Use of hydrogen and an organozinc compound for polymerization and polymer property control

摘要

Methods of controlling polymerization reactions using a synergistic amount of hydrogen and an organozinc compound are disclosed. The resulting polymers have lower molecular weights and higher melt flow indices.

主权项

1. A method of controlling a polymerization reaction in a polymerization reactor system, the method comprising:
(i) introducing a transition metal-based catalyst composition, ethylene, and an olefin comonomer into a polymerization reactor within the polymerization reactor system, wherein the transition metal-based catalyst composition comprises (a) a transition metal compound comprising chromium; (b) an activator-support comprising a solid oxide treated with an electron-withdrawing anion; and (c) a co-catalyst comprising an organoaluminum compound; (ii) contacting the transition metal-based catalyst composition with ethylene and the olefin comonomer under polymerization conditions to produce an ethylene polymer; and (iii) introducing a synergistic amount of hydrogen and an organozinc compound into the polymerization reactor system to increase a melt index (MI) of the ethylene polymer to within a range from about 1 to about 20 g/10 min;wherein:
the organozinc compound comprises diethylzinc; the olefin comonomer comprises 1-butene, 1-hexene, 1-octene, or a mixture thereof; and the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.