Comonomer Concentration In Feed Research Articles

Synthesis of Copolymers with Sterically Hindered and Polar Monomers

AbstractDifferent highly substituted C1 symmetric metallocenes have been investigated for the copolymerization of ethene and norbornene. The influence of the feed ratio and the polymerization temperature were varied to characterize the polymer by means of microstructure, thermal properties and catalysts activity. The bulky structured ligands of the catalysts lead to highly stereoregular copolymers with semi‐crystalline phases even at low norbornene incorporation. Two different allyl ethers (allyl ethyl and allyl propyl ether) have been used to copolymerize with ethene using metallocene catalyst system (rac‐[Me2Si(2‐Me‐4‐(1‐Ph)Ind)2]ZrCl2/MAO). In order to investigate the influence to ether incorporation to polymer properties, we have performed experiments varying comonomers concentration in feed, polymerization temperature and ratio Al(MAO)/Zr. The higher comonomer incorporation was followed by loss of cristallinity of the produced polymer. Additionally, the catalytic activity and melting point of the polymers also decrease with increase in comonomer concentration in feed.

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 metallocene catalyst system Cp2ZrCl2 /MAO was achieved. A reaction between the comonomer and MAO, prior to the copolymerisation, was used in order to protect, to some extent, the carboxylic group. The degree of MAO protection was 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 mole-ratio and polymerisation temperature on the copolymerisations, were investigated with respect to catalyst activity and to UA incorporation. Higher concentrations of UA in feed favour the incorporation rate but decrease the activity. The Al/Zr mole ratio shows a strong influence on activity, but not on the comonomer incorporation. Both the polymerisation activity and the UA incorporation rate present an optimal polymerisation temperature of around 40°C. DSC characterisation shows a decrease in the melting temperature of the polymers for increasing UA incorporations. Bimodal melting peaks, representative of polymer inhomogeneity, were observed for the highest UA incorporations.

The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler–Natta catalysts supported on MgCl 2(THF) 2

The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with α-olefin over vanadium (VOCl 3 and VCl 4) and titanium (TiCl 4) catalysts supported on MgCl 2(THF) 2 and activated by Et 2AlCl was studied. The results show that the introduction of a longer α-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of α-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer in the feed as well as the type of catalyst. The incorporation of α-olefin increases with the increase of the comonomer concentration in the polymerization feed and the comonomer reactivity decreases with the increase of the size of the α-olefin chain, especially in the case of comonomers longer than octene. It should be stressed, however, that both vanadium catalysts clearly demonstrate higher activity in the copolymerization process than their titanium counterpart and also produce copolymers with higher comonomer content. The density, crystallinity and melting temperature of the copolymers decrease with increase of the amount of the comonomer incorporated, but the type of the comonomer does not have a strong influence on these properties.