JP3340756B2 - Method for producing monodisperse vaterite-type calcium carbonate with controlled morphology - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to vaterite which is controlled to a specific form and has good dispersibility in the production of vaterite-type calcium carbonate of a discoid body, a stone-shaped ellipsoidal sphere, a spherical body, and a rugby ball-shaped elliptical sphere. And a method for producing calcium carbonate.

[0002]

2. Description of the Related Art At present, a carbon dioxide gas method is widely used as an industrial production method of synthetic calcium carbonate. With the carbon dioxide method, natural limestone is calcined to obtain quicklime (calcium oxide), and the quicklime is reacted with water to obtain lime milk (water suspension of calcium hydroxide).
This is a method of obtaining calcium carbonate by conducting and reacting carbon dioxide gas generated when limestone is calcined to this lime milk. Synthetic calcium carbonate produced by the carbon dioxide method is widely and widely used as a filler or pigment for rubber, plastic, paper, paint, etc., depending on the size of the primary particles. Calcium carbonate includes hexagonal calcite-type crystals, orthorhombic aragonite-type crystals, and pseudo-hexagonal vaterite-type crystals as polymorphs. Applications used are cubic or spindle-shaped calcite-type crystals,
Alternatively, most are needle-like or columnar aragonite-type crystals. On the other hand, in the case of vaterite-type calcium carbonate, it is said that due to its morphological characteristics, it has relatively good dispersibility as compared with the other two-crystal types and does not contain large coarse aggregates. Paper, paint, or rubber,
When used as a pigment or filler for plastics, it can be expected to have effects such as improved coatability and improved fillability, and will eventually lead to improvements in physical strength, gloss, whiteness, or printing characteristics of the product. .

From the above viewpoints, various methods for industrially producing vaterite-type calcium carbonate have been studied. For example, in Japanese Patent Application Laid-Open No. 60-90822,
By introducing a carbon dioxide-containing gas into a calcium hydroxide aqueous suspension containing a magnesium compound and adding a condensed alkali phosphate or an alkali metal salt thereof when a certain degree of carbonation is reached, vaterite-type calcium carbonate Japanese Patent Application Laid-Open No. 54-150397 discloses that vaterite-type calcium carbonate is prepared by coexisting ammonia in advance so that the pH of the slurry at the end of the reaction in the reaction between calcium chloride and calcium bicarbonate becomes 6.8. The method of obtaining is described.

[0004] However, all of these methods are not only extremely complicated in their production methods as compared with conventional methods for producing cubic or spindle-shaped calcium carbonate crystals,
It is difficult to control the particle size of the vaterite-type calcium carbonate particles, the primary particle size of the obtained vaterite-type calcium carbonate is not uniform, and the particles do not have good dispersibility.

[0005] Furthermore, many of the vaterite-type calcium carbonates obtained by the conventional method are generally reported to be spherical in shape. There are few examples composed of calcium, and most examples are composed of a mixture of flat elliptical sphere, thick elliptical sphere, and spherical spherical calcium carbonate.

Recently, various methods for producing vaterite-type calcium carbonate by carbonating calcium hydroxide contained in an organic solvent have been proposed. For example, in Comparative Example 1 of JP-A-59-64527, a method in which carbon dioxide gas is passed through a mixed solution of an aqueous calcium hydroxide suspension and methanol to obtain vaterite-type calcium carbonate is disclosed in JP-A-61-77622. Describes a method of blowing a carbon dioxide gas into a suspension system of calcium hydroxide, water and an alcohol to produce amorphous or crystalline calcium carbonate such as vaterite. However, in any of these methods, vaterite-type calcium carbonate can be obtained in a high yield, but the particle size and particle form of the obtained vaterite-type calcium carbonate particles cannot be arbitrarily controlled. Further, there is a disadvantage that it is not possible to stably produce vaterite-type calcium carbonate in which primary particles are uniform and monodispersed with good dispersion.

In recent years, particularly for use in advanced technical fields, in order to develop industrial products having higher functionality, the inorganic particles used have good monodispersed good dispersibility as physical properties. Needless to say, there has been a demand for inorganic particles whose particle shape can be finely controlled, and there has been a demand for the development of a method for producing inorganic particles that have good dispersibility, can accurately and finely control the form. I have. For example, in the case of polyester films used for magnetic tapes such as audio tapes and video tapes, the slipperiness and abrasion resistance of the film are high and low in the workability of the film manufacturing process and the processing process in each application, and further, the quality of the product. It is a major factor that determines the quality. When these slipperiness and abrasion resistance are insufficient, for example, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, friction between the coating roll and the film surface during application of the magnetic layer is intense. The surface of the film is also severely abraded by wrinkles, and in extreme cases, wrinkles, abrasions and the like are generated on the film surface. Also, even after slitting the film after applying the magnetic layer and processing it into audio, video, computer tape, etc., when pulling out from reels or cassettes, winding up and other operations, many guide parts, playback heads etc. Abrasion occurs significantly between the substrate and the substrate, and as a result of the occurrence of scratches, distortion, and the precipitation of a white powdery substance due to the scraping of the polyester film surface, the magnetic recording signal is often lost, that is, a large cause of dropout. .

Hitherto, many methods for lowering the friction coefficient of polyester have been proposed in which fine particles are contained in polyester to give fine and appropriate irregularities on the surface of the molded article to improve the surface smoothness of the molded article. Has been
The affinity between the fine particles and the polyester was not sufficient, and neither the transparency nor the abrasion resistance of the film was satisfactory. To further explain this method, as a means for improving the surface characteristics of polyester, a method of partially or entirely depositing a catalyst or the like used in the synthesis of polyester in a reaction step (internal particle precipitation method), calcium carbonate, and carbon dioxide Many methods of adding fine particles such as silicon during or after polymerization (external particle addition method) have been proposed. Particles that form irregularities on the surface of these polyester films are generally such that the larger the size, the greater the effect of improving slipperiness.
For magnetic tapes, especially for precision applications such as video, the large particles themselves can cause defects such as dropouts, so the surface irregularities of the film must be as fine as possible. At the same time, there is a demand to satisfy these requirements.

However, the internal particle precipitation method has a good affinity to polyester to some extent because the particles are a metal salt of a polyester component, etc., but is a method of generating particles during the reaction. It is difficult to control the amount and size of particles and to prevent the generation of coarse particles. On the other hand, in the method (1), if the particle size and the amount of addition are appropriately selected, and fine particles from which coarse particles are removed by classification or the like are added, the lubricity will be excellent. However, since the affinity between the inorganic fine particles and the polyester as the organic component is not sufficient, peeling occurs at the boundary between the particles and the polyester during stretching or the like, and voids are generated. When this void is present in the polyester, the particles are likely to be detached from the polyester film due to damage of the polyester film or the like due to contact between the polyester film or the polyester film and another substrate, for example, in the magnetic tape film as described above. It causes white powder and dropout.

[0010] The current production of polyester films involves the following:
Although the methods (1) and (2) are used in combination, the method is gradually becoming mainstream from the viewpoint of easy selection of particle size and easy reproduction of quality. However, since the inorganic fine particles used in the method have insufficient affinity with the polyester as described above, the particles are easily detached from the polyester film due to damage of the polyester film and the like, and white powder is easily generated. In order to prevent this, research and development of surface treatment agents with good inorganic fine particles from a chemical point of view, and research and development of inorganic fine particles with a shape that is difficult to detach from polyester film from a physical point of view, have been conducted in various fields. ing. With respect to the shape of the inorganic fine particles used in the method, the elliptical spherical particles and the plate-like particles are better than the spherical particles from the viewpoint of desorption from the polyester film, but on the other hand, the polyester film It is said that spherical particles are the best from the viewpoint of film running property (film sliding property), which is another important physical property required for the above.

Conventionally, as the plate-like inorganic particles in the conventional method, kaolin clay prepared by removing coarse particles using a special classification technique is mainly used. However, since kaolin used in this field is originally made of naturally occurring kaolin, the shape and particle size of the primary particles are extremely non-uniform. It has been considered difficult to completely remove the coarse particles even if the classification is repeated. For this reason, it cannot be used as an anti-blocking material for a high-grade polyester film, and there has been a long-awaited demand for developing plate-like particles having a uniform particle diameter and containing few aggregate particles and having good dispersibility.
In addition, as the spherical inorganic particles in the conventional method, monodispersed spherical silica obtained by a method such as a hydrolysis reaction and a condensation reaction of an alkoxysilane has been developed, and has a uniform particle diameter and good dispersibility in ethylene glycol. Because of its good dispersibility in polyester and polyester, its use as an anti-blocking material for polyester films, especially video tapes requiring high quality, is being studied. However, the spherical silica is not only difficult to prepare economically because the price of the alkoxysilane as a raw material is very high, but also requires a long time for the reaction due to a slow hydrolysis reaction. Also, compared to other inorganic particles added externally to the polyester, because the affinity with the polyester is insufficient, the spherical silica is easily detached from the polyester film due to damage to the polyester film, etc. It is easy to cause outbreak and dropout. Furthermore, since the spherical silica has an extremely high Mohs hardness of 6 or more, the spherical silica detached from the polyester film has a serious disadvantage that the surface of the reproducing head of the video tape recorder is easily damaged.

Accordingly, the inorganic particles used in this type of polyester film have not only uniformity and good dispersibility of the particles, but also delicate morphological control techniques such as particle shape and particle size, for example, Plate-like, stone-like, spherical, rugby ball-like, and the establishment of advanced particle morphology control technology that can arbitrarily produce particles having a particle morphology has been required,
Further, it is essential that the inorganic particles have a relatively low Mohs hardness of about 3 or so. Calcium carbonate has a Mohs hardness of about 3 and has a relatively low value among inorganic particles. Therefore, as inorganic particles to be externally added, uniformity and dispersibility of particles equal to or higher than the spherical silica described above are obtained. It has been desired to develop a calcium carbonate that can retain and further control fine morphology such as particle shape and particle diameter.

[0013]

In order to meet these high requirements, the present inventors have disclosed in Japanese Patent Application Nos. 2-137482 and 2-137483 "monodispersed spherical or elliptical spherical vaterite calcium carbonate and The manufacturing method "
And "monodispersed plate-like vaterite calcium carbonate and a method for producing the same". The method provided by these methods is a method that enables the morphological control of vaterite-type calcium carbonate, which was impossible with the conventional method of producing vaterite-type calcium carbonate, and includes spherical or elliptical spherical vaterite-type calcium carbonate and plate-like vaterite. It is intended to provide a method for arbitrarily controlling and producing type calcium carbonate.
However, in these methods as well, the distinctive production of spherical vaterite-type calcium carbonate and elliptical spherical vaterite-type calcium carbonate, the elliptical spherical vaterite-type calcium carbonate and the plate-like vaterite-type calcium carbonate are converted to a thicker particle form However, the production method such as the production of vaterite-type calcium carbonate capable of finely controlling the morphology, such as the preparation of the calcium carbonate, was not always sufficient. Further, the methods provided by these methods have relatively small tolerances for various manufacturing conditions.

[0014]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and achieves a high degree of dispersibility, uniformity of particles, and selectivity of an arbitrary particle form such as a polyester base film as described above. As a result of intensive research on vaterite-type calcium carbonate that can be used sufficiently in the required fields, carbon dioxide gas was added to a methanol suspension of quicklime and / or slaked lime containing a specific amount of quicklime and / or slaked lime and a specific amount of water. Conduct and conduct the carbonation reaction, adjust the temperature in the reaction system to a specific temperature at a specific time during the carbonation reaction, and after a specific time, control the pH in the carbonation reaction system for a specific time within a specific range As a result, it has been found that vaterite-type calcium carbonate having a desired form can be easily and stably produced, and that the obtained calcium carbonate has unique primary particle uniformity and dispersibility. The present invention has been completed based on these new findings.

That is, according to the present invention, the projected surface of a monodisperse vaterite-type calcium carbonate having a particle shape of a disk, a stone-shaped ellipsoidal sphere, a sphere, and a rugby ball-shaped ellipsoidal sphere is a plan view. In the display of the particles by the third trigonometric method, the horizontal diameter of the plan view is defined as a, the vertical diameter is defined as b, the height diameter of the front view and the side view is defined as c, and the length of the c diameter / a or b is shorter. When producing a monodisperse vaterite-type calcium carbonate having a diameter-to-length ratio of M, carbon dioxide gas is passed through a mixture system of methanol and quicklime and / or slaked lime and water to initiate a carbonation reaction, and a carbonation reaction is started. T1 hours after the electric conductivity (electric conductivity) in the system reaches the maximum value, the pH in the reaction system is within the range defined by the following formula (the total range of the following pH range 1 and pH range 2). ) Controlled for T2 time, the morphology controlled monodispersion Method for producing Teraito type calcium carbonate is to the content of. However, the concentration of quicklime and / or slaked lime in the mixed system is 0.1 to 12% by weight with respect to methanol, and the amount of water is 1 to 80 with respect to quicklime (in the case of slaked lime, it is converted to the same mole of quicklime). Times moles. M = length of c diameter / length of shorter diameter of a or b pH range 1 8.9 ≦ pH <11.5 and (−M + 10) ≦ pH ≦ (−13M / 9) + (23/2) ) PH range 2 5.5 ≦ pH <8.9 and (−29M / 3) + (293/15) ≦ pH ≦ (−29M / 12) + (53/4) T2 ≧ (T1 / 10)

Hereinafter, the present invention will be described in more detail. First, methanol and 0.1 to 12% by weight of quicklime and / or slaked lime with respect to the methanol, and 1 to 80 times mole of water with respect to the quicklime (in the case of slaked lime, converted to the same mole of quicklime), are mixed with methanol. There is no particular limitation on the preparation order of the mixed system for adjusting the mixture system of quick lime and / or slaked lime and water, and a method of adding water to a mixture of quick lime and / or slaked lime and methanol, a method of adding a mixture of methanol and water, It may be adjusted by any preparation order, such as a method of adding quicklime and / or slaked lime, and a method of adding methanol to a mixture of water and quicklime and / or slaked lime. Hereinafter, a method of adding water to a mixture of quicklime and / or slaked lime powder and methanol among the methods for preparing a mixed system of methanol and quicklime and / or slaked lime and water will be described in detail. First, quick lime powder and / or slaked lime powder are put into methanol to prepare a methanol suspension of quick lime and / or slaked lime. The concentration of quicklime and / or slaked lime may be 0.1 to 12% by weight based on methanol as converted concentration of quicklime (in the case of slaked lime, the concentration converted into quicklime of the same mole, hereinafter abbreviated as quicklime concentration). If the concentration of quicklime is less than 0.1% by weight, the unit methanol requirement increases, which is not only uneconomical, but also makes it difficult to control the reaction conditions in the subsequent carbonation reaction step. The rate gets very bad. When the concentration of quicklime exceeds 12% by weight, the inside of the system is apt to gel in the subsequent carbonation reaction step, and the reaction conditions in the system are liable to become non-uniform with the gelation, and as a result, it is finally obtained. The shape and size of the calcium carbonate particles become non-uniform, and further, calcium carbonate with a good dispersion state of the particles cannot be obtained.

Next, water is added to the methanol suspension of quicklime and / or slaked lime in an amount equivalent to 1 to 80 times the molar amount of quicklime, and (methanol + quicklime and / or slaked lime)
Prepare a + water mixture. When the amount of water to be added is less than 1 mol, the reaction system changes from a liquid state to a solid state in the subsequent carbonation reaction step, and it is often impossible to continue the carbonation reaction. If the amount exceeds mol, calcium carbonate containing a large number of crystalline calcium carbonates such as calcite and aragonite in addition to vaterite-type calcium carbonate is obtained, which is not preferable.

Next, carbon dioxide gas is passed through the mixed system of methanol + (quick lime and / or slaked lime) + water to start a carbonation reaction. As shown in FIG. 5, after the start of the carbonation reaction, the conductivity in the reaction system reaches a maximum value (point B in FIG. 5) and then T
After one hour, the object of the present invention is achieved by controlling the pH in the reaction system for T2 hours in a pH range according to the desired form of the vaterite-type calcium carbonate. In the figure, A is the carbonation reaction start point, B is the maximum point of the conductivity in the carbonation reaction system,
C is a pH control start point, and D is a pH control end point. Time T1
Is the time from when the conductivity in the carbonation reaction system reaches the maximum value to when control within the reaction system is started at a specific range of pH,
There is no particular limitation on T1, and T1 can be arbitrarily set by controlling conditions such as a conduction method and a conduction speed of the carbon dioxide gas supplied into the carbonation reaction system. In order to achieve the object of the present invention, the pH range in which the inside of the reaction system is controlled for T2 hours is a pH range of 18.9 ≦ pH <11.5 and (−M + 10) ≦ pH ≦ (−13M / 9) + (23/2) pH range 2 5.5 ≦ pH <8.9 and pH expressed by (−29 M / 3) + (293/15) ≦ pH ≦ (−29 M / 12) + (53/4) What is necessary is just the range of the sum of the range 1 and the pH range 2. M in the above formula is a morphological index of the vaterite-type calcium carbonate particles. As shown in FIGS. 1, 2, 3, and 4, the vaterite-type calcium carbonate has a particle form of a discoid body, a stone-shaped ellipsoidal sphere, a spherical body, and a rugby ball-shaped ellipsoidal sphere. The morphological index M is shown in FIGS.
It is a ratio of the length of the c-diameter / the shorter of a or b in the triangular diagrams shown in FIGS. 3 and 4, where M = the length of the c-diameter / the shorter of a or b. It is represented by Note that the particle morphology shown in FIGS. 1 to 4 is conceptually and typified by typical ones until it gets tired, and of course includes modified ones.

An object of the present invention is to provide a vaterite-type calcium carbonate having an arbitrary form which can only be produced by accident by a conventional production method, in other words, a vaterite-type carbonate having an arbitrary form index M and having a good dispersibility. Calcium particles,
It is an object of the present invention to provide a method that can be easily and selectively produced, and even if a carbonation reaction is started with the intention of producing a vaterite-type calcium carbonate having a specific form factor M,
Without controlling the pH in the carbonation reaction system for a certain time within the pH range, a vaterite-type calcium carbonate having a morphological index M cannot be obtained. Further, in the present invention, the time T2 during which the pH in the carbonation reaction system is controlled within the above-mentioned pH range is determined after the electric conductivity (electric conductivity) in the carbonation reaction system reaches the maximum value. What is necessary is just to be at least 1/10 of the time T1 until the pH control is performed. When T2 <(T1 / 10), particles of a desired form are not formed, so that a vaterite-type calcium carbonate having an intended particle form cannot be obtained. There are no particular restrictions on the conditions for conducting carbon dioxide to the reaction system in the carbonation reaction according to the present invention. From the start of the carbonation reaction
Reduce the conduction speed of the carbon dioxide gas gradually until the pH control, stop the conduction of the carbon dioxide gas from the start of the carbonation reaction until the pH control, and then until the pH control,
The carbonation reaction may be performed by a method such as intermittently conducting carbon dioxide gas into the reaction system. Regarding the method of performing pH control, when starting pH control in the system, if the pH in the system tends to increase, a small amount of carbon dioxide gas may be passed through the system, and conversely, When the pH tends to decrease, it can be achieved by adding a small amount of a mixed solution of methanol + water + (quick lime and / or slaked lime) to the system.

After the pH control in the system is completed by the above-mentioned method, it is preferable to conduct carbon dioxide gas in the system as needed to consume the remaining alkali. The vaterite-type calcium carbonate of the present invention thus obtained is a vaterite-type calcium carbonate satisfying all of the following requirements (A), (A), (C), (D), and (E), and is obtained by an electron microscope. Not only is the average particle size measured by the method described above and the average particle size measured by the particle size distribution measuring device almost similar, but also the particle size distribution is extremely sharp and monodispersed without agglomeration in the dispersion medium. (A) 0.05 μm ≦ DS ≦ 2.0 μm (A) DP3 / DS ≦ 1.25 (C) 1.0 ≦ DP2 / DP4 ≦ 2.5 (D) 1.0 ≦ DP1 / DP5 ≦ 4.0 (E) (DP2-DP4) /DP3≦1.0, where DS is the average particle diameter (μm) measured by a scanning electron microscope (SEM). "Length of a diameter" and "Length of b diameter" in the triangular diagrams shown in FIGS. 1, 2, 3, and 4 of the particles in the SEM photograph
Measure the “length of c diameter” and calculate the particle diameter by the following formula: ³ {a × ³ }
b × ³ obtained from √c (μm), calculated by calculating the average value of the particle diameter of the total particles in the SEM photograph. DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle size (μ
m) DP2: In the particle size distribution measured using the above measuring device, the particle size (μm) at 25% of the cumulative weight calculated from the larger particle diameter side DP3: In the particle size distribution measured using the above measuring device, Particle size at 50% cumulative weight calculated from particle size side (μm) DP4: Particle size at 75% cumulative weight calculated from large particle size side (μm) DP5: particle size (μm) at a cumulative weight of 90% calculated from the larger particle size side in the particle size distribution measured using the above measuring instrument.

The quicklime and slaked lime used in the present invention are:
In order to adjust the particle size to a certain level, it is preferable to use after dry grinding using a dry grinding machine or wet grinding of a methanol suspension of quicklime and slaked lime using a wet grinding machine. The methanol used in the present invention is preferably 100% methanol from the viewpoint of solid-liquid separation such as drying and concentration. However, 20% or less of the weight of methanol used is another alcohol, for example, having 4 or less carbon atoms. Monovalent, divalent, and three
It can be replaced with a hydric alcohol.

The carbonation reaction for obtaining the vaterite-type calcium carbonate of the present invention is carried out using carbon dioxide or a carbonate compound. The carbon dioxide used does not need to be a gas, and may be a solid such as dry ice. In addition, the concentration obtained from waste gas generated during limestone baking is 30
A carbon dioxide-containing gas of about% by volume may be used. Further, the dispersion obtained by dispersing the vaterite-type calcium carbonate obtained according to the present invention is concentrated, subjected to solid-liquid separation by a method such as dehydration,
Methanol obtained by solid-liquid separation can be used again for the synthesis of calcium carbonate. In the dispersion of the vaterite-type calcium carbonate obtained according to the present invention, in order to further enhance the stability of the vaterite-type calcium carbonate particles, in the obtained dispersion, by adding a carboxylic acid or an alkali salt thereof, etc. It becomes possible to obtain a dispersion of vaterite-type calcium carbonate having a long-term stable dispersibility. It is also easy to replace methanol in the dispersion with another organic solvent.For example, ethylene glycol slurry of monodispersed vaterite-type calcium carbonate is applied to polyester fiber, polyester film, etc., and has good anti-blocking properties. Demonstrate. Furthermore, if a fatty acid, a resin acid or an alkali salt thereof is added to the dispersion in which the vaterite-type calcium carbonate obtained according to the present invention is dispersed and then dried, a vaterite-type calcium carbonate powder having good dispersibility is prepared. Good optical properties, mechanical properties, good fluidity and filling as pigments for paints, inks, extenders for rubber and plastics, antiblocking agents for various synthetic resin films, pigments for papermaking, and pigments for cosmetics. Calcium carbonate having properties is prepared.

[0023]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following description, the following instruments were used for the measurement of pH and the measurement of conductivity. pH measurement: Yokogawa Electric Personal pH Meter PH8
1-11-J Measurement of electric conductivity: CM-40S electric conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. However, the reference temperature was 25 ° C. In addition, the measurement of the particle size by the light transmission type particle size distribution
The procedure was as follows. Measurement model: SA-CP3 manufactured by Shimadzu Corporation Measurement method: Solvent: ion-exchanged water and sodium polyacrylate 0.004
Preliminary dispersion: 100 seconds of ultrasonic dispersion Measured temperature: 27.5 ° C. ± 2.5 ° C. Measurement method: The following calculation example is used.

[0024]

The DP calculated from the above particle size distribution measurement results
1, 2, 3, 4, and 5 are as follows: DP1 = 2.00 + (11.0-10.0) × (3.00−2.00) 2.00 (11.0−6.0) = 2.20 DP2 = 0.80 + (28.0−25.0) × ( 1.00 −0.80) ÷ (28.0 −18.0) = 0.86 DP3 = 0.50 + (58.0 −50.0) × (0.60 −0.50) ÷ (58.0 −42.0) = 0.55 DP4 = 0.30 + (82.0 −75.0) × (0.40 −0.30) ÷ (82.0−72.0) = 0.37 DP5 = 0.15 + (94.0−90.0) × (0.20−0.15) ÷ (94.0−89.0) = 0.19 The DS of the present invention was measured using a scanning electron microscope manufactured by Hitachi, Ltd. And a magnification of 20000 times.

Preparation of Methanol Suspension Dispersions Used in Examples and Comparative Examples Granular quicklime (reagent grade) and slaked lime (reagent grade) having an activity of 82 were dried with a dry mill (Coloplex, Alpine). Pulverized, the obtained quicklime powder or slaked lime powder is put into methanol, and coarse particles are removed using a 200-mesh sieve. Then, quicklime or slaked lime having a solid content concentration of 20% as quicklime is suspended in methanol. A liquid was prepared. The methanol suspension is wet-milled (Dynomill PILOT).
(Manufactured by WAB Co., Ltd.) to prepare two dispersions of quicklime or slaked lime in a methanol suspension.

Example 1 Vaterite-type calcium carbonate having a morphological index M of 0.2 ± 0.2
For the purpose of producing a disk-shaped vaterite-type calcium carbonate of 0.1, methanol was additionally added to the above-described suspension of quicklime in a methanol suspension, and the quicklime concentration was 3.75.
The resulting mixture was diluted so as to have a weight percent, and water equivalent to 6.2 times the amount of quicklime was added to prepare a mixed system of methanol, quicklime, and water. After adjusting the mixed system containing 1000 g of quicklime to 42 ° C., carbon dioxide gas was passed through the mixed system at a conduction rate of 0.0446 mol / min per mole of quicklime to start the carbonation reaction under stirring. did. PH in the system is 11.
When reaching 3, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 40 minutes after the conductivity in the carbonation system reaches the maximum point. After (T1), the pH in the system reached 11.0. Then, in the system
Since the pH started to rise slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system, and the pH in the system was controlled at 11.0 ± 0.2 (pH control range) for 190 minutes (T2). Thereafter, the particles prepared in the system were confirmed by SEM photograph, and about 95% of the particles were confirmed.
After confirming that the% was the desired particles, carbon dioxide gas was passed again into the system, and the pH in the system was adjusted to 7.0. The vaterite-type calcium carbonate prepared in this example was a plate-like vaterite-type calcium carbonate having a morphological index M of 0.2 as intended. Table 1 shows the conditions of the carbonation reaction of this example. Further, Table 5 shows physical properties of the vaterite-type calcium carbonate prepared according to the present example, and FIG. 6 shows a photograph by a scanning electron microscope. Calcium carbonate prepared according to the present example, as a result of X-ray diffraction measurement,
It was a calcium carbonate having a 100% vaterite structure.

Example 2 The morphological index M of the vaterite-type calcium carbonate is 0.5 ±
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a goethic spheroidal vaterite-type calcium carbonate of 0.1. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 1 except that T1 was changed to 70 minutes, the pH control range was changed to 10.2 ± 0.2, and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a goethite-shaped sphere-type vaterite-type calcium carbonate having a morphological index M of 0.5 as intended. Table 1 shows the conditions of the carbonation reaction of this example. Further, Table 5 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 3 The morphological index M of vaterite-type calcium carbonate is 0.8 ±
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a goethic spheroidal vaterite-type calcium carbonate of 0.1. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 1, except that T1 was changed to 70 minutes, the pH control range was changed to 9.8 ± 0.2, and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a goethite-shaped sphere-type calcium carbonate having a morphological index M of 0.8 as intended. Table 1 shows the conditions of the carbonation reaction of this example. Further, Table 5 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 4 Vaterite-type calcium carbonate having a morphological index M of 1.0 ± 1.0
For the purpose of producing a spherical vaterite-type calcium carbonate of 0.05, a carbonation reaction was started in the same manner as in Example 1. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 1 except that T1 was changed to 70 minutes, the pH control range was changed to 9.6 ± 0.1, and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a spherical vaterite-type calcium carbonate having a morphological index M of 1.0 as intended. Table 1 shows the conditions of the carbonation reaction of this example. Further, Table 5 shows the physical properties of the vaterite-type calcium carbonate prepared in this example, and FIG. 7 shows a photograph taken by a scanning electron microscope. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 5 The morphological index M of vaterite-type calcium carbonate was 1.2 ±
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 1 except that T1 was changed to 70 minutes, the pH control range was changed to 9.4 ± 0.2, and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite-type calcium carbonate having a morphological index M of 1.2 as intended. Table 1 shows the conditions of the carbonation reaction of this example. Further, Table 5 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 6 The morphological index M of the vaterite-type calcium carbonate was 1.4 ±
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 1 except that T1 was changed to 70 minutes, the pH control range was changed to 9.0 ± 0.2, and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite-type calcium carbonate having a morphological index M of 1.4 as intended. Table 2 shows the conditions of the carbonation reaction of this example. Further, Table 6 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 7 Vaterite-type calcium carbonate had a morphological index M of 1.7 ±
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1. Thereafter, when the pH in the system reached 7.0, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and a small amount of carbon dioxide gas is intermittently conducted into the system,
25 minutes after the electric conductivity in the carbonation system reached the maximum point, the pH in the system was allowed to reach 6.7. Then, the pH in the system
, A slight amount of carbon dioxide gas was intermittently conducted into the system, and the pH in the system was controlled at 6.7 ± 0.2 for 10 minutes. Thereafter, the particles prepared in the system were confirmed by SEM photographs, and it was confirmed that about 95% of the particles were the desired particles. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite-type calcium carbonate having a morphological index M of 1.7 as intended. Table 2 shows the conditions of the carbonation reaction of this example. Further, Table 6 shows physical properties of the vaterite-type calcium carbonate prepared in this example, and FIG. 8 shows a photograph taken by a scanning electron microscope. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 8 The morphological index M of vaterite-type calcium carbonate was 2.4 ± 2.4.
A carbonation reaction was started in the same manner as in Example 1 for the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.2. Then, 30 minutes after the conductivity in the carbonation system reaches the maximum point, the pH in the system is adjusted to 6.
0, and the conduction of carbon dioxide gas was stopped. afterwards,
Since the pH in the system began to increase slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system, and the pH in the system was adjusted to 6.0 ± 0.2 by 20%.
Controlled for minutes. Then, the particles prepared in the system are
It was confirmed by an EM photograph that about 95% of the particles were the desired particles. The vaterite-type calcium carbonate prepared in this example has a morphological index M of 2.
5 was a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate. Table 2 shows the conditions of the carbonation reaction of this example. Further, Table 6 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 9 The morphological index M of vaterite-type calcium carbonate was 1.0 ± 1.0.
For the purpose of producing a spherical vaterite-type calcium carbonate of 0.1, a carbonation reaction was started in the same manner as in Example 1. When the pH in the system reached 11.3, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 30 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 9.6. Thereafter, since the pH in the system began to decrease slightly, a very small amount of a mixed system of methanol + quicklime + water (the same as described above) was intermittently added to the system to adjust the pH in the system to 9.6 ± 0. 2 in 50
Controlled for minutes. Then, the particles prepared in the system are
After confirming with an EM photograph that about 95% of the particles were the desired particles, carbon dioxide gas was passed again into the system to adjust the pH in the system to 7.0. The vaterite-type calcium carbonate prepared in this example was a spherical vaterite-type calcium carbonate having a morphological index M of 1.0 as intended. Table 2 shows the conditions of the carbonation reaction of this example. Further, Table 6 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. Calcium carbonate prepared according to the present example was found to be 10% by X-ray diffraction measurement.
It was a calcium carbonate having a 0% vaterite structure.

Example 10 Vaterite-type calcium carbonate having a morphological index M of 1.0 ± 1.0
Example 1 In order to produce a spherical vaterite-type calcium carbonate of 0.1, Example 1 was performed except that the concentration of quicklime was changed to 2.7% by weight and the amount of water added to quicklime was changed to 8.6 times equivalent mol. The carbonation reaction was started in the same manner as described above. Thereafter, the pH control range was set to 9.6 ± T for 60 minutes.
Vaterite-type calcium carbonate was prepared in the same manner as in Example 1 except that T2 was changed to 0.1 and T2 was changed to 50 minutes. The vaterite-type calcium carbonate prepared in this example was a spherical vaterite-type calcium carbonate having a morphological index M of 1.0 as intended. Also,
Table 2 shows the carbonation reaction conditions of this example. Further, Table 6 shows physical properties of the vaterite-type calcium carbonate prepared in this example, and FIG. 9 shows a photograph taken by a scanning electron microscope. The calcium carbonate prepared according to this example is
As a result of a line diffraction measurement, it was a calcium carbonate having a 100% vaterite structure.

Example 11 The morphological index M of vaterite-type calcium carbonate was 1.8 ± 1.8.
For the purpose of producing a rugby ball-shaped oval sphere vaterite type calcium carbonate of 0.2, the concentration of quicklime was adjusted to 5.3% by weight, and the amount of water added to quicklime was adjusted to 4.1 times equivalent mole, and the mixing system was adjusted. The carbonation reaction was started in the same manner as in Example 1 except that the temperature was changed to 15 ° C. Thereafter, when the pH in the system reached 7.0, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 20 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 6.6. Thereafter, since the pH in the system began to rise slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system to raise the pH in the system to 6.6 ±.
It was controlled at 0.2 for 4 minutes. Thereafter, the particles prepared in the system were confirmed by SEM photographs, and it was confirmed that about 95% of the particles were the desired particles. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite-type calcium carbonate having a morphological index M of 1.88 as intended. Table 3 shows the carbonation reaction conditions of this example. Further, Table 7 shows the physical properties of the vaterite-type calcium carbonate prepared according to this example.
A photograph taken with a scanning electron microscope is shown in FIG. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 12 Vaterite-type calcium carbonate had a morphological index M of 1.65 ±
For the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1, methanol was additionally added to the methanol suspension dispersion of slaked lime described above,
The mixture was diluted so that the concentration in quicklime was 4.1% by weight, and water was added in an amount of 5.8 times the mole of slaked lime to prepare a mixed system of methanol, slaked lime and water. After adjusting the mixed system containing 1000 g of slaked lime to 31 ° C., carbon dioxide gas was introduced into the mixed system under stirring condition at 0.04 g / mol of quicklime.
The reaction was conducted at a conduction rate of 46 mol / min to initiate the carbonation reaction. Then, except changing T1 to 30 minutes,
Except for this, a vaterite-type calcium carbonate was prepared in the same manner as in Example 7. The vaterite-type calcium carbonate prepared in this example has a morphological index M of 1.6 as intended.
Veterinary calcium carbonate of rugby ball-shaped oval sphere vaterite No. 5. Table 3 shows the carbonation reaction conditions of this example. Further, Table 7 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. The calcium carbonate prepared according to this example is
As a result of a line diffraction measurement, it was a calcium carbonate having a 100% vaterite structure.

Example 13 Vaterite-type calcium carbonate had a morphological index M of 1.6 ±
In order to produce a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1, the concentration in terms of quicklime is 1.36% by weight, and the amount of water added to slaked lime is 1%.
The carbonation reaction was started in the same manner as in Example 12, except that the molar amount was changed to 2.1 times. Thereafter, a vaterite-type calcium carbonate was prepared in the same manner as in Example 12, except that the pH control range was changed to 6.5 ± 0.4 and T2 was changed to 30 minutes. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite vaterite-type calcium carbonate having a morphological index M of 1.6 as intended. Table 3 shows the carbonation reaction conditions of this example. Further, Table 7 shows the physical properties of the vaterite-type calcium carbonate prepared in this example, and FIG. 11 shows a photograph taken by a scanning electron microscope. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 14 Vaterite-type calcium carbonate had a morphological index M of 1.6 ±
For the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1, the concentration of quicklime was set to 1.23% by weight, the amount of water added to quicklime was increased to a molar equivalent of 62 times, and the temperature of the mixed system was adjusted. Was changed to 5 ° C., and a carbonation reaction was started in the same manner as in Example 1.
Thereafter, when the pH in the system reached 12.7, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 180 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 6.8. Thereafter, since the pH in the system began to rise slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system to raise the pH in the system to 6.8 ±.
Control was performed at 0.2 for 540 minutes. Thereafter, the particles prepared in the system were confirmed by SEM photographs, and it was confirmed that about 95% of the particles were the desired particles. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite vaterite-type calcium carbonate having a morphological index M of 1.6 as intended. Also,
Table 3 shows the carbonation reaction conditions of this example. Further, Table 7 shows the physical properties of the vaterite-type calcium carbonate prepared in this example, and FIG. 12 shows a photograph taken by a scanning electron microscope. The calcium carbonate prepared according to this example is
As a result of a line diffraction measurement, it was a calcium carbonate having a 100% vaterite structure.

Example 15 The morphological index M of vaterite-type calcium carbonate was 1.0 ±
For the purpose of producing 0.05 spherical vaterite-type calcium carbonate, a carbonation reaction was started in the same manner as in Example 4. Thereafter, when the pH in the system reached 11.3, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction is advanced by the carbon dioxide gas remaining in the carbonation reaction system, and a further small amount of carbon dioxide gas is intermittently conducted into the system, and 70 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 9.6. After that, the pH in the system began to rise slightly, so that a very small amount of carbon dioxide was intermittently conducted into the system,
Was controlled at 9.6 ± 0.1 for 2 minutes, but the conduction amount of carbon dioxide gas became too large, and eventually the pH in the system became 6 hours 73 minutes after the conductivity in the carbonation system reached the maximum point. And the system pH was controlled at 6.7 ± 0.2 for 10 minutes. Thereafter, the particles prepared in the system were confirmed by SEM photographs, and it was confirmed that about 95% of the particles were particles having a uniform shape. The vaterite-type calcium carbonate prepared in this example was a rugby ball-shaped ellipsoidal vaterite vaterite-type calcium carbonate having a morphological index M of 1.6 as intended. Table 3 shows the carbonation reaction conditions of this example. Further, Table 7 shows the physical properties of the vaterite-type calcium carbonate prepared in this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Example 16 The morphological index M of vaterite-type calcium carbonate was 1.0 ±
A carbonation reaction was started in the same manner as in Example 15 for the purpose of producing a spherical vaterite-type calcium carbonate of 0.05. Thereafter, when the pH in the system reached 11.3, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 30 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 9.6. Thereafter, since the pH in the system began to decrease slightly, a very small amount of a mixed system of methanol + quicklime + water (the same as described above) was added intermittently to the system to raise the pH in the system to 9.6 ±
0.1 for 1 minute, but methanol + quicklime +
The added amount of the water mixed system becomes too large, and eventually the pH in the system becomes 1 after 32 minutes from when the conductivity in the carbonation system reaches the maximum point.
0.2 was reached, and the system pH was controlled at 10.2 ± 0.2 for 50 minutes. Thereafter, the particles prepared in the system were confirmed with SEM photographs, and after confirming that about 95% of the particles were particles having a uniform shape, carbon dioxide gas was passed again into the system, and the pH in the system was confirmed. Was adjusted to 7.0. The vaterite-type calcium carbonate prepared in this example was a goethite-shaped sphere-type vaterite-type calcium carbonate having a morphological index M of 0.5 as intended. Table 4 shows the conditions of the carbonation reaction of this example. Further, Table 8 shows the physical properties of the vaterite-type calcium carbonate prepared according to this example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this example was a calcium carbonate having a 100% vaterite structure.

Comparative Example 1 Vaterite-type calcium carbonate had a morphological index M of 1.7 ±
Except for changing the amount of water added to quicklime to 0.5 times the molar equivalent for the purpose of producing a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1,
The carbonation reaction was started in the same manner as in Example 1. Thereafter, when the pH in the system reached 7.0, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction proceeds with the carbon dioxide gas remaining in the carbonation reaction system, and further a small amount of carbon dioxide gas is intermittently conducted into the system, and 45 minutes after the conductivity in the carbonation system reaches the maximum point. Later, the pH in the system was allowed to reach 6.8. Thereafter, since the pH in the system began to decrease slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system, and the pH in the system was controlled at 6.8 ± 0.2 for 50 minutes. After that, when the particles prepared in the system were confirmed by SEM photograph, it was a mixture of irregular particles and fine particles, and desired particles could not be obtained. As confirmed by X-ray diffraction, the calcium carbonate prepared in this comparative example was amorphous and was not crystallized. Further, the control was continued for 600 minutes at the system pH of 6.8 ± 0.2, but the amorphous was not crystallized and the reaction was stopped.

Comparative Example 2 The morphological index M of the vaterite-type calcium carbonate was 1.0 ±
For the purpose of producing a spherical vaterite-type calcium carbonate of 0.1, a carbonation reaction was started in the same manner as in Example 1 except that the amount of water added to quicklime was changed to a molar equivalent of 100 times. Thereafter, the pH in the system was 11.3.
When it reached, the conduction of carbon dioxide gas was stopped. Thereafter, the carbonation reaction is advanced by the carbon dioxide gas remaining in the carbonation reaction system, and a further small amount of carbon dioxide gas is intermittently conducted into the system, and 70 minutes after the conductivity in the carbonation system reaches the maximum point. Later in the system
The pH was allowed to reach 9.6. Thereafter, since the pH in the system began to decrease slightly, a very small amount of carbon dioxide gas was intermittently conducted into the system, and the pH in the system was controlled at 9.6 ± 0.1 for 50 minutes. After that, when the particles prepared in the system were confirmed by SEM photographs, spindle-shaped aggregate particles different from the desired particles were confirmed. The desired vaterite-type calcium carbonate was not obtained at all from the calcium carbonate prepared in this comparative example. Table 4 shows the carbonation reaction conditions of this comparative example. Further, Table 8 shows the physical properties of the calcium carbonate prepared in this comparative example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this comparative example was a calcium carbonate having a 100% calcite structure.

Comparative Example 3 The morphological index M of vaterite-type calcium carbonate was 1.7 ±
In order to produce a rugby ball-shaped elliptic spherical vaterite-type calcium carbonate of 0.1, a quicklime concentration of 2
The carbonation reaction was started in the same manner as in Example 1 except that the amount of water added to quicklime was changed to a molar equivalent of 2 times to 0% by weight. However, during the carbonation reaction, the inside of the system was remarkably thickened and the inside of the system became a sherbet-like state, making it difficult to continue the carbonation reaction. Therefore, the carbonation reaction was stopped. When the sherbet-like thickened material was allowed to stand for one day and the product was observed, most of the product in the left-hand thing was vaterite-type calcium carbonate. Shape, plate shape, rugby ball shape,
Irregular shapes were mixed and large aggregates were formed. Table 4 shows the carbonation reaction conditions of this comparative example.
Further, Table 8 shows the physical properties of the calcium carbonate prepared in this comparative example. As a result of X-ray diffraction measurement, the calcium carbonate prepared in this comparative example was a calcium carbonate having a 55% vaterite structure.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

Concentration in terms of quicklime: quicklime equivalent concentration in the methanol suspension dispersion before the carbonation reaction (% by weight) Water addition amount: added to 1 mol of quicklime in the methanol suspension dispersion before the carbonation reaction Amount (mol) of water to be added T1: Time (minutes) from the time when the conductivity in the carbonation reaction system reaches the maximum value to the time when the control of pH in the reaction system is started (minutes) Control pH: Vaterite-type carbonic acid PH value in which the inside of the reaction system is controlled for a certain time in order to control the form of calcium T2: Time in which the inside of the reaction system for controlling the form of vaterite-type calcium carbonate is controlled at a certain pH (minutes)

[0051]

[Table 5]

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

[Table 8]

[0055]

As described above, according to the present invention, it is possible to easily and stably produce a vaterite-type calcium carbonate having an arbitrary shape such as a disk, a stone-shaped ellipsoidal sphere, a sphere, and a rugby ball-shaped ellipsoidal sphere. The resulting particles have a high degree of uniformity and dispersibility.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the particle morphology of a disk-shaped body.

FIG. 2 is a conceptual diagram showing a particle form of a go-stone ellipsoidal sphere.

FIG. 3 is a conceptual diagram showing a particle form of a spherical body.

FIG. 4 is a conceptual diagram showing a particle form of a rugby ball-shaped elliptical sphere.

FIG. 5 is a graph showing the relationship between the elapsed time after the start of the carbonation reaction and the electrical conductivity.

FIG. 6 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 1.

FIG. 7 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 4.

FIG. 8 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 7.

FIG. 9 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 10.

FIG. 10 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 11.

FIG. 11 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 13.

FIG. 12 is an electron micrograph showing the particle structure of calcium carbonate obtained in Example 14.

[Explanation of symbols]

 A Carbonation reaction start point B Conductivity maximum point C pH control start point D pH control end point

Continuation of front page (72) Inventor Shiro Genyoshi 1-126 Yamatedai, Okubo-cho, Akashi-shi, Hyogo (56) References JP-A-4-31315 (JP, A) JP-A-4-31316 (JP, A) JP-A-4-31317 (JP, A) JP-A-63-103824 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01F 11/18

Claims (3)

(57) [Claims] 1. A monodisperse vaterite-type calcium carbonate having a particle shape of a discoid, a stone-like ellipsoidal sphere, a sphere, or a rugby ball-like ellipsoidal sphere, in which a plane whose projected surface is closest to a circle is a plan view. In the display by the third trigonometric method, the horizontal diameter of the plan view is defined as a, the vertical diameter is defined as b, and the height diameter of the front view and the side view is defined as c. When producing a monodisperse vaterite-type calcium carbonate having a length ratio of M, carbon dioxide gas is passed through a mixed system of methanol and quicklime and / or slaked lime and water to initiate a carbonation reaction, and the conductivity in the carbonation reaction system is increased. T1 hour after the rate (electric conductivity) reached the maximum value, the pH in the reaction system was set to a value within the range defined by the following formula (the total range of the following pH range 1 and pH range 2).
A method for producing a monodisperse vaterite-type calcium carbonate whose form is controlled, wherein the method is controlled for 2 hours. However, the quicklime and / or slaked lime concentration of the mixed system is 0.1 to 12% by weight with respect to methanol, and the amount of water is 1 to 80 with respect to quicklime (in the case of slaked lime, it is converted to the same mole of quicklime). Times moles. M = length of c diameter / length of shorter diameter of a or b pH range 1 8.9 ≦ pH <11.5 and (−M + 10) ≦ pH ≦ (−13M / 9) + (23/2) ) PH range 2 5.5 ≦ pH <8.9 and (−29M / 3) + (293/15) ≦ pH ≦ (−29M / 12) + (53/4) T2 ≧ (T1 / 10) 2. The pH control in the carbonation reaction system for T2 hours in the total range of the pH range 1 and the pH range 2 is performed by passing carbon dioxide gas through the carbonation reaction system, and / or methanol and quick lime and / or slaked lime. The method according to claim 1, wherein the method is performed by adding a mixture of water and water. 3. The method according to claim 1, wherein the vaterite-type calcium carbonate satisfies all of the following requirements (A), (A), (C), (D), and (E). (A) 0.05 μm ≦ DS ≦ 2.0 μm (A) DP3 / DS ≦ 1.25 (C) 1.0 ≦ DP2 / DP4 ≦ 2.5 (D) 1.0 ≦ DP1 / DP5 ≦ 4.0 (E) (DP2-DP4) /DP3≦1.0, where DS is the average particle diameter (μm) measured by a scanning electron microscope (SEM). "Length of a diameter" and "Length of b diameter" in the triangular diagrams shown in FIGS. 1, 2, 3, and 4 of the particles in the SEM photograph
Measure the “length of c diameter” and calculate the particle diameter by the following formula: ³ {a × ³ }
b × ³ obtained from √c (μm), calculated by calculating the average value of the particle diameter of the total particles in the SEM photograph. DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle size (μ
m) DP2: In the particle size distribution measured using the above measuring device, the particle size (μm) at 25% of the cumulative weight calculated from the larger particle diameter side DP3: In the particle size distribution measured using the above measuring device, Particle size at 50% cumulative weight calculated from particle size side (μm) DP4: Particle size at 75% cumulative weight calculated from large particle size side (μm) DP5: particle size (μm) at a cumulative weight of 90% calculated from the larger particle size side in the particle size distribution measured using the above measuring instrument.