JP2011116601A - Method for producing compound composed of fine powder, and amorphous calcium carbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for synthesizing compounds including calcium carbonate using two types of ultrasonically atomized droplets, and to produce a fine powder having a BET specific surface area of about 20 to 80 m<SP>2</SP>/g. <P>SOLUTION: There is provided a method for producing a compound composed of fine powders including: atomizing a raw material solution containing a calcium source and a raw material solution containing a carbonic acid source, a sulfuric acid source, a hydroxide source, or a phosphoric acid source by ultrasonic irradiation; allowing the respective flux which are flows of produced fogs to collide in the space as a reaction field; and filtering and drying the produced droplets. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a compound comprising a fine powder such as a fine powder having a particle size of about 20 to 100 nm, such as amorphous calcium carbonate.

  Ultrasound is a sound wave that exceeds the audible region on the high frequency side of a person, but it is possible to create a high-energy reaction field in the solution by irradiating the solution with an ultrasonic wave of 20 to 100 kHz. Special environment. FIG. 1 shows the effect when low-frequency ultrasonic waves and high-frequency ultrasonic waves are applied to a liquid. When low-frequency ultrasonic waves having a frequency of 20 to 100 kHz are applied, a high-temperature and high-pressure reaction field is generated due to the occurrence of cavitation. It is possible to reduce the reaction time by dispersion and stirring action, and to realize nano-size of particles (A). When high frequency ultrasonic waves having a frequency of 1.5 to 2.4 MHz are applied, capillary waves are generated and the solution is atomized. This schematically shows that the droplet diameter can be changed by changing the frequency, the effect of the surfactant is increased, and the suspension can be atomized (B).

As an example of the synthesis of crystal particles by the method of FIG. 1 (A), ultrasonic irradiation with a frequency of 20 to 100 kHz is performed during a liquid-liquid reaction or when carbon dioxide gas is blown into a calcium hydroxide suspension. Thus, it is known that nano-sized calcium carbonate can be synthesized that is extremely fine compared to the case of synthesis without irradiation with ultrasonic waves.
However, in this method, in the case of a calcium compound having a relatively low solubility in a reaction solvent such as calcium carbonate, fine particles can be synthesized, but in the case of a calcium compound having a high solubility in a reaction solvent such as calcium hydroxide or dihydrate However, fine particles could not be synthesized even when irradiated with ultrasonic waves during synthesis.

As shown in FIG. 1B, when a high frequency ultrasonic wave of about 1.5 to 2.4 MHz is irradiated on the solution, a water column is generated, and fine water droplets are emitted therefrom. This phenomenon is called atomization, and an ultrasonic humidifier uses this phenomenon. The particle size of the droplets generated by this atomization is about several μm, usually 3 μm or less. For example, when a droplet is generated by atomizing a 0.01 mol · dm ⁻³ aqueous solution of calcium chloride, if the particle size of the droplet is 1 μm, 6.02 × 10 ⁶ calcium ions are present in the droplet. Will be included. Furthermore, if the particle size of the droplet is 10 nm, six calcium ions exist in the droplet. This is shown in FIG.

  If small droplets generated by such atomization can be used as a reaction field, very fine particles can be easily synthesized. So far, most of the synthesis using ultrasonic atomization has been a spray drying reaction in which atomized droplets are dried by heating or decomposed, but crystal formation by contact reaction between atomized droplets has been reported. Absent.

In Patent Document 1, a mixed solution of an alcohol solution of SiO ₂ sol and an aqueous solution of a compound containing a glass forming element is atomized, and the generated fine droplets are thermally decomposed to produce a fine glass powder. A method is disclosed. However, the method of Patent Document 1 is a method in which glass raw materials are mixed in advance to form a single solution, which is atomized, and a raw material solution containing a cation constituting the compound to be obtained; The raw material solution containing the anion constituting the compound to be obtained is atomized independently in an ultrasonic generator, and the droplets of each raw material solution generated by atomization are dispersed in a space as a reaction field. It is not disclosed that they collide with each other, that is, the contact reaction between atomized droplets.

JP 2002-12428 A

  An object of this invention is to provide the synthesis | combining method of the compound using the contact reaction of the droplets produced | generated by ultrasonic atomization.

According to the first aspect of the present invention, a raw material solution containing a cation constituting a compound to be obtained and a raw material solution containing an anion constituting a compound to be obtained are each irradiated with ultrasonic waves. It is characterized by atomizing and causing the generated flux of mist to collide in a space as a reaction field and filtering and drying the generated droplets.

According to a second aspect of the present invention, in the method for producing the compound of the first aspect, a flux generated by atomizing an alcohol or an alcohol aqueous solution by ultrasonic irradiation is supplied to a space as a reaction field. It is characterized by.

According to Claim 3 of the present invention, in the method for producing a compound of Claim 1 or 2, the compound to be obtained is calcium carbonate, calcium sulfate dihydrate, calcium hydroxide or calcium phosphate. Features.

According to a fourth aspect of the present invention, in the method for producing the compound of the first aspect, the compound to be obtained is an amorphous calcium carbonate represented by CaCO ₃ .0.5H ₂ O. Features.

According to a fifth aspect of the present invention, in the method for producing a compound according to the third aspect, the raw material solution containing a cation constituting the compound to be obtained is an aqueous solution of a calcium source. The raw material solution containing an anion constituting the compound to be prepared is an aqueous solution of a carbonate source, a sulfate source, a hydroxide source or a phosphate source.

A sixth aspect of the present invention is amorphous calcium carbonate represented by CaCO ₃ .0.5H ₂ O.

  According to the present invention, a fine powder having a particle size of about 20 to 100 nm can be easily produced.

The figure which shows the effect at the time of applying the low frequency ultrasonic wave and the high frequency ultrasonic wave to the liquid Diagram showing droplet formation of aqueous solution by atomization Diagram showing a simple apparatus for atomization synthesis Flow chart of the action of atomization synthesis shown in FIG. X-ray diffraction pattern of the product obtained by changing the aqueous solution concentration The figure which shows the thermal analysis (TG-DTA) curve of an amorphous calcium carbonate Diagram showing the effect of aqueous solution concentration on the specific surface area of the product X-ray diffraction pattern of calcium carbonate obtained by the apparatus of this example while changing the reaction time The figure which shows the influence of time and solution temperature on the crystallinity of the calcium carbonate obtained by the present Example apparatus Diagram showing scanning electron micrographs of calcium carbonate obtained at room temperature and in a cooling environment Flowchart for atomizing and synthesizing calcium carbonate with the apparatus shown in FIG. X-ray diffraction pattern of calcium hydroxide obtained by changing reaction time for calcium hydroxide product obtained by atomization. The figure which shows the specific surface area of the product which the state which changed reaction time affects the calcium hydroxide product synthesize | combined by atomization based on an Example apparatus. The figure which shows the ratio of the calcium hydroxide in the product which the state which changed the reaction time affects the calcium hydroxide product synthesize | combined by atomization based on an Example apparatus. The figure which shows the specific surface area after the ratio calculation of the product which the state which changed the reaction time affects the calcium hydroxide product synthesize | combined by atomization based on an Example apparatus.

  An embodiment of a method for producing a fine powder according to the present invention will be described.

In the present invention, the raw material solution containing the cation constituting the compound to be obtained and the raw material solution containing the anion constituting the compound to be obtained are atomized by ultrasonic irradiation, respectively. Mist droplets, ie, the generated mist flow, that is, fluxes are mixed in a state where they collide with each other in the reaction field, and the atomized droplets of fine cations and anions collide and react with each other. To obtain a compound.
Regarding the mixed flow of the respective fluxes in the space as the reaction field, various methods such as mixed flow by suction, mixed flow by convection, and mixed flow by focusing / diffusion are possible, and are not limited to the embodiments described later.

The compound obtained by the method of the present invention is not particularly limited as long as it can be produced by this method, but calcium compounds such as calcium carbonate, calcium sulfate dihydrate (dihydrated gypsum), calcium hydroxide, calcium phosphate, etc. , Carbonates such as calcium carbonate, magnesium carbonate, barium carbonate, and strontium carbonate. Further, according to the method of the present invention, amorphous calcium carbonate having a novel composition of CaCO ₃ .0.5H ₂ O can be produced.

Examples of the raw material containing the cation constituting the compound to be obtained, that is, the cation source, include chlorides, nitrates and acetates containing the cation constituting the compound to be obtained.
Examples of the raw material containing an anion constituting the compound to be obtained, that is, an anion source, include sodium salts, potassium salts and ammonium salts containing an anion constituting the compound to be obtained.

For example, when calcium carbonate is to be obtained, calcium chloride, calcium nitrate, calcium acetate and the like are used as the calcium source, and sodium carbonate, potassium carbonate, ammonium carbonate and the like are used as the carbonate source.
When calcium sulfate dihydrate is to be obtained, calcium chloride, calcium nitrate, calcium acetate and the like are used as the calcium source, and sodium sulfate, potassium sulfate, ammonium sulfate and the like are used as the sulfuric acid source.
In the case of obtaining calcium hydroxide, examples of the calcium source include calcium chloride, calcium nitrate, and calcium acetate, and examples of the hydroxide source include sodium hydroxide and potassium hydroxide.
In the case of obtaining calcium phosphate, examples of the calcium source include calcium chloride, calcium nitrate, and calcium acetate, and examples of the phosphate source include sodium phosphate, potassium phosphate, and ammonium phosphate.

These raw materials are usually used as an aqueous solution of 0.1 to 2.5 mol · dm ⁻³ , preferably 0.5 to 2.0 mol · dm ⁻³ , particularly preferably 0.8 to 1.5 mol · dm ^−3. Is done. The lower the concentration of the aqueous solution, the easier it is to atomize. However, if the concentration is too low, the amount of raw material contained in the generated droplets decreases, and a large amount of compound cannot be obtained. Moreover, when the density | concentration of aqueous solution is too high, it will be hard to atomize. When producing amorphous calcium carbonate, it is preferable to use a raw material aqueous solution of about 0.7 to 1.5 mol · dm ⁻³ . Within this range, even if the reaction time is long or the reaction temperature is as high as about 40 ° C., amorphous calcium carbonate can be stably synthesized in the recovered alcohol without crystallization. it can.

Further, the raw material aqueous solution tends to be heated by the energy of ultrasonic waves when high frequency ultrasonic waves are applied. The temperature of the aqueous solution is not particularly limited, but when amorphous calcium carbonate is synthesized under the condition that the concentration of the raw material aqueous solution is 0.7 mol · dm ⁻³ or less, the aqueous solution of the raw material is cooled and maintained at room temperature or lower. Is preferred.

The concentration ratio between the aqueous solution of the cation source and the aqueous solution of the anion source is preferably the same as the ratio of the theoretical amount of the compound to be obtained. For example, in the case of calcium carbonate, carbonic acid and calcium are present in the calcium carbonate in a molar ratio of 1: 1. Therefore, the ratio of the concentration of the aqueous solution of the cation source to the aqueous solution of the anion (mol · dm−3) is Preferably it is 1: 1.

The frequency of the high-frequency ultrasonic wave applied to the raw material aqueous solution is not particularly limited as long as the raw material aqueous solution can be atomized, but is usually 1.5 to 2.4 MHz.

The reaction is carried out by colliding the flux formed by atomizing the aqueous solution of the cation source and the flux formed by atomizing the aqueous solution of the anion source. In addition to these, it is preferable to supply a flux formed by atomizing alcohol or an aqueous alcohol solution.
When the flux formed by atomizing the aqueous solution of the cation source and the flux formed by atomizing the aqueous solution of the anion source are collided only with these, the liquid formed by atomizing the aqueous solution of the cation source Droplets and droplets formed by atomizing an aqueous solution of an anion source stick to each other (multiple collisions), resulting in large droplets and a large particle size of the resulting compound. Since the compound serving as the anion source has low solubility in alcohol, when it collides with a droplet formed by atomizing alcohol or an alcohol aqueous solution, the compound serving as the anion source precipitates and reacts with the compound serving as the cation source. become unable. For this reason, enlarging the particle size of the compound due to multiple collisions can be prevented by the presence of droplets that can atomize alcohol or an aqueous alcohol solution.

Examples of the alcohol include lower alcohols such as methanol and ethanol. The concentration of the aqueous alcohol solution is not particularly limited, but if it is too thin, the effect of preventing multiple collisions is lost, so it is usually at least 10% by volume, preferably about 20 to 70% by volume. If it is too thick, the particle size of the droplets generated by atomization becomes too small, and it may be difficult to deposit the compound that becomes the anion source.
The supply ratio of alcohol or an alcohol aqueous solution is not particularly limited, but if it is too large, the reaction is inhibited. Or what is necessary is just to supply so that the volume ratio of alcohol aqueous solution may be about 1: 0.5-2.0 normally, Preferably it is about 1: 0.8-1.2.

  The reaction time in the reaction of the present invention is about 10 minutes to 5 hours, and the temperature of the reaction field is about 5 to 50 ° C.

When the droplets generated by atomization collide with each other, a reaction occurs and a compound is generated. However, since the droplets are still mist-like droplets, they are collected in a collection container containing alcohol installed in the reactor. . Then, it can collect | recover as powder by performing filtration, washing | cleaning by cold water, and drying. The alcohol used for the recovery is not particularly limited, but usually a lower alcohol such as methanol or ethanol is used.
The compound thus obtained is a fine particle having a particle size of usually about 20 to 100 nm and a BET specific surface area of usually about 20 to 80 m <2> / g. The particle size is calculated from the BET method specific surface as a true sphere.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 3 shows a simple apparatus outline for atomization synthesis used in the examples. 3A conceptually shows a planar configuration of the apparatus, and FIG. 3B is a perspective view thereof. In FIG. 3B, the container C described later is not shown.
Container A contains a calcium chloride aqueous solution, container B contains a sodium carbonate aqueous solution, and container C contains a 20% methanol aqueous solution. Throwing-type ultrasonic atomizer S (Honda Electronics Co., Ltd. ultrasonic atomization unit, atomization amount: 250 cm ³ · h ⁻¹ , atomization droplet: 3 μm, frequency) : 2.4 MHz) and atomize the contained solution. The droplets generated by atomization are discharged from the small windows Aw to Cw provided in the containers A to C, respectively. The containers A to C are arranged so that the mists Ma, Mb, and Mc discharged from the three containers A to C, that is, discharged from three directions, collide in the space as the field F. The mist Mm generated by the collision mixing is collected in four sample collection containers D in which methanol is stored, and this is washed by filtration and dried. Since a known apparatus may be used as the apparatus for filtering and washing and drying, explanation and illustration are omitted.

  FIG. 4 shows a flowchart of the operation as described above. A to D in FIG. 4 correspond to the containers A to D described above.

  The material thus obtained was used as a sample, and physical properties were measured using X-ray diffraction, thermogravimetry, differential thermal analysis, and a scanning electron microscope.

<Example 1>
The aqueous solution concentrations of calcium chloride and sodium carbonate were both 1.0 mol · dm ⁻³ , and the atomization synthesis of calcium carbonate was performed according to the flowchart of FIG. Since the reaction time was 60 minutes and the atmosphere and the raw material aqueous solution were not cooled, both the reaction atmosphere and the raw material aqueous solution were about 40 ° C. at the end of the reaction.
The X diffraction pattern of the obtained substance is shown in FIG. A diffraction peak was not observed and was in an amorphous state. As a result of thermal analysis (TG-DTA) measurement, an exothermic peak accompanying crystallization from an amorphous state was observed at around 335 ° C. as shown in FIG. Moreover, results of obtaining a composition from loss of TG-DTA, the composition of the amorphous calcium carbonate was CaCO ₃ · 0.5H ₂ O. When the BET specific surface area was measured, it was about 40 m ² · g ^{−1 as} shown in FIG. When observed with a scanning electron microscope, it was confirmed to be fine particles having a particle size of about 40 nm as shown in FIG.

<Example 2>
The atomization synthesis of calcium carbonate was performed in the same manner as in Example 1 except that the aqueous solution concentrations of calcium chloride and sodium carbonate were both 0.8 mol · dm ⁻³ .
An X-ray diffraction pattern of the obtained substance is shown in FIG. A diffraction peak was not observed and was in an amorphous state. Moreover, when the BET method specific surface area was measured, it was about 60 m < ² > * g ^<-1 > as shown in FIG.

<Examples 3 and 4>
The calcium carbonate and sodium carbonate aqueous solution concentrations were 0.6 mol · dm ⁻³ (Example 3) and 0.2 mol · dm ⁻³ (Example 4), respectively. Atomization synthesis was performed. An X-ray diffraction pattern of the obtained substance is shown in FIG. The products were calcite and vaterite. Further, when the BET specific surface area was measured, as shown in FIG. 7, it was about 10 m ² · g ⁻¹ (Example 3) and about 2 m ² · g ⁻¹ (Example 4).

<Examples 5 and 6>
The aqueous solution concentrations of calcium chloride and sodium carbonate were both 0.2 mol · dm ⁻³ as in Example 4, and the reaction time was 15 minutes (Example 5) and 30 minutes (Example 6). In the same manner as in Example 1, atomization synthesis of calcium carbonate was performed. The X-ray diffraction pattern of the obtained substance is shown in FIG. In addition, the result of 60 minutes of reaction time of FIG.
From FIG. 8, when the reaction time was 15 minutes, the product was in an amorphous state, whereas when the reaction time was increased, diffraction peaks of calcite and vaterite were observed. From this, it is considered that the amorphous calcium carbonate is crystallized after the initial generation. Amorphous calcium carbonate is produced at any concentration, but it is presumed that it is crystallized over time.

<Examples 7 and 8>
The aqueous solution concentrations of calcium chloride and sodium carbonate were both 0.2 mol · dm ^{−3 in the same} manner as in Examples 4 and 6, and the temperature of the reaction field was maintained at about 20 ° C. by cooling the reaction apparatus with ice. The atomization synthesis of calcium carbonate was performed in the same manner as in Example 1 except that the time was 30 minutes (Example 7) and 60 minutes (Example 8).
An X-ray diffraction pattern of the obtained substance is shown in FIG. For comparison, FIG. 9 also shows the results of Example 4 (reaction time 60 minutes) and Example 6 (reaction time 30 minutes) performed at room temperature without cooling the reactor. When the reaction was performed at room temperature without cooling the reaction apparatus, the temperature of the reaction field was about 40 ° C. due to the energy of ultrasonic irradiation.
It can be seen from FIG. 9 that the crystallinity is lower when cooling is performed even in the same reaction time. It can be seen that a lower temperature is preferred when synthesizing amorphous calcium carbonate.
Further, FIG. 10 shows a scanning electron micrograph of the substance obtained with a reaction time of 60 minutes (Example 8). For comparison, FIG. 10 also shows the result of Example 4 in which cooling was not performed after a reaction time of 60 minutes. FIG. 10 shows that the particle size of the obtained calcium carbonate is finer when cooling is performed.

  Furthermore, the Example which atomizes and synthesizes calcium hydroxide using the apparatus for atomization synthesis shown in FIG. 3 is described below. First, in the apparatus shown in FIG. 3, the container A contains a calcium chloride aqueous solution, the container B contains a sodium hydroxide aqueous solution, and the container C contains a 20% methanol aqueous solution, which is thrown into all of these containers A to C. An ultrasonic atomizer S is installed to atomize the stored solution. The droplets generated by atomization are discharged from the small windows Aw to Cw provided in the containers A to C, respectively. The containers A to C are arranged so that the mists Ma, Mb, and Mc discharged from the three containers A to C, that is, discharged from three directions, collide in the space as the field F. The mist Mm generated by the collision mixing is collected in four sample collection containers D in which methanol is stored, and this is washed by filtration and dried. Since a known apparatus may be used as the apparatus for filtering and washing and drying, explanation and illustration are omitted.

  FIG. 11 shows a flowchart of the operation as described above. A to D in FIG. 11 correspond to the containers A to D described above.

  The sample thus obtained was used as a sample, and X-ray diffraction, thermogravimetry, and the like were performed.

<Example 9>
The aqueous solution concentrations of calcium chloride and sodium hydroxide were both 0.5 mol · dm ^{−3 and} the atomization synthesis of calcium hydroxide was performed according to the flowchart of FIG. The reaction time was set to 60 minutes, 45 minutes, 30 minutes, and 15 minutes, respectively, and a product containing calcium hydroxide produced by atomization synthesis was obtained. The X-ray diffraction pattern of the obtained substance is shown in FIG. As a result, diffraction peaks of calcite and vaterite produced by the target calcium hydroxide and its carbonation were observed at any reaction time.

<Example 10>
Next, reaction time was set to 60 minutes, 45 minutes, 30 minutes, and 15 minutes, respectively, and the product containing calcium hydroxide produced | generated by the atomization synthesis | combination was obtained. The BET specific surface area of the obtained substance was measured, and the result is shown in FIG. As is apparent from this figure, the specific surface area of the product increased in the course of the reaction time, and its peak was about 50 m ² · g ^{−1 at} 45 minutes of the reaction time.

<Example 11>
Next, reaction time was set to 60 minutes, 45 minutes, 30 minutes, and 15 minutes, respectively, and the product containing calcium hydroxide produced | generated by the atomization synthesis | combination was obtained. The proportion of calcium hydroxide in the obtained substance was measured by thermogravimetric analysis, and the result is shown in FIG. As is clear from this figure, the proportion of calcium hydroxide in the product tended to decrease over the course of the reaction time.

<Example 12>
Based on the results shown in FIGS. 13 and 14, the specific surface area of calcium hydroxide in the product was calculated, and the results are shown in FIG. In this calculation, the specific surface area of calcium carbonate was assumed to be 5 m ² · g ⁻¹ . From the results shown in FIG. 13, the specific surface area of calcium hydroxide gradually increased over the course of the reaction time, and its peak was about 120 m ² · g ⁻¹ at a reaction time of 45 minutes.

  The present invention provides a method for producing fine calcium compounds and carbonates. Specifically, according to the present invention, fine calcium carbonate, calcium hydroxide, and especially novel amorphous carbonic acid used as inorganic industrial materials including fillers such as paper, rubber, plastic and cosmetics. Calcium can be produced.

A: Container for calcium chloride aqueous solution B: Container for sodium carbonate aqueous solution C: Container for aqueous methanol solution D: Sample recovery container F: Space as a field Aw to Cw: Small windows Ma, Mb, Mc provided in the container: Mist discharged from small window Mm: Mist generated by impact mixing is methanol S: Throw-in type ultrasonic atomizer

Claims (6)

The raw material solution containing the cation constituting the compound to be obtained and the raw material solution containing the anion constituting the compound to be obtained are each atomized by ultrasonic irradiation, and a flow that is a flow of generated mist. A method for producing a compound comprising a fine powder, wherein a bundle is collided in a space as a reaction field, and the generated droplets are filtered and dried.   The method for producing a compound according to claim 1, wherein a flux generated by atomizing alcohol or an alcohol aqueous solution by ultrasonic irradiation is supplied to a space as a reaction field.   The method for producing a compound according to claim 1 or 2, wherein the compound to be obtained is calcium carbonate, calcium sulfate dihydrate, calcium hydroxide or calcium phosphate. Process for the preparation of a compound according to claim 3, compound to be obtained, characterized in that an amorphous calcium carbonate represented by CaCO 3 _· 0.5H 2 _O.   The raw material solution containing the cation constituting the compound to be obtained is an aqueous solution of a calcium source, and the raw material solution containing the anion constituting the compound to be obtained is a carbonate source, a sulfuric acid source, a hydroxide source or phosphorus. The method for producing a compound according to claim 3, wherein the compound is an aqueous solution of an acid source. Amorphous calcium carbonate represented by CaCO ₃ · 0.5H ₂ O.

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