JPH06187963A - Nonwoven fabric separator for alkaline battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a nonwoven fabric separator for an alkaline battery having favorable chemical stability in hydrophilic property, alkali resistance, acid resistance, etc., for a long period, and a manufacturing method thereof. CONSTITUTION:A separator comprises a porous body formed of polyolefine fibers of which surface is coated with chlorinated polyolefine to which sulfon group is introduced, or copolymeric resin of chlorinated polyolefine and carboxylic acid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric separator for an alkaline battery, which is preferably used for a sealed alkaline battery such as a nickel-cadmium battery, a nickel-hydrogen battery and a nickel-zinc battery, and a method for producing the same.

[0002]

2. Description of the Related Art Separator used in alkaline storage batteries is
It is required to hold the alkaline electrolyte for a long time against repeated charging / discharging for a long time to prevent a short circuit due to contact between electrodes.

At present, polyamide-based fibers, which are widely used as non-woven fabrics for alkaline battery separators, do not have sufficient chemical resistance such as alkali resistance and oxidation resistance during repeated charging / discharging for a long period of time, so that fiber deterioration is caused. However, there is a drawback that the battery life progresses and the battery life is shortened due to a short circuit between the electrodes.

On the other hand, a separator using a polyolefin fiber excellent in chemical resistance such as alkali resistance and oxidation resistance has been proposed. However, since the hydrophilicity is poor, the electrolyte retention is extremely poor and the charge and discharge are poor. There was a drawback in that the electrolyte solution was easily dried out due to repetition.

As a method for solving these drawbacks, a method in which a surfactant is added (JP-A-58-175256) and a method in which hydrophilic inorganic powder is added (JP-A-64).
No. 57568), polyethylene fibers or polypropylene fibers are sulfonated to introduce a sulfonic acid group, which is a hydrophilic group (Japanese Patent Laid-Open Nos. 1-132043 and 1-132044). There is.

[0006]

The method of applying the above-mentioned surfactant and the method of adding the hydrophilic inorganic powder are such that the surface active agent and the inorganic powder fall off from the fiber surface into the electrolytic solution due to the cell reaction. In many cases, it is difficult to maintain stable hydrophilicity over a long period of time.

The above-mentioned sulfonation treatment involves sulfonation of α-olefins with fuming sulfuric acid and the like, and it is difficult to quantitatively control the introduction of a predetermined amount of sulfone groups efficiently, and stable for a long period of time. It was difficult to maintain hydrophilicity.

An object of the present invention is to provide a non-woven fabric separator for an alkaline battery, which can maintain hydrophilicity for a long period of time and is excellent in chemical stability such as alkali resistance and oxidation resistance, and a method for producing the same. Is.

[0009]

DISCLOSURE OF THE INVENTION The present invention is formed from a polyolefin-based fiber whose surface is coated with a sulfone group-introduced chlorinated polyolefin or a copolymer resin of a chlorinated polyolefin and a carboxylic acid. .

The chlorinated polyolefin resin means a chlorinated polypropylene resin or a chlorinated polyethylene resin.

Further, the present invention is a sulfonation treatment of a nonwoven fabric sheet made of a polyolefin fiber coated with a chlorinated polyolefin or a copolymer resin of a chlorinated polyolefin and a carboxylic acid.

The sulfonation treatment conditions are not particularly limited, but treatment with a concentrated sulfuric acid bath at 30 to 90 ° C.,
It is preferable to perform low temperature treatment with 5 to 15% fuming sulfuric acid, treatment with SO ₃ gas, and the like.

[0013]

According to the present invention, the chlorinated polyolefin or the copolymer resin of chlorinated polyolefin and carboxylic acid has a sulfonation treatment, whereby the substitution reaction between the chloro group and the sulfo group is carried out very smoothly, It is possible to introduce a sufficient amount of sulfone groups, and in the case of the copolymer resin of chlorinated polyolefin and carboxylic acid, sulfone treatment is carried out on the tertiary carbon portion of the main chain to which the carboxyl group is bonded by the sulfonating treatment. The group can be stably introduced, and it is possible to configure a non-woven fabric separator for an alkaline battery which is more hydrophilic in combination with the hydrophilicity of the existing carboxyl group.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below.

Example 1 A core-sheath type composite fiber (2d × 51 mm, core-sheath weight composite ratio 50:50) composed of a polypropylene resin as a core component and a polyethylene resin as a sheath component.
70% by weight and regular polypropylene fiber (1.
(5d × 38 mm) 30% by weight of a mixed fiber fiber web is thermocompression bonded with a pair of calender rolls heated to 130 ° C. and a basis weight of 65 g / m ² and a thickness of 0.20 mm.
A non-woven fabric sheet A was obtained.

Next, the nonwoven fabric sheet A was impregnated with a toluene solution of chlorinated polypropylene resin (chlorine content 7%) and dried, and then the SO ₃ gas concentration was 8 vo1% and the temperature was 60 ° C.
A gas phase contact treatment was carried out for 30 seconds in the gas atmosphere, followed by washing with water, alkali neutralization, washing and drying to obtain a nonwoven fabric separator for an alkaline battery of Example 1.

(Example 2) Nonwoven sheet A of Example 1
Was impregnated with a toluene solution of chlorinated polypropylene resin (chlorination rate 10%) and dried, and then the SO ₃ gas concentration was 8 vo1.
%, A gas layer contact treatment was performed for 30 seconds in a gas atmosphere at a temperature of 60 ° C., followed by washing with water, alkali neutralization, washing and drying to obtain a nonwoven fabric separator for an alkaline battery of Example 2.

(Example 3) Nonwoven sheet A of Example 1
Is a copolymer resin of chlorinated polypropylene and carboxylic acid (chlorine content 10%, acrylic acid copolymerization ratio 1.7
(Mol%) in a toluene solution, dried, and then subjected to a gas phase contact treatment for 30 seconds in a gas atmosphere having a SO ₃ gas concentration of 8 vo1% and a temperature of 60 ° C., and then washed with water, neutralized with alkali, washed and dried The nonwoven fabric separator for alkaline batteries of Example 3 was obtained.

(Comparative Example) The nonwoven fabric sheet A of Example 1 was
In a gas atmosphere having a SO ₃ gas concentration of 8 vol 1% and a temperature of 60 ° C., a gas layer contact treatment was performed for 30 seconds, followed by washing with water, alkali neutralization, washing, and drying to obtain a non-woven fabric separator for alkaline batteries of a comparative example.

Table 1 below shows the results of a comparative test of various physical properties of the nonwoven fabric separators for alkaline batteries obtained in Examples 1 to 3 and Comparative Example.

[0021]

[Table 1]

The test methods for the test items in the table are as follows. Moisture content: Moisture content at 20 ° C., RH 65%, after standing for 24 hours. Liquid absorption speed: Liquid absorption height after 30 minutes of immersion of one end of a separator material having a sample width of 25 mm in a caustic potash solution having a specific gravity of 1.30. Liquid retention rate: The solution absorption rate after immersing the separator material in a caustic potash solution having a specific gravity of 1.30, suspending it for 10 minutes and draining it. Alkali resistance; 80 ℃ in caustic potash solution with specific gravity of 1.30
Weight loss rate after soaking for 30 days. Oxidation resistance: 50% in a mixed solution of 250 ml of a 5% KMnO ₄ solution and 50 ml of a caustic potash solution having a specific gravity of 1.30.
Weight loss rate after soaking for 1 hour at ℃. Strength retention rate: Retention rate of separator tensile strength before and after SO ₃ gas treatment.

Furthermore, using the nonwoven fabric separators for alkaline batteries obtained in Examples 1 to 3 and Comparative Example above, the capacity 1
FIG. 1 shows the results of testing by incorporating the battery in a 200 mA · hr Ni—Cd battery.

As shown in FIG. 1, the one using the non-woven fabric separator for alkaline batteries of Examples 1, 2 and 3 is 200
Repetition of charging and discharging 0 times (charging condition 400 mA × 4 hr,
Discharge condition 1Ω constant resistance discharge x 2hr) 70 in the test
While the capacity retention rate was shown as%, the capacity of the non-woven fabric separator for the alkaline battery of Comparative Example was decreased early after the electrolyte leakage due to the increase in internal pressure, which is thought to be due to poor hydrophilicity. It was observed.

[0025]

The non-woven fabric separator for alkaline batteries according to the present invention is excellent in hygroscopicity, can maintain the affinity with the electrolytic solution for a long period of time, and can enhance the liquid retaining property. Further, it has excellent durability due to excellent alkali resistance and oxidation resistance, and has various effects such as high capacity can be maintained during repeated charging and discharging for a long time, and battery life can be greatly improved.

[Brief description of drawings]

FIG. 1 is a curve diagram showing a change in a discharge capacity retention rate with respect to the number of times charging and discharging are repeated.

Claims (2)

[Claims] 1. A non-woven fabric separator for an alkaline battery, which is formed from a polyolefin-based fiber whose surface is coated with a sulfone group-introduced chlorinated polyolefin or a copolymer resin of a chlorinated polyolefin and a carboxylic acid. 2. A method for producing a non-woven fabric separator for an alkaline battery, which comprises subjecting a non-woven fabric sheet made of a polyolefin fiber coated with a chlorinated polyolefin or a copolymer resin of a chlorinated polyolefin and a carboxylic acid to a sulfonation treatment. .