JPH0752644B2 - Method for manufacturing negative electrode zinc plate for dry battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a zinc plate used for a negative electrode of a dry battery.

[Prior Art] A zinc plate used as a negative electrode of a dry battery is generally homogenized by forming an amalgam to prevent generation of a local current and promote uniform dissolution by discharging.

[Problems to be Solved by the Invention] However, the fact that a considerable amount of mercury is used requires a great deal of labor and cost to prevent pollution when treating a waste battery. If a zinc plate for a dry battery that can withstand practical use without particularly undergoing amalgamation can be manufactured, its industrial significance will be extremely great.

[Means for Solving Problems] The inventors of the present invention have conducted extensive studies to improve such problems, and as a result, vinyl acetate 50 to 99.8 mol% and unsaturated dicarboxylic acid 50 to 0.2 mol% It was found that the object can be achieved when a layer of a saponified copolymer in which 70 mol% or more of its vinyl acetate component is saponified is provided on the surface of a zinc plate, and the present invention has been completed. It was.

The layer of the saponified copolymer has sufficient strength to prevent physical contact between the negative electrode and the mixture, and further has excellent water retention and ion permeability, stable pH even on the acidic side, and a zinc layer. Since the adhesiveness to the saponified copolymer layer is strong and there is no possibility that foreign matters such as bubbles are contained in the interlayer portion, the above-mentioned remarkable effect of omitting amalgamation can be obtained.

Conventionally, it has been proposed to use various plastic films as a separator in order to prevent contact between the mixture and the negative electrode, but since the conventional product does not have the above-mentioned characteristics, the adhesion between the film and the zinc plate Is insufficient, bubbles may be mixed in, and the battery life may be shortened, and the effects of the present invention cannot be obtained.

As described above, the saponified copolymer used in the present invention contains 50 to 99.8 mol% of vinyl acetate and 50 to 0.2 mol% of unsaturated dicarboxylic acid as a copolymer, and 70 mol% or more of the vinyl acetate component. Must be saponified.

The effect of the present invention cannot be obtained outside this range.

Among these conditions, vinyl acetate 80-
A saponified copolymer having a content of 99.8 mol%, an unsaturated dicarboxylic acid of 20 to 0.2 mol% and a saponification degree of 70 mol% or more has further excellent performance.

Examples of unsaturated dicarboxylic acids include (anhydrous) maleic acid, fumaric acid, itaconic acid, glutaconic acid, allylmalonic acid and the like, and monoesters and diesters such as methyl, ethyl and propyl esters.

Further, if it is a small amount, another copolymerizable monomer may be copolymerized. Such a saponified copolymer is a solution of vinyl acetate and an unsaturated dicarboxylic acid which are subjected to ordinary solution polymerization so as to form a copolymer having the above ratio, and the resulting copolymer is then subjected to an alkali catalyst such as caustic soda or sodium methylate. It is produced by saponifying to a predetermined ratio with.

To form a layer of saponified copolymer on the surface of a zinc plate,
It is common to sprinkle an aqueous solution of saponified copolymer, an organic solvent solution, or a water-organic solvent mixture on a zinc plate. Of course,
The method is not limited to such a method, and a method such as once forming a saponified film of a copolymer and laminating the film on a zinc plate can also be arbitrarily performed.

The zinc plate or the like is not limited to a flat plate, and may be formed in a can shape. In the case of a can, it is also possible to form a saponified copolymer layer on the wall surface by supplying a solution of the saponified copolymer and then removing it.

The saponified copolymer layer formed is subsequently dried.
It is suitable that the drying temperature is about 40 to 90 ° C and the drying time is 5 to 120 minutes.

By further heat-treating such a saponified copolymer layer, more excellent performance is imparted. Generally, heat treatment is performed at a temperature of 110 to 200 ° C. for 1 to 360 minutes in an air or inert gas atmosphere. A layer thickness of 5 to 100μ is appropriate,
When it is difficult to obtain a uniform film by one coating operation or laminating operation, two or more coating operations or laminating operations may be performed.

In order to manufacture a dry battery using the zinc plate thus manufactured, any conventionally known means may be optionally carried out.

That is, for example, a zinc can provided with a saponified copolymer is filled with a depolarizing agent composed of manganese dioxide and acetylene black sufficiently moistened with an electrolytic solution composed of zinc chloride, ammonium chloride, water, etc. Any method such as inserting a carbon rod as a current collector into the center of the electrode mixture and sealing the opening of the zinc can can be carried out.

[Operation] In the present invention, by using a zinc plate provided with a layer of a specific saponified product of vinyl acetate-unsaturated dicarboxylic acid copolymer, a dry battery without fear of pollution and having a practical life can be easily formed. Can be manufactured.

[Examples] The method of the present invention will be specifically described with reference to examples.

Example 1 Vinyl acetate content 96.1 mol%, monomethyl maleate content
A saponified powder of monomethyl maleate-vinyl acetate copolymer having a saponification degree of 3.9 mol% and a vinyl acetate component of 98.1 mol% (295 μm or less) was dissolved in water to prepare a 10 wt% aqueous solution. Apply this solution evenly on the inner wall of AA zinc can 1.
It was dried at 75 ° C for 1 hour.

This operation was repeated twice to form a saponified copolymer layer having an average film thickness of 31μ. Then, heat treatment was performed at 140 ° C. for 3 hours.

The zinc can in which this layer was formed was filled with a depolarizing agent having a composition of 5 parts of zinc chloride, 25 parts of ammonium chloride, 80 parts of manganese dioxide sufficiently moistened with an electrolytic solution consisting of 70 parts of water, and 20 parts of acetylene black. Furthermore, a carbon rod as a current collector was inserted into the center of this depolarizing mixture, and the opening of the zinc can was sealed with microcrystalline wax to complete the battery.

The discharge capacity of 10 Ω continuous discharge immediately after the production of the thus obtained AA battery and after storage at 45 ° C. is shown as an index with the discharge capacity immediately after the production of the conventional dry battery as 100, and the discharge capacity immediately after the production is 130, It was 110 after two months and 100 after three months, which proved to be excellent performance.

Examples 2 to 4 The same method as in Example 1 was performed except that the content of monomethyl maleate was changed to 8 mol%. (Example 2) The same experiment as in Example 1 was performed except that the heat treatment condition was changed to 180 ° C for 0.25 hours. Example 3 The same experiment as in Example 1 was conducted except that itaconic acid was used instead of monomethyl maleate. (Example 4) In all cases, the same result as Example 1 was obtained.

Comparative Example 1 The same experiment as in Example 1 was carried out except that a saponified product of a monomethyl maleic acid-vinyl acetate copolymer was replaced with a polyvinyl alcohol having a saponification degree of 98.1 mol%. The results were 98 after 2 months and 85 after 3 months.

[Brief description of drawings]

FIG. 1 is a sectional view of a dry battery manufactured using a zinc plate obtained by the method of the present invention. 1 is a zinc can 2 is a saponified copolymer layer 3 is a depolarizing agent 4 is a carbon rod 5 is a microcrystalline wax.

Claims (1)

[Claims] 1. A copolymer ken which is a copolymer having a proportion of vinyl acetate of 50 to 99.8 mol% and an unsaturated dicarboxylic acid of 50 to 0.2 mol% and in which 70 mol% or more of the vinyl acetate component is saponified. A method for producing a negative electrode zinc plate for a dry battery, comprising providing a compound layer on the surface of a zinc plate and performing heat treatment at a temperature of 110 to 200 ° C for 1 to 360 minutes.