JP3012275B2 - Manufacturing method of high density apatite ceramics - Google Patents

Description

The present invention relates to a method for producing high-density apatite ceramics.

“Prior art and its problems” Since apatite ceramics have excellent biocompatibility, their application as various biomaterials is being studied. To achieve high strength suitable for use as a biomaterial, apatite ceramics must be densified, but if the Ca / P ratio is smaller than the stoichiometric ratio (insufficient calcium), the densification will be sufficient. It is known that the density is not increased. Further, even in the case of raw material powder determined to be pure hydroxyapatite by X-ray diffraction, the density is low in ordinary sintering, and the density is often not improved even if the sintering temperature is increased or the holding time is increased.

JP-A-53-81499 discloses that crystalline apatite having Ca / P = 1.67 or less is prepared in advance, an insufficient amount of Ca is mixed with an inorganic calcium compound, and reacted by a hydrothermal reaction or a solid-phase reaction. A method for producing apatite has been proposed. However, in this method, the insufficient Ca is mixed with the powder of the inorganic calcium compound, so that it is difficult to uniformly add the insufficient Ca. In addition, high-density ceramics cannot be obtained because particles are agglomerated in the process of mixing the powder and coarse particles are formed.

Further, a method capable of adjusting the Ca / P ratio of the apatite ceramic in a state of a molded body has not been conventionally known.

"Object of the Invention" It is an object of the present invention to provide a method for producing a high-density ceramic by adjusting the Ca / P ratio of apatite ceramic in the state of a powder or a compact.

`` Constitution of the invention''The method for producing high-density apatite ceramics according to the present invention comprises impregnating a powder of apatite with an aqueous solution of a water-soluble calcium salt of an organic acid, drying, molding, calcining or dry molding of apatite, It is characterized by impregnating an aqueous solution of a water-soluble calcium salt of an organic acid into a dry molded product or a pre-baked product, drying and then firing.

The method of the present invention can be applied to apatite powder or molded product. The molded body may be a green compact formed by dry molding, a dry molded body that is dried after wet molding, or a calcined molded body obtained by calcining the dried compact.

Further, in the apatite powder or molded product used in the present invention, apatite is pure apatite according to X-ray diffraction, or lacks Ca in composition, but various types such as hydroxyapatite, fluorapatite, chlorapatite, etc. Apatite.

In the present invention, calcium acetate, calcium oxalate, calcium lactate as a water-soluble calcium salt of an organic acid,
Calcium tartrate, calcium citrate and the like can be used. The amount of the water-soluble calcium salt of the organic acid depends on the amount of calcium deficient in the apatite used, but it is preferable that the impregnation amount of the calcium salt is 0.5% by weight or less in terms of CaO. This amount is 0.
If it exceeds 5% by weight, the CaO phase in the apatite phase becomes excessive, and many cracks occur in the sintered body due to the difference in the coefficient of thermal expansion during sintering.

When impregnating with an aqueous solution of a calcium salt of an organic acid, it is preferable to use a solution having a concentration as high as possible, for example, a saturated solution in consideration of the subsequent drying energy. The impregnation can be performed by dropping, spraying, or the like.

When the impregnation is performed on the powder, the powder is dried by a conventional method, then molded and fired by a conventional method. In the case where the impregnation is performed on the molded body, it may be dried and then fired by a conventional method.

"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 According to X-ray diffraction, a cylindrical green compact of 25 mm in diameter and 6.3 mm in height made of pure hydroxyapatite (weight: 5.0
g) was prepared, and this green compact was impregnated with 2.1 ml of an aqueous solution of 2.76% by weight of calcium acetate (an amount by which the impregnation amount of calcium salt became 0.5% by weight in terms of CaO) by a method of absorbing drop by drop. After allowing to air dry for about one day, it was sintered at 1050 ° C. for 4 hours. FIG. 1 shows an X-ray diffraction diagram of the obtained sintered body. Although a slight CaO peak (indicated by a in the figure) is seen in FIG. 1, it can be seen that the sintered body has an apatite structure. Further, the density of the obtained sintered body was measured, and the light transmittance was measured using an optical microscope. First result
It is shown in the table.

In addition, the evaluation of the light transmittance was performed based on the light transmittance of the sintered body of the following comparative example.

Example 2 Instead of 2.76% by weight aqueous calcium acetate solution, 4% by weight
A sintered body was produced in the same manner as in Example 1 except that the sintered body was impregnated with 2.4 ml of an aqueous solution of calcium lactate. Table 1 shows the density and light transmittance of the obtained sintered body.

Example 3 The green compact produced in Example 1 was calcined in an electric furnace set at 900 ° C. for 4 hours. 2.76 to the obtained calcined body (weight 5.0g)
After impregnating 2.1 ml of an aqueous solution of calcium acetate by weight (the amount of impregnation of calcium salt becomes 0.5% by weight in terms of CaO),
Sintering was performed at 1050 ° C. for 4 hours, and the density was measured. The results of measuring the relative density of the sample at each time point are shown below.

Green compact 52.3% Calcined body 72.4% Sintered body 98.3% Comparative example 1 The same molded body as in Example 1 was sintered under the same conditions as in Example 1 except that no impregnation was performed. The X-ray diffraction pattern is shown in FIG. 2, and the measurement results of the density and the translucency are shown in Table 1.

As is evident from these results, according to the method of the present invention, an apatite sintered body having high density and translucency was obtained.

[Effects of the Invention] According to the method of the present invention, densification is achieved by a simple operation, and apatite ceramics having high density and translucency can be obtained. Further, according to the method of the present invention, the Ca / P ratio of the apatite ceramic is adjusted even in the state of the molded body,
A high-density ceramic molded body can be manufactured.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of the surface of the sintered body manufactured in Example 1,
FIG. 2 is an X-ray diffraction diagram of the surface of the sintered body manufactured in Comparative Example 1. Explanation of code a …… CaO peak

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/00-35/22 C04B 35/447 C04B 35/64

Claims (6)

(57) [Claims] 1. A method for producing high-density apatite ceramics, comprising impregnating an apatite powder with an aqueous solution of a water-soluble calcium salt of an organic acid, drying, shaping and firing. 2. The production of a high-density apatite ceramic according to claim 1, wherein the aqueous solution of a water-soluble calcium salt of an organic acid is impregnated in an amount such that the amount of impregnation of the calcium salt with respect to the apatite powder is 0.5% by weight or less in terms of CaO. Method. 3. The method for producing a high-density apatite ceramic according to claim 1, wherein the water-soluble calcium salt of an organic acid is calcium acetate, calcium oxalate, calcium lactate, calcium tartrate, calcium citrate or the like. 4. A method for producing high-density apatite ceramics, comprising impregnating an apatite dry formed body, dried formed body or calcined form with an aqueous solution of a water-soluble calcium salt of an organic acid, followed by drying and firing. 5. The high-density apatite ceramics according to claim 4, wherein the calcium salt impregnation amount is impregnated with an aqueous solution of a water-soluble calcium salt of an organic acid in an amount of 0.5% by weight or less in terms of CaO with respect to the apatite molded body. Production method. 6. The method for producing a high-density apatite ceramic according to claim 4, wherein the water-soluble calcium salt of an organic acid is calcium acetate, calcium oxalate, calcium lactate, calcium tartrate, calcium citrate or the like.