Ethylene copolymer and use thereof in polyolefin compositions

Abstract

1. The present disclosure relates to a ethylene copolymer for use as additive, in particular as impact modifier, for polyolefin compositions, having the following features: 1) a 1-butene content C4cont from 15% to 45% by weight; 2) density from 0.840 to 0.910 g / cm3; 3) Melt Flow Rate E from 0.1 to 15 g / 10 min; 4) product r1ꞏr2 of the reactivity ratios obtained from 13C NMR triad distribution, from 0.55 to 0.95, where r1 is the reactivity ratio of ethylene to 1-butene and r2 is the reactivity ratio of 1-butene to ethylene.

Description

ETHYLENE COPOLYMER AND USE THEREOF IN POLYOLEFIN COMPOSITIONSFIELD OF THE INVENTION

[0001] The present disclosure relates to an ethylene copolymer and to its use as additive, in particular as impact modifier, for polyolefin compositions.BACKGROUND OF THE INVENTION

[0002] Impact modifiers, consisting of or comprising a prevailingly amorphous olefin copolymer, are often added in polyolefin compositions to enhance the impact resistance.

[0003] As explained for instance in W02015 / 180919, it would be also desirable to modify other valuable properties of polyolefin compositions, including mechanical and thermal properties, while enhancing impact resistance.

[0004] In answer to such need, a new ethylene copolymer is provided, which allows to obtain polyolefin compositions having an unusually favorable balance of tensile properties, flexural modulus, thermal properties (heat deflection temperature and glass transition temperature) and reduced shrinkage on cooling, while maintaining a good impact resistance.SUMMARY OF THE INVENTION

[0005] Thus the present disclosure provides an ethylene copolymer having the following features:1) a 1 -butene content C4cont from 15% to 45% by weight, preferably from 20% to 40% by weight, with respect to the weight of the ethylene copolymer;2) density from 0.840 to 0.910 g / cm3, preferably from 0.850 to 0.890 g / cm3, determined according to ISO 1183-1 :2012 at 23°C;3) Melt Flow Rate E from 0.1 to 15 g / 10 min., preferably from 0.3 to 12 g / 10 min.;4) product rl r2 of the reactivity ratios obtained from13C NMR triad distribution, from 0.55 to 0.95 or from 0.55 to 0.92, preferably from 0.6 to 0.95 or from 0.6 to 0.92, more preferably from 0.55 to 0.89 or from 0.6 to 0.92, where rl is the reactivity ratio of ethylene to 1 -butene and r2 is the reactivity ratio of 1 -butene to ethylene.DETAILED DESCRIPTION OF THE INVENTION

[0006] In general, the term “copolymer” is meant to include also polymers containing more than one kind of comonomers, such as terpolymers.

[0007] The additional comonomers are preferably selected from propylene and olefins having formula CH2=CHR wherein R is an alkyl radical, linear or branched, having from 3 to 10 carbon atoms.

[0008] Specific examples of said olefins, other than propylene, are pentene- 1, 4- methylpentene-1, hexene- 1, octene- 1 and decene- 1.

[0009] Moreover, the present ethylene copolymer can have at least one of the following additional features:- elongation at break equal to or greater than 920%, preferably equal to or higher than 950%, the upper limit being preferably of 1800%, more preferably of 1600% in all cases;- melting temperature Tm from 15 °C to 55 °C, preferably from 20 °C to 50 °C, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute;- a ratio C4cont / AHm from 0.1 to 2.5, preferably from 0.2 to 2.0;- melting enthalpy AHm equal to or lower than 60 J / g, preferably equal to or lower than 55 J / g, in particular from 5 to 60 J / g, or from 10 to 55 J / g, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute;- crystallization temperature Tc equal to or higher than 8 °C, preferably equal to or higher than 10 °C, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute, the preferred upper limit being of 55°C, more preferably of 50 °C;- glass transition temperature (Tg), measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute, from -35 to -60°C;- Shore A from 20 to 75;- an amount of total fraction XSTOT soluble in xylene at 25°C, with respect to the total weight of the ethylene copolymer, of 90 - 100% by weight, preferably of 95 - 100% by weight;- an intrinsic viscosity [q], measured in tetrahydronaphthalene at 135 °C, of 0.8 dl / g or more, in particular from 0.8 to 2.9 dl / g, more preferably from 0.9 to 2.0.

[0010] Preferably, the present ethylene copolymer may have at least one of the following properties:- a 1 -butene content C4cont from 24% to 45% by weight, preferably from 26% to 40% by weight, with respect to the weight of the ethylene copolymer;- Melt Flow Rate E from 0.8 to 15 g / 10 min., preferably from 1.0 to 12 g / 10 min.;- product rl r2 from 0.75 to 0.95, preferably from 0.77 to 0.92;- amount of BBB triads of at least 0.1%, preferably of at least 0.3%, the preferred upper limit being in all cases of 2.5%, in particular of 2%.

[0011] The above reported preferred Melt Flow Rate E values allow an easier processing of the ethylene copolymer in the molten state.

[0012] Preferably, the present ethylene copolymer may have a molecular weight distribution (Mw / Mn) lower than 4, preferably lower than 3; more preferably lower than 2.5, the lower limit being of 1.5 in all cases.

[0013] Optionally, the present ethylene copolymer may have at least one of the further following additional features:- strength at break from 1 to 15 MPa;- stress at 100% elongation from 0.5 to 5 MPa;- stress at 300% elongation from 0.5 to 5 MPa;- tension set at 100% elongation, 23 °C from 4% to 15%;- compression set at 25%, 23 °C from 15% to 45%.

[0014] The present ethylene copolymer can be obtained by polymerizing the monomers in the presence of a metallocene catalyst system obtainable by contacting:- a stereorigid metallocene compound;- an alumoxane or a compound capable of forming an alkyl metallocene cation; and, optionally,- an organo aluminum compound.

[0015] Preferably the stereorigid metallocene compound belongs to the following formula (I):wherein:M is an atom of a transition metal selected from those belonging to group 4; preferably M is zirconium;X, equal to or different from each other, is a hydrogen atom, a halogen atom, a R, OR, OR’O, OSO2CF3, OCOR, SR, NR2 or PR2 group wherein R is a linear or branched, saturated or unsaturated Ci-C2o-alkyl, C3-C2o-cycloalkyl, Ce-C20-aryl, C?-C2o-alkylaryl or C?-C2o-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R’ is a Ci-C2o-alkylidene, Ce-C2o-arylidene, C7-C2o-alkylarylidene, or C7-C2o-arylalkylidene radical; preferably X is a hydrogen atom, a halogen atom, a OR’O or R group; more preferably X is chlorine or a methyl radical;R1, R2, R5, R6, R7, R8and R9, equal to or different from each other, are hydrogen atoms, or linear or branched, saturated or unsaturated Ci-C2o-alkyl, C3-C2o-cycloalkyl, Ce-C20-aryl, C?-C2o-alkylaryl or C?-C2o-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R5and R6, and / or R8and R9can optionally form a saturated or unsaturated, 5 or 6 membered rings, said ring can bear C1-C20 alkyl radicals as substituents; with the proviso that at least one of R6or R7is a linear or branched, saturated or unsaturated Ci-C2o-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably a Ci-Cio-alkyl radical;R3and R4, equal to or different from each other, are linear or branched, saturated or unsaturated Ci-C2o-alkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R3and R4equal to or different from each other are Ci-Cio-alkyl radicals; more preferably R3is a methyl, or ethyl radical; and R4is a methyl, ethyl or isopropyl radical.

[0016] Preferably the compounds of formula (I) have formula (la):(la) wherein:M, X, R1, R2, R5, R6, R8and R9have been described above;R3is a linear or branched, saturated or unsaturated Ci-C2o-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R3is a Ci-Cio-alkyl radical; more preferably R3is a methyl, or ethyl radical.

[0017] Specific examples of metallocene compounds are dimethylsilyl{(2,4,7-trimethyl-l- indenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)} zirconium dichloride; dimethylsilanediyl{(l-(2,4,7-trimethylindenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]- dithiophene)}Zirconium dichloride and dimethylsilanediyl{(l-(2,4,7-trimethylindenyl)-7-(2,5- dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)}zirconium dimethyl.

[0018] Examples of alumoxanes are methylalumoxane (MAO), tetra-(isobutyl)alum oxane (TIBAO), tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO), tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) and tetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

[0019] Examples of compounds able to form an alkyl metallocene cation are compounds of formula D+E', wherein D+is a Bronsted acid, able to donate a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E’ is a compatible anion, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be able to be removed by an olefinic monomer. Preferably, the anion E' comprises of one or more boron atoms.

[0020] Examples organo aluminum compound are trimethylaluminum (IMA), triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA), tris(2,3- dimethylbutyl)aluminium (TDMBA) and tris(2,3,3-trimethylbutyl)aluminum (TTMBA).

[0021] Preferred Al / metallocene molar ratios are from 500 to 10000.

[0022] Hence the present ethylene copolymer can be prepared operating under known polymerization conditions in the presence of the above described catalysts.

[0023] One of the methods for preparing the present ethylene copolymer is the solution polymerization, which comprises polymerizing ethylene and 1 -butene, and possibly additional comonomers, in a liquid reaction medium capable to maintain the nascent polymer in solution.

[0024] The term solution polymerization means that the polymer is fully soluble in the polymerization medium at the polymerization temperature used.

[0025] The temperature range useful for the solution polymerization is preferably from 60° C to 200° C, more preferably from 80° C to 150° C, most preferably from 89° C to 140° C.

[0026] In selecting the optimal polymerization temperature, it is to be considered that by increasing the temperature, the polymer solubility is increased, but the catalyst decay rate is increased.

[0027] Hydrogen can be efficiently used to regulate the molecular weight of the obtained polymers. Preferably the concentration of hydrogen in the liquid phase with respect to the ethylene concentration (H2 / C2 mol ppm) ranges from 1 ppm to 20000 ppm, more preferably from 2 ppm to 18000 ppm.

[0028] One or more reactors in series or in parallel can be used.

[0029] The catalyst can be added in the first reactor only, or in more than one reactor.

[0030] The amount of comonomer(s), in particular 1 -butene, in the liquid phase, can be from 0.1% to 40% by weight, in particular from 15% to 36% by weight, with respect to the total weigh of liquid solution (monomers and liquid reaction medium) present in the concerned polymerization reactor.

[0031] The polymerization pressure is preferably from 20 to 45 barg.

[0032] Usually, the amount of polymer dissolved in the reaction medium ranges from 10 to 40% wt / vol preferably from 12 to 35% wt / vol. The amount of polymer dissolved in the liquid reaction medium is generally a compromise between the target of maximum productivity of the polymerization and the operability of the reactor, which becomes troublesome when the polymer concentration is too high.

[0033] In the latter case in fact, the viscosity of the solution does not permit an efficient stirring and the heat removal is problematic. Variations of the polymer solubility may also derive from production of polymer with different molecular weight (polymers with higher molecular weight are generally less soluble) and different chemical composition (by varying the 1 -butene content also variation in polymer solubility may be observed).

[0034] For all these reasons it is important to have an inert reaction medium that ensures the polymer solubility over an as wide as possible range of operative conditions (polymer concentration, polymer molecular weight and polymer composition).

[0035] Hence the liquid reaction medium preferably comprises a liquid hydrocarbon having a boiling point at atmospheric pressure higher than 60°C and more preferably higher than 70°C, such as toluene, cyclohexane, isododecane etc.

[0036] It has been observed that for the preparation of the present ethylene copolymer, cyclohexane is the preferred reaction medium, because it allows a great flexibility of the process conditions while maintaining the nascent polymer in solution.

[0037] The present ethylene copolymer can also contain additives commonly employed in the art, such as antioxidants, light stabilizers, heat stabilizers, colorants and fillers.

[0038] As previously said, the present ethylene copolymer can be advantageously compounded with additional polyolefins, in particular propylene polymers such as propylenehomopolymers, random copolymers, and thermoplastic elastomeric polyolefin compositions. Accordingly, the present disclosure also relates to a polyolefin composition containing the present ethylene copolymer. Preferably, the said polyolefin composition comprises at least 50% by weight, typically from 50% to 95% by weight, of one or more additional polyolefins, thus 50% or less, typically from 5% to 50% by weight, of the present ethylene copolymer, all per cent amounts being referred to the total weight of the ethylene copolymer and of the additional polyolefin or polyolefins.

[0039] Practical examples of the said additional polyolefins are the following polymers:1) crystalline propylene homopolymers, in particular isotactic or mainly isotactic homopolymers;2) crystalline propylene copolymers with ethylene and / or a C4-C10 a-olefin (a-olefin containing from 4 to 10 carbon atoms), wherein the total comonomer content ranges from 0.05 to 20% by weight with respect to the weight of the copolymer, and wherein preferred C4-C10 a-olefins are 1 -butene; 1 -hexene; 4-methyl-l -pentene and 1 -octene;3) crystalline ethylene homopolymers and copolymers with propylene and / or a C4-C10 a- olefin, such as HDPE;4) thermoplastic elastomeric compositions comprising one or more of propylene homopolymers and / or the copolymers of item 2) and an elastomeric moiety comprising one or more copolymers of ethylene with propylene and / or C4-C10 a-olefins, optionally containing minor quantities of a diene, such as butadiene, 1,4-hexadiene, 1,5-hexadiene and ethylidene-1 -norbornene, wherein the diene content is typically from 1 to 10% by weight, typically prepared according to known methods by mixing the components in the molten state or by sequential polymerization, and generally containing the said elastomeric moiety in quantities from 5 to 80% by weight.

[0040] The polyolefin composition may be manufactured by mixing the ethylene copolymer and the additional polyolefin(s) together, extruding the mixture, and pelletizing the resulting composition using known techniques and apparatus.

[0041] The polyolefin composition may also contain conventional additives such as mineral fillers, colorants, antioxidants, light stabilizers and heat stabilizers. Mineral fillers that can be included in the composition include talc, CaCCh, silica, wollastonite (CaSiCh), clays, diatomaceaous earth, titanium oxide and zeolites. Typically the mineral filler is in particle form having an average diameter ranging from 0.1 to 10 micrometers.

[0042] The present disclosure also provides final articles, in particular injection moulded articles, such as finished parts for the automotive industry, made of or comprising the said polyolefin composition.EXAMPLES

[0043] Various embodiments, compositions and methods as provided herein are disclosed below in the following examples. These examples are illustrative only, and are not intended to limit the scope of the invention.

[0044] The following analytical methods are used to characterize the polymer compositions.

[0045] 1-butene content

[0046] 13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 160.91 MHz in the Fourier transform mode at 120 °C.

[0047] The peak of the S55 carbon (nomenclature according to “Monomer Sequence Distribution in Ethyl ene-Propylene Rubber Measured by13C NMR. 3. Use of Reaction Probability Mode ” C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as an internal reference at 29.9 ppm. The samples were dissolved in 1, 1,2,2-tetrachloroethane- d2 at 120 °C with a 8 % wt / v concentration. Each spectrum was acquired with a 90° pulse, and 15 seconds of delay between pulses and CPD to removeJH-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0048] The assignments of the spectra were made according to J.C. Randal, Macromol. Chem Phys., C29, 201 (1989).

[0049] The evaluation of triad distribution and the composition were made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylenepropylene copolymers prepared with 5-titanium trichloride- diethyl-aluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) modified to consider overlaps of signals in the spectra, .using the following equations:BBB = 100 Tpp / S BBE = 100 Tpb / S EBE = 100 2B2 (EBE) / S BEB = 100 Spp / S BEE= 100 Sab / S EEE = 100 (0.25 Syb+0.5 Sbb) / S S = TPP + TP5 + 2B2 (EBE) + Spp + Sab + 0.25 Syb + 0.5 Sbb

[0050] The molar percentage of 1-butene content was evaluated using the following equation: B% mol = [EBE+BBE+BBB] E% mol = 100 - B% mol

[0051] The weight percentage of 1 -butene content was evaluated using the following equation:B (% mol) * 100 * MW BB (wt%) = -[B (% mol) * MW B] +[(100-B (% mol)) * MW E]

[0052] where B (% mol) is the molar percentage of 1 -butene content, while MW E and MW B are the molecular weights of ethylene and 1 -butene, respectively.

[0053] Density

[0054] Determined according to ISO 1183-1 :2012 at 23°C, immersion method.

[0055] Melt Flow Rate and Melt Volume-flow Rate

[0056] Determined according to ISO 1133-1 2012-03 with the specified temperature and load.

[0057] Intrinsic viscosity

[0058] The sample was dissolved in tetrahydronaphthalene at 135 °C and then was poured into the capillary viscometer. The viscometer tube (Ubbelohde type) was surrounded by a cylindrical glass jacket; this setup allows temperature control with a circulating thermostated liquid. The downward passage of the meniscus was timed by a photoelectric device.

[0059] The passage of the meniscus in front of the upper lamp starts the counter which has a quartz crystal oscillator. The meniscus stops the counter as it passes the lower lamp and the efflux time is registered: this is converted into a value of intrinsic viscosity through Huggins' equation (Huggins, M.L., / Am. Chem. Soc., 1942, 64, 2716) provided that the flow time of the pure solvent is known at the same experimental conditions (same viscometer and same temperature). One single polymer solution is used to determine the intrinsic viscosity.

[0060] Melting temperature Tm, melting enthalpy AHm, crystallization temperature Tc and glass transition temperature Tg

[0061] Determined by differential scanning calorimetry (DSC) according to ISO 11357- 3 :2018 for Tm, AHm and Tc, according to ISO 11357-2:2020 for Tg.

[0062] A sample weighting 13 ± 1 mg was heated to 200 ± 1 °C at a rate of 10 °C / min and kept at 200 ± 1 °C for 5 minutes in nitrogen stream and was thereafter cooled at a rate of 20° C / min to -90 ± 2 °C, thereby kept at this temperature for 5 min. Then, the sample was again melted at a temperature rise rate of 10 °C / min up to 200 °C ± 1. The melting scan was recorded, a thermogram was obtained, and, from this, temperatures corresponding to peaks were read. The temperature corresponding to the most intense melting peak recorded during the second fusion was taken as the melting temperature. The melting enthalpy AHmwas measured on said most intense melting peak. Obviously, if only one peak is detected, both melting temperature and AHmare provided by (i.e. measured on) such peak. To determine melting enthalpy AHm, construct the base-line by connecting the two closest points at which the melting endotherm peak deviate from the baseline. The melting enthalpy (AHm) is then calculated by integrating the area between DSC heat flow recorded signal and constructed baseline.

[0063] The glass transition temperature Tg was calculated from the second melting run. When a polymer is heated to its glass transition temperature, the heat capacity of the material shows a step increase and the thermogram of heat flow vs temperature exhibits an inflection point. The temperature at which the inflection occurs is defined as the glass transition temperature.

[0064] The crystallization temperature Tc was calculated from the cooling run. While cooling, the polymer crystallizes exhibiting an exothermic peak. The crystallization temperature Tc corresponds to the peak of the exothermic event.

[0065] Glass transition temperature Tg determination via DMTA (Dynamic Mechanical Thermal Analysis)

[0066] Molded specimen of 20 mm x 5 mm x 1 mm were fixed to the DMTA machine for tensile stress. The frequency of the sinusoidal oscillation was fixed at 1 Hz. The DMTA translate the elastic response of the specimen starting from -100°C (glassy state) to 130°C (softening point). In this way it is possible to plot the elastic response versus temperature. The elastic modulus in DMTA for a viscoelastic material is defined as the ratio between stress and strain also defined as complex modulus E*=E’+iE”. The DMTA can split the two components E’ and E” by their resonance and it is possible to plot E’ (elastic component), E” (loss modulus) and E” / E’ = tan 5 (damping factor) vs temperature. The glass transition temperature Tg is assumed to be the temperature at the maximum of the curve tan = (5) E” / E’ vs temperature.

[0067] Determination of the product of the reactivity ratios rlxr2

[0068] The product of reactivity ratios were obtained from13C NMR triad distribution according to C.J. Carman, R.A. Harrington and C.E. Wilkes, Macromolecules, 10, 536 (1977) using the following expression:

[0069] wherein B indicates a 1 -butene unit and E indicates an ethylene unit.

[0070] The same NMR apparatus and measurement conditions as for the comonomer content determination were used.

[0071] Flexural modulus*: ISO 178:2019

[0072] Tensile modulus*: ISO 527 / 1+2:2019

[0073] Tensile stress at yield and at break*: ISO 527:2019.

[0074] Elongation at break and at yield*: ISO 527:2019.

[0075] Stress @ 100% elongation and @ 300% elongation*: ISO 527:2019.

[0076] Charpy impact test*: ISO 179 / leA:2023 (notched) or ISO 179 / leU:2023 (unnotched).

[0077] The Charpy values were measured at 23 °C, -20 °C and -30 °C.

[0078] Note: * Test specimens for the tests reported in following Tables 2 and 3 were prepared via compression moulding under the following conditions.

[0079] Machine platens were set to 180 °C. An aluminum foil was put on a steel plate and a 150x150 mm template was located on it. 100 g of polymer pellets were used to fill the cavity of the template. Another aluminum foil and steel plate were used to complete the sandwich-structure. The sandwich was introduced in the compression moulding machine on the hot platen. The platens were closed, without applying any pressure, and the sample was heated for 5 min. Then, the pressure of 50 bar was applied on the sample for 5 min, maintaining the temperature of the heating platens to 180 + / - 1 °C. At the end of the heating treatment, the platens were cooled at 15 °C / min and the sandwich was extracted when the platens temperature was lower than 30 °C. The polymer plaque was so obtained, and suitable test specimens were machined from this one.

[0080] Test specimens for the tests reported in following Tables 5, 7 and 9 were prepared from injection molded multipurpose bars with special geometry moulded at 23 °C in line with EN ISO 20753:2018 Type Al.

[0081] Shore A: ISO 868:2003.

[0082] 23 °C Tension set

[0083] Tension set: specimens with dimensions 50x2x2 mm were tested at 23 + / - 1 °C. The specimens were elongated on a brass bow with elongation 200 % and kept in this position for 10 min. Then, the specimens were removed and kept at rest for additional 10 min. Finally, the length of the specimens was measured again.

[0084] Tension set was then calculated as: Tension set % = [(L- L0) / L0] * 100, where L0 = original length of the specimen and L = final length of the specimen after the described procedure.

[0085] 23 °C Compression set (@25%)

[0086] Round specimens with 28.67 mm diameter and 12.7 mm thick are required. The specimens were squashed between two flanges, which had a diameter of 130 mm, a thickness of 14 mm and a hole interaxis of 100 mm.

[0087] The flanges were used to apply a 400 lbs force on the specimens, corresponding to a 28 mm spring squashing. Firstly, the specimens were squashed for a 25 % of their original thickness between the two flanges.

[0088] The so obtained apparatus was kept at 23 °C for 22 hours. At the end, the specimens were removed, kept at rest for 30 min and finally the thickness was measured again.

[0089] The compression set was calculated as: compression set (%) = [(t0-tl) / (t0-t2)]*100, where tO = original thickness, tl = final measured thickness and t2 = the thickness of the specimen after the 25 % compression (75 % of the original thickness).

[0090] Molecular Weight Distribution Determination

[0091] The determination of the means Mw, Mn and Mz and of Mw / Mn derived therefrom was carried out by high-temperature gel permeation chromatography using a method described in ISO 16014-1, -2, -4, issue of 2003. The specifics according to the mentioned ISO standards are as follows: Solvent 1, 2, 4-tri chlorobenzene (TCB), temperature of apparatus and solutions 145°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 pre-column SHODEX UT-G and separation columns SHODEX UT 806 M (3x) and SHODEX UT 807 (Showa Denko Europe GmbH, Konrad-Zuse-Platz 4, 81829 Muenchen, Germany) connected in series was used.

[0092] The solvent was vacuum distilled under Nitrogen and was stabilized with 0.025% by weight of 2,6-di-tert-butyl-4-methylphenol. The flowrate used was 1 ml / min, the injection was 500pl 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 Agilent Technologies, Herrenberger Str. 130, 71034 Boeblingen, Germany) in the range from 580g / mol up to 11600000g / mol and additionally with Hexadecane.

[0093] 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: kps= 0.000121 dl / g, aps=0.706 and for PE kpr= 0.000406 dl / g, CU>E=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, HauptstraBe 36, D-55437 Ober-Hilbersheim, Germany) respectively.

[0094] Xylene soluble fraction

[0095] 2.5 g of polymer and 250 cm3of o-xylene were introduced in a glass flask equipped with a refrigerator and a magnetical stirrer. The temperature was raised in 30 minutes from roomtemperature up to the boiling point of the solvent (135°C). The so obtained clear solution was then kept under reflux and stirring for further 30 minutes. The closed flask was then kept in a thermostatic water bath at 25 °C for 30 minutes as well so that the crystallization of the insoluble (XI) part of the sample could take place. The so formed solid was filtered on quick filtering paper. 100 cm3of the filtered liquid was poured in a previously weighed aluminum container which was heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container was then kept in an oven at 80 °C under vacuum to dryness and then weighed after constant weight is obtained.

[0096] Thus one calculates the percent by weight of polymer soluble and insoluble in xylene at 25 °C.

[0097] Heat deflection Temperature HdT B

[0098] Measured according to ISO 75:2020.

[0099] Longitudinal and Transversal Thermal Shrinkage

[0100] A plaque of 100x195x2.5 mm is moulded in an injection moulding machine “KM-160” (where 160 stands for 160 tons of clamping force).

[0101] The injection conditions are:- Melt temperature = 220 °C;- Mold temperature = 35 °C;- Injection speed = 33 mm / sec;- Max pressure of injection = 100 bar;- Interior mould pressure which drives the change to 2ndor holding pressure = 150 bar;2ndholding pressure = 42 bar;2ndholding pressure time = 30 sec;Cool down time = 30 seconds;Screw diameter 45 mm.

[0102] The plaque is measured 48 hours after moulding, kept at 23 ± 2 °C and humidity 50% ±10%, through callipers, and the shrinkage is given by:Longitudinal shrinkage = ((195 - read_value) / 195) x 100 Transversal shrinkage = ((100 - read_value) / 100) x 100

[0103] where 195 is the length (in mm) of the plaque along the flow direction, measured immediately after moulding (mold); 100 is the length (in mm) of the plaque crosswise the flow direction, measured immediately after moulding (mold); and the read value is the plaque length in the relevant direction after 48 hours.

[0104] Examples 1 - 8 and Comparison Examples 1 - 3

[0105] Preparation of the metallocene catalyst (A-l)

[0106] Dimethylsilyl {(2,4, 7-trimethyl-l-indenyl)-7-(2,5-dimethyl-cy cl openta[l,2-b:4, 3-b’]- dithiophene)} zirconium dichloride (A-l) was prepared according to Example 32 of WO0147939.

[0107] Preparation of the catalytic solution

[0108] Under nitrogen atmosphere, 8.1 L of a solution of 4.5 %wt / v of TIBA in cyclohexane (1.84 mol of TIBA) and 760 mL of a solution 30 %wt / wt ofMAO in toluene (3.65 moles ofMAO) were loaded in a 20 L jacketed glass reactor equipped with an anchor stirrer and allowed to react at room temperature for about 1 hour under stirring.

[0109] After this time, the metallocene A-l (1.6 g, 2.75 mmol) was added and dissolved under stirring for about 30 minutes.

[0110] The final solution was discharged from the reactor into a cylinder through a filter to remove solid residues (if any).[oni] The composition of the solution is as follows:

[0112] Polymerization

[0113] The polymerization was carried out continuously in a pilot plant comprising a stirred reactor in which cyclohexane constituted the liquid medium.

[0114] The polymerization conditions are reported in Table 1.

[0115] The polymer properties are reported in Table 2.Table 1Table 1 cont.Notes: Ex. = Example; Me = metallocene catalyst (A-l); H2 = hydrogen; C2 = ethylene; C4 = 1- butene.Table 2Table 2 cont.Notes:13C NMRE = molar amount of ethylene,13C NMRB = molar amount of buene-1;13C NMR E,13C NMR B,13C NMR BBB,13C NMR BBE,13C NMR EBE,13C NMR BEB,13C NMR BEE13C NMR EEE and13C NMR rlr2 values in the tables are rounded.

[0116] The polymer particles exiting the polymerization reactor, which constitute the ethylene copolymer according to the present disclosure, were then blended by extrusion with the following additional polyoelfins, fillers, colors, pigments and additives.

[0117] Moplen ® EP300N: heterophasic propylene copolymer having Melt Flow Rate 230 °C / 2.16 kg of 15 g / 10 min. and density of 0.89 g / cm3, sold by LyondellBasell Industries;

[0118] Moplen ® EP500V: propylene copolymer having Melt Flow Rate 230 °C / 2.16 kg of 100 g / 10 min. and density of 0.90 g / cm3, sold by LyondellBasell Industries;

[0119] Black masterbatch HX 1600 / 4: polypropylene-based masterbatch, containing 40 wt.% of carbon black;

[0120] Moplen ® HF501N: propylene homopolymer having Melt Flow Rate 230 °C / 2.16 kg of 10 g / 10 min. and density of 0.90 g / cm3, sold by LyondellBasell Industries;

[0121] Moplen ® EP540N: nucleated heterophasic propylene copolymer having Melt Flow Rate 230 °C / 2.16 kg of 12 g / 10 min. and density of 0.9 g / cm3, sold by LyondellBasell Industries;

[0122] Metocene ® MF650Y: metallocene-produced propylene homopolymer having Melt Flow Rate 230 °C / 2.16 kg of 1800 g / 10 min. and density of 0.90 g / cm3, sold by LyondellBasell Industries;

[0123] Hostalen ® GC 7260: high density polyethylene copolymer having Melt Flow Rate 190 °C / 2.16 kg of 8.0 g / 10 min. and density of 0.960 g / cm3, sold by LyondellBasell Industries;

[0124] Adstif ® EA600P: propylene impact copolymer having Melt Flow Rate 230 °C / 2.16 kg of 18 g / 10 min. and density of 0.90 g / cm3, sold by LyondellBasell Industries;

[0125] Moplen ® EP300U: heterophasic propylene copolymer having Melt Flow Rate 230 °C / 2.16 kg of 70 g / 10 min. and density of 0.89 g / cm3, sold by LyondellBasell Industries;

[0126] Talc Imerys Steamic ® T1 CA: finely ground talc having median diameter - D50 of 6.0 pm, measured by laser diffraction (ISO 13320-1), sold by Imeris;

[0127] Talc Luzenac Jetfine ® 3CA: ultrafine talc, sold by Luzenac;

[0128] Irgafos 168 ®: tris(2,4-di-tert.-butylphenyl)phosphite;

[0129] Irganox 1010®: 2,2-bis[3-[,5-bis(l,l-dimethylethyl)-4-hydroxyphenyl)-l- oxopropoxy]methyl]-l,3-propanediyl-3,5-bis(l,l-dimethylethyl)-4-hydroxybenzene-propanoate;

[0130] Chimassorb® 944 FDL: Poly[[6-[(l,l,3,3-tetramethylbutyl) amino] -1,3,5-triazine- 2,4-diyl] [(2, 2, 6, 6- tetramethyl-4-piperidinyl) imino] -l,6-hexanediyl[(2,2,6,6-tetramethyl-4- piperidinyl) imino]]) (HALS), sold by BASF;

[0131] Palmarole MI.NA 08: nucleating agent, based on 1,3:2,4-Bis(3,4- dimethylobenzylideno) sorbitol, sold by Palmarole;

[0132] Dimodan® HP PEL-1 : distilled monoglyceride based antistatic agent, sold by DuPont;

[0133] BK PI Black Pearls 5840: carbon black, having a iodine number (ASTM D-1510) of 205 mg / g and density (ASTM D-1513) of 430 kg / m3, sold by Cabot.

[0134] NaBz: sodium benzoate;

[0135] Erucamide.

[0136] For comparison purpose, the ethylene / 1 -butene copolymers Engage ® 7447 and Engage ® 7467, sold by Dow Chemical, have been used in place of the ethylene copolymer according to the present disclosure. Their properties are reported in Table 3 below.Table 3

[0137] The extrusion was carried using a twin screw extruder, model Wemer&Pfleiderer ZSK40SC.

[0138] This line had a screw with a diameter (Z>) of 40 mm and a process length of approximately 48 LZD that was provided with gravimetric feeders.

[0139] A strand die plate with cooling bath and strand cutter (Scheer SGS100) was used to form pellets; vacuum degassing (barrel No. 9) was also applied to extract fumes and decomposition products.

[0140] Running conditions:Screw speed: 300 rpm;Capacity: 40-50 kg / h;Barrel Temperature: 200-240 °C.

[0141] The components used and their relative amounts are reported in Tables 4, 6 and 8. The relative amounts are expressed in weight percent with respect to the total composition, which amounts to 100%.

[0142] The properties of the so obtained compositions are reported in Tables 5, 7 and 9.Table 4Table 5Table 6Table 7Table 8Table 9

Claims

CLAIMSWhat is claimed is:

1. An ethylene copolymer having the following features:1) a 1 -butene content C4cont, measured with13C NMR, from 15% to 45% by weight, preferably from 20% to 40% by weight, with respect to the weight of the ethylene copolymer;2) density from 0.840 to 0.910 g / cm3, preferably from 0.850 to 0.890 g / cm3, determined according to ISO 1183-1 :2012 at 23°C;3) Melt Flow Rate E from 0.1 to 15 g / 10 min., preferably from 0.3 to 12 g / 10 min., measured according to ISO 1133-1 2012-03 at 190 °C, with a load of 2.16 kg;4) product rl r2 of the reactivity ratios obtained from13C NMR triad distribution, from 0.55 to 0.95 or from 0.55 to 0.92, preferably from 0.6 to 0.95 or from 0.6 to 0.92, more preferably from 0.55 to 0.89 or from 0.6 to 0.92, where rl is the reactivity ratio of ethylene to 1 -butene and r2 is the reactivity ratio of 1 -butene to ethylene.

2. The ethylene copolymer of claim 1, having elongation at break, measured according to ISO 527:2019 on compression moulded specimens, equal to or greater than 920%, preferably equal to or higher than 950%, the upper limit being preferably of 1800%, more preferably of 1600% in all cases.

3. The ethylene copolymer of claim lor 2, having a melting enthalpy AHm equal to or lower than 60 J / g, preferably equal to or lower than 55 J / g, in particular from 5 to 60 J / g, or from 10 to 55 J / g, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute.

4. The ethylene copolymer of claim lor 2, having melting temperature Tm from 15 °C to 55 °C, preferably from 20 °C to 50 °C, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute.

5. The ethylene copolymer of claim lor 2, having at least one of the following properties:- a ratio C4cont / AHm from 0.1 to 2.5, preferably from 0.2 to 2.0;- crystallization temperature Tc equal to or higher than 8 °C, preferably equal to or higher than 10 °C, measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute, the preferred upper limit being of 55°C, more preferably of 50 °C;- glass transition temperature (Tg), measured by Differential Scanning Calorimetry with a heating rate of 10°C per minute, from -35 to -60°C;- Shore A from 20 to 75, measured according to ISO 868:2003.

6. The ethylene copolymer of claim lor 2, having at least one of the following properties:- a 1 -butene content C4cont from 24% to 45% by weight, preferably from 26% to 40% by weight, with respect to the weight of the ethylene copolymer;- Melt Flow Rate E from 0.8 to 15 g / 10 min., preferably from 1.0 to 12 g / 10 min.;- product rl r2 from 0.75 to 0.95, preferably from 0.77 to 0.92;- amount of BBB triads of at least 0.1%, preferably of at least 0.3%, the preferred upper limit being in all cases of 2.5%, in particular of 2%.

7. A polyolefin composition comprising the ethylene polymer composition of claim 1, and at least 50% by weight, referred to the total weight of the polyolefin composition, of one or more additional polyolefins.

8. The polyolefin composition of claim 7, wherein the additional polyolefin or polyolefins are selected from propylene homopolymers and copolymers.

9. Formed articles comprising the polyolefin composition of claims 7 or 8.

10. Formed articles according to claim 9, in form of injection moulded articles.

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