JPH06338308A - Separator for alkaline battery - Google Patents

Abstract

PURPOSE:To restrict the lowering of hydrophilic characteristic due to the repeat of charge and discharge, and to prolong the lifetime of a battery by coating a nonwoven sheet made of polyolefinic fiber with styrene-styrenesulfonic acid soda copolymer resin. CONSTITUTION:A nonwoven sheet made of polyolefinic fiber is coated with styrene-styrenesulfonic acid soda copolymer resin. As a syrene-styrenesulfonic acid soda copolymer resin, dual copolymer resin, which includes syrene- styrenesulfonic acid soda at 30 weight% or less, is desirable. Hydrophilic characteristic is given to a separator for battery to prolong the lifetime of the battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a Ni-Cd battery, Ni
The present invention relates to an alkaline battery separator that can be suitably used for an alkaline secondary battery such as an H battery.

[0002]

2. Description of the Related Art Conventionally, it has been known that when a non-woven fabric composed of polyolefin fibers is used as a separator for alkaline batteries, the chemical resistance becomes very good. In particular, various olefin-based separators having excellent chemical resistance have been investigated because they are required to have durability against a severe battery reaction in an electrolytic solution up to around 80 ° C. which occurs in an alkaline battery. However, although polyolefin-based fibers such as polypropylene and polyethylene fibers have good alkali resistance and oxidation resistance, they have a great disadvantage that they have poor affinity with an electrolytic solution and poor retention.

In order to solve this, a polyolefin-based non-woven fabric treated with a surfactant (Japanese Patent Laid-Open No. 58-14795).
6, JP-A-58-194255, JP-A-61-39.
362), a non-woven fabric separator using vinylon (Japanese Patent Publication No. 56-26942), and an ethylene-vinyl alcohol copolymer resin fiber (JP-A-63-3484).
No. 9), a polyethylene fiber or a polypropylene fiber subjected to a sulfonation treatment (JP-A-58-17525).
6, JP-A 64-57568, JP-A 1-1320.
No. 43, JP-A No. 1-132044, EPC Publication No. 03.
16916A2) and the like.

[0004]

However, in the above-mentioned prior art, in the case where the surfactant treatment is applied, the surfactant elutes or deteriorates and decomposes due to repeated charging and discharging for a long period of time, and the hydrophilicity decreases, The materials to which vinylon fibers or ethylene vinyl alcohol copolymer fibers are applied have problems such as deterioration of resin due to oxidation reaction in a strong alkaline electrolyte solution, shortening of life due to alteration, short circuit between electrodes, and the like.

Further, the sulfonation-treated separator is a sulfonation treatment of α-polyolefin with concentrated sulfuric acid or high-concentration fuming sulfuric acid at a high temperature of 100 ° C. or higher. Due to the substitution reaction, the reaction efficiency was very poor, and it was difficult to introduce a certain amount of sulfone groups. In addition, since the fiber surface is cured by the sulfonation treatment, there is a problem that the workability during the battery manufacturing process is poor.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an alkaline battery separator capable of achieving a long life of the battery with little deterioration in hydrophilicity due to repeated charging and discharging for a long period of time. Is to provide.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a separator for an alkaline battery, characterized in that a non-woven sheet made of polyolefin fibers is coated with a styrene-sodium styrene sulfonate copolymer resin. .

The above-mentioned styrene-sodium styrene sulfonate copolymer resin contains 30 parts of styrene sodium sulfonate.
It is preferable that the content of the binary copolymer resin is not more than wt%.
When the content of sodium styrene sulfonate exceeds 30% by weight, the copolymer resin is transformed into water-soluble and the alkali resistance is lowered, which makes it unsuitable as a battery separator.

[0009]

According to the present invention, the styrene-sodium styrene sulfonate copolymer resin formed on the non-woven sheet composed of the polyolefin fibers by coating imparts good hydrophilicity to the battery separator.

[0010]

EXAMPLES Examples of the present invention will be described in detail below. The present invention should not be construed as being limited to the following examples.

(Example 1) A commercially available core-sheath type composite fiber (polyurethane fiber having a sheath component of polyethylene and polypropylene having a sheath component of 50% of 1.5d × 38 mm) (sheath: core weight composite ratio) 50:50) 0.9d
50% x 51 mm was mixed, and this mixed fiber was made into a web through a roller card machine. Next, this web 110
Pass through a pair of calender rolls heated to ℃
A non-woven fabric sheet having g / m ² and a thickness of 0.15 mm was prepared.

Next, 20 parts of sodium styrene sulfonate was added.
A styrene-sodium styrene sulfonic acid copolymer resin emulsion was prepared so that the content of the styrene-styrene sulfonic acid copolymer resin contained in the non-woven fabric sheet was D. P. This resin emulsion was coated so that U was 9%, and dried to obtain an alkaline battery separator of the example.

Comparative Example 1 A styrene-sodium styrene sulfonate copolymer resin emulsion was prepared so as to contain 30% by weight of sodium styrene sulfonate, and D. P. This resin emulsion was coated so that U was 9%, and dried to obtain an alkaline battery separator of Comparative Example 1.

(Comparative Example 2) A styrene-sodium styrene sulfonate copolymer resin emulsion was prepared so as to contain 50% by weight of sodium styrene sulfonate, and D. P. This resin emulsion was coated so that U was 9% and dried to obtain a separator for an alkaline battery of Comparative Example 2.

(Comparative Example 3) The non-woven fabric sheet prepared in Example was used as a separator for an alkaline battery in Comparative Example 3.

Comparative tests were conducted below on the alkali resistance reduction rate of the alkaline battery separators obtained in the examples and comparative examples. Table 1 shows the test results.

[0017]

[Table 1]

From Table 1 above, it is understood that in Comparative Examples 1 and 2, the alkali resistance is significantly lowered due to the resin falling off.

Further, FIG. 1 shows the test results of the battery performance using the separators obtained in the above Examples and Comparative Example 1. The above-mentioned separator was incorporated into a Ni-Cd battery with a capacity of 1200mA · hr, and the temperature was 20 ° C and the charging condition was 400mA × 4.
hr, discharge condition 1 Ω constant resistance discharge × 2 hr shows the discharge capacity retention rate when a charge / discharge test is repeated. The horizontal axis represents the number of charge / discharge cycles (cycle) and the vertical axis represents the discharge capacity. Shows the maintenance rate.

As is apparent from FIG. 1, the battery using the separator according to the present invention has a small decrease in discharge capacity even after repeated charging and discharging because of its excellent electrolyte affinity and durability. The batteries using the separators No. 2, 2 and 3 showed a decrease in discharge capacity after repeating charge and discharge about 1000 times.

From the above results, the alkaline battery separator of the example has a small decrease in discharge capacity even after repeated charging and discharging, because of its excellent hydrophilicity and alkali resistance, and therefore has a small decrease in discharge capacity over a long period of time. It turns out that it can be used.

[0022]

As described above, according to the present invention, even if charging and discharging are repeated, the deterioration of hydrophilicity and alkali resistance of the separator can be suppressed to a very small level, and the life of the battery can be extended. .

[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 Examples of the present invention and Comparative Examples.

Claims (1)

[Claims] 1. A separator for an alkaline battery, comprising a non-woven sheet made of a polyolefin fiber coated with a styrene-sodium styrene sulfonate copolymer resin.