Monodisperse spherical amorphous calcium carbonate composite particles and method of producing the same

Abstract

To provide a method of easily producing monodisperse spherical amorphous calcium carbonate composite particles formed of composited polycarboxylic amine and calcium carbonate particles, by which the particle size thereof can be adjusted, and monodisperse spherical amorphous calcium carbonate composite particles.SOLUTION: There is provided a method of producing monodisperse spherical amorphous calcium carbonate composite particles, having a step of mixing a calcium ion-containing solution including a polycarboxylic acid amine and a carbonate ion-containing substance containing a pH adjusting agent including a base.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The technology of the present disclosure relates to monodispersed spherical amorphous calcium carbonate composite particles and a method for producing the same. [Background technology]

[0002] Monodispersed spherical amorphous calcium carbonate particles may exhibit properties such as high lubricity and high packing capacity when used as an additive to various materials. In addition, they may be able to suppress variations in material quality, making them promising additives for a variety of materials.

[0003] As an example of a production method for monodispersed spherical amorphous calcium carbonate particles, Patent Document 1 discloses a method for producing a compound consisting of fine powder, in which a raw material solution containing cations constituting a compound to be obtained and a raw material solution containing anions constituting the compound to be obtained are atomized by ultrasonic irradiation, and then mixed together, and the resulting droplets are filtered and dried, wherein the cations are calcium ions, the anions are carbonate ions or hydroxide ions, and the compound to be obtained is calcium carbonate or calcium hydroxide.

[0004] Furthermore, for example, Patent Document 2 discloses a method for producing monodispersed spherical amorphous calcium carbonate particles by dissolving sublimated ammonium carbonate in an ethanol aqueous solution of calcium chloride and subjecting calcium carbonate precipitated in the ethanol aqueous solution to solid-liquid separation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5429747 [Patent Document 2] Chinese Patent No. 104261450 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the manufacturing method described in Patent Document 1, the particle size of the monodispersed spherical amorphous calcium carbonate is limited to 40 nm, and it is not possible to adjust the particle size to other sizes. In addition, a special device is required to mix the atomized compounds. Furthermore, in the manufacturing method described in Patent Document 2, the manufacturing time is long, from 6 to 48 hours, and therefore it is not possible to easily manufacture monodispersed spherical amorphous calcium carbonate particles.

[0007] The technology of the present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to solve the above problem by providing a method for producing monodispersed spherical amorphous calcium carbonate composite particles, which can easily produce monodispersed spherical amorphous calcium carbonate composite particles in which polycarboxylic acid amine and calcium carbonate particles are combined, and can adjust the particle size of the monodispersed spherical amorphous calcium carbonate composite particles, and an object of the present disclosure is to provide monodispersed spherical amorphous calcium carbonate composite particles. [Means for solving the problem]

[0008] <1> A method for producing monodisperse spherical amorphous calcium carbonate composite particles, comprising the step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine with a carbonate ion-containing substance containing a pH adjuster containing a base.

[0009] <2> A method for producing monodisperse spherical amorphous calcium carbonate composite particles, comprising the step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine, a carbonate ion-containing substance, and a pH adjuster containing a base. <3> The polycarboxylic acid amine is a dicarboxylic acid amine. <1> or <2> 1. A method for producing monodispersed spherical amorphous calcium carbonate composite particles according to claim 1.

[0010] <4> <1> ~ <3> 1. Monodispersed spherical amorphous calcium carbonate composite particles produced by the method for producing monodispersed spherical amorphous calcium carbonate composite particles according to any one of 1 to 8, wherein the polycarboxylic acid amine and calcium carbonate particles are composited.

[0011] <5> Monodispersed spherical amorphous calcium carbonate composite particles comprising a polycarboxylic acid amine and calcium carbonate particles, wherein the polycarboxylic acid amine is present on the surface of the calcium carbonate particles and is also present inside the calcium carbonate particles to form a composite. [Effects of the Invention]

[0012] According to the technology of the present disclosure, it is possible to provide a method for producing monodispersed spherical amorphous calcium carbonate composite particles, which can easily produce monodispersed spherical amorphous calcium carbonate composite particles in which polycarboxylic acid amine and calcium carbonate particles are composited, and can adjust the particle size of the monodispersed spherical amorphous calcium carbonate composite particles, and to provide the monodispersed spherical amorphous calcium carbonate composite particles. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an SEM image of monodispersed spherical amorphous calcium carbonate composite particles obtained in Example 1. [Figure 2] 1 is an X-ray diffraction pattern of monodispersed spherical amorphous calcium carbonate composite particles obtained in Example 1. [Figure 3] 1 shows the results of measurement of the monodispersed spherical amorphous calcium carbonate composite particles obtained in Example 1 using a Fourier transform infrared spectrophotometer. [Figure 4] 1 shows the results of measurement of the monodispersed spherical amorphous calcium carbonate composite particles obtained in Example 1 using a dynamic light scattering device. [Figure 5] 1 is an SEM image of calcium carbonate particles obtained in Comparative Example 1. [Figure 6] 1 is an SEM image of calcium carbonate particles obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] The upper and lower limits of the ranges described herein can be combined in any way. For example, if the ranges are "A to B" and "C to D," the ranges "A to D" and "C to B" are also included in the scope of the present disclosure. Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit.

[0015] <Method for producing monodispersed spherical amorphous calcium carbonate composite particles> The method for producing monodisperse spherical amorphous calcium carbonate composite particles of the present disclosure includes a step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine with a carbonate ion-containing substance. Furthermore, in the first method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure, the carbonate ion-containing substance contains a pH adjuster containing a base; and in the second method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure, a pH adjuster containing a base is further mixed in the mixing step.

[0016] That is, the first method for producing monodisperse spherical amorphous calcium carbonate composite particles of the present disclosure includes a step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine with a carbonate ion-containing substance containing a pH adjuster containing a base. The second method for producing monodisperse spherical amorphous calcium carbonate composite particles of the present disclosure includes a step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine, a carbonate ion-containing substance, and a pH adjuster containing a base. Hereinafter, the step in the first production method may be referred to as "mixing step 1" and the step in the second production method may be referred to as "mixing step 2."

[0017] As mentioned above, monodispersed spherical amorphous calcium carbonate particles can be used in a variety of applications, but the particle size required varies depending on the application. For example, when added to cosmetics to improve slipperiness, a particle size of 500 nm or more is preferred; when added to paper to improve smoothness or to resins as an antiblocking agent, a particle size of around 200 to 300 nm is preferred; when added to rubber for reinforcement, a particle size of around 50 nm is preferred. However, the particle size of the monodispersed spherical amorphous calcium carbonate produced by the production method described in Patent Document 1 is limited to 40 nm. Moreover, the production method described in Patent Document 2 takes a long time to produce monodispersed spherical amorphous calcium carbonate particles, and is therefore not simple.

[0018] In contrast, the method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure can produce monodispersed spherical amorphous calcium carbonate composite particles by a production method including a mixing step 1 or a mixing step 2. In addition, the particle size can be easily adjusted, and monodispersed spherical amorphous calcium carbonate composite particles in which polycarboxylic acid amine and calcium carbonate particles are composited can be simply produced in a short time (less than 1 hour). The reason for this is unclear, but is presumed to be due to the following reasons.

[0019] It is believed that under basic conditions, the degree of supersaturation of the complex formed by the coordination of the polycarboxylic acid amine or its carboxylate ion with calcium ions and the reaction rate between calcium ions and carbonate ions are appropriately controlled, resulting in the formation of monodispersed, spherical amorphous calcium carbonate composite particles. Furthermore, even after the formation of monodispersed, spherical amorphous calcium carbonate composite particles, the polycarboxylic acid amine remains complexed with the calcium carbonate particles, suppressing the dissolution or reprecipitation of the particles, thereby stabilizing the monodispersed, spherical, and amorphous state.

[0020] The manufacturing methods described in Patent Documents 1 and 2 produce monodispersed spherical amorphous calcium carbonate particles that are not particles having a structure in which organic molecules are complexed with monodispersed spherical amorphous calcium carbonate particles. In the monodisperse spherical amorphous calcium carbonate composite particles according to this embodiment, the phrase "a polycarboxylate amine and calcium carbonate particles are composited" means that the polycarboxylate amine is incorporated not only on the surface of the calcium carbonate particles but also inside the calcium carbonate particles, and is present within the particles. A method for determining whether the polycarboxylate amine and calcium carbonate particles are composited will be described later.

[0021] As described above, the method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure allows monodispersed spherical amorphous calcium carbonate composite particles to be produced easily, and the particle size can be easily adjusted depending on the type of polycarboxylic acid amine used, etc. Furthermore, since the polycarboxylic acid amine and calcium carbonate particles are composited together, monodispersed spherical amorphous particles can be obtained. Here, "monodisperse" means that when particle size distribution is measured by dynamic light scattering (DLS), the CV value (standard deviation / arithmetic mean diameter) is within 15%. Furthermore, "spherical" means that the average circularity of 100 particles randomly selected from an SEM image obtained by scanning electron microscope (SEM) observation is 0.85 or more. The circularity is calculated as A / B, where A is the particle area and PM is the perimeter, and B is the area of ​​a perfect circle relative to PM.

[0022] Generally, when calcium carbonate particles are used as an additive in an organic matrix such as a resin or rubber, the calcium carbonate particles may aggregate in the matrix. However, the monodispersed spherical amorphous calcium carbonate composite particles obtained by the method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure are expected to have relatively easy control of dispersibility in the matrix due to the presence of the complexed polycarboxylic acid amine. The method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure will be described in detail below.

[0023] [Mixing process] In the mixing step 1 according to this embodiment, a calcium ion-containing solution containing a polycarboxylic acid amine is mixed with a carbonate ion-containing substance containing a pH adjuster containing a base. In the mixing step 2 according to this embodiment, a calcium ion-containing solution containing a polycarboxylic acid amine, a carbonate ion-containing substance, and a pH adjuster containing a base are mixed together.

[0024] (Calcium ion-containing solution) The calcium ion-containing solution contains a calcium ion source, a polycarboxylic acid amine, and a solvent that dissolves both. Examples of calcium ion sources include calcium chloride (CaCl), calcium nitrate (Ca(NO)), calcium acetate (Ca(CHCOO)), and calcium hydroxide (Ca(OH)). Of these, calcium chloride (CaCl) is preferred. One calcium ion source may be used alone, or two or more may be used in combination. The polycarboxylic acid amine is a compound having an amine skeleton (-N<) and two or more carboxy groups, and for example, a polycarboxylic acid amine represented by the following formula (1) can be used.

[0025] [ka]

[0026] In formula (1), A represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 8 carbon atoms, a hydroxy group, or a carboxy group; 1 ~L 3 each independently represents a single bond or an alkylene group having 1 to 3 carbon atoms.

[0027] The alkyl group having 1 to 15 carbon atoms may be linear, branched, or cyclic, and examples thereof include a methyl group, an ethyl group, a t-butyl group, a cyclohexyl group, etc., and may further have a substituent such as a hydroxy group, a carboxy group, etc. Among the above, a linear alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group is more preferred. Examples of the aryl group having 6 to 8 carbon atoms include a phenyl group and a naphthyl group, which may further have a substituent such as a hydroxy group, a carboxy group, a sulfonic acid group, an amino group, etc. Of these, a phenyl group is preferred. The alkylene group having 1 to 3 carbon atoms may be linear or branched, and examples thereof include a methylene group and an ethylene group, and may further have a substituent such as a hydroxy group or a carboxy group. Of the above, a linear alkylene group is preferred, and a methylene group and an ethylene group are more preferred.

[0028] The number of carboxy groups in the polycarboxylic acid amine is not particularly limited as long as it is 2 or more, but is preferably 2 to 5, more preferably 2 to 3, and even more preferably 2. That is, the polycarboxylic acid amine is more preferably a dicarboxylic acid amine. Only one type of polycarboxylic acid amine may be used, or two or more types may be mixed and used.

[0029] Examples of the polycarboxylic acid amine represented by formula (1) include hydroxyethyliminodiacetic acid (sometimes abbreviated as HIDA), methyliminodiacetic acid (sometimes abbreviated as Me-IDA), benzyliminodiacetic acid (sometimes abbreviated as Benzyl-IDA), iminodiacetic acid (sometimes abbreviated as IDA), etc. These polycarboxylic acid amines have the following structure:

[0030] [ka]

[0031] The particle size of the resulting monodispersed spherical amorphous calcium carbonate composite particles can be adjusted by changing the type of polycarboxylic acid amine in the mixing step. For example, when comparing the case where hydroxyethyliminodiacetic acid is used as the polycarboxylic acid amine with the case where methyliminodiacetic acid is used, the case where hydroxyethyliminodiacetic acid is used is more likely to produce monodispersed spherical amorphous calcium carbonate composite particles with a larger particle size.

[0032] The solvent may be any solvent capable of dissolving the calcium ion source and the polycarboxylic acid amine, and typically, water may be used. However, the solvent may further contain a water-soluble organic solvent such as an alcohol, tetrahydrofuran, or oxazine.

[0033] The calcium ion source and polycarboxylic acid amine content in the calcium ion-containing solution are not particularly limited, and the calcium ion-containing solution may be prepared by dissolving the same molar amount of polycarboxylic acid amine as calcium ions in a solvent. For example, the same molar amount of polycarboxylic acid amine as calcium ions may be prepared in a solution having a calcium ion concentration of 50 to 100 mmol / L or a calcium content of 0.2 to 0.4 mass%. The mass percent concentration of polycarboxylic acid in the solution varies depending on the molecular weight of the polycarboxylic acid amine.

[0034] (carbonate ion-containing substances) The carbonate ion-containing substance is a substance that contains carbonate ions, and the substance may be in the form of a gas, liquid, or solid. The carbonate ion-containing substance used in the mixing step 1 further contains a pH adjuster containing a base in addition to carbonate ions. The carbonate ion-containing substance used in the mixing step 2 may or may not contain a pH adjuster containing a base. Hereinafter, in this specification, when simply referred to as a "carbonate ion-containing substance," it refers to a carbonate ion-containing substance that does not contain a pH adjuster containing a base. A carbonate ion-containing substance that contains a pH adjuster containing a base, such as the carbonate ion-containing substance used in mixing step 1, may be referred to as a "base and carbonate ion-containing substance."

[0035] Specific examples of carbonate ion-containing substances (carbonate ion-containing substances that do not contain a pH adjuster containing a base) that can be used include carbon dioxide gas (CO2 gas); a solution in which carbon dioxide gas (CO2 gas) is dissolved in a solvent; and a solution in which a carbonate ion source such as a metal carbonate salt such as sodium bicarbonate or sodium carbonate is dissolved in a solvent. For example, when carbon dioxide gas is used as the carbonate ion-containing substance, the step of mixing the calcium ion-containing solution containing the polycarboxylic acid amine with the carbonate ion-containing substance may be carried out by blowing carbon dioxide gas into the calcium ion-containing solution containing the polycarboxylic acid amine. Among the above, the carbonate ion source is preferably an aqueous solution of a metal carbonate, more preferably an aqueous solution of sodium carbonate, and the solvent can usually be water. The carbonate ion-containing substance may be used alone or in combination of two or more kinds.

[0036] In the mixing step 1, the carbonate ion-containing substance further contains a pH adjuster including a base. When carbon dioxide gas is used as the carbonate ion-containing substance, a pH adjuster containing a base may be added to a solution in which carbon dioxide gas is dissolved in a solvent such as water, or carbon dioxide gas may be dissolved in a solution in which a pH adjuster containing a base is dissolved in a solvent such as water. The base contained in the pH adjuster may be ammonia, methylamine, trimethylamine, tetramethylamine hydroxide, or the like, and may be used alone or in combination of two or more. The amount of pH adjuster containing a base to be added is adjusted according to the concentration and type of base contained in the pH adjuster so that the pH after mixing of the calcium-containing solution containing the polycarboxylic acid amine and the carbonate ion-containing substance containing the pH adjuster becomes a specific value of 10 or more. By changing the type of base and using an appropriate amount of a pH adjuster, the particle size of the resulting monodispersed spherical amorphous calcium carbonate composite can be adjusted. For example, when comparing the case where ammonia is used as a base with the case where trimethylamine is used, monodispersed spherical amorphous calcium carbonate composite particles having a large particle size are more easily produced when trimethylamine is used.

[0037] The concentration of the carbonate ion source in the carbonate ion-containing substance is not particularly limited, and a solution containing the carbonate ion source in the same molar equivalent amount as the calcium ion source in the calcium ion-containing solution may be prepared. When the carbonate ion-containing substance contains a pH adjuster containing a base, in other words, when preparing a "substance containing a base and carbonate ions," 2 to 8 molar equivalents of the pH adjuster containing a base are added relative to the carbonate ion source. For example, for 100 g of a 50 mmol / L to 100 mmol / L carbonate ion-containing solution, 3 mL to 6 mL of 25% by mass of ammonia water may be added.

[0038] In the mixing step 2 according to the present embodiment, in addition to mixing the calcium ion-containing solution with the carbonate ion-containing substance, a pH adjuster containing a base is further mixed in. At this time, the carbonate ion-containing substance may or may not contain the pH adjuster containing a base. The type in which a pH adjuster containing a base is mixed with a carbonate ion-containing substance is referred to as "pre-addition," while the type in which a pH adjuster containing a base is mixed in the mixing step is referred to as "post-addition." In other words, the method of adding a pH adjuster containing a base in mixing step 1 is "pre-addition," and the method of adding a pH adjuster containing a base in mixing step 2 is "post-addition."

[0039] An example of the mixing step according to this embodiment when carbon dioxide gas is used as the carbonate ion-containing substance will be described below, separately for the pre-addition and post-addition. In the case of first addition (mixing step 1), as described above, a pH adjuster is added to a solution in which carbon dioxide gas is dissolved in a solvent such as water, or carbon dioxide gas is dissolved in a solution in which a pH adjuster is dissolved in a solvent such as water. Next, the solution in which carbon dioxide gas and the pH adjuster are dissolved is mixed with a calcium ion-containing solution that includes a polycarboxylic acid amine.

[0040] In the case of post-addition (mixing step 2), the pH adjuster is added to the calcium ion-containing solution containing the polycarboxylic acid amine, and then carbon dioxide gas is blown into it. As described above, according to the method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure, monodispersed spherical amorphous calcium carbonate composite particles can be easily produced in a short time (less than 1 hour). If a pH adjuster is added in advance to mix with the carbonate ion-containing substance, the production time can be further shortened, and the monodispersed spherical amorphous calcium carbonate composite particles according to this embodiment can be produced within 20 minutes or 10 minutes.

[0041] When amines such as ammonia, methylamine, trimethylamine, and tetramethylamine hydroxide are used as the pH adjuster for post-addition, a pH adjuster containing 2 to 8 molar equivalents of a base relative to the carbonate ion source used in mixing step 2 can be used. The specific amount of addition varies depending on the type and concentration of the amines used. In addition, when post-addition is used, a metal hydroxide such as sodium hydroxide or potassium hydroxide can also be used as the pH adjuster, and a pH adjuster containing 1 to 3 molar equivalents of a base relative to the carbonate ion source used in mixing step 2 can be used.

[0042] The mixing of the components in mixing step 1 and mixing step 2 can be carried out under atmospheric pressure (0.1 MPa) and room temperature (25°C). The components can be mixed for 1 to 5 minutes using a stirrer as needed. When a pH adjuster is added later, it is preferable to add the pH adjuster to the reaction system over 40 to 50 minutes, depending on the base concentration in the pH adjuster, in order to maintain uniformity within the system. After stirring for a predetermined time, the mixture is filtered through filter paper or the like, washed with alcohol, and then the solid content on the filter paper is dried to obtain monodispersed spherical amorphous calcium carbonate composite particles.

[0043] <Monodispersed spherical amorphous calcium carbonate composite particles> The monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure are produced by the method for producing monodispersed spherical amorphous calcium carbonate composite particles of the present disclosure, and are monodispersed spherical amorphous calcium carbonate composite particles in which a polycarboxylic acid amine and calcium carbonate particles are composited. More specifically, the monodisperse spherical amorphous calcium carbonate composite particles of the present disclosure contain a polycarboxylic acid amine and calcium carbonate particles, and the polycarboxylic acid amine is present on the surface of the calcium carbonate particles and is also present inside the calcium carbonate particles to form a composite.

[0044] The fact that calcium carbonate is amorphous can be confirmed by X-ray diffraction (XRD) or Fourier transform infrared spectroscopy (FT-IR). The state of the composite of polycarboxylic acid amine and calcium carbonate particles can be confirmed using scanning electron microscope (SEM) observation, dynamic light scattering (DLS) method, total organic carbon (TOC) measurement, thermogravimetry (TG) analysis, and liquid chromatography (HPLC).

[0045] (Method for confirming the combination) The contents of calcium carbonate, polycarboxylic acid amine, water, etc. in the sample are calculated from the results of total organic carbon (TOC) measurement, thermogravimetric (TG) analysis, and liquid chromatography (HPLC). The amount of polycarboxylic acid amine per particle is calculated from these contents and the density of the contained substances. Nuclear magnetic resonance analysis (NMR, nuclide: proton) confirms that the polycarboxylic acid amine in the sample particles has the same structure as the polycarboxylic acid amine unit, and calculates the molecular size of the polycarboxylic acid amine from the density and molecular weight of the polycarboxylic acid amine unit. The polycarboxylic acid amine content per sample particle and the molecular size of the polycarboxylic acid amine are used to calculate the area that the polycarboxylic acid amine can cover without laminating the surface of the sample particle. The surface area of ​​the sample particles is also calculated from the average particle size obtained by dynamic light scattering (DLS), assuming the sample particles are spherical. When the area of ​​the particle surface that can be covered by the polycarboxylic acid amine without lamination is 1.5 times or more the surface area of ​​the sample particle, it is determined that the polycarboxylic acid amine is present not only on the surface of the sample particle but also inside the particle, and this indicates that the polycarboxylic acid amine and calcium carbonate particle are composited.

[0046] (Method for confirming monodispersity and sphericity) The composite particles of the present disclosure are monodisperse and spherical particles, which can be confirmed by scanning electron microscope (SEM) observation and dynamic light scattering (DLS) analysis. Specifically, the monodispersity of the composite particles is determined by whether the CV value (standard deviation / average particle size) is within 15% from the particle size distribution obtained by dynamic light scattering (DLS). The spherical shape of composite particles is determined by whether the average circularity of 100 particles randomly selected from an SEM image is 0.85 or more. Circularity is defined as A / B, where A is the area of ​​a particle, A is the perimeter, PM is the area of ​​a perfect circle relative to PM, and B is the perimeter. The monodisperse spherical amorphous calcium carbonate composite particles of the present disclosure usually have a primary particle size of 80 to 430 nm, and the particle size can be evaluated by a dynamic light scattering (DLS) method. [Example]

[0047] Next, the technology of the present disclosure will be specifically explained using examples, but the technology of the present disclosure is not limited to these examples in any way.

[0048] Example 1 Calcium chloride aqueous solution (50mmol / L) (Ca 2+ Hydroxyethyliminodiacetic acid (HIDA) (organic molecule) was dissolved in the source of calcium ions in an amount of 1 molar equivalent relative to calcium ions to form solution A (solution A1). The same concentration and amount of sodium carbonate solution (CO3 2- Ammonia (NH3) (base) in an amount of 8.0 molar equivalents relative to carbonate ions was added to the source of the carbonate ions to prepare solution B (solution B1). Solution A (solution A1) was added to solution B (solution B1), and the mixture was stirred at room temperature for 5 minutes, and then filtered. The product on the filter paper was washed with ethanol and then dried.

[0049] Examples 2 to 4 Liquid A was prepared in the same manner as in Example 1, except that in preparing Liquid A (Liquid A1) in Example 1, methyliminodiacetic acid (Me-IDA), benzyliminodiacetic acid (Benzyl-IDA), or iminodiacetic acid (IDA) was used as the organic molecule instead of hydroxyethyliminodiacetic acid (HIDA), as shown in Table 1. Liquid A in Example 2 will be referred to as Liquid A2, Liquid A in Example 3 as Liquid A3, and Liquid A in Example 4 as Liquid A4. In Example 1, except that liquid A (liquid A1) was replaced with liquid A (liquid A2, A3, or A4), the procedure was repeated to add liquid A to liquid B, stir at room temperature for 1 to 5 minutes, and then filter. The product on the filter paper was washed with ethanol and then dried.

[0050] Examples 5 to 7 In preparing Solution B (Solution B1) in Example 1, trimethylamine (NMe3), methylamine (MeNH2), or tetramethylamine hydroxide (NMe4(OH)) was used instead of ammonia (NH3) as the base in the pH adjuster, as shown in Table 1. The amount of each pH adjuster added was determined so that the pH of the mixed solution after mixing Solutions A and B was the same as in Example 1. Solution B was otherwise prepared in the same manner as in Example 1. Solution B in Example 5 was referred to as Solution B2, Solution B in Example 6 as Solution B3, and Solution B in Example 7 as Solution B4. In Example 1, except that liquid B (liquid B2, B3, or B4) was used instead of liquid B (liquid B1), liquid A was added to liquid B, and the mixture was stirred at room temperature for 5 minutes, filtered, and the product on the filter paper was washed with ethanol and then dried.

[0051] Examples 8 and 9 In preparing the liquid A (liquid A1) and the liquid B (liquid B1) of Example 1, the concentrations of calcium chloride and sodium carbonate were set to 75 mmol / L or 100 mmol / L as shown in Table 1, and the liquids A and B were prepared in the same manner as in Example 1. The liquids A and B of Example 8 are referred to as liquids A5 and B5, and the liquids A and B of Example 9 are referred to as liquids A6 and B6. In Example 1, except that liquid A (liquid A1) was replaced with liquid A (liquid A5 or liquid A6), and liquid B (liquid B1) was replaced with liquid B (liquid B5 or liquid B6), the procedure was repeated. Liquid A was added to liquid B, the mixture was stirred at room temperature for 5 minutes, and then filtered. The product on the filter paper was washed with ethanol and then dried.

[0052] Example 10 Solution A (solution A1) was prepared in the same manner as in Example 1, and the same amount and concentration of aqueous sodium carbonate solution was added to solution A1. To this mixed solution, 1.2 molar equivalents of aqueous sodium hydroxide solution relative to carbonate ions was added. Specifically, a total of 900 μL of 10 mol / L aqueous sodium hydroxide solution was added at 50 μL / min. After the addition of the aqueous sodium hydroxide solution was completed, the mixture was stirred for several minutes and then filtered. The product on the filter paper was washed with ethanol and then dried.

[0053] Comparative Example 1 Liquid A was prepared in the same manner as in Example 1, except that hydroxyethyliminodiacetic acid (HIDA) was not added in the preparation of Liquid A (Liquid A1) in Example 1. Liquid A in Comparative Example 1 is designated as Liquid A101. In Example 1, except that liquid A (liquid A1) was replaced with liquid A (liquid A101), the same procedure was followed. Liquid A was added to liquid B, the mixture was stirred at room temperature for 5 minutes, and then filtered. The product on the filter paper was washed with ethanol and then dried.

[0054] Comparative Examples 2 and 3 Solution A was prepared in the same manner as in Example 1, except that in preparing Solution A (Solution A1) in Example 1, glycine or bicine was used as the organic molecule instead of hydroxyethyliminodiacetic acid (HIDA), as shown in Table 1. Solution A in Comparative Example 2 is referred to as Solution A102, and Solution A in Comparative Example 3 is referred to as Solution A103. In Example 1, except that liquid A (liquid A1) was replaced with liquid A (liquid A102 or liquid A103), the procedure was repeated. Liquid A was added to liquid B, the mixture was stirred at room temperature for 5 minutes, and then filtered. The product on the filter paper was washed with ethanol and then dried.

[0055] Comparative Example 4 Liquid B (liquid B1) was prepared in the same manner as in Example 1, except that ammonia (NH3) was not used. Liquid B in Comparative Example 4 was designated liquid B104. In Example 1, the liquid A was added to the liquid B, and the mixture was stirred at room temperature for 5 minutes, in the same manner as in Example 1, except that the liquid B (liquid B104) was used instead of the liquid B (liquid B1).

[0056] <Evaluation> The products produced in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated by scanning electron microscope (SEM) observation, dynamic light scattering (DLS), X-ray diffraction (XRD), thermogravimetry (TG) analysis, total organic carbon (TOC) measurement, Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) analysis to determine whether they were crystalline or amorphous, their crystalline form if crystalline, particle shape, circularity, average particle size and particle size distribution, the content of organic matter, and the state of compositing of calcium carbonate particles and organic matter. Specific evaluation methods and measurement conditions are as follows. The evaluation results are shown in Table 1. In Comparative Example 4, the above evaluation was not carried out because no particles were precipitated. Table 1 also shows the components of solutions A and B, as well as the reaction times. 2+ "Concentration" column and "CO3 2- "mM" in the "Concentration" column means "mmol / L."

[0057] 1. Analysis by X-ray diffraction (XRD) method X-ray diffraction patterns were measured using an X-ray diffractometer (AERIS, Spectris) under the following conditions: CuKα radiation (40 kV / 7.5 mA), scan axis 2θ / θ, scan range 3–70°, scan step 0.01°, and scan speed 0.27° / min.

[0058] 2. Scanning electron microscope (SEM) observation Scanning electron microscope observation was performed using a scanning electron microscope (JCM-6000, manufactured by JEOL Ltd.) at an accelerating voltage of 15 kV. As a pretreatment, gold was evaporated onto the sample for 2 minutes using a sputtering device (Smart Coater, manufactured by JEOL Ltd.).

[0059] 3. Dynamic Light Scattering (DLS) Analysis Particle size distribution was measured using a dynamic light scattering device ("ELSZneo", manufactured by Otsuka Electronics Co., Ltd.) A suspension prepared by dispersing a predetermined amount of sample particles in ethanol was used as the analytical sample.

[0060] 4. Total organic carbon (TOC) measurement Total organic carbon (TOC) was measured using a total organic carbon analyzer ("TOC-L," manufactured by Shimadzu Corporation). The sample was dissolved in hydrochloric acid, and the inorganic carbon was removed by aeration. The resulting solution was used as the analytical sample, and the total organic carbon (TOC) was measured using the combustion oxidation method (in an air atmosphere, 680°C).

[0061] 5.Thermogravimetric analysis (TG) Using a thermogravimetric analyzer ("TGA-50", manufactured by Shimadzu Corporation), the sample was heated from room temperature to 900°C (heating rate: 10°C / min) under air flow (50 mL / min), and the weight loss of the sample was measured.

[0062] 6. Fourier transform infrared spectroscopy (FT-IR) The analysis was carried out using a Fourier transform infrared spectrophotometer ("FT / IR-4X", TGS detector, manufactured by JASCO Corporation). The measurement range was 400-4000 cm using the single reflection ATR (Attenuated Total Reflection) method ("ATR PRO ONE X", prism: high-efficiency diamond, manufactured by JASCO Corporation). -1 、 Resolution: 4 cm -1 The measurement was carried out under the following conditions.

[0063] 7.Nuclear magnetic resonance (NMR) analysis A nuclear magnetic resonance (NMR) spectrometer (AVANCEIII HD500, 500 MHz, manufactured by Bruker Japan) was used. The solvent was heavy hydrochloric acid (0.3 mol / L). 1 H-NMR was measured.

[0064] [Table 1]

[0065] The product of Example 1 was analyzed using a scanning electron microscope (SEM) ("JCM-6000", manufactured by JEOL Ltd.), an X-ray diffraction (XRD) device ("AERIS", manufactured by Spectris), a Fourier transform infrared spectrophotometer ("FT / IR-4X", TGS detector, manufactured by JASCO Corporation), and a dynamic light scattering (DLS) device ("ELSZneo", manufactured by Otsuka Electronics Co., Ltd.). The results are shown in Figures 1 to 4. In Figure 1, "2 μm" is written to the right of the white line at the bottom, which means that the length of the white line is 2 μm. In Figure 2, the vertical axis is "Intensity / cps" and the horizontal axis is "2θ(° / CuKα)". In Figure 3, the vertical axis is "Absorption / au" and the horizontal axis is "Wavenumber / cm -1 In FIG. 4, the vertical axis is "Number / %" and the horizontal axis is "Diameter / nm."

[0066] 5 and 6 show SEM images of the products of Comparative Examples 1 and 2 obtained using a scanning electron microscope (SEM) device ("JCM-6000", manufactured by JEOL Ltd.). In Figures 5 and 6, "10 μm" is written to the right of the lower white line, which means that the length of the white line is 10 μm.

[0067] The particle shape was determined to be spherical because the average circularity of 100 particles randomly selected from the SEM images including Figure 1 was 0.85 or more. The product of Example 1 was determined to be amorphous from the X-ray diffraction pattern in Figure 2 and the FT-IR analysis results in Figure 3. Furthermore, as a result of particle size distribution measurement by dynamic light scattering (DLS) in Fig. 4, the CV value (standard deviation / average particle size) was 15% or less, and therefore the product of Example 1 was determined to be monodisperse particles. Furthermore, the area that the organic matter can cover without layering, predicted from the organic matter content and molecular size of the organic matter, is thought to be about 1.5 to 8 times the particle surface area predicted from the average particle size. Therefore, it is highly likely that the organic matter is incorporated not only on the particle surface but also inside the particles, and it is expected that the product is in a composite state different from composite particles, etc., produced by surface-treating monodisperse spherical amorphous calcium carbonate particles. From the above, it can be said that the product produced in Example 1 is monodisperse, spherical amorphous calcium carbonate composite particles.

[0068] Furthermore, for the following reasons, the product produced in Example 1 is considered to be different from composite particles in which the surfaces of monodispersed, spherical amorphous calcium carbonate particles are modified with an organic substance. First, to obtain monodisperse spherical amorphous calcium carbonate composite particles whose particle surfaces are modified with an organic substance, it is necessary to (1) produce monodisperse spherical amorphous calcium carbonate particles that do not contain organic substances, and then (2) modify the particle surfaces with an organic substance. However, the manufacturing process (1) is difficult to achieve in the first place. At present, it is extremely difficult to control calcium carbonate particles to be monodisperse and spherical without additives such as organic substances, and to stably maintain the amorphous state. Furthermore, considering the affinity between Ca and carboxylate groups or carboxylate ions, it is believed that the carboxylic acid amines or their carboxylate ions in the particles are coordinated to Ca. Polycarboxylic acid amines are water-soluble (for example, the solubility of HIDA in water at 25°C is 18.61 g / L), and those not coordinated to Ca are believed to be dissolved in the aqueous solution. Furthermore, since the products produced in Example 1 and elsewhere are filtered and washed with alcohol on the filter paper, it is unlikely that additional organic matter is layered on top of the organic matter. Here, the area that can be covered by the particle surface without organic matter layering, calculated from the organic matter content per particle and the molecular size of the organic matter, is approximately 1.5 to 8 times the particle surface area predicted from the average particle size. Therefore, it is believed that the organic matter is incorporated not only on the particle surface but also inside the particle. Thus, it is difficult to incorporate organic matter into the particle interior through particle surface modification.

[0069] On the other hand, as can be seen from Figure 5, the product of Comparative Example 1 was not spherical but consisted of rhombohedral particles. Also, as can be seen from Figure 6, the product of Comparative Example 2 contained rounded particles in addition to rhombohedral particles, but these were crystalline rather than amorphous.

[0070] As can be seen from the comparison of Examples 1 to 4 in Table 1, monodispersed spherical amorphous calcium carbonate composite particles with different particle sizes can be produced by changing the type of organic molecule. Among Examples 1 to 4, the monodispersed spherical amorphous calcium carbonate composite particles of Example 1, which were produced using hydroxyethyliminodiacetic acid (HIDA) as the organic molecule, were the largest.

[0071] Furthermore, as can be seen from a comparison of Examples 1, 5, 6, and 7 in Table 1, monodispersed spherical amorphous calcium carbonate composite particles with different particle sizes can be produced by changing the type of base in the pH adjuster of Solution B and adding an appropriate amount. Among Examples 1, 5, 6, and 7, the monodispersed spherical amorphous calcium carbonate composite particles of Example 5, which were produced using trimethylamine (NMe3) as the base, were the largest.

[0072] As can be seen from the comparison of Examples 1, 8, and 9 in Table 1, monodispersed spherical amorphous calcium carbonate composite particles with different particle sizes can be produced by adjusting the calcium ion and carbonate ion concentrations in Solutions A and B. Among Examples 1, 8, and 9, the monodispersed spherical amorphous calcium carbonate composite particles of Example 1, which had calcium ion and carbonate ion concentrations of 50 mM, were the largest.

[0073] As can be seen from the comparison between Examples 1 to 9 and Example 10 in Table 1, Examples 1 to 9, in which the pH adjuster is added first and mixed with the carbonate ion-containing substance, enable monodispersed spherical amorphous calcium carbonate composite particles to be obtained in a shorter time than Example 10, in which the pH adjuster is added later. [Industrial Applicability]

[0074] According to the present embodiment, monodisperse spherical amorphous calcium carbonate composite particles can be easily produced. The monodisperse spherical amorphous calcium carbonate composite particles are expected to be used in the cosmetics field, such as by adding them to foundations to improve the smoothness and feel of the materials, in the papermaking field to enhance the smoothness of the materials, by adding them to resins that are raw materials for films to serve as antiblocking agents, and in rubber as an additive to improve the mechanical strength of the materials.

Claims

1. A method for producing monodisperse spherical amorphous calcium carbonate composite particles, comprising the step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine with a carbonate ion-containing substance containing a pH adjuster containing a base.

2. A method for producing monodisperse spherical amorphous calcium carbonate composite particles, comprising the step of mixing a calcium ion-containing solution containing a polycarboxylic acid amine, a carbonate ion-containing substance, and a pH adjuster containing a base.

3. 3. The method for producing monodispersed spherical amorphous calcium carbonate composite particles according to claim 1, wherein the polycarboxylic acid amine is a dicarboxylic acid amine.

4. 3. Monodispersed spherical amorphous calcium carbonate composite particles, which are produced by the method for producing monodispersed spherical amorphous calcium carbonate composite particles according to claim 1 or 2, and which are composite particles of polycarboxylic acid amine and calcium carbonate particles.

5. Monodispersed spherical amorphous calcium carbonate composite particles comprising a polycarboxylic acid amine and calcium carbonate particles, wherein the polycarboxylic acid amine is present on the surface of the calcium carbonate particles and is also present inside the calcium carbonate particles to form a composite.

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