Post-metallocene polyolefin catalyst compounds

Abstract

The present invention relates to a compound according to formula (1): wherein • M is a metal atom selected from Hf, Ti and Zr; • X is a halogen, a C1-C4 alkyl moiety, or a benzyl moiety; • R1 is a C1-C4 alkyl moiety; • each R2 and R3 is individually selected from hydrogen, a C1-C4 alkyl, methoxy, phenyl, benzyl, 2-phenylpropyl, 2,2'-diphenyl ethyl, 2,4,6-trimethylphenyl, 3,5- dimethylphenyl, 3,5-di-t-butyl-phenyl, 9H-carbazol-9-yl, 9-methyl-9H-fluoren-9-yl, and adamantyl; • R4 is a C1-C5 alkyl moiety, preferably R4 is selected from ethyl, propyl, n-butyl, isobutyl and isopentyl; wherein at least one R3 moiety is a methoxy moiety. Such compound allows for use as catalyst in olefin polymerisation at high degree of incorporation of desired comonomers in copolymerisation reaction of olefins, as well as high molecular weight, and broad molecular weight distribution, at particular high polymerisation activity.

Description

Post-metallocene polyolefin catalyst compounds.

[0001] The present invention relates to post-metallocene polyolefin catalyst compounds. The invention also relates to processes for manufacturing of polyolefins using such post-metallocene catalyst compounds. The invention also relates to the application of such compounds in catalytic systems suitable for use in polymerisation, such as in polymerisation of olefins. Such catalytic systems allow for the production of polymers having high degree of incorporation of desired comonomers in copolymerisation reaction of olefins, as well as high molecular weight, at particular high polymerisation activity.

[0002] Polymers of ethylene and other olefins are ubiquitously available and find widespread applications. Examples of typical olefin-based polymers include various types of polymers that are produced by reaction of a particular reaction mixture in the presence of a catalytic system. Examples of ethylene-based copolymers include for example medium-density polyethylenes (MDPE), linear low-density polyethylenes (LLDPE), polyolefin plastomers (POP), polyolefin elastomers (POE), and ethylene-propylene-diene terpolymers (EPDM). Such polymers are typically produced using transition-metal based catalyst systems. In order for these polymers to qualify as suitable materials for applications with significant commercial importance, the polymers have to have a particular molecular weight, expressed as the weight-average molecular weight (Mw), such as of at least 10 kg / mol, preferably of at least 50 kg / mol, but even more preferably of at least 100 kg / mol, and may for example be in the range of between 100 kg / mol and 500 kg / mol, to provide a polymeric product that demonstrates desirable product qualities in combination with processability via melt shaping processes, as typically used in shaping of products based on polymeric materials.

[0003] In addition, a further ethylene-based polymer produced using catalytic systems is high- density polyethylene (HDPE), such as for example bimodal HDPE, which is used in for example certain high demanding applications as pressure pipes. Such bimodal HDPE typically comprises a low molecular weight fraction of ethylene homopolymer, and a high molecular weight fraction ethylene-based copolymer. The high molecular weight fraction of such bimodal HDPE typically has an Mwof above 100 kg / mol, even above 300 kg / mol, or even above 500 kg / mol.

[0004] Also, a further commercial type of polyethylene is ultra-high molecular weight polyethylene (LIHMWPE), having a typical molecular weight of even above 1000 kg / mol, which finds its application in high-performance applications.

[0005] In order to commercially manufacture olefin-based polymers such as those referred to above, and therein providing improved process economics in the world-scale polymerisation operations in which such polymers are produced, as well as improvements in the quality of the products and the properties of the products, there remains a continued drive to develop catalyst systems to contribute thereto.

[0006] Particular aspects pertaining to the catalyst system employed in the polymerisation of olefins include the activity of the catalyst, the ability of incorporation of comonomers, and the ability to produce a polymer product having a high molecular weight. The activity of the catalyst indicates the quantity of polymeric product that is obtained per quantity of catalyst used. The ability of comonomer incorporation indicates the quantity of comonomer that is reacted into the polymer when polymerisation takes place at a given quantity of comonomer present in the reaction mixture; due to lesser reactivity of the comonomer vis-a-vis the main monomer.Therein, it is desirable to increase the reactivity of the comonomers, so that the concentration of the comonomer content in the reaction mixture can be minimised, which is required from process optimisation and economics perspective.

[0007] A further known trend in preparation of polymers based on olefins, in particular in preparation of copolymers based on ethylene and a-olefins such as a-olefins comprising 3-10 carbon atoms, is that the molecular weight of the obtained copolymer decreases with an increase of the content of the comonomer that is built into the polymer chains. The challenge that therefore continues to be present is to combine the desirable incorporation of the comonomers in the polymerisation of e.g. ethylene with the desirable high molecular weight.

[0008] Various types of catalysts have been developed over the years and have found commercial implementation in various process concepts of polymerisation, and are widely disclosed in literature. A particular group of catalysts are single-site catalysts. In such catalyst compound, a single catalytically active specie is present, which translates into a narrow polydispersity, which is defined as the molecular weight distribution (Mw / Mn), and a narrow composition distribution, which tend to result in particularly desirable mechanical properties of the obtained polymers.

[0009] This category of single-site catalysts includes the group of catalysts referred to as postmetallocene catalysts. Such post-metallocenes are to be understood to be compounds comprising a discrete transition metal compound, wherein the compound does not comprise cyclopentadienyl or substituted cyclopentadienyl moieties, which are present in metallocene catalysts.

[0010] Particularly interesting post-metallocenes are transition metal compounds containing amine-bisphenolate ligands. Transition metal compounds containing amine bisphenolate ligands are known. In such complexes, the amine group that connects the aromatic rings of the two phenolate moieties, is typically substituted via a hydrocarbon spacer to an electron donating group that can coordinate to the transition metal. For instance, in Chemical Communications, 2000 (5), p. 379-380 and in Organometallics 2002 (21) p. 662-670 by Koi et al. and in Macromolecules, 2005 (38) p. 2552-2558 by Waymouth et al., such amine bis(phenolate) zirconium compounds are described, as well as their abilities to act as catalysts for olefin polymerizations. These publications all teach that is these amine bisphenolate compounds, the nitrogen is connected to the aromatic moieties of the phenolate groups via a spacer, typically a divalent hydrocarbyl group, like for example a methylene spacer.

[0011] Still, there is a need to broaden the performance scope of catalysts, which are able to produce amorphous or semi-crystalline polyolefins in high yield, having a high reactivity for comonomer incorporation (like for example copolymerization of ethylene with 1 -hexene or other sterically encumbered olefins) and which is still giving high molecular weight copolymers.

[0012] This is now achieved according to the present invention by a compound according to formula 1:wherein• M is a metal atom selected from Hf, Ti and Zr;• X is a halogen, a C1-C4 alkyl moiety, or a benzyl moiety; • R1 is a C1-C4 alkyl moiety;• each R2 and R3 is individually selected from hydrogen, a C1-C4 alkyl, methoxy, phenyl, benzyl, 2-phenylpropyl, 2,2’-diphenyl ethyl, 2,4,6-trimethylphenyl, 3,5- dimethylphenyl, 3,5-di-t-butyl-phenyl, 9 / 7-carbazol-9-yl, 9-methyl-9 / 7-fluoren-9-yl, and adamantyl; • R4 is a C1-C5 alkyl moiety, preferably R4 is selected from ethyl, propyl, n-butyl, isobutyl, and isopentyl; wherein at least one R3 moiety is a methoxy moiety.

[0013] Such compound allows for use as catalyst in olefin polymerisation at high degree of incorporation of desired comonomers in copolymerisation reaction of olefins, as well as high molecular weight, and broad molecular weight distribution, at particular high polymerisation activity.

[0014] In a particular embodiment, the invention relates to a compound according to formula 2:

[0015] In a further particular embodiment, the invention relates to a compound according to formula 3:

[0016] In a further particular embodiment, the invention relates to a compound according to formula 4:

[0017] In a further particular embodiment, the invention relates to a compound according to formula 5:wherein each R5 is selected from hydrogen and methyl.

[0018] In the compound of the invention, M may for example be selected from Hf and Zr. Each X may for example be a methyl moiety, a benzyl moiety, or a chlorine atom, preferably both X moieties are the same. R1 may for example be a methyl moiety. Each R2 and R3 may for example be selected from hydrogen, methyl, methoxy and t-butyl.

[0019] The invention also relates, in an embodiment, to a catalyst system comprising the compound. In a preferred embodiment, such catalyst system further comprises an activator, wherein the activator is selected from an aluminoxane compound and a boron-based compound, optionally in the presence of an aluminium alkyl compound. Such aluminoxane compound may for example be selected from a methyl aluminoxane, an isobutyl aluminoxane, and a methyl-isobutyl aluminoxanes. Such boron-based compound may for example be selected from a tris(pentafluorophenyl)borane and a tetrakis(pentafluorophenyl)borate.

[0020] The catalyst system may for example comprise the compound according to the invention carried on a support material, wherein the support material is selected from a polymeric support material, a clay material, a solid aluminoxanes, or an inorganic oxide, preferably wherein the support material comprises silica, alumina or a solid aluminoxane.

[0021] The invention also relates to a process for the polymerisation of olefins, preferably wherein the polymerisation involves reaction of a reaction mixture comprising ethylene and / or propylene, in the presence of a catalyst system as described herein. It is preferred that the process is a gas-phase process, a solution process, or a slurry process. Particularly preferably, the process is a homopolymerisation process of ethylene, a homopolymerisation process of propylene, a copolymerisation process of ethylene with a comonomer, preferably selected from 1-butene, 1-hexene, 4-methyl-1 -pentene, vinyl cyclohexane, and 1-octene, or a copolymerisation process of propylene with a comonomer, preferably selected from ethylene, 1- butene, 1-hexene, 4-methyl-1 -pentene, vinyl cyclohexane, and 1-octene.

[0022] The invention in a certain embodiment also relates to a catalyst system comprising a compound according to formula 1. In a preferred embodiment, such catalyst system further comprises an activator, wherein the activator is selected from an aluminoxane compound and a boron-based compound, optionally in the presence of an aluminium alkyl compound. Such aluminoxane compound may for example be selected from a methyl aluminoxane, an isobutyl aluminoxane, and a methyl-isobutyl aluminoxanes; the boron-based compound my for example be selected from a tris(pentafluorophenyl)borane an a tetrakis(pentafluorophenyl)borate.Suitable examples of such are ammonium salts or trityl compounds of tetrakis(pentafluorophenyl)borate.

[0023] For example, the catalyst system may comprise a compound according to formula 1 carried on a support material, wherein the support material may be selected from a polymeric support material, a clay material, a solid aluminoxane, or an inorganic oxide, preferably wherein the support material comprises silica, alumina or a solid aluminoxanes, such as a solid methyl aluminoxane (MAO). Suitable support materials may also include fluorided silica-alumina supports, or sulphated alumina supports. The use of such catalyst system in a supported form may be advantageous for use in certain polymerisation processes, such as in gas-phase homo- or co-polymerisation processes for the production of polymers based on ethylene and propylene. Alternatively, such catalyst system may comprise a compound according to formula 1 in unsupported form.

[0024] In a preferred embodiment, the support is a silica having a surface area of between 200 and 900 m2 / g and / or a pore volume of > 0.5 and < 4.0 ml / g.

[0025] The invention in a further embodiment also relates to a process for the polymerisation of olefins, preferably wherein the polymerisation involves reaction of a reaction mixture comprising ethylene and / or propylene, in the presence of a catalyst system according to the invention. Such process may for example be a homopolymerisation process of ethylene, a homopolymerisation process of propylene, a copolymerisation process of ethylene with a comonomer, preferably selected from 1-butene, 1-hexene, 4-methyl-1 -pentene, vinyl cyclohexane, and 1-octene, or a copolymerisation process of propylene with a comonomer, preferably selected from ethylene, 1- butene, 1-hexene, 4-methyl-1 -pentene, vinyl cyclohexane, and 1-octene. For example, the process may for example be a gas-phase process, a solution process, or a slurry process.

[0026] In such polymerisation process, it is preferred that a main group organometallic compound is present that can act as a scavenger compound to scrub impurities from the polymerisation system that might otherwise adversely affect the catalyst activity. When X in formula 1 is a halogen, an alkoxide moiety, or an amine moiety, an additional function of this main group organometallic compound is to substitute X with an organic group, for example to substitute X with an alkyl or aralkyl moiety such as a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, or benzyl moiety. This function of the main group organometallic compound is particularly advantageous when an activator other than an aluminoxane is used. Such main group organometallic compounds are those that are able to exchange at least one of its organic moieties with X in the compounds of the invention.

[0027] For example, organolithium compounds, organomagnesium compounds, organoaluminium compounds,, organozinc compounds, or mixtures thereof, may be used as such main group organometallic compound. Preferably, the main group organometallic compound is an organoaluminium compound. Suitable organoaluminium compounds are for example trimethylaluminium, triethylaluminium, triisopropylaluminium, tri-n-propylaluminium, triisobutylaluminium, tri-n-butylaluminium, tri-tert-butylaluminium, triamylaluminium, tri-n- hexylaluminium, trioctylaluminium, isoprenylaluminium, dimethylaluminium ethoxide, diethylaluminium ethoxide, diisopropylaluminium ethoxide, di-n-propylaluminium ethyoxide, diisobutylaluminium ethoxide, di-n-butylaluminium ethoxide, dimethylaluminium hydride, diethylaluminium hydride, diisopropylaluminium hydride, di-n-propylaluminium hydride, diisobutylaluminium hydride, and di-n-butylaluminium hydride. Mixtures of these organoaluminium compounds are also suitable. Alternatively, aluminoxanes may be used as such main group organometallic compound. Examples of suitable aluminoxanes are methylaluminoxanes, methyl-isobutylaluminoxanes, isobutylaluminoxanes, and mixtures thereof.

[0028] In certain embodiments, it may be suitable to combine the main group organometallic compound with a compound containing at least one active hydrogen. Such combination may be done in-situ or ex-situ. In the present context, an active hydrogen means that the hydrogen atom is able to react with the main group organometallic compound. Suitable compounds comprising at least one active hydrogen in the context of the present invention are for example alcohol compounds, silanol compounds, and amine compounds. Suitable amine compounds are sterically encumbered amine compounds. Examples of sterically encumbered amine compounds are cyclohexylamine or an alkylamine comprising at least one aliphatic group having at least four carbon atoms. Suitable alcohol compounds are preferably sterically encumbered alcohol compounds, such as substituted phenolic compounds. In principle, any substituted mono- or polyphenolic compound may be used. Suitable substituted monophenolic compounds are for example butylated hydroxytoluene (BHT, 2,6-di-t-butyl-4-methylphenol), 2,6- di-t-butylphenol, and a-tocopherol (vitamin E). Preferably, the amount of the compound comprising at least one active hydrogen is such that after combining this compound with the main group organometallic compound, the latter still contains organometallic bonds, preferably at least one organometallic bond per main group metal atom.

[0029] The process to produce the olefin polymers may start with the reaction of a compound of the invention and an activator, optionally in the presence of the main group organometallic compound, optionally in the presence of a compound comprising at least one active hydrogen atom, optionally in the presence of a suitable support material. This reaction may be performed in the same vessel as the reaction vessel wherein the olefin polymers are produced, or may be a separate vessel. It may be advantageous to combine the inventive compound at first with a portion of the quantity of the main group organometallic compound that is to be used, optionally in the presence of the compound containing at least one active hydrogen, before mixing with the activator. The resulting mixture may be fed to a polymerisation reactor. During the reactions as described here above, an inert solvent may be used.

[0030] The activator may be an aluminoxane-based activator. When a mixture of the inventive compound and such aluminoxanes-based activator is used, the activator may preferably be used in a quantity of between 10 and 100,000 moles of aluminium, preferably of between 10 and 10,000 moles of aluminium, per mole of the transition metal in the inventive compound. When aluminoxanes are used as activators, especially methyl-aluminoxanes, it is know that such aluminoxanes may contain residual tri-methylaluminium, sometimes also referred to as free tri-methylaluminium. The amount of free tri-methylaluminium is typically specified by the supplier of the aluminoxanes, but it may also be determined by known analytical techniques. It may be suitable to treat such solutions of aluminoxanes with a compound containing at least one active hydrogen, like for example BHT. A suitable amount of the compound containing at least one active hydrogen in this case may be expressed as the molar ratio with respect to tri- methylaluminium, for example a molar ratio of active hydrogen to tri-methylaluminium in the range of 3: 1 to 0.1 : 1 , or in the range of 2: 1 to 1 : 1.

[0031] Alternatively, the activator may be an organoboron-based activator. When a mixture of the inventive compound and such organoboron-based activator is used, the activator may preferably be used in a quantity of between 0.1 and 100 moles of boron, preferably of between 0.5 and 50 moles of boron, per mole of the transition metal in the inventive compound.

[0032] The compound may also be used in catalyst systems that contain a multitude of different transition-metal compounds, for example in a mixed catalyst system. Such a mixed catalyst system that contains a multitude of different transition-metal compounds may for example be used to produce polyolefins with a specific heterogeneity. This heterogeneity may be intra- orinter-molecular in nature. For example, a mixture of different transition-metal compounds may be used to produce a mixture of polymers that differ in averaged molecular weight and / or comonomer content. For example, a mixture of different transition-metal compounds may be used to produce a polymer that has an intra-molecular heterogeneity in comonomer content, for example a block-copolymer. For example, such a mixed catalyst system may be used in a single reactor or in staged reactors. For example, when using staged reactors, it may also be that one or more of the inventive compounds is used in just one reactor and the other component of the mixed catalyst system is added to a different reactor of the staged reactors. A mixed catalyst system may for example contain one or more conventional Ziegler-Natta catalysts, Phillips type chromium catalysts, metallocenes, post-metallocenes or any other transition-metal compound that catalyses the polymerization of olefins under the applied reaction conditions.

[0033] When the polymerisation is performed in a slurry or a solution process, the solvent that is used may be any organic solvent as is typically used in olefin polymerisation processes. For example, the solvent may be benzene, toluene, xylene, propane, butane, pentane, hexane, heptane, cyclohexane, methylcyclohexane, and methylchloride. Alternatively, the olefin that is to be polymerised may be used as solvent.

[0034] In the process to produce olefin polymers, the polymerisation conditions such as temperature, time, pressure, and monomer concentration may be chosen within wide limits. The polymerisation temperature may for example be in the range of between -100°C and 300°C, preferably between 0°C and 240°C, more preferably between 50°C and 220°C. The polymerisation time may for example be in the range from 10 seconds to 20 hours, preferably from 1 minute to 10 hours, more preferably from 3 minutes to 5 hours. In the polymerisation of ethylene, the ethylene pressure may for example be in the range of from 1 to 3500 bar, preferably from 1 to 2500 bar, more preferably from 1 to 1000 bar, even more preferably from 1 to 500 bar, yet even more preferably from 1 to 100 bar.

[0035] The molecular weight of the polymer may be controlled by well-known means such as the use of hydrogen or zinc-alkyls in the polymerisation. The polymerisation may be conducted in a batch process, a semi-continuous process, or a continuous process. The polymerisation may be conducted in two or more steps of different polymerisation conditions. The polymer that is produced may be separated from the solvent that is employed in the polymerisation reactionand from residual monomers and optionally comonomers, and dried by methods known to the person skilled in the art.

[0036] In a process for the production of olefin polymers using the compounds of the present invention, the polymerisation may involve a homopolymerisation of an olefin monomer, or a copolymerisation of an olefin monomer and one or more comonomer(s). The olefin monomer may for example be ethylene or propylene. The comonomer may for example be ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1 -butene, 3,3,-dimethyl-1-butene, 4-methyl-1- pentene, 3-methyl-1 -pentene, 1-hexene, 1-octene, 1-nonene, 1-decene; a conjugated or a nonconjugated diene such as butadiene, 1 ,4-hexadiene, a substituted or unsubstituted norbornene, 5-ethylidene-2-norbornene, vinyl-norbornene, dicyclopentadiene, 4-methyl- 1 ,4-hexadiene, 1 ,9- decadiene, or 7-methyl-1 ,6-octadiene; cyclic olefins such as cyclobutene, cyclopentene; or other olefinic compounds such as isobutene, vinyl-cyclohexane, or styrene.

[0037] Preferably, the olefin monomer is ethylene. The polymer produced using ethylene as olefin monomer may be referred to as an ethylene homopolymer, or, in case that the polymerisation is a copolymerisation reaction, an ethylene copolymer. Such ethylene homopolymers and copolymers may together be referred to as polyethylenes. In the case that for example three monomers are used, one can also produce terpolymers, for example if a combination of ethylene, propylene and a third comonomer containing at least two olefinic bonds, such as norbornadiene, dicylopentadiene, ethylidene-norbornene or vinyl-norbornene, are used, one can make terpolymers that can be referred to as EPDM. Preferably, the comonomer is an olefin having 3 or more carbon atoms, for example an olefin comprising 3 to 10 carbon atoms, such as an a-olefin comprising 3 to 10 carbon atoms.

[0038] Preferably, the comonomer is selected from propene, 1-butene, 1-hexene, 1-octene, norbornene, vinyl-cyclohexane, styrene, and 4-methyl-1 -pentene. Preferably, the olefin monomer is ethylene, and the comonomer is selected from 1-butene, 1-hexene, 1-octene, norbornene, vinyl-cyclohexane, styrene, and 4-methyl-1-pentene.

[0039] Preferably, the process for the production of olefin polymers using the compounds of the present invention is copolymerisation of an olefin monomer and one or more comonomer(s), wherein the olefin monomer is ethylene, and the comonomer is selected from 1-butene, 1- hexene, 1-octene, norbornene, vinyl-cyclohexane, styrene, and 4-methyl-1 -pentene. Particularlypreferable, the process for the production of olefin polymers using the compounds of the present invention is copolymerisation of an olefin monomer and one or more comonomer(s), wherein the olefin monomer is ethylene, and the comonomer is selected from 1-butene, 1- hexene, 4-methyl-pentene-1 , vinylcyclohexane, and 1-octene.

[0040] In case that the polymerisation is a copolymerisation of an olefin and one or more comonomer(s), the olefin and the comonomer(s) are different compounds.

[0041] The olefin polymer may for example comprise from 1.0 to 80.0 wt.% of moieties derived from the comonomer, preferably from 5.0 to 60.0 wt%, more preferably from 10.0 to 50.0 wt%, or from 10.0 to 30.0 wt%, with regard to the total weight of the olefin polymer. The ethylene copolymer may for example comprise from 1.0 to 80.0 wt.% of moieties derived from the comonomer, preferably from 5.0 to 60.0 wt%, more preferably from 10.0 to 50.0 wt%, or from 10.0 to 30.0 wt%, with regard to the total weight of the ethylene copolymer.

[0042] The polyethylene may for example have a melt mass-flow rate as determined in accordance with ASTM D1238-10 at 190°C at a load of 2.16 kg (MFI2.16) of > 0.1 and < 125 g / 10 min. For example, the polyethylene may have an MFI2.16 of > 0.1 and < 50 g / 10 min, or > 0.3 and < 10.0 g / 10 min, or > 0.5 and < 5.0 g / 10 min.

[0043] The olefin polymer may for example be of very high molecular weight, for example an ultra high molecular weight polyolefin, for example Ultra High Molecular weight Polyethylene, UHMwPE.

[0044] The polyethylene may for example have a density of > 855 kg / m3and < 970 kg / m3, as determined in accordance with ASTM D1505-10. The polyethylene may for example have a density of > 855 and < 910 kg / m3, or of > 875 and < 900 kg / m3. The polyethylene may for example have a density of > 910 and < 925 kg / m3, or of > 910 and < 920 kg / m3, or of > 915 and < 920 kg / m3. The polyethylene may for example have a density of > 925 and < 940 kg / m3, or of > 930 and < 940 kg / m3. The polyethylene may for example have a density of > 940 and < 965 kg / m3, or of > 945 and < 960 kg / m3.

[0045] It has been found that using the compounds of the present invention, it is possible to produce ethylene copolymers wherein the comonomer is selected from 1-butene, 1 -hexene, 4-methyl-1 -pentene, vinyl-cyclohexane and 1-octene with particularly high incorporation of the comonomer. The amount of incorporation of the comonomer may be expressed as the amount of short chain branches per 1000 carbon atoms in the polymer. The amount of short chain branches may for example be determined using 13C NMR via the method as described by Randall, Rev. Macromol. Chem. Phys., C. 29, V. 2&3, p. 285-297. The ethylene copolymer may for example comprise at least 10, 25, or 80 short chain branches per 1000 carbon atoms in the polymer. The ethylene copolymer may comprise at most 200, 100, 50 or 25 short chain branches per 1000 carbon atoms in the polymer. The ethylene copolymer may for example comprise at least 10 and at most 200 short chain branches per 1000 carbon atoms in the polymer, or at least 15 and at most 100, or at least 20 and at most 50.

[0046] The polyethylene may have a number-average molecular weight (Mn) of between 1 ,000 and 10,000,000 g / mol, preferably between 10,000 and 1 ,000,000 g / mol, more preferably between 20,000 and 500,000 g / mol. The polyethylene may have a weight-average molecular weight (Mw) of between 2,000 and 20,000,000 g / mol, preferably between 20,000 and 2,000,000 g / mol, more preferably between 40,000 and 1 ,000,000 g / mol. The Mw and Mn are determined in accordance with ASTM D6474-12, using 1,2,4-trichlorobenzene or o-dichlorobenzene as solvent, and calibrated using polyethylene or polystyrene standards. The polyethylene may for example have a molecular weight distribution Mw / Mn of > 2.0 and < 6.0, or > 2.1 and < 4.0, or > 2.5 and < 3.5.

[0047] The invention will now be illustrated by the following non-limiting examples. In the examples as described herein, synthesis of chemical compounds was performed according to the synthetic routes described in WO2021 / 213836, further specified herein below.Synthesis of compound A:For access to the brominated MOM protected phenol, the following scheme was used:For the inventive compounds, the synthetic procedure as outlined below has been applied:MCI4, MeMgBr PhMe - Et2Owherein MOM is a -CH2-O-CH3 moiety.Similarly, the following compounds were synthesized:wherein Bn indicates a benzyl moiety.

[0048] Using the compounds as defined above, a number of polymerisation experiments were conducted to investigate the performance of the compounds as catalysts in ethylene polymerisations.

[0049] Polymerisations were carried out in a Parallel Pressure Reactor (PPR48) for olefin polymerisation, containing 48 reactors mounted in a triple glove-box, obtained from the company Freeslate. The applied polymerisation protocols were as follows:

[0050] Prior to execution of a library, the 48 PPR cells (reactors) undergo ‘bake-and-purge’ cycles overnight (8 h at 90-140°C, with intermittent dry N2flow) to remove any contaminants.After cooling to glove-box temperature (23°C), the stir tops are taken off, and the cells are fitted with disposable 10 ml glass inserts and stirring paddles, previously hot-dried under vacuum. The stir tops are then set back in place, the cells are loaded with the proper amounts of toluene (in the range of 2.0-4.0 ml), 1-hexene (in the range of 0.05-2.0 ml) and a tri-isobutyl-aluminium (TiBAI) / butylated hydroxytoluene (BHT) reaction product solution, thermostated at the required polymerisation temperature, and brought to the operating pressure of 1.0 MPa with ethylene, unless otherwise specified in the examples.

[0051] The catalyst injection sequence is as follows: proper volumes of a toluene chaser, a solution of the precatalyst in toluene (typically in the range of 0.005-0.05 mmol / l) and a toluene buffer are uptaken into the slurry needle, and then injected into the cell of destination. The reaction is left to proceed under stirring (800 rpm) at constant temperature and pressure, with continuous feed of ethylene for 5-60 minutes, and quenched by over-pressurising the cell with dry air.

[0052] After quenching, the cells are cooled down and vented, the stir-tops are removed, and the glass inserts containing the reaction phase are taken out and transferred to a Genevac EZ2- Plus centrifugal evaporator, where all volatiles are distilled out and the obtained polymers are thoroughly dried overnight. Reaction yields are double-checked against on-line monomer conversion measurements by robotically weighing the dry polymers in a Bohdan Balance Automator while still in the reaction vials, subtracting the pre-recorded tare. Polymer aliquots are then sampled out for the characterisations.

[0053] GPC curves were recorded with a Freeslate Rapid GPC setup, equipped with a set of 2 mixed-bed Agilent PLgel 10 pm columns and a Polymer Chat IR4 detector. The upper deck of the setup features a sample dissolution station for up to 48 samples in 10 ml magnetically stirred vials, 4 thermostated bays each accommodating 48 polymer solutions in 10 ml glass vials, and a dual arm robot with two heated injection needles. With robotic operation, preweighed polymer amounts (typically 1-4 mg) are dissolved in proper volumes of orthodichlorobenzene (ODCB) containing 0.40 mg / ml of 2,6-di-tert-butyl-4-methylphenol (BHT) as stabiliser, so as to obtain solutions at a concentration of 0.5 to 1.0 mg / ml. After 2-4 h at 150°C under gentle stirring to ensure complete dissolution, the samples are transferred to a thermostated bay at 145°C, and sequentially injected into the system at 145°C and a flow rate of 1.0 ml / min. In post-trigger delay operation mode, the analysis time is 12.5 min per sample. Calibration is carried out with the universal method, using 10 monodisperse polystyrenesamples (Mnbetween 1.3 and 3700 kg / mol). Before and after each campaign, samples from a known i-PP batch produced with an ansa-zirconocene catalyst are analysed for a consistency check.

[0054] 13C NMR spectra are recorded with a Bruker Avance 400 III spectrometer equipped with a 5 mm High Temperature Cryoprobe, and a robotic sample charger with a pre-heated carousel (24 positions). The samples (20-30 mg) are dissolved at 120°C in tetrachloroethane-1 ,2-d2 (0.6 ml), added with 0.40 mg / ml of BHT as stabiliser, and loaded in the carousel maintained at the same temperature. The spectra are taken sequentially with automated tuning, matching and shimming. Typical operating conditions for routine measurements are: 45° pulse; acquisition time 2.7 s; relaxation delay 5.0 s; 400-800 transients (corresponding to an analysis time of 30- 60 min). Broadband proton decoupling is achieved with a modified WALTZ16 sequence (BI_WALTZ16_32 by Bruker).

[0055] In the table below, properties of the polymerisations and the obtained polymers are presented, wherein the catalyst activity is presented as Rp, the polymerisation rate in kg polymer produced per mmol catalyst per mol of ethylene in the reactor diluent per hour. Mnis the number-average molecular weight in kg / mol. Mwis the weight-average molecular weight in kg / mol. MWD is the molecular weight distribution Mw / Mn. Mnand Mware determined according to the GPC method as described above. C6jnc is the quantity of 1 -hexene incorporation, in mol% hexene in the copolymer. The experiments were conducted at a total reactor pressure of 0.83 MPa, using a 1-hexene feed concentration of as indicated in the table (C6feed, in vol% of the feed composition), at 120°C, using N,N’-dimethylanilinium-tetrakis(pentafluorophenyl)borate (ABF20) as activator, in a molar ratio of 5:1 relative to the transition metal. A solution of the tri- isobutylaluminium / BHT reaction product (1 :1 molar ratio) was used, resulting in an aluminium concentration of 2 mmol / L in the reaction cell. In several experiments, diethylzinc was used, as indicated in the table below, indicated in mol / mol catalyst.

[0056] For comparative purposes, polymerisation examples according to the method described above were performed using the catalyst compound below:

[0057] The results of the polymerisation experiments are presented herein below:

[0058] The results as presented in the table above indicate that the compounds as per the present invention allow for use as catalysts in ethylene 1 1-hexene copolymerisation wherein the polymerisation rate, the molecular weight distribution breadth, and the quantity of 1-hexene incorporation may be increased, and a high molecular weight may be obtained.

Claims

Claims1. Compound according to formula 1 :wherein• M is a metal atom selected from Hf, Ti and Zr;• X is a halogen, a C1-C4 alkyl moiety, or a benzyl moiety;• R1 is a C1-C4 alkyl moiety;• each R2 and R3 is individually selected from hydrogen, a C1-C4 alkyl, methoxy, phenyl, benzyl, 2-phenylpropyl, 2,2’-diphenyl ethyl, 2,4,6-trimethylphenyl, 3,5- dimethylphenyl, 3,5-di-t-butyl-phenyl, 9 / 7-carbazol-9-yl, 9-methyl-9 / 7-fluoren-9-yl, and adamantyl;• R4 is a C1-C5 alkyl moiety, preferably R4 is selected from ethyl, propyl, n-butyl, isobutyl and isopentyl; wherein at least one R3 moiety is a methoxy moiety.

2. Compound according to claim 1 , according to formula 2:

3. Compound according to any one of claims 1-2, according to formula 3:

54. Compound according to claim 1 , according to formula 4:

5. Compound according to any one of claims 1-4, according to formula 5:wherein each R5 is selected from hydrogen and methyl.

6. Compound according to any one of claims 1-5, wherein M is selected from Hf and Zr.

7. Compound according to any one of claims 1-6, wherein each X is a methyl moiety, a benzyl moiety, or a chlorine atom, preferably wherein both X moieties are the same.

8. Compound according to any one of claims 1-7, wherein R1 is a methyl moiety.

9. Compound according to any one of claims 1-8, wherein each R2 and R3 is selected from hydrogen, methyl, methoxy and t-butyl.

10. Catalyst system comprising a compound according to any one of claims 1-9.

11. Catalyst system according to claim 10, further comprising an activator, wherein the activator is selected from an aluminoxane compound and a boron-based compound, optionally in the presence of an aluminium alkyl compound.

12. Catalyst system according to claim 11 , wherein the aluminoxane compound is selected from a methyl aluminoxane, an isobutyl aluminoxane, and a methyl-isobutyl aluminoxanes; or wherein the boron-based compound is selected from a tris(pentafluorophenyl)borane an a tetrakis(pentafluorophenyl)borate.

13. Catalyst system according to any one of claims 10-12, wherein the catalyst system comprises a compound according to any one of claims 1-9 carried on a support material, wherein the support material is selected from a polymeric support material, a clay material, a solid aluminoxanes, or an inorganic oxide, preferably wherein the support material comprises silica, alumina or a solid aluminoxane.

14. Process for the polymerisation of olefins, preferably wherein the polymerisation involves reaction of a reaction mixture comprising ethylene and / or propylene, in the presence of a catalyst system according to any one of claims 10-13, preferably wherein the process is a gas-phase process, a solution process, or a slurry process.

15. Process according to claim 14, wherein the process is a homopolymerisation process of ethylene, a homopolymerisation process of propylene, a copolymerisation process of ethylene with a comonomer, preferably selected from 1-butene, 1-hexene, 4-methyl-1- pentene, vinyl cyclohexane, and 1 -octene, or a copolymerisation process of propylene with a comonomer, preferably selected from ethylene, 1-butene, 1-hexene, 4-methyl-1- pentene, vinyl cyclohexane, and 1 -octene.

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