Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Reexamination Certificate
1998-11-06
2001-05-08
Langel, Wayne (Department: 1754)
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
C423S311000
Reexamination Certificate
active
06228339
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to a process for producing hydroxyapatite fibers.
II. Description of the Related Art
Hydroxyapatite is the major inorganic component constituting hard tissues such as bones and teeth, and is one of the materials having excellent bio-compatibility. Therefore, hydroxyapatite is used as materials for artificial dental root and bone prosthesis, and plays an important role in the field of biological materials. In addition, research and development of hydroxyapatite for use in industrial fields as absorbents of chromatography, ion-exchangers, sensors, catalysts and the like are also now widely made.
Thus, applications of hydroxyapatite to various uses are expected. Since the performance of hydroxyapatite is largely influenced by the shape of the hydroxyapatite particles, it is thought that control of the shape of the hydroxyapatite particles is necessary. For example, in the field of biological materials, hydroxyapatite is demanded to have high strength, high toughness and low modulus of elasticity. In general, mechanical properties of ceramics and high polymers are effectively improved by incorporating a material in the form of needles or fibers. Especially, in cases where a material is used as a biological material, the material preferably has bio-compatibility and is in the form of atoxic needles or fibers. Therefore, it has been intensively studied to obtain hydroxyapatite having bio-compatibility and is in the form of atoxic needles or fibers. As a result, needle-shaped or fiber-shaped hydroxyapatite, Ca-deficient hydroxyapatite and CO
3
-containing hydroxyapatite have been synthesized by various methods such as hydrothermal synthesis method, reflux method, agar gel method, alginate-spinning method and the like.
A process for producing needle-shaped or fiber-shaped hydroxyapatite, which is simpler than the known methods is demanded.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a process for producing hydroxyapatite fibers, which is simpler than the known processes.
The present inventors intensively studied to discover that calcium metaphosphate fibers may be converted to hydroxyapatite fibers by reacting the calcium metaphosphate with calcium oxide and water, thereby completing the present invention.
That is, the present invention provides a process for producing hydroxyapatite fibers comprising the steps of preparing a mixture of (1) calcium metaphosphate fibers and (2) calcium oxide, calcium hydroxide and/or calcium carbonate powder; heating the mixture to convert the calcium metaphosphate to hydroxyapatite; and removing calcium oxide in the heat-treated mixture by dissolving off from the resulting mixture.
By the process of the present invention, calcium metaphosphate fibers having high aspect ratio may be easily converted to hydroxyapatite fibers. Since the fibers are atoxic and have excellent bio-compatibility, novel applications of hydroxyapatite to, for example, composite materials with bio-compatible polymers are expected. Further, since the hydroxyapatite is in the form of needles or fibers having high safety to the body, various uses thereof in various industrial fields are expected.
REFERENCES:
patent: 4360625 (1982-11-01), Griffith
patent: 5227147 (1993-07-01), Yoshimura et al.
patent: 53-111000 (1978-09-01), None
Abe Yoshihiro
Iwashita Tetsushi
Kasuga Toshihiro
Ota Yoshio
Boyadjian L.
Langel Wayne
Winston & Strawn
Yabashi Industries Co., Ltd.
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