JPH1081516A - Fluid silver oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluid silver oxide having a large specific area, a large density and an improved fluidity and quantitativity by aging fine particles of the silver oxide in an alkali liquid under pressure and further treating the surface of the fine particles of the silver oxide by a sililation reagent. SOLUTION: Particles of silver oxide having 5-20μm average particle diameter, 1.2-1.7g/cm<3> bulk density, <=20ppm chlorine and sulfur content and <=30ppm alkali content are obtained by aging and recrystallizing the fine particles of the silver oxide under 2-20kg/cm<2> pressure at 80-250 deg.C for 10-30hr in an alkali solution having pH>=10, performing solid-liquid separation of the resultant silver oxide, and washing and drying the separated solid part. The objective fluid silver oxide having 0.5-1.5g sililation reagent attached thereto based on 1000g silver oxide, <=25 deg. repose angle, 1.9-2.6g/cm<3> bulk density and 4ppm-1wt.% silicon content (in terms of SiO2 ) is obtained by immersing the particles of the silver oxide into a solution containing a sililation reagent of the formula Rn SiX(4-n) (R is an alkyl; X is a halogen, an alkoxy, acyloxy, amino, etc.) and drying the resultant particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silver oxide ( _Ag2O : silver oxide) which is excellent in fluidity, has a large specific surface area and a high density, preferably has a low alkali content and the like, and is therefore suitable as silver oxide for batteries. In some cases).

[0002]

2. Description of the Related Art Silver oxide batteries use silver oxide as a positive electrode active material. The silver oxide for batteries needs to have a surface area as large as possible in order to increase the reaction efficiency of the batteries. In order to increase the capacity, particles having a large bulk density are required so that a minute space can be filled with a large amount of silver oxide particles. However, in order to increase the surface area, the particle size must be reduced. However, when the particle size is small, the bulk density also decreases, and it is difficult to increase the surface area and the bulk density simultaneously.

[0003] In addition, a certain amount of silver oxide must be filled in a battery container when packing it in a battery container. For this reason, a silver oxide having a high fluidity by granulation is usually used. ing. Poor fluidity results in uneven filling. However, there is a problem that the granular particles are liable to be caught when pressurized after filling the container.

[0004] In addition to the above physical properties of the particles, it is required that the amount of impurities derived from the production method be as small as possible. That is, the conventional silver oxide for a battery is mainly manufactured by an alkali precipitation method in which an aqueous solution of sodium hydroxide or potassium hydroxide is added to an aqueous solution of silver nitrate to precipitate silver oxide. For this reason, there is a problem that the alkali content of the silver oxide powder is high. Further, in order to grow primary particles of alkali-precipitated silver oxide, chlorine ions or sulfate ions are dissolved in the solution as a catalyst, and there is a problem that these remain in silver oxide. If the residual concentration of chlorine or alkali in silver oxide is high, corrosion of equipment is caused, and sulfate ions are decomposed to generate oxygen, thereby impairing the performance and life of the battery.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is excellent in fluidity and therefore does not need to be granulated, and has a high surface area and a high bulk density. The object of the present invention is to provide silver oxide which is optimal for batteries having a low content of chlorine and sulfur.

[0006]

According to the present invention, the following fluid silver oxide is provided. (1) Average primary particle size 5-20 μm, bulk density 1.9
Fluid silver oxide having a repose angle of up to 2.6 g / cm ³ and an angle of repose of 25 ° or less. (2) The alkali content is 30 ppm or less, the chlorine content and the sulfur content are each 20 ppm or less, and the silicon by the surface treatment of the silylating agent is reduced to 40 ppm or less in terms of silicon dioxide.
The fluid silver oxide according to the above (1), containing 1%. (3) The liquid silver oxide as described in (1) or (2) above, which is used for a battery.

Further, according to the present invention, there is provided the following production method for producing the above-mentioned liquid silver oxide. (4) The average particle size of the primary particles is 5 to 20 μm by curing the silver oxide fine particles under pressure in an alkaline solution and recrystallizing them.
m, the bulk density is adjusted to 1.2 to 1.7 g / cm ^3, and then the surface is treated with a silylating agent to reduce the angle of repose to 25 ° or less and the bulk density to 1.9 to 2.6 g / cm ³ . A method for producing a liquid silver oxide, comprising: (5) Fine particles of silver oxide having a pH of 10 or more and a pressure of 2 to 20 kg
/ cm ² , at a heating temperature of 80 to 250 ° C., by curing under pressure in an alkaline solution and recrystallizing, thereby reducing the chlorine content and the sulfur content to 20 ppm or less and the alkali content to 30 ppm, respectively.
Hereinafter, the average particle size of the primary particles is 5 to 20 μm and the bulk density is 1.
After forming silver oxide particles of 2 to 1.7 g / cm ³ , the dried silver oxide particles are brought into contact with a solution of a silylating agent and subjected to a surface treatment to reduce the angle of repose to 25 ° or less and the bulk density to 1.9. ~ 2.
The production method according to the above (4), wherein the amount is 6 g / cm ³ .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. (I) Fluid Silver Oxide The silver oxide of the present invention has an average primary particle size of 5 to 20 μm, a bulk density of 1.9 to 2.6 g / cm ³ and an angle of repose of 2
5 ° or less. If the average particle size is less than 5 μm, the bulk density becomes small, which is not preferable. If the average particle diameter exceeds 20 μm, the specific surface area becomes small, so that it is not appropriate. The specific surface area (BET value) is preferably 0.2 to ² m ² / g. On the other hand, when the bulk density is larger than 1.9 g / cm ³ , a good effect of extending the battery life is obtained, and when the bulk density is about 2.0 g / cm ³ or more, the effect of improving the battery life is high. According to the surface treatment using the silylating agent, a bulk density of about 2.6 g / cm ³ can be obtained.

Further, the silver oxide of the present invention has a repose angle of 25 °.
It is as follows. Silver oxide before the recrystallization treatment has an angle of repose of 45 ° or more.
To a degree. By subjecting this to a surface treatment using a silylating agent, the angle of repose is further reduced to 25 ° or less. The fluidity of the conventional silver oxide particles for batteries has a repose angle of about 45 °, and the silver oxide particles of the present invention have about twice the fluidity of the conventional silver oxide particles. For this reason, the handleability is good, the variation in the filling amount when filling the container is small, the filling amount is large, and the quantitativeness is improved. Also, the performance of the battery is good and the life of each battery is uniform.

The fluid silver oxide of the present invention preferably has an alkali content of 30 ppm or less, and a chlorine content and a sulfur content of 20 ppm or less, respectively. The silver oxide produced by the conventional alkali precipitation method has a majority alkali content of about 50 ppm or more and a high concentration of chlorine and sulfur. ,
By performing the recrystallization treatment in an alkaline solution, the alkali content can be limited to 30 ppm or less, preferably 20 ppm or less, and the contents of chlorine and sulfur can each be limited to 20 ppm or less. As a result, according to the silver oxide of the present invention, it is possible to obtain a battery which is less affected by alkali, chlorine, sulfur and the like.

(II) Method for Producing Fluid Silver Oxide (A) Recrystallization Step The fluid silver oxide of the present invention is obtained by curing silver oxide fine particles under pressure in an alkaline solution and recrystallizing the primary particles. Is obtained by treating the surface with a silylating agent after setting the average particle size to 5 to 20 μm and the bulk density to 1.2 to 1.7 g / cm ³ .

The raw material silver oxide may be silver peroxide. In the production method of the present invention, the fine particles of silver oxide as the raw material include fine particles of silver peroxide. By heating the silver oxide fine particles as a raw material in an alkaline solution under pressure, the surfaces of the silver oxide particles are dissolved and recrystallized (crystal growth). Since the recrystallization proceeds from the inside of the particles, the alkali residue adhering to the surface is released to the outside, and the remaining alkali amount is reduced to 30 ppm or less, preferably 20 ppm or less.

The type of alkali is not limited. Sodium hydroxide, potassium hydroxide and other alkali salts can be used. Further, as shown in Examples, calcium hydroxide may be used. Therefore, in the present invention, the alkali includes alkaline earth. The higher the alkali concentration, the more easily silver oxide dissolves in the solution and recrystallizes, thereby shortening the processing time. Generally, pH 10 or higher, preferably p
H11 or more is suitable.

The reaction is preferably carried out with stirring in an autoclave using a closed vessel. The pressure in the container is 2-20kg / c
m ² is appropriate. Air pressurization may be performed. When the internal pressure of the container is less than 2 kg / cm ² , the solubility of silver oxide is low and the silver oxide does not recrystallize. On the other hand, even if the internal pressure is higher than 20 kg / cm ^{2, the} recrystallization speed does not change so much, and it is not practical because the device design is difficult and the cost is increased.

[0015] The heating temperature is preferably from 80 to 250 ° C. 8
If the temperature is lower than 0 ° C., the crystal growth is unfavorably slow. The higher the heating temperature, the shorter the crystal growth time and the higher the density of the crystal. However, even if the temperature exceeds 250 ° C., the degree of crystal growth is not so different and is not practical. The reaction time is suitably about 10 to 30 hours under the above pressure and temperature conditions.

After the reaction, the mixture is cooled to room temperature and solid-liquid separated, and the collected precipitate is washed with pure water. After washing, dry. By this recrystallization treatment, the average particle size of the primary particles is 5 to 20 μm,
Bulk density 1.2-1.7 g / cm ³ and alkali content 3
Silver oxide particles having a low alkali density of 0 ppm or less can be obtained. In addition, since this silver oxide is not the one that grew grains using chlorine ions or sulfur ions as in the past,
Contains almost no chlorine or sulfur and their concentration is 20pp
m or less.

(B) Fluidization Step The surface properties of the silver oxide particles obtained by the recrystallization treatment are increased by a silylating agent to enhance the fluidity. The surface treatment may be performed by bringing the silver oxide particles into contact with a solution of a silylating agent. Specifically, the silylating agent is dissolved in a solvent such as benzene, the silver oxide particles are immersed in this solution, and then the silver oxide particles are collected by filtration and dried. Alternatively, the silver oxide particles are kept in a fluidized state, sprayed with a silylating agent solution, and then dried. The silylating agent is preferably used by dissolving it in a solvent such as benzene. As a result, the silylating agent uniformly adheres to the surface of the silver oxide particles. In addition, it is preferable to filter at the time of recovery so that the excess silylating agent does not adhere during drying.

The silylating agent is represented by the general formula R _n SiX
_(4-n) (R is an alkyl group, X is halogen, alkoxy,
Compounds represented by acyloxy, amino groups, etc.) are used. Generally, those widely used include those having a trimethylsilyl group and alkoxysilanes. For example, trimethylchlorosilane, triethylchlorosilane, trimethylbromosilane, dimethylaminotrimethylsilane, diethylaminotrimethylsilane, hexamethyldisilazane, and alcohol derivatives, sulfonic acid derivatives, and acetamides thereof are used.

When the surface treatment is carried out with a silylating agent, the surfaces of the silver oxide particles are rendered hydrophobic, the adhesion between the silver oxide particles is reduced, the fluidity is improved, and the whole particles are in a smooth state. Although the fluidity increases with the amount of the silylating agent used, the amount of the silylating agent used is 0.5 to 1.5 per 1000 g of silver oxide.
g is sufficient. Thereby, a fluid silver oxide having a repose angle of 25 ° or less and a bulk density of about 1.9 to 2.5 can be obtained. That is, since the fluidity increases, voids (gap) in the powder are filled, and the bulk density increases remarkably. On the other hand, the chlorine content and the sulfur content of the silver oxide obtained in the recrystallization step are each 20 ppm or less, the alkali content is 30 ppm or less, and the physical properties such as the average particle diameter of primary particles of 5 to 20 μm depend on the silylating agent. Since it does not fluctuate even after the surface treatment step, a flowable silver oxide having significantly improved fluidity and high density can be obtained while maintaining these physical properties.

[0020]

EXAMPLES AND COMPARATIVE EXAMPLES Examples 1 to 6 1000 g of silver oxide powder (purity: 4N or more) was charged into a closed autoclave vessel together with 5 liters of an aqueous sodium hydroxide solution (concentration: 100 g / l), and heated to 90 ° C. The reaction was carried out at 15 kg / cm ² for 10 hours under air pressure while stirring. After the reaction, the reaction solution was left standing at room temperature for cooling, and the precipitate was collected by filtration, washed with 5 l of pure water five times, and dried. The average particle diameter, specific surface area, and bulk density of the obtained silver oxide particles were measured. The results are shown in Table 1 together with the amount of residual alkali (Example 1). Example 1 except that the kind and concentration of the alkali, the heating temperature, the reaction time and the pressure were changed as shown in Table 1.
A recrystallized silver oxide was produced in the same manner as described above. Table 1 shows the results.
(Examples 2 to 6).

With respect to the recrystallized silver oxide, silver oxide particles are put into a benzene solution in which the silylating agent is dissolved using the silylating agent shown in Table 1, and immersed for a predetermined time. Then, the angle of repose and the bulk density were measured.
The results are shown in Table 1 together with the processing conditions. The values before surface treatment are shown in comparison.

Comparative Examples 1 and 2 Table 1 also shows the alkali content and the fluidity of a conventional silver oxide for a battery not subjected to the recrystallization treatment of the present invention as a comparative sample.

As shown in Table 1, the silver oxide particles of this embodiment have better fluidity than the conventional silver oxide for batteries.
Further, the surface area and the bulk density are higher than the average particle size.
Also, the Si content increases with the alkali content, but does not adversely affect battery performance. The content of both chlorine and sulfur is 20 ppm or less, which is much lower than conventional products, and has the most suitable properties as silver oxide for batteries.

[0024]

As described above, the silver oxide particles of the present invention have high fluidity and are therefore excellent in quantitativeness when filling in a battery container. Further, since the surface area is larger and the bulk density is twice or more higher than that of the conventional product, a high-performance battery can be obtained. Furthermore, the alkali content is 1/2 or less of that of the conventional art, and the contents of chlorine and sulfur are significantly low. Therefore, a battery having a higher voltage and a longer life than a conventional product can be obtained.

[0025]

[Table 1]

Claims (5)

[Claims] A fluid silver oxide having an average primary particle size of 5 to 20 μm, a bulk density of 1.9 to 2.6 g / cm ³ and an angle of repose of 25 ° or less. 2. An alkali content of not more than 30 ppm, a chlorine content and a sulfur content of not more than 20 ppm, respectively.
The fluid silver oxide according to claim 1, which contains 0 ppm to 1%. 3. The flowable silver oxide according to claim 1, which is used for a battery. 4. An average primary particle size of 5% by refining silver oxide fine particles under pressure in an alkaline solution and recrystallizing them.
After having a bulk density of 1.2 to 1.7 g / cm ³ and a surface treatment with a silylating agent, the angle of repose is 25 ° or less and the bulk density is 1.9 to 2.6 g / cm ³ . A method for producing a flowable silver oxide. 5. The method according to claim 5, wherein the fine particles of silver oxide have a pH of 10 or more,
２０20 kg / cm ² , at a heating temperature of 80 to 250 ° C., by curing under pressure in an alkaline solution and recrystallizing, thereby reducing the chlorine content and the sulfur content to 20 ppm or less, the alkali content to 30 ppm or less, and the primary particles, respectively. After forming silver oxide particles having an average particle size of 5 to 20 μm and a bulk density of 1.2 to 1.7 g / cm ³ , the dried silver oxide particles are brought into contact with a solution of a silylating agent to perform a surface treatment, thereby obtaining a repose angle. The method according to claim 4, wherein the temperature is 25 ° or less and the bulk density is 1.9 to 2.6 g / cm ³ .