Process for the preparation of ammonium polyphosphate

US5277887A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Thomas Staffel · Grünstadt, DE
• Wolfgang Becker · Eppstein, DE
• Herbert Neumann · Bergheim, DE

Key dates

• Filing date: Sep 25, 1992
• Grant date: Jan 11, 1994
• Expiry date: Sep 25, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01B25/405
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

To prepare essentially water-insoluble, long-chain ammonium polyphosphate, in a first stage, ammonium orthophosphate and phosphorus pentoxide are reacted in the presence of gaseous ammonia in a reactor equipped in its interior with mixing, kneading and comminution apparatus, until the drive motor of the reactor passes through the second current peak in its current consumption/time diagram. In a second stage, the material discharged from the reactor is then fed to a disk dryer, the heating disks of which are maintained at temperatures of 240.degree. to 300.degree. C., whereas its lower cooling disk has temperatures of 5.degree. to 45.degree. C. The material, which covers the disks of the disk dryer at a layer thickness of 5 to 20 mm, has a residence time of 35 to 70 minutes in the disk dryer, while ammonia-containing gas is continuously passed through the disk dryer. Finally, the ammonia-containing gas exiting the disk dryer is freed from water vapor contained therein by condensation and the ammonia-containing gas is reheated prior to its entry into the disk dryer.