JPH1111941A - Production of light calcium carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing efficiently and industrially advantageously a light calcium carbonate stable in grain shape and uniform in grain size while overcoming a fault of a conventional method by controlling the grain size using a feed crystal. SOLUTION: In the production of the light calcium carbonate in which either or both of a calcium hydroxide aq. suspension and a partially carbonated calcium hydroxide aq. suspension and the seed crystal are mixed, then carbon dioxide or a carbon dioxide-containing gas is blown into the obtained aq. suspension to carbonize it, the mixing is executed by a shearing agitating treatment of >=7 m/sec agitating peripheral speed or in the production of the light calcium carbonate in which the carbon dioxide or the carbon dioxide-containing gas is blown for carbonization while mixing the calcium hydroxide aq. suspension and the partially carbonated calcium hydroxide aq. suspension and the seed crystal, the mixing is executed by a shearing agitating treatment of >=7 m/sec agitating peripheral speed till a carbonating ratio reaches 50%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing light calcium carbonate. More specifically,
The present invention relates to an improvement in a method for controlling the particle diameter of light calcium carbonate using a calcium hydroxide aqueous suspension as a raw material and using seed crystals.

[0002]

2. Description of the Related Art Conventionally, light calcium carbonate has been industrially produced by using calcined lime obtained by calcining limestone as a raw material, and reacting this with water to prepare an aqueous suspension of slaked lime. Manufactured as light calcium carbonate by reacting with carbon, spindle-shaped, angular, columnar, needle-shaped, spherical, various forms such as agglomerates are produced, and several μm to Particles of various diameters up to coarse particles of several tens μm have been produced.

[0003] As for the control of the particle diameter, a seed crystal addition method is known industrially.
A method for producing calcium carbonate by adding calcium hydroxide to an ultrafine cubic calcium carbonate aqueous suspension having a particle size of less than μm (Japanese Patent Application Laid-Open No. 60-90818). A method of producing cubic calcium carbonate by adding an ultrafine seed crystal of 0.09 μm in the course of the carbonation reaction (Japanese Patent Publication No. 3-19165), and adding a calcium carbonate seed crystal to an aqueous solution of calcium salt at a specific ratio. After that, a method of adjusting the amount of calcium carbonate precipitated on the seed crystal surface by introducing carbon dioxide to control the average particle size (Japanese Patent Application Laid-Open No. 63-230520), a method of partially carbonated colloid A method of producing a predetermined spindle-shaped calcium carbonate having uniform and good dispersibility by adding an aqueous suspension of calcium hydroxide in a predetermined ratio until the carbonation ratio reaches a predetermined value (Japanese Patent Publication No. 8-18827) Report), a method in which an aqueous suspension of calcium oxide after wet digestion of calcium oxide is subjected to a liquid cyclone treatment and used as a raw material (JP-A-6-56422). ) Has been proposed. However, with these methods,
There is a drawback in that the amount of seed crystals necessary for controlling the particle size of calcium carbonate increases, and the amount of particles other than the desired calcium carbonate particle shape increases accordingly.
In addition, the present inventors previously added an aqueous suspension of colloidal calcium hydroxide partially carbonated as a seed crystal at 5% by weight or less until the carbonation ratio reached a predetermined value, and added the long diameter 1%. ~ 5μ
m, a method for producing spindle-shaped calcium carbonate having a minor axis of 0.3 to 1.5 μm (Japanese Patent Publication No. 8-18827) was proposed. However, in this method, the particle diameter varies, and the quality becomes unstable. There are problems such as becoming.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional method of controlling the particle size using such seed crystals,
An object of the present invention is to provide a method for producing light calcium carbonate having a stable particle shape and a uniform particle size in an industrially advantageous manner efficiently.

[0005]

The present inventors have conducted various studies to develop an industrial process for producing light calcium carbonate having the above-mentioned preferable characteristics. It has been found that the object can be achieved by performing a mixing treatment at a speed higher than a certain level, and the present invention has been completed based on this finding.

That is, the method for producing light calcium carbonate of the present invention comprises mixing a seed crystal with one or both of an aqueous suspension of calcium hydroxide and an aqueous suspension of partially carbonated calcium hydroxide. In producing light calcium carbonate by blowing carbon dioxide or a carbon dioxide-containing gas into the obtained aqueous suspension to cause carbonation, mixing is carried out by a shearing stirring treatment at a stirring peripheral speed of 7 m / s or more, or hydroxylation is performed. A method for producing light calcium carbonate by blowing carbon dioxide or a carbon dioxide-containing gas and carbonating while mixing the calcium aqueous suspension and the partially carbonated calcium hydroxide aqueous suspension with a seed crystal. The mixing was continued until the carbonation rate reached 50%.
It is characterized by performing the above-described shearing and stirring treatment.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is applicable to all light calcium carbonates produced using a seed crystal. It is also applicable when minimizing crystals, especially when minimizing crystals using seed crystals,
In particular, it is particularly effective when the carbonation reaction is carried out in a semi-batch reactor or a low-speed stirring reactor without a stirrer. This low-speed stirring type reactor is usually stirred at a low speed of 1 to 4 m / s.

[0008] Light calcium carbonate is classified into colloidal products and ordinary products by the Minor Calcium Carbonate Industrial Association. The ordinary products are calcite in which crystals are partially mixed with calcite or aragonite (hereinafter referred to as aragonite partially mixed calcium). In some cases, the mainstream is production of a crystal having a spindle type or a scalenohedral type. The usual production method is that a calcium hydroxide aqueous suspension is charged into a semi-batch reactor such as a cylindrical type or a cylindrical cone type in which only the lower part is conical, and a carbon dioxide-containing gas is introduced into the reactor. , A carbonation reaction to obtain an aqueous calcium carbonate suspension. The crystal is calcite or aragonite partially mixed calcite,
The crystal shape is spindle type or scalenohedral type (scalenoh)
Light calcium carbonate, which is edral), undergoes a carbonation reaction only with no stirring or low-speed stirring without high-speed stirring to reduce electricity costs and equipment costs, and obtains desired particles. In the case of manufacturing by the method, since the liquid stirring is weak, the miscibility between the seed crystal and the aqueous calcium hydroxide suspension is deteriorated, and problems such as instability of the quality of calcium carbonate occur. XRD is used to confirm the crystals of the obtained light calcium carbonate. A preferable crystal has a height ratio of the first peak of aragonite and the first peak of calcite of 50%.
Or less, preferably 5% or less, more preferably
Aragonite peak cannot be confirmed.

In the method of the present invention, the seed crystals may be one or both of an aqueous suspension of calcium hydroxide and an aqueous suspension of partially carbonated calcium hydroxide, ie, an aqueous suspension or part of an aqueous calcium hydroxide suspension. It is mixed with the carbonated calcium hydroxide aqueous suspension or both. This mixing treatment is carried out before, preferably immediately before, the carbonation reaction in which carbon dioxide or a carbon dioxide-containing gas is blown and carbonated, or is carried out during the carbonation reaction. It is necessary to perform the mixing treatment during the carbonation reaction until the carbonation rate reaches 50%, and it is particularly preferable to perform the mixing treatment at the beginning of the reaction. This mixing process must be performed by a shearing stirring process at a stirring peripheral speed of 7 m / s or more, preferably 10 m / s or more. The term “shear-stirring treatment” means a process of stirring a mixed component while applying a shearing force between the components. At a stirring peripheral speed of less than 7 m / s,
The miscibility of the seed crystal and the predetermined aqueous solution of calcium hydroxide is poor, the particle size varies, and the required amount of the seed crystal increases. The higher the stirring peripheral speed, the better the mixing properties of the liquid, the smaller the variation in particle diameter, and the smaller the required amount of seed crystals.

The mixing treatment is preferably carried out using a mixing tank, a mixing pump or a carbonation reaction tank for performing a carbonation reaction, which is preferably a liquid stirring type. It is preferable to install a baffle plate in these liquid stirring devices in order to increase the shearing force of the liquid. Preferred as the liquid stirring type mixing tank is a disper (also called a despar), and there are a uniaxial type and a biaxial type. Examples of the disperser include a Coreless mixer, a high-speed stirring type disperser, a Cornell disperser, a concentric twin-screw disperser, a batch ranger, a Diamix, and the like. When using a low-speed stirring type or non-stirring type carbonation reaction tank that does not satisfy the stirring peripheral speed requirement, the mixing process is performed in a mixing tank or a mixing pump that is a liquid stirring type satisfying the stirring peripheral speed requirement. preferable.

The seed crystal used in the present invention is not particularly limited as long as it is a substance commonly used for obtaining a desired particle shape, but the crystal shape is a spindle type or a scalenohedral type (sca).
In the case of obtaining lenohedral calcium carbonate, a spindle type or a scalenohedral type (scalenohedr) is used.
al) Calcium carbonate or colloidal calcium carbonate or partially carbonated colloidal calcium hydroxide is used, and when the crystals are minimized using seed crystals, colloidal calcium carbonate or partially carbonated Colloidal calcium hydroxide, especially colloidal calcium hydroxide having a carbonation rate of 10 to 50%, is preferably used. The seed crystal is added in an amount of 0.1 to 30% by weight, preferably 0.1 to 5% by weight, in terms of calcium hydroxide, based on the weight of the raw material calcium hydroxide. This addition rate varies depending on the desired particle size, and when the degree of minimization of the calcium carbonate particles is small,
When the addition amount is small and the degree of minimization is large, the addition amount is increased. If the addition ratio is less than 0.1% by weight, the effect of minimization cannot be obtained, and if it exceeds 30% by weight, the abundance ratio of particles other than the desired particles increases, and the physical properties deteriorate. Colloidal calcium carbonate is also called ultrafine calcium carbonate or ultrafine cubic calcium carbonate, 0.0
Colloidal particles of about 1 to 0.5 μm. Partially carbonated colloidal calcium hydroxide can be prepared by blowing carbon dioxide into lime milk and suspending carbonation during the production of colloidal calcium carbonate. As a preferred method of preparing the partially carbonated colloidal calcium hydroxide, a raw lime milk having a concentration of 2 to 5% by weight is adjusted to a temperature in the range of 5 to 20 ° C., and 1 kg of the starting calcium hydroxide is added. 100% carbon dioxide (1 atm, 2 atm)
3-12 L / min in terms of a gas state at 0 ° C.)
Indicates a liter), preferably by blowing a carbon dioxide-containing gas of 4 to 8 L / min, and stopping the blowing of the gas when the carbonation rate becomes 10 to 50%, preferably 15 to 25%. No. 6-56422).

The aqueous calcium hydroxide suspension used in the present invention can also be obtained by adding water to calcium hydroxide obtained by dry digestion of calcium oxide and mixing and emulsifying it. An aqueous suspension of digested calcium hydroxide is used. The aqueous calcium hydroxide suspension is preferably used after removing the residue. The removal of the residue is performed alone or in combination with a screen, a sieve, a hydrocyclone, or the like.
After removing coarse particles, fine particles are removed. This residue includes impurities such as silica and iron oxide, topsoil and wood chips, undigested calcium oxide, unfired limestone, and coarse particles of calcium hydroxide. It is preferable to make the cut point fine according to the required quality, and it is particularly preferable to use a hydrocyclone having a cut point of 20 μm or less. When the cut point is made coarse, the uniformity of the particles is lowered, and the presence of aggregated particles is also increased.

In the method of the present invention, carbon dioxide or a gas containing carbon dioxide is used for the carbonation reaction, but a gas containing carbon dioxide is industrially preferable. Preferably as a carbon dioxide-containing gas, a mixed gas containing carbon dioxide, for example, limestone fired exhaust gas such as limestone fired kiln exhaust gas,
The lime burning exhaust gas, the cement production kiln exhaust gas, the power generation boiler exhaust gas, the garbage exhaust gas, etc. of the pulp manufacturing plant are used. When the above various exhaust gases are used as the carbon dioxide-containing gas, dust such as limestone, lime, sulfur oxides, and unburned carbon is contained in the exhaust gases, so the dust is removed by using a bag filter, an electric dust collector, a dry scrubber, a wet type. Exhaust gas is purified by removing dust with a scrubber or a combination thereof. The exhaust gas may be a dry gas or a wet gas. In the case of a dry gas, after purifying to a certain extent with a bag filter or an electric dust collector in advance, and further purifying to a desired degree with a wet scrubber. In the case of a wet gas, it is preferable to purify to a desired degree with a multi-stage wet scrubber, or to purify to some extent with a wet electric precipitator before further purifying to a desired degree with a wet scrubber.

In the present invention, if necessary, a phosphorus compound can be added after the completion of the carbonation reaction or at a carbonation rate of 90% or more, whereby the zeta potential shifts to the positive side. In this case, the filler yield and opacity can be improved. The amount of the phosphorus compound to be added is preferably selected in the range of 0.05 to 2% by weight based on the dry weight of calcium carbonate. As the phosphorus compound, for example, a phosphoric acid salt such as phosphoric acid and ammonium phosphate, a condensed phosphoric acid such as hexametaphosphoric acid and its sodium salt, and a salt thereof are used.

[0015]

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

The physical properties are as follows. (1) Median diameter: It is an average diameter measured with a Microtrac SPA II type (trade name: laser type particle size distribution meter manufactured by Nikkiso Co., Ltd.). (2) +10 μm frequency: Microtrack SPA II
It is a frequency of 10 μm or more measured by a mold. (3) SEM particle diameter: SEM photograph (magnification × 10,000,
The average value of the measured values of the minor axis and the major axis of each of 50 to 100 particles observed in step 0) obtained by a digimatic caliper. (4) Solid content concentration: measured at 105 ° C. using a Mettler LP-16 type (manufactured by METTLER, infrared moisture meter). (5) Viscosity: Measured at 60 rpm (25 ° C.) using a Brooksfield type (B type) viscometer. (6) Zeta potential: Measured by a laser rotating prism type measuring device manufactured by PEN KEM.

The paper properties were measured according to the following methods. Yield: JIS P8129 Ash: JIS P8128 Whiteness: JIS P8123 Opacity: JIS P8136 Tensile strength: JIS P8113 White paper gloss: JIS P8142 Printing gloss: JIS P8142 (TKU as ink)
G-b 0.4 ml is used) Smoothness (Smooster): JAPAN TAPPI
No. 5 Smoothness (Bekk): JIS P8119 Air permeability: JIS P8117 K & N Acceptance: JAPAN TAPPI No. 46 Ink setability: Transfer of the ink after printing was measured by a Hunter whiteness meter. RI strength (dry pick): Using a RI-2 printability tester, visually check the peeled state of the paper after printing 50 times for 5-1.
(The higher the numerical value, the better the evaluation). RI strength (wet topic): After wetting with dampening water, printing was performed, and the peeling state of the paper was visually evaluated on a scale of 5 to 1 (the higher the numerical value, the better).

The calcium oxide used in each example was prepared by washing natural limestone with water, adjusting the particle size to C size (60 to 30 mm), and sieving calcium oxide equivalent to JIS special number, which was fired in a Beckenbach furnace. The particles (60 to 10 mm) are ground to 10 to 0 mm with a jaw crusher. The carbon dioxide-containing gas used in each example was 0.5 g / N
the dust concentration of m ³ a bag filter 0.005g / N
It was purified by dust by further reduced in wet scrubber to 0.003 g / m ³ to m ^3, a carbon dioxide concentration of 30% by volume of the separate case Bach type lime calciner exhaust gas.

Example 1 A 1000 L container was filled with 6 tap water from Mizuho-cho, Nishitama-gun, Tokyo.
After adding 100 L and adjusting the temperature to 60 ° C., 50 kg of calcium oxide was added while stirring at a stirring peripheral speed of 2.6 m / s (500 rpm), and stirring was continued. And filtered at 100 g /
A raw material calcium hydroxide aqueous slurry having a concentration of L was obtained.
A part of the raw material calcium hydroxide aqueous slurry is taken and tap water is added thereto to obtain a calcium hydroxide aqueous slurry having a concentration of 30 g / L. 30 L of this slurry is put into a 50 L batch type baffle-less coreless mixer (cylindrical type). Preparation,
After adjusting to 15 ° C., the stirring peripheral speed was 10 m / s (2550 r.
pm), while stirring the carbon dioxide-containing gas at 10 NL / m in terms of 100% by volume per 1 kg of calcium hydroxide.
in, and reacted until the carbonation rate became 30% to obtain a partially carbonated aqueous colloidal calcium hydroxide aqueous suspension, which was filtered through a 325 mesh sieve.
It was a seed crystal. 30 L of the aqueous calcium hydroxide slurry is placed in a 50 L batch-type boilerplate-less Coreless mixer, and the above-mentioned seed crystals are added at 1% by weight in terms of calcium hydroxide solid content, and stirred at a peripheral speed of 10 m / s (2550 rpm).
After stirring for 0 minutes, the obtained slurry was charged into a cylindrical cone type semi-batch reactor without a stirrer, adjusted to 50 ° C., and then a carbon dioxide-containing gas was supplied at a volume of 5 NL / kg of calcium hydroxide in terms of 100% by volume. The mixture was blown at a rate of min, and reacted until the carbonation rate reached 100%, to obtain an aqueous calcium carbonate suspension. The calcium carbonate obtained by filtering this through a 325 mesh sieve has a median diameter of 3.
Calcite-type spindle-shaped particles having an average major axis of 1.80 μm and an average minor axis of 0.51 μm had an SEM particle size of 82 μm.

Example 2 An aqueous calcium carbonate suspension was obtained in the same manner as in Example 1, except that the stirring peripheral speed in the above-mentioned Coreless mixer was changed to 25 m / s (6400 rpm). The calcium carbonate obtained by filtering this through a 325 mesh sieve was calcite-type spindle-shaped particles having a median diameter of 3.76 μm, an SEM particle diameter of an average major axis of 1.50 μm, and an average minor axis of 0.45 μm. .

Comparative Example 1 Example 1 was repeated except that the peripheral speed of the stirring in the above-mentioned Coreless mixer was changed to 5 m / s (1275 rpm).
In the same manner as in the above, an aqueous calcium carbonate suspension was obtained. The calcium carbonate obtained by filtering this through a 325 mesh sieve was calcite-type spindle-shaped particles having a median diameter of 4.02 μm, an SEM particle diameter of an average major axis of 2.00 μm, and an average minor axis of 0.55 μm. .

Example 3 The aqueous calcium hydroxide slurry obtained in the same manner as in Example 1 was passed through a two-liquid separation type Supercron T-10 having a cut point of 10 μm (manufactured by Oishi Kikai Co., Ltd., liquid cyclone). Median diameter of particle size distribution is 2.80μ
m, frequency of 10 μm or more is 2% by weight, concentration is 80 g / L
After preparing an aqueous slurry of the raw material calcium hydroxide, the slurry was put into a continuous mixer with a baffle plate, and seed crystals obtained in the same manner as in Example 1 were added at 2% by weight in terms of calcium hydroxide solid content, Stirring peripheral speed 10m / s (4
2,000 rpm) and an average residence time of 2 minutes. Then, the obtained slurry is charged into a cylindrical cone type semi-batch reactor without a stirrer, adjusted to 50 ° C., and carbon dioxide-containing gas is reduced to 1 kg of calcium hydroxide. 100 liters / volume and 5 NL / min.
The reaction was carried out until the concentration became 0% to obtain an aqueous calcium carbonate suspension. The calcium carbonate obtained by filtering this through a 325 mesh sieve was calcite-type spindle-shaped particles having a median diameter of 2.94 μm, an SEM particle diameter of an average major axis of 0.90 μm, and an average minor axis of 0.30 μm. .

Example 4 An aqueous calcium carbonate suspension was obtained in the same manner as in Example 3, except that the stirring peripheral speed in the stirring process with a continuous baffle-equipped Coreless mixer was changed to 25 m / s (10000 rpm). . Calcium carbonate obtained by filtering this through a 325 mesh sieve has a median diameter of 2.72 μm, SE
M particle size, average major axis 0.75μm, average minor axis 0.27μ
m calcite-type spindle-shaped particles.

Comparative Example 2 An aqueous calcium carbonate suspension was obtained in the same manner as in Example 4 except that the stirring peripheral speed in the stirring process with a continuous baffle-equipped Coreless mixer was changed to 5 m / s (2000 rpm). . The calcium carbonate obtained by filtering this through a 325 mesh sieve was calcite-type spindle-shaped particles having a median diameter of 3.12 μm, an SEM particle diameter of 1.1 μm in average major axis, and 0.35 μm in average minor axis. .

Example 5 The aqueous calcium hydroxide aqueous slurry obtained in the same manner as in Example 1 was passed through a two-liquid separation type Supercron T-10 having a cut point of 10 μm (manufactured by Oishi Kikai Co., Ltd., liquid cyclone). Median diameter of particle size distribution is 2.80μ
m, frequency of 10 μm or more is 2% by weight, concentration is 80 g / L
After preparing an aqueous slurry of the raw material calcium hydroxide, the slurry was put into a continuous mixer with a baffle plate, and seed crystals obtained in the same manner as in Example 1 were added at 2% by weight in terms of calcium hydroxide solid content, Agitation peripheral speed 25 m / s (1
0000 rpm) and an average residence time of 2 minutes, and then the obtained slurry is stirred at a peripheral speed of 3 m / s (760 rpm).
m), the mixture was charged into a cylindrical semi-batch reactor equipped with a low-speed stirrer operated at 50 ° C., and adjusted to 50 ° C., and then a carbon dioxide-containing gas was supplied at a rate of 5 NL / min in terms of 100% by volume per 1 kg of calcium hydroxide. Injection, carbonation rate 100%
To obtain an aqueous calcium carbonate suspension having a pH of 7.5. The calcium carbonate obtained by filtering this through a 325 mesh sieve has a median diameter of 2.95 μm,
SEM particle size: average major axis 0.75 μm, average minor axis 0.2
Calcite-type spindle-shaped particles having a particle diameter of 6 μm and a zeta potential of −5 mV were obtained.

Example 6 An aqueous calcium carbonate suspension having a pH of 8.5 was obtained in the same manner as in Example 5, except that the reaction was carried out until the carbonation ratio became 99.9%. To this was added 0.2% by weight of sodium hexametaphosphate in terms of calcium carbonate dry matter weight ratio. The calcium carbonate obtained by filtering this through a 325 mesh sieve has a median diameter of 2.69 μm, an SEM particle diameter of an average major axis of 0.74 μm, an average minor axis of 0.25 μm, and a zeta potential of +
It was a calcite-type spindle-shaped particle of 5 mV.

Application Example 1 The aqueous calcium carbonate slurries obtained in Examples 1 to 6 and Comparative Examples 1 and 2 were subjected to filtration and dehydration by a filter press to obtain a dehydrated cake having a solid content of 40% by weight. Was added to obtain a slurry of the dehydrated cake to obtain a calcium carbonate aqueous slurry having a solid content of 20 to 21% by weight and a viscosity of 150 to 450 cP. This slurry is appropriately diluted and mixed with 100 parts by weight of a pulp raw material obtained by mixing hardwood kraft pulp (350 csf) and softwood kraft pulp (450 csf) in a weight ratio of 7: 3. 0.2 parts by weight, 0.2 parts by weight of an alkyl ketene dimer as a neutral sizing agent, and 0.02 parts by weight of polyacrylamide as a retention aid were added.
g / m ² by hand using a square sheet machine
A calcium carbonate-filled paper was obtained. These properties are shown in Table 1 when using the calcium carbonate slurries obtained in Examples 1 and 2 and Comparative Example 1 corresponding thereto, and in Example 3
Table 2 shows the cases where the calcium carbonate slurries obtained in Comparative Examples 2 to 6 were used.

[0028]

[Table 1]

[0029]

[Table 2]

Thus, the calcium carbonate obtained in Examples 1 and 2 or Examples 3 to 6 is superior in whiteness and opacity as compared with those obtained in Comparative Examples 1 and 2. You can see that.

Application Example 2 The aqueous calcium carbonate slurries obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to filtration and dewatering by a filter press to obtain a dewatered cake having a solid content of 40% by weight, and then compressed by a belt press. Dehydration was performed to obtain a dehydrated cake having a solid concentration of 66% by weight. To the obtained dehydrated cake, SN-206 (Sodium polyacrylate dispersant, manufactured by San Nopco Co.) was added to calcium carbonate in an amount of 1.0% by weight in terms of solid content, and a Coreless mixer (6400 rpm, stirring peripheral speed 25 m / Perform primary dispersion for 5 minutes in s), and use a sand grinder SLG1 /
Secondary dispersion is performed by a type 2 (manufactured by IMEX Co., Ltd., continuous sand mill), and the solid content is 65 to 66% by weight and the viscosity is 20 to 5%.
An aqueous calcium carbonate slurry of 0 cP was obtained. This slurry was used for a pigment composition, and 100 parts by weight of starch (Japanese food processing # 4600) and 3 parts by weight of SBR (JSR
0692) 12 parts by weight, 1.5 parts by weight of Nopcoat C104 (manufactured by San Nopco, calcium stearate-based lubricant) and water are added, and the pH is adjusted with aqueous ammonia to prepare a coating color having a solid content concentration of 55% by weight. , Hand-coated on a commercial high quality paper with a coating rod (54g
/ M ² ), drying at 105 ° C. for 2 minutes, humidity control, and super calendering (linear pressure: 100 kg / cm, processing temperature: 105 ° C., processing speed: 8 m / min, number of nips: 2)
Times) and a paper quality test was performed. The results are shown in Table 3 when the calcium carbonate slurries obtained in Examples 1 and 2 and Comparative Example 1 corresponding thereto were used, and in Examples 3 and 4 and Comparative Example 2 corresponding thereto. Table 4 shows the obtained calcium carbonate slurries.

[0032]

[Table 3]

[0033]

[Table 4] From this, it can be seen that the calcium carbonate obtained in Examples 1 and 2 or Examples 3 and 4 has superior white paper gloss as compared with those obtained in Comparative Examples 1 and 2.

[0034]

According to the method of the present invention, as compared with the conventional seeding method, the particle size uniformity is improved, the particle size is uniform, the blurring is reduced, and as a result, the quality, especially the gloss of white paper, is improved. ,
In addition, the amount of seed crystals to be added can be reduced, and furthermore, light calcium carbonate having uniform and good dispersibility, particularly calcite or calcite mixed with some aragonite, has a spindle-shaped or triangular shape. Face type (scalen
light calcium carbonate can be obtained.

Claims (5)

[Claims] 1. A method comprising mixing a seed crystal with one or both of an aqueous suspension of calcium hydroxide and an aqueous suspension of partially carbonated calcium hydroxide, and adding carbon dioxide or carbon dioxide to the resulting aqueous suspension. A method for producing light calcium carbonate, wherein mixing is performed by a shearing stirring process at a stirring peripheral speed of 7 m / s or more when producing light calcium carbonate by blowing and carbonizing a carbon-containing gas. 2. Carbon dioxide or a carbon dioxide-containing gas is blown into and carbonated while mixing an aqueous suspension of calcium hydroxide and an aqueous suspension of partially carbonated calcium hydroxide with a seed crystal. A method for producing light calcium carbonate, characterized in that, in producing calcium carbonate, mixing is carried out by shearing stirring at a stirring peripheral speed of 7 m / s or more until the carbonation ratio reaches 50%. 3. A colloidal calcium carbonate particle or a partially carbonated colloidal calcium hydroxide particle is used as a seed crystal, and the amount thereof is 0.1 to 30% by weight based on calcium hydroxide. The production method according to claim 1 or 2, wherein the production range is within a range. 4. The process according to claim 1, wherein the aqueous calcium hydroxide suspension is obtained by removing the residue with a liquid cyclone. 5. After completion of the carbonation reaction or at a carbonation rate of 90
The method according to any one of claims 1 to 4, wherein the phosphorus compound is added in an amount of at least%.