JPS63100005A - Preparation of alpha-type tertiary calcium phosphate - Google Patents

Abstract

PURPOSE:To obtain alpha-type tertiary calcium phosphate having a thermodynamically stable phase by prepg. a raw material soln. by dissolving in water or an org. solvent compatible with water an inorg. compd. of Ca and an inorg. compd. of P soluble in water or in said org. solvent, and atomizing the raw material soln. into a hot zone to cause thermal decomposition reaction under a specified condition. CONSTITUTION:A raw material soln. is prepd. by dissolving a mixture of an inorg. Ca compd. and an inorg. P compd. adding, if necessary, an acid to the mixture in water alone or in an org. solvent compatible with water alone, or in a mixed solvent consisting of water and said org. solvent. Then, the raw material soln. is atomized into flame or a hot zone to cause thermal decomposition reaction. In this stage, such condition wherein the thermal decomposition reaction is caused at >=1,200 deg.C and the temp. of the powder material produced thereby is also >=1,200 deg.C is adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing α-type tricalcium phosphate.

α-type tricalcium phosphate [α-Cas(PO4)2;
α-TCP] exhibits higher hydrolyzability and hydraulic properties than β-type tricalcium phosphate (hereinafter abbreviated as β-TCP).
It is known that non-stoichiometric hydroxyapatite powder or porous hardened body, which is important as bioceramics, can be produced using TCP powder. In addition, when producing a dense sintered body of tricalcium phosphate, if β-TCP powder is used as the starting material powder, β-TCP
d At temperatures above 1180°C, α-TCP undergoes a phase transition at a rapid rate, and at this time, volumetric expansion occurs due to changes in crystal density, weakening the sintered body. To avoid this phenomenon, β It is necessary to sinter at a temperature lower than the temperature at which -TCP undergoes a phase transition to α-TCP, but as a result, there is a problem that it is difficult to obtain a dense sintered body because the sintering temperature is insufficient. On the other hand, as the starting material powder, 1
When using α-TCP, which is thermodynamically stable at temperatures above 180°C, the phase transition rate from α-TCP to β-TCP is slow. β-TCP without phase transition to
can exist thermodynamically stably (room temperature to 1180°C)
°C) and can be fired at a high temperature of 1180 °C or higher, which is the temperature range in which α-TCP can exist thermodynamically stably, resulting in a more dense sintered body. become.

Therefore, if it were possible to easily produce α-TCP powder, it would not only be sufficient for the above-mentioned uses, but also contribute to other uses as ceramic materials for general industrial use.

Conventionally, in order to produce α-TCP t-, either a dry synthesis method based on a solid phase reaction of raw material powder or a crystallization reaction by heating amorphous calcium phosphate synthesized by a wet method has been used. Even if it were, it was necessary to heat for a long time at a temperature of 1180° C. or higher, which is the stable temperature range of α-TCP. When using the wet synthesis method, it is known that α-TCP is generated at a low temperature range of 500 to 800°C depending on the conditions, but since this phase is a metastable phase, it is necessary to heat it to 800 to 1180°C. Then β-
Since a phase transition occurs in TCP, in this case as well, the stable phase α
-To make TCP, it is necessary to heat-treat the synthetic powder at a temperature of 1180°C or higher.

The present invention provides a method for directly producing thermodynamically stable α-TCP powder in a very short time using a simple method. More specifically, the present invention uses water or a water-compatible organic solvent alone as a solvent, or a mixed solvent of a water-compatible organic solvent and water as a solvent, and the calcium soluble in this solvent is used as a solvent. A solution in which an inorganic compound and an inorganic phosphorus compound are dissolved is used as a raw material solution, and it is sprayed into a flame or heating zone to cause a thermal decomposition reaction to produce α-TCP powder with a thermodynamically stable phase. It's about how to do it.

Japanese Patent Application No. 60-88479 and Japanese Patent Application No. 61-98349
In this issue, a new method for producing tricalcium phosphate using a spray pyrolysis reaction method is proposed. However, in these production methods, the tricalcium phosphate produced is α-TCP in a thermodynamically metastable phase, so in order to obtain α-TCP in a stable phase, the produced powder must be further heated. β at approximately 800-1180℃
After passing through the phase transition to -TCP, it was necessary to further heat to a high temperature of 1180'c or more.

As a result of various studies regarding the thermal decomposition reaction conditions in the above-mentioned spray pyrolysis reaction method, the present inventors found that by selecting the conditions for spray pyrolysis, the pyrolysis reaction temperature is at least 1200°C or higher, and It is possible to directly produce α-TCP in a thermodynamically stable phase by carrying out a thermal decomposition reaction under spray pyrolysis conditions such that the temperature of the resulting powder itself is 1200°C or higher. I found out.

The temperature of the produced powder itself is not necessarily uniquely determined with respect to a certain pyrolysis reaction temperature measured by a temperature sensor such as a thermocouple, and it depends on the type of raw material compound, the concentration of the raw material solution, It varies depending on many spray pyrolysis conditions, such as the content of water and organic solvent in the solution, the type of organic solvent, the feed rate of the raw material solution for spraying, and the spray pressure. That is, even if the thermal decomposition reaction temperature is constant,
The temperature of the powder itself, which is generated by the solidification and thermal decomposition of the sprayed droplets, is determined by the length of time the droplets remain in the region undergoing the thermal decomposition reaction, that is, in the flame or heating zone, and by the solidification of the droplets. It changes depending on the magnitude of the heat of vaporization required and the solidification/thermal decomposition rate of the droplets, etc., and these are influenced by the various spray pyrolysis conditions mentioned above. For example, even if the same raw material solution is used, the reaction region can be adjusted by reducing the spraying speed of the solution or the flow rate of the carrier gas that carries the droplets, or by increasing the length of the heating region in the direction of flow of the droplets. Since the residence time can be extended, the temperature of the produced powder itself can be increased, approaching the thermal decomposition reaction temperature. In addition, when the solvent in the raw material solution is a mixed solvent of an organic solvent and water, by increasing the organic solvent content and lowering the water content, when the sprayed droplets solidify, the organic solvent and water Since the amount of heat required for evaporation of water can be reduced, and in addition, the amount of heat required for combustion of the evaporated organic solvent can be increased, the temperature of the produced powder itself can also be increased. In this way, depending on the selection of the various spray pyrolysis conditions mentioned above, even if the pyrolysis reaction temperature is 1200°C or higher, for example 1300°C, the temperature of the resulting powder itself may be 1200°C or lower. , or 1200° C. or higher.

As a result of various experiments, the present inventors found that at least 1200
By selecting spray pyrolysis conditions such that the pyrolysis reaction temperature is 1200°C or higher, and the temperature of the powder itself at that time is 1200°C or higher, α-TCP in a thermodynamically stable phase can be produced.
We have discovered that it is possible to directly produce

It is clear from the following points that the α-TCP produced by the method of the present invention is not a metastable α-TCP but a stable phase α-TCP. That is, the metastable phase α−
In the case of TCP, the rate of phase transition to β-TC'P upon heating is fast; for example, when heated at approximately 5°C/min, the phase transition rate to β-TC'P is approximately 9
It is known that it easily changes to β-TCP at around 00°C, and this has also been confirmed in experiments conducted by the present inventors. However, α-TC produced by the method of the present invention
For example, even if P is heated from room temperature at a slow heating rate of 4°C/mxn, it can be heated to a high temperature of 1200°C or higher while maintaining the α-TCP phase without undergoing a phase transition to β-TCP. , this α-TCP is the stable phase α-
It is clear that it is TCP.

According to the method of the present invention, many steps such as filtration of the amorphous calcium phosphate precipitate, washing, drying, crystallization by heating, and pulverization in the wet synthesis method, and long-time under high temperature in the dry synthesis method, can be performed. A thermodynamically stable α-phase tricalcium phosphate powder (α-TCP) can be produced directly by a simple operation and an extremely short reaction time, usually a few seconds or less, without the need for a solid-phase reaction process. Can be synthesized.

Furthermore, as mentioned above, the method of the present invention is not only a new method for producing α-TCP that overcomes the drawbacks of the prior art, but also the properties of the produced α-TCP are different from those of the prior art α-TCP. It has the characteristic of being different. That is, when α-TCP obtained by the conventional technique is obtained by a dry synthesis method, it is usually obtained as a lumpy sintered body, so in order to make it into a raw material powder for various uses, Those lumps must be crushed. Moreover, the shape of the pulverized powder is amorphous and the particle size distribution is wide, so further steps such as classification operations are required to obtain a powder with a particle size and particle size distribution suitable for the purpose. This is often the case. and 9, according to the method of the present invention,
The α-TCP produced is obtained as a fine powder from the beginning, and is usually a spherical powder of submicron to several 10 microns. The particle size can be changed by selecting the type of raw material used for preparing the raw material solution, the concentration of the solution, the spray pyrolysis conditions, etc. Therefore, it has the advantage that there is no risk of time consumption due to the pulverization process and contamination of impurities.

Next, the method of the present invention will be specifically explained.

First, as a starting material, water or a water-compatible organic solvent is used alone as a solvent, or a mixed solvent of a water-compatible organic solvent and water is used. A raw material solution is prepared by adding and dissolving a soluble calcium inorganic compound and phosphorus inorganic compound to each of the i-solvents.

At this time, depending on the combination and concentration of the calcium compound, phosphorus compound, and solvent, it may be difficult to prepare a uniform solution, or the adjusted solution may become cloudy over time. However, in some cases, these problems can be overcome by adding an acid.

Further, the order of mixing the raw materials for preparing the solution aiJ at this time is not necessarily limited to the above-mentioned order, and it is sufficient that they are mixed together in an order that does not cause precipitation. The time for mixing varies depending on the raw materials selected, but it is preferable to stir sufficiently until all the raw materials are dissolved and a solution of uniform composition is obtained.

Next, the solution prepared in this manner is sprayed into a flame of a gas burner or the like using a known spraying method using a pressurized nozzle or a rotating disk, or is sprayed into a flame of a gas furnace, electric furnace, high-temperature gas, etc. spray into a heating zone that has been preheated to the desired temperature. At that time, the heat source necessary to cause the thermal decomposition reaction is the heat of a flame from a gas burner, etc., or the solvent is a flammable organic solvent that is compatible with water, or a combustible organic solvent that is compatible with water. When a mixed solvent of a flammable organic solvent and water is used as a solvent, the combustion heat due to combustion of the flammable organic solvent itself, and the organic solvent in the mixed solvent of water and an organic solvent that is compatible with water. When used to accelerate the evaporation of a mixed solvent without burning it,
When water is used alone as a solvent, the thermal decomposition reaction temperature is made to be 1200° C. or higher by using a heat source such as the above-mentioned gas furnace or a combination of these heat sources.

At that time, in order to determine the various spray pyrolysis conditions as mentioned above, for example, in systems where water is included in the solution, the temperature of the solidified powder will be lower due to evaporation of water. Considering that, the temperature of the powder itself during the pyrolysis reaction is 1
The temperature should be 200℃ or higher.

Thus, according to the method of the present invention, in an extremely short period of time of several seconds or less, the decomposer in the solution, which has become fine droplets of usually several tens of microns or less, is evaporated and burned, and the solute is solidified and thermally decomposed. α-TCP is produced by the reaction. The powder generated by the thermal decomposition reaction is collected using a cyclone or the like.

The calcium inorganic compound and phosphorus inorganic compound used in the method of the present invention include Ca(NOs)a
・4 HaOlca(cH3coo)2- H2O,C
a(HCOO)2, CaHPOm + 2 H2O, N
H, H, PO, NH4H, PO3, Bpo4, H3P
As the organic solvent, it is preferable to use alcohols such as methanol, ethanol, 2--10 q-nol, l-butanol, 2-methoxyethanol, acetone, etc. There are no particular limitations, and any combination of raw materials may be used as long as a uniform solution that does not cause precipitation can be prepared by mixing. Further, for this purpose, nitric acid or acetic acid is suitable as the acid to be added as necessary. Furthermore, the solvent used in the method of the present invention may vary depending on the pyrolysis method, the combination of raw materials, the desired powder properties of α-TCP, etc.
Water can be used alone as a solvent, or a water-compatible organic solvent as mentioned above can be used alone, or a mixed solvent of a water-compatible organic solvent and water can be used as a solvent. can. Note that even when an organic solvent that is compatible with water is used alone as a solvent, depending on the combination of raw material compounds, the reaction system may be mixed with water and organic solvent due to residual moisture or crystal water in the raw material compounds. However, in any of these cases, as long as the raw material solution can be prepared without precipitation, it can be used as a solvent in the method of the present invention. Can be done.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 Ca(NO3)z ・4 H2O28,34f about 15
Dissolve in 0 mA' ethanol and add nitric acid IQ rrr
Phosphoric acid (H3P0. content 85.6%
) A solution of 9.169 dissolved in about 100 ml of ethanol was added and mixed, and ethanol was further added thereto to prepare a raw material solution with a total volume of 400 ml.

Next, this raw material solution was supplied at a rate of 8 ml per minute and compressed air at a rate of 101 per minute to the liquid supply side and gas supply side of the two-fluid spray nozzle, and sprayed into the flame of a gas burner whose thermal power was adjusted. .

The raw material solution, which has become fine droplets, undergoes evaporation and evaporation of the solvent in a flame.
The combustion caused instantaneous heating and a thermal decomposition reaction. The thermal decomposition reaction temperature was 1470-1490°C. The powder thus produced was collected using a cyclone method. This produced powder was found to be α-TCP by X-ray diffraction measurement.
It turned out to be a powder consisting of crystals. In addition, this produced powder was heated in an air atmosphere at a temperature increase rate of 4°C/min, and 800.900.1000.1ioo1 and 120
When the temperature reached 0° C., the sample was taken out from the furnace, left to cool, and subjected to X-ray diffraction measurement. In each case, a diffraction pattern of only the α-TCP crystal phase was obtained. Separately, the resulting powder was heated to 1000°C at 5°C/min in an air atmosphere, held at 1000°C for 2 hours, then taken out of the furnace and allowed to cool, and when held at 1000°C for 4 hours. After that, the X-ray diffraction pattern when slowly cooled in the furnace at 5℃/ml is also α-TC.
It was only due to the P crystal phase.

From the above experiments, it was found that α-TCP produced by this Example 1
α-TCP is a thermodynamically stable phase, and the phase transition to β-TCP is slow when heated from room temperature. Therefore, by heating at a temperature increase rate of 4°C/min or more, α
It can be seen that the -TCP phase can be heated to a temperature of 1200° C. or higher (a temperature at which α-TCP exists thermodynamically stably).

Example 2 Ca(NO3)z ・4H207,09f! about 400
Phosphoric acid (83P04 content 85.6%) was dissolved in 2.3 ml of ethanol and added with 25 ml of nitric acid.
A solution of 05' dissolved in about 200 ml of ethanol was added and mixed, and ethanol was further added thereto to prepare a raw material solution having a total volume of 1 liter. Next, this raw material solution was sprayed into a flame in the same manner as in Example 1 to perform thermal decomposition. The thermal power of the burner has a thermal decomposition reaction temperature of 1210 to 12
It was adjusted to be stable at 60°C.

The powder obtained by this method, when this powder was heated at 4°C/min as in Example 1, and after being held at 1000°C for 1 hour, both contained only α-TCP crystal phase. It was a powder consisting of.

Example 3 Ca(NO3)2.4 H2O28,34S' about 15
Dissolve 01111 in 1-butanol and add nitric acid 10
Add 6.599 ml of phosphorous acid to the solution of about 1001 ml
+1/17) Add the solution dissolved in l-butanol and mix, then add 1-butanol to it until the total volume is 400.
A raw material solution of mj was prepared.

Next, this raw material solution was sprayed into a flame in the same manner as in Example 1 to perform thermal decomposition. The thermal decomposition reaction temperature is 145
The temperature was 5 to 1470°C. The powder obtained by this method and the powder after heat treatment in the same manner as in Example 2 were
As a result of line diffraction measurement, all of the powders were found to be α-TCP crystal phase powders.

Example 4 Add Ca to a solution of 10ml of water and 10ml of nitric acid.
(NO3) 24H2028,34f was added and dissolved in a solution, and a solution of 5 rnl of water and 5 ml of nitric acid was mixed with N.
Add H4H2PO49,29S' and add the dissolved solution, then add acetone to this and mix, until the total amount is 400
A raw material solution of at was prepared. Next, this raw material solution was sprayed into a flame to perform thermal decomposition in the same manner as in Example 1. The thermal decomposition reaction temperature was adjusted to 1490-1510°C.

The powder obtained by this method and the powder were heated at 4°C/min in an air atmosphere to 800°900.100
The X-ray diffraction pattern of the powder taken out from the furnace and left to cool when it reached 0.1100 and 1200°C is α-TC.
This was due to the P crystal phase.

Example 5 Raw material solution 1&: was prepared in the same manner as in Example 1 using methanol, 2-pro, e-ethanol, and 2-methoxyethanol instead of ethanol as the solvent in Example 1, and spray pyrolysis was performed. The reaction was carried out. The thermal decomposition reaction temperature is 1420-1435°C and 1460-14°C, respectively.
The temperature was 85°C and 1420-1445°C.

As a result of X-ray diffraction measurement, the powders obtained by these methods and the powders obtained after heat-treating the powders in the same manner as in Example 4 were found to be α-TCP crystal phase powders. .

Example 6 Ca(No:s)2+ 4H2056,68f in water 3Q
ml and further added 10 ml of nitric acid,
A solution prepared by dissolving 18.40 tons of NH4H2PO4 in 70 ml of water was added and mixed to prepare a raw material solution. Then,
Electric furnace reaction tube (30φx) preheated to 1500℃
1000 mrx) from one end, the above raw material solution is
, 3 ml! /mxn into the reaction tube.

The raw material solution, which had become fine droplets, was heated while passing through the reaction tube, causing a thermal decomposition reaction. The products were collected in a receiver connected to the other end of the reaction tube, and the gas and steam generated by thermal decomposition were sucked in with an aspirator and exhausted outside the system. As a result of X-ray diffraction measurement, the powder obtained by this method and the powder heat-treated in the same manner as in Example 4 showed that α
- It was a powder of TCP crystal phase.

Claims (1)

[Claims] An inorganic compound of calcium that is soluble in the solvent, using water or a water-compatible organic solvent alone as a solvent, or a mixed solvent of a water-compatible organic solvent and water as a solvent. and an inorganic compound of phosphorus,
A method for producing α-type tribasic calcium phosphate by further adding an acid as necessary, mixing and dissolving to prepare a raw material solution, and spraying the raw material solution into a flame or a heating zone to cause a thermal decomposition reaction. The pyrolysis reaction is carried out under spray pyrolysis conditions such that the pyrolysis reaction temperature is at least 1200°C or higher and the temperature of the resulting powder itself is also 1200°C or higher. A method for producing α-type tricalcium phosphate.