JPH0818828B2 - Method for producing agglomerated calcium carbonate - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention provides a paper having a low white paper gloss when coated on paper, excellent printability such as ink absorbency, and the like. In this case, the present invention relates to a method for producing a specific agglomerated calcium carbonate having improved yield and excellent optical properties such as whiteness and opacity of paper.

Conventional technology Calcium carbonate is used as a pigment for papermaking, but when coated on the surface of paper, it has an average particle size of 0.2 to 1.0 μm.
It is known that the glossiness of m is high and the gloss is low when the average particle size is larger than that (Japanese Patent Laid-Open No. 53-43).
No. 097), the one having a large average particle size has a drawback that the ink absorbency is low and the printability such as ink setting property is poor. Further, heavy calcium carbonate has a drawback that it is produced by crushing limestone and has a variation in particle size, so that the smoothness of the paper surface is deteriorated.

Further, when calcium carbonate is infused in paper, the yield is poor when the average particle size is small, and the optical properties such as whiteness and opacity are poor, and the yield is improved when the average particle size is large, but the particles are It is unavoidable that the diameter is too large and the optical properties are poor.

Furthermore, in OA equipment paper such as thermal recording paper, pressure-sensitive recording paper, inkjet recording paper, PPC paper, NIP paper, and LBP paper, colorization has progressed, and coated paper and internal There is a demand for high-quality paper such as matte paper or low-gloss white matte paper, and even with calcium carbonate used as a papermaking pigment, the white gloss of the coated surface is low and the printability such as ink absorption is excellent, or There has been a demand for materials having excellent optical properties such as whiteness and opacity.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention improves the drawbacks of calcium carbonate used in such conventional pigments for papermaking, and has low glossiness, printability such as ink absorption, whiteness and opacity. It is an object of the present invention to provide a method for industrially efficiently producing agglomerated calcium carbonate, which has excellent optical properties such as the above and has a good yield when internally filled.

Means for Solving the Problems The present inventors have conducted various studies on the industrial production method of the above-mentioned agglomerated calcium carbonate having good properties, and as a result, a calcium hydroxide aqueous suspension having a specific concentration and a specific viscosity, and a dioxide The carbonation reaction with carbon is performed by a specific reactor to a specific carbonation rate, then the reaction solution (hereinafter referred to as the primary reaction solution) is transferred to another specific reactor, and the pH of the reaction solution is adjusted to a predetermined value. While blowing a carbon dioxide-containing gas so as to hold the same calcium hydroxide aqueous suspension as the above, the molar ratio of each total calcium amount of the primary reaction liquid and the calcium hydroxide aqueous suspension is within a predetermined range. Continuously added until reaching, in other words, while blowing the carbon dioxide-containing gas, in order to maintain the pH of the reaction solution at a predetermined value, the same calcium hydroxide aqueous suspension as above was added, and the primary reaction When the molar ratio of each total calcium amount to the added calcium hydroxide aqueous suspension reached a predetermined range, the addition of calcium hydroxide was stopped and carbon dioxide was added until the pH of the reaction solution dropped to around 7. The carbon dioxide reaction is completed by blowing a gas containing it, or the above primary reaction liquid is transferred to another specific reactor, and the same calcium hydroxide aqueous suspension as above is added to the primary reaction liquid and the calcium hydroxide aqueous solution. After adding at a ratio such that the molar ratio of each total calcium amount with the suspension is within the predetermined range, blow carbon dioxide-containing gas until the pH of the reaction solution drops to around 7 to complete the carbonation reaction. It was found that the objective can be achieved by obtaining agglomerated calcium carbonate having a specific average particle diameter formed by aggregating calcium carbonate particles having a specific major axis, minor axis and aspect ratio. And it was completed the present invention based on these findings.

That is, the present invention is a gas dispersion stirring type reactor, concentration
A carbon dioxide-containing gas was blown into a calcium hydroxide aqueous suspension having a viscosity of 2000 centipoise or more at 40% by weight and 25 ° C adjusted to 7 to 15% by weight to obtain a carbonation rate of 70 to
Carry out a carbonation reaction up to 95%, then transfer the obtained reaction solution (referred to as the primary reaction solution) to a gas injection stirring reactor, and add a carbon dioxide-containing gas so that the pH of the reaction solution is kept at least 12. 40% by weight and 25 while blowing
A calcium hydroxide aqueous suspension having a viscosity of 2000 centipoise or more at 0 ° C has a molar ratio of the total calcium amount in the primary reaction liquid to the total calcium amount in the calcium hydroxide aqueous suspension.
Add continuously until it reaches within the range of 10: 1 to 1:20,
Further, carbon dioxide-containing gas is blown in to complete the carbonation reaction until the pH of the reaction solution is reduced to around 7, or water with a concentration of 40% by weight and a viscosity of 2000 centipoise or more at 25 ° C. in a gas dispersion stirring type reactor. A carbon dioxide-containing gas was blown into a calcium oxide aqueous suspension adjusted to 7 to 15% by weight to cause a carbonation reaction to a carbonation rate of 70 to 95%, and then the obtained reaction liquid (primary reaction liquid Was transferred to a stirred gas-stirred reactor with a concentration of 40% by weight and 25
A calcium hydroxide aqueous suspension having a viscosity of 2000 centipoise or more at 0 ° C has a molar ratio of the total calcium amount in the primary reaction liquid to the total calcium amount in the calcium hydroxide aqueous suspension.
After adding it in a ratio of 10: 1 to 1:20, the carbon dioxide-containing gas is blown in until the pH of the reaction solution decreases to around 7 to complete the carbonation reaction.
Average particle size formed by agglomeration of calcium carbonate particles having a diameter of 0.8 μm, a short diameter of 0.21 to 0.30 μm and an aspect ratio of less than 1.
It is intended to provide a method for producing agglomerated calcium carbonate of 0 to 10 μm.

 Hereinafter, the present invention will be described in detail.

In the method of the present invention, first, in a gas dispersion stirring type reactor, a calcium hydroxide aqueous suspension having a concentration of 40% by weight and a viscosity at 25 ° C. of 2000 centipoise or more is adjusted to 7 to 15% by weight, and carbon dioxide is added. A primary reaction step is carried out in which the contained gas is blown and the carbonation reaction is carried out to a carbonation rate of 70 to 95%, then the obtained primary reaction liquid is transferred to a gas blowing stirring type reactor, and the pH of the reaction liquid is at least 12%. While blowing a carbon dioxide-containing gas so that the
% By weight and a viscosity at 25 ° C. of 2000 centipoise or more in a calcium hydroxide aqueous suspension, the molar ratio of the total calcium amount in the primary reaction liquid to the total calcium amount in the calcium hydroxide aqueous suspension is 10: 1 to 1 Continuous addition until it reaches within the range of: 20, and then a carbon dioxide-containing gas is blown in until the pH of the reaction solution drops to around 7 to complete the carbonation reaction (hereinafter referred to as the continuous method), or the primary The reaction solution was blown into a gas and transferred to a stirring type reactor, and the concentration was 40% by weight and
A calcium hydroxide aqueous suspension having a viscosity of 2000 centipoise or more at 25 ° C. has a molar ratio of the total calcium amount in the primary reaction liquid to the total calcium amount in the calcium hydroxide aqueous suspension of 10: 1 to 1:20. After adding at a ratio within the range, a secondary reaction step is carried out by a method (hereinafter, referred to as a batch method) in which a carbon dioxide-containing gas is blown in to complete the carbonation reaction until the pH of the reaction solution decreases to around 7. Here, the viscosity is measured using a B type (Brooksfield type) viscometer under the condition of a rotor rotation speed of 60 rpm.

The gas dispersion stirring type reactor used in the primary reaction step,
A reactor equipped with a stirrer for enhancing gas absorption efficiency by mixing and stirring liquid and uniformly dispersing gas, preferably having a turbine-type impeller such as a turbo mixer, 10
It is a reactor that agitates at a high speed of 00 rpm or more.

In the primary reaction step, when the concentration of the aqueous calcium hydroxide suspension is less than 7% by weight, the productivity is low, and when it exceeds 15% by weight, the secondary particles are strongly aggregated with each other and lack uniformity.

The reaction initiation temperature is 5 to 50 ° C, preferably 5 to 20 ° C.
The amount of carbon dioxide-containing gas blown in is preferably 1.0 to 6.0 mol / hr per mol of calcium hydroxide, and the reactor is preferably a gas dispersion stirring type reactor. In the blow-stir reactor, the primary and secondary particles tend to lack uniformity. Further, when the carbonization rate is lower than 70%, it is unavoidable that spindle-shaped particles other than the agglomerated particles tend to be generated due to incomplete nucleation of the agglomerated calcium carbonate.

The gas blowing stirring type reactor used in the secondary reaction step is a reactor in which liquid circulation is better than that of the gas blowing reactor, and preferably has a propeller type impeller,
It is a reactor that performs stirring at a low speed rotation of 100 rpm or less.

In the secondary reaction step, the blowing amount of the carbon dioxide-containing gas is 0.1 to 3 mol / hr per mol of calcium hydroxide.
It is desirable that Furthermore, when the molar ratio of the total amount of calcium in the carbonated milk to the total amount of calcium in the aqueous calcium hydroxide suspension is higher than 10: 1, the average particle size of the aggregated calcium carbonate particles is 1.0 μm or less. Next to
Aggregation is weak, particles disintegrate when dispersed at high concentration, and the dispersion slurry thickens, and when the ratio is lower than 1:20, the reaction aggregate becomes two-component and aggregates with spindle-shaped particles. A mixture of calcium carbonate is unavoidable. Further, if the blowing of the carbon dioxide-containing gas is stopped before the pH of the reaction solution has dropped to around 7, the carbonation reaction will not be completed. Further, it is not necessary to use pure carbon dioxide, and carbon dioxide-containing gas diluted with nitrogen or the like can be used. Moreover, the viscosity of the raw material calcium hydroxide aqueous suspension may be adjusted by mechanical treatment or the like.

In the continuous system, the pH of the reaction solution is at least
A calcium hydroxide aqueous suspension is continuously added while blowing a carbon dioxide-containing gas so that the pH is maintained at 12, preferably 12 to 12.5, but when this pH is less than 12, secondary particles are formed. I cannot help avoiding it. The reaction start temperature is
Usually 10 ~ 70 ℃, preferably 10 ~ 40 ℃, the temperature of the calcium hydroxide aqueous suspension added is usually 10 ~ 70 ℃,
It is preferably 10 to 40 ° C.

Further, in the batch system, it is desirable that the concentration of the mixed milk, which is a mixture of the carbonated milk as the primary reaction liquid and the calcium hydroxide aqueous suspension, is 7 to 15% and the viscosity is 2000 centipoise or more. Starting temperature is usually 10 ~
It is desirable to be in the range of 70 ° C, preferably 10-40 ° C. When the viscosity of the mixed milk is less than 2000 centipoise, the final product is inevitably a mixture of agglomerated calcium carbonate and spindle-shaped particles.

In this way, the major axis is 0.6 to 0.8 μm and the minor axis is 0.21 to 0.30.
An average particle size of 1.0 formed by aggregating calcium carbonate particles (hereinafter referred to as primary particles) having a micrometer and an aspect ratio of less than 3
~ 10μm aggregate calcium carbonate (hereinafter referred to as secondary particles)
Can be manufactured. If the average particle size of the secondary particles is not smaller than this, the effect will not be sufficiently exhibited, and if it is larger than this, the cohesive force of the particles will be weakened and stability will inevitably be reduced. Further, if the primary particles are smaller than this, the effect of the present invention will not be sufficiently exhibited, and if they are too large, the cohesive force of the particles will be weakened and the stability will inevitably be reduced.

Further, if the aspect ratio of the primary particles is high, the primary particles will be broken when dispersed, and the stability of the slurry will be poor.

Effects of the Invention According to the method of the present invention, agglomerated calcium carbonate having a specific average particle diameter formed by aggregating calcium carbonate particles having a specific major axis, minor axis and aspect ratio is easily and efficiently industrially used. It can be manufactured.

This agglomerated calcium carbonate usually has a particle size of 0.08 to 0.1 μm.
Cube-shaped particles of the primary particles of calcium carbonate is more aggregating and less likely to disintegrate than the calcium carbonate agglomerates, filtration in the commercialization process, drying, classification, and dispersion in the papermaking process,
In the process of applying high shearing force such as coating and papermaking, the particles do not change, and the unevenness of the surface provides better adsorption performance than calcium carbonate aggregates with cubic particles as primary particles When used as a pigment for use, it reduces the glossiness of white paper and is excellent in absorbing ink, etc.
It has excellent printability such as ink set, and when the pigment is put in the paper, the yield is improved, diffuse reflection of light occurs, and excellent optical properties such as whiteness and opacity are obtained. Play.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Calcium hydroxide was suspended in water to prepare 50% by weight of lime milk, treated with a Choles mixer (high speed impeller disperser), diluted to 40% by weight, and the viscosity at 25 ° C. was measured. (B-type viscometer 60 rpm) was 2500 cp.

The obtained lime milk was adjusted to a concentration of 100 g / l and l5 ° C, and 30 l was charged into a gas dispersion stirring type reactor (hereinafter referred to as reactor R-1) to obtain a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume.
1Nm ³ / hr (3.0mol / hr per 1mol of calcium hydroxide)
Was blown in and reacted until the carbonation rate reached 85%.

The temperature of the obtained primary reaction liquid was adjusted to 20 ° C., 27 l was charged into a gas blowing stirring type reactor (hereinafter referred to as reactor R-2), and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was added to 3.
Blowing reaction was performed at 0 Nm ³ / hr. Simultaneous with reaction 100g / l, 3
The pH of the reaction solution was 12 to 12.5 using 2.7 l of the above lime milk adjusted to 0 ° C.
Was added continuously so that The amount of gas at this time was 1.0 mol / hr per 1 mol of calcium in the mixed slurry, and the molar ratio of the total amount of calcium in the primary reaction liquid to the lime milk was 10: 1. Further, the blowing of the carbon dioxide-containing gas was continued, and the blowing of the gas was stopped when the pH of the reaction solution became around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 1.2 μm, and the constituent particles have an average major axis of 0.6 μm.
m, an average minor axis of 0.21 μm, and an agglomerated calcium carbonate having an aspect ratio of 2.9 were observed.

Example 2 The primary reaction solution prepared in the same manner as in Example 1 was used as the reactor R.
-2 was charged in an amount of 15 l, and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was blown at 4.5 Nm ³ / hr for reaction. Simultaneously with the reaction, 15 g of the lime milk adjusted to 100 g / l and 26 ° C. was continuously added so that the pH of the reaction solution was maintained at 12 to 12.5.
The amount of gas at this time is per mol of calcium in the mixed slurry
It was 1.5 mol / hr, and the molar ratio of the total amount of calcium in the primary reaction liquid to the lime milk was 1: 1. Further, the blowing of the carbon dioxide-containing gas was continued, and the blowing of the gas was stopped when the pH of the reaction solution became around 7.

When the reaction product is observed by a scanning electron microscope, the average particle diameter is 3.2 μm, and the constituent particles have an average major axis of 0.6 μm.
m, average minor axis 0.22 μm, and agglomerated calcium carbonate having an aspect ratio of 2.7 was observed.

Example 3 The primary reaction solution prepared in the same manner as in Example 1 was used as the reactor R.
-2 was charged in an amount of 5 liters, and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was blown at 6.0 Nm ³ / hr for reaction. Simultaneously with the reaction, 25 g of the above lime milk adjusted to 100 g / l and 22 ° C.
H was added continuously so that the H was kept between 12 and 12.5. The amount of gas at this time is 2. per mol of calcium in the mixed slurry.
It was 0 mol / hr, and the molar ratio of the total calcium content of the primary reaction liquid and the lime milk was 1: 5. Further, the blowing of the carbon dioxide-containing gas was continued, and the blowing of the gas was stopped when the pH of the reaction solution became around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 5.0 μm, and the constituent particles have an average major axis of 0.7 μm.
m, an average minor axis of 0.25 μm, and an agglomerated calcium carbonate having an aspect ratio of 2.8 were observed.

Example 4 The primary reaction solution prepared in the same manner as in Example 1 was used as the reactor R.
-2 was charged in an amount of 1.5 l, and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was blown at 6.0 Nm ³ / hr for reaction. Simultaneously with the reaction, 28.5 l of the above lime milk adjusted to 100 g / l and 20 ° C. was continuously added so that the pH of the reaction solution was maintained at 12 to 12.5. The amount of gas at this time was 2.0 mol / hr per 1 mol of calcium in the mixed slurry, and the molar ratio of the total amount of calcium in the primary reaction liquid to the lime milk was 1:19. Further, the blowing of the carbon dioxide-containing gas was continued, and the blowing of the gas was stopped when the pH of the reaction solution became around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 9.3 μm, and the constituent particles have an average major axis of 0.8 μm.
m, average minor axis 0.30 μm, and agglomerated calcium carbonate having an aspect ratio of 2.7 was observed.

Example 1 Calcium hydroxide was suspended in water to prepare 50% by weight of lime milk, treated with a Choles mixer (high speed impeller disperser), diluted to 40% by weight, and the viscosity at 25 ° C. was measured. (B-type viscometer 60 rpm) was 2500 cp.

The obtained lime milk was adjusted to a concentration of 100 g / l and 15 ° C., 30 l was charged to the reactor R-1, and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was 9.1 Nm ³ / hr (calcium hydroxide 1 mol. (3.0 mol / hr), and reacted to a carbonation rate of 85%.

The obtained primary reaction liquid and the above lime milk were added and mixed at a molar ratio of each total calcium amount of 10: 1, and mixed,
The mixed milk concentration was adjusted to 100 g / l and the temperature was adjusted to 26 ° C., 30 l was charged to the reactor R-2, and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was 3.0 Nm ³ / hr (1.0 mol per 1 mol of calcium.
The reaction was carried out by blowing in the reaction solution at a pH of about 7 (mol / hr).

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 1.2 μm, and the constituent particles have an average major axis of 0.6 μm.
m, an average minor axis of 0.21 μm, and an agglomerated calcium carbonate having an aspect ratio of 2.9 were observed.

Example 6 The primary reaction solution and lime milk prepared in the same manner as in Example 5 were added and mixed in a ratio such that the molar ratio of each total calcium amount was 1: 1, and the mixed milk concentration was 100 g / l and the temperature was 25 ° C. To 30 liters of the reactor R-2, and the carbon dioxide concentration of 30
Gas reaction containing 4.5% by volume of carbon dioxide was performed at 4.5 Nm ³ / hr (1.5 mol / hr per 1 mol of calcium) until the pH of the reaction solution reached around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 3.2 μm, and the constituent particles have an average major axis of 0.6 μm.
m, average minor axis 0.22 μm, and agglomerated calcium carbonate having an aspect ratio of 2.7 was observed.

Example 7 The primary reaction solution and lime milk prepared in the same manner as in Example 5 were added and mixed at a ratio such that the molar ratio of each total calcium amount was 1: 5, and the mixed milk concentration was 100 g / l and the temperature was 20 ° C. To 30 liters of the reactor R-2, and the carbon dioxide concentration of 30
A gas containing carbon dioxide at a volume% of 6.0 Nm ³ / hr (2.0 mol / hr per 1 mol of calcium) was blown in and reacted until the pH of the reaction solution became around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 5.0 μm, and the constituent particles have an average major axis of 0.7 μm.
m, an average minor axis of 0.25 μm, and an agglomerated calcium carbonate having an aspect ratio of 2.8 were observed.

Example 8 The primary reaction solution and lime milk prepared in the same manner as in Example 5 were added and mixed in a ratio such that the molar ratio of each total calcium amount was 1:20, and the mixed milk concentration was 100 g / l and the temperature was 18 ° C. To 30 liters of the reactor R-2, and the carbon dioxide concentration of 30
A gas containing 9% by volume of carbon dioxide was blown and reacted at 9.0 Nm ³ / hr (3.0 mol / hr per 1 mol of calcium) until the pH of the reaction solution was around 7.

When the reaction product is observed with a scanning electron microscope, the average particle diameter is 9.4 μm, and the constituent particles have an average major axis of 0.8 μm.
m, average minor axis 0.30 μm, and agglomerated calcium carbonate having an aspect ratio of 2.7 was observed.

Comparative Example Calcium hydroxide was suspended in water and adjusted to 40% by weight.
When the viscosity at 0 ° C. was measured (B-type viscometer 60 rpm), it was 530 cp.

The obtained lime milk was reacted in the same manner as in Example 1. When the reaction product was observed with a scanning electron microscope, it was a mixture of aggregates and spindle-shaped particles.

Application Example 1 The calcium carbonates obtained in Examples 1 to 8 and Comparative Example were dehydrated using a filter press, dried, pulverized and classified.

A sodium polyacrylate dispersant (Aron manufactured by Toagosei Co., Ltd.) was added to the obtained powder in an amount of 1.0% by weight based on calcium carbonate to obtain a slurry having a solid content concentration of 60%. The viscosity of this slurry is shown in Table 1.

Next, 100 parts by weight of each calcium carbonate, 10 parts by weight of a binder (star eclipse # 4600) and SBR (JSR 0692) mixed at a weight ratio of 1: 4, and 1.5 parts by weight of a lubricant (calcium stearate). Was added and water was added to make a solid content concentration of 45% by weight, and a paper quality test was conducted using a slurry as a coating liquid. The results are shown in Table 2.

In addition, each physical property in Table 1 and Table 2 was measured as follows.

(1) Average major axis and minor axis: SEM photographs were used to measure the major axis and minor axis with digimatic calipers to obtain average values.

(2) Viscosity: Measured with a B-type viscometer at a rotor rotation speed of 60 rpm and a slurry temperature of 25 ° C.

(3) Whiteness: Measured according to JIS P 8123.

(4) White paper gloss: measured according to JIS P 8142.

(5) Print gloss: JIS using 0.4 ml of TKUG bit as ink
Measured according to P8142.

(6) K & N ink acceptability: The dichotomous value of K & N was measured with a Hunter whiteness meter.

(7) Ink Set: The transfer of ink after printing is measured by a Hunter-type whiteness meter.

Application Example 2 The calcium carbonates obtained in Examples 1 to 8 were dehydrated using a filter press, dried, pulverized and classified.

Next, add 2 parts of this calcium carbonate to pulp (100% LBKP).
After blending at a ratio of 0% by weight, and further adding a neutral sizing agent at a ratio of 0.2% by weight per calcium carbonate, hand-made with a beating degree (ccc, f, s) of 300 cc and a metric basis weight of 40 g / m ^2. Then, a paper containing calcium carbonate was obtained. The results are shown in Table 3.

In addition, each physical property in Table 3 was measured as follows.

(1) Yield: Calculated according to JIS P 8129.

(2) Whiteness: Measured according to JIS P 8123.

(3) Opacity: Measured according to JIS P 8136.

(4) Tensile strength: Measured according to JIS P 8113.

Claims (2)

[Claims] 1. A carbon dispersion containing a carbon dioxide-containing gas is prepared by adjusting a calcium hydroxide aqueous suspension having a concentration of 40% by weight and a viscosity at 25 ° C. of 2000 centipoises or more to 7 to 15% by weight in a gas dispersion stirring type reactor. Blow-in to cause a carbonation reaction to a carbonation rate of 70 to 95%, then transfer the obtained reaction solution (referred to as primary reaction solution) to a gas-blowing stirring type reactor,
While blowing a carbon dioxide-containing gas so that the pH is maintained at at least 12, a calcium hydroxide aqueous suspension having a concentration of 40 wt% and a viscosity of 2000 centipoise or more at 25 ° C. is added to the total amount of calcium in the primary reaction liquid and the water. The molar ratio of the total amount of calcium in the calcium oxide aqueous suspension is 10: 1 to 1: 1.
Continuous addition until reaching the range of 20 and further blowing carbon dioxide-containing gas until the pH of the reaction solution drops to around 7 to complete the carbonation reaction.
0.6-0.8μm, minor axis 0.21-0.30μm and aspect ratio 3
A method for producing agglomerated calcium carbonate having an average particle size of 1.0 to 10 μm, which is formed by aggregating calcium carbonate particles of less than 2. A carbon dioxide-containing gas is added to a dispersion of a calcium hydroxide aqueous solution having a concentration of 40% by weight and a viscosity of 2000 centipoise or more at 25 ° C. of 7 to 15% by weight in a gas dispersion stirring type reactor. Blow-in to cause a carbonation reaction to a carbonation rate of 70 to 95%, then transfer the resulting reaction liquid (referred to as the primary reaction liquid) to a gas-blowing stirring-type reactor, a concentration of 40 wt% and a viscosity of 2000 centipoise at 25 ° C. The above calcium hydroxide aqueous suspension is added at a ratio such that the molar ratio of the total calcium amount in the primary reaction liquid to the total calcium amount in the calcium hydroxide aqueous suspension is in the range of 10: 1 to 1:20. After that, a carbon dioxide-containing gas is blown in until the pH of the reaction solution decreases to around 7, and the carbonation reaction is completed, with a major axis of 0.6 to 0.8 μm, a minor axis of 0.21 to 0.30 μm and an aspect ratio of less than 3. Calcium carbonate grains There manufacturing method of agglomeration of calcium carbonate having an average particle diameter 1.0~10μm formed by aggregation.