KR20200004270A - Power cable - Google Patents

Abstract

The present invention relates to a power cable. Particularly, the present invention relates to a power cable which has an insulation layer which is formed of an insulation material which is environmentally friendly, has excellent heat resistance and mechanical strength, and has excellent cold resistance, flexibility, flexuosity, impact resistance, laying properties, workability, and the like which are in a trade-off with physical properties.

Description

Power cable

The present invention relates to a power cable. Specifically, the present invention is made of an insulating material that is environmentally friendly, has excellent heat resistance and mechanical strength, and has excellent cold resistance, flexibility, flexibility, impact resistance, installation properties, workability, and the like in trade-off with these physical properties. A power cable having an insulating layer.

The general power cable includes a conductor and an insulating layer surrounding the conductor, and may further include an inner semiconducting layer, an outer semiconducting layer surrounding the insulating layer, and a sheath layer surrounding the outer semiconducting layer between the conductor and the insulating layer. .

In recent years, the development of high capacity cables is required in accordance with the increasing power demand, which requires an insulating material for manufacturing an insulating layer having excellent mechanical and electrical properties.

Conventionally, crosslinked polyolefin-based polymers such as polyethylene, ethylene / propylene elastic copolymer (EPR) and ethylene / propylene / diene copolymer (EPDM) have been generally used as the base resin constituting the insulating material. This is because such conventional crosslinked resins maintain excellent flexibility and satisfactory electrical and mechanical strength even at high temperatures.

However, since the crosslinked polyethylene (XLPE) or the like, which has been used as the base resin constituting the insulating material, has a crosslinked form, the insulating layer is formed when the life span of a cable or the like including an insulating layer made of a resin such as the crosslinked polyethylene expires. It is not environmentally friendly because it is impossible to recycle the resin and can only be disposed of by incineration.

In addition, when polyvinyl chloride (PVC) is used as the material of the sheath layer, it is difficult to separate it from the crosslinked polyethylene (XLPE) constituting the insulating material, and thus it is not environmentally friendly, such as toxic chlorinated substances are produced upon incineration. 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 insulating layer at the end of the life of the cable, including the insulating layer manufactured therefrom, etc. Compared to the polyethylene (XLPE) in the form of heat resistance is inferior due to the low operating temperature has a very limited disadvantage.

On the other hand, it is possible to consider using an environmentally friendly polypropylene resin as a base resin without excellent crosslinking of the melting point of the polymer itself to 160 ℃ or more. However, the polypropylene resin has poor workability due to insufficient rigidity due to high rigidity, flexibility, flexibility, etc., resulting in poor workability when laying a cable including an insulation layer manufactured therefrom and its use. There is a problem.

Therefore, it is not only environmentally friendly and inexpensive to manufacture, but also satisfies heat resistance, mechanical strength and cold resistance, flexibility, bending resistance, impact resistance, workability, workability, and the like at the same time. There is an urgent need for cables.

An object of the present invention is to provide an environmentally friendly power cable.

In addition, an object of the present invention is to provide a power cable capable of simultaneously satisfying heat resistance, mechanical strength, and cold resistance, flexibility, bending resistance, impact resistance, installation properties, workability, and the like that are in a trade-off with them. do.

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

A power cable comprising a conductor, an inner semiconducting layer surrounding the conductor, and an insulating layer surrounding the inner semiconducting layer, wherein the insulating layer is formed from an insulating composition comprising polypropylene resin or heterophasic polypropylene resin as a base resin. , The brittle temperature (T _b ) defined by Equation 1 below is -35 ℃ or less,

[Equation 1]

T _b = T _h + ΔT [(S / 100)-(1/2)]

In Equation 1,

T _h is 5 ° C 23%, 50% relative to five specimens taken from the cable insulation layer comprising the base resin, 36.0 mm to 40.0 mm long, 5.6 mm to 6.4 mm wide and 1.8 mm to 2.2 mm thick according to ASTM D746. It is left at humidity for 40 hours or more, and the temperature is increased or decreased at -40 ° C to 5 ° C interval for 2.5 to 3.5 minutes by temperature, and then the speed of 1800 to 2200 mm / s using a striking edge. The highest temperature (° C.) at which all five specimens are destroyed or a visually visible crack occurs on the surfaces of all five specimens as a result of hitting at 90 ° to the surface of the specimen.

ΔT is a constant temperature interval that changes during each temperature experiment in accordance with ASTM D746,

S was tested as above while raising or lowering the temperature at intervals of ΔT from -40 ° C. according to ASTM D746. As a result, all five specimens were not destroyed or there were no visible cracks on the surfaces of all five specimens. It is the sum of the percentage of specimens that were broken or visually cracked on the surface among the five specimens in each temperature experiment from the lowest temperature (° C.) not occurring to T _h .

Insulation composition, wherein the xylene cost diagram as defined by Equation 2 below is 10% or less.

[Equation 2]

Xylene cost plot = (mass of insulated specimen after elution in xylene solvent / mass of insulated specimen before elution) × 100

In Equation 2,

After eluting in the xylene solvent, the mass of the insulating specimen was soaked in 0.3 g of the insulating specimen in a xylene solvent, and boiled at 150 ° C. or higher for 6 hours, cooled to room temperature, and then taken out of the insulating specimen and then again in an oven at 150 ° C. for 4 hours. Is the mass of the insulating specimen measured after drying and cooling to room temperature.

Here, the brittle temperature (T _b ) is characterized in that -80 to -35 ℃, provides a power cable.

In addition, the insulation specimen formed from the insulation composition provides a power cable, characterized in that the flexural modulus at room temperature measured according to the standard ASTM 3.D790 is 50 to 1,200 MPa.

Here, the thickness of the insulating layer in the cable is characterized in that the power cable, characterized in that 5.5 to 84.0 times of t _min according to the following equation (3).

[Equation 3]

t _min = 2.5Uo / breakdown electric field for insulated specimens

In Equation 3,

Uo is the reference voltage for voltage tests according to standard IEC 60840,

The dielectric breakdown electric field for the insulated specimen is an electric field (kV) according to the applied voltage when the electrode is contacted at each end of each of the plurality of insulated specimens, and a voltage is applied thereto and the probability of the breakdown of the plurality of insulated specimens is 63.2%. / mm).

On the other hand, the heterophasic polypropylene resin provides a power cable, characterized in that the rubbery propylene copolymer is dispersed in the crystalline polypropylene matrix.

Here, the crystalline polypropylene matrix provides a power cable, characterized in that it comprises a propylene homopolymer, a propylene copolymer or both.

In addition, the rubbery propylene copolymer is a group consisting of ethylene and C _4-12 alpha-olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene It provides a power cable, characterized in that it comprises at least one comonomer selected from.

In addition, the heterophasic polypropylene resin has a melting point (Tm) of 140 to 170 ° C measured by a differential scanning calorimeter (DSC) and a melt enthalpy of 20 to 85 J / g measured by a differential scanning calorimeter (DSC). Provided is a power cable.

Furthermore, when the base resin preheated at 180 ° C. for 10 minutes at 20 MPa for 10 minutes was pressed for 10 minutes, and then cooled, the specimen having a thickness of 1 mm was stretched at a rate of 200 mm / min. It provides a power cable, characterized in that the tensile strength of 0.7 to 3.0 kgf / mm ² and Shore D hardness of 25 to 70.

On the other hand, the insulating layer, based on 100 parts by weight of the base resin, characterized in that it further comprises 0.1 to 0.5 parts by weight of a nucleating agent (nucleating agent), provides a power cable.

In addition, the insulating layer, based on 100 parts by weight of the base resin, characterized in that it further comprises 1 to 10 parts by weight of insulating oil, provides a power cable.

And, the insulating layer, based on the total weight of the insulating layer, at least one other additive selected from the group consisting of antioxidants, impact aids, heat stabilizers, nucleating agents and acid scavengers 0.001 to It provides a power cable, characterized in that it further comprises 10% by weight.

On the other hand, the base resin, based on 100 parts by weight of the base resin, 30 to 70 parts by weight of the polypropylene resin (A) and 70 to 30 parts by weight of the heterophasic polypropylene resin (B) in which the propylene copolymer is dispersed in the polypropylene matrix. It provides a power cable, characterized in that it comprises a portion.

Here, the polypropylene resin (A) provides a power cable, characterized in that to satisfy all the conditions of a) to i) below.

a) density from 0.87 to 0.92 g / cm 3 (measured according to ISO 11883),

b) melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 ° C. according to ISO 1133),

c) tensile modulus of 930 to 980 MPa (measured at a tensile speed of 1 mm / min),

d) tensile stress at yield is 22 to 27 MPa (measured at a tensile speed of 50 mm / min),

e) tensile strain at yield is 13 to 15% (measured at a tensile speed of 50 mm / min),

f) Charpy impact strengths at 0 ° C. and 23 ° C. are 1.8 to 2.1 kJ / m 2 and 5.5 to 6.5 kJ / m 2, respectively;

g) heat deflection temperature of 6.8-7.2 ° C. (measured at 0.45 MPa),

h) Vicat softening point from 131 to 136 ° C (measured at 50 ° C / h and 10N according to specification A50), and

i) Shore D hardness of 63 to 70 (measured according to ISO 868)

In addition, the heterophasic polypropylene resin (B) provides a power cable, characterized in that all of the following conditions a) to j) are satisfied.

a) density between 0.86 and 0.90 g / cm 3 (measured according to ISO 11883),

b) melt flow rate (MFR) of 0.1 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 ° C. according to ISO 1133),

c) tensile stress at break is 10 MPa or more (measured at a tensile speed of 50 mm / min),

d) the tensile strain at break is 450% or more (measured at a tensile speed of 50 mm / min),

e) flexural strength is 95 to 105 MPa

f) Notched izod impact strength at −40 ° C., respectively, from 6.8 to 7.2 kJ / m 2,

g) heat deflection temperature of 38-42 ° C. (measured at 0.45 MPa),

h) Vicat softening point from 55 to 59 ° C. (measured at 50 ° C./h and 10 N according to standard A50),

i) Shore D hardness is 25 to 35 (measured according to ISO 868), and

j) melting point of from 155 to 170 캜

The polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylene monomer content of 1 to 10% by weight based on the total weight of the monomers, and is contained in the heterophasic polypropylene resin (B). The polypropylene matrix provides a power cable, characterized in that the propylene homopolymer.

Furthermore, the propylene copolymer contained in the heterophasic polypropylene resin (B) has a ethylene monomer content of 20 to 50% by weight based on the total weight of the monomers, and includes propylene-ethylene rubber (PER) particles. It provides a power cable, characterized in that.

Here, the content of the propylene copolymer, 60 to 80% by weight based on the total weight of the heterophasic polypropylene resin (B), provides a power cable.

In addition, the heterophasic polypropylene resin (B) provides a power cable, characterized in that the melt enthalpy measured by a differential scanning calorimeter (DSC) is 15 to 40 J / g.

The power cable according to the present invention adopts non-crosslinked propylene polymer as the insulating layer material, which is environmentally friendly, and has the effect of heat resistance and mechanical strength.

In addition, the power cable according to the present invention, by precisely controlling the insulating layer material and its brittle temperature, despite the application of an insulating layer made of a high rigid propylene polymer, cold resistance, flexibility, flexibility, impact resistance, installation, workability, etc. Excellent effect can be satisfied at the same time.

1 schematically illustrates a cross-sectional structure of one embodiment of a power cable according to the invention.
FIG. 2 schematically illustrates the 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 invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the present invention to those skilled in the art. Like numbers refer to like elements throughout.

1 and 2 show cross-sectional and stepped cross-sectional perspective views, respectively, of one embodiment of a power cable according to the present invention.

As shown in Figures 1 and 2, the power cable according to the present invention wraps the conductor 10 made of a conductive material such as copper, aluminum, and the insulating layer 30 made of an insulating polymer, the conductor 10 and the Evenly in the inner semiconducting layer 20, the shielding role of the cable and the insulating layer 30, which removes the air layer between the conductor 10 and the insulating layer 30, and alleviates local electric field concentration. It may include an outer semiconducting layer 40, a sheath layer 50 for cable protection, and the like, which serves to take one electric field.

Standards of the conductor 10, the insulating layer 30, the semiconducting layers 20 and 40, the sheath layer 50, and the like may vary according to the use of the cable, the transmission voltage, and the like. The materials constituting the entire layers 20 and 40 and the sheath layer 50 may be the same or different.

The conductor 10 may be made of a stranded wire combined with a plurality of element wires in terms of improving the cold resistance, flexibility, bendability, installation properties, workability, etc. of the power cable, in particular, a plurality of element wires are the 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 may be formed from an insulating composition comprising a non-crosslinked thermoplastic resin comprising homo- or polyphasic polypropylene resins or both.

Here, the heterophasic polypropylene resin may include a heterophasic polypropylene resin including two or more phase resins, specifically, a crystalline resin and a rubbery resin, and for example, a crystalline polypropylene resin and a rubbery propylene aerial The blended resin or the crystalline polypropylene resin and the rubbery propylene copolymer may be polymerized together to include a heterophasic polypropylene resin in which the rubbery propylene copolymer is dispersed in the crystalline polypropylene matrix resin.

Here, the homophasic polypropylene resin or the crystalline polypropylene (matrix) resin may comprise a propylene homopolymer and / or a propylene copolymer, preferably may comprise a propylene homopolymer, more preferably propylene It may comprise only homopolymers. By propylene homopolymer is meant polypropylene formed by the polymerization of at least 99% by weight, preferably at least 99.5% by weight, of propylene, based on the total weight of the monomers.

The homophasic polypropylene resin or the crystalline polypropylene (matrix) resin can be polymerized under conventional stereo-specific Ziegler-Natta catalysts, metallocene catalysts, constrained geometry catalysts, other organometallic or coordination catalysts, preferably May be polymerized under a Ziegler-Natta catalyst or a metallocene catalyst. Here, the metallocene is a generic term for bis (cyclopentadienyl) metal, which is a new organometallic compound in which a cyclopentadiene and a transition metal are bonded in a sandwich structure, and the general formula of the simplest structure is M (C ₅ H ₅ ) ₂ (where , M is Ti, V, Cr, Fe, Co, Ni, Ru, Zr, Hf and the like). Since the polypropylene polymerized under the metallocene catalyst has a low catalyst residual amount of about 200 to 700 ppm, it is possible to suppress or minimize the deterioration of the electrical properties of the insulating composition including the polypropylene by the catalyst residual amount.

On the other hand, the rubbery propylene copolymer dispersed in the crystalline polypropylene matrix resin or blended with the crystalline polypropylene resin is substantially amorphous. The rubbery propylene copolymer is selected from the group consisting of ethylene and C _4-12 alpha-olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene It may include one or more comonomers.

The rubbery propylene copolymer may be monomeric propylene-ethylene rubber (PER) or propylene-ethylene diene rubber (EPDM).

In the present invention, the particle size of the rubbery propylene copolymer may be micro or nano size. This particle size of the rubbery propylene copolymer ensures uniform dispersion of the rubbery propylene copolymer in the crystalline polypropylene matrix and can improve the impact strength of the insulating layer comprising the same. In addition, the particle size improves the likelihood of stopping already formed cracks or cracks while reducing the risk of cracks initiated by the particles.

Here, the heterophasic polypropylene resin has a melting point (Tm) of 140 to 170 ° C (measured by differential scanning calorimetry (DSC)) and a melt enthalpy of 20 to 85 J / g (measured by differential scanning calorimeter (DSC)). Can be.

If the melt enthalpy of the heterophasic polypropylene resin is less than 20 J / g, it means that the crystal size is small and the crystallinity is low, and that the heat resistance and mechanical strength of the cable are lowered, whereas the crystal size is larger than 85 J / g. It means that the larger the crystallinity is high and the electrical properties of the insulating layer 30 can be reduced.

Although the heterophasic polypropylene resin has a non-crosslinked form, its own melting point has high heat resistance, and thus, it is possible to provide a power cable with improved continuous use temperature. Effect. On the other hand, conventional cross-linked resins are not easy to recycle because they are difficult to recycle, and when cross-linking or scorch is generated early when forming the insulating layer 30, long-term extrudability is degraded, such as not being able to exhibit uniform production capacity. May cause.

In the present invention, the insulating composition forming the insulating layer 30 has a brittleness temperature (T _b ) defined by Equation 1 below the insulating specimen formed therefrom, for example, -35 ° C. or less, for example, By controlling at 80 to -35 ° C, the heat resistance and mechanical strength may be excellent, and at the same time, the cold resistance, flexibility, flexibility, impact resistance, installation properties, workability, etc., which are in a trade-off relationship with these physical properties may be excellent.

[Equation 1]

T _b = T _h + ΔT [(S / 100)-(1/2)]

In Equation 1,

T _h is 5 ° C 23%, 50% relative to five specimens taken from the cable insulation layer comprising the base resin, 36.0 mm to 40.0 mm long, 5.6 mm to 6.4 mm wide and 1.8 mm to 2.2 mm thick according to ASTM D746. It is left at humidity for 40 hours or more, and the temperature is increased or decreased at -40 ° C to 5 ° C interval for 2.5 to 3.5 minutes by temperature, and then the speed of 1800 to 2200 mm / s using a striking edge. The highest temperature (° C.) at which all five specimens are destroyed or a visually visible crack occurs on the surfaces of all five specimens as a result of hitting at 90 ° to the surface of the specimen.

ΔT is a constant temperature interval that changes during each temperature experiment in accordance with ASTM D746,

S was tested according to ASTM D746 by raising or lowering the temperature from -40 ° C to ΔT, e.g., at 5 ° C intervals, as a result of which all five specimens were not destroyed or the surfaces of all five specimens were not destroyed. It is the sum of the percentage of specimens that are broken out of five specimens or have visually observed cracks on the surface in each temperature experiment from the lowest temperature (° C.) to the T _h above which no visually visible crack occurs.

Here, the fracture of the specimen means that the specimen is separated into two or more pieces, and the crack means that the specimen is not destroyed but cracks or cracks have occurred on the surface.

In fact, examples of measuring and calculating the brittle temperature are as follows.

According to ASTM D746, three of five specimens were broken and one crack occurred as a result of a cold test at -40 ° C. The same test was carried out by raising the temperature by 5 ° C. 0 and cracks, 0 fractures and 0 cracks at -30 ° C, so that the lowest temperature at which all 5 specimens are not destroyed or there are no visible cracks on the surface of all 5 specimens is -35 ° C to be.

In addition, cold resistance test according to ASTM D746 was carried out while lowering the temperature at -40 ° C by 5 ° C. As a result, 4 fractures and 1 crack appeared at -45 ° C, so that all 5 specimens were damaged. Or the highest temperature (T _h ) at which visually observable cracks occur on the surface of all five specimens is -45 ° C.

Based on this, the number of fractures and cracks by temperature and the percentage damage / total number of specimens are as shown in Table 1 below, and the sum of the percentages (S) is 220.

Temperature (℃) Break / Crack () Damage () Damage / total percentage -30 0/0 0 (0/5) * 100 = 0 -35 2/0 2 (2/5) * 100 = 40 -40 3/1 4 (4/5) * 100 = 80 -45 4/1 5 (5/5) * 100 = 100 Sum of percentages (S) = 0 + 40 + 80 + 100 = 220

Therefore, the brittle temperature defined by Equation 1 (Tb = Th + ΔT * [(S / 100) − (1/2)]) is -45 + 5 * [220 / 100-1 / 2] =-36.5 ° C. Here, when the brittle temperature (T _b ) is less than -80 ℃ excellent cold resistance but inadequate mechanical properties it is difficult to maintain the circular shape of the cable structure due to the crushing phenomenon in the manufacture of the cable or the crushing phenomenon by the cable lamination during storage. As a result, the electrical properties of the cable may be greatly degraded, whereas the cold resistance may be extremely degraded when it is above -35 ° C.

In the present invention, the insulating composition forming the insulating layer 30 may be 10% or less of xylene insolubility of the insulating specimen formed therefrom, and a flexural modulus at room temperature of 50 to 1,200 MPa (standard Measured according to ASTM 3.D790), preferably from 200 to 1,000 MPa.

Here, the xylene insolubility may be calculated by Equation 2 below.

[Equation 2]

Xylene cost plot = (mass of insulated specimen after elution in xylene solvent / mass of insulated specimen before elution) × 100

In Equation 2,

After eluting in the xylene solvent, the mass of the insulating specimen was soaked in 0.3 g of the insulating specimen in a xylene solvent, and boiled at 150 ° C. or higher for 6 hours, cooled to room temperature, and then taken out of the insulating specimen and then again in an oven at 150 ° C. for 4 hours. Is the mass of the insulating specimen measured after drying and cooling to room temperature.

That is, the mass of the insulating specimen after elution in xylene solvent corresponds to the total mass of the crystalline polypropylene matrix and other additives remaining after removal of the rubbery polypropylene copolymer eluted from the insulating specimen into the xylene solvent. When the xylene cost is more than 10%, that is, when the content of the crystal phase portion in the insulating specimen is excessive, the flexibility, cold resistance, laying property, workability, etc. of the insulating layer 30 may be greatly reduced.

On the other hand, the flexural modulus measured in accordance with the standard ASTM D790, the fracture occurs on the surface of the insulating specimen while placing a rectangular parallelepiped insulated specimen on two supports and applying a load to the intermediate portion of the insulated specimen between the two supports or 5.0% It can be measured by measuring the applied load at the point of time when the deformation of. In addition, when the flexural modulus at room temperature of the insulating specimen is less than 50 MPa, heat resistance, mechanical properties, etc. of the insulating layer 30 may be insufficient, whereas when it exceeds 1,200 MPa, the flexibility and cold resistance of the insulating layer 30 may be insufficient. , Installability, workability, etc. can be greatly reduced.

In the present invention, the thickness of the insulating layer 30 is a × t _min on the premise that the xylene cost diagram and the flexural modulus of the insulating composition forming the insulating layer 30 satisfy the ranges described above. Can be precisely designed, wherein a is 5.5 to 84.0, and t _min can be defined by Equation 3 below.

[Equation 3]

t _min = 2.5Uo / breakdown electric field for insulated specimens

In Equation 3,

Uo is the reference voltage of the voltage test according to the standard IEC 60840 as shown in Table 2 below,

The insulation breakdown electric field for the insulation specimen is obtained by contacting the electrodes at each end of each of the 20 insulation specimens taken from the insulation layer of the cable, applying a voltage, and having a 63.2% insulation failure probability for the insulation specimen. It means the electric field (kV / mm) according to the applied voltage in the case.

In the present invention, when the thickness of the insulating layer 30 of the cable exceeds axt _min as described above, the thickness of the cable insulating layer is excessive, which may unnecessarily reduce the cable laying properties, workability, etc. , less than a × t _min may cause shortening of the life due to breakdown due to insufficient insulation strength of the cable insulation layer.

In the present invention, the insulating composition for forming the insulating layer 30 may further include a nucleating agent (nucleating agent). 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, and mixtures thereof.

The nucleating agent not only improves the productivity of the cable by promoting the curing of the non-crosslinked thermoplastic resin even if it is not rapidly quenched in the extrusion process of the cable, but also reduces the size of crystals formed 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 further, to increase the degree of crystallinity by forming a plurality of crystallization sites from which the crystals are produced, thereby improving heat resistance, mechanical strength, etc. of the insulating layer simultaneously. It is effective.

Since the nucleating agent has a high melting temperature, injection and extrusion 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 expression of the nucleating agent may be increased even at low temperatures.

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 part by weight, the heat resistance, electrical and mechanical strength of the non-crosslinked thermoplastic resin and the insulating layer including the same due to large crystal size, for example, crystal size exceeding 10 μm and uneven crystal distribution While 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 the crystal size too small, for example, the crystal size of less than 1 μm As a result, AC dielectric breakdown (ACBD) characteristics, impulse characteristics, and the like of the non-crosslinked thermoplastic resin and the insulating layer including the same may be deteriorated.

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

The insulating oil may be mineral oil, synthetic oil and the like. In particular, the insulating oil is an aromatic oil consisting of aromatic hydrocarbon compounds such as dibenzyltoluene, alkylbenzene, alkyldiphenylethane, paraffinic oil consisting of paraffinic hydrocarbon compounds, naphthenic oil consisting of naphthenic hydrocarbon compounds, silicone oil, and the like. Can be used.

Meanwhile, 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 the content of the insulating oil is greater than 10 parts by weight. In the extrusion process of forming the insulating layer 30 to the phenomenon that the insulating oil is eluted may cause a problem that the processing of the cable becomes difficult.

As described above, the insulating oil has a large rigidity, and thus, further improves flexibility, flexibility, and the like of the insulating layer 30 based on a polypropylene resin having a relatively low flexibility, and thus facilitates cable laying. At the same time, it exhibits an excellent effect of maintaining or improving the excellent heat resistance, mechanical and electrical properties of the polypropylene resin inherently. In particular, the insulating oil exhibits an excellent effect of supplementing processability, which is somewhat degraded by a rather narrow molecular weight distribution when the polypropylene resin is polymerized under a metallocene catalyst.

Furthermore, the insulating composition forming the insulating layer 30 may include a non-crosslinked thermoplastic resin including (A) a polypropylene resin and (B) a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix. Can be.

The polypropylene resin (A) may comprise a propylene homopolymer and / or a propylene copolymer, preferably a propylene copolymer. By propylene homopolymer is meant polypropylene formed by the polymerization of at least 99% by weight, preferably at least 99.5% by weight, of propylene, 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 preferably copolymers with ethylene. This is because copolymerization of propylene and ethylene shows hard and flexible properties.

The propylene copolymer may comprise a random propylene copolymer and / or a block propylene copolymer, preferably may comprise a random propylene copolymer, more preferably only a random propylene copolymer. The random propylene copolymer refers to a propylene copolymer formed by alternately arranging a propylene monomer and another olefin monomer. 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, based on the total monomer weight.

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). Under tensile load), tensile modulus of 930 to 980 MPa (measured at a tensile speed of 1 mm / min), tensile stress of 22 to 27 MPa (measured at a tensile rate of 50 mm / min), tensile strain of 13 to 15% ( 50 mm / min tensile velocity), Charpy impact strength at 0 ° C. and 23 ° C., respectively, 1.8 to 2.1 kJ / m 2 and 5.5 to 6.5 kJ / m 2, and thermal deformation temperature of 6.8 to 7.2 ° C. (measured at 0.45 MPa) , Vicat softening point can be 131 to 136 ℃ (measured at 50 ℃ / h and 10N according to the standard A50), Shore D hardness is 63 to 70 (measured according to ISO 868).

The random propylene copolymer may improve mechanical strength, such as tensile strength, of the insulating layer 30 to be formed, is suitable for transparent molded articles with high transparency, and has a relatively high crystallization temperature (Tc) for the insulation for cable manufacture. By shortening the time required for cooling after extrusion of the layer 30, the production yield of the cable can be improved, and the shrinkage rate and the heat deformation of the insulating layer 30 can be minimized. There is an advantage to reduce.

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

Although the polypropylene resin (A) has a non-crosslinked form, its own melting point is high, thereby exhibiting sufficient heat resistance, thereby providing a power cable with improved continuous use temperature. Excellent effect. On the other hand, conventional cross-linked resins are not easy to recycle because they are difficult to recycle, and when cross-linking or scorch is generated early when forming the insulating layer 30, long-term extrudability is degraded, such as not being able to exhibit uniform production capacity. May cause.

In the heterophasic polypropylene resin (B) in which a propylene copolymer is dispersed in the polypropylene matrix, the polypropylene matrix may be the same as or different from the polypropylene resin (A), and preferably includes a propylene homopolymer. And more preferably only propylene homopolymers.

In the heterophasic polypropylene resin (B), the propylene copolymer (hereinafter referred to as 'dispersed propylene copolymer') dispersed in the polypropylene matrix is substantially amorphous. Herein, the propylene copolymer is amorphous means that the melt enthalpy 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, etc. It may include one or more comonomers.

The dispersed propylene copolymer may be 60 to 90% by weight, preferably 65 to 80% by weight based on the total weight of the heterophasic polypropylene resin (B). Here, the flexibility, flexibility, impact resistance, cold resistance, etc. of the insulating layer 30 formed when the content of the dispersed propylene copolymer is less than 60% by weight may be insufficient, whereas when it exceeds 90% by weight of the insulating layer ( 30) may have insufficient heat resistance, mechanical strength, and the like.

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, based on the total weight of the monomers. Can be. When the content of the ethylene monomer is less than 20% by weight, the flexibility, bending resistance, and impact resistance of the insulating layer 30 formed may be excellent, but cold resistance may be insufficient, whereas when the content of the ethylene monomer exceeds 50% by weight, the cold resistance of the insulating layer 30 However, the heat resistance and mechanical strength are excellent, but flexibility may be reduced.

In the present invention, the particle size of the dispersed propylene copolymer may be 1 μm or less, preferably 0.9 μm or less, more preferably 0.8 μm or less. This particle size of the dispersed propylene copolymer ensures uniform dispersion of the dispersed propylene copolymer in the polypropylene matrix and can improve the impact strength of the insulating layer comprising the same. In addition, the particle size improves the likelihood of stopping already formed cracks or cracks while reducing the risk of cracks initiated by the particles.

The heterophasic polypropylene resin (B) preferably has a melt flow rate (MFR) of 0.1 to 1.0 g / 10 min, preferably measured according to ISO 1133 at a load of 2.16 kg and 230 ° C. 0.8 g / 10min, tensile stress at break of 10 MPa or more, tensile strain at break of 450% or more, flexural strength of 95 to 105 MPa, notched izod impact strength measured at -40 ° C, 6.8 to 7.2 kJ / m 2, heat distortion temperature of 38 to 42 ° C. (measured at 0.45 MPa), Vicat softening point of 55 to 59 ° C. (measured at 50 ° C./h and 10 N according to A50), Shore D hardness of 25 to 35 (ISO 868 Measured according to), the melting point (Tm) may be between 155 and 170 ° C. (measured by differential scanning calorimetry (DSC)), and the melt enthalpy may be between 15 and 40 J / g (measured by DSC).

In addition, the density of the heterophasic polypropylene resin (B) may be 0.86 to 0.90 g / cm 3, preferably 0.88 g / cm 3 when measured according to ISO 11883, wherein the density is a property of the insulating layer 30, For example, impact strength and shrinkage properties are affected.

Since the heterophasic polypropylene resin (B) includes non-crosslinked polypropylene, it is possible to improve the heat resistance of the insulating layer 30 formed by a polypropylene matrix which is environmentally friendly and excellent in heat resistance, such as being recycled. The cold resistance, the flexibility, the bendability, the impact resistance, the installability, the workability, and the like of the insulating layer 30 lowered by the rigidity of the polypropylene resin (A) can be improved.

In particular, the weight ratio (A: B) of the polypropylene resin (A) and the heterophasic polypropylene resin (B) may be 3: 7 to 7: 3, preferably 5: 5. When the weight ratio is less than 3: 7, mechanical strength such as tensile strength of the insulating layer 30 to be formed may be insufficient. If the weight ratio is greater than 7: 3, the flexibility, flexibility, impact resistance, and cold resistance of the insulating layer 30 may be insufficient. May be insufficient.

The non-crosslinked thermoplastic resin contained in the insulating layer 30 of the power cable according to the present invention is the polypropylene resin (A) exhibiting excellent heat resistance, mechanical strength, and the like, and excellent heat resistance, flexibility, bending resistance, impact resistance, cold resistance, and installability. , The combinations of the heterophasic polypropylene resins (B) exhibiting workability and the like and their compatibility, that is, heat resistance and mechanical strength and flexibility, flexibility, impact resistance, cold resistance, installation property, workability It shows an excellent effect that can achieve at the same time.

In the present invention, the insulating layer 30 may further include other additives such as antioxidants, impact aids, heat stabilizers, nucleating agents, 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 according to its type.

Meanwhile, the inner semiconducting layer 20 may include, as a base resin, a blending resin of a heterophasic polypropylene resin (B) in which a propylene copolymer is dispersed in the polypropylene matrix and another heterophasic resin (B '). . Here, the heterophasic resin (B ′) is also a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix, or the heteropropylene resin (B ′) is a heteropropylene resin because the polypropylene matrix includes a propylene lambdon copolymer. It has a low melting point and a high melt flow rate (MFR) compared to the phase polypropylene resin (B), for example, the melting point of the heterophasic resin (B ') is 140 to 150 ° C, a load of 2.16 kg and ISO at 230 ° C. The melt flow rate (MFR) measured according to 1133 may be 6 to 8 g / 10 minutes.

In addition, based on 100 parts by weight of the base resin, the content of the heterophasic polypropylene resin (B) may be 50 to 80 parts by weight and the content of the heterophasic resin (B ') may be 20 to 50 parts by weight, further It may include 35 to 70 parts by weight of carbon black, 0.2 to 3 parts by weight of antioxidant, and the like.

Here, when the content of the heterophasic polypropylene resin (B) is less than 50 parts by weight and the content of the heterophasic resin (B ′) is more than 50 parts by weight, the heat resistance and the elongation of the inner semiconducting layer 20 are greatly increased. On the other hand, when the content of the heterophasic polypropylene resin (B) is greater than 80 parts by weight and the content of the heterophasic resin (B ') is less than 20 parts by weight, the inner semiconducting layer 20 may be formed. Increasing the viscosity of the composition can lead to an increase in screw load during extrusion, which may significantly reduce workability.

In addition, when the content of the carbon black is less than 35 parts by weight of the semi-conductive properties of the inner semiconducting layer 20 may not be implemented, when the content of more than 70 parts by weight of the composition forming the inner semiconducting layer 20 Due to the increase in viscosity, the screw load increases during extrusion, which may significantly reduce workability.

When the content of the antioxidant is less than 0.2 part by weight, it may be difficult to secure long-term heat resistance of the power cable in a high temperature environment, whereas when the content of the antioxidant is greater than 3 parts by weight, the antioxidant may be whitened to the surface of the inner semiconducting layer 20. The eluting blooming phenomenon may occur and the semiconducting properties may be degraded.

On the other hand, the outer semiconducting layer 40 may include a blending resin of the heterophasic polypropylene resin (B) and ethylene copolymerization resin as a base resin, the ethylene copolymerization resin, for example ethylene butyl acrylate (EBA) , Ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene methyl acrylate (EMA), and the like, or combinations thereof.

Here, based on 100 parts by weight of the base resin, the content of the heterophasic polypropylene resin (B) may be 10 to 40 parts by weight and the content of the ethylene copolymer resin may be 60 to 90 parts by weight, carbon black 35 to 70 by weight Parts, the antioxidant may further include 0.2 to 3 parts by weight.

Here, when the content of the heterophasic polypropylene resin (B) is less than 10 parts by weight and the content of the ethylene copolymer resin 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 While the adhesion of the outer semiconducting layer 40 to (30) may be greatly reduced, the content of the heterophasic polypropylene resin (B) is greater than 40 parts by weight and the content of the ethylene copolymer resin is less than 60 parts by weight. In this case, the ease of peeling of the outer semiconducting layer 40 with respect to the insulating layer 30 may be greatly reduced.

In addition, when the content of the carbon black is less than 35 parts by weight of the semi-conducting properties of the outer semiconducting layer 20 may not be implemented, when the content of more than 70 parts by weight of the composition forming the outer semiconducting layer 20 Due to the increase in viscosity, the screw load increases during extrusion, which may significantly reduce workability.

When the content of the antioxidant is less than 0.2 part by weight, it may be difficult to secure long-term heat resistance of the power cable in a high temperature environment, whereas when the content of the antioxidant is more than 3 parts by weight, the antioxidant may be whitened to the outer semiconducting layer 20 surface. The eluting blooming phenomenon may occur and the semiconducting properties may be degraded.

EXAMPLE

1. Preparation

The base resin consisting of the components and contents shown in Table 3 below was preheated at 180 ° C. for 10 minutes, pressurized at 20 MPa for 10 minutes, and cooled to prepare insulation specimens. In addition, the base resin was extruded on the conductor to prepare cable specimens each having an insulating layer. The units of the contents shown in Table 3 are parts by weight.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Resin A 30 50 60 70 80 100 Resin B 70 50 40 30 20 0

Resin A: Polypropylene resin Resin B: Heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix

2. Property evaluation

1) Flexibility Evaluation

The specimens were manufactured in the size of width × length × thickness = 100 mm × 100 mm × 3 mm, and the Shore D hardness was measured by selecting three or more points of the specimens thus prepared.

In addition, the size of the specimen was prepared in the size of the width × length × thickness = 250mm × 250mm × 1mm, and the Dumbbell specimen was taken again in accordance with ASTM D638, the dumbbell specimen 200 mm / The flexibility and flexibility of each specimen were evaluated by measuring the tensile strength at the point where the elongation was 5% when tensile at the rate of min.

Herein, when the tensile strength was 0.7 to 3.0 kgf / mm ² and the Shore D hardness was 35 to 70, the mechanical properties and the flexibility and the flexibility in the tradeoff were evaluated as being excellent. That is, when the tensile strength is less than 0.7 kgf / mm ² and the Shore D hardness is less than 35, the flexibility and flexibility are excellent, but the mechanical strength is greatly reduced, the cable structure is changed and the electrical properties are greatly changed by the pressing phenomenon during cable manufacturing or laying. On the other hand, when the tensile strength is greater than 3.0 kgf / mm ² and the Shore D hardness is greater than 70, it was evaluated that the flexibility and flexibility are greatly reduced.

2) cold resistance evaluation

Five pieces of specimens taken from the insulation layer of the cable specimens having a length of 36.0 mm to 40.0 mm, a width of 5.6 mm to 6.4 mm, and a thickness of 1.8 mm to 2.2 mm were subjected to a cold resistance test (KS 3004) according to ASTM D746, that is, The specimen is left at 23 ° C. and 50% relative humidity for at least 40 hours, and the temperature is increased or decreased at intervals of 5 ° C. and left for 2.5 to 3.5 minutes for each temperature, followed by holding with a force of 0.56 N · m. After hitting at 90 ° to the surface of the specimen at a speed of 1800 to 2200 mm / s using a (striking edge), by observing whether the specimen breaks or cracks, the brittle temperature according to Equation 1 ( T _b ) was calculated.

Evaluation results of the physical properties are as shown in Table 4 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Shore D Hardness 54.2 63.3 66.9 69.3 71.4 75.6 Tensile strength (kgf / mm ² ) 0.82 1.93 2.36 2.99 3.43 4.42 Brittleness temperature (℃) -54.5 -48.5 -41.5 -36.5 -21.5 -1.5

As shown in Table 4, Examples 1 to 4 according to the present invention was confirmed that the mechanical strength is also sufficient by having adequate cold resistance, flexibility, flexibility, etc., while Comparative Examples 1 and 2 have cold resistance due to improper base resin It was confirmed that greatly reduced, flexibility and flexibility is greatly reduced. Although the present specification has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be thought of the invention described in the claims described below And various modifications and variations of the present invention can be made without departing from the scope thereof. Therefore, it should be seen that all modifications included in the technical scope of the present invention are basically included in the scope of the claims of the present invention.

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

Claims (20)

A polypropylene resin or a heterophasic polypropylene resin as a base resin,
The brittle temperature (T _b ) defined by Equation 1 below is less than -35 ℃,
[Equation 1]
T _b = T _h + ΔT [(S / 100)-(1/2)]
In Equation 1,
T _h is 5 ° C 23%, 50% relative to five specimens taken from the cable insulation layer comprising the base resin, 36.0 mm to 40.0 mm long, 5.6 mm to 6.4 mm wide and 1.8 mm to 2.2 mm thick according to ASTM D746. It is left at humidity for 40 hours or more, and the temperature is increased or decreased at -40 ° C to 5 ° C interval for 2.5 to 3.5 minutes by temperature, and then the speed of 1800 to 2200 mm / s using a striking edge. The highest temperature (° C.) at which all five specimens are destroyed or a visually visible crack occurs on the surfaces of all five specimens as a result of hitting at 90 ° to the surface of the specimen.
ΔT is a constant temperature interval that changes during each temperature experiment in accordance with ASTM D746,
S was tested as above while raising or lowering the temperature at intervals of ΔT from -40 ° C. according to ASTM D746. As a result, all five specimens were not destroyed or there were no visible cracks on the surfaces of all five specimens. It is the sum of the percentage of specimens that were broken or visually cracked on the surface among the five specimens in each temperature experiment from the lowest temperature (° C.) not occurring to T _h .
Insulation composition, wherein the xylene cost diagram as defined by Equation 2 below is 10% or less.
[Equation 2]
Xylene cost plot = (mass of insulated specimen after elution in xylene solvent / mass of insulated specimen before elution) × 100
In Equation 2,
After eluting in the xylene solvent, the mass of the insulating specimen was soaked in 0.3 g of the insulating specimen in a xylene solvent, and boiled at 150 ° C. or higher for 6 hours, cooled to room temperature, and then taken out of the insulating specimen and then again in an oven at 150 ° C. for 4 hours. Is the mass of the insulating specimen measured after drying and cooling to room temperature. The method of claim 1,
The brittle temperature (T _b ) is characterized in that -80 to -35 ℃, insulation composition. The method according to claim 1 or 2,
Insulation specimens formed from the insulation composition is characterized in that the flexural modulus at room temperature measured in accordance with the standard ASTM D790, 50 to 1,200 MPa. The method according to claim 1 or 2,
The heterophasic polypropylene resin is an insulating composition, characterized in that the rubbery propylene copolymer is dispersed in a crystalline polypropylene matrix. The method of claim 4, wherein
Insulation composition, characterized in that the crystalline polypropylene matrix comprises a propylene homopolymer, a propylene copolymer or both. The method of claim 4, wherein
The rubbery propylene copolymer is selected from the group consisting of ethylene and C _4-12 alpha-olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene Insulating composition, characterized in that it comprises at least one comonomer. The method according to claim 1 or 2,
The heterophasic polypropylene resin has a melting point (Tm) measured by a differential scanning calorimeter (DSC) is 140 to 170 ℃, the melt enthalpy measured by a differential scanning calorimeter (DSC) is 20 to 85 J / g Insulation composition characterized by the above-mentioned. The method according to claim 1 or 2,
Tensile at a point where elongation is 5% when the 1 mm thick specimen is stretched at a rate of 200 mm / min after pressurizing the base resin preheated at 180 ° C. for 10 minutes at 20 MPa for 10 minutes and then cooling. Insulation composition, characterized in that the strength is 0.7 to 3.0 kgf / mm ² and Shore D hardness is 25 to 70. The method according to claim 1 or 2,
The insulating composition, the insulating composition, characterized in that it further comprises 0.1 to 0.5 parts by weight of a nucleating agent (nucleating agent) based on 100 parts by weight of the base resin. The method according to claim 1 or 2,
The insulating composition, characterized in that it further comprises 1 to 10 parts by weight of insulating oil, based on 100 parts by weight of the base resin, insulating composition. The method according to claim 1 or 2,
The insulation composition further comprises from 0.001 to 10% by weight of one or more other additives selected from the group consisting of antioxidants, impact aids, heat stabilizers, nucleating agents and acid scavengers based on their total weight. Insulating composition, characterized in that. The method according to claim 1 or 2,
The base resin includes 30 to 70 parts by weight of polypropylene resin (A) and 70 to 30 parts by weight of heterophasic polypropylene resin (B) in which a propylene copolymer is dispersed in the polypropylene matrix based on 100 parts by weight of the base resin. Insulating composition, characterized in that. The method of claim 12,
The polypropylene resin (A) is characterized in that all of the following conditions a) to i), insulating composition.
a) density from 0.87 to 0.92 g / cm 3 (measured according to ISO 11883),
b) melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 ° C. according to ISO 1133),
c) tensile modulus of 930 to 980 MPa (measured at a tensile speed of 1 mm / min),
d) tensile stress at yield is 22 to 27 MPa (measured at a tensile speed of 50 mm / min),
e) tensile strain at yield is 13 to 15% (measured at a tensile speed of 50 mm / min),
f) Charpy impact strengths at 0 ° C. and 23 ° C. are 1.8 to 2.1 kJ / m 2 and 5.5 to 6.5 kJ / m 2, respectively;
g) heat deflection temperature of 6.8-7.2 ° C. (measured at 0.45 MPa),
h) Vicat softening point from 131 to 136 ° C (measured at 50 ° C / h and 10N according to specification A50), and
i) Shore D hardness of 63 to 70 (measured according to ISO 868) The method of claim 12,
The heterophasic polypropylene resin (B) satisfies all of the following conditions a) to j), insulation composition.
a) density between 0.86 and 0.90 g / cm 3 (measured according to ISO 11883),
b) melt flow rate (MFR) of 0.1 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 ° C. according to ISO 1133),
c) tensile stress at break is 10 MPa or more (measured at a tensile speed of 50 mm / min),
d) the tensile strain at break is 450% or more (measured at a tensile speed of 50 mm / min),
e) flexural strength is 95 to 105 MPa
f) Notched izod impact strength at −40 ° C., respectively, from 6.8 to 7.2 kJ / m 2,
g) heat deflection temperature of 38-42 ° C. (measured at 0.45 MPa),
h) Vicat softening point from 55 to 59 ° C. (measured at 50 ° C./h and 10 N according to standard A50),
i) Shore D hardness is 25 to 35 (measured according to ISO 868), and
j) melting point of from 155 to 170 캜 The method of claim 12,
The polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylene monomer content of 1 to 10% by weight based on the total weight of the monomers, and the poly included in the heterophasic polypropylene resin (B). Insulation composition, characterized in that the propylene matrix is a propylene homopolymer. The method of claim 12,
The propylene copolymer included in the heterophasic polypropylene resin (B) has a ethylene monomer content of 20 to 50% by weight based on the total weight of the monomers, and includes propylene-ethylene rubber (PER) particles. Insulation composition characterized by the above-mentioned. The method of claim 16,
The content of the propylene copolymer is 60 to 80% by weight based on the total weight of the heterophasic polypropylene resin (B), insulation composition. The method of claim 16,
The heterophasic polypropylene resin (B) is an insulation composition, characterized in that the melt enthalpy measured by a differential scanning calorimeter (DSC) is 15 to 40 J / g. Conductor,
An inner semiconducting layer surrounding the conductor,
A power cable surrounding the inner semiconducting layer and including an insulating layer formed from the insulating composition of claim 1. The method of claim 19,
The thickness of the insulation layer in the cable, characterized in that 5.5 to 84.0 times of t _min according to the following equation, power cable.
[Equation 3]
t _min = 2.5Uo / breakdown electric field for insulated specimens
In Equation 3,
Uo is the reference voltage for voltage tests according to standard IEC 60840,
The dielectric breakdown electric field for the insulated specimen is an electric field (kV) according to the applied voltage when the electrode is contacted at each end of each of the plurality of insulated specimens, and a voltage is applied thereto and the probability of the breakdown of the plurality of insulated specimens is 63.2%. / mm).

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