Process for preparing dialkylphosphinic acids and their salts

US6359171B1 · kind B1 · utility

Assignee

• Clariant Corporation · DE

Inventors

• Norbert Weferling · Hürth, DE
• Martin Sicken · Cologne, DE
• Gunter Kolbe · Kerpen, DE
• Hans-Peter Schmitz · Mönchengladbach, DE

Key dates

• Filing date: May 24, 2000
• Grant date: Mar 19, 2002
• Expiry date: May 24, 2020

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07F9/30
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The invention relates to a process for the preparation of dialkylphosphinic acids and salts thereof, which comprisesa) reacting elemental yellow phosphorus with alkylating agents in the presence of a base to give a mixture which comprises, as principal constituents, the (metal) salts of alkylphosphonous, phosphorous and hypophosphorous acids,b) esterifying the principal constituents of the mixture from a) to give an ester mixture,c) isolating the ester of the alkylphosphonous acid from the ester mixture,d) preparing the corresponding ester of the dialkylphosphinic acid from the ester of the alkylphosphonous acid by free-radical-initiated reaction with olefins,e) converting the ester of the dialkylphosphinic acid into the free acid or into the dialkylphosphinic acid salts of metals from groups IA, IIA, IIIA, IVA, VA, IIB, IVB, VIIB or VIIIB of the Periodic Table or of cerium.The invention likewise relates to the use of the dialkylphosphinic acids/salts prepared by this process for the preparation of various products, in particular flame retardants.