Two-step process for the preparation of a (co)polycarbonate by transesterification
AssigneeDaicel Chemical Industries, Ltd.
InventorsYasuhiro Oshino, Tatsuya Kanno
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Abstract
A process for the preparation of a (co)polycarbonate having an excellent hue, heat resistance, residence to hydrolysis and impact resistance by transesterification with the use of an aparatuses of a low price. In the first step, a dihydroxy compound is reacted with a carbonic diester in a reactor having a surface area contacting the dihydroxy compound and the carbonic diester, a made of a material containing iron in an amount of 20% by weight or less, to give a prepolymer and, in the second step, melt-polycondensing the prepolymer in a reactor other than the reactor used in the first step.
Claims3
In a process for the preparation of (co)polycarbonate by polycondensing a dihydroxy compound with a carbonic diester, the improvement which comprises (1) a first step conducted by feeding said dihydroxy compound, carbonic diester and a transesterification catalyst into a first reactor, the surface area which is made of a material containing iron in an amount of 20% by weight or less, wherein the temperature is maintained from 60.degree. to 300.degree. C. and the pressure is maintained at normal pressure to 0.1 Torr;
- and the molar ratio of carbonic diester to dihydroxy compound is 1.01 to 1.05 mol, to form a prepolymer;
- (2) a second step which comprises melt-polycondensing said prepolymer in a second reactor, the surface area which is made of a material containing iron in an amount greater than 20% by weight, in the presence of a catalyst selected from the group consisting of a boric acid salt or a nitrogen containing basic compound, wherein the second step is conducted at a temperature of from 200.degree. to 310.degree. C., a pressure of up to 10 Torr and such as to limit the phenols to 10,000 ppm or below.
Dependencies are inferred from the claim text.