Process for preparing phosphinic acids

A process for the preparation of phosphinic acids from alkali metal phosphinates, which comprises the steps of;

• reacting alkali metal phosphinates, corresponding to the formula 4, 5 and 6
• in which R1 and R2 are identical or different and are a C1 to C20-alkyl group (linear, branched or alkyl), C1 to C20-aryl group or C1 to C20 -alkylaryl group, in a polar solvent with an inorganic mineral acid;
• separating off the phosphinic acid formed;
• and filtering off an alkali metal salt, said polar solvent selected from acetic acid, propionic acid or an alcohol, said inorganic mineral acid selected from hydrochloric acid, sulfuric acid, phosphoric acid and mixtures thereof.