Preparation of conjugated diene polymers by using an iron-based catalyst system

Abstract

A process for preparing conjugated diene polymers by polymerizing conjugated diene monomers in the presence of a catalyst composition that is formed by combining an iron-containing compound, a hydrogen phosphite, and an organoaluminum compound.

What is claimed is:  
     
         1 . A process for preparing conjugated diene polymers comprising the step of: 
 polymerizing conjugated diene monomers in the presence of a catalytically effective amount of a catalyst composition that is formed by combining: 
 (a) an iron-containing compound;  
 (b) a hydrogen phosphite; and  
 (c) an organoaluminum compound.  
   
     
     
         2 . The process of  claim 1 , where the molar ratio of the organoaluminum compound to the iron-containing compound is from about 1:1 to about 100:1.  
     
     
         3 . The process of  claim 2 , where the molar ratio of the hydrogen phosphite to the iron-containing compound is from about 0.5:1 to about 50:1.  
     
     
         4 . The process of  claim 1 , where the conjugated diene monomers are 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,4-hexadiene monomers, or mixtures thereof.  
     
     
         5 . The process of  claim 4 , where the conjugated diene monomers are 1,3-butadiene monomers.  
     
     
         6 . The process of  claim 5 , where said step of polymerizing is conducted in the presence of from about 0.01 to about 2 mmol of the iron-containing compound per 100 g of the 1,3-butadiene.  
     
     
         7 . The process of  claim 5 , where the molar ratio of the organoaluminum compound to the iron-containing compound is from about 1:1 to about 100:1.  
     
     
         8 . The process of  claim 7 , where the molar ratio of the organoaluminum compound to the iron-containing compound is relatively low.  
     
     
         9 . The process of  claim 7 , where the molar ratio of the organoaluminum compound to the iron-containing compound is relatively high.  
     
     
         10 . The process of  claim 7 , where the molar ratio of the organoaluminum compound to the iron-containing compound is intermediate.  
     
     
         11 . The process of  claim 1 , where the iron atom in the iron-containing compound has an oxidation state of 0, +2, +3, or +4.  
     
     
         12 . The process of  claim 1 , where the iron-containing compound is an iron carboxylate, iron carbamate, iron dithiocarbamate, iron xanthate, iron β-diketonate, iron alkoxide, iron aryloxide, organoiron compound, or a mixture thereof.  
     
     
         13 . The process of  claim 1 , where the hydrogen phosphite is an acyclic hydrogen phosphite defined by the following keto-enol tautomeric structures:  
       
         
           
           
               
               
           
         
       
       or a cyclic hydrogen phosphite defined by the following keto-enol tautomeric structures:  
       
         
           
           
               
               
           
         
       
       or a mixture thereof, where R 1  and R 2 , which may be the same or different, are mono-valent organic groups, and where R 3  is a divalent organic group.  
     
     
         14 . The process of  claim 13 , where R 1  and R 2  are alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl, substituted alkenyl, aryl, allyl, substituted aryl, aralkyl, alkaryl, or alkynyl groups, with each group containing up to about 20 carbon atoms, and where R 3  is an alkylene, cycloalkylene, substituted alkylene, substituted cycloalkylene, alkenylene, cycloalkenylene, substituted alkenylene, substituted cycloalkenylene, arylene, or substituted arylene group, with each group containing up to about 20 carbon atoms.  
     
     
         15 . The process of  claim 1 , where the organoaluminum compound comprises at least one compound defined by the formula AlR n X 3-n , where each R, which may be the same or different, is a mono-valent organic group, where each X, which may be the same or different, is a hydrogen atom, a carboxylate group, an alkoxide group, or an aryloxide group, and where n is an integer including 1, 2 or 3.  
     
     
         16 . The process of  claim 15 , where each R is an alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl, alkaryl, or alkynyl group, with each group containing up to about 20 carbon atoms, and where each X is a carboxylate group, an alkoxide group, or an aryloxide group, with each group containing up to about 20 carbon atoms.  
     
     
         17 . The process of  claim 1 , where the organoaluminum compound comprises trihydrocarbylaluminum, dihydrocarbylaluminum hydride, hydrocarbylaluminum dihydride, dihydrocarbylaluminum carboxylate, hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum alkoxide, hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum aryloxide, hydrocarbylaluminum diaryloxide, or mixtures thereof.  
     
     
         18 . The process of  claim 1 , where the organoaluminum compound comprises an aluminoxane defined by one of the following formulas:  
       
         
           
           
               
               
           
         
       
       where x is an integer of 1 to about 100, y is an integer of 2 to about 100, and each R 4 , which may be the same or different, is a mono-valent organic group.  
     
     
         19 . The process of  claim 18 , where each R 4  is an alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl, alkaryl, or alkynyl group, with each group containing up to about 20 carbon atoms.  
     
     
         20 . A polybutadiene polymer that is prepared by a process comprising the step of: 
 polymerizing 1,3-butadiene monomer with a catalyst composition that is formed by combining (a) an iron-containing compound, (b) a hydrogen phosphite, and (c) an organoaluminum compound.