KR102339371B1 - Semiconductive composition and power cable having a semiconductive layer formed from the same - Google Patents

Abstract

The present invention relates to a semiconducting composition and a power cable having a semiconducting layer formed therefrom. Specifically, the present invention relates to a semiconducting composition that is eco-friendly, has excellent heat resistance, mechanical strength, and the like, and excellent extrudability, which is in a trade-off therewith, and a power cable having a semiconducting layer formed therefrom.

Description

Semiconductive composition and power cable having a semiconducting layer formed therefrom

The present invention relates to a semiconducting composition and a power cable having a semiconducting layer formed therefrom. Specifically, the present invention relates to a semiconducting composition that is eco-friendly, has excellent heat resistance, mechanical strength, and the like, and excellent extrudability, which is in a trade-off therewith, and a power cable having a semiconducting layer formed therefrom.

A general power cable includes a conductor and an insulating layer surrounding it, and an inner semiconducting layer between the conductor and the insulating layer, an outer semiconducting layer surrounding the insulating layer, a sheath layer surrounding the outer semiconducting layer, etc. .

Conventionally, a semiconducting composition for forming a semiconducting layer has been generally used as a base resin by crosslinking polyolefin polymers such as polyethylene, ethylene/propylene elastic copolymer (EPR), and ethylene/propylene/diene copolymer (EPDM). This is because the conventional cross-linked resin maintains excellent flexibility and satisfactory electrical and mechanical strength even under high temperature.

However, cross-linked polyethylene (XLPE), which has been used as the base resin constituting the semi-conductive composition, is a cross-linked form, so when the life of a cable including a semi-conductive layer made of a resin such as the cross-linked polyethylene is over, the semi-conductive layer is formed. It is not environmentally friendly as it is impossible to recycle the used resin and has no choice but to dispose of it by incineration.

In addition, when polyvinyl chloride (PVC) is used as a material of the sheath layer, it is difficult to separate it from cross-linked polyethylene (XLPE) constituting the semiconducting layer, etc. There are disadvantages.

On the other hand, non-crosslinked high-density polyethylene (HDPE) or low-density polyethylene (LDPE) is environmentally friendly, such as recycling of the resin constituting the semiconducting layer, when the life of a cable including a semiconducting layer manufactured therefrom has expired, but crosslinking Compared to polyethylene (XLPE) in the form of heat resistance, its use is very limited due to a low operating temperature.

Therefore, it may be considered to use an environmentally friendly polypropylene resin as a base resin because the polymer itself has excellent heat resistance without crosslinking at a melting point (Tm) of 160° C. or higher. However, the extrudability of the polypropylene resin may be greatly reduced due to its high melting point and low melting index (MI).

Furthermore, in the semi-conductive composition, a conductive additive such as carbon black is mixed in the base resin to realize semi-conductive properties, and extrudability may be greatly reduced by the conductive additive.

Accordingly, there is an urgent need for a semiconducting composition that is environmentally friendly, has excellent heat resistance and mechanical strength, and has excellent extrudability, which is in a trade-off, and a power cable having a semiconducting layer formed therefrom.

Korean Patent Publication No. 10-2014-0134836 Korean Patent Publication No. 10-2009-0080066 Korean Patent Publication No. 10-2011-0084544

An object of the present invention is to provide an eco-friendly semiconducting composition and a power cable having a semiconducting layer formed therefrom.

Another object of the present invention is to provide a semiconducting composition having excellent heat resistance, mechanical strength, and the like and simultaneously improving extrudability, which is in a trade-off relationship, and a power cable having a semiconducting layer formed therefrom.

In order to solve the above problems, the present invention,

A base resin comprising a non-crosslinked thermoplastic resin including a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix and a conductive additive, wherein the heterophasic resin has a melting point (Tm) of 155 to 170°C and a load of 2.16 kg and A heterophasic resin (A1) having a melting flow rate (MFR) of 0.1 to 1.0 g/10 min measured according to ISO 1133 at 230°C and a melting point of 140 to 150°C and a load of 2.16 kg and ISO 1133 at 230°C It provides a semiconducting composition, characterized in that it comprises a heterophasic resin (A2) having a melt flow rate (MFR) measured according to 3 to 10 g/10 min.

Here, the heterophasic resin (A1) comprises a propylene homopolymer as a polypropylene matrix and the heterophasic resin (A2) comprises a random propylene copolymer as the polypropylene matrix, providing a semiconducting composition do.

In addition, the weight ratio of the heterophasic resin (A1) to the heterophasic resin (A2) is 50:50 to 80:20, it provides a semiconducting composition.

And, the propylene copolymer dispersed in the polypropylene matrix provides a semiconducting composition, characterized in that it is amorphous having a residual crystallinity of less than 10 J/g of enthalpy of melting.

Here, the propylene copolymer dispersed in the polypropylene matrix is at least one selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. It provides a semiconducting composition, characterized in that it comprises a comonomer.

In addition, there is provided a semiconducting composition, characterized in that the propylene copolymer dispersed in the polypropylene matrix comprises 20 to 50% by weight of ethylene monomer based on the total weight thereof.

And, the content of the propylene copolymer dispersed in the polypropylene matrix provides a semiconducting composition, characterized in that 60 to 90% by weight based on the total weight of the heterophasic resin.

Furthermore, the content of the conductive additive is 30 to 70 parts by weight based on 100 parts by weight of the base resin, it provides a semiconducting composition.

In addition, based on 100 parts by weight of the base resin, it provides a semiconducting composition, characterized in that it further comprises 0.2 to 3.0 parts by weight of an antioxidant.

On the other hand, conductor; an inner semiconducting layer surrounding the conductor; and an insulating layer surrounding the inner semiconducting layer, wherein the inner semiconducting layer is formed from the semiconducting composition.

The semiconducting composition according to the present invention exhibits an excellent effect of being environmentally friendly by adopting a non-crosslinked propylene polymer as a base resin.

In addition, the semiconducting composition according to the present invention exhibits an excellent effect of simultaneously improving heat resistance, mechanical strength, and the like, and extrudability, which is in a trade-off with, by including two or more specific heterophasic resins as a base resin.

1 schematically shows a cross-sectional structure of an embodiment of a power cable according to the present invention.
FIG. 2 schematically shows a stepped cross-sectional structure of the power cable shown in FIG. 1 .

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art. Like reference numerals refer to like elements throughout.

The present invention relates to a semiconducting composition capable of forming the semiconducting layer of a power cable.

The semiconducting composition according to the present invention may be formed from a semiconducting composition comprising a non-crosslinked thermoplastic resin including a heterophasic resin (A) in which a propylene copolymer is dispersed in a polypropylene matrix as a base resin.

Here, the polypropylene matrix may be a matrix comprising a propylene homopolymer and/or a propylene copolymer, preferably a propylene homopolymer, more preferably a matrix comprising only a propylene homopolymer. The propylene homopolymer means a polypropylene formed by polymerization of at least 99% by weight, preferably at least 99.5% by weight, based on the total weight of the monomers.

The propylene copolymer dispersed in the polypropylene matrix (hereinafter referred to as 'dispersed propylene copolymer') is substantially amorphous. Here, the propylene copolymer is amorphous means that the enthalpy of melting has a residual crystallinity of less than 10 J / g. The dispersed propylene copolymer is selected from the group consisting of ethylene and _{C 4-8} alpha-olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, and the like. one or more comonomers.

The dispersed propylene copolymer may be 60 to 90 wt%, preferably 65 to 80 wt%, based on the total weight of the heterophasic resin (A). Here, when the content of the dispersed propylene copolymer is less than 60% by weight, flexibility, flexibility, impact resistance, cold resistance, etc. of the formed inner semiconducting layer 20 may be insufficient, whereas when it exceeds 90% by weight, formed The heat resistance, mechanical strength, etc. of the semiconducting layer may be insufficient.

The dispersed propylene copolymer is propylene-ethylene rubber (PER) or propylene-ethylene diene rubber (EPDM) comprising 20 to 50% by weight, preferably 30 to 40% by weight of ethylene monomer, based on the total weight of the monomers. can When the content of the ethylene monomer is less than 20% by weight, flexibility, flexibility, and impact resistance of the formed semiconducting layer are excellent, but cold resistance, etc. may be insufficient, whereas when it exceeds 50% by weight, the cold resistance, heat resistance and mechanical strength of the semiconducting layer are It is excellent, but flexibility, etc. may be deteriorated.

The dispersed propylene copolymer may have a particle size of 1 μm or less, preferably 0.9 μm or less, and more preferably 0.8 μm or less. Such a particle size of the dispersed propylene copolymer can ensure uniform dispersion of the dispersed propylene copolymer in the polypropylene matrix, and improve the impact strength of the semiconducting layer including the same. The particle size also improves the likelihood of stopping an already formed crack or crack while reducing the risk of cracking initiated by the particle.

Since the heterophasic resin (A) contains non-crosslinked polypropylene, it is environmentally friendly, such as recyclable, and at the same time, it is possible to improve the heat resistance of the semiconducting layer formed by the polypropylene matrix having excellent heat resistance.

In particular, the heterophasic resin (A) may include a blending resin of two or more heterophasic resins. Here, the at least two heterophasic resins have a melting point (Tm) of 155 to 170°C (measured by differential scanning calorimetry (DSC)) and a melt flow rate (MFR) measured according to ISO 1133 at a load of 2.16 kg and 230°C; Heterophasic resin (A1) having a melting flow rate of 0.1 to 1.0 g/10 min, preferably 0.1 to 0.8 g/10 min, and a melting point of 140 to 150° C. (measured by differential scanning calorimetry (DSC)), and 2.16 kg The melt flow rate (MFR) measured according to ISO 1133 at a load of 230° C. may include the heterophasic resin (A2) of 3 to 10 g/10 min.

In addition, the heterophasic resin (A1) preferably has a tensile stress at break of 10 MPa or more, a tensile strain at break of 490% or more, and a flexural strength of 95 to 105 MPa, notched Izod ( notched izod) impact strength of 68-72 kJ/m2, heat deflection temperature of 38-42°C (measured at 0.45 MPa), Vicat softening point of 55-59°C (measured at 50°C/h and 10N according to A50), Shore D hardness can be from 25 to 31 (measured according to ISO 868) and enthalpy of melting from 25 to 40 J/g (measured by DSC).

And, the density of the heterophasic resin (A1) may be 0.86 to 0.90 g/cm 3 , preferably 0.88 g/cm 3 when measured according to ISO 11883, and the density is the characteristic of the inner semiconducting layer 20, for example For example, it affects impact strength and shrinkage properties.

Specifically, the heterophasic resin (A1) may include a propylene homopolymer as the polypropylene matrix and the heterophasic resin (A2) may include a random propylene copolymer as the polypropylene matrix, preferably random propylene It may include only the copolymer, and the weight ratio of the heterophasic resin (A1) to the heterophasic resin (A2) may be 50:50 to 80:20.

Here, when the content of the heterophasic resin (A1) is less than 50 parts by weight and the content of the heterophasic resin (A2) is more than 50 parts by weight, the heat resistance and elongation of the inner semiconducting layer 20 may be significantly reduced. On the other hand, when the content of the heterophasic resin (A1) is more than 80 parts by weight and the content of the heterophasic resin (A2) is less than 20 parts by weight, the viscosity of the composition forming the inner semiconducting layer 20 is increased. When the screw load increases, workability may be greatly reduced.

The semiconducting composition may further include 30 to 70 parts by weight of a conductive additive such as carbon black and 0.2 to 3.0 parts by weight of an antioxidant based on 100 parts by weight of the base resin.

Here, when the content of the conductive additive, such as carbon black, is less than 30 parts by weight, the resistance of the formed semiconducting layer rapidly increases so that semiconducting properties may not be realized, whereas when the content of the conductive additive such as carbon black is more than 70 parts by weight of the composition for forming the semiconducting layer As the viscosity increases, the screw load increases during extrusion, and workability may be greatly reduced.

And, when the content of the antioxidant is less than 0.2 parts by weight, it may be difficult to secure long-term heat resistance in the high-temperature environment of the semiconducting layer formed, whereas when it is more than 3 parts by weight, the antioxidant is eluted white to the surface of the semiconducting layer blooming ( blooming) may occur and the semi-conductive properties may be deteriorated.

The present invention relates to a power cable having a semiconducting layer, in particular an inner semiconducting layer, formed from the semiconducting composition described above, Figures 1 and 2 schematically showing the structure of one embodiment of a power cable according to the invention; will be.

1 and 2, the power cable according to the present invention surrounds a conductor 10 made of a conductive material such as copper or aluminum, an insulating layer 30 made of an insulating polymer, etc., and the conductor 10, and The inner semiconducting layer 20 formed from the semiconductive composition according to the present invention described above, which removes the air layer between the conductor 10 and the insulating layer 30 and relieves local electric field concentration. It may include an external semiconducting layer 40 that serves to shield the cable and to apply an equal electric field to the insulating layer 30 , and a sheath layer 50 for protecting the cable.

Specifications of the conductor 10 , the insulating layer 30 , the semiconducting layers 20 and 40 , and the sheath layer 50 may vary depending on the use of the cable, the transmission voltage, and the like.

The conductor 10 may be formed of a stranded wire in which a plurality of wires are combined in terms of improving cold resistance, flexibility, flexibility, laying properties, workability, etc. of the power cable, and in particular, the plurality of wires is a circumference of the conductor 10 . It may include a plurality of conductor layers formed by being arranged in the direction.

The insulating layer 30 of the power cable according to the present invention is a base resin included in the inner semiconducting layer 20 described above, and a heterophasic resin (A1) and a polypropylene resin (B) in which a propylene copolymer is dispersed in a polypropylene matrix. ) may include a blended (blending) non-crosslinked thermoplastic resin as a base resin.

In addition, the polypropylene resin (B) may include a propylene homopolymer and/or a propylene copolymer, preferably a propylene copolymer. The propylene homopolymer means a polypropylene formed by polymerization of at least 99% by weight, preferably at least 99.5% by weight, based on the total weight of the monomers.

The propylene copolymer is propylene and ethylene or an α-olefin having 4 to 12 carbon atoms, for example, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, comonomers selected from 1-dodecene and combinations thereof, and the like, preferably copolymers with ethylene. This is because when propylene and ethylene are copolymerized, they exhibit hard and flexible properties.

The propylene copolymer may include a random propylene copolymer and/or a block propylene copolymer, preferably a random propylene copolymer, and more preferably only a random propylene copolymer. The random propylene copolymer means a propylene copolymer in which propylene monomers and other olefin monomers are optionally alternately arranged. The random propylene copolymer is preferably a random propylene copolymer comprising 1 to 10% by weight, preferably 1 to 5% by weight, more preferably 3 to 4% by weight of ethylene monomer, based on the total weight of the monomers.

The random propylene copolymer preferably has a density of 0.87 to 0.92 g/cm 3 (measured according to ISO 11883) and a melt flow rate (MFR) of 1.7 to 1.9 g/10 min (2.16 kg at 230° C. according to ISO 1133). measured under a load of), tensile modulus of 930 to 980 MPa (measured at a tensile rate of 1 mm/min), tensile stress of 22 to 27 MPa (measured at a tensile rate of 50 mm/min), and tensile strain of 13 to 15% ( (measured at a tensile rate of 50 mm/min), Charpy impact strength at 0°C and 23°C of 1.8 to 2.1 kJ/m and 5.5 to 6.5 kJ/m, respectively, and heat deflection temperature of 68 to 72°C (measured at 0.45 MPa) , a Vicat softening point of 131 to 136° C. (measured at 50° C./h and 10N according to Specification A50), and a Shore D hardness of 63 to 70 (measured according to ISO 868).

The random propylene copolymer can improve mechanical strength, such as tensile strength, of the insulating layer 30 to be formed, and has high transparency, which is suitable for transparent molded articles, and has a relatively high crystallization temperature (Tc), so that the insulation for cable manufacturing By shortening the time required for cooling after extrusion of the layer 30, the manufacturing yield of the cable can be improved, while the shrinkage rate and heat deformation of the insulating layer 30 can be minimized, and the cable manufacturing cost is reduced by a relatively low unit cost. There are advantages to savings.

The polypropylene resin (B) may have a weight average molecular weight (Mw) of 200,000 to 450,000. Further, the polypropylene resin (B) has a melting point (Tm) of 140 to 175°C (measured by differential scanning calorimetry (DSC)), an enthalpy of melting of 50 to 100 J/g (measured by DSC), room temperature It may have a flexural strength of 30 to 1,000 MPa, preferably 60 to 1,000 MPa (measured according to ASTM D790).

The polypropylene resin (B) can be polymerized in the presence of a conventional stereo-specific Ziegler-Natta catalyst, metallocene catalyst, constrained geometry catalyst, other organometallic or coordination catalyst, preferably Ziegler-Natta catalyst or metallocene It can be polymerized under a catalyst. Here, the metallocene is a generic term for bis(cyclopentaidenyl)metal, which is a new organometallic compound in which cyclopentadiene and a transition metal are combined in a sandwich structure, and the general formula of the simplest structure is M(C ₅ H ₅ ) ₂ (here , M is Ti, V, Cr, Fe, Co, Ni, Ru, Zr, Hf, etc.). Since the polypropylene polymerized under the metallocene catalyst has a low catalyst residual amount of about 200 to 700 ppm, deterioration of electrical properties of the insulating composition including the polypropylene by the catalyst residual amount can be suppressed or minimized.

Although the polypropylene resin (B) is non-crosslinked, it has a high melting point and exhibits sufficient heat resistance to provide a power cable with an improved continuous use temperature, and is environmentally friendly, such as recyclable because it is non-crosslinked. It shows an excellent effect. On the other hand, the conventional cross-linked resin is difficult to recycle, so it is not eco-friendly, and if cross-linking or scorch occurs at an early stage when the insulating layer 30 is formed, uniform production capacity cannot be exhibited, and long-term extrudability is lowered can cause

Since the heterophasic resin (A1) contains non-crosslinked polypropylene, it is environmentally friendly, such as recyclable, and at the same time, it is possible to improve the heat resistance of the insulating layer 30 formed by the polypropylene matrix having excellent heat resistance, and the polypropylene It is possible to improve the cold resistance, flexibility, flexibility, impact resistance, laying properties, workability, etc. of the insulating layer 30 lowered by the rigidity of the resin (B).

Specifically, the weight ratio (B:A1) of the polypropylene resin (B) and the heterophasic resin (A1) may be 3:7 to 6:4, preferably 5:5. When the weight ratio is less than 3:7, mechanical strength such as tensile strength of the formed insulating layer 30 may be insufficient, and when the weight ratio is more than 6:4, flexibility, flexibility, impact resistance, cold resistance, etc. of the insulating layer 30 are poor may be insufficient.

The non-crosslinked thermoplastic resin included in the insulating layer 30 of the power cable according to the present invention is the polypropylene resin (B), which exhibits excellent heat resistance and mechanical strength, and excellent heat resistance, flexibility, flexibility, impact resistance, cold resistance, and laying properties. , the above characteristics that are in a trade-off relationship by the combination of the heterophasic resin (A1) showing workability, and their compatibility, that is, heat resistance and mechanical strength, flexibility, flexibility, impact resistance, cold resistance, laying properties, workability, etc. It shows excellent effects that can be achieved at the same time.

Here, the non-crosslinked thermoplastic resin may have a melting point (Tm) of 150 to 160 ° C (measured by differential scanning calorimetry (DSC)) and a melting enthalpy of 30 to 80 J/g (measured by differential scanning calorimetry (DSC)). have.

When the melting enthalpy of the non-crosslinked thermoplastic resin is less than 30 J/g, it means that the size of the crystal is small and the degree of crystallinity is low, and the heat resistance and mechanical strength of the cable are deteriorated, whereas when it exceeds 80 J/g, the size of the crystal is It means that it is large and has a high degree of crystallinity, and electrical properties of the insulating layer 30 may be deteriorated.

In the present invention, the insulating layer 30 may further include a nucleating agent in addition to the non-crosslinked thermoplastic resin. The nucleating agent may be a sorbitol-based nucleating agent. That is, the nucleating agent is a sorbitol-based nucleating agent, for example, 1,3:2,4-bis(3,4-dimethyldibenzylidene) sorbitol (1,3:2,4-Bis(3,4-dimethyldibenzylidene) Sorbitol ), Bis(p-methyldibenzulidene) Sorbitol, Substituted Dibenzylidene Sorbitol, or mixtures thereof.

The nucleating agent not only improves the productivity of the cable by accelerating curing of the non-crosslinked thermoplastic resin without rapid cooling in the cable extrusion process, but also reduces the size of crystals generated during curing of the non-crosslinked thermoplastic resin, preferably 1 By limiting to 10 μm, it is possible to improve the electrical properties of the insulating layer to be manufactured, and furthermore, by forming a plurality of crystallization sites in which the crystals are formed, the degree of crystallinity is increased, thereby improving the heat resistance and mechanical strength of the insulating layer at the same time. have an effect

Since the nucleating agent has a high melting temperature, injection and extrusion processing should be performed at a high temperature of about 230°C, and it is preferable to use a combination of two or more sorbitol-based nucleating agents. When two or more different sorbitol-based nucleating agents are used in combination, the expressibility of the nucleating agent may be increased even at a low temperature.

The nucleating agent may be included in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the non-crosslinked thermoplastic resin. When the content of the nucleating agent is less than 0.1 parts by weight, the heat resistance, electrical and mechanical strength of the non-crosslinked thermoplastic resin and the insulating layer including the same due to a large crystal size, for example, a crystal size exceeding 10 μm and a non-uniform crystal distribution may be lowered, whereas when the content of the nucleating agent exceeds 0.5 parts by weight, an increase in the surface interface area between the crystal and the amorphous portion of the resin due to a too small crystal size, for example, a crystal size of less than 1 μm As a result, AC dielectric breakdown (ACBD) characteristics and impulse characteristics of the non-crosslinked thermoplastic resin and an insulating layer including the same may be deteriorated.

In the present invention, the insulating layer 30 may further include insulating oil.

The insulating oil may be mineral oil, synthetic oil, or the like. In particular, the insulating oil is an aromatic oil composed of an aromatic hydrocarbon compound such as dibenzyltoluene, alkylbenzene, and alkyldiphenylethane, a paraffinic oil composed of a paraffinic hydrocarbon compound, a naphthenic oil composed of a naphthenic hydrocarbon compound, silicone oil, etc. can be used

On the other hand, the content of the insulating oil may be 1 to 10 parts by weight, preferably 1 to 7.5 parts by weight, based on 100 parts by weight of the non-crosslinked thermoplastic resin, and when the content of the insulating oil is more than 10 parts by weight, on the conductor 10 During the extrusion process of forming the insulating layer 30 on the surface, the insulating oil may be eluted, which may cause a problem in that the processing of the cable becomes difficult.

As described above, the insulating oil has high rigidity and is made of polypropylene resin, which has somewhat low flexibility, as a base resin, and further improves the flexibility and flexibility of the insulating layer 30 to facilitate the installation of cables At the same time, it exhibits an excellent effect of maintaining or improving the excellent heat resistance and mechanical and electrical properties inherent in the polypropylene resin. In particular, when the polypropylene resin is polymerized under a metallocene catalyst, the insulating oil exhibits an excellent effect of supplementing the somewhat reduced processability due to a rather narrow molecular weight distribution.

In the present invention, the insulating layer 30 may further include other additives such as antioxidants, impact aids, heat stabilizers, nucleating agents, and acid scavengers. The other additives may be added in an amount of 0.001 to 10% by weight based on the total weight of the insulating layer 30 depending on the type thereof.

The outer semiconducting layer 40 of the power cable according to the present invention may be formed from a semiconducting composition comprising a non-crosslinked thermoplastic resin comprising a blending resin of the heterophasic resin (A1) and an ethylene copolymer as a base resin, The ethylene copolymer may include, for example, ethylene butyl acrylate (EBA), ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene methyl acrylate (EMA), or the like, or combinations thereof.

Here, based on 100 parts by weight of the base resin, the content of the heterophasic resin (A1) may be 10 to 40 parts by weight and the content of the ethylene copolymer may be 60 to 90 parts by weight, and 30 to 70 parts by weight of carbon black, It may further include 0.2 to 3 parts by weight of an antioxidant.

Here, when the content of the heterophasic resin (A1) is less than 10 parts by weight and the content of the ethylene copolymer is more than 90 parts by weight, it may be difficult for the power cable to secure heat resistance in a high-temperature environment, and the insulating layer 30 ), while the adhesiveness of the outer semiconducting layer 40 to the may be greatly reduced, when the content of the heterophasic resin (A1) is more than 40 parts by weight and the content of the ethylene copolymer is less than 60 parts by weight, the insulation The ease of peeling of the outer semiconducting layer 40 with respect to the layer 30 is greatly reduced, so that it is difficult to partially peel the outer semiconducting layer 40 from the insulating layer 30 in the cable connection process during cable laying or for a long time. It may cause problems with the required time.

In addition, when the content of the carbon black is less than 30 parts by weight, the semiconductive properties of the outer semiconducting layer 40 may not be realized, whereas when the content of the carbon black is more than 70 parts by weight, the composition for forming the outer semiconducting layer 40 As the viscosity increases, the screw load increases during extrusion, and workability may be greatly reduced.

In addition, when the content of the antioxidant is less than 0.2 parts by weight, it may be difficult for the power cable to secure long-term heat resistance in a high-temperature environment, whereas when it is more than 3 parts by weight, the antioxidant turns white to the surface of the outer semiconducting layer 40 . A blooming phenomenon that elutes may occur, thereby deteriorating semiconducting properties.

[Example]

1. Preparation example

A semiconducting layer specimen having the components and contents shown in Table 1 below was prepared. The unit of the content shown in Table 1 below is parts by weight.

resin 1 resin 2 carbon black antioxidant Example 1 50 50 60 One Example 2 80 20 60 One Comparative Example 1 40 60 60 One Comparative Example 2 90 10 60 One Comparative Example 3 50 50 25 One Comparative Example 4 50 50 75 One Comparative Example 5 50 50 60 0.1

-Resin 1: Heterophase resin in which propylene-ethylene rubber (PER) is dispersed in a propylene homopolymer matrix (melting point: 155 to 170 ° C, melt flow rate (2.16 kg, 230 ° C): 0.1 to 1.0 g/10 min)

-Resin 2: Heterophase resin in which propylene-ethylene rubber (PER) is dispersed in a propylene random copolymer matrix (melting point: 140-150℃, melt flow rate (2.16kg, 230℃): 6-8 g/10 min)

2. Physical property evaluation

1) Volume resistance evaluation

According to each of Examples and Comparative Examples, a semiconducting layer specimen having a thickness of 1 mm, a width of 30 mm, and a length of 64 mm, and coated with silver paste so that the distance between the electrodes at both ends in the longitudinal direction is 50 mm, is dried at room temperature for at least 1 hour and then applied to each electrode. With the external connection terminal connected, put it in an oven with a relative humidity of 50±5% and a temperature of 90℃, and leave it for 24 hours, then measure the resistance. The measured volume resistance should be less than 50Ωm. The measurement results are shown in Table 2 below.

2) Heat resistance evaluation

According to each of Examples and Comparative Examples, the semiconducting layer specimen having the shape shown in the figure below was placed in an oven at a temperature of 135 ° C and left for 7 days. do. The measurement results are shown in Table 2 below.

3) Extrusion evaluation

When extruding each of the semiconducting layers of Examples and Comparative Examples for the manufacture of cable specimens, it was evaluated whether the screen mesh was broken due to the extrusion load in the extruder, and the results are shown in Table 2 below.

volume resistance
(Ωm) heat resistance
(%) extrudability Example 1 34 84 normal Example 2 22 87 normal Comparative Example 1 17 65 normal Comparative Example 2 25 85 Destruction Comparative Example 3 489 87 normal Comparative Example 4 11 86 Destruction Comparative Example 5 22 71 normal

As shown in Table 2, the semiconducting layers of Examples 1 and 2 according to the present invention were excellent in volume resistance, heat resistance, and extrudability, whereas the semiconducting layer of Comparative Example 1 had a low melting point resin 2 content exceeding the standard. On the other hand, in the semiconducting layer of Comparative Example 2, the content of Resin 2 with a low melt index was lower than the standard, and the extrudability was lowered. On the other hand, in the semiconducting layer of Comparative Example 4, the content of carbon black exceeded the standard, and the extrudability was greatly reduced, and the semiconducting layer of Comparative Example 5 was lowered in heat resistance because the content of the antioxidant was less than the standard.

Although the present specification has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims described below. will be able to carry out Therefore, if the modified implementation basically includes the elements of the claims of the present invention, all should be considered to be included in the technical scope of the present invention.

10: conductor 20: inner semiconducting layer
30: insulating layer 40: outer semiconducting layer
50: sheath layer

Claims (10)

A non-crosslinked thermoplastic resin including a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix as a base resin and a conductive additive,
The heterophasic resin has a melting point (Tm) of 155 to 170 ° C. and a melt flow rate (MFR) measured according to ISO 1133 at a load of 2.16 kg and 230 ° C. of a heterophasic resin of 0.1 to 1.0 g / 10 minutes ( A1) and a heterophasic resin (A2) having a melting point of 140 to 150° C. and a melting flow rate (MFR) measured according to ISO 1133 at a load of 2.16 kg and 230° C. of 3 to 10 g/10 min. ,
The content of the conductive additive is 30 to 70 parts by weight based on 100 parts by weight of the base resin,
The weight ratio of the heterophasic resin (A1) to the heterophasic resin (A2) is 50:50 to 80:20, the semiconducting composition. According to claim 1,
The semiconducting composition, characterized in that the heterophasic resin (A1) comprises a propylene homopolymer as a polypropylene matrix and the heterophasic resin (A2) comprises a random propylene copolymer as the polypropylene matrix. delete 3. The method of claim 1 or 2,
The propylene copolymer dispersed in the polypropylene matrix is characterized in that it is amorphous with a residual crystallinity having an enthalpy of melting less than 10 J/g. 5. The method of claim 4,
The propylene copolymer dispersed in the polypropylene matrix is at least one comonomer selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. A semiconducting composition comprising a. 6. The method of claim 5,
A semiconducting composition, characterized in that the propylene copolymer dispersed in the polypropylene matrix comprises from 20 to 50% by weight of ethylene monomer, based on its total weight. 3. The method of claim 1 or 2,
The content of the propylene copolymer dispersed in the polypropylene matrix is 60 to 90% by weight based on the total weight of the heterophasic resin, the semiconducting composition. delete 3. The method of claim 1 or 2,
Based on 100 parts by weight of the base resin, the semiconducting composition, characterized in that it further comprises 0.2 to 3.0 parts by weight of an antioxidant. conductor;
an inner semiconducting layer surrounding the conductor; and
A power cable comprising an insulating layer surrounding the inner semiconducting layer,
Power cable, characterized in that the inner semiconducting layer is formed from the semiconducting composition of claim 1 or 2 .

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