Polypropylene composition for cable insulation material

Abstract

The present invention relates to a polypropylene composition comprising a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having 4 to 12 carbon atoms, the total amount of comonomer units being 10.0 to 16.0 wt%, based on the total amount of monomer units in the polypropylene composition, wherein the polypropylene composition has a xylene cold soluble (XCS) fraction of 25.0 to 50.0 wt%, based on the total weight of the polypropylene composition, the amount of comonomer units being at least 22 wt%, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, a melt flow rate MFR2 of 0.5 to 2.5 g / 10 min, a flexural modulus of not more than 385 MPa; and wherein the polypropylene composition is free of alpha-nucleating agents, to an article comprising the above polypropylene composition, preferably a cable comprising an insulation layer comprising the above polypropylene composition, and the use of the above polypropylene composition as a cable insulation material for medium and high voltage cables.

Description

Technical Field

[0001] This invention relates to a flexible polypropylene composition, articles comprising the polypropylene composition (preferably cables including an insulating layer comprising the polypropylene composition), and the use of the polypropylene composition as cable insulation material for medium-voltage and high-voltage cables. Background Technology

[0002] Currently, ethylene polymer products are used as insulation materials and semiconductor shielding for low-voltage, medium-voltage, and high-voltage cables due to their ease of processing and good electrical properties. In addition, polyvinyl chloride (PVC) is also commonly used as insulation material in low-voltage applications, usually in combination with plasticizers to achieve ideal cable flexibility. PVC is a thermoplastic that can be used over a wide temperature range by adding various plasticizers. For standard PVC, a maximum continuous conductor temperature of 70°C is normal. PVC becomes rigid at low temperatures and should be avoided at temperatures below -10°C. When the conductor temperature exceeds 100°C, the plasticizer escapes, and the material loses its flexibility. However, with the addition of specific plasticizers and stabilizers, PVC materials with conductor temperatures of 90-105°C can be produced. Essentially, PVC is mainly used in the 1kV range because the material's high dielectric constant means excessive losses at higher voltages; therefore, PVC cables are generally not used at voltages exceeding 1kV. Furthermore, to maintain high flexibility, plasticizers need to be added to PVC. Insufficient plasticizer dosage significantly reduces the low-temperature properties of PVC. From an environmental perspective, these plasticizers are not always considered problem-free and therefore need to be eliminated.

[0003] Especially for medium-voltage, high-voltage, and extra-high-voltage (MV, HV, EHV) cables, as well as high-voltage direct current (HVDC) cables, the insulation material is currently mainly cross-linked ethylene polymer (XLPE) products. These products have high operating temperatures, high electrical breakdown strength, and good mechanical properties. However, XLPE cannot be regenerated by remelting due to its cross-linking properties.

[0004] Therefore, thermoplastic materials, especially thermoplastic propylene polymers, have been explored as insulation materials for medium-voltage, high-voltage, and extra-high-voltage (MV, HV, and EHV) cables, as well as high-voltage direct current (HVDC) cables. Furthermore, grid owners are increasingly concerned about cables that can be recycled through remelting.

[0005] Therefore, there is growing interest in using thermoplastic propylene polymer-based polymer compositions as insulation layers for medium voltage (MV), high voltage (HV), ultra-high voltage (EHV), and high voltage direct current (HVDC) cables.

[0006] Therefore, propylene polymers need to exhibit a good balance of performance in terms of flexibility, mechanical properties, impact resistance, and electrical breakdown strength.

[0007] Therefore, there is a need in the art for polypropylene compositions that are suitable for cable insulation materials and exhibit a good balance of performance in terms of flexibility, mechanical properties, impact properties and electrical breakdown strength. Summary of the Invention

[0008] In one aspect, the present invention relates to a polypropylene composition comprising a copolymer of propylene and comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms, wherein the total amount of comonomer units is 10.0 to 16.0 wt%, preferably 11.0 to 15.0 wt%, and most preferably 12.0 to 14.0 wt%, based on the total amount of monomer units in the polypropylene composition.

[0009] The polypropylene composition comprises:

[0010] Based on the total weight of the polypropylene composition, the total amount of the xylene cold soluble (XCS) fraction is 25.0 to 50.0 wt%, preferably 27.5 to 45.0 wt%, more preferably 30.0 to 42.5 wt%, and most preferably 32.5 to 40.0 wt%, wherein based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of comonomer units is at least 23.0 wt%, for example 22.0 to 35.0 wt%, preferably 22.5 to 32.5 wt%, and most preferably 23.0 wt% to 30.0 wt%.

[0011] The melt flow rate (MFR2) is 0.5 to 2.5 g / 10 min, preferably 0.8 to 2.3 g / 10 min, more preferably 1.0 to 2.0 g / 10 min, and most preferably 1.2 to 1.7 g / 10 min.

[0012] The flexural modulus does not exceed 385 MPa, for example, 200 to 385 MPa, preferably 220 to 375 MPa, and most preferably 250 to 360 MPa.

[0013] The polypropylene composition does not contain α-nucleating agents.

[0014] In another respect, the present invention relates to articles comprising the polypropylene composition described above or below.

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

[0016] In another aspect, the present invention relates to the use of the polypropylene compositions described above or below as cable insulation materials for medium- and high-voltage cables.

[0017] definition

[0018] Multiphase polypropylene is a propylene copolymer having a semi-crystalline matrix phase (which can be a homopolymer of propylene or a random copolymer of propylene and at least one α-olefin comonomer) and an elastomeric phase dispersed therein. The elastomeric phase can be a propylene copolymer with a high comonomer content, where the comonomers are 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 in that it exhibits two distinct glass transition temperatures (Tg) attributable to the matrix phase and the elastomer phase.

[0020] Propylene homopolymer is a polymer that is essentially composed of propylene monomer units. Due to impurities, particularly during the commercial polymerization process, propylene homopolymer may contain up to 0.1 mol% of comonomer units, preferably up to 0.05 mol% of comonomer units, 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 along the polypropylene chains. Therefore, propylene random copolymers contain a fraction insoluble in xylene (xylene cold-insoluble (XCI) fraction), the amount of which is at least 85 wt%, most preferably at least 88 wt%, based on the total amount of the propylene random copolymer. Accordingly, propylene random copolymers do not contain an elastomeric polymer phase dispersed therein.

[0022] Typically, a propylene polymer containing at least two propylene polymer fractions (components) is referred to as "multimodal." These fractions are produced under different polymerization conditions, resulting in different (weight-average) molecular weights and / or different comonomer contents. Preferably, these fractions are produced by polymerization in multiple polymerization stages with different polymerization conditions. The prefix "multimodal" relates to the number of different polymer fractions that make up the propylene polymer. As an example of a multimodal propylene polymer, a propylene polymer consisting of only two fractions is called "bimodal," while a propylene polymer consisting of only three fractions is called "trimodal."

[0023] A unimodal 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 in comonomer content, or both.

[0025] "Functionalization" here refers to chemical modification, preferably grafting or copolymerizing with monocarboxylic or polycarboxylic compounds or derivatives of monocarboxylic or polycarboxylic compounds to provide the desired functional groups.

[0026] Viscosity reduction cracking is a post-reactor chemical process used to modify semi-crystalline polymers (such as propylene polymers). During viscosity reduction cracking, the propylene polymer backbone is degraded via β-fraction through peroxides such as organic peroxides. This degradation is generally used to increase melt flow rate and reduce molecular weight distribution.

[0027] In the following text, unless otherwise stated, quantities are given as a weight percentage (wt%). Detailed Implementation

[0028] Polypropylene composition

[0029] In one aspect, the present invention relates to a polypropylene composition comprising a copolymer of propylene and comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms, wherein the total amount of comonomer is 10.0 to 16.0 wt%, preferably 11.0 to 15.0 wt%, and most preferably 12.0 to 14.0 wt%, based on the total amount of monomer units in the polypropylene composition.

[0030] The polypropylene composition has the following characteristics:

[0031] Based on the total weight of the polypropylene composition, the total amount is 25.0 to 50.0 wt%, preferably 27.5 to 45.0 wt%, more preferably 30.0 to 42.5 wt%, and most preferably 32.5 to 40.0 wt% of xylene cold soluble (XCS) fraction, and based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of comonomer units is at least 23.0 wt%, for example 22.0 to 35.0 wt%, preferably 22.5 to 32.5 wt%, and most preferably 23.0 wt% to 30.0 wt%.

[0032] The melt flow rate (MFR2) is 0.5 to 2.5 g / 10 min, preferably 0.8 to 2.3 g / 10 min, more preferably 1.0 to 2.0 g / 10 min, and most preferably 1.2 to 1.7 g / 10 min.

[0033] The flexural modulus does not exceed 385 MPa, for example, 200 to 385 MPa, preferably 220 to 375 MPa, and most preferably 250 to 360 MPa.

[0034] The polypropylene composition does not contain α-nucleating agents.

[0035] The polypropylene composition preferably comprises a copolymer of propylene and a comonomer unit selected from ethylene and α-olefins having 4 to 12 carbon atoms, wherein the copolymer is 90.0 to 100 wt%, more preferably 92.5 to 99.9 wt%, and most preferably 95.0 to 99.8 wt%, based on the total weight of the polypropylene composition.

[0036] The polypropylene composition may also contain a polymer component that is different from a copolymer of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms, preferably 0.0 to 10.0 wt% based on the total weight of the polypropylene composition.

[0037] In one embodiment, the polymer component of the polypropylene composition consists of a copolymer of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms.

[0038] In another embodiment, the polypropylene composition comprises a polyolefin functionalized with a monocarboxylic acid or polycarboxylic acid compound or a derivative thereof, wherein the functionalized polyolefin is different from a copolymer of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms.

[0039] The functionalized polyolefin monocarboxylic or polycarboxylic acid compound or its derivative is preferably derived from the anhydride of the monocarboxylic or polycarboxylic acid, wherein the anhydride of the monocarboxylic or polycarboxylic acid can be linear or cyclic.

[0040] The functionalized polyolefin is preferably an anhydride-functionalized polyolefin, more preferably a maleic anhydride (MAH)-functionalized polyolefin, even more preferably a maleic anhydride (MAH)-functionalized polypropylene or polyethylene, even more preferably a maleic anhydride (MAH)-functionalized polypropylene, and most preferably a maleic anhydride (MAH)-grafted polypropylene, wherein the polypropylene is selected from propylene homopolymers, propylene random copolymers or multiphase propylene copolymers.

[0041] According to ISO 1133, at a load of 2.16 kg and a temperature of 230 °C, the functionalized polyolefin preferably has a high melt flow rate (MFR2) of 100 to 750 g / 10 min, more preferably 150 to 500 g / 10 min. Furthermore, the peak melting temperature of the functionalized polyolefin is preferably 140 to 180 °C, more preferably 145 to 170 °C.

[0042] Functionalized polyolefins are preferably commercially available, such as functionalized polyolefins from ExxonMobil under the trade name Exxelor PO, for example, Exxelor PO 1020.

[0043] In the embodiments described, the amount of functionalized polyolefin in the polypropylene composition is preferably 0.5 to 3.0 wt%, more preferably 0.7 to 2.5 wt%, and most preferably 0.9 to 2.0 wt%, based on the total weight of the polypropylene composition.

[0044] In addition to these polymer components, the polypropylene composition may also contain one or more additives, in an amount of 0.0 to 5.0 wt% based on the total amount of the polypropylene composition. The one or more additives are preferably acid scavengers, antioxidants, β-nucleating agents, etc. These additives are commercially available and are described in detail, for example, in Hans Zweifel's *Handbook of Plastic Additives*, 6th edition, 2009, pp. 1141-1190.

[0045] The polypropylene composition according to the present invention does not contain an α-nucleating agent. Therefore, the list of additives also does not include an α-nucleating agent.

[0046] Typically, these additives are added in amounts ranging from 1 to 50,000 ppm for each individual component.

[0047] One or more of the above additives may be added to the polymer component during the blending step.

[0048] Therefore, one or more of the above-mentioned 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 at a concentrated amount. The amount of any optional carrier polymer is calculated as the amount of additive based on the total amount of the propylene copolymer composition.

[0049] The term "β-nucleating agent" refers to any nucleating agent suitable for inducing crystallization of propylene polymers in hexagonal or pseudo-hexagonal crystal system modifications. Mixtures of these nucleating agents may also be used.

[0050] Suitable types of β-nucleating agents include (i) diamide compounds derived from C5-C8-cycloalkyl monoamines or C6-C12-aromatic monoamines and C5-C8-aliphatic, C5-C8-alicyclic, or C6-C12-aromatic dicarboxylic acids, such as N,N'-di-C5-C8-cycloalkyl-2,6-naphthalenediamide compounds, such as N,N'-dicyclohexyl-2,6-naphthalenediamide and N,N'-dicyclooctyl-2,6-naphthalenediamide, N,N'-di-C5-C8-cycloalkyl-4,4-biphenyldicarboxyl Amine compounds, such as N,N'-bicyclohexyl-4,4-biphenyldicarboxamide and N,N'-dicyclopentyl-4,4-biphenyldicarboxamide; N,N'-di-C5-C8-cycloalkyl-terephthalamide compounds, such as N,N'-dicyclohexyl-terephthalamide and N,N'-bicyclopentyl-terephthalamide; and N,N'-di-C5-C8-cycloalkyl-1,4-cyclohexanedicarboxamide compounds, such as N,N'-dicyclohexyl-1,4-cyclohexanedicarboxamide and N,N'-dicyclohexyl-1,4-cyclopentanedicarboxamide.

[0051] (ii) Diamine derivatives of C5-C8-cycloalkyl monocarboxylic acids or C6-C12-aromatic monocarboxylic acids and C5-C8-alicyclic or C6-C12-aromatic diamines, such as N,N'-C6–C12-arylene-bis-benzamide compounds, such as N,N'-p-phenylene-bis-benzamide and N,N'-1,5-naphthalene-bis-benzamide, N,N'-C5–C8-cycloalkyl-bis-benzamide compounds, such as N,N'-1,4-cyclopentane-bis- Benzamides and N,N'-1,4-cyclohexane-bis-benzamides, N,N'-p-C6-C12-arylene-bis-C5-C8-cycloalkyl formamides, such as N,N'-1,5-naphthyl-bis-cyclohexaneformamide and N,N'-1,4-phenylene-bis-cyclohexaneformamide, and N,N'-C5-C8-cycloalkyl-bis-cyclohexaneformamides, such as N,N'-1,4-cyclopentane-bis-cyclohexaneformamide and N,N'-1,4-cyclohexane-bis-cyclohexaneformamide.

[0052] (iii) Amino acid derivative diamide compounds derived from the amidation reaction of C5-C8-alkyl, C5-C8-cycloalkyl-, or C6-C12-aryl amino acids, C5-C8-alkyl-, C5-C8-cycloalkyl-, or C6-C12-aromatic monocarboxylic acid chlorides with C5-C8-alkyl-, C5–C8-cycloalkyl-, or C6–C12-aromatic monoamines, such as N-phenyl-5-(N-benzoylamino)pentanamide and N-cyclohexyl-4-(N-cyclohexyl-carbonylamino)benzamide.

[0053] Other suitable β-nucleating agents include

[0054] (iv) Quinacridones, 5,12-dihydro-quinolino[2,3-b]acrid-7,14-dione (i.e., quinacridone), dimethylquinacridone and dimethoxyquinacridone;

[0055] (v) Quinacridone quinones, such as quinolino[2,3-b]acridin-6,7,13,14(5H,12H)-tetraone (i.e., quinacridone quinone), and

[0056] (vi) Dimethoxyquinacridone quinones and dihydroquinacridones, such as 5,6,12,13-tetrahydroquinolino[2,3-b]acrid-7,14-dione (i.e., dihydroquinacridone), dimethoxyquinacridone, and dibenzodihydroquinacridone.

[0057] Further, more suitable β-nucleating agents are dicarboxylic acids of Group IIa metals in the periodic table, such as calcium pimelic acid and calcium octanoic acid; and mixtures of dicarboxylic acids and salts of Group IIa metals in the periodic table.

[0058] More suitable β-nucleating agents, such as salts of Group IIa metals of the periodic table and imines of the following formula.

[0059]

[0060] Where x = 0 to 4; R = H, -COOH, C1-C12-alkyl, C5-C8-cycloalkyl or C6-C12-aryl, and Y = C1-C12-alkyl, C5-C8-cycloalkyl or C6-C12-aryl-substituted divalent C6-C12 aromatic residues, such as calcium salts of phthaloylglycine, hexahydrophthaloylglycine, N-phthaloylalanine, phthaliminoacetic acid and / or N-4-methylphthaloylglycine.

[0061] Preferred β-nucleating agents are any one or a mixture of N,N'-dicyclohexyl-2,6-naphthalenediamide, the β-nucleating agent of EP 177961, and the β-nucleating agent of EP682066.

[0062] Particularly preferred β-nucleating agents are any one of the following or mixtures thereof:

[0063] 5,12-Dihydro-quinolino[2,3-b]acridin-7,14-dione (CAS1047-16-1) (i.e., quinacridinone), quinolino[2,3-b]acridin-6,7,13,14(5H,12H)-tetraone (CAS1503-48-6) (i.e., quinacridinone quinone), 5,6,12,,13-tetrahydroquinolino[2,3-b]acridin-7,14-dione (CAS 5862-38-4) (i.e., dihydroquinacridinone), N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide (CAS 153250-52-3) and salts of dicarboxylic acids having at least 7 carbon atoms and Group IIa metals of the periodic table, preferably calcium pimedate (CAS19455-79-9).

[0064] Particularly preferred is quinolino[2,3-b]acridin-6,7,13,14(5H,12H)-tetraone (CAS1503-48-6) (i.e., quinacridinone quinone), which is commercially available from BASF as Cinquasia CGNA-7588.

[0065] Typically, the amount of β-nucleating agent in the polypropylene composition is from 1 ppm to 2500 ppm, preferably from 10 ppm to 1000 ppm, and most preferably from 25 ppm to 500 ppm.

[0066] In the above embodiments, when the β-nucleating agent is selected from any one or a mixture of quinacridone compounds, quinacridone quinone compounds and dihydroquinacridone compounds, the β-nucleating agent is preferably present in the polypropylene composition in an amount of 1 ppm to 500 ppm, more preferably 10 ppm to 250 ppm, and most preferably 25 ppm to 150 ppm.

[0067] In another embodiment, the polypropylene composition includes an acid scavenger, such as calcium stearate. The amount of acid scavenger in the polypropylene composition is preferably 1,000 to 50,000 ppm, more preferably 2,500 to 35,000 ppm, and most preferably 5,000 to 20,000 ppm, based on the total weight of the polypropylene composition.

[0068] The antioxidant can be selected from any suitable antioxidant known in the art for use in polypropylene compositions for cable insulation materials.

[0069] Preferably, the polypropylene composition as defined above or below comprises one or more functionalized polyolefins, β-nucleating agents or acid scavengers or mixtures thereof, preferably in the amounts described above or below.

[0070] Surprisingly, polypropylene compositions as defined above, containing one or more functionalized polyolefins, β-nucleating agents, or acid scavengers in the amounts described above or below, exhibit improved electrical breakdown strength behavior.

[0071] Particularly preferred is that the polypropylene composition does not contain the dielectric fluid described in EP 2 739 679.

[0072] The polypropylene composition has high flexibility, as can be seen from its flexural modulus not exceeding 385 MPa, for example 200 to 385 MPa, preferably 220 to 375 MPa, and most preferably 250 to 360 MPa.

[0073] In addition, the polypropylene composition preferably has good impact properties, as can be seen from its Charpy notched impact strength at 23°C and -20°C.

[0074] Preferably, the polypropylene composition has a Charpy notched impact strength of at least 70.0 kJ / m at 23°C. 2 For example, 70.0 to 100.0 kJ / m 2 Preferably, it is 75.0 to 95.0 kJ / m 2 The optimal value is 78.0 to 90.0 kJ / m³. 2 .

[0075] Furthermore, preferably, the polypropylene composition has a Charpy notched impact strength of at least 3.5 kJ / m at -20°C. 2 For example, 3.5 to 10.0 kJ / m 2 Preferably, it is 4.0 to 9.5 kJ / m 2 The optimal value is 4.3 to 9.0 kJ / m 2 of.

[0076] The melt flow rate (MFR2) of the polypropylene composition is 0.5 to 2.5 g / 10 min, preferably 0.8 to 2.3 g / 10 min, more preferably 1.0 to 2.0 g / 10 min, and most preferably 1.2 to 1.7 g / 10 min.

[0077] Furthermore, the melting temperature Tm of the polypropylene composition is 125 to 159°C, preferably 127 to 157°C, and most preferably 130 to 155°C.

[0078] In addition, the crystallization temperature Tc of the polypropylene composition is 85 to 120°C, preferably 87 to 118°C, and most preferably 90 to 115°C.

[0079] The difference between the melting temperature and the crystallization temperature, Tm-Tc, is preferably 18 to 70°C, more preferably 20 to 65°C, and most preferably 22 to 60°C.

[0080] Based on the total amount of monomer units in the polypropylene composition, the total weight of the comonomer units in the polypropylene composition is 10.0 to 16.0 wt%, preferably 11.0 to 15.0 wt%, and most preferably 12.0 to 14.0 wt%.

[0081] The comonomer unit is selected from ethylene and α-olefins having 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene, or 1-octene. The polypropylene composition may contain one type of comonomer unit or two or more types of comonomer units, for example, two types of comonomer units. Preferably, the polypropylene composition contains one type of comonomer unit. Ethylene is particularly preferred.

[0082] Preferably, the intrinsic viscosity of the polypropylene composition measured in naphthalene is 185 to 350 cm⁻¹. 3 / g, preferably 200 to 325cm 3 / g, the most preferred value is 210 to 300 cm³. 3 / g.

[0083] Based on the total weight of the polypropylene composition, the polypropylene composition has a xylene cold soluble (XCS) fraction of 25.0 to 50.0 wt%, preferably 27.5 to 45.0 wt%, more preferably 30.0 to 42.5 wt%, and most preferably 32.5 to 40.0 wt%.

[0084] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the xylene cold soluble (XCS) fraction has a content of 22.0 to 35.0% wt%, preferably 22.5 to 32.5 wt%, and most preferably 23.0 to 30.0% wt% of comonomer units (preferably ethylene).

[0085] Furthermore, preferably, the intrinsic viscosity of the xylene cold soluble (XCS) fraction in naphthalene is 150 to 350 cm⁻¹. 3 / g, preferably 200 to 325cm 3 / g, the most preferred value is 225 to 300 cm³. 3 / g.

[0086] Furthermore, preferably, the weight-average molecular weight (Mw) of the xylene cold soluble (XCS) fraction is 185,000 to 350,000 g / mol, more preferably 200,000 to 325,000 g / mol, and most preferably 210,000 to 315,000 g / mol.

[0087] Furthermore, preferably, the polydispersity index (i.e., the ratio of weight-average molecular weight to number-average molecular weight, Mw / Mn) of the xylene cold soluble (XCS) fraction is 3.5 to 8.5, more preferably 3.7 to 8.0, and most preferably 4.0 to 7.5.

[0088] Furthermore, based on the total weight of the polypropylene composition, preferably, the polypropylene composition has a xylene cold insoluble (XCI) fraction of 50.0 to 75.0 wt%, more preferably 55.0 to 72.5 wt%, more preferably 57.5 to 70.0 wt%, and most preferably 60.0 to 67.5 wt%.

[0089] Preferably, the xylene cold insolubles (XCI) fraction contains comonomer units (preferably ethylene), and the amount of comonomer units is 3.0 to 9.0 wt%, preferably 4.0 to 8.5 wt%, and most preferably 4.5 to 7.5 wt%, based on the total amount of monomer units in the xylene cold insolubles (XCI) fraction.

[0090] Furthermore, preferably, the intrinsic viscosity of the xylene cold-insoluble (XCI) fraction in naphthalene is 185 to 350 cm⁻¹. 3 / g, preferably 220 to 325cm 3 / g, the most preferred value is 210 to 300 cm³. 3 / g.

[0091] Furthermore, preferably, the weight-average molecular weight (Mw) of the xylene cold insoluble (XCI) fraction is 225,000 to 450,000 g / mol, more preferably 240,000 to 425,000 g / mol, and most preferably 260,000 to 400,000 g / mol.

[0092] Furthermore, preferably, the polydispersity index (i.e., the ratio of weight-average molecular weight to number-average molecular weight, Mw / Mn) of the xylene cold insoluble (XCI) fraction is 3.5 to 7.5, more preferably 3.7 to 7.0, and most preferably 4.0 to 6.5.

[0093] The ratio of the intrinsic viscosity of the XCI fraction to the XCS fraction is preferably 0.9 to 1.5, more preferably 1.0 to 1.4, and most preferably 1.0 to 1.3.

[0094] The weight-average molecular weight ratio of the XCI fraction to the XCS fraction is preferably 1.00 to 1.50, more preferably 1.05 to 1.40, and most preferably 1.05 to 1.35.

[0095] Preferably, the polypropylene composition is produced by melt blending a copolymer of propylene with a comonomer unit selected from ethylene and α-olefins having 4 to 12 carbon atoms, optional additional polymer components (e.g., propylene polymers grafted with an acid grafting agent), and further optional additives (e.g., β-nucleating agents or acid scavengers), all as described above or below.

[0096] The copolymers of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms (hereinafter referred to as "propylene copolymers") will be described in more detail below.

[0097] propylene copolymer

[0098] The polypropylene composition according to the present invention comprises a copolymer of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms (hereinafter referred to as "propylene copolymer").

[0099] The comonomer unit is selected from ethylene and α-olefins having 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene, or 1-octene. The propylene copolymer may contain one type of comonomer unit or two or more types, for example, two types of comonomer units. Preferably, the propylene copolymer contains one comonomer unit. Particularly preferred is ethylene.

[0100] Based on the total amount of monomer units in the propylene copolymer, the total amount of comonomer units (preferably ethylene) is 10.0-16.0 wt%, preferably 11.0-15.0 wt%, and most preferably 12.0-14.0 wt%.

[0101] Preferably, the propylene copolymer is a multiphase propylene copolymer.

[0102] The multiphase propylene copolymer has a matrix phase and an elastomeric phase dispersed in the matrix phase.

[0103] The matrix phase is preferably a random copolymer of propylene.

[0104] The comonomer units of the propylene random copolymer in the matrix phase are generally the same as those of the propylene copolymer described above. Preferably, the comonomer units are selected from ethylene and α-olefins having 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-hexene, or 1-octene. The propylene random copolymer in the matrix phase may contain one type of comonomer unit or two or more types of comonomer units, for example, two types of comonomer units. Preferably, the propylene random copolymer in the matrix phase contains one comonomer unit. Ethylene is particularly preferred.

[0105] Multiphase propylene copolymers typically have at least two glass transition temperatures. These two glass transition temperatures can be attributed to the matrix phase (Tg(matrix)) and the elastomer phase (Tg(EPR)).

[0106] Preferably, the glass transition temperature of the multiphase propylene copolymer belonging to the matrix phase Tg (matrix) is -1.0 to -15.0°C, more preferably -2.5 to -12.5°C, and most preferably -5.0 to -10.0°C.

[0107] Furthermore, preferably, the glass transition temperature of the multiphase propylene copolymer attributable to the elastic phase Tg(EPR) is -40.0 to -55.0°C, more preferably -42.5 to -52.5°C, and most preferably -45.0 to -50.0°C.

[0108] In propylene copolymers, such as multiphase propylene copolymers, it is often impossible to accurately separate the matrix phase and the elastomer phase. Several methods are known to characterize the matrix and elastomer phases of multiphase propylene copolymers. One method involves extracting the fraction primarily containing the elastomer phase with xylene, thereby separating the xylene cold-soluble (XCS) fraction from the xylene cold-insoluble (XCI) fraction. The XCS fraction primarily contains the elastomer phase with only a small portion of the matrix phase, while the XCI fraction primarily contains the matrix phase with only a small portion of the elastomer phase.

[0109] Based on the total weight of the propylene copolymer, the total amount of xylene cold soluble (XCS) fraction of the propylene copolymer is preferably 25.0 to 50.0 wt%, more preferably 27.5 to 45.0 wt%, even more preferably 30.0 to 42.5 wt%, and most preferably 32.5 to 40.0 wt%.

[0110] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of copolymer monomer (preferably ethylene) in the xylene cold soluble (XCS) fraction is preferably 23.0 to 35.0 wt%, more preferably 23.5 to 32.5 wt%, and most preferably 24.0 to 30.0 wt%.

[0111] Furthermore, preferably, the intrinsic viscosity of the xylene cold soluble (XCS) fraction in naphthalene is 150 to 350 cm⁻¹. 3 / g, preferably 200 to 325cm 3 / g, the most preferred value is 225 to 300 cm³. 3 / g.

[0112] Furthermore, preferably, the propylene copolymer has a xylene cold insoluble (XCI) fraction of 50.0 to 75.0 wt%, more preferably 55.0 to 72.5 wt%, further preferably 57.5 to 70.0 wt%, and most preferably 60.0 to 67.5 wt%, based on the total weight of the propylene copolymer.

[0113] Based on the total amount of monomer units in the xylene cold insoluble matter (XCI) fraction, the amount of copolymer monomer (preferably ethylene) in the xylene cold insoluble matter (XCI) fraction is 3.0 to 9.0 wt%, preferably 4.0 to 8.5 wt%, and most preferably 4.5 to 7.5 wt%.

[0114] Furthermore, the intrinsic viscosity of the xylene cold-insoluble (XCI) fraction in naphthalene is preferably 185 to 350 cm⁻¹. 3 The property of / g is more preferably 220 to 325 cm⁻¹. 3 / g, the most preferred value is 210 to 300 cm³. 3 / g.

[0115] The ratio of the intrinsic viscosity of the XCI fraction to the XCS fraction of the propylene copolymer is preferably 0.9 to 1.5, more preferably 1.0 to 1.4, and most preferably 1.0 to 1.3.

[0116] The melt flow rate (MFR2) of the propylene copolymer before blending is preferably 0.5 to 2.5 g / 10 min, more preferably 0.8 to 2.2 g / 10 min, even more preferably 1.0 to 2.0 g / 10 min, and most preferably 1.2 to 1.9 g / 10 min.

[0117] The flexural modulus of the propylene copolymer is preferably 130 to 380 MPa, more preferably 150 to 365 MPa, and most preferably 175 to 350 MPa.

[0118] Preferably, the propylene copolymer has a Charpy notched impact strength of 40 to 110 kJ / m at 23°C. 2 More preferably 50 to 100 kJ / m 2 The optimal value is 55 to 95 kJ / m 2 .

[0119] Propylene copolymers 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" refers to the place where 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.

[0120] When the propylene copolymer is a multiphase propylene copolymer, the matrix phase of the multiphase propylene copolymer is polymerized in the first polymerization reactor to produce a unimodal matrix phase, or polymerized in the first and second polymerization reactors to produce a multimodal matrix phase.

[0121] The elastomeric phase of the multiphase propylene copolymer 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.

[0122] Preferably, the polymerization reactor is selected from slurry reactors, such as circulating reactors and / or gas-phase reactors (e.g., fluidized bed reactors), and more preferably from circulating reactors and fluidized bed reactors.

[0123] The preferred sequential multi-stage polymerization process is the "circulating-gas phase" process, such as the technology developed by Borealis A / S of Denmark (called...). (Technology), for example, as described in patent documents EP 0 887 379, WO 92 / 12182, WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or WO 00 / 68315.

[0124] Another suitable slurry-gas phase process is LyondellBasell's... Process.

[0125] Suitable sequential polymerization processes for propylene copolymers (preferably multiphase propylene copolymers) are disclosed, for example, in EP1 681 315 A1 or WO 2013 / 092620 A1.

[0126] Propylene copolymers, preferably multiphase propylene copolymers, can be polymerized in the presence of Ziegler-Natta catalysts or single-active-center catalysts.

[0127] Suitable Ziegler-Natta catalysts are disclosed, for example, 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.

[0128] Suitable single-active-site catalysts are disclosed, for example, in WO 2006 / 097497, WO 2011 / 076780 or WO2013 / 007650.

[0129] The propylene copolymer is preferably free from a viscosity-reducing cracking step, as described, for example, in WO 2013 / 092620 A1.

[0130] Multiphase propylene copolymer resins suitable as propylene copolymers are also commercially available. These resins typically already contain a stabilizer package. Therefore, when using commercially available resins as propylene copolymers, the addition of the aforementioned additives may need to be adjusted based on the available additives.

[0131] Examples of polypropylene compositions

[0132] The polypropylene compositions according to the present invention include different embodiments.

[0133] In the first embodiment, the polypropylene composition contains the β-nucleating agent as described above in the amount described above.

[0134] The polypropylene composition of the embodiments has one or more of the following properties, preferably all of them:

[0135] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of copolymer monomer units (preferably ethylene) in the xylene cold soluble (XCS) fraction is at least 23.0 wt%, for example, 23.0 to 35.0 wt%, preferably 23.5 to 32.5 wt%, and most preferably 24.0 to 30.0 wt%, or

[0136] The melting temperature Tm is 125 to 140°C, preferably 127 to 137°C, and most preferably 130 to 135°C, or

[0137] The crystallization temperature Tc is 95 to 120°C, preferably 100 to 118°C, and most preferably 105 to 115°C, or

[0138] The difference between the melting temperature and the crystallization temperature, Tm–Tc, is 18 to 35°C, preferably 20 to 30°C, and most preferably 22 to 28°C.

[0139] In addition to these properties, polypropylene compositions containing β-nucleating agents preferably satisfy all of the above properties.

[0140] In a second embodiment, the polypropylene composition comprises a polyolefin functionalized with a monocarboxylic acid or a polycarboxylic acid compound or a derivative thereof, wherein the functionalized polyolefin is different from a copolymer of propylene with a comonomer unit selected from ethylene and an α-olefin having 4 to 12 carbon atoms, and the weight of the functionalized polyolefin is 0.5 to 3.0 wt%, preferably 0.7 to 2.5 wt%, and most preferably 0.9 to 2.0 wt%, based on the total weight of the polypropylene composition.

[0141] The polypropylene composition of the embodiments has one or more of the following properties, preferably all of them:

[0142] The difference between the melting temperature and the crystallization temperature, Tm–Tc, is 45 to 70°C, preferably 47 to 65°C, and most preferably 50 to 60°C, or

[0143] • The flexural modulus is 300 to 385 MPa, preferably 325 to 385 MPa, most preferably 350 to 380 MPa, or

[0144] Based on the total weight of the polypropylene composition, the total weight of the xylene cold soluble (XCS) fraction is 25.0-50.0 wt%, preferably 30.0-45.0 wt%, more preferably 32.5-42.5 wt%, and most preferably 35.0-40.0 wt%, or

[0145] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of copolymer monomer units (preferably ethylene) in the xylene cold soluble (XCS) fraction is 22.0-32.5 wt%, more preferably 22.5-30.0 wt%, and most preferably 23.0-27.5 wt%.

[0146] In addition to these properties, polypropylene compositions of polyolefins functionalized with monocarboxylic or polycarboxylic compounds or derivatives of monocarboxylic or polycarboxylic compounds preferably satisfy all of the above properties.

[0147] In the third embodiment, the polypropylene composition contains an acid scavenger, preferably calcium stearate, and the content of the acid scavenger is 1,000 to 50,000 ppm, preferably 2,500 to 35,000 ppm, and most preferably 5,000 to 20,000 ppm, based on the total weight of the polypropylene composition.

[0148] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the polypropylene composition of the embodiment has at least 23.0 wt% copolymer monomer units (preferably ethylene) in the xylene cold soluble (XCS) fraction, for example 23.0 to 35.0 wt%, preferably 23.5 to 32.5 wt%, and most preferably 24.0 to 30.0 wt%.

[0149] In addition to these properties, polypropylene compositions containing acid scavengers preferably satisfy all of the above properties.

[0150] In the fourth embodiment, the polypropylene composition does not contain polyolefins that are not β-nucleating agents and are functionalized with monocarboxylic or polycarboxylic acid compounds or derivatives of monocarboxylic or polycarboxylic acid compounds.

[0151] The polypropylene composition of the embodiments has one or more, preferably all of the following properties:

[0152] Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of copolymer monomer units (preferably ethylene) in the xylene cold soluble (XCS) fraction is at least 23.0 wt%, for example, 23.0 to 35.0 wt%, preferably 23.5 to 32.5 wt%, and most preferably 24.0 to 30.0 wt%, or

[0153] The melting temperature Tm is 140 to 159°C, preferably 142 to 157°C, and most preferably 145 to 155°C, or

[0154] The crystallization temperature Tc is 85 to 102°C, preferably 87 to 100°C, and most preferably 90 to 98°C, or

[0155] The difference between the melting temperature and the crystallization temperature, Tm–Tc, is 50 to 70°C, preferably 51 to 65°C, and most preferably 52 to 60°C, or

[0156] • The flexural modulus is 200 to 380 MPa, preferably 250 to 360 MPa, and most preferably 300 to 355 MPa, or

[0157] • At 23°C, the Charpy notched impact strength is 78.0 to 100.0 kJ / m. 2 Preferably, it is 79.0 to 95.0 kJ / m 2 The optimal value is 79.5 to 90.0 kJ / m 2 ,or

[0158] • Charpy notched impact strength at -20℃ ranges from 3.5 to 10.0 kJ / m 2 Preferably, it is 4.0 to 9.5 kJ / m 2 The optimal value is 4.3 to 9.0 kJ / m 2 .

[0159] In the embodiments described, the polypropylene composition may contain an acid scavenger, such as calcium stearate, in an amount of 1,000 to 50,000 ppm, preferably 2,500 to 35,000 ppm, and most preferably 5,000 to 20,000 ppm, based on the total weight of the polypropylene composition.

[0160] In addition to these properties, the polypropylene compositions of the embodiments preferably satisfy all of the above properties.

[0161] Products

[0162] In another aspect, the present invention also relates to articles comprising polypropylene compositions as defined above or below.

[0163] The product preferably includes a cable with an insulation layer containing the polypropylene composition described above or below.

[0164] Cables typically include at least one conductor and at least one insulation layer comprising a polypropylene composition described above or below.

[0165] In this context, the term "conductor" refers to a conductor comprising one or more wires. Wires can be used for any purpose, such as optical, telecommunications, or electrical applications. Furthermore, a cable may include one or more such conductors. Preferably, the conductor is an electrical conductor 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 at any voltage, typically operating at voltages above 1 kV. The voltage applied to a power cable can be alternating current (AC), direct current (DC), or transient (pulse) voltage. The polypropylene composition of the present invention is particularly suitable for power cables, especially power cables operating at voltages from 6 kV to 36 kV (medium voltage (MV) cables) and power cables operating at voltages above 36 kV, referred to as high voltage (HV) cables and extra-high voltage (EHV) cables, and EHV cables are known to operate at very high voltages. These terms have well-known meanings and represent the operating levels of such cables.

[0166] For low-voltage applications, the cable system typically consists of a conductor and an insulation layer comprising a polypropylene composition described above or below, or a conductor, an insulation layer comprising a polypropylene composition described above or below, and an additional sheathing layer, or a conductor, a semiconductor layer, and an insulation layer comprising a polypropylene composition described above or below.

[0167] For medium and high voltage applications, the cable system typically consists of a conductor, an inner semiconductor layer, an insulation layer comprising a polypropylene composition described above or below, and an outer semiconductor layer, optionally covered by an additional sheathing layer.

[0168] The semiconductor layer preferably comprises a thermoplastic polyolefin composition, more preferably a thermoplastic polyolefin composition, which is preferably a polyethylene composition or a polypropylene composition containing a sufficient amount of conductive solid filler, preferably carbon black. Preferably, the thermoplastic polyolefin composition of the semiconductor layer is a polypropylene composition, more preferably a polypropylene composition containing a multiphase propylene copolymer as a polymer component. Particularly preferred is that at least one semiconductor layer, preferably both semiconductor layers of the cable, comprises a thermoplastic polyolefin composition containing the same propylene copolymer as the insulation layer, i.e., the propylene copolymer as described above or below.

[0169] The cable includes an insulation layer containing the polypropylene composition according to the present invention, which has good electrical properties expressed in terms of Weibull α and Weibull β values.

[0170] When measured on a 10kV cable, the Weibull α value of the cable is preferably 35.0 to 65.0 kV / mm, more preferably 37.5 to 65.0 kV / mm, and most preferably 40.0 to 65.0 kV / mm.

[0171] Furthermore, preferably, when measured on a 10kV cable, the Weibull β value of the cable is 5.0 to 250.0, more preferably 5.5 to 250.0, and most preferably 6.0 to 250.0.

[0172] Therefore, the insulation layer containing the polypropylene composition of the present invention can be used in medium-voltage and high-voltage cables.

[0173] When a polypropylene composition containing a β-nucleating agent according to the first embodiment described above is used as an insulation layer, preferably, when measured on a 10kV cable, the Weibull α value of the cable is 40.0 to 65.0 kV / mm, more preferably 43.0 to 65.0 kV / mm, more preferably 45.0 to 65.0 kV / mm, and most preferably 47.0 to 65.0 kV / mm.

[0174] In the second embodiment, preferably, when measured on a 10kV cable, the Weibull β value of the cable is 6.0 to 250.0, more preferably 7.5 to 250.0, and most preferably 10.0 to 250.0.

[0175] When a polypropylene composition containing a polyolefin functionalized with a monocarboxylic acid or polycarboxylic acid compound or a derivative thereof according to the second embodiment described above is used as an insulation layer, preferably, when measured on a 10kV cable, the Weibull α value of the cable is 43.0 to 65.0 kV / mm, more preferably 45.0 to 65.0 kV / mm, and most preferably 47.0 to 65.0 kV / mm.

[0176] In the second embodiment, preferably, when measured on a 10kV cable, the Weibull β value of the cable is 10.0 to 250.0, more preferably 15.0 to 250.0, and most preferably 20.0 to 250.0.

[0177] When a polypropylene composition containing an acid remover according to the third embodiment described above is used as an insulation layer, preferably, when measured on a 10kV cable, the Weibull α value of the cable is 40.0 to 65.0 kV / mm, more preferably 43.0 to 65.0 kV / mm, and most preferably 45.0 to 65.0 kV / mm.

[0178] In the third embodiment, preferably, when measured on a 10kV cable, the Weibull β value of the cable is 6.0 to 250.0, more preferably 7.5 to 250.0, and most preferably 9.0 to 250.0.

[0179] When the polypropylene composition without the additives described in the fourth embodiment above is used as the insulation layer, preferably, when measured on a 10kV cable, the Weibull α value of the cable is 35.0 to 65.0 kV / mm, more preferably 37.5 to 65.0 kV / mm, and most preferably 40.0 to 65.0 kV / mm.

[0180] In the first embodiment, preferably, when measured on a 10kV cable, the Weibull β value of the cable is 5.0 to 250.0, more preferably 5.5 to 250.0, and most preferably 6.0 to 250.0.

[0181] In another aspect, the present invention relates to the use of polypropylene compositions as described above or below as cable insulation materials for medium- and high-voltage cables.

[0182] The medium-voltage and high-voltage cables preferably meet all the performance requirements of the cables described above or below.

[0183] The beneficial effects of this invention are:

[0184] The polypropylene composition of the present invention exhibits a good balance of properties in terms of high flexibility, good mechanical strength, good impact resistance, and high crystallization and melting temperature, and can be used as a cable insulation material, for example, for medium and high voltage cables at high operating temperatures.

[0185] It has been found that by preventing nucleation in the polypropylene composition in the presence of an α-nucleating agent, the polypropylene compositions according to the invention exhibit a lower flexural modulus through comparable mechanical and impact properties. This low flexural modulus allows for the addition of additives that increase the flexural modulus but can also improve other properties of the polypropylene compositions of the invention.

[0186] Cables containing insulation layers comprising the polypropylene composition of the present invention surprisingly exhibit good AC breakdown strength, expressed in terms of Weibull α and Weibull β values.

[0187] It has been found that even at melt flow rates as low as 0.5 to 2.5 g / 10 min, the polypropylene of the present invention is readily compounded to prepare insulating layers without the need to increase melt flow rates through viscous cracking.

[0188] Without adding dielectric fluids such as those described in EP 2 739 679, good AC breakdown strength, expressed in terms of Weibull α and Weibull β values, can be obtained.

[0189] When the semiconductor composition of the semiconductor layer is adjusted to suit a propylene-based composition rather than an ethylene-based composition, the electrical properties can be further improved, particularly by a narrower distribution of electrical breakdown strength values, resulting in a higher Weibull β value. This behavior is believed to be due to enhanced adhesion between the semiconductor and insulating layers resulting from similar polymer compositions.

[0190] It was further surprising to find that the electrical properties of the polypropylene compositions of the present invention could be further improved by adding a β-nucleating agent as described above or below, a relatively high amount of 1,000 to 50,000 ppm of an acid scavenger (e.g., calcium stearate), and / or a relatively low amount of 0.5 to 3.0 wt% of a functionalized polyolefin.

[0191] Therefore, the polypropylene composition of the present invention allows for the flexible addition of additional components to obtain compositions for cable insulation materials according to different needs.

[0192] The polypropylene compositions described above or below thus exhibit an excellent balance of properties in terms of high flexibility, good mechanical strength, good impact performance, and high crystallization and melting temperatures, thereby allowing their use as cable insulation materials at high operating temperatures, such as for medium and high voltage cables, and possessing good electrical breakdown strength.

[0193] Example

[0194] Unless otherwise defined, the following definitions and methods of determination of terms apply to the above general description of the invention and the following embodiments.

[0195] 1. Measurement Method

[0196] a) Melt flow rate (MFR2)

[0197] Melt flow rate refers to the amount of polymer, expressed in grams, extruded within 10 minutes by a testing device conforming to ISO 1133 or ASTM D1238 standards under a certain temperature and load.

[0198] The melt flow rate (MFR2) of the propylene polymer and polypropylene composition was measured according to ISO 1133 at 230°C and a load of 2.16 kg.

[0199] The melt flow rate (MFR2) of the ethylene-based polymer and polyethylene composition was measured according to ISO 1133 at 190°C and a load of 2.16 kg.

[0200] b) Comonomer content

[0201] Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymer.

[0202] Quantitative analysis of comonomer content in poly(propylene-co-ethylene) copolymers

[0203] Use for 1 H and 13 A Bruker Advance III 400 NMR spectrometer, operating at 400.15 and 100.62 MHz respectively, recorded quantitative data in solution. 13 C{ 1 ¹H NMR spectroscopy. Nitrogen gas was used for all pneumatic devices at 125°C. 13 All spectra were recorded using a C-optimized 10mm extended temperature probe. Approximately 200 mg of material, along with chromium acetylacetone (Cr(acac)3), was dissolved in 3 mL of 1,2-tetrachloroethane-d2 (TCE-d2) to obtain a 65 mM solution of relaxant in solvent {8}. To ensure solution homogeneity, the NMR tube was further heated in a rotary oven for at least 1 hour after initial sample preparation in the heating block. After insertion into the magnet, the tube was rotated at 10 Hz. This setup was chosen primarily for high resolution and for the quantitative requirement of 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 two-stage WALTZ16 decoupling scheme {3,4}. A total of 6144 (6 k) transient signals were acquired for each spectrum.

[0204] 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 the structural unit is absent. Characteristic signals corresponding to the incorporation of ethylene were observed {7}.

[0205] Using the method of Wang et al. {6}, by 13 C{ 1 The integration of multiple signals across the entire spectral region of the H spectrum quantifies the comonomer fraction. This method was chosen for its robustness and ability to indicate the presence of regional defects when needed. The integration region was slightly adjusted to improve applicability across the entire range of comonomer contents encountered.

[0206] For systems where only isolated ethylene was 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:

[0207] E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

[0208] By using this set of sites, the corresponding integral equation becomes:

[0209] E = 0.5(I H +I G +0.5(I C +I D ))

[0210] Use the same notation as in Wang et al.'s article {6}. The equation for absolute propylene content has not been modified.

[0211] Calculate the molar percentage of comonomer incorporated from the molar fraction:

[0212] E[mol%]=100*fE

[0213] Calculate the weight percentage of comonomer incorporated from the mole fraction:

[0214] E[wt%]=100*(fE*28.06) / ((fE*28.06)+((1-fE)*42.08))

[0215] References:

[0216] 1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

[0217] 2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, AL, Macromolecules 30 (1997) 6251.

[0218] 3) Zhou, Z., Kuemmerle, R., Qiu,

[0219] 4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

[0220] 5)Resconi,L.,Cavallo,L.,Fait,A.,Pimontesi,F.,Chem.Rev.2000,100,1253.

[0221] 6) Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157.

[0222] 7)Cheng, HN, Macromolecules 17 (1984), 1950.

[0223] 8)Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475.

[0224] 9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.

[0225] 10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.

[0226] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0227] c) Differential scanning calorimetry (DSC) analysis, melting temperature (Tm) and crystallization temperature (Tc):

[0228] Differential scanning calorimetry (DSC) was performed on samples ranging from 5 to 7 mg using a TA Instrument Q2000. DSC was run in a heating / cooling / heating cycle at a scan rate of 10 °C / min over a temperature range of -30 °C to +225 °C, according to ISO 11357 / Part 3 / Method C2.

[0229] The crystallization temperature and heat of crystallization (Hc) are determined from the cooling step, while the melting temperature and heat of fusion (Hf) are determined from the second heating step.

[0230] When a sample displays more than two melting and / or crystallization temperatures, only the primary melting temperature (at the highest Hc) and the primary crystallization temperature (at the highest Hf) are shown in the corresponding tables. The difference between the primary melting temperature and the primary crystallization temperature (Tm-Tc) is also given.

[0231] d) Xylene cold soluble matter (XCS) content

[0232] The amount of xylene-soluble matter in polypropylene was measured according to ISO 16152 (first edition; 2005-07-01).

[0233] A weighed sample was dissolved in hot xylene under reflux at 135°C. The solution was then cooled under controlled conditions and maintained at 25°C for 30 minutes to ensure controlled crystallization of the insoluble fraction. This insoluble fraction was then separated by filtration. Xylene was distilled off from the filtrate, leaving the soluble fraction as a residue. The percentage of this fraction was determined by gravimetric analysis.

[0234]

[0235] In the formula

[0236] m0 is the mass of the sample tested, in grams.

[0237] m1 is the mass of the residue, in grams.

[0238] v0 is the initial volume of the solvent taken.

[0239] v1 is the volume of the sample taken for the measurement.

[0240] e) Intrinsic viscosity (IV) 固有 )

[0241] Specific viscosity (also known as viscosity value) η 比浓 The intrinsic viscosity [η] was determined according to ISO 1628-3 "Determination of viscosity of polymers in diluted solutions using a capillary viscometer".

[0242] The relative viscosities of a 1 mg / ml diluted polymer solution and pure solvent (naphthane stabilized with 200 ppm 2,6-bis(1,1-dimethylethyl)-4-cresol) were determined in an automated capillary viscometer (Lauda PVS1) equipped with four Ubbelohde capillaries placed in a thermostatic bath containing silicone oil. The bath temperature was maintained at 135°C. The sample was dissolved under continuous stirring until complete dissolution (typically within 90 minutes).

[0243] The outflow time of the polymer solution and the pure solvent was measured several times until the difference between three consecutive readings did not exceed 0.2 seconds (standard deviation).

[0244] The relative viscosity of the polymer solution was determined as the ratio of the average eluent times (in seconds) of the obtained solution and solvent:

[0245]

[0246] Specific viscosity (η) 比浓 Calculate using the formula:

[0247]

[0248] In the formula, C is the polymer solution concentration at 135℃: m is the polymer mass, V is the solvent volume, and γ is the ratio of the solvent density at 20℃ and 135℃ (γ = ρ). 20 / ρ 135 =1.107).

[0249] The intrinsic viscosity [η] is calculated from a single concentration measurement using the Schulz-Blaschke equation:

[0250]

[0251] Where K is a coefficient that depends on the polymer structure and concentration. For the approximate value of [η], K = 0.27.

[0252] f) Average molecular weight, polydispersity (Mn, Mw, Mz, MWD) were determined by GPC analysis.

[0253] For GPC analysis, the column set was calibrated using a universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11500 kg / mol. The PS standards were dissolved at 160 °C for 15 min, or at room temperature at concentrations of 0.2 mg / mL (for molecular weights greater than or equal to 899 kg / mol) and 1 mg / mL (for molecular weights less than 899 kg / mol). The conversion of polystyrene peak molecular weight to polyethylene molecular weight was performed using the Mark Houwink equation and the following Mark Houwink constants:

[0254] K PS =19x10 -3 ml / g, α PS =0.655

[0255] K PE =39x10 -3 ml / g, α PE =0.725

[0256] Third-order polynomial fitting was used to fit the calibration data.

[0257] The average molecular weight (Mz, Mw, and Mn), molecular weight distribution (MWD), and its width described by the polydispersity index are determined using the following formula: PD = Mw / Mn (where Mn is the number-average molecular weight and Mw is the weight-average molecular weight):

[0258]

[0259]

[0260]

[0261] g) Flexural modulus

[0262] Flexural modulus was determined according to ISO 178 Method A (3-point bending test) on an 80mm × 10mm × 4mm sample. According to this standard, a test speed of 2mm / min and a span of 16 times the thickness were used. The test temperature was 23±2℃. Injection molding was performed according to ISO 19069-2, with a melt temperature of 230℃ used for all materials, regardless of the melt flow rate.

[0263] h) Charpy notch impact strength

[0264] Charpy notched impact strength was determined according to ISO 179-1 / 1eA on notched 80mm × 10mm × 4mm specimens (specimens prepared according to ISO 179-1 / 1eA). The test temperature was 23±2℃ or -20±2℃. Injection molding was performed according to ISO 19069-2, with a melt temperature of 230℃ used for all materials, regardless of melt flow rate.

[0265] i) AC electrical breakdown strength (ACBD)

[0266] AC breakdown testing was performed on 6 / 10kV cables according to CENELEC HD 605 5.4.15.3.4. The cable was cut into six 10m effective length test samples (excluding the termination). The samples were tested for breakdown at ambient temperature using a 50Hz AC step test according to the following procedure:

[0267] • Start from 18kV and continue for 5 minutes

[0268] • Increase the voltage in 6kV increments every 5 minutes until breakdown occurs.

[0269] The Weibull parameters for the six breakdown values ​​(conductor stress, i.e., the electric field of the internal semiconductor layer) were calculated following the least-squares regression procedure described in IEC 62539 (2007). In this document, the Weibull α parameter refers to the scale parameter of the Weibull distribution, i.e., the voltage with a failure probability of 0.632. The Weibull β parameter refers to the shape parameter.

[0270] 2. Propylene copolymer composition

[0271] The following resins were used to prepare the propylene copolymer compositions of the examples:

[0272] a) Polymerization of multiphase propylene copolymer powder A1

[0273] ·catalyst

[0274] The catalyst used in the polymerization process of multiphase propylene copolymer powder A1 is a Ziegler-Natta catalyst, which is described in patent publications EP491566, EP591224, and EP586390. Triethylaluminum (TEAL) is used as a co-catalyst and dicyclopentyldimethoxysilane (D-donor) is used as a donor.

[0275] Polymerization of multiphase propylene copolymer powder

[0276] Multiphase propylene copolymer powder A1 in Borstar TM The apparatus utilizes a liquid-phase circulating reactor and two gas-phase reactors connected in series, under the conditions shown in Table 1, in the presence of the aforementioned polymerization catalyst. The first reaction zone is the circulating reactor, and the second and third reaction zones are gas-phase reactors. The matrix phase polymerizes in the circulating reactor and the first gas-phase reactor, while the elastomer phase polymerizes in the second gas-phase reactor. The catalyst, as described above, is fed into a prepolymerization reactor prior to the first reaction zone.

[0277] Table 1: Polymerization conditions for multiphase propylene copolymer powders:

[0278]

[0279]

[0280] b) Preparation of polypropylene compositions

[0281] In the first method, the multiphase propylene copolymer powder A1 produced by the polymerization reaction is compounded with different stabilizers in a twin-screw extruder to obtain the polypropylene compositions of Examples IE1, CE1 and CE2.

[0282] As comparative examples, CE1 and CE2 were supplemented with an α-nucleating agent.

[0283] As disclosed in the Examples section of WO 2017 / 198633, the composition of Comparative Example CE2 was de-thawed and cracked to a melt flow rate MFR2 (230°C, 2.16 kg) of 3.9 g / 10 min.

[0284] Table 2 lists the production overview of the polypropylene compositions of Examples IE1, CE1 and CE2.

[0285] Table 2: Blending of IE1, CE1, and CE2 in a twin-screw extruder:

[0286]

[0287]

[0288] In the second method, the composite granules of Example IE1 were compounded with different additives in a second compounding step in a Buss100MDK L / D 11D co-kneader to obtain the polypropylene compositions of Examples IE2, IE3, IE4, IE5 and IE6.

[0289] The production overview of polypropylene compositions IE2, IE3, IE4, IE5 and IE6 is shown in Table 3.

[0290] Table 3: Blending of IE2-IE6 in Buss 100MDK L / D 11D co-kneader:

[0291] IE2 IE3 IE4 IE5 IE6 Granular IE1 IE1 IE1 IE1 IE1 CaSt [wt%] - - 1.0 - - MAH-g-PP [wt%] - - - 2.0 - β-NA [wt%] - - - - 0.01 Mixer zone temperature setting [℃] 150-200 160-200 160-200 160-180 160-180 Mixer RPM 150 150 146 150 150 Specific Energy Input (SEI) [kWh / kg] 0.29 0.26 0.27 0.30 0.29

[0292] Stabilizer packs and additives:

[0293] • Stabilizer Pack 1 consists of 21.8 wt% pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate (CAS-No. 6683-19-8), 43.6 wt% tris(2,4-di-tert-butylphenyl) phosphite (CAS-No. 31570-04-4), and 34.6 wt% calcium stearate (CAS-No. 1592-23-0), all of which are commercially available from their respective companies.

[0294] • Stabilizer Pack 2 consists of 29 wt% pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate (CAS-No. 6683-19-8), 58 wt% tris(2,4-di-tert-butylphenyl) phosphite (CAS-No. 31570-04-4), and 13 wt% magnesium oxide (CAS-No. 1309-48-4), all of which are commercially available from their respective companies.

[0295] • α-nucleation via BNT is achieved by adding 2 wt% of a propylene homopolymer with MFR2 (230°C) at a rate of 8.0 g / 10 min and a melting temperature of 162°C. This homopolymer is produced by a Ziegler-Natta type catalyst in Borealis Nucleation Technology (BNT) and contains a polymer α-nucleating agent, and is distributed by Borealis AG (Austria).

[0296] • The additional calcium stearate (CAS-No. 1592-23-0) added to IE4 is available commercially from various companies.

[0297] The maleic anhydride-grafted propylene homopolymer (MAH-g-PP) used in IE5 is Exxelor PO1020 with a melt flow rate of 430 g / 10 min at 230 °C and 2.16 kg load, and is commercially available from ExxonMobil.

[0298] The β-nucleating agent used in IE6 is quinolino[2,3-b]acridin-6,7,13,14(5H,12H)-tetraone (CAS-No. 1503-48-6), which is commercially available from BASF under CGNA-7588.

[0299] The properties of polypropylene compositions CE1-CE2 and IE1-IE6 are shown in Tables 4 and 5.

[0300] Table 4: Properties of polypropylene compositions at CE1, CE2, and IE1:

[0301] IE1 CE1 CE2 α-NA no BNT BNT <![CDATA[MFR2]]> [g / 10min] 1.2 1.3 3.9 Flexural modulus [MPa] 335 370 378 Charpy NIS (-20℃) <![CDATA[[kJ / m 2 ]]]> 6.3 6.5 4.2 Charpy NIS (23℃) <![CDATA[[kJ / m 2 ]]]> 83.9 83.6 78.9 Tm [℃] 148.9 146.6 147.4 Tc [℃] 95.7 113.6 114.5 Tm-Tc [℃] 53.2 33.0 32.9 C2 (Total) [wt%] 12.4 12.4 11.3 <![CDATA[V 固有 (Total) <![CDATA[[cm 3 / g]]]> 277 268 213 XCS Classification [wt%] 35.6 34.7 35.6 C2(XCS) [wt%] 26.1 26.3 24.5 <![CDATA[V 固有 (XCS)]]> <![CDATA[[cm 3 / g]]]> 251 243 189 Mw(XCS) [g / mol] 294,500 285,000 215,000 Mn(XCS) [g / mol] 45,650 45,400 48,900 PDI(Mw / Mn)(XCS) [-] 6.4 6.3 4.4 XCI classification [wt%] 64.4 65.3 64.4 C2(XCI) [wt%] 4.8 5.5 5.8 <![CDATA[V 固有 (XCI)]]> <![CDATA[[cm 3 / g]]]> 286 275 216 Mw(XCI) [g / mol] 384,500 372,500 271,000 Mn(XCI) [g / mol] 69,500 68,100 62,000 PDI(Mw / Mn)(XCI) [-] 5.5 5.5 4.4 <![CDATA[V 固有 Ratio (XCI / XCS) [-] 1.14 1.13 1.14 Mw ratio (XCI / XCS) [-] 1.31 1.31 1.26

[0302] As can be seen, by preventing nucleation of the polypropylene composition in the presence of an α-nucleating agent, the polypropylene composition according to the invention exhibits a lower flexural modulus through comparable mechanical and impact properties. This low flexural modulus allows for the addition of additives that may increase the flexural modulus but improve other properties of the polypropylene composition of the invention, as shown in Table 5 below.

[0303] Table 5: Properties of polypropylene compositions from IE2 to IE6 from a Buss 100MDK L / D 11D co-kneader

[0304]

[0305]

[0306] Here, “nm” indicates that it was not measured; it is assumed that the corresponding value is similar to IE2 without additives.

[0307] 3. Production of 10kV cables

[0308] The 10kV test cable is produced on the Maillefer test cable production line, which is a type of catenary continuous vulcanization (CCV).

[0309] The cross-section of the conductor in the cable core is 50mm². 2 Stranded aluminum with a cross-section of 50mm 2 The inner semiconductor layer is produced from semiconductor composition SC1 or SC2 described below, and has a thickness of 1.0 mm. The insulating layer is produced from the above compositions CE1 and IE1-IE6, and has a thickness of 3.4 mm. The outer semiconductor layer is produced from semiconductor composition SC1 described below, and has a thickness of 1.0 mm.

[0310] The cable, specifically the cable core, is produced via a three-stage extrusion process. The insulation extruder is 100mm in diameter, the conductor barrier (inner semiconductor layer) extruder is 45mm, and the insulation barrier (outer semiconductor layer) extruder is 60mm. The production line speed is 6.0m / min.

[0311] The vulcanizing tube is 52.5m long and consists of a curing section followed by a cooling section. The curing section is filled with N2 at 10 bar but not heated. The 33m long cooling section is filled with water at 20-25°C.

[0312] Then, an AC breakdown test was performed on the test cable.

[0313] Semiconductor layer 1 (SC1) is produced from an off-the-shelf semiconductor composition, Borlink LE7710, which is a non-crosslinked polyvinyl composition containing carbon black and is commercially available from Borealis AG.

[0314] Semiconductor layer 2 (SC2) is produced from 66.5 wt% of a polypropylene-based composition CE2, 33.0% of carbon black Printex Alpha (available from Orion Engineered Carbons GmbH), and 0.5 wt% of maleic anhydride-grafted propylene homopolymer Exxelor PO1020, with a melt flow rate of 430 g / 10 min at 230 °C and a load of 2.16 kg, and is available from ExxonMobil.

[0315] Semiconductor layer 3 (SC3) is produced from 66.5 wt% of a polypropylene-based composition IE1, 3.3 wt% of carbon black PrintexAlpha (commercially available from Orion Engineered Carbons GmbH), and 0.5 wt% of maleic anhydride-grafted propylene homopolymer Exxelor PO1020, with a melt flow rate of 430 g / 10 min at 230 °C and a load of 2.16 kg, and is commercially available from ExxonMobil.

[0316] Table 6 shows the electrical properties of the 10kV cables in Examples C1 to C7, with a comparison of insulation layers CE1 and IE1-IE6.

[0317] Table 6: Electrical properties of 10kV cables C1 to C7

[0318] C1 C2 C3 C4 C5 C6 C7 Insulation layer CE1 IE1 IE3 IE4 IE2 IE5 IE6 Internal semiconductor layer SC1 SC1 SC2 SC2 SC3 SC3 SC3 External semiconductor layer SC1 SC1 SC1 SC1 SC1 SC1 SC1 Weibull-α (scale) [kV / mm] 47.0 48.7 40.6 46.8 43.8 48.8 50.5 Weibull-β (shape) 9.3 7.0 14.3 10.0 6.4 22.3 11.8

[0319] Both the inner and outer semiconductor layers of cables C1 and C2 are SC1.

[0320] The internal semiconductor layer of cables C3 and C4 is SC2, and the external semiconductor layer is SC1.

[0321] The internal semiconductor layer of cables C5, C6, and C7 is SC3, and the external semiconductor layer is SC1.

[0322] Table 6 lists the corresponding insulation layers.

[0323] Compared to the compositions used for cable insulation layers C1 and C2, the compositions used for cable insulation layers C3 through C7 were compounded in an additional compounding step. Since each compounding step introduces impurities into the composition, affecting electrical properties, the inherent Weibull α values ​​of cables C3 through C7 are lower than those of cables C1 and C2. This is demonstrated by comparing the Weibull α values ​​of C1, C3, and C5, all of which contain only additive-free polypropylene compositions IE1.

[0324] As can be seen from the table above, the Weibull α value of C2 is comparable to that of C1, but the Weibull B value is lower.

[0325] Comparing C3 and C4, as well as C5 and C6-C7, reveals that the introduction of additives improves dielectric properties.

[0326] Therefore, a comparison between C4 and C3 shows that the introduction of a large amount of calcium stearate increases the Weibull α value.

[0327] Compared to C5, the introduction of functionalized polypropylene Exxelor PO1020 (C6) improves Weibull α and Weibull β behavior.

[0328] Compared to C5, the introduction of a β-nucleating agent (C7) increases the Weibull β value, especially the Weibull α behavior.

Claims

1. A polypropylene composition comprising a copolymer of propylene and comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms, wherein the amount of the copolymer is 90.0 to 100 wt% based on the total weight of the polypropylene composition, and the total amount of the comonomer units is 10.0 to 14.0 wt% based on the total amount of monomer units in the polypropylene composition; The polypropylene composition wherein the polypropylene composition comprises: The total amount of xylene cold soluble (XCS) fraction is 25.0 to 50.0 wt% based on the total weight of the polypropylene composition, and the amount of at least 22.0 wt% of comonomer units is based on the total amount of monomer units in the xylene cold soluble (XCS) fraction. Melt flow rate MFR2 of 0.5 to 2.5 g / 10 min, A flexural modulus not exceeding 385 MPa, and At least 3.5 kJ / m² Charpy notched impact strength at -20°C; and The polypropylene composition does not contain α-nucleating agents; The polypropylene composition is not subjected to viscosity-reducing cracking.

2. The polypropylene composition according to claim 1, wherein the intrinsic viscosity of the xylene cold soluble (XCS) fraction in naphthalene is 150 to 350 cm³ / g.

3. The polypropylene composition according to claim 2, wherein the intrinsic viscosity of the xylene cold soluble (XCS) fraction in naphthalene is 200 to 325 cm³ / g.

4. The polypropylene composition according to claim 2, wherein the intrinsic viscosity of the xylene cold soluble (XCS) fraction in naphthalene is 225 to 300 cm³ / g.

5. The polypropylene composition according to claim 1, wherein, The polypropylene composition has a xylene cold insoluble (XCI) fraction, and the amount of comonomer units in the xylene cold insoluble (XCI) fraction is 3.0 to 9.0 wt% based on the total amount of monomer units in the xylene cold insoluble (XCI) fraction.

6. The polypropylene composition of claim 1, wherein the copolymer of propylene with comonomer units selected from ethylene and α-olefins having 4 to 12 carbon atoms is a multiphase propylene copolymer, the multiphase propylene copolymer comprising a matrix phase and an elastomeric phase dispersed in the matrix phase.

7. The polypropylene composition according to claim 1, wherein, The polypropylene composition has a melting temperature Tm of 125 to 159°C and / or a crystallization temperature Tc of 85 to 120°C.

8. The polypropylene composition according to any one of claims 1 to 7, wherein, The polypropylene composition has a Charpy notched impact strength of 3.5 to 10.0 kJ / m² at -20°C, and / or a Charpy notched impact strength of at least 70.0 kJ / m² at 23°C.

9. The polypropylene composition according to any one of claims 1 to 7, wherein, The polypropylene composition contains an acid scavenger, the amount of which is 1,000 to 50,000 ppm based on the total weight of the polypropylene composition, and the polypropylene composition has comonomer units in a xylene cold soluble (XCS) fraction, the amount of which is at least 23.0 wt% based on the total amount of monomer units in the xylene cold soluble (XCS) fraction.

10. The polypropylene composition according to any one of claims 1 to 7, wherein, The polypropylene composition contains a β-nucleating agent and has one or more of the following properties: • Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of comonomer units in the xylene cold soluble (XCS) fraction is at least 23.0 wt%, and / or • Melting temperature Tm is 125 to 140°C, and / or • Crystallization temperature Tc is 95 to 120°C, and / or • The difference between the melting temperature and the crystallization temperature, Tm – Tc, is 18 to 35°C.

11. The polypropylene composition according to any one of claims 1 to 7, wherein, The polypropylene composition comprises a polyolefin functionalized with a monocarboxylic acid or a polycarboxylic acid compound or a derivative thereof, wherein the functionalized polyolefin is different from a copolymer of propylene with a comonomer unit selected from ethylene and an α-olefin having 4 to 12 carbon atoms, and the amount of the functionalized polyolefin is 0.5 to 3.0 wt% based on the total weight of the polypropylene composition, and the polypropylene composition has one or all of the following properties: • The difference between the melting temperature and the crystallization temperature, Tm – Tc, is 45 to 70°C, and / or • Flexural modulus of 300 MPa to 385 MPa, and / or • The total amount of xylene cold solubles (XCS) fraction is 25.0-50.0 wt%, based on the total weight of the polypropylene composition, and / or •Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of comonomer units in the xylene cold soluble (XCS) fraction is 22.0-32.5 wt%.

12. The polypropylene composition according to any one of claims 1 to 7, wherein the polypropylene composition is free from any one of a β-nucleating agent and a polyolefin functionalized with a monocarboxylic acid or a polycarboxylic acid compound or a derivative thereof, and has one or all of the following properties: • Based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, the amount of comonomer units in the xylene cold soluble (XCS) fraction is at least 23.0 wt%, and / or • Melting temperature Tm is 140 to 159°C, and / or • Crystallization temperature Tc is 85 to 102°C, and / or • The difference between the melting temperature and the crystallization temperature, Tm – Tc, is 50 to 70°C, and / or • Flexural modulus of 200 MPa to 380 MPa, and / or • Charpy notched impact strength at 23°C is 78.0 to 100.0 kJ / m², and / or • Charpy notched impact strength at -20°C is 3.5 to 10.0 kJ / m².

13. The polypropylene composition according to any one of claims 1 to 7, wherein, The polypropylene composition does not contain dielectric fluid.

14. An article comprising the polypropylene composition according to any one of claims 1 to 13.

15. The article of claim 14, wherein the article is a cable having an insulation layer containing the polypropylene composition.

16. The article of manufacture according to claim 15, wherein, The product has a Weibull α value of 35.0 to 65.0 kV / mm and / or a Weibull β value of 5.0 to 250.0 when measured on a 10 kV cable.

17. Use of the polypropylene composition according to any one of claims 1 to 13 as a cable insulation material for medium-voltage and high-voltage cables.

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