Polymerisation of ethene and propene with heterogeneous Ziegler Natta catalysts. Transient comonomer effects on polymerisation kinetics

摘要

This thesis investigates the immediate effect of a series of comonomers on the active center and the polymerization kinetics by using a polymerization apparatus which allows detailed continuous monitoring of the monomer consumption and by injecting the comonomers during polymerization. The resulting polymers are characterised by differential scanning calorimetry, infrared spectroscopy and extraction with heptane. Two catalysts are used: a ball-milled catalyst containing ethyl benzoate and a precipitated catalyst containing di-iso-butyl phthalate, both MgCl(sub 2) supported TiCl(sub 4) catalysts activated by triethylaluminium. The polymerizations are performed in heptane slurry at 50 (sup o)C and 1 atmosphere. The effect of a comonomer injection can be divided into four stages: The first and the second stage, i.e. the injection shock and the injection peak, are injection artefacts. The third stage is the immediate chemical response to the comonomer. The fourth stage is the long term response of the system to the comonomer and may be of a physical or a chemical nature. Propene injections cause a permanent increase in the polymerization rate of ethene. Propene is incorporated into the polyethene. Ethene injections are followed by a temporary increase in the polymerization rate of propene, and seems to initiate new active sites rather than reactivate dormant sites. Cyclopentene and several other substances adsorb on the active sites which are polymerizing propene but do not seem to incorporate into the polypropene. The activity decrease in the polymerization rates of propene and ethene after injection of a comonomer are given. 109 refs., 68 figs., 57 tabs.