Polymer composition

Abstract

The present invention is, a) at least one polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers; b) at least one antioxidant; c) at least one crosslinking agent; and d) 2,4-diphenyl-4-methyl-1-pentene The present invention relates to a polymer composition comprising: a polyethylene copolymer, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer; and the crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I): In the above formula, R1, R2, and R3 are each independently selected from linear and branched C1-C6 alkyl groups; and R is the remainder of the organic peroxide.

Description

Technology Field

[0001] The present invention relates to a polymer composition, for example, a power cable insulation polymer composition. The present invention also relates to a process for producing a polymer composition, a crosslinked polymer composition obtainable by crosslinking the polymer composition, a power cable, a process for producing a power cable, and the use of a combination of a specific crosslinking agent and a specific additive (2,4-diphenyl-4-methyl-1-pentene) for reducing the exudation of an antioxidant from the polymer composition. Background Technology

[0002] Polyethylene produced by high-pressure (HP) processes is widely used in demanding polymer applications where the polymer must meet high mechanical and / or electrical requirements. For example, in wire and cable (W&C) applications, such as power cable applications—particularly medium voltage (MV) and especially high voltage (HV) and extra-high voltage (EHV) power cable applications—the electrical properties of the polymer composition are of significant importance. Furthermore, these important electrical properties may differ across different cable applications, such as between AC and DC cable applications.

[0003] Crosslinking of polymer compositions, for example, crosslinking of polyethylene, is particularly well known in the aforementioned W&C applications. In the crosslinking reaction of a polymer, mutual polymer crosslinks (bridges) are primarily formed. Crosslinking generally improves the heat resistance and deformation resistance, creep properties, mechanical strength, chemical resistance, and abrasion resistance of the polymer composition. Crosslinking is generally carried out with a crosslinking agent, for example, a peroxide, which decomposes under crosslinking conditions to generate free radicals. The crosslinking agent is generally incorporated into the polymer composition before the polymer composition is molded into an article or otherwise formed, for example, before a layer of the polymer composition is extruded onto one or more conductors to form a cable, and before the polymer composition is crosslinked. Such polymer compositions containing a crosslinking agent and thus having the potential to undergo crosslinking but not yet crosslinked are referred to as "crosslinkable."

[0004] Crosslinkable polymer compositions are often subjected to extended storage periods, both by the manufacturer before shipment to the customer and by the customer before use. During these storage periods, antioxidants—typically added to the polymer composition to protect it from oxidative effects of the environment, such as air—are observed to migrate and accumulate on the surface of the polymer composition (usually in pellet form). This migration (also referred to as "exudation") can lead to the depletion of the antioxidant content within the bulk of the polymer composition, which can have a serious adverse effect on the polymer composition's shelf life and stability.

[0005] Therefore, there remains a need for polymer compositions with improved storage stability. In particular, there is a need for crosslinkable antioxidant-containing polymer compositions that exhibit very little or virtually no antioxidant exudation.

[0006] In one aspect, the present invention

[0007] a) at least one polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers;

[0008] b) at least one antioxidant;

[0009] c) at least one crosslinking agent; and

[0010] d) 2,4-diphenyl-4-methyl-1-pentene

[0011] A polymer composition comprising,

[0012] The content of one or more polar comonomers among the polyethylene copolymers is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer;

[0013] The above-mentioned crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I):

[0014]

[0015] In the above formula,

[0016] R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C6 alkyl groups;

[0017] R is the remaining part of the above organic peroxide.

[0018] Preferably, the polymer composition is suitable for use in the insulation layer of a power cable.

[0019] In another aspect, the present invention provides a process for producing a polymer composition defined in any prior art of the present invention, comprising blending a polyethylene copolymer with an antioxidant, a crosslinking agent, and 2,4-diphenyl-4-methyl-1-pentene.

[0020] In another aspect, the present invention provides a crosslinked polymer composition that can be obtained by crosslinking a polymer composition defined in any prior art of the present invention, and preferably obtained.

[0021] In another aspect, the present invention provides a power cable comprising at least one conductor surrounded by at least one layer, preferably an insulating layer, which comprises a polymer composition defined in any prior art of the present invention or a cross-linked polymer composition defined in any prior art of the present invention, preferably made up of the same.

[0022] In another aspect, the present invention provides a process for producing a power cable, said process comprising:

[0023] (i) applying at least one layer, preferably an insulating layer, comprising, preferably formed therefrom, a polymer composition defined in any prior art of the present invention, preferably by (co)extrusion, onto one or more conductors; and

[0024] (ii) Optionally, a step of crosslinking the polymer composition.

[0025] In another aspect, the present invention provides a use for reducing the exudation of an antioxidant from a polymer composition comprising (i) a polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers, and (ii) a combination of a crosslinking agent and 2,4-diphenyl-4-methyl-1-pentene in a polymer composition further comprising an antioxidant, wherein the content of the one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer;

[0026] The above-mentioned crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I):

[0027]

[0028] In the above equation, R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C6 alkyl groups;

[0029] R is the remaining part of the above organic peroxide. Specific details for implementing the invention

[0030] The present invention relates to a polymer composition having improved storage stability in one aspect. In particular, in a polymer composition further comprising a specific polyethylene copolymer comprising a specific amount of polar comonomer and an antioxidant, the inventors have demonstrated that by using a combination of a specific crosslinking agent (which is an organic peroxide having a structural formula according to chemical formula (I)) and a specific additive (2,4-diphenyl-4-methyl-1-pentene), the exudation of the antioxidant from the polymer composition is unexpectedly reduced compared to the case where such a combination is not used.

[0031] Component a) - Polyethylene copolymer

[0032] The polymer composition of the present invention comprises at least one polyethylene copolymer, that is, one or more polyethylene copolymers. While it is possible to use a mixture of polyethylene copolymers in the polymer composition of the present invention, it is preferable to use a single polyethylene copolymer.

[0033] The polyethylene copolymer a) of the polymer composition of the present invention is a polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer. It will be understood that one or more polar comonomers are not present as separate components of the polymer composition but are incorporated into the polyethylene copolymer a).

[0034] In a preferred embodiment, a third monomer is present, and thus the polyethylene copolymer of the present invention becomes a polyethylene terpolymer of ethylene, one or more polar comonomers and one or more other nonpolar comonomers, wherein the content of one or more polar comonomers in the polyethylene terpolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene terpolymer.

[0035] The term "copolymer" as used herein therefore includes polyethylene comprising repeating units derived from two or more different monomers.

[0036] The term “terpolymer” as used herein includes both polyethylene comprising repeating units derived from three different monomers and polyethylene comprising repeating units derived from more than three (e.g., four or five) different monomers. However, in a preferred embodiment, polyethylene copolymer a) of the polymer composition of the present invention comprises repeating units derived strictly from three comonomers (including ethylene), namely, a polyethylene terpolymer of ethylene, one polar comonomer, and one other nonpolar comonomer. As is well known, the term “comonomer” refers to copolymerizable comonomer units.

[0037] Those skilled in the art understand that the term “non-polar comonomer” as used herein refers to a comonomer that is a hydrocarbon, for example, composed only of carbon and hydrogen atoms. In contrast, the term “polar comonomer” refers to a comonomer that is not a non-polar comonomer. Typically, polar comonomers are oxygen-containing comonomers, for example, containing CO and / or C=O bonds. In the phrase “one or more other non-polar comonomers,” the term “other” is used to distinguish the non-polar comonomers in polyethylene copolymer a) from ethylene, that is, one or more other non-polar comonomers are non-polar comonomers other than ethylene.

[0038] Polyethylene copolymer a) may be any polyethylene copolymer as defined above, such as any polyethylene copolymer a) commonly used in layers of electrical cables, for example, power cables, for example, insulation layers. Polyethylene copolymer a) may be, for example, a commercially available polyethylene copolymer, or may be manufactured according to or similarly to a polymerization process known in the chemical literature.

[0039] In a preferred embodiment, the polyethylene copolymer is, for example, a low-density polyethylene (LDPE) copolymer produced in a high-pressure (HP) process. The meaning of LDPE is well known and documented in the literature. In particular, the term "LDPE" is used to distinguish polyethylene produced in a high-pressure process from polyethylene produced in the presence of an olefin polymerization catalyst. Additionally, LDPE has certain typical characteristics, such as a different branched structure, compared to polyethylene produced in the presence of an olefin polymerization catalyst. Generally, in a high-pressure process, the polymerization of ethylene and additional comonomers is carried out in the presence of an initiator.

[0040] In one embodiment, the polyethylene copolymer is selected from the group of saturated polyethylene copolymers and unsaturated polyethylene copolymers, preferably from the group of unsaturated polyethylene copolymers. In one embodiment, the polyethylene copolymer is an unsaturated LDPE copolymer.

[0041] In one embodiment, the polar comonomer of the polyethylene copolymer is selected from the group of comonomers containing hydroxyl groups, alkoxy groups, carbonyl groups, carboxyl groups, ether groups or ester groups, and mixtures thereof. Preferably, a comonomer containing carboxyl and / or ester groups is used. More preferably, the polar comonomer of the polyethylene copolymer is selected from the group of acrylates, methacrylates, acetates, and mixtures thereof.

[0042] In a preferred embodiment, the polar comonomer of the polyethylene copolymer is selected from the group consisting of alkyl acrylates, alkyl methacrylates, vinyl acetates, and mixtures thereof. More preferably, the polar comonomer is selected from the group consisting of C1 to C6 alkyl acrylates, C1 to C6 alkyl methacrylates, vinyl acetates, and mixtures thereof. In one embodiment, the polar comonomer is selected from the group consisting of C1 to C6 alkyl acrylates, such as methyl, ethyl, propyl, or butyl acrylates, or any mixture thereof.

[0043] Surprisingly, the inventors have confirmed that when a polyethylene copolymer a) as defined above (i.e., containing one or more polar comonomers) is used in the polymer composition of the present invention, the reduction in the exudation of antioxidants is more pronounced than when a polyethylene copolymer not containing polar comonomers is used.

[0044] Where present, the nonpolar comonomer is a monounsaturated (= one double bond) comonomer, e.g., olefin, e.g., alpha-olefin, e.g., C3 to C4 10 Alpha-olefins may be selected from the group consisting of, for example, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, styrene, 1-octene, or 1-nonene. Alternatively, nonpolar comonomers are selected from the group consisting of polyunsaturated (= one or more double bonds) comonomers. Suitable polyunsaturated comonomers are further described below.

[0045] The content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer. In a preferred embodiment, the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.05 to 4.5 weight% with respect to the total weight of the polyethylene copolymer, and more preferably in the range of 0.1 to 4.0 weight%. In another embodiment, the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.05 to 3.0 weight%, 0.75 to 2.5 weight%, or 0.1 to 2.0 weight%, e.g., 0.1 to 1.75 weight%, particularly in the range of 0.1 to 1.5 weight%, 0.1 to 1.25 weight%, or 0.1 to 1.0 weight% with respect to the total weight of the polyethylene copolymer. Where the polyethylene copolymer contains more than one polar comonomer, the above range refers to the total amount of polar comonomers in the polyethylene copolymer, that is, the sum of the amounts of individual polar comonomers in the polyethylene copolymer.

[0046] The ethylene content in the polyethylene copolymer is not particularly limited, but is generally in the range of at least 50 weight% with respect to the total weight of the polyethylene copolymer, preferably at least 60 weight%, more preferably at least 70 weight%, and most preferably at least 80 weight%. In one embodiment, the ethylene content of the polyethylene copolymer is 99.9 weight% or less, e.g. 99.0 weight% or less, e.g. 90 to 99.0 weight% with respect to the total weight of the polyethylene copolymer.

[0047] Polyethylene copolymers, for example, LDPE copolymers, may optionally be unsaturated, that is, may contain carbon-carbon double bonds (-C=C-). A preferred unsaturated polyethylene copolymer, for example, an unsaturated LDPE copolymer, contains carbon-carbon double bonds per 1,000 carbon atoms in a total amount of at least 0.10 / 1,000 carbon atoms, preferably at least 0.20 / 1,000 carbon atoms, more preferably at least 0.30 / 1,000 carbon atoms, and most preferably at least 0.40 / 1,000 carbon atoms. The upper limit of the amount of carbon-carbon double bonds present in the unsaturated polyethylene copolymer, for example, an unsaturated LDPE copolymer, is not particularly limited and may be, for example, less than 5.0 / 1,000 carbon atoms, for example, less than 3.0 / 1,000 carbon atoms.

[0048] Alternatively, a polyethylene copolymer, for example, an LDPE copolymer, can be saturated. Preferably, a saturated polyethylene copolymer, for example, a saturated LDPE copolymer, has a -C=C- content of less than 0.10 / 1000 carbon atoms.

[0049] As is well known, (optional) unsaturation may be provided to polyethylene copolymers, e.g. LDPE copolymers, by comonomers, crosslinking boosters, chain transfer agents (CTAs), or low molecular weight (Mw) additive compounds such as scorch retardant additives, or any combination thereof. The total amount of double bonds refers to double bonds added by any means herein. If two or more of the sources of double bonds are chosen to be used to provide unsaturation, the total amount of double bonds in the polyethylene copolymer refers to the sum of the double bonds present. Any double bond measurement is performed prior to any crosslinking. In one embodiment, the term “total amount of carbon-carbon double bonds” refers to, if present, vinyl groups, vinylidene groups and Trans- Refers to the combined amount of double bonds derived from vinylene groups.

[0050] The crosslinking booster may be a compound containing at least two unsaturated groups, such as an aliphatic or aromatic compound, ester, ether, amine, or ketone, which contains at least two unsaturated groups, such as a cyanurate, isocyanurate, phosphate, orthoformate, aliphatic or aromatic ether, or allyl ester of a benzene tricarboxylic acid. Examples of suitable esters, ethers, amines, and ketones are compounds selected from the general group of diacrylates, triacrylates, tetraacrylates, trialyl cyanurates, trialyl isocyanurates, 3,9-divinyl-2,4,8,10-tetra-oxaspiro[5,5]-undecane (DVS), trialyl trimellitate (TATM), or N,N,N',N',N"-hexaallyl-1,3,5-triazine-2,4,6-triamine (HATATA), or any mixture thereof. The crosslinking booster may be added in an amount of, for example, less than 2.0 wt%, for example, less than 1.5 wt%, for example, less than 1.0 wt%, for example, less than 0.75 wt%, for example, less than 0.5 wt% based on the total weight of the polymer composition, and the lower limit thereof is, for example, at least 0.05 wt%, for example, at least 0.1 wt%.

[0051] In one embodiment, any unsaturation is provided by one or more of the following means: by a chain transfer agent (CTA), by one or more polyunsaturated comonomers, or by polymerization conditions. It is well known that selected polymerization conditions, such as peak temperature and pressure, can affect the level of unsaturation.

[0052] In a preferred embodiment, the polyethylene copolymer is a polyethylene terpolymer that is a terpolymer of ethylene, one or more polar comonomers and one or more polyunsaturated comonomers, that is, one or more other nonpolar comonomers are present and selected from the group of polyunsaturated comonomers.

[0053] Suitable polyunsaturated comonomers for polyethylene terpolymers include straight carbon chains having at least eight carbon atoms, wherein at least four carbon atoms are located between non-conjugated double bonds, and at least one of the double bonds is located at the terminal. For example, in one embodiment, the polyunsaturated comonomer is a diene, preferably a diene having a straight chain having at least eight carbon atoms, wherein at least four carbon atoms are located between non-conjugated double bonds, and at least one of the double bonds is located at the terminal. The preferred diene is C8 to C 14 It is selected from non-conjugated dienes or mixtures thereof, more preferably from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, or mixtures thereof. Much more preferably, the diene is selected from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, or any mixture thereof.

[0054] Accordingly, in a particularly preferred embodiment, the polyethylene terpolymer comprises one or more polar comonomers selected from ethylene, C1-C6 alkyl acrylate, C1-C6 alkyl methacrylate, and vinyl acetate, and one or more C8 to C 14 It is a terpolymer of non-conjugated diene (most preferably an LDPE terpolymer).

[0055] In a preferred embodiment, the content of one or more polyunsaturated comonomers in the polyethylene copolymer is in the range of 0.05 to 4.5 weight% with respect to the total weight of the polyethylene copolymer, and more preferably in the range of 0.1 to 4.0 weight%.

[0056] For example, it is well known that propylene can be used as a comonomer or a chain transfer agent (CTA), or both, and thereby contribute to the total amount of carbon-carbon double bonds, preferably the total amount of vinyl groups. In this invention, when a compound capable of acting as a comonomer, such as propylene, is used as a CTA to provide double bonds, said copolymerizable comonomer is not counted in the comonomer content.

[0057] If a polyethylene copolymer, for example, an LDPE copolymer, is unsaturated, it preferably contains vinyl groups, vinylidene groups, and Trans - The total amount of carbon-carbon double bonds derived from vinylene groups is at least 0.10 / 1000 carbon atoms, e.g., at least 0.20 / 1000 carbon atoms, e.g., at least 0.30 / 1000 carbon atoms, e.g., at least 0.40 / 1000 carbon atoms, e.g., at least 0.50 / 1000 carbon atoms. In unsaturated polyethylene copolymers, e.g., unsaturated LDPE copolymers, if present, vinyl groups, vinylidene groups and Trans - The maximum amount of carbon-carbon double bonds derived from the vinylene group is not specifically limited and may be, for example, less than 5.0 / 1000 carbon atoms, for example, less than 3.0 / 1000 carbon atoms.

[0058] In some embodiments, for example, where a high level of crosslinking with a low peroxide content is required, vinyl groups, vinylidene groups and, if present, within the unsaturated polyethylene copolymer Trans- The total amount of carbon-carbon double bonds derived from the vinylene group is greater than 0.40 / 1000 carbon atoms, preferably greater than 0.50 / 1000 carbon atoms, more preferably greater than 0.60 / 1000 carbon atoms.

[0059] If the polyethylene copolymer is an unsaturated polyethylene copolymer, it preferably contains at least vinyl groups, and the total amount of vinyl groups is preferably greater than 0.05 / 1000 carbon atoms, more preferably greater than 0.08 / 1000 carbon atoms, and most preferably greater than 0.11 / 1000 carbon atoms. Preferably, the total amount of vinyl groups is less than 4.0 / 1000 carbon atoms. Preferably, the polyethylene copolymer, for example, an LDPE copolymer, contains vinyl groups in a total amount of at least 0.20 / 1000 carbon atoms, more preferably at least 0.30 / 1000 carbon atoms, and most preferably at least 0.40 / 1000 carbon atoms.

[0060] In an alternative embodiment, the polyethylene copolymer is not unsaturated and has less than 0.2 C = C / 1000 C atoms, preferably less than 0.1 C = C / 1000 C atoms. In one embodiment, the polyethylene copolymer is saturated and does not contain carbon-carbon double bonds. However, since the polymer composition of the present invention is crosslinkable, the presence of unsaturation in the polyethylene copolymer, e.g., LDPE copolymer, is desirable.

[0061] Polyethylene copolymers, for example, LDPE copolymers, are typically 860 kg / m³ 3 It has a higher density. The density of polyethylene copolymers, for example, LDPE copolymers, is typically 960 kg / m³. 3 It is not higher. In one embodiment, the density of a polyethylene copolymer, for example, an LDPE copolymer, is 900 to 945 kg / m³. 3 , for example, 915 to 935 kg / m² 3 It is within the range of.

[0062] The melt flow index (MFR2) of polyethylene copolymers, for example LDPE copolymers, is typically in the range of 0.01 to 50 g / 10 min, for example 0.1 to 20 g / 10 min, for example 0.2 to 10 g / 10 min.

[0063] Polyethylene copolymers, such as LDPE copolymers, are typically produced at high pressure by free radical-initiated polymerization (referred to as high-pressure (HP) radical polymerization). The HP reactor may be, for example, a well-known tubular or autoclave reactor or a mixture thereof, preferably a tubular reactor. Adjustments of high-pressure (HP) polymerization and process conditions to further adjust other properties of the polyethylene copolymer according to a given end use are well known and described in the literature and can be readily utilized by those skilled in the art. Suitable polymerization temperatures range from a maximum of 400°C, preferably from 80 to 350°C, and pressures range from 70 MPa, preferably from 100 to 400 MPa, more preferably from 100 to 350 MPa. Pressure may be measured at least after the compression stage and / or after the tubular reactor. Temperature may be measured at multiple points during all stages.

[0064] After separation, the resulting polyethylene copolymer is generally in the form of a polymer melt, which is typically mixed and pelletized in a pelletizing section, such as a pelletizing extruder connected to the HP reactor system. Optionally, additives such as antioxidants may be added to this mixer in a known manner.

[0065] As is well known, when unsaturated polyethylene copolymers are manufactured, the carbon-carbon double bond content can be adjusted, for example, in the presence of one or more polyunsaturated comonomers, chain transfer agents, or both, by polymerizing ethylene using a desired feed ratio between the monomer, preferably ethylene, and the polyunsaturated comonomer and / or chain transfer agent, depending on the desired characteristics and amount of CC double bonds for the unsaturated LDPE copolymer. For example, WO 9308222 describes the high-pressure radical polymerization of ethylene using polyunsaturated monomers. Consequently, the unsaturation can be uniformly distributed along the polymer chain in a random copolymerization manner.

[0066] The polymer composition of the present invention preferably comprises at least 85.0 wt%, preferably at least 90.0 wt%, more preferably at least 92.5 wt%, and even more preferably at least 93.0 wt% of a polyethylene copolymer relative to the total weight of the polymer composition. In a preferred embodiment, the polymer composition comprises at least 93.5 wt%, preferably at least 95.0 wt%, and most preferably at least 95.5 wt% of a polyethylene copolymer relative to the total weight of the polymer composition. In one embodiment, the polyethylene copolymer forms up to 99 wt% of the polymer composition, for example, up to 98.5 wt%, or up to 98.0 wt% of the polymer composition.

[0067] In a preferred embodiment, the polymer composition comprises 85.0 to 99 weight percent of a polyethylene copolymer, e.g., an LDPE copolymer, relative to the total weight of the polymer composition. Preferably, the composition comprises 90.0 to 99 weight percent, e.g., 92.5 to 99 weight percent, more preferably 93.0 to 98.5 weight percent, particularly 93.5 to 98.5 weight percent, more particularly 95.0 to 98.0 weight percent, most particularly 95.5 to 98.0 weight percent, relative to the total weight of the polymer composition. It will be understood that the amount of polyethylene copolymer in the polymer composition can be calculated by determining the amount of polyethylene copolymer added during the preparation of the polymer composition (e.g., during the blending of the components of the polymer composition) relative to the total amount of all other added components.

[0068] When multiple polyethylene copolymers are used in a polymer composition, it will be understood that the above amount refers to the total amount of polyethylene copolymers in the polymer composition, that is, the sum of the amounts of individual polyethylene copolymers.

[0069] Ingredient b) - Antioxidant

[0070] The polymer composition comprises at least one, that is, one or more antioxidants. While it is preferable to use a single antioxidant, it is also possible to use a mixture of antioxidants in the polymer composition of the present invention.

[0071] The antioxidant is not particularly limited and may be any conventional antioxidant suitable for use, for example, in polymer compositions, for example in power cable polymer compositions, for example in power cable insulation polymer compositions. The antioxidant may be, for example, a commercially available antioxidant, or may be manufactured according to or similarly to processes known in the chemical literature.

[0072] In one embodiment, the antioxidant is selected from the group consisting of sterically hindered or semi-hindered phenols, aromatic amines, aliphatic sterically hindered amines, thio compounds, and mixtures thereof. Preferably, the antioxidant is a sulfur-containing phenolic antioxidant; more preferably, it is thiobisphenol such as 4,4'-thiobis(2-tert-butyl-5-methylphenol), 2,2'-thiobis(6-t-butyl-4-methylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,6-bis(octylthiomethyl)-o-cresol, or a mixture thereof. 4,4'-thiobis(2-tert-butyl-5-methylphenol) is particularly preferred. Other thio compounds, such as di-stearyl-thio-dipropionate or similar compounds having various lengths on the carbon chain; or mixtures thereof may also be used.

[0073] In one embodiment, the polymer composition does not contain, for example, nitrogen-containing antioxidants such as hindered amine light stabilizers (HALS). For example, in one embodiment, the polymer composition contains one or more sulfur-containing phenolic antioxidants, and preferably, said sulfur-containing phenolic antioxidant (e.g., thiobisphenol antioxidant) is the sole antioxidant in the polymer composition.

[0074] The amount of antioxidant in the polymer composition is not particularly limited and can be used in any conventional amount, as is well known to those skilled in the art. In one embodiment, the polymer composition comprises an antioxidant in an amount of at least 0.005 wt%, preferably at least 0.01 wt%, more preferably at least 0.02 wt%, and most preferably at least 0.04 wt%, based on the total weight of the polymer composition (100 wt%). In another embodiment, the polymer composition comprises an antioxidant in an amount of 0.50 wt% or less, preferably 0.30 wt% or less, more preferably 0.20 wt% or less, and most preferably 0.15 wt% or less, based on the total weight of the polymer composition (100 wt%). In a preferred embodiment, the polymer composition comprises an antioxidant in an amount of 0.005 to 0.50 wt%, preferably 0.01 to 0.30 wt%, more preferably 0.02 to 0.20 wt%, and most preferably 0.04 to 0.15 wt%, relative to the total weight of the polymer composition (100 wt%). It will be understood that the amount of antioxidant in the polymer composition can be calculated by knowing the amount of antioxidant added during the preparation of the polymer composition (e.g., during the blending of the components of the polymer composition) relative to the total amount of all other added components.

[0075] When multiple antioxidants are used in a polymer composition, it will be understood that the above amount refers to the total amount of antioxidants in the polymer composition, that is, the sum of the amounts of individual antioxidants.

[0076] Ingredient c) - Crosslinking agent

[0077] The polymer composition comprises at least one crosslinking agent, i.e., one or more organic peroxides having a structural formula according to chemical formula (I):

[0078]

[0079] In the above formula,

[0080] R 1 , R 2 and R 3 Each is independently selected from linear or branched C1-C6 alkyl groups;

[0081] R is the remainder of the organic peroxide.

[0082] Surprisingly, it was found that using this crosslinking agent in combination with a specific additive (2,4-diphenyl-4-methyl-1-pentene) reduces (i.e., lowers) the amount of antioxidants exuded from the polymer composition during storage, and thus improves the storage stability of the polymer composition.

[0083] While it is possible for the polymer composition to contain more than one crosslinking agent, it is preferable for the polymer composition to contain a single crosslinking agent. For example, it is preferable that the polymer composition does not contain any crosslinking agents other than those having the structural formula according to Formula (I), for example, when an organic peroxide having the structural formula according to Formula (I), or a mixture of organic peroxides each having the structural formula according to Formula (I), is the only crosslinking agent present in the polymer composition. It is particularly preferable that the polymer composition does not contain, i.e., is not, dicumyl peroxide (DCP) (CAS No. 80-43-3).

[0084] In a preferred embodiment, R of formula (I) 1 , R 2 and R 3 Each is independently selected from linear or branched C1-C4 alkyl groups. More preferably, R 1 , R 2 and R 3 (This may be the same or different) is each a methyl group or an ethyl group. In a particularly preferred embodiment, R 1 , R 2 and R 3 Each is a methyl group, that is, group R 1 , R 2 and R3 They form a tert-butyl group together with the carbon atom to which they are attached.

[0085] The remaining part "R" of the peroxide is not specifically restricted, for example, C1-C 20 Aliphatic group or C6-C 20 It may include an aromatic group. It is particularly preferred that R is a group having the structural formula -C(CH3)2Ar, where Ar is an optionally substituted phenyl group.

[0086] In a preferred embodiment, group R has the following chemical formula:

[0087]

[0088] In the above equation, R 4 , R 5 and R 6 C each independently 1-20 It is a hydrocarbon group, preferably C 1-20 Aliphatic group or C 6-20 It is an aromatic group, and more preferably C 1-20 alkyl group or C 6-20 It is an aryl group. In a preferred embodiment, R 4 , R 5 and R 6 Each is independently linear or branched C 1-12 It is an alkyl group, preferably a linear or branched C 1-6 It is an alkyl group, more preferably a linear or branched C 1-4 An alkyl group, particularly methyl or ethyl; or C 6-10 It is an aryl group, particularly a phenyl. Optionally, the R group of formula (I) includes, in addition to the group shown in formula (I), an additional peroxy group having the formula -OO-. For example, the organic peroxide may be bisperoxide. In a preferred embodiment, the group R has the following formula:

[0089]

[0090] In the above formula,

[0091] R 4' and R 5' C each independently 1-20 It is a hydrocarbon group, preferably C 1-20 Aliphatic group or C 6-20 It is an aromatic group, and more preferably C 1-20 alkyl group or C 6-20 Arilgigo;

[0092] R 6' , R 7' and R 8' C each independently 1-20 It is a hydrocarbon group, preferably C 1-20 Aliphatic group or C 6-20 It is an aromatic group, and more preferably C 1-20 alkyl group or C 6-20 Arilgigo;

[0093] L is a divalent linker, and preferably C 1-20 It is a hydrocarbon group, preferably C 1-20 alkyl group or C 2-20 alkenyl group or C 2-20 It is an alkynyl group, preferably C 1-12 alkyl group or C 2-12 alkenyl group or C 2-12 It is an alkynyl group. In a preferred embodiment, R 4' and R 5' C each independently 1-12 It is an alkyl group, preferably C 1-6 It is an alkyl group, and more preferably C 1-4 An alkyl group, particularly methyl or ethyl; or C 6-10 It is an aryl group, especially phenyl.

[0094] In a preferred embodiment, the crosslinking agent is selected from the group consisting of di-tert-amylperoxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumylperoxide, di(tert-butyl)peroxide, butyl-4,4-bis(tert-butylperoxy)-valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, bis(tert-butylperoxyisopropyl)benzene, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof. More preferably, the crosslinking agent is selected from 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, tert-butylcumyl peroxide, di(tert-butyl)peroxide, or a mixture thereof. In a particularly preferred embodiment, the crosslinking agent is tert-butylcumyl peroxide.

[0095] The amount of crosslinking agent in the polymer composition is also not particularly limited and may be any conventional amount used in polymer compositions, for example, as is well known in the art.

[0096] In a preferred embodiment, the polymer composition comprises a crosslinking agent in an amount of at least 0.2 wt%, preferably at least 0.3 wt%, more preferably at least 0.4 wt%, most preferably at least 0.5 wt%, e.g. at least 0.6 wt%, particularly at least 0.75 wt%, based on the total weight (100 wt%) of the polymer composition. In another embodiment, the polymer composition comprises a crosslinking agent in an amount of 10.0 wt% or less, preferably 8.0 wt% or less, more preferably 5.0 wt% or less, most preferably 3.0 wt% or less, e.g. 2.5 wt% or less, particularly 2.0 wt% or less, based on the total weight (100 wt%) of the polymer composition. In a preferred embodiment, the polymer composition comprises a crosslinking agent in an amount of 0.2 to 10.0 wt%, preferably 0.3 to 8.0 wt%, more preferably 0.4 to 5.0 wt%, much more preferably 0.5 to 3.0 wt%, e.g. 0.6 to 2.5 wt%, particularly 0.75 to 2.0 wt%, with respect to the total weight (100 wt%) of the polymer composition. In one embodiment, the polymer composition comprises a crosslinking agent in an amount of about 1.5 wt%, e.g., in the range of 1.35 to 1.65 wt%. In one embodiment, the amount of crosslinking agent in the polymer composition is 1.65 wt% or less, e.g. 1.5 wt% or less, or even 1.0 wt% or less. It will be understood that the amount of crosslinking agent in the polymer composition can be calculated by knowing the amount of crosslinking agent added during the preparation of the polymer composition (e.g., during the blending of the components of the polymer composition) relative to the total amount of all other added components.

[0097] It will be understood that when multiple crosslinkers of formula (I) are used in a polymer composition, the amount refers to the total amount of crosslinkers of formula (I) in the polymer composition, that is, the sum of the amounts of individual crosslinkers of formula (I).

[0098] Ingredient d) - Additives

[0099] The polymer composition additionally contains 2,4-diphenyl-4-methyl-1-pentene. Surprisingly, it has been found that using this compound in combination with a specific crosslinking agent as defined above causes a reduction (i.e., degradation) in the amount of antioxidant exuded from the polymer composition during storage, and thus improves the storage stability of the polymer composition.

[0100] In a preferred embodiment, the polymer composition comprises, with respect to the total weight (100 wt%) of the polymer composition, at least 0.05 wt% of 2,4-diphenyl-4-methyl-1-pentene, for example, more than 0.05 wt% of 2,4-diphenyl-4-methyl-1-pentene, preferably at least 0.06 wt% of 2,4-diphenyl-4-methyl-1-pentene, more preferably at least 0.07 wt% of 2,4-diphenyl-4-methyl-1-pentene, and most preferably at least 0.08 wt% of 2,4-diphenyl-4-methyl-1-pentene. In another embodiment, the polymer composition comprises, with respect to the total weight of the polymer composition, up to 1.5 wt% of 2,4-diphenyl-4-methyl-1-pentene, for example up to 0.75 wt% of 2,4-diphenyl-4-methyl-1-pentene, for example up to 0.70 wt% of 2,4-diphenyl-4-methyl-1-pentene, for example up to 0.60 wt%.

[0101] In a preferred embodiment, the polymer composition comprises 2,4-diphenyl-4-methyl-1-pentene in an amount of 0.05 to 1.5 weight%, e.g. 0.06 to 0.75 weight%, more preferably 0.07 to 0.70 weight%, e.g. 0.08 to 0.60 weight%, based on the total weight of the polymer composition. In a particularly preferred embodiment, the polymer composition comprises 2,4-diphenyl-4-methyl-1-pentene in an amount of 0.09 to 0.50 weight%, particularly 0.10 to 0.35 weight%, based on the total weight of the polymer composition. In another preferred embodiment, the polymer composition comprises 2,4-diphenyl-4-methyl-1-pentene in an amount of 0.05 to 0.40 weight% based on the total weight of the polymer composition. It will be understood that the amount of 2,4-diphenyl-4-methyl-1-pentene in the polymer composition can be calculated by knowing the amount of 2,4-diphenyl-4-methyl-1-pentene added during the preparation of the polymer composition (e.g., during the blending of the components of the polymer composition) relative to the total amount of all other added components.

[0102] In addition to the polyethylene copolymer, crosslinker, antioxidant, and 2,4-diphenyl-4-methyl-1-pentene, the polymer composition may optionally include additional components, such as additional polymer components and / or one or more additional additives. As optional additives, the polymer composition may include stabilizers, water tree retardant additives, processing aids, additional scorch retardants (other than 2,4-diphenyl-4-methyl-1-pentene), metal deactivators, crosslinking boosters, flame retardant additives, acid or ion scavengers, inorganic fillers, voltage stabilizers, or any mixture thereof. Typically, when present, these additives are present in a total amount of less than 10 weight percent with respect to the total weight of the polymer composition, preferably in an amount of less than 5 weight percent with respect to the total weight of the polymer composition. In one embodiment, the polymer composition is essentially composed of, for example, a polyethylene copolymer, a crosslinker, an antioxidant, and 2,4-diphenyl-4-methyl-1-pentene.

[0103] Polymer composition

[0104] The polymer composition of the present invention comprises components a) through d) as defined herein. The polymer composition is preferably a polyethylene composition, i.e., polyethylene-based, and, for example, at least 50 weight percent, preferably at least 70 weight percent, more preferably at least 90 weight percent, e.g., at least 95 weight percent of the polymer component in the polymer composition is a polyethylene component. In one embodiment, polyethylene is the only polymer component in the polymer composition. The polymer composition will be understood as non-crosslinked (before crosslinking). Preferably, the polymer composition is non-foamed and / or free of a foaming agent.

[0105] The polymer composition of the present invention is typically prepared by blending components a) through d). Blending may be carried out by any known method in the art, such as melt-mixing. Unless otherwise specified, the amounts of components a) through d) are given as weight percentages (weight%) of the total weight of the polymer composition. The amount of each component refers to the amount of the component added when preparing the polymer composition, which is known. The amount may also be measured in the final polymer composition (before crosslinking).

[0106] The polymer composition of the present invention exhibits low exudation of antioxidants during storage. The polymer composition is generally supplied in the form of pellets. In one embodiment, the amount of antioxidant on the surface of the pellets of the polymer composition, measured according to the method described in that section after storage at 35°C for 4 weeks under the conditions described under the heading "Determination of additive content, i.e., antioxidant content, on the surface of the pellets" in the "Measurement Methods" section, is less than 325 ppm, preferably less than 300 ppm, more preferably less than 275 ppm, and much more preferably less than 250 ppm. In a particularly preferred embodiment, the amount of antioxidant on the surface of the pellets after storage at 35°C for 4 weeks as defined above is less than 225 ppm, e.g., less than 200 ppm. In one embodiment, after storing at 35°C for 4 weeks as defined above, the amount of antioxidant on the surface of the pellet is as low as 0.1 ppm, for example as 0.5 ppm, for example as 1.0 ppm.

[0107] In a particularly preferred embodiment, the polymer composition comprises the following:

[0108] a) at least one LDPE copolymer of ethylene, one or more polar comonomers and optionally one or more other non-polar comonomers, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer;

[0109] b) at least one sulfur-containing phenolic antioxidant;

[0110] c) at least one crosslinking agent selected from the group consisting of di-tert-amylperoxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumylperoxide, di(tert-butyl)peroxide, butyl-4,4-bis(tert-butylperoxy)-valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, bis(tert-butylperoxyisopropyl)benzene, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof; and

[0111] d) at least 0.05 wt% of 2,4-diphenyl-4-methyl-1-pentene based on the total weight of the polymer composition (100 wt%).

[0112] In another particularly preferred embodiment, the polymer composition comprises the following:

[0113] Based on the total weight of the polymer composition (100 wt%)

[0114] a) at least 85.0 wt% of at least one polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 wt% with respect to the total weight of the polyethylene copolymer;

[0115] b) at least 0.005 weight% of at least one antioxidant;

[0116] c) at least 0.2 weight% of at least one crosslinking agent which is an organic peroxide having a structural formula according to chemical formula (I) previously defined herein;

[0117] d) 2,4-diphenyl-4-methyl-1-pentene at least 0.05 wt%.

[0118] In another particularly preferred embodiment, the polymer composition comprises the following:

[0119] Based on the total weight of the polymer composition (100 wt%)

[0120] a) at least 85.0 weight% of at least one low-density polyethylene (LDPE) copolymer of ethylene, one or more polar comonomers and optionally one or more other non-polar comonomers, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer;

[0121] b) at least 0.005 wt% of at least one sulfur-containing phenolic antioxidant;

[0122] c) at least 0.2 wt% of at least one crosslinking agent selected from the group consisting of di-tert-amylperoxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumylperoxide, di(tert-butyl)peroxide, butyl-4,4-bis(tert-butylperoxy)-valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, bis(tert-butylperoxyisopropyl)benzene, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof; and

[0123] d) 2,4-diphenyl-4-methyl-1-pentene at least 0.05 wt%.

[0124] In another particularly preferred embodiment, the polymer composition comprises the following:

[0125] Based on the total weight of the polymer composition (100 wt%)

[0126] a) at least 85.0 wt% of at least one low-density polyethylene (LDPE) terpolymer of ethylene, one or more polar comonomers and one or more other non-polar comonomers, wherein the content of one or more polar comonomers in the polyethylene terpolymer is in the range of 0.001 to 5.0 wt% with respect to the total weight of the polyethylene terpolymer;

[0127] b) at least 0.005 wt% of at least one sulfur-containing phenolic antioxidant;

[0128] c) at least 0.2 wt% of at least one crosslinking agent selected from the group consisting of di-tert-amylperoxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumylperoxide, di(tert-butyl)peroxide, butyl-4,4-bis(tert-butylperoxy)-valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, bis(tert-butylperoxyisopropyl)benzene, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof; and

[0129] d) 2,4-diphenyl-4-methyl-1-pentene at least 0.05 wt%.

[0130] In one aspect, the present invention relates to a crosslinked polymer composition, preferably obtained by crosslinking a polymer composition as defined above herein. Those skilled in the art know suitable conditions under which said crosslinking can be achieved. The crosslinking may be partial or substantially complete.

[0131] Process for producing a polymer composition

[0132] In one aspect, the present invention provides a process for producing a polymer composition as defined above herein, said process comprising blending a polyethylene copolymer with an antioxidant, a crosslinking agent, and 2,4-diphenyl-4-methyl-1-pentene.

[0133] The blending of the components of the polymer composition may be performed in any order. For example, in one embodiment, the polyethylene copolymer is blended with the antioxidant first (e.g., by compounding via melt-mixing) before the crosslinker and 2,4-diphenyl-4-methyl-1-pentene are added (e.g., by dispensing the crosslinker and 2,4-diphenyl-4-methyl-1-pentene onto an optionally preheated pellet comprising a blend of the polyethylene copolymer and the antioxidant). Alternatively, the crosslinker and / or 2,4-diphenyl-4-methyl-1-pentene may be added to the polyethylene copolymer before or at the same time as the antioxidant is added. During the preparation of the composition, the components may be blended and uniformly mixed, for example, by melt-mixing in an extruder. Optionally, the polymer composition may be extruded and / or pelletized.

[0134] Application

[0135] The polymer composition of the present invention may be used, for example, in the production of cables, for example, power cables. In one aspect, the present invention relates to a power cable comprising a conductor surrounded by at least one layer, preferably an insulating layer, which comprises a polymer composition (crosslinkable) as defined prior to this invention or a crosslinked polymer composition as defined prior to this invention.

[0136] In one embodiment, the power cable is a cable comprising at least one cable core capable of transmitting energy at any voltage and preferably operating at a voltage higher than 30 kV.

[0137] The voltage applied to the power cable may be alternating current (AC), direct current (DC), or impulse. Furthermore, the cable according to the present invention is preferably an AC power cable and is capable of operating at voltages such as 1-525 kV, 6-525 kV, 36-275 kV (e.g., 66-275 kV), 36-220 kV (e.g., 66-220 kV), 36-150 kV (e.g., 66-150 kV), and above 66 kV (RMS voltage, voltage between any two conductors in a three-phase cable). In one embodiment, the cable is an AC power cable capable of operating at a voltage of 36 kV or higher, preferably 66 kV or higher. In some embodiments, the cable is an AC power cable operating at a voltage lower than 550 kV, preferably lower than 525 kV, preferably lower than 400 kV, more preferably lower than 380 kV, and particularly lower than 320 kV.

[0138] Generally, a power cable, such as an AC power cable, comprises, in order, an inner semiconducting layer comprising a first semiconducting composition, an insulating layer comprising a polymer composition of the present invention, and an outer semiconducting layer comprising a second semiconducting composition.

[0139] The polymer composition of the present invention is preferably used in the insulation layer of a power cable. Ideally, the insulation layer comprises at least 95 weight percent, for example, at least 98 weight percent, for example, at least 99 weight percent of the polymer composition of the present invention. Accordingly, it is desirable that the polymer composition of the present invention be the only non-additive component used in the insulation layer of the cable of the present invention. Accordingly, it is desirable that the insulation layer is essentially composed of the polymer composition of the present invention, for example, the polymer composition of the present invention.

[0140] The insulating layer is crosslinkable (if the insulating layer comprises the crosslinkable polymer composition of the present invention) or crosslinked (if the insulating layer comprises the crosslinked polymer composition of the present invention).

[0141] The insulating layer may contain additives commonly used for W&C applications. Preferably, the insulating layer does not contain carbon black. Preferably, the polymer composition does not contain carbon black. Also, preferably, the insulating layer does not contain flame retardant additives, such as metal hydroxide-containing additives, for example, in a flame retardant amount.

[0142] The power cable of the present invention preferably comprises an inner and an outer semiconducting layer, each comprising an inner and an outer semiconducting composition. These layers may be made of any conventional material suitable for use in these layers. The inner and outer semiconducting compositions may be different or identical, and may preferably comprise a polyolefin or a mixture of polyolefins and a polymer, preferably carbon black, which is a conductive filler. Suitable polyolefins are, for example, polyethylene produced in a low-pressure process (LLDPE, MDPE, HDPE) or polyethylene produced in a high-pressure process (LDPE). The carbon black may be any conventional carbon black used in the semiconducting layer of the AC power cable, preferably in the semiconducting layer of the AC power cable. Preferably, the carbon black has one or more of the following characteristics: a) a primary particle size of at least 5 nm, defined as the number average particle diameter according to ASTM D3849-95a, dispersion procedure D; b) an iodine number of at least 30 mg / g according to ASTM D1510; and c) an oil absorption number of at least 30 ml / 100g measured according to ASTM D2414. Non-limiting examples of carbon black are, for example, acetylene carbon black, furnace carbon black, and Ketjen carbon black, preferably furnace carbon black and acetylene carbon black. Preferably, the semiconducting composition comprises 10 to 50 weight percent of carbon black based on the weight of the semiconducting composition.

[0143] In a preferred embodiment, the outer semiconducting layer and / or the inner semiconducting layer are cross-linked.

[0144] A conductor typically comprises one or more wires. Additionally, a power cable may comprise one or more such conductors. Preferably, the conductor is an electrical conductor comprising one or more metal wires or is a solid electrical conductor made of metal. Examples of suitable metals are aluminum and copper.

[0145] As is well known, cables may optionally include additional layers, such as screens, jacketing layers, other protective layers, or any combination thereof.

[0146] In one aspect, the present invention provides a process for producing a power cable, said process comprising:

[0147] (i) applying at least one layer, preferably an insulating layer, comprising and preferably composed of the (crosslinkable) polymer composition of the present invention, preferably by (co)extrusion, onto one or more conductors; and

[0148] (ii) A step of optionally crosslinking the polymer composition.

[0149] In a preferred embodiment, the process for producing a power cable includes the following:

[0150] (i) a step of applying an inner semiconducting layer, an insulating layer, and an outer semiconducting layer in that order onto one or more conductors, preferably by (co)extrusion, wherein the insulating layer comprises a (crosslinkable) polymer composition of the present invention; and

[0151] (ii) A step of optionally crosslinking the polymer composition.

[0152] More preferably, a power cable is produced, wherein the process includes the following steps:

[0153] (ia) - a step of providing and mixing an optionally crosslinkable first semiconducting composition comprising a polymer, carbon black, and optionally additional components in an inner semiconducting layer, preferably melt-mixing in an extruder,

[0154] - A step of providing and mixing the polymer composition of the present invention, preferably melt-mixing in an extruder, and

[0155] - A step of providing and mixing a second semiconducting composition optionally crosslinkable to an outer semiconducting layer and comprising a polymer, carbon black, and optionally additional components, preferably melt-mixing in an extruder,

[0156] (ib) on one or more conductors, preferably by co-extrusion,

[0157] - A molten mixture of the first semiconducting composition obtained from step (ia) to form an internal semiconducting layer,

[0158] - A molten mixture of the polymer composition of the present invention obtained from step (ia) to form an insulating layer, and

[0159] - A molten mixture of the second semiconducting composition obtained from step (ia) to form an outer semiconducting layer

[0160] Steps for applying, and

[0161] (ii) A step of optionally crosslinking any or all of the first semiconducting composition of the inner semiconducting layer of the obtained cable, the second semiconducting composition of the outer semiconducting layer, and the polymer composition of the insulating layer under crosslinking conditions.

[0162] Melt mixing generally means mixing at a temperature above the melting point of at least the main polymer component of the obtained mixture, and, although not limited thereto, is performed at a temperature at least 15°C higher than the melting point or softening point of the polymer component, for example.

[0163] The term “(co)extrusion” in this application means that, in the case of two or more layers, said layers may be extruded in separate steps, or, as is well known in the art, at least two or all of said layers may be co-extruded in the same extrusion step. The term “(co)extrusion” in this application also means that all or part of the layer(s) are formed simultaneously using one or more extrusion heads. For example, triple extrusion may be used to form three layers. Where a layer is formed using one or more extrusion heads, for example, the layers may be extruded using two extrusion heads, the first of which is for forming an inner semiconducting layer and an inner part of an insulating layer, and the second head is for forming an outer insulating layer and an outer semiconducting layer.

[0164] As is well known, the polymer composition of the present invention and any and preferred first and second semiconducting compositions can be produced before or during the cable production process.

[0165] Preferably, the polymer required to manufacture the cable of the present invention is provided to the cable production process in the form of powder, granules, or pellets. As used herein, pellets generally refer to any polymer product formed into solid polymer particles by post-reactor modification from a reactor-manufactured polymer (obtained directly from the reactor). Additives may be added to the polymer composition either as themselves or as a mixture with a carrier polymer, i.e., in the form of a so-called masterbatch.

[0166] Any crosslinking agent may be added before the cable production process or during the (melting) mixing step (a). For example, and preferably, additional components such as the crosslinking agent and also antioxidants and 2,4-diphenyl-4-methyl-1-pentene may already be present in the polymer used. The crosslinking agent is added to solid polymer particles, preferably pellets, and is preferably impregnated.

[0167] As is well known, crosslinking of the layers can be performed at an elevated temperature selected according to the type of crosslinking agent. For example, temperatures above 150°C, such as 160 to 350°C, are typical, but are not limited thereto.

[0168] Processing temperatures and devices are well known in the art, and conventional mixers and extruders, such as single or twin screw extruders, are suitable for the process of the present invention.

[0169] use

[0170] In one aspect, the present invention

[0171] (i) at least one polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers, and (ii) a combination of a crosslinking agent and 2,4-diphenyl-4-methyl-1-pentene in a polymer composition further comprising an antioxidant, the combination being used to reduce the exudation of an antioxidant from the polymer composition, wherein the content of the one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer; and the crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I):

[0172]

[0173] In the above formula,

[0174] R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C6 alkyl groups;

[0175] R is the remainder of the organic peroxide.

[0176] Surprisingly, it was found that the use of this combination of crosslinking agents and additives causes a reduction (i.e., degradation) in the amount of antioxidants exuded from the polymer composition during storage, and thus leads to an improvement in the storage stability of the polymer composition.

[0177] In one embodiment, the polymer composition does not contain an organic peroxide of formula (I) and / or 2,4-diphenyl-4-methyl-1-pentene, but otherwise exhibits reduced exudation of the antioxidant compared to the polymer composition identical to the polymer composition of the present invention. The amount of exudation can be measured according to the method described below for the examples (i.e., under heading: Determination of additive content on pellet surface, i.e., antioxidant content).

[0178] In one embodiment, reduced exudation of antioxidants is manifested as a smaller amount of antioxidants on the surface of the pellets of the polymer composition compared to a comparative polymer composition stored under the same conditions as the polymer composition of the present invention, except that the polymer composition of the present invention does not contain an organic peroxide of formula (I) and / or 2,4-diphenyl-4-methyl-1-pentene, but otherwise has been stored for 4 weeks at 35°C under the conditions described under the heading "Determination of additive content, i.e., antioxidant content, on the pellet surface" of the section "Measurement Methods". For example, the polymer composition of the present invention may exhibit a 10% lower antioxidant content, preferably a 20% lower antioxidant content, and more preferably a 30% lower antioxidant content on the pellet surface compared to the comparative polymer composition after storage under the aforementioned conditions.

[0179] It is preferably understood that the polymer composition is the polymer composition of the present invention as defined above herein. Accordingly, it is understood that embodiments including the preferred embodiments described in relation to the aspects of the present invention regarding the polymer composition are also applicable to this aspect of the present invention. For example, the preferred characteristics and amounts of components a)-d) described in relation to the polymer composition of the present invention are also applicable to the polymer composition in use of the present invention.

[0180] In another aspect, the present invention provides a method for reducing the exudation of an antioxidant from a polymer composition comprising the antioxidant, said method

[0181] - Formulating a polymer composition by combining ethylene, at least one polyethylene copolymer of one or more polar comonomers and optionally one or more other nonpolar comonomers, at least one antioxidant, at least one crosslinking agent, and 2,4-diphenyl-4-methyl-1-pentene.

[0182] Includes,

[0183] Here, the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer, and

[0184] The above-mentioned crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I):

[0185]

[0186] In the above formula,

[0187] R 1 , R 2 and R 3 Each is independently selected from linear or branched C1-C6 alkyl groups;

[0188] R is the remainder of the organic peroxide.

[0189] Preferably, the amount of 2,4-diphenyl-4-methyl-1-pentene in the prepared polymer composition is at least 0.05 weight% with respect to the total weight of the polymer composition.

[0190] In another aspect, the present invention provides the use of a combination of a crosslinking agent of formula (I) (preferably tert-butylcumyl peroxide) and 2,4-diphenyl-4-methyl-1-pentene in a polymer composition comprising an antioxidant. The polymer composition is preferably the polymer composition described in any prior art.

[0191] The invention will now be further explained with reference to the following non-limiting embodiments.

[0192] measurement method

[0193] Unless otherwise specified in the description or experimental section, the following methods were used to determine characteristics.

[0194] weight% : % based on weight

[0195] density

[0196] Density was measured according to ISO 1183-1 / Method A. Sample preparation is performed by compression molding according to ISO 17855-2:2016.

[0197] melt flow rate

[0198] The Melt Flow Index (MFR) is determined according to ISO 1133 and expressed in g / 10 min. MFR is an indicator of the fluidity, and thus processability, of the polymer, namely polyethylene. The higher the Melt Flow Index, the lower the viscosity of the polymer. MFR is determined for polyethylene at 190°C, and 2.16 kg (MFR2) or 21.6 kg (MFR 21 It can be determined at different loadings such as ).

[0199] Methods for determining the amount of double bonds in a polymer, namely polyethylene copolymer, ASTM D3124-98 and ASTM D6248-98

[0200] Methods ASTM D3124-98 and ASTM D6248-98 apply to the determination of double bonds in polyethylene copolymer component (a). In this description of the method, polyethylene copolymer component (a) is hereinafter referred to as "polymer".

[0201] method ASTM D3124-98 and ASTM D6248-98, on the one hand, include a procedure for determining the amount of double bonds per 1,000 C atoms, based on the ASTM D3124-98 method. In the ASTM D3124-98 method, a detailed description is provided for the determination of vinylidene groups per 1,000 C atoms based on 2,3-dimethyl-1,3-butadiene. In the ASTM D6248-98 method, 1-octene and, respectively, Trans Based on -3-hexene, vinyl and per 1000 C atoms Trans - A detailed description for the determination of vinylene groups is provided. The sample preparation procedure described therein is for vinyl groups per 1,000 C atoms, vinylidene groups per 1,000 C atoms, and per 1,000 C atoms in the present invention Trans - Applied herein for the determination of vinylene groups. Although the ASTM D6248-98 method suggests the possible inclusion of the bromination procedure of the ASTM D3124-98 method, the samples relating to the present invention were not brominated. For the determination of the absorption coefficients for these three types of double bonds, 1-decene for vinyl, 2-methyl-1-heptene for vinylidene, and Trans Regarding vinylene Trans The following three compounds of -4-decene were used, and the procedures described in ASTM D3124-98 and ASTM-D6248-98 were followed, with the exceptions mentioned above.

[0202] Vinyl bonds, vinylidene bonds, and of the "polymer" Trans - The total amount of vinylene double bonds is analyzed by IR spectroscopy, and vinyl bonds, vinylidene bonds, and per 1,000 carbon atoms Trans- Given as the amount of vinylene bonds.

[0203] The polymer to be analyzed was compressed into thin films with a thickness of 0.5–1.0 mm. The actual thickness was measured. FT-IR analysis was performed on a Perkin Elmer Spectrum One. Two scans were 4 cm. -1 It was recorded with the resolution of .

[0204] 1) A polymer composition comprising a polyethylene copolymer containing less than 0.4 weight% of a polar comonomer

[0205] For polyethylene copolymers containing less than 0.4 wt% polar comonomers, three types of C=C functional group content are quantified, each having characteristic absorption and corrected for other model compounds to calculate individual absorption coefficients:

[0206] · Vinyl (R-CH=CH2): 910 cm -1 Through this, based on 1-decene [de-1-en], E = 13.13 l·mol -1 ㆍmm -1 Provides.

[0207] · Vinylidene (RR'C=CH2): 888 cm -1 Through this, based on 2-methyl-1-heptene [2-methylhept-1-en], E = 18.24 l·mol -1 ㆍmm -1 Provides.

[0208] · Trans-vinylene (R-CH=CH-R'): 965 cm -1 Through this, based on trans-4-decene [(E)-de-4-en], E = 15.14 l·mol -1 ㆍmm -1 Provides.

[0209] For a polyethylene copolymer having less than 0.4 wt% polar comonomer, the linear baseline correction is about 980 to 840 cm -1 It was applied in.

[0210] 2) A polymer composition comprising a polyethylene copolymer having 0.4 weight% or more of a polar comonomer

[0211] For polyethylene copolymers containing 0.4 wt% or more of polar comonomers, two types containing C=C functional groups were quantified, each having characteristic absorption and corrected for other model compounds to calculate individual absorption coefficients:

[0212] · Vinyl (R-CH=CH2): 910 cm -1 Through this, based on 1-decene [de-1-en], E = 13.13 l·mol -1 ㆍmm -1 Provides.

[0213] · Vinylidene (RR'C=CH2): 888 cm -1 Through this, based on 2-methyl-1-heptene [2-methylhept-1-ene], E = 18.24 l·mol -1 ㆍmm -1 Provides.

[0214] For the ethylene butyl acrylate system, the linear baseline correction is approximately 920 to 870 cm -1 It was applied in.

[0215] For the ethylene ethyl acrylate system, the linear baseline correction is approximately 920 to 825 cm -1 It was applied in.

[0216] For the ethylene methyl acrylate system, the linear baseline correction is approximately 930 to 870 cm -1 It was applied in.

[0217] Methods ASTM D3124-98 and ASTM D6248-98 also include, on the other hand, a procedure for determining the molar extinction coefficient. 0.18 mol·l in at least three carbon disulfide (CS2) -1 A solution was used, and the average value of the molar extinction coefficient was used.

[0218] The amount of vinyl groups derived from the polyunsaturated comonomer per 1,000 carbon atoms was determined and calculated as follows:

[0219] The polymer to be analyzed and the reference polymer were produced in the same reactor using essentially the same conditions, such as similar peak temperature, pressure, and production rate, but the only difference is that polyunsaturated comonomers are added during the polymerization of the polymer to be analyzed, whereas they are not added during the polymerization of the reference polymer. The total amount of vinyl groups of each polymer was determined by FT-IR measurements as described herein.

[0220] The baseline level of vinyl groups formed from chain transfer agents that are naturally formed by the process (if present) and generate vinyl groups is assumed to be the same for the reference polymer and the polymer to be analyzed, and this baseline level is then subtracted from the measured amount of vinyl groups in the polymer to be analyzed to yield the amount of vinyl groups per 1,000 C atoms derived from the polyunsaturated comonomer.

[0221] comonomer content

[0222] a) Quantification of alpha-olefin content in low-density polyethylene by NMR spectroscopy:

[0223] The comonomer content was determined by quantitative 13C nuclear magnetic resonance (NMR) spectroscopy after a basic assignment (J. Randall JMS - Rev. Macromol. Chem. Phys., C29(2&3), 201-317 (1989)). Experimental parameters were adjusted to ensure the measurement of the quantitative spectrum for this specific task.

[0224] Specifically, solution-state NMR spectroscopy was performed using a Bruker AvanceIII 400 spectrometer. A homogeneous sample was prepared by dissolving approximately 0.200 g of polymer in 2.5 ml of deuterated tetrachloroethene in a 10 mm sample tube using a heat block and rotary tube oven at 140 °C. Power-gated proton-decoupled 13C single-pulse NMR spectra were recorded using the following acquisition parameters: a flip angle of 90 degrees, 4 dummy scans, 4096 transients, an acquisition time of 1.6 s, a spectral width of 20 kHz, a temperature of 125 °C, a two-stage WALTZ proton decoupling scheme, and a relaxation delay of 3.0 s. The resulting FID was processed using the following parameters: zero-filling to 32 k data points and apodization using a Gaussian window function; It was processed using automatic zero-order and first-order phase correction and automatic baseline correction using a fifth-order polynomial restricted to the region of interest.

[0225] The amount was calculated using a simple correction ratio of the signal integral of a representative region, based on methods well known in the industry.

[0226] b) Determination of the comonomer content of polar comonomers in low-density polyethylene

[0227] The comonomer content (weight%) was determined in a known manner based on Fourier transform infrared spectroscopy (FTIR) determinations calibrated by quantitative nuclear magnetic resonance (NMR) spectroscopy.

[0228] The film was pressed using a Specac film press at 150°C with approximately 5 tons for 1-2 minutes, and then cooled in cold water in an uncontrolled manner. The exact thickness of the obtained film sample was measured.

[0229] After FTIR analysis, baselines were plotted in absorbance mode for the peaks to be analyzed. The absorbance peaks for the comonomers were normalized to the absorbance peaks of polyethylene. The FTIR peak height ratios were correlated with the polar comonomer content by a reference material determined by NMR. The NMR spectroscopy calibration procedure was performed using conventional methods well documented in the literature.

[0230] Quantification of polar comonomer content in polymer by NMR spectroscopy

[0231] The polar comonomer content was determined by quantitative nuclear magnetic resonance (NMR) spectroscopy after a basic assignment (e.g., "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., "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.

[0232] The determination of the polar comonomer content of ethylene ethyl acrylate, ethylene butyl acrylate, and ethylene methyl acrylate is exemplified below.

[0233] Weight % can be converted to mole % by calculation. This is well documented in the literature.

[0234] (1) Ethylene copolymer containing butyl acrylate

[0235] Film samples of the polymer were prepared for FTIR measurements: a thickness of 0.5-0.7 mm was used for ethylene butyl acrylate with a butyl acrylate content of more than 6 wt%, and a thickness of 0.1 to 0.4 mm was used for ethylene butyl acrylate with a butyl acrylate content of less than 6 wt%.

[0236] After FT-IR analysis, 3450 cm -1 At 3510 cm⁻¹, the maximum absorbance of the peak for butyl acrylate exceeding 6 wt% is 3510 cm⁻¹. -1 The absorbance value for the baseline at was subtracted (A 부틸 아크릴레이트 - A 3510 ). Next, 2020 cm -1 At the maximum absorbance peak for the polyethylene peak at 2120 cm⁻¹ -1 The absorbance value for the baseline at was subtracted (A 2020 - A 2120 ). Next (A 부틸 아크릴레이트 - A 3510 ) and (A 2020 - A 2120 The ratio between ) was calculated using the conventional method well documented in the literature.

[0237] 1735 cm -1 At 1850 cm⁻¹, the maximum absorbance of the peak for less than 6 wt% of the comonomer butyl acrylate is 1850 cm⁻¹. -1 The absorbance value for the baseline at was subtracted (A 부틸 아크릴레이트 - A 1850 ). Next, 2660 cm -1 At 1850 cm⁻¹, at the maximum absorbance peak for the polyethylene peak. -1 The absorbance value for the baseline at was subtracted (A 2660 - A 1850 ). Next (A 부틸 아크릴레이트 - A 1850 ) and (A 2660 - A 1850 Calculated the ratio between ).

[0238] (2) Ethylene copolymer containing ethyl acrylate

[0239] A polymer film sample was prepared for FTIR measurement: a thickness of 0.5 mm was used for ethylene ethyl acrylate.

[0240] After FT-IR analysis, approximately 3205 to 3295 cm⁻¹ -1 3450 cm with linear baseline correction applied -1 Maximum absorbance of the peak for ethyl acrylate at (A 에틸 아크릴레이트 Decided on ). Then, approximately 1975 to 2120 cm -1 2020 cm with linear baseline correction applied -1 Maximum absorbance peak for the polyethylene peak at (A 2020 Decided on ). Then (A 에틸 아크릴레이트 ) and (A 2020 The ratio between ) was calculated using the conventional method well documented in the literature.

[0241] (3) Ethylene copolymer containing methyl acrylate

[0242] Film samples of the polymer were prepared for FTIR measurement: a thickness of 0.1 mm was used for ethylene methyl acrylate with a methyl acrylate content of more than 8 wt%, and a thickness of 0.05 mm was used for ethylene methyl acrylate with a methyl acrylate content of less than 8 wt%.

[0243] After analysis, 3455 cm -1 At 3510 cm⁻¹, the maximum absorbance of the peak for methyl acrylate exceeding 8 wt% is 3510 cm⁻¹. -1 The absorbance value for the baseline at was subtracted (A 메틸 아크릴레이트 - A 3510 ). Next, 2675 cm -1 At the maximum absorbance peak for the polyethylene peak at 2450 cm⁻¹ -1 The absorbance value for the baseline at was subtracted (A2675 - A 2450 ). Next (A 메틸 아크릴레이트 - A 3510 ) and (A 2675 - A 2450 The ratio between ) was calculated using the conventional method well documented in the literature.

[0244] 1164 cm -1 At 1850 cm⁻¹, the maximum absorbance of the peak for comonomer methyl acrylate <8 wt% is 1850 cm⁻¹. -1 The absorbance value for the baseline at was subtracted (A 메틸 아크릴레이트 - A 1850 ). Next, 2665 cm -1 At 1850 cm⁻¹, at the maximum absorbance peak for the polyethylene peak. -1 The absorbance value for the baseline at was subtracted (A 2665 - A 1850 ). Next (A 메틸 아크릴레이트 - A 1850 ) and (A 2665 - A 1850 Calculated the ratio between ).

[0245] Determination of the additive content in the bulk of the pellets, i.e., the antioxidant content

[0246] X-ray fluorescence (XRF) was used to measure the antioxidant content within the bulk of the pellet, that is, within the polymer composition as a whole. As is well known to those skilled in the art, XRF involves measuring the emission of characteristic X-rays from a material excited by primary X-rays or gamma rays. Different chemical elements emit X-rays with characteristic energies, and thus the spectral profile of the XRF response from the material indicates the chemical elements within. The amount of each element contained in the material can be determined using calibration with known standards. XRF analysis was performed on a Malvern Panalytical Zetium instrument. The sulfur (S) content was determined by XRF calibrated with Malvern Panalytical standards covering the measured range. For XRF analysis, the composition was melt-pressed into a 3 mm plaque using a Collin press at 200 bar for 2 minutes at 160°C. The plaque was cooled within the press at a rate of 15°C per minute. The antioxidant content was calculated from the S content in a conventional manner using the antioxidant molecular weight and composition.

[0247] Determination of additive content on the pellet surface, i.e., antioxidant content

[0248] For storage studies, 100 g of pellets of the compositions of the present invention and the comparative were placed in sealed aluminum bags. One bag of pellets was prepared for each sample collection. The bags containing the pellets were stored at 35°C for 0, 2, and 4 weeks. The content of the components on the surface of the pellets was determined by placing 100 g of the pellets into an 800 ml beaker equipped with a magnetic stirrer. 100 ml of methanol was added, and then the pellets were stirred in the methanol for 5 minutes. A 5 ml sample was taken from the solvent using a syringe. When transferring the solution from the syringe to a vial to be used for HPLC analysis, the solution was passed through a 0.45 μm PTFE filter located at the tip of the syringe. The content of the components (TBCP, DCP, antioxidant, and MSD) in the solution was determined by HPLC analysis. This test is performed not only on the 'zero' sample at the start of the storage test, but also after storing the pellets at 35°C for 2 and 4 weeks. HPLC analysis was performed using an EC-C18 (150 x 4.6 mm) column such as Poroshell. The injection volume of the methanol solution was 5 μl. Gradient elution at 1 ml / min was performed at 50°C with an 85:15% methanol-water mixture by volume for test times 0-5 min and 11-15 min, and with 100% methanol for test times 6-15 min.

[0249] Experiment Department

[0250] Components of the polymer compositions of the embodiments and comparative examples of the present invention

[0251] All polymers are low-density polyethylene produced in a high-pressure reactor.

[0252] LDPE1 : A terpolymer of ethylene, butyl acrylate (polar comonomer) and 1,7-octadiene (polyunsaturated comonomer), produced in a high-pressure tubular reactor, with a typical MFR2 of about 1.9 g / 10 min and about 0.50 vinyl / 1000 C. Content of polar comonomer = 0.36 wt%.

[0253] LDPE2 : A copolymer of ethylene and 1,7-octadiene (polyunsaturated comonomer) produced in a high-pressure tubular reactor, with an MFR2 of about 1.7 g / 10 min and about 0.60 vinyl / 1000 C (for comparison).

[0254] Antioxidant (AO) : 4,4'-Thiobis(2-tert-butyl-5-methylphenol) (CAS No. 96-69-5), commercially available.

[0255] crosslinking agent : tert-butylcumyl peroxide (TBCP) (CAS No. 3457-61-2) or dicumyl peroxide (DCP) (CAS No. 80-43-3), both are commercially available.

[0256] 2,4-Diphenyl-4-methyl-1-pentene (MSD) : CAS No. 6362-80-7, commercially available.

[0257] Preparation of polymer compositions of the embodiments and comparative examples of the present invention

[0258] In the following examples, an antioxidant was added to polyethylene (supplied in the form of pellets) by compounding through melt mixing, and then the prepared composition was re-pelletized to form pellets. Subsequently, a crosslinker was added to the composition by dispensing the crosslinker (the crosslinker is in liquid form) onto the pellets preheated at 80°C for 12 hours. The pellets and the crosslinker were stirred for 45 minutes, and then continuously heated at 80°C until the pellets were dried. When 2,4-diphenyl-4-methyl-1-pentene was used in the composition, it was added to the preheated pellets together with the crosslinker under the same conditions as described above for the crosslinker.

[0259] The results of the composition and storage studies of the polymer compositions of Examples 1-4 (IE1-IE4) and Comparative Examples 1-3 (CE1, CE2, and CE3) of the present invention are presented in Table 1.

[0260] The amounts of antioxidant (AO), crosslinking agent (TBCP) or (DCP), and (if present) 2,4-diphenyl-4-methyl-1-pentene (MSD) are given in weight% relative to the total weight of the polymer composition.

[0261] Results of the component and storage study of the polymer compositions of Examples 1-4 and Comparative Examples 1-3 of the present invention ingredient Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 polyethylene LDPE1 LDPE1 LDPE1 LDPE1 LDPE1 LDPE1 LDPE2 AO (weight%) 0.11 0.11 0.11 0.11 0.11 0.11 0.09 TBCP (weight%) 1.35 1.65 1.65 1.65 1.35 - 0.80 DCP (weight%) - - - - - 1.35 - MSD (weight%) 0.35 0.10 0.15 0.20 - 0.35 0.15 Amount of AO on pellet surface (ppm) 0 weeks <5 <5 <5 <5 <5 <5 76 2 weeks <5 61 <5 14 247 37 384 4 weeks 7 187 <5 32 384 91 497

[0262] As shown in Table 1, the polymer composition of the embodiment of the present invention, comprising both the peroxide according to the formula (I) defined herein and 2,4-diphenyl-4-methyl-1-pentene, exhibited significantly lower exudation of antioxidants, particularly after storage, compared to the polymer compositions of Comparative Examples 1 and 2, which did not contain this combination of peroxide and 2,4-diphenyl-4-methyl-1-pentene. The use of a different LDPE (LDPE2) without polar comonomers also did not result in the same reduction in antioxidant exudation. Therefore, the polymer composition of the present invention has improved storage stability.

Claims

Claim 1 a) at least one polyethylene copolymer comprising ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers; b) at least one antioxidant; c) at least one crosslinking agent; and d) a polymer composition comprising 2,4-diphenyl-4-methyl-1-pentene, wherein the content of one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer; and wherein the crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I): In the above formula, R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C6 alkyl groups; R is the remainder of the organic peroxide. Claim 2 A polymer composition according to claim 1, wherein the polyethylene copolymer is a low-density polyethylene (LDPE) copolymer, preferably an unsaturated LDPE copolymer and / or; and wherein the polyethylene copolymer comprises vinyl groups in a total amount of at least 0.20 / 1000 carbon atoms, preferably at least 0.30 / 1000 carbon atoms, more preferably at least 0.40 / 1000 carbon atoms. Claim 3 A polymer composition according to claim 1 or 2, wherein one or more polar comonomers are selected from acrylates, methacrylates, acetates, or mixtures thereof, preferably selected from C1 to C6 alkyl acrylates, C1 to C6 alkyl methacrylates, vinyl acetates, or mixtures thereof. Claim 4 In any one of claims 1 to 3, the one or more other nonpolar comonomers are present, preferably polyunsaturated comonomers having straight carbon chains having at least 8 carbon atoms, wherein at least 4 carbon atoms are located between non-conjugated double bonds and at least one of the double bonds is at the terminal; for example, a diene, e.g., C8 to C 14 A polymer composition selected from non-conjugated dienes, e.g., 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, or mixtures thereof. Claim 5 A polymer composition according to any one of claims 1 to 4, wherein the antioxidant is present in an amount of at least 0.005 weight%, preferably at least 0.01 weight%, more preferably at least 0.02 weight%, and most preferably at least 0.04 weight% with respect to the total weight (100 weight%) of the polymer composition. Claim 6 A polymer composition according to any one of claims 1 to 5, wherein the antioxidant is selected from the group consisting of sterically hindered or semi-hindered phenols, aromatic amines, aliphatic sterically hindered amines, thio compounds, and mixtures thereof; preferably, the antioxidant is a sulfur-containing phenolic antioxidant; more preferably, the polymer composition is thiobisphenol, e.g., 4,4'-thiobis(2-tert-butyl-5-methylphenol), 2,2'-thiobis(6-t-butyl-4-methylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,6-bis(octylthiomethyl)-o-cresol, or a mixture thereof. Claim 7 A polymer composition according to any one of claims 1 to 6, wherein the polymer composition comprises a crosslinking agent in an amount of at least 0.2 weight%, preferably at least 0.3 weight%, more preferably at least 0.4 weight%, most preferably at least 0.5 weight%, e.g. at least 0.6 weight%, particularly at least 0.75 weight%, based on the total weight (100 weight%) of the polymer composition. Claim 8 In any one of paragraphs 1 through 7, R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C4 alkyl groups, preferably R 1 , R 2 and R 3 A polymer composition that is identical or different and is each a methyl group or an ethyl group, particularly a methyl group. Claim 9 In any one of claims 1 to 8, the crosslinking agent is selected from the group consisting of di-tert-amyl peroxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumyl peroxide, di(tert-butyl)peroxide, butyl-4,4-bis(tert-butylperoxy)-valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, bis(tert-butylperoxyisopropyl)benzene, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof; A polymer composition preferably 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, tert-butylcumyl peroxide, di(tert-butyl)peroxide, or a mixture thereof; in particular tert-butylcumyl peroxide. Claim 10 A polymer composition according to any one of claims 1 to 9, wherein the polymer composition comprises, for example, 2,4-diphenyl-4-methyl-1-pentene in the range of 0.05% by weight of 2,4-diphenyl-4-methyl-1-pentene, preferably more than 0.05% by weight of 2,4-diphenyl-4-methyl-1-pentene, more preferably at least 0.06% by weight of 2,4-diphenyl-4-methyl-1-pentene, much more preferably at least 0.07% by weight of 2,4-diphenyl-4-methyl-1-pentene, most preferably at least 0.08% by weight of 2,4-diphenyl-4-methyl-1-pentene, for example in the range of 0.08 to 1.5% by weight, based on the total weight (100% by weight) of the polymer composition. Claim 11 A process for producing a polymer composition according to any one of claims 1 to 10, wherein the process comprises blending a polyethylene copolymer with an antioxidant, a crosslinking agent, and 2,4-diphenyl-4-methyl-1-pentene. Claim 12 A crosslinked polymer composition that can be obtained by crosslinking a polymer composition according to any one of claims 1 to 10, preferably obtained thereby. Claim 13 A power cable comprising a polymer composition according to any one of claims 1 to 10 or a cross-linked polymer composition according to claim 12, preferably comprising at least one layer formed therefrom, preferably an insulating layer, and a conductor surrounded by such a layer. Claim 14 A process for producing a power cable, wherein the process comprises: (i) applying, preferably by (co)extrusion, on one or more conductors, at least one layer comprising a polymer composition according to any one of claims 1 to 10, preferably an insulating layer; and (ii) optionally, a step of crosslinking the polymer composition. Claim 15 (i) at least one polyethylene copolymer of ethylene, one or more polar comonomers and optionally one or more other nonpolar comonomers, and (ii) a combination of a crosslinking agent and 2,4-diphenyl-4-methyl-1-pentene in a polymer composition further comprising an antioxidant, for use in reducing the exudation of the antioxidant from the polymer composition, wherein the content of the one or more polar comonomers in the polyethylene copolymer is in the range of 0.001 to 5.0 weight% with respect to the total weight of the polyethylene copolymer; and the crosslinking agent is an organic peroxide having a structural formula according to the following chemical formula (I). In the above equation, R 1 , R 2 and R 3 Each is independently selected from linear and branched C1-C6 alkyl groups; R is the remainder of the organic peroxide.

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