Polymerization process

Abstract

A process for the polymerisation of olefins is described involving the use, of a catalyst system comprising a supported transition metal compound and an activator based on an organoborane and an aluminoxane. Preferably the transition metal compound is a metallocene complex. The support is pretreated with an organoaluminium compound and the process is particularly suitable for the gas phase preparation of copolymers of ethylene and alpha-olefins having a molecular weight distribution in the range 2.5-7.0 and a melt strength in the range 3-12 cN.

1 . An olefin polymerisation process comprising contacting one or more olefin monomers with a supported catalyst composition prepared by contacting 
 (a) a transition metal compound,    (b) a support, and    (c) an activator comprising (i) an aluminoxane and (ii) an organoboron compound,    characterised in that the support is pretreated with an organoaluminium compound.    
     
     
         2 . A process according to  claim 1  wherein the organoaluminium compound is a trialkylaluminium compound.  
     
     
         3 . A process according to either of the preceding claims wherein the organoboron compound is a perfluorinated triarylboron compound.  
     
     
         4 . A process according to  claim 3  wherein the perfluorinated triarylboron compound is tris(pentafluorophenyl) borane.  
     
     
         5 . A process according to any of the preceding claims wherein the aluminoxane is methyl aluminoxane.  
     
     
         6 . A process according to any of the preceding claims wherein the ratio of boron/transition metal in the supported catalyst is in the range 0.1 to 10.  
     
     
         7 . A process according to any of the preceding claims wherein the ratio of boron/transition metal in the supported catalyst is in the range 1 to 4.  
     
     
         8 . A process according to any of the preceding claims wherein the support is silica.  
     
     
         9 . A process according to any of the preceding claims wherein the transition metal compound is a metallocene complex.  
     
     
         10 . A process according to  claim 9  wherein the metallocene complex is a monocyclopentadienyl complex.  
     
     
         11 . A process according to  claim 10  wherein the monocyclopentadienyl complex has the formula  
       
         
           
           
               
               
           
         
         wherein: 
 R′ each occurrence is independently selected from hydrogen, hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof, said R′ having up to 20 nonhydrogen atoms, and optionally, two R′ groups (where R′ is not hydrogen, halo or cyano) together form a divalent derivative thereof connected to adjacent positions of the cyclopentadienyl ring to form a fused ring structure;  
 X is a neutral z, 1   4  bonded diene group having up to 30 non-hydrogen atoms, which forms a π complex with M;  
 Y is —O—, —S—, —NR*—, —PR*—,  
 M is titanium or zirconium in the +2 formal oxidation state;  
 Z* is SiR* 2 , CR* 2 , SiR* 2 SIR* 2 , CR* 2 CR* 2 , CR*═CR*, CR* 2 SIR* 2 , or  
 GeR* 2 , wherein:  
 R* each occurrence is independently hydrogen, or a member selected from hydrocarbyl, silyl, halogenated alkyl, halogenated aryl, and combinations thereof, said R* having up to 10 non-hydrogen atoms, and optionally, two R* groups from Z* (when R* is not hydrogen), or an R* group from Z* and an R* group from Y form a ring system,  
 
       
     
     
         12 . A process according to  claim 11  wherein the metal complex is a titanium complex.  
     
     
         13 . A process according to  claim 12  wherein the metal complex is (t-butylamido) (tetramethyl-   5 -cyclopentadienyl) dimethyl silanetitanium -   4 -1,3-pentadiene.  
     
     
         14 . An olefin polymerisation process comprising contacting one or more olefin monomers with a supported catalyst composition prepared by 
 (a) addition of an aluminoxane to a support,    (b) addition to the supported aluminoxane mixture from step (a) of a transition metal compound, and    (c) addition of an organoborane compound to the resultant mixture from step (b).    
     
     
         15 . A process according to  claim 14  wherein the aluminoxane is methyl aluminoxane and the organoboron compound is tris(pentafluorophenyl) borane.  
     
     
         16 . A process according to any of the preceding claim carried out in the gas phase.  
     
     
         17 . A process according to any of the preceding claims wherein the olefin monomers comprise ethylene and alpha-olefins having from three to twenty carbon atoms.  
     
     
         18 . A process according to any of the preceding claims for the copolymerisation of ethylene and alpha-olefins having from three to eight carbon atoms.  
     
     
         19 . A process according to any of the preceding claims for the copolymerisation of ethylene and 1-hexene.  
     
     
         20 . A process for the preparation of copolymers of ethylene and alpha-olefins having 
 (a) a melt strength in the range 3 -12 cN, and    (b) a molecular weight distribution (Mw/Mn) in the range 2.5 -7.0. said process comprising contacting ethylene and one or more alpha-olefins in the presence of a supported metallocene complex.    
     
     
         21 . A process according to  claim 20  wherein the copolymers have 
 (a) a melt strength in the range 6 -9 cN, and  
 (b) a molecular weight distribution (Mw/Mn) in the range 3.0 -5.0.  
 
     
     
         22 . A process according to claims  20  or  21  wherein the supported metallocene catalyst complex is a monocyclopentadienyl complex.  
     
     
         23 . A process according to  claim 22  wherein the supported monocyclopentadienyl complex is prepared as described in claims  1  or  14 .  
     
     
         24 . A process according to any of  claims 20  to  23  carried out in the gas phase.