JP2001122622A - Method of manufacturing zinc oxide super fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of efficiently manufacturing zinc oxide super fine particle with high purity. SOLUTION: The zinc oxide super fine particle is manufactured by separating an electrolytic cell with an ion exchange membrane to form an anode chamber and a cathode chamber, using the electrolytic cell formed by mounting metal zinc as an anode and a conductive body as a cathode, passing current between the anode and the cathode to elute metal zinc of the anode, moving zinc ion from the anodes side to the cathode side through the ion exchange membrane to deposit a zinc compound in the cathode chamber, cleaning the deposited zinc compound with alkali water and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a resin having an average particle diameter of 100 n.
The present invention relates to a method for producing ultrafine zinc oxide particles of m or less.

[0002]

2. Description of the Related Art Conventionally, as a method for producing ultrafine zinc oxide particles, a method of vaporizing metallic zinc and mixing it with a gas to cause a catalytic oxidation reaction (see Japanese Patent Application Laid-Open No. 1-286919) and a spray pyrolysis method (see Japanese Patent Application Laid-Open No. 6-199502) is known.

[0003]

However, when ultrafine zinc oxide particles are produced by the above method, there are problems in operability and productivity. That is, in the method of the catalytic oxidation reaction, the degree of freedom of the operating conditions is low, and it is difficult to control the reaction rate, the reaction rate, the size and the crystallinity of the produced particles in the catalytic oxidation reaction between steam and air. In particular, in order to form ultrafine particles, it is necessary to set the vapor concentration extremely low, so that the productivity is reduced. Further, in the spray pyrolysis method, it is necessary to lower the concentration of a spray liquid containing a salt of zinc in order to produce ultrafine particles, so that the amount of generation is small and the energy efficiency is not good. Furthermore, the method using a chemical reaction has a problem that a starting material is mixed into a product as an impurity.

According to the present invention, ultrafine zinc oxide particles are efficiently produced,
It is another object of the present invention to provide a method for producing a high-purity product.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, in an electrolysis method using an ion exchange membrane, the anode is used as a raw material of ultrafine zinc oxide particles. The inventors have found that ultrafine particles of high-purity zinc oxide can be produced by using metal zinc, using a conductor protected by a thin film for the cathode, and washing the product with an alkaline aqueous solution.

That is, the present invention uses an electrolytic cell in which an electrolytic cell is partitioned by an ion exchange membrane, an anode chamber and a cathode chamber are provided, metal zinc is used as an anode, and a conductor is provided as a cathode, and electricity is supplied between the anode and the cathode. To elute the zinc metal on the anode, move zinc ions from the anode side to the cathode side through the ion exchange membrane to precipitate zinc compounds in the cathode chamber, wash the precipitated zinc compounds with an aqueous alkali solution, and then dry A gist of the present invention is a method for producing ultrafine zinc oxide particles.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Ultrafine zinc oxide particles obtained by the production method of the present invention are ultrafine particles of zinc oxide or a hydrate thereof,
The average particle size is 100 nm or less, preferably 20 nm.
６０60 nm and has a sharp particle size distribution. The average particle size here is the volume average particle size of 200 or more particles observed with a transmission electron microscope.

In the present invention, the electrolytic cell is partitioned by an ion exchange membrane, and an anode chamber and a cathode chamber are provided. The ion exchange membrane used here is a membrane having ion permeability, and preferably has an appropriate zinc ion transport number. Specifically, a cation exchange membrane is used. The ion exchange membrane may be divided into an anode chamber and a cathode chamber by one sheet.

In the present invention, metallic zinc which is a raw material of ultrafine zinc oxide particles is used for the anode. The purity of the metallic zinc is preferably at least 99.9%, more preferably at least 99.99%. The higher the purity, the higher the purity of the product, which is preferable. The shape is not particularly limited, but a flat plate, a round bar, or a mesh shape is used.

The conductor used as the cathode includes titanium, nickel, lead and the like. The cathode preferably has alkali resistance. The shape is not particularly limited, but a flat plate, a round bar, or a mesh shape is used.

In the present invention, it is effective to improve the production efficiency if the produced zinc compound is not brought into direct contact with the cathode electrode. As a means for protecting the cathode, it is effective to protect the cathode with a film. Examples of the membrane used in this case include a dialysis membrane, an anion exchange membrane, a conductive film, a cloth made of alkali-resistant fibers, and an alkali-resistant paper. This film is intended to avoid contact between the product and the cathode and to prevent metal deposition on the cathode and contamination of the target substance, and is preferably close to the cathode, more preferably, in close contact with the cathode. It is preferable that the more closely adhered, the more easily the reaction between hydroxide ion and metal ion proceeds.

In addition, as a method of not bringing the cathode into direct contact with the zinc compound, there is a method in which the cathode cell is partitioned by an anion exchange membrane into three cells, and a product is deposited in an intermediate cell. Also, a method of applying a lacquer, silicone, or the like to the cathode is effective as a method of preventing direct contact with a zinc compound.

[0013] As the anode chamber and an electrolyte placed in the cathode ^{compartment, Li +, Na +, K} +, cations such as NH ₄ ⁺ or _{^{SO 4 2-, OH, -,}} Cl -, Br -, I -, CH ₃ CO
It suffices if it contains ions having electrical conductivity such as anions such as O ⁻ and HCOO ⁻ . In addition to the above-described electrolyte, a solution of zinc sulfate, zinc acetate, zinc formate, zinc nitrate, zinc halide, or the like, which is a raw material of the zinc oxide ultrafine particles, can be used as the electrolyte on the anode side. The cathode-side electrolyte is preferably stirred by a stirrer, stirring blades, bubbles, or the like. Examples of the gas used here include oxygen and the like in addition to inert gases such as nitrogen and argon. It is not necessary to control the pH of the electrolyte on the cathode side.

In the present invention, the electrolysis may be performed using the electrolytic cell having the above-described configuration. The electricity that flows during electrolysis is
Current between anode and cathode. The current value affects the composition, average particle size, particle size distribution, and generation rate of the obtained ultrafine particles, and is particularly preferably 0.02 to 0.05 A / Cm ² , and more preferably, for increasing production efficiency. Preferably has a current value of 0.03 to 0.04 A / Cm ² .

The temperature of the electrolytic solution at the time of electrolysis affects the composition, average particle size and particle size distribution of the obtained ultrafine particles, and is preferably 50 ° C. in order to obtain fine particles.
The temperature is more preferably 30 ° C or lower.

The electrolytic reaction in the present reaction can be carried out by any of a batch system and a continuous system. In the case of the continuous system, the product is extracted by a centrifuge or the like.

The reaction time in the present invention affects the average particle size and particle size distribution of the obtained ultrafine particles.
To obtain particularly fine particles, preferably within 2 hours,
More preferably, the product is extracted within 0.5 hours.

By the above-described electrolysis, the metallic zinc at the anode is eluted and moved to the cathode chamber through the ion exchange membrane, where the zinc compound is deposited. In the present invention, it is necessary to collect the zinc compound deposited in the cathode chamber by solid-liquid separation, and then perform washing. This washing needs to be performed using an alkaline aqueous solution, and more specifically, can be performed by stirring the recovered zinc compound in an alkaline aqueous solution. Washing with an alkaline aqueous solution is performed at least once.

As the alkaline aqueous solution for washing, an aqueous solution of a strong alkaline compound such as lithium hydroxide, sodium hydroxide, potassium hydroxide or the like can be used, and the concentration thereof is 1 mmol / L to 0.5 mol / L. Is more preferable, and more preferably 0.01 to 0.1 mol / L.
It is. The addition amount of the alkaline aqueous solution (1 g) per zinc oxide weight is preferably 0.05 L / g-zinc oxide or more, and more preferably 0.1 to 1.0 L.
/ G-zinc oxide is most preferred.

After the washing of the alkaline aqueous solution, it is usually preferable to carry out washing with pure water. After washing with an alkaline aqueous solution, solid-liquid separation can be performed, and the solid content can be stirred in pure water. Per zinc oxide weight (1
g), preferably 0.05 L
/ G-zinc oxide or more, more preferably 0.1 to
1.0 L / g-zinc oxide is most preferred. Each washing is performed by stirring with a washing solution, and the stirring time is preferably 3 minutes or more, more preferably 5 minutes or more.

Finally, in the method of the present invention, the zinc oxide obtained by washing is subjected to solid-liquid separation and drying treatment.

The ultrafine zinc oxide particles obtained by the present invention can be expected to be used in various fields in addition to pigments.

[0023]

The present invention will be described below in detail with reference to examples. Ultrafine zinc oxide particles were produced using an apparatus as shown in FIG. As the anode 1, a metal zinc plate was used, and as the cathode 2, a nickel electrode covered with a dialysis membrane (Spectra / Por Membrans, model 132675, molecular weight cutoff 6-8000) was used. The electrolytic cell (capacity: 1800 ml) is composed of one piece of Nafion (manufactured by DuPont), which is a cation exchange membrane 6, and has an anode side: a cathode side = 1: 1.
The anode chamber 3 and the cathode chamber 4 were divided into two tanks. The cathode chamber was constantly stirred with nitrogen gas.

Example 1 700 ml of a 0.1M aqueous solution of zinc sulfate was injected into the anode chamber 3 and 700 ml of a 0.1M aqueous potassium acetate solution were injected into the cathode chamber.
While stirring the cathode chamber 4 at a temperature of ° C, a current of 0.04 A / Cm ² was passed between the electrodes with a DC power supply to carry out an electrolytic reaction for 10 minutes. As a result, white zinc oxide ultrafine particles are contained in the cathode chamber 4.
2g was produced. The obtained slurry is dehydrated, washed with 1000 ml of 0.1N sodium hydroxide aqueous solution, and after dehydration, further washed once with 1000 ml of pure water, and then the solid component is isolated and dried by heating at normal pressure of 100 ° C. Thus, the desired zinc oxide was obtained. FIG. 2 shows the result of X-ray diffraction of the ultrafine zinc oxide particles. FIG. 3 shows a transmission electron microscope (0.38A JEM-200CX, manufactured by JEOL) photograph of the ultrafine zinc oxide particles. From FIG. 3, ultrafine particles having a primary particle diameter of 80 nm were confirmed.

Comparative Example 1 700 ml of a 0.1 M aqueous solution of zinc sulfate was injected into the anode chamber 3, and 700 ml of a 0.1 M aqueous potassium acetate solution was injected into the cathode chamber.
While stirring the cathode chamber 4 at a temperature of ° C, a current of 0.04 A / Cm ² was passed between the electrodes with a DC power supply to carry out an electrolytic reaction for 10 minutes. As a result, white zinc oxide ultrafine particles are contained in the cathode chamber 4.
2g was produced. After dehydrating the obtained slurry, pure water 1000
After washing with water four times with ml, the solid component was isolated and dried by heating at normal pressure of 100 ° C. to obtain the desired zinc oxide.

The samples obtained in the examples and comparative examples were analyzed for impurity content by a general chemical analysis method, and the results are shown in Table 1. It was shown that washing with an alkaline aqueous solution was effective for removing impurities, particularly for removing acetate ions.

[0027]

[Table 1]

[0028]

According to the present invention, by using metallic zinc for the anode, the generation of protons on the anode can be prevented, thereby suppressing the decrease in the transport number of metal ions and efficiently using zinc oxide. Ultra fine particles can be produced. further,
The quality of zinc oxide can be improved by protecting the cathode during the electrolytic reaction and washing the product with an alkaline aqueous solution. In addition, the number of times of cleaning itself can be reduced by adding a cleaning step using an alkaline aqueous solution. Further, according to the present invention, ultrafine particles having a sharp particle size distribution can be produced by controlling the reaction temperature, the amount of current and the reaction time.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an electrolysis apparatus used in Examples.

FIG. 2 is a diagram showing an X-ray diffraction result of zinc oxide obtained in an example.

FIG. 3 is a view showing a transmission electron micrograph of zinc oxide obtained in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode 2 Cathode 3 Anode room 4 Cathode room 5 DC power supply 6 Cation exchange membrane 7 Cathode protection membrane 8 Gas blower tube

Continued on the front page F term (reference) 4G047 AA02 AB02 AD03 4K021 AB17 BA04 DB05 DB10 DB31 DC15

Claims (1)

[Claims] 1. An electrolytic cell in which an electrolytic cell is partitioned by an ion-exchange membrane, an anode chamber and a cathode chamber are provided, metal zinc is used as an anode, and an electrolytic cell is used in which a conductor is installed as a cathode. The metal zinc is eluted, zinc ions are moved from the anode side to the cathode side through the ion exchange membrane to precipitate a zinc compound in the cathode chamber, and the precipitated zinc compound is washed with an aqueous alkali solution and then dried. For producing ultrafine zinc oxide particles.