A metallocene-catalysed multimodal polyethylene copolymer, which consists of (i) 35.0 to 50.0 wt% of an ethylene-1-butene polymer component, and (ii) 50.0 to 65.0 wt% of an ethylene-1-hexene polymer component, whereby the ethylene-1-butene polymer component has a density in the range of from 920 to 950 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 2.0 to 20.0 g/10 min, a 1-butene content in the range of 0.1 to 2.0 mol%, based on the ethylene-1-butene polymer component; the ethylene polymer component has a density in the range of from 890 to 920 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 0.1 to 2.0 g/10 min a 1-hexene content in the range of 2.5 to 10.0 mol% based on the ethylene-1-hexene polymer compound; whereby the multimodal polyethylene copolymer has a density in the range of from 915 to 925 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 1.0 to 3.0 g/10 min, a molecular weight distribution Mw/Mn determined with GPC in the range of at least 4.6 up to 7.0, a ratio of the molecular weight Mw of the low crystalline fraction to the molecular weight Mw of the high crystalline fraction, Mw(Tp /Mw(Tp, determined as described in the experimental part, in the range of from 1.8 to 4.0 and a half peak breadth of the low crystalline fraction in a TREF profile with LogM>5.2, determined as described in the experimental part, in the range of 5.0 to 20.0; and wherein ethylene-1-butene polymer component consists of an ethylene-1-butene polymer fraction (A-1) and an ethylene-1-butene polymer fraction (A-2), wherein the ethylene polymer fraction (A-1) has a density in the range of from 920 to 960 kg/m 3 and an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 1.0 to 15.0 g/10 min and the ethylene polymer fraction (A-2) has a density in the range of from 925 to 950 kg/m 3, and an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, the range of 1.0 to 15.0 g/10 min. (i) 35.0 to 50.0 wt% of an ethylene-1-butene polymer component, and (ii) 50.0 to 65.0 wt% of an ethylene-1-hexene polymer component, whereby the ethylene-1-butene polymer component has a density in the range of from 920 to 950 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 2.0 to 20.0 g/10 min, a 1-butene content in the range of 0.1 to 2.0 mol%, based on the ethylene-1-butene polymer component; a density in the range of from 920 to 950 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 2.0 to 20.0 g/10 min, a 1-butene content in the range of 0.1 to 2.0 mol%, based on the ethylene-1-butene polymer component; the ethylene polymer component has a density in the range of from 890 to 920 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 0.1 to 2.0 g/10 min a 1-hexene content in the range of 2.5 to 10.0 mol% based on the ethylene-1-hexene polymer compound; a density in the range of from 890 to 920 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 0.1 to 2.0 g/10 min a 1-hexene content in the range of 2.5 to 10.0 mol% based on the ethylene-1-hexene polymer compound; whereby the multimodal polyethylene copolymer has a density in the range of from 915 to 925 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 1.0 to 3.0 g/10 min, a molecular weight distribution Mw/Mn determined with GPC in the range of at least 4.6 up to 7.0, a ratio of the molecular weight Mw of the low crystalline fraction to the molecular weight Mw of the high crystalline fraction, Mw(Tp /Mw(Tp, determined as described in the experimental part, in the range of from 1.8 to 4.0 and a half peak breadth of the low crystalline fraction in a TREF profile with LogM>5.2, determined as described in the experimental part, in the range of 5.0 to 20.0; and a density in the range of from 915 to 925 kg/m 3, an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 1.0 to 3.0 g/10 min, a molecular weight distribution Mw/Mn determined with GPC in the range of at least 4.6 up to 7.0, a ratio of the molecular weight Mw of the low crystalline fraction to the molecular weight Mw of the high crystalline fraction, Mw(Tp /Mw(Tp, determined as described in the experimental part, in the range of from 1.8 to 4.0 and a half peak breadth of the low crystalline fraction in a TREF profile with LogM>5.2, determined as described in the experimental part, in the range of 5.0 to 20.0; and wherein ethylene-1-butene polymer component consists of an ethylene-1-butene polymer fraction (A-1) and an ethylene-1-butene polymer fraction (A-2), wherein the ethylene polymer fraction (A-1) has a density in the range of from 920 to 960 kg/m 3 and an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, in the range of from 1.0 to 15.0 g/10 min and the ethylene polymer fraction (A-2) has a density in the range of from 925 to 950 kg/m 3, and an MFR 2, determined at 190°C, 2.16 kg, according to ISO 1133, the range of 1.0 to 15.0 g/10 min.