JPH0461806B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing high-purity hydroxyapatite that can be used as a raw material for bioceramics or chromatograph packing materials. [Prior art and its problems] Dry methods and wet methods are known as methods for producing hydroxyapatite (hereinafter simply referred to as apatite), but the dry method not only requires a large amount of heat but also , contained in raw materials
Remaining because _CaCO3 and other impurities remain in the product and reduce the purity of apatite
Removal of CaCO ₃ and other impurities has become a difficult problem. In addition, in the wet method, carbonate substances present in the reaction solution react with Ca ions during the reaction process.
There were problems such as CaCO ₃ and other impurities mixed in the raw materials entering the product and reducing the purity of the apatite. [Object of the Invention] An object of the present invention is to provide a method for producing apatite having an extremely low content of impurities, particularly CaCO ₃ . [Structure of the Invention] The present invention provides a method for producing apatite by reacting phosphate ions in an aqueous solution containing phosphate ions with an aqueous solution of a calcium compound at a pH of 6 or higher. It is characterized by reacting phosphate ions and calcium ions in a calcium ion-containing aqueous solution obtained by passing a calcium chloride aqueous solution through a strongly basic ion exchange resin layer under conditions where the total carbonate concentration in the reaction solution is 20 mg/or less. This is a method for producing high-purity apatite. As a result of intensive research into the production method of high-purity apatite with low content of CaCO ₃ and other impurities, the present inventors determined that the total carbon dioxide concentration in the reaction solution was 20mg/
We have discovered that highly pure apatite can be produced by reacting phosphate ions in a solution containing phosphate ions with calcium compounds under the following conditions. The total carbon dioxide concentration in the reaction solution can be reliably achieved by using an aqueous solution of CaCl ₂ obtained by passing an aqueous solution of a Ca compound through a layer of a strongly basic ion exchange resin. In other words, when using an aqueous solution of Ca(OH) ₂ , CO ₂ in the atmosphere is absorbed, and if left as is, a large amount of CaCO ₃ is produced, increasing the amount of impurities. However, CaCl ₂ is a neutral salt, and when dissolved in water Even when dissolved in water, the aqueous solution does not absorb CO ₃ from the atmosphere and does not increase impurities such as CaCO ₃ . On the other hand, when an aqueous solution of CaCOl ₂ is treated with a strongly basic ion exchange resin, the following reaction occurs. CaCl ₂ +2R−OH → Ca(OH) ₂ +2R−Cl If this reaction is carried out in a closed container, there will be no absorption of CO ₂ , and the Ca ions and OH ions necessary for the production of apatite can be supplied at the same time, and they are free from impurities. Cl ions are fixed on the ion exchange resin and SiO ₂
These impurities can be removed using an ion exchange resin, and at the same time, the total carbonic acid concentration in the reaction solution can be easily reduced to 20 mg/or less. The total carbon dioxide concentration is the CO ₂ dissolved in the solution,
This is the value obtained by converting CO ₃ ^2- or HCO ₃ ^- etc. to CO ₂ . Next, embodiments of the present invention will be described based on the drawings.
In FIG. 1, after dissolving phosphate in pure or distilled water, the aqueous solution degassed with N ₂ gas is introduced into a sealed reaction vessel 2 through tube 1, while the CaCl ₂ aqueous solution is introduced into a strong base through tube 5. After passing through a ion exchange resin layer 6, the mixture is introduced into a closed container 2, and stirred with a stirrer 3 to react. By passing an aqueous solution of CaCl ₂ through a layer of strongly basic ion exchange resin,
CO ₃ ²⁻ , HCO ₃ ⁻ , SiO ₂ , etc. are removed, and alkali (OH ⁻ ) necessary for the reaction is also supplied. Furthermore, if necessary, an alkaline solution such as NaOH solution is supplied through tube 4 to adjust the reaction solution to a pH of 6 or higher.
Preferably the pH is adjusted to 8-9. The generated apatite is discharged from the bottom of the container through the tube 8 and dried to obtain a product. The reaction waste liquid is discharged from pipe 7. If the pH is 6 or less, apatite is not generated or CaHPO ₄ is easily generated, which is not preferable. When providing a space above the closed reaction vessel 2, it is preferable to inject nitrogen gas. Figure 2 shows an example using a flow reactor, in which the phosphate solution is fed in tube 1 and the phosphate solution is fed from tube 5 through a bed of strongly basic ion exchange resin.
The CaCl ₂ aqueous solution is mixed and fed into the reactor 2', and the reaction proceeds sufficiently at the bottom of the reactor 2'.
There is no need to use a stirrer. Further, since the generated apatite forms a classification layer, a product with uniform particle size can be obtained by discharging the generated apatite from the product discharge pipe 8 at a predetermined height. The phosphate aqueous solution and the CaCl ₂ aqueous solution may be introduced separately into the bottom of the reaction vessel 2. In the present invention, the phosphate ion source is
H ₃ PO ₄ , Na ₃ PO ₄ , K ₂ HPO ₄ , NH ₄ H ₂ PO ₄ etc. can be used, and NH ₄ H ₂ PO ₄ can be used to increase the buffering properties of the solution.
It is preferable to use The addition rate of Ca ²⁺ and phosphate ions is preferably such that Ca/P (molar ratio) in the reaction solution is 1.5 to 1.7.
Preferably it is 1.67. Although pure water or distilled water can be used as water for the reaction, it is preferable to use ultrapure water when producing high-grade apatite free of germs and fine particles. After dissolving the phosphate ion source in these waters, it is preferable to reduce the carbon dioxide concentration in the water by degassing with N ₂ gas or the like. As an alkali source, an aqueous solution of HaOH or KOH can be used. As an ion exchange resin, commercially available gel type
Strongly basic ion exchange resins such as Dowex SBR, Dowex SAR, and macroporous type MSA-1-2 can be used. Furthermore, since the apatite used in the present invention is intended as a ceramic raw material, it is often required to be fine, but if coarse crystals or granules are required, the apatite produced in the present invention may be Seed crystals of pure apatite may be circulated and used at high temperatures to grow crystals. Example 1 Add ammonium phosphate to pure water as phosphorus to 1000
After dissolving the water in an amount of 1 m 2 /day and degassing with N ₂ gas to reduce the carbon dioxide concentration in the water to 5 mg/day or less, the water was supplied to the sealed reaction vessel No. 4 at a rate of 1 m ² /day. On the other hand, strongly basic ion exchange resin (Dowex
SBR, 20-45 mesh) into a tower filled with 40
%CaCl ₂ solution (solvent/pure water) at 100c.c./water, SV=
It was allowed to flow through at a rate of 1.0/hour, and the effluent was also fed to the closed reaction vessel. Then, a 1% NaOH aqueous solution was injected so that the pH of the reaction solution in the sealed reaction container was 8.5, and the reaction was carried out by stirring at 15 rpm with a blade of 80 mmφ x 40 mm to produce apatite. The total carbon dioxide concentration in the reaction solution at this time was 5 mg/or less. Example 2 Apatite was produced in the same manner as in Example 1 except that an open reaction vessel was used instead of a closed reaction vessel. The total carbon dioxide concentration in the reaction solution at this time was 18
mg/. Comparative Example 1 Example 1 except that tap water was used instead of pure water
Apatite was produced in the same manner. The total carbon dioxide concentration in the reaction solution at this time was 30 mg/. Comparative Example 2 Apatite was produced in the same manner as in Example 1, except that the CaCl ₂ solution was used as it was without passing it through the strongly basic ion exchange resin tower, tap water was used instead of pure water, and an open reaction vessel was used. was manufactured. The total carbon dioxide concentration in the reaction solution at this time was 40 mg/. The reaction products produced in Examples 1 and 2 and Comparative Examples 1 and 2 were extracted and heated at 100°C in the presence of _N2 gas.
After drying for 2 hours, its composition was analyzed. The analysis results are shown in Table-1.

[Table] Example 4 Table 2 shows the composition of the product obtained by changing the carbonic acid concentration by adding sodium bicarbonate into the reaction vessel in Example 1.

〔Effect of the invention〕

According to the present invention, high-purity apatite with low content of CaCO ₃ and other impurities can be produced, making it possible to provide materials suitable for various biological materials and chromatograph fillers.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams of a reaction apparatus for carrying out the reaction of the present invention, respectively, in which Figure 1 is a schematic diagram of an apparatus using a closed reaction vessel, and Figure 2 is a schematic diagram of an apparatus using a fluidized reaction vessel. A schematic diagram of the device is shown. 1... Phosphate solution supply pipe, 2... Sealed reaction vessel, 2'... Fluid reaction vessel, 3... Stirrer, 4...
... Alkaline solution supply pipe, 5 ... Calcium solution supply pipe, 6 ... Strong basic ion exchange resin layer, 8 ...
Apatite drainage tube.

Claims (1)

[Scope of Claims] 1. A method for producing hydroxyapatite by reacting phosphate ions in an aqueous solution containing phosphate ions with a calcium compound at pH 6 or higher, wherein the phosphate ions in an aqueous solution containing phosphate ions are reacted with a calcium compound at pH 6 or higher. and calcium ions in a calcium ion-containing aqueous solution obtained by passing a calcium chloride aqueous solution through a strongly basic ion exchange resin layer under conditions where the total carbonate concentration in the reaction solution is 20 mg/or less. Method for producing pure hydroxyapatite. 2. The method for producing high-purity hydroxyapatite according to claim 1 or 2, wherein the reaction is carried out in a closed container. 3. The method for producing high-purity hydroxyapatite according to claim 1, 2 or 3, wherein the reaction is carried out under conditions where the total carbonate concentration in the reaction solution is 10 mg/or less.