JPH0230653A - Calcined calcium phosphate-based ceramic compact and production thereof - Google Patents

Abstract

PURPOSE:To improve acid resistance and mechanical strength by containing a fluorine apatite expressed by a specific general formula as a principal component. CONSTITUTION:The above-mentioned calcined calcium phosphate-based ceramic compact contains fluorine apatite expressed by the general formula Ca10(PO4)6(OH)2-2xF2x (x is 0.1-1.0) as a principal component. The calcined compact may contain 0.1-50wt.% tricalcium phosphate in addition to the fluorine apatite expressed by the afore-mentioned general formula. If the content thereof exceeds 50wt.%, solubility is unfavorably increased. The above-mentioned calcined compact can be produced by calcining powder containing the fluorine apatite expressed by the afore-mentioned general formula as the principal component at 800-1,100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to a calcium phosphate ceramic sintered body having excellent acid resistance and a method for producing the same.

"Prior art and its problems" Hydroxyapatite Ca, oCP 04)! (OH
) Z sintered bodies have been used in clinical settings as biomaterials for artificial tooth roots, artificial bones, etc. because they have excellent biocompatibility. However, hydroxyapatite lacks acid resistance and has the disadvantage of being easily dissolved and eroded under acidic conditions. This suggests that when a material made of hydroxyapatite ceramics is implanted into a living body, the surface may be eroded, resulting in a significant decrease in the mechanical strength of the material. Also, even when used in other fields, in a humid atmosphere,
Part of the ceramic may melt, causing deterioration of the material's properties.

On the other hand, it is already known that fluoroapatite has lower solubility than hydroxyapatite.For example, a solution containing a fluorine compound is applied to the surface of a human tooth whose main component is hydroxyapatite, and the surface is coated with fluoroapatite. Attempts have been made for a long time to increase acid resistance and prevent corrosion by changing it to , and its effectiveness has been confirmed.

However, fluoroapatite sintered bodies that can be used as bioceramics for artificial teeth, bones, etc. have not been known so far.

"Objective of the Invention" An object of the present invention is to provide a calcium phosphate ceramic sintered body having excellent acid resistance and mechanical strength, and a method for manufacturing the same.

"Structure of the Invention" The calcium phosphate ceramic sintered body according to the present invention has the general formula (I) Ca+o(P 04) as a main component.1. (OH)x−zXF tx(
1) It is characterized by being a fluoroapatite represented by [wherein X represents a number from 0.1 to 1.0].

The sintered body according to the present invention contains tricalcium phosphate in addition to the fluoroapatite represented by the above general formula (I).
It may be contained in an amount of 1 to 50% by weight.

However, if the amount of tricalcium phosphate exceeds 50% by weight, the solubility will increase, which is not preferable.

Further, the calcium phosphate ceramic sintered body according to the present invention is produced by sintering powder containing fluoroapatite represented by the above general formula (I) as a main component at 800 to 1100°C.

The fluoroapatite represented by the general formula (I) is preferably produced using ammonium hydrogen fluoride as the fluorine source, as proposed in Japanese Patent Application No. 63-93191. That is, (1) a method of dropping an aqueous phosphoric acid solution to which ammonium hydrogen fluoride has been added to a calcium hydroxide slurry, (2) a method of dropping an aqueous phosphoric acid solution to a calcium hydroxide slurry to which ammonium hydrogen fluoride has been added, or (2)
In addition to the wet method, it is preferable to produce hydroxyapatite by dropping an aqueous solution of phosphoric acid into a calcium hydroxide slurry, followed by adding an aqueous ammonium hydrogen fluoride solution dropwise, followed by drying and heat treatment. ,
Fluorapatite can also be produced by a dry synthesis method in which a phosphorus compound, a calcium compound, and a fluorine compound are mixed at a predetermined ratio and reacted at high temperatures. Although fluoroapatite produced by any method may be used, it should be one that does not contain impurities that would interfere with sintering.

Note that when synthesizing fluoroapatite, a compound containing tricalcium phosphate (Ca 3 (P O4) t ) can be obtained by setting the calcium/phosphorus ratio to Ca/P<1,666. Furthermore, by changing the fluorine content, it is possible to obtain a hydroxyapatite in which the hydroxyl groups are substituted with fluorine in any proportion, but in the present invention, X in general formula (1) is 0. 1 to 1.0 is used. This is because when X is less than 0.1, no improvement in acid resistance is observed.

The liquid containing fluoroapatite as a main component obtained by the wet method as described above is pulverized by a known drying method using a spray dryer, band dryer, vacuum freeze dryer, etc. to obtain a ceramic raw material powder. I can do it.

The ceramic raw material powder used in the method of the present invention is a fine particle of 100 to 1000 particles, or a secondary particle of these particles combined with each other, and the average particle size of the secondary particle is 0.5 to 20 μm. It is desirable that the number of secondary particles is greater than 1,000, since the sintering activity will be poor if the number of secondary particles exceeds 1000.

The obtained ceramic raw material powder is calcined as necessary.
It is crushed, molded using a known ceramic molding method, and
A sintered body can be obtained by sintering at a temperature of 0 to 1100°C.

As a dry molding method, for example, compression molding using a hydrostatic press is used, and as a wet molding method, casting molding,
Extrusion molding, injection molding, sheet molding, etc. are used. In general, the molded bodies obtained by these methods become dense sintered bodies by firing, but if a porous structure is desired, such as for biomaterials or sensors, a foaming process may be incorporated during molding, or a foaming process may be incorporated into the molded body. The porous body is formed by a known porous body manufacturing method, such as mixing a predetermined ratio of substances that decompose and volatilize during firing.

These molded bodies are fired after finishing processing such as secondary processing, if necessary. Firing may be performed in air, but
It may be carried out in an inert gas atmosphere such as argon or nitrogen. Further, the firing can be performed under vacuum, normal pressure, high pressure (200 MPa), or the like.

Fluorine in fluoroapatite is easily volatilized by heating, and especially in the presence of water vapor, it is thought that the volatilization rate of fluorine increases according to the following reaction formula.

Ca+a(P Oa>hFz + 2 H!0→Ca+
o(P Os>h(OH)z+ 2 HF Furthermore, it is also possible that the hydroxyapatite produced by this reaction is decomposed according to the following formula.

Ca1o(P0n)i(OH)z-3Ca5(P
0a)t+CaO+)IzO Therefore, in order to obtain the sintered body mainly composed of fluoroapatite according to the present invention, it is preferable to perform the firing in an inert gas atmosphere containing no water vapor, in dry air, or in a vacuum. Even when calcined in air containing water vapor, calcium oxide and/or calcium fluoride are only generated on the surface, so there is no or little influence from their formation.

The firing temperature is preferably in the range of 800 to 1100°C. If it is less than 800°C, sufficient sintering will not occur, and if it exceeds 1.100°C, the amount of calcium oxide will be too large and the strength will decrease. There is a tendency to

When producing a dense sintered body by the method of the present invention,
A dense sintered body with a relative density of 95% or more can be obtained.

Conventionally, in the case of hydroxyapatite, the relative density is 9
It has been common knowledge that in order to obtain a sintered body with a density of 5% or more, firing must be performed at a temperature of at least 1000°C or higher. However, according to the method of the present invention, 100°
It has been found that a sintered body of fluoroapatite having the same crystal structure and physicochemical properties as hydroxyapatite can be obtained even when the temperature is below C.

The size of the primary particles constituting the sintered body of the present invention is 0.1
It is preferably in the range of ~30 μm. If the grain size is less than 0.1 μm, it is difficult to synthesize, and if the grain size exceeds 30 μm, the strength of the sintered body decreases due to grain growth.

In addition, when mechanical strength is required, a dense material is preferable to a porous material, but in this case, the porosity is preferably 5% or less. If the porosity exceeds 5%, the strength will decrease. This is because

However, when using the sintered body of the present invention for bioceramics, sensors, etc., it is desirable that the sintered body is a porous body having a pore size and a porosity depending on the purpose. In the case of bioceramics, the surface or overall porosity is at least 2.
It is desired that the pore size is 0 to 80% and the pore diameter is 1 μm to 2000 μm.

More preferably, the pore diameter is 10 μm to 500 μm. In addition, in the case of gas sensors, etc., 10 people to 1 o
Preferably, the material has pores of ooo.

"Examples of the Invention" Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

Example 1 A 1ON aqueous solution of 0.3M phosphoric acid in which 28.5 g of ammonium hydrogen fluoride was dissolved in a calcium hydroxide slurry 101 with a 0.5M concentration was stirred at a speed of 5 d/min using a roller pump. Dropped 0 24 hours after completion of dripping
When the time elapsed, stirring was stopped and the mixture was aged for 48 hours in a stationary state. The product was dried with a spray dryer under the following conditions and granulated.

Drying conditions Inlet temperature 200°C °Outlet temperature 80"C Drying speed 1.6f/h Spraying method Disc type atomizer - rotation speed
The 3000 Orpm granulated powder was calcined at 700°C, press-molded in a mold, and then compressed in a hydrostatic press at a pressure of 2000 kg/c1i to obtain a green molded body. When this molded body was fired in air at 860° C. for 4 hours using a box-type electric furnace, a dense sintered body with a relative density of 99% was obtained.

When the surface of the obtained sintered body was analyzed by X-ray diffraction without being crushed, the a-axis length was 9.365 angstroms, and the c-axis length was 6.883 angstroms, which partially corresponds to the data on the ASTM card. From this, it was confirmed that it was fluoroapatite. A calcium oxide peak was also detected.

The results are shown in FIG. 1, and the results of measuring the infrared reflection spectrum on the surface of the sintered body are shown in FIG. Since no absorption by hydroxyl groups near 630C1m-', which is observed in hydroxyapatite, was observed, it was confirmed that hydroxyapatite was fluoroapatite in which the hydroxyl groups of hydroxyapatite were substituted with fluorine. Furthermore, when the surface of the sintered body was observed using a scanning electron microscope, the size of the -order particles was approximately 0.
．． It was 3 μm. Note that when the sintered body was crushed and the powder was analyzed by X-ray diffraction, no calcium oxide was detected.

Example 2 In Example 1, the amount of ammonium hydrogen fluoride was changed to 14.
25 g was synthesized in the same manner, dried, calcined,
After molding, the molded body was fired in air at 1100°C for 4 hours to obtain a dense sintered body with a relative density of 99.9%.

Figure 3 shows the results of X-ray diffraction on the surface of the sintered body. On the surface,
Trace amounts of calcium oxide are produced by the decomposition of apatite. On the other hand, when the sintered body was crushed and subjected to powder X-ray diffraction analysis, no calcium oxide peak was detected. Therefore, it is thought that decomposition occurred only on a portion of the surface. When the lattice constants were determined from X-ray diffraction data, the a-axis length was 9.388, and the c-axis length was 6.8.
There were 74 people. The a-axis length is between hydroxyapatite and fluoroapatite, and the fluorine content determined by elemental analysis is 1.85%. It was found that about 1/2 was hydroxyl-fluoroapatite substituted with fluorine.

The lattice constant data in Example 1 and Example 2 are shown in FIG.

Example 3 The molded product produced in Example 1 was heated to a vacuum degree of 4×10 in a vacuum furnace.
-'tor, heating rate 200°C/hour, firing temperature 900
℃, 950℃ and 1000℃, respectively, and the diameter was 5 nm and the length was 22I! A sintered body of 1TIl was obtained.

The relative density and bending strength of each sintered body were measured, and the results are shown in Table 1 below.

In addition, the above-mentioned fluoroapatite (denoted as FAp) vacuum-fired at 1000°C and hydroxyapatite (denoted as HAp) fired in the air at 1020°C were each used at 20%
After 10 days of immersion in 0 d of distilled water and p) 15 acetate buffer, the solubility was determined by measuring the eluted calcium and phosphorus concentrations, and the results are shown in Table 2.

From the results of the examples shown in Table 1 and Table 2, in the case of hydroxyapatite, in order to obtain a dense sintered body with a relative density of 99% or more, in the case of normal pressure sintering, it is necessary to sinter at 1050°C or higher and at high pressure. However, according to the present invention, a high-density sintered body with a relative density of 99% or more can be heated in the atmosphere.
It has been found that it can be obtained at a temperature of 1000''C or less even in a vacuum.

Moreover, hydroxyapatite showed high solubility in acetate buffer, but fluoroapatite showed low solubility in acetate buffer as well as in distilled water. That is, the sintered body of the present invention has high acid resistance. Furthermore, when the vacuum-fired fluoroapatite sintered body was analyzed by X-ray diffraction, it was confirmed that no calcium oxide was present even on the surface.

Example 4 100 g of fluoroapatite powder obtained by the method shown in Example 1 was dispersed in 3% hydrogen peroxide solution, and the viscosity was 40 cp (
A slurry of centipoise was prepared. Transfer this slurry to a glass container and place it in a constant temperature bath set at 120°C for 48 hours.
Foaming and drying were performed over time to obtain a dry foam. The dried foam was fired at 1200°C for 4 hours. The heating rate is 8
00”C, 200℃/hour, 800℃ to 1200℃
°C was set at 100 °C per hour. Cut the sintered body with a diamond cutter while pouring distilled water into 1OX20X
A 30+ms rectangular block was obtained. The porosity of the block was about 40%, and the pores were composed of macropores with a diameter of 100 μm to 2000//m and micropores of about 2 μm, which were made up of gaps between secondary particles. All pores were interconnected and had an ideal structure for bioceramics.

Example 5 Calcium hydroxide slurry 101 with a concentration of 0.5M! 28.5 g of ammonium hydrogen fluoride was dissolved with stirring. 1°2 of a 0.3M aqueous phosphoric acid solution was added dropwise at a rate of 5 d/min using a roller pump. After dropping, add 0.3M phosphoric acid aqueous solution 0.451,
After stirring for 4 hours, the mixture was left to mature for 48 hours. After drying, granulating and molding the resulting slurry under the same conditions as in Example 1,
Firing was performed at 050'C for 4 hours to obtain a dense body with a relative density of 96%.

When the sintered body was analyzed by powder X-ray method, it was confirmed that it was composed of fluoroapatite and β-tricalcium phosphate. The main peak ratio of these components is approximately 7:3.
Met. Further, when the ratio of calcium to phosphorus, Ca/P, was determined by chemical analysis, the value was approximately 1.59.

"Effects of the Invention" The calcium phosphate ceramic sintered body of the present invention has excellent acid resistance and mechanical strength, and can be used not only as a biomaterial such as artificial tooth roots and artificial bones, but also as a substrate for electronic materials such as IC package substrates, and as a heat-resistant material. It is also useful as a component.

Furthermore, when the ceramic sintered body of the present invention containing tricalcium phosphate as a second component is used as an in-brand material, this tricalcium phosphate is dissolved and absorbed, and is quickly replaced with newly formed new bone. Therefore, it is an ideal bioceramic that forms a tight bond with the bone, and the other non-absorbable part (fluoroapatite part) maintains the shape of the implant site and maintains the load applied there. be.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction diagram of the surface of the sintered body obtained in Example 1, FIG. 2 is an infrared reflection spectrum of the surface of the sintered body obtained in Example 1, and FIG. 3 is an X-ray diffraction diagram of the surface of the sintered body obtained in Example 1. The X4s diffraction diagram of the surface of the sintered body obtained in FIG. 4 is a graph showing the relationship between the degree of fluorination and the lattice constant of apatite crystal.

Claims (7)

[Claims] 1. The main component has the general formula: Ca_1_0(PO_4)_6(OH)_2_-_2_
A calcium phosphate ceramic sintered body characterized by being fluoroapatite represented by xF_2_x [in the formula, x represents a number from 0.1 to 1.0]. 2. Tricalcium phosphate as second component 0.1-50
The calcium phosphate ceramic sintered body according to claim 1, wherein the calcium phosphate ceramic sintered body contains % by weight. 3. The size of the primary particles that make up the ceramic is 0.1
The calcium phosphate ceramic sintered body according to claim 1 or 2, which has a porosity of 5% or less. 4. Porosity is 20-80%, pore diameter is 1μm-200%
The porous calcium phosphate ceramic sintered body according to claim 1 or 2, wherein the porous calcium phosphate ceramic sintered body has a diameter of 0 μm. 5. General formula: Ca_1_0(PO_4)_6(OH)_2_-_2_
A calcium phosphate ceramic sintered body characterized by sintering a powder containing fluoroapatite as a main component represented by Production method. 6. 6. The method for producing a calcium phosphate ceramic sintered body according to claim 5, wherein the sintering is performed in vacuum, dry air, or an inert gas atmosphere. 7. 6. The method for producing a calcium phosphate ceramic sintered body according to claim 5, wherein the fluoroapatite is obtained by a reaction of calcium hydroxide, phosphoric acid, and ammonium hydrogen fluoride.