Semiconductive polypropylene composition

Abstract

The present invention relates to a semiconductive composition comprising (A) from 25.0 to 67.5 wt.-% of a first copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which first copolymer (A) has a melt flow rate MFR2 of from 2.0 to 6.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from more than 25.0 to 50.0 wt.-%, based on the total weight amount of the first copolymer (A); and a total comonomer content, preferably ethylene content, of from 7.5 to 20.0 wt.-%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative 13C-NMR spectroscopy from crystallization extraction (CRYSTEX); (B) from 5.0 to 50.0 wt.-% of a second copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which second copolymer (B) has a melt flow rate MFR2 of at least 2.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from 12.0 to 25.0 wt.-%, based on the total weight amount of the second copolymer (B); and a total comonomer content, preferably ethylene content, of from 4.0 to 10.0 wt.-%, based on the total weight of the second copolymer (B) and determined by FT-IR spectroscopy calibrated by quantitative 13C-NMR spectroscopy from crystallization extraction (CRYSTEX); and (C) from 15.0 to 35.0 wt.-% of carbon black, wherein all weight amounts are based on the total weight amount of the semiconductive composition, an article comprising said semiconductive composition and the use of said semiconductive composition as inner and / or outer semiconductive layer for medium voltage cables.

Description

[0001] Semiconductive Polypropylene Composition

[0002] The present invention relates to a semiconductive composition comprising two copolymers of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms differing in their total content of soluble fraction (SF) determined by crystallization extraction (CRYSTEX) and carbon black, an article comprising said semiconductive composition and the use of said semiconductive composition as inner and / or outer semiconductive layer for medium and high voltage cables.

[0003] Technical background

[0004] Compositions used for semiconductive layers of cables usually include a solid conductive filler such as carbon black in amounts of about 30 to 50 wt% in order to render these compositions semiconductive. Such high amounts of conductive filler have the drawback of poor miscibility with the polymeric components which impairs the mechanical properties of the semiconductive compositions.

[0005] As polymeric component crosslinked polyethylene resins have been generally used due to their durability in the presence of strong electrical fields.

[0006] However, due to its crosslinking the XLPE have thermosetting properties.

[0007] Lately, attempts were made to use thermoplastic material and especially thermoplastic propylene polymers as polymeric material for semiconductive layers in 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.

[0008] WO 2022 / 200395 discloses a polypropylene composition comprising (a) a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms of from 10.0 to 16.0 wt.-% and (b) an alpha-nucleating agent, wherein the polypropylene composition has an amount of XCS fraction of from 25.0 to 50.0 wt.-% with an amount of comonomer units of at least 23.0 wt.-%, a melt flow rate MFR2 of from 0.5 to 5.0 g / 10 min, and a flexural modulus of not more than 470 MPa.

[0009] EP 2 316 882 A1 discloses a heterophasic propylene resin comprising a propylene random copolymer matrix phase and an ethylene-propylene copolymer rubber phase dispersed within the matrix phase, wherein the heterophasic propylene resin has a melt flow rate MFR2 of 1.0 to 100 g / 10 min, an amount of XCS fraction of 28 to 50 wt.-% and a ratio Mw / Mn of 1 .0 to 4.0. WO 2022 / 122444 discloses a semiconductive composition comprising a heterophasic propylene copolymer as polymeric component, which shows good conductivity, good mechanical properties and low water tree formation in the presence of a rather low amount of carbon black. Said heterophasic propylene copolymer has a rather high amount of amorphous phase, which renders the semiconductive composition rather sticky during cable extrusion.

[0010] In the present invention it has been found that by carefully selecting the polymeric components a semiconductive composition having good conductivity, good mechanical properties and good extrudability can be obtained, thereby being able to further reduce the amount of carbon black. Cables comprising said semiconductive composition as semiconductive layers show good volume resistivity and superior electrical breakdown strength and are therefore especially suitable for medium and high voltage cables.

[0011] Summary of the invention

[0012] In a first aspect the present invention relates to a semiconductive composition comprising

[0013] (A) from 25.0 to 67.5 wt.-%, preferably from 35.0 to 62.5 wt.-%, more preferably from 40.0 to 61 .0 wt%, most preferably from 45.0 to 60.0 wt% of a first copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which first copolymer (A) has a melt flow rate MFR2 of from 2.0 to 6.0 g / 10 min, preferably from 2.5 to 5.5 g, still more preferably from 3.0 to 5.0 g / 10 min and most preferably from 3.3 to 4.5 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from more than 25.0 to 50.0 wt%, preferably from 30.0 to 47.5 wt%, most preferably from 32.5 to 45.0 wt%, based on the total weight amount of the first copolymer (A); and a total comonomer content, preferably ethylene content, of from 7.5 to 20.0 wt%, preferably from 9.0 to 17.5 wt%, most preferably from 10.0 to 15.0 wt%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX); (B) from 5.0 to 50.0 wt.-%, preferably from 10.0 to 40.0 wt.-%, more preferably from

[0014] 11 .0 to 35.0 wt.-%, most preferably from 12.0 to 25.0 wt.-% of a second copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which second copolymer (B) has a melt flow rate MFR2 of at least 2.0 g / 10 min such as from 2.0 to 2000 g / 10 min, preferably from 3.0 to 500 g, still more preferably from 4.0 to 100 g / 10 min and most preferably from 5.0 to 30.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from 12.0 to 25.0 wt.-%, preferably from 13.5 to 22.5 wt.-% and most preferably from 15.0 to 20.0 wt.-%, based on the total weight amount of the second copolymer (B); and a total comonomer content, preferably ethylene content, of from 4.0 to 10.0 wt.-%, preferably from 5.0 to 9.5 wt.-%, more preferably from 6.0 to 9.0 wt.-%, based on the total weight of the second copolymer (B) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX); and

[0015] (C) from 15.0 to 35.0 wt.-%, preferably from 17.5 to 32.5 wt.-%, more preferably from 20.0 to 30.0 wt.-%, most preferably from 23.0 to 28.0 wt.-% of carbon black, wherein all weight amounts are based on the total weight amount of the semiconductive composition.

[0016] In a further aspect the present invention relates to an article comprising the semiconductive composition as described above or below.

[0017] Preferably said article is a cable comprising a semiconductive layer, more preferably an inner and / or outer semiconductive layer, comprising said semiconductive composition as described above or below.

[0018] In yet another aspect the present invention relates to the use of a semiconductive composition as described above or below as inner and / or outer semiconductive layer for medium cables.

[0019] Definitions A heterophasic polypropylene is a propylene-based copolymer with a 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.

[0020] 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 respectively.

[0021] 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.

[0022] 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 crystalline fraction (CF) determined by crystallization extraction (CRYSTEX) in an amount of more than 85 wt%, such as of at least 88 wt%, most preferably of at least 90 wt%, based on the total amount of propylene random copolymer. Accordingly, the propylene random copolymer does not contain an elastomeric polymer phase dispersed therein.

[0023] 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”.

[0024] A unimodal propylene polymer only consists of one fraction. Thereby, the term “different” means that the propylene polymer fractions differ from each other in at least one property, preferably in the weight average molecular weight - which can also be measured in different melt flow rates of the fractions - or comonomer content or both.

[0025] 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 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.

[0026] In the following amounts are given in % by weight (wt%) unless it is stated otherwise.

[0027] Detailed description of the invention

[0028] Semiconductive composition

[0029] In a first aspect the present invention relates to a semiconductive composition comprising

[0030] (A) from 25.0 to 67.5 wt.-%, preferably from 35.0 to 62.5 wt.-%, more preferably from 40.0 to 61 .0 wt%, most preferably from 45.0 to 60.0 wt% of a first copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which first copolymer (A) has a melt flow rate MFR2 of from 2.0 to 6.0 g / 10 min, preferably from 2.5 to 5.5 g, still more preferably from 3.0 to 5.0 g / 10 min and most preferably from 3.3 to 4.5 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from more than 25.0 to 50.0 wt%, preferably from 30.0 to 47.5 wt%, most preferably from 32.5 to 45.0 wt%, based on the total weight amount of the first copolymer (A); and a total comonomer content, preferably ethylene content, of from 7.5 to 20.0 wt%, preferably from 9.0 to 17.5 wt%, most preferably from 10.0 to 15.0 wt%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX); (B) from 5.0 to 50.0 wt.-%, preferably from 10.0 to 40.0 wt.-%, more preferably from

[0031] 11 .0 to 35.0 wt.-%, most preferably from 12.0 to 25.0 wt.-% of a second copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which second copolymer (B) has a melt flow rate MFR2 of at least 2.0 g / 10 min such as from 2.0 to 2000 g / 10 min, preferably from 3.0 to 500 g, still more preferably from 4.0 to 100 g / 10 min and most preferably from 5.0 to 30.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from 12.0 to 25.0 wt.-%, preferably from 13.5 to 22.5 wt.-% and most preferably from 15.0 to 20.0 wt.-%, based on the total weight amount of the second copolymer (B); and a total comonomer content, preferably ethylene content, of from 4.0 to 10.0 wt.-%, preferably from 5.0 to 9.5 wt.-%, more preferably from 6.0 to 9.0 wt.-%, based on the total weight of the second copolymer (B) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy crystallization extraction (CRYSTEX); and

[0032] (C) from 15.0 to 35.0 wt.-%, preferably from 17.5 to 32.5 wt.-%, more preferably from 20.0 to 30.0 wt.-%, most preferably from 23.0 to 28.0 wt.-% of carbon black, wherein all weight amounts are based on the total weight amount of the semiconductive composition.

[0033] The semiconductive composition comprises components (A), (B) and (C) as described above or below.

[0034] The amount of components (A), (B) and (C) in the semiconductive composition is preferably in the range of from 90.0 to 100 wt.-%, preferably from 95.0 to 100 wt.-%, more preferably 97.5 to 100 wt.-%.

[0035] The semiconductive composition can further comprise polymeric components, which are different from the first copolymer (A) and the second copolymer (B), in an amount of preferably 0.0 to 10.0 wt.-% based on the total weight of the semiconductive composition. A suitable further polymeric component is e.g. a polyolefin functionalized with a mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound (D), wherein the functionalized polyolefin (C) is different from the first copolymer (A) and the second copolymer (B).

[0036] Said functionalized polyolefin (D) is preferably present in the semiconductive composition 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.

[0037] The semiconductive composition can further comprise polymeric components in addition to components (A), (B) and optionally (D). It is however preferred that the semiconductive composition does not further comprise polymeric components in addition to components (A), (B) and optionally (D), i.e. that the polymeric components of the semiconductive composition consist of components (A), (B) and optionally (D). In one embodiment the polymeric components of the semiconductive composition consist of components (A), (B) and (C). In another embodiment the polymeric components of the semiconductive composition consist of components (A) and (B).

[0038] The semiconductive composition preferably does not comprise, i.e. is free of a polymer comprising polar monomer units, such as acetate or acrylate or derivatives thereof containing monomer units.

[0039] It is preferred that the weight ratio of the first copolymer (A) to the second copolymer (B) in the semiconductive composition is in the range of from 1.5 : 1.0 to 10.0 : 1.0, preferably from 2.0 : 1 .0 to 7.5 : 1 .0, most preferably from 2.5 : 1 .0 to 5.0 : 1 .0.

[0040] The amount of the polymeric components, preferably of components (A), (B) and optionally (D), more preferably of components (A) and (B), in the semiconductive composition is preferably in the range of from 65.0 to 85.0 wt.-%, more preferably from 67.5 to 82.5 wt.-%, more preferably from 70.0 to 80.0 wt.-%, most preferably from 72.0 to 77.0 wt.-% based on the total weight amount of the semiconductive composition.

[0041] The semiconductive composition may comprise further component(s), such as additive(s), which may optionally be added in a mixture with a carrier polymer, e.g. in a so-called master batch. Also the carbon black (C) can be added in form of a master batch. In such cases the carrier polymer is not calculated to the amount of the polymer components. The amount of additives and the carrier polymer of any master batch is calculated to the total amount (100 wt.-%) of the polymer composition. Additives, if present, are preferably selected from antioxidant(s), stabilizer(s), processing aid(s), flame retardant additive(s), water tree retardant additive(s), acid or ion scavenger(s) and inorganic filler(s) as known in the polymer field.

[0042] The amount of further components in the semiconductive composition is preferably not higher than 10.0 wt.-%, such as 0 to 5.0 wt.-% or O to 2.5 wt.-% of the total amount of the semiconductive composition.

[0043] It is preferred that the semiconductive composition does not comprise, i.e. is free of 2,2,4-trimethyl-1 ,2-dihydroquinoline (TMQ). In cable applications, in which the semiconductive composition is used in semiconductive layer(s), TMQ tends to partly diffuse from the semiconductive layer(s) into the insulation layer and can cause a yellow discoloration of the insulation layer.

[0044] In one embodiment, the semiconductive composition comprises, preferably consists of components (A), (B) and (C), optional component (D) and optional further components, such as additives but is free of a polymer comprising polar monomer units and 2,2,4- trimethyl-1 ,2-dihydroquinoline (TMQ), preferably comprises, more preferably consists of components (A), (B) and (C), and optional further components, such as additives but is free of a polymer comprising polar monomer units and 2 ,2 ,4-trimethyl-1 ,2- dihydroquinoline (TMQ).

[0045] In another embodiment, the semiconductive composition consists of components (A), (B), (C) and optional component (D), preferably consists of components (A), (B) and (C).

[0046] The semiconductive composition preferably has a melt flow rate MFRs (230°C, 5.0 kg load) of from 2.0 to 100 g / 10 min, preferably from 3.0 to 75 g / 10 min, still more preferably from 4.0 to 50 g / 10 min and most preferably from 5.0 to 12 g / 10 min.

[0047] Further, the semiconductive composition preferably a melt flow rate MFR (230°C, 10 kg load) of from 12 to 600 g / 10 min, preferably from 18 to 450 g, still more preferably from 22 to 300 g / 10 min and most preferably from 25 to 50 g / 10 min. The semiconductive composition preferably has a density of from 0.850 to 1.200 g / cm3, more preferably from 0.900 to 1 .100 g / cm3, most preferably from 0.950 to 1 .075 g / cm3.

[0048] Further, the semiconductive composition preferably has a volume resistivity (VR) of from 6.0 to 55.0 Ohm -cm, preferably from 7.0 to 52.5 Ohm -cm, most preferably from 8.0 to 50.0 Ohm ■ cm, when measured at 23°C on tape specimens of 1 mm x 100 mm x 15 mm. In some embodiments the volume resistivity can be as low as 20.0 Ohm -cm, preferably as low as 17.5 Ohm -cm, most preferably as low as 15.0 Ohm -cm, measured at 23°C on tape specimens of 1 mm x 100 mm x 15 mm.

[0049] Additionally, the semiconductive composition preferably has a tensile strength of at least 10.0 MPa, more preferably at least 12.5 MPa and most preferably at least 14.0 MPa.

[0050] The upper limit of the tensile strength is preferably not more than 25.0 MPa, more preferably not more than 22.5 MPa and most preferably not more than 20.0 MPa. Further, the semiconductive composition preferably has an elongation at break of at least 350%, more preferably at least 400% and most preferably at least 450%.

[0051] The upper limit of the elongation at break is preferably not more than 750%, more preferably not more than 700% and most preferably not more than 650%.

[0052] Thus, the semiconductive composition according to the invention surprisingly shows a good balance of properties in regard of processability, conductivity, mechanical properties and surface smoothness on tapes.

[0053] It is preferred that the semiconductive composition is not crosslinked.

[0054] A crosslinked polymer composition has a typical network, i.a. interpolymer crosslinks (bridges), as well known in the field. Those bridges can be introduced by creating radicals in the polymeric chain e.g. by reaction with peroxides or exposure to radiation or introduction of a functional group into the polymeric chain which is prone to chemical reaction with another one of said functional groups. During crosslinking a crosslinked polymer composition becomes thermoset.

[0055] It is preferred that the semiconductive composition is thermoplastic. Preferably, the semiconductive composition is prepared by melt blending the components (A), (B) and (C), and optional component (D) and optional further components such as optional additives and further polymeric components, all as described above or below.

[0056] First copolymer (A)

[0057] The first copolymer (A) is a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms.

[0058] The comonomers units are selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene and 1-octene, preferably from ethylene, 1-butene and 1-hexene, most preferably from ethylene.

[0059] In a preferred embodiment the first copolymer (A) is a copolymer of propylene and ethylene.

[0060] The first copolymer (A) has a total comonomer content, preferably ethylene content, of from 7.5 to 20.0 wt.-%, preferably from 9.0 to 17.5 wt.-%, most preferably from 10.0 to 15.0 wt.-%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX).

[0061] It is preferred that the first copolymer (A) has a total propylene content of from 80.0 to 92.5 wt.-%, preferably from 82.5 to 91 .0 wt.-%, most preferably from 85.0 to 90.0 wt.-%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX).

[0062] The first copolymer 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.

[0063] Further, the first copolymer (A) has a melt flow rate MFR2 of from 2.0 to 6.0 g / 10 min, preferably from 2.5 to 5.5 g, still more preferably from 3.0 to 5.0 g / 10 min and most preferably from 3.3 to 4.5 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg.

[0064] It is preferred that the first copolymer (A) is a heterophasic propylene copolymer.

[0065] The heterophasic propylene copolymer has a matrix phase and an elastomeric phase dispersed in said matrix phase.

[0066] The matrix phase is preferably a propylene-ethylene random copolymer.

[0067] In the first copolymer (A), such as the 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 a heterophasic propylene copolymer several methods are known. One method is the crystallization extraction (CRYSTEX).

[0068] This method is described below in the determination methods section. Thereby, the polymeric part of the polypropylene composition is characterized using trichlorobenzene (TCB) as a solvent. The crystalline fraction (CF) contains for the most part the matrix phase and only a small part of the elastomeric phase and the soluble fraction (SF) contains for the most part the elastomeric phase and only a small part of the matrix phase. In some cases, this method results in more useful data compared to xylene extraction, since the crystalline fraction (CF) and the soluble fraction (SF) more accurately correspond to the matrix and elastomeric phases, respectively. Due to the differences in the separation methods of xylene extraction and crystallization extraction (CRYSTEX) the properties of XCS / XCI fractions on the one hand and crystalline / soluble (CF / SF) fractions on the other hand are not exactly the same, meaning that the amounts of matrix phase and elastomeric phase can differ as well as the properties.

[0069] Generally, the crystalline fraction (CF) content and the soluble (SF) content of a composition only relate to its polymeric components, i.e. without other components, which are insoluble and therefore not part of the dissolution and crystallization cycles as described below in the determination method.

[0070] In the present case the first copolymer (A) as well as the second copolymer (B) are usually fully soluble in trichlorobenzene (TCB) so that the crystalline fraction (CF) content and the soluble (SF) content relate to the total content of the polyolefin composition. Thus, the crystalline fraction (CF) content and the soluble fraction (SF) content preferably make up 100 wt.-% of the first copolymer (A) and the second copolymer (B).

[0071] The first copolymer (A) preferably has a crystalline fraction (CF) content, determined by crystallization extraction (CRYSTEX), in the range from 50.0 to 75.0 wt.-%, more preferably from 52.5 to 70.0 wt.-% and most preferably from 55.0 to 67.5 wt.-% based on the total weight amount of the first copolymer (A).

[0072] Said crystalline fraction (CF) preferably has comonomer content, preferably an ethylene content (C2(CF)), determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX), in the range from 1 .0 to 15.0 wt.-%, more preferably from 2.0 to 10.0 wt.-% and most preferably from 3.0 to 8.5 wt.-%, based on the total amount of monomer units in the crystalline fraction (CF).

[0073] Further, said crystalline fraction (CF) preferably has an intrinsic viscosity (iV(CF)), determined according to ISO 1628-3, in the range from 175 to 300 cm3 / g, more preferably from 185 to 275 cm3 / g and most preferably from 200 to 250 cm3 / g.

[0074] The first copolymer (A) has a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), in the range from more than 25.0 to 50.0 wt.-%, preferably from 30.0 to 47.5 wt.-%, most preferably from 32.5 to 45.0 wt.-%, based on the total weight amount of the first copolymer (A).

[0075] Said soluble fraction (SF) preferably has a comonomer content, preferably an ethylene content (C2(SF)), determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range from 20.0 to 35.0 wt.-%, more preferably from 21.5 to 32.5 wt.-%, most preferably from 22.5 to 30.0 wt.-%, based on the total amount of monomer units in the soluble fraction (SF).

[0076] Further, said soluble fraction (SF) preferably has an intrinsic viscosity (iV(SF)), determined according to ISO 1628-3, in the range from 150 to 250 cm3 / g, more preferably from 165 to 235 cm3 / g and most preferably from 175 to 225 cm3 / g.

[0077] It is preferred that the crystalline fraction (CF) and the soluble fraction (SF) make up 100 wt.-% of the first copolymer (A). The first copolymer (A) preferably has a flexural modulus of not more than 470 MPa, such as from 130 MPa to 425 MPa, more preferably of from 150 MPa to 400 MPa and most preferably of from 175 MPa to 390 MPa, determined according to ISO 178 method A.

[0078] Further, the first copolymer (A) preferably has a Charpy notched impact strength at 23°C of from 40 to 110 kJ / m2, more preferably from 50 to 100 kJ / m2and most preferably from 55 to 95 kJ / m2, determined according to ISO 179-1 / 1 eA.

[0079] Furthermore, the first copolymer (A) preferably has a melting temperature Tm of from 140 to 159°C, more preferably from 142 to 155°C, most preferably from 145 to 153°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2.

[0080] Further, the first copolymer (A) preferably has a crystallization temperature Tc of from 85 to 125°C, more preferably from 88 to 122°C, most preferably from 90 to 120°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2.

[0081] The difference of the melting temperature to the crystallization temperature Tm-Tc is preferably in the range of from 20 to 70°C, more preferably from 25 to 60°C, most preferably from 30 to 55 °C.

[0082] The first copolymer (A) preferably has a total intrinsic viscosity of from 150 to 350 cm3 / g, more preferably from 170 to 325 cm3 / g, most preferably from 190 to 300 cm3 / g, determined according to ISO 1628-3.

[0083] The first copolymer (A) preferably has a complex viscosity at a frequency of 100 rad / s eta*ioo rad / s of from 750 to 950 Pa s, more preferably from 800 to 900 Pa s, most preferably from 820 to 880 Pa s.

[0084] The first copolymer (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.

[0085] When the first copolymer (A) is a heterophasic propylene copolymer, the matrix phase of the heterophasic propylene copolymer 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.

[0086] The elastomeric phase of the heterophasic propylene copolymer 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.

[0087] 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.

[0088] 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 0 887 379, WO 92 / 12182

[0089] WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or in WO 00 / 68315.

[0090] A further suitable slurry-gas phase process is the Spheripol® process of LyondellBasell.

[0091] Suitable sequential polymerization processes for polymerizing the first copolymer (A), preferably the heterophasic propylene copolymer, are e.g. disclosed in EP 1 681 315 A1 or WO 2013 / 092620 A1.

[0092] The first copolymer (A), preferably the heterophasic propylene copolymer can be polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

[0093] Suitable Ziegler-Natta catalysts are e.g. disclosed in US 5,234,879, WO 92 / 19653, WO 92 / 19658, WO 99 / 33843, WO 03 / 000754, WO 03 / 000757, WO 2013 / 092620 A1 or WO 2015 / 091839. Suitable single site catalysts are e.g. disclosed in WO 2006 / 097497, WO 2011 / 076780 or WO 2013 / 007650.

[0094] The first copolymer (A) is preferably subjected to a visbreaking step as e.g. described in WO 2013 / 092620 A1.

[0095] In one embodiment the first copolymer (A) comprises an alpha-nucleating agent. The alpha-nucleating agent is generally not restricted.

[0096] Preferably, the alpha-nucleating agent is selected from soluble alpha-nucleating agents and polymeric alpha-nucleating agents.

[0097] The alpha-nucleating agent is preferably selected from the group consisting of

[0098] (i) dibenzylidenesorbitol (e.g. 1 ,3 : 2,4 dibenzylidenesorbitol) and Ci-Cs-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-0-[(4-propylphenyl)methylene]-nonitol, and

[0099] (ii) vinylcycloalkane polymer and vinylalkane polymer (as discussed in more detail below), and

[0100] (iii) mixtures thereof.

[0101] 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-0-[(4- propylphenyl)methylene]-nonitol, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof.

[0102] Especially preferred are vinylcycloalkane polymers such as e.g. vinylcyclohexane (VCH) polymers. Such polymers can be added e.g. using Borealis Nucleation Technology (BNT).

[0103] The alpha-nucleating agent can be added to the first copolymer (A) 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.

[0104] Preferably, in this embodiment the first copolymer (A) contains from 0.00001 to 5.00 wt%, more preferably from 0.0001 to 2.50 wt% of the alpha-nucleating agent. The amount of pure alpha-nucleating agent in the first copolymer (A) (without optional carrier polymer of a master batch) is preferably in the range of from 0.01 to 2000 ppm, more preferably from 0.1 to 1000 ppm.

[0105] In another embodiment the first copolymer (A) does not comprise, i.e. is free of alphanucleating agents.

[0106] Heterophasic propylene copolymer resins suitable as first copolymer (A) are also commercially available. These resins are usually already additivated with stabilizer packages. Thus, when using commercially available resins as first copolymer (A) the addition of additives as described above might have to be adjusted to the already present additives.

[0107] In case of a commercially available first copolymer (A) the above stated properties can be measured using a common measurement method or verified by the technical documentation provided by the supplier.

[0108] Second

[0109] The second copolymer (B) is a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms.

[0110] The comonomers units are selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene and 1-octene, preferably from ethylene, 1-butene and 1-hexene, most preferably from ethylene.

[0111] In a preferred embodiment the second copolymer (B) is a copolymer of propylene and ethylene.

[0112] The second copolymer (B) has a total comonomer content, preferably ethylene content, of from 4.0 to 10.0 wt.-%, preferably from 5.0 to 9.5 wt.-%, more preferably from 6.0 to 9.0 wt.-%, based on the total weight of the second copolymer (B) and determined by FT- IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX). It is preferred that the second copolymer (B) has a total propylene content of from 90.0 to 96.0 wt.-%, preferably from 90.5 to 95.0 wt.-%, most preferably from 91 .0 to 94.0 wt.- %, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy.

[0113] The second copolymer (B) 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.

[0114] It is preferred that the second copolymer (B) has a lower total comonomer content, preferably total ethylene content, than the first copolymer (A).

[0115] Further, the second copolymer (B) has a melt flow rate MFR2 of at least 2.0 g / 10 min, such as from 2.0 to 2000 g / 10 min, preferably from 3.0 to 500 g, still more preferably from 4.0 to 100 g / 10 min and most preferably from 5.0 to 30.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg.

[0116] It is preferred that the second copolymer (B) is a heterophasic propylene copolymer. The heterophasic propylene copolymer has a matrix phase and an elastomeric phase dispersed in said matrix phase.

[0117] The matrix phase is preferably a propylene-ethylene random copolymer.

[0118] In the second copolymer (B), such as the 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 a heterophasic propylene copolymer several methods are known. One method is the crystallization extraction (CRYSTEX) as described above for the first copolymer (A).

[0119] The second copolymer (B) preferably has a crystalline fraction (CF) content, determined by crystallization extraction (CRYSTEX), in the range from 75.0 to 88.0 wt.-%, more preferably from 77.5 to 86.5 wt.-% and most preferably from 80.0 to 85.0 wt.-% based on the total weight amount of the second copolymer (B). Said crystalline fraction (CF) preferably has comonomer content, preferably an ethylene content (C2(CF)), determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX), in the range from 1 .0 to 15.0 wt.-%, more preferably from 2.0 to 10.0 wt.-% and most preferably from 3.0 to 8.5 wt.-%, based on the total amount of monomer units in the crystalline fraction (CF).

[0120] Further, said crystalline fraction (CF) preferably has an intrinsic viscosity (iV(CF)), determined according to ISO 1628-3, in the range from 165 to 290 cm3 / g, more preferably from 175 to 265 cm3 / g and most preferably from 190 to 240 cm3 / g.

[0121] The second copolymer (B) has a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), in the range from 12.0 to 25.0 wt.-%, preferably from 13.5 to 22.5 wt.-% and most preferably from 15.0 to 20.0 wt.-%, based on the total weight amount of the second copolymer (B).

[0122] Said soluble fraction (SF) preferably has a comonomer content, preferably an ethylene content (C2(SF)), determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, in the range from 15.0 to 35.0 wt.-%, more preferably from 17.5 to 32.5 wt.-%, most preferably from 20.0 to 30.0 wt.-%, based on the total amount of monomer units in the soluble fraction (SF).

[0123] Further, said soluble fraction (SF) preferably has an intrinsic viscosity (iV(SF)), determined according to ISO 1628-3, in the range from 90 to 190 cm3 / g, more preferably from 100 to 180 cm3 / g and most preferably from 115 to 170 cm3 / g.

[0124] It is preferred that the crystalline fraction (CF) and the soluble fraction (SF) make up 100 wt.-% of the second copolymer (B).

[0125] The second copolymer (B) has a lower soluble fraction (SF) content than the first copolymer (A).

[0126] The second copolymer (B) preferably has a flexural modulus of more than 470 MPa, such as from 475 MPa to 800 MPa, more preferably of from 500 MPa to 750 MPa and most preferably of from 550 MPa to 700 MPa, determined according to ISO 178 method A.

[0127] Further, the second copolymer (B) preferably has a Charpy notched impact strength at 23°C of from 4.0 to 15.0 kJ / m2, more preferably from 5.0 to 13.0 kJ / m2and most preferably from 6.0 to 11 .5 kJ / m2, determined according to ISO 179-1 / 1 eA.

[0128] Furthermore, the second copolymer (B) preferably has a melting temperature Tm of from 130 to 150°C, more preferably from 135 to 147°C, most preferably from 140 to 145°C, determined by to DSC analysis according to ISO 11357 I part 3 / method C2.

[0129] Further, the second copolymer (B) preferably has a crystallization temperature Tc of from 80 to 120°C, more preferably from 85 to 115°C, most preferably from 90 to 110°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2.

[0130] The difference of the melting temperature to the crystallization temperature Tm-Tc is preferably in the range of from 20 to 70°C, more preferably from 25 to 60°C, most preferably from 30 to 55 °C.

[0131] The second copolymer (B) preferably has a total intrinsic viscosity of from 100 to 250 cm3 / g, more preferably from 125 to 235 cm3 / g, most preferably from 150 to 220 cm3 / g, determined according to ISO 1628-3.

[0132] The second copolymer (B) preferably has a complex viscosity at a frequency of 100 rad / s eta*ioo rad / s of from 500 to 700 Pa s, more preferably from 550 to 650 Pa s, most preferably from 570 to 630 Pa s.

[0133] The second copolymer (B) 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.

[0134] When the second copolymer (B) is a heterophasic propylene copolymer, the matrix phase of the heterophasic propylene copolymer 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.

[0135] The elastomeric phase of the heterophasic propylene copolymer 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.

[0136] 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.

[0137] 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 0 887 379, WO 92 / 12182

[0138] WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or in WO 00 / 68315.

[0139] A further suitable slurry-gas phase process is the Spheripol® process of LyondellBasell.

[0140] Suitable sequential polymerization processes for polymerizing second copolymer (B), preferably the heterophasic propylene copolymer, are e.g. disclosed in WO 2015 / 117948.

[0141] The second copolymer (B), preferably the heterophasic propylene copolymer can be polymerized in the presence of a Ziegler-Natta catalyst.

[0142] Suitable Ziegler-Natta catalysts are e.g. disclosed in WO 2015 / 117948.

[0143] The second copolymer (B) is preferably subjected to a visbreaking step as e.g. described in WO 2013 / 092620 A1 . Heterophasic propylene copolymer resins suitable as second copolymer (B)are also commercially available. These resins are usually already additivated with stabilizer packages. Thus, when using commercially available resins as second copolymer (B) the addition of additives as described above might have to be adjusted to the already present additives.

[0144] In case of a commercially available second copolymer (B) the above stated properties can be measured using a common measurement method or verified by the technical documentation provided by the supplier.

[0145] Carbon black (C)

[0146] 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.

[0147] 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.

[0148] Further, the carbon black may have one or more of the following properties:

[0149] • a primary particle size of at least 5 nm, for example 5 to 30 nm, preferably 10 to 20 nm which is defined as the average particle diameter according to ASTM D3849-14,

[0150] • 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 / or

[0151] • 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.

[0152] These properties are usually provided in the technical documentation from the supplier of commercial carbon black grades.

[0153] 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.

[0154] 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 ashcontent 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.

[0155] Furnace carbon black is a generally acknowledged term for the well-known carbon black type 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. To further 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.

[0156] Functionalized polyolefin (D)

[0157] "Functionalized with a mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound" or shortly "functionalized" means herein generally that the polymer is functionalized with carbonyl containing groups originating from said mono- or polycarboxylic acid group or a derivative thereof. The carbonyl containing 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).

[0158] Herein, the functionalized carbonyl containing compound of functionalized polyolefin (D) is understood not to mean any polar comonomer(s), e.g. an acrylate, a methacrylate or an acetate comonomer.

[0159] The functionalized polyolefin (D) is different from the first copolymer (A) and the second copolymer (B). The functionalized polyolefins (D) 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.

[0160] Preferable polycarboxylic acid compounds for functionalization are unsaturated dicarboxylic acids or derivatives thereof. More preferable carbonyl containing compounds for the functionalization are derivatives of unsaturated mono- or polycarboxylic acid compounds, more preferably derivatives of unsaturated dicarboxylic acids. Preferred carbonyl containing compounds for functionalization are anhydrides of a mono- or polycarboxylic acid, which are also referred as "acid anhydrides" or "anhydrides". The acid anhydrides can be linear or cyclic.

[0161] Preferably, the functionalized polyolefin (D) is an acid anhydride functionalized polyolefin, more preferably a maleic anhydride (MAH) functionalized polyolefin (D). Preferably, the functionalized polyolefin (D) is obtainable by grafting maleic anhydride to a polyolefin (also referred herein shortly as MAH grafted polyolefin or MAH-g-polyolefin).

[0162] Preferred polyolefin for functionalized polyolefin (D) is a functionalized polypropylene or polyethylene. Both polyolefin types are well known in the field.

[0163] In case the functionalized polyolefin (D) 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.

[0164] The MFR (190°C, 2.16 kg) of the functionalized polyethylene (D) 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.

[0165] In case the functionalized polyolefin (D) 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 (D) is MAH functionalized LLDPE, preferably MAH-g- LLDPE.

[0166] In case the functionalized polyolefin (C) 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 a mixture 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 vinyl acetate, more preferred from C1- to C4- alkyl acrylate such as methyl, ethyl, propyl or butyl 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.

[0167] In case the functionalized polyolefin (D) 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 first copolymer (A) and the second copolymer (B) and which bear said carbonyl containing groups.

[0168] Preferred polypropylene is homopolymer or a random copolymer of propylene.

[0169] According to a preferred embodiment of the polymer 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).

[0170] Preferred polyolefin for the functionalized polyolefin (D) is a functionalized polypropylene as defined above. Such polypropylene (PP) for the functionalized polyolefin (D) is preferably a maleic anhydride functionalized PP, more preferably MAH-g-PP.

[0171] The functionalized polyolefin (D), 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.

[0172] Article In another aspect the present invention relates to an article comprising the semiconductive composition as described above or below.

[0173] Preferably said article is a cable comprising a semiconductive layer, more preferably an inner and / or outer semiconductive layer, comprising, preferably consisting of said semiconductive composition as described above or below.

[0174] The semiconductive layer, more preferably the inner and / or outer semiconductive layer preferably comprises the semiconductive composition as described above or below in an amount of from 90 to 100 wt.-%, more preferably from 95 to 100 wt.-%, still more preferably from 99 to 100 wt.-%, based on the total weight of the semiconductive layer, most preferably consists of the semiconductive composition.

[0175] The cable preferably comprises a conductor surrounded by at least a semiconductive layer comprising, preferably consisting of said semiconductive composition as described above or below.

[0176] 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 polymer 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). The terms have well known meanings and indicate the operating level of such cables.

[0177] In one embodiment the cable comprises a conductor surrounded by at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer, in that order, wherein, at least the inner semiconductive layer or the inner and outer semiconductive layers comprise(s), preferably consist(s) of said semiconductive composition as described above or below. Preferably, the cable is a MV power cable.

[0178] Moreover the outer semiconductive layer can be strippable (peelable) or bonded (not peeled off), preferably bonded, which terms have a well known meaning.

[0179] As well known the cable can optionally comprise further layers, e.g. layers surrounding the insulation layer or, if present, the outer semiconductive layers, such as screen(s), a jacketing layer(s), other protective layer(s) or any combinations thereof.

[0180] The insulation layer of the cable, if present, preferably comprises, more preferably consists of a polyolefin composition, for example a polyethylene composition, such as a crosslinked polyethylene composition or a non-crosslinked polyethylene composition, or a polypropylene composition.

[0181] It is preferred that the insulation layer of the cable, if present, preferably comprises, more preferably consists of a thermoplastic polyolefin composition such as a noncrosslinked polyethylene composition or a non-crosslinked polypropylene composition.

[0182] It is especially preferred that the insulation layer of the cable, if present, preferably comprises, more preferably consists of a non-crosslinked polypropylene composition. Said non-crosslinked polypropylene composition preferably comprises a heterophasic propylene copolymer as main polymeric component.

[0183] It is especially preferred that said non-crosslinked polypropylene composition comprises the first copolymer (A) as described above or below as main polymeric component.

[0184] The cable comprising a semiconductive layer, preferably an inner semiconductive layer or an inner and outer semiconductive layer, comprising the semiconductive composition according to the invention as described above shows good electrical properties in form of good electrical properties represented by high Weibull alpha and high Weibull beta values when performing a Weibull analysis on a series of AC electrical breakdown results.

[0185] Further, the cable preferably has a Weibull alpha-value of at least 20.0 kV / mm, more preferably at least 40 kV / mm, still more preferably at least 45 kV / mm, even more preferably at least 46.0 kV / mm, yet more preferably at least 47.0 kV / mm and most preferably at least 47.0 kV / mm, when measured on a 10 kV cable in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables. The upper limit of the Weibull alpha-value is usually not more than 80.0 kV / mm, when measured on a 10 kV cable in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables.

[0186] Still further, the cable preferably has a Weibull beta-value of at least 7.5, more preferably of at least 8.0, still more preferably of at least 8.5, even more preferably of at least 9.0, and most preferably of at least 10.0, when measured on a 10 kV cable in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables.

[0187] The upper limit of the Weibull beta-value is usually not more than 250.0, when measured on a 10 kV cable in agreement with CENELEC HD 605 5.4.15.3.4 for 6 / 10 kV cables.

[0188] Thus, the semiconductive layer comprising the semiconductive composition according to the invention can be used for medium and high voltage cables.

[0189] The inner semiconductive layer comprising the semiconductive composition as described above or below preferably has a volume resistivity of not more than 15 Ohm cm, more preferably not more than 13 Ohm cm, most preferably not more than 12 Ohm cm, when measured on a 10 kV cable at 20°C.

[0190] The lower limit is usually at least 6 Ohm cm, preferably at least 7 Ohm cm, when measured on a 10 kV cable at 20°C.

[0191] Further, the inner semiconductive layer comprising the semiconductive composition as described above or below preferably has a volume resistivity of not more than 55 Ohm cm, more preferably not more than 53 Ohm cm, most preferably not more than 50 Ohm cm, when measured on a 10 kV cable at 90°C.

[0192] The lower limit is usually at least 20 Ohm cm, preferably at least 25 Ohm cm, when measured on a 10 kV cable at 90°C.

[0193] The outer semiconductive layer comprising the semiconductive composition as described above or below preferably has a volume resistivity of not more than 15 Ohm cm, more preferably not more than 13 Ohm cm, most preferably not more than 12 Ohm cm, when measured on a 10 kV cable at 20°C.

[0194] The lower limit is usually at least 6 Ohm cm, preferably at least 7 Ohm cm, when measured on a 10 kV cable at 20°C. Further, the outer semiconductive layer comprising the semiconductive composition as described above or below preferably has a volume resistivity of not more than 55 Ohm cm, more preferably not more than 53 Ohm cm, most preferably not more than 50 Ohm cm, when measured on a 10 kV cable at 90°C.

[0195] The lower limit is usually at least 20 Ohm cm, preferably at least 25 Ohm cm, when measured on a 10 kV cable at 90°C.

[0196] In yet another aspect the present invention relates to the use of a semiconductive composition as described above or below as inner and / or outer semiconductive layer for medium voltage cables.

[0197] It is preferred that the semiconductive composition as described above or below is used as inner and / or outer semiconductive layer for improving the average breakdown strength of the medium voltage cables.

[0198] Benefits of the invention

[0199] The semiconductive composition comprises a rather low amount of carbon black but nevertheless shows a good balance of conductive properties and mechanical properties.

[0200] Further, the semiconductive composition shows a good extrudability. The composition is not sticky during extrusion. Further the composition is not brittle when extruded to tapes or cable layers.

[0201] Tapes of the semiconductive composition also show excellent surface smoothness.

[0202] Cables comprising an inner and optionally an outer semiconductive layer comprising the inventive semiconductive composition surprisingly show good electrical properties in form of average AC breakdown strength, Weibull alpha-value and Weibull beta-value. When adapting the polymer composition of the insulation layer to a propylene based composition instead of an ethylene based composition the electrical properties can further be improved especially shown in a more even distribution of the electric breakdown strength and consequently a higher Weibull beta value. It is believed that this behavior results from an increased adhesion between the semiconductive and insulation layer due to the similar polymeric compositions. Further cables comprising an inner and optionally an outer semiconductive layer comprising the inventive semiconductive composition show good volume resistivity especially at high temperatures such as 90°C, which is considered the operation temperature of the cable.

[0203] The reason is that the first copolymer (A) as main polymeric component has a rather high melting temperature so that at operation temperature the first copolymer does not yet melt. As a consequence only the thermal expansion difference between the carbon black and the polymer matrix contributes to increasing the volume resistivity.

[0204] Examples

[0205] 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.

[0206] 1. Measurement methods a) Melt Flow Rate (MFR2)

[0207] The melt flow rate is the quantity of polymer in grams which the test apparatus standardized to ISO 1133 extrudes within 10 minutes at a certain temperature under a certain load.

[0208] The melt flow rate MFR2 of propylene based polymers is measured at 230°C with a load of 2.16 kg according to ISO 1133.

[0209] The melt flow rate MFR5 of propylene based polymers and the semiconductive composition is measured at 230°C with a load of 5.0 kg according to ISO 1133. The melt flow rate MFR10 of propylene based polymers and the semiconductive composition is measured at 230°C with a load of 10 kg according to ISO 1133.

[0210] The melt flow rate MFR21 of propylene based polymers and the semiconductive composition is measured at 230°C with a load of 21 .6 kg according to ISO 1133.

[0211] The melt flow rate MFR2 of the ethylene based polymers is measured at 190°C with a load of 2.16 kg according to ISO 1133. b) Density The density is measured according to ISO 1183-1 :2004 Method A on compression moulded specimen prepared according to EN ISO 1872-2 (Feb 2007) and is given in g / cm3. c) Comonomer content

[0212] 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 7,2-tetrachloroethane-c / 2 (TCE-c ) along with chromium-(lll)-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 sample preparation 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 was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content 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.

[0213] 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}.

[0214] 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.

[0215] 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:

[0216] E = 0.5 (Spp + Spy + Spb + 0.5( Sap + Say))

[0217] Through the use of this set of sites the corresponding integral equation becomes:

[0218] 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.

[0219] The mole percent comonomer incorporation was calculated from the mole fraction:

[0220] E [mol%] = 100 * fE

[0221] The weight percent comonomer incorporation was calculated from the mole fraction:

[0222] E [wt%] = 100 * (fE * 28.06 ) / ( (fE * 28.06) + ((1 -fE) * 42.08) )

[0223] Bibliographic references:

[0224] 1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

[0225] 2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251.

[0226] 3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225.

[0227] 4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

[0228] 5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0229] 6) Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157.

[0230] 7) Cheng, H. N., Macromolecules 17 (1984), 1950.

[0231] 8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475.

[0232] 9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.

[0233] 10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.

[0234] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253. d) Differential scanning calorimetry (DSC) analysis, melting temperature (Tm) and crystallization 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 I part 3 / method C2 in a heat I 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 (He) are determined from the cooling step, while melting temperature and heat of fusion (Hf) are determined from the second heating step.

[0235] When a sample shows two or more melting temperatures and / or crystallization temperatures only the main melting temperature (at the highest Hf) and main crystallization temperature (at the highest He) 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. e) Crystallization extraction (CRYSTEX)

[0236] Note: Crystallization extraction (CRYSTEX) analyses the polymeric part of each component, with non-polymeric parts, such as any fillers or particulate pigments, not contributing to the reported CRYSTEX data presented.

[0237] Determination of Crystalline and soluble fractions and their respective properties (iV and Ethylene content)

[0238] The crystalline (CF) and soluble fractions (SF) of the polypropylene (PP) compositions as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by use of the Crystex (crystallisation extraction) method. Potential instruments that can be used are Crystex QC or Crystex 42 (Polymer Char; Valencia, Spain). Details of the technique and the method can be found in literature (Ljiljana Jeremie, Andreas Albrecht, Martina Sandholzer & Markus Gahleitner (2020): Rapid characterization of high-impact ethylene-propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods, International Journal of Polymer Analysis and Characterization, 25:8, 581 - 596).

[0239] The crystalline and amorphous fractions are separated through temperature cycles of dissolution at 160°C, crystallization at 40°C and re-dissolution in 1 ,2,4-trichlorobenzene at 160°C. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an integrated infrared detector (IR4) and for the determination of the intrinsic viscosity (IV) an online 2-capillary viscometer is used.

[0240] IR4 detector is a multiple wavelength detector measuring IR absorbance at two different bands (CH3 stretching vibration (centred at app. 2960 cm-1) and the CH stretching vibration (2700-3000 cm-1) that are serving for the determination of the concentration and the Ethylene content in Ethylene-Propylene copolymers. IR4 detector is calibrated with series of 8 EP copolymers with known Ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by 13C-NMR) and each at various concentrations, in the range of 2 and 13mg / ml. To encounter for both features, concentration and ethylene content at the same time for various polymer concentration expected during Crystex analyses the following calibration equations were applied:

[0241] Cone = a + b*Abs(CH) + c*(Abs(CH))2+ d*Abs(CH3) + e*(Abs(CH3)2+ f*Abs(CH)*Abs(CH3) (Equation 1)

[0242] CH3 / 1000C = a + b*Abs(CH) + c* Abs(CH3) + d * (Abs(CH3) / Abs(CH)) + e * (Abs(CH3) / Abs(CH))2(Equation 2)

[0243] The constants a to f for equation 1 and a to e for equation 2 were determined by using least square regression analysis.

[0244] The CH3 / 1000C is converted to the ethylene content in wt.-% using following relationship: wt.-% (Ethylene in EP Copolymers) = 100 - CH3 / 1000TC * 0.3 (Equation 3)

[0245] Amount of Soluble Fraction (SF) and Crystalline Fraction (CF) are correlated through the XS calibration to the “Xylene Cold Soluble” (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various EP copolymers with XS content in the range 2-31 wt.-%. A linear calibration curve is used.

[0246] Intrinsic viscosity (iV) of the parent EP copolymer and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and are correlated to corresponding IV’s determined by standard method in decalin according to ISO 1628-3. Calibration is achieved with various EP copolymers and PP polymers with iV = 2-4 dL / g. The determined calibration curve is linear.

[0247] The samples to be analyzed are weighed out in concentrations of 10 mg / ml to 20 mg / ml. After automated filling of the vial with 1 ,2,4-TCB containing 250 mg / l 2,6-tert-butyl-4- methylphenol (BHT) as antioxidant, the sample is dissolved at 170°C until complete dissolution is achieved with either constant stirring or gentle shaking. To avoid sample degradation, polymer solution is blanketed with the N2 atmosphere during dissolution. For PP composition containing inorganic fillers or pigments or any other non-TCB soluble polymeric substances removal of these is required. This can be done by hot filtration prior injection.

[0248] A defined volume of the polymer solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline fraction is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the iV [dl / g] and the C2 [wt.-%] of the PP composition. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt.-% SF, wt.-% C2, iV). f) Intrinsic viscosity (iV)

[0249] The reduced viscosity (also known as viscosity number), qred, and intrinsic viscosity, iV, are determined according to ISO 1628-3: “Determination of the viscosity of polymers in dilute solution using capillary viscometers”.

[0250] 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).

[0251] 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: r ■ ■ ■ ■q[dimensionless]

[0252] Reduced viscosity (qred) is calculated using the equation: where C is the polymer solution concentration at 135°C: C= — , and m is the polymer mass, V is the solvent volume, and y is the ratio of solvent densities at 20°C and 135°C (y=p2o / pi35=1.1 O7).

[0253] The calculation of intrinsic viscosity iV is performed by using the Schulz-Blaschke equation from the single concentration measurement: where K is a coefficient depending on the polymer structure and concentration. For calculation of the approximate value for IV, K=0.27. g) Flexural Modulus

[0254] The flexural modulus was determined acc. to ISO 178 method A (3-point bending test) on 80 mm x 10 mm x 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. h) Tensile test

[0255] For the unfilled polymers the following procedure was used:

[0256] The tensile test (modulus, stress and strain at break and stress and strain at yield) is measured at 23°C according to ISO 527-1 (cross head speed 1 mm / min) using type 1 A directly injection moulded test specimens according to ISO 527-2(1 A). After preparation of the test specimen were prepared the polymer in the test specimens were rested at room temperature for 16 h or 96 h before testing to ensure that the polymer is fully crystallized. The accordant resting time is listed for each of the below listed properties.

[0257] For the semiconductive compositions comprising carbon black the tensile test was conducted on specimens obtained from tapes according to the following procedure: First pellets were extruded into a tape of around 0.6-0.7 mm thickness by use of a Collin Teach-Line E 20 T tape extruder using the following temperature settings: 60 °C (zone 1), 220 °C (zone 2), 220 °C (zone 3) and 220 °C (zone 4 to 6). These tapes were then used to prepare a plaque by placing all the tapes in one direction and carrying out compression moulding according to ISO 19069-2 to produce a plaque of around 2 mm thickness.

[0258] 5A specimens were then die cut from the plaque and conditioned for at least 96h at a constant temperature of 23C.

[0259] The tensile properties of the semicon materials (tensile strength, elongation at break) were determined acc. to ISO 527-1 using 5A (ISO 527-2) specimens.

[0260] Following the standard EN60811-501 , a test speed of 25 mm / min was used.

[0261] A load cell recorded the change in force and an extensometer recorded the change in elongation. i) Charpy notched impact strength

[0262] For the unfilled polymers the following procedure was used:

[0263] The Charpy notched impact strength was determined acc. to ISO 179-1 / 1 eA on notched 80 mm x 10 mm x 4 mm specimens (specimens were prepared according to ISO 179- 1 / 1 eA). 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. j) Xylene cold solubles (XCS) content

[0264] The quantity of xylene soluble matter in polypropylene is determined according to the ISO16152 (first edition; 2005-07-01).

[0265] 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 filtrate leaving the soluble fraction as a residue. The percentage of this fraction is determined gravimetrically. where mo is the mass of the sample test portion weighed, in grams rm is the mass of residue, in grams vo is the original volume of solvent taken vi is the volume of the aliquot taken for determination. k) Volume resistivity (VR)

[0266] VR measurement on tapes:

[0267] A tape of thickness 0.6-0.7 mm and 25 mm width was extruded with a Collin Teach-Line E 20 T tape extruder using the following temperature settings: 60 °C (zone 1) and 220 °C (zone 2 to 6). These tapes were then used to prepare a plaque by placing all the tapes in one direction and carrying out compression moulding according to ISO 19069-2 to produce a plaque of around 3 mm thickness.

[0268] The plaque was cut into 15 cm long specimens which were conditioned at 1 atm and 23 ± 2°C for at least 96 hours before measurement. A four-terminal electrode system as described in ISO 3915 (1999) was used to determine the resistance between the potential electrodes 10 mm apart. The resistance at elevated temperatures was determined 30 minutes after placing the assembly in the preheated oven. The volume resistivity was calculated from measured resistance and sample geometry using the formula in ISO 3915 (1999).

[0269] VR measurement on cable specimens:

[0270] Cable specimens of length 13.5 cm were conditioned at 1 atm and 60 ± 2°C for 5 ± 0.5 hours before measurement. The measurement of the resistance of the outer semiconductive layer was based on I EC 60502-2 (2005) using a four-terminal system, but with metal wires pressed against the semiconductive layer instead of silver-painted electrodes. The distance between the two potential electrodes was 50 mm.

[0271] To measure the resistance of the inner semiconductive layer, the cable was cut in two halves, removing the metallic conductor. The resistance between conductive silver paste applied on the specimen ends was used to calculate the volume resistivity. It was thus a two-terminal method where the electrode distance is about 12 cm.

[0272] The resistance at elevated temperatures was determined 30 minutes after placing the assembly in the preheated oven.

[0273] The volume resistivity was calculated from measured resistance and sample geometry using the formula in IEC 60502-2 (2005).

[0274] I) 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:

[0275] • Start at 18 kV for 5 minutes

[0276] • Voltage increasing in step of 6 kV every 5 minutes until breakdown occurs

[0277] The 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. m) Ash content

[0278] 1 g semiconductive material was placed in a quartz crucible. The crucible was then put in a microwave oven preheated to 600°C. The organic part is completely pyrolyzed after 10 min why the carbon black content (= ash content) can be calculated from the weight loss.

[0279] 2. Production of the semiconductive compositions

[0280] The following resins were used for the preparation of the propylene copolymer compositions of the examples: a) Polymerization of the heterophasic propylene copolymers HECO1 , HECO2 and HECO3

[0281] • Catalyst

[0282] The catalyst used in the polymerization process for the heterophasic propylene copolymers HECO1 and HECO3 is 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.

[0283] The catalyst used in the polymerization process for the heterophasic propylene copolymer HECO2 is a Ziegler-Natta catalyst, which is described in the example section of WO 2015 / 117948. As co-catalyst triethyl-aluminium (TEAL) and as donor dicyclo pentyl dimethoxy silane (D-donor) was used.

[0284] • Polymerization of the heterophasic propylene copolymer powders A and B Heterophasic propylene copolymers powders A and B have been produced in a Borstar™ plant in the presence 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.

[0285] Table 1 : Polymerization of heterophasic propylene copolymer powders A and B:

[0286] • Preparation of HECO1 , HECO2 and HECO3

[0287] The heterophasic propylene copolymer powders A and B from the polymerization reaction were compounded in a twin screw extruder together with a stabilizer package to obtain the polypropylene compositions of HECO1 , HECO2 and HECO3.

[0288] During compounding of HECO1 , BNT alpha-nucleating agent was added and the composition was vis-broken to a melt flow rate MFR2 (230°C, 2.16 kg) of 3.9 g / 10 min as disclosed in the example section of WO 2017 / 198633.

[0289] During compounding of HECO2, the composition was vis-broken to a melt flow rate MFR2 (230°C, 2.16 kg) of 3.9 g / 10 min as disclosed in the example section of WO 2017 / 198633.

[0290] An overview of the production of the polypropylene HECO1 , HECO2 and HECO3 is shown in Table 2.

[0291] Table 2: Compounding of compositions HECO1-3 in a twin screw extruder:

[0292] Stabilizer packages and alpha-nucleating agents:

[0293] • Stabilizer onepack 1 consists of 29 wt% Pentaerythrityl-tetrakis(3-(3’,5’-di-tert. butyl- 4-hydroxyphenyl)-propionate (CAS-No. 6683-19-8), 58 wt% Tris (2,4-di-f-butylphenyl) phosphite (CAS-No. 31570-04-4) and 13 wt% Magnesium Oxide (CAS-No. 1309-48- 4), all commercially available from a variety of companies.

[0294] • Stabilizer onepack 2 consists of 25.6 wt% Pentaerythrityl-tetrakis(3-(3’,5’-di-tert. butyl-4-hydroxyphenyl)-propionate (CAS-No. 6683-19-8), 51.3 wt% Tris (2,4-di-f- butylphenyl) phosphite (CAS-No. 31570-04-4) and 23.1 wt% synthetic hydrotalcite (CAS-No. 11097-59-9), all commercially available from a variety of companies. • Alpha-nucleation via BNT was achieved by adding 2 wt% of a propylene homopolymer with an MFR2 (230°C) of 8.0 g / 10 min and a melting temperature of 162 °C, which is produced with a Ziegler-Natta type catalyst in the Borealis nucleation technology (BNT), comprising a polymeric a-nucleating agent, and is distributed by Borealis AG (Austria).

[0295] The properties of HECO1 , HECO2 and HECO3 are listed in Table 3 below.

[0296] Table 3: Properties of HECO1 , HECO2 and HECO3

[0297] • Preparation of the semiconductive compositions

[0298] The components of the semiconductive compositions as listed above and below were compounded using a single screw kneader to semiconductive compositions IE1 , IE2, CE1 , CE2, CE3, CE4 and CE5. The amounts of the different components in the semiconductive compositions are listed below in Table 4.

[0299] Carbon black (CB) was Printex Alpha, commercially available from Orion Engineered Carbons GmbH. RaCo is a random propylene-ethylene copolymer having a melt flow rate MFR2 of 45 g / 10 min, a melting temperature Tm of 150°C, a flexural modulus of 950 MPa, a tensile modulus of 1050 MPa, and a Charpy notched impact strength at 23°C of 5.5 kJ / m2.

[0300] LDPE is a low density polyethylene having a density of 915 kg / m3(determined according to ISO1183-1 / Method A), a melt flow rate MFR2 of 15 g / 10 min and a melting temperature Tm of 104°C.

[0301] Additives:

[0302] AO1 antioxidant Irganox 1010, commercially available from BASF SE,

[0303] AO2 antioxidant Irgafos 168, commercially available from BASF SE,

[0304] AO3 antioxidant Irganox PS 802, commercially available from BASF SE, MD metal deactivator Irganox MD 1024, commercially available from BASF SE, and AS acid scavenger Zn-stearate.

[0305] Table 4: Components of semiconductive compositions

[0306] The semiconductive compositions have the following properties as listed in Table 5 below.

[0307] Table 5: Properties of semiconductive compositions n.m. = not measured

[0308] Compositions IE1 and IE2 show a superior balance of properties regarding melt flow rate, tensile strength, elongation at break and volume resistivity compared to the comparative examples. Tapes of compositions IE1 and IE2 further showed excellent surface smoothness.

[0309] The semiconductive composition CE1 was too sticky during extrusion.

[0310] The tapes of semiconductive composition CE1 were too brittle.

[0311] Due to their combination of higher melt flow rate, higher tensile strength and higher elongation at break values, the semiconductive compositions of the two examples IE1 and CE3 were chosen as inner semiconductive layer and outer semiconductive layer for cable production with the same insulation material.

[0312] 3. Production of 10 kV cables

[0313] 10 kV test cables were produced on a Maillefer pilot cable line of catenary continuous vulcanizing (CCV) type.

[0314] The conductors of the cable cores had a cross section being 50 mm2of stranded aluminium. The inner semiconductive layer was produced from the above described semiconductive compositions of examples IE1 and CE3 and had a thickness of 1 .0 mm. The insulation layer was produced from the polypropylene composition as described below, and had a thickness of 3.4 mm. The outer semiconductive layer was produced from the above described semiconductive compositions of examples IE1 and CE3 and had a thickness of 1 .0 mm.

[0315] 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.

[0316] The pilot cables were then subjected to AC breakdown testing.

[0317] The polymer composition for the insulation layer (IL) was prepared from visbroken and BNT nucleated HECO1 as described above which was compounded with 0.14 wt.-% of a stabilizer onepack consisting of 29 wt% Pentaerythrityl-tetrakis(3-(3’,5’-di-tert. butyl-4- hydroxyphenyl)-propionate (CAS-No. 6683-19-8), 58 wt% Tris (2,4-di-f-butylphenyl) phosphite (CAS-No. 31570-04-4) and 13 wt% Magnesium Oxide (CAS-No. 1309-48-4), all commercially available from a variety of companies.

[0318] Table 6 shows the electric properties of the 10 kV cables of examples C1 and C2 in which the inventive semiconductive composition IE1 of the inner and outer semiconductive layers are compared to the comparative semiconductive composition CE3 of the inner and outer semiconductive layers.

[0319] Table 6: Electric properties of 10 kV cables of C1 and C2

[0320] The test cable C1 including the inventive semiconductive composition IE1 in the inner and outer semiconductive layers shows a higher Weibull-alpha value and higher Weibull-beta value compared to test cable C2.

[0321] Further volume resistivity was measured on both the inner and outer semiconductive layer of the two test cables C1 and C2 at 20°C and 90°C (see Table 7).

[0322] Table 7: Volume resistivity of inner and outer semiconductive layers of C1 and C2

[0323] SC = inner semiconductive layer; OSC = outer semiconductive layer

[0324] For both semiconductive compositions IE1 and CE3 the increase of volume resistivity with temperature is relatively small, from 10-12 Ohm cm at 20°C to only 39-47 Ohm cm at 90 °C. IE1 shows lower volume resistivity values at 90 °C since it does not contain LDPE.

[0325] The main components of IE1 and CE1 (HECO1 and HECO3) have melting temperature around 150 °C and their crystals are not yet melting at 90 °C. Therefore only the thermal expansion difference between the carbon black and the polymer matrix is increasing the volume resistivity. This is an advantage compared to EVA-based semiconductive layers where, due to the melting of the EVA at around 90 °C, a major increase from VR < 25 Ohm cm at 20°C to 60 Ohm cm at 90 °C is usually observed.

Claims

Claims1 . A semiconductive composition comprising(A) from 25.0 to 67.5 wt.-% of a first copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which first copolymer (A) has a melt flow rate MFR2 of from 2.0 to 6.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX) in the range of from more than 25.0 to 50.0 wt.-%, based on the total weight amount of the first copolymer (A); and a total comonomer content of from 7.5 to 20.0 wt.-%, based on the total weight of the first copolymer (A) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX);(B) from 5.0 to 50.0 wt.-% of a second copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms, which second copolymer (B) has a melt flow rate MFR2 of at least 2.0 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg; a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), in the range of from 12.0 to 25.0 wt.-%, based on the total weight amount of the second copolymer (B); and a total comonomer content of from 4.0 to 10.0 wt.-%, based on the total weight of the second copolymer (B) and determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy from crystallization extraction (CRYSTEX); and(C) from 15.0 to 35.0 wt.-% of carbon black, wherein all weight amounts are based on the total weight amount of the semiconductive composition.

2. The semiconductive composition according to claim 1 , wherein the soluble fraction (SF) of the first copolymer (A) has an amount of comonomer units, determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, of from 20.0 to 35.0 wt.-%, based on the totalamount of monomer units in the soluble fraction (SF) of the first copolymer (A) and / or an intrinsic viscosity (iV(SF)), determined according to ISO 1628-3, in the range from 150 to 250 cm3 / g.

3. The semiconductive composition according to claims 1 or 2, wherein the first copolymer (A) has one or more or all of the following properties:• a melting temperature Tm of from 140 to 159°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2; and / or• a crystallization temperature Tc of from 85 to 125°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2; and / or• a difference in melting temperature to crystallization temperature Tm-Tc of from 20 to 70°C; and / or• a total intrinsic viscosity of from 150 to 350 cm3 / g, determined according to ISO 1628-3; and / or• a flexural modulus of not more than 470 MPa, determined according to ISO 178 method A; and / or• a Charpy notched impact strength at 23°C of from 40 to 110 kJ / m2, determined according to ISO 179-1 / 1 eA; and / or• a complex viscosity at a frequency of 100 rad / s eta* o rad / s of from 750 to 950 Pa s.

4. The semiconductive composition according to any one of claims 1 to 3, wherein the first copolymer (A) has been subjected to vis-breaking.

5. The semiconductive composition according to any one of claims 1 to 4, wherein the soluble fraction (SF) of the second copolymer (B) has an amount of comonomer units, determined by FT-IR spectroscopy calibrated by quantitative13C-NMR spectroscopy, of from 15.0 to 35.0 wt.-%, based on the total amount of monomer units in the soluble fraction (SF) of the second copolymer (B) and / or an intrinsic viscosity (iV(SF)), determined according to ISO 1628-3, in the range from 90 to 190 cm3 / g.

6. The semiconductive composition according to any one of claims 1 to 5, wherein the second copolymer (B) has one or more or all of the following properties:• a melting temperature Tm of from 130 to 150°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2; and / or• a crystallization temperature Tc of from 80 to 120°C, determined by to DSC analysis according to ISO 113571 part 3 / method C2; and / or• a difference in melting temperature to crystallization temperature Tm-Tc of from 20 to 70°C; and / or• a total intrinsic viscosity of from 100 to 250 cm3 / g, determined according to ISO 1628-3; and / or• a flexural modulus of more than 470 MPa, determined according to ISO 178 method A; and / or• a Charpy notched impact strength at 23°C of from 4.0 to 15.0 kJ / m2, determined according to ISO 179-1 / 1 eA; and / or• a complex viscosity at a frequency of 100 rad / s eta* o rad / s of from 500 to 700 Pa s.

7. The semiconductive composition according to any one of claims 1 to 6, wherein the second copolymer (B) has been subjected to vis-breaking.

8. The semiconductive composition according to any one of claims 1 to 7, wherein carbon black (C) has one or more or all of the following properties:• a primary particle size of at least 5 nm, which is defined as the average particle diameter according to ASTM D3849-14,• iodine adsorption number of at least 10 mg / g, when determined according to ASTM D-1510-19; and / or• oil absorption number (OAN) of at least 30 ml / 100g, when measured according to ASTM D 2414-19.

9. The semiconductive composition according to any one of claims 1 to 8 being free of a polyolefin functionalized with a mono- or polycarboxylic acid compound or a derivative of a mono- or polycarboxylic acid compound.

10. The semiconductive composition according to any one of claims 1 to 9 being free of 2 ,2,4-trimethyl-1 ,2-dihydroquinoline (TMQ).11 . The semiconductive composition according to any one of claims 1 to 10 having one or more or all of the following properties:• a melt flow rate MFRs of from 2.0 to 100 g / 10 min, determined according to ISO 1133 at 230°C and 5 kg; and / or• a melt flow rate MFR of from 12 to 600 g / 10 min, determined according to ISO 1133 at 230°C and 10 kg; and / or• a density from 0.850 to 1 .200 g / cm3, determined according to ISO 1183; and / or• a tensile strength of from 10.0 to 25.0 MPa, determined at 23°C according to ISO 527-1 ; and / or• an elongation at break of from 350 to 750 %, determined at 23°C according to ISO 527-1.

12. The semiconductive composition according to any one of claims 1 to 11 having a volume resistivity (VR) of from 6.0 to 55.0 Ohm -cm.

13. An article comprising the semiconductive composition according to any one of claims 1 to 12.

14. The article according to claim 13 being a cable comprising a semiconductive layer comprising the semiconductive composition.

15. The use of a semiconductive composition according to any one of claims 1 to 12 as inner and / or outer semiconductive layer for medium voltage cables.

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