Novel copolymers

Abstract

A copolymer of ethylene and an alpha-olefin, said copolymer having a (a) density>0.930 g/cm 3 , (b) melt index (g/10 min)>4, (c) molecular weight distribution (MWD)>3.0, and (d) FNCT>250 hours., and is described suitable for use in rotomoulding applications. In particular the novel copolymers result in improved impact strength, improved permeation resistance and improved environmetal stress crack resistance and may suitably be prepared by use of metallocene catalysts.

1 - 19 . (canceled) 
     
     
         20 . A method for the preparation of copolymers of ethylene and alpha-olefins, said copolymers having a
 (a) density>0.930 g/cm 3 ,   (b) melt index (g/10 min)>4,   (c) molecular weight distribution (MWD)>3.0, and   (d) full notch creep test (FNCT)>250 hours,   said method comprising copolymerizing ethylene and an alpha-olefin in the presence of a single catalyst in a single reactor.   
     
     
         21 . A method for the preparation of copolymers according to claim  19  wherein the single catalyst comprises a metallocene catalyst system. 
     
     
         22 . A method according to  claim 21  wherein the metallocene catalyst system comprises a monocyclopentadienyl metallocene complex. 
     
     
         23 . A method according to  claim 22  wherein the monocyclopentadienyl metallocene
 complex has the formula: 
 
       
         
           
           
               
               
           
         
         wherein:— 
         R′ each occurrence is independently selected from hydrogen, hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof, said R′ having up to 20 nonhydrogen atoms, and optionally, two R′ groups (where R′ is not hydrogen, halo or cyano) together form a divalent derivative thereof connected to adjacent positions of the cyclopentadienyl ring to form a fused ring structure; 
         X is a neutral η 4  bonded diene group having up to 30 non-hydrogen atoms, which forms a π-complex with M; 
         Y is —O—, —S—, —NR*—, —PR*—, 
         M is titanium or zirconium in the +2 formal oxidation state; 
         Z* is SiR* 2 , CR* 2 , SiR* 2 SiR* 2 , CR* 2 CR* 2 , CR*═CR*, CR* 2 SiR* 2 , or 
         GeR* 2 , wherein: 
         R* each occurrence is independently hydrogen, or a member selected from hydrocarbyl, silyl, halogenated alkyl, halogenated aryl, and combinations thereof, said R* having up to 10 non-hydrogen atoms, and optionally, two R* groups from Z* (when R* is not hydrogen), or an R* group from Z* and an R* group from Y form a ring system. 
       
     
     
         24 . A method according to  claim 21  wherein the metallocene catalyst system is supported. 
     
     
         25 . A method according to  claim 24  wherein the support is silica. 
     
     
         26 . A method according to  claim 20  performed in the gas phase. 
     
     
         27 . A method according to  claim 20  wherein the alpha-olefin has C4-C12 carbon atoms. 
     
     
         28 . A method according to  claim 27  wherein the alpha-olefin is 1-hexene. 
     
     
         29 . A method according to  claim 20  wherein said copolymers have a melt index>6. 
     
     
         30 . A method according to  claim 20  wherein said copolymers have a molecular weight distribution>3.5. 
     
     
         31 . A method according to  claim 20  wherein said copolymers have a FNCT of >500 hours. 
     
     
         32 . A method according to  claim 20  wherein said copolymers have a whiteness index (WI) of >60. 
     
     
         33 . A method according to  claim 20  wherein said copolymers have a Composition Distribution Branch Index (CDBI) between 55 and 75%.