WO2011160828A1 - Process for the production of high-strength polyolefin compositions and polyolefin compositions produced by this process - Google Patents

Abstract

The present invention refers to a process for the preparation of bimodal polyolefin nanocomposites, wherein a first precatalyst for production of ultrahigh molecular polyolefin was supported on a first support comprising metal oxide nanotubes, and separately a second precatalyst for production of lower molecular weight polyolefin was supported on a second support not comprising metal oxide nanotubes. In the presence of the two supported precatalysts and preferably an activator a polyolefin was polymerized. The invention further refers to a polymer composition comprising ultrahigh molecular polyolefin and lower molecular weight polyolefin and metal oxide nanotubes.

Description

Process for the production of high-strength polyolefin compositions and polyolefin compositions produced by this process The present invention relates to a process for producing high-strength polyolefin compositions. It further refers to high strength polyolefin compositions which can be used in a wide range of fields, and films or moldings comprising the high strength polyolefin compositions of the present invention.

Examples for applications are further various ropes, fishing lines, netting and sheeting for engineering, construction and the like, cloth and nonwoven cloth for chemical filters and separators, sportswear and protective clothing such as bulletproof vests, or as reinforcing material for composites for sport, impact-resistant composites and helmets, and particularly as various industrial materials used at from extremely low temperatures to room temperature.

There was a need for polyolefin compositions having an improved strength and in view of this ultra high molecular polyolefins are developed, which show enhanced properties in view of strength.

However, they are inferior in regards of processability.

It is, however, an object of the present invention to provide a process for preparing high strength polyolefin compositions with the right balance of properties, e.g., strength and the proper stiffness levels, as well as good processability. The object is achieved by a process for the preparation of bimodal polyolefin nanocomposites comprising the steps of supporting a first precatalyst for production of ultrahigh molecular polyolefin on a first support comprising metal oxide nanotubes,

separately supporting a second precatalyst for production of lower molecular weight polyolefin on a second support not comprising metal oxide nanotubes, and polymerizing an olefin in the presence of the two supported catalysts and optionally an activator.

The term "bimodal," when used herein to describe a polymer or polymer composition, e.g., polyethylene, means "bimodal molecular weight distribution". This means that the polymer consists of at least two components (fractions), one of which has a relatively low molecular weight and another of which has a relatively high molecular weight. Often the lower molecular weight component is an ethylene homopolymer with the higher molecular weight component being a copolymer of ethylene with an alpha olefin such as propylene, butene, or hexene. "Bimodal" according to the present invention can also mean "multimodal", i.e. that the polymer consists of more than two components (fractions) having different molecular weights.

The term "ultra high molecular weight polyolefin component" as used herein means the polyolefin component in the bimodal composition that has a higher molecular weight than the molecular weight of at least one other polyolefin component in the same composition. Preferably, that polyolefin component has an identifiable peak. When the composition includes more than two components, e.g., a trimodal composition, then the high molecular weight component is to be defined as the component with the highest weight average molecular weight. According to the present invention, an ultra high molecular weight component is a component forming a part of the bimodal composition that has a weight average molecular weight (Mw) of more than 1 ,000,000 g/mol. In different specific

embodiments, the average molecular weight of an ultra high molecular weight polyolefin component, e.g. a polyethylene component may range from 1 ,000,000 g/mol to 100,000,000 g/mol, preferably to 10,000,000 g/mol.

The term "lower molecular weight polyolefin component" as used herein means the polyolefin component in the composition that has a lower molecular weight than the molecular weight of the ultra high molecular weight polyolefin component in the same composition. Preferably, also that polyolefin component has an identifiable peak. According to the present invention, a lower molecular weight component is a component forming a part of the composition that has a weight average molecular weight (Mw) of lower than 1 ,000,000 g/mol. In different specific embodiments, the average molecular weight of the lower molecular weight component may range from 3,000 g/mol to less than 1 ,000,000 g/mol, preferably from 5,000 g/mol to 800,000 g/mol, and especially preferred from 8,000 g/mol to 500,000 g/mol.

Phyllosilicates suitable for the purposes of the invention are both natural and synthetic phyllosilicates. The term phyllosilicates generally refers to silicates in which Si0₄ tetrahedra are joined in infinite two- dimensional networks. The empirical formula of the anion is (Si₂0₅ ^2")n. The individual layers are bound to one another by the cations located between them; in the naturally occurring phyllosilicates, sodium, potassium, magnesium, aluminum or/and calcium are present as cations. Possible phyllosilicates are natural or synthetic smectite clay minerals, in particular montmorillonite, saponite, beidelite, nontronite, hevtorite, sauconite and stevensite, and also bentonite, vermiculite and halloysite. Preference is given to halloysite-nanoclay.

The phyllosilicate montmorillonite, for example, generally corresponds to the formula:

ΑΙ₂[(ΟΗ)₂/5ί₄Ο₁₀]·ηΗ₂Ο, where part of the aluminum can have been replaced by magnesium. The composition varies depending on the silicate deposit.

Metal oxide nanotubes and a method for producing the tubes are described in Chem. Mater. Vol. 18, No. 21 , 2006 "Shape-Controlled Synthesis of Zr0₂, Al₂0₃, and Si0₂ Nanotubes using Carbon Nanofibers as Templates" by Ojihara, Hitoshi et al.. Si0₂ nanotubes are synthesized on different kinds of carbon nanofibers used as templates into which a precursor diluted with organic solvents (SiCI in CCI₄) was dropped. A further method for the preparation of metal oxide nanotubes is described in the examples. The metal oxide nanotubes of the invention preferably are Si0₂ nanotubes: Especially preferred are Si0₂ having an outer diameter from 100 to 500 nm, preferably 150 to 200 nm and a wall thickness of less than 20 nm, preferably less than 15 nm and especially preferred from 4 to 10 nm. A further and preferred method of preparing such silica nanotubes is disclosed in WO2009/15804 A1.

Both materials, phyllosilicates and metal oxide nanotubes, have a tube-like structure. However, the phyllosilicates are much more inhomogeneous, i.e. there are much more deviations in wall thickness and outer diameter of the tubes. The process is especially suited for the preparation of reactor blends comprising an ultra high molecular polyethylene finely dispersed in a matrix of lower molecular weight polyethylene. I.e. the preferably used catalyst system is a mixed supported catalyst system comprising a catalyst for the production of ultra high molecular polyethylene, and a catalyst for the production of low molecular polyethylene. Preferred is the process using a catalyst system comprising a monocyclopentienyl complex and an iron or cobalt containing late transition metal complex, mostly preferred an iron complex bearing a tridentate ligand. A large number of examples for late transition metal complexes which are suitable for olefin polymerization is described in Chem. Rev. 2000, Vol. 100, No. 4, 1169 ff.. The precatalysts of the invention are organic transition metal compounds, which can form active catalysts in polymerization of olefins. These are in principle all compounds of the transition metals of groups 3 to 12 of the Periodic Table of the elements or the lanthanides which contain organic groups and form catalysts which are active in olefin polymerization, preferably after reaction with an activator, e.g. a hydrolyzed organoaluminum compound. These are usually compounds in which at least one monodentate or polydentate ligand is bound via σ or π bond to the central atom. Possible ligands include both ligands containing cyclopentadienyl radicals and ligands which are free of

cyclopentadienyl radicals. At least one organic transition metal compound has to be chosen such that an active catalyst for the production of ultra high molecular weight polyolefin, preferably ultra high molecular polyethylene is formed.

The process is particularly well-suited to organic transition metal compounds having at least one cyclopentadienyl ligand. Particularly useful complexes for forming an active catalyst for production of ultra high molecular polyethylene are constrained geometry complexes comprising an element of group 6 of the Periodic Table of the Elements. Especially preferred are complexes of the formula (I)

where the substituents and indices have the following meanings: is an element of group 6 of the Periodic Table of the Elements, preferably chromium, molybdenum or tungsten; independently of one another are fluorine, chlorine, bromine, iodine, hydrogen, C Cur alkyl, C₂-C₁₀-alkenyl, C₆-C₄₀-aryl, arylalkyl having 1 to16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part, -NR^I6 ₂, -OR¹⁶,

-SR¹⁶, -S0₃R¹⁶, -OC(0)R¹⁶, -CN, -SCN, β-diketonate, -CO, BF₄~, PF₆~ or bulky non- coordinating anions, wherein the organic radicals X¹ can also be substituted by halogens and/or at least one radical R¹⁶, and the radicals X¹ are optionally bonded with one another; t is 1 , 2 or 3 and, depending on the valence of M¹¹, has the value at which the complex of the general formula (I) is uncharged;

A¹ is an uncharged donor group containing one or more atoms of group 15 and/or 16 of the

Periodic Table of the Elements or a carbene, preferably an unsubstituted, substituted or fused, heteroaromatic ring system,

R¹¹ to R'⁴ are each, independently of one another, hydrogen, C^C^-alkyl, 5- to 7-membered cycloalkyl or cycloalkenyl, C₂-C₂2-alkenyl, C₆-C₄o-aryl, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, halogen, - NR^I72, -OR¹⁷ or -SiR^l8 3, where the organic radicals R¹ to R¹⁴ may also be substituted by halogens and/or two vicinal radicals R¹¹ to R¹⁴ may also be joined to form a five-, six- or seven-membered ring, and/or two vicinal radicals R¹¹ to R¹⁴ are joined to form a five-, six- or seven-membered heterocycle which comprises at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen and sulphur;

R^l6 and R¹⁷ are each, independently of one another, CrCio-alkyl, 5- to 7-membered cycloalkyl or cycloalkenyl, C2-C₂2-alkenyl, C₆-C₂₂-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 20 carbon atoms in the aryl part, where the organic radicals R^l6 and R¹⁷ may also be substituted by halogens and/or two radicals R^l6 and R¹⁷ may also be joined to form a five-, six- or seven-membered ring, or SiR^l8 ₃; the radicals R can be identical or different and can each be

5- to 7-membered

cycloalkyl or cycloalkenyl, C₂-C₂2-alkenyl, C6-C₂₂-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 20 carbon atoms in the aryl part, Ci-Ci₀- alkoxy or C₆-C ₀-aryloxy, where the organic radicals R¹⁸ may also be substituted by halogens and/or two radicals R¹⁸ may also be joined to form a five-, six- or seven- membered ring; and

R^l5 is

= BR¹⁹, = BNR^I9R¹¹⁰, = AIR¹⁹, -Ge-, -Sn- -0-, -S-, = SO, = S0₂, = NR¹⁹, = CO, = PR¹⁹ or = P(0)R¹⁹, where

R^l9-R¹¹⁴ are identical or different and are each a hydrogen atom, a halogen atom, a

trimethylsilyl group,

5- to 7-membered cycloalkyl or cycloalkenyl,

C₂-C₂2-alkenyl, C₆-C₂2-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 20 carbon atoms in the aryl part,

or C₆-C₁₀- aryloxy, where the organic radicals R^l9-R¹¹⁴ may also be substituted by halogens and/or two radicals R^l9-R¹¹⁴ may also be joined to form a five-, six- or seven- membered ring, and M'²-M'⁴ are each silicon, germanium or tin, preferably silicon, v is 1 or when A¹ is an unsubstituted, substituted or fused, heterocyclic ring system may also be 0. M¹¹ is a metal selected from Group 6 of the Periodic Table of the elements, preferably chromium, molybdenum or tungsten. The oxidation state of the transition metals M¹¹ in catalytically active complexes are usually known to those skilled in the art. Chromium, molybdenum and tungsten are very probably present in the oxidation state +3. However, it is also possible to use complexes whose oxidation state does not correspond to that of the active catalyst. Such complexes can then be appropriately reduced or oxidized by means of suitable activators. Particular preference is given to chromium in the oxidation states 2, 3 and 4, in particular 3.

A¹ is an uncharged donor containing an atom of group 15 or 16 of the Periodic Table or a carbene, preferably one or more atoms selected from the group consisting of oxygen, sulfur, nitrogen and phosphorus, preferably nitrogen or phosphorus. The donor function in A¹ can be bound

intermolecularly or intramolecularly to the metal M¹. The donor in A¹ is preferably bound

intramolecularly to M¹. Possible donors are uncharged functional groups containing an element of group 15 or 16 of the Periodic Table, e.g. amine, imine, carboxamide, carboxylic ester, ketone (oxo), ether, thioketone, phosphine, phosphite, phosphine oxide, sulfonyl, sulfonamide, carbenes such as N- substituted imidazol-2-ylidene or unsubstituted, substituted or fused, heterocyclic ring systems. The synthesis of the bond from A¹ to the cyclopentadienyl radical and R¹⁵ can be carried out, for example, by a method analogous to that of WO 00/35928. A¹ is preferably a group selected from among -OR¹¹⁵, -SR^{1 5}-, -NR^MV, -PR^{I 15}2, -C=NR¹¹⁵- and unsubstituted, substituted or fused heteroaromatic ring systems, in particular -NR^I15 ₂-, -C=NR¹¹⁵- and unsubstituted, substituted or fused heteroaromatic ring systems. The radicals R¹¹⁵ are, independently of one another, hydrogen, C^-C^-alky! which may be linear, cyclic or branched, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, n-nonyl, n-decyl or n-dodecyl, cycloalkyl which may in turn bear a C6-Cio-3i"y' group as substituent, e.g. cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane or cyclododecane, C₂-C₂o-alkenyl which may be linear, cyclic or branched and in which the double bond can be internal or terminal, e.g. vinyl, 1-allyl, 2-allyl, 3-allyl, butenyl, pentenyl, hexenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl or cyclooctadienyl, C₆-C₂₀-aryl which may be substituted by further alkyl groups, e.g. phenyl, naphthyl, biphenyl, anthranyl, o-, m-, p-methylphenyl, 2,3-, 2,4-, 2,5- or 2,6-dimethylphen-1-yl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trimethylphen-1-yl, arylalkyl which has from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part and may be substituted by further alkyl groups, e.g. benzyl, o-, m-, p-methylbenzyl, 1- or 2- ethylphenyl, or SiR^l16 ₃, where the organic radicals R¹¹⁶ may also be substituted by halogens such as fluorine, chlorine or bromine or nitrogen-containing groups and further (VC^o-alkyl, C₂-C₂o-alkenyl, C₆-C₂₀-aryl, arylalkyl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part or SiR^l16 ₃ groups and two vicinal radicals R¹¹⁶ may also be joined to form a five- or six- membered ring and the radicals R¹¹⁶ are each, independently of one another, hydrogen, C Czo-alkyl, C₂-C₂₀-alkenyl, C₆-C₂o-aryl or arylalkyl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part and two radicals R¹¹⁶ may also be joined to form a five- or six-membered ring.

A¹ is preferably an unsubstituted, substituted or fused heteroaromatic ring system which may contain, apart from carbon ring atoms, heteroatoms from the group consisting of oxygen, sulfur, nitrogen and phosphorus. Examples of 5-membered heteroaryl groups which may, in addition to carbon atoms, contain from one to four nitrogen atoms or from one to three nitrogen atoms and/or one sulfur or oxygen atom as ring atoms are 2-furyl, 2-thienyl, 2-pyrrolyl, 3-isoxazolyl, 5-isoxazolyl, 3-isothiazolyl, 5- isothiazolyl, 1-pyrazolyl, 3-pyrazolyl, 5-pyrazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 2-thiazolyl, 4- thiazolyl, 5-thiazolyl, 2-imidazolyl, 4-imidazolyl, 5-imidazolyl, 1 ,2,4-oxadiazol-3-yl, 1 ,2,4-oxadiazol-5-yl, 1 ,3,4-oxadiazol-2-yl or 1 ,2,4-triazol-3-yl. Examples of 6-membered heteroaryl groups which may contain from one to four nitrogen atoms and/or a phosphorus atom are 2-pyridinyl, 2-phosphaphenyl, 3-pyridazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 2-pyrazinyl, 1 ,3,5-triazin-2-yl and 1 ,2,4-triazin-3-yl, 1 ,2,4- triazin-5-yl and 1 ,2,4-triazin-6-yl. The 5-membered and 6-membered heteroaryl groups can also be substituted by CrC^-alky!, C₆-Ci₀-aryl, arylalkyl having from 1 to 10 carbon atoms in the alkyl part and 6-10 carbon atoms in the aryl part, trialkylsilyl or halogens such as fluorine, chlorine or bromine or be fused with one or more aromatics or heteroaromatics. Examples of benzo-fused 5-membered heteroaryl groups are 2-indolyl, 7-indolyl, 2-coumaronyl, 7-coumaronyl, 2-thianaphthenyl, 7- thianaphthenyl, 3-indazolyl, 7-indazolyl, 2-benzimidazolyl or 7-benzimidazolyl. Examples of benzo- fused 6-membered heteroaryl groups are 2-quinolyl, 8-quinolyl, 3-cinnolyl, 8-cinnolyl, 1-phthalazyl, 2- quinazolyl, 4-quinazolyl, 8-quinazolyl, 5-quinoxalyl, 4-acridyl, 1-phenanthridyl and 1-phenazyl. Naming and numbering of the heterocycles has been taken from L. Fieser and M. Fieser, Lehrbuch der organischen Chemie, 3rd revised edition, Verlag Chemie, Weinheim 1957. Among these heteroaromatic systems A¹, particular preference is given to unsubstituted, substituted and/or fused six-membered heteroaromatics having 1 , 2, 3, 4 or 5 nitrogen atoms in the

heteroaromatic part, in particular substituted and unsubstituted 2-pyridyl, 2-quinolyl or 8-quinolyl. It is preferred that at least one radical of R¹¹ to R¹⁴ is a substituent SiR^l8 ₃. A total of 1 , 2 or 3 radicals R^M to R¹⁴ can be a substituent SiR^l8 ₃. Preference is given to one radical R^1A to R^4A being a substituent SiR^l8 ₃.

Preference is given to substituents SiR^l8 ₃ in which R¹⁸ is Ci-C₂₂-alkyl, C₂-C₂2-alkenyl, C₆-C₂₂-aryl, arylalkyi having from 1 to 16 carbon atoms in the alkyl part and from 6 to 21 carbon atoms in the aryl part, where two radicals Rⁱ⁸ may also be joined to form a five-, six- or seven-membered ring, in particular C₁-C₂₂-alkyl. The radicals R¹⁸ are particularly preferably selected from among methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, cyclopentyl, cyclohexyl, cycloheptyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, phenyl, naphthyl, biphenyl, anthranyl, o-, m-, p-methylphenyl, 2,3-, 2,4-, 2,5-, 2,6-dimethylphenyl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trimethylphenyl and benzyl. The synthesis of such cyclopentadienyl systems having a fused-on heterocycle is described, for example, in the abovementioned WO 98/22486. "Metalorganic catalysts for synthesis and

polymerisation", Springer Verlag 1999, wen et al., p.150 ff, describes further syntheses of these cyclopentadienyl systems. Suitable as a second precatalyst for forming an active catalyst for preparation of lower polyethylene are late transition metal complexes of the general formula (II),

wherein the variables have the following meaning:

E - E independently of one another are carbon, nitrogen or phosphorus, preferably carbon,

R"¹ - R"³ are each, independently of one another, hydrogen, C₁-C₂2-alkyl, 5- to 7-membered cycloalkyl or cycloalkenyl which may in turn bear C C^-alky! groups as substituents, C₂-C₂₂-alkenyl, C₆-C₄₀-aryl, arylalkyi having from 1 to 16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part,

-NR -OR¹¹¹¹, or -SiR^ll12 ₃ or a five-, six- or seven-membered heterocycle, which comprises at least one atom from the group consisting of nitrogen, phosphorus, oxygen and sulfur, where the radicals R^IM to R"³ may also be substituted by halogen, -NR^II11 ₂, -OR¹¹¹¹, or -SiR^,l12 ₃ and/or two radicals R¹¹¹ to R"³, in particular adjacent radicals, together with the atoms connecting them may be joined to form a preferably 5-, 6- or 7-membered ring or a preferably 5-, 6- or 7-membered heterocycle which comprises at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen and sulfur, where are each, independently of one another, C^Cm-alky!, 5- to 7-membered cycloalkyl or cycloalkenyl, C₂-C -alkenyl, C₆-C -aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 20 carbon atoms in the aryl part, where the organic radicals R"¹¹ may also be substituted by halogens and/or two radicals R"¹¹ may also be joined to form a five-, six- or seven-membered ring, or SiR¹¹¹² and can be identical or different and can each be Ci-C ₍r-alkyl, 5- to 7-membered cycloalkyl or cycloalkenyl, C₂-C₂₂-alkenyl, C₆-C₂₂-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 20 carbon atoms in the aryl part,

Ci-C ₀-alkoxy or C₆-C₁₀-aryloxy, where the organic radicals R may also be substituted by halogens and/or two radicals R¹¹¹² may also be joined to form a five-, six- or seven-membered ring; independently of one another is 0 if the respective radical is bound to nitrogen or phosphorous and 1 if the respective radical is bound to carbon; are each, independently of one another, hydrogen, Ci-C₂₂-alkyl, C₂-C₂₂-alkenyl, C₆- C₄₀-aryl, arylalkyl having from 1 to 16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part, -NR^II11 ₂, or -SiR"¹² _3l where the radicals R"⁴ and R^li5 may also be substituted by halogen and/or two radicals R¹'⁴ and R¹¹⁵, may be joined to form a preferably 5-, 6- or 7-membered ring or a preferably 5-, 6- or 7-membered heterocycle which comprises at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen and sulphur; independently of one another, are 0 or 1, and when v is 0 the bond between N and the carbon atom bearing radical R"⁴ is a double bond, are each, independently of one another, hydrogen, Ci-C₂o-alkyl, 5- to 7-membered cycloalkyl or cycloalkenyl, C₂-C₂₂-alkenyl, C₆-C₄o-aryl, arylalkyl having from 1 to 10 carbon atoms in the alkyl radical and 6-20 carbon atoms in the aryl radical, halogen, -NR^{II 1} ₂, -OR¹¹¹¹ or -SiR^ll12 ₃₎ where the organic radicals R^ll6 to R¹¹¹⁰ may also be substituted by halogens and/or two vicinal radicals R"⁶ to R"¹⁰ may also be joined to form a five-, six- or seven-membered ring, and/or two vicinal radicals R"⁶ to R"¹⁰ are joined to form a five-, six- or seven-membered heterocycle which comprises at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen and sulfur, M is iron or cobalt, preferably iron,

X" independently of one another are fluorine, chlorine, bromine, iodine, hydrogen, C^-

C₁₀-alkyl, C₂-C₁₀-alkenyl, C₆-C ₀-aryl, arylalkyi having 1 to16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part, -NR^II13 ₂, -OR¹¹¹³,

-SR^LI13, -SO3R"¹³, -0C(0)R"¹³, -CN, -SCN, β-diketonate, -CO, BF₄~, PF₆~ or bulky non-coordinating anions, wherein the organic radicals X" can also be substituted by halogens and/or at least one radical R¹¹¹³, and the radicals X" are optionally bonded with one another,

R"¹³ independently of one another are hydrogen, C₁-C₂2-alkyl, C₂-C₂₂-alkenyl, C₆-C₄₀- aryl, arylalkyi having 1 to 16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part, or SiR"¹⁴ ₃, wherein the organic radicals R"¹³ can also be substituted by halogens, and/or in each case two radicals R¹¹¹³ can also be bonded with one another to form a five- or six-membered ring,

R"¹⁴ independently of one another are hydrogen,

aryl, arylalkyi having 1 to 16 carbon atoms in the alkyl part and 6 to 20 carbon atoms in the aryl part, wherein the organic radicals R¹¹¹⁴ can also be substituted by halogens, and/or in each case two radicals R¹¹¹⁴ can also be bonded with one another to form a five- or six-membered ring, s is 1 , 2, 3 or 4,

D" is an uncharged donor and t is 0 to 4.

The substituents R^ll1-R¹¹³ can be varied within a wide range. Possible carboorganic substituents R¹¹¹- R"³ are, for example, the following: C C^-alkyl which may be linear or branched, e.g. methyl, ethyl, n- propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl or n- dodecyl, 5- to 7-membered cycloalkyl which may in turn bear CVCio-alkyl groups as substituents, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclododecyl, C₂-C₂₂-alkenyl which may be linear, cyclic or branched and in which the double bond may be internal or terminal, e.g. vinyl, 1 -allyl, 2-allyl, 3-allyl, butenyl, pentenyl, hexenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl or cyclooctadienyl, C₆-C₄o-aryl which may be substituted by further alkyl groups, e.g. phenyl, naphthyl, biphenyl, anthranyl, o-, m-, p-methylphenyl, 2,3-, 2,4-, 2,5- or 2,6-dimethylphenyl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trimethylphenyl, or arylalkyi which may be substituted by further alkyl groups, e.g. benzyl, o-, m-, p-methylbenzyl, 1- or 2-ethylphenyl, where two vicinal radicals R to R are optionally joined to form a 5-, 6- or 7-membered carbon ring or a five-, six- or seven- membered heterocycle containing at least one atom from the group consisting of N, P, O and S and/or the organic radicals R"¹-R¹¹³ are unsubstituted or substituted by halogens such as fluorine, chlorine or bromine. Furthermore, R^II1-R"³ can also be amino NR^II11 ₂ or N(SiR"¹² ₃)₂, alkoxy or aryloxy OR¹¹¹¹, for example dimethylamino, N-pyrrolidinyl, picolinyl, methoxy, ethoxy or isopropoxy or halogen such as fluorine, chlorine or bromine.

Preferred radicals R^II1-R"³ are hydrogen, methyl, trifluoromethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, vinyl, allyl, benzyl, phenyl, ortho-dialkyl- or - dichloro-substituted phenyls, trialkyi- or trichloro-substituted phenyls, naphthyl, biphenyl and anthranyl. Particularly preferred organosilicon substituents are trialkylsilyl groups having from 1 to 10 carbon atoms in the alkyl radical, in particular trimethylsilyl groups.

The substituents R"⁴ and R"⁵ can also be varied within a wide range. Possible carboorganic substituents R"⁴ and R^ll5 are, for example, the following: hydrogen, d-C₂₂-alkyl which is linear or branched, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl or n-dodecyl, 5- to 7-membered cycloalkyl which is unsubstituted or bears a Ci-C₁₀-alkyl group and/or C₆-C₁₀-aryl group as substituent, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclododecyl, C₂-C₂₂-alkenyl which is linear, cyclic or branched and in which the double bond is internal or terminal, e.g. vinyl, 1-allyl, 2-allyl, 3-allyl, butenyl, pentenyl, hexenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl or cyclooctadienyl, C₆-C₂₂-aryl which is may be substituted by further alkyl groups, e.g. phenyl, naphthyl, biphenyl, anthranyl, o-, m-, p- methylphenyl, 2,3-, 2,4-, 2,5- or 2,6-dimethylphenyl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5- trimethylphenyl, or arylalkyl which may be substituted by further alkyl groups, e.g. benzyl, o-, m-, p- methylbenzyl, 1- or 2-ethylphenyl, where the organic radicals R"⁴ and R^ll5 are unsubstituted or substituted by halogens such as fluorine, chlorine or bromine. Furthermore, R"⁴ and R"⁵ can be amino NR^II11 ₂ or N(SiR^IM2 ₃)₂, for example dimethylamino, N-pyrrolidinyl or picolinyl. Possible radicals R¹¹¹² in organosilicon substituents SiR^ll12 ₃ are the same carboorganic radicals as described above for R^ll1-R¹¹³ in formula (II), where two radicals R¹¹¹² may also be joined to form a 5- or 6-membered ring, e.g.

trimethylsilyl, triethylsilyl, butyldimethylsilyl, tributylsilyl, tritert-butylsilyl, triallylsilyl, triphenylsilyl or dimethylphenylsilyl. These SiR^ll12 ₃ radicals can also be bound via nitrogen to the carbon bearing them.

Preferred radicals R"⁴ are hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n- pentyl, n-hexyl, n-heptyl, n-octyl or benzyl, in particular hydrogen or methyl.

The variable v denotes the number of R"⁵ radicals. It is especially preferred that v is 0 and R"⁵ forms a double bond to the nitrogen atom bearing the aryl substituent.

The substituents R"^S-R"¹⁰ can be varied within a wide range. Possible carboorganic substituents R"⁶- R"¹⁰ are, for example, the following: Ci-C₂₂-alkyl which may be linear or branched, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl or n-dodecyl, 5- to 7-membered cycloalkyl which may in turn bear a C Ci₀-alkyl group and/or C₆-C₁₀-aryl group as substituents, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclododecyl, C₂-C₂2-alkenyl which may be linear, cyclic or branched and in which the double bond may be internal or terminal, e.g. vinyl, 1-allyl, 2-allyl, 3-allyl, butenyl, pentenyl, hexenyl, cyclopentenyl, cyclohexenyl, cyclooctenyl or cyclooctadienyl, C₆-C₂2-aryl which may be substituted by further alkyl groups, e.g. phenyl, naphthyl, biphenyl, anthranyl, 0-, m-, p-methylphenyl, 2,3-, 2,4-, 2,5- or 2,6-dimethylphenyl, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trimethylphenyl, or arylalkyl which may be substituted by further alkyl groups, e.g. benzyl, 0-, m-, p-methylbenzyl, 1- or 2-ethylphenyl, where two vicinakl radicals R"⁶-R"¹⁰ are optionally joined to form a 5-, 6- or 7-membered ring and/or a five-, six- or seven-membered heterocycle containing at least one atom from the group consisting of N, P, O and S and/or the organic radicals R"⁶-R"¹⁰ are unsubstituted or substituted by halogens such as fluorine, chlorine or bromine. Furthermore, R"⁶-R"¹⁰ can also be amino NR^II11 ₂ or N(SiR^ll12 ₃)₂, alkoxy or aryloxy OR¹¹¹¹, for example dimethylamino, N-pyrrolidinyl, picolinyl, methoxy, ethoxy or isopropoxy or halogen such as fluorine, chlorine or bromine. Possible radicals R¹¹¹² in organosilicon substituents SiR^{ll 12}3 are the same carboorganic radicals as have been described above for in formula (II).

Preferred radicals R"⁶, R"⁷ are methyl, trifluoromethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert- butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, vinyl, allyl, benzyl, phenyl, fluorine, chlorine and bromine. Iln particular, R"⁶ are each a C^C^-alky! which may also be substituted by halogens, in particular a C_r C₂2-n-al yl which may also be substituted by halogens, e.g. methyl, trifluoromethyl, ethyl, n-propyl, n- butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, vinyl, or a halogen such as fluorine, chlorine or bromine and R"⁷ are each a halogen such as fluorine, chlorine or bromine. Particular preference is given to R"⁶ each being a Ci-C₂₂-alkyl which may also be substituted by halogens, in particular a Ci-C₂₂-n-alkyl which may also be substituted by halogens, e.g. methyl, trifluoromethyl, ethyl, n-propyl, n-butyl, n- pentyl, n-hexyl, n-heptyl, n-octyl, vinyl and R"⁷ each being a halogen such as fluorine, chlorine or bromine.

Preferred radicals R^ll8-R¹¹¹⁰ are hydrogen, methyl, trifluoromethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, vinyl, allyl, benzyl, phenyl, fluorine, chlorine and bromine, in particular hydrogen. It is in particular preferred, that R"⁹ are each methyl, trifluoromethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, vinyl, allyl, benzyl, phenyl, fluorine, chlorine or bromine and R"⁸ and R¹¹¹⁰ are each hydrogen. In the most preferred embodiment the radicals R"⁸ and R¹¹¹⁰ are identical, R"⁶ are identical, R"⁹ are identical, and R¹¹¹⁰ are identical.

The ligands X" result, for example, from the choice of the appropriate starting metal compounds used for the synthesis of the cobalt or iron complexes, but can also be varied afterwards. Possible ligands x" are, in particular, the halogens such as fluorine, chlorine, bromine or iodine, in particular chlorine. Alkyl radicals such as methyl, ethyl, propyl, butyl, vinyl, allyl, phenyl or benzyl are also usable ligands X". As further ligands x", mention may be made, purely by way of example and in no way

exhaustively, of trifluoroacetate, BF₄ ^_, PF₆- and weakly coordinating or noncoordinating anions (cf., for example, S. Strauss in Chem. Rev. 1993, 93, 927-942), e.g. B(C₆F₅)₄ ^_ Amides, alkoxides, sulfonates, carboxylates and D-diketonates are also particularly useful ligands X". Some of these substituted ligands x" are particularly preferably used since they are obtainable from cheap and readily available starting materials. Thus, a particularly preferred embodiment is that in which X is dimethylamide, methoxide, ethoxide, isopropoxide, phenoxide, naphthoxide, triflate,

p-toluenesulfonate, acetate or acetylacetonate. The number s of the ligands X" depends on the oxidation state of M". The number s can thus not be given in general terms. The oxidation state of M" in catalytically active complexes is usually known to those skilled in the art. However, it is also possible to use complexes whose oxidation state does not correspond to that of the active catalyst. Such complexes can then be appropriately reduced or oxidized by means of suitable activators. Preference is given to using iron complexes in the oxidation state +3 or +2.

D" is an uncharged donor, in particular an uncharged Lewis base or Lewis acid, for example amines, alcohols, ethers, ketones, aldehydes, esters, sulfides or phosphines which may be bound to the iron center or else still be present as residual solvent from the preparation of the iron complexes.

The number t of the ligands D" can be from 0 to 4 and is often dependent on the solvent in which the iron complex is prepared and the time for which the resulting complexes are dried and can therefore also be a nonintegral number such as 0.5 or 1.5, in particular, t is 0, 1 to 2.

Suitable compounds as cocatalysts are activating compounds which are able to react with the transition metal complexes to convert them into a catalytically active or more active compound. Such activating compounds are, for example, aluminoxanes, strong uncharged Lewis acids, ionic compounds having Lewis-acid cations or ionic compounds containing Bronsted acids as cations. For activation of both the at least two active catalyst compounds either the same kind of cocatalyst can be used or different cocatalysts can be used. In case of metallocenes and tridendate iron complexes aluminoxanes are especially preferred.

Particularly useful aluminoxanes are open-chain or cyclic aluminoxane compounds of the general formula (MIA) or (1MB)

where R are each, independently of one another, a C Ce-alkyl group, preferably a methyl, ethyl, butyl or isobutyl group and I is an integer from 1 to 40, preferably from 4 to 25.

A particularly useful aluminoxane compound is methyl aluminoxane (MAO). Furthermore modified aluminoxanes in which some of the hydrocarbon radicals have been replaced by hydrogen atoms or alkoxy, aryloxy, siloxy or amide radicals can also be used in place of the aluminoxane compounds of the formula (II I A) or (1MB) as activating compound. Boranes and boroxines are particularly useful as activating compound, such as trialkylborane, triarylborane or trimethylboroxine. Particular preference is given to using boranes which bear at least two perfluorinated aryl radicals. More preferably, a compound selected from the list consisting of triphenylborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4- fluoromethylphenyl)borane, tris(pentafluorophenyl)borane, tris(tolyl)borane, tris(3,5- dimethylphenyl)borane, tris(3,5-difluorophenyl)borane or tris(3,4,5-trifluorophenyl)borane is used, most preferably the activating compound is tris(pentafluorophenyl)borane. Particular mention is also made of borinic acids having perfluorinated aryl radicals, for example (C₆F₅)₂BOH. Compounds containing anionic boron heterocycles as described in WO 97/36937 A1 incorporated hereto by reference, such as for example dimethyl anilino borato benzenes or trityl borato benzenes, can also be used suitably as activating compounds. Further suitable activating compounds are listed in WO 00/31090 A1 and WO 99/06414 A1.

It is also possible for the catalyst system firstly to be prepolymerized with a-olefins, more preferably linear C₂-Ci₀-1 -alkenes and in particular ethylene, and the resulting prepolymerized catalyst solid then to be used in the actual polymerization.

Olefins according to the definition of the present invention are a-olefins having from 3 to 12 carbon and in particular linear C₃-C₁₀-1-alkenes such as propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene or branched C₃-C₁₀-1 -alkenes such as 4-methyl-1 -pentene. Preference is given to polymerizing ethylene.

Mixtures of two or more olefins can also be polymerized. In particular, the catalyst systems of the invention can be used for the polymerization or copolymerization of e.g. ethylene. As comonomers in the polymerization of ethylene, preference is given to using C₃-C₈-a→Dlefins, in particular 1-butene, 1- pentene, 1-hexene and/or 1-octene. Preference is given to using monomer mixtures containing at least 50 mol% of ethylene. Preferred comonomers in the polymerization of ethylene are 1 -propene and/or 1 -butene.

The polymerization can be carried out in a known manner in bulk, in suspension, in the gas phase or in a supercritical medium in the customary reactors used for the polymerization of olefins. It can be carried out batchwise or continuously in one or more stages. High-pressure polymerization processes in tube reactors or autoclaves, solution processes, suspension processes, stirred gas-phase processes or gas-phase fluidized-bed processes are all possible.

The polymerizations are usually carried out at temperatures in the range from -60 to 350°C and under pressures of from 0.5 to 4000 bar. The mean residence times are usually from 0.5 to 5 hours, preferably from 0.5 to 3 hours. The advantageous pressure and temperature ranges for carrying out the polymerizations usually depend on the polymerization method. In the case of high-pressure polymerization processes, which are usually carried out at pressures of from 1000 to 4000 bar, in particular from 2000 to 3500 bar, high polymerization temperatures are generally also set.

Advantageous temperature ranges for these high-pressure polymerization processes are from 200 to 320°C, in particular from 220 to 290°C. In the case of low-pressure polymerization processes, a temperature which is at least a few degrees below the softening temperature of the polymer is generally set. In particular, temperatures of from 50 to 180°C, preferably from 70 to 120°C, are set in these polymerization processes. The polymerization temperatures are generally in the range from -20 to 115°C, and the pressure is generally in the range from 1 to 100 bar. The solids content of the suspension is generally in the range from 10 to 80%. The polymerization can be carried out batchwise, e.g. in stirring autoclaves, or continuously, e.g. in tube reactors, preferably in loop reactors. Particular preference is given to employing the Phillips PF process as described in US-A 3 242 150 and US- A 3 248 179. The gas-phase polymerization is generally carried out in the range from 30 to 125°C.

By the process of the present invention polyolefin compositions are produced which comprise at least two polyolefin fractions with different molecular weight. The polyolefin composition comprises at least one ultra high molecular weight polyolefin fraction. The ultra high molecular weight fraction preferably is present in an amount of 0.1 to 85 weight % in regard to the total polymer composition, more preferably in an amount of 0.5 to 50 weight % and especially preferably in an amount of 1 to 10 weight%. The compositions of the present invention comprise metal oxide nanotubes, preferably metal oxide nanotubes and phyllosilicate nanoclay. It is preferred that the metal oxide nanotubes have a wall thickness of less than 20 nm, preferably less than 15 nm, and especially preferred from 4 to 10 nm. A preferred metal oxide nanotube is Si0₂. Suitable Si0₂ nanotubes e.g. have an outer diameter of 150- 200 nm.

The compostions may comprise additionally to the metal oxide nanotubes a phyllosilicate nanoclay, especially preferably halloysite.

The compositions of the present invention show high strength while at the same time are well processable.

The preferred polyethylene products of the present have a high modulus of elasticity of more than 1000 MPa, preferably more than 1200 MPa and a tensile stress at yield (F_max) of more than 45 MPa, preferably more than 50 MPa.

Although not being bound to the following theory it is supposed that the nanoparticulate character could inhibit formation of particles made of one kind of polymer. I. e. in the case of polyethylene the aggregation of UHMWPE particles (ultra high molecular weight polyethylene particles) is inhibited by the presence of particles of low molecular polyethylene. Probably, the UHMWPE particles are already embedded into a matrix of low molecular polyethylene. The matrix polymer has the effect that the polymer melt still is operable, while UHMWPE enforces the material. It is assumed that the enforcing effect is caused by the fact that different crystals of the matrix are connected by polymer chains of UHMWPE. The intimate mixing is probably caused by the fact that with separate supportation different polymer particles grow together during subsequent polymerization run. The support particles and the nano fibres present shortly after starting the polymerization run have a high specific surface area via which the particles can exchange with other particles and can form common particles, respectively, one catalyst producing the matrix-polyethylene and the other one forming the embedded UHMWPE.

Examples Description of used support materials and precatalyst complexes

Halloysite-nanoclay are alumino silicates (AI₂Si205(OH) · 2H₂0) present in nature and available from Sigma-Aldrich. The used halloysite materials are in the form of nanotubes having an outer diameter of 100 to 300 nm and a wall thickness of 10 to 30 diameter. The specific surface area is 26 m²/g.

Sylopol 948 is a spheric agglomerate of silica particles available from Grace, the agglomerate having an outer diameter of 50.000 nm and a specific surface area of 266 m²/g. The halloysite-nanoclay materials were dried at 150°C for 2 h in high vacuum and stored under Ar before use.

Fe1 : 2,6-bis-[1-(2,6-diisopropylphenylimino )ethyl] pyridine iron(ll) dichloride (M: 496.3 g/mol) was prepared by the method of Qian et al., Organometallics 2003, 22, 4312-432 in analoguous manner to 2,6-Diacetylpyridinebis(2,4,6-trimethylphenylanil)iron dichloride.

CM : 3,4,5-trimethyl-1-(8-quinolyl)-2-trimethylsilyl cyclopentadienyl chromium(lll) dichloride (M: 429.40 g/mol) was prepared as described in Example 1 of WO 2006/018264 A2. Example 1 : Preparation of hollow silica nanotubes

First a PVA fiber fleece was prepared by electrospinning a PVA solution (M_w = 16.000 g/mol, 98 - 99 mol % hydrolysis (available from Aldrich)). The PVA fibers have a mean diameter between 100 and 250 nm. The process was performed as described in detail in WO2009/015804 A1. Subsequently the PVA nanofibers were coated with Si0₂ by the following procedure. An autoclave with three accesses closed by valves was provided with the PVA fiber fleece. Vacuum and air could be applied to the apparatus via a first valve. The apparatus further was connected to a container with SiCI via a second valve and another container with water via a third valve. In the beginning the second and third valves were closed. Vacuum was applied to the autoclave and pressure was adjusted to below 1 mbar via first valve. Then, the first valve was closed and afterwards the second valve was opened until SiCI₄ began to boil. As soon as SiCI₄ stopped bubbling, the second valve was closed. Then, 5 min later, again, vacuum was applied via the first valve. The apparatus was flushed with air two times and was evacuated again. Subsequently, the third valve was opened until water was boiling. Then, the first valve was closed and 10 s later the third valve was also closed. After a reaction period of 5 min, the autoclave again was flushed with air for two times. After increase of weight of fiber fleece had reached a defined value, the PVA fibers were removed by calcination. During calcination process the temperature was slowly raised to 150°C within a period of 1 h. The temperature was kept for another 1 h and subsequently slowly raised to 450°C within a period of 5 h. The temperature of 450°C was kept for another 3 h after which the product was cooled down to room temperature within 0.5 h.

According to this procedure silica hollow nanotubes were produced which are named SHF 14-5 and had an outer diameter of 150 to 200 nm and a wall thickness of 4 to 10 nm; the specific surface area was 130 m²/g. Prior to use the silca nanotubes were dried in high vacuum. Examples 2: Preparation of the catalysts

Dry Si0₂ nanotubes as prepared in Example 1 (Support 1) were dispersed in toluene. Subsequently the dispersion was treated in an ultrasonic bath. While stirring an excess of MAO was added. A solution of 3,4, 5-trimethyl-1-(8-quinolyl)-2 -trimethylsilyl cyclopentadienyl chromium(lll) dichloride in toluene was prepared as indicated in Table 1 and added to the Si0₂ nanotube dispersion.

The procedure was repeated to prepare different concentrations of the 3,4,5-trimethyl-1 -(8-quinolyl)-2- trimethylsilyl cyclopentadienyl chromium(lll) dichloride on the support. The Si0₂ nanotube support was supported with different amounts of chromium complex. Four samples were provided, with 0-1.4 μιτιοΙ chromium complex per 100 mg support (see table 1 ). Dry halloysite nanoclay (Support 2) was dispersed in toluene. Subsequently the dispersion was treated in an ultrasonic bath. While stirring an excess of MAO was added. A solution of 2,6-bis-[1-(2,6- diisopropylphenylimino )ethyl] pyridine iron(ll) dichloride in toluene was prepared as indicated in Table 1 and added to the halloysite nanoclay dispersion. The halloysite nanoclay was supported with 2.02 μιηοΙ 2,6-bis-[1-(2,6-diisopropylphenylimino )ethyl] pyridine iron(ll) dichloride per 100 mg support.

The comparative examples were performed accordingly with halloysite nanoclay as the only support material and Sylopol 948 as the only support material.

Example 3: Polymerization of ethylene

Into a 1 I autoclave equipped with a mechanical stirrer 300 ml heptane and, subsequently, 2.0 ml (2 mmol) TiBAI (triisobutylaluminum) were added. Then, 100 mg of each catalyst prepared according to example 2 were injected. Polymerization was started by applying a pressure ethylene at a reaction temperature of 25°C. After 2 h polymerization was stopped by release of ethylene pressure. The polymer was removed from the autoclave, filtrated and subsequently dried at 60 °C under vacuum. The polymerization conditions and results are shown in the following Table 1. Table 1 :

Fe1 (2.02 pmol) immobilized on support 2; CM (0-1.4 pmol) immobilized on support 1

Halloysite- Halloysite- Comp2 0.25 11 164 7400 410 5.5 1 977±171 65+6 nanoclay nanoclay

Halloysite- Halloysite- Comp3 0.5 20 147 8200 596 8.5 6 1044+1 16 69+7 nanoclay nanoclay

Halloysite- Halloysite- Comp4 1.4 40 195 9700 611 8.0 10 1089±51 77±6 nanoclay nanoclay

Halloysite-

Inv1 SHF 14-5 0 0 154 11400 290 4.4 0 1016±80 41±1 nanoclay

Halloysite-

Inv2 SHF 14-5 0.25 11 81 5900 370 6.3 5

nanoclay 1300±100 51±3 Halloysite-

Inv3 SHF 14-5 0.5 20 109 7900 590 12.2 8

nanoclay 1510±70 99±9 Halloysite-

Inv4 SHF 14-5 1.4 40 140 10400 556 8.6

nanoclay 5 1214±60 70±7

Sylopol

Comp5 0 Sylopol 948 0 175 8700 422 6.6

948 0 436+56 42±5

Sylopol

Comp6 0.25 Sylopol 948 10 110 4400 570 9.8 5 520±45 43+2

948

Sylopol

Comp7 1.7 Sylopol 948 30 115 4300 1.150 9.8 21

948 844+184 72+19 n (CM): amount of C , theoretical value, calculated from amount used for supportation

mol% CM : calculated from n(Cr1 )/ (CM + Fe1 )-100%

Prod.: productivity

Act.: calculated from activity of both catalysts

M_w: weight average molecular weight

PD,: polydispersity index

E modulus: modulus of elasticity

Fiviax : tensile strength at yield

Weight%-UHMWPE: Part of UHMWPE, produced by CM-catalyst

Determination of molecular weight (Mw) by gel permeation chromatography:

The determination of the molar mass distribution and the mean Mw derived therefrom was carried out by high-temperature gel permeation chromatography using a method described in DIN 55672-1 :1995- 02 issue Februar 1995. The deviations according to the mentioned DIN standard are as follows: Solvent 1 ,2,4-trichlorobenzene (TCB), temperature of apparatus and solutions 135°C and as concentration detector a PolymerChar (Valencia, Paterna 46980, Spain) IR-4 infrared detector, capable for use with TCB. A WATERS Alliance 2000 equipped with the following precolumn SHODEX UT-G and separation columns SHODEX UT 806 M (3x) and SHODEX UT 807 connected in series was used. The solvent was vacuum destilled under nitrogen and was stabilized with 0.025% by weight of 2,6-di-tert-butyl-4- methylphenole. The flowrate used was 1 ml/min, the injection was 500μΙ and polymer concentration was in the range of 0.01 % < cone. < 0.05% w/w. The molecular weight calibration was established by using monodisperse polystyrene (PS) standards from Polymer Laboratories (now Varian, Inc., Essex Road, Church Stretton, Shropshire, SY6 6 AX, UK ) in the range of from 580g/mol up to

11600000g/mol and additionally hexadecane. The calibration curve was then adapted to Polyethylene (PE) by means of the Universal Calibration method (Benoit H., Rempp P. and Grubisic Z., & in J. Polymer Sci., Phys. Ed., 5, 753(1967)). The Mark-Houwing parameters used herefore were for PS: kp_S= 0.000121 dl/g, a_PS=0.706 and for PE k_PE= 0.000406 dl/g, a_PE=0.725, valid in TCB at 135°C. Data recording, calibration and calculation was carried out using NTGPC_Control_V6.02.03 and

NTGPC_V6.4.24 (hs GmbH, HauptstraGe 36, D-55437 Ober-Hilbersheim) respectively.

Weight percentage

The weight percentage of UHMW-polyethylene was determined by GPC. The program determines the area of the region bounded by the GPC graph by integration. The part of UHMWPE is the value of the integrals of > 1000 kg/mol in respect to the value of the integrals < 1000 kg/mol. In each sample series the part of UHMWPE, which is produced without CM catalyst is subtracted from calculated value. Thus, only UHMWPE produced by Cr1 catalyst is taken into consideration. PE, which is produced by the iron catalyst in a percentage of 10 weight % UHMWPE has not the same effect of enforcement like UHMWPE produced by CM catalyst.

Yield stress experiments

Yield-stress-experiments were made with a Zwick testing apparatus (Model Z-005) according to DIN 53455 (ISO 527). The modulus of elasticity was determined according to secant method (ISO 1873-2), by determining the slope of the straight line through the measurement points at 0.05% and 0.25%. Each sample was measured 5 times, the values for the modulus of elasticity and tensile strength at yield were calculated as the arithmetic means inclusive standard deviation.

Specimen for the examples were obtained by mini injection molding into special molds.

Injection mold specimen for yield stress measurements were produced in a co-rotating DSM Xplore double screw micro compounder. First, 3.3 g of the polymer stabilized with 0.5 weight % (Irganox 1010/lrgaphos 168 1/1 w/w) was filled via a special feed hopper into the micro compounder. For producing further specimen about 2.3 g were refilled into the compounder. Temperature in all 3 heating zones was applied to 180°C. The screws rotated with a velocity of 200 U/min. The exit of the compounder was closed, until all the polymer was filled into the micro compounder. Immediately thereafter the exit of the micro compounder was opened and the polymer strand was filled into a heatable transfer cylinder of the mini injection molding machine. Thereby, one piston was pressed out of the cylinder. After the cylinder was secured in a fixing of the mini injection molding machine, the injection molding program was started and polymer melt was injected via a jet into the injection mold at a pressure of 8 bar. Injection pressure of 8 bar is applied during 8 s. Immediately after the injection process was finished, the injection mold was pressed out of the heatable mold fixing and opened.

Claims

Claims

1. Process for the preparation of bimodal polyolefin nanocomposites comprising the steps of supporting a first precatalyst for production of ultrahigh molecular weight polyolefin on a first support comprising metal oxide nanotubes,

supporting a second precatalyst for production of lower molecular weight polyolefin on a second support not comprising metal oxide nanotubes, and

polymerizing an olefin in the presence of the two supported precatalysts and optionally an activator.

2. Process according to claim 1 , wherein the olefin is ethylene.

3. Process according to claim 1 or 2, wherein the second precatalyst is supported on a

phyllosilicate, preferably a halloysite-nanoclay.

4. Process according to one of claims 1 to 2, wherein the metal oxide nanotubes have a

diameter of 150-200 nm and a wall thickness of 4 to 10 nm.

5. Process according to one of the preceding claims, wherein the metal oxide nanotubes are Si0₂ nanotubes.

6. Process for the preparation of bimodal polyethylene nanocomposites according to one of the preceding claims, wherein the ultra high molecular weight polyethylene producing catalyst comprises a constrained geometry chromium complex and the lower molecular weight producing catalyst comprises a bisphenyliminoethyl pyridine iron complex.

7. Bimodal polyolefin nanocomposite comprising ultrahigh molecular polyolefin and lower

molecular weight polyolefin and metal oxide nanotubes.

8. Bimodal polyolefin nanocomposite according to claim 7, further comprising phyllosilicate

nanoclay.

9. Bimodal polyolefin nanocomposite according to claim 7 or 8, wherein the nanocomposite comprises an ultra high molecular weight polyolefin fraction of 0.1 to 85 weight% based on the total weight of polyolefin.

10. Bimodal polyethylene nanocomposite according to one of claims 7 to 9.

11. Bimodal polyethylene nanocomposite according to one of claims 7 to 10 prepared by a

process according to one of claims 1 to 6.

12. A fiber, film or molding comprising a bimodal polyethylene nanocomposite as claimed in any of claims 7 to 11 , preferably as substantial component.