JPH07134978A - Separator for alkaline battery - Google Patents

Abstract

PURPOSE:To improve electrolyte retention, to exhibit excellent hydrophilic performance for a long time, and to prolong the life of a battery by carrying out an oxidation treatment in polyolefine group nonwoven fabric composed by containing micropore polyolefine group fabric. CONSTITUTION:Oxidation treatment is applied to polyolefine group nonwoven fabric containing micropore polyolefine group fabric which is polypropylene micropore fabric or porous structure polyethylene micropore fabric having numerous micropores from the fabric surface to the inside. For the oxidation treatment, a gas phase reaction by oxygen gas is used, and following this reaction, oxygen functional groups are introduced onto the fabric surface of the polyolefine group nonwoven fabric containing the micropore polyolefine group fabric and in the micropores of the micropore polyolefine group fabric, so that hydrophilic property is exhibited. The polyolefine group nonwoven fabric contains 10-70% by weight of the micropore polyolefine group fabric. In this way, extremely excellent electrolyte retention performance is provided in an alkaline battery, while its life can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery separator used in nickel-cadmium storage batteries, nickel-hydrogen storage batteries and the like.

[0002]

2. Description of the Related Art Nonwoven fabric separators made of polyolefin fibers for alkaline batteries, which have chemical resistance,
As a separator excellent in required properties such as oxidation resistance and hydrophilicity, a sulfonation treatment is carried out to introduce a sulfonic acid group (JP-A-58-175256, JP-A-6-156256).
No. 4-57568, JP-A Nos. 1-132043 and 1-132044), those coated with a hydrophilic resin (JP-A-63-34849), and those to which a surfactant is added (JP-A-58-58). 147956, JP-A-58-
194255, JP-A-61-39362) and the like are known.

However, none of the above-mentioned conventional alkaline battery separators can maintain the above performance for a long period of time. For example, those treated with sulfonation have a reduced battery life due to deterioration of the polyolefin fibers, and those treated with hydrophilic resins and surfactants have the resin and surfactants falling into the electrolyte. It has a drawback that the hydrophilic property is deteriorated.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art. It has a good electrolyte retention performance and can exhibit an excellent hydrophilic performance for a long period of time, thereby extending the life of the battery. It is an object of the present invention to provide an alkaline battery separator that can be used.

[0005]

The alkaline battery separator of the present invention is formed by oxidizing a polyolefin-based nonwoven fabric containing microporous polyolefin-based fibers.

The microporous polyolefin fiber referred to in the present invention means a polyethylene microporous fiber or a polypropylene microporous fiber having a porous structure having innumerable micropores extending from the fiber surface to the inside. The pore size of the fine pores can be appropriately changed according to the production conditions and application of the fiber, but in the present invention, polypropylene fineness is provided in order to have strength as an alkaline battery separator and to exhibit good hydrophilicity. In the case of pore fiber, major axis x minor axis = (0.1 μm x 0.1
μm) or less, and in the case of polyethylene micropore fiber, major axis × minor axis = (2 μm × 1 μm) or less. Further, as the microporous polyolefin fiber in the present invention, polypropylene microporous fiber excellent in chemical resistance is suitable,
It can be used particularly preferably.

The oxidation treatment referred to in the present invention is a gas phase reaction by oxygen gas, and by this reaction, the fiber surface of a polyolefin-based nonwoven fabric containing fine-pore polyolefin fibers and the fine-pore polyolefin fibers are finely divided. An oxygen functional group is introduced into the pores to develop hydrophilicity.

The alkaline battery separator of the present invention is characterized in that the polyolefin non-woven fabric contains 10 to 70% by weight of microporous polyolefin fibers.

10% by weight of microporous polyolefin fiber
If it is less than 70% by weight, improvement in electrolyte retention performance and hydrophilicity is not recognized, and if it exceeds 70% by weight, the strength of the separator decreases, which is not preferable.

[0010]

According to the present invention, a hydrophilic oxygen functional group, such as a carbonyl group, which is a hydrophilic oxygen functional group by oxidation treatment, is formed on the fiber surface of the polyolefin non-woven fabric containing the microporous polyolefin fiber and in the micropores of the microporous fiber. Carboxyl group,
A hydroxyl group and the like are sufficiently introduced.

[0011]

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

(Embodiment 1) Fine pore size is major axis × minor axis = 0.1
Micro pore polypropylene fiber of μm × 0.1 μm (made by Ube Nitto Kasei, UNK micro pore polypropylene fiber, 2d ×
51 mm) 50%, and a commercially available core-sheath type composite fiber composed of polyethylene as a sheath component and polypropylene as a core component (sheath-core weight composite ratio 50:50, 0.9).
d × 38 mm) was mixed with 50% and a polyolefin non-woven fabric sheet having a basis weight of 60 g / m ² and a thickness of 0.18 mm was prepared by a known web forming means. This non-woven fabric sheet was placed in a reaction tank, vacuum degassed, and then a gas phase contact reaction with oxygen gas was performed for 10 minutes in an atmosphere of an inert gas such as nitrogen.
The alkaline battery separator of was obtained.

(Example 2) The microporous polypropylene fiber of Example 1 was used as a microporous polyethylene fiber having a micropore size of major axis x minor axis = 2 µm x 1 µm (UNK, Ube Nitto Kasei Co., Ltd., UNK).
A separator for an alkaline battery of Example 2 was obtained under the same conditions and method as in Example 1, except that the microporous polyethylene fiber was 2d × 51 mm).

(Comparative Example 1) The non-woven fabric sheet (non-oxidized non-woven fabric sheet) prepared in Example 1 was used as the alkaline battery separator of Comparative Example 1.

(Comparative Example 2) A polypropylene fiber of regular pores (2d x 5)
The alkaline battery separator of Comparative Example 2 was prepared under the same conditions and methods as those of Example 1 except that the thickness was set to 1 mm).

(Comparative Example 3) 5% by weight of the microporous polypropylene fiber of Example 1, 45% by weight of regular polypropylene fiber (2d x 51 mm), and 50% by weight of the core-sheath type binder fiber used in Example 1 %, And other conditions were the same as in Example 1, except that Comparative Example 3 was used.
The alkaline battery separator of was produced.

(Comparative Example 4) 75% by weight of the microporous polypropylene fiber of Example 1 and 2% of the binder fiber of Example 1 were used.
The alkaline battery separator of Comparative Example 4 was prepared under the same conditions and methods as in Example 1 except that the compounding amount was 5% by weight.

With respect to the alkaline battery separators of Examples 1 and 2 and Comparative Examples 1 to 4, electrolyte solution absorption rate, separator strength, and electrolyte solution retention rate tests were conducted. The results are shown in Table 1 below.

[0019]

[Table 1]

Further, as the positive electrode and the negative electrode, known strip-shaped sintered nickel hydroxide electrodes and sintered cadmium electrodes were used one by one, and the alkaline battery separator obtained in the above-mentioned embodiment was placed between these electrodes. After interposing it and winding it while pulling, it was placed in a cylindrical metal case. And inject the alkaline electrolyte mainly potassium hydroxide,
A battery lid with a safety valve was attached, and an AA sealed nickel cadmium battery with a nominal capacity of 0.7An was created. A nickel-cadmium battery was similarly prepared for the alkaline battery separator of the comparative example.

The evaluation results of the performance test of the above battery are shown in FIG.

[0022]

INDUSTRIAL APPLICABILITY As described above, the alkaline battery separator of the present invention is excellent in hydrophilicity and can be exhibited for a long period of time. Therefore, by using the alkaline battery separator of the present invention, extremely excellent electrolyte retention performance,
Moreover, an alkaline storage battery having a long life can be configured.

[Brief description of drawings]

FIG. 1 is a curve diagram showing changes in the discharge maintenance rate with respect to the number of times charging and discharging are repeated in batteries using the alkaline battery separators of Examples and Comparative Examples.

Claims (2)

[Claims] 1. A separator for an alkaline battery, which is obtained by subjecting a polyolefin-based nonwoven fabric composed of microporous polyolefin-based fibers to an oxidation treatment. 2. The alkaline battery separator according to claim 1, wherein the polyolefin-based non-woven fabric contains 10 to 70% by weight of microporous polyolefin-based fibers.