JP2003063819A - Method for producing vaterite-type spherical calcium carbonate and vaterite-type spherical calcium carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing mono dispersed vaterite- type spherical calcium carbonate having a controlled particle size in a mild condition and in a short time and also by simply operation. SOLUTION: The method comprises having carbonate ion gradually absorbed into an aqueous solution containing calcium chloride and polyamide amine dendrimer having a 4.5 generation in a condition satisfying the formula (I): Y>=210X<2> +3.7X (wherein, Y is a terminal carboxylic acid concentration (m mol/L) of the polyamide amine dendrimer having a 4.5 generation, X is calcium chloride concentration (mol/L) and satisfies 0<X<=0.5) and having a temperature of 5-40 deg.C and a pH of 7.5-9.5.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing vaterite-type spherical calcium carbonate and vaterite-type spherical calcium carbonate. More specifically, the present invention is a method for efficiently producing vaterite-type spherical calcium carbonate having a monodisperse and controlled particle size under mild conditions in a short time and by a simple operation, and obtained by this method. The present invention relates to vaterite-type spherical calcium carbonate which has excellent powder properties and is useful for various purposes.

[0002]

2. Description of the Related Art Conventionally, calcium carbonate powder has been widely used as an inorganic filler for plastic products. As the crystal form of this calcium carbonate, three types of homomorphic images of calcite type, aragonite type and vaterite type are known. Regarding the crystal shape, the calcite type is cubic, the aragonite type is columnar, and the vaterite type is spherical. Currently, industrially produced calcium carbonate is mainly a cubic calcite type that is a stable phase, and in some cases, an argonite type that is a metastable phase exists.

Incidentally, by spheroidizing the powder, various physical properties of the powder such as dispersibility, filling property, lubricity, extensibility, coating property, feel, and abrading property are improved, and preferable properties are obtained. From the point of application, attempts have been made to spheroidize various powders, and in calcium carbonate, attention has been paid to the synthesis of spherical vaterite-type calcium carbonate. However, vaterite-type spherical calcium carbonate has a drawback that it easily loses its spherical shape in a system containing water and is transformed into a cubic calcite type which is a stable phase.

Therefore, in order to solve such a problem, for example, a step of precipitating calcium carbonate in a water system in which sodium polyethylene sulfonate is dissolved, and the vaterite-type spherical calcium carbonate obtained in the above step are added to water. There has been proposed a method of improving the storage stability of spherical calcium carbonate through a two-step process of dispersing and seed-polymerizing an ethylenically unsaturated compound using this as a seed (JP-A-2-126933). ). However, this method has a drawback that it requires two steps and the operation is complicated.

Further, by crystallizing calcium carbonate in the presence of polyamidoamine dendrimers of generation 3.5 and 1.5, which have a disk shape, vaterite-type spherical calcium carbonate is stabilized in an aqueous solution. Have been reported to be obtained [[Chem. Commun.],
1931 page (1999)]. This is because after deposition of vaterite-type spherical calcium carbonate, a polyamidoamine dendrimer having a carbonyl group coordinating to calcium ions on its surface is coordinated around vaterite-type spherical calcium carbonate. However, in this method, the ratio of the dendrimer in the obtained vaterite-type spherical calcium carbonate is 27% by weight when the terminal carboxylic acid concentration of the polyamidoamine dendrimer is 8.33 mmol / liter, and a large amount of polyamide is used. An amine dendrimer is required, and it cannot be said that the method is industrially sufficiently satisfactory.

[0006]

Under the circumstances described above, the present invention provides a monodisperse, vaterite-type spherical calcium carbonate having a controlled particle size under mild conditions in a short time and with a simple method. It is an object of the present invention to provide an industrially advantageous method that can be efficiently manufactured by operation and economically.

[0007]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have focused on a polyamideamine dendrimer having a strong coordinating force and having a generation number of 4.5. By gradually dissolving carbonate ions in an aqueous solution containing calcium chloride in a specific concentration and having a pH and a temperature in a predetermined range, it is possible to stabilize vaterite-type spherical calcium carbonate with a small amount of dendrimer. It has been found that the above-mentioned objects can be achieved and the object thereof can be achieved, and the present invention has been completed based on this finding.

That is, the present invention provides (1) calcium chloride and a polyamidoamine dendrimer having a generation number of 4.5,
Formula (I) Y ≧ 210X ² + 3.7X (I) (wherein Y is the terminal carboxylic acid concentration (mmol / liter) of the polyamidoamine dendrimer having a generation number of 4.5, X
Is the concentration of calcium chloride (mol / liter), 0 <X
≦ 0.5. ), The temperature is 5 to 40 ° C., and the pH is
A method for producing vaterite-type spherical calcium carbonate, characterized by gradually dissolving carbonate ions in an aqueous solution of 7.5 to 9.5, (2) an aqueous solution containing calcium chloride and a polyamidoamine dendrimer having a generation number of 4.5 Is a spherical vaterite type according to the above item (1), wherein the relation of the formula (II) Y ≧ 210X ² + 3.7X + 8 (II) (wherein Y and X are the same as above) is satisfied. A method for producing calcium carbonate, and (3) a vaterite-type spherical calcium carbonate produced by the method described in (1) or (2) above, and (4) having an average particle size of 4 to 10 μm. A certain aspect provides the vaterite-type spherical calcium carbonate according to the above item (3).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polyamidoamine dendrimer having a generation number of 4.5 is used for controlling the structure of calcium carbonate. This polyamidoamine dendrimer has a carboxylic acid group on the outermost shell surface, and as the generation increases, the density of the carboxylic acid group in the outermost shell increases and the shape also changes from a disc shape to a spherical shape. Polyamidoamine dendrimers with a generation number of 4.5 generally have a spherical structure.

The temperature is 5 to 40 ° C. and the pH is 7.5 to 9.5.
When the carbonate ion dissolves in the calcium chloride aqueous solution in the range of, the amorphous calcium carbonate is usually precipitated, and the vaterite-type crystal and the calcite-type crystal that is the stable phase or the argonite-type crystal that is the metastable phase are formed. The crystal form will change.

The number of generations of the calcium chloride aqueous solution is 4.
When the polyamidoamine dendrimer of 5 is not contained, for example, a reaction time of 24 hours, a mixture of calcite-type cubic calcium carbonate and vaterite-type spherical calcium carbonate is obtained, but when the reaction is further advanced, for example, 96
After a period of time, the product obtained is all calcite-type cubic calcium carbonate.

In the present invention, in order to obtain calcium carbonate consisting essentially of vaterite-type spherical calcium carbonate, the above-mentioned calcium chloride and polyamidoamine dendrimer having a generation number of 4.5 are added to formula (I) Y ≧ 210X ² +3. 7X ... (I) (wherein Y is the terminal carboxylic acid concentration (mmol / liter) of the polyamidoamine dendrimer having a generation number of 4.5, X
Is the concentration of calcium chloride (mol / liter), 0 <X
≦ 0.5. ), The temperature is 5 to 40 ° C., and the pH is
A method is used in which an aqueous solution of 7.5 to 9.5 is prepared, and carbonate ions are gradually dissolved in the aqueous solution and reacted.

The value of Y is greater than 0 and [21
When the reaction is performed under a condition of less than 0X ² + 3.7X], for example, a calcite-type cubic calcium carbonate is obtained with a yield of almost 100% in a reaction time of 24 hours. It is considered that this is because the calcium ion was coordinated to the terminal carbonyl group of the polyamidoamine dendrimer to locally increase the calcium ion concentration and promote the crystallization of calcium carbonate. That is, it can be seen that the surface of the spherical polyamidoamine dendrimer with a generation number of 4.5 was used as the crystal growth field of calcium carbonate.

On the other hand, the calcium chloride concentration X (mol / liter) and the terminal carboxylic acid concentration Y (mmol / liter) of the polyamidoamine dendrimer of 4.5 generations are
When the reaction is carried out under the conditions satisfying the relation of the formula (I),
For example, with a reaction time of 24 hours, only vaterite-type spherical calcium carbonate is obtained with a yield of almost 100%. This is because the polyamidoamine dendrimer is coordinated around the generated vaterite-type spherical calcium carbonate, and the transfer to the calcite-type calcium carbonate was suppressed.

Further, the calcium chloride concentration X (mol / liter) and the terminal carboxylic acid concentration Y (mmol / liter) of the polyamideamine dendrimer having a generation number of 4.5 are expressed by the formula (II) Y ≧ 210X ² + 3.7X + 8. When the reaction is carried out under the condition satisfying the condition (II), the stability of vaterite-type spherical calcium carbonate in water is improved, and the vaterite-type spherical calcium carbonate is usually transferred to calcite-type calcium carbonate even after 4 days. To maintain. At this time, for example, the terminal carboxylic acid concentration is 8.33 mmol /
Comparing the number of generations of 3.5 and 4.5 polyamidoamine dendrimers in the liter, the ratio of polyamidoamine dendrimers in the obtained vaterite-type spherical calcium carbonate was 27% by weight in the 3.5 generation. On the other hand, it can be seen that the 4.5th generation requires a small amount of 15% by weight. This is because a polyamidoamine dendrimer with a large number of generations has a strong coordination power with respect to calcium ions.

The calcium chloride concentration X (mol / liter) and the terminal carboxylic acid concentration Y (mmol / liter) of the polyamidoamine dendrimer of 4.5 generations are
When the reaction is carried out under the conditions satisfying the relation of the formula (I),
Under the condition that the concentration of calcium chloride is uniform, the higher the terminal carboxylic acid concentration of the polyamidoamine dendrimer, the smaller the particle size of the obtained vaterite-type spherical calcium carbonate, and the average particle size can be controlled between 10 μm and 4 μm. .

In the present invention, there is no particular limitation on the upper limit of the terminal carboxylic acid concentration Y (mmol / liter) of the generation 4.5 polyamidoamine dendrimer.
From the viewpoint of economy and solubility of the dendrimer, it is usually 1
The amount is 00 mmol / liter or less, preferably 70 mmol / liter or less.

Further, if the reaction temperature is lower than 5 ° C., the crystallization rate is too slow to be practical, and if it exceeds 40 ° C., the crystallization rate is too fast, and it is expected that the variation in particle size becomes large. The preferred reaction temperature is in the range of 20-30 ° C. In the present invention, the polyamidoamine dendrimer having a generation number of 4.5 can be used either in the form in which the terminal carboxylic acid is free or in the form of salt, but it is usually used in the form of salt such as sodium salt.

In the present invention, the method of gradually dissolving carbonate ions in an aqueous solution containing calcium chloride and a polyamidoamine dendrimer having a generation number of 4.5 is not particularly limited, and for example, the method may be performed in an atmosphere containing carbon dioxide gas. A method in which the aqueous solution is allowed to stand and the carbon dioxide is dissolved from the water surface, or a method in which the aqueous solution containing carbonate ions is gradually added dropwise while the aqueous solution is slowly stirred can be used. The present invention also provides the vaterite-type spherical calcium carbonate produced by the above-described method of the present invention.

The vaterite-type spherical calcium carbonate of the present invention has an average particle size of usually 4 to 10 μm and is nearly monodisperse, and is suitable as an inorganic filler for various plastic products.

[0021]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The crystal structure of the obtained calcium carbonate was analyzed by "Perkin E" manufactured by Perkin Elmer.
lm-system 2000 "and FT-IR analysis and powder X-ray diffraction (XRD). Also, vaterite type spherical calcium carbonate is 746 cm by FT-IR analysis.
^-1 is 712 cm for calcite type cubic calcium carbonate
^The crystal structure was determined because ^-1 shows specific absorption. Furthermore, the crystal morphology and grain size can be confirmed by scanning electron microscope (SEM) "JEOL JSM5".
600B ".

Example 1 A desiccator, which was placed in a constant temperature bath at 25 ° C. and had ammonium carbonate at the bottom, was prepared. Polyamidoamine dendrimer with 4.5 generations has terminal carboxylic acid concentration of 5.3.
Prepare 10 ml of an aqueous solution containing calcium chloride at a concentration of 0.1 mol / l, while containing it in a concentration of mmol / l, and adjust the pH with an aqueous ammonia solution.
Adjusted to 8.5. This aqueous solution was transferred to a 20 ml plastic container and left in a desiccator for 24 hours. FIG. 1 shows a reactor.

The precipitate thus obtained was filtered, washed with water, and dried to obtain a white powder. FT-IR analysis was performed on this white powder. The FT-IR analysis chart is shown in FIG. As can be seen from this Fig. 2, 746 cm ^-1
Was observed to absorb vaterite-type spherical calcium carbonate, but it was 712 cm ^{-1 for} calcite-type cubic calcium carbonate.
Was not observed. FIG. 3 shows the S of the white powder.
An EM photograph is shown. The white powder was spherical and had an average particle size of 6 μm. The results are shown in Table 1 together with the yield.

Example 2 Example 2 was repeated except that the concentration of the terminal carboxylic acid of the polyamidoamine dendrimer was changed to 2.65 mmol / liter. The results are shown in Table 1.

Example 3 The procedure of Example 1 was repeated, except that the concentration of calcium chloride was changed to 0.05 mol / liter. The results are shown in Table 1.

Example 4 The same as Example 1 except that the terminal carboxylic acid concentration of the polyamidoamine dendrimer was changed to 2.65 mmol / liter and the calcium chloride concentration was changed to 0.05 mol / liter. It was carried out. The results are shown in Table 1.

Example 5 The same as Example 1 except that the terminal carboxylic acid concentration of the polyamidoamine dendrimer was changed to 6.0 mmol / liter and the calcium chloride concentration was changed to 0.15 mol / liter. It was carried out. The results are shown in Table 1.

Example 6 In Example 1, the terminal carboxylic acid concentration of the polyamidoamine dendrimer was set to 10.64 mmol / liter,
And it implemented like Example 1 except having changed the standing time to 96 hours. The results are shown in Table 1.

Example 7 In Example 1, except that the terminal carboxylic acid concentration of the polyamidoamine dendrimer was changed to 9.0 mmol / liter, the calcium chloride concentration was changed to 0.05 mol / liter, and the standing time was changed to 96 hours. Was carried out in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that the concentration of the terminal carboxylic acid of the polyamidoamine dendrimer was changed to 0.53 mmol / liter. The results are shown in Table 1.

The FT-IR analysis chart of the obtained white powder is shown in FIG. As can be seen from FIG. 4, the absorption of vaterite-type spherical calcium carbonate at 746 cm ⁻¹ was not observed, and that of the calcite-type cubic calcium carbonate was 71%.
Only an absorption of 2 cm ^-1 was observed. FIG. 5 shows an SEM photograph of this white powder. From this figure, it was confirmed that the white powder was a cube.

Comparative Example 2 Same as Example 1 except that the concentration of the terminal carboxylic acid of the polyamidoamine dendrimer was changed to 0.53 mmol / liter and the concentration of calcium chloride was changed to 0.05 mol / liter. It was carried out. The results are shown in Table 1.

Comparative Example 3 The same as Example 1 except that the terminal carboxylic acid concentration of the polyamidoamine dendrimer was changed to 4.5 mmol / liter and the calcium chloride concentration was changed to 0.15 mol / liter. It was carried out. The results are shown in Table 1.

Comparative Example 4 The procedure of Example 1 was repeated, except that the polyamidoamine dendrimer was not used. The results are shown in Table 1.

Comparative Example 5 The procedure of Example 1 was repeated except that the polyamidoamine dendrimer was not added and the calcium chloride concentration was changed to 0.05 mol / liter. The results are shown in Table 1.

Comparative Example 6 In Example 1, a polyamidoamine dendrimer with a generation number of 3.5 was used in place of the polyamidoamine dendrimer with a generation number of 4.5 so that the terminal carboxylic acid concentration was 5.3 mmol / liter. The same procedure as in Example 1 was carried out except that it was used. The results are shown in Table 1.

The FT-IR analysis chart of the obtained white powder is shown in FIG. As can be seen from FIG. 6, the absorption of vaterite-type spherical calcium carbonate at 746 cm ^{−1 and} the absorption of calcite-type cubic calcium carbonate at 712 cm ^−1.
Both absorptions were observed.

[0038]

[Table 1]

(Note) V: Vaterite type C: Calcite type C + V: Mix of calcite type and vaterite type

FIG. 7 shows Examples 1 to 7 and Comparative Examples 1 to 1.
The concentration of calcium chloride (mol / liter) and the concentration of terminal carboxylic acid of the polyamidoamine (PAMAM) dendrimer (mmol / liter) in 5 were each X
It is plotted on the axis and the Y-axis.

[0041]

According to the present invention, stable vaterite-type spherical calcium carbonate can be synthesized in an aqueous solution in one step for 24 hours under mild conditions of 25 ° C. Further, by using a polyamidoamine dendrimer with a generation number of 4.5, which has a strong coordinating power for calcium ions, it is possible to improve the stability in water with a small amount of dendrimer as compared with a polyamidoamine dendrimer with a generation number of 3.5. it can. Further, the particle size of the vaterite-type spherical calcium carbonate obtained becomes smaller as the addition amount of the polyamidoamine dendrimer increases under the condition of adjusting the calcium chloride concentration, and the average particle size can be controlled within the range of 10 μm to 4 μm.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a reaction device used in Examples and Comparative Examples.

FIG. 2 FT of calcium carbonate powder obtained in Example 1
-It is an IR analysis chart.

3 is a scanning electron micrograph of the calcium carbonate powder obtained in Example 1. FIG.

FIG. 4 FT of calcium carbonate powder obtained in Comparative Example 1
-It is an IR analysis chart.

5 is a scanning electron micrograph of the calcium carbonate powder obtained in Comparative Example 1. FIG.

FIG. 6 FT of calcium carbonate powder obtained in Comparative Example 6
-It is an IR analysis chart.

FIG. 7 is a plot diagram of calcium chloride concentration (mole / liter) and terminal carboxylic acid concentration of polyamidoamine dendrimer (mole / liter) in Examples 1 to 7 and Comparative Examples 1 to 5.

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Claims (4)

[Claims] 1. A calcium amine and a polyamidoamine dendrimer having a generation number of 4.5 are represented by the formula (I) Y ≧ 210X ² + 3.7X (I) (wherein Y is a polyamidoamine dendrimer having a generation number of 4.5). Terminal carboxylic acid concentration (mmol / l), X
Is the concentration of calcium chloride (mol / liter), 0 <X
≦ 0.5. ), And a carbonate ion is gradually dissolved in an aqueous solution having a temperature of 5 to 40 ° C. and a pH of 7.5 to 9.5. 2. An aqueous solution containing calcium chloride and a polyamidoamine dendrimer having a generation number of 4.5 has the formula (II) Y ≧ 210X ² + 3.7X + 8 (II) (wherein Y and X are the same as above). The method for producing vaterite-type spherical calcium carbonate according to claim 1, which satisfies the relationship (1). 3. A vaterite-type spherical calcium carbonate produced by the method according to claim 1. 4. The average particle diameter is 4 to 10 μm.
The vaterite-type spherical calcium carbonate described in 1.