JP2000086237A - Production of spindle shaped calcium carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conveniently control the diameter of a small grain to a desired value efficiently, stably and industrially produce spindle shaped calcium carbonate by adding a zinc compd. to a calcium hydroxide suspension and conducting a carbonation reaction. SOLUTION: The spindle shaped calcium carbonate having a small grain diameter is produced by the carbonation reaction of a calcium hydroxide suspension. One or >=2 kinds of zinc compds. selected from a group consisting of zinc oxide, zinc hydroxide and soluble zinc salt are added by 0.01-5.0 pts.wt., expressed in terms of zinc, to 100 pts.wt. of calcium hydroxide of a <=30 wt.% calcium hydroxide suspension. A carbonation reaction is applied to this suspension at 25-40 deg.C reaction initiating temp. by using a gas contg. >=5% carbon dioxide. Since the amt. of zinc compd. to be added is controlled to 0.01-5.0 pts.wt. in this way, the grain diameter of the spindle shaped calcium carbonate is stably controlled to 0.3-5.0 μm major axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a spindle-shaped calcium carbonate having a small particle size more easily on an industrial scale. More specifically, in the carbonation reaction of a calcium hydroxide suspension, by adding a compound of a specific metal, it can be suitably used as a pigment or filler for papermaking, or a filler for polymer materials such as plastic and rubber. The present invention relates to a method for producing a spindle-shaped calcium carbonate having a small particle diameter that can be produced.

[0002]

2. Description of the Related Art Calcium carbonate includes heavy calcium carbonate obtained by physically grinding natural white limestone and synthetic calcium carbonate obtained by a chemical precipitation reaction. The former heavy calcium carbonate can be produced relatively inexpensively by simply pulverizing natural products, but it has a wide particle size distribution and an irregular form peculiar to physical pulverization. It is not easy to produce a powder having an excellent function expressed due to the particle diameter and morphology.

On the other hand, since the latter synthetic calcium carbonate is produced by a chemical precipitation reaction, the particle diameter and morphology can be controlled within a certain range. Calcium carbonate, which has a unique shape such as shape and columnar shape and a narrow range of particle size, has unique functions and characteristics derived from differences in the form and particle size of each, and the functions and characteristics Utilizing it, it is used properly in papermaking and various polymer material fields.

Among these synthetic calcium carbonates, spindle-shaped calcium carbonate has a spindle shape with a major axis of 3 to 6 μm and a minor axis of 1 to 2 μm as its name suggests, and is used in large quantities mainly as pigments and fillers for papermaking. However, under normal reaction conditions, the particle size can be produced only in the above-mentioned limited range. For this reason, various studies have been made on the control of the particle size since ancient times.

That is, JP-B-54-28399 discloses a method in which calcium hydroxide is wet-milled in advance and the concentration and temperature of the suspension are strictly controlled.
No. 3765, a method of obtaining a spindle-shaped calcium carbonate of 0.5 to 1.0 μm by adding water glass or silica sol to a calcium hydroxide suspension and injecting carbon dioxide gas. In addition, there is a method of producing spindle-shaped calcium carbonate having a major axis of 0.6 to 3 μm and a minor axis of 0.1 to 1 μm.

Further, a spindle-like calcium carbonate having a diameter of 0.1 to 1.0 μm obtained by carrying out a carbonation reaction in the presence of a barium or strontium compound under the conditions for producing a basic calcium carbonate described in JP-A-5-238730. Manufacturing methods have also been proposed. However, these production methods are industrially adopted because the reaction conditions in the production process become stricter or more complicated, and all of them occur because of increased costs or use of special additives. No examples are known.

[0007]

As described above, spindle-shaped calcium carbonate is one of the most easily produced synthetic calcium carbonates and has an appropriate particle diameter, so that it is used in large quantities as a filler for papermaking. However, cubic or columnar calcium carbonate is often used as a papermaking pigment. One reason for this is the difficulty in controlling the particle size of small particle size products. If it becomes possible to easily control the particle size of this small particle size product at the industrial production level, calcium carbonate having a particle size of 0.1 to 3.0 μm, which is a blank region of the particle size of the conventional synthetic calcium carbonate, will be industrially manufactured. Since it can be manufactured at the production level, it can be used as a papermaking pigment, and further expansion of new applications to polymer materials and the like can be expected.

In view of such circumstances, the inventors of the present invention have conducted intensive studies on the control of the particle size of small-diameter particles in order to expand the use of spindle-shaped calcium carbonate, and have studied the carbonation reaction of a calcium hydroxide suspension. The present inventors have found that the problem can be solved by a simple method of adding a compound of a specific metal, and have completed the present invention. That is, an object of the present invention is to efficiently and stably produce industrially, and have a small particle diameter, particularly a small major axis, which is also excellent in economic efficiency, and can easily control the particle diameter to a desired value. It is to provide a method for producing spindle-shaped calcium carbonate.

[0009]

Means for solving the above-mentioned problems in the present invention is to produce spindle-shaped calcium carbonate by a carbonation reaction of a calcium hydroxide suspension.
By adding a zinc compound, a spindle-shaped calcium carbonate having a small particle diameter is produced. Preferably, the zinc compound at that time is one or more selected from the group consisting of zinc oxide, zinc hydroxide and a soluble salt of zinc,
The amount of the zinc compound is 0.01 to 5.0 parts by weight in terms of the amount of metal per 100 parts by weight of calcium hydroxide, which is a simple method. Solved the problem. By adjusting the amount of addition, spindle calcium carbonate having a desired small particle diameter can be produced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The lime raw material used for preparing the calcium hydroxide suspension, which is the main production raw material of the spindle-shaped calcium carbonate produced in the present invention, is not particularly limited, but calcined high quality limestone which is abundant as a domestic natural resource. Quick lime obtained by the above or slaked lime produced by further digesting the same can be used. These are suspended in water to obtain a calcium hydroxide suspension. The concentration of the suspension is 30% by weight or less, preferably 1 to 20% by weight in terms of calcium hydroxide concentration.
If the concentration is too low, the production efficiency decreases, and if the concentration is too high, sufficient stirring cannot be performed and a uniform reaction is not performed.

The use of carbon dioxide for the carbonation reaction is advantageous both in terms of quality and economy. In this case, a pure gas supplied from a cylinder may be used, or a carbon dioxide-containing gas such as a waste gas generated from a kiln or other combustion waste gas during the production of quick lime can be washed and used. . There is no limitation on the concentration of the carbon dioxide-containing gas. However, when the concentration is low, the reaction efficiency is reduced and the carbonation takes a long time, so it is preferably 5% or more, and more preferably 10% or more.

At this time, the starting temperature of carbonation is 20
The temperature is preferably 45 to 45 ° C, more preferably 25 to 40 ° C. If the temperature is too low, colloidal calcium carbonate is generated, and the desired spindle-shaped calcium carbonate cannot be obtained. On the other hand, if the temperature is too high, long columnar to acicular aragonite is mixed,
The particle size and shape of the calcium carbonate become irregular, which causes inconvenience in use.

The reason why the temperature of the carbonation reaction is particularly concerned with the starting temperature is that it has been found that there is no problem even if the starting temperature is adjusted and then left to run. For example, if the temperature rise is delayed and the temperature is not controlled, there is usually a temperature rise of 10 to 15 ° C. at room temperature until the end of carbonation due to the heat of the reaction, but the temperature is controlled and the start temperature is maintained until the end of the reaction. It was found that there was no particular difference in the product when compared with the product. Although the reason is not clear, the present inventors have observed that crystal nucleation occurs during the very first one to several minutes of carbonation, and thereafter, the effect of the reaction temperature on the product is small. Believe in things.

As for the method of adding the zinc compound, zinc carbonate, zinc hydroxide, zinc chloride and the like are added at the time of calcining limestone and mixed into quicklime as a raw material. There is no particular limitation, for example, a method of mixing a soluble salt of zinc, a method of adding a zinc oxide, zinc hydroxide or a soluble salt of zinc after preparing a calcium hydroxide suspension. In the first method of adding a zinc compound during limestone firing, zinc hydroxide, zinc chloride, and the like are changed into zinc oxide by heating during firing.

Examples of the soluble salt of zinc to be added at this time include zinc salts such as zinc chloride, zinc sulfate and zinc nitrate, zinc salts, and ammine complex salts. In addition, as the addition time of the zinc compound, it is necessary that zinc is contained in the calcium hydroxide suspension before the start of carbonation, and the expected effect may not be reduced or obtained after the start of carbonation. .

The amount of the zinc compound to be added is adjusted according to the intended particle size. That is, a spindle-shaped calcium carbonate having a desired particle size can be obtained by adjusting the amount of the zinc compound added, and the particle size can be controlled by adjusting the amount of the zinc compound. The addition amount is suitably 0.01 to 5.0 parts by weight in terms of the amount of zinc metal with respect to 100 parts by weight of calcium hydroxide.
The particle size tends to decrease as the amount added increases.
If the amount is less than 0.01 part by weight, a sufficient effect cannot be obtained, and even if added in a large amount, the effect is limited, and the product is remarkably aggregated and is not suitable for practical use.

In the carbonation reaction of this calcium hydroxide suspension, when no zinc compound is added, the obtained spindle-shaped calcium carbonate has, for example, a major axis of 3 μm and a 35 ° C. In the present invention, 0.3 to 5.0 μm is obtained by adding a zinc compound.
The particle diameter can be controlled stably continuously between 0 μm, and as a result, a spindle-shaped calcium carbonate having a desired particle diameter can be produced. As a result, it is extremely practical because it can respond to the needs of various particle sizes from users, as well as fillers for papermaking, which have been used up to now, as well as functional fillers for high-grade papermaking pigments and various polymer materials. have.

[0018]

The present invention will be described more specifically with reference to examples and comparative examples of the present invention. However, the present invention is not limited at all by these examples, but is specified by the description in the claims. It goes without saying that there is something.
In the following Examples and Comparative Examples, the amounts of zinc compounds are all parts by weight of zinc with respect to 100 parts by weight of calcium hydroxide, and the particle diameter of spindle-shaped calcium carbonate is indicated by the major axis observed with a transmission electron microscope.

[Examples 1 to 5] 1 kg of tap water was placed in a 3 liter cylindrical separable flask, into which 130 g of industrial quicklime produced by calcining limestone and a predetermined amount of a reagent zinc oxide were charged. Stirred. This calcium hydroxide suspension is passed through a 100 mesh sieve to remove coarse particles,
Further, tap water was added to adjust the total amount to 2 kg to a predetermined temperature. While stirring this suspension, the carbon dioxide concentration is 20%.
Was introduced at a rate of 1.6 L / min, and the termination of carbonation was confirmed by a sharp drop in pH (12.5 → 6.2). The particle diameter of the obtained spindle-shaped calcium carbonate was observed with a transmission electron microscope.

The results are shown in Table 1. From these results, it can be immediately understood that in Examples 1 to 3 in which spindle-shaped calcium carbonate was produced at the same temperature, the larger the amount of addition, the smaller the particle size. It can also be seen that a higher starting temperature results in a larger particle size than a lower starting temperature.
Furthermore, it is immediately understood that, in comparison with Comparative Example 1 described below, in which spindle-shaped calcium carbonate is produced at the same temperature, the particle diameter is smaller when the zinc compound of the present invention is added than when no zinc compound is added. it can.

[Examples 6 to 8] In the same manner as in Examples 1 to 5, 1 kg of tap water was placed in a cylindrical separable flask having a capacity of 3 liters, into which 130 g of industrial quicklime produced by calcining limestone was added. Stirred. The calcium hydroxide suspension was passed through a 100 mesh sieve to remove coarse particles, and the total amount was adjusted to 2 kg to a predetermined temperature. A predetermined amount of zinc sulfate heptahydrate was added to this suspension, and a mixed gas with air having a carbon dioxide concentration of 20% was added to the suspension while stirring at 500 rpm.
It was introduced at a rate of 6 liters / minute, and the completion of carbonation was confirmed by the decrease in pH. The particle diameter of the obtained spindle-shaped calcium carbonate was observed with a transmission electron microscope. Table 2 shows the results.
Shown in

Examples 9 to 11 1 kg of tap water was placed in a 3 liter cylindrical separable flask, and 110 g of industrial quicklime produced by calcining limestone was added thereto and stirred. This calcium hydroxide suspension is 100mes
h, and the coarse particles were removed therefrom, and the whole amount was adjusted to 2 kg to a predetermined temperature. A predetermined amount of zinc chloride was added to this suspension, and carbon dioxide was added for 0.5 while stirring at 500 rpm.
It was introduced at a rate of 1 liter / min, and the completion of carbonation was confirmed by lowering the pH. The particle diameter of the obtained spindle-shaped calcium carbonate was observed with a transmission electron microscope. Table 3 shows the results.

[Examples 12 to 14] 1.7 kg of tap water was placed in a 3 liter cylindrical separable flask, and limestone was calcined and digested in this, and crushed to -200 mesh to produce industrial slaked lime. 300 g were charged. After adding zinc chloride to the calcium hydroxide suspension, the temperature is adjusted to a predetermined temperature, and while the suspension is stirred at 500 rpm, carbon dioxide is introduced at a rate of 1.0 liter / min.
The completion of carbonation was confirmed by the decrease in The particle diameter of the obtained spindle-shaped calcium carbonate was observed with a transmission electron microscope. Table 4 shows the results.

Example 15 Reagent Calcium Carbonate 200
After adding 3.09 g of the reagent zinc chloride to the resulting mixture, the mixture was sufficiently mixed and then calcined at 1000 ° C. for 4 hours in an electric furnace. The zinc compound-containing calcium oxide was charged into a 3-liter cylindrical separable flask containing 1.888 kg of tap water to prepare a calcium hydroxide suspension having a zinc content of 1.0 part by weight. The suspension is maintained at 30 ° C. and 500 rpm
Carbon dioxide was introduced at a rate of 1.0 liter / min while stirring at m, and the completion of carbonation was confirmed by a decrease in pH. Observation of the obtained calcium carbonate with a transmission electron microscope revealed that it was spindle-shaped calcium carbonate having a long diameter of 1.7 μm.

Example 16 Industrial quicklime (size 20)
４０40 mm), and 1043 kg of a calcium hydroxide suspension having a temperature of 32 ° C. and a calcium hydroxide concentration of 8.3% by weight was prepared in a reaction vessel having an effective volume of 1 m ³ . After adding 2.16 kg of zinc oxide to adjust the amount of zinc to 2.0 parts by weight, a mixed gas with air having a carbon dioxide concentration of 25% was introduced at a rate of 80 liter / minute, and the pH was increased. The completion of carbonation was confirmed by the decrease in Observation of the obtained calcium carbonate with a transmission electron microscope revealed that the major axis was 2.0 μm.
m spindle-shaped calcium carbonate.

Comparative Example 1 1 kg of tap water was placed in a 3-liter cylindrical separable flask, into which 130 g of industrial quicklime produced by calcining limestone was added and stirred. This calcium hydroxide suspension was passed through a 100 mesh sieve to remove coarse particles, and the total amount was reduced to 2 kg to 30 kg.
C. While stirring the suspension, a mixed gas with air having a carbon dioxide concentration of 20% was introduced at a rate of 1.6 liter / minute, and the completion of carbonation was confirmed by a decrease in pH. Observation of the obtained calcium carbonate with a transmission electron microscope revealed that it was spindle-shaped calcium carbonate having a major axis of 3.0 μm. When this result is compared with Examples 1 to 3 in which spindle-shaped calcium carbonate was produced at the same temperature, it can be immediately understood that the particle diameter was smaller when the zinc compound of the present invention was added as described above.

Comparative Example 2 Calcium carbonate was obtained in the same manner as in Comparative Example 1, except that the carbonation start temperature was 35 ° C. and the suspension concentration was 7.17% by weight. Observation of the product with a transmission electron microscope revealed that the product was spindle-shaped calcium carbonate having a major axis of 5.0 μm.

Comparative Example 3 The calcium hydroxide suspension concentration was 7.20% by weight, and zinc oxide
Except that the amount of zinc was 0.004 parts by weight by adding 7 g.
An experiment was performed under the same procedure and conditions as in Example 2. When the obtained spindle-shaped calcium carbonate was observed with a transmission electron microscope, no effect of addition of zinc oxide was recognized, and spindle-shaped calcium carbonate having a long diameter of 3.0 μm was formed as in the case of no addition.

[Comparative Example 4] The calcium hydroxide suspension concentration was 7.28% by weight, and zinc chloride was added to the solution at 24.4%.
An experiment was conducted in the same procedure and under the same conditions as in Example 11, except that the amount of zinc was 8.04 parts by weight by adding g. Observation of the obtained spindle-shaped calcium carbonate with a transmission electron microscope revealed that although the addition amount of zinc chloride in Example 11 was 4.61 parts by weight, no change was observed in the particle diameter, but the particles were significantly aggregated. And the aggregated particle diameter was 20 to 50 μm.

Comparative Example 5 An experiment was conducted in the same procedure as in Example 2 except that the carbonation initiation temperatures were set at 15 ° C. and 50 ° C. Observation of the obtained calcium carbonate with a transmission electron microscope revealed that at 15 ° C., colloidal calcium carbonate having an average particle size of 0.04 μm was formed. At 50 ° C, the major axis is 3.
5 μm length in addition to 0 μm spindle calcium carbonate
X-ray powder diffraction revealed peaks of aragonite.

[0031]

The method for producing spindle-shaped calcium carbonate according to the present invention is a simple method of adding a zinc compound, and has an excellent effect of obtaining particles having a small particle size as compared with the case where no zinc compound is added. It is. At the same time, the particle size can be controlled by a simple method of adjusting the addition amount. As a result, it is a technology that is highly practical and easy to adopt on an industrial level.It has been used by users as a functional filler for papermaking pigments and various polymer materials, as well as papermaking fillers that have been used up to now. It has the feature of being extremely practical in that it can meet the needs regarding the particle size.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

Claims (5)

[Claims] 1. A method for producing spindle-shaped calcium carbonate by a carbonation reaction of a suspension of calcium hydroxide, the method comprising producing a spindle-shaped calcium carbonate having a small particle diameter by adding a zinc compound. 2. The method according to claim 1, wherein the zinc compound is zinc oxide, zinc hydroxide,
One or two selected from the group consisting of soluble salts of zinc
The method for producing spindle-shaped calcium carbonate according to claim 1, which is at least one kind. 3. The amount of zinc compound added is 0.01 to 100 parts by weight of calcium hydroxide in terms of zinc.
3. The method for producing spindle-shaped calcium carbonate according to claim 1, wherein the amount is 5.0 parts by weight. 4. The reaction initiation temperature of the carbonation reaction is 25-40.
4. The method for producing spindle-shaped calcium carbonate according to claim 1, wherein the temperature is ℃. 5. The process for producing spindle-shaped calcium carbonate according to claim 1, wherein the particle size is controlled by adjusting the amount of the zinc compound added.