GB1420063A - Method for isolating epsilon-caprolactam material - Google Patents

Abstract

1420063 Purification of #-caprolactam KANEBO Ltd 11 Feb1974 [12 Feb 1973] 06054/74 Heading C2C [Also in Division C3] Phosphoric acid and/or ionized metal compound impurities are removed from the monomer, oligomers and/or polymers of #-caprolactam by bringing the #-caprolactam material into contact with an aqueous solution containing 15 to 75% by weight of at least one alkali metal phosphate to extract the impurity into the alkali metal phosphate aqueous solution, which is subsequently separated from the #-caprolactam material phase. Suitable alkali metal phosphates are monoalkali metal dihydrogen phosphates, dialkali metal monohydrogen phosphates and trialkali metal phosphates. The #-caprolactam material is suitably selected from (a) reaction residue containing an #-caprolactam oligomer and/or monomer and alkali metal compounds, which has been obtained by washing #-caprolactam polymer with water and distilling the waste water-containing #-caprolactam monomer and/or oligomer in the presence of an alkali metal, hydroxide, carbonate or hydride of alkali metal or mixture of two or more of these substances, (b) distillation residues containing an #-caprolactam monomer and alkali metal compounds, which has been obtained by polymerizing an #-caprolactam monomer in the presence of water as a catalyst, a portion of the #-caprolactam monomer being evaporated together with water, and distilling the monomer in the presence of an alkaline alkali metal compound; (c) reaction residue produced in processes for depolymerizing an #-caprolactam polymer or oligomer or a mixture of the polymer and oligomer in the presence of phosphoric acid as a catalyst; (d) distillation residue, containing alkali metal compounds, resulting from distilling crude #-caprolactam monomer produced by depolymerizing an #-caprolactam polymer or oligomer or a mixture of the polymer and oligomer in the presence of phosphoric acid as a catalyst; (e) distillation residue produced by Beckmann rearrangement of cyclohexanone oxime to give crude #-caprolactam monomer and distillation of the crude #-caprolactam in the presence of an alkaline alkali metal compound; (f) reaction residue produced by depolymerizing an #-caprolactam polymer or oligomer or a mixture of the polymer and oligomer in the presence of an alkali metal compound as catalyst and (g) an #-caprolactam polymer and/ or oligomer prepared by polymerizing the monomer in the presence of one or more catalysts chosen from alkali metals and alkali metal hydroxides, carbonates and hydrides. The purified caprolactam polymer may then be subjected to depolymerization, distillation or combustion.