The present invention includes a bimodal polyethylene polymerization
process wherein metallocene catalyst to is used to adjust the hydrogen
response of a Ziegler-Natta catalyst. The polymerization may be carried
out in a single reactor or in two or more reactors in series, preferably
two or more continuously stirred tank reactors in series. In an
embodiment having two or more reactors, the Zeigler-Natta catalyst is
added to a first reactor and the metallocene catalyst is added to a
downstream reactor. In another embodiment having two or more reactors,
the Zeigler-Natta catalyst and metallocene catalyst are added to the same
reactor, preferably an upstream reactor. A preferred Zeigler-Natta
catalyst comprises TiCl.sub.4, and a preferred metallocene catalyst
comprises bis(cyclopentadienyl) titanium dichloride.