Process for the recovery of epsilon-caprolactam from polyamide 6 comprising fishing nets

A process for recovering purified epsilon-caprolactam from material derived from polyamide 6 comprising fishing nets in a plant, wherein the plant comprises

• a depolymerization section [B],
• a recovery section [C], and
• a purification section [D],
• and wherein the process comprises the steps of:
• a) charging material derived from polyamide 6 comprising fishing nets to the depolymerization section [B];
• b) depolymerizing the material derived from polyamide 6 comprising fishing nets in the depolymerization section [B] at a temperature ranging from 180° C. to 400° C. so that an epsilon-caprolactam comprising stream is obtained;
• c) discharging the epsilon-caprolactam comprising stream from the depolymerization section [B] and recovering crude epsilon-caprolactam from said stream in the recovery section [C];
• and
• d) purifying said crude epsilon-caprolactam in the purification section [D] to obtain purified epsilon-caprolactam wherein the purification comprises the steps of
• (i) extracting the crude epsilon-caprolactam with an organic solvent, whereby an organic phase is obtained, and wherein the organic phase comprises the organic solvent, epsilon-caprolactam and impurities;
• (ii) switching the solvent by replacing the organic solvent at least partially with water, whereby an aqueous phase comprising water, epsilon-caprolactam and impurities with lower- or higher-boiling points than epsilon-caprolactam is obtained and wherein the solvent switch step (ii) is selected from a process based on back-extraction with water, and a process based on solvent swap distillation, in which the organic solvent is distilled off and water is charged;
• and
• (iii) obtaining purified epsilon-caprolactam by distillative removal of impurities with lower- or higher-boiling points than epsilon-caprolactam from said aqueous phase;
• and at least one additional step comprising:
• after step d)(i), the organic phase obtained in step d)(i) is washed with water or with an aqueous alkaline solution, and
• wherein prior to the distillative removal in step d)(iii), an alkali metal hydroxide, is added to the aqueous phase.