| abstract |
This invention is a process for the selective hydrogenation of block copolymers having at least one poly(vinyl aromatic) block and at least one poly(conjugated diene) block which comprises contacting the block copolymers with hydrogen in the presence of a hydrogenation catalyst composition which comprises: n a) a metal compound cation of the formula (A)(E)M(R 4 )! + wherein M represents titanium, zirconium, or hafnium, A and E each represent ligands with structure I or II ##STR1## in which R 1 independently represents the same or different hydrocarbyl groups optionally containing heteroatoms, and R 3 independently represents the same or different hydrocarbonyl groups optionally containing heteroatoms, or a halide, and in which R 1 and R 3 may be shared between A and E to provide a bridge, wherein m is an integer from 0-5, p is an integer from 0-4, and q is an integer from 0-3, wherein R 4 represents hydrogen or hydrocarbyl group optionally containing heteroatoms, with the proviso that if A and E are both ligands with the same structure, at least one of m, p or q is at least 1, and n b) a non-coordinating stable anion. |