Patent ID: 6649792
Filing Date: 2003-11-18
Classification: C07C,C08J,Y02W

Abstract:
(Original/Currently amended) The method of chemical recycling of polyethylene terephthalate waste to terephthalic acid and ethylene glycol with the hydrolysis of polyethylene terephthalate waste, the purpose being its depolymerization, which consists of a continuous series of repeated steps, of (a) separation of the polyethylene terephthalate component of the input material by its conversion to brittle form through crystallization, grinding and subsequent sifting, followed by (b) continuous two-stage hydrolysis of the polyethylene terephthalate, carried out in the first stage by feeding steam to the polymer melt, and in the second stage, by the reaction of the products of the first stage of hydrolysis with ammonium hydroxide, followed by (c) precipitation of terephthalic acid from an aqueous solution of the second-stage hydrolysis products by an inorganic acid which is chemically stronger than terephthalic acid, and its separation by means of filtration, and finally (d) rectification separation of ethylene glycol from a solution of the products of the second stage of hydrolysis, after the separation of terephthalic acid.