Method for manufacturing an aptatite slurry

Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing

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423311, C01B 1516

Patent

active

061594377

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to apatite slurry and a method of manufacture therefor. In particular relates to an apatite slurry which comprises apatite particles which are dispersed in a water-compatible organic solvent and which has a degree of dispersion such that the average particle size of the apatite particles is 1 .mu.m or less and particles of 3 .mu.m or more are practically absent, and a method of manufacture therefor.
2. Description of the Prior Art
Apatites are well-known substances which are widely distributed in the form of phosphate ores, animal bones, etc., but recently the use of apatites has broadened to include materials for artificial bones, materials for dental repair, ion exchangers, etc. Their affinity with living tissue coupled with their environmentally friendly properties promises that they will make their way into yet other fields.
However, in apatites such as hydroxyapatite, even though the primary particles formed during manufacture ire fine particles of 1 .mu.m or less, they tend to aggregate due to Van der Waals forces, ionic charge, etc., and form aggregates of 1 .mu.m or more, especially around 10 to 100 .mu.m.
Consequently, they suffer from the problem that they cannot be used in areas requiring apatites with submicron particle sizes such as anti-blocking agents for films, etc., cosmetics, or UV blocking agents, for example, and their use cannot yet be extended to these areas.
Now, various methods have conventionally been tried which aim to overcome these problems. For example, there is a method (Japanese Patent Laid-Open No. 4-317404) in which the surface of the apatite is reformed and dried after completion of the reaction by adding a fatty acid such as stearic acid. Use of aqueous hydroxyapatite slurry as a stabilizer for suspension polymerization is also well known, and such methods as ultrasonic treatment (Japanese Patent Publication No. 47-38631) and intensive shearing treatment with homogenizers, etc., (Japanese Patents Laid-Open Nos. 7-102005 and 7-102006) have been proposed to disperse the apatite slurry.


OBJECT OF THE INVENTION

However, in the above methods, where the stabilizer for suspension polymerization is adjusted by intensive shearing treatment with homogenizers, etc., using water as a dispersion medium, it is extremely difficult to reduce the aggregated coarse particles even if the treatment is performed for a long time, and so the particles cannot all be reduced to 3 .mu.m or less and particles of 4 .mu.m or more remain. That is, even if the aqueous apatite slurry is treated as much as possible to disperse it, reduction equilibrium is reached and there is a limit to the reduction of secondary particles in the aqueous system.
Consequently, an objective of the present invention is to provide an apatite slurry in which secondary apatite particles can be practically completely redispersed, and to provide a method of manufacture therefor.


MEANS OF SOLVING THE PROBLEMS

The present inventors have considered the above problems and, as a result of extensive diligent research, have discovered that secondary particles can be reduced extremely effectively and be practically redispersed by reducing the apatite particles in a water-compatible organic solvent by means of an agitation mill, and have achieved the present invention.
That is, the apatite slurry according to the present invention is characterized in that it is an apatite slurry in which the apatite particles are dispersed in a water-compatible organic solvent and which has a degree of dispersion such that the average particle size of the apatite particles is 1 .mu.m or less and particles of 3 .mu.m or more are practically absent.
Also, the method of manufacture for apatite slurry according to the present invention is characterized in that an apatite slurry, in which the apatite particles are dispersed in a water-compatible organic solvent is fed to an agitation mill and reduction and dispersion treatment is performed until particles of 3 .mu.m or

REFERENCES:
patent: 4689351 (1987-08-01), Endo et al.
patent: 4897250 (1990-01-01), Sumita
patent: 5427754 (1995-06-01), Nagata et al.
Database WPI Section Ch, Week 9524 Derwent Publications Ltd., London, GB; Class A18, AN 95-182991, XP002115888 & JP 07 102006 A (Nippon Chem Ind Co Ltd), Apr. 18, 1995 *abstract*.
Patent Abstracts of Japan vol. 015, No. 256 (C-0845), Jun. 28, 1991 & JP 03 083805 A (Sumintomo Chem Co Ltd), Apr. 9, 1991 *abstract*.
Database WPI Section Ch, Week 9732 Derwent Publications Ltd., London, GB; Class A60, AN 97-347173 XP002115889 & JP 09 142817 A (Calseed KK), Jun. 3, 1997 *abstract*.
Chemical Abstracts, vol. 90, No. 10, Mar. 5, 1979 Columbus, Ohio, US; abstract no. 72648, Kido Kunizo Et Al: "Suspension polymerization of acrylonitrile and styrene" XP002115887 *abstract* and JP 53 126094 A (Kureha Chemical Industry Co., Ltd) Nov. 2, 1978.
Hawley's, Condensed Chemical Dictionary 13th Edition. 1997, pp. 385, 543, and 545.

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