JP2001114514A - Method for producing fusiform calcium carbonate with high dispersibility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for more easily producing on an industrial scale fusiform calcium carbonate of high dispersibility suitably usable as a loading material or the like for paper manufacturing. SOLUTION: This method for producing fusiform calcium carbonate of high dispersibility comprises introducing carbon dioxide into a calcium hydroxide slurry. Prior to or during the carbonation reaction step, at least one substance selected from fatty acids and metal salts thereof, manganese, iron, copper and zinc, and/or sparingly soluble inorganic microparticles are (is) added to the system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing spindle-shaped calcium carbonate which can be suitably used as a filler for papermaking and the like. More specifically, the present invention relates to a method for more easily producing spindle-shaped calcium carbonate having excellent dispersibility on an industrial scale by a carbonation reaction of introducing carbon dioxide into a calcium hydroxide slurry.

[0002]

BACKGROUND ART Calcium carbonate used industrially includes heavy calcium carbonate and synthetic (light) calcium carbonate. The former heavy calcium carbonate is a crushed product of limestone produced naturally, and can be produced by a relatively simple process of crushing and classification. However,
On the other hand, since the powder has a wide particle size distribution and an irregular shape peculiar to physical pulverization, it is difficult to produce a powder having excellent functionality provided by a uniform particle diameter and a uniform particle shape.

[0003] On the other hand, the latter synthetic calcium carbonate is produced by introducing carbon dioxide into a calcium hydroxide slurry and chemically precipitating the same.
By appropriately adjusting the conditions such as calcium hydroxide slurry concentration, carbonation temperature, and carbon dioxide introduction rate (carbonation rate), it is possible to control the particle shape and particle diameter in a certain range.

The shape of the synthetic calcium carbonate is as follows:
Colloidal with a particle diameter of 0.02 to 0.08 μm, cubic with a particle diameter of 0.1 to 0.2 μm, major axis 0.5 to 5.0 μm
m, spindle shape with a minor axis of 0.1 to 1.0 μm and major axis of 1.0
Columns of up to 5.0 μm and a minor diameter of 0.1 to 0.2 μm are known, and utilize the functions and characteristics expressed by their own particle diameters and particle shapes, respectively, for plastics, rubber, resins, papermaking, etc. Used in a wide range of fields.

[0005] Of these, spindle-shaped calcium carbonate is
It is widely used as a filler for papermaking. However,
It has a drawback of agglomeration during production, which hinders expansion of the field of application to other uses requiring dispersibility. In particular, for papermaking pigments, smoothness of the paper surface,
In terms of quality such as gloss and opacity and printability, high dispersibility of pigment particles is required. Therefore, cubic or columnar calcium carbonate having good dispersibility is generally used as a papermaking pigment.

[0006] On the other hand, spindle-shaped calcium carbonate can be synthesized at around normal temperature except for the disadvantage that it is agglomerated at the time of production. Cubic calcium carbonate which requires a step of repeating carbonation at low temperatures, or calcium carbonate at high temperatures As compared with columnar calcium carbonate which requires synthesis in, it can be produced relatively easily, and is excellent in terms of production equipment and production cost. Therefore, in order to provide spindle-shaped calcium carbonate having excellent dispersibility, various studies have been made since ancient times, and many proposals have been made.

For example, in the proposal, in the initial stage of the carbonation reaction, the amount of carbon dioxide to be introduced is strictly controlled to control the drop in slurry pH, and then one of water-soluble polysaccharides, sulfuric acid and sulfates is added. A method of adding the above (Patent No. 26
No. 04202), a method in which a partially carbonated colloidal particulate calcium hydroxide slurry is added to a calcium hydroxide slurry at a specific ratio (Japanese Patent No. 2730660), a method of adding high energy to a calcium hydroxide slurry as a raw material. In addition, there is a method of providing a step of converting calcium hydroxide into a finely dispersed state by performing high-shearing stirring (Japanese Patent No. 2857806).

Further, a method of adding a barium or strontium compound under the condition of generating basic calcium carbonate (Japanese Patent Laid-Open No. 5-238730), the activity of quick lime as a raw material, the method of preparing a calcium hydroxide slurry and the viscosity (JP-A-9-309723), a method of adding hydrogen peroxide and a chelating agent during the carbonation reaction (JP-A-2-243513), and the like.
It has been proposed as a method for synthesizing spindle calcium carbonate having good dispersibility.

However, any of these methods requires complicated manufacturing operations, requires special manufacturing equipment, or uses expensive additives. No examples have been adopted. In addition, although there is also known a method in which aggregated spindle-shaped calcium carbonate is crushed by a bead mill or the like to produce dispersed spindle-shaped calcium carbonate particles, equipment for crushing is required. The primary particles themselves are also destroyed by the process, and fine particles that are finer and irregular in shape than the spindle-shaped calcium carbonate are mixed, so that the uniformity of the calcium carbonate particles is reduced, and the quality of the product such as deterioration in fluidity is reduced. It will have an adverse effect.

[0010]

As described above, spindle calcium carbonate is one of the most excellent synthetic calcium carbonates in terms of easiness of production and economical efficiency. It has the disadvantage of forming agglomerates and is therefore only used in limited applications. If the disadvantages of this spindle-shaped calcium carbonate can be improved, it can be easily manufactured, and it becomes possible to manufacture spindle-shaped calcium carbonate with excellent dispersibility required on an industrial level, it will be possible to obtain highly dispersed pigments such as papermaking pigments. The present inventors have thought that the prospects for use in applications where sex is required can be opened.

In view of such circumstances, the present inventors have conducted intensive studies on a method of producing spindle calcium carbonate having excellent dispersibility in order to expand the application field of spindle calcium carbonate. The present inventors have found that the problem can be solved by a simple method of adding a specific substance in the process of producing spindle-shaped calcium carbonate by introducing carbon dioxide gas into a calcium slurry, and completed the present invention. That is, an object of the present invention is to provide a method for producing spindle-shaped calcium carbonate excellent in dispersibility by a method which can be industrially produced efficiently and stably and which is excellent in economic efficiency.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the present invention relates to a method for producing spindle-shaped calcium carbonate by introducing carbon dioxide into a calcium hydroxide slurry. Excellent dispersibility characterized by adding a compound comprising at least one selected from fatty acids or metal salts thereof, manganese, iron, copper, and zinc, and / or poorly soluble inorganic fine particles in the carbonation reaction process. A method for producing spindle-shaped calcium carbonate.

[0013] The production method of the present invention, which is a means for solving the above-mentioned problems, can be produced stably on an industrial scale efficiently and stably, and is excellent in economical efficiency. And a method for producing spindle-shaped calcium carbonate having good dispersibility.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The calcium hydroxide slurry, which is a raw material for the spindle-shaped calcium carbonate production method of the present invention, is a slurry obtained by adding water to quicklime containing calcium oxide as a main component and digesting it. The quick lime which is a raw material for producing calcium hydroxide slurry used in the present invention is not particularly limited, and it is a limestone which is produced naturally or a by-product in a production process of seafood such as shells, paper and sugar. It is obtained by calcining calcium carbonate or a calcium compound, such as a calcium carbonate-containing substance, which is discharged.

The quick lime digestion performed during the production process of the calcium hydroxide slurry includes a wet digestion method by adding water to quick lime and a dry digestion method by steam, both of which include a ratio of quick lime to water and a digestion temperature. It is known that the properties of the generated calcium hydroxide differ depending on the conditions described above. About calcium hydroxide that can be used in the present invention,
Although there is no particular limitation, considering that the carbonation reaction raw material is in a slurry state of calcium hydroxide, a quick concentration of calcium hydroxide slurry is prepared by digesting quicklime with a wet method, and then diluting or concentrating it. It is most efficient to do so.

The concentration of the calcium hydroxide slurry is not particularly limited, but is preferably adjusted within a range of 5 to 20% by weight. The reason is that the slurry concentration is 5
If it is less than 10% by weight, the amount of calcium carbonate obtained in one reaction is small, which is disadvantageous in terms of production efficiency. Also, 2
If the content exceeds 0% by weight, the viscosity of the slurry increases, and sufficient stirring becomes difficult, which may cause a problem in performing a uniform carbonation reaction.

As the carbon dioxide to be introduced into the calcium hydroxide slurry, it is most economical to use a carbon dioxide-containing gas such as an exhaust gas generated during the production of quick lime or another combustion step, directly or after washing. It is a target. At this time, the concentration of carbon dioxide in the gas is not particularly limited, but if the concentration is low, the efficiency of the carbonation reaction is reduced.
Desirably, it is not less than the capacity%.

As conditions for introducing carbon dioxide into the calcium hydroxide slurry to carry out the carbonation reaction, the temperature of the slurry at the start of the carbonation reaction and the introduction rate of carbon dioxide become important. If these conditions are not properly adjusted, the desired spindle-shaped calcium carbonate may not be produced.

The slurry temperature for starting the carbonation reaction is 2
The temperature is preferably adjusted to 0 to 50 ° C. If the temperature is lower than this, colloidal calcium carbonate is apt to be generated, and if it is too high, aragonite of columnar calcium carbonate is easily mixed into the product, and the particle shape and particle size of the product become inhomogeneous. Often causes inconvenience. The temperature of the slurry after the start of the carbonation reaction does not need to be particularly adjusted within the range of 0 to 70 ° C. until the reaction is completed.

The amount of the carbon dioxide-containing gas introduced into the calcium hydroxide slurry is preferably 0.1 to 10 liter / min per kg of calcium hydroxide in terms of carbon dioxide. If the amount is smaller than this, columnar aragonite is more likely to be mixed, and if it is larger, colloidal calcium carbonate is more likely to be generated.

The present invention provides a method for producing a fatty acid or a metal salt thereof in a reaction process for carbonating a calcium hydroxide slurry.
It is characterized by adding a compound comprising at least one selected from manganese, iron, copper and zinc, and / or hardly soluble inorganic fine particles. The additive substance is selected from fatty acids or metal salts thereof, compounds composed of manganese, iron, copper, and zinc, and hardly soluble inorganic fine particles. One or more of a group of compounds consisting of at least one selected from iron, copper, and zinc and a group of hardly soluble inorganic fine particles may be used, or two or more of them may be used. Good. Further, two or more types may be selected from two or more groups.

The fatty acid or its metal salt to be added may be a pure substance or a mixture as long as it has 18 or less carbon atoms, and is preferably a straight-chain saturated fatty acid having 14 or less carbon atoms or its metal salt. Specifically, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid,
Caprylic acid, capric acid, lauric acid, myristic acid,
Palmitic acid, stearic acid, palmitoleic acid, oleic acid or metal salts thereof such as sodium, potassium, lithium, magnesium, calcium, strontium, barium, aluminum, iron, manganese and zinc can be used.

[0023] The amount of calcium hydroxide
The amount is preferably from 1 mmol to 10 mol per kg, and if less than this, there is no effect on dispersibility. In addition, even if it is added in an amount of 10 mol or more per 1 kg of calcium hydroxide, the effect on dispersibility is not changed from that in the case of less than 10 mol. In addition, as a form at the time of addition, if it is a fatty acid that is liquid at normal temperature, it may be in a liquid state or diluted with a solvent such as water, or if it is a solid fatty acid or a metal salt thereof at normal temperature, it may be in a solid state What is necessary is just to add in the state melt | dissolved in solvents, such as water.

The time for the addition is preferably before the start of the carbonation reaction or after the start of the carbonation reaction and before the carbonation ratio reaches 60%. If the addition time is later than this, the effect on the dispersibility is almost lost. The carbonation rate in the present invention is represented by the following equation. Carbonation rate (%) = (weight of calcium in generated calcium carbonate / total weight of calcium present in reaction system) ×
100

The compound comprising manganese, iron, copper and zinc to be added may be any industrially usable oxide, hydroxide, inorganic acid salt or organic acid salt. Specifically, for example, manganese compounds such as manganese chloride, manganese borate, manganese sulfate, manganese carbonate, and manganese acetate; iron compounds such as iron sulfate, iron chloride, and iron nitrate; copper nitrate, copper sulfate, copper chloride, and pyrophosphoric acid Copper compounds such as copper and zinc compounds such as zinc oxide, zinc chloride, zinc carbonate and zinc sulfate can be used.

The amount of addition is 0.05 to 100 g per 1 kg of calcium hydroxide in terms of metal weight. If it is less than this, there is no effect on dispersibility, and if it is more than this, the desired spindle-shaped calcium carbonate is formed. It may be difficult. The form of addition may be a solid, a solution dissolved in a solvent such as water, or a suspension. The addition is preferably performed before the start of the carbonation reaction or after the start of the carbonation reaction and before the carbonation ratio reaches 60%. If the addition time is later than this, the effect on the dispersibility is almost lost.

The hardly soluble inorganic fine particles to be added are inorganic fine particles at least a part of which can be stably present as a solid in a calcium hydroxide slurry at the minimum value of the amount of addition described below. , Kaolin, heavy calcium carbonate and the like can be used. The particle shape is not particularly limited, but the average particle size is preferably 50 μm or less, more preferably 30 μm or less. Selection of the average particle size is most effective for forming spindle-shaped calcium carbonate having good dispersibility.

Titanium oxide is classified into anatase type and rutile type depending on the crystal structure. Both types can be used, and titanium oxide treated with an aluminum, silicon, zinc, zirconium type surface treating agent or an organic type surface treating agent can be used. Good. The talc is preferably obtained by finely pulverizing ore produced in nature or finely pulverized, or, in applications requiring whiteness such as papermaking, desirably improving the whiteness by removing iron.

As the kaolin, there can be used fine-grained kaolin, delaminated kaolin, or calcined kaolin obtained by calcining, which is obtained by finely pulverizing ore produced in nature. Heavy calcium carbonate is obtained by finely pulverizing naturally occurring limestone, but the limestone used as the raw material is white in crystalline white limestone, such as for papermaking, rather than general gray cryptic microcrystalline limestone. It is preferable for applications that require a certain degree.

The amount of addition may be 1 g or more per 1 kg of calcium hydroxide, and if less than this, the effect on dispersibility is hardly obtained. Further, even if 2 kg or more is added per 1 kg of calcium hydroxide, no change is observed in the dispersibility as compared with the case of less than 2 kg, but an amount exceeding 2 kg may be added at all.

Regarding the form of the hardly soluble inorganic fine particles at the time of addition, they may be added as powder or in the form of a suspension dispersed in water or the like. The timing of addition is preferably before the start of the carbonation reaction or after the start of the carbonation reaction and before the carbonation rate reaches 80%. If the addition time is later than this,
Almost no effect on decentralization.

The addition of one or more compounds selected from fatty acids or metal salts thereof, manganese, iron, copper, and zinc, and the hardly soluble inorganic fine particles during the carbonation process may be carried out from any one group. Not only when one or two or more kinds are selected and performed, two or more kinds may be selected from two or more groups and added. The amount of addition at that time may be performed under the same conditions as in the range of the above-mentioned addition conditions, that is, the case where one or two or more kinds are selected from any one group.

The completion of the carbonation reaction in the present invention can be determined by the pH of the slurry being reduced to near neutrality. That is, during the carbonation reaction, the pH of the slurry is 1 due to the presence of unreacted calcium hydroxide.
Although it shows an alkalinity of 1 to 13, the pH of the slurry becomes near neutral when the reaction is completed and the calcium hydroxide is consumed.

The spindle-shaped calcium carbonate obtained by the above method has a major axis of 0.5 to 5 μm and a minor axis of 0.1 to 1.0 μm.
It has a spindle shape of μm. Spindle-like calcium carbonate obtained by a known manufacturing method has poor dispersibility and is mostly 5 to 10
In contrast to the formation of a strong aggregate of μm, the production method of the present invention provides spindle calcium carbonate having extremely excellent dispersibility, and the spindle calcium carbonate requires a pigment for papermaking and a high dispersibility. Demonstrates excellent performance in other applications.

[0035]

EXAMPLES 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 to these examples and the like, and is understood by the description of the claims. It goes without saying that it is a thing.

Example 1 1.5 kg of industrial quicklime was added to 70
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, after removing digestion residue with a 100-mesh aperture sieve, tap water was added and 8.5% by weight.
20 kg of a calcium hydroxide slurry was prepared. After adjusting the temperature of the calcium hydroxide slurry to 30 ° C., a carbonation reaction was performed by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 14.0 liter / min per kg of calcium hydroxide.

At that time, when the carbonation rate became 5%, 0.5 mol of sodium acetate (calcium hydroxide 1
(0.29 mol per kg) and the mixture gas was continuously introduced to continue the carbonation reaction.
When the number reached 7, the carbonation reaction was terminated. In the obtained product, observation by a scanning electron microscope (SEM) showed that the primary particles were spindle-shaped calcium carbonate having a major axis of 1.5 μm and a minor axis of 0.3 μm, of which about 30% were monodisperse particles. .

Example 2 20 kg of a 8.7% by weight calcium hydroxide slurry prepared in the same manner as in Example 1 was adjusted so that the slurry temperature became 35 ° C., and an industrial fatty acid soap (Nippon Oil & Fats Co., Ltd.) 0.17 mol (Calcium hydroxide 1k)
(0.10 mol per g) was added, and a carbonation reaction was performed by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 13.5 liter / min per kg of calcium hydroxide. In the obtained product, observation by SEM showed that the primary particles were spindle-shaped calcium carbonate having a major axis of 1.5 μm and a minor axis of 0.3 μm, of which about 50% were monodisperse particles.

Example 3 2.0 kg of industrial quicklime was added to 70
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, digestion residue was removed with a 100-mesh aperture sieve, and tap water was added to prepare 20 kg of a 10.2% by weight calcium hydroxide slurry. After adjusting the temperature of the calcium hydroxide slurry to 40 ° C., a carbonation reaction was carried out by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 16.5 liter / min per kg of calcium hydroxide.

At that time, when the carbonation rate became 10%,
10.0 g of zinc chloride (2.4 g per 1 kg of calcium hydroxide in terms of the amount of metal) as a reagent was added, and a mixed gas was continuously introduced to continue the carbonation reaction. When the slurry pH reached 7, The carbonation reaction was terminated. In the obtained product, primary particles are spindle-shaped calcium carbonate having a major axis of 0.8 μm and a minor axis of 0.2 μm as observed by SEM, of which about 30% are monodisperse particles, and the aggregates also have an aggregate particle size. It was as small as about 2 μm.

Example 4 20 kg of a 10.6% by weight calcium hydroxide slurry prepared in the same manner as in Example 3
Is adjusted to 30 ° C. and 3.0 g of copper nitrate as a reagent (0.48 g per 1 kg of calcium hydroxide in terms of the amount of metal)
Was added thereto, and a carbonation reaction was performed by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 15.0 liter / min per 1 kg of calcium hydroxide. In the obtained product, primary particles are spindle-shaped calcium carbonate having a major axis of 1.0 μm and a minor axis of 0.2 μm as observed by SEM, of which about 40% are monodisperse particles, and the aggregates also have an aggregate particle size. It was as small as 2 μm.

Example 5 20 kg of a 10.8% by weight calcium hydroxide slurry prepared in the same manner as in Example 3
Was adjusted to 30 ° C., and 25.0 g of ferrous chloride as a reagent (5.1 per kg of calcium hydroxide in terms of the amount of metal) was adjusted.
g), a mixed gas of carbon dioxide and air having a concentration of 25% by volume was mixed with 15.1 per kg of calcium hydroxide.
Carbonation reaction was carried out by introducing at a rate of liter / min.
In the obtained product, primary particles were spindle-shaped calcium carbonate having a major axis of 1.5 μm and a minor axis of 0.3 μm as observed by SEM, and about 30% of the primary particles were monodisperse particles.

Example 6 20 kg of a 10.5% by weight calcium hydroxide slurry prepared in the same manner as in Example 3
Was adjusted to 35 ° C., and the reagent manganese chloride hexahydrate was used.
After adding 0 g (5.6 g per kg of calcium hydroxide in terms of the amount of metal), a mixed gas of carbon dioxide and air having a concentration of 25% by volume was fed at a rate of 14.2 l / min per kg of calcium hydroxide. To carry out a carbonation reaction. In the obtained product, primary particles are spindle-shaped calcium carbonate having a major axis of 0.5 μm and a minor axis of 0.1 μm as observed by SEM, of which about 40% are monodisperse particles and the aggregates have an aggregate particle size of 1 to 10. It was as small as 2 μm.

Example 7 1.0 kg of industrial quicklime was added to 70
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, digestion residue was removed with a 100-mesh opening sieve, and tap water was added to prepare 20 kg of a 5.1% by weight calcium hydroxide slurry. After adjusting the slurry temperature to 28 ° C., a carbonation reaction was performed by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 7.9 liter / min per kg of calcium hydroxide.

At this time, when the carbonation ratio became 5%, fine titanium oxide (Taipe A-10 manufactured by Ishihara Sangyo Co., Ltd.) was used.
0, anatase type, particle size 0.15 μm) 200 g (200 g per 1 kg of calcium hydroxide) was added and the mixture gas was continuously introduced to continue the carbonation reaction. When the slurry pH reached 7, the carbonation reaction was started. Finished. Observation by SEM of the obtained product showed that the primary particles were spindle-shaped calcium carbonate having a major axis of 2.0 μm and a minor axis of 0.4 μm, of which about 60% were monodisperse particles.

[Embodiment 8] The same operation as in Embodiment 7 is performed to obtain 5.0.
Prepare 20 kg of calcium hydroxide slurry by weight%,
After adjusting the slurry temperature to 30 ° C., a mixed gas of carbon dioxide and air having a concentration of 25% by volume was mixed with 1 k of calcium hydroxide.
Carbon dioxide was introduced at a rate of 8.2 l / min per g to carry out a carbonation reaction.

At that time, when the carbonation rate became 5%, talc (Kinseimatic Co., Ltd., average particle diameter 12 μm) was used.
m) 300 g (300 kg / kg of calcium hydroxide)
g) was added and a mixed gas was continuously introduced to continue the carbonation reaction. When the slurry pH reached 7, the carbonation reaction was terminated. In the obtained product, the primary particles were spindle-shaped calcium carbonate having a major axis of 1.5 μm and a minor axis of 0.3 μm as observed by SEM, and about 20% of them were monodisperse particles.

[Embodiment 9] The operation is performed in the same manner as in Embodiment 7 and 5.2.
Prepare 20 kg of calcium hydroxide slurry by weight%,
After adjusting the slurry temperature to 30 ° C., a mixed gas of carbon dioxide and air having a concentration of 25% by volume was mixed with 1 k of calcium hydroxide.
The mixture was introduced at a rate of 8.0 liter / min per g to carry out a carbonation reaction.

At that time, when the carbonation rate became 15%,
Kaolin (Engelhard Co., average particle size 2μm) 3
00g (290 g per 1 kg of calcium hydroxide), and the carbonation reaction was continued.
When H reached 7, the carbonation reaction was terminated. In the obtained product, the primary particles had a major diameter of 1.
Spindle-shaped calcium carbonate having a diameter of 0 μm and a minor diameter of 0.2 μm, of which about 40% was monodisperse particles.

Example 10 3.0 kg of industrial quicklime was added to 7
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, digestion residue was removed with a 100 mesh sieve, and tap water was added to prepare 20 kg of a 15.2% by weight calcium hydroxide slurry. After adjusting the slurry temperature to 30 ° C., 1 kg of calcium hydroxide was mixed with a mixed gas of carbon dioxide and air having a concentration of 25% by volume.
At a rate of 17.8 liters / min to perform a carbonation reaction.

At this time, when the carbonation rate became 35%, 600 g of heavy calcium carbonate (manufactured by Nippon Steel Mining Co., Ltd., average particle size 1.2 μm) (200 g / kg of calcium hydroxide) was suspended. The carbonation reaction was continued by adding the liquid and continuously introducing a mixed gas. When the slurry pH reached 7, the carbonation reaction was terminated. Observation by SEM showed that the primary particles had a major axis of 1.5 μm.
m, a spindle-shaped calcium carbonate having a minor axis of 0.3 μm, of which about 50% was monodisperse particles.

Example 11 1.5 kg of industrial quicklime was added to 7
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, digestion residue was removed with a 100 mesh sieve, and tap water was added to add 7.4% by weight.
20 kg of a calcium hydroxide slurry was prepared. The slurry temperature was adjusted to 30 ° C., and the reagent, zinc sulfate, 5.0 g
(Converted to the amount of metal, 1.
After adding 4 g) of the aqueous solution, a carbonation reaction was performed by introducing a mixed gas of carbon dioxide and air having a concentration of 25% by volume at a rate of 9.9 liter / min per kg of calcium hydroxide.

At this time, when the carbonation rate reached 15%, sodium laurate (0.23 mol, 0.15 mol per 1 kg of calcium hydroxide) was added, and a mixed gas was continuously introduced. Was continued, and the carbonation reaction was terminated when the slurry pH reached 7. In the obtained product, primary particles are spindle-shaped calcium carbonate having a major axis of 1.0 μm and a minor axis of 0.2 μm as observed by SEM, of which about 70% are monodisperse particles, and the particle aggregate is also an aggregate particle size. Was as small as 1 to 2 μm.

Example 12 In the same manner as in Example 11, 20 kg of a 7.6% by weight calcium hydroxide slurry was prepared, and the slurry temperature was adjusted to 30 ° C. 1.0 g of copper sulfate as a reagent (calculated as 1 kg of calcium hydroxide
0.26 g per 1 kg), and a mixed gas of carbon dioxide and air having a concentration of 25% by volume is mixed with 1 kg of calcium hydroxide.
At a rate of 2.5 liters / min per unit to carry out a carbonation reaction.

At this time, when the carbonation ratio became 10%, fine titanium oxide (Taipe A manufactured by Ishihara Sangyo Co., Ltd.) was used.
−100, particle size 0.15 μm) 200 g (130 g per kg of calcium hydroxide) was added, and a mixed gas was continuously introduced to continue the carbonation reaction.
When H reached 7, the carbonation reaction was terminated. In the obtained product, primary particles were 0.8 μm in major axis and 0.15 μm in minor axis in the form of spindle-shaped calcium carbonate observed by SEM, of which about 60% were monodisperse particles, and the aggregates also had an aggregate particle size. It was as small as 1-2 μm.

Example 13 In the same manner as in Example 11, 20 kg of a 7.5% by weight calcium hydroxide slurry was prepared, and the slurry temperature was adjusted to 35 ° C. Heavy calcium carbonate (manufactured by Nippon Steel Mining Co., Ltd., average particle size 1.2 μm) 25
After adding 0 g (170 g per kg of calcium hydroxide), a mixed gas of carbon dioxide and air having a concentration of 25% by volume was added to 10.3 l / kg of calcium hydroxide.
The carbonation reaction was performed by introducing at a rate of min.

At that time, when the carbonation rate became 5%,
20 mmol of butyric acid (13 mmol per 1 kg of calcium hydroxide) as a reagent was added, and a mixed gas was continuously introduced to continue the carbonation reaction. When the slurry pH reached 7, the carbonation reaction was terminated. The obtained product has a primary particle having a major axis of 2.0 μm as observed by SEM,
Spindle-shaped calcium carbonate having a minor axis of 0.4 μm, of which about 50% was monodisperse particles.

[Comparative Example 1] 1.5 kg of industrial quicklime was added to 70
It was poured into 10 kg of tap water heated to 0 ° C., stirred for 30 minutes and digested. Subsequently, digestion residue was removed with a 100-mesh aperture sieve, and tap water was added to prepare 2 kg of a 8.6% by weight calcium hydroxide slurry. After adjusting the calcium hydroxide slurry temperature to 30 ° C.,
A mixed gas of volume% carbon dioxide and air was introduced at a rate of 14.5 liters / min per kg of calcium hydroxide, and the reaction was terminated when the pH of the slurry reached 7. The obtained product was spindle-shaped calcium carbonate having a primary particle diameter of 1.5 μm in major axis and a minor axis of 0.3 μm in observation by SEM, but formed a strong aggregate of 5 to 10 μm and was dispersed. No particles were found.

Comparative Example 2 A calcium hydroxide slurry was prepared in the same manner as in Comparative Example 1, the slurry temperature was adjusted to 30 ° C., and then 0.1 mmol of acetic acid reagent (0.06 mmol per 1 kg of calcium hydroxide). Was added, and a carbonation reaction was performed under the same conditions as in Comparative Example 1. The obtained product had a primary particle diameter of major axis 1.
Although it was a spindle-shaped calcium carbonate having a diameter of 5 μm and a minor diameter of 0.3 μm, a strong aggregate of 5 to 10 μm was formed, and the presence of dispersed particles was not recognized.

Comparative Example 3 A calcium hydroxide slurry was prepared in the same manner as in Comparative Example 1, the slurry temperature was adjusted to 30 ° C., and then 0.05 g of copper nitrate (in terms of metal amount, water After adding 0.02 g per 1 kg of calcium oxide), a carbonation reaction was performed under the same conditions as in Comparative Example 1. The obtained product was spindle-shaped calcium carbonate having a primary particle diameter of 1.5 μm in major axis and a minor axis of 0.3 μm in observation by SEM, but formed a strong aggregate of 5 to 10 μm and was dispersed. No particles were found.

[Comparative Example 4] A calcium hydroxide slurry was prepared in the same manner as in Comparative Example 1, the slurry temperature was adjusted to 30 ° C, and then 500 g of iron chloride reagent (calculated as metal After adding 170 g / kg), a carbonation reaction was performed under the same conditions as in Comparative Example 1.
The obtained product was colloidal calcium carbonate having a primary particle size of 0.06 μm as observed by SEM.

[Comparative Example 5] A calcium hydroxide slurry was prepared in the same manner as in Comparative Example 1, the slurry temperature was adjusted to 30 ° C, and a mixed gas of carbon dioxide and air having a concentration of 25% by volume was added to water. Carbon dioxide was introduced at a rate of 14.4 liters / min per kg of calcium oxide to carry out a carbonation reaction.

At that time, when the carbonation rate became 10%,
Reagent behenic acid 0.5mol (calcium hydroxide 1kg
(0.3 mol / mol) was added and a mixed gas was continuously introduced to continue the carbonation reaction. When the slurry pH reached 7, the carbonation reaction was terminated. The obtained product was spindle-shaped calcium carbonate having a primary particle diameter of 1.5 μm in major axis and 0.3 μm in minor axis as in Comparative Example 1 as observed by SEM, but a strong aggregate of 5 to 10 μm was formed. And the presence of dispersed particles was hardly observed.

[0064]

According to the present invention, in a process for producing spindle-shaped calcium carbonate, a fatty acid or a metal salt thereof, a compound composed of manganese, iron, copper, or zinc, and / or poorly soluble inorganic fine particles are added during the carbonation reaction. In addition to the simple method described above, there is an excellent effect that a spindle-shaped calcium carbonate excellent in dispersibility can be obtained by a method using a compound that is safe and easily available. The spindle-shaped calcium carbonate having excellent dispersibility obtained by the production method of the present invention exhibits excellent performance in applications requiring high dispersibility, such as papermaking pigments.

Continued on front page F term (reference) 4G076 AA16 AB06 AB21 AB26 AC02 BA34 BB05 BB06 BB08 BC02 BD01 BD02 CA03 CA05 DA02 4L055 AG04 AG06 AG07 AG08 AG10 AG11 AG12 AG19 AG20 AG23 AG26 AG27 AG34 AG94 AH01 EA30 EA32 FA30

Claims (7)

[Claims] 1. A method for producing spindle-shaped calcium carbonate by introducing carbon dioxide into a calcium hydroxide slurry, wherein a carbonic acid is selected from fatty acids or metal salts thereof, manganese, iron, copper and zinc during the carbonation reaction. A method for producing spindle-shaped calcium carbonate having excellent dispersibility, characterized by adding a compound comprising at least one compound and / or poorly soluble inorganic fine particles. 2. The method according to claim 1, wherein the fatty acid or its metal salt has 1 carbon atom.
The method for producing spindle-shaped calcium carbonate according to claim 1, wherein the fatty acid or the metal salt thereof is 8 or less. 3. The method according to claim 1, wherein the fatty acid or the metal salt thereof has 1 carbon atom.
The process for producing spindle-shaped calcium carbonate according to claim 1 or 2, which is not more than 4 straight-chain saturated fatty acids or metal salts thereof. 4. The process for producing spindle-shaped calcium carbonate according to claim 1, wherein the amount of the fatty acid or its metal salt added is 1 mmol to 10 mol per 1 kg of calcium hydroxide. 5. The method according to claim 1, wherein the amount of the compound comprising at least one selected from manganese, iron, copper and zinc is 0.05 to 100 g per kg of calcium hydroxide in terms of metal weight. Manufacturing method of spindle calcium carbonate. 6. The method for producing spindle-shaped calcium carbonate according to claim 1, wherein the hardly soluble inorganic fine particles are one or more selected from titanium oxide, talc, kaolin, and heavy calcium carbonate. 7. The method for producing spindle-shaped calcium carbonate according to claim 1, wherein the addition amount of the hardly soluble inorganic fine particles is 1 g or more per 1 kg of calcium hydroxide.