JP2001342021A - Method of preparing zinc oxide fine particles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preparing zinc oxide fine particles having high transparency to visible light and excellent UV shading. SOLUTION: This method comprises the steps of introducing carbon dioxide gas into an aqueous slurry containing zinc oxide to form basic zinc carbonate, drying it, and pyrolyzing the dried basic zinc carbonate by rotary kiln or the like under pulverization by steel balls or the like to obtain zinc oxide fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing zinc oxide fine particles having high transparency to visible light and excellent ultraviolet shielding properties.

[0002]

2. Description of the Related Art In recent years, the environmental problem of depletion of the ozone layer has become a major issue, and recent dermatological research has shown that exposure to ultraviolet light may cause spots, freckles and aging of the skin. It has become clear that ultraviolet rays have an unexpectedly adverse effect on skin, and there has been a great interest in protecting the human body from harmful ultraviolet rays.

[0003] Zinc oxide is conventionally known as a material for shielding such harmful ultraviolet rays, and is suitable as an ultraviolet ray shielding agent.

[0004] However, as an ultraviolet shielding agent, when it is simultaneously incorporated into cosmetics, sunscreens, paints, varnishes, etc., it forms a film or a film transparent to visible light, and has no natural turbidity. It is strongly required to have a color.

[0005] Theoretically, when zinc oxide is made into fine particles and the particle size is reduced to below the wavelength of visible light, visible light can pass through the zinc oxide and be substantially transparent.

Several methods are known as methods for producing such zinc oxide fine particles, but one of the most practical methods is to produce zinc oxalate or basic zinc carbonate in an oxidizing atmosphere such as air. This is a method in which an oxide is obtained by thermal decomposition (hereinafter, may be referred to as a thermal decomposition method).

For example, Japanese Patent Publication No. 33766/1985 discloses that an aqueous solution of a water-soluble zinc salt such as zinc chloride or zinc nitrate is dropped into an aqueous solution of oxalic acid to cause precipitation of insoluble zinc oxalate fine crystals. A method is disclosed in which this is separated by filtration, dried, and then thermally decomposed to form zinc oxide. The particle size of zinc oxide obtained by this method has a specific surface area (47 m ² /
g) (based on the BET method; the same applies hereinafter).
It is estimated to be about 0.02 μm.

As another example of the thermal decomposition method, a method is known in which a basic zinc carbonate is precipitated by adding an aqueous solution of sodium carbonate or the like to an aqueous solution of zinc chloride or the like, which is separated by filtration and then thermally decomposed. In order to avoid the contamination of impurities, as described in JP-A-60-255620, a water slurry of zinc oxide was stirred in a closed vessel and brought into contact with carbon dioxide gas to cause a reaction. A method has been proposed in which zinc oxide is precipitated as zinc carbonate, separated by filtration, and then thermally decomposed to produce zinc oxide. The resulting zinc oxide has a specific surface area of 15 m ² / g, and the average particle diameter calculated from this is: 0.07 μm.

As a method for improving this, Japanese Patent Publication No. 7-5308 discloses a method in which carbon dioxide gas is blown into a water slurry containing zinc oxide to cause a reaction, thereby producing basic zinc carbonate. A method for producing zinc oxide fine particles that is mechanically pulverized and then finely divided and then thermally decomposed has been proposed.
It is said to be zinc oxide of about 0.02 to 0.1 μm.

[0010]

As described above, when the conventional thermal decomposition method is used, the wavelength is less than the wavelength of visible light, more precisely, １ ／ of the wavelength of visible light (about 0.1 μm).
It is said that fine zinc oxide particles having a smaller size of about 0.02 to 0.1 μm can be obtained.

However, according to the study by the present inventors, when these zinc oxide fine particles are actually dispersed in a medium such as a cosmetic or a paint, a desired ultraviolet shielding ability is exhibited, Visible light transmittance was not sufficient. This is because although the particle diameter calculated from the specific surface area and the microscopic observation is certainly smaller than １ ／ wavelength (0.1 μm) of visible light, these zinc oxide fine particles are fine particles. Therefore, it is generally assumed that secondary agglomeration has not occurred and, under actual use conditions, it has not been substantially dispersed to 0.1 μm or less, and visible light has not been sufficiently transmitted. Is done. As described above, the zinc oxide fine particles obtained by the conventional method have a small apparent particle size, but when dispersed in a medium such as cosmetics, the aggregation cannot be avoided. Are not substantially fine particles to obtain transparency.

The present invention has been made in view of the above,
It is an object of the present invention to provide zinc oxide fine particles having a substantially sufficient fine particle diameter, which blocks ultraviolet rays and is transparent to visible light, that is, has a small particle diameter and good dispersibility.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method for improving the transparency to visible light, and as a result, in the conventional method, basic zinc carbonate or the like produced as a water slurry was not used. Since the precipitate is subjected to a solid-liquid separation operation such as filtration, and then dried, it has been found that agglomeration of the basic zinc carbonate fine particles generated in this process is promoted. Therefore, when thermally decomposing, it is necessary to mechanically pulverize the agglomerated cake and re-micronize the cake, but once agglomerated and dried, the cake is firmly agglomerated and solidified. For this reason, it is not possible to substantially reduce the size of the material by the usual grinding means.

As described above, in the case where zinc oxide is produced by thermally decomposing basic zinc carbonate accompanying coagulation, since the coagulated state is substantially supported as it is in the heat decomposition process, it can be finely dispersed. Obtaining zinc oxide is quite difficult.

The present inventors have conducted intensive studies on a method for producing fine and highly dispersible zinc oxide particles, which was not obtained by the conventional method. As a result, carbon dioxide was added to a dilute aqueous slurry containing zinc oxide. Gas is blown in to synthesize fine basic zinc carbonate, and the resulting basic zinc carbonate slurry is separated into solid and liquid by filtration, etc. After drying (approximately semi-dried), by heating and decomposing while pulverizing, it has been found that zinc oxide fine particles having excellent dispersibility and excellent transparency to visible light can be obtained, and the present invention has been completed. I came to.

That is, according to the present invention, the following inventions are provided. (1) a step of introducing carbon dioxide gas into a water slurry containing a raw material zinc oxide to generate basic zinc carbonate, a step of drying the obtained basic zinc carbonate, and a step of drying the dried basic zinc carbonate. A method for producing zinc oxide fine particles, comprising a step of heating and decomposing into zinc oxide while pulverizing (hereinafter sometimes referred to as a method of the present invention).

(2) A method for producing zinc oxide fine particles according to (1), wherein the basic zinc carbonate is thermally decomposed while being pulverized by a pulverizing medium.

(3) A method for producing zinc oxide fine particles according to (2), wherein the grinding medium is a ball or a rod.

(4) A method for producing zinc oxide fine particles in which the concentration of the aqueous slurry containing the raw material zinc oxide is reduced to 10% by mass or less and carbon dioxide gas is introduced and reacted.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the present invention, first, a step of introducing carbon dioxide gas into a water slurry containing a raw material zinc oxide to produce basic zinc carbonate (hereinafter, may be referred to as a basic zinc carbonate producing step). I do.

As the zinc oxide used as a raw material,
Any kind of so-called zinc oxide may be used,
For example, the French method of melting and evaporating zinc and oxidizing it in the gas phase, the American method of calcining, coke-reducing and oxidizing zinc ore, and adding soda ash to a zinc salt solution to precipitate basic zinc carbonate, followed by drying and firing Although it may be manufactured by any of a wet method (thermal decomposition method) or the like, it is preferable to use zinc oxide with high purity in order to obtain high-purity zinc oxide fine particles.

The water in which the raw material zinc oxide is suspended to form a slurry is not particularly limited, and tap water, ionic water, etc., from which impurity particles such as iron rust are removed in accordance with the required purity of the product zinc oxide. Either exchanged pure water or distilled water may be used. The carbon dioxide gas to be introduced into the slurry is not particularly limited, and is generally commercially available liquefied carbon dioxide gas, clean combustion exhaust gas,
Carbon dioxide gas or the like obtained by calcining limestone is preferably used. The carbon dioxide gas may be used as it is as a pure gas, but in some cases, it may be used after being diluted to an appropriate concentration with a diluent gas such as air or nitrogen.

The apparatus for performing the basic zinc carbonate generation step is not particularly limited, but includes, for example, a stirring means, a heating means, and a gas introduction / dispersion means, and is capable of floating zinc oxide particles without precipitating them. It is preferable to use a stirred tank type reactor in which the slurry is kept in a slurry state, carbon dioxide gas is introduced into the slurry, and the zinc oxide particles are sufficiently brought into contact with the carbon dioxide gas to carry out the reaction.

The slurry concentration of the raw material zinc oxide is at least 0.1 to 20% by mass, preferably 0.1 to 10% by mass.
It is desirable to have a relatively low concentration of 1% by mass, more preferably 1% to 5% by mass. When the slurry concentration exceeds this range, basic zinc carbonate having a large particle diameter is generated or aggregated particles are easily generated, and it is difficult to obtain fine particles having the desired dispersibility in the present invention. On the other hand, if the slurry concentration is much lower than this, the amount of water to be removed in the subsequent drying step or the like becomes excessive, which lowers the production efficiency and is not preferable in terms of energy.

In the present invention, a reaction in which zinc oxide particles react with carbon dioxide gas to produce basic zinc carbonate (hereinafter, may be referred to as a basic zinc carbonate producing reaction).
Is estimated to occur as follows. That is, zinc oxide itself is poorly soluble in water, but zinc oxide dissolved in water is slightly saturated in the boundary film near the particle surface (for example, about 0.5% by mass at 18 ° C.). Here, carbon dioxide gas (for example, Henry's constant E: 0.14 × 10 ⁴ ) relatively well soluble in water diffuses in the liquid body to the vicinity of the particle surface, and this solid-liquid in boundary film at the interface, in accordance _{5ZnO + 2CO 2 + 3H 2 O} → 2ZnCO 3 · 3Zn (OH) 2 (1) becomes equation (1), the liquid phase reaction.

It is considered that the generated basic zinc carbonate is a salt which is hardly soluble in water, and has substantially no supersaturation solubility, and immediately precipitates as fine particles. As described above, this reaction is a gas-liquid-solid reaction.

As a method for introducing the carbon dioxide gas, any method can be used as long as the slurry and the gas can come into effective contact, and the method is not particularly limited. For example, a perforated plate or a diffuser tube is provided at the bottom of the reaction tank. A gas disperser (sparger) is installed, and carbon dioxide gas is blown into the liquid through the sparger. More preferably, the gas is subdivided with stirring blades, and the carbon dioxide gas is dispersed as fine bubbles into the entire slurry. A method in which a closed vessel is used as a reaction vessel, a pressurized carbon dioxide gas is introduced, and a gas is absorbed from the free surface of the upper part of the slurry can be adopted. In the latter case, it is more preferable to form a vortex by stirring, forcibly renew the surface of the slurry, and promote gas absorption.

As the stirring means, any of ordinary stirrers, for example, a paddle stirrer, a propeller stirrer, a turbine stirrer and the like are suitably used.

The basic zinc carbonate forming reaction of the present invention can be carried out by various methods in practice. For example, first, a zinc oxide slurry is charged into a reaction tank, and carbon dioxide gas is continuously added thereto. Semi-continuous method (semi-batch method) in which the basic zinc carbonate slurry is produced by supplying the zinc oxide slurry and the carbon dioxide gas to the reaction vessel continuously to produce the basic zinc carbonate slurry. A method such as a continuous method in which the generated basic zinc carbonate slurry is continuously overflowed from the reaction tank and withdrawn is preferably employed.

In the case of the continuous method, a single reaction tank may be used. However, according to a conventional method, two or more reaction tanks are connected in series to form a multi-stage tank system, so that the residence time distribution in the tank can be entirely controlled. And the production yield of basic zinc carbonate can be improved by approaching the extrusion flow.

The reaction temperature for the basic zinc carbonate formation reaction is not particularly limited, but is 10 to 80 ° C., preferably 20 to 60 ° C. The reaction rate itself of equation (1) proceeds at a higher speed as the temperature is higher, but the solubility of carbon dioxide gas in water decreases as the temperature increases, and the gas concentration in the liquid decreases. Therefore, whether the reaction temperature is lower or higher than the above-mentioned temperature range, the overall reaction rate is undesirably slow. The reaction time (in the case of the continuous method, the average residence time in the reaction vessel) can vary depending on the reaction temperature, the concentration of carbon dioxide introduced, and the like.
Minutes to 10 hours, preferably about 30 minutes to 5 hours.
In order to maintain the temperature, it is preferable that the reactor is provided with a heating means, a heat keeping means and a temperature control means.

After completion of the reaction, the obtained basic zinc carbonate slurry is adjusted to a water content of 5 to 40% by mass, more preferably 5 to 10% by mass.
The mixture is filtered and dried to a powder of about mass% to obtain a powder. In this case, for example, the powder does not need to be dried to a completely dry state, and may be a semi-dry powder containing a certain amount of water.

As a drying apparatus for performing this drying,
There is no particular limitation, for example, a flash dryer, a spray dryer, a fluidized bed dryer, a stirring dryer, a cylindrical dryer, a box dryer, a band dryer, a hot air dryer, a vacuum dryer, and a vibration dryer. Or a spray dryer.

In the present invention, a step of subjecting the dried (semi-dried) basic zinc carbonate thus obtained to thermal decomposition (calcination) while pulverizing to obtain zinc oxide is performed.

The thermal decomposition temperature is a temperature at which the basic zinc carbonate is decomposed into finely divided zinc oxide having good dispersibility.
A temperature of 1000 ° C, preferably 200-500 ° C, more preferably 250-350 ° C is desirable. If the temperature is too low, the decomposition will be insufficient, and if the temperature is too high, the particles will grow too much due to aggregation and sintering, and both are unfavorable because the dispersibility deteriorates. The thermal decomposition time may vary depending on the treatment amount of the basic zinc carbonate, the heating temperature, the type of the heating furnace, etc., but is usually 30 minutes.
The time is from about minutes to 20 hours, preferably about 1 to 10 hours.

Thermal decomposition is carried out in an oxidizing atmosphere such as air.
The heating is performed in a heating furnace capable of heating the basic zinc carbonate particles to the above-mentioned temperature. In the present invention, it is necessary that the heating furnace be of a type capable of simultaneously performing pulverization and heating, and in particular, a cylindrical horizontal rotary heating furnace ( Rotary kiln) is preferred. The heating system may be either an internal heating system or an external heating system.

In a rotary kiln, a rotatable cylinder forming a furnace chamber is installed with a slight inclination, and while rotating, a raw material is charged from an upper supply port, and the charged raw material is heated and decomposed. The heating furnace moves downward in the kiln (cylinder) by the rotation while receiving the rotation, and is discharged from the lower discharge port.

In the present invention, it is preferable to add a grinding medium when supplying the basic zinc carbonate particles to the rotary kiln. The grinding medium (grinding medium) is usually a spherical steel ball (ball) or a rod-shaped steel rod (rod). In a rotary cylinder of a rotary kiln, the grinding medium is lifted along with the rotation of the cylinder along the inner wall of the cylinder, Repeat falling and falling by gravity. When the steel ball falls and falls, it exerts a strong impact action and a grinding action on the basic zinc carbonate particles, whereby the pulverization is effectively performed. The ball or the like serving as a crushing medium is not particularly limited as long as it has no mingling of impurities and has a crushing effect, and may be made of ceramics (so-called cobblestone) in addition to steel.

As described above, in the present invention, the basic zinc carbonate particles charged from the upper supply port of the rotary kiln undergo the pulverizing operation while moving in the kiln together with the pulverizing medium, and are ignited. Heated and decomposed,
It becomes zinc oxide in which particles are well dispersed and is discharged from the lower outlet.

The zinc oxide fine particles after thermal decomposition have excellent dispersibility, and can be used for various applications as they are. Incidentally, if desired, further pulverization treatment by a fine pulverizer such as a ball mill, a rod mill, a hammer mill, an edge runner mill, a colloid mill, a hammer mill, a conical mill, an attrition mill, a jet mill, a jet miser, a micronizer, and a micron mill. It can be used afterwards. These pulverizers are appropriately selected according to the cosmetics and paints to be mixed.

The zinc oxide fine particles obtained by the method of the present invention are excellent in dispersibility at the same time as being fine particles, and are suitably used for various applications requiring transparency at the same time as ultraviolet shielding of cosmetics and paints.

In the method of the present invention, unlike the conventional method for producing zinc oxide, the basic zinc carbonate which has been separated by filtration is not completely dried until it is solidified, but is dried in a rotary kiln in a semi-dry state or the like. It is presumed that by heating and decomposing while pulverizing with a pulverizing medium, zinc oxide fine particles with suppressed aggregation can be obtained.

[0044]

The present invention will be described below with reference to examples. However, these are merely examples of the embodiments, and the technical scope of the present invention is not construed as being limited thereto.

The dispersibility of the zinc oxide particles was evaluated according to the following dispersibility evaluation test. That is,

Zinc oxide particles were added to a 10% by volume aqueous solution of polyvinyl alcohol so that the concentration became 3% by mass.
Disperse with a homogenizer to form a paint. This paint is
The ET film is applied using an applicator having a coating thickness of 50 μm and dried. The light transmittance at each wavelength of the obtained film was measured using a spectroscope (manufactured by JASCO Corporation).
At a wavelength of 350 nm, the transmittance of ultraviolet light is 550 nm.
To measure the transmittance of visible light, respectively, and compare the ultraviolet shielding ability and the visible light transmittance.

Example 1 JI obtained by the French method
SK1410 A 1% by mass zinc oxide slurry was prepared using one kind of zinc oxide and ion-exchanged water. 30 L of this slurry was charged into a reaction vessel equipped with a stirrer having an inner volume of 50 L and a diffuser tube at the bottom and provided with a heat retaining mechanism, and the temperature was kept at 30 ° C., and carbon dioxide gas was blown at 10 L / min with stirring. After 2 hours, the blowing was terminated, and the product was analyzed by XRD to confirm that basic zinc carbonate had been formed.

The slurry was filtered and dried at 80 ° C. for 1 hour with a stirring dryer to obtain a semi-dried basic zinc carbonate powder having a water content of 12% by mass. The particle size of the particles was about 110 μm.

A chrome steel ball having a diameter of 10 mm was used as a grinding medium. The semi-dried powder of the basic zinc carbonate is converted into a batch type rotary kiln (350 mmφ × 400 mmL,
(15 rpm) together with steel balls, and was heated and decomposed at 300 ° C. for 5 hours. The charged basic zinc carbonate particles were heated and decomposed while undergoing a pulverizing operation while rotating together with the steel balls in the kiln, and zinc oxide fine particles in which the particles were well dispersed were obtained.

The specific surface area of the obtained zinc oxide was 49 m ² / g when measured by the BET method. The particle size calculated from this specific surface area is about 0.02 μm.

In order to evaluate the dispersibility of the obtained zinc oxide fine particles, the above-described dispersibility evaluation test was performed, and the light transmittance in the ultraviolet region and the visible light region was measured. The results are shown in Table 1. As is clear from the table, it is recognized that the zinc oxide fine particles produced by the method of the present invention have high visible light transmittance and ultraviolet shielding ability and are excellent in dispersibility.

Comparative Example 1 JI obtained by French method
SK1410 A 20% by mass zinc oxide slurry was prepared using one kind of zinc oxide and ion-exchanged water. 7 L of this slurry was charged into a reaction vessel equipped with a stirrer having an internal volume of 10 L and a diffuser tube at the bottom, and carbon dioxide gas was blown at 10 L / min with stirring. After 4 hours, the blowing was stopped, and the product was analyzed by XRD to confirm that basic zinc carbonate had been formed. This slurry was filtered using a Nutsche, and the filter cake was dried using a box drier. The dried cake was finely pulverized using a pulverizer manufactured by Hosokawa Micron Corporation to obtain basic zinc carbonate particles. The particle size of the particles was about 2 μm.

The particles were placed in a box-type electric furnace heated to 250 ° C., and thermally decomposed for 5 hours to obtain fine zinc oxide particles. When the specific surface area of the obtained zinc oxide was measured by the BET method, it was 47 m ² / g. The particle size calculated from this specific surface area is 0.02 μm.

In order to measure the dispersibility of the obtained zinc oxide fine particles, the above-mentioned dispersibility evaluation test was performed, and the light transmittance was measured. Table 1 shows the results. As is clear from the table, the zinc oxide of the comparative example according to the conventional method has a smaller visible light transmittance than that of Example 1 even though the particle diameter of the basic zinc carbonate before the thermal decomposition is small. It is recognized that the shielding ability is low and the dispersibility is poor.

Example 2 JI obtained by the French method
SK1410 A 3% by mass zinc oxide slurry was prepared using three types of zinc oxide and ion-exchanged water. 30 L of this slurry was charged into a reaction vessel equipped with a stirrer having an inner volume of 50 L and a diffuser tube at the bottom and equipped with a heat retaining mechanism. The temperature was kept at 40 ° C., and carbon dioxide gas was blown at 10 L / min with stirring. After 4 hours, the blowing was stopped and the product was analyzed by XRD to confirm that basic zinc carbonate had been formed.

This slurry was filtered and dried at 80 ° C. for 1 hour with a stirring dryer to obtain a semi-dried powder of basic zinc carbonate having a water content of 10% by mass. The particle size of the particles was about 420 μm.

The particles were heated and decomposed while being pulverized under the same conditions with the same rotary kiln as used in Example 1 to obtain fine zinc oxide particles. The specific surface area of the obtained zinc oxide was measured by the BET method 34m ²
/ G. The particle size calculated from this specific surface area is about 0.03 μm.

In order to evaluate the dispersibility of the obtained zinc oxide fine particles, the above-mentioned dispersibility evaluation test was performed, and the light transmittance in the ultraviolet region and the visible light region was measured.
The results are shown in Table 1. As is clear from the table, it is recognized that the zinc oxide produced by the method of the present invention has high visible light transmittance and ultraviolet shielding ability and is excellent in dispersibility.

Example 3 JI obtained by the French method
SK1410 A 1% by mass zinc oxide slurry was prepared using one kind of zinc oxide and ion-exchanged water. This slurry was supplied at a rate of 41 mL / min to a reaction vessel equipped with a stirrer having an internal volume of 10 L and an air diffusion tube at the bottom and equipped with a heat retaining mechanism. At this time, the temperature of the reaction vessel was maintained at 40 ° C., and carbon dioxide gas was continuously supplied at a rate of 15 L / min. XRD analysis of the product in the slurry overflowing from the reactor confirmed that it had been converted to basic zinc carbonate.

The slurry was filtered and dried at 80 ° C. for 1 hour with a stirring drier to obtain a semi-dried powder of basic zinc carbonate having a water content of 14% by mass. The particle size of the particles was about 280 μm.

These particles were heated and decomposed by the same rotary kiln as used in Example 1 while being pulverized under the same conditions to obtain fine zinc oxide particles. When the specific surface area of the obtained zinc oxide was measured by the BET method, it was 48 m ^2.
/ G. The particle size calculated from this specific surface area is about 0.02 μm.

In order to evaluate the dispersibility of the obtained zinc oxide fine particles, the above-mentioned dispersibility evaluation test was conducted, and the results of measuring the light transmittance in the ultraviolet region and the visible light region are shown in Table 1. As is clear from the table, it is recognized that the zinc oxide fine particles produced by the method of the present invention have high visible light transmittance and ultraviolet shielding ability and are excellent in dispersibility.

[0063]

[Table 1]

[0064]

The zinc oxide fine particles produced by the method of the present invention are useful because they have good transparency to visible light and excellent dispersibility while shielding ultraviolet rays.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Takagi, 669 Yokota, Oaza, Iizuka-shi, Fukuoka Prefecture (72) Inventor Takashi Nagai 669, Yokota, Oaza, Iizuka-shi, Fukuoka F-term ( Reference) 4G047 AA02 AB02 AD03 4J037 AA11 CA08 EE25 EE29 EE35 EE43 FF02 FF04 FF15

Claims (4)

[Claims] 1. A step of introducing carbon dioxide gas into a water slurry containing a raw material zinc oxide to produce basic zinc carbonate;
A method for producing zinc oxide fine particles, comprising: a step of drying the obtained basic zinc carbonate; and a step of pulverizing the dried basic zinc carbonate and subjecting it to heat decomposition to form zinc oxide. 2. The method for producing zinc oxide fine particles according to claim 1, wherein the basic zinc carbonate is thermally decomposed while being crushed by a crushing medium. 3. The method according to claim 2, wherein the grinding medium is a ball or a rod. 4. The method for producing zinc oxide fine particles according to claim 1, wherein the concentration of the aqueous slurry containing the raw material zinc oxide is adjusted to 10% by mass or less, and carbon dioxide gas is introduced and reacted.