Rotomolding resin
Resins suitable for rotomolded articles comprise a bimodal polyethylene copolymer comprising from 0.1 to 5 weight % of one or more C 6-8 alpha olefins and the balance ethylene, comprising from 20 to 50 weight % of a higher molecular weight polymer component having an Mw greater than 120,000 and correspondingly from 80 to 50 weight % of a lower molecular weight polymer component having an Mw less than 100,000 having a density greater than 0.942 g/cc [but less than 0.965 g/cc] and a bent strip ESCR as determined by ASTM D 1693 in 100% Igepal® CO-630 (ethoxylated nonylphenols) for conditions A and B of greater than 1000 hours. The resulting articles have a very good balance of properties and significant ESCR.
1. A bimodal polyethylene copolymer comprising from 0.1 to 5 weight % of one or more C 6-8 alpha olefins and the balance ethylene, comprising from 20 to 50 weight % of a higher molecular weight polymer component having an Mw greater than 120,000 and correspondingly from 80 to 50 weight % of a lower molecular weight polymer component having an Mw less than 100,000 having a density greater than 0.942 g/cc but less than 0.965 g/cc, an Mz/Mw from 2.4 to 3.2 and a bent strip ESCR (f 50 ) as determined by ASTM D 1693 in 100% Igepal CO-630 (ethoxylated nonylphenols) for conditions A and B of greater than 1000 hours.
2. The polyethylene copolymer according to claim 1 , wherein the higher molecular weight component has an Mw from 140,000 to 300,000.
3. The polyethylene copolymer according to claim 2 , wherein the lower molecular weight component has an Mw from 20,000 to 80,000.
4. The polyethylene copolymer according to claim 3 , wherein the higher molecular weight component is present in an amount from 30 to 40 weight % based on the weight of the copolymer.
5. The polyethylene copolymer according to claim 4 , wherein the higher molecular weight component has a density from 0.918 to 0.934 g/cc.
6. The polyethylene copolymer according to claim 5 , wherein the lower molecular weight component has a density greater than 0.942 to 0.960 g/cc.
7. The polyethylene copolymer according to claim 6 , wherein the density difference between the higher molecular weight component and the lower molecular weight component is less than 0.030 g/cc.
8. The polyethylene copolymer according to claim 7 , having a density greater than 0.942 g/cc.
9. The polyethylene copolymer according to claim 8 , having a flat to reverse comonomer incorporation.
10. The polyethylene copolymer according to claim 9 , having a degree of internal unsaturation from 0.1 to 0.5 per 1000 carbon atoms.
11. A rotomolded article, which comprise the resin according to claim 1 .