Published: November 2012
Zimmer AG's continuous two-stage polymerization process is widely licensed for the production of polyamide 6 (nylon 6). The polymerization of caprolactam with a catalyst is performed in a two-stage process using two vertical tube reactors in series. The two-stage process reduces the polymerization reaction time and allows the production of medium to high viscosity polyamide 6, as required for tire cord-grade products. Polymer chips are formed with an underwater granulator and transfer to an extraction unit. Caprolactam and oligomers extracted in water from the polymer chips are recovered in the monomer recovery section. The polymer chips are then dried. In this review, the process economics for polyamide 6 chip production using a process similar to the Zimmer® continuous two-stage polymerization process are presented. The evaluation was based on a single-line plant with a capacity of 90,000 TPA of polyamide 6 chips.