Rotomoulded articles, resins, and processes to produce such articles

Abstract

The disclosure is about rotomoulded article and a process to produce said article The article is a mono-layered article or a multi-layered article wherein the mono-layer or at least one of the layers comprises a polyethylene resin having a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C; a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and a flow activation energy fulfilling the following relationship: Eact (kJ / mole) > 70 - 12 ln (MI2).

Description

[0001]ROTOMOULDED ARTICLES, RESINS, AND PROCESSES TO PRODUCE SUCHARTICLES TECHNICAL FIELDThe present disclosure relates to rotomoulded articles as well as resins and processes toproduce such rotomoulded articles. TECHNICAL BACKGROUND Rotomoulding is used for the manufacture of simple to complex, hollow plastic products. It canbe used to mould a variety of materials such as polyethylene, polypropylene, polycarbonate, orPVC. Polyethylene represents more than 80 % of the polymers used in the rotomoulding market. This is due to the outstanding resistance of polyethylene to thermal degradation during processing,its easy grinding, good flowability, and low-temperature impact properties.Polyethylenes prepared with a Ziegler-Natta catalyst are generally used in rotomoulding, butmetallocene-produced polyethylenes are desirable because their narrow molecular distribution allows better impact properties and shorter cycle time in processing.Recycled polyethylene materials such as post-consumer resins (PCR) available from bottlesmay contain a high content of chromium-catalyzed polyethylene with a low melt index and high density that cannot allow them to be used in rotomoulding applications. Recycled polyethylene materials such as post-consumer resins (PCR) are also available from films. However, they often contain LDPE and show a shear modulus (G’) too low to be used in rotomoulding applications.Post-industrial resins (PIR) may be useful but are not often available. There is nevertheless aneed for rotomoulded articles made from recycled polyethylene material.There is a continuous need for improvement of polyethylene resin properties and improvementof the rotomoulded articles made from these resins.In particular, polyethylene resins with a high flow activation energy are desirable in rotomouldingapplications.Rotomoulding involves heating a powdered resin inside a mold, where it melts and coats theinterior surface of the mold cavity. Without being sure of the mechanism, it is observed thatwhen, in the next step of the thermoforming process, cooling is considered, resins containinglong chain branches (so resins with a high flow activation energy) crystallize better and more uniformly. Whatever the precise mechanism could be, resins containing a few long chainbranches allow for obtaining a more uniform and consistent final product.High flow activation energy resins are mainly linked to the presence of long-chain branching.High flow activation energy resins, due to the consequences in terms of nucleation and thicknessrepartition in the rotomoulding process, often have a better balance of mechanical propertiesincluding tensile strength and impact resistance. This is beneficial for rotomoulded products thatrequire durability and strength, such as storage tanks, containers, playground equipment, and automotive parts. While it may seem counterintuitive, a resin with higher flow activation energy can sometimes lead to shorter molding cycle times in rotomoulding. This is because it can solidify more rapidly due to its higher viscosity. Faster solidification means shorter overall processing times, which can increase productivity and reduce manufacturing costs.EP1632505 A1 discloses an ethylene-based polymer which is a copolymer obtained fromethylene and a C3 to C10 alpha-olefin and satisfies the following requirements (i), (ii), (iii) and (iv) simultaneously provides a blow-molded product and an extrusion-molded product excellent in moldability, mechanical strength and outward appearance. (i) melt flow rate under a loading of 2.16 kg at 190°C is in the range of 0.01 to 10, (ii) melt tension and the above melt flow ratesatisfy the following relationship: MT ≥ 3.2 × MFR 2 -0.55 , (iii) an activation energy of fluidizationis less than 30 (KJ / mol), and (iv) swell ratio is 1.36 or more.JP 2012188652 A relates to an injection molded product having high brilliance and transparency,and with hardly noticeable flow mark. The injection molded product includes a resin compositionincluding 50-5 wt.% of below the ethylene-α-olefin copolymer (A) and 95-50 wt.% of below the ethylene-α-olefin copolymer (B), and having a melt flow rate of 1-100 g / 10 minutes. The ethylene-α-olefin copolymer (A) has a melt flow rate of 0.4-5 g / 10 minutes, an activation energy for fluid of 50-100 kJ / mol, a molecular weight distribution of 5-15 and three or less flexion points in a melting curve range at 25°C-150°C. The ethylene-α-olefin copolymer (B) is an ethylene-α- olefin copolymer other than the ethylene-α-olefin copolymer (A) and has a melt flow rate of 1- 100 g / 10 minutes and a swell ratio of 1.15 or less. US 2018 / 298129 A1 is about a polyolefin having a density of greater than about 0.930 g / ml which when extruded at a temperature in the range of from about 590° F. to about 645° F. and then coated onto a substrate at a rate of from about 300 ft / min to about 1000 ft / min has an edge weave of from about 0 in / side to about 2.5 in / side and a neck-in of less than about 3.0 in / side.There is a need for a polyethylene resin with high flow activation energy for rotomouldingapplications because it offers improved flow properties and enhanced balance of mechanicalproperties. There is a continuous need for higher-quality products and increased efficiency inthe manufacturing process.There is a need for rotomoulded articles, resins, and processes to produce rotomoulded articlesthat show good processability as well as a good balance of properties that are produced at lowcost and in an effective way. SUMMARY Surprisingly, it has been found that the above objectives can be attained either individually or inany combination, by the use of a specific resin with high flow activation energy in rotomouldedarticles. According to a first aspect, the disclosure provides for a rotomoulded article being a mono-layered article or a multi-layered article and is remarkable in that the mono-layer or at least oneof the layers comprises a polyethylene resin having -a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).In an embodiment, the polyethylene resin is metallocene-catalyzed; with preference,polyethylene resin is metallocene-catalyzed with a catalyst system based on a bis-indenyl or a bis-cyclopentadienyl metallocene component. For example, the polyethylene resin has a Mw / Mn ranging of at most 4.5. In another embodiment, the polyethylene resin is or comprises one or more recycledpolyethylene resins (rPE), and / or the polyethylene resin comprises from 0.1 to 8.0 wt.% of apolymer different from polyethylene based on the total weight of the polyethylene resin and asdetermined by 13C NMR, wherein the polymer different from polyethylene is selected frompolypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof.For example, the polyethylene resin has an Mw / Mn ranging of at most 15.0; preferably of atmost 12.0, more preferably of at most 10.0; and even more preferably at most 8.0.For example, the polyethylene resin is or comprises recycled chromium-catalyzed polyethyleneresins and / or recycled Ziegler Natta-catalyzed polyethylene resins.Whatever the embodiment selected, the polyethylene resin is preferably selected to have anunsaturation index higher than 2,000 wherein the unsaturation index is the product of the Mn in Dalton and the vinyl unsaturation units per 1,000 carbon atoms as determined by ASTM D6248- 98:2004.For example, the polyethylene resin has a density from 0.930 to 0.980 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23°C; preferably, from 0.931 to 0.970 g / cm3.For example, the polyethylene resin has a density of at least 0.931 g / cm3; preferably, at least0.932 g / cm3; and more preferably, at least 0.933 g / cm3.For example, the polyethylene resin has a density of at most 0.980 g / cm3; preferably, at most0.975 g / cm3; more preferably, at most 0.970 g / cm3; most preferably, at most 0.965 g / cm3; mostpreferably, at most 0.960 g / cm3; preferably at most 0.955 g / cm3; preferably, at most 0.950 g / cm3;preferably at most 0.945 g / cm3; and even most preferably at most 0.942 g / cm3; For example, the polyethylene resin has a melt index MI2 ranging from 4.0 to 28.0 g / 10 min asdetermined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably from 5.0to 25.0 g / 10 min; more preferably from 6.0 to 20.0 g / 10 min. For example, the polyethylene resin has a ratio of complex viscosity at a frequency of 1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of at most 3.5, wherein the complex viscosities are measured at 190°C. In an embodiment, the polyethylene resin has a complex viscosity at 1 rad / sec at 190 °C of at most 2,000 Pa·s. For example, the polyethylene resin has a complex viscosity at 1 rad / sec at190 °C ranging from 100 to 2,000 Pa·s, wherein the complex viscosity is measured at 190°C.In an embodiment, the polyethylene resin has a complex viscosity at 100 rad / sec at 190 °C ofat most 1,000 Pa·s. For example, the polyethylene resin has a complex viscosity at 100 rad / secat 190 °C ranging from 100 to 1,000 Pa·s For example, the polyethylene resin has a z-average molecular weight (Mz) of at least 50,000Da as determined by gel permeation chromatography.For example, the polyethylene resin has a z-average molecular weight (Mz) of at most 120,000Da as determined by gel permeation chromatography; preferably at most 95,000 Da.For example, the polyethylene resin has a number average molecular weight (Mn) of at least3,000 Da as determined by gel permeation chromatography.For example, the polyethylene resin has a number average molecular weight (Mn) of at most45,000 Da as determined by gel permeation chromatography. For example, the polyethylene resin has a Carreau-Yasuda a of at least 0.50.For example, the article has an Impact peak energy greater than 40 J at -40°C as determinedaccording to ISO 6603, and / or the article has a tensile modulus of at least 500 MPa asdetermined according to ISO 527-1 standard (Measurements performed with an ISO 727 type1A sample, at a temperature of 23°C, at a traction speed of 50 mm / min for measuring strengthand elongation and 1 mm / min for measuring modulus).According to a second aspect, the disclosure provides for a process to produce a rotomouldedarticle according to the first aspect, wherein the process is remarkable in that it comprises a step(a) of providing a polyethylene resin and a step (b) of rotomoulding the polyethylene resin into a rotomoulded article, wherein polyethylene resin has:- a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 – 12 ln (MI2).In a preferred embodiment, step (a) comprises a step of preparing the polyethylene resin byperforming a thermal treatment on a raw polyethylene material wherein the thermal treatment isperformed in an extruder at a temperature of at least 300°C with a residence time of at most10.0 min. With preference, the temperature is at least 315°C and / or at most 450°C. With preference, the residence time is at most 5.0 min; preferably at most 2.0 min.With preference, the screw profile comprises two or more hot zones wherein a first hot zonecomprises successive kneading blocks elements over a length of at least 4 D followed by a left- handed element with D being the screw diameter, and one or more additional hot zones placeddownstream of the first hot zone are filled mixing zones, each comprising kneading blockselements over a length of at least 4 D followed by a kneading left-handed element or by a left- handed element with D being the screw diameter. With preference, the successive kneading blocks elements of at least one hot zone of the extruder comprise disks with disks offset by 90 degrees and a disk width of at least 0.3 D wherein D being the screw diameter and / or in that one hot zone of the extruder is or comprises the melting zone of the extruder. With preference, the raw polyethylene material is selected to have a melt index (MI2) ranging from 0.2 to less than 3.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C undera load of 2.16 kg and / or a density of at least 0.928 g / cm3 as determined according to ISO 1183-1:2012 at 23 °C.In an embodiment, the raw polyethylene material is or comprises a virgin polyethylene material.With preference, the virgin polyethylene material is metallocene-catalyzed; preferably with acatalyst system based on a bis-indenyl or a bis-cyclopentadienyl metallocene component. Withpreference, the virgin polyethylene material is metallocene-catalyzed and has a Mw / Mn rangingof at most 4.5. In an embodiment, the raw polyethylene material is or comprises one or more recycled- polyethylene resins (rPE) and / or the raw polyethylene material comprises from 0.3 to 8.0 wt.% based on the total weight of the polyethylene resin, as determined by13C NMR, of a polymer different from polyethylene selected from polypropylene (PP), polyacrylate (PA), polyethyleneterephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof. Withpreference, the one or more recycled-polyethylene resins (rPE) have an Mw / Mn ranging of atmost 30.0.With preference the raw polyethylene material is or comprises recycled chromium-catalyzedpolyethylene resins and / or recycled Ziegler Natta-catalyzed polyethylene resins.According to a third aspect, the disclosure provides for the use of a raw polyethylene materialto manufacture a rotomoulding article wherein the raw polyethylene material has a density of atleast 0.928 g / cm3 as determined according to ISO 1183-1:2012 at 23°C and a melt index MI2ranging from 0.2 to less than 3.0 g / 10 min, and the use includes thermal treatment of the raw polyethylene material to raise its melt index to range from 3.0 to 30.0 g / 10 min as determinedaccording to ISO 1133-2011 at 190 °C under a load of 2.16 kg to obtain polyethylene resinwherein polyethylene resin further has a density of at least 0.930 g / cm3as determined accordingto ISO 1183-1:2012 at 23°C; a flow activation energy fulfilling the following relationship;: Eact(kJ / mole) > 70 - 12 ln (MI2); .With preference, the raw polyethylene material is or comprises one or more recycled-polyethylene resins (rPE). More preferably, the raw polyethylene material is or comprisesrecycled chromium-catalyzed polyethylene resins and / or recycled Ziegler Natta-catalyzedpolyethylene resins. From the above definition of the process and the use, a clear benefit of the invention can be easily understood. Indeed, surprisingly, it was discovered that it is possible to produce rotomoulded articles from resins that are initially not suitable for rotomoulded applications,wherein a thermal treatment of the resins allows these resins to be upgraded. In addition, it wasdiscovered that such treatment allows for improvement in the properties of the resins such as their flow activation energy to a range that was not attainable for straight reactor grade resins produced by the same catalyst and with a similar melt index.In the polymer industry, it is known to produce grades adapted to each application. This resultsin an extended catalog wherein some grades are produced in such small quantities that the grade is delisted after a while. It is still possible to produce the grade upon a specific request,but this takes time and is expensive. The invention provides a solution to offer polymer gradesupon request, in a fast and cost-effective way.Also, recycled materials are provided as commercial flux having an average melt index. Someabundant recycled polymer fluxes have low melt index values, typically close to MI2 of 0.2 g / 10min when originating from small containers (shampoo bottles, …) and close to MI2of 1.0 g / 10min when originating from films. These recycled polymers have therefore melt indexes whichmakes them rather unsuitable for rotomoulding applications and hence, limits the applicationsof recycled polyethylene-containing materials. The invention allows for treating these recycledpolyethylene-containing materials to transform them into polyethylene resins that are suitable for rotomoulding applications. Thermal treatment of polyethylene resins is known from WO2023 / 151995 and WO2023 / 151996.These documents disclose a polyethylene composition for injection molding and a process toproduce such a polyethylene composition comprising providing a twin-screw extruder withthermal regulation devices; providing an initial polyethylene-containing material comprising atleast 50 wt.% of polyethylene based on the total weight of the initial polyethylene-containing material; extruding the initial polyethylene-containing material to obtain a polyethylene composition; wherein extrusion is performed with a residence time of less than 20 min; and recovering a polyethylene composition; wherein extruding comprises a thermal treatment of the initial polyethylene-containing material at a temperature of at least 300°C in one or more hot zones of the extruder by self-heating to have a maximum barrel temperature ranging from 300 to 460°C in at least one hot zone of the extruder. According to a fourth aspect, the disclosure provides for a polyethylene resin for use inrotomoulding applications remarkable in that it shows:- a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2). With preference, the polyethylene resin has:- a ratio of complex viscosity at a frequency of 1 rad / sec to the complex viscosity at afrequency of 100 rad / sec of at most 3.5 wherein the complex viscosities are measured at190°C; and / or- a number average molecular weight (Mn) of at least 3,000 Da as determined by gelpermeation chromatography. According to a fifth aspect, the disclosure provides for the use of a polyethylene resin accordingto the fourth on grinding machines to prepare micropellets or powder.According to a sixth aspect, the disclosure provides for micropellets or powder prepared from a polyethylene resin according to the fourth aspect. DESCRIPTION OF THE FIGURES -Figure 1: screw profile introduced in the Leistritz ZSE 18 HPe extruder (L / D = 40 – MPOlaboratory) and used to produce the CR-PE -Figure 2: SEC curves for CR-PE 8 and references- Figure 3: SEC curves for CR PE 17 and references- Figure 4: Linear viscoelastic curves for CR-PE 8, CR-PE 17, and references- Figure 5: Van Gurp-Palmen curves- Figure 6: Flow activation energy as a function of the phase angle- Figure 7: Flow activation energy as a function of the melt indexDETAILED DESCRIPTION It is to be understood that this disclosure is not limited to particular processes or compositions described, as such processes or compositions may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting since the scope of the present disclosure will be limited only by the appended claims.When describing the polymers, uses, and processes of the disclosure, the terms employed areto be construed by the following definitions, unless a context dictates otherwise. For the disclosure, the following definitions are given: As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context dictates otherwise. By way of example, "a composition" means one composition or more than one composition. The terms "comprising", "comprises" and "comprised of as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of" also include the term “consisting of”. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g., 1 to 5 can include 1, 2, 3, 4, 5 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the endpoint values themselves (e.g., from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein. All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference. Indication of a standard method to determine a parameter implies referring to the standard in force at the priority date of the application, in case the year of the standard is not indicated. Reference throughout this specification to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connection with the embodiment isincluded in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the disclosure and form different embodiments, as would be understood by those in the art. For example, in the following claims and statements, any of the embodiments can be used in any combination. Unless otherwise defined, all terms used in disclosing the disclosure, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present disclosure.The terms “polyethylene” (PE) and “ethylene polymer” may be used synonymously. The term“polyethylene” encompasses ethylene homopolymer as well as ethylene copolymer resin which can be derived from ethylene and one or more comonomers selected from the group consisting of C3-C20 alpha-olefins, such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. The terms “polyethylene resin” or “ethylene homopolymer resin” or “ethylene copolymer resin” refer to polyethylene fluff or powder that is extruded, and / or melted and / or pelletized and can be produced through compounding and homogenizing of the polyethylene resin as taught herein, for instance, with mixing and / or extruder equipment. Unless otherwise stated, all parametersused to define the polyethylene resin are as measured on pellets, i.e., after extrusion.As used herein, the term “polyethylene” may be used as a shorthand for “polyethylene resin”.The terms “fluff” or “powder” refer to polyethylene material with the hard catalyst particle at the core of each grain and is defined as the polymer material after it exits the polymerization reactor (or the final polymerization reactor in the case of multiple reactors connected in series). The terms “Post-Consumer Resin”, which may be abbreviated as “PCR”, is used to denote the components of domestic waste, household waste or end-of-life vehicle waste. In other words,the PCRs are made of recycled products from waste created by consumers. The terms “Post-Industrial Resin”, which may be abbreviated as “PIR”, is used to denote the waste componentsfrom pre-consumer resins during packaging processes. In other words, the PIRs are made ofrecycled products created from scrap by manufacturers. The term “recycled polyethylene resin” or “recycled polyethylene-containing material” contrastswith the term “virgin polyethylene resin” “virgin polyethylene-containing material”, the term“virgin” is used to denote a polyethylene resin or material directly obtained from a polyethylenepolymerization plant. The terms “directly obtained” is meant to include that the polyethylene resin may optionally be passed through a pelletization step or an additivation step or both. Under normal production conditions in a production plant, it is expected that the melt index (MI2, HLMI, MI5) will be different for the fluff than for the polyethylene resin. Under normal productionconditions in a production plant, it is expected that the density will be slightly different for the fluffthan for the polyethylene resin (if PCR resins are considered, it is not a question of fluff (powder)or pellets but it is a question of flakes or pellets). Unless otherwise indicated, density and melt index for the polyethylene resin refer to the density and melt index as measured on the polyethylene resin as defined above. The present disclosure provides a polyethylene resin suitable for rotomoulding application, a rotomoulded article comprising such a resin, and a process to produce the resin and the rotomoulded article. The present disclosure also encompasses the use of a thermally treated polyethylene resin in a rotomoulded article or in a process to manufacture such a rotomouldedarticle. The resin, the article, the process, and the use will be described jointly.According to the disclosure, the rotomoulded article being a mono-layered article or a multi-layered article is characterized in that the mono-layer or at least one of the layers comprises a polyethylene resin having -a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190°C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).In one or more embodiments, the polyethylene resin has a melt index (MI2) ranging from 4.0 to28.0 g / 10 min from 4.5 to 27.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably, ranging from 5.0 to 25.0 g / 10 min; more preferably ranging from 5.5 to 22.0 g / 10 min; even more preferably ranging from 6.0 to 20.0 g / 10 min.For example, the polyethylene resin has a melt index (MI2) has a melt index of at least 3.2 g / 10min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably, atleast 3.5 g / 10 min or at least 3.8 g / 10 min; more preferably, at least 4.0 g / 10 min or at least 4.2g / 10 min; even more preferably, at least 4.5 g / 10 min or at least 4.8 g / 10 min; most preferably,at least 5.2 g / 10 min; even most preferably, at least 5.5 g / 10 min; or preferably, at least 5.8 g / 10 min; or preferably, at least 6.0 g / 10 min; or preferably, at least 6.2 g / 10 min.In particular, the polyethylene resin has a ratio of complex viscosity at a frequency of 1 rad / secto the complex viscosity at a frequency of 100 rad / sec of at most 3.5, said ratio being measured at 190 °C; preferably, of at most 3.2; more preferably, of at most 3.0; even more preferably, of at most 2.8; and most preferably, of at most 2.5. In an embodiment, the polyethylene resin has a complex viscosity at 1 rad / sec at 190 °C of at most 2,000 Pa·s; preferably at most 1,800 Pa.s; more preferably at most 1,600 Pa.s; even more preferably of at most 1,500 Pa.s most preferably of at most 1,200 Pa.s. In an embodiment, the polyethylene resin has a complex viscosity at 1 rad / sec at 190 °C ranging from 100 to 2,000 Pa·s; preferably from 150 to 1,800 Pa.s; more preferably from 200 to 1,600Pa.s; even more preferably from 250 to 1,500 Pa.s; most preferably from 300 to 1,400 Pa.s; andeven most preferably from 350 to 1,300 Pa.s; or from 400 to 1,200 Pa.s, or from 450 to 1,100Pa.s; wherein the complex viscosity is measured at 190°C.In an embodiment, the polyethylene resin has a complex viscosity at 100 rad / sec at 190 °C ofat most 1,000 Pa·s; preferably at most 800 Pa·s; even more preferably at most 600 Pa.s andmost preferably at most 570 Pa.s and even most preferably at most 550 Pa.s; or at most 520Pa.s, wherein the complex viscosity is measured at 190°C.In an embodiment, the polyethylene resin has a complex viscosity at 100 rad / sec at 190 °Cranging from 100 to 1,000 Pa·s; preferably from 150 to 800 Pa.s; more preferably from 180 to600 Pa.s; even more preferably from 200 to 570 Pa.s; most preferably from 220 to 550 Pa.s;and even most preferably from 250 to 520 Pa.s; wherein the complex viscosity is measured at190°C.For example, the polyethylene resin has a Carreau-Yasuda a of at least 0.50 as determined bythe method of the description.With preference, the polyethylene resin has a z average molecular weight (Mz) of at most120,000 Da as determined by gel permeation chromatography; preferably of at most 110,000Da; more preferably of at most 100,000 Da or at most 95,000 Da.With preference, the polyethylene resin has a z-average molecular weight (Mz) of at least 40,000Da as determined by gel permeation chromatography; preferably of at least 50,000 Da; morepreferably of at least 60,000 Da or at least 65,000 Da. With preference, the polyethylene resin has a number average molecular weight (Mn) of at least3,000 Da as determined by gel permeation chromatography; preferably at least 4,000 Da; morepreferably, at least 6,000 Da; even more preferably at least 8,000 Da, and most preferably atleast 10,000 Da. With preference, the polyethylene resin has a number average molecular weight (Mn) of at most45,000 Da as determined by gel permeation chromatography; preferably at most 42,000 Da;more preferably at most 40,000 Da. With preference, the polyethylene resin has an Mz / Mw of at most 7.0 as determined by size exclusion chromatography; preferably at most 6.0; more preferably at most 5.0; even more preferably at most 4.0; and most preferably at most 3.0.For example, the polyethylene resin has an Mz / Mw of at least 1.5 as determined by sizeexclusion chromatography.For example, the polyethylene resin further has an Mw / Mn ranging from 2.0 to 15.0 asdetermined by size exclusion chromatography; preferably from 2.0 to 12.0 or from 2.0 to 10.0;more preferably from 2.0 to 8.0 or from 2.1 to 6.0; even more preferably from 2.1 to 5.0; mostpreferably from 2.2 to 4.5; and even most preferably from 2.3 to 4.0; or from 2.3 to 3.5; or from2.3 to 3.0.In an embodiment, the polyethylene resin further has an Mw / Mn of at most 15.0 or at most 12.0as determined by size exclusion chromatography; preferably of at most 10.0 or at most 8.0;more preferably of at most 7.0 or at most 6.0; even more preferably of at most 5.0; mostpreferably of at most 4.5; and even most of at most 4.0, or at most 3.5, or at most 3.0.For example, the polyethylene resin has a density of at least 0.928 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23 °C. For example, the polyethylene resin has a density ofat least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23 °C; preferably, at leastpreferably, at least 0.932 g / cm3; more preferably, at least 0.935 g / cm3; even more preferably ofat least 0.936 g / cm3; and most preferably, of at least 0.938 g / cm3.In an embodiment, the polyethylene resin has a density of at most 0.980 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23 °C; preferably, of at most 0.975 g / cm3 or at most 0.970g / cm3; and more preferably, of at most 0.965 g / cm3; and even more preferably, of at most 0.960g / cm3;or at most 0.958 g / cm3; preferably at most 0.955 g / cm3; preferably, at most 0.950 g / cm3; preferably at most 0.945 g / cm3; and even most preferably at most 0.942 g / cm3, or at most 0.941 g / cm3.For example, the polyethylene resin has a density ranging from 0.930 g / cm3 to 0.980 g / cm3 asdetermined according to ISO 1183-1:2012 at 23 °C; preferably, ranging from 0.932 g / cm3 to0.975 g / cm3; more preferably, ranging from 0.935 g / cm3 to 0.970 g / cm3.For example, the polyethylene resin has an unsaturation index higher than 2,000 or higher than 3,500 wherein the unsaturation index is the product of the Mn in Dalton and the vinyl unsaturation units per 1,000 carbon atoms as determined by ASTM D6248-98:2004; preferably higher than 5000, even preferably higher than 7000; wherein the unsaturation index is the product of the Mn, in Dalton, and the vinyl unsaturation units per 1,000 carbon atoms. The polyethylene resin comprises at least 50 wt.% of polyethylene based on the total weight of the polyethylene resin. With preference, the polyethylene resin comprises at least 55 wt.% of polyethylene based on the total weight of the polyethylene resin; preferably, at least 60 wt.%; preferably, at least 70 wt.%; preferably, at least 80 wt.%; preferably, at least 90 wt.%; preferably, at least 95 wt.%. In an embodiment, the polyethylene resin is a virgin material and consists of polyethylene (i.e. comprises 100 wt.% of polyethylene). In an embodiment, the polyethylene resin is or comprises one or more recycled polyethylene resins (rPE). Recycled-polyethylene resins may contain one or more polymers different from polyethylene. In an embodiment, and in particular wherein the polyethylene resin is or comprises one or morerecycled polyethylene resins (rPE). the polyethylene resin comprises at least one polymerdifferent from polyethylene in a content ranging from 0 to 50 wt.% based on the total weight of the polyethylene resin as determined by13C NMR wherein at least one polymer different from polyethylene is selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof. With preference, the polyethylene resin comprises at least one polymer different frompolyethylene in a content ranging from 0 to 40.0 wt.% based on the total weight of thepolyethylene resin as determined by 13C NMR; preferably from 0.1 to 20.0 wt.%; more preferablyfrom 0.2 to 10.0 wt.%; even more from 0.3 to 8.0 wt.%; and most preferably from 0.5 to 5.0 wt.%or from 0.5 to 4.5 wt.%. For example, PCR polyethylene classically contains a small part of polypropylene (such as less than 5 wt.%). Producing the polyethylene resin In a preferred embodiment, the polyethylene resin is obtained by thermal treatment of raw polyethylene material to increase its melt index. However, surprisingly, the treatment performedalso provides other features to the polyethylene resin that make it particularly suitable forrotomoulding. Thus, the disclosure also provides the above-defined polyethylene resin being produced by a process comprising the following steps: a) providing a twin-screw extruder with thermal regulation devices; b) providing a raw polyethylene material comprising at least 50 wt.% of polyethylene basedon the total weight of the raw polyethylene material; c) extruding the raw polyethylene material to obtain a polyethylene resin; wherein extrusionis performed with a residence time of at most 10.0 minutes; andd) recovering a polyethylene resin;wherein step (c) of extruding comprises a thermal treatment of the raw polyethylene material ata temperature of at least 300°C in one or more hot zones of the extruder; preferably, at least315°C. In an embodiment, the thermal treatment is performed by self-heating of the material wherein the one or more hot zones have a total length equal to or greater than 6 D with D being the screw diameter, wherein the extrusion is performed with mechanical specific energy greater thanor equal to 0.25 kWh / k or greater than or equal to 0.4 kWh / kg, wherein the screw profilecomprises at least one hot zone with successive kneading blocks elements over a length of at least 4 D followed by a left-handed element with D being the screw diameter, wherein the thermal regulation devices are set to initial imposed barrel temperatures ranging between 240 and 290 °C and are switched off when the barrel temperature in the zone spontaneously exceeds the imposed barrel temperature by at least 1 °C without the need of external heat application.In another embodiment, the thermal treatment is performed by heating the material using thethermal regulation devices of the extruder to have a maximum barrel temperature ranging from315 to 460°C in at least one hot zone of the extruder.The process of treating raw polyethylene material involves increasing the melt index of the saidraw polyethylene material to produce a polyethylene resin with a melt index that is increased bya factor k of more than 6.0; preferably by a factor k of at least 7.0; preferably by a factor k of at least 8.0; preferably by a factor k of at least 10.0; preferably by a factor k of at least 15.0; preferably by a factor k of at least 20.0; preferably by a factor k of at least 30.0; preferably by a factor k of at least 35.0; preferably by a factor k of at least 40.0. So that the ratio of the melt index of the polyethylene resin (MI2) to the melt index of the rawpolyethylene material (MI2) is more than 6.0; preferably of at least 7.0, preferably by at least 8.0;preferably at least 10.0; preferably at least 15.0; preferably at least 20.0; preferably at least 30.0; preferably at least 35.0; preferably at least 40.0. The twin-screw extruder with thermal regulation devices and the step (c) of extruding the rawpolyethylene material to obtain a polyethylene resinThe treatment of the raw polyethylene material to obtain a polyethylene resin is performed byextrusion wherein extrusion is performed with a residence time of at most 10.0 min and whereinstep (c) of extruding comprises a thermal treatment of the raw polyethylene material at atemperature of at least 300°C in one or more hot zones of the extruder. The extruder is a twin-screw extruder. The extruder can be provided with a standard configuration for the screw profile (for example when the process comprises a thermal treatmentby heating the material using the thermal regulation devices) or is provided with a screw profilethat shows an aggressive design, as shown in figure 1, to impart high mechanical energy to theraw polyethylene material (for example when the process comprises a thermal treatment by self-heating or by heating the material using the thermal regulation devices) As known to the person skilled in the art, thermal regulation devices can be used as a heatingmeans to impart thermal energy to the raw polyethylene material in the extruder, in addition tothe thermal energy already generated by the mixing. Extrusion mixing varies with the type of screw and screw profile and is capable of significant generation of mechanical energy, such as shear energy and / or elongation energy. Therefore,energy is introduced into the extrusion process in terms of mechanical energy and thermalenergy. Heating and / or cooling of the barrels can be achieved, for example, electrically, by steam, or by the circulation of thermally controlled liquids such as oil or water. The extruder screw comprises a screw main body, that is composed of cylindrical elements and an axis of rotation supporting the elements. The axis of rotation extends straight from its basal end to its tip. In a state in which the extruder screw is rotatably inserted in the cylinder of the barrel, the basal end of the extruder screw is positioned on one end side of the barrel, on which the supply port is provided, and the tip of the extruder screw is positioned on the other end side of the barrel, on which the discharge port is provided. Screw extruders have a modular system that allows different screw elements to be drawn into the central shaft to build a defined screw profile. The extruder screw may comprise one or more elements selected from conveying elements, kneading elements, right-handed (normal) screwelements, left-handed (inverse) screw elements, and any combination thereof. The elementsare arranged in a defined order from the basal end to the tips of the extruder screw and this order, as well as the type and number of elements involved, define the screw profile. Extruders and screw elements are commercially available for example at Leistritz.In an embodiment of the disclosure, the treatment of the raw polyethylene material is handledby mechanical energy. When high mechanical energy is requested, the extruder provided has a specific screw profile that is built to be “aggressive”, meaning that high mechanical energy will be imparted to the rawpolyethylene material. High mechanical energy will increase the temperature in the extruder asknown to the person skilled in the art so that the thermal treatment is performed by self-heating of the material. In such an embodiment, the twin-screw extruder is selected to comprise one or more hot zones, preferably being filled mixing zones, wherein the total length of the one or more hot zones is equal to or greater than 6 D with D being the screw diameter. It is understood that in case the screw profile is selected to comprise a single hot zone, then the total length of the said hot zone is equal to or greater than 6 D with D being the screw diameter. In such a case, the hot zone is also the melting zone of the twin-screw extruder. In case, the screw profile comprises two or more hot zones, then a first hot zone comprises successive kneading blocks elements over a length of at least 4 D followed by a left-handed element with D being the screw diameter, and one or more additional hot zones placed downstream of the first hot zone are filled mixing zones, each comprising kneading blocks elements over a length of at least 4 D followed by a kneading left-handed element or by a left- handed element with D being the screw diameter. For example, the twin-screw extruder comprises two filled mixing zones wherein each of the filled mixing zones has a length equal to or greater than 4 D with D being the screw diameter. Preferably the first hot zone is or comprises the melting zone of the extruder. Various mixing elements could be considered in the one or more hot zones but the most preferred ones do not drive any forward conveying (dispersive kneading blocks elements withdisks offset by 90 degrees). Other disk offset angles could be considered (for example, 30degrees, 45 degrees, and / or 60 degrees) but 90 degrees is preferred. The preferred minimum width of the disk is 0.3 D. Thus, preferably, the successive kneading blocks elements of at least one hot zone comprise disks with disks offset by 90 degrees and a disk width of at least 0.3 D wherein D is the screw diameter. For example, the twin-screw extruder comprises more than two filled mixing zones wherein the total length of filled mixing zones is equal to or greater than 8 D with D being the screw diameter. For example, the strong melting zone of the twin-screw extruder is made of successive mixing elements over a length of 4 D, with D being the screw diameter, followed by a left-handed element; preferably a full-flight left-handed element. In a preferred embodiment, the thermal regulation devices of the twin-screw extruder allow cooling the barrels and the process comprises switching off the thermal regulation devices when the barrel temperature in the zone spontaneously exceeds the imposed barrel temperature byat least 1 °C without the need of external heat application; preferably, by at least 2 °C, preferably,by at least 3 °C; more preferably by at least 5 °C; even more preferably, by at least 8 °C; and most preferably, by at least 10 °C. Indeed, when starting extrusion, thermal regulation devices will be switched on, in particular inthe melting zone to allow the material to melt. Then, when the polymer is self-heating, thethermal regulation devices are switched off to allow an increase in the temperature inside theextruder.In a preferred embodiment, step (c) of extruding the raw polyethylene material comprisesperforming the extrusion with mechanical specific energy greater than or equal to 0.25 kWh / kg,preferably greater than or equal to 0.28 kWh / kg; more preferably greater than or equal to 0.30kWh / kg; even more preferably greater than or equal to 0.35 kWh / kg; most preferably greater than or equal to 0.40 kWh / kg. In an embodiment, step (c) of extruding the raw polyethylene material comprises performing the extrusion with mechanical specific energy greater than or equal to 0.45 kWh / kg, preferably greater than or equal to 0.5 kWh / kg; more preferably greater than or equal to 0.6 kWh / kg. High rotation screw speeds are preferred, but the precise value of a high rotation screw speed is “extruder diameter” dependent. For example, when considering a diameter D of 18 mm twin- screw extruder, high rotational screw speed is considered to be higher than 500 rpm, preferably higher than 800 rpm. For example, when considering a diameter D = 58 mm twin-screw extruder, high rotational screw speed is considered to be higher than 250 rpm, preferably higher than 350 rpm. Non-limiting examples of suitable extruder screws with specific screw profiles are illustrated inFigure 1.When the thermal treatment is performed by heating the material, the extruder provided can show either an extruder screw with a standard screw profile or with a specific screw profile (i.e., aggressive configuration). In such an embodiment, step c) is performed at a maximum barrel temperature of at least300 °C; preferably at least 310 °C; more preferably at least 315 °C; even more preferably atleast 320 °C.When the thermal treatment is performed by self-heating of the material, the thermal treatmentof material in step c) is preferably performed at a maximum barrel temperature ranging from 300to 400 °C; preferably, ranging from 305 °C to 390 °C; more preferably ranging from 310 °C to380 °C; even more preferably, ranging from 315 °C to 370 °C and most preferably, ranging from320 °C to 360 °C. The maximum barrel temperature is the highest temperature amongst theimposed or measured temperatures along the extruder.When the thermal treatment is performed by heating of the material, the thermal treatment ofmaterial in step c) is preferably performed at a maximum barrel temperature ranging from 300to 460 °C; preferably, ranging from 305 °C to 440 °C; more preferably ranging from 310 °C to420 °C; even more preferably, ranging from 315 °C to 400 °C and most preferably, ranging from320 °C to 390 °C. The maximum barrel temperature is the highest temperature amongst the imposed or measured temperatures along the extruder.The temperature of the thermal treatment is the maximum barrel temperature. The extrusionconditions may be adapted by the person skilled in the art to impart sufficient energy to obtain a polyethylene resin with a melt index (MI2) in the targeted range. Screw speed can be adapted in function of the targeted maximum barrel temperature and of the capacity of the extruder. Higher screw speed allows a higher increase in the polymertemperature. For example, the screw speed ranges from 100 to 1200 rpm; preferably from 110rpm to 1200 rpm; more preferably from 150 rpm to 1100 rpm; even more preferably from 200 rpm to 1000 rpm; most preferably from 300 rpm to 900 rpm; and even most preferably from 320 to 800 rpm or from 350 to 800 rpm. In an 18 mm screw diameter twin-screw extruder, the preferred screw speed is higher than 500 rpm; in a 58 mm screw diameter twin-screw extruder, the preferred screw speed is higher than 250 rpm.Whatever the thermal treatment is performed by heating or by self-heating, the thermaltreatment of material in step (c) is performed with a residence time of at most 10.0 min;preferably of at most 8.0 min; more preferably at most 5.0 min, even more preferably at most 4.0 min; most preferably at most 3.0 min, even most preferably at most 2.0 min or at most 100 seconds.For example, step (c) of extruding the raw polyethylene material comprises performing theextrusion with a residence time ranging from 10 seconds to at most 10.0 minutes or to less than10.0 minutes; preferably with a residence time ranging from 10 seconds to 8.0 minutes; or witha residence time ranging from 10 seconds to 5.0 minutes or from 10 to 360 seconds; morepreferably with a residence time ranging from 10 to 240 seconds or from 15 to 200 seconds;even more preferably, from 20 to 180 seconds; most preferably, from 40 to 150 seconds; andeven most preferably, from 50 to 120 seconds or from 60 to 100 seconds.The raw polyethylene material and step (b) of providing a raw polyethylene materialThe process according to the disclosure comprises a step b) of providing a raw polyethylenematerial comprising at least 50 wt.% of polyethylene based on the total weight of the rawpolyethylene material.The raw polyethylene material can be a virgin polyethylene-containing material, a recycledpolyethylene-containing material, or a mixture of virgin and recycled polyethylene-containingmaterials.In a first embodiment, the raw material is or comprises metallocene-catalyzed; for example, theraw material is or comprises virgin polyethylene metallocene-catalyzed. More preferably, theraw material is prepared with a catalyst system based on a bis-indenyl or a bis-cyclopentadienylmetallocene component. In a preferred embodiment, the virgin polyethylene material ismetallocene-catalyzed and has an Mw / Mn ranging of at most 4.5. When the raw polyethylene material is or comprises polyethylene resins, the raw polyethylenematerial has an Mw / Mn of at most 4.5 as determined by gel permeation chromatography;preferably at most 4.2; more preferably at most 4.0; even more preferably at most 3.8; and most preferably, at most 3.5. The metallocene used to prepare the polyethylene can be a bis-indenyl represented by the general formula: R"(Ind)2 MQ2 (I) or a bis-cyclopentadienyl represented by the formula: (Cp)2 MQ2 (II) wherein (Ind) is an indenyl or an hydrogenated indenyl, substituted or unsubstituted, Cp is a cyclopentadienyl ring substituted or unsubstituted, R" is a structural bridge between the two indenyls to impart stereorigidity that comprises a C1-C4 alkylene radical, a dialkyl germanium or silicon or siloxane, or a alkyl phosphine or amine radical, which bridge is substituted orunsubstituted; Q is a hydrocarbyl radical having from 1 to 20 carbon atoms or a halogen, and Mis a group IVb transition metal or Vanadium. In formula (I), each indenyl or hydrogenated indenyl compound may be substituted in the same way or differently from one another at one or more positions in the cyclopentadienyl ring, thecyclohexenyl ring, and the bridge.In formula (I), each substituent on the indenyl may be independently chosen from those offormula XRv in which X is chosen from group IVA, oxygen, and nitrogen, and each R is the sameor different and chosen from hydrogen or hydrocarbyl of from 1 to 20 carbon atoms and v+1 is the valence of X. X is preferably C. If the cyclopentadienyl ring is substituted, its substituentgroups must be so bulky as to affect the coordination of the olefin monomer to the metal M.Substituents on the cyclopentadienyl ring preferably have R as hydrogen or CH3. More preferably, at least one and most preferably both cyclopentadienyl rings are unsubstituted. In a particularly preferred embodiment, both indenyls are unsubstituted. In formula (II), each cyclopentadienyl ring may be substituted in the same way or differently from one another at one or more positions in the cyclopentadienyl ring. In formula (II), each substituent on the cyclopentadienyl may be independently chosen fromthose of formula XR*v in which X is chosen from group IVA, oxygen, and nitrogen and each R*is the same or different and chosen from hydrogen or hydrocarbyl of from 1 to 20 carbon atomsand v+1 is the valence of X. X is preferably C and the most preferred substituent is n- butyl. R" is preferably a C1-C4 alkylene radical (as used herein to describe a difunctional radical, also called alkylidene), most preferably an ethylene bridge (as used herein to describe a difunctional radical, also called ethylidene), which is substituted or unsubstituted. The metal M is preferably zirconium, hafnium, or titanium, most preferably zirconium. Each Q is the same or different and can be a hydrocarbyl or hydrocarboxy radical having 1 to 20 carbon atoms or a halogen. Suitable hydrocarbyls include aryl, alkyl, alkenyl, alkylaryl, or arylalkyl. Each Q is preferably halogen. Among the preferred metallocenes used in the present invention, one can cite bis tetrahydro- indenyl compounds and bis indenyl compounds as disclosed for example in WO 96 / 35729 or bis (cyclopentadienyl) compounds. The most preferred metallocene catalysts are ethylene bis (4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride and bis (n-butyl-cyclopentadienyl) zirconium dichloride. The metallocene may be supported according to any method known in the art. In the event it is supported, the support used in the present invention can be any organic or inorganic solids, particularly porous supports such as talc, inorganic oxides, and resinous support material such as polyolefin. Preferably, the support material is an inorganic oxide in its finely divided form. The addition, on the support, of an agent that reacts with the support and has an ionising action, creates an active site. Preferably, alumoxane is used to ionise the catalyst during the polymerization procedure, and any alumoxane known in the art is suitable. The preferred alumoxanes comprise oligomeric linear and / or cyclic alkyl alumoxanes represented, for oligomeric, linear alumoxanes, by the formula: And, for oligomeric, cyclic alumoxanes, by the formula: (V) wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3-20 and R is a Cl-C8 alkyl group and preferably methyl. Methylalumoxane is preferably used. One or more aluminiumalkyl(s) can be used as catalyst in the reactor. An aluminiumalkyl represented by the formula AIR3can be used wherein each R is the same or different and isselected from halides or alkoxy or alkyl groups having from 1 to 12 carbon atoms. Especiallysuitable aluminiumalkyl is trialkylaluminium, the most preferred being triisobutylaluminium (TIBAL).Further, the catalyst may be prepolymerised before introducing it in the reaction zone and / orbefore the stabilization of the reaction conditions in the reactor.The polymerisation of the metallocene-catalyzed polyethylene can be carried out in gas, solutionor slurry phase. Slurry polymerisation is preferably used to prepare the polyethylene. The polymerisation temperature ranges from 20 to 125°C, preferably from 60 to 95°C and the pressure ranges from 0.1 to 5.6 MPa, preferably from 2 to 4 MPa, for a time ranging from 10 minutes to 4 hours, preferably from 1 and 2.5 hours.A continuous single-loop reactor is preferably used for conducting the polymerisation underquasi steady state conditions. A double loop reactor can also be used to produce eithermonomodal or bimodal resins, such as a resin consisting of a first fraction produced in the firstreactor under first polymerisation conditions and a second fraction produced in the secondreactor under second polymerisation conditions, said two fractions having the same molecular weight and different densities. The average molecular weight is controlled by adding hydrogen during polymerisation. The relative amounts of hydrogen and olefin introduced into the polymerisation reactor are from 0.001 to 15 mole percent hydrogen and from 99.999 to 85 mole percent olefin based on total hydrogen and olefin present, preferably from 0.2 to 3 mole percent hydrogen and from 99.8 to 97 mole percent olefin. The density of the polyethylene is regulated by the amount of comonomer injected into thereactor; examples of comonomer that can be used include 1-olefins, typically C3 to C20 olefinsamong which propylene, butene, hexene, octene, 4-methyl-pentene are preferred, the most preferred being hexene. An example of a polyethylene suitable to be used as raw material is Lumicene® M3410 EP,which is commercially available from TotalEnergies. Lumicene® M3410 EP is a metallocene-based Medium Density Polyethylene with hexene as comonomer. Lumicene® M3410 EP has adensity of 0.934 g / cm3, and a melt index of 0.9 g / 10 min.In a second embodiment, which may be complementary to the first embodiment, the rawpolyethylene material is a recycled polyethylene-containing material. As used herein, the terms “recycled polyethylene resin” encompasses both Post-Consumer Resins (PCR) and Post- Industrial Resins (PIR).With preference the raw polyethylene material is or comprises recycled chromium-catalyzedpolyethylene resins and / or recycled Ziegler Natta-catalyzed polyethylene resins.When the raw polyethylene material is or comprises chromium-catalyzed polyethylene resinsand / or Ziegler Natta-catalyzed polyethylene resins, the raw polyethylene material has an Mw / Mnranging from 3.0 to 30.0 as determined by gel permeation chromatography; preferably rangingfrom 4.0 to 25.0; more preferably from 5.0 to 20.0; even more preferably from 6.0 to 15.0; andmost preferably, from 7.0 to 12.0.In an embodiment, the raw polyethylene material is a recycled polyethylene-containing material. Recycled polyethylene-containing material may contain one or more polymers different from polyethylene.In an embodiment, and in particular wherein the raw polyethylene material is a recycledpolyethylene-containing material; the raw polyethylene material comprises at least one polymer different from polyethylene in a content ranging from 0 to 50 wt.% based on the total weight ofthe raw polyethylene material as determined by 13C NMR wherein at least one polymer differentfrom polyethylene is selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof. With preference, the raw polyethylene material comprises at least one polymer different frompolyethylene in a content ranging from 0 to 40.0 wt.% based on the total weight of the rawpolyethylene material as determined by 13C NMR; preferably from 0.1 to 20.0 wt.%; morepreferably from 0.2 to 10.0 wt.%; even more from 0.3 to 8.0 wt.%; and most preferably from 0.5to 5.0 wt.%.For example, PCR polyethylene classically contains a small part of polypropylene (such as less than 5 wt.%). In some embodiment, the raw material is a mixture of one or more resins selected from virginmetallocene-catalyzed polyethylene resins, recycled metallocene-catalyzed polyethyleneresins, virgin chromium-catalyzed polyethylene resins, recycled chromium-catalyzedpolyethylene resins, virgin Ziegler Natta-catalyzed polyethylene resins, and recycled Ziegler Natta-catalyzed polyethylene resins.Whatever is the catalyst, the following may be used to further define the raw material.Suitable polyethylene includes but is not limited to a homopolymer of ethylene, copolymer ofethylene, and a higher alpha-olefin comonomer. Thus, preferably, the raw polyethylene material comprises one or more polyethylene homopolymers, one or more polyethylene copolymers, and any mixture thereof. The term "copolymer" refers to a polymer, which is made by linking two different types of monomers in the same polymer chain. Preferred comonomers are alpha-olefins having from 3 to 20 carbon atoms or from 3 to 10 carbon atoms. More preferred comonomers are selected from the group comprising propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1,nonene-1, decene-1, and any mixture thereof. Even more preferred comonomers are selectedfrom the group comprising butene-1, hexene-1, octene-1, and any mixture thereof. The mostpreferred comonomer is hexene-1. The term “homopolymer” refers to a polymer that is made by linking only one monomer in the absence of comonomers. Ethylene homopolymers are therefore essentially without any comonomer. By "essentially without" is meant that no comonomer is intentionally added duringthe production of the polyethylene, but can nevertheless be present in up to 0.2 wt.%, preferablyin up to 0.1 wt.% and most preferably in up to 0.05 wt.%, relative to the total weight of the polyethylene.The raw polyethylene material is selected to comprise at least 50 wt.% of polyethylene basedon the total weight of the raw polyethylene material. With preference, the raw polyethylenematerial is selected to comprise at least 55 wt.% of polyethylene based on the total weight ofthe raw polyethylene material; preferably, at least 60 wt.%; preferably, at least 70 wt.%; preferably, at least 80 wt.%; preferably, at least 90 wt.%; preferably, at least 95 wt.%.In an embodiment, the raw polyethylene material is a virgin material and consists ofpolyethylene (i.e. comprises 100 wt.% of polyethylene).In an embodiment, the raw polyethylene material has a high load melt index (HLMI R) of at least1.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 21.6 kg; preferably at least 1.2 g / 10 min; more preferably at least 1.5 g / 10 min.In an embodiment the raw polyethylene material has a melt index (MI2) of at least 0.10 g / 10 minas determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at least 0.15 g / 10 min; more preferably at least 0.2 g / 10 min; even more preferably at least 0.5 g / 10 min; most preferably at least 0.8 g / 10 min and even most preferably at least 0.9 g / 10 min.For example, the raw polyethylene material is selected to have a melt index ranging from a highload melt index (HLMI R) as determined according to ISO 1133-2011 at 190 °C under a load of 21.6 kg of at least 1.0 g / 10 min to a melt index (MI2) of at most 3.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.In an embodiment the raw polyethylene material has a melt index (MI2) of less than 4.0 g / 10 minas determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at most3.5 g / 10 min or at most 3.0 g / 10 min; more preferably at most 2.8 g / 10 min or at most 2.5 g / 10min; even more preferably at most 2.2 g / 10 min, most preferably at most 2.0 g / 10 min and evenmost preferably at most 1.8 g / 10 min, or at most 1.6 g / 10 min.For example, the raw polyethylene material has a melt index (MI2) ranging from 0.6 to 2.5 g / 10min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably, ranging from 0.7 to 2.2 g / 10 min; more preferably ranging from 0.8 to 2.0 g / 10 min; even more preferably ranging from 0.9 to 1.8 g / 10 min.For example, the raw polyethylene material has a density of at least 0.925 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23 °C; preferably, at least 0.925 g / cm3; preferably, at least 0.928g / cm3; more preferably, at least 0.930 g / cm3; even more preferably of at least 0.932 g / cm3; andmost preferably, of at least 0.934 g / cm3.For example, the raw polyethylene material has a density of at most 0.980 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23 °C; preferably, of at most 0.975 g / cm3; more preferably, ofat most 0.970 g / cm3; even more preferably, of at most 0.962 g / cm3 or of at most 0.960 g / cm3;most preferably, of at most 0.950 g / cm3 and most preferably, of at most 0.945 g / cm3.For example, the raw polyethylene material has a density ranging from 0.925 g / cm3 to 0.980g / cm3as determined according to ISO 1183-1:2012 at 23 °C; preferably, ranging from 0.928g / cm3 to 0.970 g / cm3; more preferably, ranging from 0.930 g / cm3 to 0.960 g / cm3; and even morepreferably, ranging from 0.932 g / cm3 to 0.945 g / cm3.In an embodiment, the raw polyethylene material is selected to have a melt index (MI2) rangingfrom 0.8 to 2.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of2.16 kg and a density ranging from 0.928 g / cm3 to less than 0.960 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23 °C; preferably from 0.930 g / cm3 to 0.950 g / cm3.In some embodiments, the raw polyethylene material has an Mz / Mw of at least 1.5 asdetermined by gel permeation chromatography; preferably, ranging from 1.5 to 10.0; morepreferably, from 1.6 to 8.0; even more preferably, from 1.7 to 6.0; and most preferably, from 1.8to 4.0.In some embodiments, the raw polyethylene material has a ratio of complex viscosity at afrequency of 1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of more than 3.5 wherein the complex viscosities are measured at 190°C; preferably, of at least 3.6; more preferably, of at least 3.8; and even more preferably of at least 4.0.In an aspect, the disclosure provides the use of a raw polyethylene material to manufacture arotomoulding article wherein the raw polyethylene material has a density of at least 0.928 g / cm3as determined according to ISO 1183-1:2012 at 23°C and a melt index MI2 ranging from 0.2 toless than 3.0 g / 10 min, and the use includes thermal treatment of the raw polyethylene materialto raise its melt index to range from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg to obtain polyethylene resin wherein polyethylene resinfurther has a density of at least 0.930 g / cm3as determined according to ISO 1183-1:2012 at23°C; a flow activation energy fulfilling the following relationship;: Eact (kJ / mole) > 70 - 12 ln(MI2); ; with preference, the raw polyethylene material is or comprises one or more recycled-polyethylene resins (rPE)Step (d) of recovering a polyethylene resinStep (d) comprises recovering the polyethylene resin as defined above that is the treated raw polyethylene material. In one ormore embodiment the recovered polyethylene resin for use in rotomoulding applications shows: -a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).With preference, it further shows -a ratio of complex viscosity at a frequency of 1 rad / sec to the complex viscosity at afrequency of 100 rad / sec of at most 3.5 wherein the complex viscosities are measured at 190°C; and / or -a number average molecular weight (Mn) of at least 3,000 Da as determined by gelpermeation chromatography. The said polyethylene can be used on grinding machines to prepare micropellets or powder, and the disclosure is also about micropellets or powder prepared from said polyethylene resin. For example, the polyethylene resin has a VOC content lower than the VOC content of the raw polyethylene material.VOC is the amount of volatile organic compounds (VOC) in ppm wherein the volatilecompounds are defined to be chains with 12 carbon atoms or a lower number. This reduction of VOC is beneficial but a very significant decrease of such content is needed to eliminate the odour. The present disclosure encompasses articles produced from the polyethylene resin as definedabove wherein the article is a rotomoulded article; preferably, the article is selected from a bottleor a container. The present disclosure encompasses a process to produce a rotomoulded article comprising a) of providing a polyethylene resin and b) a step of rotomoulding the polyethylene resin into a rotomoulded article, wherein polyethylene resin has: -a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at 23°C;- a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).In on e or more embodiments, step a) comprises a step of preparing the polyethylene resin byperforming a thermal treatment on a raw polyethylene material wherein the thermal treatment isperformed in an extruder at a temperature of at least 300 °C with a residence time of at most10.0 min. With preference, the raw polyethylene material is selected to have a melt index (MI2)ranging from 0.2 to less than 3.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and / or a density of at least 0.928 g / cm3as determined according to ISO 1183-1:2012 at 23 °C. For example, the raw polyethylene material is or comprises one or more recycled-polyethylene resins (rPE) and / or in that the raw polyethylene material comprises from 0.3 to 8.0 wt.% based on the total weight of the polyethylene resin, as determined by13C NMR, of a polymer different from polyethylene selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof. For example, the article is produced using from 40 wt.% to 100 wt.% of raw polyethylene material being a recycled polyethylene-containing and has a VOC content lower than the raw polyethylene material.For example, the article has an Impact peak energy greater than 40 J at -40°C as determinedaccording to ISO 6603, and / or the article has a tensile modulus of at least 500 MPa asdetermined according to ISO 527-1 standard (Measurements performed with an ISO 727 type1A sample, at a temperature of 23°C, at a traction speed of 50 mm / min for measuring strengthand elongation and 1 mm / min for measuring modulus). In a preferred embodiment, the polyethylene resin is ground using known grinding machines to prepare micropellets or powder suitable for rotomoulding application. Test methods The melt flow index MI2of the polyethylene is determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.The HLMI of the polyethylene is determined according to ISO 1133-2011 at 190 °C under a loadof 21.6 kg.The Mn, Mw, Mz, Mw / Mn and Mz / Mw: The molecular weight (Mn (number average molecularweight), Mw (weight average molecular weight)) and molecular weight distributions D (Mw / Mn)were determined by size exclusion chromatography (SEC). Briefly, a GPC-IR5 from PolymerChar was used: 10 mg polyethylene sample was dissolved at 160 °C in 10 ml of trichlorobenzenefor 1 hour. Injection volume: about 400 µl, automatic sample preparation and injectiontemperature: 160 °C. Column temperature: 145 °C. Detector temperature: 160 °C. Two ShodexAT-806MS (Showa Denko) and one Styragel HT6E (Waters) columns were used with a flow rateof 1 ml / min (eluent: trichlorobenzene). Detector: Infrared detector (2800-3000 cm-1). Calibration:narrow standards of polystyrene (PS) (commercially available). Calculation of molecular weight Mi of each fraction i of eluted polyethylene is based on the Mark-Houwink relation (log10(MPE) =0.965909 x log10(MPS) – 0.28264) (cut off on the low molecular weight end at MPE = 1000).The molecular weight averages used in establishing molecular weight / property relationships are the number average (Mn), weight average (Mw) and z average (Mz) molecular weight. These averages are defined by the following expressions and are determined from the calculated Mi: ^^Here Niand Wiare the number and weight, respectively, of molecules having molecular weight Mi. The third representation in each case (farthest right) defines how one obtains these averages from SEC chromatograms. hiis the height (from baseline) of the SEC curve at the ithelution fraction and Miis the molecular weight of species eluting at this increment.The molecular weight distribution (MWD) is then calculated as Mw / Mn.The 13C-NMR analysis is performed using a 400 MHz or 500 MHz Bruker NMR spectrometerunder conditions such that the signal intensity in the spectrum is directly proportional to the total number of contributing carbon atoms in the sample. Such conditions are well-known to theskilled person and include, for example, sufficient relaxation time, etc. In practice, the intensityof a signal is obtained from its integral, i.e., the corresponding area. The data are acquired using proton decoupling, 2000 to 4000 scans per spectrum with 10 mm room temperature through or240 scans per spectrum with a 10 mm cryoprobe, a pulse repetition delay of 11 seconds and aspectral width of 25000 Hz (+ / - 3000 Hz). The sample is prepared by dissolving a sufficientamount of polymer in 1,2,4-trichlorobenzene (TCB, 99%, spectroscopic grade) at 130 °C and occasional agitation to homogenize the sample, followed by the addition of hexadeuterobenzene (C6D6, spectroscopic grade) and a minor amount of hexamethyldisiloxane (HMDS, 99.5+ %), with HMDS serving as an internal standard. To give an example, about 200 mg to 600 mg of polymer is dissolved in 2.0 mL of TCB, followed by the addition of 0.5 mL of C6D6 and 2 to 3 drops of HMDS. Following data acquisition, the chemical shifts are referenced to the signal of the internal standard HMDS, which is assigned a value of 2.03 ppm.The comonomer content in polyethylene is determined by 13C-NMR analysis of pellets accordingto the method described by G.J. Ray et al. (Macromolecules, 1977, 10, (4), 773-778).Crystallization temperature (Tc) and Melting temperature (Tm) are determined according to ISO11357-3:2018 on a DSC Q2000 instrument by TA Instruments. To erase the thermal history thesamples are first heated to 220 °C and kept at 220 °C for 3 minutes. Then the polymer is cooledat -20 °C / min up to 20 °C and kept at 20 °C for 3 minutes. The crystallization temperature isdetermined during this cooling step. The crystallization temperature Tc corresponds to the temperature of the extremum of the spectrogram presenting the heat flux associated with the polymer as a function of the temperature during its cooling. The polymer is then melted up to 220 °C at 20 °C / min and the melting temperature is determined during this heating step. The melting temperature corresponds to the temperature of the extremum of the spectrogram presenting the heat flux associated with the polymer as a function of the temperature during its melting.The density was measured according to the method of standard ISO 1183-1:2012 (immersionmethod) at a temperature of 23 °C.Complex shear modulus and viscosity: The complex shear modulus G*(w)=G’(w)+jG’’(w) (J2=-1, G’(w): storage modulus and G’’(w): loss modulus) was determined using a DHR-2, a stress- controlled rheometer from TA Instruments. Frequency sweeps have been carried out in the linear domain (1 % strain) at 190°C from 100 to 0.01 rad.s-1under nitrogen flow to prevent thermaloxidative degradation. The used geometry was 25 mm diameter parallel plates with a 2 mm gap. The samples (25 mm diameter, 2 mm thickness) for these experiments were obtained beforehand using an injection press (Babyplast type).The complex viscosity ^∗(^) is calculated according to the following equation of the linearviscoelasticity: ^ ^^⁄ ^ Impact properties were determined according to ISO 6603.Flow Activation Energy (Ea) Measurement The bulk dynamic rheological properties (e.g., G’, G” and ^∗) of the polypropylene compositionwere measured at 170 °C, 190 °C and 210 °C. At each temperature, scans were performed asa function of angular shear frequency (from 300 to 0.1 rad / s) at a constant shears strain appropriately determined by the above procedure.The dynamic rheological data was then analyzed using the Rheometrics Software. The followingconditions were selected for the time temperature (t-T) superposition and the determination of the flow activation energies (Ea) according to Arrhenius equation: aT= exp (Ea / kT), which relates the shift factor (aT) to Ea: Rheological Parameters: G’(ω), G”(ω) and η*(ω)Reference temperature: 190 °CShift mode: 2D (i.e., horizontal and vertical shifts)Shift Accuracy: HighInterpolation Mode: SplineIt is known to the man skilled in the art that ethylene polymers show a non-Newtonian viscosity,i.e., a viscosity changing with the shear rate. The Carreau-Yasuda (CY) model allows an analytical expression of the non-Newtonian viscosity curves. The CY model is a power functionof the molecular weight (Mw) and is represented by equation (1):(1) ɳ = ɳ^ / (1 + (^^)^)((^^^) / ^) where:- ɳ = viscosity (Pa.s)- W = shear rate (1 / s)- a = rheological breadth parameter [which describes the transition region between the zero-shear-rate region and the power-law region]- ^ = relaxation time (s) [which describes the location in time of the transition region]- ɳ0 = viscosity at zero shear rate (Pa.s) [which defines the Newtonian plateau]- n = power-law constant [which defines the final slope of the high shear rate region]Rheological breadth refers to the breadth of the transition region between Newtonian and power- law type shear rate for a polymer or the frequency dependence of the viscosity of the polymer. The rheological breadth is a function of the relaxing time distribution of a polymer resin, which in turn is a function of the resin molecular structure of architecture. The rheological breadth may be calculated by fitting the flow curves generated in linear-viscoelastic dynamic oscillatoryfrequency sweep experiments with a CY model. In the present disclosure, the rheologicalanalysis, such as the zero-shear viscosity determination, were determined at 190°C. Details of the significance and interpretation of the CY model and derived parameters may be found in R. B. Bird, R. C. Armstrong and O. Hasseger, Dynamics of polymeric Liquids, Volume 1, page 171-172, Fluid Mechanics, 2ndEdition, John Wiley & Sons (1987), which is incorporated by reference herein. EXAMPLES Example 1Preparation of the CR-PE roto-grade resinsTo produce “Control-Rheology polyethylene” (CR-PE) suitable for rotomoulding, SR-PE 1 (i.e.Lumicene® M3410 EP polyethylene grade) was selected. Grades were produced characterizedby a melt index of 8 and 17 g / 10 min, which could be compared to, respectively, straight reactorpolyethylene (SR-PE) suitable for rotomoudling applications, namely SR-PE 8 (Lumicene®M3581 UV - lot D131222856) and SR-PE 17 (Lumicene® M35160- lot H402E00118) grades.SR-PE1, and SR-PE 8SR-PE 17 are commercially available from TotalEnergies®.The screw profile presented in Figure 1 was introduced in the Leistritz ZSE 18 HPe extruder(L / D = 40 – MPO-laboratory). It contains three sequences of “mixing elements followed by areverse element”. For the production of the two grades called CR-PE 8 and CR-PE 17, an additional content of Irganox B225 was added (1500 ppm) in the hopper of the extruder. This was imposed as these grades will be later used in the rotomoulding process and the stability of the grades during thisprocess needs to be certain.Extrusion was performed with an output of 2 kg / h. For CR-PE 8, the maximum barreltemperature was 320°C and the screw speed was 780 rpm. For the CR-PE 17, the maximumbarrel temperature was 327°C and the screw speed was 1050 rpm.Analysis of the CR-PE roto-grade resins obtainedThe properties of the resins have been tested and compared to the straight reactor grades.Results are provided in Tables 1 to 5Table 1: Molecular designMn Mw Mz Mw / Mn Mz / Mw MI2 DensitySR-PE 1 32,900 84,800 157,000 2.6 1.9 0.9(*) 0.934(*)CR-PE 8 20,500 49,000 89,600 2.4 1.8 8.76 0.9388SR-PE 8 20,500 53,100 101,000 2.6 1.9 6.42 0.9347CR-PE 17 17,400 40,200 71,400 2.3 1.8 18.07 0.9408SR-PE 17 16,900 42,900 78,700 2.5 1.8 17.65 0.9337(*) value from the datasheet.From Table 1, it can be seen that, by comparison to the starting material PE1, a decrease in themean molecular masses was observed for CR-PE 8 and CR-PE 17. A narrowing of themolecular weight distribution was also observed. Density was increased.Table 2: Rheological propertiesRDA at 190°C η 1 η 10 η 100 η 1 rads / Eact70 - 12 lnrads rads rads η 100 rads (kJ / mole) (MI2). SR-PE 1 5,040 2,690 1,250 4.03 42.2 71.3CR-PE 8 1,094 829 500 2.19 48.0 43.9SR-PE 8 1,265 934 560 2.26 46.8 47.6CR-PE 17 475 419 290 1.64 44.3 35.2SR-PE 17 489 437 321 1.52 34.3 35.5Table 2 (continued)Sample CY1 (eta0 –CY2 CY3 (a) CY4 (n) Pa*s) (s) SR-PE 1 33435 0.000398 0.1465 0CR-PE 8 1273 0.07744 0.5369 0.636SR-PE 8 1542 0.02952 0.4369 0.533CR-PE 17 496 0.03733 0.7163 0.698SR-PE 17 518 0.005002 0.5269 0.519As regards the rheological properties, the evolution of the viscosity as a function of the frequencyis presented in Figure 4. A shift of the whole viscosity curves towards lower viscosity values isobserved for CR-PE8 and CR-PE 17 by comparison to SR-PE1. However, at a similar melt index, the viscosity curves associated with CR-PE 8 and CR-PE 17 are close but not precisely the same as those of the metallocene straight-reactor polyethylene (SR-PE) grade with a similar melt index.The viscoelastic properties of CR-PE grades when compared to the SR-PE grade of equivalentmelt index are also observed when considering van Gurp Palmen (VGP) plots (Figure 5) andthe evolution of the flow activation energy as a function of the phase angle (Figure 6).Considering the VGP plots, the “bump” in the δ = f(G*) dependence observed aroundG = 10 000 Pa and considered as clear evidence of long chain branching (LCB) 5, is morepronounced in the CR-PE 8 grade than in the SR-PE 8. The δ = f(G*) dependence of the SR-PE 17 looks very close to those of a linear polymer grade whereas the dependence of the CR-PE 17 is comparatively clearly shifted towards lower δ values, specifically around G = 10000Pa. In other words, a “bump” clearly exists in the CR-PE 17 VGP plot, demonstrating the LCBpresence.As regards the evolution of the flow activation energy as a function of the phase angle (Figure6), a peak is observed in the SR-PE1 representative curve at a phase angle close to 65 degrees.Such a peak is shifted towards a higher phase angle and lower flow activation energies whendecreasing the average molecular masses of the polyethylene grade.Comparing CR-PE and SR-PE grades at equivalent melt index, a shift of the representativecurves towards a lower phase angle is systematically observed for CR-PE grades. It wasattributed to additional branched polymer chains with higher molecular masses.In conclusion, the CR-PE roto grades are comparable to the targeted SR-PE grades but withdifferences between their molecular weight distribution and their long chain branchingarchitecture. Table 3: Tmelt (°C) Δ Hmelt (j / g)CR-PE 8 122.8 156.8CR-PE 17 123.1 166.7SR-PE 8 120.1 147.4SR-PE 17 118.1 152.6Example 2 use of the resins in rotomoulding applications.The four grades (CR-PE 8, CR-PE 17, SR-PE 8SR-PE 8, and SR-PE 17) were tested inrotomoulding application. The products were first ground and then rotomoulded, producing smallcontainers. Each grade was rotomoulded at two different PIAT (Peak Internal Air Temperature– Table 4), leading to 8 containers.During the rotomoulding process, the CR-PEs grades behave similarly to the SR-PE 8 and SR-PE 17 grades. No significant difference between the grades is observed, for example whencomparing the temperature profiles recorded during the process. Properties of the rotomoulded containers Impact properties at various temperatures (23, -20 and -40°C) and tensile tests were performedwith the rotomoulded containers (See Tables 4 and 5). Thickness was 4.5 mm.Table 4: Tensile propertiesTensile test Sample Ref PIAT (°C)Modulus (MPa) Elongation at break (%) CR-PE 8T9 199 666 112T1 208 671 96CR-PE 17T3 194 744 115T4 215 749 103SR-PE 8T7 205 560 247T8 219 558 157SR-PE 17T6 197 554 167T5 218 554 109From the results, it can be seen that the CR-PE containers are all characterized by a highermodulus and a lower elongation at break than those of the containers produced with the SR-PE8 and the SR-PE 17 grades.Table 5: Impact properties as determined according to ISO 6603SampleImpact at 23°C Impact at -20°C Impact at -40°CRef Peak Total Peak Total Peak Total energy (J) energy (J) energy (J) energy (J) energy (J) energy (J) T9 32 53 42 69 50 75T1 31 54 45 96 48 70T3 32 60 49 87 53 92T4 30 57 50 90 55 101T7 28 48 44 71 50 72T8 29 49 46 75 46 61T6 25 49 44 80 50 90T5 28 52 48 87 42 75From the results, it can be seen that the CR-PEs containers are better than those of thecontainers produced with the SR-PE 8 and the SR-PE 17 grades.Surprisingly, it can be seen that the inventive polyethylene resin shows greater flow activationenergy and, at the same time good (or improved) impact properties.

Claims

CLAIMS 1. A rotomoulded article being a mono-layered article or a multi-layered article ischaracterized in that the mono-layer or at least one of the layers comprises apolyethylene resin having- a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at23°C; -a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).

2. The rotomoulded article according to claim 1 is characterized in that the polyethyleneresin has a complex viscosity at 100 rad / sec at 190 °C of at most 1,000 Pa·s whereinthe complex viscosity is measured at 190°C; and / or in that the polyethylene resin has a Mw / Mn ranging of at most 4.5.

3. The rotomoulded article according to claim 1 is characterized in that the polyethyleneresin is or comprises one or more recycled-polyethylene resins (rPE) and / or in that thepolyethylene resin comprises from 0.1 to 8.0 wt.% based on the total weight of the polyethylene resin, as determined by13C NMR, of a polymer different from polyethylene selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof.

4. The rotomoulded article according to any one of claims 1 to 3 is characterized in that thepolyethylene resin has a density at least 0.932 g / cm3 as determined according to ISO1183-1:2012 at 23°C; and / or at most 0.970 g / cm3.

5. The rotomoulded article according to any one of claims 1 to 4 is characterized in that thepolyethylene resin has a melt index MI2 ranging from 4.0 to 28.0 g / 10 min as determinedaccording to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably from 6.0 to20.0 g / 10 min.

6. The rotomoulded article according to any one of claims 1 to 5 is characterized in that thepolyethylene resin has a ratio of complex viscosity at a frequency of 1 rad / sec to thecomplex viscosity at a frequency of 100 rad / sec of at most 3.5, wherein the complexviscosities are measured at 190°C; and / or in that it has a complex viscosity at 1 rad / secat 190 °C ranging from 100 to 2,000 Pa·s wherein the complex viscosity is measured at190°C.

7. The rotomoulded article according to any one of claims 1 to 6 is characterized in that thepolyethylene resin has number average molecular weight (Mn) of at least 3,000 Da asdetermined by gel permeation chromatography; and / or in that it has a z average molecular weight (Mz) of at most 95,000 Da as determined by gel permeation chromatography.

8. The rotomoulded article according to any one of claims 1 to 7 is characterized in that thearticle has an Impact peak energy greater than 40 J at -40°C as determined accordingto ISO 6603 and / or in that the article has a tensile modulus of at least 500 MPa asdetermined according to ISO 527-1 standard (Measurements performed with a ISO 727type 1A sample, at a temperature of 23°C, at a traction speed of 50 mm / min for measuring strength and elongation and 1 mm / min for measuring modulus).

9. A process to produce a rotomoulded article according to any one of claim 1 to 8comprising a) of providing a polyethylene resin and b) a step of rotomoulding thepolyethylene resin into a rotomoulded article, wherein polyethylene resin has:- a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at23°C; -a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).

10. The process according to claim 9 is characterized in that step a) comprises a step ofpreparing the polyethylene resin by performing a thermal treatment on a rawpolyethylene material wherein the thermal treatment is performed in an extruder at atemperature of at least 300 °C with a residence time of at most 10.0 min.

11. The process according to claim 10 is characterized in that the raw polyethylene materialis selected to have a melt index (MI2) ranging from 0.2 to less than 3.0 g / 10 min asdetermined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and / or adensity of at least 0.928 g / cm3 as determined according to ISO 1183-1:2012 at 23 °C.

12. The process according to claim 8 or 11 is characterized in that the raw polyethylenematerial is or comprises one or more recycled-polyethylene resins (rPE) and / or in thatthe raw polyethylene material comprises from 0.3 to 8.0 wt.% based on the total weightof the polyethylene resin, as determined by13C NMR, of a polymer different from polyethylene selected from polypropylene (PP), polyacrylate (PA), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and any mixture thereof.

13. Use of a raw polyethylene material to manufacture a rotomoulding article characterizedin that the raw polyethylene material has a density of at least 0.928 g / cm3 as determinedaccording to ISO 1183-1:2012 at 23°C and a melt index MI2 ranging from 0.2 to less than3.0 g / 10 min, and the use includes thermal treatment of the raw polyethylene material toraise its melt index to range from 3.0 to 30.0 g / 10 min as determined according to ISO1133-2011 at 190 °C under a load of 2.16 kg to obtain polyethylene resin whereinpolyethylene resin further has a density of at least 0.930 g / cm3as determined according to ISO 1183-1:2012 at 23°C; a flow activation energy fulfilling the following relationship;:Eact (kJ / mole) > 70 - 12 ln (MI2); with preference, the raw polyethylene material is orcomprises one or more recycled-polyethylene resins (rPE).

14. Polyethylene resin for use in rotomoulding applications characterized in that it shows:- a density of at least 0.930 g / cm3 as determined according to ISO 1183-1:2012 at23°C; -a melt index MI2 ranging from 3.0 to 30.0 g / 10 min as determined according to ISO1133-2011 at 190 °C under a load of 2.16 kg; and- a flow activation energy fulfilling the following relationship:Eact (kJ / mole) > 70 - 12 ln (MI2).

15. The polyethylene resin according to claim 14 is characterized in that it has:- a ratio of complex viscosity at a frequency of 1 rad / sec to the complex viscosity ata frequency of 100 rad / sec of at most 3.5 wherein the complex viscosities aremeasured at 190°C; and / or- a number average molecular weight (Mn) of at least 3,000 Da as determined bygel permeation chromatography.

16. Use of a polyethylene resin according to claim 14 or 15 on grinding machines to preparemicropellets or powder.

17. Micropellets or powder prepared from a polyethylene resin according to claim 14 or 15.

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