Sintered body raw material calcium carbonate, porous calcium carbonate sintered body, dense calcium carbonate sintered body, and methods for producing them

Abstract

To provide a calcium carbonate raw material for a sintered body in which a sintering temperature range of calcium carbonate is precisely controlled to prevent both discoloration and decrease in mechanical strength of the sintered calcium carbonate.SOLUTION: A calcium carbonate raw material for a sintered body is a mixture of calcium carbonate having a purity of 99.95 mass% or more and a compound of one or more metallic elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium and rare earth elements. The calcium carbonate sintered body raw material contains 0.01-10 mass% of the metal element compound based on the mass of the calcium carbonate raw material for the sintered body. Also provided are a production method of the calcium carbonate raw material for the sintered body, a dense sintered body of calcium carbonate using the calcium carbonate raw material for the sintered body, a calcium carbonate porous sintered body and a production method thereof.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sintered body raw material calcium carbonate and a porous sintered calcium carbonate body, and also to a method for producing the same. [Background technology]

[0002] Calcium carbonate sinters are expected to be used in biomedical applications such as growth nuclei for artificial pearls and artificial bones, as well as in water quality modifiers that adsorb fluorine, phosphorus, etc. Conventionally, calcium carbonate sinters have generally been produced by isostatically pressing a mixture of calcium carbonate and a sintering aid to form a compact, and then sintering this compact in a carbon dioxide gas atmosphere (Patent Document 1 and Non-Patent Document 1). In order to use calcium carbonate sintered bodies safely for biological applications, it was necessary to reduce the amount of impurities contained in the calcium carbonate sintered bodies. Therefore, a method for producing calcium carbonate sintered bodies using high-purity calcium carbonate with reduced impurity content was proposed (Patent Document 2). The ease of sintering calcium carbonate sinters is affected by the purity of the calcium carbonate used as the raw material. Generally, the higher the purity, the easier it is to sinter, since it can be sintered at a lower temperature. On the other hand, for use in biological applications, calcium carbonate sintered bodies require increased flexibility in shape and improved functionality. To this end, attempts have been made to obtain calcium carbonate sintered bodies of various shapes, including porous bodies, by adding organic components such as dispersants, thickeners, gelling agents, and foaming agents to a mixture of calcium carbonate and sintering aids to form a molded body and then sintering this molded body in carbon dioxide gas. However, when high-purity calcium carbonate and organic components are sintered, the sintering temperature range of calcium carbonate overlaps with the decomposition temperature range of the organic components, and carbonized organic components remain inside or on the surface of the resulting calcium carbonate sintered body, resulting in black discoloration. Therefore, sintering calcium carbonate sintered bodies at high temperatures to prevent discoloration can sometimes result in a decrease in the mechanical strength of the resulting calcium carbonate sintered body. To prevent both discoloration and a decrease in mechanical strength, precise control of the sintering temperature range of calcium carbonate is required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-254240 [Patent Document 2] Japanese Patent Application Publication No. 2017-214238 [Non-Patent Document 1] Satoko Miyamatsuri et al., Effect of Starting Materials on Sintering of Calcium Carbonate, Abstracts of the Society of Inorganic Materials, Vol. 105th, pp. 46-47

[0004] Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to obtain a raw material calcium carbonate for a sintered body having a controlled sintering temperature range by adding a controlled amount of a metal element compound to high-purity calcium carbonate. Another object of the present invention is to prevent discoloration and a decrease in mechanical strength of the calcium carbonate sintered body, which may occur during sintering, by using the raw material calcium carbonate for a sintered body of the present invention having an appropriately controlled sintering temperature range. In addition to the above object, another object of the present invention is to provide a calcium carbonate sintered body having a dense structure obtained by molding and firing the raw material calcium carbonate for a sintered body, and a calcium carbonate sintered body having a porous structure obtained by firing a foaming gel mixture containing the raw material calcium carbonate for a sintered body, a gelling agent, and a foaming agent. [Means for solving the problem]

[0006] One aspect of the present invention is a raw material calcium carbonate for a sintered body, which is obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, and the raw material calcium carbonate for a sintered body contains the compound of the metal element in an amount of 0.01 to 10% by mass based on the mass of the raw material calcium carbonate for the sintered body.

[0007] In the raw material calcium carbonate for a sintered body, the compound of a metal element is preferably one or more compounds selected from the group consisting of oxides, carbides, nitrides, borides, carbonates, silicates, and sulfates. The number of compounds of the metal elements contained in the raw material calcium carbonate for a sintered body is preferably four or less.

[0008] In addition, the average particle diameter (D 50 ) is 0.05 to 0.30 μm, and the 90% particle diameter (D 90 ) is 20 μm or less, and the BET specific surface area is 5 to 25 m 2 / gram is preferred.

[0009] A second aspect of the present invention is a method for producing a raw material calcium carbonate for a sintered body, comprising a step of mixing, with calcium carbonate having a purity of 99.95% by mass or more, a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass, based on the mass of the raw material calcium carbonate for the sintered body. Furthermore, it is preferable that the number of types of compounds of the metal elements to be mixed be four or less.

[0010] In the above-mentioned method for producing raw material calcium carbonate for a sintered body, the compound of the metal element is preferably one or more compounds selected from the group consisting of oxides, carbides, nitrides, borides, carbonates, silicates, and sulfates.

[0011] A third aspect of the present invention is calcium carbonate having a purity of 99.95% by mass or more. and, Compounds of one or more metallic elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium and rare earth elements and a sintered body raw material calcium carbonate, The compound of the metal element is based on the mass of the calcium carbonate raw material for the sintered body. 0.01~10% by mass containing, Sintered body raw material calcium carbonate 、 The calcium carbonate is a dense sintered body obtained by sintering.

[0012] A fourth aspect of the present invention is a method for producing a porous sintered body, comprising: preparing a dispersion containing a raw material calcium carbonate for a sintered body, the raw material calcium carbonate being a mixture of calcium carbonate having a purity of 99.95% by mass or more and a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the raw material calcium carbonate for the sintered body; and a gelling agent; adding a foaming agent to the dispersion and stirring the mixture to prepare a foamed mixture; gelling the foamed mixture to prepare a gelled foamed mixture; and firing the gelled foamed mixture to obtain a porous sintered body.

[0013] In the above-mentioned method for producing a porous sintered calcium carbonate body, the dispersion is preferably prepared so as to contain 20% by volume or more of the calcium carbonate as the raw material for the sintered body.

[0014] In addition, in the method for producing a porous sintered calcium carbonate body, it is preferable to degrease and sinter the foamed mixture gel in an air atmosphere, and then perform main firing in a carbon dioxide atmosphere to obtain a porous sintered calcium carbonate body.

[0015] A fifth aspect of the present invention is a porous sintered calcium carbonate body obtained by firing a foaming mixture gel containing a sintered body raw material calcium carbonate obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with 0.01 to 10% by mass of a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, a gelling agent, and a foaming agent.

[0016] The porous sintered calcium carbonate body preferably contains 99.7% by mass or more of calcium carbonate and has a porosity of 50% by volume or more, and more preferably contains 99.9% by mass or more of calcium carbonate.

[0017] Other aspects of the present invention are a bone filling material containing the above-mentioned porous sintered calcium carbonate, a 3D printer pigment ink containing the above-mentioned sintered body raw material calcium carbonate, and a dielectric material containing the above-mentioned dense sintered calcium carbonate. [Effects of the Invention]

[0018] The sintering temperature can be controlled by adding a controlled amount of a metal element compound to high-purity calcium carbonate. Using calcium carbonate with a controlled sintering temperature, a porous sintered calcium carbonate body that is free from discoloration and has excellent mechanical strength can be obtained. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a photograph of the porous sintered calcium carbonate bodies obtained in Example 1 and Comparative Example 1. [Figure 2] FIG. 2 is a photograph of the porous sintered calcium carbonate bodies obtained in Example 2 and Comparative Example 1, respectively. [Figure 3] Figure 3 shows photographs of a dense sintered calcium carbonate body and a porous sintered calcium carbonate body. DETAILED DESCRIPTION OF THE INVENTION

[0020] Each embodiment will be described below, but the following embodiments are merely examples and the present invention is not limited to the following embodiments.

[0021] One embodiment of the present invention is a raw material calcium carbonate for a sintered body, which is obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, and the compound of the metal element is contained in an amount of 0.01 to 10% by mass based on the mass of the raw material calcium carbonate for a sintered body. In all of the embodiments described below, calcium carbonate refers to a calcium salt represented by the chemical formula CaCO3. While calcium carbonate is found in abundance in nature, such as in seashells, limestone, and eggshells, the calcium carbonate used in the embodiments is chemically synthesized light calcium carbonate (synthetic calcium carbonate). Light calcium carbonate can be produced, for example, by reacting calcium hydroxide with carbon dioxide. Calcium hydroxide can be produced, for example, by reacting calcium oxide with water. Calcium oxide can be produced by mixing limestone ore with coke or the like and calcining the mixture. In this case, carbon dioxide is generated during calcination, and calcium carbonate can be produced by injecting this carbon dioxide into an aqueous suspension of calcium hydroxide and reacting it with calcium hydroxide. Other methods for producing light calcium carbonate include a causticizing reaction in which calcium hydroxide is reacted with a slurry (green liquor) containing sodium carbonate; a method in which calcium chloride solution, a by-product of the ammonia soda process, is reacted with a sodium carbonate or ammonium carbonate solution; or a carbonation method for the exhaust gas from a combustion furnace such as an industrial boiler. Precipitated calcium carbonate comes in various crystalline forms, such as calcite, aragonite, and vaterite, but it is particularly preferable to use synthetic calcium carbonate in the form of calcite. Furthermore, the particles of the precipitated calcium carbonate are preferably spherical, as well as roughly cubic, spindle-shaped, or needle-shaped.

[0022] The sintered body raw material calcium carbonate of the embodiment is preferably obtained using calcium carbonate with a purity of 99.95% by mass or more. The purity of calcium carbonate is more preferably 99.97% by mass or more, and even more preferably 99.99% by mass or more. Such high-purity calcium carbonate can be produced, for example, by the conventional method disclosed in JP 2012-240872 A. By using high-purity calcium carbonate, the amount of sintering aid required during sintering can be reduced. The upper limit of the purity of calcium carbonate is not particularly limited, but is generally 99.9999% by mass.

[0023] The sintered body raw material calcium carbonate of the embodiment is obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements. The sintered body raw material calcium carbonate of the embodiment is obtained by intentionally mixing a compound of a metal element with the above-mentioned high-purity calcium carbonate. Here, the compound of a metal element is one or more compounds selected from the group consisting of a metal oxide, a metal carbide, a metal nitride, a metal boride, a metal carbonate, a metal silicate, and a metal sulfate. Examples of compounds of metal elements that can be mixed with high-purity calcium carbonate include calcium oxide, calcium carbide, calcium sulfate, calcium silicate, silicon dioxide, aluminum oxide, zinc dioxide, magnesium dioxide, barium dioxide, strontium oxide, boron oxide, stannous oxide, stannic oxide, gallium (III) oxide, lanthanum oxide, cerium oxide, silicon carbide, tetraaluminum tricarbide, dialuminum hexacarbide, zinc carbide, barium carbide, strontium dicarbide, boron carbide, silicon nitride, and aluminum nitride. Examples of suitable metal compounds include aluminum, zinc nitride, magnesium nitride, barium nitride, strontium nitride, boron nitride, tin nitride, gallium nitride, yttrium nitride, silicon boride, aluminum diboride, magnesium diboride, barium boride, strontium hexaboride, aluminum carbonate, zinc carbonate, magnesium carbonate, barium carbonate, strontium carbonate, tin carbonate, iron oxide, iron nitride, iron carbonate, iron sulfide, titanium oxide, titanium nitride, titanium sulfide, zirconium oxide, zirconium nitride, and zirconium carbonate. These compounds may be used alone or in combination of two or more. Among these compounds, silicon dioxide, calcium silicate, or magnesium carbonate is particularly preferred. It is preferable to use one or more, and preferably one or more, of compounds of such metal elements in combination of two or more.In the embodiment, the reason why metal element compounds are mixed with calcium carbonate having a purity of 99.95% by mass or more is to control the sintering temperature range during sintering and thereby improve the appearance and strength of the calcium carbonate sintered body, as will be described later. However, if too many metal element compounds are mixed, the compounds may interact with each other and cause adverse effects. Therefore, it is preferable that the number of types of metal element compounds to be mixed is four or less, or two or less.

[0024] The compound of the metal element is preferably mixed with high-purity calcium carbonate in an amount of 0.01 to 10% by mass based on the mass of the calcium carbonate as a raw material for the sintered body. Controlling the amount of the compound of the metal element is important because it is related to the sintering temperature when obtaining a sintered body, as will be described later. The amount of the compound of the metal element is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the mass of the calcium carbonate as a raw material for the sintered body.

[0025] The sintered body raw material calcium carbonate of the embodiment has an average particle diameter (D 50 The average particle diameter (D) is preferably 0.05 to 0.30 μm. 50 The average particle diameter (D) is more preferably in the range of 0.08 to 0.3 μm, and even more preferably in the range of 0.1 to 0.25 μm. 50 When a sintered body is produced using calcium carbonate as a raw material for a sintered body having the above properties, a sintered body with high density can be produced. The particle size distribution by transmission electron microscope observation can be determined by observing the calcium carbonate to be measured using a transmission electron microscope and measuring 1,000 or more calcium carbonate particles.

[0026] The sintered body raw material calcium carbonate of the embodiment has a 90% particle diameter (D 90 ) is preferably 5 μm or less. 90) is more preferably 3 μm or less, and even more preferably 2 μm or less. 90 When a sintered body is manufactured using calcium carbonate as a raw material for sintered bodies having a particle size distribution of 90%, D , the resulting sintered body has less unevenness, regardless of whether it is dense or porous. 90 ) can be determined from the particle size distribution measured from the light intensity distribution pattern obtained by irradiating a particle with a laser beam and analyzing the diffracted light and scattered light emitted from the particle.

[0027] The sintered body raw material calcium carbonate of the embodiment has a BET specific surface area of ​​5 to 25 m 2 The BET specific surface area is preferably 7 to 20 m / g. 2 / g, more preferably 8 to 15m 2 / g. By setting the BET specific surface area of ​​the sintered body raw material calcium carbonate within the above range, the sintering temperature can be lowered, thereby facilitating sintering. The BET specific surface area can be determined by adsorbing gas molecules (such as nitrogen) with a known adsorption area onto a substance and measuring the amount of adsorption. The BET specific surface area of ​​calcium carbonate can be measured in accordance with Japanese Industrial Standard JIS Z 8830, "Method for measuring the specific surface area of ​​powder (solid) by gas adsorption." The sintered body raw material calcium carbonate of the embodiment can be used, for example, as a component of 3D printer pigment ink, and can also be used as a raw material for porous sintered calcium carbonate.

[0028] A second embodiment of the present invention is a method for producing raw material calcium carbonate for a sintered body, comprising a step of mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the raw material calcium carbonate for a sintered body. The second embodiment is a method for producing the raw material calcium carbonate for a sintered body of the first embodiment. The calcium carbonate used in the production method of the second embodiment preferably has a purity of 99.95% by mass or more. The purity of the calcium carbonate used is more preferably 99.97% by mass or more, and even more preferably 99.99% by mass or more. Such high-purity calcium carbonate can be produced, for example, by a conventional method disclosed in Japanese Patent Laid-Open No. 2012-240872. By using high-purity calcium carbonate as a raw material, the amount of sintering aid required during sintering can be reduced. The upper limit of the purity of calcium carbonate is not particularly limited, but is generally 99.9999% by mass. Meanwhile, the compound of a metal element used in the second embodiment is one or more compounds selected from the group consisting of metal oxides, metal carbides, metal nitrides, metal borides, metal carbonates, metal silicates, and metal sulfates.Examples of compounds of metal elements that can be mixed with high-purity calcium carbonate include calcium oxide, calcium carbide, calcium sulfate, calcium silicate, silicon dioxide, aluminum oxide, zinc dioxide, magnesium dioxide, barium dioxide, strontium oxide, boron oxide, stannous oxide, stannic oxide, gallium (III) oxide, lanthanum oxide, cerium oxide, silicon carbide, tetraaluminum tricarbide, dialuminum hexacarbide, zinc carbide, barium carbide, strontium dicarbide, boron carbide, silicon nitride, and aluminum nitride. Examples of suitable metal compounds include yttrium nitride, zinc nitride, magnesium nitride, barium nitride, strontium nitride, boron nitride, tin nitride, gallium nitride, yttrium silicon boride, aluminum diboride, magnesium diboride, barium boride, strontium hexaboride, aluminum carbonate, zinc carbonate, magnesium carbonate, barium carbonate, strontium carbonate, tin carbonate, iron oxide, iron nitride, iron carbonate, iron sulfide, titanium oxide, titanium nitride, titanium sulfide, zirconium oxide, zirconium nitride, and zirconium carbonate. These compounds may be used alone or in combination of two or more. Among these compounds, silicon dioxide, magnesium hydroxide, or calcium silicate is particularly preferred. It is preferable to use one or more, and preferably one or more, of compounds of such metal elements in combination of two or more. In the embodiment, the reason why metal element compounds are mixed with calcium carbonate having a purity of 99.95% by mass or more is to control the sintering temperature range during sintering and thereby improve the appearance and strength of the calcium carbonate sintered body, as will be described later. However, if too many metal element compounds are mixed, the compounds may interact with each other and cause adverse effects. Therefore, it is preferable that the number of types of metal element compounds to be mixed is four or less, or two or less.

[0029] The sintered body raw material calcium carbonate is obtained by mixing the above-mentioned high-purity calcium carbonate with the above-mentioned metal compound. The metal compound is preferably mixed with the high-purity calcium carbonate in an amount of 0.01 to 10% by mass, based on the mass of the sintered body raw material calcium carbonate. Controlling the amount of the metal compound is important because it affects the sintering temperature when obtaining the sintered body, as described below. The amount of the metal compound is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the mass of the sintered body raw material calcium carbonate. The high-purity calcium carbonate and the metal compound are preferably mixed by weighing predetermined amounts of calcium carbonate and metal compound, and mixing them using a solid mixer or solid stirrer, while minimizing the destruction of the high-purity calcium carbonate raw material particles. Preferably, the high-purity calcium carbonate and the metal compound are dispersed in an appropriate dispersion medium using a ball mill and wet-mixed.

[0030] A third embodiment of the present invention is a dense sintered calcium carbonate obtained by sintering a raw material calcium carbonate for a sintered body, which is obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the raw material calcium carbonate for a sintered body. The third embodiment is a dense sintered calcium carbonate obtained by sintering the raw material calcium carbonate for a sintered body of the first embodiment. In the embodiment, the term "dense" refers to a calcium carbonate having an average particle size (D) in the particle size distribution of the raw material calcium carbonate for a sintered body. 50 ), and for example, it refers to a structure in which the relative density is approximately 70% or more. The relative density is calculated by multiplying the bulk density of the compact by the theoretical density of calcium carbonate (2.711 g / cm 3) divided by the mass ratio. The bulk density of the compact can be measured by Archimedes' method. The calcium carbonate used in the third embodiment preferably has a purity of 99.95% by mass or more. The purity of the calcium carbonate used is more preferably 99.97% by mass or more, and even more preferably 99.99% by mass or more. Such high-purity calcium carbonate can be produced, for example, by the conventional method disclosed in JP 2012-240872 A. By using high-purity calcium carbonate as a raw material, the amount of sintering aid required during sintering can be reduced. The upper limit of the purity of calcium carbonate is not particularly limited, but is generally 99.9999% by mass. On the other hand, the compound of a metal element used in the third embodiment is one or more compounds selected from the group consisting of metal oxides, metal carbides, metal nitrides, metal borides, metal carbonates, metal silicates, and metal sulfates. Examples of compounds of metal elements that can be mixed with high-purity calcium carbonate include calcium oxide, calcium carbide, calcium sulfate, calcium silicate, silicon dioxide, aluminum oxide, zinc dioxide, magnesium dioxide, barium dioxide, strontium oxide, boron oxide, stannous oxide, stannic oxide, gallium (III) oxide, lanthanum oxide, cerium oxide, silicon carbide, tetraaluminum tricarbide, dialuminum hexacarbide, zinc carbide, barium carbide, strontium dicarbide, boron carbide, silicon nitride, and aluminum nitride. Examples of suitable inorganic fillers include aluminum, zinc nitride, magnesium nitride, barium nitride, strontium nitride, boron nitride, tin nitride, gallium nitride, yttrium nitride, silicon boride, aluminum diboride, magnesium diboride, barium boride, strontium hexaboride, aluminum carbonate, zinc carbonate, magnesium carbonate, barium carbonate, strontium carbonate, tin carbonate, iron oxide, iron nitride, iron carbonate, iron sulfide, titanium oxide, titanium nitride, titanium sulfide, zirconium oxide, zirconium nitride, and zirconium carbonate. These compounds may be used alone or in combination of two or more. Among these compounds, silicon dioxide, magnesium hydroxide, or calcium silicate is particularly preferred.It is preferable to use a combination of one to four, preferably one to two, types of such metal element compounds. In the embodiment, the reason for mixing metal element compounds with calcium carbonate with a purity of 99.95% by mass or higher is to control the sintering temperature range during sintering and thereby improve the appearance and strength of the calcium carbonate sintered body, as will be described later. However, mixing too many metal element compounds may cause adverse effects due to interactions between the metal element compounds. Therefore, it is preferable to mix four or two or fewer types of metal element compounds.

[0031] A dense calcium carbonate sinter can be obtained by sintering the sintered body raw material calcium carbonate of the embodiment. The sintering of the sintered body raw material calcium carbonate is preferably carried out by firing in a carbon dioxide atmosphere. Firing in a carbon dioxide atmosphere is carried out at a temperature of 500 to 900°C, preferably 700 to 900°C. Firing is carried out to sinter calcium carbonate to obtain a dense calcium carbonate sinter. The dense calcium carbonate sinter is produced using a sintered body raw material calcium carbonate, which is one embodiment, containing high-purity calcium carbonate and a compound of a metal element as a raw material. Firing of the sintered body raw material calcium carbonate can be carried out using a firing furnace, electric furnace, gas furnace, or the like capable of controlling the atmospheric gas. Firing may be carried out by irradiating the sintered body raw material calcium carbonate with a laser, or by irradiating a laser using a 3D printer or the like. The dense calcium carbonate sintered body of the embodiment can be used itself as a dielectric, for example, or as a dense bone filler, building material, or the like. Dense sintered calcium carbonate has a generally uniform structure, as can be seen, for example, in the right side of the photograph in Figure 3.

[0032] A fourth embodiment of the present invention is a method for producing a dense sintered calcium carbonate. The method for producing a dense sintered calcium carbonate includes the following steps: mixing calcium carbonate having a purity of 99.95% by mass or higher with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass, based on the mass of the raw material calcium carbonate, to obtain a raw material calcium carbonate; and then firing the raw material calcium carbonate. The first step of the fourth embodiment can be performed in the same manner as in the second embodiment. A dense sintered calcium carbonate can be obtained by firing the raw material calcium carbonate obtained in the same manner as in the second embodiment. In the embodiments, "dense" refers to a generally uniform structure with few or no pores, and refers to a structure having a relative density of, for example, approximately 70% or higher, preferably 90% to 100%, and more preferably 95% to 100%. The sintered body raw material calcium carbonate is preferably fired in a carbon dioxide atmosphere. Firing in a carbon dioxide atmosphere is performed at a temperature of 500 to 900°C, preferably 700 to 900°C. Firing is performed to sinter calcium carbonate to obtain a dense calcium carbonate sintered body. The sintered body raw material calcium carbonate can be fired using a firing furnace, electric furnace, gas furnace, or the like that can control the atmospheric gas. Firing may be performed by irradiating the sintered body raw material calcium carbonate with a laser, or by irradiating a laser using a 3D printer or the like. The dense calcium carbonate sintered body of the embodiment can be used by itself, for example, as a dielectric material, or can be used as a dense bone filling material, building material, or the like.

[0033] The sintered body of the present invention is desirably compression molded before sintering, and the compression molding is preferably uniaxial molding. A porous sintered body of calcium carbonate having a high density can be produced using a body molded by uniaxial molding. In addition to uniaxial molding, a molded body may be produced by a conventionally known molding method such as isostatic pressing, doctor blade molding, or slip casting. The relative density of the molded body is preferably 50% or more, more preferably 55% or more, and even more preferably 58% or more. The relative density of the molded body is determined by multiplying the bulk density of the molded body by the theoretical density of calcium carbonate (2.711 g / cm). 3 The bulk density of the compact can be measured by the Archimedes method. The relative density of the compact is 196.1 MPa (2000 kgf / cm 2 ) is preferably obtained by uniaxial press molding at a molding pressure of 1000 kJ / cm2. By adjusting the relative density within the above range, a high-purity porous sintered body of calcium carbonate with a higher density can be obtained. The dense calcium carbonate sintered body obtained by the manufacturing method of the embodiment has a generally uniform structure, as can be seen, for example, in the right part of the photograph in Fig. 3. Note that the present embodiment can also be carried out by using the calcium carbonate as the raw material for the sintered body of one embodiment and firing it.

[0034] A fifth embodiment of the present invention is a method for producing a porous sintered calcium carbonate body. The method for producing a porous sintered calcium carbonate body includes the following steps: preparing a dispersion containing a sintered body raw material calcium carbonate, which is obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the sintered body raw material calcium carbonate, and a gelling agent; adding a foaming agent to the dispersion and stirring the mixture to prepare a foamed mixture; gelling the foamed mixture to prepare a gelled foamed mixture; and firing the gelled foamed mixture to obtain a porous sintered calcium carbonate body. In this embodiment, the term "porous" refers to the average particle size (D ) in the particle size distribution of the sintered body raw material calcium carbonate, regardless of whether it is fine pores or large pores. 50 ) and refers to a structure in which there are multiple pores larger than the pore size, for example, a structure in which the porosity is approximately 10%. The pores present in a porous sintered body may be either closed pores or interconnected pores.

[0035] A sintered body raw material calcium carbonate obtained by mixing calcium carbonate having a purity of 99.95% by mass or higher with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the sintered body raw material calcium carbonate is the sintered body raw material calcium carbonate of the first embodiment described above, and can be obtained by the sintered body raw material calcium carbonate manufacturing method of the second embodiment described above. A dispersion is prepared by mixing the sintered body raw material calcium carbonate, a gelling agent, and an appropriate dispersion medium. The gelling agent is an agent that increases the viscosity of the sintered body raw material calcium carbonate dispersion to form a gel. Examples of gelling agents that can be used include polymer surfactants such as poly(meth)acrylates, such as sodium polyacrylate, potassium polyacrylate, and sodium polymethacrylate. The sintered body raw material calcium carbonate and gelling agent are gradually added to a dispersion medium such as water, and the sintered body raw material calcium carbonate is dispersed using a device with strong stirring power such as a disperser, mixer, or ball mill. The sintered body raw material calcium carbonate is generally mixed so that the concentration in the dispersion liquid is 20% by volume or more, preferably 30 to 70% by volume. The gelling agent can be added in an amount of 0 to 3 parts by mass, preferably 0.1 to 1 part by mass, per 100 parts by mass of the sintered body raw material calcium carbonate.

[0036] A foaming agent is added to the thus-obtained dispersion of calcium carbonate as a raw material for a sintered body and stirred to prepare a foamed mixture. The foaming agent is used to foam the dispersion of calcium carbonate as a raw material for a sintered body to obtain a porous sintered body. Examples of foaming agents that can be used include alkyl sulfate ester salts such as triethanolamine lauryl sulfate, polyoxyethylene alkyl ether sulfate ester salts, polyoxyethylene alkyl ether acetate salts, and alkyl polyglucosides. The foaming agent can be added so that its concentration in the dispersion is approximately 0.01 to 10% by mass, preferably 0.01 to 1% by mass. The dispersion is preferably stirred using a hand mixer, a disperser, or the like. Since the temperature of the dispersion may rise during stirring, the dispersion may be cooled while stirring, if necessary.

[0037] The foam mixture is then gelled to form a foam mixture gel. The gelling of the foam mixture is achieved by increasing the temperature. The foam mixture can be gelled by increasing the temperature up to 100°C, preferably up to 80°C.

[0038] If necessary, a filler or sintering aid can be added to the foamed mixture gel. The filler can increase the strength of the bubbles in the foamed mixture gel and stabilize the shape of the foamed mixture gel. Examples of fillers that can be used include starch, dextrin, polyvinyl alcohol, polypropylene glycol, pectin, alginic acids, and sodium salt of carboxycellulose. The sintering aid is used to adjust the firing temperature of the foamed mixture gel. The sintering aid preferably contains at least two carbonates selected from lithium, sodium, and potassium, and has a melting point of 600°C or less. The melting point of the sintering aid is preferably 550°C or less, more preferably 530°C or less, and even more preferably in the range of 450 to 520°C. By setting the melting point of the sintering aid within the above range, a porous calcium carbonate sintered body can be produced by firing at a lower temperature. Alternatively, a mixture of potassium fluoride, lithium fluoride, and sodium fluoride may be used as the sintering aid. It is preferable that such a mixture also has the melting point within the above range. An example of such a sintering aid is a mixture having a composition range of 10 to 60 mol % potassium fluoride, 30 to 60 mol % lithium fluoride, and 0 to 30 mol % sodium fluoride. By using such a range, a porous sintered calcium carbonate body can be produced with a higher density by firing at a lower temperature.

[0039] The resulting foamed mixture gel is fired to obtain a porous sintered calcium carbonate body. The firing of the foamed mixture gel is preferably carried out by first debinding and sintering in an air atmosphere, followed by main firing in a carbon dioxide atmosphere. The debinding and sintering in an air atmosphere can be carried out at a temperature at which decarbonation of calcium carbonate does not occur, specifically, at a temperature in the range of 200 to 600°C, preferably 300 to 550°C. The debinding and sintering is a process for decomposing and burning off (debinding) the foaming agent, gelling agent, and, in some cases, organic substances used as excipients. Meanwhile, the main firing in a carbon dioxide atmosphere is carried out at a temperature of 500 to 900°C, preferably 700 to 900°C. The main firing is a process for sintering calcium carbonate to obtain a porous sintered calcium carbonate body. The production of a porous sintered calcium carbonate body is preferably carried out using, as a raw material, a sintered calcium carbonate material containing high-purity calcium carbonate and a compound of a metal element, which is one embodiment of the present invention. Generally, when calcium carbonate with a purity of 99.95% or higher is used as the raw material for a sintered body, the sintering temperature is lowered, which tends to facilitate sintering. However, if the sintering temperature of calcium carbonate is lowered and overlaps with the temperature range where organic substances such as foaming agents and gelling agents decompose (approximately below 500°C, depending on the organic substance used), the carbonized organic substances may deposit and remain near the surface of the porous sintered calcium carbonate, resulting in coloration of the porous sintered calcium carbonate. Therefore, it is preferable to use raw material calcium carbonate for a sintered body, which is a mixture of calcium carbonate with a purity of 99.95% by mass or higher and a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements. When a metal element compound is added to calcium carbonate with a purity of 99.95% or higher so that the compound is contained in an amount of 0.01 to 10 mass% based on the mass of the calcium carbonate raw material for the sintered body, the sintering temperature rises slightly (approximately 600°C or higher, depending on the metal element compound added), and the sintering temperature does not overlap with the decomposition temperature of organic matter.Therefore, when firing the foamed mixture gel, a two-stage firing process is possible: first, firing is performed in an air atmosphere at temperatures up to 600°C to promote decomposition of organic matter (debinding sintering), and then firing is performed at a higher temperature in a carbon dioxide atmosphere to obtain a porous sintered calcium carbonate body. This firing process makes it possible to obtain a porous sintered calcium carbonate body free of carbonized organic matter. The foamed mixture gel can be sintered using an oven capable of controlling the atmospheric gas. The foamed mixture gel can be sintered by irradiating it with a laser, or it can also be sintered by irradiating it with a laser using a 3D printer or the like.

[0040] The foamed mixture gel may be freeze-dried before being fired. Freeze-drying the foamed mixture gel allows the shape of the foamed mixture gel to be easily maintained, and a porous sintered calcium carbonate body with a good shape can be obtained. Specifically, it is preferable to pre-freeze the foamed mixture gel at −40°C or less under normal pressure for 2 hours or more, and then gradually increase the temperature while sublimating the ice crystals under reduced pressure. The reduced pressure is preferably 20 Pa or less, more preferably 10 Pa or less. The temperature is desirably gradually increased while maintaining the reduced pressure within a range that does not cause the ice crystals to melt, and can generally be controlled within the range of −40°C to 60°C.

[0041] A porous sintered calcium carbonate body having a desired shape can be obtained by sintering a molded body obtained by previously molding and drying the foaming mixture gel. The molding may be performed by a conventional molding method such as doctor blade molding or slip casting. The porous sintered calcium carbonate body obtained by the manufacturing method of the embodiment has a structure with multiple pores, as shown in the left side of the photograph in Fig. 3.

[0042] The porous sintered calcium carbonate of the sixth embodiment of the present invention can be obtained by the manufacturing method of the porous sintered calcium carbonate of the fifth embodiment. The porous sintered calcium carbonate has a structure with a plurality of pores, as shown, for example, in the left photograph of Fig. 3. The porous sintered calcium carbonate of the embodiment can be used for biological applications such as bone filling material, as well as for water purification agents, ceramic filters, etc.

[0043] Specific examples according to the embodiment will be described below, but the present invention is not limited to these examples. [Example]

[0044] <Experimental Example 1: Production of dense sintered calcium carbonate using silicon-added calcium carbonate> (Calcium carbonate) Purity: 99.99% by mass. Average particle size (D 50 ) 4 μm, 90% particle diameter (D 90 )15μm, BET specific surface area 10m 2 / g calcium carbonate (developed by Shiraishi Central Research Institute, Inc.) was prepared. The purity of calcium carbonate was calculated by the following difference method: using an inductively coupled plasma emission spectrometer, the amount of impurities in a test solution in which a sample of known mass had been dissolved was measured, the sum of the obtained results was taken as the impurity content, and the value obtained by subtracting the impurity content from the total was taken as the purity. The average particle diameter (D 50 The particle diameter of 1,500 calcium carbonate particles was measured using a transmission electron microscope, and the particle diameter was calculated from the particle diameter distribution. The 90% particle diameter (D 90 ) was determined from the particle size distribution measured from the light intensity distribution pattern obtained by irradiating particles with a laser beam and analyzing the diffracted and scattered light emitted from the particles. The BET specific surface area was measured by the single-point method using a Shimadzu FlowSorb 2200. Using the above calcium carbonate, a dense sintered calcium carbonate body was produced as follows.

[0045] (Production of dense sintered calcium carbonate) Tetraethyl orthosilicate (hereinafter referred to as "TEOS") was hydrolyzed with aqueous ammonia. TEOS formed a sol whose main component was silicon dioxide (SiO2). 20 g of the above calcium carbonate was dispersed in distilled water to prepare a slurry, to which the sol was added and wet-mixed. The sol clung to the surface of the calcium carbonate particles to form a composite. The amount of sol added relative to the calcium carbonate was calculated in terms of SiO2 so that the value of SiO2 / (SiO2+CaCO3) x 100 was 0.02%, 0.2%, 0.6%, and 2.0%, respectively. Each wet-mixed slurry was dehydrated and then crushed in a mortar to obtain silicon-doped calcium carbonate powder. A calcium carbonate slurry without sol (i.e., SiO2 / (SiO2 + CaCO3) × 100 = 0%) was also prepared. A small amount of ethanol was added to each of the resulting powders, and the mixture was wet-mixed. The resulting powders were then formed into cylindrical shapes using an isostatic press capable of uniaxial and cold isostatic pressing to obtain pre-fired samples. The pre-fired samples were gradually heated to 900°C in a carbon dioxide atmosphere and fired. The shrinkage behavior during firing was measured using a thermal shrinkage measurement device. The initial sintering completion temperature was used as an indicator for evaluating the shrinkage behavior during firing. The initial sintering completion point was defined as the point at which a shrinkage rate of 4% (linear shrinkage rate of 1.4%) was reached. The temperatures at which sintering was completed for calcium carbonate with silicon contents of 0%, 0.02%, 0.2%, 0.6%, and 2.0% were 450°C, 600°C, 740°C, 750°C, and 770°C, respectively.

[0046] <Experimental Example 2: Production of dense sintered calcium carbonate using magnesium-added calcium carbonate> Magnesium-added calcium carbonates were prepared in the same manner as in Experimental Example 1, except that magnesium hydroxide was used instead of TEOS. Calcium carbonates with Mg(OH)2 / (Mg(OH)2 + CaCO3) × 100 values ​​of 0%, 0.05%, and 0.2% were obtained. Cylindrical pre-fired samples were prepared using these calcium carbonates as in Experimental Example 1. They were then fired in a carbon dioxide atmosphere at a gradually elevated temperature up to 900°C, and their shrinkage behavior during firing was measured using a thermal shrinkage measuring device. As in Experimental Example 1, the initial sintering completion point was determined when a shrinkage rate of 4% (linear shrinkage rate of 1.4%) was reached. The sintering completion temperatures for calcium carbonates with magnesium contents of 0%, 0.05%, and 0.2% were 450°C, 480°C, and 610°C, respectively.

[0047] The above two experimental examples show that high-purity calcium carbonate with a purity of 99.99% by mass has a low sintering temperature, that the sintering temperature increases when silicon compounds, magnesium compounds, etc. are added to it, and that the sintering temperature can be controlled by controlling the amounts of these compounds added. Therefore, porous sintered calcium carbonate was produced using silicon-added calcium carbonate and magnesium-added calcium carbonate with controlled sintering temperatures.

[0048] <Production of porous sintered calcium carbonate> [Example 1] Pure water was placed in a polyethylene bottle containing an appropriate amount of zirconia balls, and the silicon-added calcium carbonate (SiO content 0.6% by mass) used in Experimental Example 1 was added to the pure water to make a 39% by volume solution. Next, 0.8 parts by mass of polyvinyl alcohol as an excipient and 2.5 parts by mass of a polymer surfactant (special polycarboxylic acid type polymer surfactant, manufactured by Kao Corporation, trade name "Poise 520") as a dispersant were added to 100 parts by mass of calcium carbonate, and then wet-mixed for 12 hours using a pod mill. A 19% by mass aqueous solution of polyoxyethylene alkyl ether as a foaming agent was added to the resulting slurry to make a dispersion, with 2 ml per 10 g of slurry. The dispersion was foamed using a hand mixer to obtain a foamed mixture. The resulting foamed mixture was heated to 80°C to gel, obtaining a foamed mixture gel. This foamed mixture gel was poured into a mold and freeze-dried in this state. The freeze-drying conditions were as follows: pre-freezing at -40°C under normal pressure for 12 hours, followed by holding at 30°C under a reduced pressure of 10 Pa for 48 hours. The freeze-dried foamed mixture gel was heated in an air atmosphere to the firing temperature (500°C) at a rate of 10°C per minute, and then fired for 10 hours. After cooling, it was heated in a carbon dioxide atmosphere at the same heating rate to the main firing temperature (700°C), and then fired for 3 hours to obtain a porous sintered calcium carbonate body. A white porous sintered calcium carbonate body with no visible burn marks on the surface was obtained. The porosity of the porous sintered calcium carbonate body was 85%.

[0049] [Example 2] Pure water was placed in a polyethylene bottle containing an appropriate amount of zirconia balls, and the magnesium-added calcium carbonate used in Experimental Example 2 (Mg(OH)2 content 0.2% by mass) was added to the pure water to make a 39% by volume solution. Next, 0.8 parts by mass of polyvinyl alcohol as an excipient and 2.5 parts by mass of a polymer surfactant (special polycarboxylic acid type polymer surfactant, manufactured by Kao Corporation, trade name "Poise 520") as a dispersant were added to 100 parts by mass of calcium carbonate, and then wet-mixed for 12 hours using a pod mill. To the resulting slurry, a 19% by mass aqueous solution of polyoxyethylene alkyl ether as a foaming agent was added to make a dispersion, so that 2 ml per 10 g of slurry was obtained. The dispersion was foamed using a hand mixer to obtain a foamed mixture. The resulting foamed mixture was heated to 80°C to gel, obtaining a foamed mixture gel. This foamed mixture gel was poured into a mold and freeze-dried in this state. The freeze-drying conditions were as follows: pre-freezing at -40°C under normal pressure for 12 hours, followed by holding at 30°C under a reduced pressure of 10 Pa for 48 hours. The freeze-dried foamed mixture gel was heated in an air atmosphere to the firing temperature (500°C) at a rate of 10°C per minute, and then fired for 10 hours. After cooling, it was heated in a carbon dioxide atmosphere at the same heating rate to the main firing temperature (700°C), and then fired for 3 hours to obtain a porous sintered calcium carbonate body. A white porous sintered calcium carbonate body with no visible burn marks on the surface was obtained. The porosity of the porous sintered calcium carbonate body was 85%.

[0050] The porosity of the porous sintered calcium carbonate body was determined by cutting the sintered body into a rectangular parallelepiped block, calculating the density from the weight and apparent volume of the block, and calculating the true density of calcium carbonate, 2.711 g / cm 3 The relative density was calculated by dividing the density by 1 / 2, and the value obtained by subtracting the relative density from the total was taken as the porosity.

[0051] [Comparative Example 1] Example 1 was repeated, except that high-purity calcium carbonate with an SiO content of 0 mass%, i.e., a purity of 99.99 mass%, was used instead of silicon-added calcium carbonate with an SiO content of 0.6 mass%. A porous sintered calcium carbonate body with a black, dull surface was obtained.

[0052] [Observation of porous sintered calcium carbonate] The right side of Fig. 1 shows the porous sintered calcium carbonate obtained in Example 1, and the left side of Fig. 1 shows the porous sintered calcium carbonate obtained in Comparative Example 1. The right side of Fig. 2 shows the porous sintered calcium carbonate obtained in Example 2, and the left side of Fig. 2 shows the porous sintered calcium carbonate obtained in Comparative Example 1. When the raw material calcium carbonate for a sintered body of the present invention, in which a metal element compound is added to high-purity calcium carbonate, is used, a white porous sintered calcium carbonate can be obtained. In particular, when the raw material calcium carbonate for a sintered body of the present invention is sintered in two stages, namely, degreasing and sintering and firing, a white porous sintered calcium carbonate can be obtained, as shown on the right side of Fig. 1 and Fig. 2. The porous sintered calcium carbonate of Comparative Example 1 (left side of Figs. 1 and 2), which was obtained by using high-purity calcium carbonate as the raw material calcium carbonate for a sintered body, showed blackening due to decomposition of organic matter, etc.

Claims

1. Calcium carbonate having a purity of 99.95% by mass or more; and a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, The raw material calcium carbonate for a sintered body contains the compound of the metal element in an amount of 0.01 to 10 mass % based on the mass of the raw material calcium carbonate for a sintered body.

2. 2. The sintered body raw material calcium carbonate according to claim 1, wherein the compound of the metal element is one or more compounds selected from the group consisting of oxides, carbides, nitrides, borides, carbonates, silicates, and sulfates.

3. 3. The sintered body raw material calcium carbonate according to claim 1, which is obtained by mixing four or less kinds of compounds of said metal elements.

4. The average particle size (D) in the particle size distribution measured by transmission electron microscopy ５０ ) is 0.05 to 0.30 μm, and the 90% particle diameter (D ９０ ) is 20 μm or less, and the BET specific surface area is 5 to 25 m ２ The sintered body raw material calcium carbonate according to any one of claims 1 to 3, wherein the sintered body raw material calcium carbonate has a sintering strength of 10 ...

5. A method for producing a sintered body raw material calcium carbonate, comprising: A method for producing the raw material calcium carbonate for a sintered body, comprising a step of mixing a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements with calcium carbonate having a purity of 99.95% by mass or more, in an amount of 0.01 to 10% by mass relative to the mass of the raw material calcium carbonate for a sintered body.

6. 6. The method for producing a sintered body raw material calcium carbonate according to claim 5, wherein the compound of the metal element is one or more compounds selected from the group consisting of oxides, carbides, nitrides, borides, carbonates, silicates, and sulfates.

7. 7. The method for producing a raw material calcium carbonate for a sintered body according to claim 5, wherein four or less kinds of compounds of said metal elements are mixed.

8. Calcium carbonate having a purity of 99.95% by mass or more; and a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, A dense sintered calcium carbonate body is obtained by sintering a raw material calcium carbonate containing the compound of the metal element in an amount of 0.01 to 10 mass % based on the mass of the raw material calcium carbonate.

9. A method for producing a sintered body by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements in an amount of 0.01 to 10% by mass based on the mass of the sintered body raw material calcium carbonate, and then The method for producing a dense sintered calcium carbonate body comprises sintering the calcium carbonate as a raw material for the sintered body.

10. a dispersion liquid containing a sintered body raw material calcium carbonate obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium and rare earth elements in an amount of 0.01 to 10% by mass relative to the mass of the sintered body raw material calcium carbonate, and a gelling agent; adding a foaming agent to the dispersion and stirring to prepare a foamed mixture; gelling the foam mixture to form a foam mixture gel; The foamed gel mixture is fired to obtain a porous sintered calcium carbonate body.

11. 11. The method for producing a porous sintered calcium carbonate body according to claim 10, wherein the dispersion liquid is prepared so as to contain 20% by volume or more of the raw material calcium carbonate for the sintered body.

12. The method for producing a porous sintered calcium carbonate body according to claim 10 or 11, wherein the foamed mixture gel is degreased and sintered in an air atmosphere, and then fired in a carbon dioxide atmosphere to obtain a porous sintered calcium carbonate body.

13. A porous sintered calcium carbonate body is obtained by firing a foaming mixture gel containing a sintered body raw material calcium carbonate obtained by mixing calcium carbonate having a purity of 99.95% by mass or more with 0.01 to 10% by mass of a compound of one or more metal elements selected from the group consisting of calcium, silicon, aluminum, zinc, magnesium, barium, strontium, boron, tin, gallium, iron, titanium, zirconium, and rare earth elements, a gelling agent, and a foaming agent.

14. 14. The porous sintered calcium carbonate body according to claim 13, which contains calcium carbonate in an amount of 99.7% by mass or more and has a porosity of 50% by volume or more.

15. 15. The calcium carbonate porous sintered body according to claim 13, which contains calcium carbonate in an amount of 99.9 mass% or more.

16. A bone filling material comprising the porous sintered calcium carbonate according to any one of claims 13 to 15.

17. A 3D printer pigment ink comprising the sintered body raw material calcium carbonate according to any one of claims 1 to 3.

18. A dielectric material comprising the dense sintered calcium carbonate body according to claim 8.

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