Method for polymerizing aromatic bischloroformate composition to polycarbonate
First Claim
1. A method for preparing a linear polycarbonate which comprises the steps of:
- (A) preparing a bischloroformate oligomer composition by passing phosgene into a heterogeneous mixture consisting essentially of water, a substantially inert, substantially water-insoluble organic liquid and at least one dihydroxyaromatic compound in a tank reactor, and simultaneously introducing an aqueous alkali or alkaline earth metal base solution at a rate to maintain the aqueous phase of said mixture at a pH in the range of 8-11;
the temperature of said mixture being maintained in the range of about 15°
-50°
C., the volume ratio of aqueous to organic phase at the conclusion of phosgenation being in the range of about 0.4-1.0;
1 and the total amount of phosgene employed being at least about 1.1 mole per mole of dihydroxyaromatic compound;
said mixture being agitated under conditions sufficient to prevent segregation of the aqueous and organic liquid phases;
(B) passing an interfacial polycarbonate formation catalyst into a mixture of said bischloroformate composition, water and a substantially inert, substantially water-insoluble organic liquid in a tank reactor, with effective agitation, and simultaneously introducing an aqueous alkali or alkaline earth metal base solution at a rate to maintain the aqueous phase of said mixture at a pH in the range of about 10-14, the rate of catalyst addition being adjusted to effect polycarbonate formation under controlled conditions; and
(C) recovering said linear polycarbonate.
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Abstract
Bischloroformate oligomer compositions are prepared by passing phosgene into a heterogeneous aqueous-organic mixture containing at least one dihydroxyaromatic compound, with simultaneous introduction of a base at a rate to maintain a specific pH range and to produce a specific volume ratio of aqueous to organic phase. By this method, it is possible to employ a minimum amount of phosgene. The reaction may be conducted batchwise or continuously. The bischloroformate composition may be employed for the preparation of cyclic polycarbonate oligomers or linear polycarbonate, and linear polycarbonate formation may be integrated with bischloroformate composition formation in a batch or continuous process.
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Citations
10 Claims
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1. A method for preparing a linear polycarbonate which comprises the steps of:
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(A) preparing a bischloroformate oligomer composition by passing phosgene into a heterogeneous mixture consisting essentially of water, a substantially inert, substantially water-insoluble organic liquid and at least one dihydroxyaromatic compound in a tank reactor, and simultaneously introducing an aqueous alkali or alkaline earth metal base solution at a rate to maintain the aqueous phase of said mixture at a pH in the range of 8-11;
the temperature of said mixture being maintained in the range of about 15°
-50°
C., the volume ratio of aqueous to organic phase at the conclusion of phosgenation being in the range of about 0.4-1.0;
1 and the total amount of phosgene employed being at least about 1.1 mole per mole of dihydroxyaromatic compound;
said mixture being agitated under conditions sufficient to prevent segregation of the aqueous and organic liquid phases;(B) passing an interfacial polycarbonate formation catalyst into a mixture of said bischloroformate composition, water and a substantially inert, substantially water-insoluble organic liquid in a tank reactor, with effective agitation, and simultaneously introducing an aqueous alkali or alkaline earth metal base solution at a rate to maintain the aqueous phase of said mixture at a pH in the range of about 10-14, the rate of catalyst addition being adjusted to effect polycarbonate formation under controlled conditions; and (C) recovering said linear polycarbonate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification