Semiconductive composition for cable and preparation method therefor

Abstract

The present invention provides a semiconductive composition for a cable, comprising: (a) a polyolefin-based resin containing at least one functional group selected from the group consisting of maleimide-based one and allyl ester-based one; and (b) a carbon-based material containing at least one selected from the group consisting of carbon black and carbon nanotubes. According to the present invention, space charge characteristics are improved such that problems of electric field distortion or long-term insulation lifetime deterioration can be solved, mechanical properties and processability are excellent, cross-linking characteristics and scorch stability can be improved, and high-temperature volume resistance, electrical characteristics allowing withstanding of high direct-current voltage and surface smoothness can be excellent. In addition, space charge in the direct-current power cable can be suppressed to ensure long-term reliability and long-distance power transportation is enabled.

Description

Semiconductive composition for cables and method for manufacturing the same

[0001] The present invention relates to a semiconducting composition for cables and a method for manufacturing the same. More specifically, the present invention relates to a semiconducting composition for cables having excellent mechanical properties, electrical characteristics, and surface smoothness, and a method for manufacturing the same.

[0002]

[0003] With environmental pollution issues recently emerging globally, the demand for renewable energy is increasing. In particular, the cable industry is focusing on High Voltage Direct Current (HVDC) cables for long-distance power transmission connecting offshore and land using wind power generation. Consequently, there is a need to develop new insulators and semiconducting compositions suitable for DC power cables, which are affected by space charge unlike conventional AC systems.

[0004] The aforementioned space charge is formed when charges injected from electrodes accumulate within the insulator, posing a problem by distorting the electric field and degrading the insulation lifespan over the long term. To address this, various methods have been proposed to prevent space charge accumulation in insulators. Representative methods include reducing crosslinking byproducts in the insulator, adding nanofillers such as MgO and ZnO, or adding organic materials capable of forming deep charge traps, such as MAH.

[0005] Furthermore, as a method to prevent space charge accumulation in semiconducting compositions, crosslinking byproducts are reduced, or acetylene black with excellent dispersibility and low metallic impurity content is used to increase the surface smoothness of the interface between the insulator and the semiconducting material. However, research on the base resin of semiconducting compositions has not been sufficiently conducted.

[0006] Therefore, it is necessary to develop a semiconducting composition for cables and a method for manufacturing the same that can stably maintain electrical characteristics, processability, mechanical properties, and crosslinking properties capable of withstanding high DC voltage.

[0007]

[0008] Related prior art is Korean Patent Publication No. 10-2000-0060308.

[0009]

[0010] The objective of the present invention is to provide a semiconducting composition for cables and a method for manufacturing the same, which can solve problems such as electric field distortion or long-term insulation life degradation by improving space charge characteristics.

[0011] Another objective of the present invention is to provide a semiconducting composition for cables with excellent mechanical properties and processability, and a method for manufacturing the same.

[0012] Another objective of the present invention is to provide a semiconducting composition for cables with improved crosslinking properties and scorch stability, and a method for manufacturing the same, with reduced surface protrusions.

[0013] Another objective of the present invention is to provide a semiconducting composition for cables having excellent high-temperature volume resistance, electrical properties capable of withstanding high DC voltage, and surface smoothness, and a method for manufacturing the same.

[0014] Another objective of the present invention is to provide a power cable capable of long-term reliability by suppressing space charge in a DC power cable and enabling long-distance power transmission.

[0015] The above and other objectives of the present invention can all be achieved by the present invention described below.

[0016]

[0017] 1. One aspect of the present invention relates to a semiconducting composition for cables. The semiconducting composition for cables comprises: (a) a polyolefin resin comprising one or more functional groups selected from the group consisting of maleimide series and allyl ester series; and (b) a carbon-based material comprising one or more selected from the group consisting of carbon black and carbon nanotubes.

[0018] 2. In the above 1 embodiment, the maleimide series functional group may include one or more selected from the group consisting of maleimide, N-cyclohexyl maleimide, N-methyl maleimide, N-ethyl maleimide, N-carbamoyl maleimide, N-phenyl maleimide, N,N'-ethylene dimaleimide, and N-(4-anilinophenyl)maleimide.

[0019] 3. In the above 1 to 2 embodiments, the functional group of the allyl ester series may include one or more selected from the group consisting of allyl ester, allyl hexanoate, allyl butyrate, allyl methyl carbonate, allyl acetoacetate, allyl oxalyl chloride, allyl chloroacetate, and allyl bromoacetate.

[0020] 4. In the above 1 to 3 embodiments, the polyolefin resin (a) may include one or more selected from the group consisting of polyolefin resin, polyolefin elastomer, and polyolefin plastomomer.

[0021] 5. In the above 1 to 4 embodiments, the polyolefin resin may include one or more selected from the group consisting of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, and polypropylene.

[0022] 6. In the above 1 to 5 embodiments, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the polyolefin resin (a) may be 5 g / 10 min to 30 g / 10 min.

[0023] 7. In the above 1 to 6 embodiments, the weight-average molecular weight of the polyolefin resin (a) may be 10,000 g / mol to 200,000 g / mol.

[0024] 8. In the above 1 to 7 embodiments, the carbon black may include one or more selected from the group consisting of furnace black and acetylene black.

[0025] 9. In the above embodiments 1 to 8, the carbon black has a bulk density of 100 kg / m³ 3 up to 500 kg / m² 3 and the specific surface area measured according to ASTM D3037-89 is 30 m² 2 / g to 150 m 2 It can be / g.

[0026] 10. In the above 1 to 9 embodiments, the semiconducting composition for the cable may comprise 60 to 90 weight% of the polyolefin-based resin (a) and 10 to 40 weight% of the carbon-based material (b).

[0027] 11. In the above 1 to 10 embodiments, the semiconducting composition for the cable may further include an antioxidant, a crosslinking agent, and a crosslinking co-agent.

[0028] 12. In the above 1 to 11 embodiments, the antioxidant may include one or more selected from the group consisting of hindered phenolic compounds and hindered amineic compounds.

[0029] 13. In the above 1 to 12 embodiments, the semiconducting composition for the cable may comprise 0.05 to 2 weight% of the antioxidant, 0.05 to 2 weight% of the crosslinking agent, and 0.05 to 2 weight% of the crosslinking co-agent.

[0030] 14. In the above 1 to 13 embodiments, the semiconducting composition for the cable may have a volume resistivity of 500 Ω·m or less at 90°C as measured by ASTM D991.

[0031] 15. In the above 1 to 14 embodiments, the semiconducting composition for the cable may have a scorch time of 10 minutes or more as measured at 145°C, ts1 according to ASTM D5289 standards.

[0032] 16. In the above embodiments 1 to 15, the semiconducting composition for cables has a tensile strength of 1.5 kgf / mm² as measured by ASTM D638. 2 This is the case, and the growth rate can be 150% or more.

[0033] 17. Another aspect of the present invention relates to a power cable comprising a semiconducting layer formed from the semiconducting composition for cables of embodiments 1 to 16 above.

[0034] 18. Another aspect of the present invention relates to a power cable comprising: a conductor; an inner semiconducting layer surrounding the conductor; an insulating layer surrounding the inner semiconducting layer; and an outer semiconducting layer surrounding the insulating layer. The inner semiconducting layer and the outer semiconducting layer are formed from the semiconducting compositions for cables of embodiments 1 to 16.

[0035] 19. In the above 18 embodiments, the power cable may be a DC power cable.

[0036] 20. Another aspect of the present invention relates to a method for manufacturing a semiconducting composition for a cable according to embodiments 1 to 16 above. The method comprises the steps of: introducing and mixing raw materials of the semiconducting composition for a cable; and extruding and cooling the mixed raw materials.

[0037] 21. In the above 20 embodiments, in the cooling step, the mixed raw materials may be cooled after being extruded into pellet form.

[0038]

[0039] According to the present invention, space charge characteristics are improved to solve problems such as electric field distortion or long-term insulation life degradation, and mechanical properties and processability are excellent. Furthermore, crosslinking characteristics and scorch stability can be improved, and electrical characteristics capable of withstanding high-temperature volume resistance and high DC voltage, as well as surface smoothness, can be excellent. In addition, long-term reliability can be ensured by suppressing space charge in DC power cables, and long-distance power transmission can be enabled.

[0040]

[0041] Figure 1 shows the volume charge density according to the distance from the electrode of Example 1.

[0042]

[0043] The present invention will be described in more detail below. Where terms such as 'comprising,' 'having,' and 'consisting of' are used in this specification, other parts may be added unless 'only' is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0044] In this specification, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0045] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term "approximately" in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where a numerical range is disclosed herein, such range is continuous and, unless otherwise indicated, includes all values ​​from the minimum value of such range to the maximum value including the maximum value. Moreover, where such range refers to an integer, it includes all integers from the minimum value to the maximum value including the maximum value, unless otherwise indicated.

[0046] In this specification, where a range is described for a variable, it will be understood that the variable includes all values ​​within the described range, including the described endpoints of the range. For example, the range “5 to 10” will be understood to include not only the values ​​5, 6, 7, 8, 9, and 10, but also any sub-ranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and any values ​​between integers valid for the category of the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Also, for example, the range “10% to 30%” will be understood to include all integers including values ​​such as 10%, 11%, 12%, 13%, etc. and up to 30%, as well as any sub-range such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between valid integers within the stated range category such as 10.5%, 15.5%, 25.5%, etc.

[0047] Unless otherwise noted, "polyolefin" means a polymer containing at least 50% by weight of the total polymer weight of the polymerized olefin monomer and optionally containing at least one comonomer. Examples may include, but are not limited to, polyethylene, polypropylene, polybutene, polyisopropene, polyhexene, polyoctene, polydecene, ethylene-propylene copolymer, ethylene-octene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-decene copolymer, propylene-butene copolymer, ethylene-nonadene copolymer, etc.

[0048] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0049] Hereinafter, a semiconducting composition for cables and a method for manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0050]

[0051] Conventionally, methods to suppress space charge accumulation in semiconducting compositions include reducing crosslinking byproducts or improving the surface smoothness of the interface between the insulating layer and the semiconducting layer by using acetylene black, which contains low levels of metallic impurities and exhibits excellent dispersibility. However, methods to prevent space charge accumulation by modifying the base resin of the semiconducting composition have not been sufficiently presented.

[0052] A semiconducting composition for a cable according to one embodiment of the present invention comprises (a) a polyolefin-based resin comprising one or more functional groups selected from the group consisting of maleimide series and allyl ester series; and (b) a carbon-based material comprising one or more selected from the group consisting of carbon black and carbon nanotubes; thereby improving electrical properties, processability, and mechanical properties. In addition, it is characterized by improved space charge characteristics, which can solve problems such as electric field distortion or long-term insulation life degradation.

[0053]

[0054] (a) Polyolefin resin

[0055] The above polyolefin resin comprises one or more functional groups selected from the group consisting of maleimide series and allyl ester series.

[0056] More specifically, the polyolefin resin comprises a vinyl group or a double bond that can be bonded to the backbone of a non-polar polyolefin base resin, and includes a polar functional group and a charge-inducing functional group. The functional group comprises one or more selected from the group consisting of maleimide series and allyl ester series, and can be implemented in a form grafted onto the base resin. In this way, the polyolefin resin can suppress the accumulation of space charge in the insulator by modifying the base resin, and can produce a semiconducting composition with excellent processability and mechanical properties through the diversification of the base resin.

[0057] When the above-mentioned maleimide or allyl ester functional groups are included, the mobility of molecules is increased at high temperatures when thermally bonded with the insulating layer, allowing polar or charge-inducing functional groups to be appropriately positioned at the interface between the insulating layer and the semiconducting layer. The functional groups can form deep traps that impede charge mobility, thereby improving space charge characteristics.

[0058] The functional groups of the above maleimide series may include one or more selected from the group consisting of maleimide, N-cyclohexyl maleimide, N-methyl maleimide, N-ethyl maleimide, N-carbamoyl maleimide, N-phenyl maleimide, N,N'-ethylene dimaleimide, and N-(4-anylinophenyl) maleimide.

[0059] The functional group of the above allyl ester series may include one or more selected from the group consisting of allyl ester, allyl hexanoate, allyl butyrate, allyl methyl carbonate, allyl acetoacetate, allyl oxalyl chloride, allyl chloroacetate, and allyl bromoacetate.

[0060] When functional groups of the above maleimide and allyl ester series are included, polar or charge-inducing functional groups moved by heat at the interface with the insulating layer can form deep traps that impede charge mobility, thereby improving space charge characteristics.

[0061] The above polyolefin resin may include one or more selected from the group consisting of polyolefin resin, polyolefin elastomer, and polyolefin plastomomer.

[0062] The above polyolefin resin may preferably include one or more selected from the group consisting of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, and polypropylene.

[0063] The above polyolefin elastomer may include one or more selected from the group consisting of copolymers polymerized with ethylene as the main monomer and olefins such as octene, hexene, butene, or decene as comonomers. In a specific example, the above polyolefin elastomer may include an ethylene-octene copolymer, an ethylene-hexene copolymer, an ethylene-butene copolymer, etc.

[0064] The above polyolefin plastomer is preferably based on ultra-low density polyethylene, low density polyethylene, or linear low density polyethylene, and has a density of 0.87 g / cm³ 3 Up to 0.91 g / cm³ 3 It may include one or more selected from the group consisting of polymers having a low density and a degree of crystallinity of 10% to 40%. In a specific example, the polyolefin plastomer may include an ethylene-octene copolymer, an ethylene-hexene copolymer, an ethylene-decene copolymer, etc.

[0065] The melt index (ASTM D 1238, 190°C, 2.16 kg) of the above polyolefin resin may be 5 g / 10 min to 30 g / 10 min. In a specific example, the melt index may be 10 g / 10 min to 30 g / 10 min, for example, 15 g / 10 min to 25 g / 10 min. Within this range, it may have processability suitable for processes such as extrusion.

[0066] The weight-average molecular weight of the above polyolefin resin may be 10,000 g / mol to 200,000 g / mol. In a specific example, the weight-average molecular weight may be 20,000 g / mol to 170,000 g / mol, for example, 30,000 g / mol to 150,000 g / mol. Within the above range, the mechanical properties of the semiconducting composition for cables may be excellent.

[0067]

[0068] (b) carbonaceous materials

[0069] The above carbon-based material includes one or more selected from the group consisting of carbon black and carbon nanotubes.

[0070] When the above carbon-based material is mixed with the above polyolefin-based resin, the electrical properties of the semiconducting composition can be stabilized, and by uniformly dispersing it using kneader equipment with excellent dispersion power, the increase in volume resistivity can be suppressed even at high temperatures, and the surface of the semiconducting layer can be made uniform to reduce defects or non-uniformity that may occur at the bonding interface with the insulating layer.

[0071] More specifically, the carbon black of the carbon-based material has a low content of metallic impurities, allowing it to maintain excellent electrical properties and thermal stability even at high temperatures. Additionally, it is uniformly dispersed within the semiconducting composition, which improves the surface smoothness of the semiconducting layer and enhances interfacial bonding with the insulating layer. This mitigates the electric field concentration phenomenon that may occur between the insulating layer and the semiconducting layer, thereby extending the insulation lifespan and ensuring electrical stability.

[0072] The above carbon black may include one or more selected from the group consisting of furnace black and acetylene black.

[0073] The above carbon black has a bulk density of 100 kg / m³ 3 up to 500 kg / m² 3 It may be. In a specific example, the bulk density is 150 kg / m³. 3 Up to 450 kg / m² 3 , for example, 200 kg / m² 3 up to 400 kg / m² 3 It could be. In the above range It can have excellent high-temperature volume resistance, electrical characteristics capable of withstanding high DC voltage, and surface smoothness.

[0074] The above carbon black has a specific surface area of ​​30 m² as measured by ASTM D3037-89 standards. 2 / g to 150 m 2 It may be / g. In a specific example, the specific surface area is 40 m² 2 / g to 130 m 2 / g, for example, 50 m 2 / g to 100 m 2 / g can be. In the above range It can have excellent high-temperature volume resistance, electrical characteristics capable of withstanding high DC voltage, and surface smoothness.

[0075] The carbon nanotubes of the above-mentioned carbon-based material can maintain stable conductivity by minimizing electrical performance degradation even at high temperatures, and can improve mechanical properties and thermal stability. Furthermore, they can prevent space charge accumulation in the semiconducting composition, alleviate electric field concentration, and improve the smoothness of the semiconducting layer. This ensures long-term reliability and electrical stability of the cable.

[0076]

[0077] Semiconductive composition for cables

[0078] One aspect of the present invention relates to a semiconducting composition for cables.

[0079] The above semiconducting composition for cables comprises a polyolefin resin comprising one or more functional groups selected from the group consisting of maleimide series and allyl ester series; and a carbon-based material comprising one or more selected from the group consisting of carbon black and carbon nanotubes. The above semiconducting composition for cables may further comprise an antioxidant, a crosslinking agent, and a crosslinking co-agent.

[0080] The above semiconducting composition for cables may comprise 60 to 90 weight% of the polyolefin-based resin and 10 to 40 weight% of the carbon-based material. In a specific example, it may comprise 62 to 88 weight% of the polyolefin-based resin, for example, 65 to 85 weight%, and 15 to 35 weight% of the carbon-based material, for example, 20 to 33 weight% of the carbon-based material. Within the above range, space charge characteristics are improved to solve problems such as electric field distortion or long-term insulation life degradation, and mechanical properties, processability, high-temperature volume resistivity, electrical properties capable of withstanding high DC voltage, and surface smoothness may be excellent.

[0081] The above antioxidant may include one or more selected from the group consisting of hindered phenolic compounds and hindered amine compounds, which can suppress thermal oxidation reactions at high temperatures and prevent changes in the resistance of the composition due to oxidation, thereby maintaining electrical properties and mechanical strength, and improving durability and oxidation stability.

[0082] In a specific example, the hindered phenolic compound is 4,4'-thiobis(3-methyl-6-tert-butylphenol), tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, bis[(beta-(3,5-di-tert-butyl-4-hydroxybenzyl)-methylcarboxyethyl)]sulfide, N,N'-propane-1,3-dibis(3-3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocyanamide), 2,6-di-tert-butyl-4-methyl-phenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and It may contain tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane.

[0083] In a specific example, the hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, N-methyl-3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, N-acetyl-3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, Poly({6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triadin-2,4-diine}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}), bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, 1,2,2,6,6-pentamethyl-4-piperidyl 3,5-di-tert-butyl-4-hydroxybenzoate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, It may include 1,2-dehydro-2,2,4-trimethylquinoline.

[0084] The above semiconducting composition for the cable may contain 0.05 to 2 weight percent of the antioxidant. In a specific example, it may contain 0.08 to 1.8 weight percent of the antioxidant, for example, 0.12 to 1.5 weight percent. Oxidation stability may be excellent within the above range.

[0085] The above-mentioned crosslinking agent induces a crosslinking reaction, which can improve the mechanical strength, chemical resistance, and thermal stability of the semiconducting composition for cables, and increase stability during the extrusion process.

[0086] In a specific example, the crosslinking agent may include one or more selected from t-butyl cumyl peroxide, benzoyl peroxide, lauryl peroxide, cumene hydroperoxide, dicumyl peroxide, methyl ethyl ketone peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, di-t-butyl peroxide, t-butyl peroxy benzoate, α,α-bis(t-butyl peroxy isopropyl)benzene, and α,α-bis(t-butyl peroxy)-1,3-diisopropylbenzene.

[0087] The above semiconducting composition for cables may contain 0.05 to 2 weight% of the crosslinking agent. In a specific example, it may contain 0.07 to 1.95 weight% of the crosslinking agent, for example, 0.1 to 1.7 weight%. Within this range, the crosslinking properties and scorch stability may be excellent.

[0088] The above-mentioned crosslinking agent can be used to improve the physical properties of a semiconductive composition for cables by assisting the above-mentioned crosslinking agent to increase the efficiency of the crosslinking reaction and controlling the reaction rate. By using the above-mentioned crosslinking agent in combination with the above-mentioned crosslinking agent, crosslinking characteristics and scorch stability can be improved, and surface protrusions can be reduced.

[0089] In a specific example, the crosslinking agent may include one or more selected from trialyl isocyanurate (TAIC), trimethylallyl isocyanurate (TMAIC), trialyl cyanurate (TAC), trialyl trimethate (TAM), trimethylopropane trimethacrylate (TMPTMA), ethylene glycol dimethacrylate, and α-methyl styrene dimer.

[0090] The above semiconducting composition for cables may contain 0.05 to 2 weight% of the crosslinking agent. In a specific example, it may contain 0.08 to 1.6 weight% of the crosslinking agent, for example, 0.1 to 1.3 weight%. Within this range, the crosslinking properties and scorch stability may be excellent.

[0091] The above semiconducting composition for cables may have a volume resistivity of 500 Ω·m or less at 90°C as measured according to ASTM D991 standards. In a specific example, the volume resistivity may be 300 Ω·m or less, for example 250 Ω·m or less, preferably 200 Ω·m or less, and more preferably 30 Ω·m to 150 Ω·m.

[0092] The above semiconducting composition for cables may have a scorch time of 10 minutes or more as measured at 145°C, ts1 according to ASTM D5289 standards. In a specific example, the scorch time may be 12 minutes or more, for example, 15 minutes or more, preferably 18 minutes or more, and more preferably 20 to 30 minutes.

[0093] The above semiconducting composition for cables has a tensile strength of 1.5 kgf / mm² as measured by ASTM D638 standards. 2 The above is the case, and the elongation rate may be 150% or more. In a specific example, the tensile strength is 1.6 kgf / mm 2 Above, for example, 1.7 kgf / mm 2 Ideally, 1.75 kgf / mm 2 Ideally, 1.8 kgf / mm 2 Up to 4.0 kgf / mm 2 It may be. In addition, in a specific example, the elongation rate may be 160% or more, for example 170% or more, preferably 175% or more, and more preferably 180% to 700%.

[0094]

[0095] power cable

[0096] Another aspect of the present invention relates to a power cable comprising a semiconducting layer formed from the semiconducting composition for cables described above. The semiconducting layer formed from the semiconducting composition for cables can ensure long-term reliability by suppressing space charge in a DC power cable, and can enable the production of cables for long-distance power transmission by providing excellent processability and scorch stability.

[0097] Another aspect of the present invention relates to a power cable comprising: a conductor; an inner semiconducting layer surrounding the conductor; an insulating layer surrounding the inner semiconducting layer; and an outer semiconducting layer surrounding the insulating layer. The inner semiconducting layer and the outer semiconducting layer are formed from the semiconducting composition for cables described above.

[0098] More specifically, the conductor may include materials such as aluminum or copper that have high conductivity and can minimize resistance loss. The conductor may be formed by arranging a plurality of wires in the circumferential direction of the conductor and may be located at the center of the power cable to support the overall structure. The insulating layer may include an insulating polymer having high heat resistance and chemical resistance. The inner semiconducting layer can strengthen electrical junctions by removing the air layer between the conductor and the insulating layer and prevent damage to the insulating layer by mitigating local electric field concentration. The outer semiconducting layer can maintain the balance of the electric field applied to the insulating layer by uniformly dispersing the electric field and can perform a shielding role for the cable. Additionally, a sheath layer may be further included, which may be provided with materials such as vinyl chloride, polyethylene, or nylon, to protect the power cable.

[0099] The thickness of the insulating layer is 1.5 mm or more, and in a specific example, 5 mm or more. For example, it may be 15 mm to 100 mm. The thicknesses of the inner semiconducting layer and the outer semiconducting layer may each be 0.1 mm or more, and in a specific example, 0.5 mm or more, for example, 0.8 mm to 3 mm. Within the above range, the long-term reliability of the power cable may be excellent.

[0100] The above power cable may be a DC power cable. The above DC power cable is intended for long-distance power transmission and, unlike existing AC systems, can be significantly affected by space charge. Accordingly, the present invention can provide a power cable comprising a semiconducting layer formed from a semiconducting composition having excellent space charge characteristics as well as high-temperature volume resistivity, mechanical properties, crosslinking characteristics, scorch stability, processability, and surface smoothness, which are basic characteristics required of existing ultra-high voltage AC power cables.

[0101]

[0102] Method for manufacturing a semiconducting composition for cables

[0103] Another aspect of the present invention relates to a method for manufacturing the above-described semiconducting composition for cables. The method comprises the steps of: introducing and mixing raw materials of the semiconducting composition for cables; and extruding and cooling the mixed raw materials.

[0104] More specifically, a semiconducting composition for a cable can be prepared by adding and mixing a carbon-based material containing one or more functional groups selected from the group consisting of carbon black and carbon nanotubes, an antioxidant, a crosslinking agent, a crosslinking co-agent, and any additives to a polyolefin resin containing one or more functional groups selected from the group consisting of maleimide series and allyl ester series, which are raw materials for the semiconducting composition for the cable. The addition and mixing can be performed by mixing the raw materials of the semiconducting composition in a co-kneader, a single screw, a twin screw extruder, etc. The temperature during the mixing may be 150°C to 300°C. In a specific example, the temperature may be 155°C to 290°C, for example, 160°C to 280°C. Long-term reliability of the cable can be ensured within this range.

[0105] The above extrusion may be performed by extruding the mixed raw materials into pellet form using an extruder. The pellet form may be produced using pelletizing equipment such as a pelletizing extruder. The temperature during the extrusion may be 70°C to 160°C. In a specific example, the temperature may be 75°C to 150°C, for example, 80°C to 140°C. Long-term reliability of the cable can be ensured within this range.

[0106] The cooling step described above may be performed after extruding the mixed raw materials into pellet form. The cooling step stabilizes the extruded composition to convert it into a solid state, thereby ensuring the composition possesses mechanical properties and dimensional stability. More specifically, internal stress and defects can be minimized during cooling to form a homogeneous structure, prevent the composition from shrinking or deforming at high temperatures, and optimize mechanical strength and electrical properties. The temperature during cooling may be 20°C to 80°C. In a specific embodiment, the temperature may be 25°C to 75°C, for example, 30°C to 70°C. Long-term reliability of the cable can be ensured within this range.

[0107]

[0108] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments of the present invention. However, the following embodiments are intended to aid in understanding the present invention, and the scope of the present invention is not limited to the following embodiments.

[0109]

[0110] Example 1

[0111] A semiconducting composition in the form of pellets with a diameter of 2 mm was prepared by sequentially adding 28.5 wt% of acetylene black and carbon nanotubes, 0.5 wt% of an antioxidant of 1,2-dihydro-2,2,4-trimethylquinoline, 0.5 wt% of a crosslinking agent of α,α-bis(t-butyl peroxyisopropyl)benzene, 0.5 wt% of a crosslinking co-agent of trialyl isocyanurate, and other additives to 70 wt% of maleimide-grafted low-density polyethylene resin and mixing the mixture at 200°C for 10 minutes, extruding the mixture at 160°C using a uniaxial extruder, and cooling it at 25°C.

[0112]

[0113] Example 2

[0114] It was prepared in the same manner as Example 1, except that a polyethylene elastomer grafted with allyl chloroacetate was used instead of a low-density polyethylene resin grafted with maleimide.

[0115]

[0116] Example 3

[0117] It was prepared in the same manner as Example 1, except that an N-cyclohexyl maleimide grafted polyethylene platomer was used instead of a maleimide grafted low-density polyethylene resin.

[0118]

[0119] Comparative Example 1

[0120] It was prepared in the same manner as Example 1, except that a low-density polyethylene resin grafted with diacetone acrylamide was used instead of a low-density polyethylene resin grafted with maleimide.

[0121]

[0122] Comparative Example 2

[0123] It was prepared in the same manner as Example 1, except that vinyl ester-grafted low-density polyethylene resin was used instead of maleimide-grafted low-density polyethylene resin.

[0124]

[0125] The physical properties of the examples and comparative examples were evaluated by the following methods, and the results are shown in Table 1:

[0126]

[0127] Physical property evaluation method

[0128] (1) Volume resistance (Ω·m)

[0129] According to ASTM D991 standards, the volume resistivity of each of the five semiconducting layer specimens containing a rectangular semiconducting composition was measured for 20 minutes in an oven preheated to 90°C for at least 2 hours under a relative humidity of 50±5%.

[0130]

[0131] (2) Scotch time (minutes)

[0132] The scorch time (ts1, 145℃) was measured according to ASTM D5289 standards. The above ts1 is the lowest viscosity (M L This indicates the time required to increase by 1 point in units.

[0133]

[0134] (3) Tensile strength (kgf / mm 2 ), Growth rate (%)

[0135] Tensile strength and elongation were measured according to ASTM D638 standards.

[0136]

[0137] (4) Machinability (torque (N·m))

[0138] To evaluate processability, the torque generated during the extrusion process of the semiconducting composition was measured.

[0139]

[0140] (5) Surface smoothness (pieces / m) 2 )

[0141] Surface smoothness was measured by using a microscope to measure the diameter of the protrusions and the width of the indentations of the wrinkles on one side (observation area of ​​1 m² or more) of a semiconducting layer specimen containing a rectangular semiconducting composition, classifying them according to the range specified in the standard, and recording the number.

[0142] [Table 1]

[0143]

[0144] Referring to Table 1 above, it can be seen that Examples 1 to 3, unlike Comparative Examples 1 to 2, simultaneously satisfy low volume resistivity, high tensile strength and elongation, excellent processability due to low torque, low surface smoothness, and excellent scorch characteristics.

[0145]

[0146] Figure 1 shows the volume charge density according to the distance from the electrode of Example 1. As shown in Figure 1 below, Example 1 has a low volume charge density, which reduces electric field distortion and exhibits excellent electrical characteristics capable of withstanding high DC voltage, and can confirm the improvement of space charge characteristics.

[0147]

[0148] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be within the scope of the present invention.

Claims

1. (a) a polyolefin resin comprising one or more functional groups selected from the group consisting of maleimide series and allyl ester series; and (b) a carbon-based material comprising one or more selected from the group consisting of carbon black and carbon nanotubes; a semiconducting composition for cables comprising 2. In Paragraph 1, A semiconducting composition for cables, wherein the above-mentioned maleimide series functional group comprises one or more selected from the group consisting of maleimide, N-cyclohexyl maleimide, N-methyl maleimide, N-ethyl maleimide, N-carbamoyl maleimide, N-phenyl maleimide, N,N'-ethylene dimaleimide, and N-(4-anilinophenyl)maleimide.

3. In Paragraph 1, A semiconducting composition for cables, wherein the functional group of the allyl ester series comprises one or more selected from the group consisting of allyl ester, allyl hexanoate, allyl butyrate, allyl methyl carbonate, allyl acetoacetate, allyl oxalyl chloride, allyl chloroacetate, and allyl bromoacetate.

4. In Paragraph 1, A semiconducting composition for cables, wherein the above polyolefin resin (a) comprises one or more selected from the group consisting of polyolefin resin, polyolefin elastomer, and polyolefin plastomomer.

5. In Paragraph 4, A semiconducting composition for cables, wherein the above polyolefin resin comprises one or more selected from the group consisting of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, and polypropylene.

6. In Paragraph 1, A semiconducting composition for cables, wherein the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above polyolefin resin (a) is 5 g / 10 min to 30 g / 10 min.

7. In Paragraph 1, A semiconducting composition for cables, wherein the weight-average molecular weight of the polyolefin resin (a) is 10,000 g / mol to 200,000 g / mol.

8. In Paragraph 1, A semiconducting composition for cables, wherein the carbon black comprises one or more types selected from the group consisting of furnace black and acetylene black.

9. In Paragraph 1, The above carbon black has a bulk density of 100 kg / m³ 3 up to 500 kg / m² 3 and the specific surface area measured according to ASTM D3037-89 is 30 m² 2 / g to 150 m 2 Semiconductive composition for cables, which is / g.

10. In Paragraph 1, The above semiconducting composition for a cable comprises 60 to 90 weight% of the polyolefin-based resin (a) and 10 to 40 weight% of the carbon-based material (b).

11. In Paragraph 1, The above-mentioned semiconducting composition for cables further comprises an antioxidant, a crosslinking agent, and a crosslinking co-agent.

12. In Paragraph 11, A semiconducting composition for cables comprising one or more antioxidants selected from the group consisting of hindered phenolic compounds and hindered amineic compounds.

13. In Paragraph 11, The above semiconducting composition for a cable comprises 0.05 to 2 weight% of the antioxidant, 0.05 to 2 weight% of the crosslinking agent, and 0.05 to 2 weight% of the crosslinking co-agent.

14. In Paragraph 1, The above semiconducting composition for cables is a semiconducting composition for cables having a volume resistivity of 500 Ω·m or less at 90°C as measured by ASTM D991 standards.

15. In Paragraph 1, The above semiconducting composition for cables is a semiconducting composition for cables having a scorch time of 10 minutes or more as measured at 145°C, ts1 according to ASTM D5289 standards.

16. In Paragraph 1, The above semiconducting composition for cables has a tensile strength of 1.5 kgf / mm² as measured by ASTM D638 standards. 2 A semiconducting composition for cables having an elongation rate of 150% or more.

17. A power cable comprising a semiconducting layer formed from a semiconducting composition for a cable according to any one of claims 1 to 16.

18. Conductor; An inner semiconducting layer surrounding the above conductor; An insulating layer surrounding the above-mentioned inner semiconducting layer; and A power cable comprising an outer semiconducting layer surrounding the above-mentioned insulating layer; A power cable in which the inner semiconducting layer and the outer semiconducting layer are formed from a semiconducting composition for a cable according to any one of claims 1 to 16.

19. In Paragraph 18, The above power cable is a power cable that is a DC power cable.

20. A method for manufacturing a semiconducting composition for a cable according to any one of claims 1 to 16, wherein the method comprises: A step of introducing and mixing the raw materials of the above-mentioned semiconducting composition for the cable; and A method for manufacturing a semiconductive composition for cables comprising the step of extruding the above-mentioned mixed raw materials and then cooling.

21. In Paragraph 20, A method for manufacturing a semiconductive composition for cables, wherein in the cooling step above, the mixed raw materials are extruded into pellet form and then cooled.

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