US5405436A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the preparation of hydroxyapatite
Assignee: BK Giulini Chemie GmbH
•
Filing: 1993-09-27
•
Granted: 1995-04-11
•
Expires: 2013-09-27
Abstract
Abstract A process for the preparation of a hydroxyapatite, which is suitable as a tooth-cleaning substance, by precipitation from aqueous phosphoric acid and calcium hydroxide solution, in which a calcium-doped phosphoric acid solution is fed to an intensive mixer with a suspension of calcium hydroxide/oxide in a molar ratio of Ca:P=1.667 corresponding to the hydroxyapatite of and reacted there at precipitation temperatures of 60°-100° C., preferably 80°-90° C. and a pH of 4-8, preferably of 6.5-7.5. Also disclosed in a tooth-cleaning substance containing the hydroxyapatite.
Inventors
- 👤 Alexander Maurer
- 👤 Gudrun Raab
- 👤 Guenter Raab
- 👤 Reinhold Schmitt
- 👤 Detlev Schober
- 👤 Richard Taenzler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 22:33
CPC Classifications
D; D06; D06P; D06P3/00; D06P3/34; D06P3/52; D06P3/54; A; A61; A61K; A61K8/00; A61K8/18; A61K8/19; A61K8/24; A61Q; A61Q11/00; C; C01; C01B; C01B25/00; C01B25/16; C01B25/26; C01B25/32; C01B25/322; D06P1/00; D06P1/44; D06P1/64; D06P1/642; D06P1/649; D06P1/6491; D06P3/523
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
98 words
A process for the preparation of a hydroxyapatite suitable as a tooth-cleaning substance, comprising the steps of simultaneously feeding an acidic calcium phosphate solution having a molar ratio of Ca:P of from about 0.2:1 to 1:1 and a calcium suspension to an intensive mixer in a substantially stoichiometric molar ratio of Ca:P to provide a reaction mixture; reacting the reaction mixture under intensive mixing at a temperature of from about 60° to about 100° C. and at a pH of from about 4 to 8 to obtain a hydroxyapatite suspension; and separating a hydroxyapatite product from the suspension.
Claim 2
Dependent Claim
98 words
A process for the preparation of a hydroxyapatite suitable as a tooth-cleaning substance, comprising the steps of simultaneously feeding an acidic calcium phosphate solution having a molar ratio of Ca:P of from about 0.2:1 to 1:1 and a calcium suspension to an intensive mixer in a substantially stoichiometric molar ratio of Ca:P to provide a reaction mixture; reacting the reaction mixture under intensive mixing at a temperature of from about 60° to about 100° C. and at a pH of from about 4 to 8 to obtain a hydroxyapatite suspension; and separating a hydroxyapatite product from the suspension.
Claim 3
Dependent Claim
20 words
A process according to claim 1, wherein said separating step includes washing the separated hydroxyapatite; and drying the washed hydroxyapatite.
Claim 4
Dependent Claim
28 words
A process according to claim 1, wherein the calcium phosphate solution comprises a solution containing a concentration of calcium phosphate of from about 20 to 50% by weight.
Claim 5
Dependent Claim
29 words
A process according to claim 1, wherein the calcium suspension comprises a calcium hydroxide suspension having a concentration of calcium hydroxide of from about 5 to 30% by weight.
Claim 6
Dependent Claim
57 words
A process according to claim 1, wherein said reacting step comprises the additional step of transferring the hydroxyapatite suspension to a separate vessel and permitting said suspension to continue reacting in said separate vessel under stirring conditions at a temperature between about 60° and 90° C. for a period of time of up to about 5 hours.
Claim 7
Dependent Claim
26 words
A process according to claim 1, wherein said pH is between about 6.75 and 7.5, and said temperature is between about 80° and 90 ° C.
Claim 8
Dependent Claim
15 words
A process according to claim 6, wherein said pH is between about 7 and 7.5.
Claim 9
Dependent Claim
18 words
A process according to claim 5, wherein said continued reaction time is between about 1 and 2 hours.
Claim 10
Dependent Claim
26 words
A process according to claim 5, wherein said continued reaction is monitored by X-ray diffraction for selection of final degree of crystallization of the hydroxyapatite product.
Claim 11
Dependent Claim
15 words
A process according to claim 1, further comprising the step of grinding the hydroxyapatite product.
Claim 12
Dependent Claim
70 words
A hydroxyapatite composition produced according to claim 1 and having a relative abrasiveness according to the RDA method of between about 110-150, a high crystallinity of a degree of crystallization of greater than about 95 %, a surface area determined by BET of at most about 10 m 2 /g, and an average grain size of between about 1-20 μm, and wherein said hydroxyapatite composition contains substantially no dicalcium phosphate.
Claim 13
Dependent Claim
28 words
A hydroxyapatite composition according to claim 11, wherein the surface area is between about 0.1-5 m 2 /g, and the average grain size is between about 4-8 μm.
Claim 14
Dependent Claim
19 words
In a tooth cleaning composition, the improvement comprising that the composition Contains hydroxyapatite as defined according to claim 11.
Claim 15
Dependent Claim
18 words
A process according to claim 1, wherein said molar ratio of Ca:P is between about 0.3:1 to 0.5:1.
Claim 16
Dependent Claim
15 words
A process according to claim 1, wherein said hydroxyapatite product contains substantially no dicalcium phosphate.
Claim 17
Dependent Claim
24 words
A process according to claim 1, wherein said hydroxyapatite product has a high crystallinity of a degree of crystallization of greater than about 95%.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-04-10 | 1998-10-10 | 1999-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-04-10 | 2002-10-10 | 2003-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-04-10 | 2006-10-10 | 2007-04-11 | $7700.00 | Window Closed / Lapsed |