JPH0415166B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for producing calcium-phosphorus apatite. Calcium-phosphorus apatite has unique performance as an adsorbent for biopolymers, fluorine ions, heavy metal ions, etc., and in recent years, it has been used as a chromatographic material for separating proteins, enzymes, etc. by utilizing its biocompatibility. It is a substance that is seen as promising as a filler for graphics, and is also attracting attention as a material for bioceramics such as artificial bones and artificial teeth. Conventionally, many methods for producing calcium-phosphorus apatite have been known for a long time, and they can be broadly classified into the following methods. (1) A method of synthesizing apatite using a solid-state diffusion reaction called the dry synthesis method. (2) A method of synthesizing apatite by reaction under high pressure, called hydrothermal synthesis. This is done primarily for the purpose of obtaining large crystals. (3) A method called the wet synthesis method in which apatite is precipitated linearly using ions in an aqueous solution. However, the dry synthesis method (1) requires a long reaction time at high temperatures, which consumes a lot of energy, and because it is a solid-solid reaction, there are problems with uniformity of composition. The hydrothermal synthesis method (2) requires expensive equipment because the reaction is carried out under high pressure, and the operation is complicated.Furthermore, the wet synthesis method (3) has the disadvantage that the apatite produced by the reaction Both methods have drawbacks, such as the need for many steps such as separation of precipitates, washing and drying, and complicated handling and operations. A number of wet synthesis methods for apatite have been proposed to date, but the common idea among these conventional wet synthesis methods is, for example, that a calcium chloride solution and an aqueous phosphorus compound solution are heated at 90 to 100°C.
As can be seen in the example of the method of mixing in a decarboxylated atmosphere while maintaining the pH around 8 to form a precipitate, apatite is directly formed as a precipitate, and the apatite is extracted from an aqueous solution by filtration or other operations. This is based on the concept of separating and recovering the waste. However, according to this method, the process of mixing an aqueous solution of a calcium salt and an aqueous solution of a phosphorus compound, forming a precipitate through a direct reaction of ions, and crystallizing it into apatite depends on the type and concentration of the raw material salt, and the mixing procedure of the raw materials. It is difficult to obtain a precipitate with the exact composition as it is affected by many factors such as mixing rate, pH adjustment, etc., and the molar ratio of calcium and phosphorus (Ca/P) and the physical chemistry of the resulting powder. It has been extremely difficult to control the characteristics with good reproducibility. In addition, it requires multiple steps such as excessive washing, drying, and pulverization of the precipitate, as well as a large number of devices, and its operation requires skill. The present inventors have conducted various studies on a method for producing calcium-phosphorus apatite using a simple method that eliminates the drawbacks of the prior art as described above, and has a small number of steps.As a result, the present inventors have developed the present invention. It has come to completion. Regarding one of the technical features of the method of the present invention,
First, in order to solve the difficulties in the precipitation formation and crystallization process in the conventional wet synthesis method, water or a water-compatible organic solvent was used alone as a solvent, or a water-compatible organic solvent was used as a solvent. A mixed solvent of a solvent and water is used as a solvent, and an inorganic compound of calcium or an inorganic compound of calcium acetate and phosphorus that is soluble in the solvent is added and mixed with an acid as necessary to dissolve and precipitate. The method is to prepare an acidic solution that does not generate acid and use this as a raw material solution. This is different from the conventional wet synthesis method in which the pH of the solution is controlled to be alkaline in order to precipitate apatite from the solution through a direct reaction of ions. On the contrary, it keeps the solution acidic, prevents the formation of precipitates due to reactions between components, and maintains a solution with a uniform composition. Added. Next, the above-mentioned raw material solution is subjected to a spray pyrolysis reaction, but during this spray pyrolysis reaction, the segregation of components during the reaction is extremely small, and the uniformity of the composition when it is a solution is brought to the product. I can do it. Also,
The time required for this reaction is several seconds or less. As described above, the method of the present invention also overcomes the drawback of the dry synthesis method of the prior art, which requires a long reaction time at high temperature. While conventional techniques require a long time and numerous steps to synthesize apatite, the method of the present invention allows the synthesis reaction to be carried out in an extremely short time of only a few seconds or less. Moreover, it has the excellent advantage that apatite powder can be obtained directly without any complicated steps such as filtration, washing, and drying. Furthermore, the method of the present invention has the advantage that apatite containing halogens such as chlorine and bromine can be easily synthesized. For example, in the past, chlorapatite was synthesized only by high-temperature solid phase reaction or pressurized hydrothermal reaction, and not by normal pressure wet method, but in the method of the present invention, CaCl ₂ .
By using a chlorine-containing calcium compound such as 2H ₂ O as a raw material, chlorapatite or a solid solution apatite of chlorapatite and hydroxyapatite can be easily synthesized. Regarding bromine apatite and bromine solid solution apatite, _CaBr2・
This can be done using calcium compounds such as 2H ₂ O and the like. One feature of the method of the present invention is that the apatite component in the raw material solution is spray-pyrolyzed as it is without precipitating it, making it possible to easily produce apatite product having the same blending ratio of calcium and phosphorus in the raw material solution. Therefore, it is not only possible to easily obtain apatite with a theoretical composition [Ca/P=5/3] that is difficult to achieve using the wet method, but also to intentionally mix calcium and phosphorus according to the purpose and use. The method of the present invention makes it possible to easily control the molar ratio of calcium and phosphorus in the composition of apatite, such as easily producing apatite with a composition in which the molar ratio of calcium and phosphorus is shifted from the theoretical composition ratio. It can be said that this method has excellent reproducibility. Furthermore, as mentioned above, the manufacturing method of the present invention is not only a new method for manufacturing apatite that overcomes the drawbacks of the prior art, but also has many features such as the property of the apatite itself that is different from the apatite produced by the prior art. has. That is, when the apatite obtained by the conventional technique is obtained by the wet synthesis method,
Normally, the precipitate is obtained as a dried lump, and in the case of dry synthesis, the product is obtained as a lump-like sintered body, so it can be used as a raw material for various purposes. To obtain powder, these agglomerates 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. In contrast, according to the method of the present invention, the apatite produced is obtained as a fine powder from the beginning,
It is usually a powder in which submicron particles are densely or coarsely fixed and sintered, resulting in a spherical shape of submicron to several tens of microns as a whole. The particle size of the spherical powder 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, not only is there no risk of time consumption due to the grinding process and contamination of impurities, but also excellent filling properties due to the spherical powder, and furthermore, easy control of the molar ratio of calcium and phosphorus. Taking advantage of this, it is possible to produce apatite whose molar ratio deviates from the theoretical composition ratio, and therefore, apatite suitable for use as a highly surface-active adsorbent, catalyst, or packing material for chromatography can be obtained. . In addition, when used as a raw material for ceramics, the apatite molded body is sintered at high temperature.
The apatite raw material powder used for this must have excellent thermal stability, and for that purpose, apatite whose molar ratio of calcium to phosphorus is the theoretical composition ratio is desirable. From this point of view, it can be said that apatite produced by the dry synthesis method, which makes it easy to synthesize apatite with a theoretical composition, is also suitable as a raw material for ceramics. Since the reaction is carried out at high temperature, due to its thermal history,
When the powder is crushed and used as a raw material for ceramics, the sintering activity of the powder becomes small. Therefore, in order to obtain a dense sintered body, it is necessary to sinter at a higher temperature.
Higher temperatures have the disadvantage that the rate at which apatite decomposes increases. On the other hand, the apatite powder obtained by the method of the present invention has high reaction activity because it is not subjected to a long thermal history at high temperatures as is the case with the dry synthesis method, and it is easy to synthesize apatite with a theoretical composition. Therefore, it has excellent sinterability,
It is possible to provide raw material powder for ceramics with high thermal stability. Therefore, the method of the present invention is suitable for use as a raw material for bioceramics such as artificial bones. Furthermore, regarding the raw materials for producing apatite having such characteristics, the calcium compound and phosphorus compound used in the method of the present invention are both commercially available and inexpensive inorganic compounds.
As mentioned above, it is of great industrial significance that high-grade apatite can be stably produced using such raw materials in a very short time and by a simple method. 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 as a solvent. , a soluble calcium inorganic compound and a phosphorus inorganic compound, and if necessary, an acid is added and mixed, and the whole is dissolved to prepare an acidic raw material solution. The order of mixing the raw materials for preparing the solution at this time is not necessarily limited to the above-mentioned order, and it is sufficient that the raw materials are mixed together in an order that does not cause precipitation. The time for mixing varies depending on the raw materials selected, but sufficient stirring is performed until all the raw materials are dissolved and a solution of uniform composition is obtained. Next, the solution prepared in this way is sprayed into a flame such as a gas burner by a known spraying method using a pressurized nozzle or a rotating disk, or is sprayed into a flame such as a gas furnace, electric furnace, high temperature gas, etc. The raw material solution is sprayed into a heating zone that has been preheated to a desired temperature in the temperature range where thermal decomposition occurs. Thus, in an extremely short period of time of several seconds or less, the solvent in the solution, which has become fine droplets of usually several tens of microns or less, evaporates and burns, and the solute undergoes solidification and thermal decomposition reactions. As a solvent,
a flammable organic solvent that is compatible with water;
When a mixed solvent of water and a flammable organic solvent that is compatible with water is used as the solvent, the combustion heat generated by combustion of the flammable organic solvent itself can also be used as a heat source necessary for the thermal decomposition reaction. In addition, when used to promote evaporation of a mixed solvent of water and an organic solvent that is compatible with water without burning the organic solvent, or when using water alone as a solvent, Requires a source of heat, such as a gas furnace as described above. Alternatively, the heat of combustion of an organic solvent,
Both heating sources such as a gas furnace can also be used together. The powder generated by the thermal decomposition reaction is collected using a cyclone method or the like. The powder produced by the spray pyrolysis reaction may be an amorphous phase or contain both an apatite crystalline phase and an amorphous phase, depending on the type and combination of raw material compounds and spray pyrolysis conditions. There are various cases in which apatite is mixed with unreacted components and by-products, but all of them are powders with high reactivity, and depending on the use and purpose, powders with high reactivity may be used. In some cases, it may be preferable to use powder. Furthermore, depending on other uses and purposes, it may be desirable to reduce the reaction activity, increase the degree of crystallinity, or reduce or eliminate unreacted components and by-products. The powder produced by the spray pyrolysis reaction is further heated in various atmospheres such as air, air with water vapor added, and an inert atmosphere at a desired temperature within the temperature range in which apatite can stably exist without decomposing. By heat treatment,
Apatite can be obtained with various powder properties such as crystallinity controlled. For example, for hydroxyapatite, the above-mentioned objective can be achieved by heat-treating it at a desired temperature of 1400° C. or less in an air atmosphere. Regarding chlorapatite, by appropriately selecting the raw material solution preparation conditions and spray pyrolysis conditions, when the resulting spray pyrolysis product is heated, calcium chloride phosphate (Ca ₂ It is also possible to obtain a product that changes to chlorapatite (PO ₄ Cl) and then changes back to chlorapatite at high temperatures below 1000°C. Therefore, in this case as well, chlorapatite can be obtained by appropriate heat treatment. The calcium inorganic compound and phosphorus inorganic compound used in the method of the present invention include Ca
(NO ₃ ) ₂・4H ₂ O, CaCl ₂・2H ₂ O, CaBr ₂・2H ₂ O,
_{CaHPO4 ・ 2H2O , NH4H2PO4 , NH4H2PO3 ,}
Examples of the organic solvent include NH ₄ H ₂ PO ₂ , H ₃ PO ₄ , H ₃ PO ₃ , H ₃ PO ₂ and the like, and examples of the organic solvent include methanol,
It is preferable to use alcohols such as ethanol, isopropanol, and acetone, but the use is not limited to these, and any combination of raw materials that can be mixed to produce a uniform solution that does not cause precipitation can be used. Either is fine. For this purpose, nitric acid and hydrochloric acid are suitable as acids to be added as necessary. For example, when synthesizing hydroxyapatite, nitric acid is suitable as the acid to be used, and when synthesizing apatite containing chlorine, hydrochloric acid can also be used in addition to nitric acid. Further, as the solvent used in the method of the present invention, depending on the pyrolysis method, the combination of raw materials, the powder characteristics of the target apatite, etc., water may be used alone as a solvent, or water may be used as the solvent as described above. A compatible organic solvent alone can be used as the solvent, or a mixed solvent of a water-compatible organic solvent and water can be used as the solvent. 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 as a crystal may be mixed with water and organic solvents due to residual moisture or crystal water in the raw material compounds. In some cases, the system uses a mixed solvent with a solvent, but in any of these cases, as long as a raw material solution that does not cause precipitation can be prepared, it can be used as a solvent in the method of the present invention. I can do it. To explain the apatite used in the method of the present invention, the molar ratio of calcium and phosphorus in calcium-phosphorus apatite with a stoichiometric composition is usually Ca/P.
However, in the actual reaction in the method of the present invention, if a solution with a composition in which the molar ratio Ca/P of calcium and phosphorus in the raw material solution is in the range of 1.60 to 1.85, in any case, the main component However, an apatite product is obtained. Also, Ca/P is less than 1.60 or
It has been experimentally confirmed that even when the ratio is 1.85 or more, a product whose main component is apatite can be obtained depending on the combination of raw materials. In this way, if the Ca/P ratio deviates from 5/3, unreacted components and byproducts may be mixed in depending on the conditions, but depending on the use and purpose, the product may have sufficient performance to be used. Therefore, such products are naturally included in the range of calcium-phosphorus apatite used in the method of the present invention. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 A solution of 3.11 g of NH ₄ H ₂ PO ₂ dissolved in 35 ml of water was added to a solution of 14.76 g of Ca(NO ₃ ) _{2.4H 2} O dissolved in 50 ml of water, and mixed, and then 100 ml of ethanol was added. The mixture was stirred and mixed to prepare a raw material solution. This raw material solution was then supplied to a two-fluid spray nozzle at a rate of 20 ml/min and compressed air at a rate of 10/min to atomize into the flame of a gas burner. The raw material solution, which had become fine droplets, was instantaneously heated by evaporation and combustion of the solvent in the flame, causing a thermal decomposition reaction. The generated powder was collected using a cyclone method and observed under an electron microscope, and as a result, it was found to be a spherical powder consisting of densely sintered particles of 0.1 to 0.5 microns. The results of X-ray diffraction measurements of this produced powder are shown in FIG. As is clear from FIG. 1, the powder produced by this method was hydroxyapatite with well-grown crystals. The three main peaks are the (211) diffraction peak at a diffraction angle of 2θ = 31.7°, the (112) diffraction peak at 2θ = 32.2°, and the (300) diffraction peak at 2θ = 32.9°. Measured. Example 2 Dissolve 9.52 g of Ca(NO ₃ ) ₂・4H ₂ O in 40 ml of water,
Furthermore, to the solution prepared by adding 5 ml of nitric acid, a solution of 8.59 g of phosphoric acid (H ₃ PO ₄ content 85.6%) dissolved in 20 ml of water was added and mixed, and then 120 ml of ethanol was added to the solution.
ml and stirred to prepare a raw material solution. Next, this raw material solution was sprayed into a flame to perform thermal decomposition in the same manner as in Example 1. As a result of X-ray diffraction measurement of the powder obtained by this method,
The powder contained a crystalline phase of hydroxyapatite and a slight amorphous phase. Example 3 The powder obtained by the method of Example 2 was heated at a rate of 5°C/min in an air atmosphere, and then heated to 1300°C for 1 hour.
Heat treatment was performed for a time, and cooling was performed at a rate of 5° C./min. As a result of X-ray diffraction measurement of the product obtained by this heat treatment, it was found that the hydroxyapatite had grown more crystalline than the hydroxyapatite obtained in Example 2, and no decomposition was observed at high temperatures. Nakatsuta. Therefore, it was confirmed that hydroxyapatite with high thermal stability and well-grown crystals can be obtained by heat treatment. Example 4 To a solution prepared by dissolving 18.38 g of CaCl ₂ 2H ₂ O in 35 ml of water and adding 5 ml of hydrochloric acid,
Dissolve 8.63g of NH ₄ H ₂ PO ₄ in 20ml of water and add 5ml of hydrochloric acid.
The solution prepared by adding was added and mixed, and 120 ml of ethanol was further added thereto and mixed with stirring to prepare a raw material solution. Next, this raw material solution was prepared in Example 1.
Thermal decomposition was carried out by spraying into a flame in the same manner as described above. The results of X-ray diffraction measurements of the powder obtained by this method are shown in FIG. As is clear from Figure 2, this powder shows a diffraction pattern due to chlorapatite, and the main peak is at the diffraction angle 2θ=
A diffraction peak of (211) at 31.4° and overlapping diffraction peaks of (112) and (300) at 2θ = 32.2° were measured. Example 5 Dissolve 14.76 g of Ca(NO ₃ ) ₂・4H ₂ O in 50 ml of water,
Add 5 ml of nitric acid to the solution, add 4.31 g of NH ₄ H ₂ PO ₄
A solution prepared by dissolving the above in 35 ml of water was added and mixed to prepare a raw material solution. Next, the above raw material solution was sprayed into the reaction tube at a rate of 2 ml/min from one end of the reaction tube (30φ x 1000 mm) in an electric furnace that had been preheated to 1200°C. The raw material solution, which became 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 the thermal decomposition were sucked in by an aspirator and exhausted to the outside of the system. As a result of X-ray diffraction measurement, the powder obtained by this method contained a mixture of crystalline and amorphous phases of hydroxyapatite, and a slight peak of calcium carbonate was also observed. Example 6 Dissolve 3.08g of phosphorous acid in 190ml of methanol,
Further, 6.94 g of CaCl ₂ was dissolved in this solution to prepare a raw material solution. Next, this raw material solution was sprayed into a flame in the same manner as in Example 1 to carry out a thermal decomposition reaction. The generated powder was heated at 5℃/in an air atmosphere.
The temperature was raised at a rate of 5°C/min, heat treatment was performed at 1300°C for 1 hour, and the mixture was cooled at a rate of 5°C/min. The obtained product was confirmed to be solid solution apatite of hydroxyapatite and chlorapatite based on the detection of chlorine using a silver nitrate solution and the results of X-ray diffraction measurements. Examples 7 to 17 Examples 7 to 17 were conducted according to the operations of Examples 1 and 5 using the raw materials and their blending ratios shown in Table 1, and various calcium-phosphorus apatites were obtained. Ta. The thermal decomposition temperature, heat treatment conditions, and main components of the product are as shown in Table 1.

【table】

[Table]

[Brief explanation of drawings]

FIG. 1 is a diagram showing an X-ray diffraction pattern of hydroxyapatite obtained by the method of Example 1 of the method of the present invention, and FIG. 2 is a diagram showing the X-ray diffraction pattern of hydroxyapatite obtained by the method of Example 4 of the method of the present invention. FIG. 3 is a diagram showing an X-ray diffraction diagram of chlorapatite.

Claims (1)

[Claims] 1. 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 as a solvent; A soluble calcium inorganic compound or calcium acetate and phosphorus inorganic compound are added and mixed, dissolved to prepare an acidic raw material solution, and the raw material solution is sprayed into a flame or heating zone to undergo thermal decomposition. A method for producing calcium-phosphorus apatite, which is characterized by producing calcium-phosphorus apatite through a reaction. 2. 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 as a solvent, and an inorganic compound of calcium or Calcium acetate and phosphorus inorganic compounds are added and mixed, dissolved to prepare an acidic raw material solution, and the raw material solution is sprayed into a flame or heating zone to generate calcium-phosphorus apatite through a pyrolysis reaction. A method for producing calcium-phosphorus apatite, which comprises further heat-treating the calcium-phosphorus apatite powder.