Polyethylene composition suitable for injection molding

Abstract

The invention relates polyethylene composition, comprising an ethylene polymer comprising or consisting of: a) a low molecular weight component (A); and b) a high molecular weight component (B); wherein the ethylene polymer has a C3-C8 alpha olefin comonomer and wherein the polyethylene composition has:. a melt flow index (MFI5) of ≥ 4.0 and ≤ 18.0 dg / min, determined in accordance with ISO1133-1:2011 at 190 ºC and measured at 5.0 kg; and. a melt flow ratio of ≥ 15.0 and ≤ 40.0, preferably ≥ 17.0 and ≤ 22.0, preferably ≥ 17.0 and ≤ 21.0; and. a density of ≥ 956.0 and ≤ 965.0 kg / m3, preferably ≥ 957.0 and ≤ 962.0 kg / m3, preferably ≥ 957.0 and ≤ 961.0 kg / m3, determined in accordance with ISO 1183; and. a complex viscosity (η100) at a shear rate of 100 rad / s of ≥ 580 and ≤ 700 Pa.s, determined in accordance with ISO 6721-10 at 190 ºC; and. a complex viscosity (η5000) at a shear rate of 5000 rad / s of ≥ 45.0 Pa.s and ≤ 60.0 Pa.s, determined in accordance with ISO 6721-10 at 190 ºC. The invention further relates to an article comprising the polyethylene composition and the use of the polyethylene composition for manufacturing an injection molded article.

Description

POLYETHYLENE COMPOSITION SUITABLE FOR INJECTION MOLDINGFIELD OF INVENTION

[0001] The invention relates to a polyethylene composition and to articles, for example caps or closure, that are prepared from such a polyethylene composition.BACKGROUND

[0002] Compositions comprising an ethylene copolymer are used in many application fields for example in the production of pipes and films as well as in blow-molding and injection molding applications. Injection molding is a molding process commonly used to produce, for example, household and industrial containers. One such article is a cap and closure articles typically used in household and industrial application. Ethylene based products are used in caps and closure applications to produce a wide variety of manufactured articles, e.g. caps for carbonated or non-carbonated fluids, as well as dispensing closures including closures with a living-hinge functionality.

[0003] Such caps and closures are typically produced using conventional injection or compression molding processes. To injection mold a part, such as a cap and closure, polyethylene thermoplastic pellets, granules or powders are melted and injected under pressure into the cavity of a mold where the melted resin is solidified by cooling for subsequent removal. More detailed discussion of injection molding may be found in Ullman's Encyclopedia of Industrial Chemistry, vol. A20, Plastics Processing, pages 688-696 (VCH Publishers, 1992).

[0004] Important properties of the polymer to be molded are its mechanical properties and processability which, in turn, determine the properties of the final molded article and make the process of manufacturing more efficient. In the past, blends of polyethylene resins have been proposed to improve physical properties, including impact strength, environmental stress crack resistance (ESCR), and chemical resistance while retaining processability. Processability is related to the ability of the material to flow and fill up completely all the cavities of the mold. A suitable indicator to understand the extent of processability is the extent of shear thinning, and lowering of viscosity under high shear rate.

[0005] On the other hand, high slow crack growth resistance and stiffness allow for downgauging of material required for the blow molded part, making the process more sustainable andresource efficient. Typically, polyethylene resins with high density and high melt index perform well in processability and stiffness, but show a poor ESCR and melt strength. In the past use of carbon black and cross-linking of the polymer have been done to achieve one or more such balance of properties. However, the use of such additives may affect the processability and in certain situations the mechanical properties of the polymer.

[0006] Therefore, there is a need for polyethylene resins for manufacturing injection molded products such as caps and closures that show an improved balance of ESCR, melt strength, processability and stiffness even without the need of additives such as carbon black or crosslinking. Accordingly, it is an objective of the present invention to provide a polyethylene composition that is suitable for manufacturing injection molded product that shows an excellent balance of ESCR, melt strength, processability and stiffness.DESCRIPTION

[0007] Accordingly, the one or more objectives of the present invention is achieved by a polyethylene composition, comprising an ethylene polymer comprising or consisting of : a) > 60.0 and < 75.0 wt.%, preferably > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 10,000 g / mol and < 70,000 g / mol, preferably > 30,000 g / mol and < 65,000 g / mol, preferably > 30,000 g / mol and < 60,000 g / mol, preferably wherein the weight average molecular weight (Mw) is determined in accordance with ASTM D6474-12; and b) > 25.0 and < 40.0 wt.%, preferably > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 700,000 g / mol, preferably > 100,000 g / mol and < 600,000 g / mol, preferably > 100,000 g / mol and < 400,000 g / mol; and preferably wherein the low molecular weight component (A) is an ethylene homopolymer or an ethylene copolymer; and preferably wherein the high molecular weight component (B) is a copolymer of ethylene and a C3-C20 comonomer,preferably the high molecular weight component (B) is a copolymer of ethylene and a Cs-Cs alpha olefin; wherein the polyethylene composition has:• a melt flow index (MFIs) of > 4.0 and < 18.0 dg / min, preferably > 5.0 and <15.0 dg / min, preferably > 6.0 and < 12.0 dg / min, preferably > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio (MF 21.6 / 5.0) of > 15.0 and < 40.0, preferably > 17.0 and < 22.0, preferably > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and• a density of > 956.0 and < 965.0 kg / m3, preferably > 957.0 and < 962.0 kg / m3, preferably> 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 580 and < 700 Pa.s, preferably> 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 45.0 Pa.s and < 60.0 Pa.s, preferably > 48.0 Pa.s and < 60.0 Pa.s, preferably > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

[0008] Preferably, the present invention is achieved by a polyethylene composition, comprising an ethylene polymer comprising or consisting of : a) > 60.0 and < 75.0 wt.%, preferably > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 10,000 g / mol and < 70,000 g / mol, preferably > 30,000 g / mol and < 65,000 g / mol, preferably > 30,000 g / mol and < 60,000 g / mol, wherein the weight average molecular weight (Mw) is determined in accordance with ASTM D6474-12; and b) > 25.0 and < 40.0 wt.%, preferably > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 700,000 g / mol, preferably > 100,000 g / mol and < 600,000 g / mol, preferably > 100,000 g / mol and < 400,000 g / mol, wherein the weight average molecular weight (Mw) of the highmolecular weight component (B) is determined in accordance with deconvolution technique based on ASTM D6474-12; and wherein the low molecular weight component (A) is an ethylene homopolymer; and wherein the high molecular weight component (B) is a copolymer of ethylene and a Cs-Cs alpha olefin; wherein the polyethylene composition has:• a melt flow index (MFIs) of > 4.0 and < 18.0 dg / min, preferably > 5.0 and <15.0 dg / min, preferably > 6.0 and < 12.0 dg / min, preferably > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio (MF 21.6 / 5.0) of > 15.0 and < 40.0, preferably > 17.0 and < 22.0, preferably > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and• a density of > 956.0 and < 965.0 kg / m3, preferably > 957.0 and < 962.0 kg / m3, preferably> 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 580 and < 700 Pa.s, preferably> 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 45.0 Pa.s and < 60.0 Pa.s, preferably > 48.0 Pa.s and < 60.0 Pa.s, preferably > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

[0009] Preferably, the polyethylene composition has a complex viscosity (r|o.oi) at a shear rate of 0.01 rad / s of > 5.0 kPa.s and < 15.0 Pa.s, preferably > 6.0 Pa.s and < 12.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

[0010] Preferably the polyethylene composition, comprising the ethylene polymer comprises or consists of: a) > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 30,000 g / mol and < 60,000 g / mol; andb) > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 400,000 g / mol; wherein the polyethylene composition has:• a melt flow index (MFIs) of > 5.0 and <15.0 dg / min, preferably > 6.0 and < 12.0 dg / min, preferably > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio (MF 21.6 / 5.0) of > 17.0 and < 22.0, preferably > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and 5.0 kg respectively; and• a density of > 957.0 and < 962.0 kg / m3, preferably > 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

[0011] Preferably, the polyethylene composition, comprising the ethylene polymer comprises or consists of: a) > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 30,000 g / mol and < 60,000 g / mol; and b) > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 400,000 g / mol; and preferably wherein the low molecular weight component (A) is an ethylene homopolymer or an ethylene copolymer having a density of > 962.0 kg / m3and < 978.0 kg / m3, preferably > 964.0 kg / m3and < 972.0 kg / m3; and preferably wherein the high molecular weight component (B) is acopolymer comprising polymeric units derived from ethylene and a Cs-Cs alpha olefin comonomer; wherein the polyethylene composition has:• a melt flow index (MFIs) of > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio of > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and• a density of > 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a Strain Hardening modulus of > 15.0 MPa and < 22.0 MPa as measured in accordance with ISO 18488; and• total content of polymeric units derived from 1-hexene comonomer of > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition.

[0012] Advantageously, the polyethylene composition of the present invention has an excellent balance of processability of environmental stress cracking resistance (ESCR), melt strength, processability and stiffness. In an aspect of the invention, the invention relates to the use of the polyethylene composition of the present invention for improving the properties of stiffness, processability during injection molding, hardness and environmental stress cracking resistance (ESCR) of an article, preferably wherein the article is a cap or a closure. As a further advantage, the polyethylene composition is free of carbon black based additives or being cross-linked.

[0013] Preferably, the polyethylene composition has at least one of: a) a Bell Test resistance F50 of > 100 hours and < 300 hours when determined in accordance with ASTM DI 693 Method B at 50 °C in 10% IGEPAL; and / orb) a Yield stress of > 26.0 MPa and < 35.0 MPa, preferably > 26.0 MPa and < 32.0 MPa, preferably > 26.5 MPa and < 31.0 MPa as measured according to ISO 527-2 at 23 °C; and / or c) a tensile modulus value of > 1350 MPa and < 1550 MPa, preferably > 1380 MPa and < 1450 MPa as measured according to ISO 527-2 at 23 °C.

[0014] Preferably, the polyethylene composition has: a) a Bell Test resistance F50 of > 100 hours and < 300 hours when determined in accordance with ASTM DI 693 Method B at 50 °C in 10% IGEPAL; and b) a Yield stress of > 26.0 MPa and < 35.0 MPa, preferably > 26.0 MPa and < 32.0 MPa, preferably > 26.5 MPa and < 31.0 MPa as measured according to ISO 527-2 at 23 °C; and c) a tensile modulus value of > 1350 MPa and < 1550 MPa, preferably > 1380 MPa and < 1450 MPa as measured according to ISO 527-2 at 23 °C.

[0015] The polyethylene composition of the present invention demonstrates desired shear thinning behavior when subjected to high stress. The polyethylene composition according to the invention has a relatively low viscosity at a relatively high shear rate, which results in a good processability for injection molding.

[0016] For example, the polyethylene composition has a complex viscosity (r|sooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721- 10 at 190 °C; and complex viscosity (qioo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C.

[0017] Preferably, wherein the polyethylene composition has a Strain Hardening modulus of > 12.0 MPa and < 25.0 MPa, preferably > 12.0 MPa and < 22.0 MPa as measured in accordance with ISO 18488.

[0018] By ethylene polymer is meant a polymer, the majority by weight of which is derived from ethylene monomer units. The ethylene polymer may be an ethylene homopolymer or a copolymer of ethylene and a C3-C20 comonomer, preferably C3-C8 alpha-olefin comonomer.

[0019] Preferably, the polyethylene composition has a total content of polymeric units derived from Cs-Cs alpha olefin of > 0.2 and < 0.8 mol.%, preferably > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition, preferably wherein the mole content of the polymeric units in the polyethylene composition is determined using Infra Red spectroscopy.

[0020] Preferably the polyethylene composition has a total content of polymeric units derived from ethylene of > 99.2 and < 99.8 mol.%, preferably > 99.4 and < 99.7 mol.%, with regard to the total moles of the polyethylene composition.

[0021] Preferably, the Cs-Cs alpha olefin comonomer is 1 -hexene, and preferably wherein the total content of polymeric units derived from 1-hexene comonomer is from > 0.3 and < 0.5 mol.%, with regard to the total moles of the polyethylene composition.

[0022] The comonomer content influences the degree of low chain branching which in turn influences the degree of processability. Preferably, the polyethylene composition has a Long Chain Branch Index of > 0.2 and < 1.2, preferably > 0.2 and < 1.0, wherein LCB index is determined bywherein po.oi is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in Pa*s, and Mw is the weight average molecular weight expressed in kg / mol.

[0023] Preferably, the polyethylene composition has weight average molecular weight (Mw) of > 100 kg / mol and < 250 kg / mol, preferably > 100 kg / mol and < 200 kg / mol, preferably > 100 kg / mol and < 180 kg / mol, determined in accordance with ASTM D6474-12.

[0024] Preferably, the polyethylene composition has weight average molecular weight (Mw) of > 100 kg / mol and < 250 kg / mol, preferably > 100 kg / mol and < 200 kg / mol, preferably > 100 kg / mol and < 180 kg / mol, determined in accordance with ASTM D6474-12; and / or wherein the polyethylene composition has a Z-average molecular weight (Mz) of > 700 kg / mol and < 2000 kg / mol, determined in accordance with ASTM D6474-12.

[0025] Preferably, the polyethylene composition has a molecular weight distribution (Mw / Mn) is > 10.0 and < 25.0, preferably > 10.0 and < 20.0, preferably > 10.0 and < 18.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight as determined in accordance with ASTM D6474-12.

[0026] Preferably, the polyethylene composition has a Peak Ratio ranging from > 1.8 and< 10.0, preferably > 1.8 and < 8.0, wherein Peak Ratio is defined as:wherein:(dW / dLogMw)at MwPeak,LMWF is the value of the molecular weight distribution for the low molecular weight component (A) of the ethylene polymer at the maximum value of the molecular weight distribution as measured (Mw peak);(dW / dLogMw)at MwPeak,HMWF is the value of the molecular weight distribution for the high molecular weight component (B) of the ethylene polymer at the maximum value of the molecular weight distribution as measured (Mw peak);(PolymerSplit)LMWF is the weight fraction of the low molecular weight component (A) of the ethylene polymer with regard to the total weight of the ethylene polymer;(PolymerSplit)HMWF is the weight fraction of the high molecular weight component (B) of the ethylene polymer with regard to the total weight of the ethylene polymer.

[0027] The PEAK ratio may for example quantify the spread between the low and high molecular weight components of the ethylene polymer and is indicative of the degree of processability of the polyethylene composition.Low molecular weight component (A) of the ethylene polymer

[0028] The low molecular weight component (A) of the ethylene polymer may be an ethylene homopolymer or an ethylene copolymer. Preferably, the low molecular weight component (A) is an ethylene homopolymer. Preferably, the low molecular weight component (A) of the ethylene polymer is an ethylene homopolymer. The low molecular weight component(A) is present in an amount of > 60.0 and < 75.0 wt.%, preferably > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer.

[0029] Preferably the low molecular weight component (A) is an ethylene homopolymer or an ethylene copolymer having a density of > 962.0 kg / m3and < 978.0 kg / m3, preferably > 964.0 kg / m3and < 972.0 kg / m3, preferably the low molecular weight component is an ethylene homopolymer having a density of > 964.0 kg / m3and < 978.0 kg / m3, preferably > 967.0 kg / m3and < 972.0 kg / m3. The density of the low molecular weight component (A) may be determined in accordance with ISO 1183.

[0030] Preferably, the low molecular weight component (A) has a ratio of Mw / Mn of > 5.0 and < 11.0, preferably > 6.0 and < 10.0. The weight average molecular weight (Mw) and number average molecular weight is determined in accordance with ASTM D6474-12.

[0031] Preferably, the low molecular weight component (A) of the ethylene polymer has a melt flow index (MFI1.2) of > 15.0 and < 70.0 dg / min, preferably > 35.0 and < 60.0 dg / min, preferably > 45.0 and < 55.0 dg / min determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 1.2 kg.High molecular weight component (B) of the ethylene polymer

[0032] The high molecular weight component (B) is present in an amount of > 25.0 and < 40.0 wt.%, preferably > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer.

[0033] Preferably, the high molecular weight component (B) has a ratio of Mw / Mn of > 4.0 and < 8.0. The weight average molecular weight (Mw) and the number average molecular (Mn)weight may be measured by any known standards for example by deconvolution technique based on ASTM D6474-12.

[0034] The weight average molecular weight (Mw) for the high molecular weight component (B) may be measured using any known techniques using ISO and ASTM standards such as deconvolution technique based on ASTM D6474-12.

[0035] Preferably, the high molecular weight component (B) has a density of > 920 and < 950 kg / m3, preferably > 920 and < 946 kg / m3. The density of the high molecular weight component (B) may be determined in accordance with ISO 1183.

[0036] Preferably, the high molecular weight component (B) has a melt flow rate as measured according to ISO 1133-1 :2011 at 190 °C and 21.6 kg of > 0.05 and < 2.0 dg / min, preferably > 0.08 and < 1.0 dg / min, preferably > 0.10 and < 0.5 dg / min.

[0037] The high molecular weight component (B) of the ethylene copolymer may be a copolymer of ethylene and a C3-C20 comonomer. The C3-C20 comonomer is preferably selected from the group consisting of C3-10 alpha-olefins, more preferably C3-8 alpha-olefins such as propylene, 1-butene, 1-hexene and 1-octene. For example, the high molecular weight component (B) is a copolymer comprising polymeric units derived from ethylene and a C3-C8 alpha olefin comonomer.

[0038] Preferably, the high molecular weight component (B) is a copolymer of ethylene and 1-butene or ethylene and 1-hexene. Most preferably, component (B) is a copolymer of ethylene and 1-hexene. For example, the high molecular weight component (B) is a copolymer of consisting of polymeric units derived from ethylene and 1-hexene.

[0039] The high molecular weight component (B) of the ethylene polymer may be a copolymer of ethylene and a C3-C20 comonomer, preferably a C3-C8 alpha olefin comonomer. Preferably, the high molecular weight component (B) of the ethylene copolymer is a copolymer of ethylene and a C3-C8 alpha olefin comonomer.

[0040] Preferably, the high molecular weight component (B) is a copolymer comprising polymeric units derived from of ethylene and a Cs-Cs comonomer. The amount of Cs-Cs comonomer can be from > 0.2 and < 0.8 mol.%, preferably > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition.

[0041] Preferably the Cs-Cs comonomer is selected from propylene, 1 -butene, 1 -hexene and 1 -octene. Preferably, the high molecular weight component (B) is a copolymer of ethylene and 1 -butene or an ethylene and 1 -hexene. Most preferably, the high molecular weight component (B) is a copolymer of ethylene and 1 -hexene.Low Molecular Weight component (A) and high molecular weight component (B)

[0042] Preferably the low molecular weight component (A) is an ethylene homopolymer or an ethylene copolymer having a density of > 962.0 kg / m3and < 978.0 kg / m3, preferably > 964.0 kg / m3and < 972.0 kg / m3; and preferably wherein the high molecular weight component (B) is a copolymer comprising polymeric units derived from ethylene and a Cs-Cs alpha olefin comonomer, preferably a copolymer comprising polymeric units derived from ethylene and 1- hexene.

[0043] Preferably the low molecular weight component (A) is an ethylene homopolymer having a density of > 964.0 kg / m3and < 978.0 kg / m3, preferably > 967.0 kg / m3and < 972.0 kg / m3; and / or wherein the high molecular weight component (B) is a copolymer of ethylene and 1 -butene or ethylene and 1 -hexene, preferably wherein, the high molecular weight component (B) is a copolymer of ethylene and 1 -hexene.Polyethylene composition

[0044] Preferably the polyethylene composition, comprising the ethylene polymer comprises or consists of :a) > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 30,000 g / mol and < 60,000 g / mol; and b) > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 400,000 g / mol; and wherein the polyethylene composition has:• a melt flow index (MFIs) of > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio of (MF 21.6 / 5.0) of > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and 5.0 kg; and• a density of > 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a Strain Hardening modulus of > 15.0 MPa and < 22.0 MPa as measured in accordance with ISO 18488; and• total content of polymeric units derived from 1-hexene comonomer of > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition.

[0045] Preferably the polyethylene composition, comprising the ethylene polymer comprises or consists of: a) > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 30,000 g / mol and < 60,000 g / mol; and b) > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 400,000 g / mol; andwherein the polyethylene composition has:• a melt flow index (MFIs) of > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio of (MF 21.6 / 5.0) of > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and 5.0 kg respectively; and• a density of > 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a Strain Hardening modulus of > 15.0 MPa and < 22.0 MPa as measured in accordance with ISO 18488; and• total content of polymeric units derived from 1-hexene comonomer of > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition; and• the polyethylene composition has a molecular weight distribution (Mw / Mn) is > 10.0 and < 25.0, preferably > 10.0 and < 20.0, preferably > 10.0 and < 18.0, where Mw is the weight average molecular weight and Mn is the number average molecular weight as determined in accordance with ASTM D6474-12.

[0046] The polyethylene composition may comprise the polyethylene composition comprising > 80.0 wt.% and < 100.wt.%, preferably > 90.0 wt.% and < 100.wt.%, preferably > 95.0 wt.% and < 100.wt.%, preferably > 98.0 wt.% and < 100.wt.% of the ethylene polymer with regard to the total weight of the polyethylene composition; and wherein the polyethylene composition comprises > 0.0 wt.% and < 20.0 wt.%, preferably > 0.0 wt.% and < 10.0 wt.%, preferably > 0.0 wt.% and < 5.0 wt.%, preferably > 0.0 wt.% and < 2.0 wt.%, of additives, preferably wherein the additives are selected from anti-oxidants, carbon black, fillers, process stabilisers, anti-oxidants, light and / or heat stabilisers, cross-linking agents and combinations thereof.

[0047] Preferably the polyethylene composition is free of carbon black and crosslinking. Preferably the additives are selected from the group consisting of anti-oxidants, fillers, process stabilisers, anti-oxidants, light and / or heat stabilisers, and combinations thereof.

[0048] In an aspect of the invention, it is preferred polyethylene composition comprises > 98.0 wt.% and < 100.wt.% of the ethylene polymer with regard to the total weight of the polyethylene composition; and wherein the polyethylene composition comprises > 0.0 wt.% and < 2.0 wt.% of additives, preferably wherein the additives are selected from anti-oxidants, carbon black, fillers, process stabilisers, anti-oxidants, light and / or heat stabilisers, cross-linking agents and combinations thereof.Preparing the ethylene polymer and the polyethylene composition

[0049] The ethylene polymer according to the invention may be prepared by a process comprising the steps of producing the low molecular weight component and the high molecular weight component as a bimodal ethylene polymer made by polymerizing the low molecular weight component (component A) and subsequently polymerizing the high molecular weight component (component B) in the presence of the low molecular weight component (component A).

[0050] Accordingly, the invention provides a process for the preparation of the ethylene polymer according to the invention, wherein the process comprises a sequential polymerization process comprising at least two reactors connected in series, wherein said process may comprise the steps of: a) preparing the low molecular weight component (high molecular weight component) in a first reactor using the first set of conditions, b) transferring the low molecular weight component (high molecular weight component) and unreacted monomers of the first reactor to a second reactor, c) feeding monomers to the second reactor, d) preparing the high molecular weight component (low molecular weight component) in the second reactor in the presence of the low molecular weight component (high molecular weight component) to obtain the ethylene polymer.

[0051] Each of the ethylene polymer components A and B and the optional further ethylene polymer component s) may be produced in the presence of known catalyst systems such as a Ziegler Natta catalyst system or a metallocene catalyst system, preferably a Ziegler Natta catalyst system. The polymerization can be carried out in the presence of an anti-static agent or anti fouling agent in an amount ranging between for example 1 and 500 ppm related to the total amount of reactor contents.

[0052] The multi-step slurry polymerization process may be carried out using cascaded reactors and in the presence of a Ziegler Natta catalyst system.

[0053] In such a case, the properties of the fractions produced in the second reactor can either be inferred from polymers, which are separately produced in a single stage by applying identical polymerisation conditions (e.g. identical temperature, partial pressures of the reactants / diluents, suspension medium, reaction time) with regard to the stage of the multistage process in which the fraction is produced, and by using a catalyst on which no previously produced polymer is present.

[0054] Alternatively, the properties of the fractions produced in a higher stage of the multistage process may also be calculated, e.g. in accordance with B. Hagstrom, Conference on Polymer Processing (The Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19 to 21 , 1997, 4: 13. Thus, although not directly measurable on the multistage process products, the properties of the fractions produced in higher stages of such a multistage process can be determined by applying either or both of the above methods. The skilled person will be able to select the appropriate method.

[0055] Alternatively, the ethylene polymer according to the invention may be prepared by a process comprising melt-mixing or solution blending the low molecular weight component and the high molecular weight component made in different reactors to obtain the ethylene polymer. The melt-mixing or solution blending may be carried out in any conventional blending apparatus.The low molecular weight component and the high molecular weight component to be melt-mixed or solution blended may be produced by any known process.

[0056] The ethylene polymer once obtained may be compounded with additives such as carbon black, anti-oxidant, masterbatch, color pigments to obtain the polyethylene composition. The amount of additives may not exceed 10 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.

[0057] In an aspect of the invention, the invention relates to an article comprising the polyethylene composition. Preferably the article is selected from a container, cap or a closure.

[0058] Preferably, the article comprises > 95.0 wt.%, preferably > 98.0 wt.%, preferably 100 wt.%, with regard to the total weight of the article, of the polyethylene composition.

[0059] The invention will now be demonstrated with the following non-limiting examples.EXAMPLES

[0060] Purpose: To evaluate the properties of sample specimen prepared from the polyethylene composition of the present invention.

[0061] Catalyst preparation:

[0062] Catalyst 1 - Preparation of a hydrocarbon solution comprising the organic oxygen containing magnesium compound and the organic oxygen containing titanium compound 100 grams of granular Mg(OC2Hs)2 and 150 millilitres of Ti(OC4H9)4 were brought 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, 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 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 and was used as obtained. Analyses on the solution showed a titanium concentration of 0.25 mol / 1.Preparation o f the catalyst

[0063] In a 0.8 liters glass reactor, equipped with baffles, reflux condenser and stirrer, 424 ml hexanes and 160 ml of the complex from Example I were dosed. The stirrer was set at 1200RPM. In a separate flask, 100 ml of 50% ethyl aluminum di chloride (EADC) solution was added to 55 mL of hexanes. 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.

[0064] The solids were washed 3 times using 500 ml of hexanes. The solids were taken up in 0.5 L of hexanes and the resulting slurry was stored under nitrogen. The solid content was 64 g ml’1. Catalyst analysis results: Ti 10.8 wt%; Mg 11.2 wt%; Al 5.0 wt%; CI 65 wt%; OEt 3.2 wt% and OBu 2.6 wt%.

[0065] Preparation of the ethylene polymer -

[0066] Inventive Example 1 (IE1) - A Continuous Stirred Tank Reactor (CSTR) reactor with 20 liters total volume and 15 liters of operating volume was operated at 85 °C and 11.2 barg total pressure. For producing a first polymer fraction, 700 g / h of ethylene and 1.3 g / h of hydrogen were added to the polymerization reactor, along with 4200 g / h of linear and branched C7 alkanes mixtures. In addition, Catalyst 1 was introduced into the reactor at the rate needed to keep the total pressure of the reactor constant, along with Tri-isobuyl-aluminium (TIBA) as cocatalyst. No additional comonomer was introduced into the reactor. The conditions in the reactor are shown in Table 1.

[0067] The polymer slurry was withdrawn from the reactor and transferred to an adiabatic flash vessel were pressure was manipulated in order to get 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 total and operating volumes as the first CSTR reactor.

[0068] The second CSTR reactor was operated at 70 °C and 4.8 barg total pressure. Into the reactor were introduced ethylene at a rate of 377 g / h, linear and branched C7 alkanes mixtures at a rate of 4950 g / h, 1 -hexene at a rate of 190 g / h and nitrogen in order to keep the total pressure constant at 4.8 barg. The conditions in the second CSTR reactor are shown in table 1. The slurrywithdrawn from the second CSTR reactor was transferred into a centrifugal decanter where the polymer and diluent were separated.

[0069] The resulting polymer was then dried under vacuum at 60 °C overnight. The dry polymer was stabilized with 3000 ppm of a mixture of Calcium Stearate, Irgafos 168 and Irganox 1010 in weight ratio 50 / 37.5 / 12.5 respectively and then extruded into pellets in a Coperion ZSK- 18 co-rotating twin screw extruder system, so that the extruder throughput was 1.8 kg / h.

[0070] Inventive example 2 (IE2) - Inventive examples 2 was identical to inventive example 1 except that the polymerization conditions and feeds are as shown in Table 1.

[0071] Comparative examples 3 to 5 Comparative examples 3 to 5 (CEx3-5) are commercial HDPE materials for Injection Molding (Caps and Closures), applications. Comparative Example 3 (CEx3), is a commercially available monomodal resin made with Ziegler-Natta catalyst and 1 -butene for high flowability caps and closures.

[0072] Comparative Example 4 (CEx3), is a commercially available bimodal HDPE made with Ziegler-Natta catalyst and 1 -butene as comonomer for injection moulding applications with excellent flow and ESCR performance. Comparative Example 5 (CEx5), is a commercially available multimodal HDPE made with Ziegler-Natta catalyst and 1 -butene as comonomer for injection molding applications with a good balance of ESCR and Stiffness.

[0073] Processing parameters for the preparation of ethylene polymer -Table 1

[0074] The resulting ethylene polymer was then dried under vacuum at 60 °C overnight. The dry polymer was stabilized with 3000 ppm of a mixture of Calcium Stearate, Irgafos 168 and Irganox 1010 in weight ratio 50 / 37.5 / 12.5 respectively and then extruded into pellets in a Coperion ZSK-18 co-rotating twin screw extruder system, so that the extruder throughput was 1.8 kg / h to obtain pellets of the polyethylene composition. The extrusion conditions are provided below:Table 2

[0075] Various properties of the pellets of the polyethylene composition of IE1 to IE2 and CEx3 to CEx5 were measured as reported in Table 3.Table 3

[0076] It can be understood that the polyethylene composition according to the invention in particular IE2, has a combination of excellent processability due to the low viscosity values at both, 100 rad / s and 5000 rad / s (rpoo and rpooo respectively), a superior ESCR, given the high value of Bell test, and very high stiffness, given by the density, yield stress and tensile modulus values.

[0077] In comparison, polyethylene composition (CEx3) has a similar or poorer processability as measured by the viscosity values at a shear rate of 100 rad / s and 5000 rad / s, similar stiffness as given by the yield stress and density, but a much lower ESCR resistance. CEx4 shows similar viscosity values at very high shear rate, but it shows much lower ESCR resistance, eventhough it has a higher content of comonomer as indicated by the much lower density (stiffness), compared to either IE1 or IE2.

[0078] CEx5 shows poorer viscosity values than either IE1 or IE2, mostly due to the higher overall molecular weight of the material, and also lower stiffness, as given by the lower tensile modulus and density. Even with the higher molecular weight and lower density it also shows significant lower ESCR resistance than the materials of the invention.Measurement methodology of various parameters:

[0079] MFI was measured according to ISO 1133-1 :2011 under a load of 1.2 kg (Mil.2), 2.16 kg (MI5) or 21.6 kg (MI21.6) at 190°C. The term Melt Flow Index and Melt Flow Rate (MFR) may for example be used interchangeably for the purposes of the present invention.

[0080] Density - Density of the ethylene polymer powder samples was measured by preparing polymer test plaques of 40 x 40 x 1.6 mm, following ISO 17855-2 in a Fontyne press model TP200. The compression cycle had a temperature set at 180 C, with 10 minutes of contact pressure. Cooling was performed with an initial time of 30 seconds without pressure increase, followed by pressure increase until 200 kN and maintaining the pressure level during the time needed for the sample to reach 23 C at a cooling rate of 15 ± 2 °C / min. Mass of the test plaque was determined in air (Analytical Balance XS104 Mettler Toledo). Subsequently, the test plaque was immersed in 4 liters of water at 100 °C (Automatic Densimeter D-H100 from Toyo Seiki equipped with a thermostatic bath MX7LR-20 from WMR) for 10 minutes after which the heat was turn off and the sample was cooled down to room temperature. The density is determined as follows:ps= Density of the test plaque (g / cm3) ms,atr=Mass of the test plaque in air (g)Pwater=Density of demineralized water (g / cm3) at test temperature (23°C) ms+nc, water=Mass of the test plaque and sinker in water (g) mnc, water=Mass of the sinker clamp in water (g)Note: since density of polyethylene is lower than water, a sinker is used to keep the test plaque immersed.

[0081] Density of polymer pellet samples (polyethylene composition) was measured by following ISO 1183 A with the immersion method.

[0082] Comonomer content using Spectroscopic method - Samples were pressed into 70 micron films using a Specac Atlas manual hydraulic press constant thickness film maker. Press temperature is set to 170 °C, preheat time is 1 minute, press time is 1 minute, press pressure is 2 tons and the spacer is an E-ring. Films are pressed in between PTFE foils.

[0083] Samples were subsequently measured via Infrared with a Perkin Elmer Spectrum 100 in transmission measurement mode. 9 scans are made in the scan rage 4400-400 cm’1with an spectral resolution of 4 cm’1with CO2 / H2O water correction active.

[0084] The infrared results are transformed into comonomer mol% by the use of 6 calibration (calibration type multivariate), and 3 validation sample standards in the comonomer range 0.25 to 1.75 mol%.Molecular weight Distribution (MWD) and moments of the MWD

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

[0086] A high-temperature chromatograph Polymer Char GPC-IR system equipped with IR5 MCT detector and Polymer Char viscometer (Polymer Char S.A., Spain) was used at 160°C to determine the MWD and SCB as function of molecular weight. Three columns of Polymer Laboratories 13pm PLgel Olexis, 300 x 7.5mm, were used in series for GPC separation. 1,2,4- trichlorobenzene stabilized with Ig / L butylhydroxytoluene (also known as 2,6-di- / c / 7-butyl-4- methylphenol or BHT) was used as eluent at a flow rate of ImL / min. Sample concentration was around 0.7mg / mL and injection volume was 300pL.

[0087] The molar mass was determined based on the Universal GPC-principle using a calibration made with PE narrow and broad standards (in the range of 0.5-2800kg / mol, Mw / Mn -4 to 15) in combination with known Mark Houwink constants of PE-calibrant (alfa = 0.725 and log K = -3.721).Deconvolution technique to calculate Mw / Mn for high molecular weight polymer component B using ASTM D 6474-12

[0088] The molecular weight distribution moments for the polymer component B (Mn and Mw) can be calculated by using a deconvolution technique employing the data obtained experimentally using the ASTM D 6474-12 standard for the low molecular weight component (Fraction A) and the final polyethylene composition. Such techniques for example has been described in WO99 / 14271.

[0089] For polymers manufactured using a Ziegler-Natta catalyst system such as the ones employed for the inventive examples of the invention, Catl and Cat2, the molecular weight distribution follows a log-normal distribution, defined by Equation [3]:Where: wi is the weight component of polymer with molecular weight MiMo is the peak molecular weightP is a parameter which characterizes the width of the log-normal distribution

[0090] The MWD deconvolution technique involves a two parameter fit, Mo and P, as per equation [3], Both parameters values are fitted by minimizing the error defined by Eqn 4.

[0091] This is the error between the experimentally determined molecular weight distribution for the polyethylene composition (final product) obtained using ASTM D 6474- 12, and the fitted distribution obtained by the addition of fractions A and B of the final composition. The molecular weight distribution data for fraction A and for the final composition was obtained by using ASTM D 6474-12 on the collected inventive examples of Table 1, and molecular weight distribution data for fraction B was calculated from themolecular weight distribution data from final polyethylene composition and fraction A, as described below.

[0092] The minimization error is expressed as:Where: wi, experimental is the weight fraction of polymer with a molecular weight Mi for the polymer composition of the invention. It is determined experimentally for the polyethylene composition following ASTM D 6474-12. wi, calculated is the weight fraction of polymer with a molecular weight Mi calculated for the polyethylene composition of the invention.

[0093] It is determined from the addition of the weight fraction of polymer with same molecular weight Mi for the fraction A, determined experimentally following ASTM D 6474- 12, times the weight component of polymer fraction A in the total polyethylene composition and the addition of the weight fraction of polymer with same molecular weight Mi for the fraction B, calculated with Equation [3], times the weight component of polymer fraction B in the final polyethylene composition. The weight components of fractions A and B with respect to the total polyethylene composition can be found for each inventive example in Table 1. The error was minimized by using Solver Excel minimization algorithm iterating over the values of Mo and p.

[0094] Mn and Mw for the calculated molecular weight distribution of component B are calculated by the formulas described in ASTM D 6474-12.

[0095] Peak ratio: A ratio of the value of the peak of the molecular weight distributions of the low molecular weight component (A) and the value of the peak of the high molecular weight component (B) was calculated as follows: The molecular weight distribution for the high molecular weight component (B) and the low molecular weight component (A) was resolved by deconvolution of the ethylene polymer molecular weight distribution. There after using known split values the value was determined using the equation -

[0096] Then, the ratio value was calculated from the dW / dLogMw value at the peak molecular weight of the low molecular weight component multiplied by the corresponding molecular weight component.

[0097] Environmental Stress Crack Resistance was measured according to ASTM D1639 Method B at 50 C in 10% Igepal (F50).

[0098] Dynamic Mechanical Properties (complex viscosity n): The vi scosity values at each shear rate are calculated by fitting flow curves generated by oscillatory rheometer according to ISO 6721-10 between 0.01 and 100 rad / s at 190 C on parallel plates with 25 mm diameter and 1.2 mm gap with a modified Carreau- Yasuda model, which is represented by the following equation: = o - [1 + U ■ / )“]“ [1] where q is the viscosity in Pa.s ro is 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) rpoo is the viscosity value in Pa.s at 190 °C and a shear rate of 100 rad / s as calculated by equation [1] previously fitted to the flow curve data generated by oscillatory rheometry between 100 and 5000 rad / s at 190 C according to ISO 6721-10 on parallel plates with 25 mm diameter and 1.2 mm gap.

[0099] 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 derivedparameters 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).

[0100] For complex viscosity at 5000 rad / s, the data is obtained by extrapolation using the methodology described in the patent (Carreau Yasuda equation) and the data used for the extrapolation is obtained following ISO 6721-10 at 190 °C.Determination of Long Chain Branching

[0101] Long Chain Branching in polyethylene can be diagnosed 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). The cited reference is included only for the purpose of establishing that that there is a relationship between the long chain branching in polyethylene and low or zero shear viscosity and the molecular weight. One such relationship that can be used for the purpose of the invention is as below [2]:

[0102] Long Chain Branching content in the polymers of the invention has been characterized by the following relationship:where:

[0103] LCBindex diagnoses the amount of Long Chain Branching present in the polymer T|o.oi is the viscosity of the polymer at 190 °C and 0.01 rad / s in Pa*s and expressed in Pa*s, and Mw is the weight average molecular weight expressed in kg / mol.

[0104] 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, with average results from 5 specimens at 23 °C.

[0105] Strain hardening modulus: Strain hardening modulus was determined according to ISO 18488.

[0106] Impact resistance was measured by Charpy method following ISO 179-1 / leA, non instrumented test at -10 °C, 0 °C and 23 °C on specimens with dimensions 80 x 10 x 4 mm and a notch of type A. The result obtained was the average of 5 specimens that was tested. The directionof the blow is 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. Final specimens were prepared by machining from the compression molded plaque.

Claims

CLAIMS1. A polyethylene composition, comprising an ethylene polymer comprising or consisting of: a) > 60.0 and < 75.0 wt.%, preferably > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 10,000 g / mol and < 70,000 g / mol, preferably > 30,000 g / mol and < 65,000 g / mol, preferably > 30,000 g / mol and < 60,000 g / mol, preferably wherein the weight average molecular weight (Mw) is determined in accordance with ASTM D6474-12; and b) > 25.0 and < 40.0 wt.%, preferably > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 700,000 g / mol, preferably > 100,000 g / mol and < 600,000 g / mol, preferably > 100,000 g / mol and < 400,000 g / mol; and preferably wherein the low molecular weight component (A) is an ethylene homopolymer or an ethylene copolymer and preferably wherein the high molecular weight component (B) is a copolymer of ethylene and a C3-C20 comonomer, preferably the high molecular weight component (B) is a copolymer of ethylene and a C3-C8 alpha olefin; wherein the polyethylene composition has:• a melt flow index (MFIs) of > 4.0 and < 18.0 dg / min, preferably > 5.0 and <15.0 dg / min, preferably > 6.0 and < 12.0 dg / min, preferably > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio of > 15.0 and < 40.0, preferably > 17.0 and < 22.0, preferably > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and 5.0 kg respectively; and• a density of > 956.0 and < 965.0 kg / m3, preferably > 957.0 and < 962.0 kg / m3, preferably> 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 580 and < 700 Pa.s, preferably> 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 45.0 Pa.s and < 60.0 Pa.s, preferably > 48.0 Pa.s and < 60.0 Pa.s, preferably > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C.

2. The polyethylene composition according to claim 1, wherein the polyethylene composition has a total content of polymeric units derived from Cs-Cs alpha olefin of > 0.2 and < 0.8 mol.%, preferably > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition, preferably wherein the mole content of the polymeric units in the polyethylene composition is determined using Infra Red spectroscopy.

3. The polyethylene composition according to any one of claims 1 -2, wherein the Cs-Cs alpha olefin comonomer is 1 -hexene, and preferably wherein the total content of polymeric units derived from 1-hexene comonomer is from > 0.3 and < 0.5 mol.%, with regard to the total moles of the polyethylene composition.

4. The polyethylene composition according to any one of claims 1-3, wherein the polyethylene composition has weight average molecular weight (Mw) of > 100 kg / mol and < 250 kg / mol, preferably > 100 kg / mol and < 200 kg / mol, preferably > 100 kg / mol and < 180 kg / mol, determined in accordance with ASTM D6474-12; and / or wherein the polyethylene composition has a Z-average molecular weight (Mz) of > 700 kg / mol and < 2000 kg / mol, determined in accordance with ASTM D6474-12.

5. The polyethylene composition according to any one of claims 1-4, wherein the polyethylene composition has a complex viscosity (T]O.OI) at a shear rate of 0.01 rad / s of > 5.0 kPa.s and < 15.0 kPa.s, preferably > 6.0 kPa.s and < 12.0 kPa.s, determined in accordance with ISO 6721-10 at 190 °C.

6. The polyethylene composition according to any one of claims 1-5, wherein the polyethylene composition has a molecular weight distribution (Mw / Mn) is > 10.0 and < 25.0, preferably > 10.0 and < 20.0, preferably > 10.0 and < 18.0, where Mw is the weightaverage molecular weight and Mn is the number average molecular weight as determined in accordance with ASTM D6474-12.

7. The polyethylene composition according to any one of claims 1-6, wherein the polyethylene composition has a Long Chain Branch Index of > 0.2 and < 1.2, preferably > 0.2 and < 1.0, wherein LCB index is determined by LCBIndexT|o.oi is the complex viscosity of the polyethylene composition at 190 °C and at 0.01 rad / s and expressed in Pa*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 Strain Hardening modulus of > 12.0 MPa and < 25.0 MPa, preferably > 12.0 MPa and < 22.0 MPa, as measured in accordance with ISO 18488.

9. The polyethylene composition according to any one of claims 1-8, wherein the polyethylene composition, comprising the ethylene polymer comprises or consists of: a) > 62.0 and < 68.0 wt.%, with regard to the total weight of the ethylene polymer, of a low molecular weight component (A) having a weight average molecular weight of > 30,000 g / mol and < 60,000 g / mol; and b) > 32.0 and < 38.0 wt.%, with regard to the total weight of the ethylene polymer, of a high molecular weight component (B) having a weight average molecular weight of > 100,000 g / mol and < 400,000 g / mol; and wherein the polyethylene composition has:• a melt flow index (MFIs) of > 7.0 and < 12.0 dg / min, determined in accordance with ISO1133-1 :2011 at 190 °C and measured at 5.0 kg; and• a melt flow ratio of > 17.0 and < 21.0, where melt flow ratio is the ratio of melt flow index measured according to ISO1133-1 :2011 at 190 °C and at 21.6 and at 5.0 kg respectively; and• a density of > 957.0 and < 961.0 kg / m3, determined in accordance with ISO 1183; and• a complex viscosity (rpoo) at a shear rate of 100 rad / s of > 585 and < 680 Pa.s determined in accordance with ISO 6721-10 at 190 °C; and• a complex viscosity (rpooo) at a shear rate of 5000 rad / s of > 50.0 Pa.s and < 58.0 Pa.s, determined in accordance with ISO 6721-10 at 190 °C; and• a Strain Hardening modulus of > 15.0 MPa and < 22.0 MPa as measured in accordance with ISO 18488; and• total content of polymeric units derived from 1-hexene comonomer of > 0.3 and < 0.6 mol.%, with regard to the total moles of the polyethylene composition.

10. The polyethylene composition according to any one of claims 1-9, wherein the polyethylene composition has at least one of:(a) a Bell Test resistance F50 of > 100 hours and < 300 hours when determined in accordance with ASTM DI 693 Method B at 50 °C in 10% IGEPAL; and / or(b) a Yield stress of > 26.0 MPa and < 35.0 MPa, preferably > 26.0 MPa and < 32.0 MPa, preferably > 26.5 MPa and < 31.0 MPa as measured according to ISO 527-2 at 23 °C; and / or(c) a tensile modulus value of > 1350 MPa and < 1550 MPa, preferably > 1380 MPa and < 1450 MPa as measured according to ISO 527-2 at 23 °C.

11. The polyethylene composition according to any one of claims 1-10, wherein the polyethylene composition comprises > 80.0 wt.% and < 100.wt.%, preferably > 90.0 wt.% and < 100. wt.%, preferably > 95.0 wt.% and < 100. wt.%, preferably > 98.0 wt.% and < 100. wt.% of the ethylene polymer with regard to the total weight of the polyethylene composition; and wherein the polyethylene composition comprises > 0.0 wt.% and < 20.0 wt.%, preferably > 0.0 wt.% and < 10.0 wt.%, preferably > 0.0 wt.% and < 5.0 wt.%, preferably > 0.0 wt.% and < 2.0 wt.%, of additives, preferably wherein the additives are selected from anti-oxidants, carbon black, fillers, process stabilisers, anti-oxidants, light and / or heat stabilisers, cross-linking agents and combinations thereof.

12. The polyethylene composition according to any one of claims 1-11, wherein the low molecular weight component (A) of the ethylene polymer has a melt flow index (MFI1.2) of > 15.0 and < 70.0 dg / min, preferably > 35.0 and < 60.0 dg / min, preferably > 45.0 and < 55.0 dg / min determined in accordance with ISO1133-1:2011 at 190 °C and measured at 1.2 kg.

13. The polyethylene composition according to any one of claims 1-12, wherein the low molecular weight component (A) is an ethylene homopolymer having a density of > 964.0 kg / m3and < 978.0 kg / m3, preferably > 967.0 kg / m3and < 972.0 kg / m3determined in accordance with ISO 1183; and / or wherein the high molecular weight component (B) is a copolymer of ethylene and 1 -butene or ethylene and 1 -hexene, preferably wherein, the high molecular weight component (B) is a copolymer of ethylene and 1 -hexene.

14. An article comprising the polyethylene composition as claimed in claims 1-13, preferably wherein the article is selected from a container, cap or a closure.

15. Use of the polyethylene composition as claimed in claims 1-13, for improving the properties of stiffness, processability during injection molding, hardness and environmental stress cracking resistance (ESCR), of an article, preferably wherein the article is a cap or a closure.

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