Polymer for power cable insulation

Abstract

The present invention relates to a multimode polyethylene composition having a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B), wherein The above low molecular weight component is (ai) a first fraction comprising an ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins; and (aii) A second fraction comprising a different ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins Including; The above multimode polymer composition has a density of 930 kg / m³ or more, for example, 938 to 955 kg / m³ (ISO1183), an MFR2 in the range of 0.05 to 10 g / 10 min (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less, for example, 300 to 800 MPa (ISO 178:2010).

Description

Technology Field

[0001] The present invention relates to a multimode polyethylene composition suitable for use in the insulation layer of a power cable, for example, a high voltage direct current (HV DC) power cable. The present invention also relates to a power cable comprising the multimode polyethylene composition defined herein in a layer such as the insulation layer. In a further embodiment, the present invention relates to a method for manufacturing a multimode polyethylene composition and a method for manufacturing a cable comprising said multimode polyethylene composition. Background Technology

[0002] Polyolefins produced by high-pressure (HP) processes are widely used in demanding polymer applications. The polymers must meet high mechanical and / or electrical requirements. For example, the electrical properties of the polymer composition are critical in power cable applications, particularly in medium voltage (MV), high voltage (HV), and extra-high voltage (EHV) cable applications. Furthermore, important electrical properties may vary depending on the cable application, such as between AC and DC cable applications.

[0003] A typical power cable comprises a conductor surrounded in sequence by an inner semiconducting layer, an insulating layer, and an outer semiconducting layer. Cables are generally produced by extruding layers on the conductor. LDPE is often used as the polymer in the insulating layer of these cables. The LDPE polymer is often crosslinked in the layer(s) of the cable to improve the polymer's thermal and deformation resistance, creep properties, mechanical strength, chemical resistance, and abrasion resistance. The crosslinking reaction creates crosslinks (bridges). Crosslinking can be achieved using free radical-generating compounds, such as peroxides. Free radical-generating agents are typically incorporated into the layer material before or during the extrusion of the layer(s) on the conductor. After the formation of the layered cable, the cable undergoes a crosslinking step to initiate radical formation and cause a crosslinking reaction.

[0004] Peroxides are very common free radical-generating compounds used in the polymer industry for polymer modification. The resulting peroxide decomposition products are undesirable because they can be volatile and have a negative impact on the properties of the cable. Therefore, volatile decomposition products, such as methane (for example, dicumyl peroxide), are typically reduced to a minimum or removed after the crosslinking and cooling steps. This removal step is generally known as the degassing step. Since the degassing step consumes time and energy, it is a costly operation in the cable manufacturing process.

[0005] Therefore, the inventors found an alternative to cross-linked LDPE in the insulation layer of a cable.

[0006] It is known that polymers suitable for use in the insulation layer of power cables must possess specific characteristics. They must have exceptionally low conductivity, such as low DC electrical conductivity. High DC conductivity in insulating materials can lead to thermal runaway under high stress / high temperature conditions, potentially resulting in the failure of the insulation system. Therefore, the DC conductivity must be sufficiently low to prevent thermal runaway. It would be advantageous if the polymer possessed improved thermal conductivity compared to LDPE. It is also beneficial if the polymer is flexible (e.g., having a low elastic modulus). A lower elastic modulus offers advantages, particularly in relation to Ziegler-Natta-derived polymers, which tend to have much higher elastic moduli. A lower elastic modulus implies a more flexible polymer, which is important in cable applications.

[0007] Therefore, it would be useful to manufacture a polymer for cable insulation layers that satisfies the voltage increase requirements of power cables, particularly direct current (DC) power cables. It would be useful to manufacture a polymer for cable insulation layers that satisfies the requirements for lowering DC conductivity. It would be useful to manufacture a polymer for cable insulation layers that has a low elastic modulus and improved thermal conductivity.

[0008] The inventors have discovered that a specific multimode intermediate / high-density polyethylene composition provides an ideal solution to this problem.

[0009] Low-pressure polyethylene (i.e., non-LDPE) has been proposed in the literature for use in power cables. WO2012 / 150286 describes a combination of ordinary unimodal HDPE and hydrotalcite as a means of minimizing conductivity in cable insulation.

[0010] WO2017 / 220609 describes a blend of LDPE and other polymers in cable insulation. The second component is UHMW PE or metallocene MDPE or LLDPE.

[0011] WO2016 / 097250 describes the use of single-site based polyethylene in cable insulation. This exemplifies a specific bimodal metallocene-catalyzed MDPE terpolymer having a density lower than that required by the present invention.

[0012] In EP3252085, Examples 1 and 2 of the present invention are ethylene copolymers comprising an ethylene butene copolymer produced in a loop reactor (A2) and an ethylene hexene copolymer produced in a gas phase reactor (A3). There is also a prepolymerization step. There is no disclosure that the LMW component (A) comprises two fractions (ai) and (aii).

[0013] EP 2182524 describes a power cable enclosed in one or more layers comprising a multimode ethylene copolymer. The multimode ethylene copolymer does not contain an LMW component having two fractions.

[0014] In one aspect, the present invention provides a multimode polyethylene composition having a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B);

[0015] The LMW component comprises two fractions (ai) and (aii);

[0016] The above polymer composition is 930 kg / m² 3 It has a density of the above (ISO1183), an MFR2 in the range of 0.05 to 10 g / 10 min (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less, for example, 300 to 800 MPa (ISO 178:2010).

[0017] In another aspect, the present invention provides a multimode polyethylene composition having a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B);

[0018] Low molecular weight ingredients include the following:

[0019] (ai) a first fraction comprising an ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins; and

[0020] (aii) A second fraction comprising a different ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins.

[0021] In another aspect, the present invention provides a multimode polyethylene composition produced by polymerizing ethylene in two or more slurry reactors and one or more gas-phase reactors connected in series, and said polyethylene composition

[0022] Comprising a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B) (wherein a single-site catalyst is used for the polymerization of one or more of the LMW or HMW components);

[0023] The LMW component comprises two fractions (ai) and (aii) produced in the first and second slurry loop reactors, respectively;

[0024] The polymer composition is 930 kg / m² 3 It has a density of the above (ISO1183), an MFR2 in the range of 0.05 to 10 g / 10 min (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less, for example, 300 to 800 MPa (ISO 178:2010).

[0025] In another aspect, the present invention provides a cable comprising a conductor surrounded by one or more layers comprising the multimode polyethylene composition defined above.

[0026] In another aspect, the present invention provides a cable comprising a conductor surrounded by an inner semiconducting layer, an insulating layer, and an outer semiconducting layer, wherein at least the insulating layer comprises a multimode polyethylene composition as defined herein.

[0027] In another aspect, the present invention provides a method for preparing a multimode polyethylene composition comprising a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B), said method

[0028] (I) a step of polymerizing ethylene and optionally one or more C3-10 alpha-olefin comonomers in the presence of a single-site catalyst in a first slurry reactor to produce a fraction (ai);

[0029] (II) polymerizing ethylene and optionally one or more C3-10 alpha-olefin comonomers in the presence of a single-site catalyst and fraction (ai) in a second slurry reactor to produce fraction (aii), which together with fraction (ai) forms the low molecular weight ethylene homopolymer or copolymer component (A); and

[0030] (III) A step of polymerizing ethylene and one or more C3-10 alpha-olefin comonomers in the presence of the LMW ethylene homopolymer or copolymer component (A) and the single-site catalyst to form the high molecular weight ethylene copolymer component (B).

[0031] Including;

[0032] At this time, the above multimode polyethylene composition is 930 kg / m² 3 It has a density of the above, an MFR2 in the range of 0.05 to 10 g / 10 min (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less.

[0033] When fractions (ai) and (aii) are produced in the first and second slurry reactors and component (B) is produced in the gas phase reactor, it is particularly desirable that all three reactors be connected in series.

[0034] Accordingly, in another aspect, the present invention provides a method for producing a multimode polyethylene composition by polymerizing ethylene in at least two slurry reactors and one or more gas-phase reactors connected in series, said multimode polyethylene composition

[0035] It comprises a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B), wherein a single-site catalyst is used for the polymerization of one or more of the LMW or HMW components, and

[0036] The above composition is 930 kg / m² 3Having a density greater than or equal to, an MFR2 in the range of 0.05 to 10 g / 10 min (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less;

[0037] Fraction (A) comprises two fractions (ai) and (aii), wherein fraction (ai) is produced in a first slurry loop reactor and fraction (aii) is produced in a second slurry loop reactor.

[0038] In another aspect, the present invention provides a use of the polymer defined herein in the manufacture of an insulating layer of a cable, particularly a power cable.

[0039] In another aspect, the present invention

[0040] - A step of applying a layer comprising a multimode polyethylene composition as defined herein onto a conductor, preferably by (co)extrusion.

[0041] A method for manufacturing a cable including a cable is provided.

[0042] In another aspect, the present invention

[0043] - A step of applying, in order, an inner semiconducting layer comprising a first semiconducting composition, an insulating layer comprising an insulating composition, and an outer semiconducting layer comprising a second semiconducting composition onto a conductor, preferably by (co)extrusion, wherein one or more layers, preferably the insulating layer, comprises a multimode polyethylene composition as defined herein.

[0044] A method for manufacturing a cable including is provided. Specific details for implementing the invention

[0045] The present invention relates to a multimode polyethylene composition ideally suitable for use in the insulation layer of a cable. Unexpectedly, the multimode polyethylene composition of the present invention has favorable mechanical and electrical properties, for example, low DC electrical conductivity of the polymer. This is achieved without any crosslinking by a crosslinking agent such as a peroxide.

[0046] In addition, the uncrosslinked multimode polyethylene composition of the present invention is flexible (having a low elastic modulus), which is desirable and is a key feature of the present invention. Flexible polymers are ideally suitable for manufacturing cables. The melting point of the multimode polyethylene composition is preferably at least 122°C, e.g., 122 to 135°C, more preferably 123 to 132°C, particularly in the range of 124 to 130°C. The combination of reduced flexural modulus and a high melting point is a key aspect of the present invention.

[0047] Multimode polyethylene composition

[0048] The multimode polyethylene composition of the present invention is 930 kg / m² 3 Ideally, 938 kg / m² 3 Above, for example, 938 to 955 kg / m² 3 It is a medium-density or high-density multimode polyethylene composition having a density (measured using ISO 1183).

[0049] The preferred range is 934 to 955 kg / m² 3 , for example, 938 to 950 kg / m² 3 , more preferably 938 kg / m² 3 Up to 946 kg / m² 3 , especially 940 to 945 kg / m² 3 am.

[0050] The term multimode refers to a multimode associated with molecular weight distribution (MWD = Mw / Mn). Generally, a polymer comprising two or more polymer fractions produced under different polymerization conditions resulting in different (weight-average) molecular weights and molecular weight distributions for the fractions is called "multimode." The prefix "multimode" relates to the number of different polymer fractions present in the polymer. Thus, for example, a multimode polymer includes a so-called "dimode" polymer composed of two fractions. The shape of the molecular weight distribution curve—that is, the shape of the polymer weight fraction graph as a function of molecular weight of the multimode polymer—shows two or more maximums or is typically magnified distinctly when compared to the curves for individual fractions.

[0051] For example, when polymers are produced in a sequential multi-stage process using reactors connected in series and different conditions in each reactor, the polymer fractions produced in the different reactors will each have a unique molecular weight distribution and weight-average molecular weight. When recording the molecular weight distribution curves of such polymers, the individual curves from these fractions typically combine to form an enlarged molecular weight distribution curve for the entire polymer product produced.

[0052] Accordingly, unless otherwise stated herein, the term "multimodal" means multimodality at least in relation to molecular weight distribution (MWD = Mw / Mn) and includes bimodal polymers.

[0053] It is preferable that the multimode polyethylene composition of the present invention is triple-mode.

[0054] It is preferable that the multimode polyethylene composition of the present invention is composed of low molecular weight and high molecular weight components.

[0055] It is preferable that the low molecular weight components consist of fractions (ai) and (aii) (and optionally a prepolymer component), and thus the multimode polyethylene composition of the present invention preferably consists of fractions (ai) and (aii) and a higher molecular weight component (and optionally a prepolymer component).

[0056] The multimode polyethylene composition may have an Mw / Mn (MWD) of at least 4, for example, 5 to 15, preferably 5 to 12.

[0057] The multimode polyethylene composition may have an MFR2 (ISO1133 at 190°C and a 2.16 kg load) of 0.05 to 5.0 g / 10 min, preferably 0.1 to 4.0 g / 10 min, more preferably 0.25 to 3.5 g / 10 min.

[0058] The multimode polyethylene composition has an MFR of 10 to 100 g / 10 min, preferably 15 to 90 g / 10 min. 21 It can have (ISO1133, at 190℃ and a 21.6kg load).

[0059] The multimode polyethylene composition comprises one or more C3-10 alpha-olefin comonomer(s), preferably one or more C3-8 alpha-olefin comonomer(s). In some embodiments, the multimode polyethylene composition comprises at least two C3-10 alpha-olefin comonomers, preferably at least two C3-8 alpha-olefin comonomers. As used herein, the term comonomer refers to a monomer unit other than ethylene that is copolymerizable with ethylene.

[0060] The olefin comonomer(s) are preferably C 4-10 Alpha-olefins, for example, 1-butene, 1-hexene, or 1-octene. Particularly preferred multimode polyethylene compositions include 1-butene and 1-hexene as comonomers.

[0061] The amount of comonomer(s) present in the multimode polyethylene composition of the present invention may be 0.25 to 2.0 mol%, e.g. 0.5 to 1.5 mol%, preferably 0.5 to 1.0 mol%. This can be determined using NMR.

[0062] The multimode polyethylene composition of the present invention may have a flexural modulus of 800 MPa or less, for example, 200 to 800 MPa, more preferably 300 to 800 MPa, for example, 500 to 775 MPa.

[0063] The multimode polyethylene composition of the present invention may also have an eta300 value of less than 1000 Pa.s, for example, 100 to 800 Pa.s.

[0064] The multimode polyethylene composition of the present invention may also have an eta0.05 value greater than 3000 Pa.s, e.g., 3500 to 7000 Pa.s.

[0065] The multimode polyethylene composition of the present invention may also have a melting point of at least 123°C, e.g., 125 to 135°C. In one embodiment, the ratio between the flexural modulus and the melting point is 4.5 to 6.5 (flexural modulus (MPa) / melting point (Celsius)), preferably 5.0 to 6.0. This is a key feature that defines a low flexural modulus while maintaining a high melting point.

[0066] The multimode polyethylene composition of the present invention may have a Shore D hardness of 55 to 65 after 3 seconds.

[0067] The multimode polyethylene composition of the present invention may have a fracture tensile strain of 600 to 800%.

[0068] The multimode polyethylene composition of the present invention may have a fracture tensile stress of 25 to 45 MPa, particularly 30 to 40 MPa.

[0069] The multimode polyethylene composition of the present invention may also have a DC electrical conductivity of 20 fS / m or less, for example 10 fS / m or less, for example 5.0 fS / m or less, for example 0.05 to 20 fS / m, for example 0.05 to 10 fS / m, or 0.05 to 5.0 fS / m when measured according to the DC conductivity method described in the “determination method” at 30 kV / mm. In one embodiment, the DC conductivity of the multimode polyethylene composition of the present invention is less than 7.0 fS / m when measured on a 0.5 mm plaque sample made of polymer at 70°C and an average electric field of 30 kV / mm.

[0070] In an embodiment of the present invention, the multimode composition has a DC electrical conductivity of 25 fS / m or less, for example, 20 fS / m or less, for example, 15 fS / m or less, for example, 0.05 to 20 fS / m, for example, 0.05 to 10 fS / m, preferably 0.05 to 5.0 fS / m, when measured according to the DC conductivity method described in the “determination method” at, for example, 30 kV / mm.

[0071] Components of a multimode polyethylene composition

[0072] The multimode polyethylene composition of the present invention comprises an LMW component which is an ethylene homopolymer or copolymer and an HMW component which is an ethylene copolymer. The expression "ethylene homopolymer" according to the present invention relates to an ethylene polymer that is substantially composed of ethylene and comprises only ethylene monomer units.

[0073] The comonomer(s) present in the LMW and HMW components may be the same or different, preferably different. The comonomers present in fractions (ai) and (aii) of the LMW component may be the same or different, preferably the same. For example, 1-butene may be used in the fraction of the LMW component and 1-hexene may be used in the HMW component. Where two or more different comonomers are present, the multimode polyethylene composition of the present invention is considered herein as a terpolymer.

[0074] Any component or fraction of the multimode polyethylene composition may also be a terpolymer, meaning that one or more components (A) or (B) or fractions (ai) or (aii) comprise ethylene and at least two different C3-10 alpha-olefin comonomers.

[0075] The LMW component may be a homopolymer or an ethylene copolymer having one or more C4-10 alpha olefins, in particular an ethylene 1-butene copolymer.

[0076] Preferably, the HMW component is an ethylene copolymer having one or more C4-10 alpha-olefins, in particular an ethylene 1-hexene copolymer or an ethylene 1-octene copolymer.

[0077] In a further embodiment, the HMW component is an ethylene terpolymer having at least two C4-10 alpha-olefins, in particular ethylene, 1-butene, and 1-hexene terpolymers.

[0078] The multimode polyethylene composition defined herein comprises a lower weight-average molecular weight (LMW) component (A) and a higher weight-average molecular weight (HMW) component (B). The LMW component has a lower molecular weight than the HMW component (e.g., by at least 5,000 mass units). Alternatively, the LMW component has a higher MFR2 than the HMW component (e.g., by at least 1.0 g / 10 min).

[0079] The multimode polyethylene composition preferably comprises the following:

[0080] (A) a homopolymer of low molecular weight ethylene or a copolymer component with one or more C3-8 alpha-olefins; and

[0081] (B) A copolymer component of one or more C3-8 alpha-olefins of ethylene with high molecular weight.

[0082] More preferably, the multimode polyethylene composition comprises the following:

[0083] (A) a low molecular weight ethylene copolymer component having one or more C3-8 alpha-olefins; and

[0084] (B) A high molecular weight ethylene copolymer component having one or more C3-8 alpha olefins.

[0085] The split between components (A) and (B) can be controlled. The multimode polyethylene composition of the present invention may have 35 to 60 weight%, preferably 35 to 55 weight% of the low molecular weight component (A) and 40 to 65 weight%, preferably 45 to 65 weight% of the high molecular weight component (B), preferably 38 to 52 weight% of the low molecular weight component (A) and 48 to 62 weight% of the high molecular weight component (B).

[0086] The LMW component (A) may have an MFR2 of 20 to 500 g / 10 min, for example, 20 to 200 g / 10 min. Since the HMW component tends to be generated in the presence of the LMW component in a multi-stage process, its characteristics cannot often be measured directly, but can be estimated using the Hagstrom equation.

[0087] The density of the LMW component (A) is 940 to 970 kg / m³ 3 It could be.

[0088] The LMW component (A) itself of the multimode polyethylene composition consists of two fractions (ai) and (aii). Accordingly, the low molecular weight component comprises the following:

[0089] (ai) a first fraction comprising an ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins; and

[0090] (aii) A second fraction comprising a different ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins.

[0091] Preferably, the low molecular weight component comprises the following:

[0092] (ai) 40 to 60 weight% of the first fraction; and

[0093] (aii) 40 to 60 weight percent of the second fraction.

[0094] Preferably, the low molecular weight component comprises the following:

[0095] (ai) 40 to 60 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0096] (aii) 40 to 60 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins.

[0097] In a preferred embodiment, (ai) may be 45 to 55 weight% and (aii) may be 55 to 45 weight%.

[0098] It is preferable that the comonomer used in the two fractions of the LMW component is the same, and even more preferable that it is 1-butene. Alternatively, the LWM component (A) may be a homopolymer, that is, both fractions (ai) and (aii) are homopolymers. These fractions must still differ, for example, in terms of density or MFR.

[0099] It is desirable that the MFR2 of fraction (ai) is lower than that of fraction (aii) (e.g., at least 1.0 g / 10 min).

[0100] The fraction (ai) preferably has an MFR2 of 10 to 40 g / 10 min.

[0101] The fraction (ai) is for a density of 945 to 980 kg / m³ 3 It is desirable that it is.

[0102] The characteristics of the low molecular weight components discussed herein may be considered as the characteristics of the combination of fractions (ai) and (aii) (and optionally the prepolymer components).

[0103] More preferably, the multimode polyethylene composition comprises a low molecular weight ethylene 1-butene copolymer component; and a high molecular weight ethylene 1-hexene copolymer component, wherein in particular the low molecular weight component is

[0104] (ai) first ethylene 1-butene copolymer fraction; and

[0105] (aii) A second different ethylene 1-butene copolymer fraction

[0106] Includes

[0107] Regardless of theory, it is thought that using such a split low molecular weight component structure reduces the flexural modulus to some extent.

[0108] Accordingly, it is desirable that each fraction (ai) and (aii) form at least 5.0 weight percent of the total multimode polyethylene composition. It is desirable that each fraction (ai) and (aii) form at least 7.5 weight percent of the total multimode polyethylene composition.

[0109] Each fraction (ai) and (aii) of the LMW components ideally forms at least 10 weight percent of the multimode polyethylene composition, for example, at least 12 weight percent of the multimode polyethylene composition.

[0110] Each fraction (ai) and (aii) of the LMW components ideally forms 10 to 30 weight percent of the multimode polyethylene composition, for example, at least 12 to 30 weight percent of the multimode polyethylene composition.

[0111] The weight ratio between fractions (ai) and (aii) of the LMW component is preferably 1:5 to 5:1, for example 4:1 to 1:4. Each fraction (ai) and (aii) preferably forms at least 20 weight% of the LMW component, for example 30 weight% or more of the LMW component.

[0112] If a multimode polyethylene composition contains a prepolymer component, such component is considered to form part (but not all) of fraction (ai). Therefore, fraction (ai) is not represented as the prepolymer alone.

[0113] In a highly preferred embodiment, the present invention defines a multimode polyethylene composition comprising the following:

[0114] (A) 35 to 60 weight% of a low molecular weight ethylene homopolymer or copolymer component comprising the following:

[0115] (ai) 40 to 60 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0116] (aii) 40 to 60 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0117] (B) 40 to 65 weight% of a high molecular weight ethylene copolymer component of ethylene and one or more C3-10 alpha-olefins.

[0118] In a highly preferred embodiment, the present invention defines a multimode polyethylene composition comprising two or more C3-10 alpha-olefin comonomers, said composition

[0119] (A) A low molecular weight ethylene homopolymer or copolymer component comprising the following:

[0120] (ai) 40 to 60 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0121] (aii) 40 to 60 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0122] (B) 40 to 65 weight% of a high molecular weight ethylene copolymer component of ethylene and one or more C3-10 alpha-olefins

[0123] Includes

[0124] Alternatively, the present invention defines a multimode polyethylene composition comprising the following:

[0125] (ai) 14 to 36 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0126] (aii) 14 to 36 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0127] (B) 40 to 65 weight% of a high molecular weight ethylene copolymer component of ethylene and one or more C3-10 alpha-olefins.

[0128] It is preferable that the multimode polyethylene composition includes the following.

[0129] (ai) 16 to 28 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0130] (aii) 16 to 28 weight percent of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins.

[0131] In all embodiments of the present invention, the multimode polyethylene composition is preferably not crosslinked. Alternatively, the multimode polyethylene composition is thermoplastic.

[0132] Another feature of the present invention is that the thermal conductivity of the polymer is improved. High thermal conductivity provides higher power transmission capacity or lower losses.

[0133] All of the above characteristics can be determined by the presence or absence of standard additives.

[0134] Accordingly, in the most preferred embodiment, the present invention, 930 kg / m² 3 Ideally, 938 kg / m² 3 The present invention provides a multimode polyethylene composition comprising the following, having a density of the above, an MFR2 in the range of 0.05 to 10 g / 10 min, and a flexural modulus of 800 MPa or less (ISO 178:2010):

[0135] (a) 35 to 55 weight% of a low molecular weight ethylene homopolymer or copolymer component comprising the following:

[0136] (ai) 40 to 60 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0137] (aii) 40 to 60 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha-olefins; and

[0138] (B) 65 to 45 weight% of a high molecular weight ethylene copolymer component of ethylene and one or more C3-10 alpha-olefins.

[0139] Catalyst for the preparation of multimode compositions

[0140] The multimode polyethylene composition of the present invention is preferably prepared using a single-site catalyst, preferably a metallocene catalyst, in particular having two cyclopentadienyl type ligands. Preferably, all components are prepared using the same catalyst.

[0141] The expression "single-site polyethylene (SSPE)" means that polyethylene is polymerized in the presence of a single-site catalyst, which is a conventional coordination catalyst. The single-site catalyst may suitably be a metallocene catalyst. Such a catalyst comprises a transition metal compound containing a cyclopentadienyl, indenyl, or fluorenyl ligand. The catalyst preferably contains two cyclopentadienyl, indenyl, or fluorenyl ligands that can be crosslinked by a group containing silicon and / or carbon atoms. Additionally, the ligand may have substituents such as alkyl groups, aryl groups, arylalkyl groups, alkylaryl groups, silyl groups, siloxy groups, alkoxy groups, etc. Suitable metallocene compounds are known in the art, and are disclosed in particular WO-A-97 / 28170, WO-A-98 / 32776, WO-A-99 / 61489, WO-A-03 / 010208, WO-A-03 / 051934, WO-A-03 / 051514, WO-A-2004 / 085499, EP-A-1752462 and EP-A-1739103.

[0142] In particular, metallocene compounds must be able to produce polyethylene with a sufficient molecular weight, which is necessary to ensure, for example, the excellent mechanical properties of power cable insulation.

[0143] One example of a suitable metallocene compound is a group of metallocene compounds having zirconium, titanium, or hafnium as a transition metal, and one or more ligands having an indenyl structure containing a siloxy substituent, such as [ethylenebis(3,7-di(tri-isopropylsiloxy)indene-1-yl)]zirconium dichloride (both rac and meso), [ethylenebis(4,7-di(tri-isopropylsiloxy)indene-1-yl)]zirconium dichloride (both rac and meso), [ethylenebis(5-tert-butyldimethylsiloxy)indene-1-yl)]zirconium dichloride (both rac and meso), bis(5-tert-butyldimethylsiloxy)indene-1-yl)zirconium dichloride, and [dimethylsilylenebis(5-tert-butyldimethylsiloxy)indene-1-yl)]zirconium dichloride (rac and meso Both), (N-tert-butylamido)(dimethyl)(η 5 There are -inden-4-yloxy)silantimium dichloride and [ethylenebis(2-(tert-butyldimethylsiloxy)inden-1-yl)]zirconium dichloride (both rac and meso).

[0144] Another example is a group of metallocene compounds having zirconium or hafnium as a transition metal atom and containing a cyclopentadienyl type ligand, such as bis(n-butylcyclopentadienyl)hafnium / Zr dichloride, bis(n-butylcyclopentadienyl)dibenzylhafnium / Zr, dimethylsilylenebis(n-butylcyclopentadienyl)hafnium / Zr dichloride (both rac and meso), and bis[1,2,4-tri(ethyl)cyclopentadienyl]hafnium / Zr dichloride.

[0145] Another example is a group of metallocene compounds containing tetrahydrodenyl ligands, such as bis(4,5,6,7-tetrahydrodenyl)zirconium dichloride, bis(4,5,6,7-tetrahydrodenyl)hafnium dichloride, ethylenebis(4,5,6,7-tetrahydrodenyl)zirconium dichloride, and dimethylsilylenebis(4,5,6,7-tetrahydrodenyl)zirconium dichloride. The use of bis(1-methyl-3-n-butylcyclopentadienyl)zirconium(IV) chloride is particularly preferred.

[0146] Therefore, a suitable single-site catalyst may be an alumoxic acid-containing, supported catalyst containing metallocene bis(1-methyl-3-n-butylcyclopentadienyl) zirconium(IV) chloride, in particular, using Albemarle (Grace) Corporation’s enhanced ActivCat® activator technology.

[0147] Single-site catalysts typically also include an activator. Commonly used activators are aluminoxan compounds, such as methylalumonic acid (MAO), tetraisobutylalumonic acid (TIBAO), or hexaisobutylalumonic acid (HIBAO). Additionally, boron activators such as those disclosed in US-A-2007 / 049711 may be used. The aforementioned activators may be used alone or in combination with aluminum alkyls, such as triethylaluminum or tri-isobutylaluminum.

[0148] Depending on the polymerization process, a single-site catalyst may be supported. The support may be a microparticle support comprising an inorganic oxide support, e.g., silica, alumina, or titanium, or a polymer support, e.g., a polymer support including styrene or divinylbenzene.

[0149] The catalyst can also be prepared according to emulsion solidification technology. Such catalysts are disclosed in particular in EP-A-1539775 or WO-A-03 / 051934.

[0150] process

[0151] A multimode polyethylene composition is formed by mechanically blending two or more distinct polymer components together, or preferably in situ during the polymerization process ( in-situ It can be produced by blending. Both mechanical and in-situ blending are well known in the field. The multimode polyethylene composition of the present invention is preferably produced in two or more reactors or zones connected in series, as described in EP-A-0517868.

[0152] Polymerization may be carried out in bulk, slurry, solution, or gaseous conditions, or any combination thereof. In one embodiment, the multi-stage process comprises a first polymerization step (LMW component) carried out in one or more slurries, e.g., a loop, a reactor, preferably two slurry reactors, and a second polymerization step (HMW component) in a gaseous reactor.

[0153] In addition to the actual polymerization step, the process may include a prepolymerization step. Optionally and advantageously, the main polymerization step may be preceded by prepolymerization, in which case a prepolymer is produced, most preferably in an amount of, for example, 0.1 to 5 weight percent or 1 to 3 weight percent of the total polymer amount. The prepolymer may be an ethylene homopolymer or copolymer.

[0154] In the case where prepolymerization occurs, all catalysts are preferably charged into a first prepolymerization reactor, and the prepolymerization is carried out as slurry polymerization. Thus, the prepolymerization step can be carried out in a loop reactor. This polymerization reduces finer particles produced in the next reactor and ultimately obtains a more uniform product.

[0155] Pre-polymerization is preferably carried out in an inert diluent, typically a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low-boiling point hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons.

[0156] In the present invention, it is preferable that the prepolymerization be carried out at a temperature of 40 to 70°C, more preferably 50 to 65°C, preferably 50 to 70 bar, more preferably 55 to 65 bar.

[0157] The molecular weight of the prepolymer can be controlled by hydrogen as is known in the art. It should be noted that if a prepolymerization step is used, all weight percent of the product produced in such step should be considered as part of component (A) and should be taken into account when determining the weight percent of component (A). In particular, the prepolymer may be considered as part of fraction (ai) of the LMW component, but the prepolymer alone is not considered as one of the fractions defined in claim 1.

[0158] After prepolymerization, the main polymerization preferably takes place in two slurry reactors, and then in a gas phase reactor.

[0159] The LMW component is ideally produced in a first polymerization step, preferably slurry polymerization. Slurry polymerization generally takes place in an inert diluent, typically a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or a mixture thereof. Preferably, the diluent is a low-boiling point hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons. A particularly preferred diluent is propane, possibly containing small amounts of methane, ethane, and / or butane.

[0160] The ethylene content in the fluid phase of the slurry may be 1 to about 50 mol%, preferably about 2 to about 20 mol%, particularly about 2 to about 10 mol%.

[0161] The temperature of the first slurry reactor is typically 60 to 100°C, preferably 70 to 90°C. Excessively high temperatures should be avoided to prevent the polymer from partially dissolving in the diluent and to prevent fouling of the reactor. The pressure may be in the range of 40 to 70 bar, preferably 50 to 60 bar.

[0162] The temperature of the second slurry reactor is typically 60 to 100°C, preferably 70 to 90°C. The pressure may be in the range of 40 to 70 bar, preferably 50 to 60 bar.

[0163] Slurry polymerization can be carried out in any known reactor used for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. It is particularly preferable to carry out polymerization in a loop reactor.

[0164] Hydrogen can be introduced to control the MFR2 of the LMW component. The amount of hydrogen required to reach the desired MFR depends on the catalyst used and the polymerization conditions.

[0165] The comonomer can be introduced into the first polymerization stage. The amount of comonomer required to reach the desired density depends on the type of comonomer, the catalyst used, and the polymerization conditions.

[0166] The average residence time in the first polymerization step is typically 20 to 120 minutes, preferably 30 to 80 minutes.

[0167] It is preferable that the LMW component is produced in two loop reactors connected in series. The first loop reactor forms the first fraction and the second loop reactor forms the second fraction of the LMW component.

[0168] The MFR2 after loop 2 can be up to 2 times or 1.5 times the MFR2 after loop 1. Therefore, the MFR2 of the first fraction (ai) is lower than the MFR2 of the LMW component overall. Ideally, the MFR increases from the first fraction to the second fraction.

[0169] Generally, the amount of catalyst used will vary depending on the properties of the catalyst, the type and conditions of the reactor, and the desired characteristics of the polymer product.

[0170] Gas phase polymerization can be carried out using known conditions. Generally, the temperature of gas phase polymerization is typically 60 to 105°C, for example, 70 to 90°C. The pressure is 10 to 40 bar, for example, 15 to 20 bar.

[0171] The obtained polymerization product may be optionally mixed with additive(s) in a known manner and pelletized for further use.

[0172] The resulting final product consists of an intimate mixture of polymers from three main reactors, and the different molecular weight distribution curves of these polymers together form a molecular weight distribution curve with a broad maximum or three maximums (i.e., the final product is a trimodal polymer mixture).

[0173] It is most preferable that polymerization be carried out in a prepolymerization reactor / two slurry loop reactors / gas phase reactor. Preferably, the polymerization conditions of the preferred 4-step method are selected such that fraction (ai) is produced in one step in the first slurry loop reactor, fraction (aii) is produced in the second step in the second slurry loop reactor, and fraction (B) is produced in an additional step, preferably in the third reactor. However, the order of these steps may be reversed.

[0174] cable

[0175] The multimode polyethylene composition of the present invention is ideally used in a layer of a cable, such as an insulating layer of a cable. Typically, a polymer composition comprising the multimode polyethylene composition of the present invention and one or more additional components, such as additives, is prepared and can be used in an insulating layer of a cable. Such an insulating layer may comprise at least 80 weight percent of the multimode polyethylene composition, for example, at least 90 weight percent of the multimode polyethylene composition.

[0176] In some embodiments, the multimode polyethylene composition is the only polymer component present in the insulating layer (rather than any masterbatch carrier polymer that may be present).

[0177] The insulating layer may include additional components other than the multimode polyethylene composition, for example, additives that can be optionally added to a mixture with a carrier polymer, i.e., a so-called master batch.

[0178] The insulating layer of the cable may contain, in addition to the multimode polyethylene of the present invention, additional components such as antioxidant(s), stabilizers(s), processing aids(s), flame retardant additive(s), water tree retardant additive(s), acid or ion scavenger(s), inorganic fillers(s), and voltage stabilizers(s) known in the field of polymers.

[0179] Non-limiting examples of antioxidants may include, for example, sterically hindered or semi-hindered phenols, aromatic amines, aliphatic sterically hindered amines, organic phosphites or phosphonites, thio compounds, and mixtures thereof.

[0180] In addition, the insulating layer may not contain carbon black, that is, it does not contain it.

[0181] The multimode composition of the present invention is suitable for use in low voltage (LV), medium voltage (MV), high voltage (HV) and / or extra-high voltage (EHV) power cables.

[0182] High Voltage Direct Current (HV DC) is generally considered to operate at voltages higher than 36 kV and up to 320 kV DC, while Extra High Voltage Direct Current (EHV DC) is generally considered to operate at voltages exceeding 320 kV DC. High Voltage Alternating Current (HV AC) is generally considered to operate at voltages up to 220 kV AC, while Extra High Voltage Alternating Current (EHV AC) is generally considered to operate at voltages exceeding 220 kV AC. Typically, High Voltage Direct Current (HV DC) and Extra High Voltage Direct Current (EHV DC) power cables operate at voltages of 40 kV or higher, and even 50 kV or higher. Power cables operating at very high voltages are actually known in the technical field as Extra High Voltage Direct Current (EHV DC) power cables, which can operate at 900 kV or, if possible, even higher.

[0183] HV and EHV DC power cables must have very low DC electrical conductivity in the insulation layer. Otherwise, leakage current flowing through the insulation layer can become too high. Since leakage current generates heat, it can lead to thermal breakdown of the power cable. For this reason, low DC electrical conductivity in the insulation layer is of the utmost importance for HV and EHV DC power cables.

[0184] In one embodiment of the present invention, the power cable is a high voltage (HV) and / or extra-high voltage (EHV) power cable.

[0185] The present invention further provides a direct current (DC) power cable.

[0186] In the most preferred embodiment, the power cable is a high voltage direct current (HV DC) and / or extra-high voltage direct current (EHV DC) power cable.

[0187] Therefore, low DC electrical conductivity makes the multimode polyethylene composition of the present invention desirable for power cable applications. In DC power cable applications, the voltage applied to the power cable is direct current (DC). A DC power cable is defined as a DC cable that transmits energy operating at any DC voltage level, typically operating at a DC voltage higher than 1 kV.

[0188] The present invention also relates to a power cable, for example, a direct current (DC) power cable comprising a conductor surrounded in order by at least an inner semiconducting layer, an insulating layer, and an outer semiconducting layer, wherein one or more layers, for example, at least the insulating layer, comprises a multimode composition of the present invention.

[0189] The outer semiconducting layer preferably comprises a second semiconducting composition that is not crosslinked, for example, and is composed thereof. The inner semiconducting layer comprises, for example, a first semiconducting composition that is not crosslinked, for example, and is composed thereof.

[0190] The first and second semiconducting compositions may be different or identical and comprise, for example, a polyolefin, or a polymer(s) which is a mixture of a polyolefin and a conductive filler, such as carbon black. Suitable polyolefin(s) are, for example, polyethylene produced in a low-pressure process or polyethylene produced in an HP process (LDPE).

[0191] In this document, the term "conductor" means that the conductor comprises one or more wires. Furthermore, the cable may comprise one or more such conductors. Additionally, the conductor may be a DC electrical conductor and may comprise one or more metal wires.

[0192] As is well known, the cable may optionally include additional layers, for example, a layer surrounding the insulating layer, or, if present, an outer semiconducting layer, such as screen(s), jacket layer(s), other protective layer(s), or any combination thereof.

[0193] The present invention also provides a method for manufacturing a power cable, for example, a direct current (DC) power cable, and said manufacturing method

[0194] - On a conductor, for example by (co)extrusion, an inner semiconducting layer comprising a first semiconducting composition, an insulating layer comprising an insulating composition, and an outer semiconducting layer comprising a second semiconducting composition are applied in sequence, wherein the insulating layer comprises the multimode polyethylene composition of the present invention.

[0195] In addition, power cables, for example, direct current (DC) power cables can be manufactured, wherein the process includes the following steps:

[0196] (a) - a step of providing and mixing a first semiconducting composition comprising a polymer, carbon black, and optionally additional component(s) for an internal semiconducting layer, e.g., melt-mixing in an extruder,

[0197] - A step of providing and mixing the multimode polyethylene composition of the present invention and optional additives, for example, melt-mixing in an extruder,

[0198] - A second semiconducting composition comprising a polymer, carbon black, and optionally additional component(s) for an outer semiconducting layer, and a step of mixing, for example, melt-mixing in an extruder, and

[0199] (b) on a conductor, for example by co-extrusion,

[0200] - A molten mixture of the first semiconducting composition obtained in step (a) for forming an internal semiconducting layer,

[0201] - A molten mixture of the multimode polyethylene composition of the present invention obtained in step (a) for forming an insulating layer, and

[0202] - A molten mixture of the second semiconducting composition obtained in step (a) for forming an outer semiconducting layer

[0203] Step of applying.

[0204] The term “(co)extrusion” as used herein, as is known in the art, means that in the case of two or more layers, said layers may be extruded in separate steps, or that two or more or all of said layers may be co-extruded in the same extrusion step. The term “(co)extrusion” as used herein also means that all or part of the layer(s) are formed simultaneously using one or more extrusion heads. For example, three layers may be formed using a triple extrusion head. When forming layers using more than one extrusion head, for example, two extrusion heads may be used to extrude the layers, wherein the first extrusion head is for forming the inner semiconducting layer and the inner part of the insulating layer, and the second extrusion head is for forming the outer insulating layer and the outer semiconducting layer.

[0205] The advantages of the present invention may include the following:

[0206] - High electrical performance of the insulation system of HV DC cables.

[0207] - Robust high-speed extrusion is possible, resulting in no or very low risk of scorching (unwanted premature crosslinking) in the semiconducting and insulating layers, allowing for extended stable production periods at higher extrusion speeds and quality. In principle, this means the extruder can be operated for a longer period. Consequently, longer maximum cable lengths can be produced, requiring fewer joints in power cable systems.

[0208] - The degassing step can be omitted, which eliminates the need to remove unwanted crosslinking byproducts, namely decomposition products formed from any crosslinking agent, thereby accelerating the entire cable production process.

[0209] - Inline jacketing can be performed as degassing cables are not required.

[0210] The thickness of the insulation layer of a power cable, e.g., a DC power cable, e.g., an HV DC power cable, is typically 2 mm or more, e.g., at least 3 mm, e.g., at least 5 to 100 mm, e.g., 5 to 50 mm, e.g., typically 5 to 40 mm, e.g., 5 to 35 mm, when measured at the cross-section of the insulation layer of the cable. The thickness of the inner and outer semiconducting layers is typically smaller than the thickness of the insulation layer, e.g., in an HV DC power cable, e.g., greater than 0.1 mm, e.g., 0.3 to 20 mm, e.g., 0.3 to 10 mm, e.g., an inner semiconducting layer and an outer semiconducting layer. The thickness of the inner semiconducting layer is e.g., 0.3 to 5.0 mm, e.g., 0.5 to 3.0 mm, e.g., 0.8 to 2.0 mm. The thickness of the outer semiconducting layer is, for example, 0.3 to 10 mm, for example, 0.3 to 5 mm, for example, 0.5 to 3.0 mm, for example, 0.8 to 3.0 mm. The thickness of the layers of a power cable, for example, a direct current (DC) power cable, depends on the intended voltage level of the cable for the final application field and can be selected accordingly.

[0211] Experimental section

[0212] measurement method

[0213] Unless otherwise noted in the description or experiment section, the following methods were used for characteristic measurement.

[0214] wt% : weight%

[0215] Melting flow rate

[0216] Melt Flow Rate (MFR) is measured according to ISO 1133 and expressed in g / 10 min. MFR is an indicator of the polymer's fluidity, or processability. The higher the melt flow rate, the lower the viscosity of the polymer. MFR is measured for polyethylene at 190°C. MFR is 2.16 kg (MFR2) or 21.6 kg (MFR 21 It can be measured under various loads such as ).

[0217] density

[0218] Density was measured according to ISO 1183-2. Sample preparation was carried out according to ISO 1872-2 Table 3 Q (Compression Molding).

[0219] DC conductivity method

[0220] Plaque Sample Procedure:

[0221] A circular plaque was compression-molded from pellets of the test polymer composition, i.e., the polymer composition of the present invention, using a 0.5 mm thick stainless steel frame with a 330 mm circular hole. Thus, the thickness of the final plaque was 0.5 mm and the diameter was 330 mm. A Teflon film was placed between the polymer and the press surface.

[0222] The test polymer composition was press-molded at 130°C for 60 seconds under a pressure of 26 kPa. Then, the pressure was increased to 2.6 MPa while the temperature was gradually increased until it reached 180°C after 200 seconds. The temperature was maintained constant at 180°C for 340 seconds. Finally, the temperature was lowered at a cooling rate of 15°C / min until it reached room temperature, and the pressure was released.

[0223] Measurement Procedure:

[0224] A high-voltage source was connected to the upper electrode to apply voltage to the test plaque sample. The current generated through the sample, i.e., the sample of the polymer composition of the present invention, was measured using a potentiometer. The measurement cell was a three-electrode system with a brass electrode placed in an oven at 70°C. The diameter of the measurement electrode was 100 mm.

[0225] A DC voltage of 15 kV was applied, resulting in an average electric field of 30 kV / mm. The current passing through the plaque, i.e., the polymer composition of the present invention, was recorded for 11 hours, and the conductivity of the insulation at 30 kV / mm was calculated using the current during that time. Then, the voltage was increased to 22.5 kV to induce an average electric field of 45 kV / mm. The current passing through the plaque, i.e., the polymer composition of the present invention, was recorded for 6 hours, and the conductivity of the insulation at 45 kV / mm was calculated using the current during that time. Then, the voltage was increased to 30 kV to induce an average electric field of 60 kV / mm. The current passing through the plaque, i.e., the polymer composition of the present invention, was recorded for 6 hours, and the conductivity of the insulation at 60 kV / mm was calculated using the current during that time.

[0226] GPC

[0227] Its broadness, described by the molecular weight average (Mz, Mw, and Mn), molecular weight distribution (MWD), and polydispersity index PDI = Mw / Mn (where Mn is the number-average molecular weight and Mw is the weight-average molecular weight), is determined by gel permeation chromatography (GPC) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003, and ASTM D 6474-12 using the following formulas:

[0228]

[0229] For a constant elution volume interval ΔVi, where Ai and Mi are the chromatographic peak slice region and polyolefin molecular weight (MW) associated with the elution volume Vi, respectively, and N is equal to the number of data points obtained from the chromatogram between integration limits.

[0230] A high-temperature GPC instrument equipped with an infrared (IR) detector (IR4 or IR5 from PolymerChar (Valencia, Spain)) and 3 x Agilent-PLgel Olexis and 1 x Agilent-PLgel Olexis Guard columns was used. 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-di-tert-butyl-4-methyl-phenol was used as the solvent and mobile phase. The chromatography system was operated at 160°C at a constant flow rate of 1 mL / min. 200 μL of sample solution was injected per analysis. Data acquisition was performed using Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0231] The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11,500 kg / mol. The PS standards were dissolved at room temperature over several hours. The conversion of polystyrene peak molecular weights to polyolefin molecular weights was performed using the Mark Houwink formula and the following Mark Houwink constant.

[0232]

[0233] A third-order polynomial fit was used to fit the calibration data. All samples were prepared in a concentration range of 0.5–1 mg / ml and dissolved at 160°C with continuous gentle shaking for 2.5 hours for PP and 3 hours for PE.

[0234] Flexural modulus

[0235] The bending modulus was determined according to ISO 178, which describes the 3-point bending test procedure. Test specimens were prepared by milling a sample of 80*15*4mm from a 4mm thick compression-molded plaque prepared according to EN ISO 17855-2:2016, and tested at a cross-head speed of 2mm / min using a 100N load cell.

[0236] melting point

[0237] The melting point was measured using a TA Instruments DSC Q2000 instrument:

[0238] Fan: Tzero Al Fan

[0239] Method: According to ISO-11357-3:

[0240] Primary heating 10℃ / min, 30-180℃

[0241] Isothermal 180℃, 2 minutes

[0242] Cooling 10℃ / min, 180-(-30)℃

[0243] Isothermal (-30)℃, 2 minutes

[0244] Secondary heating 10℃ / min, (-30)-180℃ .

[0245] Rheology, Dynamic (Viscosity) Method ISO 6721-1:

[0246] The dynamic rheological properties of the polymer (here, polymer composition) can be determined using a controlled stress rheometer with a parallel-plate geometry (diameter 25 mm) and a 1.3 mm gap between the upper and lower plates. Before testing, the sample must be stabilized by dry blending the pellet with 0.25-0.3% Irganox B225. Irganox B225 is a blend of 50% Irganox 1010, Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), CAS No. 6683-19-8, and 50% lrgafos 168, tris(2,4-di-tert-butylphenyl)phosphite, CAS No. 31570-04-4. Adding an antioxidant (here, Irganox B225) is generally not a standard procedure of Method 15 ISO 6721-1.

[0247] Frequency sweep tests, specifically the "rheology, dynamic (viscosity) method," were performed in the angular frequency range of 628–0.01 rad / s according to the ISO standard method ISO 6721-1. All experiments were conducted under a nitrogen atmosphere at a constant temperature of 190°C and strain within the linear viscoelastic region. During the analysis, the storage modulus (G'), loss modulus (G"), complex modulus (G*), and complex viscosity (η*) were recorded and plotted against frequency (ω). The measurements of complex viscosity (η*) at angular frequencies of 0.05 and 300 rad / s were taken from the experiments. The abbreviations for these parameters are η*0.05 and η*300, respectively.

[0248] The zero viscosity η*0 value is calculated using the Carreau-Yasuda model. If using this model to estimate zero shear viscosity is not recommended, a rotary shear test is performed at a low shear rate. This test is conducted for 0.001 to 1 s -1The shear rate range is limited to 190℃ and the temperature is limited to 190℃.

[0249] Tensile strength - ISO527-2 / 5A 50mm / min

[0250] Specimens were prepared for tensile testing (stress and strain at fracture) and measured according to ISO 527-2 / 5A by die cutting from a 1.8 mm thick compression molded plaque tested at 23°C and 50% relative humidity using a 1 kN load cell, a tensile test speed of 50 mm / min, a grip distance of 50 mm, and a gauge length of 20 mm.

[0251] Shore D

[0252] Shore D (3s) is measured according to ISO 868 on a 4 mm thick molded specimen. Shore hardness is measured 3 seconds after the pressure foot firmly contacts the specimen. The specimen was molded according to EN ISO 1872-2.

[0253] comonomer content

[0254] Quantification of polymer comonomer content by NMR spectroscopy

[0255] The comonomer content was measured by quantitative nuclear magnetic resonance (NMR) spectroscopy after basic assignment (e.g., literature ["NMR Spectra of Polymers and Polymer Additives", AJ Brandolini and DD Hills, 2000, Marcel Dekker, Inc., New York]). Experimental parameters were adjusted to ensure the measurement of the quantitative spectrum for this specific task (e.g., literature ["200 and More NMR Experiments: A Practical Course", S. Berger and S. Braun, 2004, Wiley-VCH, Weinheim]). The amount was calculated using a simple correction ratio of the signal integral of representative sites in a manner known in the art.

[0256] Catalyst manufacturing

[0257] As a catalyst, Albemarle (Grace) Corporation’s enhanced ActivCat® activator technology was used, and an alumoxic acid-containing, supported catalyst containing metallocene bis(1-methyl-3-n-butylcyclopentadienyl) zirconium(IV) chloride was used.

[0258] manufacturing of polyethylene

[0259] A multimode polyethylene composition was prepared using a prepolymerization reactor, first and second slurry-loop reactors, and a gas phase reactor. The prepolymerization stage was performed under conditions of a feed of a catalyst (as prepared above), monomer, antistatic agent, and diluent (propane (C3)) as disclosed in Table 1, and using the same at a temperature of 50 dm 3 It was performed as a slurry in a loop reactor.

[0260] The obtained slurry is mixed with the prepolymerized catalyst at 150 dm 3 It was continuously introduced into the first loop reactor. The polymer slurry was continuously withdrawn from the first loop reactor at 300 dm 3 It was transferred to a second loop reactor. The slurry was continuously taken from the second loop reactor to a flash stage where hydrocarbons are removed from the polymer. Then, the polymer was transferred to a gas phase reactor where polymerization continued. The conditions and feed / feed ratios in the loop and gas phase polymerization stages are disclosed in Tables 2 and 3.

[0261] [Table 1]

[0262]

[0263] [Table 2a]

[0264]

[0265] [Table 2b]

[0266]

[0267] [Table 3]

[0268]

[0269] In all tables:

[0270] C2: Ethylene

[0271] H2: Hydrogen

[0272] C4: 1-butene

[0273] C6: 1-Hexene.

[0274] The polymer obtained from the gas-phase reactor is a 1:1 mixture of 0.22 wt% pentaerythrityl-tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)-propionate CAS No. 6683-19-8 and tris(2,4-di-t-butylphenyl)phosphite CAS No. 31570-04-4, 0.15 wt% calcium stearate CAS No. 1592-23-0, and a dimethyl succinate polymer CAS No. 65447-77-0 with 0.3 wt% 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol and It is pelletized into a 1:1 mixture of poly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidyl)imino)-1,6-hexanediyl((2,2,6,6-tetramethyl-4-piperidyl)imino)) CAS number 71878-19-8.

[0275] The characteristics are determined in the pellets. An embodiment of the present invention has a density of 945 kg / m³. 3 and is compared with commercial imod HDPE with an MFR of 21.89 g / 10 min.

[0276] [Table 5]

[0277]

[0278] [Table 6]

[0279]

[0280] As can be seen from Table 6, the multimode polyethylene composition of the present invention exhibits excellent low DC conductivity and low flexural modulus. This performance is superior to that of similar monomodal copolymers. The polyethylene according to the present invention is suitable for use in power cables, for example, for insulation thereof.

Claims

Claim 1 A multimodal polyethylene composition having a lower molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a higher molecular weight ethylene copolymer component (B), wherein the lower molecular weight component (ai) comprises a first fraction comprising an ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins; and (aii) a second fraction comprising a different ethylene homopolymer or a copolymer of ethylene and one or more C3-10 alpha-olefins, wherein fraction (ai) has an MFR2 lower than fraction (aii), and each fraction (ai) and (aii) of the LMW component forms 10 weight% or more of the multimodal polyethylene composition, and the multimodal polymer composition has a molecular weight of 930 kg / m² 3 A multimodal polyethylene composition having a density of 0.05 to 10 g / 10 min (ISO1133) in the range of 0.05 to 10 g / 10 min, and a flexural modulus of 800 MPa or less (ISO 178:2010). Claim 2 A multimode polyethylene composition according to claim 1, comprising: (A) a low molecular weight ethylene homopolymer or copolymer component comprising: (ai) 40 to 60 weight% of a first ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha olefins; and (aii) 40 to 60 weight% of a second different ethylene homopolymer fraction or a copolymer fraction of ethylene and one or more C3-10 alpha olefins; and (B) a high molecular weight ethylene copolymer component of ethylene and one or more C3-10 alpha olefins. Claim 3 A multimode polyethylene composition according to claim 1, comprising: (A) a homopolymer of low molecular weight ethylene or a copolymer component with one or more C3-8 alpha olefins; and (B) a copolymer component of high molecular weight ethylene with one or more C3-8 alpha olefins. Claim 4 A multimode polyethylene composition according to claim 1, comprising 35 to 60 weight% of the low molecular weight component and 40 to 65 weight% of the high molecular weight component. Claim 5 A multimode polyethylene composition according to claim 1, comprising a low molecular weight ethylene homopolymer or ethylene 1-butene copolymer; and a high molecular weight ethylene 1-hexene copolymer component. Claim 6 A multimode polyethylene composition according to claim 5, wherein the low molecular weight copolymer comprises (ai) a first ethylene homopolymer or ethylene 1-butene copolymer fraction; and (aii) a second different homopolymer or ethylene 1-butene copolymer fraction. Claim 7 A multimode polyethylene composition obtained using a single-site catalyst in claim 1. Claim 8 A multimode polyethylene composition according to claim 1, obtained using a metallocene catalyst and having an Mw / Mn of 5 to 12. Claim 9 In claim 1, a non-crosslinked, multimode polyethylene composition. Claim 10 A multimode polyethylene composition according to claim 1, having a melting point of at least 122°C. Claim 11 In claim 1, (a) MFR2 of 0.05 to 5.0 g / 10 min (ISO1133 at 190°C and 2.16 kg load); (b) 938 to 950 kg / m² 3 A multimode polyethylene composition having a density of the range; or both (a) and (b). Claim 12 A multimode polyethylene composition according to claim 1, having one or more of: a flexural modulus of 500 to 775 MPa; a comonomer content of 0.5 to 1.0 mol%; an Mw / Mn of 5 to 12; a DC conductivity of less than 7.0 fS / m when measured at an average electric field of 70°C and 30 kV / mm on a 0.5 mm plaque sample composed of said polymer; an eta300 value of less than 1000 Pa·s; and an eta0.05 value greater than 3000 Pa·s. Claim 13 A multimode polyethylene composition according to claim 1, wherein the ratio between the flexural modulus and the melting point (flexural modulus (MPa) / melting point (Celsius)) is 4.5 to 6.

5. Claim 14 A multimode polyethylene composition according to claim 1, wherein each fraction (ai) and (aii) of the LMW component forms 12 weight percent or more of the multimode polyethylene composition. Claim 15 A multimode polyethylene composition according to claim 1, wherein the weight ratio between fractions (ai) and (aii) of the LMW component is in the range of 1:5 to 5:

1. Claim 16 A multimode polyethylene composition according to claim 1, wherein each fraction (ai) and (aii) forms 20 weight percent or more of the LMW component. Claim 17 A cable comprising a conductor surrounded by one or more layers comprising a multimode polyethylene composition according to any one of claims 1 to 16. Claim 18 A cable according to claim 17, comprising a conductor surrounded by an inner semiconductive layer, an insulating layer, and an outer semiconductive layer, wherein at least the insulating layer comprises the multimode polyethylene composition. Claim 19 A cable according to claim 17, wherein the multimode polyethylene composition forms at least 80 weight percent of the layer in which it is present. Claim 20 In Clause 17, a cable that is a power cable. Claim 21 A method for preparing a multimode polyethylene composition comprising a low molecular weight (LMW) ethylene homopolymer or copolymer component (A) and a high molecular weight ethylene copolymer component (B), wherein the method comprises: (I) polymerizing ethylene and optionally one or more C3-10 alpha-olefin comonomers in the presence of a single-site catalyst in a first slurry reactor to produce a fraction (ai); (II) polymerizing ethylene and optionally one or more C3-10 alpha-olefin comonomers in the presence of a single-site catalyst and the fraction (ai) in a second slurry reactor to produce a fraction (aii), which together with the fraction (ai) forms the low molecular weight ethylene homopolymer or copolymer component (A); and (III) a step of polymerizing ethylene and one or more C3-10 alpha-olefin comonomers in the presence of the LMW ethylene homopolymer or copolymer component (A) and the single-site catalyst to form the high molecular weight ethylene copolymer component (B), wherein each fraction (ai) and (aii) of the LMW component forms 10 weight% or more of the multimode polyethylene composition, and the multimode polyethylene composition has a molecular weight of 930 kg / m³ 3 A method of manufacturing having a density of 0.05 to 10 g / 10 min, an MFR2 (ISO1133 at 190°C and 2.16 kg load), and a flexural modulus of 800 MPa or less.

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