JP2005029432A - Method of manufacturing sintered compact and sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a sintered compact by which the sintered compact having high light transmittance, particularly capable of transmitting light of a wide wavelength region is manufactured, and to provide the sintered compact manufactured by the sintered compact manufacturing method. <P>SOLUTION: The sintered compact manufacturing method has: a step 1 for preparing hydroxyapatite powder; a step 2 for molding a green compact; a step 3 for shaping the green compact; a primary firing step 4; and a secondary firing step 5. A pressing method in the step 2 is preferably an isotropic pressing method, more preferably a hydrostatic pressing method. The pressure of the press is preferably ≥1 ton/cm<SP>2</SP>. As the hydrostatic pressing, the cold isostatic press (CIP) method of pressing at 5 to 50°C is suitably used. In the step 4, the green compact is fired (primary firing) in an oxygen-containing atmosphere where oxygen occupies ≥50 vol.% of the gas existing in the firing furnace, and in the step 5, the body sintered in the step 4 is fired (secondary firing) in a less active atmosphere. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a sintered body and a sintered body.

  Hydroxyapatite has high biocompatibility and is used as a biomaterial such as artificial bone, artificial tooth root, medical or dental cement.

  Hydroxyapatite also has high affinity with cells, proteins, and the like, and is used as a carrier for cell culture, a protein separation material, and the like.

  For example, Patent Document 1 discloses a technique using an apatite sheet as a cell culture carrier.

  However, in the apatite sheet described in Patent Document 1, SEM is used to observe the state of attached cells. However, when observing cells with an SEM or the like, the cells naturally die. Further, when observing cells with an optical microscope, it is possible to observe the cells while they are alive, but it is difficult to observe the interface between the cells and the apatite sheet. This is because this apatite sheet does not have optical transparency and it is difficult to observe optical cells.

  Further, as a method for easily measuring the protein concentration, there is a method using ultraviolet rays. However, since the apatite sheet described above does not have optical transparency, it is difficult to measure the protein concentration by such a simple method.

JP 2003-047461 A

  An object of the present invention is to provide a sintered body having a high light transmittance, in particular, a method for producing a sintered body capable of producing a sintered body capable of transmitting light having a wide range of wavelengths, and a method for producing such a sintered body. It is providing the sintered compact manufactured by this.

  Such an object is achieved by the present inventions (1) to (21) below.

(1) a step of pressing the apatite powder at a pressure of 1 ton / cm ² or more to obtain a green compact;
The green compact is sintered by subjecting the green compact to first firing in an oxygen-containing atmosphere in which oxygen accounts for 50 vol% or more of the gas present in the firing furnace. Obtaining a step;
A step of subjecting the sintered body to a second firing in a low activity atmosphere.
Thereby, the sintered compact which can permeate | transmit the light of a high density and a wide range of wavelengths can be obtained.

(2) The method for producing a sintered body according to (1), wherein in the step of obtaining the green compact, the pressing is performed isotropically.
Thereby, a higher density sintered body can be obtained.

(3) The said isotropic pressurization is a manufacturing method of the sintered compact as described in said (2) performed by hydrostatic pressure pressurization.
Thereby, a higher density sintered body can be obtained.

(4) The method for producing a sintered body according to (3), wherein the hydrostatic pressure is performed at a temperature of 5 to 50 ° C.
Such a method for producing a green compact can be performed with a simple apparatus, and is excellent in practicality as a production process for industrial products.

(5) The method for manufacturing a sintered body according to any one of (1) to (4), wherein in the first firing step, an oxygen partial pressure of the oxygen-containing atmosphere is 380 mmHg or more.
Thereby, a higher density sintered body can be obtained.

(6) The method for manufacturing a sintered body according to any one of (1) to (5), wherein in the first firing step, the pressure of the oxygen-containing atmosphere is 900 mmHg or less.
Thereby, the sintered compact which has higher light transmittance can be obtained.

(7) The method for manufacturing a sintered body according to any one of (1) to (6), wherein the temperature at which the green compact is fired in the first firing step is 850 to 1350 ° C.
Thereby, a green compact can be sintered more reliably.

(8) The method for manufacturing a sintered body according to any one of (1) to (7), wherein in the second firing step, the low activity atmosphere is a nitrogen gas atmosphere or an inert gas atmosphere.
These gases are preferred because of their extremely low reactivity with apatite.

(9) The method for manufacturing a sintered body according to any one of the above (1) to (8), wherein the temperature at which the sintered body is fired is 1000 to 1350 ° C. in the second firing step.
By setting the temperature in the second firing in such a range, the sintered body can surely transmit light having a shorter wavelength than visible light.

(10) The method for producing a sintered body according to any one of (1) to (9), wherein an average particle diameter of the apatite powder is 40 μm or less.
Thereby, a higher density sintered body can be obtained.

(11) The method for manufacturing a sintered body according to any one of (1) to (10), wherein the two firing steps are performed in a single firing furnace by changing a firing atmosphere.
This makes it possible to manufacture a sintered body in a shorter time.

(12) The method for producing a sintered body according to any one of (1) to (10), wherein the apatite powder is a hydroxyapatite powder.
By using hydroxyapatite as the apatite, the sintered body can be made suitable for application to biomaterials and cell culture carriers.

(13) The hydroxyapatite powder is synthesized by a wet synthesis method using at least one of a calcium source and a phosphoric acid source as a solution, and is produced using a slurry obtained in the synthesis. The manufacturing method of the sintered compact as described in 11).
Thus, it is possible to synthesize hydroxyapatite easily and efficiently without requiring expensive production equipment.

(14) The sintered body according to (12), wherein the calcium source includes calcium hydroxide or calcium oxide as a main component, and the phosphoric acid source includes phosphoric acid as a main component. Production method.
Thereby, hydroxyapatite can be synthesized more efficiently and inexpensively.

(15) The said hydroxyapatite powder is a manufacturing method of the sintered compact as described in said (13) which is manufactured using the said slurry whose content of tricalcium phosphate is 0.1 wt% or less.
Thereby, a higher density sintered body can be obtained.

(16) The method for producing a sintered body according to (13) or (14), wherein the hydroxyapatite powder is produced using the slurry that satisfies the following condition A.
Condition A: A part of the slurry is taken out and compression molded at a molding pressure of ² ton / cm ² to form a sample molded body having a detection surface, and then the sample molded body is fired in the atmosphere at 1200 ° C. for 2 hours. When the substance present on the detection surface (surface roughness Ra = 10 μm) of the obtained sample is analyzed by X-ray diffraction, the peak intensity derived from hydroxyapatite is the largest among the obtained peaks, and No peak derived from tricalcium phosphate is observed.
By using such a slurry, a particularly high-density sintered body can be obtained.

(17) The sintered body according to any one of (12) to (15), wherein the hydroxyapatite powder is produced using the slurry having a calcium hydroxide or calcium oxide content of 3 wt% or less. A method for producing a knot.
Thereby, a higher density sintered body can be obtained.

(18) The method for producing a sintered body according to any one of (13) to (16), wherein the hydroxyapatite powder is produced using the slurry that satisfies the following condition B.
Condition B: When a part of the slurry is taken out and dried at 200 ° C., and this sample is baked in the atmosphere at 1200 ° C. for 20 minutes, the substance present in the sample is analyzed by powder X-ray diffraction. When the intensity of the peak derived from apatite is X and the intensity of the peak derived from calcium oxide is Y, the relationship Y / X <1/10 is satisfied.
By using such a slurry, a particularly high-density sintered body can be obtained.

(19) The method for manufacturing a sintered body according to any one of (1) to (17), wherein the sintered body obtained by performing the first firing has a relative density of 99% or more.
As a result, the sintered body can more reliably transmit light having a shorter wavelength than visible light.

(20) A sintered body is produced so as to have a plate shape with a thickness of 0.5 mm, and when the sintered body is irradiated with light having a wavelength of 300 nm, the light transmittance is 10% or more ( The manufacturing method of the sintered compact in any one of 1) thru | or (18).
Such a sintered body (test piece) can be judged to be capable of efficiently transmitting light on the shorter wavelength side than visible light, and a sintered body manufactured under the same conditions also has a shorter wavelength side than visible light. It can be determined that light can be transmitted efficiently.

  (21) A sintered body produced by the method for producing a sintered body according to any one of (1) to (20).

  The sintered body of the present invention has a high density and an extremely high mechanical strength. For this reason, the sintered compact of this invention can be used conveniently as biomaterials, such as artificial bones, such as a vertebral spacer and an ossicle, and an artificial tooth root.

  In addition, since the sintered body of the present invention has high light transmittance, it can also be suitably applied to cell culture carriers (containers), analytical containers (cells) and the like.

  When the sintered body of the present invention is applied to a cell culture carrier (container), the state of cells attached and grown on the carrier can be observed by a method of optical observation (for example, a method using an optical microscope or the like). . According to this method, there is an advantage that cells can be observed relatively easily without requiring a large facility.

  Furthermore, since the sintered body of the present invention can transmit light having a wavelength in the ultraviolet region, when applied to a cell culture vessel or an analysis vessel, the concentration of the protein present in the solution is changed to ultraviolet rays (wavelength 280-280). The advantage that it can be easily measured is obtained by a simple method using about 300 nm).

  According to the present invention, a sintered body having high light transmittance, in particular, a sintered body capable of transmitting light having a wide range of wavelengths can be obtained.

  Hereinafter, the manufacturing method of the sintered compact of this invention and suitable embodiment of a sintered compact are described in detail.

  Here, as the apatite used in the present invention, for example, hydroxyapatite, fluorapatite, and at least a part of calcium ions included in these are replaced with other metal ions (for example, Ni ions, Co ions, Mn ions, etc.). And the like. Moreover, these things can also be used 1 type or in combination of 2 or more types.

  In the following, hydroxyapatite will be described as a representative example as an example of apatite.

FIG. 1 is a process diagram showing a method for producing a sintered body of the present invention.
The sintered body manufacturing method shown in FIG. 1 includes a hydroxyapatite powder manufacturing process 1, a green compact molding process 2, a green compact shaping process 3, a first firing process 4, and a second sintering process. And a firing step 5. Hereinafter, each process will be described sequentially.

[1] Production of hydroxyapatite powder First, a calcium source and a phosphate source are reacted to synthesize hydroxyapatite (HAp). In addition, the hydroxyapatite in this specification points out that whose Ca / P molar ratio is 1.60 to 1.70.

  Any method such as a wet synthesis method, a dry synthesis method, or a hydrothermal synthesis method may be used for the synthesis of the hydroxyapatite, but a wet synthesis method using at least one of a calcium source and a phosphate source as a solution is used. Is preferred. Thus, it is possible to synthesize hydroxyapatite easily and efficiently without requiring expensive production equipment.

  When the wet synthesis method is used, as the calcium source, for example, calcium hydroxide, calcium oxide, calcium nitrate or the like can be used. On the other hand, phosphoric acid, ammonium phosphate, or the like can be used as the phosphoric acid source.

  Among these, in particular, those having calcium hydroxide or calcium oxide as a main component as a calcium source and those having phosphoric acid as a main component as a phosphoric acid source are preferable. By using such calcium source and phosphate source, hydroxyapatite can be synthesized more efficiently and inexpensively.

  Hereinafter, a case where a calcium source having calcium hydroxide or calcium oxide as a main component and a phosphoric acid source having phosphoric acid as a main component are used will be described.

In this case, the hydroxyapatite (HAp) is prepared by dropping a phosphoric acid (H ₃ PO ₄ ) solution into a suspension of calcium hydroxide (Ca (OH) ₂ ) or calcium oxide (CaO) in a container, for example. , Synthesized by mixing.

This reaction is represented by the following formula (I) or (II).
10Ca (OH) ₂ + 6H ₃ PO ₄ → 2Ca ₅ (PO ₄ ) ₃ (OH) + 18H ₂ O (I)
10CaO + 10H ₂ O + 6H ₃ PO ₄ → 2Ca ₅ (PO ₄ ) ₃ (OH) + 18H ₂ O (II)
Here, when the progress of the synthesis is insufficient, unreacted substances (Ca (OH) ₂ and CaO) exist as impurities in a slurry-like mixture (hereinafter simply referred to as “slurry”). It will be.

When the reaction is further continued, tricalcium phosphate (TCP) is produced as a secondary reaction product by the reaction represented by the following formula (III).
3Ca ₅ (PO ₄ ) ₃ (OH) + H ₃ PO ₄ → 5Ca ₃ (PO ₄ ) ₂ + 3H ₂ O (III)

  As this reaction proceeds, tricalcium phosphate, which is a secondary reaction product, will be present as impurities in the slurry.

  Hydroxyapatite powder is produced using the slurry containing hydroxyapatite thus synthesized. At this time, it is possible to obtain a high-density sintered body by making the above-described impurities hardly exist in the slurry. And this high-density sintered compact has a high light transmittance (translucency).

Hereinafter, suitable ranges of the contents (concentrations) of tricalcium phosphate and unreacted substances (Ca (OH) ₂ and CaO) in the slurry will be described.

[Tricalcium phosphate]
The content (concentration) of tricalcium phosphate in the slurry is not particularly limited, but is preferably 0.1 wt% or less, more preferably not present. Thus, a higher density sintered body can be obtained by using a slurry having a low content of tricalcium phosphate.

Furthermore, a slurry that satisfies the following condition A is optimal.
Condition A: A part of the slurry is taken out and compression molded at a molding pressure of ² ton / cm ² to form a sample molded body having a detection surface, and then the sample molded body is fired in the atmosphere at 1200 ° C. for 2 hours. The substance present on the detection surface (surface roughness Ra = 10 μm) of the sample obtained in this way is analyzed by X-ray diffraction. At this time, the peak intensity derived from hydroxyapatite is the highest among the obtained peaks, and no peak derived from tricalcium phosphate is observed.

  In such an analysis method, during the firing, the particle growth of hydroxyapatite precedes due to the difference in sintering rate between hydroxyapatite and impurities, and as a result, the impurities are pushed out from the interstices, and the sample surface (particularly the detection surface) The presence of impurities can be confirmed by analyzing the detection surface by X-ray diffraction using the precipitation in (1). According to this analysis method, the presence of impurities in the slurry can be confirmed with high accuracy.

  And if a slurry satisfies the said conditions A, this will be understood that even if it does not contain tricalcium phosphate or contains tricalcium phosphate, it is a very small amount. For this reason, a particularly high-density sintered body can be obtained by using such a slurry.

[Unreacted material]
The content (concentration) of the unreacted material in the slurry is not particularly limited, but is preferably 3 wt% or less, and more preferably about 0.025 to 1 wt%. When a relatively small amount of unreacted material is present in the slurry, calcium oxide (note that unreacted calcium hydroxide is converted to calcium oxide by firing) is present even in a slight amount. This condition is appropriate because it does not affect the density). If the content of the unreacted material in the slurry exceeds the upper limit, it may be difficult to obtain a high-density sintered body depending on the firing conditions of the green compact described later.

Furthermore, a slurry that satisfies the following condition B is optimal.
Condition B: A part of the slurry is taken out, dried at 200 ° C., and the material present in the sample obtained by firing this sample at 1200 ° C. for 20 minutes in the atmosphere is analyzed by powder X-ray diffraction. At this time, when the intensity of the peak derived from hydroxyapatite is X and the intensity of the peak derived from calcium oxide is Y, a relationship of Y / X <1/10 (particularly, a relationship of Y / X <1/100). ) Is satisfied.

  As described above, according to the analysis method, it is possible to confirm the presence of impurities in the slurry with high accuracy. As a result, if the slurry satisfies the condition B, this contains unreacted substances. It can be seen that the amount is very small. For this reason, a particularly high-density sintered body can be obtained by using such a slurry.

  Note that the slurry may be one in which either the content of tricalcium phosphate or the content of unreacted material is in the above range, but those in which both are in the above range are preferred. Thereby, an extremely high density sintered body can be obtained.

  Next, a hydroxyapatite powder (hereinafter simply referred to as “powder”) is produced by subjecting the slurry thus obtained to, for example, spray drying.

  The average particle size of the powder is not particularly limited, but is preferably 40 μm or less, and more preferably about 8 to 25 μm. By using a powder having such an average particle diameter, a higher density sintered body can be obtained.

  In addition, in order to obtain a more compact green compact, the obtained powder is heat treated under, for example, a processing condition of about 500 to 800 ° C. for about 2 to 6 hours, and then pulverized with, for example, a jet mill or a turbo mill, The average particle size may be about 6 to 20 μm (average particle size of about 50 to 80% before pulverization).

[2] Molding of compacted powder Next, pressure is applied to the obtained powder (or the compacted product in advance into a desired shape) to make it compact.

  The method of pressurization may be any one of a method of isotropic pressurization, a method of pressurizing only in one direction (uniaxial direction) like a uniaxial press, etc., a method of isotropic pressurization, Hydrostatic pressure is particularly preferable. Thereby, the density of the green compact after pressurization can be made uniform, and as a result, a higher density sintered body can be obtained.

  As the hydrostatic pressure pressurization, for example, a CIP (Cold Isostatic press) method in which pressurization is performed at a temperature of about 5 to 50 ° C. (preferably about 10 to 30 ° C.) is suitable. This CIP method can be carried out with a simple apparatus, has the advantage that the heat resistance is not required for the film described later, and is excellent in practicality as a manufacturing process for industrial products. In addition, as a method of pressurization, a HIP (Hot Isostatic Press) method, a Hot press method, or the like that is pressurized under heating (for example, 80 ° C. or more) can be used.

  As a specific method of hydrostatic pressure pressurization, the surface of the powder is covered with a liquid-blocking coating, and this is loaded into a hydrostatic pressurizer and subjected to hydrostatic pressurization.

  In the case of the CIP method, as the coating, for example, a resin material such as polyvinyl chloride, polyethylene, or polypropylene, or a rubber material such as natural rubber or isoprene rubber can be used. This coating can be formed, for example, by dipping or vacuum packing.

The pressure of the pressure (pressurizing pressure) is not particularly limited, but is preferably 1 ton / cm ² or more, more preferably about 1~3ton / cm ^2, 1.5~2.5ton / cm More preferably, it is about ² . If this pressure is too low, the effect of sufficient pressurization (particularly uniform density) may not be expected, and even if the pressure is made higher than the above upper limit value, no improvement in the effect is observed. Large equipment is required, and the equipment becomes expensive.

  The green compact after pressurization thus obtained has a high density and the density becomes uniform. For this reason, when it sinters by the 1st baking mentioned later, a green compact comes to shrink uniformly. Therefore, the obtained sintered body has a high dimensional accuracy and a uniform density.

As described above, the sintered body having a uniform density is suppressed from the occurrence of sintering defects such as cracks and defects, and as a result, is hardly broken (excellent in mechanical strength).
In addition, after pressurization, the coating on the surface is removed by a predetermined method.

[3] Shaping of green compact Next, the shape or size of the obtained green compact is adjusted as necessary.

  The shaping of the green compact is performed, for example, by subjecting the green compact to predetermined machining. Examples of the machining include cutting, grinding, polishing, and the like, and one or more of these can be combined.

  Since the green compact itself has a much lower hardness than the finally obtained sintered body, shaping of the green compact by machining or the like can be performed easily. It can also be used, and the machining speed is high.

[4] First firing The green compact obtained as described above is subjected to the first firing in an oxygen-containing atmosphere in which, for example, in a firing furnace, oxygen accounts for 50 vol% or more of the gas present in the firing furnace. Bake. Thereby, the green compact is sintered to obtain a sintered body.

  As a result of intensive studies, the inventor has baked (sintered) the green compact in an oxygen-containing atmosphere in which oxygen accounts for 50 vol% or more (preferably 75 vol% or more) of the gas present in the baking furnace. In particular, it has been found that a sintered body having a high density and a high light transmittance can be obtained.

  A typical example of such an oxygen-containing atmosphere (firing atmosphere) is a pure oxygen atmosphere. As the oxygen-containing atmosphere, a mixed gas of oxygen and another gas (especially, a mixed gas mainly containing oxygen) is used. You can also.

  The oxygen partial pressure of such an oxygen-containing atmosphere (in the case of a pure oxygen atmosphere, the pressure in the firing furnace) is preferably 380 mmHg or more, and more preferably 550 mmHg or more. Thereby, the relative density and light transmittance of the obtained sintered compact can be made higher.

  Further, the pressure of the oxygen-containing atmosphere (pressure in the firing furnace) is preferably 900 mmHg or less, and more preferably 600 mmHg or less. Thereby, the transmittance | permeability of the light of a sintered compact can be improved more. In firing under reduced pressure, 50% or more of the gas occupying the space during firing may be oxygen.

  Note that in order to increase the oxygen partial pressure of the oxygen-containing atmosphere at atmospheric pressure, the volume of oxygen in the oxygen-containing atmosphere (firing atmosphere) may be increased (concentration increased).

  In addition, the present inventor makes the temperature (firing temperature) in the first firing relatively low by firing the green compact (first firing) in such an oxygen-containing atmosphere with a high oxygen concentration. In addition, in this case, the green compact can be sintered while suppressing the particle growth of hydroxyapatite, and as a result, a sintered body having higher density and higher light transmittance is obtained. I also found that I can do it.

  In addition, by firing the green compact at such a relatively low temperature, it is possible to shorten the firing time, reduce the energy required for firing, reduce the cost of the heating element used in the firing furnace, and the like. There are also advantages.

  The temperature (firing temperature) in the first firing is preferably about 850 to 1350 ° C., and preferably about 950 to 1250 ° C. Note that if the firing temperature is too low, the green compact may not be sintered efficiently.

  The holding time (baking time) of the baking temperature is preferably about 30 minutes to 8 hours, and more preferably about 2 to 4 hours.

  The sintered body thus obtained has a high density and high light transmittance. Specifically, such a sintered body can transmit light having a wavelength longer than visible light.

[5] Second Firing Next, the sintered body is subjected to second firing in a low activity atmosphere in, for example, a firing furnace.

  As a result of intensive studies to obtain a sintered body capable of transmitting a wider range of light (light having a shorter wavelength than visible light), the present inventor has re-fired the sintered body in a low activity atmosphere (No. 1). 2), the obtained sintered body was found to be capable of transmitting light having a shorter wavelength than visible light.

  Here, the low activity atmosphere is not particularly limited as long as the main component is a gas that does not substantially react with hydroxyapatite (apatite). For example, a nitrogen gas atmosphere, an argon gas atmosphere, a helium gas atmosphere, An inert gas atmosphere such as a neon gas atmosphere is preferred. These gases are preferable because of their extremely low reactivity with hydroxyapatite (apatite).

These gases may be mixed and used as necessary.
The temperature in the second firing (firing temperature) is preferably about 1000 to 1350 ° C., and preferably about 1100 to 1250 ° C. When the temperature in the second baking is less than the lower limit value, the above-described effect may not be sufficiently obtained. On the other hand, even if the temperature in the second baking exceeds the upper limit value, it is more than that. In addition to the above effects, hydroxyapatite may be thermally decomposed.

  The holding time (baking time) of the baking temperature is preferably about 30 minutes to 8 hours, and more preferably about 2 to 4 hours.

  The pressure in the low activity atmosphere (pressure in the firing furnace) is preferably about 3 to 900 mmHg, and more preferably about 5 to 800 mmHg. Here, the amount of oxygen present in the firing atmosphere may be small.

  In addition, it is preferable that the sintered compact provided to this process [5] is a thing whose relative density is 99% or more (especially 99.5% or more). Thereby, after this process [5], a sintered compact can permeate | transmit the light of a short wavelength side more than visible light more reliably.

Moreover, although this process [5] may be performed using a firing furnace different from the firing furnace used in the above-mentioned process [4], it is performed by replacing the firing atmosphere using the same firing furnace. preferable. Thereby, since two processes (baking) can be performed continuously, without taking out the object used for baking from the inside of a baking furnace, the manufacturing time of a sintered compact can be aimed at.
The sintered body of the present invention is obtained through the steps as described above.

  The sintered body of the present invention has a high density and an extremely high mechanical strength. For this reason, the sintered compact of this invention can be used conveniently as biomaterials, such as artificial bones, such as a vertebral spacer and an ossicle, and an artificial tooth root.

  In addition, since the sintered body of the present invention has high light transmittance, it can also be suitably applied to cell culture carriers (containers), analytical containers (cells) and the like.

  When the sintered body of the present invention is applied to a cell culture carrier (container), the state of cells attached and grown on the carrier can be observed by a method of optical observation (for example, a method using an optical microscope or the like). . According to this method, there is an advantage that cells can be observed relatively easily without requiring a large facility.

  Furthermore, since the sintered body of the present invention can transmit light having a wavelength in the ultraviolet region, when applied to a cell culture vessel or a container for analysis, the concentration of the protein present in the solution is changed to ultraviolet rays (wavelength 280 to 280). The advantage that it can be easily measured is obtained by a simple method using about 300 nm). In particular, in this case, the sintered body of the present invention preferably has the following characteristics.

  That is, when a test piece (sintered body) is produced so as to have a plate shape with a thickness of 0.5 mm, and the test piece is irradiated with light having a wavelength of 300 nm, the transmittance of the light is 10% or more (particularly 15% or more).

Here, the reason for using the test piece will be described. The actual sintered body is appropriately set in shape, size, etc. according to its intended use. For this reason, even if the light transmittance is measured under the same conditions, the evaluation may not be performed uniformly.
Therefore, a test piece is prepared according to the method for manufacturing a sintered body described above, and if the test piece has the above characteristics, an actual sintered body manufactured under the same conditions as this is also a test piece. This is because it can be estimated that a characteristic corresponding to the confirmed characteristic is obtained.

  And it can be judged that the test piece having the above characteristics can efficiently transmit light having a shorter wavelength than visible light, and a sintered body manufactured under the same conditions also has a shorter wavelength than visible light. It can be determined that light can be transmitted efficiently.

  As mentioned above, although the manufacturing method and sintered compact of the sintered compact of this invention were demonstrated, this invention is not limited to these.

  For example, in the present invention, for any purpose, a pre-step of step [1], an intermediate step existing between steps [1] to [5], or a post-step of step [5] (for example, of the sintered body) A surface treatment process or the like may be provided.

Next, specific examples of the method for producing a sintered body of the present invention will be described.
[Production of sintered body]
The sintered bodies of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured as follows.

(Example 1)
<1> First, 140 g of calcium hydroxide is dispersed in 6 L of pure water, and a phosphoric acid aqueous solution having a phosphoric acid concentration of 2 wt% is dropped therein, and the mixture is sufficiently stirred and mixed to synthesize hydroxyapatite. Hydroxyapatite A slurry containing was obtained.

  Next, the slurry was spray-dried using a spray dryer to obtain a hydroxyapatite powder having an average particle size of 14 μm.

At this time, a part of the slurry is taken out and compression molded at a molding pressure of ² ton / cm ² to form a sample molded body having a detection surface, and then the sample molded body is fired in the atmosphere at 1200 ° C. for 2 hours. The substance present on the detection surface (surface roughness Ra = 10 μm) of the sample obtained in this manner was analyzed by X-ray diffraction. The sample dimensions were 15 mm in diameter and 8 mm in height.

As a result, a peak derived from tricalcium phosphate (TCP) was not confirmed.
A part of the slurry was sampled, dried at 200 ° C., and calcined at 1200 ° C. for 20 minutes in the air, and analyzed by powder X-ray diffraction.

  As a result, the intensity of the peak derived from calcium oxide (CaO) was 1/250 of the intensity of the peak derived from hydroxyapatite (HAp).

  Furthermore, the obtained hydroxyapatite powder was heat-treated at 600 ° C. for 4 hours, and then pulverized by a jet mill. Thereby, a hydroxyapatite powder having an average particle size of 13 μm was obtained.

<2> Next, this hydroxyapatite powder is hardened into a disk shape with a compression molding machine, and then packed in a vinyl bag and vacuum-packed, and hydrostatic pressure is applied at room temperature (24 ° C.). Compression molding was performed at a pressure of 1 ton / cm ² to obtain a disk-shaped green compact having a diameter of 28 mm and a thickness of 1 mm.

  <3> Next, the green compact was cut (machined) with a diamond cutter to form a disk with a diameter of 25 mm and a thickness of 0.8 mm.

  <4> Next, the green compact was fired in a firing furnace (first firing) to be sintered to obtain a sintered body.

  The firing conditions were 1200 ° C. × 2 hours in a pure oxygen atmosphere (firing atmosphere). The pressure in the firing furnace was 76 mmHg.

  Moreover, the relative density of the obtained sintered body (sintered body after the first firing) was 99.6%. This relative density was determined in consideration of the specific gravity based on the volume value and the weight value determined from the external dimensions.

  <5> Next, the sintered body was fired (second firing) in the same firing furnace as in the step <4>.

The firing conditions were 1200 ° C. × 2 hours in an argon gas atmosphere (firing atmosphere). The pressure in the firing furnace was 380 mmHg.
The relative density of the sintered body after the second firing was 99.8%.

  <6> Next, optical polishing was performed on both surfaces of the sintered body. Thus, the diameter was 20 mm and the thickness was 0.5 mm.

(Example 2)
In the step <4>, the firing condition is 1200 ° C. × 2 hours in a pure oxygen atmosphere (pressure in the firing furnace: 350 mmHg), and in the step <5>, the firing condition is set in an argon gas atmosphere. A sintered body was manufactured in the same manner as in Example 1 except that the temperature was 1100 ° C. × 2 hours.

  The relative density of the sintered body after the first firing was 99.6%, and the relative density of the sintered body after the second firing was 99.7%.

(Example 3)
In the step <4>, the firing conditions are 1050 ° C. × 2 hours in a pure oxygen atmosphere (pressure in the firing furnace: 760 mmHg), and in the step <5>, the firing conditions are set in an argon gas atmosphere. A sintered body was produced in the same manner as in Example 1 except that the temperature was 1050 ° C. × 2 hours.

  The relative density of the sintered body after the first firing was 99.5%, and the relative density of the sintered body after the second firing was 99.5%.

(Comparative Example 1)
A sintered body was produced in the same manner as in Example 3 except that the step <5> was omitted.
The relative density of the obtained sintered body was 99.5%.

(Comparative Example 2)
A sintered body was produced in the same manner as in Example 1 except that the step <4> was omitted.
The relative density of the obtained sintered body was 99.0%.

(Comparative Example 3)
A sintered body was produced in the same manner as in Example 1 except that instead of the steps <4> and <5>, the green compact was fired at 1,200 ° C. for 2 hours in an atmosphere of 1 atm.
The relative density of the obtained sintered body was 99.1%.

[Evaluation]
1. Measurement of the wavelength of light that can be transmitted The wavelength of light that can be transmitted was measured for each of the sintered bodies manufactured in each of the examples and the comparative examples. For this measurement, a spectrophotometer “U-4000” manufactured by Hitachi, Ltd. was used.

2. Measurement of light transmittance The sintered bodies produced in each of the examples and the comparative examples were each irradiated with light having a wavelength of 300 nm, and the light transmittance was measured.
The results of evaluations 1 to 3 are shown in Table 1 together with the production conditions of the sintered body.

  As shown in Table 1, each of the sintered bodies (sintered bodies of the present invention) manufactured in each example can transmit light having a wavelength of 275 nm or more, and has high transmittance for light having a wavelength of 300 nm. It was a thing.

  On the other hand, all of the sintered bodies produced in the respective comparative examples could not transmit light having a wavelength shorter than 295 nm, and hardly transmitted light having a wavelength of 300 nm.

It is process drawing which shows the manufacturing method of the sintered compact of this invention.

Explanation of symbols

1 Production of hydroxyapatite powder 2 Molding of green compact 3 Shaping of green compact 4 First firing 5 Second firing

Claims (21)

Pressing the apatite powder at a pressure of 1 ton / cm ² or more to obtain a green compact;
The green compact is sintered by subjecting the green compact to first firing in an oxygen-containing atmosphere in which oxygen accounts for 50 vol% or more of the gas present in the firing furnace. Obtaining a step;
A step of subjecting the sintered body to a second firing in a low activity atmosphere.   The method for producing a sintered body according to claim 1, wherein in the step of obtaining the green compact, the pressurization is performed isotropically.   The method for producing a sintered body according to claim 2, wherein the isotropic pressurization is performed by hydrostatic pressurization.   The method for producing a sintered body according to claim 3, wherein the hydrostatic pressure is performed at a temperature of 5 to 50 ° C. 5.   5. The method for manufacturing a sintered body according to claim 1, wherein, in the first firing step, an oxygen partial pressure of the oxygen-containing atmosphere is 380 mmHg or more.   The method for manufacturing a sintered body according to any one of claims 1 to 5, wherein, in the first firing step, the pressure of the oxygen-containing atmosphere is 900 mmHg or less.   The method for manufacturing a sintered body according to any one of claims 1 to 6, wherein a temperature at which the green compact is fired in the first firing step is 850 to 1350 ° C.   The method for manufacturing a sintered body according to any one of claims 1 to 7, wherein in the second firing step, the low activity atmosphere is a nitrogen gas atmosphere or an inert gas atmosphere.   The method for producing a sintered body according to any one of claims 1 to 8, wherein in the second firing step, a temperature at which the sintered body is fired is 1000 to 1350 ° C.   The method for producing a sintered body according to any one of claims 1 to 9, wherein an average particle diameter of the apatite powder is 40 µm or less.   The method for producing a sintered body according to any one of claims 1 to 10, wherein the two firing steps are performed in a single firing furnace by changing a firing atmosphere.   The method for producing a sintered body according to any one of claims 1 to 10, wherein the apatite powder is a hydroxyapatite powder.   The said hydroxyapatite powder is synthesize | combined by the wet synthesis method which uses at least one of a calcium source and a phosphoric acid source as a solution, and is manufactured using the slurry obtained in the said synthesis | combination. The manufacturing method of the sintered compact of this.   The method for producing a sintered body according to claim 12, wherein the calcium source is mainly composed of calcium hydroxide or calcium oxide, and the phosphoric acid source is mainly composed of phosphoric acid.   The method for producing a sintered body according to claim 13, wherein the hydroxyapatite powder is produced using the slurry having a tricalcium phosphate content of 0.1 wt% or less. The method for producing a sintered body according to claim 13 or 14, wherein the hydroxyapatite powder is produced using the slurry that satisfies the following condition A.
Condition A: A part of the slurry is taken out and compression molded at a molding pressure of ² ton / cm ² to form a sample molded body having a detection surface, and then the sample molded body is fired in the atmosphere at 1200 ° C. for 2 hours. When the substance present on the detection surface (surface roughness Ra = 10 μm) of the obtained sample is analyzed by X-ray diffraction, the peak intensity derived from hydroxyapatite is the largest among the obtained peaks, and No peak derived from tricalcium phosphate is observed.   The method for producing a sintered body according to any one of claims 12 to 15, wherein the hydroxyapatite powder is produced using the slurry having a calcium hydroxide or calcium oxide content of 3 wt% or less. The method for manufacturing a sintered body according to any one of claims 13 to 16, wherein the hydroxyapatite powder is manufactured using the slurry that satisfies the following condition B.
Condition B: When a part of the slurry is taken out and dried at 200 ° C., and this sample is baked in the atmosphere at 1200 ° C. for 20 minutes, the substance present in the sample is analyzed by powder X-ray diffraction. When the intensity of the peak derived from apatite is X and the intensity of the peak derived from calcium oxide is Y, the relationship Y / X <1/10 is satisfied.   18. The method for producing a sintered body according to claim 1, wherein the sintered body obtained by performing the first firing has a relative density of 99% or more.   A sintered body is produced so as to have a plate shape with a thickness of 0.5 mm, and when the sintered body is irradiated with light having a wavelength of 300 nm, the light transmittance is 10% or more. The manufacturing method of the sintered compact in any one of. A sintered body produced by the method for producing a sintered body according to any one of claims 1 to 20.

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