JPH06127938A - Hollow spherical calcite type calcium carbonate and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a hollow spherical calcite type calcium carbonate and also to provide a method enabling to simply produce the hollow spherical calcite type calcium carbonate by a simple process using raw materials easily available. CONSTITUTION:The hollow spherical calcite type calcium carbonate is produced by atomizing an aqueous solution of a water-soluble calcium salt together with carbonic acid gas into a reaction vessel heated to 300-1500 deg.C to react the calcium salt with the carbonic acid gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hollow spherical calcite type calcium carbonate and a method for producing the same.

[0002]

2. Description of the Related Art Calcium carbonate is known to have three crystal forms: rhombohedral calcite, rod-shaped aragonite, and spherical vaterite.

Spherical calcium carbonate has attracted attention in order to improve physical properties such as filling property, fluidity and dispersibility, and various proposals have been made for a method for producing spherical vaterite type calcium carbonate. However, vaterite-type calcium carbonate has a problem that it is unstable to water. That is, vaterite-type calcium carbonate is stable at room temperature and normal pressure in an atmosphere where water is not present, but easily transforms into rhombohedral calcite in an atmosphere containing water, and the spherical morphology collapses to give an excellent spherical shape. Characteristics will be lost. Therefore, if spherical calcite-type calcium carbonate can be produced, since it is stable to water, it is expected that the spherical shape can be stably maintained for a long period of time in an atmosphere containing water.

Japanese Unexamined Patent Publication (Kokai) No. 57-92521 discloses that calcium carbonate having a spherical vaterite type structure is added to
It is disclosed that spherical calcite type calcium carbonate can be obtained by heat treatment at a temperature of 800 ° C. for 0.5 to 24 hours. However, JP-A-57-92521
In the method for producing spherical calcite-type calcium carbonate described in the publication, it is necessary to produce spherical vaterite-type calcium carbonate used as a raw material thereof, and it is troublesome to produce spherical vaterite-type calcium carbonate. The manufacturing process itself is an extra process for manufacturing spherical calcite-type calcium carbonate. Further, since vaterite-type calcium carbonate is unstable to water, the vaterite-type calcium carbonate retains its spherical shape and does not contain water until it is used in the step of producing the spherical calcite-type calcium carbonate. There is a problem that it must be stored in an atmosphere.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hollow, spherical type calcite type calcium carbonate. Another object of the present invention is to provide a method for producing hollow spherical calcite-type calcium carbonate, which is capable of producing hollow and spherical calcite-type calcium carbonate in a simple process using easily available raw materials. Especially.

[0006]

The present invention is a hollow, spherical calcite-type calcium carbonate.

Another aspect of the present invention is characterized in that an aqueous solution of a water-soluble calcium salt is sprayed together with carbon dioxide into a reaction vessel heated to 300 to 1500 ° C. to react the calcium salt with carbon dioxide. The method for producing hollow spherical calcite-type calcium carbonate is as follows.

Preferred aspects of the present invention are as follows.

(1) The above-mentioned hollow and spherical calcite-type calcium carbonate having a particle diameter of 0.1 to 100 μm.

(2) The method for producing the hollow spherical calcite-type calcium carbonate, wherein the aqueous solution of the water-soluble calcium salt further dissolves ammonia.

(3) The temperature in the reaction vessel is 500 to 100.
The method for producing the hollow spherical calcite-type calcium carbonate is characterized in that the temperature is 0 ° C.

The hollow and spherical calcite-type calcium carbonate of the present invention (sometimes referred to as "hollow spherical calcite-type calcium carbonate") has a spherical and hollow, ie, as shown in FIG. 1 and FIG. It is a calcite-type calcium carbonate having cavities inside.

FIG. 1 shows the S of hollow spherical calcite type calcium carbonate produced by the production method of the present invention in Example 1.
2 is an EM (scanning electron microscope) photograph, FIG. 2 is a partially enlarged photograph of FIG. 1, and FIG. 3 is a diagram in which the photograph of FIG. 2 is traced.

As is apparent from FIG. 1, the hollow spherical calcite-type calcium carbonate of the present invention has a substantially spherical appearance from large particles to small particles. In the present specification, the term “sphere” means a sphere, a spheroid, and shapes of these similar shapes, and the ratio of major axis / minor axis is 1/1 to 1/2. Means including shapes.

From FIGS. 2 and 3, it is clear that the hollow spherical calcite type calcium carbonate of the present invention is a hollow body. That is, in the center of FIG. 2, there is shown a particle (a particle A shown in FIG. 3) in which a hole is formed in the shell and a cavity is formed inside, and in the lower right of this particle, it is cracked in half. The remaining particles (particle B shown in FIG. 3) are shown, and it is clear from these that the hollow spherical calcite-type calcium carbonate of the present invention is hollow and spherical.

Further, it is a SEM (scanning electron microscope) photograph taken by embedding the hollow spherical calcite type calcium carbonate produced in Example 1 in a resin and hardening it, and coating the cut surface with carbon. In No. 4, it was shown that the cut surface of the particles was annular, which also reveals that the hollow spherical calcite-type calcium carbonate of the present invention is hollow and spherical. Further, it can be seen that the hollow spherical calcite type calcium carbonate of the present invention has a very small shell thickness as compared with the outer diameter.

FIG. 5A shows an X-ray diffraction image of the hollow spherical calcite-type calcium carbonate produced in Example 1. FIG. 5B is an X-ray diffraction image of calcite-type calcium carbonate of a standard sample (ASTM X-Ray Powder Data F
ile 5-0586), and by comparing (a) and (b) of FIG. 5, it is clear that the hollow spherical calcite-type calcium carbonate of the present invention is substantially calcite-type.

The size of the hollow spherical calcite type calcium carbonate of the present invention is not particularly limited, but when it is used as a filler, it exhibits excellent properties in physical properties such as filling property, fluidity and dispersibility. In order to
It is preferable that the particles have a particle diameter of m, particularly 0.5 to 30 μm.

The hollow spherical calcite type calcium carbonate of the present invention has excellent physical properties such as filling property, fluidity and dispersibility because it is spherical, and since it is substantially calcite type, it is particularly suitable for water. On the other hand, it is extremely stable and can be stored for a long period of time, and because it is hollow, it has a low bulk specific gravity and is lightweight and easy to handle and transport. It is possible to improve the heat insulating property and the sound insulating property of the formed article. Therefore, it can be used as a filler for concrete, secondary cement / concrete products, synthetic resin molded products, etc., and is widely used in the fields of building materials, packaging materials, pharmaceuticals, deodorants, fragrances, toners, liquid crystal display devices, etc. Can be used.

The method for producing hollow spherical calcite type calcium carbonate of the present invention comprises:
It is a method characterized in that the calcium salt is reacted with carbon dioxide gas by spraying into a reaction vessel heated to 300 to 1500 ° C. together with carbon dioxide gas.

The method for producing the hollow spherical calcite type calcium carbonate of the present invention will be described with reference to FIG.

FIG. 6 is a schematic view showing an example of a production apparatus used for carrying out the method for producing a hollow spherical calcite type calcium carbonate of the present invention on a laboratory scale. In FIG. 6, a hollow spherical calcite type calcium carbonate manufacturing apparatus 1 includes a calcium salt aqueous solution tank 2 for storing an aqueous solution of a water-soluble calcium salt as a raw material, a carbon dioxide gas cylinder 3,
Reactant raw material ejection pipe 4 for ejecting the calcium salt aqueous solution and carbon dioxide together, a reaction vessel 5, a horizontal electric furnace 6, and a collector for collecting the product, hollow spherical calcite type calcium carbonate 7, a heater 8 for keeping the collector 7 warm, an exhaust pump 9, a thermometer 10 for measuring the temperature in the reaction vessel 5, and a control valve 11 for adjusting the supply amount of the aqueous solution of water-soluble calcium. It consists of
The reaction material jetting pipe 4 has a double pipe structure made of glass, and a calcium salt aqueous solution is passed through the inner pipe 4a to form the inner pipe 4
Carbon dioxide is passed under pressure between a and the outer tube 4b, and the jet port 4
The aqueous solution of calcium salt is sprayed into the reaction vessel 5 by ejecting carbon dioxide gas from c. The reaction vessel 5 is composed of an alumina core tube.

The water-soluble calcium salt used as a raw material is not particularly limited as long as it is a calcium salt that is easily soluble in water, and any one, for example, calcium nitrate, calcium chloride, calcium bromide or the like can be used. Furthermore, for example, calcium hydroxide is easily soluble in an aqueous solution of ammonium chloride or an acidic aqueous solution, and a calcium salt that is easily soluble in an acidic and / or basic aqueous solution is also used as a raw material water-soluble calcium salt. Can be used. In the present invention, calcium nitrate is particularly preferable as the water-soluble calcium salt as a raw material.

The concentration of the water-soluble calcium salt in the aqueous solution is
Generally, it is preferably in the range of 20 to 900 g / l. It is desirable that the calcium salt is completely dissolved in the aqueous solution, but some of the calcium salt may not be dissolved and may remain suspended.

When ammonia is further dissolved in the aqueous solution of the water-soluble calcium salt, the conversion rate and conversion rate of the water-soluble calcium salt to calcium carbonate are increased, and the production amount of calcium carbonate per unit time and the obtained calcium carbonate are increased. It is preferable because the purity is improved. By including ammonia (as NH ₄ OH) in the aqueous solution of the water-soluble calcium salt, the dissolution of carbon dioxide gas in the aqueous solution of the water-soluble calcium salt is promoted during the reaction operation, and the above effects are obtained. It is considered to be a thing. It is sufficient that the amount of ammonia used is 2 mol times or less than the amount of the water-soluble calcium salt used, and use of more ammonia is not harmful to the reaction, but more effects can be obtained. Cannot be achieved, resulting in an increase in cost.

The carbon dioxide gas as a raw material may be only carbon dioxide gas or may be diluted with an inert gas such as nitrogen or air. Even if oxygen is contained in the carbon dioxide gas to be used, there is no particular problem as long as the carbon dioxide concentration is sufficiently secured (generally 20% or more, preferably 30% or more). It is preferably 50% or less of the concentration. When the concentration of carbon dioxide is too low, the production rate of calcium carbonate tends to decrease, and when the reaction temperature is high, thermal decomposition of calcium carbonate tends to occur. Ammonia may be mixed with carbon dioxide.

In the method for producing the hollow spherical calcite type calcium carbonate of the present invention, the water-soluble calcium salt aqueous solution is passed through the inner tube 4a of the reaction material jetting tube 4, and the inner tube 4a and the outer tube 4b are used as described above. And carbon dioxide gas are passed under pressure between them and the carbon dioxide gas is ejected from the ejection port 4c, thereby ejecting the water-soluble calcium salt aqueous solution into the reaction vessel 5 together with the carbon dioxide gas. Means for spraying a liquid together with a gas using such a double-tube ejector is known (see, for example, the Chemical Society of Japan, 1979, (10), pp. 1309 to 1315), and used in the production method of the present invention. Even in such a case, such device, operating method, and operating condition can be used.

In the production method of the present invention, the supply amount of carbon dioxide gas is an amount sufficient to convert the supplied water-soluble calcium salt into calcium carbonate, and the water-soluble calcium salt generally supplied as CO _2. It is preferably 10 to 5,000 mol times. The flow rate of carbon dioxide gas at the jet port 4c is preferably 10 to 300 m / sec. The supply amounts of the water-soluble calcium salt and carbon dioxide gas per unit time are appropriately changed according to the size of the apparatus used.

In the production method of the present invention, the reaction between the water-soluble calcium salt and carbon dioxide is carried out at 300 to 1500 ° C, preferably 500 to 1000 ° C. When the reaction temperature is lower than the above range, the reaction is not sufficiently carried out, the productivity is lowered, and the unreacted water-soluble calcium salt remains in the reaction product to lower the purity of calcium carbonate. If the reaction temperature is higher than the above range, calcium carbonate once formed may be decomposed.

The reaction between the water-soluble calcium salt and carbon dioxide can be carried out under pressure or under reduced pressure, but it is generally preferable to carry out at or near atmospheric pressure.

The generated hollow spherical calcite type calcium carbonate is collected in the collector 7, and the gas from the reaction vessel 5 is exhausted to the outside of the system by the exhaust pump 9.

The obtained hollow spherical calcite-type calcium carbonate is a substance substantially composed of the hollow and spherical calcite-type calcium carbonate of the present invention as described above, and may be used as it is, if necessary. It can also be used after appropriately classifying. When the obtained hollow spherical calcite-type calcium carbonate contains unreacted water-soluble calcium salt, the water-soluble calcium salt can be removed by washing with water to increase the purity. Since hollow spherical calcite type calcium carbonate is stable against water, there is no particular problem even if it is washed with water.

FIG. 6 shows a manufacturing apparatus on a laboratory scale. However, when the manufacturing method of the present invention is carried out on a large scale industrially, an apparatus having an appropriate size and structure according to the scale is used. Of course, it can be used.

[0034]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Calcium carbonate was produced by using calcium nitrate as a water-soluble calcium salt and carbon dioxide gas from a carbon dioxide gas cylinder using a production apparatus as shown in FIG.

The inner tube 4a (outer diameter: 1.
From 23 mm, inner diameter: 0.60 mm, calcium nitrate (purity: 99.0%) and aqueous ammonia solution (calcium nitrate 82.0 g / l, ammonia (as NH ₃ ))
17.0 g / l) was supplied at a rate of 1.0 ml / min, and the inner tube 4a and the outer tube 4b (outer diameter: 3.21) of the reaction material injection tube 4 were supplied.
mm, inner diameter: 2.04 mm), carbon dioxide gas (purity: 99.9%) was supplied at a rate of 8.0 liters / minute, and an ammonia aqueous solution of calcium nitrate and carbon dioxide gas were put together into a reaction vessel. 5 was sprayed.

The temperature inside the reaction vessel 5 is maintained at 800 ° C.,
Keep the temperature of the collector 7 at 370 ° C.
It went for 0 minutes. Most of the produced calcium carbonate was collected in the collector 7.

An SEM (scanning electron microscope) photograph of the obtained calcium carbonate is shown in FIG. Further, a partially enlarged photograph of FIG. 1 is shown in FIG. 2, and a diagram obtained by tracing the photograph of FIG. 2 is shown in FIG. Further, FIG. 4 shows an SEM (scanning electron microscope) photograph taken by embedding the obtained calcium carbonate in a resin, hardening the resin, and coating the cut surface with carbon.

As is apparent from FIGS. 1 to 4, Example 1
The calcium carbonate obtained in 1. has a substantially spherical appearance from large particles to small particles, and is a hollow body.

Further, FIG. 5A showing the X-ray diffraction image of the obtained calcium carbonate and the X-ray diffraction image of the standard sample calcite-type calcium carbonate (ASTM X-Ray Powder Da
By comparing with taFile 5-0586) (b) of FIG. 5, it is clear that the calcium carbonate obtained in Example 1 is substantially of calcite type.

Table 1 shows the results of measuring the particle size distribution of the obtained calcium carbonate using a Microtrac SPA particle size analyzer (manufactured by Nikkiso Co., Ltd.).

[0042]

[Table 1] Table 1 ────────────────────── CH CH particle size cumulative frequency ────────────────── ───── 1 0.17 0.00 0.00 2 0.24 0.00 0.00 3 0.34 0.00 0.00 4 0.43 0.00 0.00 5 0.66 0.31 0.31 6 1.01 1.55 1.24 7 1.69 4.78 3.23 8 2.63 10.47 5.69 9 3.73 17.89 7.42 10 5.27 29.68 11.79 11 7.46 46.36 16.68 12 10.55 65.81 19.45 13 14.92 82.71 16.90 14 21.10 94.90 12.19 15 29.85 100.00 5.10 16 42.21 100.00 0.00 ──────────────────────

[Example 2] The supply rate of the aqueous solution of calcium nitrate was changed to 1.3 ml / min, and the temperature in the reaction vessel was changed to 9
Calcium carbonate was produced in the same manner as in Example 1 except that the temperature was changed to 50 ° C.

The obtained calcium carbonate was inspected in the same manner as in Example 1, and as a result, a hollow, spherical calcite-type calcium carbonate having a particle size distribution similar to that of the calcium carbonate obtained in Example 1. Was confirmed.

Example 3 Without using ammonia, the concentration of calcium nitrate in an aqueous solution of calcium nitrate was adjusted to 80.
Calcium carbonate was produced in the same manner as in Example 1 except that the supply rate of the calcium nitrate aqueous solution was changed to 1.2 ml / min instead of 0 g / l.

The obtained calcium carbonate was examined in the same manner as in Example 1, and as a result, a hollow, spherical calcite-type calcium carbonate having a particle size distribution similar to that of the calcium carbonate obtained in Example 1. Was confirmed.

[Example 4] The concentration of calcium nitrate in an aqueous solution of calcium nitrate was changed to 83.3 g / l, and the concentration of ammonia (NH ₃ ) was changed to 25.0 g / l. Calcium carbonate was produced in the same manner as in Example 1 except that the feeding rate was changed to 0.9 ml / min.

The obtained calcium carbonate was examined in the same manner as in Example 1. As a result, a hollow, spherical calcite-type calcium carbonate having a particle size distribution similar to that of the calcium carbonate obtained in Example 1 was obtained. Was confirmed.

[0049]

INDUSTRIAL APPLICABILITY The hollow spherical calcite type calcium carbonate of the present invention is excellent in physical properties such as filling property, fluidity and dispersibility because it is spherical, and is particularly calcite type. It is extremely stable against water and can be stored for a long period of time, and because it is hollow, it has a low bulk specific gravity and is lightweight, making it easy to handle and transport. It is a novel substance having a remarkably excellent effect that the heat insulating property, the sound insulating property and the like of an article filled with can be improved. Therefore, the hollow spherical calcite-type calcium carbonate of the present invention can be widely used in the fields of building materials, packaging materials, pharmaceuticals, deodorants, aromatics, toners, liquid crystal display devices and the like.

Further, in the method for producing the hollow spherical calcite type calcium carbonate of the present invention, the hollow spherical calcite type calcium carbonate of the present invention can be produced in a simple process using easily available raw materials. It has a remarkably excellent effect.

[Brief description of drawings]

FIG. 1 is an SEM (scanning electron microscope) photograph of the hollow spherical calcite-type calcium carbonate produced in Example 1.

FIG. 2 is a partially enlarged photograph of FIG.

FIG. 3 is a diagram in which the photograph of FIG. 2 is traced.

FIG. 4 is a SEM (scanning electron microscope) photograph taken by embedding the hollow spherical calcite-type calcium carbonate prepared in Example 1 in a resin to solidify it and coating the cut surface with carbon. Is.

5 (a) is a view showing an X-ray diffraction image of the hollow spherical calcite-type calcium carbonate produced in Example 1. FIG. FIG. 5B is an X-ray diffraction image of calcite-type calcium carbonate as a standard sample (ASTM X-Ray Powder Data).
File 5-0586).

FIG. 6 is a schematic view showing an example of a production apparatus used for carrying out the method for producing hollow spherical calcite type calcium carbonate of the present invention on a laboratory scale.

[Explanation of symbols]

 1 Hollow Spherical Calcite Type Calcium Carbonate Manufacturing Device 2 Calcium Salt Aqueous Solution Tank 3 Carbon Dioxide Gas Tank 4 Reactant Raw Material Injection Pipe 5 Reaction Vessel 6 Horizontal Electric Furnace 7 Collector 8 Heater 9 Exhaust Pump 10 Thermometer 11 Control Valve

Claims (2)

[Claims] 1. A hollow, spherical calcite-type calcium carbonate. 2. A hollow spherical calcium carbonate characterized by spraying an aqueous solution of a water-soluble calcium salt together with carbon dioxide into a reaction vessel heated to 300 to 1500 ° C. to react the calcium salt with carbon dioxide. Method for producing site-type calcium carbonate.