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Abstract

This invention provides an improvement in anionic polymerization processes which comprise both a batch polymerization step to form and partially grow living polymer chains and a subsequent continuous or semi-continuous step in which growth of the chains is continued. For purposes of this improvement, the transition to the continuous or semi-continuous step takes place before the molar concentration of monomer in the batch polymerization step is depleted to a level below that of the living chains. Anionic polymerization processes are recognized as particularly useful for the production of polymers having narrow molecular weight distributions. Practice under the invention is found to enhance the narrow distribution of the polymer product by controlling thermal die-out of chains which has occurred in conventional processes during the transition from batch to continuous or semi-continuous polymerization steps.

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First Claim