JP2584265B2 - Production method of octacalcium phosphate - Google Patents

Description

The present invention relates to a novel method for producing octacalcium phosphate (hereinafter referred to as "OCP").

<Prior Art> A conventionally known method for producing OCP is as follows.

Extremely diluted H ₃ PO ₄ -NaOH solution (phosphoric acid concentration 5 mmol, pH = 7.
5) The method poles lean obtained by 24 hours aging at about 40 ° C. by adding CaCl ₂ to a _{CaO-P 2 O 5 -H 2} O system solution (Ca concentration 0.4～4M mo
1, a method of recovering the product obtained by dropping an alkali at a P concentration of 0.8 to 10 mmol).

0.04 M-Ca (NO ₃ ) ₂ and 0.03 M-Na ₂ HPO ₄ are adjusted to pH 6.5 to 6.6
In 0.2M-CH3 COONa at the same time, and aging at 50-60 ° C for several hours.

Methods that may be hydrolyzed under conditions of pH <6.1 the CaHPO ₄ · 2H ₂ O in 0.5M-CH ₃ COONa in.

A method obtained by hydrolyzing Ca ₃ (PO ₄ ) ₂ at around pH 6.

<Problems to be Solved by the Invention> However, the above-mentioned method involves a large amount of water treatment,
There is a problem from the viewpoint of mass production, and the method is a problem of wastewater treatment and a problem of raw material cost.
There is a problem in that it is difficult to convert to a single phase, and there is a problem in that all of the above methods cannot produce a large amount of OCP at once, and there are drawbacks as an industrial production method. There was no established industrial manufacturing method.

Thus, the present inventors have found that a large amount of OCP can be produced at a time by using a dibasic calcium phosphate slurry having a specific electric conductivity as a raw material, and obtained the present invention.

<Means for Solving the Problems> That is, the present invention has an electric conductivity of 300 μs / cm at 25 ° C.
A method for producing octacalcium phosphate, characterized by mixing and reacting the following second calcium phosphate slurry and slaked lime slurry at pH 4 to 7.

It is important that the dibasic calcium phosphate slurry used in the present invention has an electric conductivity at room temperature of 300 μs / cm or less. However, the lower limit may be 100 μs / cm in consideration of the solubility of dicalcium phosphate.

If it exceeds 300 μs / cm, OCP is likely to be formed even if the pH control described later is taken into consideration, and a mixture with hydroxyapatite dibasic calcium phosphate is likely to be formed.

Therefore, as long as the slurry is used, its production history is not particularly problematic. That is, after adjusting the dibasic calcium phosphate by a known method, in order to obtain a predetermined electrical conductivity,
After sufficient washing, it is used as a raw material in the next step.

The concentration of the second calcium phosphate slurry is not particularly limited, but is preferably 5 to 40% by weight for handling.

Similarly, the concentration of slaked lime slurry is also 3 to 35% by weight.
Is preferred.

In the method according to the present invention, the following reaction and a slurry of a second calcium phosphate slurry and the slaked lime having the above electric _{conductivity; 6CaHPO 4 · 2H 2 O +} 2Ca (OH) → CaH 2 (PO 4) 6 · 5H 2 O In accordance with the following.

For this reason, it is important to control the pH of the reaction system in the range of 4 to 7.

In other words, the OCP formation region is narrow and unstable, and if the pH control is not taken into account, the formation of a single crystalline phase
OCP is not available. In particular, exceeding pH 7 must be avoided. If the pH exceeds 7, hydroxyapatite tends to be formed, and if the pH is less than 4, the reaction to OCP does not proceed because the dibasic calcium phosphate is stable.

Therefore, in many cases, in the present invention, the pH of the reaction system is
The range of 4.8 to 5.8 is particularly suitable for substantially proceeding the above reaction.

As a reaction method, a method in which slaked lime slurry is added to the second calcium phosphate slurry to cause a reaction is preferable, but simultaneous addition may be used.

 The reaction temperature is preferably 20 to 100 ° C.

The reason for this is that if the temperature is lower than 20 ° C., the product is in a gel state and is difficult to handle.

The reaction time depends on the amount of addition, the time of addition and the like, but is generally preferably about 0.5 to 4 hours.

Next, after completion of the reaction, the product is aged for a while, then separated by a conventional method, washed with water, etc., and then filtered and dried to obtain OC.
Get P.

 Confirmation of OCP can be performed by an X-ray diffraction diagram.

<Example> Example 1 180 g of 85% phosphoric acid is diluted with water to 1020 g. CaCO ₃ 1
A slurry obtained by repulping 62 g with water to 1620 g is added dropwise to the phosphoric acid at 40 ° C. over about 1 hour. Stop dripping at pH 3.5 and ripen for about 15 minutes. At this time, the remaining amount of the CaCO ₃ slurry was 137 g.

The dibasic calcium phosphate obtained by filtering and washing the product is
It was 270 g. Using this dicalcium phosphate as a raw material,
When a slurry of 10% by weight was prepared by repulping to 2.2, the electric conductivity of the slurry was 124 μs / cm.

Next, the temperature of the slurry was raised to 65 ° C., and Ca (OH) was added thereto.
₂ Re-pulp 38.56g to 385.6g slaked lime slurry (1
0% by weight) at 3.6 ml / min. At this time, the pH was controlled so as not to exceed 5.5.

After dripping for about 15 minutes after dropping the whole amount, it was dried at 60 ° C. for 8 hours. The X-ray diffraction pattern of the product shows a single phase of OCP, Ca / P =
It was 1.33.

Example 2 A dibasic calcium phosphate slurry (slurry concentration: 10% by weight) having an electrical conductivity of 145 μs / cm and a slaked lime slurry (slurry concentration: 10% by weight) separately prepared were simultaneously poured into water having a pH of 5.0. And individually and gradually added. The pH at this time is always between 4.8 and 5.3 and the temperature is 65 ° C
Was controlled to be constant.

Thereafter, the hand product was recovered by the same operation as in Example 1 and confirmed to be OCP single phase, with Ca / P = 1.33.

<Effect of the Invention> According to the method of the present invention, a large amount of OCP can be produced at a time in a simple process, which is advantageous as an industrial production method.

Further, the OCP produced according to the present invention is useful as a starting material for the synthesis of hydroxyapatite, and in particular, can be used as a starting material for the synthesis of hydroxyapatite containing various cations or anions, which has been conventionally difficult. There are advantages that can be done.

Claims (1)

(57) [Claims] 1. A process for producing octacalcium phosphate, comprising mixing and reacting a slurry of dicalcium phosphate having an electric conductivity of not more than 300 μs / cm at 25 ° C. with a slurry of slaked lime at a pH of 4 to 7.