Process for the preparation of ammonium polyphosphate

US5139758A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Thomas Staffel · Grünstadt, DE
• Renate Adrian · Hürth, DE

Key dates

• Filing date: Jul 17, 1991
• Grant date: Aug 18, 1992
• Expiry date: Jul 17, 2011

Classification

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

Abstract

To prepare essentially water-insoluble, chain-form ammonium polyphosphate from equimolar amounts of di- ammonium phosphate and phosphorus pentoxide in the presence of ammonia at temperatures of from 170.degree. to 350.degree. C. with constant mixing, kneading and comminution, at least some of the diammonium phosphate and phosphorus pentoxide is replaced by partially ammoniated polyphosphoric acid. A plant for carrying out this process can comprise a sealed reactor (1) which is provided with metering devices (2, 3) and feed tubes (4, 5) for phosphorus pentoxide and diammonium orthophosphate, an ammonia feed tube (8), an ammonium polyphosphate discharge tube (9) and a line for offgas. Rotatable mixing, kneading and comminution elements are provided inside the reactor (1). Furthermore, a heatable stirred tank (11) which can be charged with polyphosphoric acid via a feed line (13) is provided and can be used to remore water vapor and ammonia from the offgas flowing from the reactor (1) via the line (20) and from which partially ammoniated polyphosphoric acid can be introduced into the reactor (1) via an outlet line (17).