Making poly(alkylene carbonates) of controlled molecular weight
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United States of America Patent
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Jul 24, 1990
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N/A
app pub date -
Jun 8, 1989
filing date -
Jun 8, 1989
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Abstract
Poly(alkylene carbonates) of controlled molecular weight are made by copolymerizing carbon dioxide and one or more oxirane compounds using zinc polycarboxylate catalyst in the presence of a sterically hindered organic proton donor. The acidity of the donor is in the range of 3 to 20 pK.sub.a and the steric quality of the donor is such that it has a steric parameter (E.sub.s) of -0.38 or less. The molecular weight of the polymer can be regulated by altering the level of proton donor over a range which does not adversely affect catalyst productivity. Benzoic acid and phenol are examples of suitable proton donors. The preferred catalyst is one made from zinc oxide and a dicarboxylic acid, such as glutaric acid or adipic acid.
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