JP5664271B2 - Method for producing acicular strontium carbonate particles, and acicular strontium carbonate particles - Google Patents

Description

The present invention relates to a method for producing fine and acicular strontium carbonate particles.

In the use of optical parts such as optical films, sheets, and lenses, studies have been made using fine needle-like inorganic compounds such as strontium carbonate for the purpose of controlling the orientation birefringence of a polymer used as a raw material.

Patent Document 1 describes a method of producing acicular strontium carbonate by mixing a strontium hydroxide aqueous solution or suspension while stirring and introducing carbon dioxide gas with air or nitrogen gas.

Patent Document 2 discloses that acicular particles can be obtained by introducing carbon dioxide gas into a strontium hydroxide solution in the presence of an ammonium salt and an alkyl ammonium salt of a carboxylic acid as an agent for preventing crystal growth. It has been reported.

Japanese Patent No. 4140884 JP 2010-132555 A

An object of the present invention is to provide a method for industrially efficiently producing acicular strontium carbonate particles having a small particle diameter in a simple production step.

That is, the present invention is a method for producing acicular strontium carbonate particles,
Including a step of performing a wet reaction of a strontium source and a carbonic acid source in the presence of a particle shape control agent,
The reaction is in a reactor equipped with a stirring means, a manufacturing method that is performed under stirring at a stirring power density of ^{1.0 × 10 2 kW / m 3} ~1.0 × 10 4 kW / m 3.

By the method for producing strontium carbonate particles of the present invention, fine acicular strontium carbonate particles can be produced industrially efficiently. The strontium carbonate particles produced according to the present invention are suitable for optical film applications.

It is the figure which represented roughly reaction using a pump which is one of preferable embodiment of this invention. 2 is a transmission electron micrograph of strontium carbonate particles obtained in Example 1. FIG. 2 is a transmission electron micrograph of strontium carbonate particles obtained in Example 2. FIG. 2 is a transmission electron micrograph of strontium carbonate particles obtained in Comparative Example 1. FIG.

(Method for producing strontium carbonate)
The method for producing acicular strontium carbonate particles according to the present invention includes a wet reaction step of a strontium source and a carbonic acid source, and is performed under constant high-speed stirring.

The strontium source is not particularly limited, but it is preferable to use a strontium compound that can be adjusted to a solution, for example, one selected from the group consisting of strontium hydroxide, strontium chloride, strontium nitrate, and strontium acetate.

The strontium source is preferably used in the form of a solution. The concentration of the strontium-containing solution is preferably 1.25 to 10% by mass, more preferably 1.25 to 5% by mass. The strontium source-containing solution is not particularly limited, but can be prepared at a temperature of 25 ° C to 80 ° C.

The carbonic acid source is not particularly limited, but carbon dioxide such as carbon dioxide (carbon dioxide gas), carbonic acid and dry ice, carbonates such as sodium carbonate, potassium carbonate and ammonium carbonate, carbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate. It can be selected from hydrogen salts and urea. Other carbonic acid sources except gaseous carbon dioxide are preferably prepared in a solution state and then used for the reaction.

The concentration of the carbonic acid source is not particularly limited, but it is preferably introduced at a ratio of 1.0 to 1.5 mol with respect to 1 mol of the strontium source.

The method of introducing the strontium source into the reactor is not particularly limited, but can be selected from a batch system introduced in advance into the reactor and a continuous system introduced continuously. In the case of a reactor that cannot be introduced batchwise, such as a pump, continuous introduction is preferred.

The reaction between the strontium source and the carbonic acid source is performed wet. The solvent is not particularly limited, but water is preferable. In addition to water, a water-soluble organic solvent may be included.

The feature of the present invention is that stirring is performed at a constant high speed during the reaction. The stirring means that can be used in the present invention is not particularly limited, and examples thereof include a pump, a micro agitator, a sand mill, and a ball mill. More suitable reactors for obtaining high stirring power density are micro agitators, pumps, and sand mills.

There are a turbo type pump, a positive displacement pump, and a special type pump, and any of these can be used. Examples of the turbo pump include a centrifugal pump such as a centrifugal pump and a diffuser pump, a mixed flow pump such as a spiral mixed flow pump and a diffuser mixed flow pump, and an axial flow pump. Positive displacement pumps include reciprocating pumps such as piston pumps, plunger pumps, and diaphragm pumps, rotary pumps such as gear pumps, vane pumps, and screw pumps. Special types of pumps include pumps that use jet injection force of water or steam and compression. An example is a pump that uses air. When implemented on an industrial scale, centrifugal pumps, mixed flow pumps, axial flow pumps, and rotary pumps are preferred.

One embodiment of the reaction using a pump is shown below. However, the present invention is not limited to this embodiment. Moreover, the schematic is shown in FIG.

First, a strontium source solution, a carbonic acid source solution or carbon dioxide gas, and a particle size controlling agent solution are successively introduced into the pump through the pump inlet, and reacted in the pump casing. Strontium carbonate produced by the reaction is discharged in a suspension state from the discharge port of the pump. The raw material solution is introduced into the reaction pump by using a device capable of feeding the liquid, for example, a liquid feed pump different from the reaction pump.

In the present invention, the degree of stirring can be represented by the stirring power density. The stirring power density is the stirring power (kW) per volume (m ³ ) in the reactor. When a certain volume of material is stirred, the higher the stirring power density, the higher the stirring speed. Means.

The stirring power density in the production method of the present invention is 1.0 × 10 ² kW / m ^{3 to} 1.0 × 10 ⁴ kW / m ³ . If the stirring power density is less than 1.0 × 10 ² kW / m ³ , the particle diameter of strontium carbonate tends to increase, and desired fine particles may not be obtained. On the other hand, a stirring power density exceeding 1.0 × 10 ⁴ kW / m ³ is not preferable because it is difficult to achieve in a general manufacturing apparatus and may involve danger.

In the production method of the present invention, a particle size controlling agent is used. Although it does not specifically limit as said particle size control agent, Hydroxycarboxylic acid, polyhydric alcohol, carboxylic acid, and these salts are mentioned.

The hydroxycarboxylic acid is not particularly limited, and examples thereof include glycolic acid, lactic acid, citric acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, mevalonic acid, and pantoic acid.

Although it does not specifically limit as said polyhydric alcohol, Ethylene glycol, glycerin, xylitol, propylene glycol, and sorbitol are mentioned.

The carboxylic acid is not particularly limited, and examples thereof include oxalic acid, butyric acid, formic acid, acetic acid, propionic acid, and valeric acid.

Among these, citric acid, malic acid, and sorbitol are suitable for expressing the needle shape.

The particle size controlling agent is introduced in the range of 0.45 to 4.5 mass% with respect to the strontium carbonate to be produced. If it is less than 0.45% by mass, the effect as a particle shape control agent becomes insufficient, and there is a tendency that a needle-like shape is difficult to obtain. On the other hand, when it exceeds 4.5 mass%, the shape of the produced strontium carbonate tends to be indefinite.

A preferred embodiment of the production method of the present invention will be described. However, the present invention is not limited to this embodiment.

(Example of preferred embodiment)
Preparing a solution containing a strontium source,
The solution containing a strontium source, a particle shape controlling agent, and a gaseous or solution carbonic acid source are introduced into a reactor equipped with stirring means, and 1.0 × 10 ² kW / Under stirring at a stirring power density of m ^{3 to} 1.0 × 10 ⁴ kW / m ³ , a suspension having a pH of 6 to 11 is prepared, and the generated acicular strontium carbonate particles are recovered from the suspension. .

First, a solution containing a strontium source is prepared. The above-mentioned strontium sources can be used. As the solvent, water and a water-soluble organic solvent can be used, but water or a mixture of water and a water-soluble organic solvent is preferable.

Next, a strontium source, a particle shape controlling agent, and a carbonic acid source are introduced into a reactor equipped with stirring means. The order of introduction into the reactor is not particularly limited, and may be introduced from any of the strontium source, the particle shape control agent, and the carbonic acid source, or two or more of the three raw materials may be introduced simultaneously. In addition, the raw materials may be introduced batchwise or continuously into the reactor. When the carbon dioxide source is carbon dioxide, it is preferable to introduce carbon dioxide while monitoring the progress of the reaction after introducing the strontium source and the particle size control agent into the reactor.

The above-mentioned thing can be used as a carbonic acid source. When the carbonic acid source is a gas, it is introduced into the reactor as a gas as it is. When the carbonate source is a solid, the carbonate source can be introduced as a solution containing the carbonate. As the solvent, water or a water-soluble organic solvent can be used, but water or a mixture of water and a water-soluble organic solvent is preferable.

In the said reactor, a suspension is obtained by stirring with the stirring power density of 1.0 * 10 < ² > kW / m < ³ > -1.0 * 10 < ⁴ > kW / m < ³ >. The stirring means is not particularly limited, but a micro agitator, a pump, and a sand mill are preferable. By using a micro agitator, a pump, and a sand mill, high-speed stirring can be achieved.

In this embodiment, the pH of the suspension is 6-11. The pH is preferably 7-10.

Thereafter, the produced acicular strontium carbonate particles are recovered from the suspension. Typically, the desired strontium carbonate particles can be recovered by filtering the suspension and drying the resulting solids.

(Strontium carbonate particles)
The strontium carbonate particles obtained by the production method of the present invention have an average major axis diameter of 100 to 6000 nm, preferably 100 to 200 nm, and an average aspect ratio (= average major axis diameter / average minor axis diameter) of 4. It is an acicular particle in the range of -10.

In the present invention, the average major axis diameter of strontium carbonate is obtained by measuring the major axis diameter of particles in a transmission electron micrograph for a specific number (for example, 50 or more) and obtaining the average value. It is. Similarly, the aspect ratio is a value obtained by obtaining an average minor axis diameter from a transmission electron micrograph and dividing the average major axis diameter by the average minor axis diameter.

Examples of the present invention will be described below, but the present invention is not limited to these examples. Note that “%” represents “mass%” unless otherwise specified.

[Example 1]
A reaction vessel was charged with 950 g of water heated to 60 ° C. and 50 g of strontium hydroxide octahydrate to prepare a 5 mass% strontium hydroxide aqueous solution. To this, 25 ml of a 2.0% by mass aqueous citric acid solution (1.8% by mass with respect to the produced strontium carbonate) was added and stirred well. A pH meter electrode was inserted into the reaction vessel, and carbon dioxide gas was introduced at 500 mL / min while stirring with a micro agitator. The stirring power density at this time was 6.6 × 10 ³ kW / m ³ . The introduction of carbon dioxide gas was stopped when the pH reached 6-8. After filtering the suspension, the solid content was dried at 105 ° C. to obtain strontium carbonate particles. When the shape of strontium carbonate was observed with a transmission electron microscope, the average major axis diameter was 100 nm and the aspect ratio was 5.

[Example 2]
3 kg of strontium hydroxide octahydrate was added to 57 L of water heated to 80 ° C. to prepare a 5 mass% strontium hydroxide aqueous solution. The first pump (Sato Pump Industry Co., Ltd.) was continuously prepared at 13 L / min for the strontium hydroxide aqueous solution prepared in the above procedure, 87 L / min for carbon dioxide gas, and 750 ml / min for 2.0% by mass citric acid aqueous solution. Carbonation reaction was carried out by introducing into a company “Swirl Pump”, model S-252G). The suspension discharged from the outlet of the first pump was continuously charged into a second pump (“Yokata Suction Centrifugal Pump”, model UEN-0510 manufactured by Yokota Manufacturing Co., Ltd.). At this time, the stirring power density of the first unit was 5.8 × 10 ³ kW / m ³ . The pH of the suspension discharged from the outlet of the second pump was 10.6. After filtering the suspension, the solid content was dried at 105 ° C. to obtain strontium carbonate particles. When the shape of strontium carbonate was observed with a transmission electron microscope, it had an average major axis diameter of 230 nm and an aspect ratio of 6.

[Comparative Example 1]
750 g of strontium hydroxide octahydrate was added to 6750 g of water heated to 80 ° C. to prepare a 10 mass% strontium hydroxide aqueous solution. 400 g and 750 g of water were added to the first and second stage reaction vessels, respectively. While stirring with a stirrer (mixer equipped with a stirring blade), the aqueous strontium hydroxide solution prepared in the above procedure was continuously added to the first stage reaction vessel at 60 ml / min, and at the same time carbon dioxide gas was 280 mL / min. The carbonation reaction was carried out by introducing the carbon dioxide. The suspension discharged from the first-stage reaction vessel was continuously charged into the second-stage reaction vessel, and carbon dioxide gas was introduced at 280 mL / min while stirring with a stirrer. At this time, the first stage stirring power density was 3.8 kW / m ³ , and the second stage stirring power density was 5.3 kW / m ³ . The pH of the suspension discharged from the second-stage reactor was 10.5. After filtering the suspension, the solid content was dried at 105 ° C. to obtain strontium carbonate particles. When the shape of strontium carbonate was observed with a transmission electron microscope, the average major axis diameter was 420 nm and the aspect ratio was 2.

The conditions and results of the above examples and comparative examples are shown in Table 1. In addition, transmission electron micrographs of strontium carbonate particles obtained in Examples and Comparative Examples are shown in FIGS.

Claims (5)

A method for producing acicular strontium carbonate particles,
Including a step of performing a wet reaction of a strontium source and a carbonic acid source in the presence of a particle shape control agent,
The reaction is carried out in a reactor equipped with a stirring ^{means, 1.0 × 10 2 kW / m} 3 ~1.0 × 10 manufacturing method carried out under stirring at a stirring power density of 4 kW / ^{m 3.} Preparing a solution containing a strontium source,
The solution containing a strontium source, a particle shape controlling agent, and a gaseous or solution carbonic acid source are introduced into a reactor equipped with stirring means, and 1.0 × 10 ² kW / m in the reactor. ^2. A suspension having a pH of 6 to 11 is prepared under stirring at a stirring power density of ^{3 to} 1.0 × 10 ⁴ kW / m ³ , and the produced strontium carbonate particles are recovered from the suspension. The manufacturing method as described. The method according to claim 1 or 2, wherein the stirring means is a micro agitator or a sand mill. The method according to claim 1 or 2, wherein the stirring means is a pump. The production method according to any one of claims 1 to 4, wherein the particle shape controlling agent is hydroxycarboxylic acid, polyhydric alcohol or carboxylic acid, or a salt thereof.