Process for polymerization of α-olefins and catalysts therefor
This is a continuation of application Ser. No. 337,553, filed Jan. 6, 1982, now abandoned, which is a continuation of application Ser. No. 116,726, filed Jan. 30, 1980, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a process for the stereospecific polymerization of α-olefins and a catalyst therefor. 
     Methods of supporting the titanium compound of Ziegler-Natta catalysts on a carrier to improve the catalyst activity have been developed in a commercial scale for polymerization of α-olefins and generally, have being employed for a catalyst for polymerization of ethylene. 
     However, in case of polymerization of α-olefins such as propylene and butene, a useful, crystalline polymer can not be obtained unless the polymeric chain has an isotactic structure in which alkyl groups such as methyl or ethyl are stereospecifically regulated. Accordingly, catalysts improved only in polymerization activity as the case of ethylene polymerization cannot be considered to be a useful catalyst for polymerization of α-olefins and thus, regulating the stereospecificity of polymer is a significant matter. 
     In connection with this, there is, for example in British Pat. No. 1,435,768 provided a catalyst comprising a titanium composition, an organoaluminum compound and an electron donative compound, said titanium composition being prepared by copulverizing magnesium halide, a solid organic substance, an organic acid ester and titanium halide. Also, Japanese Patent Publication No. 52-50037 discloses a catalyst comprising a titanium composition and an organoaluminum compound, said titanium composition being obtained by reacting a copulverized product of magnesium halide and an organic acid ester with titanium tetrachloride. These catalysts are, however, still insufficient in a polymerization activity and a crystallinity of polymers obtained. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a process for the stereospecific polymerization of α-olefins, obtaining polymers of high stereospecificity with a high polymerization activity. 
     Another object of this invention is to provide a carrier type of the titanium catalyst component, obtaining a poly-α-olefin with an improved polymerization activity and stereospecificity. 
     According to this invention, polymerization of α-olefins is carried out in the presence of a catalyst comprising a carrier type titanium compound, an organoaluminum compound and an electron donative compound, said carrier type titanium compound being obtained by contact treatment of copulverized products of magnesium halide, an organosilicon compound having at least one alkoxyl group and a halogenated hydrocarbon with titanium halide. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Magnesium halide which may be used in the preparation of the carrier type titanium compound is, preferably, a substantially anhydrous magnesium halide and particularly, magnesium chloride is preferred. 
     An organosilicon compound having at least one alkoxyl group which may be used in the preparation of the titanium compound may be represented by the formula, 
     
         Si(OR).sub.m X.sub.n Y.sub.p 
    
     wherein R is a hydrocarbyl group, X and Y which may be the same or different are a hydrocarbyl group, halogen atom or a carbonyloxy group represented by the formula, ##STR1## wherein R&#39; is a hydrocarbyl group, m is 1˜4, n is 0˜3, p is 0˜3 and m+n+p is 4. Preferred R and R&#39; are aliphatic, alicyclic or aromatic hydrocarbons of 1˜10 carbon atoms. In case X or Y are hydrocarbyl groups, aliphatic, alicyclic or aromatic hydrocarbons of 1˜10 carbon atoms are preferred. Examples of these compounds include Si(OC 2  H 5 ) 3  Cl, Si(OC 2  H 5 ) 2  Cl 2 , Si(OCOCH 3 )(OC 2  H 5 )Cl 2 , Si(OC 2  H 5 ) 4 , Si(C 2  H 5 ) 2  (OC 2  H 5 ) 2 , Si(C 6  H 5 ) 3 , Si(CH 3 )(C 6  H 5 )(OCH 3 ) 2  and the like. Particularly, preferred are those having at least two alkoxyl groups, such as Si(C 2  H 5 )(OC 2  H 5 ) 3 , Si(OC 2  H 5 ) 4 , Si(C 2  H 5 ) 2  (OC 2  H 5 ) 2  and Si(C 6  H 5 )(OC 2  H 5 ) 3 . An amount of the organosilicon compound is not particularly limited, though 0.02˜0.18 moles per 1.0 mole of magnesium halide are preferred. 
     A halogenated hydrocarbon which may be used in the preparation of the titanium catalyst component is halogen-substituted aliphatic, alicyclic and aromatic hydrocarbons. Particularly, preferred are halogenated hydrocarbons of 1˜20 carbon atoms having 1˜10 halogen atoms substituted therefor, e.g. α,α,α-trichlorotoluene, α, α-dichlorotoluene, monochlorobenzene, dichlorobenzene, methylene chloride, 1,2-dichloroethane, carbon tetrachloride, perchloroethylene, ethylidene bromide and the like. 
     Further, preferred are halogenated hydrocarbons of liquid at an ambient temperature. 
     With use of the liquid halogenated hydrocarbons, catalytic activity and stereospecificity of polymers obtained are markedly improved as compared with use of halogenated hydrocarbons of solid at an ambient temperature. An amount of the halogenated hydrocarbons is not particularly limited, though 0.01˜0.1 mole per 1.0 mole of magnesium halide are preferred. 
     In the preparation of the activated titanium component, first, the organosilicon compound having at least one alkoxyl group and the halogenated hydrocarbon are pulverized together with magnesium halide as a carrier. 
     In this pulverization procedure a part or all of the halogenated hydrocarbon may be displaced by an aromatic hydrocarbon of 6˜20 carbon atoms. Examples of the aromatic hydrocarbons are benzene, toluene, xylene, cumene, α-methylstyrene, styrene and methoxystyrene. By way of example, copulverized products of 20 g of magnesium chloride, 2 ml of tetraethoxysilane and 4 ml of cumene or α-methylstyrene are obtained in accordance with the process of Example 1-(I) described later. 
     The pulverization procedure may be conducted under vacuum or atmosphere of an inert gas and should be effected in substantially the absence of oxygen and moisture. The pulverization conditions are not particularly limited, though the temperature is comprised between 0° C. and 80° C. in general. The pulverization time varies depending on type of pulverizers, but is normally comprised between 2 and 100 hours. 
     Next, the copulverized products thus obtained are subject to contact treatment with titanium halide. Examples of titanium halide which may be used include titanium tetrachloride, titanium tetrabromide and the like and particularly, titanium tetrachloride is preferred. The contact treatment may be conveniently effected by suspending the above copulverized products in titanium halide or in its solution in an inert solvent, maintaining the contact at temperatures of 0°˜135° C. and then separating solid materials, followed by drying or removing free titanium halide by washing with an inert solvent to obtain the activated titanium catalyst component. The term of inert solvents used herein means aliphatic, alicyclic or aromatic hydrocarbons and mixtures thereof. 
     In accordance with this invention, the activated titanium component thus obtained is combined with an organoaluminum compound and an electron donative compound to form a catalyst of high activity for polymerization of α-olefins. 
     The organoaluminum compound which may be used is represented by the formula, 
     
         AlR&#34;.sub.m X&#39;.sub.3-m 
    
     wherein R&#34; is a hydrocarbyl group, X&#39; is an alkoxyl group or hydrogen or halogen atoms and m is 1.5˜3. 
     The typical examples include triethylaluminum, tri-n-butylaluminum, tri-isobutylaluminum, tri-n-hexylaluminum, diethylaluminum monochloride, diethylaluminum hydride, diethylaluminum ethoxide and others. They may be used alone or in mixture of two or more. A mole ratio of the organoaluminum compound to titanium metal of the activated titanium component is not limited, though it is within preferably, the range of 1 to 500. 
     Electron donative compounds which are usually used in the α-olefin polymerization may be used in the catalysts of this invention. Preferred electron donative compounds are organic acid esters, the above-mentioned organosilicon compounds having at least one alkoxyl group and aromatic orthocarboxylic acid esters represented by the formula, ##STR2## wherein R 1  is an aromatic hydrocarbyl group of 6˜15 carbon atoms and each of R 2 , R 3  and R 4  which may be the same or different is a hydrocarbyl group of 1˜10 carbon atoms. 
     Examples of the organic acid ester are methyl formate, amyl acetate, methyl acrylate, methyl methacrylate, methyl benzoate, ethyl benzoate, methyl toluylate, methyl anisate and others. 
     Examples of the aromatic orthocarboxylic acid ester include methyl orthobenzoate, ethyl orthobenzoate, methyl orthotoluylate, ethyl orthotoluylate, ethyl orthoanisate and the like. 
     The electron donative compound may be brought into contact with other components at any time during the preparation of catalyst. 
     Generally, there are methods of contacting the electron donative compound after contact of the activated Ti component with the organoaluminum compound, contacting the activated Ti component after contact of the organoaluminum compound with the electron donative compound, contacting the organoaluminum compound after contact of the activated Ti component with the electron donative compound or contacting the three components at the same time. It is, particularly, preferred that a part or all of the electron donative compound to be added is allowed of exist when contacting the activated titanium component with the organoaluminum compound to polymerize polymerizable monomers. An amount of the electron donative compound is within, preferably, the range of 0.1 to 0.5 moles per 1.0 mole of the organoaluminum compound. When the amount exceeds 0.5 moles, it would result in a sudden decrease in polymerization activity without a further increase in stereospecificity. 
     This invention may be applied to a homopolymerization or copolymerization of α-olefins having the formula, 
     
         R&#39;&#34;--CH=CH.sub.2 
    
     wherein R&#39;&#34; is an alkyl group of 1-10 carbon atoms, or a copolymerization of the above α-olefin with ethylene. Examples of the α-olefin are propylene, butene-1, hexen-1, 4-methyl-pentene-1 and the like. 
     The polymerization procedure according to this invention may be carried out in the conventional method using usual conditions. The polymerization temperature is generally in the range of 0°-100° C., preferably 20°-90° C. and the pressure is in the range of from normal pressure to 50 atm., preferably from normal pressure to 40 atm. 
     In the polymerization reaction, a solvent such as an aliphatic, alicyclic or aromatic hydrocarbon or mixture thereof may be used and may be, for example, propane, butane, pentane, hexane, heptane, cyclohexane, benzene, toluene or mixtures thereof. Also, a bulk polymerization may be employed using liquid monomers themselves as the solvent. Alternatively, the polymerization reaction may be conducted in the vapour phase wherein gaseous monomers are directly contacted with the catalyst without use of a solvent. 
     The molecular weight of polymers produced by the method of this invention varies depending on the manner of reaction, kind of catalyst and polymerization conditions. However, the molecular weight may be controlled by adding to the reaction system, for example, hydrogen, an alkyl halide and a dialkyl zinc, if necessary. 
     This invention will be illustrated by way of the following examples. Also, for the purpose of comparison there are set forth Reference Examples which are beyond the scope of this invention. 
     As is apparent from the Examples, in accordance with this invention there are provided poly-α-olefins having a Total I I about 2% higher than and a yield per a unit amount of catalyst about 30˜60% higher than polymers by conventional catalysts. Also, in case of using an aromatic hydrocarbon such as cumene and α-methylstyrene instead of the halogenated hydrocarbon, there are provided poly-α-olefins having a Total I I about 1.0% higher than and a yield per an unit amount of catalyst about 10˜25% higher than polymers by conventional catalysts. 
    
    
     EXAMPLE 1 
     (I) 20.0 g of magnesium chloride, 4 ml of tetraethoxysilane, and 2 ml of α,α,α-trichlorotoluene were added under nitrogen atmosphere to a vibration mill provided with a pot of 600 ml in inner volume, in which 80 steel balls with a diameter of 12 mm had been placed and then, pulverized for 40 hours. 10 g of the pulverized products thus obtained and 50 ml of TiCl 4  were charged into a 200 ml round-bottomed flask and stirred at 80° C. for two hours and thereafter, the supernantant liquid was removed by decantation. Next, after repeating seven times a washing treatment consisting of the steps of stirring with 100 ml of n-heptane at 80° C. for 15 minutes and removing the supernatant liquid by decantation, further 100 ml of n-heptane were added to obtain an activated Ti component slurry. A part of the activated Ti component slurry was sampled and subjected to analysis after evaporating n-heptane. As a result a Ti content of the activated Ti component was 2.00% by weight. (II) 1.0 l of n-heptane, 70 mg of the above activated Ti component, 0.375 ml of triisobutylaluminum, 0.24 ml of diethylaluminum chloride and 0.14 ml of ethyl benzoate were charged into a 3.0 l stainless steel autoclave under nitrogen atmosphere. After exhausting the nitrogen gas from the autoclave by means of a vacuum pump, gaseous hydrogen was fed till the partial pressure of 0.1 Kg/cm 2  Gauge. The autoclave was heated and after 5 minutes, the inner temperature was elevated to 70° C. 
     While feeding propylene to maintain the pressure at 5 Kg/cm 2  Gauge, polymerization was continued at 70° C. for one hour. 
     After cooling the autoclave, unreacted propylene was purged and the contents were removed, filtered and dried at 60° C. under reduced pressure. Thus 258 g of a white powdery polypropylene were obtained. 
     Extraction residue of polymer with boiling n-heptane (hereinafter referred to as &#34;Powder I I&#34;) was 98.6%, bulk density 0.29 g/ml and limiting viscosity number (135° C., tetralin) 1.58. 
     On the other hand, 4.8 g of polymers soluble in n-heptane were obtained by concentration of the filtrate. A ratio of the extraction residue of polymer with boiling n-heptane to the total polymer (hereinafter referred to as &#34;Total I I&#34;) was 96.8%. 
     A polymerization activity of the catalyst in this polymerization reaction was 187.7 Kg/g.Ti.hr (Formation rate of polymer per gram of activated Ti per hour). 
     REFERENCE EXAMPLE 1 
     An activated Ti component was obtained in the same manner as in Example 1-(I) except omitting the use of α,α,α-trichlorotoluene during the pulverization. The Ti content of the activated Ti component was 3.37% by weight. 
     Propylene was polymerized in the same manner as in Example 1-(II) except using 92 mg of the above activated Ti component. The results are set forth in Table 1. 
     REFERENCE EXAMPLE 2 
     An activated Ti component was prepared in the same procedure as in Example 1-(I) except omitting the use of tetraethoxysiliane during the pulverization. The Ti content of the activated Ti component was 1.37% by weight. Propylene was polymerized in the same manner as in Example 1-(II) except using 102 mg of the above Ti component. The results are set forth in Table 1. 
     REFERENCE EXAMPLE 3 
     An activated Ti component was prepared in the same manner as in Example 1-(I) except using 5 ml of ethyl benzoate instead of α,α,α-trichlorotoluene during the pulverization. The Ti content of the activated Ti component was 2.42% by weight. Propylene was polymerized in the same procedure as in Example 1-(II) except using 68 mg of the above Ti component. The results are set forth in Table 1. 
     
                                           TABLE 1                                 
__________________________________________________________________________
Reference             Yield of                  Limiting                  
                                                     Bulk                 
Example               Powders                                             
                           Activity        Total I I                      
                                                Viscosity                 
                                                     Density              
No.   Activated Ti Component                                              
                      g    g/g · Ti-Cat · hr            
                                    Kg/g · Ti ·         
                                           %r   Number                    
                                                     g/ml                 
__________________________________________________________________________
1     Tetraethoxy-                                                        
              --      134  1457     43     93.1 1.31 0.30                 
      silane, 4 ml                                                        
2     --     α,α,α-Trichloro-                           
                       76   745     54     83.9 1.33 0.27                 
             toluene, 2 ml                                                
3     Tetraethoxy-                                                        
             Ethyl Benzoate                                               
                      145  2132     88     93.9 1.69 0.30                 
      silane, 4 ml                                                        
             5 ml                                                         
__________________________________________________________________________
 
    
     EXAMPLES 2-4 
     An activated Ti component was prepared in the same manner as in Example 1-(I) except using ethyltriethoxysilane, phenyltriethoxysilane and diethoxydimethylsilane, respectively instead of tetraethoxysilane. Using the activated Ti component thus obtained, polymerization of propylene was carried out in the same procedure as in Example 1-(II). The results are set forth in Table 2. 
     EXAMPLES 5-11 
     An activated Ti component was prepared in the same manner as in Example 1-(I) except using carbon tetrachloride, carbon tetrabromide, chlorobenzene, perchloroethylene, 1,1,1-trichloroethane, 1,2-dichloroethane and 1,1-dichloroethane, respectively instead of α,α,α-trichlorotoluene in the pulverization step. Using the activated Ti component thus obtained, polymerization of propylene was carried out in the same manner as in Example 1-(II). The results are set forth in Table 2. 
     EXAMPLES 12-14 
     In these Examples the activated Ti component prepared in Example 1-(I) was used. Using triethoxyphenylsilane, tetraethoxysilane and methyl orthobenzoate, respectively as the electron donative compound in the polymerization, the procedure of Example 1-(II) was conducted at 70° C. under a polymerization pressure of 5 Kg/cm 2  Gauge. The results are set forth in Table 3. 
     
                                           TABLE 2                                 
__________________________________________________________________________
                       Ti   Yield of             Total                    
                                                     Limiting             
                                                          Bulk            
Example                Content                                            
                            Powders                                       
                                 Activity        I I Viscosity            
                                                          Density         
No.   Activated Ti Component                                              
                       %    g    g/g · Ti Cat ·         
                                          Kg/g · Ti ·   
                                          hr     %   Number               
                                                          g/ml            
__________________________________________________________________________
2     Ethyltriethoxy-                                                     
              α,α,α-Trichloro-                          
                       1.62 165  2357     145    94.8                     
                                                     1.38 0.37            
      silane, 4 ml                                                        
              toluene, 2 ml                                               
3     Phenyltrietho-                                                      
              α,α,α-Trichloro-                          
                       1.86 205  2929     157    94.9                     
                                                     1.42 0.35            
      xysilane, 4 ml                                                      
              toluene, 2 ml                                               
4     Diethoxydime-                                                       
              α,α,α-Trichloro-                          
                       1.52 192  2743     180    95.2                     
                                                     1.40 0.36            
      thylsilane, 4 ml                                                    
              toluene, 2 ml                                               
5     Tetraethoxy-                                                        
              Carbon tetra-                                               
                       3.14 245  3500     111    94.5                     
                                                     1.39 0.29            
      silane, 4 ml                                                        
              chloride, 2 ml                                              
6     Tetraethoxy-                                                        
              Carbon tetra-                                               
                       2.34 180  2365     101    93.9                     
                                                     1.41 0.29            
      silane, 4 ml                                                        
              bromide, 3 g                                                
7     Tetraethoxy-                                                        
              Monochloro-                                                 
                       2.99 159  2270      76    96.6                     
                                                     1.48 0.34            
      silane, 4 ml                                                        
              benzene, 1 ml                                               
8     Tetraethoxy-                                                        
              Perchloro-                                                  
                       3.82 262  3742      98    93.8                     
                                                     1.89 0.38            
      silane, 4 ml                                                        
              ethylene, 1 ml                                              
9     Tetraethoxy-                                                        
              1,1,1-Trichloro-                                            
                       2.01 210  2830     141    94.9                     
                                                     1.42 0.34            
      silane, 4 ml                                                        
              ethane, 2 ml                                                
10    Tetraethoxy-                                                        
              1,2-Dichloro-                                               
                       3.05 218  2910      95    95.4                     
                                                     1.38 0.32            
      silane, 4 ml                                                        
              ethane, 2 ml                                                
11    Tetraethoxy-                                                        
              1,1-Dichloro-                                               
                       2.42 201  2653     109    94.6                     
                                                     1.29 0.30            
      silane, 4 ml                                                        
              ethane, 2 ml                                                
__________________________________________________________________________
 
    
     
                                           TABLE 3                                 
__________________________________________________________________________
Activated                Electron                                         
                                Yield of                                  
                                     Activity    Total                    
                                                     Limiting             
                                                          Bulk            
Example                                                                   
      Ti    Org. Al Compound                                              
                         Donative                                         
                                Powders                                   
                                     g/g · Ti                    
                                                 I I Viscosity            
                                                          Density         
No.   Component                                                           
            (C.sub.2 H.sub.5).sub.2 AlCl                                  
                   (C.sub.2 H.sub.5).sub.3 Al                             
                         Compound                                         
                                g    Cat · hr                    
                                          Kg/g · Ti ·   
                                          hr     %   Number               
                                                          g/ml            
__________________________________________________________________________
12    120 mg                                                              
            0.07 ml                                                       
                   0.12 ml                                                
                         Triethoxy-                                       
                                261  2219 111    94.5                     
                                                     1.48 0.34            
                         phenylsilane                                     
                         0.09 ml                                          
13    133   0.07   0.12  Tetraethoxy-                                     
                                188  1508 75     93.1                     
                                                     1.23 0.33            
                         silane                                           
                         0.09                                             
14    159   0.20   0.20  Methyl 249  1598 80     92.1                     
                                                     1.59 0.36            
                         Ortho-                                           
                         benzoate                                         
                         0.08                                             
__________________________________________________________________________
 
    
     EXAMPLES 15-16 
     An activated Ti component was prepared in the same manner as in Example 1-(I) except using 3 g of hexachlorobenzene and 3 g of polyvinyl chloride (Number average molecular weight, about 70,000), respectively instead of α,α,α-trichlorotoluene in the pulverization step. 
     Using the activated Ti component thus obtained, polymerization of propylene was carried out in the same manner as in Example 1-(II). The results are set forth in Table 4. 
     
                                           TABLE 4                                 
__________________________________________________________________________
                   Yield of                  Limiting                     
                                                  Bulk                    
Example            Powders                                                
                        Activity        Total I I                         
                                             Viscosity                    
                                                  Density                 
No.  Activated Ti Component                                               
                   g    g/g · Ti-Cat · hr               
                                 Kg/g · Ti · hr         
                                        %    Number                       
                                                  g/ml                    
__________________________________________________________________________
15   Tetraethoxy-                                                         
            Hexachloro-                                                   
                   129  1230     35     92.8 1.91 0.26                    
     silane, 4 ml                                                         
            benzene 3 g                                                   
16   Tetraethoxy-                                                         
            Polyvinyl                                                     
                   105  1050     21     90.0 1.61 0.24                    
     silane, 4 ml                                                         
            chloride 3 g                                                  
__________________________________________________________________________