Polyolefin composition for cable insulation

Abstract

The present invention relates to a polyolefin composition, to an article comprising said polyolefin composition, preferably to a cable comprising an insulating layer comprising said polyolefin composition, and to the use of said polyolefin composition as cable insulation for medium-voltage, high-voltage, extra-high-voltage and extra-high-voltage cables, the polyolefin composition having a total ethylene content of greater than 32.5 to 60.0 wt% based on the total weight of the polyolefin composition and determined by Crystallization Extraction (CRYSTEX) by FT-IR spectroscopy calibrated by Quantitative 13C-NMR spectroscopy; a melt flow rate MFR2, determined according to ISO 1133 at 230 DEG C and 2.16 kg, of greater than 2.5 to 6.0 g / 10 min; a crystalline fraction (CF) content determined by crystallization extraction (CRYSTEX) in an amount, based on the total weight of the polyolefin composition, in the range of 75.0 to 95.0 wt.%, the crystalline fraction (CF) having an ethylene content (C2 (CF)) determined by FT-IR spectroscopy calibrated by quantitative 13C-NMR spectroscopy in the range of greater than 32.5 to 62.5 wt.%, based on the total amount of monomer units in the crystalline fraction (CF), and a soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), in an amount, based on the total weight of the polyolefin composition, in the range of 5.0 to 25.0 wt%, said soluble fraction (SF) having an intrinsic viscosity (iV (SF)), determined according to ISO 1628-3, in the range of 85 to 200 cm3 / g.

Description

Technical Field

[0001] This invention relates to a polyolefin composition, articles comprising the polyolefin composition, preferably including cables comprising an insulation layer comprising the polyolefin composition, and the use of the polypropylene composition as cable insulation for medium-voltage and high-voltage cables, especially for high-voltage (HV), ultra-high-voltage (EHV), and extra-high-voltage (UHV) cables. Background Technology

[0002] Today, ethylene polymer products are used as insulation and semiconductor shielding for medium-voltage, high-voltage, and ultra-high-voltage cables due to their ease of processing and favorable electrical properties. However, according to IEC 62895, the maximum operating temperature (i.e., the highest conductor operating temperature under normal operating conditions) of thermoplastic ethylene polymer products (PE and HDPE) used in high-voltage DC cables up to 320 kV is limited to 80°C.

[0003] Therefore, thermoplastic propylene polymers were explored as insulation materials for medium-voltage, high-voltage, and ultra-high-voltage (MV, HV, and EHV) cables, as well as high-voltage direct current (HVDC) cables. Propylene polymers offer particular advantage for high-voltage and ultra-high-voltage cables due to their relatively high maximum operating temperature.

[0004] WO 2022 / 200395 A1 and WO 2022 / 200396 A1 disclose flexible polypropylene compositions suitable for cable insulation, both comprising flexible multiphase copolymers of propylene and ethylene. These compositions exhibit an excellent balance of properties regarding flexibility, impact strength, and electrical properties, making them particularly suitable for medium-voltage cables.

[0005] However, for high voltage, ultra-high voltage and extra-high voltage cables, especially for high voltage DC cables, specific minimum mechanical requirements are required, as described in CIGRE TB852 recommendation for HVDC cable systems.

[0006] In this invention, a polyolefin composition having a considerably low amount of soluble fraction in crystallization extraction (CRYSTEX), which is a measure of the amorphous phase of the polyolefin composition, is presented. This polyolefin composition exhibits a balance of improved tensile and indentation properties as well as improved thermal conductivity, and further demonstrates good performance during cable extrusion. Therefore, this polyolefin composition is suitable for cable insulation, and particularly meets all CIGRE TB852 recommendations for HVDC cable systems. Summary of the Invention

[0007] In one aspect, the present invention relates to a polyolefin composition having

[0008] Based on the total weight of the polyolefin composition and obtained by crystallization extraction (CRYSTEX) through quantitative... 13 The total ethylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is greater than 32.5 to 60.0% by weight, preferably 33.0 to 55.0% by weight, more preferably 33.5 to 52.5% by weight, and even more preferably 34.0 to 50.0% by weight.

[0009] The melt flow rate MFR2, as determined according to ISO 1133 at 230°C and 2.16 kg, is greater than 2.5 to 6.0 g / 10 min, preferably 2.6 to 5.5 g / 10 min, even more preferably 2.7 to 5.0 g / 10 min, and most preferably 2.8 to 4.5 g / 10 min.

[0010] The content of crystalline fraction (CF) determined by crystallization extraction (CRYSTEX) is based on the total weight of the polyolefin composition and is in the range of 75.0 to 95.0% by weight, preferably in the range of 77.5 to 93.5% by weight, more preferably in the range of 80.0 to 92.5% by weight, and most preferably in the range of 82.5 to 91.0% by weight.

[0011] The crystal fraction (CF) has a content based on the total amount of monomer units in the crystal fraction (CF) in the range of greater than 32.5 to 62.5 wt%, preferably in the range of 35.0 to 60.0 wt%, and most preferably in the range of 36.0 to 55.0 wt%, by quantitative analysis. 13 Ethylene content (C2(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, and

[0012] The soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), is in the range of 5.0 to 25.0% by weight, preferably in the range of 6.5 to 22.5% by weight, more preferably in the range of 7.5 to 20.0% by weight, and most preferably in the range of 9.0 to 17.5% by weight, based on the total weight of the polyolefin composition.

[0013] The soluble fraction (SF) has a concentration of 85 to 200 cm⁻¹ 3 Within the range of / g, more preferably within 95 to 175 cm 3 Within the range of / g and most preferably in the range of 100 to 150 cm 3 Intrinsic viscosity (iV(SF)) measured according to ISO 1628-3 within the range of / g.

[0014] In another respect, the present invention relates to articles comprising polyolefin compositions as described above or below.

[0015] Preferably, the article is a cable including an insulation layer comprising a polyolefin composition as described above or below.

[0016] In another aspect, the present invention relates to the use of polyolefin compositions as described above or below as cable insulation for medium-voltage cables, high-voltage cables, ultra-high-voltage cables and extra-high-voltage cables, preferably for high-voltage cables and ultra-high-voltage cables, and more preferably for high-voltage DC (HVDC) cables and ultra-high-voltage DC (EHVDC) cables.

[0017] definition

[0018] Multiphase polypropylene is a propylene-based copolymer having a semi-crystalline matrix phase and an elastomeric phase dispersed therein. The semi-crystalline matrix phase can be a propylene homopolymer or a random copolymer of propylene and at least one α-olefin comonomer. The elastomeric phase can be a propylene copolymer with a high comonomer content, wherein the comonomer is not randomly distributed in the polymer chain, but rather distributed in comonomer-rich block structures and propylene-rich block structures.

[0019] Multiphase polypropylene typically differs from single-phase propylene copolymers because it exhibits two distinct glass transition temperatures (Ti) attributed to the matrix phase and the elastomer phase. g .

[0020] Propylene homopolymers are polymers that consist essentially of propylene monomer units. Due to impurities, especially during commercial polymerization processes, propylene homopolymers may contain up to 0.1 mol% of comonomer units, preferably up to 0.05 mol% and most preferably up to 0.01 mol% of comonomer units.

[0021] Propylene random copolymers are copolymers of propylene monomer units and comonomer units, wherein the comonomer units are randomly distributed on the polypropylene chains. Therefore, propylene random copolymers include at least 85% by weight, and most preferably at least 88% by weight, a fraction insoluble in xylene (xylene cold insoluble (XCI) fraction) based on the total amount of the propylene random copolymer. Therefore, propylene random copolymers do not contain an elastomeric polymer phase dispersed therein.

[0022] Typically, a propylene polymer comprising at least two propylene polymer fractions (components) is referred to as "multimodal," which are produced under different polymerization conditions (resulting in different (weight-average) molecular weights and / or different comonomer contents), preferably by polymerization in multiple polymerization stages with different polymerization conditions. The prefix "multimodal" refers to the number of different polymer fractions constituting the propylene polymer. As examples of multimodal propylene polymers, a propylene polymer consisting of only two fractions is referred to as "bimodal," while a propylene polymer consisting of only three fractions is referred to as "trimodal."

[0023] A single-peak propylene polymer consists of only one fraction.

[0024] Therefore, the term "different" means that the propylene polymer fractions are different from each other in at least one property, preferably in weight-average molecular weight (which can also be measured at different melt flow rates of the fractions) or comonomer content or both.

[0025] Elastomers are polymers that exhibit viscoelasticity and weak intermolecular forces. The term "elastomer" can be used interchangeably with "rubber".

[0026] Polyolefin-based elastomers (such as polypropylene-based elastomers, i.e. elastomers having a molar majority of olefin monomer units (such as propylene monomer units)) are typically thermoplastic elastomers.

[0027] Thermoplastic elastomers possess the properties of both thermoplastics and elastomers.

[0028] Polyolefin-based elastomers (such as polypropylene-based elastomers) typically exhibit low density and low viscosity. They can be propylene homopolymers or propylene-α-olefin copolymers, such as propylene-ethylene copolymers. A specific class of polypropylene-based elastomers are propylene homopolymers or propylene-α-olefin copolymers (such as propylene-ethylene copolymers), which are typically polymerized in solution polymerization methods in the presence of a single active site catalyst.

[0029] Viscosity reduction cracking is a post-reactor chemistry process used to modify semi-crystalline polymers, such as propylene polymers. During the viscosity reduction cracking process, the propylene polymer backbone is degraded via β-fracture, for example, by means of peroxides (such as organic peroxides). Degradation is typically used to increase melt flow rate and narrow molecular weight distribution.

[0030] Low-density polyethylene (LDPE) is a polymer primarily composed of ethylene monomers, polymerized via free radical polymerization under high pressure. LDL is characterized by long polymer side chains, which reduce the polymer's density regardless of the amount of comonomers.

[0031] According to CIGRE TB852 recommendations for HVDC transmission cable systems, high voltage (HV) refers to a voltage of up to and including 400 kV for DC systems.

[0032] Ultra-high voltage (EHV) refers to voltages exceeding 400 kV to 800 kV and including 800 kV for DC systems.

[0033] Although not explicitly mentioned in the recommendations, ultra-high voltage (UHV) therefore refers to voltages greater than 800 kV for DC systems.

[0034] In the following text, unless otherwise stated, quantities are given as % by weight (wt%). Detailed Implementation

[0035] Polyolefin compositions

[0036] The polyolefin compositions described above or below have

[0037] Based on the total weight of the polyolefin composition and obtained by crystallization extraction (CRYSTEX) through quantitative... 13 The total ethylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is greater than 32.5 to 60.0% by weight, preferably 33.0 to 55.0% by weight, more preferably 33.5 to 52.5% by weight, and even more preferably 34.0 to 50.0% by weight; and

[0038] The melt flow rate MFR2, as determined according to ISO 1133 at 230°C and 2.16 kg, is greater than 2.5 to 6.0 g / 10 min, preferably 2.6 to 5.5 g / 10 min, even more preferably 2.7 to 5.0 g / 10 min, and most preferably 2.8 to 4.5 g / 10 min.

[0039] The polymer portion of the polyolefin composition was characterized using crystallization extraction (CRYSTEX) with trichlorobenzene (TCB) as the solvent. This method is described in the determination method section below. The crystalline fraction (CF) contains the majority of the matrix phase and only a small portion of the elastomeric phase, while the soluble fraction (SF) contains the majority of the elastomeric phase and only a small portion of the matrix phase. In some cases, this method yields more useful data than xylene extraction because the crystalline fraction (CF) and soluble fraction (SF) correspond more accurately to the matrix and elastomeric phases, respectively. Due to the different separation methods used in xylene extraction and crystallization extraction (CRYSTEX), the performance of the XCS / XCI fraction is not entirely the same as that of the crystalline fraction / soluble fraction (CF / SF), meaning that the amounts and properties of the matrix and elastomeric phases can differ.

[0040] Typically, the content of the crystalline fraction (CF) and the soluble fraction (SF) of a composition is only related to its polymeric components, i.e., there are no other components that are insoluble and therefore not part of the dissolution and crystallization cycle described below in the assay method.

[0041] In the present case, polyolefin compositions are generally completely soluble in trichlorobenzene (TCB), such that the content of the crystalline fraction (CF) and the soluble fraction (SF) are related to the total content of the polyolefin composition. Therefore, the content of the crystalline fraction (CF) and the soluble fraction (SF) are preferably 100% by weight of the polyolefin composition.

[0042] The polyolefin composition has a crystallization fraction (CF) content determined by crystallization extraction (CRYSTEX) in an amount in the range of 75.0 to 95.0% by weight, preferably in the range of 77.5 to 93.5% by weight, more preferably in the range of 80.0 to 92.5% by weight, and most preferably in the range of 82.5 to 91.0% by weight, based on the total weight of the polyolefin composition.

[0043] The crystal fraction (CF) has a content based on the total amount of monomer units in the crystal fraction (CF) in the range of greater than 32.5 to 62.5 wt%, preferably in the range of 35.0 to 60.0 wt%, and most preferably in the range of 36.0 to 55.0 wt%, by quantitative analysis. 13 Ethylene content (C2(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0044] Preferably, the crystal fraction (CF) has a content based on the total amount of monomer units in the crystal fraction (CF) in the range of 37.5% to less than 67.5% by weight, more preferably in the range of 40.0% to 65.0% by weight, and most preferably in the range of 45.0% to 64.0% by weight, obtained by quantitative analysis. 13 Propylene content (C3(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0045] Furthermore, the crystal fraction (CF) preferably has a density of 100 to 250 cm⁻¹. 3 Within the range of / g, more preferably within 125 to 225 cm 3 Within the range of / g and most preferably in the range of 140 to 210 cm 3 Intrinsic viscosity (iV(CF)) measured according to ISO 1628-3 within the range of / g.

[0046] The polyolefin composition has a soluble fraction (SF) content determined by crystallization extraction (CRYSTEX) in an amount from 5.0 to 25.0% by weight, preferably from 6.5 to 22.5% by weight, more preferably from 7.5 to 20.0% by weight, and most preferably from 9.0 to 17.5% by weight, based on the total weight of the polyolefin composition.

[0047] The soluble fraction (SF) has a concentration of 85 to 200 cm⁻¹ 3 Within the range of / g, more preferably within 95 to 175 cm 3 Within the range of / g and most preferably in the range of 100 to 150 cm 3 Intrinsic viscosity (iV(SF)) measured according to ISO 1628-3 within the range of / g.

[0048] Furthermore, the soluble fraction (SF) preferably has a content of 22.5 to 42.5% by weight, more preferably 25.0 to 40.0% by weight, and most preferably 30.0 to 35.0% by weight, based on the total amount of monomer units in the soluble fraction (SF), by quantitative analysis. 13 Ethylene content (C2(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0049] Preferably, the soluble fraction (SF) has a content based on the total amount of monomer units in the soluble fraction (SF) in the range of 57.5 to 77.5% by weight, more preferably in the range of 60.0 to 75.0% by weight, and most preferably in the range of 62.5 to 70.0% by weight, obtained by quantitative analysis. 13 Propylene content (C3(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0050] The polyolefin composition preferably has a ratio of ethylene content of the soluble fraction to the crystalline fraction of ethylene content of 0.50 : 1.00 to 1.00 : 1.00, more preferably 0.55 : 1.00 to 0.95 : 1.00, and most preferably 0.60 : 1.00 to 0.90 : 1.00, C2(SF) / C2(CF).

[0051] Furthermore, the polyolefin composition preferably has an intrinsic viscosity ratio of 0.40 : 1.00 to 0.95 : 1.00, more preferably 0.50 : 1.00 to 0.85 : 1.00, and most preferably 0.55 : 1.00 to 0.75 : 1.00, of the intrinsic viscosity of the soluble fraction to the intrinsic viscosity of the crystalline fraction, iV(SF) / iV(CF).

[0052] The polyolefin composition preferably has a content of 100 to 210 cm.3 / g, more preferably 120 to 200 cm 3 / g, most preferably 130 to 190 cm 3 The intrinsic viscosity / g as determined according to ISO 1628-3.

[0053] Preferably, the polyolefin composition contains, based on the total weight of the polyolefin composition, and is obtained by crystallization extraction (CRYSTEX) by quantitative determination. 13 The total propylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is 40.0 to less than 67.5% by weight, preferably 45.0 to 67.0% by weight, more preferably 47.5 to 66.5% by weight, and even more preferably 49.0 to 66.0% by weight.

[0054] The polymer portion of the polyolefin composition preferably consists of propylene monomer units and ethylene monomer units.

[0055] The polyolefin composition preferably has a good balance of properties with respect to tensile strength, fracture strain and indentation, as indicated by the following properties:

[0056] The polypropylene composition preferably has a tensile strength of 8.5 to 50 MPa, more preferably 15 to 45 MPa, and more preferably 20 to 40 MPa, measured on a 5A injection-molded test specimen at 23°C and 25 mm / min according to ISO 527-2 prior to aging.

[0057] The polypropylene composition preferably has a tensile strength of 8.5 to 50 MPa, more preferably 15 to 45 MPa, and more preferably 20 to 40 MPa, after aging at 135°C for 10 days, as determined according to ISO 527-2 on a 5A injection-molded test specimen at 23°C and 25 mm / min.

[0058] Furthermore, the polyolefin composition preferably has a fracture strain of 350 to 650%, more preferably 360 to 600%, and more preferably 375 to 575% as determined prior to aging on a 5A injection-molded test specimen at 23°C and a speed of 25 mm / min according to ISO 527-2.

[0059] Furthermore, the polyolefin composition preferably has a fracture strain of 350 to 650%, more preferably 360 to 600%, and more preferably 375 to 575% as determined by ISO 527-2 on a 5A injection-molded test specimen at 23°C and 25 mm / min after aging at 135°C for 10 days.

[0060] In addition, the polyolefin composition preferably has 0 to 50%, preferably 0 to 45%, of indentation in a compression test determined by a cylindrical indenter on a compression-molded plate according to Method 1 of CIGRE TB852 recommendation, which is performed at 130°C for 1 h.

[0061] Furthermore, the polyolefin composition preferably has a thermal conductivity of at least 0.245 W / Km, such as 0.245 to 0.400 W / Km, preferably 0.250 to 0.375 W / Km, and more preferably 0.260 to 0.350 W / Km, as determined by ISO 22007-2 at 22°C.

[0062] Furthermore, the polyolefin composition preferably has a thermal conductivity of at least 0.240 W / Km, such as 0.240 to 0.375 W / Km, preferably 0.245 to 0.350 W / Km, and more preferably 0.248 to 0.325 W / Km, as determined by ISO 22007-2 at 22°C.

[0063] Therefore, the polyolefin composition preferably meets all CIGRE TB852 recommendations for HVDC cable systems, even after aging.

[0064] In addition, the polyolefin composition exhibits good thermal conductivity over a wide temperature range of 22 to 100 °C.

[0065] Preferably, the polyolefin composition contains

[0066] 40.0% by weight to less than 70.0% by weight, preferably 45.0% to 69.0% by weight, more preferably 47.5% to 67.5% by weight of a copolymer of propylene and ethylene, and

[0067] Greater than 30.0 to 60.0% by weight, preferably 31.0 to 55.0% by weight, more preferably 32.5 to 52.5% by weight of low-density polyethylene.

[0068] All weights are based on the total weight of the polyolefin composition.

[0069] Based on the total weight of the polyolefin composition, the polyolefin composition may further include polymer components other than propylene and ethylene, and low-density polyethylene in an amount preferably from 0.0 to 10.0% by weight.

[0070] In a preferred embodiment, the polymer component of the polyolefin composition consists of a copolymer of propylene and ethylene and low-density polyethylene.

[0071] In addition to these polymer components, the polyolefin composition may also contain one or more additives in an amount of 0.0 to 5.0% by weight based on the total weight of the polyolefin composition. The one or more additives are preferably selected from acid removers, antioxidants, α-nucleating agents, β-nucleating agents, etc. Such additives are commercially available and are described, for example, in Hans Zweifel's "Plastic Additives Handbook," 6th edition, 2009 (pp. 1141-1190).

[0072] Typically, these additives are added in amounts ranging from 1 to 50,000 ppm for each individual component.

[0073] One or more additives can be added to the polymer component during the blending step.

[0074] Therefore, one or more additives can be added to the polymer component in the form of a masterbatch, wherein one or more additives are blended with the carrier polymer in a concentrated amount. Based on the total weight of the polyolefin composition, any optional carrier polymer is included in the amount of additives.

[0075] Preferably, the polyolefin composition contains 0 to 5.00% by weight of an α-nucleating agent based on the total amount of the polyolefin composition, more preferably 0 to 2.50% by weight.

[0076] Based on the total amount of the polyolefin composition, the amount of pure α-nucleating agent in the polyolefin composition (excluding the optional carrier polymer of the masterbatch) is preferably in the range of 0 to 5000 ppm, more preferably in the range of 0 to 4000 ppm.

[0077] α-nucleating agents are generally unrestricted.

[0078] Preferably, the α-nucleating agent is selected from soluble α-nucleating agents and polymeric α-nucleating agents.

[0079] The α-nucleating agent is preferably selected from the group consisting of:

[0080] (i) Dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol) and C1-C8-alkyl-substituted dibenzyl sorbitol derivatives, such as methyl dibenzyl sorbitol, ethyl dibenzyl sorbitol, or dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methylbenzyl)sorbitol), or substituted nonitol derivatives, such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, and

[0081] (ii) Vinylcycloalkane polymers and vinylalkane polymers (discussed in more detail below), and

[0082] (iii) Its mixture.

[0083] The α-nucleating agent is preferably selected from dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol), dibenzyl sorbitol derivatives, preferably dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methylbenzyl)sorbitol), or substituted nonitol derivatives, such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, vinyl cycloalkane polymers, vinyl alkane polymers, and mixtures thereof.

[0084] Vinylcycloalkane polymers, such as vinylcyclohexane (VCH) polymers, are particularly preferred. Such polymers can be added, for example, using Borealis nucleation technology (BNT).

[0085] In a preferred embodiment, the α-nucleating agent is a soluble α-nucleating agent, more preferably selected from dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol) and C1-C8-alkyl-substituted dibenzyl sorbitol derivatives, such as methyl dibenzyl sorbitol, ethyl dibenzyl sorbitol, or dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methylbenzyl)sorbitol), or substituted nonitol derivatives, such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol and mixtures thereof, as soluble α-nucleating agents.

[0086] α-nucleating agents can be added to polyolefin compositions as a separate raw material or in a mixture with a carrier polymer, known as a masterbatch. Therefore, the amount of carrier polymer in the masterbatch is included in the amount of α-nucleating agent.

[0087] In one embodiment, the polyolefin composition contains an α-nucleating agent.

[0088] In the embodiments described, the amount of pure α-nucleating agent is preferably in the range of 0.1 to 5000 ppm, more preferably in the range of 1 to 5000 ppm.

[0089] In another embodiment, the polyolefin composition does not contain an α-nucleating agent.

[0090] In the embodiment described, the amount of pure α-nucleating agent was 0 ppm.

[0091] Preferably, the polyolefin composition is prepared by melt blending a copolymer of propylene and ethylene and low-density polyethylene, optional additional polymer components, and optional other additives, all as described above or below.

[0092] The polyolefin composition preferably has not undergone viscosity-reducing cracking.

[0093] In one embodiment, the polyolefin composition does not contain dielectric fluid, i.e., it does not contain dielectric fluid, such as that described, for example, in EP2 739 679.

[0094] The copolymers of propylene and ethylene, as well as low-density polyethylene, will be described in more detail below.

[0095] copolymer of propylene and ethylene

[0096] The polyolefin compositions described above or below preferably comprise a copolymer of propylene and ethylene.

[0097] The copolymer of propylene and ethylene is preferably present in the polyolefin composition in an amount of 40.0 to less than 70.0% by weight, preferably 45.0 to 69.0% by weight, and more preferably 47.5 to 67.5% by weight, based on the total weight of the polyolefin composition.

[0098] The copolymer of propylene and ethylene preferably has a content based on the total weight of the copolymer of propylene and ethylene and is obtained by crystallization extraction (CRYSTEX) by quantitative determination. 13 The total ethylene content is 4.0 to 11.0% by weight, more preferably 5.0 to 10.0% by weight, even more preferably 5.5 to 9.5% by weight, and most preferably 6.0 to 9.0% by weight, as determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0099] Furthermore, the copolymer of propylene and ethylene preferably has a content based on the total weight of the copolymer of propylene and ethylene and is obtained by crystallization extraction (CRYSTEX) through quantitative... 13 The total propylene content is 89.0 to 96.0% by weight, more preferably 90.0 to 95.0% by weight, even more preferably 90.5 to 95.5% by weight, and most preferably 91.0 to 94.0% by weight, as determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0100] The copolymer of propylene and ethylene is preferably composed of propylene and ethylene. Therefore, it is preferred that the total ethylene content and the total propylene content account for 100% by weight of the copolymer of propylene and ethylene.

[0101] The copolymer of propylene and ethylene preferably has a melt flow rate MFR2 of greater than 2.5 to 6.0 g / 10 min, more preferably 2.8 to 5.5 g / 10 min, even more preferably 3.0 to 5.0 g / 10 min, and most preferably 3.3 to 4.5 g / 10 min, as determined according to ISO 1133 at 230 °C and 2.16 kg.

[0102] Preferably, the copolymer of propylene and ethylene is a multiphase copolymer of propylene and ethylene.

[0103] The multiphase copolymer of propylene and ethylene has a matrix phase and an elastomeric phase dispersed in the matrix phase.

[0104] The matrix phase is preferably a random copolymer of propylene and ethylene.

[0105] In copolymers of propylene and ethylene (such as multiphase copolymers of propylene and ethylene), the matrix phase and the elastomeric phase are often not completely separable from each other. Several methods are known to characterize the matrix and elastomeric phases of multiphase copolymers of propylene and ethylene. One method is the CRYSTEX method for polyolefin compositions, as described above.

[0106] The copolymer of propylene and ethylene preferably has a crystallization fraction (CF) content determined by crystallization extraction (CRYSTEX) in the range of 75.0 to 90.0% by weight, more preferably in the range of 77.0 to 88.0% by weight, even more preferably in the range of 78.5 to 86.5% by weight, and most preferably in the range of 80.0 to 85.0% by weight, based on the total weight of the copolymer of propylene and ethylene.

[0107] The crystal fraction (CF) preferably has a content of 1.0 to 15.0 wt% based on the total amount of monomer units in the crystal fraction (CF), more preferably in the range of 2.0 to 10.0 wt%, and most preferably in the range of 3.0 to 8.5 wt%, obtained by quantitative analysis. 13 Ethylene content (C2(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0108] Furthermore, the crystal fraction (CF) preferably has a range of 185 to 325 cm⁻¹. 3 Within the range of / g, more preferably within 200 to 300 cm 3 Within the range of / g, and most preferably in the range of 225 to 270 cm⁻¹ 3 Intrinsic viscosity (iV(CF)) measured according to ISO 1628-3 within the range of / g.

[0109] The copolymer of propylene and ethylene preferably has a soluble fraction (SF) content determined by crystallization extraction (CRYSTEX) in the range of 10.0 to 25.0% by weight, more preferably in the range of 12.0 to 23.0% by weight, even more preferably in the range of 13.5 to 21.5% by weight, and most preferably in the range of 15.0 to 20.0% by weight, based on the total weight of the copolymer of propylene and ethylene.

[0110] The soluble fraction (SF) preferably has a content of 20.0 to 35.0% by weight based on the total amount of monomer units in the soluble fraction (SF), more preferably in the range of 21.5 to 32.5% by weight, and most preferably in the range of 23.0 to 30.0% by weight, obtained by quantitative analysis. 13 Ethylene content (C2(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy.

[0111] Furthermore, the soluble fraction (SF) preferably has a concentration between 90 and 190 cm⁻¹. 3 Within the range of / g, more preferably within 100 to 175 cm 3 Within the range of / g and most preferably in the range of 115 to 150 cm 3 Intrinsic viscosity (iV(SF)) measured according to ISO 1628-3 within the range of / g.

[0112] The copolymer of propylene and ethylene preferably has a ratio of ethylene content of the soluble fraction to the crystalline fraction of 1.5:1.0 to 10.0:1.0, more preferably 2.5:1.0 to 7.5:1.0, and most preferably 4.0:1.0 to 6.0:1.0, of ethylene content C2(SF) / C2(CF).

[0113] Furthermore, the copolymer of propylene and ethylene preferably has an intrinsic viscosity ratio of soluble fraction to crystalline fraction of 0.35 : 1.00 to 0.90 : 1.00, more preferably 0.40 : 1.00 to 0.80 : 1.00, and more preferably 0.50 : 1.00 to 0.70 : 1.00, iV(SF) / iV(CF).

[0114] The copolymer of propylene and ethylene preferably has a thickness of 185 to 325 cm. 3 Within the range of / g, more preferably within 200 to 300 cm 3 Within the range of / g, and most preferably in the range of 225 to 270 cm⁻¹ 3 Total intrinsic viscosity (iV (total)) measured according to ISO 1628-3 within the range of / g.

[0115] Preferably, the crystalline fraction (CF) and the soluble fraction (SF) account for 100% by weight of the copolymer of propylene and ethylene.

[0116] The copolymer of propylene and ethylene preferably has a flexural modulus of greater than 470 MPa to 750 MPa, more preferably 475 MPa to 700 MPa, and most preferably 500 MPa to 650 MPa, as determined according to ISO 178 Method A.

[0117] Furthermore, the copolymer of propylene and ethylene preferably has a strength of 5.0 to 30.0 kJ / m³. 2 More preferably 7.0 to 25.0 kJ / m 2 And the most preferred value is 9.0 to 20.0 kJ / m 2 Notched impact strength of a simply supported beam at 23°C, as determined by ISO 179-1 / 1eA.

[0118] Furthermore, the copolymer of propylene and ethylene preferably has a strength of 0.8 to 5.0 kJ / m³. 2 More preferably 0.8 to 4.0 kJ / m 2 And the most preferred value is 0.8 to 3.5 kJ / m 2 Notched impact strength of a simply supported beam at -20°C, as determined by ISO 179-1 / 1eA.

[0119] Furthermore, the copolymer of propylene and ethylene preferably has a melt temperature Tm determined by DSC analysis according to ISO 11357 / Part 3 / Method C2, which is 132 to 155°C, more preferably 135 to 150°C, and most preferably 137 to 147°C.

[0120] Furthermore, the copolymer of propylene and ethylene preferably has a crystallization temperature Tc determined by DSC analysis according to ISO 11357 / Part 3 / Method C2, which is 85 to 115°C, more preferably 90 to 110°C, and most preferably 95 to 107°C.

[0121] The difference T between melting temperature and crystallization temperature m -T c Preferably, the temperature is in the range of 35 to 55°C, more preferably in the range of 37 to 52°C, and most preferably in the range of 39 to 50°C.

[0122] The copolymer of propylene and ethylene preferably has a content of 650 to 900. More preferably 700 to 850 The preferred value is 725 to 800. The complex viscosity η* at a frequency of 100 rad / s 100 rad / s .

[0123] Copolymers of propylene and ethylene 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 a 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" should indicate that the main polymerization occurs. Therefore, in the case where the process consists of four polymerization reactors, this definition does not exclude the option of including a prepolymerization step, for example, in a prepolymerization reactor, throughout the process.

[0124] When the copolymer of propylene and ethylene is a multiphase copolymer of propylene and ethylene, the matrix phase of the multiphase copolymer of propylene and ethylene is polymerized in a first polymerization reactor to produce a unimodal matrix phase, or polymerized in a first and a second polymerization reactor to produce a multimodal matrix phase.

[0125] The elastomeric phase of the multiphase copolymer of propylene and ethylene is preferably polymerized in one or two subsequent polymerization reactors in the presence of the matrix phase to produce a unimodal or multimodal elastomeric phase.

[0126] Preferably, the polymerization reactor is selected from slurry-phase reactors, such as loop reactors and / or gas-phase reactors, such as fluidized bed reactors, and more preferably from loop reactors and fluidized bed reactors.

[0127] Preferred sequential multi-stage polymerization methods are “loop-gas phase” methods, such as those developed by Borealis A / S of Denmark (known as BORSTAR® technology), as described in, for example, patent documents such as EP 0 887 379, WO 92 / 12182, WO2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or WO 00 / 68315.

[0128] Another suitable slurry-gas phase method is LyondellBasell's Spheripol. ® method.

[0129] Suitable sequential polymerization methods for polymerizing copolymers of propylene and ethylene, preferably multiphase copolymers of propylene and ethylene, are disclosed, for example, in WO 2015 / 117948.

[0130] Copolymers of propylene and ethylene, preferably multiphase copolymers of propylene and ethylene, can be polymerized in the presence of a Ziegler-Natta catalyst.

[0131] Suitable Ziegler-Natta catalysts are disclosed, for example, in WO 2015 / 117948.

[0132] The copolymer of propylene and ethylene preferably has not undergone the viscous cracking step described, for example, in WO 2013 / 092620 A1.

[0133] Multiphase propylene copolymer resins suitable as copolymers of propylene and ethylene are also commercially available. These resins typically already contain a stabilizer package. Therefore, when using commercially available resins as copolymers of propylene and ethylene, the addition of additives as described above may need to be adjusted to the existing additives.

[0134] In the case of commercially available copolymers of propylene and ethylene, the properties described above can be measured using common measurement methods or verified using technical documentation provided by the supplier.

[0135] Low-density polyethylene

[0136] The polyolefin compositions described above or below preferably comprise low-density polyethylene.

[0137] Low-density polyethylene is preferably present in the polyolefin composition in an amount of 30.0 to 60.0% by weight, preferably 31.0 to 55.0% by weight, and more preferably 32.5 to 52.5% by weight, based on the total weight of the polyolefin composition.

[0138] The preferred material is low-density polyethylene, which is a homopolymer of ethylene.

[0139] Low-density polyethylene preferably has a melt flow rate (MFR2) of 0.1 to 2.5 g / 10 min, more preferably 0.2 to 2.3 g / 10 min, even more preferably 0.3 to 2.0 g / 10 min, and most preferably 0.5 to 1.5 g / 10 min, as determined according to ISO 1133 at 190°C and 2.16 kg.

[0140] Furthermore, low-density polyethylene preferably has a density of 915 to 932 kg / m³. 3 Preferably 917 to 930 kg / m 3 More preferably 918 to 928 kg / m 3 The density is determined according to ISO 1183.

[0141] Furthermore, the low-density polyethylene preferably has a melt temperature Tm of 105 to 125°C, more preferably 107 to 120°C, and more preferably 109 to 117°C, as determined by DSC analysis according to ISO 11357 / Part 3 / Method C2.

[0142] Furthermore, the low-density polyethylene preferably has a Vicat A50 softening temperature of 85 to 105°C, more preferably 87 to 102°C, and more preferably 90 to 100°C, as determined according to ISO 306 at 10 N.

[0143] Low-density polyethylene preferably has a density of 600 to 800. More preferably 625 to 775 The most preferred value is 650 to 750. The complex viscosity η* at a frequency of 100 rad / s 100 rad / s .

[0144] Low-density polyethylene is preferably selected such that the complex viscosity (η*) of the propylene copolymer at a frequency of 100 rad / s is... 100 rad / s (PP) and the complex viscosity (η*) of low-density polyethylene at a frequency of 100 rad / s 100 rad / s The difference between (LDPE) Not greater than η* 100 rad / s (PP) ±20%, preferably not greater than η* 100 rad / s (PP) ±15%.

[0145] Low-density polyethylene is polymerized using free radical polymerization in high-pressure polymerization methods, preferably tubular high-pressure polymerization. Such high-pressure polymerization methods, especially tubular high-pressure polymerization methods, are well known in the art.

[0146] Suitable low-density polyethylene resins are also commercially available. These resins typically already contain a stabilizer package. Therefore, when using commercially available resins as low-density polyethylene, the addition of additives as described above may need to be adjusted to match the existing additives.

[0147] In the case of commercially available low-density polyethylene, the properties described above can be measured using common measurement methods or verified using technical documents provided by the supplier.

[0148] Products

[0149] In another aspect, the present invention also relates to articles comprising polyolefin compositions as defined above or below.

[0150] The article is preferably a cable, preferably a medium-voltage cable, a high-voltage cable, an ultra-high-voltage cable or a super-high-voltage cable, more preferably a high-voltage cable or an ultra-high-voltage cable, and even more preferably a high-voltage DC (HVDC) cable or an ultra-high-voltage DC (EHVDC) cable, comprising an insulation layer containing a polyolefin composition as described above or below.

[0151] The insulating layer preferably comprises 90 to 100% by weight, more preferably 95 to 100% by weight, and even more preferably 99 to 100% by weight of a polyolefin composition based on the total weight of the insulating layer, and most preferably consists of a polyolefin composition.

[0152] Preferably, the product meets all CIGRE TB852 recommendations for HVDC cable systems.

[0153] The cable typically includes at least one conductor and at least one insulation layer, which comprises a polyolefin composition as described above or below.

[0154] In this document, the term "conductor" as used above and below refers to a conductor comprising one or more wires. The wire can be used for any purpose and can be, for example, a telecommunications line or electrical wire. Furthermore, a cable may include one or more such conductors. Preferably, the conductor is conductive and comprises one or more metallic wires. The cable is preferably a power cable. A power cable is defined as a cable that transmits energy and operates at any voltage (typically above 1 kV). The voltage applied to the power cable can be alternating current (AC), direct current (DC), or transient (pulse). The polyolefin compositions of the present invention are particularly suitable for power cables.

[0155] As used herein, the term "cable" is intended to refer to a cable comprising at least one cable core, optionally two cable cores, or three cable cores. Each "cable core" as used herein comprises a conductor surrounded by at least an inner semiconductor layer, an insulation layer, and an outer semiconductor layer. One or more cable cores in a cable may be surrounded by at least one reinforcing layer and / or armoring layer suitable for the mechanical protection of the cable. The armoring layer may comprise metallic wire, braid, sheath, or low-loss armor. These variations and cable constructions are familiar to those skilled in the art. The armoring layer may extend through various sections of the cable.

[0156] The term "DC cable" refers to a direct current (DC) cable that typically includes one or more cable cores, preferably one or two cable cores.

[0157] The cable according to the invention is very advantageously a DC power cable, which can be, for example, a medium voltage (MV), high voltage (HV), or ultra-high voltage (EHV) or extra-high voltage (UHV) DC cable, as is well known, these terms indicate the level of operating voltage.

[0158] DC power cables can operate at voltages of at least 30 kV, such as HVDC, EHVDC, or UHVDC cables. For HVDC, EHVDC, or UHVDC cables, the operating voltage is defined in this document as the voltage between the ground and the conductor of the high-voltage cable.

[0159] The cable can be an HVDC, EHVDC, or UHVDC power cable operating at 40 kV or higher, even 50 kV or higher, or even 60 kV or higher. In some embodiments, the operating voltage can be higher than 80 kV. There is no upper limit. The practical upper limit can be as high as 1100 kV.

[0160] As is well known, cables may optionally include additional layers, such as layers surrounding an outer semiconductor layer, such as one or more screens, sheaths, one or more other protective layers, or any combination thereof.

[0161] In another aspect, the present invention relates to the use of polyolefin compositions as described above or below as cable insulation for medium-voltage cables, high-voltage cables, ultra-high-voltage cables and extra-high-voltage cables, preferably for high-voltage cables and ultra-high-voltage cables, and more preferably for high-voltage DC (HVDC) cables and ultra-high-voltage DC (EHVDC) cables.

[0162] Benefits of the present invention:

[0163] The polyolefin composition exhibits a good balance of tensile and indentation properties, which allows it to be used, for example, as cable insulation for medium-voltage, high-voltage, ultra-high-voltage, and extra-high-voltage cables operating at high temperatures, particularly for high-voltage DC (HVDC) and ultra-high-voltage DC (EHVDC) cables.

[0164] The relatively low soluble fraction (SF) content of the polyolefin composition, not exceeding 25.0% by weight, allows for improved extrudability during cable extrusion.

[0165] By incorporating low-density polyethylene into the polyolefin composition, the fracture strain is improved, while the indentation in the pressure test remains low even after aging, enabling the polyolefin composition to meet all CIGRE TB852 recommendations for HVDC cable systems.

[0166] In addition, the addition of low-density polyethylene improves the thermal conductivity of the polyolefin composition over a wide temperature range.

[0167] Example

[0168] Unless otherwise defined, the following definitions of terms and measurement methods apply to the general description of the invention above and the following embodiments.

[0169] 1. Measurement Method

[0170] a) Melt Flow Rate (MFR2)

[0171] Melt flow rate is the amount of polymer extruded within 10 minutes at a specific temperature and under a specific load using test equipment standardized according to ISO 1133, and the unit is grams.

[0172] The melt flow rate (MFR2) of propylene-based polymer and polyolefin compositions was measured at 230°C under a load of 2.16 kg, according to ISO 1133.

[0173] The melt flow rate (MFR5) of the polyolefin composition was measured according to ISO 1133 at 230°C under a load of 5.0 kg.

[0174] The melt flow rate (MFR2) of the ethylene-based polymer was measured according to ISO 1133 at 190°C under a load of 2.16 kg.

[0175] b) Density

[0176] Density was measured according to ISO 1183-1:2004 Method A on compression-molded specimens prepared according to EN ISO 1872-2 (February 2007), in kg / m³. 3 Provided.

[0177] c) Comonomer content

[0178] Quantitative analysis of comonomer content in poly(propylene-co-ethylene) copolymers

[0179] Use for 1 H and 13 Quantitative data were recorded in solution using a Bruker Avance NEO 400 NMR spectrometer operating at 400.15 and 100.62 MHz, respectively. 13 C{ 1 ¹H NMR spectroscopy. Nitrogen was used for all pneumatic devices, and all spectra were performed using… 13 A C-optimized 10 mm extended temperature probe was used for recording at 125 °C. Approximately 200 mg of material was dissolved in 3 mL of 1,2-tetrachloroethane-d2 (TCE-d2) along with chromium acetylacetone (Cr(acac)3) and approximately 3 mg of BHT (2,6-di-tert-butyl-4-methylphenol, CAS 128-37-0) to obtain a 60 mM solution of relaxant in solvent {8}. To ensure a homogeneous solution, the NMR tube was further heated in a rotary oven for at least 1 hour after initial sample preparation in a heating block. After insertion into the magnet, the tube was rotated at 10 Hz. This setup was chosen primarily for its high resolution and quantitative requirement due to the need for accurate ethylene content quantification. A standard single-pulse excitation without NOE was used with an optimized tip angle, a 1 s cycle delay, and a dual-stage WALTZ16 decoupling scheme {3,4}. A total of 6144 (6 k) transient values ​​were acquired for each spectrum.

[0180] Quantitative analysis was performed using a dedicated computer program. 13 C{ 1 The ¹H NMR spectra were processed, integrated, and the relevant quantitative properties were determined from the integration. The chemical shifts of the solvent were used, with all chemical shifts indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm. This method allows for comparable references even if this structural unit is absent. Characteristic signals corresponding to the incorporation of ethylene were observed {7}.

[0181] Using the method of Wang et al. {6}, by analyzing... 13 C{ 1 The comonomer fraction is quantified by integrating multiple signals across the entire spectral region of the H spectrum. This method is chosen for its robustness and ability to indicate the presence of regional defects when needed. Slight adjustments are made to the integration region to improve applicability across the entire range of comonomer contents encountered.

[0182] For systems where only isolated ethylene is observed in the PPEPP sequence, the method of Wang et al. was modified to reduce the influence of non-zero integrals from sites that are known to be absent. This method reduces the overestimation of ethylene content in such systems and is achieved by reducing the number of sites used to determine the absolute ethylene content to the following:

[0183]

[0184] By using this set of sites, the corresponding integral equation becomes:

[0185] E = 0.5(I H +I G + 0.5(I C + I D ))

[0186] The same notation as used in the article by Wang et al. {6} is employed. The equations for absolute propylene content have not been modified.

[0187] Calculate the molar percentage of comonomer incorporated from the molar fraction:

[0188] E [moles %] = 100 * fE

[0189] Calculate the weight percentage of comonomer incorporated using mole fraction:

[0190] E [weight %] = 100 * (fE * 28.06) / ((fE * 28.06) + ((1-fE) * 42.08))

[0191] bibliography:

[0192] 1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

[0193] 2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, AL,Macromolecules 30 (1997) 6251.

[0194] 3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A.,Baugh, D. Winniford, B., J. Mag. Reason. 187 (2007) 225.

[0195] 4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn,J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

[0196] 5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev.2000, 100, 1253.

[0197] 6) Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157.

[0198] 7) Cheng, HN, Macromolecules 17 (1984), 1950.

[0199] 8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009),475.

[0200] 9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules15 (1982) 1150.

[0201] 10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29,201.

[0202] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev.2000, 100, 1253.

[0203] d) Differential scanning calorimetry (DSC) analysis, melting temperature (Tm) and crystallization temperature (Tc):

[0204] Samples of 5 to 7 mg were measured using a TA Instrument Q2000 differential scanning calorimetry (DSC) system. The DSC was run at a scan rate of 10 °C / min in a heating / cooling / heating cycle within a temperature range of -30 °C to +225 °C, according to ISO 11357 / Part 3 / Method C2.

[0205] The crystallization temperature and heat of crystallization (Hc) are determined by the cooling step, while the melting temperature and heat of fusion (Hf) are determined by the second heating step.

[0206] When a sample exhibits two or more melting and / or crystallization temperatures, only the primary melting temperature (at the highest Hf) and primary crystallization temperature (at the highest Hc) are shown in the corresponding table. The difference between the melting and crystallization temperatures (Tm-Tc) used for the primary melting and primary crystallization temperatures is given.

[0207] e) Crystallization Extraction (CRYSTEX) Analysis

[0208] Note: Crystallization extraction (CRYSTEX) analyzes the polymer fraction of each component; non-polymer fractions (such as any fillers or particulate pigments) do not contribute to the reported CRYSTEX data presentation.

[0209] Determination of crystallization fraction and soluble fraction and their respective properties (iV and ethylene content)

[0210] The crystalline fraction (CF) and soluble fraction (SF) of polypropylene (PP) compositions, along with the comonomer content and intrinsic viscosity of the corresponding fractions, were analyzed using the Crystex (crystallization extraction) method. Potential instruments that can be used are the Crystex QC or Crystex 42 (Polymer Char; Valencia, Spain). Details of the technique and method can be found in the literature (Ljiljana Jeremic, 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, pp. 581-596).

[0211] The crystalline and amorphous fractions were separated by temperature cycling of dissolution at 160 °C, crystallization at 40 °C, and redissolution at 160 °C in 1,2,4-trichlorobenzene. Quantification of SF and CF, as well as determination of ethylene content (C2), were achieved using an integrated infrared detector (IR4), and intrinsic viscosity (IV) was determined using an online 2-capillary viscometer.

[0212] The IR4 detector operates in two different wavelength bands (CH3 stretching vibration (center at approximately 2960 cm)). -1 (at location) and CH stretching vibration (2700 cm) -1 Up to 3000 cm -1 A multi-wavelength detector measuring IR absorbance at two different wavelengths is used to determine the concentration and ethylene content in ethylene-propylene copolymers. The IR4 detector is calibrated with a series of eight EP copolymers having known ethylene contents ranging from 2% to 69% by weight (via...). 13 (Determined by C-NMR spectroscopy), and each EP copolymer had multiple concentrations in the range of 2 and 13 mg / ml. To simultaneously capture both characteristics of the various polymer concentrations expected during Crystex analysis, concentration and ethylene content, the following calibration equation was applied:

[0213] Concentration = a + b * absorbance (CH) + c * (absorbance (CH)) 2 + d*Absorbance (CH3) + e*(Absorbance (CH3) 2 + f*Absorbance(CH)*Absorbance(CH3) (Equation 1)

[0214] CH3 / 1000C = a + b * absorbance (CH) + c * absorbance (CH3) + d * (absorbance (CH3) / absorbance (CH)) + e * (absorbance (CH3) / absorbance (CH)) 2 (Equation 2)

[0215] The constants a to f used in Equation 1 and the constants a to e used in Equation 2 were determined using least squares regression analysis.

[0216] Use the following relationship to convert CH3 / 1000C to ethylene content in weight percent:

[0217] Weight % (ethylene in EP copolymer) = 100 - CH3 / 1000TC * 0.3 (Equation 3)

[0218] The amounts of soluble fraction (SF) and crystalline fraction (CF) were correlated, respectively, with the amounts of "cold soluble xylene" (XCS) and cold insoluble xylene (XCI) fractions determined according to standard gravimetric analysis in accordance with ISO 16152 via XS calibration. XS calibration was achieved by testing various EP copolymers with XS contents ranging from 2% to 31% by weight. Linear calibration curves were used.

[0219] The intrinsic viscosity (iV) of the parent EP copolymer and its soluble and crystalline fractions was determined using an online 2-capillary viscometer and correlated with the corresponding IV determined by standard method in decahydronaphthalene according to ISO 1628-3. Calibration was performed using various EP copolymers and PP polymers with iV = 2 to 4 dL / g. The determined calibration curves were linear.

[0220] Weigh out the sample to be analyzed at a concentration of 10 mg / ml to 20 mg / ml.

[0221] After autofilling vials with 1,2,4-TCB containing 250 mg / L of 2,6-tert-butyl-4-methylphenol (BHT) as an antioxidant, the sample was dissolved at 170°C until complete dissolution was achieved with continuous stirring or gentle agitation. To prevent sample degradation, the polymer solution was covered with an N2 atmosphere during dissolution. For PP compositions containing inorganic fillers, pigments, or any other non-TCB-soluble polymeric substances, these substances need to be removed. This can be done by hot filtration prior to injection.

[0222] A defined volume of polymer solution was injected into a column packed with an inert support, where crystallization of the sample and separation of the soluble fraction from the crystalline fraction were performed. This process was repeated twice. During the first injection, the entire sample was measured at high temperature, and the iV [dl / g] and C2 [wt%] of the PP composition were determined. During the second injection, the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) were measured using a crystallization cycle (wt% SF, wt% C2, iV).

[0223] f) Intrinsic viscosity (iV)

[0224] Specific viscosity (also known as viscosity number) η red The intrinsic viscosity iV was determined according to ISO 1628-3: "Determination of the viscosity of polymers indilute solution using capillary viscometers".

[0225] The relative viscosities of a 1 mg / ml diluted polymer solution and pure solvent (decahydronaphthalene stabilized with 200 ppm 2,6-bis(1,1-dimethylethyl)-4-methylphenol) were determined in an automated capillary viscometer (Lauda PVS1) equipped with four Ubbelohde capillary tubes placed in a thermostatic bath filled with silicone oil. The bath temperature was maintained at 135 °C. The sample was dissolved under continuous stirring until complete dissolution was achieved (typically within 90 min).

[0226] Measure the outflow time of the polymer solution and the pure solvent multiple times until the difference between three consecutive readings does not exceed 0.2 s (standard deviation).

[0227] The relative viscosity of the polymer solution is determined as the ratio of the average effluent times (in seconds) obtained for both the polymer solution and the solvent:

[0228] Dimensionless

[0229] Specific viscosity (η) red Calculate using the following equation:

[0230] [dl / g]

[0231] Where C is the polymer solution concentration at 135℃: ,

[0232] And m is the polymer mass, V is the solvent volume, and γ is the ratio of solvent density at 20℃ and 135℃ (γ=ρ 20 / ρ 135 =1.107).

[0233] Intrinsic viscosity iV was calculated from a single concentration measurement using the Schulz-Blaschke equation:

[0234]

[0235] Where K is a coefficient that depends on the polymer structure and concentration. To calculate an approximation of IV, K = 0.27.

[0236] g) Xylene cold soluble matter (XCS) content

[0237] The amount of xylene-soluble matter in polypropylene was determined according to ISO 16152 (first edition; 2005-07-01).

[0238] A weighed sample was dissolved in hot xylene under reflux at 135°C. The solution was then cooled under controlled conditions and held at 25°C for 30 minutes to ensure controlled crystallization of the insoluble fraction. The insoluble fraction was then separated by filtration. Xylene was evaporated from the filtrate, leaving the soluble fraction as a residue. The percentage of this fraction was determined by gravimetric analysis.

[0239]

[0240] in

[0241] m0 is the mass of the weighed sample test portion, in grams.

[0242] m1 is the mass of the residue, in grams.

[0243] v0 is the original volume of the solvent taken.

[0244] v1 is the volume of the aliquots of the sample used for the determination.

[0245] h) Rheology:

[0246] Dynamic rheological measurements were performed using Rheometrics RDA-II QC at 200°C under a nitrogen atmosphere on compression-formed specimens using a 25 mm diameter plate and plate geometry. Oscillatory shear tests were conducted within the linear viscoelastic strain range at frequencies from 0.01 to 500 rad / s. (ISO 6721-1)

[0247] As a function of frequency (ω), the values ​​of storage modulus (G´), loss modulus (G”), complex modulus (G*), and complex viscosity (η*) were obtained.

[0248] Zero-shear viscosity (η0) is calculated using complex mobility, which is defined as the reciprocal of complex viscosity. The real and imaginary parts are therefore defined by the following equation:

[0249] f´(ω) = η´(ω) / [η´(ω) 2 + η” (ω) 2 ],and

[0250] f” (ω) = η”(ω) / [η´(ω) 2 + η” (ω) 2 ]

[0251] According to the following equation:

[0252] η´ = G” / ω and η” = G´ / ω

[0253] We can obtain:

[0254] f´(ω) = G” (ω) * ω / [G´(ω) 2 + G” (ω) 2 ]

[0255] f"(ω) = G"(ω) * ω / [G´(ω) 2 + G” (ω) 2 ].

[0256] i) Flexural modulus

[0257] The flexural modulus was determined according to ISO 178 Method A (3-point bending test) on an 80 mm × 10 mm × 4 mm specimen. According to this standard, a test speed of 2 mm / min and a span length of 16 times the thickness were used. The test temperature was 23 ± 2 °C. All materials were injection molded at a melt temperature of 230 °C according to ISO 19069-2, regardless of the melt flow rate.

[0258] j) Notched impact strength of simply supported beam

[0259] The notched impact strength of simply supported beams was determined according to ISO 179-1 / 1eA on notched specimens of 80 mm × 10 mm × 4 mm (the specimens were prepared according to ISO 179-1 / 1eA). The test temperature was 23±2℃ or -20±2℃. All materials were injection molded at a melt temperature of 230℃ according to ISO 19069-2, regardless of the melt flow rate of the material.

[0260] k) Tensile strength and fracture strain

[0261] Tensile strength and strain at break were determined on 5A injection-molded tensile specimens according to ISO 527-2. Tensile tests were performed at +23°C at a rate of 25 mm / min, as recommended in IEC 60811-501 version 1.0 2012-03. The 5A injection-molded tensile specimens were aged at 135°C for 10 days to determine the aged tensile strength and strain at break.

[0262] l) Indentation during pressure testing

[0263] Indentation performance at high temperatures was determined by pressure testing according to Method 1 of CIGRE TB852 recommendation, using a cylindrical indenter on a compression-molded plate for 1 hour at 130°C.

[0264] m) Thermal conductivity

[0265] The thermal conductivity at 22°C and 100°C was measured according to ISO 22007-2 on a 20 mm × 20 mm × 3 mm compression molded specimen.

[0266] 2. Polyolefin composition

[0267] The polyolefin compositions in the examples were prepared using the following resins:

[0268] Preparation of multiphase propylene copolymer HECO

[0269] catalyst

[0270] The catalyst used in the polymerization process of the multiphase propylene copolymer powder is a Ziegler-Natta catalyst, which is described in the Examples section of WO 2015 / 117948. Triethylaluminum (TEAL) is used as a co-catalyst, and dicyclopentyldimethoxysilane (D-donor) is used as the donor.

[0271] Polymerization of multiphase propylene copolymer powder

[0272] Multiphase propylene copolymer powders were produced in a Borstar™ unit using a liquid-phase loop reactor and two gas-phase reactors connected in series under the conditions shown in Table 1, in the presence of the polymerization catalyst described above. 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 reactor and the first gas-phase reactor, and the elastomer phase was polymerized in the second gas-phase reactor. The catalyst, as described above, was fed into a prepolymerization reactor prior to the first reaction zone.

[0273] Table 1: Polymerization conditions for multiphase propylene copolymer powders:

[0274]

[0275] Blending conditions and performance of HECO blends

[0276] Multiphase propylene copolymer powder from the polymerization reaction is compounded together with a stabilizer package in a twin-screw extruder to obtain a compounded HECO.

[0277] An overview of the compounding conditions for HECO is shown in Table 2.

[0278] Table 2: HECO formulation in twin-screw extruders:

[0279]

[0280] Stabilizer Pack 1 consists of 25.6% by weight of pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No. 6683-19-8), 51.3% by weight of tris(2,4-di-tert-butylphenyl) phosphite (CAS No. 31570-04-4), and 23.1% by weight of synthetic hydrotalcite (CAS No. 11097-59-9), all of which are commercially available from multiple companies.

[0281] The performance of HECO is listed in Table 3.

[0282] Table 3: Performance of HECO

[0283]

[0284] Preparation of polyolefin compositions

[0285] In order to produce the polyolefin compositions of Examples IE1 and IE2 of the present invention and Comparative Example CE2, HECO and LDPE were compounded in a Coperion ZSK18 co-rotating twin-screw extruder with a diameter of 18 mm and a diameter of 40 mm in the compounding step.

[0286] Comparative Example CE1 reflects the HECO compound without additional compounding steps.

[0287] Table 4 provides an overview of the polyolefin compositions CE1, CE2, IE1, and IE2. Table 5 shows the properties of CE1, CE2, IE1, and IE2.

[0288] Table 4: Composition of CE1, CE2, IE1, and IE2:

[0289]

[0290] LDPE is a low-density ethylene homopolymer produced in commercial high-pressure tubular reactors.

[0291] Typically, high-pressure radical polymerization of ethylene can be carried out in tubular reactors or autoclaves at pressures ranging from 1200 to 3500 bar and temperatures ranging from 120 to 350 °C. Further details on high-pressure radical polymerization are given in the Encyclopedia of Polymer Science and Engineering, Volume 6 (1986), pp. 383–410, and in the Encyclopedia of Materials: Science and Technology, Elsevier Science Ltd., “Polyethylene: High Pressure,” R. Klimesch, D. Littmann, and F.-O. Mähling, pp. 7181–7184 (2001), which are incorporated herein by reference.

[0292] LDPE has 923 kg / m 3 The density, melt flow rate MFR2 (190℃, 2.16 kg) of 0.75 g / 10min, melt temperature Tm of 112℃, Vicat A50 softening temperature of 95℃, and 682 Complex viscosity η* 100 rad / s .

[0293] LDPE was chosen because of its complex viscosity η* 100 rad / s 682 The complex viscosity η* of HECO 100 rad / s 760 Therefore, HECO's η* 100 rad / s η* with LDPE 100 rad / s The difference between For η* 100 rad / s10.3% of (HECO).

[0294] Performance of polyolefin compositions

[0295] The results are reported in Table 5, which were calculated from the median of measurements from at least 5 tensile tests and 3 compressive tests, respectively.

[0296] Table 5: Properties of the compound compositions of CE1, CE2, IE1 and IE2:

[0297]

[0298] As can be observed, CE1 exhibits high tensile strength and no indentation, but the fracture strain after aging is below the acceptable limit of 350%.

[0299] When 65% by weight of LDPE (CE2) is added, the fracture strain before aging is too low and the indentation is 100%.

[0300] For IE1 with 50% wt% LDPE and IE2 with 35% wt% LDPE, the tensile strength and indentation still meet the indentation requirements, while the fracture strain before aging is higher than 350%, and the fracture strain after aging even increases.

Claims

1. A polyolefin composition having Based on the total weight of the polyolefin composition and obtained by crystallization extraction (CRYSTEX) through quantitative... 13 The total ethylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is greater than 32.5 to 60.0% by weight, preferably 33.0 to 55.0% by weight, more preferably 33.5 to 52.5% by weight, and even more preferably 34.0 to 50.0% by weight. The melt flow rate MFR2, as determined according to ISO 1133 at 230°C and 2.16 kg, is greater than 2.5 to 6.0 g / 10 min, preferably 2.6 to 5.5 g / 10 min, even more preferably 2.7 to 5.0 g / 10 min, and most preferably 2.8 to 4.5 g / 10 min. The content of crystalline fraction (CF) determined by crystallization extraction (CRYSTEX) is based on the total weight of the polyolefin composition and is in the range of 75.0 to 95.0% by weight, preferably in the range of 77.5 to 93.5% by weight, more preferably in the range of 80.0 to 92.5% by weight, and most preferably in the range of 82.5 to 91.0% by weight. The crystal fraction (CF) has a content based on the total amount of monomer units in the crystal fraction (CF) in the range of greater than 32.5 to 62.5 wt%, preferably in the range of 35.0 to 60.0 wt%, and most preferably in the range of 36.0 to 55.0 wt%, by quantitative analysis. 13 Ethylene content (C2(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, and The soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), is in the range of 5.0 to 25.0% by weight, preferably in the range of 6.5 to 22.5% by weight, more preferably in the range of 7.5 to 20.0% by weight, and most preferably in the range of 9.0 to 17.5% by weight, based on the total weight of the polyolefin composition. The soluble fraction (SF) has a concentration of 85 to 200 cm⁻¹ 3 Within the range of / g, more preferably within 95 to 175 cm 3 Within the range of / g and most preferably in the range of 100 to 150 cm 3 Intrinsic viscosity (iV(SF)) within the range of / g, as determined according to ISO 1628-3.

2. The polyolefin composition according to claim 1, wherein the crystalline fraction has a crystallinity of 100 to 250 cm⁻¹ 3 Within the range of / g, more preferably within 125 to 225 cm 3 Within the range of / g and most preferably in the range of 140 to 210 cm 3 The intrinsic viscosity (iV(CF)) measured according to ISO 1628-3 within the range of / g; and / or the total amount of monomer units in the crystallization fraction (CF) in the range of 37.5 to less than 67.5% by weight, preferably in the range of 40.0 to 65.0% by weight, and most preferably in the range of 45.0 to 64.0% by weight, by quantitative analysis. 13 The propylene content (C3(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy; and / or the soluble fraction (SF) having a concentration in the range of 22.5 to 42.5 wt%, preferably in the range of 25.0 to 40.0 wt%, and most preferably in the range of 30.0 to 35.0 wt%, determined by quantitative analysis. 13 Ethylene content (C2(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, and / or in the range of 57.5 to 77.5 wt%, preferably in the range of 60.0 to 75.0 wt%, and most preferably in the range of 62.5 to 70.0 wt%, by quantitative analysis. 13 The propylene content (C3(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy is based on the total amount of monomer units in the soluble fraction (SF).

3. The polyolefin composition according to claim 1 or 2, having a ratio of ethylene content of the soluble fraction to the crystalline fraction of ethylene content C2(SF) / C2(CF) of 0.50:1.00 to 1.00:1.00, more preferably 0.55:1.00 to 0.95:1.00, most preferably 0.60:1.00 to 0.90:1.00, and / or a ratio of intrinsic viscosity of the soluble fraction to the crystalline fraction of intrinsic viscosity iV(SF) / iV(CF) of 0.40:1.00 to 0.95:1.00, more preferably 0.50:1.00 to 0.85:1.00, most preferably 0.55:1.00 to 0.75:1.00, of 1.00, and / or 0.50:1.00 to 0.75:1.00, of ethylene content of the soluble fraction.

4. The polyolefin composition according to any one of claims 1 to 3, comprising, based on the total weight of the polyolefin composition, and obtained by crystallization extraction (CRYSTEX) by quantitative... 13 The total propylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is 40.0 to less than 67.5% by weight, preferably 45.0 to 67.0% by weight, more preferably 47.5 to 66.5% by weight, and even more preferably 49.0 to 66.0% by weight.

5. The polyolefin composition according to any one of claims 1 to 4, having all of the following properties: Tensile strength of 8.5 to 50 MPa, preferably 15 to 45 MPa, more preferably 20 to 40 MPa, measured on a 5A injection-molded test specimen at 23°C and 25 mm / min in accordance with ISO 527-2 before aging; Tensile strength of 8.5 to 50 MPa, preferably 15 to 45 MPa, more preferably 20 to 40 MPa, measured on a 5A injection-molded test specimen at 23°C and 25 mm / min according to ISO 527-2 after aging at 135°C for 10 days. 350 to 650%, preferably 360 to 600%, more preferably 375 to 575% of the fracture strain measured before aging on a 5A injection-molded test specimen at 23°C and 25 mm / min according to ISO 527-2; 350% to 650%, preferably 360% to 600%, more preferably 375% to 575% of the fracture strain measured on a 5A injection-molded test specimen at 23°C and 25 mm / min according to ISO 527-2 after aging at 135°C for 10 days; and 0 to 50%, preferably 0 to 45%, of the indentation measured in the pressure test according to Method 1 of CIGRE TB852 recommendation, which is performed at 130°C for 1 hour using a cylindrical indenter on a compression-molded plate.

6. The polyolefin composition according to any one of claims 1 to 5, comprising: 40.0% by weight to less than 70.0% by weight, preferably 45.0% to 69.0% by weight, more preferably 47.5% to 67.5% by weight of a copolymer of propylene and ethylene, and Greater than 30.0 to 60.0% by weight, preferably 31.0 to 55.0% by weight, more preferably 32.5 to 52.5% by weight of low-density polyethylene. All weights are based on the total weight of the polyolefin composition.

7. The polyolefin composition according to claim 6, wherein the copolymer of propylene and ethylene has one or more of the following properties, or all of the following properties: Based on the total weight of the copolymer of propylene and ethylene and obtained by crystallization extraction (CRYSTEX) through quantitative analysis... 13 The total ethylene content, determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, is 4.0 to 11.0% by weight, preferably 5.0 to 10.0% by weight, more preferably 5.5 to 9.5% by weight, and even more preferably 6.0 to 9.0% by weight. The content of crystalline fraction (CF) determined by crystallization extraction (CRYSTEX) is in the range of 75.0 to 90.0% by weight, preferably in the range of 77.0 to 88.0% by weight, more preferably in the range of 78.5 to 86.5% by weight, and most preferably in the range of 80.0 to 85.0% by weight, based on the total weight of the polyolefin composition. The crystal fraction (CF) has a content of 1.0 to 15.0 wt% based on the total amount of monomer units in the crystal fraction (CF), preferably in the range of 2.0 to 10.0 wt%, and most preferably in the range of 3.0 to 8.5 wt%, by quantitative analysis. 13 Ethylene content (C2(CF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, and Between 185 and 325 cm 3 Within the range of / g, more preferably within 200 to 300 cm 3 Within the range of / g, and most preferably in the range of 225 to 270 cm⁻¹ 3 Intrinsic viscosity (iV(CF)) within the range of / g, as determined according to ISO 1628-3; and The soluble fraction (SF) content, determined by crystallization extraction (CRYSTEX), is based on the total weight of the copolymer of propylene and ethylene in the range of 10.0 to 25.0% by weight, preferably in the range of 12.0 to 23.0% by weight, more preferably in the range of 13.5 to 21.5% by weight, and most preferably in the range of 15.0 to 20.0% by weight. The soluble fraction (SF) has a content of 20.0 to 35.0% by weight, preferably 21.5 to 32.5% by weight, and most preferably 23.0 to 30.0% by weight, based on the total amount of monomer units in the soluble fraction (SF), by quantitative analysis. 13 Ethylene content (C2(SF)) determined by FT-IR spectroscopy calibrated by C-NMR spectroscopy, and Between 90 and 190 cm 3 Within the range of / g, more preferably within 100 to 175 cm 3 Within the range of / g and most preferably in the range of 115 to 150 cm 3 Intrinsic viscosity (iV(SF)) within the range of / g, as determined according to ISO 1628-3; A melt flow rate MFR2, measured according to ISO 1133 at 230°C and 2.16 kg, greater than 2.5 to 6.0 g / 10 min, preferably 2.8 to 5.5 g / 10 min, even more preferably 3.0 to 5.0 g / 10 min, and most preferably 3.3 to 4.5 g / 10 min; and / or A flexural modulus greater than 470 MPa to 750 MPa, more preferably 475 MPa to 700 MPa, and most preferably 500 MPa to 650 MPa, as determined according to ISO 178 Method A; and / or 5.0 to 30.0 kJ / m 2 More preferably 7.0 to 25.0 kJ / m 2 And the most preferred value is 9.0 to 20.0 kJ / m 2 Notched impact strength of a simply supported beam at 23°C, as determined according to ISO 179-1 / 1eA; and / or 0.8 to 5.0 kJ / m 2 More preferably 0.8 to 4.0 kJ / m 2 And the most preferred value is 0.8 to 3.5 kJ / m 2 Notched impact strength of a simply supported beam at -20°C, as determined according to ISO 179-1 / 1eA; and / or The melting temperature Tm, determined by DSC analysis according to ISO 11357 / Part 3 / Method C2, is 132 to 155°C, preferably 135 to 150°C, and most preferably 137 to 147°C; and / or The crystallization temperature Tc determined by DSC analysis according to ISO 11357 / Part 3 / Method C2, at 85 to 115°C, preferably 90 to 110°C and most preferably 95 to 107°C; and / or The difference between the melting temperature and the crystallization temperature, Tm-Tc, is within the range of 35 to 55°C, preferably within the range of 37 to 52°C, and most preferably within the range of 39 to 50°C; and / or 650 to 900 More preferably 700 to 850 The preferred value is 725 to 800. The complex viscosity η* at a frequency of 100 rad / s 100 rad / s .

8. The polyolefin composition according to claim 6 or 7, wherein the copolymer of propylene and ethylene has not undergone viscous cracking.

9. The polyolefin composition according to any one of claims 6 to 8, wherein the low-density polyethylene is polymerized in a tubular high-pressure polymerization method and has one or more of the following properties, or all of the following properties: A melt flow rate MFR2 measured according to ISO 1133 at 190°C and 2.16 kg, from 0.1 to 2.5 g / 10 min, preferably 0.2 to 2.3 g / 10 min, even more preferably 0.3 to 2.0 g / 10 min, and most preferably 0.5 to 1.5 g / 10 min; and / or 915 to 932 kg / m 3 Preferably 917 to 930 kg / m 3 More preferably 918 to 928 kg / m 3 The density as determined according to ISO 1183; and / or The melting temperature Tm, determined by DSC analysis according to ISO 11357 / Part 3 / Method C2, is 105 to 125°C, preferably 107 to 120°C, more preferably 109 to 117°C; and / or The Vicat A50 softening temperature, determined according to ISO 306 at 10 N, is 85 to 105°C, preferably 87 to 102°C, more preferably 90 to 100°C; and / or 600 to 800 More preferably 625 to 775 The most preferred value is 650 to 750. The complex viscosity η* at a frequency of 100 rad / s 100 rad / s .

10. The polyolefin composition according to any one of claims 6 to 9, wherein the complex viscosity (η*) of the propylene copolymer at a frequency of 100 rad / s 100 rad / s (PP) and the complex viscosity (η*) of the low-density polyethylene at a frequency of 100 rad / s. 100 rad / s The difference between (LDPE) Not greater than η* 100 rad / s (PP) ±20%, preferably not greater than η* 100 rad / s (PP) ±15%.

11. The polyolefin composition according to any one of claims 6 to 10, further comprising 0 to 5000 ppm, preferably 0 to 4000 ppm, of an α-nucleating agent, preferably a soluble α-nucleating agent or a polymeric α-nucleating agent, more preferably selected from dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol) and C1-C8-alkyl-substituted dibenzyl sorbitol derivatives, such as methyl dibenzyl sorbitol, ethyl dibenzyl sorbitol, or dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methylbenzyl)sorbitol), or substituted nonitol derivatives, such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol and mixtures thereof, of a soluble α-nucleating agent.

12. The polyolefin composition according to any one of claims 1 to 11, wherein it is free of dielectric fluid.

13. An article comprising the polyolefin composition according to any one of the preceding claims.

14. The article of claim 13, which is a cable, preferably a medium-voltage cable or a high-voltage cable, more preferably a high-voltage cable, and even more preferably a high-voltage DC (HVDC) cable, comprising an insulation layer comprising the polyolefin composition, preferably wherein the insulation layer comprises 90 to 100% by weight, preferably 95 to 100% by weight, and even more preferably 99 to 100% by weight of the polyolefin composition based on the total weight of the insulation layer, and most preferably composed of the polyolefin composition.

15. The article of claim 14, which satisfies all CIGRE TB852 recommendations for HVDC cable systems.

16. The polyolefin composition according to any one of claims 1 to 12 is used as cable insulation for medium-voltage cables, high-voltage cables, ultra-high-voltage cables and extra-high-voltage cables, preferably for high-voltage cables and ultra-high-voltage cables, more preferably for high-voltage DC (HVDC) cables and ultra-high-voltage DC (EHVDC) cables.

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