KR20210030094A - Semi-conductive composition for power cable joint - Google Patents

Abstract

The present invention relates to a semi-conductive composition for a power cable. More particularly, the present invention relates to a semi-conductive composition for a power cable, having excellent mechanical and electrical properties. More specifically, the present invention relates to a semi-conductive composition for a junction box of a power cable, which has improved scorch stability and improved space charge accumulation suppression properties through an excellent electric field relaxation effect, and thus can be applied to a junction box of high-voltage and ultra-high voltage DC power cables.

Description

Semi-conductive composition for intermediate junction box of power cable {SEMI-CONDUCTIVE COMPOSITION FOR POWER CABLE JOINT}

The present invention relates to a semiconductive composition of an intermediate junction box for a power cable. More specifically, it relates to an inner and outer semiconducting composition of an intermediate junction box for a power cable having excellent electrical properties and mechanical properties.

More specifically, it relates to a semiconductive composition of an intermediate junction box for a power cable, which improves the ability to suppress insulation breakdown and suppress the accumulation of space charges by evenly dispersing an electric field generated from a conductor of a power cable.

In addition, the present invention provides a semiconducting composition applied to an inner semiconducting layer and an outer semiconducting layer in an intermediate connection structure including a conductor, an inner semiconducting layer, an insulating layer, and an outer semiconducting layer.

The intermediate junction box at the connection part of a high-voltage or ultra-high voltage power cable is composed of an inner semiconducting layer, an insulating layer, and an outer semiconducting layer, and the inner and outer semiconducting layers uniformly distribute the electric field from the conductor.

Semiconducting compositions for intermediate junction boxes are generally manufactured by mixing silicone rubber and conductive fillers, but this structure does not have a sufficient dispersing effect of the electric field and requires continuous performance over a long period of time, so the polymer composite material constituting it is It requires excellent electrical properties and durability, and should satisfy long-term reliability that maintains stable initial performance even when used for a long time.

In order to satisfy these characteristics, Korean Patent Registration No. 1865267 improves excellent electrical conductivity with silicon resin and carbon nanotubes as the main components. However, since the workability and electric field dispersion effect are insufficient, there is still a need to improve electrical characteristics. In addition, there is still a problem in that the dispersibility between the base resin and the conductive particles is reduced.

The present invention provides an internal and external semiconducting composition that has excellent electric field dispersion effect in an intermediate connection structure of high-voltage and ultra-high voltage cables and satisfies excellent mechanical properties by solving the above problems.

Korean Registered Patent Publication No. 10-1865267 (2018.05.31)

The present invention has been devised to solve the above problems, and provides a semiconductive composition of an inner and outer semiconducting layer in an inner semiconducting layer, an insulating layer, and an outer semiconducting layer of an intermediate junction box in which a power cable surrounds a conductor.

An object of the present invention is to provide a semiconducting composition used in a power cable, more specifically a connection structure of a high-voltage and ultra-high voltage power cable, which satisfies excellent mechanical properties and at the same time significantly reduces volume resistance.

In the present invention, the semiconductive composition can reduce the electric charge and the amount of electric charge due to polarity reversal according to the conversion of AC/DC/AC, and has excellent mechanical properties and excellent dispersion characteristics of a conductive filler. There is an object to provide a malleable composition.

In addition, it is an object to apply a technology for securing dispersibility of carbon black and carbon nanotubes, which are conductive fillers, and to reduce the additive phenomenon at the interface with the insulating layer through the application.

In addition, the present invention is to provide a technology for securing excellent dispersion characteristics of high-purity carbon nanotubes having poor dispersibility in order to satisfy the metal ion impurity content standard required in an ultra-high voltage cable.

One aspect of the present invention for achieving the above object

(A) ML(1+4) base resin comprising an ethylene-propylene-diene elastomer having a viscosity of 25 to 55 at 100° C. and having an ethylene content of 50 to 60 mol%,

(B) carbon black,

(C) high purity carbon nanotubes,

(D) a crosslinking agent and

(E) a polyolefin resin having a kinematic viscosity of 200 to 500 at 40°C,

It is to provide a semiconductive composition comprising a.

In one aspect of the present invention, based on 100 parts by weight of the (A) ethylene-propylene-diene-based elastomer, (B) 20 to 60 parts by weight of carbon black, (C) 2 to 10 parts by weight of high-purity carbon nanotubes (D) It may include 1 to 5 parts by weight of a crosslinking agent and 15 to 30 parts by weight of (E) a polyolefin resin.

In one aspect of the present invention, the carbon black has a sieve residue content of 10 ppm or less of 25 mesh (45 μm) according to ASTM D1514-01, and an ash content according to ASTM D1506-99. It is more preferable to include those having a specific surface area of 60 to 150 m 2 /g according to ASTM D3037-89 and less than 0.02 wt%.

In one aspect of the present invention, the high-purity carbon nanotube may be a multi-walled carbon nanotube having a metal ionic impurity content of 20,000 ppm or less, of which iron (Fe) content is less than 100 ppm.

In addition, the high-purity carbon nanotubes satisfy the metal ion impurity standards required for semiconducting materials in ultra-high voltage cables because the purity of the carbon nanotubes is 98-100%. Space charge reduction can be achieved. In particular, in the present invention, when the iron content of the carbon nanotubes is maintained at 100 ppm or less, compared to using the carbon black alone, the reduction in volume resistance is reduced to 1/2 or less, 1/3 or less, very preferably 1 It can be kept below /10. In addition, when the carbon nanotubes have an iron content of 100 ppm or less and a calcium content of 10 ppm or less, the above properties are more excellent, and thus more preferable.

More specifically, one aspect of the present invention is based on 100 parts by weight of the (A) ethylene-propylene-diene-based elastomer, (B) 20 to 60 parts by weight of carbon black, and (C) the content of metal ionic impurities is 20,000 ppm or less. And 2 to 10 parts by weight of carbon nanotubes having an iron (Fe) content of less than 100 ppm (D) 1 to 5 parts by weight of a crosslinking agent, and (E) 15 to 30 parts by weight of polyethylene having a weight average molecular weight of 1000 to 15000. In the case of, the volume resistance is lower and the mechanical properties are excellent, and by forming the matrix of the semiconductive composition together with the non-polar polymer and the polar polymer, excellent dispersion characteristics of the conductive filler can be imparted, so it is more preferred.

In one aspect of the present invention, it is possible to provide a semiconducting composition for a power cable further comprising a polyethylene-based resin grafted with maleic anhydride. More specifically, the present invention can provide a semiconductive composition comprising 0.1 to 5 parts by weight of the polyethylene-based resin grafted with maleic anhydride (A) based on 100 parts by weight of the base resin. When the polyethylene-based polar resin grafted with maleic anhydride is used, a matrix is formed with a non-polar ethylene-propylene-diene-based elastomer to improve the dispersion characteristics of the conductive filler between compounding processes, thus dispersing the electric field. It is preferred because the effect shows more excellent properties.

In addition, in one aspect of the present invention, the composition may further include any one or more additives selected from antioxidants and stabilizers.

In addition, in one aspect of the present invention, the antioxidant may be any one or a mixture of two or more selected from the group consisting of a hindered phenol compound and a hindered amine compound.

In addition, in one aspect of the present invention, the crosslinking agent is 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 peroxyisopropyl)benzene and α,α-bis It may be any one or a mixture of two or more selected from (t-butyl peroxy)-1,3-diisopropylbenzene.

In addition, in one aspect of the present invention, the semiconductive composition has a scorch time of 100 minutes or more, measured at 100°C and t5 according to ASTM D 1646, and a volume resistance of 250 Ωcm, measured at a high temperature (90°C) according to ASTM D991. It may be the following.

In the present invention, by introducing a conductive material containing high-purity carbon nanotubes (CNT) having a low impurity content along with carbon black, the volume resistance is reduced, the electric field relaxation effect is excellent, it is advantageous for injection molding processing, and the mechanical and electrical properties are also It is possible to provide a satisfactory semiconductive composition.

In addition, the present invention secures more excellent volume resistance characteristics by rearranging CNTs by heat inside the semiconducting composition not only at room temperature but also at high temperature (130°C), and through this, excellent electric field relaxation in high-temperature environments due to heat generated from conductors. As an effect, the space charge can be greatly reduced, thereby solving the problem of insulation breakdown caused by the accumulation of space charge.

Hereinafter, the present invention will be described in more detail through specific examples or examples including the accompanying drawings. However, the following specific examples or examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

In addition, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The terms used in the description in the present invention are merely for effectively describing specific embodiments and are not intended to limit the present invention.

In addition, the singular form used in the specification and the appended claims may be intended to include the plural form unless otherwise indicated in the context.

In addition, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

The inventors of the present invention can provide a composition excellent in rheological properties, mechanical properties and electrical properties by using ethylene-propylene-diene elastomer as a matrix resin, and in the present invention, a specific carbon nanotube (CNT) and By combining carbon black, it was found that the dispersion characteristics of the conductive material can be improved, the volume resistance can be reduced, and the accumulation of space charges can be further suppressed.

In addition, by combining the other components of the present invention with the ethylene-propylene-diene elastomer, the present invention discovered that it was possible to provide a semiconductive composition for a junction box of a power cable that also satisfies electrical properties including mechanical and volume resistance. Was completed.

One aspect of the present invention for achieving the above object

(A) ML(1+4) base resin comprising an ethylene-propylene-diene elastomer having a viscosity of 25 to 55 at 100° C. and having an ethylene content of 50 to 60 mol%,

(B) carbon black,

(C) high purity carbon nanotubes,

(D) a crosslinking agent and

(E) a polyolefin resin having a kinematic viscosity of 200 to 500 at 40°C,

It is to provide a semiconductive composition comprising a.

In addition, in the present invention, it is more preferable that the carbon nanotube has a metal ion impurity content of 20,000 ppm or less, of which iron (Fe) content is less than 100 ppm.

Further, the polyolefin resin is more preferably polyethylene having a weight average molecular weight of 1000 to 15000 g/mol.

In addition, the present invention is more preferable that the carbon black contains an ash content of 0.02% by weight or less according to ASTM D1506-99, and a specific surface area of 60 to 150 m 2 /g according to ASTM D3037-89.

One aspect of the present invention is more specifically, based on 100 parts by weight of the (A) ethylene-propylene-diene-based elastomer, (B) 20 to 60 parts by weight of carbon black, (C) the content of metal ionic impurities is 20,000 ppm Semiconducting properties including 2 to 10 parts by weight of carbon nanotubes, of which iron (Fe) content is less than 100 ppm (D) 1 to 5 parts by weight of a crosslinking agent, and (E) 15 to 30 parts by weight of polyethylene having a weight average molecular weight of 1000 to 15000 It is to provide a composition.

In addition, the present invention may further include 0.05 to 3 parts by weight of each of at least one component selected from a primary antioxidant, a secondary antioxidant, a stabilizer, a lubricant, a crosslinking agent, and the like.

The ethylene-propylene-diene-based elastomer (EPDM) of the present invention is prepared by including a small amount of a third component (diene) in ethylene and propylene, and various EPDMs in which a double bond is introduced in the main chain can be used. As EPDM, a variety of products are provided based on the difference in the type or amount of the third component. Representative diene components include, for example, ethylidene norbornene (ENB), 1,4-hexadiene (1,4-HD). ), dicyclopentadiene (DCP), and the like.

The EPDM used in the present invention has a viscosity of 25 to 55 at 100°C (ML(1+4)), and the content of ethylene is 50 to 60 mol% in the composition of the present invention. There is no occurrence, and the dispersibility of the carbon nanotubes and carbon black is further improved, and the surface characteristics of the injection product are remarkably improved, which is even better.

In one aspect of the present invention, the crosslinking agent is 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( It may be any one or a mixture of two or more selected from t-butyl peroxy)-1,3-diisopropylbenzene.

In one aspect of the present invention, the semiconducting composition includes both an inner semiconducting layer and an outer semiconducting layer for a connection structure of a cable having a semiconducting layer.

In one aspect of the present invention, the semiconducting composition has a scorch time of 100 minutes or more, preferably 140 minutes or more, measured at 125°C and t5 according to ASTM D 1646, and a volume resistance measured at 90°C according to ASTM D991. It may be 200 Ωcm, preferably 100Ωcm or less, more preferably 50Ωcm or less.

In the present invention, the carbon black may be one selected from acetylene black and furnace black, or a mixture thereof. Specifically, the carbon black has a sieve residue content of 25 mesh (45 μm) according to ASTM D1514-01 of 10 ppm or less, more specifically 1 to 10 ppm, and according to ASTM D1506-99. Ash content of 0.02% by weight or less, more specifically 0.005 to 0.020% by weight, and a specific surface area according to ASTM D3037-89 of 60 to 150 m 2 /g may be used. High conductivity can be expressed in the above range, excellent kneading property with EPDM resin, and dispersion characteristics can be improved, so it is preferable, but is not limited thereto.

The content of the carbon black is not limited as long as it is an amount sufficient to express conductivity, but specifically, for example, (A) 20 to 60 parts by weight, more specifically 20 to 50 parts by weight based on 100 parts by weight of the base resin. It may be to use. In the above range, it is preferable that dispersibility is excellent, kneading property with other components is excellent, and physical properties having excellent electrical properties can be expressed, but the present invention is not limited thereto.

In one aspect of the present invention, the carbon nanotubes having very excellent electrical conductivity and stiffness are mixed with the carbon black to achieve better volume resistance even by applying a relatively small amount of conductive filler (CNT+C/B). Can be achieved, and can have excellent mechanical properties. In addition, the use of high specific gravity carbon black can be remarkably reduced, thereby reducing the weight of materials. However, when a large amount of carbon nanotubes are used as a conductive material, the geometric characteristics of the acicular structure affect the rheological characteristics of the product, which is not good because it weakens the flowability and processability.

In particular, in the present invention, when the high purity (98-100%) carbon nanotubes are used and carbon nanotubes having an Fe ion content of 100 ppm or less are mixed with the carbon black, the use of carbon black alone In comparison, it is better to keep the reduction in volume resistance to be less than 1/2, and very preferably to less than 1/10, and it is better to use a mixture of carbon nanotubes and carbon black that do not belong to the present invention. Compared to the case, the volume resistance reduction rate is more excellent.

In the present invention, the content of the carbon nanotubes is preferably 1 to 10 parts by weight based on 100 parts by weight of EPDM. In the above range, the mixed composition technology of carbon nanotubes and carbon black complements the relatively weak electrical properties of carbon black and the weak rheological properties of carbon nanotubes, thereby improving dispersibility of conductive particles in the EPDM matrix, and It is preferable, but is not limited thereto, because it improves the electric field relaxation ability of the semiconducting layer and can clearly exhibit the effect of reducing the space charge through this.

In one aspect of the present invention, the antioxidant is intended to secure a long life by suppressing the oxidation reaction of the semiconducting layer in a high-temperature environment, thereby ensuring long-term durability of the junction box, so that it is not particularly limited as long as it is used in this field, but specifically For example, using one or a mixture of two or more selected from hindered phenolic compounds and hindered amine compounds, in which phenol is substituted with an alkyl group at both adjacent positions of the hydroxy group, secures the long-term reliability of the cable junction box. In this case, it is possible to exhibit more excellent properties.

The hindered phenolic compound is not limited, but specifically, for example, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] , Triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate, 1,6-hexanediol-bis[3-(3,5-di-t-) Butyl-4-hydroxyphenyl) propionate, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3, 5-triazine, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-( 3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, triethylene glycol -Bis-3(3-t-butyl-4-hydroxy-5-methylphenyl)propionate, tetrakis-methylene (3,5-di-t-butyl-4-hydroxycinanate)-methane, N ,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydroxynamamide), 3,5-di-t-butyl-4-hydroxy-benzylphosphasponate- Diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-butyl-4-hydroxybenzyl)benzene, bis(3,5-di-t-butyl-4- Ethyl calcium hydroxybenzylsulfonate, tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, stearyl-β-(3,5-di-t-butyl-4- Hydroxyphenyl)propionate, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,9-bis[1,1-dimethyl-2-[β -(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3,5-trimethyl- 2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris(3',5'-di-t-butyl-4'-hydro Oxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, d-α-tocopherol, etc. These may be used alone or in combination of two or more. It is possible.

The hindered amine compound is not limited, but specifically, for example, 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonic acid bis(1, 2,2,6,6-pentamethyl-4-piperidyl), 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]- 4-[3-(3,5-t-butyl-hydroxyphenyl)propionyloxy]2,2,6,6-tetramethylpiperidine, and the like. These may be used alone or in combination of two or more.

When the above hindered phenolic antioxidant and hindered amine antioxidant are used, compared to other antioxidants, the anti-scorch property is significantly increased, resulting in an unexpected effect of increasing the surface smoothness of the extruded semiconducting layer. May also appear and may be more preferred. More specifically, when 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] is used, the scorch time increases and the space charge decreases. The effect is more excellent and may be preferred, but is not limited thereto.

The content of the antioxidant is not limited, but specifically, for example, (A) based on 100 parts by weight of the base resin, 0.05 to 3 parts by weight, more specifically 0.1 to 1 parts by weight may be used. Since the anti-scorch effect is remarkable in the above range, it is preferable, but is not limited thereto.

In one aspect of the present invention, the crosslinking agent is for forming a composite having a network structure such as a net by forming a crosslinking bond in the EPDM matrix resin, and any crosslinking agent commonly used in the art for this purpose is used. It is also okay. Even better, the half-life of the crosslinking agent at the processing temperature is much longer than the residence time in the metering part of the injection machine when manufacturing the intermediate junction box of the cable. Otherwise, some scorch may occur in the metering part before injection into the mold during the injection process, and this may act as a cause of molding defects such as lowering of flowability and non-molding. It can cause electric field concentration problems due to the back.

Specifically, the type of crosslinking agent is, for example, 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 peroxyisopropyl)benzene and α,α-bis Any one or a mixture of two or more selected from (t-butyl peroxy)-1,3-diisopropylbenzene, etc. may be used, but is not limited thereto. More specifically, the use of α,α-bis(t-butyl peroxy)-1,3-diisopropylbenzene may facilitate crosslinking and improve scorch stability, so it may be preferred, but is not limited thereto. .

The content of the crosslinking agent is not limited, but specifically, for example, 1 to 5 parts by weight may be used based on 100 parts by weight of the EPDM base resin. In the above range, the present invention can prevent scorch from occurring within the processing temperature and processing time for the composition of one aspect, and at the same time, the crosslinking is appropriately made to realize a uniform crosslinking density and excellent mechanical properties in the thickness direction. Therefore, it is preferable, but is not limited thereto.

Next, a polyolefin resin having a kinematic viscosity of 200 to 500 at a weight average molecular weight of 40°C of the present invention will be described. When the polyolefin resin of the present invention is mixed with the EPDM, CNT, and carbon black, excellent processing properties are obtained by implementing excellent rheological properties required for injection molding, thereby avoiding molding defects such as non-molding that may occur between injection molding. Can be solved.

In the present invention, the content of the polyolefin resin having a kinematic viscosity of 200 to 500 at 40°C can be used in an amount of 15 to 30 parts by weight based on 100 parts by weight of the EPDM base resin. It acts fragile from the side and may cause problems such as unmolding, as well as relatively soft insulation due to high hardness characteristics in the process of molding the insulating material through the insert injection method using pre-molded semi-conductive material. There is a disadvantage in that the interfacial properties between the layer and the hardened semiconducting layer become weak. If the amount is used in an amount of 30 parts by weight or more, mechanical properties are significantly lowered due to a decrease in crosslinking density, and agglomeration of carbon black and carbon nanotubes occurs during processing, making it difficult to achieve the original electric field relaxation effect in the semiconducting layer. , More preferably the content of the present invention.

In addition, in one aspect of the present invention, the composition may further include a polyethylene-based resin grafted with maleic anhydride from the viewpoint of further improving mechanical properties, dispersibility, and long-term extrusion properties. The content is not limited, but (A) 0.1 to 5 parts by weight, more specifically 0.5 to 3 parts by weight, based on 100 parts by weight of the base resin may be used. It is preferable to further express the desired physical properties in the above range, but is not limited thereto.

The polyethylene-based resin grafted with maleic anhydride may be grafted with maleic anhydride of 0.05 to 10% by weight, and a melting point of 100 to 105°C is preferably used, but the present invention is not limited thereto.

In addition, the present invention can further add various processing aids, if necessary.

The following examines the processing method of the present invention.

In the present invention, the composition is weighed and a pressurized kneader is kneaded. For example, it is preferable to sufficiently knead the composition for a period of 15 to 30 minutes at a rotational speed of 20 to 40 rpm at 80 to 130 °C. Do. When the kneading process is completed, a finished product of the semiconductive composition is manufactured in a ribbon shape using an extruder. At this time, the temperature of the extruder is preferably controlled to be less than 120°C so that crosslinking of the product does not occur, but is not limited thereto.

The physical properties measured by preparing a ribbon manufactured by the above process as a specimen are 145°C according to ASTM D 1646, the scorch time measured at t5 is 100 minutes or more, and the volume resistance measured at 90°C according to ASTM D991 is 250 Ωcm or less, preferably 100 Ωcm or less, more preferably 50 or less.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are only one example for describing the present invention in more detail, and the present invention is not limited by the following Examples and Comparative Examples.

First, prior to describing the embodiments of the present invention, the properties of the semiconducting resin composition for an ultra-high voltage power cable manufactured according to the embodiments of the present invention, such as specific gravity, electrical volume resistance, and tensile strength, were measured by the following test method. .

(1) Mooney viscosity

Viscosity was measured using the model name MV2000 (Korea, Labtech Co., Ltd.). Measure and read the value 4 minutes after starting the rotor in 1 minute of preheating at 100°C and display as 100ML1+4. Here, the meaning of 100ML1+4 is M is Mooney viscosity, L is the size of the rotor (Rotor size: L type-Ø38.10×5.5 mm, S type-Ø30.48×5.5 mm), 1 is the preheating time for 1 minute. , 4 is the time the rotor rotates at 2 rpm for 4 minutes, and 100 is the test temperature (℃).

(2) Scotch time

Scorch is partially crosslinked during injection of the semiconductive composition material into the mold between injection molding processes.When scorch occurs, the gate connecting the injection molding machine and the mold and the flowability of the semiconducting composition inside the mold are inhibited and injection is defective. It can act as a cause. Therefore, the longer the scotch time is, the more advantageous it is to secure the excellent appearance of the molded product. However, if the scorch time is designed to be longer than necessary, the time required for crosslinking time between injection molding processes becomes longer, which may adversely affect productivity. The scorch time was measured using the model name MV2000 (Korea, Labtech Co., Ltd.).

The scorch time represents the scorch time of a sample measured by a viscometer, and the test temperature is 125°C. At the scorch time (t5, 125°C), t5 represents the time required to rise 5 points in units from the lowest viscosity (ML). In general, the longer the scorch time is, the better the long-term extrudability is.

(3) Volume Resistance (Ω·cm)

Prepare a specimen with a width of 30 mm and a length of 115 mm as a sheet with a thickness of 1 mm, and volume resistance characteristics at room temperature (23 °C) by using a jig with a distance between electrodes of 50 mm at both ends of the specimen according to ASTM D991, Put the sample in an oven preheated to 90 ℃ and 130 ℃, leave for 30 minutes, and measure the volume resistance.

(4) Space charge measurement

Space Charge is the main factor that causes electric field distortion in the insulator under DC electric field, and is a key electrical characteristic in ultra-high voltage DC power cables. This is a phenomenon that occurs only in DC with constant voltage polarity unlike AC where voltage polarity is alternating. When the space charge is not accumulated, the electric field in the insulator is uniform, for example, at a level of 50 kV/mm, but when the space charge is accumulated, a portion may increase by 50% to 75 kV/mm. This becomes a problem for long-term reliability and makes insulation design impossible. In DC cables, in order to suppress the accumulation of space charges, the injection and accumulation of space charges by semiconducting materials must be small, like insulators. The specimens for measuring space charge were prepared by crosslinking reactions at 180° C. for 20 minutes at 200 kg/cm 2 using a press tester to form sheets with a thickness of 0.2 mm, respectively. Thereafter, the insulator sheet was dried in an air oven at 70° C. for 24 hours for degassing. Then, a semiconducting specimen was placed on the upper electrode and an insulator specimen was placed on the lower electrode. The applied electric field is measured for 60 min at 50 kV/mm and room temperature (23° C.). A voltage is applied through the upper electrode to generate electric charge, and a piezoelectric element PVDF (polyvinylidend fluoride) film is placed for acoustic wave measurement through the lower electrode, and a damper, PMMA (Polymethyl Methacrylate) is placed behind it to reflect the signal. Prevent distortion. It was measured using the PEA (Pulsed Electro-Acoustic Method) method, one of the non-destructive measurement methods, and if a space charge appeared different from the standard signal, it was judged as a defect. That is, the electric charge distribution inside the insulating material was measured according to the selection of the composition of the composition of the semiconducting material.

It is the number of'+' indicated in the space charge category, which indicates the relative amount of accumulated charge. '-' indicates that there is no charge accumulation,'+' indicates that there is some accumulation of charge,'++' indicates that there is a little more accumulation of charge, and'+++' indicates that there is accumulation of charge. This indicates very much. Therefore, the more the space charge accumulation is not'-', the better it is.

(5) density

The density was measured using the model name EW-300SG (Japan, Alfa Mirage Co., Ltd.). At room temperature and 1 atmosphere, the semiconductive resin composition is measured by ASTM D 792 (Standard Test Method for Density and Specific Gravity of Plastics by Displacement, Annual Book of ASTM Standards D792).

[Examples and Comparative Examples]

Examples and comparative examples were prepared in the composition shown in Table 1 below.

In a pressurized kneader, EPDM, which is a base resin, is first put in, and then soviet for 5 minutes at 90°C at a rotational speed of 25 rpm, then the ingredients excluding the crosslinking agent are added, kneaded sufficiently for 15 minutes, and open to 110°C or less. After cooling on a roller, a crosslinking agent was added and kneaded, and then a ribbon was manufactured using a single-axis ribbon extruder.

In order to prepare the test piece for evaluation, a chemical crosslinking reaction was carried out at 170° C. for 20 minutes at 200 kg/cm 2 using a press tester to produce a sheet form having a width of 150 mm each and a thickness of 1 mm. Thermal, electrical, mechanical, and structural properties were measured using the prepared sheet-shaped specimen. The results are listed in the table below.

The raw materials in Tables 1 and 2 are as follows, and the unit is parts by weight.

EPDM: ML(1+4) 100℃: 40, Ethylene content(%) 55%

Carbon black: acetylene carbon black with an Ash content of 0.010 wt% according to ASTM D1506-99 and a specific surface area of 69 ㎡/g according to ASTM D3037-89

CNT(1): High-purity carbon nanotubes with Fe content of 30 ppm and Ca content of 8 ppm when analyzed by ICP

CNT(2): High purity carbon nanotubes with 58 ppm Fe and 15 ppm Ca content as analyzed by ICP

CNT (3): High purity carbon nanotubes with 235 ppm Fe and 15 ppm Ca content as analyzed by ICP

Polyolefin resin: Polyethylene resin with a kinematic viscosity of 368 at 40℃

Antioxidant: 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]

Stabilizer: Decaglycerin Heptasterate

Lubricant: Polysiloxane

Crosslinking agent: α,α-bis(t-butyl peroxy)-1,3-diisopropylbenzene

MAH-g-LDPE: Low-density polyethylene grafted with maleic anhydride with a melt index of 3 g/10min measured at 230°C according to ASTM D1238 and a VICAT softening point of 82°C according to ASTM D1525

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 2 Example 6 EPDM 100 100 100 100 100 100 100 100 Carbon black 50 40 20 30 35 40 40 40 CNT(1) 0 8 8 4 4.2 - - 8 CNT(2) 0 - - 8 - - CNT(3) 0 - - - - - 8 Polyolefin 30 30 30 30 30 30 30 30 MAH-g-LDPE - - - - - - - 1.5 Crosslinking agent 3 3 3 3 3 3 3 3 stabilizator 5 5 5 5 5 5 5 5 Lubricant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

Properties unit Comparative Example 1 Example Comparative Example 2 Example 6 One 2 3 4 5 Rheology
Properties Viscosity
(ML1+4,100℃) - 45.9 88.8 61.2 50.1 56.5 67.3 57.8 70.1 Scorch
(t5, 125℃) min:sec 43:52 121:34 111:12 119:48 152:04 121:34 104:21 156: 41 Electrical
characteristic volume
resistance 23℃ Ωcm 599 16 32 187 88 187 288 15 90℃ Ωcm 455 24 56 123 80 153 144 20 130℃ Ωcm 315 16 16 99 72 87 128 13 Space charge
(23℃) - + + ++ + + + +++ - Dispersion
characteristic Standard deviation of volume resistance % 95 91 76 85 89 87 84 98 Mechanical
characteristic The tensile strength N/mm ² 11.1 9.4 6.7 5.9 6.9 9.5 9.8 10.1 Elongation % 374 288 197 269 292 279 256 233

It can be seen that the present invention can secure the same level of mechanical properties even though the content of the conductive filler is significantly reduced. That is, 50 parts by weight of carbon black was used in Comparative Example 1, but even if only 28 parts by weight of the conductive agent was used in Example 2, sufficiently excellent electrical properties, space charge reduction, and rheological properties could be achieved.

As shown in Table 2, Examples 1 to 5 and 6 including all the components of the present invention exhibit remarkably excellent properties in electrical properties such as rheological properties such as scorch properties, volume resistance, and space resistance. It can be seen that it represents. However, when comparing the physical properties of Comparative Example 2 and Example 6, where the content of iron ions in CNT is different from the present invention while adopting the same composition, the scorch characteristic, volume resistance characteristic, space charge characteristic It showed excellent physical properties in the same physical properties.

As described above, those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof.

Therefore, all of the embodiments described above are illustrative and should be understood as non-limiting. The scope of the present invention should be construed as including all changed or modified forms derived from the meaning and scope of the claims to be described later rather than the above detailed description, and equivalent concepts thereof.

Claims (9)

(A) ML(1+4) base resin comprising an ethylene-propylene-diene-based elastomer having a viscosity of 25 to 55 at 100° C. and having an ethylene content of 50 to 60 mol%,
(B) carbon black,
(C) high purity carbon nanotubes,
(D) a crosslinking agent and
(E) a polyolefin resin having a kinematic viscosity of 200 to 500 at 40°C,
Semiconductive composition comprising a. The method of claim 1,
With respect to 100 parts by weight of the (A) ethylene-propylene-diene-based elastomer, (B) 20 to 60 parts by weight of carbon black, (C) 2 to 10 parts by weight of high-purity carbon nanotubes (D) 1 to 5 parts by weight of a crosslinking agent, and (E) A semiconductive composition containing 15 to 30 parts by weight of a polyolefin resin. The method of claim 1,
The high-purity carbon nanotube is a multi-walled carbon nanotube having a metal ionic impurity content of 20,000 ppm or less, of which iron (Fe) content is less than 100 ppm. The method of claim 1,
The polyolefin resin is a semiconductive composition of polyethylene having a weight average molecular weight of 1000 to 15000 g/mol. The method of claim 1,
The carbon black has a sieve residue content of 25 mesh (45 μm) according to ASTM D1514-01 of 10 ppm or less, an ash content of 0.02 wt% or less according to ASTM D1506-99, and ASTM Semiconductive composition with a specific surface area of 60 to 150 m 2 /g according to D3037-89. The method of claim 1,
The composition further comprises any one or more additives selected from antioxidants and stabilizers. The method of claim 6,
The antioxidant is a semiconducting composition of any one or a mixture of two or more selected from the group consisting of hindered phenolic compounds and hindered amine compounds. The method of claim 1,
The crosslinking agent is 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)- A semiconductive composition that is any one selected from 1,3-diisopropylbenzene, or a mixture of two or more. The method of claim 1,
The semiconductive composition has a scorch time of 100 minutes or more at 100°C and t5 according to ASTM D 1646, and a volume resistance of 250 Ωcm or less at 90°C according to ASTM D991.