Low Molecular Weight Ethylene/Propylene Copolymers. Effect of Process Parameters on Copolymerization with Homogeneous Cp2ZrCl2 Catalyst

Pietikäinen, Pirjo; Seppälä, Jukka V.

doi:10.1021/ma00084a007

Cited by 35 publications

(16 citation statements)

References 5 publications

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“…17 (c) The chain termiwith 1-hexene comonomer. 18 nation reaction by b-elimination is a mechanism related with the control of the polymer molecular weight. The b-agostic elimination CONCLUSIONS is more favored in the ethylene/1-hexene copolymer (E a Å 4.7 kcal/mol) against the eth-1.…”

Section: Ethylene/1-hexene Copolymerizationmentioning

confidence: 99%

“…The geometries obtained with the PM3(tm) ylene homopolymer (E a Å 6.2 kcal/mol), in method for reactants, transition states and agreement with the lower molecular weight products for the first ethylene insertion are experimentally found for ethylene/1-hexene in good agreement with those obtained with copolymers compared to ethylene homopolyother more sophisticated methods such as mers. 18 HF, MP2, and DFT. In fact, the values ob-3.…”

Section: Ethylene/1-hexene Copolymerizationmentioning

confidence: 99%

“…18 the advantage that they allow quantum chemical treatment of systems consisting of several tenths of atoms without large computational resources.…”

mentioning

confidence: 99%

See 2 more Smart Citations

A theoretical study of the comonomer effect in the ethylene polymerization with zirconocene catalytic systems

Cruz

Muoz-Escalona²,

Martínez‐Salazar

1998

J. Polym. Sci. A Polym. Chem.

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Section: Ethylene/1-hexene Copolymerizationmentioning

confidence: 99%

Section: Ethylene/1-hexene Copolymerizationmentioning

confidence: 99%

See 1 more Smart Citation

A theoretical study of the comonomer effect in the ethylene polymerization with zirconocene catalytic systems

Cruz

Muoz-Escalona²,

Martínez‐Salazar

1998

J. Polym. Sci. A Polym. Chem.

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“…Usually, the molecular weight of copolymers decreases with increasing comonomer contents. Actually, decreasing molecular weight of ethylene/propylene copolymers with increasing propylene feed ratio with rac-Et(Ind) 2 ZrCl 2 / MAO 14) or Cp 2 ZrCl 2 /MAO 15) catalysts has already been reported. For ethylene/propylene copolymerization with rac-Me 2 Si(H 4 Ind) 2 ZrCl 2 /MAO catalyst, minimum molecular weight was observed at about 80% of propylene in the copolymer 16) .…”

Section: Ethylene/1-hexene Copolymerization With Ph 2 C(cp)(flu)zrcl mentioning

confidence: 96%

Novel zirconocene catalysts for the production of high molecular weight LLDPE in high-temperature polymerization

Yano¹,

Sone

Hasegawa

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: Ethylene polymerization and ethylene/a-olefin copolymerization were conducted using diphenylmethylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride (Ph 2 C(Cp)(Flu)ZrCl 2 ) as a catalyst activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH N B(C 6 F 5 ) 4 )/triisobutylaluminium (i-Bu 3 Al) at high temperature and different ethylene pressure. This catalyst produces high molecular weight polyethylene with high activity. The molecular weight of the copolymers hardly decreases with increasing amount of comonomer in the feed. This is attributed to the control of b-H transfer from the propagating chain containing primary inserted comonomer. The occurrence of inner trisubstituted double bonds was confirmed. These bonds are probably formed by dehydrogenation reactions after b-H transfer from the propagating chain followed by ethylene insertion. Therefore, this reaction might play an important role in the production of high molecular weight ethylene/1-hexene copolymers at high temperature. At high ethylene pressure, isomerization reactions from inserted ethylene or primary inserted a-olefin as terminal units, which were observed under low ethylene pressure, can be controlled at low level.

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“…Catalyst performances at high temperature are therefore important. It is well known that the molecular weights of the copolymers decrease with increasing polymerization temperature 3) . Thus catalysts that produce high molecular weight copolymers with good activity even at high polymerization temperature are needed for the production of LLDPE in the solution and high-pressure process.…”

Section: Introductionmentioning

confidence: 99%

Homo- and copolymerization of ethylene at high temperature with cationic zirconocene catalysts

Yano¹,

Sone²,

Yamada³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: Homo-and copolymerization of ethylene with 1-hexene were conducted at different temperature and ethylene pressure with several zirconocenes activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH N B(C 6 F 5 ) 4 )/triisobutylaluminium (i-Bu 3 Al) to study the effect of ligand structure and polymerization conditions on catalytic activity, molecular weight and chain transfer reactions. At high temperature and low ethylene pressure, rac-ethylene(bisindenyl)zirconium dichloride (rac-Et(Ind) 2 ZrCl 2 ) activated with Me 2 PhNH N B(C 6 F 5 ) 4 /i-Bu 3 Al initially gives a highly active catalyst that is rapidly deactivated. trans-Vinylene double bonds, which were not formed at low temperature, were detected in polyethylene synthesized at high temperature and low ethylene pressure. They reasonably arise from b-H transfer after isomerization reaction. The molecular weight of ethylene/1-hexene copolymers decreases with increasing 1-hexene feed, followed by the formation of vinylidene end groups. This reveals that b-H transfer from propagating chains containing primary inserted 1-hexene as a terminal unit is predominant. This reaction is influenced by the ligand structure. At high temperature and high ethylene pressure, trans-vinylene and vinylidene contents decrease and the vinyl content increases, indicating that the high ethylene pressure controls b-H transfer after isomerization reaction.

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Low Molecular Weight Ethylene/Propylene Copolymers. Effect of Process Parameters on Copolymerization with Homogeneous Cp2ZrCl2 Catalyst

Cited by 35 publications

References 5 publications

A theoretical study of the comonomer effect in the ethylene polymerization with zirconocene catalytic systems

A theoretical study of the comonomer effect in the ethylene polymerization with zirconocene catalytic systems

Novel zirconocene catalysts for the production of high molecular weight LLDPE in high-temperature polymerization

Homo- and copolymerization of ethylene at high temperature with cationic zirconocene catalysts

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