JPS624324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydroxyapatite with high crystallinity, constant quality, and high chemical activity.

Hydroxyapatite has the theoretical formula Ca ₁₀ (PO ₄ ) ₆
It is a basic calcium phosphate represented by (OH) ₂ , and is a major inorganic component in living organisms that make up bones, teeth, etc. Since hydroxyapatite has excellent affinity with organic compounds, it is attracting attention as a new inorganic material. Various methods are known for synthesizing hydroxyapatite, such as a dry method using a solid phase reaction and a wet method using a precipitation reaction.
In order to produce hydroxyapatite with high chemical activity, it is said that a wet method in which a calcium salt aqueous solution and a phosphate aqueous solution or calcium hydroxide and phosphoric acid are mixed and reacted and then aged is advantageous. However, the known wet method and the hydroxyapatite obtained by the method have the following drawbacks. (i) Requires a long aging process at high temperatures;
(ii) The stoichiometric Ca/P molar ratio of hydroxyapatite is 1.67. However, in the wet method, amorphous calcium phosphate (Ca/
In the process in which calcium ion-deficient hydroxyapatite, calcium octaphosphate, etc. (hereinafter referred to as precursors) are finally transformed into hydroxyapatite crystals through aging, the crystallization rate, Changes in Ca/P molar ratio, temperature,
Because it is easily influenced by pH, aging time, and many other factors, the Ca/P molar ratio of hydroxyapatite crystals varies within the range of 1.48 to 1.67, and the properties of the powder are difficult to be homogeneous. (iii) The hydroxyapatite precipitate obtained by the wet method generally has a low crystallinity and tends to form a gel-like substance, making the precipitation operation complicated, which is also a factor in changing the Ca/P molar ratio.

The present inventor has conducted various experiments and research in view of the problems of the known wet production method of hydroxyapatite, and as a result, the present inventor has found that this method can be achieved by combining a grinding treatment with the reaction process of the raw calcium source and the phosphorus source. It has been found that these problems can be greatly reduced or virtually eliminated. That is, the present invention involves reacting an aqueous solution or suspension containing at least one of calcium hydroxide and a calcium salt with an aqueous solution or suspension containing at least one of phosphoric acid and a phosphate while grinding; The present invention relates to a method for producing hydroxyapatite, which is characterized by carrying out a grinding reaction after mixing.

According to the method of the present invention, the crystallinity is high and Ca/P
Hydroxyapatite, which has a molar ratio very close to 1.67 and has high chemical activity, can be easily produced within a short time without requiring long-term aging at high temperatures. Moreover, the product can be made into highly pure hydroxyapatite by a simple water washing operation.

In the present invention, the calcium source is
Ca(OH) ₂ or CaCl ₂ , Ca(NO ₃ ) ₂ ,
(CH ₃ COO) ₂ Ca, (CaO) ₄・P ₂ O ₅ , Ca ₂ (HPO ₄ )
One or more calcium salts such as (OH) ₂ are used as an aqueous solution or suspension, and the phosphorus source is H ₃ PO ₄ or NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , Ca
One or more phosphates such as (H ₂ PO ₄ ) ₂ and CaHPO ₄ are used as an aqueous solution or suspension. Ca
The concentration of (OH) ₂ and/or calcium salt in the liquid is usually about 4 to 15% by weight as Ca(OH) ₂ (hereinafter % indicates weight %), H ₃ PO ₄ and/or phosphoric acid. The concentration of salt in the liquid is usually about 2 to 8% as H ₃ PO ₄ , the Ca/P molar ratio at the time of reaction is about 1.60 to 1.70, and the solid content concentration at the time of grinding is about 5 to 20%. Both liquids are mixed while being triturated, or mixed and then triturated to react. If the concentration of the raw material is too low, it will be economically disadvantageous, while if the concentration is too high, the grinding time will be longer to transfer the generated precursor to hydroxyapatite, so it will be economically disadvantageous. disadvantageous to The temperature during the reaction is not particularly limited, but is preferably 100°C or less, and generally room temperature is sufficient. The pH of the reaction system may be 7 or higher.

In the present invention, it is essential to react the calcium source raw material and the phosphorus source raw material while grinding the generated precursor. As a grinding means,
Examples include agitated mills using a grinding medium such as vibrating mills, sand mills, and grain mills. Simply stirring the liquid, for example with a rotary blade, without using a grinding medium cannot sufficiently promote the transition of the precursor to hydroxyapatite;
Furthermore, the properties of the obtained hydroxyapatite cannot be said to be satisfactory. The grinding employed in the present invention is
Refers to an operation in which the object to be treated is mechanochemically crushed using a large number of media that move continuously in a container, and the media have a specific gravity of 2.0 to 8.0 g/cm ³ ,
Balls of about 0.5 to 50 mm and preferably weighing 2.2 to 6.0 g/cm ³ are usually used. As the media, media made of ceramic such as alumina balls and glass beads are preferred.

The hydroxyapatite obtained by the method of the present invention is
Because it has high crystallinity, high purity, large specific surface area, and excellent chemical activity, it is useful as a manufacturing raw material for dental materials, artificial bones, etc., as an adsorbent, and as an additive for foods and other products.

Example 1 1 mm glass beads (specific gravity 2.5 g/cm ³ ) 7.5 kg
A sand mill with a volume of 14 and a concentration of 10
%, calcium hydroxide suspension (PH
13.1) 0.6 kg of phosphoric acid aqueous solution with a concentration of 40% was added dropwise over about 4 minutes while stirring at 600 rpm, and stirring and grinding were continued for an additional 10 minutes. The Ca/P molar ratio of the reaction system was 1.67.
The X-ray diffraction pattern of the resulting water suspension of hydroxyapatite, which was dehydrated using a filter press and then dried by heating, is as shown in Figure 1, with good peak separation and a narrow half-width. , indicating the high degree of crystallinity of the sample. Further, the specific surface area (by BET method) of the dried product was 150 m ² /g, and the Ca/P molar ratio was 1.66.

Comparative Example 1 (a) A reaction product was obtained in the same manner as in Example 1, except that glass beads were not used as the grinding medium. The X-ray diffraction pattern of the reaction product obtained by dehydrating it with a filter press and drying it by heating is as shown in Figure 2. The peak separation is poor, the half width is narrow, and the peaks of components other than hydroxyapatite are present. (a) and (b) are accepted.

(b) The X-ray diffraction pattern of the reaction product obtained in the same manner as in (a) above was left in the reaction solution at room temperature for 24 hours, dehydrated with a filter press, and dried by heating. Similarly, impurity peaks were shown, indicating that highly pure hydroxyapatite could not be obtained with this degree of ripening.

Example 2 Hydroxyapatite crystals were obtained in the same manner as in Example 1, except that 0.6 kg of a 40% phosphoric acid aqueous solution was dropped over about 20 minutes.

The X-ray diffraction pattern of the obtained crystal was similar to that shown in FIG. 1, and the Ca/P molar ratio was 1.67.

Example 3 2.58 kg of dicalcium phosphate (CaHPO ₄ 2H ₂ O) suspension with a concentration of 10% was placed in a sand mill with a capacity of 14 using 7.5 kg of 1 mm size glass beads as the grinding medium, and the rotation speed was 600 rpm. While rotating, 0.744 kg of a 10% calcium hydroxide suspension was dropped over about 1 minute. According to the X-ray diffraction results of the dry powder obtained by sampling the reaction solution over time from the start of dropping, dehydrating and drying it, the precursor was converted to hydroxyapatite 40 minutes after the start of dropping. The termination of the project was approved.

Comparative Example 2 The calcium hydroxide suspension was added dropwise to the dibasic calcium phosphate suspension in the same manner as in Example 3, except that no grinding material was used, and then stirred at room temperature for 6 hours.
It was left for another 24 hours. A peak of dibasic calcium phosphate was observed in the X-ray diffraction pattern of the dehydrated and dried reaction product.

Example 4 1.76Kg of calcium acetate aqueous solution with 10% concentration and concentration
After mixing with 0.79 kg of 10% diammonium phosphate aqueous solution and adjusting the pH to 8.5 with 40% ammonia water, it was placed in a sand mill with a capacity of 14 using 7.5 kg of glass beads with a diameter of 1 mm as the grinding medium, and the rotation speed was at 600rpm
The mixture was stirred and ground for 10 minutes. The resulting aqueous suspension was dehydrated and dried, and the Ca/P molar ratio was 1.61, and the X-ray diffraction pattern showed hydroxyapatite diffraction.

Comparative Example 3 A diammonium phosphate aqueous solution was added to a calcium acetate aqueous solution in the same manner as in Example 4, and the mixed solution was adjusted to pH 8.5 with aqueous ammonia. The mixture was placed in a sand mill with a capacity of 14 without using any grinding material, and the number of revolutions was increased.
Stirred at 600 rpm for 6 hours. The resulting aqueous suspension was dehydrated and dried, and the Ca/P molar ratio was 1.49.
The X-ray diffraction diagram showed peaks other than hydroxyapatite, indicating that the product had low crystallinity.

[Brief explanation of the drawing]

FIG. 1 shows an X-ray diffraction pattern of hydroxyapatite obtained by the method of the present invention shown in Example 1, and
The figure shows an X-ray diffraction pattern of hydroxyapatite obtained in Comparative Example 1.

Claims (1)

[Claims] 1 Reaction of an aqueous solution or suspension containing at least one of calcium hydroxide and a calcium salt with an aqueous solution or suspension containing at least one of phosphoric acid and a phosphate, or a grinding reaction after mixing. A method for producing hydroxyapatite, the method comprising: