The characteristic features of LLDPE polymerization with ZN catalyst are the time drift effect during polymerization and the bending effect when trying to decrease density of the copolymer by adding more comonomer to the polymerization. The time drift in LLDPE polymerization is revealed by a constant decrease of comonomer incorporation during polymerization time. The bending is revealed by difficulties in lowering the density of LLDPE material below the density of 920 kg/ m 3 . With increasing comonomer content during polymerization, the density does not decrease, but the soluble fraction increases. To try to observe if these phenomena are connected, two types of catalysts, SiO 2 supported and precipitated MgCl 2 ZN catalysts, were studied. A short time (10 min) and an extended time (60 min) copolymerization test series where the polymerizations were performed in the presence of a gradually increasing comonomer amount. Both catalysts show a strong bending when density is presented as a function of 1-hexene both in 10-and 60-min polymerization, indicating no connection between time drift and bending. The density, melting point, and crystallinity results all indicate that both catalysts are making similar copolymer material with identical chemical composition distribution.

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system. Ziegler-Natta (ZN) catalysts generally dominate in PE and PP production, but they have their limitations when higher α-olefins are used for copolymerization. The disadvantages of ZN systems in this case are uneven and limited comonomer incorporation. The comonomer is incorporated randomly along the polymer chain, with a tendency to higher comonomer concentrations in the low-molecular weight fractions and less in the high molecular weight part. Further, ZN catalysts lead to broad molecular weight distributions (MWDs), which may be problematic with respect to the amount of extractable material.Higher-branched low molecular weight parts lead to a faster degradation which reduces the durability of the polymer material. Therefore, polyolefines with a homogeneous comonomer incorporation show beneficial properties concerning tensile strength, film transparency, and environmental stress cracking, which results in advantages for many applications, such as films and pipes. Metallocenes can tackle these requirements, as they can polymerize longer α-olefins (up to C26), yield narrow and homogeneous MWDs, and support comonomer incorporation of up to 20%. The demand for metallocene-based polyolefins, especially PE, is increasing significantly. The Various MgCl 2 -supported Ziegler-Natta (ZN) catalysts are synthesized with the intention to influence polymerization performance and 1-butene incorporation in an ethylene copolymer. Modifications are introduced during different steps in the synthesis process, namely support preparation, titanation, and catalyst workup. While multiple different effects are observed upon modification, heat treatment during titanation shows the greatest impact. Increasing the heat-treatment temperature increases polymerization activity. More importantly, the 1-butene distribution can be shifted toward a more homogeneous profile. The amount of 1-butene incorporated is similar to both for short-and for very long-chain molecules. This behavior has so far been known only from metallocene-based polyethylene and suggests that active sites are distributed more homogeneously in the ZN catalyst.

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