JPS61246394A - Diaphragm for electrolysis - Google Patents

Abstract

PURPOSE:To obtain a diaphragm for electrolysis having superior dimensional stability and mechanical strength and used in a halogen-zinc cell or the like by uniformly sticking a perfluoror type ion exchange resin to a polytetrafluoroethylene resin film having a specified porosity. CONSTITUTION:A perfluoro type ion exchange resin is uniformly impregnated into or stuck to a polytetrafluoroethylene resin film having >=35%, especially >=40% porosity by 10-30%, and the resulting membrane of 204n504mm thickness is used as a diaphragm for electrolysis used in a halogen-zinc cell or an alkaline cell. The diaphragm has superior mechanical strength even under dry conditions, lowers hardly the electric resistance by reduction in thickness and also has superior coulomb efficiency.

Description

Detailed Description of the Invention ``Object of the Invention'' The present invention relates to the creation of an electrolytic diaphragm, which has excellent dimensional stability in liquid, etc. as an electrolytic diaphragm in zinc-carbon batteries, alkaline batteries, etc., and also under dry conditions. The aim is to provide products with excellent mechanical strength.

Industrial applications Electrolytic diaphragms in halogen-zinc batteries, alkaline batteries, etc.

BACKGROUND OF THE INVENTION As a separator for halogen-zinc batteries, alkaline batteries, etc., ion exchange resin films have been known and have already been put into practical use. Also known are membranes in which acrylic acid or methacrylic acid is graft-polymerized onto microporous natural polymer films such as cellophane or plastic films.

Problems to be Solved by the Invention However, the above-mentioned conventional devices still have problems. In other words, films made of ion exchange resins have the advantage of not being attacked by oxidizing agents, but if they are made into thin films or have a low exchange capacity, they will have poor strength and dimensional stability in liquids. However, in a dry state, the mechanical strength is drastically reduced and cracks are likely to occur, and in a condition containing water, it swells extremely, and in any case, the workability is poor.

Made of microporous natural polymer film, it is oxidized by oxidizing agents such as manganese dioxide used in the anode mixture, resulting in significant deterioration. In the case of a plastic film in which acrylic acid or the like is graft-polymerized, the electrical resistance is low, but the positive electrode active material diffuses to the counter electrode, shortening the battery life.

Particularly in the case of diaphragms for halogen-zinc batteries, self-discharge of halogen increases and coulombic efficiency decreases.
It is highly corrosive because the halogenated gas is used dissolved in zinc halide.

``Structure of the Invention'' Means for Solving the Problems An electrolytic diaphragm characterized in that a perfluorinated ion exchange resin is uniformly impregnated and integrated with a polytetrafluoroethylene film having a porosity of 35% or more.

A polytetrafluoroethylene film having a working porosity of at least 35% provides mechanical strength and dimensional stability. A perfluoro-based ion exchange resin membrane can be obtained as a thin film by using a ferrous film as a base material, which can lower electrical resistance and increase coulombic efficiency. Adjust the amount of ion exchange resin to be impregnated, mixed, and laminated, and PTF
The amount of diffusion of the active material is controlled by adjusting the specific gravity of the E membrane.

Examples Specific embodiments of the invention as described above are shown in the accompanying drawings.The non-invention is polytetrafluoroethylene (hereinafter referred to as PTFE) with a porosity of 35% or more, particularly 40% or more. A perfluorinated ion exchange resin is uniformly attached and integrated with a resin film.

As a specific method for uniformly adhering and integrating the above-mentioned PTFE film and perfluorinated ion exchange resin, any of the following methods may be used.

(2) The porous PTFE film obtained by stretching is sufficiently impregnated with a perfluorinated ion exchange resin solution to form a dense diaphragm.

(2) In the above (2), the membrane is impregnated with a perfluorinated ion exchange resin liquid in an insufficient state to obtain a diaphragm that still has porous properties.

■ Mix ion exchange resin liquid with PTPK resin to form a dense diaphragm.

(2) During film formation in (2) above, the film is stretched to form a porous diaphragm.

■Ion exchange resin is first formed into a thin film, and this is then
E Laminate and adhere to the porous membrane.

In either case, the ratio of perfluorinated ion exchange resin to PTFE is generally 3 to 90% by weight, particularly preferably 10 to 30%. The thickness of the diaphragm is generally 3 to 300 μm, especially 20 to 300 μm.
It is 50 μm.

When the diaphragm obtained by pressing as described above is used as a separator for a halogen-zinc battery, it has excellent mechanical strength and dimensional stability even if it is thin because it is molded using a PTFE membrane as a base material. Furthermore, since it is a perfluoro-based material, it is not subject to deterioration due to electrolytes, has low electrical resistance, and has excellent coulombic efficiency. Also, the battery life can be compared to the conventional one.
Its performance can be significantly improved.

This also applies to separators for alkaline batteries, and since the electric resistance can be reduced as described above, a desirable product can be obtained with excellent ability to prevent diffusion of the positive electrode active material to the counter electrode.

A specific manufacturing example of the product according to the present invention will be described below.

Porous PT with a porosity of 5O1s in which countless fine fibers are formed in a spider-like shape between many micronodules by stretching treatment.
A diaphragm for a halogen-zinc battery having a dense structure with a thickness of 25 μm was obtained by impregnating an FE membrane material with a perfluorinated ion exchange resin liquid.

"Effects of the Invention" According to the present invention as explained above, the mechanical strength of the electrolytic diaphragm can be improved to obtain a product with a sufficiently thin film, and it also exhibits excellent characteristics such as dimensional stability. In addition, it is a highly effective invention industrially because it can provide a diaphragm with low electrical resistance and excellent Coulombic efficiency due to the thinning of the film as described above.

s Permission m People Japan Gore Texts Co., Ltd. Inventor Hirodo Kato Koma 1) - Immediate question
-An Tetsu 5'- Agent Patent Attorney Shirakawa -21iIE? ”'
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Claims (1)

[Claims] An electrolytic diaphragm comprising a polytetrafluoroethylene film having a porosity of 35% or more and a perfluoro ion exchange resin uniformly attached and integrated therein.