Polyethylene composition suitable for impact resistance pipe

Abstract

The invention relates to a polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) ≥ 50.0 and ≤ 58.0 wt.%, preferably ≥ 51.0 and ≤ 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A; and b) ≥ 42.0 and ≤ 50.0, wt.%, preferably ≥ 45.0 and ≤ 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has: • a density of ≥ 945.0 and ≤ 955.0 kg / m3; and • a melt flow rate (MFR5.0) of ≥ 0.2 and ≤ 0.5 dg / min, determined in accordance with ISO1133- 1:2011 at 190 ºC and measured at 5.0 kg; and • a complex viscosity (η300) determined at a shear rate of 300 rad / s of ≥ 900.0 Pa.s and ≤ 1050.0 Pa.s, determined in accordance with ISO 6721-10 at 190 ºC; and • a z-average molecular weight (Mz) of ≥ 1250 kg / mol and ≤ 2500 kg / mol, determined in accordance with ASTM D 6474-12; and • a weight average molecular weight (Mw) of ≥ 230 kg / mol and ≤ 320 kg / mol, determined in accordance with ASTM D 6474-12. The invention further relates to a pipe comprising the polyethylene composition.

Description

POLYETHYLENE COMPOSITION SUITABLE FOR IMPACT RESISTANCE PIPEFIELD OF INVENTION

[0001] The invention relates to a polyethylene composition and to pipes prepared from such polyethylene composition. The invention further relates to a process for preparing such pipes.BACKGROUND

[0002] A multimodal ethylene copolymer is used in many application fields such as pipes. Polyethylene pipes are typically used for transport of water, gas as well as industrial liquids and slurries. Due to their combination of properties, ease of production and installation, non-corrosivity as well as low friction coefficients, their use is constantly increasing.

[0001] New pipe installation techniques, such as trenchless and sand bed free installation, demand polyethylene pipes resins with enhanced or increased resistance to slow crack growth with high impact. In particular, industry practitioners require polyethylene compositions that have a suitable combination of processability and impact resistance.

[0002] With regard to processability, there is a demand for polyethylene compositions, with relatively low viscosity so that the composition can be extruded at lower temperature and / or lower energy input during the extrusion processes of making the pipe. However, lowering the viscosity of polyethylene compositions comes at the cost of adversely affecting the strain hardening modulus and impact properties of the polyethylene composition. Strain hardening is necessary for early pipe mechanical failures, low viscosity is necessary for ensuring processability during extrusion while impact strength is required for preparing pipes suitable for installation and transportation of fluids under pressure. Further pipe manufacturers often add carbon black masterbatches to improve protection against UV induced degradation. However, the addition of master-batches and especially carbon black based master-batch adversely impacts processability and mechanical properties of the polyethylene composition owing to the presence of the carrier resin present in the masterbatch.

[0003] Published patent literature have described various polyethylene compositions that are suitable for making pipes. For example, W02020088987 describes polyethylene composition suitable for pipes comprising a base resin having a density of from 952.0 kg / m3to 960.0 kg / m3and has a melt flow rate MFR21 (190°C, 21.16 kg), of from 1.0 to 7.5 g / 10 min, a complex viscosity at a frequency of 0.05 rad / s eta0.05 from 750 kPa-s to 1900 kPa-s.

[0004] Yet another example, W02022008607A1 relates to a polyethylene composition suitable for pipes comprising a base resin, which comprises (A) a first ethylene homo- or copolymer fraction, and (B) a second ethylene -hexene -1 copolymer fraction.

[0005] Although the technical solutions proposed in these patent applications are promising, there remains a need to develop polyethylene compositions which have a suitable balance of impact properties, processability and strain hardening.

[0006] Therefore, it is an objective of the present invention to provide for polyethylene compositions which have a suitable balance of impact properties, processability, strain hardening and increased slow crack growth resistance. It is yet another objective of the present invention to provide for a pipe, which has high impact property while being prepared with high processability. It is yet another objective of the present invention to provide polyethylene composition without the need of adding carbon black masterbatch.DESCRIPTION

[0007] Accordingly, the one or more objectives of the present invention is achieved by a polyethylene composition comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3, determined in accordance with ISO 1183; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight determined in accordance with ASTM D 6474-12; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12.

[0008] Preferably the ethylene copolymer fraction (B) comprises polymeric units derived from ethylene and polymeric units derived from 1 -hexene. Preferably, the ethylene homopolymer fraction (A) has a ratio of Mz / Mw of > 35.0 and < 50.0, preferably of > 40.0 and < 48.0.

[0009] Preferably, a polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s,; and• a z-average molecular weight (Mz) of > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol.

[0010] Preferably, the polyethylene composition, comprises > 95.0 wt.%, preferably > 98.0 wt.%, preferably > 98.0 wt.% and < 100.0 wt.%, of the ethylene polymer with regard to the total weight of the polyethylene composition. Preferably, the polyethylene composition, comprises > 90.0 wt.% and < 100 wt.% of the ethylene polymer, with regard to the total weight of the polyethylene composition and > 0 wt.% and < 10.0 wt.% of additives selected from antioxidants, color pigments, metal stearates and any combinations thereof.

[0011] Preferably, wherein the polyethylene composition is free of carbon black.

[0012] Advantageously, the polyethylene composition of the present invention has a sufficiently low weight average molecular weight (Mw) and low viscosity even at low shear rates enabling the ease of processability while surprisingly retaining high melt strength and impact property. In particular, the polyethylene composition of the invention has a combination of a high processability, suitable strain hardening modulus, a low viscosity at high shear rate, while imparting high impact strength to articles made from such polyethylene composition. As a further advantage, such combination of properties enables energy efficient production of polyethylene pipes with increased slow crack growth resistance.

[0013] In particular, the complex viscosity (rpoo) of the polyethylene composition determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s. Such low viscosity at high shear rate is indicative of improved processability and lower energy demand (higher energy efficiency) during pipe production process.

[0014] Preferably, the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a z-average molecular weight (Mz) of > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12.

[0015] Preferably, polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR5 0) of > 0.27 and < 0.32 dg / min determined in accordance with ISO1133- 1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12.

[0016] Preferably, polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR5 0) of > 0.27 and < 0.32 dg / min determined in accordance with ISO1133- 1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12; and• complex viscosity (r]ooi) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

[0017] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of:a) > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3; and• a melt flow rate (MFR50) of > 0.24 and < 0.35 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 930.0 Pa.s and < 1050.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12.

[0018] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR5 0) of preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol.

[0019] Preferably, the polyethylene composition, comprises at least 90.0 wt.% and < 100. wt.%, of an ethylene polymer and > 0 wt.% and < 10.0 wt.% of additives selected antioxidants, color pigments, metal stearates and any combinations thereof, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol.

[0020] Preferably the polyethylene composition has a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0, wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively.

[0021] Preferably, the polyethylene composition has a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0 wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and / or wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa, preferably > 88.0 MPa and < 93.0 MPa.

[0022] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3,determined in accordance with ISO 1183; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of preferably > 0.27 and < 0.32 dg / min determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa, preferably > 88.0 MPa and < 93.0 MPa.

[0023] Preferably, the polyethylene composition has a melt flow rate ratio (FRR) of > 30.0 and < 37.0, wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO 18488 of > 80.0 MPa and < 95.0 MPa, preferably > 88.0 MPa and < 93.0 MPa.

[0024] Preferably, the polyethylene composition has a molecular weight distribution (Mw / Mn) of > 25.0 and < 35.0, preferably > 25.0 and < 33.0, preferably > 25.0 and < 30.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight.

[0025] Preferably, the polyethylene composition has a Long Chain Branch (LCB) Index of > 0.8 and < 1.5, preferably > 0.8 and < 1.45, preferably > 0.8 and < 0.9, wherein LCB index is determined by: LCBIndex= , wherein T|0oi is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in kPa*s, and Mw is the weight average molecular weight expressed in kg / mol.

[0026] Preferably, the polyethylene composition has a molecular weight distribution (Mw / Mn) of > 25.0 and < 35.0, preferably > 25.0 and < 33.0, preferably > 25.0 and < 30.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight; and / or the polyethylene composition has a Long Chain Branch (LCB) Index of > 0.8 and < 1.5, preferably > 0.8 and < 1.45, preferably > 0.8 and < 0.9, wherein LCB index is determined by:L CBindex = ^ wherein r|0oi is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in kPa*s, and Mw is the weight average molecular weight expressed in kg / mol.

[0027] Preferably, the polyethylene composition has a molecular weight distribution (Mw / Mn) of > 25.0 and < 33.0, preferably > 25.0 and < 30.0; and the polyethylene composition has a Long Chain Branch (LCB) Index of > 0.8 and < 0.9, wherein LCB index is determined by:

[0028] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s,; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 33.0, preferably > 25.0 and < 30.0; anda melt flow rate ratio (FRR) of > 30.0 and < 37.0; and a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 80.0 MPa and < 95.0 MPa.

[0029] Preferably, the polyethylene composition has a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0, wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and / or wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa; and / or SH wherein the polyethylene composition satisfies the equation - - — > —0.0339 ■ MFR5+ 0.0985, whereSH and MFR5are as defined herein.

[0030] Preferably, the polyethylene composition has a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0, wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa; and SH wherein the polyethylene composition satisfies the equationDensity— —0.0339 ■ MFR5+ 0.0985, where SH and MFR5 are as defined herein.

[0031] Preferably, the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa; preferably > 88.0 MPa and < 93.0 MPa; and / or wherein the polyethylene composition satisfies CLJ the equation - Density > —0.0339 ■ MFR5+ 0.0985, where SH and MFR5 are as defined herein.

[0032] Preferably, the polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; andb) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s,; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0; and• a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa; andSH• wherein the polyethylene composition satisfies the equationDensity—0.0339 ■ MFR5+ 0.0985, where SH and MFR5are as defined herein.

[0033] Preferably, the polyethylene composition a total content of polymeric units derived from Cs-Cs alpha olefin co-monomer of > 0.5 and < 0.85 mol.%, preferably > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition, and wherein the polyethylene composition and a total content of polymeric units derived from ethylene of > 99.15 and < 99.5 mol.%, preferably > 99.28 and < 99.35 mol.%, with regard to the total moles of the polyethylene composition, where the mole content of the polyethylene composition is determined using13C NMR spectroscopy. Preferably the Cs-Cs alpha olefin co-monomer is selected from propylene, 1 -butene, 1 -hexene, 4-methyl 1 -pentene, 1 -octene, preferably the Cs-Cs alpha olefin co-monomer is any one of 1-butene or 1-hexene, more preferably the Cs-Cs alpha olefin co-monomer is 1-hexene.

[0034] Preferably, the polyethylene composition a total content of polymeric units derived from 1-hexene of > 0.5 and < 0.85 mol.%, with regard to the total moles of the polyethylene composition, and wherein the polyethylene composition and a total content of polymeric units derived from ethylene of > 99.15 and < 99.5 mol.%, with regard to the total moles of the polyethylene composition, where the mole content of the polyethylene composition is determined using13C NMR spectroscopy.

[0035] Preferably, the polyethylene composition has a total content of polymeric units derived from 1-hexene of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition, and wherein the polyethylene composition and a total content of polymeric units derived from ethylene of > 99.28 and < 99.35 mol.%, with regard to the total moles of the polyethylene composition, where the mole content of the polyethylene composition is determined using13C NMR spectroscopy.

[0036] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 33.0, preferably > 25.0 and < 30.0; and• a melt flow rate ratio (FRR) of > 30.0 and < 37.0; and• a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 85.0 MPa and < 95.0 MPa; and• total content of polymeric units derived from 1-hexene alpha-olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition, a total content of polymeric units derived from ethylene of > 99.28 and < 99.35 mol.%, with regard to the total moles of the polyethylene composition.

[0037] Preferably, the polyethylene composition has a Long Chain Branch (LCB) Index of > 0.8 and < 1.5, preferably > 0.8 and < 1.45, preferably > 0.8 and < 0.9, wherein LCB index is determined by: LCBIndex=e36296.in(0M, )_83439, wherein T|0oi is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in kPa*s and Mw is the weight average molecular weight as expressed in kg / mol. The branching index is indicative of sufficient amount of branching to enable processability and imparting sufficient melt strength to the polyethylene composition.

[0038] Preferably, the polyethylene composition has a shear index (SHE 7 / 210) of > 60.0 and < 77.0, preferably > 63.0 and < 73.0, wherein shear index is defined as the ratio of complex viscosity at a storage modulus (G*) of 2.7 kPa, to the complex viscosity at a storage modulus (G*) of 210 kPa, where storage modulus (G*) is determined in accordance with ISO 6721-10.

[0039] Preferably, the polyethylene composition has a complex viscosity (T|O01) at a shear rate of 0.01 rad / s of > 125.0 kPa.s and < 260.0 k.Pa.s, preferably > 185.0 kPa.s and < 255.0 k.Pa.s preferably > 195.0 kPa.s and < 230.0 k.Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and wherein the polyethylene composition has a complex viscosity (r|o 05) at a shear rate of 0.05 rad / s of > 80.0 kPa.s and < 160.0 k.Pa.s, preferably > 135.0 kPa.s and < 155.0 kPa.s, preferably > 135.0 kPa.s and < 147.0 kPa.s, determined in accordance with ISO 6721-10 at 190 °C. Such viscosity at low shear rate results in a better homogeneity and surface aspect of the pipes produced.

[0040] Preferably, the polyethylene composition has a complex viscosity (T|O01) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s; and wherein the polyethylene composition has a complex viscosity (po os) at a shear rate of 0.05 rad / s of > 135.0 kPa.s and < 147.0 kPa.s.Ethylene homopolymer fraction (A)

[0041] Preferably, the ethylene homopolymer fraction (A) has a ratio of Mw / Mn of > 8.5 and < 12.0, preferably of > 9.0 and < 11.5; and / or the ethylene homopolymer fraction (A) has a ratio of Mz / Mwof > 35.0 and < 50.0, preferably of > 40.0 and < 48.0; and / or a melt flow rate (MFRi 2) of > 70 and < 130 dg / min, preferably > 70 and < 110 dg / min, determined in accordance with ISO1133-1:2011 at 190 °C and measured at 1.2 kg. The broad molecular weight distribution is a result of using Ziegler Natta catalyst.

[0042] Preferably, the ethylene homopolymer fraction (A) of the ethylene polymer has a weight average molecular weight (Mw) of > 45.0 kg / mol and < 70.0 kg / mol, preferably > 50.0 kg / mol and < 65.0 kg / mol, determined in accordance with ASTM D 6474-12.

[0043] Preferably, the ethylene homopolymer fraction (A) has a ratio of Mw / Mn of > 9.0 and < 11.5; and the ethylene homopolymer fraction (A) has a ratio of Mz / Mw of > 35.0 and < 50.0, preferably of > 40.0 and < 48.0; and a melt flow rate (MFRi 2) of > 70 and < 90 dg / min; and is present in an amount of > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer.Ethylene copolymer fraction (B)

[0044] Preferably the ethylene copolymer fraction (B) comprises polymeric units derived from ethylene and from Cs-Cs alpha olefin comonomer selected from propylene, 1 -butene, 1 -hexene, 4-methyl 1 -pentene, 1 -octene, preferably the Cs-Cs alpha olefin comonomer is any one of 1 -butene or 1 -hexene, more preferably the Ci-C’s alpha olefin comonomer is 1 -hexene.

[0045] Preferably, the ethylene copolymer fraction (B) comprises polymeric units derived from ethylene and polymeric units derived from 1 -hexene.

[0046] Preferably, the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR50) of > 0.27 and < 0.32 dg / min determined in accordance with ISO1133- 1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 30.0; anda total content of polymeric units derived from 1-hexene alpha olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition; and

[0047] Preferably, the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 30.0; and• a total content of polymeric units derived from 1-hexene alpha olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition; and• a shear index (SHI27 / 210) of > 63.0 and < 73.0; and• a Long Chain Branch (LCB) Index of > 0.8 and < 0.9; and• a complex viscosity (r|o 01) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s; and• a complex viscosity (r|o 05) at a shear rate of 0.05 rad / s of > 135.0 kPa.s and < 147.0 kPa.s.

[0048] Preferably, the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.27 and < 0.32 dg / min determined in accordance with ISO1133- 1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 30.0; and• a total content of polymeric units derived from 1-hexene alpha olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition; and• a shear index (SHI27 / 210) of > 63.0 and < 73.0; and• a Long Chain Branch (LCB) Index of > 0.8 and < 0.9; and• a complex viscosity (r|o 01) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s; and• a complex viscosity (r|o os) at a shear rate of 0.05 rad / s of > 135.0 kPa.s and < 147.0 kPa.s; and• wherein the polyethylene composition is free of carbon black.

[0049] Preferably, the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR5 0) of > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s,; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 30.0; and• a total content of polymeric units derived from 1-hexene alpha olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition; and• a shear index (SHI27 / 210) of > 63.0 and < 73.0; and• a Long Chain Branch (LCB) Index of > 0.8 and < 0.9; and• a complex viscosity (T]001) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s; and• a complex viscosity (r|o os) at a shear rate of 0.05 rad / s of > 135.0 kPa.s and < 147.0 kPa.s; and• a melt flow rate ratio (FRR) of > 30.0 and < 37.0; and• a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 80.0 MPa and < 95.0 MPa.

[0050] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa; andSH• wherein the polyethylene composition satisfies the equationDensity—0.0339 ■ MFR5+ 0.0985, where SH and MFR5are as defined herein; and• wherein the polyethylene composition is free of carbon black.

[0051] Preferably, the polyethylene composition, comprises at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3, determined in accordance with ISO 1183; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR5 0) of preferably > 0.27 and < 0.32 dg / min determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 33.0, preferably > 25.0 and < 30.0; and• a melt flow rate ratio (FRR) of > 30.0 and < 37.0; and• a Strain Hardening Modulus (SH) as determined in accordance with ISO18488 of > 80.0 MPa and < 95.0 MPa; andSH• wherein the polyethylene composition satisfies the equationDensity—0.0339 ■ MFR5+ 0.0985, where SH and MFR5 are as defined herein.

[0052] Preferably, the polyethylene composition satisfies the following relation:[Area under curve for the Size Exclusion Chromatographt SEC) curve for LogM < 3.4]— 1.405 x 105x [Split(%wt)Fraction Ax M F 2, Fraction A ~ 0.008543 wherein area under the SEC curve with LogM < 3.4 is the polymer amount in weight fraction for the polyethylene composition that has a weight average molecular weight (Mw) equal or lower to LogMw = 3.4, as measured by ASTM D 6474-12, Split(%wt) is the weight percentage of the ethylene homopolymer fraction (A) in the polyethylene composition and MFRi 2, A is the melt flow rate determined in accordance with ISO 1133-1 :2011 under a load of 1.2 kg for the ethylene homopolymer fraction (A) in the polyethylene composition.

[0053] In a Size Exclusion Chromatogram (SEC), on the x-axis the Logarithm of weight average molecular weight LogMw (base 10 logarithm of the molecular weight of the polymer), is represented, and on the y-axis, the dW / dLogMw, or weight fraction of the polymer at that LogM is represented. The area under the curve may be calculated as described in US7803629.

[0054] SEC chromatograms are typically normalized and the total area under the molecular weight distribution curve equals 1. Detailed description for SEC data interpretation can be found in J.M. Evans, Polymer Engineering and Science, Vol. 13, No. 6, November 1973. The area under the SEC curve may be numerically calculated by any known numerical integration method.

[0055] For example, the area under the curve may be calculated by using the equation -

[0056] where “i” indicates the LogM values starting from 1.4 to 3.4 with an interval of 0.05 units. In accordance with the present invention, the area under the SEC curve is that corresponding to the polymer molecular weight represented by LogM = 3.4 (or Mw = 2511.9 g / mol).

[0057] Yet another suitable indicator for the balance of properties of impact strength, processability and Slow Crack Growth Resistance is given by the relationship between complex viscosity value at 300 rad / s (rpoo) divided by the product of shear index (SHE 7 / 210) x Charpy Impact Strength.

[0058] Preferably, the polyethylene composition satisfies at least one of the following relations: nd / orwherein (SHI2.7 / 210) is the shear index and wherein the Charpy Impact strength is measured in accordance with ISO 179-leA at the temperature indicated and wherein the (MFR5.0) is the melt flow rate determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg.

[0059] Preferably, the polyethylene composition satisfies each of the following relations:- SHI2.7 / 2io*Charpy ^Im22p -actStrength-3O°c < 2.7258 * MFRS + 0.5459; (Eqn 1); and- — - < 2.3373 ■ MFR. + 0.1663; (Eqn 2); andSHI 2.7 -CharpyImpactEnergy-20 °c 210

[0060] The equations Eqn 1-4, are indicative of the balance of properties of impact strength with the ease of processability of the polyethylene composition of the present invention. Typically, the high impact strength comes at the cost of high viscosity or in other words lower processability. However, as indicated by the above relationships (Eqn 1-4), the polyethylene composition demonstrates a suitable balance of processability and impact strength.

[0061] Preferably, polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3; and• a melt flow rate (MFR50) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12;• the polyethylene composition satisfies the following relation:SHI2 7 / 2W*CharpyImpactStrength_30°c< 2.7258 * MFRS + 0.5459; (Eqn 1)• the polyethylene composition satisfies the following relation:- SHI2.7 / 2W-CharpyIm -pactEnergy23°c < 0.1278 ■ MFR. + 0.3726;(Eqn 4) wherein (SHE.7 / 210) is the shear index and wherein the Charpy Impact strength is measured in accordance with ISO 179-leA at -30°C, and at 23 °C wherein the (MFR5.0) is the melt flow rate determined in accordance with ISO 1133-1:2011 at 190 °C and measured at 5.0 kg and complex viscosity (r]300).

[0062] Preferably, polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / ; and• a melt flow rate (MFR50) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol;• the polyethylene composition satisfies the following relation: 2.7258 * MFRS + 0.5459 (Eqn 1); and• the polyethylene composition satisfies the following relation:- — - < 0.1278 ■ MR + 0.3726 (Eqn 4); andSHI 2.7 ‘Ch,arpyImpactEnergy23 °cSH• wherein the polyethylene composition satisfies the relation - Density > —0.0339 ■ MFR + 0.0985, where SH and MFR5 are as defined herein.

[0063] Preferably, the polyethylene composition according to the invention has a yield stress determined according to ISO527-1 at 23 °C of 22 to 26 MPa. Preferably, the polyethylene composition has a Charpy impact strength as determined according to ISO 179-1 / leA at -30 °C of at least 10 kJ / m2, preferably of at least 14 kJ / m2.Preparing the ethylene polymer and the polyethylene composition

[0064] The ethylene polymer may be produced in a process comprising a sequential polymerization process comprising at least two reactors, for example Continuous Stirred Tank Reactor (CSTR), connected in series, wherein the process may comprise the steps of: a) preparing the ethylene homopolymer fraction (A) in a first reactor in presence of a Ziegler Natta catalyst; b) transferring at least partially the ethylene homopolymer fraction (A) and any unreacted monomers from the first reactor to a second reactor; c) feeding further monomers comprising ethylene and alpha olefin monomers to a second reactor; and d) preparing the ethylene copolymer fraction (B) in the second reactor in presence of the ethylene homopolymer fraction (A) to obtain the ethylene polymer.

[0065] Accordingly, the ethylene polymer present in the polyethylene composition is a reactor blend of two different ethylene polymer fractions. The ethylene polymer once obtained may be compounded with additives such as antioxidants, color pigments to obtain the polyethylene composition. Preferably, the polyethylene composition is free of carbon black.

[0066] The amount of additives compounded may not exceed 10.0 wt.% with regard to the total weight of the polyethylene composition, preferably the amount of additive is not greater than 2.0 wt.% with regard to the total weight of the polyethylene composition.Polymerization Catalyst

[0067] Preferably, the ethylene polymer is obtained by or obtainable by a process comprising the step of polymerizing an ethylene monomer in presence of a Ziegler Natta catalyst, preferably the Ziegler Natta catalyst comprises titanium, magnesium, aluminum, chloride moieties and a cocatalyst, wherein the cocatalyst is an alkyl aluminum compound having an alkyl chain with less than four carbon atoms, preferably wherein the co-catalyst is tri -ethyl -aluminium (TEA); and wherein the Ziegler Natta catalyst has a ratio of chloride content to the total content of titanium, magnesium, aluminum moieties of > 1.0 and < 2.0.

[0068] In an aspect of the invention, the invention relates to a pipe comprising the polyethylene composition of the present invention. Preferably the polyethylene composition comprises > 95.0 wt.%, preferably > 97.0 wt.%, preferably 100.0 wt.%, with regard to the total weight of the pipe.

[0069] In another aspect of the invention, the process for preparing the pipe of the present invention involves the step of extruding the polyethylene composition of the present invention.

[0070] The invention will now be demonstrated with the following non-limiting examples.EXAMPLES

[0071] Purpose: To evaluate the properties of sample specimen prepared from the polyethylene composition of the present invention.Measurement methodology of various parameters:

[0072] Melt Flow Rate (MFR): was measured according to ISO 1133-1:2011 under a load of 1.2 kg (MFR12), 5.0 kg (MFR5) or 21.6 kg (MFR21 e) at 190°C.

[0073] Density - Density of polymer pellet samples was measured by following the procedure laid out under ISO 1183 A using the immersion method.

[0074] Comonomer content using NMR - Samples were dissolved at 125 °C in C2D2C14 containing DBPC (2,6-di-tert-butyl-paracresol) as stabilizer. The 13C NMR spectra were recorded on a Bruker Avance500 NMR spectrometer equipped with a 10mm cryogenically-cooled probe head operating at 125°C. Data were processed using Bruker Topspin 3.6.Dynamic Mechanical Properties (complex viscosity n):

[0075] The viscosity values at each shear rate were calculated by fitting flow curves generated by oscillatory rheometer according to ISO 6721-10 between 0.01 and 100 rad / s at 190 °C with parallel plates having 25 mm diameter and 1.2 mm gap between the plates and using a modified Carreau-Yasuda model, which is represented by the following equation:?7 = ?7o ■ [1 + (A ■ y)a]~ [6] where r| is the viscosity in Pa.sT|0is the zero shear viscosity (Pa.s) a is the rheological breadth parameter n is the power law constant, set to 0 in the present case (defines the slope of the high shear rate region) y is the shear rate (1 / s)X is the relaxation time (s)

[0076] To facilitate model fitting, the power law constant is held at a constant value, in this case zero. Details of the significance and interpretation of the Carreau-Yasuda model and derived parameters may be found in: C.A. Hieber and H.H. Chiang, Rheol Acta, 28, 321 (1989); C.A. Hieber and H.H. Chiang, Polym. Eng. Sci., 32, 931 (1992); and R.B. Bird, R.C. Armstrong and O. Hasseger, Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, 2ndEdition, John Wiley & Sons (1987).

[0077] r|3oo, T]O OI, T]o05 is the complex viscosity determined at a shear rate of 300 rad / s, 0.01 rad / s0.05 rad / s respectively using oscillatory rheometer.

[0078] The storage modulus (G*) at each shear rate was determined by oscillatory rheometer according to ISO 6721-10 and operated between 0.01 and 100 rad / s at 190 °C with parallel plates having 25 mm diameter and 1.2 mm gap between the plates.

[0079] Shear index (SHI27 / 210) defined as the ratio of complex viscosity at a storage modulus (G*) of 2.7 kPa, to the complex viscosity at a storage modulus (G*) of 210 kPa, where storage modulus (G*) was determined in accordance with ISO 6721-10.Determination of Long Chain Branching

[0080] Long Chain Branching in polyethylene was determined through the relationship between low or zero-shear viscosity and molecular weight as shown in J. Janzen, R.H. Colby, Journal of Molecular Structure, 485-489 (1999). Long Chain Branching content in the polymers of the invention has been characterized by the following relationship:where:

[0081] LCBindex denotes the amount of Long Chain Branching present in the polyethylene composition, T|001 is the complex viscosity expressed in kPa*s and measured at 190 °C and at 0.01 rad / s in accordance with ISO 6721-10.

[0082] Yield stress was measured following ISO527-1 at 1 mm / min for modulus and at 50 mm / min for the tensile test, on bars of type IB at 23 °C.

[0083] Strain Hardening Modulus was determined according to ISO 18488.

[0084] Charpy Impact Resistance was measured by Charpy method following ISO 179-1 / leA, non-instrumented test at -30°C and 23 °C on specimens with dimensions 80 x 10 x 4 mm and a notch of type A. The direction of the blow was edgewise. Specimens were prepared by compression molding following ISO17855-2, at a compression molding temperature of 180 °C, with a compression molding cooling rate of 15 °C / min and a plaque thickness of 4 mm.Molecular weight (MW) and MWD

[0085] Mw (weight average molecular weight), Mn (number average molecular weight) and Mz (z-average molecular weight) were measured in accordance with ASTM D6474-12 (Standard Test Methodfor Determining molecular weight distribution and molecular weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography).

[0086] Catalyst preparation:

[0087] Catalyst 1 - 100 grams of granular Mg(OC2H5)2 and 150 millilitres of Ti(OC4H9)4 were provided in a 2 litre round bottomed flask equipped with a reflux condenser and stirrer. While gently stirring, the mixture was heated to 180 °C and subsequently stirred for 1.5 hours. During this process, a clear liquid was obtained. The mixture was cooled down to 120 °C and subsequently diluted with 1480 ml of hexane. Upon addition of the hexane, the mixture was cooled further down to 67 °C. The mixture was kept at this temperature for 2 hours and subsequently cooled down to room temperature. The resulting clear solution containing a complex was stored under a nitrogen atmosphere. Analysis of the complex showed a titanium concentration of 0.25 mol / 1.

[0088] Subsequently, in a 1.0-liter glass reactor, equipped with baffles, reflux condenser and stirrer, 286 ml hexane and 170 ml of the complex as obtained above were dosed. The stirrer was set at 1400 rpm. In a separate flask, 75 ml of 50% ethyl aluminium dichloride (EADC) solution was added to a 43 ml of hexane. The resulting EADC solution was dosed into the reactor in 15 minutes using a peristaltic pump. Subsequently, the mixture was refluxed for 2 hours. After cooling down to ambient temperature, the obtained red / brown suspension was transferred to a glass P4 filter and the solids were separated. The solids were washed 4 times using 500 ml of hexanes. The solids were taken up in 0.3 litre of hexane and the resulting slurry was stored under nitrogen. The solid content was 30 g / 1.

[0089] Elemental analysis of the catalyst showed: Ti 9.7 wt% Mg 10.4 wt% Al 4.6 wt% Cl 49 wt.% OEt 9.0 wt.% and OBu 12.0 wt.%. Ratio of chloride content to the total content of titanium, magnesium, aluminum moieties is 1.98.

[0090] Catalyst 2 -

[0091] 100 grams of granular Mg(OC2H5)2 and 150 millilitres of Ti(OC4H9)4 were brought in a2 litre round bottomed flask equipped with a reflux condenser and stirrer. While gently stirring, the mixture was heated to 180°C and subsequently stirred for 1.5 hours until a clear liquid was obtained. The mixture was cooled down to 120°C and subsequently diluted with 1480 ml of hexane. Upon addition of the hexane, the mixture was cooled further down to 67°C. The mixture was kept at this temperature for 2 hours and subsequently cooled down to room temperature. The resulting clear solution was stored under nitrogen atmosphere. Analyses on the solution showed a titanium concentration of 0.25 mol / 1.

[0092] In a 0.8 liters glass reactor, equipped with baffles, reflux condenser and stirrer, 424 ml hexane and 160 ml of the clear solution was dosed. The stirrer was set at 1200 RPM. In a separate flask, 100 ml of 50% ethyl aluminum dichloride (EADC) solution was added to 55 mL of hexane. The resulting EADC solution was dosed into a reactor for 15 minutes using a peristaltic pump. Subsequently, the mixture was refluxed for 2 hours. After cooling down to ambient temperature, the obtained red / brown suspension was transferred to a glass P4 filter and the solids were separated. The solids were washed 3 times using 500 ml of hexane. The solids were taken up in 0.5 L of hexane and the resulting slurry was stored under nitrogen. The solid content was 64 g ml1.

[0093] Catalyst analysis results: Elemental analysis of Catalyst 2 showed - Ti 10.8 wt%^ Mg 11.2 wt.%; Al 5.0 wt%; Cl 65 wt%; OEt 3.2 wt% and OBu 2.6 wt%. Ratio of chloride content to the total content of titanium, magnesium, aluminum moieties is 2.4.

[0094] Inventive Example 1 (IE1) - A Continuous Stirred Tank Reactor (CSTR) polymerization reactor (First CSTR) with 20 liters total volume and 15 liters of operating volume was operated at around 85 °C and at 7.0 barg total pressure. For producing the ethylene hompolymer fraction (A), 500 g / h of ethylene and 0.4 g / h of hydrogen were added to the polymerization reactor, along with 4200 g / h of hexane. Catalyst 1 was introduced into the reactor at the rate required to keep the total pressure of the reactor constant, along with Tri-ethyl-aluminium (TEA) as the cocatalyst. No additional comonomer was introduced into the reactor. The conditions in the reactor are as shown in Table 1.

[0095] The polymer slurry formed, was subsequently withdrawn from the reactor and transferred to an adiabatic flash vessel where pressure was manipulated in order to achieve the desired H2 / C2 gas phase ratio in the second reactor. After this flashing step, the polymer slurry was withdrawn from the flash vessel and transferred to a second CSTR reactor with same operating volume as the first CSTR reactor.

[0096] The second CSTR reactor was operated at 82 °C and at 5.1 barg total pressure. Into the second reactor, ethylene was introduced at a rate of 461 g / h, a mixture of heptane isomers was introduced at a rate of 4950 g / h, 1 -hexene at a rate of 160 g / h and nitrogen in order to keep the total pressure constant at 5.1 barg. The conditions in the second CSTR reactor are shown in Table 1. The slurry withdrawn from the second CSTR reactor was subsequently transferred into a centrifugal decanter where the polymer and hexane were separated. The resulting polymer retrieved was dried overnight under vacuum at 60 °C.

[0097] Inventive example 2-4 (IE2, IE3 and IE4) - Inventive examples 2-4 were prepared in the manner identical to Inventive Example 1 (IE 1) except that the polymerization conditions and feeds are as shown in Table 1.

[0098] Comparative examples 1-6 (CExl-CEx6): Comparative experiments 1 to 6 were identical to that of the inventive example 1 (IE 1) except that:

[0099] The polymerization conditions and feeds are as shown under Table 1. Catalyst 2 was catalyst system used for CExl to CEx4 and for CEx6 while Catalyst 1 was used for CEx5. The cocatalyst used was tri -isobutyl -aluminium (TIB A) for CExl to CEx4 and CEx6 while for CEx5 tri -ethyl -aluminium (TEA) was used.

[0100] Comparative example 7 (CEx7) is a commercial PE 100 material made with a metallocene catalyst produced in a gas phase reactor (with carbon black). Comparative example 8 (CEx8) is a commercial PE100 material, HE3490-LS-H (with carbon black).

[0101] Polymerization Conditions: The table below provides the polymerization conditions:Table 1

[0102] Polyethylene composition - The dry ethylene polymer once obtained was stabilized with 3000 ppm of a mixture of Calcium Stearate, Irgafos 168 and Irganox 1010 present at a weight ratio of 50 / 37.5 / 12.5 respectively and then extruded into pellets using a ZSK18 MegaLab - 18 mm, a co-rotating twin screw extruder unit with a throughput of 1.8 kg / h. The properties of the polymer composition are provided below:Table 2

[0103] Conclusion: The polyethylene compositions (IE1-IE4) prepared in accordance with the invention, demonstrate excellent balance of impact properties, processability and strain hardening even without the addition of carbon black.

[0104] For example, the polyethylene composition (IE1 and IE2) demonstrated desired impact resistance at -30 °C (e.g. 14.0 and 15.0 kJ / m2respectively) combined with excellent processability due to the relatively low complex viscosity at high shear of 300 rad / s (1006 and 1012 Pa.s).

[0105] This balance of property imparted by the polyethylene composition allow pipe manufacturers to prepare pipes having excellent impact property without compromising on its processability during its manufacture. Further, the polyethylene composition for example IE1 and IE2 (90.9 and 92.9 MPa) has suitable strain hardening modulus for imparting the desired slow crack growth resistance behavior.

[0106] The strain hardening modulus of the inventive polyethylene compositions for example (90.9 and 92.9 MPa as shown for IE1 and IE2) imparts Slow Crack Growth Resistance. Such a property enables efficient pipe installations, such as trenchless installation, and at yield stress values typically equal or above 23 MPa, for ensuring the adequate pressure resistance.

[0107] In particular, the polyethylene composition demonstrated suitable shear index - sufficiently high for imparting the desired sagging behavior while being sufficiently low for avoiding melt fracture and high surface roughness, at the desired pipe extrusion speeds for ensuring process efficiency.

[0108] A suitable indicator for the balance of properties is given by the relationship between complex viscosity value at 300 rad / s (rpoo) divided by the product of SHI2.7 / 210 x Charpy Impact, as disclosed in Table 2. This relationship captures the balanced properties described above, while the relationship between the Strain Hardening modulus divided by the density of the composition in natural form captures the slow crack growth and stiffness (or pressure resistance) behavior.

[0109] All the inventive polyethylene compositions of the present invention satisfies each of the equations: 2.7258 ■ MFR5+ 0.5459 ;- - < 0.1278 ■ MFR5+ 0.3726 ; andSHI 2.7 ■CharpyImpactStrength23 °c 210DeSnHsity > -0.0339 ■ MFR5+ 0.0985.

[0110] In comparison, formulations CExl to CEx4 and CEx6 to CEx8 show an overall lower balance of properties representing a poorer performance with respect to processability, and impact resistance at comparable melt flow rates. Further, for the comparative formulations the strain hardening values are lower, for similar MFR5 and density values as those of the inventive samples IE1-IE4. Thepolyethylene composition CEx 7 prepared using metallocene catalyst has a lower impact strength and higher viscosity compared to the inventive compositions such as IE1 and IE2.

[0111] In comparison, CEx5, prepared with the same catalyst / cocatalyst system but with different polymer recipe (i.e lower amount of homopolymer content) than IE1-IE4, shows a poorer Strain Hardening modulus value and impact resistance values.

Claims

1. CLAIMS1. A polyethylene composition, comprising at least 90.0 wt.% of an ethylene polymer, wherein the ethylene polymer comprises or consists of: a) > 50.0 and < 58.0 wt.%, preferably > 51.0 and < 55.0 wt.%, with regard to the total weight of the ethylene polymer, of an ethylene homopolymer fraction (A) having a density of > 967 kg / m3and < 978 kg / m3, determined in accordance with ISO 1183; and a molecular weight distribution (Mw / Mn) of > 8.0 and < 13.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight determined in accordance with ASTM D 6474-12; and b) > 42.0 and < 50.0, wt.%, preferably > 45.0 and < 49.0, wt.%, with regard to the total weight of the ethylene polymer, of an ethylene copolymer fraction (B); wherein the polyethylene composition has:• a density of > 945.0 and < 955.0 kg / m3, preferably > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / m3determined in accordance with ISO 1183; and• a melt flow rate (MFR5 0) of > 0.2 and < 0.5 dg / min, preferably > 0.2 and < 0.4 dg / min, preferably > 0.24 and < 0.35 dg / min, preferably > 0.24 and < 0.32 dg / min, preferably > 0.27 and < 0.32 dg / min determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg; and• a complex viscosity (rpoo) determined at a shear rate of 300 rad / s of > 900.0 Pa.s and < 1050.0 Pa.s, preferably > 930.0 Pa.s and < 1050.0 Pa.s, preferably > 980.0 Pa.s and < 1030.0 Pa.s, preferably > 1000.0 Pa.s and < 1020.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a z-average molecular weight (Mz) of > 1250 kg / mol and < 2500 kg / mol, preferably > 1500 kg / mol and < 2500 kg / mol, preferably > 2000 kg / mol and < 2400 kg / mol, determined in accordance with ASTM D 6474-12; and• a weight average molecular weight (Mw) of > 230 kg / mol and < 320 kg / mol, preferably > 270 kg / mol and < 320 kg / mol, preferably > 280 kg / mol and < 315 kg / mol, preferably > 300 kg / mol and < 315 kg / mol determined in accordance with ASTM D 6474-12.

2. The polyethylene composition of claim 1, wherein the ethylene homopolymer fraction (A) has a ratio of Mw / Mn of > 8.5 and < 12.0, preferably of > 9.0 and < 11.5; and / or the ethylene homopolymer fraction (A) has a ratio of Mz / Mw of > 35.0 and < 50.0, preferably of > 40.0 and < 48.0; and / or a melt flow rate (MFRi ,2) of > 70 and < 130 dg / min, preferably > 70 and < 110 dg / min, determined in accordance with ISO1133-1:2011 at 190 °C and measured at 1.2 kg.

3. The polyethylene composition according to any one of claims 1-2, wherein the polyethylene composition has a Strain Hardening Modulus (SH) as determined in accordance with ISO 18488 of > 75.0 MPa and < 110.0 MPa, preferably > 80.0 MPa and < 95.0 MPa; preferably > 88.0 MPa andSH< 93.0 MPa; and / or wherein the polyethylene composition satisfies the equation - Density >—0.0339 ■ MFR5+ 0.0985, where SH and MFR5 are as defined herein.

4. The polyethylene composition according to any one of claims 1-3, wherein the polyethylene composition has a melt flow rate ratio (FRR) of > 27.0 and < 40.0, preferably > 30.0 and < 37.0, preferably > 30.0 and < 34.0, wherein the melt flow rate ratio is the ratio of melt flow rate measured according to ISO 1133-1:2011 at 190 °C and at 21.6 and at 5.0 kg respectively.

5. The polyethylene composition according to any one of claims 1-4, wherein the polyethylene composition a total content of polymeric units derived from Cs-Cs alpha olefin co-monomer of > 0.5 and < 0.85 mol.%, preferably > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition, and wherein the polyethylene composition and a total content of polymeric units derived from ethylene of > 99. 15 and < 99.5 mol.%, preferably > 99.28 and < 99.35 mol.%, with regard to the total moles of the polyethylene composition, where the mole content of the polyethylene composition is determined using13C NMR spectroscopy; preferably wherein the C’s-Cs alpha olefin comonomer is selected from propylene, 1 -butene, 1 -hexene, 4-methyl 1 -pentene, 1 -octene, preferably wherein the Cs-Cs alpha olefin comonomer is any one of 1 -butene or 1 -hexene, more preferably the Cs-Cs alpha olefin comonomer is 1-hexene.

6. The polyethylene composition according to any one of claims 1-5, wherein the polyethylene composition has a molecular weight distribution (Mw / Mn) of > 25.0 and < 35.0, preferably > 25.0 and < 33.0, preferably > 25.0 and < 30.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight.

7. The polyethylene composition according to any one of claims 1-6, wherein the polyethylene composition has a Long Chain Branch (LCB) Index of > 0.8 and < 1.5, preferably > 0.8 and < 1.45, preferably > 0.8 and < 0.9, wherein LCB index is determined by:1 is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in kPa*s, and Mw is the weight average molecular weight expressed in kg / mol.

8. The polyethylene composition according to any one of claims 1-7, wherein the polyethylene composition has a shear index (SHI27 / 210) of > 60.0 and < 77.0, preferably > 63.0 and < 73.0, wherein shear index is defined as the ratio of complex viscosity at a storage modulus (G*) of 2.7 kPa, to the complex viscosity at a storage modulus (G*) of 210 kPa, where storage modulus (G*) is determined in accordance with ISO 6721-10.

9. The polyethylene composition according to any one of claims 1-8, wherein the polyethylene composition has a complex viscosity (r|o 01) at a shear rate of 0.01 rad / s of > 125.0 kPa.s and < 260.0 k.Pa.s, preferably > 185.0 kPa.s and < 255.0 k.Pa.s preferably > 195.0 kPa.s and < 230.0 k.Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and wherein the polyethylene composition has a complex viscosity (po os) at a shear rate of 0.05 rad / s of > 80.0 kPa.s and < 160.0 k.Pa.s, preferably > 135.0 kPa.s and < 155.0 kPa.s, preferably > 135.0 kPa.s and < 147.0 kPa.s, determined in accordance with ISO 6721-10 at 190 °C.

10. The polyethylene composition according to any one of claims 1-9, wherein the ethylene copolymer fraction (B) comprises polymeric units derived from ethylene and from Cs-Cs alpha olefin comonomer selected from propylene, 1-butene, 1 -hexene, 4-methyl 1-pentene, 1 -octene, preferably the C3-C8alpha olefin comonomer is any one of 1-butene or 1 -hexene, more preferably the Cs-Cs alpha olefin comonomer is 1 -hexene.

11. The polyethylene composition of according to any one of claims 1-10, wherein the polyethylene composition has:• a density of > 948.0 and < 952.0 kg / m3, preferably > 948.0 and < 950.0 kg / ; and• a melt flow rate (MFR50) of > 0.27 and < 0.32 dg / min; and• a complex viscosity (rpoo) at a shear rate of 300 rad / s of > 1000.0 Pa.s and < 1020.0 Pa.s; and• a z-average molecular weight (Mz) of > 2000 kg / mol and < 2400 kg / mol; and• a weight average molecular weight (Mw) of > 300 kg / mol and < 315 kg / mol; and• a molecular weight distribution (Mw / Mn) of > 25.0 and < 30.0; and• a total content of polymeric units derived from 1-hexene alpha olefin co-monomer of > 0.65 and < 0.72 mol.%, with regard to the total moles of the polyethylene composition; and• a shear index (SHI27 / 210) of > 63.0 and < 73.0; and• a Long Chain Branch (LCB) Index of > 0.8 and < 0.9; and• a complex viscosity (r|o 01) at a shear rate of 0.01 rad / s of > 195.0 kPa.s and < 230.0 k.Pa.s; and• a complex viscosity (r|o 05) at a shear rate of 0.05 rad / s of > 135.0 kPa.s and < 147.0 kPa.s; and• wherein the polyethylene composition is free of carbon black.

12. The polyethylene composition according to any one of claims 1-11, wherein the ethylene polymer is obtained by or obtainable by a process comprising the step of polymerizing an ethylene monomer in presence of a Ziegler Natta catalyst, preferably the Ziegler Natta catalyst comprises titanium, magnesium, aluminum, chlorine and a cocatalyst; and wherein the cocatalyst is an alkyl aluminum compound having an alkyl chain with less than four carbon atoms, preferably wherein the cocatalyst is tri-ethyl-aluminium (TEA); and wherein the Ziegler Natta catalyst has a ratio of chloride content to the total content of titanium, magnesium, aluminum moieties of > 1.0 and < 2.0.

13. The polyethylene composition according to any one of claims 1-12, wherein the polyethylene composition satisfies the following relation:[Area under curve for the Size Exclusion Chromatography SEC) curve for LogM < 3.4] <1.4050.008543 wherein area under the SEC curve with LogM < 3.4 is the polymer amount in weight fraction for the polyethylene composition that has a weight average molecular weight (Mw) equal to or lower than LogMw = 3.4, as measured by ASTM D 6474- 12, Split(%.wt) is the weight percentage of the ethylene homopolymer fraction (A) in the polyethylene composition and MFRi 2, Fraction A is the melt flow rate determined in accordance with ISO 1133-1 :2011 under a load of 1.2 kg for the ethylene homopolymer fraction (A) in the polyethylene composition.

14. The polyethylene composition according to any one of claims 1-13, wherein the polyethylene composition satisfies at least one of the following relations: 2.7258 * MFRS + 0.5459;(Eqn (1); and / orwherein (SHI2.7 / 210) is the shear index and wherein the Charpy Impact strength is measured in accordance with ISO 179-leA at the indicated temperature and wherein the (MFR5.0) is the melt flow rate determined in accordance with ISO1133-1:2011 at 190 °C and measured at 5.0 kg.

15. A pipe comprising the polyethylene composition as claimed in any one of claims 1-14, preferably wherein the polyethylene composition comprises > 95.0 wt.%, preferably > 97.0 wt.%, preferably 100.0 wt.%, with regard to the total weight of the pipe.

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