Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-11-27
2003-07-15
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S403000, C428S407000, C427S376100, C427S376200, C241S015000, C241S016000
Reexamination Certificate
active
06592989
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of synthesizing hydroxy apatite, hydroxy apatite composite and method of manufacturing the composite, more particularly relates to a synthesizing method, hydroxy apatite composite and method of manufacturing the same that are capable of manufacturing the hydroxy apatite and composite thereof having a high uniformity, fineness and an excellent dispersing property and capable of producing the hydroxy apatite and composite in a short time through a simple process.
BACKGROUND ART
A composition and structure of hydroxy apatite (Ca
10
(PO
4
)
6
(OH)
2
, hereinafter referred to simply as “HAp”) are extremely similar to those of bone and tooth as biological inorganic components for constituting an organism body, so that HAp has a high affinity to the organism body. Therefore, HAp has been used as biomaterials, for example, as artificial organ material and medical material for constituting bone and tooth or the like. Further, HAp has been expected to be widely applied to various applications such as a material for absorbing/separating protein, amino acid, saccharides, DNA or the like; catalyst; inorganic ion-exchanger; and antibacterial agent or the like.
Conventionally, above described HAp has been manufactured in accordance with the following methods such as dry-method, wet-method and hydrothermal method. That is, as indicated by a combination of &bgr;-TCP with calcium carbonate or by a combination of calcium pyrophosphate with calcium carbonate, the dry method is a method of synthesizing the HAp, and the method comprises the steps of mixing calcium source and phosphoric acid source as starting materials to prepare a mixture; heating the mixture to a high temperature; and causing dry-type solid phase reaction thereby to synthesize HAp.
Further, for example, as indicated by a combination of calcium hydroxide suspended solution with phosphoric acid solution, the wet method is a method of synthesizing the HAp, and the method comprises the steps of mixing and reacting calcium source with phosphoric acid source as starting materials in a liquid phase to prepare a reaction product; and aging the reaction product at a high temperature thereby to synthesize HAp.
Furthermore, the hydrothermal method is a method of synthesizing the HAp, and the method comprises the steps of pressurizing a raw material of CaHPO
4
or the like in an autoclave to a pressure of several hundred atms; and heating the material to a temperature of 200° C. or more, thereby to synthesize HAp of single crystalline having a large grain size.
Thus synthesized HAp is excellent in affinity to organism body, so that applications of HAp as organism material have been tried and advanced in these years. However, the HAp synthesized by treating the raw material at a high temperature has a remarkably higher mechanical strength than that of organism bone. Therefore, when the HAp is assembled into the organism body as an alternate bone, there is raised a problem such that the HAp may damage or break an organism bone locating at circumference of the HAp. In addition, since the HAp as an inorganic compound has a small plastic deformability, it is difficult to utilize the HAp as the alternate bone.
To cope with this situation, there has been developed a HAp composite formed by compositing HAp with organic compounds such as collagen or the like that are capable of imparting the plastic deformability to the composite. As a method of manufacturing the composite of HAp and the organic compound for the purpose of synthesizing above bone-alternating material, the following methods have been tried.
Namely, there are used: a method comprising the steps of preparing a suspended solution into which calcium hydroxide is dissolved, preparing a phosphoric acid solution into which collagen is dissolved, and dropping the phosphoric solution into the suspended solution; a method comprising the steps of previously synthesizing a HAp precursor, mixing the HAp precursor into a collagen suspended solution to form a mixture, and thereafter, freeze-drying (lyophilizing) the mixture; and a method in which a HAp-collagen composite is synthesized in a solution into which anionic or cationic polymer in place of the above collagen is dissolved.
As described above, as a method of synthesizing the HAp and a method of manufacturing the HAp composite composed of HAp and the organic compound, various methods have been adopted.
The above dry-method as a method of synthesizing HAp is more excellent than the wet-method in a point that HAp having a stoichiometric composition can be synthesized. In contrast, however, the dry-method may pose problems such that a pulverizing operation after completion of a heat treatment is required to be continued for a long period of time, so that there is a disadvantage in productivity, and crystals cannot be uniformly formed and stable characteristics cannot be obtained.
Further, according to the wet-method, it becomes possible to obtain a HAp powder having a relatively fine grain size and a large specific surface area. In contrast, however, in order to secure the stoichiometric composition, a strict pH control and temperature adjustment are required, thus making a operation control of the manufacturing apparatus complicate. Further, the wet-method poses problem such that a production efficiency is extremely lowered because the synthesizing reaction requires a long period of time and the aging process to be performed at the high temperature also requires a long period of time.
On the other hand, according to the hydrothermal method, there can be obtained HAp whiskers composed of plate crystals having a high crystallizing property or HAp whiskers, having an extremely large size, of which crystal axis is extended in a C-axis direction. In contrast, however, the hydrothermal method requires a high-pressure and heat resisting apparatus as a synthesizing apparatus, so that an apparatus initial cost would be remarkably increased and the method requires long period of time for performing the synthesizing reaction, whereby there is posed a problem that the manufacturing efficiency is disadvantageously lowered.
The above problem is commonly revealed in any of the methods of manufacturing the HAp composite composed of HAp and organic compound. In any of the methods, there is posed problems such that manufacturing process and operation control of the apparatus are complicated, a long term manufacturing time is required and the resultant HAp product is formed to be coarse and non-uniform.
The present invention had been achieved to solve the aforementioned problems and an object of the present invention is to provide a method of synthesizing HAp, the method being capable of directly synthesizing HAp crystalline powder having fine and uniform size by a single process in a short time under a normal temperature and normal pressure without treating material at high temperature and high pressure and without forming a precursor as formed in the conventional methods.
Further, another object of the present invention is to provide HAp composite which can be used as a bone-alternating material by utilizing the aforementioned synthesizing method, and to provide a manufacturing method which can synthesize the composite through a simple and single process.
DISCLOSURE OF THE INVENTION
In order to achieve the aforementioned objects, the inventors of the present invention had prepared HAp powders under various conditions by using various material powders, reacting synthesizing method and pulverizing devices (grinding machines). Then, through the many experiments, the inventors had comparatively reviewed the influences of the differences in the manufacturing conditions onto characteristics and manufacturing cost of the HAp powder and the HAp composite.
As a result, the inventors had found and obtained the following knowledge. That is, when calcium hydroxide powder as a raw material and organic compound particles as required are mixed into phosphoric acid solution thereby to prepare a mixed material slurry th
Isobe Tetsuhiko
Kanayama Manabu
Senna Mamoru
Kiliman Leszek
Nara Machinery Co., Ltd.
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