JPH04292414A - Method for growing particle of vaterite-type calcium carbonate and controlling its shape - Google Patents

Abstract

PURPOSE:To easily and stably produce vaterite-type calcium carbonate having arbitrary particle size and shape and excellent decomposability by using a vaterite-type calcium carbonate as a matrix. CONSTITUTION:The objective method for controlling the growth and shape of vaterite-type calcium carbonate particle is characterized by introducing carbon dioxide gas into a mixed system consisting of a vaterite-type calcium carbonate matrix, methanol, water and quick lime and/or slaked lime and satisfying the following conditions (a) and (b) and carrying out the carbonization reaction while controlling the pH of the carbonization reaction system to 5.6-11.5 and the temperature to 15-60 deg.C. (a) The amount of water existing in the carbonization reaction system is 3-30 times mol equivalent based on the amount of calcium carbonate and the quick lime and/or slaked lime (in terms of quick lime) existing in the carbonization reaction system and (b) the solid concentration of calcium carbonate and the quick lime and/or slaked lime (in terms of quick lime) existing in the carbonization reaction system is 0.5-12wt.% based on methanol existing in the carbonization reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling particle growth and morphology of vaterite-type calcium carbonate, and more specifically,
A vaterite-type calcium carbonate having a shape of an ellipsoid, a sphere, a plate, etc. is used as a base material, and the particle size and particle shape of the base material vaterite-type calcium carbonate are changed, and the particle size and particle size are different from that of the base material vaterite-type calcium carbonate. The present invention relates to a method for controlling particle growth and morphology of vaterite-type calcium carbonate, which prepares vaterite-type calcium carbonate having a shape and good dispersibility. [0002]Currently, the carbon dioxide gas method is widely used as an industrial method for producing synthetic calcium carbonate. This carbon dioxide gas method involves obtaining quicklime (calcium oxide) by burning naturally occurring limestone, and reacting this quicklime with water to obtain milk of lime (an aqueous suspension of calcium hydroxide).
This is a method of obtaining calcium carbonate by introducing carbon dioxide gas generated when calcining limestone into this milk of lime and causing a reaction. Synthetic calcium carbonate produced by this carbon dioxide gas method is widely used in large quantities as a filler or pigment for rubber, plastic, paper, paint, etc., depending on the size of its primary particles. In addition, in order to further improve the physical properties of synthetic calcium carbonate used for these purposes, the particle surface is generally treated with various inorganic or organic treatment agents depending on the purpose of use. ing. However, synthetic calcium carbonate produced by this carbon dioxide gas method originally has a very strong cohesive force between primary particles, and many primary particles aggregate to form large secondary particles (primary particles). It is said that it is impossible to disperse this slurry of secondary particles into almost primary particles even if the slurry is vigorously stirred for a long time. When synthetic calcium carbonate containing a large number of aggregates of primary particles is used as a filler or pigment for rubber, plastic, paper, paint, etc., the secondary particles behave just like primary particles, causing dispersion. Good physical properties such as defects, decreased strength, decreased gloss, and poor fluidity cannot be obtained, and the blending effect that would normally be obtained when primary particles are blended cannot be obtained. Similarly, even if synthetic calcium carbonate containing a large number of aggregates is treated with an inorganic or organic surface treatment agent, only the surface of the secondary particles will be treated, and the effect will not be sufficient. Not enough to demonstrate. [0004] Up to now, many methods for dispersing these primary particle aggregates have been reported, but generally ball mills,
A method of powerfully crushing and destroying the material using a sand grinder mill or the like is used. However, since this method involves grinding and grinding using a large amount of energy, the primary particles are destroyed at the same time as the aggregates are dispersed.
As a result, particles with extremely unstable surface conditions and even smaller than the desired primary particle size and secondary agglomerated particles with incomplete dispersion coexist, resulting in a wide particle size distribution, so this is the preferred method. It's hard to say that it is. In addition, such wet grinders such as sand grinders usually use minute glass beads as the grinding media, but since the surface of these glass beads is also crushed and broken during the crushing process of calcium carbonate, it is difficult to A large number of coarse glass pieces of around 20 μm are mixed into the calcium carbonate, and calcium carbonate used as a filler for a thin film with a thickness of around 15 μm, for example, is dispersed and prepared using such a wet grinding method. I don't like that. [0005] Calcium carbonate includes hexagonal calcite crystals, orthorhombic aragonite crystals, and pseudohexagonal vaterite crystals as allomorphs, but among these, industrially produced Most of the crystals used in various applications are cubic or spindle-shaped calcite crystals, or needle-shaped or columnar aragonite crystals. On the other hand, in the case of vaterite-type calcium carbonate, its morphological characteristics indicate that it has relatively good dispersibility compared to other two-crystalline types and does not contain large coarse aggregates. Therefore, when used as a pigment or filler for paper, paint, rubber, or plastic, it can be expected to improve coating properties and fillability, and ultimately improve the physical strength, gloss, whiteness, etc. of the product. Alternatively, it is believed that it leads to an improvement in printing characteristics.From the above viewpoint, various methods for industrially producing vaterite-type calcium carbonate have been studied. For example, in JP-A-60-90822,
By introducing a carbon dioxide-containing gas into an aqueous suspension of calcium hydroxide containing a magnesium compound and adding alkali condensed phosphate or an alkali metal salt thereof when a certain carbonation rate is reached, vaterite-type calcium carbonate can be produced. JP-A-54-150397 discloses a method for obtaining vaterite-type calcium carbonate by preliminarily coexisting ammonia in the reaction of calcium chloride and calcium hydrogen carbonate so that the pH of the slurry at the end of the reaction is 6.8. It describes how to obtain. However, all of these methods are not only much more complicated to produce than conventional methods for producing cubic or spindle-shaped calcium carbonate crystals, but also difficult to control the particle size of vaterite-type calcium carbonate particles. However, the primary particle size of the obtained vaterite-type calcium carbonate is non-uniform, and the dispersibility is also not good. Recently, various methods have been proposed for producing vaterite-type calcium carbonate by carbonating calcium hydroxide contained in an organic solvent. For example, Comparative Example 1 of JP-A No. 59-64527 describes a method of introducing carbon dioxide gas into a mixed solution of calcium hydroxide aqueous suspension and methanol to obtain vaterite-type calcium carbonate; describes a method of producing amorphous or crystalline calcium carbonate such as vaterite by blowing carbon dioxide gas into a suspension system of calcium hydroxide, water, and alcohol. However, although it is possible to obtain vaterite-type calcium carbonate in high yield with any of these methods, it is not possible to arbitrarily control the particle size and particle morphology of the vaterite-type calcium carbonate particles obtained. Furthermore, it has the disadvantage that it is not possible to stably produce spherical, ellipsoidal, or plate-like vaterite-type calcium carbonate with uniform and monodispersed primary particles and good dispersion. As a result of intensive research to solve the above-mentioned problems, the present inventors have found that carbonic acid is added to a methanol suspension of quicklime and/or slaked lime containing a specific amount of quicklime and/or slaked lime and a specific amount of water. The time required for the conductivity within the reaction system to reach a specific value from the start of the carbonation reaction, by conducting the carbonation reaction by conducting the gas, and adjusting the temperature within the reaction system to a specific temperature at a specific point during the carbonation reaction. By specifying the desired spherical shape,
It is confirmed that elliptic spherical or plate-like vaterite-type calcium carbonate can be easily and stably produced, and that the obtained spherical, ellipsoid-shaped or plate-like vaterite-type calcium carbonate has unique primary particle uniformity and dispersibility. Found (Patent Applications Hei 2-137482, Hei 2-137483, Hei 2-137
484). [0009]Vaterite-type calcium carbonate having various shapes has unique and good properties, and therefore, its use in various applications is being actively investigated. However, for applications in particularly advanced technical fields, in order to further bring out its properties and develop industrial products with more advanced functionality, the particle size may be slightly adjusted while maintaining the properties of vaterite-type calcium carbonate. There is a need for vaterite-type calcium carbonate with controlled particle size and vaterite-type calcium carbonate with finely controlled particle shape, and it is necessary to develop a manufacturing method for vaterite-type calcium carbonate that can precisely and delicately control particle growth and morphology. requested. For example, in the case of polyester films used in magnetic tapes such as audio tapes and video tapes, the slipperiness and abrasion resistance of the film depend on the workability of the film manufacturing process and the processing process in each application, as well as the quality of the product. This is a major factor that determines whether it is good or bad. When these slip properties and abrasion resistance are insufficient, for example, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, the friction between the coating roll and the film surface during application of the magnetic layer is severe, and this The friction on the film surface is also severe, and in extreme cases, wrinkles, scratches, etc. may occur on the film surface. Furthermore, even after slitting the film coated with the magnetic layer and processing it into audio, video, or computer tapes, there is a problem when pulling it out from a reel or cassette, winding it, or other operations.
Significant friction occurs between many guide parts, playback heads, etc., causing scratches, distortion, and even white powder deposits due to scratches on the surface of the polyester film, resulting in missing magnetic recording signals, that is, dropouts. It is often a major cause of [0010] Conventionally, as a method for reducing the coefficient of friction of polyester, many methods have been proposed in which fine particles are contained in polyester to impart fine and appropriate irregularities to the surface of the molded product, thereby improving the surface smoothness of the molded product. However, the affinity between the fine particles and polyester was not sufficient, and the transparency and abrasion resistance of the film were both unsatisfactory. To further explain this method, conventional methods for improving the surface properties of polyester include (1) a method in which part or all of the catalyst used during polyester synthesis is precipitated in the reaction process (internal particle precipitation method); ■Method of adding fine particles such as calcium carbonate or silicon dioxide during or after polymerization (external particle addition method). Many have been proposed. Generally speaking, the larger the size of the particles that form the irregularities on the surface of the polyester film, the greater the effect of improving slipperiness, but for precision applications such as magnetic tape, especially video, The large size of the particles itself can cause defects such as dropouts, so the unevenness on the film surface must be as fine as possible, and there is a need to simultaneously satisfy these contradictory characteristics. This is the current situation. However, in the internal particle precipitation method (2), since the particles are metal salts of polyester components, the affinity with polyester is good to some extent, but on the other hand, it is a method in which particles are generated during the reaction. It is difficult to control the amount and diameter of particles, and to prevent the formation of coarse particles. On the other hand, in method (2), if the particle size and amount added are appropriately selected, and fine particles from which coarse particles have been removed by classification or the like are added, excellent lubricity can be obtained. However, since the affinity between the inorganic fine particles and the organic component polyester is not sufficient, peeling occurs at the boundary between the particles and the polyester during stretching, etc., and voids are generated. If these voids exist in the polyester, particles tend to separate from the polyester film due to damage to the polyester film due to contact between the polyester films or between the polyester film and another base material. It causes white powder and dropout. [0012] Current polyester film production involves the following steps:
Although methods (1) and (2) are used in combination, method (2) is gradually becoming mainstream from the viewpoint of ease of particle size selection and ease of quality reproduction. However, as mentioned above, the inorganic fine particles used in method (2) do not have sufficient affinity with polyester, so the particles tend to detach from the polyester film due to damage to the polyester film, resulting in white powder. In order to prevent this, research is being conducted in various fields to develop good surface treatment agents for inorganic fine particles from a chemical standpoint, and from a physical standpoint to develop inorganic fine particles that have a shape that is difficult to detach from polyester films. It is being said. Regarding the shape of the inorganic fine particles used in method (2), it is said that elliptic spherical particles and plate-shaped particles are better than spherical particles from the viewpoint of detachment from polyester films, but on the other hand, polyester films From the viewpoint of film running properties (film slipperiness), which is another important physical property required for film production, spherical particles are said to be the best. Therefore, the inorganic particles used in this type of polyester film must not only have particle uniformity and good dispersibility, but also have fine form control technology such as particle shape and particle size, such as elliptic spherical particles. Particle shape control technology that changes ellipsoidal particles to more spherical particles, elliptic spherical particles to spherical particles, spherical particles to plate-shaped particles, or plate-shaped particles to thicker plate-shaped particles, as well as spherical particles, There is a growing demand for the establishment of advanced particle form control techniques, such as particle size control techniques that increase the particle size of elliptic spherical particles and plate-like particles while maintaining three-dimensionally similar shapes. Regarding calcite type calcium carbonate and aragonite type calcium carbonate, which are allomorphs of vaterite type calcium carbonate, the shape non-uniformity of these particles,
Ignoring poor dispersibility, various methods have been reported from various fields to control particle diameter while maintaining the shape of cubic particles or acicular particles. However, with regard to vaterite-type calcium carbonate, especially vaterite-type calcium carbonate, which has good dispersibility and particle uniformity, there is currently no report on particle shape control technology or even particle size control technology. This was a problem that needed to be resolved as soon as possible. SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a method for controlling particle growth and morphology of vaterite-type calcium carbonate. [Means for Solving the Problem] As a result of intensive research in order to solve the above problems, the present inventors have determined that using vaterite type calcium carbonate as a base material, methanol, the base material vaterite type calcium carbonate, and water. By preparing a mixed system of and controlling the pH and temperature within the carbonation reaction system to specific values to carry out the carbonation reaction, it is possible to form any particle size and shape using vaterite-type calcium carbonate as a base material. It has been found that vaterite-type calcium carbonate having good dispersibility can be easily and stably produced. The present invention was completed based on these new findings. That is, the present invention introduces carbon dioxide into a mixed system of vaterite-type calcium carbonate, methanol, water, quicklime, and/or slaked lime that satisfies the following conditions (a) and (b). , pH in the carbonation reaction system is 5.6~
11.5, a method for controlling the particle growth and morphology of vaterite-type calcium carbonate, which is characterized by controlling the temperature at 15 to 60° C. to carry out the carbonation reaction. . (a) The amount of water present in the carbonation reaction system is 3 to 30 times the molar equivalent of the quicklime equivalent value of calcium carbonate and quicklime and/or slaked lime present in the carbonation reaction system. (a) The solid content concentration of calcium carbonate, quicklime and/or slaked lime present in the carbonation reaction system is 0.5 to 12% by weight based on the methanol present in the carbonation system.
To be. The present invention will be explained in more detail below. In the present invention, the solid content concentration of vaterite-type calcium carbonate, quicklime and/or slaked lime as a base material in terms of quicklime is preferably 0.5 to 12% by weight, more preferably 1 to 12% by weight based on methanol.
8% by weight, and the amount of water is 3 to 3% of the quicklime equivalent value of vaterite type calcium carbonate and quicklime and/or slaked lime.
Introducing carbon dioxide into a mixed system of vaterite-type calcium carbonate, methanol, water, quicklime and/or slaked lime in a 0-fold molar equivalent, preferably 5 to 20-fold molar equivalent,
The pH in the carbonation reaction system is 5.6 to 11.5, preferably 5.8 to 10.0, and the temperature is 15 to 60°C, preferably 3.
This is achieved by carrying out the carbonation reaction at a temperature of 5 to 55°C. [0018] Vaterite type calcium carbonate as a base material,
If the solid content concentration of quicklime and/or slaked lime in terms of quicklime is less than 0.5% by weight based on methanol, not only will the amount of methanol required per unit increase, which will be uneconomical, but it will also affect the reaction conditions in the subsequent carbonation reaction step. Since control becomes difficult, the yield of vaterite calcium carbonate of the present invention tends to be very poor. Moreover, if it exceeds 12% by weight, the system tends to gel in the subsequent carbonation reaction step, and the shape and size of the resulting calcium carbonate particles tend to be non-uniform, and the dispersion state of the particles also tends to deteriorate. . If the amount of water is less than 3 times the molar equivalent value of vaterite-type calcium carbonate and quicklime and/or slaked lime in terms of quicklime, gelation tends to occur in the subsequent carbonation reaction step, and if it exceeds 30 times the molar amount, This is not preferable since calcium carbonate containing a large number of crystalline calcium carbonates such as calcite and aragonite in addition to the vaterite calcium carbonate of the present invention is obtained. If the pH within the carbonation reaction system is less than 5.6, it is not a preferable method because it is necessary to introduce excess carbon dioxide into the carbonation reaction system, which is uneconomical. In addition, if the pH in the carbonation reaction system exceeds 11.5, new vaterite-type calcium carbonate will not precipitate on the surface of the base material vaterite-type calcium carbonate, and particle growth and morphological changes of the base material vaterite-type calcium carbonate will not occur. . Furthermore, if the pH within the carbonation reaction system is more than 10.3 and less than 10.7, although particle growth and morphological change of the matrix vaterite-type calcium carbonate are achieved, the particle growth rate tends to be slow. Furthermore, the pH within the carbonation reaction system is 10.7 to 11.
In case 3, the purpose of the present invention can be effectively achieved when vaterite-type calcium carbonate having a specific shape is used as the base material, but when applied to the base material vaterite-type calcium carbonate of all shapes, the pH The tolerance range for other carbonation reaction conditions, such as reaction temperature and amount of added water, tends to become narrower. Regarding the temperature inside the carbonation reaction system, 15°C
If it is less than 1, it is difficult for new vaterite-type calcium carbonate to precipitate on the surface of the base material vaterite-type calcium carbonate, and the morphology of the obtained calcium carbonate particles tends to become non-uniform, which is not preferable. Furthermore, if the temperature exceeds 60°C, it becomes necessary to use a pressure-resistant reactor as the reaction vessel, which is not economically preferable. [0022] The dispersibility of vaterite-type calcium carbonate, which is the base material, greatly affects the quality characteristics of the vaterite-type calcium carbonate prepared by the method of the present invention, so it is used in fields that require particularly good dispersibility. In order to prepare vaterite-type calcium carbonate, the following (
It is preferable to use spherical, ellipsoidal, or plate-like vaterite-type calcium carbonate as the base material, which satisfies the requirements of a) to (g). (a) 0.1μm≦DS1≦2.0μm (b) 0.04
μm≦DS2≦2.0μm (c) 1.0≦DS1/DS
2≦20 (d) DP3/DS1≦1.25 (e) 1.0≦DP2/DP4≦2.5 (f) 1.0≦
DP1/DP5≦4.0(g)(DP2-DP4)/D
P3≦1.0 However, DS1: The average particle diameter of the major axis of the primary particles examined by a scanning electron microscope (SEM) (μm) DS2: The average particle diameter of the minor axis of the primary particles examined by the above microscope (μm) ) DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle diameter (μm
) DP2: In the particle size distribution measured using the above measuring device, the particle diameter (μm) when the cumulative weight is 25% starting from the large particle size side DP3: In the particle size distribution measured using the above measuring device, large particles Particle diameter (μm) when the cumulative weight is 50% calculated from the diameter side DP4: Particle diameter (μm) when the cumulative weight is 75% from the large particle size side in the particle size distribution measured using the above measuring device DP5: Particle size (μm) when the cumulative weight is 90% starting from the larger particle size side in the particle size distribution measured using the above measuring device [0023] Even when only slaked lime is used, carbonic acid, which is the objective of the present invention, is obtained. Although calcium can be obtained, the permissible range of reaction conditions in the carbonation reaction process tends to be very narrow compared to when quicklime is used as a raw material, and the content of vaterite-type calcium carbonate in the calcium carbonate obtained after the carbonation reaction is completed. Vaterite-type calcium carbonate, which tends to decrease in yield and has problems with stability over time, may be obtained.
Preferably, a mixture of quicklime and slaked lime, more preferably quicklime, is used for preparing the aforementioned methanol suspension. The reason why quicklime is preferable is not necessarily clear, but rather than turning quicklime into calcium carbonate with slaked lime and carbon dioxide, as is done in a normal quicklime-water reaction, the quicklime-methanol-method of the present invention is not. This is presumed to be due to the fact that organic calcium such as calcium methoxide is produced in the aqueous reaction, and the organic calcium reacts with carbon dioxide to become calcium carbonate. [0024] The preferred activity of quicklime is 80 or more, which is measured by the following method. Activity: Pour 500 ml of deionized water at 40°C into a 1000 cc beaker, add 2 to 3 drops of phenolphthalein while stirring with a stirrer, then add 10 g of quicklime all at once and start timing with a stopwatch. 1
After a minute has passed, 4N-HCl is continuously added dropwise so that the solution remains slightly reddish. Record the amount of 4N-HCl dropped every minute and continue this operation for 20 minutes. The activity is determined by the cumulative amount of drops after 10 minutes (
ml). [0025] The quicklime and slaked lime used in the present invention are
In order to adjust the particle size to a certain level, it is preferable to use the powder after performing dry pulverization using a dry pulverizer or wet pulverization of a methanol suspension of quicklime or slaked lime using a wet pulverizer. [0026] There are no particular restrictions on the method of carrying out the present invention as long as the above-mentioned conditions are met. For example, (1) a method of introducing carbon dioxide into a mixed system of vaterite-type calcium carbonate, methanol, water, quicklime and/or slaked lime as a base material prepared within the range that satisfies the above-mentioned conditions, (2) a method of introducing carbon dioxide into the mixed system of (1) A method of dropping a mixed system of methanol, water, quicklime, and/or slaked lime into a methanol suspension of vaterite-type calcium carbonate as a base material, (2) A method of dropping a mixed system of methanol, water, quicklime, and/or slaked lime into a methanol suspension of vaterite-type calcium carbonate as a base material, and (2) a method of dropping a mixed system of methanol, water, quicklime, and/or slaked lime into a methanol suspension of vaterite-type calcium carbonate as a base material; A method of dropping a methanol suspension of quicklime and/or slaked lime into a mixed system; ■ Dropping a mixed system of methanol, water, quicklime, and/or slaked lime into a mixed system of matrix vaterite-type calcium carbonate, methanol, and water; The following methods are used: Among the above methods, method (2) will be explained below. [0027] Using vaterite type calcium carbonate as a base material,
A methanol suspension of the base material vaterite-type calcium carbonate, in which the solid content concentration of the base material vaterite-type calcium carbonate is 0.5 to 12% by weight as a quicklime equivalent solid content concentration,
While introducing carbon dioxide into a mixed system of methanol, base material vaterite type calcium carbonate, and water, which is prepared by adding water in an amount equivalent to 3 to 30 times the molar equivalent of the quicklime equivalent value of the base material vaterite type calcium carbonate, Quicklime equivalent concentration is 0
．． Methanol and slaked lime prepared by adding water in an amount equivalent to 3 to 30 times the molar amount of quicklime (in the case of slaked lime, converted to the same molar amount of quicklime) to a methanol suspension of quicklime and/or slaked lime having a concentration of 5 to 12% by weight. A mixed system of quicklime and/or slaked lime and water is added dropwise to adjust the pH of the carbonation reaction system to 5.6 to 11.
5. The carbonation reaction may be carried out by controlling the temperature at 15 to 60°C. First, vaterite-type calcium carbonate as a base material is poured into methanol to prepare a methanol suspension of the base material vaterite-type calcium carbonate. The solid content concentration of the base material vaterite type calcium carbonate may be 0.5 to 12% by weight, preferably 1 to 8% by weight as solid content concentration in terms of quicklime. Next, water is added in an amount equivalent to 3 to 30 times the molar amount, preferably 5 to 20 times the molar equivalent of the quicklime equivalent value of the base material vaterite type calcium carbonate, and methanol, the base material vaterite type calcium carbonate, and water are mixed. A system (hereinafter referred to as mixed system M1) is prepared. Next, quicklime powder and/or slaked lime powder is poured into methanol to prepare a methanol suspension of quicklime and/or slaked lime. The concentration of quicklime and/or slaked lime is 0.5 to 12% by weight of methanol, preferably 1 to 12% by weight in terms of quicklime conversion concentration (in the case of slaked lime, the concentration converted to the same mole of quicklime, hereinafter referred to as quicklime concentration).
It may be 8% by weight. Next, to this methanol suspension of quicklime and/or slaked lime, water in an amount equivalent to 3 to 30 times the molar amount of quicklime, preferably water in an amount equivalent to 5 to 20 times the amount of quicklime is added, and methanol and quicklime and/or slaked lime are added. A mixed system of water and water (hereinafter referred to as mixed system M2) is prepared. Next, carbon dioxide is introduced into the mixed system M1 of methanol, base material vaterite type calcium carbonate, and water, and at the same time, the mixed system M2 of methanol, quicklime and/or slaked lime, and water is added dropwise to form carbonic acid. Perform a chemical reaction. The pH within the carbonation reaction system is 5.6 to 11.5, preferably 5.
．． It may be controlled to 8 to 10.3 or 10.7 to 11.3, more preferably 5.8 to 10, and the temperature in the carbonation system is controlled to 15 to 60°C, preferably 35 to 55°C. The present invention can be easily achieved by carrying out the carbonation reaction. The amount of the mixed system M2 to be dropped into the mixed system M1 depends on the particle size of the vaterite-type calcium carbonate to be prepared;
It may be selected as appropriate depending on the particle form. For example, a vaterite-type calcium carbonate having a spherical shape is selected as the base material, and the mixture system M1 contains the same amount of quicklime as the quicklime equivalent amount of the base material spherical vaterite-type calcium carbonate in the mixture system M1. When system M2 is added dropwise and the carbonation reaction is performed by selecting reaction conditions that allow spherical particle growth to occur,
New spherical vaterite-type calcium carbonate particles having a particle size approximately 1.25 times that of the base material spherical vaterite-type calcium carbonate are prepared. The dropping speed of the mixing system M2 to be dropped into the mixing system M1 may be appropriately selected depending on the particle size and particle form of the vaterite-type calcium carbonate to be prepared, as well as the shape and capacity of the reaction vessel. From the viewpoint of improving the uniformity of individual particles of the obtained vaterite-type calcium carbonate, the above-mentioned conditions, that is, the same amount as the amount of quicklime equivalent of the base material spherical vaterite-type calcium carbonate in the mixed system M1 is added to the mixed system M1. When dropping the mixed system M2 containing quicklime, the dropping rate should be adjusted so that the dropping time is preferably 1 hour or more, more preferably 2 hours or more. Furthermore, the method for controlling the morphology of vaterite-type calcium carbonate particles in the present invention can be easily achieved by appropriately selecting the pH within the carbonation reaction system from the pH range of the present invention described above. For example, if plate-shaped vaterite-type calcium carbonate is selected as the base material vaterite-type calcium carbonate and the carbonation reaction is carried out by controlling the pH in the carbonation system to 11, the shape of the new vaterite-type calcium carbonate obtained is , is a plate-like vaterite-type calcium carbonate that is almost geometrically similar to the matrix plate-like vaterite-type calcium carbonate particles, and the pH in the carbonation system is
When the carbonation reaction is carried out with the carbonation reaction controlled to 9.5, the shape of the new vaterite-type calcium carbonate obtained is a plate-like vaterite-type calcium carbonate that is thicker than the base material plate-like vaterite-type calcium carbonate and has a smaller aspect ratio. becomes. Furthermore, an oval spherical vaterite-type calcium carbonate was selected as the base material vaterite-type calcium carbonate, and p in the carbonation system was
When the carbonation reaction is carried out by controlling H to 9.8, the shape of the new vaterite-type calcium carbonate obtained is spherical vaterite-type calcium carbonate. [0032] Thus, according to the present invention, mainly:
By controlling the shape of the base material vaterite-type calcium carbonate, the dropping amount of the mixture system M2, and the pH in the carbonation reaction system, it is possible to prepare vaterite-type calcium carbonate in any form with any particle size, Not only can vaterite-type calcium carbonate base materials with spherical, ellipsoidal, and plate-like shapes be grown into geometrically similar particles, but also spherical vaterite-type calcium carbonate base materials can be grown into vaterite-type calcium carbonate with ellipsoidal and plate-like shapes. It becomes possible to control the particle morphology, such as converting it into calcium carbonate. [0033] Furthermore, when vaterite-type calcium carbonate having a specific good dispersibility is adopted as the base material vaterite-type calcium carbonate, the obtained new vaterite-type calcium carbonate has an average particle size and particle size measured by an electron microscope. Not only is the average particle diameter measured by the distribution measuring device almost approximate, but the particle size distribution is also extremely sharp, and vaterite-type calcium carbonate can be obtained that is monodispersed without agglomeration in the dispersion medium. The methanol used in the present invention is preferably 100% methanol from the viewpoint of solid-liquid separation such as drying and concentration. The following monohydric, dihydric, and trihydric alcohols may be substituted. The carbonation reaction for obtaining the vaterite-type calcium carbonate of the present invention is carried out using carbon dioxide. The carbon dioxide used does not need to be a gas, and may be a solid such as dry ice. Alternatively, a carbon dioxide-containing gas with a concentration of about 30% by volume obtained from waste gas generated during limestone calcination may be used. Additionally, it may be carbon dioxide from carbonate compounds. According to the present invention, the obtained dispersion in which vaterite calcium carbonate is dispersed is subjected to solid-liquid separation by methods such as concentration and dehydration, and methanol obtained by solid-liquid separation can be used again for the synthesis of calcium carbonate. In order to further increase the stability of the vaterite-type calcium carbonate particles obtained by the present invention, by adding carboxylic acid or an alkali salt thereof, etc. to the vaterite calcium carbonate dispersion, vaterite which has stable dispersibility for a long period of time. It becomes possible to obtain a dispersion of calcium carbonate. In addition, it is easy to replace methanol in the dispersion with another organic solvent, such as monodispersed spherical,
Ethylene glycol slurry of oval spherical or plate-like vaterite type calcium carbonate is applied to polyester fibers, polyester films, etc., and exhibits good anti-blocking properties. Furthermore, if a fatty acid, a resin acid, or an alkali salt thereof, etc. are added to the dispersion in which the vaterite-type calcium carbonate obtained by the present invention is dispersed, and then dried, a vaterite calcium carbonate powder with good dispersibility can be prepared. Calcium carbonate is prepared as an extender pigment for paints and inks, as a filler for rubber and plastics, as a pigment for paper manufacturing, and as a pigment for cosmetics.It has good optical properties, mechanical properties, and good fluidity and fillability. . [0036] In the present invention, the particle diameter is measured and calculated in the following manner using a light transmission type particle size distribution analyzer. Measuring model: SA-CP3 manufactured by Shimadzu Corporation Measuring method: Solvent: Sodium polyacrylate 0.004 in ion exchange water
Preliminary dispersion of aqueous solution containing % by weight dissolved: Ultrasonic dispersion for 100 seconds Measurement temperature: 25.0°C ± 2.5°C Measurement method: As per the calculation example below. DP1, 2, 3 calculated from the above particle size distribution measurement results
, 4, 5 are as follows DP1 = 2.00 + (11.0 -10.0) × (3
．． 00 -2.00) ÷ (11.0 -6.0) = 2
．． 20DP2=0.80+(28.0 -25.0)
×(1.00 -0.80) ÷(28.0 -18.
0) =0.86DP3=0.50+(58.0 -5
0.0) × (0.60 -0.50) ÷ (58.0
-42.0) =0.55DP4=0.30+(82
．． 0 -75.0) × (0.40 -0.30) ÷
(82.0 -72.0) =0.37DP5=0.1
5+(94.0 -90.0) ×(0.20 -0.
15) ÷ (94.0 -89.0) =0.19 0
[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. In addition, p
Measure H using a personal pH meter manufactured by Yokogawa Electric.
PH81-11-J was used. Reference Example 1 Preparation of methanol suspension dispersion used in Examples and Comparative Examples: Granular quicklime (special grade reagent) or slaked lime (special grade reagent) with an activity of 82 was ground using a dry pulverizer (Coloplex, manufactured by Alpine). ), put the resulting quicklime powder or slaked lime powder into methanol, and remove coarse particles using a 200 mesh sieve. A suspension was prepared. The methanol suspension was processed using a wet pulverizer (Dyno Mill PILOT type,
(manufactured by WAB) to prepare two methanol suspension dispersions of quicklime or slaked lime. Reference Example 2 Base material spherical vaterite type calcium carbonate A and its methanol-water suspension: Methanol was additionally added to the methanol suspension dispersion of quicklime of Reference Example 1, and the quicklime concentration was 3.0.
The methanol-quicklime-water mixed system was prepared by diluting the mixture to % by weight and adding water in an amount equivalent to 11 times the mole of quicklime. After the mixed system containing 200 g of quicklime was adjusted to 42° C., carbon dioxide gas was introduced into the mixed system under stirring conditions to initiate a carbonation reaction. Carbonation reaction start 13
When the pH within the system reached 10 minutes later, the supply of carbon dioxide gas was stopped. Even after stopping the carbon dioxide supply, the system continues to be stirred.
Twenty minutes after the start of the carbonation reaction, the pH in the system reached 9.7, and stirring was stopped to obtain a methanol-water suspension of the base material spherical vaterite type calcium carbonate A. The physical properties of the base material spherical vaterite type calcium carbonate A are shown in Table 1, and a photograph taken with a scanning electron microscope is shown in FIG. Reference Example 3 Base material oval spherical vaterite type calcium carbonate B and its methanol-water suspension: Methanol was additionally added to the methanol suspension dispersion of quicklime of Reference Example 1, and the quicklime concentration was 3.
．． Dilute to 0% by weight and further add 1% to quicklime.
A 1-fold equivalent molar amount of water was added to prepare a methanol-quicklime-water mixed system. After the mixed system containing 200 g of quicklime was adjusted to 42° C., carbon dioxide gas was introduced into the mixed system under stirring conditions to initiate a carbonation reaction. When the pH within the system reached 9.2 15 minutes after the start of the carbonation reaction, the supply of carbon dioxide gas was stopped. Stirring in the system was continued even after the supply of carbon dioxide gas was stopped, and stirring was stopped when the pH in the system reached 8 to obtain a methanol-water suspension of the base material ellipsoidal vaterite type calcium carbonate B. The physical properties of the base material oval spherical vaterite type calcium carbonate B are shown in Table 1, and a photograph taken with a scanning electron microscope is shown in FIG. Reference Example 4 Base material plate-like vaterite type calcium carbonate C and its methanol-water suspension: Methanol was additionally added to the methanol suspension dispersion of quicklime of Reference Example 1, and the quicklime concentration was 3.8.
The methanol-quicklime-water mixed system was prepared by diluting the mixture to % by weight and adding water in an amount equivalent to 11 times the mole of quicklime. After the mixed system containing 200 g of quicklime was adjusted to 42° C., carbon dioxide gas was introduced into the mixed system under stirring conditions to initiate a carbonation reaction. 300 minutes after the start of the reaction, the pH in the system reached 6.8, and the supply of carbon dioxide gas was stopped to obtain a methanol-water suspension of platy vaterite-type calcium carbonate. Furthermore, methanol was further added to the methanol-water suspension of the plate-like vaterite-type calcium carbonate, and the concentration of vaterite-type calcium carbonate was diluted to 3.0% by weight in terms of quicklime based on the total methanol. A methanol-water suspension of calcium carbonate C was obtained. The physical properties of the matrix plate-like vaterite-type calcium carbonate C are shown in Table 1, and a photograph taken with a scanning electron microscope is shown in FIG. Example 1 Methanol was additionally added to the methanol suspension dispersion of quicklime in Reference Example 1, diluted so that the quicklime concentration was 3.0% by weight, and water was added in an amount equivalent to 11 times the molar amount of quicklime. was added to prepare a methanol-quicklime-water mixed system. 2
The mixed system containing 00 g of quicklime was collected, and the mixed system was dropped into the methanol-water suspension of the base material spherical vaterite type calcium carbonate A of Reference Example 2, and at the same time, carbon dioxide gas was introduced to cause a carbonation reaction. I did it. The dropping rate of the above mixed system was controlled to 0.833 g/min as the amount of quicklime, the temperature inside the carbonation reaction system to 41 ± 1°C, and the pH inside the carbonation system to 8.8 ± 0.1. The dropwise carbonation reaction was completed approximately 240 minutes after the start of the dropwise carbonation reaction. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 1 was found to have a 100% vaterite structure. In addition, the calcium carbonate obtained in Example 1 has extremely uniform particle size, and has a geometric particle size approximately 1.25 times that of the spherical vaterite-type calcium carbonate A used as the base material. It is a spherical vaterite-type calcium carbonate similar to the above, and its dispersibility was extremely good. Table 2 shows the preparation conditions for calcium carbonate in Example 1, Table 4 shows the physical properties, and FIG. 4 shows a photograph taken with a scanning electron microscope. Example 2 Methanol was additionally added to the methanol suspension dispersion of quicklime in Reference Example 1, diluted so that the quicklime concentration was 3.0% by weight, and water was further added in an amount equivalent to 11 times the molar amount of quicklime. was added to prepare a methanol-quicklime-water mixed system. 1
The mixed system containing 600 g of quicklime was collected, and the mixed system was mixed with the base material spherical vaterite type calcium carbonate A of Reference Example 2.
was added dropwise to a methanol-water suspension, and carbon dioxide gas was introduced at the same time to carry out a carbonation reaction. The dropping rate of the above mixed system is 0.833 g/min in terms of the amount of quicklime, the temperature inside the carbonation reaction system is 41 ± 1°C, and the pH inside the carbonation system is 8.8 ± 0.1.
The carbonation reaction was carried out under controlled conditions, and the dropwise carbonation reaction was completed approximately 32 hours after the start of the dropwise carbonation reaction. Example 2
As a result of X-ray diffraction measurement, the calcium carbonate prepared by the above method was found to have a 100% vaterite structure. In addition, the calcium carbonate obtained in Example 2 has extremely uniform particle size, and has a geometric particle size approximately 2.0 times that of the spherical vaterite-type calcium carbonate A used as the base material. It is a spherical vaterite-type calcium carbonate similar to the above, and its dispersibility was extremely good. Table 2 shows the preparation conditions of calcium carbonate in Example 2, Table 4 shows the physical properties, and FIG. 5 shows a photograph taken with a scanning electron microscope. Example 3 In Example 2, the methanol-water suspension of Reference Example 2 was changed to the methanol-water suspension of Reference Example 3, and "16
The mixed system containing 00g of quicklime was collected, and ``8''
The mixed system containing 00g of quicklime was collected, and the pH in the carbonation system was changed to 9.8±0.
．． The carbonation reaction was carried out in the same manner as in Example 2, except that the amount was changed to 1. The dropwise carbonation reaction was completed approximately 16 hours after the start of the dropwise carbonation reaction. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 3 was found to have a 100% vaterite structure. In addition, the calcium carbonate obtained in Example 3 is a spherical vaterite-type calcium carbonate with extremely uniform particle size,
Its dispersibility was extremely good. Table 2 shows the preparation conditions for calcium carbonate in Example 3, Table 4 shows the physical properties, and FIG. 6 shows a photograph taken with a scanning electron microscope. Example 4 In Example 1, the methanol-water suspension of Reference Example 2 was changed to the methanol-water suspension of Reference Example 4, and the pH in the carbonation system was adjusted to 8.8±0.1. The carbonation reaction was carried out in the same manner as in Example 1 except that the value was changed to 11.0±0.1. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 4 was found to have a 100% vaterite structure. The calcium carbonate obtained in Example 4 has extremely uniform particle size, and is about 1.2 times larger than the plate-like vaterite-type calcium carbonate C used as the base material.
It was a geometrically similar plate-like vaterite type calcium carbonate having a particle size 5 times larger, and its dispersibility was extremely good. Table 2 shows the preparation conditions for calcium carbonate in Example 4, Table 5 shows the physical properties, and FIG. 7 shows a photograph taken with a scanning electron microscope. Example 5 In Example 4, the pH in the carbonation system was 11.0±0.1.
The carbonation reaction was carried out in the same manner as in Example 4, except that the value was changed to 9.5±0.1. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 5 was found to have a 100% vaterite structure. The calcium carbonate obtained in Example 5 is plate-like calcium carbonate with extremely uniform particle size, and its shape is thicker than vaterite-type calcium carbonate C used as the base material. type calcium carbonate, and its dispersibility was extremely good. Table 2 shows the preparation conditions for calcium carbonate in Example 5, Table 5 shows the physical properties, and FIG. 8 shows a photograph taken with a scanning electron microscope. Example 6 Methanol was additionally added to the methanol suspension dispersion of quicklime in Reference Example 1, diluted so that the quicklime concentration was 3.0% by weight, and water was further added in an amount equivalent to 11 times the molar amount of quicklime. was added to prepare a methanol-quicklime-water mixed system. 5
The mixed system containing 0 g of quicklime was collected and mixed with the methanol-water suspension of the base material spherical vaterite type calcium carbonate A of Reference Example 2, and the base material spherical vaterite type calcium carbonate A- A mixed system of quicklime-methanol-water was prepared, and at the same time, carbon dioxide gas was passed through the system to carry out a carbonation reaction. The temperature inside the carbonation reaction system was 41±1℃, and the p inside the carbonation system was
The carbonation reaction was carried out by controlling H to 11.4 to 8.5, and about 60 minutes after the start of the dropping carbonation reaction, the pH in the carbonation reaction system was
The carbonation reaction was terminated when H reached 8.5. Thereafter, methanol-quicklime-water containing 50 g of quicklime was mixed again into the carbonated system, and the carbonation reaction was repeated three more times under the same conditions. A total of 200 g of quicklime was subjected to carbonation reaction. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 6 was found to have a 98% vaterite structure. Example 6
Most of the calcium carbonate obtained was geometrically similar spherical vaterite calcium carbonate having a particle size about 1.25 times that of the spherical vaterite calcium carbonate A used as the base material. The calcium carbonate contained spherical vaterite-type calcium carbonate with a small particle size, and was slightly inferior in terms of particle uniformity and dispersibility compared to the spherical vaterite-type calcium carbonate obtained in Example 1. . Table 2 shows the preparation conditions for calcium carbonate in Example 6, and Table 5 shows the physical properties. Example 7 In Example 2, a methanol-quicklime-water mixed system containing 1600 g of quicklime was mixed with a quicklime equivalent amount of 160 g.
Methanol containing slaked lime equivalent to 0g - slaked lime -
The carbonation reaction was carried out in the same manner as in Example 2, except that the mixture system was changed to water. As a result of X-ray diffraction measurement, the calcium carbonate prepared in Example 7 was found to have a 90% vaterite structure. Most of the calcium carbonate obtained in Example 7 was geometrically similar spherical vaterite calcium carbonate having a particle size about 2.0 times that of the spherical vaterite calcium carbonate A used as the base material. However, it contained some spherical vaterite-type calcium carbonate with a fine particle size, and compared to the spherical vaterite-type calcium carbonate obtained in Example 2, the particle uniformity and
The calcium carbonate was slightly inferior in terms of dispersibility. Table 2 shows the preparation conditions for calcium carbonate of Example 7, Table 5 shows the physical properties, and FIG. 9 shows a photograph taken with a scanning electron microscope. Comparative Example 1 In Example 1, the temperature inside the carbonation reaction system was changed to 41±1°C by 3°C.
At 7±1°C, the pH in the carbonation system was 8.8±1 to 11.7±.
The carbonation reaction was carried out in the same manner as in Example 1 except that the concentration was changed to 0.1. The calcium carbonate obtained in Comparative Example 1 was 0
．． Calcium carbonate contains many very fine calcium carbonate particles with a particle size of 1 μm or less, and the particle size is non-uniform.The particle shape is also non-uniform, with a mixture of spherical, plate-like, and oval-spherical calcium carbonate. It is calcium carbonate, and no particle growth was observed in the spherical vaterite-type calcium carbonate used as the base material. The preparation conditions for calcium carbonate of Comparative Example 1 are shown in Table 3, the physical properties are shown in Table 6, and the photograph taken with a scanning electron microscope is shown in FIG. Comparative Example 2 In Example 1, the temperature inside the carbonation reaction system was changed to 41±1°C by 5°C.
The carbonation reaction was carried out in the same manner as in Example 1, except that the temperature was changed to ±1°C. However, during the carbonation reaction, the viscosity inside the carbonation reaction system increases, making it impossible to control reaction conditions such as stirring the reaction system, conducting carbon dioxide gas, and controlling the pH within the carbonation reaction system. has been discontinued. Table 3 shows the conditions for preparing calcium carbonate in Comparative Example 2. Comparative Example 3 Water was further added to the methanol-water suspension of Reference Example 2,
A methanol-water suspension of the base material spherical vaterite type calcium carbonate A was prepared, in which the amount of water was 35 times the molar equivalent of the quicklime equivalent value of the base material spherical vaterite type calcium carbonate A. In addition, methanol was additionally added to the methanol suspension dispersion of quicklime in Reference Example 1, and the quicklime concentration was 3.0.
The methanol-quicklime-water mixed system was prepared by diluting the mixture to % by weight and adding water in an amount equivalent to 35 times the mole of quicklime. The mixed system containing 1600 g of quicklime was collected, and the mixed system was converted into a base material spherical vaterite type in which the amount of water is 35 times the amount of water in terms of quicklime equivalent value of the base material spherical vaterite type calcium carbonate A described above. The mixture was added dropwise to a methanol-water suspension of calcium carbonate A, and at the same time, carbon dioxide gas was passed through the solution to carry out a carbonation reaction under the same dropwise carbonation conditions as in Example 2. The calcium carbonate obtained in Comparative Example 3 also contains spherical vaterite-type calcium carbonate, which is a particle-grown version of the spherical vaterite-type calcium carbonate used as the base material, but also contains aragonite-type calcium carbonate, which is a needle-shaped crystal, and cubic calcium carbonate. The calcium carbonate contained many large aggregates of calcite-type calcium carbonate, which is a crystalline form of calcium carbonate. The preparation conditions for calcium carbonate of Comparative Example 3 are shown in Table 3, the physical properties are shown in Table 6, and a photograph taken with a scanning electron microscope is shown in FIG. Comparative Example 4 Methanol was additionally added to the methanol suspension dispersion of quicklime of Reference Example 1 and diluted to a quicklime concentration of 3.0% by weight to prepare a methanol-quicklime mixed system. 1
The mixed system containing 600 g of quicklime was collected, and the mixed system was dropped into the methanol-water suspension of the base material spherical vaterite type calcium carbonate A, and at the same time, carbon dioxide gas was introduced to perform a carbonation reaction. Ta. The dropping speed of the above mixed system is
The carbonation reaction was carried out by controlling the amount of quicklime to be 0.833 g per minute, the temperature within the carbonation reaction system to 41±1° C., and the pH within the carbonation system to 8.8±0.1. Approximately 12 hours after the start of the carbonation reaction, when the methanol-quicklime mixture containing 600 g of quicklime was dropped, the viscosity of the carbonation reaction system increased, stirring in the reaction system, conducting carbon dioxide gas, and carbonating the reaction system. It became impossible to control reaction conditions such as pH control within the reaction system, and the carbonation reaction was discontinued. The total amount of water present in the carbonation system at the time the carbonation reaction was stopped was 2.75 times the molar equivalent of the quicklime equivalent values of calcium carbonate and quicklime present in the carbonation reaction system. Table 3 shows the conditions for preparing calcium carbonate in Comparative Example 4. Comparative Example 5 To the methanol suspension dispersion of quicklime with a solid concentration of 20% by weight as quicklime in Reference Example 1, water was added in an amount equivalent to 8 times the mole of quicklime, and methanol-quicklime-water was mixed. A system was prepared. The mixed system containing 1,600 g of quicklime was collected, and the mixed system was dropped into the methanol-water suspension of the base material spherical vaterite type calcium carbonate A, and at the same time, carbon dioxide gas was introduced to perform a carbonation reaction. Ta. The dropping rate of the above mixed system is 0.833 g/min as the amount of quicklime, the temperature inside the carbonation reaction system is 41±1℃, and the pH inside the carbonation system is 8.8.
The carbonation reaction was carried out under control of ±0.1. Approximately 5.7 hours after the start of the dropping carbonation reaction, when the methanol-quicklime mixture containing 286 g of quicklime was dropped, the viscosity of the carbonation reaction system increased, stirring the reaction system, conducting carbon dioxide gas, It became impossible to control reaction conditions such as pH control within the carbonation reaction system, and the carbonation reaction was discontinued. At the time when the carbonation reaction was stopped, the concentration of solid content of calcium carbonate and quicklime present in the carbonation system in terms of quicklime was 13% by weight based on the methanol present in the carbonation reaction system. Table 3 shows the conditions for preparing calcium carbonate in Comparative Example 5. [Table 1] Carbonation condition 1: The amount of water present in the carbonation reaction system (double moles) relative to the quicklime equivalent value of calcium carbonate and quicklime or slaked lime present in the carbonation reaction system. Carbonation condition 2: Solid content concentration (wt%) of calcium carbonate, quicklime, or slaked lime in terms of quicklime present in the carbonation reaction system for methanol present in the carbonation system Carbonation condition 3: pH in the carbonation reaction system Carbonation condition 4: Temperature in carbonation reaction system (°C) 0056
[Table 2] [Table 3] (Note) In Comparative Examples 2, 4, and 5, the carbonation reaction was stopped midway due to thickening of the carbonation reaction system. The values at the time point are listed. [Table 4] [Table 5] [Table 5] [Table 6] [Effects of the Invention] As mentioned above, according to the present invention, the base material vaterite type calcium carbonate is used as the base material. , it is possible to easily and stably produce vaterite-type calcium carbonate having any particle size and shape and having excellent dispersibility.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph showing the particle structure of the base material spherical vaterite-type calcium carbonate A obtained in Reference Example 2.

FIG. 2 is an electron micrograph showing the particle structure of the base material spherical vaterite-type calcium carbonate B obtained in Reference Example 3.

FIG. 3 is an electron micrograph showing the particle structure of the base material spherical vaterite-type calcium carbonate C obtained in Reference Example 4.

FIG. 4 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 1.

FIG. 5 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 2.

FIG. 6 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 3.

FIG. 7 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 4.

FIG. 8 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 5.

FIG. 9 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Example 7.

FIG. 10 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Comparative Example 1.

FIG. 11 is an electron micrograph showing the particle structure of vaterite-type calcium carbonate obtained in Comparative Example 3.

Claims (5)

[Claims] Claim 1: Conducting a carbonation reaction by introducing carbon dioxide into a mixed system of vaterite-type calcium carbonate, methanol, water, quicklime and/or slaked lime as a base material, which satisfies the following conditions (a) and (b). Particle growth of vaterite-type calcium carbonate, characterized in that the carbonation reaction is carried out by controlling the pH in the system to 5.6 to 11.5 and the temperature to 15 to 60 ° C.
Form control method. (a) The amount of water present in the carbonation reaction system is 3 to 30 times the molar equivalent of the quicklime equivalent value of calcium carbonate and quicklime and/or slaked lime present in the carbonation reaction system. (a) The solid content concentration of calcium carbonate, quicklime and/or slaked lime present in the carbonation reaction system is 0.5 to 12% by weight based on the methanol present in the carbonation system.
To be. 2. Methanol of vaterite-type calcium carbonate having a base material of vaterite-type calcium carbonate, wherein the solid content concentration of the base material vaterite-type calcium carbonate is 0.5 to 12% by weight as a quicklime equivalent solid content concentration. Carbon dioxide is added to the mixed system of methanol, base material vaterite type calcium carbonate, and water, which is prepared by adding 3 to 30 times the molar equivalent of water to the quicklime equivalent value of the base material vaterite type calcium carbonate to the suspension. 3 to 30 times the molar equivalent of quicklime (in the case of slaked lime, converted to the same mole of quicklime) to a methanol suspension of quicklime or slaked lime with a quicklime equivalent concentration of 0.5 to 12% by weight. A mixed system of methanol and quicklime and/or slaked lime and water prepared by adding water was added dropwise to adjust the pH of the carbonation reaction system to 5.6 to 11.
5. The method for controlling particle growth and morphology according to claim 1, wherein the carbonation reaction is carried out at a temperature of 15 to 60°C. [Claim 3] The pH within the carbonation reaction system is set to 5.8 to 10.
．． 3. The method for controlling particle growth and morphology of vaterite-type calcium carbonate according to claim 1 or 2, wherein the carbonation reaction is carried out by controlling the carbonation reaction to zero. [Claim 4] The base material vaterite-type calcium carbonate is
The method for controlling particle growth and morphology according to claim 1 or 2, wherein the calcium carbonate is spherical, ellipsoidal, or plate-like vaterite type calcium carbonate that satisfies the following requirements (a) to (g). (a) 0.1μm≦DS1≦2.0μm (b) 0.04
μm≦DS2≦2.0μm (c) 1.0≦DS1/DS
2≦20 (d) DP3/DS1≦1.25 (e) 1.0≦DP2/DP4≦2.5 (f) 1.0≦
DP1/DP5≦4.0(g)(DP2-DP4)/D
P3≦1.0 However, DS1: The average particle diameter of the major axis of the primary particles examined by a scanning electron microscope (SEM) (μm) DS2: The average particle diameter of the minor axis of the primary particles examined by the above microscope (μm) ) DP1: Light transmission type particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
In the particle size distribution measured using CP3), the particle diameter (μm
) DP2: Particle size (μm) when the cumulative weight is 25% starting from the larger particle size side in the particle size distribution measured using the above measuring device DP3: Large particles in the particle size distribution measured using the above measuring device Particle diameter (μm) when the cumulative weight is 50% calculated from the diameter side DP4: Particle diameter (μm) when the cumulative weight is 75% from the large particle size side in the particle size distribution measured using the above measuring device DP5: Particle size (μm) when the cumulative weight is 90% starting from the larger particle size side in the particle size distribution measured using the above measuring device [Claim 5] The temperature in the carbonation reaction system is set at 35 to 55°C.
3. The method for controlling particle growth and morphology of vaterite-type calcium carbonate according to claim 1 or 2, wherein the carbonation reaction is carried out in a controlled manner.