PREPARATION OF FLAME-RETARDANT POLYCARBONATE

• Main Authors: YUUJIN POORINGU BOODEN, PIITAA DEBITSUTO FUERUPUSU
• Format: Patent
• Language: English
• Published: 16.05.1995
• Edition: 6
• Subjects: CHEMISTRY; COMPOSITIONS BASED THEREON; MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONSONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP

A method for making flame retardant polycarbonates comprises: (a) adding phosgene to a tetrahalobisphenol mixt. under interfacial reaction conditions at a pH of 9-11 and in the presence of a condensation catalyst mixt. (A); (b) altering the pH to 10.5-12 to eliminate chloroformate gps. in the reaction mixt. of (a); and (c) introducing into the mixt. of (b) up to a 3 mole % excess of phosgene based on the total moles of phenolic hydroxy gps. in the bisphenol mixt. of (a). At step (a), phosgene is added until up to about 90 mole % required to react with the available phenolic hydroxy gps. in the mixt. has been introduced. The tetrahalobisphenol mixt. comprises up to 50 mole % of a bisphenol of formula (I). X to X3 = halogen; Y = O, S, -SO, -SO2, -CO, or -CR2 and R = 1-4C alkyl. Catalyst mixt. (A) consists of a tert. organic amine and a phase transfer catalyst.