CATALYST SUPPORTS AND USES THEREOF

Abstract

Catalyst supports prepared from Ni.sup.2+-containing layered double hydroxides are disclosed. together with processes by which they are made and catalyst compositions comprising them. When used in the polymerisation of an olefin. the catalyst supports give control over the molecular weight distribution of the resulting polyolefin.

Claims

1. A process for preparing a catalyst support, the process comprising the steps of: a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; and c) contacting the thermally treated layered double hydroxide with an organoaluminium compound.

2. The process of claim 1, wherein Ni.sup.2+ accounts for at least 30 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a).

3. The process of claim 1 or 2, wherein one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+, Cu.sup.2+ and Mn.sup.2+ form the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a), and one or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a).

4. The process of claim 1, 2 or 3, wherein Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a).

5. The process of any one of the preceding claims, wherein Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a).

6. The process of any one of the preceding claims, wherein one or more inorganic oxyanion accounts for all anions present within the layered double hydroxide provided in step a).

7. The process of claim 1, wherein the layered double hydroxide provided in step a) is of formula (I) ##STR00014## wherein M.sup.2+ is at least one divalent metal cation; M.sup.3+ is at least one trivalent metal cation; 0.1?w?1; 0<x<0.9; 0?b?10; 0?c?10; X is an anion n is the charge on anion X a=x; and Q is an organic solvent capable of hydrogen bonding to water.

8. The process of claim 7, wherein M.sup.2+ is one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+, Cu.sup.2+ and Mn.sup.2+ and M.sup.3+ is one or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+.

9. The process of claim 7 or 8, wherein M.sup.2+ is Mg.sup.2+.

10. The process of claim 7, 8 or 9, wherein M.sup.3+ is Al.sup.3+ and X is an inorganic oxyanion.

11. The process of any one of claims 7 to 10, wherein the inorganic oxyanion is carbonate.

12. The process of any one of claims 7 to 11, wherein 0.5?w?1.

13. The process of any one of claims 7 to 12, wherein Q is one or more selected from acetone, ethanol, methanol and 1-hexanol.

14. The process of any one of claims 7 to 13, wherein 0<c?10.

15. The process of any one of the preceding claims, wherein step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 150-450? C.

16. The process of any one of the preceding claims, wherein step c) comprises contacting the thermally treated layered double hydroxide with 10-70 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide, wherein the organoaluminium compound is an alkyl aluminoxane.

17. A process for preparing a catalyst composition, the process comprising the steps of: a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; c) contacting the thermally treated layered double hydroxide with an organoaluminium compound; and d) supporting an olefin polymerisation catalyst on the thermally treated layered double hydroxide; wherein step d) is performed before, concurrent with, or after step c).

18. The process of claim 17, wherein step a), b) and/or c) is respectively as defined for step a), b) and/or c) in any one of claims 1 to 16.

19. The process of claim 17 or 18, wherein the olefin polymerisation catalyst is a metallocene, ansa-metallocene, half-metallocene or ansa-half-metallocene.

20. The process of claim 17, 18 or 19, wherein the olefin polymerisation catalyst is a bis-cyclopentadienyl zirconcene compound or a bis-indenyl zirconocene compound.

21. The process of claim any one of claims 17 to 20, wherein the olefin polymerisation catalyst is any one of the following: ##STR00015##

22. A catalyst support obtainable by the process of any one of claims 1 to 16.

23. A catalyst composition obtainable by the process of any one of claims 17 to 21.

24. An olefin polymerisation process comprising the step of polymerising an olefin in the presence of the catalyst composition of claim 23.

25. The process of claim 24, wherein the olefin is ethylene and wherein the olefin polymerisation process is performed in the slurry phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0021] The term (m-nC) or (m-nC) group used alone or as a prefix, refers to any group having m to n carbon atoms.

[0022] The term alkyl as used herein refers to straight or branched chain alkyl moieties, typically having 1, 2, 3, 4, 5 or 6 carbon atoms. This term includes reference to groups such as methyl, ethyl, propyl (n-propyl or isopropyl), butyl (n-butyl, sec-butyl or tert-butyl), pentyl, hexyl and the like. Most suitably, an alkyl may have 1, 2, 3 or 4 carbon atoms.

[0023] The term alkenyl as used herein refers to straight or branched chain alkenyl moieties, typically having 1, 2, 3, 4, 5 or 6 carbon atoms. The term includes reference to alkenyl moieties containing 1, 2 or 3 carbon-carbon double bonds (C?C). This term includes reference to groups such as ethenyl (vinyl), propenyl (allyl), butenyl, pentenyl and hexenyl, as well as both the cis and trans isomers thereof.

[0024] The term alkynyl as used herein refers to straight or branched chain alkynyl moieties, typically having 1, 2, 3, 4, 5 or 6 carbon atoms. The term includes reference to alkynyl moieties containing 1, 2 or 3 carbon-carbon triple bonds (C?C). This term includes reference to groups such as ethynyl, propynyl, butynyl, pentynyl and hexynyl.

[0025] The term alkoxy as used herein refers to O-alkyl, wherein alkyl is as defined herein. In one class of embodiments, alkoxy has 1, 2, 3 or 4 carbon atoms. This term includes reference to groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, hexoxy and the like.

[0026] The term aryl or aromatic as used herein means an aromatic ring system comprising 6, 7, 8, 9 or 10 ring carbon atoms. Aryl is often phenyl but may be a polycyclic ring system, having two or more rings, at least one of which is aromatic. This term includes reference to groups such as phenyl, naphthyl and the like.

[0027] The term heteroaryl or heteroaromatic means an aromatic mono-, bi-, or polycyclic ring incorporating one or more (for example 1-4, particularly 1, 2 or 3) heteroatoms selected from nitrogen, oxygen or sulfur. Examples of heteroaryl groups are monocyclic and bicyclic groups containing from five to twelve ring members, and more usually from five to ten ring members. The heteroaryl group can be, for example, a 5- or 6-membered monocyclic ring or a 9- or 10-membered bicyclic ring, for example a bicyclic structure formed from fused five and six membered rings or two fused six membered rings. Each ring may contain up to about four heteroatoms typically selected from nitrogen, sulfur and oxygen. Typically, the heteroaryl ring will contain up to 3 heteroatoms, more usually up to 2, for example a single heteroatom.

[0028] The term aryloxy as used herein refers to O-aryl, wherein aryl is as defined herein. Suitably, aryl is optionally substituted phenyl.

[0029] The term halogen or halo as used herein refers to F, Cl, Br or I. In a particular, halogen may be F or Cl, of which CI is more common.

[0030] The term substituted as used herein in reference to a moiety means that one or more, especially up to 5, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. Preferably, substituted as used herein in reference to a moiety means that 1, 2 or 3, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. Even more preferred, substituted as used herein in reference to a moiety means that 1 or 2, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. The term optionally substituted as used herein means substituted or unsubstituted.

[0031] It will, of course, be understood that substituents may only be at positions where they are chemically possible, the person skilled in the art being able to decide (either experimentally or theoretically) without inappropriate effort whether a particular substitution is possible.

[0032] Throughout the entirety of the description and claims of this specification, where subject matter is described herein using the term comprise (or comprises or comprising), the same subject matter instead described using the term consist of (or consists of or consisting of) or consist essentially of (or consists essentially of or consisting essentially of) is also contemplated.

[0033] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0034] Features described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any of the specific embodiments recited herein. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0035] Unless otherwise specified, where the quantity or concentration of a particular component of a given product is specified as a weight percentage (wt. % or % w/w), said weight percentage refers to the percentage of said component by weight relative to the total weight of the product as a whole. It will be understood by those skilled in the art that the sum of weight percentages of all components of a product will total 100 wt. %. However, where not all components are listed (e.g. where a product is said to comprise one or more particular components), the weight percentage balance may optionally be made up to 100 wt. % by unspecified ingredients.

Catalyst Supports

[0036] According to a first aspect of the present invention there is provided a process for preparing a catalyst support, the process comprising the steps of: [0037] a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; [0038] b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; and [0039] c) contacting the thermally treated layered double hydroxide with an organoaluminium compound.

[0040] Through rigorous investigations, the inventors have devised catalyst supports useful in the preparation of polyolefins having tuneable MWD properties. In particular, when used in conjunction an olefin polymerisation catalyst (e.g. an ansa-metallocene) the catalyst supports of the invention allow for the preparation of a polyolefin, especially a polyethylene, having a multimodal (e.g. bimodal) MWD. When compared with the aforementioned prior art techniques for controlling the MWD of polyolefins, the catalyst supports of the invention represent a sophisticated yet simple means of accessing multimodal polyolefins. Thus, the catalyst supports are suitable for supporting an olefin polymerisation catalyst, such as one of those described herein.

[0041] The catalyst supports of the invention are prepared from Ni.sup.2+-containing layered double hydroxides. The structure of layered double hydroxides will be readily familiar to one of ordinary skill in the art as comprising a stack of positively charged, brucite-like layers of octahedral metal hydroxides intercalated by exchangeable, charge-balancing anions, where water typically provides hydrogen bonding between the positively charged layers. The layers of metal hydroxides are typically formed from a mixture of divalent and trivalent metal cations, although variants in which the divalent cation is replaced by (or supplemented with) a monovalent cation and/or the trivalent cation is replaced by (or supplemented with) a tetravalent cation are known.

[0042] The layered double hydroxides used to prepare the catalyst supports of the invention comprise Ni.sup.2+ (i.e. divalent nickel cations) in the positively charged metal hydroxide layers. The inventors have surprisingly found that increasing the quantity of Ni.sup.2+ in the layered double hydroxide renders the resulting catalyst support capable of affording a multimodal polyolefin (especially a bimodal polyethylene) despite using only a single olefin polymerization catalyst. Therefore, the quantity of Ni.sup.2+ in the catalyst support can be used to tune the MWD of a polyolefin, such as polyethylene.

[0043] Ni.sup.2+ may account for at least 10 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). The quantity of Ni.sup.2+ in the layered double hydroxide can be readily determined by, for example, elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS). Suitably, Ni.sup.2+ accounts for at least 30 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). More suitably, Ni.sup.2+ accounts for at least 50 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). Even more suitably, Ni.sup.2+ accounts for at least 70 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). Yet more suitably, Ni.sup.2+ accounts for at least 90 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). Yet even more suitably, Ni2+accounts for at least 95 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a).

[0044] In particular embodiments, Ni.sup.2+ may account for substantially all (or all) monovalent and divalent metal cations present within the layered double hydroxide provided in step a). The mole ratio of Ni.sup.2+ to all trivalent and tetravalent metal cations present within the layered double hydroxide (e.g., Al.sup.3+) may be 1.9:1 to 3.1:1, or more suitably 2:1 to 3:1 (e.g., 2:1 or 3:1).

[0045] One or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+, Cu.sup.2+ and Mn.sup.2+ may form the optional balance of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). The term optional balance will be understood to refer to all non-Ni.sup.2+ monovalent and divalent metal cations present within the layered double hydroxide, recognising that in particular embodiments, Ni.sup.2+ may account for substantially all (or all) monovalent and divalent metal cations present within the layered double hydroxide. Accordingly, the term optional balance encompasses two alternatives: i) where Ni.sup.2+ accounts for all monovalent and divalent metal cations present within the layered double hydroxide (i.e., no balance of monovalent and divalent metal cations exists), and ii) where Ni.sup.2+ does not account for all monovalent and divalent metal cations present within the layered double hydroxide (i.e., a balance of monovalent and divalent metal cations exists). Suitably, Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a).

[0046] As discussed hereinbefore, it will be understood that the layered double hydroxide provided in step a) comprises at least one trivalent or tetravalent metal cation. One or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+ may account for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a). Suitably, Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a).

[0047] In particular embodiments, Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a) and Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a).

[0048] As discussed hereinbefore, it will be understood that the layered double hydroxide provided in step a) comprises at least one anion. One or more of a halide, an inorganic oxyanion and a surfactant may account for all anions present within the layered double hydroxide provided in step a). Exemplary halides include fluoride, chloride and bromide, of which chloride is preferred. Exemplary inorganic oxyanions include carbonate, bicarbonate, nitrate, nitrite, sulfate, borate and phosphate, of which carbonate is preferred. Exemplary surfactants include fatty acid salts, such as sodium dodecyl sulfate and sodium stearate. Suitably, one or more inorganic oxyanions account for all anions present within the layered double hydroxide provided in step a). More suitably, carbonate accounts all anions present within the layered double hydroxide provided in step a).

[0049] In particular embodiments, Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a), Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a), and one or more inorganic oxyanions account for all anions present within the layered double hydroxide provided in step a). Suitably, the one or more inorganic oxyanions is carbonate.

[0050] The layered double hydroxide provided in step a) may be of formula (I):

##STR00001##

wherein [0051] M.sup.2+ is at least one divalent metal cation; [0052] M.sup.3+ is at least one trivalent metal cation; [0053] 0.1?w?1; [0054] 0<x<0.9; [0055] 0?b?10; [0056] 0?c?10; [0057] X is an anion [0058] n is the charge on anion X [0059] a=x; and [0060] Q is an organic solvent capable of hydrogen bonding to water.

[0061] M.sup.2+ may be one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+ , Cu.sup.2+ and Mn.sup.2+. Suitably, M.sup.2+ is one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+ and Ca.sup.2+. More suitably, M.sup.2+ is Mg.sup.2+.

[0062] M.sup.3+ may be one or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+. Suitably, M.sup.3+ is one or more of Al.sup.3+, Ga.sup.3+ and Fe.sup.3+. More suitably, M.sup.3+ is Al.sup.3+.

[0063] In particular embodiments, M.sup.2+ is Mg.sup.2+ and M.sup.3+ is Al.sup.3+.

[0064] X may be one or more selected from a halide, an inorganic oxyanion and a surfactant. Exemplary halides include fluoride, chloride and bromide, of which chloride is preferred. Exemplary inorganic oxyanions include carbonate, bicarbonate, nitrate, nitrite, sulfate, borate and phosphate, of which carbonate is preferred. Exemplary surfactants include fatty acid salts, such as sodium dodecyl sulfate and sodium stearate. Suitably, X is an inorganic oxyanion. More suitably, X is carbonate.

[0065] In particular embodiments, M.sup.2+ is Mg.sup.2+, M.sup.3+ is Al.sup.3+ and X is carbonate.

[0066] Suitably, 0.3?w?1. More suitably, 0.5?w?1. Even more suitably, 0.7?w?1. Yet more suitably, 0.9?w$1. Yet even more suitably, 0.95?w?1. It will be understood that the symbol ? (i.e., less-than-or-equal-to) encompasses two alternatives, namely less than and equal to. Therefore, in any of the aforementioned ranges, w may be <1. In particular embodiments, w=1.

[0067] Alternatively, 0.25?w?0.75. In particular embodiments, w=0.33, 0.5 or 0.66.

[0068] Suitably, 0.1?x?0.5. More suitably, 0.2?x?0.4.

[0069] Q may be an organic solvent capable of donating hydrogen bonds to, or accepting hydrogen bonds from, water. Organic solvents containing hydrogen bond donating and accepting moieties will be readily familiar to one of ordinary skill in the art. Particular, non-limiting classes of organic solvents capable of hydrogen bonding to water are alcohols, ketones and aldehydes. Suitably, Q is one or more selected from acetone, ethanol, methanol and 1-hexanol. In particular embodiments, Q is ethanol.

[0070] Suitably, 0<c?10. Layered double hydroxides in which c>0 have physical properties that make them particularly suitable for use in the preparation of catalyst supports. In particular, such layered double hydroxides may exhibit an increased surface area, increased pore volume and/or a reduced density relative to layered double hydroxides in which c=0. In particular embodiments, 0<c?10 and Q is ethanol.

[0071] Layered double hydroxides in which 0<c?10 can be readily prepared by one of skill in the art. For example, such layered double hydroxides can be produced by first precipitating a layered double hydroxide from an aqueous (i.e. water-containing) solvent, and then contacting (e.g. by washing or dispersing) the resulting, water-wet layered double hydroxide with one or more organic solvents, Q as defined herein. The term water-wet will be understood to mean that the precipitated layered double hydroxide is not allowed to become dry before it is contacted with the one or more organic solvents, Q. The precipitated layered double hydroxide may be washed with water before it is contacted with (e.g. washed with or dispersed in) the one or more organic solvents, Q.

[0072] The layered double hydroxide may be a layered double hydroxide of formula (Ia):

##STR00002##

wherein w is 0.33, 0.66 or 1, and b, c and Q are as defined hereinbefore in relation to formula (I). Suitably, 0<c?10 and Q is ethanol. In some embodiments, w is 0.33 or 0.66.

[0073] The layered double hydroxide may be a layered double hydroxide of formula (Ib):

##STR00003##

wherein w is 0.5 or 1, and b, c and Q are as defined hereinbefore in relation to formula (I). Suitably, 0<c?10 and Q is ethanol. In some embodiments, w is 0.5.

[0074] The layered double hydroxide may be a layered double hydroxide of formula (Ic):

##STR00004##

wherein w is 0.33, 0.66 or 1, and b and c are as defined hereinbefore in relation to formula (I). Suitably, 0<c?10. In some embodiments, w is 0.33 or 0.66.

[0075] The layered double hydroxide may be a layered double hydroxide of formula (Id):

##STR00005##

wherein w is 0.5 or 1, and b and c are as defined hereinbefore in relation to formula (I). Suitably, 0<c?10. In some embodiments, w is 0.5.

[0076] In step b), the layered double hydroxide is thermally treated (suitably under vacuum) to a temperature of 100-600? C. to yield a thermally treated layered double hydroxide. Suitably, step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 125-500? C. More suitably, step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 150-450? C. Even more suitably, step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 300-425? C. The layered double hydroxide may be thermally treated to the stated temperature at a rate of 3-20 K/minute, more suitably 5-15 K/minute. Once at the stated temperature, the layered double hydroxide may be heated for 0.5-5 hours, more suitably, 2-4 hours.

[0077] In particular embodiments, step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 300-425? C. at a rate of 3-20 K/minute, and is then held at 300-425? C. for 2-4 hours. In such embodiments, step b) is suitably conducted under vacuum.

[0078] The organoaluminium compound used in step c) may be one or more of an alkyl aluminoxane and a trialkylaluminium compound. Exemplary alkyl aluminoxanes include, without limitation, those in which the alkyl group is methyl (i.e. methylaluminoxane, MAO), ethyl (i.e. ethylaluminoxane, EAO) and isobutyl (i.e. isobutylaluminoxane, IBAO), as well as those containing a mixture of two or more of the aforementioned alkyl groups. Exemplary trialkylaluminium compounds include, without limitation, trimethyl aluminium, triethyl aluminium and triisobutyl aluminium. Suitably, the organoaluminium compound is an alkyl aluminoxane, and is most suitably methylaluminoxane.

[0079] The amount of the organoaluminium compound used in step c) may be 10-70 wt % relative to the mass of the thermally treated layered double hydroxide. Suitably, step c) comprises contacting the thermally treated layered double hydroxide with 25-55 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide. More suitably, step c) comprises contacting the thermally treated layered double hydroxide with 35-45 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide.

[0080] In particular embodiments, the organoaluminium compound is an alkyl aluminoxane, suitably methylaluminoxane, and step c) comprises contacting the thermally treated layered double hydroxide with 35-45 wt % of the alkyl aluminoxane relative to the mass of the thermally treated layered double hydroxide.

[0081] A person of skill in the art will be able to select suitable reaction conditions (e.g. solvents, temperature, pressure, reaction times, agitation etc.) for step c). In particular embodiments, step c) is conducted in an organic solvent, such as toluene. Suitably, step c) is performed at a temperature of 50-100? C.

[0082] The process may further comprises a step of isolating the material resulting from step c), for example by filtration and vacuum drying.

[0083] According to a third aspect of the present invention, there is provided a catalyst support obtainable, obtained or directly obtained by the process of the first aspect.

Catalyst Compositions

[0084] According to a second aspect of the present invention there is provided a process for preparing a catalyst composition, the process comprising the steps of: [0085] a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; [0086] b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; [0087] c) contacting the thermally treated layered double hydroxide with an organoaluminium compound; and [0088] d) supporting an olefin polymerisation catalyst on the thermally treated layered double hydroxide;
wherein step d) is performed before, concurrent with, or after step c).

[0089] As alluded to hereinbefore, the catalyst compositions of the invention are useful in the preparation of polyolefins having tuneable MWD properties, in particular polyethylenes having a multimodal (e.g. bimodal) MWD.

[0090] The olefin polymerisation catalyst may be a metallocene, ansa-metallocene, half-metallocene or ansa-half-metallocene, examples of which will be readily familiar to one of skill in the art.

[0091] The olefin polymerisation catalyst may have a structure according to formula (II):

##STR00006## [0092] M.sup.1 is zirconium, hafnium or titanium; [0093] L.sup.1 and L.sup.2 are each independently a ligand comprising a cyclopentadienyl moiety, said cyclopentadienyl moiety being ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another; and [0094] Y.sup.1 and Y.sup.2 are each independently a ligand selected from hydride, halo and (1-3C)alkyl.

[0095] In embodiments, L.sup.1 and L.sup.2 are each independently an optionally-substituted cyclopentadienyl group that is ?.sup.5 bound to M.sup.1, an optionally-substituted indenyl group that is ?.sup.5 bound to M.sup.1, or an optionally-substituted fluorenyl group that is ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another. More suitably, L.sup.1 and L.sup.2 are each independently an optionally-substituted cyclopentadienyl group that is ?.sup.5 bound to M.sup.1 or an optionally-substituted indenyl group that is ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another. In particular embodiments, L.sup.1 and L.sup.2 are each independently an optionally-substituted indenyl group that is ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another.

[0096] In embodiments, L.sup.1 and L.sup.2 are optionally linked to one another by an alkylene or a silylene linking group. L.sup.1 and L.sup.2 are optionally linked to one another by an ethylene group or a dimethylsilylene group.

[0097] In embodiments, M1 is zirconium.

[0098] In embodiments, Y1 and Y2 are each independently selected from hydride, chloro and methyl.

[0099] It will be understood that the optional substituents present in L.sup.1 and L.sup.2 may be selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, aryl (e.g. phenyl), aryl(1-2C)alkyl (e.g. benzyl), aryloxy (e.g. phenoxy) and heteroaryl. Particularly suitable optional substituents are selected from (1-4C)alkyl, (1-4C)alkoxy and phenyl.

[0100] In particular embodiments, the olefin polymerisation catalyst is a bis-cyclopentadienyl zirconcene compound or a bis-indenyl zirconocene compound.

[0101] Particularly suitable olefin polymerisation catalysts include:

##STR00007##

[0102] Most suitably, the olefin polymerisation catalyst is:

##STR00008##

[0103] Steps a), b) and c) of the second aspect are respectively analogous to steps a), b) and c) of the first aspect. It will therefore be appreciated that steps a), b) and/or c) of the second aspect may respectively be as defined hereinbefore in relation to steps a), b) and/or c) of the first aspect.

[0104] Having regard to step d) of the process for preparing the catalyst composition, the person of ordinary skill in the art will be readily aware of techniques for supporting catalysts on supporting substrates, and will therefore be able to select appropriate reaction conditions (e.g. solvents, temperature, pressure, reaction times, agitation etc.). In particular embodiments, step d) is conducted in an organic solvent, such as toluene. Suitably, step d) is performed at a temperature of 30-100? C.

[0105] Step d) can be performed before, simultaneously with, or after step c). In other words, the olefin polymerisation catalyst can be supported (i.e. immobilized) onto the thermally-treated layered double hydroxide before, after, or at the same time as the thermally-treated layered double hydroxide is reacted with the organoaluminium compound. Typically, step d) is performed after step c).

[0106] The amount of olefin polymerisation catalyst used in step d) may be such that the mole ratio of olefin polymerisation catalyst to aluminium (from the organoaluminium compound) in the resulting catalyst composition is 1:50 to 1:300, more suitably 1:75 to 1:150.

[0107] The process may further comprises a step of isolating the catalyst composition resulting from performing steps a) to d), for example by filtration and vacuum drying.

[0108] According to a fourth aspect of the present invention, there is provided a catalyst composition obtainable, obtained or directly obtained by the process of the second aspect.

Olefin Polymerisation

[0109] According to a fifth aspect of the present invention there is provided an olefin polymerisation process comprising the step of polymerising an olefin in the presence of the catalyst composition of the fourth aspect.

[0110] As alluded to hereinbefore, the catalyst compositions of the invention are useful in the preparation of polyolefins having tuneable MWD properties, in particular polyethylenes having a multimodal (e.g. bimodal) MWD.

[0111] In particular embodiments, the olefin is ethylene.

[0112] The olefin polymerisation process may be performed in the slurry phase. The skilled person will be readily able to select appropriate polymerisation conditions (e.g. solvents, pressure, reaction times, agitation etc.). In particular embodiments, the solvent is n-hexanes.

[0113] The olefin polymerisation process may be conducted in the presence of a co-catalyst. Suitably, the co-catalyst is an organoaluminium compound. Exemplary organoaluminium compounds include trimethyl aluminium, triethyl aluminium and triisobutyl aluminium, of which triisobutyl aluminium is favoured.

[0114] The olefin polymerisation process is suitably conducted at a temperature of 70-120? C. The temperature of the olefin polymerisation process can be used to tune the MWD of the resulting polyolefin. More suitably, the olefin polymerisation process is conducted at a temperature of 75-110? C. Even more suitably, the olefin polymerisation process is conducted at a temperature of 80-105? C. In particularly suitable embodiments, the olefin polymerisation process is conducted at a temperature of 85-95? C.

[0115] The following numbered statements 1 to 76 are not claims, but instead serve to define particular aspects and embodiments of the claimed invention: [0116] 1. A process for preparing a catalyst support, the process comprising the steps of: [0117] a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; [0118] b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; and [0119] c) contacting the thermally treated layered double hydroxide with an organoaluminium compound. [0120] 2. The process of statement 1, wherein Ni.sup.2+ accounts for at least 10 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0121] 3. The process of statement 1, wherein Ni.sup.2+ accounts for at least 30 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0122] 4. The process of statement 1, wherein Ni.sup.2+ accounts for at least 50 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0123] 5. The process of statement 1, wherein Ni.sup.2+ accounts for at least 70 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0124] 6. The process of statement 1, wherein Ni.sup.2+ accounts for at least 90 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0125] 7. The process of statement 1, wherein Ni.sup.2+ accounts for at least 95 mol % of all monovalent and divalent metal cations present within the layered double hydroxide provided in step a). [0126] 8. The process of any one of the preceding statements, wherein one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+, Cu.sup.2+ and Mn.sup.2+ form the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a). [0127] 9. The process of any one of statements 1 to 7, wherein Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a). [0128] 10. The process of any one of the preceding statements, wherein one or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a). [0129] 11. The process of statement 10, wherein Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a). [0130] 12. The process of any one of statements 1 to 7, wherein Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a), and wherein Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a). [0131] 13. The process of any one of the preceding statements, wherein one or more of a halide, an inorganic oxyanion and a surfactant accounts for all anions present within the layered double hydroxide provided in step a). [0132] 14. The process of statement 13, wherein one or more inorganic oxyanion accounts for all anions present within the layered double hydroxide provided in step a). [0133] 15. The process of statement 14, wherein the inorganic oxyanion is carbonate. [0134] 16. The process of any one of statements 1 to 7, wherein Mg.sup.2+ forms the optional balance of all monovalent and divalent metal cations within the layered double hydroxide provided in step a), and wherein Al.sup.3+ accounts for all trivalent and tetravalent metal cations present within the layered double hydroxide provided in step a); and wherein carbonate accounts for all anions present within the layered double hydroxide provided in step a). [0135] 17. The process of statement 1, wherein the layered double hydroxide provided in step a) is of formula (I)

##STR00009## [0136] wherein [0137] M.sup.2+ is at least one divalent metal cation; [0138] M.sup.3+ is at least one trivalent metal cation; [0139] 0.1?w?1; [0140] 0<x<0.9; [0141] 0?b?10; [0142] 0?c?10; [0143] X is an anion [0144] n is the charge on anion X [0145] a=x; and [0146] Q is an organic solvent capable of hydrogen bonding to water. [0147] 18. The process of statement 17, wherein M.sup.2+ is one or more of Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Ca.sup.2+, Cu.sup.2+ and Mn.sup.2+. [0148] 19. The process of statement 17, wherein M.sup.2+ is Mg.sup.2+. [0149] 20. The process of statement 17, 18 or 19, wherein M.sup.3+ is one or more of Al.sup.3+, Ga.sup.3+, Fe.sup.3+, Co.sup.3+, Mn.sup.3+ and V.sup.3+. [0150] 21. The process of statement 20, wherein M.sup.3+is Al.sup.3+. [0151] 22. The process of statement 17, wherein M.sup.2+is Mg.sup.2+ and M.sup.3+ is Al.sup.3+. [0152] 23. The process of any one of statements 17 to 22, wherein X is one or more selected from a halide, an inorganic oxyanion and a surfactant. [0153] 24. The process of statement 23, wherein X is an inorganic oxyanion. [0154] 25. The process of statement 24, wherein the inorganic oxyanion is carbonate. [0155] 26. The process of statement 17, wherein M.sup.2+ is Mg.sup.2+, M.sup.3+ is Al.sup.3+ and X is carbonate. [0156] 27. The process of any one of statements 17 to 26, wherein 0.3?w?1. [0157] 28. The process of statement 27, wherein 0.5?w?1. [0158] 29. The process of statement 27, wherein 0.7?w?1. [0159] 30. The process of statement 27, wherein 0.9?w?1. [0160] 31. The process of statement 27, wherein 0.95?w?1. [0161] 32. The process of any one of statements 17 to 31, wherein 0.1?x?0.5. [0162] 33. The process of statement 32, wherein 0.2?x?0.4. [0163] 34. The process of any one of statements 17 to 33, wherein Q is one or more selected from acetone, ethanol, methanol and 1-hexanol. [0164] 35. The process of statement 34, wherein Q is ethanol. [0165] 36. The process of statement 17, M2+is Mg2+, M3+is Al3+, X is carbonate and Q is ethanol. [0166] 37. The process of any one of statements 17 to 35, wherein 0<c?10. [0167] 38. The process of any one of the preceding statements, wherein step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 125-500? C. [0168] 39. The process of statement 38, wherein step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 150-450? C. [0169] 40. The process of statement 38, wherein step b) comprises thermally treating the layered double hydroxide provided in step a) to a temperature of 300-425? C. [0170] 41. The process of any one of the preceding statements, wherein step b) comprises thermally treating the layered double hydroxide at a rate of 3-20 K/minute. [0171] 42. The process of statement 41, wherein step b) comprises thermally treating the layered double hydroxide at a rate of 5-15 K/minute. [0172] 43. The process of any one of the preceding statements, wherein the layered double hydroxide is thermally treated at 100-600? C. (or at 125-500? C., 150-450? C. or 300-425? C.) for 0.5-5 hours. [0173] 44. The process of statement 43, wherein the layered double hydroxide is thermally treated at 100-600? C. (or at 125-500? C., 150-450? C. or 300-425? C.) for 2-4 hours. [0174] 45. The process of any one of the preceding statements, wherein step b) is performed under vacuum. [0175] 46. The process of any one of the preceding statements, wherein step c) comprises contacting the thermally treated layered double hydroxide with 10-70 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide. [0176] 47. The process of statement 46, wherein step c) comprises contacting the thermally treated layered double hydroxide with 25-55 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide. [0177] 48. The process of statement 46, wherein step c) comprises contacting the thermally treated layered double hydroxide with 35-45 wt % of the organoaluminium compound relative to the mass of the thermally treated layered double hydroxide. [0178] 49. The process of any one of the preceding statements, wherein step c) is conducted in an organic solvent (e.g. toluene). [0179] 50. The process of any one of the preceding statements, wherein the organoaluminium compound is an alkyl aluminoxane. [0180] 51. The process of statement 50, wherein the alkyl aluminoxane is a methyl aluminoxane. [0181] 52. A process for preparing a catalyst composition, the process comprising the steps of: [0182] a) providing a layered double hydroxide, the layered double hydroxide comprising Ni.sup.2+; [0183] b) thermally treating the layered double hydroxide to a temperature of 100-600? C.; [0184] c) contacting the thermally treated layered double hydroxide with an organoaluminium compound; and [0185] d) supporting an olefin polymerisation catalyst on the thermally treated layered double hydroxide; [0186] wherein step d) is performed before, concurrent with, or after step c). [0187] 53. The process of claim 52, wherein step a), b) and/or c) is respectively as defined for step a), b) and/or c) in any one of claims 1 to 51. [0188] 54. The process of statement 52 or 53, wherein the olefin polymerisation catalyst is a metallocene, ansa-metallocene, half-metallocene or ansa-half-metallocene. [0189] 55. The process of statement 52, 53 or 54, wherein the olefin polymerisation catalyst has a structure according to formula (II):

##STR00010## [0190] M.sup.1 is zirconium, hafnium or titanium; [0191] L.sup.1 and L.sup.2 are each independently a ligand comprising a cyclopentadienyl moiety, said cyclopentadienyl moiety being ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another; and [0192] Y.sup.1 and Y.sup.2 are each independently a ligand selected from hydride, halo and (1-3C)alkyl. [0193] 56. The process of statement 55, wherein L.sup.1 and L.sup.2 are each independently an optionally-substituted cyclopentadienyl, optionally-substituted indenyl, or optionally-substituted fluorenyl group that is n5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another. [0194] 57. The process of statement 55, wherein L.sup.1 and L.sup.2 are each independently an optionally-substituted indenyl group that is ?.sup.5 bound to M.sup.1, wherein L.sup.1 and L.sup.2 are optionally linked to one another. [0195] 58. The process of statement 55, 56 or 57, wherein L.sup.1 and L.sup.2 are optionally linked to one another by an alkylene or a silylene linking group. [0196] 59. The process of statement 58, wherein the alkylene linking group is ethylene and the silylene linking group is dimethylsilylene. [0197] 60. The process of any one of statements 55 to 59, wherein M.sup.1 is zirconium. [0198] 61. The process of any one of statements 55 to 60, wherein Y.sup.1 and Y.sup.2 are each independently selected from hydride, chloro and methyl. [0199] 62. The process of statements 52, 53 or 54, wherein the olefin polymerisation catalyst is a bis-cyclopentadienyl zirconcene compound or a bis-indenyl zirconocene compound. [0200] 63. The process of statement 52, 53 or 54, wherein the olefin polymerisation catalyst is any one of the following:

##STR00011## [0201] 64. The process of statement 52, 53 or 54, wherein the olefin polymerisation catalyst is:

##STR00012## [0202] 65. The process of any one of statements 52 to 64, wherein step d) is performed after step c). [0203] 66. The process of any one of statements 52 to 65, wherein the amount of olefin polymerisation catalyst used in step d) is such that the mole ratio of olefin polymerisation catalyst to aluminium (from the organoaluminium compound) in the resulting catalyst composition is 1:50 to 1:300. [0204] 67 A catalyst support obtainable by the process of any one of statements 1 to 51. [0205] 68. A catalyst composition obtainable by the process of any one of statements 52 to 66. [0206] 69. An olefin polymerisation process comprising the step of polymerising an olefin in the presence of the catalyst composition of statement 68. [0207] 70. The process of statement 69, wherein the olefin is ethylene. [0208] 71. The process of statement 69 or 70, wherein the olefin polymerisation process is performed in the slurry phase. [0209] 72. The process of statement 69, 70 or 71, wherein the olefin polymerisation process is performed in the presence of a co-catalyst. [0210] 73. The process of any one of statements 69 to 72, wherein the olefin polymerisation process is conducted at a temperature of 70-120? C. [0211] 74. The process of any one of statements 69 to 72, wherein the olefin polymerisation process is conducted at a temperature of 75-110? C. [0212] 75. The process of any one of statements 69 to 72 wherein the olefin polymerisation process is conducted at a temperature of 80-105? C. [0213] 76. The process of any one of statements 69 to 72, wherein the olefin polymerisation process is conducted at a temperature of 85-95? C.

EXAMPLES

[0214] One or more examples of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which:

[0215] FIG. 1 shows XRD powder patterns of Ni.sub.xMg.sub.2-xAl LDH.

[0216] FIG. 2 shows XRD powder patterns of Ni.sub.x(Mg.sub.3-x)Al LDH.

[0217] FIG. 3 shows TGA curves of Ni.sub.xMg.sub.2-xAl-LDH.

[0218] FIG. 4 shows TGA curves for Ni.sub.xMg.sub.3-xAl-LDH.

[0219] FIG. 5 shows unit cell parameter, a, corresponding to the metal-metal distance showing a near linear decrease with nickel content.

[0220] FIG. 6 shows a plot of the residual weight at 800? C. as determined by TGA analysis, showing an approximately linear increase in weight with nickel content.

[0221] FIG. 7 shows a plot of the residual weight after calcination under nitrogen, (400? C., 3 h with a 10 K.Math.min-.sup.?1 ramp from 30-400? C.) showing an approximately linear increase in weight with nickel content.

[0222] FIG. 8 shows the productivity of catalysts based on calcined LDH supports (Ni.sub.xMg.sub.2-xAl).

[0223] FIG. 9 shows the productivity of catalysts based on calcined LDH supports (Ni.sub.xMg.sub.3-xAl).

[0224] FIG. 10 shows: a) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Mg.sub.2Al LDH at various temperatures; b) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from NiMgAl LDH at various temperatures; c) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Ni.sub.2Al LDH at various temperatures.

[0225] FIG. 11 shows: a) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Mg3Al LDH at various temperatures; b) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from NiMg.sub.2Al LDH at various temperatures; c) MWD of polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Ni.sub.2MgAl LDH at various temperatures; d) MWD of polyethylene produced by (EBI)ZrCl2 immobilised on supports derived from Ni3Al LDH at various temperatures.

[0226] FIG. 12 shows MWD of polyethylene produced using two selected catalysts based on Ni.sub.xMg.sub.2-xAl-LDH and the silica reference at 70? C.

[0227] FIG. 13 shows MWD of polyethylene produced using two selected catalysts based on Ni.sub.xMg.sub.2-xAl-LDH and the silica reference at 90? C.

[0228] FIG. 14 shows the change in dispersity (M.sub.w/M.sub.n) with temperature for catalysts based on Ni.sub.x(Mg.sub.2-x)Al supports. Reference catalyst based on a silica support is also included.

[0229] FIG. 15 shows the change in dispersity (M.sub.w/M.sub.n) at 90? C. showing an increase with increasing nickel content for catalysts based on Ni.sub.xMg.sub.2-xAl and Ni.sub.xMg.sub.3-xAl LDH supports.

[0230] FIG. 16 shows: a) the change in molecular weight (M.sub.w) with temperature for polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Ni.sub.xMg.sub.2-xAl LDH and a silica reference; b) the change in molecular weight (M.sub.w) with temperature for polyethylene produced by (EBI)ZrCl.sub.2 immobilised on supports derived from Ni.sub.xMg.sub.3-xAl LDH and a silica reference.

[0231] FIG. 17 shows DSC of polyethylene produced at 90? C. using selected catalysts based on supports derived from Mg.sub.2Al, NiMgAl and Ni.sub.2Al.

[0232] FIG. 18 shows TGA curves of inorganic material collected after reference polymerisations and the bimodal polyethylene produced by (EBI)ZrCl.sub.2 immobilized on a support derived from Ni.sub.2Al LDH at 90? C.

General Considerations

[0233] All air-sensitive chemistry was carried out under an inert atmosphere using Schlenk line or glove-box techniques. Toluene and n-hexanes were collected from an MBraun SPS, degassed on a Schlenk line and stored over a potassium mirror for at least 12 hours before use.

[0234] d-MAO used was dried Axion CA1330 provided by Chemtura, dried on a Schlenk line and then stored in a glove-box before use. (EBI)ZrCl.sub.2 (STREM Chemicals) and TiBA (Aldrich) were stored in a glovebox prior to use.

[0235] Al(NO.sub.3).sub.3.Math.9H.sub.2O (99.999% trace metals), Mg(NO.sub.3).sub.2.Math.6H.sub.2O (99.999% trace metals) and Ni(NO.sub.3).sub.2.Math.6H.sub.2O (99.999% trace metals), NaOH (>98%, pellets), ethanol (>99.8%) and pentanes (>99%) were purchased from Aldrich and used as received.

[0236] Powder X-ray diffraction (PXRD) analysis was carried out using a PANAnalytical XPert Pro Diffractometer in scanning mode using Cu K? radiation (?1=1.540598 ?, ?2=1.544426 ?) in reflection mode at 40 kV and 40 mA. The samples were packed on stainless steel holders which can result in peaks at 43.36, 44.29, and 50.51? but which did not interfere with the analysis. Signals between 2?=2?70? were recorded with step size 0.0167?.

[0237] Thermogravimetric analyses (TGA) were performed under a nitrogen atmosphere using a PerkinElmer TGA 8000. The weight change was recorded from 30-800? C. (5 K.Math.min.sup.?1). For calcination under nitrogen, the weight change was recorded from 30-400? C. (10 K.Math.min.sup.?1) and over the 3 hour hold period.

[0238] Polymerisations were run in duplicate, if results were not consistent (defined here as within 10% of the mean) a third polymerisation was carried out and the average value reported is that of the two consistent runs. If the third polymerisation was consistent with both original runs, or if after three runs no consistent results were obtained the average value reported is that of all three runs.

[0239] HT-GPC were carried out by AS-Norner, each sample was run in duplicate on a high temperature gel permeation chromatograph with a IR5 infrared detector (GPC-IR5) Samples were dissolved in trichlorobenzene (TCB) with 300 ppm of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) at 160? C. for 90 minutes and filtered with a 10 ?m filter. Samples were run using TCB (300 ppm BHT) at a flow rate of 0.5 mL.Math.min.sup.?1 as a mobile phase with 1 mg/mL BHT added as a flow rate marker. The GPC column and detector were set at 145 and 160? C. respectively.

Synthesis

Preparation of Ni.SUB.x.(Mg.SUB.3-x.)Al LDH ([(Ni.SUB.x.Mg.SUB.1-x.).SUB.0.75.Al.SUB.0.25.(OH).SUB.2.](CO.SUB.3.).SUB.0.125..Math.bH.SUB.2.O.Math.c(Ethanol))

[0240] 25 mmol Al(NO.sub.3).sub.3.Math.9H.sub.2O and the appropriate amounts of Mg(NO.sub.3).sub.2.Math.6H.sub.2O and Ni(NO.sub.3).sub.2.Math.6H.sub.2O (75 mmol in total) were dissolved in 100 mL deionised water. This was then added at 100 mL.Math.h.sup.?1 to a sodium carbonate solution (12.5 mmol in 100 mL deionised water), throughout the addition the pH was monitored and the solution was maintained at pH 10 using 5 M NaOH. After the addition was complete the white suspension was stirred overnight (18 hours). The white solid was then filtered off and washed with deionised water until the filtrate was neutral. The white solid was then washed with 1 litre of ethanol, before resuspending the solid in 600 mL ethanol and stirring for four hours. The white solid was then collected by filtration, washed with 400 mL ethanol and dried overnight in a vacuum oven (<30 mBar, R.T.).

Preparation of Ni.SUB.x.(Mg.SUB.2-x.)Al LDH ([(Ni.SUB.x.Mg.SUB.1-x.).SUB.0.66.Al.SUB.0.33.(OH).SUB.2.](CO.SUB.3.)).SUB.0.175..Math.bH.SUB.2.O.Math.c(Ethanol))

[0241] 25 mmol Al(NO.sub.3).sub.3.Math.9H.sub.2O and the appropriate amounts of Mg(NO.sub.3).sub.2.Math.6H.sub.2O and Ni(NO.sub.3).sub.2.Math.6H.sub.2O (50 mmol in total) were dissolved in 75 mL deionised water. This was then added at 100 mL.Math.h.sup.?1 to a sodium carbonate solution (12.5 mmol in 75 mL deionised water), throughout the addition the pH was monitored and the solution was maintained at pH 10 using 5 M NaOH. After the addition was complete the white suspension was stirred overnight (18 hours). The white solid was then filtered off and washed with deionised water until the filtrate was neutral. The white solid was then washed with 1 litre of ethanol, before resuspending the solid in 600 mL ethanol and stirring for four hours. The white solid was then collected by filtration, washed with 400 mL ethanol and dried overnight in a vacuum oven (<30 mBar, R.T.).

Vacuum Calcination of Ni.SUB.x.(Mg.SUB.y-x.)Al LDH (y=3 or 2)

[0242] 500 mg of Ni.sub.x(Mg.sub.y-x)Al LDH was placed in a ceramic crucible, which was then placed in a quartz tube. This tube was placed in a tube furnace, connected to a Schlenk line and carefully placed under vacuum. Once a suitably low vacuum was reached (<2?10.sup.?1 mBar) the sample was heated to 400? C. at a heating rate of 10 K.Math.min.sup.?1, once the furnace reached 400? C. this temperature was maintained for 3 hours. The tube was under dynamic vacuum throughout the calcination and after calcination the tube was sealed and brought into a glovebox where the calcined supports [Ni.sub.x(Mg.sub.y-x)Al (400? C., 3 h, 10 K.Math.min.sup.?1)] were stored.

Preparation of Catalyst Support [Ni.SUB.x.(Mg.SUB.y-x.)Al (400? C., 3 h, 10 K.Math.min.SUP.?1.)/40 wt.% d-MAO]

[0243] 250 mg of calcined support Ni.sub.x(Mg.sub.y-x)Al (400? C., 3 h, 10 K.Math.min.sup.?1) and 100 mg d-MAO were weighed out and mixed as solids. Toluene (50 mL) was then added and the sample was heated to 80? C. To ensure an even distribution of d-MAO on the support the suspension was swirled continuously for 15 minutes and then swirled every 5 minutes for 105 minutes. After 2 hours, the suspension was allowed to cool and the toluene was filtered off. The wet solid was dried under vacuum and the catalyst support [Ni.sub.x(Mg.sub.y-x)Al (400? C., 3 h, 10 K.Math.min-.sup.?1)/40 wt.% d-MAO] stored in a glovebox.

Preparation of Catalyst Composition [Ni.SUB.x.(Mg.SUB.y-x.)Al (400? C., 3 h, 10 K.Math.min.SUP.?1.)/40 wt. % d-MAO/(EBI)ZrCl.SUB.2.]

[0244] 200 mg of catalyst support [Ni.sub.x(Mg.sub.y-x)Al (400? C., 3 h, 10 K.Math.min.sup.?1)/40 wt. % d-MAO] and 4.2 mg (EBI)ZrCl.sub.2 (10 ?mol Zr, approx. 100:1 Al.sub.[MAO]:Zr) were weighed out and mixed as solids. Toluene (15 mL) was then added and the sample heated to 60? C. To ensure an even distribution of (EBI)ZrCl.sub.2 on the catalyst support, the suspension was swirled as toluene was added and swirled continuously for 15 minutes and then swirled every 5 minutes for 45 minutes. After 1 hour, the suspension was allowed to cool and the toluene was decanted. The wet solid was dried under vacuum and the catalyst [Ni.sub.x(Mg.sub.y-x)Al (400? C., 3 h, 10 K.Math.min.sup.?1)/40 wt. % d-MAO/(EBI)ZrCl.sub.2] stored in a glovebox.

##STR00013##

Polymerisation

General Procedure

[0245] In a glovebox, approx. 150 mg of TiBA was dissolved in 10 mL n-hexanes and added to a 150 mL ampoule and 10 mg of catalyst was then added. A further 40 mL of n-hexanes was then added, and the ampoule sealed and brought out of the glovebox. The ampoule was cycled on to a Schlenk line, heated to the desired temperature using an oil bath and stirred using a magnetic stirrer bar at 1000 rpm. The ampoule was carefully evacuated, and then pressurised to 2 Bar with ethylene. Polymerisation was carried out for 30 minutes, after which the ampoule was vented carefully, and the polymer isolated by filtration and washed with pentanes (50 mL) before air drying.

Results and Discussion

[0246] The purity of the LDHs can be seen to be in the good agreement between the theoretical and actual nickel contents (Table 1), the XRD powder patterns (Ni.sub.xMg.sub.2-xAl shown in FIG. 1, Ni.sub.xMg.sub.3-xAl shown in FIG. 2) and the TGA curves (Ni.sub.xMg.sub.2-xAl shown in FIG. 3, Ni.sub.xMg.sub.3-xAl shown in FIG. 4).

TABLE-US-00001 TABLE 1 LDH Supports Synthesised in this Study and their Composition Support Theoretical Actual Theoretical Actual Residual Sample Ni:Mg Ni:Mg M (II) Ni M(II) Ni Weight at Metal-Metal Name Ratio.sup.a Ratio.sup.b Content (%).sup.c Content (%).sup.d 800? C. (%).sup.e Distance (?).sup.f Mg.sub.2Al 0:2 0:0.82 0 0 52.1 3.0362 NiMgAl 1:1 0.98:0.99 50 49.6 56.9 3.0302 Ni.sub.2Al 2:0 1.95:0 100 100 60.1 3.0186 Mg.sub.3Al 0:3 0:2.87 0 0 52.4 3.0576 NiMg.sub.2Al 1:2 0.94:1.92 33.3 32.9 55.7 3.0546 Ni.sub.2MgAl 2:1 1.92:0.96 66.7 66.81 58.9 3.0470 Ni.sub.3Al 3:0 2.89:0 100 100 62.3 3.0408 .sup.aBased on molar ratios of metal nitrates used in the synthesis, relative to Al. .sup.bDetermined by ICP-MS, relative to Al. .sup.cBased on ratios of metal nitrates used in the synthesis. .sup.dAs determined by ICP-MS. .sup.eAs determined by TGA, 30-800? C., 5 K .Math. min.sup.?1. .sup.fDetermined from the 110 peak in the XRD powder pattern.

[0247] These XRD powder patterns show the expected peaks associated with an LDH. There is a shift in the 110 peak to higher values of 2? as the M(II) nickel content is increased. This is observed for both the Ni.sub.xMg.sub.3-xAl and the Ni.sub.xMg.sub.2-xAl series and is consistent with a decrease in the metal-metal distance a decreasing as the larger Mg.sup.2+ ion is replaced with the smaller Ni.sup.2+ ion. Values for the metal-metal distance can be determined using Bragg's law (given in Table 1) and plotting these against the theoretical M(II) nickel content reveals an approximately linear trend for both series (FIG. 5).

[0248] The TGA curves show the expected weight losses associated with calcination of an LDH. Below 200? C. there is loss of interlayer solvent molecules (ethanol and water) seen as distinct maxima in the DTGA at approximately 90 and 170? C. respectively. As the nickel content changes the ratio between these two peaks changes suggesting a change in the composition of the interlayer solvents. Above 200? C., dehydroxylation of OH bonds in the LDH occurs, this is associated with the partial loss of the carbonate anion and formation of amorphous mixed metal oxides..sup.7, 8 The dehydroxylation temperature has been previously shown to be dependent on the nature of the M(OH)M.sub.2 bonds (amongst other factors) and as nickel content increases the dehydroxylation temperature decreases. For both series as the nickel content increases, the residual weight at 800? C. increases as the magnesium ions are replaced by heavier nickel ions.

[0249] Importantly, the residual weight at 800? C. correlates with the theoretical M(II) nickel content (FIG. 6), suggesting there are no amorphous impurities in the samples which were not observed in the powder XRD patterns. In combination these measurements suggest that these nickel supports are synthetically pure and suitable for use in studying the influence of the nickel content on polymerisation.

[0250] To generate an appropriate mixed metal oxide support, the LDH were calcined at 400? C. under vacuum for 3 hours, the supports were then treated with d-MAO (40 wt. %) to generate an appropriate support for a metallocene and (EBI)ZrCl.sub.2 was immobilised onto the support. Polymerisations were carried out using hexanes as the diluent and TiBA as a scavenger. A catalyst using silica (PQ-ES70X) as the support is included for comparison purposes (Table 2).

TABLE-US-00002 TABLE 2 Polymerisation using LDH Supports with Varying Nickel Contents.sup.a Temperature Productivity.sup.b Activity.sup.b M.sub.w.sup.c Support (? C.) (kg.sub.PE .Math. g.sub.cat.sup.?1 .Math. h.sup.1) (kg.sub.PE .Math. mol.sub.Zr.sup.?1 .Math. h.sup.?1) (kg .Math. mol.sup.1) M.sub.w/M.sub.n.sup.c Mg.sub.2Al 70 0.212 4330 194 3.6 80 0.210 4290 181 3.8 90 0.256 5220 127 3.8 NiMgAl 70 0.147 3000 172 5.6 80 0.133 2710 135 6.4 90 0.095 1940 115 7.0 Ni.sub.2Al 70 0.141 2880 173 5.9 80 0.115 2350 160 7.7 90 0.147 3000 151 12.2 Mg.sub.3Al 70 0.078 1590 190 5.7 80 0.085 1730 161 5.3 90 0.070 1430 140 5.3 NiMg.sub.2Al 70 0.125 2550 196 5.2 80 0.125 2550 153 5.7 90 0.108 2200 129 6.7 Ni.sub.2MgAl 70 0.052 1060 185 6.3 80 0.058 1180 153 7.4 90 0.056 1140 115 7.7 Ni.sub.3Al 70 0.214 4370 267 7.2 80 0.220 4490 224 9.0 90 0.187 3820 199 11.3 Silica (PQ- 70 0.044 900 274 5.6 ES70X).sup.d 80 0.065 1330 207 5.5 90 0.079 1600 227 5.5 .sup.aPolymerisation conditions: 10 mg supported catalyst (0.49 ?mol Zr), 50 mL hexanes, 150 mg TiBA, 2 bar ethylene, 30 minutes. .sup.bAverage based on two consistent polymerisations. .sup.cDetermined by HT-GPC, carried out by AS-Norner, all measurements carried out in duplicate, values from single measurement. .sup.dSilica support calcined at 400? C. for 6 h.

[0251] Productivity of the LDH supports is either comparable to the silica reference or significantly higher (see FIGS. 8 and 9) However, no clear trends in terms of nickel content have been observed.

[0252] However, the dramatic change comes in the MWD of the polymer produced. While a broad MWD (M.sub.w/M.sub.n>5) is obtained for nearly all the supports used here, for the LDH series containing nickel a much broader MWD can be obtained, especially at higher temperatures.

[0253] While an approximately monomodal MWD is obtained for all catalysts at 70? C., at 90? C. catalysts based on supports with a high nickel content (e.g. Ni.sub.2Al) have clearly become bimodal, while those based on nickel free LDH supports (e.g. Mg.sub.2Al) and the silica reference retain their monomodal distribution (see, for example, FIGS. 12-14).

[0254] Clearly, when a metallocene is immobilized on an LDH containing nickel, a lower molecular weight fraction is produced. This low molecular weight fraction must still be generated by the metallocene and is likely the result of a distinct ion pair forming under polymerization conditions, which has distinct reactivity with (for example) the scavenger TiBA. The enhanced rate of chain termination, relative to propagation associated with the low molecular weight fraction may also explain the generally lower productivity of these catalysts as reinsertion following termination is generally considered to have a higher barrier than for insertion into a polymer chain.

[0255] The polymers produced are clearly linear and display sharp melting and crystallization curves with peak melting temperatures typical of HDPE produced by metallocenes, even when a clearly bimodal polyethylene is produced (see FIG. 17). Reference polymerisations were carried out (see Table 3) for the calcined Ni.sub.x(Mg.sub.2-x)Al series, treated with d-MAO, but omitting the metallocene. Polymerisations were carried out under the same conditions, but only at 90? C., as this is the temperature when the bimodality is most significant and therefore if the second fraction comes from the support it will be the temperature when the support produces most polymer.

TABLE-US-00003 TABLE 3 Polymerisation using LDH catalyst supports..sup.a Average Productivity Productivity Support Support (mg) Yield (g) (kg .Math. g.sub.cat.sup.?1 .Math. h.sup.?1) (kg .Math. g.sub.cat.sup.?1 .Math. h.sup.?1) Mg.sub.2Al 9.5 0.010 0.002 0.002 10.4 0.006 0.001 NiMgAl 9.5 Trace n/a 0.003 9.9 0.014 0.003 Ni.sub.2Al 9.6 0.005 0.001 0.003 10.5 0.027 0.005 .sup.aPolymerisation conditions: Approx. 10 mg catalyst support [Ni.sub.x(Mg.sub.y?x)Al (400? C., 3 h, 10 K .Math. min.sup.?1)/40 wt. % d-MAO], 150 mg TiBA (scavenger), 50 mL hexanes (diluent), 2 bar ethylene, 90? C., 30 minutes.

[0256] In all cases minimal solids are recovered, which were assumed to be residues of the inorganic support and potentially traces of the partially decomposed scavenger. TGA of the samples carried out under N.sub.2 from 50-800? C. showed TGA curves that are consistent with mixed metal oxides that have partially reconstructed to LDH under atmospheric exposure, with considerable mass remaining even at 800? C. By contrast the bimodal polyethylene produced by (EBI) ZrCl.sub.2 immobilized on a support derived from Ni.sub.2Al LDH at 90? C. shows a typical TGA profile of polyethylene, with almost all weight being lost in a single step at 510? C. (see FIG. 18). The reference experiments therefore clearly demonstrate the role of the metallocene in producing the low molecular weight fraction

[0257] The observed bimodality is temperature sensitive (see, for example, FIGS. 12-14), but it can also be tuned by the nickel content of the support (FIG. 15). As the nickel content is increased, the bimodality increases, as can be observed by the change in dispersity (M.sub.w/M.sub.n) this triples from approximately 4 (for Mg.sub.2Al) to over 12 (for a Ni.sub.2Al LDH support at 90? C.). The ability to exert control over the modality of the MWD of the resulting polymer (e.g., the extent to which it displays a bimodal distribution) is industrially advantageous.

[0258] In conclusion, incorporating nickel into an LDH based support allows for generation of bimodal polyethylene from a single catalyst on a single support. This bimodality can be tuned by the degree of nickel in the support and is also influenced by polymerisation temperature.

[0259] While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

REFERENCES

[0260] 1. Tervoort, T. A.; Visjager, J.; Smith, P., On Abrasive Wear of Polyethylene. Macromolecules 2002, 35 (22), 8467-8471. [0261] 2. St?rzel, M.: Mihan, S.: M?lhaupt, R., From Multisite Polymerization Catalysis to Sustainable Materials and All-Polyolefin Composites. Chem. Rev. 2016, 116 (3), 1398-433. [0262] 3. Lafleur, S.; Berthoud, R.; Ensinck, R.; Cordier, A.; De Cremer, G.; Philippaerts, A.; Bastiaansen, K.; Margossian, T.; Severn, J. R., Tailored bimodal ultra-high molecular weight polyethylene particles. J. Polym. Sci. A. 2018, 56 (15), 1645-1656. [0263] 4. Mecking, S., Reactor blending with early/late transition metal catalyst combinations in ethylene polymerization. Macromol. Rapid. Comm. 1999, 20 (3), 139-143. [0264] 5. Liu, H.; Bastiaansen, C. W. M.; Goossens, J. G. P.; Schenning, A. P. H. J.; Severn, J. R., Bimodal Ultrahigh Molecular Weight Polyethylenes Produced from Supported Catalysts: The Challenge of Using a Combined Catalyst System. Macromol. Chem. Phys. 2017, 218 (5). [0265] 6. Zhong, F.; Thomann, R.; M?lhaupt, R., Tailoring Mono-, Bi-, and Trimodal Molar Mass Distributions and All-Hydrocarbon Composites by Ethylene Polymerization on Bis(imino)pyridine Chromium(III) Supported on Ultrathin Gibbsite Single Crystal Nanoplatelets. Macromolecules 2019, 52 (7), 2701-2711. [0266] 7. Bellotto, M.; Rebours, B.; Clause, O.; Lynch, J.; Bazin, D.; Elka?m, E., Hydrotalcite Decomposition Mechanism: A Clue to the Structure and Reactivity of Spinel-like Mixed Oxides. J. Phys. Chem. 1996, 100 (20), 8535-8542. [0267] 8. Yang, W.; Kim, Y.; Liu, P. K. T.; Sahimi, M.; Tsotsis, T. T., A study by in situ techniques of the thermal evolution of the structure of a MgAlCO3 layered double hydroxide. Chem. Eng. Sci. 2002, 57 (15), 2945-2953.