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AssigneeGeneral Electric Company
InventorsHenricus H. M. van Hout, Christianus J. J. Maas, Laurus van der Wekke, Martin H. Oyevaar
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The invention relates to a method of preparing a compound of formula 1 ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 correspond to H, a branched or non-branched, optionally substituted alkyl group, or an optionally substituted aryl group, suitable as a chain stopper in the preparation of an aromatic polycarbonate, by reaction of a compound of formula 2 ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 have the meanings described hereinbefore, with phosgene, comprising the continuous supply of the compound of formula 2 and phosgene to a solution of phosgene in a solvent, the temperature being kept at a value between 0.degree. and 15.degree. C. and the pH being kept at a value between 1 and 6.
A method of preparing an aromatic polycarbonate comprising preparing a compound of formula 1 ##STR6## by continuously supplying to a solution of phosgene in a solvent a compound of formula 2 ##STR7## wherein R.sub.1, R.sub.2 and R.sub.3 in formulas 1 and 2 are each independently of H, a branched or non-branched, substituted or unsubstituted alkyl group, or an unsubstituted or substituted aryl group and phosgene in an amount whereby the molar ratio of phosgene to the compound of formula 2 is from 1.5:1 to 3:1 in which solvent the compound of formula 2 reacts with phosgene at a temperature maintained between 0.degree. and 15.degree. C. and a pH between 1 and 6, removing the compound of formula 1 containing no more than 0.5% by weight of dimeric compounds from the solvent;
A method of preparing an aromatic polycarbonate comprising preparing a compound of formula 1 ##STR8## by continuously supplying to a solution of phosgene in a solvent a compound of formula 2 ##STR9## wherein R.sub.1, R.sub.2 and R.sub.3 in formulas 1 and 2 are each independently H, a branched or non-branched, substituted or unsubstituted alkyl group, or an unsubstituted or substituted aryl group and phosgene in an amount whereby the molar ratio of phosgene to the compound of formula 2 is from 1.5:1 to 3:1 in which solvent the compound of formula 2 reacts with phosgene at a temperature maintained between 0.degree. and 15.degree. C. and a pH between 1 and 6;
Dependencies are inferred from the claim text.