Method for recovering bis hydroxy aromatic organic values and bis aryl carbonate values from scrap aromatic polycarbonate

• Main Author: SHAFER, SHELDON JAY
• Format: Patent
• Language: English; French; German
• Published: 04.08.1999
• Edition: 6
• Subjects: ACYCLIC OR CARBOCYCLIC COMPOUNDS; APPARATUS THEREFOR; CHEMISTRY; GENERAL METHODS OF ORGANIC CHEMISTRY; METALLURGY; ORGANIC CHEMISTRY

Recovering dihydric phenol and diarylcarbonate values from scrap aromatic polycarbonate with carbonate repeat units of formula -OROC(O)- (I), where R is 6-30C divalent aromatic, comprises (a) heating the scrap aromatic polycarbonate at 60-250 deg.C in presence of 3-50 mol. of a monohydric phenol of formula R1OH (II), where R1 is 6-13C monovalent organic gp., per mol. of carbonate repeat unit and an effective amt. of a basic depolymerisation catalyst to produce a mixt. comprising the monohydric phenol, dihydric phenol of formula HOROH (III) and diarylcarbonate of formula R1OC(O)OR1 (IV), (b) initially filtering insoluble polycarbonate contaminants if present, then distilling monohydric phenol from the resulting mixt. until the conc. of dihydric phenol is 10-35 wt.%, (c) sepg. the dihydric phenol/monohydric phenol adduct from the mixt. at 40-80 deg.C, (d) vacuum distilling monohydric phenol from the resulting mother liquor in the presence of an effective amt. of an organic acid, and (e) vacuum distilling diarylcarbonate from the residue from the mixt. Pref. scrap aromatic polycarbonate is scrap bisphenol A polycarbonate, diaryl carbonate is diphenylcarbonate, organic acid is salicylic acid and monohydric phenol is hydroxy benzene.