WO2025125124A1

WO2025125124A1 - Polypropylene composition for wire and cable applications

Info

Publication number: WO2025125124A1
Application number: PCT/EP2024/085192
Authority: WO
Inventors: Gisella Biondini; Monica Galvan; Stefano Pasquali; Eleonora Ciaccia
Original assignee: Basell Poliolefine Italia SRL
Current assignee: Basell Poliolefine Italia SRL
Priority date: 2023-12-14
Filing date: 2024-12-09
Publication date: 2025-06-19
Anticipated expiration: 2026-06-14

Abstract

Cable having good thermal conductivity comprising an electrical conductor and a thermoplastic layer surrounding the electrical conductor, wherein the thermoplastic layer comprises a polyolefin composition (I) comprising: - 10-40 wt% of a fraction (a) comprising a propylene homopolymer or copolymer with up to and including 10 wt% of a comonomer selected from ethylene and C4-C10 alpha-olefins, the fraction (a) having solubility in xylene at 25°C ≤ 15 wt%; - 20-60 wt% of a fraction (b) comprising an ethylene homopolymer or an ethylene copolymer with a comonomer selected from C4-C10 alpha-olefins and containing at least 75 wt% units deriving from ethylene; and - 30-60 wt% of a fraction (c) comprising an ethylene copolymer with at least one comonomer selected from propylene and C4-C10 alpha-olefins and from 40 to less than 75 wt% by weight of units deriving from ethylene.

Description

TITLE

POLYPROPYLENE COMPOSITION FOR WIRE AND CABLE APPLICATIONS

FIELD OF THE INVENTION

[0001] The present disclosure relates to a polypropylene composition containing propylene polymers and ethylene polymers, which is suitable for use in wire and cable applications.

BACKGROUND OF THE INVENTION

[0002] In the ever-evolving landscape of electrical and communication systems, the development of advanced wire and cable solutions has played a pivotal role in enabling the efficient and reliable transmission of power, data, and signals across a multitude of industries and applications.

[0003] Polyolefins have proven to be excellent materials for cables insulation, being endowed with good electrical and mechanical properties.

[0004] For instance, the patent application WO2020/229687 disclose a polyolefin composition for use in cable insulation having good creep resistance, the composition comprising a combination of LDPE, propylene homopolymer and a low amount of random heterophasic propylene copolymer.

[0005] The patent document EP3033390B1 discloses a polymer composition with good mechanical and electrical properties suitable to manufacture an electrical insulation layer, the polymer composition comprising an ethylene-propylene copolymer and a propylene homopolymer in weight ratio from 90:10 to 10:90.

[0006] The patent document EP3747030B1 discloses a cable insulation or jacketing comprising an ethylene interpolymer Tl), a peroxide and a component T2) containing a propylene homopolymer A), an ethylene/alpha-olefin copolymer B) and an ethylene/propylene copolymer C), the cable having improved crush resistance.

[0007] The international patent application WO2012/000885 discloses a composition suitable for wire and cable applications containing a propylene homo or copolymer A) having solubility in xylene lower than 20 wt.%, an ethylene/propylene copolymer containing 42-70 wt.% of ethylene and a blend of an ethylene copolymer with Shore A lower than 90 with a propylene copolymer having a Shore A) lower than 90, the composition having low hardness and very good rheological properties.

[0008] The European patent EP2528968B1 discloses an energy cable having at least one polypropylene nanocomposite electrically insulating layer, wherein the insulating layer comprises at least one heterophasic copolymer.

[0009] Polypropylene-based insulating materials used in cables usually have excellent electrical properties but unsatisfactory thermal conductivity. In this context, there still exists a pressing need for insulating materials for use in wire and cable systems, having good thermal conductivity to improve heat dissipation of wire and cable systems including a polyolefin insulating layer.

[0010] The applicant found that a polyolefin composition containing a combination of propylene polymers and ethylene polymers has good thermal conductivity, while retaining good mechanical properties if compared with known insulating materials for use in wire and cable systems.

SUMMARY OF THE INVENTION

[0011] An object of the present disclosure is to provide a cable comprising an electrical conductor and a thermoplastic layer surrounding the electrical conductor, wherein the thermoplastic layer comprises a polyolefin composition (I) comprising:

[0012] - from 10 to 40% by weight of a fraction (a) comprising a propylene homopolymer or a propylene copolymer with up to and including 10.0% by weight, based on the weight of fraction (a), of a comonomer selected from ethylene and C4-C10 alpha-olefins, the fraction (a) having solubility in xylene at 25°C equal to or lower than 15.0% by weight, based on the weight of fraction (a);

[0013] - from 20 to 60% by weight of a fraction (b) comprising an ethylene homopolymer or an ethylene copolymer with a comonomer selected from C4-C10 alpha-olefins, the ethylene copolymer containing at least 75.0% by weight of units deriving from ethylene, based on the weight of fraction (b); and [0014] - from 30 to 60% by weight of a fraction (c) comprising an ethylene copolymer with at least one comonomer selected from propylene and C4-C10 alpha-olefins, the copolymer containing from 40.0 to less than 75.0% by weight of units deriving from ethylene, based on the weight of fraction (c),

[0015] wherein the amount of fractions (a), (b) and (c) is based on the total weight of fractions (a), (b) and (c).

[0016] A further object of the present disclosure is to provide a method to insulate an electrical conductor comprising the steps of:

[0017] (i) providing an electrical conductor;

[0018] (ii) providing the polyolefin composition (I) as described in the foregoing; and

[0019] (iii) surrounding the electrical conductor with the polyolefin composition (I).

[0020] The polyolefin composition (I) of the present disclosure has good thermal conductivity in combination with good mechanical properties, resulting in an insulating layer with a corresponding good combination of properties.

[0021] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In the context of the present disclosure;

[0023] - the percentages are expressed by weight, unless otherwise specified;

[0024] - the total weight of a polymer composition sums up to 100% by weight, unless otherwise specified;

[0025] - the term “comprising” referred to a polymer or to a polymer composition, mixture or blend should be construed to mean “comprising or consisting essentially of’;

[0026] - the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in the material, provided that the essential characteristics of the material are not materially affected by their presence. Examples of components that, when present in customary amounts, do not materially affect the characteristics of a polymer or of a polyolefin composition, mixture or blend are catalyst residues, antistatic agents and processing aids;

[0027] - the term “copolymer” is referred to a polymer deriving from the intentional polymerization of at least two different comonomers, i.e. the term “copolymer” includes terpolymers.

[0028] In a first aspect, the present disclosure provides a cable comprising an electrical conductor and a thermoplastic layer surrounding the electrical conductor, wherein the thermoplastic layer comprises a polyolefin composition (I) comprising:

[0029] - from 10 to 40% by weight, preferably from 10 to 30% by weight, of a fraction (a) comprising a propylene homopolymer or a propylene copolymer with up to and including 10.0% by weight, based on the weight of fraction (a), of a comonomer selected from ethylene and C4- C10 alpha-olefins, the fraction (a) having solubility in xylene at 25°C equal to or lower than 15.0% by weight, based on the weight of fraction (a);

[0030] - from 20 to 60% by weight of a fraction (b), preferably from 30 to 40% by weight, comprising an ethylene homopolymer or an ethylene copolymer with a comonomer selected from C4-C10 alpha-olefins, the ethylene copolymer containing at least 75.0% by weight of units deriving from ethylene, based on the weight of fraction (b); and

[0031] - from 30 to 60% by weight of a fraction (c), preferably from 40 to 50% by weight, comprising an ethylene copolymer with at least one comonomer selected from propylene and C4- C10 alpha-olefins, the copolymer containing from 40.0 to less than 75.0% by weight of units deriving from ethylene, based on the weight of fraction (c),

[0032] wherein the amount of fractions (a), (b) and (c) is based on the total weight of fractions

(a), (b) and (c).

[0033] Preferably, the C4-C10 alpha olefin of fractions (a), (b) and (c) is independently selected from butene- 1, hexene- 1, octene- 1, 3 -methyl- 1 -pentene, and decene- 1; butene- 1 is particularly preferred.

[0034] In the following the individual polymer fractions (a), (b) and (c) of the polyolefin composition (I) are defined in more detail. [0035] The polymer fraction (a) preferably has at least one, more preferably all, the following features:

[0036] - comprises a propylene homopolymer having solubility in xylene at 25 °C equal to or lower than 5.0% by weight, based on the weight of the fraction (a), or a propylene-ethylene copolymer containing from 0.5 to 7.0% by weight, preferably from 1.0 to 6.0% by weight, more preferably from 1.5 to 4.5% by weight, based on the weight of the polymer fraction (a), of units deriving from ethylene, the copolymer having solubility in xylene at 25°C equal to or lower than 12.0% by weight, based on the weight of the polymer fraction (a); and/or

[0037] - melt flow rate MFR(a) (ISO 1133-1 :2011, 230°C/2.16 kg) ranging from 10 to 150 g/lOmin, more preferably from 30 to 120 g/lOmin.

[0038] The polymer fraction (b) preferably has at least one, more preferably all, the following features:

[0039] - comprises an ethylene homopolymer having solubility in xylene at 25 °C equal to or lower than 7.0% by weight, based on the weight of the polymer fraction (b), or an ethylene/butene- 1 copolymer containing from 0.1 to 20.0% by weight, preferably from 5.0 to 15.0% by weight, more preferably from 7.0 to 12.0% by weight of units deriving from butene- 1, based on the weight of the polymer fraction (b) and having solubility in xylene at 25°C equal to or lower than 25.0% by weight, preferably equal to or lower than 17.0% by weight, based on the weight of the polymer fraction (b); and/or

[0040] - density (ISO 1183-l/A:2019 at 23°C) in the range from 940 to 965 Kg/m³.

[0041] In one embodiment, the polymer fraction (c) comprises an ethylene-propylene copolymer containing from 45.0 to 70.0% by weight of units deriving from ethylene, preferably from 45.0 to 65.0% by weight, more preferably from 50.0 to 60.0% by weight, based on the weight of the polymer fraction (c), and has solubility in xylene at 25°C of from 65.0 to 95.0% by weight, preferably from 75.0 to 85.0% by weight, based on the weight of the polymer fraction (c).

[0042] In a preferred embodiment, the polymer fraction (c) comprises an ethylene/propylene/butene-1 terpolymer containing:

[0043] - from 45.0 to 65.0% by weight, preferably from 48.0 to 62.0% by weight, more preferably from 50.0 to 57.0% by weight, of units deriving from ethylene, based on the weight of the fraction (c); [0044] - from 10.0 to 30.0% by weight, preferably from 12.0 to 25.0% by weight, more preferably from 15.0 to 22.0% by weight, of units derived from butene- 1, based on the weight of fraction (c), and

[0045] - up to and including 100% by weight, based on the weight of fraction (c), with units deriving from propylene; preferably from 5 to 45% by weight, more preferably from 13 to 40% by weight, still preferably from 21 to 35% by weight, of units deriving from propylene, based on the weight of fraction (c).

[0046] Preferably, the polyolefin composition (I) has at least one, more preferably all, the following features:

[0047] - melt flow rate MFR(I) (ISO 1133-1:2011, 230°C/2.16 kg) in the range from 0.5 to

10.0 g/lOmin, more preferably from 1.0 to 5.0 g/lOmin; and/or

[0048] - xylene soluble fraction XS(I) at 25°C equal to or lower than 60.0% by weight, preferably in the range from 30.0 to 55.0% by weight, based on the total weight of fractions (a), (b) and (c); and/or

[0049] - density (ISO 1183-l/A:2019 at 23°C) equal to or lower than 910 Kg/m³, preferably in the range of from 890 to 910 Kg/m³, more preferably from 895 to 905 Kg/m³.

[0050] The polyolefin composition (I) is more preferably endowed also with at least one, more preferably all, the following features:

[0051] - the ratio of the density [Kg/m³] to the total ethylene content (wt.%) is equal to or lower than 25, preferably equal to or lower than 20, more preferably equal to or lower than 18; and/or

[0052] - total ethylene content equal to or greater than 50.0% by weight, based on the weight of the polyolefin composition (I); and/or

[0053] - Charpy impact strength (ISO 179-1 :2010 eA) equal to or greater than 50 kJ/m² at

23°C, preferably also not higher than 100 kJ/m² at 23°C; and/or

[0054] - Charpy impact strength (ISO 179-1 :2010 eA) equal to or greater than 85 kJ/m² at -

40°C, preferably also not higher than 180 kJ/m² at -40°C; and/or

[0055] - Tensile modulus (ISO 527-1 , -2) in the range of from 120 to 350 MPa, preferably from

170 to 300 MPa; and/or [0056] - Vicat softening temperature (ISO 306, A50) equal to or greater than 60°C, preferably equal to or greater than 70°C more preferably ranging from 70° to 90°C; and/or

[0057] - Heat Deflection Temperature B (ISO 75B-l,-2, 0.45 MPa, 48h, unannealed) in the range of from 33° to 50°C, preferably from 35° to 43°C; and/or

[0058] - Thermal conductivity at 90°C equal to or greater than 220.0 mV/m»K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range of from 250.0 to 280.0 mV/m«K, wherein the thermal conductivity is measured with the method described in the example section.

[0059] The polyolefin composition (I) is preferably prepared by polymerizing the relevant monomers in sequential polymerization stages, with all polymerization stages but the first being conducted in the presence of the polymeric material formed and the catalyst used in the immediately preceding polymerization stage. Preferably, the polymer fraction (a) is prepared in a first polymerization stage, the polymer fraction (b) is prepared in a second polymerization stage, and the polymer fraction (c) in a third polymerization stage, each stage following the first polymerization stage being carried out in the presence of the polymeric material prepared in the immediately preceding polymerization stage. The amounts of fractions (a), (b) and (c) correspond to the split between the polymerization stages. Each polymerization stage is carried out in at least one polymerization reactor.

[0060] The polymerization stages are preferably carried out in the presence of a Ziegler-Natta catalyst. More preferably, the polymerization stages are carried out in the presence of a Ziegler- Natta catalyst comprising the reaction product of:

[0061] i) a solid catalyst component comprising Ti, Mg, Cl, and at least an internal electron donor compound;

[0062] ii) an alkylaluminum compound and,

[0063] iii) an external electron-donor compound.

[0064] The internal electron donor compound is preferably selected from ethers, ketones, lactones, organic compounds containing N, P and/or S atoms, and esters of mono or di carboxylic organic acids, such as benzoates, malonates, phthalates and certain succinates. Examples of internal donors are described in US4,522,930, EP045977A2 and international patent applications WOOO/63261 and W001/57099. Particularly suited are the phthalic acid esters, such as diisobutyl, dioctyl and diphenyl phthalate, benzyl-butyl phthalate and succinic acid esters. Further internal electron donor compounds particularly suited are 1,3-diethers, as illustrated in EP361493A1 and EP728769.

[0065] The particles of solid component (i) can have substantially spherical morphology and average diameter ranging between 5 and 150pm, preferably from 20 to 100pm and more preferably from 30 to 90pm. 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.

[0066] According to one method, the solid catalyst component (i) 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 USP4,399,054 and US4,469,648. 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 of 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; the mixture is heated up to 80°-130°C and kept at this temperature for 0.5-2 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.

[0067] The alkyl-Al compound (ii) is preferably 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. The Al/Ti ratio is higher than 1 and may preferably range between 50 and 2000.

[0068] Among external electron preferred are silicon compounds having the general formula: (R¹)a(R²)bSi(OR³)c, where 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; R¹, R², and R³, are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

[0069] Particularly preferred are the silicon compounds (iii) in which a is 1, b is 1, c is 2, at least one of R¹ and R² is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms, optionally containing heteroatoms, and R³ is a Cl -CIO alkyl group, in particular a methyl group. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (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.

[0070] Silicon compounds in which a is 0, c is 3, R² is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R³ is methyl are also preferred. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.

[0071] The external electron donor compound (iii) is used in such an amount to give a molar ratio between the organoaluminum compound and said external electron donor compound (iii) of from 0.1 to 200, preferably from 1 to 100 and more preferably from 3 to 50.

[0072] All the polymerization stages preferably occur in gas phase. The reaction temperature of each polymerization stage is independently selected from values from 40° to 90°C. The pressure of each polymerization stage independently ranges from 5 to 30 bar. The residence times of the two stages depend on the desired ratio between the fractions (a) and (b), and preferably range from 15 minutes to 8 hours. Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen or ZnEt2), are optionally used.

[0073] Examples of polymerization processes for the preparation of the polyolefin composition (I) can be found in W02020/148105, W02020/148106 and W02020/144102, the relevant part of which is incorporated herein by reference. [0074] If needed, the polymer obtained at the end of the polymerization reaction can be optionally subject to a chemical treatment with organic peroxides in order to lower the average molecular weight and to increase the melt flow rate up to the value needed for specific applications. [0075] Optionally, the polyolefin composition (I) comprises up to and including 5.0% by weight, more preferably from 0.01% to 5.0% by weight, of an additive (d) preferably selected from the group consisting of nucleating agents, anti-oxidants, light stabilizers, slipping agents, antiacids, melt stabilizers, pigments and combinations thereof, wherein the amount of the additive (d) is based on the total weight of the polyolefin composition (I) including the additive.

[0076] The polyolefin composition (I) has good thermal conductivity and a good balance of physical-mechanical properties and it is particularly but not exclusively suited to be used in an insulating layer for power cables.

[0077] The cable of the present disclosure comprises at least one electrical conductor, wherein the electrical conductor is at least one metal wire or rod, preferably the electrical conductor is a bundle of wires.

[0078] In a preferred embodiment, the electrical conductor is made of aluminium or copper.

[0079] The cable of the present disclosure is preferably a power cable, transferring energy at any voltage level, like at low voltage (LV, below 1 kV), at medium voltage (MV, from 1 kV to 35 kV), at high voltage (HV, above 35 kV) or at extra high voltage (EHV, above 35 kV).

[0080] The cable of the present disclosure optionally comprises one or more semi-conductive layers interposed between the electrical conductor and the thermoplastic layer comprising the polyolefin composition (I), the thermoplastic layer being the insulating layer. Preferably the cable of the present disclosure further comprises a jacketing layer surrounding the insulating layer.

[0081] The cable of the present disclosure is prepared by extruding the thermoplastic layer comprising the polyolefin composition (I) around the electrical conductor or around the semi- conductive layers surrounding the electrical conductor, if present. One or more semi-conductive layers and/or jacketing layers are optionally extruded over the thermoplastic layer comprising the polyolefin composition (I).

[0082] In the cable of the present disclosure, the thermoplastic layer comprising or consisting of the polyolefin composition (I) preferably has thermal conductivity at 90°C equal to or greater than 220.0 mV/m»K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range from 250.0 to 280.0 mV/m»K, wherein the thermal conductivity is measured with the method described in the example section.

[0083] In a further aspect, the present disclosure provides a method to insulate an electrical conductor comprising the steps of:

[0084] (i) providing an electrical conductor;

[0085] (ii) providing the polyolefin composition (I) as described in the foregoing; and

[0086] (iii) surrounding the electrical conductor with the polyolefin composition (I).

[0087] Preferably, the step (i) comprises providing at least one metal wire or rod, more preferably a bundle of wires.

[0088] Preferably the at least one electrical conductor is made of aluminum or copper.

[0089] Preferably, step (iii) is carried out by surrounding the electrical conductor with a continuous layer of the polyolefin composition (I). In a preferred embodiment, step (iii) comprises extruding the polyolefin composition (I) over the electrical conductor, thereby forming an insulating thermoplastic layer comprising or consisting of the polyolefin composition (I).

[0090] In a further aspect, the present disclosure provides the use of the polyolefin composition

(I) as described in the foregoing to form an insulating layer over an electrical conductor.

[0091] In particular, the polyolefin composition (I) is used according to the present disclosure to form an insulating layer with thermal conductivity of 220.0 mV/m«K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range from 250.0 to 280.0 mV/m»K, over an electrical conductor, wherein the thermal conductivity is measured with the method described in the example section.

[0092] Preferably, the polyolefin composition (I) is used according to the present disclosure to form an insulating layer over an electrical conductor being one or more metal wires or rods, preferably comprising or consisting of aluminum or copper.

[0093] Accordingly, in a further aspect, the present disclosure refers to a method for making a power cable comprising an electrical conductor and an insulating layer comprising:

[0094] (I) providing an electrical conductor,

[0095] (II) providing a polyolefin composition (I) as described in the foregoing; and

[0096] (III) at least partially surrounding the electrical conductor with the polyolefin composition (I), [0097] wherein the insulating layer has thermal conductivity at 90°C of 220.0 mV/m»K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range from 250.0 to 280.0 mV/m»K, and wherein the thermal conductivity is measured with the method described in the example section.

[0098] Step (I) comprises providing an electrical conductor being preferably one or more metal wires or rods, preferably comprising or consisting of aluminum or copper.

[0099] Preferably, step (III) is carried out by completely surrounding, the electrical conductor with a continuous layer comprising or consisting of the polyolefin composition (I). In a preferred embodiment, step (III) comprises extruding a continuous layer comprising or consisting of the polyolefin composition (I) over the electrical conductor, thereby forming an insulating thermoplastic layer comprising or consisting of the polyolefin composition (I).

[0100] The features describing the subject matter of the present disclosure are not inextricably linked to each other. Hence, preferred ranges of one feature may be combined with more or less preferred ranges of a different feature, independently from their level of preference.

EXAMPLES

[0101] The following examples are given to illustrate the present invention without limiting purpose.

[0102] CHARACTERIZATION METHODS: the following methods are used to determine the properties indicated in the description, claims and examples.

[0103] Melt Flow Rate: Determined according to the method ISO 1133-1 :2011 (230°C/2.16 kg).

[0104] Solubility in xylene at 25°C: 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) can be 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.

[0105] Ethylene content of propylene-ethylene copolymers by NMR: 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. The peak of the SPP carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode”, C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. The samples were dissolved in l,l,2,2-tetrachloroethane-d2 at 120°C with a 8 % wt/v concentration. Each spectrum was 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 were made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with 8-titanium trichloride- diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:

PPP = 100 Tpp/S PPE = 1OO TP8/S EPE = 100 T88/S

PEP = 100 SPP/S PEE= 100 SP5/S EEE = 100 (0.25 Sy8+0.5 S88)/S

S = TPP + TP8 + T88 + SPP + Sp8 + 0.25 Sy8 + 0.5 S88

[0106] The molar percentage of ethylene content was evaluated using the following equation: E% mol = 100 * [PEP+PEE+EEE]

[0107] The weight percentage of ethylene content was evaluated using the following equation: 100 * E% mol * MWE

E% wt. = >

E% mol * MWE + P% mol * MWp

[0108] where P% mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

[0109] The tacticity of Propylene sequences was 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).

[0110] Density: determined according to ISO 1183-l/A:2019 at 23°C.

[0111] Tensile properties: determined according to ISO 527-1, -2 on 4mm-thick injection molded t-bars.

[0112] Charpy impact strength: determined according to ISO 179-1 :2010 eA on 4mm-thick injection molded t-bars.

[0113] Preparation of injection molded specimens: test specimens 80 x 10 x 4 mm were obtained according to the method ISO 1873-2:2007.

[0114] Vicat softening temperature: ISO 306, A50.

[0115] Heat deflection temperature: ISO 75B-l,-2, 0.45 MPa, 48h, unannealed.

[0116] Thermal conductivity: 75 x 75 x 6mm injection molded plaques were tested at 90°C using Hot Disk® instrument TPS 3500, operating on the basis of the method ISO/FDIS 22007-2. Testing conditions: bulk module; sensor 5465 (r=3.189mm); power 15 mW; time=40 s.

[0117] Volume resistivity: ASTM D257.

[0118] Dielectric strength: ASTM D149.

[0119] Examples E1-E3 and comparative example CE4

[0120] The following polyolefin compositions were tested:

[0121] PP(1): the polyolefin composition was prepared according to the procedure reported in example 1 of W02020/148105A1 and has the following composition:

- 22% by weight of a polymer fraction (a) comprising a propylene homopolymer having solubility in xylene at 25°C of 4.5% by weight and a MFR(a) of 45 g/lOmin;

- 34% by weight of a polymer fraction (b) comprising an ethylene homopolymer having solubility in xylene at 25°C of 3.8% by weight; and - 44% by weight of a fraction (c) comprising an ethylene-propylene-butene terpolymer containing 53% by weight of units deriving from ethylene and 16 % by weight of units deriving from butene- 1, wherein the amounts of polymer fraction (a), (b) and (c) are based on the total weight fractions (a), (b) and (c).

The composition was additivated with 0.1% by weight of Irganox 1010 (Pentaerythritol tetrakis(3- (3,5-di-tert-butyl-4-hydroxyphenyl)propionate marketed by BASF) and 0.1% by weight of Irgafos 168 (Tris(2,4-di-tert-butylphenyl) phosphite marketed by BASF), based on the total weight of the additivated composition. The characterization is reported in table 1.

[0122] PP(2): the polyolefin composition was prepared according to the procedure reported in example 1 of W02020/148106A1. The polyolefin composition comprises:

- 22% by weight of a polymer fraction (a) comprising a propylene-ethylene copolymer containing 3.0% by weight of units deriving from ethylene, having solubility in xylene at 25°C of 9.3% by weight and a MFR(a) of 100 g/lOmin;

- 34% by weight of a polymer fraction (b) comprising an ethylene homopolymer having solubility in xylene at 25°C of ca. 6.8% by weight; and

- 44% by weight of a fraction (c) comprising an ethylene-propylene-butene terpolymer containing 53% by weight of units deriving from ethylene and 16 % by weight of units deriving from butene- 1, wherein the amounts of polymer fraction (a), (b) and (c) are based on the total weight fractions (a), (b) and (c).

[0123] PP(3): the polyolefin composition was prepared according to the procedure reported in example 1 of W02020/144102A1. The polyolefin composition comprises:

- 20% by weight of a polymer fraction (a) comprising a propylene homopolymer having solubility in xylene at 25°C of 4.2% by weight and a MFR(a) of 100 g/lOmin; - 34% by weight of a polymer fraction (b) comprising an ethylene-butene copolymer containing 10.5% by weight of units deriving from butene-1, having solubility in xylene at 25°C of ca. 14.2% by weight; and

- 46% by weight of a fraction (c) comprising an ethylene-propylene copolymer containing 54% by weight of units deriving from ethylene and having solubility in xylene of 81% by weight, based on the weight of the ethylene-propylene copolymer, wherein the amounts of polymer fraction (a), (b) and (c) are based on the total weight fractions (a), (b) and (c).

[0124] CA7441A: Hifax CA7441 A marketed by LyondellBasell.

Table 1

Claims

CLAIMS What is claimed is:

1. A cable comprising an electrical conductor and a thermoplastic layer surrounding the electrical conductor, wherein the thermoplastic layer comprises a polyolefin composition (I) comprising:

- from 10 to 40% by weight of a fraction (a) comprising a propylene homopolymer or copolymer with up to and including 10.0% by weight, based on the weight of fraction (a), of a comonomer selected from ethylene and C4-C10 alpha-olefins, the fraction (a) having solubility in xylene at 25°C equal to or lower than 15.0% by weight, based on the weight of fraction (a);

- from 20 to 60% by weight of a fraction (b) comprising an ethylene homopolymer or an ethylene copolymer with a comonomer selected from C4-C10 alpha-olefins, the ethylene copolymer containing at least 75.0% by weight of units deriving from ethylene, based on the weight of fraction (b); and

- from 30 to 60% by weight of a fraction (c) comprising an ethylene copolymer with at least one comonomer selected from propylene and C4-C10 alpha-olefins, the copolymer containing from 40.0 to less than 75.0% by weight of units deriving from ethylene, based on the weight of fraction (c), wherein the amount of fractions (a), (b) and (c) is based on the total weight of fractions (a), (b) and (c).

2. The cable according to claim 1, wherein the polyolefin composition (I) comprises:

- from 10 to 30% by weight of fraction (a),

- from 30 to 40% by weight of fraction (b), and

- from 40 to 50% by weight of fraction (c).

3. The cable according to any one of the preceding claims, wherein the fraction (a) has melt flow rate MFR(a) in the range from 10 to 150 g/lOmin, preferably from 30 to 120 g/lOmin (ISO 1133-1:2011, 230°C/2.16 kg).

4. The cable according to any one of the preceding claims, wherein the fraction (a) comprises a propylene homopolymer having solubility in xylene equal to or lower than 5.0% by weight, based on the weight of the fraction (a), or a propylene-ethylene copolymer containing from 0.5 to 7.0% by weight, preferably from 1.0 to 6.0% by weight, more preferably from 1.5 to 4.5% by weight, based on the weight of the polymer fraction (a), of units deriving from ethylene, the copolymer having solubility in xylene at 25 °C equal to or lower than 12.0% by weight, based on the weight of the polymer fraction (a).

5. The cable according to any one of the preceding claims, wherein the polymer fraction (b) comprises an ethylene homopolymer having solubility in xylene at 25 °C equal to or lower than 7.0% by weight, based on the weight of the polymer fraction (b), or an ethylene/butene- 1 copolymer containing from 0.1 to 20.0% by weight, preferably from 5.0 to 15.0% by weight, more preferably from 7.0 to 12.0% by weight of units deriving from butene- 1, based on the weight of the polymer fraction (b), the copolymer having solubility in xylene at 25°C equal to or lower than 25.0% by weight, preferably equal to or lower than 17.0% by weight, based on the weight of the polymer fraction (b).

6. The cable according to any one of the preceding claims, wherein the polymer fraction (b) has density in the range from 940 to 965 Kg/m³ (ISO 1183-l/A:2019 at 23°C).

7. The cable according to any one of the preceding claims, wherein the polymer fraction (c) comprises a terpolymer of propylene, ethylene and butene- 1 containing, based on the weight of the polymer fraction (c):

- from 45.0 to 65.0% by weight, preferably from 48.0 to 62.0% by weight, more preferably from 50.0 to 57.0% by weight, of units deriving from ethylene;

- from 10.0 to 30.0% by weight, preferably from 12.0 to 25.0% by weight, more preferably from 15.0 to 22.0% by weight, of units derived from butene- 1, and

- up to 100% by weight with units deriving from propylene.

8. The cable according to any one of the preceding claims, wherein the polyolefin composition (I) has melt flow rate MFR(I) in the range from 0.5 to 10.0 g/lOmin, preferably from 1.0 to 5.0 g/10 min (ISO 1133-1 :2011, 230°C/2.16 kg).

9. The cable according to any one of the preceding claims, wherein the polyolefin composition (I) has density equal to or lower than 910 Kg/m³, preferably in the range from 890 to 910 Kg/m³, more preferably from 895 to 905 Kg/m³ (ISO 1183-l/A:2019 at 23°C).

10. The cable according to any one of the preceding claims, wherein the polyolefin composition (I) further comprises up to and including 5.0% by weight, preferably from 0.01 to 5.0 % by weight, based on the total weight of the polyolefin composition (I), of at least one additive (d) preferably selected from the group consisting of nucleating agents, anti-oxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, pigments and combinations thereof.

11. The cable according to any one of the preceding claims, wherein the electrical conductor is at least one metal wire or rod, preferably is a bundle of wires.

12. The cable according to any one of the preceding claims, wherein the electrical conductor is made of aluminum or copper.

13. A method to insulate an electrical conductor comprising the steps of:

(i) providing an electrical conductor;

(ii) providing a polyolefin composition (I) according to any one of claims 1-10;

(iii) surrounding the electrical conductor with the polyolefin composition (I) as described in any one of claims 1-10.

14. The method of claim 13, wherein step (i) comprises providing at least one metal wire or rod, preferably a bundle of wires.

15. The method of claim 13 or 14, wherein the electrical conductor is made of aluminum or copper.

16. Use of the polyolefin composition (I) as described in any one of claims 1-10 to form an insulating layer over an electrical conductor.

17. Use according to claim 16 wherein the insulating layer has thermal conductivity of 220.0 mV/m»K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range from 250.0 to 280.0 mV/m»K, wherein the thermal conductivity is measured with the method described in the example section.

18. Use according to claim 16 or 17 wherein the electrical conductor is one or more metal wires or rods, preferably comprising or consisting of aluminum or copper.

19. A method for making a power cable comprising an electrical conductor and an insulating layer comprising:

(I) providing an electrical conductor,

(II) providing a polyolefin composition (I) as described in any one of claims from 1 to 10; and

(III) at least partially shielding the electrical conductor with the polyolefin composition (I), wherein the insulating layer has thermal conductivity at 90°C of 220.0 mV/m»K, preferably equal to or greater than 230.0 mV/m»K, more preferably in the range from 250.0 to 280.0 mV/m«K, and wherein the thermal conductivity is measured with the method described in the example section.

20. Method according to claim 19 wherein the electrical conductor is one or more metal wires or rods, preferably comprising or consisting of aluminum or copper.

1. Method according to claim 19 or 20 wherein step (III) comprises extruding the polyolefin composition (I) over the electrical conductor, thereby forming an insulating thermoplastic layer comprising the polyolefin composition (I).