Metallocene-catalysed copolymerisation of ethylene with 10-undecenoic acid: The effect of experimental conditions

The copolymerisation of ethylene with 10-undecenoic acid (UA) using the met allocene catalyst system Cp2Zr Cl-2/MAO was achieved. A reaction between th e comonomer and MAO, prior to the copolymerisation, was used in order to pr otect, to some extent, the carboxylic group. The degree of MAO protection w as found to be dependent on the Al/UA ratio used in the precontact mixture. The interaction between the two compounds was investigated by means of NMR spectroscopy. The influences of comonomer concentration in feed, Al/Zr mol e-ratio and polymerisation temperature on the copolymerisations, were inves tigated with respect to catalyst activity and to UA incorporation. Higher c oncentration of UA in feed favour the incorporation rate but decrease the a ctivity. The Al/Zr mole ratio shows a strong influence on activity, but not on the comonomer incorporation rate present an optimal polymerisation temp erature of around 40 degreesC. DSC characterisation shows a decrease in the melting temperature of the polymers for increasing UA incorporations. Bimo dal melting peaks, representative of polymer inhomogeneity, were observed f or the highest UA incorporations.