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Molecular weight and molecular weight distribution control in HDPE with VOCl 3 ‐based Ziegler—Natta catalysts
Author(s) -
Mortimer George A.
Publication year - 1976
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1976.070200105
Subject(s) - alkoxide , molar mass distribution , catalysis , polymerization , natta , polymer , ethylene , polyethylene , materials science , polymer chemistry , high density polyethylene , alcohol , hydrogen , chemistry , organic chemistry
Some characteristics of alkoxylated catalysts derived from VOCl 3 and trialkylaluminum compounds have been examined for ethylene polymerization. Specifically studied were catalysts resulting from reaction of VOCl 3 with either an alcohol or an alkylaluminum alkoxide, or both, prior to reduction with a trialkylaluminum compound (R 3 Al). Although the two methods of preparing alkoxylated catalysts did not give identical results, certain overall generalizations can be drawn. In general, as the alkoxide content was increased, the molecular weight distribution was narrowed (by a simultaneous increase in M̄ n and decrease in M̄ w ), polymerization rate was decreased, and the polymer melt index increased at a constant hydrogen level. Alkoxides had a negative effect on rate which could largely be overcome by raising the R 3 Al/V ratio or using continuous addition of R 3 Al. By suitably adjusting the alkoxide and hydrogen amounts, the complete range of molecular weights and molecular weight distribution of current commercial HDPE products can be made.