The syntheses of low-mol.-wt. polyethylene (PE), in the presence of catalysts based on five different metallocene frameworks, have been compared. High yields and low mol. masses, typical of industrially relevant PE waxes, can be easily achieved by using overpressure of hydrogen. Particularly suitable for the prodn. of PE waxes are catalytic systems based on the C2 sym. rac-dimethylsilylbis(2-methyl-4-phenyl-1-indenyl)-zirconium dichloride (1) and the C2v sym. bis-cyclopentadienyl-zirconium dichloride (5). The wax yields can be substantially increased by increasing the MAO/Zr molar ratio. The control of the PE mol. wt. allows an easy control of phys. properties. In fact, as Mn increases in the range 103-104 g/mol, the degree of crystallinity decreases from nearly 85 to 60% while the melting temp. increases from 125 up to 135.
Polyethylene waxes by metallocenes.
NAPOLI, Mariagrazia;IMMEDIATA, Ivano;LONGO, Pasquale;GUERRA, Gaetano
2011-01-01
Abstract
The syntheses of low-mol.-wt. polyethylene (PE), in the presence of catalysts based on five different metallocene frameworks, have been compared. High yields and low mol. masses, typical of industrially relevant PE waxes, can be easily achieved by using overpressure of hydrogen. Particularly suitable for the prodn. of PE waxes are catalytic systems based on the C2 sym. rac-dimethylsilylbis(2-methyl-4-phenyl-1-indenyl)-zirconium dichloride (1) and the C2v sym. bis-cyclopentadienyl-zirconium dichloride (5). The wax yields can be substantially increased by increasing the MAO/Zr molar ratio. The control of the PE mol. wt. allows an easy control of phys. properties. In fact, as Mn increases in the range 103-104 g/mol, the degree of crystallinity decreases from nearly 85 to 60% while the melting temp. increases from 125 up to 135.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
