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Continuous production of polycarbonates

  • US 5,235,026 A
  • Filed: 05/29/1992
  • Issued: 08/10/1993
  • Est. Priority Date: 06/04/1991
  • Status: Expired due to Term
First Claim
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1. In the two phase interfacial process for the continuous production of polycarbonate from diphenols and phosgene and the optional chain terminators, catalysts and branching agents in a mixture of an aqueous alkaline phase and an organic solvent phase wherein organic phase comprise phosgene and a solvent for polycarbonate, and wherein aqueous phase contains water and a mixture of alkali metal hydroxide diphenols and the optional chain terminators and branching agents and wherein said organic phase and said aqueous phase are continuously combined in a tube containing a mixer the improvement comprising(i) limiting the amount of said alkali metal hydroxide in said aqueous phase to the minimum amount necessary to cause dissolution of said diphenols and the optional chain terminators and branching agents at the prevailing reaction temperatures and pressures,(ii) adjusting the volume ratio of said organic phase to said aqueous phase to form a water-in-oil emulsion during the subsequent phosgene reaction where between 0.5 and 0.7 mol of phosgene is reacted per mol of phenolic OH,(iii) continuously monitoring the concentration of the formed chlorocarbonic acid ester and(iv) introducing additional alkali metal hydroxide at, or shortly after reaching, the maximum concentration of chlorocarbonic acid ester so that an OH concentration of 0.1 to 0.5% by weight is established in the aqueous phase, and(v) condensing the oligomer thus produced with the addition of at least one catalyst to form high molecular weight polycarbonate.

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