JP7454158B2 - Fired body and its manufacturing method - Google Patents

Description

The present invention relates to a sintered body and a method for producing the same, and more specifically to a sintered body and a method for producing the same, which are characterized by being produced by sintering a composition containing a layered silicate mineral and hydroxyapatite.

Since ancient times, ceramics have been produced by kneading clay such as layered silicate minerals, shaping them, and firing them at high temperatures, and are used in a variety of products including tableware, lighting equipment, and furniture. Ceramic technology is also being applied industrially as fine ceramic products, and the fields of use are expanding significantly, including bearings, dentistry, electronic components, ceramic magnetic materials, sensors, and fuel cell components.

Ceramics are classified into earthenware, stoneware, pottery, and porcelain, depending on the presence or absence of glaze and firing temperature. The common feature is that they are obtained by molding, molding, and firing at a high temperature of several hundred degrees Celsius or higher.

As mentioned above, the fields of use of ceramics and ceramic products are expanding, and new materials and manufacturing methods are required to accommodate a variety of uses.

As a result of extensive studies, the present inventors found that a new ceramic fired body can be obtained by blending hydroxyapatite with layered silicate minerals and firing the mixture, preferably at 500 to 1500°C. This discovery led to the completion of the present invention.

The present invention is as follows [1] to [11].
[1] A fired body produced by firing a composition containing a layered silicate mineral and hydroxyapatite.
[2] A fired body produced by firing a composition containing a layered silicate mineral and hydroxyapatite at a temperature of 500 to 1500°C.
[3] The fired body of [1] or [2], wherein the layered silicate mineral is kaolin.
[4] The fired body according to any one of [1] to [3], wherein the composition further contains feldspar.
[5] The fired body according to any one of [1] to [4], wherein the content of hydroxyapatite in the composition is 1 to 40% by mass.
[6] The fired body of any one of [1] to [5], which is a translucent fired body.
[7] The fired body of any one of [1] to [5], which is a porous fired body.
[8] The hydroxyapatite is a hydroxyapatite with a crystallite size of 10 to 200 Å calculated from a peak at 2θ = 31.5 to 32.5° in X-ray diffraction using CuKα rays as a radiation source [ 1] to [7].
[9] The fired body according to any one of [1] to [8], wherein the hydroxyapatite is a hydroxyapatite obtained using biologically derived calcium as a raw material.
[10] A method for producing a fired body, comprising the steps of mixing a layered silicate mineral and hydroxyapatite to obtain a composition, molding the composition, and then firing it.
[11] A method for producing a fired body, which comprises the steps of mixing a layered silicate mineral and hydroxyapatite to obtain a composition, molding the composition, and then firing it at 500 to 1500°C.

The fired body of the present invention has excellent translucency and water absorption. Furthermore, by containing hydroxyapatite, it also has adsorption properties for various substances that hydroxyapatite has. Further, according to the method for producing a fired body of the present invention, it is possible to use hydroxyapatite, which can be artificially synthesized, while reducing the amount of layered silicate mineral, which is a clay mineral and whose production areas are limited.

FIG. 2 is a graph showing the results of X-ray diffraction of hydroxyapatite in Example 1. FIG. 2 is a graph showing the results of X-ray diffraction of crystalline hydroxyapatite. FIG. 2 is a graph showing the results of X-ray diffraction of low-crystalline hydroxyapatite. FIG. 2 is a graph showing the results of X-ray diffraction of amorphous hydroxyapatite.

[Layered silicate mineral]
The layered silicate mineral of the present invention can be used without particular limitation as long as it is a layered silicate mineral contained in clay. Layered silicate minerals have a basic structure in which Si-O tetrahedra are connected in a planar manner, and in addition to this unit structure consisting of tetrahedra, other structures such as octahedral sheets may be included. There are variations due to. Examples of the layered silicate minerals of the present invention include serpentine, kaolinite, talc, pyrophyllite, smectite, vermiculite, mica, chlorite, montmorillonite, silica, and silica. Preferred are kaolin and montmorillonite, with kaolin being most preferred.
Furthermore, the layered silicate mineral can be used in combination with other clay minerals, and can also be mixed with hydroxyapatite in the form of clay and used.
Although the average particle size of the layered silicate mineral is not particularly limited, it is preferably 5 μm or less. The average particle size can be measured by laser diffraction dispersion method.
The amount of the layered silicate mineral in the composition is preferably 20 to 90% by mass, more preferably 30 to 80% by mass.

[Other clay minerals]
Other clay minerals include allophane, hydrated aluminum silicate, imogolite, hisingerite, ferrihydrite, opal, zeolite, carlosternite, and the like.

[Hydroxyapatite]
The hydroxyapatite of the present invention is, for example, a calcium-phosphorus complex represented by Ca10(PO ₄ ) ₆ (OH) ₂ , and commercially available products can be used as appropriate. Hydroxyapatite can also be produced by dropping and mixing calcium oxide or calcium hydroxide with phosphoric acid.

The hydroxyapatite used in the present invention preferably has a crystallite size of a peak appearing at 2θ of 31.500 to 32.500° in X-ray structural analysis of 10 to 200 Å, more preferably 30 to 150 Å, and even more preferably It is a hydroxyapatite with a thickness of 50 to 120 Å (hereinafter also referred to as "specific hydroxyapatite" for the sake of explanation). An example of X-ray structural diffraction of specific hydroxyapatite is shown in FIG. The crystallite size represents the size of crystal grains and is a numerical value that serves as a guideline for crystallinity. The larger the value of the crystallite size, the higher the crystallinity of the substance to be measured. Hydroxyapatite with a crystallite size within the above range is a mixture of non-crystalline (non-crystalline) hydroxyapatite alone or amorphous hydroxyapatite and less crystallized (low-crystalline) hydroxyapatite. means. Here, "non-crystalline hydroxyapatite" in the present invention means a substance that can obtain a chart as shown in FIG. 4 by X-ray analysis. In addition, "low-crystalline hydroxyapatite" in the present invention means that a chart obtained by X-ray analysis has a peak when compared with a chart obtained by X-ray analysis of crystalline hydroxyapatite (for example, see the chart in FIG. 2). It is a substance with a relatively low degree of separation (a chart like the one shown in FIG. 3 is obtained).
The crystallite size can be measured, for example, using an X-ray analyzer model number: RINT2200V/PC manufactured by Rigaku Co., Ltd.

The hydroxyapatite used in the present invention is preferably hydroxyapatite derived from living organisms, preferably fossil corals, shells, or eggshells. Biologically derived hydroxyapatite refers to hydroxyapatite obtained from calcium obtained from biological materials such as shells and eggshells.

The hydroxyapatite of the present invention preferably has an average particle diameter of 1 to 130 μm, more preferably 1 to 20 μm, and still more preferably 1 to 10 μm. The average particle diameter can be measured by laser light scattering diffraction method.

The content of hydroxyapatite in the composition is preferably 1 to 60% by mass, more preferably 5 to 50% by mass.

[Example of manufacturing method for specific hydroxyapatite]
An example of a method for producing a specific hydroxyapatite suitably used in the present invention will be explained.
This manufacturing method involves adding a phosphoric acid solution (additive liquid) to a calcium oxide suspension or calcium hydroxide suspension (additive liquid), or adding a calcium oxide suspension (additive liquid) to a phosphoric acid solution (additive liquid). liquid) to obtain the hydroxyapatite dispersion.
When adding the additive liquid to the liquid to be added, any conventional addition method can be used. A specific method includes, for example, a method in which a liquid to be added is placed in a container and the liquid to be added is dropped into the container using a device such as a dropping funnel. In addition, when using a calcium oxide suspension as an additive liquid, it is preferable to drip the calcium oxide suspension (or calcium hydroxide suspension) placed in a dropping funnel or the like while stirring.
The addition rate of the additive liquid is, for example, calculated in terms of calcium oxide (calcium hydroxide) or phosphoric acid contained in the additive liquid per 1 mole of calcium oxide (calcium hydroxide) or phosphoric acid contained in the liquid to be added. The amount is preferably 0.01 to 8.0 mol/h, more preferably 0.05 to 5.0 mol/h, and even more preferably 0.1 to 2.0 mol/h. By setting the addition rate within the above numerical range, it is possible to suppress the production of calcium phosphate compounds other than hydroxyapatite.

In the method for producing specific hydroxyapatite, when adding the additive liquid to the liquid to be added, it is not necessary to add an alkaline agent such as sodium hydroxide for pH adjustment.
The ratio of the total amount of calcium oxide in the calcium oxide suspension to the total amount of phosphoric acid in the phosphoric acid solution is, for example, such that the molar ratio of calcium ions:phosphate ions is 10:6 to 9:6. It is preferable. Of course, it is also possible to change the above ratio depending on the reaction conditions and the like. The molar ratio can be adjusted by adjusting the concentrations and amounts of the additive liquid and the liquid to be added.

The temperature condition when adding phosphoric acid to calcium salt such as calcium oxide or when adding calcium salt to phosphoric acid is 90° C. or lower. In this case, it is preferable to keep both the additive liquid and the liquid to be added at 90° C. or lower. More preferably, the temperature of the additive liquid and the liquid to be added is in the range of 5 to 90°C, more preferably in the range of 20 to 80°C, even more preferably in the range of 40 to 70°C. . By controlling the temperature of the additive liquid and the liquid to be added within the above range, it is possible to suppress the crystallization of hydroxyapatite and to smoothly proceed the reaction for obtaining hydroxyapatite.
It is also possible to add the additive liquid while stirring the liquid to be added.

By adding the additive liquid to the liquid to be added under the above temperature conditions, in X-ray structure analysis, the crystallite size of the peak appearing at 2θ of 31.500° to 32.500° is 10 to 200 Å, preferably 30 Å. A dispersion liquid (reaction liquid) in which fine particles of hydroxyapatite having a diameter of ~150 Å, more preferably 50 ~ 120 Å are dispersed is obtained. This dispersion may be blended into the composition before firing as it is, or it may be blended into the composition after adjusting the concentration by diluting it with a solvent such as water or concentrating by evaporating the solvent. However, it is preferable to heat the dispersion liquid (reaction liquid) to 80° C. or higher and dry it. The drying temperature is more preferably 80 to 500°C, even more preferably 120 to 400°C. By drying, a specific hydroxyapatite powder is obtained, and the specific hydroxyapatite can be incorporated into a composition without worrying about the amount of solvent.

[Calcium oxide suspension or calcium hydroxide suspension]
In the present invention, calcium oxide or calcium hydroxide can be used as a starting material when obtaining the specific hydroxyapatite. In the present invention, it is preferable to use calcium oxide or calcium hydroxide in the form of a suspension obtained by adding it to a solvent. In the above method for producing specific hydroxyapatite, there is no need to add an acidic or alkaline substance to dissolve calcium oxide or calcium hydroxide and/or to adjust the pH, and many steps can be omitted.
As the calcium oxide used when preparing the calcium oxide suspension, commercially available calcium oxide can be used. Similarly, commercially available calcium hydroxide can be used for the calcium hydroxide suspension. Calcium oxide (calcium hydroxide) suspensions are obtained by adding calcium oxide to a solvent. The amount of calcium oxide (calcium hydroxide) to be added is, for example, preferably 0.2 to 9.0 mol, more preferably 1.0 to 5.0 mol, and 1 mol to 1 liter of solvent. It is more preferable to add .5 to 4.0 mol. As the solvent, a solvent selected from alcohol solvents such as methanol or ethanol, and water can be used. From the viewpoint of production efficiency and operational safety, it is preferable to use water as the solvent.

Further, it is preferable to prepare a calcium oxide suspension by adding to the solvent a powder obtained by firing the outer shell, scales and/or bones of an organism, particularly shells and eggshells. The calcium oxide suspension prepared in this manner is more preferable because it does not contain impurities that have an adverse effect on the human body due to the use of biologically derived raw materials. Examples of the outer shell of living things include fossil corals and shells of scallops, pearl oysters, and the like. Examples of biological scales include scales of fish and reptiles. Examples of bones of living organisms include bones of mammals, fish, reptiles, and amphibians. An example of the eggshell is a chicken eggshell. It is more preferable to use the outer shell of an organism, such as a scallop or pearl oyster shell or eggshell, because it is easy to obtain and process.
The powder can be prepared by baking shells or eggshells, for example, at a temperature of 800 to 1050°C for 1 to 96 hours, preferably 5 to 72 hours. Shells and eggshells may be powdered before firing, or may be powdered after firing.
When adding the powder to water to prepare a calcium oxide suspension, the amount of the powder to be added is 0.2 to 9.0 mol in terms of calcium oxide per 1 liter of the solvent. It is preferable to add 1.0 to 5.0 mol, more preferably 1.5 to 4.0 mol. The amount of calcium oxide contained in the powder can be confirmed by a conventional method such as hydrochloric acid titration.

[Phosphoric acid solution]
The phosphoric acid solution used in the present invention can be prepared by dissolving commercially available phosphoric acid in a solvent selected from an alcoholic solvent such as ethanol or methanol, and water. From the viewpoint of production efficiency and operational safety, it is preferable to use water as the solvent. From the viewpoint of achieving better production efficiency of the base material, the concentration of the phosphoric acid solution is, for example, preferably 0.5 to 10.0 M, more preferably 1.0 to 7.0 M, It is more preferable to set it to 2.0 to 5.0M.

[Feldspar]
In the fired body of the present invention, the composition before firing preferably contains feldspar. Feldspar is a type of tectosilicate with a three-dimensional structure whose main component is aluminosilicate of alkali metals, alkaline earth metals, etc. In the present invention, alkali feldspar is preferred. The amount of feldspar contained in the composition before firing is preferably 1 to 40% by mass.

[Other ingredients]
The fired body of the present invention can contain components other than layered silicate minerals and hydroxyapatite in the composition before firing. Other ingredients include clay, limestone (calcium carbonate), deflocculants, and dispersants. Examples of deflocculants include cellulose nanofibers and sodium silicate. Examples of the dispersant include acrylic acid dispersants.
The amount of limestone blended is preferably 1 to 10% by mass in the composition before firing. The amount of the deflocculant added is preferably 1 to 30% by mass in the composition before firing. The blending amount of the dispersant is preferably 0.1 to 30% by mass in the composition before firing.

[Firing temperature]
The fired body of the present invention is obtained by firing a composition containing a layered silicate mineral and hydroxyapatite at a temperature of 500 to 1500°C.
Interestingly, when the firing temperature is in the range of more than 1,260°C but not more than 1,500°C, a fired product with translucent properties is obtained, while when the firing temperature is in the range of 500 to 1,260°C, the translucent property is low but the product has water absorption properties. A fired body is obtained.

[Method for producing fired body]
The method for producing a fired body of the present invention is characterized by having a step of mixing a layered silicate mineral and hydroxyapatite to obtain a composition, molding the composition, and then firing it at 500 to 1500°C. It is something to do. For the other steps, steps in a general method of manufacturing ceramics (ceramic products) can be adopted. For example, the shaping methods for ceramics before firing include extrusion molding, potter's wheel molding (hand potter's wheel, mechanical potter's wheel, roller machine), injection molding, press molding, slurry casting, mud casting, pressure casting, and solid casting. , tape molding, etc., all of which can be used. Particularly preferred are potter's wheel molding, slurry casting, and slurry casting.

The potter's wheel molding is a method in which potting clay (in the present invention, a composition containing a layered silicate mineral and hydroxyapatite) is placed on a rotating disk, swirled, and molded using centrifugal force. Cup soil is obtained by pulverizing and mixing layered silicate minerals, hydroxyapatite, and other ingredients as necessary using a ball mill, etc., dewatering the mixture using a filter press, etc., and then kneading the mixture using a clay kneader. It will be done.

In slurry casting, powder (in the present invention, a composition containing a layered silicate mineral and hydroxyapatite) is added and suspended in a liquid such as water, and the slurry is poured into a mold such as a plaster mold. , is a molding method to obtain the desired shape.
Sludge casting is a method of pouring slurry into a mold, solidifying the slurry on the inner surface of the mold, and then discharging the slurry to obtain a molded body.
The slurry is made by adding powder (in the present invention, a composition containing a layered silicate mineral and hydroxyapatite) to a liquid such as water, suspending it, and dewatering it using a filter press or the like. It can also be produced by adding a deflocculant (dispersing agent) and water.
Further, the molded body may be dried after molding and before firing.

Hereinafter, the content of the present disclosure will be explained in more detail with reference to Examples. It goes without saying that the scope of the present disclosure is not limited by the examples.

[Example 1]
Biologically derived synthetic hydroxyapatite (hydroxyapatite obtained using calcium oxide obtained by calcining calcium carbonate derived from chicken eggshells, with a 2θ of 31.500 to 32.500° in X-ray structural analysis) 40% by mass of hydroxyapatite whose crystallite size of the peak appearing in To 100 parts by mass of the mixture obtained by mixing, 70 parts by mass of water, 2 parts by mass of cellulose nanofibers, 0.3 parts by mass of sodium silicate, and 1 part by mass of acrylic acid dispersant were added, and the mixture was wet-pulverized in a ball mill for 3 hours. A composition (sludge) for casting was obtained. The slurry obtained here was cast into a plaster mold of 150 mm in diameter x 300 mm in height, removed from the mold after being applied, dried, and fired at 1280° C. to obtain translucent porcelain.
The obtained translucent porcelain had excellent translucency and was useful for lighting equipment such as covers for indirect lighting.

[Example 2]
Obtained by mixing 40% by mass of biologically derived synthetic hydroxyapatite (same as in Example 1), 5% by mass of limestone, 20% by mass of feldspar, 35% by mass of kaolin and clay minerals (30% by mass of kaolin, 5% by mass of clay minerals). To 100 parts by mass of the mixture, 70 parts by mass of water, 2 parts by mass of cellulose nanofibers, 0.3 parts by mass of sodium silicate, and 1 part by mass of an acrylic acid dispersant were added, wet milled in a ball mill for 3 hours, and cast. A composition for molding (sludge) was obtained. The slurry obtained here was cast into a plaster mold of 150 mm in diameter x 300 mm in height, removed from the mold after being inked, dried, and fired at 1100° C. to obtain a fired body (porous pottery).
The obtained porous pottery had water absorption properties.

[Example 3]
100% by mass of a mixture consisting of 40% by mass of biologically derived synthetic hydroxyapatite (same as in Example 1), 5% by mass of limestone, 20% by mass of feldspar, 35% by mass of kaolin and clay minerals (20% by mass of kaolin, 15% by mass of clay minerals) 45 parts by mass of water and 5 parts by mass of cellulose nanofibers were kneaded to obtain a composition (clay). The clay obtained here was formed into a bowl shape of Φ100 x H100 mm using a potter's wheel, shaved, dried, and fired at 1280°C to obtain a fired body (translucent porcelain).
The obtained translucent porcelain had excellent translucency and was useful for lighting equipment such as covers for indirect lighting.

[Example 4]
Based on 100 parts by mass of a mixture consisting of 40% by mass of biologically derived synthetic hydroxyapatite (same as Example 1), 5% by mass of limestone, 20% by mass of feldspar, kaolin and clay minerals (20% by mass of kaolin, 15% by mass of clay minerals). , 45 parts by mass of water, and 5 parts by mass of cellulose nanofibers were kneaded to obtain clay. The clay obtained here was formed into a bowl shape of Φ100 x H100 mm using a potter's wheel, shaved, dried, and fired at 1100°C to obtain a fired body (porous pottery).
The obtained porous pottery had water absorption properties.

As described above, the fired body of the present invention is useful as translucent porcelain or porous ceramic for use in tableware, lighting equipment, and the like. Furthermore, since it contains hydroxyapatite, it has excellent heat resistance and alkali resistance, and is suitable for applications that require heat resistance and alkali resistance.

Claims (2)

A method for producing a translucent fired body, the method comprising firing a composition containing a layered silicate mineral and hydroxyapatite ,
The hydroxyapatite is hydroxyapatite having a crystallite size of 10 to 200 Å calculated from the peak at 2θ = 31.5 to 32.5° in X-ray diffraction using CuKα rays as a radiation source. How the body is manufactured . A method for producing a porous fired body, the method comprising firing a composition containing a layered silicate mineral and hydroxyapatite ,
A porous fired body in which the hydroxyapatite is hydroxyapatite having a crystallite size of 10 to 200 Å calculated from a peak at 2θ = 31.5 to 32.5° in X-ray diffraction using CuKα rays as a radiation source. manufacturing method .