Process for the recovery of epsilon-caprolactam from nylon 6-containing multi-component material

A process for recovering purified epsilon-caprolactam derived from a Nylon 6-containing multi-component material in an industrial scale plant with a production capacity for epsilon-caprolactam of at least 500 tons/year if operated all the time, wherein the plant comprises

• a Nylon 6-depolymerization section comprising one or more depolymerization reactors that are operated in at least one of series and parallel,
• a recovery section comprising one or more condensers, and
• a purification section comprising one or more pieces of extraction equipment, one or more pieces of solvent switch equipment, and one or more pieces of distillation equipment,
• and wherein the process comprises the steps of:
• a) providing a pre-concentrated Nylon 6-containing material that has been obtained by extracting a Nylon 6-containing multi-component material with one or more organic solvents to obtain a solid pre-concentrated Nylon 6-containing material, which is enriched in Nylon 6 as compared to the Nylon 6-containing multi-component material;
• b) depolymerizing the pre-concentrated Nylon 6-containing material in the depolymerization section in the presence of water to obtain a vapor stream comprising water and epsilon-caprolactam in a weight to weight ratio of 2:1 to 15:1;
• c) recovering crude epsilon-caprolactam from said vapor stream in the recovery section;
• and
• d) purifying said crude epsilon-caprolactam in the purification section to obtain purified epsilon-caprolactam,
• wherein
• the purification comprises the steps of
• (i) extracting the crude epsilon-caprolactam with an organic solvent, whereby an aqueous phase and an organic phase are 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;
• wherein after step d)(i), the organic phase obtained in step d)(i) is washed with water or with an aqueous alkaline solution;
• wherein step d)(ii) is followed by oxidation by an oxidant selected from potassium permanganate, sodium permanganate and hydrogen peroxide;
• and
• wherein the Nylon 6-containing multi-component material is a multi-layer packaging film that is a thin sheet with a thickness of less than 1 mm and contains at least one layer comprising or consisting of Nylon 6 and at least one layer not comprising Nylon 6, wherein the at least one layer comprising or consisting of Nylon 6 is sandwiched in between two or more layers not comprising Nylon 6.