Process for producing polyamide 6 for spinning purposes

Polyamide 6 with amino and carboxyl end group contents within certain limits is obtained by hydrolytic polymerisation of caprolactam in presence of a monocarboxylic acid and a 4-amino-2,2,6,6-tetra-alkyl piperidine, a (cyclo)aliphatic diamine with one prim. and one tert. amino group and/or an alpha -dialkylamino caprolactam. Production of polyamide 6 (PA 6) involves the hydrolytic polymerisation of caprolactam (Ia) or polycondensation of epsilon -aminocaproic acid (Ib), in the presence of 0.05-0.7 wt.% monocarboxylic acid (II), 0-0.7 wt.% dicarboxylic acid (III), 0-0.7 wt.% 4-amino-2 ,2,6,6-tetra-alkyl piperidine (IV), 0-0.5 wt.% (cyclo)aliphatic diamine (V) with one prim. and one tert. amino group, 0-0.7 wt.% alpha -dialkyl amino caprolactam (VI), 0-0.7 wt.% dialkyl phenol (VII), and 0-0.5 wt.% linear or branched aliphatic, cycloaliphatic or aromatic 6-18 C mono-amine (VIII). At least one of the components (IV)-(VI) is present. The components (II)-(VIII) are attached to the polymer chain by amide bonds, so t