JPH03279204A - Production of apatite - Google Patents

Abstract

PURPOSE:To obtain a high-density sintered apatite compact according to ordinary sintering by dropping a phosphoric acid compound into an aqueous solution or suspension of a calcium compound so as to satisfy a specific Ca/P ratio. CONSTITUTION:An aqueous solution of a phosphoric acid compound is dropped into an aqueous solution or suspension of a calcium compound and reacted therewith to produce apatite. In the process, the aqueous solution of the calcium compound is dropped so as to provide a Ca/P ratio within the range of >1.67 and <=1.76. For example, phosphoric acid, potassium dihydrogenphosphate and ammonium hydrogenphosphate are cited as the phosphoric acid compound and, e.g. calcium hydroxide, calcium chloride and calcium nitrate are cited as the calcium compound.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to an apatite manufacturing method capable of producing a high-density apatite sintered body.

"Prior art and its problems" Since apatite has excellent biocompatibility, its application as a variety of biomaterials is being considered.

In order to achieve high strength suitable for use as a biomaterial, apatite sintered bodies must be densified.
Apatite with a Ca/P ratio lower than the stoichiometric ratio (lack of calcium) has poor sinterability and is not sufficiently densified.
It has been said that hydroxyapatite with a stoichiometric composition is the best because it does not increase density. However, even raw material powder determined to be pure hydroxyapatite by X-ray diffraction has a low density when normally sintered, and the density often does not improve even if the sintering temperature or holding time is increased.

"Objective of the Invention" An object of the present invention is to provide a method for producing apatite that can produce a high-density apatite sintered body through normal sintering.

"Structure of the Invention" The method for producing apatite according to the present invention is a method for producing apatite by adding dropwise an aqueous solution of a phosphoric acid compound to an aqueous solution or suspension of a calcium compound and causing a reaction. It is characterized in that the addition is carried out so that the Ca/P ratio exceeds 1.67 and falls within the range of 1.76 or less.

Since CaO does not sinter at the normal sintering temperature of apatite, it was previously thought that apatite with excess calcium has poor sintering properties, but according to the research of the present inventors, CaO
It has been found that apatite containing excess calcium with an a/P ratio of more than 1.67 and less than 1.76 has excellent sinterability and produces a high-density sintered body by normal sintering. Ta.

The phosphoric acid compound and calcium compound used as starting materials may be those commonly used in the wet synthesis of apatite, and examples of the phosphoric acid compound include phosphoric acid, potassium dihydrogen phosphate, ammonium hydrogen phosphate, etc. Examples of calcium compounds include calcium hydroxide, calcium chloride, and calcium nitrate.

Generally, when producing apatite by a wet method, an aqueous solution of a phosphoric acid compound is added dropwise to an aqueous solution or suspension of a calcium compound to advance the reaction, and the Ca/P ratio of the product is adjusted to 1.67. When this happens, a method is adopted in which the addition is terminated, assuming that pure apatite has been produced. In the method of the present invention, the end point of the dropwise addition is when the CaZP ratio exceeds 1.67 and falls within the range of 1.76 or less. In this way, Ca-excess apatite is produced by the method of the present invention, but
Ca-excess apatite in this range produces an apatite sintered body with a higher density than apatite outside this range under normal firing conditions.

Furthermore, in the present invention, the apatite may be hydroxyapatite, fluoroapatite, chlorapatite, or the like.

"Examples of the Invention" Next, the present invention will be described in more detail based on Examples, but the present invention is not limited thereto.

Example 1 A phosphoric acid aqueous solution was dropped into a calcium hydroxide slurry, and C
Three types of apatite slurries with a/P ratios adjusted to 1.70, 1.67 and 1.60 were prepared, each of which was dried separately, molded and processed, and then fired into round bars (diameter 5
mm, length 25 mm) for samples A, B and C, respectively.
And so. The relationship between the relative density and Ca/P ratio of this sample was measured, and the results are shown in Table 1 below.

Table 1 From this result, the Ca/P ratio is thicker than 1.67.
In other words, in a Ca-excess state, a remarkable increase in density is observed,
On the contrary, it can be seen that the density decreases when the Ca/P ratio is smaller than 1.67. From this, it is thought that by controlling the Ca/P ratio, a higher density sintered body can be obtained.

Note that the appearance of the sintered body clearly changes when the relative density reaches 99.2%. Translucency increases when the relative density is 99.3% or more.

"Effects of the Invention" According to the present invention, apatite that produces a high-density apatite sintered body can be easily and consistently produced by a scientific method.

Claims (1)

[Claims] 1. In a method of producing apatite by adding dropwise an aqueous solution of a phosphoric acid compound to an aqueous solution or suspension of a calcium compound and causing a reaction, the dropwise addition of the phosphoric acid compound aqueous solution is
A method for producing apatite, characterized in that the process is carried out so that the P ratio is in the range of more than 1.67 and less than 1.76.