Activating Agents for Hafnium-Based Metallocene Components

Abstract

The present invention discloses an active metallocene catalyst system prepared with a hafnium-based metallocene catalyst system and an activating agent comprising an aluminoxane and a sterically hindered Lewis base.

1 - 13 . (canceled) 
     
     
         14 . A metallocene catalyst system comprising:
 (a) a hafnium-based metallocene catalyst component described by formula I
   R″(CpR 4 )(FluR′ 8 )Hf Q 2   (I) 
   
       wherein Cp is a cyclopentadienyl ring; Flu is a fluorenyl ring; each R is the same or different and is hydrogen or a hydrocarbyl radical containing from 1 to 20 carbon atoms or two carbon atoms are joined together to form a C 4 -C 6  ring; each R′ is the same or different and is hydrogen or a hydrocarbyl radical containing from 1 to 20 carbon atoms; R″ is a structural bridge between two Cp rings; Q is a hydrocarbyl radical having from 1 to 20 carbon atoms, a hydrocarboxy radical having from 1 to 20 carbon atoms or a halogen and can be the same or different from each other; 
       or by the formula II
   R″(FluR′ m )X Hf Q 2   (II) 
 
       wherein R″, Flu, R′ and Q are as previously defined and wherein X is a hetero atom ligand with one or two lone pair electrons selected from the group 15 or 16, substituted or unsubstituted, and structural bridge R″ is between the fluorenyl group and the heteroatom; and
 (b) an activating agent having a low or no co-ordinating capability comprising an aluminoxane and a sterically hindered lewis base; 
 
     
     
         15 . The metallocene catalyst system of  claim 14  wherein in formula II, X is nitrogen, phosphorus, oxygen or sulphur. 
     
     
         16 . The metallocene catalyst system of  claim 15  wherein all R and R′ in formulae I and II are hydrogen.  
     
     
         17 . The metallocene catalyst system of  claim 14  wherein in hafnium-based catalyst component I, position 3 of the cyclopentadienyl group is occupied by a non-hydrogen substituent and all other R and R′ are hydrogen. 
     
     
         18 . The metallocene catalyst system of  claim 17  wherein the substituent at position 3 of the cyclopentadienyl group is methyl or tert-butyl. 
     
     
         19 . The metallocene catalyst system of  claim 14  wherein the sterically hindered Lewis base is a compound of formula R* a-c E (G-R* b-1 ) c  or of formula R*(G-R* b-1 ) c  wherein G is a group 15 or 16 element of the Periodic Table, b is equal to the valency of G, E is a group 14 or 15 element of the Periodic Table, a is the coordination number of E, c is an integer from 1 to 4, at most equal to a and each R* is independently a hydrogen or an unsubstituted or substituted hydrocarbyl. 
     
     
         20 . The metallocene catalyst system of  claim 19  wherein the sterically hindered Lewis base is a sterically hindered bulky phenol. 
     
     
         21 . A method for polymerising alpha-olefins comprising: injecting into a reactor the catalyst system of claim  1 ; injecting into the reactor monomer and optional comonomer; maintaining polymerising conditions thereby obtaining polyolefin. 
     
     
         22 . The method of  claim 21  wherein the monomer is propylene.