Polymer Composition

Abstract

1. A polymer composition comprising: (i) 4.95 to 95.0% by weight of low-density polyethylene (LDPE) (hereinafter referred to as component (i)); (ii) 4.95 to 95.0% by weight of polypropylene (hereinafter referred to as component (ii)); and (iii) 0.00 to 30.0% by weight of a styrene block copolymer (hereinafter referred to as component (iii)); (iv) 0.05 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler (hereinafter referred to as component (iv)); Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition; The polymer composition.

Description

[Technical field]

[0001] The present invention relates to a polymer composition having advantageously low direct current (DC) conductivity. In particular, the present invention relates to a polymer composition comprising a blend of low density polyethylene (LDPE), polypropylene, optionally a styrene block copolymer, and an aliphatically functionalized inorganic nanoparticle filler, and to the use of this composition in the manufacture of cables, in particular in the manufacture of insulation layers for power cables. Ideally, the compositions and cables of the present invention are peroxide-free. The present invention also relates to a method for preparing such cables. [Background technology]

[0002] Polyolefins produced in high-pressure (HP) processes are widely used in demanding polymer applications, such as power cable applications, where the polymer must meet high mechanical and / or electrical requirements. A typical power cable comprises a conductor surrounded by at least an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The cable is usually manufactured by extruding a layer onto the conductor. The polymer material in one or more of the layers is then often crosslinked.

[0003] Particularly in medium voltage (MV), and especially high-pressure (HV) and extra high voltage (EHV) cable applications, the electrical properties of the polymer composition are of great importance. Moreover, the important electrical properties may differ depending on the cable application, such as alternating current (AC) and direct current (DC) cable applications.

[0004] DC electrical conductivity is an important material property for insulating materials, e.g. in high voltage direct current (HVDC) cables. Firstly, the strong temperature and electric field dependence of this property will affect the electric field. The second issue concerns the heat generated in the insulation due to the leakage current flowing between the inner and outer semiconducting layers. This leakage current depends on the electric field and the electrical conductivity of the insulation.

[0005] Thus, in HVDC cables, the insulation is partially heated by leakage currents. For a particular cable design, the heating is a function of the insulation conductivity times the voltage. 2 is proportional to.

[0006] There is a strong demand to increase the voltage of direct current (DC) power cables. Increasing the voltage level allows to increase the transmission capacity and / or reduce losses in HVDC power cables. However, when the voltage is increased, more heat will be generated. This can lead to thermal runaway and subsequently electrical breakdown. Therefore, to further increase the voltage level of HVDC cables, insulating materials with low DC conductivity are required.

[0007] WO2017 / 149086 and WO2017 / 149087 relate to the use of nanoparticle fillers in polymer compositions. However, the use of said fillers in blends of low density polyethylene (LDPE), polypropylene, and optionally styrene block copolymers is not disclosed, and the electrical conductivity of the exemplified compositions is still relatively high.

[0008] European Patent No. EP3261095 relates to cables comprising polymer compositions including blends of LDPE and HDPE. However, the use of nanoparticle fillers is not disclosed and the electrical conductivity of the exemplified compositions is still relatively high.

[0009] Thus, there remains a need for new polymer compositions with reduced DC conductivity, which should also have sufficiently good mechanical properties required for demanding power cable applications. In addition, there is a need for new polyolefin compositions that avoid the drawbacks associated with peroxides, but also provide attractive properties.

[0010] Often, the polymeric material in one of the semiconductive and / or insulating layers is crosslinked to, for example, improve heat and deformation resistance, creep properties, mechanical strength, chemical resistance, and abrasion resistance. Crosslinking can be accomplished, for example, using a free radical generating compound, which is typically incorporated into the layer material prior to extruding one or more layers onto the conductor. After formation of the layered cable, the cable is then subjected to a crosslinking step to generate radicals and thereby initiate the crosslinking reaction.

[0011] Peroxides are very commonly used as free radical generating compounds. However, crosslinking with peroxides has some drawbacks. For example, low molecular weight by-products are generated during crosslinking, which have an unpleasant odor. These decomposition products of peroxides are often undesirable because they may include volatile by-products, which can adversely affect the electrical properties of the cable. Therefore, volatile decomposition products, such as methane, are conventionally minimized or removed after the crosslinking and cooling steps. Such removal steps, commonly known as degassing steps, consume time and energy and cause extra costs.

[0012] Thermoplastic insulating materials can offer several advantages. Eliminating the crosslinking and degassing steps can result in faster, less complicated, and more cost-effective cable manufacturing. The process is faster and cleaner in terms of reduced extruder output and cleaning interruptions. However, the absence of crosslinking materials can result in reduced dimensional stability at elevated temperatures.

[0013] The possibility of using non cross-linked LDPE in the insulation layer of cables is not new. In WO 2011 / 113685, a LDPE having a density of 922 kg / m 3 and MFR 2 LDPE of 1.90 g / 10 min is proposed for use in the insulation layer of the cable. WO 2011 / 113685 also proposes the use of other polymers individually in the non-crosslinked insulation layer of the cable. Summary of the Invention [Problem to be solved by the invention]

[0014] In view of the above, there remains a need for new polymer compositions with even lower DC conductivity, thereby avoiding the drawbacks associated with peroxides, while the polymer compositions should also have sufficiently good mechanical properties.

[0015] SUMMARY OF THE PRESENT APPLICATION It is an object of the present invention to provide novel polyolefin compositions that exhibit reduced DC conductivity while providing such properties suitable for use in demanding power cable applications without the use of any peroxides. [Means for solving the problem]

[0016] The inventors have found that a polymer composition comprising a blend of low density polyethylene (LDPE), polypropylene, optionally a styrene block copolymer, and an aliphatically functionalized inorganic nanoparticle filler has a surprisingly low DC conductivity and is thereby particularly suitable in the manufacture of high voltage power cables.

[0017] While it is known that nanoparticle agglomerates or aggregates can lead to premature cable failure, the inventors have found that the claimed combination of ingredients results in extremely low DC conductivity and, advantageously, does not require the use of peroxides to initiate crosslinking.

[0018] Thus, in one aspect, the present invention provides a polymer composition comprising: (i) 4.95 to 95.0 wt.% low-density polyethylene (LDPE); (ii) 4.95 to 95.0% by weight of polypropylene; and (iii) 0.00 to 30.0 weight percent of a styrene block copolymer; (iv) 0.05 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0019] Viewed from another aspect, the present invention relates to a method for preparing a polymer composition as defined hereinbefore, said method comprising the steps of: (i) 4.95 to 95.0 wt.% low-density polyethylene (LDPE); (ii) 4.95 to 95.0% by weight of polypropylene; and (iii) 0.00 to 30.0 weight percent of a styrene block copolymer; (iv) 0.05 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Blending the wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above method is provided.

[0020] Viewed from a further aspect, the present invention provides a cable comprising a conductor surrounded by one or more layers, at least one of which comprises the polymer composition as defined hereinbefore.In a still further aspect, the present invention provides a power cable, such as a direct current (DC) power cable, comprising a conductor surrounded, in that order, by at least an inner semiconductive layer, an insulating layer and an outer semiconductive layer, wherein at least one layer, such as at least the insulating layer, comprises the polymer composition as defined hereinbefore.

[0021] Viewed from a still further aspect, the present invention provides the use of the polymer composition as defined hereinbefore in the manufacture of a layer in a cable, preferably a layer in a power cable, more preferably an insulating layer of a power cable.

[0022] Viewed from another aspect, the present invention provides the use of a polymer composition as defined hereinbefore in the manufacture of a regenerated insulation layer of a cable, preferably a power cable.

[0023] definition

[0024] The word “molecular weight M w When used herein, "weight average molecular weight" is meant.

[0025] The term "polyethylene" will be understood to mean an ethylene-based polymer, i.e., one that contains at least 50 weight percent ethylene, based on the total weight of the polymer as a whole. The terms "polyethylene" and "ethylene-based polymer" are used interchangeably herein and refer to a polymer that contains a majority weight percent polymerized ethylene monomer (based on the total weight of polymerizable monomers), and may optionally contain at least one polymerized comonomer. An ethylene-based polymer may contain more than 50 weight percent, or more than 60 weight percent, or more than 70 weight percent, or 80 weight percent or more, or 90 weight percent or more of units derived from ethylene (based on the total weight of the ethylene-based polymer).

[0026] The term "polypropylene" will be understood to mean a propylene-based polymer, i.e. one that contains at least 50% by weight of propylene, based on the total weight of the whole polymer.

[0027] The term "styrenic block copolymer" defines a block copolymer containing multiple blocks, each block made of the same type of monomer (or mixture of monomers), but with one or more different monomer types between the blocks.

[0028] The non-crosslinked polymer composition or cable layer is considered to be a thermoplastic.

[0029] The polymer compositions of the present invention may also be referred to herein as polymer blends, the terms being used interchangeably.

[0030] The low density polyethylene (LDPE) of the present invention is polyethylene produced in a high pressure process. Typically, the polymerization of ethylene and optionally further comonomers in a high pressure process is carried out in the presence of one or more initiators. The meaning of the term "LDPE" is well known and described in the literature. The term "LDPE" describes high pressure polyethylene, which is produced in the presence of an olefin polymerization catalyst, as distinct from low pressure polyethylene. LDPE has certain typical characteristics, such as a different branching structure. The typical density range for LDPE is 0.910-0.940 g / cm. 3 It is.

[0031] The term "conductor" as used herein means a conductor comprising one or more wires. The wires may be of any type, such as optical wires, telecommunication wires or electrical wires. Moreover, the cable may comprise one or more such conductors. Preferably, the conductors are electrical conductors and comprise one or more metal wires. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] [Detailed Description of the Invention] The present invention relates to a polymer composition, the polymer composition comprising: (i) 4.95 to 95.0 wt.% low-density polyethylene (LDPE); (ii) 4.95 to 95.0% by weight of polypropylene; and (iii) 0.00 to 30.0 weight percent of a styrene block copolymer; (iv) 0.05 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. Regarding the above polymer composition.

[0033] It is understood that the amounts of components (i)-(iv) in the composition may be varied independently.

[0034] The invention also relates to a cable, at least one layer of which comprises this polymer composition. In all embodiments, the polymer composition or the layer of the cable is ideally peroxide-free.

[0035] The polymer composition may optionally be crosslinked. In a preferred embodiment, the polymer composition is not crosslinked. A "non-crosslinked" polymer composition means that in the final form, for example in a layer of a cable, the polymer composition is not crosslinked and is therefore thermoplastic.

[0036] The preferred definitions of LDPE, polypropylene and styrene block copolymer below apply to all aspects of the present invention unless otherwise stated.

[0037] Component (i) - Low Density Polyethylene (LDPE)

[0038] Component (i) of the polymer composition according to the present invention is a low density polyethylene (LDPE).

[0039] Low density polyethylene (LDPE) is an ethylene-based polymer. As used herein, the term "ethylene-based polymer" refers to a polymer that contains a majority weight percent polymerized ethylene monomer (based on the total weight of polymerizable monomers) and, optionally, at least one polymerized comonomer. The ethylene-based polymer may contain more than 50 weight percent, or more than 60 weight percent, or more than 70 weight percent, or more than 80 weight percent, or more than 90 weight percent of units derived from ethylene (based on the total weight of the ethylene-based polymer).

[0040] The LDPE may be a low density homopolymer of ethylene (referred to herein as LDPE homopolymer) or a low density copolymer of ethylene and one or more comonomers (referred to herein as LDPE copolymer). The one or more comonomers of the LDPE copolymer are preferably selected from one or more polar comonomers, one or more non-polar comonomers, or a combination of one or more polar comonomers and one or more non-polar comonomers. Moreover, the LDPE homopolymer or LDPE copolymer may optionally be unsaturated. Preferably, the LDPE is a homopolymer.

[0041] As polar comonomers for the LDPE copolymer, one or more comonomers containing one or more hydroxyl groups, one or more alkoxy groups, one or more carbonyl groups, one or more carboxyl groups, one or more ether groups or one or more ester groups, or a combination thereof, can be used. More preferably, one or more comonomers containing one or more carboxyl groups and / or one or more ester groups are used as the polar comonomer. Even more preferably, the one or more polar comonomers of the LDPE copolymer are selected from the group of one or more acrylates, one or more methacrylates or one or more acetate(s), or a combination thereof.

[0042] If present in the LDPE copolymer, the one or more polar comonomers are preferably selected from the group of alkyl acrylates, alkyl methacrylates or vinyl acetates, or combinations thereof. More preferably, the polar comonomers are selected from C1-C6 alkyl acrylates, C1-C6 alkyl methacrylates or vinyl acetates. Even more preferably, the LDPE copolymer is a copolymer of ethylene and a C1-C4 alkyl acrylate, such as methyl, ethyl, propyl or butyl acrylate, or vinyl acetate, or combinations thereof.

[0043] The one or more non-polar comonomers for the LDPE copolymers are preferably selected from one or more monounsaturated (=one double bond) comonomers, (e.g., alpha-olefins, more preferably C3 to C10 alpha-olefins, such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, styrene, 1-octene, 1-nonene); one or more polyunsaturated (=more than one double bond) comonomers; one or more silane group-containing comonomers; or any combination thereof. The one or more polyunsaturated comonomers are further described below.

[0044] When the LDPE is a copolymer it preferably contains from 0.001 to 35% by weight of one or more comonomers, even more preferably less than 30% by weight, more preferably less than 25% by weight. Preferred ranges include 0.5 to 10% by weight, for example 0.5 to 5% by weight of comonomers.

[0045] LDPE polymers may be optionally unsaturated, i.e., contain carbon-carbon double bonds (-C=C-). Preferred "unsaturated" LDPEs contain carbon-carbon double bonds / 1000 carbon atoms in a total amount of at least 0.4 / 1000 carbon atoms. When non-crosslinked LDPE is used in the final cable, the LDPE is typically not unsaturated as defined above. By "not unsaturated" it is meant that the C=C content is preferably less than 0.2 / 1000 carbon atoms, for example not more than 0.1 / 1000 C atoms.

[0046] As is well known, unsaturation can occur in the form of comonomers, low molecular weight (M wThe unsaturation may be provided to the LDPE polymer by an additive compound such as a chain transfer agent or a scorch retarder additive, or any combination thereof. As used herein, the total amount of double bonds means the double bonds added by any means. When more than one of the above double bond sources is selected for use to provide unsaturation, the total amount of double bonds in the LDPE polymer means the sum of the double bonds present. Measurement of any double bonds is done prior to any crosslinking.

[0047] The term "total amount of carbon-carbon double bonds" means the combined amount of double bonds resulting from vinyl groups, vinylidene groups and trans-vinylene groups (if present).

[0048] When the LDPE homopolymer is unsaturated, the unsaturation can be provided by a chain transfer agent (CTA), such as propylene, and / or by the polymerization conditions. When the LDPE copolymer is unsaturated, the unsaturation can be provided by one or more of the following means: by a chain transfer agent (CTA), by one or more polyunsaturated comonomers, or by one or more of the polymerization conditions. It is well known that the selected polymerization conditions, such as peak temperature and pressure, can have an effect on the unsaturation level. In the case of an unsaturated LDPE copolymer, it is preferably an unsaturated LDPE copolymer of ethylene and at least one polyunsaturated comonomer, and optionally one or more other comonomers, such as one or more polar comonomers, preferably selected from acrylate or one or more acetate comonomers. More preferably, the unsaturated LDPE copolymer is an unsaturated LDPE copolymer of ethylene and at least one polyunsaturated comonomer.

[0049] The polyunsaturated comonomer suitable as the non-polar comonomer preferably consists of a straight chain of carbons having at least 8 carbon atoms and at least 4 carbons between the non-conjugated double bonds, at least one of which is terminal, more preferably the polyunsaturated comonomer is a diene, preferably a diene containing at least 8 carbon atoms, the first carbon-carbon double bond is terminal, and the second carbon-carbon double bond is non-conjugated to the first carbon-carbon double bond. The preferred diene is selected from C8 to C14 non-conjugated dienes or combinations thereof, more preferably selected from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, or combinations thereof. More preferably, the diene is selected from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, or any combination thereof, but is not limited to the above dienes.

[0050] For example, it is well known that propylene can be used as a comonomer or as a chain transfer agent (CTA), or both, thereby contributing to the total amount of carbon-carbon double bonds, preferably to the total amount of vinyl groups. In this specification, when a compound that can also act as a comonomer, such as propylene, is used as a CTA to provide double bonds, the copolymerizable comonomer is not calculated into the comonomer content.

[0051] When the LDPE polymer is unsaturated, the total amount of carbon-carbon double bonds resulting from vinyl, vinylidene and trans-vinylene groups, if present, is preferably greater than 0.4 / 1000 carbon atoms, preferably greater than 0.5 / 1000 carbon atoms. The upper limit of the amount of carbon-carbon double bonds present in the LDPE is not particularly limited, and may be preferably less than 5.0 / 1000 carbon atoms, more preferably less than 3.0 / 1000 carbon atoms.

[0052] When the LDPE is an unsaturated LDPE as defined above, it preferably contains at least vinyl groups, the total amount of vinyl groups being preferably higher than 0.05 / 1000 carbon atoms, more preferably higher than 0.08 / 1000 carbon atoms, and most preferably higher than 0.11 / 1000 carbon atoms. Preferably, the total amount of vinyl groups is lower than 4.0 / 1000 carbon atoms, more preferably lower than 2.0 / 1000 carbon atoms. More preferably, the LDPE contains vinyl groups higher than 0.20 / 1000 carbon atoms, more preferably higher than 0.30 / 1000 carbon atoms.

[0053] However, it is preferred that the LDPE of the present invention is not unsaturated and has less than 0.2 C=C / 1000 C atoms, preferably less than 0.1 C=C / 1000 C atoms. It is also preferred if the LDPE is a homopolymer. Since the polymer composition of the present invention is not designed for crosslinking, the presence of unsaturation in the LDPE is not required or desired.

[0054] The LDPE polymer may have a high melting point, which may be particularly important as a thermoplastic insulating material. Melting points of 112°C or more, such as 114°C or more, especially 116°C or more, for example 112-130°C, are envisaged.

[0055] The LDPE is 915 to 940 kg / m 3 , preferably 918 to 935 kg / m 3 , especially 920-932 kg / m 3 , for example, about 922 to about 930 kg / m 3 , may have a density of

[0056] MFR of LDPE 2 (2.16 kg, 190° C.) is preferably 0.05 to 30.0 g / 10 min, more preferably 0.1 to 20 g / 10 min, most preferably 0.1 to 10 g / 10 min, particularly preferably 0.1 to 5.0 g / 10 min. In a preferred embodiment, the MFR of the LDPE 2 is 0.1 to 4.0 g / 10 min, particularly 0.5 to 4.0 g / 10 min, and particularly 1.0 to 3.0 g / 10 min.

[0057] The LDPE has a weight average molecular weight (M w ).

[0058] Although it is possible to use combinations of LDPEs in the polymer composition of the present invention, it is preferred when a single LDPE is used. When a combination of LDPEs is used, the weight percentages refer to the total content of LDPE present.

[0059] The LDPE polymer is produced at high pressure by free radical initiated polymerization (referred to as high pressure (HP) radical polymerization). The HP reactor can be, for example, a well-known tubular reactor or an autoclave reactor, or a combination thereof, preferably a tubular reactor. High pressure (HP) polymerization and the adjustment of process conditions to further adjust other properties of the LDPE depending on the desired end use are well known and described in the literature and can be easily used by a person skilled in the art. Suitable polymerization temperatures are up to about 400°C, preferably 80-350°C, and pressures are 70 MPa, preferably 100-400 MPa, more preferably 100-350 MPa. The pressure can be measured at least after the compression stage and / or after the tubular reactor. The temperature can be measured at several points during the entire process.

[0060] After separation, the resulting LDPE is typically in the form of a polymer melt, which is usually mixed and pelletized in a pelletising section, such as a pelletising extruder, disposed in connection with the HP reactor system. Optionally, one or more additives, such as antioxidants, can be added in the mixer in known manner.

[0061] Further details of the production of ethylene (co)polymers by high pressure radical polymerization can be found, inter alia, in Encyclopaedia of Polymer Science and Engineering, Vol. 6 (1986), pp 383-410 and Encyclopaedia of Materials: Science and Technology, 2001 Elsevier Science Ltd.: “Polyethylene: High-pressure, R. Klimesch, D. Littmann and F.-O. Mahling pp. 7181-7184.

[0062] Most preferably, the LDPE is a low density homopolymer of ethylene.

[0063] The LDPE in the polymer composition of the present invention is preferably present in an amount of from 4.95 to 95% by weight, based on the total weight of the polymer composition.

[0064] In one embodiment, the weight percentage of LDPE in the polymer composition of the present invention is advantageously 5.0 wt% or more, or 10.0 wt% or more, or 15.0 wt% or more, or 20.0 wt% or more, or 25.0 wt% or more, or 30.0 wt% or more, based on the total weight of the polymer composition.

[0065] It is further understood that the upper limit for the weight percent of LDPE in the polymer composition relative to the total weight of the polymer composition is 95.0 wt% or less, or 92.5 wt% or less, or 90.0 wt% or less, or 87.5 wt% or less, or 85.0 wt% or less, or 82.5 wt% or less.

[0066] In a preferred embodiment of the polymer composition according to the invention, the weight percentage of LDPE in the polymer composition, based on the total weight of the polymer composition, is in the range of 10.0-90.0 wt%, 20.0-85.0 wt%, or 25.0-80.0 wt%, or 25.0-82.5 wt%, preferably up to 80.0 wt%, for example 25.0-80.0 wt%, or 30.0-77.5 wt%, in particular 35.0-75.0 wt%, based on the total weight of the polymer composition as a whole.

[0067] The LDPE of the present invention is new and not commercially available.

[0068] Component (ii) - Polypropylene (PP)

[0069] Component (ii) of the polymer composition according to the present invention is polypropylene.

[0070] Polypropylene is a propylene-based polymer. As used herein, the term "propylene-based polymer" refers to a polymer that contains a majority weight percent of polymerized propylene monomers (based on the total weight of polymerizable monomers) and may optionally contain at least one polymerized comonomer. A propylene-based polymer may contain more than 50 weight percent, or more than 60 weight percent, or more than 70 weight percent, or more than 80 weight percent, or more than 90 weight percent of units derived from propylene (based on the total weight of the propylene-based polymer).

[0071] The polypropylene may be a propylene homopolymer or a propylene copolymer. Preferably, the propylene is a homopolymer.

[0072] In most embodiments, component (ii) comprises a heterophasic polypropylene copolymer, preferably a random heterophasic polypropylene copolymer. The inventors have found that when polypropylene component (ii) comprises a heterophasic polypropylene copolymer, the presence of component (iii) is less important.

[0073] Heterophasic polypropylenes are propylene-based copolymers having a semi-crystalline matrix phase which is a propylene homopolymer or a random copolymer of propylene and at least one alpha-olefin comonomer, and an elastomeric phase dispersed therein, which can be a propylene copolymer with a large amount of the comonomer not randomly distributed in the polymer chain, but distributed in comonomer-rich and propylene-rich block structures.

[0074] Heterophasic polypropylenes typically have two distinct glass transition temperatures, T, due to the matrix phase and the elastomeric phase. g It differs from one-phasic propylene copolymer in that it exhibits the following properties:

[0075] The comonomer may be an α-olefin, such as ethylene, or a C4-20 linear, branched, or cyclic α-olefin. Non-limiting examples of suitable C4-20 α-olefins include 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. The α-olefins may also contain cyclic structures, such as cyclohexane or cyclopentane, resulting in α-olefins, such as 3-cyclohexyl-1-propene (allylcyclohexane) and vinylcyclohexane. While not α-olefins in the classical sense, for purposes of this disclosure, certain cyclic olefins, such as norbornene and related olefins, particularly 5-ethylidene-2-norbornene, are α-olefins and may be used in place of some or all of the α-olefins described above. Similarly, styrene and its related olefins (e.g., α-methylstyrene, etc.) are α-olefins for purposes of this disclosure. Exemplary propylene polymers include ethylene / propylene, propylene / butene, propylene / 1-hexene, propylene / 1-octene, propylene / styrene, etc. Exemplary terpolymers include ethylene / propylene / 1-octene, ethylene / propylene / butene, propylene / butene / 1-octene, ethylene / propylene / diene monomer (EPDM), and propylene / butene / styrene. The copolymers can be random copolymers.

[0076] In a particularly preferred embodiment, the polypropylene is a homopolymer, such as a syndiotactic propylene homopolymer, most preferably an isotactic propylene homopolymer. The isotactic propylene homopolymer used may be of capacitor grade.

[0077] Typically, the polypropylene has a MFR of 0.1 to 100 g / l min, preferably 0.5 to 50 g / l min, determined according to ISO 1133 (230° C.; 2.16 kg load). 2Most preferably, the compound has MFR 2 is in the range of 1.0 to 5.0 g / 10 min, for example, 1.5 to 4.0 g / 10 min.

[0078] The density of polypropylene, when determined according to ISO 1183, is typically between 890 and 940 kg / m 3 , ideally 0.895 to 0.920 g / cm 3 , preferably 0.900 to 0.915 g / cm 3 , more preferably 0.905 to 0.915 g / cm 3 , the range may be:

[0079] Propylene has an M range of 200 kg / mol to 600 kg / mol. w The polypropylene polymer may preferably have a molecular weight distribution M of less than 4.5, for example from 2.0 to 4.0, for example 3.0. w / M n where the molecular weight distribution M w / M n is the weight average molecular weight M w and number average molecular weight M n This is the ratio of

[0080] Typically, the melting temperature of the polypropylene is in the range of 135 to 170° C., preferably in the range of 140-168° C., more preferably in the range of 142-166° C., as determined by differential scanning calorimetry (DSC) according to ISO 11357-3. Ideally, the polypropylene has a melting temperature (Tm) of greater than 140° C., preferably greater than 150° C.

[0081] The polypropylene may be prepared by any suitable method known in the art or may be obtained commercially.

[0082] Although it is possible to use a combination of polypropylenes in the polymer composition of the present invention, it is preferred that a single polypropylene is used. When a combination of polypropylenes is used, the weight percentages quoted refer to the total content of polypropylene present.

[0083] The polypropylene in the polymer composition of the present invention is preferably present in an amount of from 4.95 to 95% by weight, based on the total weight of the polymer composition.

[0084] In one embodiment, the weight percentage of polypropylene in the polymer composition of the present invention is advantageously 5.0 wt.% or more, or 7.5 wt.% or more, or 10.0 wt.% or more, or 12.5 wt.% or more, or 15.0 wt.% or more, or 17.5 wt.% or more, or 20.0 wt.% or more, relative to the total weight of the polymer composition.

[0085] The upper limit for the weight percent of polypropylene in the polymer composition relative to the total weight of the polymer composition is 95.0 wt% or less, or 90.0 wt% or less, or 80.0 wt% or less, or 70.0 wt% or less, or 60.0 wt% or less, or 50.0 wt% or less, or 45.0 wt% or less, or 40.0 wt% or less.

[0086] In a preferred embodiment of the polymer composition according to the invention, the weight percentage of polypropylene in the polymer composition relative to the total weight of the polymer composition ranges from 5.0 to 85.0% by weight, or from 10.0 to 80.0% by weight, or from 15.0 to 70.0% by weight, preferably less than 60.0% by weight, for example from 15.0 to 50.0% by weight, or from 17.5 to 45.0% by weight, in particular from 20.0 to 40.0% by weight, relative to the total weight of the polymer composition as a whole.

[0087] The polypropylenes of the present invention are not new. These polymers are readily available from polymer suppliers. For example, Borealis grades of Borclean 商標 The HC300BF is suitable for use in the present invention.

[0088] Component (iii)—Styrene block copolymer

[0089] Component (iii) of the polymer composition according to the present invention is a styrene block copolymer.

[0090] Styrenic block copolymers are block copolymers that contain styrene monomer and one or more other comonomers. The term "block copolymer" is well known to those skilled in the art and refers to a copolymer that contains blocks of different polymerized monomers. Block copolymers contain multiple blocks, where each block is made of the same type of monomer (or mixture of monomers), but the type of one or more monomers differs between the blocks.

[0091] The one or more comonomers may be one or more monounsaturated (=one double bond), preferably an olefin, more preferably an alpha-olefin, even more preferably a C2-C10 alpha-olefin, such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-nonene; one or more polyunsaturated (=one or more double bonds), preferably consisting of a linear or branched carbon chain having at least 4 carbon atoms and at least one terminal double bond, more preferably a diene, such as butadiene or isoprene; or a combination thereof.

[0092] In one embodiment, the styrenic block copolymer is a terpolymer, ie, comprises three different monomers (styrene and two different comonomers).

[0093] It is particularly preferred that the styrenic block copolymer is selected from the group consisting of styrene-ethylene / butylene-styrene (SEBS) block copolymer, styrene-ethylene / propylene-styrene (SEPS) block copolymer, styrene-butadiene-styrene (SBS) block copolymer, and styrene-isoprene-styrene (SIS) block copolymer, or a combination thereof. Most preferably, the styrenic block copolymer is a styrene-ethylene / butylene-styrene (SEBS) block copolymer.

[0094] The styrene block copolymer may have a styrene content of 40% by weight or less, more preferably 35% by weight or less, and even more preferably 30% by weight or less. On the other hand, the styrene content in the styrene block copolymer should not be less than 10% by weight. Therefore, the preferred range is 10-40% by weight, more preferably 12-35% by weight, and even more preferably 15-30% by weight.

[0095] Further, the styrene block copolymer preferably has a melt flow rate MFR of at least 0.1 g / 10 min, more preferably at least 0.2 g / 10 min, and even more preferably at least 0.5 g / 10 min. 5 (230°C / 5.0kg). On the other hand, the melt flow rate MFR 5 (230°C / 5.0 kg) is preferably 30 g / 10 min or less. Therefore, the preferred melt flow rate MFR 5 (230° C. / 5.0 kg) is in the range of 0.1 to 30 g / 10 min, more preferably 0.2 to 25 g / 10 min, and further preferably 0.5 to 20 g / 10 min.

[0096] The styrenic block copolymer may also be defined by its density, which is preferably less than or equal to 0.950 g / cm 3 Less than or equal to 0.940 g / cm 3 Typically, the density of the styrene block copolymer is at least 0.900 g / cm 3, more preferably 0.910 g / cm 3 The following is the summary.

[0097] The styrenic block copolymers may be prepared by any suitable method known in the art or may be obtained commercially.

[0098] Although it is possible to use a mixture of styrene block copolymers in the polymer composition of the present invention, it is preferred that a single styrene block copolymer is used. When a mixture of styrene block copolymers is used, the weight percentages quoted refer to the total content of styrene block copolymer present. In a preferred embodiment of the present invention, the styrene block copolymer is present and is used primarily as a compatibilizer to aid in the mixing of the LDPE and polypropylene components. The styrene block copolymer reduces phase separation and results in a blend with advantageous thermomechanical properties. Furthermore, the inclusion of the styrene block copolymer can provide a reduced DC conductivity. The reduced DC conductivity can allow for higher operating temperatures of the power cable, which in principle allows for a higher power transmission capacity.

[0099] In one embodiment of the invention, the polymer composition does not comprise a styrenic block copolymer (iii) as defined above.

[0100] In a preferred embodiment of the invention, a styrene block copolymer (iii) is present in the polymer composition. The inventors have found that, although not essential, the styrene block copolymer can act as a compatibilizer to aid in the mixing of the LDPE and polypropylene components. The styrene block copolymer reduces phase separation and results in a blend with advantageous thermomechanical properties. Moreover, by including the styrene block copolymer, reduced DC conductivity can also be imparted. Reduced DC conductivity can allow for higher operating temperatures of the power cable, which in principle allows for higher power transmission capacity.

[0101] The styrene block copolymer (iii) in the polymer composition of the present invention is preferably present in an amount of 0.0 to 30.0% by weight, based on the total weight of the polymer composition.

[0102] In one embodiment, the weight percentage of the styrene block copolymer (iii) in the polymer composition of the present invention is advantageously 0.5 wt.% or more, or 1.0 wt.% or more, or 1.5 wt.% or more, or 2.0 wt.% or more, or 2.5 wt.% or more, or 3.0 wt.% or more, or 3.5 wt.% or more, or 4.0 wt.% or more, relative to the total weight of the polymer composition.

[0103] The upper limit for the weight percentage of the styrenic block copolymer (iii) in the polymer composition relative to the total weight of the polymer composition is 30.0 wt% or less, or 25.0 wt% or less, 23.0 wt% or less, 22.0 wt% or less, 21.5 wt% or less, 21.0 wt% or less, 20.5 wt% or less, or 20.0 wt% or less.

[0104] In a preferred embodiment of the polymer composition according to the invention, the weight percentage of the styrene block copolymer (iii) in the polymer composition, relative to the total weight of the polymer composition, is in the range of 0.5-30.0% by weight, or 1.0-25.0% by weight, or 2.0-23% by weight, preferably not more than 22.5% by weight, for example 3.0-22.0% by weight, or 3.5-21.0% by weight, in particular 4.0-20.0% by weight, relative to the total weight of the polymer composition as a whole.

[0105] When a mixture of styrenic block copolymers is used, these percentages refer to the total amount of all styrenic block copolymers.

[0106] These polymers are readily available from polymer supply companies, e.g., Kraton TM available from Kraton Corporation. 商標 G1642 HU is suitable for use in the present invention.

[0107] Component (iv) - Nanoparticle Filler

[0108] Component (iv) of the polymer composition according to the present invention is an aliphatically functionalized inorganic nanoparticle filler, preferably an alkyl-functionalized inorganic nanoparticle filler.As used herein, the term "aliphatically functionalized inorganic nanoparticle filler" refers to an inorganic nanoparticle filler in which the nanoparticle is modified to incorporate one or more aliphatic functional groups on the surface of the nanoparticle.Such modifications are well known in the art and are discussed, for example, in International Publication No. WO2006 / 081400.In a preferred embodiment, the aliphatic functional group is an alkyl group, and thus the nanoparticle filler is an alkyl-functionalized inorganic nanoparticle filler.

[0109] The nanoparticles are less than 1000 nm, preferably less than 500 nm, in particular less than 250 nm. The nanoparticles preferably have a diameter of 10 nm or more, for example 25 nm or more. The nanoparticles preferably have a diameter of 10 to 100 nm, for example 25 to 75 nm. A diameter of 40 to 60 nm is most preferred. These diameters can be determined using TEM analysis.

[0110] Component (iv) forms 0.05 to 10% by weight of the total polymer composition.

[0111] In one embodiment, the weight percentage of component (iv) in the polymer composition of the present invention is advantageously 0.1 wt% or more, or 0.25 wt% or more, or 0.5 wt% or more, or 0.6 wt% or more, or 0.7 wt% or more, or 0.8 wt% or more, or 0.9 wt% or more, or 1.0 wt% or more, based on the total weight of the polymer composition.

[0112] The upper limit for the weight percentage of component (iv) in the polymer composition, relative to the total weight of the polymer composition, is 10.0 wt% or less, or 9.5 wt% or less, or 9.0 wt% or less, or 8.5 wt% or less, or 8.0 wt% or less, or 7.5 wt% or less, or 7.0 wt% or less, or 6.5 wt% or less, or 6.0 wt% or less, or 5.5 wt% or less, or 5.0 wt% or less.

[0113] In a preferred embodiment of the polymer composition according to the invention, the weight percentage of component (iv) in the polymer composition, relative to the total weight of the polymer composition, ranges from 0.05 to 9.5 wt%, or from 0.5 to 9.0 wt%, or from 0.75 to 8.5 wt%, preferably less than 8.0 wt%, for example from 0.8 to 7.5 wt%, or from 0.9 to 6.5 wt%, in particular from 1.0 to 5.0 wt%, preferably relative to the total weight of the polymer composition as a whole.

[0114] In one embodiment, component (iv), the nanoparticle filler, comprises nanoparticles selected from inorganic oxides, hydroxides, carbonates, fullerenes, nitrides, carbides, kaolin clays, talc, borates, alumina, titania or titanates, silica, silicates, zirconia, zinc oxide, glass fibers or particles, or any combination thereof. In one embodiment, the nanoparticle filler comprises inorganic oxide nanoparticles, such as aluminum oxide nanoparticles, magnesium oxide nanoparticles, zinc oxide nanoparticles, silica nanoparticles, titanium oxide nanoparticles, iron oxide nanoparticles, barium oxide nanoparticles, calcium oxide nanoparticles, strontium oxide nanoparticles, or combinations thereof.

[0115] In one embodiment, the nanoparticle filler, component (iv), is selected from the group consisting of MgO nanoparticles, SiO 2 Nanoparticles, TiO 2 Nanoparticles, ZnO nanoparticles, Al 2 O 3 Nanoparticles, Fe 3 O 4The nanoparticle filler comprises nanoparticles of Al, barium oxide, calcium oxide, strontium oxide, or a combination thereof. Preferably, the nanoparticle filler comprises aluminum oxide, magnesium oxide, zinc oxide, or a combination thereof. Most preferably, the nanoparticle filler comprises aluminum oxide nanoparticles. In a preferred embodiment, the nanoparticle filler comprises Al 2 O 3 Nanoparticles, MgO nanoparticles, ZnO nanoparticles or combinations thereof, most preferably Al 2 O 3 It consists of nanoparticles.

[0116] The nanoparticle filler, component (iv) according to the present invention, is functionalized with one or more aliphatic groups, such as alkyl groups, alkenyl groups, cycloalkyl groups, alkylcycloalkyl groups. In a preferred embodiment, the one or more aliphatic groups are one or more alkyl groups, and thus the nanoparticle filler is an alkyl-functionalized inorganic nanoparticle filler. The one or more alkyl groups are preferably C1-20 alkyl groups, such as C4-20 alkyl groups, preferably C6-C20 alkyl groups. In a preferred embodiment, the alkyl groups are C6-C12 alkyl groups, such as C8 alkyl groups.

[0117] The one or more aliphatic groups may be linear or branched, preferably linear. In a preferred embodiment, the one or more aliphatic groups are linear alkyl groups, such as linear C1-20 alkyl groups, particularly linear C4-20 alkyl groups. In a preferred embodiment, the alkyl group is linear C6-12 alkyl group, such as n-octyl.

[0118] The nanoparticles forming the nanoparticle filler can be functionalized by any known method. In one embodiment, the nanoparticle filler is functionalized by reaction with an aliphatically functionalized silane, such as an alkylsilane. The aliphatic group on such silane is an aliphatic group as described above for functionalized nanoparticles. In a preferred embodiment, the nanoparticle filler is functionalized by reaction with an alkyl(trialkoxy)silane, a dialkyl(dialkoxy)silane or a trialkyl(alkoxy)silane, preferably an alkyl(trialkoxy)silane.

[0119] The alkyl portion of the alkoxy group of the silane may be the same as or different from the alkyl group of the silane. In a preferred embodiment, the alkoxy group is 1~10 Alkoxy groups, especially linear C 1~10 Alkoxy groups, such as methoxy or ethoxy. For example, in one embodiment, the nanoparticle fillers are functionalized by reaction with n-octyl(triethoxy)silane, n-octyl(trimethoxy)silane, di(n-octyl)(diethoxy)silane, or di(n-octyl)(dimethoxy)silane.

[0120] The nanoparticle fillers are typically in the form of a solid powder, but can be carried in a medium, such as mineral spirits, e.g., heptane, such that a mixture of the filler and carrier forms a colloidal dispersion.

[0121] In one embodiment, the aliphatically functionalized inorganic nanoparticle fillers have a diameter of less than 1000 nm, preferably less than 500 nm, in particular less than 250 nm. The aliphatically functionalized inorganic nanoparticle fillers preferably have a diameter of 10 nm or more, for example 25 nm or more. The aliphatically functionalized inorganic nanoparticle fillers preferably have a diameter of 10-100 nm, for example 25-75 nm. A diameter of 40-60 nm is most preferred.

[0122] The reaction of the nanoparticles of the nanoparticle filler with the aliphatic functionalized silane can be carried out in a solution. Suitable solvents are known to those skilled in the art and include polar and non-polar solvents. In one embodiment, the reaction can be carried out in a solution, such as the above solutions, including water, propanol, or combinations thereof. In some embodiments, a catalyst, such as ammonium hydroxide, can be used to promote the hydrolysis and condensation of the silane.

[0123] Optional Further Ingredients

[0124] However, additionally, the polymer composition of the present invention may include, in addition to components (i) to (iv), one or more further components known in the polymer art, such as one or more polymer components and / or one or more additives, such as one or more additives, such as one or more antioxidants, one or more scorch retarders (SR), one or more crosslinking boosters, one or more dielectric fluids, one or more stabilizers, one or more processing aids, one or more flame retardant additives, one or more water tree retardant additives, one or more acid or ion scavengers and one or more voltage stabilizers. The polymer composition may, for example, contain one or more additives conventionally used for wire and cable (W&C) applications, such as at least one antioxidant, and optionally one or more scorch retarders or one or more crosslinking boosters, such as at least one antioxidant. Suitable additives and amounts of addition are conventionally known in the art.

[0125] Typically, the amount of further components as defined above, if present, is from 0.1% to 20% by weight, more preferably from 0.1% to 15% by weight, most preferably from 0.1% to 10% by weight, relative to the total weight of the polymer composition.

[0126] Polymer Composition

[0127] Although it is within the scope of the present invention for the polymer composition to include other polymer components in addition to the LDPE, polypropylene and styrene block copolymer, it is preferred when the polymer composition consists essentially of the LDPE, polypropylene and styrene block copolymer as the only polymer components.

[0128] It will be appreciated that the polymer composition further comprises a nanoparticle filler (iv), and may further comprise further components, such as standard polymer additives, as discussed in more detail above.

[0129] The term "consisting essentially of" means excluding any other polymeric components, but allows for the presence of further components, such as additives, which may be part of a masterbatch.

[0130] Generally, it is understood that the total weight percentages of components (i), (ii), (iii) and (iv) add up to 100% by weight. However, this does not exclude the presence of further components, as described above. If further components are present, the total weight percentages of the further components and components (i), (ii), (iii) and (iv) add up to 100% by weight.

[0131] It is further understood that all definitions and preferences as set forth above apply equally to all further embodiments described below.

[0132] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 4.5 to 95.0% by weight of low-density polyethylene (LDPE); (ii) 4.5 to 95.0% by weight of polypropylene; and (iv) 0.5 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler; Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0133] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 4.0 to 95.0% by weight of low-density polyethylene (LDPE); (ii) 4.0 to 95.0% by weight of polypropylene; and (iii) 0.5 to 30.0 weight percent of a styrene block copolymer; (iv) 0.5 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0134] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 35 to 75.0 wt.% low-density polyethylene (LDPE); (ii) 20.0 to 40.0% by weight of polypropylene; and (iv) 1.0 to 8.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0135] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 35 to 75.0 wt.% low-density polyethylene (LDPE); (ii) 20.0 to 40.0% by weight of polypropylene; and (iii) 4.0 to 25.0 wt. % of a styrene block copolymer; and (iv) 1.0 to 8.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0136] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 35 to 75.0% by weight of LDPE homopolymer; (ii) 20.0 to 40.0% by weight of a polypropylene homopolymer; and (iii) 0.0 to 25.0% by weight of a styrene block copolymer; and (iv) 1.0 to 8.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler; Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0137] In a preferred embodiment, the present invention relates to a polymer composition comprising: (i) 35 to 75.0% by weight of LDPE homopolymer; (ii) 20.0 to 40.0% by weight of a polypropylene homopolymer; and (iii) 0.0 to 20.0% by weight of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), poly[styrene-b-(ethylene-co-propylene)-b-styrene] (SEPS), poly[styrene-b-(butadiene)-b-styrene] (SBS), and poly[styrene-b-(isoprene)-b-styrene] (SIS), preferably SEBS; and (iv) 1.0 to 8.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Including, wherein the weight percentage (wt%) is expressed relative to the total weight of the polymer composition. The above polymer composition is provided.

[0138] In one embodiment, the present invention provides a polymer composition comprising a sum of at least 30 wt.%, preferably at least 40 wt.%, more preferably at least 50 wt.%, and even more preferably at least 60 wt.%, of components (i), (ii) and (iii), wherein said weight percentages (wt.%) are expressed relative to the total weight of the polymer composition.

[0139] In any of the above embodiments, the use of peroxides can be significantly reduced or avoided entirely.

[0140] Thus, the polymer composition of the present invention is preferably substantially free of peroxides (e.g., contains less than 0.5% by weight of peroxide, preferably less than 0.1% by weight of peroxide, e.g. less than 0.05% by weight of peroxide, based on the total weight of the composition).Even more preferably, the polymer composition does not contain any peroxides (i.e., contains 0% by weight of peroxide, based on the total weight of the composition), and most preferably does not contain any radical formers.

[0141] In one embodiment, the composition is thermoplastic. Thus, the compositions of the present invention are preferably not crosslinked.

[0142] The polymer composition of the present invention preferably has a DC conductivity of 0.5 to 10 fS / m, preferably 0.5 to 6.0 fS / m, more preferably 0.5 to 4 fS / m, and even more preferably 0.5 to 3.5 fS / m, when measured after 18 hours at 30 kV / mm and a temperature of 70°C.

[0143] Direct current conductivity is measured according to the "DC Conductivity Measurement" described under "Determination Methods".

[0144] In a preferred embodiment, the polymer composition has a viscosity of at least 5.0x10 at 120°C, as determined according to the method described under "Experimental Section".6 Pa, more preferably at least 1.0x10 at 120°C 7 The elastic modulus (E') is 0.01 Pa.

[0145] In a preferred embodiment, the polymer composition has a viscosity of at least 1.0x10 at 140°C, as determined according to the method described under "Experimental Section". 6 Pa, more preferably at least 5.0x10 at 140°C 6 It has a storage modulus (E') of 1.0 Pa.

[0146] method

[0147] In one aspect, the present invention provides a method for the preparation of a polymer composition as defined herein. It is further understood that all definitions and preferences set forth above apply equally to all further embodiments described below.

[0148] The method comprises: (i) 4.95 to 95.0 wt.% low-density polyethylene (LDPE); (ii) 4.95 to 95.0% by weight of polypropylene; and (iii) 0.00 to 25.0 weight percent of a styrene block copolymer; (iv) 0.05 to 10.0 wt. % of an aliphatic, preferably alkyl, functionalized inorganic nanoparticle filler. Blending the Here, the weight percentage (wt %) is expressed relative to the total weight of the polymer composition.

[0149] During preparation of the polymer composition, the components may be blended, for example melt mixed in an extruder.

[0150] Typically, the process will be carried out by compounding, for example by extrusion compounding. Preferably, the process does not involve the use of peroxides. As a result, the process for preparing the polymer composition of the present invention typically does not include a degassing step.

[0151] Typically this involves heating to a temperature of at least 150° C., preferably at least 160° C., for example at least 170° C. The process generally involves heating to a temperature of up to 300° C., for example up to 250° C.

[0152] In one embodiment, the method further comprises the step of crosslinking the polymer composition.Crosslinking can be carried out by any conventional means known in the art, such as peroxide crosslinking, more particularly organic peroxide crosslinking, such as dicumyl peroxide crosslinking.Preferably, the polymer composition is not crosslinked.

[0153] cable

[0154] In one aspect, the present invention provides a cable, typically a power cable, such as an AC cable or a DC cable, comprising the polymer composition defined herein. It is further understood that all definitions and preferences as set out above apply equally to all further embodiments described below.

[0155] A power cable is defined as a cable that transmits energy operating at any voltage level, typically above 1 kV. Power cables can be low voltage (LV), medium voltage (MV), high voltage (HV) or extra high voltage (EHV) cables, the terms indicating the level of operating voltage, as is well known.

[0156] The polymer composition is even more preferably used in an insulating layer for DC power cables operating at voltages higher than 36 kV, such as HVDC cables, where the operating voltage is defined herein as the voltage between the ground and the conductor of the high voltage cable.

[0157] Preferably, the HVDC power cable of the invention operates at a voltage of 40 kV or more, even 50 kV or more. More preferably, the HVDC power cable operates at a voltage of 60 kV or more. The invention is also feasible in very demanding cable applications, a further cable of the invention is an HVDC power cable operating at a voltage of 70 kV or more. Voltages of 100 kV or more are targeted, for example 200 kV or more, more preferably 300 kV or more, particularly preferably 400 kV or more, more particularly preferably 500 kV or more. Voltages of 640 kV or more, for example 700 kV, are also envisaged. The upper limit is not particularly limited. A practical upper limit can be up to 1500 kV, for example up to 1100 kV. Thus, the cable of the invention works well in demanding extra HVDC power cable applications operating at 400-850 kV, for example 650-850 kV.

[0158] A cable, such as a power cable (e.g., a DC power cable), comprises one or more conductors surrounded by at least one layer. The polymer composition of the present invention may be used in at least one of the layers. Preferably, the cable comprises, in this order, an inner semiconductive layer, an insulating layer and an outer semiconductive layer.

[0159] The polymer composition of the present invention is preferably used in the insulation layer of the cable. Ideally, at least one layer, preferably the insulation layer, as a whole comprises at least 95% by weight, such as at least 98% by weight, such as at least 99% by weight, of the polymer composition of the present invention, based on the total weight of the layer. Ideally, the layer consists of the polymer composition. It is therefore preferred that the polymer composition of the present invention is the only non-additive component used in the insulation layer of the cable of the present invention. The term "consisting essentially of" is used herein to mean that the only polymer composition present is as defined herein. It will be understood that the insulation layer may include standard polymer additives, such as water tree retarders, antioxidants, etc. These are not excluded by the term "consisting essentially of". It is also noted that these additives may also be added as part of a masterbatch and thus carried on a polymer carrier. The use of masterbatch additives is not excluded by the term "consisting essentially of". Such layers are preferably peroxide-free.

[0160] The cable layer of the present invention preferably has a DC conductivity of 0.5 to 10 fS / m, preferably 0.5 to 6.0 fS / m, more preferably 0.5 to 4 fS / m, even more preferably 0.5 to 3.5 fS / m, when measured at 30 kV / mm and a temperature of 70°C after 18 hours.

[0161] It is preferred that the insulating layer be free of cross-linking agents, and therefore ideally free of peroxides and therefore free of by-products of peroxide decomposition.

[0162] Of course, the non-crosslinked embodiment also simplifies the cable manufacturing process, and typically crosslinked cables need to be degassed after crosslinking to remove the by-products of these chemicals, whereas in their absence, no such degassing step is required.

[0163] In addition to the polymer composition of the present invention, the insulating layer may contain one or more further components, such as additives, as known in the polymer art, such as one or more antioxidants, one or more scorch retarders (SR), one or more crosslinking boosters, one or more stabilizers, one or more processing aids, one or more flame retardant additives, one or more water resin retardant additives, one or more acids or ion scavengers, one or more inorganic fillers, one or more dielectric liquids and voltage stabilizers. Typically, however, no scorch retarders are present.

[0164] The insulating layer may therefore include one or more additives conventionally used in W&C applications, such as one or more antioxidants. Non-limiting examples of antioxidants can include, for example, sterically hindered or semi-hindered phenols, aromatic amines, aliphatic sterically hindered amines, organic phosphites or phosphonites, thio compounds, and combinations thereof.

[0165] Preferably, the insulating layer does not include carbon black. Also preferably, the insulating layer does not include one or more flame retardant additives, such as a metal hydroxide containing a flame retarding amount of the additive.

[0166] The amount of additive used is conventional and well known to those skilled in the art, and is, for example, 0.1 to 1.0% by weight.

[0167] The cable of the present invention typically also comprises an inner semiconductive layer and an outer semiconductive layer, which may be made of any conventional material suitable for use in these layers. The inner and outer semiconductive layers may be different or the same and may comprise one or more polymers, preferably polyolefins or mixtures of polyolefins with conductive fillers, preferably carbon black. Suitable one or more polyolefins are, for example, polyethylenes produced in a low pressure process (LLDPE, MDPE, HDPE), polyethylenes produced in a HP process (LDPE) or polypropylene.

[0168] In one embodiment, the polymer composition of the present invention may be used in the manufacture of an inner semiconductive layer and / or an outer semiconductive layer.

[0169] The inner and outer semiconductive layers may comprise carbon black. The carbon black can be any conventional carbon black used in semiconductive layers of power cables, preferably in semiconductive layers of power cables. Preferably, the carbon black has one or more of the following properties: a) a primary particle size of at least 5 nm, defined as the number average particle size according to ASTM D3849-95a, Dispersion Procedure D, b) an iodine number of at least 30 mg / g according to ASTM D1510, c) an oil absorption of at least 30 ml / 100 g, measured according to ASTM D2414. Non-limiting examples of carbon black are e.g. acetylene carbon black, furnace carbon black and Ketjen carbon black, preferably furnace carbon black and acetylene carbon black. Preferably, the one or more semiconductive layers comprise 10-50 wt. % carbon black, based on the total weight of the layer.

[0170] In one embodiment, the outer semiconductive layer is crosslinked. In another embodiment, the inner semiconductive layer is preferably non-crosslinked. Overall, it is preferred that the inner semiconductive layer, the outer semiconductive layer and the insulating layer remain non-crosslinked. However, it is possible that the inner semiconductive layer and the insulating layer remain non-crosslinked when the outer semiconductive layer is crosslinked. Therefore, the peroxide crosslinking agent can be provided only on the outer semiconductive layer.

[0171] The conductor typically comprises one or more wires. Moreover, the cable comprises one or more such conductors. Preferably, the conductor is an electrical conductor and comprises one or more metal wires. Cu wires or Al wires are preferred.

[0172] As is well known, the cable may optionally include additional layers, such as one or more screens, one or more jacket layers, one or more other protective layers, or any combination thereof.

[0173] Cable Manufacturing

[0174] The invention also provides a method for manufacturing a cable, the method comprising the steps of applying, preferably by (co)extrusion, on one or more conductors, in that order, an inner semiconductive layer, an insulating layer and an outer semiconductive layer, wherein the insulating layer comprises the composition of the invention. It is further understood that all definitions and preferences as set out above apply equally to all further embodiments described below.

[0175] The method may optionally include crosslinking either the inner or outer semiconductive layer or both without crosslinking the insulating layer. Overall, it is preferred that the inner and outer semiconductive layers, and the insulating layer, remain uncrosslinked.

[0176] More preferably, a cable is manufactured, the method comprising the steps of: (a) providing and mixing, preferably melt mixing in an extruder, an optionally crosslinkable first semiconductive composition comprising a polymer, carbon black and, optionally, one or more additional components for the inner semiconductive layer; providing and mixing, preferably melt mixing in an extruder, a polymer composition of the present invention; and Providing and mixing, preferably melt mixing in an extruder, a second semiconductive composition, which is optionally crosslinkable and includes a polymer, carbon black, and optionally one or more additional ingredients for the outer semiconductive layer. (b) applying, preferably by coextrusion, onto one or more conductors; melt mixing the first semiconductive composition resulting from step (a) to form the inner semiconductive layer; melt mixing the polymer composition of the present invention obtained from step (a) to form the insulating layer; and melt mixing the second semiconductive composition resulting from step (a) to form the outer semiconductive layer; and (c) optionally crosslinking one or both of the first semiconductive composition of the inner semiconductive layer and the second semiconductive composition of the outer semiconductive layer, and / or the insulating layer of the resulting cable under crosslinking conditions.

[0177] Alternatively, in step (c), both the first semiconductive composition of the inner semiconductive layer and the second semiconductive composition of the outer semiconductive layer, as well as the insulating layer, of the resulting cable are crosslinked.

[0178] Melt blending refers to blending above the melting point of at least the major polymer component(s) of the resulting blend, for example, but not limited to, at least 15° C. above the melting or softening point of the polymer component(s).

[0179] The term "(co)extrusion" as used herein means that in the case of two or more layers, the layers can be extruded in separate steps, or at least two or all of the layers can be coextruded in the same extrusion step, as is known in the art. The term "(co)extrusion" as used herein also means that all or a portion of one or more layers are formed simultaneously using one or more extrusion heads. For example, triple extrusion can be used to form three layers. When a layer is formed using two or more extrusion heads, for example, the layer can be extruded using two extrusion heads, where the first head is for forming the inner semiconductive layer and the inner portion of the insulating layer, and the second head is for forming the outer insulating layer and the outer semiconductive layer.

[0180] As is well known, the polymer composition of the present invention and the optional and preferred first and second semiconductive compositions can be prepared prior to or during the cable manufacturing process.

[0181] Preferably, the polymers required to manufacture the cables of the present invention are fed to the cable manufacturing process in the form of powders, grains or pellets, where pellets generally means any polymer product formed by post-reactor modification of the reactor-produced polymer (obtained directly from the reactor) into solid polymer particles.

[0182] Thus, the components can be premixed, e.g., melt mixed together and pelletized, prior to mixing, or alternatively, preferably, the components can be made into separate pellets and fed to the (melt) mixing step (a) where the pellets are blended together.

[0183] The (melt) mixing step (a) of the provided polymer composition of the present invention with the preferred first and second semiconductive compositions is preferably carried out in a cable extruder. Step a) of the cable manufacturing process may optionally include a separate mixing step, for example a mixing step in a mixer arranged to connect to and precede the cable extruder of the cable manufacturing line. The preceding mixing in a separate mixer can be carried out by mixing with or without external heating (heating by an external source) of the components.

[0184] The optional crosslinking agent can be added before the cable manufacturing process or during the (melt) mixing step (a). For example, preferably the crosslinking agent and also any further components, such as additives, can already be present in the polymer used. The crosslinking agent is added, preferably impregnated, onto the solid polymer particles, preferably onto the pellets.

[0185] The molten mixture of the polymer composition resulting from the (melt) mixing step (a) preferably consists of the LDPE (i), the polypropylene (ii) and, optionally, the styrene block copolymer (iii) as the sole polymer components. Component (iv) and, optionally, one or more preferred additives can be added to the polymer composition as such or in a mixture with a carrier polymer, i.e. in the form of a masterbatch.

[0186] Crosslinking of the other layers can be carried out at elevated temperatures selected depending on the type of crosslinking agent, as is well known, for example, above 150°C, e.g., 160-350°C, is typical, but not limited to these.

[0187] Processing temperatures and equipment are well known in the art, for example, conventional mixers and extruders, such as single or twin screw extruders, are suitable for processing according to the invention.

[0188] The thickness of the insulation layer of a cable, more preferably a power cable, when measured from a cross section of the insulation layer of the cable, is typically 2 mm or more, preferably at least 3 mm or more, preferably at least 5 to 100 mm, more preferably 5 to 50 mm, and conveniently 5 to 40 mm, for example 5 to 35 mm.

[0189] The thickness of the inner and outer semiconductive layers is typically less than the thickness of the insulating layer, and in a power cable, the inner and outer semiconductive layers may be greater than 0.1 mm, for example 0.3-20 mm, for example 0.3-10 mm. The thickness of the inner semiconductive layer is preferably 0.3-5.0 mm, preferably 0.5-3.0 mm, preferably 0.8-2.0 mm. The thickness of the outer semiconductive layer is preferably 0.3-10 mm, for example 0.3-5 mm, preferably 0.5-3.0 mm, preferably 0.8-3.0 mm. It will be clear to the skilled person and within the skill of the skilled person that the thickness of the layers of a power cable depends on the intended voltage level of the end-use cable and can be selected accordingly.

[0190] The invention will now be described with reference to the following non-limiting Examples and the accompanying drawings. [Brief description of the drawings]

[0191] [Figure 1] Figure 1 shows the electrical conductivity as a function of temperature for the samples disclosed in Table 1. The examples of the invention comprising LDPE (i), polypropylene (ii), and optionally a styrene block copolymer (iii) and nanoparticle filler (iv) have significantly lower electrical conductivity than the comparative examples consisting of LDPE (i) alone, or LDPE + nanoparticle filler alone. [Diagram 2] FIG. 2 shows the storage modulus (E') of the samples disclosed in Table 1 as a function of temperature.

[0192] Experimental section

[0193] Unless otherwise stated in the detailed description and experimental section, the following methods were used for the physical property determinations: (wt%=weight%)

[0194] density The density of the polymer samples was measured according to ISO 1183-2.

[0195] Molecular weight (Mw) Molecular weight (weight average molecular weight M w The molecular weight and polydispersity index, as well as the branching ratio, were determined by size exclusion chromatography (SEC) at 150 °C in 1,3,4-trichlorobenzene using an Agilent PL-GPC 220 system; universal calibration with polystyrene standards.

[0196] Melt Flow Rate (MFR) Melt flow rate (MFR) is determined according to ISO 1133 and is given in units of g / 10 min. MFR is an indication of the fluidity of a polymer and therefore its processability. The higher the melt flow rate, the lower the viscosity of the polymer. Unless otherwise specified, as used herein, the term "MFR" refers to the MFR 2 Polypropylene MFR 2 is determined at a temperature of 230°C and a load of 2.16 kg.

[0197] Polyethylene MFR 2 is determined at a temperature of 190°C and a load of 2.16 kg.

[0198] DC conductivity measurement Prior to the measurements, 0.3 mm thick film samples were dried in a vacuum oven at 70°C for 24 hours and stored in a desiccator between drying and SC measurements. The DC test cell consisted of a three-electrode setup (measurement area of ​​φ=60 mm), placed in an oven at 70°C, and connected to a high voltage power supply (Glassman FJ60R2). To ensure that the desired temperature of 70°C was achieved, the samples were placed in the measurement cell for 1 hour before the measurements.

[0199] A DC voltage of 9 kV (30 kV / mm) was applied to the specimen film with a thickness of 0.3 mm for 19 hours. The DC conductivity (σ DC ) was calculated based on the leakage current obtained after 18 h. Volume leakage currents were recorded with a Keithley 6517B electrometer and dynamically averaged. In addition, a low-pass filter was added to the high-voltage side circuit to limit the current during specimen destruction and to eliminate high-frequency noise.

[0200] Storage modulus (E') Dynamic mechanical analysis (DMA) was performed in tensile mode using a TA Q800 DMA on 35 mm × 6 mm pieces cut from 1.9 mm thick melt-pressed films. Variable temperature measurements were performed with a heating rate of 3°C / min, a maximum strain of 0.05% and a frequency of 0.5 Hz. The results are shown in Figure 2.

[0201] material The materials used in this work are as follows: Component (i): LDPE homopolymer having a MFR of about 2 g / 10 min (190° C. / 2.16 kg) is available from Borealis AB (M w The copolymer had a PDI of about 9 and a long chain branching index of about 1.9. Component (ii): iPP-isotactic polypropylene having a MFR of about 3.3 g / 10 min (230° C. / 2.16 kg) was obtained from Borealis AB (M wApproximately 411 kg / mol, PDI approximately 8.5). Component (iii): Poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) having an MFI of less than about 1 g / 10 min. (230° C. / 2.16 kg, measured according to ASTM D 1238) and a polystyrene content of 18.5-22.5% was obtained from Kraton Corporation (Kraton G1642 HU). Component (iv),C 8 -Al 2 O 3 The adjustment method is described below.

[0202] Preparation of component (iv)

[0203] Aluminum oxide nanoparticles (Nanodur from Nanophase Inc, CAS number 1344-28-01, density 3.97 g / cm 3 ) were coated with n-octyltriethoxysilane (Sigma-Aldrich, CAS number 3069-42-9). The reaction was carried out in a mixed medium of 2-propanol and water. Ammonia hydroxide (aqueous 25%) was used as a catalyst to promote the hydrolysis and condensation of silane. After surface modification, the nanoparticles were dried in a vacuum oven (Fisher Scientific Vacucell, MMT Group) at 80 °C for 20 h. The spherical Al 2 O 3 The average diameter of the nanoparticles was 50 nm according to TEM image analysis.

[0204] Preparation of the Polymer Composition Component (iv) according to the invention and the octyl-coated aluminum oxide nanoparticles (C8-Al 2 O 3) was dispersed in n-heptane (0.3 ml n-heptane / 1 g polymer) and sonicated for 5 min, after which 0.02 wt% of the antioxidant Irganox 1076 (Ciba Speciality Chemicals, CAS number 2082-79-3) was added. Low density polyethylene (LDPE) was added to the nanoparticle suspension, resulting in a C8-Al suspension with a solids content of 3 wt%. 2 O 3 The result was nanoparticles and 97 wt% LDPE. LDPE:C8-Al 2 O 3 The slurry was shaken for 1 h in a Vortex Genie 2 shaker (Scientific Instruments Inc) and dried overnight at 80° C. After drying, the powder was shaken for an additional 30 min and then compounded (Micro 15 cc twin screw compounder, Xplore instruments) at 150° C. and 100 rpm for 6 min. The extrudate was chopped into pellets of 2-3 mm length.

[0205] Pelletized LDPE: C8-Al 2 O 3 The nanocomposite was dried in a vacuum oven at 80° C. for 17 hours. As shown in Table 1 below, the nanocomposite consisted of SEBS, iPP, and 3 wt.% C8-Al. 2 O 3 Contains LDPE: C8-Al 2 O 3 Polymer compositions according to the invention were prepared by compounding different combinations of nanocomposites under nitrogen gas using an Xplore Micro Compounder MC5 at 200° C. for 4 minutes with a screw speed of 70 rpm, followed by extrusion at a die temperature of 210° C. The extrudates were melt pressed into 0.3 mm thick films for electrical measurements and 1.9 mm thick films for mechanical analysis using a LabPro 200 Fontijne press by applying a pressure of 150 kPa at 200° C. for 1 minute, followed by cooling at a rate of −10° C. / min.

[0206] The comparative polymer composition is a mixture of neat LDPE, iPP, SEBS, and 3 wt. % C8-Al, as shown in Table 1 below. 2 O 3 Contains LDPE: C8-Al 2 O 3 The nanocomposite was compounded and prepared in the same manner as the inventive example.

[0207] result The compositions and properties of the samples of the polymer compositions according to the invention (IE1-3) and the comparative compositions (CE1-6) are shown in Table 1 below. The DC conductivity of each sample at each temperature is shown graphically in FIG.

[0208] [Table 1]

[0209] The inventors have demonstrated that the compositions of the present invention have superior (i.e., lower) DC conductivity. Referring to the data in Table 1 and Figure 1, it can be seen that the DC conductivity of the compositions IE1-3 of the present invention is unexpectedly at least an order of magnitude lower than that of the neat LDPE composition of CE1.

[0210] Surprisingly, the conductivity of the inventive examples is significantly reduced compared to the conductivity of the blends of LDPE, iPP and SEBS (CE2-4) or the blends of LDPE and nanoparticle fillers (CE5-6) alone. The reduction in DC conductivity may even be synergistic.

[0211] The conduction mechanism is LDPE / iPP or LDPE / iPP / SEBS blend and LDPE / Al 2 O 3 It is surprising that the conductivity of the polymer composition of the present invention is so low, considering the difference between the systems. Therefore, it is not expected that the conductivity of the combined polymer composition would be lower than that of the comparative example.

[0212] Moreover, this reduction in DC conductivity is obtained while at least maintaining the thermomechanical properties (e.g. in terms of storage modulus) of the polymer composition. This is despite the presence of nanoparticle fillers, which would be expected to reduce the thermomechanical performance. Without being bound by this theory, the inventors believe that the introduction of PP and SEBS into LDPE forms a system that is melt-miscible and phase-separated. This results in the formation of domains of PP and SEBS, which endow the system with much better thermomechanical properties. The introduction of the nanoparticles would be expected to upset this delicate balance, but surprisingly does not. Analysis of the blends suggests that the thermomechanical properties of the inventive examples are maintained, at least with respect to the comparative examples (see Figure 2).

[0213] The low electrical conductivity of the compositions according to the invention makes them particularly suitable for use in applications where low electrical conductivity is essential, such as the insulating layers of power cables.

Claims

1. A polymer composition, wherein the polymer composition comprises: (i) 4.95 to 95.0 wt% of low density polyethylene (LDPE) (hereinafter referred to as component (i)); (ii) 4.95 to 95.0 wt% of polypropylene (hereinafter referred to as component (ii)); and (iii) 0.00 to 30.0 wt% of a styrene block copolymer (hereinafter referred to as component (iii)); (iv) 0.05 to 10.0 wt% of an aliphatically functionalized inorganic nanoparticle filler (hereinafter referred to as component (iv)); wherein the weight percentages (wt%) are expressed relative to the total weight of the polymer composition, said polymer composition.

2. The polymer composition according to claim 1, wherein the nanoparticle filler component (iv) comprises inorganic oxide nanoparticles.

3. The polymer composition according to claim 1, wherein the nanoparticle filler component (iv) comprises aluminum oxide nanoparticles, magnesium oxide nanoparticles, zinc oxide nanoparticles, or a combination thereof.

4. The polymer composition according to claim 1, wherein the nanoparticle filler component (iv) comprises aluminum oxide nanoparticles.

5. The polymer composition according to claim 1, wherein the aliphatic group of component (iv) is alkyl.

6. The polymer composition according to claim 5, wherein the aliphatic group of component (iv) is a C1-20 alkyl group.

7. The polymer composition according to claim 6, wherein the alkyl group is a C4-20 alkyl group.

8. The polymer composition according to claim 7, wherein the alkyl group is a C6-12 alkyl group.

9. The polymer composition according to claim 8, wherein the alkyl group is an n-octyl group.

10. The polymer composition according to claim 1, wherein the nanoparticle filler component (iv) is functionalized by reaction with an alkylsilane.

11. The polymer composition according to claim 1, wherein the nanoparticle filler component (iv) is functionalized by reaction with an alkyl(trialkoxy)silane or a dialkyl(dialkoxy)silane.

12. The polymer composition according to claim 1, wherein the LDPE component (i) is a low density polyethylene homopolymer, and / or the polypropylene component (ii) is a propylene homopolymer, and / or the styrene block copolymer component (iii) is selected from the group consisting of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), poly[styrene-b-(ethylene-co-propylene)-b-styrene] (SEPS), poly[styrene-b-(butadiene)-b-styrene] (SBS), and poly[styrene-b-(isoprene)-b-styrene] (SIS) and combinations thereof.

13. The polymer composition according to claim 1, wherein the polypropylene component (ii) is an isotactic polypropylene homopolymer.

14. The polymer composition according to claim 1, wherein the styrene block copolymer component (iii) is SEBS.

15. The polymer composition according to claim 1, having a DC conductivity of 0.5 to 10 fS / m when measured after 18 hours at 30 kV / mm and a temperature of 70 °C according to the DC conductivity measurement method described in the description herein.

16. The polymer composition according to claim 1, which is not crosslinked.

17. The polymer composition according to claim 1, wherein the polymer composition comprises (i) 35 to 75.0 wt% of an LDPE homopolymer component (i); (ii) 20.0 to 40.0 wt% of a polypropylene homopolymer component (ii); and (iii) 0.0 to 25.0% by weight of a styrene block copolymer component (iii); and, (iv) 1.0 to 8.0% by weight of an aliphatically functionalized inorganic nanoparticle filler component (iv) comprising, wherein said weight percentages (% by weight) are expressed relative to the total weight of said polymer composition, said polymer composition.

18. A method for preparing a polymer composition according to any one of claims 1 to 17, said method comprising: (i) 4.95 to 95.0% by weight of low density polyethylene (LDPE) (hereinafter referred to as component (i)); (ii) 4.95 to 95.0% by weight of polypropylene (hereinafter referred to as component (ii)); and, (iii) 0.00 to 30.0% by weight of a styrene block copolymer (hereinafter referred to as component (iii)); (iv) 0.05 to 10.0% by weight of an aliphatically functionalized inorganic nanoparticle filler (hereinafter referred to as component (iv)) blending, wherein said weight percentages (% by weight) are expressed relative to the total weight of said polymer composition, said method.

19. A cable comprising a conductor surrounded by one or more layers, wherein one or more of said layers comprises a polymer composition according to any one of claims 1 to 17, said cable.

20. A power cable comprising a conductor surrounded in this order by at least an inner semiconductive layer, an insulating layer and an outer semiconductive layer, wherein at least one layer comprises a polymer composition according to any one of claims 1 to 17, said power cable.

21. The power cable according to claim 20, wherein said power cable is a high voltage (HV) power cable or an ultra high voltage (UHV) power cable.

22. Method of using the polymer composition according to claims 1 to 17 in the manufacture of a cable layer.

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