KR20140134836A

KR20140134836A - Power cable

Info

Publication number: KR20140134836A
Application number: KR1020130054720A
Authority: KR
Inventors: 정현정; 남진호; 유익현; 김형준
Original assignee: 엘에스전선 주식회사
Priority date: 2013-05-15
Filing date: 2013-05-15
Publication date: 2014-11-25
Also published as: KR102038709B1

Abstract

The present invention relates to power cables. Specifically, the present invention relates to a resin composition which is environmentally friendly, has excellent heat resistance and mechanical strength, and is made of an insulating material excellent in flexibility, bending property, impact resistance, cold resistance, To a power cable having an insulating layer.

Description

Power cable {Power cable}

A typical power cable includes a conductor and an insulating layer surrounding the conductor. In the case of a high-voltage or ultra-high voltage cable, an inner semiconductive layer between the conductor and the insulating layer, an outer semiconductive layer surrounding the insulating layer, a sheath layer surrounding the outer semiconductive layer May be further included.

In recent years, the development of high-capacity cables has been required in accordance with the increasing demand for electric power, and it has become necessary to provide an insulating material for manufacturing an insulating layer having excellent mechanical and electrical characteristics. Conventionally, a polyolefin-based polymer such as polyethylene, an ethylene / propylene elastic copolymer (EPR), or an ethylene / propylene / diene copolymer (EPDM) has been used as a base resin constituting the insulating material. 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 is in a crosslinked form, when the life of a cable or the like including an insulating layer made of a resin such as the crosslinked polyethylene is shortened, It is impossible to recycle the resin to be disposed of by incineration and is not environmentally friendly. 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, toxic chlorinated materials are generated during incineration, There are disadvantages.

On the other hand, non-crosslinked high-density polyethylene (HDPE) or low-density polyethylene (LDPE) is eco-friendly because it can recycle the resin constituting the insulating layer at the end of its lifetime, Type polyethylene (XLPE), which is inferior in heat resistance, and its application is very limited due to its low operating temperature. Further, there is known a technique of adding inorganic particles such as carbon black to improve the heat resistance and the like of the non-crosslinked polyethylene. However, since the production cost is increased by the addition of the carbon black and the compatibility of the carbon black with the resin, That is, the dispersibility of the carbon black to the resin must be solved, and the manufacturing process of the insulating material may be complicated.

On the other hand, it can be considered to use an environment-friendly polypropylene resin as a base resin because it has excellent heat resistance without crosslinking at a melting point of the polymer itself of 160 캜 or higher. However, due to insufficient flexibility and flexibility due to the high rigidity of the polypropylene resin, the workability of the cable including the insulation layer produced therefrom is low and the use thereof is limited there is a problem.

In this connection, Korean Patent Laid-Open Nos. 10-2011-0084544, 10-2009-0037945, and 10-2007-0086013 disclose various insulating materials including polypropylene resin, it is very insufficient to simultaneously satisfy the rigidity, flexibility, bending property, impact resistance, resistance to load, installation property and workability of the resin in the trade-off.

Therefore, a new insulating material which can satisfy not only environmental friendliness and low manufacturing cost but also flexibility, bending property, impact resistance, cold resistance, installation property and workability in trade-off with heat resistance and mechanical strength And a power cable having an insulating layer manufactured therefrom.

It is an object of the present invention to provide a power cable having an insulation layer made of an insulating material which is environmentally friendly, such as being able to be recycled after its end of life, and which requires no process for crosslinking and is low in manufacturing cost.

The present invention also provides a power cable having an insulating layer made of an insulating material capable of simultaneously satisfying flexibility, bending property, impact resistance, cold resistance, installation property, workability and the like in a trade-off relationship with heat resistance and mechanical strength And to provide the above objects.

In order to solve the above problems,

1. A power cable comprising at least one conductor, an inner semiconductive layer surrounding each conductor, an insulation layer surrounding the inner semiconductive layer, an outer semiconductive layer surrounding the insulation layer, and a sheath layer surrounding the outer semiconductive layer, The insulating layer is composed of a non-crosslinked thermoplastic resin (B) having a polypropylene resin (A) and a polypropylene matrix (B) in which a propylene copolymer-dispersed heterophasic resin is blended at a weight ratio (A: B) of 2: 8 to 6: A resin, and a resin.

Here, the polypropylene resin (A) satisfies all of the conditions a) to i) below.

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

b) a melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)

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

d) a tensile stress at break of 22 to 27 MPa (measured at a tensile rate of 50 mm / min)

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

f) a charpy impact strength at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, respectively,

g) heat distortion temperature of 68 to 72 DEG C (measured at 0.45 MPa),

h) Vicat softening point of 131-136 占 폚 (measured at 50 占 폚 / h and 10N according to specification A50), and

i) Shore D hardness is 67

Also, the above-mentioned heterophasic resin (B) satisfies all of the following conditions a) to j).

a) a density of 0.86 to 0.90 g / cm < 3 > (measured in accordance with ISO 11883)

b) a melt flow rate (MFR) of 0.5 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)

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

d) a tensile strain at break of 13 to 15% (measured at a tensile rate of 50 mm / min)

e) a flexural strength of 95 to 105 MPa

f) a notched izod impact strength at -40 DEG C of 68 to 72 kJ / m2,

g) heat distortion temperature of 38 to 42 DEG C (measured at 0.45 MPa),

h) Vicat softening point of 55 to 59 캜 (measured at 50 캜 / h and 10 N according to Specification A50)

i) the Shore D hardness is 28, and

j) a melting point of 155 to 165 DEG C

On the other hand, the polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylene monomer content of 1 to 5% by weight based on the total weight of the monomers, and the poly Wherein the propylene matrix is a propylene homopolymer.

The propylene copolymer contained in the heterophasic resin (B) is preferably a propylene-ethylene rubber having an ethylene monomer content of 20 to 30% by weight and a particle size of 1 m or less based on the total weight of the monomers (EPR ) Particles. &Lt; / RTI >

Here, the content of the propylene copolymer is 42 to 49% by weight, based on the total weight of the heterophasic resin (B).

Further, the above-mentioned heterophasic resin (B) is characterized in that the melting enthalpy measured by differential scanning calorimetry (DSC) is 25 to 40 J / g.

Further, the insulating layer may further include 0.1 to 0.5 parts by weight of a nucleating agent based on 100 parts by weight of the non-crosslinked thermoplastic resin, wherein the polypropylene resin (A) has a crystal size of 1 to 10 μm And a power cable.

The insulating layer further comprises 1 to 10 parts by weight of insulating oil based on 100 parts by weight of the non-crosslinked thermoplastic resin.

On the other hand, the insulating layer may contain, based on the total weight of the insulating layer, one or more other additives selected from the group consisting of an antioxidant, a shock absorber, a heat stabilizer, a nucleating agent, and acid scavengers, By weight, based on the total weight of the composition.

The non-crosslinked thermoplastic resin has a melting point (Tm) as measured by a differential scanning calorimeter (DSC) of 150 to 160 ° C and a melting enthalpy as measured by a differential scanning calorimeter (DSC) of 50 to 85 J / g , And a solubility in xylene of 19 to 36% (measured in accordance with D5492-10 by adding 2 g of resin to xylene at 135 캜).

Further, the non-crosslinked thermoplastic resin has a flexural strength of 200 to 650 MPa or less as measured according to ASTM D790.

INDUSTRIAL APPLICABILITY The power cable according to the present invention is environmentally friendly and requires no process for crosslinking by using non-crosslinked polypropylene, which is excellent in heat resistance, as a base resin of the insulating layer.

The power cable according to the present invention is excellent in heat resistance and mechanical strength as well as excellent in flexibility, flexibility, impact resistance, cold resistance, installation property, workability and the like in trade-off with them Effect.

1 is a cross-sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.
2 is a longitudinal sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.

1 and 2 show an embodiment of a power cable according to the present invention.

1 and 2, a power cable according to the present invention includes a conductor 1 made of a conductive material such as copper or aluminum, an insulating layer 3 made of an insulating polymer, (3), thereby suppressing partial discharge at the interface with the conductor (1), eliminating the air layer between the conductor (1) and the insulating layer (3) An outer semiconductive layer 4 serving as a shielding function of the cable and an electric field equivalent to the insulator, a sheath layer 5 for protecting the cable, and the like have.

The dimensions of the conductor 1, the insulating layer 3, the semiconductive layer 2 and 4, and the sheath layer 5 may vary depending on the use of the cable, the transmission voltage, etc. The insulating layer 3, The materials constituting the entire layers (2, 4) and the sheath layer (5) may be the same or different.

The insulating layer 3 of the power cable according to the present invention may comprise a non-crosslinked thermoplastic resin blended with a polypropylene resin and (B) a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix have.

The polypropylene resin (A) may include a propylene homopolymer and / or a propylene copolymer. The propylene homopolymer refers to a polypropylene formed by polymerization of propylene at 99 wt% or more, preferably 99.5 wt% or more, based on the total weight of the monomers.

The propylene copolymer is obtained by copolymerizing propylene with ethylene or an? -Olefin having 4 to 12 carbon atoms, such as 1-butene, 1-pentene, 4-methyl-1-pentene, Dodecene, and combinations thereof, and the like, preferably a copolymer with ethylene. This is because copolymerization of propylene and ethylene shows a hard and flexible property.

The propylene copolymer may include a random propylene copolymer and / or a block propylene copolymer, preferably a random propylene copolymer, and more preferably a random propylene copolymer. The random propylene copolymer means a propylene copolymer in which propylene monomer and other olefin monomers are 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, based on the total monomer weight of ethylene monomer.

The random propylene copolymer preferably has a density of from 0.87 to 0.92 g / cm 3 (measured according to ISO 11883), a melt flow rate (MFR) of from 1.7 to 1.9 g / 10 min (measured at a tensile rate of 1 mm / min), a tensile stress of 22 to 27 MPa (measured at a tensile rate of 50 mm / min), a tensile strain of 13 to 15% (Measured at a tensile rate of 50 mm / min), Charpy impact strengths at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, thermal deformation temperatures of 68 to 72 占 폚 ), A Vicat softening point of 131 to 136 占 폚 (measured at 50 占 폚 / h and 10 N according to Specification A50) and a Shore D hardness of 67.

The random propylene copolymer can improve the mechanical strength such as the tensile strength of the insulating layer 3 to be formed and is suitable for a transparent molded product because of its high transparency and has a relatively high crystallization temperature Tc, It is possible to shorten the time required for cooling after the layer 3 is extruded to thereby improve the production yield of the cable and to minimize the shrinkage and thermal deformability of the insulating layer 3 and to reduce the cable manufacturing cost There is an advantage that can be saved.

The polypropylene resin (A) may have a weight average molecular weight (Mw) of 200,000 to 450,000, and thus a melt index (MI) of 3 to 10 dg / min (as measured by ASTM D-1238) have. Further, the polypropylene resin (A) has a melting point (Tm) of 140 to 175 ° C (as measured by a differential scanning calorimeter (DSC)), a melting enthalpy of 30 to 85 J / g (as measured by DSC) May be 30 to 1,000 MPa, preferably 60 to 1,000 MPa (measured in accordance with ASTM D790).

The polypropylene resin (A) can be polymerized under conventional stereospecific Ziegler-Natta catalysts, metallocene catalysts, restrained geometric catalysts, other organometallic or coordination catalysts, preferably Ziegler-Natta catalysts or metallocenes Can be polymerized under a catalyst. Here, the metallocene is a generic name of a bis (cyclopentadienyl) metal, which is a novel organometallic compound in which cyclopentadiene and a transition metal are bonded in a sandwich structure. The general formula of the simplest structure is M (C ₅ H ₅ ) ₂ , M is Ti, V, Cr, Fe, Co, Ni, Ru, Zr, Hf, etc.). Since the amount of catalyst remaining in the polypropylene polymerized under the metallocene catalyst is as low as about 200 to 700 ppm, it is possible to suppress or minimize the deterioration of the electrical characteristics of the insulating composition including the polypropylene due to the residual amount of the catalyst.

Although the polypropylene resin (A) has a high melting point due to its own melting point, the polypropylene resin (A) can exhibit sufficient heat resistance to provide a power cable having an improved continuous use temperature and is environmentally friendly And exhibits excellent effects. On the other hand, conventional cross-linked resin is not environmentally friendly because it is difficult to recycle, and when cross-linking or scorch occurs early in forming insulating layer 3, uniform production ability can not be exhibited, . &Lt; / RTI >

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

In the above-mentioned heterophasic resin (B), the propylene copolymer dispersed in the polypropylene matrix (hereinafter referred to as 'dispersed propylene copolymer') is substantially amorphous. Here, the amorphous propylene copolymer means that the propylene copolymer has a residual crystallinity with a melting enthalpy 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, And may include one or more comonomers.

The dispersed propylene copolymer may be 40 to 50 wt%, preferably 42 to 49 wt%, based on the total weight of the heterophasic resin (B). If the content of the dispersed propylene copolymer is less than 40% by weight, the flexibility, bending property, impact resistance and cold resistance of the formed insulating layer 3 may be insufficient, while if it exceeds 50% by weight, 3) may have insufficient heat resistance and mechanical strength.

The dispersed propylene copolymer may be a propylene-ethylene rubber (EPR) or propylene-ethylene diene rubber (EPDM) comprising 20 to 30% by weight of ethylene monomer based on the total weight of the monomers. If the content of the ethylene monomer is less than 20% by weight, the flexibility, bending property, impact resistance and cold resistance of the insulating layer 3 may be insufficient. On the other hand, if the content of the ethylene monomer is more than 30% by weight, The mechanical strength and the like may be insufficient.

In the present invention, the particle size of the dispersed propylene copolymer may be 1 占 퐉 or less, preferably 0.9 占 퐉 or less, and more preferably 0.8 占 퐉 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 insulating layer containing the dispersed propylene copolymer. In addition, the particle size improves the likelihood of stopping already formed cracks or cracks while reducing the risk of fracture initiated by the particles.

The heterophasic resin (B) preferably has a melt flow rate (MFR) of 0.5 to 1.0 g / 10 min, preferably 0.8 g / 10 min, measured according to ISO 1133 at 230 DEG C and a load of 2.16 kg / 10 min, a tensile stress at break of 10 MPa or more, a tensile strain at break of 490% or more, a bending strength of 95 to 105 MPa, a notched Izod impact strength of 68 to 72 kJ / (Measured at 50 占 폚 / h and 10 N according to A50), a shore D hardness of 28, a melting point (Tm) of 155 占 폚, a heat distortion temperature of 38 to 42 占 폚 (measured at 0.45 MPa), a Vicat softening point of 55 to 59 占To 165 캜 (as measured by differential scanning calorimetry (DSC)) and a melting enthalpy of 25 to 40 J / g (as measured by DSC).

The density of the heterophasic resin (B) may be 0.86 to 0.90 g / cm 3, preferably 0.88 g / cm 3, when measured according to ISO 11883, In turn, impact strength and shrinkage properties are affected.

Since the above-mentioned heterophasic resin (B) contains non-crosslinked polypropylene, it can be recycled and can improve the heat resistance of the insulating layer 3 formed of a polypropylene matrix which is environment-friendly and excellent in heat resistance. Flexibility, bending resistance, impact resistance, cold resistance, installation property, workability, etc. of the insulating layer 3 lowered by the rigidity of the resin (A) can be improved.

The weight ratio (A: B) of the polypropylene resin (A) and the heterophasic resin (B) may be from 2: 8 to 6: 4. If the weight ratio is less than 2: 8, the mechanical strength such as tensile strength of the insulating layer 3 formed may be insufficient. If the weight ratio is more than 6: 4, the flexibility, bending property, impact resistance, cold resistance, It may be insufficient.

The non-crosslinked thermoplastic resin contained in the insulating layer (3) of the power cable according to the present invention is excellent in heat resistance, flexibility, bending property, impact resistance, cold resistance, , The combination of the above-mentioned heterophasic resin (B) exhibiting workability and the like, and the above-mentioned characteristics that are in conflict with each other due to their compatibility, that is, heat resistance and mechanical strength and flexibility, flexibility, impact resistance, cold resistance, And exhibits excellent effects that can be achieved at the same time.

The non-crosslinked thermoplastic resin preferably has a flexural strength of 200 to 650 MPa or less, a melting point (Tm) of 150 to 160 DEG C (as measured by a differential scanning calorimeter (DSC)) and a melting enthalpy of 50 to 85 J / Measured by a scanning calorimeter (DSC)) and the solubility in xylene (measured in accordance with D5492-10 by adding 2 g of resin to xylene at 135 캜) of 19 to 36%.

When the flexural strength of the non-crosslinked thermoplastic resin exceeds 650 MPa, flexibility, bending property, impact resistance, cold resistance, installation property, workability, etc. of the cable may be insufficient. When the melting point (Tm) If the melting enthalpy is less than 50 J / g, it means that the crystal size is small and the crystallinity is low, and the heat resistance and mechanical strength of the cable are lowered. On the other hand, when the enthalpy of melting exceeds 85 J / g, Is high and the crystallinity is high, and the electrical characteristics of the insulating layer 3 may be deteriorated. In addition, when the solubility of xylene exceeds 36%, the isotacticity of the resin may be excessively low and the mechanical strength may be insufficient. When the solubility is less than 19%, the stereoregularity of the resin is excessively high and the flexibility, Impact resistance, cold resistance and the like may be lowered.

In the present invention, the insulating layer 3 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 such as 1,3: 2,4-bis (3,4-dimethyl dibenzylidene) sorbitol (1,3: ), Bis (p-methyldibenzulidene) sorbitol, Substituted Dibenzylidene Sorbitol, and mixtures thereof.

The non-crosslinked thermoplastic resin can be cured by heating the non-crosslinked thermoplastic resin. The non-crosslinked thermoplastic resin can be cured by heating the non-crosslinked thermoplastic resin. To 10 mu m, it is possible to improve the electrical characteristics of the insulating layer to be produced, and furthermore, to increase the degree of crystallization by forming a plurality of crystallization sites in which the crystals are formed, thereby improving the heat resistance and mechanical strength of the insulating layer 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 two or more sorbitol nucleating agents in combination. When two or more different sorbitol nucleating agents are used in combination, the expression of the nucleating agent can be enhanced even at a low temperature.

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

In the present invention, the insulating layer 3 may further include insulating oil.

The insulating oil may be mineral oil, synthetic oil, or the like. Particularly, the insulating oil is selected from the group consisting of 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, 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, There is a problem that the insulation oil is eluted during the extrusion process of forming the insulating layer 3 on the insulating layer 3, thereby making it difficult to process the cable.

As described above, the insulating oil is improved in flexibility, bending property, and the like of the insulating layer 3 made of a base resin made of a polypropylene resin having a high rigidity and a somewhat low flexibility, And at the same time exhibits an excellent effect of maintaining or improving the excellent heat resistance, mechanical and electrical properties inherent in the polypropylene resin. In particular, the insulating oil exhibits excellent effects of supplementing the somewhat deteriorated processability due to a rather narrow molecular weight distribution when the polypropylene resin is polymerized under a metallocene catalyst.

In the present invention, the insulating layer 3 may further include other additives such as an antioxidant, a shock absorber, a heat stabilizer, a nucleating agent, and acid scavengers. The other additives may be added in an amount of 0.001 to 10 wt% based on the total weight of the insulating layer 3, depending on the type thereof.

[Example]

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

1. Manufacturing Example

An insulating composition according to each of Examples and Comparative Examples was prepared with the components and contents as shown in Tables 1 and 2 below, extruded using a single screw extruder (manufacturer: Royle, USA) A sheet having a thickness of 2 mm and a size of 30 cm x 30 cm was produced. In Table 2 below, the unit of content is parts by weight.

Properties Unit (Measurement condition) Resin 1 Resin 2 density g / cm3 0.88 0.900 Melt flow rate g / 10 min
(230 DEG C / 2.16 kg) 0.8 1.8 Tensile modulus MPa (1 mm / min) - 950 Tensile stress at yield MPa (50 mm / min) - 25.0 Tensile strain at yield % (50 mm / min) - 14 Tensile stress at break MPa (50 mm / min) > 11 - Tensile strain at break % (50 mm / min) > 500 - Flexural strength MPa 100 - Notch Izod impact strength
kJ / m < 2 > (23 DEG C) No fracture - kJ / m < 2 > (-40 DEG C) 70 - Charpy impact strength
kJ / m < 2 > (0 DEG C) - 2.00 kJ / m < 2 > (23 DEG C) - 6.00 Heat distortion temperature (0.45 MPa) 40 70.0 Vicat softening point Lt; 0 > C (A50 (50 [deg.] C / h 10N) 57 134 Melting point ℃ 160 - Shore D hardness 28 67

- Resin 1: a heterophasic resin in which propylene-ethylene rubber (EPR) particles of 1 占 퐉 or less are dispersed in a propylene homopolymer matrix

- Resin 2: Random propylene-ethylene copolymer (ethylene content: 3% by weight)

Constituent Example Comparative Example One 2 3 4 One 2 3 4 Resin 1 80 70 50 40 100 90 30 Resin 2 20 30 50 60 100 10 70

2. Property evaluation

1) Evaluation of mechanical properties after room temperature and heating

The tensile strength of each of the sample sheets prepared in Examples and Comparative Examples was measured at room temperature and at an elongation rate of 10% at a tensile rate of 250 mm / min in accordance with the IEC-60811-1-1 standard.

2) Evaluation of melting temperature and melting enthalpy

The melting temperature (Tm) was measured at the temperature at which the endothermic peak was observed while heating at 10 ° C / min. The melting enthalpy was compared by the integral at the melting temperature Calculated.

3) Evaluation of solubility of xylene

D5492-10. 2 g of the sample was dissolved in xylene at 135 DEG C while stirring, and then dried at room temperature and then compared. The higher the xylene solubility of the resin, the lower the isotacticity and propylene copolymer content.

4) Cold resistance evaluation

In accordance with KSC IEC 60811-1-4, an internal strength test was carried out at -40 ° C, and the results of observation of the crack / break / break phenomenon were recorded.

5) Evaluation of heat distortion

According to KSC IEC 60811-3-1, a strain of 0.75 mm in width with a load of 160 g was tested at 130 ° C for 6 hours, and then the strain should not exceed 50%.

6) Flexibility evaluation

The flexural strength was measured according to the ASTM D790 standard. When the flexural strength was 200 to 650 MPa, it was judged that the balance of impact resistance, flexibility, bending property, pourable property, heat resistance and mechanical strength was good.

The results of the physical property evaluation are shown in Table 3 below.

Properties Example Comparative Example One 2 3 4 One 2 3 4 Tensile strength (kg / ㎟) 0.87 1.04 1.46 1.56 0.6 2.68 0.65 1.78 Melting temperature (캜) 158 156 152 151 162 147 159 150 Melting enthalpy (J / g) 66 63 60 54 33 110 40 82 Solubility of xylene (%) 33 32 25 19 38 6 37 10 Cold resistance Good Good Good Good Good Destruction Good Destruction Heat Strain (%) 21 9 5.8 4.5 ≥70 ≤4 ≥70 4 Flexural Strength (MPa) 250 350 530 620 100 1,000 100 800

As shown in Table 3, since the insulating specimens of Comparative Examples 1 and 3 were made from non-crosslinked thermoplastic resin containing only Resin 1 having excellent flexibility, bending property or the like and containing excess resin 1, flexibility, , Cold resistance and the like can be increased, but mechanical strength such as tensile strength is insufficient due to low melting enthalpy, that is, low crystallinity, and the manufacturing cost is increased by the resin 1 which is relatively expensive.

In addition, since the insulating specimens of Comparative Examples 2 and 4 were made from non-crosslinked thermoplastic resin containing only resin 2 having excellent mechanical strength or containing excess resin 2, it is possible to increase the mechanical strength such as tensile strength of the produced cable However, flexibility, flexibility, cold resistance and the like are insufficient, and in particular, Comparative Example 2 can exhibit a high melting enthalpy, that is, a decrease in electrical properties due to an increase in crystallinity and crystal size, and a decrease in heat resistance due to a low melting temperature .

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. . It is therefore to be understood that the modified embodiments are included in the technical scope of the present invention if they basically include elements of the claims of the present invention.

1: conductor 2: inner semiconductive layer
3: insulating layer 4: outer semiconductive layer
5: Sheath layer

Claims

A power cable comprising at least one conductor, an inner semiconductive layer surrounding each conductor, an insulation layer surrounding the inner semiconductive layer, an outer semiconductive layer surrounding the insulation layer, and a sheath layer surrounding the outer semiconductive layer,
The insulating layer is formed by blending a polypropylene resin (A) and a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix (B) at a weight ratio (A: B) of 2: 8 to 6: A power cable comprising a thermoplastic resin.

The method according to claim 1,
Characterized in that the polypropylene resin (A) satisfies all of the conditions a) to i) below.
a) a density of 0.87 to 0.92 g / cm 3 (measured according to ISO 11883),
b) a melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)
c) a tensile modulus of 930 to 980 MPa (measured at a tensile rate of 1 mm / min)
d) a tensile stress at break of 22 to 27 MPa (measured at a tensile rate of 50 mm / min)
e) tensile strain at yield of 13 to 15% (measured at a tensile rate of 50 mm / min)
f) a charpy impact strength at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, respectively,
g) heat distortion temperature of 68 to 72 DEG C (measured at 0.45 MPa),
h) Vicat softening point of 131-136 占 폚 (measured at 50 占 폚 / h and 10N according to specification A50), and
i) Shore D hardness is 67

3. The method of claim 2,
Wherein said heterophasic resin (B) satisfies all of the following conditions a) to j).
a) a density of 0.86 to 0.90 g / cm < 3 > (measured in accordance with ISO 11883)
b) a melt flow rate (MFR) of 0.5 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)
c) tensile stress at break of 10 MPa or more (measured at a tensile rate of 50 mm / min)
d) a tensile strain at break of 13 to 15% (measured at a tensile rate of 50 mm / min)
e) a flexural strength of 95 to 105 MPa
f) a notched izod impact strength at -40 DEG C of 68 to 72 kJ / m2,
g) heat distortion temperature of 38 to 42 DEG C (measured at 0.45 MPa),
h) Vicat softening point of 55 to 59 캜 (measured at 50 캜 / h and 10 N according to Specification A50)
i) the Shore D hardness is 28, and
j) a melting point of 155 to 165 DEG C

4. The method according to any one of claims 1 to 3,
The polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylenic monomer content of 1 to 5% by weight based on the total weight of the monomers, and the polypropylene matrix (B) Is a propylene homopolymer.

4. The method according to any one of claims 1 to 3,
The propylene copolymer contained in the heterophasic resin (B) is preferably a propylene-ethylene rubber (EPR) particle having an ethylene monomer content of 20 to 30% by weight and a particle size of 1 m or less based on the total weight of monomers Wherein the power cable is a cable.

6. The method of claim 5,
Wherein the content of the propylene copolymer is 42 to 49% by weight, based on the total weight of the heterophasic resin (B).

4. The method according to any one of claims 1 to 3,
Characterized in that said heterophasic resin (B) has a melting enthalpy of from 25 to 40 J / g as measured by differential scanning calorimetry (DSC).

4. The method according to any one of claims 1 to 3,
Wherein the insulating layer further comprises 0.1 to 0.5 parts by weight of a nucleating agent based on 100 parts by weight of the non-crosslinked thermoplastic resin, and the polypropylene resin (A) has a crystal size of 1 to 10 mu m Power cable.

4. The method according to any one of claims 1 to 3,
Wherein the insulating layer further comprises 1 to 10 parts by weight of insulating oil based on 100 parts by weight of the non-crosslinked thermoplastic resin.

4. The method according to any one of claims 1 to 3,
Wherein the insulating layer comprises, based on the total weight of the insulating layer, 0.001 to 10 wt% of at least one other additive selected from the group consisting of antioxidants, impact aids, heat stabilizers, nucleating agents, and acid scavengers Lt; RTI ID = 0.0 >%.&Lt; / RTI >

4. The method according to any one of claims 1 to 3,
The non-crosslinked thermoplastic resin has a melting point (Tm) of 150 to 160 占 폚 as measured by a differential scanning calorimeter (DSC), a melting enthalpy of 50 to 85 J / g as measured by a differential scanning calorimeter (DSC) Characterized in that the solubility in Rhen is from 19 to 36% (measured in accordance with D5492-10 by adding 2 g of resin to xylene at 135 DEG C).

4. The method according to any one of claims 1 to 3,
Wherein the non-crosslinked thermoplastic resin has a flexural strength of 200 to 650 MPa or less as measured according to ASTM D790.