JPS5925164A - Separator for alkaline battery - Google Patents

Abstract

PURPOSE:To obtain a separator for alkaline battery in which the fiber is increased in its density, arranged in the mutually entangled status, provided with resistance to electrolyte and high working efficiency without any short-circuit by thermally contracting the web consisting of alkaline treated cotton and thermally contractive fibers. CONSTITUTION:A web is formed by web former such as a card machine or land machine from a mixed fiber consisting of the cotton fiber of 70-50% which is previously processed through the alkaline liquid bath treatment and the thermally contractive synthetic fiber of 30-50%. Moreover, the web fibers are mutually entangled a little and temporarily fixed as required by the needle punch machine. The web is submerged into the hot water bath of 100 deg.C for two minutes. The web contracted thereby is subjected to dehydration and desiccation. Thereby, a separator to be used for an alkaline battery such as alkaline-manganese battery, nickel-cadmium battery, air-zinc-lead battery and silver battery etc. can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in separators used in alkaline batteries such as alkaline manganese batteries, nickel-cadmium batteries, zinc-air batteries, and silver batteries, and provides a sufficient machine for efficient battery assembly work. The purpose of this invention is to obtain a separator that has an electrolytic strength and a sufficient amount of electrolyte retention required for the electromotive reaction of the battery.

In general, the properties that a separator for alkaline batteries should have are excellent resistance to corrosive electrolytes made of highly concentrated alkaline aqueous solutions such as potassium hydroxide, sodium hydroxide, or mixtures thereof, and good resistance to deterioration and shrinkage. The permeability of the electrolyte is quickly achieved without causing any electromotive reaction, and a sufficient amount of the electrolyte required for the electromotive reaction is well retained, and ions are rapidly diffused to reduce internal resistance. small,
Furthermore, the battery is required to have mechanical properties such as maintaining a certain level of mechanical strength during and after battery assembly.

Conventionally, natural cellulose fibers such as cotton and pulp have been used to provide such properties, but while they have excellent electrolyte absorption properties, they have poor resistance to electrolytes. Due to its low resistance, deterioration and shrinkage occurred, making it unable to perform satisfactorily as a separator. In addition, since the mechanical strength is not sufficient, it is difficult to handle during the battery assembly process, and since the separator is weak, the separator may break during insertion, causing a short-circuit phenomenon in the battery. Among the above-mentioned drawbacks, cotton 1009
It is seen that the web of No. 6 was temporarily fixed chemically and mechanically and then shrunk in an alkaline bath, but it was difficult to shrink it uniformly, and the product had many uneven thicknesses (= J), which resulted in mechanical damage. The drawback is that it does not have sufficient strength.

Furthermore, in order to eliminate the above-mentioned drawbacks, a web or felt-like material made of synthetic fibers such as polyamide or polyolefin is bonded with an alkali-resistant binder, or a heat-fusible fiber is mixed with the synthetic fiber. A separator bonded by heat fusion has been proposed. However, the constituent fibers of such a separator are more hydrophobic than natural cellulose such as cotton or pulp, and the binder that binds the fibers is also hydrophobic, resulting in extremely poor hydrophilicity. As a result, during the battery assembly process, the electrolyte penetrates quickly, and it takes a considerable amount of time to absorb and retain the electrolyte, resulting in lower work efficiency and a decrease in internal resistance. The problem is that it increases and the discharge capacity i decreases.

The present invention solves this problem by heat-shrinking a web made of cotton that has been treated with alkali in advance and astringent fibers, thereby increasing the density between the fibers and increasing the density between the fibers. The present invention provides a separator for alkaline batteries which has excellent electrolyte resistance and workability, and does not cause short circuit phenomenon.

One embodiment of the present invention will be described in detail below.

A mixed fiber of 6% cotton fibers which have been pre-soaked in a 20% sodium hydroxide solution and treated with alkali and 40% heat-shrinkable polypropylene fibers having a thickness of 2 denier is processed by a web forming machine such as a card machine or a land machine. A web of t 90 ct/i is formed. If necessary, the web fibers can be lightly entangled with each other using a needle punch machine and temporarily fixed. Next, the web is immersed in a hot water bath at 100'C for 2 minutes. The web was shrunk, dehydrated and dried to obtain a separator for alkaline batteries with a basis weight of 130 g/i.

In addition, the mixing ratio of alkali-treated cotton fiber and heat-shrinkable synthetic fiber should be 70% to 50% cotton fiber, polyolefin fiber, polyamide fiber, etc., taking into consideration the strength and liquid absorption of the resulting separator, as well as workability. Heat-shrinkable synthetic fiber 30%~
It is preferably in the range of 50%, and the heat shrinkage of the web may be performed by calender rolls, dry heat treatment such as hot air blowing, wet heat treatment such as steam blowing, or a combination thereof.

The table below shows the measurement results of the properties of the separator for alkaline batteries according to the present invention constructed as described above and a conventional separator prepared by shrinking a 10096 cotton web treated with alkali as a comparative example.

As is clear from the table, the separator for alkaline batteries of the present invention has a density of about 3% compared to the conventional separator at the same thickness.
0% increase, liquid retention amount is 20% or more, and strength is 50%
It increased by more than %.

Since the present invention has the above structure, durability is improved without causing fatigue or shrinkage due to electrolyte, and tensile strength and liquid retention capacity are increased due to increased density, improving work efficiency and preventing batteries and short circuits. This invention has various effects such as prevention, battery capacity, etc.

Claims (2)

[Claims] (1) 70% cotton fibers that have been previously treated with an alkaline solution bath.
1. A separator for an alkaline battery, characterized in that a fiber web formed from a mixed fiber of ~50% and 30% to 50% of heat-shrink type synthetic fibers is heat-shrinked to terminate the web-forming fibers. (2) The alkaline battery separator according to claim 1, wherein the fibrous web is mechanically bonded by needle punching.