METHOD OF PRODUCING PURIFIED DIESTER STREAM BY DEPOLYMERISATION OF ESTER CONTAINING OPAQUE POLYETHYLENE TEREPHTHALATE Russian patent published in 2024 - IPC C08J11/24 C08L67/02 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for depolymerisation of polyester material containing opaque PET, comprising: a) a conditioning step, b) a glycolysis step, c) a step for separating a diol, d) a step for separating into a stream of heavy impurities and a pre-purified monomer stream, e) a step for decolouration of the preliminarily purified monomer stream by adsorption of the mixture. Mixture contains 20 wt.% to 90 wt.% of the preliminarily purified monomer stream and a solvent. Adsorption is carried out at temperature of 100 °C to 200 °C, pressure from 0.1 MPa to 1.0 MPa and in the presence of at least one adsorbent. Glycolysis stage is performed at temperature of 180 °C to 400 °C, residence time from 0.1 to 10 hours in the presence of diol. Diol separation step is carried out at temperature of 100 °C to 250 °C, pressure lower than at step b), to obtain a diol stream and a monomer-rich stream. Stage of separation into a stream of heavy impurities and a pre-purified monomer stream is carried out at temperature below 250 °C, pressure below 0.001 MPa and residence time less than 10 minutes.

EFFECT: invention provides improved decolouration of diester wastes and production of purified colourless or almost colourless diester wastes.

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