JPS60100369A - Production method of zinc alloy powder for alkaline cell - Google Patents

Abstract

PURPOSE:To obtain zinc alloy powder with little oxide generation on the particle surface by mixing soluble mercury salt, a soluble salt aqueous solution of a specific tertiary metal, and zinc alloy powder and surface-treating the mixture, removing a mother liquid and washing it, then quickly dehydrating and drying it by means of hydrocarbon halide. CONSTITUTION:A soluble salt aqueous solution of soluble mercury salt or an element selected among I b, IIb, IIIb, IVb, and Vb groups and zinc alloy powder are stirred and mixed, and the mixture is surface-treated and amalgamated. Next, a mother liquid is removed, then it is washed and the washing liquid is removed. The wet zinc alloy powder thus obtained is fed to a dehydrating tank, and it is immersed in a hydrocarbon halide liquid containing a small quantity of a surface active agent or low-quality alcohol such as trichloro trifluoroetane to remove the moisture. Next, it is exposed in the vapor of hydrocarbon halide and is quickly dehydrated and dried. According to such a method, zinc alloy powder for an alkaline cell with an amalgamation factor of 0-3wt% can be produced in a short time.

Description

[Detailed Description of the Invention] The invention relates to an improvement in a method for producing zinc alloy powder, which is a negative electrode material for various alkaline zinc batteries such as silver oxide batteries, mercury oxide batteries, alkaline manganese batteries, and zinc-air batteries. As a result, less oxides are formed on the surface of zinc alloy particles.
This provides a negative electrode material with excellent performance.

Zinc or zinc alloy powder, which is generally used as a negative electrode material for alkaline batteries, can be produced by a variety of methods. Sokuji'1
The 1L solution method includes powder obtained by crushing dendritic lead, and powder made from specially processed spherical particles, but the most commonly used method is the Monoke atomization method. Sprayed zinc powder consisting of a group of irregularly shaped particles produced by oxidation, with a particle diameter (minor diameter) of 61 to 350 μm
Chill with 8 degrees. This kind of zinc powder has a high hydrogen gas generation rate in an alkaline electrolyte, and also has a high chemical polarization when discharged in a battery where the amount of electrolyte is extremely limited. Amalgamatio
It was common to use ``n''. In this case, a freezing rate of 5 to 15% by weight of the bulk frozen zinc powder was generally used.

As is well known, mercury is a pollution control substance, and in order to reduce the mercury content in zinc negative electrodes, changes can be made to the zinc alloy composition, the surface treatment of zinc particles, and the addition of corrosion inhibitors (Inh) to the alkaline electrolyte.
Research on the addition of ibitor has been carried out in various countries. At present, it has not yet been put into practical use, but it is expected that it will be put into practical use in the not-too-distant future, as research has reached a certain level.

A typical method being researched is alloying with a third element that is added to zinc to increase its hydrogen overvoltage without deteriorating its polarization properties. Most of the elements proposed as substances are included in Group 1B, Group NB, Group MB, Group 1Vb, and Group VB. Such a zinc alloy powder containing a third element is used as it is, or after a secondary treatment, for example, it is hydrated to a low hydration rate in an aqueous solution containing a soluble mercury salt.

Another point is that when zinc is deposited or adsorbed on the surface of zinc particles, it increases its hydrogen overvoltage and does not reduce the polarization characteristics. This is a method of surface treatment by immersing zinc alloy powder to precipitate or adsorb a third element onto the particle surface. In this case, a soluble mercury salt is also included in the aqueous solution, and mercury and a third element are often co-deposited on the particle surface. Some proposed for this purpose (D elements 'llb group, group 11b, group nib, group ■b, group v
The main ones are those belonging to group B.

Water obtained as described above and having a hydration rate significantly lower than that of conventionally commonly used salivary lead hydrate (iceation rate 5 to 15i% by weight), for example, a hydration rate of 3% by weight or less. Both hydrated lead powder (hereinafter referred to as low-hydration zinc) and zinc alloy powder that does not contain any mercury (hereinafter referred to as de-icing zinc) are subjected to hydration treatment or other treatment in an aqueous solution during the manufacturing process. Surface treatment, that is, wet treatment, is carried out, and after finishing the treatment and washing with water, the wet salivary lead alloy powder obtained is finally dried. The conventional manufacturing method has been to heat and dry under normal pressure or under reduced pressure.

However, this conventional method not only takes a long time to dry, but also tends to generate IC oxides (oxides in a broad sense, including hydroxides, etc.) on the surface of zinc alloy particles, and the amount of oxides produced is low. It had defects that varied with each operation and were difficult to stabilize. This is because the surface of the zinc alloy particles is dried while being wet with water for a considerable period of time. As will be described later, this has an undesirable effect on the characteristics of batteries manufactured using the keratin. Another drawback was that a small amount of mercury vapor was generated during the drying process, which required countermeasures.

The main purpose of this invention is to reduce the amount of oxides on the surface of zinc alloy particles by improving the production method of zinc alloy powder with low hydration or no ice. K Ruru provides.

That is, the method of the present invention uses a zinc alloy powder to which a third element is added which has a corrosion-preventing effect in an alkaline electrolyte and does not have an inhibiting effect on polarization properties, and a soluble mercury salt and/or a similar effect. After performing surface treatment by stirring and mixing with an aqueous solution containing a soluble salt of a certain third element, the mother liquor was removed, and the wet zinc alloy powder obtained by washing with pure water and removing the washing solution was mixed with a small amount of wet zinc alloy powder. This method involves rapid dehydration and drying by treating with a halogenated hydrocarbon liquid containing a surfactant or a lower alcohol and/or the organic solvent vapor, and allows rapid drying at low temperatures within a short time. Therefore, the oxide content on the surface of the zinc alloy particles obtained is low,
Moreover, the variation is also small. Therefore, when used in an alkaline battery, it is possible to suppress a decrease in the discharge utilization rate due to a decrease in the amount of effective active material or diffusion inhibition during discharge. Productivity is also improved, such as by shortening the drying time and eliminating the generation of mercury vapor.

The present invention will be described in detail below using length examples.

Example 1 A zinc alloy containing small amounts of each of lead, gallium, and indium was atomized to obtain particles with a particle size (minor diameter) of 100 to 300μ.
! 11 atomized zinc alloy powder 100/11. g of mercuric chloride was put into a reaction tank filled with 31 kg of an aqueous solution containing 5.76% of mercuric chloride and acetic acid (1.90% by weight), and stirred vigorously for 60 minutes to complete the reaction.Next After removing as much of the mother liquor as possible using a Zyfon, pure water is injected and washing is performed with stirring, followed by removing the washing liquid.

Next, a 1% acetic acid aqueous solution was injected to perform stirring and washing, and then the washing water was removed. Next, washing with pure water and removing the washing liquid were repeated five times, and finally it was confirmed that no acetate ion was qualitatively observed in the washing liquid.

The obtained wet low-hydration zinc alloy powder is immediately sent to a dehydration tank for rapid drying. That is, first, a wet d↓'1 low-permanence zinc alloy powder was placed in a container made of Naishin fiber and immersed in trichlorotrifluoroethane containing 6% by weight of ethanol at 40'O for 4 minutes without applying ultrasonic vibration. and remove moisture. The removed water floats to the top of the organic solvent due to the difference in specific gravity and is taken out of the immersion liquid through a flow. The dehydrated low-hydration zinc alloy powder was then exposed to trichlorotrifluoroethane/ethanol azeotropic vapor for 2 minutes, and then slowly taken out of the cooling chamber into the air and placed in a container lined with polypropylene. Store in a tightly capped container.

Example 2゜100 kg of atomized zinc alloy powder with a particle size (minor diameter) of 100 to 300 μm obtained by atomizing a zinc alloy containing small amounts of each of lead and cadmium was mixed with 5.80% by weight of mercuric chloride.
, 0.11% by weight of indium chloride and a trace amount of a nonionic surfactant into a reaction tank filled with 36 kg of an aqueous solution and press 1 for 90 minutes to complete the surface treatment. Step 1: Remove the mother liquor using the same procedure as shown in Example 1,
Washing with pure water, removal of washing liquid, and rapid dehydration drying of the obtained wet low hydration zinc alloy powder are performed.

Example 3 Atomized zinc alloy containing small amounts of lead and gallium was added to 100% of atomized zinc alloy powder with a particle diameter of 00 to 300 μm, and 9 was added to 2% by weight of indium chloride and nonionic surfactant. The aqueous solution containing a trace amount of the agent was poured into a reaction tank filled with 20.23 A:g and stirred gently for 120 minutes to complete the surface treatment. After that, the mother liquor was removed, purified water was washed, and the washing liquid was removed in the same manner as shown in Example 1).Then, the obtained wet and ice-free zinc alloy powder was placed in a container made of nylon fiber, and the oil-soluble surfactant Ultrasonic vibration in a trichlorotrifluoroethane solution containing 0.5% by weight of Nh? Soak for 5 minutes at room temperature while feeding. The removed water floats on top of the organic solvent due to the difference in specific gravity, so it overflows and is taken out of the immersion liquid. Next, the dehydrated anhydrous zinc alloy powder is taken out of the immersion solution and re-immersed in a trichlorotrifluoroethane solution containing no additives for 3 minutes at room temperature to remove a small amount of surfactant that has adhered.

Next, after being exposed to chlorotrifluoroethane vapor for 2 minutes in an rc chamber, it was removed from the cooling chamber into the air and stored tightly in a container lined with polypropylene.

The drying time required for producing low water or ice-free zinc alloy powder using the production method of the present invention and the drying conditions commonly used in the conventional production of zinc hydrate powder, The oxide content and its dispersion are shown in Table 1.

(Left below) Table 1 In Table 1, oxide content refers to zinc oxide in a broad sense,
In other words, the total amount of oxides, hydroxides, basic salts, etc. is expressed as ZnO, and the zinc contained therein is calculated and expressed as ZnO. In addition, the variation in oxide content (1 indicates the difference between the maximum and minimum values of oxides contained in the same sample when manufacturing is repeated six times for approximately 100 kg under the same manufacturing conditions. B and O were manufactured according to the above-mentioned Examples 1, 2 and 3 using the manufacturing method of the present invention, and D was the same surface treatment and water washing as in Example 1. The powder was further washed once with a small amount of Ingropanol/7sen mixed solvent, and the resulting wet low-hydration zinc alloy powder was dried with hot air at 80°C under conventional drying conditions. Further, E refers to the product obtained by performing the same surface treatment and washing with water as in Example 3, and then drying the obtained wet anhydrous zinc alloy powder under reduced pressure at 20 am Hg and 60°C, which are conventional drying conditions. It is.

From Table 1, when the production method of the present invention is used, the drying time is significantly shortened compared to the conventional method, and the oxide content and its dispersion of the resulting low-fragility or anhydrous zinc alloy powder are reduced. It turns out that it becomes smaller.

The meaning of this oxide content will be further explained below. Conventionally, the hydrogen gas generation rate when low-fragility or anhydrous zinc alloy powder manufactured under certain conditions is immersed in an alkaline electrolyte, and the discharge characteristics when used in an alkaline battery, are determined by sample preparation. Depending on the history of lots and storage conditions, samples may not always match, and the causes of this are conventionally known differences in the microscopic surface condition of particles,
It was thought that this was caused by a trace amount of impurities mixed in during the manufacturing process. However, as a result of research, it was found that a considerable part of the above causes were also caused by the formation of slags on the particle surface. In other words, an increase in the oxide content not only reduces the amount of effective active material in the zinc alloy powder, which reduces the discharge capacity when used in a battery, but also causes a diffusion hindrance when discharging the battery.
It has been found that this makes it difficult to reproduce the amount of hydrogen gas generated.

In this case, it depends not only on the oxide content, but also on the differences in its chemical form and the hardness of the oxide film, such as whether it is a barrier JN film or a discontinuous film. Although it is difficult to express a simple relationship, an increase in the oxide content reduces the dielectric properties of the alkaline battery.

When an alkaline battery is discharged at room temperature under a relatively high load of tQ'l, VC may suffer significant damage due to slight differences in oxide content.
Under severe conditions such as No. 1, if a lead alloy powder with an oxide content of i+'6 is used for the negative electrode, the negative electrode will change to an I state during discharge and lose its function as a negative electrode. It was observed that the time required to pass the discharge (pass on time) was short and the discharge utilization rate of zinc tended to decrease. Second
The table shows the button-type alkaline manganese battery LR4 using three types of low hydration zinc alloy powders with different oxide contents manufactured under almost the same conditions as A in Table 1 and Df in Table 1.
The contents of the present invention will be further explained as follows: Add.

In the examples, the removal of the mother liquor after surface treatment and the subsequent removal of the washing liquid were carried out using a siphon, but this could be done using other methods such as pumping, tilting, pressurization or vacuum filtration, This can be carried out by any method such as centrifugal dehydration, and by using these methods, water can be poured and drained continuously.

In addition, the halogenated hydrocarbon Q used for drying the express vehicle of the present invention is inert to 1°C hydrated to 11E lead alloy under the working conditions, and the main solvent is easily separated from the water removed. It is essential that it is not compatible with water and that the difference in specific gravity between it and water is large. It is desirable that the dissolution IJI of water in the main solvent is less than 1 weight φ at the working temperature. It is desirable that the boiling point is higher than possible room temperature (15 to 35°C/1 atnl), not more than 0% (10,000 or less), and has a large vapor content. Also, i from inside the dehydration tank.
'fl Steam specific gravity (Air = 1) to prevent dissipation of medium vapor
As thick as possible, practically (preferably d 3 or more)
ll14 or higher is suitable. Such a clause ft=
Chlorinated hydrocarbon λζ, e.g. 1,1.1
-) Lichloroethane (011,s CCj ls ),
Trichlorethylene (0Ii0.6 = 004), tetrachloroethene (L! 0112-=CO/2
), methylene chloride (C)+2 (172), etc. can be used. Even when these solvents are used, they are relatively stable against low-fragility or anhydrous sub-41 alloy powders under practical working conditions, and undesirable reactions such as oxidation, hydrolysis, and dehalogenation of the solvent are minimal. be. However, when chloro-fluoro-substituted methane or ethane is used, it is more stable than chlorinated hydrocarbons, has extremely low toxicity, and has low surface tension and viscosity, and is therefore more suitable for the purpose of the present invention. There are several types of such solvents. It is also possible to use a mixture of a chlorofluoro-substituted product of methane or ethane and a chlorinated hydrocarbon. Next, a small amount of a lower alcohol such as ethanol or isopropanol or a surfactant is added to the halogenated hydrocarbon that is the main solvent. Bringing the parent 11th nature of 3j & degree to both sides of hydrogen/
It is the ζth. That is, when the Wenzhou zinc alloy particles are immersed in the above mixed solvent solution, the interaction between the interfacial tension of the halogenated hydrocarbon and the moderate 11 force of the surfactant or lower alcohol on both water and the halogenated hydrocarbon occurs. , the halogenated hydrocarbon envelops water and peels it off from the surface of the first-generation lead alloy particles, and the halogenated hydrocarbon covers the particle surface instead of water, while the peeled water becomes a halogenated hydrocarbon liquid. Because it has no compatibility with the mixed solvent, it floats to the surface of the mixed solvent due to the difference in specific gravity. By removing the water that has floated to the surface to the outside by overflowing or other methods, the dehydration effect is reduced, and 1.11 continuous operations are also possible.

Although wet n-zinc alloy powder may be simply immersed in a mixed solvent, adding ultrasonic vibration ηb during immersion has the effect of further increasing the dehydration efficiency or surface activity (1). Good results were obtained.

As stated in the paper, the zinc alloy powder obtained using the production method of the present invention has a small oxide content and its variation, and can improve the characteristics when used in alkaline / #+C ponds.
It has great industrial value, as it can significantly shorten the time required for drying during the production of zinc-donated powder, and it also generates less mercury vapor during the drying process.

Claims (1)

[Claims] (1) Soluble mercury group and/or @Ib group, su
Group b, #ff l1lb group, IglVb group, group ■b [
A first step of performing surface treatment by mixing an aqueous solution containing a soluble salt of one or several selected elements from the group of metallic elements 4-j with stirring and zinc alloy powder. The second step is to remove the mother liquor from the surface-treated lead or zinc alloy powder, wash it with water, and then remove the cleaning solution.The wet zinc alloy powder from which the cleaning solution has been removed is treated with a small amount of surfactant or The third step is rapid dehydration and drying by immersion in a halogenated hydrocarbon liquid containing lower alcohols and/or exposure to a mixed vapor of halogenated hydrocarbons and lower alcohols. For alkaline batteries with a commercial capacity of 0 to 3, i+Ii m is 1 ba.
1lJl;:'+ zu-i 9J,. (2) The zinc alloy powder used in the first step is
A patent characterized in that it contains one or more elements arbitrarily selected from the group of all class elements belonging to Group B, Group NB, Group MB, Group 1Vb, and Group VB. A method for producing zinc alloy powder for alkaline batteries as set forth in claim 1. +3) The zinc alloy powder for alkaline batteries according to claim 1, characterized in that the main component of the halogenated hydrocarbon used in the m3 step is methane or ethane, p-substituted and fluoro-substituted. Production method 1: (4) Zinc for alkaline batteries according to claim 1, characterized in that (4) the wet zinc alloy powder is subjected to ultrasonic vibration when immersed in a halogenated hydrocarbon liquid. Method for producing alloy powder.