JPH01130464A - Separator for battery - Google Patents

Abstract

PURPOSE:To enhance the alkali electrolyte absorbing capacity by using a sheet consisting of chitin fiber or a one consisting of chitin fibril. CONSTITUTION:A separator for battery is made from a sheet of chitin fiber or a one of chitin fibril. The chitin consists of amino polysaccharide and its derivative extracted from exoskeletons of Crustacea, Insecta, etc., wherein the polysaccharide is obtained as residues of those skeletons which are subjected to hydrochloric acid treatment and sodium hydroxide treatment followed by removal of ashes and proteins. The chitin fiber or fibril shall preferably be manufactured by wet type molding method. Sheet shall favorably be manufactured by such a method as dispersing in water together with binder and then removing the water to turn it into the from of sheet, followed by heating and compression. This gives the separator a high resistance against electrolyte which is alkaline, and excellent absorptiveness of alkali electrolyte can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a separator for batteries, and more specifically to alkaline separators such as alkaline manganese batteries, silver oxide batteries, mercury batteries, nickel cadmium batteries, etc. The present invention relates to a battery separator particularly suitable for dry batteries using electrolyte.

(Prior Art) A battery separator is interposed between an anode and a cathode for the purpose of separating the anode active material and the cathode active material, which are electrolytic substances in the battery.

In addition to the function of effectively isolating the active materials of both electrodes, the separator itself must be capable of absorbing and retaining a sufficient amount of electrolyte, effectively promoting chemical reactions, and smoothly promoting ionic conduction between the three electrodes.

Therefore, paper made of chemical fibers or synthetic fibers that are resistant to alkaline liquid is used as a separator.

Currently, this function is satisfied by using absorbent paper that is excellent in absorbing electrolyte. Nonwoven fabrics of polyamide, polyvinyl alcohol, or polypropylene are commonly used as papers that are resistant to alkaline liquids, and laminates of cotton linter valve sheets are commonly used as absorbent papers that are highly absorbent of electrolyte liquids. Furthermore, recently, attempts have been made to make paper from a blend of polyvinyl alcohol fiber or polypropylene fiber and natural fiber and use it as a separator.

(JP-A-61-39451, JP-A-61-128)
(See Publication No. 460) (Problems to be Solved by the Invention) In general, a separator for alkaline batteries is required to have various performances, but among them, good electrolyte absorption is important. .

However, the absorption capacity of conventional separators for electrolytes and alkaline electrolytes is not necessarily satisfactory, and there are problems when it is desired to further improve performance such as rapid discharge performance, continuous discharge performance, and charging performance for photographic flash. was there.

An object of the present invention is to provide a battery separator that has an excellent ability to absorb alkaline electrolyte.

(Means for Solving the Problems) The present inventors have conducted extensive research to develop a battery separator that is free from the problems described above.

The inventors have discovered that a sheet made of chitin fibers or fibrils can achieve the above objects, and have thus arrived at the present invention.

That is, the gist of the present invention is a battery separator made of a sheet made of chitin fibers or a sheet made of chitin fibrils.

In the present invention, chitin refers to the remaining aminopolysaccharide obtained by treating the exoskeleton of crustaceans, insects, etc. with hydrochloric acid and hydrochloric acid to remove ash and protein, and its derivatives. Preferred chitin derivatives include:

Various deacetylated products include those with a degree of deacetylation of a few percent to those with a degree of deacetylation of 80% or more, so-called chitosan. Further examples include etherified products, esterified products, carboxymethylated products, hydroxyethylated products, and 0-ethylated products of the aminopolysaccharides or their deacetylated products.

The method for producing chitin fibers or chitin fibrils is not particularly limited, and various known methods can be used, but a wet molding method is preferably employed. As a solvent for chitin, if the degree of deacetylation is 20% or less,
A mixture of N-methylpyrrolidone or dimethylacetamide and lithium chloride, a mixture of trichloroacetic acid and a halogenated hydrocarbon are preferably used, while an aqueous acetic acid solution is preferably used when the degree of deacetylation is 70% or more. It will be done. As the coagulating liquid, water or an organic solvent is preferably used when the former solvent is used, and water or an aqueous alkaline solution is preferably used when the latter solvent is used. Adjustment of deacetylation degree of chitin fibers.

This can be carried out by treating the obtained chitin fibers with an alkali or with an organic solvent containing acetic anhydride. In addition, for those having a high degree of deacetylation, it is also a preferable method to improve water resistance by crosslinking with, for example, glutaraldehyde.

Chitin fibers have a fineness of 0.3 to 10 d, especially 0.
．． Those with a length of 5 to 3 d and a length of 0.5 to 201 mm are preferably used. Furthermore, chitin rhypolls having a diameter of 2 to 100 μm and a length of 10 μ to 10 mm are preferably used.

Various known methods can be used to produce sheets from chitin fibers or chitin fibrils, including dispersing them together with a binder in water, removing water to form sheets, and then heating.

A method such as compression can be preferably employed. As the binder, one that melts when heated is preferably used,
An example of such a binder is meltable polyvinyl alcohol fiber (Unitika Kasei, SML). In addition, in order to increase the water retention property of the sheet, cellulose fibers are added to chitin fibers or chitin fibrils by
A 50% by weight mixture is also a preferred method. Cellulose fibers include cotton, lignin in cotton linters,
Impurities such as hemicellulose are removed by steaming and decomposition to make the α-cellulose content 98% or more, and mercerized bulbs made from chemically treated wood bulbs (SP) treated with alkali are eluted and fallen off components in alkaline solutions. It is preferably used because it has low alkali resistance and excellent alkali resistance.

(Example) The present invention will be explained in more detail below with reference to Examples.

Example 1. Comparative Example 1 Chitin powder (manufactured by Shin Nippon Chemical, degree of deacetylation 5%) was
A chitin dope was obtained by dissolving it in a dimethylacetamide solution containing lithium chloride at a concentration of 9 W/W%. The obtained dope was filtered through a wire mesh of 1480 mesh and left to defoam, then introduced into a tank, and then transported under pressure with a gear pump, with a diameter of 0.08++n per caliber.
It was discharged into hot water at 80° C. from a nozzle with 5,000 holes, solidified, taken out at a speed of 10 m/min, washed and dried to obtain chitin fibers with a single filament denier of 1.5 d. After cutting the obtained chitin fiber into a length of 3n+, the chitin fiber, cotton linter pulp, and a binder (polyvinyl alcohol fiber, Unitika Kasei, S
ML) at a weight ratio of 7:3:2 and paper was made using a paper machine to obtain separates having the basis weights (g/ad) shown in Table 1.

For comparison, vinylon fiber (1dX
A separate was obtained in the same manner as in Example 1 except that 311).

The obtained separate was immersed in a 42% KOH solution at room temperature for 30 minutes to determine the amount of KOH absorbed [K absorbed in the separator].
The ratio of the weight of OH (A) and the weight of the separator (B),
(A)/(B)) was measured. In addition, using these separates, we prototyped an alkaline manganese dry battery with an electromotive force of 1.5 volts, and the terminal voltage was 0 with a load resistance of 2 ohms.
．． The discharge time was measured when continuous discharge was performed at room temperature until the voltage reached 9 volts. The results are shown in Table 1.

As is clear from Table 1, the separates of the examples have higher electrolyte absorption properties than the separates of the comparative examples, and the dry batteries obtained from them have a higher absorbency than those of the comparative examples. It was possible to discharge for a long time.

Note that the discharge time of a commercially available alkaline manganese dry battery measured in the same manner was 980 hours.

Table 1 Example 2. Comparative Example 2 Chitosan powder (Shin Nippon Kagaku type) was dissolved in a 0.2 M acetic acid aqueous solution to a concentration of 8-/-% to obtain a transparent chitosan dope. The obtained dope was filtered through a wire mesh of 1480 mesh, left to defoam, then introduced into a tank, and then transported under pressure with a gear pump, with a diameter of 0.07+n per caliber.
Discharged into a 0.5 N strength soda aqueous solution from a nozzle with 10,000 holes.

After coagulating, it was taken off at a speed of 10 m/min, then neutralized with 0.2N hydrochloric acid, washed and dried to obtain white chitosan fibers with a single denier of 0.8 d. The obtained chitosan fibers were mixed with 5 g/l of acetic anhydride.
The mixture was treated in methanol at 0°C for 1 hour.

Then, it was cut into a length of 31 m, and this chitosan fiber and
Kotton linter pulp and binder (polyvinyl alcohol fiber, Unitika Kasei, SML) are mixed at a weight ratio of 7:2:2, and paper is made using a paper machine to make a second paper.
Separates having the basis weight (g/aJ) shown in the table were obtained.

For comparison, separates were obtained in the same manner as in Example 1, except that polypropylene fibers (1,5d x 3 fins) were used instead of chitosan fibers.

The obtained separate was subjected to KO in the same manner as in Example 1.
The amount of H absorbed and the discharge time were measured. The results are shown in Table 2.

Table 2 As is clear from Table 2, the separates of the examples exhibited superior absorbency and discharge performance compared to the separates of the comparative examples.

(Effects of the Invention) The separate of the present invention has high resistance to alkaline electrolytes and excellent absorption of alkaline electrolytes, so it can be used for alkaline manganese batteries, silver oxide batteries, mercury batteries, nickel cadmium batteries, etc. The present invention can be suitably used in a dry battery using an alkaline electrolyte, and can provide a dry battery with a long discharge time.

Claims (1)

[Claims] (1) A battery separator made of a sheet made of chitin fibers or a sheet made of chitin fibrils.