is significantly reduced when it is dissolved in the electrolytic solution. More preferably, it is 40 to 60% by weight. The weight ratio of the ethylene-vinyl alcohol copolymer component 2 as described above can be controlled by the mixing ratio of the raw material pellets and the supply amount of the melt during the composite spinning or the mixed spinning.

In order to improve the affinity of the composite fiber 3 with respect to the electrolytic solution and further improve the retention of the electrolytic solution, glow discharge treatment, corona discharge treatment, high frequency discharge treatment, microwave discharge treatment, or these discharges is performed. Plasma treatment obtained by the treatment, sulfonation treatment by contact with fuming sulfuric acid, fluorination treatment by contact with a reactive gas composed of oxygen or sulfurous acid gas and fluorine gas,
Alternatively, it is more preferable to perform a hydrophilic treatment such as adding a surfactant.

A fiber sheet is formed from the composite fibers 3 obtained by the composite spinning or the mixed spinning as described above. In addition to these composite fibers, other fibers such as polyolefin fibers such as polypropylene fibers are mixed. You may form a fiber sheet. The mixing amount of the other fibers with respect to the composite fiber 3 is preferably less than 50% by weight so as not to impair the electrolyte retaining property of the composite fiber 3.

The form of the fiber sheet may be a woven fabric such as a plain weave, a twill weave, a satin weave, a knitted fabric, a thread lace, a net, a flat braid or a non-woven fabric, but is not particularly limited.
Woven fabrics and non-woven fabrics can be suitably used because they are excellent in morphological stability, insulating properties between electrode plates, and structurally excellent in retaining electrolyte.

The nonwoven fabric may be produced, for example, by a fibrous web obtained by a card method, an air lay method, a wet method, a spun bond method, a melt blow method, or the like, which is obtained by binding with an adhesive, composite spinning, or mixed spinning. 3 or other fibers to be mixed by thermal fusion bonding, entanglement by a fluid flow such as a needle or water flow, or stitch bonding.

The fiber sheet obtained as described above is used as the separator of the present invention. Examples of the separator of the present invention will be described below, but the invention is not limited to the following examples.

[0022]

Example 1 Ethylene with an ethylene content of 29 mol%
25 parts of a vinyl alcohol copolymer and 25 parts of a polypropylene resin were mixed in a pellet state and melt-kneaded in an extruder, and 50 parts of the same ethylene-vinyl alcohol copolymer as the above was melted in the extruder. After the polymer melt B and the speed ratio of the gear pump were weighed at a ratio of 7: 6 and subjected to composite spinning, the mixture was drawn at 130 ° C. to 2.7 times and cut, and the fineness was 2.6 denier and the fiber length was 50 mm. The composite fiber 3 of was obtained. As shown in FIG. 2 (a), the cross-sectional shape of this composite fiber 3 is centered on the ethylene-vinyl alcohol resin component 2
Was formed, and the island region made of the ethylene-vinyl alcohol resin component was located in the sea region of the polypropylene resin around the circular inner island region.

A fiber web obtained by carding 100% of this composite fiber was needle punched to have a basis weight of 70 g / m ² ,
After forming a non-woven fabric having a thickness of 0.20 mm, 0.5% by weight of a nonionic surfactant was attached to obtain a separator.

(Example 2) Composite spinning was carried out in the same manner as in Example 1 to obtain a composite fiber 3 having a fineness of 2.6 denier and a fiber length of 50 mm. As shown in FIG. 2 (b), the cross-sectional shape of this composite fiber 3 has eight circular inner island regions composed of the ethylene-vinyl alcohol copolymer component 2, and the polypropylene resin around these inner island regions. The island region composed of the ethylene-vinyl alcohol resin component was located in the sea region. A fiber web obtained by carding 100% of this composite fiber was needle-punched into a nonwoven fabric having a basis weight of 70 g / m ² and a thickness of 0.20 mm, and 0.5% by weight of a nonionic surfactant was adhered to the nonwoven fabric. A separator was obtained.

(Example 3) The speed ratio of the gear pump of the same mixed polymer melt A as in Example 1 and the polymer melt B of the ethylene-vinyl alcohol copolymer 2 was measured at a ratio of 3: 7. In the same manner as in Example 1, the composite spinning was performed to obtain a composite fiber 3 having a fineness of 2.6 denier and a fiber length of 50 mm. The cross-sectional shape of this composite fiber 3 is as shown in FIG.
It has eight fan-shaped inner island regions made of the ethylene-vinyl alcohol copolymer component 2, and the island regions made of the ethylene-vinyl alcohol resin component are located in the sea region of the polypropylene resin around the inner island regions. It was a thing. A fiber web obtained by carding 100% of this composite fiber was needle punched to have a fabric weight of 70 g / m ² and a thickness of 0.1.
After making a 20 mm non-woven fabric, add a nonionic surfactant to 0.
5 wt% was adhered to obtain a separator.

Example 4 Ethylene content is 29 mol%
2. The polymer melt A of 50 parts of the ethylene-vinyl alcohol copolymer and the polymer melt B of 50 parts of the polypropylene resin were weighed in a ratio of 2: 8 at the speed ratio of the gear pump and composite-spun, and the fineness was 2. A composite fiber 3 having a denier of 6 and a fiber length of 50 mm was obtained. The cross-sectional shape of this composite fiber 3 is shown in FIG.
As shown in (a), the area of the polypropylene resin was divided into eight by the area of the ethylene-vinyl alcohol copolymer component 2 extending radially from the center. A fiber web obtained by carding 100% of this composite fiber was needle punched to have a fabric weight of 70 g / m ² and a thickness of 0.20 mm.
Then, 0.5% by weight of a nonionic surfactant was attached to obtain a separator.

(Example 5) Ethylene content was 29 mol%
Of ethylene-vinyl alcohol copolymer of 25 parts and polypropylene of 25 parts, and a polymer melt B of 50 parts of ethylene-vinyl alcohol copolymer were mixed at a speed ratio of a gear pump of 8: 2. The composite fiber was weighed in a ratio and subjected to composite spinning to obtain a composite fiber 3 having a fineness of 2.6 denier and a fiber length of 50 mm. As shown in FIG. 4B, the cross-sectional shape of the composite fiber 3 is such that the area of the polypropylene resin component is divided into eight by the area of the ethylene-vinyl alcohol copolymer component 2 that extends radially from the center. The island region made of the ethylene-vinyl alcohol resin component was located in the resin component region. A fiber web obtained by carding 100% of this composite fiber was needle punched to have a fabric weight of 70 g / m ² and a thickness of 0.20 mm.
Then, 0.5% by weight of a nonionic surfactant was attached to obtain a separator.

Example 6 Ethylene content is 29 mol%
Of ethylene-vinyl alcohol copolymer of 25 parts and polypropylene of 25 parts, and a polymer melt B of 50 parts of polypropylene resin were measured at a gear pump speed ratio of 7: 6 to form a composite. Spin and fineness 2.
A composite fiber 3 having a denier of 6 and a fiber length of 50 mm was obtained. As shown in FIG. 1 (a), the cross-sectional shape of this composite fiber 3 was such that the sea area of the polypropylene resin component and the island area of the ethylene-vinyl alcohol copolymer component 2 were located only near the fiber surface. . A fiber web obtained by carding 100% of this composite fiber was needle punched to have a basis weight of 70.
After forming a non-woven fabric having a thickness of g / m ² and a thickness of 0.20 mm, 0.5% by weight of a nonionic surfactant was adhered to obtain a separator.

Example 7 Ethylene content is 29 mol%
50 parts of ethylene-vinyl alcohol copolymer component of
A mixed polymer melt with 50 parts of polypropylene was weighed and spun at a speed ratio of a gear pump of 5: 5 to obtain a conjugate fiber 3 having a fineness of 2.6 denier and a fiber length of 50 mm. As shown in FIG. 1 (b), the cross-sectional shape of this composite fiber 3 was such that the sea area of the polypropylene resin component and the island area of the ethylene-vinyl alcohol copolymer component 2 were located throughout the fiber. A fiber web obtained by carding 100% of this composite fiber was needle punched to have a basis weight of 70 g /
After forming a non-woven fabric with m ² and a thickness of 0.20 mm, 0.5% by weight of a nonionic surfactant was attached to obtain a separator.

(Comparative Example) A fineness 2 having a cross-sectional shape as shown in FIG. 2 (a) was obtained in the same manner except that a polyamide resin was used in place of the ethylene-vinyl alcohol copolymer of Example 1. A composite fiber having a denier of 0.6 and a fiber length of 50 mm was obtained. A fiber web obtained by carding 100% of this composite fiber was needle-punched into a non-woven fabric having a basis weight of 70 g / m ² and a thickness of 0.20 mm, and 0.5% by weight of a nonionic surfactant was applied thereto. , A separator was obtained.

(Wettability) Each of the separators of Examples 1 to 7 and Comparative Example was cut into 2 × 15 cm, and the lower end of the test piece was immersed in an aqueous potassium hydroxide solution having a specific gravity of 1.3 for 0.5 cm, The wettability was evaluated by the liquid absorption height after 30 minutes. This test was performed before and after the battery charge / discharge test described below. The wettability test after the battery charge / discharge test was performed after the separator was thoroughly washed with water and dried. The results are shown in Table 1.

[0032]

[Table 1]

(Battery Charge / Discharge Test) Using each of the separators of Examples 1 to 7 and Comparative Example, the battery capacity was 1200 mA.
A nickel-cadmium battery of h was made. After activating this battery, place each battery in a constant temperature bath at 20 ° C for 24 hours.
After charging for 6 hours with a current of 0mA, pause for 30 minutes, then 240mA
The discharge to the final voltage of 0.8 V with the current of 1 was set as one cycle, and the charge / discharge was repeated, and the number of times until the charge / discharge was impossible was measured. The results are also shown in Table 1.

[0034]

The composite fiber used in the alkaline battery separator of the present invention mainly comprises an alkali resistant resin component and an ethylene-vinyl alcohol copolymer component, and the ethylene-vinyl alcohol copolymer component is a partial component. Since it is located on the fiber surface, it has excellent affinity with the electrolytic solution and excellent liquid retention. Further, even if the ethylene-vinyl alcohol copolymer component is eluted into the electrolytic solution, the electrolytic solution can be retained in the space occupied by the ethylene-vinyl alcohol copolymer component, so that the retaining property of the electrolytic solution does not decrease. In addition, since the resin to be eluted is an ethylene-vinyl alcohol copolymer component and does not cause self-discharge unlike polyamide resin, the separator using this composite fiber has a long service life.

In the fiber cross section, there is an internal island region made of the ethylene-vinyl alcohol copolymer component located inside, and a sea region made of the alkali-resistant resin component located around this internal island region. The separator containing the composite fiber in which the island region of the ethylene-vinyl alcohol copolymer component is located so as to connect the island region and the fiber surface, in the space where the ethylene-vinyl alcohol copolymer component is eluted during use of the battery. Since it can hold the electrolytic solution, it is excellent in holding the electrolytic solution.

In the separator having the composite fiber in which the region of the alkali-resistant resin component is divided by the region of the ethylene-vinyl alcohol copolymer component radially extending from the center in the cross section of the fiber, the separator may be ethylene during use of the battery. -Even when the vinyl alcohol copolymer component is eluted, the fibers are divided and finely divided, and therefore the electrolyte solution is excellent in retention due to the capillary effect.

The alkaline battery separator of the present invention as described above includes primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries and air batteries, nickel-cadmium batteries, nickel-zinc batteries and nickel-hydrogen batteries. It can be used as a secondary battery.

[Brief description of drawings]

FIG. 1A is an example of a schematic sectional view of a composite fiber. FIG. 1B is another example of a schematic sectional view of a composite fiber.

FIG. 2 (a) Another example of cross-sectional schematic diagram of conjugate fiber (b) Another example of cross-sectional schematic diagram of conjugate fiber

FIG. 3 Another example of cross-sectional schematic view of composite fiber

FIG. 4 (a) Another example of schematic sectional view of conjugate fiber (b) Another example of schematic sectional view of conjugate fiber

[Explanation of symbols]

 1 Alkali-resistant resin component 2 Ethylene-vinyl alcohol copolymer component 3 Composite fiber

Claims (3)

[Claims] 1. An alkali-resistant resin component 1 is mainly used,
An alkali comprising a fiber sheet comprising an ethylene-vinyl alcohol copolymer component 2 and a composite fiber 3 in which the ethylene-vinyl alcohol copolymer component 2 is partially located on the fiber surface. Battery separator. 2. The fiber cross section has an internal island region composed of the ethylene-vinyl alcohol copolymer component 2 located inside, and a sea region composed of the alkali-resistant resin component 1 located around the internal island region. The separator for an alkaline battery according to claim 1, wherein the composite fiber 3 has an island region of the ethylene-vinyl alcohol copolymer component 2 positioned so as to connect the internal island region and the fiber surface. 3. A composite fiber 3 in which a region of an alkali-resistant resin component 1 is divided by a region of an ethylene-vinyl alcohol copolymer component 2 extending radially from the center in a fiber cross section. The alkaline battery separator according to claim 1.