Co-catalysts for metallocene complexes in olefin polymerization reactions

Abstract

The present invention provides cocatalysts for activating metallocene complexes in olefin polymerization reactions, and metallocene catalyst systems using the cocatalysts. The cocatalysts of the present invention include: (a) a halo-organoaluminum compound of the formula Al n R m X 3n-m , where Al is aluminum, each R is independently a C l to C 4 alkyl group, X is a halide, n is 1 or 2, and m is determined by the valency of Al; and (b) a dialkylmagnesium compound of the formula MgR′ 2 , where Mg is magnesium and R′ is a C 2 to C 6 alkyl group. The components (a) and (b) are used in amounts such that the molar ratio of Al:Mg is at least 2, preferably from 2:1 to 5:1.

We claim:  
     
       1. A catalyst composition comprising: 
       (a) a metallocene; and  
       (b) a cocatalyst comprising:  
       (i) a halo-organoaluminum compound of the formula  
       
         
           Al n R m X 3n-m    
         
       
        where Al is aluminum, each R is independently a C 1  to C 4  alkyl group, X is a halide, n is 1 or 2, and m is determined by the valency of Al; and  
       (ii) a dialkylmagnesium compound of the formula  
       
         
           MgR′ 2    
         
       
        where Mg is magnesium and R′ is a C 2  to C 6  alkyl group.  
     
     
       2. The catalyst composition of  claim 1 , wherein each R is independently ethyl or methyl. 
     
     
       3. The catalyst composition of  claim 1 , wherein X is chloride or fluoride. 
     
     
       4. The catalyst composition of  claim 1 , wherein R′ is butyl or hexyl. 
     
     
       5. The catalyst composition of  claim 1 , wherein the halo-organoaluminum compound is selected from the group consisting of AlEt 2 Cl, AlMe 2 Cl, Al 2 Et 3 Cl 3  and AlEt 2 F, where Me is methyl and Et is ethyl. 
     
     
       6. The catalyst composition of  claim 1 , wherein the halo-organoaluminum compound is AlEt 2 Cl, where Et is ethyl. 
     
     
       7. The catalyst composition of  claim 1 , wherein the dialkylmagnesium compound is MgBu 2 , where Bu is butyl. 
     
     
       8. The catalyst composition of  claim 1 , wherein the halo-organoaluminum compound and the dialkylmagnesium compound are present in amounts such that the molar ratio of Al to Mg is at least 2. 
     
     
       9. The catalyst composition of  claim 1 , wherein the halo-organoaluminum compound and the dialkylmagnesium compound are present in amounts such that the molar ratio of Al to Mg is from 2:1 to 5:1. 
     
     
       10. The catalyst composition of  claim 1 , wherein the metallocene catalyst is a titanocene, zirconocene or a hafnocene. 
     
     
       11. The catalyst composition of  claim 1 , further comprising a support. 
     
     
       12. The catalyst composition of  claim 11 , wherein the support is silica. 
     
     
       13. A supported metallocene catalyst comprising: 
       (a) a support;  
       (b) a titanocene, zirconocene or hafnocene; and  
       (c) a cocatalyst comprising:  
       (i) a halo-organoaluminum compound of the formula  
       
         
           Al n R m X 3n-m    
         
       
        where Al is aluminum, each R is independently methyl or ethyl, X is chlorine or fluorine, n is 1 or 2, and m is determined by the valency of Al;  
       and  
       (ii) a dialkylmagnesium compound of the formula  
       
         
           MgR′ 2    
         
       
        where Mg is magnesium and R′ is hexyl or butyl.  
     
     
       14. The supported metallocene catalyst of  claim 13 , wherein the halo-organoaluminum compound is selected from the group consisting of AlEt 2 Cl, AlMe 2 Cl, Al 2 Et 3 Cl 3  and AlEt 2 F, where Me is methyl and Et is ethyl. 
     
     
       15. The supported metallocene catalyst of  claim 13 , wherein the halo-organoaluminum compound and the dialkylmagnesium compound are present in amounts such that the molar ratio of Al to Mg is from 2:1 to 5:1. 
     
     
       16. The supported metallocene catalyst of  claim 13 , wherein the support is silica. 
     
     
       17. A method of forming a polyolefin catalyst, the method comprising: 
       (a) providing a supported metallocene catalyst comprising a support, a metallocene and an activator, the activator comprising:  
       (i) a halo-organoaluminum compound of the formula  
       
         
           Al n R m X 3n-m    
         
       
        where Al is aluminum, each R is independently a C 1  to C 4  alkyl group, X is a halide, n is 1 or 2, and m is determined by the valency of Al; and  
       (ii) a dialkylmagnesium compound of the formula  
       
         
           MgR′ 2    
         
       
        where Mg is magnesium and R′ is a C 2  to C 6  alkyl group;  
       (b) providing a monomer selected from the group consisting of ethylene, C 3 -C 20  alpha-olefins, and mixtures thereof, and  
       (c) contacting the monomer with the supported metallocene catalyst system for a time and under conditions sufficient to polymerize the monomers to form a polyolefin polymer.  
     
     
       18. The method of  claim 17 , wherein the monomer is ethylene. 
     
     
       19. The method of  claim 17 , wherein the monomer is a mixture of ethylene and at least one C 3 -C 20  alpha olefin. 
     
     
       20. The method of  claim 17 , wherein the monomer is a mixture of ethylene and 1 -hexene.