Polyolefin composition for rotomolding

Abstract

A polymer composition suitable for rotomoulding comprising I) An ethylene homopolymer or copolymer with at least one other C 3-10 a olefin, having a melt flow rate of 0.5 to 30, a molecular weight distribution (Mw/Mn) of less than 4, an Mw of 50,000 to 110,000, a density of 0.940 g/cm 3 to 0.970 g/cm 3 and a melting point of 100 to 145° C.; or I) a propylene homopolymer or copolymer with at least one other C 2-10 α olefin, having a melt flow rate of 0.5 to 30, a molecular weight distribution (Mw/Mn) of less than 4, an Mw of 150,000 to 300,000, and a melting point of 100 to 170° C.; and II) an ethylene homo or copolymer with at least one other C 3-10 α-olefin, having a melt flow rate of within 40% of the melt flow rate of component (I), a molecular weight distribution of (Mw/Mn) of less than 4, an Mw of within 30% of the Mw of component (I), a density of 0.880 g/cm 3 to 0.940 g/cm 3 said density being at least 0.010 g/cm 3 less than the density of component (I) and a melting point of at least 5+ C. less than that of component (I); or II) a propylene homo or copolymer with at least one other C 2-10 α-olefin having a melt flow rate of within 40% of the melt flow rate of component (I), a molecular weight distribution of (Mw/Mn) of less than 4, an Mw of within 30% of the Mw of component (I), and a melting point of at least 10° C. less than that of component (I).

1 - 19 . (canceled) 
   
   
       20 . A polymer composition suitable for rotomoulding comprising
 I) an ethylene copolymer with at least one other C 3-10  α-olefin, having a melt flow rate of 0.5 to 30 g/10 min, a molecular weight distribution (Mw/Mn) of less than 4, an Mw of 50,000 to 110,000, a density of 0.940 g/cm 3  to 0.970 g/cm 3  and a melting point of 100 to 145° C.; and   II) an ethylene copolymer with at least one other C 3-10  α-olefin, having a melt flow rate of within 40% of the melt flow rate of component (I), a molecular weight distribution of (Mw/Mn) of less than 4, an Mw of within 30% of the Mw of component (I), a density of 0.880 g/cm 3  to 0.940 g/cm 3  said density being at least 0.010 g/cm 3  less than the density of component (I) and a melting point of at least 5° C. less than that of component (I).   
   
   
       21 . A composition as claimed in  claim 20  wherein both components (I) and (II) are made by single site catalysts. 
   
   
       22 . A composition as claimed in  claim 20  wherein the melting point of component (II) is at least 10° C. less than that of component (I). 
   
   
       23 . A composition as claimed in  claim 20  wherein component (II) is an ethylene copolymer with butene, hexene or octene. 
   
   
       24 . A composition as claimed in  claim 20  wherein component (II) is an ethylene copolymer with hexene. 
   
   
       25 . A composition as claimed in any one of  claims 21  to  23  wherein the melt flow rates of components (I) and (II) are 4 to 10 g/10 min. 
   
   
       26 . A composition as claimed in  claim 20  wherein the melt flow rates of components (I) and (II) 6 to 8 g/10 min. 
   
   
       27 . A composition as claimed in  claim 20  wherein the molecular weight distribution of the composition is less than 4. 
   
   
       28 . A composition as claimed in  claim 20  wherein the density of component (II) is 0.910 g/cm 3  to 0.930 g/cm 3 . 
   
   
       29 . A composition as claimed in  claim 20  wherein the density of composition is in the range 0.925 to 0.950 g/cm 3 . 
   
   
       30 . A composition as claimed in  claim 20  wherein the density of composition is in the range 0.930 to 0.940 g/cm 3 . 
   
   
       31 . A composition as claimed in  claim 20  wherein the melting point of component (I) is in the range 125° C. to 135° C. and the melting point of component (II) is in the range 100° C. to 125° C. 
   
   
       32 . A composition as claimed  claim 20  wherein the molecular weight distribution each of components (I) and (II) is less than 3. 
   
   
       33 . A composition as claimed in  claim 20  wherein the ratio of component (I) to (II) is from 4:1 to 1:4. 
   
   
       34 . A rotomoulded article formed from a polymer composition as claimed in  claim 20 . 
   
   
       35 . An article as claimed in  claim 34  being a liquid container. 
   
   
       36 . A process for the preparation of a rotomoulded article comprising rotomoulding a composition comprising
 I) an ethylene copolymer with at least one other C 3-10  α-olefin, having a melt flow rate of 0.5 to 30 g/10 min, a molecular weight distribution (Mw/Mn) of less than 4, an Mw of 50,000 to 110,000, a density of 0.940 g/cm 3  to 0.970 g/cm 3  and a melting point of 100 to 145° C.; and   II) an ethylene copolymer with at least one other C 3-10  α-olefin, having a melt flow rate of within 40% of the melt flow rate of component (I), a molecular weight distribution of (Mw/Mn) of less than 4, an Mw of within 30% of the Mw of component (I), a density of 0.880 g/cm 3  to 0.940 g/cm 3  said density being at least 0.010 g/cm 3  less than the density of component (I) and a melting point of at least 5° C. less than that of component (I).   
   
   
       37 . A process as claimed in  claim 36  wherein rotomoulding is effected at a rotation speed of 9/1.4 RPM; heating for 13 minutes in oven at 270° C.; fan assisted cooling for 10 minutes followed by 6 minutes ambient cooling in the absence of a fan. 
   
   
       38 . A rotomoulded article as claimed in  claim 34  wherein both components (I) and (II) are made by metallocene catalysts.