JPH05221634A - Production of cubic calcium carbonate - Google Patents

Abstract

PURPOSE:To produce cubic calcium carbonate having uniform particle size and 0.1-1.0mum average particle diameter. CONSTITUTION:In forming calcium carbonate by introducing a carbon dioxide gas-containing gas to lime water, at a point of time when carbonation ratio of primary lime water is 10-40%, secondary lime water ground by wet method and activated, of low temperature and low concentration is added to the primary lime water and further the carbon dioxide gas-containing gas is successively introduced to carbonate the lime water. Calcium carbonate particles having uniform particles size and extremely less secondary aggregation are obtained and functions of calcium carbonate as coated pigment, reinforcing pigment, extender and filler are enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine cubic calcium carbonate which has a uniform particle size and very little secondary aggregation.

[0002]

2. Description of the Related Art Generally, for filling or constitutional calcium carbonate, heavy calcium carbonate obtained by crushing and classifying crystalline limestone and calcium carbonate to lime milk obtained by hydrating mainly dense limestone are hydrated. There is synthetic calcium carbonate that produces gas by introducing gas. Further, synthetic calcium carbonate includes spindle-shaped light calcium carbonate having a major axis of 1 μm or more and cubic colloidal calcium carbonate having a particle size of less than 1 μm. Light calcium carbonate is mainly used as a filler in the paper manufacturing industry and other industries such as rubber and plastics.

Cubic calcium carbonate having a particle size of less than 1 μm is utilized as a reinforcing filler for its functionality, but the opacity, glossiness, and indispensability required when it is used for coated paper in the paper manufacturing industry as described above. In order to develop whiteness, surface smoothness, printability, etc., or to satisfy thixotropy (gloss), glossiness, etc. for paints and sealants, it is preferable to use particles with a particle size of less than 0.1 μm rather than dispersibility The cubic calcium carbonate having a particle size of 0.1 to 1.0 μm exhibits excellent suitability even for secondary agglomerated particles. Such cubic calcium carbonate is strongly desired not only in the paper manufacturing industry but also in the textile industry.

According to the prior art, the particle size is 0.1-1.0 μm.
As a means for producing cubic calcium carbonate, the average particle size is 0.
A technique for growing crystals by repeatedly spraying an aqueous suspension containing less than 1 μm of already-carbonated cubic calcium carbonate and calcium hydroxide into carbon dioxide gas is disclosed in JP-B-54-28397. It is described in the official gazette. Further, there is disclosed a technique in which calcium carbonate having a particle size of less than 0.1 μm is used as a seed crystal, and lime milk or partially carbonated lime milk is added to the seed crystal for carbonation to grow the crystal.
No. 0818 or Japanese Patent Publication No. 58-43331. Furthermore, while the carbon dioxide gas was introduced under the condition that the pH value during the partial carbonation of lime milk was not decreased by 0.2 or more and the plate-like basic calcium carbonate was produced, ultrafine calcium carbonate was added to make the particle size smaller. A technique for producing cubic calcium carbonate of 0.1 to 0.55 μm is disclosed in Japanese Examined Patent Publication No. 3-19165.

[0005]

[Problems to be Solved by the Invention] Particle size is 0.1 to 1.0 μ
According to the prior art for obtaining cubic calcium carbonate of m, in each case it is necessary to use seed crystals in the process of carbonation, which seed crystals must all be calcium carbonate which has been carbonated. There is a problem that it must be done. In addition, according to the known method for producing colloidal calcium carbonate, while having a cubic shape in which the above-mentioned functionality is expressed, even if it is a secondary agglomerated particle, it is 0.1 to 1.0 μm.
There is a problem that it is difficult to produce particles having an arbitrary particle size within the range. The present invention solves each of the problems described above, without using the already carbonated calcium carbonate as a seed crystal, and more particularly, the average particle size of 0.1 to 1.
It is intended to provide a method for producing cubic calcium carbonate having an arbitrary particle size within the range of 0 μm.

[0006]

In order to achieve the above-mentioned object, the method for producing cubic calcium carbonate according to the present invention comprises the steps of introducing a carbon dioxide gas into lime milk to produce calcium carbonate, Carbonation rate of primary lime milk is 10-40
%, The activated low temperature, low concentration secondary lime milk is added, and then the introduction of the carbon dioxide gas-containing gas is continued to carbonate.

To carbonate the primary lime milk, the primary lime milk having a temperature of 10 to 25 ° C. and a concentration of calcium hydroxide of 2 to 30 g / 100 ml contains carbon dioxide gas of 10 to 40 vol%. Gas is 40 for 1 g of calcium hydroxide in the primary lime milk.
It is preferable to introduce at a rate of -80 ml / min. By introducing this carbon dioxide-containing gas into the primary lime milk, the carbonation rate is 10%.
At the time of carbonation up to -40%, the minor axis is 0.01 ± 0.00
Formation of acicular basic calcium carbonate with an aspect ratio of 50 to 200 with a diameter of 5 µm and a major axis of 1.0 ± 0.5 µm is observed.

Next, to the primary lime milk in such a state, the secondary lime milk activated by wet grinding in advance by using a sand mill or the like is added. The secondary lime milk has a temperature of 5 to 15 ° C and a concentration of calcium hydroxide of 1 to 1.
It is preferable that the amount of calcium hydroxide in the range of 5 g / 100 ml is 10 to 100 parts by weight of calcium hydroxide in the secondary lime milk relative to 100 parts by weight of calcium hydroxide in the primary lime milk. Even after the addition of the secondary lime milk, the carbon dioxide gas was continuously introduced at a rate of 80 to 120 ml / min with respect to the total amount 1 g of calcium hydroxide in the primary lime milk and the secondary lime milk. It is a preferred embodiment to complete the carbonation.

Upon completion of this carbonation, the average particle size of 0.1-
Cubic calcium carbonate of 1.0 μm is obtained. In addition,
The carbonation rate (%) is given as a percentage of the weight of carbonated calcium hydroxide to the weight of calcium hydroxide in lime milk.

[0010]

[Function] By controlling the amount of carbon dioxide-containing gas introduced into the primary lime milk and the temperature and concentration of the primary lime milk, first, acicular basic calcium carbonate with an aspect ratio of 50 to 200 is firstly prepared. to make. Next, at a point of carbonation rate of 10 to 40% where carbonation has not yet been completed, low-temperature, low-concentration secondary lime milk obtained by wet grinding lime milk with a sand mill etc. After the addition of lime milk, the carbonation is completed with the introduction amount of carbon dioxide gas increased to produce cubic calcium carbonate having any average particle size within the range of 0.1 to 1.0 μm. You can

[0011]

EXAMPLES Next, specific examples of the present invention will be described in comparison with comparative examples. Example 1 To 769 l of primary lime milk having a temperature of 15 ° C. and a concentration of calcium hydroxide of 4 g / 100 ml, a carbon dioxide gas containing 20 vol% concentration was added to 1 g of calcium hydroxide in the primary lime milk.
Was introduced at a flow rate of 60 ml / min. When the carbonation rate was 20%, the secondary lime milk activated by wet grinding for 1 hour in advance with a sand mill using 2 mmφ glass beads had a concentration of calcium hydroxide of 2 g / 10 at a temperature of 10 ° C.
In the condition of 0 ml, 231 l was added to the primary lime milk. By adding this secondary lime milk, 15 parts by weight of calcium hydroxide contained in the secondary lime milk is added to 100 parts by weight of calcium hydroxide contained in the primary lime milk, that is, the addition rate is 15%. It has been added. Hereinafter, the amount of calcium hydroxide contained in the added secondary lime milk with respect to the amount of calcium hydroxide contained in the primary lime milk is referred to as an addition rate. After the secondary lime milk was added, a carbon dioxide gas-containing gas having a concentration of 20 vol% was continuously introduced at a rate of 100 ml / min with respect to 1 g of calcium hydroxide in the whole lime milk. Cubic calcium carbonate was obtained by the completion of carbonation, and the obtained calcium carbonate particles were observed with an electron microscope to find that the average particle size was 0.2 μm. The average particle diameters of cubic calcium carbonate in the following Examples or Comparative Examples are all those observed with an electron microscope.

Example 2 Under the same conditions as in Example 1 except that the primary lime milk was 625 l and the secondary lime milk was 375 l to give a calcium hydroxide addition rate of 30%. Calcium carbonate was produced. Upon completion of carbonation, cubic calcium carbonate with an average particle size of 0.4 μm was obtained.

Example 3 Calcium carbonate was produced under the same conditions as in Example 1 except that the primary lime milk was 385 l and the secondary lime milk was 615 l to make the addition rate 80%. did. Upon completion of carbonation, cubic calcium carbonate with an average particle size of 0.8 μm was obtained.

Example 4 Calcium hydroxide was added at a temperature of 20 ° C. and a concentration of calcium hydroxide of 6 g / ml by using 625 l of primary lime milk and 375 l of secondary lime milk. Rate is 20%,
Calcium carbonate was produced under the same conditions as in Example 1, except that the carbonation rate was 35%. Upon completion of carbonation, cubic calcium carbonate with an average particle size of 0.9 μm was obtained.

Comparative Example 1 Similar to Example 1, 1000 l of primary lime milk was mixed with a gas containing carbon dioxide at a concentration of 20 vol% at a flow rate of 60 ml / min with respect to 1 g of calcium hydroxide in the primary lime milk. Introduced in. Under these conditions, carbonation up to 100% resulted in an average particle size of 0.04
μm cubic calcium carbonate was obtained.

Comparative Example 2 Calcium carbonate was produced under the same conditions as in Example 1, except that 961 l of primary lime milk and 39 l of secondary lime milk were added to make the addition rate 2%. did. Upon completion of carbonation, cubic calcium carbonate with an average particle size of 0.08 μm was obtained.

Comparative Example 3 318 l of primary lime milk having a temperature of 20 ° C. and a concentration of calcium hydroxide of 10 g / 100 ml was used, and the concentration of the secondary lime milk added to this primary lime milk was water. Calcium oxide 7g / 100
Calcium carbonate was produced under the same conditions as in Example 1, except that the addition rate was adjusted to 150% by adding 682 l of the solution in ml. Upon completion of carbonation, spindle-shaped calcium carbonate with an average particle size of 1.2 μm and a short diameter of 0.5 μm was obtained.

Table 1 shows the manufacturing conditions of Examples 1 to 4 and Comparative Examples 1 to 3. The properties of the obtained calcium carbonate are also shown in Table 1.

[Table 1]

[0019]

According to the present invention, the obtained cubic calcium carbonate has a uniform particle size and very little secondary agglomeration, and its average particle size can be controlled to a cubic value in the range of 0.1 to 1.0 μm. is there. As a result, the range of use as a filler or a bulking agent is improved and expanded to the range of functional compounding agents, and the paper industry, paints, sealants, fibers,
It has become possible to meet the functional requirements in a wide range of fields such as rubber products, plastic products, inks, and cosmetics.

Claims (12)

[Claims] 1. When a carbon dioxide-containing gas is introduced into lime milk to produce calcium carbonate, when the carbonation rate of the primary lime milk is 10 to 40%, activated low temperature and low concentration are obtained. The method for producing cubic calcium carbonate, characterized in that after the secondary lime milk is added, the introduction of a carbon dioxide-containing gas is continued to carbonate. 2. The method for producing cubic calcium carbonate according to claim 1, wherein the secondary lime milk is activated by wet grinding lime milk. 3. The method for producing cubic calcium carbonate according to claim 1, wherein the temperature at which the primary lime milk is carbonated is in the range of 10 to 25 ° C. 4. The method for producing cubic calcium carbonate according to claim 1, wherein the concentration of the primary lime milk when carbonized is in the range of 2 to 30 g / 100 ml of calcium hydroxide. 5. The method for producing cubic calcium carbonate according to claim 1, wherein the temperature when the secondary lime milk is added to the primary lime milk is in the range of 5 to 15 ° C. 6. The concentration of the secondary lime milk when added to the primary lime milk is 1 to 5 g / 100 ml of calcium hydroxide.
The method for producing cubic calcium carbonate according to claim 1, wherein 7. The carbonation rate of the primary lime milk is 10 to 40%
Carbonated basic calcium carbonate at the time of
The method for producing cubic calcium carbonate according to claim 1, which is a needle-like crystal having a minor axis of 0.01 ± 0.005 µm and a major axis of 1.0 ± 0.5 µm and an aspect ratio of 50 to 200. 8. The addition ratio of the secondary lime milk is 10 to 100 parts by weight of calcium hydroxide in the secondary lime milk relative to 100 parts by weight of calcium hydroxide in the primary lime milk. 2. The method for producing cubic calcium carbonate according to claim 1, which is in the range of parts. 9. The amount of the carbon dioxide gas-containing gas introduced into the primary lime milk before the addition of the secondary lime milk is from 40 to 1 g of calcium hydroxide in the primary lime milk. 80 ml /
The method for producing cubic calcium carbonate according to claim 1, which is a minute. 10. The amount of the carbon dioxide gas-containing gas introduced into the total lime milk after the addition of the secondary lime milk is the total amount of calcium hydroxide in the primary lime milk and the secondary lime milk. The method for producing cubic calcium carbonate according to claim 1, wherein the amount is 80 to 120 ml / min per 1 g. 11. The carbon dioxide-containing gas is carbon dioxide gas.
The method for producing cubic calcium carbonate according to claim 9 or 10, which is a gas containing 10 to 40 vol%. 12. The method for producing cubic calcium carbonate according to claim 1, wherein the average particle size of calcium carbonate obtained by carbonating the whole lime milk is 0.1 to 1.0 μm.