IMPROVED METHOD FOR DEPOLYMERISATION OF POLYESTER CONTAINING POLYETHYLENE TEREPHTHALATE Russian patent published in 2024 - IPC C08J11/24 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for depolymerisation of polyester stock containing PET, which includes an improved stage of conditioning said stock. At the conditioning step, at least one conditioning section is used to obtain a conditioned feed stream and a mixing section to obtain a mixed stream, wherein said conditioning section is fed at least said polyester raw material, and it operates at temperature from 225 °C to 275 °C, into said mixing section at least said stream of conditioned raw material obtained in conditioning section, and a diol stream which contains ethylene glycol in an amount of at least 95 wt.%, the section is implemented in a static or dynamic mixer, at temperature of 225 °C to 275 °C, dwell time from 0.5 seconds to 20 minutes, and so that the weight ratio of the diol to the polyester material is 0.1 to 1.0. Further, a depolymerisation step is carried out by glycolysis, to which at least a mixed stream and possibly a make-up diol are supplied, in order to achieve a total amount of diol fed to said depolymerisation step at level of 1–20 mol of diol per mole of diester fed to the depolymerisation step, where the depolymerisation step is carried out at temperature of 180 °C to 400 °C and residence time from 0.1 to 10 hours. After the depolymerisation step, a diol separation step is carried out, which produces a diol stream and a liquid stream rich in monomers, followed by a liquid stream separation step, rich in monomers, leaving the stage of diol separation into a stream of heavy impurities and a pre-purified monomer stream. After the liquid flow separation step, the pre-purified monomer flow is decoloured in the presence of adsorbents.

EFFECT: improved homogenisation of the mixture of raw material with at least one flow of diol in the reaction section, which increases efficiency of depolymerisation while simultaneously reducing the mixing power required for this homogenisation in the reaction section.

9 cl, 1 dwg, 1 tbl, 1 ex