Process for the preparation of mixtures of methylenephosphonic acid-substituted hydroxyethylethylenediamines and use of the mixtures

摘要

The invention relates to a process for the preparation of a mixture of hydroxyethylethylenediaminetris(methylenephosphonic acid) and hydroxyethylethylenediaminebis(methylenephosphonic acid) from hydroxyethylethylenediamine, formaldehyde and phosphorous acid in a hydrochloric acid environment, which is characterised in that the molar ratio HCl : hydroxyethylethylenediamine is adjusted to a range of 1 to 4 : 1, and the use of such mixtures, in which the weight ratio hydroxyethylethylenediaminetris(methylenephosphonic acid) and hydroxyethylethylenediaminebis(methylenephosphonic acid) is in the range from 1 to 12 : 1, possibly together with scale inhibitors known per se, in compositions to inhibit the settling of sparingly soluble precipitation systems.