Outer sheath layer for power or communication cable
View Patent ↗A power or communications cable having an outer sheath layer made of a polyethylene composition including a base resin which comprises (A) a first ethylene homo- or copolymer fraction, and (B) a second ethylene homo- or copolymer fraction, wherein fraction (A) has a lower molecular weight than fraction (B), and the base resin has a molecular weight distribution M w /M n of more than 14.
1. A power or communications cable comprising an outer sheath layer made of a polyethylene composition comprising a base resin which comprises
(A) a first ethylene homo- or copolymer fraction,
(B) a second ethylene homo- or copolymer fraction, and
(C) a third ethylene homo- or copolymer fraction in an amount of up to 20 wt % of the total base resin,
wherein fraction (A) has a lower molecular weight than fraction (B), and the base resin has a molecular weight distribution M w /M n of more than 14, and fraction (C) has an MFR 2 of 0.1 g/10 min or lower.
2. Cable according to claim 1 wherein the base resin has a molecular weight distribution M w /M n of 23 or more.
3. Cable according to claim 1 wherein the base resin has a MFR 21 of at least 90 g/10 min.
4. Cable according to claim 1 wherein the base resin has a MFR 2 of 0.05 to 5 g/10 min.
5. Cable according to claim 4 wherein the base resin has a MFR 2 of 0.5 to 1.2 g/10 mm.
6. Cable according to claim 1 wherein the base resin has a density of 0.915 to 0.960 g/cm 3 .
7. Cable according to claim 6 wherein the base resin has a density of 0.918 to 0.928 g/cm 3 .
8. Cable according to claim 1 wherein the base resin has a flow rate ratio FRR of 50 to 150.
9. Cable according to claim 8 wherein the base resin has a flow rate ratio FRR of 80 to 130.
10. Cable according to claim 1 wherein fraction (A) has a MFR 2 of 50 to 5000 g/10 min.
11. Cable according to claim 1 wherein fraction (A) has a density of 0.930 to 0.975 g/cm 3 .
12. Cable according to claim 1 wherein fraction (A) is an ethylene copolymer with at least one further alpha-olefin.
13. Cable according to claim 1 wherein fraction (B) has a MFR 2 of 0.01 to 1 g/10 min.
14. Cable according to claim 1 wherein fraction (B) has a density of 0.880 to 0.930 g/cm 3.
15. Cable according to claim 1 wherein fraction (B) is a copolymer of ethylene with at least one further alpha-olefin.
16. Cable according to claim 1 wherein fraction (C) is present in the base resin in an amount of 1 wt % to 5 wt %.
17. Cable according to claim 1 wherein fraction (C) has a MFR 21 of less than 1 g/10 min.
18. Cable according to claim 1 wherein the weight ratio of fractions (A):(B) in the base resin is 40:60 to 60:40.
19. Cable according to claim 1 wherein the composition has a SHI (2.7/210) of 5 to 300.
20. Cable according to claim 1 wherein the base resin is an in-situ blend.
21. A polyethylene composition comprising a base resin which comprises
(A) a first ethylene homo- or copolymer fraction,
(B) a second ethylene homo- or copolymer fraction, and
(C) a third ethylene homo- or copolymer fraction in an amount of up to 20 wt % of the total base resin,
wherein fraction (A) has a lower molecular weight than fraction (B), and the base resin has a molecular weight distribution M w /M n of more than 14 and fraction (C) has a MFR 2 of 0.1 g/10 min or lower for the production of an outer sheath layer of a power or communication cable.