Polypropylene composition for cable insulation

Abstract

The present invention relates to a flexible polypropylene composition comprising a copolymer of propylene (A) and an epoxidized natural oil (B), an article comprising said polypropylene composition, preferably a cable comprising an insulation layer comprising said polypropylene composition and the use of said polypropylene composition as cable insulation and / or as semiconductive layer for medium and high voltage cables.

Description

[0001]Polypropylene composition for cable insulation The present invention relates to a flexible polypropylene composition, an article comprising said polypropylene composition, preferably a cable comprising an insulation layer comprising said polypropylene composition and the use of said polypropylene composition as cable insulation and / or as semiconductive layer for medium and high voltage cables. Technical background Nowadays, ethylene polymer products are used as insulation and semiconducting shields for medium and high voltage cables, due to easy processability and their beneficial electrical properties. In addition, in low voltage applications polyvinyl chloride (PVC) is also commonly used as insulation material, usually in combination with softeners to reach desirable softness of cables. PVC is a thermoplastic which by incorporation of various plasticizers can be used in a wide temperature range. For standard PVC a continuous conductor temperature of max.70°C is normal. At low temperatures PVC becomes rigid and usage temperatures below -10°C should be avoided. At conductor temperatures over 100°C the plasticizers migrate out and the materials lose their flexibility. However, with the addition of special plasticizers and stabilizers, PVC materials can be produced for conductor temperatures of 90-105°C. But in essence, PVC is mainly used for the 1 kV area, as the higher permittivity and dissipation factor of the material means that the losses increase too much at higher voltages and therefore PVC cables are normally not used over 1 kV. In addition, softeners have to be added to PVC in order to maintain a high level of flexibility. Insufficient amounts of softeners reduce low temperature properties of PVC significantly. From an environmental point of view, these softeners are not always regarded as problem-free, making them desirable to eliminate. WO 2014 / 082750 discloses the use of epoxidized oils as softener for PVC-based cable layers. Especially for medium, high and extra high voltage (MV, HV and EHV) cables insulation material presently is dominated by crosslinked ethylene polymer (XLPE) products. These products have a high operation temperature, a high electric breakdown strength and good mechanical properties. Due to crosslinking XLPE has thermosetting properties. Lately, attempts were made using thermoplastic material and especially thermoplastic propylene polymers as insulation material for medium, high and extra high voltage (MV, HV and EHV) cables. Further, transmission system operators are expressing an increasing interest for recycling cable components at end-of-life. Thus, there is an increasing interest in polymer compositions based on thermoplastic propylene polymers for insulation layers of medium voltage (MV), high voltage (HV), extra high voltage (EHV) and high-voltage direct current (HVDC) cables. Thereby, the propylene polymers need to show a good balance of properties as regards flexibility, mechanical properties, impact properties and electrical breakdown strength. Thus, there is a need in the art for polypropylene compositions suitable for cable insulation and shows a good balance of properties as regards flexibility, mechanical properties, impact properties and electric breakdown strength, when used as cable insulation for MV or HV cables. Summary of the invention In one aspect the present invention relates to a polypropylene composition comprising(A) from 90.0 to 99.99 wt.-%, preferably from 92.5 to 99.9 wt.%, more preferably from95.0 to 99.8 wt.-%, most preferably from 97.5 to 99.5 wt.-%, based on the total weight of the polypropylene composition, of a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms having a total comonomer content, preferably a total ethylene content, of from 10.0 to 16.0 wt.-%, preferably from 11.0 to 15.0 wt.-%, most preferably from 12.0 to 14.0 wt.-%, based on the total weight of the copolymer of propylene (A) and determined by quantitative13C{1H} NMR measurement; a melt flow rate MFR2of from 0.5 to 2.5 g / 10 min, preferably from 0.8 to 2.3 g / 10 min, still more preferably from 1.0 to 2.0 g / 10 min and most preferably from 1.2 to 1.7 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; and a xylene cold soluble (XCS) fraction in a total amount of from 25.0 to 50.0 wt%, preferably from 27.5 to 45.0 wt%, more preferably from 30.0 to 42.5 wt% and most preferably from 32.5 to 40.0 wt%, based on the total weight amount of the copolymer of propylene (A) and determined according to ISO16152; and(B) from 0.01 to 10.0 wt.-%, preferably from 0.1 to 7.5 wt.-%, more preferably from 0.2to 5.0 wt.-%, most preferably from 0.5 to 2.5 wt.-%, based on the total weight of the polypropylene composition, of an epoxidized natural oil. In another aspect the present invention relates to an article comprising the polypropylene composition as described above or below. Preferably said article is a cable comprising an insulation layer comprising the polypropylene composition as described above or below. In yet another aspect the present invention relates to the use of the polypropylene composition as described above or below as cable insulation and / or as semiconductive layer for medium and high voltage cables. Definitions A heterophasic polypropylene is a propylene-based copolymer with a semi-crystalline matrix phase, which can be a propylene homopolymer or a random copolymer of propylene and at least one alpha-olefin comonomer, and an elastomeric phase dispersed therein. The elastomeric phase can be a propylene copolymer with a high amount of comonomer, which is not randomly distributed in the polymer chain but are distributed in a comonomer-rich block structure and a propylene-rich block structure. A heterophasic polypropylene usually differentiates from a one-phasic propylene copolymer in that it shows two distinct glass transition temperatures Tg which are attributed to the matrix phase and the elastomeric phase. A propylene homopolymer is a polymer, which essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes a propylene homopolymer can comprise up to 0.1 mol% comonomer units, preferably up to 0.05 mol% comonomer units and most preferably up to 0.01 mol% comonomer units. A propylene random copolymer is a copolymer of propylene monomer units and comonomer units in which the comonomer units are distributed randomly over the polypropylene chain. Thereby, a propylene random copolymer includes a fraction, whichis insoluble in xylene – xylene cold insoluble (XCI) fraction – in an amount of at least 85wt%, most preferably of at least 88 wt%, based on the total amount of propylene random copolymer. Accordingly, the propylene random copolymer does not contain an elastomeric polymer phase dispersed therein. Usually, a propylene polymer comprising at least two propylene polymer fractions (components), which have been produced under different polymerization conditions resulting in different (weight average) molecular weights and / or different comonomer contents for the fractions, preferably produced by polymerizing in multiple polymerization stages with different polymerization conditions, is referred to as “multimodal”. The prefix “multi” relates to the number of different polymer fractions the propylene polymer is consisting of. As an example of multimodal propylene polymer, a propylene polymer consisting of two fractions only is called “bimodal”, whereas a propylene polymer consisting of three fractions only is called “trimodal”. A unimodal propylene polymer only consists of one fraction. Thereby, the term “different” means that the propylene polymer fractions differ from eachother in at least one property, preferably in the weight average molecular weight – whichcan also be measured in different melt flow rates of the fractions – or comonomercontent or both. Vis-breaking is a post reactor chemical process for modifying semi-crystalline polymers such as propylene polymers. During the vis-breaking process, the propylene polymer backbone is degraded, for example by means of peroxides, such as organic peroxides, via beta scission. The degradation is generally used for increasing the melt flow rate and narrowing the molecular weight distribution. In the following amounts are given in % by weight (wt%) unless it is stated otherwise. Detailed description of the invention In one aspect the present invention relates to a polypropylene composition comprising(A) from 90.0 to 99.99 wt.-%, preferably from 92.5 to 99.9 wt.%, more preferably from95.0 to 99.8 wt.-%, most preferably from 97.5 to 99.5 wt.-%, based on the total weight of the polypropylene composition, of a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms having a total comonomer content, preferably a total ethylene content, of from 10.0 to 16.0 wt.-%, preferably from 11.0 to 15.0 wt.-%, most preferably from 12.0 to 14.0 wt.-%, based on the total weight of the copolymer of propylene (A) and determined by quantitative13C{1H} NMR measurement; a melt flow rate MFR2 of from 0.5 to 2.5 g / 10 min, preferably from 0.8 to 2.3 g / 10 min, still more preferably from 1.0 to 2.0 g / 10 min and most preferably from 1.2 to 1.7 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; and a xylene cold soluble (XCS) fraction in a total amount of from 25.0 to 50.0 wt%, preferably from 27.5 to 45.0 wt%, more preferably from 30.0 to 42.5 wt% and most preferably from 32.5 to 40.0 wt%, based on the total weight amount of the copolymer of propylene (A) and determined according to ISO16152; and(B) from 0.01 to 10.0 wt.-%, preferably from 0.1 to 7.5 wt.-%, more preferably from 0.2to 5.0 wt.-%, most preferably from 0.5 to 2.5 wt.-%, based on the total weight of the polypropylene composition, of an epoxidized natural oil.The polypropylene composition preferably comprises the copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms (A) in an amount of from 90.0 to 99.99 wt.-%, preferably from 92.5 to 99.9 wt.%, more preferably from 95.0 to 99.8 wt.-%, most preferably from 97.5 to 99.5 wt.-% and the epoxidized natural oil (B) in an amount of from 0.01 to 10.0 wt.-%, preferably from 0.1 to 7.5 wt.-%, more preferably from 0.2 to 5.0 wt.-%, most preferably from 0.5 to 2.5 wt.-%, all based on the total weight of the polypropylene composition. In the following the copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms (A) is also denoted component (A) and the epoxidized natural oil (B) is also denoted component (B). The polypropylene composition can further comprise polymeric components, which are different from the component (A), in an amount of preferably 0.0 to 10.0 wt% based onthe total weight of the polypropylene composition.In a preferred embodiment the polymeric components of the polypropylene composition consist of component (A). Besides these polymeric components the polypropylene composition can comprise one or more additives in an amount of from 0.0 up to 5.0 wt%, based on the total weight of the polypropylene composition. The one or more additives are preferably selected from acid scavengers, antioxidants, alpha nucleating agents, beta nucleating agents, etc. Such additives are commercially available and for example described in “Plastic Additives Handbook”, 6thedition 2009 of Hans Zweifel (pages 1141 to 1190). Usually, these additives are added in quantities of 1 to 50000 ppm for each single component. Preferably, the polypropylene composition contains from 0 to 5.00 wt.-%, more preferably from 0 to 2.50 wt.-% of the alpha-nucleating agent, based on the total amount of the polypropylene composition. The amount of pure alpha-nucleating agent in the polypropylene composition (without optional carrier polymer of a master batch) is preferably in the range of from 0 to 5000 ppm, more preferably from 0 to 4000 ppm, based on the total amount of the polypropylene composition. The alpha-nucleating agent is generally not restricted. Preferably, the alpha-nucleating agent is selected from soluble alpha-nucleating agents and polymeric alpha-nucleating agents. The alpha-nucleating agent is preferably selected from the group consisting of(i) dibenzylidenesorbitol (e.g. 1,3 : 2,4 dibenzylidenesorbitol) and C1-C8-alkyl-substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g.1,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1,2,3- trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, and(ii) vinylcycloalkane polymer and vinylalkane polymer (as discussed in more detailbelow), and(iii) mixtures thereof.The alpha-nucleating agent is preferably selected from the group consisting of dibenzylidenesorbitol (e.g.1,3 : 2,4 dibenzylidene sorbitol), dibenzylidenesorbitol derivative, preferably dimethyldibenzylidenesorbitol (e.g.1,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4- propylphenyl)methylene]-nonitol, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof. Especially preferred are vinylcycloalkane polymers such as e.g. vinylcyclohexane (VCH) polymers. Such polymers can be added e.g. using Borealis Nucleation Technology (BNT). In a preferred embodiment the alpha-nucleating agent is a soluble alpha-nucleating agent, more preferably a soluble alpha-nucleating agent selected from dibenzylidenesorbitol (e.g.1,3 : 2,4 dibenzylidenesorbitol) and C1-C8-alkyl-substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g.1,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1,2,3- trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol and mixtures thereof. The alpha-nucleating agent can be added to the polypropylene composition as an isolated raw material or in a mixture with a carrier polymer, i.e. in a so-called master batch. The amount of the carrier polymer of the master batch thereby is calculated to the amount of the alpha-nucleating agent. In one embodiment the polypropylene composition comprises an alpha-nucleating agent. In said embodiment, the pure amount of alpha-nucleating agent is preferably in the range of from 0.1 to 5000 ppm, more preferably from 1 to 5000 ppm. In another embodiment, the polypropylene composition does not comprise an alpha- nucleating agent. In said embodiment, the pure amount of alpha-nucleating is 0 ppm. The one or more additives can be added to the components (A) and (B) in a blending step. Thereby, the one or more additives can be added to the polymeric components in form of master batches in which one or more additives are blended with a carrier polymer in concentrated amounts. Any optional carrier polymer is calculated to the amount of additives, based on the total weight of the propylene copolymer composition. The polypropylene composition preferably has a total amount of units derived from ethylene of from 7.5 to 20.0 wt.-%, preferably 8.0 to 18.5 wt.-%, more preferably from9.0 to 17.5 wt.-%, most preferably from 10.0 to 15.0 wt.-%, based on the total amount ofmonomer units in the polypropylene composition. Further, the polypropylene composition preferably has a total amount of units derived from propylene of from 75.0 to 92.5 wt.-%, preferably 76.5 to 92.0 wt.-%, more preferably from 77.5 to 91.0 wt.-% and most preferably from 80.0 to 90.0 wt.-%, based on the total amount of monomer units in the polypropylene composition. Still further, the polypropylene composition preferably has a total amount of epoxy groups per 1000 carbon atoms (EX / 1000 C) of from 0.01 to 2.5 / 1000 C, more preferably from 0.1 to 1.5 / 1000 C, most preferably from 0.2 to 1.0 / 1000 C, determined using1H NMR spectroscopy. The polypropylene composition preferably has a xylene cold soluble (XCS) fraction in a total amount of from 25.0 to 50.0 wt.-%, more preferably from 27.5 to 45.0 wt.-%, still more preferably from 30.0 to 42.5 wt.-% and most preferably from 32.5 to 40.0 wt.-%, based on the total weight amount of the polypropylene composition. The xylene cold soluble (XCS) fraction preferably has a total amount of units derived from ethylene (C2(XCS)) of from 20.0 to 35.0 wt.-%, more preferably from 21.0 to 32.5 wt.-% and most preferably from 22.0 to 30.0 wt.-%, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction. Further, the xylene cold soluble (XCS) fraction preferably has a total amount of units derived from propylene (C3(XCS)) of from 65.0 to 79.0 wt.-%, more preferably from 67.5 to 78.0 wt.-% and most preferably from 70.0 to 77.5 wt.-%, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction. Further, the polypropylene composition has a fraction insoluble in cold xylene (XCI) preferably in a total amount of from 50.0 to 75.0 wt.-%, preferably from 55.0 to 72.5 wt.- %, more preferably from 57.5 to 70.0 wt.-% and most preferably from 60.0 to 67.5 wt.-%,based on the total weight amount of the polypropylene composition. In the polypropylene composition the xylene cold soluble (XCS) fraction and the fraction insoluble in cold xylene (XCI) add to 100 wt% of the polypropylene composition. The fraction insoluble in cold xylene (XCI) preferably has a total amount of units derived from ethylene (C2(XCI)) of from 2.5 to 10.0 wt.-%, preferably from 3.0 to 8.5 wt.-% and most preferably from 4.0 to 7.5 wt.-%, based on the total amount of monomer units in the fraction insoluble in cold xylene (XCI). Further, the fraction insoluble in cold xylene (XCI) preferably has a total amount of units derived from propylene (C3(XCI)) of from 85.0 to 97.5 wt.-%, more preferably from 86.5 to 97.0 wt.-% and most preferably from 87.5 to 96.0 wt.-%, based on the total amount of monomer units in the fraction insoluble in cold xylene (XCI). The polypropylene composition preferably has a good balance of properties in regard of flexibility, mechanical properties, thermal properties and impact properties as illustrated by the following properties: The polypropylene composition preferably has a melt flow rate MFR2 of from 0.5 to 3.0 g / 10 min, more preferably from 0.8 to 2.7 g / 10 min, still more preferably from 1.0 to 2.5 g / 10 min and most preferably from 1.2 to 2.2 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg. The polypropylene composition preferably has a flexural modulus of from 150 MPa to 400 MPa, more preferably of from 175 MPa to 390 MPa and most preferably of from 200 MPa to 380 MPa, determined according to ISO 178 method A. Further, the polypropylene composition preferably has a Charpy notched impact strength at 23°C of from 50 to 110 kJ / m², more preferably from 60 to 100 kJ / m² and most preferably from 65 to 95 kJ / m², determined according to ISO 179-1 / 1eA. Still further, the polypropylene composition preferably has a Charpy notched impact strength at -20°C of from 4.0 to 25.0 kJ / m², more preferably from 4.5 to 20.0 kJ / m² and most preferably from 5.0 to 15.0 kJ / m², determined according to ISO 179-1 / 1eA. Furthermore, the polypropylene composition preferably has a melting temperature Tm of from 140 to 159°C, more preferably from 143 to 157°C and most preferably from 145 to 153°C, determined by to DSC analysis according to ISO 11357. Additionally, the polypropylene composition preferably has a crystallization temperature Tc of from 85 to 130°C, more preferably from 87 to 128°C and most preferably from 90 to 125°C, determined by to DSC analysis according to ISO 11357. The difference of the melting temperature to the crystallization temperature Tm-Tc is preferably in the range of from 35 to 65°C, more preferably 40 to 60°C and most preferably from 45 to 55°C. Further, the polypropylene composition preferably has a shear thinning index SHI1 / 100of from 5.0 to 22.5, more preferably from 7.5 to 20.0 and most preferably from 9.0 to 17.5. Additionally, the polypropylene composition preferably has a polydispersity index PI of from 1.5 to 5.0 s-1, more preferably from 2.0 to 4.5 s-1and most preferably from 2.3 to 4.0 s-1.Preferably, the polypropylene composition is prepared by melt blending the copolymer ofpropylene (A) and the epoxidized natural oil (B), the optional additional polymeric components and the optional further additives, all as described above or below.The polypropylene composition is preferably not subjected to vis-breaking.In one embodiment the polypropylene composition does not comprise, i.e. is free of adielectric fluid different from component (B), such as e.g. described in EP 2739679. In the following, the copolymer of propylene and comonomer units selected fromethylene and alpha-olefins having from 4 to 12 carbon atoms (A) (abbreviated“copolymer of propylene (A)” or component (A)) and the epoxidized natural oil (B)(abbreviated “copolymer of ethylene (B)” or component (B)) are described in more detail. Copolymer of propylene (A) The polypropylene composition according to the invention comprises a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms (A) (in the following “copolymer of propylene (A)”). The comonomer units are selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene or 1-octene. The copolymer of propylene (A) can comprise one type of comonomer units or two or more types such as two types of comonomer units. It is preferred that the copolymer of propylene (A) comprises one type of comonomer units. Especially preferred is ethylene. The copolymer of propylene (A) has a total amount of comonomer units, preferably of ethylene, of from 10.0 to 16.0 wt%, preferably from 11.0 to 15.0 wt%, most preferably from 12.0 to 14.0 wt%, based on the total amount of monomer units in the copolymer of propylene (A) and determined by quantitative13C{1H}-NMR spectroscopy. Further, the copolymer of propylene (A) preferably has a total propylene content of from 84.0 to 90.0 wt.-%, more preferably from 85.0 to 89.0 wt.-%, most preferably from 86.0 to 88.0 wt.-%, based on the total weight of the copolymer of propylene and ethylene and determined by quantitative13C{1H}-NMR spectroscopy. The copolymer of propylene (A) preferably consists of propylene and ethylene. Thus, it is preferred that the total ethylene content and the total propylene content make up 100 wt.-% of the copolymer of propylene and ethylene.The copolymer of propylene (A) has a melt flow rate MFR2 of from 0.5 to 2.5 g / 10 min,preferably from 0.8 to 2.3 g / 10 min, still more preferably from 1.0 to 2.0 g / 10 min and most preferably from 1.2 to 1.7 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg. It is preferred that the copolymer of propylene (A) is a heterophasic copolymer of propylene and ethylene.The heterophasic copolymer of propylene and ethylene has a matrix phase and anelastomeric phase dispersed in said matrix phase. The matrix phase is preferably a propylene-ethylene random copolymer. Heterophasic propylene copolymers are typically characterized by comprising at least two glass transition temperatures. Said two glass transition temperatures can be attributed to the matrix phase (Tg (matrix)) and the elastomeric phase (Tg (EP)). The heterophasic propylene copolymer preferably has a glass transition temperature attributed to the matrix phase Tg (matrix) in the range of from -1.0 to -15.0°C, preferably from -2.5 to -12.5°C and most preferably from -5.0 to -10.0°C. Further, the heterophasic propylene copolymer preferably has a glass transition temperature attributed to the elastomeric phase Tg (EP) in the range of from -40.0 to - 55.0°C, preferably from -42.5 to -52.5°C and most preferably from -45.0 to -50.0°C. In a copolymer of propylene (A), such as a heterophasic propylene copolymer, the matrix phase and the elastomeric phase usually cannot exactly be divided from each other. In order to characterize the matrix phase and the elastomeric phase of aheterophasic polypropylene copolymer several methods are known. One method is theextraction of a fraction, which contains to the most part the elastomeric phase with xylene, thus separating a xylene cold solubles (XCS) fraction from a xylene cold insoluble (XCI) fraction. The XCS fraction contains for the most part the elastomeric phase and only a small part of the matrix phase whereas the XCI fraction contains for the most part the matrix phase and only a small part of the elastomeric phase.The copolymer of propylene (A) preferably has a xylene cold soluble (XCS) fraction in atotal amount of from 25.0 to 50.0 wt%, more preferably from 27.5 to 45.0 wt%, still more preferably from 30.0 to 42.5 wt% and most preferably from 32.5 to 40.0 wt%, based on the total weight amount of the copolymer of propylene (A). The xylene cold soluble (XCS) fraction preferably has an amount of comonomer units, preferably of ethylene, of from 23.0 to 35.0 wt%, more preferably from 23.5 to 32.5 wt% and most preferably from 24.0 wt% to 30.0 wt%, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction. Further, the xylene cold soluble (XCS) fraction preferably has an intrinsic viscosity of from 150 to 350 cm³ / g, preferably from 200 to 325 cm³ / g and most preferably from 225 to 300 cm³ / g, measured in decalin. Additionally, the xylene cold soluble (XCS) fraction preferably has a weight average molecular weight Mw of from 185000 to 350000 g / mol, more preferably from 200000 to 325000 g / mol and most preferably from 210000 to 315000 g / mol. Furthermore, the xylene cold soluble (XCS) fraction preferably has a polydispersity index, being the ratio of the weight average molecular weight and the number average molecular weight Mw / Mn, of from 3.5 to 8.5, preferably from 3.7 to 8.0 and most preferably from 4.0 to 7.5.Further, the copolymer of propylene (A) has a fraction insoluble in cold xylene (XCI)preferably in a total amount of from 50.0 to 75.0 wt%, more preferably from 55.0 to 72.5 wt%, still more preferably from 57.5 to 70.0 wt% and most preferably from 60.0 to 67.5 wt%, based on the total weight amount of the copolymer of propylene (A). The fraction insoluble in cold xylene (XCI) preferably has an amount of comonomer units, preferably of ethylene, of from 3.0 to 9.0 wt%, preferably from 4.0 to 8.5 wt% and most preferably from 4.5 to 7.5 wt%, based on the total amount of monomer units in the fraction insoluble in cold xylene (XCI). Further, the fraction insoluble in cold xylene (XCI) preferably has an intrinsic viscosity of from 185 to 350 cm³ / g, preferably from 220 to 325 cm³ / g and most preferably from 210 to 300 cm³ / g, measured in decalin. Additionally, the fraction insoluble in cold xylene (XCI) preferably has a weight average molecular weight Mw of from 225000 to 450000 g / mol, more preferably from 240000 to 425000 g / mol and most preferably from 260000 to 400000 g / mol. Furthermore, the fraction insoluble in cold xylene (XCI) preferably has a polydispersity index, being the ratio of the weight average molecular weight and the number average molecular weight Mw / Mn, of from 3.5 to 7.5, preferably from 3.7 to 7.0 and most preferably from 4.0 to 6.5. The ratio of the intrinsic viscosities of the XCI fraction to the XCS fraction of the copolymer of propylene is preferably in the range of from 0.9 to 1.5, more preferably from 1.0 to 1.4 and most preferably from 1.0 to 1.3. The copolymer of propylene (A) preferably has a flexural modulus of from 130 MPa to 400 MPa, more preferably of from 150 MPa to 390 MPa and most preferably of from 175 MPa to 380 MPa, determined according to ISO 178 method A. Further, the copolymer of propylene (A) preferably has a Charpy notched impact strength at 23°C of from 50 to 110 kJ / m², more preferably from 65 to 100 kJ / m² and most preferably from 75 to 95 kJ / m², determined according to ISO 179-1 / 1eA. Still further, the copolymer of propylene (A) preferably has a Charpy notched impact strength at -20°C of from 5.0 to 10.0 kJ / m², more preferably from 5.5 to 9.0 kJ / m² and most preferably from 6.0 to 8.0 kJ / m², determined according to ISO 179-1 / 1eA. Furthermore, the copolymer of propylene (A) preferably has a melting temperature Tm of from 140 to 159°C, more preferably from 143 to 157°C and most preferably from 145 to 153°C, determined by to DSC analysis according to ISO 11357. Further, the copolymer of propylene (A) preferably has a crystallization temperature Tc of from 85 to 130°C, more preferably from 87 to 128°C and most preferably from 90 to 125°C, determined by to DSC analysis according to ISO 11357. The difference of the melting temperature to the crystallization temperature Tm-Tc is preferably in the range of from 20 to 65°C, more preferably 25 to 60°C and most preferably from 27 to 55°C. The copolymer of propylene (A) can be polymerized in a sequential multistage polymerization process, i.e. in a polymerization process in which two or more polymerization reactors are connected in series. Preferably, in the sequential multistage polymerization process, two or more, more preferably three or more, such as three or four, polymerization reactors are connected in series. The term “polymerization reactor” shall indicate that the main polymerization takes place. Thus in case the process consists of four polymerization reactors, this definition does not exclude the option that the overall process comprises for instance a pre-polymerization step in a pre- polymerization reactor. When the copolymer of propylene (A) is a heterophasic copolymer of propylene and ethylene, the matrix phase of the heterophasic copolymer of propylene and ethylene is polymerized in first polymerization reactor for producing a unimodal matrix phase or in the first and second polymerization reactor for producing a multimodal matrix phase. The elastomeric phase of the heterophasic copolymer of propylene and ethylene is preferably polymerized in the subsequent one or two polymerization reactor(s) in the presence of the matrix phase for producing a unimodal elastomeric phase or a multimodal elastomeric phase. Preferably, the polymerization reactors are selected from slurry phase reactors, such as loop reactors and / or gas phase reactors such as fluidized bed reactors, more preferably from loop reactors and fluidized bed reactors. A preferred sequential multistage polymerization process is a “loop-gas phase”-process, such as developed by Borealis A / S, Denmark (known as BORSTAR® technology)described e.g. in patent literature, such as in EP 0887379, WO 92 / 12182WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or in WO 00 / 68315.A further suitable slurry-gas phase process is the Spheripol®process of LyondellBasell. Suitable sequential polymerization processes for polymerizing copolymer of propylene (A), preferably the heterophasic copolymer of propylene and ethylene, are e.g. disclosed in WO 2015 / 117948. The copolymer of propylene (A), preferably the heterophasic copolymer of propylene and ethylene can be polymerized in the presence of a Ziegler-Natta catalyst. Suitable Ziegler-Natta catalysts are e.g. disclosed in WO 2015 / 117948. The copolymer of propylene (A) is preferably not subjected to a visbreaking step as e.g. described in WO 2013 / 092620 A1. Heterophasic propylene copolymer resins suitable as copolymer of propylene and ethylene are also commercially available. These resins are usually already additivated with stabilizer packages. Thus, when using commercially available resins as copolymer of propylene (A) the addition of additives as described above might have to be adjusted to the already present additives. In case of a commercially available copolymer of propylene (A) the above stated properties can be measured using a common measurement method or verified by the technical documentation provided by the supplier. Epoxidized natural oil (B) The polypropylene composition according to the invention comprises an epoxidized natural oil (B). A natural oil is a mixture of organic compounds from natural sources comprising triglycerides, i.e. glycerol esters of fatty acids. The triglycerides preferably comprise unsaturated fatty acids and optionally saturated fatty acids. The unsaturated fatty acids are preferably selected from mono-unsaturated fatty acids and poly-unsaturated fatty acids having a hydrocarbon chain with 12 to 26 carbon atoms, preferably with 14 to 22 carbon atoms. Examples of unsaturated fatty acids are myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, alpha-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and docosahexanenoic acid. Epoxidation is introduced into the natural oil by chemical reaction of a peroxide or peracide with the carbon-carbon double bonds e.g. of the unsaturated fatty acids and optionally other components of the natural oil in the presence of a catalyst, thereby forming an oxirane ring. Epoxidation reaction of unsaturated hydrocarbons is well known in the art. The presence and quantification of epoxy-groups in a natural oil can be determined by usual methods such as1H-NMR,13C-NMR or IR spectroscopy, preferably1H-NMR spectroscopy. The epoxidized natural oil (B) can be selected from an epoxidized vegetable natural oil, an epoxidized animal fat, an epoxidized microbial oil and mixtures thereof. Examples of epoxidized vegetable oils are epoxidized canola oil, epoxidized tall oil, epoxidized soybean oil, epoxidized safflower oil, epoxidized linseed oil, epoxidized corn oil, epoxidized sunflower oil, epoxidized olive oil, epoxidized canola oil, epoxidized sesame oil, epoxidized cottonseed oil, epoxidized palm-based oils, epoxidized rapeseed oil, epoxidized tung oil, epoxidized peanut oil, epoxidized jatropha oil, epoxidized castor oil, and mixtures thereof, preferably epoxidized soybean oil, epoxidized lineseed oil,, epoxidized castor oil and mixtures thereof, more preferably epoxidized soybean oil. Examples of epoxidized animal fats are fish oil, lard, tallow and mixtures thereof. Examples of epoxidized microbial oils are algal oil. It is preferred that the epoxidized natural oil (B) is selected from an epoxidized vegetable natural oil, such as epoxidized canola oil, epoxidized tall oil, epoxidized soybean oil, epoxidized safflower oil, epoxidized linseed oil, epoxidized corn oil, epoxidized sunflower oil, epoxidized olive oil, epoxidized canola oil, epoxidized sesame oil, epoxidized cottonseed oil, epoxidized palm-based oils, epoxidized rapeseed oil, epoxidized tung oil, epoxidized peanut oil, epoxidized jatropha oil, epoxidized castor oil, and mixtures thereof, preferably epoxidized soybean oil, epoxidized lineseed oil,, epoxidized castor oil and mixtures thereof. It is especially preferred that the epoxidized natural oil (B) is epoxidized soybean oil. The epoxidized natural oil (B) preferably has a melting temperature Tm of from -20 to 20°C, more preferably from -15 to 15 °C, still more preferably from -10 to 10°C, determinable by to DSC analysis according to ISO 11357. Further, the epoxidized natural oil (B) preferably has a density of from 985 to 1010 kg / m³, more preferably from 987 to 1005 kg / m³, still more preferably from 990 to 1000 kg / m³, determinable according to ASTM D1298. Additionally, the epoxidized natural oil (B) preferably has a kinematic viscosity at 25°C of from 200 to 750 cPs, more preferably from 250 to 600 cPs, still more preferably from 300 to 550 cPs, determinable according to ASTM D445. Furthermore, the epoxidized natural oil (B) preferably has an iodine value of from 0 to 5.0, more preferably from 0.01 to 4.0, still more preferably from 0.1 to 3.0, determinable according to EN 14111:2003. Further, the epoxidized natural oil (B) preferably has an oxirane content of from 4.0 to 15.0 %, preferably from 5.0 to 12.5 %, still more preferably from 6.0 to 10.0 %, determinable according to ASTM D1652-11. Epoxidized natural oils, such as epoxidized soybean oil, suitable as epoxidized natural oils (B) are commercially available. Commerically available epoxidized soybean oil has the Cas. No.8013-07-8. In case of a commercially available epoxidized natural oil the above stated properties can be measured using a common measurement method or verified by the technical documentation provided by the supplier. Semiconductive composition In another aspect, the present invention provides a semiconductive composition comprising the polypropylene composition as described above or below and a conductive filler such as carbon black, preferably a semiconductive composition for use as semiconductive layer for medium and high voltage cables. It is understood that all embodiments and aspects of the polypropylene composition as described above or below apply to the polypropylene composition present in the semiconductive composition. The preferences for the semiconductive composition according to the present invention are described in more detail below. Article In a further aspect the present invention further relates to an article comprising the polypropylene composition as defined above or below. The article is preferably a cable comprising an insulation layer comprising the polypropylene composition as described above or below. The cable usually comprises of at least one conductor and at least one insulation layer comprising the polypropylene composition as described above or below. It is preferred that the insulation layer comprises from 90 to 100 wt.-%, preferably from 95 to 100 wt.-%, still more preferably from 99 to 100 wt.-%, based on the total weight ofthe insulation layer, most preferably consists of the polypropylene composition asdescribed above or below. The term "conductor" means herein above and below that the conductor comprises one or more wires. The wire can be for any use and be e.g. optical, telecommunication or electrical wire. Moreover, the cable may comprise one or more such conductors. Preferably the conductor is an electrical conductor and comprises one or more metal wires. The cable is preferably a power cable. A power cable is defined to be a cable transferring energy operating at any voltage, typically operating at voltages higher than 1 kV. The voltage applied to the power cable can be alternating (AC), direct (DC), or transient (impulse). The polypropylene composition of the invention is very suitable for power cables, especially for power cables operating at voltages 6 kV to 36 kV (medium voltage (MV) cables) and at voltages higher than 36 kV, known as high voltage (HV) cables and extra high voltage (EHV) cables, which EHV cables operate, as well known, at very high voltages. The terms have well known meanings and indicate the operating level of such cables. For low voltage applications the cable system typically either consists of one conductor and one insulation layer comprising the polypropylene composition as described above or below, or of one conductor, one insulation layer comprising the polypropylene composition as described above or below and an additional jacketing layer, or of one conductor, one semiconductive layer and one insulation layer comprising the polypropylene composition as described above or below. For medium and high voltage applications the cable system typically consists of one conductor, one inner semiconductive layer, one insulation layer comprising the polypropylene composition as described above or below and one outer semiconductive layer, optionally covered by an additionally jacketing layer. The semiconductive layers mentioned preferably comprise, more preferably consist of a thermoplastic polyolefin composition, preferably a polyethylene composition or a polypropylene composition, containing a sufficient amount of electrically conducting solid fillers preferably carbon black. It is preferred that the thermoplastic polyolefin composition of the semiconductive layer(s) is a polypropylene composition, more preferably a polypropylene composition comprising a heterophasic propylene copolymer as polymeric component. It is especially preferred that the thermoplastic polyolefin composition of the at least one semiconductive layer, preferably both semiconductive layers of the cable, comprise the same copolymer of propylene as the insulation layer, i.e. the copolymer of propylene as described above or below. In a second embodiment the article is preferably a cable comprising a semiconductive layer comprising a semiconductive composition, which comprises the polypropylene composition as described above or below. It is preferred that the cable comprises an inner semiconductive layer and / or an outer semiconductive layer comprising a semiconductive composition, which comprises the polypropylene composition as described above or below. The semiconductive layer, preferably the inner semiconductive layer and / or an outer semiconductive layer preferably comprises from 90 to 100 wt.-%, preferably from 95 to 100 wt.-%, still more preferably from 99 to 100 wt.-%, based on the total weight of thesemiconductive layer, most preferably consists of the semiconductive composition.The semiconductive composition preferably comprises at least 52.0 wt.-%, preferably from 55.0 to 90.0 wt.-%, more preferably from 60.0 to 85.0 wt.-%, most preferably from 65.0 to 80.0 wt.-% of the polypropylene composition and from 5.0 to 40.0 wt.-%, preferably from 10.0 to 38.0 wt.-%, more preferably from 15.0 to35.0 wt.-%, most preferably from 20.0 to 33.0 wt.-% of a conductive filler, preferablycarbon black, all based on the total weight amount of the semiconductive composition. The semiconductuve composition can further comprise a polyolefin functionalized with amono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acidcompound. Said functionalized polyolefin is preferably present in an amount of not more than 5.0 wt.-%, preferably from 0.05 to 2.5 wt.-%, more preferably from 0.1 to 1.0 wt.-%, most preferably from 0.2 to 0.8 wt.-%, based on the total weight amount of the semiconductive composition.It is understood that all embodiments and aspects of the polypropylene composition asdescribed above or below apply to the polypropylene composition present in thesemiconductive composition according to the invention.Any carbon black which is electrically conductive can be used. Typically, the carbon black will be a speciality carbon black or a P-type black. Non-limiting examples of suitable carbon blacks include furnace blacks. The carbon black may have a nitrogen adsorption surface area (NSA) of 5 to 400 m2 / g, for example of 10 to 300 m2 / g, e.g. of 30 to 200 m2 / g, when determined according to ASTM D6556-19. Further, the carbon black may have one or more of the following properties:i) a primary particle size of at least 5 nm, for example 5 to 30 nm, preferably 10 to 20nm which is defined as the average particle diameter according to ASTM D3849-14,ii) iodine adsorption number of at least 10 mg / g, for example 10 to 300 mg / g,preferably 30 to 250 mg / g, more preferably 30 to 200 mg / g, such as 30 to 60 mg / g, or 80 to 140 mg / g, when determined according to ASTM D-1510-19; and / oriii) oil absorption number (OAN) of at least 30 ml / 100g, for example 30 to 140 ml / 100g,preferably 50 to 130 ml / 100g, more preferably 70 to 130 ml / 100g, when measured according to ASTM D 2414-19. These properties are usually provided in the technical documentation from the supplier of commercial carbon black grades. One group of suitable furnace blacks have a primary particle size of 28 nm or less. Particularly suitable furnace blacks of this category may have an iodine adsorption number between 60 and 300 mg / g. It is further suitable that the oil absorption number (of this category) is between 50 and 225 ml / 100g, for example between 50 and 200 ml / 100g. Other suitable carbon blacks can be made by any other process or can be further treated. Suitable carbon blacks for semiconductive cable layers are suitably characterized by their cleanliness. Therefore, suitable carbon blacks have an ash- content of less than 0.2wt% measured according to ASTM D1506, a 325 mesh sieve residue of less than 30 ppm according to ASTM D1514 and have less than 3 wt%, preferably less than 1 wt% total sulphur according to ASTMD1619.Furnace carbon black is a generally acknowledged term for the well-known carbon blacktype that is produced in a furnace-type reactor. As examples of carbon blacks, the preparation process thereof and the reactors, reference can be made to i.a. EP629222 of Cabot, US 4,391,789, US 3,922,335 and US 3,401,020. As an example of commercial furnace carbon black grades N115, N351, N293, N220 and N550 can be mentioned. Tofurther increase the suitability of such carbon blacks in semiconductive compounds,modifications of these commercial carbon blacks e.g. in terms of cleanliness, pellet properties and surface area are advantageous. Furnace carbon blacks are conventionally distinguished from acetylene carbon blacks."Functionalized with a mono- or polycarboxylic acid compound or a derivative of amono- or polycarboxylic acid compound" or shortly "functionalized" means hereingenerally that the polymer is functionalized with carbonyl containing groups originatingfrom said mono- or polycarboxylic acid group or a derivative thereof. The carbonylcontaining compound used for the functionalization is typically unsaturated. Such compound contains preferably at least one ethylenic unsaturation and at least one carbonyl group. Such carbonyl containing groups can be incorporated to a polymer by grafting a compound bearing said carbonyl containing group(s) or by copolymerising a monomer with a comonomer(s) bearing such carbonyl containing group(s). Herein, the functionalized carbonyl containing compound of functionalized polyolefin is understood not to mean any polar comonomer(s), e.g. an acrylate, a methacrylate or an acetate comonomer. The functionalized polyolefin is different from the copolymer of propylene (A) and the copolymer of ethylene (B). The functionalized polyolefins suitable for the present invention are well known and are commercially available or can be produced according to the known processes described in the chemical literature. Preferable polycarboxylic acid compounds for functionalization are unsaturated dicarboxylic acids or derivatives thereof. More preferable carbonyl containingcompounds for the functionalization are derivatives of unsaturated mono- orpolycarboxylic acid compounds, more preferably derivatives of unsaturated dicarboxylic acids. Preferred carbonyl containing compounds for functionalization are anhydrides of amono- or polycarboxylic acid, which are also referred as "acid anhydrides" or"anhydrides". The acid anhydrides can be linear or cyclic. Preferably, the functionalized polyolefin is an acid anhydride functionalized polyolefin, more preferably a maleic anhydride (MAH) functionalized polyolefin. Preferably, the functionalized polyolefin is obtainable by grafting maleic anhydride to a polyolefin (also referred herein shortly as MAH grafted polyolefin or MAH-g-polyolefin). Preferred polyolefin for functionalized polyolefin is a functionalized polypropylene or polyethylene. Both polyolefin types are well known in the field. In case the functionalized polyolefin is a functionalized polyethylene, then it is preferably selected from a polyethylene produced in a low pressure process using a coordination catalyst or a polyethylene produced in a high pressure (HP) polymerization process and which bears said carbonyl containing groups. Both meanings are well known in the field. The MFR (190°C, 2.16 kg) of the functionalized polyethylene is preferably of above 0.05 g / 10 min, preferably from 0.1 to 200 g / 20 min, preferably from 0.80 to 100 g / 10 min, more preferably from 1.0 to 50.0 g / 10 min. In case the functionalized polyolefin is a functionalized polyethylene produced in a low pressure process using a coordination catalyst, then it is preferably selected from copolymers of ethylene with one or more comonomer(s), preferably alpha-olefin(s). Such polyethylene copolymers have preferably a density of from 850 to 950 kg / m3, preferably from 900 to 945 kg / m3, preferably from 910 to 940 kg / m3. Such functionalized polyethylene copolymer is preferably a functionalized linear low density polyethylene copolymers (LLDPE) which preferably has a density from 915 to 930 kg / m3. Preferable LLDPE as functionalized polyolefin is MAH functionalized LLDPE, preferably MAH-g- LLDPE. In case the functionalized polyolefin is a functionalized polyethylene produced in a HP process, then the polyethylene is preferably produced by radical polymerization in a HP process in the presence of an initiator(s). The HP reactor can be e.g. a well known tubular or autoclave reactor or a mixture thereof, preferably a tubular reactor. The high pressure (HP) polymerization and the adjustment of process conditions for further tailoring the other properties of the polyolefin depending on the desired end application are well known and described in the literature, and can readily be used by a skilled person. Suitable polymerization temperatures range up to 400 °C, preferably from 80 to 350°C and pressure from 70 MPa, preferably 100 to 400 MPa, more preferably from 100 to 350 MPa. Pressure can be measured at least after compression stage and / or after the tubular reactor. Temperature can be measured at several points during all steps. Such functionalized polyethylene produced in a HP process is preferably a low density polyethylene (LDPE) which is functionalized and preferably has a density of from 900 to 950 kg / m3, preferably from 910 to 940 kg / m3, preferably from 915 to 930 kg / m3. More preferably, the functionalized LDPE polymer is selected from a LDPE homopolymer or a LDPE copolymer of ethylene with one or more comonomers (referred herein also as functionalized polar LDPE copolymer), which bears said carbonyl containing groups.Suitable comonomers for functionalized LDPE copolymer are selected from olefins,preferably alpha-olefins, or polar comonomers, or any mixtures thereof. As said above such polar comonomers may additionally be present and are differentiated from the carbonyl containing compounds used for the functionalization. Functionalized LDPE copolymer of ethylene with polar comonomer may optionally comprise other comonomer(s), such as alpha-olefin(s). Polar comonomer is preferably selected from a comonomer containing hydroxyl group(s), alkoxy group(s), carbonyl group(s), carboxyl group(s), ether group(s) or ester group(s), or a mixture thereof, more preferably from a comonomer(s) containing carboxyl and / or ester group(s), still more preferably, the polar comonomer(s) is selected from the group of acrylate(s), methacrylate(s) acrylic acids, methacrylic acids or acetate(s), or any mixtures thereof. The polar comonomer(s) for the functionalized polar LDPE copolymer is more preferably selected from the group of alkyl acrylates, alkyl methacrylates, acrylic acids, methacrylic acids or vinyl acetate, or amixture thereof. It is further preferred that the comonomers are selected from C1- to C6-alkyl acrylates, C1- to C6 -alkyl methacrylates, acrylic acids, methacrylic acids and vinylacetate, more preferred from C1- to C4- alkyl acrylate such as methyl, ethyl, propyl orbutyl acrylate, or vinyl acetate, or any mixture thereof. The amount of the polar comonomer in the functionalized LDPE copolymer is preferably from 5 to 50 wt% based on the total amount of the composition, more preferred up to 30 wt%, most preferred up to 25 wt%. Functionalized LDPE homopolymer or LDPE copolymer is preferably selected from a MAH functionalized LDPE homopolymer, a MAH functionalized LDPE copolymer which is preferably selected from a MAH functionalized ethylene methyl acrylate (EMA), a MAH functionalized ethylene ethyl acrylate (EEA), a MAH functionalized ethylene butyl acrylate (EBA) or MAH functionalized ethyl vinyl acrylate (EVA), more preferably from MAH-g-LDPE homopolymer or MAH-g-LDPE copolymer, more preferably from MAH-g-EMA, MAH-g-EEA, MAH-g-EBA or MAH-g-EVA. In case the functionalized polyolefin is a functionalized polypropylene, then it is preferably selected from homopolymers of propylene, random copolymers of propylene or a heterophasic copolymer of propylene, which have the same meaning and properties as given above under the general description for the copolymer of propylene (A) and which bear said carbonyl containing groups. Preferred polypropylene is homopolymer or a random copolymer of propylene. According to a preferred embodiment of the semiconductive composition, the maleic anhydride functionalized, preferably grafted, polyolefin is maleic anhydride functionalized, preferably grafted, polypropylene (MAH-g-PP) or maleic anhydride functionalized, preferably grafted, polyethylene (MAH-g-PE). Preferred polyolefin for the functionalized polyolefin is a functionalized polypropylene as defined above. Such polypropylene (PP) for the functionalized polyolefin is preferably a maleic anhydride functionalized PP, more preferably MAH-g-PP. The functionalized polyolefin, more preferably the MAH functionalized PP, more preferably MAH-g-PP, has an MFR2 (230°C, 2.16 kg) of from 0.5 to 500 g / 10 min, preferably from 1.0 to 500 g / 10 min. The cable comprising a layer comprising the polypropylene composition according to the invention as described above shows AC electrical breakdown strength in form of Weibull alpha-value and Weibull beta-value. The cable preferably has a Weibull alpha-value of from 40.0 to 75.0 kV / mm, more preferably from 42.5 to 75.0 kV / mm and most preferably from 45.0 to 75.0 kV / mm, when measured on a 10 kV cable in agreement with CENELEC HD 6055.4.15.3.4 for 6 / 10 kV cables. Still further, the cable preferably has a Weibull beta-value of from 5.0 to 250.0, more preferably from 5.5 to 250.0, most preferably from 6.0 to 250.0, when measured on a 10 kV cable in agreement with CENELEC HD 6055.4.15.3.4 for 6 / 10 kV cables. Thus, the insulation layer comprising the polypropylene composition according to the invention can be used for medium and high voltage cables. Alternatively, the semiconductive layer comprising the polypropylene composition according to the invention can be used for medium and high voltage cables. In yet another aspect the present invention relates to the use of the polypropylene composition as described above or below as cable insulation and / or as semiconductive layer for medium and high voltage cables. Said medium and high voltage cables preferably meet all properties requirements as described for the cables above and below. Benefits of the invention: The polypropylene composition shows a good balance of properties regarding high flexibility, a good mechanical strength, good impact properties and high crystallization and melting temperature which allow the use as cable insulation e.g. for medium and high voltage cables at high operation temperatures. The polypropylene composition can be easily compounded to prepare the insulation layer without need of increasing the melt flow rate via visbreaking the composition or the copolymer of propylene (A). Cables comprising an insulation layer comprising the inventive polypropylene composition surprisingly show good AC breakdown strength in form of Weibull alpha- value and Weibull beta-value. Thereby, the addition of the epoxidized natural oil (B) to the polypropylene composition further improves the AC breakdown strength in form of higher Weibull alpha values compared to polypropylene compositions, which only include the copolymer of propylene (A) as polymeric compound. The good AC breakdown strength in form of Weibull alpha-value can be obtained without addition of a dielectric fluid different from the epoxidized natural oil (B) such as e.g. described in EP 2739679. Examples The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined. 1. Measurement methodsa) Melt Flow Rate (MFR2)The melt flow rate is the quantity of polymer in grams which the test apparatus standardized to ISO 1133 or ASTM D1238 extrudes within 10 minutes at a certain temperature under a certain load. The melt flow rate MFR2 of propylene based polymers and the polypropylene composition is measured at 230°C with a load of 2.16 kg according to ISO 1133. The melt flow rate can also be measured according to ASTM D 1238. b) DensityDensity is measured according to ISO 1183. Sample preparation is done by compression moulding in accordance with ISO 17855-2. The density can also be measured according to ASTM D 792.c) Comonomer contentMethod I (HECOs) Comonomer content quantification of poly(propylene-co-ethylene) copolymers Quantitative13C{1H} NMR spectra were recorded in the solution-state using a Bruker Avance NEO 400 NMR spectrometer operating at 400.15 and 100.62 MHz for1H and13C respectively. All spectra were recorded using a13C optimised 10 mm extended temperature probe head at 125°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d2 (TCE-d2) along with chromium-(III)-acetylacetonate (Cr(acac)3) resulting in a 60 mM solution of relaxation agent in solvent {8} and with approximately 3 mg BHT (2,6-di-tert-butyl-4-methylphenol CAS 128-37-0) . To ensure a homogenous solution, after initial samplepreparation in a heat block, the NMR tube was further heated in a rotatory oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup waschosen primarily for the high resolution and quantitatively needed for accurate ethylenecontent quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme {3, 4}. A total of 6144 (6k) transients were acquired per spectra. Quantitative13C{1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed {7}. The comonomer fraction was quantified using the method of Wang et. al. {6} through integration of multiple signals across the whole spectral region in the13C{1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regiodefects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents. For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:E = 0.5 (Sββ + Sβγ + Sβδ + 0.5( Sαβ + Sαγ)) Through the use of this set of sites the corresponding integral equation becomes: E = 0.5 (IH +IG + 0.5(IC + ID)) using the same notation used in the article of Wang et al. {6}. Equations used for absolute propylene content were not modified. The mole percent comonomer incorporation was calculated from the mole fraction: E [mol%] = 100 * fE The weight percent comonomer incorporation was calculated from the mole fraction: E [wt%] = 100 * (fE * 28.06 ) / ( (fE * 28.06) + ((1-fE) * 42.08) ) Bibliographic references:1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30(1997) 6251.3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D.Winniford, B., J. Mag. Reson.187 (2007) 225.4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G.,Macromol. Rapid Commun.2007, 28, 1128.5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.6) Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157.7) Cheng, H. N., Macromolecules 17 (1984), 1950.8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 285 (2009), 475.9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 12530.d) Quantification of Epoxy groupsQuantitative1H NMR spectra recorded in solution-state using a Bruker Avance Neo 400 NMR spectrometer operating at 400.15 and 100.62 MHz for1H and13C respectively. Allspectra were recorded using a 13C optimised 10 mm selective excitation probehead at125°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in approximately 3 ml of 1,2-tetrachloroethane-d2(TCE-d2) along with approximately 3 mg BHT (2,6-di-tert-butyl-4-methylphenol CAS 128-37-0). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory oven until full dissolving of sample. Standard single-pulse excitation was employed utilising a 30 degree pulse, a relaxation delay of 3 s and 10 Hz sample rotation.128 transients were acquired per spectra using 4dummy scans. A total of 32k data points were collected per FID, spectral window ofapprox.20 ppm and 0.3 Hz line-broadening applied. Quantitative1H NMR spectra were processed, integrated and quantitative properties determined. All chemical shifts were internally referenced to the residual protonated solvent signal at 5.95 ppm. Characteristic signals corresponding to epoxy groups resulting from epoxidized sojbeanoil and aliphatic bulk were observed (A.J. Brandolini, D.D. Hills, “NMR spectra of polymers and polymer additives”, Marcel Deker Inc., 2000). The relative number of epoxy groups (NEPOX) was quantified using the integral of the signals between 2.8 ppm and 3.2 ppm (IESO_EPOX) assigned to the methines in an epoxy group, accounting for the number of reporting epoxy groups: NEPOX= IESO_EPOX / 2 Characteristic signals resulting from the additional use of BHT as stabiliser were observed. For the BHT compensation, the integral of the signal at 7.0 ppm assigned to the –CH site of BHT was used: BHT = IBHT / 2 As is typical the total amount of carbons can be determined even though1H NMR spectroscopy was applied. The relative amount of total carbons (NBULK) was quantifiedusing the integral of the bulk aliphatic signal (IBULK) between 0 – 2.5 ppm compensatingfor additional carbons from epoxidized sojbeanoil IESO_EPOXand IESO_GLYC(assigned to the methylene protons in glycrine part of epoxidized soybean oil between 4.0 ppm and 4.4 ppm) as well as for signals of BHT:NBULK = [(Ibulk - (21*BHT)) / 2 ] + IESO_EPOX + (IESO_GLYC / 4 * 6)The amount of epoxy groups (EX) per 1000C was calculated as: EX / 1000C = NEPOX *1000 / NBULK e) Differential scanning calorimetry (DSC) analysis, melting temperature (Tm) andcrystallization temperature (Tc): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357 in a heat / cool / heat cycle with a scan rate of 10°C / min in the temperature range of -30°C to +225°C. Crystallization temperature and heat of crystallization (Hc) are determined from the cooling step, while melting temperature and heat of fusion (Hf) are determined from the second heating step. When a sample shows two or more melting temperatures and / or crystallization temperatures only the main melting temperature (at the highest Hc) and main crystallization temperature (at the highest Hf) are displayed in the accordant table. The difference of melting temperature and crystallization temperature (Tm-Tc) is given for the main melting temperature and the main crystallization temperature. f) Glass transition temperature (Tg)Glass transition temperature Tg was determined by dynamic mechanical analysis (DMTA) according to ISO 6721-7. The measurements were done in torsion mode on compression moulded samples (40x10x1 mm3) between -100°C and +150°C with a heating rate of 2°C / min and a frequency of 1 Hz. Tg was determined from the curve of the loss angle (tan(δ)). g) Xylene cold solubles (XCS) contentThe quantity of xylene soluble matter in polypropylene is determined according to the ISO16152 (first edition; 2005-07-01). A weighed amount of a sample is dissolved in hot xylene under reflux conditions at 135°C. The solution is then cooled down under controlled conditions and maintained at 25°C for 30 minutes to ensure controlled crystallization of the insoluble fraction. This insoluble fraction is then separated by filtration. Xylene is evaporated from the filtrateleaving the soluble fraction as a residue. The percentage of this fraction is determined gravimetrically. where m0 is the mass of the sample test portion weighed, in grams m1 is the mass of residue, in gramsv0is the original volume of solvent taken v1 is the volume of the aliquot taken for determination.h) Intrinsic viscosity (IV)The reduced viscosity (also known as viscosity number), ηred, and intrinsic viscosity, IV, are determined according to ISO 1628-3: “Determination of the viscosity of polymers in dilute solution using capillary viscometers”. Relative viscosities of a diluted polymer solution with concentration of 1 mg / ml and of the pure solvent (decahydronaphthalene stabilized with 200 ppm 2,6-bis(1,1- dimethylethyl)-4-methylphenol) are determined in an automated capillary viscometer (Lauda PVS1) equipped with 4 Ubbelohde capillaries placed in a thermostatic bath filled with silicone oil. The bath temperature is maintained at 135 °C. The sample is dissolved with constant stirring until complete dissolution is achieved (typically within 90 min). The efflux time of the polymer solution as well as of the pure solvent are measured several times until three consecutive readings do not differ for more than 0.2s (standard deviation). The relative viscosity of the polymer solution is determined as the ratio of averaged efflux times in seconds obtained for both, polymer solution and solvent: [dimensionless] Reduced viscosity (ηred) is calculated using the equation: m where C is the polymer solution concentration at 135°C: C= , V ^and m is the polymer mass, V is the solvent volume, and γ is the ratio of solventdensities at 20°C and 135°C (γ=ρ20 / ρ135=1.107). The calculation of intrinsic viscosity IV is performed by using the Schulz-Blaschke equation from the single concentration measurement: ^ IV= red 1^K^C^^red where K is a coefficient depending on the polymer structure and concentration. For calculation of the approximate value for IV, K=0.27.i) Flexural ModulusThe flexural modulus was determined acc. to ISO 178 method A (3-point bending test) on 80 mm × 10 mm × 4 mm specimens. Following the standard, a test speed of 2 mm / min and a span length of 16 times the thickness was used. The testing temperature was 23±2° C. Injection moulding was carried out according to ISO 19069-2 using a melt temperature of 230°C for all materials irrespective of material melt flow rate. j) Charpy notched impact strengthThe Charpy notched impact strength was determined acc. to ISO 179-1 / 1eA on notched 80 mm × 10 mm × 4 mm specimens (specimens were prepared according to ISO 179- 1 / 1eA). Testing temperatures were 23±2° C or -20±2° C. Injection moulding was carried out acc. to ISO 19069-2 using a melt temperature of 230°C for all materials irrespective of material melt flow rate. k) Rheological measurementsDynamic Shear Measurements (frequency sweep measurements) The characterisation of melt of polymer composition or polymer as given above or below in the context by dynamic shear measurements complies with ISO standards 6721-1 and 6721-10. The measurements were performed on an Anton Paar MCR501 stress controlled rotational rheometer, equipped with a 25 mm parallel plate geometry. Measurements were undertaken on compression moulded plates, using nitrogen atmosphere and setting a strain within the linear viscoelastic regime. The oscillatory shear tests were done at 190 °C applying a frequency range between 0.01 and 600 rad / s and setting a gap of 1.3 mm. In a dynamic shear experiment the probe is subjected to a homogeneous deformation at a sinusoidal varying shear strain or shear stress (strain and stress controlled mode, respectively). On a controlled strain experiment, the probe is subjected to a sinusoidal strain that can be expressed by^^(^^) = ^^^ sin(^^^^) (1)If the applied strain is within the linear viscoelastic regime, the resulting sinusoidal stress response can be given by ^^^ and ^^^ are the stress and strain amplitudes, respectively^^ is the angular frequency^^ is the phase shift (loss angle between applied strain and stress response)t is the time Dynamic test results are typically expressed by means of several different rheological functions, namely the shear storage modulus G’, the shear loss modulus, G’’, the complex shear modulus, G*, the complex shear viscosity, η*, the dynamic shearviscosity, η', the out-of-phase component of the complex shear viscosity η” and the losstangent, tan δ which can be expressed as follows:^^^ = ^^^^ cos^^ [Pa] (3)^^^^ = ^^^^ sin^^ [Pa] (4)^^∗ = ^^^ + ^^^^′′ [Pa] (5)η∗ = η^ − iη′′ [Pa∙s] (6)^^^η^ = ^ [Pa∙s] (7) The determination of so-called Shear Thinning Index, which correlates with MWD and is independent of Mw, is done as described in equation 9. For example, the SHI(1 / 100) is defined by the value of the complex viscosity, in Pa∙ s, determined for a value of G* equal to 1 kPa, divided by the value of the complex viscosity, in Pa∙ s, determined for a value of G* equal to 100 kPa. The values of storage modulus (G'), loss modulus (G"), complex modulus (G*) and complex viscosity (η*) were obtained as a function of frequency (ω). Thereby, e.g. η*300rad / s(eta*300rad / sor eta300) is used as abbreviation for the complex viscosity at the frequency of 300 rad / s and η*0.05rad / s(eta*0.05rad / sor eta0.05) is used as abbreviation for the complex viscosity at the frequency of 0.05 rad / s. The polydispersity index, PI, is defined by equation 10. where ωCOPis the cross-over angular frequency, determined as the angular frequency for which the storage modulus, G', equals the loss modulus, G". The values are determined by means of a single point interpolation procedure, as defined by Rheoplus software. In situations for which a given G* value is not experimentally reached, the value is determined by means of an extrapolation, using the same procedure as before. In both cases (interpolation or extrapolation), the option from Rheoplus "Interpolate y-values to x-values from parameter" and the "logarithmic interpolation type" were applied. References: [1] Rheological characterization of polyethylene fractions” Heino, E.L., Lehtinen, A., Tanner J., Seppälä, J., Neste Oy, Porvoo, Finland, Theor. Appl. Rheol., Proc. Int. Congr. Rheol, 11th (1992), 1, 360-362 [2] The influence of molecular structure on some rheological properties of polyethylene”, Heino, E.L., Borealis Polymers Oy, Porvoo, Finland, Annual Transactions of the Nordic Rheology Society, 1995.). [3] Definition of terms relating to the non-ultimate mechanical properties of polymers, Pure & Appl. Chem., Vol.70, No.3, pp.701-754, 1998. l) AC electric breakdown strength (ACBD)The AC breakdown tests were performed in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables. The cable was thus cut into six test samples of 10 meter active length (terminations in addition). The samples were tested to breakdown with a 50 Hz AC step test at ambient temperature, according to the following procedure:• Start at 18 kV for 5 minutes• Voltage increasing in step of 6 kV every 5 minutes until breakdown occursThe calculation of the Weibull parameters of the data set of six breakdown values (conductor stress, i.e. the electric field at the inner semiconductive layer) follows the least squares regression procedure as described in IEC 62539 (2007). The Weibull alpha parameter in this document refers to the scale parameter of the Weibull distribution, i.e. the voltage for which the failure probability is 0.632. The Weibull beta value refers to the shape parameter. 2. Propylene copolymer compositionThe following resins were used for the preparation of the propylene copolymer compositions of the examples: a) Polymerization of the heterophasic propylene copolymer powder A^ CatalystThe catalyst used in the polymerization process for the heterophasic propylene copolymer powder A1 was a Ziegler-Natta catalyst, which is described in patent publications EP491566, EP591224 and EP586390. As co-catalyst triethyl-aluminium (TEAL) and as donor dicyclo pentyl dimethoxy silane (D-donor) was used. ^Polymerization of the heterophasic propylene copolymer powderHeterophasic propylene copolymer powder A1 was produced in a Borstar™ plant in thepresence of the above described polymerization catalyst using one liquid-phase loop reactor and two gas phase reactors connected in series under conditions as shown in Table 1. The first reaction zone was a loop reactor and the second and third reaction zones were gas phase reactors. The matrix phase was polymerized in the loop and first gas phase reactor and the elastomeric phase was polymerized in the second gas phase reactor. The catalyst as described above was fed into a prepolymerization reactor which precedes the first reaction zone. Table 1: Polymerization conditions of the heterophasic propylene copolymer powder: b) Preparation of the polypropylene compositionsThe heterophasic propylene copolymer powder A from the polymerization reaction wascompounded in a twin screw extruder together with different stabilizer packages to obtain the polypropylene composition of reference example RE1. An overview of the production of the polypropylene composition of example RE1 is shown in Table 2. Table 2: Compounding of RE1 in a twin screw extruder: The polypropylene composition RE1 shows the properties as listed below in Table 3. Table 3: Properties of polypropylene composition RE1: For the production of the polymer compositions of the inventive example IE1 and comparative example CE1 the compounded pellets of reference example RE1 were compounded in a second compounding step in a Buss 100 MDK L / D 11D co-kneader together with different additives. An overview of the production of the polypropylene compositions CE1 and IE1 are shown in Table 4. Table 4: Compounding of IE1-IE3 and CE1 in a Buss 100 MDK L / D 11D co-kneader: 9 Stabilizer packages and additives: ^Stabiliser onepack consists of 21.8 wt% Pentaerythrityl-tetrakis(3-(3’,5’-di-tert. butyl-4-hydroxyphenyl)-propionate (CAS-No.6683-19-8), 43.6 wt% Tris (2,4-di-t- butylphenyl) phosphite (CAS-No. 31570-04-4) and 34.6 wt.-% Calcium stearate(CAS-No.1592-23-0), all commercially available from a variety of companies. ^ESPO is an epoxidized soybean oil having an iodine value of <3.0, a density of 0.99g / cm³, a kinematic viscosity of 320-500 cPs and an oxirane content of >6.8 %, commercially available as Cargill Vikoflex® 7170 from Cargill (all properties from TDS). 3. Production of 10 kV cables10 kV test cables were produced on a Maillefer pilot cable line of catenary continuous vulcanizing (CCV) type. The conductors of the cable cores had a cross section being 50 mm² of stranded aluminium and had a cross section of 50 mm². The inner semiconductive layer was produced from semiconductive composition SC2 as described below and had athickness of 1.0 mm. The insulation layer was produced from the above described compositions CE1 and IE1, and had a thickness of 3.4 mm. The outer semiconductive layer was produced from semiconductive compositions SC1 as described below andhad a thickness of 1.0 mm. The cables, i.e. cable cores, were produced by extrusion via a triple head. The insulation extruder had size 100 mm, the extruder for conductor screen (inner semiconductive layer) 45 mm, and the extruder for insulation screen (outer semiconductive layer) 60 mm. The line speed was 6.0 m / min. The vulcanisation tube had a total length of 52.5 meter consisting of a curing section followed by a cooling section. The curing section was filled with N2 at 10 bar but not heated. The 33-meter-long cooling section was filled with 20-25°C water. The pilot cables were then subjected to AC breakdown testing. The composition for semiconductive layer 1 (SC1) was prepared from ready-to-use semiconductive composition Borlink LE7710, which is a non-crosslinkable polyethylene based composition comprising carbon black, commercially available from Borealis AG. The composition for semiconductive layer 2 (SC2) was prepared from 66.5 wt% of the polypropylene based composition of RE1 with 33.0 wt% of carbon black Printex Alpha, commercially available from Orion Engineered Carbons GmbH and 0.5 wt.-% maleic anhydride functionalized polypropylene Exxelor PO1020, commercially available from Exxon Mobil. Table 5 shows the electric properties of the 10 kV cables of examples C1 and C2 in which the composition for inventive insulation layer IE1 is compared to that for comparative insulation layer CE1. Table 5: Electric properties of 10 kV cables of C1 and C2 It can be seen that the cable comprising the inventive insulation layer IE1 shows an increased Weibull-alpha value compared to the cable comprising the accordant comparative insulation layer CE1.

Claims

Claims1. A polypropylene composition comprising(A) from 90.0 to 99.99 wt.-%, preferably from 92.5 to 99.9 wt.%, more preferablyfrom 95.0 to 99.8 wt.-%, most preferably from 97.5 to 99.5 wt.-%, based on the total weight of the polypropylene composition, of a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms having a total comonomer content, preferably a total ethylene content, of from 10.0 to 16.0 wt.-%, preferably from 11.0 to 15.0 wt.-%, most preferably from 12.0 to 14.0 wt.-%, based on the total weight of the copolymer of propylene (A) and determined by quantitative13C{1H} NMR measurement; a melt flow rate MFR2of from 0.5 to 2.5 g / 10 min, preferably from 0.8 to 2.3 g / 10 min, still more preferably from 1.0 to 2.0 g / 10 min and most preferably from 1.2 to 1.7 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; and a xylene cold soluble (XCS) fraction in a total amount of from 25.0 to 50.0 wt%, preferably from 27.5 to 45.0 wt%, more preferably from 30.0 to 42.5 wt% and most preferably from 32.5 to 40.0 wt%, based on the total weight amount of the copolymer of propylene (A) and determined according to ISO16152; and (B) from 0.01 to 10.0 wt.-%, preferably from 0.1 to 7.5 wt.-%, more preferablyfrom 0.2 to 5.0 wt.-%, most preferably from 0.5 to 2.5 wt.-%, based on the total weight of the polypropylene composition, of an epoxidized natural oil.

2. The polypropylene composition according to claim 1, wherein the xylene coldsoluble (XCS) fraction of the copolymer of propylene (A) has an amount of comonomer units, preferably of ethylene, of from 23.0 to 35.0 wt%, more preferably from 23.5 to 32.5 wt% and most preferably from 24.0 wt% to 30.0 wt%, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction and determined by quantitative13C{1H} NMR measurement, and / or an intrinsic viscosity of from 150 to 350 cm³ / g, preferably from 200 to 325 cm³ / g and most preferably from 225 to 300 cm³ / g, measured in decalin according to ISO 1628-3.

3. The polypropylene composition according to claims 1 or 2, wherein the copolymerof propylene (A) has a fraction insoluble in cold xylene (XCI) in a total amount of from 50.0 to 75.0 wt%, more preferably from 55.0 to 72.5 wt%, still more preferably from 57.5 to 70.0 wt% and most preferably from 60.0 to 67.5 wt%, based on the total weight amount of the copolymer of propylene (A) and determined according to ISO16152, and wherein the fraction insoluble in cold xylene (XCI) preferably has an amount of comonomer units, preferably of ethylene, of from 3.0 to 9.0 wt%, preferably from 4.0 to 8.5 wt% and most preferably from 4.5 to 7.5 wt%, based on the total amount of monomer units in the fraction insoluble in cold xylene (XCI) and determined using quantitative13C{1H} NMR measurement, and / or an intrinsic viscosity of preferably from 185 to 350 cm³ / g, more preferably from 220 to 325 cm³ / g and most preferably from 210 to 300 cm³ / g, measured in decalin according to ISO 1628-3.

4. The polypropylene composition according to any one of claims 1 to 3, wherein thecopolymer of propylene (A) has one or more or all of the following properties: ^a flexural modulus of from 130 MPa to 400 MPa, preferably of from 150 MPa to390 MPa and most preferably of from 175 MPa to 380 MPa, determined according to ISO 178 method A; and / or ^a Charpy notched impact strength at 23°C of from 50 to 110 kJ / m², preferablyfrom 65 to 100 kJ / m² and most preferably from 75 to 95 kJ / m², determined according to ISO 179-1 / 1eA; and / or ^a Charpy notched impact strength at -20°C of from 5.0 to 10.0 kJ / m², preferablyfrom 5.5 to 9.0 kJ / m² and most preferably from 6.0 to 8.0 kJ / m², determined according to ISO 179-1 / 1eA; and / or ^a melting temperature Tm of from 140 to 159°C, preferably from 143 to 157°Cand most preferably from 145 to 153°C, determined by DSC analysis according to ISO 11357; and / or ^a crystallization temperature Tc of from 85 to 130°C, preferably from 87 to128°C and most preferably from 90 to 125°C, determined by DSC analysis according to ISO 11357; and / or ^a difference of the melting temperature to the crystallization temperature Tm-Tcin the range of from 20 to 65°C, preferably 25 to 60°C and most preferably from 27 to 55°C.

5. The polypropylene composition according to any one of claims 1 to 4, wherein thecopolymer of propylene (A) is a heterophasic copolymer of propylene whichcomprises a matrix phase and an elastomeric phase dispersed in said matrix phase, which preferably comprises a first glass transition temperatures attributed to the matrix phase and a second glass transition temperatures attributed to the elastomeric phase, wherein the first glass transition temperature attributed to the matrix phase Tg (matrix) is in the range of from -1.0 to -15.0°C, preferably from -2.5 to -12.5°C and most preferably from -5.0 to -10.0°C and / or the second glass transition temperature attributed to the elastomeric phase Tg (EP) is in the range of from -40.0 to -55.0°C, preferably from -42.5 to -52.5°C and most preferably from - 45.0 to -50.0°C, wherein Tg (matrix) and Tg (EP) are determined by dynamic mechanical analysis according to ISO 6721-7.

6. The polypropylene composition according to any one of claims 1 to 5, wherein thecopolymer of propylene (A) is not subjected to vis-breaking.

7. The polypropylene composition according to any one of claims 1 to 6, wherein theepoxidized natural oil (B) is selected from epoxidized vegetable oil, such as epoxidized canola oil, epoxidized tall oil, epoxidized soybean oil, epoxidized safflower oil, epoxidized linseed oil, epoxidized corn oil, epoxidized sunflower oil, epoxidized olive oil, epoxidized canola oil, epoxidized sesame oil, epoxidized cottonseed oil, epoxidized palm-based oils, epoxidized rapeseed oil, epoxidized tung oil, epoxidized peanut oil, epoxidized jatropha oil, epoxidized castor oil, and mixtures thereof, preferably epoxidized soybean oil, epoxidized linseed oil,, epoxidized castor oil and mixtures thereof, more preferably epoxidized soybean oil.

8. The polypropylene composition according to any one of claims 1 to 7, wherein theepoxidized natural oil (B) has one or more or all of the following properties: ^a melting temperature Tm of from -20 to 20°C, more preferably from -15 to 15°C, still more preferably from -10 to 10°C, determinable by DSC analysis according to ISO 11357;^ a density of from 985 to 1010 kg / m³, more preferably from 987 to 1005 kg / m³,still more preferably from 990 to 1000 kg / m³, determinable according to ASTM D1298; ^a kinematic viscosity at 25°C of from 200 to 750 cPs, more preferably from 250to 600 cPs, still more preferably from 300 to 550 cPs, determinable according to ASTM D445; ^an iodine value of from 0 to 5.0, more preferably from 0.01 to 4.0, still morepreferably from 0.1 to 3.0, determinable according to EN 14111:2003; ^an oxirane content of from 4.0 to 15.0 %, preferably from 5.0 to 12.5 %, stillmore preferably from 6.0 to 10.0 %, determinable according to ASTM D1652- 11.

9. The polypropylene composition according to any one of claims 1 to 8 having one ormore or all of the following properties: ^a total amount of epoxy groups per 1000 carbon atoms (EX / 1000 C) of from0.01 to 2.5 / 1000 C, more preferably from 0.1 to 1.5 / 1000 C, most preferably from 0.2 to 1.0 / 1000 C, determined using1H NMR spectroscopy; and / or ^a melt flow rate MFR2 of from 0.5 to 3.0 g / 10 min, more preferably from 0.8 to2.7 g / 10 min, still more preferably from 1.0 to 2.5 g / 10 min and most preferably from 1.2 to 2.2 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; and / or ^a flexural modulus of from 150 MPa to 400 MPa, more preferably of from 175MPa to 390 MPa and most preferably of from 200 MPa to 380 MPa, determined according to ISO 178 method A; and / or ^a Charpy notched impact strength at 23°C of from 50 to 110 kJ / m², morepreferably from 60 to 100 kJ / m² and most preferably from 65 to 95 kJ / m², determined according to ISO 179-1 / 1eA; and / or ^a Charpy notched impact strength at -20°C of from 4.0 to 25.0 kJ / m², morepreferably from 4.5 to 20.0 kJ / m² and most preferably from 5.0 to 15.0 kJ / m², determined according to ISO 179-1 / 1eA; and / or ^a melting temperature Tm of from 140 to 159°C, more preferably from 143 to157°C and most preferably from 145 to 153°C, determined by DSC analysis according to ISO 11357; and / or^ a crystallization temperature Tc of from 85 to 130°C, more preferably from 87to 128°C and most preferably from 90 to 125°C, determined by DSC analysis according to ISO 11357; and / or ^a difference of the melting temperature to the crystallization temperature Tm-Tcin the range of from 35 to 65°C, more preferably 40 to 60°C and most preferably from 45 to 55°C; and / or ^a shear thinning index SHI1 / 100 of from 5.0 to 22.5, more preferably from 7.5 to20.0 and most preferably from 9.0 to 17.5, determined by dynamic shear measurements; and / or ^a polydispersity index PI of from 1.5 to 5.0 s-1, more preferably from 2.0 to 4.5s-1and most preferably from 2.3 to 4.0 s-1, determined by dynamic shear measurements.

10. The polypropylene composition according to any one of claims 1 to 9 furthercomprising from 0 to 5000 ppm, preferably from 0 to 4000 ppm of an alpha- nucleating agent, preferably a soluble or polymeric alpha-nucleating agent, more preferably from a soluble alpha-nucleating agent selected from dibenzylidenesorbitol (e.g.1,3 : 2,4 dibenzylidenesorbitol) and C1-C8-alkyl- substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g.1,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1,2,3- trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol and mixtures thereof.

11. The polypropylene composition according to any one of claims 1 to 10 being free ofa dielectric fluid different from the epoxidized natural oil (B).

12. An article comprising the polypropylene composition according to any one of claims1 to 11, wherein the article preferably is a cable, more preferably a medium voltage cable or high voltage cable, still more preferably a medium voltage cable, comprising an insulation layer comprising the polypropylene composition, preferablywherein the insulation layer comprises from 90 to 100 wt.-%, preferably from 95 to 100 wt.-%, still more preferably from 99 to 100 wt.-%, based on the total weight of the insulation layer, most preferably consists of the polypropylene composition.

13. The article according to claim 12 being a cable, preferably a medium voltage cableor high voltage cable, more preferably a medium voltage cable, comprising a semconductive layer, preferably an inner semiconductive layer and / or an outer semiconductive layer, which comprises a semiconductive composition which comprises at least 52.0 wt%, preferably from 55.0 to 90.0 wt%, more preferably from 60.0 to 85.0 wt%, most preferably from 65.0 to 80.0 wt% of the polypropylene composition and from 5.0 to 40.0 wt%, preferably from 10.0 to 38.0 wt%, more preferably from 15.0 to 35.0 wt%, most preferably from 20.0 to 33.0 wt% of a conductive filler, preferably carbon black, all based on the total weight amount of the semiconductive composition.

14. The article according to claims 12 or 13 having an AC breakdown strength asexpressed by a Weibull alpha-value of from 40.0 to 75.0 kV / mm, preferably from 42.5 to 75.0 kV / mm and most preferably from 45.0 to 75.0 kV / mm and / or a Weibull beta-value of from 5.0 to 250.0, preferably from 5.5 to 250.0, most preferably from 6.0 to 250.0, measured on a 10 kV cable in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables.

15. The use of a polypropylene composition according to any one of claims 1 to 11 ascable insulation and / or as semiconductive layer for medium and high voltage cables, preferably for medium voltage cables.

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