Polymerization process
This application is a division of application Ser. No. 788,031, filed Apr. 15, 1977, now U.S. Pat. No. 4,112,210 which application Ser. No. 788,031 is a continuation-in-part of application Ser. No. 659,905, filed Feb. 20, 1976 (now abandoned). 
    
    
     The present invention relates to a process of producing homopolymers of conjugated dienes or copolymers of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds. 
     From British Pat. No. 1,246,914, it is already known to prepare in solution homopolymers of conjugated dienes or copolymers of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds by means of organometallic compounds of an alkaline earth metal of the formula M 1  M 2  R 1  R 2  R 3  R 4  in which M 1  represents calcium, barium, or strontium, M 2  represents zinc or cadmium, and R 1 , R 2 , R 3 , R 4  represent a hydrocarbon radical. The polymers obtained have a very low intrinsic viscosity of between 0.24 and 0.62. 
     It is known (Chemical Abstracts, Vol. 78; 85 514 (1973) and RAPRA No. 23 738 L (1974)) to prepare in a hydrocarbon reaction medium homopolymers of conjugated dienes or copolymers of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds by means of organometallic compounds of an alkaline earth metal and aluminum. However, the polymers obtained by this process, like the polymers mentioned above, have a very low intrinsic viscosity and, therefore, do not have elastomeric properties which are sufficient to permit their use as the principal component of mixtures serving for the manufacture of tires. Furthermore, such a process of manufacture cannot be applied industrially due to the very low homopolymerization or copolymerization reaction velocity. 
     Finally, it is widely known that the organo-metallic compounds of aluminum have an extremely low or even zero intrinsic catalytic activity and that they are not considered initiators for the homopolymerization or copolymerization of conjugated dienes. 
     The applicant has discovered a new process which makes it possible industrially to obtain within relatively short times and with good yield homopolymers of conjugated dienes or copolymers of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds having an elasticity similar to rubber and which can be used in the manufacture of pneumatic tires. 
     Therefore, the object of the present invention is a process for the homopolymerization of conjugated dienes or the copolymerization of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds to form elastomeric products which comprise reacting the monomers at a temperature between 50° C. and 120° C. in the presence of a catalytic system formed of the reaction product of 
     (a) an organometallic compound of a metal of Group IIIA of the Mendeleev periodic table of elements having one of the following formulas: 
     Me 1  Me 3  R 1  R 2  R 3  R 4   
     Me 2  (Me 3  R 1  R 2  R 3  R 4 ) 2   
     Me 3  R 1  R 2  R 3   
     Me 1  O Me 3  R 1  R 2   
     in which Me 1  represents an alkali metal, Me 2  represents an alkaline earth metal, Me 3  represents a metal of Group IIIA, R 1 , R 2  and R 3  represent an alkyl or aralkyl radical and R 4  represents an alkyl or aralkyl radical or a radical XB in which X represents an oxygen, sulfur or nitrogen atom and B represents an alkyl or aralkyl radical, or a radical Me 3  (R 5  R 6 ) in which R 5  and R 6  represent an alkyl or aralkyl radical; with 
     (b) at least one electron-donor compound containing at least one hetero-atom selected from the group consisting of aprotic polar compounds, protic polar compounds and compounds formed of the reaction product of protic polar compounds with an alkali metal or with an alkaline earth metal. 
     The applicant has surprisingly found that the reaction product of compounds which, taken alone, are not initiators of the homopolymerization or of the copolymerization of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds or which have only an extremely low intrinsic initiating activity constitutes an intitiating catalytic system for the homopolymerization of conjugated dienes or the copolymerization of conjugated dienes with other conjugated dienes or with vinyl aromatic compounds which can be used industrially as elastomers. 
     The organometallic compounds of a metal of Group IIIA which are particularly suitable as a component of the catalytic system are those in which the alkali metal is lithium, sodium, or potassium, those in which the alkaline earth metal is magnesium, calcium, strontium or barium, and those in which the metal of Group IIIA is boron, aluminum, gallium, indium or thallium. By way of example, the following compounds can be mentioned: Al(Ch 3 ) 3 , Al(C 2  H 5 ) 3 , Al(i-C 4  H 9 ) 3 , Li [Al(C 2  H 5 ) 4  ], Na[Al (C 2  H 5 ) 4  ], K[Al(C 2  H 5 ) 4  ], Li [Al(C 2  H 5 ) 3  O C 2  H 5  ], Li [Al(C 2  H 5 ) 3  O Al(C 2  H 5 ) 2  ], Mg [Al(C 2  H 5 ) 4  ] 2 , C 2  H 5  Mg Al (C 2  H 5 ) 4 , Ca [Al(C 2  H 5 ) 4  ] 2 , Sr [Al(C 2  H 5 ) 4  ] 2  , Ba [Al(C 2  H 5 ) 4  ] 2 , Ba [Al(C 2  H 5 ) 3  O C 2  H 5  ] 2 , Ba [Al-(iso C 4  H 9 ) 4  ] 2 , Li O Al(C 2  H 5 ) 2 , Na O Al(C 2  H 5 ) 2 , B (CH 3 ) 3 , B (C 2  H 5 ) 3 , Li B(C 2  H 5 ) 4 , Li B(C 2  H 5 ) 3  C 4  H 9 , Ga(C 2  H 5 ) 3 , In(C 2  H 5 ) 3 , Tl(C 2  H 5 ) 3 . 
     By way of examples of aprotic polar compounds, there are especially suitable the ethers and particularly the cyclic ethers, such as tetrahydrofuran and dioxane, as well as the corresponding thioethers, such as thiodiisobutyl; the tertiary amines, such as N,N,N&#39;,N&#39;-tetramethylethylenediamine (TMED); the aromatic amines and in particular the pyridine derivatives, such as 4-methylpyridine, and the corresponding oxides; phosphorous compounds, such as the phosphines and their oxides, the phosphites, the phosphoramides and in particular hexamethylphosphorotriamide (HMPT); the ketones and particularly acetone; the nitriles and particularly acetonitrile; the aldehydes; the esters; the amides; the nitro-aliphatic or aromatic compounds; the sulfoxides and particularly dimethyl sulfoxide; the sulfones; and the sulfites. 
     As protic polar compounds there are suitable in particular water; the alcohols and particularly methanol; the primary or secondary amines; the phenols; and the thiols. 
     As compounds formed of the reaction product of protic polar compounds with an alkali metal or with an alkaline earth metal there are particularly suited the alcoholates and phenates of alkali metals or alkaline earth metals, such as lithium isopropylate, barium nonylphenate and sodium or potassium tert-amylate; the alkali metal or alkaline earth metal mercapto and thiophenates; as well as the ether-alcoholates and amine-alcoholates of alkali metals or alkaline earth metals, such as the lithium alcoholate of ethyl diglycol and lithium N,N-diethylamino-2-ethanolate. 
     The organometallic compound of a metal of Group IIIA and the electron-donor compound or compounds can be introduced into the reaction medium either individually in any order or preformed. In accordance with the second variant, the catalytic system is &#34;preformed&#34; by mixing the various components and then bringing the mixture to a temperature of between 20° C. and 100° C. for 5 to 60 minutes. 
     The two components of the catalytic system can be used in variable proportions but it is preferably to use them in proportions such that the molar ratio of the electron donor compound or compounds to the organometallic compound of a metal of Group IIIA is between 0.01:1 and 100:1. For a given concentration of organometallic compound of a metal of Group IIIA, a modification of the value of the molar ratio may modify both the intrinsic viscosity and the microstructure of the polymer formed as well as the polymerization and copolymerization reaction velocity. Among the organometallic compounds of a metal of Group IIIA organo-aluminum compounds are preferred due both to their advantageous method of manufacture and to their extensive availability on the market. 
     In the case of catalytic systems formed of an organometallic compound of aluminum having the formula Me 2  [Al R 1  R 2  R 3  R 4  ] 2 , such as defined above, and one or more polar compounds of the class of aprotic polar compounds, for a given concentration of an aluminum organometallic compound when the value of the molar ratio of the aprotic polar compound or compounds to the organo-aluminum compound increases, the reaction velocity and the intrinsic viscosity of the polymer formed increase without the micro-structure of the polymer being changed. This is all the more surprising, since the addition of polar compounds to organo-lithium initiators leads to a system which does not change the intrinsic viscosity of the polymer but changes the microstructure thereof. 
     In the case of catalytic systems formed of an organometallic compound of aluminum having the formula Me 2  (Me 3  R 1  R 2  R 3  R 4 ) 2 , as defined previously, and a polar compound selected from among those having one of the formulas R (O CH 2  CH 2 ) n  O Me 1 , or (R) 2  N CH 2  CH 2  O Me 1  in which Me 1  represents an alkali metal, R represents an alkyl radical and n is a whole number, polymers and copolymers having a very high content of trans-1,4 linkages (up to 92%) and a very low content of 1,2 or 3,4 linkages, that is to say less than 4%, and which retain an elastomeric character can be obtained. The copolymers of butadiene and styrene (SBR) thus obtained have a resistance to elongation similar to that of natural rubber when in crude state (nonvulcanized) and when filled in accordance with the customary formulations used for the manufacture of the automobile tires. 
     The homopolymerization of copolymerization reaction is carried out either in an inert hydrocarbon solvent which may, for instance, be an aliphatic or alicyclic hydrocarbon, such as pentane, hexane, heptane, iso-octane, cyclohexane, or an aromatic hydrocarbon, such as benzene, toluene, xylene, or in bulk polymerization. 
     The reaction is generally carried out at a temperature of between 50° C. and 120° C. and preferably between 80° C. and 100° C., under a pressure which corresponds to the vapor pressure of the reagents. The process of the invention can be carried out batch-wise or continuously. 
     The process not only makes it possible to obtain high yields of macromolecular compounds per unit of weight of the catalytic system but it also makes it possible to regulate to the desired extent the molecular weight of the homopolymers or copolymers prepared. 
     The process furthermore makes it possible to obtain homopolymers or copolymers which during the reaction can give rise to grafting reactions with all reagents capable of reacting with living polymers. 
     As representative examples of conjugated dienes which are suitable for the homopolymerization and copolymerization mention may be made of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 2-ethyl butadiene. 
     As representative examples of suitable vinyl aromatic compounds mention may be made of styrene; ortho-, meta-, and para-methyl styrene; di- and polymethylstyrene; para-tert-butylstyrene; the vinyl naphthalenes; the methoxystyrenes; the halostyrenes; and divinylbenzene. 
     The products obtained by the process of preparation employing the catalytic system in accordance with the invention furthermore have a broad molecular weight distribution and a high intrinsic viscosity, that is to say sufficient so that the products can be used as the principal component of mixes serving for the manufacture of pneumatic tires, and a microstructure which may vary extremely. As a matter of fact, the content of trans-1,4 linkages may be between 20% and 90% and the content of 1,2-linkages may be between 1% and 60%. Furthermore, these products are very well suited for mechanical working on tools. 
    
    
     The invention will be fully understood from the following examples which, by way of illustration, describe special manners for carrying it out. In all the examples the intrinsic viscosities were determined at 25° C. in solution of 1 g. per liter in toluene, the concentrations of catalysts are expressed in micromols per 100 g. of monomers and the homopolymerization or copolymerization reactions were stopped when the rate of conversion reached 80% (except in Examples 19, 23 and 27), by addition of methanol in suitable quantities (1%). The percentages of trans-1,4 linkages and 1,2 linkages are expressed with reference to the polybutadiene portion while the percentage of styrene is expressed with reference to the total amount of polymer obtained. 
     EXAMPLE 1 
     Two liters of heptane were introduced as solvent into a reactor under the pressure of rectified nitrogen whereupon 205 g. of butadiene and 69 g. of styrene were introduced and the temperature was increased to 80° C. The catalytic system formed of Ba [Al(C 2  H 5 ) 4  ] 2  and of tetrahydrofuran (THF) in variable quantities was then introduced in succession in four tests. When the rate of conversion was reached, the reaction was stopped and the copolymer recovered. 
     The results of the four tests are set forth in the following table: 
     
                                           TABLE                                   
__________________________________________________________________________
Catalytic System       SBR Copolymers                                     
Test             Reaction                                                 
                       Intrinsic                                          
                             Steric                                       
No. Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                  
             THF Time  Viscosity                                          
                             Configuration                                
__________________________________________________________________________
                             % tr.                                        
                                  %  % Sty.                               
                             1,4  1,2                                     
                                     Incorp.                              
T   1820     0   40 hr.                                                   
                       0.8   85   3  15                                   
1   1100     1100                                                         
                  8 hr.                                                   
                       1.6   81   3  15                                   
                 30 min.                                                  
2   1100     2200                                                         
                  6 hr.                                                   
                       2.1   80   3  16                                   
3   1100     4400                                                         
                  4 hr.                                                   
                        2.45 80   4  16                                   
__________________________________________________________________________
 
    
     It was found that the reaction time is 5 to 10 times less (Test T versus Tests 1-3) and that when the value of the molar ratio of THF to Ba[Al(C 2  H 5 ) 4  ] 2  increases, the reaction velocity and the intrinsic viscosity of the SBR copolymer increase while the microstructure of the SBR copolymer remains unchanged. 
     EXAMPLE 2 
     Four tests were carried out repeating the procedure of Example 1 with different catalytic systems. The results are set forth in Table II below: 
     
                                           TABLE II                                
__________________________________________________________________________
Catalytic System           SBR Copolymers                                 
Test                 Reaction                                             
                           Intrinsic                                      
                                 Steric                                   
No.                                                                       
   Organometallic Compound                                                
                 THF Time  Viscosity                                      
                                 Configuration                            
__________________________________________________________________________
                                 % tr.                                    
                                      %  % Sty.                           
                                 1,4  1,2                                 
                                         Incorp.                          
1  Ca[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
              640                                                         
                 1920                                                     
                      3 hr.                                               
                           1.3   73   7  10                               
2  Sr[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
             1100                                                         
                 3500                                                     
                      2 hr.                                               
                           1.4   73   7  12                               
                     20 min.                                              
3  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
             1100                                                         
                 3300                                                     
                      4 hr.                                               
                           2.25  80   4  16                               
                     30 min.                                              
4  Ba[Al(isoC.sub.4 H.sub.9).sub.4 ].sub.2                                
              860                                                         
                 2580                                                     
                      2 hr.                                               
                           1     74   5  15                               
__________________________________________________________________________
 
    
     EXAMPLE 3 
     Three tests were carried out. Into a 250 ml. Steinie bottle under pressure of rectified nitrogen there were introduced 100 ml. of heptane as solvent and 13.6 g. butadiene. The catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and methanol was then introduced. The bottle was placed in a thermostatically controlled tank at 80° C. in which it was agitated. 
     At the end of the reaction, the polybutadiene was recovered in ordinary manner. The results are set forth in Table III below. 
     
                       TABLE III                                                   
______________________________________                                    
Catalytic System Reac-   Polybutadiene                                    
Test             Meth-   tion  Intrinsic                                  
                                      Steric                              
No.  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                 
                 anol    Time  Viscosity                                  
                                      Configuration                       
______________________________________                                    
                                      % tr. %                             
                                      1,4   1,2                           
1    1100         74     7 hr. 1.64   86    3                             
2    1100        222     6 hr. 1.59   84    3                             
3    1100        444     5 hr. 1.50   81    3                             
______________________________________                                    
 
    
     EXAMPLE 4 
     A test was carried out repeating the procedure of Example 3 and using similar conditions except that a catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and water was employed. The results are set forth in Table IV below. 
     
                       TABLE IV                                                    
______________________________________                                    
Catalytic System         Polybutadiene                                    
Test                    Reaction                                          
                               Intrinsic                                  
                                      Steric                              
No.  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                 
                 H.sub.2 O                                                
                        Time   Viscosity                                  
                                      Configuration                       
______________________________________                                    
                                      % tr. %                             
                                      1,4   1,2                           
1    1100        440    17 hr. 1.55   87    2                             
______________________________________                                    
 
    
     EXAMPLE 5 
     Three tests were conducted, the reaction being carried out in a reactor under pressure of rectified nitrogen. Two liters of heptane were introduced as solvent followed by 191 g. of butadiene and 82 g. of styrene. The temperature was increased to 80° C. and the catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and of lithium isopropylate was added. At the end of the reaction, the copolymer was recovered in a customary manner. The results are set forth in Table V below. 
     
                                           TABLE V                                 
__________________________________________________________________________
Catalytic System       SBR Copolymers                                     
Test       Lithium                                                        
                  Reaction                                                
                       Intrinsic                                          
                            Steric                                        
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           Isopropylate                                                   
                  Time Viscosity                                          
                            Configuration                                 
__________________________________________________________________________
                            % tr.                                         
                                %  % Sty.                                 
                            1,4 1,2                                       
                                   Incorp.                                
1  340     2400   4 hr.                                                   
                       3    83  4  21                                     
2  380     2600   4 hr.                                                   
                       2.6  83  3  20                                     
3  550     1380   4 hr.                                                   
                       1.7  81  4  23                                     
__________________________________________________________________________
 
    
     EXAMPLE 6 
     Two tests were carried out. Two liters of solvent (heptane) followed by 205 g. of butadiene and 69 g. of styrene were introduced into a reactor under the pressure of rectified nitrogen. The temperature was brought to 80° C. and then the components of the catalytic system, i.e., N,N,N&#39;,N&#39;-tetramethylethylenediamine (TMED) and Ba[Al(C 2  H 5 ) 4  ] 2 , were introduced one after the other. The results are set forth in Table VI below: 
     
                                           TABLE VI                                
__________________________________________________________________________
Catalytic System     SBR Copolymers                                       
Test            Reaction                                                  
                     Intrinsic                                            
                          Steric                                          
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           TMED Time Viscosity                                            
                          Configuration                                   
__________________________________________________________________________
                          % tr.                                           
                              %  % Sty.                                   
                          1,4 1,2                                         
                                 Incorp.                                  
1  2440    1220  5 hr.                                                    
                     0.8  84  4  15                                       
                45 min.                                                   
2  2440    2440  5 hr.                                                    
                     1.5  81  4  16                                       
__________________________________________________________________________
 
    
     EXAMPLE 7 
     Two liters of heptane, 205 g. of butadiene and 69 g. of styrene were introduced into a reactor under pressure of rectified nitrogen whereupon the temperature was increased to 80° C. and 4-methylpyridine or γ-picoline and Ba[Al(C 2  H 5 ) 4  ] 2  were added one after the other. The results are set forth in Table VII below. 
     
                                           TABLE VII                               
__________________________________________________________________________
Catalytic System   SBR Copolymers                                         
              Reaction                                                    
                   Intrinsic                                              
                        Steric                                            
Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                      
        γ-picoline                                                  
              Time Viscosity                                              
                        Configuration                                     
__________________________________________________________________________
                        % tr.                                             
                            %  % Sty.                                     
                        1,4 1,2                                           
                               Incorp.                                    
1100    1100   1 hr.                                                      
              40 min.                                                     
                   1.30 60  7  18                                         
__________________________________________________________________________
 
    
     EXAMPLE 8 
     Two tests were carried out repeating the procedure of Example 3 using the catalytic system of Ba[Al(C 2  H 5 ) 4  ] 2  and acetonitrile. The results are set forth in Table VIII below. 
     
                       TABLE VIII                                                  
______________________________________                                    
                     Polybutadiene                                        
Catalytic System   Re-              Steric                                
Test                       action                                         
                                 Intrinsic                                
                                        Config-                           
No.  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                 
                 Acetonitrile                                             
                           Time  Viscosity                                
                                        uration                           
______________________________________                                    
                                        % tr.                             
                                             %                            
                                        1,4  1,2                          
1    1100         74        3 hr.                                         
                                 1.6    77   3                            
                           45 min.                                        
2    1100        222        3 hr.                                         
                                 1.7    75   5                            
                           15 min.                                        
______________________________________                                    
 
    
     EXAMPLE 9 
     Three tests were carried out repeating the procedure of Example 3 and using similar conditions except that acetone and Ba[Al(C 2  H 5 ) 4  ] 2  were used as the catalytic system. The results are set forth in Table IX below: 
     
                       TABLE IX                                                    
______________________________________                                    
                    Polybutadiene                                         
Catalytic System               Stearic                                    
Test             Ace-    Reaction                                         
                                Intrinsic                                 
                                       Config-                            
No.  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                 
                 tone    Time   Viscosity                                 
                                       uration                            
______________________________________                                    
                                       % tr. %                            
                                       1,4   1,2                          
1    1100         74      7 hr. 1.6    82    3                            
2    1100        222      6 hr. 1.8    78    3                            
                         30 min.                                          
3    1100        444      5 hr. 2.0    75    4                            
                         30 min.                                          
______________________________________                                    
 
    
     EXAMPLE 10 
     The procedure of Example 3 was repeated using similar conditions except that thiodiisobutyl and Ba[Al(C 2  H 5 ) 4  ] 2  were used as the catalytic system. The results are set forth in Table X below. 
     
                       TABLE X                                                     
______________________________________                                    
Catalytic System         Polybutadiene                                    
          Thiodi-  Reaction  Intrinsic                                    
                                    Stearic                               
Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                      
          isobutyl Time      Viscosity                                    
                                    Configuration                         
______________________________________                                    
                                    % tr.  %                              
                                    1,4    1,2                            
1100      222      22 hr.    1.50   85     2                              
______________________________________                                    
 
    
     EXAMPLE 11 
     Three tests were carried out repeating the procedure of Example 3 and using similar conditions except that hexamethylphosphorotriamide (HMPT) and Ba[Al(C 2  H 5 ) 4  ] 2  were used as the catalytic system. The results are set forth in Table XI below: 
     
                       TABLE XI                                                    
______________________________________                                    
Catalytic System Re-     Polybutadiene                                    
Test                     action                                           
                               Intrinsic                                  
                                      Stearic                             
No.  Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                 
                 HMPT    Time  Viscosity                                  
                                      Configuration                       
______________________________________                                    
                                       % tr. %                            
                                       1,4   1,2                          
1    1100        222      3 hr.                                           
                               1.55    82    2                            
2    1100        444      2 hr.                                           
                               1.68    80    3                            
                         15 min.                                          
3    1100        888      2 hr.                                           
                               2.48    78    3                            
______________________________________                                    
 
    
     EXAMPLE 12 
     Two tests were carried out repeating the procedure of Example 3 and using similar conditions except that a catalytic system formed of Ba[Al(C 2  H 5 ) 3  OR] 2 , OR being the nonylphenate radical, and lithium isopropylate were used. The results are set forth in Table XII below: 
     
                       TABLE XII                                                   
______________________________________                                    
Catalytic System           Polybutadiene                                  
                  Lithium  Re-          Steric                            
Test              Isopro-  action                                         
                                 Intrinsic                                
                                        Config-                           
No.  Ba[Al(C.sub.2 H.sub.5).sub.3 OR ].sub.2                              
                  pylate   Time  Viscosity                                
                                        uration                           
______________________________________                                    
                                        % tr.                             
                                             %                            
                                        1,4  1,2                          
1    1450         2900     18 hr.                                         
                                 1.15   76   4                            
2    1450         5800     17 hr.                                         
                                 1.33   78   4                            
______________________________________                                    
 
    
     Under the same conditions the use of Ba[Al(C 2  H 5 ) 3  OR] 2  by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 13 
     Two tests were carried out repeating the procedure of Example 3 and using similar conditions except that Li Al(C 2  H 5 ) 4  and lithium isopropylate were used as the catalytic system. The results are set forth in Table XIII below: 
     
                       TABLE XIII                                                  
______________________________________                                    
                     Polybutadiene                                        
Catalytic System   Re-              Steric                                
Test            Lithium Iso-                                              
                           action                                         
                                 Intrinsic                                
                                        Config-                           
No.  Li Al(C.sub.2 H.sub.5).sub.4                                         
                propylate  Time  Viscosity                                
                                        uration                           
______________________________________                                    
                                        % tr.                             
                                             %                            
                                        1,4  1,2                          
1    1450        725        3 hr.                                         
                                 1.22   60   8                            
                           30 min.                                        
2    1450       1450        3 hr.                                         
                                 1.24   60   8                            
                           30 min.                                        
______________________________________                                    
 
    
     Under the same conditions, the use either of Li Al(C 2  H 5 ) 4  alone or of lithium isopropylate alone did not lead to any trace of polymer even after 48 hours of reaction. 
     EXAMPLE 14 
     A test was carried out repeating the procedure of Example 3 and using Li Al(C 2  H 5 ) 4 , lithium isopropylate and barium nonylphenate as components of the catalytic system. The results are set forth in Table XIV below: 
     
                       TABLE XIV                                                   
______________________________________                                    
Catalytic System           Polybutadiene                                  
         Barium   Lithium  Re-          Steric                            
         Nonyl-   Isopro-  action                                         
                                 Intrinsic                                
                                        Config-                           
Li Al(C.sub.2 H.sub.5).sub.4                                              
         phenate  pylate   Time  Viscosity                                
                                        uration                           
______________________________________                                    
                                        % tr.                             
                                             %                            
                                        1,4  1,2                          
1450     725      2900      1 hr.                                         
                           30 min.                                        
                                 2.3    79   4                            
______________________________________                                    
 
    
     As compared with the preceding Example 13, the addition of the barium nonylphenate had the effect of orienting the microstructure. 
     EXAMPLE 15 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of Li Al(C 2  H 5 ) 4 , and sodium tert-amylate. The results are set forth in Table XV below: 
     
                       TABLE XV                                                    
______________________________________                                    
Catalytic System         Polybutadiene                                    
         Sodium Tert-                                                     
                    Reaction Intrinsic                                    
                                    Steric                                
Li Al(C.sub.2 H.sub.5).sub.4                                              
         amylate    Time     Viscosity                                    
                                    Configuration                         
______________________________________                                    
                                    % tr. %                               
                                    1,4   1,2                             
1450     2900       14 hr.   3.30   34    36                              
______________________________________                                    
 
    
     EXAMPLE 16 
     Two tests were carried out repeating the procedure of Example 3 except that a catalytic system formed of Na Al(C 2  H 5 ) 4  and potassium tert-amylate (ROK) was used. The results are set forth in Table XVI below: 
     
                       TABLE XVI                                                   
______________________________________                                    
                    Polybutadiene                                         
                    In-                                                   
Catalytic System          trinsic                                         
Test                     Reaction                                         
                                Vis-  Steric                              
No.  Na Al(C.sub.2 H.sub.5).sub.4                                         
                ROK      Time   cosity                                    
                                      Configuration                       
______________________________________                                    
                                      % tr. %                             
                                      1,4   1,2                           
1    1450        725     5 hr.  3.12  37    38                            
2    1450       1450     5 hr.  2.55  40    36                            
______________________________________                                    
 
    
     Under the same conditions the use of Na Al(C 2  H 5 ) 4  by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 17 
     Two tests were carried out repeating the procedure of Example 3 except that a catalytic system formed of K Al(C 2  H 5 ) 4  and potassium tert-amylate (ROK) was used. The results are set forth in Table XVII below: 
     
                       TABLE XVII                                                  
______________________________________                                    
Catalytic System         Polybutadiene                                    
Test                    Reaction                                          
                               Intrinsic                                  
                                      Steric                              
No.  KAl(C.sub.2 H.sub.5).sub.4                                           
                ROK     Time   Viscosity                                  
                                      Configuration                       
______________________________________                                    
                                      % tr. %                             
                                      1,4   1,2                           
1    1450       360      4 hr. 1.37   50    26                            
                        30 min.                                           
______________________________________                                    
 
    
     Under the same conditions the use of KAl (C 2  H 5 ) 4  by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 18 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of ##STR1## and barium nonylphenate. 
     The results are set forth in Table XVIII below: 
     
                                           TABLE XVIII                             
__________________________________________________________________________
Catalytic System            Polybutadiene                                 
 ##STR2##       Barium Nonyl- phenate                                     
                        Reaction Time                                     
                             Intrinsic Viscosity                          
                                  Steric Configuration                    
__________________________________________________________________________
                                 % tr.                                    
                                     %                                    
                                 1,4 1,2                                  
1450           725     10 hr.                                             
                            1.6  80  4                                    
__________________________________________________________________________
 
    
     Under the same conditions, the use of ##STR3## by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 19 
     A test was carried out repeating the procedure of Example 3 employing a catalytic system cosisting of LiOAl(C 2  H 5 ) 2  and barium nonylphenate. The polymerization reaction was stopped when the conversion rate reached 60% instead of 80%. The results are set forth in Table XIX below. 
     
                       TABLE XIX                                                   
______________________________________                                    
                   Polybutadiene                                          
Catalytic System  Reac-            Steric                                 
          Barium Nonyl-                                                   
                      tion    Intrinsic                                   
                                     Config-                              
Li O Al(C.sub.2 H.sub.5).sub.2                                            
          phenate     Time    Viscosity                                   
                                     uration                              
______________________________________                                    
                                     % tr. %                              
                                     1,4   1,2                            
2960      740         5 hr.   1.9    63    6                              
______________________________________                                    
 
    
     Under the same conditions the use of LiOAl(C 2  H 5 ) 2  by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 20 
     Two tests were carried out repeating the procedure of Example 3 using a catalytic system consisting of Li[Al(C 2  H 5 ) 3  O Al(C 2  H 5 ) 2  ] and lithium isopropylate. The results are set forth in Table XX below. 
     
                                           TABLE XX                                
__________________________________________________________________________
Catalytic System            Polybutadiene                                 
Test            Lithium Iso-                                              
                       Reaction                                           
                            Intrinsic                                     
                                 Steric                                   
No.                                                                       
   Li[Al(C.sub.2 H.sub.5).sub.3 O Al(C.sub.2 H.sub.5).sub.2 ]             
                propylate                                                 
                       Time Viscosity                                     
                                 Configuration                            
__________________________________________________________________________
                                 % tr.                                    
                                      %                                   
                                 1,4  1,2                                 
1  1100         370     5 hr.                                             
                            1.78 58   9                                   
                       30 min.                                            
2  1100         1100    5 hr.                                             
                            1.95 59   9                                   
                       30 min.                                            
__________________________________________________________________________
 
    
     Under the same conditions the use of Li[Al(C 2  H 5 ) 3  O Al(C 2  H 5 ) 2  ] by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 21 
     Two tests were carried out repeating the procedure of Example 3 using a catalytic system consisting of Al(C 2  H 5 ) 3 , lithium isopropylate, and barium nonylphenate. The results are set forth in Table XXI below: 
     
                                           TABLE XXI                               
__________________________________________________________________________
Catalytic System             Polybutadiene                                
Test     Lithium Iso-                                                     
                Barium Nonyl-                                             
                        Reaction                                          
                             Intrinsic                                    
                                  Steric                                  
No.                                                                       
   Al(C.sub.2 H.sub.5).sub.3                                              
         propylate                                                        
                phenate Time Viscosity                                    
                                  Configuration                           
__________________________________________________________________________
                                  % tr.                                   
                                      %                                   
                                  1,4 1,2                                 
1  2900  3600   360     5 hr.                                             
                             1.7  88  3                                   
2  2900  3600   720     5 hr.                                             
                             1.35 85  3                                   
__________________________________________________________________________
 
    
     Under the same conditions the use of Al(C 2  H 5 ) 3  by itself did not lead to any trace of polymer, even after 48 hours of reaction. 
     EXAMPLE 22 
     A test was carried out repeating the procedure of Example 3 except that a catalytic system consisting of Li B(C 2  H 5 ) 3  C 4  H 9  and barium nonylphenate was used. The results are set forth in Table XXII below: 
     
                       TABLE XXII                                                  
______________________________________                                    
Catalytic System           Polybutadiene                                  
                  Barium   Reac-        Steric                            
Test              Nonyl-   tion  Intrinsic                                
                                        Config- -No. Li B(C.sub.2         
                                        H.sub.5).sub.3 C.sub.4 H.sub.9 phe
                                        nate Time Viscosity uration       
______________________________________                                    
                                        % tr.                             
                                             %                            
                                        1,4  1,2                          
1    5900         100      4 hr. 1.6    83   3                            
______________________________________                                    
 
    
     Under the same conditions the use of Li B(C 2  H 5 ) 3  C 4  H 9  by itself did not lead to any trace of polymer even after 48 hours of reaction. 
     EXAMPLE 23 
     A mixture of heptane, butadiene and styrene having a weight ratio of monomers to solvent of 1:5 and of butadiene to styrene of 3:1 was introduced continously into a reactor. Ba[Al(C 2  H 5 ) 4  ] 2  and lithium isopropylate were also introduced continuously in a molar ratio of 1:10 with such a speed that there was 960 μ mols of Ba[Al(C 2  H 5 ) 4  ] 2  in the reactor for 100 g. of monomers and that there was an average time of stay in the reactor of 11/2 hours. The copolymerization was effected at 90° C. and the reaction was stopped when the percentage conversion reached was 60% rather than 80%. The copolymer was recovered at the outlet of the reactor. It contained 16% styrene and had an intrinsic viscosity of 1.64, a trans-1,4 linkage content of 81% and a 1,2 linkage content of 3%. 
     EXAMPLE 24 
     Two liters of heptane, 191 g. of butadiene and 82 g. of styrene were introduced into a reactor under the pressure of rectified nitrogen and the temperature was increased to 80° C. There was then added in succession the catalytic system formed of 460 μ mols of Ba[Al(C 2  H 5 ) 4  ] 2  per 100 g. of monomers and 1380 μ mols per 100 g. of monomers of lithium isopropylate. When the rate of conversion reached 80% (2 hours), 50 cc. of copolymer were recovered in customary manner and the reaction stopped by the addition of methanol. An amount of diphenyl carbonate (CDP) was then added to the reactor such that the ratio of CDP : Ba[Al(C 2  H 5 ) 4  ] 2  was equal to 0.5:1. 
     The copolymer obtained was recovered by a conventional method. The microstructure of the copolymer obtained before grafting and of the grafted copolymer was: 81% trans-1,4 linkages, 4% of 1,2 linkages and 24% incorporated styrene. 
     The intrinsic viscosity of the ungrafted copolymer was 1.7 and that of the grafted copolymer was 2.6. 
     EXAMPLE 25 
     (1) Preparation of the Copolymer 
     Two liters of heptane, 191 g. of butadiene and 82 g. of styrene were introduced into a reactor under the pressure of rectified nitrogen whereupon the temperature was increased to 80° C. The catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and lithium isopropylate was then gradually added. When a rate of conversion of 80% had been reached, the reaction was stopped and the copolymer recovered in customary manner. The elastomer obtained was then diluted with 37.5 parts of aromatic oil (Exarol MX 140, marketed by Compagnie Francaise de Raffinage) per 100 parts of dry elastomer. The results are set forth in Table XXV A. 
     
                                           TABLE XXV A                             
__________________________________________________________________________
                    SBR Steric Configuration                              
                    Intrinsic                                             
                    Viscosity                                             
Catalytic System    Before                                                
                        After                                             
        Lithium Iso-                                                      
               Reaction                                                   
                    Dilution                                              
                            % tr.                                         
                               % % Styr.                                  
Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                      
        propylate                                                         
               Time With the Oil                                          
                            1,4                                           
                               1,2                                        
                                 Incorp.                                  
__________________________________________________________________________
1000    7100    5 hr.                                                     
                    2.67                                                  
                        1.96                                              
                            84 4 22                                       
               30 min.                                                    
__________________________________________________________________________
 
    
     (2) Rubber Making Mix: 
     The elastomer described above was used to form a mixture having the following formula in parts by weight: 
     100 --Elastomer diluted with 37.5 parts of aromatic oil 
     2 --Stearic acid 
     3 --ZnO 
     1 --antioxidant (Santoflex 13: N-(dimethyl,3-butyl N&#39;-phenyl-p-phenylene diamine) 
     50 --HAF Black (Philblack O) 
     5 --aromatic oil (Sundex 8125, PM 380, density 0.995 marketed by Sun Oil) 
     1 --Santocure (N-cyclohexyl-mercaptobenzothiazole sulfenamide) 
     1.8 --Sulfur 
     The same mixture was prepared with a butadiene/styrene copolymer (SBR 1712) available on the market as a control. The two mixtures were then vulcanized for 60 minutes at 144° C. 
     The mechanical properties obtained are set forth in Table XXV B below: 
     
                       TABLE XXV B                                                 
______________________________________                                    
                   Control                                                
Properties         (SBR 1712)   Test SBR                                  
______________________________________                                    
Modulus at 100% elongation                                                
                   16           14.9                                      
(kg/cm.sup.2)                                                             
Modulus at 300% elongation                                                
                   67.5         58                                        
(kg/cm.sup.2)                                                             
Hysteresis loss at 60° C.                                          
                   29           24.6                                      
Index of coefficient of                                                   
                   100          84                                        
 friction at 20° C. (SRT)                                          
Scott rupture index                                                       
 elongation at rupture (%)                                                
                   570          540                                       
 rupture force (kg/cm.sup.2)                                              
                   231          222                                       
 Shore A hardness  62           60                                        
______________________________________                                    
 
    
     SBR 1712 is a butadiene/styrene copolymer comprising 23.5% styrene, 15-16% of 1,2 linkages, 60% of trans-1,4 linkages and 37.5 parts of aromatic oil. 
     It was found that the elastomer in accordance with the invention has properties substantially equal to those of the above conventional copolymer. It can be used as the principal component of a mix for the manufacture of pneumatic tires. 
     EXAMPLE 26 
     This example relates to the preparation of butadiene/styrene copolymers; six tests were carried out. 
     The copolymerization was effected in a reactor in an inert atmosphere (rectified nitrogen) at 80° C. in the presence of heptane as solvent. The weight ratio of monomers to solvent was 1:5. The reaction was stopped when the rate of conversion reached 80%. The conditions of the tests and the results obtained are set forth in Table XXVI. 
     
                       TABLE XXVI                                                  
______________________________________                                    
Catalytic System                                                          
              Test Nos.                                                   
______________________________________                                    
Ba [Al(C.sub.2 H.sub.5).sub.4 ].sub.2 and                                 
C.sub.2 H.sub.5 (OCH.sub.2 CH.sub.2).sub.2 OLi                            
              1      2      3    4    5    6                              
Molar ratio Li/Ba                                                         
              1      1      1.5  1.5  2    2                              
Initial styrene content                                                   
               24     32     24   32   24   32                            
(% by weight)                                                             
Quantity of   730    600    910  750  400  1300                           
Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                      
Reaction time (in                                                         
              140    200    190  270  270  330                            
minutes)                                                                  
Copolymers                                                                
Intrinsic Viscosity                                                       
               2.17   2.08   1.86                                         
                                  2.09                                    
                                      2.1   1.90                          
Content of trans-1,4 (%)                                                  
               85     85     87   87   90   90                            
Content of 1,2(%)                                                         
              3      3      3    3    3    3                              
Content of incorporated                                                   
               15     23     15   23   15   23                            
styrene (% by weight)                                                     
______________________________________                                    
 
    
     On test pieces of the copolymer of Test 5 and of natural rubber (NR) filled in accordance with the formulation of Example 25 but not vulcanized, force-elongation measurements (measurement of the green strength) were carried out at 25° C. The force elongation measurements were carried out on &#34;dumbbell&#34; test specimens of a thickness of 2.5 mm. and effected with the use of an &#34;Instron&#34; electronic dynamometer 24 hours after molding and with a rate of traction of 10 cm./minute. The results obtained are set forth in the graph of the drawing, the ordinate of which represents the force exerted in g./mm 2  and the abscissa represents the elongation (in %). It was found that the copolymer prepared by the improved method of the invention had a resistance to elongation similar to that of natural rubber. 
     EXAMPLE 27 
     A mixture of toluene, butadiene and styrene in proportions such that the weight ratio of monomers to solvent was equal to 1:5 and the ratio of butadiene to styrene was equal to 3:1 was introduced continuously into a reactor. Ba[Al(C 2  H 5 ) 4  ] 2  and C 2  H 5  (OCH 2  CH 2 ) 2  OLi were also introduced continuously in quantities such that their molar ratio was 1:2. The rate of flow was such that there were 1000 micromols of Ba[Al(C 2  H 5 ) 4  ] 2  in the reactor per 100 g. of monomers and that an average time of stay in the reactor of 1 hour was obtained. The copolymerization was effected at 90° C. and the reaction was stopped when the percentage conversion reached was 65% rather than 80%. The copolymer formed was recovered continuously at the outlet of the reactor. It contained 15% by weight of styrene and had an intrinsic viscosity of 1.6. The content of 1,2 linkages was 3% and that of trans-1,4 linkages was 83%. 
     EXAMPLE 28 
     The catalytic system of Ba[Al(C 2  H 5 ) 4  ] 2  and (C 2  H 5 ) 2  NCH 2  CH 2  OLi was used. 100 ml. of heptane as solvent and 13.6 g. of butadiene were introduced into a 250 ml. Steinie bottle under the pressure of rectified nitrogen. The catalytic system was then added whereupon the bottle was placed in a tank which was thermostatically controlled at 80° C., in which it was agitated. 
     At the end of the reaction, when the percent of conversion reached 80%, the polybutadiene formed was recovered by an ordinary method. The results are set forth in Table XXVIII. 
     
                                           TABLE XXVIII                            
__________________________________________________________________________
Catalytic System           Polybutadiene                                  
                      Reaction                                            
Test                  Time Intrinsic                                      
                                % tr.                                     
                                   %                                      
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           (C.sub.2 H.sub.5).sub.2 NCH.sub.2 CH.sub.2 OLi                 
                      (in min.)                                           
                           Viscosity                                      
                                1,4                                       
                                   1,2                                    
__________________________________________________________________________
1  100     200        60   1.75 85 4                                      
__________________________________________________________________________
 
    
     EXAMPLE 29 
     A test was carried out repeating the procedure of Example 28 and using similar conditions except that a catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and C 2  H 5  (OCH 2  CH 2 ) 2  ONa was used. The results are set forth in Table XXIX below: 
     
                                           TABLE XXIX                              
__________________________________________________________________________
Catalytic System          Polybutadiene                                   
Test                 Reaction                                             
                          Intrinsic                                       
                               % tr.                                      
                                   %                                      
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           C.sub.2 H.sub.5 (OCH.sub.2 CH.sub.2).sub.2 ONa                 
                     Time Viscosity                                       
                               1,4 1,2                                    
__________________________________________________________________________
1      100 100       3 hr.                                                
                          5    88  3                                      
__________________________________________________________________________
 
    
     EXAMPLE 30 
     A test was carried out repeating the procedure of Example 29 and using similar conditions except that a catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and C 2  H 5  (OCH 2  CH 2 ) 3  OLi was employed. The results are set forth in Table XXX below: 
     
                                           TABLE XXX                               
__________________________________________________________________________
Catalytic System     Reaction                                             
                          Polybutadiene                                   
Test                 Time Intrinsic                                       
                               % tr.                                      
                                   %                                      
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           C.sub.2 H.sub.5 (OCH.sub.2 CH.sub.2).sub.3 OLi                 
                     (in min.)                                            
                          Viscosity                                       
                               1,4 1,2                                    
__________________________________________________________________________
1  100     100       60   2.8  80  4                                      
__________________________________________________________________________
 
    
     EXAMPLE 31 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of LiAl(C 2  H 5 ) 4  and barium nonylphenate. The results are set forth in Table XXXI below: 
     
                                           TABLE XXXI                              
__________________________________________________________________________
Catalytic System       Polybutadiene                                      
Test       Barium Nonyl-                                                  
                  Reaction                                                
                       Intrinsic                                          
                            Steric                                        
No.                                                                       
   Li Al(C.sub.2 H.sub.5).sub.4                                           
          phenate Time Viscosity                                          
                            Configuration                                 
__________________________________________________________________________
1  1450   725      3 hr.                                                  
                       1.88 % tr.                                         
                                %                                         
                  30 min.   1,4 1,2                                       
                            70  5                                         
__________________________________________________________________________
 
    
     EXAMPLE 32 
     Three tests were conducted, the reaction being carried out in a 250 ml. Steinie bottle under pressure of rectified nitrogen. There were introduced 100 ml. of heptane as solvent and 4.08g. of styrene followed by 9.68g. of butadiene. The catalytic system formed of Ba[Al(C 2  H 5 ) 4  ] 2  and barium nonylphenate was then introduced. The bottle was placed in a thermostatically controlled tank at 80° C. in which it was agitated. 
     At the end of the reaction, the SBR copolymers were recovered in ordinary manner. The results are set forth in Table XXXII below: 
     
                                           TABLE XXXII                             
__________________________________________________________________________
Catalytic System        SBR Copolymers                                    
Test       Barium Nonyl-                                                  
                   Reaction                                               
                        Intrinsic                                         
                             Steric                                       
No.                                                                       
   Ba[Al(C.sub.2 H.sub.5).sub.4 ].sub.2                                   
           phenate Time Viscosity                                         
                             Configuration                                
__________________________________________________________________________
                             % tr.                                        
                                 %  % Sty.                                
                             1,4 1,2                                      
                                    Incorp.                               
1  735      73     6 hr.                                                  
                        1.8  57  5  20                                    
2  735     157     4 hr.                                                  
                        1.7  61  5  23                                    
3  735     367     3 hr.                                                  
                         1.75                                             
                             70  4  22                                    
__________________________________________________________________________
 
    
     EXAMPLE 33 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of Al(C 2  H 5 ) 3  and lithium isopropylate. The results are set forth in Table XXXIII below: 
     
                                           TABLE XXXIII                            
__________________________________________________________________________
Catalytic System      Polybutadiene                                       
Test                                                                      
         Lithium Iso-                                                     
                 Reaction                                                 
                      Intrinsic                                           
                            Steric                                        
No.                                                                       
   Al(C.sub.2 H.sub.5).sub.3                                              
         propylate                                                        
                 Time Viscosity                                           
                            Configuration                                 
__________________________________________________________________________
                            % tr.                                         
                                %                                         
                            1,4 1,2                                       
1  2200  3200    15 hr.                                                   
                      1.09  59  7                                         
__________________________________________________________________________
 
    
     EXAMPLE 34 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of Al(C 2  H 5 ) 3  and (C 2  H 5  OCH 2  CH 2  O) 2  Ba, i.e., barium ethylglycolate. The results are set forth in Table XXXIV below. 
     
                                           TABLE XXXIV                             
__________________________________________________________________________
Catalytic System           Polybutadiene                                  
Test                  Reaction                                            
                           Intrinsic                                      
                                Steric                                    
No.                                                                       
   Al(C.sub.2 H.sub.5).sub.3                                              
         (C.sub.2 H.sub.5 OCH.sub.2 CH.sub.2 O).sub.2 Ba                  
                      Time Viscosity                                      
                                Configuration                             
__________________________________________________________________________
                                % tr.                                     
                                    %                                     
                                1,4 1,2                                   
1  2950  2950         10 hr.                                              
                           1.3  60  6                                     
__________________________________________________________________________
 
    
     EXAMPLE 35 
     A test was carried out repeating the procedure of Example 3 using a catalytic system consisting of NaOAl(C 2  H 5 ) 2   and lithium isopropylate. The results are set forth in Table XXXV below. 
     
                                           TABLE XXXV                              
__________________________________________________________________________
Catalytic System       Polybutadiene                                      
Test       Lithium                                                        
                  Reaction                                                
                       Intrinsic                                          
                            Steric                                        
No.                                                                       
   NaOAl(C.sub.2 H.sub.5).sub.2                                           
           Isopropylate                                                   
                  Time Viscosity                                          
                            Configuration                                 
__________________________________________________________________________
                            % tr.                                         
                                %                                         
                            1,4 1,2                                       
1  1100    3300   6 hr.                                                   
                       1.5  42  26                                        
__________________________________________________________________________