Process for the preparation of a syndiotactic polyolefin and catalyst therefor

Abstract

A syndiotactic polyolefin is obtained in a high yield by polymerization or copolymerization of an olefin of the formula R a --CH═CH--R b in the presence of a catalyst consisting of a metallocene of the formula I ##STR1## and an aluminoxane. This polyolefin has a very high syndiotactic index. At a low polymerization temperature, a polyolefin having a low average molecular weight and narrow molecular weight distribution is obtained, and at a high polymerization temperature a polymer having a high average molecular weight and a wide molecular weight distribution is obtained. Shaped articles produced from the polymers are distinguished by a high transparency, flexibility, tear strength and excellent surface gloss.

We claim: 
     
       1. A process for the prepartion of a syndiotactic polyolefin by polymerization or copolymerization of an ethylene, propylene, 1-butene, or 4methyl-1-pentene olefin which comprises carrying out said process at a temperature of -60° C. to 200° C. under a pressure of 0.5 to 100 bar in solution, in suspension or in the gas phase in the presence of a catalyst which comprises a transition metal component and an aluminoxane of the formula II ##STR13## for the linear type and/or of the formula III ##STR14## for the cyclic type, in which, in the formulae II and III, R 9  denotes a C 1  -C 6  -alkyl group or a C 6  -C 10  -aryl group or benzyl and n is an integer from 2 to 50, wherein the transition metal component of said catalyst is an (arylalkylidene)(fluoroenyl)(cyclopentadienyl)-hafnium dichloride or a (diarylmethylene)(fluorenyl)(cyclopentadienyl)-hafnium dichloride, in which the aryl of said hafnium compounds is a C 6  to C 10  aryl group and the alkyl of said hafnium compounds is a C 1  to C 10  alkyl group. 
     
     
       2. The process as claimed in claim 1, wherein, the transition metal component comprises (methyl)(phenyl)methylene)(fluorenyl)(cyclopentadienyl)-hafnium dichloride or (diphenylmethylene)-(fluorenyl)(cyclopentadienyl)-hafnium dichloride. .Iadd. 
     
     
       3.  A metallocene compound having the formula ##STR15## wherein: Hal is hydrogen, R 6  is C 6  -C 8  -aryl, and   R 7  is the same as or different from R 6  and is C 6  -C 8  -aryl or C 1  -C 3  -alkyl. .Iaddend..Iadd.   
     
     
       4.  A metallocene as claimed in claim 3, wherein Hal is chlorine and R 6  is phenyl. .Iaddend..Iadd.5. A metallocene as claimed in claim 3, wherein said metallocene is (methyl)(phenyl)-methylene)(fluorenyl)(cyclopentadienyl)-hafnium dichloride. .Iaddend..Iadd.6. A metallocene as claimed in claim 3, wherein said metallocene is (diphenylmethylene)(fluorenyl)(cyclopentadienyl)-hafnium dichloride. 
     
     
        .Iaddend..Iadd.7.  A catalyst composition comprising a metallocene as claimed in claim 3 and an aluminoxane. .Iaddend..Iadd.8. A catalyst composition comprising a metallocene as claimed in claim 4 and an 
     
     
        aluminoxane. .Iaddend..Iadd.9.  A catalyst composition comprising a metallocene as claimed in claim 5 and an aluminoxane. .Iaddend..Iadd.10. A catalyst composition comprising a metallocene as claimed in claim 6 and an aluminoxane. .Iaddend..Iadd.11. A catalyst composition as claimed in claim 7, wherein the aluminoxane has the formula II ##STR16## for a linear aluminoxane and/or the formula III ##STR17## for a cyclic aluminoxane, in which, in the formulae II and III, R 9  denotes a C 1  -C 6  -alkyl group or a C 6  -C 10  -aryl group 
     
     
        or benzyl and n is an integer from 2 to 50. .Iaddend..Iadd.12.  A catalyst composition as claimed in claim 11, wherein, in said formula for said metallocene, Hal is chlorine and R 6  is phenyl. .Iaddend.