A multimodal polyethylene copolymer comprising: (III) 35 to 55 wt % of a lower molecular weight ethylene homopolymer component having an MFR 2 of 200 to 400 g/10 min; (IV) 45 to 65 wt % of a higher molecular weight ethylene copolymer component of ethylene and at least one C3-12 alpha olefin comonomer; wherein said multimodal polyethylene copolymer has a density of 955 to 962 kg/m 3 , an MFR 2 of 2.0 to 10 g/10 min and an Mw/Mn of more than 9.0.
1. A cap or closure comprising a multimodal polyethylene copolymer comprising:
(I) 35 to 55 wt % of an ethylene homopolymer component having an MFR 2 of 200 to 400 g/10 min;
(II) 45 to 65 wt % of an ethylene copolymer component of ethylene and at least one C3-12 alpha olefin comonomer having a higher molecular weight than the ethylene homopolymer;
wherein said multimodal polyethylene copolymer has a density of 955 to 962 kg/m 3 , an MFR 2 of 2.0 to 10 g/10 min, an Mw/Mn of more than 9.0 and of 30.0 or below, and a shear thinning index (SHI 2.7/210) in the range of 7.0 to 18.0.
2. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has an Mw/Mn of more than 10.0.
3. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has an MFR 2 of 2.0 to 4.9 g/10 min.
4. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer is prepared using a Ziegler Natta catalyst.
5. A cap or closure as claimed in claim 1 wherein said copolymer component comprises at least one C3-12 alpha olefin.
6. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has 45 to 60 wt % of the ethylene copolymer a component and 40 to 55 wt % of the ethylene homopolymer component.
7. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has a shear thinning index (SHI 2.7/210) in the range of 8.0 to 15.0.
8. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer is a copolymer with a comonomer 1-butene.
9. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has an ESCR of more than 20 hrs.
10. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has a charpy impact strength measured at 23° C. of 4.0 to 10.0 kJ/m 2 .
11. A cap or closure as claimed in claim 1 wherein a spiral flow length of the multimodal polyethylene copolymer under conditions of 190° C. at 1000 bar pressure is 14.0 to 21.0 cm and/or
the spiral flow length of the multimodal polyethylene copolymer under conditions of 220° C. at 1000 bars is 16.0 to 24.0 cm.
12. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer has a density of 956 to 962 kg/m 3 .
13. A cap or closure as claimed in claim 1 wherein said multimodal polyethylene copolymer comprises:
(I) 40 to 55 wt % of the weight ethylene homopolymer component having an MFR 2 of 200 to 400 g/10 min;
(II) 45 to 60 wt % of the ethylene copolymer component of ethylene and at least one C3-12 alpha olefin comonomer having a higher molecular weight than the ethylene homopolymer;
wherein said multimodal polyethylene copolymer has a density of 956 to 959 kg/m 3 , an MFR 2 of 2.0 to 4.9 g/10 min, an ESCR of 20 to 59 hrs, an SHI (2.7/210) of 8.0 to 15.0 and an Mw/Mn of more than 9.0.
14. A cap or closure as claimed in claim 1 which is injection or compression moulded.
15. A process for the preparation of the polyethylene copolymer as claimed in claim 1 comprising:
polymerising ethylene in the presence of a Ziegler Natta catalyst so as to form 35 to 55 wt % of the ethylene homopolymer component having an MFR 2 of 200 to 400 g/10 min; and subsequently
polymerising ethylene and the at least one C3-12 alpha olefin comonomer in the presence of the ethylene homopolymer component and in the presence of the same Ziegler Natta catalyst so as to form 65 to 45 wt % of the ethylene copolymer component having a higher molecular weight than the ethylene homopolymer component.
16. A cap or closure as claimed in claim 3 wherein said multimodal polyethylene copolymer has an MFR 2 of 3.0 to 4.9 g/10 min.
17. A cap or closure as claimed in claim 5 wherein said copolymer component comprises but-1-ene, hex-1-ene or oct-1-ene.
18. A cap or closure as claimed in claim 6 having 48 to 52 wt % of the ethylene copolymer component and 52 to 48 wt % of the ethylene homopolymer component.
19. A cap or closure as claimed in claim 11 wherein the spiral flow length under conditions of 190° C. at 1000 bar pressure is 16.0 to 19.0 cm and/or
the spiral flow length under conditions of 220° C. at 1000 bars is 17.5 to 20.0 cm.
20. A cap or closure as claimed in claim 13
wherein the spiral flow length under conditions of 190° C. at 1000 bar pressure is 16.0 to 21.0 cm; and/or
the spiral flow length under conditions of 220° C. at 1000 bars is 17.5 to 20.0 cm.