Gel-free process for making hydrogenated functionalized anionically polymerized polymers

Abstract

This invention relates to a gel-free process for making hydrogenated functionalized polymers that mitigates the problem of ionic gel. When multi-alkali metal initiators are used to make these polymers anionically, the process comprises anionically polymerizing at least one monomer with a multi-alkali metal initiator, usually a lithium alkyl, in a hydrocarbon solvent, capping the polymer by adding to the polymer a capping agent that reacts with the ends of the polymer chains such that strongly associating chain ends are formed wherein a strongly associating polymer gel is formed, adding a trialkyl aluminum compound to the polymer gel, whereby the gel dissipates, optionally terminating the polymerization by addition of an alcohol, washing the polymer with aqueous acid, preferably aqueous mineral acid, most preferably phosphoric acid, wherein there is at least one mole of phosphoric acid per mole of alkali metal and at least three moles of phosphoric acid per mole of aluminum, and hydrogenating the polymer with a hydrogenation catalyst. In a second embodiment, the present invention relates to a process for making such polymers which comprises anionically polymerizing them as described and adding a trialkyl aluminum compound prior to the addition of the functionalizing agent and washing the product prior to hydrogenation as described above. In the first embodiment, a gel is formed and then removed. In the second embodiment, the gel never is formed because of the presence of the trialkyl aluminum compound.