Salts of heterocyclic diols as catalysts for melt polycarbonate
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United States of America Patent
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Aug 19, 2003
Grant Date -
Jun 19, 2003
app pub date -
Oct 25, 2001
filing date -
Oct 25, 2001
priority date (Note) -
Expired
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Abstract
The present invention relates to a synthetic method in which one or more diaryl carbonates is reacted with one or more dihydroxy aromatic compounds in the presence of a transesterification catalyst under melt polymerization conditions to afford a product polycarbonate. The transesterifcation catalysts used according to the method of the present invention are alkali metal salts and alkaline earth metal salts of heterocyclic diols in combination with tetraalkylammonium or tetraalkylphosphonium compounds which serve as co-catalysts. The furan diol derivative dimethyl 3,4-dihydroxy-2,5-furandiacarboxylate disodium salt, structure IV, was shown to possess excellent activity as a transesterifcation catalyst for the preparation of polycarbonate under melt polymerization conditions. The catalysts employed according to the method of the present invention provide polycarbonates having substantial molecular weight (M.sub.n.about.8000-10000 daltons) and reduced levels of Fries rearrangement product relative to conventionally prepared melt polycarbonate having a similar molecular weight.
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