PROCESS FOR THE RECOVERY OF ε-CAPROLACTAM FROM EXTRACT WATER Russian patent published in 2018 - IPC C07D201/16 C07D223/10 

FIELD: biochemistry.

SUBSTANCE: invention relates to a method for recovering ε-caprolactam from the aqueous extract of polycaprolactam obtained by hydrolytic polymerization. Method involves the following process steps: a) using one- or multi-stage distillation, the aqueous extract is concentrated by separating water, thereby obtaining a first intermediate product stream, a concentration of εcaprolactam in which is increased in comparison with the aqueous extract; b) the first intermediate product stream is separated by distillation into a first vapor phase εcaprolactam-water and the liquid phase of the oligomer-ε-caprolactam; c) into the liquid phase of the oligomer-ε-caprolactam, steam is introduced in the presence of a catalyst, the oligomers ε-caprolactam are hydrolytically depolymerized into a monomeric ε-caprolactam, and ε-caprolactam is distilled from the phase by steam, thereby obtaining a second vapor phase εcaprolactam-water, and wherein the impurities not depolymerizing are withdrawn from the process in the form of a bottom product; d) a first vapor phase εcaprolactam-water formed in step b) and a second phase ε-caprolactam-steam formed in step c), unite in a single phase ε-caprolactam-water, from which water is recovered by distillation, and thus a non-oligomeric and water-containing phase is obtained εcaprolactam in the form of a second intermediate product stream. Method is also characterized in that the phase εcaprolactam obtained in step d) as a stream of the second intermediate product, is fed to a distillation comprising at least two stages in an additional step e), thereby obtaining a stream of the final product depleted of the highly volatile impurities and in that, at least, a portion of the first intermediate product stream and/or the second intermediate product stream is withdrawn from the process and fed to the polymerization process.

EFFECT: present invention makes it possible to meet the requirements for both low and high purity polymer.

6 cl, 1 dwg