Polyethylene composition having high melt flow

Abstract

Polyethylene comprising an ethylene homo- and / or copolymer either of virgin origin biobased or a PCR material wherein the copolymer is a copolymer of ethylene with C3-C20-alkene, the polyethylene has a ratio of weight average molecular weight Mw to number average molecular weight Mn of Mw / Mn in their range of from 8 to 15, and a density of from 0.934 to 0.944 g / cm3, a weight average molar mass Mw of from 40 000 to 300 000 g / mol, and Mz in the range from 100,000 g / mol to 500, 000 g / mol, preferably in the range from 200,000 g / mol to 400,000 g / mol, preferably in the range from 250 000 g / mol to 300, 000 g / mol, and a melt flow rate of from 8 to 15 g / 10 min, FNCT at least 1000, and shows good processabilities and mechanical properties when used in rotomoulding, and other energy consuming powder processing methods, such like injection moulding, extrusion processes for pipes, wherein the processed article comprising the polyethylene as disclosed therein uses less energy for heating up the polyethylene and saves time as cooling is much faster and therefore resulting in less carbon footprint.

Description

POLYETHYLENE COMPOSITION HAVING HIGH MELT FLOWFIELD OF INVENTION

[0001] The present invention relates to a novel polyethylene having a high melt flow used for rotomoulded articles.BACKGROUND OF THE INVENTION

[0002] Polyethylene is used for different applications, due to its extraordinaire broad field of applications. It is crucial for industry and daily life because it is easy to process and its mechanical properties can be tailored to suit a wide range of applications. Besides easy processing, high mechanical properties.

[0003] One method to obtain large hollow articles, such as water tanks and the like, is rotomoulding, which is a moulding technique suitable for moulding large, hollow objects. A mould is prefilled with a flowable, granulated polymer, then heated with a certain temperature profile firstly softening the material, and finally for some shorter period melting down the material, then cooling down again. All this is done whilst the mould is kept in motion, for allowing of even distribution of the material, filling even minor cavities of the mould and ideally achieving even, controllable wall thickness.

[0004] One of the most desired features and properties for rotomoulding is a high melt index, to have an easy melting and distribution process, besides high stress crack resistance. Stress crack formation in plastics is a physicochemical process which does not change the polymer molecules. It is proposed that stress crack formation is caused, inter alia, by gradual yielding or untangling of the connected molecular chains. Stress crack formation occurs less readily the higher the mean molecular weight is, the broader the molecular weight distribution and the higher the degree of molecular branching and depends on the quality of mixing.

[0005] It is known to design properties of polymer blends comprising a high molecular weight, low-density ethylene copolymer component and a low molecular weight component, high-density ethylene homopolymer, which has good stress cracking resistance, for producing e.g., hollow bodies and pressure pipes.

[0006] Besides that, it is also known to produce bimodal polyethylene blends using reactor cascades, i.e., two or more polymerization reactors connected in series, and thepolymerization of the low molecular weight component occurs in one reactor and that of the high molecular weight component in the next.

[0007] A disadvantage of blends obtained by these methods is, that relatively large amounts of hydrogen must be added to produce the desired low molecular weight component, which needs to be controlled. The polymers obtained in this way therefore have a low content of vinyl end groups, especially in the low molecular weight component. In addition, the process is technically complex to control e.g., level of comonomer and the hydrogen flow during the reaction.

[0008] The use of a mixture of different catalystsse.g., of the Ziegler type or the metallocene type is well known.

[0009] For example, it is possible to use a combination of two catalysts to produce a polyethylene, having a certain molar weight distribution (WO 95 / 11264).

[0010] The use of polyethylene in different energy consuming application processes, such as rotomoulding, injection moulding or extrusion is well known in the state of the art. A higher flow rate allows for better mold filling and an improved material distribution inside the mold, resulting in more uniform and consistent wall thickness in the final product.

[0011] In rotomoulding processes typically best result are achieved with polyolefins having a low viscosity and high melt flow rate, increasing the homogenous distribution of the polymer in the mould. Unfortunately, polyethylene having a high MI2Despite the improved processability, when polyethylene is applied with an extremely high melt flow index (M2I over 9 g / 10 min), to leads to other issues like process dripping, and loss of mechanical properties in the final product arise.

[0012] Another aspect is that cooling is faster when polyethylene with high MI2 is used, high melt flow polyethylene shows long cooling periods, and as a rapid cooling period is desired to shorten production time. The long cooling period can even lead to uneven surface and distribution, caused by uneven cooling of the polyethylene.

[0013] To minimize the occurrence of bubbles, manufacturers take various measures and try to adjust molding parameters and take different extra steps like pre-drying steps of polar materials to remove moisture and ensuring adequate venting in the mold to release trapped air during the molding process. For efficient processes, short oven times are desirable, but the level of trapped air inside is then very high, which then causes the final parts to be brittle.

[0014] Therefore, to overcome the disadvantages as mentioned above and prevent gas inclusions in the final product the oven time needs to be extended. Application of tempering steps, longer heating and cooling periods are needed to obtain high quality products.

[0015] To avoid losses in mechanical properties and face sagging in the final product, the polyethylene used for rotomoulding normally has a much lower MI2 than 6.0 g / 10 min (according to ISO 1133, 190 °C, 2.16 kg), typically with MI2 in the range of 2.0 to 6 g / 10 min (according to ISO 1122, 190°C, 2.16 kg).

[0016] In the state of the art there are polyethylene based rotomoulding articles known, such as the EP 2467408B1 or EP1888659B1 which relates to copolymers and their use for rotomoulding.

[0017] So, there is a strong need to make rotomoulding processes and other processes like injection moulding and extruding profitable, cost and time efficient.

[0018] An object of the present invention is to provide high melt flow polyethylene with improved processability in rotomoulding processes and have extraordinary even and smooth surface appearance, combined with low deformation, less gas and air trapping and provide extraordinary mechanical properties such as impact resistance and resistance to environmental stress cracking. In particular for the production of thick walled articles, and result in rotomoulded products and articles with extraordinary mechanical strength and properties.Hence, there is a strong need to find a polyethylenematerial which solves the disadvantages known from the state of the art.. So, it is an object of the present invention to devise a new, improved polyethylene, suitably used to produce rotomoulded articles, by using less processing energy and less processing time. This object is solved by the polyethylene described in the following.SUMMARY OF THE INVENTION

[0019] The present disclosure provides a polyethylene, having a high melt flow rate and a medium density, being suitable for rotomoulding. The polyethylene is used in rotomoulding processes, to obtain rotomoulded products and articles with excellent mechanical properties, low warpage and less trapped air and less bubble formation, while still having a high impact resistance and a high environmental stress cracking resistance (ESCR), which helps to save cost and energy by short processing and oven times.

[0020] Polyethylene, consisting of either an ethylene homo- and / or copolymer, or a mixture thereof, a) wherein the copolymer is a copolymer of ethylene with C3 to C20-alkene, preferably of C4 to C8- alkene, preferably of C4 or C6-alkene, b) wherein the polyethylene has a molar mass distribution width Mw / Mn in the range from 8 to 15, preferably in the range from 9 to 12, preferably in the range from 10 to 11, c) a density in the range from 0.934 to 0.944 g / cm3, preferably in the range from 0.935 to 0.945 g / cm3, preferably in the range from 0.936 to 0.942 g / cm3 (according to ISO 1183), d) a weight average molar mass Mw in the range from 40,000 g / mol to 300,000 g / mol, preferably in the range from 50,000 g / mol to 250,000 g / mol, preferably in the range from 60,000 g / mol to 200,000 g / mol, e) a Mz in the range from 50,000 g / mol to 300,000 g / mol, preferably in the range from 100,000 g / mol to 250,000 g / mol, preferably 150,000 g / mol to 200,000 g / mol, f) a MI2 in the range from 8 to 15 g / 10 min, preferably in the range from 9 to 14 g / 10 min, preferably in the range from 11 to 13 g / 10 min (according to ISO 1133, at 190 °C, 2.16 kg), g) a FNCT in the range from 1000 to 2200 h, preferably in the range from 1100 to 2000 h, preferably in the range from 1200 to 1800 h (according to ISO 16770, at 6 MPa, 60 °C, 2 % Arkopal), h) a Charpy / AZK is in the range from 125 to 300 kJ / m2 (according to ISO 179 at 23°C), i) wherein the polyethylene has been prepared in one polymerization step in a single reactor by a mixed catalyst system comprising at least one metallocene,wherein the polyethylene is obtained by a polymerization process in the presence of a catalyst composition comprising at least two different single-site polymerization catalysts A and B, whereinA) is at least one polymerization catalyst based on a hafnocene single-site catalyst, andB) is at least one polymerization catalyst based on an iron component having a tridentate ligand bearing at least two aryl radicals, preferably with each said aryl radicals bearing a halogen or tert, alkyl substituent in the ortho-position.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and claims, and accompanying drawings where:

[0022] Figure 1 shows data from measuring the PIAT at 130 °C and 150 °C. Comparison of the standard rotomoulding commercially available polyethylene grade, based, with MI2 of 5.0 g / 10 min according to figure 1 reaches 30 % ductility at 190 °C and will get to 100 % by about 195 °C PIAT which is fairly normal in rotomoulding, compared to other polyethylene material according to the present disclosure which is immediately at 130 °C PIAT is 100 % elastic and stays there as the temperature or PIAT rises. So, Figure 1 show, that a standard polyethylene having a MI2 of 3.0 g / 10 min needs longer heating than the inventive polyethylene, and helps to reduce gas and time of at least 51 % of oven time, 31 % of cooling time and an overall total saving in time of 40 %.

[0023] The comparison of the example of the inventive polyethylene (having a MI2 of 12 g / 10 min) and the commercial available polyethylene having a melt flow rate of MI2 of 5 g / 10 min, show that ARM impact ductility vs PIAT results are exceedingly better than the results of the commercially available polyethylene grade. Consequently Figure 1 show, that a standard polyethylene having a MI2 in the range of 3 to 5 g / 10 min needs longer heating than the inventive polyethylene, and helps to reduce gas and time of at least 51 % of oven time, 31 % of cooling time and an overall total saving in time of 40 %.

[0024] Table 2 shows data from polyethylene slimline tanks, comprising a commercial avaiblabe polyethylene having a MI2 of 3 g / 10 min (according to ISO 1133, 190°C, 2.16 kg)compared to polyethylene according to the present disclosure MI2 of 12 g / 10 min (according to ISO 1133, 190°C, 2.16 kg).

[0025] This large slimline tank is usually made using a tank grade with polyethylene with MI2 in the range from 3 to 3.5 g / 10 min (according to ISO 1133, 190 °C, 2.16 kg). Switching to polyethylene according to present disclosure with MI2 of 12 g / 10 min (according to ISO 1133, 190°C, 2.16 kg) applying the polyethylene disclosed herein shows an improved wall thickness on the moulded through hole besides reduced oven time of a massive 26 minutes with a PIAT reduction of 27 °C to 167 °C.

[0026] Table 3 shows data from polyethylene underground tanks, standard rotomoulding polyethylene with MI2 of 4.0 g / 10 min (according to ISO 1133, 190°C, 2.16 kg) compared to the polyethylene with polyethylene according to present disclosure with MI2 of 12.0 g / 10 min (according to ISO 1133, 190 °C, 2.16 kg). It shows, that moving from PIAT 183 °C to 173 °C, provides a saving of 300 1 of gas per moulding and a reduction in time of 6 minutes shorter oven time was achieved.

[0027] Figure 2 shows a diagram of the reduction of PIAT with the polyethylene according to present disclosure with where there is no longer a need to sinter the moulding to remove the bubbles, it shows that even at 130 °C measured PIAT the heat distribution in the oven and around the tool will need to be very even.DETAILED DESCRIPTION OF THE INVENTION

[0027] The present disclosure provides a polyethylene, having a high melt flow rate and a medium density, being suitable for rotomoulding. The polyethylene is used in rotomoulding processes, to obtain large hollow, rotomoulded products and articles with excellent mechanical properties, low warpage and less trapped air and less bubble formation, while still having a high impact resistance and a high environmental stress cracking resistance (ESCR) measured via full notch creep test (FNCT), which helps to save cost and energy by short processing and oven times.

[0028] Polyethylene, consisting of either an ethylene homo- and / or copolymer, or a mixture thereof, a) wherein the copolymer is a copolymer of ethylene with C3 to C20-alkene, preferably of C4 to C8- alkene, preferably of C4 or C6-alkene,b) wherein the polyethylene has a molar mass distribution width Mw / Mn in the range from 8 to 15, preferably in the range from 9 to 12, preferably in the range from 10 to 11, c) and a density in the range from 0.934 to 0.944 g / cm3, preferably in the range from 0.935 to 0.945 g / cm3, preferably in the range from 0.936 to 0.942 g / cm3 (according to ISO 1183), d) a weight average molar mass Mw in the range from 40,000 g / mol to 300,000 g / mol, preferably in the range from 50,000 g / mol to 250,000 g / mol, preferably in the range from 60,000 g / mol to 200,000 g / mol, e) a Mz in the range from 50,000 g / mol to 300,000 g / mol, preferably in the range from 100,000 g / mol to 250,000 g / mol, preferably 150,000 g / mol to 200,000 g / mol, f) a MI2 in the range from 8 to 15 g / 10 min, preferably in the range from 9 to 14 g / 10 min, preferably in the range from 11 to 13 g / 10 min (according to ISO 1133, at 190 °C, 2.16 kg), g) a FNCT in the range from 1000 to 2200 h, preferably in the range from 1100 to 2000 h, preferably in the range from 1200 to 1800 h (according to ISO 16770, at 6 MPa, 60 °C, 2 % Arkopal), h) a Charpy / AZK (23°C) is in the range from 125 to 300 kJ / m2, i) wherein the polyethylene has been prepared in one polymerization step in a single reactor by a mixed catalyst system comprising at least one metallocene, wherein the polyethylene is obtained by a polymerization process in the presence of a catalyst composition comprising at least two different single-site polymerization catalysts A and B, whereinA) is at least one polymerization catalyst based on a hafnocene single-site catalyst, andB) is at least one polymerization catalyst based on an iron component having a tridentate ligand bearing at least two aryl radicals, preferably with each said aryl radicals bearing a halogen or tert, alkyl substituent in the ortho-position.

[0029] The polyethylene is a copolymer of ethylene and at least one alkene selected from the group consisting of C3 to C20- alkenes, preferably an C4 to C8- alkene preferably a C4 and / or C6- alkene.

[0030] The polyethylene disclosed herein enables faster processing at lower heating temperature resulting in an shorter cooling period. Which means that using the inventive polyethylene for rotomoulded articles results in a lower carbon footprint as less time is used for heating up the polyethylene in the mould.

[0031] This inventive polyethylene has a Mw / Mn ratio in the range from8 to 15, preferably in the range from 9 to 12, preferably in the range from 10 to 11.

[0032] The density is in the range from 0.934 to 0.944 g / cm3, preferably in the range from 0.934 to 0.945 g / cm3, preferably in the range from 0.935 to 0.942 g / cm3 (according to ISO 1183).

[0033] The weight average molar mass Mw is in the range from 40,000 g / mol to 300,000 g / mol, preferably in the range from 50,000 g / mol to 250,000 g / mol, preferably in the range from 60,000 g / mol to 200,000 g / mol.

[0034] The average molecular weight Mz is in the range from 200,000 g / mol to 800,000 g / mol, preferably in the range from 250,000 g / mol to 700,000 g / mol, preferably 300,000 g / mol to 600,000 g / mol. The definition of z- average molar mass M2 is e.g., defined in Peacock, A. (ed.), Handbook of PE, and is published in High Polymers, Raff und Doak, Interscience Publishers, John Wiley & Sons, 1965, S. 443.

[0035] The polyethylene according to the invention shows when tested using the Charpy or AZK testing methods values in the range from 125 to 300 kJ / m2, preferably in the range from 130 to 280 kJ / m2, preferably in the range from 140 to 250 kJ / m2 (according to ISO 179, at 23 °C). The Charpy values measured at a temperature of - 30 °C is in the range from 65 to 90 kJ / m2, preferably in the range from 70 to 85, preferably in the range from 73 to 83 kJ / m2.

[0036] The polyethylene comprises an ethylene homo- and / or copolymer having a high melt flow rate MI2 in the range from 8 to 15 and more, preferably the MI2 in the range from 9 to 14, preferably in the range from 10 tol3 (according to ISO 1133, at 190°C, 2.16 kg).

[0037] The inventive polyethylene provides short oven times when processed via rotomoulding, or other processing methods like injection moulding, or extrusion while saving cost, energy and time and reducing the carbon footprint to obtain rotomoulded articles with outstanding high mechanical properties and stability and substantially no air bubbles are trapped in the walls of the articles, and lower pinholes. It is understood, that also other energyconsuming polyethylene processing methods, like injection moulding, extrusion processes for pipes e.g., are disclosed herein.

[0038] Wherein the polyethylene shows excellent mechanical properties, outstanding processing properties and can be used in rotomoulding processes to obtain rotomoulded, or injection moulded, or extruded products with low sagging and substantially no trapped air, and is low in porosity immediately after melting, while still maintaining high impact resistance and high ESCR and saving cost and energy by shortening processing and cutting oven time by obtaining products with extraordinary mechanical properties, e.g. being ductile at - 40 °C and with high ESCR values (Table 1).

[0039] Wherein the polyethylene shows excellent mechanical properties, outstanding processing properties and can be used in rotomoulding processes, or injection molding, or extrusion processes to obtain rotomoulded and other products with low sagging and substantially no trapped air while still maintaining high impact resistance and high ESCR and saving cost and energy by shortening processing and cutting oven time by obtaining products with extraordinary mechanical properties, e.g. being ductile at - 40 °C and with high ESCR values (Table 1, Table 2, Table 3), shows low porosity immediately after melting. Especially, as the so obtained products helps saving energy as oven temperatures are much lower (Figure 2, Table 2 and Table 3) resulting in less cooling time, which increases the effectiveness in production of articles.

[0040] The polyethylene comprises at least one C3 to C20- alkene, preferably C4 to C8- alkene, preferably C4 and / or C6- alkene in the range from an amount of at least 2.0 wt% based on the total weight of the polyethylene.

[0041] In a preferred embodiment though, a 'copolymer' is a truly binary copolymerizate of ethylene and of substantially one or more species of comonomer. Which is defined as one or more species, preferably means that > 97 % (w / w) of comonomer amounts to one comonomer molecule.

[0042] The copolymer comprises in the range from 1.0 to 4.5 wt%, preferably 2.0 to 4.0 wt%, preferably 2.5 to 3.5 wt% (w / w) (Table 2 and Table 3) of a comonomer in addition to ethylene, based on total weight of said copolymer.

[0043] According to one form of the present disclosure, the polyethylene, optionally is addressed as polyethylene homopolymer or polymer copolymer or polyethylene component or polyethylene composition hereafter, which most preferably is a polyethylene homo- and / orethylene copolymer which is a copolymer of ethylene with C3 to C20-alkene, preferably of C4 to C8- alkene, more preferably C4- and / or C6-alkene, meaning butene or hexene.

[0044] Examples of suitable CrC20-alkenes according to the present invention are e.g., u- olefins such as propene, 1 -butene, 1 -pentene, 1 -hexene, 4-methyl-l -pentene, 1 -heptene or 1- octene. Preferably, the C3 to C20- alkenes are u-olefins. The ethylene homo- and / or copolymer preferably comprises u-alkenes having from C4 to C8- carbon atoms in copolymerized form as comonomer unit. Particular preference is given to using u-alkenes selected from the group consisting of 1 -butene, 1 -hexene and 1 -octene.

[0045] The polyethylene disclosed herein has molar mass distribution width Mw / Mn in the range from 8 to 15, in the range from 9 to 12, in the range from 10 to 11.

[0046] Furthermore, inventive polyethylene can easily be processed to rotomoulded products and articles with extraordinary good mechanical properties. As the polyethylene has a high MI2 of 8 to 15 g / 10 min, the processability is extraordinary and can therefore easily be processed showing much shorter oven time, reducing time, and cost than polyethylene known from the state of the art (with MI2 for rotomoulded articles normally in the range of 3 to5 g / 10 min). This results in an extraordinary economic effect. In one form of the present disclosure oven times are cut in a third or more preferably in a half, which saves also significant amounts of cooling time (Table 2 and Table 3).

[0047] The polyethylene of the present disclosure allows the use of polyethylene with reduced viscosity but without suffering from adverse, balancing effects, like formation of bubbles etc. As of the opposite, the obtained material does not show any substantial amounts of bubbles in the article’s walls.

[0048] Preferably, the melt index "M12" is the melt rheology value determined at the same temperature but under a load of 2.16 kg (according to ISO 1133, 190 °C, 2.16 kg) according to said standard method.

[0049] Further, the amount or weight fraction of the polyethylene of the invention having a molar mass of < 1 Mio. g / mol, as determined by GPC for standard determination of the molecular weight distribution, is preferably above 95.5 % by weight, preferably above 96 % by weight and particularly preferably above 97 % by weight. This is determined in the usual course of the molar mass distribution measurement by applying the WIN-GPC software of the company HS-Entwicklungsgesellschaft fur wissenschaftliche Hard-und Software mbH, Ober- Hilbersheim / Germany, for instance.

[0050] By using a medium density polyethylene copolymer according to the present invention, a melt flow index (M2I, at 2.16 kg) of from 8 to 15 g / 10 min improved and even better impact properties than typical high flow grades are obtained, resulting in lower PIAT.

[0051] Per definition PIAT refers to a specialized process and testing method used to define the ductility of a testing material in dependence of the temperature (please see Figure 1).

[0052] It was discovered that when rotomoulded, or processed via injection moulding, or extrusion, the polyethylene according to the present disclosure, it was both very tough but also very fast processing. Using less energy as the heating processes were accomplished in even shorter time, saving oven time and / or heating time for e.g. more than 50 %, cooling time for about 30 %, as the polyethylene needs less energy to melt resulting in less cooling time of the article. This sum up in a total time saving in about 40 % (please see Table 2, Table 3, Figure 2). We realized that with the very high cost of energy, like gas, required for heating the rotomoulding tools that this polyethylene homo- and / or copolymer of the present invention represent a chance to save users significant amounts of energy and also CO2 resulting in lower carbon footprint.

[0053] Furthermore, Figure 2 shows that the oven time is short while the PIAT is flat lined at 130 °C and there can be a shortening of the cooling time too because you have less energy to remove from the system. Therefore, with shorter oven time the energy input is reduced and enables saving both energy and time.

[0054] Per definition the term “carbon footprint” refers to the total amount of energy, such as gas used for heating during rotomoulding, or electricity required for running the process and the like, all kinds of greenhouse relevant gases, primarily carbon dioxide, and other carbon compounds that are emitted directly or indirectly as a result for heating using e.g., fossil fuel and / or processing activities as contribution to climate change through the release of greenhouse gases. It is typically measured in units of carbon dioxide equivalents (CO2) and encompasses emissions from various sources, such as energy consumption, manufacturing, transportation, and other processes.

[0055] According to the present disclosure the use of 1.0 kg of polyethylene according to the present disclosure to process rotomoulding articles or injection moulded or extruded articles reduces CO2 in the range of 0.1 to 0.8 kg per kilo polyethylene. CO2 via less consumption of energy and gas for heating and saves in the range from 10 to 30 %, preferably in the range from 10 %, at preferably in the range from 20 % to30 % of consumed time forheating and cooling in the process, compared to standard rotomoulding or injection moulding polyethylene grades.

[0056] Furthermore, the carbon footprint for the disclosed polyethylene is reduced as less fossil fuel is used to heat the polymer to produce the rotomoulded article as less energy is consumed for processing. This polyethylene homo- and / or copolymer according to the present disclosure therefore is a sustainable option to produce and obtain roto molding materials and articles with less carbon footprint compared to the ones obtainable from the state of the art.

[0057] The polyethylene of the invention preferably has a vinyl group content in the range from in 0.1 to 3.0 vinyl groups / 1000 carbon atoms, preferably in the range from 0.3 to 2.0 vinyl groups / 1000 carbon atoms and more preferably in the range from 0.4 to 1.5 vinyl groups / 1000 carbon atoms and even more preferably in the range from 0.5 to 1.0 vinyl groups / 1000 carbon atoms.

[0058] The content of vinyl groups / 1000 carbon atoms is determined by means of IR, according to ASTM D 6248-98. For the present purposes, the expression vinyl groups refers to -CH=CH2 groups. This can be determined by solvent-nonsolvent fractionation, called Holtrup fractionation as described in W. Holtrup, Makromol. Chem. 178, 2335 (1977), coupled with IR measurement of the different fractions, with the vinyl groups being measured in accordance with ASTM D 6248-98. Xylene and ethylene glycol diethyl ether at 130 °C were used as solvents for the fractionation.

[0059] The branching of the polyethylene of the disclosure is in the range from 0.01 to 20.0 branches / 1000 carbon atoms, preferably in the range from 0.5 to 10.0 branches / 1000 carbon atoms and particularly preferably in the range from 1.5 to 8.0 branches / 1000 carbon atoms.

[0060] The branches / 1000 carbon atoms are determined by means of 13 C- NMR, as described by James. C. Randall, JMS-REV. Macromol. Chem. Phys., C29 (2, 3), 201- 317 (1989), and refers to the total content of CH3 groups / 1000 carbon atoms including end groups. The branching contents is to be understood as side chains measured as CH3 / 1000 carbon atoms, preferably from 1 to 10 CH3 / 1000 carbon atoms. It is particularly preferred in polyethylene copolymerized with 1-butene, 1-hexene or 1-octene to have of from 0.01 to 20 ethyl, butyl, or hexyl short chain branches / 1000 carbon atoms, more preferably from 1 to 10 ethyl, butyl, or hexyl branches / 1000 carbon atoms and particularly preferably of from 2 to 6 ethyl, butyl, or hexyl branches / 1000 carbon atoms. Furthermore the short chain branching' (SCB) refers also to branches having side chains comprising C2 up to C6-alkenes.

[0061] According to the present invention, the polyethylene component a) has a substantially multimodal, preferably bimodal, distribution in TREF analysis, determining the comonomer content based on crystallinity behavior / melting temperature essentially independent of molecular weight of a given polymer chain. A polymer chain is a single molecule constituted by covalent bonding and obtained from polymerization of olefines, said polymer chain having a molecular weight of at least 5000. A TREF -multimodal distribution means that TREF analysis resolves at least two or more distinct maxima indicative of at least two differing branching rates and hence comonomer insertion rates during polymerization reactions. TREF analysis analyzes comonomer distribution based on short side chain branching frequency essentially independent of molecular weight, based on the crystallization behavior (Wild, L., Temperature rising elution fractionation, Adv. Polymer Sci. 98: 1-47, (1990), also see description in US 5008204 incorporated herewith by reference).

[0062] The number of side chains formed by incorporation of the comonomer and their distribution, is very different when using the different catalyst systems. The number and distribution of the side chains has a critical influence on the crystallization behavior of the ethylene copolymers. While the flow properties and thus the processability of these ethylene copolymers depend mainly on their molar mass and molar mass distribution, the mechanical properties are therefore particularly dependent on the distribution of short chain branching. The crystallization behavior of the ethylene copolymers influences the properties of the obtained polymer. The correct combination of catalysts for a balanced combination of catalysts for a balanced combination of good mechanical properties and good processability is a crucial factor here. The vinyl group content is determined by means of IR in accordance with ASTM D 6248- 98.

[0063] The polyethylene of the present invention comprising component a) which comprises at least two, preferably two, different polymeric subfractions synthesized preferably by different single-site catalysts, namely a first preferably non- metallocene having a lower comonomer content, a high vinyl group content and preferably a broader molecular weight distribution, and a second, preferably metallocene catalyst, having a higher comonomer contents, a more narrow molecular weight distribution and, optionally, a lower vinyl group contents.

[0064] According to the present disclosure, a polyethylene copolymer is to be understood as a copolymer of ethylene with at least one comonomer, that is, a 'copolymer' according to the present invention also encompasses terpolymer and higher, multiple comonomer co-polymerizates. in contrast to a homopolymer, the copolymer comprises in therange from 0.1 to 5.0 wt%, preferably 2.0 to 4.0 wt%, preferably 1.5 to 3.5 wt% of a comonomer in addition to ethylene, based on total weight of said copolymer.

[0065] Further preferred, typically, the numeric value for the z-average molecular weight of the first or non-metallocene subfraction will be smaller or ultimately substantially the same as the z-average molecular weight of the second or metallocene subfraction. Preferably, according to TREF analysis, the 40 % by weight or mass fraction, more preferably 5.0 to 40 %, most preferably 20 % by weight of the polyethylene component A) having the higher comonomer content (and lower level of crystallinity) have a degree of branching of from 2 to 40 branches / 1000 carbon atoms and / or the 40 % by weight or mass fraction, more preferably 5 to 40 %, most preferably 20 % by weight of the polyethylene component A) having the lower comonomer content (and higher level of crystallinity) have a degree of branching of less than 2, preferably in the range from 0.01 to 2.0 branches / 1000 carbon atoms.

[0066] Likewise it may be said that where the polyethylene component displays a multimodal, that is at least bimodal distribution in GPC analysis, preferably in the range from 5 to 40 % by weight of the polyethylene of the invention having the highest molar masses, preferably 10 to, 30% by weight and particularly preferably 20 % by weight, have a degree of branching in the range from 1 to 40 branches / 1000 carbon atoms, more preferably in the range from 2 to 20 branches / 1000 carbon atoms. It is a characteristic of the product of the metallocene catalyst A) giving rise to this subfraction of the polyethylene. Likewise it may preferably be said that due to the preferably more broadly distributed non-metallocene catalyst subfraction of component A), usually both with bimodal or substantially monomodal GPC distribution curves for component a), the 30 %, preferably 15 %, more preferably 5 % by weight of the polyethylene having the lowest molar masses have a degree of branching of less than 5 branches / 1000 carbon atoms, more preferably of less than 2 branches / 1000 carbon atoms.

[0067] Furthermore, it is preferred that at least 70 % of the branches of side chains larger than CH3 in the polyethylene of the invention are present in the 50 % by weight of the polyethylene having the highest molar masses. The part of the polyethylene having the lowest or highest molar mass is determined by the method of solvent- nonsolvent fractionation, later called Holtrup fractionation as described and referenced in the forgoing already. As before said 8 fractions are subsequently examined by 13 C-NMR spectroscopy.

[0068] The degree of branching in the various polymer fractions can be determined by means of 13 C- NMR as described by James, C. Randall, JMS-REV. Macromol. Chem. Phys., C29 (2, 3), 201-317 (1989). The degree of branching simply is the total CH3 group content / 1000 carbon atoms, preferably in the high molecular weight fractions, and reflects the comonomerincorporation rate. The branching contents is to be understood as side chains measured as CH3 / IOOO carbon atoms, preferably from 1 to 10 CH3 / IOOO carbon atoms. Furthermore, it is particularly preferred that in polyethylene copolymerized with 1 -butene, 1 -hexene or 1 -octene as the 1-alkene to have of from 0.01 to 20 ethyl, butyl, or hexyl short chain branches / 1000 carbon atoms, more preferably from 1 to 10 ethyl chain branches.

[0069] While the flow properties and the resulting processability of these ethylene copolymers depend mainly on their molar mass and molar mass distribution, the mechanical properties are in particularly dependent on the short chain branching distribution (SCBD).

[0070] The synthesis of branched polymers from ethylene without use of a comonomer using bimetallic catalysts in which one catalyst oligomerizes part of the ethylene and the other copolymerizes the oligomers formed in this way with ethylene has been described.

[0071] Intrinsic viscosity in polymers refers to the measure of a polymer's resistance to flow within a solvent. It provides insight into polymer chain length and branching, affecting material properties like molecular weight and viscosity. Typical values range from 0.5 to 2.5 deciliters per gram (dL / g), depending on factors like molecular weight and processing conditions. These values help in optimizing the materials flow behavior and processing characteristics during rotomoulding or injection moulding or extrusion. Preferably, the r|(vis) value of the polyethylene component in the range from 0.4 up to 3.0, more preferably in the range from 0.5 to 2.5 dL / g t, more preferably in the range from 0.6 to 2.0 dL / g or optionally more preferably in the range from 0.8 to 1.8 dL / g. r|(vis) is determined according to ISO 1628- 1 and -3 in Decalin at 135 °C by capillary viscosity measurement.

[0072] In one form of the disclosure the polyethylene further comprising at least one non- polymeric additive such as lubricant(s), antioxidant(s) and / or UV stabilizer(s), e.g. Zn Stearate, stabilizer AOK Pep-36 (from Adeka Palmarole Inc., substance is CAS No. 80693-00- 1 , Bis(2,6-ditert.butyl-e-methylphenyl)pentaerythritol-diphosphite, Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) (Irganox 1010), Tris(2,4-di-tert- butylphenyl)phosphite (Irgafos 168).

[0073] Furthermore, the disclosed polyethylene according to the disclosure, being devoid of densification aids, preferably being substantially free of polymeric densification aids.

[0074] Besides that, the processability might be improved or there might be a need in higher heat resistance, then processing aids can be added. But as the polyethylene with high MI2 has extraordinarily good processability and shows also high PIAT results it cuts cost as no further aids are needed.

[0075] According to the present disclosure the rotomoulded article or object comprises the polyethylene. The process to obtain such a rotomoulded article results in less carbon footprint as the oven time in some cases is cut almost in half, as shown in Figure 1, table 2 and table 3.

[0076] The rotomoulded article comprising the polyethylene with MI2 in the range from 8 tol5 according to the disclosure, being substantially free from air pockets, trapped air and / or bubbles, with smooth surface and high mechanical properties, more impact resistant, much quicker to process than compared to other polyethylene grades, and is low in porosity immediately after melting.

[0077] Especially, the polyethylene according to the present disclosure with MI2 in the range of 8 to 15 g / mol (according to ISO 1133, 190°C, 2.16 kg) has also a higher ESCR and shows cold temperature ductility as shown in Figure 1. Additionally, immediately after melting it can be cooled and removed from the tool, the strength of the rotomoulded article or object comprising the polyethylene according to the disclosure is developed and stays the same. Due to the fact, that a smaller number of bubbles or air pockets are trapped in the material, the ductility does not change at all, which is unlike normal rotomoulding polyethylene resins known from the state of the art, which always take time to remove the bubbles and then become ductile after all air has been removed. This means another time saving as processing the polyethylene for rotomoulding or injection moulding or extrusion means that the only processing required is enough time to just melt it, until the inside surface is to smooth or near smooth (Figure 2).

[0078] Another aspect is that cooling is faster when polyethylene with high MI2 is used. Rapid cooling is desired as it shortens production time. The reason for improved cooling is that the amount of heat trapped in the rotomoulded item, or article produced via injection moulding or extruded article is lower than for standard processed materials. Therefore, a lower amount of cooling is necessary before the plastic becomes cool enough to remove from the mould.

[0079] According to the invention, the rotomoulded article comprising the inventive polyethylene with MI2 in the range from 8 to 15 g / 10 min, preferably in the range from 9 to 14 g / 10 min, preferably MI2 in the range from 11 to 13 g / 10 min (according to ISO, 190°C, 2.16 kg) and more shows a smooth inner and superb impact being substantially free from air pockets, as substantially no air has been trapped and no bubbles were formed.

[0080] In one aspect of the present disclosure the rotomoulded article, exhibits exceptional ARM Impact Ductility with no changes in elasticity for PIAT of 130°C up to 190 °C. In the state of the art normally ductility in dependence of PIAT is improved for high temperatures, as the standard rotomoulding commercially available polyethylene with MI2 5material reaches 30 % ductility at 190 °C and 100 % at 195 °C. Surprisingly, the rotomoulded article comprising the polyethylene according to the present disclosure reaches already at PIAT of 130 °C 100 % elasticity and does not show any changes in ARM impact ductility even when temperature rises up to 190 °C. As shown in table 1, when temperature rises the elasticity of the MI5 material also is influenced and changes. In contrast to that, the polyethylene according to the disclosure immediately reaches 100 % ductility and stays at 100 % even if temperatures elevate which means there occurs no further changes in ductility. In figure 1, it is the ARM Impact Ductility (at - 40 °C, 3.2 mm) vs PIAT (Peak Internal Air Temperature) shown. In the table 1 it is an ARM (Association of Rotomoulders) lab data on ductile impact behaviour at 40 °C of the polyethylene according to the present disclosure and a commonly used testing material (MI5) shown. This results in outstanding impact properties compared to typical high flow grades with MI2 of 5 and as shown also lower PIAT.

[0081] In a preferred embodiment, is the polyethylene obtained by polymerization in the presence of a catalyst composition comprising at least two different single-site polymerization catalysts, preferably of which single-site catalyst.

[0082] Incorporated by reference, catalyst preparation and polymerizationA) is at least one polymerization catalyst based on a hafnocene (A) and preferably single-site catalystB) is at least one polymerization catalyst based on an iron component having a tridentate ligand bearing at least two aryl radicals, preferably with each said aryl radicals bearing a halogen or tert, alkyl substituent in the ortho-position.

[0083] The polyethylene according to this disclosure having a high flow index and a bimodal composition provides an outstanding combination of environmental stress crack resistance (ESCR) and ductility in rotomoulded articles. The composition is easy to process / mold, wherein the polyethylene disclosed herein has been prepared in one polymerization step in a single reactor by a mixed catalyst system comprising at least one metallocene.

[0084] The conjunction with employing a mixed system of at least two single-site catalysts according to the present invention, the polyethylene has a substantially monomodal molecular mass distribution curve as determined by GPC, hence is monomodal in GPC, whilst it truly is a pseudo-monomodal product obtained by post-reactor blending or, particularly preferred according to the present invention, obtained as an in situ blend reaction product ofdifferent catalysts, preferably single site catalysts, whose individual molecular weight distributions overlap and do not resolve as to display two distinct maxima any more.

[0085] Modality in the present context is defined as the number of instances where the value of the differential function of said mass distribution is 0 (i.e., slope 0) and wherein said differential value changes from positive to negative sign for increasing molar masses at said point having said functional value of 0. The mass distribution curve is not required to be perfectly bell-shaped, therefore it is merely 'substantially' monomodal. Most preferably, such (pseudo-) monomodal reaction product being one component of the adhesive composition of the present invention is obtained in situ in a one-pot reaction with a mixed or hybrid catalyst system, preferably with mixed single-site catalysts, giving rise to a particularly homogenous, in-situ mixture of different catalyst's products which homogeneity is not obtainable by conventional blending techniques. The polyethylene of the invention preferably has a mixing quality measured in accordance with ISO 13949 (1997) in the range from 0 to 5.0, preferably in the range from 1.0 to 3.0, preferably in the range from 1.5 to 2.5. This value is based on the polyethylene taken directly from the reactor, i.e., the polyethylene powder without prior melting in an extruder.

[0086] The polyethylene is obtainable by polymerization in a single reactor. The mixing quality of a polyethylene powder obtained directly from the reactor can be tested by assessing thin slices ("microtome sections") of a sample under an optical microscope inhomogeneities show up in the form of specks or "white spots". The specs or "white spots" are predominantly high molecular weight, high-viscosity particles in a low-viscosity matrix (e.g., U. Burkhardt et al. in" Aufbereiten von Polymeren mit neuartigen Eigenschaften", VDI Verlag Dusseldorf 1995, p. 71). Such inclusions can reach a size of up to 300 pm, they cause stress cracks and result in brittle failure of components. The better the mixing quality of a polymer, the fewer and smaller are these inclusions observed. The mixing quality of a polymer is determined quantitatively in accordance with ISO 13949. According to the measurement method, a microtome section is prepared from a sample of the polymer, the number and size of these inclusions are counted, and a grade is determined for the mixing quality of the polymer according to a set assessment scheme.

[0087] The polyethylene of the invention preferably has a degree of long chain branching 'A (lambda) in the range from 0 to 2 long chain branches / 1000 carbon atoms, preferably in the range from 0.1 to 1.5 of long chain branches / 1000 carbon atoms, preferably 0.5 to 1.0 of long chain branches / 1000 carbon atoms. The degree of long chain branching 'A (lambda) was measured by light scattering as described, for example, in ACS Series 521, 1993,Chromatography of Polymers, Ed. Theodore Provder; Simon Pang and Alfred Rudin: Size- Exclusion Chromatographic- Assessment-of long- Chain- Branch-Frequency- in- Polyethylene, p. 254-269.CATALYST PREPARATION

[0088] Hybrid Catalysts have been found to deliver an excellent combination of high mechanical properties in combination with extraordinary high melt index enabling significant lowering of processing temperatures when used in rotomoulding, injection molding or compression molding which is unprecedented in known polyethylene world.

[0089] In general mixing of the additives and the polyethylene of the invention can be carried out by all known methods, though preferably directly by means of an extruder such as a twin-screw extruder. The extruder technique is described e.g., in US 3862265, US 3953655 and US 4001172, incorporated herewith by reference.

[0090] The polyethylene of the invention is obtainable using the catalyst system described below and in particular at least one of the preferred embodiments. Preferably, a single site catalyst or single site catalyst system is employed for providing said polyethylene according to the present invention. More preferably, the present invention further employs a catalyst composition comprising at least two different single-site polymerization catalysts A) and B) of which A) is at least one metallocene polymerization catalyst, preferably wherein A) is a hafnocene (A), and of which B) is at least one polymerization catalyst based on a nonmetallocene transition metal complex, preferably wherein B) is an iron complex component which iron complex more preferably has a tridentate ligand (B), bearing at least two aryl radicals, preferably with each said aryl radicals bearing a halogen or tert, alkyl substituent in the ortho-position. Suitable metallocene and in particular hafnocene - catalysts A) are referenced and disclosed in WO 2005 / 103095 from the same inventors, said disclosure being incorporated herewith by reference.

[0091] Catalyst preparation is hereby incorporated by reference of WO 2009 / 103516. The polymer was produced using the catalyst according to example 1 as defined in WO 2009 / 103516. The ratio of the catalyst components of hafnium to iron is of at least 4, preferably 5.

[0092] D. Rotomoulding

[0093] The polyethylene product obtained from the polymerization step was used for rotomoulding of symmetrically shaped vessels having an even wall of constant thickness. The polyethylene of the present disclosure allows of devising rotomoulded objects having highFNCT (Full Notch CreepTest, according to ISO 16770:2004 E, at 6 MPa, 500 °C) whilst not requiring the aid of densification agents for rotomoulding, in particular no polymeric one.

[0094] Further, the polyethylene allows of easier processing due to its enhanced melt flow rate. Except for the additives, the rotomoulding process given in EP1749058, inclusive the temperature profile given in the examples section there, is applied. The following additives were used for the experimental grade according to the present disclosure, devised by a catalyst system according to preferably example 3 above: Zn Stearate, stabilizer ADK Pep-36 (from Adeka Palmarole Inc., substance is CAS No. 80693-00-1, Bis(2,6- ditert-butyl-e-methyl- phenyl)penta-erythritol-diphosphite, further 3 different antioxidants.

[0095] In another form of the disclosure, the rotomoulded article can be processed with short oven times. Normally for rotomoulding large items only polymers with low MI2 are used. Besides outstanding mechanical properties with less trapped air and low amount of surface pinholes, the use of the polyethylene with e.g. MI2 of 12 shows (please see Table 2 and figure 2), that heating / oven times are cut in half (51 %) with a PIAT reduction of 23 °C, which reduces gas consumption and reduces carbon footprint of the product. And saving cooling time of 31 %, which makes the whole process more efficient and faster with saving of total time of 40 %.

[0096] According tothe disclosure, the rotomoulded article can be processed with short oven times. Even for really large tanks, e.g., 5000 1 tanks, the time and energy saving are remarkable when low PIAT are used. This means that when really high amounts of rotomoulded articles comprising the polyethylene according to the present disclosure are processed, the carbon footprint, time, energy and therefore costs are significantly reduced.

[0097] Normally for rotomoulding only polymers with low MI2 are used. Besides outstanding mechanical properties with less trapped air and low amount of pinholes, the use of the polyethylene with e.g. MI2 of 12 g / 10 min (according to ISO 1133, 190°C, 2.16 kg) shows (please see

[0098] Table 3), that heating / oven times are reduced by at least 15 % with a PIAT reduction of 10 °C, which reduces gas consumption and reduces carbon footprint of the product. And saving cooling time of 8 %, which makes the whole process more efficient and faster even with saving of total time of 11 %.

[0099] The rotomoulded article comprising polyethylene according to the disclosure, which is a tank of at least 500 1 volume, preferably which is a tank.

[0100] Furthermore, the rotomoulded article comprising the inventive polyethylene disclosed and bio-based ethylene in a ratio of at least 1.0 wt% up to 100 wt% as homo-and / or copolymer.

[0101] In another aspect of the present disclosure, the rotomoulded article comprising the polyethylene, which comprises a recyclate in a ratio in the range of 30 wt% up to 700 wt% based on the overall weight of the polyethylene. Wherein the recyclate is based on mixtures of polyethylene comprising LLDPE; LDPE; MDPE; and HDPE in a ratio of at least 1.0 wt% up to 100 wt%, wherein the recyclate comprises homo- and / or copolymers. Per definition “PCR ethylene” and “PCR polyethylene" refers to recycled material that comes from products that have been used by consumers, discarded, and then collected for recycling, mechanically and / or chemically has been processed to be reused in a sustainable function.MEASUREMENT METHODS

[0102] The branches / 1000 carbon atoms are determined by means of 13 C-NMR, as described by James, C. Randall, JMS-REV. Macromol. Chem. Phys., C29 (2&3), 201-317 (1989), and are based on the total content of CHs-groups / lOOO carbon atoms. The side chains larger than CH3 and especially ethyl, butyl and hexyl side chain branches / 1000 carbon atoms are likewise determined in this way. The degree of branching in the individual polymer mass fractions are determined by the method of Holtrup (W. Holtrup, MakromoL Chem. 178, 2335 (1977)) coupled, 13, 11; with C-NMR. C-NMR high temperature spectra of polymer were acquired on a Bruker DPX- 400 spectrometer operating at 100.61 MHz in the Fourier transform mode at 120 °C.

[0103] The peak S55 [CJ. Carman, R.A. Harrington, and CE. Wilkes, Macromolecules, 10, 3, 536 (1977)] carbon was used as internal reference at 29.9 ppm. The samples were dissolved in 1,1 ,2,2- tetrachloroethane-c / 2 at 120 °C with a 8.0 % concentration. Each spectrum was acquired with a Of) 90° pulse, 15 seconds of delay between pulses and CPD (WALTZ 16) to remove 1 H-13C coupling. About 1500-2000 transients were stored in 32K data points using a spectral window of 6000 or 9000 Hz. The assignments of the spectra were made referring to Kakugo [M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 15, 4, 1150, (1982)] and J. C. Randal, Macromol. Chem Phys., C29, 201 (1989). NMR samples were placed in tubes under inert gas and, if appropriate, melted. The solvent signals served as internal standard in the NMR spectra and their chemical shift was converted into the values relative to TMS.

[0104] The density [g / cm3] was determined in accordance with ISO 1183.

[0105] The determination of the molar mass distributions and the means Mn, Mw, Mz and Mw / Mn derived therefrom was carried out by high-temperature gel permeation chromatography using a method essentially described in DIN 55672-1 : 1995-02 issue February 1995. The methodological deviations applied in view of the mentioned DIN standard are as follows: Solvent was 1, 2, 4-tri chlorobenzene (TCB), temperature of apparatus and solutions was 1350 C and as a concentration detector, use of a Polymer Char (Valencia, Paterna 46980, Spain) IR-4 infrared detector, capable for use with TCB.

[0106] A WATERS Alliance 2000 equipped with the following precolumn SHODEX UT-G and separation columns SHODEX UT 806 M (3x) and SHODEX UT 807 connected in series was used. The solvent was vacuum distilled under Nitrogen and was stabilized with 0.025 % by weight of 2,6-di- 40tert-butyl-4-m ethylphenol. The flowrate used was 1 ml / min, the injection was 500pl and polymer concentration was in the range of 0.01 % to 0.05 %.

[0107] The molecular weight calibration was established by using monodisperse polystyrene (PS) standards from Polymer Laboratories (now Varian, Inc., Essex Road, Church Stretton, Shropshire, SY6 6AX1 UK) in the range from 580 g / mol up to 1 1600000g / mol and additionally Hexadecane. The calibration curve was then adapted to Polyethylene (PE) by means of the Universal Calibration method (Benoit H., Rempp P., and Grubisic Z., in J. Polymer Sci., Phys. Ed., 5, 753(1967)). The Mark-Houwing parameters used herefore were for PS: kPS = 0.000121 dl / g, aPS =0.706 and for PE kPE = 0.000406 dl / g, aPE = 0.725, valid in TCB at 1350 C. Data recording, calibration and calculation was carried out using NTGPC_Control_V6.02.03 and NTGPC V6.4.24 (hs GmbH, Hauptstra[3e 36, D-55437 Ober- Hilbersheim) respectively.

[0108] The stress crack resistance ('full notch creep test', FNCT)) was determined in [h] according to 18016770:2004 E at a pressure of 6.0 Mbar at 50 °C in a 2.0 % by weight solution of Arkopal N 100 (Trademark of Clariant AG, Muttenz / Switzerland, which detergent is CAS 9016-45 9-(4- nonylphenyl)polyethylenglycolmonoether, with n=10 for the repeat units in the PEG chain) in water, including test specimen preparation as a compressed plate as described in ISO 16770:2004 E.

[0109] The stress crack resistance ('full notch creep test', FNCT)) was determined in [h] according to IS016770:2004 E at a pressure of 6.0 Mbar at 50 °C in a 2.0 % by weight solution of Akropal N100 (Trademark of Clariant AG, Muttenz / Switzerland, which detergent is GAS 9016-45-9, (4-nonlyphenyl)polyethylenglycolmonoether, with n=10 for the repeat units in the PEG chain) in water, including test specimen preparation as a compressed plate as described in ISO 16770:2004 E. The time to failure is shortened by initiating a crack by means of the notchin 2% Arkopal solution as a stress crack promoting medium. The dimension of the notch are given in the ISO standard.

[0110] The density [g / cm3] was determined in accordance with ISO 1183.The determination of the molar mass distributions and the means Mn, Mw, Mz and Mw / Mn derived therefrom was carried out by high-temperature gel permeation chromatography using a method essentially described in DIN 55672-1 : 1995-02 issue Februar 1995. The methodological deviations applied in view of the mentioned DIN standard are as follows: Solvent was 1,2,4-trichlorobenzene (TCB), temperature of apparatus and solutions was 135°C and as a concentration detector, use of a PolymerChar (Valencia, Paterna 46980, Spain) IR-4 infrared detector, capable for use with TCB.

[0111] The AZK measurement or Charpy measurements are performed according to ISO 179-1 or ISO 179-2. Impact tests according to the Charpy method are used for the characterization of a plastic material at high strain rates. The abrupt load is applied in a 3 -point flexure fixture. In the classic method, the result is presented in terms of the energy absorption of the specimen. Instrumented measurement methods furthermore present force-travel diagrams, provide additional material information, as well as automatic assignment of the break type. In the context of the standard for single-point data ISO 10350-1, Charpy according to ISO 179-1 is the preferred test method for the measurement of impact strength. The test is ideally performed on unnotched specimens with edgewise impact. If the specimen does not break in this configuration, the test is performed using notched specimens. The test results are therefore not directly comparable. If specimen break can also not be achieved with notched specimens, the tensile impact method to ISO 8256 is used.DEFINITION

[0112] According to this disclosure, “substantially free” means that no or almost negligible or hardly detectably or undetectable amounts of air are present in the product. This means, that the amount of air bubbles is so minimally present that it has practically no impact on the desired property or function of the product or process. It refers to an almost complete absence or such a small amount of air that is has no practical impact on the final product or process.

[0113] Per definition “Bio based ethylene” refers to ethylene which is derived from renewable biological sources like plants or biomass rather than fossil fuels. Bio based ethylene can be derived from organic matter, such as plants, wood, agricultural residues, and otherbiological materials to be used as renewable source converted into biofuels through fermentation and chemical reactions.

[0114] Per definition, a “copolymer” according to the present invention also encompasses a comonomer, with only one alkene besides ethylene, but also mixtures of different alkenes in the range of C3 to C20, therefore even terpolymers and higher polymers and multiple comonomer co-polymerizates are “copolymers” in the sense of the present invention.

[0115] For the purposes of this invention as it is well known to the skilled person, the expression "HLMI" means "high load melt index" and is determined at 190 °C under a load of 21.6 kg (according to ISO 1133, at 190 °C, 21.6 kg).

[0116] According to this disclosure, substantially free means that no or almost negligible or hardly detectably or undetectable amounts are present in the product. This means, that the aids can be present, but they have practically no impact on the desired property or function of the product or process. It refers to an almost complete absence or such a small amount of any densification aids that they have no practical impact on the final product or process.

[0117] In the sense of the present invention a recyclate is either derived from post consumer polyethylene waste and / or post industrial polyethylene waste, comprising a copolymer or homopolymer.Table 1: Examples of Polyethylene with high MI2.Table 2Table 3

Claims

CLAIMS1. Polyethylene, consisting of either an ethylene homo- and / or copolymer, or a mixture thereof, a) an ethylene homo- and / or copolymer, or a mixture thereof wherein the copolymer is a copolymer of ethylene with C3 to C2o-alkene, b) wherein the polyethylene has a molar mass distribution width Mw / Mn in the range from 8 to 15, c) a density of from 0.934 to 0.44 g / cm3(according to ISO 1183), d) a weight average molar mass Mw of from 40,000 g / mol to 300,000 g / mol, a Mz in the range from 200,000 g / mol to 800,000 g / mol, e) a Mz in the range from 50,000 g / mol to 300,000 g / mol, preferably in the range from 100,000 g / mol to 250,000 g / mol, preferably 150,000 g / mol to 200,000 g / mol, f) a MI2 in the range from 8 to 15 g / 10 min (according to ISO 1133, at 190 °C, 2.16 kg), g) a FNCT in the range from 1000 to 2200 h (according to ISO 16770, at 6 MPa, 60 °C,2 % Arkopal), h) a Charpy / AZK (23°C) is in the range from 125 to 300 kJ / m2, i) wherein the polyethylene is prepared in a polymerization step in a single reactor by a mixed catalyst system comprising at least one metallocene, wherein the polyethylene is obtained by a polymerization process in the presence of a catalyst composition comprising at least two different single-site polymerization catalysts A and B, whereinA) is at least one polymerization catalyst based on a hafnocene single-site catalyst, andB) is at least one polymerization catalyst based on an iron component having a tridentate ligand bearing at least two aryl radicals, preferably with each said aryl radicals bearing a halogen or tert, alkyl substituent in the ortho-position.

2. Polyethylene according to claim 1, wherein the polyethylene comprises homopolymeric and copolymeric subfractions, and wherein the polyethylene taken as whole has of from 0.7 to 20 CH3 / 1000 carbon atoms as determined by 13C-NMR.

3. Polyethylene according to any of the preceding claims, wherein the copolymer comprises at least one C3 to C2o-alkene in an amount of greater than 2 wt% based on the total weight of the polyethylene.

4. Polyethylene according to any of the preceding claims, wherein the polyethylene has a vinyl group content in the range from 0.1 to 3.0 vinyl groups / 1000 C atoms (measured according to ASTM D 6248-98).

5. Polyethylene according to any of the preceding claims, wherein the r|(vis) value is in the range of from 0.4 to 3.0 dl / g and wherein r|(vis) is the intrinsic viscosity as determined according to ISO 1628-1 and 1628 -3 in Decalin at135 °C.

6. Polyethylene according to any of the preceding claims, being substantially free of densification aids, and / or being substantially free of polymeric densification aids.

7. Polyethylene according to any of the preceding claims, wherein the polyethylene is obtained by copolymerizing ethylene with one or several 1- alkenes of formula R 1 CH=CH 2, wherein-R 1 is hydrogen or an alkyl radical with 1 bis 10 carbon atoms, at a temperature of from 20 to 200 °C and at a pressure range of from 0.05 to 1.0 MPa.

8. Rotomoulded article or object, comprising the polyethylene according to any one of the preceding claims.

9. Rotomoulded article according to claim 8, wherein with reduced oven of at least 25 % time, compared to standard rotomoulding material, depending on the wall thickness of the article, in the range from 10 to 30 %, and / or savings in the range of 0.1 to 0.8 kg CO2 / kg polyethylene.

10. Rotomoulded article or object according to any of the preceding claims, having substantially no densification additive, preferably substantially no polymeric densification additive, and / or more preferably which is low in porosity immediately after melting.

11. Rotomoulded article according to any of the preceding claims, with a reduced carbon footprint of 0.6 kg CCh / kg polyethylene.

12. Rotomoulded article according to any of the preceding claims, wherein the polyethylene comprises a bio-based ethylene homo- and / or copolymer.

13. Rotomoulded article according to any of the preceding claims, wherein the polyethylene comprises a recyclate in the range of 30 wt% to 70 wt%, based on the overall weight of the polymer.

14. Rotomoulding article according to any of the preceding claims, wherein a) the cooling time is reduced in a range of 8 to 50 %, b) oven time is reduced in a range of 10 to 60 %.

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