Cable comprising layer of crosslinkable polyethylene composition having increased crosslinking speed

Abstract

The present invention relates to a cable comprising a layer comprising a crosslinkable polyethylene composition comprising one or more ethylene copolymers containing monomer units having polar groups and monomer units having hydrolysable silane groups, and a sulfonic acid, the monomer units having polar groups are present in an amount of 0.02 to 25 mol%, wherein the layer thickness is at least 0.9 mm.

Description

Technical Field

[0001] The present invention relates to cables, in particular low voltage (LV) and medium voltage (MV) cables, which comprise a layer containing a crosslinkable polyethylene composition, wherein the layer is relatively thick. Background Art

[0002] Low voltage power cables, i.e., power cables with a voltage below 6 kV, usually comprise an electrical conductor coated with an insulating layer. Such cables are also referred to as single-wire cables. Optionally, two or more such single-wire cables are surrounded by a common outermost sheath layer (sheath).

[0003] The insulating layer of low voltage power cables is usually made of a polymer composition containing a polymer matrix resin (such as polyolefin). The material commonly used as the matrix resin is polyethylene. In addition, in the final cable, the polymer matrix resin is usually crosslinked.

[0004] For this and other applications, such as for welding cables or electric vehicle charging cables, peroxide-crosslinked EPR (ethylene propylene rubber) is currently mainly used. However, the manufacturing process of these cables is very complex because the insulating layer needs to be crosslinked in a vulcanization tube first, then the sheath is coated, and it is passed through the vulcanization tube again to crosslink the sheath. Therefore, for such flexible cables, it is most common that both the insulating layer and the sheath are crosslinked. For standard non-flexible cables, only the insulating layer is crosslinked.

[0005] For example, WO 00 / 68957 A1 discloses a different method for providing crosslinking in a cable layer, in which a cable is disclosed having at least one insulating layer or protective layer composed of a crosslinked ethylene-(meth)acrylic acid alkyl ester-unsaturated silane terpolymer composition (such as ethylene-(meth)acrylic acid alkyl ester-vinyltrialkoxysilane terpolymer). In this type of composition, the silanol groups can be crosslinked by wet curing.

[0006] There is a continuing need for such polyethylene compositions that provide improved crosslinking behavior (such as in terms of the time required for crosslinking the material, especially at ambient temperature).

[0007] For example, EP 2251365 A1 and EP 2363267 A1 disclose the use of vinyltris(acetoxy)silane as a comonomer in an ethylene terpolymer, which can result in an improved hydrolysis reactivity of the acyl silane relative to the alkoxysilane, thus increasing the crosslinking speed.

[0008] Therefore, the object of the present invention is to provide a polyethylene composition for a cable layer, which shows an increased crosslinking speed, especially when the crosslinking is carried out at ambient temperature and the cable layer has a relatively high thickness (such as a thickness of 0.9 mm or more). Summary of the Invention

[0009] The present invention can achieve this object based on the following discovery: It is possible to provide a cable having a layer thickness of at least 0.9 mm and comprising a polyethylene containing crosslinkable silane groups and polar comonomer units, and if a sulfonic acid silanol condensation catalyst is used in the composition, especially when crosslinking at ambient temperature, its crosslinking rate will be greatly increased.

[0010] Accordingly, the present invention provides a cable comprising a layer containing or consisting of a crosslinkable polyethylene composition, said crosslinkable polyethylene composition comprising or consisting of the following substances:

[0011] (A1) One or more ethylene copolymers, said ethylene copolymers containing monomer units having polar groups and monomer units having hydrolyzable silane groups, wherein, based on the total polyethylene composition, the amount of monomer units having polar groups is 0.02 to 25 mol%, preferably 1 to 15 mol%, more preferably 2.5 to 15 mol%, preferably 4 to 12 mol%, and

[0012] (B) Sulfonic acid,

[0013] wherein the layer thickness is at least 0.9 mm, preferably at least 1.2 mm, more preferably at least 2.0 mm, most preferably at least 3.0 mm. The layer thickness is preferably at most 8.0 mm, preferably in the range of 1.2 mm to 5.5 mm, preferably in the range of 1.4 mm to 3.6 mm, preferably in the range of 2.4 mm to 3.6 mm. For low-voltage cables (<6 kV), the thickness is preferably in the range of 1.2 mm to 3.0 mm, preferably in the range of 2.4 mm to 3.0 mm. For medium-voltage cables (>6 kV to 68 kV), the thickness is preferably greater than 3.00 mm and at most 8.0 mm, preferably in the range of 3.2 mm to 5.5 mm, preferably in the range of 3.2 mm to 3.6 mm.

[0014] The cables of the present invention exhibit highly improved crosslinking behavior, for example, the crosslinking rate is greatly increased in the crosslinkable layer containing the crosslinkable polyethylene composition, especially when crosslinking at ambient temperature, and this effect is even more obvious when the layer thickness increases.

[0015] Obviously, this effect is caused by the synergistic effect between the sulfonic acid used as the silanol condensation catalyst and the crosslinkable polyethylene composition used in the cable layer, and this synergistic effect does not exist when using other known silanol condensation catalysts (such as tin-containing catalysts).

[0016] Ambient temperature is generally defined as 20 °C to 25 °C, most preferably 23 °C. Detailed Embodiments

[0017] The polyolefin composition of the present invention comprises one or more ethylene copolymers (A1) or consists of one or more ethylene copolymers (A1). Preferably, the polyolefin composition comprises two ethylene copolymers (A1) different from each other or consists of two ethylene copolymers (A1) different from each other.

[0018] The one or more ethylene copolymers (A1) containing monomer units having a polar group can be prepared, for example, by grafting a polyolefin with a compound containing a polar group, i.e., by chemically modifying the polyolefin polymer by adding a compound containing a polar group (mainly in a radical reaction). Grafting is described, for example, in US 3,646,155 and US 4,117,195.

[0019] However, preferably, the one or more polyolefin copolymers (a) are prepared by copolymerizing ethylene in the presence of monomer units having a polar group and monomer units having a hydrolyzable silyl group.

[0020] In the case of copolymerization, the complete monomer unit having a polar group is represented by the expression "monomer unit having a polar group". Thus, the weight fraction of the monomer unit having a polar group in the polyolefin copolymer obtained by copolymerization can be simply calculated by using the weight ratio of the monomer unit having a polar group polymerized into the polyolefin copolymer. For example, when an ethylene copolymer containing a polar group is prepared by copolymerizing an ethylene monomer with a vinyl compound containing a polar group, the vinyl moiety forming the polymer main chain portion after polymerization also contributes to the weight fraction of the "monomer unit having a polar group".

[0021] Preferably, the monomer unit having a polar group is selected from siloxane, amide, acid anhydride, carboxylic acid, carbonyl, hydroxyl, ester, and / or epoxy group.

[0022] As examples of the monomer unit having a polar group, the following can be mentioned: (a) vinyl carboxylates, such as vinyl acetate, vinyl pivalate, and mixtures thereof; (b) (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and mixtures thereof; (c) ethylenically unsaturated carboxylic acids, such as (meth)acrylic acid, maleic acid, fumaric acid, and mixtures thereof; (d) (meth)acrylic acid derivatives, such as (meth)acrylonitrile, (meth)acrylamide, and mixtures thereof; and (e) vinyl ethers, such as vinyl methyl ether, vinyl phenyl ether, and mixtures thereof.

[0023] Among these monomers, vinyl esters of monocarboxylic acids having 1 to 4 carbon atoms, such as vinyl acetate, and (meth)acrylates of alcohols having 1 to 4 carbon atoms, such as methyl (meth)acrylate, and mixtures thereof are preferred.

[0024] Particularly preferred monomers are butyl acrylate, ethyl acrylate, methyl methacrylate, methyl acrylate and / or mixtures thereof. Two or more such ethylenically unsaturated compounds can be used in combination. The term “(meth)acrylic acid” is intended to include acrylic acid and methacrylic acid.

[0025] Preferably, based on the total polyethylene composition, the amount of monomer units having polar groups is from 0.02 to 25 mol%, preferably from 0.1 to 20 mol%, more preferably from 0.2 to 15 mol%, more preferably from 1.0 to 15 mol%, more preferably from 2.5 to 15 mol%, preferably from 4 to 12 mol%, and most preferably from 7 to 12 mol%.

[0026] Specifically, when component (A2) in any of the embodiments described below is also present in the polyethylene composition, based on the total polyethylene composition, the amount of monomer units having polar groups is preferably from 1 to 15 mol%, more preferably from 4 to 15 mol%, and even more preferably from 7 to 12 mol%.

[0027] In addition to monomer units having polar groups, the ethylene copolymer (a) further comprises monomer units having hydrolyzable silyl groups. These silyl groups can be introduced into the polymer by grafting as described in US 3,646,155 and US 4,117,195, or preferably by ethylene copolymerization in the presence of monomer units having polar groups and monomer units having hydrolyzable silyl groups.

[0028] In the case of using copolymerization, the complete monomer having a silyl group is represented by the expression “monomer unit having a hydrolyzable silyl group”.

[0029] Preferably, the ethylene copolymer (a) has been obtained by copolymerization. The copolymerization is preferably carried out with monomer units having hydrolyzable silyl groups, which are represented by the following formula

[0030] R 1 SiR 2 q Y 3-q (I)

[0031] Wherein

[0032] R 1 is an ethylenically unsaturated hydrocarbon group, a hydrocarbyloxy group or a (meth)acryloyloxyhydrocarbyl group,

[0033] R 2is an aliphatic saturated hydrocarbon group, Y may be the same or different and is a hydrolyzable organic group, and q is 0, 1 or 2.

[0034] Specific examples of monomer units having a hydrolyzable silyl group are the following monomer units, where R 1 is vinyl, allyl, isopropenyl, butenyl, cyclohexyl or γ-(meth)acryloyloxypropyl; Y is methoxy, ethoxy, formyloxy, acetyloxy, propionyloxy, alkylamino or arylamino; if present, R 2 is methyl, ethyl, propyl, decyl or phenyl.

[0035] Preferred monomer units having a hydrolyzable silyl group are represented by the following formula

[0036] CH2=CHSi(OA)3 (II)

[0037] wherein A is a hydrocarbon group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms.

[0038] The most preferred monomer units having a hydrolyzable silyl group are vinyltrimethoxysilane, vinylbis(methoxyethoxy)silane, vinyltriethoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane and vinyltriacetoxysilane.

[0039] In the presence of monomer units having a polar group and monomer units having a hydrolyzable silyl group, the copolymerization of ethylene can be carried out under any suitable conditions that result in the copolymerization of ethylene and the two monomer units. Therefore, the resulting ethylene copolymer (A1) can also be labeled as a terpolymer.

[0040] Preferably, based on the total polyethylene composition, the amount of monomer units having a hydrolyzable group is from 0.001% by weight to 15% by weight, more preferably from 0.01% by weight to 5% by weight, and most preferably from 0.1% by weight to 2% by weight.

[0041] Preferably, as measured according to ISO 1133 at a temperature of 190 °C and a load of 2.16 kg, the MFR of one or more ethylene copolymers of (A1) 2.16 is from 1 g / 10 min to 50 g / 10 min, preferably from 2 g / 10 min to 45 g / 10 min, and preferably from 3.0 g / 10 min to 40 g / 10 min.

[0042] The crosslinkable polyolefin composition in the cable layer of the present invention contains sulfonic acid as a silanol condensation catalyst (component (B)).

[0043] Preferably, based on the total polyethylene composition, the amount of the sulfonic acid present is from 0.0001 to 9% by weight, more preferably from 0.0005 to 7% by weight, even more preferably from 0.001 to 5% by weight, still even more preferably from 0.005 to 4% by weight, still even more preferably from 0.01 to 3% by weight, still even more preferably from 0.025 to 2% by weight, and most preferably from 0.05 to 1% by weight.

[0044] Preferably, the sulfonic acid contains 10 or more C atoms, more preferably 12 or more C atoms, and most preferably 14 or more C atoms. The sulfonic acid further contains at least one aromatic group, for example, it may be a benzene, naphthalene, phenanthrene or anthracene group. One, two or more sulfonic acid groups may be present in the organic sulfonic acid, and the sulfonic acid group may be attached to a non-aromatic group of the organic sulfonic acid or preferably to an aromatic group.

[0045] Even more preferably, the sulfonic acid includes the structural element:

[0046] Ar(SO3H) x (III)

[0047] wherein Ar is an aryl group, which may be substituted or unsubstituted, and x is at least 1, such as 1, 2 or 3.

[0048] The organoaromatic sulfonic acid silanol condensation catalyst may include the structural unit according to formula (III) one or more times, such as two or three times. For example, two structural units according to formula (III) may be connected to each other by a bridging group (such as an alkylene group).

[0049] Preferably, Ar is an aryl group substituted by at least one C4 to C 30 hydrocarbyl group, more preferably a C4 to C 30 alkyl group substituted aryl group.

[0050] The aryl group Ar is preferably a phenyl group, a naphthyl group or an aromatic group containing three fused rings, such as phenanthrene and anthracene.

[0051] Preferably, in formula (III), x is 1, 2 or 3, more preferably, x is 1 or 2.

[0052] In addition, preferably, the compound used as the organoaromatic sulfonic acid silanol condensation catalyst has 10 to 200 C atoms, more preferably 14 to 100 C atoms.

[0053] In a preferred embodiment, Ar is a hydrocarbyl group substituted aryl group, and the total compound contains 14 to 28 carbon atoms, and still further preferably, the Ar group is a hydrocarbyl group substituted benzene ring or naphthalene ring. In the case of benzene, the hydrocarbyl group contains 8 to 20 carbon atoms, and in the case of naphthalene, the hydrocarbyl group contains 4 to 18 atoms.

[0054] More preferably, the hydrocarbyl group is an alkyl substituent having from 10 to 18 carbon atoms, and even more preferably, the alkyl substituent contains 12 carbon atoms and is selected from dodecyl and tetrapropyl. Due to commercial availability, the aryl group is most preferably a benzene substituent having an alkyl substituent containing 12 carbon atoms.

[0055] The currently most preferred compounds are dodecylbenzenesulfonic acid and tetrapropylbenzenesulfonic acid.

[0056] The silanol condensation catalyst can also be a precursor of a sulfonic acid compound, including all of its preferred embodiments mentioned, i.e., a compound which is converted to such a compound by hydrolysis. Such a precursor is, for example, an acid anhydride of a sulfonic acid compound, or a sulfonic acid having a hydrolysable protecting group (such as acetyl) which can be removed by hydrolysis.

[0057] In a second preferred embodiment, the sulfonic acid catalyst is selected from those described in EP 1 309 631 and EP 1 309 632, i.e.,

[0058] a) Compounds selected from the group consisting of:

[0059] (i) An alkylated naphthalene monosulfonic acid substituted with 1 to 4 alkyl groups, wherein each alkyl group is a straight-chain or branched-chain alkyl group having 5 to 40 carbon atoms, each alkyl group being the same or different, and wherein the total number of carbon atoms in the alkyl groups is in the range of 20 to 80 carbon atoms;

[0060] (ii) An arylalkylsulfonic acid, wherein the aryl group is a phenyl or naphthyl group and is substituted with 1 to 4 alkyl groups, wherein each alkyl group is a straight-chain or branched-chain alkyl group having 5 to 40 carbon atoms, each alkyl group being the same or different, and wherein the total number of carbon atoms in the alkyl groups is in the range of 12 to 80;

[0061] (iii) Derivatives of (i) or (ii) which are hydrolysable to the corresponding alkylnaphthalene monosulfonic acid or arylalkylsulfonic acid, selected from their acid anhydrides, esters, acetylates, epoxy-closed esters and amine salts;

[0062] (iv) Metal salts of (i) or (ii), wherein the metal ion is selected from copper, aluminum, tin and zinc; and

[0063] b) Compounds selected from the group consisting of:

[0064] (i) An alkylated aryl disulfonic acid, selected from structure (IV):

[0065]

[0066] and structure (V):

[0067]

[0068] Wherein, R1 and R2 are each the same or different and are straight-chain or branched alkyl groups having 6 to 16 carbons, y is from 0 to 3, z is from 0 to 3, provided that y + z is from 1 to 4, n is from 0 to 3, and X is a divalent moiety selected from the group consisting of: –C(R3)(R4)–, wherein R3 and R4 are each H or independently are straight-chain or branched alkyl groups having 1 to 4 carbons, and n is 1; –C(=O)–, wherein n is 1; –S–, wherein n is from 1 to 3; and –S(O)2–, wherein n is 1; and

[0069] (ii) derivatives of (i) which are hydrolyzable to alkylated aryl disulfonic acids, selected from their acid anhydrides, esters, epoxy-blocked sulfonates, acetylates, and amine salts,

[0070] and all preferred embodiments of those sulfonic acids described in the aforementioned European patent.

[0071] More preferably, the sulfonic acid is an acid according to formula (VI)

[0072] ArSO3H (VI)

[0073] or a precursor thereof, where Ar is a hydrocarbon-substituted aryl group and the total compound contains 14 to 28 carbon atoms.

[0074] Preferably, the Ar group is a hydrocarbon-substituted benzene ring or naphthalene ring. In the case of benzene, the hydrocarbon group contains 8 to 20 carbon atoms, and in the case of naphthalene, the hydrocarbon group contains 4 to 18 carbon atoms.

[0075] More preferably, the hydrocarbon group is an alkyl substituent having 10 to 18 carbon atoms, and even more preferably the alkyl substituent contains 12 carbon atoms and is selected from dodecyl and tetrapropyl. Due to commercial availability, the most preferred aryl group is a benzene substituent having an alkyl substituent containing 12 carbon atoms.

[0076] Preferably, the sulfonic acid-based catalyst includes dodecylbenzenesulfonic acid, tetrapropylbenzenesulfonic acid, alkylated naphthalenesulfonic acid, arylalkylsulfonic acid, alkylated aryl disulfonic acid, or a mixture thereof, preferably consisting of dodecylbenzenesulfonic acid or tetrapropylbenzenesulfonic acid.

[0077] The silanol condensation catalyst can also be a precursor of the compound of formula (VI), i.e., a compound that is converted to the compound of formula (VI) by hydrolysis. Such a precursor is, for example, the acid anhydride of the sulfonic acid compound of formula (VI). Another example is a sulfonic acid of formula (VI) having a hydrolyzable protecting group, such as an acetyl group, which can be removed by hydrolysis to give the sulfonic acid of formula (VI).

[0078] The silanol condensation catalyst is preferably added as a crosslinking catalyst masterbatch (CM) to the crosslinkable polyolefin composition of the present invention. The masterbatch preferably comprises the above-mentioned silanol condensation catalyst and a polymer carrier, as well as optional other additives such as antioxidants. The polymer carrier is preferably an ethylene copolymer, more preferably a copolymer of ethylene and a monomer containing an alkyl acrylate group, and most preferably an ethylene butyl acrylate copolymer.

[0079] The crosslinkable polyolefin composition preferably further comprises a copolymer (A2) of ethylene and a C3 to C8 α-olefin comonomer, having a density of 850 to 970 kg / m 3 , and an MFR2 of 0.1 to 50 g / 10 min measured according to ISO 1133 at a temperature of 190 °C and a load of 2.16 kg.

[0080] If the ethylene copolymer (A2) is present in the crosslinkable polyethylene composition, the effect of improving the crosslinking behavior (e.g., in terms of the required crosslinking time) is particularly significant.

[0081] Thus, in a preferred embodiment, the crosslinkable polyethylene composition of the layers in the cables of the present invention comprises the components (A1), (A2) and (B) in any of the embodiments described herein or consists of the components (A1), (A2) and (B) in any of the embodiments described herein.

[0082] The ethylene copolymer (A2) may include high-density, medium-density, low-density or even very low-density ethylene copolymers. Its density is preferably in the range of 850 to 970 kg / m 3 , more preferably in the range of 860 to 930 kg / m 3 , even more preferably in the range of 860 kg / m 3 to 915 kg / m 3 .

[0083] Measured according to ISO 1133, the MFR2 of the ethylene copolymer (A2) is preferably 0.5 to 25 g / 10 min, more preferably 1.0 to 15 g / 10 min, and even more preferably 1.5 to 10 g / 10 min.

[0084] The ethylene copolymer (A2) is preferably a copolymer of ethylene and a C3 to C 12 α-olefin comonomer (such as propylene, 1-butene, 1-hexene, 1-octene and 1-decene). More preferably, it is a copolymer of ethylene and 1-octene. Measured according to ISO 1183-187, the density of the copolymer of ethylene and 1-octene is preferably in the range of 850 kg / m 3 to 930 kg / m 3 , more preferably in the range of 855 kg / m 3 to 920 kg / m3 in the range of, and even more preferably at 870 kg / m 3 to 910 kg / m 3 .

[0085] Preferably, ethylene-1-butene or ethylene-1-octene copolymers (plastomers) can be used. Any copolymer of ethylene and 1-butene or 1-octene having the properties defined above can be used. Preferred materials are commercially available, such as those with the trade name Queo from Borealis, the trade name Engage or Affinity from DOW Chemical Corp (USA), or the trade name Tafmer from Mitsui Chemicals.

[0086] Alternatively, the preparation of these plastomers can be carried out in the following manner by known methods: in a single-stage or two-stage polymerization process, including solution polymerization, slurry polymerization, gas-phase polymerization, or a combination thereof, in the presence of suitable catalysts known to those skilled in the art (such as vanadium oxide catalysts or single-site catalysts, such as metallocenes or constrained geometry catalysts). Preferably, metallocene-type catalysts are used.

[0087] Preferably, these plastomers are prepared by a single-stage or two-stage solution polymerization process, especially by a high-temperature solution polymerization process above 100 °C.

[0088] Such processes are mainly based on polymerizing monomers and suitable comonomers in a liquid hydrocarbon solvent, and the resulting polymer is soluble in this solvent. The polymerization is carried out at a temperature above the melting point of the polymer, thereby obtaining a polymer solution. The solution is flash-evaporated to separate the polymer from unreacted monomers and solvents. Then the solvent is recovered in the process and recycled.

[0089] Preferably, the solution polymerization process is a high-temperature solution polymerization process using a polymerization temperature above 100 °C. More preferably, the polymerization temperature is at least 110 °C, and even more preferably at least 150 °C. The polymerization temperature can be up to 250 °C.

[0090] The pressure in this solution polymerization process is preferably in the range of 10 to 100 bar, more preferably 15 to 100 bar, and even more preferably 20 to 100 bar. The liquid hydrocarbon solvent used is preferably a C 5-12 hydrocarbon, which can be unsubstituted or substituted by a C 1-4 alkyl group, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, and hydrofined naphtha. More preferably, an unsubstituted C 6-10 hydrocarbon solvent is used.

[0091] A known solution technique applicable to the process according to the present invention is Borceed TM technology.

[0092] The crosslinkable polyethylene composition in a cable comprising a layer containing the crosslinkable polyethylene composition preferably has a density of 915 kg / m 3 or more, more preferably 920 kg / m 3 or more, and most preferably 925 kg / m 3 or more.

[0093] Generally, the density of the crosslinkable polyethylene composition is 970 kg / m 3 or less.

[0094] The polyolefin composition in a cable comprising a layer containing the crosslinkable polyethylene composition can be crosslinked.

[0095] Preferably, the crosslinking is carried out at ambient temperature.

[0096] The crosslinking is preferably carried out by so-called moisture curing known in the art. For example, refer to WO 95 / 17463 and WO 00 / 36612. In the first step, the silyl groups of the ethylene copolymer are hydrolyzed under the influence of water or steam, resulting in the cleavage of alcohols and the formation of silanol groups. In the second step, the silanol groups are crosslinked by a condensation reaction with water cleavage. In both steps, the silanol condensation catalysts described herein are preferably used as catalysts.

[0097] The crosslinking is preferably carried out under ambient conditions, preferably at a relative humidity of 45% to 65% and a temperature of 20°C to 25°C, and most preferably at a relative humidity of 55% and a temperature of 23°C.

[0098] By measuring the thermal deformation under a load of 200°C and 20 N / cm 2 and determined according to IEC 60811-507, the crosslinkable polyolefin composition in a cable comprising a layer containing the crosslinkable polyethylene composition can preferably have a thermoset elongation not exceeding 180%, more preferably not exceeding 100%, and even more preferably not exceeding 80%.

[0099] By measuring the thermal deformation under a load of 200°C and 20 N / cm 2 and determined according to IEC 60811-507, the crosslinkable polyolefin composition in a cable comprising a layer containing the crosslinkable polyethylene composition can preferably have a thermoset elongation of not less than 10%, more preferably not less than 15%, and even more preferably not less than 20%. For the thermoset elongation, each lower limit can be combined with each upper limit shown.

[0100] The cable of the present invention is preferably a low voltage (LV) or medium voltage (MV) cable.

[0101] At least one layer of the cable is preferably an insulating layer or a sheath layer.

[0102] The present invention also relates to a method for crosslinking a crosslinkable polyethylene composition for a cable layer according to any one of the embodiments described herein, wherein the crosslinking is carried out at ambient temperature.

[0103] Preferably, in the method of the present invention, the crosslinking time to reach a degree of thermosetting elongation of less than 100% is 100 hours or shorter, more preferably 75 hours or shorter, and most preferably 50 hours or shorter.

[0104] Furthermore, preferably, in the method of the present invention, the crosslinking time to reach a degree of thermosetting elongation of less than 80%, more preferably less than 70%, and most preferably less than 60% is 100 hours or shorter.

[0105] The present invention also relates to the use of a crosslinkable polyethylene composition according to any one of the embodiments described herein for crosslinking at a faster rate in a layer of a cable according to any one of the embodiments described herein having a thickness of at least 0.9 mm at ambient temperature, preferably under ambient conditions.

[0106] The present invention is further described below by way of examples with reference to the accompanying drawings. Description of the Drawings

[0107] Figure 1 The change in the thermosetting elongation of tapes of ethylene polymer compositions (A) and comparative compositions with different thicknesses over time is shown.

[0108] Figure 2 The change in the thermosetting elongation of tapes of ethylene polymer compositions (B) and comparative compositions with different thicknesses over time is shown.

[0109] Examples

[0110] 1. Measurement Methods

[0111] a) Melt Flow Rate (MFR)

[0112] The melt flow rate (MFR) is measured according to ISO 1133, and the unit is g / 10 min. MFR represents the fluidity of the polymer and thus also represents the processability of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer.

[0113] The MFR2 of polyethylene (co)polymers is measured at a temperature of 190 °C and a load of 2.16 kg.

[0114] b) Density

[0115] The density of the polymer is measured on compression-molded samples prepared according to EN ISO 1872-2 according to the method A of ISO 1183-1:2004, and the unit is kg / m 3 .

[0116] c) Comonomer content

[0117] Quantify microstructure by NMR spectroscopy

[0118] Quantitative nuclear magnetic resonance (NMR) spectroscopy is used to quantify the comonomer content of polymers.

[0119] Quantitative 1 1H NMR spectra in the molten state were recorded using a Bruker Avance III 500 NMR spectrometer operating at a frequency of 500.13 MHz. All spectra were recorded at 150 °C using a 13C optimized 7 mm magic angle spinning (MAS) probe, and nitrogen was used for all pneumatic devices. Approximately 200 mg of the material was loaded into a zirconia MAS rotor with an outer diameter of 7 mm and spun at a speed of 4 kHz. This setting was chosen primarily because of its high sensitivity required for rapid identification and accurate quantification {klimke06, parkinson07, castignolles09}. Standard single-pulse excitation was employed with a recycle delay of 2 s {pollard04, klimke06}. A total of 16 transients were acquired for each spectrum.

[0120] Process, integrate, and quantify 1 1H NMR spectra using a custom automated spectral analysis program and determine the quantitative properties. All chemical shifts were internally referenced to the bulk ethylene methylene signal at 1.33 ppm.

[0121] Assignment of methacrylate (MA) incorporation {brandolini01}:

[0122] Characteristic signals arising from methacrylate incorporation were observed and may be present in various comonomer sequences. The integral of the signal at 3.6 ppm assigned to the 1MA site was used to quantify the overall methacrylate incorporation, taking into account the number of reported nuclei for each comonomer:

[0123] MA = I 1MA / 3

[0124] The integral of the bulk aliphatic (I bulk ) signals between 0.00 – 3.00 ppm was used to quantify the ethylene content. The total ethylene content was calculated based on this bulk integral and compensated for the observed comonomers:

[0125] E = (1 / 4)*[I bulk - 3*MA]

[0126] The total mole fraction of methacrylate in the polymer was calculated as follows:

[0127] fMA = MA / (E + MA)

[0128] The total comonomer incorporation of methacrylate (mole percentage) is calculated from the mole fraction according to the standard method:

[0129] MA [mol.%] = 100 * fMA

[0130] The total comonomer incorporation of methacrylate (weight percentage) is calculated from the mole fraction according to the standard method:

[0131] MA [wt%] = 100 * (fMA * 86.09) / ((fMA * 86.09) + ((1 - fMA) * 28.05))

[0132] klimke06: Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207: 382.

[0133] parkinson07: Parkinson, M., Klimke, K., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2007; 208: 2128.

[0134] pollard04: Pollard, M., Klimke, K., Graf, R., Spiess, H.W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37: 813.

[0135] castignolles09: Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50(2009) 2373.

[0136] brandolini01: A.J. Brandolini, D.D. Hills, “NMR spectra of polymers and polymer additives”, Marcel Deker Inc., 2000.

[0137] d) FTIR

[0138] The amount of vinyltrimethoxysilane in the polymer was measured by Fourier transform infrared spectroscopy (FTIR). The weight percentage of vinyltrimethoxysilane was determined from the silane peak at 945 cm -1 and compared with the polyethylene peak at 2665 cm -1 .

[0139] e) Heat-set elongation (%)

[0140] To determine whether the crosslinkable polyethylene composition cures properly, the heat-set elongation and permanent deformation are determined according to IEC 60811-507 by measuring at a load of 20 N / cm 2 at 200 °C. Three dumbbell test specimens are prepared from the tape composed of the polyethylene composition to be tested by cutting test specimens from the tape. Each test specimen is vertically fixed at its upper end in an oven, and a load of 20 N / cm 2 is attached to the lower end of each test specimen. After 15 minutes, the distance between the pre-marked lines in the oven at 200 °C is measured, the percentage of heat-set elongation is calculated, and expressed as the heat-set elongation in %.

[0141] For the permanent deformation %, the tensile force (weight) is removed from the test specimen, and after recovering for 5 minutes at 200 °C, it is allowed to cool to ambient temperature at room temperature. The permanent deformation % is calculated based on the distance between the marked lines.

[0142] f) Tensile strength

[0143] 2. The tensile strength is determined according to ISO 527-2 (crosshead speed = 50 mm / min; 23 °C) using compression-molded specimens (dog-bone shape, 2 mm) as described in EN ISO 1873-2.

[0144] Materials

[0145] In the examples of the present invention, the following materials were used:

[0146] The ethylene polymer (a1) is a terpolymer of ethylene (76.1 wt%), methyl acrylate (22.5 wt%) and vinyltrimethoxysilane (1.4 wt%), with a density of 945 kg / m 3 and an MFR2 (190 °C, 2.16 kg) of 3.5 g / 10 min.

[0147] The ethylene polymer (a2) is a copolymer of ethylene and 1-octene, with a density of 902 kg / m 3, the MFR2 (190 °C, 2.16 kg) is 1.1 g / 10 min, the flexural modulus is 72 MPa, the tensile strength is 36 MPa, the elongation at break is 715%, and the melting temperature Tm is 97 °C. The ethylene copolymer (a2) can be purchased from Borealis AG in Vienna under the trade name Queo TM 0201.

[0148] The ethylene polymer (b) is a terpolymer of ethylene (89.45 wt%), butyl acrylate (9.5 wt%) and vinyltrimethoxysilane (1.05 wt%), with a density of 922 kg / m 3 , and the MFR2 (190 °C, 2.16 kg) is 1.0 g / 10 min.

[0149] The ethylene polymer (c) is an ethylene / vinyltrimethoxysilane (VTMS) copolymer with a density of 923 kg / m 3 , the MFR2 is 1 g / 10 min, and the VTMS content is 1.1 wt%.

[0150] MB1 is a catalyst masterbatch, including a matrix resin (ethylene-butyl acrylate copolymer, butyl acrylate content is 17 wt%, density is 924 kg / m 3 , and the MFR2 is 47.0 g / 10 min) and 1.5 wt% of dodecylbenzenesulfonic acid.

[0151] MB2 is a catalyst masterbatch, including a matrix resin (ethylene-butyl acrylate copolymer, butyl acrylate content is 17 wt%, density is 924 kg / m 3 , and the MFR2 is 47.0 g / 10 min) and 2.4 wt% of dioctyltin dilaurate.

[0152] Preparation of the polymer composition

[0153] The polymer composition (A) consisting of 85 wt% of the ethylene polymer (a1) and 15 wt% of the ethylene polymer (a2) is prepared as follows: Mix the components together in a BUSS co-kneader (46 mm), the screw speed is 225 rpm, the set temperature of the kneading section is 40, 160, 180, 200 °C, and the set temperature of the pelletizing extruder is 200 °C. The mixer screw is heated to 120 °C. The extruder screw temperature is 160 °C, the barrel is heated to 170 °C, and the speed is 4 rpm. All components are added to port 1.

[0154] The polymer compositions (B) and (C) correspond to 100 wt% of the ethylene polymers (b) and (c) respectively.

[0155] As further disclosed below, prior to extrusion, the crosslinking catalyst masterbatch MB1 or MB2 was added to the respective compositions A, B, and C at a concentration of 5% by weight.

[0156] Manufacture of the belt

[0157] Belts were produced on a Collin TeachLine E20T belt extruder for determining the thermoset elongation. The extruder was equipped with a 4.2:1, 20D compression screw with a diameter of 20 mm and different thicknesses as shown below.

[0158] The temperature profile was 150 / 160 / 170 °C and the screw speed was 55 rpm.

[0159] Prior to extrusion, the crosslinking catalyst masterbatch MB1 or MB2 was added to all formulations at a concentration of 5% by weight.

[0160] The compositions tested are shown in Table 1.

[0161] Table 1: Polyethylene compositions tested

[0162]

[0163] Prior to conducting the thermosetting test, the belts were crosslinked at a humidity of 50% RH and ambient temperature (23 °C), and the crosslinking time was as Figure 1 and Figure 2 shown.

[0164] The results of the thermosetting test are as Figure 1 and Figure 2 shown. It can be seen from the slopes of the crosslinking curves of the examples of the present invention (IE1 to IE6) and the comparative examples (CE1 to CE6) that the crosslinking rate of the polyethylene composition contained in the cable layer of the present invention is much faster compared to using conventional polyethylene containing hydrolyzable silane groups and / or conventional tin-based silanol condensation catalysts. This effect is more obvious when the thickness is larger.

[0165] In addition, the tensile strengths of polymer (A) and polymer (B) were measured. The tensile strength of polymer (A) was 16.5 MPA and the tensile strength of polymer (B) was 11 MPa. Therefore, the addition of component (a2) further increased the tensile strength of the crosslinked polymer.

Claims

1. A cable comprising a layer containing a crosslinkable polyethylene composition, said crosslinkable polyethylene composition comprising (A1)One or more ethylene copolymers, the ethylene copolymers containing monomer units having polar groups and monomer units having hydrolyzable silyl groups, wherein, Based on the total polyethylene composition, the monomer units having polar groups are present in an amount of 0.02 to 25 mol%, preferably 1 to 15 mol%, more preferably 2.5 to 15 mol%, preferably 4 to 12 mol%, and (B) sulfonic acid, wherein the layer has a thickness of at least 0.9 mm, preferably at least 1.2 mm, more preferably at least 2.0 mm, and most preferably at least 3.0 mm.

2. The cable according to claim 1, wherein, Determined according to ISO 1133 at a temperature of 190 °C and a load of 2.16 kg, the MFR of the one or more ethylene copolymers of (A1) 2.16 is from 1 g / 10 min to 50 g / 10 min, preferably from 2 g / 10 min to 45 g / 10 min, more preferably from 3.0 g / 10 min to 40 g / 10 min.

3. The cable according to claim 1 or 2, wherein Based on the total polyethylene composition, component A1 is present in the polyethylene composition in an amount of 50 to 99% by weight, and wherein the polyethylene composition further comprises (A2) A copolymer based on the total polyethylene composition, comprising 1 to 50% by weight of ethylene and a C3 to C8 α-olefin comonomer, having a density of 850 to 970 kg / m 3 , and a melt flow rate (MFR) measured according to ISO 1133 at a temperature of 190 °C and a load of 2.16 kg 2.16 of 0.1 to 50 g / 10 min.

4. The cable according to any one of the preceding claims, wherein, Crosslinking is carried out at ambient temperature.

5. The cable according to any one of the preceding claims, wherein, The monomer units having polar groups are selected from butyl acrylate, ethyl acrylate, methyl acrylate and methyl methacrylate and mixtures thereof.

6. The cable according to any one of the preceding claims, wherein, The monomer units having hydrolyzable silyl groups are selected from vinyltrimethoxysilane, vinylbis(methoxyethoxy)silane, vinyltriethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, vinyltriacetoxysilane and mixtures thereof.

7. The cable according to any one of the preceding claims, wherein, Based on the total polyethylene composition, the monomer units having hydrolyzable groups are present in the one or more ethylene copolymers (a) in an amount of 0.001% to 15% by weight.

8. The cable according to any one of the preceding claims, wherein, Based on the total polyethylene composition, the sulfonic acid (B) is present in an amount of 0.0001 to 9% by weight.

9. The cable according to any one of the preceding claims, wherein, The sulfonic acid (B) is an aromatic organic sulfonic acid, which includes the structural element: Ar(SO3H) x (III) wherein Ar is an aryl group which may be substituted or unsubstituted, and x is at least 1, for example 1, 2 or 3.

10. The cable according to claim 9, wherein, Ar is an aryl group substituted with a hydrocarbon group, and among them, the sulfonic acid contains a total of 14 to 28 carbon atoms. Preferably, the Ar group is C8-C 20 hydrocarbon group-substituted benzene or C 14 -C 18 hydrocarbon group-substituted naphthalene.

11. The cable according to any one of the preceding claims, wherein, The at least one layer is an insulating layer or a sheath layer.

12. The cable according to any one of the preceding claims, wherein, The cable is a low-voltage cable, and the layer thickness is in the range of 1.2 mm to 3.0 mm, preferably in the range of 2.4 mm to 3.0 mm, or wherein the cable is a medium-voltage cable, and the layer thickness is greater than 3.00 mm and up to 8.0 mm, preferably in the range of 3.2 mm to 5.5 mm, preferably in the range of 3.2 mm to 3.6 mm.

13. A crosslinking method for a crosslinkable polyethylene composition of a cable layer according to any one of claims 1 to 12, wherein, Crosslinking is carried out at ambient temperature.

14. The crosslinking method according to claim 13, wherein, The crosslinking time to achieve a thermosetting elongation rate of 100% or less is 100 hours or shorter, and the thermosetting elongation rate is determined by measuring the thermal deformation at 200 °C and a load of 20 N / cm 2 according to IEC 60811-507.

15. Use of a crosslinkable polyethylene composition for crosslinking at an accelerated rate at room temperature in a layer of a cable having a thickness of at least 0.9 mm, said crosslinkable polyethylene composition comprising (A1)One or more ethylene copolymers, the ethylene copolymers containing monomer units having polar groups and monomer units having hydrolyzable silyl groups, wherein, Based on the total polyethylene composition, the monomer units having polar groups are present in an amount of 0.02 to 25 mol%, preferably 1 to 15 mol%, more preferably 2.5 to 15 mol%, preferably 4 to 12 mol%, and (B) sulfonic acid.

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