Rotomoulded articles prepared with polyethylene

Abstract

The present invention is concerned with rotomoulded articles having very low warpage and shrinkage and consisting essentially of polyethylene prepared with a catalyst system based on a bis-indenyl or on a bis(n-butylcyclopentadienyl) metallocene component.

1 - 14 . (canceled)  
   
   
       15 . A hollow article produced by rotational molding of a polyethylene resin and having a wall structure comprising of a polyethylene resin produced by the polymerization of ethylene in the presence of a metallocene catalyst having a bis-cyclopentadienyl ligand structure or a bridged bis-indenyl ligand structure.  
   
   
       16 . The article of  claim 15  wherein said polyethylene resin is produced by polymerization of ethylene in the presence of a metallocene having a bridged tetrahydroindenyl ligand.  
   
   
       17 . The article of  claim 16  wherein said metallocene is ethylene bis (4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride.  
   
   
       18 . The article of  claim 15  wherein said resin is produced by the polymerization of ethylene in the presence of a metallocene having a bis(n-butyl-cyclopentadienyl) ligand structure.  
   
   
       19 . The article of  claim 18  wherein said metallocene is bis(n-butyl-cyclopentadienyl) zirconium dichloride.  
   
   
       20 . The article of  claim 15  wherein said resin is an ethylene homopolymer.  
   
   
       21 . The article of  claim 15  wherein said resin is a copolymer of ethylene and a C 3 -C 20  alpha olefin.  
   
   
       22 . The article of  claim 21  wherein said alpha olefin is selected from a group consisting of propylene, butene, hexene, octene and 4-methyl-pentene.  
   
   
       23 . The article of  claim 15  wherein said polyethylene resin has a density within the range of 0.915-0.95 g/cm 3  and a melt index within the range of 0.5-30 g/10 min.  
   
   
       24 . The article of  claim 23  wherein said polyethylene resin has a density within the range of 0.925-0.945 g/cm 3  and a melt index within the range of 2.0-20.0 g/10 min.  
   
   
       25 . The article of  claim 15  wherein said wall structure has a warpage factor which is less than the warpage factor of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       26 . The article of  claim 15  wherein said wall structure has an elastic modulus which is less than the elastic modulus of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       27 . The article of  claim 15  wherein said wall structure has a shrinkage factor which is less than the shrinkage factor of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       28 . The article of  claim 15  wherein said wall structure has a permeability which is less than the permeability of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       29 . The article of  claim 15  wherein said wall structure has a resistance to degradation by nitric acid which is less than the resistance to degradation by nitric acid of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       30 . The article of  claim 15  wherein the surface of said wall structure has a higher gloss than the gloss of the surface of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       31 . The article of  claim 15  wherein said wall structure has a microstructure which is finer than the microstructure of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       32 . The article of  claim 15  wherein said polyethylene resin has a molecular weight distribution which is less than that of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.  
   
   
       33 . The article of  claim 15  wherein said wall structure has an elastic modulus which is less than the elastic modulus of the wall structure of a comparative hollow article arrived at by rotational molding under the same conditions as employed in producing said first recited hollow article of a corresponding polyethylene resin produced by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst.