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Titolo:
Triisobutylaluminum as cocatalyst for zirconocenes. II. Triisobutylaluminum as a component of a cocatalyst system and as an effective cocatalyst for olefin polymerization derived from dimethylated zirconocenes
Autore:
Panin, AN; Dzhabieva, ZM; Nedorezova, PM; Tsvetkova, VI; Saratovskikh, SL; Babkina, ON; Bravaya, NM;
Indirizzi:
Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region, Russia Russian Acad Sci Chernogolovka Moscow Region Russia 142432 Region, Russia Russian Acad Sci, NN Semenov Chem Phys Inst, Moscow 117977, Russia RussianAcad Sci Moscow Russia 117977 m Phys Inst, Moscow 117977, Russia
Titolo Testata:
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
fascicolo: 11, volume: 39, anno: 2001,
pagine: 1915 - 1930
SICI:
0887-624X(20010601)39:11<1915:TACFZI>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
PROPYLENE POLYMERIZATION; ELASTOMERIC POLYPROPYLENE; ETHYLENE POLYMERIZATION; PROPENE POLYMERIZATION; GROUP-4 METALLOCENES; CATALYST SYSTEMS; COMPLEXES; KINETICS; CATION; METAL;
Keywords:
metallocene catalysts; ethylene polymerization; propylene polymerization; perfluorophenyl borates; trialkylaluminums; activation; active site; reaction parameters;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
52
Recensione:
Indirizzi per estratti:
Indirizzo: Bravaya, NM Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region, Russia Russian Acad Sci Chernogolovka Moscow Region Russia 142432 ia
Citazione:
A.N. Panin et al., "Triisobutylaluminum as cocatalyst for zirconocenes. II. Triisobutylaluminum as a component of a cocatalyst system and as an effective cocatalyst for olefin polymerization derived from dimethylated zirconocenes", J POL SC PC, 39(11), 2001, pp. 1915-1930

Abstract

Bn investigation of the catalytic behavior of the dimethylated zirconocenes Me2SiCp*(NBuZrMe2)-Bu-t [Cp* C-5(CH3)(4); 1Me], Me2SiCp2ZrMe2 (2Me), Cp2ZrMe2 (3Me) Ind(2)ZrMe(2) (4Me), Me(2)SiInd(2)ZrMe(2) (5Me), Et(2-MeInd)(2)ZrMe2 (6Me), and Me2Si(2-MeInd)(2)ZrMe2 (7Me) with the combined activator triisobutylaluminum (TIBA)/CPh3B(C6F5)(4) (Al/Zr = 250; B/Zr = 1) in ethylenepolymerizations at increased monomer pressures (5-11 bar, 30 degreesC) wascarried out. Sterically opened zirconocenes in ternary catalysts gave riseto active species effective in the formation of low molecular weight polyethylenes (PEs). These active species tended to increase the PE molecular weight [1Me (2100) < 2Me (20,000) < 5Me (89,000) < 3Me (94,500)] under similar conditions. PE obtained with 4Me showed a bimodal gel permeation chromatography curve with a 64% peak area [weight-average molecular weight (M-w) = 43,000] and a 36% peak area (M-w = 255,000). The increase in sterical demands from the zirconocenes was also demonstrated by the reduction of the chain transfer to monomer, the reinsertion of vinyl-ended PE chains, and their ability for isomerization. These reactions were most pronounced for the zirconocenes 1Me and 2Me. The active species responsible for the formation of low molecular weight PEs deactivated quickly. The zirconocenes 6Me, 7Me, and (2-PhInd)(2)ZrMe, (8Me) bearing substituent at the 2-position of the indenyl ring was activated with TIBA alone, yielding active species effective in ethylene and propylene polymerizations. PEs formed with 6Me-8Me complexesactivated with TIBA had high molecular weights. An increase in the Al/Zr ratio in the catalytic system 8Me/TIBA from 50 to 300 led to an enhancement of the molecular weight of polypropylene (PP) samples from oligomeric products to an viscosity-average molecular weight of 220,000. The increase in the molecular weights of PPs with an increase in the propylene concentration was also observed. An analysis of the catalytic performance of the 8Me/TIBAsystem showed first-order dependency of the initial polymerization rates on the TIBA concentration and close to second-order dependency on propylene. The second-order dependency on the monomer concentration is explained in terms of the monomer participation in the initiation step of the polymerization reaction. (C) 2001 John Wiley & Sons, Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 31/10/20 alle ore 03:41:09