Phase boundary process for the preparation of aromatic polycarbonates using a chlorinated aromatic hydrocarbon as the polymer solvent

US4038252A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Hugo Vernaleken · Walsrode, DE
• Uwe Hucks · Alpen, DE

Key dates

• Filing date: Mar 4, 1975
• Grant date: Jul 26, 1977
• Expiry date: Mar 4, 1995

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G64/06
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

The present invention provides a process for the preparation of a polycarbonate by the phase boundary condensation method, by phosgenation of an aqueous alkali metal salt solution of one or more aromatic dihydroxy compounds, in which process an aromatic chlorinated hydrocarbon is used as the solvent and the synthesis of the polycarbonate is carried out in two stages, in the first stage of which the reaction of the alkali metal salt solution of the aromatic dihydroxy compound(s) with phosgene is carried out at an OH concentration of between 0.01 and 0.1% by weight of OH, relative to the aqueous phase, in the presence of 0.1 to 2.5 mol% of trialkylamine, relative to aromatic dihydroxy compound(s), and at a temperature higher than 70.degree. C, with a dwell time of less than 5 minutes, while in the second stage the polycondensation is effected by adjusting the OH concentration to 0.20 to 0.50% by weight of OH, relative to the aqueous phase, optionally with further addition of trialkylamine, at a temperature higher than 80.degree. C and with a dwell time of more than 1 minute.