Polyolefin production

Abstract

Use of a metallocene compound of general formula Ind 2 R″MQ 2 as a component of a catalyst system for the production of a polyethylene copolymer substantially in the absence of comonomer, wherein each Ind is the same or different and is indenyl or substituted indenyl; R″ is a bridge which comprises a C 1 to C 4 alkylene radical, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine, which bridge is substituted or unsubstituted, M is a Group IV metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3.

1 . A catalyst comprising a metallocene compound of general formula Ind 2 R″MQ 2 , wherein each Ind is the same or different and is indenyl or substituted indenyl; R″ 0  is a bridge which comprises a C 1  to C 4  alkylene radical, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine, which bridge is substituted or unsubstituted, M is a Group IV metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3.  
     
     
         2 . A catalyst according to  claim 1 , wherein R″ is an ethylene bridge, which is substituted or unsubstituted.  
     
     
         3 . A catalyst according to  claim 1 , wherein the cyclopentadienyl ring of at least one of the indenyls is unsubstituted.  
     
     
         4 . A catalyst according to  claim 3 , wherein both indenyls is unsubstituted.  
     
     
         5 . A catalyst according to  claim 1 , wherein M is Zr.  
     
     
         6 . A catalyst according to  claim 1 , wherein the Q is halogen.  
     
     
         7 . A catalyst according to  claim 1 , wherein the bis indenyl compound is ethylbenzene 1-indenyl-zirconium dichloride.  
     
     
         8 . A catalyst accordingly to  claim 1 , wherein the catalyst further comprises a cocatalyst capable of activating, the metallocene compound.  
     
     
         9 . The catalyst according to  claim 8 , wherein the cocatalyst, which activates the metallocene compound, comprises an aluminum-containing cocatalyst or a boron-containing cocatalyst.  
     
     
         10 . A catalyst according to  claim 8 , wherein the cocatalyst comprises an aluminum-containing cocatalyst comprising an alumoxane, an alkyl aluminum and/or a Lewis acid.  
     
     
         11 . A catalyst according to  claim 1 , wherein the catalyst further comprises an inert support.  
     
     
         12 . A process for the preparation of a polyethylene copolymer, which comprises polymerization ethylene, optionally with hydrogen, in a substantially comonomer-free reaction medium which comprises a catalyst comprising 
 (a) a metallocene compound of general formula Ind 2 R″MQ 2 , wherein each Ind is the same or different and is indenyl or substituted indenyl; R″ is a bridge which comprises a C 1  to C 4  alkylene radical, a dialkyl germanium or silicon or siloxane, alkyl phosphine or amine, which bridge is substituted or unsubstituted, M is a Group IV metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3.    (b) a cocatalyst which activates the metallocene compound; wherein the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3.    
     
     
         13 . A process according to  claim 12 , wherein the polyethylene formed thereby has short chain branching arising from C 4  incorporation in the backbone of the polyethylene.  
     
     
         14 . A process according to  claim 12 , wherein the polyethylene formed thereby has long chain branching.  
     
     
         15 . A process according to  claim 14 , wherein the polyethylene formed thereby has a shear ratio of at least 20.  
     
     
         16 . A process according to  claim 12 , wherein the catalyst further comprises an inert support.  
     
     
         17 . A long chain branched polyethylene copolymer formed by a process comprising copolymerization ethylene, optionally with hydrogen, in a reaction medium, which comprises a solution or slurry of a catalyst comprising 
 (a) a metallocene compound of general formula Ind 2 R″MQ 2 ; and    (b) a cocatalyst, which activates the metallocene compound; wherein the ratio of meso to racemic forms of the metallocene in the catalyst system is at least 1:3 so that the polyethylene formed thereby, has long chain branching.    
     
     
         18 . A catalyst according to  claim 17 , wherein R″ is an ethylene bridge, which is substituted or unsubstituted.  
     
     
         19 .  3 . A catalyst according to  claim 17 , wherein the cyclopentadienyl ring of at least one of the indenyls is unsubstituted.  
     
     
         20 . A catalyst according to  claim 17 , wherein both indenyls are unsubstituted.  
     
     
         21 . A catalyst according to  claim 17 , wherein M is Zr.  
     
     
         22 . A catalyst according to  claim 17 , wherein the Q is halogen.  
     
     
         23 . A catalyst according to  claim 17 , wherein the bis indenyl compound is ethylbenzene 1-indenyl zirconium dichloride.  
     
     
         24 .  8 . A catalyst accordingly to  claim 17 , wherein the catalyst further comprises a cocatalyst capable of activating the metallocene compound.  
     
     
         25 . The catalyst according to  claim 17 , wherein the cocatalyst, which activates the metallocene compound, comprises an aluminum-containing cocatalyst or a boron-containing cocatalyst.  
     
     
         26 . A catalyst according to  claim 17 , wherein the cocatalyst comprises an aluminum-containing cocatalyst comprising an alumoxane, an alkyl aluminum and/or a Lewis acid.  
     
     
         27 . A catalyst according to  claim 17 , wherein the catalyst further comprises an inert support.