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Kinetic studies of the injection of comonomers during polymerization of ethene and propene with MgCl 2 ‐supported Ziegler‐Natta catalysts
Author(s) -
Wester Thale Sofie,
Ystenes Martin
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980524
Subject(s) - comonomer , propene , cyclopentene , polymerization , chemistry , polymer chemistry , ziegler–natta catalyst , heptane , active center , catalysis , styrene , photochemistry , copolymer , organic chemistry , polymer
The effects of injecting ethene, propene, 1‐hexene, 2‐methylpropene, 3,3‐dimethyl‐1‐butene, cis ‐2‐butene, trans ‐2‐butene, 2,3‐dimethyl‐2‐butene, cyclopentene, styrene, 1,3‐butadiene and 1,4‐pentadiene during polymerizations of ethene and propene have been investigated. Catalysts used were a supported MgCl 2 /EB/TiCl 4 ballmilled catalyst and precipitated MgCl 2 /2‐EH/TiCl 4 /DIBP catalysts activated with triethylaluminium in presence of EB. (EB = ethyl benzoate, 2‐EH = 2‐ethylhexanol, DIBP = diisobutyl phthalate). The polymerizations were performed at 50°C, in a heptane slurry at 1 atm (1.00 · 10 5 Pa) total pressure. The instantaneous polymerization rate was observed by continuous monitoring of the monomer consumption, the time resolution of the measurements being less than one second. Two different kinetic effects can be observed after injection of the comonomer. First there is an immediate rate change, usually a rate reduction. Then a secondary effect may follow, which is a slow, and sometimes significant and persistent, activation. The two effects obviously have different causes, and for none of these we found single causes that can explain all the observations. The strongest immediate effect was observed after addition of dienes and indicates a direct association of the comonomer to the active center. A marked nonlinearity in the response may hint to inhomogeneity in the structural environment of the active centers. Addition of α‐olefins during ethene polymerization gave the strongest secondary effect. In general the immediate effects were stronger during propene polymerization than during the polymerization of ethene. A significant difference in the effects of cis ‐2‐butene and trans ‐2‐butene in the polymerization of propene indicates that steric effects may be important.