Process for recovery of dihydric phenols from thermoplastic polymers

摘要

A method of recovering a dihydric phenol from a composition containing a thermoplastic polymer having the reaction residue of dihydric phenol units in the polymer structure, comprises: (a) granulating a composition containing a thermoplastic polymer having the reaction residue of dihydric phenol units in the polymer structure; (b) treating the granulated particles of the thermoplastic composition with an organic swelling solvent that is miscible with water and is easily distilled off from an aqueous solution and for a time sufficient to swell the particles; (c) contacting the swelled granulated particles with an aqueous ammoniacal solution of sufficient molar strength to severe selectively the ester bonds of the reaction residue of the dihydric phenol units in the thermoplastic polymer and at least 25 deg C, forming a solid phase and a liquid phase; (d) separating the liquid phase from the solid phase; (e) distilling the ammonia and the organic swelling solvent from the liquid phase; (f) adding sufficient water to the residue which contains dissolved urea and partially precipitated dihydric phenol forming a liquid and a solid phase of dihydric phenol; and (g) separating the insoluble; solid dihydric phenol portion from the liq. phase. Also claimed is the polycarbonate prepared from bisphenol-A obtained by a preferred method.