Polyethylene copolymers for film layers

Abstract

Metallocene catalyzed multimodal medium density polyethylene (mMDPE), the use of multimodal medium density polyethylene (mMDPE) in film applications and films comprising the mMDPE of the invention.

Description

[0001] The present invention relates to metallocene-catalyzed multimodal medium density polyethylene (mMDPE), the use of multimodal medium density polyethylene (mMDPE) in film applications and films comprising the mMDPE of the invention.

[0002] State-of-the-art mLLDPE (metallocene-catalyzed linear low-density polyethylene) is widely used in daily life, such as packaging, due to its excellent cost-performance ratio.

[0003] Unimodal mLLDPE is typically used for film applications. Unimodal LLDPE has good optical properties, such as low haze, but melt processing of such polymers is not satisfactory, for example, from a production point of view and may also lead to quality problems in the final product. Multimodal mLLDPE with two or more different polymer components is easier to process, but melt homogenization of multimodal PE may be problematic, leading to inhomogeneous final products, such as high gel content in the final product.

[0004] Multimodal mLLDPE are known in the art.

[0005] WO 202100918, WO 2021009190 and WO 2021009191 of Borealis disclose a process for preparing a multimodal PE polymer in two loop reactors and a gas phase reactor in the presence of a silica-supported metallocene catalyst based on the metallocene complex bis(1-methyl-3-n-butylcyclopentadienyl)zirconium(IV) dichloride.

[0006] Film properties such as tensile modulus (TM) and impact strength (Dart Drop Impact, DDI) are not mentioned at all.

[0007] WO 2021009192 also discloses this method.

[0008] Again, there is no mention at all of the film properties such as tensile modulus (TM) and impact resistance (Dart Drop Impact, DDI).

[0009] There is a growing need to find multimodal PE polymers with different balances of properties to provide tailor-made solutions that meet the growing demands of end-use producers, such as reducing production costs while maintaining or even improving the properties of the final product. There is also a need for tailor-made polymer solutions to meet the requirements of evolving equipment technologies in the end-use areas.

[0010] Therefore, there is a need in the art to provide a material that provides good mechanical properties, particularly tensile modulus and dart drop (impact resistance).

[0011] The present inventors have now found that metallocene-catalyzed medium density polyethylene (mMDPE) prepared with a specific metallocene catalyst and having a specific polymer design produces films with improved mechanical properties, especially tensile modulus and dart drop (impact strength). In addition, mMDPE with this specific design can be easily processed by adding polyethylene wax as a processing aid, rather than the commonly used fluorine-based processing aids, which are concerned about human and environmental health due to their fluorine content. Summary of the invention

[0012] Therefore, the present invention relates to a metallocene-catalyzed multimodal medium density polyethylene consisting of:

[0013] (i) 35.0 to 55.0 wt% of a polyethylene component (A) based on mMDPE, and

[0014] (ii) 45.0 to 65.0 wt% of a polyethylene component (B) based on mMDPE,

[0015] wherein the polyethylene polymer component (A) has

[0016] 930 to 975 kg / m 3 Density in the range (ISO 1183),

[0017] MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 10.0 to 200.0 g / 10 min;

[0018] The polyethylene component (B) has

[0019] 870 to 910 kg / m 3 Density in the range (ISO 1183),

[0020] MFR2 in the range of 0.0001 to 0.5 g / 10 min (190°C, 2.16 kg, ISO 1133);

[0021] Among them, metallocene-catalyzed medium-density polyethylene (mMDPE) has

[0022] 915 to 945 kg / m 3 Density in the range (ISO 1183),

[0023] MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 0.1 to 2.0 g / 10 min, and

[0024] MFR in the range of 37 to 75 21Ratio of MFR (190℃, 21.6kg, ISO 1133) to MFR2 (190℃, 2.16kg, ISO1133) 21 / MFR2, and the difference between the density of the polyethylene component (A) and the density of the final metallocene-catalyzed mMDPE (Δdensity: density of the polyethylene component (A) - density of the final metallocene-catalyzed mMDPE) is in the range of 28 to 70 kg / m 3 within the range.

[0025] In one embodiment of the present invention the polyethylene component (A) of the metallocene-catalyzed multimodal medium density polyethylene (mMDPE) consists of an ethylene polymer fraction (A-1) and an ethylene polymer fraction (A-2).

[0026] In another embodiment, the metallocene-catalyzed multimodal medium density polyethylene (mMDPE) may be blended with 0.1 to 3.0 wt% of a polyethylene wax as a processing aid, based on the total weight of the blend.

[0027] Surprisingly, such mMDPE or a mixture of such mMDPE with a polyethylene wax provides films with improved mechanical properties, in particular tensile modulus and dart drop (impact resistance).

[0028] Therefore, the present invention further relates to a film comprising at least one layer comprising an mMDPE as defined above.

[0029] definition

[0030] Where the term "comprising" is used in the present description and claims, it does not exclude other, not specifically stated, elements of major or minor functional importance. For the purposes of the present invention, the term "consisting of" is considered to be a preferred embodiment of the term "comprising". If a group is defined hereinafter as comprising at least a certain number of embodiments, this is also to be understood as disclosing the group, which preferably consists only of these embodiments.

[0031] Whenever the terms "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above.

[0032] When an indefinite or definite article is used when referring to a singular noun, for example "a", "an" or "the", this includes a plural of that noun unless otherwise stated.

[0033] Medium density polyethylene (MDPE) is defined in the present invention as having a density of 915 to 945 kg / m 3 range of polyethylene.

[0034] Metallocene-catalyzed medium density polyethylene (mMDPE) is defined in the present invention as a medium density polyethylene produced in the presence of a metallocene catalyst.

[0035] For the purposes of the present invention, "medium density polyethylene (MDPE) comprising a polyethylene component (A) and a polyethylene component (B)" means that the MDPE is produced in at least a two-step sequential polymerization process, wherein component (A) is produced first and then, in a subsequent polymerization step, component (B) is produced in the presence of component (A) to produce the MDPE, or vice versa, i.e. component (B) is produced first and then, in a subsequent polymerization step, component (A) is produced in the presence of component (B) to produce the MDPE.

[0036] MDPE produced in a multistage process is also known as an "in-situ" blend or a "reactor" blend. The resulting final product consists of an intimate mixture of polymers from two or more reactors whose different molecular weight distribution curves together form a molecular weight distribution curve with a broad maximum or two or more maxima, i.e., the final product is a multimodal polymer mixture.

[0037] In the context of medium density polyethylene (MDPE), the term "multimodal" refers herein to the multimodality of the melt flow rate (MFR) of at least two polyethylene components, i.e. the two polyethylene components have different MFR values. The multimodal medium density polyethylene may additionally or alternatively have multimodality between the two polyethylene components with respect to one or more other properties (such as density, comonomer type and / or comonomer content), which will be described below. DETAILED DESCRIPTION

[0038] Metallocene-catalyzed multimodal medium density polyethylene (mMDPE)

[0039] The metallocene-catalyzed multimodal mMDPE according to the present invention has a molecular weight of 915 to 945 kg / m 3 , preferably 918 to 940 kg / m 3 , more preferably 920 to 935 kg / m 3 Density within the range (ISO 1183).

[0040] The MFR2 (190°C, 2.16 kg, ISO 1133) of the metallocene-catalyzed mMDPE is in the range of 0.1 to 2.0 g / 10 min, preferably 0.2 to 1.8 g / 10 min, more preferably 0.3 to 1.5 g / 10 min, even more preferably 0.4 to 1.0 g / 10 min.

[0041] MFR of metallocene-catalyzed mMDPE 21(190°C, 21.6 kg, ISO 1133) is in the range of 10.0 to 80.0 g / 10 min, preferably in the range of 15.0 to 70.0 g / 10 min, more preferably in the range of 20.0 to 60.0 g / 10 min, most preferably in the range of 22.0 to 50.0 g / 10 min.

[0042] The metallocene-catalyzed mMDPE according to the present invention also has an MFR in the range of 37 to 75, preferably 40 to 70, more preferably 42 to 65. 21 / MFR2 flow rate ratio (FRR).

[0043] In one embodiment, the metallocene-catalyzed mMDPE has

[0044] a) 918 to 940 kg / m 3 , preferably 920 to 935 kg / m 3 Density within the range (ISO1183).

[0045] In another embodiment, the metallocene-catalyzed mMDPE has

[0046] b) MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 0.2 to 1.8 g / 10 min, preferably 0.3 to 1.5 g / 10 min, more preferably 0.4 to 1.0 g / 10 min.

[0047] In another embodiment, the metallocene-catalyzed mMDPE has

[0048] c) MFR in the range of 15.0 to 70.0 g / 10 min, preferably in the range of 20.0 to 60.0 g / 10 min, more preferably in the range of 22.0 to 50.0 g / 10 min 21 (190℃, 21.6kg, ISO 1133).

[0049] In another embodiment, the metallocene-catalyzed mMDPE has

[0050] d) a flow rate ratio (FRR) MFR in the range of 40 to 70, preferably 42 to 65 21 / MFR2.

[0051] Preferably, the metallocene-catalyzed mMDPE has two or more, preferably all, of properties a) - d).

[0052] Furthermore, the metallocene-catalyzed MDPE may have a molecular weight distribution (MWD) Mw / Mn in the range of 3.5 to 12.0, preferably 4.0 to 10.0, more preferably 4.2 to 8.0.

[0053] In addition, the metallocene-catalyzed mMDPE according to the present invention may have one or more or all of the properties described below:

[0054] Weight average molecular weight Mw

[0055] The weight average molecular weight Mw of the metallocene-catalyzed MDPE may be at least 90,000 g / mol, preferably in the range of 92,000 to 140,000 g / mol, more preferably 95,000 to 130,000 g / mol, still more preferably 100,000 to 120,000 g / mol.

[0056] Z-average molecular weight Mz

[0057] The z-average molecular weight Mz may be in the range of 200,000 to 500,000 g / mol, preferably 230,000 to 400,000 g / mol, more preferably 250,000 to 350,000 g / mol.

[0058] Mz / Mw ratio

[0059] The Mz / Mw ratio may be in the range of 2.0 to 4.0, preferably 2.2 to 3.5, more preferably 2.3 to 3.2.

[0060] Metallocene-catalyzed mMDPE consists of:

[0061] (i) 35.0 to 55.0 wt%, preferably 38.0 to 52.0 wt%, more preferably 40.0 to 50.0 wt% of a polyethylene component (A) relative to the total weight of mMDPE, having a molecular weight of 930 to 975 kg / m 3 A density in the range of 10.0 to 200 g / 10 min and an MFR2 (190°C, 2.16 kg, ISO 1133); and

[0062] (ii) 45.0 to 65.0 wt%, preferably 48.0 to 62.0 wt%, more preferably 50.0 to 60.0 wt% of a polyethylene component (B) relative to the total weight of mMDPE, having a molecular weight of 870 to 910 kg / m 3 The invention relates to a polymer having a density in the range of 0.0001 to 0.5 g / 10 min and a MFR2 (190°C, 2.16 kg, ISO 1133) of 0.0001 to 0.5 g / 10 min.

[0063] The amounts of components (A) and (B) add up to 100 wt%.

[0064] The difference between the density of the polyethylene component (A) and the density of the final metallocene-catalyzed mMDPE (Δdensity: density of the polyethylene component (A) - density of the final metallocene-catalyzed mMDPE) is in the range of 28 to 70 kg / m3 , preferably 30 to 55 kg / m 3 , more preferably 32 to 45 kg / m 3 within the range.

[0065] The polyethylene components (A) and / or (B) may be homopolymers or ethylene copolymers.

[0066] Preferably, the mMDPE may have two copolymer components or one copolymer component and one homopolymer component, whereby preferably both components are ethylene copolymers, or the polyethylene component (A) is a homopolymer and the polyethylene component (B) is a copolymer, or vice versa (the polyethylene component (A) is a copolymer and the polyethylene component (B) is a homopolymer).

[0067] In a preferred embodiment, the polyethylene component (A) is a copolymer and the polyethylene component (B) is a copolymer.

[0068] In another preferred embodiment, the polyethylene component (A) is a copolymer and the polyethylene component (B) is a homopolymer.

[0069] Preferred ethylene copolymers use α-olefins (e.g., C3-12 α-olefins) as comonomers. Examples of suitable α-olefins include 1-butene, 1-hexene, and 1-octene. 1-Butene and 1-hexene are particularly preferred comonomers.

[0070] For the purposes of the present invention, a polyethylene homopolymer is a polymer comprising at least 99.0 wt%, in particular at least 99.5 wt% of ethylene monomer units. Thus, a polyethylene homopolymer may contain up to 1.0 wt%, but preferably only up to 0.5 wt%, for example up to 0.2 wt% or even only up to 0.1 wt% of comonomer units.

[0071] In one embodiment of the present invention, the amount of comonomer in the polyethylene homopolymer component is 13 C-NMR was undetectable.

[0072] Preferably, polyethylene component (B) is composed of a single ethylene copolymer or a single ethylene homopolymer. Polyethylene component (A) can be composed of a single ethylene homopolymer or copolymer. Alternatively, polyethylene component (A) can be an ethylene polymer mixture comprising a first ethylene polymer portion (A-1) and a second ethylene polymer portion (A-2) (e.g., composed thereof), wherein the two portions are either homopolymers or copolymers. Polyethylene component (A) can be unimodal or multimodal. In the case where polyethylene component (A) is an ethylene copolymer mixture, preferably the comonomers in the first and second ethylene copolymer portions are identical.

[0073] Most preferably, the polyethylene component (A) is an ethylene-1-butene copolymer and the polyethylene component (B) is an ethylene-1-hexene copolymer or an ethylene homopolymer.

[0074] The MFR2 of the polyethylene component (A) is preferably in the range of 15.0 to 150 g / 10 min, more preferably 20.0 to 100 g / 10 min, even more preferably 22.0 to 90.0 g / 10 min, most preferably 25.0 to 80.0 g / 10 min.

[0075] The density of the polyethylene component (A) is preferably in the range of 935 to 972 kg / m 3 , more preferably 940 to 970 kg / m 3 , even more preferably 945 to 968 kg / m 3 , still more preferably 950 to 968 kg / m 3 , most preferably 955 to 968 kg / m 3 , such as 960 to 968 kg / m 3 within the range.

[0076] It is further preferred that the polyethylene component (A) consists of two parts, namely a first ethylene polymer part (A-1) and a second ethylene polymer part (A-2), preferably a first ethylene copolymer part (A-1) and a second ethylene copolymer part (A-2). More preferably, both parts (A-1) and (A-2) are ethylene-1-butene copolymers.

[0077] It is possible to produce fraction (A-1) first and then, in a subsequent reactor, produce fraction (A-2) in the presence of fraction (A-1), or vice versa, i.e., produce fraction (A-2) first and then, in a subsequent reactor, produce fraction (A-1) in the presence of fraction (A-2). Preferably, fraction (A-1) is produced first.

[0078] The MFR2 and / or density of fractions (A-1) and (A-2) may be the same or may be different from each other.

[0079] Therefore, the MFR2 (190°C, 2.16 kg, ISO 1133) of the ethylene polymer part (A-1) is preferably in the range of 3.0 to 80.0 g / 10 min, preferably 5.0 to 60.0 g / 10 min, more preferably 8.0 to 40.0 g / 10 min, even more preferably 10.0 to 30.0 g / 10 min.

[0080] The ethylene polymer portion (A-2) preferably has an MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 10.0 to 1000 g / 10 min, preferably 20.0 to 800.0 g / 10 min, more preferably 30.0 to 700.0 g / 10 min, most preferably 35.0 to 600.0 g / 10 min, such as 40.0 to 500 g / 10 min.

[0081] Preferably, the MFR2 of fraction (A-2) is higher than the MFR2 of fraction (A-1).

[0082] The density of the ethylene polymer portion (A-1) is preferably in the range of 930 to 970 kg / m 3 , preferably 940 to 965 kg / m 3 , even more preferably 950 to 960 kg / m 3 within the range.

[0083] The density of the ethylene polymer portion (A-2) is 930 to 980 kg / m 3 , more preferably 940 to 980 kg / m 3 , even more preferably 950 to 979 kg / 10 kg / m 3 within the range.

[0084] Preferably, the density of fraction (A-2) is higher than the density of fraction (A-1).

[0085] The MFR2 of the polyethylene component (B) is preferably in the range of 0.001 to 0.1 g / 10 min, more preferably 0.003 to 0.08 g / 10 min, even more preferably 0.005 to 0.05 g / 10 min.

[0086] The density of the polyethylene component (B) is preferably in the range of 875 to 908 kg / m 3 , more preferably 880 to 906 kg / m 3 , even more preferably 885 to 904 kg / m 3 within the range.

[0087] In one embodiment of the present invention, in case the polyethylene component (A) consists of 2 ethylene polymer parts, the ratio of the MFR2 of the ethylene polymer part (A-1) of the metallocene-catalyzed mMDPE to the MFR2 of the polyethylene component (A) is in the range of 0.10 to 0.85, preferably 0.15 to 0.75.

[0088] In another embodiment of the present invention, the ratio of MFR2 of the polyethylene component (A) of the metallocene-catalyzed mMDPE to the MFR2 of the final metallocene-catalyzed mMDPE is in the range of 10.0 to 500, preferably 20.0 to 300, more preferably 30.0 to 200, even more preferably 40.0 to 100.

[0089] Metallocene-catalyzed mMDPE can be produced by polymerizing with a metallocene catalyst system using conditions that produce a multimodal (eg, bimodal) polymer product.

[0090] Thus, metallocene-catalyzed mMDPE can be produced in a two-stage process, preferably comprising a slurry reactor (loop reactor), wherein the slurry (loop) reactor is connected in series with a gas phase reactor (GPR), whereby polyethylene component (A) or polyethylene component (B) is produced in the loop reactor, and then the other ethylene polymer component is produced in the GPR in the presence of the first produced ethylene polymer component to produce metallocene-catalyzed mMDPE, preferably, polyethylene component (A) is produced in the loop reactor and polyethylene component (B) is produced in the GPR in the presence of polyethylene component (A) to produce metallocene-catalyzed mMDPE.

[0091] In case the polyethylene component (A) of the metallocene-catalyzed mMDPE consists of ethylene polymer fractions (A-1) and (A-2), the metallocene-catalyzed mMDPE may be produced in a three-stage process, which preferably comprises a first slurry reactor (loop reactor 1), wherein the first slurry loop reactor is connected in series to a further slurry reactor (loop reactor 2), such that the first ethylene polymer fraction (A-1) produced in loop reactor 1 is fed to loop reactor 2, where the second ethylene polymer fraction (A-2) is produced in the presence of the first fraction (A-1). Fraction (A-1) may be produced first and then, in a subsequent reactor, fraction (A-2) is produced in the presence of fraction (A-1), or vice versa, i.e., fraction (A-2) is produced first and then, in a subsequent reactor, fraction (A-1) is produced in the presence of fraction (A-2). Preferably, fraction (A-1) is produced first.

[0092] Within the scope of the present invention, the first and second ethylene polymer parts (A-1 and A-2) of the polyethylene component (A) are present in a weight ratio of 4:1 to 1:4, for example 3:1 to 1:3, or 2:1 to 1:2, or 1:1, based on the total weight of the polyethylene component (A).

[0093] The first and second polymerisation stages of the three stage process are preferably slurry polymerisation steps.

[0094] Slurry polymerization is usually carried out in an inert diluent, which is usually a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of these hydrocarbons. A particularly preferred diluent is propane, which may contain small amounts of methane, ethane and / or butane.

[0095] The temperature of the first and second polymerization stages is generally from 60 to 100° C., preferably from 70 to 90° C. Excessively high temperatures should be avoided to prevent partial dissolution of the polymer into the diluent and contamination of the reactor. The pressure is from 1 to 150 bar, preferably from 40 to 80 bar.

[0096] Slurry polymerization can be carried out in any known reactor for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. Slurry polymerization is particularly preferably carried out in a loop reactor. In such a reactor, the slurry is circulated at high speed along a closed pipeline by using a circulating pump. Loop reactors are well known in the art, and examples are given, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654. Therefore, it is preferred to carry out the first and second polymerization stages in the form of slurry polymerization in two continuous loop reactors.

[0097] The slurry can be withdrawn from each reactor continuously or intermittently. A preferred mode for intermittent withdrawal is to use settling legs, wherein the slurry is concentrated and then a batch of concentrated slurry is withdrawn from the reactor. The use of settling legs is disclosed in US-A-3374211, US-A-3242150 and EP-A-1310295. Continuous withdrawal is disclosed in EP-A-891990, EP-A-1415999, EP-A-1591460 and WO-A-2007 / 025640. As disclosed in EP-A-1310295 and EP-A-1591460, continuous withdrawal is advantageously combined with a suitable concentration method. Preferably, the slurry is withdrawn continuously from each of the first and second polymerization stages.

[0098] Hydrogen is usually introduced into the first and second polymerisation stages for controlling the MFR2 of the first and second ethylene polymers. The amount of hydrogen required to achieve the desired MFR depends on the catalyst used and the polymerisation conditions.

[0099] Therefore, the last loop reactor is connected in series to a gas phase reactor (GPR) such that the polyethylene component (A) leaving the second slurry reactor is fed to the GPR to produce a trimodal polyethylene copolymer. In this case, the reaction conditions in the two slurry reactors are selected such that products different in MFR and / or density are produced in the two slurry reactors.

[0100] The third polymerization stage is a gas phase polymerization step, ie carried out in a gas phase reactor. Any suitable gas phase reactor known in the art may be used, such as a fluidized bed gas phase reactor.

[0101] For gas phase reactors, the reaction temperature used is usually 60-115° C. (e.g. 70-110° C.), the reactor pressure is usually in the range of 10-25 bar, and the residence time is usually 1-8 hours. The gas used is usually a non-reactive gas, such as nitrogen or a low boiling hydrocarbon, such as propane and a monomer (e.g. ethylene).

[0102] A chain transfer agent, such as hydrogen, is usually added to the third polymerization stage.

[0103] Such processes are described inter alia in WO 2016 / 198273, WO 2021009189, WO 2021009190, WO 2021009191 and WO 2021009192. Full details of how to prepare suitable multimodal polymers can be found in these references.

[0104] A suitable process is the Borstar PE process or the Borstar PE 3G process.

[0105] Therefore, the metallocene-catalyzed mMDPE according to the present invention is preferably produced in a loop-loop-gas phase cascade.Such a polymerization step may be preceded by a prepolymerization step.

[0106] The purpose of prepolymerization is to polymerize a small amount of polymer onto the catalyst at low temperature and / or low monomer concentration. By prepolymerization, the performance of the catalyst in slurry can be improved and / or the properties of the final polymer can be changed. The prepolymerization step is preferably carried out in slurry. Therefore, the prepolymerization step can be carried out in a loop reactor.

[0107] Then, the prepolymerization is preferably carried out in an inert diluent, which is generally a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low-boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of these hydrocarbons.

[0108] The temperature in the prepolymerization step is usually from 0 to 90°C, preferably from 20 to 80°C, more preferably from 45 to 75°C.

[0109] The pressure is not critical and is generally 1 to 150 bar, preferably 40 to 80 bar.

[0110] The amount of monomer is usually such that 0.1 to 1000 grams of monomer are polymerized per gram of solid catalyst component in the prepolymerization step. As known to those skilled in the art, the catalyst particles recovered from the continuous prepolymerization reactor do not all contain the same amount of prepolymer. On the contrary, each particle has its own characteristic amount, which depends on the residence time of the particle in the prepolymerization reactor. Because some particles stay in the reactor for a relatively long time, and some stay for a relatively short time, the amount of prepolymer on different particles is also different, and some single particles may contain the amount of prepolymer beyond the above range. However, the average amount of prepolymer on the catalyst is usually within the above range.

[0111] As is known in the art, the molecular weight of the prepolymer can be controlled by hydrogen.In addition, antistatic additives can be used to prevent the particles from sticking to each other or to the reactor walls, as disclosed in WO-A-96 / 19503 and WO-A-96 / 32420.

[0112] When there is a prepolymerization step, the catalyst components are preferably all introduced into the prepolymerization step. However, when the solid catalyst component and the cocatalyst can be fed separately, it is possible that only a part of the cocatalyst is introduced into the prepolymerization stage, while the rest is introduced into the subsequent polymerization stage. Moreover, in this case, it is necessary to introduce so much cocatalyst into the prepolymerization stage in order to obtain a sufficient polymerization reaction therein.

[0113] It is to be understood that within the scope of the present invention the amount of polymer produced in the prepolymerisation is within 1.0 to 5.0 wt% relative to the final metallocene catalysed mMDPE. This can be counted as part of the first polyethylene component (A).

[0114] catalyst

[0115] The metallocene-catalyzed mMDPE of the present invention is mMDPE prepared using a metallocene catalyst. The metallocene catalyst comprises a metallocene complex and a cocatalyst. The metallocene compound or complex is also referred to herein as an organometallic compound (C).

[0116] The organometallic compound (C) comprises a transition metal (M) from Groups 3 to 10 of the Periodic Table of Elements (IUPAC 2007) or from the actinides or lanthanides.

[0117] According to the present invention, the term "organometallic compound (C)" includes any metallocene or non-metallocene compound of a transition metal, which carries at least one organic (coordinating) ligand and exhibits catalytic activity alone or together with a cocatalyst. Transition metal compounds are well known in the art, and the present invention encompasses compounds of metals from Groups 3 to 10, e.g. Groups 3 to 7, or Groups 3 to 6, e.g. Groups 4 to 6, of the Periodic Table (IUPAC 2007), as well as lanthanides or actinides.

[0118] In one embodiment, the organometallic compound (C) has the following formula (I):

[0119]

[0120] Wherein each X is independently a halogen atom, C 1-6 -alkyl, C 1-6 - alkoxy, phenyl or benzyl;

[0121] Each Het is independently a monocyclic heteroaromatic group containing at least one heteroatom selected from O or S; L is -R'2Si-, wherein each R' is independently a C substituted by an alkoxy group having 1 to 10 carbon atoms; 1-20 -Hydrocarbon or C 1-10 -alkyl;

[0122] M is Ti, Zr or Hf;

[0123] Each R 1 Same or different, is C 1-6 -alkyl or C 1-6 - alkoxy;

[0124] Each n is 1 to 2;

[0125] Each R 2 Same or different, is C 1-6 -alkyl, C 1-6 -alkoxy or -Si(R)3 group;

[0126] Each R is optionally replaced by 1 to 3 C 1-6 -alkyl substituted C 1-10 - alkyl or phenyl; and

[0127] Each p is from 0 to 1.

[0128] Preferably, the compound of formula (I) has the structure

[0129]

[0130] Wherein each X is independently a halogen atom, C 1-6 -alkyl, C 1-6- alkoxy, phenyl or benzyl;

[0131] L is Me2Si-;

[0132] Each R 1 Same or different and C 1-6 - alkyl, for example methyl or tert-butyl;

[0133] Each n is 1 to 2;

[0134] R 2 is -Si(R)3alkyl; each p is 1;

[0135] Each R is C 1-6 -alkyl or phenyl.

[0136] Highly preferred complexes of formula (I) are

[0137]

[0138] Most preferably, the complex dimethylsilanediylbis[2-(5-trimethylsilylfuran-2-yl)-4,5-dimethylcyclopentadien-1-yl]zirconium dichloride is used.

[0139] More preferably, the polyethylene components (A) and (B) of the metallocene-catalyzed mMDPE are prepared using the same metallocene catalyst, ie in the presence of the same metallocene catalyst.

[0140] To form the catalyst, a cocatalyst, also called an activator, well known in the art is used. Cocatalysts containing Al or B are well known and can be used here. Preferably, an aluminoxane (such as MAO) or a boron-based cocatalyst (such as a borate) is used.

[0141] In contrast to Ziegler Natta catalysis, polyethylene copolymers made using single-site catalysis have characteristics that distinguish them from Ziegler Natta materials. In particular, the comonomer distribution is more uniform. This can be shown using TREF or Crystaf techniques. Catalyst residues can also be indicative of the catalyst used. For example, Ziegler Natta catalysts do not contain Zr or Hf Group (IV) metals.

[0142] The metallocene-catalyzed mMDPE may contain additives and / or fillers.

[0143] Optional additives and fillers and the amounts used are customary in the field of film applications. Examples of such additives are, inter alia, antioxidants, UV stabilizers, pigments, fillers, antistatic additives, antiblocking agents, nucleating agents, acid scavengers and polymer processing aids (PPAs).

[0144] In one embodiment of the present invention, the metallocene-catalyzed mMDPE does not contain a fluorine-based polymer processing agent (PPA).

[0145] In this embodiment, the metallocene-catalyzed mMDPE of the present invention may be blended with 0.1 to 3.0 wt% of a polyethylene wax based on the total weight of the blend.

[0146] In this embodiment, polyethylene wax is added in place of the fluorine-based polymer processing agent.

[0147] The amount of polyethylene wax added is preferably in the range of 0.5 to 2.8 wt%, more preferably 0.8 to 2.6 wt%, even more preferably 1.0 to 2.5 wt%, based on the total weight of the blend of wax and mMDPE.

[0148] The polyethylene wax in the present invention refers to a homopolymer of ethylene, a copolymer of ethylene and α-olefin, or a blended product thereof.

[0149] The polyethylene wax may have a weight average molecular weight (determined by a viscosity method) of 1,000 to 20,000 g / mol, preferably 1,500 to 15,000, and more preferably 2,000 to 10,000.

[0150] Polyethylene wax can be 960kg / m 3 Or higher high-density polyethylene wax, density 940-950kg / m 3 Medium density polyethylene wax or density 930kg / m 3 Preferably, a low-density polyethylene wax with a density of 900 to 930 kg / m 3 Range of low density polyethylene waxes.

[0151] The density is measured according to JIS K6760 or ISO 1183 (depending on the manufacturer of the wax).

[0152] Suitable polyethylene waxes may have a melt viscosity measured at 140°C in the range of 15 to 10 000 mPa.s, preferably in the range of 20 to 8 000 mPa.s, more preferably in the range of 50 to 7 000 mPa.s, even more preferably in the range of 60 to 6 500 mPa.s.

[0153] The melt viscosity can be measured according to DIN 53019.

[0154] The polyethylene wax may alternatively or additionally be characterized by a dropping point in the range of 115 to 140°C, preferably 118 to 135°C, more preferably 120 to 132°C, measured according to ASTM 3954 and / or a softening point in the range of 90 to 140°C, preferably 92 to 135°C, more preferably 95 to 130°C, still more preferably 98 to 125°C, measured according to JIS K 2207.

[0155] Polyethylene waxes can be prepared by using a Ziegler-Natta catalyst or by using a metallocene catalyst.

[0156] Such polyethylene waxes are commercially available.

[0157] Specific examples of commercially available polyethylene waxes include Hi-WAX series and Excerex series from Mitsui Chemicals, or Licowax PE series and Licocene PE series from Clarinat.

[0158] As mentioned above, the metallocene-catalyzed mMDPE or the blend of metallocene-catalyzed mMDPE and polyethylene wax according to the present invention provides improved mechanical properties, in particular tensile modulus and dart drop (impact strength).

[0159] Therefore, the present invention further relates to a film comprising at least one layer comprising the above metallocene-catalyzed mMDPE or a blend of the above metallocene-catalyzed mMDPE and a polyethylene wax.

[0160] membrane

[0161] The film of the present invention comprises at least one layer comprising a metallocene-catalyzed mMDPE as defined above (respectively a blend thereof with a polyethylene wax). The film may be a monolayer film comprising the polyethylene composition defined above or a multilayer film wherein at least one layer comprises the polyethylene composition defined above. The terms "monolayer film" and "multilayer film" have well-known meanings in the art.

[0162] Preferably, at least one layer of the present invention comprises at least 50 wt%, more preferably at least 60 wt%, even more preferably at least 70 wt%, yet more preferably at least 80 wt% of the metallocene-catalyzed mMDPE (respectively its blend with a polyethylene wax) of the present invention. Most preferably, said at least one layer of the film of the present invention consists of a metallocene-catalyzed mMDPE (respectively its blend with a polyethylene wax).

[0163] The film is preferably produced by any conventional film extrusion process known in the art, including cast film and blown film extrusion. Most preferably, the film is a blown film or cast film, especially a blown film. For example, blown film is produced by extruding through an annular die and blowing into a tubular film by forming bubbles, which burst between rollers after solidification. The film can then be cut, cut or converted (e.g., folded) as required. Traditional film production techniques can be used in this regard. If preferred blown film or cast film is a multilayer film, each layer is typically coextruded. The technician will know suitable extrusion conditions.

[0164] The film according to the present invention may be subjected to post-treatment processes, such as surface modification, lamination or orientation processes, etc. Such orientation processes may be uniaxial (MDO) or biaxial orientation, wherein uniaxial orientation is preferred.

[0165] In another preferred embodiment, the film is non-oriented.

[0166] Preferred films according to the invention are monolayer blown films.

[0167] The thickness of the single-layer film of the present invention may be 20 to 120 μm, preferably 30 to 100 μm, and more preferably 35 to 80 μm.

[0168] The film according to the invention has the following properties:

[0169] a) the film of the invention has a dart drop impact strength (DDI) of at least 700 g to at most 2000 g, preferably 800 g to at most 1500 g, more preferably 850 g to at most 1100 g, measured according to ISO 7765-1:1988 on a 40 μm single layer test blown film, and

[0170] b) The films according to the invention have good stiffness (tensile modulus measured on 40 μm monolayer test blown films according to ISO 527-3), ie >250 MPa (in both directions).

[0171] Thus, the tensile modulus of the films according to the invention (measured on 40 μm monolayer test blown films according to ISO 527-3) is in the range of >250 MPa to 1000 MPa, preferably 300 MPa to 600 MPa in the machine direction (MD) and in the range of 300 MPa to 1000 MPa, preferably 350 MPa to 600 MPa in the transverse direction (TD).

[0172] The films according to the invention are very suitable for use in a variety of packaging applications.

[0173] Furthermore, the film according to the invention can be used as a layer in a multilayer polyethylene-based blown film, preferably as a core layer in a multilayer polyethylene-based blown film.

[0174] The present invention will be further described with reference to the following non-limiting examples.

[0175] Determination method

[0176] Unless otherwise stated in the description or the experimental section, the following methods were used to determine the properties of the polymers (including parts and components thereof) and / or any sample preparations thereof as described in the text or in the experimental section.

[0177] Melt flow rate

[0178] The melt flow rate (MFR) is determined according to ISO 1133 and is expressed in g / 10 min. The MFR is an indicator of the flowability of the polymer and therefore of its processability. The MFR of polyethylene is determined at 190°C. The MFR can be determined at different loads, for example 2.16 kg (MFR2), 5 kg (MFR5) or 21.6 kg (MFR 21 ).

[0179] Calculation of MFR2 of component B and part (A-2)

[0180] logA=x·logB+(1-x)·logC

[0181]

[0182] For component B:

[0183] B = MFR2 of component (A)

[0184] C = MFR2 of component (B)

[0185] A = Final MFR2 of multimodal mMDPE (blend)

[0186] X = weight fraction of component (A).

[0187] For part (A-2):

[0188] B = MFR2 of the first part (A-1)

[0189] C = MFR2 of the second part (A-2)

[0190] A = Final MFR2 of cyclic polymer (= component (A)) (mixture)

[0191] X = weight fraction of the first part (A-1).

[0192] density

[0193] The density of polymers is measured according to ISO 1183 and is expressed in kg / m 3Given, the sample preparation was carried out according to ISO 1872-2.

[0194] GPC

[0195] The average molecular weight (M z 、M w and M n ), molecular weight distribution (MWD) and its breadth described by the polydispersity index PDI = Mw / Mn (where Mn is the number average molecular weight and Mw is the weight average molecular weight) are calculated by gel permeation chromatography (GPC) using the following formula:

[0196]

[0197] For a constant elution volume interval ΔV i , where A i and M i and elution volume V i The associated chromatographic peak slice area and the polyolefin molecular weight (MW), where N equals the number of data points obtained from the chromatogram between the integration limits.

[0198] A high temperature GPC instrument equipped with an infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain)) and equipped with 3x Agilent-PLgel Olexis and 1x Agilent-PLgel Olexis Guard columns was used. 1,2,4-Trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol was used as solvent and mobile phase. The chromatographic system was operated at a constant flow rate of 1 mL / min at 160°C. 200 μL of sample solution was injected for each analysis. Data collection was performed using Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0199] The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11500 kg / mol. The PS standards were dissolved at room temperature for several hours. The conversion of polystyrene peak molecular weight to polyolefin molecular weight was accomplished by using the Mark Houwink equation and the following Mark Houwink constants:

[0200] K PS =19x 10 -3 mL / g, α PS =0.655

[0201] K PE =39x 10-3 mL / g, α PE =0.725

[0202] K PP =19x 10 -3 mL / g, α PP =0.725

[0203] A third-order polynomial fit was used to fit the calibration data.

[0204] All samples were prepared in the concentration range of 0.5-1 mg / ml and dissolved at 160°C for 2.5 hours for PP or 3 hours for PE with continuous gentle shaking.

[0205] To exclude the influence of additives such as irganox 1010, irgafos 168 or some other low molecular weight oligomers, the low molecular weight integration limit was set at the valley between the antioxidant peak and the polymer peak (logM of the analyzed sample was about 2.8 (PE equivalent)).

[0206] Dart Drop Intensity (DDI): Determination of impact resistance by free falling dart method

[0207] DDI was measured according to ISO 7765-1:1988 / Method A on films (non-oriented films and laminates) produced as shown below. This test method covers the determination of the energy that will cause film failure under specified conditions of impact with a dart falling freely from a specified height, which will cause 50% of the test specimens to fail (Step Method A). A uniform increment of the missile mass was used during the test, and after each specimen test, the missile weight was reduced or increased by a uniform increment depending on the observed result (failure or no failure) of the specimen.

[0208] Standard conditions:

[0209] Adjustment time: >96h at 50±2℃±10%rh

[0210] Test temperature: 23℃

[0211] Dart head material: phenolic resin

[0212] Dart diameter: 38mm

[0213] Drop height: 660mm

[0214] result:

[0215] Impact failure weight - 50% [g]

[0216] Tensile modulus

[0217] The tensile tests were carried out according to ISO 527-3, and in addition the modulus of elasticity (secant modulus between 0.05% and 0.25% elongation) was determined. Type 2 (parallel-sided specimens) specimens were used.

[0218] During the test, the specimen is extended along its long axis and the tensile properties are determined at a constant test speed (crosshead speed) until the specimen breaks. During this procedure, the load borne by the specimen and the elongation measured by the crosshead are measured.

[0219] Standard conditions:

[0220] Adjustment time: >96h at 50±2℃±10%rh

[0221] Test temperature: 23℃

[0222] Clamping distance: 100mm

[0223] Gauge length: 100mm

[0224] Secant modulus: 0.05%-0.25%

[0225] Test speed modulus: 1mm / min

[0226] Test speed: 200mm / min

[0227] Membrane sample preparation

[0228] Film samples were produced using a W&H semi-commercial production line. Films with a thickness of 40 μm were produced using BUR 1:3. The melt temperature was ~222°C, and the frost line distance was 700 mm, the screw speed was 126 rpm, and the discharge speed was 18.8 m / min.

[0229] Example:

[0230] Catalyst Example: Catalyst Preparation of CAT1 for Examples IE1 and IE2 of the Present Invention and Comparative Examples CE1 and CE2:

[0231] SiO2 loading:

[0232] 10 kg of silica (PQ Corporation ES757, calcined at 600°C) was added from a feed bucket and inerted in the reactor until the O2 level reached less than 2 ppm.

[0233] Preparation of MAO / tol / MC:

[0234] At 25°C (oil circulation temperature) and 95rpm stirring, a 30wt% MAO toluene solution (14.1kg) was added from a balance to another reactor, followed by toluene (4.0kg). After adding toluene, the stirring speed was increased from 95rpm to>200rpm, with a stirring time of 30 minutes. Metallocene racemic-dimethylsilanediylbis{2-(5-(trimethylsilyl)furan-2-yl)-4,5-dimethylcyclopentadiene-1-yl}zirconium dichloride 477g was added from a metal cylinder, followed by 4kg toluene rinse (total toluene was 8.0kg). The reactor stirring speed was changed to 95rpm for MC feeding, returned to 200rpm and continued for 3h reaction time. After the reaction time, the MAO / tol / MC solution was transferred to a feed container.

[0235] Preparation of catalyst:

[0236] The reactor temperature was set to 10°C (oil circulation temperature) and stirring was adjusted to 40 rpm during the addition of MAO / tol / MC. MAO / tol / MC solution (22.2 kg) was added over 205 min, followed by a stirring time of 60 min (oil circulation temperature set to 25°C). After stirring, the "dry mix" was stabilized at 25°C (oil circulation temperature) for 12 h with a stirring speed of 0 rpm. The reactor was rotated 20° (back and forth) and stirred several times per hour at a speed of 5 rpm.

[0237] After stabilization, the catalyst was dried at 60°C (oil circulation temperature) for 2 h under a 2 kg / h nitrogen flow, followed by drying under vacuum for 13 h (same nitrogen flow rate, stirring at 5 rpm). The dried catalyst was sampled and the HC content was measured using a Sartorius moisture analyzer (model MA45) in a glove box using thermogravimetry. The target HC level was <2% (actual 1.3%).

[0238] Catalyst Example: Catalyst Preparation of CAT2 of CE3

[0239] ZN catalyst prepared according to Example 1 of EP 1378528: The catalyst was used with triethylaluminium co-catalyst such that the Al / Ti molar ratio was about 15.

[0240] polymerization:

[0241] The Borstar pilot plant has a three-reactor set-up (Loop 1 – Loop 2 – GPR1) and a prepolymerization loop reactor.

[0242] Table 1: Aggregation conditions for IE1, IE2, CE1 to CE3

[0243]

[0244]

[0245] The polymer was mixed with 0.027 wt% FX 5922 (3M dynamic polymer processing additive), 0.05 wt% Irganox 1010 FF (BASF) and 0.20 wt% Irgafos 168 FF (BASF), compounded and extruded on a ZSK 57 twin screw extruder, where the wt% is relative to the total weight of the composition (total of mMDPE powder + additives = 100%). The melt temperature was 224°C and the production rate was 221 kg / h.

[0246] For Example 3 of the present invention, IE3 compounded the base polymer IE2 of Table 1 with 0.05 wt% Irganox 1010 FF (BASF), 0.20 wt% Irgafos 168 FF (BASF) and 2.0 wt% Excerex 40800 (Mitsui) as PPA instead of FX 5922, wherein the wt% is relative to the total weight of the composition (the sum of mMDPE powder + additives = 100%).

[0247] Table 2: Material properties

[0248] Material IE1 IE2 IE3 CE1 CE2 CE3 <![CDATA[MFR2 (g / 10 min) (final)]]> 0.6 0.6 0.6 0.5 0.7 0.5 <![CDATA[MFR 21 (g / 10min)]]> 26.3 33.6 35.9 17.9 17.9 40.0 <![CDATA[MFR 21 / MFR2(FRR)]]> 43.1 59.9 56.2 35.8 25.6 80.0 <![CDATA[Density (kg / m 3 )(Final)]]> 928.4 927.3 927.8 924.8 930.9 924.0 Mz(g / mol) 291000 289000 293000 nm nm 672500 Mw(g / mol) 110000 105000 105000 nm nm 141500 Mn(g / mol) 24600 14800 14000 nm nm 11350 Mz / Mw 2.65 2.75 2.79 - - 4.75 Mw / Mn(MWD) 4.47 7.09 7.50 - - 12.47 MFR(A-1) / MFR(A) 0.7 0.2 0.2 1.1 8.6 0.9 MFR(A) / MFR(final) 52.0 95.6 95.6 9.4 0.7 600 Density(A)-Density(final) 34.2 39.9 39.4 13.8 na 26.0

[0249] nm not measured

[0250] naNot applicable

[0251] Single layer blown film

[0252] Table 3: Properties of blown films

[0253] IE1 IE2 IE3 CE1 CE2 CE3 TM / MD MPa 359 356 358 235 344 316 TM / TD MPa 409 384 429 245 354 407 DDI g 949 1055 865 668 99 180

[0254] As can be seen from Table 3 above, films based on the composition using metallocene-catalyzed mMDPE according to the present invention have improved stiffness and / or impact resistance.

[0255] Even IE3 based on metallocene-catalyzed mMDPE according to the invention and using polyethylene wax as PPA instead of fluorinated PPA has improved stiffness and / or impact resistance.

Claims

1. A metallocene-catalyzed multimodal medium density polyethylene (mMDPE) consisting of (i) 35.0 to 55.0 wt% of a polyethylene component (A) based on mMDPE, and (ii) 45.0 to 65.0 wt% of a polyethylene component (B) based on mMDPE, wherein the polyethylene polymer component (A) has 930 to 975 kg / m 3 Density in the range (ISO 1183), MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 10.0 to 200.0 g / 10 min; The polyethylene component (B) has 870 to 910 kg / m 3 Density in the range (ISO 1183), MFR2 in the range of 0.0001 to 0.5 g / 10 min (190°C, 2.16 kg, ISO 1133); Among them, metallocene-catalyzed medium-density polyethylene (mMDPE) has 915 to 945 kg / m 3 Density in the range (ISO 1183), MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 0.1 to 2.0 g / 10 min, and MFR in the range of 37 to 75 21 (190℃, 21.6kg, ISO 1133) and MFR2 (190℃, 2.16kg, ISO 1133) Ratio MFR 21 / MFR2, and The difference between the density of the polyethylene component (A) and the density of the final metallocene-catalyzed mMDPE (Δdensity: density of the polyethylene component (A) - density of the final metallocene-catalyzed mMDPE) is in the range of 28 to 70 kg / m 3 within the range.

2. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to claim 1, wherein the metallocene-catalyzed mMDPE has at least one, preferably two or more, more preferably all of the properties a) to d): a) 918 to 940 kg / m 3 , preferably 920 to 935 kg / m 3 Density within the range (ISO1183), b) an MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 0.2 to 1.8 g / 10 min, preferably 0.3 to 1.5 g / 10 min, more preferably 0.4 to 1.0 g / 10 min, c) in the range of 10.0 to 80.0 g / 10 min, preferably in the range of 15.0 to 70.0 g / 10 min, More preferably, the MFR is in the range of 20.0 to 60.0 g / 10 min, most preferably in the range of 22.0 to 50.0 g / 10 min. 21 (190℃, 21.6kg, ISO 1133), d) a flow rate ratio (FRR) MFR in the range of 40 to 70, preferably 42 to 65 21 / MFR2.

3. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to claim 1 or 2, wherein the metallocene-catalyzed mMDPE has The molecular weight distribution (MWD) Mw / Mn was between 3.5 and 12.0 as measured by GPC as described in the experimental section. It is preferably in the range of 4.0 to 10.0, more preferably in the range of 4.2 to 8.

0.

4. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims 1 to 3, wherein the metallocene-catalyzed mMDPE further has one or more, or preferably all, of the following properties: The weight average molecular weight Mw is at least 90000 g / mol, preferably in the range of 92000 to 140000 g / mol, more preferably 95000 to 130000 g / mol, still more preferably 100000 to 120000 g / mol, The z-average molecular weight Mz is between 200,000 and 500,000 g / mol, preferably between 230,000 and 400,000 g / mol, More preferably in the range of 250000 to 350000 g / mol, The Mz / Mw ratio may be in the range of 2.0 to 4.0, preferably 2.2 to 3.5, more preferably 2.3 to 3.2, wherein Mw and Mz are measured by GPC as described in the experimental part.

5. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims 1 to 4, wherein in the metallocene-catalyzed mMDPE, The polyethylene component (A) has a molecular weight of 935 to 972 kg / m 3 , preferably 940 to 970 kg / m 3 , more preferably 945 to 968 kg / m 3 , still more preferably 950 to 968 kg / m 3 Density within range (ISO1183) and an MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 15.0 to 150 g / 10 min, preferably 20.0 to 100 g / 10 min, more preferably 22.0 to 90.0 g / 10 min, and The polyethylene component (B) has a molecular weight of 875 to 908 kg / m 3 , preferably 880 to 906 kg / m 3 , more preferably 885 to 904 kg / m 3 Density in the range (ISO1183) and 0.001 to 0.1 g / 10 min, An MFR2 (190° C., 2.16 kg, ISO 1133) in the range of 0.003 to 0.08 g / 10 min is preferred, more preferably 0.005 to 0.05 g / 10 min.

6. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims 1 to 5, wherein in the metallocene-catalyzed mMDPE, the polyethylene component (A) and / or (B) may be a homopolymer or an ethylene copolymer, Preferably, both components are ethylene copolymers, or the polyethylene component (A) is a homopolymer and the polyethylene component (B) is a copolymer, or vice versa, the polyethylene component (A) is a copolymer and the polyethylene component (B) is a homopolymer, more preferably, the polyethylene component (A) is an ethylene-1-butene copolymer and the polyethylene component (B) is an ethylene-1-hexene copolymer or homopolymer.

7. A metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims 1 to 6, wherein in the metallocene-catalyzed mMDPE, the polyethylene component (B) consists of a single ethylene copolymer or a single ethylene homopolymer and the polyethylene component (A) consists of a single ethylene homopolymer or copolymer, or the polyethylene component (A) can be an ethylene homopolymer or copolymer mixture, which comprises, preferably consists of, a first ethylene polymer portion (A-1) and a second ethylene polymer portion (A-2), wherein both portions are either homopolymers or copolymers.

8. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to claim 7, wherein the polyethylene component (A) is a polyethylene copolymer mixture comprising, preferably consisting of, a first ethylene copolymer fraction (A-1) and a second ethylene copolymer fraction (A-2), wherein the ethylene polymer portion (A-1) has MFR2 (190°C, 2.16 kg, 400 g / 10 min) in the range of 3.0 to 80.0 g / 10 min, preferably 5.0 to 60.0 g / 10 min, more preferably 8.0 to 40.0 g / 10 min, even more preferably 10.0 to 30.0 g / 10 min ISO 1133), and 930 to 970 kg / m 3 , preferably 940 to 965 kg / m 3 , more preferably 950 to 960 kg / m 3 Density within the range (ISO1183) and The ethylene polymer portion (A-2) has an MFR2 (190°C, 2.16 kg, ISO 1133) in the range of 10.0 to 1000 g / 10 min, preferably 20.0 to 800 g / 10 min, more preferably 30.0 to 700 g / 10 min, more preferably 35.0 to 600 g / 10 min, most preferably 40.0 to 500 g / 10 min, and 930 to 980 kg / m 3 , preferably 940 to 980 kg / m 3 , more preferably 950 to 979 kg / m 3 Density within the range (ISO1183).

9. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to claim 8, wherein the ratio of the MFR2 of the ethylene polymer fraction (A-1) to the MFR2 of the polyethylene component (A) is in the range of 0.10 to 0.85, preferably 0.15 to 0.

75.

10. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims, wherein the ratio of the MFR2 of the polyethylene component (A) to the MFR2 of the final metallocene-catalyzed mMDPE is in the range of 10.0 to 500, preferably 20.0 to 300, more preferably 30.0 to 200, even more preferably 40.0 to 100.

11. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims, wherein the difference between the density of the polyethylene component (A) and the density of the final metallocene-catalyzed mMDPE (Δdensity: density of polyethylene component (A) - density of the final metallocene-catalyzed mMDPE) is in the range of 30 to 55 kg / m 3 , preferably 32 to 45 kg / m 3 within the range.

12. A metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims, wherein the mMDPE is produced in the presence of a metallocene complex of formula (I): Wherein each X is independently a halogen atom, C 1-6 -alkyl, C 1-6 - alkoxy, phenyl or benzyl; Each Het is independently a monocyclic heteroaromatic group containing at least one heteroatom selected from O or S; L is -R'2Si-, wherein each R' is independently a C substituted with an alkoxy group having 1 to 10 carbon atoms. 1-20 -Hydrocarbon or C 1-10 -alkyl; M is Ti, Zr or Hf; Each R1 is the same or different, is C 1-6 -alkyl or C 1-6 - alkoxy; Each n is 1 to 2; Each R2 is the same or different, and is C 1-6 -alkyl, C 1-6 -alkoxy or -Si(R)3 group; Each R is optionally replaced by 1 to 3 C 1-6 -alkyl substituted C 1-10 - alkyl or phenyl; and Each p is from 0 to 1.

13. The metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims, wherein the mMDPE is blended with 0.1 to 3.0 wt% of a polyethylene wax, based on the total weight of the blend.

14. A film comprising the metallocene-catalyzed multimodal medium density polyethylene (mMDPE) according to any one of the preceding claims 1 to 12 or the blend according to claim 13.

15. The film of claim 14, wherein the film a) a dart drop impact strength (DDI) of at least 700 g to at most 2000 g, preferably 800 g to at most 1500 g, more preferably 850 g to at most 1100 g, measured on a 40 μm single layer test blown film according to ISO 7765-1:1988, and b) tensile modulus (measured on 40 μm monolayer test blown films according to ISO 527-3) in the range of >250 MPa to 1000 MPa, preferably 300 MPa to 600 MPa in the machine direction (MD) and in the range of 300 MPa to 1000 MPa, preferably 350 MPa to 600 MPa in the transverse direction (TD).

16. Use of the film according to any of the preceding claims 14 to 15 in packaging applications or as a layer in a multilayer polyethylene-based blown film, preferably as a core layer in a multilayer polyethylene-based blown film.

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