Patent ID: 6852829

Claim:
A process for the simultaneous preparation of polyamide-6 with at least two different viscosities in different reaction zones in a single reactor or in at least two reactors or reaction zones placed in series, comprising prepolymerising molten ε-caprolactam and/or other polyamide-6 precursors in the presence of water, wherein at least part of the necessary water is supplied to the prepolymerisation via the a gas phase in contact with molten phase; sequentially condensing-polymerizing the obtained prepolymer in the presence of inert gas in at least two condensation reaction zones or reactors, placed in series, wherein the reaction conditions are varied in the different reaction zones or reactor thereby obtaining polyamide-6 with different viscosities wherein the different viscosities are relative viscosities above 1.6, and the prepolymerisation and condensation reactions are carried out in said reactor(s) or reaction zones having a molten phase with a large surface/volume ratio and wherein the molten phase is relatively strongly mixed to renew the interface between the molten phase and the gas phase.