Method for producing calcitic calcium carbonate granules

Abstract

The purpose of the present invention is to provide a novel method for producing calcium carbonate having a controlled particle diameter and controlled pores with high yield through a relatively simple process that is different from conventional methods.　The present invention relates to a method for producing calcitic calcium carbonate granules, the method comprising the following steps: a step for mixing calcitic calcium carbonate particles, gelatin, and water, followed by heating and stirring, to obtain a mixed slurry A of gelatin / calcitic calcium carbonate particles; a step for dissolving a surfactant in oil, followed by stirring, to obtain a solution B; a step for mixing the mixed slurry A of gelatin / calcitic calcium carbonate particles with the solution B, followed by stirring, to obtain a milky emulsion solution C; a step for adding a crosslinking agent to the milky emulsion solution C, followed by stirring, to obtain a milky solution D containing composite particles of gelatin / calcitic calcium carbonate; a step for centrifuging the milky solution D containing the composite particles of gelatin / calcitic calcium carbonate to obtain composite particles of gelatin / calcitic calcium carbonate; and a step for firing the composite particles of gelatin / calcitic calcium carbonate to obtain calcitic calcium carbonate granules.

Description

Method for producing calcite-type calcium carbonate granules

[0001] The present invention relates to a method for producing calcite-type calcium carbonate granules.

[0002] Calcium carbonate is widely used as a reinforcing filler in rubber, plastics, paper, sealants, paints, inks, etc., a calcium fortifier in foods, feeds, etc., and an alkaline agent in fertilizers, etc. The calcium carbonate used for these purposes is roughly divided into light calcium carbonate, which is obtained by injecting carbon dioxide gas into an aqueous suspension of calcium hydroxide to cause a carbonation reaction, and heavy calcium carbonate, which is obtained by mechanically crushing and classifying high-quality limestone.

[0003] Calcium carbonate is known to have three crystalline phases: calcite, aragonite, and vaterite. Of these, calcite is the most stable crystalline phase, and vaterite, for example, transforms into calcite over time. Calcite-type calcium carbonate is generally a rhombohedral or cubic crystal with a dense structure. That is, calcium carbonate with a higher structure obtained by crystal growth of calcium carbonate using conventional methods almost always becomes stable calcite crystals with a rhombohedral or cubic shape. Calcite-type calcium carbonate with a spherical or porous structure, rather than a rhombohedral or cubic shape, would be highly valuable industrially. Therefore, there is a need for an efficient production of calcium carbonate with a calcite-type crystalline phase and desired particle size and shape.

[0004] Patent Document 1 discloses the carbonation method for introducing carbon dioxide gas into an aqueous calcium hydroxide suspension to produce spherical calcium carbonate with an average particle size of 11 μm to 20 μm, free of aggregates of microparticles. The spherical calcium carbonate obtained by the method of Patent Document 1 does not have a porous structure, and the production method is quite complicated, requiring special exhaust equipment, etc. Furthermore, the method of Patent Document 1 requires the disposal of unreacted carbon dioxide gas, which can be said to have some safety issues. On the other hand, Patent Document 2 discloses a solution method for reacting an aqueous calcium chloride solution, an aqueous sodium carbonate solution, and an aqueous glycine solution to obtain spherical calcium carbonate microparticles with crystallite sizes of 3 nm to 30 nm. The method of Patent Document 2 is primarily intended to produce vaterite-type calcium carbonate, and the microparticles obtained by the method of Patent Document 2 are a mixture of vaterite, calcite, and amino acids.

[0005] Patent Document 3 discloses a method for producing synthetic calcium carbonate spherical porous granules having a particle size of 10 mm or less, by using synthetic calcium carbonate as a starting material with a particle size of 0.1 μm or less, adding a desired amount of water and calcium oxide and / or calcium hydroxide as a granulation aid, granulating the granules into spherical granules having a particle size of 10 mm or less, and then carrying out a carbonation step after the granulation. The method of Patent Document 3 requires that carbonation be initiated and completed on the surface of the calcium carbonate powder, which is always difficult. The method of Patent Document 3 may result in residual granulation aids after the reaction, and the desired synthetic calcium carbonate spherical porous granules can only be obtained by carefully controlling the reaction conditions. Patent Document 4 discloses a method for producing calcium carbonate by reacting calcium chloride and sodium carbonate on the surface of spherical micelles formed by polyvinylpyrrolidone (PVP) and polyoxyethylene sorbitan monooleate (Tween-80) as a template, to obtain calcium carbonate, which is then dried in an oven at about 80°C to obtain calcium carbonate microspheres. The calcium carbonate microspheres obtained by the method of Patent Document 4 are a mixture of calcite and vaterite.

[0006] Meanwhile, attempts have been made to produce hollow spheres as calcium carbonate particles with a more complex structure. Patent Document 5 discloses that a gas bubble interfacial synthesis method was used to react calcium ions with carbonate ions at the interface of carbon dioxide gas bubbles to obtain hollow, spherical calcium carbonate particles composed of a porous shell. Non-Patent Document 1 also discloses that a porous hollow aragonite calcium carbonate was produced by covering the surface of polystyrene beads with a microemulsion supersaturated with calcium bicarbonate using the currently most common template method, followed by high-temperature firing.

[0007] The method of Patent Document 5 requires strict control of the gas amount, and the safety of unreacted gas is also an issue. Furthermore, the calcium carbonate obtained is of the vaterite type, which has low stability against water. The method of Non-Patent Document 1 has the problems of requiring the preparation of a template in advance, and of making it difficult for the microemulsion to coat the surface of the template, and if this does not occur, it is not possible to stably obtain porous hollow bodies. Furthermore, the calcium carbonate spherical hollow bodies obtained by the method of Non-Patent Document 1 are aragonite calcium carbonate.

[0008] Japanese Patent No. 4575293 Japanese Patent Application Publication No. 2013-60320 Japanese Patent Application Publication No. 3775569 Chinese Patent Application Publication No. 103232051 Japanese Patent Application Publication No. 2005-281034

[0009] Nature, 1995, 377, 320-323

[0010] Therefore, an object of the present invention is to provide a novel method for producing calcite-type calcium carbonate granules having a controlled particle size and controlled pores from calcite-type calcium carbonate as a raw material in a high yield through a relatively simple process different from conventional methods.

[0011] An aspect of the present invention is a method for producing calcite-type calcium carbonate granules, comprising the following steps: a step of mixing calcite-type calcium carbonate particles, gelatin, and water, and heating and stirring to obtain a gelatin / calcite-type calcium carbonate particle mixed slurry A; a step of dissolving a surfactant in oil and stirring to obtain a solution B; a step of mixing the gelatin / calcite-type calcium carbonate particle mixed slurry A with solution B and stirring to obtain an emulsion C; a step of adding a crosslinking agent to emulsion C and stirring to obtain an emulsion D containing gelatin / calcite-type calcium carbonate composite particles; a step of centrifuging emulsion D containing gelatin / calcite-type calcium carbonate composite particles to obtain gelatin / calcite-type calcium carbonate composite particles; and a step of firing the gelatin / calcite-type calcium carbonate composite particles to obtain calcite-type calcium carbonate granules.

[0012] In this embodiment, in the gelatin / calcite-type calcium carbonate particle mixed slurry A, the mass ratio of gelatin to calcite-type calcium carbonate particles is preferably in the range of 5:10 to 25:10.

[0013] In solution B, the volume ratio of surfactant to oil is preferably in the range of 1:100 to 5:100.

[0014] The volume ratio of the gelatin / calcite-type calcium carbonate particle mixed slurry A to the solution B is preferably in the range of 1:10 to 10:10.

[0015] It is preferred to add a crosslinking agent to emulsion C so that the mass ratio of gelatin to crosslinking agent is in the range of 4:1 to 30:1.

[0016] The gelatin / calcite-type calcium carbonate composite particles are preferably fired at a temperature of 530°C or higher and lower than 650°C.

[0017] The production method of the present invention can produce calcite-type calcium carbonate granules in a high yield using a relatively simple process. By loading various drugs into the pores of the produced calcite-type calcium carbonate, the granules can be used in drug delivery systems, cosmetic additives, food additives, health foods, catalyst supports, etc.

[0018] FIG. 1 is an electron microscope photograph (magnification: 500x) of calcium carbonate granules obtained by the method of Example 1. FIG. 2 is an electron microscope photograph (magnification: 20,000x) of calcium carbonate granules obtained by the method of Example 1. FIG. 3 is an electron microscope photograph (magnification: 500x) of calcium carbonate granules obtained by the method of Example 1. FIG. 4 is an electron microscope photograph (magnification: 500x) of calcium carbonate granules obtained by the method of Example 4. FIG. 5 is an electron microscope photograph (magnification: 20,000x) of calcium carbonate granules obtained by the method of Example 4. FIG. 6 is an X-ray diffraction pattern (magnification: 500x) of calcium carbonate granules obtained by the method of Example 4.

[0019] The embodiments of the present invention will be described in more detail below, but the present invention is not limited to the following embodiments.

[0020] One embodiment is a method for producing calcite-type calcium carbonate granules, comprising the following steps: a step of mixing calcite-type calcium carbonate particles, gelatin, and water, and heating and stirring to obtain a gelatin / calcite-type calcium carbonate particle mixed slurry A; a step of dissolving a surfactant in oil and stirring to obtain a solution B; a step of mixing the gelatin / calcite-type calcium carbonate particle mixed slurry A with solution B and stirring to obtain an emulsion C; a step of adding a crosslinking agent to the emulsion C and stirring to obtain an emulsion D containing gelatin / calcite-type calcium carbonate composite particles; a step of centrifuging the emulsion D containing the gelatin / calcite-type calcium carbonate composite particles to obtain gelatin / calcite-type calcium carbonate composite particles; and a step of firing the gelatin / calcite-type calcium carbonate composite particles to obtain calcite-type calcium carbonate granules.

[0021] Calcium carbonate has the formula CaCO ３ and is a calcium carbonate represented by the formula (I) and is the main component of seashells, eggshells, limestone, chalk, etc. Calcium carbonate is classified into heavy calcium carbonate (natural calcium carbonate) obtained by crushing and classifying limestone, and light calcium carbonate (synthetic calcium carbonate) obtained by chemical reaction, but the calcium carbonate produced in this embodiment is a type of light calcium carbonate. In this specification, when simply referring to calcium carbonate, it refers to light calcium carbonate (synthetic calcium carbonate) unless otherwise specified. Calcium carbonate exists in crystal polymorphs such as calcite crystals (trigonal rhombohedral crystals), aragonite crystals (orthorhombic crystals), and vaterite crystals (hexagonal crystals), but the calcium carbonate particles used in this embodiment are of the calcite type, and the calcium carbonate granules produced in this embodiment are also of the calcite type.

[0022] Here, the calcium carbonate particles used in the embodiments refer to calcium carbonate particles, and include primary particles, secondary particles formed by aggregation of primary particles, and particles having a higher-order structure. The calcium carbonate particles used in the embodiments may have a dense structure (i.e., a structure that is not hollow) or a hollow structure with cavities. In the embodiments, the calcite-type calcium carbonate particles refer to primary particles, secondary particles, and higher-order particles of calcium carbonate having a calcite crystal structure.

[0023] On the other hand, calcium carbonate granules produced by the production method of the embodiment refer to calcium carbonate particles having a relatively large and uniform particle size. The granules are secondary particles or higher-order particles formed by aggregation of primary particles of calcium carbonate, and generally have properties that make them prone to collapse, such as having pores. The calcite-type calcium carbonate granules produced by the embodiment may have a dense structure (i.e., a structure that is not hollow) or a hollow structure with cavities.

[0024] The manufacturing method of the embodiment includes a step of mixing calcite-type calcium carbonate particles, gelatin, and water, heating and stirring, and obtaining a gelatin / calcite-type calcium carbonate particle mixed slurry A. The calcium carbonate used as a raw material in this step is calcite-type, and its primary particle diameter is 10-300 nm, preferably 30-150 nm, more preferably 50-120 nm, and most preferably 80-100 nm. The gelatin used in this step is a protein obtained by extracting collagen fibers contained in animal bones and skin with hot water. Gelatin can be derived from any of bovine, porcine, and fish. When calcite-type calcium carbonate particles, gelatin, and water are mixed and stirred at 50-60°C, preferably 50-55°C, an aqueous slurry in which gelatin and calcite-type calcium carbonate particles are dispersed is obtained. In this case, gelatin and calcite-type calcium carbonate are mixed so that the mass ratio of gelatin to calcite-type calcium carbonate particles in the gelatin / calcite-type calcium carbonate particle mixed slurry A is in the range of 5:10 to 25:10, more preferably 10:10 to 20:10. If the mass of gelatin relative to the mass of calcite-type calcium carbonate particles is reduced, the calcite-type calcium carbonate granules finally obtained in this embodiment tend to have a dense structure rather than a hollow structure. If the mass of gelatin relative to the mass of calcite-type calcium carbonate particles is increased, the calcite-type calcium carbonate granules finally obtained in this embodiment tend to have a hollow structure. It is also preferable to use water in an amount 2.5 to 6 times, preferably 3 to 4.5 times the total mass of gelatin and calcite-type calcium carbonate.

[0025] The manufacturing method of the embodiment includes, apart from the step of obtaining the gelatin / calcite-type calcium carbonate particle mixed slurry A, a step of dissolving a surfactant in oil and stirring to obtain a solution B. The surfactant used in this step may be any surfactant that dissolves in the oil described below, and can be selected from, for example, anionic surfactants such as monoalkyl sulfates, alkyl polyoxyethylene sulfates, alkyl benzene sulfonates, and monoalkyl phosphates; cationic surfactants such as alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, and alkyl benzyl dimethyl ammonium salts; amphoteric surfactants such as alkyl carboxybetaine; and nonionic surfactants such as polyoxyethylene alkyl ethers, fatty acid sorbitan esters, alkyl polyglycosides, fatty acid diethanolamides, and alkyl monoglyceryl ethers. In particular, water-soluble nonionic surfactants such as polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monopalmitate, and polyoxyethylene sorbitan monolaurate, known as Tween or polysorbates, and sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate, and sorbitan monolaurate, known as SPAN, are preferred. Furthermore, oils that are liquid at room temperature, such as paraffinic base oils, naphthenic base oils, vegetable or animal edible oils, and industrial oils and fats, can be used as oils to dissolve the surfactants. Paraffinic base oils or edible oils are particularly preferred. The volume ratio of surfactant to oil can be in the range of 1:100-5:100, preferably 1:100-2:100.

[0026] After obtaining the gelatin / calcite-type calcium carbonate particle mixed slurry A and solution B, a step of mixing and stirring the gelatin / calcite-type calcium carbonate particle mixed slurry A with solution B is carried out to obtain an emulsion C. The gelatin / calcite-type calcium carbonate particle mixed slurry A is added to solution B and mixed so that the volume ratio of the gelatin / calcite-type calcium carbonate particle mixed slurry A to solution B is in the range of 1:10 to 10:10, preferably in the range of 1:10 to 2:10. When mixing the two, the gelatin / calcite-type calcium carbonate particle mixed slurry A may be added to solution B all at once, or solution B may be added dropwise while stirring solution B. Alternatively, solution B may be added all at once to the gelatin / calcite-type calcium carbonate particle mixed slurry A, or solution B may be added dropwise while stirring the gelatin / calcite-type calcium carbonate particle mixed slurry A. The mixture of the two can be stirred using an existing stirring device such as a magnetic stirrer, a stirrer equipped with various stirring blades, or an ultrasonic stirrer. The stirring speed is, for example, 300-1500 rpm, preferably 700-1200 rpm. In this manner, emulsion C is obtained. Emulsion C is a liquid in which aggregates of gelatin and calcite-type calcium carbonate particles are emulsified (dispersed) in oil. By appropriately changing the stirring speed in this step, the aggregation morphology of the gelatin and calcite-type calcium carbonate particles can be changed. In general, slowing the stirring speed tends to result in a structure in which gelatin (hydrophilic portion) and calcite-type calcium carbonate (hydrophobic portion) are randomly aggregated around large aggregates of gelatin (hydrophilic portion), and the diameter of the aggregates tends to be relatively large. Furthermore, if the stirring speed is increased, the gelatin (hydrophilic portion) and the calcite-type calcium carbonate (hydrophobic portion) tend to form a structure in which they are randomly aggregated, and the diameter of the aggregates tends to become relatively small.

[0027] Next, a crosslinking agent is added to the emulsion C, followed by stirring to obtain an emulsion D containing gelatin / calcite-type calcium carbonate composite particles. Any compound can be used as the crosslinking agent as long as it can crosslink the gelatin contained in the gelatin / calcite-type calcium carbonate particles emulsified and dispersed in the emulsion D. Examples of crosslinking agents include 3-ethylcarbodiimide hydrochloride (1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride, etc.), 3-ethylcarbodiimide sulfate (1-(3-dimethylaminopropyl-3-ethylcarbodiimide sulfate, etc.), 3-ethylcarbodiimide nitrate (1-(3-dimethylaminopropyl-3-ethylcarbodiimide nitrate, etc.), transglutaminase, olefin-maleic anhydride copolymer, ammonia reaction products with ethylenically unsaturated anhydride-maleic anhydride copolymer, polyamide epoxy resin, Glutaraldehyde or genipin can be used. In this case, the crosslinking agent can be added to emulsion C so that the mass ratio of gelatin to crosslinking agent is in the range of 4:1 to 30:1, preferably 5:1 to 20:1. When the crosslinking agent is added to emulsion C and stirred, the gelatin in the gelatin / calcite-type calcium carbonate particles is crosslinked to form gelatin / calcite-type calcium carbonate composite particles. In other words, emulsion D is a liquid in which gelatin / calcite-type calcium carbonate composite particles are emulsified and dispersed in oil.

[0028] Next, emulsion D containing the gelatin / calcite-type calcium carbonate composite particles is centrifuged to obtain gelatin / calcite-type calcium carbonate composite particles. The obtained gelatin / calcite-type calcium carbonate composite particles are granular solids formed by the combination of crosslinked gelatin and calcite-type calcium carbonate, and may be, for example, composite particles having a sea-island structure, in which islands of crosslinked gelatin are contained within a sea structure of calcite-type calcium carbonate. Furthermore, gelatin / calcite-type calcium carbonate composite particles may also be obtained in which specifically crosslinked gelatin aggregates in the center, with the crosslinked gelatin and calcite-type calcium carbonate forming a sea-island structure around the center. The gelatin / calcite-type calcium carbonate composite particles obtained by centrifugation can be washed with a cleaning solvent such as water or alcohol, and then appropriately dried. The particle size of the gelatin / calcite type calcium carbonate particles depends on the stirring speed and the amount of crosslinking agent in the step of obtaining emulsion C, and is usually in the range of 1 to 500 μm, preferably 5 to 200 μm.

[0029] The gelatin / calcite-type calcium carbonate composite particles thus obtained are then calcined to obtain calcite-type calcium carbonate granules. The gelatin / calcite-type calcium carbonate composite particles are calcined in air, carbon dioxide, or an inert gas atmosphere such as nitrogen or argon at a temperature of 430°C or higher but lower than 650°C, preferably 450°C or higher but lower than 600°C. When calcined in air, the temperature can be 530°C or higher but lower than 600°C; when calcined in carbon dioxide, the temperature can be 450°C or higher but lower than 500°C; and when calcined in an inert gas, the temperature can be 500°C or higher but lower than 600°C. The gelatin / calcite-type calcium carbonate composite particles can be calcined using an existing ceramics calcination furnace. When the gelatin / calcite-type calcium carbonate composite particles are calcined, the gelatin portion is incinerated (burned), leaving only the calcite-type calcium carbonate portion. That is, only the island structure portion (gelatin) of the gelatin / calcite-type calcium carbonate particles is removed by incineration (combustion), leaving only the sea structure portion (calcite-type calcium carbonate), i.e., the resulting particles have a pore-like shape in places. Such a shape is referred to as granules in this specification. If the firing temperature is too low, the gelatin portion remains in the calcite-type calcium carbonate granules and is partially carbonized. On the other hand, if the firing temperature is too high, some of the calcium carbonate will turn into calcium oxide, and a pore-like structure may not be obtained. The diameter of the resulting calcite-type calcium carbonate granules is almost the same as that of the gelatin / calcite-type calcium carbonate particles obtained in the previous step, and is usually in the range of 1-500 μm, preferably in the range of 5-200 μm, or slightly smaller than that of the gelatin / calcite-type calcium carbonate particles obtained in the previous step. The calcite-type calcium carbonate granules are generally spherical, but there are cases where they have a large hole (cavity) in the center (hollow shape) and cases where they do not have a large hole in the center.

[0030] The production method of the embodiment is suitable for large-scale production of calcite-type calcium carbonate because it can produce calcite-type calcium carbonate granules in high yield using a relatively simple process. The calcite-type calcium carbonate granules obtained are porous with fine pores, and various drugs can be supported in these pores. The calcite-type calcium carbonate produced by the embodiment can be used, for example, as a drug delivery system, a catalyst carrier, an additive for cosmetics and fragrances, a food additive, a health food, or a daily necessities.

[0031] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following examples.

[0032] <Production of Calcite-Type Calcium Carbonate Granules> [Example 1] Gelatin (Fujifilm Wako Pure Chemical Corporation) and calcite-type calcium carbonate with a particle size of 80 nm (Shiraishi Central Research Institute Co., Ltd.) were dispersed in water at a mass ratio of 1:1. The mixture was heated to 50-60°C and stirred using a stirrer to obtain a gelatin / calcite-type calcium carbonate particle mixed slurry (gelatin / calcite-type calcium carbonate particle mixed slurry A). Meanwhile, a surfactant (Span 80, Fujifilm Wako Pure Chemical Corporation) and liquid paraffin (Fujifilm Wako Pure Chemical Corporation) were mixed at a volume ratio of 2:100 and stirred to obtain a solution (Solution B). Next, the gelatin / calcite-type calcium carbonate particle mixed slurry A was added to solution B so that the volume ratio of the gelatin / calcite-type calcium carbonate particle mixed slurry A to solution B was 2:10, and the mixture was stirred at room temperature at a stirring speed of 700 rpm to obtain an emulsion (emulsion C). A crosslinking agent, carbodiimide hydrochloride (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, FUJIFILM Wako Pure Chemical Industries, Ltd.), was added to emulsion C so that the mass ratio of gelatin to crosslinking agent was 4:1. Upon stirring, an emulsion containing gelatin / calcite-type calcium carbonate particles (emulsion D) was obtained. Emulsion D was separated using a centrifuge, and the obtained solid portion was washed five times with acetone and dried at room temperature in the air to obtain gelatin / calcite-type calcium carbonate composite particles. The gelatin / calcite-type calcium carbonate composite particles were fired in a firing furnace at 530° C. in the atmosphere to obtain porous calcium carbonate granules.

[0033] FIG. 1-A is an electron microscope photograph (magnification: 500x) of calcium carbonate granules obtained by the method of Example 1. Porous granules with particle sizes of approximately 10 μm to 30 μm were observed within the field of view. FIG. 1-B is an electron microscope photograph at a magnification of 20,000x, in which the presence of a pore structure on the surface of the granules can be observed. The pore size distribution of the calcium carbonate granules obtained in Example 1 was measured by mercury intrusion porosimetry (Japanese Industrial Standards JIS 1655:2003), and it was found that pores existed in the calcium carbonate granules, as shown in FIG. 2. Furthermore, crystal structure analysis by X-ray diffraction revealed that the calcium carbonate was a calcite crystal (FIG. 3).

[0034] [Examples 2-3] Example 1 was repeated, except that the stirring speed of the gelatin / calcite-type calcium carbonate composite particles was set to 500 rpm. Porous calcite-type calcium carbonate granules were obtained (Example 2). An electron microscope photograph (magnification: 500x) of the calcium carbonate granules obtained in Example 2 is shown in Figure 4. Example 1 was repeated, except that the firing temperature of the gelatin / calcite-type calcium carbonate composite particles was set to 570°C. Porous calcite-type calcium carbonate granules were obtained (Example 3).

[0035] Example 4 Gelatin (FUJIFILM Wako Pure Chemical Corporation) and calcite-type calcium carbonate with a particle size of 80 nm (Shiraishi Central Research Institute Co., Ltd.) were dispersed in water at a mass ratio of 2:1. The mixture was heated to 50-60°C and stirred using a stirrer to obtain a gelatin / calcite-type calcium carbonate particle mixed slurry (gelatin / calcite-type calcium carbonate particle mixed slurry A). Meanwhile, a surfactant (Span 80, FUJIFILM Wako Pure Chemical Corporation) and liquid paraffin (FUJIFILM Wako Pure Chemical Corporation) were mixed at a volume ratio of 1:100 and stirred to obtain a solution (Solution B). Solution B was cooled with ice water. Next, the gelatin / calcite-type calcium carbonate particle mixed slurry A was added to solution B cooled with ice water so that the volume ratio of gelatin / calcite-type calcium carbonate particle mixed slurry A to solution B was 1:10, and the mixture was stirred at 0°C and 1000 rpm to obtain an emulsion (emulsion C). A crosslinking agent, carbodiimide hydrochloride (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, Fujifilm Wako Pure Chemical Industries, Ltd.), was added to emulsion C so that the mass ratio of gelatin to crosslinking agent was 10:1. Upon stirring, an emulsion containing gelatin / calcite-type calcium carbonate particles (emulsion D) was obtained. Emulsion D was separated using a centrifuge, and the resulting solid portion was washed five times with acetone and dried at room temperature in the air to obtain gelatin / calcite-type calcium carbonate composite particles. When the gelatin / calcite type calcium carbonate composite particles were fired at 530° C. in air using a firing furnace, porous calcium carbonate granules having a hollow shape with a hole in the center were obtained.

[0036] Figure 5-A is an electron microscope photograph (magnification: 500x) of calcium carbonate granules obtained by the method of Example 4, in which cracks were observed in some granules. This photograph reveals that the calcium carbonate granules have a hollow structure with a hole in the center. Figure 5-B, like Figure 1-B, is an electron microscope photograph of calcium carbonate granules at a magnification of 20,000x. A porous structure can be observed on the surface. Crystal structure analysis of the calcium carbonate granules obtained in Example 4 by X-ray diffraction revealed that the calcium carbonate was calcite crystals (Figure 6).

[0037] [Examples 5-7] Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 450°C. Porous calcite-type calcium carbonate granules were obtained (Example 5). Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 460°C. Porous calcite-type calcium carbonate granules were obtained (Example 6). Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 470°C. Porous calcite-type calcium carbonate granules were obtained (Example 7).

[0038] Example 8 Gelatin (FUJIFILM Wako Pure Chemical Corporation) and calcite-type calcium carbonate with a particle size of 80 nm (Shiraishi Central Research Institute Co., Ltd.) were dispersed in water at a mass ratio of 2:1. The mixture was heated to 50-60°C and stirred using a stirrer to obtain a gelatin / calcite-type calcium carbonate particle mixed slurry (gelatin / calcite-type calcium carbonate particle mixed slurry A). Separately, a surfactant (Span 80, FUJIFILM Wako Pure Chemical Corporation) and liquid paraffin (FUJIFILM Wako Pure Chemical Corporation) were mixed at a volume ratio of 1:100 and stirred to obtain a solution (Solution B). Solution B was cooled with ice water. Next, the gelatin / calcite-type calcium carbonate particle mixed slurry A was added to solution B cooled with ice water so that the volume ratio of gelatin / calcite-type calcium carbonate particle mixed slurry A to solution B was 1:10, and the mixture was stirred at 0°C and 1000 rpm to obtain an emulsion (emulsion C). A crosslinking agent, carbodiimide hydrochloride (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, Fujifilm Wako Pure Chemical Industries, Ltd.), was added to emulsion C so that the mass ratio of gelatin to crosslinking agent was 10:1. Upon stirring, an emulsion containing gelatin / calcite-type calcium carbonate particles (emulsion D) was obtained. Emulsion D was separated using a centrifuge, and the resulting solid portion was washed five times with acetone and dried at room temperature in the air to obtain gelatin / calcite-type calcium carbonate composite particles. When the gelatin / calcite type calcium carbonate composite particles were fired in a firing furnace at 450° C. under carbon dioxide gas, porous calcium carbonate granules having a hollow shape with a hole in the center were obtained.

[0039]

[0040]

[0041] [Comparative Examples] Example 1 was repeated except that the gelatin / calcite-type calcium carbonate composite particles were fired at 500°C. Calcite-type calcium carbonate granules containing residual gelatin carbonized material were obtained (Comparative Example 1). Example 1 was repeated except that the gelatin / calcite-type calcium carbonate composite particles were fired at 650°C. Dense calcite-type calcium carbonate granules in which some calcium carbonate had been converted to calcium oxide were obtained (Comparative Example 2). Example 1 was repeated except that the gelatin / calcite-type calcium carbonate composite particles were fired at 750°C. Calcium oxide particles were obtained (Comparative Example 3).

[0042] Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 400°C. Calcite-type calcium carbonate granules containing residual gelatin carbonized material were obtained (Comparative Example 4). Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 650°C. Dense calcite-type calcium carbonate granules in which some calcium carbonate had been converted to calcium oxide were obtained (Comparative Example 5). Example 1 was repeated, except that the gelatin / calcite-type calcium carbonate composite particles were calcined under carbon dioxide gas at a temperature of 750°C. Calcium oxide particles were obtained (Comparative Example 6).

[0043]

[0044]

[0045] Using the manufacturing method of the present invention, calcite-type calcium carbonate granules could be manufactured through a relatively simple process. The manufactured calcite-type calcium carbonate is a porous granule, and various drugs and the like can be supported in the pores. The manufacturing method of the present invention can also manufacture calcite-type calcium carbonate granules with a hollow center. The obtained calcite-type calcium carbonate granules can be used in drug delivery systems, cosmetic additives, food additives, health foods, catalyst supports, and the like.

Claims

1. The following steps: mixing calcite calcium carbonate particles, gelatin, and water, heating and stirring to obtain a gelatin / calcite calcium carbonate particle mixed slurry A; dissolving a surfactant in oil and stirring to obtain a solution B; mixing the gelatin / calcite calcium carbonate particle mixed slurry A and the solution B and stirring to obtain an emulsion emulsion C; adding a crosslinking agent to the emulsion emulsion C and stirring to obtain an emulsion D containing gelatin / calcite calcium carbonate composite particles; centrifuging the emulsion D containing gelatin / calcite calcium carbonate composite particles to obtain gelatin / calcite calcium carbonate composite particles; and firing the gelatin / calcite calcium carbonate composite particles to obtain calcite calcium carbonate granules. A method for producing calcite calcium carbonate granules comprising these steps.

2. The method for producing calcite calcium carbonate granules according to claim 1, wherein in the gelatin / calcite calcium carbonate particle mixed slurry A, the mass ratio of gelatin to calcite calcium carbonate particles is in the range of 5:10 - 25:

10.

3. The method for producing calcite calcium carbonate granules according to claim 2, wherein in the solution B, the volume ratio of the surfactant to the oil is in the range of 1:100 - 5:

100.

4. The method for producing calcite calcium carbonate granules according to claim 2, wherein the volume ratio of the gelatin / calcite calcium carbonate particle mixed slurry A to the solution B is in the range of 1:10 - 10:

10.

5. The method for producing calcite calcium carbonate granules according to claim 3, wherein the volume ratio of the gelatin / calcite calcium carbonate particle mixed slurry A to the solution B is in the range of 1:10 - 10:

10.

6. The method for producing calcite calcium carbonate granules according to claim 2, wherein the crosslinking agent is added to the emulsion emulsion C such that the mass ratio of gelatin to the crosslinking agent is in the range of 4:1 - 30:

1.

7. The method for producing calcite calcium carbonate granules according to claim 3, wherein the crosslinking agent is added to the emulsion emulsion C such that the mass ratio of gelatin to the crosslinking agent is in the range of 4:1 - 30:

1.

8. The method for producing calcite calcium carbonate granules according to claim 4, wherein the crosslinking agent is added to the emulsion emulsion C such that the mass ratio of gelatin to the crosslinking agent is in the range of 4:1 - 30:

1.

9. The method for producing calcite-type calcium carbonate particles according to claim 5, wherein a crosslinking agent is added to the emulsion emulsion C such that the mass ratio of gelatin to the crosslinking agent is in the range of 4:1 to 30:

1.

10. The method for producing calcite-type calcium carbonate particles according to any one of claims 1 to 9, wherein the gelatin / calcite-type calcium carbonate composite particles are fired at a temperature of 530 °C or higher and lower than 650 °C.

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