Ziegler-natta bimetallic catalysts, catalytic systems including the same and processes for polymerizing linear alpha-olefins

Abstract

The present invention relates to Ziegler-Natta bimetallic catalysts supported on MgCl2, which contains: titanium in the oxidation state +3 (Ti(III)), and optionally titanium in the oxidation state +4 (Ti(IV)); and at least one metal selected from hafnium in the oxidation state +4 (Hf(IV)) and zirconium in the oxidation state +4 (Zr(IV)). The Mg / Ti molar ratio is from 0.5 to less than 3.0; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0. Moreover, said Ziegler-Natta bimetallic catalysts is treated with at least one Si-containing compound of formula SiR1 p(OR2)(4-p) wherein: p is zero or an integer from 1 to 3; the R1 groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10 aryl groups; the R2 groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10 aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0. Said catalytic system may be used in a process for polymerizing at least one linear α-olefin.

Description

[0001] ZIEGLER-NATTA BIMETALLIC CATALYSTS, CATALYTIC SYSTEMS INCLUDING THE SAME AND PROCESSES FOR POLYMERIZING LINEAR ALPHA-OLEFINS

[0002] The present invention relates to Ziegler-Natta bimetallic catalysts, to catalytic systems including the same and to processes for polymerizing linear a-olefins wherein said catalytic system is used.

[0003] BACKGROUND OF THE INVENTION

[0004] Poly-α-olefins having high molecular weights and stereoregularity are usually obtained by polymerization of C2-C10a-olefins by means of catalytic systems based on Ziegler-Natta catalysts, which are usually made of a titanium compound and an organoaluminum compound as co-catalyst, possibly supported on MgCl2.

[0005] Bimetallic Ti-Hf catalyst systems have been studied in the polymerization of ethylene and a-olefins in order to understand the synergy between the two metals and in particular the role of hafnium. Bimetallic Ti-Hf catalysts and monometallic Ti-based catalysts, both supported on MgCl2, prepared according to the procedure described in EP 0 243 327 Al, give comparable polymer yields, but in the case of the bimetallic Ti-Hf catalysts higher molecular weights are obtained (see F. Masi, S. Malquori, L. Barazzoni, C. Ferrero, A. Moalli, F. Menconi, R. Invernizzi, Makromol. Chem. Suppl. 1989, 15, 147-165).

[0006] WO 2012 / 084920 Al relates to a catalyst comprising titanium, magnesium, aluminum, chlorine and at least one metal M selectedfrom hafnium and zirconium, and the synthesis process thereof. The catalyst is characterized by the following atomic or molar ratios: M / Ti = 0.2-5.0; Mg / Ti = 3.0-20.0; R-COOH / (Mg + M) = 1-8, wherein M = Hf or Zr. The catalyst is pretreated with a siloxane compound, so that the ratio Si / Ti = 0.2-2.0. The above catalyst is used in a process for the synthesis of poly-α-olefins at temperatures above 50°C.

[0007] WO 2016 / 016355 Al relates to a process for preparing a catalyst comprising titanium, magnesium, aluminum, chlorine and optionally at least one metal M selected from hafnium and zirconium. The catalyst is characterized by the following atomic or molar ratios: M / Ti = 0.0-5.0; Mg / Ti = 3.0-15.0; R-COOH / (Mg + M) = 1.5-8, wherein M = Hf or Zr. The above catalyst is used in a process for the synthesis of poly-α-olefins at temperatures from 20°C to 300°C.

[0008] WO 2011 / 060958 Al relates to a catalyst for the polymerization of a-olefins, comprising titanium, magnesium, aluminum, chlorine and at least one metal M selected from hafnium and zirconium. The catalyst is characterized by the following atomic or molar ratios: M / Ti = 0.2-5.0; Mg / Ti = 3.0-15.0; Al / Ti = 0.1-4.0; Cl / Ti = 15.0-60.0, wherein M = Hf or Zr. The above catalyst is used in a process for the synthesis of poly-α-olefins at temperatures from 20°C to 300°C.

[0009] WO 2000 / 58368 Al relates to a catalyst for the polymerization of a-olefins, comprising titanium, magnesium, aluminum, chlorine and at least one metal M selected from hafnium and zirconium. The catalyst is characterized by the followingatomic or molar ratios: M / Ti = 0.1-10.0; Mg / Ti = 1.0-20.0; Al / Ti = 0.01-6.0 Cl / Ti = 2.0-70.0; R-COO / Ti = 0.1-10.0, wherein M = Hf or Zr. The above catalyst is used in a process for the synthesis of poly-α-olefins at temperatures from 20°C to 300°C.

[0010] US 7,348,383 B2 relates to a process for preparing a Ziegler-Natta bimetallic catalyst comprising magnesium, titanium, another transition metal comprising hafnium and optionally silica, wherein a solution of the respective precursors in an organic solvent containing hydroxyl functionality is subjected to spray-drying, and the product is subsequently halogenated by means of an organoaluminum and / or organoborate halide. The catalyst is characterized by a Ti / Hf molar ratio from 0.05 to 100.0, preferably from 0.1 to 10 (which corresponds to a Hf / Ti molar ratio from 0.01 to 20, preferably from 0.1 to 10 ). The above catalyst, combined with a triethylaluminum as a co-catalyst, is used in a polymerization process of C2-C20 olefins.

[0011] WO 2023 / 204618 Al relates to a process for preparing a Ziegler-Natta catalyst comprising magnesium ( obtained in-situ by reacting dialkyl magnesium with an inorganic halide to form the support with a characteristic XRD pattern for the 5-MgCl2phase ), titanium, a second transition metal ( zirconium and / or hafnium and / or vanadium and / or niobium and / or tantalum), aluminum and chlorine. The catalyst is synthetized by reacting a titanium compound with MgCl2in the following molar ratios: 1:0.1 to 1:30, 1:0.1 to 1:30, 1:5 to 1:30, 1:8 to 1:25, 1:10 to 1:25, 1:11 to 1:22, or 1:12 to 1:21. The above ratios correspond to obtain acatalyst having a Mg / Ti molar ratio ranging from 0. 1 to 30, from 5 to 30, from 8 to 25, from 10 to 25, from 11 to 22, from 12 to 21. The above catalyst is used in a polymerization process for producing low density olefin copolymers ( from 0.91 to 0.94 g / ml).

[0012] US 9,255,160 B2 relates to a process for preparing a Ziegler-Natta multimetal catalyst comprising magnesium, obtained in-situ by reacting a hydrocarbon-soluble organomagnesium compound or complex thereof and a non-metallic or metallic halide to form a halogenated magnesium support. Such support is then contacted with a conditioning compound containing an element selected from the group consisting of boron, aluminum, gallium, indium and tellurium. The conditioned magnesium halide support is then contacted with a compound containing titanium, to form a supported titanium compound. The latter is then contacted with a second metal and a third metal independently selected from the group consisting of zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten, provided that the second metal and the third metal are not the same. The catalyst is characterized by a Mg / Ti molar ratio from 8.0 to 80.0, and a Mg / (Ti + 2nd metal + 3rd metal) molar ratio of from 5.0 to 30.0. The above catalyst is used to produce polyethylene having a density from 0.90 to 0.96 g / ml.

[0013] US 8,809,220 B2 relates to a process for preparing a Ziegler-Natta bimetallic catalyst comprising magnesium, titanium, hafnium and / or zirconium, aluminum, chlorine and a filler at neutral pH to make the catalyst workable by spraydrying technique. The catalyst is represented as MgxTiHfyZrz,where x is from 1 to 20, y is from 0 to 10 and z is from 0 to 10, with the proviso that y+z > 0. Therefore, the catalyst is characterized by a Mg / Ti molar ratio from 1.0 to 20.0, and (Hf and / or Zr) / Ti molar ratio higher than zero and not higher than 10.0. The particles of the bimetallic catalyst have a spherical shape with an average size (D50) from 10 to 70 pm. The above catalyst is used in an olefin polymerization process carried out in gas or slurry phase, in the presence of at least one cocatalyst.

[0014] US 11,939,417 B2 relates to a process for preparing a bimetallic heterogeneous catalyst comprising magnesium, titanium, and a second metal M selected from the group comprising vanadium, scandium, zirconium, niobium, magnesium, calcium, in the form of a metal complex of formula (L)nM(Y)m(XR2)b, aluminum or silica, chlorine; X is a heteroatom and, preferably, XR2 is an alkoxide or a carboxylate. The catalyst is characterized by a Ti / Mg molar ratio from 0.005 to 0.25 (which corresponds to a Mg / Ti molar ratio from 4 to 200). The above catalyst is used in a solution polymerization process for producing ethylene-based copolymers, in the presence of an organoaluminum compound as cocatalyst.

[0015] A particular class of poly-α-olefins is known in the art with the term amorphous poly-α-olefins (APAOs), which are obtained from the polymerization of long-chain a-olefins and have a high molecular weight, e. g. a weight average molecular weight (Mw) higher than about 105g / mole. The APAOs are commonly used as drag reducers, i. e. as additives for reducing frictionin fluids conveyed in long pipelines.

[0016] It is known that the main requirement to transport a fluid through a pipeline is that the pressure at the pumping station is such as to guarantee final pressure and flow rate suitable for the intended use. When fluids are transported through a pipeline, generally in turbulent flow conditions, for example in case of transport of oil or hydrocarbons, there is usually a pressure drop of the transported fluid, due to the friction between the internal wall of the pipeline and the fluid itself. This issue is more relevant when fluids are transported over long distances.

[0017] Specific additives, called drag reducers, to be added to the transported fluid have been studied, developed, and used to solve the above problem. The quantitative definition of the phenomenon of drag reduction is calculated as a comparison of the pressure loss with and without the presence of a drag reducer, as reported in the equation ( I ):

[0018] ΔP untreated- P treated. > >

[0019] %DR - - 100 ( I )

[0020] ΔP untreated

[0021] wherein:

[0022] - ΔP untreated is the pressure drop in the pipeline with no drag reducer added to the fluid;

[0023] - AP treated is the pressure drop in the pipeline with a drag reducer added to the fluid, by assuming that the flow rate of the fluid in the pipeline is constant.

[0024] The APAOs are the most employed class of products used as drag reducing additives. See for instance US 3,692,676, WO2008 / 073293 and US 2016 / 0024369.

[0025] The Applicant has faced the problem of providing Ziegler-Natta bimetallic catalysts, suitable for processes of polymerization of linear a-olefins, which allow to employ process conditions more convenient for an industrial application, to achieve a high monomer conversion.

[0026] In particular, the Applicant has faced the problem of producing amorphous poly-a-olef in (APAOs) to be used as drag reducers for fluids conveyed in pipelines, by means of bimetallic Ziegler-Natta catalysts which are able to regulate the polymerization process so as to improve the drag reducing effect.

[0027] Surprisingly, the Applicant has found that it is possible to solve the above stated technical problems by means of a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5. 0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5. Moreover, the above Ziegler-Natta bimetallic catalyst is treated with at least one Si-containing compound of formula SiR1p(OR2)(4-p)wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

[0028] Therefore, the Ziegler Natta catalyst supported on MgCl2may contain titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5; at least one Si-containing compound of formula SiR1p(OR2)(4-p)wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: Ci-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

[0029] The treated Ziegler-Natta bimetallic catalyst as disclosed above, when combined with an organoaluminum co-catalyst, forms a catalytic system which can be advantageously used in a process for polymerizing linear a-olefins. Such process may be carriedout at a temperature from -10°C to 20°C, more preferably from -5°C to 15°C, to produce poly-α-olefins with a high monomer conversion. Moreover, in the case of APAOs, the obtained APAOs have improved properties when used as drag reducers for fluids conveyed in pipelines, particularly an improved drag reduction effect, which does not sharply decrease over time.

[0030] SUMMARY OF THE INVENTION

[0031] Therefore, in a first aspect, the present invention relates to a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:

[0032] titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) );

[0033] at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;

[0034] said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein theamount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

[0035] Therefore, said Ziegler Natta catalyst supported on MgCl2may contain titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5; at least one Si-containing compound of formula SiR1p(OR2)(4-p)wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: Ci-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

[0036] In a second aspect, the present invention relates to a process for preparing a Ziegler-Natta bimetallic catalyst supported on MgCl2as defined above, said process comprising:

[0037] (a) mixing at least one titanium compound, at least one metal compound selected from hafnium (Hf ) compounds and zirconium (Zr) compounds, MgCl2, and at least one carboxylic acid of formula R-COOH, wherein R is a linear or branched hydrocarbonradical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine, in a hydrocarbon liquid medium at a temperature from 40°C to 200°C, preferably from 60°C to 130°C, to obtain a catalyst precursor;

[0038] (b) adding to the catalyst precursor at least one organoaluminum compound of formula AlyClxyR3y-xy, wherein R is an alkyl having from 1 to 10 carbon atoms, x is a number from 1.0 to 2.0 and y is an integer equal to 1 or 2, to obtain the bimetallic catalyst;

[0039] (c) adding to the bimetallic catalyst obtained in step (b) at least one Si-containing compound of formula SiR1p(OR2)(4-p)wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

[0040] In a third aspect, the present invention relates to a Ziegler-Natta bimetallic catalyst supported on MgCl2obtainable, or obtained, by the process reported above.

[0041] In a fourth aspect, the present invention relates to a catalytic system comprising:

[0042] (i) a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:

[0043] titanium in the oxidation state +3 (Ti ( III ) ), andoptionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1. 0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;

[0044] said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0;

[0045] (ii) at least one organoaluminum co-catalyst of formula AlRnX(3-n), wherein: the R groups, equal or different from each other, are linear or branched Ci-Ce alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

[0046] In a fifth aspect, the present invention relates to a catalytic system comprising:

[0047] (i) a Ziegler-Natta bimetallic catalyst supported on MgCl2according to the process reported above;

[0048] (ii) at least one organoaluminum co-catalyst of formula AlRnX (3-n), wherein: the R groups, equal or different from eachother, are linear or branched C1-C6 alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

[0049] In a sixth aspect, the present invention relates to a process for polymerizing at least one linear a-olefin, said process being carried out from -10°C to 20°C, more preferably from -5°C to 15°C, by using a catalytic system comprising:

[0050] (i) a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:

[0051] titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;

[0052] said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; R1are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; R2are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0;

[0053] (ii) at least one organoaluminum co-catalyst of formulaAlRnX(3-n), wherein: the R groups, equal or different from each other, are linear or branched Ci-Ce alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

[0054] Preferably, the above process for polymerizing at least one linear a-olefin is a mass polymerization process, namely a bulk polymerization process, carried out in the absence of a solvent, in which the reaction medium is substantially formed by the monomers, and the catalyst is preferably suspended in said reaction medium.

[0055] For the purpose of the present disclosure and of the claims that follow, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Moreover, all numerical ranges include any single value within the ranges and the extremes thereof, and also any intermediate ranges therein, which may or may not be specifically enumerated.

[0056] For the purpose of the present disclosure and of the claims that follow, except where otherwise indicated, the terms "comprise" or "include" encompass also the terms "consist of" or "consist essentially of".

[0057] BRIEF DESCRIPTION OF THE FIGURE:

[0058] Figure 1: it is a schematic representation of an apparatus used to determine the drag reduction effect (DR%) of an additive added to a fluid, as described in the examples reported hereinunder.

[0059] DETAILED DESCRIPTION OF THE INVENTIONPreferably, the linear a-olefin monomer has formula CH2=CH-R, wherein R is H or a linear C1-C12 alkyl group. Preferably, R is a linear C2-C10 alkyl group. Even more preferably, the linear a-olefin monomer is selected from: 1-hexene, 1-octene, 1-decene and 1-dodecene, or mixtures thereof. Even more preferably, the linear a-olefin monomer is selected from: 1-octene, 1-decene, 1-dodecene, and mixtures thereof.

[0060] According to a first preferred embodiment, the bimetallic catalyst contains: titanium in the oxidation state +3 ( Ti ( I I I ) ), and optionally titanium in the oxidation state +4 ( Ti ( IV) ); and hafnium in the oxidation state +4 (Hf ( IV) ).

[0061] According to a second preferred embodiment, the bimetallic catalyst contains: titanium in the oxidation state +3 ( Ti ( I I I ) ), and optionally titanium in the oxidation state +4 ( Ti ( IV) ); and zirconium in the oxidation state +4 ( Zr ( IV) ).

[0062] Preferably, at least 70% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight, of titanium in the bimetallic catalyst is Ti ( I I I ), the percentage being calculated on the total weight of Ti.

[0063] The amount of titanium present in the bimetallic catalyst preferably does not exceed 10% by weight, more preferably is from 1. 6% to 10% by weight, with respect to the total weight of the bimetallic catalyst.

[0064] In the catalytic system of the present invention, aluminum and titanium are preferably present in a molar ratio from 3: 1 to 500: 1, more preferably from 5: 1 to 100: 1, even more preferably from 10: 1 to 40: 1.According to a preferred embodiment, the Ziegler-Natta bimetallic catalyst supported on MgCl2according to the present invention comprises at least carboxylate group deriving from a carboxylic acid of formula R-COOH, wherein R is a linear or branched hydrocarbon radical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine. Preferably, said at least one carboxylate group is present in an amount so as to have a (carboxylate group) / Ti molar ratio from 0.1 to 0.8, more preferably from 0.4 to 0. 6. The expression "at least one carboxylate group" encompasses the case that more than one carboxylate group is present. When more than one carboxylate group is present, the numerator of said molar ratio is the sum of the moles of each carboxylate group if more than one carboxylate is present in the bimetallic catalyst.

[0065] According to a preferred embodiment, the Ziegler-Natta bimetallic catalyst supported on MgCl2according to the present invention has the following formula:

[0066] TiiMgxHfyAlzClw (R-COO)k

[0067] wherein:

[0068] R is a linear or branched hydrocarbon radical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine;

[0069] x = 0.5 - 2.7 (preferably 1.0 - 2.5);

[0070] y = 1.0 - 4.0 (preferably 1.5 - 3.5);

[0071] z = 0.5 - 1.2 (preferably 0.7 - 0.9);

[0072] w = 13.0 - 25.0 (preferably 19.0 - 21.0);

[0073] k = 0.1 - 0.8 (preferably 0.4 - 0. 6).As regards the organoaluminum co-catalyst of formula AlRnX(3-n), the linear or branched Ci-Ce alkyl groups R are preferably selected from: methyl, ethyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl. Particularly preferred are trialkylaluminum compounds, such as: triethylaluminum, tri-n-butylaluminum, triisobutylaluminum and trihexyl aluminum.

[0074] The titanium, hafnium and zirconium compounds used to produce the Ziegler-Natta bimetallic catalyst according to the present invention may be selected from a wide range of inorganic or organometallic compounds comprising said metals. Preferably, such compounds are selected from: chlorides, bromides, alcoholates, hydrides, p-diketonates, p-acyl esters, amides, carbonates, carboxylates, phosphates, or mixtures thereof. Particularly preferred are titanium chlorides, hafnium chlorides and zirconium chlorides.

[0075] In the process for producing the Ziegler-Natta bimetallic catalyst according to the present invention, the carboxylic acid of formula R-COOH is added in step (i) for partially or completely dissolving the solids in the reaction medium.

[0076] The carboxylic acid of formula R-COOH has a relatively large number of carbon atoms in the chain to promote dissolution in a hydrocarbon type liquid medium. The group R in the formula above may be a linear or branched hydrocarbon radical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine. More preferably, R is a linear or branched hydrocarbon radical having from 3 to 16 carbonatoms. Non-limiting examples of said group R are:

[0077] linear alkyl groups containing at least 3 carbon atoms, preferably not more than 16 carbon atoms, for example n-hexyl, n-octyl, n-nonyl, n-decyl or n-undecyl;

[0078] branched alkyl groups having a linear chain containing from 2 to 10 carbon atoms and a branching chain in the alpha or beta position of the linear chain with respect to the carbon atom of the carboxylic group, said branching chain being selected from: linear Ci-Ce alkyl groups, branched Ci-Ce alkyl groups, phenyl, cyclopentyl, cyclohexyl.

[0079] Preferably, the carboxylic acid of formula R-COOH is selected from: 2-ethylhexanoic acid, 2-methylhexanoic acid, 2-propylhexanoic acid, 2-butylhexanoic acid. Particularly preferred is 2-ethylhexanoic acid.

[0080] Preferably, the organoaluminum compound of formula AlyClxyR3y-xy, used in step (b) of the process for preparing a Ziegler-Natta bimetallic catalyst according to the present invention, is selected from: ethyl aluminum sesquichloride (EASC), ethylaluminum dichloride (EADC), isobutylaluminum dichloride ( IBADIC) and diethylaluminium chloride (DEAC). More preferably, it is EASC.

[0081] Preferably, the Si-containing compound of formula SiR1p(OR2) (4-p) as defined above is selected from: tetraethoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, isobutyl isopropyldimethoxysilane, diisopropyldimethoxysilane, cyclopentyl isobutyldimethoxysilane, dicyclohexyldimethoxysilane, phenyl triethoxysilane,diphenyldimethoxysilane, dicyclohexyldimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, or mixtures thereof. More preferably, the Si-containing compound of formula SiR1p(OR2) (4-p) as defined above is diisopropyldimethoxysilane.

[0082] Preferably, during step (c) of the process for preparing a Ziegler-Natta bimetallic catalyst supported on MgCl2according to the present invention, at least one siloxane compound is mixed with the bimetallic catalyst obtained in step (b) at a temperature from -10°C to 120°C, preferably from 20°C to 50°C. Preferably, at least one Si-containing compound is mixed with the bimetallic catalyst obtained in step (b) for a time from 1 min to 120 min, preferably from 10 min to 60 min.

[0083] Preferably, the catalytic system according to the present invention comprises up to 10% by weight, more preferably from 1 to 5% by weight, of the above carboxylic acid R-COOH, the percentage being calculated on the basis of the total weight of the catalytic system.

[0084] The catalytic system according to the present invention may be prepared in advance, outside the polymerization reactor, by mixing and reacting the Ziegler-Natta bimetallic catalyst, supported on MgCl2and treated with the at least one Si-containing compound, with the at least one organoaluminum cocatalyst of formula AlRnX(3-n).

[0085] Alternatively, the catalytic system according to the present invention may be prepared in the polymerization reactor, where the bimetallic catalyst, supported on MgCl2and treated with the at least one Si-containing compound, is introduced andreacted with the organoaluminum co-catalyst previously added therein.

[0086] During the preparation of the catalytic system, other additives may be added, commonly used for the production of Ziegler-Natta catalysts, such as: olefins, ethers, tertiary amines, non-polymerizable alcohols, halogenated hydrocarbons, preferably chlorinated hydrocarbons.

[0087] The bimetallic catalyst or the catalytic system may be introduced into the polymerization reactor, where the polymerization process is carried out, in the form of a dispersion or of a solution in a saturated aliphatic hydrocarbon, preferably selected from: propane, pentane, hexane, decane, and mixtures thereof.

[0088] The process for polymerizing at least one linear a-olefin according to the present invention may be carried out according to known techniques. Preferably, the polymerization process is a mass polymerization carried out in an inert atmosphere, preferably in a nitrogen atmosphere having an oxygen content not higher than 1 ppm (by weight).

[0089] The mass polymerization process may be carried out continuously or batch-wise.

[0090] The catalytic system in the polymerization reactor is used in an amount so as to obtain a titanium concentration preferably from 100 mmol / 1 to 200 mmol / 1, equal to approximately 4.5-9 g / 1, said concentration being calculated on the basis of the total monomer volume used in the polymerization.

[0091] The polymerization may be generally carried out for areaction time from 24 to 360 hours, preferably from 48 to 200 hours, more preferably from 72 to 120 hours.

[0092] The polymerization process according to the present invention has a high monomer conversion, usually more than 40.0%, preferably more than 80.0%, even more preferably more than 85.0%.

[0093] The present invention is further described by means of some examples as reported hereinbelow, which are provided only for illustrative purposes and cannot be construed as a limitation to the claim scope.

[0094] EXAMPLES.

[0095] The following commercial reagents were used (purity degrees are reported as % according to the producer's technical data sheet):

[0096] sodium hydroxide (CAS 1310-73-2, purity ≥ 98.0%)

[0097] n-decane (CAS 124-18-5, purity ≥ 99.0%)

[0098] magnesium chloride (CAS 7786-30-3, purity ≥ 98.0%) hafnium tetrachloride (CAS 13499-05-3, purity 98.0%) titanium tetrachloride (CAS 7550-45-0, purity 99.9%)

[0099] 2-ethylhexanoic acid (CAS 149-57-5, purity 99.0%)

[0100] ethyl aluminum sesquichloride (CAS 12075-68-2, purity 99.9%)

[0101] 1-decene (CAS 872-05-9, purity 95.0%)

[0102] triisobutyl aluminum (CAS 100-99-2, purity 99.9%) diisopropyl dimethoxysilane (CAS 18230-61-0, purity ≥ 95.0%)

[0103] xylene, mixture of isomers (CAS 1330-20-7, purity ≥ 98.5%) magnesium stearate (CAS 557-04-0, purity 99.0%)soybean oil (CAS 8001-22-7, purity 99.0%)

[0104] n-hexane (CAS 110-54-3, purity ≥ 99.0%)

[0105] n-dodecene (CAS 112-41-4, purity ≥ 99.0%)

[0106] n-octene (CAS 111-66-0, purity ≥ 99.0%).

[0107] EXAMPLE 1 (reference)

[0108] Preparation of a bimetallic catalyst Ti-Hf / MgCl2.

[0109] TABLE 1

[0110] Reagents Quantity Moles

[0111] n-decane 1000 ml 5.0794 magnesium chloride 2.0 g 0. 0206 hafnium tetrachloride 9.1 g 0. 0278 titanium tetrachloride 1.8 g 0. 0095 2-ethylhexanoic acid (EHA) 21.0 g 0. 1442 ethyl aluminium 58.0 g 0.2341

[0112]

[0113] sesquichloride (EASC)

[0114] All the glassware was previously dried in an oven at 100°C for 24 hours (to eliminate traces of residual humidity and oxygen, which are poisons for the reaction and for the reagents themselves).

[0115] An apparatus was set up consisting of a 1000 ml four-necked glass flask, equipped with a 500 ml drip funnel connected to a trap containing 100 ml of a 20% sodium hydroxide solution in water (to neutralise the hydrochloric acid that developed during the reaction), a magnetic stirrer with stir bar, a capillary forgas inlet and a thermometer.

[0116] The apparatus was cooled to room temperature in a stream of dry nitrogen and keep in an inert atmosphere until use.

[0117] 50 ml of dry n-decane were introduced into the flask (pretreated with 4A, 5A, 10A molecular sieves, to ensure drying).

[0118] Magnesium chloride and hafnium tetrachloride were added, previously stored inside the dry box, in the quantities indicated in Table 1.

[0119] In a tailed test tube (sample tube) placed in the dry box, a titanium tetrachloride solution in n-decane ( 1.8027 g in 50 ml of solvent) was prepared. The content of the tailed test tube was transferred by siphoning into the flask, maintaining a slow magnetic stirring (about 300 rpm). The tailed test tube was washed with 50 ml of n-decane. The quantity of 2-ethylhexanoic acid indicated in Table 1 was then added.

[0120] The mixture was heated to 90°C in the previously closed flask with a small vent to avoid pressurization of the flask (the temperature was reached in 45 minutes max), the magnetic stirring was increased to about 800 rpm, and the stirred mixture was maintained at the indicated temperature for 2 hours (to obtain a substantially complete solubilization of the salts). The mixture was slowly cooled to room temperature, maintaining stirring and inert atmosphere.

[0121] Ethyl aluminum sesquichloride (EASC) was then added to the precursor while stirring ( 800 rpm), maintaining the temperature at about 40°C. The mixture was heated to 90°C and maintained at that temperature for 2 hours. Stirring was then interrupted andthe mixture was cooled to room temperature, allowing the solid to decant (about 4 hours).

[0122] The supernatant was extracted by siphoning, being very careful not to aspirate the solid catalyst, and collected in a tailed bottle in an inert atmosphere. It was then slowly added to a 10% sodium hydroxide aqueous solution.

[0123] About 250 ml of decane was then added to the solid residue and stirring was maintained for a few minutes at room temperature and in inert atmosphere. Stirring was stopped and the solid was left to settle again. The operation was repeated three more times so as to obtain an Al / Ti ratio in the supernatant lower than 1.2 mol / mol. The solid was diluted with decane, to obtain the desired catalyst concentration.

[0124] A catalyst was obtained, whose formula was the following: Ti1MgxHfyAlzClw(2-EHA)k

[0125] wherein:

[0126] x = 1.9

[0127] y = 3.0

[0128] z = 0.5

[0129] w = 19.9

[0130] k = 0.5

[0131] EXAMPLE 2 (comparative)

[0132] Preparation of a Ti-Hf / MgCl2bimetallic catalyst.

[0133] The procedure described in Example 1 was repeated, but using different quantities of the various components of the catalyst, so as to obtain a catalyst whose formula was the following:

[0134] Ti1MgxHfyAlzClw(2-EHA)kwherein:

[0135] x = 5.2

[0136] y = 1.0

[0137] z = 0.9

[0138] w = 18.3

[0139] k = 0.5.

[0140] EXAMPLE 3 (comparative)

[0141] Preparation of a Ti-Hf / MgCl2bimetallic catalyst.

[0142] The procedure described in Example 1 was repeated, but using different quantities of the various components of the catalyst, so as to obtain a catalyst whose formula was the following:

[0143] Ti1MgxHfyAlzClw(2-EHA)k

[0144] wherein:

[0145] x = 0.2

[0146] y = 1.1

[0147] z = 0.4

[0148] w = 10.1

[0149] k = 0.5.

[0150] EXAMPLE 4 (comparative)

[0151] Preparation of a Ti-Hf / MgCl2bimetallic catalyst.

[0152] The procedure described in Example 1 was repeated, but using different quantities of the various components of the catalyst, so as to obtain a catalyst whose formula was the following:

[0153] Ti1MgxHfyAlzClw(2-EHA)k

[0154] wherein:

[0155] x = 1.4

[0156] y = 0.3z = 0.3

[0157] w = 7.8

[0158] k = 0.5.

[0159] EXAMPLE 5 (reference)

[0160] Preparation of a Ti-Zr / MgCl2bimetallic catalyst.

[0161] The procedure described in Example 1 was repeated, with the following differences:

[0162] hafnium tetrachloride was replaced with zirconium tetrachloride;

[0163] - different quantities of the various components of the catalyst were used, so as to obtain a catalyst whose formula was the following:

[0164] Ti1MgxZryAlzClw(2-EHA)k

[0165] wherein:

[0166] x = 1.7

[0167] y = 2.4

[0168] z = 0. 6

[0169] w = 17.3

[0170] k = 0.1.

[0171] EXAMPLE 6 (comparative)

[0172] Preparation of the Ti / MgCl2monometallic catalyst.

[0173] 330 ml of n-decane and 3.24 g of magnesium chloride (34 mmol) were charged into a 1 liter glass reactor equipped with a stirrer and j acket, maintained under a continuous nitrogen flow.

[0174] The mixture was stirred for 10 minutes to homogenize, then 1.36 g of titanium ( TV) butoxide (OButyl) ( 4 mmol) and 36.8 g of 2-ethylhexanoic acid (2-EHA) (255 mmol).The temperature was set to 90°C and stirring was maintained for two hours.

[0175] 50 ml of the obtained solution was taken and added into a 1 liter glass reactor equipped with stirring and j acket, previously maintained in an inert atmosphere by washing with anhydrous nitrogen and brought to 40°C; then 200 ml of n-decane were added and stirring was maintained at 40 °C until homogenization.

[0176] 16 mmol of soluble AlCl3octyl ether complex (1:1) diluted to 50 ml with n-decane were added dropwise, so as to obtain a Al / (OButyl + 2-EHA) molar ratio equal to 1, referred to the total quantity of organic groups present in the initial solution of the precursor. During the addition, the precipitation of a white solid was noted, which ended at about half the added volume of the AlCl3octyl ether complex.

[0177] The suspension was brought to 60°C and maintained at that temperature under stirring for 1 hour. The suspension was then cooled to room temperature, stirring was stopped and the clear supernatant liquid was sampled for analysis: the solid contains substantially all the magnesium chloride, while substantially all the titanium remained in the soluble form.

[0178] The suspension was treated with a 50% solution of diethyl aluminum chloride (DEAC) in n-decane to obtain the reduction to Ti ( III ) and the consequent precipitation of TiCl3.

[0179] The amount of DEAC, expressed as pure product, was 0. 6 g, equal to 5 mmol, so as to obtain an Al / Ti molar ratio equal to 10.0.After the addition, the mixture was heated to 90°C and stirred for 2 hours. Then the reaction mixture was cooled to room temperature and a portion of the suspension was filtered through a G3 sintered glass septum and dried in a dry nitrogen flow.

[0180] A catalyst having the following formula was obtained:

[0181] Ti1MgxAlyClz(2-EHA)w

[0182] wherein:

[0183] x = 8. 6

[0184] y = 2.9

[0185] z = 26.8

[0186] w = 0.5.

[0187] EXAMPLES 7-12.

[0188] Treated catalyst

[0189] In a dry box under nitrogen flow, a quantity of diisopropyl dimethoxysilane was added by using a 10 µL Eppendorf pipette into a glass test tube where the catalyst prepared in Example 1 was previously inserted, so as to have a molar ratio of silicon to titanium equal to 0. 6, with respect to the fed titanium. The test tube containing the catalyst and the Si-containing compound was heated in a water / oil bath at 50°C for a maximum of 30 minutes.

[0190] The same procedure was followed with the catalysts prepared in Examples 2-6, so as to provide Examples 8-12. Examples 7 and 11 were according to the invention, whereas Examples 8, 9, 10 and 12 were comparative.

[0191] EXAMPLES 13-17.Catalyst systems were prepared by using the catalyst of Examples 7-12, and then such catalyst systems were used for polymerizing 1-decene to produce APAOs. The procedure was as follows. Examples 13 and 17 were according to the invention, whereas Examples 14, 15 and 16 were comparative.

[0192] About 400 g of 1-decene were added into a dry box continuously fluxed with anhydrous nitrogen and molecular sieves MS-4A (Grace Davison) were added in large excess (about 60 g); the mixture was maintained at room temperature (23 °C) for 30 hours before use.

[0193] A previously dried polyethylene bottle (500 ml) was placed into the dry box; 333 g of dried 1-decene (about 450 ml) were poured into the polyethylene bottle, then the bottle was closed and brought to 5°C.

[0194] 0.4 g of a co-catalyst (triisobutyl aluminum) were diluted in 1.1 g of n-decane; the solution was poured into the bottle containing 1-decene, the bottle was closed and shaken manually for one minute.

[0195] 150 mg (corresponding to approximately 0.4 ml) of the bimetallic catalyst suspension obtained in the previous examples was poured into the bottle, so that the monomer / Ti weight ratio was 400 ppm, while the co-catalyst / Ti molar ratio was 20.

[0196] The entire procedure described above was carried out in the dry box as quickly as possible. The bottle was closed and shaken manually for one minute.

[0197] The bottle was then placed in a refrigerator stabilized at 5°C and maintained at that temperature for 96 hours, so as tocarry out the polymerization.

[0198] The bottle was cut using a cutter and the solid was separated from the liquid by using a colander. The liquid contained the unreacted monomer. Then the solid was chopped into small pieces (4-6 mm); the solid pieces were dried at room temperature and pressure for 12 hours. The solid contained the polymer.

[0199] EXAMPLE 18 (comparative).

[0200] Example 13 was repeated with the following differences: the bimetallic catalyst of Example 1 was used directly, without the pre-treatment procedure according to Examples 7; the polymerization temperature was set to 5°C and maintained for 96 hours.

[0201] EXAMPLE 19 (comparative).

[0202] Example 13 was repeated with the following differences: 47.9 mg (corresponding to approximately 2 ml) of the untreated monometallic catalyst suspension of Example 6 was used;

[0203] 0.32 g of co-catalyst (triisobutyl aluminum) was used. EXAMPLE 20 (comparative).

[0204] Example 13 was repeated with the following differences: 47.9 mg (corresponding to approximately 2 ml) of the monometallic catalyst suspension of Example 6, treated as in Example 12, was used;

[0205] 0.32 g of co-catalyst (triisobutyl aluminum) was used. EXAMPLE 21.

[0206] Preparation of APAO solutions.The APAOs prepared in Examples 13-20 were dissolved in xylene to produce APAO solutions as follows.

[0207] 0.292 g of APAO and 1000.0 g of commercial xylene were introduced into a Schott bottle. The bottle was closed and shaken by an orbital shaker at 180 rpm, at room temperature for 24 hours. 400.0 g of the obtained APAO solution was transferred into a smaller Schott bottle.

[0208] Preparation of APAO suspensions.

[0209] The APAOs prepared in Examples 13 to 20 were suspended in soybean oil to produce APAO suspensions as follows.

[0210] An ultracentrifugal mill (Retsch, model ZM200) was set up, assembling a 2 mm mesh filter and adjusting the speed of the vibrating conveyor to approximately 2 cm / sec. The rotor-stator assembly and the conveyor were filled with solid carbon dioxide pellets.

[0211] 100 parts of the APAO polymer were cut into small pieces (about 5-10 mm) and placed in a container. Liquid nitrogen was added to cover the APAO pieces. After 15 minutes, the APAO pieces were removed and placed in a polyethylene bag. 40 parts of magnesium stearate powder (anti-sticking agent) were added, to obtain a total of 140 parts ( 100 parts APAO + 40 parts antisticking agent). The bag was shaken to mix the materials and then such materials (kept into the bag) were ground using a pestle in a mortar. This was done quickly to ensure that the APAO was maintained below its glass transition temperature. 100 parts solid carbon dioxide pellets were then introduced into the bag, which was shaken vigorously to mix the various materials.The ultracentrifugal mill was started at a speed of 15, 000 rpm, and the content of the bag was gradually transferred into the mill conveyor. The ground material was collected in a container previously filled with liquid nitrogen for approximately 10 minutes. The 2 mm mesh filter in the mill was replaced with a 0.12 mm mesh filter. The mill was cooled again by filling the conveyor and the rotor-stator assembly with solid carbon dioxide pellets.

[0212] 100 parts of solid carbon dioxide pellets were introduced into a new polyethylene bag, and the ground material was quickly removed from the nitrogen-filled container. The bag was vigorously shaken to distribute the carbon dioxide pellets. The ultracentrifugal mill was started and the material contained in the bag was poured into the mill conveyor to be ground, using the same procedure as indicated above (except for the size of the filter mesh). The ground material was placed into a previously chilled Schott bottle, an aliquot of previously weighed soybean oil was added and mixed vigorously.

[0213] The final composition of the APAO suspension was as follows: APAO: 20.0% wt;

[0214] magnesium stearate: 8.0% wt;

[0215] soybean oil: 72.0% wt.

[0216] Measurement of the drag reduction effect (test loop) The APAOs as prepared above were tested to measure the drag reduction effect (test loop), according to the following procedure.

[0217] The apparatus for measuring the drag reduction effect (testloop ) is shown in Figure 1.

[0218] The apparatus comprised: a test section unit ( 8 ) connected to two steel tubes ( 11, 12 ); two pressure transducers ( 7, 9 ) inserted on said steel tubes ( 11, 12 ), to measure the pressure drop; one Coriolis mass flow meter ( 6 ), to measure mass flow rate; a progressive cavity pump ( 3 ); a drain valve ( 5 ), used to drain the circuit after the test; a vent valve ( 10 ), positioned at the top point of the loop, used after starting the pump, to ensure that no air bubbles were trapped in the circuit; a stirred vessel ( 1 ) having a net volume of about 6. 5 1 and a heat j acket. The fluid to be tested was fed from the vessel ( 1 ) to the pump ( 3 ) by means of the steel pipe ( 2 ) and returns to the vessel ( 1 ) by means of the steel pipe ( 11 ).

[0219] The test section ( 8 ) consisted o f a 30-meter-long tube in perfluoroalkoxy material ( PFA AP-230 ), having outer diameter 9. 982 mm and wall thickness 1. 499 mm, produced / distributed by Swagelok ( Swagelok code PFA-T10M- 1. 5M-30M, lot #02924214- 1 ). The PFA tube was connected both ends to steel tubes ( 11, 12 ), which had outer diameter 10 mm and 1. 5 mm thickness, therefore substantially the same internal diameter of the test section ( 8 ). On said steel tubes ( 11, 12 ) two pressure transducers ( 7, 9 ) were inserted j ust before the beginning and after the end of the test section ( 8 ) to measure the pressure drop of the test section alone. The pressure transducers were Rosemount model 3051 CG 4 ( Gage transducers, - 0. 97 to 20. 68 bar ( g) ). The mass flow rate was measured by means of a Coriolis mass flow meter ( 6 ), which was a Corimass Flow Meter MFC 085 Smart 10G+, nominalrate 10 kg / min. The pump (3) was a progressive cavity pump (Nova Rotors, model DN 05K2, s / n A1607201 ), driven by a reducer (VARMEC RCV 191 NF160 1=4.71 ), frequency converter (Motive, model NEO-WI-FI-3kW NVR) and motor (Motive, model 90S-4, n. 2006DG0309). The mass flow rate, read by flow meter ( 6), was regulated by acting on the frequency set in the frequency converter of the pump, so that a constant flow rate of 2.8 kg / min was ensured. A drain valve (5) was used to drain the circuit after every test. A vent valve ( 10), positioned at the top point of the loop, was used after starting the pump, to ensure that no air bubbles were trapped in the circuit.

[0220] Vessel ( 1 ) was a stirred glass container having a net volume of about 6.5 1 and a heat j acket. A transparent silicone oil heat transfer fluid was used as the fluid for thermal regulation. The j acket temperature was kept equal to ambient temperature (23°C), so that all the system could be considered at the constant temperature of 23°C. The stirrer was an anchor type stirrer, with fixed speed of 50 rpm. The pump suction was connected to the bottom of the vessel ( 1 ) by means of a steel pipe (2 ), while the pump delivery was connected to the flowmeter ( 6) and drain (5) by means of steel pipes (4 ).

[0221] 3500.0 g of n-hexane (Sigma-Aldrich 1.04394 ) were weighed and added into the vessel ( 1 ). Nitrogen was fed by the opening valve ( 13), while keeping the vessel vent open (valve 14 ), the same used to charge the solution) to keep atmospheric pressure inside the vessel. The nitrogen flow rate was low to avoid any stripping action. Said nitrogen flow was used only to reduce theoxygen ( from air) in the vessel. The stirrer was set to 50 rpm. The pump was started, and the pump speed was regulated by means of its frequency converter to set the measured flow rate to 4.3 1 / min (the mass flow meter measures the mass flow but also the density, so it is also possible to compute the volumetric flow rate).

[0222] After 10 minutes, the recording of the pressure of the two pressure transducers was started. The pressure values were recorded every 200 milliseconds, for a total sampling time of 60 seconds.

[0223] The computed pressure drops ("ΔP") was the numeric average of the recorded pressure values at the inlet of the test section, minus the numeric average of the recorded pressure values at the outlet of the test section. Therefore, the computed pressure drop was the one-minute average pressure drop measured between minute 10 and minute 11 after the pump started. Then, the pump was stopped.

[0224] 400 g of xylene containing 117 mg (292 ppm) of the APAO to be tested were added into vessel ( 1 ) by means of the inlet on the valve ( 14 ).

[0225] Then, 100 ml of n-hexane were withdrawn from the purge (valve 5) and added to the Schott bottle that contained the composition (solution or suspension) comprising the APAO. The bottle was shaken to mix / dissolve the residual APAO, then the content of the bottle was fed again to the vessel. This rinsing operation was repeated 3 times, to be sure to add all the APAO was fed to the test apparatus.The pump was started again but this time in reverse pumping (that is, the direction of pumping was reversed). In this way, all the content of the test section was emptied, filling the vessel with the content of the tube.

[0226] The stirrer of the vessel was set to 150 rpm and the solution was kept under stirring for 24 hours.

[0227] After this period of continuous stirring, the pump was started again in normal direction (not reversed) and with flow rate regulated to 4.3 1 / min.

[0228] After 10 minutes, the recorder was started again and the values of the two pressure transducers were recorded for one minute, as done for the solution without APAO. The computed pressure drops ("ΔP treated with APAO") was the 1-min-time average of the pressure at the inlet of the test section minus the 1-min-time average of the pressure at the outlet of the test section.

[0229] The drag reduction power was computed by the following formula:

[0230] ΔP untreated — AP treated with APAO

[0231] DR = - - - * 100

[0232] ΔP untreated

[0233]

[0234] The results are reported in Table 2.TABLE 2

[0235] Ex. Catalyst Monomer Treated Temperature Time DR@10min with Si- [ °C] [hr] [ %] containing

[0236] compound

[0237] 13 Example 1 1-decene YES 5 96 42. 3 14* Example 2* 1-decene YES 5 96 10. 8 15* Example 3* 1-decene YES 5 96 4. 8 16* Example 4* 1-decene YES 5 96 0. 0 17 Example 5 1-decene YES 5 96 21. 9 18* Example 1 1-decene NO* 5 96 15.5 19* Example 6* 1-decene NO* 5 96 6.7 20* Example 6* 1-decene YES 5 96 14. 8

[0238]

[0239] comparative

[0240] TABLE 3

[0241] Ex. Catalyst Monomer Treated Temperature Time DR@ Polymeriza with Si- [ °C] [hr] lOmin tion yield containing [ %] [ %] compound

[0242] Example

[0243] 13 1-decene YES 5 96 42. 3 86.3

[0244] 1

[0245] Example

[0246] 18* 1-decene NO 5 96 15.5 87. 0

[0247] 1

[0248]

[0249] comparative

[0250] The polymerization yield was computed by the following formula:

[0251] Polymeritaizon Yield = mass of solid product (g) / mass of initial monomer (g) * 100(II)The solid product is the solid separated from the liquid by the colander.

[0252] The results are reported in Table 3.

[0253] COMMENTS ON THE RESULTS

[0254] From the results reported in Table 2, it is evident that the Ziegler-Natta bimetallic catalysts (molar ratio Mg / Ti from 0.5 to < 3 and molar ratio (Hf or Zr) / Ti 0. 5-5.0 and treated with a Si-containing compound) used to obtain the catalytic systems according to the present invention allow to obtain APAOs which show a very high drag reduction (DR) value, particularly 42.3% (Example 13), when the second metal is Hf, and 21.9% (Example 17 ), when the second metal is Zr.

[0255] The APAOs obtained using catalytic systems obtained by Ziegler-Natta bimetallic catalysts not according to the invention (i. e. outside the following ranges: molar ratio Mg / Ti from 0.5 to < 3 and molar ratio (Hf or Zr) / Ti 0. 5-5.0) show a much lower DR value, even if they were treated with a Si-containing compound, in particular 0.0% (Example 16), 4.8% (Example 15) and 10.8% (Example 14 ).

[0256] The advantages of the Ziegler-Natta bimetallic catalysts used to obtain the catalytic systems according to the present invention are also highlighted in comparison with the Ti-based Ziegler-Natta monometallic catalyst, which led to the formation of APAOs having a reduced DR value, in particular 6.7% (Example 19) if the catalyst is not treated with Si-containing compound, and 16.7% (Example 20) if the catalyst is treated with Si-containing compound.From the results reported in Table 3, it can also be inferred that by using a Ziegler-Natta bimetallic catalyst inside the claimed compositions (molar ratio Mg / Ti from 0.5 to < 3 and molar ratio (Hf or Zr) / Ti 0. 5-5.0) the DR values increase if the Ziegler-Natta bimetallic catalysts inside the claimed compositions were treated with a Si-containing compound despite the polymerization yields, computed as reported in formula II, were comparable.

Claims

CLAIMS1. A Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) );at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

2. The Ziegler-Natta bimetallic catalyst according to claim 1, which contains: titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and hafnium in the oxidation state +4 (Hf ( IV) ).

3. The Ziegler-Natta bimetallic catalyst according toclaim 1, which contains: titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and zirconium in the oxidation state +4 (Zr ( IV) ).

4. The Ziegler-Natta bimetallic catalyst according to any one of the preceding claims, wherein at least 70% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, of titanium in the bimetallic catalyst is Ti ( III ), the percentage being calculated on the total weight of Ti.

5. The Ziegler-Natta bimetallic catalyst according to any one of the preceding claims, wherein the amount of titanium does not exceed 10% by weight, preferably is from 1. 6% to 10% by weight, with respect to the total weight of the bimetallic catalyst.

6. The Ziegler-Natta bimetallic catalyst according to any one of the preceding claims, which contains at least one carboxylate group deriving from at a carboxylic acid of formula R-COOH, wherein R is a linear or branched hydrocarbon radical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine.

7. The Ziegler-Natta bimetallic catalyst according to claim 6, wherein said at least one carboxylate group is present in an amount so as to have a (carboxylate group) / Ti molar ratio from 0.1 to 0.8, preferably from 0.4 to 0. 6.

8. The Ziegler-Natta bimetallic catalyst according to any one of the preceding claims, wherein the at least one Si-containing compound of formula SiR1p(OR2) <4-P) is selected from: tetraethoxysilane, tetrabutoxysilane, dimethyldimethoxysilane,isobutyl isopropyldimethoxysilane, diisopropyldimethoxysilane, cyclopentyl isobutyldimethoxysilane, dicyclohexyldimethoxysilane, phenyl triethoxysilane, diphenyldimethoxysilane, dicyclohexyldimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, or mixtures thereof.

9. A process for preparing a Ziegler-Natta bimetallic catalyst supported on MgCl2according to any one of the preceding claims, said process comprising:(a) mixing at least one titanium compound, at least one metal compound selected from hafnium (Hf ) compounds and zirconium (Zr) compounds, MgCl2, and at least one carboxylic acid of formula R-COOH, wherein R is a linear or branched hydrocarbon radical having from 2 to 30 carbon atoms, possibly substituted with at least one halogen, e. g. fluorine or chlorine, in a hydrocarbon liquid medium at a temperature from 40°C to 200°C, preferably from 60°C to 130°C, to obtain a catalyst precursor;(b) adding to the catalyst precursor at least one organoaluminum compound of formula AlyClxyR3y-xy, wherein R is an alkyl having from 1 to 10 carbon atoms, x is a number from 1.0 to 2.0 and y is an integer equal to 1 or 2, to obtain the bimetallic catalyst;(c) adding to the bimetallic catalyst obtained in step (b) at least one Si-containing compound of formula SiR1p(OR2)(4-p)wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0.

10. The process for preparing a Ziegler-Natta bimetallic catalyst according to claim 9, wherein, in the at least one carboxylic acid of formula R-COOH, the group R is a linear or branched hydrocarbon radical having from 3 to 16 carbon atoms.

11. The process for preparing a Ziegler-Natta bimetallic catalyst according to claim 10, wherein, in the at least one carboxylic acid of formula R-COOH, R is selected from:linear alkyl groups containing at least 3 carbon atoms, and not more than 16 carbon atoms, for example n-hexyl, n-octyl, n-nonyl, n-decyl or n-undecyl;branched alkyl groups having a linear chain containing from 2 to 10 carbon atoms and a branching chain in the alpha or beta position of the linear chain with respect to the carbon atom of the carboxylic group, said branching chain being selected from: linear Ci-Ce alkyl groups, branched Ci-Ce alkyl groups, phenyl, cyclopentyl, cyclohexyl.

12. The process for preparing a Ziegler-Natta bimetallic catalyst according to any one of claims from 9 to 11, wherein the at least one Si-containing compound of formula SiR1p(OR2)(4-p)is selected from: tetraethoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, isobutyl isopropyldimethoxysilane, diisopropyldimethoxysilane, cyclopentyl isobutyldimethoxysilane,dicyclohexyldimethoxysilane, phenyl triethoxysilane, diphenyldimethoxysilane, dicyclohexyldimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, or mixtures thereof.

13. The process for preparing a Ziegler-Natta bimetallic catalyst according to any one of claims from 9 to 12, wherein during step (c) the at least one Si-containing compound is mixed with the bimetallic catalyst obtained in step (b) at a temperature from -10°C to 120°C, preferably from 20°C to 50°C.

14. The process for preparing a Ziegler-Natta bimetallic catalyst according to any one of claims from 9 to 13, wherein during step (c) the at least one Si-containing compound is mixed with the bimetallic catalyst obtained in step (b) for a time from 1 min to 120 min, preferably from 10 min to 60 min.

15. The process for preparing a Ziegler-Natta bimetallic catalyst according to any one of claims from 9 to 14, wherein the at least one organoaluminum compound of formula AlyClxyR3y-xy is selected from: ethyl aluminum sesquichloride (EASC), ethylaluminum dichloride (EADC), isobutylaluminum dichloride ( IBADIC) and diethylaluminium chloride (DEAC).16 A Ziegler-Natta bimetallic catalyst supported on MgCl2obtainable by the process according to any one of claims from 9 to 15.

17. A catalytic system comprising:(i) a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:titanium in the oxidation state +3 (Ti ( III ) ), andoptionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) ) and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0; (ii) at least one organoaluminum co-catalyst of formula AlRnX(3-n), wherein: the R groups, equal or different from each other, are linear or branched Ci-Ce alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

18. The catalytic system according to claim 17, wherein the Ziegler-Natta bimetallic catalyst supported on MgCl2is defined according to any one of claims from 2 to 8.

19. The catalytic system according to any one of claims from 17 to 18, wherein, in the at least one organoaluminum cocatalyst of formula AlRnX(3-n), the linear or branched Ci-Ce alkylgroups R are selected from: methyl, ethyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl.

20. The catalytic system according to claim 19, wherein the at least one organoaluminum co-catalyst of formula AlRnX(3-n) is a trialkylaluminum compound, preferably selected from: triethylaluminum, tri-n-butylaluminum, triisobutylaluminum and trihexyl aluminum.

21. The catalytic system according to any one of claims from 17 to 20 wherein aluminum and titanium are present in a molar ratio from 3: 1 to 500: 1, more preferably from 5: 1 to 100: 1, even more preferably from 10: 1 to 40: 1.22 A catalytic system comprising:(i) a Ziegler-Natta bimetallic catalyst supported on MgCl2according to claim 16;(ii) at least one organoaluminum co-catalyst of formula AlRnX(3-n), wherein: the R groups, equal or different from each other, are linear or branched Ci-Ce alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

23. A process for polymerizing at least one linear a-olefin, said process being carried out at a temperature from -10°C to 20°C, more preferably from -5°C to 15°C, by using a catalytic system comprising:(i) a Ziegler-Natta bimetallic catalyst supported on MgCl2, which contains:titanium in the oxidation state +3 (Ti ( III ) ), and optionally titanium in the oxidation state +4 (Ti ( IV) ); and at least one metal selected from hafnium in the oxidation state +4 (Hf ( IV) )and zirconium in the oxidation state +4 (Zr ( IV) ); wherein: the Mg / Ti molar ratio is from 0.5 to less than 3.0, preferably from 0.5 to 2.7, more preferably from 1.0 to 2.5; and the (Hf and / or Zr) / Ti molar ratio is from 0.5 to 5.0, preferably from 1.0 to 4.0, more preferably from 1.5 to 3.5;said Ziegler-Natta bimetallic catalyst supported on MgCl2being treated with at least one Si-containing compound of formula SiR1p(OR2) (4-p) wherein: p is zero or an integer from 1 to 3; the R1groups are independently selected from: hydrogen, halogen (preferably chlorine), C1-C10linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; the R2groups are independently selected from: C1-C10 linear or branched alkyl groups, C5-C6 cycloalkyl groups, C6-C10aryl groups; wherein the amount of the at least one Si-containing compound is such as to obtain a Si / Ti molar ratio from 0.2 to 2.0;(ii) at least one organoaluminum co-catalyst of formula AlRnX(3-n), wherein: the R groups, equal or different from each other, are linear or branched Ci-Ce alkyl groups; X is halogen, preferably chlorine; n is 1, 2 or 3.

24. The process for polymerizing at least one linear a-olefin according to claim 23, wherein the linear a-olefin monomer has formula CH2=CH-R, wherein R is H or a linear C1-C12, preferably linear C2-C10, alkyl group.

25. The process for polymerizing at least one linear a-olefin according to claim 24, wherein the at least one linear a-olefin monomer is selected from: 1-hexene, 1-octene, 1-decene and 1-dodecene, or mixtures thereof.

26. The process for polymerizing at least one linear a-olefin according to any one of claims from 23 to 25, wherein said process is a mass polymerization process.

27. The process for polymerizing at least one linear a-olefin according to claim 26, wherein said process is a mass polymerization carried out in an inert atmosphere, preferably in a nitrogen atmosphere having an oxygen content not higher than 1 ppm (by weight).

28. The process for polymerizing at least one linear a-olefin according to any one of claims from 23 to 27, wherein the catalytic system is used in an amount so as to obtain a titanium concentration from 100 mmol / 1 to 200 mmol / 1, equal to approximately 4.5-9 g / 1.

29. The process for polymerizing at least one linear a-olefin according to any one of claims from 23 to 28, wherein said process is carried out for a reaction time from 24 to 360 hours, preferably from 48 to 200 hours, more preferably from 72 to 120 hours.

30. The process for polymerizing at least one linear a-olefin according to any one of claims from 23 to 29, wherein the catalytic system is defined according to any one of claims from 17 to 22.

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