Enhanced hydrogenation catalyst removal from block copolymers by reduction in polymer cement viscosity by increasing the vinyl content of the block copolymers

Abstract

In a process for producing hydrogenated block copolymers of conjugated dienes and/or vinyl aromatic hydrocarbons which comprises anionically polymerizing the monomers in an inert hydrocarbon solvent in the presence of an alkali metal initiator whereby a polymer cement is produced, contacting the cement with hydrogen under hydrogenation conditions in the presence of a hydrogenation catalyst, and then removing the hydrogenation catalyst residue by washing the polymer cement with water or an aqueous acid, the improvement which comprises reducing the viscosity of the polymer cement by polymerizing the block copolymer under conditions such that the vinyl content of the polymer produced in the polymerization step is in the range from 45 to 80 percent by weight.

We claim:  
     
       1. In a process for producing hydrogenated block copolymers of conjugated dienes and/or vinyl aromatic hydrocarbons which comprises anionically polymerizing the monomers in an inert hydrocarbon solvent in the presence of an alkali metal initiator whereby a polymer cement is produced, contacting the cement with hydrogen under hydrogenation conditions in the presence of a hydrogenation catalyst, and then removing the hydrogenation catalyst residue by washing the polymer cement with water or an aqueous acid, the improvement which comprises reducing the viscosity of the polymer cement by polymerizing the block copolymer under conditions such that the vinyl content of the polymer produced in the polymerization step is in the range from 45 to 80 percent by weight.