JPH02258663A - Calcium phosphate-based substance and production thereof - Google Patents

Abstract

PURPOSE:To readily improve density and mechanical strength, etc., of product by mixing fixed amount of specific transition-suppresser and oxide or salt of rare earth in production of calcium phosphate-based substance containing beta-Ca3(PO4)2 as principal crystalline phase. CONSTITUTION:(A) Calcium carbonate is mixed with (B) phosphoric acid, (C) transition-suppresser selected from oxide or salt of Mg, Si or Al, kaolin and mullite and (D) oxide of rare earth (e.g., Y2O3) or salt of rare earth in a fixed ratio. Next, the mixture is calcined and crushed to obtain a dense calcium phosphate-based substance containing beta-Ca3(PO4)2 as principal crystalline phase, 1-40 pts.wt. component C and 1-40 pts.wt. component D. The resultant calcium phosphate-based substance is suitably used for organism material such as bone, root of tooth or arthrosis, and further, suitably used for various structural materials as light weight and readily processable.

Description

[Detailed description of the invention] (Industrial application field) TECHNICAL FIELD This invention relates to calcium phosphate-based substances.

For more details, see Ca3 (P 04) z (hereinafter referred to as TC
The present invention relates to a calcium phosphate-based material which is dense and has improved strength properties and whose main component is β-TCP represented by the general formula (abbreviated as P), and a method for producing the same.

(Prior art) Conventionally, metal materials and organic materials have been used as biomaterials, but metal materials have poor chemical resistance and corrosion resistance, and are not compatible with living organisms, and organic materials have poor mechanical resistance. In recent years, research on the use of inorganic materials in living organisms has rapidly spread due to their poor thermal properties and heat resistance, and their applications include artificial tooth roots, artificial bones, and artificial joints.

It has rapidly become popular as a cavity filling agent, and has achieved success. Among these inorganic materials, especially Ca-o
(P 04) * (OH) 2 (hereinafter referred to as apatite) and TCP are similar in composition to bones and teeth in living organisms, and their crystal structures are also similar, so they are more similar to living organisms than other inorganic materials. It has an extremely high affinity for , and its research is being widely conducted, and its applications to living organisms and other areas are rapidly expanding. When apatite is heated in air, 100
Hydroxyl groups are gradually released from around 0°C, and decomposition begins at around 1300°C, and when fired at temperatures above 1300°C for a long time, H2O is released and becomes TCP and CaO. 13 in the air to get
Firing at temperatures below 00°C is required. In order to perform firing at a temperature of 1300° C. or lower, powder consisting of fine particles that are easily sinterable is required. For example, a fine precipitate synthesized by the wet precipitation method can be made into a cake-like form without drying for 10 minutes.
There is also a method of densification by firing at a temperature range of 00 to 1250°C, but this has the disadvantage that it is difficult to obtain a homogeneous and strong material because the shrinkage rate after firing is large and cracks are likely to occur. In addition, a method in which fine powder synthesized by wet precipitation is dried, molded, and fired at 1300°C or less has a small shrinkage rate after firing, and it is possible to obtain a homogeneous material, but it is difficult to synthesize the raw material powder. , dry two-grain size blending, molding, and sintering, all processes require advanced technology. If advanced technology is not available, the mechanical strength of the apatite sintered body will be significantly reduced.

For example, it is reported that the bending strength of an apatite sintered body obtained under advanced technical control is about 2000 kg/cd, but in reality it is often less than 11000) c/aJ. Furthermore, the apatite sintered body has the disadvantage of being weak against mechanical shock. These drawbacks have delayed the practical application of apatite-based materials.

The bending strength of natural bone is said to be about 700 kg/J, but in order for artificial bone to serve as a replacement material for natural bone, it needs to have a bending strength three times or more that of natural bone.

It has the same biocompatibility as the TCP-based substance Patite,
It is also said to have greater mechanical strength than apatite-based materials. TCP has a high-temperature α phase and a low-temperature β phase. The α phase has poor water resistance and expands when transitioning from the β phase to the α phase, inhibiting IIk densification. However, if a TCP-based substance is used, it is important that it be β-TCP.

However, when β-TCP is heated in air, it transforms into α-TCP at around 1120°C to 1180°C. Therefore, in order to obtain dense β-TCP, it is necessary to prepare ultrafine powder that can be sintered at 1120° C. or lower. For example, phosphoric acid is gradually added dropwise to an alkaline aqueous solution containing Ca ions.
The theoretical density (3,07
g/cd) is obtained. However, with this method, the shrinkage after firing is large and the bending strength is also low. In order to obtain a material that can be baked at higher temperatures, β phase →
It is necessary to suppress the transition to the α phase. For this purpose, various metastasis inhibitors have been developed. One example is MgO.

5i02. A1zOi+kaolin, mullite, etc.

When these transition inhibitors are used, β-
It is TCP. β-TCP powder can be easily synthesized by mixing calcium pyrophosphate and calcium carbonate and performing a solid phase reaction in air at 1100°C, but since the particle size of the synthesized powder is large, a pregelatinization inhibitor is added and the mixture is heated at high temperatures. It did not become dense even after firing, so we created a superdifferential by wet precipitation method, added a transition inhibitor, and heated it to 1200℃ and 1300℃.
℃.

It has become possible to improve density and mechanical strength by firing at high temperatures such as 1400°C. As a result, the bulk specific gravity of the obtained material was densified to 97% or more of the theoretical density, and the bending strength of the material was 1500 to 2000 kg/-. However, synthesizing TCP powder using the wet precipitation method requires the same advanced technology as the preparation of fine powder of abaite, and there is also the problem of treating wastewater after filtration and washing, which is generated in large quantities.

By conventional technology, the bending strength of TCP material is 1500 ~
Although the mechanical strength was improved to 2000 kg/J, it is related to the withdrawal material of the obtained β-TCP-based material. That is, no matter how fine the starting material is and no matter how efficient the metastasis inhibitor, the mechanical strength is determined by the microstructure of the final product obtained. For example, even if the starting powder is fine or a dislocation inhibitor is added, at high temperatures the constituent β-TCP particles will either grow uniformly or non-uniformly, resulting in increased bulk. Even if the density is close to the theoretical density, the mechanical strength may be low.

Conventional techniques provide insufficient control of grain growth. Furthermore, the methods for producing ultrafine powder that have been researched to date have the drawbacks of complicated processes and high costs.

(Problems to be Solved by the Invention) Conventional methods for producing TCP-based substances require complicated processes, require advanced technology, and are expensive. Moreover, if the powder is fired at high temperature for a long time to achieve high density, α-T
It is easy to become CP and often causes non-uniform grain growth, so there are problems in that density does not improve and mechanical strength tends to decrease. This invention attempts to solve these problems.

(Means for Solving the Problems) As a result of various studies conducted by the inventors on methods for producing calcium phosphate-based powders containing β-TCP as the main crystal phase, the inventors found that calcium carbonate and phosphoric acid as reagents and a dislocation inhibitor (M g+
A method in which calcium carbonate and phosphoric acid as reagents are blended in a predetermined ratio with oxides or salts such as "S i+ and a metastasis inhibitor in a predetermined ratio, heated and melted in an electric furnace at a temperature of 1,350°C or higher for several hours, rapidly cooled, made into glass, finely ground, and a rare earth oxide or rare earth salt in a predetermined ratio. A method of blending calcium carbonate and phosphoric acid as reagents, a transition inhibitor, and rare earth oxides or rare earth salts in a predetermined ratio, melting by heating in an electric furnace at a temperature of 1350°C or higher for several hours, and then rapidly cooling the glass. We have developed a method to create powder by pulverizing it. This method is advantageous in terms of equipment and management, does not require industrial wastewater, and even when fired at high temperatures, the main crystal phase is β-TCP. Since α-TCP is not generated and grain growth is suppressed, the density of the sintered body is improved.

It was also found that the mechanical strength of the sintered body was significantly improved because the microstructure of the sintered body was uniform. Furthermore, by adding appropriate amounts of dislocation inhibitors and rare earth element oxides or salts, the composite effect of materials can be achieved (for example, when excessive aluminum phosphate or mullite is added, needle-shaped crystals become TCP).
(precipitated at the grain boundaries of the crystals) appears, further improving mechanical properties.

Further, while the fine powder synthesized by the conventional wet precipitation method has the disadvantage of large shrinkage upon firing, the glass powder of the present invention has the advantage of low shrinkage upon firing. The present invention has been accomplished based on the above findings.

Generally, in sintering an inorganic material, when the growth rate of one grain is higher than the movement of pores, the pores are trapped inside the grains and a high-density sintered body cannot be obtained. In such cases, the diffusion coefficient that governs the grain growth rate can be reduced to suppress the grain growth rate and reduce the number of pores. This is possible under the conditions that the elements constituting the additive and the elements constituting the substance to be added have similar ionic radii and different ionic valences. In this invention, when comparing the rare earth elements constituting the additive and Ca, the main element constituting the TCP, the ionic radii of both are similar to each other, so the rare earth elements easily dissolve in solid solution in the TCP.
In addition, since the ion valence is trivalent or tetravalent for the former and divalent for the latter, the diffusion coefficient decreases, grain growth of TCP is suppressed, and pores are pushed out without entering the crystal during firing. Since the density of the sintered body is increased and grain growth is suppressed, the structure becomes uniform, and mechanical strength is improved due to one or more comprehensive effects.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. In addition, each test and structure observation on each side were performed as follows.

(1) Bulk specific gravity measurement, apparent porosity measurement: 1 sintered sample
The sample was thoroughly dried at a temperature of 05 to 120°C, and the weight of the sample was determined.

The bulk specific gravity and apparent porosity of the sample in water were measured. Measurements were performed five times and averaged.

(2) Firing shrinkage rate: Calculated from the sample length of the molded body and the sample length after firing. Measurements were performed five times and averaged.

(3) Bending strength test: The bending strength of the sintered body was measured according to "JIS R1601r Fine Ceramics Bending Strength Test Method". Measurements were performed five times and averaged.

(4) Structure observation: The structure of the surface and fracture surface of the sintered body was observed using a scanning electron microscope.

(5) Fixation of the product: Performed by powder X-ray diffraction (CuKa radiation). [Example I] 342 g of calcium carbonate, a commercially available special grade reagent.

After thoroughly mixing 57 g of aluminum oxide and 235 ml of phosphoric acid, the mixture was calcined in an electric furnace at 1000°C for 2 hours.
Then, the mixture was melted by heating at 1370° C. for 1 hour, poured into a suitable container, and rapidly cooled to obtain a transparent glass. This glass was ground in a ball mill for 48 hours to obtain a fine powder. 1.2,5,710.15,20,25 of this finely powdered commercially available dysprosium oxide (99.9% purity)
, 30, 35.40 parts by weight, mixed in a pot mill for 48 hours, calcined in an electric furnace at 1000°C for 2 hours, and pulverized in a ball mill for 48 hours.
Approximately 60+nm by applying pressure of CIP & iron 2t/aJ
A rod-shaped molded body having a length (6 nm in diameter) was obtained. The relative density of the molded body is about 60%. This molded body was placed in an electric furnace and fired in air at 1340°C for 4 hours. A sample to which no dysprosium oxide was added melted when fired at 1340°C, but when dysprosium oxide was added, the melting point became higher, so the sample did not melt and was sintered densely. The bulk density increases as the amount of dysprosium oxide increases, and 7
% of the added sample was 3.0 g/alf, and the apparent porosity was 1% or less. In addition, the firing shrinkage rate is 10 to 1
It was about 4%. According to electron microscopy, most of the particles observed are uniformly spherical, with a size of 3 μm.
m or less. Further, fine needle-like aluminum phosphate crystals (length: 2 μm or less) were present between the TCP grains. According to powder X-ray diffraction, the main crystal phase is β-T
CP, and a small amount of aluminum phosphate was formed thereon, but no other products were observed. However, if the amount of Dy20° added exceeds 15%, D! /
203 were recognized. The measurement results of bending strength are shown in FIG. 1. As shown in FIG. 1, the bending strength value of the material to which only 2% of dysprosium oxide was added exceeded 1,500 kg/aJ, and the maximum flexural strength value of 2,500 kg/a was obtained when 7% of dysprosium oxide was added. Furthermore, as the amount of dysprosium oxide added increased, the strength began to decrease.This means that excess dysprosium oxide began to precipitate between the grains, and a difference in thermal expansion between TCP and dysprosium oxide occurred. It is thought that this is why minute cranks have begun to form.

[Example 2] 342 g of calcium carbonate, a commercially available special grade reagent.

Mix 57 g of aluminum oxide and 235 ml of phosphoric acid, and add 1.2 g of dysprosium oxide to the thoroughly mixed powder.
,5,7,10,15,20,25°30.35,40
After blending parts by weight and mixing thoroughly, 1 part by weight was added in an electric furnace.
A transparent glass was obtained by calcining at 000° C. for 2 hours, then heating and melting at 1450° C. for 1 hour, pouring this into a suitable container, and rapidly cooling it. This glass was milled in a ball mill for 48
Pulverization was performed to obtain a fine powder. A pressure of 2 t/aJ was applied to this fine powder using CIP to obtain a rod-shaped compact having a length of about 6011 a (diameter 6 am). The relative density of the molded body is about 60%. This molded body was placed in an electric furnace and fired in air at 1340°C for 4 hours. A sample to which no dysprosium oxide was added melted when fired at 1340°C, but when dysprosium oxide was added, the melting point became higher, so the sample did not melt and was sintered densely. The bulk density, apparent porosity, firing shrinkage rate, microstructure determined by electron microscopy, and crystal phase determined by powder X-ray diffraction were the same as in Example 1. However, the measurement results of 1 bending strength were somewhat different from those of Example 1, and the bending strength was significantly improved compared to Example 1.

The results are shown in FIG. The material containing 2% dysprosium oxide had a bending strength of over 1700 kg/d, and the material containing 7% dysprosium oxide had a maximum strength of 3000 kg/cd.

Furthermore, as the amount of dysprosium oxide added increased, the strength decreased as in Example 1. The reason for this is also in Example 1.
is the same as The feature of Example 2 is that it was sintered from glass powder containing all the elements, and it is thought that the strength was increased because the microstructure was more dense and uniform than in Example 1.

[Example 3] Glass fine powder was obtained in the same manner as in Example 1 except that the dysprosium oxide used in Example 1 was replaced with yttrium oxide, and the glass powder was molded by CIP to form 6 molded bodies (length 6
0I, rod-shaped with a diameter of 6III11), the relative density is about 60%. This molded body was placed in an electric furnace and heated to 1340°C in the air.
It was baked at ℃ for 4 hours. As a result, the bulk density is 9 of the theoretical density.
It was densified to 5% or more. The results of measuring the microstructure by scanning electron microscope IR observation, the main crystal phase by powder X-ray diffraction, and the bending strength were almost the same as in Example 1. However, Y2O
, Y2O was observed when the amount of addition was 15% or more.

From the above, it has been found that even if the type of rare earth element changes somewhat, the effect of adding the rare earth element is almost the same.

[Example 4] 342g of calcium carbonate, a commercially available special grade reagent.

After mixing 57 g of aluminum oxide and 235 ml of Rin-san and mixing thoroughly, add commercially available high-purity mullite (9
10 parts by weight of 9.99% (particle size ≤ 1 μm) and 10 parts by weight of dysprosium oxide were mixed thoroughly, calcined at 1000°C in an electric furnace, and pulverized in a ball mill for 48 hours. The obtained differential powder was subjected to CIP at 2t/c.
A rod-shaped molded body with a length of about 60++n (diameter 6 m) was obtained by applying a pressure of j. This molded body was placed in an electric furnace and fired in air at 1340°C for 4 hours. The bulk density of the obtained sample was 2.8 g/d, the apparent porosity was 2 to 3%,
According to scanning electron microscopy, the size of the constituent particles is 1
It is about 5μ or so, and the bending strength is 1700 to 2000k.
g/alt. According to powder X-ray circulation, the main crystalline phase is β-TCP and small amounts of aluminum phosphate and acicular mullite, and α-TCP is not recognized.

Compared to Examples 1, 2.3, the density of the material is slightly lower and the bending strength is also lower. The reason for this is that Examples 1, 2, and 3 all use glass powder as the starting material.
It can be said that densification is easier when glass powder is used as a starting material. However, the method of Example 4 is characterized by simple steps and low cost. In addition, since it is easy to polish and cut, there are many uses that take advantage of these advantages, so it can be used as an industrial material. According to the research results by the inventors, even if commercially available calcium carbonate, phosphoric acid, and a transfer inhibitor are simply added, mixed, calcined, molded, and baked at high temperatures, the material will never become densified, and no such reports have been found. 8 The method of this invention is characterized in that it can be sufficiently densified simply by mixing commercially available chemicals.

(Effects of the Invention) The calcium phosphate-based substance of the present invention can be easily controlled under 7 conditions during production, and when starting from glass powder, the firing shrinkage is small. , equipment and management are very advantageous. Furthermore, since it has high mechanical strength, it can be applied to biomaterials such as bones, tooth roots, and joints.

Additionally, the material is lightweight and easy to polish and cut, making it suitable for a wide range of applications, including structural materials and containers.

[Brief explanation of drawings]

FIG. 1 is a chart showing the measurement results of bending strength in Example 1 of the present invention, and FIG. 2 is a chart showing the measurement results of bending strength in Example 2 of the same.

Claims (1)

[Claims] 1. In a calcium phosphate-based substance, the main crystal phase is β-
Composed of Ca_3(PO_4)_2, and Mg, Si
, Al oxide or salt, kaolin, mullite, and one or more substances selected from rare earth oxides or rare earth salts. material. 2 In the above substances, the content of Mg, Si, Al oxides or salts, kaolin, mullite is 1 part by weight or more and 40 parts by weight or less, and the content of rare earth oxides or rare earth salts is 1 part by weight or more. A method for producing a calcium phosphate-based substance containing 40 parts by weight or less.