Polimerização de etileno com zirconoceno-mao suportado em peneiras moleculares

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

In this work, it was studied the polymerisation of ethylene catalysed by bis- ciclopentadienilzirconium(IV) dichloride supported in three molecular sieves (Zeolite Y, AlPO-VPI-5 and MCM-41). The zirconocene (Cp2ZrCI2) it was prepared by the reaction of the cyclopentadienylsodium with zirconium(IV) chloride, in tetrahydrofuran. The molecular sieves were synthesised in agreement with method described in the literature. The zeolite Y was donated by Degussa and used as received. The catalyst were prepared by stirring the molecular sieves and MAO in toluene for 4 to 20 h, filtering and washing with toluene. The slurry obtained was dried in vacuum (10 mm Hg) and the resulting solid impregnated with bis-cyclopentadienylzirconium(IV) dichloride, under vigorous stirring in toluene. The catalyst was then washed and dried in vacuum. Zr contents of the supported catalyst were determined with an ICP-OES spectrometer (Perkin Elmer). Viscosity-average molecular weights (Mv) of the polymers were measured in decalin at 135°C. The thermal characteristics of the polymers were examined using a DSC 4 ((Perkin Elmer) with a heating rate of 20°C/min. Melting points (m.p.) are related to the 2nd heating process. The polymerisation experiments were carried out in a 1 L Büchi autoclave at 50-80°C and 1-6 bar of ethylene using 50-100 mg of catalyst and 0,5-2,0 mL of the MAO (10% in toluene) in 200 mL of toluene. With heterogenization of Cp2ZrCl2 on molecular sieves, the amounts of MAO could be reduced, without significant effect on the catalytic activity (about 3000 kgPE/moIZr.h.bar). The polymers obtained with the heterogeneous catalysts showed higher melting points, molecular weights, than that obtained with the homogeneous catalyst precursor. With the heterogenization of metallocene it was obtained granulate polymers, differently of the homogeneous catalysts, that produce polyethylene in the powder form.

ASSUNTO(S)

polietileno

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