Process for the preparation of dicalcium phosphate

US5024825A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Horst Buhl · Waiblingen, DE
• Josef Holz · Lechenich, DE
• Franz-Josef Dany · Lechenich, DE

Key dates

• Filing date: May 10, 1990
• Grant date: Jun 18, 1991
• Expiry date: May 10, 2010

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01B25/322
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

For the preparation of dicalcium phosphate dihydrate stabilized with dimagnesium phosphate trihydrate and sodium pyrophosphate, an aqueous suspension of calcium carbonate is introduced into a reactor and recirculated by pumping through a high-speed mixer at 3,500 to 8,000 rpm which is in flow connection with the lower and upper portion of the reactor. Into the mixer an amount of phosphoric acid is introduced which is at least sufficient for the quantitative formation of dicalcium phosphate dihydrate and then an oxygen-containing magnesium compound is introduced into the reactor. Finally, lime milk is metered into the reactor up to a maximum pH of 6.9, before the sodium pyrophosphate is added to the reactor. The resulting suspension which has a stabilized dicalcium phosphate dihydrate content of 20 to 33% by weight is spray-dried. An apparatus for carrying out the process comprises besides a stirred reactor 1 two stirrer-equipped slurry containers (6, 7) and an intermediate container 16 from which a line 17 leads into a spray tower 18 where it ends above an atomizer wheel 19. The spray tower 18 is also the end point for hot air lines 20 and is in flow connection with a filter 22. Th…