Process for producing polycarbonate
AssigneeMitsubishi Chemical Corporation
InventorsMichiaki Fuji, Shingo Namiki, Masaki Yamamoto
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Abstract
A subject for the invention is to provide a polycarbonate having excellent mechanical strength, heat resistance, a low refractive index, a large Abbe number, reduced birefringence, and excellent transparency. The invention relates to a polycarbonate characterized by being obtained by subjecting one or more dihydroxy compounds including a dihydroxy compound having at least one linking group —CH2—O— in the molecule thereof to melt polycondensation with a carbonic acid diester, and by having a reduced viscosity of from 0.40 dL/g to 1.70 dL/g and a formic acid content lower than 5 ppm by weight.
Claims36
A process for producing a polycarbonate, comprising subjecting one or more dihydroxy compounds comprising a dihydroxy compound having at least one linking group —CH2—O— in a molecule thereof to melt polycondensation with a carbonic acid diester in at least two serially arranged reactors to produce a polycarbonate, wherein, in at least one of the reactors, a difference between a temperature of a polymer and a temperature of a heating medium is regulated to 80° C. or smaller when the polycarbonate yielded has a reduced viscosity of 0.10 dL/g or lower, or to 60° C. or smaller when the polycarbonate yielded has a reduced viscosity exceeding 0.10 dL/g but not higher than 0.40 dL/g, or to 40° C. or smaller when the polycarbonate yielded has a reduced viscosity exceeding 0.40 dL/g.
A process for producing a polycarbonate by subjecting one or more dihydroxy compounds comprising a dihydroxy compound having at least one linking group —CH2—O— in a molecule thereof to melt polycondensation with a carbonic acid diester by heating with a heating medium, comprising
- carrying out a first-stage polycondensation, wherein a mixture of the dihydroxy compounds and the carbonic acid diester is fed in a molten state to a vertical reactor equipped with a vertical rotating shaft and a stirring blade attached to the vertical rotating shaft, and a polycondensation reaction is conducted at a temperature of 150° C. to 270° C. to obtain a polycarbonate having a reduced viscosity of 0.03-0.40 dL/g and
- carrying out a second-stage polycondensation, wherein the polycarbonate obtained in the first-stage polycondensation is fed to a horizontal stirring reactor which has a horizontal rotating shaft and mutually discontinuous stirring blades attached approximately perpendicularly to the horizontal rotating shaft and wherein when a length of the horizontal rotating shaft and a rotation diameter of the stirring blades are respectively expressed by L and D, then L/D is in a range of from 1 to 15, and a polycondensation reaction is conducted at a temperature of 210° C. to 270° C. to obtain a polycarbonate having a reduced viscosity of from 0.20 to 1.70 dL/g.
A polycarbonate obtained by a process comprising subjecting one or more dihydroxy compounds comprising a dihydroxy compound having at least one linking group —CH2—O— in a molecule thereof to melt polycondensation with a carbonic acid diester, and by having a reduced viscosity of from 0.40 dL/g to 1.70 dL/g and a formic acid content lower than 5 ppm by weight.
Dependencies are inferred from the claim text.