Process for the preparation of an .alpha.-amino .omega.-ester monoamide and process for the manufacture of a polyamide

A process for the preparation of an .alpha.-amino .omega.-ester monoamide of formula (IV):

• H.sub.2 N--B--NH--CO--A--COOR.sub.1 (IV)
• in which:
• B denotes a diamine residue and
• A denotes a residue of a diacid
• R.sub.1 denotes an alkyl group containing from 1 to 6 carbon atoms,
• said process comprising
• mixing a diamine of formula:
• H.sub.2 N--B--NH.sub.2 (II)
• and a diester of formula:
• R.sub.1 OOC--A--COOR.sub.1 (III)
• in a molar ratio of between 0.8 and 1.2,
• maintaining the mixture in liquid phase at a temperature below the melting or crystallization temperature of the .alpha.-amino .omega.-ester monoamide formed, until the precipitation of the said .alpha.-amino .omega.-ester monoamide, and
• recovering the precipitate formed.