BigPatents India

The invention relates to a process for preparing polyamides from caprolactam or from a mixture of caprolactam and further monomers selected from enanthlactam, lauryllactam, alkane dicarboxilic acids having from 6 to 12 carbon atoms and C4-C12- alkyldiamines, which process comprises a) concentrating the was water extract from the extraction of polyamide to an extractables content from 70 to 85% by weight, the polyamide being obtained from a caprolactam polymerization process, b) adjusting the water content of the resulting concentrate to from 0.5 to 13% by weight by addition of fresh caprolactam, c) subjecting the resulting mixture to a polymerization under polyamide- forming conditions, wherein the reaction mixture is brought to a temperature within the range from 230 to 310 C and to a pressure within the range from 5 to 40 bar, and d) effecting at least one adiabatic expansion of the reaction mixture to a pressure within the range from 0.1 mbar to 1.8 bar, whereby the water content of the reaction mixture is reduced, and postpolymerizing the product obtained after said expansion in at least one reaction zone.