Polyethylene copolymer for a film layer

Abstract

The present invention relates to a metallocene-catalysed multimodal polyethylene copolymer (P), to the use of the multimodal copolymer (P) of ethylene in film applications and to a film comprising the polymer composition of the invention.

Description

[0001] POLYETHYLENE COPOLYMER FOR A FILM LAYER

[0002] The present invention relates to a metallocene-catalysed multimodal polyethylene copolymer (P), to the use of the multimodal polyethylene copolymer (P) in film applications and to a film comprising the polymer composition of the invention.

[0003] State of the art mLLDPE (metallocene catalysed linear low density polyethylene) is widely used everywhere in daily life, like packaging, due to its excellent cost I performance ratios. One of the famous drawback is the narrow molecular weight distribution and therefore less shear thinning, which leads to the problem in film conversion, e.g. limiting the throughput. In addition, higher throughputs in the plastic processing industry are further limited by melt flow instabilities, which change the appearance and properties of the final product and have economic and also environmental consequences.

[0004] Unimodal mLLDPEs are usually used for film application. Unimodal LLDPEs have for instance good optical properties, like low haze, but for instance, the melt processing of such polymers is not satisfactory in production point of view and may cause quality problems of the final product as well. Multimodal mLLDPEs with two or more different polymer components are better to process, but e.g. melt homogenization of the multimodal PE may be problematic resulting to inhomogeneous final product evidenced e.g. with high gel content of the final product.

[0005] Films produced from mLLDPE resins are known for their excellent mechanical properties, such as, for example, impact resistance measured in the dart drop impact (DDI) test, but often at the expense of poor extrusion processability, melt strength, and bubble stability.

[0006] In some end-uses, such as blown film applications, it can be beneficial to have the properties of a metallocene catalyzed LLDPE copolymers, but with improved processability, melt strength, and bubble stability.

[0007] One common solution for improving the processability of a polymer melt is the addition of so-called processing aids. Unfortunately, the majority of suitable processing aids are fluorobased polymers, which are due to their fluoro content under concerns in view of human and environmental health.

[0008] As mentioned above, the processability is also influenced by the molecular structure. Multimodal PE polymers with two or more different polymer components are known to be better to process, but e.g. melt homogenization of the multimodal PE may be problematic resulting to inhomogeneous final product evidenced e.g. with high gel content of the final product. Multimodal PE polymers are known in the art.

[0009] WO 2021009189, WO 2021009190 and WO 2021009191 of Borealis disclose a process for preparing multimodal PE polymers in two loop reactors and one 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.

[0010] The polymers produced in the Examples have a total density of 938 or 939 kg / m3. The MFR2 (190°C, 2.16 kg, ISO 1133) of the polymer components produced in the first loop reactor is about 22 or 23 g / 10 min.

[0011] Film properties, like impact strength, sealing initiation temperature or processing parameters, like melt pressure are not mentioned at all.

[0012] Also WO 2021009192 discloses such a process. The polymer produced in the Examples has an even higher density of 951 kg / m3. The MFR2 (190°C, 2.16 kg, ISO 1133) of the polymer component produced in the first loop is 32 g / 10 min.

[0013] Film properties, like impact strength, sealing initiation temperature or processing parameters, like melt pressure are not mentioned at all.

[0014] WO 2023012254 discloses a process for preparing multimodal PE polymers in two loop reactors and one gas phase reactor in the presence of a silica supported metallocene catalyst based on the metallocene complex Rac-dimethylsilanediylbis{2-(5- (trimethylsilyl)furan-2-yl)-4,5-dimethylcyclopentadien-1-yljzirconium dichloride.

[0015] The polymer fractions produced in the two loops in the inventive example have only slightly different MFR2, resulting in a ratio MFR2(A-2) / MFR2(A-1) of 1.04, which is due to a more or less unimodal polymer design in the two loops.

[0016] Film properties, like impact strength and sealing initiation temperature are not mentioned.

[0017] Also WO 2023012256 discloses a process for preparing multimodal PE polymers in two loop reactors and one gas phase reactor in the presence of a silica supported metallocene catalyst based on the metallocene complex Rac-dimethylsilanediylbis{2-(5- (trimethylsilyl)furan-2-yl)-4,5-dimethylcyclopentadien-1-yljzirconium dichloride.

[0018] The polymer fractions produced in the two loops in the inventive example have only slightly different MFR2, resulting in a ratio MFR2(A-2) / MFR2(A-1) in the range of 1.04 to 2.8, which is due to a more or less unimodal polymer design in the two loops. Sealing properties are not mentioned.

[0019] EP3538572 describes ethylene-based polymers, which show improved processability and melt strength combined with good impact strength and tear strength. These polymers are made by a dual catalyst system and have an ATREF profile characterized by a peak ATREF temperature (temperature of the highest peak on the ATREF curve) in a range from about 68 to about 78 °C. The inventive examples show only one significant peak on the ATREF curve. Example 12, being a Comparative example, shows a trimodal TREF profile, but no films were made out of this polymer.

[0020] According to the description, films made of such polymers can contain one or more additives, non-limiting examples of which are an antioxidant, an acid scavenger, an antiblock additive, a slip additive, a colorant, a filler, a processing aid, a UV inhibitor, and the like, as well as combinations thereof.

[0021] It is desirable to maximise the processability of multimodal PE polymers, which have good processability without the need of processing aid addition. It goes without saying that any manipulation of the polymer properties to enable improved processability should not be detrimental to the final film properties.

[0022] The inventors have now found that a metallocene-catalysed multimodal polyethylene copolymer (P) made with a specific metallocene catalyst and having a specific polymer design has at the same time good processability (in terms of melt pressure) and low sealing initiation temperature, while keeping mechanical properties, like impact strength on a high level.

[0023] In accordance with this invention, the ethylene polymers described herein have a unique ATREF profile.

[0024] Description of the invention The present invention is therefore directed to a metallocene-catalysed multimodal polyethylene copolymer (P) being a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, whereby the multimodal polyethylene copolymer (P) has a density (ISO 1183) in the range of from 910 to 925 kg / m3, a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min, and whereby the multimodal polyethylene copolymer (P) is furthermore characterized by an ATREF profile, determined as is described in the experimental part, showing a trimodal chemical composition distribution (CCD), which is composed of a) 35.0 wt.-% to 50.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a low crystalline fraction (LCF), which elutes between > 35 to 70 °C, b) 20.0 wt.-% to 37.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a medium crystalline fraction (MCF), which elutes between > 70 to 90 °C and c) 3.0 wt.-% to 30.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a high crystalline fraction (HCF), which elutes between > 90 and 105 °C, d) whereby the sum of low crystalline fraction (LCF), medium crystalline fraction (MCF) and high crystalline fraction (HCF) add up to at least 95.0 wt.-%, e) the remaining percentage of the multimodal polyethylene copolymer (P) elutes at a temperature < 35 °C, and whereby the ratio of medium crystalline fraction to high crystalline fraction MCF / HCF is in a range of from 0.6 and 3.0.

[0025] In an embodiment of the present invention, the multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, with a density (ISO 1183) in the range of from 910 to 925 kg / m3, a MFR2(190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min and a total comonomer content, determined by quantitative12C{1H} NMR as described in the experimental part, in the range of from 1.1 to 8.0 mol-%, which consists of an in-situ-blend of

[0026] (i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A-

[0027] 1) and an ethylene polymer fraction (A-2), and

[0028] (ii) an ethylene copolymer component (B), wherein the ethylene copolymer component (A) is a copolymer of ethylene and one or two Cs-Cs-alpha olefin comonomers with a total comonomer content in the range of from 0.2 to 3.0 mol-%, based on the total weight of the ethylene copolymer component (A), whereby the ethylene polymer fraction (A-1) has a comonomer content, determined by quantitative13C{1H} NMR as described in the experimental part, in the range of from 0.1 to 2.0 mol-%, based on the total weight of the ethylene polymer fraction (A-1), and the ethylene polymer fraction (A-2) has a higher comonomer content than the ethylene polymer fraction (A-1), and wherein the difference between the comonomer content of the ethylene polymer fraction (A-2) and the ethylene polymer fraction (A-1) is in the range of from 0.3 to 3.0 mol- %, whereby the comonomer content of the ethylene polymer fraction (A-2) is calculated according to formula (l-a) cc(A-2) = [cc(A) - x*(cc(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A), cc(A-2) is the calculated comonomer content of ethylene polymer fraction (A-2) cc(A-1) is the comonomer content of the ethylene polymer fraction (A-1) and cc(A) is the comonomer content of the ethylene copolymer component (A) whereby cc(A-1) and cc(A) are determined by quantitative13C{1H} NMR as described in the experimental part, and wherein the ethylene copolymer component (B) is a copolymer of ethylene and one or two Cs-Cs-alpha olefin comonomers the ethylene copolymer component (B) having at least one comonomer being different from that of the ethylene copolymer component (A) and wherein the comonomer content of the ethylene copolymer component (B) is higher than the comonomer content of the ethylene copolymer component (A) whereby the comonomer content of the ethylene copolymer component (B) is calculated according to formula (l-b) cc(B) = [cc(P) - x*(cc(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), cc(B) is the calculated comonomer content of ethylene copolymer component (B), cc(A) is the comonomer content of the ethylene copolymer component (A) and cc(P) is the comonomer content of the multimodal polyethylene copolymer (P), whereby cc(A) and cc(P) are determined by quantitative13C{1H} NMR as described in the experimental part.

[0029] In a further embodiment of the present invention the multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, with a density (ISO 1183) in the range of from 910 to 925 kg / m3and a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min, which consists of an in-situ-blend of

[0030] (i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A- 1) and an ethylene polymer fraction (A-2), and

[0031] (ii) an ethylene copolymer component (B), wherein the ethylene copolymer component (A) has a density (ISO 1183) in the range of from 930 to 950 kg / m3and a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.2 to 500 g / 10 min, wherein the density (ISO 1183) of fractions (A-1) and (A-2) is in the range of from 930 to 950 kg / m3, and the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) is in the range of from 0.1 to 100 g / 10 min, the MFR2 (190°C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) is higher than the MFR2 of ethylene polymer fraction (A-1) and wherein the ratio of the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A- 2) to the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1), MFR2(A- 2) / MFR2(A-1), is in the range of from 4 to 200, wherein the MFR2 of ethylene polymer fraction (A-2) is calculated according to formula (II- a)

[0032] [(logMFS(A) - x * log MF / ?(A - 1)] MFR(A — 2) = 10 (1 -2 -i_x5- 1 wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A),

[0033] MFR(A-2) is the calculated MFR2 of ethylene polymer fraction (A-2)

[0034] MFR(A-1) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) and MFR(A) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A), and wherein the ethylene copolymer component (B) has a lower density and lower MFR2 than ethylene copolymer component (A), wherein the MFR2 is calculated according to formula (I l-b) wherein x is the weight fraction of ethylene copolymer component (A), with respect to the multimodal polyethylene copolymer (P),

[0035] MFR(B) is the calculated MFR2 of ethylene copolymer component (B)

[0036] MFR(P) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of the multimodal polyethylene copolymer (P), and

[0037] MFR(A) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A), and the density is calculated according to formula (III) density(B) = [density(P) - x*(density(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), density(B) is the calculated density of ethylene copolymer component (B), density(A) is the density (ISO 1183) of ethylene copolymer component (A) and density(P) is the density (ISO 1183) of the multimodal polyethylene copolymer (P).

[0038] In another embodiment of the present invention the sealing initiation temperature (SIT) measured as described in the experimental part on 40 pm test blown films made of the multimodal polyethylene copolymer (P) follows in-equation (X)

[0039] SIT < 97 - 30*(MFR2HMW) (X) wherein MFR2HMW is the MFR2 (190 °C, 2.16 kg, ISO 1133) of the ethylene copolymer component (B) as calculated by formula (I l-b) as described above.

[0040] Unexpectedly the multimodal polyethylene copolymer (P) of the invention can be processed into films without the need of processing aid addition and has at the same time a lower sealing initiation temperature compared to bimodal polymers having similar MFR2HMWand density, whereby mechanical properties, especially dart impact strength are kept on a high level.

[0041] The present invention is further directed to a film comprising the multimodal polyethylene copolymer (P) and to the use of this film.

[0042] Definitions Where the term "comprising" is used in the present description and claims, it does not exclude other non-specified 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 of". If hereinafter a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments.

[0043] For the purpose of the present invention the term “consists of an in-situ blend of (i) and (ii)”, does not exclude the presence of any additive, which may be added to the multimodal polyethylene copolymer (P). It only refers to the number of polymer components, i.e. copolymer component (A) and copolymer component (B).

[0044] Whenever the terms "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above.

[0045] Where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an" or "the", this includes a plural of that noun unless something else is specifically stated. Metallocene catalysed multimodal polyethylene copolymer is defined in this invention as multimodal polyethylene copolymer (P), which has been produced in the presence of a metallocene catalyst.

[0046] Polyethylene polymers made using single site, e.g. metallocene catalysis, as opposed to Ziegler Natta catalysis, have characteristic features that allow them to be distinguished from Ziegler Natta materials. In particular, the comonomer distribution is more homogeneous. This can be shown using TREF or Crystaf techniques. Catalyst residues may also indicate the catalyst used. Ziegler Natta catalysts would not contain a Zr or Hf group (IV) metal for example.

[0047] Term “multimodal” in context of multimodal polyethylene copolymer (P) means herein multimodality with respect to the comonomer content and the melt flow rate (MFR) of the ethylene copolymer components (A) and (B), respectively of the ethylene polymer fractions (A-1) and (A-2), i.e. the ethylene copolymer components (A) and (B) as well as the fractions (A-1) and (A-2) have different MFR values and comonomer content. The multimodal polyethylene copolymer (P) can have further multimodality with respect to one or more further properties between the ethylene copolymer components (A) and (B), as will be described later below. For the purpose of the present invention “metallocene catalysed multimodal polyethylene copolymer (P) which consists of an in-situ blend of an ethylene copolymer component (A) and an ethylene copolymer component (B)” means that the multimodal polyethylene copolymer (P) is produced in an at least 2-stage sequential polymerization process, wherein first component (A) is produced and component (B) is then produced in the presence of component (A) in a subsequent polymerization step, yielding the multimodal polyethylene copolymer (P).

[0048] The multimodal polyethylene copolymer (P) of the invention as defined above, below or in claims is also referred herein shortly as “multimodal PE” or “multimodal copolymer (P)”.

[0049] The following preferable embodiments, properties and subgroups of multimodal PE and the ethylene polymer components (A) and (B) thereof, as well as the ethylene polymer fractions (A-1) and (A-2) and the film of the invention including the preferable ranges thereof, are independently generalizable so that they can be used in any order or combination to further define the preferable embodiments of the multimodal PE and the article of the invention.

[0050] Multimodal polyethylene copolymer (P), as well as ethylene copolymer components (A) and (B) and ethylene polymer fractions (A-1) and (A-2)

[0051] The metallocene-catalysed multimodal polyethylene copolymer (P) according to the present invention is characterized by a specific ATREF profile, determined as is described in the experimental part, showing a trimodal chemical composition distribution (CCD).

[0052] The specific ATREF profile shows a) 35.0 wt.-% to 50.0 wt.-%, preferably 38.0 wt.-% to 50.0 wt.-%, more preferably 40.0 wt.- % to 50.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a low crystalline fraction (LCF), which elutes between > 35 to 70 °C, b) 20.0 wt.-% to 37.0 wt.-%, preferably 22.0 wt.-% to 37.0 wt.-%, more preferably 25.0 wt.- % to 37.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a medium crystalline fraction (MCF), which elutes between > 70 to 90 °C and c) 3.0 wt.-% to 30.0 wt.-%, preferably 8.0 wt.-% to 28.0 wt.-%, more preferably 10.0 wt.-% to 26.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a high crystalline fraction (HCF), which elutes between > 90 and 105 °C, d) whereby the sum of low crystalline fraction (LCF), medium crystalline fraction (MCF) and high crystalline fraction (HCF) add up to at least 95.0 wt.-%, preferably to at least 97.0 wt.-% and more preferably to at least 97.5 wt.-%, e) the remaining percentage of the multimodal polyethylene copolymer (P) elutes at a temperature of < 35 °C.

[0053] The sum of low crystalline fraction (LCF), medium crystalline fraction (MCF), high crystalline fraction (HCF) and e), i.e. the part of the multimodal polyethylene copolymer (P) eluting at a temperature < 35 °C, add up to 100 wt.-%.

[0054] The ratio of medium crystalline fraction to high crystalline fraction MCF / HCF is in a range of from 0.6 to 3.0, preferably 0.8 to 2.8 and more preferably 1.0 to 2.6.

[0055] Definition of High crystalline fraction (HCF), Medium crystalline fraction (MCF) and Low crystalline fraction (LCF):

[0056] The high crystalline fraction (HCF) is the amount in wt.-% of the polymer fraction with a crystallization temperature of > 90°C up to 105°C, which mainly contains homopolyethylene chains or chains with a very low branching content.

[0057] The medium crystalline fraction (MCF) is the amount in wt.-% of the polymer fraction with a crystallization temperature between > 70°C to 90°C.

[0058] The low crystalline fraction (LCF) is the amount in wt.-% of the polymer fraction with a crystallization temperature between > 35 to 70°C.

[0059] In an embodiment of the present invention, the metallocene-catalysed multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers, which consists of an in-situ-blend of

[0060] (i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A-1) and an ethylene polymer fraction (A-2), and

[0061] (ii) an ethylene copolymer component (B).

[0062] Preferably, the metallocene produced multimodal polyethylene copolymer (P) consists of (i) 35.0 to 50.0 wt.-%, more preferably 38.0 to 48.0 wt.-%, based on the total weight of the multimodal polyethylene copolymer (P), of the ethylene copolymer component (A), and (ii) 50.0 to 65.0 wt.-%, more preferably 52.0 to 62.0 wt.-%, based on the total weight of the multimodal polyethylene copolymer (P), of the ethylene copolymer component (B).

[0063] The amount of (A) and (B) add up to 100.0 wt.-%.

[0064] It is within the scope of the invention, that the first and the second ethylene polymer fraction (A-1 and A-2) of the ethylene copolymer component (A) are present in a weight ratio of 4:1 up to 1 :4, such as 3:1 to 1 :3, or 2:1 to 1 :2, or 1 :1.

[0065] The metallocene produced multimodal polyethylene copolymer (P) is referred herein as “multimodal”, since the ethylene copolymer component (A), respectively the ethylene polymer fractions (A-1) and (A-2), and ethylene copolymer component (B) have been produced under different polymerization conditions resulting in different comonomer contents and different Melt Flow Rates (MFR, e.g. MFR2). I.e. the multimodal PE is multimodal at least with respect to difference in comonomer content and MFR2 of the ethylene copolymer components (A) and (B) as well as of the ethylene polymer fractions (A-1) and (A-2).

[0066] As stated above the metallocene produced multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, which consists of an in-situ-blend of

[0067] (i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A- 1) and an ethylene polymer fraction (A-2), and

[0068] (ii) an ethylene copolymer component (B).

[0069] Cs-Cs-alpha olefin comonomers are for example propylene, 1 -butene, 1 -pentene, 1 -hexene and 1 -octene. Preferred comonomers are 1 -butene, 1 -hexene and 1 -octene. Especially preferred are 1 -butene and 1 -hexene.

[0070] The ethylene copolymer component (A) is a copolymer of ethylene and one or two C3-C8- alpha olefin comonomers.

[0071] Thus, the ethylene copolymer component (A) can be a copolymer of ethylene and one C3- Cs-alpha olefin comonomer or a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers. Preferably the ethylene copolymer component (A) is a copolymer of ethylene and one comonomer selected from 1 -butene, 1 -hexene and 1 -octene, more preferably selected from 1 -butene and 1 -hexene.

[0072] In a preferred embodiment the ethylene copolymer component (A) is a copolymer of ethylene and 1 -butene.

[0073] As the ethylene copolymer component (A) consists of an ethylene polymer fraction (A-1) and an ethylene polymer fraction (A-2), these two fractions may have the same type of C3- Cs-alpha olefin comonomer or may have different Cs-Cs-alpha olefin comonomers.

[0074] For example ethylene fraction (A-1) may be an ethylene-1 -butene copolymer and ethylene fraction (A-2) may be an ethylene-1 -hexene copolymer.

[0075] Preferably both fractions have the same kind of Cs-Cs-alpha olefin comonomer(s), more preferably both fractions are copolymers of ethylene and one comonomer selected from 1- butene, 1 -hexene and 1 -octene, more preferably selected from 1 -butene and 1 -hexene.

[0076] In a preferred embodiment both ethylene polymer fractions (A-1 and A-2) are copolymers of ethylene and 1 -butene.

[0077] The ethylene copolymer component (B) is also a copolymer of ethylene and one or two C3- Cs-alpha olefin comonomers, the ethylene copolymer component (B) having at least one comonomer being different from that of ethylene copolymer component (A).

[0078] Thus, the ethylene copolymer component (B) can be a copolymer of ethylene and one C3- Cs-alpha olefin comonomer or a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers.

[0079] Preferably the ethylene copolymer component (B) is a copolymer of ethylene and one comonomer selected from 1 -butene, 1 -hexene and 1 -octene, more preferably selected from 1 -butene and 1 -hexene.

[0080] In a preferred embodiment the ethylene copolymer component (B) is a copolymer of ethylene and 1 -hexene.

[0081] The comonomer content of components (A) and (B) can be measured, or, in case, and preferably, one of the components is produced first and the other thereafter in the presence of the first produced in so called multistage process, then the comonomer content of the first produced component, e.g. component (A), can be measured and the comonomer content of the other component, e.g. component (B), can be calculated. In addition the comonomer content of ethylene polymer fraction (A-2) can also be calculated.

[0082] Thus, the comonomer content of the ethylene polymer fraction (A-2) is calculated according to formula (l-a) cc(A-2) = [cc(A) - x*(cc(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A), cc(A-2) is the calculated comonomer content of ethylene polymer fraction (A-2) cc(A-1) is the comonomer content of the ethylene polymer fraction (A-1) and cc(A) is the comonomer content of the ethylene copolymer component (A) whereby cc(A-1) and cc(A) are determined by quantitative13C{1H} NMR as described in the experimental part.

[0083] The comonomer content of the ethylene copolymer component (B) is calculated according to formula (l-b) cc(B) = [cc(P) - x*(cc(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), cc(B) is the calculated comonomer content of ethylene copolymer component (B), cc(A) is the comonomer content of the ethylene copolymer component (A) and cc(P) is the comonomer content of the multimodal polyethylene copolymer (P), whereby cc(A) and cc(P) are determined by quantitative13C{1H} NMR as described in the experimental part.

[0084] In case that only one comonomer, e.g. 1-butene, is present in the ethylene copolymer component (A), and the comonomer content has of the ethylene copolymer component (A) has not been measured, a simplified formula (l-c) can be applied, to calculate the comonomer content of ethylene copolymer component (A), i.e.

[0085] [C4]A = [C4]P / wA; wA being the weight fraction of ethylene copolymer component (A) with respect to the multimodal copolymer (P),

[0086] [C4]A being the calculated 1-butene content of ethylene copolymer component (A) and [C4]P being the measured 1-butene content of the multimodal polyethylene copolymer (P).

[0087] The same is true, if there is only one comonomer, e.g. 1 -hexene, added during the production of the ethylene copolymer component (B). Here the simplified formula (l-d) can be applied:

[0088] [C6]B = [C6]P / wB; wB being the weight fraction of ethylene copolymer component (B) with respect to the multimodal copolymer (P)

[0089] [C6]B being the calculated 1 -hexene content of ethylene copolymer component (B) and [C6]P being the measured 1-hexe content of the multimodal polyethylene copolymer (P).

[0090] The polyethylene copolymer (P) has a total comonomer content, determined by quantitative13C{1H} NMR as described in the experimental part, in the range of from 1.1 to 8.0 mol-%, preferably 1.4 to 6.5 mol-%, more preferably 1.8 to 5.0 mol-%.

[0091] In the polyethylene copolymer (P) being a terpolymer of ethylene and two different Ca-Cs- alpha olefin comonomers, the total amount of the first Cs-Cs-alpha olefin comonomer, preferably of the 1-butene or 1 -hexene or 1 -octene, more preferably of the 1-butene or 1- hexene and most preferred of the 1-butene, based on the multimodal polymer (P) is in the range of from 0.1 to 2.0 mol-%, preferably 0.1 to 1.5 mol-% and more preferably 0.2 to 1.0 mol-%.

[0092] The second Cs-Cs-alpha olefin comonomer, being different from the first Cs-Cs-alpha olefin comonomer, preferably of the 1-butene or 1 -hexene or 1 -octene, more preferably of the 1- butene or 1 -hexene and most preferred of the 1 -hexene, is present in an amount of from 1.0 to 6.0 mol-%, preferably 1.3 to 5.0 mol-%, more preferably 1.6 to 4.0 mol-%, based on the multimodal polymer (P).

[0093] The ethylene copolymer component (A) has a total comonomer content in the range of from 0.2 to 3.0 mol-%, preferably 0.3 to 2.5 mol-%, more preferably 0.4 to 2.0 mol%, based on the total weight of the ethylene copolymer component (A).

[0094] The ethylene polymer fraction (A-1) has a comonomer content in the range of from 0.1 to 2.0 mol-%, preferably 0.1 to 1.8 mol-%, more preferably 0.2 to 1.6 mol-%, based on the total weight of the ethylene polymer fraction (A-1), and the ethylene polymer fraction (A-2) has a higher comonomer content than the ethylene polymer fraction (A-1). The difference between the comonomer content of the ethylene polymer fraction (A-2) and the ethylene polymer fraction (A-1) is in the range of from 0.3 to 3.0 mol-%, preferably 0.4 to 2.0 mol-%, more preferably 0.5 to 1.5 mol-%.

[0095] As mentioned above the comonomer of ethylene polymer fraction (A-2) is calculated according to formula (l-a) and the comonomer content of the ethylene copolymer component (A) is either determined by quantitative13C{1H} NMR as described in the experimental part or calculated according to formula (l-c).

[0096] The comonomer content of ethylene copolymer component (B) can be calculated either via formula (l-b) or via formula (l-d).

[0097] As stated above, the comonomer of the ethylene copolymer component (B) is higher than the comonomer content of the ethylene copolymer component (A).

[0098] Thus the content of comonomer increases from (A-1) to (B), i.e. comonomer contend (A-1) < (A-2) < (B).

[0099] The ethylene copolymer component (A) has a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.2 to 500 g / 10 min, preferably 0.5 to 300 g / 10 min and more preferably 1 to 200 g / 10 min, like 2 to 100 g / 10 min.

[0100] The MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) is in the range of from 0.1 to 100 g / 10 min, preferably 0.2 to 50 g / 10 min, more preferably 0.3 to 30 g / 10 min. The MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) is higher than the MFR2 of ethylene polymer fraction (A-1).

[0101] The MFR2 of the ethylene polymer fraction (A-2) is calculated according to formula (I l-a) [(logMFS(A) - x * log MF / ?(A - 1)] MFR(A — 2) = 10 (1 -2 -i_x5- 1 wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A),

[0102] MFR(A-2) is the calculated MFR2 of ethylene polymer fraction (A-2)

[0103] MFR(A-1) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) and MFR(A) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A).

[0104] According to the present invention the ratio of the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) to the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2), MFR2(A-2) / MFR2(A-1), is in the range of from 4 to 200, preferably 4 to 150, more preferably 4 to 100 and even more preferably 8 to 50.

[0105] The MFR2 of the ethylene copolymer component (B) is calculated according to formula (II- b) wherein x is the weight fraction of ethylene copolymer component (A), with respect to the multimodal polyethylene copolymer (P),

[0106] MFR(B) is the calculated MFR2 of ethylene copolymer component (B)

[0107] MFR(P) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of the multimodal polyethylene copolymer (P), and

[0108] MFR(A) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A).

[0109] In a further embodiment of the present invention the multimodal polyethylene copolymer (P) has a ratio of the MFR21 (190 °C, 21.6 kg, ISO 1133) to the MFR2(190 °C, 2.16 kg, ISO 1133), MFR21 / MFR2, in the range of from 23 to 60, preferably 24 to 55, more preferably 25 to 50 and even more preferably 28 to 44.

[0110] Even more preferably the multimodal polymer (P) of the invention is further multimodal with respect to difference in density between the ethylene copolymer component (A) and ethylene copolymer component (B). Preferably, the density of ethylene copolymer component (A) is different, preferably higher, than the density of the ethylene copolymer component (B).

[0111] The density (ISO 1183) of the ethylene copolymer component (A) is in the range of from 930 to 950 kg / m3, preferably 932 to 948 kg / m3, more preferably 934 to 946 kg / m3.

[0112] The density of the ethylene copolymer component (B) is calculated according to formula (HI) density(B) = [density(P) - x*(density(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), density(B) is the calculated density of ethylene copolymer component (B), density(A) is the density (ISO 1183) of ethylene copolymer component (A) and density(P) is the density (ISO 1183) of the multimodal polyethylene copolymer (P).

[0113] The polymer fractions (A-1) and (A-2) have a density (ISO 1183) in the range of from 930 to 950 kg / m3, preferably of 932 to 948 kg / m3, more preferably of 934 to 946 kg / m3.

[0114] The density of polymer fraction (A-1) and (A-2) may be the same or may be different from each other.

[0115] The density of ethylene polymer fraction (A-2) is calculated according to formula (IV) density(A-2) = [density(A) - x*(density(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1) with respect to ethylene copolymer component (A), density(A-2) is the calculated density of ethylene polymer fraction (A-2), density(A) is the density (ISO 1183) of ethylene copolymer component (A) and density(A-l) is the density (ISO 1183) of ethylene polymer fraction (A-1).

[0116] The metallocene catalysed multimodal copolymer (P) is preferably a linear low density polyethylene (LLDPE) which has a well-known meaning.

[0117] More preferably the multimodal copolymer (P) is multimodal at least with respect to, i.e. has a difference between, the MFR2, the comonomer content as well as with respect to, i.e. has a difference between the density of the ethylene copolymer components, (A) and (B), as defined above, below or in the claims including any of the preferable ranges or embodiments of the polymer composition.

[0118] The metallocene catalysed multimodal copolymer (P), can be produced with a 3-stage process, preferably comprising a first slurry reactor (loop reactor 1), whereby the first slurry loop reactor is connected in series with another slurry reactor (loop reactor 2), so that the first ethylene polymer fraction (A-1) produced in the loop reactor 1 is fed to the loop reactor 2, wherein the second ethylene polymer fraction (A-2) is produced in the presence of the first fraction (A-1). The loop reactor 2 is thereby connected in series to a gas phase reactor (GPR), so that the first ethylene copolymer 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 chosen in a way that in the two slurry reactors different products in view of MFR and comonomer content are produced.

[0119] Such a process is described inter alia in WO 2016198273, WO 2021009189, WO 2021009190, WO 2021009191 and WO 2021009192. Full details of how to prepare suitable metallocene catalysed multimodal copolymer (P) can be found in these references.

[0120] A suitable process is the Borstar PE process or the Borstar PE 3G process.

[0121] The metallocene catalysed multimodal copolymer (P) according to the present invention is therefore preferably produced in a loop loop gas cascade. Such polymerization steps may be preceded by a prepolymerization step. The purpose of the prepolymerization is to polymerize a small amount of polymer onto the catalyst at a low temperature and / or a low monomer concentration. By prepolymerization it is possible to improve the performance of the catalyst in slurry and / or modify the properties of the final polymer. The prepolymerization step is preferably conducted in slurry and the amount of polymer produced in an optional prepolymerization step is counted to the amount (wt.-%) of ethylene copolymer component (A), respectively to the amount (wt.-%) of the ethylene polymer fraction (A-1).

[0122] The catalyst components are preferably all introduced to the prepolymerization step when a prepolymerization step is present. However, where 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 and the remaining part into subsequent polymerization stages. Also in such cases it is necessary to introduce so much cocatalyst into the prepolymerization stage that a sufficient polymerization reaction is obtained therein.

[0123] It is understood within the scope of the invention, that the amount or polymer produced in the prepolymerization lies within 1 to 5 wt.-% in respect to the final metallocene catalysed multimodal copolymer (P). This can counted as part of the first ethylene polymer component (A), respectively to the amount (wt.-%) of the ethylene polymer fraction (A-1).

[0124] Catalyst

[0125] The metallocene catalysed multimodal copolymer (P) used in the process of the invention is one made using a metallocene catalyst. A metallocene catalyst comprises a metallocene complex and a cocatalyst. The metallocene compound or complex is referred herein also as organometallic compound (C).

[0126] The organometallic compound (C) comprises a transition metal (M) of Group 3 to 10 of the Periodic Table (IIIPAC 2007) or of an actinide or lanthanide.

[0127] The term "an organometallic compound (C)" in accordance with the present invention includes any metallocene or non-metallocene compound of a transition metal, which bears at least one organic (coordination) ligand and exhibits the catalytic activity alone or together with a cocatalyst. The transition metal compounds are well known in the art and the present invention covers compounds of metals from Group 3 to 10, e.g. Group 3 to 7, or 3 to 6, such as Group 4 to 6 of the Periodic Table, (IIIPAC 2007), as well as lanthanides or actinides.

[0128] In an embodiment, the organometallic compound (C) has the following formula (Y): wherein each X is independently a halogen atom, a Ci-6-alkyl group, Ci-6-alkoxy group, phenyl or benzyl group; each Het is independently a monocyclic heteroaromatic group containing at least one heteroatom selected from O or S;

[0129] L is -R'2Si-, wherein each R’ is independently Ci-20-hydrocarbyl or Ci- -alkyl substituted with alkoxy having 1 to 10 carbon atoms;

[0130] M is Ti, Zr or Hf; each R1is the same or different and is a Ci-6-alkyl group or Ci-6-alkoxy group; each n is 1 to 2; each R2is the same or different and is a Ci-6-alkyl group, Ci-6-alkoxy group or -Si(R)3 group; each R is Ci-w-alkyl or phenyl group optionally substituted by 1 to 3 Ci-6-alkyl groups; and each p is 0 to 1.

[0131] Preferably, the compound of formula (Y) has the structure wherein each X is independently a halogen atom, a Ci-6-alkyl group, Ci-6-alkoxy group, phenyl or benzyl group;

[0132] L is a Me2Si-; each R1is the same or different and is a Ci-6-alkyl group, e.g. methyl or t-Bu; each n is 1 to 2; R2is a -Si(R)3 alkyl group; each p is 1; each R is Ci-6-alkyl or phenyl group.

[0133] Highly preferred complexes of formula (Y) are

[0134] Most preferably the complex dimethylsilanediylbis[2-(5-trimethylsilylfuran-2-yl)-4,5- dimethylcyclopentadien-1-yl] zirconium dichloride is used.

[0135] More preferably the ethylene polymer components (A) and (B) of the multimodal copolymer (P) are produced using, i.e. in the presence of, the same metallocene catalyst.

[0136] To form a catalyst, a cocatalyst, also known as an activator, is used, as is well known in the art. Cocatalysts comprising Al or B are well known and can be used here. The use of aluminoxanes (e.g. MAO) or boron based cocatalysts (such as borates) is preferred.

[0137] The metallocene catalysed multimodal copolymer (P) may contain optional additives and / or fillers.

[0138] The optional additives and fillers and the used amounts thereof are conventional in the field of film applications. Examples of such additives are, among others, antioxidants, UV- stabilizers, pigments, fillers, antistatic additives, antiblock agents, nucleating agents and acid scavengers.

[0139] In an embodiment of the present invention the metallocene catalysed multimodal copolymer (P) does not contain any processing aid, especially does not contain any fluoro based polymer processing aid. It is understood herein that any of the additives and / or fillers can optionally be added in so- called master batch, which comprises the respective additive(s) together with a carrier polymer. In such case the carrier polymer is not calculated to the polymer components of the metallocene catalysed multimodal copolymer (P), but to the amount of the respective additive(s), based on the total amount of polymer composition (100 wt.-%).

[0140] Film of the invention

[0141] The film of the invention comprises at least one layer comprising the metallocene catalysed multimodal copolymer (P). The film can be a monolayer film comprising the metallocene catalysed multimodal copolymer (P) or a multilayer film, wherein at least one layer comprises the metallocene catalysed multimodal copolymer (P). The terms “monolayer film” and multilayer film” have well known meanings in the art.

[0142] The layer of the monolayer or multilayer film of the invention may consist of the metallocene catalysed multimodal copolymer (P) as such or of a blend of the metallocene catalysed multimodal copolymer (P) together with further polymer(s). In case of blends, any further polymer is different from the metallocene catalysed multimodal copolymer (P) and is preferably a polyolefin. Part of the above mentioned additives can optionally added to the metallocene catalysed multimodal copolymer (P) during the film preparation process.

[0143] Preferably, the at least one layer of the 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 catalysed multimodal copolymer (P) of the invention. Most preferably said at least one layer of the film of invention consists of the metallocene catalysed multimodal copolymer (P).

[0144] Accordingly, the films of the present invention may comprise a single layer (i.e. monolayer) or may be multilayered. Multilayer films typically, and preferably, comprise at least 3 layers.

[0145] The films are preferably produced by any conventional film extrusion procedure known in the art including cast film and blown film extrusion. Most preferably, the film is a blown or cast film, especially a blown film. E.g. the blown film is produced by extrusion through an annular die and blowing into a tubular film by forming a bubble which is collapsed between nip rollers after solidification. This film can then be slit, cut or converted (e.g. gusseted) as desired. Conventional film production techniques may be used in this regard. If the preferable blown or cast film is a multilayer film then the various layers are typically coextruded. The skilled man will be aware of suitable extrusion conditions.

[0146] Films according to the present invention may be subjected to post-treatment processes, e.g. surface modifications, lamination or orientation processes or the like. Such orientation processes can be mono-axially (MDO) or bi-axially orientation, wherein mono-axial orientation is preferred.

[0147] In another preferred embodiment, the films are unoriented.

[0148] The resulting films may have any thickness conventional in the art. The thickness of the film is not critical and depends on the end use. Thus, films may have a thickness of, for example, 300 pm or less, typically 6 to 200 pm, preferably 10 to 180 pm, e.g. 20 to 150 pm or 20 to 120 pm. If desired, the polymer of the invention enables thicknesses of less than 100 pm, e.g. less than 50 pm. Films of the invention with thickness even less than 20 pm can also be produced whilst maintaining good mechanical properties.

[0149] Furthermore, the present invention is also directed to the use of the inventive article as packing material, in particular as a packing material for food and / or medical products.

[0150] The specific design of the metallocene catalysed multimodal copolymer (P) of the invention makes the polymer very beneficial for making films. Benefits can be seen in low required melt pressure, which is expected to increase the output of a blown film process, in combination with low sealing initiation temperature and in addition high impact strength.

[0151] The sealing initiation temperature (SIT) measured as described in the experimental part on 40 pm test blown films made of the multimodal polyethylene copolymer (P) follows inequation (X)

[0152] SIT < 97 - 30*(MFR2HMW) (X) wherein MFR2HMW is the MFR2(190°C, 2.16 kg, ISO 1133) of the ethylene copolymer component (B), calculated according to formula (ll-b).

[0153] Alternatively or additionally the films of the invention are characterized by a dart-drop impact strength (DDI) measured according to ISO 7765-1 :1988 / Method A on a 40 pm monolayer test blown film of at least 1100 g up to 2500 g, preferably 1300 g to 2300 g and more preferably 1500 g to 2200 g. The invention will be further described with reference to the following non-limiting examples.

[0154] Determination methods:

[0155] Unless otherwise stated in the description or in the experimental part, the following methods were used for the property determinations of the polymers (including its fractions and components) and / or any sample preparations thereof as specified in the text or experimental part.

[0156] Melt Flow Rate

[0157] The melt flow rate (MFR) was determined according to ISO 1133 and is indicated in g / 10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR is determined at 190 °C for polyethylene. MFR may be determined at different loadings such as 2.16 kg (MFR2), 5 kg (MFR5) or 21.6 kg (MFR21).

[0158] Calculation of MFR2 of Component B and of Fraction (A-2)

[0159] MFR2of ethylene polymer fraction (A-2) is calculated according to formula (I l-a) [(logMFS(A) - x * log MFF(A - 1)] MFR(A — 2) = 10 (1 -2 -i_x5- 1 wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A),

[0160] MFR(A-2) is the calculated MFR2of ethylene polymer fraction (A-2)

[0161] MFR(A-1) is the MFR2(190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) and MFR(A) is the MFR2(190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A).

[0162] For ethylene copolymer component (B) the MFR2is calculated according to formula (I l-b) wherein x is the weight fraction of ethylene copolymer component (A), with respect to the multimodal polyethylene copolymer (P),

[0163] MFR(B) is the calculated MFR2of ethylene copolymer component (B) MFR(P) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of the multimodal polyethylene copolymer (P), and

[0164] MFR(A) is the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (A).

[0165] Density

[0166] Density of the polymer was measured according to according to ISO 1183-1 on compression moulded specimen prepared according to EN ISO 1872-2 and is given in kg / m3.

[0167] The density of the ethylene copolymer component (B) is calculated according to formula (HI) density(B) = [density(P) - x*(density(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), density(B) is the calculated density of ethylene copolymer component (B), density(A) is the density (ISO 1183) of ethylene copolymer component (A) and density(P) is the density (ISO 1183) of the multimodal polyethylene copolymer (P).

[0168] The density of ethylene polymer fraction (A-2) is calculated according to formula (IV) density(A-2) = [density(A) - x*(density(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1) with respect to the ethylene copolymer component (A), density(A-2) is the calculated density of ethylene polymer fraction (A-2), density(A) is the density (ISO 1183) of the ethylene copolymer component (A) and density(A-l) is the density (ISO 1183) of the ethylene component (A-1).

[0169] Comonomer contents:

[0170] Quantification of microstructure by NMR spectroscopy

[0171] Quantitative nuclear-magnetic resonance (NMR) spectroscopy as described in EP4108435 A1 was used to quantify the comonomer content of the polymers. The comonomer content of ethylene polymer fraction (A-2) is calculated according to formula (l-a) cc(A-2) = [cc(A) - x*(cc(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A), cc(A-2) is the calculated comonomer content of ethylene polymer fraction (A-2) cc(A-1) is the comonomer content of the ethylene polymer fraction (A-1) and cc(A) is the comonomer content of the ethylene copolymer component (A) whereby cc(A-1) and cc(A) are determined by quantitative13C{1H} NMR as described above.

[0172] The comonomer content of ethylene copolymer component (B) is calculated according to formula (l-b) cc(B) = [cc(P) - x*(cc(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), cc(B) is the calculated comonomer content of ethylene copolymer component (B), cc(A) is the comonomer content of ethylene copolymer component (A) and cc(P) is the comonomer content of the multimodal polyethylene copolymer (P), whereby cc(A) and cc(P) are determined by quantitative13C{1H} NMR as described above.

[0173] In case that only one comonomer, e.g. 1-butene, is present in the ethylene copolymer component (A), and the comonomer content of the ethylene copolymer component (A) has not been measured, a simplified formula (l-c) can be applied, to calculate the comonomer content of ethylene copolymer component (A), i.e.

[0174] [C4]A = [C4]P / wA; wA being the weight fraction of ethylene copolymer component (A) with respect to the multimodal copolymer (P),

[0175] [C4]A being the calculated 1-butene content of ethylene copolymer component (A) and [C4]P being the measured 1-butene content of the multimodal polyethylene copolymer (P).

[0176] If there is only one comonomer, e.g. 1-hexene, added during the production of the ethylene copolymer component (B) asimplified formula (l-d) can be applied: [C6]B = [C6]P / wB; wB being the weight fraction of ethylene copolymer component (B) with respect to the multimodal copolymer (P)

[0177] [C6]B being the calculated 1 -hexene content of ethylene copolymer component (B) and

[0178] [C6]P being the measured 1-hexe content of the multimodal polyethylene copolymer (P).

[0179] Molecular weights, molecular weight distribution, Mn, Mw, MWD:

[0180] Molecular weight averages (Mz, Mw and Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI= Mw / Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) were determined by Gel Permeation Chromatography (GPC) according to ASTM D 6474-12 using the following formulas:

[0181] For a constant elution volume interval AVj, where Aj, and Mj are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, Vj, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

[0182] A high temperature GPC instrument, equipped with either infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain) or differential refractometer (Rl) from Agilent Technologies, equipped with 3 x Agilent-PLgel Olexis and 1x Agilent-PLgel Olexis Guard columns was used. As the solvent and mobile phase 1 ,2,4-trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-Di tert butyl-4-methyl-phenol) was used. The chromatographic system was operated at 160 °C and at a constant flow rate of 1 mL / min. 200 pL of sample solution was injected per analysis. Data collection was performed using either Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0183] The column set was calibrated using universal calibration with 19 narrow MWD polystyrene (PS) standards in the range of 0,5 kg / mol to 11 500 kg / mol. The PS standards were dissolved at room temperature over several hours. The conversion of the polystyrene peak molecular weight to polyolefin molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants: 0.655 0.725

[0184] A third order polynomial fit was used to fit the calibration data.

[0185] All samples were prepared in the concentration range of 0.5 -1 mg / ml and dissolved at 160 °C for 3 hours for PE under continuous gentle shaking.

[0186] Analytical Temperature Rising Elution Fractionation (ATREF)

[0187] The chemical composition distribution was determined by analytical Temperature Rising Elution fractionation as described by Soares, J.B.P., Fractionation, In: Encyclopedia Of Polymer Science and Technology, John Wiley & Sons, New York, pp. 75-131 , Vol. 10, 2001. The separation of the polymer in TREF is according to their crystallinity in solution. The TREF profiles were generated using a CRYSTAF-TREF 200+ instrument manufactured by PolymerChar S.A. (Valencia, Spain).

[0188] The polymer sample was dissolved in 1 ,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-Di tert butyl-4-methyl-phenol) at a concentration between 1.5 and 2.0 mg / ml at 150 °C for 180 min and 1.8 mL of the sample solution was injected into the column (8 mm inner diameter, 15 cm length, filled with inert support e.g. glass beads). The column oven was then rapidly cooled to 110 °C and held at 110 °C for 30 min for stabilization purpose and it was later slowly cooled to 35 °C under a constant cooling rate (0.1 °C / min). The polymer was subsequently eluted from the column with 1 ,2,4-trichlorobenzene (stabilized with 250 mg / L 2,6-Di tert butyl-4-methyl-phenol) at a flow rate of 0.5 mL / min at 35 °C for a period of 10 min followed by a temperature increase from 35 °C to 135 °C at a constant heating rate of 0.5 °C / min with a flow rate of 0.5 ml / min. The concentration of the polymer during elution was recorded by an infrared detector (measuring the C-H absorption at 3.5 micrometer wavelength). The detector response was plotted as a function of the temperature. The normalized concentration plot was presented as fractogram together with the cumulative concentration signal normalized to 100.

[0189] The low crystalline (LCF), medium crystalline and high crystalline fraction are defined as the weight fraction which is eluting above 35 °C up to 70 °C for the LCF, above 70 °C up to 90 °C for the MCF and above 90 °C up to 105° C for the HCF and can be calculated using the following formula:

[0190] Dart drop strength (DDI): Impact resistance by free-falling dart method

[0191] The DDI was measured according to ISO 7765-1 :1988 I Method A from the films as produced indicated below. This test method covers the determination of the energy that causes films to fail under specified conditions of impact of a free-falling dart from a specified height that would result in failure of 50 % of the specimens tested (Staircase method A). A uniform missile mass increment is employed during the test and the missile weight is decreased or increased by the uniform increment after test of each specimen, depending upon the result (failure or no failure) observed for the specimen.

[0192] Standard conditions:

[0193] Conditioning time: > 96 h

[0194] Test temperature: 23 °C

[0195] Dart head material: phenolic

[0196] Dart diameter: 38 mm

[0197] Drop height: 660 mm

[0198] Results:

[0199] Impact failure weight - 50% [g]

[0200] Sealing initiation temperature (SIT); sealing end temperature (SET), sealing range:

[0201] The method determines the sealing temperature range (sealing range) of polyethylene films, in particular blown films or cast films. The sealing temperature range is the temperature range, in which the films can be sealed according to conditions given below. The lower limit (heat sealing initiation temperature (SIT)) is the sealing temperature at which a sealing strength of 5 N is achieved. The upper limit (sealing end temperature (SET)) is reached, when the films stick to the sealing device.

[0202] The measurement was done according to the slightly modified ASTM F1921 - 12. Deviating from ASTM F1921 - 12, the test parameters sealing pressure, sealing time, delay time and clamp separation rate are modified. The determination of the force / temperature curve is continued until thermal failure of the film. In addition to failure mode evaluations described in the standard, additional failure modes are used.

[0203] The sealing range was determined on a J&B Universal Sealing Machine Type 4000 with a blown film of 40 pm thickness with the following further parameters: Conditioning time: > 96 h Specimen width: 25 mm

[0204] Sealing pressure: 0.4 N / mm2(PE)

[0205] Sealing time: 1 sec

[0206] Delay time: 30 sec

[0207] Sealing jaws dimension: 50x5 mm

[0208] Sealing jaws shape: flat

[0209] Sealing jaws coating: Niptef

[0210] Sealing temperature: ambient - 240 °C

[0211] Sealing temperature interval: 5 °C

[0212] Start temperature: 50 °C

[0213] Grip separation rate: 42 mm / sec

[0214] Film sample preparation

[0215] The monolayer test films consisting of the inventive multimodal copolymer (P) and respective comparative polymer of 40 pm thickness, were prepared using a W&H semicommercial line. Film samples were produced with BUR 1 :2.5. Melt temperature -235 to 245 °C and frost line distance 600 mm, screw speed 108 - 122 rpm and uptake speed -22 m / min. Experimental part

[0216] Cat.Example: Catalyst preparation (CAT1)

[0217] Loading of SiO2:

[0218] 10 kg of silica (PQ Corporation ES757, calcined 600°C) was added from a feeding drum and inertized in the reactor until O2 level below 2 ppm was reached.

[0219] Preparation of MAO / tol / MC:

[0220] 30 wt.-% MAO in toluene (14.1 kg) was added into another reactor from a balance followed by toluene (4.0 kg) at 25 °C (oil circulation temp) and stirring was done with 95 rpm. Stirring speed was increased from 95 rpm to 200 rpm after toluene addition, stirring time was 30 min. Metallocene (MC) Rac-dimethylsilanediylbis{2-(5-(trimethylsilyl)furan-2-yl)-4,5- dimethylcyclopentadien-1-yl}zirconium dichloride (477 g) was added from a metal cylinder followed by flushing with 4 kg toluene (total toluene amount 8.0 kg). Reactor stirring speed was changed to 95 rpm for MC feeding and returned back to 200 rpm for 3 h reaction time. After reaction time the MAO / tol / MC solution was transferred into a feeding vessel.

[0221] Preparation of catalyst:

[0222] Reactor temperature was set to 10 °C (oil circulation temp) and stirring to 40 rpm for MAO / tol / MC addition. MAO / tol / MC solution (22.2 kg) was added within 205 min followed by 60 min stirring time (oil circulation temp was set to 25 °C). After stirring the “dry mixture” was stabilised for 12 h at 25 °C (oil circulation temp), stirring was set to 0 rpm. Reactor was turned to 20 °C (back and forth) and stirring was turned on with 5 rpm for few rounds once an hour.

[0223] After stabilisation the catalyst was dried at 60 °C (oil circulation temp) for 2 h under nitrogen flow 2 kg / h, followed by 13 h under vacuum (same nitrogen flow with stirring 5 rpm). Dried catalyst was sampled and HC content was measured in the glove box with Sartorius Moisture Analyser, (Model MA45) using thermogravimetric method. Target HC level was < 2% (actual 1.3 %).

[0224] Polymerization: Inventive Examples: Inventive multimodal polyethylene copolymer (P) (IE1 to IE4) and comparative Examples (CE1 and CE2)

[0225] Borstar pilot plant with a 3-reactor set-up (loopl - Ioop2 - GPR 1) and a prepolymerization loop reactor. The inventive multimodal copolymers (P) of IE1 to IE4 as well as of the comparative examples (CE1 and CE2) were produced by using the polymerization conditions as given in Table 1.

[0226] Table 1 : Polymerization conditions

[0227] N / A not analyzed

[0228] * calculated according to formula [C4]A = [C4]P / wA;

[0229] ** calculated according to formula [C6]B = [C6]P / wB; The polymers of IE1 to IE4, as well as of CE1 and CE2 were mixed with only 2000 ppm of Irganox 1010 FF and 500 ppm of Irgafos 168 FF (no PPA added), compounded and extruded under nitrogen atmosphere to pellets by using a twin screw extruder ZSK57; melt temperature -230 to 235 °C. Table 2: Material properties of inventive multimodal copolymers (P) and comparative copolymers, as well as film parameters

[0230] As can be seen from above Table 2 (and Figures 2) the inventive examples have, due to the trimodality (achieved through production of the materials with different MFR in both loop reactors) an ATREF profile with specific character, which differs from the comparative examples although all examples have similar final MFR, density (final and for components (A) and (B)) and GPR split.

[0231] This trimodality of the inventive examples translates into lower SIT, which is reduced by about 2 - 3 °C for the inventive examples vs. the comparative example with similar MFR2HMW and final density as well as similar densities for components (A) and (B), see Figure 1 and Tables above.

[0232] At the same time, it can be seen that the excellent impact resistance of the resulting films and melt pressure required to produce such films, are not compromised.

Claims

Claims1. Metallocene-catalysed multimodal polyethylene copolymer (P), being a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, whereby the multimodal polyethylene copolymer (P) has a density (ISO 1183) in the range of from 910 to 925 kg / m3, a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min, and whereby the multimodal polyethylene copolymer (P) is furthermore characterized by an ATREF profile, determined as is described in the experimental part, showing a trimodal chemical composition distribution (CCD), which is composed of a) 35.0 wt.-% to 50.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a low crystalline fraction (LCF), which elutes between > 35 to 70 °C, b) 20.0 wt.-% to 37.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a medium crystalline fraction (MCF), which elutes between > 70 to 90 °C and c) 3.0 wt.-% to 30.0 wt.-%, based on the multimodal polyethylene copolymer (P), of a high crystalline fraction (HCF), which elutes between > 90 and 105 °C, d) whereby the sum of low crystalline fraction (LCF), medium crystalline fraction (MCF) and high crystalline fraction (HCF) add up to at least 95.0 wt.-%, e) the remaining percentage of the multimodal polyethylene copolymer (P) elutes at a temperature of < 35 °C, and whereby the ratio of medium crystalline fraction to high crystalline fraction MCF / HCF is in a range of from 0.6 to 3.0.

2. The metallocene-catalysed multimodal polyethylene copolymer (P) according to claim 1 , wherein the multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, with a density (ISO 1183) in the range of from 910 to 925 kg / m3, a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min and a total comonomer content, determined by quantitative13C{1H} NMR as described in the experimental part, in the range of from 1.1 to 8.0 mol-%, which consists of an in-situ-blend of(i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A-1) and an ethylene polymer fraction (A-2), and(ii) an ethylene copolymer component (B), wherein the ethylene copolymer component (A)is a copolymer of ethylene and one or two Cs-Cs-alpha olefin comonomers with a total comonomer content in the range of from 0.2 to 3.0 mol-%, based on the total weight of the ethylene copolymer component (A), whereby the ethylene polymer fraction (A-1) has a comonomer content, determined by quantitative13C{1H} NMR as described in the experimental part, in the range of from 0.1 to 2.0 mol-%, based on the total weight of the ethylene polymer fraction (A-1), and the ethylene polymer fraction (A-2) has a higher comonomer content than the ethylene polymer fraction (A-1), and wherein the difference between the comonomer content of the ethylene polymer fraction (A-2) and the ethylene polymer fraction (A-1) is in the range of from 0.3 to 3.0 mol-%, whereby the comonomer content of the ethylene polymer fraction (A-2) is calculated according to formula (l-a) cc(A-2) = [cc(A) - x*(cc(A-1))] / (1-x), wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A), cc(A-2) is the calculated comonomer content of ethylene polymer fraction (A-2) cc(A-1) is the comonomer content of ethylene polymer fraction (A-1) and cc(A) is the comonomer content of ethylene copolymer component (A) whereby cc(A-1) and cc(A) are determined by quantitative13C{1H} NMR as described in the experimental part, and wherein the ethylene copolymer component (B) is a copolymer of ethylene and one or two Cs-Cs-alpha olefin comonomers, the ethylene copolymer component (B) having at least one comonomer being different from that of the ethylene copolymer component (A) and wherein the comonomer content of the ethylene copolymer component (B) is higher than the comonomer content of the ethylene copolymer component (A), whereby the comonomer content of the ethylene copolymer component (B) is calculated according to formula (l-b) cc(B) = [cc(P) - x*(cc(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (A) with respect to the multimodal polyethylene copolymer (P), cc(B) is the calculated comonomer content of ethylene copolymer component (B), cc(A) is the comonomer content of ethylene copolymer component (A) and cc(P) is the comonomer content of the multimodal polyethylene copolymer (P),whereby cc(A) and cc(P) are determined by quantitative13C{1H} NMR as described in the experimental part.

3. The metallocene-catalysed multimodal polyethylene copolymer (P) according to any one of the preceding claims, wherein the multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two different Cs-Cs-alpha olefin comonomers, having a total amount of the first Cs-Cs-alpha olefin comonomer, preferably of the 1 -butene or 1- hexene or 1 -octene, more preferably of the 1 -butene or 1 -hexene and most preferred of the 1-butene, based on the multimodal polymer (P), in the range of from 0.1 to 2.0 mol-%, preferably 0.1 to 1.5 mol-% and more preferably 0.2 to 1.0 mol-% and wherein the second Cs-Cs-alpha olefin comonomer, being different from the first Cs-Cs-alpha olefin comonomer, preferably of the 1-butene or 1 -hexene or 1 -octene, more preferably of the 1-butene or 1 -hexene and most preferred of the 1 -hexene, is present in an amount of from 1.0 to 6.0 mol-%, preferably 1.3 to 5.0 mol-%, more preferably 1.6 to 4.0 mol-%, based on the multimodal polymer (P).

4. The metallocene-catalysed multimodal polyethylene copolymer (P) according to any of the preceding claims, wherein the multimodal polyethylene copolymer (P) is a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers with a density (ISO 1183) in the range of from 910 to 925 kg / m3and a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.3 to 1.5 g / 10 min, which consists of an in-situ-blend of(i) an ethylene copolymer component (A), consisting of an ethylene polymer fraction (A-1) and an ethylene polymer fraction (A-2), and(ii) an ethylene copolymer component (B), wherein the ethylene copolymer component (A) has a density (ISO 1183) in the range of from 930 to 950 kg / m3and a MFR2 (190 °C, 2.16 kg, ISO 1133) in the range of from 0.2 to 500 g / 10 min, wherein the density (ISO 1183) of fractions (A-1) and (A-2) is in the range of from 930 to 950 kg / m3, and the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-1) is in the range of 0.1 to 100 g / 10 min, the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) is higher than the MFR2 of ethylene polymer fraction (A-1), andwherein the ratio of the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) to the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2), MFR2(A-2) / MFR2(A-1), is in the range of 4 to 200; and wherein the MFR2 of ethylene polymer fraction (A-2) is calculated according to formula (ll-a)[(logMFS(A) - x * log MFF(A - 1)] MFR(A — 2) = 10 (1 -2 - i -x- - - wherein x is the weight fraction of ethylene polymer fraction (A-1), with respect to the ethylene copolymer component (A),MFR(A-2) is the calculated MFR2 of ethylene polymer fraction (A-2)MFR(A-1) is the MFR2 (190°C, 2.16 kg, ISO 1133) of the ethylene polymer fraction (A- 1) andMFR(A) is the MFR2 (190°C, 2.16 kg, ISO 1133) of ethylene copolymer component (A), and wherein the ethylene copolymer component (B) has a lower density and lower MFR2 than ethylene copolymer component (A), wherein the MFR2 is calculated according to formula (IMFR(wherein x is the weight fraction of ethylene copolymer component (A), with respect to the multimodal polyethylene copolymer (P),MFR(B) is the calculated MFR2 of ethylene copolymer component (B)MFR(P) is the MFR2 (190°C, 2.16 kg, ISO 1133) of the multimodal polyethylene copolymer (P), andMFR(A) is the MFR2 (190°C, 2.16 kg, ISO 1133) of ethylene copolymer component (A), and the density is calculated according to formula (III) density(B) = [density(P) - x*(density(A))] / (1-x), wherein x is the weight fraction of ethylene copolymer component (B) with respect to the multimodal polyethylene copolymer (P), density(B) is the calculated density of ethylene copolymer component (B), density(A) is the density (ISO 1183) of the ethylene copolymer component (A) and density(P) is the density (ISO 1183) of the multimodal polyethylene copolymer (P).

5. The metallocene-catalysed multimodal polyethylene copolymer (P) according to any of preceding claims 2 to 4, wherein the ethylene copolymer component (A) is a copolymer of ethylene and one Cs-Cs-alpha olefin comonomer or a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers, whereby the ethylene polymer fraction (A-1) and the ethylene polymer fraction (A-2), may have the same type of Cs-Cs-alpha olefin comonomer or may have different Cs-Cs-alpha olefin comonomers, preferably both fractions have the same kind of Cs-Cs-alpha olefin comonomer(s), and wherein the ethylene copolymer component (B) is a copolymer of ethylene and one Cs-Cs-alpha olefin comonomer or a terpolymer of ethylene and two Cs-Cs-alpha olefin comonomers, with at least one comonomer being different from that of the ethylene copolymer component (A), preferably the ethylene copolymer component (B) is a copolymer of ethylene and one comonomer selected from 1 -butene, 1 -hexene and 1 -octene, more preferably selected from 1 -butene and 1 -hexene.

6. The metallocene-catalysed multimodal polyethylene copolymer (P) according to claim 5, wherein the ethylene copolymer component (A) is a copolymer of ethylene and 1- butene; the ethylene polymer fraction (A-1) and the ethylene polymer fraction (A-2), are copolymers of ethylene and 1 -butene and wherein the ethylene copolymer component (B) is a copolymer of ethylene and 1- hexene.

7. The metallocene-catalysed multimodal polyethylene copolymer (P) according to any one of the preceding claims, wherein the multimodal polyethylene copolymer (P) has a ratio of the MFR21 (190 °C, 21.6 kg, ISO 1133) to the MFR2(190°C, 2.16 kg, ISO 1133), M FR21 / M FR2, in the range of 23 to 60, preferably 24 to 55, more preferably 25 to 50 and even more preferably 28 to 44.

8. The metallocene-catalysed multimodal polyethylene copolymer (P) according to any of the preceding claims 2 to 7, wherein the ratio of the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2) to the MFR2 (190 °C, 2.16 kg, ISO 1133) of ethylene polymer fraction (A-2), MFR2(A-2) / MFR2(A-1), is in the range of 4 to 150, preferably 4 to 100 and more preferably 8 to 50.

9. The metallocene-catalysed multimodal copolymer (P) according to any of the preceding claims, wherein the multimodal copolymer (P) is produced in the presence of metallocene complex of formula (Y):wherein each X is independently a halogen atom, a Ci-6-alkyl, Ci-6-alkoxy group, phenyl or benzyl group; 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 Ci-20-hydrocarbyl or Ci- -alkyl substituted with alkoxy having 1 to 10 carbon atoms;M is Ti, Zr or Hf; each R1is the same or different and is a Ci-6-alkyl group or Ci-6-alkoxy group; each n is 1 to 2; each R2is the same or different and is a Ci-6-alkyl group, Ci-6-alkoxy group or -Si(R)3 group; each R is Ci-w-alkyl or phenyl group optionally substituted by 1 to 3 Ci-6-alkyl groups; and each p is 0 to 1 .

10. Film comprising a metallocene-catalysed multimodal copolymer (P) according to any of the preceding claims 1 to 9.11 . The film according to claim 10, wherein the film comprises at least one layer comprising the metallocene-catalysed multimodal copolymer (P), whereby the at least one layer comprises at least 50 wt.-%, more preferably at least 60 wt.-%, even more preferably atleast 70 wt.-%, yet more preferably at least 80 wt.-%, of the metallocene catalysed multimodal copolymer (P) according to any of the preceding claims 1 to 9.

12. The film according to any of the preceding claims 10 to 11 , wherein the sealing initiation temperature (SIT) measured as described in the experimental part on 40 pm test blown films follows in-equation (X)SIT < 97 - 30*(MFR2HMW) (X) wherein MFR2HMW is the MFR2(190 °C, 2.16 kg, ISO 1133) of ethylene copolymer component (B), whereby the MFR2is calculated according to formula (I l-b)wherein x is the weight fraction of ethylene copolymer component (A), with respect to the multimodal polyethylene copolymer (P),MFR(B) is the calculated MFR2of ethylene copolymer component (B)MFR(P) is the MFR2(190 °C, 2.16 kg, ISO 1133) of the multimodal polyethylene copolymer (P) .

13. The film according to any of the preceding claims 10 to 12, wherein the film is characterized by a dart-drop impact strength (DDI) measured according to ISO 7765- 1 :19881 Method A on a 40 pm monolayer test blown film of at least 1100 g up to 2500 g, preferably 1300 g to 2300 g and more preferably 1500 g to 2200 g.

14. Use of a film according to any of the preceding claims 10 to 13 as packing material, in particular as a packing material for food and / or medical products.

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