Polyethylene composition for insulating layer

Abstract

This disclosure relates to an insulating layer for cables. In one embodiment, the insulating layer comprises a silane-crosslinked polyethylene composition comprising (A) 90% to 99% by weight of a base bimodal ethylene / C4-C8α-olefin copolymer. The base ethylene / C4-C8α-olefin copolymer before silane crosslinking has (i) a density of 0.91 g / cc to 0.93 g / cc and (ii) 90 to 140 I 21 The insulating layer has (iii) a Mw / Mn ratio of 7.0 to 15.0, (iv) a SHI (n0.1 / n100) value of 5.0 to 30.0, (v) boron of 0 ppb to 80 ppb, and (vi) fluorine of 0 ppm to 5 ppm. The insulating layer also contains (B) 0.5 wt% to 2.0 wt% hydrolyzed silane monomer. The insulating layer has (1) a surface roughness Ra value of 50 μ-in to 150 μ-in, (2) a dissipation rate of 0.0001 radians or less, (3) a dielectric constant of 2.0 to less than 2.29, and (4) 5.00 × 10⁻¹⁰ 16 ~8.00 x 10 17 It has a volume resistivity, (5) a high-temperature creep value of 20% to 30%, and characteristics selected from the group consisting of combinations thereof.

Description

[Technical Field]

[0001] Linear low-density polyethylene (LLDPE) is widely used as an insulating base resin for power cables due to several desirable characteristics. LLDPE has a low dielectric constant, providing good electrical insulation between conductive elements. LLDPE is easily crosslinked, providing mechanical stability for cable insulation.

[0002] One drawback of LLDPE is that, because it is metallocene-catalyzed in a single reactor, it typically has a narrow molecular weight distribution (MWD) and a polydispersity of less than 5.0. This narrow MWD results in significant shear flow deformation when LLDPE is extruded through annular dies at the high shear rates that occur in the production of wire or cable jacket layers. When LLDPE is extruded at high speed onto a cable, the significant shear flow deformation causes the surface of the cable insulation to become rough. This rough surface reduces electrical performance because the surface roughness concentrates the electric field within the cable jacket.

[0003] Chromium-catalyzed olefin polymerization is known to produce LLDPE with a broad MWD, which is due to a high melt flow ratio, particularly above 80. 21Characterized by its I² value. On the other hand, catalysts and activators typically used in solution-phase polymerization systems (i.e., non-chromium catalyst systems) produce LLDPE with a narrow molecular weight distribution (polydispersity less than 5.0), which results in a rough insulating surface during extrusion and can lead to electrical stress concentration and interfacial problems when cables are coated. Furthermore, in wire and / or cable coating applications, a smooth surface is required for LLDPE cable insulation to maximize electrical performance and provide aesthetically acceptable consumer end products. Therefore, in this art, a wide MWD and high shear viscosity reduction (i.e., I² greater than 80) are desired to have good processability at high extrusion shear rates, form a smooth cable insulation layer for wire and / or cable coating, and maximize insulation performance such as low conductivity and high resistivity. 21 The need for polyethylene compositions having a ratio of 1 / I2, particularly LLDPE compositions, has been recognized.

[0004] This disclosure relates to an insulating layer for cables. In one embodiment, the insulating layer comprises a silane-crosslinked polyethylene composition comprising (A) 90% to 99% by weight of a base bimodal ethylene / C4-C8α-olefin copolymer. The base ethylene / C4-C8α-olefin copolymer before silane crosslinking has (i) a density of 0.91 g / cc to 0.93 g / cc and (ii) 90 to 140 I 21 The insulating layer has (iii) a Mw / Mn ratio of 7.0 to 15.0, (iv) a SHI (n0.1 / n100) value of 5.0 to 30.0, (v) boron of 0 ppb to 80 ppb, and (vi) fluorine of 0 ppm to 5 ppm. The insulating layer also contains (B) 0.5 wt% to 2.0 wt% hydrolyzed silane monomer. The insulating layer has (1) a surface roughness Ra value of 50 μ-in to 150 μ-in, (2) a dissipation rate of 0.0001 radians or less, (3) a dielectric constant of 2.0 to less than 2.29, and (4) 5.00 × 10⁻¹⁰ 16 ~8.00 x 10 17 It has a volume resistivity, (5) a high-temperature creep value of 20% to 30%, and characteristics selected from the group consisting of combinations thereof.

[0005] The present disclosure also provides a cable. In one embodiment, the cable includes a conductor and an insulating layer on the conductor. The insulating layer is composed of (A) a silane-crosslinked polyethylene composition composed of 90% to 99% by weight of a base bimodal ethylene / C4-C8 α-olefin copolymer. The base bimodal ethylene / C4-C8 α-olefin copolymer before silane crosslinking has (i) a density of 0.91 g / cc to 0.93 g / cc, (ii) an I 21 / I2 ratio of 90 to 140, (iii) a Mw / Mn of 7.0 to 15.0, and (iv) a SHI(n0.1 / n100) value of 5.0 to 30.0. The insulating layer also contains 0.5% to 2.0% by weight of a hydrolyzed silane monomer.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a chart showing the chemical structures of different types of carbon-carbon double (unsaturation in the polymer chain) bonds of vinylene, trisubstituted, vinyl, and vinylidene. [Figure 2] FIG. 2 is a schematic diagram of the flow pattern of a two-reactor polymerization system according to an embodiment of the present disclosure.

[0007] Definitions Any reference to the Periodic Table of the Elements is a reference to the Periodic Table of the Elements published by CRC Press, Inc. in 1990 - 1991. References to groups of elements in this table are according to the new notation for numbering the groups.

[0008] For the purposes of U.S. patent practice, the contents of any referenced patent, patent application, or publication are incorporated by reference in their entirety (or the corresponding U.S. version is incorporated as such by reference) insofar as they do not conflict with any definitions specifically provided in this disclosure.

[0009] The numerical ranges disclosed in this specification include all values from the lower limit value to the upper limit value (including the lower limit value and the upper limit value). In the case of a range including explicit values (for example, 1 or 2, or 3 to 5, or 6, or 7), any sub-range between any two explicit values is included (for example, in the range of 1 to 7 above, sub-ranges such as 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc. are included).

[0010] Unless otherwise stated, unless implied from the context, or unless not customary in the art, all parts and percentages are by weight and all test methods are the latest at the filing date of this disclosure.

[0011] A "bimodal" polyethylene composition contains two polyethylene fractions produced under different polymerization conditions including any differences in process conditions and / or catalyst systems, such that the molecular weight and / or comonomer content of the fractions are different. The first polyethylene fraction is a high molecular weight component. The second polyethylene fraction is a low molecular weight component. Bimodal polyethylene is an in-reactor blend of a high molecular weight component and a low molecular weight component, whereby one component is produced and then it is present during the production of the second component.

[0012] When used, the term "blend" or "polymer blend" refers to a mixture of two or more polymers. A blend may be miscible or immiscible (not phase-separated at the molecular level). A blend may be phase-separated or not phase-separated. A blend may or may not contain one or more domain structures determined from transmission electron spectroscopy, light scattering, x-ray scattering, and other methods known in the art. A blend can be affected by physically mixing two or more polymers at the macro level (for example, melt blending or compounding of resins) or at the micro level (for example, simultaneous formation in the same reactor).

[0013] The term "composition" refers to a mixture of the materials constituting the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0014] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the existence of any additional components, processes, or procedures, whether or not they are specifically disclosed. To avoid any doubt, all compositions claimed through the use of the term “comprising” may, unless otherwise stated, include any additional additives, adjuvants, or compounds, whether or not they are polymers. In contrast, the term “consisting essentially of” excludes any other components, processes, or procedures from the scope of any prior description, except those not essential for operability. The term “consisting of” excludes any components, processes, or procedures that are not specifically described or enumerated. The term “or” refers to the enumerated members individually and in any combination, unless otherwise stated.

[0015] An "ethylene-based polymer" is a polymer containing more than 50 mole percent (by weight) of polymerizable ethylene monomers (based on the total amount of polymerizable monomers) and optionally containing at least one comonomer. Ethylene-based polymers include ethylene homopolymers and ethylene copolymers (meaning units derived from ethylene and one or more comonomers). The terms "ethylene-based polymer" and "polyethylene" can be used interchangeably. Ethylene-based polymers include α-olefins (e.g., C3-C 12 It may contain ethylene copolymerized with α-olefin or C4-C8α-olefin.

[0016] As used herein, the terms "ethylene monomer" or "ethylene" refer to a chemical unit having two carbon atoms with a double bond between them, and each carbon atom being bonded to two hydrogen atoms, which polymerizes with other such chemical units to form an ethylene-based polymer composition.

[0017] A "heteroatom" is an atom other than carbon and hydrogen. Heteroatoms can be non-carbon atoms from groups IV, V, VI, and VII of the periodic table. Non-restrictive examples of heteroatoms include F, N, O, P, B, S, and Si.

[0018] A hydrocarbon is a compound containing only hydrogen and carbon atoms. Hydrocarbons can have a linear, cyclic, or branched structure.

[0019] "Linear low-density polyethylene" (or "LLDPE") is composed of ethylene-derived units and at least one C3-C 10 LLDPE is a linear ethylene / α-olefin copolymer containing a heterogeneous short-chain branching distribution, comprising α-olefin comonomers, or units derived from at least one C4-C8α-olefin comonomer, or at least one C6-C8α-olefin comonomer. In contrast to conventional LDPE, LLDPE is characterized by the presence of only a small amount of long-chain branching, if any. LLDPE has densities of 0.910 g / cc to 0.940 g / cc, or 0.910 g / cc to 0.930 g / cc, or 0.915 g / cc to 0.930 g / cc, or 0.915 g / cc to 0.925 g / cc.

[0020] Low-density polyethylene (LDPE) is composed of ethylene homopolymers or ethylene copolymers having acrylates, vinyl acetate, and / or vinylsilane as comonomers. LDPE has a density of 0.915 g / cc to 0.940 g / cc and contains long-chain branching with a broad molecular weight distribution (MWD). LDPE is typically produced by high-pressure free-radical polymerization (tubular reactors or autoclaves using free-radical initiators). Non-limiting examples of LDPE include LDPE products from Chevron Phillips (MarFlex®), LyondellBasell (LUPOLEN®), Borealis, Ineos, and ExxonMobil.

[0021] "Olefins" are unsaturated aliphatic hydrocarbons that have a carbon-carbon double bond.

[0022] An "olefin polymer" (commonly referred to as "polyolefin") is a polymer that contains a majority by weight percent of polymerizable olefin monomers (based on the total amount of polymerizable monomers) and may optionally contain at least one comonomer. Non-limiting examples of olefin polymers include ethylene polymers and propylene polymers.

[0023] As used herein, the terms “polymer” or “polymer material” refer to compounds prepared by polymerizing monomers, whether of the same or different types, providing multiple and / or repeating “units” or “mer units” constituting the polymer in a polymeric form. Thus, the general term polymer encompasses the term homopolymer, which is commonly used to refer to polymers prepared from only one type of monomer, and the term copolymer, which is commonly used to refer to polymers prepared from at least two types of monomers. It also encompasses all forms of copolymers, such as random and block copolymers. The terms “ethylene / α-olefin polymer” and “propylene / α-olefin polymer” refer to the aforementioned copolymers prepared by polymerizing ethylene or propylene with one or more additional polymerizable α-olefin monomers, respectively. Polymers are often referred to as "made of" one or more specified monomers, "based on" a specified monomer or type of monomer, or "containing" a specified monomer content. However, it should be noted that in this context, the term "monomer" is understood to refer to the polymerization residue of a specified monomer, and not to the non-polymerized species. In general, polymers as used herein are referred to in terms of "units," which are the polymerization forms of the corresponding monomers.

[0024] When used in relation to a cable, a "sheath" includes an insulating coating or layer, a protective jacket, etc.

[0025] A "wire" is a single strand of a conductive metal, such as a single strand of copper or aluminum, or a single strand of an optical fiber.

[0026] Test Method 13 13C NMR. 13 13C nuclear magnetic resonance ( 13 13C NMR) is used to determine the short-chain branches in a polymer, i.e., the type and amount of comonomer. 13 Samples for 13C NMR were prepared by adding approximately 3 g of 1,1,2,2-tetrachloroethane (TCE)-d2 at 25 wt% and 0.025 M Cr(AcAc)3 in a 10 mm NMR tube to approximately 0.10 g of the polymer sample. The sample was dissolved and homogenized by heating the tube and its contents to 135 °C using a heating block and a vortex mixer. Each dissolved sample was visually inspected to ensure homogeneity. The sample was thoroughly mixed immediately before analysis and kept from cooling until inserted into the heated NMR sample holder. All data were collected using a Bruker 600 MHz spectrometer equipped with a 10 mm high-temperature cryoprobe. 13C data were acquired using a 7.8 s pulse repetition delay, a 90° flip angle, and inverse-gated decoupling at a sample temperature of 120 °C 13 13C data were obtained. All measurements were made on non-rotating samples in lock mode. The sample was thermally equilibrated before data acquisition. 13 13C NMR chemical shifts were referenced to the EEE triad at 30.0 ppm. The composition was determined from the assignments and integrals from Liu, W.; Rinaldi, P. L.; McIntosh, L. H.; and Quirk, R. P.; Macromolecules, 34, 2001, 4757-4767 (for ethylene-co-octene polymers), Sahoo, S. K., et al., Macromolecules 36, 2003, 4017-4028 (for ethylene-co-butene polymers) 13The composition was determined using 13C NMR spectra, and the vector equation s = fM (where M is the assignment matrix, s is the row vector representation of the spectrum, and f is the composition vector of the mole fractions) was solved. The elements of f were assumed to be E and O (octene) or B (butene) triads with all possible rearrangements of E and O or B (butene). The assignment matrix M was constructed with one row for each triad in f and each column for the integrated NMR signal. The elements of the matrix were integer values ​​determined by referring to the assignments in (Liu, W.; Rinaldi, PL; McIntosh, LH; and Quirk, RP; Macromolecules, 34, 2001, 4757-4767), or Sahoo, SK, et al., Macromolecules 36, 2003, 4017-4028. This equation is solved by comparing s with the integral of each sample. 13 The error function between the C data and the target data was solved by varying the elements of f as needed to minimize the error. This was done in Microsoft Excel using the Solver function.

[0027] 1 1H NMR. 1 H nuclear magnetic resonance ( 1 H nuclear magnetic resonance, 1¹H NMR was used to quantify the following types of carbon-carbon double bonds ("unsaturated") in the polymer: "Vinylen" is a carbon-carbon double bond with the formula R1-CH=CH-R2, where R1 and R2 are each one or more atoms bonded to a hydrogen atom. "Trisubstituted" is a carbon-carbon double bond in which the carbon of the double bond is bonded to a total of three carbon atoms, where R1, R2, and R3 (in Figure 1) are each carbon atoms. "Vinyl" is a carbon-carbon double bond with the formula R-CH=CH2, where R is a carbon atom. "Vinylidene" is a carbon-carbon double bond with the formula R1(R2)C=CH2, where R1 and R2 are each one or more carbon atoms bonded to a hydrogen atom. The total degree of unsaturation (or "total") is the sum of vinylene, trisubstituted, vinyl, and vinylidene in the polymer. The chemical structures of vinylene, trisubstituted vinyl, and vinylidene are shown in Figure 1. 1 Samples for 1H NMR were prepared in a 10 mm NMR tube by adding approximately 3 g of a 50 / 50 mixture of 1,1,2,2-tetrachloroethane (TCE-d2) and perchloroethylene (PCE) containing 0.001 M Cr(AcAc)3 to approximately 0.10 g of a polymer sample. 1 ¹H NMR was performed using a Bruker 600MHz spectrometer equipped with a 10mm high-temperature cryoprobe at a sample temperature of 120°C. Spectra were obtained by performing two experiments: a control spectrum to quantify total polymer protons, and a double pre-saturation experiment to suppress strong polymer backbone peaks and enable a highly sensitive spectrum for quantifying end groups. The control spectrum was performed with a ZG pulse, 16 scans, AQ 1.64 seconds, and D1 14 seconds. The double pre-saturation experiment was performed with a modified pulse sequence, 64 scans, AQ 1.64 seconds, pre-saturation delay 2 seconds, and relaxation delay 12 seconds.

[0028] Density was measured according to ASTM D792, Method B. The results were recorded in grams per cubic centimeter (g / cc).

[0029] The dielectric constant and dissipation rate were measured at 2.47 GHz using a high-frequency resonant cavity according to D924-08.

[0030] Dynamic Mechanical Spectroscopy (DMS). DMS was used to measure the polymer melt viscosity. The resin was compressed into a 3mm thick x 1-inch circular plate at 350°F for 5 minutes under a pressure of 25,000 psi in air. The sample was then removed from the compressor and allowed to cool on a counter. Under nitrogen purging, a constant temperature-frequency sweep was performed using TA Instruments' Advanced Rheometric Expansion System (ARES) with 25mm diameter parallel plates. The sample was placed on the plates and melted at 190°C for 5 minutes. The plates were then closed to a 2mm gap, the sample was trimmed (excess sample extending beyond the circumference of the 25mm diameter plate was removed), and the test was initiated. This method incorporated an additional 5-minute delay to allow for temperature equilibrium. Experiments were conducted over a frequency range of 0.1–100 radians / second at 190°C. Strain amplitude was constant at 10%. Complex viscosity η * From these data, tan(δ), i.e., tan delta, viscosity at 0.1 radians / second (V0.1), viscosity at 100 radians / second (V100), and viscosity ratio (V0.1 / V100) were calculated.

[0031] Elemental analysis. Boron elemental analysis was determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). 0.25 grams (nominal) was weighed into a 15 mL Teflon test tube, and a double sample was prepared for ICP metal analysis by adding 1 ml (mL) of deionized water, 2 mL of concentrated nitric acid, and 0.15 mL of hydrofluoric acid. The test tubes were then placed in a Milestone Ultrawave sealed container microwave decomposition system and decomposed at 240°C for 30 minutes. After decomposition, the sample was removed from the microwave and diluted to a final volume of 10 mL using deionized water. The sample was transferred to an autosampler test tube and prepared for ICP-MS analysis.

[0032] The prepared solutions were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) with an Agilent 7900x instrument. The instrument was calibrated over the range of 0–10 ng / mL using calibration standards (SPEX CertiPrep, Multi-element Standards) prepared in 5% nitric acid and 1.5% hydrofluoric acid at concentrations of 0, 0.5, 1.0, 5.0, and 10 ng / mL. The operating conditions of the instrument used for this analysis are shown in Table A below. Where possible, multiple isotopes of the analyte were monitored in gas-free, hydrogen, and helium modes. This was done in case of potential interference from the sample matrix.

[0033] [Table 1]

[0034] All other elements were determined using Neutron Activation Analysis (NAA). A double sample was prepared by transferring approximately 3.5 grams of resin to a pre-washed 2-drum polyethylene vial. A double fluorine standard was prepared in a similar vial from NIST fluorobenzoic acid standards. The fluorine standard was diluted to 6 mL with 2-propanol and heat-sealed. Similarly, Mg, Al, Ti, Hf, Cr, and Zr standards were prepared from their standard solutions (SPEX Certi.pure) and placed in 2-drum polyethylene vials. They were diluted to 6 mL with milli-Q pure water and the vials were heat-sealed. The samples and standards were then analyzed using a Dow Mark I TRIGA nuclear reactor according to the standard NAA procedure for these elements, Global-SOP-01101.02. For the analysis of Mg, Al, Ti, Hf, Cr, and Zr, samples were transferred to unirradiated vials before gamma-ray spectroscopy. For fluorine, background contributions were addressed by using clean vials and performing multiple runs in different vials. The reactions and experimental conditions used for these elements are summarized in Table B below. Elemental concentrations were calculated using Canberra® software and standard comparison techniques.

[0035] [Table 2]

[0036] Gel permeation chromatography. The average molecular weight and molecular weight distribution of ethylene-based polymers were determined by gel permeation chromatography (GPC). The chromatography system consisted of a high-temperature GPC chromatograph from PolymerChar GPC-IR (Valencia, Spain) equipped with an internal IR5 infrared detector (IR5), and a 4-capillary viscometer (DV) coupled to a Precision Detectors (now Agilent Technologies) 2-angle laser light scattering (LS) detector Model 2040. A 15-degree angle was used for all absolute light scattering measurements. The autosampler oven compartment was set to 160°C, and the column and detector compartments were set to 150°C. The columns used were four Agilent "Mixed A" 30 cm, 20 micron linear mixed-bed columns. The chromatography solvent used was 1,2,4-trichlorobenzene, containing 200 ppm butylated hydroxytoluene (BHT). The solvent source was spurged with nitrogen. The injection volume used was 200 microliters, and the flow rate was 1.0 ml / min.

[0037] The GPC column set was calibrated using 21 polystyrene standards with narrow molecular weight distributions ranging from 580 to 8,400,000, placed in six "cocktail" mixtures with at least a 10-fold gap between individual molecular weights. The standards were purchased from Agilent Technologies. Polystyrene standards were prepared using 0.025 grams in 50 ml of solvent for molecular weights above 1,000,000, and 0.05 grams in 50 ml of solvent for molecular weights below 1,000,000. The polystyrene standards were pre-dissolved at 80°C with gentle stirring for 30 minutes, then cooled, and the room temperature solution was transferred to an autosampler dissolution oven at 160°C for 30 minutes and cooled. The peak molecular weights of the polystyrene standards were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).

[0038]

number

[0039] A quintic polynomial was used to fit each polyethylene equivalent calibration point.

[0040] The total plate count of the GPC column set was performed using decane introduced into blank samples via a micropump controlled by the PolymerChar GPC-IR system. The plate count of the chromatography system should be greater than 18,000 for four Agilent "Mixed A" 30 cm² 20 micron linear mixed-bed columns.

[0041] The sample was prepared semi-automatically using PolymerChar's "Instrument Control" software, with a target weight of 2 mg / mL. The solvent (containing 200 ppm BHT) was added to a vial with a pre-nitrogen-spurged septum cap via a PolymerChar high-temperature autosampler. The sample was dissolved at 160°C for 2 hours under "low-speed" shaking.

[0042] Mn (GPC) , Mw (GPC) , and Mz (GPC) The calculations were based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph, according to Equations 2 to 4, using PolymerChar's GPCOne® software, IR chromatograms with baselines subtracted at each equally spaced data acquisition point (i), and polyethylene equivalent molecular weights obtained from the narrow standard calibration curve for point (i) in Equation 1.

[0043]

number

[0044] To monitor deviations over time, a flow rate marker (decane) was introduced into each sample via a micropump controlled by the PolymerChar GPC-IR system. Using this flow rate marker (FM), the pump flow rate (nominal flow rate) for each sample was linearly corrected by matching the RV (RV(FM sample)) of each decane peak in the sample with the RV (RV(FM calibrated)) of the calibrated decane peak in the narrow standard material. It was assumed that any temporal change in the decane marker peak corresponds to a linear shift in the flow rate (effective flow rate) over the entire run. After calibrating the system based on the flow rate marker peaks, the effective flow rate (relative to the narrow standard calibration) was calculated using Equation 5. The processing of the flow rate marker peaks was performed via PolymerChar GPCOne® software. An acceptable flow rate correction is required so that the effective flow rate is within ±0.5% of the nominal flow rate. Effective flow rate = Nominal flow rate * (RV(FM calibrated) / RV(FM sample))(Equation 5) High-temperature creep was measured at 200°C for 15 minutes according to ICEA T-28-562. The elongation of the sample from its initial value was recorded after exposing the sample to the oven for 15 minutes without removing it from the oven.

[0045] Melt Index. As used herein, the term “Melt Index” or “MI” refers to a measure of how easily a thermoplastic polymer flows when in a molten state. The Melt Index, or “I2”, is measured according to ASTM D1238 Method A, conditions 190°C / 2.16 kg, and reported as grams eluted per 10 minutes (g / 10 min). 21 The value is measured according to ASTM D 1238 Method A, conditions 190°C / 21.6 kg, and reported as grams eluted per 10 minutes (g / 10 min). Melt flow rate ratio "I 21 / I2" is I 21 It is calculated from these individual values ​​by dividing the value by the I2 value. The melt flow rate ratio is dimensionless.

[0046] The shear viscosity index (SHI) was calculated as the ratio of the dynamic viscosity measured at 0.1 radians / second and 190°C to the dynamic viscosity measured at 100 radians / second.

[0047] Surface roughness. The surface roughness of the cable jacket was evaluated by the average surface roughness Ra, measured using a Mitutoyo Surftest SJ-400 surface roughness tester. Results are reported in microinches or μ-in.

[0048] Volume resistivity (or resistivity) was measured using a Hewlett-Packard High Resistance Meter with a 50 mil plaque, according to ASTM D257-07. Results are reported in ohms / cm. [Modes for carrying out the invention]

[0049] This disclosure provides an insulating layer. In one embodiment, the insulating layer comprises a silane-crosslinked polyethylene composition. The silane-crosslinked polyethylene composition comprises (A) 90% to 99% by weight of a base bimodal ethylene / C4-C8α-olefin copolymer. The base bimodal ethylene / C4-C8α-olefin copolymer before silane crosslinking has one, some, or all of the following properties: namely (i) a density of 0.910 g / cc to 0.930 g / cc, and (ii) a density of 90 to 140. 21 The ratios are (iii) Mw / Mn of 7.0 to 15.0 and (iv) SHI (n0.1 / n100) of 5.0 to 30.0. The silane crosslinked polyethylene composition also contains (B) 0.5% to 2.0% by weight of hydrolyzed silane monomer. The insulating layer has properties selected from one, some, or all of the following: (1) surface roughness / roughness Ra value of 50 μ-in to 150 μ-in, (2) dissipation rate of 0.0001 radians or less, (3) dielectric constant of 2.0 to less than 2.29, (4) volume resistivity of 5.00E+16 to 8.00E+17, and (5) high-temperature creep value of 20% to 30%.

[0050] This composition contains silane-crosslinked polyethylene. The silane-crosslinked polyethylene contains a base bimodal ethylene / C4-C8α-olefin copolymer. As used herein, "base bimodal ethylene / C4-C8α-olefin copolymer" refers to the ethylene / C4-C8α-olefin copolymer before it is crosslinked with silane. When referring to the bimodal ethylene / C4-C8α-olefin copolymer, the terms "base" and "pre-crosslinked" are used interchangeably.

[0051] 1. Bimodal ethylene / C4-C8α-olefin copolymer This composition contains a base bimodal ethylene / C4-C8α-olefin copolymer. As used herein, "base bimodal ethylene / C4-C8α-olefin copolymer" refers to the ethylene / C4-C8α-olefin copolymer before crosslinking.

[0052] Base ethylene / α-olefin copolymer is a bimodal ethylene / α-olefin copolymer. α-olefin is C3-C 20The comonomer is a C4-C8 comonomer. Non-limiting examples of suitable α-olefin comonomers include butene, hexene, and octene. A "bimodal ethylene / α-olefin copolymer" is an ethylene / C4-C8α-olefin copolymer having two distinct populations, which often exhibit two peaks on the GPC curve. These distributions are viewed statistically, i.e., as statistical distributions. Thus, if there is one peak, the distribution has one mode and is unimodal. Two peaks are bimodal. Two or more peaks are multimodal. In one embodiment, a bimodal ethylene / C4-C8α-olefin copolymer has a high molecular weight portion and a low molecular weight portion, thereby defining the "bimodal molecular weight distribution". The "high molecular weight portion" of the bimodal ethylene / α-olefin copolymer has a molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol, while the "low molecular weight portion" of the bimodal ethylene / α-olefin copolymer has a molecular weight (Mw) of 1,000 g / mol to less than 100,000 g / mol. The bimodal ethylene / α-olefin copolymer has a molecular weight (Mw / Mn) of 7.0 to 15.0, or 7.0 to 13.0, or 7.1 to 12.0. In one embodiment, the bimodal ethylene / C4-C8 α-olefin is an ethylene / octene copolymer.

[0053] In one embodiment, a base bimodal ethylene / C4-C8α-olefin copolymer is produced by a solution polymerization process. “Solution polymerization process” refers to one or more continuous solution polymerization reactors operating under polymerization conditions, wherein the polymer (e.g., polyethylene) is produced from a monomer (e.g., ethylene) and a comonomer (e.g., C3-C4-C4-C4-α-olefin copolymer). 20 The polymer is formed in a liquid polymerization solvent to which α-olefins (or C4-C8α-olefins) are added together with a catalyst / co-catalyst (activator). As used herein, the term "polymerization conditions" refers to process parameters in which ethylene and comonomers are copolymerized in the presence of a catalytic system. Polymerization conditions include, for example, those that affect polymerization reactor conditions (reactor type), reactor pressure, reactor temperature, reagent and polymer concentrations, solvent, support, residence time and distribution, molecular weight distribution and polymer structure.

[0054] In one embodiment, the base bimodal ethylene / α-olefin copolymer is produced in a two-reactor solution polymerization system, thereby allowing effluent from the first solution polymerization reactor to flow into the second solution polymerization reactor. The first catalyst and co-catalyst (or first activator) are injected into the first solution polymerization reactor, and the second catalyst and co-catalyst (or second activator) are injected into the second solution polymerization reactor. The first and second catalysts are either chromium-free or chromium-free. The first and second co-catalysts are either boron-free and fluorine-free or fluorine-free. Some boron and / or fluorine species are known to be detrimental to the insulating properties of coated conductors.

[0055] In one embodiment, a two-reactor solution polymerization system is used to obtain the following characteristics, namely (i) Densities of 0.910 g / cc to 0.930 g / cc, or 0.915 to 0.925 g / cc, and / or (ii) 90-140, or 92-135, or 93-130 21 / I2 ratio, and / or (iii) Mw / Mn of 7.0-15.0, or 7.1-13.0, or 7.1-12.0, and / or (iv) Mz less than 600,000 g / mol, or 100,000 g / mol to 500,000 g / mol, or 200,000 g / mol to 400,000 g / mol, or 300,000 g / mol to 400,000 g / mol, and / or (v) SHI values ​​(η0.1 / η100) of 5.0~30.0, or 7.0~28, or 8.0~27, or 9.0~23.0, and / or (vi) Boron in 0 part pervilions (ppb), or greater than 0 ppb to 80 ppb, or 1 ppb to 50 ppb. (vii) 0 parts per million (ppm), or greater than 0 ppm to 5 ppm, or 1 ppm to 3 ppm of fluorine, and / or (viii) Chromium at 0 ppb, or chromium at more than 0 ppb but less than 100 ppb, and / or (ix) I2 values ​​of 0.6g / 10 min to 1.2g / 10 min, or 0.7g / 10 min to 1.1g / 10 min, and / or (x) End vinyl content of 0.22 / 1000 carbon atoms (1000C) to 0.70 / 1000C, or 0.22 / 1000C to 0.50 / 1000, or 0.23 / 1000C to 0.4 / 1000C, and / or (xi) A base bimodal ethylene / α-olefin copolymer is produced as an ethylene / C4-C8 α-olefin copolymer or ethylene / octene copolymer having one, some, or all of the total unsaturation degrees of 0.25 / 1000C to 1.0 / 1000C, or 0.25 / 1000C to 0.45 / 1000C (hereinafter referred to as Composition 1).

[0056] The insulating layer contains 90% to 99% by weight, or 91% to 95% by weight, of base ethylene / C4-C8α-olefin copolymer.

[0057] 2. Silane bridge The silane crosslinked polyethylene composition also contains a hydrolyzable silane monomer.

[0058] The base bimodal ethylene / C4-C8α-olefin copolymer is crosslinked with a reactive unsaturated silane compound and a moisture-curing catalyst (also interchangeably called a "crosslinkable polyethylene composition"). A non-limiting example of a silane crosslinking process is the MONOSIL process.

[0059] In one embodiment, a base bimodal ethylene / C4-C8α-olefin copolymer, a free radical initiator, a reactive silane compound, and a moisture-curing catalyst (also known as a silanol condensation catalyst) are fed into an extruder and melt-extruded into a desired form, such as an insulating layer for wires or cables, and subsequently thermo-cured and / or moisture-cured.

[0060] In one embodiment, the free radical initiator is an organic peroxide. Non-limiting examples of suitable organic peroxides include monofunctional and difunctional peroxides. As used herein, “monofunctional peroxide” means a peroxide having a pair of covalently bonded oxygen atoms (e.g., having the structure ROOR). As used herein, “difunctional peroxide” means a peroxide having two pairs of covalently bonded oxygen atoms (e.g., having the ROOROOR structure). In one embodiment, the organic peroxide is a monofunctional peroxide. Examples of organic peroxides include dicumyl peroxide ("DCP"), tert-butyl peroxybenzoate, di-tert-amyl peroxide ("di-tert-amyl peroxide, DTAP"), bis(t-butyl-peroxyisopropyl)benzene ("bis(t-butyl-peroxy isopropyl)benzene, BIM"), isopropylcumyl t-butyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane-3, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, isopropylcumyl peroxide, butyl 4,4-di(tert-butylperoxy)valerate, di(isopropylcumyl) peroxide, and mixtures of two or more of these. In various embodiments, only a single type of organic peroxide is used. In one embodiment, the organic peroxide is dicumyl peroxide. The organic peroxide may be present in the crosslinkable polyethylene composition in an amount of 0.05% to 5% by weight, or 0.07 to 3% by weight, 0.07 to 1.5% by weight, 0.1 to 0.5% by weight, or 0.1% to 0.4% by weight, based on the total weight of the crosslinkable polyethylene composition.

[0061] In one embodiment, the reactive unsaturated silane compound is a hydrolyzable silane monomer. A hydrolyzable silane monomer has a hydrolyzable silane group. "Hydrolyzable silane group" and similar terms refer to a silane group that reacts with water. These include alkoxysilane groups on a monomer or polymer that can be hydrolyzed to produce a silanol group, which can then be condensed to crosslink the monomer or polymer. Ethylene / C4-C8α-olefin copolymers are crosslinked by functionalization with hydrolyzable silane groups. In the presence of water, hydrolyzable silane groups undergo hydrolysis and condensation reactions to generate Si-O-Si bonds and form a crosslinking network between ethylene / C4-C8α-olefin copolymer chains (also known as moisture crosslinking or moisture curing). Functionalization of ethylene / C4-C8α-olefin copolymers can be achieved either by copolymerizing monomers having hydrolyzable silane groups with the above-mentioned ethylene and comonomers, or by grafting hydrolyzable silane groups onto the backbone of an ethylene-based interpolymer in a post-reactoral process.

[0062] In one embodiment, the hydrolyzable silane monomer has structure (1)

[0063] [ka] (In the formula, R' is a hydrogen atom or a methyl group, x is either 0 or 1, n is an integer between 1 and 12 (including both ends), or between 1 and 4, and each R'' independently has a hydrolyzable organic group, for example, an alkoxy group having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group (e.g., phenoxy), an aryloxy group (e.g., benzyloxy), an aliphatic acyloxy group having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), an amino group or a substituted amino group (alkylamino, arylamino), or a lower alkyl group having 1 to 6 carbon atoms (including both ends), provided that at least one of the three R'' groups is alkyl.

[0064] In one embodiment, a hydrolyzable silane monomer is grafted onto a base ethylene / C4-C8α-olefin copolymer using a suitable amount of organic peroxide and a moisture-curing catalyst. Suitable hydrolyzable silane monomers include unsaturated silanes containing an ethylenically unsaturated hydrocarbyl group, e.g., vinyl, allyl, isopropenyl, butenyl, cyclohexenyl, or gamma(meth)acrylooxyallyl group, and a hydrolyzable group, e.g., hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group. Examples of hydrolyzable groups include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and alkyl or arylamino groups. Preferred silanes are unsaturated alkoxysilanes that can be grafted onto the polymer or copolymerized in a reactor with other monomers (e.g., ethylene and acrylate). These silanes and methods for preparing them are further described in U.S. Patent No. 5,266,627 by Meverden et al. Suitable hydrolyzable silane monomers include, but are not limited to, vinyltrimethoxysilane ("VTMS"), vinyltriethoxysilane ("VTES"), vinyltriacetoxysilane, and gamma-(meth)acrylooxypropyltrimethoxysilane. The hydrolyzable silane monomer constitutes 0.2% to 10% by weight, or 0.5% to 5.0% by weight, or 1.0% to 3.0% by weight, or 1.0% to 1.5% by weight of the crosslinked polyethylene composition, where the weight percentage is based on the total weight of the crosslinked polyethylene composition.

[0065] In one embodiment, the hydrolyzable silane monomer undergoes hydrolysis and condensation in the presence of water to form Si-O-Si bonds between polymer chains. Upon hydrolysis, the hydrolyzable silane monomer becomes a "hydrolyzed silane monomer," and then a crosslinking network is formed between the polymer chains by condensation, thereby forming a "silane crosslinked polyethylene composition."

[0066] In one embodiment, a peroxide-initiated reaction between vinyltrimethoxysilane and a base bimodal ethylene / C4-C8α-olefin copolymer yields a graft polymer having a polyethylene backbone structure containing pendant ethyltrimethoxysilyl moieties. In the crosslinking reaction, the methoxy groups are hydrolyzed to form methanol and pendant ethyldimethoxysilanolyl groups, which condense with other ethyldimethoxysilanolyl groups to remove water, forming Si-O-Si bonds between the pendant silyl moieties, and thus forming a silane-crosslinked polyethylene composition. A moisture-curing catalyst may be included in the catalyst masterbatch blend, and the catalyst masterbatch is included in the crosslinkable polyethylene composition. Non-limiting examples of suitable catalyst masterbatches include those sold under the trade name SI-LINK® by The Dow Chemical Company, including SI-LINK® DFDA-5481 Natural and SI-LINK® AC DFDA-5488 NT. In one embodiment, the crosslinkable polyethylene composition contains a moisture-curing catalyst masterbatch ranging from 0.001% by weight, or 0.01% by weight, or 0.5% by weight, or 1.0% by weight, or 2.0% by weight, or 3.0% by weight, or 4.0% by weight, to 5.0% by weight, or 6.0% by weight, or 7.0% by weight, or 8.0% by weight, or 9.0% by weight, or 10.0% by weight, based on the total weight of the polymer composition. The silane-grafted bimodal ethylene / C4-C8α-olefin copolymer is cured in a water bath to form a silane-crosslinked polyethylene composition.

[0067] In one embodiment, the moisture-curing catalyst is dibutyltin dilaurate.

[0068] In one embodiment, the insulating layer is (A) The following characteristics, (i) a density of 0.910 g / cc to 0.930 g / cc, or 0.915 to 0.925 g / cc, and / or (ii) 90-140, or 92-135, or 93-130 21 / I2 ratio, and / or (iii) Mw / Mn of 7.0-15.0, or 7.1-13.0, or 7.1-12.0, and / or (iv) Mz less than 600,000 g / mol, or 100,000 g / mol to 500,000 g / mol, or 200,000 g / mol to 400,000 g / mol, or 300,000 g / mol to 400,000 g / mol, and / or (v) SHI values ​​(η0.1 / η100) of 5.0~30.0, or 7.0~28, or 8.0~27, or 9.0~23.0, and / or (vi) Boron in 0 part pervilions (ppb), or greater than 0 ppb to 80 ppb, or 1 ppb to 50 ppb. (vii) 0 parts per million (ppm), or greater than 0 ppm to 5 ppm, or 1 ppm to 3 ppm of fluorine, and / or (viii) 0 ppm of chromium, or chromium greater than 0 ppb but less than 100 ppb, and / or (ix) I2 values ​​of 0.6g / 10 min to 1.2g / 10 min, or 0.7g / 10 min to 1.1g / 10 min, and / or (x) End vinyl content of 0.22 / 1000 carbon atoms (1000C) to 0.70 / 1000C, or 0.22 / 1000C to 0.50 / 1000, or 0.23 / 1000C to 0.4 / 1000C, and / or (xi) 90% to 99% or 91% to 95% by weight of a pre-silane crosslinked base bimodal ethylene / C4-C8α-olefin copolymer having one, some, or all of the total unsaturation degrees of 0.25 / 1000C to 1.0 / 1000C, or 0.25 / 1000C to 0.45 / 1000C, and (hereinafter referred to as Composition 1), (B) A silane crosslinked polyethylene composition comprising 0.5% to 2.0% by weight or 1.0% to 1.5% by weight of hydrolyzed silane monomer (e.g., VTMS), The insulating layer has the following characteristics: (1) Surface roughness Ra value of 50 μ-in to 150 μ-in, or 52 μ-in to 125 μ-in, and / or (2) Dissipation rate of 0.0001 radians or less, and / or (3) Dielectric constants of 2.0 to less than 2.29, and / or (4) 5.00 x 10 16 ~8.0 x 10 17 , or 8.0 x 10 16 ~6.0 x 10 17 The volume resistivity, and / or (5) Having one, some, or all of the following high-temperature creep values: 20% to 30%, or 21% to 26%.

[0069] In one embodiment, the catalyst of composition 1 is derived from a catalyst masterbatch, and the insulating layer contains 3% to 6% by weight of a second polyethylene (carrier resin of the catalyst masterbatch), based on the total weight of the insulating layer. The second polyethylene is LLDPE, LDPE, or a combination thereof.

[0070] The insulating layer may contain one or more optional additives. If present, non-limiting examples of suitable additives include antioxidants, colorants, corrosion inhibitors, lubricants, moisture-curing catalysts, ultraviolet (UV) absorbers or stabilizers, anti-blocking agents, coupling agents, compatibilizers, plasticizers, fillers, processing aids, and combinations thereof.

[0071] 3. Cable This disclosure provides a cable. In one embodiment, the cable includes (i) a conductor and (ii) an insulating layer on the conductor. The insulating layer is (A) The following characteristics, (i) a density of 0.910 g / cc to 0.930 g / cc, or 0.915 g / cc to 0.925 g / cc, and / or (ii) 90-140, or 92-135, or 93-130 21 / I2 ratio, and / or (iii) Mw / Mn of 7.0-15.0, or 7.1-13.0, or 7.1-12.0, and / or (iv) Mz less than 600,000 g / mol, or 100,000 g / mol to 500,000 g / mol, or 200,000 g / mol to 400,000 g / mol, or 300,000 g / mol to 400,000 g / mol, and / or (v) SHI values ​​(η0.1 / η100) of 5.0~30.0, or 7.0~28, or 8.0~27, or 9.0~23.0, and / or (vi) Boron in 0 part pervilions (ppb), or greater than 0 ppb to 80 ppb, or 1 ppb to 50 ppb. (vii) 0 parts per million (ppm), or greater than 0 ppm to 5 ppm, or 1 ppm to 3 ppm of fluorine, and / or (viii) 0 ppm of chromium, or chromium greater than 0 ppb but less than 100 ppb, and / or (ix) I2 values ​​of 0.6g / 10 min to 1.2g / 10 min, or 0.7g / 10 min to 1.1g / 10 min, and / or (x) End vinyl content of 0.22 / 1000C to 0.70 / 1000C, or 0.22 / 1000C to 0.50 / 1000, or 0.23 / 1000C to 0.4 / 1000C, and / or (xi) 90% to 99% or 91% to 95% by weight of a pre-silane crosslinked base bimodal ethylene / C4-C8α-olefin copolymer having one, some, or all of the total unsaturation degrees of 0.25 / 1000C to 1.0 / 1000C, or 0.25 / 1000C to 0.45 / 1000C, and (hereinafter referred to as Composition 1), (B) A silane crosslinked polyethylene composition comprising 0.5% to 2.0% by weight or 1.0% to 1.5% by weight of a hydrolyzed silane monomer or a hydrolyzed silane monomer formed from vinyltrimethoxysilane. The insulating layer has the following properties: (1) Surface roughness Ra value of 50 μ-in to 150 μ-in, and / or (2) Dissipation rate of 0.0001 radians or less, and / or (3) Dielectric constants of 2.0 to less than 2.29, and / or (4) Volume resistivity of 5.00E+16 to 8.00E+17, and / or (5) High-temperature creep value of 20% to 30%, and (1) to (5) have one, some, or all of any combination of these.

[0072] As used herein, "conductor" refers to one or more wires or fibers for conducting heat, light, and / or electricity. A conductor may be a single wire / fiber or multiple wires / fibers, and may be in stranded or tubular form. Non-limiting examples of suitable conductors include metals such as silver, gold, copper, carbon, and aluminum. A conductor may also be an optical fiber made from either glass or plastic.

[0073] As used herein, “cable” refers to at least one wire or optical fiber within a sheath, for example, within an insulating layer or protective outer jacket. Typically, a cable is two or more wires or two or more optical fibers bonded together, typically within a common insulating layer or insulating sheath and / or protective jacket. Individual wires or fibers within the sheath may be exposed, covered, or insulated. A combined cable may contain both electrical wires and optical fibers. A cable may be designed for telecommunications applications. A cable may be designed for low-voltage, medium-voltage, and / or high-voltage applications. AC cables may be prepared according to this disclosure and may be low-voltage, medium-voltage, high-voltage, or ultra-high-voltage cables. Furthermore, DC cables may be prepared according to this disclosure and may include high-voltage or ultra-high-voltage cables. An insulating conductor typically includes a conductive core covered by an insulating layer. The conductive core may be solid or braided (e.g., a bundle of threads). Some insulating conductors may also include one or more additional elements such as a semiconductor layer (or multiple layers) and / or a protective cover (e.g., winding, tape, or sheath). Examples include coated metal wires and electrical cables, including those used at low voltage ("LV", 0 to <5 kilovolts (kV) for distribution / transmission applications), medium voltage ("MV", 5 to <69kV), high voltage ("HV", 69 to 230kV), and ultra-high voltage ("EHV", >230kV). AEIC / ICEA standards and / or IEC test methods can be used to evaluate power cables.

[0074] The cable comprises a conductor and an insulating layer that is on or surrounding the conductor. The insulating layer comprises a silane-crosslinked polyethylene composition (as previously disclosed herein) comprising (A) a bimodal ethylene / C4-C8α-olefin copolymer and (B) a hydrolyzed silane monomer. In one embodiment, the silane-crosslinked polyethylene composition insulating layer is in direct contact with the conductor. The term "direct contact" refers to a layer configuration in which the insulating layer is located directly adjacent to the conductor and there is no intervening layer or structure between the conductor and the insulating layer. Alternatively, the insulating layer is in indirect contact with the conductor.

[0075] Rather than being limiting, some embodiments of this disclosure are described in detail in the following examples. [Examples]

[0076] 1. Polymerization of bimodal ethylene / C4-C8α-olefin copolymers Before introducing them into the reaction environment, all raw materials (monomers and comonomers) and the process solvent (high-purity isoparaffin solvent with a narrow boiling point range, Isopar-E) are purified using molecular sieves. Hydrogen is supplied under pressure as a high-purity grade and is not purified further. The monomer feed stream to the reactor is pressurized to exceed the reaction pressure via a mechanical compressor. The solvent and comonomer feed streams are pumped to a pressure higher than the reaction pressure. Individual catalyst components are manually batch-diluted with the purified solvent and pressurized to exceed the reaction pressure. All reaction feed streams are measured using a mass flow meter and controlled independently by a computer-automated valve control system.

[0077] Two reactor systems are used in series. The first continuous solution polymerization reactor consists of a liquid-filled, non-adiabatic, isothermal circulating loop reactor that mimics a continuous stirred tank reactor (CSTR) with heat removal. All fresh solvent, monomer, comonomer, hydrogen, and catalyst component feeds are independently controllable. All fresh feed flows to the first reactor (solvent, ethylene monomer, octen comonomer, and hydrogen) are temperature-controlled to maintain a single solution phase by passing the feed flows through a heat exchanger. All fresh feeds to the first polymerization reactor are injected into the reactor at three positions where the reactor volume between each injection position is approximately equal. The fresh feed is controlled so that each injector receives one-third of the total mass flow rate of the fresh feed. Catalyst components are injected into the polymerization reactor at two different positions with similar reactor volume between each injection position. The primary catalyst component feed is computer-controlled to maintain reactor monomer conversion at a specified target value. Co-catalyst components are supplied to maintain a specific Al concentration in the reactor. Immediately after each reactor feed or catalyst injection point, the feed material is mixed with the circulating polymerization reactor contents by a static mixing element. The reactor contents are continuously circulated at the temperature of the coolant side, which maintains an isothermal reaction environment at a specified temperature, through a heat exchanger, which plays a role in removing most of the reaction heat. The circulation around the reactor loop is provided by a pump.

[0078] The second continuous solution polymerization reactor consists of a liquid-filled, non-adiabatic, isothermal circulating loop reactor that mimics a continuous stirred tank reactor (CSTR) with heat removal. All fresh solvent, ethylene monomer, octen comonomer, hydrogen, and catalyst component feeds are independently controlled. All fresh feed flows to the second reactor (solvent, ethylene monomer, octen comonomer, and hydrogen) are temperature-controlled by passing the feed flows through a heat exchanger. All fresh feeds to the second polymerization reactor are injected into the reactor at two locations where the reactor volume between each injection position is approximately equal. Fresh feeds are controlled by each injector, receiving half of the total mass flow of fresh feeds. Catalyst components are injected into the polymerization reactor through injection stingers. The primary catalyst component feed is computer-controlled to maintain reactor monomer conversion at a specified target value. Co-catalyst components are supplied based on a calculated, specified molar ratio to the primary catalyst component. Immediately after the injection point of each reactor feed, the feed is mixed with the circulating polymerization reactor contents by a static mixing element. The reactor contents are continuously circulated at the temperature of the coolant side, which plays a role in maintaining an isothermal reaction environment at a specified temperature, through a heat exchanger, which plays a role in removing most of the reaction heat. Circulation around the second reactor loop is provided by a pump.

[0079] The effluent from the first polymerization reactor (containing solvent, ethylene monomer, octen comonomer, hydrogen, catalyst components, and polymer) exits the first reactor and is added to the second reactor. Exiting the second reactor loop, the second / final reactor effluent enters a post-reactoral insulated pipe with a total volume of approximately 21.4% of the combined total volume of the two loop reactors. The reaction continues through this pipe before entering the mixing zone, where it is inactivated by the addition and reaction of a suitable reagent (water). At this same reactor outlet location, other additives such as tetrakis(methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate))methane are added for polymer stabilization during production and extrusion.

[0080] Following catalyst deactivation and additive addition, the reactor effluent enters a devolving system where the polymer is removed from the non-polymer stream. The isolated polymer molten material is pelletized and collected. The non-polymer stream passes through various devices that separate most of the ethylene removed from the system. Most of the solvent and unreacted comonomers are recycled back into the reactor after passing through a purification system. Small amounts of solvent and comonomers are purged from the process.

[0081] The reactor feed data flow corresponding to the values ​​in Table 1A used to generate the examples is graphically represented in Figure 2. The data is presented to take into account the complexity of the solvent recycling system and to allow for easier processing of the reaction system as a through-flow diagram. The polymerization conditions are shown in Table 1A below, and the catalyst and co-catalyst components are listed in Table 1B below.

[0082] Table 1A below shows the polymerization conditions for the comparative sample ("CS") and the examples of the present invention ("IE"), as well as the ethylene monomer and octencomonomer. In Table 2A, comparative sample 1 is DFDA-7530 NT, and comparative sample 2 is DFDK-6050 NT.

[0083] [Table 3]

[0084] [Table 4]

[0085] The properties of the base bimodal ethylene / α-olefin C4-C8α-olefin are shown in Tables 2A and 2B below.

[0086] [Table 5] * Butene comonomer (all other samples are octen comonomers) $ per 1000C @ CS1 is DFDA-7530 NT. ^ CS2 is DFDK-6050 NT.

[0087] [Table 6] * Butene comonomer, % g / mol, # η0.1 / η100 + Ra was measured for the cable jacket extruded onto the wire. @ CS1 is DFDA-7530 NT. ^ CS2 is DFDK-6050 NT.

[0088] 2. Silane bridge The MONOSIL formulation was first prepared by immersing base resin pellets in VTMS (UniqueChem) and 0.1 wt% Luperox 101 (Arkema), and then mixing these pellets with catalyst pellets (DFDA-5481 from Dow) in a Brabender single-screw extruder with a double mixing head, extruding at 150°F / 170°F / 190°F / 195°F, 40 rpm, and through a 40 / 40 mesh screen pack. The resulting 4-inch wide and 50-mil thick tape (recreating the insulating layer) was then cured in a 90°C water bath for 4 hours.

[0089] The properties of the insulating layer composed of silane-crosslinked polyethylene are shown in Table 3 below.

[0090] [Table 7] & Ohm / cm

[0091] Examples 1 to 5 of the present invention have high electrical resistivity (5.0 x 10 16 Since it exceeds (), CS2 has a lower electrical resistivity (2.85 × 10⁻⁶). 16 Unlike the previous example, Examples 1-5 of the present invention are suitable for electrical insulation. Fluorine is present in CS2 (7 ppm) in Table 2B, while each of IE1-5 does not contain fluorine (<3 ppm or 0 ppm). CS2 also has the highest dielectric constant (2.2917) compared to the dielectric constant range of IE1-5 (2.2785-2.2874). Despite the different catalyst activators, the vinyl content in each of IE1-5 (0.21-0.33) (from Table 2A) exceeds that of CS2 (0.18). Surprisingly, the lower vinyl content of each of IE1-5 (0.21-0.33) compared to the vinyl content of CS1 (0.76) had little effect on crosslinking, as measured by high-temperature creep. The high-temperature creep values ​​for each of IE1-5 were less than 30%, indicating a high degree of crosslinking.

[0092] The broad molecular weight distribution (Mw / Mn) (7.03~10.58) for each of IE1-5 is much larger than that of CS2 (6.18) and CS3 (4.52). The Mw / Mn (7.03~10.58) of IE1-5 approaches and exceeds that of gas-phase LLDPE (10.35) in CS1. The gas-phase synthesis of CS1 is confirmed by its chromium content (440 ppm) in Table 2B, while each of IE1-5 contains no chromium (less than 100 ppm Cr, or 0 ppm Cr). Nevertheless, the broad Mw / Mn (7.03~10.58) achieved for each of IE1-5 is high η for IE1-5. 0.1 / η 100 As seen in the values ​​(9.5~25.8), and the melt flow ratio (I) for CS2 (52.8) and CS3 (53.4) 21 / I2) and I for gas-phase LLDPE in CS1(83.2) 21 Compared to the I2 ratio, the melt flow ratio for each of IE1-5 is high (I 21As seen in (I2)(94.8~129.1), it provides high shear viscosity reduction. The effect of this shear viscosity reduction can be seen in the surface roughness of the extruded tape (simulating the insulating layer). The surface roughness, measured by mean roughness height (Ra), is much lower (55~141 μ-in) for each of IE1~5 compared to the surface roughness of CS3.

[0093] This disclosure is not limited to the embodiments and examples contained herein, but is specifically intended to include modified forms of those embodiments, including some embodiments or combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims.

Claims

1. (A) (i) Density of 0.91 g / cc to 0.93 g / cc, (ii) I of 90-140 ２１ / I ２ ratio, (iii) Mw / Mn for 7.0 to 15.0, (iv) SHI (n0.1 / n100) values ​​from 5.0 to 30.0, (v) Boron in concentrations of 0 ppb to 80 ppb, and (vi) Fluorine at 0 ppm to 5 ppm A base bimodal ethylene / C2 before silane crosslinking has ４ -C ８ α-olefin copolymer 90% to 99% by weight, (B) An insulating layer comprising a silane crosslinked polyethylene composition comprising 0.5% to 2.0% by weight of hydrolyzed silane monomer, The insulating layer is (1) Surface roughness Ra value of 50 μ-in to 150 μ-in, (2) Dissipation rate of 0.0001 radians or less, (3) Dielectric constant between 2.0 and less than 2.29, (4) 5.00 x 10 １６ ~8.00 x 10 １７ Volume resistivity, (5) High-temperature creep value of 20% to 30%, An insulating layer having properties selected from the group consisting of combinations thereof.

2. The bimodal ethylene / C ４ ４ -C ８ ８ α-olefin copolymer has a melt index I of 0.6 g / 10 min to 1.2 g / 10 min, ２ The insulating layer according to claim 1.

3. The aforementioned bimodal ethylene / C ４ -C ８ α-olefin copolymer, End vinyl content of 0.22 / 1000C to 0.70 / 1000C, Total degree of unsaturation from 0.25 / 1000C to 1.0 / 1000C, and An insulating layer according to claim 1 or 2, having characteristics selected from the group consisting of these combinations.

4. The aforementioned bimodal ethylene / C ４ -C ８ The insulating layer according to any one of claims 1 to 3, wherein the α-olefin copolymer has an Mz of less than 600,000 g / mol.

5. The insulating layer according to any one of claims 1 to 4, wherein the insulating layer contains 0 ppb of boron.

6. The insulating layer according to any one of claims 1 to 5, wherein the insulating layer contains 0 ppm of fluorine.

7. The insulating layer according to any one of claims 1 to 6, wherein the hydrolyzed silane monomer is formed from vinyltrimethoxysilane.

8. The insulating layer according to any one of claims 1 to 4, wherein the insulating layer comprises 3% to 6% by weight of a second ethylene-based polymer.

9. A conductor and The insulating layer on the conductor, wherein the insulating layer is (A) (i) Density of 0.91 g / cc to 0.93 g / cc, (ii) I of 90-140 ２１ / I ２ ratio, (iii) Mw / Mn for 7.0 to 15.0, (iv) SHI (n0.1 / n100) values ​​from 5.0 to 30.0 A base bimodal ethylene / C2 before silane crosslinking has ４ -C ８ α-olefin copolymer 90% to 99% by weight, (B) A cable comprising an insulating layer comprising a silane crosslinked polyethylene composition containing 0.5% to 2.0% by weight of hydrolyzed silane monomer.

10. The insulating layer, (1) Surface roughness Ra value of 50 μ-in to 150 μ-in, (2) Dissipation rate of 0.0001 radians or less, (3) Dielectric constant between 2.0 and less than 2.29, (4) 5.00 x 10 １６ ~8.00 x 10 １７ Volume resistivity, (5) High-temperature creep value of 20% to 30%, and The cable according to claim 9, having characteristics selected from the group consisting of these combinations.

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