Ethylene Homo‐ and Copolymerization Using a Bis‐IndZrCl₂ Metallocene Catalyst: Structural Composition Distribution of the Copolymer

Abstract

A bis‐IndZrCl2 catalyst was synthesized and used for ethylene homo‐ and copolymerization. The activity of the catalyst increases with increasing Al/Zr ratio; optimum activity was reached at 60 °C. $\overline M _{\rm v}$ of the polymer decreased as the polymerization temperature increased; increasing reaction pressure increased both $\overline M _{\rm v}$ and catalyst activity. The copolymerization of ethylene with different α‐olefins was studied using the same catalyst system. The results indicate that under identical conditions there was a general decrease in the rate of polymerization as compared to the homopolymerization. The CCD and the lamellar thickness were investigated using DSC. The heterogeneity of the CCD increased with increasing comonomer content and molar mass.magnified image

Indirect Synthesis of Bis(2‐PhInd)ZrCl2 Metallocene Catalyst, Kinetic Study and Modeling of Ethylene Polymerization

“…It is obvious that MAO has three roles in the polymerization reaction. It removes adventitiously and impurities as a scavenger, alkylation, and ionizes the metal center to produce the active site [3,41]. As can be seen, by increasing the [Al]:[Zr] ratio up to 2333:1, the activity of the catalyst increases significantly.…”

“…After huge investment in research on metallocene catalysts, these catalysts became more important by generating metallocene-based polyolefins [1][2][3][4]. Modification of the metallocene's structure has led to improvement of productivity and to attainment of predefined polymer microstructure.…”

Complex interplay of short- and long-chain branching on thermal and rheological properties of ethylene/α-olefin copolymers made by metallocene catalysts with oscillating ligand structure

“…Toluene (450 ml) was introduced in a 1L Büchi reactor and dissolved air was removed by several times saturation and evacuation by nitrogen followed by several round of similar cycles using ethylene gas. Comonomer, MAO ([Al]/[Zr]=4000:1) and catalyst solution (1 μmol) were introduced respectively, and reaction temperature and pressure was increased to the set points (60 °C and 4 bar, respectively) [2,3]. The propylene comonomer was introduced continuously as determined in Table 1, but the liquid 1-hexene and 1-octene comonomers were added batch-wise in the beginning of polymerizations as mentioned.…”

“…The diverse comonomer affinities should be more evident in thermal behavior. Melting (T m ) and crystallization (T c ) temperatures are dictated by the length of ethylene sequence and are therefore affected by the introduction of comonomer [2,3]. The crystallization and melting peaks of the three synthesized sets of samples are compared in Figure 2 and the corresponding T c and T m values are listed in Table 1.…”

“…The catalytic copolymerization of ethylene with α-olefins is a typical way of introducing shortchain branching (SCB) in the polymer molecules and, thereby, causing significant changes in the physical polymer properties, such as melting and glass transition temperatures, mechanical, and optical properties, all of which define the type and useful range of their application [1][2][3]. New generations of catalysts and technologies are leading to new families of polyethylenes due to the ability of these systems to introduce controlled amounts of α-olefins into polyethylene with multifarious distribution patterns [4][5][6][7][8][9].…”