Colloidal dispersion of calcium phosphate tablets and method of obtaining the same
The invention provides colloidal dispersions of calcium phosphate platelets comprising at least one polymer which complexes the calcium and in which the length of the platelets, L, is between 5 and 500 nm and in which the thickness of the platelets is between 0.5 and 20 nm. Another subject-matter of the invention is the calcium phosphate platelets obtained by drying the colloidal dispersion according to the invention. The invention also provides a process for preparing these colloidal dispersions of calcium phosphate platelets according to the invention. Finally, another subject-matter of the invention is the use of the abovementioned colloidal dispersions of platelets as food additive, reinforcing filler, thermal insulation filler, pharmaceutical excipient, polishing agent, building materials, additive for oral formulations, in particular dentifrices, or encapsulating agent.
1. A method for preparing dispersions of calcium phosphate platelets, wherein the length of the platelets, L, is between 5 and 500 nm and the thickness of the platelets is between 0.5 and 20 nm, and at least one polymer which complexes calcium comprising the steps of:
i) preparing a solution of calcium salts and adjusting the pH to a selected value of between 4 and 6;
ii) adding a phosphate solution to the solution obtained in step i) over a period of time of between 30 minutes and 4 hours, so as to obtain a calcium to phosphorus molar ratio of between 1 and 2.5, wherein the pH is maintained constant at the selected value of between 4 and 6 until a calcium phosphate platelet dispersion is formed;
iii) heat treating the dispersion obtained in step ii) at a temperature of between 50° C. and 95° C.;
iv) washing the dispersion obtained in step iii);
v) adding a dispersion agent to the dispersion obtained in step iv);
vi) separating the colloidal dispersion obtained in step v);
wherein in at least one of steps i) or ii), the solutions further comprise ammonium ions; and
wherein at least one polymer which complexes calcium is added during step i) or ii).
2. The method according to claim 1 , wherein the calcium solution is a CaCl 2 or Ca(NO 3 ) 2 solution.
3. The method according to claim 1 , wherein the concentration of the calcium solution is between 0.25M and 2.5M.
4. The method according to claim 1 , wherein the phosphate salt solution is a solution of one of ammonium phosphate or sodium phosphate.
5. The method according to claim 1 , wherein the calcium to phosphorus molar ratio in the solution of step ii is between 1.3 and 1.7.
6. The method according to claim 1 , wherein the temperature of the heat treatment in step iii) is between 60° C. and 90° C.