Polymerization catalyst system using di-sec-butyldimethoxysilane for preparation of polypropylene

Abstract

It has been discovered that using di-sec-butyldialkoxysilanes, such as di-sec-butyldimethoxysilane (DSBDMS), as external electron donors for Ziegler-Natta catalysts can provide a catalyst system that may prepare polypropylene films with improved properties and processing. The catalyst systems of the invention provide high activity, high bulk density, moderate hydrogen response, moderate donor response and high polydispersity (MWD). Suitable di-sec-butyldialkoxysilanes have the formula ( s Bu) 2 Si(OR″) 2 , where R″ is independently a straight or branched alkyl group of 1-5 carbon atoms.

1 - 7 . (canceled)  
   
   
       8 . Polypropylene comprising a propylene polymer or copolymer having a melt flow ranging from about 1-100 decigrams/min., a polydispersity ranging from about 7 to about 11, and xylene solubles ranging from about 0.5 to about 6 wt %.  
   
   
       9 . Polypropylene formed by a process comprising: 
 providing a Ziegler-Natta catalyst, and in any order: 
 contacting the catalyst with an organoaluminum compound;  
 contacting the catalyst with at least one electron donor comprising a di-sec-butyldialkoxysilane simultaneously with or subsequent to contacting the catalyst with an organoaluminum compound, where the di-sec-butyldialkoxysilane has the formula ( s Bu) 2 Si(OR″) 2 , where R″ is independently a straight or branched alkyl group of 1-5 carbon atoms;  
 introducing the catalyst into a polymerization reaction zone containing the organoaluminum compound, the electron donor and propylene monomer; and  
 removing polypropylene homopolymer or copolymer from the polymerization reaction zone.  
   
   
   
       10 . The polypropylene of  claim 9  where the polypropylene has a higher polydispersity and higher bulk density as compared to an otherwise identical polypropylene formed in the absence of a di-sec-butyldialkoxysilane.  
   
   
       11 . An article formed from polypropylene comprising a propylene polymer or copolymer having a melt flow ranging from about 1-100 decigrams/min. and xylene solubles of not more than about 6% formed by a process comprising: 
 providing a Ziegler-Natta catalyst, and in any order: 
 contacting the catalyst with an organoaluminum compound;  
 contacting the catalyst with at least one electron donor comprising a di-sec-butyldialkoxysilane simultaneously with or subsequent to contacting the catalyst with an organoaluminum compound, where the di-sec-butyldialkoxysilane has the formula ( s Bu) 2 Si(OR″) 2 , where R″ is independently a straight or branched alkyl group of 1-5 carbon atoms;  
 introducing the catalyst into a polymerization reaction zone containing the organoaluminum compound, the electron donor and propylene monomer; and  
 removing polypropylene homopolymer or copolymer from the polymerization reaction zone.  
   
   
   
       12 . The article of  claim 11  where the article is biaxially oriented polypropylene (BOPP) film.  
   
   
       13 . The article of  claim 11  where the article is high crystallinity polypropylene (HCPP).