Pyridazine-modified ziegler-natta catalyst system
A modified Ziegler-Natta catalyst system, a method for preparing the catalyst system, and a process for polymerizing an olefin in the presence of the catalyst system are disclosed. The catalyst system comprises a titanium or vanadium compound, an aluminum compound, and a pyridazine. Improved properties such as increased molecular weight and narrowed molecular weight distribution are obtained.
1 - 10 . (canceled)
11 . A process for making polyethylene, comprising polymerizing ethylene and an olefin selected from the group consisting of 1-butene, 1-hexene, and 1-octene in the presence of a modified Ziegler-Natta catalyst system comprising: (a) a titanium or vanadium compound; (b) an aluminum compound selected from the group consisting of trialkyl aluminums, dialkyl aluminum halides, alkyl aluminum dihalides, and combinations thereof; and (c) a pyridazine having the structure:
wherein each R is independently H, Cl, Br, or C 1 -C 16 hydrocarbyl and wherein two adjacent R groups may be joined together to form a ring; and
wherein the weight-average molecular weight (M w ) of the polyethylene is increased compared with that of a polyethylene produced using the catalyst system without the pyridazine.
12 . The process of claim 11 wherein the wherein the titanium or vanadium compound is selected from the group consisting of titanium halides, titanium alkoxides, vanadium halides, vanadium oxyhalides, vanadium alkoxides, and combinations thereof.
13 . The process of claim 11 wherein each R in the pyridazine is hydrogen.
14 . The process of claim 11 wherein the pyridazine is benzo[c]cinnoline.
15 . The process of claim 11 wherein the molar ratio of pyridazine to titanium or vanadium is from 50:1 to 1:1.
16 . The process of claim 11 wherein the catalyst is made by a method comprising: (a) reacting a pyridazine with an aluminum compound selected from the group consisting of trialkyl aluminums, dialkyl aluminum halides, alkyl aluminum dihalides, and combinations thereof; and (b) contacting the reaction mixture from step (a) with a titanium or vanadium compound.