Metallocene Catalysts Used for the Hydrogenation of Polystyrene-b-Polybutadiene-b-Polystyrene Block Copolymers

Catalytic effectiveness of three metallocenes (Cp 2 Co, Cp 2 Ni, and Cp 2 TiCl 2 ), in the presence of various reducing agents ( n -butyllithium, phenyllithium, and triethylaluminum), have been studied for hydrogenating polystyrene- b -polybutadiene- b -polystyrene (SBS) thermoplastic elastomers. The CP 2 Co / n -butyllithium system was found the most active. A n -butyllithium to cobaltocene molar ratio of 1~2, a 15~25 kg/cm 2 H 2 pressure, and a minimal 80°C temperature were necessary in order to achieve a high extent of hydrogenation. UV spectroscopy of the catalyst system showed the formation of CpLi indicating that some Cp ligands in the original Cp 2 Co were displaced by n -butyllithium.