EP4646447A1

EP4646447A1 - Polyolefin composition and process of producing it

Info

Publication number: EP4646447A1
Application number: EP23832744.9A
Authority: EP
Inventors: Michele Grazzi; Claudio Cavalieri; Monica Galvan
Original assignee: Basell Poliolefine Italia SRL
Current assignee: Basell Poliolefine Italia SRL
Priority date: 2023-01-03
Filing date: 2023-12-14
Publication date: 2025-11-12
Also published as: WO2024146764A1

Abstract

A polyolefin composition comprising: - from 20% to 45% of a polymer fraction (A) of a propylene polymer containing up to 12.0%, of units deriving from ethylene or a CH₂=CHR¹alpha-olefin and a combination thereof, wherein R¹ is a linear or branched C₂-C₈ alkyl group; and - from 55% to 80% of a polymer fraction (B) of a copolymer of ethylene containing from 18.0% to 40.0% of units derived from, ethylene and containing propylene and/or a CH₂=CHR¹ alpha-olefin as comonomer, wherein R¹ is a linear or branched C₂-C₈ alkyl group; wherein the polyolefin composition has solubility in n-pentane at 25°C equal to or lower than 2.0%.

Description

TITLE

POLYOLEFIN COMPOSITION AND PROCESS OF PRODUCING IT

TECHNICAL FIELD

[0001] The present invention relates to a polyolefin composition and a process of producing it. The present invention also relates to a sheet or film comprising such a polyolefin composition and uses thereof.

BACKGROUND OF THE DISCLOSURE

[0002] Polypropylene is the material of choice for many applications, for example in the automotive industry, the construction industry, for medical applications as well as for packaging. For instance, polypropylene compositions are used in articles in the automotive interior. Polypropylene compositions are - generally speaking - well processable and can be individually customized.

[0003] WO2011/076664 and WO03/011962 disclose polypropylene compositions with very interesting physical-mechanical characteristics. However, these polypropylene compositions can show a tendency of soiling pick-up. Such phenomena are accelerated and enhanced in hot climates and in presence of highly polluted air.

[0004] For this reason, other types of polymer materials are often chosen for some applications, such as for the outside of building roofs.

[0005] The object of the present disclosure is to provide a polyolefin composition, a process of producing it, a sheet or film comprising it and uses thereof, that allow the drawbacks of the known art to be at least partially overcome, and which are, at the same time, simple and inexpensive to implement.

SUMMARY

[0006] According to the disclosure there is provided a polyolefin composition, a process of producing it, a sheet or film comprising it and uses thereof according to the appended independent claims and, preferably, according to any one of the claims directly or indirectly depending on the independent claims. DETAILED DESCRIPTION

[0007] In this text, unless otherwise specified, “C_x-C_y” refers to a group and/or a compound which is intended having x to y carbon atoms.

[0008] In this text, the term “copolymer” refers to polymers obtained by the polymerization of at least two different monomers. Hence, the term copolymer also refers to terpolymers.

[0009] when the term “comprising” is referred to a polymer or to a polyolefin composition, it should be construed to mean “comprising or consisting essentially of’. [0010] In the context of the present disclosure, the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in a polymer or in a polyolefin composition, provided that the essential characteristics of the polymer or of the composition are not materially affected by their presence, like catalyst residues.

[0011] In this text, the term “film” refers to a thin-layered material having thickness lower than 5000 microns.

[0012] In this text, a “sheet” is a layer of material having thickness equal to or greater than 5000 microns.

[0013] In accordance with a first aspect of the present disclosure it is herein provided a polyolefin composition comprising:

[0014] - from 20% to 45% by weight, of a polymer fraction (A) comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, wherein the propylene copolymer contains up to and including 12.0% by weight, based on the weight of the of the polymer fraction (A), of units deriving from a first comonomer selected from ethylene, a CH2=CHR¹ alpha- olefin and a combination thereof, wherein R¹ is a linear or branched C2-C8 alkyl group, and

[0015] - from 55% to 80% by weight of a polymer fraction (B) comprising a copolymer of ethylene with a second comonomer selected from propylene, a CH2=CHR¹ alpha-olefin, wherein R¹ is a linear or branched C2-C8 alkyl group, and combinations thereof, wherein the copolymer of ethylene contains from 18.0% to 40.0% by weight, based on the weight of the polymer fraction (B), of units derived from ethylene,

[0016] the polyolefin composition having solubility at 25°C in n-pentane equal to or lower than 2.0% by weight, preferably equal to or lower than 1.8% by weight, based on the weight of the polyolefin composition, the lower limit of the solubility at 25°C in n-pentane being preferably 0.1% by weight for each upper limit.

[0017] In this text, unless otherwise specified, the percentages by weight of the polymer fraction (A) and of the polymer fraction (B) are with respect to the sum of weights of the polymer fraction (A) and of the polymer fraction (B), the sum being 100%.

[0018] The polyolefin composition of the present disclosure are endowed with low flexural modulus, low Shore A and Shore D values and a surprisingly high impact resistance at low temperatures, as evidenced by high Charpy impact resistance at - 30°C.

[0019] Moreover, the polyolefin composition of the present disclosure have a reduced tendency of soiling pick-up.

[0020] Advantageously but not necessarily, the polyolefin composition comprises from 25% to 42% by weight, preferably from 28% to 38% by weight, of the polymer fraction (A).

[0021] Advantageously but not necessarily, the polyolefin composition comprises from 58% to 75% by weight, more preferably from 62% to 72% by weight, of the polymer fraction (B).

[0022] More precisely but not necessarily, the polyolefin composition mainly (in particular at least 90%by weight - more in particular, at least 95% by weight - with respect to the total weight of the polyolefin composition) consists of the polymer fraction (A) and the polymer fraction (B).

[0023] Advantageously but not necessarily, the polyolefin composition has a solubility in diethyl ether at 25°C equal to or lower than 2.5% by weight, preferably equal to or lower than 2.2% by weight, based on the weight of the polyolefin composition, the lower limit being preferably 0.1% by weight for each upper limit.

[0024] Advantageously but not necessarily, the polyolefin composition has cumulative value of solubility in n-pentane and diethyl ether at 25°C equal to or lower than 4.0 % by weight, based on the weight of the polyolefin composition, preferably ranging from 2.5% to 4.0% by weight.

[0025] According to some non-limiting embodiments, the polyolefin composition has at least one, preferably all, the following features: [0026] (i) solubility in xylene at 25°C equal to or greater than 60.0% by weight, based on the weight of the polyolefin composition, preferably ranging from 60.0% to 95.0% by weight; and/or

[0027] (ii) intrinsic viscosity of the fraction soluble in xylene at 25°C equal to or greater than 3.0 dl/g, preferably ranging from 3.0 to 6.0 dl/g; and/or

[0028] (iii) melt flow rate equal to or lower than 2.0 g/10 min, preferably ranging from 0.01 to 2.0 g/10 min (determined according to the method ISO 1133-1 :2011, 260°C/2.16Kg); and/or

[0029] (iv) flexural modulus equal to or lower than 150 MPa, in particular, ranging from 15 to 150 MPa (determined according to the method ISO 178:2010); and/or [0030] (v) Shore A lower than 90 (determined according to the method ISO 868,

15 sec.) and preferably greater than 30; and/or

[0031] (vi) Shore D lower than 40 (determined according to the method ISO 868, 15 sec.) and preferably greater than 15; and/or

[0032] (vii) Charpy impact resistance at -30°C equal to or greater than 90 KJ/m², preferably equal to or greater than 100 KJ/m², the upper limit being preferably 130 KJ/m² for each lower limit (determined according to the method ISO 179-leA, and ISO 1873-2).

[0033] In some non-limiting cases, the CH2=CHR¹ alpha-olefin is selected from the group consisting of: butene- 1, pentene- 1, 4-methyl-l -pentene, hexene- 1, octene- 1 and combinations thereof. In particular, the CH2=CHR¹ alpha-olefin is selected from the group consisting of: butene-1 and hexene-1 and combinations thereof. The CH2=CHR¹ alpha-olefin comprised in the fraction (A) can be the same or can be different from the CH2=CHR¹ alpha-olefin comprised in the fraction (B).

[0034] According to a preferred embodiment, the first comonomer is ethylene. [0035] In addition or alternatively, the second comonomer is preferably propylene. [0036] Advantageously but not necessarily, the propylene polymer comprised in the polymer fraction (A) contains at most 10.0%, in particular, at most 8.0%; in particular at most 5.0% by weight, with respect to the overall weight of the polymer fraction (A), of units deriving from a first comonomer selected from ethylene, a CH2=CHR¹ alpha-olefin and combinations thereof, the lower limit being preferably 0.1% by weight, more preferably 0.5% by weight, based on the weight of the polymer fraction (A), for each upper limit. [0037] Copolymers of propylene with ethylene and/or the CH2=CHR¹ alpha-olefin are preferred for the polymer fraction (A), because they confer transparency to the compositions.

[0038] According to some non-limiting embodiments, the polymer fraction (A) preferably has solubility in xylene at 25°C equal to or lower than 10.0% by weight, preferably ranging from 2.0% to 8.0% by weight, more preferably from 2.5% to 7.0% by weight; still more preferably from 3.0% to 6.0% by weight, based on the weight of the polymer fraction (A).

[0039] In a preferred embodiment, the polymer fraction (A) comprises a propylene copolymer containing up to and including 10.0% by weight, preferably from 0.1% to 10.0% by weight; more preferably from 0.5 to 5.0% by weight, based on the weight of the polymer fraction (A), of units deriving from ethylene and has a solubility in xylene at 25°C equal to or lower than 10.0% by weight, preferably ranging from 2.0% to 8.0% by weight, more preferably from 2.5% to 7.0% by weight; still more preferably from 3.0% to 6.0% by weight, based on the weight of the polymer fraction (A).

[0040] Preferably, the polymer fraction (A) has a melt flow rate MFR(A) (ISO 1133-1 :2011, 260°C/2.16kg) ranging from 5.0 to 50 g/10 min, preferably from 10 to 40 g/10 min; more preferably from 15 to 35 g/10 min.

[0041] Optionally, the ethylene polymer of the polymer fraction (B) contains from 0.5% to 10.0% by weight, with respect to the overall weight of the polymer fraction (B), of a diene.

[0042] Examples of dienes are: butadiene, 1,4-hexadiene, 1,5 -hexadiene, and ethylidene-1- norbornene.

[0043] In some non-limiting cases, the copolymer of ethylene comprised in the polymer fraction (B) is a ethyl ene-propylene copolymer containing 18.0% to 35.0% by weight, preferably from 20.0% to 30.0% by weight, of units derived from ethylene, based on the weight of the polymer fraction (B).

[0044] According to some non-limiting embodiments, the polymer fraction (B) comprises an ethyl ene-propylene copolymer comprising:

[0045] - a first part (Bl), containing from 15.0% to 32.0% by weight, with respect to the overall weight of the first part (Bl), of units derived from ethylene; and

[0046] - a second part (B2), containing more than 32.0% up to 45.0% by weight, with respect to the overall weight of the second part (B2), of units derived from ethylene. [0047] The weight ratio of the first part (Bl) over the second part (B2) is from 5 : 1 to 1 :5.

[0048] Preferably, the first part (Bl) has a has a xylene soluble fraction at 25°C whose intrinsic viscosity ranges from about 3.0 to about 5.0 dl/g.

[0049] Preferably, the second part (B2) has a xylene soluble fraction at 25 °C whose intrinsic viscosity ranges from about 4.0 to about 6.5 dl/g.

[0050] According to some non-limiting embodiments, the polyolefin composition further comprises up to and including 5.0% by weight, preferably from 0.1% to 5.0% by weight, based on the overall weight of the polyolefin composition, of a first additive selected from the group consisting of an antistatic agent, an antioxidant, an antiacid, a melt stabilizer, a nucleating agent, a light stabilizer and a combination thereof.

[0051] In addition or alternatively, the polyolefin composition optionally comprises up to and including 50.0% by weight, preferably from 0.5% to 50% by weight, based on the overall weight of the polyolefin composition, of a second additive selected from the group consisting of a filler, a pigment, an extension oil, a flame retardants (e.g. aluminum trihydrate), a light stabilizer, a lubricant (e.g., oleamide), an anti -blocking agent, a wax, a coupling agent for the filler, and combinations thereof.

[0052] The polymer fraction (A) and the polymer fraction (B) are obtained by polymerizing the relevant monomers in the presence of a catalyst system comprising: [0053] - a solid catalyst component (1) comprising Mg, Ti, Cl, Bi and at least one stereoregulating electron donor compound and from 0.1% to 50% by weight, based on the total weight of the solid catalyst component (1), of Bi;

[0054] - optionally but preferably, an alkylaluminum compound (2); and

[0055] - optionally but preferably, a further electron donor compound (3) (external donor).

[0056] In this way it is possible to obtain a polyolefin composition, which, when used for making products, has experimentally shown an unexpected reduced tendency of soiling pick-up.

[0057] Preferably, in the solid catalyst component (1) has at least one, more preferably all, the following features:

[0058] - the content of Bi ranges from 0.5% to 40% by weight, more preferably from 1.0% to 35%, especially from 2.0% to 25%, still more preferably from 2% to 20% by weight; and/or [0059] - the content of Mg ranges from 8% to 30% by weight, more preferably from 10% to 25% by weight; and/or

[0060] - the content of Ti ranges from 0.5% to 5.0% by weight, more preferably from 0.7% to 3.0% by weight, with respect to the weight of the solid catalyst component (1).

[0061] Advantageously but not necessarily, the Bi atoms derive from one or more Bi compounds not having Bi-C bonds. In particular, the Bi compound are preferably selected from Bi halides, Bi carbonate, Bi acetate, Bi nitrate, Bi oxide, Bi sulphate, Bi sulfide. Compounds in which Bi has the valence 3⁺ are preferred. Among Bi halides, preferred are Bi trichloride and Bi tribromide. The most preferred Bi compound is BiCh.

[0062] The Mg/Ti molar ratio is preferably equal to or greater than 13, preferably ranging from 14 to 40, and more preferably from 15 to 40. Correspondingly, the Mg/stereoregulating electron donor molar ratio is preferably greater than 16, more preferably greater than 17, usually ranging from 18 to 50.

[0063] According to some non-limiting embodiments, the stereoregulating electron donor compound is selected from: alkyl and aryl esters of optionally substituted aromatic polycarboxylic acids, such as esters of benzoic and phthalic acids. Specific examples of such esters are n-butylphthalate, di-isobutylphthalate, di-n-octylphthalate, ethyl-benzoate and p-ethoxy ethyl -benzoate.

[0064] The preparation of the solid catalyst component (1) can be carried out according to several methods.

[0065] According to one method the solid catalyst component can be prepared by reacting a titanium compound of formula Ti(OR)q-yXy, where q is the valence of titanium and y is a number between 1 and q, preferably TiCh, with a magnesium chloride deriving from an adduct of formula MgCh’pROH, where p is a number between 0.1 and 6, preferably from 2 to 3.5, and R is a hydrocarbon radical having 1- 18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride, operating under stirring conditions at the melting temperature of the adduct (100°-130°C). Then, the adduct is mixed with an inert hydrocarbon immiscible with the adduct thereby creating an emulsion which is quickly quenched causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in USP 4,399,054 and USP 4,469,648. The so obtained adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (80°-130°C) so as to obtain an adduct in which the number of moles of alcohol is generally lower than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCh (generally at 0°C); the mixture is heated up to 80°-130°C and kept at this temperature for 0.5-2.0 hours. The treatment with TiCh can be carried out one or more times. The electron donor compound can be added in the desired ratios during the treatment with TiCh.

[0066] Several ways are available to add one or more Bi compounds in the catalyst preparation. According to a first option, the Bi compound(s) is/are incorporated directly into the MgCh’pROH adduct during its preparation. In this embodiment, the Bi compound is added at the initial stage of adduct preparation by mixing it together with MgCh and the alcohol.

[0067] Alternatively, the Bi compound(s) can be added to the molten adduct before the emulsification step. The amount of Bi introduced ranges from 0.1 to 1.0 mole per mole of Mg in the adduct. Preferred Bi compound(s) to be incorporated directly into the MgCh’pROH adduct are Bi halides and in particular is BiCh.

[0068] According to an alternative embodiment, the Bi compound(s) is/are introduced into the catalyst component during the step of reaction between the MgCh’pROH adduct and the Ti compound. In particular, the Bi compound(s) is/are dissolved or dispersed in the liquid Ti compound, preferably TiCh, which is then reacted with the said adduct. An example of such technique is described in WO20 17/042058.

[0069] Advantageously but not necessarily, the particles of the solid catalyst component (1) have substantially spherical morphology and average diameter ranging between 5 and 150 microns, preferably from 20 to 100 microns and more preferably from 30 to 90 microns. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.

[0070] According to some non-limiting embodiments, the Al-containing cocatalyst (2) is an alkyl-Al compound and, in particular, is chosen among the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n- butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt2Cl and AhEtsCh, possibly in mixture with the above cited trialkylaluminums. In particular, the Al/Ti ratio is higher than 1 and is generally comprised between 50 and 2000.

[0071] According to some non-limiting embodiments, suitable further electrondonor compounds (3) include silicon compounds, ethers, esters, amines, heterocyclic compounds and particularly 2,2,6,6-tetramethylpiperidine and ketones.

[0072] A preferred class of further electron-donor compounds (3) is that of silicon compounds of formula (I):

[0073] (R^A)_a(R^c)bSi(OR^B)c (I),

[0074] wherein a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R^A, R^B, and R^c, are independently selected from alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms, optionally containing heteroatoms. Particularly preferred are the silicon compounds in which a is 1, b is 1, c is 2, at least one of R^A and R^c is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms and R^B is a Ci-Cio alkyl group, in particular methyl. Examples of such preferred silicon compounds are: cyclohexylmethyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl-t- butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), diisopropyldimethoxysilane, (2-ethylpiperidinyl)t-butyldimethoxysilane, (2- ethylpiperidinyl)thexyldimethoxysilane, (3,3,3-trifluoro-n-propyl)-(2- ethylpiperidinyl)-dimethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane. The silicon compounds in which a is 0, b is 1 and c is 3, R^c is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R^B is methyl are also preferred. Examples of such silicon compounds are cyclohexyl trimethoxysilane, t- butyl trimethoxysilane and thexyl trimethoxysilane.

[0075] In a particularly preferred embodiment, the further electron-donor (3) is cyclohexylmethyldimethoxy silane (donor C).

[0076] The polyolefin composition obtained in a process making use of said preferred further electron donor compound (3) has low n-hexane extractable fraction and particularly low tendency to soiling.

[0077] Advantageously but not necessarily, the further electron-donor compound (3) is used in such an amount to give a molar ratio between the Al-containing cocatalyst (2) and the further electron donor compound (3) of from 0.1 to 500, preferably from 1 to 300 and more preferably from 3 to 100 (in particular, to 50). [0078] The polymerization processes to produce the polyolefin composition of the present disclosure are already known in the art, like gas-phase polymerization processes operating in one or more fluidized or mechanically agitated bed reactors, slurry polymerization using an inert hydrocarbon solvent, or bulk polymerization using the liquid monomer (for example propylene) as a reaction medium.

[0079] The polypropylene composition of the present disclosure is preferably obtained by a sequential polymerization process in two or more stages, in which the polymer fraction (A) is obtained in a first stage and then the polymer fraction (B) is obtained in a second stage, in the presence of the catalyst system and the polymer coming from the immediately preceding polymerization stage. Each stage is preferably in gas-phase, operating in one or more fluidized or mechanically agitated bed reactor. [0080] Typically, but not necessarily, the polymerization is carried out in continuous mode in a series of two or more reactors equipped with devices to transfer the product from one reactor to the one immediately next to it. Preferably, the two or more reactors are fluidized bed gas-phase reactors.

[0081] Advantageously but not necessarily, the polyolefin composition is obtained by polymerizing the relevant monomers in a first polymerization step (a) and a second polymerization step (b). The first polymerization step (a) is carried out (in at least one first reactor) in the presence of a catalyst system as described above so as to obtain the polymer fraction (A). The second polymerization step (b) is carried out (in at least one second reactor) in the presence of the polymer and of the catalyst system of the first polymerization step (a), so as to obtain the polymer fraction (B).

[0082] The amount of the polymer fraction (A) and of the polymer fraction (B) correspond to the amount of polymer produced in the first polymerization step (a) and in the second polymerization step (b) respectively.

[0083] The polymerization is generally carried out at temperature of from 20° to 120°C, preferably of from 40° to 80°C. When the polymerization is carried out in gasphase, the operating pressure is generally between 0.5 and 5.0 MPa, preferably between 1.0 and 4.0 MPa. In the bulk polymerization the operating pressure is generally between 1.0 and 8.0 MPa, preferably between 1.5 and 5.0 MPa. Hydrogen is typically used as a molecular weight regulator.

[0084] In accordance with a second aspect of the present disclosure, there is provided a film or sheet comprising the polyolefin composition as defined above. [0085] In particular, the film or sheet can be obtained starting from the polyolefin composition described above by means of the techniques commonly known in the art, such as extrusion, injection molding, thermoforming and so on.

[0086] The polyolefin composition of the present disclosure can be advantageously used in the several fields and in particular for the following applications: automotive flooring, interior automotive applications, panels and profiles, pipe coating, polymer modifier, single ply roofing, soft profile and sheets, TPO foils and skins, TPO residential flooring, wire & cable. Particularly useful, are the application for production material for roofing.

[0087] In accordance with a third aspect of the present disclosure, there is provided a use of the polyolefin composition of the present disclosure (in particular, the above mentioned film or sheet) in the building industry, more preferably, for roofing.

[0088] In accordance with a fourth aspect of the present disclosure there is provided process of producing of the polyolefin composition as disclosed with respect to the first aspect of the present disclosure. The process comprises a first polymerization step (a), during which propylene is polymerized in the presence of a catalyst system, optionally together with the first comonomer, to obtain the polymer fraction (A); a second polymerization step (b), during which ethylene is polymerized together with the second comonomer in the presence of the polymer fraction (A) and of the catalyst system of the first polymerization step (a), to obtain the polymer fraction (B).

[0089] The catalyst system is as defined above with respect to the first aspect of the present disclosure.

[0090] According to some non-limiting embodiments, the second polymerization steps (b) is carried out in two reactors connected in series. In the first reactor, ethylene is polymerized together with the second comonomer in the presence of the polymer fraction (A) and of the catalyst system of the first polymerization step (a), to obtain a first part (Bl) of polymer fraction (B). In the second reactor, ethylene is polymerized together with the second comonomer (which can be the same to or different from the second monomer used in the first reactor) in the presence of the catalyst system, of the polymer fraction (A) and of the first part (Bl), to obtain a second part (B2) of polymer fraction (B).

[0091] The polymerization process is carried out as defined above with respect to the first aspect of the present disclosure. [0092] Further characteristics of the present invention will be apparent from the following description of non-limiting examples provided purely for illustrative purposes.

EXAMPLES

[0093] The following examples are illustrative only, and are not intended to limit the scope of the disclosure in any manner whatsoever.

[0094] CHARACTERIZATION METHODS: the following methods are used to determine the properties indicated in the description, claims and examples.

[0095] Determination of ethylene and propylene content

[0096] ¹³ C NMR spectra are acquired on a Bruker AV-600 spectrometer equipped with cry oprobe, operating at 160.91 MHz in the Fourier transform mode at 120°C. The peak of the Spp carbon (nomenclature according to "Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by ¹³ C NMR. 3. Use of Reaction Probability Mode" C. I. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. About 30 mg of polymer are dissolved in 1, 1,2,2- tetrachloroethane-d2 at 120°C in 0.5ml of l,l,2,2-tetrachloroethane-d2 added with 0.1 mg/ml of Irganox 1010 (AO1010) as antioxidant . Each spectrum is acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz. The assignments of the spectra, the evaluation of triad distribution and the composition are made according to M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 4, 1150-1152 using the following equations:

PPP = 100 Tpp/S PPE = 100 Tpg /S EPE = 100 T_ss/S

PEP = 100 Spp/S PEE= 100 Sp₅ /S EEE = 100 (0.25 S_y5 +0.5 S₅₅)/S

S = Tpp + Tps + Tss + Spp + Spg + 0.25 S_Ys + 0.5 Sgg

[0097] The molar content of ethylene and propylene is calculated from triads using the following equation:

[Ejmol = EEE + PEE + PEP

[P]moZ = PPP + PPE + EPE

[0098] The weight percentage of ethylene content (E% wt) is calculated using the following equation : wherein

[P] mol = the molar percentage of propylene content;

MWE = molecular weights of ethylene

MWP = molecular weight of propylene.

[0099] The product of reactivity ratio rm is calculated according to Carman (C.J. Carman, R A. Harrington and C E. Wilkes, Macromolecules, 1977; 10, 536) as:

[0100] The tacticity of propylene sequences is calculated as mm content from the ratio of the PPP mmTpp (28.90-29.65 ppm) and the whole Tpp (29.80-28.37 ppm).

[0101] The amount of ethylene of component B) is calculated from the total ethylene content of the polymer (C2(tot) wt%) using the formula:

C2(tot) wt% = W(A)xC2(A) wt% + W(B)xC2(B) wt% wherein W(A) and W(B) are the relative amounts of components (A) and (B) (W(A)+W(B)=1), and C2(A) wt% and C2(B) wt% are the weight percentages of ethylene in component (A) and in component (B) respectively.

[0102] Solubility in diethyl ether

[0103] 25g of polymer are exactly weighted in an aluminum cup on an analytical balance (Pl : sample weight) and added to 500 ml of diethyl ether (analytical grade) in a 1000 ml Erlenmeyer flask. The flask is put in a thermostatic bath set at 40 °C and the soluble polymer fraction is extracted under reflux (with a condenser) for 4 hours without stirring. Filter and wash the residual material with 50-100 ml of fresh diethyl ether. Transfer the filtrate (diethyl ether + polymer soluble fraction) to a Rotavapor (Bath temperature 40-45°C), and reduce the volume to 100-150 ml; pour into a preweighed aluminum pan and place it in an IR drying unit to evaporate and remove the residual solvent. After evaporation put the aluminum pan into a vacuum oven at 70°C for 20-30 min, until constant weight is reached. Put the sample in an desiccator and weight the residue (P2: weight of the fraction extractable with diethyl ether). The amount of fraction soluble in diethyl ether is calculated using the formula

P2

% soluble in diethyl ether = — X 100 [0104] Solubility in n-pentane

[0105] The fraction extractable in diethyl ether obtained as described above is put in a vacuum oven at 70°C for 16-18 h, cooled to 25°C in a desiccator and weighted (P3: weight of the residue after extraction with diethyl ether). The residue P3 is added to 500 ml of n-pentane (analytical grade) in a 1000 ml Erlenmeyer flask. The flask is put in a thermostatic bath set at 40 °C and the soluble polymer fraction is extracted under reflux (with a condenser) for 4 hours without stirring. Filter and wash the residual material with 50-100 ml of fresh n-pentane. Transfer the filtrate (n-pentane + polymer soluble fraction) to a Rotavapor (Bath temperature 40-45°C), and reduce the volume to 100-150 ml; pour into a pre-weighed aluminum pan and place it in an IR drying unit to evaporate and remove the residual solvent. After evaporation put the aluminum pan into a vacuum oven at 70°C for 20-30 min, until constant weight is reached. Put the sample in an desiccator and weight the residue (P4: weight of the fraction extractable with n-pentane). The amount of fraction soluble in diethyl ether is calculated using the formula

P4

% soluble in n-pentane = — x 100

[0106] Melt Flow Rate

[0107] Determined according to ISO 1133-1 :201 lat 260°C with a load of 2.16kg.

[0108] Solubility in xylene at 25°C

[0109] 2.5 g of polymer sample and 250 ml of xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to 135°C. The obtained clear solution is kept under reflux and stirring for further 30 minutes. The solution is cooled in two stages. In the first stage, the temperature is lowered to 100°C in air for 10 to 15 minute under stirring. In the second stage, the flask is transferred to a thermostatically controlled water bath at 25°C for 30 minutes. The temperature is lowered to 25°C without stirring during the first 20 minutes and maintained at 25 °C with stirring for the last 10 minutes. The formed solid is filtered on quick filtering paper (eg. Whatman filtering paper grade 4 or 541). 100 ml of the filtered solution (SI) is poured in a previously weighed aluminum container, which is heated to 140°C on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80°C under vacuum until constant weight is reached. The amount of polymer soluble in xylene at 25°C is then calculated. XS(I) and XSA values are experimentally determined. The fraction of component (B) soluble in xylene at 25°C (XSB) is calculated from the formula:

XS = W(A)x(XSA) + W(B)x(XSB) wherein W(A) and W(B) are the relative amounts of components (A) and (B), respectively, and W(A)+ W(B)=1.

[0110] Intrinsic viscosity

[oni] To calculate the value of the intrinsic viscosity IV, the flow time of a polymer solution is compared with the flow time of the solvent (THN). A glass capillary viscometer of Ubbelohde type is used. The oven temperature is adjusted to 135°C. Before starting the measurement of the solvent flow time tO the temperature must be stable (135° ± 0.2°C). Sample meniscus detection for the viscometer is performed by a photoelectric device. Sample preparation: 100 ml of the filtered solution (SI) is poured in a beaker and 200 ml of acetone are added under vigorous stirring. Precipitation of insoluble fraction must be complete as evidenced by a clear solid-solution separation. The suspension is filtered on a weighed metallic screen (200 mesh), the beaker is rinsed and the precipitate is washed with acetone so that the o- xylene is completely removed. The precipitate is dried in a vacuum oven at 70°C until a constant weight is reached. 0.05g of precipitate are weighted and dissolved in 50ml of tetrahydronaphthalene (THN) at a temperature of 135°C. The efflux time t of the sample solution is measured and converted into a value of intrinsic viscosity [r] using Huggins' equation (Huggins, M.L., J. Am. Chem. Soc. 1942, 64, 11, 2716-2718) and the following data:

- concentration (g/dl) of the sample;

- the density of the solvent at a temperature of 135°C;

- the flow time tO of the solvent at a temperature of 135°C on the same viscometer.

One single polymer solution is used to determine [q],

[0112] Determination of Mg and Ti

[0113] The determination of Mg and Ti content in the solid catalyst component (1) is carried out via inductively coupled plasma emission spectroscopy on "LC.P Spectrometer ARL Accuris". The sample is prepared by analytically weighting, in a "Fluxy" platinum crucible", 0.1H).3 grams of catalyst and 2 grams of lithium metaborate/tetraborate 1/1 mixture. After addition of some drops of KI solution, the crucible is inserted in a special apparatus "Claisse Fluxy" for the complete burning. The residue is collected with a 5% v/v HN03 solution and then analyzed via ICP at the following wavelengths: Magnesium, 279.08 nm; Titanium, 368.52 nm.

[0114] Determination of Bi

[0115] The determination of Bi content in the solid catalyst component (1) is carried out via inductively coupled plasma emission spectroscopy on "LC.P Spectrometer ARL Accuris". The sample was prepared by analytically weighting in a 200 ml volumetric flask 0.1-H).3 grams of catalyst. After slow addition of ca. 10ml of 65% v/v HNO3 solution and ca. 50ml of distilled water, the sample undergoes a digestion for 4^6 hours. Then the volumetric flask is diluted to the mark with deionized water. The resulting solution is directly analysed via ICP at the following wavelength: Bismuth, 223.06 nm.

[0116] Determination of internal donor content

[0117] The determination of the content of internal donor in the solid catalyst component (1) is done by Gas Chromatography. The solid catalyst component is dissolved in acetone, an internal standard is added, and a sample of the organic phase is analysed in a gas chromatograph, to determine the amount of donor present at the starting catalyst compound.

[0118] Determination of Shore A and Shore D

[0119] Determined on 4mm-thick compression molded plaques according to the method ISO 868 (15 sec).

[0120] Flexural modulus

[0121] Determined according to the method ISO 178:2010.

[0122] Charpy impact resistance

[0123] Determined according to the methods ISO 179-1-eA and ISO 1873-2 at - 30°C.

[0124] Examples E1-E4

[0125] Procedure for the preparation of the spherical adduct

[0126] Microspheroidal MgCh PC2H5OH adduct was prepared according to the method described in Example 2 of W098/44009. The solid spherical particles obtained, containing 57 wt% of ethanol, underwent a dealcoholation step under warm nitrogen flow until the level of ethanol reached 35 wt%.

[0127] Into a 500 ml round bottom flask, equipped with mechanical stirrer, cooler and thermometer, 300ml of TiCh were introduced at room temperature under nitrogen atmosphere. After cooling to 0°C, while stirring, BiC13 in powder form and in an amount to meet Mg/Bi molar ratio of 40, diisobutylphthalate (DIBP) and 15.0 g of the microspheroidal adduct prepared as described above were sequentially added into the flask. The amount of fed internal donor was such to meet a Mg/donor molar ratio of 8. The temperature was raised to 100°C and maintained for 1 hour. Thereafter, stirring was stopped, the solid product was allowed to settle, and the supernatant liquid was siphoned off at 100°C. After the supernatant liquid was removed, additional fresh TiCh was added at room temperature to reach the initial liquid volume again. The mixture was then heated at 120°C and kept at this temperature for 30 minutes. Stirring was stopped again, the solid was allowed to settle and the supernatant liquid was siphoned off at 100°C. The solid was washed with anhydrous heptane four times in temperature gradient down to 90°C and one time at 25°C. The obtained solid was then dried under vacuum.

[0128] Prepolymerization treatment

[0129] Before introducing it into the polymerization reactors, the solid catalyst component described above was precontacted with triethyl aluminum (TEAL) and methylcyclohexyldimethoxysilane (C donor) or dicyclohexyldimethoxysilane (D donor) in the amounts reported in table 1. The resulting mixture was subjected to prepolymerization as reported in the same table 1.

[0130] Polymerization

[0131] The polymerization run is carried out in continuous mode in a series of two gas-phase reactors equipped with devices to transfer the product from one reactor to the one immediately next to it. A propylene-ethylene copolymer is prepared in the first reactor and an ethyl ene-propylene copolymer is prepared in the second reactor in the presence of the copolymer coming from the first reactor. Hydrogen is used as molecular weight regulator.

[0132] The gas phase (propylene, ethylene and hydrogen) is continuously analysed via gas-chromatography.

[0133] The main polymerization conditions are reported in table 1. Properties of the polyolefin compositions are reported in table 2.

[0134] Comparative example CE5

[0135] A polypropylene composition was prepared according to the procedure reported in Comparative Example 1 of WO03/011962. The characterization is reported in table 2. Table 1

Table 2

[0136] The materials of examples E1-E4 had a lower tendency to soiling if compared to the material of comparative example CE5.

Claims

CLAIMS What is claimed is:

1. A polyolefin composition comprising:

- from 20% to 45% by weight, preferably from 25% to 42% by weight, more preferably from 28% to 38% by weight, of a polymer fraction (A) comprising a propylene polymer selected from a propylene homopolymer, a propylene copolymer and combinations thereof, wherein the propylene copolymer contains up to and including 12.0% by weight, based on the weight of the polymer fraction (A), of units deriving from a first comonomer selected from ethylene, a CH2=CHR¹ alpha-olefin and a combination thereof, wherein R¹ is a linear or branched C2-C8 alkyl group; and

- from 55% to 80% by weight, preferably from 58% to 75% by weight, more preferably from 62% to 72% by weight, of a polymer fraction (B) comprising a copolymer of ethylene with a second comonomer selected from propylene, a CH2=CHR¹ alpha-olefin, wherein R¹ is a linear or branched C2-C8 alkyl group, and combinations thereof, wherein the copolymer of ethylene contains from 18.0% to 40.0% by weight, based on the weight of the polymer fraction (B), of units derived from ethylene, wherein the percentages by weight of the polymer fraction (A) and of the polymer fraction (B) are with respect to the sum of weights of the polymer fraction (A) and of the polymer fraction (B), and wherein the polyolefin composition has solubility in n-pentane at 25°C equal to or lower than 2.0% by weight, preferably equal to or lower than 1.8% by weight, based on the weight of the polyolefin composition.

2. The polyolefin composition according to claim 1 and having a solubility in diethyl ether at 25°C equal to or lower than 2.5% by weight, preferably equal to or lower than 2.2% by weight, based on the weight of the polyolefin composition.

3. The polyolefin composition according to claim 1 or 2 and having at least one, preferably all, the following features: (i) solubility in xylene at 25°C equal to or greater than 60.0% by weight, based on the weight of the polyolefin composition; and/or

(ii) an intrinsic viscosity of the xylene soluble fraction equal to or greater than 3.0 dl/g; and/or

(iii) melt flow rate (ISO 1133-1 :2011, 260°C/2.16kg) equal to or lower than 2.0 g/10 min; and/or

(iv) flexural modulus (ISO 178:2010) equal to or lower than 150 MPa; and/or

(v) Shore A lower than 90 (ISO 868, 15 sec.); and/or

(vi) Shore D lower than 40 (ISO 868, 15 sec.); and/or

(vii) Charpy impact resistance at -30°C equal to or greater than 90 KJ/m² (ISO 179-leA and ISO 1873-2).

4. The polyolefin composition according any one of the previous claims, wherein the CH2=CHR¹ alpha-olefin is selected from the group consisting of: butene-1, pentene- 1, 4-m ethyl- 1 -pentene, hexene- 1, octene- 1 and combinations thereof; butene-1 and hexene- 1 being particularly preferred.

5. The polyolefin composition according any one of the previous claims, wherein the polymer fraction (A):

- comprises a propylene copolymer containing at most 10.0%, in particular, at most 8.0%; in particular at most 5.0% by weight, with respect to the overall weight of the polymer fraction (A), of units deriving from a first comonomer selected from ethylene, a CH2=CHR¹ alpha-olefin and combinations thereof, the lower limit being preferably 0.1% by weight, more preferably 0.5% by weight, based on the weight of the polymer fraction (A), for each upper limit; and/or

- has a solubility in xylene at 25°C equal to or lower than 10.0% by weight, preferably ranging from 2.0% to 8.0% by weight, more preferably from 2.5% to 7.0% by weight, still more preferably from 3.0% to 6.0% by weight, based on the weight of the polymer fraction (A).

6. The polyolefin composition according any one of the previous claims, wherein the polymer fraction (A) has a melt flow rate MFR(A) (ISO 1133-1 :2011, 260°C/2.16kg) ranging from 5.0 to 50 g/10 min, preferably from 10 to 40 g/10 min, more preferably from 15 to 35 g/10 min.

7. The polyolefin composition according any one of the previous claims, wherein the copolymer of ethylene comprised in the polymer fraction (B) is a ethylenepropylene copolymer containing 18.0% to 35.0% by weight, preferably from 20.0% to 30.0% by weight, of units derived from ethylene, based on the weight of the polymer fraction (B).

8. A polyolefin composition comprising:

- from 55% to 80% by weight, preferably from 58% to 75% by weight, more preferably from 62% to 72% by weight, of a polymer fraction (B) comprising a copolymer of ethylene with a second comonomer selected from propylene, a CH2=CHR¹ alpha-olefin, wherein R¹ is a linear or branched C2-C8 alkyl group, and combinations thereof, wherein the copolymer of ethylene contains from 18.0% to 40.0% by weight, based on the weight of the polymer fraction (B), of units derived from ethylene; wherein the polymer fraction (A) and the polymer fraction (B) are obtained by polymerizing the relevant monomers in the presence of a catalyst system comprising:

(1) a solid catalyst component comprising Mg, Ti, Cl, Bi, and at least one stereoregulating electron donor compound, wherein the solid catalyst component comprises from 0.1% to 50% by weight of Bi, based on the total weight of the solid catalyst component (1);

(2) optionally, but preferably, an Al-containing cocatalyst; and

(3) optionally, but preferably, a further electron-donor compound; wherein the percentages by weight of the polymer fraction (A) and of the polymer fraction (B) are with respect to the sums of weights of the polymer fraction (A) and of the polymer fraction (B).

9. The polyolefin composition according to claim 8, wherein said catalyst system comprises the further electron-donor compound (3), which is a silicon compound having the general formula (I):

(R^A)a(R^c)bSi(OR^B)_c (I), wherein a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R^A, R^B, and R^c, are independently selected from alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms, optionally containing heteroatoms, preferably a is 1, b is 1, c is 2 and at least one of R^A and R^c is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms, optionally containing heteroatoms, and R^B is a Ci-Cio alkyl group, in particular methyl.

10. The polyolefin composition according to claim 9, wherein the further electrondonor (3) is cyclohexylmethyldimethoxysilane.

11. The polyolefin composition according to any one of claims 1 to 7 obtained by polymerizing the relevant monomers in a first polymerization step (a) and a second polymerization step (b), wherein the first polymerization step (a) is carried out in the presence of a catalyst system as described in any one of claims from 8 to 10 so as to obtain the polymer fraction (A), and the second polymerization step (b) is carried out in the presence of the polymer fraction (A) and of the catalyst system of the first polymerization step (a), so as to obtain the polymer fraction (B).

12. A film or sheet comprising the polyolefin composition according to any one of the previous claims.

13. Use of the film or sheet as according to claim 12 for roofing.

14. A process of producing of the polyolefin composition according to any one of Claims 1 to 11, comprising: - a polymerization step (a), during which propylene is polymerized in the presence of a catalyst system, optionally together with the first comonomer, to obtain the polymer fraction (A);

- a polymerization step (b), during which ethylene is polymerized together with the second comonomer in the presence of the polymer fraction (A) and of the catalyst system of the polymerization step (a), to obtain the polymer fraction (B); the catalyst system comprising:

(1) a solid catalyst component comprising Mg, Ti, Cl, Bi, and at least one stereoregulating electron donor compound, wherein the solid catalyst component comprises from 0.1% to 50% by weight of Bi, based on the total weight of the solid catalyst component;

(2) optionally, but preferably, an Al-containing cocatalyst; and

(3) optionally, but preferably, a further electron-donor compound.

15. The process according to claim 14, wherein the catalyst system comprises the further electron-donor compound (3), which is a silicon compound having the general formula (I):

(R^A)a(R^c)bSi(OR^B)_c (I), wherein a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum (a+b+c) is 4; R^A, R^B, and R^c, are independently selected from alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms, optionally containing heteroatoms, preferably a is 1, b is 1, c is 2 and at least one of R^A and R^c is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms and R^B is a Ci-Cio alkyl group, in particular methyl, more preferably further electron-donor (3) is cyclohexylmethyldimethoxy silane.