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Abstract

A method is provided to hydrogenate a polymer containing ethylenic unsaturation comprising the steps of: providing a solution or suspension of the polymer containing ethylenice unsaturation with an amount of Group VIII metal alkoxide or carboxylate and metal alkyl hydrogenation catalyst effective to permit hydrogenation of the ethylenic unsaturation upon exposure to hydrogen; exposing the polymer solution or suspension to a hydrogen partial pressure for a time period sufficient to hydrogenate greater than about 90 percent of the ethylenic unsaturation; adding additional Group VIII metal alkoxide or carboxylate and metal alkyl hydrogenation catalyst to the polymer solution or suspension after greater than about 90 percent of the ethylenic unsaturation has been hydrogenated; mixing the hydrogenated polymer solution or suspension with the additional Group VIII metal alkoxide or carboxylate and metal alkyl hydrogenation catalyst with an aqueous solution of an acid; and separating a hydrogenated polymer solution or suspension that contains less than about 0.8 percent by weight water from the aqueous solution. The invention utilizes a surprising discovery that addition of the hydrogenation catalyst above that necessary or desirable for hydrogenation of ethylenic unsaturation results in improved separation of the catalyst metals, and the aqueous phase, from the polymer solution or suspension.

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First Claim